016-P6U1A-Recent Advances and Future Trends in

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A_review_of_advanced_and_practical_lithium_battery_materials

A review of advanced and practical lithium battery materialsRotem Marom,*S.Francis Amalraj,Nicole Leifer,David Jacob and Doron AurbachReceived 3rd December 2010,Accepted 31st January 2011DOI:10.1039/c0jm04225kPresented herein is a discussion of the forefront in research and development of advanced electrode materials and electrolyte solutions for the next generation of lithium ion batteries.The main challenge of the ﬁeld today is in meeting the demands necessary to make the electric vehicle fully commercially viable.This requires high energy and power densities with no compromise in safety.Three families of advanced cathode materials (the limiting factor for energy density in the Li battery systems)are discussed in detail:LiMn 1.5Ni 0.5O 4high voltage spinel compounds,Li 2MnO 3–LiMO 2high capacity composite layered compounds,and LiMPO 4,where M ¼Fe,Mn.Graphite,Si,Li x TO y ,and MO (conversion reactions)are discussed as anode materials.The electrolyte is a key component that determines the ability to use high voltage cathodes and low voltage anodes in the same system.Electrode–solution interactions and passivation phenomena on both electrodes in Li-ion batteries also play signiﬁcant roles in determining stability,cycle life and safety features.This presentation is aimed at providing an overall picture of the road map necessary for the future development of advanced high energy density Li-ion batteries for EV applications.IntroductionOne of the greatest challenges of modern society is to stabilize a consistent energy supply that will meet our growing energy demands.A consideration of the facts at hand related to the energy sources on earth reveals that we are not encountering an energy crisis related to a shortage in total resources.For instancethe earth’s crust contains enough coal for the production of electricity for hundreds of years.1However the continued unbridled usage of this resource as it is currently employed may potentially bring about catastrophic climatological effects.As far as the availability of crude oil,however,it in fact appears that we are already beyond ‘peak’production.2As a result,increasing oil shortages in the near future seem inevitable.Therefore it is of critical importance to considerably decrease our use of oil for propulsion by developing effective electric vehicles (EVs).EV applications require high energy density energy storage devices that can enable a reasonable driving range betweenDepartment of Chemistry,Bar-Ilan University,Ramat-Gan,52900,Israel;Web:http://www.ch.biu.ac.il/people/aurbach.E-mail:rotem.marom@live.biu.ac.il;aurbach@mail.biu.ac.ilRotem MaromRotem Marom received her BS degree in organic chemistry (2005)and MS degree in poly-mer chemistry (2007)from Bar-Ilan University,Ramat Gan,Israel.She started a PhD in electrochemistry under the supervision of Prof.D.Aurbach in 2010.She is currently con-ducting research on a variety of lithium ion battery materials for electric vehicles,with a focus on electrolyte solutions,salts andadditives.S :Francis AmalrajFrancis Amalraj hails from Tamil Nadu,India.He received his MSc in Applied Chemistry from Anna University.He then carried out his doctoral studies at National Chemical Laboratory,Pune and obtained his PhD in Chemistry from Pune University (2008).He is currently a postdoctoral fellow in Prof.Doron Aurbach’s group at Bar-Ilan University,Israel.His current research interest focuses on the synthesis,electrochemical and transport properties of high ener-getic electrode materials for energy conversion and storage systems.Dynamic Article Links CJournal ofMaterials ChemistryCite this:DOI:10.1039/c0jm04225k /materialsFEATURE ARTICLED o w n l o a d e d b y B e i j i n g U n i v e r s i t y o f C h e m i c a l T e c h n o l o g y o n 24 F e b r u a r y 2011P u b l i s h e d o n 23 F e b r u a r y 2011 o n h t t p ://p u b s .r s c .o r g | d o i :10.1039/C 0J M 04225KView Onlinecharges and maintain acceptable speeds.3Other important requirements are high power density and acceptable safety features.The energy storage ﬁeld faces a second critical chal-lenge:namely,the development of rechargeable systems for load leveling applications (e.g.storing solar and wind energy,and reducing the massive wasted electricity from conventional fossil fuel combustion plants).4Here the main requirements are a very prolonged cycle life,components (i.e.,relevant elements)abun-dant in high quantities in the earth’s crust,and environmentally friendly systems.Since it is not clear whether Li-ion battery technology can contribute signiﬁcantly to this application,battery-centered solutions for this application are not discussedherein.In fact,even for electrical propulsion,the non-petroleum power source with the highest energy density is the H 2/O 2fuel cell (FC).5However,despite impressive developments in recent years in the ﬁeld,there are intrinsic problems related to electrocatalysis in the FCs and the storage of hydrogen 6that will need many years of R&D to solve.Hence,for the foreseeable future,rechargeable batteries appear to be the most practically viable power source for EVs.Among the available battery technologies to date,only Li-ion batteries may possess the power and energy densities necessary for EV applications.The commonly used Li-ion batteries that power almost all portable electronic equipment today are comprised of a graphite anode and a LiCoO 2cathode (3.6V system)and can reach a practical energy density of 150W h kg À1in single cells.This battery technology is not very useful for EV application due to its limited cycle life (especially at elevated temperatures)and prob-lematic safety features (especially for large,multi-cell modules).7While there are ongoing developments in the hybrid EV ﬁeld,including practical ones in which only part of the propulsion of the car is driven by an electrical motor and batteries,8the main goal of the battery community is to be able to develop full EV applications.This necessitates the development of Li-ion batteries with much higher energy densities compared to the practical state-of-the-art.The biggest challenge is that Li-ion batteries are complicated devices whose components never reach thermodynamic stability.The surface chemistry that occurs within these systems is very complicated,as described brieﬂy below,and continues to be the main factor that determines their performance.9Nicole Leifer Nicole Leifer received a BS degree in chemistry from MIT in 1998.After teaching high school chemistry and physics for several years at Stuyvesant High School in New York City,she began work towards her PhD in solid state physics from the City University of New York Grad-uate Center.Her research con-sisted primarily of employing solid state NMR in the study of lithium ion electrode materialsand electrode surfacephenomena with Prof.Green-baum at Hunter College andProf.Grey at Stony Brook University.After completing her PhD she joined Prof.Doron Aurbach for a postdoctorate at Bar-Ilan University to continue work in lithium ion battery research.There she continues her work in using NMR to study lithium materials in addition to new forays into carbon materials’research for super-capacitor applications with a focus on enhancement of electro-chemical performance through the incorporation of carbonnanotubes.David Jacob David Jacob earned a BSc from Amravati University in 1998,an MSc from Pune University in 2000,and completed his PhD at Bar-Ilan University in 2007under the tutelage of Professor Aharon Gedanken.As part of his PhD research,he developed novel methods of synthesizing metal ﬂuoride nano-material structures in ionic liquids.Upon ﬁnishing his PhD he joined Prof.Doron Aurbach’s lithium ionbattery group at Bar-Ilan in2007as a post-doctorate and during that time developed newformulations of electrolyte solutions for Li-ion batteries.He has a great interest in nanotechnology and as of 2011,has become the CEO of IsraZion Ltd.,a company dedicated to the manufacturing of novelnano-materials.Doron Aurbach Dr Doron Aurbach is a full Professor in the Department of Chemistry at Bar-Ilan Univer-sity (BIU)in Ramat Gan,Israel and a senate member at BIU since 1996.He chaired the chemistry department there during the years 2001–2005.He is also the chairman of the Israeli Labs Accreditation Authority.He founded the elec-trochemistry group at BIU at the end of 1985.His groupconducts research in thefollowing ﬁelds:Li ion batteries for electric vehicles and for otherportable uses (new cathodes,anodes,electrolyte solutions,elec-trodes–solution interactions,practical systems),rechargeable magnesium batteries,electronically conducting polymers,super-capacitors,engineering of new carbonaceous materials,develop-ment of devices for storage and conversion of sustainable energy (solar,wind)sensors and water desalination.The group currently collaborates with several prominent research groups in Europe and the US and with several commercial companies in Israel and abroad.He is also a fellow of the ECS and ISE as well as an associate editor of Electrochemical and Solid State Letters and the Journal of Solid State Electrochemistry.Prof.Aurbach has more than 350journals publications.D o w n l o a d e d b y B e i j i n g U n i v e r s i t y o f C h e m i c a l T e c h n o l o g y o n 24 F e b r u a r y 2011P u b l i s h e d o n 23 F e b r u a r y 2011 o n h t t p ://p u b s .r s c .o r g | d o i :10.1039/C 0J M 04225KAll electrodes,excluding 1.5V systems such as LiTiO x anodes,are surface-ﬁlm controlled (SFC)systems.At the anode side,all conventional electrolyte systems can be reduced in the presence of Li ions below 1.5V,thus forming insoluble Li-ion salts that comprise a passivating surface layer of particles referred to as the solid electrolyte interphase (SEI).10The cathode side is less trivial.Alkyl carbonates can be oxidized at potentials below 4V.11These reactions are inhibited on the passivated aluminium current collectors (Al CC)and on the composite cathodes.There is a rich surface chemistry on the cathode surface as well.In their lithiated state,nucleophilic oxygen anions in the surface layer of the cathode particles attack electrophilic RO(CO)OR solvents,forming different combinations of surface components (e.g.ROCO 2Li,ROCO 2M,ROLi,ROM etc.)depending on the electrolytes used.12The polymerization of solvent molecules such as EC by cationic stimulation results in the formation of poly-carbonates.13The dissolution of transition metal cations forms surface inactive