The hot blow forming of AZ31 Mg sheet: Formability assessment and application development

The hot blow forming of magnesium sheet offers significant opportunity for forming complex, lightweight parts for automotive applications. This paper characterizes the elevated-temperature formability of AZ31 magnesium sheet materials and the effect of processing conditions on the performance of these materials. In addition, magnesium sheet application development at General Motors Corporation is reviewed.     

Simulation of Strength Distribution in Ground Ceramics by Incorporating Residual Stress Effect

Strength of ground ceramics may be affected by residual stress as well as surface flaws induced by grinding. Strength prediction for ground ceramics is convenient for mechanical design of ceramic components. In this article, a numerical procedure based on fracture mechanics was proposed to estimate strength distribution of ground ceramics by considering grinding-induced residual stress. Bending strength and residual stress of ground ceramics were measured for three grinding-conditions. By comparison of simulated results with experimental ones, it was revealed that strength characteristics in experiments were well simulated by using the proposed procedure.     

Cholesterol‐imprinted polymer receptor prepared by a hybrid imprinting method

A novel cholesterol‐imprinted polymer (CMIP‐H) was prepared by a hybrid method of covalent imprinting and non‐covalent imprinting. This approach involves the copolymerization of a template‐containing monomer, cholesteryl 2‐hydroxyethyl methacrylate carbonate, and a cross‐linker, followed by hydrolysis to afford a flexible guest‐binding site accompanied with the easy and efficient removal of a ‘sacrificial spacer’. The effect of solvent on the binding capacity of CMIP‐H towards cholesterol was studied, indicating that a good binding capacity towards cholesterol could be achieved in a less‐polar solvent. The binding experiments of CMIP‐H towards a series of structural analogues of cholesterol, including cholesterol acetate, progesterone and stigmasterol, were carried out in hexane. The results showed that CMIP‐H almost did not bind cholesterol acetate at all because the hydrogen‐bonding site is blocked. It exhibited a similar binding towards both cholesterol and stigmasterol, but much higher binding towards progesterone. Copyright © 2005 Society of Chemical Industry     

即时通讯软件的安全性分析

在互联网服务中,即时通讯已成为了最流行的服务模式之一,人们对即时通讯的依赖程度也与日俱增。但是, 频频出现的病毒和黑客攻击使广大用户深受其害,即时通讯的安全问题也日益严峻。为了从根本上解决问题,本文对即时通讯软件的架构和协议进行了深入分析,目的是找出漏洞根源,给开发者和使用者提供防止漏洞的依据。     

Broad-band MMICs based on modified loss-compensation method using 0.35-/spl mu/m SiGe BiCMOS technology

Using the concept of loss compensation, novel broad-band monolithic microwave integrated circuits (MMICs), including an amplifier and an analog multiplier/mixer, with LC ladder matching networks in a commercial 0.35-mum SiGe BiCMOS technology are demonstrated for the first time. An HBT two-stage cascade single-stage distributed amplifier (2-CSSDA) using the modified loss-compensation technique is presented. It demonstrates a small-signal gain of better than 15 dB from dc to 28 GHz (gain-bandwidth product=157 GHz) with a low power consumption of 48 mW and a miniature chip size of 0.63 mm² including testing pads. The gain-bandwidth product of the modified loss-compensated CSSDA is improved approximately 68% compared with the conventional attenuation-compensation technique. The wide-band amplifier achieves a high gain-bandwidth product with the lowest power consumption and smallest chip size. The broad-band mixer designed using a Gilbert cell with the modified loss-compensation technique achieves a measured power conversion gain of 19 dB with a 3-dB bandwidth from 0.1 to 23 GHz, which is the highest gain-bandwidth product of operation among previously reported MMIC mixers. As an analog multiplier, the measured sensitivity is better than 3000 V/W from 0.1 to 25 GHz, and the measured low-frequency noise floor and corner frequency can be estimated to be 20 nV/sqrt(Hz) and 1.2 kHz, respectively. The mixer performance represents state-of-the-art result of the MMIC broad-band mixers using commercial silicon-based technologies     

