10.2-BSSPAR-Capacity Spectral Efficiency Features
Toward green and soft a 5G perspective
I NTRODUCTIONWith the maturing of fourth generation (4G)standardization and the ongoing worldwide deployment of 4G cellular networks, research activities on 5G communication technologies have emerged in both the academic and industri-al communities. Various organizations from dif-ferent countries and regions have taken initiatives and launched programs aimed at potential key technologies of 5G: 5GNOW and METI S launched under the European Telecommunica-tions Standards Institute’s (ETSI’s) Framework 7study new waveforms and the fundamentals of 5G to meet the requirements in 2020; the 5G Research Center was established in the UnitedKingdom to develop a world-class testbed of 5G technologies; the Third Generation Partnership Project (3GPP) has drawn up its draft evolution roadmap to 2020; and China has kicked off its IMT-2020 Forum to start the study of user demands, spectrum characteristics, and technolo-gy trends [1]. There is a broad consensus that 5G requirements include higher spectral efficiency (SE) and energy efficiency (EE), lower end-to-end latency, and more connection nodes. From the perspective of China Mobile, 5G should reflect two major themes: green and soft.As global carbon emissions increase and sea levels rise, global weather and air pollution inmany large cities across the world is becoming more severe [2]. Consequently, energy saving has been recognized as an urgent issue rmation and communications technologies (ICT) take up a considerable proportion of total energy consumption. In 2012, the annual average power consumption by ICT industries was over 200 GW, of which telecoms infrastructure and devices accounted for 25 percent [3]. In the 5G era, it is expected that millions more base sta-tions (BSs) with higher functionality and billions more smart phones and devices with much high-er data rates will be connected. The largest mobile network in the world consumed over 14billion kWh of energy in 2012 in its network of 1.1 million BSs. If green communications tech-nologies are universally deployed across this net-work, significant energy savings can be realized,enabling larger infrastructure deployments for 4G and 5G capacity upgrades without requiring significant increase in average revenue per user (ARPU). Dramatic improvements in EE will be needed; consequently, new tools for jointly opti-mizing network SE and EE will be essential.Several research groups and consortia have been investigating EE of cellular networks,including Mobile VCE, EARTH, and Green-Touch. Mobile VCE has focused on the BS hard-ware, architecture, and operation, realizing energy saving gains of 75–92 percent in simula-tions [4]. EARTH has devised an array of new technologies including low-loss antennas, micro direct transmission (DTX), antenna muting, and adaptive sectorization according to traffic fluctu-ations, resulting in energy savings of 60–70 per-cent with less than 5 percent throughput degradation [5]. GreenTouch has set up a much more ambitious goal of improving EE 1000 times by 2020 [6]. Several operators have been actively developing and deploying green technologies,including green BSs powered solely by renew-able energies, and green access infrastructure such as cloud/collaborative/clean radio access network (C-RAN) [7].Carrier grade networks are complex and com-posed of special-purpose nodes and hardware.New standards and features often require a vari-ety of equipment to be developed and integrat-ed, thus leading to very long launch cycles. In order to accommodate the explosive mobileA BSTRACTAs the deployment and commercial operation of 4G systems are speeding up, technologists worldwide have begun searching for next genera-tion wireless solutions to meet the anticipated demands in the 2020 era given the explosive growth of mobile Internet. This article presents our perspective of the 5G technologies with two major themes: green and soft. By rethinking the Shannon theorem and traditional cell-centric design, network capacity can be significantly increased while network power consumption is decreased. The feasibility of the combination of green and soft is investigated through five inter-connected areas of research: energy efficiency and spectral efficiency co-design, no more cells,rethinking signaling/control, invisible base sta-tions, and full duplex radio.Chih-Lin I, Corbett Rowell, Shuangfeng Han, Zhikun Xu, Gang Li, and Zhengang Pan, China Mobile Research InstituteT oward Green and Soft: A 5G PerspectiveInternet traffic growth and a large number of new applications/services demanding much short-er times to market, much faster turnaround of new network capabilities is required. Dynamic RAN reconfiguration can handle both temporal and spatial domain variation of mobile traffic without overprovisioning homogeneously. Soft technologies are the key to resolve these issues.By separating software and hardware, control plane and data plane, building software over general-purpose processors (GPPs) via program-ming interfaces and virtualization technology, it is possible to achieve lower cost and higher effi-ciency using software defined networks (SDNs) and network functions virtualization (NFV) [8]. The OpenRoad project at Stanford University introduced Open-flow, FlowVisor, and SNMPVi-sor to wireless networks to enhance the control plane. Base station virtualization from NEC con-centrated on slicing radio resources at the medi-um access control (MAC) layer. CloudEPC from Ericsson modified Long Term Evolution (LTE) control plane to control open-flow switches. CellSDN from Alcatel-Lucent considered a logi-cally centralized control plane, and scalable dis-tributed enforcement of quality of service (QoS) and firewall policies in the data plane. C-RAN implements a soft and virtualized BS with multi-ple baseband units (BBUs) integrated as virtual machines on the same server, supporting multi-ple radio access technologies (RATs). A soft end-to-end solution from the core network to the RAN can enable the 5G goals of spectraland energy efficiency.In the following sections, this article will elab-orate on a green and soft 5G vision. In additionto the traditional emphasis on maximizing SE,EE must be positioned side by side for jointoptimization. We present an EE and SE co-design framework. The concept of no more cellsis highlighted later with user-centric design andC-RAN as key elements of a soft cell infra-structure. The rationale for a fundamentalrethinking of signaling and control design in 5Gis provided. This article further discusses theidea of invisible BSs incorporating line-sideanswer supervision (LSAS) technology. Finally,the fundamental interference management issuesin networks based on full duplex technologiesand potential solutions are identified; we thensummarize this article.R ETHINK S HANNON:EE AND SE C O-D ESIGNGiven limited spectrum and ever increasingcapacity demand, SE has been pursued fordecades as the top design priority of all majorwireless standards, ranging from cellular net-works to local and personal area networks. Thecellular data rate has been improved from kilo-bits per second in 2G to gigabits per second in4G. SE-oriented designs, however, have over-looked the issues of infrastructure power con-sumption. Currently, RANs consume 70 percentof the total power. In contrast to the exponentialgrowth of traffic volume on mobile Internet,both the associated revenue growth and the net-work EE improvement lag by orders of magni-tude. A sustainable future wireless network musttherefore be not only spectral efficient but alsoenergy efficient. Therefore EE and SE jointoptimization is a critical part of 5G research.Looking at traditional cellular systems, thereare many opportunities to become greener, fromequipment level such as more efficient poweramplifiers using envelop tracking, to networklevel such as dynamic operation in line with traf-fic variations both in time and space. For funda-mental principles of EE and SE co-design, onemust first revisit the classic Shannon theory andreformulate it in terms of EE and SE.In classic Shannon theory, the channel capac-ity is a function of the log of the transmit power(P t), noise power spectral density (N0), and sys-tem bandwidth (W). The total system power con-sumption is a sum of P t and the circuit power P c,that is,where r is power amplifier (PA) efficiencydefined as the ratio of the input of the PA to theoutput of the PA. From the definition of EE [9],EE is equal to the channel capacity normalizedby the system power consumption. SE is thechannel capacity normalized by system band-width. The relationship of EE and SE can beshown as a function of PA efficiency and P c inFig. 1a. From Fig. 1a, it can be observed thatwhen P c is zero, there is a monotonic trade-offbetween h EE and h SE as predicted by the classicShannon theory. For nonzero P c, however, h EEincreases in the low SE region and decreases inthe high SE region with h SE(for a given h EE,there are two values of h SE). As P c increases, theEE-SE curve appears flatter. Furthermore, whentaking the derivative of h EE over h SE, the maxi-mum EE (h*EE) and its corresponding SE (h*SE)then satisfy the following: log2h*EE= log2r/(N0ln2) –h*SE. This means there is a linear relation-ship between log2h*EE and h*SE, and the EE-SErelationship at the EE optimal points is indepen-dent of P c. This observation implies that as P cdecreases, an exponential EE gain may beobtained at the cost of linear SE loss.Figure 1b compares the EE-SE performanceof current Global System for Mobile Communi-cations (GSM) and LTE BSs. LTE performs bet-ter than GSM in terms of both SE and EE; both,however, are working in a low SE region, indi-cating room for improvement.Antenna muting is proposed in EARTH toimprove EE, while LSAS stipulates EE improve-ment by increasing the number of antennas. Theseemingly contradicting conclusions are actuallyconsistent with the analysis presented abovewhere the difference is that the former operatesin a low SE region, whereas the latter operatesin a high SE region.While some progress has been made in EEand SE co-design investigation, there is still along way to go to develop a unified frameworkand comprehensive understanding in this area.Ideally, the EE-SE curve in future systemsshould achieve the following criteria:•The EE value should be improved for eachSE operation point.ρ=+PPP,tottcAngle φ (degrees)Angle θ (degrees)80604020040806020806040200020406080arrival/angle of departure (AoA/AoD) and large-scale fading with regard to different antennas are assumed to be the same due to the regular spacing in the traditional 2D array. With irregu-lar antenna arrays, however, the spacing and rel-ative position of each antenna may invalidate the above assumption where AoA /AoD and large-scale fading may be different for each ray with regard to different LSAS antennas; therefore, modification to the current channel modeling is needed.F ULL D UPLEX R ADIOCurrent cellular systems are either frequency-division duplex (FDD) or TDD. To double SE as well as improve EE, full duplex operation should be considered for 5G. A full duplex BS transmits to and receives from different termi-nals simultaneously using the same frequency resource. Self-interference cancellation is the key to the success of a full duplex system since high DL interference will make the receivers unable to detect the UL signal. Significant research progress has been made recently in self-interference cancellation technologies, including antenna placement, orthogonal polarizations, analog cancellation, and digital cancellation [13]. Most of the research, however, has been on either point-to-point relay or a single-cell BS scenario. There is also inter-user UL-to-DL interference in the single-cell full duplex system.To mitigate such interference, the inter-userinterference channel must be measured andreported. The full duplex BS can then scheduleproper UL and DL user pairs, possibly with jointpower control.In the case of a multi-cell full duplex network,interference management becomes significantlymore complex. For current TDD or FDD sys-tems, the DL-to-DL interference received at UEand UL-to-UL interference received at BSs havebeen studied extensively in literature and stan-dardization bodies (e.g., CoMP in 3GPP LTE-Advanced and IEEE 802.16m). In a full duplexsystem, however, there are new interference situ-ations. For example, if there are two BSs, therewill be additional interference in the UL and DLbetween multiple UE mobile devices with thesame frequency and time resources. In additionto intracell interference, there are inter-BS DL-to UL-interference and intercell inter-user UL-to-DL interference. These additional types ofinterference will adversely impact full duplex sys-tem performance. Traditional transmit or receivebeamforming schemes can be applied to mitigateinter-BS DL-to-UL interference. The intracellinterference mitigation can be extended to han-dle intercell inter-user UL-to-DL interference.C ONCLUSIONSThis article has presented five promising areasof research targeting a green and soft 5G system.The fundamental differences between classicShannon theory and practical systems are firstidentified and then harmonized into a frame-work for EE-SE co-design. The characteristics ofno more cells are described from the perspectiveof infrastructure and architecture variations withparticular emphasis on C-RAN as a typical real-ization in order to enable various soft technolo-gies. Rethinking signaling/control based ondiverse traffic profiles and network loading isthen explored, and initial redesign mechanismsand results are discussed. Virtually invisible basestations with irregular LSAS array are envi-sioned to provide much larger capacity at lowerpower in high-density areas when integrated intobuilding signage. Optimal configuration oftransceivers and active antennas is investigatedin terms of EE-SE performance. Finally, newinterference scenarios are identified in fullduplex networks, and several candidate solutionsare discussed. These five areas provide potentialfor fundamental breakthroughs, and togetherwith achievements in other research areas, theywill lead to a revolutionary new generation ofstandards suitable for 2020 5G deployment.A CKNOWLEDGMENTThe authors would like to express gratitude toYami Chen, Jiqing Ni, Chengkang Pan, HualeiWang, and Sen Wang in the Green ResearchCommunication Center of the China MobileResearch Institute.R EFERENCES[1] .[2] .[3] T. C. Group, “Smart 2020: Enabling the Low CarbonEconomy in the Information Age,” 2008.[4] .[5] P. Skillermark and P. Frenger, “Enhancing Energy Effi-ciency in LTE with Antenna Muting,” IEEE VTC Spring’12, 2012, May 2012, pp. 1–9.[6] .[7] C. M. R. Institute, “C-RAN: The Road Towards GreenRAN,” Oct. 2011, available: /cran.[8] M. Chiosi, D. Clarke, and P. Willis, “Network FunctionsVirtualization,” Oct. 2012.[9] G. Y. Li et al., “Energy-Efficient Wireless Communica-tions: Tutorial, Survey, and Open Issues,” IEEE WirelessCommun., vol. 18, no. 6, Dec. 2011, pp. 28–35.[10] M. Gupta et al., “Energy Impact of Emerging MobileInternet Applications on LTE Networks: Issues and Solu-tions,” IEEE Commun. Mag., vol. 51, no. 2, Feb. 2013,pp. 90–97.[11] F. Rusek et al., “Scaling Up MIMO: Opportunities andChallenges with Very Large Arrays,” IEEE Signal Proc.Mag., vol. 30, no. 1, Jan. 2013, pp. 40–60.[12] T. Marzetta, “Noncooperative Cellular Wireless withUnlimited Numbers of Base Station Antennas,” IEEETrans. Wireless Commun., vol. 9, no. 11, Nov. 2010,pp. 3590–3600.[13] E. Aryafar et al., “Midu: Enabling MIMO Full Duplex,”Proc. ACM Mobicom ’12, 2012.B IOGRAPHIESC HIH L IN I(icl@) received her Ph.D. degreein electrical engineering from Stanford University and hasalmost 30 years experience in wireless communications.She has worked at various world-class companies andresearch institutes, including the Wireless CommunicationFundamental Research Department of AT&T Bell Labs; theheadquarters of AT&T, as director of Wireless Communica-tions Infrastructure and Access Technology; ITRI of Taiwan,as director of Wireless Communication Technology; HongKong ASTRI, as vice president and founding group directorof the Communications Technology Domain. She receivedthe IEEE Transactions on Communications Stephen RiceBest Paper Award and is a winner of the CCCP National1000 Talent program. Currently, she is China Mobile’s chiefscientist of wireless technologies in charge of advancedwireless communication R&D efforts of the China MobileResearch Institute. She established the Green Communica-tions Research Center of China Mobile, spearheading majorinitiatives including 5G key technologies R&D; high energyefficiency system architecture, technologies, and devices;green energy; and C-RAN and soft base stations. She was an elected Board Member of IEEE ComSoc, Chair of the ComSoc Meetings and Conferences Board, and Founding Chair of the IEEE WCNC Steering Committee. She is cur-rently an Executive Board Member of GreenTouch and a Network Operator Council Member of ETSI NFV. Her research interests are green communications, C-RAN, net-work convergence, bandwidth refarming, EE-SE co-design,massive MIMO, and active antenna arrays.C ORBETT R OWELL (corbettrowell@) received his B.A. degree (honors) in physics from the University of California Santa Cruz, his M.Phil. degree in electrical and electronic engineering from Hong Kong University of Sci-ence and Technology, and his Ph.D. degree in electrical and electronic engineering from Hong Kong University. He has worked extensively in industry with experience inside startups, research institutes, antenna manufacturers, and operators, designing a wide variety of products including cellular antennas, digital repeaters, radio units, MRI, NFC,MIMO, and base station RF systems. Currently, he is the research director of Antenna and RF Systems in the Green Communication Research Center at the China Mobile Research Institute in Beijing and is designing large-scale antenna systems for TD-LTE and future 5G systems. He has over 30 granted patents and 20 published papers with over 1300 citations. His research interests are digital RF,FPGA, miniature antennas, antenna arrays, active antennas,beamforming, isolation, and sensor arrays.SHUANGFENG H AN (hanshuangfeng@)received his M.S. and Ph.D. degrees in electrical engineer-ing from Tsinghua University in 2002 and 2006 respective-ly. He joined Samsung Electronics in Korea as a senior research engineer in 2006 working on MultiBS MIMO,MIMO codebook design, small cell/HetNet, millimeter wave communication, D2D, and distributed radio over fiber. Cur-rently he is a senior project manager in the Green Commu-nication Research Center at the China Mobile Research Institute. He has over 30 patent applications, and has pub-lished over 10 conference and journal papers. His research interests include green technologies R&D in 5G wireless communication systems, including large-scale antenna sys-tems, active antenna systems, a co-frequency co-time full duplex non-orthogonal multiple access scheme, and EE-SE co-design.Z HIKUN X U (xuzhikun@) received B.S.E. and Ph.D. degrees in electrical and computer engineering from Beihang University in 2007 and 2013, respectively. He was a visiting researcher in the School of Electrical and Com-puter Engineering, Georgia Institute of Technology, from 2009 to 2010. After graduation, he joined the Green Com-munication Research Center of the China Mobile Research Institute as a project manager. His current interests include green technologies, the fundamental relationships between energy efficiency and spectral efficiency, energy-efficient network deployment and operation, cross-layer resource allocation in cellular networks, and advanced signal pro-cessing and transmission techniques.G ANG L I (ligangyf@) received his B.A.degree in telecommunication engineering and M.E. degree in automation engineering from Sichuan University. After graduation, he worked for Lucent Technologies for four years as a team leader and software developer for the core network. He is now a senior researcher at the Green Com-munication Research Center of the China Mobile Research Institute and is working on the key technologies of next generation 5G wireless communication systems. His research interests include radio access network architecture optimization, service-aware signaling/control redesign, and radio and core network convergence.Z HENGANG P AN (panzhengang@) received his B.S.E. from Southeast University in Nanjing and his Ph.D. degree in electrical and electronic engineering from Hong Kong University. After graduation, he worked for NTT DoCoMo Beijing Communication Labs and ASTRI in Hong Kong working on wireless communication (WiFi, WiMax,LTE), mobile digital TV (T-DMB, DVB-T/H, CMMB), and wire-line broadband access (HomePlug, MoCA) for both sys-tem/algorithm design and terminal SoC chip implementation. He is currently a principal staff member of the Green Communication Research Center at the China Mobile Research Institute and is now leading a team work-ing on the key technologies for the next generation 5G wireless communication systems. He has published more than 40 papers in top journals and international confer-ences, and filed 45 patents (20 granted). His research inter-ests are time/frequency/sampling synchronization technology for OFDM/A-based systems, channel estimation,forward error correction coding, MIMO, space-time pro-cessing/coding, and cross-layer optimization.。
2020年在nature catalysis上发表重要成果
2020年在nature catalysis上发表重要成果
2020年，在《Nature Catalysis》杂志上发表了一项重要成果，该成果由某科研团队经过多年努力终于成功研发出一种新型的催化剂，能够有效地将废弃塑料转化为高附加值的产品。
这项成果的研发背景是，随着人类对塑料的依赖程度不断加深，废弃塑料的污染问题日益严重，给生态环境带来了巨大的压力。
因此，科研团队一直在寻找一种能够有效处理废弃塑料的方法。
该科研团队通过多年的研究，成功研发出这种新型催化剂。
该催化剂能够在常温常压下将废弃塑料中的聚乙烯和聚丙烯等塑料成分转化为燃料和化学品等高附加值的产品。
这种转化过程不仅能够有效处理废弃塑料，而且能够产生经济效益，具有很高的应用价值。
该成果的发表引起了广泛关注。
在《Nature Catalysis》杂志上，该论文被选为封面文章，并得到了编辑部的特别推荐。
该论文的发表不仅证明了该科研团队在催化剂研究方面的实力，也标志着人类在解决废弃塑料污染问题方面取得了重要进展。
未来，该科研团队将继续优化这种新型催化剂的制备工艺和应用范围，希望能够为解决全球废弃塑料污染问题做出更大的贡献。
同时，他们也希望通过与产业界的合作，将这种技术应用于实际生产中，为人类创造更加美好的生态环境和可持续发展未来。
李永舫, 苯基侧链,有机太阳能电池受体 -回复
李永舫, 苯基侧链,有机太阳能电池受体-回复李永舫、苯基侧链和有机太阳能电池受体近年来，随着对可再生能源的需求日益增长，太阳能电池成为一种备受关注的能源技术。
传统的硅基太阳能电池虽然具有较高的效率，但制造成本较高且制作过程耗能。
相对而言，有机太阳能电池则具有制造成本低、制作过程绿色环保等优势。
而作为有机太阳能电池中的关键组成部分，有机受体材料的设计和性能优化对于提高效率至关重要。
李永舫教授是中国科学院化学所研究员，也是中国具有国际影响力的能源材料领域专家。
他在有机太阳能领域的研究中提出了一种创新的苯基侧链结构，被广泛应用于有机太阳能电池的受体材料中。
苯基侧链是指在有机分子结构中，将苯环基团通过共享碳原子与中心芳香芷构成共轭结构。
这种共轭结构可以提供更大的π共轭体积，增强分子的电子输运性能，从而提高有机太阳能电池的光电转换效率。
与传统的较长碳链相比，苯基侧链不仅具有较短的π共轭长度，还具有较高的空间共轭度，从而改善了分子在电子传输过程中的空间阻碍问题。
有机太阳能电池的受体材料是决定其性能的关键因素之一。
李永舫教授通过对苯基侧链的设计和合成，成功地开发出了一系列具有优良光电转换性能的受体材料。
他的研究团队通过调整苯基链的长度、增加侧链的氢键吸收基团等方法，有效地提高了受体材料的光电转换效率和稳定性。
除了苯基侧链的设计，李永舫教授还探索了其他改进有机太阳能电池性能的方法。
例如，在受体材料中引入大体积的侧链基团，可以增加受体材料与电子受体之间的空间间隔，从而提高光生载流子的扩散长度。
此外，引入不对称的侧基还可以在受体材料分子中引入极化，从而改善分子的吸光性能和光电转换效率。
通过对李永舫教授的研究和贡献的深入了解，我们可以看到他在有机太阳能电池受体材料的设计中的创新思路和成果。
他的苯基侧链设计不仅提高了有机太阳能电池的光电转换效率，还优化了材料的稳定性和可制备性。
他的研究不仅在学术界引起了广泛关注，而且在工业上也有着重要的应用潜力。
SCI写作句型汇总
S C I论文写作中一些常用的句型总结(一)很多文献已经讨论过了一、在Introduction里面经常会使用到的一个句子：很多文献已经讨论过了。
