Pseudogap effects on the charge dynamics in the underdoped copper oxide materials
关于Formal
关于Formal Charge与Partial Charge的区别要知道，⼀种不管formal charge还是partial charge都不是实际能够直接经过实验看到的原⼦性质。
实际上分⼦不是由线将点连起来的，即使是同⼀个分⼦，不⼀样价键表达⽅式下，该分⼦中的formal charge可能定位不同（⽐如去质⼦化的羧酸，可以表⽰为开库勒式与芳⾹式，两种⽅式的formal charge定位完全不同），不⼀样的partial charge计算⽅法也会给同⼀个分⼦中的同⼀个原⼦分配不⼀样的电荷，⽐如苯环可以表⽰为[cH+]1[cH-][cH+][cH-][cH+][cH-]1。
两者的区别⾸先, 出于⽤价键表征分⼦的需要，formal charge 为整数.与原⼦价、键级以及连接性⼀起定义分⼦.第⼆，partial charge为浮点数，⽤在计算化学与分⼦模拟中。
它的值⽤来表⽰电⼦分布或分⼦的波函数，⽤⼀套分布于各个原⼦的点电荷来近似地的模拟分⼦的静电场。
Partial chargePartial atomic chargesPartial charges are created due to the asymmetric distribution of electrons in chemical bonds. The resulting partial charges are a property only of zones within the distribution, and not the assemblage as a whole. For example, chemists often choose to look at a small space surrounding the nucleus of an atom: When an electrically neutral atom bonds chemically to another neutral atom that is more electronegative, its electrons are partially drawn away. This leaves the region about that atom's nucleus with a partial positive charge, and it creates a partial negative charge on the atom to which it is bonded.In such a situation, the distributed charges taken as a group always carries a whole number of elementary charge units. Yet one can point to zones within the assemblage where less than a full charge resides, such as the area around an atom's nucleus. This is possible in part because particles are not like mathematical points--which must be either inside a zone or outside it--but are smeared out by the uncertainty principle of quantum mechanics. Because of this smearing effect, if one defines a sufficiently small zone, a fundamental particle may be both partly inside and partly outside it.UsesPartial atomic charges are used in molecular mechanics force fields to compute the electrostatic interaction energy using Coulomb's law. They are also often used for a qualitative understanding of the structure and reactivity of molecules. Methods of determining partial atomic chargesDespite its usefulness, the concept of a partial atomic charge is somewhat arbitrary, because it depends on the method used to delimit between one atom and the next (in reality, atoms have no clear boundaries). As a consequence, there are many methods for estimating the partial charges. According to Cramer (2002), all methods can be classified in one of four classes: Class I charges are those that are not determined from quantum mechanics, but from some intuitive or arbitraryapproach. These approaches can be based on experimental data such as dipoles and electronegativities.Class II charges are derived from partitioning the molecular wave function using some arbitrary, orbital based scheme.Class III charges are based on a partitioning of a physical observable derived from the wave function, such as electron density.Class IV charges are derived from a semiempirical mapping of a precursor charge of type II or III to reproduceexperimentally determined observables such as dipole moments.The following is a detailed list of methods, partly based on Meister and Schwarz (1994).Population analysis of wavefunctionsMulliken population analysisCoulson's chargesNatural chargesCM1, CM2, CM3 charge modelsPartitioning of electron density distributionsBader charges (obtained from an atoms in molecules analysis)Density fitted atomic chargesHirshfeld chargesMaslen's corrected Bader chargesPolitzer's chargesVoronoi Deformation Density chargesCharges derived from density-dependent propertiesPartial derived chargesDipole chargesDipole derivative chargesCharges derived from electrostatic potentialChelpChelpG, Breneman modelMK, Merz-KollmanCharges derived from spectroscopic dataCharges from infrared intensitiesCharges from X-ray photoelectron spectroscopy (ESCA)Charges from X-ray emission spectroscopyCharges from X-ray absorption spectraCharges from ligand-field splittingsCharges from UV-vis intensities of transition metal complexesCharges from other spectroscopies, such as NMR, EPR, EQRCharges from other experimental dataCharges from bandgaps or dielectric constantsApparent charges from the piezoelectric effectCharges derived from adiabatic potential energy curvesElectronegativity-based chargesOther physicochemical data, such as equilibrium and reaction rate constants, thermochemistry, and liquiddensities.Formal chargesFormal chargeIn chemistry, a formal charge (FC) is the charge assigned to an atom in a molecule, assuming that electrons in a chemical bond are shared equally between atoms, regardless of relative electronegativity.The formal charge of any atom in a molecule can be calculated by the following equation:FC = V - N - B/2Where V is the number of valence electrons of the atom in isolation (atom in ground state); N is the number of non-bonding electrons on this atom in the molecule; and B is the total number of electrons shared in covalent bonds with other atoms in the molecule.When determining the correct Lewis structure (or predominant resonance structure) for a molecule, the structure is chosen such that the formal charge (without sign) on each of the atoms is minimized.Formal charge is a test to determine the efficiency of electron distribution of a molecule. This is significant when drawing structures.Examples:Carbon in methane: FC = 4 - 0 - (8÷2) = 0Nitrogen in NO2-: FC = 5 - 2 - (6÷2) = 0double bonded oxygen in NO2-: FC = 6 - 4 - (4÷2) = 0single bonded oxygen in NO2- FC = 6 - 6 - (2÷2) = -1An alternative method for assigning charge to an atom taking into account electronegativity is by oxidation number. Other related concepts are valence which counts number of electrons that an atom uses in bonding and coordination number, the number of atoms bonded to the atom of interest.Contents1 Examples2 Alternative method3 Formal Charge vs. Oxidation State4 References5 External linksExamplesAmmonium NH4+ is a cationic species. By using the vertical groups of the atoms on the periodic table it is possible to determine that each hydrogen contributes 1 electron, the nitrogen contributes 5 electrons, and the charge of +1 means that 1 electron is absent. The final total is 8 total electrons (1 × 4 + 5 − 1). Drawing the Lewis structure gives an sp3 (4 bonds) hybridized nitrogen atom surrounded by hydrogen. There are no lone pairs of electrons left. Thus, using the definition of formal charge, hydrogen has a formal charge of zero (1- (0 + ½ × 2)) and nitrogen has a formal charge of +1 (5− (0 + ½ × 8)). After adding up all the formal charges throughout the molecule the result is a total formal charge of +1, consistent with the charge of the molecule given in the first place.Note: The total formal charge in a molecule should be as close to zero as possible, with as few charges on the molecule as possibleExample: CO2 is a neutral molecule with 16 total valence electrons. There are three different ways to draw the Lewis structureCarbon single bonded to both oxygen atoms (carbon = +2, oxygens = -1 each, total formal charge = 0)Carbon single bonded to one oxygen and double bonded to another (carbon = +1, oxygen double = 0, oxygen single = −1, total formal charge = 0)Carbon double bonded to both oxygen atoms (carbon = 0, oxygens = 0, total formal charge =0)Even though all three structures gave us a total charge of zero, the final structure is the superior one because there are no charges in the molecule at all.Alternative methodAlthough the formula given above is correct, it is often unwieldy and inefficient to use. A much quicker and still accurate method is to do the following:Draw a circle around the atom for which the formal charge is requested (as with carbon dioxide, below)Count up the number of electrons in the atom's "circle." Since the circle cuts the covalent bond "in half," each covalent bond counts as one electron instead of two.Subtract the number of electrons in the circle from the group number of the element (the Roman numeral from the older system of group numbering, NOT the IUPAC 1-18 system) to determine the formal charge.The formal charges computed for the remaining atoms in this Lewis structure of carbon dioxide are shown below. Again, this method is just as accurate as the one cited above, but is much easier to use. It is important to keep in mind that formal charges are just that-formal, in the sense that this system is a formalism. Atoms in molecules do not have "signs around their necks" indicating their charge. The formal charge system is just a method to keep track of all of the valence electrons that each atom brings with it when the molecule is formed.Formal Charge vs. Oxidation StateThe concept of oxidation states constitutes a competing method to assess the distribution of electrons in molecules. If the formal charges and oxidation states of the atoms in carbon dioxide are compared, the following values are arrived at:The reason for the difference between these values is that formal charges and oxidation states represent fundamentally different ways of looking at the distribution of electrons amongst the atoms in the molecule. With formal charge, the electrons in each covalent bond are assumed to be split exactly evenly between the two atoms in the bond (hence the dividing by two in the method described above). The formal charge view of the CO2 molecule is essentially shown below:The covalent (sharing) aspect of the bonding is overemphasized in the use of formal charges, since in reality there is a higher electron density around the oxygen atoms due to their higher electronegativity compared to the carbon atom. This can be most effectively visualized in an electrostatic potential map.With the oxidation state formalism, the electrons in the bonds are "awarded" to the atom with the greater electronegativity. The oxidation state view of the CO2 molecule is shown below:Oxidation states overemphasize the ionic nature of the bonding; most chemists agree that the difference in electronegativity between carbon in oxygen is insufficient to regard the bonds as being ionic in nature.In reality, the distribution of electrons in the molecule lies somewhere between these two extremes. The inadequacy of the simple Lewis structure view of molecules led to the development of the more generally applicable and accurate valence bond theory of Slater, Pauling, et al., and thenceforth the molecular orbital theory developed by Mulliken and Hund.。
静电成像方式英语作文
静电成像方式英语作文Title: The Principle and Applications of Electrostatic Imaging。
Electrostatic imaging, a technique utilized in various fields including medical diagnostics, security screening, and scientific research, relies on the manipulation of electrostatic forces to generate images. This essay delves into the principle behind electrostatic imaging, its applications, and the advancements in this technology.### Principle of Electrostatic Imaging。
Electrostatic imaging operates on the fundamental principle of electrostatic attraction and repulsion. It involves the creation of an electric field between acharged object and a grounded substrate. When an object is charged, the electric field interacts with nearby particles, causing redistribution of charges and resulting invariations in the electric potential across the surface. Bymeasuring these potential differences, an image of theobject's surface or internal structure can be reconstructed.### Components of Electrostatic Imaging Systems。
