EVALUATION OF THE CARCINOGENIC RISK OF BIOCHEMICALLY INERT INSOLUBLE PARTICLES BY THE EPA USING RAT INHALATION DATA

Regulations pertaining to inhalable particulate matter are promulgated primarily by three program offices of the U.S. Environmental Protection Agency (EPA): Pollution Prevention and Toxic Substances (OPPTS), Air Quality Planning and Standards (OAQPS), and Mobile Sources (OMS). Risk assessment for these agents are carried out either by the program offices or by the National Center for Environmental Assessment (NCEA), formerly the Office of Health and Environmental Assessment (OHEA). Particular matter pollutants within the regulatory domain of OAQPS for which either quantitative or qualitative assessment of cancer risk has been carried out include asbestos, beryllium, cadmium, nickel refinery dust, nickel subsulfide, and ambient particulate matter of less than 10 µm diameter (PM10). OPPTS has qualitatively evaluated manmade mineral fibers, titanium dioxide, and vermiculite. Asbestos is the only fiber for which cancer quantitation has been carried out. For several of these agents, risk is based upon human data with animal studies providing supporting data. Both qualitative and quantitative assessment of cancer risk from exposure to diesel engine emissions is under development by NCEA for OMS. Quantitative assessment of cancer risk from exposure to this agent is described as an example of EPA's approach to the use of rats for evaluation of cancer risk. The major uncertainties relating to this assessment include the appropriateness of rat data for assessing human risk and the selection of a low-dose extrapolation model.     

运用振动反分析方法计算振动荷载

本文研究运用振动反问题理论求解振动荷载时程的问题。在Newmark法求解运动平衡方程的基础上,推导了求解振动荷载的公式。采用最小二乘法估计最可置信的荷载系数。提出了由结构对振动荷载的反应求振动荷载时程的有限元方法。通过算例验证了方法的有效性。本文为计算振动荷载提供了一种新的方法。     

CALIBRATION OF SPHERICAL PARTICLES BY LIGHT SCATTERING USING PHOTON CORRELATION SPECTROSCOPY

Photon Correlation Spectroscopy, also known as Quasi-Elastic or Dynamic Light-Scattering, can be a convenient method of size measurement for suspensions of monodisperse spherical particles in the 20-500 nanometer (nm) size range [0.02 to 0.5 micrometer (μm)]. The results obtained vary widely, depending on the concentration and condition of the sample, as well as environmental factors. Techniques have been developed that improve the accuracy and precision of the measurements. These techniques include controlling the concentration, uniformity and dispersion of the sample. The improved method was verified by measuring particle-size standards.     

用桩顶脉冲响应信号估计基桩桩身形状

本文提出了一种用实测桩顶脉冲响应信号估计基桩桩身形状的方法，该方法能定量确定桩身缺陷的位置、延伸范围以及严重程度。文中给出了两根模型桩桩身形状估计的应用实测。     

通过可控微乳液聚合制备聚苯乙烯超微粒子

初步研究了苯乙烯的反向原子转移自由基微乳液聚合．探讨了盐的同离子效应对提高反应可控性的作用和通过可控微乳液聚合制备聚合物超微粒子的可行性．研究结果表明．控制AIBN／CuCl2／bpy的摩尔比和在聚合体系中加入少量小分子电解质NaCl,均可提高反应的可控性;通过微乳液条件下苯乙烯的反向原子转移自由基聚合可以获得聚苯乙烯超微粒子．     

ANALYSIS OF FATIGUE LIFE DATA USING THE BOX-COX TRANSFORMATION

Fatigue life data customarily analyzed using the logarithmic transformation may be better analyzed using the Box-Cox transformation. This transformation has the advantages of stabilizing the variance, simplifying the model and transforming to approximate normality. In addition, simple schemes for imputing run-outs can be constructed and the endurance limit can be easily calculated. This paper considers in detail the use of the transformation on fatigue life data from a thick plate Al-Zn-Cu-Mg alloy. It presents a simplified method for determining the transformation, and then uses the transformation to determine distinctions in quality between different lots and confidence intervals on the lifetime.     

ESTIMATION OF THE AVERAGE ASPECT RATIO OF LAMELLAE-SHAPED PARTICLES BY LASER DIFFRACTOMETRY

Reinforcing properties for polymers and elastomers, rheological properties of high density aqueous slurries, hidding power, lubricating properties of platey particles strongly depend on their size distribution and shape factor or aspect ratio (A.R.).

