BISLN中ATM轮询系统的研究

本文通过对网络中轮询系统的研究，设计了基于ＡＴＭ（异步转移模式）的采用轮询系统模型的ＢＩＳＬＮ（宽带综合业务局域网）原型，同时ＢＩＳＬＮ轮询系统模型已在实验室环境下实现。     

基于LPC2368的操作系统设计

在嵌入式系统开发的过程中,有时由于系统规模小、资源少而无需嵌入操作系统,这给习惯在操作系统下编程的开发人员带来很大的不便,针对这种情况该文在LPC2368上设计了一个轻型操作系统,实现了轮询式的任务调度,解决了无操作系统环境下编程的困扰。     

On the correlation between radiation-induced oxide- and border-trap effects in the gate-oxide nMOSFET’s

In this study, combined voltage- and frequency-charge pumping techniques were used to investigate the generation and evolution of border-traps in degraded NMOS transistors by using 1.25 MeV ⁶⁰Co γ-rays. In addition, gate length effects on border-trap charge density were discussed. First result, both border- and oxide-trap reveal two behaviors as function of total dose at low dose rate. Primarily, there is an increase of both trapped charges, followed later by a decrease of their net charge. Second result, border-trap presents a strong dependence on designed transistor channel length. Transistors with longer gate lengths exhibit less important border-trap during irradiation than transistors with smaller gate lengths. This is due to differences in the near-interfacial stress. However, the same effects were observed for oxide-traps. These results show a great correlation between radiation-induced border- and oxide-trap behaviors at low dose rate. Therefore, this similarity strengthens the idea that both border- and oxide-trap could have the same defect (E^′).     

Proof of soundness (integrity) of cryptographic protocols

In 1990 a workshop on the Mathematical Concepts (or Principles) of Dependable Systems was held at the Mathematisches Forschungsinstitut Oberwolfach in Germany. The purpose of the workshop was to examine mathematical techniques developed to make it possible to prove the proper functioning of complex systems—where the system could be either hardware, software, information protocols, etc., or combinations of these components. Principal researchers in each of these areas were invited to take part in the workshop, and did—but as is so often the case at scientific meetings, one area emerged as a clear center of gravity for the workshop. This was the topic of applying formal methods to the proof of soundness or correctness of information or cryptographic protocols. The organizers of the workshop felt that the results reported in this area were so important to the cryptology community they deserved publication as a whole, as opposed to publication as separate and isolated papers: hence this special section. This paper, which is essentially an introduction for the invited paper that follows, describes the background for the workshop and the challenge problem(s) that provided a unifying theme for the three systems of formal analysis treated in it.For reasons beyond the control of either the authors or the editors, this special section has been unusually long delayed in publication; so long in fact that a great deal of related work has been done in the interim. It would have been desirable to summarize these developments in this preface, but this would have changed the nature of the preface from a brief note describing the circumstances that led to the invitation to the authors to prepare the paper that makes up the special section, to a full fledged survey paper in itself. After careful consideration, it was decided that this would be inconsistent with the original intent for the special section.     

Interconnect Geometry Optimization Using Modular Artificial Neural Networks

This paper describes a methodology for crosstalk prediction and minimization in interconnect wiring using artificial neural networks. Neural networks are used as parameterized models to achieve two important mappings. The first—forward map—maps the geometric and material parameters of interconnects (for example width, length, separation, conductivity, dielectric constant k) to equivalent electrical parameters (for example, R,L,C,G). Such a relationship would normally require quasi-TEM solutions of EM problems. The second—reverse map—is the reverse of the first mapping equivalent electrical parameters to interconnect geometric and material parameters. The crosstalk minimization approach proposed involves topological decomposition of interconnect into standard cells—portions of interconnect referred to as wirecells—and the derivation of the above two mappings for each wirecell. Crosstalk is iteratively minimized in the domain of SPICE circuit parameters and the resulting optimized SPICE equivalent circuit mapped back into the wirecell geometric domain using the reverse neural net mapping. For computational efficiency and high accuracy, the technique initially establishes a library of re-usable neural wirecell models using a field solver coupled with a circuit simulator and a neural network multi-paradigm prototyping system. The approach offers two important advantages. First, the simultaneous effect of multiple non-correlated geometric and material wirecell characteristics on crosstalk can be accurately computed and crosstalk minimized by iterative modification of interconnect geometry and material characteristics. Second, the approach produces—as a by-product—system level contours of equicoupling called isocouples to guide design activities such as placement and route. Crosstalk prediction and minimization results are presented for a high performance operational transconductance amplifier in which reduction in crosstalk by variation of interconnect layout geometry resulted in a 41% increase in gain.     