Li x MO y phases.14Their precipitation on the anode side destroys the passivation of the negative electrodes.15Red-ox reactions with solution species form inactive LiMO y with the transition metal M at a lower oxidation state.14LiMO y compounds are spontaneously delithiated in air due to reactions with CO 2.16Acid–base reactions occur in the LiPF 6solutions (trace HF,water)that are commonly used in Li-ion batteries.Finally,LiCoO 2itself has a rich surface chemistry that inﬂuences its performance:4LiCo III O 2 !Co IV O 2þCo II Co III 2O 4þ2Li 2O !4HF4LiF þ2H 2O Co III compounds oxidize alkyl carbonates;CO 2is one of the products,Co III /Co II /Co 2+dissolution.14Interestingly,this process seems to be self-limiting,as the presence of Co 2+ions in solution itself stabilizes the LiCoO 2electrodes,17However,Co metal in turn appears to deposit on the negative electrodes,destroying their passivation.Hence the performance of many types of electrodes depends on their surface chemistry.Unfortunately surface studies provide more ambiguous results than bulk studies,therefore there are still many open questions related to the surface chemistry of Li-ion battery systems.It is for these reasons that proper R&D of advanced materials for Li-ion batteries has to include bulk structural and perfor-mance studies,electrode–solution interactions,and possible reﬂections between the anode and cathode.These studies require the use of the most advanced electrochemical,18structural (XRD,HR microscopy),spectroscopic and surface sensitive analytical techniques (SS NMR,19FTIR,20XPS,21Raman,22X-ray based spectroscopies 23).This presentation provides a review of the forefront of the study of advanced materials—electrolyte systems,current collectors,anode materials,and ﬁnally advanced cathodes materials used in Li-ion batteries,with the emphasis on contributions from the authors’group.ExperimentalMany of the materials reviewed were studied in this laboratory,therefore the experimental details have been provided as follows.The LiMO 2compounds studied were prepared via self-combus-tion reactions (SCRs).24Li[MnNiCo]O 2and Li 2MnO 3$Li/MnNiCo]O 2materials were produced in nano-andsubmicrometric particles both produced by SCR with different annealing stages (700 C for 1hour in air,900 C or 1000 C for 22hours in air,respectively).LiMn 1.5Ni 0.5O 4spinel particles were also synthesized using SCR.Li 4T 5O 12nanoparticles were obtained from NEI Inc.,USA.Graphitic material was obtained from Superior Graphite (USA),Timcal (Switzerland),and Conoco-Philips.LiMn 0.8Fe 0.2PO 4was obtained from HPL Switzerland.Standard electrolyte solutions (alkyl carbonates/LiPF 6),ready to use,were obtained from UBE,Japan.Ionic liquids were obtained from Merck KGaA (Germany and Toyo Gosie Ltd.,(Japan)).The surface chemistry of the various electrodes was charac-terized by the following techniques:Fourier transform infrared (FTIR)spectroscopy using a Magna 860Spectrometer from Nicolet Inc.,placed in a homemade glove box purged with H 2O and CO 2(Balson Inc.air puriﬁcation system)and carried out in diffuse reﬂectance mode;high-resolution transmission electron microscopy (HR-TEM)and scanning electron microscopy (SEM),using a JEOL-JEM-2011(200kV)and JEOL-JSM-7000F electron microscopes,respectively,both equipped with an energy dispersive X-ray microanalysis system from Oxford Inc.;X-ray photoelectron spectroscopy (XPS)using an HX Axis spectrom-eter from Kratos,Inc.(England)with monochromic Al K a (1486.6eV)X-ray beam radiation;solid state 7Li magic angle spinning (MAS)NMR performed at 194.34MHz on a Bruker Avance 500MHz spectrometer in 3.2mm rotors at spinning speeds of 18–22kHz;single pulse and rotor synchronized Hahn echo sequences were used,and the spectra were referenced to 1M LiCl at 0ppm;MicroRaman spectroscopy with a spectrometerfrom Jobin-Yvon Inc.,France.We also used M €ossbauer spec-troscopy for studying the stability of LiMPO 4compounds (conventional constant-acceleration spectrometer,room temperature,50mC:57Co:Rh source,the absorbers were put in Perspex holders.In situ AFM measurements were carried out using the system described in ref.25.The following electrochemical measurements were posite electrodes were prepared by spreading slurries comprising the active mass,carbon powder and poly-vinylidene diﬂuoride (PVdF)binder (ratio of 75%:15%:10%by weight,mixed into N -methyl pyrrolidone (NMP),and deposited onto aluminium foil current collectors,followed by drying in a vacuum oven.The average load was around 2.5mg active mass per cm 2.These electrodes were tested in two-electrode,coin-type cells (Model 2032from NRC Canada)with Li foil serving as the counter electrode,and various electrolyte puter-ized multi-channel battery analyzers from Maccor Inc.(USA)and Arbin Inc.were used for galvanostatic measurements (voltage vs.time/capacity,measured at constant currents).Results and discussionOur road map for materials developmentFig.1indicates a suggested road map for the direction of Li-ion research.The axes are voltage and capacity,and a variety of electrode materials are marked therein according to their respective values.As is clear,the main limiting factor is the cathode material (in voltage and capacity).The electrode mate-rials currently used in today’s practical batteries allow forD o w n l o a d e d b y B e i j i n g U n i v e r s i t y o f C h e m i c a l T e c h n o l o g y o n 24 F e b r u a r y 2011P u b l i s h e d o n 23 F e b r u a r y 2011 o n h t t p ://p u b s .r s c .o r g | d o i :10.1039/C 0J M 04225Ka nominal voltage of below 4V.The lower limit of the electro-chemical window of the currently used electrolyte solutions (alkyl carbonates/LiPF 6)is approximately 1.5V vs.Li 26(see later discussion about the passivation phenomena that allow for the operation of lower voltage electrodes,such as Li and Li–graphite).The anodic limit of the electrochemical window of the alkyl carbonate/LiPF 6solutions has not been speciﬁcally determined but practical accepted values are between 4.2and 5V vs.Li 26(see further discussion).With some systems which will be discussed later,meta-stability up to 4.9V can be achieved in these standard electrolyte solutions.Electrolyte solutionsThe anodic stability limits of electrolyte solutions for Li-ion batteries (and those of polar aprotic solutions in general)demand ongoing research in this subﬁeld as well.It is hard to deﬁne the onset of oxidation reactions of nonaqueous electrolyte solutions because these strongly depend on the level of purity,the presence of contaminants,and the types of electrodes used.Alkyl carbonates are still the solutions of choice with little competition (except by ionic liquids,as discussed below)because of the high oxidation state of their central carbon (+4).Within this class of compounds EC and DMC have the highest anodic stability,due to their small alkyl groups.An additional beneﬁt is that,as discussed above,all kinds of negative electrodes,Li,Li–graphite,Li–Si,etc.,develop excellent passivation in these solutions at low potentials.The potentiodynamic behavior of polar aprotic solutions based on alkyl carbonates and inert electrodes (Pt,glassy carbon,Au)shows an impressive anodic stability and an irreversible cathodic wave whose onset is $1.5vs.Li,which does not appear in consequent cycles due to passivation of the anode surface bythe SEI.The onset of these oxidation reactions is not well deﬁned (>4/5V vs.Li).An important discovery was the fact that in the presence of Li salts,EC,one of the most reactive alkyl carbonates (in terms of reduction),forms a variety of semi-organic Li-con-taining salts that serve as passivation agents on Li,Li–carbon,Li–Si,and inert metal electrodes polarized to low potentials.Fig.2and Scheme 1indicates the most signiﬁcant reduction schemes for EC,as elucidated through spectroscopic measure-ments (FTIR,XPS,NMR,Raman).27–29It is important to note (as reﬂected in Scheme 1)that the nature of the Li salts present greatly affects the electrode surface chemistry.When the pres-ence of the salt does not induce the formation of acidic species in solutions (e.g.,LiClO 4,LiN(SO 2CF 3)2),alkyl carbonates are reduced to ROCO 2Li and ROLi compounds,as presented in Fig. 2.In LiPF 6solutions acidic species are formed:LiPF 6decomposes thermally to LiF and PF 5.The latter moiety is a Lewis acid which further reacts with any protic contaminants (e.g.unavoidably present traces of water)to form HF.The presence of such acidic species in solution strongly affects the surface chemistry in two ways.One way is that PF 5interactswithFig.1The road map for R&D of new electrode materials,compared to today’s state-of-the-art.The y and x axes are voltage and speciﬁc capacity,respectively.Fig.2A schematic presentation of the CV behavior of inert (Pt)elec-trodes in various families of polar aprotic solvents with Li salts.26D o w n l o a d e d b y B e i j i n g U n i v e r s i t y o f C h e m i c a l T e c h n o l o g y o n 24 F e b r u a r y 2011P u b l i s h e d o n 23 F e b r u a r y 2011 o n h t t p ://p u b s .r s c .o r g | d o i :10.1039/C 0J M 04225Kthe carbonyl group and channels the reduction process of EC to form ethylene di-alkoxide species along with more complicated alkoxy compounds such as binary and tertiary ethers,rather than Li-ethylene dicarbonates (see schemes in Fig.2);the other way is that HF reacts with ROLi and ROCO 2Li to form ROH,ROCO 2H (which further decomposes to ROH and CO 2),and surface LiF.Other species formed from the reduction of EC are Li-oxalate and moieties with Li–C and C–F bonds (see Scheme 1).27–31Efforts have been made to enhance the formation of the passivation layer (on graphite electrodes in particular)in the presence of these solutions through the use of surface-active additives such as vinylene carbonate (VC)and lithium bi-oxalato borate (LiBOB).27At this point there are hundreds of publica-tions and patents on various passivating agents,particularly for graphite electrodes;their further discussion is beyond the scope of this paper.Readers may instead be referred to the excellent review by Xu 32on this subject.Ionic liquids (ILs)have excellent qualities that could render them very relevant for use in advanced Li-ion batteries,including high anodic stability,low volatility and low ﬂammability.Their main drawbacks are their high viscosities,problems in wetting particle pores in composite structures,and low ionic conductivity at low temperatures.Recent years have seen increasing efforts to test ILs as solvents or additives in Li-ion battery systems.33Fig.3shows the cyclic voltammetric response (Pt working electrodes)of imidazolium-,piperidinium-,and