高效焊管新工艺——金属管液相扩散焊

采用镍基非晶态箔带作中间层,在加压情况下(约几MPa)使之熔化、保温,进行了钢管瞬间液相 (TLP)扩散焊试验。结果表明,可以获得无夹杂的致密界面;接头过渡区的最终厚度显著变薄;焊后中间层主组元由焊前的Ni变为Fe;容易获得性能合格接头。值得指出的是,焊接时间约为3min,远低于手弧焊所需时间。     

CO2体积分数对燃煤细颗粒物在水汽环境中凝结长大的影响

为研究燃煤烟气中CO₂体积分数对细颗粒物在水汽环境中凝结长大效果的影响,建立了计算模型并搭建了实验平台,分别从理论计算和实验研究两方面探讨了CO₂体积分数对细颗粒物凝结长大效果的影响。结果表明:随着CO₂体积分数升高,混合烟气的热、质扩散系数均降低,生长管内平均过饱和度增加,细颗粒物长大效果明显;管壁温度越高,随着CO₂体积分数的提高,细颗粒物粒径越大。     

Radiation-absorption,chemical reaction,Hall and ion slip impacts on magnetohydrodynamic free convective flow over semi-infinite moving absorbent surface

The investigation of radiation-absorption,chemical reaction,Hall and ion-slip impacts on unsteady MHD free convective laminar flow of an incompressible viscous,electrically conducting and heat generation/absorbing fluid enclosed with a semi-infinite porous plate within a rotating frame has been premeditated.The plate is assumed to be moving with a constant velocity in the direction of fluid movement.A uniform transverse magnetic field is applied at right angles to the porous surface,which is absorbing the fluid with a suction velocity changing with time.The non-dimensional governing equations for present inves-tigation are solved analytically making use of two term harmonic and non-harmonic functions.The graphical results of velocity,temperature and concentration distributions on the analytical solutions are displayed and discussed with reference to pertinent parameters.It is found that the velocity profiles decreased with an increasing in Hartmann number,rotation parameter,the Schmidt number,heat source parameter,while it increased due to an increase in permeability parameter,radiation-absorption param-eter,Hall and ion slip parameters.However,the temperature profile is an increasing function of radiation-absorption parameter,whereas an increase in chemical reaction parameter,the Schmidt num-ber Sc or frequency of oscillations decrease the temperature profile on cooling.Also,it is found that the concentration profile is decreased with an escalating in the Schmidt number or the chemical reaction parameter.     

基于漂移扩散模型方程的IGCT电路模型

现有基于双极扩散方程(ADE)的功率半导体器件模型只能准确描述准中性区载流子分布,应用于高压器件建模时精度有限。提出一种基于漂移扩散模型(DDM)的集成门极换流晶闸管(IGCT)电路模型的建模方法以提高模型精度。通过分析发现,求解变量数量级相差较大,以及由高掺杂浓度决定的特征参数是影响模型特性的主要因素。由此,通过边界高掺杂区域的解析建模、简化基区求解的边界条件以及应用移动网格法求解DDM提高了模型的稳定性和计算速度。最后,IGCT双脉冲测试仿真与实验对比结果表明在仿真耗时接近的前提下,该方法相对于现有基于ADE模型可以更好地仿真器件在关断振荡以及穿通时的特性。     

基于平流矢量场和弥散流改进的几何活动轮廓模型

几何活动轮廓通过水平集演化捕获目标边界,然而传统方法忽略了前景物体涉及的全局运动及局部形变,从本质上限制了轮廓的动态谐调范围。提出一种由隐式流驱动的几何活动轮廓方法,用于分割形变对象的动态轮廓。根据流体力学,对平流及弥散的隐式流进行建模,从而直接引导水平集的更新。根据图像序列之间有限的运动观测,采用具有平滑和稀疏项的回归算法以拟合平流矢量场。然后,引入受空间梯度约束的非均匀弥散方程,将最终叠加的隐式流用于水平集演化。提出的几何活动轮廓方法构成了一个统一的扩展框架,保留了已有模型对轮廓拓扑变化的适应性。对多个场景下的动态轮廓分割实验表明,提出方法能准确地分割具有全局运动及不规则形变的前景目标,且具有收敛速度快、稳定性强的优点。     

Physiological Imaging Methods for Evaluating Response to Immunotherapies in Glioblastomas