Loss and Noise Characteristics of Microwave Direct Modulated Optical Links

Loss and noise figure of optical links transmitting microwave signals —e.g. for remote antennas in wireless communications — are dealt with.Conditions are rather general and include arbitrary matching conditions, shotnoise, and laser relative intensity noise. Specific and somewhat surprisingcharacteristics are derived. Among others, it is shown, that — likepassive, purely microwave systems — noise figure is not proportional toelectrical loss and it can be even lower than loss itself. Optical powershould be as low as possible — this limit is mainly determined by therequired dynamic range of the system. Loss and noise figure were measured inan experimental setup. Results of the measurements proved the theoreticalfindings rather well. Preliminary results on the transmission of 32TCM signalsover the link are briefly presented.     

Compensator-based position control of an electrorheological actuator

This paper addresses the question of whether compensator-based controllers can be used to successfully control the position of a model scale robot arm attached to the output shaft of an electrorheological (ER) actuator, with a view of recommending the actuator for robotic applications and providing an alternative control strategy to proportional plus integral plus derivative, (PID), control. An ER actuator is a device that uses a ‘smart’ material, called an ER fluid or suspension, as a coupling medium between the prime mover running at a constant speed and a load. Three compensator-based controllers—the phase-lag, the phase-lead and lead-lag compensators—were designed and implemented on the ER actuator-arm system. The phase-lead and phase-lag compensators gave reasonable performance. The lead-lag compensator, on the other hand, was impossible to implement.     

Application of expert systems to systems reliability evaluation

An expert system for diagnosing rough ride problems in heavy trucks has been developed and can be used on a personal computer. The system operates on two levels of knowledge data base: shallow — acquired from truck service personnel and causal obtained from a multiprobe vibration analysis system (MVAS) through a preprocessing neural network. The justification for selecting neural networks is presented as are virtues and drawbacks of the developed system.     

On Reversible Skeletonization Using Anchor-Points from Distance Transforms

In many applications thinning of objects is of great interest. We here present a skeletonization algorithm that is based on the idea of iteratively thinning the distance transform of an object layer by layer until either an anchor-point is reached or the connectivity breaks. Our algorithm is general in the sense that any metric and any connectivity can be used. Also, it is based on ideas that are not specific for 2D. The properties of the resulting skeletons are evaluated according to the “Lee–Lam–Suen properties.”     

Organic Networks

The topic of organic networks derives from the confluence of two distinct bodies of research that have been proceeding independently in the Media Lab for the past several years — 'Viral Networks', which focuses on the enabling technology underpinning end-to-end, grassroots communications systems, and 'Influence Networks', which encompasses ways that both first-world and third-world societies bend the technology of easy connectivity to suit their own economic, cultural and social interests. While the general method of research in the Media Laboratory (semi-autonomous groups following largely independent research tracks) implies that these two themes are somewhat segregated, their intersection carries implications and lessons in and of itself that are too strong to be ignored — hence this co-ordinated set of papers.     

Profit analysis of two-unit priority standby system with rest period of the operator

This paper deals with profit analysis of a single-server two-unit (one priority and the other ordinary) cold standby system with two modes—normal and total failure. The priority unit gets preference both for operation and repair. After working a random amount of time, the operator of the system needs rest for a random amount of time and during the rest period of the operator the system becomes down but not failed. the system failure occurs when both the units are in total failure mode. Identifying the system at suitable regenerative epochs, the integral equations are set up for the probabilities of system being in the ‘up’, ‘down’ or ‘failed’ state and to solve these equations Laplace transform technique is adopted. Various reliability characteristics are obtained to carry out the cost-benefit analysis and numerical results pertaining to particular cases are also presented.     

无线局域网IEEE 802.11的一种高效调度方案

深入分析了无线局域网IEEE 802.11系列标准的现有调度方案,提出了一种基于IEEE 802.11e标准中HCF接入模式的高效调度方案SA-Multipoll.设计了调度帧结构和调度时序,推导了满足时延和带宽要求的准入协商和调度效率公式.通过数值计算和仿真结果证实了SA-Multipoll的调度效率高于singlepoll,也高于现有multipoll方案中效率较高的CP-Multipoll方案.     