pyrrolidinium-based ILs with N(SO 2CF 3)2Àanions containing LiN(SO 2CF 3)2salt.34This ﬁgure reﬂects the very wide electrochemical window and impressive anodic stability (>5V)of piperidium-and pyr-rolidium-based ILs.Imidazolium-based IL solutions have a much lower cathodic stability than the above cyclic quaternary ammonium cation-based IL solutions,as demonstrated in Fig.3.The cyclic voltammograms of several common electrode mate-rials measured in IL-based solutions are also included in the ﬁgure.It is clearly demonstrated that the Li,Li–Si,LiCoO 2,andLiMn 1.5Ni 0.5O 4electrodes behave reversibly in piperidium-and pyrrolidium-based ILs with N(SO 2CF 3)2Àand LiN(SO 2CF 3)2salts.This ﬁgure demonstrates the main advantage of the above IL systems:namely,the wide electrochemical window with exceptionally high anodic stability.It was demonstrated that aluminium electrodes are fully passivated in solutions based on derivatives of pyrrolidium with a N(SO 2CF 3)2Àanion and LiN(SO 2CF 3)2.35Hence,in contrast to alkyl carbonate-based solutions in which LiN(SO 2CF 3)2has limited usefulness as a salt due to the poor passivation of aluminium in its solutions in the above IL-based systems,the use of N(SO 2CF 3)2Àas the anion doesn’t limit their anodic stability at all.In fact it was possible to demonstrate prototype graphite/LiMn 1.5Ni 0.5O 4and Li/L-iMn 1.5Ni 0.5O 4cells operating even at 60 C insolutionsScheme 1A reaction scheme for all possible reduction paths of EC that form passivating surface species (detected by FTIR,XPS,Raman,and SSNMR 28–31,49).Fig.3Steady-state CV response of a Pt electrode in three IL solutions,as indicated.(See structure formulae presented therein.)The CV presentations include insets of steady-state CVs of four electrodes,as indicated:Li,Li–Si,LiCoO 2,and LiMn 1.5Ni 0.5O 4.34D o w n l o a d e d b y B e i j i n g U n i v e r s i t y o f C h e m i c a l T e c h n o l o g y o n 24 F e b r u a r y 2011P u b l i s h e d o n 23 F e b r u a r y 2011 o n h t t p ://p u b s .r s c .o r g | d o i :10.1039/C 0J M 04225Kcomprising alkyl piperidium-N(SO2CF3)2as the IL solvent and Li(SO2CF3)2as the electrolyte.34Challenges remain in as far as the use of these IL-based solutions with graphite electrodes.22Fig.4shows the typical steady state of the CV of graphite electrodes in the IL without Li salts.The response in this graph reﬂects the reversible behavior of these electrodes which involves the insertion of the IL cations into the graphite lattice and their subsequent reduction at very low potentials.However when the IL contains Li salt,the nature of the reduction processes drastically changes.It was recently found that in the presence of Li ions the N(SO2CF3)2Àanion is reduced to insoluble ionic compounds such as LiF,LiCF3, LiSO2CF3,Li2S2O4etc.,which passivate graphite electrodes to different extents,depending on their morphology(Fig.4).22 Fig.4b shows a typical SEM image of a natural graphite(NG) particle with a schematic view of its edge planes.Fig.4c shows theﬁrst CVs of composite electrodes comprising NG particles in the Li(SO2CF3)2/IL solution.These voltammograms reﬂect an irreversible cathodic wave at theﬁrst cycle that belongs to the reduction and passivation processes and their highly reversible repeated Li insertion into the electrodes comprising NG. Reversible capacities close to the theoretical ones have been measured.Fig.4d and e reﬂect the structure and behavior of synthetic graphiteﬂakes.The edge planes of these particles are assumed to be much rougher than those of the NG particles,and so their passivation in the same IL solutions is not reached easily. Their voltammetric response reﬂects the co-insertion of the IL cations(peaks at0.5V vs.Li)together with Li insertion at the lower potentials(<0.3V vs.Li).Passivation of this type of graphite is obtained gradually upon repeated cycling(Fig.4e), and the steady-state capacity that can be obtained is much lower than the theoretical one(372mA h gÀ1).Hence it seems that using graphite particles with suitable morphologies can enable their highly reversible and stable operation in cyclic ammonium-based ILs.This would make it possible to operate high voltage Li-ion batteries even at elevated temperatures(e.g. 4.7–4.8V graphite/LiMn1.5Ni0.5O4cells).34 The main challenge in thisﬁeld is to demonstrate the reasonable performance of cells with IL-based electrolytes at high rates and low temperatures.To this end,the use of different blends of ILs may lead to future breakthroughs.Current collectorsThe current collectors used in Li-ion systems for the cathodes can also affect the anodic stability of the electrolyte solutions.Many common metals will dissolve in aprotic solutions in the potential ranges used with advanced cathode materials(up to5V vs.Li). Inert metals such as Pt and Au are also irrelevant due to cost considerations.Aluminium,however,is both abundantand Fig.4A collection of data related to the behavior of graphite electrodes in butyl,methyl piperidinium IL solutions.22(a)The behavior of natural graphite electrodes in pure IL without Li salt(steady-state CV is presented).(b)The schematic morphology and a SEM image of natural graphite(NG)ﬂakes.(c)The CV response(3ﬁrst consecutive cycles)of NG electrodes in IL/0.5lithium triﬂuoromethanesulfonimide(LiTFSI)solution.(d and e)Same as(b and c)but for synthetic graphiteﬂakes.DownloadedbyBeijingUniversityofChemicalTechnologyon24February211Publishedon23February211onhttp://pubs.rsc.org|doi:1.139/CJM4225Kcheap and functions very well as a current collector due to its excellent passivation properties which allow it a high anodic stability.The question remains as to what extent Al surfaces can maintain the stability required for advanced cathode materials (up to 5V vs.Li),especially at elevated temperatures.Fig.5presents the potentiodynamic response of Al electrodes in various EC–DMC solutions,considered the alkyl carbonate solvent mixture with the highest anodic stability,at 30and 60 C.37The inset to this picture shows several images in which it is demonstrated that Al surfaces are indeed active and develop unique morphologies in the various solutions due to their obvious anodic processes in solutions,some of which lead to their effective passivation.The electrolyte used has a critical impact on the anodic stability of the Al.In general,LiPF 6solutions demonstrate the highest stability even at elevated temperatures due to the formation of surface AlF 3and even Al(PF 6)3.Al CCs in EC–DMC/LiPF 6solutions provide the highest anodic stability possible for conventional electrode/solution systems.This was demonstrated for Li/LiMn 1.5Ni 0.5O 4spinel (4.8V)cells,even at 60 C.36This was also conﬁrmed using bare Al electrodes polarized up to 5V at 60 C;the anodic currents were seen to decay to negligible values due to passivation,mostly by surface AlF 3.37Passivation can also be reached in Li(SO 2CF 3),LiClO 4and LiBOB solutions (Fig.5).Above 4V (vs.Li),the formation of a successful passivation layer on Al CCs is highly dependent on the electrolyte formula used.The anodic stability of EC–DMC/LiPF 6solutions and Al current collectors may be further enhanced by the use of additives,but a review of additives in itself deserves an article of its own and for this readers are again referred to the review by Xu.32When discussing the topic of current collectors for Li ion battery electrodes,it is important to note the highly innovative work on (particularly anodic)current collectors by Taberna et al.on nano-architectured Cu CCs 47and Hu et al.who assembled CCs based on carbon nano-tubes for ﬂexible paper-like batteries,38both of whom demonstrated suberb rate capabilities.39AnodesThe anode section in Fig.1indicates four of the most promising groups of materials whose Li-ion chemistry is elaborated as follows:1.Carbonaceous materials/graphite:Li ++e À+C 6#LiC 62.Sn and Si-based alloys and composites:40,41Si(Sn)+x Li ++x e À#Li x Si(Sn),X max ¼4.4.3.Metal oxides (i.e.conversion reactions):nano-MO +2Li ++2e À#nano-MO +Li 2O(in a composite structure).424.Li x TiO y electrodes (most importantly,the Li 4Ti 5O 12spinel structure).43Li 4Ti 5O 12+x Li ++x e À#Li 4+x Ti 5O 12(where x is between 2and 3).Conversion reactions,while they demonstrate capacities much higher than that of graphite,are,practically speaking,not very well-suited for use as anodes in Li-ion batteries as they generally take place below the thermodynamic limit of most developed electrolyte solutions.42In addition,as the reactions require a nanostructuring of the materials,their stability at elevated temperatures will necessarily be an issue because of the higher reactivity (due to the 1000-fold increase in surface area).As per the published research on this topic,only a limited meta-stability has been demonstrated.Practically speaking,it does not seem likely that Li batteries comprising nano-MO anodes will ever reach the prolonged cycle life and stability required for EV applications.Tin and silicon behave similarly upon alloying with Li,with similar stoichiometries and >300%volume changes upon lith-iation,44but the latter remain more popular,as Si is much more abundant than Sn,and Li–Si electrodes indicate a 4-fold higher capacity.The main approaches for attaining a workable revers-ibility in the Si(Sn)–Li alloying reactions have been through the use of both nanoparticles (e.g.,a Si–C nanocomposites 45)and composite structures (Si/Sn–M1–M2inter-metalliccompounds 44),both of which can better accommodate these huge volume changes.The type of binder used in composite electrodes containing Si particles is very important.Extensive work has been conducted to determine suitable binders for these systems that can improve the stability and cycle life of composite silicon electrodes.46As the practical usage of these systems for EV applications is far from maturity,these electrodes are not dis-cussed in depth in this paper.However it is important to note that there have been several recent demonstrations of how silica wires and carpets of Si nano-rods can act as much improved anode materials for Li battery systems in that they can serveasFig.5The potentiodynamic behavior of Al electrodes (current density measured vs.E during linear potential scanning)in various solutions at 30and 60 C,as indicated.The inset shows SEM micrographs of passivated Al surfaces by the anodic polarization to 5V in the solutions indicated therein.37D o w n l o a d e d b y B e i j i n g U n i v e r s i t y o f C h e m i c a l T e c h n o l o g y o n 24 F e b r u a r y 2011P u b l i s h e d o n 23 F e b r u a r y 2011 o n h t t p ://p u b s .r s c .o r g | d o i :10.1039/C 0J M 04225K。

