Adapting the overlap-add method to the synthesis of noise
银饰制作工艺作文英语
银饰制作工艺作文英语Title: The Craftsmanship of Silver Jewelry Making。
Silver jewelry making is an art form that has been practiced for centuries, blending tradition with innovation to create timeless pieces of adornment. From ancient civilizations to modern artisans, the craft of shaping silver into intricate designs has captivated the imagination and delighted the senses. In this essay, we delve into the fascinating world of silver jewelry making, exploring its techniques, history, and significance.First and foremost, the craftsmanship of silver jewelry making requires skill, patience, and precision. Artisans employ various techniques to manipulate silver into desired shapes and forms. One of the primary methods is casting, where molten silver is poured into molds to createintricate patterns and designs. This process allows for the production of multiple identical pieces with intricate details.Another commonly used technique is fabrication, which involves shaping silver using tools such as hammers, files, and saws. This method allows artisans to create unique,one-of-a-kind pieces that showcase their creativity and craftsmanship. Additionally, techniques like soldering and engraving are often employed to add embellishments and personalization to the jewelry.Beyond technical proficiency, silver jewelry making is steeped in history and cultural significance. Throughout the ages, silver has been prized for its lustrous beauty and versatility. In many cultures, silver jewelry holds symbolic meaning, representing wealth, status, or spiritual beliefs. For example, in ancient Egypt, silver was associated with the moon and believed to possess protective powers. Similarly, in Hindu culture, silver jewelry is often worn during religious ceremonies and celebrations.Furthermore, silver jewelry making has evolved over time, adapting to changes in fashion, technology, and societal norms. While traditional craftsmanship techniquesare still valued and practiced, contemporary artisans are also exploring innovative methods such as 3D printing and computer-aided design (CAD). These advancements have expanded the possibilities of silver jewelry design, allowing artisans to push the boundaries of creativity and expression.In addition to its aesthetic appeal, silver jewelry holds practical value as well. Silver is a durable and hypoallergenic metal, making it suitable for everyday wear. Unlike other metals, such as nickel or brass, silver is less likely to cause skin irritation or allergic reactions, making it an ideal choice for people with sensitive skin.Moreover, silver jewelry making plays a significantrole in the global economy, providing employment opportunities for artisans and supporting local economies. In regions where silver mining is prevalent, such as Mexico and Peru, jewelry making serves as a vital source of income for communities. Artisanal silver jewelry is also highly sought after in the international market, contributing to the growth of the global jewelry industry.In conclusion, silver jewelry making is a time-honored craft that combines technical skill with artistic expression. From ancient civilizations to modern-day artisans, the allure of silver jewelry continues to captivate people around the world. Whether through traditional techniques or innovative methods, the craftsmanship of silver jewelry making reflects the rich tapestry of human creativity and cultural heritage.。
自考英语二的单词和考研英语二的单词重复 -回复
自考英语二的单词和考研英语二的单词重复-回复全文共3篇示例，供读者参考篇1Overlapping Vocabulary: The Shared Lexical Terrain ofSelf-Study and Grad School English ExamsAs a diligent student striving to conquer the linguistic frontiers that await, I find myself traversing a rugged lexical landscape fraught with challenges – one where the paths of self-study and graduate school admissions exams intertwine in an intricate dance of overlapping vocabulary. This phenomenon, a linguistic Venn diagram of sorts, is a subject worthy of closer examination, for it holds the potential to streamline one's journey through the vast expanse of the English language.At the core of this exploration lies the realization that the self-taught English Test Level 2 (henceforth referred to as SET-2) and the Graduate School English Test Level 2 (hereafter abbreviated as GSET-2) share a significant portion of their respective word lists. This intersection, a lexical common ground, presents both opportunities and challenges for the intrepid learner.On the one hand, the existence of this shared vocabulary can be seen as a boon, a literal gift from the linguistic gods. By mastering the words that grace both examinations, one effectively kills two birds with one stone, so to speak. The time and effort invested in committing these terms to memory yield dividends in the form of enhanced performance on not just one, but two pivotal assessments. It is akin to embarking on a hike and discovering that a single trail leads to multiple breathtaking vistas.However, this linguistic overlap also presents a potential pitfall, a treacherous crevasse that must be navigated with care. The risk lies in the false assumption that familiarity with a word in one context automatically translates to mastery in another. Words, much like chameleons, can take on subtle shades of meaning depending on the context in which they are employed.A term that may seem innocuous in the realm of self-study could harbor nuanced complexities when encountered in the crucible of graduate-level discourse.It is therefore imperative that the diligent student approach this shared lexical territory with a discerning eye and an open mind. One must be willing to peel back the layers of each word, to explore its various connotations and applications, lest theyfind themselves ensnared in a web of linguistic misunderstanding.To illustrate this point, let us consider the seemingly innocuous term "hypothesis." In the context of the SET-2, this word may be presented as a simple proposition or educated guess, a stepping stone on the path to scientific inquiry. However, in the rarefied air of graduate-level academia, the notion of a hypothesis takes on a far more nuanced and sophisticated form. It becomes a carefully constructed theoretical framework, a lens through which entire bodies of research are viewed and interpreted. Failing to grasp this subtle distinction could lead to a fundamental misunderstanding of the very foundations upon which academic discourse is built.Thus, the wise student must approach the shared vocabulary of these two examinations with a balanced perspective. On one hand, they should embrace the efficiency and convenience afforded by this lexical overlap, recognizing the opportunity to streamline their studies and make the most of their efforts. On the other, they must remain vigilant, ever mindful of the potential for linguistic nuance and the need to adapt their understanding of words to the specific context in which they are encountered.In this regard, the journey through the shared lexical terrain of the SET-2 and GSET-2 becomes a metaphorical trek through a dense linguistic forest. The path may be well-trodden, but it is far from straightforward. It is a journey that demands patience, perseverance, and a willingness to delve deeper into the rich tapestry of language that surrounds us.As one navigates this intricate lexical landscape, it is essential to cultivate a spirit of curiosity and a thirst for knowledge. Each new word encountered should be treated not merely as a hurdle to be surmounted, but as an opportunity for intellectual growth and linguistic enrichment. By embracing this mindset, the diligent student transforms their studies from a mere exercise in memorization into a voyage of discovery, where the true depths and nuances of language are gradually unveiled.Moreover, it is imperative to recognize that language is a living, breathing entity, ever-evolving and adapting to the changing currents of human thought and expression. The words that grace the pages of today's examinations may take on new meanings or fall into disuse by the time tomorrow's assessments are conceived. As such, the journey through the shared lexical terrain must be viewed not as a finite destination, but as a continuous process of exploration and adaptation.In this light, the overlapping vocabulary of the SET-2 and GSET-2 becomes more than just a practical consideration; it becomes a microcosm of the broader linguistic landscape, a microcosmic representation of the rich tapestry that is the English language. By navigating this terrain with care and dedication, the diligent student not only prepares themselves for success on these specific examinations, but also cultivates the linguistic dexterity and adaptability that will serve them well in countless future endeavors.As I reflect upon this lexical odyssey, I am reminded of the words of the great linguist and philosopher Ludwig Wittgenstein, who once stated, "The limits of my language mean the limits of my world." In embracing the shared vocabulary of the SET-2 and GSET-2, we transcend those limits, expanding our linguistic horizons and opening ourselves to a world of possibilities that lie beyond the confines of any single examination.So, let us forge ahead, my fellow linguistic explorers, with a sense of wonder and a thirst for knowledge that knows no bounds. Let us navigate the shared lexical terrain with equal parts diligence and curiosity, ever mindful of the nuances that lurk beneath the surface of each word we encounter. For in doing so, we not only increase our chances of success on these pivotalassessments, but we also embark on a journey of personal growth and linguistic enrichment that will serve us well long after the echoes of these examinations have faded into the annals of memory.