The Long-Term Drift of Triple-Point-of-Water Cells

As the triple point of water is of great importance for the International Temperature Scale of 1990 (ITS-90) and for the definition of the unit of thermodynamic temperature, its long-term stability has attracted a great deal of attention. In a study of long-term stability, a mystery has been uncovered. Some triple-point-of-water cells remain stable for many decades, while others decrease with increasing age of the cells, which is called long-term drift. To investigate this mystery, we used cells with different manufacture dates ranging from 1974 to 2002 and compared their analyses, which were done in 1984 and 2003. Using the same model of long-term drift as that used by Hill, the long-term drift rates of the two data sets are –4.7 μK·year⁻¹ and –9.2 μK·year⁻¹, respectively. One is consistent with the observed depression of about –4 μK·year⁻¹ measured by Hill, whereas the other differs greatly from Hill’s result. In addition, corresponding factors influencing long-term drift are discussed in this paper.     

An Experimental Investigation of the Long-Term Stability of Triple-Point-of-Water Cells

Contamination of triple-point-of-water (TPW) cells by the chemical components of the borosilicate glass that contains the water is now widely recognized as the principal contributor to long-term drift of the cell temperature. To add to the available experimental data, a comparison of 24 TPW cells of various ages (from 10 years to 59 years), manufacturers (NRC, Jarrett, Isotech), and materials (borosilicate glass and fused quartz) was undertaken in 2013. Twelve cells from this group were compared to one another in 1997. By comparing the current inter-cell temperature differences to those determined 16 years earlier, it was found that some cells have remained stable, others have become colder (as might be expected from ongoing dissolution of the glass), and one or two show an apparent increase in temperature that seems anomalous. Also included among the 24 cells are five cells of borosilicate glass and five of fused quartz that were purchased 10 years ago. By comparing the relative temperature differences among this group of borosilcate and fused-quartz-encapsulated cells to the values obtained when they were last compared 6 years ago, it was found that the average temperature of the borosilcate group of cells decreases by \(-6\,\upmu \mathrm{K}\,{\cdot }\,\mathrm{year}^{-1}\,({\pm }2\,\upmu \mathrm{K}\,{\cdot }\,\mathrm{year}^{-1})\) , in reasonable agreement with an average drift of \(-4\,\upmu \mathrm{K}\,{\cdot }\,\mathrm{year}^{-1}\) suggested 12 years ago. It was concluded that fused quartz is the superior container for TPW cells.     

不同晶粒度钨合金动态力学性能研究

采用拉格朗日实验分析技术对1～3μm,10～15μm和30～40μm三种不同晶粒度细化钨合金材料91W-6.3Ni-2.7Fe在高应变率下的动态力学性能进行研究.得到三种不同晶粒度的钨合金在不同冲击速度下各拉氏位置的应力时程曲线.利用拉氏分析方法对钨合金在高应变率下的力学性质进行探讨,分析各拉氏位置的应变,比容,密度,应变率,比内能,质点速度等物理量的变化历史,讨论不同晶粒度尺寸对钨合金在高应变率下动态力学性能的影响,给出钨合金在应变率为104～105s-1时的应力应变曲线.     

Estimation Techniques for Common Cause Failure Data With Different System Sizes

Modeling of system lifetimes becomes more complicated when external events can cause the simultaneous failure of two or more system components. Models that ignore these common cause failures lead to methods of analysis that overestimate system reliability. Typical data consist of observed frequencies in which i out of m (identical) components in a system failed simultaneously, i = 1,…, m. Because this attribute data is inherently dependent on the number of components in the system, procedures for interpretation of data from different groups with more or fewer components than the system under study are not straightforward. This is a recurrent problem in reliability applications in which component configurations change from one system to the next. For instance, in the analysis of a large power-supply system that has three stand-by diesel generators in case of power loss, statistical tests and estimates of system reliability cannot be derived easily from data pertaining to different plants for which only one or two diesel generators were used to reinforce the main power source. This article presents, discusses, and analyzes methods to use generic attribute reliability data efficiently for systems of varying size.     

液氮冻制冰套法对水三相点温度的影响

介绍了液氮作为冷却剂在水三相点容器内冻制冰套的方法。利用该方法同时在两个不同真空度的水三相点容器内分别冻制冰套。通过实验，研究了此方法对所复现的水三相点温度的影响。实验结果表明：冻制过程中产生的应力以及开始生成的小冰晶引起水三相点温度偏低；并且，其对水三相点温度的影响随着水三相点容器内真空度的降低而增大。随着应力慢慢消除，小冰晶逐渐长大为大冰晶，所复现的水三相点值逐渐回升并趋于稳定。因此，为了高精度复现和准确测量水三相点，采用该冻制方法时，必须将冰套老化至少5天以后，才可以消除其对水三相点温度的影响。     

Pressure-Induced Structural Transitions of the Zinc Sulfide Nano-particles with Different Sizes

ZnS nano-particles with average sizes of 10 nm and 5 nm were fabricated by sol-gel method, and their pressure-induced phase transformations were in-situ examined in a diamond anvil cell by energy dispersive X-ray diffraction （EDXD） from ambient pressure to 35.0 GPa. From the obtained interplanar spacing data,the volume compression ratios were derived at different pressures, and then the bulk modulus and its pressure derivative were obtained by fitting to the Murnaghan equation. It is found that both ZnS nano-particles initially in the zinc-blende phase transformed to cubic NaCl structure in the presence of pressure and the transition was reversible when the pressure was released. Moreover, it is suggested that a smaller particle size will induce a larger transition pressure.     