Recent_Progress_in_Catalytic_Materials_for_Catalyt

Material Sciences 材料科学, 2011, 1, 10-16doi:10.4236/ms.2011.11003 Published Online April 2011 (/journal/ms/)Recent Progress in Catalytic Materials for Catalytic Combustion of Chlorinated Volatile OrganicCompounds#Xuehua Yang1, Aidong Tang1*, Xianwei Li21School of Chemistry and Chemical Engineering, Central South University, Changsha2Institute of Environment and Resource, Baosteel Co., Ltd., ShanghaiReceived: Mar. 14th, 2011; revised: Apr. 15th, 2011; accepted: Apr. 20th, 2011.Abstract: The research progress in the catalytic combustion of Cl-VOCs(Chlorinated Volatile Organic Compounds) is reviewed. In this review, the effects of the active species, catalyst support, water vapor and coking on the catalytic combustion reaction were summarized. The research related to noble metal catalysts mainly focuses on developing new supports and dual noble catalysts. The research on non-noble metal cata-lysts concentrate on the development of transition metal mixed oxide, perovskites and spinel catalysts; The chlorination of active species is regarded as an important reason for catalyst deactivation. Besides, the effects of water vapor and coking deactivation on the catalytic combustion process are discussed with considering the practical application. This review will be helpful in choosing an appropriate catalyst and the optimal reac-tion conditions for the removal of Cl-VOCs by catalytic combustion with high activity and high stability. Keywords:Catalyst; Noble metal; Metal oxide; Chlorinated Volatile Organic Compounds; Deactivation催化燃烧Cl-VOCs催化材料的研究进展#杨学华1，唐爱东1*，李咸伟21中南大学化学化工学院，长沙2宝钢股份研究院环境与资源研究所，上海收稿日期：2011年3月14日；修回日期：2011年4月15日；录用日期：2011年4月20日摘要：从催化剂活性组分、催化剂载体、催化剂失活三个方面，对近年来催化燃烧含氯挥发性有机物(Cl-VOCs)催化剂的研究进行了总结。

The Physical Properties of Carbon Nanotubes

The Physical Properties of CarbonNanotubesCarbon nanotubes (CNTs) are one of the most fascinating materials developed in the past few decades. They are cylindrical nanostructures composed of carbon atoms arranged in a hexagonal pattern. CNTs have unique properties, including high strength and stiffness, small size, exceptional electrical conductivity, and thermal conductivity. These properties make them preferable for numerous applications in several fields, including electronics, materials science, aerospace, and biotechnology.Structure of carbon nanotubesCarbon nanotubes have two primary structural types: single-walled nanotubes (SWNTs) and multi-walled nanotubes (MWNTs). SWNTs consist of a single rolled sheet, while MWNTs contain multiple rolled sheets. The diameter of SWNTs ranges from 0.4to 2 nm, while MWNTs have diameters ranging from 2 to 100 nm. The length of CNTs is usually several micrometers, but they can be longer.Thanks to their small dimensions and tubular structure, CNTs have a high aspect ratio, which means that their length is much greater than their diameter. This aspect ratio gives CNTs their unique mechanical properties. They are exceptionally strong and stiff, with a Young's modulus three to four times higher than that of steel. Moreover, CNTs are quite resilient, and their deformation before failure is much more elevated than conventional materials, making them perfect for use in new structural materials.Electrical properties of carbon nanotubesOne of the most remarkable properties of CNTs is their electrical conductivity. They have excellent electrical properties, which means they can conduct electricity even better than copper. SWNTs are metallic or semiconducting depending on their chiral angle, while MWNTs are usually metallic.SWNTs have particular band structures, and their electrical properties depend heavily on their atomic structure. The electronic properties of CNTs make them ideal for use in electronic applications, such as field-effect transistors, diodes, and sensors. CNTs have the potential to improve the performance of transistors and other electronic devices significantly.Thermal properties of carbon nanotubesCNTs also have exceptional thermal conductivity, making them useful in thermal management materials. The thermal conductivity of CNTs is approximately seven times higher than that of copper. Moreover, CNTs are excellent heat conductors at the nanoscale, which gives them the potential to improve the efficiency of thermal management materials in electronic devices.Other physical properties of carbon nanotubesIn addition to their excellent mechanical, electrical, and thermal properties, CNTs also exhibit some other unique physical properties that make them advantageous for several applications. They are lightweight and can be dispersed in solvents, allowing them to be used in coatings, composites, and other materials.Furthermore, because of their nanoscale dimensions, CNTs have a high surface area-to-volume ratio, which makes them an effective adsorbent for gas and liquid molecules. This property makes CNTs promising candidates for gas storage and separation, as well as water purification.ConclusionCNTs are exceptional materials that have unique physical properties that lend themselves to several applications. They are lightweight, strong, stiff, and excellent electrical and thermal conductors, making them preferable for use in several fields, including electronics, materials science, and aerospace. Their physical properties make CNTs promising candidates for improving the performance of electronic devices, structural materials, and energy storage systems.。

我最喜欢的发明英语作文

In the vast expanse of human history,countless inventions have shaped the way we live,work,and interact with the world around us.Among these,there is one particular invention that has captured my heart and admiration:the Internet.The Dawn of ConnectivityThe Internet,a global network of interconnected computers,was born out of the need for a robust and flexible communication system.Its origins can be traced back to the late 1960s with the development of ARPANET,a project funded by the U.S.Department of Defense.Over the decades,it has evolved from a tool used primarily by researchers and academics to a ubiquitous presence in the daily lives of billions.The Power of InformationWhat makes the Internet my favorite invention is its unparalleled ability to disseminate information.It has democratized access to knowledge,allowing anyone with a connection to learn about virtually any subject.From the comfort of ones home,one can explore the depths of the ocean,the mysteries of the universe,or the intricacies of ancient civilizations.The Catalyst for InnovationThe Internet has also been a catalyst for innovation,spawning new industries and transforming existing ones.Ecommerce,online education,telemedicine,and social media are just a few examples of how the Internet has revolutionized the way we conduct business and maintain social relationships.The Bridge to Global CommunityMoreover,the Internet has served as a bridge to a global community,breaking down geographical barriers and fostering a sense of interconnectedness.It has enabled people from different cultures and backgrounds to collaborate,share ideas,and build friendships that transcend borders.The Challenges and OpportunitiesWhile the Internet has brought about remarkable benefits,it has also presented challenges, such as issues of privacy,security,and the digital divide.These challenges,however,are opportunities for further innovation and improvement,as we strive to create a more inclusive and secure digital environment.The Future of the InternetAs we look to the future,the potential of the Internet continues to expand with advancements in technology like artificial intelligence,virtual reality,and the Internet of Things.The possibilities are endless,and the Internet remains a testament to human ingenuity and our relentless pursuit of progress.In conclusion,the Internet is more than just an invention it is a living,breathing entity that continues to evolve and shape our world in ways we are only beginning to understand.It is a source of inspiration,a tool for empowerment,and a symbol of our collective potential.For these reasons and more,the Internet holds a special place in my heart as my favorite invention.。

英语科技文献阅读期末总结

英语科技文献阅读期末总结Introduction:The field of technology is advancing rapidly, with new discoveries and developments revolutionizing various industries. In this paper, I will present a summary of several research papers that I have read throughout the semester. Each paper focuses on a different aspect of technological advancements and their impact on society. The topics covered include artificial intelligence, nanotechnology, biotechnology, and renewable energy. Through these summaries, we will gain a deeper understanding of the new frontiers in science and technology.1. Artificial Intelligence:The first paper explores the impact of artificial intelligence (AI) on various industries. It discusses how AI has improved productivity, efficiency, and decision-making processes through automation. Additionally, it examines the ethical concerns surrounding AI and machine learning, such as job displacement and privacy issues. The paper concludes that while AI has tremendous potential, proper regulations and guidelines need to be implemented to ensure a balance between innovation and societal well-being.2. Nanotechnology:The second paper focuses on nanotechnology and its applications. It highlights how nanomaterials have revolutionized industries such as electronics, medicine, and energy. It discusses the potential of nanotechnology in enhancing drug delivery systems, developing more efficient solar cells, and improving energy storage devices. The paper also addresses the challenges of scaling up nanotechnology from the lab to commercial production, emphasizing the need for safe manufacturing processes and responsible use of nanomaterials.3. Biotechnology:The third paper explores the advancements in biotechnology, specifically in the field of genetic engineering. It discusses the potential of gene editing techniques, such as CRISPR-Cas9, in treating genetic diseases and improving agricultural yields. The paper also examines the ethical implications of manipulating DNA, including the need for informed consent in human gene editing and the impact of genetically modified organisms on the environment. The paper concludes that while biotechnology holds great promise, rigorous ethical and safety considerations need to be undertaken.4. Renewable Energy:The final paper investigates the progress made in renewable energy technologies. It discusses the importance of transitioning from fossil fuels to clean energy sources to mitigate climate change. The paper evaluates various renewable energy options, includingsolar, wind, hydroelectric, and geothermal power. It analyzes the challenges associated with the intermittent nature of renewable energy sources and the need for efficient energy storage systems. The paper concludes that a comprehensive approach, combining renewable energy generation, energy storage, and smart grid technologies, is necessary to achieve a sustainable and clean energy future.Conclusion:In conclusion, the four research papers discussed in this summary demonstrate the significant impact of technological advancements in various fields. The papers highlighted the potential benefits and challenges associated with AI, nanotechnology, biotechnology, and renewable energy. It is crucial for policymakers, scientists, and the public to work together to ensure responsible and ethical use of these technologies. As we move forward, continuous research and development are essential to leverage technology for the betterment of society.。