Determinations of A.R. of fine particles by conventional methods are time-consuming and require sophisticated equipment. A method based upon later light diffractometry has been developed to meet control requirements in industry, the average A.R. can be determined within 5 to 10 minutes, depending upon the number of measurements made using a commercial laser granulometer.

The method relies on:

a cylindrical model (disc) of platey particles.

determinations of the projected area of particles in dilute suspensions of controlled solids concentrations.

calibration of the instrument, using isodiametric particles

simple material balance to derive the average thickness h of the platey particles from projected area measurements and volume of the solid.

A.R. is defined as d50(S)/h. where d50(S) is the mean projected area diameter and h the average thickness attributed to all particles occurring in the sample.     

用正弦波拟合法评价数据采集系统的通道间延时

本文介绍了数据采集系统通道间延时的一种简单实用的评价方法,讨论了评价过程的误差来源,以及减小其评价误差的几种对策;同时,给出了评价过程的计算机仿真结果。     

COAGULATION OF SUSPENDED PARTICLES BY BROWNIAN MOTION FOR THE QUASI-SELF-PRESERVING CASE

An analytic solution is developed for the aerosol coagulation problem in the transition regime. The size distribution of a coagulating aerosol is represented by log-normal functions and particle size distribution is assumed 10 pass through a series of quasi-self-preserving size distributions. The effects of Knudsen number on the Brownian coagulation are discussed along with the results. It is confirmed that after a sufficient period of elapsed time, a self-preserving log-normal size distribution develops whose geometric standard deviation remains unchanged. Such a distribution is found to be narrower than that for the continuum regime and depends upon the Knudsen number. It is shown that the current model serves as the upper bound for the transition regime coagulation problem while the continuum regime constitutes the lower bound. Good agreement was obtained when the present analytic solution was compared with existing numerical studies on transition regime coagulation for the regime up to the Knudsen number of about 1.     

扫描电镜测量微米级长度的不确定度评定

对扫描电镜测量微米级长度的不确定度进行了评定。对引起不确定度性的许多因素,如扫描电镜的分辨率、测量的重复性以及标尺的标定误差等作了分析和计算,特别对输入变量相关时的合成问题作了研究。最后得到了S-4200型扫描电镜微米级测量长度的不确定度。     

ATRP法合成PMMA-b-PS-b-PFx-14三嵌段共聚物

首先通过原子转移自由基聚合(ATRP)得到了末端含卤素的聚甲基丙烯酸甲酯,以这种PMMA为大分子引发剂,引发苯乙烯的ATRP反应,得到了末端含卤素的PMMA-PSt双嵌段共聚物。再以这种双嵌段共聚物大分子为引发剂,引发含氟丙烯酸酯Fx-14的ATRP反应,得到了一种PMMA-PSt-Fx-14三嵌段共聚物．通过GPC、核磁、粘度等数据证实了该聚合物的结构,并详细讨论了由于PMMA-PSt-Fx-14在溶液中的线团行为所产生的GPC测试中出现的特殊现象。     

洁净系统中激光诱导颗粒污染物的分析与评估

高功率激光系统要求在洁净环境中运行,若光学元件表面在工作过程中附着污染物,将导致光学元件的损伤及整个系统负载能力的下降。针对洁净系统中激光与材料作用而产生的颗粒物,分析其作用机制,探讨用于评估的理论依据,讨论测量的需求和方法,并对系统表面存在的颗粒污染物进行了实际测量分析,提出了深入开展高功率激光系统中颗粒污染物测量与评估的技术途径。     

THE DETERMINATION OF HYSTERESIS LOOPS IN THERMO-MECHANICAL FATIGUE USING ISOTHERMAL STRESS-STRAIN DATA

Abstract— Thermo-mechanical fatigue stress-strain data on ferritic/austenitic steels and superalloys from a variety of sources are analysed with regard to hysteresis loop stress asymmetry. This arises from a decoupling of the thermal and mechanical strain signals in the test technique so that many tension-compression load combinations are possible. Data from simplified isothermal and bithermal tests are also examined. Taking a typical example of an "out-of-phase" thermo-mechanical loop on a 1/2 CrMoV steel cycled between 200 and 550°C, isothermal stress-strain data were generated at 50°C intervals on material from the same cast and, used in conjunction with the elastic characteristics of the apparatus, an attempt was made to re-create this loop. The methods employed were (i) a graphical construction between appropriate isothermal yield contours (ii) a tangent modulus calculation (iii) a secant modulus calculation. Method (i) appeared to give the closest agreement in the present case.     