它的可能的说法有很多很多，这里列举几种我很久以前搜集的：A.??Solar energy conversion by photoelectrochemical cells?has been intensively investigated.?(Nature 1991, 353, 737 - 740?)B.?This was demonstrated in a number of studies that?showed that composite plasmonic-metal/semiconductor photocatalysts achieved significantly higher rates in various photocatalytic reactions compared with their pure semiconductor counterparts.C.?Several excellent reviews describing?these applications are available, and we do not discuss these topicsD.?Much work so far has focused on?wide band gap semiconductors for water splitting for the sake of chemical stability.（DOI:10.1038/NMAT3151）E.?Recent developments of?Lewis acids and water-soluble organometalliccatalysts?have attracted much attention.（Chem. Rev. 2002, 102, 3641?3666）F.?An interesting approach?in the use of zeolite as a water-tolerant solid acid?was described by?Ogawa et al（Chem.Rev. 2002, 102, 3641?3666）G.?Considerable research efforts have been devoted to?the direct transition metal-catalyzed conversion of aryl halides toaryl nitriles. (J. Org. Chem. 2000, 65, 7984-7989) H.?There are many excellent reviews in the literature dealing with the basic concepts of?the photocatalytic processand the reader is referred in particular to those by Hoffmann and coworkers,Mills and coworkers, and Kamat.(Metal oxide catalysis,19,P755)I. Nishimiya and Tsutsumi?have reported on（proposed）the influence of the Si/Al ratio of various zeolites on the acid strength, which were estimated by calorimetry using ammonia. (Chem.Rev. 2002, 102, 3641?3666)二、在results and discussion中经常会用到的：如图所示A. GIXRD patterns in?Figure 1A show?the bulk structural information on as-deposited films.?B.?As shown in Figure 7B,?the steady-state current density decreases after cycling between 0.35 and 0.7 V, which is probably due to the dissolution of FeOx.?C.?As can be seen from?parts a and b of Figure 7, the reaction cycles start with the thermodynamically most favorable VOx structures（J. Phys. Chem. C 2014, 118, 24950?24958）这与XX能够相互印证：A.?This is supported by?the appearance in the Ni-doped compounds of an ultraviolet–visible absorption band at 420–520nm (see Fig. 3 inset), corresponding to an energy range of about 2.9 to 2.3 eV.B. ?This?is consistent with the observation from?SEM–EDS. (Z.Zou et al. / Chemical Physics Letters 332 (2000) 271–277)C.?This indicates a good agreement between?the observed and calculated intensities in monoclinic with space groupP2/c when the O atoms are included in the model.D. The results?are in good consistent with?the observed photocatalytic activity...E. Identical conclusions were obtained in studies?where the SPR intensity and wavelength were modulated by manipulating the composition, shape,or size of plasmonic nanostructures.?F.??It was also found that areas of persistent divergent surfaceflow?coincide?with?regions where convection appears to be consistently suppressed even when SSTs are above 27.5°C.(二)1. 值得注意的是...A.?It must also be mentioned that?the recycling of aqueous organic solvent is less desirable than that of pure organic liquid.B.?Another interesting finding is that?zeolites with 10-membered ring pores showed high selectivities (>99%) to cyclohexanol, whereas those with 12-membered ring pores, such as mordenite, produced large amounts of dicyclohexyl ether. (Chem. Rev. 2002, 102,3641?3666)C.?It should be pointed out that?the nanometer-scale distribution of electrocatalyst centers on the electrode surface is also a predominant factor for high ORR electrocatalytic activity.D.?Notably,?the Ru II and Rh I complexes possessing the same BINAP chirality form antipodal amino acids as the predominant products.?(Angew. Chem. Int. Ed., 2002, 41: 2008–2022)E. Given the multitude of various transformations published,?it is noteworthy that?only very few distinct?activation?methods have been identified.?(Chem. Soc. Rev., 2009,?38, 2178-2189)F.?It is important to highlight that?these two directing effects will lead to different enantiomers of the products even if both the “H-bond-catalyst” and the?catalyst?acting by steric shielding have the same absolute stereochemistry. (Chem. Soc. Rev.,?2009,?38, 2178-2189)G.?It is worthwhile mentioning that?these PPNDs can be very stable for several months without the observations of any floating or precipitated dots, which is attributed to the electrostatic repulsions between the positively charge PPNDs resulting in electrosteric stabilization.(Adv. Mater., 2012, 24: 2037–2041)2.?...仍然是个挑战A.?There is thereby an urgent need but it is still a significant challenge to?rationally design and delicately tail or the electroactive MTMOs for advanced LIBs, ECs, MOBs, and FCs.?（Angew. Chem. Int. Ed.2 014, 53, 1488 – 1504）B.?However, systems that are?sufficiently stable and efficient for practical use?have not yet been realized.C.??It?remains?challenging?to?develop highly active HER catalysts based on materials that are more abundant at lower costs. (J. Am. Chem.Soc.,?2011,?133, ?7296–7299)D.?One of the?great?challenges?in the twenty-first century?is?unquestionably energy storage. (Nature Materials?2005, 4, 366 - 377?)众所周知A.?It is well established (accepted) / It is known to all / It is commonlyknown?that?many characteristics of functional materials, such as composition, crystalline phase, structural and morphological features, and the sur-/interface properties between the electrode and electrolyte, would greatly influence the performance of these unique MTMOs in electrochemical energy storage/conversion applications.（Angew. Chem. Int. Ed.2014,53, 1488 – 1504）B.?It is generally accepted (believed) that?for a-Fe2O3-based sensors the change in resistance is mainly caused by the adsorption and desorption of gases on the surface of the sensor structure. (Adv. Mater. 2005, 17, 582)C.?As we all know,?soybean abounds with carbon,?nitrogen?and oxygen elements owing to the existence of sugar,?proteins?and?lipids. (Chem. Commun., 2012,?48, 9367-9369)D.?There is no denying that?their presence may mediate spin moments to align parallel without acting alone to show d0-FM. (Nanoscale, 2013,?5, 3918-3930)(三)1. 正如下文将提到的...A.?As will be described below（也可以是As we shall see below）,?as the Si/Al ratio increases, the surface of the zeolite becomes more hydrophobic and possesses stronger affinity for ethyl acetate and the number of acid sites decreases.（Chem. Rev. 2002, 102, 3641?3666）B. This behavior is to be expected and?will?be?further?discussed?below. (J. Am. Chem. Soc.,?1955,?77, 3701–3707)C.?There are also some small deviations with respect to the flow direction,?whichwe?will?discuss?below.（Science, 2001, 291, 630-633）D.?Below,?we?will?see?what this implies.E.?Complete details of this case?will?be provided at a?later?time.E.?很多论文中，也经常直接用see below来表示，比如：The observation of nanocluster spheres at the ends of the nanowires is suggestive of a VLS growth process (see?below). (Science, 1998, ?279, 208-211)2. 这与XX能够相互印证...A.?This is supported by?the appearance in the Ni-doped compounds of an ultraviolet–visible absorption band at 420–520 nm (see Fig. 3 inset), corresponding to an energy range of about 2.9 to 2.3 eVB.This is consistent with the observation from?SEM–EDS. (Chem. Phys. Lett. 2000, 332, 271–277)C.?Identical conclusions were obtained?in studies where the SPR intensity and wavelength were modulated by manipulating the composition, shape, or size of plasmonic nanostructures.?（Nat. Mater. 2011, DOI: 10.1038/NMAT3151）D. In addition, the shape of the titration curve versus the PPi/1 ratio,?coinciding withthat?obtained by fluorescent titration studies, suggested that both 2:1 and 1:1 host-to-guest complexes are formed. (J. Am. Chem. Soc. 1999, 121, 9463-9464)E.?This unusual luminescence behavior is?in accord with?a recent theoretical prediction; MoS2, an indirect bandgap material in its bulk form, becomes a direct bandgapsemiconductor when thinned to a monolayer.?(Nano Lett.,?2010,?10, 1271–1275)3.?我们的研究可能在哪些方面得到应用A.?Our ?ndings suggest that?the use of solar energy for photocatalytic watersplitting?might provide a viable source for?‘clean’ hydrogen fuel, once the catalyticef?ciency of the semiconductor system has been improved by increasing its surface area and suitable modi?cations of the surface sites.B. Along with this green and cost-effective protocol of synthesis,?we expect that?these novel carbon nanodots?have potential applications in?bioimaging andelectrocatalysis.(Chem. Commun., 2012,?48, 9367-9369)C.?This system could potentially be applied as?the gain medium of solid-state organic-based lasers or as a component of high value photovoltaic (PV) materials, where destructive high energy UV radiation would be converted to useful low energy NIR radiation. (Chem. Soc. Rev., 2013,?42, 29-43)D.?Since the use of?graphene?may enhance the photocatalytic properties of TiO2?under UV and visible-light irradiation,?graphene–TiO2?composites?may potentially be usedto?enhance the bactericidal activity.?(Chem. Soc. Rev., 2012,?41, 782-796)E.??It is the first report that CQDs are both amino-functionalized and highly fluorescent,?which suggests their promising applications in?chemical sensing.(Carbon, 2012,?50,?2810–2815)(四)1. 什么东西还尚未发现/系统研究A. However,systems that are sufficiently stable and efficient for practical use?have not yet been realized.B. Nevertheless,for conventional nanostructured MTMOs as mentioned above,?some problematic disadvantages cannot be overlooked.（Angew. Chem. Int. Ed.2014,53, 1488 – 1504）C.?There are relatively few studies devoted to?determination of cmc values for block copolymer micelles. (Macromolecules 1991, 24, 1033-1040)D. This might be the reason why, despite of the great influence of the preparation on the catalytic activity of gold catalysts,?no systematic study concerning?the synthesis conditions?has been published yet.?(Applied Catalysis A: General2002, 226, ?1–13)E.?These possibilities remain to be?explored.F.??Further effort is required to?understand and better control the parameters dominating the particle surface passivation and resulting properties for carbon dots of brighter photoluminescence. (J. Am. Chem. Soc.,?2006,?128?, 7756–7757)2.?由于/因为...A.?Liquid ammonia?is particularly attractive as?an alternative to water?due to?its stability in the presence of strong reducing agents such as alkali metals that are used to access lower oxidation states.B.?The unique nature of?the cyanide ligand?results from?its ability to act both as a σdonor and a π acceptor combined with its negativecharge and ambidentate nature.C.?Qdots are also excellent probes for two-photon confocalmicroscopy?because?they are characterized by a very large absorption cross section?(Science ?2005,?307, 538-544).D.?As a result of?the reductive strategy we used and of the strong bonding between the surface and the aryl groups, low residual currents (similar to those observed at a bare electrode) were obtained over a large window of potentials, the same as for the unmodified parent GC electrode. (J. Am. Chem. Soc. 1992, 114, 5883-5884)E.?The small Tafel slope of the defect-rich MoS2 ultrathin nanosheets is advantageous for practical?applications,?since?it will lead to a faster increment of HER rate with increasing overpotential.(Adv. Mater., 2013, 25: 5807–5813)F. Fluorescent carbon-based materials have drawn increasing attention in recent years?owing to?exceptional advantages such as high optical absorptivity, chemical stability, biocompatibility, and low toxicity.(Angew. Chem. Int. Ed., 2013, 52: 3953–3957)G.??On the basis of?measurements of the heat of immersion of water on zeolites, Tsutsumi etal. claimed that the surface consists of siloxane bondings and is hydrophobicin the region of low Al content. (Chem. Rev. 2002, 102, 3641?3666)H.?Nanoparticle spatial distributions might have a large significance for catalyst stability,?given that?metal particle growth is a relevant deactivation mechanism for commercial catalysts.?3. ...很重要A.?The inhibition of additional nucleation during growth, in other words, the complete separation?of nucleation and growth,?is?critical(essential, important)?for?the successful synthesis of monodisperse nanocrystals. (Nature Materials?3, 891 - 895 (2004))B.??In the current study,?Cys,?homocysteine?(Hcy) and?glutathione?(GSH) were chosen as model?thiol?compounds since they?play important (significant, vital, critical) roles?in many biological processes and monitoring of these?thiol?compounds?is of great importance for?diagnosis of diseases.(Chem. Commun., 2012,?48, 1147-1149)C.?This is because according to nucleation theory,?what really matters?in addition to the change in temperature ΔT?(or supersaturation) is the cooling rate.(Chem. Soc. Rev., 2014,?43, 2013-2026)(五)1. 相反/不同于A.?On the contrary,?mononuclear complexes, called single-ion magnets (SIM), have shown hysteresis loops of butterfly/phonon bottleneck type, with negligiblecoercivity, and therefore with much shorter relaxation times of magnetization. (Angew. Chem. Int. Ed., 2014, 53: 4413–4417)B.?In contrast,?the Dy compound has significantly larger value of the transversal magnetic moment already in the ground state (ca. 10?1?μB), therefore allowing a fast QTM. （Angew. Chem. Int. Ed., 2014, 53: 4413–4417）C.?In contrast to?the structural similarity of these complexes, their magnetic behavior exhibits strong divergence.?(Angew. Chem. Int. Ed., 2014, 53: 4413–4417)D.?Contrary to?other conducting polymer semiconductors, carbon nitride ischemically and thermally stable and does not rely on complicated device manufacturing. (Nature materials, 2009, 8(1): 76-80.)E.?Unlike?the spherical particles they are derived from that Rayleigh light-scatter in the blue, these nanoprisms exhibit scattering in the red, which could be useful in developing multicolor diagnostic labels on the basis not only of nanoparticle composition and size but also of shape. (Science 2001,? 294, 1901-1903)2. 发现，阐明，报道，证实可供选择的词包括：verify, confirm, elucidate, identify, define, characterize, clarify, establish, ascertain, explain, observe, illuminate, illustrate，demonstrate, show, indicate, exhibit, presented, reveal, display, manifest，suggest, propose, estimate, prove, imply, disclose，report, describe，facilitate the identification of?举例：A. These stacks appear as nanorods in the two-dimensional TEM images, but tilting experiments?confirm that they are nanoprisms.?(Science 2001,? 294, 1901-1903)B. Note that TEM?shows?that about 20% of the nanoprisms are truncated.?(Science 2001,? 294, 1901-1903)C. Therefore, these calculations not only allow us to?identify?the important features in the spectrum of the nanoprisms but also the subtle relation between particle shape and the frequency of the bands that make up their spectra.?(Science 2001,? 294, 1901-1903)D. We?observed?a decrease in intensity of the characteristic surface plasmon band in the ultraviolet-visible (UV-Vis) spectroscopy for the spherical particles at λmax?= 400 nm with a concomitant growth of three new bands of λmax?= 335 (weak), 470 (medium), and 670 nm (strong), respectively. (Science 2001,? 294, 1901-1903)E. In this article, we present data?demonstrating?that opiate and nonopiate analgesia systems can be selectively activated by different environmental manipulationsand?describe?the neural circuitry involved. (Science 1982, 216, 1185-1192)F. This?suggests?that the cobalt in CoP has a partial positive charge (δ+), while the phosphorus has a partial negative charge (δ?),?implying?a transfer of electron density from Co to P.?(Angew. Chem., 2014, 126: 6828–6832)3. 如何指出当前研究的不足A. Although these inorganic substructures can exhibit a high density of functional groups, such as bridging OH groups, and the substructures contribute significantly to the adsorption properties of the material,surprisingly little attention has been devoted to?the post-synthetic functionalization of the inorganic units within MOFs. (Chem. Eur. J., 2013, 19: 5533–5536.)B.?Little is known,?however, about the microstructure of this material. (Nature Materials 2013,12, 554–561)C.?So far, very little information is available, and only in?the absorber film, not in the whole operational devices. （Nano Lett.,?2014,?14?(2), pp 888–893）D.?In fact it should be noted that very little optimisation work has been carried out on?these devices. (Chem. Commun., 2013,?49, 7893-7895)E. By far the most architectures have been prepared using a solution processed perovskite material,?yet a few examples have been reported that?have used an evaporated perovskite layer. (Adv. Mater., 2014, 27: 1837–1841.)F. Water balance issues have been effectively addressed in PEMFC technology through a large body of work encompassing imaging, detailed water content and water balance measurements, materials optimization and modeling,?but very few of these activities have been undertaken for?anion exchange membrane fuel cells,? primarily due to limited materials availability and device lifetime. (J. Polym. Sci. Part B: Polym. Phys., 2013, 51: 1727–1735)G. However,?none of these studies?tested for Th17 memory, a recently identified T cell that specializes in controlling extracellular bacterial infections at mucosal surfaces. (PNAS, 2013,?111, 787–792)H. However,?uncertainty still remains as to?the mechanism by which Li salt addition results in an extension of the cathodic reduction limit. (Energy Environ. Sci., 2014,?7, 232-250)I.?There have been a number of high profile cases where failure to?identify the most stable crystal form of a drug has led to severe formulation problems in manufacture. (Chem. Soc. Rev., 2014,?43, 2080-2088)J. However,?these measurements systematically underestimate?the amount of ordered material. ( Nature Materials 2013, 12, 1038–1044)(六)1.?取决于a.?This is an important distinction, as the overall activity of a catalyst will?depend on?the material properties, synthesis method, and other possible species that can be formed during activation.?(Nat. Mater.?2017,16,225–229)b.?This quantitative partitioning?was determined by?growing crystals of the 1:1 host–guest complex between?ExBox4+?and corannulene. (Nat. Chem.?2014,?6177–178)c.?They suggested that the Au particle size may?be the decisive factor for?achieving highly active Au catalysts.(Acc. Chem. Res.,?2014,?47, 740–749)d.?Low-valent late transition-metal catalysis has?become indispensable to?chemical synthesis, but homogeneous high-valent transition-metal catalysis is underdeveloped, mainly owing to the reactivity of high-valent transition-metal complexes and the challenges associated with synthesizing them.?(Nature2015,?517,449–454)e.?The polar effect?is a remarkable property that enables?considerably endergonic C–H abstractions?that would not be possible otherwise.?(Nature?2015, 525, 87–90)f.?Advances in heterogeneous catalysis?must rely on?the rational design of new catalysts. (Nat. Nanotechnol.?2017, 12, 100–101)g.?Likely, the origin of the chemoselectivity may?be also closely related to?the H?bonding with the N or O?atom of the nitroso moiety, a similar H-bonding effect is known in enamine-based nitroso chemistry. (Angew. Chem. Int. Ed.?2014, 53: 4149–4153)2.?有很大潜力a.?The quest for new methodologies to assemble complex organic molecules?continues to be a great impetus to?research efforts to discover or to optimize new catalytic transformations. (Nat. Chem.?2015,?7, 477–482)b.?Nanosized faujasite (FAU) crystals?have great potential as?catalysts or adsorbents to more efficiently process present and forthcoming synthetic and renewablefeedstocks in oil refining, petrochemistry and fine chemistry. (Nat. Mater.?2015, 14, 447–451)c.?For this purpose, vibrational spectroscopy?has proved promising?and very useful.?(Acc Chem Res. 2015, 48, 407–413.)d.?While a detailed mechanism remains to be elucidated and?there is room for improvement?in the yields and selectivities, it should be remarked that chirality transfer upon trifluoromethylation of enantioenriched allylsilanes was shown. (Top Catal.?2014,?57: 967.?)e.?The future looks bright for?the use of PGMs as catalysts, both on laboratory and industrial scales, because the preparation of most kinds of single-atom metal catalyst is likely to be straightforward, and because characterization of such catalysts has become easier with the advent of techniques that readily discriminate single atoms from small clusters and nanoparticles. (Nature?2015, 525, 325–326)f.?The unique mesostructure of the 3D-dendritic MSNSs with mesopore channels of short length and large diameter?is supposed to be the key role in?immobilization of active and robust heterogeneous catalysts, and?it would have more hopeful prospects in?catalytic applications. (ACS Appl. Mater. Interfaces,?2015,?7, 17450–17459)g.?Visible-light photoredox catalysis?offers exciting opportunities to?achieve challenging carbon–carbon bond formations under mild and ecologically benign conditions. (Acc. Chem. Res.,?2016, 49, 1990–1996)3. 因此同义词：Therefore, thus, consequently, hence, accordingly, so, as a result这一条比较简单，这里主要讲一下这些词的副词词性和灵活运用。
The properties of carbon nanotubes
The properties of carbon nanotubesCarbon nanotubes (CNTs) have emerged as one of the most promising materials in the world of nanotechnology. Since their discovery in the early 1990s, they have been the subject of intense research due to their extraordinary physical and mechanical properties. CNTs are cylindrical structures made of carbon atoms, which are arranged in a honeycomb lattice. They can be single-walled or multi-walled, depending on the number of layers of carbon atoms.CNTs have many unique properties, including high tensile strength, thermal conductivity, and electrical conductivity. These properties make them suitable for a wide range of applications, from electronics to energy storage. In this article, we will explore the properties of CNTs in more detail.Tensile StrengthOne of the most remarkable properties of CNTs is their incredible tensile strength. In fact, CNTs are the strongest materials known to man. They are up to 100 times stronger than steel, yet only a fraction of the weight. This makes them ideal for use in materials that require high strength and low weight. For example, CNTs could be used to make stronger and lighter aircraft engines and components.Thermal ConductivityCNTs also have a high thermal conductivity, which makes them excellent heat conductors. This means that CNTs can quickly transfer heat from one point to another. This makes them ideal for use in heat sinks, which are used to dissipate heat from electronic devices. Additionally, CNTs can be used to improve the efficiency of energy storage devices, such as batteries and supercapacitors.Electrical ConductivityCNTs are also excellent electrical conductors, which makes them ideal for use in electronics. They have a very high current carrying capacity, which means they can carrya large amount of electricity without overheating. Additionally, they have a low resistance, which means that electrical signals can travel through them quickly and efficiently. CNTs could be used to make faster and more efficient computer chips, as well as more durable electronic components.Chemical StabilityCNTs are also very chemically stable, meaning they are resistant to chemical reactions. This is due to the strong covalent bonds between the carbon atoms in the honeycomb lattice. This property makes CNTs ideal for use in environments with harsh chemicals, such as in the oil and gas industry. They could be used to make stronger and more durable pipes and other components that are needed in these environments.ConclusionIn conclusion, CNTs have many unique and fascinating properties that make them ideal for a wide range of applications. From their incredible tensile strength to their high thermal and electrical conductivity, CNTs are proving to be one of the most promising materials in the world of nanotechnology. As research continues, it is likely that we will discover even more amazing properties of CNTs that could revolutionize the way we live and work.。
太阳能电池材料一区英文文献
太阳能电池材料一区英文文献太阳能电池是一种将太阳能转化为电能的装置，它是可再生能源的重要组成部分。
太阳能电池的效率和性能取决于所使用的材料。
在过去的几十年里，科学家们一直在寻找更高效、更稳定的太阳能电池材料。
本文将介绍一些在太阳能电池材料研究领域中被广泛引用的一区英文文献。
首先，我们来看一篇题为“Perovskite solar cells with a planar heterojunction structure prepared using room-temperature solution processing techniques”的文献。
这篇文章由杨XX等人于2012年在《Nature》杂志上发表。
文章介绍了一种采用室温溶液处理技术制备的具有平面异质结构的钙钛矿太阳能电池。
该研究表明，这种新型太阳能电池具有高效率和稳定性，可以成为替代传统硅基太阳能电池的有力竞争者。
接下来，我们来看一篇题为“High-efficiency solution-processed perovskite solar cells with millimeter-scale grains”的文献。
这篇文章由李XX等人于2015年在《Science》杂志上发表。
文章介绍了一种采用溶液处理技术制备的高效率钙钛矿太阳能电池。
研究人员通过优化晶体生长条件，成功地制备出具有毫米级晶粒的钙钛矿薄膜，从而提高了太阳能电池的效率和稳定性。
此外，还有一篇题为“Organometal halide perovskite solar cells: degradation and stability”的文献。
这篇文章由李XX等人于2016年在《Energy & Environmental Science》杂志上发表。
文章主要讨论了钙钛矿太阳能电池的降解和稳定性问题。
研究人员通过对太阳能电池材料的长期稳定性进行研究，发现了一些导致钙钛矿太阳能电池降解的机制，并提出了一些改进措施，以提高太阳能电池的稳定性。
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Future Wireless Networks
3G
systems has 384 Kbps peak rates MIMO, adaptive techniques, “ICIC”
Greater spectral efficiency (bits/s/Hz)
Through 20
Flexible use of up to 100 MHz of spectrum
Current Wireless Systems
Cellular Systems Wireless LANs Convergence of Cellular and WiFi WiGig and Wireless HD Satellite Systems Zigbee radios
BASE STATION
MTSO
Generated by Foxit PDF Creator © Foxit Software For evaluation only.
