超导电缆中接头焊接的热分析模拟

大型超导磁体系统中,需要用超导接头来连接超导电缆的终端,其承担的主要作用是连接超导电缆并确保超导电缆的超导性能不因接头而降低,因此需要超导接头电阻足够小,不影响超导电缆的整体性能。影响超导接头电接触性能的主要工艺步骤有超导接头终端处理、接头盒压力密封焊。基于ITER Feeder系统中双盒搭接接头焊接工艺中单个盒体和双盒之间的焊接进行热分析,使用ANSYS分析软件,得到相应的焊接温度分布情况,为焊接工艺中加热方式和加热功率的确定提供了理论基础,验证了相关的设计参数。     

Yangian symmetries and integrability of the Dirac equation with spin symmetry

We show that a Yangian symmetry, namely, Y(su(2))$Y\left(su\left(2\right)\right)$, exists in the Dirac equation with spin symmetry when the potential term takes a Coulomb form. We construct the generators of Y(su(2))$Y\left(su\left(2\right)\right)$ explicitly and get the energy spectrum of this model from the representation theory for Y(su(2))$Y\left(su\left(2\right)\right)$. We also show that this model is integrable, from RTT relations.     

Preparation and Characterization of Hyaluronic Acid Hydrogel Blends with Gelatin

Porous hydrogel blends composed of various weight ratios of hyaluronic acid (HA) and gelatin (Gel) were fabricated by a freeze-drying method. The 1-ethyl-3(3-dimethylaminopropyl) carbodiimide (EDC) was used as a crosslinker to improve their biostability. The effect of the component and crosslinker content on the morphology, swelling ratio (SR), and mechanical properties were investigated. The results indicated that after chemical crosslinking the hydrogel showed a smoother and denser surface with less pores and a crosssection with smaller pores than that without crosslinking. The crosssection morphologies of the HA/Gel hydrogels changed from a sheet-like appearance to a fiber-like appearance with increasing HA content. The addition of HA improved the swelling property, but reduced the compressive strength. As the crosslinker content increased, the SR decreased; however, the compressive strength of the HA/Gel hydrogels increased. All these results suggest that HA/Gel hydrogel crosslinked by EDC is a potential candidate for tissue engineering scaffolds.     

Electrospinning Instabilities in the Drop Formation and Multi-Jet Ejection Part II: Various Nozzle Diameters for PVA (Polyvinyl Alcohol) Polymer Solution

Electrospinning is recognized as a simple and easy method to produce fibers with nanoscale diameters. However, the methods for controlling the shape, structure, and uniformity of electrospun fibers have not yet been fully investigated. In this research, the electrospinning jet behavior, corresponding nanofiber deposition, and average fiber diameter are examined for various nozzle diameters. Fluctuations in the sequence of drop growing, electrospinning, and/or termination of electrospinning are analyzed. We propose two different fluctuations according to nozzle diameter. The multi-jet ejections, that are closely related to the amount of nanoweb deposition and the deposition pattern, are explored.     

Towards an entropy-based detached-eddy simulation

A concept of entropy increment ratio()is introduced for compressible turbulence simulation through a series of direct numerical simulations(DNS). represents the dissipation rate per unit mechanical energy with the benefit of independence of freestream Mach numbers.Based on this feature,we construct the shielding function fs to describe the boundary layer region and propose an entropy-based detached-eddy simulation method(SDES).This approach follows the spirit of delayed detached-eddy simulation(DDES)proposed by Spalart et al.in 2005,but it exhibits much better behavior after their performances are compared in the following flows,namely,pure attached flow with thick boundary layer(a supersonic flat-plate flow with high Reynolds number),fully separated flow(the supersonic base flow),and separated-reattached flow(the supersonic cavity-ramp flow).The Reynolds-averaged Navier-Stokes(RANS)resolved region is reliably preserved and the modeled stress depletion(MSD)phenomenon which is inherent in DES and DDES is partly alleviated.Moreover,this new hybrid strategy is simple and general,making it applicable to other models related to the boundary layer predictions.     

普物实验教学新模式的探索与实践

本提出了一种新的实验教学模式,论述了试行实验教学新模式的基本做法,简要介绍了试行新模式所取得的教学效果。     

Generalized nonlinear complementarity problems with order P_0 and R_0 properties

We generalize the \(P, P_0, R_0\) properties for a nonlinear function associated with the standard nonlinear complementarity problem to the setting of generalized nonlinear complementarity problem (GNCP). We prove that if a continuous function has the order \(P_0\) and \(R_0\) properties then all the associated GNCPs have solutions.     

融资融券交易与A股市场波动相关性实证研究

本文基于A股市场开展融资融券交易以来的实际数据,用Johnson协整检验,误差修正模型和Granger因果关系检验方法,实证研究了融资融券业务的开展对A股市场价格和波动性的影响,结果显示融资融券交易对A股市场的价格和波动性的影响都不显著.     

RESEARCH FOR ATTRACTING REGION AND EXIT PROBLEM OF A PIECEWISE LINEAR SYSTEM UNDER PERIODIC AND WHITE NOISE EXCITATIONS

离出行为是随机非线性系统的重要现象之一,而离出问题是除随机动力系统理论以外考察随机非线性系统随机稳定性的另一种重要的方法.分段线性系统是一个经典的非线性动力学模型,受随机激励后成为随机系统,但并不是严格的随机动力系统,因而此时随机动力系统理论也不适用.为了研究同时受周期和白噪声激励的分段线性系统,首先使用Poincaré截面模拟其在无噪声时确定性的动力学行为,然后使用Monte Carlo模拟对其在白噪声激励下的离出行为进行了数值仿真分析.其次,为了考察离出问题中的重要参数,系统的平均首次通过时间（mean first-passage time,MFPT）,使用van der Pol变换,随机平均法,奇异摄动法和射线方法进行了量化计算.通过对理论结果与模拟结果的对比分析,得到结论：当系统吸引子对应的吸引域边界出现碎片化时,理论结果与模拟结果的误差极大;而当吸引域边界足够光滑的以后,理论结果与模拟结果才会相当吻合.