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101.
隔水管固有频率的精确计算对保证隔水管的安全使用和防止共振的发生有着极为重要的意义.在分析中,考虑了分布轴向力和顶张力的共同作用,建立了隔水管横向振动力学模型;基于牛顿定律和纵横弯曲梁理论,对微单元受力分析,得到隔水管横向自由振动的四阶偏微分方程;利用分离变量法将四阶偏微分方程简化为四阶变系数常微分方程;采用积分法求解四阶变系数常微分方程,得到隔水管横向自由振动固有频率的解析解.结果表明:(1)分布轴向力作用下隔水管横向自由振动的固有频率和振型,与将分布轴向力简化为集中力作用下隔水管的固有频率和振型有很大差别;(2)顶张力一定时,随着分布轴向力减小,隔水管固有频率增大;分布轴向力一定时,随着顶张力增大,隔水管固有频率增大;(3)采用积分法求解隔水管横向振动特性时,计算精度高,为隔水管的优化设计提供了可靠的理论依据. 相似文献
102.
为提高数字高速多幅相机的像面照度,简化光学系统结构,提出一种离轴光学系统设计方法。该系统使用多组相同物镜,采用圆心一组,圆周均匀分布多组的方式平行阵列排布。分布于圆周上的物镜,其像面接收器相对物镜轴心平移离轴,以获得与圆心物镜相同的物面图像。分析了单物镜像面照度、畸变等与视场有关参数对光学系统各像面匹配的影响。在此基础上给出一个5通道离轴光学系统设计实例,系统空间分辨率优于30 lp/mm,畸变小于0.1%,F数2.0。相比目前广泛采用的棱锥、棱镜分幅方式,该离轴光学系统像面照度增加5倍以上,系统结构简易。 相似文献
103.
Siyin Ding Peng Liu Chong Gao Feng Wang Yanfen Ding Shimin Zhang Mingshu Yang 《先进技术聚合物》2019,30(4):1116-1125
Amino‐functionalized nanosilica (SiO2‐NH2) was prepared through cocondensation method using aminopropyltriethoxysilane as comonomer to hydrolyze and cocondense with tetraethylorthosilicate. The synergistic effect of combination of ammonium polyphosphate and pentaerythritol with SiO2‐NH2 on the thermal and flame‐retardant properties of intumescent flame‐retardant (IFR) polypropylene (PP) has been investigated by thermogravimetric analysis (TGA), scanning electron microscopy, Raman spectra, X‐ray diffraction (XRD), limiting oxygen index (LOI), and UL 94 tests. When 1.0 wt.% SiO2‐NH2 was added, the LOI value of the PP/IFR composite with 25 wt.% of IFR increased from 26.6% to 31.7%, while the UL 94 rating raised from not classified to V‐0. The TGA data demonstrated that the SiO2‐NH2 nanoparticles increased the charred residue of the PP/IFR composites. The morphological structures and the orderliness of the charred residue proved that SiO2‐NH2 promoted the formation of compact intumescent charred layer, which effectively protected the underlying polymer from burning. The XRD patterns of the charred residue indicated that nanosilica reacted with APP to form SiP2O7 crystal structure during combustion, which was beneficial to the formation of compact charred layers. In comparison with the inorganic SiO2‐cal nanoparticles, the amino‐functionalized nanosilica revealed much more efficient synergistic flame‐retardant effect due to the difference of surface properties. 相似文献
104.
通过对现有的两种混凝土损伤评估模型的分析,本文以刚度退化和累积滞回耗能两个指标来描述在低周反复荷载下再生混凝土的损伤累积过程,提出了一种适用于再生混凝土柱的双参数地震损伤模型.通过24 组文献数据拟合出模型参数的合理值与耗能因子β 同再生混凝土多因素之间关系的表达式.同时对再生混凝土柱的损伤量化标准进行了细分.最后将本文提出的损伤模型同另外两种模型作了比较.对比表明,本文所提出的损伤模型计算出来的损伤值标准差较小,离散性较低,能够更好地反映再生混凝土柱的累积损伤过程. 相似文献
105.
