Simulating the Self-Heating Effect for MOSFETs with Various Configurations of Buried Oxide

Russian Microelectronics - SOI MOSFETs have the worst properties of heat removal from an active region, which negatively affects the reliability and efficiency of integrated circuits. Using TCAD...     

Mechanical Losses Due to Frictional Heat in Bi-2223 Tapes With Structural Materials of Various Thermal Expansion Properties

We have experimentally studied relation between mechanical losses and thermal expansion properties in superconducting coils. For the experiments, three kinds of structural materials (GFRP, DGFRP, and ZFRP) were used. A glass fiber reinforced plastic (GFRP) contracts with decreasing temperature; on the contrary, a Dyneema and grass fiber reinforced plastic (DGFRP) and a Zylon fiber reinforced plastic (ZFRP) expand with the decrease of temperature. We used sample holders made of those plastics and measured AC current losses of a Bi-2223 tape in liquid nitrogen. Even if the magnetic field applied to the tape and an AC transport current of the tape were same, the loss depended on the sample holder materials. When the sample holder is the GFRP, the loss was largest in the three kinds of plastics, and in case of the ZFRP, the loss was smallest. The ZFRP has the largest expansion property of the three materials, that is, the loss decreased with expansion of the sample holder's materials.     

Temperature Dependence of Total AC Loss in High-Temperature Superconducting Tapes

A versatile experimental facility was designed and set up to measure transport ac losses, magnetization ac losses, and total ac losses in high-temperature superconductors at variable temperatures. Several sets of measurements were carried out in the temperature range of 35 K to 100 K. Sample temperature during the measurements could be controlled within ${pm}$0.5 K of set temperature. Temperature dependence of transport losses reflects variation of critical current density of the tapes with temperature. Temperature dependence of magnetization losses exhibits an interesting behavior with a peak, whose position shifts to lower temperatures as the magnetic field is increased. Experimental data of ac losses at various temperatures are compared with those calculated using numerical methods. Generally, the simulated results reproduce well the experimental data.      

Numerical Study on AC Loss Characteristics of HTS Coils With Various Cross Sections and Methods of AC Loss Reduction

AC loss characteristics of high temperature superconducting coils wound by Bi2223/Ag tape with various cross sections are numerically investigated. The numerical results show that the smaller coil aspect ratio, the smaller AC losses in the HTS coil. It was considered from the numerical results that the coil aspect ratio giving the minimum coil volume is the better shape judging from the many aspects such as the required length of tape, the stored energy, the central magnetic field and the critical current together with the AC loss. It was also shown by the numerical study that the optimal coil design giving the reduced AC loss can be done by employing the stepped cross section coil and the turn number graded coil.     

Label Stacking in Photonic Packet-Switched Networks With Spectral Amplitude Code Labels

Label stacking is used for hierarchical addressing to reduce the size of lookup tables and to increase the speed of the routing process. We propose an optical label stacking using spectral-amplitude codes (SAC) as labels to accomplish ultrafast packet forwarding. We discuss the advantages of this label architecture compared to other proposals in the literature and present experimental results. We experimentally examine two types of optical packets, one with separable SAC labels and the other one with SAC-encoded payloads. In the first case, the SAC label is a collection of spectral tones modulated at the packet rate (low rate), and the payload is on a separate wavelength modulated at the data rate (fast rate). In the second case, the payload data modulates the collection of wavelengths that constitute the code. We implement a network with two forwarding nodes, and we transmit the packets with two labels in the label stack over 80 km of fiber and measure the bit error rate (BER) after two hops. We achieve error-free transmission (BER<10 ^-9) for the packets with SAC labels and SAC-encoded payload at payload bit rates of 10 and 2.5 Gb/s, respectively. This is the first experimental demonstration of optical label stacking to our knowledge     

Processing and Characterization of Ni Base Coated Superconductor Substrate Tapes With Layered Architecture

