局部强化对金属冷、热切圆锯片振动特性的影响

本文针对金属冷、热切圆锯片在锯切轧件过程中出现的振动问题，利用有限元软件ANSYS对其进行模态分析，同时研究局部厚度发生变化及旋转离心力对锯片振动特性的影响。并初步研究了激光强化锯片基体对锯片振动特性的影响。     

视角和信息量对静态图像短时记忆的影响

采用2种视角条件和2种信息量,以回忆正确率作为绩效测量指标,要求40名被试在不同条件下回忆在计算机屏幕上学习过的静态矩阵图像中的特征信息,考察静态图像的视角和信息量对图像短时记忆的影响。实验结果表明:①信息量对静态图像的短时记忆有显著影响,目标信息量越少,回忆正确率越高;②视角大小对静态图像的短时记忆有显著影响,呈现视角较大的图像的回忆正确率显著较高;③视角和信息量存在交互作用,视角大小的影响主要发生在信息量较大的时候,大视角有利于静态图像的短时记忆。     

硬脂酸盐复合物的形成及对聚氯乙烯的热稳定化作用

通过红外光谱(FT-IR)、广角X射线衍射和DSC等研究了硬脂酸钡(BaSt2)/硬脂酸锌(ZnSt2)复合物的形成。研究表明,在一定温度下熔融共混后,BaSt2和ZnSt2羰基特征吸收峰、晶面间距和熔点均发生了明显的变化,表明BaSt2和ZnSt2在此条件下形成了复合物。与BaSt2/ZnSt2混合物相比,BaSt2-ZnSt2复合物能改善聚氯乙烯(PVC)的初期色泽稳定性和静态热稳定性。BaSt2-ZnSt2复合物能够阻止ZnCl2的形成,从而抑制ZnCl2对PVC的催化降解作用。     

Measuring the 2D Residual Surface Stress Mapping in Tempered Glass under the Cooling Jets: the Influence of Process Parameters on the Stress Homogeneity and Isotropy

Abstract: In glass products, thermally tempered on industrial lines for automotive and architectural industries, the distribution of residual stress is highly inhomogeneous and, in certain situations, can produce optical defects that are more visible in sunlight because of the impact of the cooling jets on the hot glass during the tempering process. To analyse the influence of the process parameters on stress inhomogeneity, flat square glass samples were tempered with PRELCO tempering production unit without oscillation and with oscillation under cooling jets, thus reproducing the current industrial practice for the latter. To measure the residual stress distributions in the tempered glass samples, we developed a fully automatic system that combines the scattered light polariscope (SCALP) and a four‐axis machine, with three linear axes and one rotational one. Using the SCALP manually with the dedicated software makes it possible to access the glass surface at the laser beam’s entering point. With a four‐axis Computer Numerical Control (CNC) machine, we determined the 2D residual stress distribution under the cooling jets and analysed the influence of the cooling rate and oscillation on the homogeneity and the isotropy of the residual surface stress in the tempered glass samples.     

The Effect of Structural Defects on the Thermal Conductivity of ZnS, ZnSe, and CdTe Polycrystals

ZnS, ZnSe, and CdTe polycrystals are experimentally investigated. Mechanisms are treated which restrict the thermal conductivity in samples prepared by recrystallization pressing and by deposition from the vapor phase and subjected to additional strain. Anomalies are observed on the temperature dependences of the thermal resistance of investigated samples, which are due to the special features of their phonon spectra and to the variation of the contribution made by longitudinal and transverse phonon branches to the heat transfer in the Debye temperature region and higher.     

The Effect of the Surrounding Medium and Its Pressure on Data Obtained in Thermal Diffusivity Measurements Using the Flash Method

This work describes experimental measurements made with a high temperature–high pressure flash thermal diffusivity instrument, using nitrogen, argon, and helium as environment. Data was generated using pressures from vacuum to 30 bar in the temperature range of ambient to 1000°C. NIST SRM 8425 (Poco AXM 5Q, fine grain graphite) was used for the tests. A total of 2.970 data points were obtained, showing a clear and prominent shift in the data, depending on the pressure and the thermal properties of the surrounding gas. Preliminary conclusions drawn from the work indicate the influence of heat conduction, convection, and diffusion through the environmental gas, on the thermal diffusivity results.     

The Algebra of Geometric Impossibility: Descartes and Montucla on the Impossibility of the Duplication of the Cube and the Trisection of the Angle

Today we credit Pierre Wantzel with the first proof (1837) of the impossibility of doubling a cube and trisecting an arbitrary angle by ruler and compass. However two centuries earlier Descartes had put forward what probably counts as the first proof of these impossibilities. In this paper I analyze this proof, as well as the later related proof given by Montucla (1754) and the brief version of this proof published by Condorcet (1775) . I discuss the many novelties of these early arguments and highlight the problematic points addressed by Gauss (1801) and Wantzel. In particular I show that although Descartes developed many of the algebraic techniques used in later proofs he failed to provide an algebraic impossibility proof and resorted to a geometric argument. Montucla and Condorcet turned this proof into an algebraic one. I situate the analysis of the early proof of the impossibility of the two classical problems in the general context of early modern mathematics where mathematics was primarily viewed as a problem solving activity. Within such a paradigm of mathematics impossibility results arguably do not play the role of proper mathematical results, but rather the role of meta-results limiting the problem solving activity.     

The Influence of Nitrogen and Boron Implant into Silicon Substrate on the Phase and Internal Stress of c-BN Films

Cubic boron nitride(c-BN) film was deposited on a Si (100) substrate by the RF-magnetron sputtering.The mainly problems for fabrication of c-BN films are the low purity and high intrinsic compressive stress. In order to solve the two problems, the c-BN film with the buffer interlayer was deposited on the substrate which had been implanted with nitrogen and/or boron ions. The results show: the implantation of nitrogen ions can obviously increase c-BN content and reduce the internal stress slightly; while the implantation of boron shows no obvious improvement to the content of c-BN, which can reduce the internal stress in the film obviously. In addition, it is suggested that the implantation of nitrogen and boron shows the best result, which not only can increase the content of c-BN, but also reduce the internal stress in the c-BN film obviously.