新一代大学英语发展篇综合教程2答案

新一代大学英语发展篇综合教程2答案Unit 1 Philosophy and thoughtsiExplore 11-5 iExplore 1:Building your languageTASK 11. charisma2. brilliant3. uglyTASK 21. awkward /razor-sharp2. straightforward3. toughTASK 31. Using a counter-example2. debate their ideas3. begin a conversationTASK 41. question the assumption2. reveal the limits3. understand the natureTASK 5B B B A B BiExplore 21-7 iExplore 2:Building your languageTASK 11. been painted as2. is counted among3. known asTASK 21. reforms2. brought about3. laid down the rules4. formulate the creedTASK 31. under the impulsion of2. played a role of some importance3. grown in size and influenceTASK 4Reference:1. Many descendants of Confucius were identified and honored by successive imperial governments with titles of nobility and official posts.2. Sima Niu. one of Confucius' disciples, came of noble ancestry from the Song state.3. As a member of the craft or artisan class. Mozi lived in humble circumstances and his philosophy was distinctively anti-aristocratic.4. Jiang Taigong was more than 70 years old, but the ruler did not give him an office and people all referred to him as a mad fellow.5. After Confucius resigned his post in the state of Lu, he began a series of journeys around the small kingdoms of northeast and central China, including the states of Wei.Song, Chen, and Cai.6. By Confucius age, the Zhou kings had been reduced to mere figureheads, and real power was put into the hands of various local rulers.iProduce1-8 Unit project1-8 Unit project 1-3Reference:Great minds think alike?Good morning, ladies and gentlemen. Today I'm going to talk about two great thinkers. Socrates and Confucius. two men with great minds. Both English and Chinese have a saying about great minds,"Great minds think alike" and "英雄所见略同."Then do Socrates and Confucius think alike?I will try to compare the two great minds interms of their lives.thoughts and influence. Now let's get started.Both Socrates and Confucius seemed to lead a meaningful and colorful life. As a young man, Socrates had been a brave soldier fighting in a war. Confucius'early life seemed to be equally difficult, since he had to earn his living at menial tasks. After that, it seems that Socrates and Confucius followed different ways in their lives. In middle age.Socrates did nothing but ask people questions in the marketplace. By contrast, Confucius tried all possible ways to achieve his dream. For example, he had been a teacher.gathering young men to study his doctrines. He was also given an office in the government, although he did not have real power. When he saw that he could accomplish nothing.he resigned his post and set off on travels to advocate his Way in other states. After that, he resumed his teaching. Socrates and Confucius spent their lives in different ways.because they had different pursuits. Socrates spent his whole life pursuing wisdom by asking questions. For Socrates,wisdom meant understanding the true nature of our existence,including the limits of what we can know. He declared that if we do not think about what we are doing, then life is not worth living. Therefore. he kept asking questions to himself and to others. By doing this, he helped people understand such concepts as moral and courage and realize what they knew and what they didn't. Socrates would die rather than give up his pursuit of wisdom and truth. Confucius, however, pursued common welfare, that is, the well-being of all the common people. During his times, the common people lived a miserable and tragic life. Confucius could not tolerate these conditions and resolved to devote his life to trying to right them. According to Confucius, in a natural and normal state of society men should Confucius and the rulers should aim to bring about thewelfare and happiness of all the common people. As I have mentioned,he tried all possible methods to achieve this goal. He taught young men to promote his doctrines; he worked in the government to put his teachings into practice;he also travelled around many states to find a ruler who would use his Way.Socrates and Confucius pursued different things, but both had great influence. Socrates laid the foundation of Western philosophy. With him the subject really took off. However.the two thinkers have influenced the Western tradition and the Chinese tradition in different ways. Following Socrates'pursuit of truth and wisdom. Western thinkers seemed to be more interested in studying the physical world. After Confucius, Chinese thinkers paid more attention to interpersonal relationships. Then, do great minds think alike? Well, they may have different pursuits, but they have the same devotion to their pursuits. That is what I have learned about Socrates and Confucius. Thank you.iAssess1-10 Unit testPart I1. eccentric2. irritating3. enforce4. restore5. allegiance6. betrayed/betray7. strives8. intriguedPart ⅡB C A B B APart ⅢPart III 1-1Reference:和很多人一样，亚里士多德也因最好的论点并不总能赢得辩论而困扰。

recent advances in electrical -回复

recent advances in electrical -回复There have been several recent advances in the field of electrical engineering. Here are some notable ones:1. Internet of Things (IoT): The IoT has revolutionized the way devices are connected and interact with each other. It has enabled smart homes, smart grids, and improved industrial automation. Electrical engineers play a crucial role in designing and implementing IoT systems.2. Renewable Energy: The development of renewable energy sources, such as solar and wind power, has gained significant traction in recent years. Electrical engineers are involved in designing and improving energy conversion and storage systems, making renewable energy more efficient and accessible.3. Electric Vehicles (EVs): The rise of electric vehicles has led to significant advancements in battery technologies, charging infrastructure, and power management systems. Electrical engineers are at the forefront of developing and improving these technologies to enhance the performance and range of EVs.4. Power Electronics: Power electronics has seen significant advancements in recent years, leading to the development of more efficient and compact power conversion and control systems. This has applications in various fields, including renewable energy, electric vehicles, and consumer electronics.5. Artificial Intelligence (AI) in Electrical Engineering: AI has been integrated into various electrical engineering applications,such as power system optimization, smart grid management, and fault diagnosis. AI algorithms are used to improve the performance and reliability of electrical systems.6. Nanotechnology: Nanotechnology has had a profound impact on electrical engineering by enabling the development of smaller and more efficient electronic components. This has led to advancements in fields such as semiconductor devices, sensors, and energy storage systems.7. Wireless Power Transfer: Wireless power transfer technology has made significant strides, allowing for the transmission of electricity over short distances without the need for physical connections. This has applications in wireless charging of devices, electric vehicle charging, and medical implants.These recent advances in electrical engineering have not only improved existing technologies but also opened up new opportunities for innovation and development in various industries.。

科技和创新的英语作文

In the contemporary world,the role of technology and innovation is paramount. Here is a detailed essay on the subject:Introduction:The essence of human progress has always been intertwined with the development of technology and the spirit of innovation.From the invention of the wheel to the creation of the internet,each leap in technological advancement has marked a significant shift in the way we live,work,and communicate.The Impact of Technology:Technology has revolutionized various sectors,including healthcare,education, transportation,and communication.For instance,medical technology has enabled the development of advanced diagnostic tools and treatments,improving patient outcomes and extending life expectancy.In education,digital platforms and online learning have made knowledge accessible to a global audience,breaking geographical barriers. Innovation as a Catalyst:Innovation is the driving force behind technological progress.It is the process of translating an idea or invention into a good or service that creates value or for which customers will pay.Innovations such as smartphones,electric cars,and renewable energy technologies have not only created new markets but have also spurred economic growth and job creation.The Role of Research and Development:Investment in research and development RD is crucial for fostering innovation. Governments and private sectors alike must allocate resources to support RD activities in various fields.This not only leads to the creation of new technologies but also encourages a culture of creativity and problemsolving.Challenges and Ethical Considerations:While technology and innovation bring numerous benefits,they also present challenges. Issues such as privacy,cybersecurity,and the digital divide are pressing concerns that need to be addressed.Moreover,ethical considerations must guide the development and application of new technologies to ensure they are used responsibly and for the greater good.The Future of Technology and Innovation:Looking ahead,the integration of artificial intelligence,machine learning,and quantum computing is expected to bring about unprecedented changes.These technologies hold the potential to solve complex problems,from climate change to personalized medicine,but they also require careful stewardship to navigate the ethical and societal implications. Conclusion:In conclusion,technology and innovation are the cornerstones of modern society.They have the power to transform lives,economies,and the world at large.It is imperative that we continue to invest in and support these areas,while also ensuring that we address the challenges and ethical dilemmas they present.By doing so,we can harness the full potential of technology and innovation for the benefit of all.。

高中生英语作文《科技进步与隐私保护》

高中生英语作文《科技进步与隐私保护》Title: The Progress of Technology and Privacy ProtectionIn recent years, technological advancements have been revolutionizing our lives, making tasks easier and more convenient.From smartphones to artificial intelligence, these developments have transformed the way we live, work, and communicate.However, along with these benefits, there is a growing concern about privacy protection.On one hand, technology has brought about unprecedented convenience.We can now easily connect with friends and family across the globe, access a wealth of information at our fingertips, and perform various tasks with ease.Moreover, businesses have been able to streamline their operations, improve efficiency, and reach a wider customer base.On the other hand, the same technology that has brought us these benefits has also raised concerns about privacy.With the advent of social media platforms, messaging apps, and other online services, our personal information is increasingly vulnerable to unauthorized access and misuse.Data breaches, surveillance, and invasion of privacy have become more prevalent, raising questions about the extent to which technology companies should be allowed to collect and use our data.To address these concerns, it is crucial for governments and businesses to prioritize privacy protection.This can be achieved throughthe implementation of strict data protection laws and regulations.For instance, the European Union's General Data Protection Regulation (GDPR) imposes strict rules on how companies handle personal data, giving individuals more control over their information.Additionally, technology companies should be transparent about their data collection and usage policies.They should inform users about the types of data they collect, how they use it, and who they share it with.Moreover, users should be given the option to opt-out of data collection and usage practices that they find objectionable.In conclusion, while technological advancements have undoubtedly brought about numerous benefits, it is essential to balance these progresses with the need for privacy ernments, businesses, and individuals must work together to establish policies and practices that safeguard our personal information and uphold our right to privacy.Only by doing so can we fully reap the rewards of technology while mitigating its potential risks.。

