3号英文Role of microwave radiation in curing the fly ash geopolymer

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高三宇宙奥秘英语阅读理解30题

高三宇宙奥秘英语阅读理解30题1<背景文章>Black holes are one of the most fascinating and mysterious phenomena in the universe. A black hole is formed when a massive star collapses at the end of its life. The gravitational pull of a black hole is so strong that nothing, not even light, can escape from it.The formation of a black hole begins with the collapse of a massive star. As the star runs out of fuel, it can no longer support its own weight and begins to collapse. The collapse continues until the star reaches a critical density, at which point it becomes a black hole.Black holes have several unique characteristics. One of the most notable is their event horizon, which is the boundary beyond which nothing can escape. Another characteristic is their intense gravitational field, which can distort the space and time around them.Black holes can have a significant impact on the surrounding celestial bodies. They can attract and swallow nearby stars and planets, and their gravitational pull can also affect the orbits of other celestial bodies.Scientists are still working to understand black holes better. They use a variety of tools and techniques, such as telescopes and computer simulations, to study these mysterious objects. Despite significant progressin recent years, there is still much that we don't know about black holes.1. What is a black hole formed by?A. A small star collapsing.B. A massive star collapsing.C. A planet collapsing.D. A moon collapsing.答案：B。

嫦娥三号英语ppt

la unche dຫໍສະໝຸດ 2013 C ha ng ' e la unche -3 d C ha ng 'e 2010 -2 Created a full
high-resolution map of the moon and highdefinition images of the lunar landscape.
WHAT IS MOON ROVER NAME?
Yutu is a white pet rabbit
Yutu
The rover has two wings, stands on six wheels, weighs 140 kg and will be powered by solar energy.
The timeline of China's lunar mission development：
la unche d C ha ng 'e 2007 -1 Retrieved lunar
data and carried out an initial mapping of the surface.
Moon rover's name
After a month-long (from Sept 25 to Oct 25 ) online poll, 190,000 proposals were received . By a 14-member jury board selected the ten most popular ， the final result has been announced in November 26.
China's lunar mission
China's lunar mission is divided into three stages: orbiting, landing, and return

人类探索宇宙的意义是什么,英文作文

人类探索宇宙的意义是什么,英文作文The Wonders of Space ExplorationEver since I was a little kid, I've been fascinated by space. The twinkling stars in the night sky, the mysterious planets, and the vast unknown of the cosmos have always captured my imagination. I often find myself gazing upwards and wondering what incredible secrets the universe holds.I think exploring space is one of the most exciting and important things humans can do. By venturing out into the great beyond, we can learn so much about our universe and our place in it. Every new discovery opens up even more questions and mysteries to unravel!One of the coolest things about space is just howmind-bogglingly massive it is. The distances between planets, stars, and galaxies are almost too huge for my brain to comprehend. But that's what makes it so fascinating! The deeper we probe into the cosmic ocean, the more we realize how little we truly know.Space is also incredibly old - the universe itself is around 13.8 billion years old! That's billions of years older than even the dinosaurs. When I think about that vast stretch of time, and allthe crazy events that must have unfolded, it boggles my mind. By studying planets, stars, galaxies, and the cosmic microwave background radiation left over from the Big Bang itself, scientists are slowly piecing together the history of the entire universe. How cool is that?Another great thing about space is all the breathtaking phenomena out there like black holes, neutron stars, supernovas, and star nurseries where new stars and planets are being born. We may think we have some pretty neat things on Earth like auroras, volcanic eruptions, and hurricanes. But compared to the scales, temperatures, and energy levels involved in cosmic events, our terrestrial phenomena seem tiny and quaint in comparison.To me, one of the most exciting frontiers is the search for extraterrestrial life. With billions of galaxies in the observable universe, each containing billions of stars, surely there must be other planets out there with life? Maybe even intelligent civilizations far more advanced than we are? Just imagining that possibility sparks my sense of wonder. I really hope we make contact with alien beings someday so we can learn about their cultures, technologies, and philosophies. Who knows, they might even help us solve some of our biggest problems here on Earth!By exploring space, we are also enhancing our technology capabilities in many important areas. Building advanced rockets, landers, rovers, telescopes, and satellites requires us to really push the boundaries of engineering, materials science, computing, and so much more. Many of the cutting-edge technologies pioneered for space end up having widespread applications that improve life for everyone on Earth as well.Another key reason space exploration is vital is that it may be crucial for the long-term survival of our species. Considering the many existential threats facing us on Earth like climate change, nuclear war, asteroid impacts, and more - having a backup planetary home could be our insurance policy. By establishing self-sustaining human colonies on the Moon, Mars, or other bodies in space, we increase our odds of riding out any global catastrophe that may befall our home planet. As a big fan of our species, I feel we have an obligation to secure a foothold across the cosmos.Speaking of Mars, I can't wait until we finally send humans to walk on the Red Planet! Watching the Mars rover missions has been amazing, but there's nothing quite like actually having human explorers visit another world. Just imagining people stepping onto the rusty sands of Mars and gazing across itsancient river valleys and towering volcanoes gives me goosebumps. What will it be like to stand on an alien landscape and look up at the familiar stars and planets from a whole new worldview? I desperately want to experience that someday.Of course, the journey of space exploration is difficult, dangerous, and expensive. Many unmanned probes and robotic explorers have been lost over the years due to accidents, technical glitches, and just the extreme challenges of operating in space. And the tragedy of lost human lives like the crews of the Challenger and Columbia space shuttles is profoundly sobering. I have deep respect and admiration for the brave astronauts, cosmonauts, mission controllers, engineers, and everyone working to push the boundaries of space exploration in the face of such risks.But in my view, the rewards of gaining new knowledge about our cosmos far outweigh the costs and hardships. Throughout history, many of humanity's greatest achievements and periods of rapid progress have been driven by epic journeys of exploration into the unknown. The Age of Exploration created by pioneers like Columbus, Magellan, and others ushered in a cross-pollination of ideas, technologies, and cultures that radically reshaped human society.I believe the impetus of space exploration can spur a similar flourishing and renaissance for our species. By striving to reach the stars, we will be forced to collaborate globally, invent brilliant new technologies, and evolve our philosophical perspectives. Our descendants may spread out from this single planetary cradle to inhabit a vast realm of uncountable worlds. We could eventually become a multi-planet species, at home across the entire galaxy!Most importantly to me though, space exploration nourishes something deep within the human spirit - our curiosity, our sense of adventure, and our need to find our place in the grand scheme of things. I think there is something profound and beautiful about our existential drive to keep journeying, to keep asking "what's out there?", and to push the boundaries of our knowledge.As a wise person once said, "We choose to go to the Moon and do other things, not because they are easy, but because they are hard." That stirring sentiment resonates with me. Grand challenges like space travel inspire us to muster our ingenuity, courage, and determination to overcome the seemingly impossible. Rising to confront the vast mysteries of the cosmos ennobles our species and brings out the very best in us.For all these reasons and more, I am convinced that exploring the universe is not only immensely fascinating and wondrous - it is a vital and incredible chapter in the eternal human quest to understand our origins and our cosmic destiny. That's a journey I want to be a part of!While I may only be a kid now, I dream of someday contributing to humanity's great journey among the stars. Whether it's as an astronaut, an engineer, a science communicator, or in some role I can't even imagine yet, I want to dedicate my life and passions to pushing the frontiers of space exploration. Because in doing so, I believe I can help expand the boundaries of human knowledge and experience in a way that benefits us all.To me, there is no greater calling than being part of that grand adventure - to gaze upon worlds never before seen, to experience the majesty of the cosmos firsthand, and to unravel its deepest secrets. It's an exciting quest that will fill our descendants with awe and wonder just as it does me today. The universe is a vast ocean brimming with breathtaking splendor, sobering mysteries, and untold potential - and we humans have only begun to get our feet wet. So let's keep exploring out there among the stars together! Our journey is just beginning.。