无机超细粒子表面聚合物包覆改性研究进展

文中就聚合物对无机粒子表面进行包覆改性的原位聚合方法,包括接枝聚合法和乳液聚合法的研究现状进行了综述。介绍了接枝聚合法中的预先接枝不饱和基团、预先接枝引发基团以及预先接枝终止基团等方法和乳液聚合法中的无皂乳液聚合法、预处理乳液聚合法以及微乳液聚合法等方法,并分析了它们对无机粒子进行表面改性的优劣。     

用超声波技术测量螺栓轴向紧固应力

超声波速度会因材料中加载应力而产生微小的变化，这一现象特别适用于测量螺栓的轴向应力。根据螺栓的轴向应力与超声波传播时间变化率的关系，作者研究了一种可直接测量螺栓轴同应力的仪器。实验结果显示，本项技术十分适合现场的实际应用。     

溶胶—凝胶法制备二元炭质—TiO2气凝胶前驱体

以炭质水笥中间相和四氯化钛为原料,分别制取了炭质溶胶－凝胶和钛溶胶０－凝胶,然后将二者充分搅拌混合后,再进行超临界干燥制得了二元炭质／二氧化钛气凝胶粉末前驱体,利用ＦＴ－ＩＲ,ＸＥＤ和ＴＥＭ技术对二元炭质／氧化钛粉末进行了表征。研究结果表明,二元炭质／氧化钛粉末具有小于１０ｎｍ的颗粒尺寸,炭和氧化钛混合均匀且具有较高的比表面和疏松的表观结构。     

基于尺寸效应的爆炸粉末烧结颗粒间摩擦升温计算

针对爆炸粉末烧结过程中颗粒间的摩擦效应建立了无夹角斜碰撞模型,分析了烧结过程中颗粒间摩擦力随颗粒温度的变化规律,借助于LS-DYNA有限元程序对孔隙闭合时间进行了研究,并在此基础上用积分法对颗粒间热力耦合的摩擦力引起的界面温升进行了计算,在计算过程中考虑了颗粒尺度效应的影响,给出了发生“尺度效应”的临界尺寸。计算结果表明:材料的界面温升随着颗粒尺度的增大和冲击压力的变大而变大;当颗粒尺度从微米到纳米量级变化时,只有当颗粒尺度和冲击压力足够大时,颗粒表面温度才能达到材料的熔点。     

PSA空气分离吸附过程中的压降特性研究

根据PSA分离空气制氧的基本理论，通过对我们自行研制的产氧量为Q＝（1－5）L／min的双吸附柱的小型PSA分离空气制氧系统进行的吸附过程的压力降的计算，分析了影响空气流经多孔吸附介质压降特性的操作参数，分子筛结构参数等重要因素。结果表明：（1）空气流经PSA吸附柱多孔吸附介质的压降随流速的增大而增大，在较低流速范围内（v=0.05m/s-0.1m/s)，流速对压降的影响较小，在流速较高时，流速对压降的影响较大；（2）压降随空隙率的增大而减小，对于较高流速，低空隙率范围内（ε＝0．32－0．4）空隙率对压降影响很大，是影响压降的最主要因素；（3）压降随多孔吸附介质颗粒直径的增大而减小，在吸附介质颗粒直径较小的范围内（d=1.6-2.0mm)这种变化较明显。     

神经网络预测爆炸密实引起的地表沉降

爆炸密实法用于地基处理已有很长的历史,用此方法处理时所引起的地表沉降是衡量其处理效果的一个重要指标,许多学者提出了引起地表沉降量的统计预测模型。本文尝试建立了预测爆炸密实引起地表沉降的神经网络模型,由于用来训练网络的原始样本太少,难以训练出一个具有高精度的预测模型,为此采用了遗传算法与神经网络相结合的方法,得到了一个只有小样本输入却能得到高精度输出的神经网络模型。对检验样本的预测结果表明,所建立的神经网络模型具有很强的预测能力,其预测精度比已有的统计预测模型高。