22年9月英语四级作文

22年9月英语四级作文作文：Technology has rapidly transformed our lives in recent decades, reshaping the way we communicate, consume information, and interact with others. While this technological advancement offers numerous benefits, it also poses potential challenges and ethical dilemmas that warrant careful consideration.Benefits of Technological Advancement:Enhanced Connectivity: Technology has dramatically increased our ability to connect with people across geographical boundaries. Social media platforms, messaging apps, and video conferencing tools facilitate real-time communication and foster global communities.Access to Information: The internet has become an invaluable resource for accessing vast amounts ofinformation. From scientific research to cultural perspectives, technology empowers us to expand our knowledge and stay informed.Improved Efficiency: Automation and artificial intelligence (AI) have streamlined tasks and increased productivity in various sectors. From manufacturing to customer service, technology enhances efficiency and reduces costs.Entertainment and Leisure: Technology has revolutionized the way we experience entertainment. Streaming services, gaming consoles, and virtual reality headsets immerse us in worlds of imagination, fostering relaxation and enjoyment.Challenges and Ethical Dilemmas:Digital Divide: Despite its prevalence, access to technology remains unevenly distributed. Socioeconomic factors and geographical constraints can create a digital divide, limiting opportunities for those without adequateaccess.Privacy Concerns: The proliferation of personal data collected by technology companies raises concerns about privacy and data security. The potential for data misuse, surveillance, and identity theft necessitates robust regulations and ethical guidelines.Impact on Mental Health: While technology offers entertainment and social connection, excessive use can negatively impact mental health. Social media comparison, cyberbullying, and sleep disruption are among the potential risks associated with prolonged screen time.Job Displacement: Automation and AI have the potential to displace human workers in certain industries. This raises concerns about economic inequality and the need for reskilling and retraining programs.Ethical Bias: AI algorithms may inadvertently perpetuate biases and discrimination based on factors such as race, gender, or socioeconomic status. Ensuring fairnessand inclusivity in technology design is crucial.Mitigating the Challenges and Maximizing the Benefits:To fully harness the benefits of technology while mitigating its challenges, a multifaceted approach is required:Bridging the Digital Divide: Governments and organizations should prioritize expanding access to technology, particularly in underserved communities. This includes providing affordable internet connectivity,digital literacy training, and access to devices.Protecting Privacy: Regulatory frameworks should be established to protect personal data, prevent unauthorized access, and promote transparency in data collection practices. Individuals should also be empowered with tools and knowledge to control their online privacy.Promoting Digital Well-being: Education campaigns and initiatives should raise awareness about the potentialrisks of excessive screen time and encourage healthy technology habits. Schools and workplaces should prioritize digital well-being as part of their overall health and wellness programs.Preparing for the Future of Work: Governments and educational institutions should invest in programs that equip individuals with the skills and knowledge necessary to adapt to the changing job market. This includesreskilling and upskilling opportunities, as well as support for entrepreneurship and innovation.Addressing Ethical Bias: Developers and policymakers must take proactive steps to identify and mitigate biasesin AI algorithms. This involves fostering diversity in technology teams, implementing transparent and accountable decision-making processes, and promoting ethical training and certification programs.Conclusion:The technological revolution brings both opportunitiesand challenges. By embracing the benefits while addressing the ethical dilemmas, we can leverage technology to enhance our lives, foster societal progress, and create a more equitable and sustainable future. As technology continues to evolve, ongoing dialogue and collaboration among policymakers, industry leaders, and the public areessential to ensure that its development aligns with our human values and serves the betterment of humanity.。

中国石油大学高级英语译文及答案

Unit 1 Sources of EnergyText APetroleumSentence structure analysis1. Instead of originating in accumulating woody matter, petroleum may be the product of the accumulating fattymatter of ocean organisms such as plankton, the myriads of single-celled creatures that float in the surface layer of the ocean. (Para.2) 石油，并不是来自于逐渐积聚的木质物质，而可能是来自于逐渐积聚的海洋生物的脂肪物质。

比如浮游生物：大量浮游在海水表层的单细胞生物。

这是一个简单句，主语petroleum，谓语动词may be，表语product，构成句子主干。

instead of 介词短语作状语，such as plankton是product一词的同位语，the myriads of single-celled creatures that float in the surface layer of the ocean是名词性短语，做plankton的同位语。

2. It is only necessary that the organisms settle down into the ooze underlying shallow arms of the ocean underconditions of oxygen shortage. (Para. 3) 生物有机体只需在缺氧的条件下沉积到海湾浅水处的淤泥里。

该句的框架为：it is +adj.+that从句，it做形式主语，真正的主语是that从句的内容。

现在分词短语underlying…做后置定语修饰ooze。

初中七下英语外研社第六单元u一的作文

探索未来：科技与生活的融合In the age of rapid technological advancements, the integration of technology into our daily lives has become increasingly apparent. The sixth unit of the seventh grade English textbook published by Foreign Languages Teachingand Research Press explores this integration, focusing on the intersection of technology and lifestyle.Imagine waking up in the morning and being greeted by your smart home system, which automatically adjusts the lighting and temperature to your preferences. As youprepare for the day, you grab your smartphone to check your schedule and the news, all while your coffee machine prepares your favorite brew. This seamless blend of technology and lifestyle is not just a vision of the future; it is becoming a reality for many.The unit highlights the convenience and efficiency that technology brings to our lives. From online shopping to virtual reality experiences, technology has transformed the way we interact with the world. However, this integration also raises important questions about the impact of technology on our well-being and society.One of the main themes explored in the unit is the need for balance. While technology has made our lives more convenient, it is essential to maintain a healthy lifestyle and social connections. Excessive use of technology can lead to issues such as eye strain, neck pain, and even psychological problems like anxiety and depression. Therefore, it is crucial to find a balance between technology use and physical and mental well-being.Additionally, the unit discusses the ethical implications of technology. As we become more reliant on technology, there are concerns about privacy, security, and the potential misuse of personal data. It is important to be aware of these issues and take necessary precautions to protect our privacy and security.In conclusion, the integration of technology into our daily lives presents both opportunities and challenges. While technology has brought remarkable convenience and efficiency to our lives, it is crucial to maintain a healthy balance and be aware of its potential downsides. By doing so, we can harness the power of technology to enhanceour lives while protecting our well-being and societal values.**探索未来：科技与生活的融合**在科技飞速发展的时代，科技与我们日常生活的融合变得日益明显。

英语六级预测作文

英语六级预测作文Title: The Future of Work: Embracing Technological Advancements。

In recent years, the rapid advancement of technology has significantly transformed the way we work. Fromartificial intelligence to automation, these innovations have reshaped industries and job markets worldwide. As we look to the future, it becomes imperative to examine the implications of these changes and how individuals and societies can adapt to thrive in this evolving landscape.One significant aspect of the future of work is the integration of artificial intelligence (AI) and automation into various industries. AI algorithms and robotics are increasingly capable of performing tasks traditionally carried out by humans, leading to concerns about job displacement. However, while some jobs may indeed become obsolete, new opportunities will emerge in fields related to technology, such as software engineering, data analysis,and cybersecurity. Therefore, it is essential forindividuals to develop skills that are in high demand inthe digital age, such as critical thinking, problem-solving, and digital literacy.Furthermore, the future of work is characterized by remote and flexible employment arrangements. The COVID-19 pandemic has accelerated the adoption of remote work practices, demonstrating that many jobs can be performed effectively from home. This trend is likely to continue as companies recognize the benefits of remote work, such as increased productivity and cost savings. However, remote work also presents challenges, such as maintaining work-life balance and fostering collaboration among team members. Therefore, both employers and employees need to adapt by implementing effective communication strategies and leveraging technology to facilitate virtual collaboration.Another aspect of the future of work is the gig economy, where individuals work on a freelance or contract basis rather than being employed full-time by a single company. Platforms such as Uber, Airbnb, and Upwork have enabledmillions of people to earn income independently, offering flexibility and autonomy. However, the gig economy also raises concerns about job security, benefits, and labor rights. Policymakers need to address these issues by implementing regulations that protect the rights of gig workers while fostering innovation and entrepreneurship.In addition to technological advancements, demographic shifts are also shaping the future of work. The aging population in many countries is leading to a growing demand for healthcare services and eldercare. Moreover, increasing diversity in the workforce brings new perspectives and challenges related to inclusion and equity. Therefore, organizations need to embrace diversity and implement policies that promote inclusivity and equal opportunity for all employees.In conclusion, the future of work is characterized by technological advancements, remote employment, the gig economy, and demographic shifts. While these changes bring both opportunities and challenges, individuals andsocieties can adapt by developing relevant skills,embracing remote work practices, supporting gig workers,and fostering diversity and inclusion in the workforce. By embracing these changes and harnessing the power of technology, we can create a future where work is fulfilling, inclusive, and sustainable.。

