热轧低密度钢Fe-1.80Mn-1.05Al-0.09C的高温热塑性

采用Gleeble 3500热模拟试验机对一种低合金系热轧低密度钢进行了高温(760～1200℃)热塑性研究,并结合光学显微镜、体视显微镜以及扫描电镜对拉断后的断口附近组织和断口形貌进行了表征。结果表明,随着拉伸温度升高,断口面积逐渐缩小,韧窝也逐渐变大变深,断面收缩率总体表现良好,均达到80%以上,表现出了良好的高温热塑性。但是试验钢在900～1000℃进行拉伸时,出现了多处颈缩现象,900～1000℃时存在理论塑性低谷区,应避免在900～1000℃进行铸坯矫直或轧制。     

Continuous synthesis of Zn2SiO4:Mn fine particles in supercritical water at temperatures of 400-500 °C and pressures of 30-35 MPa

Sub-micron sized Zn₂SiO₄:Mn²⁺ phosphors particles were continuously synthesized in supercritical water with a flow reactor. Colloidal silica or sodium silicate was used as the Si source. Zn and Mn sources were chosen from their nitrates, sulfates, and acetates. The syntheses were carried out at temperatures from 400 to 500 °C, at pressures from 30 to 35 MPa, at NaOH concentrations from 0.014 to 0.025 M, and for residence times from 0.025 to 0.18 s. Sodium silicate formed α- and β-Zn₂SiO₄:Mn²⁺ phases regardless of the Zn and Mn sources, while colloidal silica formed phases dependent on the type of Zn and Mn sources used in addition to the use of alkali. As the reaction temperature increased, the crystallinity of α-Zn₂SiO₄:Mn²⁺ phase increased and the Mn substitution into the Zn sites of the α-Zn₂SiO₄ phase decreased. Of the conditions studied, the most highly crystalline α-Zn₂SiO₄:Mn²⁺ was produced at a temperature of 400 °C, a pressure of 30 MPa, a NaOH concentration of 0.14 M, and a residence time of 0.13 s with Zn and Mn sulfates and colloidal silica as starting materials. The α-Zn₂SiO₄:Mn²⁺ fine particles synthesized were round in shape, had an average diameter of 268 nm, and exhibited a green-emission with a peak wavelength of 524 nm.     

残余元素对涟钢CSP热冷轧卷质量的影响

钢中的残余元素问题是钢铁冶金面临的重要问题之一,高性能新钢种必须考虑残余元素的有害影响.涟钢矿石来源多而杂,导致铁水中As,Cu,Pb,Sn,Sb等残余元素增加.从残余元素(As,Cu,Pb,Sn,Sb等)对涟钢热轧卷、冷轧卷表面质量和力学性能的影响进行分析.分析结果表明:送检的热轧卷发现表面氧化铁与试样基体的界面有铜的富集;晶界处铜的富集会成为热轧卷产生裂纹的原因之一;冷轧卷酸洗后表面有黑点,黑点处发现有Cu,As,Sn,Sb等残余元素的富集;对特定时期的热轧卷力学性能进行多次逐步回归分析发现Sb对屈服强度有显著的负相关.     

Mesophase structure discovered through in-situ X-ray measurement in drawing process of poly(ethylene 2,6-naphthalene dicarboxylate) fiber

The structure development in the continuous laser-heated drawing process of poly(ethylene 2,6-naphthalene dicarboxylate) (PEN) fiber was analyzed by in-situ X-ray diffraction measurement. Because of the rapid and uniform laser heating, and the resultant steady-state nature of the necking-drawing, the structure development after the on-set of necking could be measured in the time resolution of several hundred microseconds. We found for the first time the temporal appearance of meridional (001′) diffraction at several milliseconds after the on-set of necking indicating that the mesophase structure similar to the one reported for poly(ethylene terephthalate) was also formed in the initial stage of fiber structure development of PEN. The d-spacing of the (001′) diffraction 1.230 ± 0.003 nm was shorter than the c-axis lengths of both α and β crystals.     

共振隧穿二极管的压阻特性测试与研究

设计并搭建了检测共振隧穿二极管(RTD)压阻特性的实验系统,测试了RTD结构在不同应力状态下I-V特性曲线的漂移.实验结果表明RTD结构压阻特性的灵敏度大于1×10-8Pa-1.为了更精确地定量表达其压阻特性,研究了同一RTD结构I-V特性的一致性,得到相同环境条件下RTD电阻的最大相对漂移量小于3%,其中1%由测试仪器造成.     

