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141.
In this article, the characteristics of InP/InGaAs heterostructure-emitter bipolar transistors with 30 n-InP layer tunneling layers and a five-period InP/InGaAs superlattice are demonstrated and comparatively investigated by experimentally results and analysis. In the three devices, a 200 Å n-In0.53Ga0.47As layer together with an n-InP tunneling emitter layer (or n-InP/n-InGaAs superlattice) forms heterostructure emitter to decrease collector-emitter offset voltage. The results exhibits that the largest collector current and current gain are obtained for the tunneling transistor with a 30 Å n-InP tunneling emitter layer. On the other hand, some of holes injecting from base to emitter will be blocked at n-InP/n-InGaAs heterojunction due to the relatively small hole transmission coefficient in superlattice device, which will result in a considerable base recombination current in the n-InGaAs layer. Therefore, the collector current and current gain of the superlattice device are the smallest values among of the devices. 相似文献
142.
M. Gunawan E. H. Wong S. G. Mhaisalkar L. T. Davila Yu Hong J. F. J. M. Caers T. K. Tsai 《Journal of Electronic Materials》2004,33(9):1041-1047
Adhesive interconnections are considered to be attractive alternatives to lead or lead-free solder interconnects because of
their lower processing temperatures and extendability to fine pitch applications. However, reliability issues, such as moisture-induced
delamination and viscoelastic relaxation of the adhesive in both steady-state and cyclic loading, continue to pose a challenge
to widespread implementation. To date, the static and cyclic relaxation characteristics of nonconductive adhesives (NCAs)
are yet to be understood. This paper attempts to provide insights into this static and cyclic relaxation behavior through
experimental characterization and modeling. The viscoelastic property of a typical NCA material was characterized, and a simulation
program with integrated circuit emphasis (SPICE) modeling program was used to model the cyclic relaxation behavior. The modeling
results were successfully validated with a series of experiments. This showed that cyclic relaxation of the adhesive can be
successfully modeled using linear-viscoelastic property. The phenomenon of slower relaxation of the adhesive under cyclic
loading than that in static loading suggests that accelerated reliability testing used in solder-joint fatigue durability
investigations may not be directly applicable to the adhesive interconnections. A rework methodology applicable to adhesive
interconnects using cyclic loading has also been proposed. 相似文献
143.
H. Jonathan Chao Cheuk H. Lam Xiaolei Guo 《International Journal of Communication Systems》2001,14(7):663-678
Input–output queued switches have been widely considered as the most feasible solution for large capacity packet switches and IP routers. In this paper, we propose a ping‐pong arbitration scheme (PPA) for output contention resolution in input–output queued switches. The challenge is to develop a high speed and cost‐effective arbitration scheme in order to maximize the switch throughput and delay performance for supporting multimedia services with various quality‐of‐service (QoS) requirements. The basic idea is to divide the inputs into groups and apply arbitration recursively. Our recursive arbiter is hierarchically structured, consisting of multiple small‐size arbiters at each layer. The arbitration time of an n‐input switch is proportional to log4?n/2? when we group every two inputs or every two input groups at each layer. We present a 256×256 terabit crossbar multicast packet switch using the PPA. The design shows that our scheme can reduce the arbitration time of the 256×256 switch to 11 gates delay, demonstrating the arbitration is no longer the bottleneck limiting the switch capacity. The priority handling in arbitration is also addressed. Copyright © 2001 John Wiley & Sons, Ltd. 相似文献
144.
Shu-Jen Tsai Li Zhang Phadke A.G. Yilu Liu Ingram M.R. Bell S.C. Grant I.S. Bradshaw D.T. Lubkeman D. Le Tang 《IEEE transactions on circuits and systems. I, Regular papers》2007,54(8):1819-1828
A global view of power system's frequency behavior opens up a new window for analyzing system's dynamics. With the aid of global positioning system, measurements from different locations would have synchronous time; therefore a system-wide observation and analysis would be possible. As part of the US-wide power frequency monitoring network project this paper focus on simulation study results of power frequency dynamics of the Eastern U.S. system. The study assesses the frequency measurement accuracy needed to observe frequency dynamics from events such as remote generation drops. Electromechanical-wave propagation phenomena during system disturbances have been observed. The speeds of electromechanical-wave propagation in different areas of the U.S. systems were estimated and their characteristics were discussed. 相似文献
145.
Han-Ping Tsai 《IEEE transactions on information theory / Professional Technical Group on Information Theory》1992,38(6):1829-1833
Two new singly-even extremal, self-dual codes are constructed: a [52,26,10] code and a [54,27,10] code 相似文献
146.