4G/LTE Cellular
Much higher data rates than 3G (50-100 Mbps)
Careful what you wish for…
ata D bile o al M
ti n e n po wth x E ro G
Leading to mass ive spec deficit trum
Source: FCC
2024年江苏新高考一卷英语试题.doc
2024年江苏新高考一卷英语试题2024年江苏新高考一卷英语试题及答案例：How much is the shirt?A.E19.15.B.E9.18.C.E9.15.答案是C.1.What is Kate doing?A.Boarding a flight.B.Arranging a tripC.Seeing a friend off.2.What are the speakers talking about?A.pop star.B.An old songC.A radio program3.What will the speakers do today?A.Goto an art show.B.Meet the mans aunt.C.Eat out with Mark4.What does the man want to do?A.Cancel an order.B.Ask for a receipt.C.Reschedule a delivery5.When will the next train to Bedford leave?A.At 9:45.B.At 10:15C.At 11:00.第二节 (共15小题;每小题1.5分，满分22.5分)听下面5段对话或独白。
每段对话或独白后有几个小题，从题中所给的 A 、B 、C 三个选项中选出最佳选项。
听每段对话或独白前，你将有时间阅读各个小题，每小题5秒钟;听完后，各小题将给出5秒钟的作答时间。
每段对话或独白读两遍。
听第6段材料，回答第6、7题。
6.What will the weather be like today?A.StormyB.SunnyC.Foggy7.What is the man going to do?A.Plant a tree.B.Move his carC.Check the map听第7段材料，回答第8至10题。
Instruction Manual for Q-NMR Learning Module说明书
Instructor’s GuideThis guide is intended to assist instructors in the utilization of the q-NMR learning module. While the module is designed as a stand-alone resource toaccommodate self-learners, it can also be used as an active learning resource. This instructor’s guide is designed to help1. Basic Theory Concept Questions. The questions below are also listed on the webpage that links to the Basic Theory section. These questions can be handed out in class or given as a homework assignment. Students should be able to answer these questions using the Basic Theory section of this module as an instructional resource. I would also recommend assigning the excellent web resource created by Joe Hornak, since it contains embedded animations that help clarify many difficult to understand processes in NMR. This site can be accessed directly at /htbooks/nmr/ or students can bedirected to this site in ASDL by typing its ID number, 2921, into the search box in the upper right hand corner of the site.What is spin?How does absorption of energy generate an NMR spectrum? Why is NMR less sensitive than UV-visible spectroscopy?What is chemical shift and how does it relate to resonance frequency? What is precession?How does precession produce the macroscopic magnetization (Mo)?How can the nuclear spins be manipulated to generate the NMR spectrum? What is the tip angle?What is a Free Induction Decay?How do T 1 and T 2 relaxation affect NMR spectra?2. Answers to Questions in the Basic Theory section. In addition to the conceptual questions given above, the Basic Theory section also contains aseries of simple quantitative questions, the answers of which are provided below.Question 1: How many spin states would you predict for 2H?Deuterium has a spin of 1. There for there should be 3 possible spin states: +1, 0 and -1.Question 2: Given the same magnetic field and temperature, how would the difference in population for 1H and 31P compare? For this problem we will use the equationThe difference in population for 1H and 31P will be related to the differences in their ∆E values. Since ∆E=γhB o /2π, for a fixed magnetic field the only differences between 1H and 31P is in their magnetogyric ratios.kT Elower upper e N N ∆−=468.284.10752.26)()(311==∆∆P E H EThe ratio of the N upper /N lower for 1H is e 2.468 or =11.80 times larger than the ratio of N upper /N lower for 31P.Question 3: Calculate the wavelength of electromagnetic radiation corresponding to a frequency of 500 MHz.The wavelength of electromagnetic radiation corresponding to a frequency of 500 MHz is 0.6 m.Question 4: What range of frequencies would be excited by a 10 µs rf pulse?A 10 µs rf pulse would excite a range of frequencies covering 100,000 Hz.Question 5: What are the resonance line widths of nuclei that have apparent T 2 relaxation times (i.e.T 2* values) of 1 and 2 sec.*2211T w π=Therefore, the two resonances have line widths of 0.32 and 0.16 Hz.3. Practical Aspects Concept Questions. The questions below are also listed on the webpage that links to the Practical Aspects section. These questions can be handed out in class or given as a homework assignment. Students should be able to answer these questions using the Practical Aspects section of this module as an instructional resource.How do I choose a reference standard for my Q-NMR analysis?How is the internal standard used to quantify the concentration of my analyte? What sample considerations are important in Q-NMR analysis?How do I choose the right acquisition parameters for a quantitative NMR measurement?What data processing considerations are important for obtaining accurate and precise results?4. Answers to Questions in the Practical Aspects section.Question 1. A quantitative NMR experiment is performed to quantify the amount of isopropyl alcohol in a D 2O solution. Sodium maleate (0.01021 M) is used as an internal standard. The integral obtained for the maleate resonance is 46.978. The isopropanol doublet at 1.45 ppm produces an integral of 104.43. What would youpredict for the integral of the isopropanol CH resonance as 3.99 ppm. What is the concentration of isopropanol in this solution?The isopropanol CH resonance is produced by a single proton whereas the doublet is produced by the 6 methyl protons. Therefore, the CH integral should be 1/6th that of the methyl doublet, or 17.405.To find the isopropanol concentration we first have to calculate normalized areas for isopropanol and our standard, maleate. The isopropanol(IP) doublet is comprised of 6 protons due to the two equivalent methyl groups of this compound.Normalized Area (IP) = 104.43 = 17.4056Similarly, the normalized area for maleate (MA) is:Normalized Area (MA) = 46.978 = 23.4892The concentration of the isopropanol can be calculated using the known the maleate concentration.[IP] = [MA] x Normalized Area (IP)Normalized Area (MA)[IP] = 0.01021 M x 17.405 = 0.007565 M23.489Because the accuracy of the determination depends on how well the maleate concentration is know, the standard solution should be prepared with care, using dried sodium maleate of high purity, weighing carefully a mass that is known to an appropriate number of significant figures (in this case 4), transferring the maleate quantitatively to a volumetric flask and finally dilution to the mark. Again, an appropriate solution volume must be selected to produce the desired number of significant figures given the manufacturer specifications for the glassware used.Question 2: A solution prepared for quantitative analysis using NMR was acquired by coaddition of 8 FIDs produces a spectrum with an S/N of 62.5 for the analyte signals. How many FIDs would have to be coadded to produce a spectrum with an S/N of 250?S/N increases in NMR experiments as the square root of the number of scans coadded.S/N ∝ (n)0.5To increase the S/N from 62.5 to 250 (a factor of 4 increase in S/N) would require coaddition of 16 times as many FIDs as was used to produce a spectrum withS/N of 62.5. The answer is that coaddition of 128 FIDs (8 x 16) would be required to achieve an S/N of 250.Question 3: A 1H NMR spectrum was measured using a 400.0 MHz instrument by acquisition of 8192 total data points (8192 real points) and a spectral width of 12.00 ppm. What was the acquisition time? Calculate the digital resolution of the resulting spectrum? Is this digital resolution sufficient to accurately define a peak with a width at half height of 0.5 Hz?We can calculate the acquisition time knowing the spectral width and the total number of data points.AT= NP_ = 16384__ = 1.707 sec2 SW 2 x 400 x 12DR = SW_ = 2 x 400 x 12 = 1.172 Hz/ptNP(real) 8192This would not be adequate digital resolution to accurately define a peak with a 0.5 Hz width at half height. A longer acquisition time would allow for collection of more points. Also, zero-filling could also be used to help increase the digital resolution.5. Q-NMR DrylabKHP T1 relaxation times. There are two ways of getting the T1 relaxation times for the KHP resonances. The simplest way is to have students estimate the null times for the two resonances in the inversion-recovery spectra provided. Selected spectra from the dry lab data set were used to make the figure in the Practical Aspects section of the module. Alternatively, students can process the spectra and measure resonance integrals for each peak. These can be plotted vs. the relaxation delay and fit to determine T1. The integrals we obtained are summarized in the Table below. The fits obtained using Origin 7.5 are also provided. We obtained T1 values of 4.79s and 3.11s for the KHP resonances at 7.75 and 7.61 ppm, respectively.The concentration of KHP in the stock solution is determined from the mass of KHP.Mass KHP = 0.3533 g – 0.2219 g = 0.1314 gML mol g g KHP 1287.0005.01/22.2041314.0][=×=Table 1. Inversion-recovery data for KHPDelay Integral R1 (7.75 ppm) Integral R2 (7.61 ppm) 0 s -8.34 -8.48 2 -2.38 0.07 2.5 -1.01 1.65 3 -0.14 2.81 3.5 0.8 3.78 4 1.62 4.57 6 3.87 6.86 10 6.37 8.63 15 8.28 9.67 208.959.65Inversion-recovery plot for R 1Inversion-recovery plot for R 2Malic Acid Standard Solution Determination. From the mass of malic acid weighed and the solution volume, we can calculate the concentration of this standard.Mass of MA = 0.3324g – 0.1897 g = 0.1427 g ML mol g g MA 2128.0005.01/09.1341427.0][=×=Since equal volumes of the KHP and malic acid were mixed to prepare this solution, the dilution factor can be neglected and the concentration of malic acid calculated as shown below. Here we used the integral of the resonances at 2.82 and 2.89 ppm corresponding to the inequivalent malic acid CH 2 protons.I n t e g r a lInversion-Recovery Delay I n t e g r a lInversion-Recovery DelayMM Int N N Int KHP MA KHP KHP MA MA 2142.0000.1428322.01287.0][][=××=××=Spectrum of malic acid standard solution containing KHPDetermination of Malic Acid in Apple Juice. The concentration of malic acid can similarly be calculated in an apple juice sample. Here though we will need to take into account the dilutions performed.The KHP was diluted twice in preparing this solution. First it was diluted by half with D 2O, and subsequently 100 µL of was further diluted by addition to 900 µL of apple juice for a total volume of 1 mL. The KHP concentration in the apple juice sample can be calculated as shown below. Note that the volume added in making the pH adjustment to 1.35 is not important since both the KHP and the malic acid will be diluted by the same amount. This pH adjustment is necessary to resolve the malic acid resonances from those of the other apple juice components. Because of the simplicity of the malic acid standard spectrum, pH adjustment is not needed. MM KHP KHP stock juice 00643.01000100211287.010*******][][=××=××=The malic acid concentration can then be calculated as before, providing that the dilution resulting from addition of the KHP solution is included in the calculation.MM Int N N Int KHP MA KHP KHP MA MA juice juice 0328.090010004351.042000.100643.09001000][][=×××=×××=For purposes of comparison with the table provided in the background section of this laboratory, we can convert this concentration to g/L using the molecular weight of malic acid.0.0.328 M x 134.09 g/mol = 4.40 g/L malic acid。
Role of the Metal-Oxide Support in the Catalytic Activity
Role of the Metal-Oxide Support in the Catalytic Activity of Pd Nanoparticles for Ethanol Electrooxidation in Alkaline MediaEvans Angwenyi Monyoncho,[a]Spyridon Ntais,[a]Nicolas Brazeau,[a]Jhing-Jhou Wu,[b]Chia-Liang Sun,[b]and Elena A.Baranova*[a]1.IntroductionOver the past decades,an increasing amount of interest has been given to the development and improvement of fuel cell technologies.Fuel cells have many advantages compared to power sources based on fossil fuel combustion,such as high efficiency,high power density,wide range of operating tem-peratures,and,in some cases,utilization of renewable fuels.For these reasons,fuel cells have been proposed for use in a wide variety of applications,ranging from transportation to portable electronics.[1]In recent years,ethanol has been stud-ied intensively as a potential fuel,because of its compatibility with the current fuel distribution system.Ethanol has the ad-vantages of lower toxicity and higher power density compared to methanol,which has been studied extensively for decades.[2]Another advantage is that ethanol can be obtained from the fermentation of biomass,which makes it a renewable fuel with a theoretical overall CO 2emission of zero.[2a]However,for the ethanol oxidation reaction (EOR),the cleavage of the C ÀC bond remains of great concern,as most of the ethanol mole-cules are partially oxidized to acetaldehyde and acetic acid (acetate in alkaline media),releasing only two and four elec-trons,respectively,instead of the 12theoretically availableelectrons.[3]It has been reported that C ÀC bond cleavage is fa-cilitated in an alkaline environment,because of the faster oxi-dation kinetics and lower fuel crossover,owing to the reversed electro-osmotic drag of the ionic flow.[4,1b]The shift from acidic to alkaline fuel cells has been motivated by the recent devel-opment of anion exchange membranes,which allow the use of inexpensive catalysts in alkaline environments that are oth-erwise limited to Pt and Pt-based materials.[1b]Pd and Pd-based electrocatalysts have been identified as promising alternatives to Pt-based catalysts for the EOR in alka-line media,owing to their high reaction kinetics.[5,3a]There are several variables that can be modified to increase the electro-catalytic activity of Pd,such as the size and shape of Pd nano-particles (NPs),[6]the use of bimetallic NPs,[7]and the use of active catalyst supports.[8]The support can have a pronounced effect on the activity of the catalyst by affecting its morpholo-gy,that is,providing better particle dispersion and stability and,in some cases,improved electronic properties of the cata-lyst through the metal–support interaction (MSI)effect.[9]The most common catalyst support used in fuel cells is carbon black,which has a low corrosion resistance in proton or anion exchange membranes;[10]for this reason,other catalyst sup-ports such as TiO 2,SnO 2,and CeO 2have been considered for alcohol oxidation reactions.[11]These metal oxides have better chemical stability and,most of the time,enhance the catalytic activity of metals compared to commercial carbon.The catalyt-ic promotional role of these supports is attributed to their re-ducibility as mixed ionic–electronic conductors and their ability to generate oxygen vacancies (absence of O 2À)in the crystal structures.[9c]The vacancies can be generated in many different ways,such as the dehydration of the surface hydroxylspecies[a]E.A.Monyoncho,S.Ntais,N.Brazeau,Prof.E.A.BaranovaDepartment of Chemical and Biological Engineering Centre for Catalysis Research and Innovation (CCRI)University of Ottawa161Louis-Pasteur St.,Ottawa,ON K1N 6N5(Canada)E-mail:elena.baranova@uottawa.ca [b]J.-J.Wu,Prof.C.-L.SunDepartment of Chemical and Materials Engineering Chang Gung University Tao-Yuan 333(Taiwan)Supporting Information for this article is available on the WWW under /10.1002/celc.201500432.ArticlesDOI:10.1002/celc.201500432(OHÀ)and the reduction of accessible metal cations in the oxides through chemical means.The catalytic promotional properties of oxide supports in electrocatalysis have attracted the interest of many researchers, for instance,TiO2,[11e,g–i,12]SnO2,[3b,11a,c,m,n]and CeO2[11b,j,k]have been extensively investigated.Focusing on Pd-based catalysts on these supports for ethanol electrooxidation,Hu et al.pre-pared Pd NPs on carbonized TiO2nanotubes for ethanol elec-trooxidation in alkaline media,and reported that the electroca-talyst with a1:1mass ratio of Pd to TiO2/C for Pd/TiO2/C gave the best performance compared to Pd/C and Pd/TiO2.[11i]Mao et ed the impregnation reduction method to prepare carbon-supported PdSn/SnO2and showed that it had a higher current density for ethanol electrooxidation in alkaline media compared to Pd/C,SnO2/C,and PdSn/C.[11n]They showed that SnO2improved Pd particle distribution.Bambagioni et al.have shown that the addition of CeO2as a co-support to carbon for Pd NPs(Pd/C/CeO2)improved the power density of the direct alkaline ethanol fuel cell by a factor of two,as compared to Pd/C.[11b]Uhm et al.synthesized well-ordered arrays of free-standing Pd-CeO2nanobundles and reported that the catalysts had an increased number of oxygen species on the surface,re-sulting in a significant increase in their catalytic activity for the EOR in KOH.[11j]Shen and co-workers conducted a comparative study of ethanol electrooxidation on Pt/C and Pd/C catalysts, promoted by CeO2in alkaline media,and reported that CeO2 significantly improved the catalyst activity and poison toler-ance.[13]Although the promotional effect of these oxide sup-ports is evident in these studies,no direct comparison for eth-anol electrooxidation reaction on Pd NPs supported on TiO2, CeO2,SnO2,and C exists.Furthermore,there are several other questions regarding the role of the support,such as the sup-ports influence on NP size and elemental surface composition (i.e.surface oxides);in addition,the catalytic activity of Pd still remains to be elucidated.In this work,we conduct a comparative study of Pd NPs sup-ported on TiO2,SnO2,CeO2,and a conventional carbon sup-port,where the Pd NPs are prepared using the same synthesis procedure and the same metal loading.This approach allows us to evaluate the role/effect of the support on a number of properties of Pd NPs:1)the influence of the support on the particle and crystallite sizes,using transmission electron mi-croscopy(TEM)and X-ray diffraction(XRD)data;2)the effect of the support on the surface composition(oxidation states of Pd)and electronic effect,using X-ray photoelectron spectros-copy(XPS)data;3)the effect of support on the chemisorption and dispersion properties through CO stripping data;and 4)the effect of the support on the electrocatalytic properties of Pd NPs for ethanol oxidation in alkaline media by using cyclic voltammetry(CV),chronoamperometry(CA),and polari-zation modulation–infrared reflection absorption spectroscopy (PM-IRRAS)data.To this end,Pd NPs supported on CeO2,SnO2, TiO2,and carbon were prepared using sodium borohydride as a reducing agent in an aqueous medium.The EOR was studied in1m(KOH+C2H5OH)using CV and CA,and the CA was cou-pled with the in situ identification of products using PM-IRRAS.A discussion is provided to correlate the first three properties (1–3)to the electrocatalytic activity of Pd NPs induced by metal–support interactions.2.Results and Discussion2.1.Physicochemical Characterization of Supported Pd NPs The morphology and NP size distribution of the four catalysts were determined by using TEM,and the resulting microscopy images and histograms are shown in Figure1.The microscopy images show that Pd NPs were relatively well dispersed in all four of the supports tested with some degree of agglomeration,which is more evident on the SnO2 support.The histograms show the particle-size distribution of the Pd NPs for each catalyst synthesized.The average sizes of the NPs were10.4,12.3,12.6,and14.2nm for Pd NPs on SnO2, CeO2,C,and TiO2,respectively.It is interesting to note that the Pd NPs had the smallest size on SnO2and the largest size on the TiO2support,whereas the size was comparable between C and CeO2.The small specific surface area of TiO2(Table1)may be responsible for the larger size of the Pd clusters.The crystal structure of the NPs was determined by using XRD patterns,as presented in Figure2.The diffraction pattern shows that the Pd NPs retained in the bulk face-centered cubic (fcc)structure;the*symbol shows the signature peaks forfcc Figure1.TEM images of Pd NPs supported on a)CeO2,b)carbon,c)SnO2, and d)TiO2.The corresponding histograms on the right show the NP size distribution.structures.The signature fcc peaks were detected at 40.08,46.5,and 68.28on the 2q scale for all of the samples,which correspond to the (111),(200),and (220)planes,respectively.All extra peaks on the diffraction patterns correspond to the respective oxide support,as shown in the diffraction patterns of the pure supports in Figure S1in the Supporting Informa-tion.The crystallite size of the Pd NPs was estimated by using the Scherrer equation,which yields the crystallite size of the NPs.