We report the microwave-induced electrophilic addition of single-walled carbon nanotubes (SWNTs) with alkylhalides using Lewis acid as a catalyst followed by hydrolysis. The reaction results in the attachment of alkyl and hydroxyl groups to the surface of the nanotubes. This rapid and high-energy microwave radiation is found to be highly efficient for this reaction, which only needs as low as several minutes. The resulting nanotubes were characterized with FTIR, UV-vis-NIR, Raman, TGA, TEM and AFM. It demonstrates that iodo-alkanes show higher reaction activity with SWNTs than chloro- and bromo-alkanes. 相似文献
106.
XUE Zengquan LIU Weimin HOU Shimin SHI Zujin GU Zhennan LIU Hongwen ZHAO Xingyu ZHANG Zhaoxiang WU Mianlei PENG Lianmao WU Quande 《中国科学A辑(英文版)》2000,43(11):1182-1188
Single-wall carbon nanotubes (SWCNTs) were synthesized and purified. A water colloid of SWCNTs was prepared and used to assemble
SWCNTs onto a gold film surface. Scanning tunneling microscopy (STM) images showed that short SWCNTs stood on gold film surfaces.
Using STM tips made of SWCNTs, a crystal grain image of a gold thin film and an atomic resolution image of highly oriented
pyrolytic graphite were successfully obtained. The electrical properties of short SWCNTs, which stood on the surface of gold
film, were measured using STM. That SWCNTs stand on gold thin films is a promising technique for studying structures and properties
of carbon nanotubes, as well as assembling and fabricating high-intensity coherent electron sources, field emission flat panel
display, tips for scanning probe microscopes, new nanoelectronic devices, etc. 相似文献
107.
用无外给电子体Ziegler-Natta催化剂催化丙烯聚合的研究 总被引:8,自引:0,他引:8
采用 9,9 双 (甲氧基甲基 )芴 (BMMF)为内给电子体合成MgCl2 /TiCl4 /BMMF催化剂 ,以三乙基铝为助催化剂在无需外给电子体的情况下得到高等规度的聚丙烯 .该催化剂具有高活性和高立体定向性 ,并与以邻苯二甲酸二丁酯 (Phthalate)为内给电子体 ,二苯基二甲氧基硅 (DDS)为外给电子体合成的MgCl2 /TiCl4 /Phthalate AlEt3 /DDS催化剂的性能进行比较 ,结果表明无外给电子体催化剂具有较高的活性 ,且聚丙烯的等规度大于 95 % .研究了聚合温度 ,铝钛比等聚合条件对催化剂的活性 ,聚合物的分子量、等规度和熔点的影响 ,并用13 C NMR对聚合物的序列结构进行了分析 相似文献
108.
109.
Shimin Zhang Jingkun Xu Baoyang Lu Leiqiang Qin Long Zhang Shijie Zhen Daize Mo 《Journal of polymer science. Part A, Polymer chemistry》2014,52(14):1989-1999
2‐((2,3‐Dihydrothieno[3,4‐b]dioxin‐2‐yl)methoxy)methyl oxirane (EDOT‐MO) was successfully synthesized by the reaction of epichlorohydrin with hydroxymethylated‐3,4‐ethylenedioxylthiophene (EDOT‐MeOH), which was synthesized via a simple four‐step sequence. Poly(hydroxymethylated‐3,4‐ethylenedioxylthiophene) (PEDOT‐MeOH) and poly(2‐((2,3‐dihydrothieno[3,4‐b]dioxin‐2‐yl)methoxy)methyl oxirane) (PEDOT‐MO) were electrosynthesized through electropolymerization of EDOT‐MeOH and EDOT‐MO, respectively. Structural, electrochemical, optical, and thermal properties of as‐formed polymers were investigated by FTIR, cyclic voltammetry, UV–vis, and thermogravimetry. Spectroelectrochemistry studies demonstrated that PEDOT‐MeOH and PEDOT‐MO could be reversibly oxidized and reduced accompany with obvious color changes. Further kinetic studies demonstrated that the introduction of hydroxymethyl or ethylene oxide group significantly improved electrochromic properties of 3,4‐ethylenedioxythiophene (PEDOT) and resulted in high contrast ratios (57.3% at 585 nm) and coloration efficiencies (338.5 cm2 C?1), low switching voltages, and fast response time. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 1989–1999 相似文献
110.