hartle 广义相对论英文

hartle 广义相对论英文General relativity, developed by Albert Einstein, is a theory that describes the gravitational force as a curvature of spacetime caused by mass and energy. This theory has had a profound impact on our understanding of the universe and has been confirmed by numerous experiments and observations. In this response, I will discuss various aspects of general relativity, including its historical development, its key concepts and predictions, its applications in astrophysics and cosmology, itsimplications for our understanding of space and time, and its significance for our everyday lives.First and foremost, the historical development of general relativity is a fascinating story. Einstein spent years working on the theory, which culminated in the publication of his field equations in 1915. It was a revolutionary departure from Newtonian physics, as it replaced the concept of gravity as a force with the idea that massive objects deform the fabric of spacetime itself.This theory was later confirmed by the famous Eddington expedition in 1919, which observed the bending of starlight during a solar eclipse, providing strong evidence for the theory.One of the key concepts of general relativity is the equivalence principle, which states that the effects of gravity are indistinguishable from the effects of acceleration. This means that an observer in a closed room cannot determine whether the room is accelerating or in a gravitational field. This principle has profound implications for our understanding of gravity and has been confirmed by numerous experiments, such as the Pound-Rebka experiment, which measured the gravitational redshift of gamma rays.General relativity also makes several predictions that have been confirmed by observations. For example, it predicts the existence of black holes, which are regions of spacetime where gravity is so strong that nothing, not even light, can escape. The recent detection of gravitational waves by the LIGO and Virgo collaborations provides directevidence for the existence of black holes and other extreme astrophysical phenomena. General relativity also predicts the expansion of the universe, which has been confirmed by the observation of the redshift of distant galaxies.In addition to its theoretical and observational successes, general relativity has numerous practical applications in astrophysics and cosmology. It is used to study the behavior of stars, galaxies, and other celestial objects, as well as the large-scale structure and evolution of the universe. General relativity also plays a crucial role in the study of cosmological phenomena such as the cosmic microwave background radiation and the formation of large-scale structures in the universe.Furthermore, general relativity has profound implications for our understanding of space and time. According to the theory, spacetime is not a fixed background, but a dynamic entity that can be curved and deformed by matter and energy. This means that the geometry of spacetime is not absolute, but depends on thedistribution of mass and energy. General relativity alsopredicts the existence of wormholes, which are hypothetical shortcuts through spacetime that could potentially allowfor faster-than-light travel.Finally, the significance of general relativity extends beyond the realm of theoretical physics and astrophysics.It has practical applications in our everyday lives, suchas in the operation of the Global Positioning System (GPS). GPS relies on precise timing measurements, which areaffected by the curvature of spacetime due to Earth's mass. Without the corrections provided by general relativity, GPS would accumulate errors of several kilometers per day.In conclusion, general relativity is a remarkabletheory that has revolutionized our understanding of gravity, space, and time. Its historical development, key concepts and predictions, applications in astrophysics and cosmology, implications for our understanding of space and time, and everyday significance all contribute to its profound impact on our scientific knowledge and technological advancements. General relativity is a testament to the power of humanimagination, creativity, and intellectual curiosity in unraveling the mysteries of the universe.。