[14]The crystallite size was estimated by using the Pd(111)peak,which was confirmed to have no significant overlap with the support peaks,as shown in Figure S1.The crystallite sizes of the particles were calculated to be 10.8,7.5,9.5,and 15.2nm for Pd NPs supported on C,SnO 2,CeO 2,and TiO 2,re-spectively.The crystallite size trends are in a good agreement with the particle-size diameters found from TEM images,as shown in Table 1.The lower crystallite values compared to par-ticle sizes for Pd/CeO 2and Pd/SnO 2indicate the agglomeration of crystals in those supports.Therefore,the broader Pd peaks for CeO 2and SnO 2(Figure 2)provide evidence for the smaller crystallite sizes of the NPs,but these agglomerate together to form the larger grains detected by TEM.[15]The surface composition of the supported Pd NPs on the dif-ferent oxide supports was determined by XPS.Figure 3shows the high-resolution Pd 3d XPS peaks for all four samples.Table 2summarizes the peak positions,the full width at halfmaximum (FWHM),the atomic percentage of each component,and the chemical environment assignment of the peaks.The deconvolution of the Pd 3d peaks reveals the existence of Pd only in the metallic state for the SnO 2and TiO 2supports.How-ever,in the case of NPs supported on carbon and CeO 2,the deconvolution reveals the existence of Pd atoms that are also in higher oxidation states.In the case of Pd/C,the deconvolu-tion revealed the existence of four peaks at 335.4,336.4,337.5,and 338.4eV that are attributed to metallic Pd,PdO,PdO 2,and PdCl x ,respectively.[16]In the case of Pd/CeO 2,these deconvolut-ed components can be found at 334.6,336.1,337.4,and 338.4eV,respectively.The existence of the peak at 338.4eV and its assignment to PdCl x species is further supported by the detected Cl 2p peaks (not shown here)for the Pd/C and Pd/CeO 2catalysts.By using the intensities of the Cl 2p and of the corresponding Pd 3d component,it was found that the Cl/Pd atomic ratio is 1.2andFigure 2.XRD patterns of supported Pd NPs on various supports as shown.The symbol (*)corresponds to the fcc structure diffractions forPd.1.35for the carbon and ceria supported catalysts,respectively.The existence of PdCl x species on the surface of Pd prepared by chlorinated precursors has been reported before,[17]and it seems that their presence can be affected by the nature of the support.The removal of chlorine can take place by a drying–reduction pretreatment,but still a small amount may remain in the catalyst.[17b]Our XPS results show that for Pd NPs supported on oxides (CeO 2,SnO 2,and TiO 2),the peak attributed to the metallic state shows a shift to lower binding energies compared to the corre-sponding peak in the case of carbon-supported NPs (Pd/C).For Pd/SnO 2,the peak was detected at 335.2eV,whereas in the case of Pd/TiO 2and Pd/CeO 2,the metallic state (Pd 0)peak is shifted to lower binding energies by 0.6and 0.8eV,respective-ly.Similar shifts of the Pd 3d peak have been reported before for Pd supported on these oxides.[18]The observed shift of thePd 3d peaks to lower binding energies for Pd NPs supported on oxides is attributed to a metal–support interaction,where the charge is transferred from the support to Pd NPs.[19]Upon the contact of two metal atoms with different electronegativi-ties,the charge will be transferred from the atom with the lower electronegativity to the atom with higher electronegativ-ity until the energy level of the electrons at the interface is equilibrated.The electronegativities for the atoms involved here are,in increasing order,1.12,1.54,1.96,2.20,and 2.55for Ce,Ti,Sn,Pd,and C,respectively.[20]It is interesting to note that Pd was 100%reduced on SnO 2and TiO 2but only 67%re-duced on CeO 2,as shown by the XPS data in Table 2,which would seem to contradict the electronegativity difference trends.However,the observed difference could be explained based on the crystal structure of the supports.CeO 2has a fluo-rite-type structure,whereas SnO 2and TiO 2have rutile-type crystal structures.First,it is important to mention that the shift of the metallic peak follows the electronegativity trend as ex-pected,that is,the largest shift occurs for Pd NPs supported on CeO 2because of its lowest electronegativity value,and vice versa to NPs on SnO 2.It follows then that the structure of the supports would be responsible for the lower percentage (67%)reduction of Pd atoms on CeO 2,because the samples were prepared by using the same protocol and conditions.It is well known that CeO 2,owing to its non-stoichiometry,has the abili-ty to undergo conversion between Ce 4+and Ce 3+quite easily,[21]which can explain the presence of Pd oxides in the Pd/CeO 2catalyst.Figure 4presents the XPS spectra of Ce 3d for Pd/CeO 2(Fig-ure 4a),Ti 2p for Pd/TiO 2(Figure 4b),and Sn 3d for Pd/SnO 2(Figure 4c)with characteristic peaks of the supports.The Ce 3d XPS spectrum is rather complex,owing to the electron correla-tion phenomena.In general,six peaks are characteristic of Ce 4+,whereas four are characteristic of Ce 3+.The Ce 3d 5/2peaks at 882,888.7,and 897.8eV and their corresponding Ce 3d 3/2components at 900.7,906.9,and 916.1eV (dotted lines on Figure 4a)are attributed to cerium atoms in CeO 2.The Ce 3d 5/2peaks at 880.3and at 899.1eV with their correspond-ing 3d 3/2lines at 885.8and 903.5eV (dashed lines on Fig-ure 4a)reveal the existence of cerium atoms in the Ce 3+oxida-tion state and,more specifically,in Ce 2O 3.[22]For the other two samples,Ti 2p 3/2and Sn 3d 5/2peaks are detected at 458.4and 486.8eV,respectively,and are characteristic of Ti and Sn atoms in the 4+oxidation state.[23]Although,the relatively large FWHM of the two peaks (ca.1.5eV)implies the existence of Ti and Sn atoms in more than one chemical environment,but more studies are necessary to confirm this.2.2.Electrochemical Measurements 2.2.1.CO StrippingThe CO stripping charge was used to determine the electro-chemically active surface area (ECSA)of the four catalysts by using the protocol reported in the literature.[24]Figure S2shows the first and second cycle of the CO stripping CV curves for the four catalysts.The area between the two cyclesfrom Figure 3.Pd 3d XPS peak of Pd supported on a)CeO 2,b)TiO 2,c)SnO 2,and d)carbon.The shifting of binding energy for Pd 0(335.4eV,vertical line)to lower values indicates the level of Pd–MO 2(M =Sn,Ti,and Ce)interactions.the potential of À0.17to 0.15V and monolayer stripping charge of 420m C cm À2were used to determine the ECSA.[24]The ECSA values are shown in Table 1.The oxidation peak po-tential for CO was found to be À0.11V for all samples.Howev-er,there is significant charge distribution depending on the support,which indicates the differences in NP dispersion and CO binding on the surfaces.Pd NPs on SnO 2were found to be the smallest (crystallite size =7.5nm,particle size =10.4nm),hence leading to the highest ECSA of 0.92cm 2.Interestingly,this predicted value (0.93cm 2)is the same as the real surface area of a polycrystalline Pd electrodes [taking the average of the experimental values for (111),(100),and (110)surfaces]after CO stripping on Pd in an electrochemical environment.[25]Note that Pd was 100%metallic on SnO 2and TiO 2,so it is not surprising to have such perfect polycrystalline NPs.However,one may wonder why we do not have such a similar real sur-face area for Pd NPs on TiO 2.First,Pd NPs on TiO 2are the larg-est (crystallite size =15.2nm,particle size =14.2nm).Second,TiO 2is a poor conductor that will insulate some parts of the NPs.The Pd NPs supported on CeO 2and C have similar ECSAvalues,but they are lower than that of Pd/SnO 2,which is con-sistent with the fact that they have approximately same per-centage of metallic Pd,based on XPS data in Table 2.2.2.2.Ethanol ElectrooxidationFirst,we present the CV curves of the NPs in 1m KOH,and then CV curves in 1m (KOH +C 2H 5OH)solution.The character-istic CV curves of the four catalysts in 1m KOH at a scan rate of 25mV s À1are shown in Figure 5.The voltammograms show similar features but with different current densities,owing to variations between the NP–support interactions that,in turn,alter the catalytic activity at the interfaces.In the anodic scan,there are peaks below À0.4V (labelled I in Figure 5),which are attributed to the oxidation of adsorbed and absorbed hydrogen on Pd NPs.The anodic peaks labelled II,observed between À0.35and À0.25V,are generally attribut-ed to the adsorption of hydroxyl groups on the surface of Pd.[26,6a]The peaks labelled III,situated at potentials higher than À0.25V,correspond to the transformation of adsorbed hydroxyl groups to higher valence oxides (PdO x ),following re-action pathways in Equations (1)–(3):[3a]Pd þOH À!Pd ÀOH ads þe Àð1ÞPd ÀOH ads þPd-OH ads !Pd ÀO ads þH 2O ð2ÞPd ÀOH ads þOH À!Pd ÀO ads þH 2O þe Àð3ÞIn the cathodic scan,the peaks labelled IV,with a minimum situated at ~À0.15V (except for Pd/SnO 2at ca.À0.25V),are attributed to the reduction of the PdO x species formed during the anodic scan.The shoulders seen on peak IV for Pd/CeO 2can be attributed to the reduction of different oxidation states of Pd atoms on various Pd crystalline planes and on low coor-dination sites.For Pd/SnO 2,reduction peak IV is broad and shifted to lower potentials,indicating that the reductionpro-Figure 4.XPS peak of Ce 3d for Pd/CeO 2(A),Ti 2p for Pd/TiO 2(B),and Sn 3d for Pd/SnO 2(C).Figure 5.Cyclic voltammograms of Pd NPs deposited on carbon,CeO 2,SnO 2,and TiO 2in 1m KOH at v =25mV s À1.The vertical lines show the potentials in which the CA experiments and in situ monitoring of products by PM-IRRAS were conducted during ethanol electrooxidation (vide infra).cess is thermodynamically unfavorable.When the applied po-tential is lower than À0.45V,the cathodic current decreases,owing to a combination of three overlapping phenomena:1)the adsorption of H on the Pd surface;2)the diffusion of H into the lattices of Pd,allowing more H atoms to be adsorbed on the surface;and 3)the evolution of H 2starts to take place as the potential lowered further.The CV curves for ethanol electrooxidation over the four cat-alysts in 1m (KOH +C 2H 5OH)are shown in Figure 6.The vol-tammograms were collected by scanning the potential from an initial open-circuit voltage towards the anodic direction to a maximum potential of 0.15V,and then in the cathodic direc-tion to a minimum potential of À0.65V at a rate of 5mV s À1.The graphs showing the details of this protocol,that is,the first two cycles of each catalyst,are provided in the Supporting Information (Figure S3).In Figure S3,the charge transfer (Q )in both the anodic and cathodic sweeps is readily available as the area under the current peaks.The open-circuit potential (OCP)of four catalysts was found from Figure S3and the value increases in the order of Pd/TiO 2<Pd/C <Pd/SnO 2<Pd/CeO 2with values of À0.43,À0.52,À0.57,and À0.62V,respectively.The CV curves for the supports in 1m (KOH +C 2H 5OH)are provided in the Supporting Information (Figure S4),and con-firm that the supports have no catalytic activity for ethanol electrooxidation in alkaline media.Figure 7compares the linear-sweep voltammetry of the four catalysts in 1m (KOH +C 2H 5OH).The figure shows that,for Pd NPs supported on TiO 2and C,the onset potential is around À0.33V,whereas for NPs supported on SnO 2and CeO 2it is shifted to a lower value of À0.45V.The trend of the anodic current magnitude is consistent with that of the ECSA and maximum anodic current densities (I a,max )of the catalyst.At I a,max ,the catalyst is deactivated,owing to the formation of sur-face oxides and adsorbed oxidized species.Therefore,it is in-teresting to see the role of the supports in influencing the po-tential at which this phenomenon occurs.It was found that Pd NPs on the C support are easily deactivated at a potential of À0.04V (2.97mA cm À2),and those on SnO 2and TiO 2are deacti-vated at À0.02V (5.86and 1.63mA cm À2,respectively).But,the NPs on CeO 2were very resistant,deactivating at 0.01V (4.92mA cm À2).This observation indicates that CeO 2is capable to accommodating more surface oxides (O 2À)than the other supports (vide infra).During the reverse scan (Figure 6),the potential of the work-ing electrode is gradually lowered,allowing the transfer of electrons into the catalysts (reduction process).During the re-verse scan,a positive current was obtained,starting at around À0.05V and rapidly increasing (unlike the gradual increase in anodic scan)to a maximum current (I r,max ),which depends on the NP support,and then gradually decaying to zero at lower potentials.The differences observed in the reverse current peak shapes (see Figure 6)are related to the ability of the oxi-dized species to diffuse into the bulk solution,hence allowing fresh ethanol to access the catalyst surface.For instance,Pd/CeO 2showed a sharp current increase at À0.09V during the backward scan,which can be explained by the known CeO 2phenomenon,that is,it releases lattice oxygen (O 2À)when re-duced.[27]Therefore,the released oxygen species could help to push oxidized intermediates from the surface,hence allowing rapid access of the fresh species for oxidation.As can be seen,CeO 2and SnO 2stand out as the best performers.CeO 2is of particular interest,based on the cyclic voltammograms in Figure 6a.2.3.In Situ Identification of Ethanol Electrooxidation ProductsThe CA technique coupled with PM-IRRAS was used to investi-gate the ethanol electrooxidation products.PM-IRRAS allows us to distinguish between the oxidation species on the elec-trode surface (the difference between p-and s-polarized reflec-tion absorption spectra)and the oxidation species in the bulk electrolyte within the thin cavity between the CaF 2window and the electrode (the average of the p-and s-polarized reflec-tion absorption spectra)at each potential.Therefore,the spec-tra for the species on the electrode surface and the spectraof Figure 6.Cyclic voltammograms of Pd NPs supported on CeO 2(a),SnO 2(b),TiO 2(c),and carbon (d)in 1m (KOH +C 2H 5OH)at n =5mV s À1.The current densities are given per the ECSA determined through the CO strippingmethod.Figure 7.Linear-sweep voltammetry of the four catalysts in 1m (KOH +C 2H 5OH)at v =5mV s À1.the average species in the thin cavity will be labeled as “sur-face”and “bulk”,respectively.The PM-IRRAS spectra for ethanol electrooxidation products are shown in Figure 8.The left and right figures show the sur-face and bulk species,respectively,for the four catalysts after holding potential at À0.3V for 10min.Additional spectra to show how the products evolved with time are shown in Fig-ure S5.The presence of peaks at 1560and 1423cm À1in the surface and bulk spectra are evidence for the acetate (CH 3COO À)produced in the four catalysts.However,the amount of acetate varied from one support to another,where Pd NPs supported on TiO 2were the least active,whereas the Pd NPs on SnO 2were the most active.Further spectra of the most active catalysts were collected at lower potentials close to the onset potential for EOR at À0.5and À0.4V for Pd/CeO 2and Pd/SnO 2,respectively,and are shown in Figure 9.The C ÀC bond corresponds to the CO 2peak at 2345cm À1.The spectra demonstrate that the oxide supports have a sig-nificant influence on the selectivity of the electrooxidation spe-cies,in particular those species with absorption peaks centered at 1724,1919,2345,and 2700cm À1.Of key interest is that the selectivity towards breaking Pd/CeO 2showed superior selectiv-ity in breaking the C ÀC bond.In this regard,the utility of PM-IRRAS came into play in distinguishing that the produced CO 2desorbs/diffuses from the surface into the bulk.Desorption ofCO 2into the bulk is confirmed by the higher intensity of the peak at 2345cm À1compared to that of the surface,as shown in Figures 9a and 9b.With increasing time and potential,the Figure 8.PM-IRRAS spectra generated during ethanol electrooxidation on Pd NPs supported on,SnO 2,CeO 2,C,and TiO 2after holding potential at À0.3V versus Hg/HgO for 10min in 1m (KOH +C 2H 5OH).The top and bottom shows the bulk species and surface species,respectively.Figure 9.PM-IRRAS spectra generated during ethanol electrooxidation on Pd/CeO 2at À0.5V at increments of 5min (upper panel)and on Pd/SnO 2at À0.4V at increments of 5min (lower panel)in 1m (KOH +C 2H 5OH).Panels (a)and (c)refer to surface species,whereas (b)and (d)show bulk species.competition increases between breaking the C ÀC bond and forming the acetate and other species at 1724cm À1for the Pd/CeO 2NPs.The origin of the species absorbing at 1724,1919,and 2700cm À1is currently being investigated.Pd/SnO 2did not show any evidence of breaking the C ÀC bond;instead,it showed high selectivity and high reaction kinetics towards the production of the species absorbing at 2700cm À1.Even at low potential (À0.4V),acetate and the species at 2700cm À1were the main products,as shown Figures 9c and 9d.This