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In a previous paper we discussed co-crystallization in a LDPE/HDPE blend using TREF and DSC. As part of that study it was observed that pure HDPE showed an unexpected fractionation behavior when quench crystallized in TREF. The overall peak broadened and two peaks appeared instead of the previously observed single peak for slow cooled HDPE.The development of two peaks was observed for all commercial HDPEs investigated, independent of their melting indices and densities. TREF and GPC were used in an attempt to evaluate the origin of the two HDPE components.The authors appreciate support from CAPES-BRAZIL (C.A.F.). Additional thanks go to Dr. G. W. Knight in Dow Chemical Company for kindly providing the polymer samples and performing the GPC analysis. 相似文献
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F. Pereira Dos Santos J. Léonard Junmin Wang C. J. Barrelet F. Perales E. Rasel C. S. Unnikrishnan M. Leduc C. Cohen-Tannoudji 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2002,19(1):103-109
We recently observed a Bose-Einstein condensate in a dilute gas of 4He in the 23S1 metastable state. In this article, we describe the successive experimental steps which led to the Bose-Einstein transition
at 4.7 μK: loading of a large number of atoms in a MOT, efficient transfer into a magnetic Ioffé-Pritchard trap, and optimization
of the evaporative cooling ramp. Quantitative measurements are also given for the rates of elastic and inelastic collisions,
both above and below the transition.
Received 15 October 2001 相似文献
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固体材料激光冷却的实验研究及其最新进展 总被引:1,自引:1,他引:0
近年来,基于反斯托克斯荧光制冷(Anti—Stokes Fluorescent Cooling)的固体材料激光冷却技术得到了快速发展。本文首先简单介绍了固体材料激光冷却的基本原理及其技术;其次,详细介绍了各种固体激光冷却的新材料、新方案和新结果及其最新实验进展;最后,就固体激光冷却技术的应用前景及其未来发展方向等问题进行了简单讨论与展望。 相似文献
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A hybrid cavity magnomechanical system to transfer the bipartite entanglements and achieve the strong microwave photon–phonon entanglement based on the reservoir engineering approach is constructed. The magnon mode is coupled to the microwave cavity mode via magnetic dipole interaction and to the phonon mode via magnetostrictive force (optomechanical-like). It is shown that the initial magnon-phonon entanglement can be transferred to the photon-phonon subspace in the case of these two interactions cooperating. In the reservoir-engineering parameter regime, the initial entanglement is directionally transferred to the photon-phonon subsystem, so a strong bipartite entanglement in which the magnon mode acts as the cold reservoir to effectively cool the Bogoliubov mode delocalized over the cavity and the mechanical deformation mode is obtained. Moreover, dual-mode cooling is realized by engineering the dissipation of photon and phonon modes within the target mode, which allows entanglement to be further enhanced. The results indicate that the steady-state entanglement is robust against temperature. The dual-mode cooling reservoir engineering scheme can potentially be extended to other three-mode quantum systems. 相似文献
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高分子材料注塑固化阶段的残余应力分析 总被引:3,自引:0,他引:3
在结晶性高分子材料注塑过程的固化阶段,温度分布、材料细观结构和应力应变之间相互耦合,因而其变化规律非常复杂.本文在井上等人考虑材料细观结构变化的金属热加工工艺应力分析[3~6]的基础上,发展了一套用于高分子注塑固化阶段残余应力分析的本构描述和有限元分析方法.在本构模型中,同时考虑了温度变化、结晶和“冻结取向”对变形的贡献. 相似文献
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All metallic, hollow sandwich cylinders having ultralight two-dimensional (2D) prismatic cores are optimally designed for maximum thermo-mechanical performance at minimum mass. The heated cylinder is subjected to uniform internal pressure and actively cooled by forced air convection. The use of two different core topologies is exploited: square- and triangular-celled cores. The minimum mass design model is so defined that three failure modes are prevented: facesheet yielding, core member yielding, and core member buckling. The intersection-of-asymptotes method, in conjunction with the fin analogy model, is employed to build the optimization model for maximum heat transfer rate. A non-dimensional parameter is introduced to couple the two objectives—structural and thermal—in a single cost function. It is found that the geometry corresponding to maximum heat transfer rate is not unique, and square-celled core sandwich cylinders outperform those having triangular cells. The eight-layered sandwich cylinders with square cells have the best overall performance in comparison with other core topologies. Whilst a sandwich cylinder with shorter length is preferred for enhanced thermo-mechanical performance, the influence of the outer radius of the cylinder is rather weak. 相似文献