微波炉的工作原理（Theworkingprincipleofmicrowaveoven）

微波炉的工作原理（The working principle of microwave oven）The working principle of microwave ovenIn 1946, Spence was a fellow of Raytheon Corporation in the United states. By chance, he found that the microwave dissolved the candy. It has been proved that microwave radiation can cause molecular vibrations in food and produce heat. In 1947, the first microwave oven came out.As the name suggests, the microwave oven is to use microwave to cook cook. Microwave is an electromagnetic wave. This electromagnetic energy than radio waves are often much larger, but also a strong "personality", microwave an encounter took place reflective metal, the metal there is no way to absorb or transfer it; microwave can pass through glass, ceramics, plastics and other insulating materials, but it will not consume energy; and water containing food, microwave not only through its energy but will be absorbed.Microwave ovens are made with these characteristics of microwaves. The outer shell of the microwave oven is made of stainless steel and other metal materials, and the microwave can be prevented from escaping from the furnace so as not to influence the health of the people. Food containers are made of insulating material. The heart of a microwave oven is a magnetron. The electron tube, called a magnetron, is a microwave generator that produces microwaves with a frequency of 2 billion 450 million vibrations per second. This invisible microwave can penetrate the food to 5cm depth, and also move the water molecules in the food. Intense movement produces a large amount of heat energy, so the food is cooked. This is theprinciple of microwave heating. When cooking food from an ordinary stove, heat is always coming from the outside of the food into the food. Microwave cooking, the heat is directly into the food inside, so the cooking speed faster than other stoves 4 to 10 times, thermal efficiency of more than 80%. At present, the thermal efficiency of other stoves can not be compared with that of other stoves.The microwave oven, for its short cooking time, can keep the vitamins and natural flavors in the food very well. For example, cooking green peas in a microwave can almost do without vitamin C. In addition, the microwave can also disinfect and sterilize.The use of microwave ovens should be careful not to empty "burning", because the "empty" "burning" when the microwave energy can not be absorbed, so that it is easy to damage the magnetron. In addition, the human body contains a lot of moisture, must be stopped after the magnetron, and then open the door to extract food.Basic structure of microwave ovenBasic shape and structure of microwave ovenDoor safety interlock switch - to ensure that the door is open, microwave oven can not work, the door closed, microwave oven can work;Screen window - with metal screen, can observe the cooking of food through the mesh;Ventilation - ensure good ventilation during cooking;Turntable support - drive glass turntable rotation;Glass turntable - packed food containers placed on the turntable, heating turntable rotation, so that food cooking evenly;The control panel control stall cooking;The door switch: this switch, the door is open.Working principle(1) furnace chamber. The furnace cavity is a microwave resonant cavity, which is a space where microwave energy is changed into heat energy to heat food. In order to make the food in the furnace heated evenly, a special device is arranged in the cavity of the microwave oven. The microwave oven originally produced is equipped with metal fan pages at the top of the furnace cavity, that is, microwave mixers to interfere with the propagation of microwave in the furnace cavity, thus heating the food more evenly. At present, it is loaded by a micro motor driven glass turntable at the bottom of the oven cavity of the microwave oven, the food is heated on the turntable and the disk around the motor shaft rotation, the high frequency electromagnetic field and the furnace for the relative movement, to achieve the purpose of uniform heating furnace of food. The original automatic lifting turntable makes the heating more uniform and the cooking effect more ideal.(2) the furnace door: the door is the import and export of food, and also an important part of the chamber of the microwave oven. It is very demanding, that is, from outside the door can observe the heating of food in the furnace cavity, but also can not let the microwave leak out. The furnace door is made up of metal frames and glass viewing windows. The glass interlayer in the observation window has a layer of metal microporous net, which can see the food through it and prevent the microwave leakage.Because the mesh size of the metal mesh in the glass interlayer is carefully calculated, the penetration of the microwave can be prevented completely.In order to prevent the leakage of microwave, the switch system of microwave oven is composed of multiple safety interlocking micro switch device. When the door is not closed, the microwave oven can not be worked, and the microwave oven doesn't work, so there is no microwave leakage.In order to prevent the microwave oven door shut after microwave from the gap between the door and the leaking out of the cavity, the microwave oven door around with an anti groove structure, or a microwave absorbing material, such as silicone rubber by doing door seals, a small amount of microwave can be absorbed leakage. Anti groove is a groove shaped structure is arranged inside the door, it has guided microwave phase reversal effect. In the anti microwave groove at the entrance, it will be the reverse reflection wave offset, so microwave will not leak.Because the door seal is easy to damage or aging effects caused by anti leakage reduction, so now most microwave ovens are usedto prevent microwave leakage anti groove structure, rarely used silicone rubber door seals. Anti groove structure is the principle of microwave radiation on the method of preventing the leakage of microwave stable *. Guangdong Galanz enterprise (Group) by using Galanz microwave oven production company is the most advanced anti groove structure and production process, with the development of multiple anti leakage microwave technology, microwave leakage control technology has reached the international advanced level.(3) electric circuit: the electric circuit divides the high voltage circuit, the control circuit and the low voltage circuit three parts.(a) high voltage circuit: after high-voltage transformer secondary winding circuit is high voltage circuit, mainly including magnetron, high-voltage capacitor, high voltage transformer, high voltage diode.(b) magnetron: the magnetron is the heart of the microwave oven, and microwave energy is produced and emitted by it. Magnetron operation requires a high pulsating DC anode voltage and a cathode voltage of 3 to 4V. The voltage doubler rectifier circuit composed of high voltage transformer, high voltage capacitor and high voltage diode provides the working voltage for magnetron to meet the above requirements.(c) low voltage circuit: the circuit between the primary winding of the high voltage transformer and the microwave power inlet is a low voltage circuit, and also includes a control circuit. It mainly includes safety tube, thermal circuitbreaker protection switch, interlocking micro switch, lighting lamp, timer and power distributor switch, turntable motor, fan motor, etc..(4) timer. Microwave ovens usually have two timing modes, namely mechanical timing and computer timing. The basic function is to select the set working time. After setting the time, the timer automatically cuts off the main circuit of the microwave oven.(5) power divider. The power divider is used to adjust the average operating time of the magnetron (i.e., the ratio of "work" and "stop" time) during the intermittent operation of the magnetron, so as to achieve the purpose of regulating the average output power of the microwave oven. The mechanical control type usually has 3~6 scale bits, and the computer controlled microwave oven can have 10 adjusting positions.(6) interlock microswitch. The interlocking micro switch is a group of important safety devices in microwave oven. The utility model has the function of multiple interlocking, and is controlled by the door button on the door of a furnace door or the door opening button on a door handle. When the furnace door is not closed or the furnace door is opened, the circuit is disconnected so that the microwave oven stops working.(7) thermal circuit breaker. A thermal circuit breaker is a component used to monitor the operating temperature of a magnetron or furnace chamber. When the operating temperature exceeds a certain limit, the thermal circuit breaker will immediately cut off the power supply, so that the microwave ovenwill stop working.Taboos on the use and maintenance[microwave] should be placed in the ventilation area, do not have magnetic material nearby, so as not to disturb the uniform state of the magnetic field in the furnace cavity, so that the work efficiency is reduced. Also with the TV, radio, a certain distance away, otherwise it will affect the visual and listening effects.[two] do not work with electricity when the cooking food is not in the oven. The microwave oven can not be operated without load, otherwise it will damage the magnetron. In order to avoid the negligence and cause the no-load operation, a glass filled with water can be installed in the furnace cavity.[three] all metal cutlery,Bamboo, plastic container, lacquer and other heat-resistant glass, concave and convex, are not suitable for use in microwave oven. Porcelain dishes must not be lined with gold or silver lace. The containers for the food must be placed in a microwave oven, not in the chamber.[four] microwave oven heating time depends on the amount of material and dosage, but also with food freshness, moisture content. As the heating time of various foods is different, it is necessary to take a shorter time when the heating time of the food is not certain. After heating, the heating time can be added to the degree of the cooked food. Otherwise, if thetime is too long, it will make the food become hard and lose its fragrance, color and flavor. Adjust the timing and power (temperature) knob according to the type and cooking requirements of the food. You can read the instructions carefully and learn more about them.[five] eggs with shells, sealed packaged food, can not be cooked directly. In case of explosion.[six] be sure to close the door and make sure that the interlock switch and the safety switch are closed. After the microwave oven is switched off, it is not advisable to take out the food immediately. Therefore, there is still waste heat in the oven and the food can be cooked again. It should be taken out after 1 minutes.Seven) the furnace should be kept clean. After breaking off the power supply, use a damp cloth and a neutral detergent to wipe off, do not flush, do not let the water flow into the furnace.[eight] regularly check the door around the door and the door, if damaged or closed bad, should stop using, in case of microwave leakage. Should not be close to the microwave oven window, to prevent eye damage due to microwave radiation. Should not be a long time by microwave irradiation, in order to prevent dizziness, dizziness, fatigue, weight loss, hair loss and other symptoms, so that the human body damage.9 taboos in using microwave ovens1., avoid using ordinary plastic containers: first, hot foodwill make plastic containers deformed; two, ordinary plastic will release toxic substances, pollution of food, endanger human health. Use a special microwave oven to hold the food and heat it in a microwave oven,2., avoid using metal utensils: because the furnace into the iron, aluminum, stainless steel, enamel and other vessels, microwave heating will produce sparks and reflect microwave, both damage furnace and heating unfamiliar food.3., avoid using closed containers: heating liquid should use wide mouth containers, because in closed containers, the heating of food is not easy to emit, so that the pressure in the container is too high, easy to cause blasting accidents. Even in the boiling shelled food, but also advance the shell punctured with a needle or chopsticks, to avoid heating caused by the burst, splashing dirty furnace wall, or spill wounding.4. avoid over heating: food into the microwave defrosting or heating, if forgotten to take out, if the time is more than 2 hours, should be thrown away, do not avoid food poisoning.5., avoid heating the meat to half cooked, then microwave heating: because in the half cooked food, bacteria will still grow, second times and then microwave heating, because the time is short, it is impossible to kill all bacteria. Frozen meat must be thawed in a microwave oven before being heated for cooked food.6. meat then frozen by microwave thawing: because meat after thawing in the microwave oven, actually has the outside layerof low temperature heating, this temperature bacteria are capable of reproduction, though again refrigerant can make its reproduction stop, but not live bacteria killing. The meat which has been thawed by microwave oven must be heated to full cooked if it is frozen in the refrigerator.7. avoid fried food: because of high temperature oil