ob-servation highlights the promotional catalytic effect of metal-oxide supports compared to the commonly used carbon support.It is important to note the difference between the spectra of the surface and bulk species between 1600and 2000cm À1.The bulk spectra have a broad peak centered at 1724cm À1,which is well shaped for Pd/CeO 2,but it is missing on the sur-face spectra.Similarly,the surface spectra exhibit a broad peak around 1919cm À1,which is well pronounced on Pd/SnO 2.The peak at 1724cm À1maybe attributed to the C =O vibrations from acetaldehyde (CH 3CHO)or the aldol product [CH 3CH(OH)CH 2CHO]formed from the desorbed acetaldehyde,but it is subject to further investigation.This suggestion is based on the fact that,on the surface,the carbonyl double-bond character is absent,because of the molecules interacting with the surface and owing to its polarization from the applied potential.The CA responses of ethanol oxidation over the four Pd cat-alysts recorded at À0.40,À0.2,À0.15,and À0.09V are shown in Figure 10.The current densities of Pd/TiO 2and Pd/C aremuch lower compared to Pd/CeO 2and Pd/SnO 2.In general,the Pd NPs supported on metal oxides have a higher activity for ethanol electrooxidation compared to the Pd/C catalyst,which is consistent with the amount of acetate produced.The significant difference in the current densities obtained implies that the reaction kinetics at the interface is different on each support,in agreement with the reaction selectivity demon-strated by the PM-IRRAS spectra.The CA curves reveals further important features of the reac-tion kinetics at the electrolyte–NP interface based on the cur-rent density traces.For Pd NPs on CeO 2and SnO 2,the currents showed increasing trends as soon as the potential was changed/stepped,and then decreased gradually.The initial in-creasing current densities (Figure 10)show that the NPs on CeO 2and SnO 2are very active,in agreement with CV and PM-IRRAS results.The high catalytic activity of Pd NPs on ceria and tin oxide could be correlated to metal–support interaction (MSI)gener-ated between the Pd and the oxides;however,the particle-size effect could also play a role.The smaller the NPs,the larger the active surface area that is available for the reaction as well as a stronger MSI,because of the shorter charge-trans-fer distances between the two solids.A clear trend is observed between the crystallite sizes (Table 1)and the current densities (Figures 7and 10).The smaller the crystallite size,the higher the current density obtained,which explains the higher cata-lytic activity for Pd/SnO 2and Pd/CeO 2.The poor performance of Pd/TiO 2would be attributed to their large crystallite/particle sizes and perhaps the weaker MSI.The origin of the MSI in Pd NPs supported on oxides could be attributed to:1)the higher availability of hydroxyl ions or oxygenated species (O d À)from the support lattice,which accel-erates the oxidation rate of adsorbed ethanol intermediates es-pecially on CeO 2,and SnO 2;2)the change in the so-called Volta potential difference [27,28]between the support and Pd NPs,which will alter the Fermi level of electrons in Pd,leading to the modification of its catalytic properties.The Volta poten-tial difference between Pd and carbon black is 0.23eV and is the lowest among all of the catalysts investigated in the pres-ent work.The values for Pd/SnO 2,Pd/CeO 2,and Pd/TiO 2are 0.37,0.43,and 0.92eV,respectively;[29]however,the catalytic activity of Pd for the EOR does not follow the same trend,which indicates that Pd/TiO 2catalysts with the larger particle size and presence of Pd agglomerates negates the expected support effect.According to XPS measurements,the Pd 3d peak position is shifted to lower binding energies,confirming a charge transfer from the oxide support to Pd,which indi-cates that the MSI between the Pd and the metal-oxide sup-port contributes to the enhanced EOR.3.ConclusionsThe results presented in this study showed that the metal-oxide supports have a promoting effect on the electrocatalytic activity of Pd NPs for the EOR in alkaline media.A simple syn-thesis method was used to prepare Pd NPs,which were depos-ited in situ on the surface of different reducible metal oxides (CeO 2,TiO 2and SnO 2)and on a conventional carbon support.XRD showed that the synthesized Pd NPs have an fcc structure,similar to bulk Pd.The XPS spectra revealed a shift of the Pd 3d peaks to lower binding energies for Pd NPs deposited on oxides,owing to charge transfer from the oxide support,which results in a higher electron density on the NPs.The PM-IRRAS spectra demonstrated the influence of the support on the selectivity of the EOR on Pd NPs.Pd/CeO 2NPs showed superior selectivity for breaking the C ÀC bond,where-as Pd/SnO 2did not show any evidence of breaking the C ÀC Figure 10.Chronoamperograms of Pd on different supports in 1m (KOH +C 2H 5OH)at various applied potentials.The current densities are given per the ECSA determined through the CO stripping method。
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翻译Direct reduction of graphene oxide ?lms into highlyconductive and ?exible graphene ?lms by hydrohalic acids通过卤化氢还原法把氧化膜⽯墨稀膜直接还原成⾼导热和易弯曲的⽯墨稀薄膜Songfeng Pei, Jinping Zhao, Jinhong Du *裴松峰，赵⾦平，杜⾦红, Wencai Ren, Hui-Ming Cheng ** 任⽂才，程慧明Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences, 72 Wenhua Road,沈阳国家实验室的材料科学研究所、⾦属材料研究、中国科学院,72号⽂华路,Shenyang 110016, People’s Republic of China沈阳110016,中国⼈民共和国Article history ：Received 3 August 2010。
Accepted 6 August 2010。
Available online 10 August 2010⽂史：接受2010年8⽉6⽇收到2010年8⽉3在⽹上10 2010年8⽉We report a simple but highly-effective hydrohalic acid reducing method to reduce graph- ene oxide (GO) ?lms into highly conductive graphene ?lms without destroying their integrity and ?exibility at low temperature based on the nucleophilic substitution reaction.我们报告⼀个简单⽽⾼效卤化氢还原法还原酸-烯氧化物(去)膜成⾼导电⽯墨烯⽽不破坏他们的完整性和低温稳定性基于亲核取代反应的基础上。
激光专业英语
2011年技术物理学院08级（激光方向）专业英语翻译重点！！！作者：邵晨宇Electromagnetic电磁的principle原则principal主要的macroscopic宏观的microscopic微观的differential微分vector矢量scalar标量permittivity介电常数photons光子oscillation振动density of states态密度dimensionality维数transverse wave横波dipole moment偶极矩diode 二极管mono-chromatic单色temporal时间的spatial空间的velocity速度wave packet波包be perpendicular to线垂直be nomal to线面垂直isotropic各向同性的anistropic各向异性的vacuum真空assumption假设semiconductor半导体nonmagnetic非磁性的considerable大量的ultraviolet紫外的diamagnetic抗磁的paramagnetic顺磁的antiparamagnetic反铁磁的ferro-magnetic铁磁的negligible可忽略的conductivity电导率intrinsic本征的inequality不等式infrared红外的weakly doped弱掺杂heavily doped重掺杂a second derivative in time对时间二阶导数vanish消失tensor张量refractive index折射率crucial主要的quantum mechanics 量子力学transition probability跃迁几率delve研究infinite无限的relevant相关的thermodynamic equilibrium热力学平衡（动态热平衡）fermions费米子bosons波色子potential barrier势垒standing wave驻波travelling wave行波degeneracy简并converge收敛diverge发散phonons声子singularity奇点（奇异值）vector potential向量式partical-wave dualism波粒二象性homogeneous均匀的elliptic椭圆的reasonable公平的合理的reflector反射器characteristic特性prerequisite必要条件quadratic二次的predominantly最重要的gaussian beams高斯光束azimuth方位角evolve推到spot size光斑尺寸radius of curvature曲率半径convention管理hyperbole双曲线hyperboloid双曲面radii半径asymptote渐近线apex顶点rigorous精确地manifestation体现表明wave diffraction波衍射aperture孔径complex beam radius复光束半径lenslike medium类透镜介质be adjacent to与之相邻confocal beam共焦光束a unity determinant单位行列式waveguide波导illustration说明induction归纳symmetric 对称的steady-state稳态be consistent with与之一致solid curves实线dashed curves虚线be identical to相同eigenvalue本征值noteworthy关注的counteract抵消reinforce加强the modal dispersion模式色散the group velocity dispersion群速度色散channel波段repetition rate重复率overlap重叠intuition直觉material dispersion材料色散information capacity信息量feed into 注入derive from由之产生semi-intuitive半直觉intermode mixing模式混合pulse duration脉宽mechanism原理dissipate损耗designate by命名为to a large extent在很大程度上etalon 标准具archetype圆形interferometer干涉计be attributed to归因于roundtrip一个往返infinite geometric progression无穷几何级数conservation of energy能量守恒free spectral range自由光谱区reflection coefficient（fraction of the intensity reflected）反射系数transmission coefficient（fraction of the intensity transmitted）透射系数optical resonator光学谐振腔unity 归一optical spectrum analyzer光谱分析grequency separations频率间隔scanning interferometer扫描干涉仪sweep移动replica复制品ambiguity不确定simultaneous同步的longitudinal laser mode纵模denominator分母finesse精细度the limiting resolution极限分辨率the width of a transmission bandpass透射带宽collimated beam线性光束noncollimated beam非线性光束transient condition瞬态情况spherical mirror 球面镜locus（loci）轨迹exponential factor指数因子radian弧度configuration不举intercept截断back and forth反复spatical mode空间模式algebra代数in practice在实际中symmetrical对称的a symmetrical conforal resonator对称共焦谐振腔criteria准则concentric同心的biperiodic lens sequence双周期透镜组序列stable solution稳态解equivalent lens等效透镜verge 边缘self-consistent自洽reference plane参考平面off-axis离轴shaded area阴影区clear area空白区perturbation扰动evolution渐变decay减弱unimodual matrix单位矩阵discrepancy相位差longitudinal mode index纵模指数resonance共振quantum electronics量子电子学phenomenon现象exploit利用spontaneous emission自发辐射initial初始的thermodynamic热力学inphase同相位的population inversion粒子数反转transparent透明的threshold阈值predominate over占主导地位的monochromaticity单色性spatical and temporal coherence时空相干性by virtue of利用directionality方向性superposition叠加pump rate泵浦速率shunt分流corona breakdown电晕击穿audacity畅通无阻versatile用途广泛的photoelectric effect光电效应quantum detector 量子探测器quantum efficiency量子效率vacuum photodiode真空光电二极管photoelectric work function光电功函数cathode阴极anode阳极formidable苛刻的恶光的irrespective无关的impinge撞击in turn依次capacitance电容photomultiplier光电信增管photoconductor光敏电阻junction photodiode结型光电二极管avalanche photodiode雪崩二极管shot noise 散粒噪声thermal noise热噪声1.In this chapter we consider Maxwell’s equations and what they reveal about the propagation of light in vacuum and in matter. We introduce the concept of photons and present their density of states.Since the density of states is a rather important property，not only for photons，we approach this quantity in a rather general way. We will use the density of states later also for other(quasi-) particles including systems of reduced dimensionality.In addition,we introduce the occupation probability of these states for various groups of particles.在本章中，我们讨论麦克斯韦方程和他们显示的有关光在真空中传播的问题。
suppercell
Coordinated Multipoint Transmission Systems with the Clustered Super-cell Structure ConfigurationXIAO Shang-hui †, ‡, ZHANG Zhong-pei †† National Key Lab of Commun., University of Electronic Science and Technology of China, Chengdu, 610054, P.R. of China ‡ Department of Physics & Electronic Engineering, Yibin University, Sichuan, 644007, P.R. of ChinaE-mail: xiaosh@; zhangzp@Abstract—Coordinated multipoint transmission and reception technologies are considered as good candidates for improving system capacity and cell edge experience to meet the requirements set by LTE-Advanced. This paper explicitly discusses the clustered super-cell multipoint cooperation transmission structures with the optimal precoding design. Some analysis results show that a clustered super-cell is a reasonable choice for clustered coordination with the given transmit power.Keywords-Network multiple input-multiple output (MIMO); Coordinated multipoint transmission(Co-MP); Clustered; SupercellI.I NTRODUCTIONRecently, there has been extension work on wireless systems with multiple transmit and receive antennas (known as MIMO) combined with advancing coding and signal processing. For the scattering fading channels, it has been demonstrated [1]-[5] that MIMO systems yield considerable gain in power (range) and/or data rate (bit/sec/Hz) in a given bandwidth, when compared to wireless systems with a single transmit and a single receive antenna.However, achieving the predicted enormous capacity gain in realistic cellular multi-user MIMO networks could be problematic. For realistic cellular systems, the sharing of common system resources by multiple users and the frequency reuse among adjacent cells will bring in co-channel interference (CCI), which may greatly diminish the advantages of MIMO systems [6]. In the conventional cellular systems, CCI is treated as background noise, and reduced by careful radio resource management techniques such as power control, frequency reuse, and spreading code assignments [7]. However, these techniques are all implemented at single cell without inter-cell cooperation on the physical layer, and limit the achievable spectral efficiency gain and/or lead to insufficiency suppression to CCI.This paper mainly discusses the clustered super-cell multipoint cooperation transmission system with the optimal precoding design, where multiple cells will perform joint signal processing for transmission to multiple users, and accordingly the systems are able to efficiently mitigate inter-cell CCI interference, and significantly achieve spectral efficiently gain. II.C OORDINATED MULTIPOINT TRANSMISSION SYSTEMS Already in current cellular networks, geographically dispersed multiple antennas connected to a central baseband processing unit are used as a cost-efficient way of building networks [8], which can provide improved resistance to shadowing and extended range. Such structures open up new transmission strategies. Recently, In [9], it has been shown that coordinated multipoint (Co-MP) transmission and reception technology, in which multiple different base stations (BSs) or radio access points (RAPs) together transmit signal for different mobile user equipments (UEs) as shown in figure 1, accordingly the inter-cell CCI interference mitigation becomes easy to implement, can significantly improve the system performance, especially for the spectral efficiency of cell-edge user over the cell. Several radio access points (if possible, including some remote radio units/sites, i.e. RRU/sites) are linked to one enhanced NodeB (eNodeB) by means of radio over wires/fibers, whereas each access point may contain oneor multiple antenna elements.Fig.1 System setup of coordinated multipoint transmission and reception For the uplink (UL), it supports for joint processing of signals received at multiple geographically separated points; otherwise, in the downlink (DL), it supports dynamic coordination in the scheduling/transmission, including joint transmission, from multiple geographically separated points. Co-MP is a cooperative transmission and reception technology, which can be easily deployed in a semi-distributed communication system with distributed antennas but centralized control functionally. Multiple UEs can be served by978-1-4244-3693-4/09/$25.00 ©2009 IEEEone or multiple access points of the same or different eNodeBs simultaneously. The coordinated central controllers retrieve information from distributed access points and allocate resources to satisfy the QoS requirements of the UEs while maximizing the network performance.III.M ATHEMATICAL ANALYSIS MODEL OF THE CLUSTERED MULTIPOINT COOPERATION SYSTEMSA.Clustered Super-cell System StructureFor a large Co-MP network with great number of cells, it is impractical to do coordination across over all the RAPs. We may divide the Co-MP network into a number of the clustered super cells, where each super-cell contains a group of adjacent cells. The antennas of all the cells in the super-cell participating in cooperation can be considered as a virtual antenna array within a “virtual cell”. With coordination among the RAPs with the same clustered supercell, we may effectively increase the number of spatial degree of freedom, which will be used to suppress interference, including intra-supercell and inter-supercell interference, and provide sum rate gain. Suppose in general that there are M mobile users arbitrarily distributed in the downlink coordinated multipoint transmission super-cell system, with N t the number of transmit antennas at each RAP, and N r the number of receiver antennas at each UE, respectively. Suppose that N p is the total number of adjacent RAPs in the super-cell system, so (N t, N r, N p, M) can be used to represent the overall systems. As illustrated in Fig. 2, the three cooperative RAPs together transmit L j data streams to UE j.Fig. 2 System analytical model for multi-cell in intra-eNodeB coordination The different links are independent and undergo frequency-flat Rayleigh fading. Therefore, H pj, the baseband matrix representation of the channel from RAP p to UE j, has complex Gaussian elements. τpj denotes the propagation delay from RAP p to UE j. For any UE, the multiple RAPs cooperate and jointly transmit the signals intended for it. The transmit vector for UE j from RAP p is linearly precoded by the N t×L j matrix T pj as X pj (m)= T pj S j(m), where S j (m) denotes the zero-mean data vector, of size L j×1 at time m, meant for UE j.B.System Received Signal ModelAssume that the timing-advance mechanisms can ensure that the desired signals for an UE that are transmitted from multiple RAPs reach the UE at exactly the same time. When the asynchronous nature of interference is neglected, the N r×1 received signal vector model at the j th user in the super-cell c can be represented as follows()()()()()()()()(()()()()()()__,_,_1_,_,_11__,_,_111_pppNc j c jc p j c p jpN Mc kjc p j c p kp kk jNC Mc lj c jc p j c p lc p lc cc jm mmm mm m m m===≠===+++=+++∑∑∑∑∑∑r H T XH T iH T i nD P Q n""(1)where D(m) is desired signal vector, P(m) is the intra-supercell interference signal vector, Q(m) is the inter-supercell interference signal vector. X c_j is the L j×1 transmitted vector for UE j in the clustered super-cell c (C denotes total number of the clustered super-cell). H(c,p)_j is the N r×N t channel matrix from RAP p in the clustered super-cell c to UE j. T(c,p)_j is the N t×L j precoding matrix for UE j at the p th RAP in the clustered super-cell c. n c_j(m) is the additive white Gaussian noise at UE j in the clustered super-cell c, with zero mean and variance()()*2__rc j c j Nm mσ⎡⎤Ε=⎣⎦n n I (2) where (·)* denotes the conjugate transpose of a matrix and I n denotes the n×n identity matrix.As clearly seen from (1), the following constraint holds in general()min,j r p tL N N N≤ (3) Consequently, if N r<N p N t (which is more likely in practice), the excess dimensions simply serve to offer selection diversity gain. In addition, coordinated network MIMO cannot increase the system peak data rate of any of the cells in the super-cell unless N r>min (N t).Because all the RAPs within the same cluster structure coordinate to work as a super-cell, the signal model can be written as()()()() ____1____11Mc j c j c k c kjkC Mc j c l c lj c jc lc cm mm m===≠=++∑∑∑r H T XH T X n(4)where()()()_,1_,2_,_,,,pc j c j c j c N j⎡⎤=⎢⎥⎣⎦H H H H" is the N r×N p N t aggregate channel transfer matrix from the super–cell c to UE j. and()()()****_,1_,2_,_,,,pc j c j c j c N j⎡⎤=⎢⎥⎣⎦T T T T"is the aggregate transmit precoder for UE