“最小键级原理”的从头算证实———苯和苯胺类硝基衍生物

感度是爆炸物对外界刺激的敏感程度 ,是火药、炸药和起爆药的基本属性 .在外界撞击作用下炸药发生爆炸的难易程度即该炸药的撞击感度 .感度通常依靠实测 ,从理论上加以判别是人们追求的目标 ,故研究炸药感度与结构的关系一直是该领域的热点 .根据撞击引起热解、热解引起爆炸、撞击感度主要与热解引发步骤相关联等思想 ,我们建议了“最小键级原理 (PSBO)”[1- 4] :对系列结构相似爆炸物 ,其热解引发键键级 (或重叠布居 )越小 ,则撞击感度越大 ;热解引发键键级越大 ,则撞击感度越小 .该判据已在多系列炸药中获得证实和应用[1- 4] .“热解引…     

Projections on Convex Sets in the Relaxed Limit

The paper establishes the continuity of the best approximation, or the projection, of a function in L _p for p[1,), on a closed convex set in the space, when the set varies and converges to a limit set in the Young-measure relaxation of the space. To this end a strong-type convergence and a convexity structure are identified on the space of Young measures. The appropriate convergence of sets with respect to which the continuity holds is the Mosco convergence of sets associated with the strong-type convergence of functions.     

Primal-Dual Solution Perturbations in Convex Optimization

Solutions to optimization problems of convex type are typically characterized by saddle point conditions in which the primal vector is paired with a dual multiplier vector. This paper investigates the behavior of such a primal-dual pair with respect to perturbations in parameters on which the problem depends. A necessary and sufficient condition in terms of certain matrices is developed for the mapping from parameter vectors to saddle points to be single-valued and Lipschitz continuous locally. It is shown that the saddle point mapping is then semi-differentiable, and that its semi-derivative at any point and in any direction can be calculated by determining the unique solutions to an auxiliary problem of extended linear-quadratic programming and its dual. A matrix characterization of calmness of the solution mapping is provided as well.     

Population and coherence transfer induced by double frequency sweeps in half-integer quadrupolar spin systems

We have recently shown that the sensitivity of single- and multiple-quantum NMR experiments of half-integer (N/2) quadrupolar nuclei can be increased significantly by introducing so-called double frequency sweeps (DFS) in various pulse schemes. These sweeps consist of two sidebands generated by an amplitude modulation of the RF carrier. Using a time-dependent amplitude modulation the sidebands can be swept through a certain frequency range. Inspired by the work of Vega and Naor (J. Chem. Phys. 75, 75 (1981)), this is used to manipulate +/-(m - 1) <--> +/-m (3/2 < or = m < or = N/2) satellite transitions in half-integer spin systems simultaneously. For (23)Na (I = 3/2) and (27)Al (I = 5/2) spins in single crystals it proved possible to transfer the populations of the outer +/-m spin levels to the inner +/-1/2 spin levels. A detailed analysis shows that the efficiency of this process is a function of the adiabaticity with which the various spin transitions are passed during the sweep. In powders these sweep parameters have to be optimized to satisfy the appropriate conditions for a maximum of spins in the powder distribution. The effects of sweep rate, sweep range, and RF field strength are investigated both numerically and experimentally. Using a DFS as a preparation period leads to significantly enhanced central transition powder spectra under both static and MAS conditions, compared to single pulse excitation. DFSs prove to be very efficient tools not only for population transfer, but also for coherence transfer. This can be exploited for the multiple- to single-quantum transfer in MQMAS experiments. It is demonstrated, theoretically and experimentally, that DFSs are capable of transferring both quintuple-quantum and triple-quantum coherence into single-quantum coherence in I = 5/2 spin systems. This leads to a significant enhancement in signal-to-noise ratio and strongly reduces the RF power requirement compared to pulsed MQMAS experiments, thus extending their applicability. This is demonstrated by (27)Al 3QMAS experiments on 9Al(2)O(3). 2B(2)O(3) and the mineral andalusite. In the latter compound, Al experiences a quadrupolar-coupling constant of 15.3 MHz in one of the sites. Finally a 5QMAS spectrum on 9Al(2)O(3). 2B(2)O(3) demonstrates the sensitivity enhancement of this experiment using a double frequency sweep.     

