Morris-Lecar系统中通道噪声诱导的自发性动作电位研究

在生物物理学中, 越来越多的现象是由于分段确定性的动力系统与连续时间马氏过程之间的耦合作用而产生的. 因为这种耦合性, 相关的数学模型更适合取为随机混合系统而不是扩散过程(基于It?随机微分方程). 本文从理论上和数值上研究了在弱噪声条件下无鞍点状态的随机混合Morris-Lecar系统中, 由通道噪声诱导的自发性放电现象. 一个动作电位的初始阶段可视为噪声诱导的逃逸事件, 其最优路径和拟势可由辅助Hamilton系统给出. 由于系统不存在鞍点, 因此可选择虚拟分界线(ghost separatrix)为阈值, 研究噪声诱导的自静息态的逃逸事件. 通过计算在阈值处的拟势, 便可发现其值有一个明显的最小值, 其作用类似于鞍点. 通过改进的Monte Carlo模拟方法, 计算了历程概率分布, 其结果对初始阶段和兴奋阶段的理论解均给出了验证. 此外, 基于前人将拟势等高线作为阈值的另一种选择, 我们对两种阈值取法的优劣性进行了比较. 最后, 本文研究了钠离子和钾离子通道噪声的不同组合对最优路径和拟势的影响. 结果表明: 钾离子通道噪声在自发性放电过程中起主导作用, 且两种噪声强度存在一个最优比例能使总的噪声强度达到最小.      

估计感度分布中位数的两阶段优化序贯试验设计方法研究

感度试验在爆炸科学领域有非常广泛的应用,其中位数是含能材料的一个关键性能指标.高效估计感度分布中位数是实际工程应用中的重要问题.文章提出一种两阶段的优化序贯试验设计方法来估计感度分布的中位数,并将正交设计与两阶段优化序贯试验设计方法相结合给出了筛选影响含能材料安定性重要因子的试验设计方法.广泛的模拟比较验证了所提方法在小样本情况下可以获得感度分布中位数的准确估计,并且对模型假设和初始参数猜测具有一定的稳健性.当因子效应不是太小的时候,因子筛选方法可以准确地筛选出有显著影响的因子.     

热源塔热泵系统夏季工况优化运行实验研究

由于热源塔在冬夏季工况下的换热能力存在较大差异,按冬季工况设计的热源塔热泵系统,在夏季工况下运行时存在换热能力过剩的问题,影响系统性能。为解决上述问题,本文构建了热源塔热泵系统,实验研究了其冬夏季工况的性能差异。在此基础上,对夏季工况下的优化运行进行了实验研究,结果表明,通过调节空气和溶液流量,将热源塔的逼近度和冷幅分别控制在3.5℃和4.3℃,可使得系统性能系数由3.6提升至3.9,并对其节能机理进行了分析。     

Space-time finite element methods stabilized using bubble function spaces

ABSTRACT

In this paper, a stabilized space-time finite element method for solving linear parabolic evolution problems is analyzed. The proposed method is developed on a base of a space-time variational setting, that helps on the simultaneous and unified discretization in space and in time by finite element techniques. Stabilization terms are constructed by means of classical bubble spaces. Stability of the discrete problem with respect to an associated mesh dependent norm is proved, and a priori discretization error estimates are presented. Numerical examples confirm the theoretical estimates.     

热光伏能量转换器件的热力学极限与优化性能预测

受不可逆损失的影响,热光伏能量转换器件在高品位热能回收与利用方面受到限制.本文揭示不可逆损失来源,提供热光伏能量转换器件性能提升方案.利用半导体物理和普朗克热辐射理论,确定热光伏能量转换器件在理想条件下的最大效率.进而考虑Auger与Shockley-Reed-Hall非辐射复合和不可逆传热损失对光伏电池的电学、光学和热学特性的影响,预测热光伏器件优化性能.确定功率密度、效率和光子截止能量的优化区间.结果表明:相比于理想热光伏器件,非理想热光伏器件的开路电压、短路电流密度和效率有所降低;优化热光伏电池电压、光子截止能量和热源温度,可提升器件的功率密度和效率.通过对比发现理论与实验结果较一致,所得结果可为实际热光伏能量转换器件的研制提供理论指导.     

政府监管下的医院医疗信息分享演化博弈分析

在分析政府监管下医院间医疗信息分享特征的基础上,结合我国当前正在推行的医联体医院间信息分享运作模式,引入梅特卡夫定律并考虑患者评价的影响,分析了监管部门与医院各自的利益组成,建立了监管部门与医院两者之间的演化博弈模型,并采用复制动态方程研究了不同情形下医院间信息分享的演化博弈轨迹。研究表明,政府通过监管并建立激励惩罚机制等引导措施对医院最终达到的演化稳定态具有极大影响;降低医院主体信息分享的风险成本、规范提高医院分享信息的质量、引导患者增强对医院信息分享的关注、制定有吸引力和威慑力的奖惩政策,是促进医院医疗信息分享的关键。研究结果可为政府监管部门预测医院间的信息分享趋势和制定精准化政策以促进分享提供参考。     

复合材料失效判据有效性验证方法研究

为系统地验证复合材料失效判据计算精度和有效性范围,给出了4种材料体系、6种铺层形式的层合板在单轴、双轴载荷下的失效试验数据,用以评估复合材料失效判据在单向层合板失效包线、多向层合板初始失效包线、多向层合板最终失效包线、层合板变形及层合板的破坏特性等五个方面的预测能力。并根据验证方法和有效性评估策略对失效判据计算精度进行量化考核,给出了失效判据在五个层面上的计算精度。     

CRISPR-Cas12a System for Biosensing and Gene Regulation

Clustered regularly interspaced short palindromic repeats (CRISPR) is a promising technology in the biological world. As one of the CRISPR-associated (Cas) proteins, Cas12a is an RNA-guided nuclease in the type V CRISPR-Cas system, which has been a robust tool for gene editing. In addition, due to the discovery of target-binding-induced indiscriminate single-stranded DNase activity of Cas12a, CRISPR-Cas12a also exhibits great promise in biosensing. This minireview not only gives a brief introduction to the mechanism of CRISPR-Cas12a but also highlights the recent developments and applications in biosensing and gene regulation. Finally, future prospects of the CRISPR-Cas12a system are also discussed. We expect this minireview will inspire innovative work on the CRISPR-Cas12a system by making full use of its features and advantages.     

Collective Strategy Condensation: When Envy Splits Societies

Human societies are characterized by three constituent features, besides others. (A) Options, as for jobs and societal positions, differ with respect to their associated monetary and non-monetary payoffs. (B) Competition leads to reduced payoffs when individuals compete for the same option as others. (C) People care about how they are doing relatively to others. The latter trait—the propensity to compare one’s own success with that of others—expresses itself as envy. It is shown that the combination of (A)–(C) leads to spontaneous class stratification. Societies of agents split endogenously into two social classes, an upper and a lower class, when envy becomes relevant. A comprehensive analysis of the Nash equilibria characterizing a basic reference game is presented. Class separation is due to the condensation of the strategies of lower-class agents, which play an identical mixed strategy. Upper-class agents do not condense, following individualist pure strategies. The model and results are size-consistent, holding for arbitrary large numbers of agents and options. Analytic results are confirmed by extensive numerical simulations. An analogy to interacting confined classical particles is discussed.