Synthesis,characterization and ion exchange properties of zirconium(IV) tungstoiodophosphate,a new cation exchanger

Zirconium(IV) tungstoiodophosphate has been synthesized under a variety of conditions. The most chemically and thermally stable sample is prepared by adding a mixture of aqueous solutions of 0·5 mol L⁻¹ sodium tungstate, potassium iodate and 1 mol L⁻¹ orthophosphoric acid to aqueous solution of 0·1 mol L⁻¹ zirconium(IV) oxychloride. Its ion exchange capacity for Na⁺ and K⁺ was found to be 2·20 and 2·35 meq g⁻¹ dry exchanger, respectively. The material has been characterized on the basis of chemical composition, pH titration, Fourier transform infrared spectroscopy (FTIR) and thermogravimetric analysis. The effect on the exchange capacity of drying the exchanger at different temperatures has been studied. The analytical importance of the material has been established by quantitative separation of Pb²⁺ from other metal ions.     

Viable：设计折射生活体验

从上个世纪九十年代中期开始，无定型的造型在设计中占据了主导。十年之后，人们的审美和设计标准发生了变化。几何原理的广泛应用使得生活物品的设计出现了“硬边”（产品的棱线和轮廓）与“精确”之风的回潮。也许是人们渴望在这个不稳定的世界中寻求稳定的元素，也许是为了用简单直白的设计来掩饰以往设计中复杂计算的造型。总之，设计师对成熟稳重的几何形式表现得情有独钟。这种席卷而来的感觉体现了一种设计的成熟，而Viable工作室的设计就是其中的代表；不仅如此，他们的设计还反映出了每个人对生活的不同理解。[编者按]     

A One-Dimensional Nonlocal Damage-Plasticity Model for Ductile Materials

This paper presents a new 1-D non-local damage-plasticity deformation model for ductile materials. It uses the thermodynamic framework described in Houlsby and Puzrin (2000) and holds, nevertheless, some similarities with Lemaitre’s (1971) approach. A 1D finite element (FE) model of a bar fixed at one end and loaded in tension at the other end is introduced. This simple model demonstrates how the approach can be implemented within the finite element framework, and that it is capable of capturing both the pre-peak hardening and post-peak softening (generally responsible for models instability) due to damage-induced stiffness and strength reduction characteristic of ductile materials. It is also shown that the approach has further advantages of achieving some degree of mesh independence, and of being able to capture deformation size effects. Finally, it is illustrated how the model permits the calculation of essential work of rupture (EWR), i.e. the specific energy per unit cross-sectional area that is needed to cause tensile failure of a specimen.     

Effects of contact shape on biological wet adhesion

Wet adhesion is widely adopted in biological adhesion systems in nature. Wet adhesion is studied in this paper with the focus on the effect of different contact shapes (flat, concave, convex, and ring-like) on the adhesion force. The evolution of the liquid bridge between a fiber tip and substrate during the detaching process shows two transition points. The first transition from the radius-controlled to the contact-angle controlled process is critical to influence the strength and robustness of adhesion. We show that a concave shape is more effective than a flat one, while a convex shape has no advantage. A ring-like contact shape has advantages in a hydrophobic environment and on a rough surface.     

Dielectric behavior of Cu–GeO<Subscript>2</Subscript> cermet thin films

Capacitance and dielectric loss measurements were carried out using an Al/Cu–GeO₂/Al sandwich structure for 0 to 10 vol% Cu films, 120–400 nm thick, deposited at 0.4–1.5 nm/s in the frequency and temperature range 1–10⁶ Hz and 90–573 K, respectively. The variation of capacitance and dielectric loss with frequency and temperature follows the Goswami and Goswami model. Capacitance decreases slowly with increasing thickness and also varies with the change in deposition rate of the cermet film.