旋转陶瓷片约束TIG电弧形态分析

收缩电弧是提高TIG电弧的能量密度的有效途径.提出一种新的约束TIG电弧方法,用两片平行旋转的陶瓷片,对电极附近的电弧进行约束.通过电弧形态的观察分析,以及焊缝形状的测量,试验研究了不同旋转陶瓷片约束条件下电弧的形态和加热特性.结果表明,旋转陶瓷片可以有效地对TIG电弧进行非轴对称约束.在垂直于陶瓷片旋转平面的方向上,电弧中心的载流区域稳定收缩.两陶瓷片之间距离的减小,电弧进入陶瓷片深度的增加,都会使电弧中心载流区的宽度减小,从而使焊缝的熔深增加.同时发现,随电弧受约束程度的增加,电弧电压略有上升.     

降温模式对甲烷水合物形成的影响

在定容条件下,以两种不同的降温模式(缓慢降温和快速降温)进行甲烷水合物在沉积物中的形成实验. 结果表明,甲烷水合物在沉积物中的形成过程包括气液溶解、核化、生长、稳定4个阶段. 在相同的初始条件下,降温模式对水合物生成的热力平衡影响较小,但对水合物生成动力学有显著改变. 快速降温下水合物生长速度明显快于缓慢降温,随着水合物初始条件不同,缓慢降温比快速降温水合物形成时间约增加21.4%~28.8%.     

Application of functionalized magnetic silica nanoparticles for selective induction of three coumarin metastable polymorphs

The precise control of active pharmaceutical ingredient(API) crystal nucleation and polymorphism is a key consideration in pharmaceutical manufacturing.In this study,tunable nanoparticles were developed to regulate the nucleation process of coumarin.Magnetic silica nanoparticles with four different functional groups(-NH₂,-COOH,-SH,-NCO) were prepared and coated on the substrate for inducing the crystallization of coumarin.Confined melt crystallization and microspacing sublimation crys...     

Insights into the confinement effect on isobutane alkylation with C4 olefin catalyzed by zeolite catalyst: A combined theoretical and experimental study

Elucidating the confinement effect harbours tremendous significance for isobutane alkylation with C₄ olefin. Herein, the confinement effect over zeolite catalysts was elucidated by combining DFT calculations, experiments(using the novel Beta zeolite exposing only external surfaces(Beta-E) and conventional Beta-I zeolite with both external and internal surfaces) and multi-techniques(e.g., TGA-DTG,HRTEM, SEM and XRD). It is found that the main active sites for C₄ alkylation r...     

Nb-V-Ti 微合金化低合金钢 SG610E 250 mm×2 000 mm连铸尾坯封顶工艺试验与实践

针对低合金钢SG610E250 mm×2000 mm连铸尾坯封顶工艺进行了试验研究,结果表明,传统的打水封顶工艺,在距离铸坯尾部2 000 mm范围内存在严重的中心缩孔,而低拉速无水封顶可以将缩孔尾坯长度减小到了 900 mm.但是由于低拉速无水封顶工艺,拉速≤0.2 m/min持续时间长,导致连铸坯表面温度降低,进入...     

Application of Homology Modeling by Enhanced Profile–Profile Alignment and Flexible-Fitting Simulation to Cryo-EM Based Structure Determination

Application of cryo-electron microscopy (cryo-EM) is crucially important for ascertaining the atomic structure of large biomolecules such as ribosomes and protein complexes in membranes. Advances in cryo-EM technology and software have made it possible to obtain data with near-atomic resolution, but the method is still often capable of producing only a density map with up to medium resolution, either partially or entirely. Therefore, bridging the gap separating the density map and the atomic model is necessary. Herein, we propose a methodology for constructing atomic structure models based on cryo-EM maps with low-to-medium resolution. The method is a combination of sensitive and accurate homology modeling using our profile–profile alignment method with a flexible-fitting method using molecular dynamics simulation. As described herein, this study used benchmark applications to evaluate the model constructions of human two-pore channel 2 (one target protein in CASP13 with its structure determined using cryo-EM data) and the overall structure of Enterococcus hirae V-ATPase complex.     

Normal vector generation for sampled data using fourier filtering

A three-dimensional surface is a useful graphic representation of a two-dimensional function which has been sampled on a regular grid. Shading the surface to simulate the effects of direct lighting makes visible small changes in the surface orientation, and enhances realism when the data represents a physical surface such as terrain. Shading interpolation calculations and surface patch generation techniques require the specification of a surface normal vector (or related slope information) at each sample point. These normal vectors are usually generated by averaging local data such as the normal vectors of the surfaces of a triangular mesh connecting the points. This paper describes a technique which uses Fourier filtering to generate normal vectors for two-dimensional sampled data. Images and analysis of frequency spectra are included to show how this technique preserves detail which is lost using the averaging method. Performance figures show that this enhancement of detail in the final image can be achieved for only a small increase in computation time.     

Ka波段低剖面宽频带平板缝隙天线研究

针对传统平板缝隙天线带宽窄,以及常用宽带平板缝隙天线腔体分层数多,剖面高的缺点,设计了一种新型低剖面宽带平板缝隙天线。该设计对传统方案的辐射单元与馈电网络均进行了改进,增加了缝隙间距的同时,通过合理增加调配块达到宽带良好匹配的效果。缝隙间距的增大,使馈电网络同层化设计得以实现,从而降减少了天线分层数,降低了天线剖面。本文对新型平板天线进行了HFSS仿真优化,仿真结果表明,该新型平板缝隙天线相对带宽可达到15%、分层只有2层,具有宽频带、分层少、剖面低的优点,该新型平板缝隙天线可以作为未来平板缝隙天线主要方案。     

HIRFL-CSR荧光靶束流剖面测控系统

介绍了在HIRFL-CSR束流诊断系统改造中,基于单片机技术研制开发的荧光靶驱动控制器和视频信号控制器的设计结构及原理.阐述了基于网络控制技术的分布式束流剖面测控系统.