浅谈数字图像抠图技术

本文对Photoshop中一些常用的抠图方法进行了分析和研究，希望能为Photoshop爱好者提供一定的帮助。     

Space‐time ring‐TCM codes with CPM based on the decomposed model for transmission over Rayleigh fading channels

Space–time (ST) coding is a proved technique for achieving high data rates in 3G mobile systems that combines coding, modulation and multiple transmitters and receivers. A novel algorithm is proposed for ST ring trellis‐coded modulation (ST‐RTCM) systems with continuous‐phase modulation (CPM) when the channel coefficients are known to the receiver. This algorithm is based on the CPM decomposed model, which exploits the memory properties of this modulation method, resulting in a straightforward implementation of joint ST coding and CPM, which is particularly suitable for ring codes. This new scheme is used to investigate the performance of the delay diversity code with CPM over slow Rayleigh fading channels, in particular with MSK which is one of the most widely used modulation methods of continuous phase. Furthermore, a feedback version of delay diversity allowed by the decomposition is tested in 1REC and 1RC systems. This feedback configuration is seen to provide good results for low signal‐to‐noise ratios. Simulations results are also provided for multilevel ST‐RTCM codes that achieve a higher throughput than MSK‐coded systems. Additionally the serial concatenation of an outer Reed–Solomon code with an ST‐RTCM code is shown, this combination further reduces the error probability and achieves even more reliable communications. Copyright © 2005 John Wiley & Sons, Ltd.     

16通道声纳浮标信号接收机设计

详细介绍了基于软件无线电技术的16通道声纳浮标信号接收机的结构、组成、设计方法以及关键技术的实现。     

MIMO Channel Characterization for Short Range Fixed Wireless Propagation Environments

This paper reports results from wideband MIMO measurements performed in short range fixed wireless environments at 5.2 GHz. The objective is to provide MIMO channel characterization results for the measured environments and contribute to the limited available similar studies. Two kinds of propagation scenarios are investigated, rooftop to rooftop and street to rooftop, at three different sites always under LOS propagation conditions. The analysis of measurement data is performed in the context of non physical modeling, providing insight into the statistics of the measured channels. In particular, the slow time varying nature of the channel is studied and the narrow Doppler spectrum shape is approximated. Furthermore, frequency correlation results are obtained and the typical delay dispersion measures are extracted. Then, the antenna correlation is studied and the error of the Kronecker product approximation is evaluated. Finally, capacity results are provided and the channel measurements are characterized in terms of spatial multiplexing quality and multipath richness through condition number analysis. Nikolaos D. Skentos received his Diploma in Electrical and Computer Engineering from the National Technical University of Athens (NTUA), Greece in October 2000. Since January 2001 he has been a research associate at the Mobile Radio Communications Laboratory at the NTUA, and he is currently working towards the Ph.D. degree. His research interests include channel measurements, MIMO channel characterization, MIMO algorithms and space time processing. He has been active in the IST STINGRAY project, the COST 273 Action and the ACE Network of Excellence. He is also a member of the National Technical Chamber of Greece since 2001. Athanasios G. Kanatas received the Diploma in Electrical Engineering from the National Technical University of Athens, Greece, in 1991, the M.Sc. degree in Satellite Communication Engineering from the University of Surrey, Surrey, UK in 1992, and the Ph.D. degree in Mobile Satellite Communications from the National Technical University of Athens, Greece in February 1997. From 1993 to 1994 he was with National Documentation Center of National Research Institute. In 1995 he joined SPACETEC Ltd. where he was Technical Project Manager for VISA/EMEA VSAT Project in Greece. In 1996 he joined the Mobile Radio Communications Laboratory as a research associate. From 1999 to 2002 he was with the Institute of Communication & Computer Systems. In 2000 he became a member of the Board of Directors of OTESAT S.A. He is an Assistant Professor in the Department of Technology Education and Digital Systems at University of Piraeus. His current research interests include channel characterization and estimation, simulation and modeling for mobile, mobile satellite, and future wireless communication systems. He has been a Senior Member of IEEE since 2002, and is also a member of the Technical Chamber of Greece. In 1999 he was elected Chairman of the Communications Society of the Greek IEEE Section. Panagiotis I. Dallas was born 1967 in Thessaloniki, Greece. He obtained his diploma and Ph.D. degree from the Electrical and Computer Engineering Department of Aristotle University of Thessaloniki, Greece, in 1990 and 1997, respectively. Since 1998 he joined with INTRACOM where he currently is Section Manager of Advanced Communications Technologies branch of Emerging Technologies & Markets department, leading the next generation of broadband wireless access systems for internal and EU projects. He runs the relevant standardization activities (IEEE 802.16 and ETSI/BRAN HIPERMAN) in INTRACOM and he represents the company in WiMAX forum. Finally, he has over 30 publications in international journals and conferences. Philip Constantinou received the Diploma in Physics from the National University of Athens in 1972, the Master of Applied Science in Electrical Engineering from the University of Ottawa, Ontario, Canada in 1976, and the Ph.D. degree in Electrical Engineering in 1983 from Carleton University, Ottawa, Ontario, Canada. From 1976 to 1979 he was with Telesat Canada as a Communications System Engineer. In 1980 he joined the Ministry of Communications in Ottawa, Canada where he was engaged in the area of Mobile Communication. From 1984 to 1989 he was with the National Research Center Demokritos in Athens, Greece where he was involved in several research projects in the area of Mobile Communications. In 1989 he joined the National Technical University of Athens where he is currently a Professor and Director of the Mobile Radio Communications Laboratory. His current research interests include Personal Communications, Mobile Satellite Communications, and Interference Problems on Digital Communications Systems.     