Glioblastoma (GBM) is the most malignant brain tumor in adults, with a dismal prognosis despite aggressive multi-modal therapy. Immunotherapy is currently being evaluated as an alternate treatment modality for recurrent GBMs in clinical trials. These immunotherapeutic approaches harness the patient’s immune response to fight and eliminate tumor cells. Standard MR imaging is not adequate for response assessment to immunotherapy in GBM patients even after using refined response assessment criteria secondary to amplified immune response. Thus, there is an urgent need for the development of effective and alternative neuroimaging techniques for accurate response assessment. To this end, some groups have reported the potential of diffusion and perfusion MR imaging and amino acid-based positron emission tomography techniques in evaluating treatment response to different immunotherapeutic regimens in GBMs. The main goal of these techniques is to provide definitive metrics of treatment response at earlier time points for making informed decisions on future therapeutic interventions. This review provides an overview of available immunotherapeutic approaches used to treat GBMs. It discusses the limitations of conventional imaging and potential utilities of physiologic imaging techniques in the response assessment to immunotherapies. It also describes challenges associated with these imaging methods and potential solutions to avoid them.     

Characterization of the Functional Cross-Talk between Surface GABAA and Dopamine D5 Receptors

The γ-aminobutyric acid type A receptor (GABA_AR) plays a major role in fast inhibitory synaptic transmission and is highly regulated by the neuromodulator dopamine. In this aspect, most of the attention has been focused on the classical intracellular signaling cascades following dopamine G-protein-coupled receptor activation. Interestingly, the GABA_AR and dopamine D5 receptor (D5R) have been shown to physically interact in the hippocampus, but whether a functional cross-talk occurs is still debated. In the present study, we use a combination of imaging and single nanoparticle tracking in live hippocampal neurons to provide evidence that GABA_ARs and D5Rs form dynamic surface clusters. Disrupting the GABA_AR–D5R interaction with a competing peptide leads to an increase in the diffusion coefficient and the explored area of both receptors, and a drop in immobile synaptic GABA_ARs. By means of patch-clamp recordings, we show that this fast lateral redistribution of surface GABA_ARs correlates with a robust depression in the evoked GABAergic currents. Strikingly, it also shifts in time the expression of long-term potentiation at glutamatergic synapses. Together, our data both set the plasma membrane as the primary stage of a functional interplay between GABA_AR and D5R, and uncover a non-canonical role in regulating synaptic transmission.     

陶瓷/金属钎焊与扩散连接的研究现状

工程陶瓷由于具有优异的综合性能,在许多领域得到广泛应用,但其加工性能差,通常需要与金属组成复合结构.实现陶瓷与金属之间的可靠连接是推进陶瓷材料应用的关键,钎焊和扩散连接被认为是陶瓷/金属连接中较为适合的方法.文中对近年来国内外陶瓷/金属钎焊和扩散连接技术领域的研究现状进行了综述,认为活性金属钎焊和部分瞬间液相连接发展比较成熟,部分瞬间液相连接充分结合了活性钎焊和固相扩散连接两者的优点,将成为未来陶瓷/金属连接的发展方向.     

Sulfuric acid recovery from rare earth sulphate solutions by diffusion dialysis

1 Introduction As an important industrial chemical, sulfuric acids are widely used in metallurgical and chemical processes, in which some waste solutions containing free sulfuric acids and metallic ions are therefore produced[1, 2]. If these waste acids …     

5%Si高硅奥氏体不锈钢元素偏析及均匀化处理

 高硅奥氏体不锈钢由于高含量硅元素的加入使其具有优异的耐高温腐蚀性能和较低的成本,在制酸行业有着潜在的应用价值。然而,该合金中高含量硅元素的加入会促进凝固过程中溶质再分配,进而造成显著的元素偏析,最终导致合金内部产生枝晶组织和大量的有害相。对铸锭组织进行均匀化处理能够有效消除枝晶与元素偏析,促进析出相回溶和枝晶消融,从而改善材料的热塑性,有效应对热变形开裂问题。因此,采用金相显微镜(OM)、扫描电镜能谱分析(SEM/EDS)、电子探针(EPMA)、JMatPro软件计算等方法,研究了实验室条件下制备的5%Si高硅奥氏体不锈钢铸锭的显微组织和元素分布状态,通过残余偏析指数、扩散动力学计算并结合均匀化处理试验验证,最终确定了5%Si高硅奥氏体不锈钢合理的均匀化处理工艺。结果表明,5%Si高硅奥氏体不锈钢凝固过程中钼元素偏析最为严重,通过残余偏析指数模型计算得到的均匀化动力学方程可用来指导该成分合金的均匀化处理工艺;5%Si高硅奥氏体不锈钢经过1 150 ℃×12 h均匀化处理后,铸锭内枝晶消融,元素偏析基本消除,析出相与铁素体回溶到基体中,合金转变为全奥氏体组织,热塑性得到改善;当加热温度达到1 250 ℃时,合金出现过烧现象,晶界开始熔化。