损伤变量对复合材料损伤演化过程的影响分析

复合材料层合板损伤模型中的刚度退化需要通过损伤变量来实现。针对通常采用的2种损伤变量定义,给出了统一表达式。此外,损伤刚度矩阵是损伤变量的函数,基于应变等效假设推导了三维损伤刚度矩阵,从而避免了对损伤刚度矩阵的人为假定。最后,通过复合材料层合板在冲击载荷作用下的数值模拟,讨论了损伤变量的2种定义对数值结果的影响,表明损伤变量的不同定义对分层和基体损伤分布存在一定的影响,对冲击载荷的影响不大。建议在复合材料损伤模拟中,应予关注损伤变量。     

Engineering all-aromatic polyamide surface from hydrophilic to superhydrophobic and the accelerated strategy

Being a new kind of nanomaterials, aromatic polyamide nanofibers (ANF) have been much highlighted in recent studies. We here demonstrate an isopropyl alcohol (IPA) accelerated chemical cleavage on poly (p-phenylene terephthalamide) chopped fibers, which provides an efficient preparation method of ANF. The comprehensive study on the processes accelerated by different alcohols revealed that the preparation time of ANF in the mixed medium of dimethyl sulfoxide (DMSO)-alcohol (20:1 in volume) was shorten to 45 min and 75 min for methanol (ethanol) and isopropanol, respectively. However, the nanofibers prepared in DMSO-IPA exhibited the minimum in axial and radial dimensions, providing the finest and most uniform diameter of 16 nm. The corresponding ANF films through vacuum assisted filtration also showed the highest tensile strength of 150 MPa, in comparison with those of the ANF films prepared using other alcohols, which were about 110 MPa. Furthermore, ANF/silicon hybrid films were prepared by the ionic ring-opening reaction followed by the alkoxysilane condensation and nanoparticle fabrication. By changing the organo functional groups in the alkoxysilane, the surface of the films were adjustable in a wide contact angle range from 56° (hydrophilic) to 150° (superhydrophobic), suggesting the amendable interfacial properties potential applicable to composite fabrication with most of the resin matrix.     

强油非导向变压器热特性分析及优化设计

本文中作者借助流体软件对强油非导向变压器进行了热特性分析,并对变压器内部散热油路及冷却器进行了优化设计.     

Preparation and characterization of GaN films grown on Ga-diffused Si （111） substrates

Hexagonal GaN films were prepared by nitriding Ga2O3 films with flowing ammonia. Ga2O3 films were deposited on Ga-diffused Si (111) substrates by radio frequency (r.f.) magnetron sputtering. This paper have investigated the change of structural properties of GaN films nitrided in NH3 atmosphere at the temperatures of 850, 900, and 950℃ for 15 min and nitrided at the temperature of 900℃ for 10, 15, and 20 rain, respectively. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS) were used to analyze the structure, surface morphology and composition of synthesized samples. The results reveal that the as-grown films are polycrystalline GaN with hexagonal wurtzite structure and GaN films with the highest crystal quality can be obtained when nitrided at 900℃ for 15 min.     

冷轧工作辊摩擦不稳定分析及其抑制对策

对冷轧机工作辊由于摩擦力引起的垂直、横向振动作了定性分析，指出了它们的危害，提出了预防措施。     

新时期研究生挫折教育略论

加强对研究生的挫折教育,已成为新时期研究生教育的一项非常重要而迫切的任务。研究生挫折教育的途径主要有:培养研究生树立良好的挫折观;将远大志向与正确、切实的短期目标有机结合;研究生导师要将挫折教育作为自身工作的重要职责和内容;要创设挫折情境,加强实践体验;在研究生中积极开展抗挫互助活动;帮助研究生学会自我调适、自我超越、自我教育。     

Camouflage texture evaluation using a saliency map

Multimedia Systems - Camouflage effect evaluation and examination is an important procedure in digital camouflage pattern design as it is helpful in improving the objectivity and effectiveness...     

岩土工程勘察的重点分析

近年来,岩土工程勘察技术发展得非常快,研究领域不断拓展,取得了较多的成就。但是,在发展过程中也存在一些不足。重点分析了岩土工程勘察工作,并结合实际工作提出一些个人意见,以期能为相关工作提供帮助。     

对高校图书馆智能化管理的探究

随着现代信息的蔓延,学校素质教育的全面推进,学校图书馆的地位在不断提高,作用也会逐渐的凸现出来.图书馆是落实素质教育的一个重要阵地,把图书活动作为一个栽体,充分发挥图书馆现有的物质基础,大力开展全校师生的读书活动,形成爱书,读书的良好风尚,使图书馆成为师生最大、最亲近的学习课堂.由此,大力加强和广泛发展高校图书馆的建设,是一项非常重要而迫切的艰巨任务,也是高校图书馆顺应时代发展的必要,这样就要求正确面对管理,加强对图书馆智能化的探究.     

模拟器在嵌入式软件开发中的应用实现

嵌入式系统在电子产品中的应用,加快了电子产品更新换代的速度,要想在技术竞争中立于不败之地,唯有加快应用软件开发进程,缩短产品开发周期.模拟器在嵌入式系统应用软件开发中的使用,大大简化了软件调试过程.本文基于μ C/OS-II嵌入式实时操作系统,研究开发出一款利用模拟器进行应用软件开发的多媒体播放器智能菜单,具有很大的实际应用价值,加快了产品的开发速度,增加了产品的核心竞争力.