An Accurate and Universal HEOM Approach to Strongly Correlated Quantum Impurity Systems

A hierarchical equations of motion(HEOM)approach is developed for general open quantum systems coupled to fermionic environment.The HEOM method is in principle formally exact,as it resolves nonperturbatively the combined effects of many-body interaction,system-bath dissipation,and non-Markovian memory.In practice,the HEOM approach is highly accurate and efficient for the characterization of strongly correlated quantum impurity sys-     

耗散结构视角下生态型物流园区进化模型研究

为探究生态型物流园区实现可持续发展的进化机理,运用耗散结构理论对生态型物流园区已具备的条件进行分析,构建了基于logistic生长曲线的进化模型,发现生态型物流园区的发展经历了物种植入期、种群发展期、郁闭稳定期和种群蜕变期4个阶段,并循环往复、不断演进,进而形成了进化的复合logistic生长曲线.研究表明,生态型物流园区实现可持续发展,有两个主要途径:一是通过园区内部的不断集成与优化引入负熵流,从而减缓总熵的增加速度;二是通过对园区内外部要素的调控,使得园区功能不断升级,从而进入新的演化周期.     

兆瓦级风电变流器IGBT模块的热特性分析

以某企业建立的采用液冷冷却系统的IGBT模块实验平台为基础,对一3MW紧凑型风电机组的IGBT模块的热特性进行了分析.根据在动态实验中采集到的数据,得出了逆变器输出功率与时间的关系,并结合实验数据对模块温度以及发热量的变化特性进行了分析,得到了兆瓦级风电变流器中IGBT模块温度与发热量随时间的变化关系.实测结果表明,该风电机组逆变器的效率为98.62%,IGBT模块的最终工作温度保持在50~56℃,说明采用的液冷冷却系统对大功率IGBT模块具有良好的冷却效果.     

Constructal entransy optimizations for insulation layer of steel rolling reheating furnace wall with convective and radiative boundary conditions

Based on the entransy dissipation extremum principle for thermal insulation process, the constructal optimizations for a plane insulation layer of the steel rolling reheating furnace wall with convective and radiative boundary conditions are carried out by taking the minimization of entransy dissipation rate as optimization objective. The optimal construct of the plane insulation layer is obtained. The results show that for the convective heat transfer boundary condition, the optimal constructs of the insulation layer obtained based on the minimizations of the entransy dissipation rate and heat loss rate are obvi- ously different. Comparing the optimal construct obtained based on the minimization of the entransy dissipation rate with that based on the minimization of the heat loss rate, the entransy dissipation rate is reduced by 5.98 %, which makes the global thermal insulation performance of the insulation layer improve. For the combined convective and radiative heat transfer boundary condition, compared the insulation layer having an increasing thickness with that having constant thickness and a decreasing thickness, the entransy dissipation rates are reduced by 16.59 % and 39.72 %, respectively, and the global thermal insulation performance of the insulation layer is greatly improved.There exits an optimal constant coefficient α2,opt which leads to the minimum dimensionless entransy dissipation rate of the insulation layer. The difference between the optimal constant coefficients α2,opt obtained based on the minimizations of the entransy dissipation rate and the maximum temperature gradient of the insulation layer is small. This makes the corresponding thermal stress obtained based on the minimum dimensionless entransy dissipation rate also be small, and the global thermal insulation performance and thermal safety of the insulation layer are improved simultaneously. The results obtained can provide some guidelines for the optimal designs of the insulation layers.     

LED平板筒灯散热模型研究

为了解决IED平板筒灯散热问题,利用FloEFD建立IED平板筒灯散热模型,分析筒灯壳体上散热肋片的数量对散热情况的影响,对实物LED平板筒灯多点进行了温度测量,并与仿真结果进行了比较。在此基础上,对其结温进了理论计算,保证LED芯片工作在合理的温度范围之内。通过仿真分析表明,所设计的LED平板筒灯具有良好的散热效果。     

框架填充墙破坏机理研究及其耗能设计

对影响框架填充墙破坏机制的三大因素（填充墙与框架连接方式、砌体材料、填充墙高宽比）及其应力分布情况进行了分析,阐述了框架填充墙耗能设计方法。分析认为：框架填充墙的设计缺乏统一合理的设计标准,需进一步深入了解其破坏机制,从而提高填充墙耗能能力以及框架填充墙的整体抗震水平。     

Different effects of substrates on the morphologies of single-walled carbon nanotubes

In this work, different effects of substrates on the morphologies of single-walled carbon nanotubes （SWNTs） are studied. SWNTs were produced by floating catalytic chemical vapor deposition using CH4 as carbon source gas and Ar as carrier gas. Then the SWNTs were deposited on lithography-patterned different substrates. The as-grown SWNTs at the boundaries between SiO2 and metal were characterized by scanning electron microscopy, atomic force spectroscopy and Raman spectroscopy. It is found that SWNTs deposited on low-conductivity substrates trend to have curved morphologies and some of them form rings, while SWNTs deposited on metal sub- strates remain straight and orientated. The mechanism of these effects was also discussed, which is closely related to the thermal conductivities and the principle of energy dissipation.     

消力池消能效果影响因素的研究

通过VOF(volume of fluid)方法,模拟了水闸泄水时消力池内的流场情况。通过慈溪龙山排涝出海闸工程实例对模型精确性进行校核,在此基础上对消能效果的因素进行了研究。结果表明增加消力坎角度、消力坎高度和泄水水头高度可以增大消能率;结论可为低水头泄水工程的设计提供依据与参考。     

不同高径比石膏试样破坏特性及其能量耗散

采用RMT-150B岩石力学试验机,对七种不同高径比的石膏试样进行了单轴压缩试验,分析其力学特性及其破坏特征.根据单轴压缩力学试验结果,利用能量耗散理论,分析其能量耗散特性.研究结果表明:随轴压应力的增加,石膏试样内部微裂隙先闭合,而后在其尖端产生了新裂隙;新裂隙随轴压应力的增加而逐渐地扩展、贯通、形成破裂面,最终发生剪切滑移破坏;石膏试样的体积应变随轴压应力的增大,经历了先压缩后增加,最后急剧膨胀,表现出明显的非线性变形;石膏试样的峰值应力、弹性模量随高径比的减小而增大;轴向应变和横向应变随高径比的减小而减小;变形模量与高径比之间的关系不明确,不能用其表征石膏试样的变形特性;高径比越大的石膏试样受压后容易发生剪切破坏,破坏时吸收的能量增量越快,属于脆性破坏,而高径比越小的石膏试样则发生压酥破坏,属于塑性破坏.     

聚氨酯/环氧树脂互穿网络硬泡循环压缩

制备了聚氨酯(PU)/环氧树脂(ER)互穿聚合物网络硬泡，研究了互穿聚合物网络(IPN)硬泡的化学结构及微观结构形态.傅里叶红外光谱(FTIR)分析表明，IPN硬泡的网络间存在接枝反应.扫描电子显微镜(SEM)分析发现，IPN硬泡泡孔结构形状都比较均一.循环压缩实验研究表明：随循环次数增加，应力下降，单次循环的能量损耗下降；随ER含量增加，IPN硬泡的压缩模量和强度提高，相同应变下应力增加，每次循环耗能增加；循环压缩的加卸载应力 应变曲线可用改进的Ogden模型表示；累积能量损耗可用Weibull方程表示.