ADS堆功率控制研究及其在DCS系统的实施

研究了基于加速器束流强度调节来控制中国加速器驱动嬗变研究装置(CiADS)次临界堆功率的方法.束流强度的调节是通过比较堆功率的测量值和设定值,由PID(比例-积分-微分)控制器自动控制可调光阑的孔径大小完成的.为了评估所提出的自动控制方法,基于点堆动力学方程建立了CiADS次临界堆堆芯模型.基于CiADS堆芯模型的仿真...     

NAB和NYAB晶体的斯塔克能级

在液氮温度下测量ＮＡＢ和ＮＹＡＢ的全波段吸收光谱，并由此初步指认了ＮＡＢ和ＮＹＡＢ的斯塔克能级，利用Ｊ－Ｒ理论首次对ＮＡＢ和ＮＹＡＢ的斯塔克能级进行了全谱项拟合计算，并作了正确的指认。     

Estimation in the presence of many nuisance parameters: Composite likelihood and plug-in likelihood

We consider the incidental parameters problem in this paper, i.e. the estimation for a small number of parameters of interest in the presence of a large number of nuisance parameters. By assuming that the observations are taken from a multiple strictly stationary process, the two estimation methods, namely the maximum composite quasi-likelihood estimation (MCQLE) and the maximum plug-in quasi-likelihood estimation (MPQLE) are considered. For the MCQLE, we profile out nuisance parameters based on lower-dimensional marginal likelihoods, while the MPQLE is based on some initial estimators for nuisance parameters. The asymptotic normality for both the MCQLE and the MPQLE is established under the assumption that the number of nuisance parameters and the number of observations go to infinity together, and both the estimators for the parameters of interest enjoy the standard root-n$n$ convergence rate. Simulation with a spatial–temporal model illustrates the finite sample properties of the two estimation methods.     

Formation and interaction of hydrated alkali metal ions at the graphite-water interface

Ion hydration at a solid surface ubiquitously exists in nature and plays important roles in many natural processes and technological applications. Aiming at obtaining a microscopic insight into the formation of such systems and interactions therein, we have investigated the hydration of alkali metal ions at a prototype surface-graphite (0001), using first-principles molecular dynamics simulations. At low water coverage, the alkali metal ions form two-dimensional hydration shells accommodating at most four (Li, Na) and three (K, Rb, Cs) waters in the first shell. These two-dimensional shells generally evolve into three-dimensional structures at higher water coverage, due to the competition between hydration and ion-surface interactions. Exceptionally K was found to reside at the graphite-water interface for water coverages up to bulk water limit, where it forms an "umbrellalike" surface hydration shell with an average water-ion-surface angle of 115 degrees . Interactions between the hydrated K and Na ions at the interface have also been studied. Water molecules seem to mediate an effective ion-ion interaction, which favors the aggregation of Na ions but prevents nucleation of K. These results agree with experimental observations in electron energy loss spectroscopy, desorption spectroscopy, and work function measurement. In addition, the sensitive dependence of charge transfer on dynamical structure evolution during the hydration process, implies the necessity to describe surface ion hydration from electronic structure calculations.     

On the Geodesic Hypothesis in General Relativity

In this paper, we give a rigorous derivation of Einstein’s geodesic hypothesis in general relativity. We use small material bodies ${\phi^\epsilon}$ governed by the nonlinear Klein–Gordon equations to approximate the test particle. Given a vacuum spacetime ${([0, T]\times\mathbb{R}^3, h)}$ , we consider the initial value problem for the Einstein-scalar field system. For all sufficiently small ε and δ ≤ ε ^q , q > 1, where δ, ε are the amplitude and size of the particle, we show the existence of the solution ${([0, T]\times\mathbb{R}^3, g, \phi^\epsilon)}$ to the Einstein-scalar field system with the property that the energy of the particle ${\phi^\epsilon}$ is concentrated along a timelike geodesic. Moreover, the gravitational field produced by ${\phi^\epsilon}$ is negligibly small in C ¹, that is, the spacetime metric g is C ¹ close to the given vacuum metric h. These results generalize those obtained by Stuart in (Ann Sci École Norm Sup (4) 37(2):312–362, 2004, J Math Pures Appl (9) 83(5):541–587, 2004).     

