SHOCK INITIATION OF EXPLOSIVES INVESTIGATED WITH SMALL PARTITION EXPERIMENT AND NUMERICAL SIMULATION

In order to investigate the shock ignition of high energy solid explosives by shock waves,we carry out Lagrangian experiments with 2-D Lagrangian technique which uses composite manganin-constantan(CMC).The efects of the shock sensitivity of pressed solid high explosives,TNT,and the efect of the lateral rarefaction wave were studied.Based on the measured pressure histories and the radial displacements,we formulate the Ignition and Growth reactive flow models for the pressed TNT.The shock initiation process simulated by Ignition and Growth model agreed well with experimental data.This pressed TNT model can be applied to shock initiation scenarios which are highly unpredictable and have not been or cannot be tested experimentally.     

钇铝石榴石对撞增强型相位共轭腔的研究

报道了一种新型的相位共轭腔——对撞型钇铝石榴石受激布里渊散射相位共轭激光腔,实验结果发现该腔具有较低的启动阈值和100mJ以上的输出能量,它能输出稳定的20ns左右的自调Q脉冲,发散角为1．3mrad。在一定范围内,抽运电压越高,输出脉宽越窄;相位共轭腔越长,输出脉宽越宽;聚焦透镜对输出脉宽也有影响,焦距越短,脉宽越窄;焦距与介质池相对长点,输出能量相对高,远场发散角相对小些。实验给出了不同条件下的输出能量、脉冲宽度和光束发散角的情况。     

微量热法比较黄连中四种生物碱的抗菌作用

采用微量热法研究和比较中药黄连中四种生物碱(BAs)的抗菌(大肠杆菌)作用。这四种生物碱分别为小檗碱、黄连碱、巴马汀和药根碱。用LKB-2277生物活性检测系统,以停留法测定了37 ℃时大肠杆菌在BAs作用下的热流功率-时间曲线,并记录生长速率常数k, 指数生长期和稳定期的最大热功率Pm, log、Pm, stat, 生长抑制率I, 传代时间tg,指数生长期的总产热量Qt, log,半数抑菌浓度IC50等热动力学参数。结果显示这四种生物碱具有相异的抗大肠杆菌生长代谢的作用,k, Pm, log和Qt, log值随BAs浓度的增加而相应的减少。综合分析k, Pm, log, Qt, log, I 和IC50值可以看出,BAs抑制大肠杆菌生长代谢强度按小檗碱、黄连碱、巴马汀、药根碱的顺序依次减弱。构效关系研究表明,母环C-2和C-3上连接的亚甲二氧基比甲氧基更能显著增强相应化合物的抗菌作用,而C-9和C-10上连接的亚甲二氧基或甲氧基对这种抗菌作用影响不大。     

基于微量热法和主成分分析的盐酸巴马汀抗白色念珠菌作用的研究

采用LKB-2277生物活性检测系统, 测定了37 ℃时白色念珠菌在巴马汀作用下生长代谢的热谱曲线, 并获得9个相应的定量热动力学参数, 经主成分分析综合评价巴马汀的抗白色念珠菌作用. 结果表明巴马汀的抗白色念珠菌作用主要受热谱曲线第二指数生长期的生长速率常数k2和最大产热功率 的影响, 通过分析这两个主要参数的数值变化, 能更方便、快捷和准确地评价巴马汀的抗白色念珠菌作用, 为进一步评价其它药物和化合物的抗菌作用提供了有用的方法和基础.     

Tandem antagonistic games

We study an antagonistic sequential game of two players that undergoes two phases. Each phase is modeled by multi-dimensional random walk processes. During phase 1 (or game 1), the players exchange a series of random strikes of random magnitudes. Game 1 ends whenever one of the players sustains damages in excess of some lower threshold. However, the total damage does not exceed another upper threshold which allows the game to continue. Phase 2 (game 2) is run by another combination of random walk processes. At some point of phase 2, one of the players, after sustaining damages in excess of its third threshold, is ruined and he loses the entire game. We predict that moment, along with the total casualties to both players, and other critical information; all in terms of tractable functionals. The entire game is analyzed by tools of fluctuation theory.     

时间反转聚焦在组织中形成损伤的数值建模

为考察基于时间反转方法的高强度聚焦超声治疗在预设目标点处的组织损伤情况,使用三维有限差分算法求解Westervelt方程,建立非线性声波传播数值模型,采用97阵元相控阵结合虚拟源的时间反转方法进行超声聚焦,分析其形成的声场和热场,并考察目标点偏离轴线时的组织损伤形成规律。结果表明随着目标点偏轴距离的增大,声压旁瓣开始增多。旁瓣的温升较低,不足以形成组织损伤。时间反转方法可用于多点聚焦,在一定的范围内,形成多点目标损伤而不产生额外的周围组织损伤。同时多点聚焦可以形成一个较大的损伤区域,减少超声治疗时间。     

Relaxations and approximations of chance constraints under finite distributions

Optimization problems with constraints involving stochastic parameters that are required to be satisfied with a prespecified probability threshold arise in numerous applications. Such chance constrained optimization problems involve the dual challenges of stochasticity and nonconvexity. In the setting of a finite distribution of the stochastic parameters, an optimization problem with linear chance constraints can be formulated as a mixed integer linear program (MILP). The natural MILP formulation has a weak relaxation bound and is quite difficult to solve. In this paper, we review some recent results on improving the relaxation bounds and constructing approximate solutions for MILP formulations of chance constraints. We also discuss a recently introduced bicriteria approximation algorithm for covering type chance constrained problems. This algorithm uses a relaxation to construct a solution whose (constraint violation) risk level may be larger than the pre-specified threshold, but is within a constant factor of it, and whose objective value is also within a constant factor of the true optimal value. Finally, we present some new results that improve on the bicriteria approximation factors in the finite scenario setting and shed light on the effect of strong relaxations on the approximation ratios.     

Distributionally robust simple integer recourse

The simple integer recourse (SIR) function of a decision variable is the expectation of the integer round-up of the shortage/surplus between a random variable with a known distribution and the decision variable. It is the integer analogue of the simple (continuous) recourse function in two-stage stochastic linear programming. Structural properties and approximations of SIR functions have been extensively studied in the seminal works of van der Vlerk and coauthors. We study a distributionally robust SIR function (DR-SIR) that considers the worst-case expectation over a given family of distributions. Under the assumption that the distribution family is specified by its mean and support, we derive a closed form analytical expression for the DR-SIR function. We also show that this nonconvex DR-SIR function can be represented using a mixed-integer second-order conic program.     

求解隐式差分方程的加速迭代并行算法

1、引言 近年来,求解抛物型方程的有限差分并行迭代算法有了较大发展．针对稳定性好且难于并行化的隐式差分方程,文第一次提出了构造分段隐式的思想,建立了分段显-隐式（ASE-Ⅰ）方法和交替分段Crank-Nicolson（ASC-N）方法,实现了分而治之原则,