piezoelectric effect 原理英文
piezoelectric effect 原理英文全文共3篇示例，供读者参考篇1Piezoelectric Effect PrincipleIntroductionThe piezoelectric effect is a phenomenon in which certain materials generate an electric charge in response to mechanical stress. This effect is widely used in various applications such as sensors, actuators, and energy harvesting devices. Understanding the principles behind the piezoelectric effect is crucial for optimizing the performance of these devices.Principle of Piezoelectric EffectThe piezoelectric effect is based on the unique properties of certain crystals, ceramics, and polymers that exhibit piezoelectric behavior. These materials have a crystalline structure that allows them to generate an electric charge when subjected to mechanical stress. This occurs because the application of stress causes the material's atoms to shift slightly from their equilibrium positions, creating a separation of positive and negative charges within the material.When a mechanical force is applied to a piezoelectric material, the material deforms and generates an electric charge as a result of the shift in atomic positions. This charge separation is known as the direct piezoelectric effect. Conversely, when an external electric field is applied to a piezoelectric material, it causes the material to deform, known as the inverse piezoelectric effect.Applications of Piezoelectric EffectThe piezoelectric effect has numerous applications across various industries due to its ability to convert mechanical energy into electrical energy and vice versa. Some common applications of the piezoelectric effect include:1. Sensors: Piezoelectric materials are used in sensors to detect pressure, force, acceleration, and vibration. These sensors are widely used in industrial, automotive, and medical applications.2. Actuators: Piezoelectric materials are also used in actuators to convert electrical energy into mechanical motion. These actuators are used in precision positioning systems, valves, and pumps.3. Energy Harvesting: The piezoelectric effect can be used to harvest energy from ambient vibrations and mechanical movements. This energy can be used to power small electronic devices and sensors.4. Medical Imaging: Piezoelectric materials are used in medical imaging devices such as ultrasound transducers. These transducers generate and receive ultrasound waves to create detailed images of internal body structures.5. Piezoelectric Fans: Piezoelectric fans use the piezoelectric effect to generate airflow without the need for rotating blades. These fans are quieter and more energy-efficient than traditional fans.ConclusionThe piezoelectric effect is a fascinating phenomenon that has revolutionized various industries with its ability to convert mechanical energy into electrical energy and vice versa. Understanding the principles behind the piezoelectric effect is essential for designing and optimizing devices that rely on this effect. As technology advances, the applications of the piezoelectric effect are expected to expand further, offering new opportunities for innovation and sustainability.篇2The piezoelectric effect is a phenomenon in which certain materials generate an electric charge when subjected to mechanical stress. This effect was first discovered by the Curie brothers, Pierre and Jacques Curie, in 1880. It has since been widely studied and utilized in various fields, including physics, engineering, and materials science.At the heart of the piezoelectric effect is the concept of polarized ions within a crystalline structure. In a piezoelectric material, such as quartz or lead zirconate titanate (PZT), the atoms are arranged in a symmetric pattern with positive and negative charges balanced. When an external force is applied to the material, it causes the lattice structure to deform, which in turn displaces the polarized ions. This displacement of charges creates an electric field within the material, resulting in the generation of an electric voltage.The piezoelectric effect can be categorized into two types: direct and inverse. In the direct piezoelectric effect, mechanical stress leads to the production of electrical charge within the material. This effect is commonly used in sensors, actuators, and transducers. For example, piezoelectric sensors are oftenemployed in pressure sensing applications, while piezoelectric actuators are utilized in precision positioning systems.Conversely, the inverse piezoelectric effect involves the application of an electric field to induce mechanical strain in the material. This effect is commonly utilized in piezoelectric motors, ultrasonic transducers, and acoustic devices. For instance, ultrasound imaging systems rely on the inverse piezoelectric effect to generate high-frequency sound waves for imaging purposes.The practical applications of the piezoelectric effect are vast and diverse. In the field of energy harvesting, piezoelectric materials are used to convert mechanical vibrations into electrical energy. This technology can be employed in wearable devices, wireless sensors, and self-powered electronics. Piezoelectric materials are also utilized in medical devices, such as ultrasound probes and bone-conduction hearing aids.In conclusion, the piezoelectric effect is a fundamental principle that has revolutionized various industries. Its ability to convert mechanical energy into electrical energy, and vice versa, has paved the way for innovative technologies and advancements in science. As research in piezoelectric materialscontinues to progress, we can expect to see even more exciting developments in the future.篇3The piezoelectric effect is a fascinating phenomenon that has been studied and utilized in various fields of science and technology. In this document, we will discuss the principles behind the piezoelectric effect and its applications in different industries.Piezoelectric materials are substances that have the ability to generate an electric charge in response to mechanical stress. This effect was first discovered by French physicists Jacques and Pierre Curie in 1880 when they observed that certain crystals, such as quartz, produced an electric charge when subjected to pressure. This discovery led to the development of the piezoelectric effect, which has since been studied extensively and applied in various devices and technologies.The piezoelectric effect is based on the concept of polarization, which is the separation of positive and negative charges within a material. When a piezoelectric material is deformed or compressed, the crystal lattice structure of the material is disturbed, causing the positive and negative chargesto separate and generate an electric charge. This electric charge can be harnessed and used to power devices or sensors.One of the most common applications of the piezoelectric effect is in sensors and transducers. Piezoelectric sensors are widely used in industries such as automotive, aerospace, and healthcare to measure pressure, force, acceleration, and vibration. For example, piezoelectric sensors can be used in accelerometers to detect changes in speed and direction, or in ultrasound devices to generate and receive sound waves for medical imaging.Piezoelectric materials are also used in actuators, which are devices that convert electrical energy into mechanical motion. Piezoelectric actuators can be found in devices such as inkjet printers, where they are used to control the movement of the printer nozzle and dispense ink onto the paper. They are also used in precision positioning systems, microscopy, and robotics.Another area where the piezoelectric effect is utilized is in energy harvesting. Piezoelectric materials can convert mechanical energy from sources such as vibration, motion, or pressure into electrical energy, which can be stored and used to power electronic devices. This technology is particularly useful inremote or inaccessible locations where traditional power sources are not available.In addition to these practical applications, the piezoelectric effect has also been studied in research and development for its potential in other areas. For example, researchers are exploring the use of piezoelectric materials in energy-efficient buildings, where they can be used to generate electricity from ambient vibrations and movements in the structure. They are also investigating the use of piezoelectric materials in biomedical devices, such as implants and medical sensors.Overall, the piezoelectric effect is a powerful phenomenon that has revolutionized various industries and technologies. Its ability to convert mechanical energy into electrical energy makes it a valuable tool in sensors, actuators, energy harvesting, and many other applications. As researchers continue to explore and develop new uses for piezoelectric materials, the potential for innovation and advancement in this field is limitless.。
半导体英语面试题目(3篇)
第1篇Introduction:This document provides a comprehensive list of potential English interview questions for semiconductor positions. These questions are designed to assess the candidate's technical knowledge, problem-solving skills, communication abilities, and cultural fit within the semiconductor industry. The questions are categorized into different sections, including technical, behavioral, situational, and cultural.I. Technical Questions1. Can you explain the difference between NMOS and PMOS transistors?2. What is the purpose of a diffusion process in semiconductor manufacturing?3. Describe the concept of short-channel effects in MOSFETs.4. How does a DRAM differ from a SRAM in terms of structure and operation?5. Explain the role of a CMOS inverter in digital circuits.6. What are the main challenges in scaling down the size of transistors?7. Describe the process of photolithography in semiconductor manufacturing.8. How does thermal oxidation affect the quality of silicon wafers?9. What are the differences between NMOS and CMOS technology?10. Explain the concept of threshold voltage and its importance in MOSFET design.II. Problem-Solving Questions1. You are given a task to design a low-power CMOS inverter. What design considerations should you take into account?2. How would you troubleshoot a process issue in a semiconductor manufacturing line?3. Describe a situation where you had to optimize a semiconductor design for performance and power consumption.4. What steps would you take to improve the yield of a particular semiconductor product?5. How would you design a feedback loop to control the current in a CMOS inverter?6. Discuss the challenges and potential solutions for integrating analog and digital circuits on the same semiconductor chip.7. How would you approach the task of designing a high-speed data communication interface for a semiconductor device?8. Explain how you would simulate and analyze the performance of a semiconductor device under different operating conditions.III. Communication and Interpersonal Skills Questions1. Describe a time when you had to explain a complex technical concept to a non-technical team member. How did you approach the task?2. How do you handle feedback or criticism from your peers or superiors?3. Give an example of a situation where you