用于双色全息存储(Fe,Cu)∶LiNbO3晶体的参量优化计算

在确定Cu在LiNbO3晶体中对应于365 nm和633 nm的激发系数、复合系数、光伏系数的基础上,采用龙格库塔(Runge-Kutta)数值方法理论研究了双掺杂(Fe,Cu)∶LiNbO3晶体的深浅能级的掺杂组分比、氧化还原状态对双色全息存储的记录灵敏度和动态范围的影响,并探讨了同时取得尽可能大的灵敏度和动态范围的晶体条件。结果表明,为了同时得到较大的记录灵敏度和动态范围,在实际应用中选用浅能级掺杂浓度为5.0×1025m-3,深能级掺杂浓度为3×1024~3×1025m-3之间的弱氧化晶体是合适的。     

Nanoporous silicon doped by Cu for gas-sensing applications

The effect of hydrogen sulphide on the current–voltage characteristics of metal–insulator–semiconductor (MIS) structures based on nanoporous silicon (Si_nanopor) under copper doping has been investigated. Scanning electron (SEM), atomic force (AFM) and optic microscopes and/or secondary ion mass spectroscopy (SIMS) were used to obtain detailed characterisation of copper cluster distribution present at the surface and pores, respectively. SIMS spectra reveal that finite gradient in copper distribution along the pores and oxidation of nanoporous silicon simultaneously can be obtained successfully under electroless deposition process. It was also shown that the doping of nanoporous silicon by Cu leads to enhanced hydrogen sulphide sensitivity of MIS structures even without catalytic active top electrodes (for example, Pd) at room temperature. Furthermore, for different types of familiar MIS structures based on nanoporous silicon, e.g., MIS structures doped or undoped by copper and by using Pd metal electrodes, the hydrogen sulphide detection at room temperature mainly depends on the modification in the height of barrier of hetero- (Al–Cu–Si_nanopor–c-Si) or Schottky-like (Pd–Cu–Si_nanopor–c-Si) structures resulting the chemical interaction of molecular H₂S gas with copper clusters at the surface and in the pores. It is demonstrated that MIS structures based on the nanoporous silicon with copper doping are more sensitive to H₂S action at room temperature. In addition, the physical mechanism explaining the observed phenomena is also discussed.     

CVD金刚石薄膜探测器性能研究

通过实验测量和理论分析, 从载流子动力学角度研究了用于脉冲辐射探测的CVD金刚石薄膜探测器的适用结构、电荷收集效率和时间响应性能. 结果表明, CVD金刚石薄膜可以制成均匀型结构的探测器; 薄膜中的缺陷会降低探测器的电荷收集效率, 探测器的电荷收集效率随场强增大而增大直至饱和. 已研制的CVD金刚石探测器电荷收集时间可达719ps, 在2.5V/μm场强下达到饱和, 电荷收集效率 达60.5%; 晶格散射是影响探测器时间响应的主要因素, 选用大晶粒甚至单晶金刚石薄膜可以提高探测器时间响应.     

GaAs探测器实验标定

叙述了在闪光Ⅰ上用6MV轫致辐射实验标定快响应GaAs光电探测器的原理实验结果以及分析讨论。     

THE SATELLITE STRUCTURE TOPOLOGY OPTIMIZATION BASED ON HOMOGENIZATION METHOD AND ITS SIZE SENSITIVITY ANALYSIS

With the development of satellite structure technology, more and more design parameters will affect its structural performance. It is desirable to obtain an optimal structure design with a minimum weight, including optimal configuration and sizes. The present paper aims to describe an optimization analysis for a satellite structure, including topology optimization and size optimization. Based on the homogenization method, the topology optimization is carried out for the main supporting frame of service module under given constraints and load conditions, and then the sensitivity analysis is made of 15 structural size parameters of the whole satellite and the optimal sizes are obtained. The numerical result shows that the present optimization design method is very effective.