Immunohistochemical study of calpain-mediated alpha-crystallin proteolysis in the UPL rat hereditary cataract

The purpose of this study is to examine if microencapsulated PC12 cells may provide long term effects to the hemiparkinsonian rats. A modified technique was used to encapsulate PC12 cells into gelled microspheres. We found that the PC12 cells can survive in the modified microcapsules in vitro. Most of the PC12 cells formed cluster 3 weeks after incubation. The PC12 cell-loaded microcapsules were also examined in vitro. Adult Sprague-Dawley rats, anesthetized with chloral hydrate, were injected unilaterally with 6-hydroxydopamine into the medial forebrain bundle. The effectiveness of this lesion was tested by measuring apomorphine or methamphetamine-induced rotation one month after lesioning. The unilaterally lesioned rats were transplanted with microencapsulated PC12 cells. Results showed that apomorphine and methamphetamine-induced rotations were greatly suppressed after transplantation. One year after the grafting, the animals were anesthetized with urethane for the voltammetric study. Low dose of KCl was directly injected into the grafted striatum through pressure microejection. We found that KCl-induced DA release, as measured by voltammetric techniques, was regenerated in the striatum. The animals were later sacrificed for histological examination. We found that capsules were present in the lesioned striatum one year after grafting. Most of the capsules contained no PC12 cell. However, some capsules were filled entirely with PC12 cells. Taken together, our data suggested that PC12 cells can survive in the capsule in vitro and may provide long-term dopaminergic effects to the hemiparkinsonian rats.     

A yang-mills type minimal coupling theory for materials with dislocations and disclinations

Noting that the group $\text{S0(3) ? T(3)}$ may be viewed as a 6-parameter gauge group that leaves the Lagrangian of elasticity theory invariant, the Yang-Mills universal gauge theory construction is used to erect a complete continuum theory of material bodies with dislocation and disclination fields. Breaking of the homogeneity of the action of $\text{S0(3)}$ is shown to give rise to disclinations and rotational dislocations while homogeneity breaking of $\text{T(3)}$ gives rise to translational dislocations. A rigorous justification for replacing displacement gradients by the components of the distortion tensor and Newtonian kinematic velocity by distortional velocity is obtained. Exact determinations are made of the elastic excess forces, the forces on dislocations and the forces on disclinations, and these forces are shown to be totally equilibrating in all instances. Implications of the theory are given and an analysis is made of the field equations and associated dispersion relations that obtain in a disclination free material in the linear elasticity approximation.     

A percentile system optimization approach with and without path enumeration

In this paper we deal with the travel time reliability PUE (probabilistic user equilibrium) problem studied by Lo et al. (2006) [12] and Nie (2011) [15] and we propose an alternative model that assumes a location-scale family for the path travel times, whose means and variances are evaluated in terms of link travel times. This avoids the use of the central limit theorem and convolutions providing a flexible and simple alternative. Contrary to the most existing models that require path enumeration or an iterative method to add paths sequentially, we present a percentile system optimization in its two versions: with and without path enumeration. Two examples of applications, one of them real, are used to illustrate the power of the proposed method. The cpu times required to solve the problem seem reasonable. In addition, we answer an open question raised by Nie (2011) [15] about the permutability of percentiles and partial derivatives of route travel times with respect to route flows. A family of counterexamples is given to demonstrate that the two operations: (a) obtain percentiles and (b) partial derivation of route travel times do not commute. Finally, to reproduce the trial-and-error sequence followed by users when selecting paths, we also present an algorithm that simulates this iterative process and shows that the final long-term user behavior coincides with PUE (probabilistic user equilibrium) problem resulting from some existing models.     

Cell Culture on MEMS Platforms: A Review

Microfabricated systems provide an excellent platform for the culture of cells, and are an extremely useful tool for the investigation of cellular responses to various stimuli. Advantages offered over traditional methods include cost-effectiveness, controllability, low volume, high resolution, and sensitivity. Both biocompatible and bio-incompatible materials have been developed for use in these applications. Biocompatible materials such as PMMA or PLGA can be used directly for cell culture. However, for bio-incompatible materials such as silicon or PDMS, additional steps need to be taken to render these materials more suitable for cell adhesion and maintenance. This review describes multiple surface modification strategies to improve the biocompatibility of MEMS materials. Basic concepts of cell-biomaterial interactions, such as protein adsorption and cell adhesion are covered. Finally, the applications of these MEMS materials in Tissue Engineering are presented.