had to work effectively witha team to achieve a common goal.4. How do you prioritize tasks when you have multiple deadlines?5. Describe a time when you had to resolve a conflict with a colleague. What was your approach?6. How do you maintain a positive and professional attitude in a high-pressure work environment?7. What strategies do you use to build and maintain strong professional relationships with your colleagues?8. How do you ensure that your communication is clear and concise, especially when dealing with technical information?IV. Situational Questions1. You are assigned a project that requires you to meet tight deadlines. However, you realize that the project requirements are not clear. How would you handle this situation?2. You are working on a team, and one of your teammates is consistently late with their tasks. How would you address this issue?3. Your manager asks you to make a decision about which technology to use for a new product. You have strong opinions about both options. How would you proceed?4. You are involved in a cross-functional project, and you believe that your team's approach is superior to the one proposed by another team. How would you present your team's solution to senior management?5. You are working on a semiconductor design, and during the testing phase, you discover a significant issue that requires a redesign. How would you communicate this to your team and management?V. Cultural Fit and Industry Knowledge Questions1. What do you know about the semiconductor industry, and why are you interested in working in this field?2. Describe a recent technological advancement in the semiconductor industry that you find particularly interesting.3. How do you stay updated with the latest trends and developments in the semiconductor industry?4. What are your thoughts on the future of the semiconductor industry, especially in the context of emerging technologies like AI and quantum computing?5. How would you approach a situation where your personal beliefs or values conflict with company policies or industry standards?6. Describe a time when you had to adapt to a new culture or work environment. What did you learn from the experience?7. How do you prioritize work-life balance in a high-stress industrylike semiconductor engineering?8. What are your expectations for professional growth and development ina semiconductor company?Conclusion:This list of semiconductor English interview questions is intended to help candidates prepare for their interviews and demonstrate their qualifications, skills, and potential contributions to a semiconductor company. By addressing these questions, candidates can showcase their technical expertise, problem-solving abilities, communication skills,and cultural fit within the industry.第2篇Introduction:The interview for a semiconductor engineer position is a critical stepin the hiring process. It is designed to assess your technical expertise, problem-solving skills, understanding of the industry, and your ability to communicate effectively. Below are a variety of questions and topics that might be covered in a semiconductor engineering interview. The responses should be tailored to showcase your knowledge and experiencein the field.Technical Questions:1. Explain the difference between CMOS and NMOS transistors.- Discuss the basic structure of both transistors.- Highlight the advantages and disadvantages of each.2. What are the primary steps in the semiconductor manufacturing process?- Describe the photolithography process.- Explain the role of etching, doping, and ion implantation.3. How do you ensure the quality and reliability of semiconductor devices?- Discuss the importance of wafer testing and characterization.- Explain the concept of yield and how it is measured.4. Describe the concept of short-channel effects in MOSFETs.- Explain the physical mechanisms behind these effects.- Discuss the impact on device performance and how to mitigate them.5. What are the different types of semiconductor packaging, and what are their advantages and disadvantages?- List common packaging types such as SOP, QFP, and BGA.- Discuss the considerations for choosing the right packaging for a given application.6. How do you perform thermal analysis on semiconductor devices?- Explain the principles of thermal modeling and simulation.- Discuss the importance of thermal management in semiconductor packaging.7. What is the significance of parasitic elements in semiconductor circuits?- Describe the impact of capacitance, inductance, and resistance on circuit performance.- Discuss techniques to minimize the effects of parasitics.8. Explain the operation of a charge pump circuit.- Describe the basic principle and design considerations.- Discuss the applications of charge pumps in power conversion.9. How do you analyze and optimize the power consumption of a semiconductor device?- Discuss the concept of power efficiency and its importance.- Explain techniques such as dynamic voltage and frequency scaling (DVFS).10. What are the different types of lithography techniques used in semiconductor manufacturing?- Describe the principles of optical, electron beam, and nanoimprint lithography.- Discuss the limitations and future trends in lithography.Behavioral and Situational Questions:1. Describe a challenging project you have worked on in the past. How did you overcome the challenges?- Provide a brief background of the project.- Explain the challenges you faced and the steps you took to address them.2. How do you stay updated with the latest advancements in the semiconductor industry?- Discuss the resources you use, such as conferences, journals, and online forums.- Explain how you apply this knowledge to your work.3. You are assigned to lead a team on a new project. How do you ensure effective communication and collaboration?- Describe your approach to team leadership.- Discuss strategies for conflict resolution and team motivation.4. You discover a defect in a device that has already been released to the market. How do you handle this situation?- Explain the steps you would take to investigate and address the issue.- Discuss the importance of maintaining customer trust and satisfaction.5. Describe a time when you had to prioritize tasks with competing deadlines. How did you manage the situation?- Provide an example of a situation where you had multiple tasks with tight deadlines.- Explain the criteria you used to prioritize and the outcome of your decisions.Industry Knowledge Questions:1. What are the current challenges in semiconductor manufacturing, and how are they being addressed?- Discuss the impact of Moore's Law and the need for advanced process nodes.- Explain the role of new materials and processes in overcoming these challenges.2. How do you see the future of semiconductor technology evolving in the next decade?- Discuss potential advancements in materials, devices, and manufacturing processes.- Consider the impact of emerging technologies such as AI and quantum computing.3. What are the key trends in semiconductor packaging, and how do they impact system design?- Discuss the trend towards 3D packaging and its benefits.- Explain how packaging trends influence the design of integrated circuits.4. How do you think environmental concerns will affect the semiconductor industry in the future?- Discuss the importance of sustainable practices in semiconductor manufacturing.- Explain how companies are addressing environmental issues such as energy consumption and e-waste.5. What are the implications of geopolitical tensions on the global semiconductor supply chain?- Discuss the impact of trade disputes and sanctions on the industry.- Explain how companies are adapting to these challenges.Closing Questions:1. What questions do you have for us about the company or the role?- Show your interest in the company and the specific role you are applying for.- Prepare thoughtful questions that demonstrate your research and engagement with the company.2. How do you envision your role contributing to the success of the company?- Discuss your skills and experience that align with the company's goals.- Explain how you plan to grow and contribute to the team.Remember, while the questions provided here are extensive, the actual interview will likely be tailored to the specific company, position, and your personal experiences. It is essential to prepare thoroughly, not only by reviewing the material but also by thinking about how your experiences and skills can be effectively communicated to the interviewers.第3篇IntroductionThe semiconductor industry is a highly competitive field, and English proficiency is often a crucial factor in securing a position, especially for international candidates or those working in multinational corporations. This document provides a comprehensive list of potential English interview questions that one might encounter during a semiconductor industry interview. Each question is followed by a suggested answer to help candidates prepare for the interview.Technical Questions1. What is the difference between an N-type and P-type semiconductor?- Answer: N-type and P-type semiconductors are created by doping pure silicon with impurities. N-type semiconductors are doped withpentavalent impurities (like phosphorus) which introduce extra electrons, while P-type semiconductors are doped with trivalent impurities (like boron) which create "holes" or positive charge carriers.2. Explain the function of a MOSFET.- Answer: Metal-Oxide-Semiconductor Field-Effect Transistor (MOSFET) is a type of field-effect transistor that is widely used in digital circuits. It operates by controlling the flow of current between the source and drain terminals using a voltage applied to the gate terminal, which controls the conductance of the channel between the source and drain.3. What is the purpose of a diode in a semiconductor circuit?- Answer: A diode allows current to flow in only one direction and is used for rectification, voltage regulation, and signal modulation in semiconductor circuits.4. How does the CMOS inverter work?- Answer: The CMOS inverter consists of a pair of complementary transistors (N-channel and P-channel MOSFETs). When the input is high, the N-channel transistor conducts and the P-channel transistor is turnedoff, allowing current to flow from the output to the ground. Conversely, when the input is low, the N-channel transistor is turned off and the P-channel transistor conducts, allowing current to flow from the power supply to the output.5. What are the advantages of CMOS technology over TTL technology?- Answer: CMOS technology has lower power consumption, higher noise immunity, and better scalability compared to TTL technology. It also allows for higher operating speeds and lower power dissipation.Behavioral Questions1. Describe a challenging project you have worked on in the semiconductor industry.- Answer: In my previous role at XYZ Semiconductor, I was part of a team tasked with optimizing the yield of a new process node. The project involved extensive data analysis, process adjustments, and cross-functional collaboration with engineers from different departments. Despite the initial setbacks, our team managed to achieve a 15% increase in yield within three months.2. How do you handle pressure in a fast-paced environment?