Analysis of a two unit standby redundant fail-safe system

This paper evaluates reliability and fail-safety of a two unit cold standby fail-safe redundant system. Three modes of failure—(1) failure due to human error, (2) failure due to unit faults and (3) failure due to switchover faults—are considered. The complete failure states of the system are divided into two categories, fail-safe state and fail-dangerous state. Several fail-safety measures of interest to a fail-safe system designer are defined and evaluated, such as safety function, safety ratio and danger ratio.     

DCP, a distributed-control polling MAC protocol: specifications andcomparison with DQDB

The authors describe and analyze a novel MAC (media access control) protocol called distributed-control polling (DCP), which has been designed to bring together the most interesting features of distributed-control MAC protocols (e.g. distributed queue dual bus or DQDB) and centralized token-passing MAC protocols (e.g. FASNET, FDDI or fiber distributed data interface, and Express-ent). From the fully distributed MAC protocols. DCP acquires the ability to guarantee both a complete utilization of the medium capacity and an access delay of only a few slots at light loads. From the centralized token-passing MAC protocols, DCP inherits a more predictable and fair behavior at heavy loads. The basic ideas of the proposal are: a cycle for acquiring transmission rights, and a balancing function between reservations and empty slots. It is shown that DCP guarantees a complete utilization of the medium capacity and that its behavior at light loads is close to that of DQDB, while at heavy loads it approaches a polling system with limited service and zero reply interval     

Fabrication and enhanced field emission properties of novel silicon nanostructures

We reported the fabrication and the field emission properties of two-tier novel silicon nanostructures. First, silicon nanopillars with ordered high aspect ratio were achieved by using conventional lithographic techniques to act as the field emission sources. Second, sharp-edged well-aligned silicon nanograss was fabricated on top of the nanopillars by means of hydrogen plasma dry etching to induce the field emission characteristics. The turn-on fields were obtained as 10.5 and 14.4 V/μm under current density of 0.01 mA/cm² for two-tier patterns separated by respective 5 μm and 2 μm spaces. The excellent field emission property from these novel nanostructures exhibited a great potential as high-performance field emitter arrays towards future nanoelectronic devices.     

Contention‐free approaches for WiFi MAC design for VoIP services: performance analysis and comparison

The exponential growth in the demand of voice over internet protocol (VoIP) services along with the increasing demand for mobility in VoIP services has attracted great research efforts towards provisioning of VoIP services in IEEE 802.11‐based Wireless LANs (WiFi networks). We address one of the important research problems, namely, the quality of service (QoS)‐aware efficient silence suppression in the bursty voice traffic, for provisioning VoIP services in WiFi networks. The research works in the recent literature on silence suppression in voice calls have been surveyed categorising them on how the activity arrival is notified to the access point (AP). In most of the recent schemes, notification of uplink activity arrival is done through contention based medium access mechanisms such as the distributed coordination function (DCF). Contention‐based medium access causes non‐deterministic delays, therefore such schemes are not suited to voice traffic which require strict delay bound guarantees. This paper focuses on the schemes which do not use contention based approaches for silence suppression in voice traffic. Analytical performance evaluation and comparison of such schemes is carried out. Two very important performance metrics are modelled mathematically. One is the expected polling overhead time that the schedulers in these schemes can save per voice call during one voice activity cycle as compared to that in the round‐robin polling scheduler. The other is the expected unnecessary wireless channel access delay that a typical first talk‐spurt frame experiences due to the specific design of each scheme. The numerical results of this evaluation lead us to the conclusion whether or not and to what extent each of these schemes is viable. Copyright © 2008 John Wiley & Sons, Ltd.     

Impact of Polarization Mode Dispersion in Multi-Hop and Multi-Rate WDM Rings

Fiber polarization mode dispersion (PMD) is perhaps the most critical transmission impairment in optical networks at transmission rates of 10 Gb/s and higher. Since the bandwidth-distance product, or transparency,of the optical circuit is limited by PMD, the overall network design and cost may be significantly altered by the actual fiber PMD values. The paper has three objectives. First, an accurate model for evaluating the PMD effects is presented and verified experimentally. Second, the cost increase of WDM rings due to PMD in a number of design scenarios—first generation, single-hop,multi-hop, and multi-rate networks—is assessed. Third, the polynomial-time algorithm proposed in Cerutti et al. [1] is modified to provide sub-optimal solutions for the above WDM rings, taking into account the limited bandwidth-distance product imposed by PMD. Presented results reveal that at high transmission rates, the cost of the multi-hop ring is less affected by PMD than the costs of first generation and single-hop rings.