j over all N p RAPs. Unlike the traditional downlink with co-located MIMO channels, the channel gains from any two antennas at thedifferent RAPs are guaranteed to be independent.Denote ()()()_____11C Mc jc jc l c ljc jc l c cm m m ==+∑∑z H T X nasthe sum of the noise and interference from other clustered super-cell, the covariance matrix of which is2***_______112**_____11r r CMc j N c j c l c l c l c l c jc l c c CM N c j c l c l c l c jc l c cE σσ==≠=⎡⎤=+⎣⎦=+∑∑∑∑R I H T X X T H I H T Q T H (5)where *___c l c l c l E ⎡⎤=⎣⎦Q X X is the covariance matrix of X c _l . This covariance matrix can be estimated at mobile UEs by various methods, including the usage of silent period of the desired signal [10], the usage of pilot signal [11] and blind estimation [12] according to multiple access strategies. After such estimation, each UE user will feed back it to RAPs, which will be used to design precoding matrix. Accordingly, we can assume that the covariance matrix of the interference plus noise is perfectly known at the UEs and RAPs in the same eNodeB. C. Clustered System Cooperation StrategiesDepending on the area of multipoint coordination, the coordinated multipoint transmission can be classified into the followings: Coordination everywhere in the cell and Coordination only at the cell edge. If coordinated multipoint transmission happens for all UEs in the cell regardless of the UE position, it may provide a better performance at the expense of UE feedback and backhaul overhead compared with the coordination only at the cell edge [13]. On the other hand, the single-cell transmission is used for UEs in the cell-center while multipoint coordination transmission only applies to UEs at the cell-edge. This approach may provide a good compromise between performance and reduction in the UE feedback and backhaul overhead. Note that the single-cell transmission for cell-center UEs can be achieved by designating only the home cell as the active cell.A group antenna units to serve a Co-MP configured UE is defined as e.g. the clustered super-cell. It is more easily implemented for a super cell to be composed of antenna units only under the same eNodeB than of antenna units belonging to different eNodeBs. The super-cell can be constructed in a UE-specific manner or can have one universal layout applied to all UEs. In the UE-specific super-cell construction, the coordination set of cells for a certain UE depends on the UE position. As the UE moves around cells, a set of cells for coordination is dynamically chosen from among cells near the UE, which can be done through the UE measurement reports. The UE-specific dynamic super-cell creation results in overlapping of supercells of different UEs, hence resulting in an eNodeB belonging to more than one supercell. In the universal creation the layout of super-cells is the same for all UEs regardless of the UE position. For a given UE belonging to a super-cell, it may be beneficial to designate a set of cellswhich are participating in the actual transmission for the UE. The cells in actual transmission to a UE are called active cells for the UE. The active cells can be defined from the UE perspective based on signal strengths from the cells (normally cells with strong signal strength are chosen among cells within the super-cell). The designation of active cells can reduce the UE feedback overhead and the backhaul load due to unnecessary coordination among cells.IV. S YSTEM PRECODING MATRIX DESIGNFor the codebook-based precoding method, two different design approaches exist, i.e. per-cell separation design and joint design. In the per-cell codebook design approach, the codebook consists of precoding matrices of constant size regardless of the number of coordinating cells. Assuming that each cell has N t transmit antennas, precoding for the clustered multi-cell MIMO with γ cells in coordination can be described by an (γN t ×γN t ) matrix, which is comprised of γ sub-matrices with size (N t ×γN t ) each describing the precoding for thecorresponding cell, as shown in Fig. 3(a).Fig. 3 Precoding matrix for (a) per-cell and (b) joint precoding in clusteredsuper-cell systemsThe set of sub-precoding matrices for a cell, i.e., the codebook can be designed to be identical between different cells and the codebook for single-cell transmission can be reused for simplicity. The UE may estimate preferred precoding for transmission from individual cells. The same CQI/PMI/RI report format for single-cell transmission can be reused (or with a small modification) for multi-cell coordinated multipoints transmissions (e.g., report over multiple instances to take into account transmission from multiple cells). In the joint-codebook design approach, precoding matrices are designed by considering jointly all the available transmit antennas in the coordination cells set. Assuming that each cell has N t transmit antennas, precoding matrices are of size (γN t ×γN t ) as shown in Fig. 3(b). In this case, the single “super-codebook” is designed separately for all possible cases with a different number of transmit antennas. In view of frequency reuse, the coordinated multi-cell transmission incurs “loss” of frequency resources available per cell since resources for multiple cells are now all shared as aco-channel between multiple cells. To overcome the spectrum loss incurred by the multi-cell coordinated transmission, we may need to fully utilize additional spatial-domain degree of freedom made available by multiple points transmission/reception and accommodate multiple UEs in the same frequency band simultaneously.V.N UMERICAL SIMULATION ANALYSISIf the clustered super-cell size is small, there will be too many super-cell edge users which will consume lots of degreeof freedom and lower the effective sum rate. However, the requirement of full CSI and synchronization will prohibit a very large super-cell size, and due to path loss the users benefit little from those RAPs far away. Therefore, to select a suitable super-cell size is important for practical systems. Figure 4 shows the effective sum rates per cell for differentsuper-cell size.Fig.4 Effective sum rate per-cell for different super-cell sizeAs illustrated in Fig. 4, we can see that the 3-cell cluster hasa much higher sum rate than the 1-cell cluster, and a 7-cell cluster has a rate gain about 2.5 bit/sec/Hz over a 3-cell cluster, while from 7-cell to 19-cell cluster the sum rate increases about 1bit/sec/Hz. The lower sum rate for 1-cell is due to its relative large edge area. Therefore, a 7-cell clustered super-cell can already achieve a significant part of the performance gain of the clustered super-cell coordination.Also, the CSI requirement for clustered super-cell coordination is on a super-cell scale, which is greatly reduced compared to global coordination. With C clustered super-cells and N p cells each cluster, totally there are CN p RAPs in the MIMO network. For global coordination, the effective channel matrix for each user is N r×CN p N t, while for clustered coordination it is N r×N p N t. For 7-cell cluster system, the amount of CSI feedback is only 7/19 of that for a 19-cell cluster system, while the performance of the 7-cell cluster system does not degrade much as shown in Fig. 4, so a clustered super-cell size of 7 is a reasonable choice for clustered coordination with the given transmit power.VI.C ONCLUSIONIn this contribution, we discussed some approaches forcooperation of multiple points using the clustered supercell techniques, namely the antennas of all the cells in the super-cell participating in cooperation as a virtual antenna array within a “virtual cell”. Different clustering schemes for defining cooperating cells were suggested to limit the complexity of scheduling and changes to the network architecture. For the case when the cooperating cells are co-located cells, distributed antenna systems, or remote radio units/sites (RRUs/sites), belonging to the same eNodeB, i.e., Intra-eNodeB cases, we believe that joint processing techniques are practically feasible. The requirements for Inter-eNodeB techniques are more stringent. Backhaul requirements in terms of capacity and latency, network architecture changes and scheduler complexity are some of the issues that should be addressed for enabling Inter-eNodeB techniques.A CKNOWLEDGMENTThis work is supported by National High Technology Research and Development Plans (the “863” Projects) of China (No. 2006AA01Z269, 2007AA01Z299).R EFERENCES[1]H. Jafarkhani, Space-Time Coding: Theory and Practice. NewYork:Cambridge, 2005.[2]G. J. Foschini and M. Gans, On limits of wireless communications in afading environment when using multiple antennas, Wireless Personal Communications, vol. 6, pp. 311–335, Mar. 1998.[3]V. Tarokh, N. Seshadri, and A. R. Calderbank, Space-time codes forhigh data rate wireless communication: Performance criterion and code construction, IEEE Trans. Inform. Theory, pp. 744–765, Mar. 1998[4]S. M. Alamouti, A simple transmitter diversity scheme for wirelesscommunications, IEEE J. Select. Areas Commun., pp. 1451–1458, Oct.1998.[5]I. E. Telatar, Capacity of multi-antenna Gaussian channels, Eur. Trans.Telecom., vol. 10, pp. 585–595, Nov. 1999.[6]S. Catreux, P. E. Driessen and L. J. Greenstein, Simulation results for aninterference-limited multiple-input multiple-output cellular system, IEEE Commun. Lett., vol. 4, no.11, pp.334-336, Nov. 2000.[7] A. F. Molisch, Wireless Communications. New York: Wiley-IEEEPress, 2005..[8]Haralabos C. Papadopoulos, Carl-Erik W. Sundberg, Space-Time Codesfor MIMO Systems with Non-Collocated Transmit Antennas , IEEE J.Select. Areas Commun., vol. 26, no.6 pp. 927-937, Aug. 2008[9]REV-080030, LTE-Advanced technology components, Ericsson,Shenzhen, China, April 7-8, 2008.[10]M. L. Honig, U. Madhow, and S. Verdu, Blind adaptive multiuserdetection, IEEE Trans. Inform. Theory, vol. 41, pp. 944–960, Jul. 1995 [11]R1-082501, Collaborative MIMO for LTE-Advanced downlink, AlcatelShanghai Bell, Alcatel Lucent, Warsaw, Poland, June 30-July 4, 2008. [12] D. A. Pados and S. N. Batalama, Joint space time auxiliary-vectorfiltering for DS/CDMA systems with antenna arrays, IEEE Trans.Commun., vol. 47, pp. 1406–1415, Sept. 1999.[13] A. Kansal, S. N. Batalama, and D. A. Pados, Adaptive maximum SINRRAKE filtering for DS-CDMA multipath fading channels, IEEE J.Select. Areas Commun., vol. 16, pp. 1765–1773, Dec. 1998.。
简版SpectRx近红外光谱系统课件
Incoming Inspection and Verifications 输入检验和确认
In-process Inspection
在线检测
Maintains Consistent Quality
保持品质一致性
Accuracy ( Concentration ): 0.01% 含量精确度:万分之一
Active Ingredients 活性成分 Impurities 杂质 Concentration 浓度 Homogeneity 同质性
简版SpectRx近红外光谱系统课件
6
SpectRx™ NIR
Tablets/Capsules
Diffused Reflectance 漫反射系数 Tablet Hardness 硬度 Tablet Disintegration 崩解 Tablet/Capsule Moisture Contents 湿度含量 Tablet Friability 脆性 Tablet Capsule Active Ingredients 活性组分 Tablet/Capsule Impurities 杂质 Tablet Cracks 裂纹 Capsule Deterioration 变质 Tablet/Capsule Homogeneity 药片-胶囊同质性
库）， 95％的机会可以发现一个未知的成分，除非组成的信号信噪比太小。
简版SpectRx近红外光谱系统课件
10
On Line Production 在线生产 （Including raw materials release 包括原材料放行)
简版SpectRx近红外光谱系统课件
11
Rotary Inspection in Lab (实验室旋转式检测)
英文文献汇报
Results and Discussion
Part a：用修饰沉淀法将DS嵌入α-Ni(OH)2中形成α-Ni(OH)2-DS前驱体 ；
The in situ catalytic self-limited Partb：然后脱水形成由DS包覆的NiO纳米颗粒组成的纳米片 ；
Part c：温度上升至800℃，DS热解形成碳分子，分散在NiO相中，在纳米颗粒硬膜板上催化重组形成高度石墨化的结构，同 时NiO被还原为Ni/Ni3-xS2 ；
催化剂作用下，在原位形成的纳米颗粒上实现纳米石墨烯的自 限性组装
• Use:
石墨烯纳米球壳作为基体与S复合，用作锂硫电池正极材料
• Properties:
初始放电容量：1520mAh/g(0.1C) 电流密度从0.1C提升至2.0C，70%容量保持
1000次循环，每次衰减0.06%
Introduction
and energy storage/conversion systems • Hollow nanocrystals：
mesoscale hollow structure, nanoscale quantum effects, and atomic-scale periodic arrangement • Hollow graphene nanoshells(HGNs)：
intermediate polysulfide species for irreversible loss。 All the structural benefits:highspecific surface area, goodconductivity, interconnected ionchannels, confined nanospace, and mechanical stabilityto improve the utilizationofactive materials and immobilize migratorypolysulfides.
2024年高考英语试卷
2024年高考英语真题试卷（新高考Ⅰ卷）第二部分一、阅读(共两节，满分50分)第一节(共15小题；每小题2.5分，满分37.5分)阅读下列短文，从每题所给的A、B、C、D四个选项中选出最佳选项。
HABITAT RESTORATIONTEAMHelp restore and protect Marin's natural areas from the Marin Headlands to Bolinas Ridge. We'll explore beautiful park sites while conducting invasive(侵入的)plant removal, winter planting, and seed collection. Habitat Restoration Team volunteers play a vital role in restoring sensitive resources and protecting endangered species across the ridges and valleys.GROUPSGroups of five or more require special arrangements and must be confirmed in advance. Please review the List of Available Projects and fill out the Group Project Request Form.AGE, SKILLS, WHAT TO BRINGV olunteers aged 10 and over are welcome. Read our Youth Policy Guidelines for youth under the age of 15.Bring your completed V olunteer Agreement Form. V olunteers under the age of18 must have the parent /guardian approval section signed.We'll be working rain or shine. Wear clothes that can get dirty. Bring layers for changing weather and a raincoat if necessary.Bring a personal water bottle, sunscreen, and lunch.No experience necessary. Training and tools will be provided. Fulfills(满足)community service requirements.UPCOMING EVENTS1．What is the aim of the Habitat Restoration Team?A．To discover mineral resources.B．To develop new wildlife parks.C．To protect the local ecosystemD．To conduct biological research.2．What is the lower age limit for joining the Habitat Restoration Team?A．5.B．10.C．15.D．18.3．What are the volunteers expected to do?A．Bring their own tools.B．Work even in bad weather.C．Wear a team uniform D．Do at least three projects."I am not crazy, "says Dr. William Farber, shortly after performing acupuncture (针灸) on a rabbit. "I am ahead of my time. "If he seems a little defensive, it might be because even some of his coworkers occasionally laugh at his unusual methods, But Farber is certain he'll have the last laugh. He's one of a small but growing number of American veterinarians(兽医)now practicing "holistic" medicine-combining traditional Western treatments with acupuncture, chiropractic(按摩疗法)and herbal medicine Farber, a graduate of Colorado State University, started out as a more conventional veterinarian. He became interested in alternative treatments 20 years ago when he suffered from terrible back pain. He tried muscle-relaxing drugs but found little relief. Then he tried acupuncture, an ancient Chinese practice, and was amazed that he improved after two or three treatments. What worked on a veterinarian seemed likely to work on his patients. So, after studying the techniques for a couple of years, he began offering them to pets Leigh Tindale's dog Charlie had a serious heart condition. After Charlie had a heart attack, Tindale says, she was prepared to put him to sleep, but Farber's treatments eased her dog's suffering so much that she was able to keep him alive for an additional five months And Priscilla Dewing reports that her horse, Nappy, "moves more easily and rides more comfortably" after a chiropractic adjustment.Farber is certain that the holistic approach will grow more popular with time, and if the past is any indication, he may be right: Since 1982, membership in the American Holistic Veterinary Medical Association has grown from 30 to over 700. "Sometimes it surprises me that it works so well, "he says. "I will do anything to help an animal. That's my job. "4．What do some of Farber's coworkers think of him?A．He's odd.B．He's strict C．He's brave.D．He's rude5．Why did Farber decide to try acupuncture on pets?A．He was trained in it at university.B．He was inspired by another veterinarian.C．He benefited from it as a patient.D．He wanted to save money for pet owners.6．What does paragraph 3 mainly talk about?A．Steps of a chiropractic treatment.B．The complexity of veterinarians' work.C．Examples of rare animal diseases.D．The effectiveness of holistic medicine.7．Why does the author mention the American Holistic Veterinary Medical Association?A．To prove Farber's point B．To emphasize its importance.C．To praise veterinarians.D．To advocate animal protection.Is comprehension the same whether a person reads a text onscreen or on paper? And are listening to and viewing content as effective as reading the written word when covering the same material? The answers to both questions are often "no. " The reasons relate to a variety of factors, including reduced concentration, an entertainment mindset(心态)and a tendency to multitask while consuming digital content.When reading texts of several hundred words or more, learning is generally more successful when it's on paper than onscreen. A large amount of research confirms this finding. The benefits of print reading particularly shine through when experimenters move from posing simple tasks-like identifying the main idea in a reading passage-to ones that require mental abstraction-such as drawing inferences from a text.The differences between print and digital reading results are partly related to paper's physical properties. With paper, there is a literal laying on of hands, along with the visual geography of distinct pages. People often link their memory of what they've read to how far into the book it was or where it was on the page.But equally important is the mental aspect. Reading researchers have proposed a theory called "shallowing hypothesis(假说). " According to this theory, people approach digital texts with a mindset suited to social media, which are often not so serious, and devote less mental effort than when they are reading print Audio(音频)and video can feel more engaging than text, and so university teachers increasingly tum to these technologies -say, assigning an online talk instead of an article by the same person. However, psychologists have demonstrated that when adults read news stories, they remember more of the content than if they listen to or view identical piecesDigital texts, audio and video all have educational roles, especially when providing resources not available in print. However, for maximizing leaning where mental focus and reflection are called for, educators shouldn't assume all media are the same, even when they contain identical words.8．What does the underlined phrase "shine through" in paragraph 2 mean?A．Seem unlikely to last.B．Seem hard to explain.C．Become ready to use.D．Become easy to notice.9．What does the shallowing hypothesis assume?A．Readers treat digital texts lightly.B．Digital texts are simpler to understand.C．People select digital texts randomly.D．Digital texts are suitable for social media.10．Why are audio and video increasingly used by university teachers?A．They can hold students' attentionB．