Sui-Ying Hsu Chih-Hung Tsai Chun-Yang Lu Yu-Tang Tsai Tsung-Wei Huang Yuan-Hsuan Jhang Yan-Fang Chen Chung-Chih Wu Yen-Shan Chen 《Organic Electronics》2012,13(5):856-863
We report an effective way to produce nanoporous Pt counter electrodes of dye-sensitized solar cells by the glancing-angle deposition (GLAD) technique. By controlling the orientation of the substrate relative to the incident Pt vapor flux during the deposition, nanoporous films composed of inclined nm-scale columns were produced through the self-shadowing effect. Pt counter electrodes having varied nanoporous structures were characterized for their morphological and electrochemical properties, and were subjected to device studies to establish the correlation with DSSC characteristics/performances. The results suggest that the nanoporous GLAD Pt electrodes can effectively enhance active surface areas, the catalytic ability and charge exchange at the Pt/electrolyte interface of a DSSC. As a result, the quantum efficiency, short-circuit current, and power conversion efficiency of the DSSC can be enhanced by up to 12–13% with using the nanoporous GLAD Pt counter electrodes. 相似文献
147.
Facebook is a well-known computer-mediated communication platform considered popular among adolescents and young adults. New media scholars have coined the term “intensity of Facebook use” (IFU) for the concept that measures the emotional and affective attitude towards Facebook use among young people. IFU is an important service use concept that has been positively linked with the different psychosocial outcomes of student well-being. However, only a limited amount of the prior literature has investigated the relationship between IFU and different Facebook uses and gratifications (U&G). The existing literature suggests inconsistent findings with a sole emphasis on young adults. To address these gaps, the present study has investigated the differential role of different Facebook U&G among adolescents and young adults in predicting IFU. A total of three cross-sectional data sets (N = 373, 107, 105) represented adolescents and university-attending young-adult Facebook users. The study results suggest that process U&G do and content U&G do not play any significant role in predicting IFU. Adolescents and young adults differ in their sought Facebook U&G. In addition to this, cultural differences were observed in the sought Facebook U&G and their differential role in predicting IFU. 相似文献
148.
Chia-Yang Tsai Hsueh-Ming Hang 《Journal of Visual Communication and Image Representation》2010,21(8):917-929
A rate-distortion model for describing the motion prediction efficiency in interframe wavelet video coding is proposed in this paper. Different from the non-scalable video coding, the scalable wavelet video coding needs to operate under multiple bitrate conditions and it has an open-loop structure. The conventional Lagrangian multiplier, which is widely used to solve the rate-distortion optimization problems in video coding, does not fit well into the scalable wavelet structure. In order to find the rate-distortion trade-off due to different bits allocated to motion and textual information, we suggest a motion information gain (MIG) metric to measure the motion prediction efficiency. Based on this metric, a new cost function for mode decision is proposed. Compared with the conventional Lagrangian method, our experiments show that the proposed method is less extraction-bitrate dependent and generally improves both the PSNR performance and the visual quality for the scalability cases. 相似文献
149.
The quantum efficiency (QE) in HgCdTe photovoltaic pixel arrays employing a photon-trapping (PT) structure realized with a periodic array of pillars intended to provide broadband operation was investigated. It was found that the QE depends heavily on the passivation of the pillar surface. This is due to the presence of large fixed positive charge on the surface of pillars passivated with anodic oxide. A three-dimensional numerical simulation model was used to study the effect of the surface charge density and surface recombination velocity on the exterior of the pillars. Then, the QE of this structure was evaluated subject to different surface conditions. It was found that alone the surface charge density or surface recombination is detrimental to the QE but that the QE is recovered when both phenomena are present. Subsequently, the crosstalk was analyzed and the superior performance of the PT structure was demonstrated by evaluating the modulation transfer function. 相似文献
150.
Paul D. Coleman Jonathan J. Wierer 《Journal of Infrared, Millimeter and Terahertz Waves》1995,16(1):3-32
Using new experimental data from modeling the p-Ge laser pulse plus literature data, basic laser parameters are obtained so that one can solve the laser equations of Pantell and Puthoff to obtain formulas for calculating all laser quantities of interest. Values, calculated using the formulas, such as gain, saturation intensity, pump population differences, power generated, output coupling, efficiency, etc. are in excellent agreement with available experimental data. This work contributes to problems in determining laser line transitions, the laser cycle, and the optimization of the laser performance. 相似文献