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41.
42.
The chromatographic separation properties of long, thin adsorption tubes enable substance-specific quantitative enrichment and reduction to be achieved when sampling and thermal desorption are carried out in the same flow direction. The specific retention volumes, and also the breakthrough and peak end volumes, of 69 compounds in the boiling range between-164 and 126°C and of a relative molecular mass between 16 and 119 were determined at temperatures between 30 and 130°C: normal alkanes, isoalkanes, cycloalkanes, alkenes, polyenes, alkynes, aromatics, ethers, alcohols, aldehydes, ketones, carboxylic acids and their esters, nitroalkanes, O-heterocycles, S-heterocycles, chloroalkanes, water, nitrogen monoxide, nitrogen dioxide, carbon dioxide, and sulfur dioxide. The correlation between adsorbent temperature and specific retention volume of these components, presented in the form of diagrams, permits the required quantity of adsorbent to be determined for a given sample volume. Contrary to literature sources, even extremely volatile compounds such as propane, propene, methanol, formaldehyde, formic acid, and chloromethane can be quantitatively retained on Tenax provided the operating conditions are appropriately selected. 相似文献
43.
M. Nagy 《Colloid and polymer science》1985,263(3):245-265
44.
45.
Tsutomu Takeichi Nobuyuki Takahashi Rikio Yokota 《Journal of polymer science. Part A, Polymer chemistry》1994,32(1):167-174
Polyimide/polyimide molecular composite (MC) films comprised of a rigid polyimide derived from biphenyltetracarboxylic dianhydride (BPDA) and p-phenylenediamine (PDA) and a flexible polyimide derived from BPDA and bis (3,3'-diaminodiphenyl) acetylene (intA) and/or oxydianiline (ODA) were prepared by blending the polyamic acid solutions in 7 : 3 weight ratio, and then imidizing the blend films. Acetylene content in the flexible polyimide backbone was controlled by the ratio of intA and ODA. Cold-drawing of the blend polyamic acid films, followed by imidization, gives high modulus polyimide/polyimide MC films. The modulus of the MC films increased almost linearly with the draw ratio, reaching 25.5 GPa for the 40% drawn film. Acetylene groups in the flexible polyimide can be thermally cured to crosslink. The onset of exotherm appeared at 340°C on DSC, reaching maximum at 398°C. After the thermal crosslinking, the MC films maintained the high modulus, though elongation became small. Taking advantage of the crosslinkable acetylene units, two MC films were laminated and processed at 400°C for 20 min under 100 kg/cm2 to give a good-quality laminate film. The interface of the two films was strongly bonded through the crosslinking of acetylene groups. Laminate films maintained the high modulus afforded by the cold-drawing. © 1994 John Wiley & Sons, Inc. 相似文献
46.
纳米MnO2超级电容器的研究 总被引:24,自引:0,他引:24
用固相合成法制备纳米MnO2,作为超级电容器材料,通过循环伏安、交流阻抗与恒电流充放电等测试手段对MnO2电极进行分析.结果表明,以1 mol•L-1 KOH为电解液, MnO2电极在-0.1~0.6 V(vs. Hg/HgO)的电压范围内具有良好的法拉第电容性能.在不同电流密度下,电极比容量达240.25到325.21 F•g-1.恒电流充放电5000次后,电极容量衰减不超过10%. 相似文献
47.
用X-射线衍射、动态力学测定等手段研究了不同拉伸倍数的超高分子量聚丙烯薄膜的力学性能的变化.以X-射线衍射法并基于串联力学模型的假设得到的各样品的表观晶区模量E_c~(app)约为34-38GPa.样品模量E_b随拉伸倍数增加而逐渐增大,其变化趋势与非晶区取向因子的变化相类似,说明非晶区取向是左右样品模量的重要因素.室温下,69倍拉伸样品的模量为27GPa,约为表观结晶模量的3/4,且其值在-150-160℃的温度范围内没有急剧变化,说明超拉伸明显改善了材料的力学性能及热稳定性.在各拉伸样品中,考虑伸直链结晶生成的可能性,利用并串联力学模型对伸直链结晶的体积分数做了估算,并对X-射线衍射法所得表观结晶模量进行了修正,认为室温下聚丙烯的真正晶区模量约为47GPa. 相似文献
48.
计算了计入次近邻相互作用后一维点阵在低温下的定"长"比热,结果表明次近邻的影响使比热减小.比热;次近邻作用 相似文献
49.
E. P. Dolzhenko 《Mathematical Notes》1996,60(2):130-136
Letd(;z, t) be the smallest diameter of the arcs of a Jordan curve with endsz andt. Consider the rapidity of decreasing ofd(;)=sup{d(;z, t):z, t , ¦z–t¦} (as 0,0) as a measure of nicety of . Letg(x) (x0) be a continuous and nondecreasing function such thatg(x)x,g(0)=0. Put¯g(x)=g(x)+x, h(x)=(¯g(x))2. LetH(x) be an arbitrary primitive of 1/h
–1(x). Note that the functionH
–1
x is positive and increasing on (–, +),H
–1 0 asx– andH
–1+ asx +. The following statement is proved in the paper.Translated fromMatematicheskie Zametki, Vol. 60, No. 2, pp. 176–184, August, 1996.This research was supported by the Russian Foundation for Basic Research under grant No. 93-01-00236 and by the International Science Foundation under grant No. NCF000. 相似文献
50.
LetX be a Brownian motion defined on the line (withX(0)=0) and letY be an independent Brownian motion defined on the nonnegative real numbers. For allt0, we define theiterated Brownian motion (IBM),Z, by setting
. In this paper we determine the exact uniform modulus of continuity of the process Z.Research supported by NSF grant DMS-9122242. 相似文献