Ni/Ni-5at.%Mo and Ni/Ni-5at.%Mo/Ni multilayer tapes were prepared from elemental powders by a powder metallurgy route for coated superconductor substrate applications. The development of cube texture $({001}langle 100rangle)$ following heavy cold rolling ($sim$ 95%) and annealing has been studied in the Ni side(s) of these multilayer tapes and compared to a nonalloyed Ni tape. Although the deformation textures in the Ni side(s) of these multilayer tapes appear quite similar to that of the nonalloyed Ni tape cold rolled to a similar deformation level, the volume fraction of the cube grains in the Ni side(s) of the multilayer tapes following annealing shows marked improvement as compared to the nonalloyed Ni tape after different annealing treatments. X-ray area mapping from typical cross-sectional areas of the multilayer compacts in the sintered condition reveals significant diffusion of the alloying element Mo from the alloy side(s) to the Ni side. These facts amply corroborate the earlier observation on the beneficial role of Mo on the development of cube texture in Ni. The yield strength of the annealed multilayer tapes shows marked improvement over nonalloyed Ni tapes.      

Magnetization Loss in a Striated YBCO Coated Conductor Considering the Intrinsic Critical Current Distribution

In this work we present numerical analysis results of the magnetization loss in a perpendicular AC magnetic field. The numerical analysis is based on the relation of the linkage magnetic flux to current distribution, and takes into account the$J_ c-B$characteristic, and$n$value-$B$characteristic. We discuss the relation between the magnetization losses with striated superconducting tape and the semicylindrical intrinsic critical current density distribution across the width of the superconducting tape. The result shows that the magnetization loss of monocore superconducting tape in a low magnetic field is affected by the intrinsic semicylindrical critical current density distribution. With a striated structure, the influence of the intrinsic critical current density distribution is reduced.     

Numerical Analysis of AC Loss Characteristics of Cable Conductor Assembled by HTS Tapes in Polygonal Arrangement

Numerical studies on AC loss characteristic of a assembled conductors of multiple HTS tapes with high aspect ratio simulating YBCO tape in polygonal arrangement were presented in this paper. We developed a numerical model to analyze the AC loss in the HTS tape in the polygonally assembled conductor based on our previously developed model. The relations between the geometrical configuration and the AC loss properties of the conductor were made clear by the numerical simulation. The numerical results give the important information for the design of the cable conductor assembled by the HTS tapes with high aspect ratio such as YBCO tapes.     

Modeling and Simulation of Various Hybrid-Electric Configurations of the High-Mobility Multipurpose Wheeled Vehicle (HMMWV)

Although hybrid-electric vehicles have been studied mainly with the aim of increasing fuel economy, little has been done in order to improve both fuel economy and performance. However, vehicular-dynamic-performance characteristics such as acceleration and climbing ability are of prime importance in military vehicles such as the high-mobility multipurpose wheeled vehicle (HMMWV). This paper concentrates on the models that describe hybridized HMMWV vehicles and the simulation results of those models. Parallel and series configurations have been modeled using the advanced-vehicle-simulator software developed by the National Renewable Energy Laboratory. Both a retrofit approach and a constant-power approach have been tested, and the results are compared to the conventional model results. In addition, the effects of using smaller engines than the existing ones in hybrid HMMWV drive trains have been studied, and the results are compared to the data collected from an actual implementation of such a vehicle. Moreover, the integrated-starter/alternator (ISA) configuration has been considered, and the results were encouraging     

Avoiding Data Loss With Hard and Soft DVB-H Handovers

Digital Video Broadcasting-Handheld (DVB-H) allows the efficient transmission of rich multimedia services to small, handheld terminals. Such portable terminals pose specific requirements on the transmission technology, such as the need for seamless cell handover. This paper first presents mechanisms which allow loss-free hard handovers with DVB-H using only a single receiver front-end. It is then shown how even 3G-like soft handovers are possible with DVB-H, still using only a single receiver front-end. The proposed schemes are evaluated using simulations and field measurements.      

