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In Bayesian analysis, the Markov Chain Monte Carlo (MCMC) algorithm is an efficient and simple method to compute posteriors. However, the chain may appear to converge while the posterior is improper, which will leads to incorrect statistical inferences. In this paper, we focus on the necessary and sufficient conditions for which improper hierarchical priors can yield proper posteriors in a multivariate linear model. In addition, we carry out a simulation study to illustrate the theoretical results, in which the Gibbs sampling and Metropolis-Hasting sampling are employed to generate the posteriors.     

先进超导导体测试装置设计分析

针对聚变工程大型超导导体样品在高场下的性能测试需求,设计了内径0.6m、磁场13T的背景磁体系统。磁体系统由6层12个分离式超导线圈组成,线圈采用常规的螺线管结构,由外至内分别使用NbTi、Nb₃Sn和YBCO三种超导材料绕制而成;在直径500mm的测试区域范围内产生最高达13.22T的背景磁场,均匀性不低于95%。介绍了磁体线圈主要设计参数,用有限元软件完成电磁、结构分析。结果表明,设计合理可靠,能够满足导体测试装置的需求。     

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As one of the breeding blanket candidates for China Fusion Engineering Test Reactor (CFETR), the water-cooled ceramic blanket (WCCB) was proposed to use binary mixed breeding pebble bed in order to increase the packing factor and meet tritium breeding ratio requirement. The DEM method was used to establish the packing structure of binary pebble bed which can meet the neutronics requirements and the flow characteristic of helium in the pebble bed was analyzed by CFD simulation. Porosity distribution, velocity distribution and pressure drop in the pebble bed were discussed.     

Synthesis and characterization of poly(p-arylene sulfide ketone/Schiff base) copolymers

Poly(p-arylene sulfide ketone/Schiff base) copolymers(PASK/SB) were prepared by solution polycondensation of 4,4’-diflurobenzophenone(DFBP) and N-phenyl(4,4’-diflurodiphenyl) ketimine(DFBI) with sodium sulfide in the presence of sodium hydroxide under normal pressure.Elemental analyses,FT-IR,NMR,DSC,TGA and XRD were used to characterize the resultant copolymers.It was found that the copolymers had good thermal properties with glass transition temperature(T_g) of 155.0-172.0°C,melting temperature(T_m) of 298-344°C,5%weight loss temperatures(T_d) of 471.0-501.5°C.These copolymers were almost amorphous with the content of DFBI beyond 30%.The polymer with 100% DFBI had excellent solubility,and it could dissolve in some solvents such as tetrahydrofuran(THF) and N-methyl-2- pyrrolidone(NMP).The processability of polymers was improved.Meantime the viscosity of PASK made from hydrolysis of PASK/SB(H-PASK/SB) was greatly improved from 0.135 dL/g to 0.605 dL/g.     

Tracy-Widom�ֲ�����Ӧ��

??Tracy and Widom found a new type of probability distribution in the study of high dimensional random matrices in the 1990s, which is nowadays normally called Tracy-Widom distribution. It is used to described the limiting distribution of the extremal eigenvalues in Gaussian Unitary Ensemble. Later on, the study in the past two decades indicates that Tracy-Widom distribution is universal like normal distribution and can be well used to describe a lot of seemingly distinct random phenomena. As illustrations, the paper briefly review nine widely studied random models, each of which is more or less related to Tracy-Widom distribution. Compared to normal distribution, Tracy-Widom distribution has horribly intricate distribution function, density function and moments. people need to use deep mathematical knowledge and advanced computation technology in order to extend and to apply Tracy-Widom distribution in practice. But it is absolutely worthy further study on account of its importance.     

HL-2A װ�õ��Ӳ�ϵͳ�߹����ٵ��ܵ���

A test platform for the TH2103A klystrons and the high power microwave components is developed. The RF driver, four port circulator, RF load and high power cathode power supply are installed on the test bed. A short pulse test is carried out on the test bed. The parameters of the 4 klystrons are optimized by scanning the currents in the 3 focusing coils and the high power microwave transmission components are conditioned. The output power of the 4 klystrons reached 449kW, 417kW, 460kW and 450kW when the pulse duration was 30ms, respectively. The test result is an important reference for the LHCD system on HL-2A tokamak.     

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Under the condition that the coefficients are Lipschitz continuous, we study the infinitesimal generator of Markov semigroup corresponding to the multivalued stochastic equation. In order to provide a core of the infinitesimal generator, we investigate the associated multivalued elliptic equation and its viscosity solutions.     

Dispersion stability and rheological behavior of suspensions of polystyrene coated fumed silica particles in polystyrene solutions

Polystyrene coated silica（SiO₂@PS） core-shell composite particles with averaged diameter of about 290 nm were prepared by in situ emulsion polymerization of styrene on the surface ofγ-methacryloxypropyltrimethoxysilane grafted SiO₂ nanoparticles of 20-50 nm in diameter.Rheological behavior and dispersion stability of SiO₂@PS suspension in 10 wt%PS solution were compared with suspensions of untreated SiO₂ and silane modified SiO₂ nanoparticles.Suspensions of the untreated and the silane modified SiO₂ exhibited obvious shear thinning.The SiO-2@PS suspension exhibits shear viscosity considerably smaller than suspensions of untreated and silane modified SiO₂ at low shear rates.Transmission electron microscopy showed that the composite particles can uniformly and stably disperse in PS solution compared to other suspensions,implying that the PS shell can effectively enhance the particle compatibility with PS macromolecules in solution.     

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The charging characteristic of the capacitor charging power supply was analyzed with practical series resonant topology. The method that setting two current taps and regulating PWM switching frequency was putted forward with close loop controlling algorithm to charge the multi-group capacitor banks with constant current. A capacitor charging power supply with the max output current 6.5A and the max output voltage 2000V is designed. Experimental results show that, this power supply can charge the four capacitor banks to any four different voltages in 1 minute with charging accuracy less than 1%, and meet the requirements of J-TEXT ohmic field power system.