基于EFEN-SP3方法的pin-by-pin中子动力学计算方法研究

为能直接给出安全分析所需的最热棒功率而不引入组件均匀化近似和精细功率重构近似，本文研究了基于栅元均匀化的pin-by-pin中子动力学计算方法。通过全隐式向后差分对多群时空中子动力学方程组的时间变量进行离散，采用指数函数展开节块-SP₃（EFEN-SP₃）方法求解含裂变介质的多群中子固定源方程组，通过高阶源展开技术消除了中子源分布与缓发中子先驱核分布形状不一致的问题。采用Ks因子、LW外推和粗网再平衡等加速技术提高计算效率。三维pin-by-pin中子动力学问题的数值结果表明：pin-by-pin中子动力学计算能直接给出单棒功率密度分布；高阶源展开技术可有效抑制计算偏差随时间步的累加效应；加速技术可将SP₃动力学计算的求解速度提高134.9倍。     

Gelation properties of goose liver protein recovered by isoelectric solubilisation/precipitation process

Isoelectric solubilisation/precipitation (ISP) process was applied to goose liver (GL) for protein extraction. The gelation properties of proteins extracted by acid processes (ACP, pH 2.0, 2.5 and 3.0) and alkaline processes (ALP, pH 11.0, 11.5 and 12.0) were estimated, where the unextracted ground GL was set as the control. Nearly 58.39~79.00% of GL proteins were recovered by ISP treatments. High molecular weight (100~250 kDa) proteins were found to be partially hydrolysed by ACP, while few changes in proteins occurred during ALP. As evidenced by rheological and textural measurements, ALP proteins formed gels with high elasticity and superior texture, whereas ACP proteins had inferior gelation properties. Moreover, ALP proteins were able to form a highly interconnected and homogeneous three‐dimensional microstructure. Predominantly, gels produced by 11.0 had optimal texture and the lowest cooking loss (P < 0.05). These results suggested that the ISP process (ALP) is a potential method to improve the economic value of GL.     

浅谈化工教学的与时俱进问题

面对化学工程新的发展态势,化工教学与时俱进的问题值得关注。文章以化工原理和传递过程两门课程为例,分析了教学内容的调整;以 MOOC和虚拟仿真教学为例,阐述了教学模式的改革。文章认为,化工教学的与时俱进是任课教师不断提升自身教学能力、改进教学方法的过程。     

Stable Organic Titanium Catalysts and Reactive Distillation Used for the Transesterification of Dimethyl Carbonate with Phenol

The transesterification of dimethyl carbonate with phenol to methyl phenyl carbonate (MPC) was investigated on novel catalysts such as titanium diisopropoxide bis(ethyl acetoacetate) and titanium dibutoxide bis(ethyl acetoacetate) in a closed batch reactor at 185–206 °C under high pressure. The produced methanol could be removed efficiently by reactive distillation in order to overcome the equilibrium. The prepared catalysts have higher resistance to water than titanium alkoxides. Phenol conversion as high as 86.4 % with an MPC selectivity of 99.4 % was achieved under optimal reaction conditions within 9 h. Most of the catalytic activity was retained after repeated use for ten times.     

A miniature triaxial apparatus for investigating the micromechanics of granular soils with in situ X-ray micro-tomography scanning

The development of a miniature triaxial apparatus is presented. In conjunction with an X-ray micro-tomography (termed as X-ray μCT hereafter) facility and advanced image processing techniques, this apparatus can be used for in situ investigation of the micro-scale mechanical behavior of granular soils under shear. The apparatus allows for triaxial testing of a miniature dry sample with a size of \mathrm{8}\hspace{0.17em}\mathrm{mm}\times \mathrm{16}\hspace{0.17em}\mathrm{mm} (diameter \times height). In situ triaxial testing of a 0.4–0.8 mm Leighton Buzzard sand (LBS) under a constant confining pressure of 500 kPa is presented. The evolutions of local porosities (i.e., the porosities of regions associated with individual particles), particle kinematics (i.e., particle translation and particle rotation) of the sample during the shear are quantitatively studied using image processing and analysis techniques. Meanwhile, a novel method is presented to quantify the volumetric strain distribution of the sample based on the results of local porosities and particle tracking. It is found that the sample, with nearly homogenous initial local porosities, starts to exhibit obvious inhomogeneity of local porosities and localization of particle kinematics and volumetric strain around the peak of deviatoric stress. In the post-peak shear stage, large local porosities and volumetric dilation mainly occur in a localized band. The developed triaxial apparatus, in its combined use of X-ray μCT imaging techniques, is a powerful tool to investigate the micro-scale mechanical behavior of granular soils.     

高速激光热丝钎焊表面成形质量的控制

高速激光钎焊会引起熔池流动紊乱导致焊缝成形质量恶化,从而限制了其在汽车制造领域的应用。通过正交试验研究了高速下激光功率、送丝角度等工艺参数对焊缝成形质量的影响,发现焊缝成形质量随激光功率增加和送丝角度减小而提升。激光功率是通过影响熔池获得的热输入,从而影响熔池表面扰动的铺展来影响焊缝成形质量的。送丝角度是通过影响焊丝送入熔池的位置,从而影响焊丝对熔池的扰动强度和扰动的铺展速度来影响焊缝成形质量的。采用正交试验获得的最优工艺参数组合进行试验,获得了表面光滑平整无缺陷的高质量焊缝,为激光钎焊在高速下的应用发展奠定了基础。     

热轧双相钢生产现状、存在问题及发展趋势浅析

介绍了国内外热轧双相钢的发展现状；对热轧双相钢的成分体系和关键生产工艺进行了总结，指出了目前热轧双相钢在生产过程中存在的问题；提出了未来热轧双相钢的主要发展方向为低成本、高强度、低负荷、高表面质量和“以热代冷”。     

远程控制超声扫描的远端操纵系统

针对远程超声扫描,研制了一种远端操纵系统,并实现了超声探头的人机协作控制。探头控制中利用远端操纵系统网传信号实时复现远端操作员的扫描动作,并在此基础上利用阻抗控制方式自动控制探头对皮肤的压力。实验结果表明:近端超声探头的位置误差和姿态误差分别保持在±2.0 mm和±1.5°以内,能较好地复现操作员的扫描动作;探头压力跟踪误差稳定在±0.5 N的范围内,不但能将操作员的扫描手感真实地施加到皮肤上来提升其临场感,而且为进一步提高超声图像的质量,增强超声扫描的安全性提供了参考。     

并联有源滤波器的改进重复控制策略研究

针对三相整流负载产生的6k±1次谐波,提出静止坐标系下的改进型6k±1重复控制策略。同时将比例控制与改进型重复控制相结合,设计改进重复控制并联比例的复合控制结构。为减小改进重复控制中延时环节不为整数的影响,采用基于Lagrange插值近似的FIR滤波器逼近分数延时特性。最后对系统进行稳定性分析和详细设计方法进行推导。通过Matlab仿真验证改进重复控制策略能有效跟踪6k±1次谐波且具有良好的补偿效果,动态响应较快。