Risk-based grouping for checked baggage screening systems

With millions of bags checked at over 7000 baggage screening locations in US daily, the checked baggage screening system may be exploited by the terrorists to do harm to the homeland security. Due to such a huge amount of luggage, how to improve the effectiveness and efficiency of the screening system becomes a challenging task. In this paper, we propose a risk-based cost-effectiveness model where checked bags are classified into several risk classes according to their risk characteristics. According to their risk levels, bags from different classes may go through different device combinations sequentially. For a multiple-device screening system, we determine the optimal sequence of the screening devices and the separate grouping strategies for bags from different risk classes with the objective of minimizing the expected cost per bag. Based on a detailed numerical study, we compare our model with three other cost-effectiveness models (the first model assumes that there is only one risk class, the second model assumes that there is only one group for each risk class, and the third model assumes that all devices in a device combination need to be gone through). Our major conclusions are that our proposed model is beneficial compared with other three models and moreover, the relative benefit becomes larger when the authority commands a stricter upper bound for the probability of false clear.     

Materials applications of photoelectron emission microscopy

Photoelectron emission microscopy (PEEM) is a versatile technique that can image a variety of materials including metals, semiconductors and even insulators. Under favorable conditions the most advanced aberration corrected instruments have a spatial resolution approaching 2 nm. Although PEEM cannot compete with transmission or scanning electron microscopies for ultimate resolution, the technique is much gentler and has the unique advantage of imaging structure as well as electronic and magnetic states on the nanoscale. Since the image contrast is derived from spatial variations in electron photoemission intensity, PEEM is ideal for interrogating both static and dynamic electronic properties of complex nanostructured materials. Here, we review the key principles and contrast mechanisms of PEEM and briefly summarize materials applications of PEEM.     

Reinforced Wool Keratin Fibers via Dithiol Chain Re-bonding

Regenerated wool keratin fibers (RWKFs) have heretofore attracted tremendous interest according to environmental friendliness, ample resource, and intrinsic biocompatibility for broad applications. In this realm, both uncontrollable keratin fibril assembly procedure and resultant insufficient mechanical strength, have greatly hindered their large-scale manufacture and commercial viability. Herein, a continuous wet-spinning strategy is put forward to rebuild wool keratin into compact regenerated bio-fibers with improved strength via disulfide re-bonding. Dithiothreitol (DTT) has been introduced to renovate disulfide linkage inside keratin polypeptide chains, and bridge keratin fibrils via covalent thiol bonding to form a continuous backbone as mechanical support. A thus-derived RWKF manifests a tensile strength of 186.1 ± 7.0 MPa and Young's modulus of 7.4 ± 0.2 GPa, which exceeds those of natural wool, feathers, and regenerated wool or feather keratin fibers. The detailed wet-spinning technical parameters, such as coagulation, oxidation, and post-treatment, have been systematically optimized to guarantee the continuous preparation of high-strength regenerated keratin fibers. This work offers insight into solving the concurrent challenges for continuous manufacture of regenerated protein fibers and sustainability concerns about biomass waste.     

基于语音控制的舞蹈机器人的设计与制作

本文主要介绍了基于语音控制的舞蹈机器人的设计与制作过程。通过对舞蹈机器人机械、电气和程序的设计与实现,使机器人完成优美的舞蹈动作。行走电机采用继电器控制,以AT89S51单片机为中央处理器,实现各种舞蹈动作,采用语音识别技术实现语音控制。     

Improved low-distortion sigma-delta ADC with DWA for WLAN standards

An improved low distortion sigma-delta ADC(analog-to-digital converter) for wireless local area network standards is presented.A feed-forward MASH 2-2 multi-bit cascaded sigma-delta ADC is adopted;however,this work shows a much better performance than the ADCs which have been presented to date by adding a feedback factor in the second stage to improve the performance of the in-band SNDR(signal to noise and distortion ratio),using 4-bit ADCs in both stages to minimize the quantization noise.Data weighted ...     

A 2.4GHz Quadrature Output Frequency Synthesizer

A design and implementation for a 2.4GHz quadrature output frequency synthesizer intended for bluetooth in 0.35μm CMOS technology are presented.A differentially controlled quadrature voltage-controlled oscillator (QVCO) is employed to generate quadrature (I/Q) signals.A second-order loop filter,with a unit gain transconductance amplifier having the performance of a third-order loop filter,is exploited for low cost.The measured spot phase noise is –106.15dBc/Hz@1MHz.Close-in phase noise is less than -70dBc/Hz.The synthesizer consumes 13.5mA under a 3.3V voltage supply.The core size is 1.3mm×0.8mm.     

编队电子战信息融合仿真系统设计

根据编队电子战系统信息融合的特点,构造信息融合仿真系统结构,阐述了编队电子战系统多源信息融合方法和策略．提出了信息融合评估的数学模型以及编队电子战系统信息融合需重点解决的问题。     

The L(2,1)-labeling and operations of graphs

Motivated by a variation of the channel assignment problem, a graph labeling analogous to the graph vertex coloring has been presented and is called an L(2,1)-labeling. More precisely, an L(2,1)-labeling of a graph G is a function f from the vertex set V(G) to the set of all nonnegative integers such that |f(x)-f(y)| /spl ges/ 2 if d(x,y)=1 and |f(x)-f(y)| /spl ges/ 1 if d(x,y) = 2. The L(2,1)-labeling number /spl lambda/(G) of G is the smallest number k such that G has an L(2,1)-labeling with max{f(v):v/spl isin/V(G)}=k. A conjecture states that /spl lambda/(G) /spl les/ /spl Delta//sup 2/ for any simple graph with the maximum degree /spl Delta//spl ges/2. This paper considers the graphs formed by the Cartesian product and the composition of two graphs. The new graph satisfies the conjecture above in both cases(with minor exceptions).     

侧墙技术在相变存储器中的应用

从相变存储器(phase change random access memory,PCRAM)的基本结构和工作原理出发,首先介绍了PCRAM的技术优势、面临的技术挑战、常用的解决策略以及存在的相应问题;接着阐述了在微电子加工中广泛应用的关键工艺——侧墙技术,并将其在PCRAM中的应用成果进行了分类;然后从加热电极的制备、相变材料限制结构的制备、新相变材料的制备与表征和器件间互联等4个方面展开叙述;最后展望了该技术在相变存储领域应用发展的趋势。侧墙技术因其具备自对准的特点,制备工艺可控性好,制备精度不依赖于光刻精度,在纳米技术飞速发展的今天,侧墙技术将会在更高精度上发挥其作用。     

Design and Implementation of VW550 Multi-video Display System

提出了一种VW550多路图像集成显示系统的硬件、软件设计方案,以及在基于DLP或者LCD的拼接大屏幕显示系统中的应用方法.本应用系统基于Altera公司的SoPC技术,采用大规模FPGA作为多路图像集成显示处理系统的控制核心.该处理系统由主控板卡、视频矩阵板卡、VGA矩阵板卡组成,详细介绍了多块板卡的组成结构与工作原理,并针对基于硬件描述语言设计实现的PCI适配协议进行了分析.系统硬件设计简洁、软件可扩展性好,实验部分给出了完整的硬件平台和拼接屏幕控制效果.