Light and Strong SiC Networks

The directional freezing of microfiber suspensions is used to assemble highly porous (porosities ranging between 92% and 98%) SiC networks. These networks exhibit a unique hierarchical architecture in which thin layers with honeycomb‐like structure and internal strut length in the order of 1–10 μm in size are aligned with an interlayer spacing ranging between 15 and 50 μm. The resulting structures exhibit strengths (up to 3 MPa) and stiffness (up to 0.3 GPa) that are higher than aerogels of similar density and comparable to other ceramic microlattices fabricated by vapor deposition. Furthermore, this wet processing technique allows the fabrication of large‐size samples that are stable at high temperature, with acoustic impedance that can be manipulated over one order of magnitude (0.03–0.3 MRayl), electrically conductive and with very low thermal conductivity. The approach can be extended to other ceramic materials and opens new opportunities for the fabrication of ultralight structures with unique mechanical and functional properties in practical dimensions.     

{雕刻时光}索尼DVD 602E

对于索尼602E而言，雕刻已经不仅仅是一种艺术，而是一种时尚、一股潮流。[编者按]     

Morphology Transformation Pathway of Block Copolymer-Directed Cooperative Self-Assembly of ZnO Hybrid Films Monitored In Situ during Slot-Die Coating

Cooperative self-assembly (co-assembly) of diblock copolymers (DBCs) and inorganic precursors that takes inspiration from the rich phase separation behavior of DBCs can enable the realization of a broad spectrum of functional nanostructures with the desired sizes. In a DBC assisted sol–gel chemistry approach with polystyrene-block-poly(ethylene oxide) and ZnO, hybrid films are formed with slot-die coating. Pure DBC films are printed as control. In situ grazing-incidence small-angle X-ray scattering measurements are performed to investigate the self-assembly and co-assembly process during the film formation. Combining complementary ex situ characterizations, several distinct regimes are differentiated to describe the morphological transformations from the initially solvent-dispersed to the ultimately solidified films. The comparison of the assembly pathway evidences that the key step in the establishment of the pure DBC film is the coalescence of spherical micelles toward cylindrical domains. Due to the presence of the phase-selective precursor, the formation of cylindrical aggregates in the solution is crucial for the structural development of the hybrid film. The pre-existing cylinders in the ink impede the domain growth of the hybrid film during the subsequent drying process. The precursor reduces the degree of order, prevents crystallization of the PEO block, and introduces additional length scales in the hybrid films.     

等离子体激励对飞行器流场影响的数值研究

针对传统飞行器控制方式的缺点,采用小尺度等离子体流动控制技术对飞行器流场影响进行研究。在前人的实验模型及飞行参数进行研究的基础上建立三维模型,采用数值仿真方法,研究了等离子体激励器位置和注入能量大小对飞行器流场及表面压力分布的影响。仿真结果表明：等离子体与边界层的相互作用可改变飞行器外部激波的初始结构,并在激励位置附近形成局部高压区;随着注入能量的增加,高压区峰值及作用范围分别扩大;等离子体激励产生的扰动具有三维传播特性,对飞行器侧壁面甚至对整个壁面周向压力分布产生影响。     

数字播控系统若干技术问题的探讨

随着数字技术和计算机技术的迅猛发展 ,电视技术的数字化进程十分迅速。两年前尚未被人们提上议事日程的“电视台播控系统数字化”问题 ,眼下已成为各家电视台必须考虑的当务之急。部分电视台已完成了播控系统的数字化建设和改造。目前较为常见的是用数字切换台播出系统取代模拟切换台播出系统 ,也有用数字矩阵播出系统取代模拟切换台或模拟矩阵播出系统的。模拟放像机被硬盘服务器或数字放像机 (兼容模拟 )所取代。在前者情况下 ,传统磁带放像机起着节目上载机及作为应急播出机的作用。总控系统则由原来的模拟视音频矩阵改造为数字矩阵 (采…     

航天器贮箱液体的有效转动惯量(上)

分析整理了航天器圆环筒形平底贮箱内液体的有效转动惯量计算方法,修正了现有文献中的错误,在常用的参数范围内对液体的有效转动惯量进行了计算,对其变化规律和影响因素做了物理分析,推导了液体滚转有效转动惯量的计算公式,并给出了适用的近似计算方法.对于纵向挡板引起的液体滚转有效转动惯量,给出了工程计算方法,能够确定滚转时液体的有...     

多媒体教学资源云共享平台的构建研究

随着云计算技术的发展,多媒体教学资源的云共享平台的建设引起了人们的高度重视。将多媒体教学资源与云平台建设结合起来,可以有效的解决在多媒体教学资源在网络学习平台建设中存在的种种问题,提高多媒体教学资源的利用率。本文主要研究,多媒体教学资源的特点,多媒体教学资源网络平台建设中存在的问题,云计算和云共享理论、多媒体教学资源云共享平台的构建。     

Growth of GaAs1−xPx/GaAs and InAsxP1−x/InP strained quantum wells for optoelectronic devices by gas-source molecular beam epitaxy

In this paper we show that pseudomorphically strained heterostructures of InAs _x P_1−x /InP may be an alternative to lattice-matched heterostructures of In_1−x Ga _x As _y P_1−y /InP for optoelectronic applications. We first studied the group-V composition control in the gas-source molecular beam epitaxy (GSMBE) of the GaAs_1-x P _x /GaAs system. Then we studied GSMBE of strained InAs _x P_1−x /InP multiple quantum wells with the ternary well layer in the composition range 0.15 <x < 0.75. Structural and optical properties were characterized by high-resolution x-ray rocking curves, transmission electron microscopy, absorption and low-temperature photoluminescence measurements. High-quality multiple-quantum-well structures were obtained even for highly strained (up to 2.5%) samples. The achievement of sharp excitonic absorptions at 1.06, 1.3 and 1.55μm at room temperature from InAs _x P_1−x /InP quantum wells suggests the possibility of long-wavelength optoelectronic applications.     

空调系统清洗引起的污染分析

分析了在空调系统清洗中,由于不合适的清洗方法及清洗手段、不合适的清洗设备和清洗程序所引起的空调系统的再污染。提出空调系统清洗的规范和有序是我国新型的空调清洗行业健康发展的关键。     

基于LPC2104的视频切换矩阵设计

本文介绍一种以AD81084作为视频切换器件,以LPC2104ARM微控制器作为控制单元的智能型视频切换器,并简述了其工作过程、硬件构成、软件设计。