will splash, lead to fire. In case of accidentally causing fire in the furnace, be sure not to open the door, but should first turn off the power supply, wait until the fire is extinguished, then open the door to cool down.8. avoid placing the micro heater in the bedroom, and be careful not to cover the cooling windows of the microwave oven with articles.9. avoid long time in front of microwave oven: after opening micro furnace, people should stay away from microwave oven or person, at least 1 meters away from microwave oven.How to remove the dirt of microwave ovenAfter the use of microwave oven if not immediately wipe easily in the internal form of grease, so I had to use special cleaning tricks: a container with hot water in the microwave heat for two or three minutes, so that the microwave oven is filled with steam,This can cause the stubborn dirt to become soft and easy to remove because of the moisture content.When cleaning, wipe it again with water diluted neutral detergent, then washed with water and dry cloth cloth for final cleaning, if you still can not get rid of the stubborn dirt, can use plastic cards to scrape, do not use metal scraping, so as not to hurt inside. Finally, don't forget to turn on the microwave oven door and let the inside air dry thoroughly.Microwave oven principleSummaryMicrowave energy is produced by microwave generator, microwave generator includes microwave tube and microwave tube power supply two parts. Among them, the microwave tube power supply (referred to as power or microwave source) is the role of the common AC energy into DC energy, microwave tubes for the work of the creation of conditions. Microwave tube is the core of microwave generator. It converts DC energy into microwave energy.Microwave tubes have two major categories: microwave transistors and microwave transistors. Microwave transistors have less power output, and are generally used in measurement and communications. There are many kinds of microwave tubes, such as magnetron, klystron, TWT and so on. They are widely used in radar, navigation, communications, electronic countermeasures and heating, scientific research and so on, because of their different working principles, different structures and different performances. Because of its simple structure, high efficiency, low operating voltage, simple power supply and strong adaptability to load change, magnetronis especially suitable for other applications of microwave heating and microwave energy. Magnetron can be divided into two categories: pulsed magnetron and continuous wave magnetron because of their different working conditions. Microwave heating equipment mainly works in continuous wave state, so multi use continuous wave magnetron.Magnetron is an electric vacuum device used to generate microwave energy. Essentially a diode in a constant magnetic field. The tube in electronic control perpendicular constant magnetic field and constant electric field, interact with the high frequency electromagnetic field, the energy into microwave energy from the constant electric field, so as to achieve the purpose of generating microwave energy.There are many kinds of magnetron, and the multi cavity continuous wave magnetron is mainly introduced here.The magnetron consists of a tube core and a magnetic steel (or electromagnet). The structure of the core includes anode, cathode, energy output and magnetic circuit system, etc. four parts. Maintain a high vacuum inside the pipe. The following sections introduce the structure and function of each part.1 anodeThe anode is one of the major components of the magnetron, which together with the cathode constitutes the space between electrons and the high frequency electromagnetic field. Under the influence of a constant magnetic field and a constant electric field, electrons perform the task of energy conversionin this space. The anode of the magnetron collects electrons as well as the anode of the common diode, and plays a decisive role in the oscillation frequency of the high frequency electromagnetic field.The anode is composed of conductive metal material good (such as copper) is made, and a plurality of resonant cavity, resonant cavity must be an even number, the more the number of high frequency tube more. The type of anode resonant cavity is usually hole, groove, fan and groove fan. Each small resonant cavity on the anode is equivalent to a parallel 2C oscillation loop. Taking the slot fan cavity as an example, it can be considered that the groove part of the cavity mainly constitutes the capacitance of the oscillating loop, while the fan part mainly constitutes the inductance of the oscillating circuit. According to the microwave technology theory, the resonant frequency of the resonant cavity is inversely proportional to the geometrical size of the cavity. The larger the cavity is, the lower its operating frequency is. As a result, we can estimate the working frequency of the cavity according to the size of the cavity. The anode of a magnetron is coupled together by many resonant cavities to form a complex resonant system. The resonant cavity frequency of this system is mainly determined by the resonant frequency of each resonant cavity, and we can estimate the operating frequency band of the magnetron according to the size of the small resonant cavity.The anode resonant system of magnetron can produce the required electromagnetic oscillation, and can also generate many kinds of electromagnetic oscillations with different characteristics. In order to make the magnetron stable work inthe desired mode, commonly used "isolation belt" to isolate the interference pattern. The isolation belt anode wing an interval of a connection, in order to increase the frequency interval between the working mode and the adjacent interference pattern.In addition, due to the electron energy exchange also has a certain energy, these electrons hit the anode anode temperature, more electrons collected (i.e. the anode current is larger), or more electron energy (energy conversion rate is low), anode temperature is higher, therefore, the anode need cooling capacity good. The power generally adopts forced air cooling tube, the anode with heat sink. Then use water cooling pipe of high power, a cooling water jacket on the anode.2 cathode and its leadThe cathode of a magnetron, the emitter of electrons, is a part of the interaction space. The performance of the cathode has a great effect on the operating characteristics and life of the pipe and is regarded as the heart of the whole pipe.There are many kinds of cathodes with different properties. A direct heated cathode used in a continuous wave magnetron. It is formed from a tungsten filament or a pure tungsten filament into a spiral shape. The current is heated to a prescribed temperature and has the ability to emit electrons. The cathode has many advantages, such as short heating time and high electron bombardment resistance, and has been widely used in continuous wave magnetron.The cathode heating current is large, requiring the cathodelead to be short and thick, and the connecting parts should be in good contact. The cathode leads of high power tubes work at high temperature and are usually cooled by forced air cooling. When the magnetron works, the cathode is connected to negative high voltage, so the lead wire part should have good insulation performance and meet the requirement of vacuum sealing. In order to prevent the anode from overheating due to the electronic bombardment, the magnetron should be operated to reduce the cathode current so as to extend the service life.3 energy output deviceAn energy output device is a device that delivers microwave energy from an interaction space to a load. The function of the energy output device is that the vacuum sealing of the pipe is ensured through the microwave without loss and without breakdown. Meanwhile, the device can be conveniently connected with the external system. Small power continuous wave magnetron mostly uses coaxial output in the high frequency magnetic field of anode resonant cavity. A coupling loop is placed to generate high-frequency induction currents on the ring when the flux across the torus is so high that the high-frequency power is introduced out of the ring. The larger the coupling ring area is, the stronger the coupling is.An axial energy output device is commonly used in high-power continuous wave magnetron. The output antenna is connected to the anode fin through the hole of the pole shoe. The antenna is usually made of bars or round rods or cones. The whole antenna is sealed by the output window.The output window is usually made of glass or ceramic with low loss characteristics. It does not have to guarantee the microwave energy to pass without loss and has a good vacuum tightness. The output window of a large power tube is usually forced to cool down to reduce the heat generated by dielectric loss.4 magnetic circuit systemWhen the magnetron works normally, it requires a strong constant magnetic field, and its magnetic induction intensity is usually thousands of Gauss. The higher the working frequency, the stronger the magnetic field. The magnetic circuit system of a magnetron is a device for generating a constant magnetic field. The magnetic circuit system is divided into two major categories: permanent magnetic and electromagnetic. The permanent magnet system is generally used for small power tubes, and the magnetic steel and the tube core are firmly combined into a whole to form the so-called packing type. A large power tube electromagnet is used to generate a magnetic field, and the tube core and the electromagnet are used together. The upper and lower pole boots are arranged in the tube core to fix the distance of the magnetic gap. When magnetron works, the output power and working frequency can be adjusted conveniently by changing the magnitude of the magnetic field. In addition, the anode current can be fed into an electromagnetic wire package to improve the stability of the pipe.Proper use of 5 magnetronMagnetron is the heart of microwave equipment, so the correctuse of magnetron is the necessary condition to maintain the normal operation of microwave equipment. When using magnetron, we should pay attention to the following problems:First, the load should match.Whatever device requires the output load of the magnetron to match as much as possible, that is, its voltage to the Bobbi should be as small as possible. Large standing wave not only reflects large power, reduces the actual power of the material to be processed, but also causes the jump of the magnetron and the overheating of the cathode, and seriously damages the pipe. When the die is switched on, the anode current suddenly falls. Causes of skip die except for the small degree of separation of the pipe itself,The main aspects are as follows:(1) the internal resistance of the power supply is too large, and the non load mode causes non PI mode.(2) the load is seriously mismatched, and the reflection of the unfavorable phase weakens the interaction between the high frequency field and the electron flow, but can not sustain the normal mode oscillation.(3) insufficient heating of the filament causes insufficient emission, or because of the outgassing in the tube, the cathode poisoning causes insufficient emission, and the pipe current required for the oscillation of the PI mode can not be provided.In order to avoid the occurrence of skip mode, the internal resistance of the power supply should not be too large, the load should match, and the heating current of the filament should comply with the requirements of the instructionTwo, cooling.Cooling is one of the normal working conditions of the magnetron tube, common anode cooling high power magnetron, the cathode filament leads and output ceramic window simultaneously forced air cooling, some also use air-cooled or water-cooled electromagnet. Poor cooling will overheat the pipe and will not work properly. It will burn out the pipe in serious condition. Should not work under the condition of insufficient cooling.Three. Adjust the cathode heating power reasonably.When the magnetron is started, the cathode is overheated due to the unfavorable electron returning cathode, and the cathode overheating will aggravate the material evaporation, shorten the service life, and burn the cathode when serious. The way to prevent the cathode from overheating is to adjust the cathode heating power according to the regulation.Four 、 installation and debugging.目前常用的微波加热设备中磁控管放在激励腔上直接?だ湎低场＜だ患词悄芰考だ爸茫质谴湎低车囊徊糠帧Ｒ虼思だ坏男阅芏源趴毓艿墓ぷ饔跋旒蟆＜だ挥δ芙苣诓奈⒉ 芰坑行У拇涓涸亍Ｎ锎四康模だ槐旧淼纳杓仆猓茏釉诩だ簧系淖芭淝榭龆怨ぷ鞯奈榷ㄐ杂跋旒蟆Ｕ９ぷ魇惫茏拥难艏爰だ唤哟ゲ糠钟泻艽蟮母咂档缌魍ü 咧浔匦胗辛己玫慕哟ィ哟ゲ涣冀鸶咂荡蚧稹Ｌ煜卟迦爰だ坏纳疃戎苯佑跋炷芰康拇浜凸茏拥墓ぷ髯刺 Π此得魇楣娑ň 淖芭洹?Five. Preservation and transportationThe electrode material of magnetron is oxygen free copper, which can be easily oxidized in acid, alkali and moisture. Therefore, the preservation of the magnetron should be moisture-proof and avoid the acid-base atmosphere. Prevent high temperature oxidation. The packaging type magnetron shall be made of magnetic steel, and the magnetic changes of the magnetic steel shall be prevented. There shall be no ferromagnetic substance within 10 cm of the tube when it is present. In the course of pipe transportation, special vibration proof packing box shall be put in order to avoid damage caused by vibration and impact.。