理论设计ZnTiS3化合物光电性能的第一性原理计算

根据实验上合成LiNbO₃(LN)构型的ZnTiO₃铁电化合物,基于第一性原理的方法设计研究了化合物LN-ZnTiS₃(LN构型)的特性。计算结果表明LN-ZnTiS₃化合物满足力学稳定条件。根据化学势平衡相图分析,LN-ZnTiS₃在常压下不会形成稳定结构,但施加外部压力可以形成稳定结构。电子态密度和带隙的计算结果表明,LN-ZnTiS₃的价带顶(VBM)主要由S-p轨道组成,导带底(CBM)则由Ti-d轨道组成,硫原子的替代可以促进体系费米能级以上的电子状态大幅度下降到较低的能级,从而减小LN-ZnTiS₃的带隙。LN-ZnTiS₃的带隙计算值为1.04 eV,可以促进可见光的吸收,可以看出LN-ZnTiS₃是一种潜在的高效率光伏材料。     

An SIRS model with a nonlinear incidence rate

The global dynamics of an SIRS model with a nonlinear incidence rate is investigated. We establish a threshold for a disease to be extinct or endemic, analyze the existence and asymptotic stability of equilibria, and verify the existence of bistable states, i.e., a stable disease free equilibrium and a stable endemic equilibrium or a stable limit cycle. In particular, we find that the model admits stability switches as a parameter changes. We also investigate the backward bifurcation, the Hopf bifurcation and Bogdanov–Takens bifurcation and obtain the Hopf bifurcation criteria and Bogdanov–Takens bifurcation curves, which are important for making strategies for controlling a disease.     

PW1700X射线衍射仪织构分析应用软件的功能开发

由Ｐｈｉｌｉｐｓ引进的ＰＷ１７００Ｘ射线衍射仪织构测量系统只能用反射法，按螺旋线扫测极目数据，测绘极角。α≤８５°的不完整极图。经功能开发后，建立了织构分析测算系统，织构分析应用软件包，包括不完整极图测量与ＯＤＦ（取向分布函数）计算，回算全极图与反极图，可彩色屏显考贝，并能进行织构的定量分析。适用于立方和六方品系多晶织构材料分析。近两年应用表明，软件功能优异。     

国债发行与国民经济发展关系的定量研究

改革开发以来,中国国债发行规模逐年扩大,国债已影响到了国民经济的各个层面.国债发行规模适度问题已成为国债研究的中心问题.影响我国国债发行规模的最主要因素是什么?怎样度量中国国债的适度规模?这些问题已引起理论界的广泛注意,但迄今未有定论.本文采用现代经济计量及统计分析方法,对国债发行与国民经济发展之间的关系进行了定量分析,得出国债发行对国民经济发展的积极推动作用.希望所得结论能对国债规模管理提供参考.本文是以"实际数据蕴涵着规律"观点为基础,从三方面定量探索了国债发行与国民经济发展的关系.     

Influence of environmental factors on corrosion damage of aircraft structure

Corrosion is one of the important structural integrity concerns of aging aircraft, and it is estimated that a significant portion of airframe maintenance budgets is directed towards corrosion-related problems for both military and commercial aircraft. In order to better understand how environmental factors influence the corrosion damage initiation and propagation on aircraft structure and to predict pre-corrosion test pieces of fatigue life and structural integrity of an effective approach, this paper uses the cellular automaton (CA) method to character the effect of electrolyte concentrations, dissolution probabilities, and temperature on the corrosion damage of a metal structure exposed to an aggressive environment, and the procedure for applying the local rules between the cells of the CA to simulate the corrosion damage evolution is formulated. The simulation results show that the different electrolyte concentrations, dissolution probabilities and temperature, the laws of the dissolution current with time are investigated and they obey the time power function.