智能变电站安全稳定控制装置的内部通信设计

智能电网的发展和智能变电站的应用,对电网安全稳定控制装置的内部通信结构提出了更高要求.文章从稳控专业、智能变电站、广域稳控系统等需求出发,总结稳控装置需要在内部通信结构做出的改进;提出一种适用于稳控装置内部和装置间通信的标准通信结构.该结构的基础是一种集成链路层、传输层、网络层等多层协议,基于FPGA的IP核设;计,可灵活重用的通信模块.文章对应用此技术的稳控装置内部通信的方案、通信模块的技术和实现、实际的通信性能测试等方面进行阐述.工程应用的结果表明,该设计能够满足智能变电站对稳控装置的技术要求.     

Reliability and degradation of small molecule-based organiclight-emitting devices (OLEDs)

Studies of degradation mechanisms in small molecule-based organic light-emitting devices (OLEDs) are reviewed. A special emphasis is given to OLEDs based on tris (8-hydroxyquinoline) aluminum (AlQ₃), an emitter and electron transport material used in the majority of OLEDs emitting from the green to the red part of the spectrum. Different strategies used for increasing device stability are addressed and the models proposed to explain experimental observations related to OLED operational stability are discussed. Although none of the presently proposed models can explain all experimental observations, the largest body of experimental evidence appears to be consistent with a model based on the instability of cationic AlQ₃ species, produced by the injection of holes into the AlQ₃ electron transport and emitter layer. Other models may be of importance in explaining degradation behavior on different time scales. Models based on redistribution of space charge appear to be responsible for reversible short-term degradation, while a model based on indium migration may be important for degradation on very long time scales     

Modeling heating effects in nanoscale devices: the present and the future

In this review paper we give an overview on the present state of the art in modeling heat transport in nanoscale devices and what issues we need to address for better and more successful modeling of future devices. We begin with a brief overview of the heat transport in materials and explain why the simple Fourier law fails in nanoscale devices. Then we elaborate on attempts to model heat transport in nanostructures from both perspectives: nanomaterials (the work of Narumanchi and co-workers) and nanodevices (the work of Majumdar, Pop, Goodson and recently Vasileska, Raleva and Goodnick). We use our own simulation results which we have used to examine heat transport in nanoscaling devices to point out some important issues such as the fact that thermal degradation does not increase as we decrease feature size due to the more pronounced non-stationary transport and ballistic transport effects in nanoscale devices. We also point out that instead of using SOI, if one uses Silicon on Diamond technology there is much less heat degradation and better spread of the heat in the Diamond material. We also point out that tools for thermal modeling of nanoscale devices need to be improved from the present state of the art as 3D tools are needed, for example, to simulate heat transport and electrical transport in a FinFET device. Better models than the energy balance equations for the acoustic and optical phonons what we presently use in our simulators are also welcomed. The ultimate goal is to design the tool that can be efficient enough but at the same time can simulate most accurately both electrons and phonons within the particle pictures by solving their corresponding Boltzmann transport equations self-consistently. Investigations in integration of Peltier coolers with CMOS technology are also welcomed and much needed to reduce the problem of heat dissipation in nanoscale devices and interconnects.     

Can silicon FinFETs satisfy ITRS projections for high performance 10 nm devices?

We utilize a fully self-consistent quantum mechanical simulator based on CBR method to optimize 10 nm FinFET devices to meet ITRS projections for High Performance (HP) logic technology devices. Fin width, gate oxide thickness, and doping profiles are chosen to reflect realistic values. We find that the device on-current approaching the value projected by ITRS for HP devices can be obtained using unstrained conventional (Si) channel. Our simulation results also show that quantum nature of transport in ultra small devices significantly enhances the intrinsic switching speed of the device. In addition, small signal analysis has been performed. Sensitivity of device performance to the process variation at room temperature has also been investigated.     

SIP协议与ISUP协议互通研究

会话初始协议(SIP)是IETF定义的基于IP的应用层控制协议，是NGN网络控制的核心协议；ISDN用户部分(ISUP)协议是7号信令系统的一种主要协议。文章介绍并深入分析了SIP和ISUP协议，从互通的层面对二者进行了分析比较，给出了2种协议之间具体的互通结构、映射方法以及呼叫流程。基于网络融合的思想做了有益的探索和实践，为设计MGC／软交换核心设备提供了依据，为实现PSTN网络向软交换网络的平滑过渡提供了解决方案。     

Perspectives on solid-state flying qubits

We review recent efforts toward the numerical modeling of prototypes of one- and two-qubit gates based on coherent electron transport in semiconductor quantum wires. The basics of the proposed devices are presented and a theoretical approach aimed at quantifying the decoherence induced by electron-electron coupling is described.     

