PCI接口芯片s5935及其应用

s5935是AMCC公司生产的PCI接口芯片 ,可实现直通 (PASS-THRU)、邮箱 (MAILBOX)、FI FO/DMA三种工作方式。文章简要介绍了这三种工作方式 ,并给出了s5935的WDM驱动编程。     

吐哈盆地巴喀油田特低渗砂岩油层裂缝分布特征

巴喀油田中侏罗统砂岩属特低渗透裂缝 孔隙型储集层 ,平均渗透率为 0 .3× 10 - 3μm2 ;地下基质岩块孔隙度为7.4%,渗透率为 0 .16× 10 - 3μm2 。砂岩储集层发育的主要裂缝类型有构造层理缝、正向正交缝、斜向正交缝和羽裂等 ,裂缝宽度一般为 0 .3～ 3 .2mm ,纵向切深为 0 .1～ 0 .8m ,水平延伸长度为 0 .2～ 2 .1m。裂缝以半充填为主 ,其分布受岩性、层厚和构造位置的影响 ,纵向、横向均呈带状分布 ,被裂缝切割而成的基质岩块尺寸取决于裂缝频率 ,岩块长轴方向以北西西向为主 ,与构造轴向基本一致。图 3表 4参 8     

An object replication algorithm for real-time distributed databases

A real-time distributed database system (RTDDBS) must maintain the consistency constraints of objects and must also guarantee the time constraints imposed by each request arriving at the system. Such a time constraint of a request is usually defined as a deadline period, which means that the request must be serviced on or before its time constraint. Servicing these requests may incur I/O costs, control-message transferring costs or data-message transferring costs. As a result, in our work, we first present a mathematical model that considers all these costs. Using this cost model, our objective is to service all the requests on or before their respective deadline periods and minimize the total servicing cost. To this end, from theoretical standpoint, we design a dynamic object replication algorithm, referred to as Real-time distributed dynamic Window Mechanism (RDDWM), that adapts to the random patterns of read-write requests. Using competitive analysis, from practical perspective, we study the performance of RDDWM algorithm under two different extreme conditions, i.e., when the deadline period of each request is sufficiently long and when the deadline period of each request is very short. Several illustrative examples are provided for the ease of understanding. Recommended by: Ashfaq Khokhar     

Personal telecommunication radiation safety and the precautionary principle

The approach to risk management for RF and microwave radiation has been to establish guidelines for maximum permissible levels of exposure. These guidelines are based on evaluations of the relevant scientific literature and, with safety margins to account for uncertainties and gaps in scientific knowledge, offer a significant level of protection against established hazards of RF and microwave radiation for short-term exposures. One can argue, on this basis, that the precautionary principle - specifically, safety factors -have been used to guide the making and promulgation of existing permissible-exposure standards for RF and microwave radiation. Therefore, discussions on the appropriateness of the precautionary principle for RF radiation may be "much ado about nothing". Clearly, this approach to "pre caution" neither has stifled technological development, nor has it helped to enforce the acceptance of zero risk, but it provided a basis for action when science was unable to give a clear answer.     

Graph-theoretic construction of low-density parity-check codes

This article presents a graph-theoretic method for constructing low-density parity-check (LDPC) codes from connected graphs without the requirement of large girth. This method is based on finding a set of paths in a connected graph, which satisfies the constraint that any two paths in the set are either disjoint or cross each other at one and only one vertex. Two trellis-based algorithms for finding these paths are devised. Good LDPC codes of practical lengths are constructed and they perform well with iterative decoding.     

膜电极结构对质子交换膜燃料电池性能的影响

膜电极(MEA)作为质子交换膜燃料电池(PEMFC)的核心组件之一，其结构和组成对电池的性能有着重要的影响。提高膜电极性能的一个重要的指导思想是在催化粒子的周围形成良好的质子、电子和气体通道。以此为主线，从电极制备工艺的发展历程，Nafion的使用与质子通道的改进、电子通道的改进、阴极催化等几个方面详细地总结和讨论了近年来MEA的研究状况，并在此基础上对MEA的进一步研究提出了若干建议。     

垂直铺膜防渗技术在大堤防渗加固工程中的应用

在高水河大堤防渗加固工程中,根据堤身的实际情况,结合地质和施工条件,采用压力灌浆及砼地下连续墙相结合的方法来进行垂直铺膜防渗加固。通过对垂直铺膜前后测压管水头对比研究,分析了大堤外观干、湿土变化和大堤内干土质量密度、密实度的变化,说明了垂直铺膜防渗技术在大堤防渗应用造价低,防渗效果显著,有利于改善大堤的稳定性和安全性。垂直铺膜防渗技术应用于临时防渗及平原低水头水库和河道堤防等工程,实用性强,具有推广价值。     

New hybrid fuzzy controller for direct torque control induction motor drives

A new hybrid fuzzy controller for direct torque control (DTC) induction motor drives is presented in this paper. The newly developed hybrid fuzzy control law consists of proportional-integral (PI) control at steady state, PI-type fuzzy logic control at transient state, and a simple switching mechanism between steady and transient states, to achieve satisfied performance under steady and transient conditions. The features of the presented new hybrid fuzzy controller are highlighted by comparing the performance of various control approaches, including PI control, PI-type fuzzy logic control (FLC), proportional-derivative (PD) type FLC, and combination of PD-type FLC and I control, for DTC-based induction motor drives. The pros and cons of these controllers are demonstrated by intensive experimental results. It is shown that the presented induction motor drive is with fast tracking capability, less steady state error, and robust to load disturbance while not resorting to complicated control method or adaptive tuning mechanism. Experimental results derived from a test system are presented confirming the above-mentioned claims.     

A new Pd-oxide-Al/sub 0.3/Ga/sub 0.7/As MOS hydrogen sensor

A new and interesting Pd-oxide-Al/sub 0.3/Ga/sub 0.7/As MOS hydrogen sensor has been fabricated and studied. The steady-state and transient responses with different hydrogen concentrations has been measured at various temperatures. Based on the large Schottky barrier height and presence of oxide layer, the studied device exhibits a high hydrogen detection sensitivity and wide temperature operating regime. The studied device exhibits the low-leakage current and obvious current changes when exposed to hydrogen-contained gas. Even at room temperature, a very high hydrogen detection sensitivity of 155.9 is obtained when a 9090 ppm H/sub 2//air gas is introduced. Furthermore, when exposed to hydrogen-contained gas at 95/spl deg/C, both the forward and reverse currents are substantially increased with increased hydrogen concentration. In other words, the studied device can be used as a hydrogen sensor under the applied bidirectional bias. Under the applied voltage of 0.35 V and 9090 ppm H/sub 2//air hydrogen ambient, a fast adsorption response time about 10 s is found. The transient and steady-state characteristics of hydrogen adsorption are also investigated.