篇2The Road Less Traveled: Navigating the Vocabulary LabyrinthAs students, we often find ourselves knee-deep in anever-ending sea of academic challenges, each one more daunting than the last. Among these trials, the conquest of English vocabulary stands as a formidable foe, its tentacles reaching far and wide across various realms of study. For those of us treading the path of self-taught English proficiency and aspiring to conquer the hallowed grounds of graduate school, the overlap between these two domains can be both a blessing and a curse.The notion of overlapping vocabulary might initially seem like a godsend, a lifeline amidst the chaos of memorization and comprehension. After all, what could be more reassuring than recognizing familiar words across multiple contexts? It's akin tostumbling upon an oasis in the desert, a momentary respite from the relentless pursuit of linguistic mastery.However, as with most things in academia, the reality is far more nuanced. While the shared lexicon between self-taught English and the graduate school entrance exam may appear to be a shortcut, it is a path riddled with pitfalls and potential misunderstandings. It's a treacherous maze where a single misstep can lead to disastrous consequences, akin to a hapless adventurer stumbling into a labyrinth without a trusty ball of thread.The crux of the matter lies in the subtle variations that words can take on in different contexts. A word that holds a particular meaning in the realm of self-taught English might undergo a metamorphosis, donning a new guise when encountered in the rarefied atmosphere of graduate-level examinations. It's a linguistic shapeshifter, a chameleon that adapts to its surroundings, leaving unsuspecting students bewildered and disoriented.Take, for instance, the unassuming word "critical." In the realm of self-taught English, it might evoke notions of importance, significance, or even a dire situation. However, in the hallowed halls of graduate-level discourse, "critical" takes on adifferent hue, often implying a more analytical or evaluative stance. A student who fails to grasp this subtle distinction might find themselves adrift, their comprehension hindered by the very words they thought they knew.The perils don't end there, for the overlap between vocabularies can breed a false sense of security, a dangerous complacency that lulls students into a state of overconfidence. It's akin to a hiker believing they've mastered the trail, only to find themselves lost in the wilderness, their map rendered useless by unexpected detours and treacherous terrain.Yet, despite these obstacles, there is a glimmer of hope, a beacon that guides us through the linguistic labyrinth. It lies in the cultivation of a critical mindset, a willingness to question assumptions and embrace the nuances that words can harbor. By approaching each word with a healthy dose of skepticism and an eagerness to unravel its multifaceted nature, we can navigate the treacherous waters of vocabulary overlap with greater ease.It is a journey of constant learning, a perpetual odyssey where every word is a potential ally or adversary, depending on our ability to wield it with precision. We must become linguistic chameleons ourselves, adapting our understanding to theever-changing landscape of academic discourse, shedding preconceptions like a snake sheds its skin.In this odyssey, collaboration becomes our compass, our guiding light. By engaging in discourse with peers, mentors, and scholars, we can illuminate the nuances that words conceal, uncovering their hidden depths and complexities. It is a collective endeavor, a symphony of perspectives that harmonize to create a richer, more nuanced understanding of the vocabulary we wield.Moreover, we must embrace the power of context, for words are not mere vessels of meaning; they are living, breathing entities that draw sustenance fromtheir surroundings. A word's true essence can only be understood when viewed through the lens of its context, be it academic, cultural, or historical. To neglect this vital aspect is to risk misinterpreting the very language we seek to master.As we navigate the labyrinth of overlapping vocabularies, it is imperative that we cultivate a growth mindset, an unwavering belief in our ability to adapt and evolve. For just as words can shape-shift, so too must we, shedding our preconceptions and embracing the ever-changing landscape of language with open arms.The road ahead is arduous, fraught with challenges and pitfalls that would test the mettle of even the most seasoned linguist. Yet, it is a journey worth undertaking, for within the tangled web of words lies a treasure trove of knowledge, a gateway to intellectual enlightenment and personal growth.So, let us embrace the challenge, fellow travelers. Let us don our linguistic armor and venture forth into the unknown, armed with a critical mind, a collaborative spirit, and an unwavering determination to conquer the vocabulary labyrinth. For in doing so, we not only unlock the doors to academic excellence but also forge a path towards a deeper understanding of ourselves and the world around us.篇3Sure, here's an essay of around 2000 words, written from a student's perspective, discussing the overlap between vocabulary words in self-taught English Level 2 exams and postgraduate English Level 2 exams, in English:English Level 2: Navigating the Vocabulary OverlapAs a diligent student striving to conquer the realms of higher education, I've found myself entangled in the intricate web of English language proficiency examinations. Specifically, I've beengrappling with the daunting task of mastering the vocabulary required for both the self-taught English Level 2 and the postgraduate English Level 2 exams. While these two assessments may seem worlds apart, a closer inspection reveals a surprising overlap in their respective word lists.The journey began with my preparation for the self-taught English Level 2 exam, a rite of passage for those seeking academic advancement through unconventional routes. As I delved into the vast repository of vocabulary, I encountered words that seemed to transcend the boundaries of mere lexical knowledge. Words like "candid," "empirical," and "pragmatic" not only adorned the pages of my study materials but also resonated with the very essence of academic discourse.Little did I know that this initial foray into the depths of English vocabulary would pave the way for my subsequent encounter with the postgraduate English Level 2 exam. As I embarked on this new endeavor, the familiarity of certain words struck me like a comforting embrace amidst the sea of unfamiliar terms. Words like "paradigm," "dichotomy," and "ubiquitous" appeared to be old friends, their meanings etched into my memory from previous encounters.This realization ignited a newfound sense of confidence within me, as I recognized the value of the foundational knowledge I had acquired. It became evident that the mastery of these shared words not only facilitated a smoother transition between the two exams but also fostered a deeper understanding of the nuances that permeate academic discourse.However, the overlap extended beyond mere word recognition; it also encompassed the intricate web of relationships that words weave with one another. Phrases like "inextricably linked," "juxtaposed against," and "paradigm shift" revealed themselves as recurring patterns, stitching together the fabrics of both examinations. This realization underscored the importance of not merely memorizing isolated words but also grasping their contextual usage and interrelationships.As I navigated through the intricacies of these shared vocabularies, I couldn't help but marvel at the profound impact they had on my intellectual growth. Words like "epistemology," "seminal," and "discourse" introduced me to the realms of philosophy, academia, and critical thinking, broadening my horizons and challenging me to think beyond the confines of mere definitions.Moreover, the overlap in vocabulary served as a testament to the universality of academic discourse. It became evident that certain words and phrases transcended disciplinary boundaries, functioning as linguistic threads that wove together the tapestry of knowledge. Words like "dialectic," "synthesis," and "discourse analysis" found their way into diverse fields, from literature to sociology, from psychology to political science.This realization instilled in me a deeper appreciation for the interconnectedness of knowledge and the power of language to bridge divides. It reinforced the notion that true mastery of a subject extends beyond its narrow confines and necessitates an understanding of the broader intellectual landscape.As I continue to navigate the labyrinth of academic pursuits, the overlap between the vocabulary of the self-taught English Level 2 and the postgraduate English Level 2 exams serves as a reminder of the incremental nature of learning. Each word, each phrase, builds upon the foundations laid by previous encounters, creating a tapestry of knowledge that grows richer and more intricate with every new experience.In retrospect, the journey through these shared vocabularies has been nothing short of transformative. It has instilled in me a heightened sense of resilience, enabling me to approach newchallenges with the confidence born of familiarity. It has fostered a deeper appreciation for the interconnectivity of knowledge and the power of language to bridge intellectual divides.As I look ahead, I carry with me the invaluable lessons gleaned from this experience, ready to embrace the next phase of my academic odyssey. For within the confines of these shared words lies a world of possibilities, a gateway to unprecedented intellectual growth and a testament to the enduring power of language to shape our understanding of the world around us.。
诱导契合 变构调节
诱导契合变构调节英文回答：Inducing rapport and adjusting to the conversation partner's speech style are two important aspects of effective communication. When it comes to inducing rapport, it means creating a sense of connection and harmony with the other person. This can be achieved through various means such as mirroring body language, using similar vocabulary and tone of voice, and showing genuine interest in the other person's thoughts and feelings.For example, if I am speaking to someone who speaks in a more formal and polite manner, I would adjust my speech style to match theirs. I would use formal language, avoid slang or informal expressions, and maintain a respectful tone. This helps to establish a sense of mutual understanding and respect between us.On the other hand, if I am speaking to someone who ismore casual and uses a lot of slang, I would adapt my speech style accordingly. I might use more informal language, incorporate some slang expressions, and adopt a more relaxed tone. This helps to create a sense of camaraderie and makes the conversation more enjoyable for both parties.In addition to inducing rapport, adjusting to the conversation partner's speech style is also important. This means adapting one's language and communication style to match the other person's preferences. For example, if I am speaking to someone who speaks English as a second language and may struggle with complex vocabulary or grammar, I would try to simplify my language and use more common words and phrases. This helps to ensure that the other person can understand and follow the conversation more easily.Similarly, if I am speaking to someone who is very knowledgeable in a specific field, I would adjust my language to include more technical terms and jargon that they are familiar with. This shows that I respect their expertise and helps to establish a sense of credibility andtrust.Overall, inducing rapport and adjusting to the conversation partner's speech style are essential skillsfor effective communication. By creating a sense of connection and adapting to the other person's preferences, we can enhance understanding, build relationships, and make the conversation more enjoyable for everyone involved.中文回答：诱导契合和变构调节是有效沟通的两个重要方面。
无线网络
ABSTRACT
• We consider the problem of efficient MAC design for long-distance Wi-Fi-based mesh networks. Prior work has shown that these characteristics make traditional CSMA-based MACs a poor choice for long-distance mesh networks, prompting several recent research efforts exploring the use of TDMA-based approaches to media access. In this paper, we present JazzyMac, a simple, practical and efficient MAC protocol that addresses the above limitations. JazzyMac achieves efficiency by enabling variable-length link transmissions slots; each node can adapt the length of their transmission slots in accordance with changing traffic demands.