First principles modeling of disorder scattering in graphene

It is important to investigate impurity scattering phenomena when modeling graphene nanoscale devices, as impurities are invariably present in any realistic system and can significantly influence graphene carrier transport. We present a short review of quantum transport where density functional theory (DFT) is carried out within the nonequilibrium Green’s function formalism (NEGF), focusing on a recent extension of this framework in the form of nonequilibrium vertex correction (NVC) that captures random graphene impurity scattering in a systematic fashion. Our results show that disorder effects significantly alters the electronic and transport properties of graphene devices. We argue that disorder effects should not be ignored if one were to model graphene nanoscale devices in realistic situations, including arriving at fundamental electronic properties such as Ohm’s law.     

基于以太网的分布式发电厂电气监控系统实现

提出了一种基于以太网的分布式发电厂电气监控系统（ECS）,系统由间隔层、通信层、系统层组成。间隔层完成继电保护、模拟量和开关量的采集以及断路器的控制;通信层完成所有实时数据的分类转发,并实现与集散控制系统（DCS）的接口通信;系统层实现全厂电气系统信息的集中处理,提供各种站级应用功能。结合工程实践经验,阐述了一种典型的ECS组网方案,并指出了实践中的一些特殊问题及解决方案。     

CMT‐CQA: Cross‐layer QoS‐aware adaptive concurrent multipath data transfer in heterogeneous networks

Stream control transport protocol (SCTP)‐based concurrent multipath transfer (CMT) can help multi‐homed devices to increase their throughput by making use of parallel transmissions over multiple paths and bandwidth aggregation. However, if CMT cannot identify wireless error, it cannot really achieve the desired performance. Furthermore, if CMT only utilizes all available paths for data delivery, it will undoubtedly degrade application‐level performance since the asymmetric paths may involve large quality differences. This paper proposes a novel cross‐layer quality‐of‐service (QoS)‐aware adaptive CMT (CMT‐CQA) with the following aims: (i) to provide an adaptive ‘CMT‐to‐partial CMT’ adjustment strategy for efficient bandwidth aggregation by jointly considering transport layer QoS, MAC layer QoS, and path history information; (ii) to address an enhanced congestion window (cwnd) fast recovery mechanism to reduce bursty transmission in multi‐homed wireless network environments where fail‐over occurs frequently; and (iii) to introduce a proper multimedia transmission behavior to improve users' quality of experience (QoE) for multimedia streaming service. Simulation results show that CMT‐CQA outperforms the existing CMT solutions in terms of performance and QoS. © 2014 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Modeling of Shallow Quantum Point Contacts Defined on AlGaAs/GaAs Heterostructures: The Effect of Surface States

We have developed a program for the simulation of devices defined by electrostatic confinement on the two-dimensional electron gas in AlGaAs/GaAs heterostructures. Our code is based on the self-consistent solution of the Poisson-Schrödinger equation in three dimensions, and can take into account the effects of surface states at the semiconductor-air interface and of discrete impurities in the doped layer. We show results from the simulation of quantum point contacts with different lithographic gaps, whose conductance is computed by means of a code based on the recursive Green's functions formalism.     

Quantum correction for DG MOSFETs

The characteristics of modern semiconductor devices are strongly influenced by quantum mechanical effects. Due to this fact, purely classical device simulation is not sufficient to accurately reproduce the device behavior. For instance, the classical semiconductor equations have to be adapted to account for the quantum mechanical decrease of the carrier concentration near the gate oxide. Several available quantum correction models are derived for devices with one single inversion layer and are therefore only of limited use for thin double gate (DG) MOSFETs where the two inversion layers interact. We present a highly accurate quantum correction model which is even valid for extremely scaled DG MOSFET devices. Our quantum correction model is physically based on the bound states that form in the Si film. The eigenenergies and expansion coefficients of the wave functions are tabulated for arbitrary parabolic approximations of the potential in the quantum well. Highly efficient simulation of DG MOSFET devices scaled in the decananometer regime in TCAD applications is made possible by this model.     

Full quantum treatment of surface roughness effects in Silicon nanowire and double gate FETs

We review recent results on the effect of surface roughness on the transport properties of ultra-short devices like Silicon nanowire and double-gate FETs. We use a full quantum treatment within the non equilibrium Green’s function (NEGF) formalism which allows us to take into account quantum confinement, quantum phase interference, out-of-equilibrium, and quasi-ballistic transport and focus on transfer characteristics and low-field mobility.     

