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.     

简单断面孔型计算机绘图系统简介

介绍了简单断面孔型计算机绘图系统的编制方法、使用范围 ,计算机绘图的步骤及特点     

基于MATLAB的热定型机PID张力控制器设计

文章介绍了热定型机的工作原理,及其定型过程中张力系统控制结构图,并以此为基础建立了张力控制系统的数学模型.基于比例积分微分(PID)控制器的原理,利用MATLAB软件设计了张力控制器,其编写的PID参数整定函数能作为MATLAB函数进行直接调用.实验和仿真结果表明:该控制器完全满足张力控制系统的性能要求,降低了超调量,提高了系统的动静态性能;同时设计简单、易于实现.     

多目标优化理论在蜂窝夹芯结构设计中的应用

在确定了设计变量及目标函数的基础上,根据结构本身的要求,推导出用于多目标优化的5个约束条件.根据多目标优化理论,采用乘除法对蜂窝夹芯结构进行了评价函数的构造,并用VC语言编制了钢质蜂窝夹芯减振板结构的优化程序,该程序可实现结构尺寸及性能的优化,并计算出各目标函数的最终值.     

激光快速成形Rene′88DT高温合金的时效强化研究

研究了时效时间对激光快速成形后时效硬化镍基高温合金Rene′88DT中沉淀相组织演化和力学性能的影响。发现随时效时间的增加，沉淀相y’略有长大，颗粒之间发生大颗粒吞噬小颗粒的粗化，时效40h后沉淀相颗粒粗化明显。对经不同时间时效后的激光快速成形Rene′88DT试样进行了硬度测试。结果显示，在时效时间为28h时，硬度有一峰值HRC49。在此基础上，采用1165℃，2h固溶、空冷＋760℃，28h时效的热处理工艺对激光快速成形标准拉伸棒样进行了热处理，拉伸结果显示成形件的抗拉强度较激光沉积态提高了400MPa，屈服强度接近同种材料的粉末锻造水平。     

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...     

Bounds on multipartite concurrence and tangle

We present an analytical lower bound of multipartite concurrence based on the generalized Bloch representations of density matrices. It is shown that the lower bound can be used as an effective entanglement witness of genuine multipartite entanglement. Tight lower and upper bounds for multipartite tangles are also derived. Since the lower bounds depend on just part of the correlation tensors, the result is experimentally feasible.     

面向能力培养的嵌入式系统课程群建设研究

能力型、创新型人才是社会发展的需求,也是高等教育的培养目标。为了培养具备能力和创新素质的嵌入式系统方面的人才,本文进行了嵌入式系统课程群的建设,研究了相应的教学方法,从理论和实践上培养学生的能力,培养创新素质。