Scour Downstream of an Apron Due to Submerged Horizontal Jets

The results of an experimental investigation on scour of noncohesive sediment beds (uniform and nonuniform sediments) downstream of an apron due to a submerged horizontal jet issuing from a sluice opening are presented. Attempts are made to explain the similarity existing in the scour process and profiles (including dune in the downstream of the scour hole). The scour profiles at different times follow a particular geometrical similarity and can be expressed by the combination of two polynomials. Using experimental scour depth at different times, the time variation of scour depth is scaled by an exponential law, where time scale increases linearly with densimetric Froude number. The equilibrium scour depth, related to the sediment size relative to the sluice opening, decreases with increase in sediment size and sluice opening. On the other hand, the equilibrium scour depth increases with increase in densimetric Froude number. The variation of equilibrium scour depth with tailwater depth indicates a critical tailwater depth corresponding to a minimum equilibrium scour depth. The effect of sediment gradation on scour depth is pronounced for nonuniform sediments, which reduce scour depth significantly due to formation of an armor layer, and therefore prompted study of the reduction of scour depth by a launching apron placed downstream of the rigid apron. The results show that the average reduction of scour depth by placing a launching apron was 39%, having a maximum of 57.3% and a minimum of 16.2%. The characteristic parameters affecting maximum equilibrium scour depth are identified based on the physical reasoning and dimensional analysis. Equation of maximum equilibrium scour depth obtained empirically agrees well with the experimental data.     

长江中下游鹅头型分汊河道的演变特征及形成条件

本文对长江中下游鹅头型分汊河道的形态特征进行了描述了对其演变及成因进行了分析，最后对治理措施提出了建议。     

Effects of stagnant and dispersion conductivities on non-darcian forced convection in square Packed-Sphere channels

This paper presents a numerical and experimental investigation of the effects of stagnant and dispersion conductivities on non-Darcian forced convection in square packed-sphere channels. The theoretical prediction of Nusselt number are found to be in good agreement with the experimental data. A larger near-wall damping of stagnant conductivity is found for the present water-steel medium than for that described by the mixing rule based on the volume fraction. A nonlinear Peclet number dependence, Pe^λ and λ = 0,88, for dispersion conductivity is found to induce better agreement between the theoretical and experimental results especially for the cases of high Peclet number and high D_c/d.     

Micromixers to produce cosmetic emulsions

In the cosmetics industry, emulsions play a key-role in active solubilization and texture/efficacy optimization. However, depending on their physico-chemical properties, the active ingredients are often more stable in a single phase: for example, Vitamin A is more stable in an oily phase than in a water phase. We have developed a special mixing device which produces an emulsion in the body of the pump, immediately before application on the skin. The mixing unit consists of two silicon chips. Each chip has several Y-shaped microchannels and intersections etched on its upper surface. When the two etched surfaces are bonded together, they produce series of interconnecting micromixing elements which permit the repeat mixing of the two phases, thus producing an extremely homogenous emulsion. These micromixers require carefully designed formulae in which the physico-chemical properties of each raw material are essential to obtain a spontaneous emulsion. This device has been incorporated into a spray pack and optimized to deliver the spontaneous emulsion when finger pressure is applied.     

探索有效的培训方式,促进企业发展

通过培训达到提高职工队伍整体素质的目的,采用的培训形式有两种,一是因地制宜,立足企业内部力量进行培训;二是突出重点,"走出去,请进来",拓宽培训渠道.     

Resilient-optimal interactive consistency in constant time

For a complete network of n processors within which communication lines are private, we show how to achieve concurrently many Byzantine Agreements within constant expected time both on synchronous and asynchronous networks. As an immediate consequence, this provides a solution to the Interactive Consistency problem. Our algorithms tolerate up to (n-1)/3 faulty processors in both the synchronous and asynchronous cases and are therefore resilient-optimal. In terms of time complexity, our results improve a time bound of (for n concurrent agreements) which is immediately implied by the constant expected time Byzantine Agreement of Feldman and Micali (synchronous systems) and of Canetti and Rabin (asynchronous systems). In terms of resiliency, our results improve the resiliency bound of the constant time, -resilient algorithm of Ben-Or. An immediate application of our protocols is a constant expected time simulation of simultaneous broadcast channels over a network with private lines.Received: April 2001, Accepted: September 2002, Michael Ben-Or: Research supported by Israel Academy of Sciences and by United States - Israel Binational Science Foundation grant BSF-87-00082