面内阶跃载荷下矩形薄板的塑性动力屈曲

对于面内阶跃载荷作用下矩形薄板的塑性动力屈曲问题,将临界应力和屈曲惯性项指数参数作为双特征参数求解.由相邻平衡准则导出失稳控制方程,由动力屈曲发生瞬间的能量转换和守恒准则,导出波阵面上的屈曲变形补充约束条件.失稳控制方程、边界条件、塑性波阵面上的连续条件和补充约束条件构成了定量求解两个特征参数和动力屈曲模态的完备条件.研究了矩形薄板塑性动力屈曲过程中板的厚宽比、冲击载荷大小、屈曲模态以及切线模量和临界屈曲长度之间的关系.     

伯努利定理适用条件分析

本文分析了以理想流体的运动微分方程推导伯努利定理时所利用的限制条件,对有势力作用下不可压缩流动的流场中应用伯努利定理的矢径微分量、速度、涡量之间的关系进行了深入讨论. 分析结果表明当流动为无旋流动或螺旋流时,伯努利常数在流场各点取相同值;伯努利常数在流涡面上各点取值相等,沿流线或涡线积分均为在流涡面上积分的特殊情况.     

纳米流体中气体水合物生成条件

为了研究纳米粒子对制冷剂水合物热力学生成条件的影响,建立了新型纳米流体中制冷剂水合物相平衡热力学模型,理论研究了HFC134a(R134a)气体水合物的热力学生成条件,并用实验验证了模拟结果.结果表明:新型纳米流体中制冷剂水合物热力学相平衡模型能够较好地反映纳米流体中制冷剂气体水合物相平衡特征,相同温度下相平衡最大相对误差为7.3%,平均相对误差为5.3%.     

模糊选择函数半序合理的充分条件

在G?del t-模下,研究了模糊选择函数的半序合理性.首先给出了模糊选择函数的合理性条件FA1.然后研究了该条件与模糊选择函数半序合理性之间的关系,得到了半序合理的一个充分条件.     

Superconvergence analysis of the finite element method for nonlinear hyperbolic equations with nonlinear boundary condition

This paper discusses the semidiscrete finite element method for nonlinear hyperbolic equations with nonlinear boundary condition. The superclose property is derived through interpolation instead of the nonlinear H^1 projection and integral identity technique. Meanwhile, the global superconvergence is obtained based on the interpolated postprocessing techniques.     

Optimization of Transducer Location for Novel Non-Intrusive Methodologies of Diagnosis in Diesel Engines

The health monitoring has been studied to ensure integrity of design of engine structure by detection, quantification, and prediction of damages. Early detection of faults may allow the downtime of maintenance to be rescheduled, thus preventing sudden shutdown of machines. In cylinder pressure developed, vibrations and noise emissions data provide a rich source of information about condition of engines. Monitoring of vibrations and noise emissions are novel non-intrusive methodologies for which positioning of various transducers are important issue. The presented work shows applicability of these diagnosis methodologies adopted in case of diesel engines. The effects of changing various fuel injection parameters was analyzed. Scope of using non-intrusive technique has been analyzed by changing locations of microphone. Novelty of this worklies in exploring signal processing methods for various locations around the engine test set up. Various frequency ranges of contributing noise and vibration sources were identified. Time-Frequency analysis showed the onset of various cyclic. Based on the identification of various frequency bands, it is possible to device suitable filters in order to extract more information.     

热处理条件对PVA薄膜阻氢性能的影响

采用XRD测定了PVA薄膜在不同热处理条件下的结晶度,并用自行设计的渗氢系数测量系统研究了在不同热处理条件下的PVA薄膜阻氢性能的变化规律。结果表明,PVA薄膜的热处理温度越高,其结晶度越高,越有利于提高PVA薄膜的阻氢性能,但热处理温度宜选择在180℃以下,以防止PVA薄膜热降解,另一方面,在PVA的玻璃化转变温度以下进行热处理同样能够提高PVA薄膜的阻氢性能,而醇解度较低的PVA薄膜在玻璃化转变温度以下经热处理后的阻氢性能提高的幅度较大。     

Simplified sonochemical preparation of titania embedded with selected metals for purification of benzene and toluene

Titania (TiO₂) photocatalysts, each embedded with one of six metals (Ag, Ce, Co, Fe, Mg, and Mn), were prepared using a simplified ultrasonic process. The characteristics of the prepared metal-embedded TiO₂ (metal–TiO₂) were determined using transmission electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction spectroscopy, photoluminescence emission spectroscopy, UV–visible spectroscopy, and nitrogen adsorption–desorption. Except for Co–TiO₂, the metal–TiO₂ photocatalysts showed improved performance for the decomposition of gaseous benzene and toluene, which are two of the most problematic indoor air pollutants that can cause a variety of adverse health symptoms, under daylight lamp irradiation. Photocatalytic activity was greatest for the Mg–TiO₂ sample, followed by, in order, the Ag–TiO₂, Ce–TiO₂, Fe–TiO₂, Mn–TiO₂, unmodified TiO₂, and Co–TiO₂ samples. Although Mg–TiO₂ showed the least redshift in its light absorption and the highest electron–hole recombination rate among the metal–TiO₂ photocatalysts, it yielded the highest photocatalytic activity, likely because of its increased adsorption capacity and anatase composition. The degradation of benzene and toluene over Mg–TiO₂ improved as ultrasound treatment amplitude increased from 20 to 37 μm, then decreased gradually as amplitude was further increased to 49 μm. Degradation efficiency also improved as ultrasound operation time increased from 30 to 60 min, then decreased gradually as amplitude was further increased to 90 min. Overall, this process could be utilized to prepare metal–TiO₂ photocatalysts with improved performance for the decomposition of gas phase pollutants under daylight lamp irradiation.     

Necessary and sufficient conditions for Hölder continuity of Gaussian processes

The continuity of Gaussian processes is an extensively studied topic and it culminates in Talagrand’s notion of majorizing measures that gives complicated necessary and sufficient conditions. In this note we study the Hölder continuity of Gaussian processes. It turns out that necessary and sufficient conditions can be stated in a simple form that is a variant of the celebrated Kolmogorov–Čentsov condition.     

半定矩阵秩极小的非凸精确松弛

本文主要研究半定矩阵秩极小问题(P)的非凸精确松弛及其性质.首先,为求解问题(P),我们引入其Schatten p-范数(0＜p＜1)松弛,记为(Sp).其次,通过定义半定限制等距常数和半定限制正交常数,我们给出了问题(P)有唯—解的充分条件.最后,利用半定限制等距性质,我们给出了问题(P)和(Sp)有相同唯一解的充分条件.特别地,对任意0＜p＜1,我们还得到—个一致的精确恢复条件.