科技信息日益发展英语作文

科技信息日益发展英语作文Technology is advancing at an unprecedented pace, with new innovations and breakthroughs happening every day. From artificial intelligence to virtual reality, thepossibilities seem endless.The impact of technology on our daily lives cannot be overstated. We rely on smartphones, tablets, and other devices to stay connected and informed. The way we communicate, work, and entertain ourselves has been completely transformed by technology.One of the most exciting developments in technology is the rise of renewable energy sources. Solar panels, wind turbines, and other green technologies are revolutionizing the way we power our world. This shift towardssustainability is not only good for the environment, but also for our future.The field of medicine has also been greatly influencedby technological advancements. From new surgical techniques to personalized medicine, technology has improved the quality of healthcare and saved countless lives.As technology continues to evolve, so do the ethical and moral questions that come with it. Issues such as data privacy, artificial intelligence, and genetic engineering raise important concerns that we must address as a society.In conclusion, the rapid development of technology is reshaping our world in ways we never thought possible. Itis up to us to harness the power of technology for the greater good and ensure that it benefits all of humanity.。

冬奥会科技发展作文英语

冬奥会科技发展作文英语Title: The Role of Technological Advancements in Winter Olympics Development。

Introduction。

The Winter Olympics, a celebration of athletic prowess and human resilience against the backdrop of snow-capped mountains and icy landscapes, has always been a testament to the fusion of sports and technology. In recent years, technological advancements have played an increasingly significant role in shaping the Winter Olympics, revolutionizing everything from equipment design to event management. This essay delves into the profound impact of technology on the development of the Winter Olympics, exploring its influence on athlete performance, audience experience, and the overall spectacle of the games.Technological Innovations in Equipment Design。

One of the most visible manifestations of technological progress in the Winter Olympics is evident in the design and engineering of sports equipment. From skis and snowboards to speed skating suits and bobsleds, every piece of gear undergoes rigorous innovation to enhance performance and optimize aerodynamics. For instance, the introduction of carbon fiber materials has significantly reduced the weight of ski equipment while increasing its durability and flexibility. Similarly, advancements in materials science have led to the development of streamlined and aerodynamically efficient suits for speed skaters, enabling them to slice through the air with minimal resistance. These innovations not only giveathletes a competitive edge but also push the boundaries of what is physically achievable in winter sports.Data Analytics and Performance Tracking。

2022年12月英语六级第一套作文

2022年12月英语六级第一套作文The rapid advancement of technology has brought about significant changes in our daily lives. As we stand at the cusp of the digital age, the impact of technology on our language learning and communication skills has become increasingly apparent. The 2022 December CET-6 First Test Essay prompts us to explore the ways in which technology has influenced and transformed the landscape of English language education.One of the most profound impacts of technology on language learning is the accessibility and availability of educational resources. The internet has revolutionized the way we access and consume information, providing learners with a vast array of online tools, platforms, and materials to enhance their English language proficiency. From language learning apps and interactive websites to virtual classrooms and video tutorials, the options for self-directed and personalized learning have never been more abundant.This accessibility has democratized the learning process, empowering individuals from diverse backgrounds and locations to engage withthe English language at their own pace and convenience. The ubiquity of mobile devices and the proliferation of user-friendly language learning applications have made it possible for learners to practice and improve their skills anytime, anywhere. This flexibility has been particularly valuable during the COVID-19 pandemic, where remote learning became the norm, and technology served as a lifeline to maintain educational continuity.Moreover, the integration of technology in language instruction has transformed the classroom experience. Teachers now have access to a wide range of digital resources, such as multimedia presentations, interactive whiteboards, and language-learning software, which can be seamlessly incorporated into their lesson plans. These tools not only make learning more engaging and interactive but also provide opportunities for personalized feedback, targeted skill development, and collaborative learning.The advent of online communication platforms has also had a significant impact on language learning. Video conferencing tools, instant messaging applications, and social media platforms have facilitated the creation of global learning communities, where students can engage in cross-cultural exchanges, practice their language skills with native speakers, and receive feedback from peers and instructors worldwide. This exposure to authentic language use and diverse cultural perspectives can greatly enhance languageacquisition and cultural understanding.Additionally, the rise of artificial intelligence (AI) and machine learning has introduced new avenues for language learning and assessment. AI-powered chatbots and virtual tutors can provide personalized feedback, grammar correction, and customized learning paths, catering to the unique needs and learning styles of individual students. Furthermore, AI-driven language assessment tools can offer more accurate and comprehensive evaluation of language proficiency, enabling learners to identify their strengths and weaknesses and track their progress more effectively.However, the integration of technology in language education is not without its challenges. The increasing reliance on digital resources and platforms has raised concerns about the potential for technological distractions, reduced face-to-face interaction, and the development of over-reliance on technology. It is crucial that language learners and educators strike a balance between the advantages of technology and the importance of traditional language learning methods, such as classroom discussions, language immersion, and interpersonal communication.Moreover, the digital divide, which refers to the unequal access to technology and digital resources, poses a significant barrier to inclusive and equitable language education. Ensuring that all learners,regardless of their socioeconomic status or geographical location, have access to the necessary technological infrastructure and financial resources to fully benefit from technology-enhanced language learning is a crucial consideration.Despite these challenges, the potential of technology to revolutionize language education is undeniable. As we move forward, it is essential that language learning institutions, policymakers, and educators work collaboratively to harness the power of technology in a way that enhances, rather than replaces, traditional language learning approaches. By striking a balance and leveraging the strengths of both digital and traditional methods, we can create a more inclusive, engaging, and effective language learning landscape that prepares learners for the demands of the 21st century.In conclusion, the integration of technology in language education has transformed the ways in which we access, consume, and engage with the English language. From the availability of online resourcesto the incorporation of AI-driven tools, the technological advancements have opened up new possibilities for personalized, collaborative, and adaptive language learning. As we continue to navigate this evolving digital landscape, it is crucial that we address the challenges and ensure that technology serves as a catalyst for more inclusive, engaging, and effective language education.。

冬奥会科技发展的作文英语

冬奥会科技发展的作文英语The Winter Olympics and the development of technology have always gone hand in hand. From the early days of the Games to the present, technological advancements have played a significant role in enhancing the athletes' performance, improving the spectator experience, and ensuring the smooth running of the event.In the realm of sports equipment, technological innovations have revolutionized the way athletes compete. From lighter and more aerodynamic skis to advanced snowboards with improved stability, these advancements have allowed athletes to push the boundaries of their performance. The use of high-tech materials such as carbon fiber and titanium has also contributed to the development of faster and more durable equipment, giving athletes a competitive edge on the slopes.Another area where technology has made a significant impact is in the field of data analysis. With the advent ofwearable devices and sensors, athletes can now track and analyze their performance in real-time. These devices provide valuable insights into an athlete's heart rate, speed, and technique, allowing them to make adjustments and improve their performance. Coaches and trainers can also use this data to tailor training programs and identify areas for improvement, leading to more efficient and effective training methods.The Winter Olympics have also seen advancements in broadcasting technology, allowing spectators from around the world to experience the Games like never before. High-definition cameras, drones, and virtual reality technology have brought viewers closer to the action, providing a more immersive and engaging experience. Live streaming platforms and social media have further expanded the reach of the Games, allowing fans to connect and share their experiences in real-time.In addition to enhancing the athlete and spectator experience, technology has also played a crucial role in ensuring the smooth running of the Games. From ticketingsystems to security measures, technological advancements have streamlined operations and improved efficiency. Automated systems for athlete registration, event scheduling, and result management have reduced the margin of error and ensured accurate and timely information dissemination.As we look towards the future, it is clear that technology will continue to shape the Winter Olympics. From advancements in artificial intelligence and robotics to innovations in sustainable energy and venue design, the possibilities are endless. The Winter Olympics will not only showcase the world's best athletes but also serve as a platform for technological advancements that will benefit society as a whole.In conclusion, the Winter Olympics and technology are inseparable. Technological advancements have revolutionized sports equipment, data analysis, broadcasting, and event operations, enhancing the athlete and spectator experience. As we move forward, we can expect even more excitingdevelopments that will further push the boundaries of what is possible in winter sports.。

冬奥会的科技发展作文英语

冬奥会的科技发展作文英语The Technological Advancements of the Winter Olympics。

The Winter Olympics have been a platform for showcasing the latest technological advancements in sports equipment, broadcasting, and venue infrastructure. Over the years, the Winter Olympics have witnessed significant technological advancements that have revolutionized the way athletes compete, spectators watch, and organizers manage the games. This essay discusses the technological advancements of the Winter Olympics and their impact on the games.One of the most significant technological advancementsof the Winter Olympics is in sports equipment. The development of new materials and designs has led to lighter, more durable, and more aerodynamic equipment. For example, skis have become shorter, lighter, and more flexible, allowing athletes to maneuver more easily. Similarly, ice-skating blades have become thinner and sharper, providing better grip and speed. The development of new materials,such as carbon fiber, has also led to the creation of stronger and lighter helmets and protective gear.Another significant technological advancement of the Winter Olympics is in broadcasting. The use of high-definition cameras, slow-motion replays, and virtualreality technology has transformed the way spectators watch the games. Broadcasters can now provide viewers with a more immersive and engaging experience, allowing them to feel like they are right in the middle of the action. The use of drones and cameras mounted on athletes' helmets has also provided unique perspectives and angles that were previously impossible to capture.The development of venue infrastructure has also been a significant technological advancement of the Winter Olympics. The construction of new stadiums, arenas, and ski resorts has provided athletes with state-of-the-art facilities to train and compete. The use of artificial snow-making machines has also allowed ski resorts to maintain consistent snow conditions, even in warmer climates. Furthermore, the use of renewable energy sources,such as solar and wind power, has made the Winter Olympics more sustainable and environmentally friendly.The impact of these technological advancements on the Winter Olympics has been significant. Athletes are now able to perform at a higher level, breaking world records and achieving new heights. Spectators can now watch the gamesin a more immersive and engaging way, feeling like they are part of the action. Organizers can now manage the gamesmore efficiently, ensuring that everything runs smoothlyand on schedule.In conclusion, the technological advancements of the Winter Olympics have transformed the way athletes compete, spectators watch, and organizers manage the games. The development of new sports equipment, broadcasting technology, and venue infrastructure has led to significant improvements in performance, engagement, and sustainability. As technology continues to evolve, we can expect even more exciting advancements in the Winter Olympics to come.。