• 2.1 Using SynOp to avoid interference • 2.2 MAC protocols forWiLD links
2.1 Using SynOp to avoid interference
温度反演经典文章
(This is a sample cover image for this issue.The actual cover is not yet available at this time.)This article appeared in a journal published by Elsevier.The attached copy is furnished to the author for internal non-commercial research and education use,including for instruction at the authors institutionand sharing with colleagues.Other uses,including reproduction and distribution,or selling or licensing copies,or posting to personal,institutional or third partywebsites are prohibited.In most cases authors are permitted to post their version of thearticle(e.g.in Word or Tex form)to their personal website orinstitutional repository.Authors requiring further informationregarding Elsevier’s archiving and manuscript policies areencouraged to visit:/copyrightReviewSatellite-derived land surface temperature:Current status and perspectivesZhao-Liang Li a ,b ,⁎,Bo-Hui Tang a ,Hua Wu a ,Huazhong Ren c ,Guangjian Yan c ,Zhengming Wan d ,Isabel F.Trigo e ,f ,JoséA.Sobrino gaState Key Laboratory of Resources and Environmental Information System,Institute of Geographic Sciences and Natural Resources Research,Beijing 100101,China bLSIIT,UdS,CNRS,Boulevard Sebastien Brant,BP10413,67412Illkirch,France cState Key Laboratory of Remote Sensing Sciences,School of Geography,Beijing Normal University,Beijing 100875,China dERI,University of California,Santa Barbara,CA 93106,USA eInstituto Português do Mar e da Atmosfera,Lisbon,Portugal fInstituto Dom Luiz,University of Lisbon,Portugal gImage Processing Laboratory,University of Valencia,Valencia 46071,Spaina b s t r a c ta r t i c l e i n f o Article history:Received 24May 2012Received in revised form 19October 2012Accepted 11December 2012Available online xxxx Keywords:Land surface temperature Land surface emissivity RetrievalThermal infraredLand surface temperature (LST)is one of the key parameters in the physics of land surface processes from local through global scales.The importance of LST is being increasingly recognized and there is a strong interest in de-veloping methodologies to measure LST from space.However,retrieving LST is still a challenging task since the LST retrieval problem is ill-posed.This paper reviews the current status of selected remote sensing algorithms for estimating LST from thermal infrared (TIR)data.A brief theoretical background of the subject is presented along with a survey of the algorithms employed for obtaining LST from space-based TIR measurements.The discussion focuses on TIR data acquired from polar-orbiting satellites because of their widespread use,global applicability and higher spatial resolution compared to geostationary satellites.The theoretical framework and methodolo-gies used to derive the LST from the data are reviewed followed by the methodologies for validating satellite-derived LST.Directions for future research to improve the accuracy of satellite-derived LST are then suggested.©2012Elsevier Inc.All rights reserved.Contents 1.Introduction ...............................................................152.Basic theoretical background .......................................................152.1.Radiative transfer equation .....................................................162.2.Dif ficulties and problems in the retrieval of LST from space measurements ..............................173.Estimation of LST from space .......................................................183.1.LST retrieval with known LSEs ...................................................183.1.1.Single-channel method ..................................................183.1.2.Multi-channel method ..................................................193.1.3.Multi-angle method ....................................................213.2.LST retrieval with unknown LSEs ..................................................223.2.1.Stepwise retrieval methods ................................................223.2.2.Simultaneous LST and LSE retrieval methods with known atmospheric information ......................233.2.3.Simultaneous retrieval of LST,LSEs,and atmospheric pro files ..........parison and analysis of different methods ............................................264.Validation of satellite derived LST .....................................................294.1.Temperature-based method (T-based)...............................................294.2.Radiance-based method (R-based).................................................294.3.Cross validation method ................................ (30)Remote Sensing of Environment 131(2013)14–37⁎Corresponding author at:LSIIT,UdS,CNRS,Boulevard Sebastien Brant,BP10413,67412Illkirch,France.Tel.:+33368854516.E-mail address:lizl@ (Z.-L.Li).0034-4257/$–see front matter ©2012Elsevier Inc.All rights reserved./10.1016/j.rse.2012.12.008Contents lists available at SciVerse ScienceDirectRemote Sensing of Environmentj o u r n a l h om e p a g e :ww w.e l s e v i e r.c o m /l o c a t e /r s e5.Future development and perspectives (30)5.1.Methodology to simultaneously derive LST,LSE,and atmospheric profiles(atmospheric quantities)from hyperspectral TIR data (30)5.2.Methodology to simultaneously derive LST and LSE from the new generation of geostationary satellites with multispectral andmulti-temporal data (31)5.3.Refinement of LST retrieval algorithms with the consideration of aerosol and cirrus effects (31)5.4.Retrieval of component temperatures in heterogeneous pixels (31)5.5.Methodology for retrieving LST from passive microwave data and for combining LSTs retrieved from TIR and passive microwave data..315.6.Methodology for angular normalization of LST (32)5.7.Methodology for temporal(time)normalization of LST (32)5.8.Concerns on the newly developed Hyperspectral Infrared Imager (32)5.9.Physical meaning of satellite-derived LST and its applications (33)5.10.Validation of satellite-derived LST (33)Acknowledgments (33)References (33)1.IntroductionAs the direct driving force in the exchange of long-wave radiation and turbulent heatfluxes at the surface–atmosphere interface,land sur-face temperature(LST)is one of the most important parameters in the physical processes of surface energy and water balance at local through global scales(Anderson et al.,2008;Brunsell&Gillies,2003;Karnieli et al.,2010;Kustas&Anderson,2009;Zhang et al.,2008).Knowledge of the LST provides information on the temporal and spatial variations of the surface equilibrium state and is of fundamental importance in many applications(Kerr et al.,2000).As such,the LST is widely used in a variety offields including evapotranspiration,climate change,hy-drological cycle,vegetation monitoring,urban climate and environ-mental studies,among others(Arnfield,2003;Bastiaanssen et al., 1998;Hansen et al.,2010;Kalma et al.,2008;Kogan,2001;Su,2002; Voogt&Oke,2003;Weng,2009;Weng et al.,2004)and has been recog-nized as one of the high-priority parameters of the International Geosphere and Biosphere Program(IGBP)(Townshend et al.,1994). Due to the strong heterogeneity of land surface characteristics such as vegetation,topography,and soil(Liu et al.,2006;Neteler,2010),LST changes rapidly in space as well as in time(Prata et al.,1995;Vauclin et al.,1982)and an adequate characterization of LST distribution and its temporal evolution,therefore,requires measurements with detailed spatial and temporal sampling.Given the complexity of surface temper-ature over land,ground measurements cannot practically provide values over wide areas.With the development of remote sensing from space,satellite data offer the only possibility for measuring LST over the entire globe with sufficiently high temporal resolution and with complete spatially averaged rather than point values.Satellite-based thermal infrared(TIR)data is directly linked to the LST through the radiative transfer equation.The retrieval of the LST from remotely sensed TIR data has attracted much attention,and its his-tory dates back to the1970s(McMillin,1975).To better understand the Earth system at the regional scale and to get the evapotranspiration with an accuracy better than10%,LST must be retrieved at an accuracy of1K or better(Kustas&Norman,1996;Moran&Jackson,1991;Wan& Dozier,1996).However,direct estimation of LST from the radiation emitted in the TIR spectral region is difficult to perform with that accuracy,since the radiances measured by the radiometers onboard sat-ellites depend not only on surface parameters(temperature and emis-sivity)but also on atmospheric effects(Li&Becker,1993;Ottlé& Stoll,1993;Prata et al.,1995).Therefore,besides radiometric calibration and cloud screening,the determination of LSTs from space-based TIR measurements requires both emissivity and atmospheric corrections (Li&Becker,1993;Vidal,1991).Many studies have been carried out, and different approaches have been proposed to derive LSTs from satel-lite TIR data,using a variety of methods to deal with the emissivity and atmospheric effects(Becker&Li,1990b;Gillespie et al.,1998; Hook et al.,1992;Jiménez-Muñoz&Sobrino,2003;Kealy&Hook,1993;Kerr et al.,1992;Pozo Vazquez et al.,1997;Price,1983,1984; Qin et al.,2001;Susskind et al.,1984;Tonooka,2001;Wan&Dozier, 1996;Wan&Li,1997).Consequently,there have been quite a large number of publications on LST retrieval algorithms and methods.It is important to present an overview of the state of the art in LST retrieval algorithms and to direct future research into improving the accuracy of satellite-derived LST.Although there have been earlier reviews on LST retrieval from space,presented by Prata et al.