Linear periodically time-varying discrete-time systems: Aliasing and LTI approximations

Linear periodically time-varying (LPTV) systems are abundant in control and signal processing; examples include multirate sampled-data control systems and multirate filter-bank systems. In this paper, several ways are proposed to quantify aliasing effect in discrete-time LPTV systems; these are associated with optimal time-invariant approximations of LPTV systems using operator norms.     

聚醚多元醇钻井液研制及应用

以新研制的多功能聚醚多元醇SYP-1为主剂,对聚合物包被剂、防塌剂和降滤失剂进行了优选实验.在此基础上,研制了一种新型的聚醚多元醇钻井液.对聚醚多元醇钻井液的抑制性、流变性、滤失造壁性、润滑性以及对油气层的保护性能进行了室内评价实验,并分析了该钻井液的作用机理.在LN3-6H井和HD4-23H井进行的聚醚多元醇钻井液现场试验表明,在钻进过程中井壁稳定,井径规则,起、下钻畅通,井下安全,测井、下套管及固井作业顺利.室内实验和现场应用表明,聚醚多元醇钻井液具有优良的防塌性和润滑性,能有效地抑制岩屑分散,起到稳定井壁和保护油气层的作用,满足复杂地质条件下钻井的需要.     

多路FM－SCM光波系统研制

介绍我们研制的多路ＦＭ－ＳＣＭ（调频副载波复用）光波系统及其性能，讨论了ＳＣＭ光波系统的噪声。该系统主要可用于多路ＣＡＴＶ光纤传输。采用Ｆ－Ｐ腔ＬＤ和ＰＩＮ－ＦＥＴ接收组件，通过系统优化，实现了接收端输出电视图象信号ＳＮＲ＞５５ｄＢ。     

Dynamic Reservation Multiple Access (DRMA): A new multiple access scheme for Personal Communication System (PCS)

To improve the spectrum efficiency of integrated voice and data services in Personal Communication System (PCS), several reservation-type multiple access schemes, such as Packet Reservation Multiple Access (PRMA), Dynamic Time Division Multiple Access (D-TDMA), Resource Auction Multiple Access (RAMA), etc., have been proposed. PRMA uses the data packet itself to make a channel reservation, and is inefficient in that each unsuccessful reservation wastes one slot. However, it does not have a fixed reservation overhead and offers shorter access delay. On the other hand, fixed reservation overhead is unavoidable in both RAMA and D-TDMA. Compared to D-TDMA and PRMA, RAMA is superior in the sense that its slot assignment is independent of the traffic load. But its implementation is difficult. With these observations, a new reservation protocol, called Dynamic Reservation Multiple Access (DRMA), is proposed in this paper. With this new protocol, the success probability of channel access is greatly improved at the expense of slightly increased system complexity. It solves the problem of inefficiency in PRMA, but without introducing the fixed reservation overhead as in D-TDMA and RAMA. In addition, it is more suited to the dynamic behavior of the integrated traffic because there is no fixed boundary between voice and data slots (which is mandatory in D-TDMA and RAMA). Our numerical results indicate that its performance is superior to the existing reservation protocols, especially in the integrated traffic scenario. Moreover, the soft capacity feature is exhibited when the traffic load increases.     

Analysis of Surface Plasmon Polariton Using Anisotropic Finite Elements

The anisotropic finite-element mesh is deployed in a vector finite-element method to numerically derive surface plasmon polaritons (SPPs) more efficiently. The superiority of the anisotropic mesh lies in the fact that SPP modes, predictably, have a sharp field variation in the surface-normal direction, whereas the variation along the surface-tangent direction is comparably gentle. A case study on metallic fiber shows that the employment of anisotropic finite elements reduces the problem size by a factor of seven.     

基于微机的X射线分析自动测量系统

本文介绍了一个基于微机的X射线分析自动测量系统。该系统有三个基本功能:自动获取数据、自动换样和处理谱数据。     

Biomimetic engineering of non-adhesive glycocalyx-like surfaces using oligosaccharide surfactant polymers

The external region of a cell membrane, known as the glycocalyx, is dominated by glycosylated molecules, which direct specific interactions such as cell-cell recognition and contribute to the steric repulsion that prevents undesirable non-specific adhesion of other molecules and cells. Mimicking the non-adhesive properties of a glycocalyx provides a potential solution to the clinical problems, such as thrombosis, that are associated with implantable devices owing to non-specific adsorption of plasma proteins. Here we describe a biomimetic surface modification of graphite using oligosaccharide surfactant polymers, which, like a glycocalyx, provides a dense and confluent layer of oligosaccharides. The surfactant polymers consist of a flexible poly(vinyl amine) with dextran and alkanoyl side chains. We show that alkanoyl side chains assemble on graphite through hydrophobic interaction and epitaxial adsorption. This constrains the polymer backbone to lie parallel to the substrate, with solvated dextran side chains protruding into the aqueous phase, creating a glycocalyx-like coating. The resulting biomimetic surface is effective in suppressing protein adsorption from human plasma protein solution.     

ℋ2-optimal design of multirate sampled-data systems

Treating causality constraints, this paper studies optimal synthesis of multirate sampled-data systems with an ℋ₂ performance criteria. An explicit solution is obtained by input-output space extensions (lifting) and frequency-domain techniques     

Chronic interleukin-6 alters NMDA receptor-mediated membrane responses and enhances neurotoxicity in developing CNS neurons

Recent studies show that the cytokine interleukin-6 (IL-6) is expressed at elevated levels in the CNS in several disease states and contributes to the neuropathological process. The mechanisms through which IL-6 exerts its CNS effects are primarily unknown. We have investigated the pathophysiological effects of IL-6 on developing CNS neurons using a culture model system and a chronic treatment paradigm. Here, we show, using current- and voltage-clamp recordings, that chronic IL-6 treatment of developing cerebellar granule neurons increases the membrane and current response to NMDA and that these effects are the primary mechanism through which IL-6 produces an enhanced calcium signal to NMDA. We also show that calcium influx through voltage-sensitive calcium channels contributes to the enhanced calcium signal to NMDA in the IL-6-treated neurons in a developmentally regulated manner and that the membrane depolarization to NMDA is more sensitive to the NMDA receptor antagonist ifenprodil in the IL-6-treated neurons compared with control neurons at a late developmental stage, consistent with a larger proportion of NMDA receptors containing the NMDAR2B subunit in the IL-6-treated neurons. Additional studies show that IL-6 treatment reduces the number of granule neurons in culture and enhances neurotoxicity involving NMDA receptors. These results support a pathological role for IL-6 in the CNS and indicate that NMDA receptor-mediated functions are likely to play a critical role in neuropathological changes observed in CNS diseases associated with elevated CNS levels of IL-6.