Maximal contractions in Boolean algebras

In the present paper,the concepts of deductive element and maximal contraction are introduced in Boolean algebras,and corresponding theories of consistency and maximal contractions are studied.An algorithm principle is proposed to compute all maximal contractions for a consistent set with respect to its refutation in Boolean algebras.It is pointed out that the quotient algebra of the first-order language with respect to its provable equivalence relation constitutes a Boolean algebra,and hence the computation of R-contractions for closed formulas in first-order languages can be converted into the one in Boolean algebras proposed in this paper.Furthermore,the concept of basic element is introduced in Boolean algebras,which contributes to the definitions of clause and Horn clause transplanted from logic to a special type of Boolean algebras generated by basic elements.It is also pointed out that the computation of R-contractions for clauses in the classical propositional logic can be converted into the one in Boolean algebras generated by basic elements proposed in this paper.     

Probabilistic analysis on mesh network fault tolerance

Mesh networks are among the most important interconnection network topologies for large multicomputer systems. Mesh networks perform poorly in tolerating faults in the view of worst-case analysis. On the other hand, such worst cases occur very rarely in realistic situations. In this paper, we study the fault tolerance of 2-D and 3-D mesh networks under a more realistic model in which each network node has an independent failure probability. We first observe that if the node failure probability is fixed, then the connectivity probability of these mesh networks can be arbitrarily small when the network size is sufficiently large. Thus, it is practically important for multicomputer system manufacture to determine the upper bound for node failure probability when the probability of network connectivity and the network size are given. We develop a novel technique to formally derive lower bounds on the connectivity probability for 2-D and 3-D mesh networks. Our study shows that these mesh networks of practical size can tolerate a large number of faulty nodes thus are reliable enough for multicomputer systems. For example, it is formally proved that as long as the node failure probability is bounded by 0.5%$0.5\%$, a 3-D mesh network of up to a million nodes remains connected with a probability larger than 99%$99\%$.     

水平式MOCVD系统生长速度均匀性的研究

本文讨论了影响生长速度的因素,如主载气流量、金属有机源流量(在一定蒸气压下),衬底放置位置,及掺杂和非掺杂情况等.对实验结果进行了计论,并与其它文献进行了比较.着重阐述了改善侧向均匀性问题.     

千年绍兴酒 溯源会稽山

会稽山是我国五大“镇山”之一，位列古代九大名山之首。历史上，大禹葬于会稽山，秦始皇亲临会稽山并命宰相李斯刻石颂功，会稽山也因此扬名后世。如果说鉴湖是“绍兴酒之母”，那么会稽山则是“绍兴酒之父”。绍兴老酒鉴湖水，鉴湖之源会稽山。绍兴酒2400多年的历史和会稽山息息相关。本文试就会稽山的历史渊源及其作为绍兴酒的品牌内涵作一分析，并对绍兴酒独特、精湛、高超的酿酒技艺进行阐述.     

一种新的开关磁阻电机数字电流控制方法与实现

根据开关磁阻电机的特性，提出了一种新的数字电流控制方法，并编制了相应的软件程序，最后在三相（12／8）结构15kW开关磁阻电动机上进行实验。实验结果表明，该数字电流控制方案取得了比较理想的效果。     

丁腈橡胶/聚氯乙烯共混胶在钢丝编织液压胶管中的应用研究

研究了丁腈橡胶/聚氯乙烯共混胶(NV5075)替代丁腈橡胶和氯丁橡胶,用作钢丝编织液压胶管的胶料。试验表明,该共混物作为胶管内胶、中胶和外胶有许多优点,诸如耐臭氧老化优良、耐油性能提高、抗撕裂性能改善、门尼焦烧时间长(加工安全)、挤出性能好、表面光滑、不赶胶、挤出的内外管坯挺性好、挤出膨胀率低、尺寸稳定性好等。通过合理的配方设计,胶管成品的全部检验项目均符合国家标准GB/T 3683—2011的要求。     

Box-Cox变量变换拟合法估计三参数P—S—N曲线的研究

提出一种基于变量变换法的Box-Cox变量变换拟合法,可以解决不同应力水平下对数疲劳寿命不满足正态线性Gauss-Markov假设的三参数P-S-N曲线拟合问题;选取LC4、40CrNiMo和LY12CS材料的试验数据对文中方法的有效性和可靠性进行验证.数据分析表明,文中方法估计的三参数P-S-N曲线比利用最小二乘法的拟合效果更好.在两种可靠度下曲线拟合的相对误差可降低至最小二乘法拟合的1/2,最大可降低至1/4,使变换后的模型残差达到最小.改善并稳定了回归模型的残差分布,得到回归系数估计值的最佳无偏估计,还原变换后得到非线性能力较强的幂函数模型,从而提高原始数据的三参数P-S-N曲线的拟合精度和可信度.     

Flow admission control for multi-channel multi-radio wireless networks

Providing Quality of Service (QoS) is a major challenge in wireless networks. In this paper we propose a distributed call admission control protocol (DCAC) to do both bandwidth and delay guaranteed call admission for multihop wireless mesh backbone networks, by exploiting the multi-channel multi-radio (mc-mr) feature. We propose a novel routing metric for route setup, and present an efficient distributed algorithm for link reservation that satisfies the required bandwidth and reduces the delay by a local scheduling that minimizes one hop delay. To the best of our knowledge, this is the first distributed protocol that embeds mc-mr feature in Time Division Medium Access (TDMA) to do QoS call admission in wireless backbone networks. Extensive simulation studies show that our protocol significantly improves network performance on supporting QoS sessions compared with some widely used protocols.     

General axisymmetric active earth pressure obtained by the characteristics method based on circumferential geometric condition

Existing solutions for axisymmetric active earth pressure are based on certain hypotheses of the circumferential stress, lacking of strict basis. This article presents a technique for deriving the actual circumferential stress according to the circumferential geometric condition, the Drucker-Prager criterion and incremental theory. Based on the actual circumferential stress, a new characteristics method for determining the axisymmetric active earth pressure in plastic flow is developed in this article. In this new method, the inclined angle of boundaries, interface friction of contact interface, dilatation effect and flow velocity of soil are considered at the same time. The validity of the new method is confirmed using several sets of experimental data from the literature. The pressure coefficients are investigated individually in detail, and some different conclusions are found. Finally, a practical formula for calculating axisymmetric active earth pressure is presented based on the linear superposition principle, and related tables of coefficients are also provided for engineering application.     

Laser cutting of thermoplastic film: Mechanism and processing technology

The mechanism of ultraviolet(UV) nanosecond laser cutting of thermoplastic films and the influence of process parameters on process quality are systematically discussed.The photothermal effect plays a dominant role in the interaction between the UVnanosecond laser and thermoplastic materials.In this photothermal reaction,a heat source with the focal point as the core is formed,around which a thermal carbonization layer,a thermal melting layer,and a thermal expansion layer are formed in order fro...