(1995)and Dash et al. (2002),since then there have been several new developments in LST re-trieval algorithms and this review is intended to supplement those re-views with latest approaches.The objective of this paper is to review the progress in estimation of LST from TIR data primarily taken using sensors onboard polar-orbit satellites which have been acquiring data since the mid-eighties and to suggest directions for future research on the subject.Section2provides the theoretical basis for retrieving the LST from satellite TIR data and briefly discusses some major difficulties in LST retrieval from space measurements,including:(i)the coupling of the LST,the land surface emissivity(LSE)and the atmosphere;(ii)the physical meaning of satellite-derived LST;and(iii)validation problems related to satellite-derived LST.Section3presents an overview of a variety of methods and algorithms for estimating the LST.For each method or algorithm,the main theoretical basis and assumptions in-volved in the development of the model will be outlined,and the method's advantages,drawbacks and potential will be highlighted. Section4reviews methods of validating satellite-derived LST.Finally, Section5suggests future developments and provides perspectives on retrieving LST from remotely sensed data.2.Basic theoretical backgroundAll objects with temperatures greater than absolute zero emit radia-tion,and the amount of radiation from a black body in thermal equilib-rium at wavelengthλand temperature T is described by Planck's law: BλTðÞ¼C1λ5exp C2λT−1h i;ð1Þwhere Bλ(T)is the spectral radiance(W m−2μm−1sr−1)of a black body at temperature T(K)and wavelengthλ(μm);C1and C2are physical constants(C1=1.191×108Wμm4sr−1m−2,C2=1.439×104μm·K). Because most natural objects are non-black bodies,the emissivityε, which is defined as the ratio between the radiance of an object and that of a black body at the same temperature,must be taken into account. The spectral radiance of a non-black body is given by the spectral emis-sivity multiplied by Planck's law as shown in Eq.(1).Obviously,if the atmosphere exerts no influence on the measured radiance,LST(i.e.T) can be retrieved by making temperature as the subject of Eq.(1)once the emitted radiance and emissivity are known.The wavelengthλmax15Z.-L.Li et al./Remote Sensing of Environment131(2013)14–37of the peak monochromatic radiance at a given temperature (T)is given by Wien's displacement law:T λmax ¼2897:9K μm :ð2ÞAccording to this equation,the wavelength λmax at which maxi-mum emission occurs varies roughly from 11.6μm to 8.8μm if the LST ranges from 250K to 330K with the average temperature of the Earth being approximately 288K.The wavelength region be-tween 8and 13μm coincides within a clear window in the atmo-sphere which is most transparent to TIR radiation.In cases where the temperature of the surface exceeds 330K,the wavelength peak moves to shorter and shorter wavelengths,for example for a wild fire (about 800K),the maximum emission is around 3.6μm in the mid-infrared (MIR)region (3–5μm)which also coincides with a clear window in the atmosphere.2.1.Radiative transfer equationAn infrared sensor onboard a satellite viewing the Earth's surface measures the radiation from the Earth and its atmosphere along the line of ing the radiative transfer equation (RTE)and assum-ing a cloud-free atmosphere under local thermodynamic equilibrium,as illustrated in Fig.1,the channel infrared radiance I i received by a sensor at the top of the atmosphere (TOA)can be written as I i θ;φðÞ¼R i θ;φðÞτi θ;φðÞ|fflfflfflfflfflfflfflfflfflfflfflffl{zfflfflfflfflfflfflfflfflfflfflfflffl}Surf ace outgoing radiation term attenuated by the atmosphereþR at i ↑θ;φðÞ|fflfflfflfflfflfflffl{zfflfflfflfflfflfflffl}Atmospheric emission termþR sl i ↑θ;φðÞ|fflfflfflfflfflfflffl{zfflfflfflfflfflfflffl}Atmospheric scattering term;ð3Þwith R i being the channel radiance observed in channel i at ground level given byR i θ;φðÞ¼εi θ;φðÞB i T s ðÞ|fflfflfflfflfflfflfflfflfflffl{zfflfflfflfflfflfflfflfflfflffl}Surf ace emission termþ1−εi θ;φðÞ½ R at i ↓|fflfflfflfflfflfflfflfflfflfflfflfflfflffl{zfflfflfflfflfflfflfflfflfflfflfflfflfflffl}Surf ace ref lected downwelling atmospheric emissiontermþ1−εi θ;φðÞ½ R sl i ↓|fflfflfflfflfflfflfflfflfflfflfflfflffl{zfflfflfflfflfflfflfflfflfflfflfflfflffl}Surf ace ref lected downwelling atmospheric scattering termþρb i θ;φ;θs ;φs ðÞE i cos θs ðÞτi θs ;φs ðÞ|fflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflffl{zfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflffl}Surf ace ref lected downwelling solar beam term;ð4Þin which θand φrepresent the zenithal and azimuthal viewing angles.For simplicity,the zenithal and azimuthal viewing angles are ignored in the following expressions.τi is the effective transmittance of the atmosphere in channel i .R i τi is the radiance observed at ground level attenuated by the atmosphere (path ①in Fig.1).R ati ↑is the upward at-mospheric thermal radiance (path ②in Fig.1).R sli ↑is the upward solar diffusion radiance resulting from atmospheric scattering of the solar ra-diance (path ③in Fig.1).εi and T s are the effective surface emissivity and surface temperature in channel i .εi B i (T s )represents the radiance emitted directly by surface (path ④in Fig.1).R ati ↓is the downward atmospheric thermal radiance.R sli ↓is the downward solar diffusion ra-diance.(1-εi )R ati ↓and (1-εi )R sli ↓represent the downward atmospheric thermal radiance and solar diffusion radiance re flected by the surface (paths ⑤and ⑥in Fig.1).ρbi is the bi-directional re flectivity of the sur-face,E i is the solar irradiance at the TOA,θs and φs are the solar zenithal and azimuthal angles.ρbi E i cos(θs )τi (θs ,φs )is the direct solar radiance re flected by the surface (path ⑦in Fig.1).Because the contribution of solar radiation at the TOA is negligible in the 8–14μm window during both day and night and in the 3–5μm window at night,theFig.1.Illustration of radiative transfer equation in infrared regions (see the text for the de finitions of symbols).Here,I i is the radiance measured by channel i at the top of atmo-sphere.Path ①represents the radiance observed at ground level attenuated by the atmosphere.Paths ②and ③represent the upward atmospheric thermal radiance and the up-ward solar diffusion radiance,respectively.Path ④represents the radiance emitted directly by the surface.Paths ⑤and ⑥represent the downward atmospheric thermal radianceand solar diffusion radiance re flected by the surface,respectively.Path ⑦represents the direct solar radiance re flected by the surface.16Z.-L.Li et al./Remote Sensing of Environment 131(2013)14–37solar-related items (paths ③,⑥and ⑦in Fig.1)in Eqs.(3)and (4)can be neglected without loss of accuracy.For convenience and mathematical shorthand,the radiances I i and R i measured at the TOA and at ground level are generally expressed in terms of the brightness temperatures where the emissivity is fixed at 1.0.The TOA and ground level brightness temperatures T i and T gi are de fined respectively by B i T i ðÞ¼I iand B i T gi¼R ið5ÞIt is worth noting that all variables/parameters in Eqs.(3)–(5),ex-cept for the angles (θ,φ,θs and φs ),are channel-effective values.Most satellite sensors measure the outgoing radiation with a finite spectral-bandwidth,and the channel-effective quantities of interest are therefore a weighted average expressed by:X i ¼∫λ2λ1g i λðÞX λd λ∫λ2λ1g iλðÞd λ;ð6Þwhere g i (λ)is the spectral response function in channel i ;λ1and λ2are the lower and upper boundaries of the wavelength in channel i ;and X stands for B (T ),I ,R ,R at ↑,R sl ↑,R at ↓,R sl ↓,E ,ε,τ,or ρb .Eqs.(3)and (4)are actually approximations to the theoretical RTE in which monochromatic quantities are replaced with channel-effective values,but these approximations or simpli fications require several important preconditions:•The integral of a product is assumed to be equal to the product of the integrals.This assumption is true only if the variables are con-stant within the integration limits,which is rarely the case.Fortu-nately,the bandwidth of the channel is generally narrow,and the various spectral quantities X λinvolved in Eq.(6)should not feature rapid variations.Therefore,the use of the weighted averages de-fined by Eq.(6)in Eqs.(3)and (4)is a good approximation to the RTE with monochromatic quantities.•Either the surface is assumed to be Lambertian or the downward at-mospheric and solar diffuse radiation are assumed to be isotropic in the calculation of the downward radiations re flected by the surface (paths ⑤and ⑥in Fig.1).In practice,these conditions are never ful filled.However,because the surface-re flected downward atmo-spheric thermal radiation term is much smaller than the surface thermal emission,and the surface-re flected diffuse solar radiation term is much smaller than the surface-re flected direct solar term,this simpli fication of Eqs.(3)and (4)is reasonable and does not in-troduce signi ficant errors.2.2.Dif ficulties and problems in the retrieval of LST from space measurementsAs seen from Eqs.(3)and (4),estimating the LST from the radi-ance measured at the TOA requires corrections for both atmospheric and emissivity effects.Applying these corrections is not a simple task,and some key dif ficulties and problems involved in the retrieval of the LST must be overcome and resolved.These key dif ficulties and problems are the following:(1)The retrieval of the LST from space is mathematicallyunderdetermined and unsolvable (Hook et al.,1992;Kealy &Hook,1993).The RTE described in Eqs.(3)and (4)shows that,if the radiance is measured in N channels,there will always be N +1unknowns,corresponding to N emissivities in each channel and an unknown LST for N equations,even if quantities other than the emissivities and LST are known a priori.Such an ill-posed problem makes the solution of the RTE sets underdetermined at ground level even if the atmospheric quantities involved in Eqs.(3)and (4)are accurately estimated.To make LSTdeterministic,one or more of the LSEs must be known,or the LST and LSEs have to be simultaneously solved with the aid of some assumptions or constraints on the LSEs (Dash et al.,2002;Gillespie et al.,1996;Hook et al.,1992;Kealy &Hook,1993).