一种基于关系图的Web应用测试生成方法

Web应用的迅猛发展及其自身的复杂特性给其测试带来了一定的难度,使得传统的测试方法已不能满足需求,迫切需要新的Web测试方法和技术.定义了Web应用模式并构造其关系图以对Web应用进行建模.关系图用来建立产生路径表达式的路径生成图,继而提出一种测试路径生成方法.若提供输入值,则测试路径可以很容易地构造测试用例.为了说明问题,给出了一个简单Web登录系统作为案例.此外,根据"分而治之"的原理,当被测Web应用过于复杂时,给出了一种路径生成策略.该策略使得Web应用简单而易控制,在某种程度上限制了状态空间的爆炸.最后,从理论上阐明了本文给出方法和规则的通用性及正确性.     

场景切换视频自适应帧间码率控制

针对视频帧中可能出现的大量场景切换,提出一种基于非连接点的场景切换检测算法,提高编码性能,该场景检测算法复杂度低,在运动估计的同时,完成视频场景切换检测。场景切换将导致GOP(group of pictures)长度的变化,并可能出现GOP长度太短的情况。提出改进的自适应GOP时域滤波技术,避免由于GOP太短引起的编码性能下降。针对视频场景切换检测分割出的不同长度的GOP,提出一种基于率失真模型的帧间码率控制算法,利用视频的失真与码率及视频帧复杂度的关系,对帧间码率分配进行优化,提高重构视频帧的总质量。实验结果表明,基于场景检测的自适应帧间码率控制算法能够获得较好的编码性能。     

Unintentionally produced dioxin-like polychlorinated biphenyls during cooking

The formation and distribution of dioxin-like polychlorinated biphenyls (dl-PCBs) during cooking was investigated. Concentrations of dl-PCBs in liquid residues, cooked beef, and oil fumes generated during heating were determined by isotope dilution HRGC/HRMS. Although the levels of dl-PCBs in well-done beef were lower compared with those of raw beef, relatively high concentrations of dl-PCBs were detected in the oil fumes produced during heating. This suggests that dl-PCBs in raw beef may have volatilized into the oil fumes during the cooking process. Sucralose and chloropropanols contained in raw materials may have resulted in increased dl-PCB concentrations and the level of toxic equivalents (TEQ) in the oil fumes produced under high temperature during cooking. Concentrations of dl-PCBs did not vary greatly in cooked beef, except when higher levels of chloropropanols were presented in the uncooked raw materials. Results indicate that sucralose and chloropropanols may promote the formation of dl-PCBs during the cooking process. The newly produced dl-PCBs from raw beef cooking were mainly present in oil fumes, which gave rise to high levels of TEQ in oil fumes.     

The load-balanced multi-dimensional bin-packing problem

The bin-packing problem is one of the most investigated and applicable combinatorial optimization problems. In this paper we consider its multi-dimensional version with the practical extension of load balancing, i.e. to find the packing requiring the minimum number of bins while ensuring that the average center of mass of the loaded bins falls as close as possible to an ideal point, for instance, the center of the bin. We formally describe the problem using mixed-integer linear programming models, from the simple case where we want to optimally balance a set of items already assigned to a single bin, to the general balanced bin-packing problem. Given the difficulty for standard solvers to deal even with small size instances, a multi-level local search heuristic is presented. The algorithm takes advantage of the Fekete–Schepers representation of feasible packings in terms of particular classes of interval graphs, and iteratively improves the load balancing of a bin-packing solution using different search levels. The first level explores the space of transitive orientations of the complement graphs associated with the packing, the second modifies the structure itself of the interval graphs, the third exchanges items between bins repacking proper n-tuples of weakly balanced bins. Computational experiments show very promising results on a set of 3D bin-packing instances from the literature.     

一种基于Multisim2001的偏置共射放大电路仿真分析的教学研究

介绍了一种EDA仿真软件Multisim2001的主要功能及特点，并用该软件对分压式偏置单管共射放大电路进行了参数扫描分析，对课堂教学取得良好的教学效果。     

建立企业环境会计 树立企业环保新形象

环境会计是环境科学与会计学科交叉渗透而形成的应用型学科,是一门新兴的会计分支。本文从微观角度对建立我国企业环境会计的必要性与可能性加以论述,并在此基础上提出了相应的措施和建议。     

Does the tender,auction and listing system in land promote higher housing prices in China?

Using monthly data on national housing prices from July 1998 to June 2015, we investigate the effect of the ‘Tender, Auction and Listing’ (hereafter TAL) system on housing prices in land, implemented on 31 August 2004. We apply the additional polynomial regression discontinuity method which effectively eliminates the effects of several confounding factors such as financial crisis, ‘New National Ten Provisions’ and ‘9.30 New Regime’. We find that, although the TAL has caused the national average housing prices to go up by 10%, accounting for 11% of total increase in housing prices in the last year, it does not constitute the major driver for housing prices. Furthermore, our results indicate that TAL has exerted a larger impact on commercial and residential properties, especially in the middle and west regions. By examining the transmission mechanisms, we find that the effects of TAL are mainly via government’s starvation-style land supply effect and market-reshuffling effect.     

基于加权空间直方图的均值漂移目标跟踪

目标模型内的背景像素会造成目标跟踪定位偏差。为了减少背景像素对跟踪造成的定位偏差,首先通过目标区域像素和目标区域周围背景像素的颜色直方图定义了一个加权系数,然后将该加权系数引入到空间直方图的计算中,提出了一种基于加权空间直方图的均值漂移(MS)目标跟踪算法。在此基础上,给出了一种模型更新方法。仿真实验表明,该算法具有很好的跟踪精度,对遮挡具有更好的鲁棒性。     

Stripline bandpass filters with step-impedance resonators

Research results for stripline bandpass filters with step-impedance resonators formed on Al₂O₃ (Alumina, polycor) and operating in the frequency band 1500–2500 MHz are presented in this article. Use of step-impedance resonators breaks repetition factor in frequency positioning of passbands in such filters. This allows suppressing harmonics of output signal in transmitters and widening stopband for parasitic signals in receivers.