- Answer: I believe in maintaining a calm demeanor and prioritizing tasks based on their urgency and importance. I also find it helpful to communicate openly with my team members to ensure everyone is on the same page and to share the workload effectively.3. Can you give an example of a time when you had to solve a problem creatively?- Answer: During a recent project, we faced a shortage of a critical component. Instead of waiting for the component to become available, we redesigned the circuit using alternative components that were readily available. This creative solution saved us time and resources.Communication and English Proficiency Questions1. Tell me about yourself.- Answer: My name is [Your Name], and I have a Bachelor’s degree in Electrical Engineering with a focus on semiconductor technology. I have been working in the semiconductor industry for the past five years, where I have gained experience in process development, yield improvement, and quality control.2. What are your strengths and weaknesses?- Answer: My strengths include a strong analytical mindset, excellent problem-solving skills, and the ability to work well in a team. However, I recognize that I can sometimes be overly meticulous, which can sometimes slow down my decision-making process.3. How would you explain a complex semiconductor concept to a non-technical audience?- Answer: I would start by using simple analogies to make the concept more relatable. For example, I might compare a semiconductor to a water faucet, where the flow of electrons can be controlled by adjusting the voltage applied to the faucet.4. What is the importance of English in the semiconductor industry?- Answer: English is the primary language of the global semiconductor industry. It is essential for effective communication with international colleagues, accessing technical literature, and participating in global projects.Scenario-Based Questions1. You are working on a project, and the deadline is approaching. Your team is facing unexpected technical challenges. How would you handle the situation?- Answer: I would first assess the severity of the challenges and prioritize the tasks that need to be addressed immediately. I would then communicate with the team to ensure everyone is aware of the situation and allocate resources accordingly. If necessary, I would consult with senior management to seek additional support or adjust the project timeline.2. You have just been promoted to a supervisory role. How would you motivate your team to achieve their goals?- Answer: I would focus on recognizing and rewarding individual and team achievements. I would also ensure that the team is clear abouttheir roles and responsibilities, provide them with the necessary resources and support, and foster a positive and collaborative work environment.ConclusionPreparing for a semiconductor industry English interview requires a combination of technical knowledge, effective communication skills, and the ability to handle various scenarios. By practicing the questions and answers provided in this document, candidates can gain confidence and improve their chances of success in their interviews.。
毕设翻译英文
轨道交通学院毕业设计（论文）外文翻译题目：列车车载的直流恒流源的设计专业电子信息工程班级10115111学号1011511137姓名赵士伟指导教师陈文2014 年3 月 3 日本文摘自：IEEE TRANSACTIONS ON INDUSTRY AND GENERAL APPLICATIONS VOL. IGA-2, NO.5 SEPT/OCT 1966Highly Regulated DC Power Supplies Abstract-The design and application of highly regulated dc power supplies present many subtle, diverse, and interesting problems. This paper discusses some of these problems (especially inconnection with medium power units) but emphasis has been placed more on circuit economics rather than on ultimate performance.Sophisticated methods and problems encountered in connection with precision reference supplies are therefore excluded. The problems discussed include the subjects of temperature coefficient,short-term drift, thermal drift, transient response degeneration caused by remote sensing, and switching preregualtor-type units and some of their performance characteristics.INTRODUCTIONANY SURVEY of the commercial de power supply field will uncover the fact that 0.01 percent regulated power supplies are standard types and can be obtained at relatively low costs. While most users of these power supplies do not require such high regulation, they never-theless get this at little extra cost for the simple reason that it costs the manufacturer very little to give him 0.01 percent instead of 0.1 percent. The performance of a power supply, however, includes other factors besides line and load regulation. This paper will discuss a few of these-namely, temperature coefficient, short-term drift, thermal drift, and transient response. Present medium power dc supplies commonly employ preregulation as a means of improving power/volume ratios and costs, but some characteristics of the power supply suffer by this approach. Some of the short-comings as well as advantages of this technology will be examined.TEMPERATURE COEFFICIENTA decade ago, most commercial power supplies were made to regulation specifications of 0.25 to 1 percent. The reference elements were gas diodes having temperature coefficients of the order of 0.01 percent [1]. Consequently, the TC (temperature coefficient) of the supply was small compared to the regulation specifications and often ignored. Today, the reference element often carries aTC specification greater than the regulation specification.While the latter may be improved considerably at little cost increase, this is not necessarily true of TC. Therefore,the use of very low TC zener diodes, matched differential amplifier stages, and low TC wire wound resistors must be analyzed carefully, if costs are to be kept low.A typical first amplifier stage is shown in Fig. 1. CRI is the reference zener diode and R, is the output adjustment potentiometer.Fig. 1. Input stage of power supply.Fig. 2. Equivalent circuit of zener reference.Let it be assumed that e3, the output of the stage, feedsadditional differential amplifiers, and under steady-state conditions e3 = 0. A variation of any of the parameters could cause the output to drift; while this is also true of the other stages, the effects are reduced by the gain of all previous stages. Consequently, the effects of other stages will be neglected. The following disculssion covers the effects of all elements having primary and secondary influences on the overall TC.Effect of R3The equivalent circuit of CRI -R3 branch is shown in Fig. 2. The zener ha's been replaced with its equivalent voltage source E/' and internal impedance R,. For high gain regulators, the input of the differential amplifier will have negligible change with variations of R3 so thatbefore and after a variation of R3 is made.If it is further assumed that IB << Iz; then from (1)Also,Eliminating I, from (2b),andNow, assuming thatthen,Equation (2b) can also be writtenThe Zener DiodeThe zener diode itself has a temperature coefficient andusually is the component that dominates the overall TCof the unit. For the circuit of Fig. 1, the TC ofthe circuit describes, in essence, the portion of the regulator TC contributed by the zener. If the bridge circuit shown in Fig. 1 were used in conjunction with a dropping resistor so that only a portion of the output voltage appeared across the bridge circuit shown, the TC of the unit and the zener would be different. Since the characteristic of zeners is so well known and so well described in the literature, a discussion will not be given here [2].Variation of Base-Emitter VoltagesNot only do the values of V,, of the differential am-plifier fail to match, but their differentials with tem perature also fail to match. This should not, however,suggest that matched pairs are required. The true reference voltage of Fig. 1 is not the value E,, but E, + (Vie, -Vbe2)-Since, for most practical applicatioinsthe TC of the reference will be the TC of the zener plusConsidering that it is difficult to obtain matched pairs that have differentials as poor as 50 V/°C, it becomes rather apparent that, in most cases, a matched pair bought specifically for TC may be overdesigning.Example 2: A standard available low-cost matched pair laims 30AV/°C. In conjunction with a 1N752, the ontribution to the overall TC would beTests, performed by the author on thirteen standard germanium signal transistors in the vicinity of room temperature and at a collector current level of 3 mA,indicated that it is reasonable to expect that 90 to 95 percent of the units would have a base-emitter voltage variation of -2.1 to -2.4 mV/°C. Spreads of this magnitude have also been verified by others (e.g., Steiger[3]). The worst matching of transistors led to less than 400 ,V/°C differential. In conjunction with a 1N752,even this would give a TC of better than 0.007%/0C.Variation of Base CurrentsThe base current of the transistors is given byA variation of this current causes a variation in signal voltage at the input to the differential amplifier due to finite source impedances. Matching source impedances is not particularly desirable, since it reduces the gain of the system and requires that transistors matched for I,o and A be used. Hunter [4 ] states that the TC of a is in the range of +0.2%/0C to -0.2%7/'C and that 1,, may be approximated bywhere Ao is the value at To.β is also temperature dependent and Steiger [3] experimentally determined the variation to be from about 0.5%/°C to 0.9%/0C.And，Fig. 3. Input circuit of Q2.The current AIB flows through the source impedance per Fig. 3. The drops in the resistance string, however, are subject to the constraint that EB (and AEB) are determined by the zener voltage and the base-emitter drops of Q1 and Q2. Consequently, if in going from temperature T1to T2 a change AEB occurs,The change in output voltage isAndExample 3: For Q2 (at 25°C)(see Example 1)∴Variation of R,The effects of a variation of the TC between RIA and RIB is sufficiently self-evident so that a discussion of the contribution is not included.SHORT-TERM DRIFTThe short-term drift of a supply is defined by the National Electrical Manufacturers Association (NEMA) as "a change in output over a period of time, which change is unrelated to input, environment, or load [5]."Much of the material described in the section on temperature coefficient is applicable here as well. It has been determined experimentally, however, that thermal air drafts in and near thevicinity ofthe powersupplycontributesenormouslyto theshort-termcharacteristics. Thecooling effects of moving air are quite well known, but it is not often recognized that even extremely slow air movements over such devices as zeners and transistors cause the junction temperature of these devices to change rapidly. If the TC of the supply is large compared to the regulation, then large variations in the output will be observed. Units having low TC's achieved by compensation-that is, by canceling out the effects of some omponents by equal and opposite effects of others may still be plagued by these drafts due to the difference in thermal time constants of the elements.Oftentimes, a matched transistor differential amplifier in a common envelope is used for the first amplifier just to equalize and eliminate the difference in cooling effects between