(2)Measurements in the TIR region are highly correlated,implying that instrumental noise and errors in the atmospheric corrections exert strong in fluences on the accuracy of the LST retrieval.This correlation represents a problem even if the LST is made solvable either by reducing the number of unknowns or by increasing the number of equations through reasonable assumptions or con-straints on the LSEs (Gillespie et al.,1996;Li et al.,2013).These highly correlated measurements make LST retrieval unsta-ble and have hampered the methodological development of LST retrieval.(3)It is dif ficult to decouple the LST,the LSEs,and the downward at-mospheric radiance in the measured radiances.As seen from Eq.(4),the downward atmospheric radiance and the surface emitted radiance are coupled together through LSEs.The non-unity LSE of a natural surface reduces the surface-emitted radiance while increasing the re flection of the down-ward atmospheric radiance back to the atmosphere,which com-pensates partly for the reduction in the surface-emitted radiance.This process can reduce or increase the total surface-leaving radi-ance depending on the atmospheric and surface conditions.This coupling of the re flected downwelling and surface-emitted radi-ation can be used to retrieve LST with the online/of fline method but requires high spatial resolution data.However in passively observed multispectral TIR data,it is impossible to separate,on a physical basis,the contributions of the LST from the contribu-tions of the LSEs and the atmosphere in the observed radiance.For this reason,determining LST from space requires not only the atmospheric corrections but also the knowledge of the LSEs and vice versa.(4)The atmospheric corrections are dif ficult to implement.The pres-ence of the atmosphere between the surface and the sensors af-fects the radiances measured by a radiometer at the TOA.These radiances result primarily from emission/re flection at the surface modulated by the effects of the attenuation,and emission of the atmosphere.The atmospheric corrections thus consist of correcting the radiance measured by the sensors for the effects of atmospheric attenuation,emission and emission-re flection.Correcting for the atmospheric effects requires accurate knowl-edge of the vertical pro files of atmospheric water vapor and tem-perature both of which are highly variable (Perry &Moran,1994).(5)During the daytime,the re flected solar radiation is dif ficult to re-move in the MIR measurements.As mentioned earlier,the highly correlated TIR measurements make LST retrieval unstable even if the solution of the RTE sets becomes deterministic through some assumptions and constraints on the LSEs.In the MIR since the di-rect solar irradiation re flected by the surface is on the same order of magnitude as the radiance directly emitted by the surface,if the surface albedo is about 0.1,the introduction of the MIR chan-nels in LST retrieval signi ficantly reduces the correlation of the RTE sets and greatly improves the accuracy of the estimated LST (Li et al.,2013).Additionally,MIR channels are less sensitiv-ity to the water vapor in the atmosphere compared with TIR channels,and the LST retrieval from the MIR is only half as sensi-tive to errors in emissivity as that from the TIR (Mushkin et al.,2005).Therefore,LST retrieval with the MIR instead of the TIR sounds more appropriate.However,solar effects are dif ficult to eliminate in the MIR during the daytime because the separation of solar irradiation from the total energy measured in the MIR re-quires not only the accurate atmospheric information but also the knowledge of the bidirectional re flectivity of the surface.This information is typically unknown and affected by several factors (Adams et al.,1989;Mushkin et al.,2005),resulting in17Z.-L.Li et al./Remote Sensing of Environment 131(2013)14–37large uncertainties that can lead to an even larger error on the LST retrieved from MIR measurements.Therefore,while the in-troduction of the MIR channels may benefit the retrieval of the LST in certain cases,it can also introduce even larger uncer-tainties in others.(6)How to physically interpret the results of the LST measurementremains a crucial question.As noted by Prata et al.(1995),the def-inition of the surface temperature may depend strongly on the type of application and the method of measurement.Because the surface temperature T s in Eq.(4)is defined using the radiance emitted by a surface,this temperature is called the radiometric temperature(or the skin temperature)that corresponds to the ra-diation emitted from depths less than the penetration depth of a given wavelength(Becker&Li,1995;Norman&Becker,1995).The penetration depth is usually within a few millimeters in the TIR region(Wan,1999).This radiometric temperature physically differs from other definition of temperatures,such as the thermo-dynamic temperature defined for a medium in thermal equilibri-um and measured by a thermometer.For homogeneous and isothermal surfaces,the radiometric and thermodynamic temper-atures are reported to be equivalent.As the thermodynamic tem-perature is actually hard to measure in reality,even for water,the radiometric temperature is often the only practical measure for the homogeneous and isothermal surface.However,most surfaces are not in equilibrium and for heterogeneous and non-isothermal surfaces,these two temperatures are different.Considering that the spatial resolution of the current onboard sys-tems varies approximately from10−2to10km2,there may be several surface types with different temperatures and emissivities within one pixel,which complicates the physical understanding of the LST values retrieved from space and the relation of the ra-diometric temperature at large scales to other temperatures used in different applications.To date,no consensus has been reached on the definition of the LST for heterogeneous and non-isothermal surfaces,but the definition by Becker and Li (1995),which depends on the distributions of the LST and the LSE within a pixel,is measurable from space and is thus recommended for LST retrieval from space.(7)Validation of LST retrieved from spaceborne measurements atthe scale of the sensor's pixels is also challenging.Validation is problematic due to the difficulty of conducting in situ LST mea-surements,and in obtaining representative LST data at the scale of a single pixel.Generally,temperatures over the land surfaces vary strongly in space and time(Prata et al.,1995),and it is not unusual for the LST to vary by more than10K over just a few centimeters of distance or by more than1K in less than a minute over certain cover types.Appropriately scaling the satellite-derived LSTs to those measured at ground level,especially at large scale is also difficult.The strong spatial heterogeneity and temporal variation of the LST limits ground-based validation to several relatively homogeneous land surfaces,such as lakes,de-serts,and densely vegetated land using direct comparisons of in situ temperature measurements with temperatures retrieved from the satellite data(e.g.Hook et al.,2005,2003,2007).A com-plementary approach is to use sites which are homogenous in terms of emissivity using the radiance based validation approach (Hulley et al.,2009).Sand dunes can be one example of this type of sites which are referred to as pseudo-invariant sites(Hulley et al.,2009).Furthermore,how to perform a representative mea-surement of the LST of a complex heterogeneous surface is alsoa critical question.Scaling methods should be developed to relatethe measurements at different scales and help validate the re-trieved LST(Liu et al.,2006;Wu&Li,2009).Besides the difficulties mentioned above in the retrieval of LST from space,the accuracy of the LST data also depends on the performance of the cloud mask used to isolate clear sky data and on the quality of the TIR data,i.e.,the stability of the spectral response function g i(λ),the SNR and the accuracy of the radiometric calibration.3.Estimation of LST from spaceOver the past several decades,LST estimation from satellite TIR mea-surements has significantly improved.Many algorithms have been pro-posed to treat the characteristics of various sensors onboard different satellites and utilizing different assumptions and approximations for the RTE and LSEs.These algorithms can be roughly grouped into three categories:single-channel methods,multi-channel methods,and multi-angle methods,provided that the LSEs are known a priori.If the LSEs are not known,then the algorithms can be categorized into three types:stepwise retrieval method,simultaneous retrieval of LSEs and LST with known atmospheric information,and simultaneous retrieval with unknown atmospheric information.3.1.LST retrieval with known LSEs3.1.1.Single-channel methodThe single TIR channel method,also called the model emissivity method(Hook et al.,1992),uses the radiance measured by the satellite sensor in a single channel,chosen within an atmospheric window,and corrects the radiance for residual atmospheric attenuation and emission using atmospheric transmittance/radiance code that requires input data on the atmospheric profiles.LST is then retrieved from the radiance measured in this channel by inverting the RTE given in Eqs.(3)and(4), provided that the LSE is well known or estimated in advance(Chédin et al.,1985;Hook et al.,1992;Li et al.,2004a;Mushkin et al.,2005;Ottlé& Vidal-Madjar,1992;Price,1983;Susskind et al.,1984).Accurate deter-mination of the LST using this method requires high-quality atmospher-ic transmittance/radiance code to estimate the atmospheric quantities involved in Eqs.