数字隔离器提供易于使用的隔离式USB选项

正通用串行总线(USB)是个人计算机(PC)通过电缆与外设实现通信的常用方法。某些应用中,需要隔离USB通信以满足安全要求,或中断接地环路。遗憾的是,隔离任务不易完成,因为USB电缆上有双向数据流。本文将讨论这个问题,并探讨实现易于使用的隔离式USB方案面临的其他挑战,最后对解决方案进行比较。一个理想的透明解决方案能将隔离对     

Radar polarimetry towards a future standardization

Nine research institutes from the European Union joined their efforts in a project to work out theory and applications for radar polarimetry. The reason why this specific research network has been set up is that the impact of polarimetric methods has not yet attained its expected potential, although this particuliar branch of science is rapidly influencing the scenarios of terrestrial remote sensing, microwave and optical measurements, weather prediction and telecommunications. One main reason for this delayed appreciation is the lack of a fully coherent and structured polarimetric theory. This project will seek to redress this imbalance. Improvements are expected to increase the sophistication of existing remote sensing systems. The main objectives and the scientific originality of thistmr network which has a duration of 36 months (1998-04-01 till 2001-03-31) are summarized.     

Experimental Study of an Adding Interferometer at Millimeter Waves

In order to study an original detection architecture for future cosmology experiments based on wide band adding interferometry, we have tested a single baseline bench instrument based on commercial components. The instrument has been characterized in the laboratory with a wide band power detection setup. A method which allows us to reconstruct the complete transfer function of the interferometer has been developed and validated with measurements. This scheme is useful to propagate the spurious effects of each component till the output of the detector.     

Combinatorial auctions for exchanging resources over a grid network

In grid systems, users compete for different types of resources such that they may execute their applications. Traditional grid systems are formed of organisations that join together for the purpose of collaborative projects. Resources of each of the participating organisation are pooled such that members of individual organisations may access the shared infrastructure. In general, each participant is both a provider and a consumer of resources. Whilst such systems address large organisations, in this paper we address democratic grid systems to satisfy needs of small organisations and even individuals, where on-demand grids may be formed by drawing idling resources available on the Internet. Whilst traditional grid systems resort to allocations that satisfy system specific objectives such as maximization of the resource utilisation, market mechanisms try to obtain allocations that are efficient economically. Economic mechanisms permit to achieve equilibrium between supply and demand and furthermore provide incentives for providers. Combinatorial auction has been argued as an effective mechanism to address the problem of resource allocation within grid systems. Auctions within which multiple types of resources in varying quantities may be traded eliminate the exposure problem by addressing co-allocation. In this paper, we describe a combinatorial exchange where multiple providers and multiple consumers may participate. We describe the winner determination problem that incorporates the time dimension, i.e. resource bundles may be requested for different time ranges, and describe a set of heuristics that have been designed to be fast. We show that these achieve a high level of efficiency as compared to exact solutions. The second part focusses on the pricing problem. The objective is to compute prices that represent the state of the market and bring trustworthy feedback to participants. Drawing on the approach taken by Kwasnica et al. (Manage Sci 51(3):419–434, 2005), we propose a pricing model that computes per-item pricing. Per-item pricing allows users to deduce the price of bundles that they require by linear summation. Furthermore, we propose a model that computes prices as a function of time, thus permitting users, in particular consumers to adjust their demand trading off price and time of execution.     

Virtual RF system platform dedicated to heterogeneous complex SoC design

In this paper, we propose to develop a hierarchical library associated with various simulators that can be used in a single platform, called TrustMe-ViP, which enables a unique simulation framework and full model interoperability. Such platform is dedicated to complex SoC design, such as trusted personal devices where cost and time-to-market are very important constraints. To validate this methodology, we present the estimation of BER and power consumption for a Bluetooth transceiver.     