micro开头的前缀的单词

micro开头的前缀的单词1. microbe- 单词释义：微生物，尤指病菌。

- 单词用法：可作可数名词，在科学研究、医学、卫生等话题中常用。

例如“The scientist is studying a new type of microbe.”- 近义词：germ, bacterium。

- 短语搭配：harmful microbe（有害微生物），microbe culture（微生物培养）。

- 双语例句：- “Oh my god! There might be millions of mic robes on this dirty dish. Yuck!”- “I heard that some microbes can make you really sick. It's likethey're tiny little invaders in your body.”- “You know, a single microbe can multiply and become a whole army of troublemakers in no time.”- “She's so care ful about cleaning because she knows those pesky microbes are everywhere.”- “If you don't wash your hands often, microbes will be all over you, just waiting to pounce.”2. microcosm- 单词释义：微观世界；小宇宙；缩影。

- 单词用法：常作可数名词，用于描述一个小的体系能反映出大的整体的情况。

如“This small community can be seen as a microcosm of the whole city.”- 近义词：miniature, epitome。

微波辐射对环氧树脂固化行为的影响

第 31 卷第 4 期 2004 年
北京化工大学学报 J OU RNAL OF B EIJ IN G UN IV ERSIT Y OF CHEM ICAL TECHNOLO GY
Vol. 31 , No. 4 2004
微波幅射对环氧树脂固化行为的影响
张军营蔡晓霞谷晓昱刘玲
(北京化工大学材料科学与工程学院 ,北京 100029)
表 1 装置两边的温度 Table 1 Temperatures of two sides of equipment
加热时间/ min
油浴温度/ ℃ 微波炉中的温度/ ℃
15
89
90
15
150
150
15
180
180
表中数据证明通过控制油浴的温度 ,可以准确地控制整个体系的温度。
© 1995-2006 Tsinghua Tongfang Optical Disc Co., Ltd. All rights reserved.
参考文献
[ 1 ] Wei J , Jow J , DeLong J . Comparative study of continu2 ous2power and pulsed2power microwave curing of epoxy resins[J ] . SAMPE ,1991 , 27(33) : 973 - 978
[ 2 ] Liu F , Li Y , Xu W , et al . Comparative calorimetric study of epoxy cure by microwave vs t hermal energy[J ] . Chem Res Chin Univ , 1993 ,19(20) :168 - 173

微波工程第三版英文版课后练习题含答案

微波工程第三版英文版课后练习题含答案1. IntroductionThis document contns the answers to the exercise questions at the end of each chapter in the third edition of Microwave Engineering by David M. Pozar. The questions are intended to help readers review and reinforce their understanding of the concepts and principles presented in the book.2. Chapter 1 Questions and AnswersQuestion 1.1What is the wavelength of a 1 GHz signal in free space?Answer:The speed of light in free space is approximately 3 x 10^8 m/s. Therefore, the wavelength of a 1 GHz signal is:λ = c / f = 3 x 10^8 / 1 x 10^9 = 0.3 metersQuestion 1.2What is an isotropic radiator?Answer:An isotropic radiator is an idealized antenna that radiates equally in all directions. It is often used as a reference for comparing the radiation patterns of other antennas.Question 1.3What is Friis transmission formula?Answer:Friis transmission formula is a formula used to calculate the power received by an antenna from a distant transmitting antenna, taking into account losses in the transmitted signal, the receiving antenna, and the medium between them. The formula is:Pr = Pt Gt Gr (λ / 4πd)^2where: - Pr is the received power - Pt is the transmitted power - Gt is the gn of the transmitting antenna - Gr is the gn of the receiving antenna - λ is the wavelength - d is the distance between the antennas Question 1.4What is a microwave circuit?Answer:A microwave circuit is a circuit that operates at microwave frequencies, which are typically considered to be in the range of 300 MHz to 300 GHz. These circuits can be used for a variety of purposes, including communication, radar, sensing, and others. Microwave circuits are typically made up of a combination of passive and active components, such as inductors, capacitors, resistors, transistors, and others.3. Chapter 2 Questions and AnswersQuestion 2.1What is a transmission line?Answer:A transmission line is a structure used to transfer electromagnetic energy from one point to another. It consists of two or more conductors separated by a dielectric, such as r, plastic, or ceramic. Transmission lines are used for a variety of purposes, including signal transmission, power transmission, and impedance matching.Question 2.2What is the characteristic impedance of a transmission line?Answer:The characteristic impedance of a transmission line is the ratio of the voltage and current wave amplitudes on the line. It is a property of the line itself and is independent of the load and source impedances. The characteristic impedance is determined by the line’s geometry and dielectric properties and is typically given in units of ohms.Question 2.3What is a standing wave?Answer:A standing wave is a wave that appears to be standing still, rather than traveling. It is formed when two waves with the same frequency and amplitude traveling in opposite directions on a transmission line interfere with each other. The resulting wave pattern has regions of maximum and minimum amplitudes, which appear to be standing still.Question 2.4What is a Smith chart?Answer:A Smith chart is a graphical tool used to analyze and design transmission lines and other microwave circuits. It is a polar plot of the reflection coefficient (or impedance) of a load as a function of frequency. Smith charts can be used to determine the input impedance ofa transmission line, the reflection coefficient of a load, and other important properties of microwave circuits. They are also used for impedance matching and tuning.4. ConclusionThe questions and answers presented in this document are intended to help readers review and reinforce their understanding of the conceptsand principles presented in the third edition of Microwave Engineeringby David M. Pozar. They cover a range of topics related to microwave circuits and transmission lines, and provide an opportunity for readers to test their knowledge and evaluate their understanding of the material.。