Accurate Hybrid-Mode Finline Configurations Including Analysis of Various Multilayered Dielectrics, Finite Metallization Thickness, and Substrate Holding Grooves

An accurate analysis of various finline configurations is introduced. The method of field expansion into suitable eigenmodes used considers the effects of finite metallization thickness as well as waveguide wall grooves to fix the substrate. Especially for millimeter-wave range applications, the propagation constant of the fundamental mode is found to be lower than by neglecting the finite thickness of metallization. For increasing groove depth in cases of asymmetrical and "isolated finline," higher order mode excitation reduces the monomode bandwidth significantly. In contrast to hitherto known calculations, this parameter only causes negligible influence on a fundamental mode if the groove depth is lower than hall of the waveguide height.     

Evanescent-Coupled Ge p-i-n Photodetectors on Si-Waveguide With SEG-Ge and Comparative Study of Lateral and Vertical p-i-n Configurations

Si-waveguide-integrated lateral Ge p-i-n photodetectors using novel Si/SiGe buffer and two-step Ge-process are demonstrated for the first time. Comparative analysis between lateral Ge p-i-n and vertical p-Si/i-Ge/n-Ge p-i-n is made. Light is evanescently coupled from Si waveguide to the overlaying Ge- detector, achieving high responsivity of 1.16 A/W at 1550 nm with f_{3 dB} bandwidth of 3.4 GHz for lateral Ge p-i-n detector at 5 V reverse bias. In contrast, vertical p-Si/i-Ge/n-Ge p-i-n has lower responsivity of 0.29 A/W but higher bandwidth of 5.5 GHz at -5 V bias. The higher responsivity of lateral p-i-n detectors is attributed to smaller optical mode overlap with highly doped Ge region as in vertical p-i-n configuration.     

Electrical Characteristics of Triple‐Gate RSO Power MOSFET (TGRMOS) with Various Gate Configurations and Bias Conditions

In this paper, we propose a triple‐gate trench power MOSFET (TGRMOS) that is made through a modified RESURF stepped oxide (RSO) process, that is, the nitride_RSO process. The electrical characteristics of TGRMOSs, such as the blocking voltage (BV_DS) and on‐state current (I_D,MAX), are strongly dependent on the gate configuration and its bias condition. In the nitride_RSO process, the thick single insulation layer (SiO₂) of a conventional RSO power MOSFET is changed to a multilayered insulator (SiO₂/SiN_x/TEOS). The inserted SiN_x layer can create the selective etching of the TEOS layer between the gate oxide and poly‐Si layers. After additional oxidation and the poly‐Si filling processes, the gates are automatically separated into three parts. Moreover, to confirm the variation in the electrical properties of TGRMOSs, such as BV_DS and I_D,MAX, simulation studies are performed on the function of the gate configurations and their bias conditions. BV_DS and I_D,MAX are controlled from 87 V to 152 V and from 0.14 mA to 0.24 mA at a 15‐V gate voltage. This I_D,MAX variation indicates the specific on‐resistance modulation.     

Optical Analysis of Color Distribution in White LEDs With Various Packaging Methods

Uniform color distribution is essential for the packaging of light emitting diodes (LEDs). The Monte Carlo ray tracing method is applied to analyze the color distribution of white LEDs. Five packaging methods are investigated and the location of phosphor layer is varied. Results reveal that the packaging method is the primary factor affecting the color distribution and a nonreflector packaging method presents better color uniformity. The location of phosphor has a small impact on the color uniformity but remote location, if too far, can reduce the uniformity significantly. The reduction of color uniformity may exceed 88%.      

Loss Probabilities of Hand-in Traffic under Various Protocols,I: Models and Algebraic Results

Mobile telephone traffic business demands that a given base station be able to handle both newly originating traffic and hand-in traffic from neighbouring base stations, with priority to be given to the latter, existing traffic. Starting from a baseline standard model in which all channels are available to all traffic, this note examines three other models, each with its own access control protocol that allocates a reserve capacity R amongst the N _tot channels to give priority to the hand-in traffic. These different protocols give different loss probabilities for the two types of traffic. All the results are proved on the basis of assuming a Poisson arrival process and independent exponential service times. This paper concentrates on presenting explicit expressions for many of the loss probabilities, some of them given by the Erlang B loss formula or variants, as well as simple approximations and bounds. A companion paper presents results comparing the various models.     