the junctions. Approximations to this method include cementing or holding the transistors together, imbedding the transistors in a common metal block, etc. Excellent results were achieved by the author by placing the input stage and zener reference in a separate enclosure. This construction is shown in Fig. 4. The improvement in drift obtained by means of the addition of the metal cover is demonstrated dramatically in Fig. 5.Fig. 5. Short-term drift of a power supply similar to the one shown in Fig. 4 with and without protective covers. The unit was operated without the cover until time tl, when the cover was attached. The initial voltage change following t, is due to a temperaturerise inside the box.Fig. 5. Short-term drift of a power supply similar to the one shown n Fig. 4 withand without protective covers. The unit was operated without the cover until time tl, when the cover was attached. The initial voltage change following t, is due to atemperature rise inside the box.If potentiometers are used in the supply for output adjustment (e.g., RI), care should be used in choosing the value and design. Variations of the contact resistance can cause drift. It is not always necessary, however, to resort to the expense of high-resolution multiturn precision units to obtain low drift. A reduction in range of adjustment, use of low-resistance alloys and low-resolution units which permit the contact arm to rest firmly between turns, may be just as satisfactory. Of course, other considerations should include the ability of both the arms and the wire to resist corrosion. Silicone greases are helpful here. Periodic movement of contact arms has been found helpful in "healing" corroded elements.THERMAL DRIFTNEMA defines thermal drift as "a change in output over a period of time, due to changes in internal ambient temperatures not normally related to environmental changes. Thermal drift is usually associated with changes in line voltage and/or load changes [5]."Thermal drift, therefore, is strongly related to the TC of the supply as well as its overall thermal design. By proper placement of critical components it is possible to greatly reduce or even eliminate the effect entirely. It is not uncommon for supplies of the 0.01 percent(regulation) variety to have drifts of between 0.05 to 0.15 percent for full line or full load variations. In fact, one manufacturer has suggested that anything better than 0.15 percent is good. Solutions to reducing thermal drift other than the obvious approach of improving the TC and reducing internal losses include a mechanical design that sets up a physical and thermal barrier between the critical amplifier components and heat dissipating elements. Exposure to outside surfaces with good ventilation is recommended. With care, 0.01 to 0.05 percent is obtainable.TRANSIENT RESPONSEMost power supplies of the type being discussed have a capacitor across the load terminals. This is used for stabilization purposes and usually determines the dominant time constant of the supply. The presence of this capacitor unfortunately leads to undesirable transient phenomena when the supply is used in the remote sensing mode①. Normally, transistorized power supplies respond in microseconds, but as the author has pointed out [6], the response can degenerate severely in remote sensing .The equivalent circuit is shown in Fig. 6. The leads from the power supply to the load introduce resistance r. Is is the sensing current of the supply and is relatively constant.Under equilibrium conditions,A sudden load change will produce the transient of Fig. 7. The initial "spike" is caused by an inductive surge Ldi/dt; the longer linear discharge following is the resultof the capacitor trying to discharge (or charge). The discharge time iswhereandThe limitations of I,, are usually not due to available drive of the final amplifier stages but to other limitations, current limiting being the most common. Units using pre regulators of the switching type (transistor or SCR types) should be looked at carefully if the characteristics mentioned represent a problem.①Remote sensing is the process by which the power supply senses voltage directly at the load.Fig. 6. Output equivalent circuit at remote sensing.Fig. 7. Transient response, remote sensing.Fig. 8. Block diagram.Preregulated supplies are used to reduce size and losses by monitoring and controlling the voltage across the class-A-type series passing stage (Fig. 8). Since the main regulator invariably responds much quicker than the preregulator, sufficient reserve should always be built into the drop across the passing stage. Failure to provide this may result in saturation of the passing stage when load is applied, resulting in a response time which is that of the preregulator itself.SWITCHING PREREGULATOR-TYPE UNITS The conventional class-A-type transistorized power supply becomes rather bulky, expensive, and crowded with passing stages, as the current and power level of the supply increases. The requirement of wide output adjustment range, coupled with the ability of the supply to be remotely programmable, aggravates the condition enormously. For these reasons the high-efficiency switching regulator has been employed as a preregulator in commercial as well as military supplies for many years. The overwhelming majority of the supplies used silicon controlled rectifiers as the control element. For systems operating from 60-cycle sources, this preregulator responds in 20 to 50 ms.Recent improvements in high-voltage, high-power switching transistors has made the switching transistor pproach more attractive. This system offers a somewhat lower-cost, lower-volume approach coupled with a submillisecond response time. This is brought about by a high switching rate that is normally independent of line frequency. The switching frequency may be fixed, a controlled variable or an independent self-generated (by the LC filter circuit) parameter [7], [8]. Faster response time is highly desirable since it reduces the amount of reserve voltage required across the passing stage or the amount of (storage) capacity required in the preregulator filter.A transistor suitable for operating as a power switch has a high-current, high-voltage rating coupled with low leakage current. Unfortunately, these characteristics are achieved by a sacrifice in thermal capacity, so that simultaneous conditions of voltage and current leading to high peak power could be disastrous. It therefore becomes mandatory to design for sufficient switch drive during peak load conditions and also incorporate current-limiting or rapid overload protection systems.Commercial wide-range power supplies invariably have output current limiting, but this does not limit the preregulator currents except during steady-state load conditions (including short circuits). Consider, for example, a power supply operating at short circuit and the short being removed suddenly. Referring to Fig. 8, the output would rise rapidly, reduce the passing stage voltage, and close the switching transistor. The resulting transient extends over many cycles (switching rate) so that the inductance of the preregulator filter becomes totally inadequate to limit current flow. Therefore, the current will rise until steady state is resumed, circuit resistance causes limiting, or insufficient drive causes the switch to come out of saturation. The latter condition leads to switch failure.Other operating conditions that would produce similar transients include output voltage programming and initial turn-on of the supply. Momentary interruption of input power should also be a prime consideration.One solution to the problem is to limit the rate of change of voltage that can appear across the passing stage to a value that the preregulator can follow. This can be done conveniently by the addition of sufficient output capacitance. This capacitance inconjunction with the current limiting characteristic would produce a maximum rate of change ofwhereC0 = output capacity.Assuming that the preregulator follows this change and has a filter capacitor Cl, then the switch current isDuring power on, the preregulator reference voltage rise must also be limited. Taking this into account,whereER = passing stage voltageTl = time constant of reference supply.The use of SCR's to replace the transistors would be a marked improvement due to higher surge current ratings, but turning them off requires large energy sources. While the gate turn-off SCR seems to offer a good compromise to the overall problem, the severe limitations in current ratings presently restrict their use.REFERENCES[1] J. G. Truxal, Control Engineer's Handbook. New York: McGrawHill, 1958, pp. 11-19.[2] Motorola Zener Diode/Rectifier Handbook, 2nd ed. 1961.[3] W. Steiger, "A transistor temperature analysis and its applica-tion to differential amplifiers," IRE Trans. on Instrumentation,vol. 1-8, pp. 82-91, December 1959.[4] L. P. Hunter, Handbook of Semi-Conductor Electronics. NewYork: McGraw Hill, 1956, p. 13-3.[5] "Standards publication for regulated electronic dc powersupplies," (unpublished draft) Electronic Power Supply Group,Semi-Conductor Power Converter Section, NEMA.[6] P. Muchnick, "Remote sensing of transistorized power sup-plies," Electronic Products, September 1962.[7] R. D. Loucks, "Considerations in the design of switching typeregulators," Solid State Design, April 1963.[8] D. Hancock and B. Kurger, "High efficiency regulated powersupply utilizing high speed switching," presented at the AIEEWinter General Meeting, New York, N. Y., January 27-February 1, 1963.[9] R. D. Middlebrook, Differential Amplifiers. New York: Wiley,1963.