Surface‐modifiers of clay on mechanical properties of rigid polyurethane foams/organoclay nanocomposites

Three different surface modifiers, octadecyl trimethyl ammonium (ODTMA), octadecyl primary ammonium (ODPA), and decanediamine (DDA) were used to modify Na⁺? montmorillonite (MMT), and the resultant organoclays were coded as ODTMA‐MMT, ODPA‐MMT, DDA‐MMT, respectively. Rigid PU foams/organoclay composites were prepared by directly using organoclay as the blowing agent without the addition of water. Investigation shows that the morphology of the nanocomposites is greatly dependent on the surface modifiers of clay used in the composites. In detail, DDA‐MMT is partially exfoliated in the PU matrix with the smallest cell size, while two others are intercalated in the PU matrices with smaller cell sizes. The sequence of their cell sizes is pristine PU foams > rigid PU foams/ODTMA‐MMT > rigid PU foams/ODPA‐MMT > rigid PU foams/DDA‐MMT, and the average cell size of rigid PU foams/DDA‐MMT composites decreases evidently from 0.30 to 0.07 mm. Moreover, all rigid PU foams/organoclay composites show remarkable enhanced compressive and tensile strengths as well as dynamic properties than those of PU foams, and the enhancement degree coincides well with the relative extent of internal hydrogen bonding of materials and gallery spacing of organoclay. For example, in the case of rigid PU foams/DDA‐MMT composite, 214% increase in compressive strength and 148% increase in tensile strength compared with those of pure PU foams were observed. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

Homogeneous Fluidization Characteristics of Vibrating Fluidized Beds

The effects of vibration parameters, operating conditions and material properties on fluidization quality were investigated by the measurement and analysis of voidage fluctuation signals in a vibrating fluidized bed with a diameter of 148 mm. The fluctuation deviation of the bed voidage and the enhancement index of the bed derived can describe bed homogeneity and its extension. A new criterion of homogeneity, consisting of the material parameter (Ar), operating parameters (H₀, u/u_mf) and vibration parameters (a, ω), is proposed to predict a suitable range of homogeneous fluidization. Experimental results on eight kinds of solids, five static bed heights and different vibration parameters were used to propose guidelines for the reasonable selection of operating conditions for vibrating fluidization and better operating conditions.     

嵌入式火控软件时间性能测试

嵌入式实时操作系统是能在确定的时间内执行计算或处理功能并能对外部事件做出响应的系统,由此可见时间逻辑会影响软件系统的正确性,时间指标一般指任务切换、完成时间和中断响应时间。根据这些特点,文中简要介绍了静态分析方法,着重介绍了一种利用8253可编程间隔定时器进行插装的实时动态检测时间指标的方法。此方法在嵌入式火控系统软件时间性能指标的测试中得到了充分利用,取得很好的应用效果,同时也介绍了此方法的局限性,便于在其他测试项目中更充分的运用。     

应用于临床生存时间预测的二次学习算法研究

生存时间预测在医学、经济和工程等领域有着广泛的应用。随着机器学习技术和数据挖掘技术的发展和广泛应用,研究人员提出了很多基于机器学习技术的生存时间预测算法。这些算法虽然都取得了良好的效果,但预测精度均有提升的空间。因此,提出了一种基于二次学习风范的生存时间预测算法,并结合最近邻算法在截尾样本估计上的应用以及支持向量机在泛化性能上的优势,实现了对临床生存时间的建模。实验结果表明,该算法能够获取精确的生存时间,且具有预测精度上的性能优势。     

异构信息网络数据上的融合概率图模型

针对异构信息网络中存在多种数据目标类型,以及多种数据连接关系的问题,将多个主题模型和马尔科夫逻辑网相结合,提出了一种融合概率图模型。多个主题模型可以分别描述不同数据目标子空间的主题分布,实现对多种数据目标的预处理。用一阶逻辑子句描述的连接规则构建马尔科夫逻辑网,将每个主题模型中的不同数据目标连接起来。通过使用Gibbs采样,可以对异构网络进行参数学习和推理。在国际通用的异构信息网络DBLP数据集上的实验结果表明,使用融合概率图模型能够更好地表示不同的数据目标和连接关系。实验对比了4种典型的分类方法,多次采样得到的分类结果稳定,对作者、文章和会议取得了较好的分类结果。     

节水型洗衣粉的研制

本文论述研制节水型洗衣粉的必要性及其制造过程。并对洗衣粉的表面活性剂、助剂、消泡剂进行配方优选，研制出去污力强的节水型洗衣粉。     

An algorithm and observability research of autonomous navigation and joint attitude determination in asteroid exploration descent stage

In this paper, an autonomous relative navigation and joint attitude determination algorithm in asteroid exploration descent stage is researched based on feature point information of perpendicular asteroid surface image observed by optical navigation camera, distance vectors from spacecraft to asteroid measured by three angled installed lidars and relative velocity increment measured by accelerometer when the relative distance vector to the centroid of asteroid can not be obtained. The inertial attitude of spacecraft is determined by sun vector, star vectors and inertial angular velocity respectively measured by sun sensor, star trackers and inertial reference unit. Also, in order to obtain measurement error model transferred from sensor noise, a covariance matrix solver considering error correlation is presented via the error model of normalized vector to first order. Numerical simulation and improved observability evaluation of filtering are undertaken to discuss the results of complete sensor observation and weak observation of lidars, and verify the effectiveness of the presented relative navigation and attitude determination algorithm.     

Gaussian sampling of lattices for cryptographic applications

Gaussian sampling is the major class of algorithms for solving the close vector problem(CVP)of lattices.In this paper we present a novel Gaussian sampling algorithm,which has the same cryptographic applications with original Gaussian sampling algorithms.Our novel Gaussian sampling algorithm has smaller deviations,meaning smaller space sizes of lattice based public-key ciphers.The shape of our novel algorithm is almost repeated implementations of original algorithm,with random repeating times.Major result is that the deviation can be reduced to 0.64～0.75 of that of original Gaussian sampling algorithm without clearly increasing the average time cost.     

PLC系统信号干扰与防范措施

结合现场,分析PLC控制系统中信号产生干扰的原因,和可能引起模板故障的因素,并提出相应解决方法.     

Photocatalytic behavior of TiO_2 and ZnO prepared with different methods under ultraviolet and visible light irradiation

IntroductionIn recent years photocatalytic oxidation hasreceived considerable attention as an alternativeremediation technology since the method offers anumber of advantages over conventionaltechnologies [1,2] Elimination o…