SOAR: Simple Opportunistic Adaptive Routing Protocol for Wireless Mesh Networks

Multihop wireless mesh networks are becoming a new attractive communication paradigm owing to their low cost and ease of deployment. Routing protocols are critical to the performance and reliability of wireless mesh networks. Traditional routing protocols send traffic along predetermined paths and face difficulties in coping with unreliable and unpredictable wireless medium. In this paper, we propose a Simple Opportunistic Adaptive Routing protocol (SOAR) to explicitly support multiple simultaneous flows in wireless mesh networks. SOAR incorporates the following four major components to achieve high throughput and fairness: 1) adaptive forwarding path selection to leverage path diversity while minimizing duplicate transmissions, 2) priority timer-based forwarding to let only the best forwarding node forward the packet, 3) local loss recovery to efficiently detect and retransmit lost packets, and 4) adaptive rate control to determine an appropriate sending rate according to the current network conditions. We implement SOAR in both NS-2 simulation and an 18-node wireless mesh testbed. Our extensive evaluation shows that SOAR significantly outperforms traditional routing and a seminal opportunistic routing protocol, ExOR, under a wide range of scenarios.     

D类音频放大器设计:概念、原理和方法(下)

本文详细阐述了D类音频放大器技术及其设计要素,并介绍了ADI公司的D类放大器的产品特点.     

Cyanate Ester-Based Encapsulation Material for High-Temperature Applications

Cyanate ester resin-based composite materials have been proposed as potential encapsulants for high-temperature applications. The objective of this study is to develop a cyanate ester-based encapsulant, which can also serve as a flip-chip underfill as well as for traditional encapsulation. Two different materials, quartz and alumina fillers, have been studied. The impact of shapes and sizes of the fillers on the overall thermomechanical properties has been investigated. The adhesion strengths of the materials to the ceramic substrate, Kovar lid, and silicon die have also been characterized. The modulus of the resin and the shape of the fillers play a pivotal role in minimizing thermal stress, generated by coefficient of thermal expansion mismatches. Smaller filler particles were found to have better adhesion to the cyanate ester resin. The high-temperature performance of the cyanate ester-based encapsulants was evaluated by thermal aging at 300°C for up to 500 h.     

Multi-objective module placement for 3-D system-on-package

System-on-package (SOP) is a viable alternative to system-on-chip (SOC) for meeting the rigorous requirements of today's mixed-signal system integration. Thermal integrity is arguably the most crucial issue in three-dimensional (3-D) SOP due to the compact nature of the 3-D integration. In addition, the power supply noise issue becomes more serious as the supply voltage continues to decrease while the number of active devices consuming power increases. We propose a 3-D module and decap (decoupling capacitance) placement algorithm that evenly distributes the thermal profile and reduces the power supply noise. In addition, we allocate white spaces around the modules that require decaps to suppress the power supply noise while minimizing the area overhead. In our experimentation, we achieve improvements in both maximum temperature and decap amount with only small increase in area, wirelength, and runtime.     

Hydrogen‐Bonded Organic Semiconductors as Stable Photoelectrocatalysts for Efficient Hydrogen Peroxide Photosynthesis

Research on semiconductor photocatalysts for the conversion of solar energy into chemical fuels has been at the forefront of renewable energy technologies. Water splitting to produce H₂ and CO₂ reduction to hydrocarbons are the two prominent approaches. A lesser‐known process, the conversion of solar energy into the versatile high‐energy product H₂O₂ via reduction of O₂ has been proposed as an alternative concept. Semiconductor photoelectrodes for the direct photosynthesis of H₂O₂ from O₂ have not been applied up to now. Photoelectrocatalytic oxygen reduction to peroxides in aqueous electrolytes by hydrogen‐bonded organic semiconductor is observed photoelectrodes. These materials have been found to be remarkably stable operating in a photoelectrochemical cell converting light into H₂O₂ under constant illumination for at least several days, functioning in a pH range from 1 to 12. This is the first report of a semiconductor photoelectrode for H₂O₂ production, with catalytic performance exceeding prior reports on photocatalysts by one to two orders of magnitude in terms of peroxide yield/catalyst amount/time. The combination of a strongly reducing conduction band energy level with stability in aqueous electrolytes opens new avenues for this widely available materials class in the field of photo(electro) catalysis.