不同粒径膨胀石墨的制备及其微观结构

对化学法制备膨胀石墨的工艺条件的选择进行了分析,以硝酸与磷酸的混酸为插层剂、高锰酸钾为氧化剂制备出了不同粒径的膨胀石墨,利用正交实验和平行实验确定了最佳工艺条件;研究了石墨粒度效应对氧化剂用量的影响;并对不同粒径膨胀石墨的微观结构进行了研究。研究结果表明,制备大鳞片膨胀石墨的最佳工艺为：石墨与混酸的质量体积比为1：4,...     

货物大小自动分类包装机的设计

目的针对目前网络销售货物存在的包装效率低下、人工成本高等问题,设计一台可实现对不同尺寸货物进行自动分类的包装机。方法通过距离光电传感器检测货物的大小,将尺寸不同的货物进行分类,用机械手臂拾取分类好的货物,并放到传送带运送的盒子内,再利用气缸的运动将货物进行封装,最后利用自动打包机将封装好的货物进行外部包装。结果所设计的货物分类包装机能实现对货物进行快速分类、包装,采用气缸带动机器运动,实现了自动化控制,不需人为操作,结构更简单,操作更方便。结论货物自动分类包装机可以用于多种尺寸商品的分类、包装,既可以帮助大型商店、物流公司整理繁杂的货物,又可以帮助小型网店快速整理、包装多品种货物,提高了效率,减少了人工资源浪费。     

An Assessment of the Impact of SiO2 Nanoparticles of Different Sizes on the Rest/Wake Behavior and the Developmental Profile of Zebrafish Larvae

In this study, zebrafish larvae are introduced as an in vivo platform to examine the neurotoxicity and developmental toxicity associated with continuous exposure to a concentration gradient of different sizes of SiO₂ nanoparticles (15 nm and 50 nm diameter) to determine the dose effect and size effect of SiO₂ nanoparticle (NP)‐induced toxicity. Bovine serum albumin (BSA‐V) is utilized as a stabilizing agent to prevent coagulation of the SiO₂ nanoparticles. To the best of our knowledge, this study is the first to describe locomotor activity assays linking rest/wake behavioral profiles for the purpose of investigating the neurotoxicity of NPs. In addition, developmental toxicological endpoints including mortality, LC₅₀, malformation, and cartilaginous deformity are assessed. The results show a concentration‐dependent increase in behavioral neurotoxicity, mortality, and malformation among larvae treated with the SiO₂ nanoparticles of 15 nm and 50 nm. A comparison of the 15 nm and 50 nm NPs by K‐means clustering analysis demonstrates that the 15 nm NPs have a greater neurotoxic effect than the 50 nm NPs, with the 50 nm NPs exhibiting greater developmental toxicity on the zebrafish larvae than the 15 nm NPs.     

不同尺寸异形纤维对复合材料性能的影响

自行设计、委托加工了几组不同形状、不同尺寸的纺丝模口,生产出相应的纤维,并用该纤维与PE-起,制备相应的复合材料,研究了纤维对其增强复合材料性能的影响.结果表明:无论是圆形纤维、还是各种异形纤维,其纤维/PE复合材料的断裂强度均明显高于纯PE的断裂强度,纤维材料的加入明显提高了基体的断裂强度;在复合材料中,横截面积相等的异形纤维和圆形纤维,长度相等时,它们的体积也相等,但异形纤维表面积大于圆形纤维,所以异形纤维和基体的结合力更大,更能增强复合材料的强度.     

颗粒尺寸对反应烧结碳化硅摩擦磨损特性的影响

研究了碳化硅颗粒尺寸对反应烧结碳化硅材料摩擦磨损性能的影响.结果表明:随着碳化硅颗粒尺寸的增加,不论干摩擦还是水润滑条件下,反应烧结碳化硅的摩擦系数和磨损率均表现为先增加,后降低的趋势.粒度为42μm的反应烧结碳化硅的摩擦系数和磨损率最大,而粒度为14μm的最小.水润滑时的摩擦系数和磨损率比干摩擦时的成倍降低.     