英语作文高中关于冬奥会

The Winter Olympics, also known as the Olympic Winter Games, is an international multisport event held once every four years. It features winter sports where athletes from around the globe compete in various disciplines such as skiing, ice skating, and snowboarding. Heres a high school English essay about the Winter Olympics:The Winter Olympics: A Celebration of Athletic Excellence and Global UnityThe Winter Olympics is a beacon of hope and inspiration, showcasing the pinnacle of human endurance and skill in the face of the harshest conditions. It is not merely a sporting event it is a testament to the spirit of competition, the joy of camaraderie, and the unifying power of sports.Origins and SignificanceThe first Winter Olympics took place in Chamonix, France, in 1924, with 16 nations participating. Since then, the games have evolved to include a diverse range of winter sports, attracting thousands of athletes and millions of viewers worldwide. The Olympics symbolize the pursuit of excellence, where athletes push their limits and inspire others to do the same.Cultural Exchange and Global ParticipationOne of the most significant aspects of the Winter Olympics is the cultural exchange it fosters. Athletes from different countries, each with unique backgrounds and stories, come together to compete and celebrate their shared passion for winter sports. This event transcends political, social, and economic barriers, bringing the world closer through the universal language of sports.Technological Advancements and InnovationThe Winter Olympics have also been a platform for technological advancements in sports equipment and training methods. Innovations in materials, such as lighter and stronger skis and snowboards, have improved performance and safety. Moreover, the use of highspeed cameras and data analysis has revolutionized the way athletes train and coaches strategize.Environmental Awareness and SustainabilityWith the increasing awareness of climate change, the Winter Olympics have taken steps towards sustainability. Organizers and participants are increasingly mindful of the environmental impact of the games. Efforts to reduce carbon footprints, use renewable energy sources, and promote ecofriendly practices are becoming integral to the planning and execution of the games.Personal Stories of Triumph and Overcoming AdversityThe stories of individual athletes are what truly bring the Winter Olympics to life. From overcoming injuries to achieving personal bests, these stories of perseverance and determination resonate with audiences around the world. They serve as a reminder that with hard work and dedication, one can overcome any obstacle.ConclusionThe Winter Olympics is more than just a competition it is a celebration of human spirit, a display of athletic prowess, and a symbol of global unity. As we watch these events unfold, we are reminded of the power of sports to bring people together, inspire greatness, and leave a lasting impact on the world.In conclusion, the Winter Olympics is a unique event that combines the thrill of competition with the warmth of global unity. It is a reminder of our shared humanity and our collective ability to achieve greatness, no matter the conditions.This essay highlights the multifaceted nature of the Winter Olympics, touching upon its history, cultural significance, technological impact, environmental considerations, and the personal stories of the athletes involved.。

the advances of science的动词搭配

the advances of science的动词搭配一、引言"the Advances of Science"（科学的进步）这个词语在英语中常常出现，它描绘的是科学领域不断发展和前进的过程。

在这个过程中，一些特定的动词搭配起到了关键的作用，它们形象地表达了科学进步的各个方面。

本文将对这些常用的动词搭配进行详细的介绍。

二、动词搭配1.advance in：这个搭配通常用于描述在某一特定科学领域或者技术方面的进步。

例如，"advance in AI technology"（人工智能技术的进步），"advance in medical research"（医学研究的进步）。

2.push forward：这个动词搭配意为“向前推进”，常用于描述科学理论或者科学方法的进步。

例如，"pushing forward the boundaries of human knowledge"（向前推进人类知识的边界）。

3.leap forward：这个动词搭配通常用于描述科技有重大突破的进步。

例如，"leap forward in space exploration"（在太空探索中的重大突破）。

4.make progress：这个动词搭配是最广泛使用的，可以用来描述任何形式的科学进步。

例如，"making progress in understanding the universe"（在理解宇宙方面取得进展）。

5.advance towards：这个动词搭配通常用于描述向着某个目标或者理想状态的进步。

例如，"advance towards a more sustainable future"（迈向更可持续的未来）。

6.propel forward：这个动词搭配常用于描述某种力量或者趋势推动科学的发展。

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有趣是, 注意到日本在东京与大阪间建造了一超导铁路，火车将利用由50MV· A GTO PWM逆变器馈电的线性同步电机传动。永磁(PM) 同步电机传动，特别是梯形机构的无刷直流电机(BLDM) 已有了更为广泛的普及应用。PW电机比较昂贵，但较高的效率使寿命周期（life cycle）的费用较低。
P6U1A Recent Advances and Future Tends in Electrical Machine Drivers 电机传动系统的最新进展和未来趋势
Recent Advances and Future Trends in Electrical Machine Drivers Electrical machines have been used in industry for more than a century and its technology evolution has been very slow unlike that of power devices, converters and control techniques of drives. The machine is a formidably complex electrical, mechanical and thermal system. No doubt there have been so many national and international conferences with such a large number of papers in this area. 电机在工业中的应用已超过一个世纪，不象电源设备、逆变器和传动控制技术，其技术发展很慢。电机是一个强大、复杂的电力、机械和热力系统。毫无疑问，在许多国内和国际会议上都有大量此类领域的论文。
பைடு நூலகம்
P6U1A Recent Advances and Future Tends in Electrical Machine Drivers 电机传动系统的最新进展和未来趋势
Synchronous reluctance machines have also been recently improved to give comparable performance with induction motor drives. In the future, as cost decreases, it is expected that every machine (whether variable or fixed speed) will have a convener in the front end. As harmonic regulation becomes more rigorous, variable frequency starter will be increasingly accepted. 同步磁阻电机最近也被改进，以产生可与感应电机传动相比较的性能。将来，当费用下降时，希望每一个电机（变速或恒速）在其前端均有一个逆变器。当谐波调节更为严峻时，变频起动器将会愈加被接受。
高能量的 NdFeB 磁铁已用于替代传统的铁酸盐材料，特别是对于高密度、低惯性的伺服机构的应用。开关磁阻电机(SRM) 最近在文献中得到了广泛的关注，要求“电机（electrical machine）” 简单、结实、容错、低成本并能高速运转，但存在脉动转矩和声学噪音问题。除了特别应用，SRM 是否能与一般用途的感应电机传动系统竞争是值得怀疑的。
P6U1A Recent Advances and Future Tends in Electrical Machine Drivers 电机传动系统的最新进展和未来趋势
It is interesting to note that Japan is recently building superconductive railway system between Tokyo and Osaka. The train will use linear synchronous motor drive that will be fed by 50MV.A GTO PWM inverter. Permanent magnet (PM) synchronous motor drives, particularly the brushless dc motor (BLDM) using trapezoidal machine, have found wide popularity of applications. The PM machines are more expensive, but higher efficiency makes its life cycle cost lower.
P6U1A Recent Advances and Future Tends in Electrical Machine Drivers 电机传动系统的最新进展和未来趋势
The studies related to machine modeling, estimation, identification, measurement, simulation, and interaction with the converters are exciting R & D topics today to drive system engineers. It is interesting to see that the traditional machine engineers are now identifying themselves in the power electronics community. DC machines have been traditionally used in variable speed drives, and still count as the majority, but they have absolutely no future. 电机建模、预测、识别、测量、仿真和与逆变器相互作用的相关研究是当今传动系统工程师感兴趣的研究与发展课题。可以有趣的看到，传统的机电工程师现在把自己看成是电力电子工程师。直流电机在传统上应用于变速传动中，并在数量上仍属多数，但是他们完全没有前途。
P6U1A Recent Advances and Future Tends in Electrical Machine Drivers 电机传动系统的最新进展和未来趋势
Very large multi-megawatt wound-field machines with brushless excitation are popularly used in pumps, compressors, rolling mill and ship propulsion. The machine is more expensive, gives better efficiency, and can operate near unity power factor demanding less power rating of the converter. Recently, attempt is being made to replace large cycloconverter-fed synchronous motor drives by double-sided PWM converter-fed induction motor drives. 非常大的几兆瓦特的无刷激励绕线励磁电机在泵、压缩机、滚压机和船舶发动机的应用中很受欢迎，此电机比较昂贵，有比较高的效率，能够在单位功率因数附近运转，并要求低于逆变器的额定功率。近来，正企图用双面 PWM 馈电变频器（double-sided converter-fed）感应电机传动替代馈电交-交变频器同步电机。
P6U1A Recent Advances and Future Tends in Electrical Machine Drivers 电机传动系统的最新进展和未来趋势
High-energy NdFeB magnets have been used to replace the conventional ferrite material particularly for high-density low inertia servo type applications. Switched reluctance machines (SRM) are recently receiving a lot of attention in the literature. The "electrical machine" is claimed to be simple, rugged, faulttolerant, low cost, and can operate at high speed, but there are pulsating torque and acoustic noise problems. Except specialized applications, it is doubtful whether SRM will ever compete general purpose induction motor drives.
P6U1A Recent Advances and Future Tends in Electrical Machine Drivers 电机传动系统的最新进展和未来趋势
Cage type induction machine is the workhorse for majority of today's variable and fixed frequency industrial applications, and will remain so in the future. The slip power recovery drives (Kramer and Scherbius drives) using wound-rotor induction machines were once popular, but expensive machine and poor drive performance are already tending to make them obsolete. Synchronous motor drives are often close competitors to induction motor drives. 鼠笼式感应电机在当今大多数的变频和恒频工业应用中是主要设备，并在将来也是如此。使用绕线转子感应电机的转差功率再生传动(Kramer and Scherbius drives)一度很受欢迎，但由于昂贵的电机和低劣的传动性能已趋于淘汰。同步电机传动通常是感应电机传动的有力竞争者。