Ultrasonic oscillations effect on rheological and processing properties of metallocene‐catalyzed linear low density polyethylene

The effects of ultrasonic oscillations and die materials on die pressure, productivity of extrusion, melt viscosity of metallocene‐catalyzed linear low density polyethylene (mLLDPE), as well as their mechanism were studied in a special ultrasonic oscillations extrusion system developed in our lab. Die materials used in our experiment included steel, brass, and polytetrafluoroethylene (PTFE)_. The experimental results showed that ultrasonic oscillations as well as die materials have great influence on the rheological and processing behavior of mLLDPE. Ultrasonic oscillations can greatly increase the productivity of mLLDPE melt extruded through different dies, and can decrease the die pressure and the melt viscosity of mLLDPE. Compared with steel or brass die, mLLDPE melt extruded through PTFE die is more sensitive to ultrasonic oscillations. A possible mechanism for the improved processability of mLLDPE is proposed in this article. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 1873–1878, 2003     

Structural and Electric Properties of Sol–Gel-Derived Ba0.9Sr0.1TiO3 Multilayers

Crack-free Ba_0.9Sr_0.1TiO₃ (BST) and Mn-doped Ba_0.9Sr_0.1TiO₃ (BSTM) multilayers with thickness over 2 μm have been prepared by chemical solution deposition based on one single precursor. Both multilayers exhibit good performance as Bragg reflectors. Mn doping tends to suppress the leakage current in BST multilayers effectively by smoothing the layers and the reduction of the charge carries. The Mn-doped BST multilayer displays an excellent ferroelectric property, with an average remnant polarization ( P _r⁺– P _r⁻)/2 of 12.69 μC/cm² and an average coercive field ( E ⁺ – E ⁻ )/2 of about 72.95 kV/cm under an applied field of 440 kV/cm.     

复合相刚玉颗粒构成对出铁沟浇注料抗热震稳定性的改善

根据本文中的机理A(引入热膨胀系数失配的第二相)机理B(引进热膨胀系数小的第二相),通过引入热膨胀系数不同的第二、三相形成复合相刚玉颗粒构成,使出铁沟浇注料抗热震稳定性得到改善。     

浅析无线网现状及相关技术

无线网作为一种现代化的技术手段,随着网络信息技术的不断发展完善,在实际中的应用越来越广泛和普遍,对于无线网技术的研究与关注内容也越来越多,进行无线网现状以及相关技术的研究分析,有利于促进无线网在实际应用中的改进和提升,具有积极的作用和意义。下文将结合无线网在实际网络通信传输中的应用现状,以网络建设中的安全管理为例,对其安全保护现状以及存在的问题、解决措施等进行分析论述。     

基于统一身份认证的数据加密技术在网络安全中的应用简

随着计算机技术的不断发展,网络应用到生活中的各个方面,网络在广泛应用的同时,网络安全问题也越来越多,使得用户在网络应用中要不断的进行身份认证来保证自身数据的安全。然而重复进行身份认证过程繁琐,同时也存在数据信息泄露的安全隐患,因此,提出了统一身份的认证系统。本文主要对统一身份认证系统和数据加密技术进行介绍,并对kerboeros网络认证协议的认证过程进行探讨,旨在提高网络的安全性。     

循环经济的生态化学工程技术支撑

阐述了循环经济的工程科学内涵及循环经济的技术支撑体系,着重论述了生态化学工程对实施循环经济的技术支撑作用.     

Quantized output feedback stabilization of uncertain systems with input nonlinearities via sliding mode control

This paper is concerned with the quantized output feedback stabilization problem for a class of uncertain systems with nonsmooth nonlinearities in the actuator device via sliding mode control schemes. It is assumed that system signals are quantized before being transmitted through communication channels. First, a dynamical compensator is developed to estimate unmeasurable system state. Then a sliding surface, in the augmented space using the system output and the estimated state, is proposed, and an adaptive sliding mode control scheme with a static adjustment law of the quantization parameter is established. It is shown that the proposed quantized feedback control strategy is able to tackle parameter uncertainty, external disturbances, and nonsymmetric input nonlinearity simultaneously and guarantees the reachability of the sliding modes of the uncertain system. Finally, an example is given to verify the validity of the theoretical results. Copyright © 2012 John Wiley & Sons, Ltd.     

Asynchronous fault detection filter design approach for discrete‐time switched linear systems

This paper is concerned with the problem of the fault detection filter design for discrete‐time switched linear systems with average dwell‐time. The designed fault detection filters are also switched systems, which are assumed to be asynchronously switched with the original switched systems. Improved results on the weighted l₂ performance and the H _? performance are first given, and the multiple Lyaounov‐like functions during matched period and unmatched period for the running time of one subsystem are used. By the aid of multiple Lyapunov‐like functions combined with Projection Lemma, the FD filters are designed such that the augmented systems under asynchronous switching are exponentially stable, and the residual signal generated by the filters achieves the weighted l₂‐gain for disturbances and guarantees the H _? performance for faults. Sufficient conditions are formulated by linear matrix inequalities, and the filter gains are characterized in terms of the solution of a convex optimization problem. Finally, examples are provided to demonstrate the effectiveness of the proposed design method. Copyright © 2012 John Wiley & Sons, Ltd.     

Polyurethane‐infiltrated carbon foams: A coupling of thermal and mechanical properties

The thermal and mechanical properties of polyurethane‐infiltrated carbon foam of various densities were investigated. By combining the high thermal conductivity of the carbon foam with the mechanical toughness of the pure polyurethane, a mechanically tough composite (relative to the unfilled foam) that could be used at higher temperatures than the polyurethane's degradation was formed. Both the tensile strength and the modulus increased by an order of magnitude for the composites compared to unfilled foam, while the compressive and shear strengths and moduli of the composites approached values exhibited by pure polyurethane. At both 300 and 400°C, the rectangular blocks of pure polyurethane lost their mechanical integrity due to decomposition in air. Thermogravimetric analysis confirms substantial initial weight loss above 290°C. Filled carbon foam blocks, however, maintain their mechanical integrity at both 300 and 400°C indefinitely, although the bulk of the rectangular block mass is polyurethane. Three different carbon foam densities are examined. As expected, the higher density foams show greater heat transfer. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 87: 2348–2355, 2003     

基于Android平台的盲人手机系统设计与开发

人们生活中的绝大部分信息都是通过视觉获得的,所以盲人能够从外界获取的信息量很少,但这并不能阻止他们努力提高生活质量的渴望。智能手机的快速发展给盲人提供了前所未有的机遇。开发盲人手机具有极大的应用价值。该文主要介绍了在Android平台上设计和实现的一款盲人手机系统,该系统使用了语音识别、语音合成及Web Service等相关技术,实现了语音拨打电话、语音接听电话、语音发送短信、语音播报来电短信、语音报时、语音播报日期和语音播报天气等功能,并能在Android手机中稳定运行,方便盲人使用手机,具有较高的实用价值。