(3)and(4),good knowledge of the channel LSE,an ac-curate atmospheric profile,and a correct consideration of the topo-graphic effects(Sobrino et al.,2004b).Generally,the accuracy of atmospheric transmittance/radiance code is primarily limited by the radiative transfer model(RTM)used in the code and by the uncertainties in atmospheric molecular absorption co-efficients and aerosol absorption/scattering coefficients(Wan,1999). The most popular atmospheric RTMs,such as the series of MODTRAN (Berk et al.,2003)and4A/OP(Chaumat et al.,2009),have been widely used to perform atmospheric corrections and/or to simulate satellite TIR data.A few studies have shown that the accuracy of the different RTMs ranges from0.5%to2%within known atmospheric windows,such as 3.4–4.1μm and8–13μm,leading to uncertainties in the retrieved LST of0.4K to1.5K(Wan,1999).It is worth noting that the incomplete characterizations of atmospheric profiles used in compensation for at-mospheric absorption and path radiance constitute a serious problem even if the RTM itself is completely error-free(Gillespie et al.,2011). Studies have also demonstrated that an error of1%in the LSE can give rise to an error in the LST ranging from0.3K for a hot and humid atmo-sphere to0.7K for a cold and dry atmosphere(Dash et al.,2002).As the single channel is usually chosen around10μm where the LSE for most land surfaces can be known within a few percent,the uncertainty in LSE may lead to an error of1K to2K in LST if the single-channel meth-od is used.However,if the LSE is known at a wavelength within the TIR atmospheric window,then any error will be solely due to incorrect re-moval of the atmospheric contribution.Atmospheric profiles are gener-ally obtained either from ground-based atmospheric radiosoundings, from satellite vertical sounders or from meteorological forecasting models.Due to the high spatial and temporal variability of the atmo-spheric water vapor,the use of ground-based radiosoundings far from the area of interest and/or far from the time of satellite overpass may re-sult in large errors in the LST(Cooper&Asrar,1989).On top of these, radiosoundings reported measurement errors are of the order of0.5K18Z.-L.Li et al./Remote Sensing of Environment131(2013)14–37。
法律道德英语作文
法律道德英语作文英文回答：In the intricate tapestry of human existence, where the threads of law and morality intertwine, I stand as an observer, contemplating the profound relationship that binds these two essential elements of our collective experience. Both law and morality, though distinct in their nature, share an inextricable connection, influencing and shaping each other in myriad ways.Law, in its essence, is a system of rules and regulations established by a governing authority to regulate the conduct of individuals within a society. It provides a framework for social order, defines acceptable behavior, and prescribes consequences for transgressions. Morality, on the other hand, encompasses a set of values, principles, and ethical beliefs that guide individual actions and shape our understanding of right and wrong.While law and morality may occasionally overlap, they are not synonymous. Laws are often codified and enforced through external sanctions, while morality relies on internalized values and the dictates of conscience. For example, a law may prohibit murder, but it cannot preventan individual from harboring murderous thoughts. Conversely, morality may condemn certain actions, such as lying or stealing, even though they may not be explicitly forbidden by law.The relationship between law and morality is a dynamic one, constantly evolving and adapting to changing societal norms and values. Laws may be enacted or repealed toreflect shifts in moral sensibilities, while moralprinciples can influence the interpretation and enforcement of laws. For instance, the abolition of slavery in many countries was driven by growing moral outrage against this inhumane practice.In some instances, law and morality may come into conflict, presenting individuals with ethical dilemmas. A law may require a person to do something that they believeis morally wrong, or it may prohibit an action that they believe is morally justified. In such cases, individuals must navigate the tension between legal obligations and moral convictions, often making difficult decisions that test their integrity.The interplay between law and morality is evident in countless aspects of our lives. Consider the legal duty to report crimes, which stems from a moral obligation to protect society from harm. Or, the ethical considerations that guide the medical profession, balancing legal requirements with the moral imperative to preserve patient autonomy and well-being.In conclusion, the relationship between law and morality is a complex and multifaceted one. While distinct in their nature, they are interconnected and mutually influential. Law provides a foundation for social order, while morality shapes our individual actions and ethical choices. By understanding the interplay between these two essential elements, we can navigate the complexities of human behavior and strive to live in a just and virtuoussociety.中文回答：法律与道德，这两大要素在人类存在的复杂图景中交织在一起，构成了社会秩序的经纬线。
增强采样方法 计算化学公社
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在大学遇到的问题,怎样解决的英语作文
在大学遇到的问题,怎样解决的英语作文全文共3篇示例，供读者参考篇1The Trials and Triumphs of University LifeWhen I arrived at university, I was filled with a heady mix of excitement and trepidation. Having grown up in a small town, the big city campus felt like an alien world - crowded, chaotic, and more than a little intimidating. I knew university would be challenging, but I had no idea just how many hurdles lay ahead. Looking back now after four years, I can't help but feel immense pride at how far I've come and the obstacles I've overcome.My first major problem hit me like a ton of bricks just a few weeks into my first semester - I completely bombed my first round of midterm exams. Maybe it was overconfidence from breezing through high school or just poor time management skills, but I did not take my studying seriously enough. When I saw those abysmal grades, I felt like the wind had been knocked out of me. I started questioning whether I had what it took to make it in university. Calling my parents in tears, I remember my dad giving me some tough love: "This is a wake-up call, but it'snot the end of the world. You can turn this around, but it'll take hard work."And hard work it was. I drastically overhauled my entire study process - I started meticulously planning out my days, formed study groups with classmates, and spent endless hours poring over textbooks and notes in the library. Bit by bit, I felt myself steadily improving. By the time final exams rolled around, I was getting A's and B's. That feeling of accomplishment was unbeatable. I had learned studying wasn't just about brute force grinding, but developing strategies and habits tailored for my learning style. More importantly, I gained confidence that I could overcome even my biggest academic shortcomings.My second year brought fresh challenges in the form of managing my social life. It's easy to get swept up in the party culture of university, and I'll admit I probably went a bit overboard at times with nights out. I struggled to find that balance between having fun and staying on top of my studies. There were too many mornings waking up hungover and dreading my 8am lectures. By the end of first semester, my grades had slipped and I felt like I was losing my way a bit.This time, thankfully, I was able to self-correct before things went totally off the rails. I reconnected with my priorities andscaled back on going out as much. I deleted some time-wasting apps off my phone. And I surrounded myself with positive friendships with people who were focused on their goals. Having a solid support system made such a difference in keeping me grounded and motivated. I'm grateful I was able to turn that around before throwing away all the hard work I had put in.One of the biggest tests of my time in university, however, wasn't directly academic at all. Towards the end of my third year, my mom was diagnosed with breast cancer. It was a scary, uncertain time, and I considered taking a leave of absence to go home and be with my family. Thankfully, my professors were incredibly understanding and accommodating, allowing me to keep up with my coursework remotely when I could. But there were still many emotional ups and downs that took a toll on my state of mind and made focusing difficult.Counseling services on campus were a huge help in getting me through this challenging period. Having an outlet to process what I was going through, manage my stress and anxiety, and develop healthy coping mechanisms was vital. I also made sure to prioritize self-care, whether that was exercise, reading for pleasure, or just getting away from it all for a bit. Dealing with this kind of seismic life event while juggling a full academic loadpushed me to my limits in some ways. But I'm proud that I was able to persevere and make it through one of the toughest times in my life so far.Now, as I prepare to graduate and take that nerve-wracking step into the "real world", I feel a tremendous sense of growth and maturity compared to the bright-eyed but slightly naive teenager who first stepped onto campus. The academics have been grueling at times, but it's battling all the other unexpected adversities that has given me invaluable perspective, resilience, and self-awareness. I've gained priceless problem-solving abilities from overcoming setbacks in my studies, social life, mental health, and personal life.More than anything, university has taught me that no matter how daunting the challenge, there is always a way forward if you stay determined and ask for help when needed. I've learned the importance of work-life balance, self-care, and having a strong support network. Perhaps most importantly, I've developed unshakable belief in my capabilities to adapt and overcome even the most trying of circumstances.The path has been winding with many bumps along the way, but that's ultimately what has made this journey so rewarding. I may be leaving this campus with a degree, but the real prize isthe perseverance, grit, and perspective that no classroom could teach. While I'll forever cherish the incredible experiences of university life, I'm also excited to take these hard-earned lessons into whatever new challenges lie ahead. Bring it on, world - thanks to these last four years, I've got this.