微波辅助合成英语

微波辅助合成英语Microwave-Assisted SynthesisMicrowave-assisted synthesis, a revolutionary technique in the field of organic chemistry, has gained widespread recognition for its efficiency, versatility, and environmentally friendly nature. This powerful methodology has revolutionized the way chemists approach the synthesis of various organic compounds, offering significant advantages over traditional heating methods.At the core of microwave-assisted synthesis is the utilization of electromagnetic radiation in the microwave region of the electromagnetic spectrum. This radiation interacts directly with the reaction mixture, causing the molecules to vibrate and generate heat through molecular friction and dipole rotation. This targeted heating approach leads to a rapid and uniform rise in temperature, dramatically accelerating the reaction kinetics and often resulting in higher yields and increased selectivity compared to conventional heating methods.One of the primary benefits of microwave-assisted synthesis is the significant reduction in reaction times. Whereas traditional heatingmethods can take hours or even days to complete a reaction, microwave irradiation can often complete the same process in a matter of minutes or even seconds. This time-saving advantage is particularly valuable in the pharmaceutical and fine chemical industries, where rapid optimization and scale-up are crucial for efficient and cost-effective production.Another compelling aspect of microwave-assisted synthesis is its ability to promote the formation of novel and complex molecular structures. The intense and localized heating generated by microwaves can drive the formation of products that may be difficult to obtain through conventional heating methods. This unique property has been exploited in the synthesis of a wide range of organic compounds, including heterocyclic molecules, natural products, and pharmaceutically relevant compounds.Importantly, microwave-assisted synthesis also offers environmental benefits. By reducing reaction times and energy consumption, this technique contributes to a more sustainable and eco-friendly approach to chemical synthesis. Additionally, the precise control over reaction conditions and the ability to use smaller reaction volumes can lead to a significant reduction in waste production, further enhancing the green credentials of this method.The versatility of microwave-assisted synthesis is another keyadvantage. It can be applied to a diverse range of organic transformations, including esterifications, oxidations, reductions, cycloadditions, and cross-coupling reactions, among others. This versatility has led to its widespread adoption in both academic and industrial settings, where it has become an indispensable tool in the arsenal of modern organic chemists.Furthermore, the development of specialized microwave reactors and instrumentation has further expanded the capabilities of this technique. These advanced systems allow for the precise control of temperature, pressure, and irradiation power, enabling researchers to fine-tune reaction conditions and optimize the synthesis of target compounds.In the field of medicinal chemistry, microwave-assisted synthesis has played a crucial role in the rapid development and optimization of drug candidates. The ability to quickly screen and synthesize large numbers of compounds has accelerated the drug discovery process, leading to the identification of promising lead compounds and the efficient exploration of structure-activity relationships.Beyond organic synthesis, microwave-assisted techniques have also found applications in a variety of other scientific disciplines, such as materials science, analytical chemistry, and even biology. The versatility and efficiency of this approach have made it an invaluabletool for researchers working in diverse fields.In conclusion, microwave-assisted synthesis has emerged as a game-changing technique in the world of organic chemistry. Its ability to dramatically reduce reaction times, promote the formation of novel structures, and contribute to more sustainable and environmentally friendly practices has cemented its place as an indispensable tool in the modern chemical laboratory. As research and development in this field continue to progress, the impact of microwave-assisted synthesis is poised to grow even further, revolutionizing the way we approach the synthesis of complex organic compounds.。

百香果酸的提取工艺流程

百香果酸的提取工艺流程英文回答：Extraction Process of Passion Fruit Acid.Introduction.Passion fruit acid, also known as ascorbic acid, is a valuable nutrient found in various fruits and vegetables. It is a potent antioxidant that plays a crucial role in maintaining overall health and well-being. Due to its numerous health benefits, there is a growing demand for passion fruit acid as a natural ingredient in various industries, including food and beverage, cosmetics, and pharmaceuticals. To meet this demand, efficient and reliable extraction techniques are essential.Extraction Methods.There are several methods used for extracting passionfruit acid, each with its own advantages and disadvantages. The most common methods include:1. Solvent Extraction: This method involves using organic solvents, such as ethanol or methanol, to dissolve the passion fruit acid from the fruit matrix. The solvents are then evaporated, leaving behind the concentrated passion fruit acid extract.2. Supercritical Fluid Extraction (SFE): SFE utilizes compressed carbon dioxide as a solvent to extract the passion fruit acid under specific temperature and pressure conditions. This method offers advantages such as reduced environmental impact and improved extract purity.3. Microwave-Assisted Extraction (MAE): MAE employs microwave radiation to heat the passion fruit matrix, enhancing the extraction process. This method can significantly reduce extraction time and improve yield compared to conventional extraction techniques.4. Enzymatic Extraction: Enzymes are used to break downthe cell walls of the passion fruit, releasing the passion fruit acid. This method is often combined with other extraction techniques to improve efficiency.Process Flowchart.A typical extraction process of passion fruit acid involves the following steps:1. Preparation: The passion fruit is harvested and washed to remove impurities. The fruit is then crushed or blended to create a pulp.2. Extraction: The chosen extraction method is applied to the pulp to extract the passion fruit acid. The specific parameters, such as solvent type, temperature, and extraction time, vary depending on the method used.3. Filtration and Clarification: The extract isfiltered to remove any remaining solids or impurities. It may also undergo further clarification steps, such as centrifugation or membrane filtration, to improve purity.4. Concentration: The extract is concentrated to remove excess solvents or water, resulting in a more potent and stable extract.5. Standardization: The extract is standardized to ensure consistent quality and potency. This may involve adjusting the concentration of passion fruit acid or adding other stabilizers or excipients.Quality Control.Rigorous quality control measures are essential to ensure the safety and efficacy of the passion fruit acid extract. This includes testing for:Acidity: The pH value of the extract is measured to determine its acidity.Concentration: The content of passion fruit acid in the extract is quantified using analytical techniques.Impurities: The extract is tested for the presence of any harmful impurities, such as heavy metals or pesticides.Stability: The stability of the extract is evaluated under various storage conditions to ensure its shelf life and efficacy.Applications.Passion fruit acid has numerous applications across various industries:Food and Beverage: As an antioxidant and natural flavoring agent in juices, smoothies, and other food products.Cosmetics: As an anti-aging and skin brightening ingredient in skincare products.Pharmaceuticals: As a dietary supplement or ingredient in medicines for immune support and disease prevention.Conclusion.The extraction of passion fruit acid is a critical process for meeting the growing demand for this valuable nutrient. By utilizing efficient and reliable extraction techniques, high-quality passion fruit acid extracts can be obtained, ensuring the delivery of its numerous health benefits to consumers across various industries.中文回答：百香果酸提取工艺流程。