[10] Sorensen Controlled Power Catalog and Handbook. Sorensen,Unit of Raytheon Company, South Norwalk, Conn.With the rapid development of electronic technology, application field of electronic system is more and more extensive, electronic equipment, there are more and more people work with electronic equipment, life is increasingly close relationship. Any electronic equipment are inseparable from reliable power supply for power requirements, they more and more is also high. Electronic equipment miniaturized and low cost in the power of light and thin, small and efficient for development direction. The traditional transistors series adjustment manostat is continuous control linear manostat. This traditional manostat technology more mature, and there has been a large number of integrated linear manostat module, has the stable performance is good, output ripple voltage small, reliable operation, etc. But usually need are bulky and heavy industrial frequency transformer and bulk and weight are big filter.In the 1950s, NASA to miniaturization, light weight as the goal, for a rocket carrying the switch power development. In almost half a century of development process, switch power because of its small volume, light weight, high efficiency, wide range, voltage advantages in electric, control, computer, and many other areas of electronic equipment has been widely used. In the 1980s, a computer is made up of all of switch power supply, the first complete computer power generation. Throughout the 1990s, switching power supply in electronics, electrical equipment, home appliances areas to be widely, switch power technology into the rapid development. In addition, large scale integrated circuit technology, and the rapid development of switch power supply with a qualitative leap, raised high frequency power products of, miniaturization, modular tide.Power switch tube, PWM controller and high-frequency transformer is an indispensable part of the switch power supply. The traditional switch power supply is normally made by using high frequency power switch tube division and the pins, such as using PWM integrated controller UC3842 + MOSFET is domestic small power switch power supply, the design method of a more popularity.Since the 1970s, emerged in many function complete integrated control circuit, switch power supply circuit increasingly simplified, working frequency enhances unceasingly, improving efficiency, and for power miniaturization provides the broad prospect. Three end off-line pulse width modulation monolithic integrated circuit TOP (Three switch Line) will Terminal Off with power switch MOSFET PWM controller one package together, has become the mainstream of switch power IC development. Adopt TOP switch IC design switch power, can make the circuit simplified, volume further narrowing, cost also is decreased obviouslyMonolithic switching power supply has the monolithic integrated, the minimalist peripheral circuit, best performance index, no work frequency transformer can constitute a significant advantage switching power supply, etc. American PI (with) company in Power in the mid 1990s first launched the new high frequency switching Power supply chip, known as the "top switch Power", with low cost, simple circuit, higher efficiency. The first generation of products launched in 1994 represented TOP100/200 series, the second generation product is the TOPSwitch - debuted in 1997 Ⅱ. The above products once appeared showed strong vitality and he greatly simplifies thedesign of 150W following switching power supply and the development of new products for the new job, also, high efficiency and low cost switch power supply promotion and popularization created good condition, which can be widely used in instrumentation, notebook computers, mobile phones, TV, VCD and DVD, perturbation VCR, mobile phone battery chargers, power amplifier and other fields, and form various miniaturization, density, on price can compete with the linear manostat AC/DC power transformation module.Switching power supply to integrated direction of future development will be the main trend, power density will more and more big, to process requirements will increasingly high. In semiconductor devices and magnetic materials, no new breakthrough technology progress before major might find it hard to achieve, technology innovation will focus on how to improve the efficiency and focus on reducing weight. Therefore, craft level will be in the position of power supply manufacturing higher in. In addition, the application of digital control IC is the future direction of the development of a switch power. This trust in DSP for speed and anti-interference technology unceasing enhancement. As for advanced control method, now the individual feels haven't seen practicability of the method appears particularly strong,perhaps with the popularity of digital control, and there are some new control theory into switching power supply.（1）The technology: with high frequency switching frequencies increase, switch converter volume also decrease, power density has also been boosted, dynamic response improved. Small power DC - DC converter switch frequency will rise to MHz. But as the switch frequency unceasing enhancement, switch components and passive components loss increases, high-frequency parasitic parameters and high-frequency EMI and so on the new issues will also be caused.（2）Soft switching technologies: in order to improve the efficiency ofnon-linearity of various soft switch, commutation technical application and hygiene, representative of soft switch technology is passive and active soft switch technology, mainly including zero voltage switch/zero current switch (ZVS/ZCS) resonance, quasi resonant, zero voltage/zero current pulse width modulation technology (ZVS/ZCS - PWM) and zero voltage transition/zero current transition pulse width modulation (PWM) ZVT/ZCT - technical, etc. By means of soft switch technology can effectively reduce switch loss and switch stress, help converter transformation efficiency （3）Power factor correction technology (IC simplifies PFC). At present mainly divided into IC simplifies PFC technology passive and active IC simplifies PFC technology using IC simplifies PFC technology two kinds big, IC simplifies PFC technology can improve AC - DC change device input power factor, reduce the harmonic pollution of power grid.（4）Modular technology. Modular technology can meet the needs of the distributed power system, enhance the system reliability.（5）Low output voltage technology. With the continuous development of semiconductor manufacturing technology, microprocessor and portable electronic devices work more and more low, this requires future DC - DC converter can provide low output voltage to adapt microprocessor and power supply requirement of portable electronic devicesPeople in switching power supply technical fields are edge developing related power electronics device, the side of frequency conversion technology, development of switch between mutual promotion push switch power supply with more than two year growth toward light, digital small, thin, low noise and high reliability, anti-interference direction. Switching powersupply can be divided into the AC/DC and DC/DC two kinds big, also have AC/AC DC/AC as inverter DC/DC converter is now realize modular, and design technology and production process at home and abroad, are mature and standardization, and has approved by users, but the AC/DC modular, because of its own characteristics in the process of making modular, meet more complex technology and craft manufacture problems. The following two types of switch power supply respectively on the structure and properties of this.Switching power supply is the development direction of high frequency, high reliability, low consumption, low noise, anti-jamming and modular. Because light switch power, small, thin key techniques are changed, so high overseas each big switch power supply manufacturer are devoted to the development of new high intelligent synchronous rectifier, especially the improvement of secondary devices of the device, and power loss of Zn ferrite (Mn) material? By increasing scientific and technological innovation, to enhance in high frequency and larger magnetic flux density (Bs) can get high magnetic under the miniaturization of, and capacitor is a key technology. SMT technology application makes switching power supply has made considerable progress, both sides in the circuitboard to ensure that decorate components of switch power supply light, small, thin. The high frequency switching power supply of the traditional PWM must innovate switch technology, to realize the ZCS ZVS, soft switch technology has becomethe mainstream of switch power supply technical, and greatly improve the efficiency of switch power. For high reliability index, America's switch power producers, reduce by lowering operating current measures such as junction temperature of the device, in order to reduce stress the reliability of products made greatly increased.Modularity is of the general development of switch power supply trend can be modular power component distributed power system, can be designed to N + 1 redundant system, and realize the capacity expansion parallel. According to switch power running large noise this one defect, if separate the pursuit of high frequency noise will increase its with the partial resonance, and transform circuit technology, high frequency can be realized in theory and can reduce the noise, but part of the practical application of resonant conversion technology still have a technical problem, so in this area still need to carry out a lot of work, in order to make the technology to practional utilization.Power electronic technology unceasing innovation, switch power supply industry has broad prospects for development. To speed up the development of switch power industry in China, we must walk speed of technological innovation road, combination with Chinese characteristics in the joint development path, for I the high-speed development of national economy to make the contribution. The basic principle and component functionAccording to the control principle of switch power to classification, we have the following 3 kinds of work mode:1) pulse width adjustment type, abbreviation Modulation PulseWidth pulse width Modulation (PWM) type, abbreviation for. Its main characteristic is fixed switching frequency, pulse width to adjust by changing voltage 390v, realize the purpose. Its core is the pulse width modulator. Switch cycle for designing filter circuit fixed provided convenience. However, its shortcomings is influenced by the power switch conduction time limit minimum of output voltage cannot be wide range regulation; In addition, the output will take dummy loads commonly (also called pre load), in order to prevent the drag elevated when output voltage. At present, most of the integrated switch power adopt PWM way.2) pulse frequency Modulation mode pulse frequency Modulation (, referred to PulseFrequency Modulation, abbreviation for PFM) type. Its characteristic is will pulse width fixed by changing switch frequency to adjust voltage 390v, realize the purpose. Its core is the pulse frequency modulator. Circuit design to use fixed pulse-width generator to replace the pulse width omdulatros and use sawtooth wave generator voltage? Frequency converter (for example VCO changes frequency VCO). It on voltage stability principle is: when the output voltage Uo rises, the output signal controller pulse width unchanged and cycle longer, make Uo 390v decreases, and reduction. PFM type of switch power supply output voltage range is very wide, output terminal don't meet dummy loads. PWM way and way of PFM respectively modulating waveform is shown in figure 1 (a), (b) shows, tp says pulse width (namely power switch tube conduction time tON), T represent cycle. It can be easy to see the difference between the two. But they have something in common: (1) all use time ratio control (TRC) on voltage stability principle, whether change tp, finally adjustment or T is。
基于对数函数的非局部总变分图像修复模型
科技英语写作高级教程参考答案