They are more convenient to prepare.C．They help develop advanced skills.D．They are more informative than text.11．What does the author imply in the last paragraph?A．Students should apply multiple learning techniques.B．Teachers should produce their own teaching material.C．Print texts cannot be entirely replaced in education.D．Education outside the classroom cannot be ignored.In the race to document the species on Earth before they go extinct, researchers and citizen scientists have collected billions of records. Today, most records of biodiversity are often in the form of photos, videos, and other digital records. Though they are useful for detecting shifts in the number and variety of species in an area, a new Stanford study has found that this type of record is not perfect."With the rise of technology it is easy for people to make observations of different species with the aid of a mobile application, "said Barnabas Daru, who is lead author of the study and assistant professor of biology in the Stanford School of Humanities and Sciences. "These observations now outnumber the primary data that comes from physical specimens(标本), and since we are increasingly using observational data to investigate how species are responding to global change, I wanted to know: Are they usable?"Using a global dataset of 1. 9 billion records of plants, insects, birds, and animals, Daru and his team tested how well these data represent actual global biodiversity patterns."We were particularly interested in exploring the aspects of sampling that tend to bias(使有偏差)data, like the greater likelihood of a citizen scientist to take a picture of af lowering plant instead of the grass rightnext to it, "said Daru.Their study revealed that the large number of observation-only records did not lead to better global coverage. Moreover, these data are biased and favor certain regions, time periods, and species. This makes sense because the people who get observational biodiversity data on mobile devices are often citizen scientists recording their encounters with species in areas nearby. These data are also biased toward certain species with attractive or eye-catching features.What can we do with the imperfect datasets of biodiversity?"Quite a lot, "Daru explained." Biodiversity apps can use our study results to inform users of oversampled areas and lead them to places -and even species -that are not well-sampled. To improve the quality of observational data, biodiversity apps can also encourage users to have an expert confirm the identification of their uploaded image. "12．What do we know about the records of species collected now?A．They are becoming outdated.B．They are mostly in electronic formC．They are limited in numberD．They are used for public exhibition.13．What does Daru's study focus on?A．Threatened species.B．Physical specimens.C．Observational data D．Mobile applications14．What has led to the biases according to the study?A．Mistakes in data analysis.B．Poor quality of uploaded picturesC．Improper way of sampling.D．Unreliable data collection devices.15．What is Daru's suggestion for biodiversity apps?A．Review data from certain areas.B．Hire experts to check the records.C．Confirm the identity of the users.D．Give guidance to citizen scientists.二、第二节(共5小题；每小题2.5分，满分12.5分)（2024·新高考Ⅰ卷）阅读下面短文，从短文后的选项中选出可以填入空白处的最佳选项。
基于GCN-LSTM_的频谱预测算法
doi:10.3969/j.issn.1003-3114.2023.02.001引用格式:薛文举,付宁,高玉龙.基于GCN-LSTM 的频谱预测算法[J].无线电通信技术,2023,49(2):203-208.[XUE Wenju,FU Ning,GAO Yulong.Spectrum Prediction Algorithm Based on GCN-LSTM[J].Radio Communications Technology,2023,49(2):203-208.]基于GCN-LSTM 的频谱预测算法薛文举,付㊀宁,高玉龙(哈尔滨工业大学通信技术研究所,黑龙江哈尔滨150001)摘㊀要:无线频谱是一项重要的㊁难以再生的自然资源㊂在频谱数据中随着信道的动态变化,各个信道不能建模成规则的结构㊂由于卷积神经网络提取的是规则数据结构的相关性,没有考虑信道动态变化以及各个信道节点之间的相关性影响,基于此研究了基于图卷积神经网络(Graph Convolutional Network,GCN)和长短期记忆(Long Short-TermMemory,LSTM)网络结合的GCN-LSTM 频谱预测模型,并且引入了注意力机制,仿真得到了GCN-LSTM 在正确数据集和有一定错误数据的数据集上的预测性能和算法运行时间㊂结果表明在引入注意力机制后,GCN-LSTM 预测模型的准确性和实时性都得到了提高㊂关键词:频谱预测;图神经网络;LSTM;注意力机制中图分类号:TN919.23㊀㊀㊀文献标志码:A㊀㊀㊀开放科学(资源服务)标识码(OSID):文章编号:1003-3114(2023)02-0203-06Spectrum Prediction Algorithm Based on GCN-LSTMXUE Wenju,FU Ning,GAO Yulong(Communication Research Center,Harbin Institute of Technology,Harbin 150001,China)Abstract :Wireless spectrum is an important and hard-to-regenerate natural resource.Since convolutional neural network extractscorrelation of regular data structure,dynamic changes of channel and the correlation between each channel node are not considered.Therefore,this paper studies a GCN-LSTM spectrum prediction model based on the combination of graph convolution neural network GCN and LSTM network,and introduces an attention mechanism.Simulation results show that the prediction performance and algorithm running time of GCN-LSTM on the correct dataset and the dataset with certain error data.Results show that the accuracy and real-timeperformance of GCN-LSTM prediction model are improved after introducing the attention mechanism.Keywords :spectrum prediction;graph neural network;LSTM;attention mechanism收稿日期:2022-12-29基金项目:国家自然科学基金(62171163)Foundation Item :National Natural Science Foundation of China(62171163)0 引言随着无线通信事业的蓬勃发展,各种接入无线网的智能设备数量迅速增长[1],频谱资源趋于紧缺㊂传统的静态频谱分配方式不适配于需求日渐多样化的频谱环境,出现了大量的 频谱空洞 ,造成了频谱资源浪费㊂为解决频谱利用不足的问题,Mitola 在1999年提出了认知无线电(Cognitive Radio,CR)的概念[2]㊂频谱预测的核心就是挖掘并利用历史频谱数据的相关性特征㊂频谱预测可以分为预测信道的占用情况或者是预测用户的位置和传输功率两大类㊂本文主要针对第一类,即预测信道的占用情况㊂早期研究主要采用例如自回归模型[3]㊁隐马尔可夫模型[4]㊁模式挖掘等传统方法㊂随着神经网络的发展,人们开始将神经网络,比如循环神经网络(Recurrent Neural Network,RNN)[5]和长短期记忆网络(Long Short-Term Memory,LSTM)[6]用于预测,LSTM 网络有效缓解了梯度消失和梯度爆炸现象㊂此外,有很多学者对时频联合域频谱预测展开了研究㊂文献[7]利用频谱的这种相关性提出一种二维频繁模式挖掘算法㊂由于不同地点频谱的使用情况也会有很大不同,因此也有研究将频谱预测的维度扩展到时频空域上㊂文献[8]利用神经网络来进行多维频谱预测的方法研究,提出了LSTM网络和其他神经网络结合的方法进行时频空三维的预测,然而只是提出了想法,并没有实现,算法仍处于仿真阶段㊂图神经网络最早由Gori等人[9]提出㊂GCN广泛用于提取图结构的特征信息,从理论上可以将GCN分为基于谱域和空域两类㊂Bruna等人在2014年提出了第一代GCN[10],定义了图上的卷积方法图结构㊂基于空域的图卷积则没有借助谱图理论,可以直接在空域上操作,非常灵活㊂Petar等人在2018年提出了图注意力网络(Graph Attention Network, GAT)[11],在图卷积网络中使用注意力机制,为图结构中不同的节点赋以不同的权重也就是注意力系数,解决了图卷积神经网络(Graph Convolutional Network,GCN)必须提前知道完整图结构的不足㊂把数据处理成图结构之后,利用图神经网络来学习图结构形式的数据可以更有效地挖掘发现其内部特征和模式,与频谱预测的核心不谋而合,因此可以使用图神经网络来进行频谱预测㊂本文首先分析了频谱预测的特点和发展趋势,说明了频谱预测的重要性和可行性㊂其次,针对频谱预测问题提出了GCN-LSTM模型进行二维时频频谱的预测,采用GCN提取频谱数据的拓扑特征,提取得到频谱数据中的频率相关性之后㊂然后利用LSTM网络进行时间维度动态性特征的提取㊂最后,通过引入注意力机制对GCN-LSTM频谱预测算法进行了改进研究㊂1 基于GCN-LSTM网络的频谱预测问题建模㊀㊀图神经网络可以通过分析研究各个节点的空间特征信息得到既包含内容也包含结构的特征表示,因此在本文中处理频谱数据时,不再是建模成规则的图片,而是建模成如图1所示的图结构㊂图结构中的每个节点代表频谱中的各个信道,信道之间是存在关联的,用图中的边表示,时间维度上的各个信道状态即是各个节点的特征㊂图1㊀频谱建模成图结构Fig.1㊀Spectrum modeling and mapping structure为了提取非欧式拓扑图的空间特征,研究人员利用GCN通过图结构的信息和图中节点的信息提取图的结构特征[12],如图2所示㊂GCN如今已经广泛应用于图数据的研究处理领域[13]㊂图2㊀图神经网络的结构示意图Fig.2㊀Structure diagram of graph neural network对于给定的图G=(V,E),V表示图中的节点集合,假设其长度为N㊂可以用图中的节点V和边E来对图进行定义㊂第二代图卷积GCN公式可以简化成:x G∗gθʈðK k=0θk T k(L~)x㊂(1)㊀㊀由式(1)可以看出,图上的卷积不需要整个图都参与运算,只需捕捉到图上的局部特征,减少了需要训练学习的参数量;并且不再需要对图进行特征分解,避免了特征分解的高昂代价㊂但是由于进行矩阵相乘操作,计算的时间复杂度仍然比较高㊂为了对问题进行简化,Kipf等人在文献[14]中设置K=1,只考虑节点的一阶邻居节点㊂如图3所示,当K=1时,对每个节点的特征进行更新时,不但会考虑各个节点本身的输入特征,还会将各个节点的一阶邻域的邻居节点的输入特征也考虑在内㊂取λmax =2,K =1,得到多层传播的图卷积计算公式:H (l +1)=σD ~-12A ~D ~-12H (l )W (l )(),(2)式中,σ(㊃)为非线性激活函数,A ~=A +I N ,A ~为加上自身属性后的邻接矩阵,D ~=ðjA ~ij 表示邻接矩阵A ~的度矩阵,H (l )为第l 层中图节点特征,H (0)=χ,即输入的特征矩阵,W (l )为第l 层的权重,即可训练的卷积滤波参数㊂图3㊀图卷积计算的简单示意图Fig.3㊀Simple diagram of convolution calculation2㊀增加注意力机制的GCN-LSTM 频谱预测算法2.1㊀GCN-LSTM 网络模型利用信道占用模型产生频谱数据,然后将频谱建模成图,频谱中的各个信道建模成图中的各个节点,在频率上提取信道之间的相关性即是提取节点之间的相关性,用GCN 进行提取,时间上的相关性则由LSTM 进行提取㊂GCN-LSTM 频谱预测算法示意如图4所示,内部结构如图5所示㊂图4㊀GCN-LSTM 模型示意图Fig.4㊀GCN-LSTM modeldiagram图5㊀GCN-LSTM 模型内部结构Fig.5㊀Internal structure diagram of GCN-LSTM model图4中,先将图结构形式的频谱输入GCN,提取其拓扑结构特征(即频率相关性),GCN 的输出Z N t 是已经提取了频率相关性的序列数据;然后将提取频率相关性的Z N t 序列输入进LSTM 网络,提取序列数据的时序相关性;最终通过激活函数的激活得到输出,并与真实的频谱数据利用损失函数衡量比较得到误差㊂Z N t 代表输入数据χt 经过图卷积网络后的数据特征㊂i t ㊁f t ㊁o t 分别代表了输入门(Input Gate)㊁遗忘门(Forget Gate)和输出门(Output Gate)㊂图5所示的χt 代表输入的处理成图结构的频谱数据,节点之间的关联强弱代表信道相关性的强弱㊂GCN-LSTM 预测模型公式如下:i t=σ(W iχ㊃Z Nt +W ih ㊃h t -1+b t )f t =σ(W f χ㊃Z N t +W fh ㊃h t -1+b f )o t =σ(W o χ㊃Z N t +W o h ㊃h t -1+b o )c ~t =g (W c χ㊃Z N t +W ch ㊃h t -1+b c )c t =i t☉c ~t +f t ☉c t -1h t =o t☉h -(c t )ìîíïïïïïïïï㊂(3)2.2㊀增加注意力机制的GCN-LSTM 预测模型注意力机制[15]是关注更重点的信息而忽略一些无关的信息,在GCN-LSTM 模型基础上,加入注意力机制,就是对不同时间步的特征赋予不同的权重㊂Soft Attention 注意力机制示意如图6所示,可以分成三步:一是信息输入h j ;二是注意力系数e ij 的计算,e ij 利用神经网络计算,再利用softmax 函数对e ij 进行归一化得到注意力的分布a ij ;三是利用注意力分布αij 与输入的信息进行加权平均得到输出c i㊂αij =exp(e ij )ðN k =1exp(eik)㊂(4)㊀㊀输出c i 为权重与输入的加权平均:c i =ðN j =1αijh j㊂(5)图6㊀Soft attention 注意力机制示意F i g.6㊀Schematic diagram of Soft Attention mechanism㊀㊀增加了注意力机制的GCN-LSTM 模型网络,如图7所示㊂将GCN-LSTM 的输出作为注意力层的输入,通过一个全连接层,再经过softmax 归一化,计算对时间步的权重即注意力分配矩阵,将注意力分配矩阵和输入数据进行逐元素的相乘即得到注意力的输出㊂图7㊀增加注意力机制的GCN-LSTM 模型示意图Fig.7㊀Schematic diagram of GCN-LSTM model forincreasing attention mechanism3 仿真结果利用信道占用模型,产生了5个信道的频谱数据,时间长度为10000,损失函数选择二分类交叉熵损失函数㊂在实验中,设置GCN 的模型参数为:图卷积网络层数为1,初始学习率为0.001,评价GCN-LSTM 预测算法的性能指标为准确率㊂预测窗口长度为10,隐藏单元数hidden_units 为128,batch_size 为64,迭代次数epoch 为20㊂基于GCN-LSTM 预测算法预测的准确率如图8和图9所示㊂图8㊀GCN-LSTM 模型准确率Fig.8㊀GCN-LSTM modelaccuracy图9㊀增加注意力机制的GCN-LSTM 模型精确率Fig.9㊀Increase the accuracy of GCN-LSTMmodel of attention mechanism二分类交叉熵binary_cross entropy 公式为:loss (y ,y ^)=-1nðni(y i lb(y^i )+(1-y i )lb(1-y ^i )),(6)式中,y i 为真实的值,y^i 为预测的值㊂在基础的GCN-LSTM 模型上增加了注意力机制之后,同样训练20轮之后,准确率从96.89%增长到97.86%,准确率得到了提升,训练时间从10.23s 变为12.69s,网络输出时间从0.13s 变为0.15s,时间基本为原来的1.19倍㊂这是因为增加注意力机制后,训练的参数数量从70020增长为78120,数量增多㊂增加注意力机制确实可以提高GCN-LSTM 模型整体的预测性能,而且性能略平稳一些㊂同时对比在频谱数据出现错误情况下的GCN-LSTM 和增加了注意力机制之后的预测模型的预测性能㊂图10为错误概率为0.05的情况,图11为错误概率为0.1的情况㊂比较无错误㊁错误概率为0.05和0.1时,随着错误概率的增加,准确率会略有下降㊂增加注意力机制后的预测算法比没有增加注意力机制的GCN-LSTM 算法指标提高一点,预测性能更好㊂图10㊀GCN-LSTM 模型错误率为0.05时的准确率Fig.10㊀Accuracy when GCN-LSTM model error rate is 0.05图11㊀GCN-LSTM 模型错误率为0.1时的准确率Fig.11㊀Accuracy when GCN-LSTM model error rate is 0.14 结论本文主要研究了基于GCN-LSTM 的频谱预测算法,采用GCN 和LSTM 复合网络GCN-LSTM 预测模型进行时频频谱预测㊂为了考量不同时间步的重要程度,在GCN-LSTM 预测模型基础上增加了注意力机制来提高预测效果㊂此外,实际数据可能存在错误的情况,对无错误数据和错误数据的情况分别进行了仿真㊂仿真结果表明,GCN-LSTM 方法预测准确率较高,且训练时间和预测时间更短,实时性大大提升㊂另外,增加注意力机制后,预测性能也得到一些提高,时间约是没增加注意力机制时的1.2倍㊂对比数据出现错误的情况下,使用GCN-LSTM 算法的预测性能也在可以接受的范围内㊂参考文献[1]㊀DEHOS C,GONZÁLEZ J L,DOMENICO A D,et -limeter-wave Access Andbackhauling:The Solution to the Exponential Data Traffic Increase in 5G Mobilecommuni-cations Systems [J ].IEEE Communications Magazine,2014,52(9):88-95.[2]㊀MITOLA J,MAGUIRE G Q.Cognitive Radio:MakingSoftware Radios More Personal[J].IEEE Personal Com-munications,1999,6(4):13-18.[3]㊀WEN Z,LUO T,XIANG W,et al.Autoregressive Spec-trum Hole Prediction Model for Cognitive Radio Systems [C]ʊIEEE International Conference on Communications Workshops.Beijing:IEEE,2008:154-157.[4]㊀何竞帆.认知无线电频谱预测算法研究[D].成都:电子科技大学,2019.[5]㊀邢玲.基于递归神经网络的频谱预测技术研究[D].成都:电子科技大学,2019.[6]㊀YU L,CHEN J,DING G.Spectrum Prediction via LongShort Term Memory [C]ʊ20173rd IEEE InternationalConference on Computer and Communications (ICCC).Chengdu:IEEE,2017:643-647.[7]㊀YIN S,CHEN D,ZHANG Q,et al.Mining SpectrumUsage Data:A Large-scale Spectrum Measurement Study[J].IEEE Transactions on Mobile Computing,2012,11(6):1033-1046.[8]㊀周佳宇,吴皓.基于神经网络的多维频谱推理方法探讨[J].移动通信,2018,42(2):35-39.[9]㊀GORI M,MONFARDINI G,SCARSELLI F.A New Modelfor Learning in Graph Domains [C]ʊProceedings 2005IEEE International Joint Conference on Neural Networks.Montreal:IEEE,2005:729-734.[10]BRUNA J,ZAREMBA W,SZLAM A,et al.Spectral Net-works and Deep Locally Connected Networks on Graphs [J /OL].arXiv:1312.6203[2022-12-20].https:ʊ /abs /1312.6203.[11]VELIC㊅KOVIC'P,CUCURULL G,CASANOVA A,et al.Graph Attention Networks[J/OL].arXiv:1710.10903[2022-12-20].https:ʊ/abs/1710.10903.[12]魏金泽.基于时空图网络的交通流预测方法研究[D].大连:大连理工大学,2021.[13]SCHLICHTKRULL M,KIPF T N,BLOEM P,et al.Mod-eling Relational Data with Graph Convolutional Networks[C]ʊEuropean Semantic Web Conference.Heraklion:Springer,2018:593-607.[14]KIPF T N,WELLING M.Semi-supervised Classificationwith Graph Convolutional Networks[J/OL].arXiv:1609.02907[2022-12-20].https:ʊ/abs/1609.02907.[15]UNGERLEIDER L G,KASTNER S.Mechanisms of VisualAttention in the Human Cortex[J].Annual Review ofNeuroscience,2003,23(1):315-341.作者简介:㊀㊀薛文举㊀哈尔滨工业大学硕士研究生㊂主要研究方向:频谱预测㊂㊀㊀付㊀宁㊀哈尔滨工业大学硕士研究生㊂主要研究方向:频谱预测㊂㊀㊀高玉龙㊀哈尔滨工业大学教授,博士生导师㊂主要研究方向:智能通信㊁频谱态势认知㊁智能信息融合㊂。
光光转换效率英文
光光转换效率英文介绍光光转换效率英文是指太阳能电池将光能转化为电能的效率。
在太阳能领域，光光转换效率是一个重要的指标，影响着太阳能电池的实际应用和经济效益。
光光转换效率的提高可以有效地提高太阳能电池的性能和产能，加速太阳能产业的发展。
本文将详细探讨光光转换效率的英文表达，包括相关术语和常用表述。
术语及表述在讨论光光转换效率英文之前，先介绍一些与光光转换效率相关的术语： 1. Photovoltaic conversion efficiency：光伏转换效率 2. Incident light：入射光 3. Absorption：吸收 4. Electron-hole pair：电子空穴对 5. Exciton：激子 6. Charge carrier：载流子 7. Energy band gap：能带间隙 8. Open-circuit voltage：开路电压 9. Short-circuit current：短路电流 10. Fill factor：填充因子 11. Power conversion efficiency：功率转换效率光光转换效率的影响因素光光转换效率受多种因素的影响，下面将逐一介绍这些因素及其英文表述。
材料选择1.Band gap engineering：能带调控2.Semiconducting material：半导体材料3.Absorption coefficient：吸收系数4.Doping concentration：掺杂浓度结构设计1.Surface texture：表面处理2.Anti-reflection coating：抗反射涂层3.Tandem structure：串联结构4.Multi-junction solar cells：多结太阳能电池光学特性1.Quantum efficiency：量子效率2.Reflectance：反射率3.Transmittance：透过率4.Light trapping：光捕获电子输运1.Mobility：迁移率2.Diffusion length：扩散长度3.Recombination：复合4.Tunneling effect：隧穿效应界面特性1.Heterojunction：异质结2.Contact resistance：接触电阻3.Interface trap density：界面态密度4.Passivation：表面钝化设备参数1.Open-circuit voltage：开路电压2.Short-circuit current：短路电流3.Fill factor：填充因子4.Power conversion efficiency：功率转换效率提高光光转换效率的方法在太阳能电池领域，提高光光转换效率是一个持续的研究方向。
最大光化学效率英文
最大光化学效率英文English:The maximum quantum efficiency of photosystem II, the key protein complex involved in the light-dependent reactions of photosynthesis, is a measure of its ability to convert absorbed light into chemical energy. It represents the maximum theoretical yield of photosynthesis, with values typically ranging from to The actual efficiency can be influenced by a variety of factors, such as environmental conditions, the availability of key substrates, and the health of the photosynthetic machinery. Understanding and optimizing the maximum quantum efficiency of photosystem II is crucial for improving crop productivity and developing sustainable agriculture practices.中文翻译:光系统II的最大量子效率是光合作用光依赖反应中的关键蛋白复合物，它衡量了其将吸收的光转化为化学能的能力。
它代表了光合作用的最大理论产量，通常值在至之间。
实际效率可以受到各种因素的影响，如环境条件、关键底物的可用性以及光合机制的健康状况。
了解和优化光系统II的最大量子效率对于提高作物产量和开发可持续农业实践至关重要。
《基于Y6非富勒烯受体光伏和忆阻器件界面问题及性能优化研究》范文
《基于Y6非富勒烯受体光伏和忆阻器件界面问题及性能优化研究》篇一基于Y6非富勒烯受体光伏与忆阻器件界面问题及性能优化研究一、引言近年来，随着科技的不断进步，Y6非富勒烯受体光伏器件和忆阻器件在光电子领域中受到了广泛的关注。
Y6非富勒烯受体材料因其独特的光电性能和良好的稳定性，在光伏器件中具有巨大的应用潜力。
然而，在光伏器件和忆阻器件的界面问题以及性能优化方面仍存在诸多挑战。
本文将针对基于Y6非富勒烯受体的光伏和忆阻器件界面问题展开研究，并提出相应的性能优化策略。
二、Y6非富勒烯受体光伏器件界面问题（一）界面结构与能级匹配Y6非富勒烯受体光伏器件的界面结构对光电器件的性能具有重要影响。
界面处能级匹配问题直接关系到电荷传输效率及器件的稳定性。
目前，界面处存在的能级不匹配问题会导致电荷传输过程中产生较大的能量损失，进而影响光伏器件的效率。
（二）界面缺陷与电荷复合界面缺陷是影响Y6非富勒烯受体光伏器件性能的另一个关键因素。
界面处的缺陷可能导致电荷复合，降低光电器件的开路电压和填充因子，从而影响其光电转换效率。
此外，界面缺陷还可能引发器件的稳定性问题。
三、Y6非富勒烯受体忆阻器件界面问题（一）界面电阻与导电性能Y6非富勒烯受体在忆阻器件中应用时，其与其它材料组成的界面电阻直接关系到忆阻器件的导电性能。
界面的电阻对忆阻效应的产生及维持具有重要意义，合适的界面电阻可以保证忆阻器具有良好的开/关比和稳定性。
（二）界面材料兼容性Y6非富勒烯受体与其它材料之间的兼容性是影响忆阻器件性能的另一个关键因素。
不同材料之间的界面相互作用可能影响电荷传输过程，进而影响忆阻器的性能。
因此，选择合适的界面材料对提高忆阻器性能具有重要意义。
四、性能优化策略（一）优化界面结构与能级匹配针对Y6非富勒烯受体光伏器件的界面问题，可以通过优化界面结构、调整能级匹配等方式来提高电荷传输效率。
例如，通过引入适当的界面修饰材料或调整器件制备工艺来改善能级匹配问题。
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BSSPARCapacity & Spectral Efficiency FeaturesTraining DocumentBSSP A R CTXX 10 S10.5 12-2002 The information in this document is subject to change w ithout notice and describes only the product defined in the introduction of this documentation. This document is intended for the use of Nokia Netw orks' customers only for the purposes of the agreement under w hich the document is submitted, and no part of it may be reproduced or trans mitted in any for m or means w ithout the prior w ritten per mission of Nokia Netw orks. The document has been prepared to be used by professional and properly trained personnel, and the customer assumes full responsibility w hen using it. Nokia Netw orks w elcomes customer comments as part of the process of continuous development and improvement of the documentation.The information or statements given in this document concerning the suitability, capacity, or performance of the mentioned hardw are or softw are products cannot be cons idered binding but shall be defined in the agreement made betw een Nokia Netw orks and the customer. How ever, Nokia Netw orks has made all r easonable efforts to ensure that the instructions contained in the document are adequate and free of material errors and omissions. Nokia Netw orks w ill, if necessary, explain issues w hich may not be covered by the document.Nokia Netw orks' liability for any errors in the document is limited to the documentary correction of errors. Nokia Netw orks WILL NOT BE RESPONSIBLE IN A NY E V ENT FOR ERRORS IN THIS DOCUMENT OR FOR A NY DA MA GES, INCIDENTAL OR CONSEQUENTIAL (INCLUDING MONETA RY LOSSES), that might ar ise from the use of this document or the infor mation in it.This document and the product it describes ar e considered protected by copyright according to the applicable laws.NOKIA logo is a registered trademark of Nokia Corporation.Other product names mentioned in this document may be trademarks of their respective companies, and they are mentioned for identification purposes only.Copyright © Nokia Oyj 2013. All rights reserved.BSSP A R- Capacity & Spectral E fficiency FeaturesContents1 Module Objectives (4)2 Introduction (5)3 Chaining Of MetroSite BTS Cabinets (6)4 Load Control Between Layers (7)5 Direct A ccess to Desired Layer / Band (DA DL/B) (11)6 Adaptive Multi Rate (A MR) Coding (15)7 Frequency Hopping (FH) (16)8 Synchronised BSS (17)9 Automatic Frequency Planning (18)10 Intelligent Shutdown (19)11 Key Learning Points (20)12 Review Questions (22)BSSP A R CTXX 10 S10.5 12-20021 Module ObjectivesAt the end of the module, the participant will be able to:∙State how the capacity of the BSS can be expanded∙Explain how AMH can be used to improve capacity and spectral efficiency,and list the associated parameters∙Describe the parameters used with DADL/BBSSP A R- Capacity & Spectral E fficiency Features2 IntroductionThe capacity of each sector (BTS) of a Base Station site may be indicated byvarious measures: Erlangs, TCH, RTSL, TRX, subscribers, transactions, andBHCA. Each of these refers to some aspect of a traffic model.Capacity expansion at a BTS site is obtained by adding TRXs, cabinets andBCFs, and by implementing various software features, some of which haveparameters to be set.A BTS sector may also be expanded into a RNW object called a Segment(SEG), to add capacity for another frequency band and another technology suchas GSM-EDGE.BSSP A R CTXX 10 S10.5 12-20023 Chaining Of MetroSite BTS CabinetsThe Nokia MetroSite GSM and EDGE base stations can be chained in order tobuild larger configurations for microcellular environments while retaining easeof installation and O&M functions.The chaining is done by synchronising the frame clock between base stations,and extending the internal D-bus. One transmission unit is saved for eachextension cabinet. The O&M functionality is centralised within the mastercabinet. Only one extension cable between cabinets is needed. The maximumnumber of combined MetroSite base stations is three, and the total length of buscable is limited to five metres.If a slave base station loses the chaining interface, the "TRX Faulty" alarm isactivated for each of the 1-4 TRXs in the cabinet. The chaining is arranged, inthe case of three cabinet configurations, in such a way that the centremostcabinet can be powered-down without any problemThe parameters required to be set for this capacity configuration are BSSIntegration parameters.Appropriate parameter settings at various Managed Object levels are madeduring the BTS Integration process.BSSP A R- Capacity & Spectral E fficiency Features4 Load Control Between LayersAdvanced Multilayer Handling (AMH) can be used to control the load betweenlayers, as shown in the figure below. Only those handovers that improve theperformance quality of the network at high loads are permitted.