Negative differential resistance in graphene-nanoribbon–carbon-nanotube crossbars: a first-principles multiterminal quantum transport study

We simulate quantum transport between a graphene nanoribbon (GNR) and a single-walled carbon nanotube (CNT) where electrons traverse vacuum gap between them. The GNR covers CNT over a nanoscale region while their relative rotation is 90^°, thereby forming a four-terminal crossbar where the bias voltage is applied between CNT and GNR terminals. The CNT and GNR are chosen as either semiconducting (s) or metallic (m) based on whether their two-terminal conductance exhibits a gap as a function of the Fermi energy or not, respectively. We find nonlinear current-voltage (I–V) characteristics in all three investigated devices—mGNR-sCNT, sGNR-sCNT and mGNR-mCNT crossbars—which are asymmetric with respect to changing the bias voltage from positive to negative. Furthermore, the I–V characteristics of mGNR-sCNT crossbar exhibits negative differential resistance (NDR) with low onset voltage V _NDR?0.25 V and peak-to-valley current ratio ?2.0. The overlap region of the crossbars contains only ?460 carbon and hydrogen atoms which paves the way for nanoelectronic devices ultrascaled well below the smallest horizontal length scale envisioned by the international technology roadmap for semiconductors. Our analysis is based on the nonequilibrium Green function formalism combined with density functional theory (NEGF-DFT), where we also provide an overview of recent extensions of NEGF-DFT framework (originally developed for two-terminal devices) to multiterminal devices.     

Monte Carlo simulation of low-field mobility in strained double gate SOI transistors

Electron transport in strained double gate silicon on insulator transistors has been studied by Monte Carlo method. Poisson and Schroedinger equations have been self-consistently solved in these devices for different silicon layer thicknesses both for unstrained and strained silicon channels. The results show that the strain of the silicon layer leads to a larger population of the no-primed subbands, thus decreasing the average conduction effective mass. However, strain also contributes to a larger confinement of the charge close to the two Si/SiO₂ interfaces, thus weakening the volume inversion effect, and limiting the potential increase of the phonon limited mobility.     

Space charge formation at the interface between a charge transportlayer and a polyester film

The organic photoconductor structure used in a copying machine consists of electron-conductive and ion-conductive layers, a charge generation layer, and a charge transport layer. We applied the pulsed electroacoustic method, which has been used to evaluate HV insulation, to measure the space charge behavior of the charge transport layer coated on a polyester film. On the surface of the charge transport layer, various electrodes were evaporated. An internal space charge accumulated at the interface between the charge transport layer and the polyester film under a dc electric field. We show that the charge distribution is formed by the injection of holes from the anode and by the surface charge, and that the hole injection is influenced by the anode material     

Materials and Process Development for ZnMgO/ZnO Light-Emitting Diodes

We report on the fabrication of UV LEDs based on a p-n junction p-ZnMgO/n-ZnO/n-ZnMgO double heterostructure. Pulsed-laser deposition was used to grow the complete heterostructure on c -plane sapphire templates. The LEDs were patterned by simple wet etching. Band-edge electroluminescence emission most likely associated with ZnO excitonic transitions was observed at room temperature. However, the devices show sensitivity to the presence of hydrogen in the measurement ambient due to formation of a surface conduction layer. The results show the potential of ZnO-based materials for UV emitters of potentially lower cost and with comparable or higher emission intensity than AlGaN/GaN devices provided adequate surface passivation techniques are developed.     

Fourier approach to semiconductor device modelling

A novel procedure for the numerical modelling of current transport in semiconductor devices is presented. The method is based on high-order trigonometric expansions (Fourier series) of the solution. The expansion coefficients are calculated in a Galerkin-type algorithm. The method offers infinite-order accuracy regardless of the number of spatial dimensions of the model. Well-conditioning and diagonal dominance of the discrete equations render the numerical procedure stable and effective. Significant advantages are expected, particularly for the solution of strongly non-linear multidimensional device models. Properties of the algorithm are demonstrated on standard semiconductor devices.     

基于软交换的智能电网可信网络连接模型研究

传统可信网络连接模型难以适应智能电网环境下接入网络复杂异构的实际情况,同时,由于下层传输协议的安全措施缺失,传统TNC模型存在安全隐患.针对上述问题,文章首先对传统TNC的模型和工作流程进行分析,设计了基于软交换的TNC改进模型.该模型将网络访问请求时的控制流和媒体流分离,对各类接入设备进行透明控制和统一管理,同时,对下层通信协议进行安全加密.性能分析结果显示,该模型中数据包被破解的概率小于传统TNC模型,且数据传输效率与传统模型相同.可见,该模型在不降低数据传输效率的前提下,提高了网络的安全性能.