一体化的信号源分析仪

与美国同行争分夺秒抢占市场先机不同,欧洲测量仪器厂商Rohde&Schwarz公司的产品策略则相对稳健,他们的产品更专注于功能的多样化     

Personal Trusted Devices for Web Services: Revisiting Multilevel Security

In this paper we revisit the concept of mandatory access control and investigate its potential with personal digital assistants (PDA). Only if applications are clearly separated and Trojans cannot leak personal information can these PDAs become personal trusted devices. Limited processing power and memory can be overcome by using Web services instead of full-fledged applications – a trend also in non-mobile computing. Web services, however, introduce additional security risks, some of them specific for mobile users. We propose an identification scheme that can be effectively used to protect privacy and show how this system builds upon a light-weight version of mandatory access control.     

Covalent Adaptable Microstructures via Combining Two-Photon Laser Printing and Alkoxyamine Chemistry: Toward Living 3D Microstructures

Manufacturing programmable materials, whose mechanical properties can be adapted on demand, is highly desired for their application in areas ranging from robotics, to biomedicine, or microfluidics. Herein, the inclusion of dynamic and living bonds, such as alkoxyamines, in a printable formulation suitable for two-photon 3D laser printing is exploited. On one hand, taking advantage of the dynamic covalent character of alkoxyamines, the nitroxide exchange reaction is investigated. As a consequence, a reduction of the Young´s Modulus by 50%, is measured by nanoindentation. On the other hand, due to its “living” characteristic, the chain extension becomes possible via nitroxide mediated polymerization. In particular, living nitroxide mediated polymerization of styrene results not only in a dramatic increase of the volume (≈8 times) of the 3D printed microstructure but also an increase of the Young's Modulus by two orders of magnitude (from 14 MPa to 2.7 GPa), while maintaining the shape including fine structural details. Thus, the approach introduces a new dimension by enabling to create microstructures with dynamically tunable size and mechanical properties.     

Reliability of a two-way circular consecutively connected system with multistate components

A two-way circular consecutively connected system with multistate components (two-way circular CCSMC) consists of n cyclically ordered components e₁,…,e_n, i.e. e_i+1, succeeds e₁, iε«ng l, …, n − 1ång;, e, succeeds e_n- Each component is capable of sending a signal in left-hand and right-hand directions. All components operate independently. The whole system is functioning if both left-hand and right-hand signals are received by each component. A recursive procedure evaluating the reliability of a two-way circular CCSMC is presented.     

A parallel algorithm evaluating the reliability of a system with known minimal cuts (paths)

A system with known minimal cuts is considered. In order to compute its reliability a binary tree is constructed with nodes being assigned numerical values. The value of each non-leaf node is a linear combination of its child nodes' values. The values of leaf nodes can be computed in a very simple way. The value of the root node is the system's reliability. The presented method is a memory saving one. Moreover, it is possible to apply parallel computation to the nodes located on the same level, which may significantly reduce the computing time.     

Single and multiple satellite visibility statistics of first-generation non-GEO constellations for personal communications

The first generation of global satellite systems for personal and mobile communications is preparing to start commercial services. Service quality and availability are paramount to the user's acceptance of the service. For satellite systems, service quality and availability build up from satellite visibility, propagation conditions and equipment availability. This paper discusses the impact of elevation angle on visibility and propagation, that of azimuth separation between visible satellites, and compares multiple visibility statistics of all first-generation non-geostationary communications systems, namely Iridium, Globalstar, ICO, Ellipso and ECCO. © 1998 John Wiley & Sons, Ltd.     

Capacitively coupled transmission line pulsing cc-TLP––a traceable and reproducible stress method in the CDM-domain

This paper describes a new test method called capacitively coupled transmission line pulsing cc-TLP. It is applied to different test circuits which were mounted on specially designed package emulators with a defined background capacitance. The test results are compared with the ESD thresholds obtained by CDM tests. The cc-TLP results correlate well with the CDM data.     

ATM‐based wireless broadband access in the local loop

Broadband networks using wireless transmission techniques are a quick and flexible means of implementing subscriber access. Unoccupied frequency bands with sufficient bandwidth to allow the transmission of digital signals at very high bit rates are found only in the microwave bands. Because the path loss is fairly high at these frequencies, the diameter of radio cells is limited to a maximum of a few kilometres. This results in a microcellular system, which is best implemented in the form of a point‐to‐multipoint system, where one radio‐base station serves all subscribers registered in that radio cell. An interactive, broadband, ATM‐based radio local loop has undergone successful trials in Munich. Copyright © 2001 John Wiley & Sons, Ltd.     

Advanced IX projection photolithography

Pattern techniques in the semiconductor industry are driven by the need to improve cost/performance per bit. The key to reducing cost per bit and improving performance is increased density. Tighter photolithography ground rules (smaller images with reduced line width and registration tolerances) are primary sources of increased density. Enhanced ground rules coupled with larger wafers are certain to form the basis for the next generation of VLSI chips. The trend toward tighter ground rules and larger wafers is causing many semiconductor manufacturers to migrate away from IX projection tools, the workhorses of present-day production lines, to step and repeat exposure tools. The higher numerical aperture of step and repeat tools, coupled with chip-by-chip focus, guarantees improved resolution compared to today’s IX projection tools. The price paid for increased numerical aperture is reduced field size and, subsequently, reduced throughput and higher exposure cost per wafer. Ideally, it would be preferable to improve the resolution of the IX projection tool/process to make it competitive with the step and repeat tool, while maintaining the high throughput of IX systems. Effective use of shorter exposure (< 350 nm) wavelengths in IX systems is the key to extending resolution capability.     

Lyso platelet activating factor (LysoPAF) and its enantiomer. Total synthesis and carbon-13 NMR spectroscopy

Described is a reaction sequence for the total synthesis of lyso platelet activating factor (lysoPAF; 1-O-alkyl-sn-glycero-3-phosphocholine) and its enantiomer. The procedure is versatile and yields optically pure isomers of defined chain length. The synthesis is equally suited for the preparation of lysoPAF analogues and its enantiomers with unsaturation in the long aliphatic chain. First,rac-1(3)-O-alkylglycerol is prepared by alkylation ofrac-isopropylideneglycerol with alkyl methanesulfonate followed by acid-catalyzed removal of the ketal group. The primary hydroxy group of alkylglycerol is then protected by tritylation, the secondary hydroxy group is acylated, and the protective trityl group is removed under mild acidic conditions with boric acid on silicic acid, essentially without acyl migration. Condensation of the diradylglycerol with bromoethyl dichlorophosphate in diethyl ether, hydrolysis of the resulting chloride, and nucleophilic displacement of the bromine with trimethylamine givesrac-1-O-alkyl-2-acylglycero-3-phosphocholine in good overall yield. The racemic alkylacylglycerophosphocholine is finally treated with snake venom phospholipase A₂ (Ophiophagus hannah) which affords 1-O-alkyl-sn-glycero-3-phosphocholine (lysoPAF) of natural configuration in optically pure form. The “unnatural” 3-O-alkyl-2-O-acyl-sn-glycerol-1-phosphocholine enantiomer, which is not susceptible to phospholipase A₂ cleavage, gives 3-O-alkyl-sn-glycero-1-phosphocholine upon deacylation with methanolic sodium hydroxide. Homogeneity and structure of the intermediates and final products were ascertained by carbon-13 nuclear magnetic resonance spectroscopy on monomeric solutions.