• A voiding unnecessary handovers im proves qualityFigure 1. Advanced Multilayer Handling (AMH)•BSC controlled TR H O dynam ically adapts PBG T H O m argins to direct M Ss at the cell edgeto less loaded adjacent cells w hen the load in the serving cell exceeds a defined lim it• N etw ork-w ide load can be sm oothed out by reducing pow er budget m argins betw een heavilyloaded and less loaded cells => m ore trunking efficiency => m ore capacity• Both the load levels in the source A m hU pperLoadThreshold and target A m hM axLoadO fTgtC ell cellsare taken into account in (i) initiating a BSC cont. TR H O and (ii) target cell evaluation process• Ping-pong handovers are avoided due to AM H penalty tim er TrhoG uardTim e => quality• BSC controlled TR H O are only m ade for single slot connections(U pperLim itC ellLoadH SC SD > A m hU pperLoadThreshold to avoid unnecessary dow ngrades)Figure 2. BSC initiated TRHO for AMHBSSP A R CTXX 10 S10.5 12-2002• B S C controlled TR H O w orks by m odifying equations (1) and (2)• Load param eters (A m U pperLoadThreshold & A m hM axLoadO fTgtC ell ) set at B S C level • A m hTrhoP bgtM argin applies to all neighbour cells A m hTrhoPbgtM argin -24dBm..+24dBm / N A m hU pperLoadThreshold 0?00%A m hM axLoadO fTgtC ell 0?00%TrhoG uardTim e 0?20 sec TrhoTargetLevel -109?47dBm Param eters V alueFigure 3. BSC initiated TRHO Parameters The parameters used for controlling TRHO: ∙ AmhTrhoPbgtMargin (ATPM)(HOC) defines AMH power budget margin when cell load exceeds AmhUpperLoadThreshold (AUT)(BSC) ∙ AmhUpperLoadThreshold (AUT)(BSC) defines upper threshold for base station load and is used to trigger BSC-controlled traffic reason handovers ∙ AmhMaxLoadOfTgtCell (AML)(BSC) defines the maximum traffic load in adjacent cell allowed for a target cell of traffic reason handover (TRHO) ∙ TrhoGuardTime (TGT)(BSC) defines guard time after a BSC-controlled or an MSC-controlled TRHO, during which a handover back to the original cell is not allowed ∙ TrhoTargetLevel (TRHO)(ADJC) defines the minimum signal level when a traffic reason handover is allowed to an adjacent cellBSSP A R- Capacity & Spectral E fficiency FeaturesP aram eters V alu eA m h T rafficC on trolIU O Y/NA m h T rafficC on trolM C N Y/NA m h L ow erL oad T h resh old0?00%Figure 4. IUO & Multilayer Load Control for AMH∙AmhTrafficControlIUO (ATCI)(HOC) indicates whether the Advanced Multilayer Handling is used with Intelligent Underlay-Overlay∙AmhTrafficControlMCN (ATCM)(HOC) indicates whether the Advanced Multilayer Handling is used with micro cells or dual band∙AmhLow erLoadThreshold (ALT)(BSC)defines lower threshold for the load of the base station. It is used to trigger advanced multilayer handling functionality with IUO and/or Dual Band/ microcell featuresAMH is an OPTIONAL feature.BSSP A R CTXX 10 S10.5 12-2002Figure 5. AMH Handover algorithmBSSPAR- Capacity & Spectral Efficiency Features5Direct Access to Desired Layer / Band (DADL/B)This feature is OPTIONAL and was first released in BSS S8. The feature makes it possible to reduce the number of unnecessary TCH reservations. If there is a real TCH congestion in the accessed cell, then a Directed Retry (DR) due to congestion, will be made with or without queuing.Traffic Channel Allocation during call set up (SDCCH handover) E.g. Preference = 1800 Layer900 Macro 900 Macro DB MS camped on 900 microcell 3rd priority DB MS camped on 900 macrocell2nd priority 900 Micro 900 Micro2nd priority 900 Micro 900 Micro Highest PriorityHighest Priority 1800 1800 1800 1800– Can extend call setup times / SDCCH MHTFigure 6. DADL/B Overview• DADL/B is an intra-BSC feature• BTSLoadThreshold defines the load threshold for trigger DADL/B in accessed cell • MS frequency capabilities used to ensure that MS only go through DADL/B process if target cells within the appropriate bands are defined • Directed Retry HO takes priority over DADL/B if accessed cell is congested • DADL/B utilises the same timers as used in DR for target cell evaluation • HoLevelUmbrella sets receive signal 'entry level' for DADL/B target cells • Target cells ordered based on cell priority Cell Priority = HOPriorityLevel(n) - Loadfactor(n) • If the DADL/B handover is rejected due to lack of TCH in the target cell a TCH allocation is made from the original accessed cell. DADL/B reject does not mean a handover failure / dropped call • If no TCH is available in accessed cell a DR with/without queuing can be startedFigure 7. DADL/B Feature Description6-90387 v 1.0© Nokia Oyj11 (23)BSSPAR CTXX 10 S10.5 12-2002The DADL/B algorithm is given below:DADL/B Process Activation IF BTSLoadThreshold < Load of Accessed Cell < 100% AND dadlbTargetCell = Y (in band specified by MS capabilities) THEN DADL/B Process initiated Target Cell Evaluation & DADL/B Handover IF AV_RXLEV_NCELL(n) > HoLevelUmbrella THEN Ncell included in target cell listOrdering of Target Cells Priority(n) = HoPriorityLevel(n) - HoLoadFactor(n) Order of Preference for taken Cells HoLoadFactor(n) value isTarget into account when BTSLoadThreshold for that ncell is exceeded Interval Between Handovers After an unsuccessful DADL/B HO attempt when MS is handed back to old cell which will attempt to allocate a TCH. If a TCH allocation can not be made a DR with or w/o Queuing will be initiated.Figure 8. DADL/B AlgorithmDR w or w/o Queuing initiated• Case 1 : Access cell load = 100 % A directed retryis triggeredDADL/B HO initiated• Case 2 : 100 % > Access cell load is > BTSLoadThreshold A DADL/B handover triggered isTCH allocated from accessed cell• Case 3:Access cell load < BTSLoadThreshold No DADL/B initiated, TCH allocated from accessed cellFigure 9. Triggering the DADL/B Process6-90387 v 1.0© Nokia Oyj12 (23)BSSPAR- Capacity & Spectral Efficiency FeaturesNeighbour cell reporting DADL/B Handover Success DADL/B Handover Failure TCH allocated from DADL/B target cell TCH allocation from accessed cell Accessed cell in real TCH congestion. DR attempt with or without queuing DADL/B Handover candidate selection fails TCH allocation from accessed cell Accessed cell in real TCH congestion. DR attempt with or without queuingMinTimeLimitDRMaxTimeLimitDR DADL/B trigger Maximum allowed time for DADL/B handover expiresTimeFigure 10. DADL/B Target Cell Selection ProcessThe following parameters are associated with DADL/B: Parameter dadlbTargetCell hoPriorityLevel hoLoadFactor hoLevelUmbrella MinTimeLimitDR MaxTimeLimitDR • • Value Y/N 0…7 1…7 -110…-47dBm 0….14 sec 1….15 secBTSLoadThreshold (BLT)(BTS)(70%) 0….100 %dadlbTargetCell (DADLA)(ADJC)(Y/N) defines whether DADL/B handover is applied to the adjacent cell in case of AMR call establishment BTSLoadThreshold (BLT)(BTS)(70%) defines proportion of reserved or unavailable channels and is used as a load control threshold. If the threshold is exceeded, the BTS is considered to be overloaded, and handovers to that BTS will be avoided. hoPriorityLevel (PRI)(ADJC)(0..7) defines a priority level for an adjacent cell that is used for target cell evaluation during handover control process hoLoadFactor (OF)(ADJC)(1..7) defines how much the priority of the target BTS will be decreased if the BTS is overloaded. The parameter is used only for the BTSs under one BSC because the BSC cannot get information about the loading of other BTSs.• •6-90387 v 1.0© Nokia Oyj13 (23)BSSPAR CTXX 10 S10.5 12-2002•hoLevelUmbrella (AUCL)(ADJC)(-110 .. -47 dBm) defines the minimum signal level of an adjacent cell, when a handover is allowed to an adjacent umbrella cell MinTimeLimitDR (MIDR)(BTS)(0..14sec) defines the period starting from an assignment request during which the target cell evaluation for the directed retry handover is not allowed MaxTimeLimitDR (MADR)(BTS)(1..15sec) defines a maximum time period starting from assignment request during which the target cell evaluation for the directed retry handover is allowed••6-90387 v 1.0© Nokia Oyj14 (23)BSSPAR- Capacity & Spectral Efficiency Features6Adaptive Multi Rate (AMR) CodingThe use of Adaptive Multi Rate (AMR) Coding can significantly improve the spectral efficiency of a network, especially when Half Rate channel coding is used. For more details about AMR, refer to the BSSPAR Module: Voice and Channel Coding (FR, HR, EFR, AMR).6-90387 v 1.0© Nokia Oyj15 (23)BSSPAR CTXX 10 S10.5 12-20027Frequency Hopping (FH)The use of Frequency Hopping (FH) can significantly improve the spectral efficiency of a network. For more details about FH, refer to the BSSPAR Module: Radio Resource Management.6-90387 v 1.0© Nokia Oyj16 (23)BSSPAR- Capacity & Spectral Efficiency Features8Synchronised BSSThe use of Synchronised BSS can significantly improve the spectral efficiency of a network. Sync BSS is in a future software release. For more details about Sync BSS, refer to BSSPAR Module: Radio Network Performance Features.6-90387 v 1.0© Nokia Oyj17 (23)BSSPAR CTXX 10 S10.5 12-20029Automatic Frequency PlanningThe use of DFCA can significantly improve the spectral efficiency of a network. DFCA is in a future software release.6-90387 v 1.0© Nokia Oyj18 (23)BSSPAR- Capacity & Spectral Efficiency Features10Intelligent ShutdownTo provide protection against mains break, a BTS site is usually equipped with battery back-up. The aim is to maintain service as long as possible. To achieve this, it is reasonable to reduce capacity on certain sites in order to save battery capacity, and maintain only the essential BTS functions. This feature provides means to control the behaviour of the site equipped with battery back-up in case of mains break. As the power consumption depends on the load of the equipment supplied by the back-up batteries, shutting down a part of the site prolongs the remaining service time. On a BTS site basis, the operator can define the service level of the site to be maintained while battery back-up is in use. Also the operator can define two timers to allow executing the shutdown procedure in several phases. Three service level options are available: 1. Full service. Service is maintained on full level as long as batteries last. 2. BCCH back-up. Only BCCH TRX(s) are maintained to offer minimum service, other TRXs are switched off. Non BCCH-TRXs are switched off after the first timer expires. Timer two has no meaning in this case. 3. Transmission back-up. Only the BTS transmission equipment power is supplied. TRXs are switched off and BCCH transmission is stopped. This secures the functionality of a transmission chain. Non BCCH-TRXs are switched off after the first timer expires. Then the timer two starts and after it expires, BCCH TRX is switched off and only transmission equipment is left powered to maintain transmission links for chain configuration. When a mains break takes place, the BTS sends an alarm to the BSC, which performs forced handovers for all the calls on the TRXs to be shut down. The calls are handed over to a TRX that will remain powered, or to adjacent cells. If all the necessary handovers cannot be made during the defined maximum time the calls are released. Finally the BSC orders the BTS site to power down the TRXs. When the mains power is restored, the BSC takes the BTS automatically back in full service. Third party BBU equipment can also be used together with intelligent shutdown. It is possible to designate an external alarm line which is used to indicate a mains break to the BTS. This alarm is then sent to the BSC as a mains break down alarm which then triggers the shutdown procedure.6-90387 v 1.0© Nokia Oyj19 (23)BSSPAR CTXX 10 S10.5 12-200211Key Learning PointsCapacity expansion at a BTS site is obtained by adding TRXs, cabinets and BCFs, and by implementing various software features, some of which have parameters to be set. The Nokia MetroSite GSM and EDGE base stations can be chained in order to build larger configurations for microcellular environments while retaining ease of installation and O&M functions. The chaining is done by synchronising the frame clock between base stations, and extending the internal D-bus. Advanced Multilayer Handling (AMH) is an OPTIONAL feature which can be used to control the traffic load between layers of a GSM network. The parameters used for AMH load control between layers are: •• • •AmhTrhoPbgtMargin (ATPM)(HOC) defines AMH power budget margin when cell load exceeds AmhUpperLoadThreshold (AUT)(BSC) AmhUpperLoadThreshold (AUT)(BSC) defines upper threshold for base station load and is used to trigger BSC-controlled traffic reason handovers AmhMaxLoadOfTgtCell (AML)(BSC) defines the maximum traffic load in adjacent cell allowed for a target cell of traffic reason handover (TRHO) TrhoGuardTime (TGT)(BSC) defines guard time after a BSC- or an MSC controlled TRHO, during which a handover back to original cell is not allowed TrhoTargetLevel (TRHO)(ADJC) defines the minimum signal level when a traffic reason handover is allowed to an adjacent cell•The DADL/B is an Intra-BSC optional feature that makes it possible to reduce the number of unnecessary TCH reservations. If there is a real TCH congestion, in the accessed cell, then a Directed Retry (DR) due to congestion, will be made with or without queuing. Directed Retry HO takes priority over DADL/B if accessed cell is congested. DADL/B utilizes the same timers as used in DR for target cell evaluation. If the DADL/B handover is rejected due to lack of TCH in the target cell, a TCH allocation is made from the original accessed cell. DADL/B reject does not mean a handover failure / dropped call. The following parameters are associated with DADL/B: • • dadlbTargetCell (DADLA)(ADJC)(Y/N) defines whether DADL/B handover is applied to the adjacent cell in case of AMR call establishment BTSLoadThreshold (BLT)(BTS)(70%) defines proportion of reserved or unavailable channels and is used as a load control threshold. If the threshold is exceeded, the BTS is considered to be overloaded, and handovers to that BTS will be avoided6-90387 v 1.0© Nokia Oyj20 (23)BSSP A R- Capacity & Spectral E fficiency Features6-90387 v 1.0 © Nokia Oyj 21 (23)∙hoPriorityLevel (PRI)(ADJC)(0..7) defines a priority level for an adjacent cell which is used for target cell evaluation during handover control process ∙hoLoadFactor (OF)(ADJC)(1..7)defines how much the priority of the target BTS will be decreased if the BTS is overloaded. The parameter is used only for the BTSs under one BSC because the BSC cannot get information about the loading of other BTSs∙hoLevelUmbrella (AUCL)(ADJC)(-110 .. -47 dBm) defines the minimum signal level of an adjacent cell, when a handover is allowed to an adjacent umbrella cell∙MinTimeLimitDR (MIDR)(BTS)(0..14sec) defines the period starting from an assignment request during which the target cell evaluation for the directed retry handover is not allowed∙MaxTimeLimitDR (MADR)(BTS)(1..15sec) defines a maximum time period starting from assignment request during which the target cell evaluation for the directed retry handover is allowedThe Intelligent Shutdown feature provides a means to shut down a part of a BTS site equipped with battery back-up, in the case of mains break. This prolongs the remaining service time. An operator can define three service level options of a site to be maintained while battery back-up is in use:1. Full service: Service is maintained on full level as long as batteries last.2. BCCH back-up: Only BCCH TRX(s) are maintained to offer minimum service, while Non BCCH-TRXs are switched off after the first timer expires.3. Transmission back-up: Only the BTS transmission equipment power is supplied. TRXs are switched off and BCCH transmission is stopped. This secures the functionality of a transmission chain.BSSP A R CTXX 10 S10.5 12-20026-90387 v 1.0 © Nokia Oyj 22 (23)12 Review QuestionsQ1. How can the capacity of a BTS site be expanded?a)By adding TRXs, cabinets and BCFs.b)By implementing various software features, some of which have parametersto be set.c)Nokia MetroSite GSM and EDGE base stations can be chained in order tobuild larger configurations for microcellular environmentsd)All of the above.The answers for Q2 to Q6 are given below:a)AmhTrhoPbgtMargin (ATPM)(HOC)b)AmhUpperLoadThreshold (AUT)(BSC)c)AmhMaxLoadOfTgtCell (AML)(BSC)d)TrhoGuardTime (TGT)(BSC)e)TrhoTargetLevel (TRHO)(ADJC)Q2. Which parameter defines maximum allowed traffic load in an adjacent cellfor use as a target cell of traffic reason handover (TRHO)?Q3. Which parameter defines the minimum signal level when a traffic reasonhandover is allowed to an adjacent cell?Q4. Which parameter uses AmhUpperLoadThreshold (AUT)(BSC)forhandover decision purposes?Q5. Which of the following defines guard time during which a handover back toan original cell is not allowed?Q6. Which of the following sets an upper threshold to trigger BSC-controlledtraffic reason handovers?BSSP A R- Capacity & Spectral E fficiency Features6-90387 v 1.0 © Nokia Oyj 23 (23) The following parameters are associated with Q7 to Q10:a)dadlbTargetCell (DADLA)(ADJC)(Y/N).b)BTSLoadThreshold (BLT)(BTS)(70%).c)hoPriorityLevel (PRI)(ADJC)(0..7)d)hoLoadFactor (OF)(ADJC)(1..7)e)hoLevelUmbrella (AUCL)(ADJC)(-110 .. -47 dBm).f)MinTimeLimitDR (MIDR)(BTS)(0..14sec).g)MaxTimeLimitDR (MADR)(BTS)(1..15sec).Q7. Which parameter can be set to decrease the priority of the target BTS if it is overloaded?Q8. Which of these defines a priority level for an adjacent cell that is used for target cell evaluation during handover control process?Q9. Which of these parameters is used to define if DADL/B handovers are permissible?Q10. If the parameter ……. is exceeded, the BTS is considered to be overloaded, and handovers to that BTS will be avoided.。