一个新的具有指定接收者(t,n)门限签名加密方案

提出了一个具有指定接收考验证的签名加密方案。该方案是数字签名与公钥密码体制的有机集成。与普通数字签名方案相比，除了具有认证性、数据完整性外还具有保密性和接收方的隐私性。然后又利用门限方案首次构造了一个（t,n)门限签名加密方案。该(t,n)门限签名方案具有数据传输安全、顽健性、通信代价更小、执行效率更高等特点。     

Contribution of Lactobacillus plantarum and Leuconostoc mesenteroides subsp. mesenteroides to Atypical Odors of Beef Strip Loins

Sterile beef strip loin tissue was inoculated with Lactobacillus plantarum or Leuconostoc mesenteroides subsp. mesenteroides, placed in sterile sample bottles which were purged with CO₂, and stored up to 28 days at 3°C. Volatile compounds detected in the headspace of these samples included acetone, toluene, acetic acid, ethyl acetate, a C₇ hydrocarbon, and trichloromethane. The profile of volatiles in packaged sterile loin tissue stored for up to 28 days was similar. However, the inoculated samples spoiled (soured) at a faster rate.     

Physical, Chemical and Sensory Changes in Irradiated Fresh Pork Packaged in Modified Atmosphere

The effects of irradiation dose (0, 0.5 and 1.0 kGy), headspace oxygen (0, 10 and 20% O₂, balance nitrogen) and storage temperature (5, 15 and 25°C) on the physical, chemical and sensory changes in fresh pork were studied using factorial design experiments. Irradiation in the absence of oxygen extended the sensory shelf life of pork from 9 to 26 days at 5°C and from & lt; 2 to 2 days at 25°C. Oxygen in the package headspace combined with irradiation adversely affected physical, chemical and sensory characteristics of the end product.     

基于模糊度测度和改进遗传算法的图像分割

为了利用模糊集理论进行图像分割,本文提出了一种模糊度测度函数,它衡量了背景模糊集和某一个二值图像的相似性:模糊度越小,这种相似程度越大;并且对模糊度的计算只需要进行简单的比较运算和加法运算,便于硬件实现。本文利用遗传算法求取最佳阈值,针对遗传算法的某些不足之处.我们利用精英策略和模拟退火的思想,对其做了一些修正。实验结果表明:相对于Shannon熵方法和模糊熵方法,本文方法取得了较好的分割结果,并且具有较强的抗噪声能力。     

Age effects in coding tasks: Componential analysis and test of the sensory deficit hypothesis.

Multiple forms of a symbol-digit substitution task were used to provide a componential analysis of age differences in coding task performance. The results demonstrated age differences in feature encoding, memory, and visual search. A 2nd experiment was conducted with young adults to investigate a sensory deficit as a locus of age differences. The spatial contrast sensitivity deficit of older adults was simulated on forms by applying a digital filter. Persons in the age-simulated contrast condition performed worse than those in the normal contrast condition. The stimulus degradation effect was linked to visual search speed. The study illustrates the utility of componential analysis and offers direct support for the hypothesis that sensory deficits affect performance on tasks used to assess intelligence (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

汽车侧倾稳定性的动态仿真(一) --数学模型的建立

本文通过对独立悬架和非独立悬架侧倾运动特性的分析并结合采用已有的轮胎力学模型，建立了反映独立悬架和非独立悬架侧倾运动特性的数学模型。在此基础上，根据汽车侧倾时悬挂质量对前后悬架的力和力矩作用来组合前后悬架，我们得到了双轴汽车在稳态转向时侧倾运动的数学模型。通过组合不同的前后悬架，这个数学模型可以反映各种悬架配置的双轴汽车。它主要是针对汽车进行稳态转向时的侧倾情况，考虑了汽车的结构参数、惯性参数以及悬架、轮胎的柔性形变对汽车侧倾运动特性和抗侧翻能力的影响。它可以用来计算一定横向加速度下汽车的侧倾反应和轮胎的载荷变化，也可以用来计算一辆确定的汽车在保持侧倾稳定性的前提下所能达到的最大横向加速度，还可以用来分析各项参数对汽车侧倾稳定性的影响。     

Influence of polymer modulus on the percolation threshold of latex-based composites

Monodispersed copolymer emulsions with different glass transition temperatures were synthesized to investigate the effect of room temperature polymer matrix modulus on the electrical properties of carbon black (CB) filled segregated network composites. The emulsion with the highest modulus at room temperature produced composites with the lowest percolation threshold. The threshold for a composite made from a copolymer latex containing an equal ratio of butyl acrylate and methyl methacrylate (BA5) is 1.5 vol%, while the percolation threshold for the much lower modulus BA7 (7:3 BA/MMA ratio) is 4.93 vol%. The microstructure of each composite shows significant differences in the level of CB dispersion within the polymer matrix. Higher modulus polymer particles push the CB more efficiently into the interstitial space between them, resulting in a lower percolation threshold. This modulus effect was confirmed by increasing the drying temperature, where the moduli of latexes (BA5, BA5.5, and BA6) were more similar and the percolation thresholds for three composites also become closer to one another.     

Empirical assessment of a threshold model for sylvatic plague.

Plague surveillance programmes established in Kazakhstan, Central Asia, during the previous century, have generated large plague archives that have been used to parameterize an abundance threshold model for sylvatic plague in great gerbil (Rhombomys opimus) populations. Here, we assess the model using additional data from the same archives. Throughout the focus, population levels above the threshold were a necessary condition for an epizootic to occur. However, there were large numbers of occasions when an epizootic was not observed even though great gerbils were, and had been, abundant. We examine six hypotheses that could explain the resulting false positive predictions, namely (i) including end-of-outbreak data erroneously lowers the estimated threshold, (ii) too few gerbils were tested, (iii) plague becomes locally extinct, (iv) the abundance of fleas was too low, (v) the climate was unfavourable, and (vi) a high proportion of gerbils were resistant. Of these, separate thresholds, fleas and climate received some support but accounted for few false positives and can be disregarded as serious omissions from the model. Small sample size and local extinction received strong support and can account for most of the false positives. Host resistance received no support here but should be subject to more direct experimental testing.     

Improvement on threshold proxy signcryption scheme

Signcryption is a public key or asymmetric cryptographic method that provides simultaneously both message confidentiality and integrity at a lower computational and communication cost. This paper presents a （t, n） threshold proxy signcryption scheme in which no less than t proxy agents in the proxy group can produce the signcryption cryptogram. combines the functionality of threshold proxy signing and encryption. The proposed scheme combines the functionality of both threshold proxy signing and encryption, and provides fair protection for the sender and the proxy agents. This scheme is secure against attack of public key substitution. It also satisfies security properties such as confidentiality and authenticity.