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)14、an(甚至当积分区间并不是无穷时，能够恰当地显示一个时函数的傅氏变换的仪器是多么重要啊～)II、1. Dr. Emmet graduated from Harvard University in 2001.2. Professor Li earned his Ph.D. degree in mechanical engineeringfrom the Xi’anUniversity of Technology in 1988.3. Now we shall turn to the discussion of local area networks.4. The Bainbridge mass spectrometer is as important aninstrument as the opticalspectrometer.5. How long a time [或How much time] is required to this experiment? The densityof a substance is its mass per unit volume.6. An increase in pressure always causes a decrease in volume.7. Fig. (2-5) shows what is expressed by Eq. (2-2).8. The unit of inductance is the henry.III、1. The UASMA protocol employs a unique frame structure.2. Finally, a broad stepped impedance transformer is designed bythis method.3. Dynamic analysis and evaluation of the security of a proactive secret sharingsystem4. The approach can be applied to the one-dimensional potentialbarrier with anarbitrary profile.5. We propose a numerical method based on Newton’s iterative method.练习2I、1. This circuit consists of a battery, an inductor and a capacitor.2. Compute the electric fields at points a, b, and c.3. This satellite is used for communications between the United States and Great Britain, France and Italy.4. We assume that the antenna is vertical and that its loss iszero.5. Chapters 6, 7, and 8 deal with transmission lines.II、121. Its error is six parts in 10.2. This computer stores four times more information than that one (does).3. The demand for this kind of equipment in the near future will be 20 times what it is.4. The voltage across this component is a few tenths of a volt.5. Now its internal pressure is one sixteenth what it was.III、1. This object is over five times heavier than that one is.2. Unless otherwise stated, it is assumed that silicon transistors are used and that I CBOcan be neglected.3. This circuit has the advantages of simple structure and easy adjustment.4. Figs. 1, 2, and 3 show this process in detail.5. For further information, consult references [3, 5, 9].练习3I、1. This new type of computer has many advantages over the general type.2. It is not difficult to solve this differential equation for the unknown quantity.3. Of these five new chapters, the first one deals with the basic principles of negative feedback.o4. At this point/time, current differs in phase from voltage by 90.5. By analyzing [By the analysis of] the parameters of the instrument, we canunderstand its performance.6. We will find out its average velocity over this distance.7. The science of electronics is too important in the world today.8. They solved this problem with great difficulty.II、1. For x,1, there is no solution to this equation [this equation has no solution].2. Upon [On] substituting [substitution of] these values into [in] theequation, we obtained the following expression..3. This circuit is similar in operation to that of Fig. 1-10.4. This computer is very good in performance.5. These waves travel only in one direction.III、1. This paper presents a new method for the recognition of radar targets.2. The influence of the moving state of the target on the tracking accuracy of the EKF is great.th3. Another comsat was launched on the morning of the 8 of October.4. Voltage is measured in volts.5. They will leave for Beijing to attend an international conference on mobile communication.6. Unless otherwise stated, it is assumed that silicon transistors are used and that I can be neglected. CBO7.练习4I、1. The force acts perpendicular to the surface of the table.2. The three coefficients here remains to be determined.3. The two equations below will be often (frequently) used in later chapters/in thechapters which follow.4. Here we use two metal balls 10 cm apart.5. The output remains/stays constant/unchanged/fixed/unaltered/the same.6. All the textbooks available discuss this problem.7. Accurate in operation and high in speed, computers have found wide applications.8. The answer to this problem looks correct.9. Two parallel wi res a distance (o f)δapart carry the currenti.10. The problem now is how to measure the voltage across this component.11. These data will be sent to the computing center 2 kilometers away.12. Upon rearranging the equation above, we have [get, obtain] the following expression.13. These charges can interact with other charges present.14. Forces can be transmitted without contact, contrary to the common belief.15. This coefficient is typically 0.35.II、1. In this case, the input does not fall; nor [neither] does the output. […; the output does not fall, either.]2. The resistance of a conductor depends not only on the material of which theconductor is made, but also on the size and temperature of the conductor.3. These scientists are very interested in this topic.4. This parameter can hardly be measured.5. In this laboratory, this instrument is more expensive than any other one/ any oneelse.6. The features of this device are small size and light weight.练习5I、1. This equation can be solved in either of the following two ways/the two wayswhich follow.2. This baseball will soon come to rest because of its interaction with the ground.3. Our choice of this coefficient as 1 is correct.4. From its definition as the ratio of a force to a length, we can see that k has thesame unit as work (does).5. Our analysis of the machine is of great significance.6. This facilitates their use in circuit analysis.II、1. This police car is equipped with a receiver the size of a matchbox.2. Wires one hundredth the diameter of a silk thread are used to connect thesecomponents.3. We must water cool these equipments/devices.4. In the past, telephone calls were operator connected.5. AC can be changed/turned/converted/transformed/translated into/to DC, a process called/known as/referred to as rectification.6. A magnet attracts iron materials, a familiar phenomenon.7. Computers are capable of processing information, a process that previouslycould be accomplished only inside our heads.8. An instrument for measuring current, voltage, and resistance, the multimeter iswidely used in electrical engineering.III、1. Secs. 1.1 and 1.2 will discuss several other problems.2. Problems are listed/given on pp. 1-5.3. In the equations above, all h’s a re the hybrid parame ters.4. The mass of the standard pound is equal to 0.4535924277 kilograms.5. All a’s and b’s in Eq. (5-1) are related to the impedance R. o6. We must take the effect of temperature on [upon] semiconductorsintoaccount.7. In this case, the variation of output with input is very small.8. This curve shows the dependence of distance on/upon speed.IV、1. None of them can solve this special type of differential equation.2. They do not know whether this material can stand so largea force or not.3. There are M polygons altogether, each of which has N vertexes.4. These two engineers are busy (in) designing a new kind ofsoftware.5. Iron is almost as good a conductor as aluminum.练习6I、1. This image, it will be noticed, is a real image.2. This technical problem, we hope, will be solved soon.103. 2 is approximately 1000, a fact that we think is very useful in the study of digitalelectronics.4. A resistor of say 100 ohms should be used here.II、1. None of those textbooks have/has mentioned this point.2. All of these x values cannot satisfy the equation.3. Neither of the two conditions is satisfied here.4. In the preceding/previous chapter, we discussed all kinds of force.5. This paper describes a new method for designing aircraft.6. By the end of the last century, the company had manufactured 5 000 radars.7. Since 2008, this research institute has been developing a special kind of robot. III、1. In Section 1-2, the concept of force was introduced.2. As early as the 1940s, it was found that semiconductors are very useful.3. This result can also be arrived at in another way.4. At that time no use was made of this phenomenon/…, thisphenomenon was made no use of.5. This point will be dealt with in the next section.IV、1. This computer works much better than that one(does)/This computer is much betterin performance than that one (is)..2. This computer requires many more components that that one (does).3. The distance of the moon from the earth is as great as 240 000 miles.4. The greater the resistance, the longer time it takes for the capacitor to reach itsmaximum voltage/…, the longer time is required for the capacitor to reach its maximumvoltage.)5. The current as small as 0.1 A cannot produce enough heat.V、1. It is easy for us to determine the weight of the body. 或:We can determine theweight of the body easily.2. The two engineers are busy (in) designing a new type of computer.3. We find this concept very difficult to explain.4. None of these windows can withstand so large a force.5. Work equals [is equal to] force multiplied by/times distance.6. The results obtained agree with the experimental values. [… arein agreement withthe experimental values.]练习7I、1. It will take a few months to design this kind of aircraft withthe help of a computer.2. It is left as a problem to [for] the reader to show that this expression holds.3. The program to be executed is stored in this unit.4. This valley acts as the foundation on which to build the dam.5. In this laboratory there are many kinds of instrument forstudents to choose from.6. Let t equal/be equal to zero. 07. The farther away the target (is), the longer time it takes forthe echo to return.8. For the series to converge, x must be less than 1.9. We find this concept very difficult to understand.10. This method makes it much easier to detect targets.11. This factor will affect the ability of a computer to store information.12. We have to find out how large to make r so as for the series to converge.13. This is a pen to draw pictures with.14. Elasticity is the tendency of a body to return to its original condition after beingdeformed.15. Ordinary matter is said to be electrically neutral.16.This property makes it possible for metals to be made into any shape.17. This table is unfit for a student to do experiments on.18. Now we consider what path of integration to take.II、1. The sine law of the variation of light intensity with the cylinder diameter has beenemphasized.2. Not only do temperature and light affect the conductivity, but the addition ofimpurities to semiconductors also makes it change greatly.3. Various satellites are frequently launched to obtain information about/on space.4. Our semiconductor industry came into being at the end of the 1950s.5. My colleagues and I would like to express our thanks to Professor W. Smith for hisgreat help.练习8I、1. The amplifier amplifies the received signals.2. Moving molecules have kinetic energy.5. Fig. 1 – 3 shows the photo of a freely falling body.3. Speed equals distance divided by time.4. Voltage equals/is equal to current multiplied by resistance.5. The resistance of air increases with the increased/increasing/an increase in speed.6. A transformer is a device consisting of two or more coils wound on/round an iron core.7. It is necessary to find out the current flowing through this component.8. This book, properly used, will be of great help to the reader.9. Flowing through a circuit, the current will lose part of its energy.10. Given/Knowing time and speed, we/one can find out distance.11. Having studied this chapter, the student will understand/will have understood theprinciple of a computer.12. The speed of light being extremely great, we cannot measure it by ordinary methods.13. Several comsats were launched, all of them (being) high-altitude satellites.14. Called “the mother of all networks,” the Internet is a widely used internationalnetwork.15. This force can be resolved into two components, one (being) horizontal and the othervertical.II、1. Let us construct/draw a circle with the origin as the center and of radius R.2. This parameter should be measured with E grounded.3. With no resistance in the circuit,the current will increase indefinitely.4. With this in view, we have written this book.5. This paper introduces a new design method/technique, with emphasis on its principle. III、1. Let us consider designing a computer.2. We refer to these components as being passive.3. This involves taking the Fourier transform.4. On/Upon rearranging the above equations, we obtain the following set ofequations.5. In using this equation, it does not matter which plane is considered as 1.IV、1. Given/Knowing resistance and current, one/we candetermine/calculate voltage.2. The price of this instrument is high.3. A robot is a special kind of electronic device.4. The current starts flowing at the very moment we close thecircuit.5. They have been designing a new type of computer these six months.