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Original Research PaperRole of microwave radiation in curing the ﬂy ashgeopolymerPrinya Chindaprasirt a ,Ubolluk Rattanasak b ,⇑,Sompop Taebuanhuad ba Sustainable Infrastructure Research and Development Center,Department of Civil Engineering,Faculty of Engineering,Khon Kaen University,Khon Kaen 40002,Thailand bDepartment of Chemistry and Center for Innovation in Chemistry,Faculty of Science,Burapha University,Chonburi 20131,Thailanda r t i c l e i n f o Article history:Received 14August 2012Received in revised form 19November 2012Accepted 27December 2012Available online 10January 2013Keywords:GeopolymerMicrowave radiation MicrostructureCompressive strengtha b s t r a c tFly ash geopolymer requires rather long heat curing to obtain reasonable strength development at an early age.However,the long heat curing period limits the application of the ﬂy ash geopolymer.High strength development and a reduction in heat curing duration have been considered for energy saving.Therefore,this research proposed a process using 90-W microwave radiation for 5min followed by con-ventional heat curing for high-calcium ﬂy ash geopolymer.Results showed that the compressive strengths of geopolymer with microwave radiation followed by conventional heat curing were compara-ble to those of the control cured at 65°C for 24h.Microwave radiation gave the enhanced densiﬁcation.In addition,SEM images showed that the gels formed on the ﬂy ash particles owing to the promoted dis-solution of amorphous phases from ﬂy ash.This method accelerated the geopolymerization and gave the high compressive strength comparable to the conventional curing.Ó2012The Society of Powder Technology Japan.Published by Elsevier B.V.and The Society of PowderTechnology Japan.All rights reserved.1.IntroductionCoal-ﬁred power plants currently produce 40%of the global electricity for households and industries.Besides generating power energy,coal wastes,i.e.ﬂy ash and bottom ash are obtained and utilized related to the environmental aspect [1,2].In addition to the use of ﬂy ash to partially replace Portland cement,the high content ﬂy ash usage has been introduced and termed ‘‘geopoly-mer’’which is a low heat cured alumino-silicate material [3].Ow-ing to the endothermic reaction,heat curing at 65°C was employed in order to gain high early strength of lignite ﬂy ash geopolymers with good physical and mechanical properties [4,5].However,the 24-h or longer heat curing periods limit the application of geo-polymer.Although the room temperature curing has been consid-ered for energy saving,the prolonged curing duration was required to obtain reasonable strength for lignite ﬂy ash geopolymer [6].Heat curing has been applied to construction materials espe-cially for the precast concrete to improve the strength develop-ment process.This concrete attains sufﬁcient strength in short curing time,so the moulds can be reused,and the ﬁnal products can be rapidly delivered to the site [7].For the conventional heat-ing technique,heat is distributed in the specimen from the exterior to the interior leading to the non-uniform and long heating period to attain the required temperature.In contrast,the microwave technique allows a uniform and fast heating due to the interaction between the polar molecules and microwave electric ﬁelds [7–11].Application of microwave to the fresh concrete results in removal of water,collapse of capillary pore and densiﬁcation of sample.However,microwave radiation is mostly used in concrete curing and the radiation period is usually long (more than 1h with high wattage)[7,8].This could limit the use of microwave curing due to the energy cost.Therefore,this research proposed the process to reduce the microwave curing duration and energy using the short-time micro-wave radiation in addition to the convention heat curing for the ﬂy ash geopolymer.Microwave radiation could play the role in the geopolymer formation and strength enhancement.Additionally,this method could shorten the curing time of geopolymer,acceler-ate the geopolymerization and give the high compressive strength at an early age compared to the conventional curing.2.Experimental procedure 2.1.MaterialsCoal ﬂy ash from Mae Moh power plant in the north of Thailand was used as raw material.This ﬂy ash was generated from the pul-verized coal combustion process (1200°C)using lignite coal as the feed.The properties of this ﬂy ash are tabulated in Table 1.In addi-tion to Al 2O 3and SiO 2,this ﬂy ash had high contents of CaO and magnetite (Fe 3O 4).Sodium hydroxide pellet (NaOH)dissolved in the deionized water to obtain 10M NaOH solution,and sodium sil-icate solution (Na 2SiO 3)with SiO 2:Na 2O mass ratio of 3.2was also used.The viscosities of 10M NaOH and Na 2SiO 3were 9.3,and 60.6cps (centipoises),respectively.The graded river sand with ﬁneness0921-8831/$-see front matter Ó2012The Society of Powder Technology Japan.Published by Elsevier B.V.and The Society of Powder Technology Japan.All rights reserved./10.1016/j.apt.2012.12.005Corresponding author.Tel.:+6638103066;fax:+6638393494.E-mail address:ubolluk@buu.ac.th (U.Rattanasak).modulus of2.8and speciﬁc gravity of2.65was employed to pre-pare the mortar specimen for strength test.2.2.Geopolymer preparationTo prepare the liquor,10M NaOH and Na2SiO3were mixed in a container with the Na2SiO3/NaOH mass ratio of1.5.The liquor was then added to theﬂy ash in a pan mixer and the paste was thor-oughly mixed.Theﬂy ash-to-liquor mass ratio of 1.86(ﬂy ash=65wt%and liquor=35wt%).The paste was continuously mixed for5min and then cast into50-mm cubic acrylic mould (1-cm thickness).The paste specimens were vibrated for10s and covered with clingﬁlm to avoid the moisture evaporation during the heat curing.For geopolymer mortar preparation,sand was added to the paste mixture with the sand-to-ﬂy ash mass ratio of1.5and mixed for another2min.The mixture was then cast into50-mm cubic ac-rylic mould.The curing condition was the same as for the paste pressive strength test was performed on the geo-polymer mortars.2.3.Microwave and conventional curing temperature proﬁleIn this study,the2.45-GHz household microwave and the con-ventional oven were employed.Owing to preliminary results,90-and180-W microwave power levels were applied on the geopoly-mer mortars for3,5and10min to obtain the temperature proﬁle at the middle of the samples.Higher wattage resulted in rapid evaporation in short time,heat evolution and cracks on the surface of specimens.Result is reported as an average ofﬁve samples.In addition,the effect of microwave and conventional curing on the compressive strength of geopolymer mortar was evaluated.90-W microwave curing for5min was selected in addition to the con-vention heat curing at65°C for3,6and12h.After heat curing, specimens were cooled down and cured continuously at25°C. The compressive strength was tested at the age of7days.The re-ported results were the averages ofﬁve samples.Table2shows the curing conditions.Curing at65°C for24h(system1)was the control.2.4.XRD,SEM and degree of reactionGeopolymer paste was prepared for the testing of XRD,SEM and degree of reaction.90-W microwave radiation for5min in addition to the conventional heat curing at65°C for3,6and12h was used. XRD and SEM analyses were performed on the hardened samples. In addition,degree of reaction was determined both on geopoly-mer paste andﬂy ash by identiﬁcation of unreactedﬂy ash in spec-imen using the dissolution of the powdery sample in2M HCl and 5wt%Na2CO3[12–14].The hardened geopolymer pastes were ground to obtain particles that passed a150-l m sieve.A100-mL beakerﬁlled with powdered samples(5g)and2M HCl(30mL) was placed in a60°C water bath and stirred for20min to acceler-ate the dissolution.Solid phase was thenﬁltered using a vacuum ﬁlter.The remaining solid was washed with warm water thrice to completely remove HCl.Acetone was applied in the lastﬁltra-tion to remove water before drying at70°C for2h.Degree of reac-tion was calculated using Eq.