无线Mesh网络的组网及其相关标准

从无线Mesh网络（WMN）的特点出发,根据网络中节点的不同功能,给出了三种WMN的组网方式,并逐一进行了分析。针对不同IEEE标准化组织对WMN所做的工作进行了介绍。最后给出了相关结论。     

系统设计中测试构型研究及应用

对系统可测试性设计而言,测试接口具有系统意义.如何揭示出测试接口位置逻辑上的本质特征是一个重要问题.以规范的、系统结构化分析方法——数据流图为工具,以产品可测试性为视角,一般性地将产品测试接口分布划分为3种测试构型,并分别分析了每种构型在系统测试层面的意义.     

Defect Bragg Fiber With Low Loss for Broadband and Zero Dispersion Slow Light

Narrow bandwidth and large group velocity (v_g) dispersion are two fatal limitations of slow light in Bragg fibers. In this paper, by introducing a well-designed defect layer into the cladding of the Bragg fiber, the modal characteristics are modified by the coupling between the core mode and the defect mode. The defect location mainly determines the coupling strength and, thus, exerts a strong influence on v_g and dispersion. The defect thickness mainly determines the resonant wavelength of the defect waveguide and, thus, the wavelength where the modal coupling takes place. Consequently, the two limitations of the slow-light propagation in the Bragg fiber are overcome through proper optimization of the defect parameters. Around 1550 nm, a slow-light bandwidth up to 90 nm is achieved at an average v_g of c/5 (c is the light velocity in a vacuum) under N = 2, whereas an average v_g of c/10 is achieved with a bandwidth of 20 nm under N = 5. On the other hand, the slow-light propagation of v_g = 0.074c with both zero dispersion and zero dispersion slope is achieved, which is able to support applications requiring a subterahertz bandwidth of optical pulse. All of the fiber designs ensure sufficient low losses and good optical field distribution. The results are helpful in developing various Bragg-fiber-based slow-light devices.     

真空转移系统中各种气体对光电阴极的影响

论述了真空转移系统中各种气体对光电阴极灵敏度影响以及防止的方法。实验得出一氧化碳和水蒸地光电阴极灵敏度的损害最大。光电阴极由碱环境转移到无碱环境中,其光电灵敏度不受影响,而是残余气体分子撞击光电阴极表面,引起铯剥脱使得灵敏度下降。     

Simultaneous Cancellation of Fiber Loss, Dispersion, and Kerr Effect in Ultralong-Haul Optical Fiber Transmission by Midway Optical Phase Conjugation Incorporated With Distributed Raman Amplification

An alternative application of distributed Raman amplification (DRA) for ultralong-haul optical fiber transmission is proposed. In our study, the DRA is employed in a transmission system using midway optical phase conjugation (OPC) for amplifying an optical signal and, at the same time, for constructing signal power evolution, which is symmetrical with respect to the midpoint of the system where the OPC is performed. Then, the nonlinear signal waveform distortions that are caused by the Kerr effect, as well as fiber dispersion, are almost completely compensated by the OPC, whereas the fiber loss is compensated by the DRA. Three possible symmetrical signal power maps - a power map that has a reverse sign of the power map that is caused by lump amplification, a flat signal power map, and an arbitrary symmetrical signal power map - are numerically designed by using appropriate Raman pump powers. We show that the flat power map exhibits smaller difference from the target and a higher optical signal-to-noise ratio and requires lower pump power than the other two power maps. Numerical simulation results demonstrate that, by employing the flat power maps with a span of 40 km, a single-wavelength signal whose data rate is 160 Gb/s can be successfully transmitted over 5000 km, and the Kerr effect is sufficiently suppressed near limitation due to the nonlinear accumulation of noise. Finally, we study the feasibility of expanding our method to wavelength-division-multiplexed signal transmission by designing a DRA gain with multiple-wavelength pumping to simultaneously obtain a flat power map and a wide-and-flat gain bandwidth. By using four-wavelength Raman pumps while carefully choosing pump wavelengths and their powers, we achieve the DRA gain that simultaneously gives a fluctuation of the signal power of only 3.5%, a gain ripple of only 5.3%, and, at the same time, a gain bandwidth of as wide as 46 nm.