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111.
M. Alvarez‐Lainez M. A. Rodriguez‐Perez J. A. DE Saja 《Journal of Polymer Science.Polymer Physics》2008,46(2):212-221
The thermal conductivity and the cellular structure of novel open‐cell polyolefin foams produced by compression molding and based on blends of an ethylene‐vinyl acetate copolymer (EVA) and a low‐density polyethylene (LDPE) have been studied in the temperature range between 24 and 50 °C. The experimental results have shown that the cellular structure of the analyzed materials has interconnected cells because of the presence of large and small holes in the cell walls, this structure being clearly different to the typical structure of open‐cell polyurethane foams. It has been found that at low temperatures the materials have a slightly higher thermal conductivity than closed‐cell polyolefin foams of similar densities. The different mechanisms of heat flow, conduction, convection, and radiation have been analyzed by using experimental measurements and a theoretical model. It has been proved that, in spite of having an open‐cell structure, the convention mechanism is negligible, being the radiation mechanism the one which made different the conductivity of materials with varying cellular structures. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 212–221, 2008 相似文献
112.
本文采用水热合成法制备了β-Na(Y1.5-x-yNa0.5)F6:YbxTmy(x=0.2~1.0,y=0.001~0.008)纳米颗粒,并利用X射线粉末衍射仪、透射电子显微镜和F-4600荧光分光光度计表征了其样品的物相、形貌和发光性质.结果表明样品物相为六角相,颗粒平均直径约22nm,并探讨了Yb3+和Tm3+掺杂浓度对样品的上转换发光性质的影响,结果表明敏化剂Yb3+的最佳掺杂浓度为60%,而激活剂Tm3+的最佳掺杂浓度为0.6%. 相似文献
113.
In this paper we solve the problemof desingularization of an absolutely isolatedsingularity of a differential equation, including thedicritical case. As an application, we prove thefiniteness of the number of dicritical points in theblowing up tree of an absolutely isolated singularity. 相似文献
114.
Joseph C. Calabrese 《有机化学》1993,(2)
The mechanism of decarboxylative cyclization of allylic cyclic carbamates 1 leading to 2-substituted △~3-piperidines and-pyrrolidines, as well as its applications to the total synthesis of (--)codonopsine, are described. 相似文献
115.
用75%乙醇回流法提取出藏药"西藏猫乳(生等)"的有效成分并浓缩精制后,采用HPLC梯度洗脱法,在选定的色谱条件{DuPont ZORBAX ODS C18色谱柱(4.6 mm×25 cm),用甲醇(A)-甲酸铵水溶液(pH=3.5,1.0 mL·min-1,B)进行梯度洗脱(甲醇浓度0~10 min,20%~25%;10~20 min,25%~40%;20~55 min,40%~55%;55~75 min,55%~75%;75~85 min,75%~90%),检测波长为290 am}下,对藏药"生等"的提取液进行了有效的分离与检测,并建立了"生等"药材的数字化色谱指纹谱(DFPS).所建立的方法能对藏药的产地归属进行有效的分辨. 相似文献
116.
J.P. Remeika G.P. Espinosa A.S. Cooper H. Barz J.M. Rowell D.B. McWhan J.M. Vandenberg D.E. Moncton Z. Fisk L.D. Woolf H.C. Hamaker M.B. Maple G. Shirane W. Thomlinson 《Solid State Communications》1980,34(12):923-926
A new family of rare earth-rhodium-tin intermetallic compounds, with the representative formula (RE)RhxSny, has been synthesized in single crystal form. The compounds containing the heavier rare earths are superconducting and those with the lighter rare earths are generally magnetic. The compound ErRh1.1Sn3.6 exhibits reentrant superconductivity with Tc = 0.97 K and Tm = 0.57 K as determined from ac magnetic susceptibility measurements. The synthesis and X-ray characterization of the series are described and the results of electrical resistivity, upper critical magnetic field, magnetic susceptibility, specific heat and neutron scattering measurements on the Er compound are given. 相似文献
117.
We study the relaxation limit for the Aw-Rascle system of traffic flow. For this we apply the theory of invariant regions and the compensated compactness method to get global existence of Cauchy problem for a particular Aw-Rascle system with source, where the source is the relaxation term, and we show the convergence of this solutions to the equilibrium state. 相似文献
118.
采用水热与溶剂热结合的方法,在乙二醇-正己醇体系中,通过调节KF与RE(RE=La,Yb,Er)的量比、反应温度和反应时间实现了由LaF_3(六角相)到KLaF_4(立方相、六角相)晶型的控制合成。借助透射电子显微镜(TEM)和X射线粉末衍射(XRD)对样品的结构和微观形貌进行表征。结果表明,当KF/RE比例为2. 25时,制备的样品为片状的六角相LaF_3纳米颗粒;当KF/RE比例为3. 00时,得到具有近似球形的立方相KLaF_4纳米颗粒;当KF/RE比例为4. 25时,得到了六角相(KLaF_4)_(1. 5)纳米颗粒。上转换发射光谱显示:所有的样品在近红外光(980 nm)激发下,均有3个明显的发射峰,在522 nm、544 nm处分别对应于Er~(3+)的~4S_(3/2),~2H_(11/2)→~4I_(15/2)能级跃迁,655 nm处属于Er~(3+)的~4F_(9/2)→~4I_(15/2)能级跃迁。 相似文献
119.
D.E. Moncton 《Solid State Communications》1973,13(11):1779-1782
The 120 K phase transition in ZrV2 has been investigated for magnetic and crystallographic effects using neutron diffraction. A cubic-rhombohedral martensitic transformation was observed at 116.7 K. No local magnetic moments, either ordered or disordered, were found to exist between 5.4 K and 300 K. 相似文献
120.
J.W. Lynn D.E. Moncton W. Thomlinson G. Shirane R.N. Shelton 《Solid State Communications》1978,26(8):493-496
The neutron scattering technique has been used to investigate the magnetic properties of the ternary Chevrel-phase superconductor HoMo6S8. Magnetic critical scattering is observed in the superconducting phase, with the magnetic correlation range increasing with decreasing temperature. At the transition in which the normal state is reentered, the system is found to develop long range ferromagnetic order, with a saturated magnetic moment at low temperatures of 9.06 ± .3 μB and the spin direction along the unique [111] trigonal axis. 相似文献