结构独立开放并有QoS保证的异构无线网漫游方案

未来移动通信将包含多种不同的无线网络存取技术与标准 ,移动终端如何运转在不同的无线网络系统下 ,如何使用不同的无线存取技术 ( UMTS,cdma2 0 0 0 ,GSM/GPRS,WLAN,WPAN等 ) ,这是本篇要考虑的问题。并提出了一个结构独立开放并有 Qo S保证的基于 All- IP的异构无线网漫游方案     

Inside Front Cover: Freely Suspended Layer‐by‐Layer Nanomembranes: Testing Micromechanical Properties (Adv. Funct. Mater. 5/2005)

A study of the micromechanical properties of layer‐by‐layer nanomembranes composed of a center layer of gold nanoparticles is reported by Tsukruk and co‐workers on p. 771. The micro‐ and nanomechanical properties of these membranes are measured using a combination of resonance‐frequency tests, bulging tests, and point‐load nanodeflection experiments. These freely suspended nanomembranes (right) with an elastic modulus of 5–10 GPa are very robust and can sustain multiple significant deformations (left, image obtained by B. Rybak and P. Kladitis). They are sensitive to variations in pressure and therefore have potential applications in pressure and acoustic sensors. Freely suspended nanocomposite layer‐by‐layer (LbL) nanomembranes composed of a central layer of gold nanoparticles sandwiched between polyelectrolyte multilayers are fabricated via spin‐assisted LbL assembly. The diameter of the circular membranes is varied from 150 to 600 μm and the thickness is kept within the range of 25–70 nm. The micro‐ and nanomechanical properties of these membranes are studied using a combination of resonance‐frequency and bulging tests, and point‐load nanodeflection experiments. Our results suggest that these freely suspended nanomembranes, with a Young's modulus of 5–10 GPa are very robust and can sustain multiple significant deformations. They are very sensitive to minor variations in pressure, surpassing ordinary semiconductor and metal membranes by three to four orders of magnitude and therefore have potential applications as pressure and acoustic microsensors.     

Selective Ion Transport and Complexation in Layer‐by‐Layer Assemblies of p‐Sulfonato‐ calix[n]arenes and Cationic Polyelectrolytes

The first study of ion transport across self‐assembled multilayered films of p‐sulfonato‐calix[n]arenes and poly(vinyl amine) (PVA) is presented. The films are prepared by the alternate electrostatic layer‐by‐layer assembly of the anionic calixarenes and cationic PVA on porous polyacrylonitrile (PAN) supports. We use tetra‐p‐sulfonato‐calix[4]arene (calix4), hexa‐p‐sulfonato‐calix[6]arene (calix6), and octa‐p‐sulfonato‐calix[8]arene (calix8) as the calixarenes. Ultraviolet (UV) studies indicate that dipping solutions of pH 6.8, without a supporting electrolyte, are most suited for film preparation. Calix8 is adsorbed in higher concentrations per layer than calix6 or calix4, probably because desorption is less pronounced. The permeation rates, P_Rs, of monovalent alkali‐metal chlorides (Li, Na, K, Cs), magnesium chloride, divalent transition‐metal chlorides (Ni, Cu, Zn), trivalent lanthanide chlorides (La, Ce, Pr, Sm), and sodium sulfate across the calix4/PVA, calix6/PVA, and calix8/PVA membranes are studied and compared with the corresponding P_R values across a poly(styrene sulfonate) (PSS)/PVA multilayer membrane prepared under the same conditions. The P_R values of the alkali‐metal salts are between 4 and 17 × 10^–6 cm s^–1, those of magnesium chloride and the transition‐metal salts are 0.2–1.3 × 10^–6 cm s^–1, and those of the lanthanide salts are about 0.1 × 10^–6 cm s^–1. Possible origins for the large differences are discussed. Ion transport is first of all controlled by electrostatic effects such as Donnan rejection of di‐ and trivalent ions in the membrane, but metal‐ion complexation with the calixarene derivatives also plays a role. Complexation occurs especially between Li⁺ or Na⁺ and calix4, Mg²⁺, or Cu²⁺ and calix6, Cu²⁺, Zn²⁺, or the lanthanide ions and calix8. Divalent sulfate ions are found to replace the calixarene polyanions in the membrane. UV studies of the permeate solutions indicate that calix4 especially is displaced during sulfate permeation.     

汉风唐茶赋新意 山环水绕蕴古风 “川西明珠”雅安生态绿地系统规划

中国十大魅力城市之一的雅安,拥有独特的地理环境,丰富的自然生物资源,以及厚重的历史文化,通过系统规划构筑成具有地方特色的“圈层模式”生态绿地系统。本文分析了雅安绿地布局以及景观规划,并对如何将人文历史融入于不同层面的圈层绿地系统作了进一步探讨。     

多碱光电阴极层状模型的一个证据：铯处理多碱光电阴极的附加厚度

根据多碱光电阴极制备过程中的光谱响应在０．４￣０．５μｍ之间光电流减少这一事实，分析了Ｃｓ处理多碱光电阴极的厚度。结果表明：第一次Ｃｓ处理，０．４μｍ处的光电流由６ｍＡ／Ｗ下降到３．８ｍＡ／Ｗ．第二次处理进一步降至１．６ｍＡ／Ｗ。其主要原因是Ｃｓ处理形成的Ｋ２ＣｓＳｂ具有一定厚度，光电子在运输过程中由于厚度增加导致散射几率增加，逸出几率下降，从而导致光电发射下降。在Ｓｂ、Ｃｓ交替后，计算结果表明，     

W阻挡层对Al/TiSi_2/Si接触系统热稳定性的影响

用X射线衍射及I—V测量技术研究了W在Al/TiSi_2/Si接触系统中的作用,并与不加W阻挡层的情况作了比较。热稳定性的研究表明:在高达100℃退火时,W阻挡层能够阻止Al与TiSi_2的完全反应。对Al/W/TiSi_2/Si接触二极管的I—V测试表明,在480℃以内退火,势垒高度变化不大。当退火温度达500℃时,Si通过TiSi_2层扩散至W阻挡层而使之失效.     

HART协议物理层(上)

本文描述了HART协议物理层的设备类型，配置准则，以及一些特性。     

Occurrence of aflatoxins B 1 , B 2 , G 1 and G 2 in some Brazilian pet foods

The presence of cereals and grains in the formulation of pet foods suggests the need to control aflatoxin contamination in these foods. The objective of the study was to analyse domestic pet food to determine the occurrence of aflatoxins as well as their risk to animal health. One hundred food samples (45 for dogs, 25 for cats, 30 for birds) were collected at random from pet shops in Alfenas city, south-east Brazil. Thin-layer chromatography was used for separation, identification and quantification of the compounds after validation of the method. Aflatoxins were detected in 12.0% of the samples. Levels of aflatoxins (B 1 + B 2 + G 1 + G 2 ) above the maximum limit established in Brazil (50 µg kg -1 ) for animal food were detected in five of the 12 positive samples (41.7%). The concentration of total aflatoxins was 15-374 µg kg -1 (mean 131 µg kg -1 ). All samples containing peanuts were positive for aflatoxin B 1 . Aflatoxins are carcinogenic and their consumption might be a risk for domestic animal health. The high prevalence of aflatoxin B 1 in foods prepared for birds, species highly susceptible to aflatoxins, shows the need for the re-evaluation of the use of peanuts (present in seven of the eight samples positives for aflatoxin) and/or the addition of fungicides to the food.