练习9I、1. The problem was not solved until a completely different method was introduced.2. Nearly 100 years passed before the existence/presence of subatomic particles was confirmed by experiment/experimentally.3. The year this device was invented, World War II broke out.4. Small as they are, atoms are made up of still smaller particles.5. These two resistors should be selected/chosen so that the transistor can operate normally.6. The body is in such a state that it can do work.II、1. The relation that voltage is the product of current andresistance applies to all the dc circuits.2. The discovery that magnetism can produce current is extremely important in the field of electricity.3. An equation is an algebraic statement that two algebraic expressions are equal.4. There is evidence that no life exists on the moon.5. The question now arises whether the algorithm is of practical use.6. In this case there is no guarantee that the series is convergent.7. There is a growing/increasing awareness that thesetechniques/methods are veryuseful.8. One of/Among the most noteworthy achievements at that time wasthe realization thatlight consists of electromagnetic waves.9. This is due to/is caused by/results from the fact that there are many free electrons inconductors.10. Besides/In addition to the fact that the properties of thematerial should be included inthe analytical model, we must take other factors into account.III、1. These features make it difficult for electronic counter-measure systemsto intercept, analyze and jam this kind of signal.2. The existence of and the ability to control these phenomena make those devicespossible.3. The variation of/in the number of the filter’s teeth has a greater effect on the performance of its passband than the variationof/in its dimensions.4. Scalar detection will result in the loss of some phase information.5. Fig. 6 shows the schematic diagram of measuring scatter parameters by the natural parameter transformation method.练习10I、1. Now it remains to be determined when the series converges.2. It is clear from Dubamel’s Theorem that this limit exists.3. It follows from Maxwell’s hypo thesis that whenever there is a change in an electricfield, a magnetic field is produced.4. It does not matter whether the magnet is moved in this case.5. Temperature determines in what direction the transfer of heat will take place.6. It is now a well-known fact that all matter consists of tiny particles.II、1. What a generator does is (to) change mechanical energy into electrical energy.2. What this chapter describes/What is described in this chapter is of great importance.3. Matter is what can occupy space.4. What we have discovered in this experiment is the entirely new realm of electricalphenomenon.5. This direction is opposite to what has been assumed.6. Magnitude, direction, and place of application are what we call the three elements of aforce.7. These numbers constitute what is known as the real number system.8. In what follows, we shall acquaint ourselves with somebasic concepts. III、1. An x-band wave-guide test system is shown in Fig.7. [或:Fig.7 shows …].2. This method lowers the requirement for the hardware of a sample network.3. On the basis of the above analysis of the decomposition of the polynomial, a novelconfiguration results. [或:The above analysis of the decompositionof the polynomial resultsin a novel configuration.]4. Finally, an analysis of packet loss probability is made bycomputer simulation.5. The sparse ratio of the resulting impedance matrix is as high as 40%.练习11I、1. The meter (that/which) we use to measure the voltage across a resistor is called avoltmeter.2. Computers are the most efficient assistants (that) man has ever had.3. Now this disease is no longer the serious problem (that) it once was.4. Radar can measure the time (that) it takes for the radio echo to return.5. We must calculate the distance (that/through which) the body is lifted.6. The direction (that/in which) a body moves is also very important.7. The number of times (that/by which) this particle vibrates per/a second iscalled/termed/named/known as/spoken of as/referred to as frequency.。
基于电荷泵技术的si--sio2界面电荷分布特性研究
ｆｏｕｎｄ ｔｈａｔ ｔｈｅ ｇｅｎｅｒａｔｉｏｎ ｏｆ ｉｎｔｅｒｆａｃｅ ｔｒａｐ ｉｓ ｒｅｓｐｏｎｓｉｂｌｅ ｆｏｒ ｔｈｅ ｅｌｅｃｔｒｉｃａｌ ｐａｒａｍｅｔｅｒ
ｄｅｇｒａｄａｔｉｏｎ ｕｎｄｅｒ Ｉｂｍｘ ｃｏｎｄｉｔｉｏｎ，ａｎｄ ｌｉｎｅａｒ ｄｒａｉｎ ｃｕｒｒｅｎｔ ｄｅｇｒａｄａｔｉｏｎ ｉｓ ｔｈｅ ｗｏｒｓｔ．Ｉｔ ｉｓ ａｌｓｏ
ｆｏｕｎｄ ｔｈａｔ ｔｈｅ ｇｅｎｅｒａｔｉｏｎ ｏｆ ｉｎｔｅｒｆａｃｅ ｓｔａｔｅｓ ｗｉｌｌ ｍｏｖｅ ｔｏｗａｒｄ ｔｈｅ ｓａｔｕｒａｔｉｏｎ ａｆｔｅｒ ２０００ｓ ｉｎ
０．１ ８ｕｍ ＮＭＯＳＦＥＴ．Ｒｅｓｕｌｔ ｓｈｏｗｓ ｔｈａｔ ｅｌｅｃｔｒｉｃａｌ ｐａｒａｍｅｔｅｒｓ ｄｅｇｒａｄａｔｉｏｎ ｉｓ ｍｏｒｅ ｓｅｒｉｏｕｓ ｗｉｔｈ
Ｔｈｅ ＣＰ ｍｅｔｈｏｄ ｈａｖｅ ｂｅｅｎ ｆｕｒｔｈｅｒ ｉｎｖｅｓｔｉｇａｔｅｄ，ｉｔ ｉｓ ｓｈｏｗｎ ｔｈａｔ ｔｈｅ ｐｕｌｓｅ ｆｒｅｑｕｅｎｃｙ， ｒｅｖｅｒｓｅ ｖｏｌｔａｇｅ，ｐｕｌｓｅ ｖｏｌｔａｇｅ ａｍｐｌｉｔｕｄｅ ａｎｄ ｄｕｔｙ ｃｙｃｌｅ ｍｕｓｔ ｂｅ ｓｔｒｉｃｔｌｙ ｃｈｏｓｅｎ ｔｏ ｇｕａｒａｎｔｅｅ ｔｈｅ ａｃｃｕｒａｃｙ ｏｆ ｍｅａｓｕｒｅｍｅｎｔ．Ｔｈｅ ｅｍｉｓｓｉｏｎ ｔｈｅｏｒｙ ｏｆ ｅｌｅｃｔｒｏｎ ａｎｄ ｈｏｌｅ Ｗａｇ ｉｎｔｒｏｄｕｃｅｄ ｔｏ ｅｘｐｌａｉｎ ｔｈｅ ｄｅｖｉａｔｉｏｎｓ ｆｒｏｍ ｔｈｅ ｓｉｍｐｌｅ ＣＰ ｔｈｅｏｒｙ．Ｔｈｅ ｈｉｇｈ ｌｏｗ ｆｒｅｑｕｅｎｃｙ ｃｈａｒｇｅ ｐｕｍｐｉｎｇ
Ｍ．Ｅ．Ｃａｎｄｉｄａｔｅ：Ｗｅｉｊｉａ Ｈｕ
Ｓｕｐｅｒｖｉｓｏｒ：Ｐｒｏｆ．Ｋｏｎｇ Ｘｕｅｄｏｎｇ
吸附氢与气相的零点能的差值
吸附氢与气相的零点能的差值英文回答：The difference in zero-point energy between adsorbed hydrogen and gas phase can be attributed to several factors. Firstly, the adsorption process itself involves the interaction between the hydrogen molecule and the surfaceof the adsorbent material. This interaction can lead to a change in the vibrational and rotational modes of the hydrogen molecule, resulting in a difference in the zero-point energy compared to the gas phase.Additionally, the confinement of the hydrogen molecule on the surface of the adsorbent material can also affectits zero-point energy. When adsorbed, the hydrogen molecule is restricted in its motion, leading to a reduction in its zero-point energy compared to the freely moving gas phase. This confinement effect can be observed in various systems, such as hydrogen adsorbed on carbon nanotubes or metal surfaces.Furthermore, the presence of other molecules or species in the adsorbed state can also influence the zero-point energy of hydrogen. For example, if hydrogen is adsorbed on a metal surface in the presence of other gases, such as oxygen or nitrogen, the interactions between these molecules can affect the zero-point energy of hydrogen. This is because the presence of other molecules can lead to additional interactions and energy exchanges, resulting in a difference in the zero-point energy compared to the gas phase.In summary, the difference in zero-point energy between adsorbed hydrogen and gas phase can be attributed to the interaction between the hydrogen molecule and the adsorbent surface, the confinement effect on the surface, and the presence of other molecules in the adsorbed state. These factors can lead to changes in the vibrational and rotational modes of the hydrogen molecule, resulting in a difference in the zero-point energy compared to the gas phase.中文回答：吸附氢与气相的零点能差异可以归因于几个因素。
压电英文版知识点总结
压电英文版知识点总结Piezoelectricity, derived from the Greek word "piezein" meaning to press or squeeze, refers to the generation of voltage in certain crystals when subjected to external pressure. Conversely, the application of a voltage across certain crystal faces can result in a slight deformation of the crystal shape. This phenomenon was discovered by two French physicists, Pierre and Paul-Jacques Curie, in 1880.Crystals, in the scientific sense, are solids with atoms or molecules arranged in a highly regular pattern, repeating a basic unit cell at regular intervals. This regularity in the crystal's structure is reflected in its piezoelectric properties. The atoms in a piezoelectric crystal are arranged asymmetrically, but the positive and negative charges within the crystal cancel each other out, resulting in an overall neutral charge for the crystal.Piezoelectricity is a reflection of the coupling between the elastic and dielectric properties of a crystal.It manifests in two forms: positive piezoelectric effect and converse piezoelectric effect. In the positive piezoelectric effect, when a dielectric material is mechanically deformed along a certain direction, aninternal polarization occurs, resulting in the generation of opposite charges on its two opposing surfaces. Once the external force is removed, the material returns to its electrically neutral state. Conversely, in the converse piezoelectric effect, the application of an electric field along the polarization direction of a dielectric material causes it to deform. When the electric field is removed, the deformation disappears.The root cause of the piezoelectric effect is the displacement of ionic charges within the crystal lattice of the dielectric material under the influence of an applied stress. This displacement results in a net polarization and the accompanying generation of an electric field, manifesting as the piezoelectric effect. The charge density generated is linearly related to the applied force, and reversing the direction of the applied force also reverses the polarity of the generated charges.Piezoelectric materials are those that exhibit this stress-field and electric-field coupling due to the unique arrangement of atoms within their crystal lattice. These materials are characterized by their ability to convert mechanical energy into electrical energy (via the positive piezoelectric effect) and vice versa (via the converse piezoelectric effect).The piezoelectric effect is not limited to crystals with a non-centrosymmetric structure but can also be observed in materials with a centrosymmetric structure under certain conditions, such as the presence of defects or an applied stress that alters their symmetry.The piezoelectric effect finds applications in various fields, including sensors and actuators, energy conversion and harvesting, and ultrasonic devices. In sensors and actuators, the piezoelectric effect is used to measure or generate mechanical displacements, pressures, or forces by converting them into electrical signals or vice versa. In energy conversion and harvesting, piezoelectric materialsare used to convert mechanical vibrations or deformations into electrical energy, which can be used to power electronic devices. In ultrasonic devices, thepiezoelectric effect is employed to generate or detect ultrasonic waves.In conclusion, piezoelectricity is a fascinating phenomenon that arises from the coupling of elastic and dielectric properties in certain materials. It manifests in the generation of an electric field in response to mechanical deformation and vice versa, offering a unique way to convert mechanical energy into electrical energy and vice versa. This property has found widespread applications in various fields, ranging from sensors and actuators to energy conversion and harvesting, and ultrasonic devices.。