(1).The degree of reaction of theﬂy ash particles was also determined and assigned as‘‘blank.’’All the results were subtracted with blank to obtain the corrected de-gree of reaction.The reported results were the averages of three samples.Degree of reaction¼m sampleÀm residuem sampleÂ100ð1Þwhere m sample is the weight of powdery sample(g)and m residue is the weight of dried residue(g).3.Results and discussion3.1.Temperature proﬁle of microwave curingThe temperature proﬁles of the50-mm cube geopolymer mor-tar are reported in Fig.1.Application of90-and180-W microwave power levels generated high temperature in the specimen in a short period of time.At5min microwave radiation,90-and180-W gave slightly different temperatures.For10-min microwave radiation,the temperature difference was noticeable.Increase in the microwave radiation time led to high temperature,however, longer radiation time and increase in wattage resulted in rapid evaporation,high heat evolution and sequential cracks on the sur-face of specimens owing to the energy beyond the requirement for water removal in materials[15].For this reason,90-W microwave radiation for5min was selected for further study.3.2.Effect of microwave and conventional curing on the compressive strengthTo study the effect of curing conditions on the properties of geo-polymer mortars,the compressive strength was primarily focused in this section.Table3presents the strengths of the specimensTable1Properties ofﬂy ash.Chemical composition(wt%)SiO239.2Al2O319.7CaO16.9Fe3O412.1SO3 2.8Others9.3Median particle size(l m)19.0Table2Curing conditions of geopolymer.System Curing conditions Note165°C oven curing for1,3,6,12and24h65°C oven curing265°C oven curing for1,3,6,12and24h?90W MW curing for3min65°C oven curing before MW radiation 390W MW curing for3min MW radiation only490W MW curing for5min MW radiation only590W MW curing for10min MW radiation only690W MW curing for3min?65°C oven curing for1,3,6,12and24h MW radiation before65°C oven curing 790W MW curing for5min?65°C oven curing for1,3,6and12h MW radiation before65°C oven curing 890W MW curing for10min?65°C oven curing for1,3,6and12h MW radiation before65°C oven curing 925°C curing for7and28days(room temp.,RT)No heat curing704P.Chindaprasirt et al./Advanced Powder Technology24(2013)703–707cured with microwave radiation,heat curing and room tempera-ture curing.Curing at65°C for24h(system1)was the control and the strength result of this condition was compared to the oth-ers.The control had the compressive strength of32.7MPa.The strength of system2with the same heat curing time was similar at32.4MPa.From this result,it could be noted that the additional microwave radiation after the normal heat curing did not improve the strength of geopolymer.This was due to the complete geopoly-merization after the optimum duration of heat curing.With no heat curing or room temperature curing(system9),the specimens gained the strength with age and the strengths at7and28days were20.0and35.8MPa respectively.Without heat curing,the strength development of theﬂy ash geopolymer mortar was extre-mely slow.The heat curing contributed to the strength of geopoly-mer at the early age.However,the use of only microwave radiations for3–10min(systems3–5)gave the samples with strength up to28–50%of the control strength.The use of microwave radiation followed by conventional heat curing provided the high strength gain of geopolymer as shown in systems6–8.The optimum time of microwave radiation short-ened the required time of conventional heat curing.For3min of 90-W radiation,the additional heating of12h slightly increased the strength of the geopolymer mortar to29.0MPa compared to 21.2MPa of that with6-h heat curing alone.To obtain the strength of over32.7MPa(control),the additional heat curing time of24h was still required owing to the low accelerated temperature of the microwave radiation(3min of90-W).However,for the microwave radiation of5–10min,only6-h additional heat curing was needed to obtain the strength equiva-lent to the control.Extension of radiation time to more than 10min could increase the accelerated temperature beyond65°C and risked getting close to the boiling temperature of water.This resulted in rapid water evaporation,high pressure and subsequent cracks in sample.The results of bulk densities of the geopolymer mortar(systems 6–8)are presented in Fig.2.The microwave radiation enhanced the densiﬁcation compared with those entirely cured with conven-tional heat curing.This result implied that the microwave radiation overcame the activation energy of geopolymerization.The micro-wave effect,in the presence of an external electricﬁeld,resulted in the densiﬁcation of the matrices.In contrast to the conventional heating,the preferential interaction of the microwaves gave lower porosity leading to the accelerated densiﬁcation[16].High com-pressive strengths of the samples were,thus,achieved.3.3.XRD patterns of microwave radiation cured geopolymersFig.3shows the X-ray diffraction(XRD)patterns of geopolymer pastes under microwave radiation followed by the conventional heat curing for3,6and12h.The results of originalﬂy ash and the24-h heat cured sample(control)are also presented.Numerous peaks of crystalline quartz(SiO2),calcium sulfate(CaSO4)and cal-cium oxide(CaO)of this high calciumﬂy ash were identiﬁed.In addition,the XRD pattern ofﬂy ash showed many sharp peaks ow-ing to the crystalline phases in the sample.For geopolymer pastes,the product was semi-crystalline with a high amount of amorphous gel as indicated by the broad hump and some sharp peaks of crystallinity.The broad hump of these pastes appeared at22–38°,indicating the highly disorder silicate glass phase in geopolymer[17].The calcium silicate compounds from the reaction between high calciumﬂy ash,silica and silicate solu-tion were also detected.In addition,samples with microwave radi-ation exhibited the sharp peaks of crystalline phases with high degree of amorphous phase of the semi-crystalline geopolymer.3510Microwave curing time (min)90 WattFig.1.Temperature proﬁle of geopolymer mortar.Table3Compressive strengths of geopolymer mortars at various curing conditions.System Curingconditions Compressive strength(MPa)Additional curing time in65°CovenRT1h3h6h12h24h7d28d165°C13.015.722.221.232.7a265°C?90W(3min)9.916.625.223.932.4390W(3min)9.4490W(5min)16.2590W(10min)17.4690W(3min)?65°C12.917.421.229.033.8–790W(5min)?65°C21.929.235.542.5890W(10min)?65°C20.027.434.641.4925°C(RT)20.035.8 Bolditalic values=strengths equal to or higher than that of the control.a Comparative strength (control).3612 Additional heat curing (hr)of geopolymer mortars90W microwaveP.Chindaprasirt et al./Advanced Powder Technology24(2013)703–707705706P.Chindaprasirt et al./Advanced Powder Technology24(2013)703–707Microstructure of geopolymer pastes with microwave radiation and additional65°C heat curing;(a)3h,(b)6h,(c)12h,dissolution of glassy phase in the alkaline solution.Higher densiﬁ-cation of matrices compared with those cured in the electric oven could be obtained.Additional heat curing provided the additional reaction products.Therefore,the early-stage microwave radiation followed by the conventional heating effectively enhanced the geo-polymerization.The main advantages are the reduction in curing time and energy and hence the associated reduced cost.3.5.Degree of reactionThe degrees of reaction of geopolymer pastes with microwave radiation are presented in Fig.5.With partial microwave radiation and heat curing for3,6,and12h,the degrees of reaction were 11.9%,13.9%and17.9%,respectively compared to18.6%degree of reaction of the control.The control with entire24-h heat curing had similar degree of reaction to that with microwave radiation and12-h conventional curing.The results suggested that the time for normal curing could be reduced by half using the radiation.The results conformed to the results of the SEM and the strengths. 4.ConclusionsMicrowave radiation effectively enhanced the geopolymeriza-tion and compressive strength ofﬂy ah geopolymer.The micro-wave radiation followed by conventional heat curing reduced the heat curing time and energy.The90-W microwave radiation for 5min followed by6-h at65°C additional heat curing produced geopolymer mortar with strength comparable to that of the control (24-h at65°C).The microwave radiation resulted in the densiﬁca-tion of the matrices and increase in the bulk density of the samples. 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