液-液循环流化床动态制冰特性

建立了液-液循环流化床制取流体冰的热态试验装置,在多工况条件下对该新技术的动态制冰特性进行了试验研究.通过对所获得的冰晶颗粒进行粒径的测量与统计整理,分析了冰晶粒径分布,并对影响冰晶尺寸的关键因素进行了探讨:通过计算机实时记录循环系统各测点温度,对载冷介质的沿程温变进行了分析;最后考察平衡工况下喷水量与载冷油介质循环量的关系.结果表明,所获得的冰晶粒径早离散性分布,主要集中在1mm～2mm区间;冰晶粒径与载流介质流量、喷水量及喷嘴内径密切相关,体现为随载流介质流量降低而减小,随喷水量增加呈先增大后减小的变化趋势,在喷水量为120mL·min-1时达到最大值,在喷嘴内径较小时,冰晶粒径明显减小;流化床内载流介质温升梯度沿床高而减小;载流介质循环量随喷水量的增加呈先增大后减小的变化趋势.在液-液雾化中形成体积微小的雾化液滴,是提高系统运行经济性有效的途径.     

颗粒粒径对气力输送影响的数值模拟与分析

在气力输送实验台上,以空气为输送介质,砂石为输送物料,进行水平管道流动特性实验;并以Euler方法为基础,建立数学模型,利用Fluent软件进行模拟。结果表明:水平管道底部颗粒浓度沿轴向不断增大,接近管道尾部时浓度减小;气相输送速度相同时,颗粒粒径越小,则水平管道内压降越小,颗粒在管道内分布越均匀,越容易获取加速度;通过对比可知,模拟所得结论与实际测量结果相符。     

冰晶对黏附成骨细胞损伤的实验研究

低温冻结保存过程中,冰晶是造成细胞损伤的主要因素之一.本研究运用研制的方向性冰晶生长实验台,定量研究了胞外冰晶对黏附成骨细胞的损伤.结果表明,当冰晶生长方向与黏附成骨细胞中轴线的夹角在0～30度之间时,细胞存活率高达89.3±18.9%,而当它们之间的夹角在30～60度以及60～90度之间时,细胞的存率分别为49.0±19.0%,42.8±15.8%,表明细胞存活率与胞外冰晶与黏附细胞的接触面积有关.     

不同粉末粒度的粉末轧制多孔钛板的孔隙性能研究

为满足湿法冶金、氯碱、水处理、制药等行业对多孔钛板过滤元件的需求,以粉末轧制法制备多孔钛板为出发点,开展了满足轧制工艺要求的多孔钛板粉末轧制、烧结、性能测试等研究。通过对不同性能的钛粉进行粉末轧制、真空烧结,制得了宽度为420 mm、厚度不同、组织均匀的多孔钛板,研究了不同粉末性能对其孔隙度、最大孔径和透气度的影响。结果表明:随着粉末粒度的减小,多孔钛板的密度有所增大,孔隙度、最大孔径和透气度逐渐减小。其中,多孔钛板最大孔径和透气度的变化规律与模压多孔材料的相同。在追求孔隙度最大化时,以最小的轧制压力轧制成型多孔钛板,粉末粒度越大,其厚度越大。当粉末粒度相同时,多孔钛板厚度越大,其内部孔道路径越长,孔结构越复杂,气体在透过多孔结构通道时所消耗的能量也越多,透气度则越低。     

Cytotoxicity and Immunological Response of Gold and Silver Nanoparticles of Different Sizes

The immunological response of macrophages to physically produced pure Au and Ag nanoparticles (NPs) (in three different sizes) is investigated in vitro. The treatment of either type of NP at ≥10 ppm dramatically decreases the population and increases the size of the macrophages. Both NPs enter the cells but only AuNPs (especially those with smaller diamter) up‐regulate the expressions of proinflammatory genes interlukin‐1 (IL‐1), interlukin‐6 (IL‐6), and tumor necrosis factor (TNF‐α). Transmission electron microscopy images show that AuNPs and AgNPs are both trapped in vesicles in the cytoplasma, but only AuNPs are organized into a circular pattern. It is speculated that part of the negatively charged AuNPs might adsorb serum protein and enter cells via the more complicated endocytotic pathway, which results in higher cytotoxicity and immunological response of AuNPs as compared to AgNPS.     

Sample Sizes for Comparison of Proportions

This paper examines the problem of determining sample sizes for comparing sample proportions from n independent binomial populations under the null hypothesis that the population proportions are different. For specified precisions and sampling costs, it is shown that the problem of determining optimal sample sizes can be formulated as a convex programming problem. In addition, the problem of obtaining the best precision within a budgeted cost of sampling is examined. This methodology is illustrated with an example application.     

装药位置对冰凌爆破效果影响的数值模拟

目前对冰凌的定点爆破方式主要有水下药包爆破、冰中钻孔爆破及冰上裸露药包爆破,使用大型有限元软件ANSYS/LS-DYNA模拟了3种爆破方式冰层中压碎区及裂隙区的生成过程,对冰层的破坏半径、碎冰的飞散特点和水中冲击波强度进行了定量比较分析,分析结果显示水下药包爆破破坏半径是其他爆破方式的1.2至2.0倍,生成水中冲击波强度是其他爆破方式的近14倍。数值模拟结果与以往工程实践相互印证,对爆破法防凌具有一定参考意义。