篇2Problems at University and How I Overcame ThemWhen I started university, I was incredibly excited but also quite nervous. I had heard so many stories about the challenges of being a student - the heavy workload, the difficulty in managing your time, finding a balance between academics and social life. Little did I know just how many obstacles I would face during those pivotal years. However, I'm proud to say that through determination and resourcefulness, I was able to overcome many of the problems that initially seemed insurmountable. Here are some of the key issues I grappled with and the strategies I used to resolve them.The Transition from High SchoolOne of the very first hurdles I ran into was simply adjusting to the vastly different environment and expectations of university compared to high school. In high school, the classeswere smaller, the teachers handheld you through assignments, and the overall workload was much lighter. All of a sudden at university, I was one student among hundreds in huge lecture halls. The professors trained you through a fire hose of information and you were expected to be an independent,self-motivated learner.It took me quite a while to adapt to this new academic culture. At first, I was completely overwhelmed trying to take verbatim notes on every single thing the professors said. I soon realized this approach was inefficient and caused me to lose focus during lectures. Through trial and error, I developed the skill of summarizing key concepts in my own words as the lecturer spoke. I also got into the habit of reviewing material soon after class so it would solidify in my memory.Developing better study habits such as this was crucial, but I also had to mentally prepare myself that university required a much higher level of self-discipline than high school. There was no one keeping tabs on whether I was getting assignments done or not. If I didn't hold myself accountable, my grades would quickly suffer. It was a harsh wake-up call, but slowly ingraining habits like time blocking, prioritization of tasks, and working ahead of deadlines allowed me to stay on top of my coursework.Managing My FinancesBesides adapting academically, another major challenge I faced was handling my finances independently for the first time. My parents gave me a modest monthly allowance, but It was up to me to budget for expenses like groceries, transportation, textbooks, and entertainment. This was made even trickier with a constantly fluctuating class and work schedule each semester.Early on, I definitely made some mistakes with spending beyond my means, wasting money on frivolous things, and not tracking my purchases diligently. However, I knew I needed to get a handle on my finances before I dug myself into debt. I started by analyzing all my fixed costs like rent and estimating variable expenses like food and going out. Then I set a weekly allowance for discretionary spending that I stuck to rigidly.I became addicted to finding student discounts and looking for deals wherever possible. Instead of buying costly new textbooks, I would rent them or buy used copies online. Rather than constantly getting food delivered, I learned to meal prep at home for the week. Finding a part-time job on campus for some income was also a big help for making ends meet.It took discipline but I slowly optimized where I was spending my money versus where I could be saving. Creating abudget and monitoring every expense with financial apps was a major turning point in taking control of my spending habits.Maintaining a Social LifeAlong with the financial strain, another difficulty I wrestled with was preserving a social life amidst the demands of academics. In high school, you naturally saw your friends every day so maintaining those relationships was relatively frictionless. At university however, people had vastly different schedules of classes, jobs, clubs and so on. If you didn't be proactive about it, it was easy to become isolated.At the start of each semester, I would map out all my friend's schedules and find the small pockets of overlap where we could connect. Coordinating everyone's availability was like a game of Tetris, but I made sure to block off those times as sacred. Even if it was just for a meal together or to sit and chat between classes, it was so important for staying sane.I also consciously built out my social circles through joining clubs and intramural sports teams related to my interests. This allowed me to meet new people with common passions outside of just my classes. I can't emphasize enough how crucial it was to have both a solid friend group as well as some non-academic outlets for alleviating stress.Believe it or not, forming study groups for certain courses also turned out to be a lifeline socially and academically. It provided built-in time to be around colleagues while keeping each other accountable towards shared goals.At first I was apprehensive about studying with others, but it quickly became some of my most productive sessions.Impostor Syndrome and Self-DoubtDespite my best efforts, there were still many moments when I felt in over my head and started to question my capabilities. Impostor syndrome - that feeling of being a fraud who didn't truly belong - weighed heavily on me at times. In university, you're surrounded by brilliant classmates and faculty who can make you feel very small.Whenever I received a poor test score or negative feedback, I would become consumed with doubt about whether I had what it took. My self-confidence would plummet and I would enter a spiral of negative thoughts. It took me a long time to develop strategies for safeguarding my belief in myself.One of the most powerful revelations was that everyone doubts themselves from time to time - even the most accomplished students and professors. Normalizing those feelings of insecurity and separating them from my intrinsicself-worth was huge. It allowed me to still feel those doubts, but not be dragged down into paralysis by them.Building a positive self-talk loop was also transformative. Whenever I caught myself slipping into harsh, self-critical thoughts, I would counter them with affirmations about my strengths and capabilities based on evidence of past achievements. Positive mantras like "You've got this" or "Trust the process" became grounding forces.I also had to learn to contextualize failures as part of the learning journey rather than defining my entire self-worth in that moment. If I didn't perform well on an assignment, I would dispassionately analyze what I could improve on without judgement. Then I would make a concrete plan for applying those lessons on the next opportunity. Bottomline, I learned to be kinder and more compassionate with myself through those bouts of self-doubt.Overall, university presented me with a crash course on prioritizing, problem-solving, and believing in my abilities to overcome obstacles. The challenges I described were some of the most formidable, but there were countless other speed bumps along the way too. What I can say is that each issue I was able to resolve made me more resilient and confident.By the time I walked across that stage at graduation, earning my degree was one of my proudest moments. However, the true accomplishment was the perseverance, ingenuity, and growth that I demonstrated in facing down every single challenge head-on. Those skills of learning how to adapt, grind through adversity, and maintain balance will be invaluable to me no matter what other curveballs life throws my way. For that invaluable education outside the classroom, I'll be forever grateful for my university experience.篇3Problems Encountered at University and How to Overcome ThemCollege life is often romanticized as the best years of one's life – a time of intellectual awakening, personal growth, and forging lifelong friendships. While this can certainly be true, the reality is that university also brings with it a unique set of challenges that many students struggle to overcome. From time management issues to mental health concerns and financial difficulties, the obstacles faced during these formative years can feel overwhelming. However, with the right mindset and coping strategies, it is possible to navigate these hurdles and emerge stronger on the other side.One of the most common problems faced by students is the struggle to balance academic demands with personal responsibilities and social activities. The transition from high school to university often comes with a newfound sense of freedom, which can be both exhilarating and overwhelming. Suddenly, students are responsible for managing their own schedules, attending classes, completing assignments, and studying for exams – all while trying to maintain a social life and potentially juggling a part-time job.Time management is key to striking this delicate balance. Creating a structured routine and prioritizing tasks can help prevent procrastination and ensure that academic obligations are met without sacrificing self-care or leisure time. Utilizing tools like calendars, to-do lists, and productivity apps can also aid in staying organized and on track.Additionally, it's important to recognize when one is struggling and seek help when needed. Many universities offer academic advising services, tutoring programs, and writing centers to assist students in overcoming academic challenges. Building a support network of peers, mentors, and professors can also provide invaluable guidance and encouragement.Another significant challenge faced by many students is the impact of university life on mental health. The pressures of academic performance, social dynamics, and newfound independence can take a toll on emotional well-being. Feelings of anxiety, depression, and loneliness are not uncommon, particularly during the first year of college.Prioritizing self-care is crucial in maintaining good mental health. This can include practices such as regular exercise, mindfulness or meditation, getting enough sleep, and engaging in hobbies or activities that bring joy and relaxation. It's also essential to cultivate a strong support system, whether it's through joining student organizations, attending campus events, or seeking counseling services offered by the university.Financial difficulties can also pose a significant challenge for many students. The rising costs of tuition, housing, textbooks, and living expenses can create substantial financial strain, leading to stress and potentially impacting academic performance.To alleviate financial burdens, students may need to explore various options, such as applying for scholarships, grants, or student loans. Additionally, seeking part-time employment or work-study programs can help offset expenses while gainingvaluable work experience. Careful budgeting and financial literacy are also essential skills to develop during this time.Despite these challenges, the university experience can be incredibly rewarding and provide opportunities for personal and intellectual growth that shape the rest of one's life. By developing effective coping strategies, seeking support when needed, and maintaining a balanced perspective, students can not only overcome the obstacles they face but also emerge as more resilient and well-rounded individuals.One invaluable lesson that university teaches is the importance of adaptability and perseverance in the face of adversity. The ability to problem-solve, think critically, and navigate complex situations are skills that will serve students well beyond their academic careers. Embracing challenges as opportunities for growth and learning can transform what may initially seem like insurmountable obstacles into stepping stones towards success.Furthermore, the university experience fosters independence and self-discovery. Away from the familiar comforts of home, students are forced to confront their own values, beliefs, and aspirations, ultimately shaping their sense of identity and purpose. This process of self-exploration can be bothexhilarating and daunting, but it is an essential step towards becoming a well-rounded, self-aware individual.Ultimately, the challenges faced during university years are not unique to any one student; rather, they are shared experiences that bind together the broader community of learners. By embracing a spirit of resilience, seeking support when needed, and maintaining a balanced perspective, students can not only overcome the obstacles they face but also emerge as more resilient and well-rounded individuals, equipped with the skills and knowledge to navigate the complexities of life beyond the campus gates.。
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ADAPTING THE OVERLAP-ADD METHOD TO THE SYNTHESIS OF NOISEPierre HANNASCRIME-LaBRIUniversit´e de Bordeaux1F-33405Talence Cedex,France hanna@labri.fr Myriam DESAINTE-CATHERINE SCRIME-LaBRIUniversit´e de Bordeaux1F-33405Talence Cedex,France myriam@labri.frABSTRACTSpectral synthesis techniques often use the OverLap-Add method. But in the case of noise synthesis,both experiments and theory show that this method introduces intensityfluctuations which im-ply audible artifacts.We propose here new methods to avoid these variations.Thefirst one consists in multiplying the resulting signal by another weighting window to compensate dynamicfluctuations. The second one defines a new OLA weighting window.The third one concerns only noises synthesized with sinusoidal components and uses time-shifting to cancel artifacts.1.INTRODUCTIONMany noise synthesis methods use the OverLap-Add(OLA)tech-nique.Noises can be produced temporally by randomly draw-ing samples according to a constant distribution(uniform,normal, ...).Samples are thenfiltered.However all real-time implementa-tion needs to synthesize sounds frame by frame.That’s why OLA technique is often used to avoid clicks.Noises can also be generated using sinusoidal components. For example,in SMS[1],the application of inverse-Fourier trans-form to synthesize the stochastic part implies a frame-by-frame synthesis,and therefore the application of the OLA technique.These existing methods can be used to synthesize noises with-out previously having performed an analysis process.In this case, the resulting temporal signal does not taper to0at the boundaries of each frame.This can be the cases at times,even with an analysis process,if sounds are transformed.This is the reason why these methods utilize the OLA technique.2.OLA TECHNIQUE IN THE SYNTHESIS OF NOISE 2.1.DefinitionOLA technique involves in synthesizing overlapping temporal fra-mes of samples(seefigure1).Let be the number of frames:(1) where is the hop size(or the time advance)and is the frame number.Each temporal frame is multiplied by a weighting window :(2)This window must satisfy the condition that the sum of all the weights of the different overlapped windows must be equal to:(3)If the overlapped and added analysis windows do not sum to unity,then the output sound is amplitude modulated by a periodicsignal.Figure1:Overlap-Add with Bartlett window(2.3.Experiments2.3.1.Synthesis after analysis processBefore synthesizing a noise,some models(for example[1])extract parameters from sounds.This analysis is often performed with overlap-add technique.For example,if a white noise is analyzed, each temporal frame is not a stationary white noise:variance of this random signal periodically varies in time because of the window multiplication.This is shown with experiences in table1. And as the variance is directly linked to the perceived intensity of the sound,it provokes audible dynamicfluctuations.Moreover doing an OLA analysis implies that each sound seg-ment are not independent(seefigure2).That’s why synthesis al-ways perfectly works in this case.But it is obvious that this oper-ation is useless if no modification(time stretching,pitch shifting,...)of the analyzed sound is performed before synthesis.These transformations may lead to make sound segments independent, and thus to audible artifacts(see section2.4).Analyzed soundsound segment1sound segment2 Figure2:Analysis:two sound segments are not independent.2.3.2.Synthesis without analysis processIf the OLA method is used without analysis process,some artifacts appear.For example,if two white noises are synthesized indepen-dently by random(uniform,normal,...)draw of samples,and then are added with classical window(Hann,Bartlett,...),the resulting signal is white noise with different statistical properties. The variance is not constant.Some experimental results are shown in tab1.var()var() ()()()Table1:Evolution of the variance of the addition of two ran-dom signals(normal distribution,Bartlett window,real-izations).An example of such sounds with Bartlett window can be seen infigure3.This example shows the periodicfluctuations of inten-sity.These effects can be explained perfectly as in the following by the study of statistical properties of the sounds.2.4.TheoryWe have seen in section2that two temporal frames are multiplied by a weighting window before being added.Any window type is,0.0000.2230.4460.6690.892 1.115 1.337 1.560 1.783 2.006 2.229-32768-26214-19661-13107-6554655413107196612621432768Figure3:Example of white noise synthesized with OLA.it must satisfy equation3.By denoting the synthesized signal, one can write using equation2:(4)In the case of white noise,()are realiza-tions of the same random variable.They have the same statis-tical properties and we want the resulting signal to have also the same properties.Let be the random variable associated with.Then the mean of stays the same but the second order moment vary.Let be the variance of:(5)If an analysis is performed but no transformation,are not inde-pendent(see section2.3.1)and we verify.We consider here the case when there is no analysis process.Since are then independent:(6)Since are realizations of the same random variable,one can write:(7)The definition of is,which leads to:this sum is not constant.That’s why will vary periodically in time.Assuming that and are equal,this calculus leads to the condition about,:(8)DAFX-2For example,in the case of.Variations in case (b)perfectly correspond to the intensity fluctuations of the figure 3.1.00.90.80.70.60.50.40.30.20.10.00.0000.2230.4460.6690.892 1.115 1.337 1.560 1.783 2.006 2.229(b)(c)(a)Variance variationtime (s)Figure 4:Variations of the variance of the signal with (a)Hann window (b)Bartlett (triangular)window (c)Hamming window.3.PROPOSED METHODSWe now propose three methods to avoid these intensity fluctua-tions.The two first ones can be used with all type of noise syn-thesis whereas the third one only concerns noise synthesized with sinusoidal components.3.1.Amplitude compensationAs we know ,it is possible to compensate the in-tensity fluctuations by multiplying the temporal signal by another weighting window inversely proportional to the theoretical varia-tions (equation 9).For example,in the Bartlett window case and with.This win-dow is simply defined with a sinusoid function and is represented in figure 5:Amplitudefor the number of partials doTimeFigure6:amplitude modulations induced by sinusoidal windowmethod(dashed lines)and amplitude compensation method(dot-ted lines).3.3.Sinusoidal component offsetsThis method concerns the synthesis of noise by summing sinu-soidal components(denoted)with random phase[2].It con-sists in shifting the start of each sinusoidal component in eachframe in order to distribute the intensity variations introduced bythe weighting windows.Thus each component starting time(with)is set to different values before beingmultiplied by the weighting window.A general algorithm1is pro-posed.The resulting signal can be written as:(15)One can calculate the variance of this random signal:(16)where are sinusoidal components.By choosing equallyspaced over the half window,one can show that this sum of sinu-soids leads to noise with constant statistical properties.There are many ways to determine the offset values.For ex-ample,they can be randomly drawn according to a uniform distri-bution.But this method may lead to artifacts because many offsetmay have the same value,which introduces variancefluctuationsas previously seen in section2.4.To avoid these probabilities,weprefer choosing these values by dividing the half window inbins.So each offset equals。