Entropy Could Quantify Brain Activation Induced by Mechanical Impedance-Restrained Active Arm Motion: A Functional NIRS Study

Brain activation has been used to understand brain-level events associated with cognitive tasks or physical tasks. As a quantitative measure for brain activation, we propose entropy in place of signal amplitude and beta value, which are widely used, but sometimes criticized for their limitations and shortcomings as such measures. To investigate the relevance of our proposition, we provided 22 subjects with physical stimuli through elbow extension-flexion motions by using our exoskeleton robot, measured brain activation in terms of entropy, signal amplitude, and beta value; and compared entropy with the other two. The results show that entropy is superior, in that its change appeared in limited, well established, motor areas, while signal amplitude and beta value changes appeared in a widespread fashion, contradicting the modularity theory. Entropy can predict increase in brain activation with task duration, while the other two cannot. When stimuli shifted from the rest state to the task state, entropy exhibited a similar increase as the other two did. Although entropy showed only a part of the phenomenon induced by task strength, it showed superiority by showing a decrease in brain activation that the other two did not show. Moreover, entropy was capable of identifying the physiologically important location.     

壬基酚聚氧乙烯醚型Gemini季铵盐表面活性剂的合成 及其表面性质的研究

合成了系列壬基酚聚氧乙烯醚型Gemini季铵盐表面活性剂(GNPQA), 用核磁、红外和元素分析对它们的结构进行了表征, 考察了反应条件对转化率的影响, 并用表面张力法和稳态荧光探针法对GNPQA的表面性能及胶束聚集数(N)进行了研究. 结果表明, 较优的反应条件: 反应时间为12 h, 反应温度为70 ℃, 反应原料摩尔比为n(双聚壬基酚聚氧乙烯醚)∶n(三乙胺)∶n(环氧氯丙烷)＝1∶1∶1; GNPQA的临界胶束浓度(CMC)值较相应的单体壬基酚聚氧乙烯醚型季铵盐表面活性剂(NPQA)降低了1～2个数量级, 显示了较高的表面活性; 当GNPQA溶液浓度为5～9倍CMC时, N值随浓度增大而线性增大; 随着氧乙烯(EO)单元数的增长, GNPQA的CMC和N值均逐渐减小; 结合GNPQA的表面性能参数和N值的变化规律, 探讨了这类表面活性剂表面及胶束聚集体的结构形态.     

几类特定边界值条件下的常微分方程特征值问题

在文献[1]的基础上,借助于图形分析方法,讨论了几类特定边界值条件下的特征值问题.同时,本文对文献[1]中的错误结论作出了更正.本文给出的方法对讨论非线性边值问题的可解性提供了一种新的途径.     

渐变段倾角对渐变复合腔特性影响的分析

利用模式耦合理论,在考虑多模耦合的情况下,对渐变结构复合腔进行了冷腔分析,计算了H51-H52模式对下,各个模式的耦合及场幅值分布情况,分析了渐变段的倾角对渐变复合腔的Q值及场幅值分布的影响。研究表明：渐变段的倾角对渐变结构复合腔的高频特性有很大的影响,特别是各模式的场分布及Q值,合适地选择渐变角度,能使场幅值放大率比较大,这将有利于提高注-波互作用效率。     

An explicitly solvable kinetic model for semiconductors

We consider a simple model for the electron Boltzmann equation in a semiconductor and show that specific boundary value problems can be explicitly solved. Cases of both homogeneous and inhomogeneous electric fields are considered.     

Light ion fusion in deformation model

Experiments with heavy ions at moderate energies show the importance of deformation in heavy ion collisions. A deformation model which takes deformation dynamically into account is developed. Having described fusion and deep inelastic collision for a very heavy system (Xe + Bi) and a medium heavy system (Ar + Th) at various energies successfully, we turn to some comparatively lighter heavy ions where fusion is the most dominant feature. Fusion cross-sections for six pairs of lighter systems (³⁵Cl +¹¹⁶Sn,⁵⁸Ni+⁶²Ni,³⁵Cl+⁶²Ni,³²S+²⁴Mg,²⁴Mg+²⁴Mg and¹²C+²⁷Al) have been obtained using our deformation model which agree well with experiment. The two-slope-behaviour of fusion excitation function which is an important feature of light ion fusion systematics is also obtained, in our model calculations for all the systems studied.     

Subleading long-range interactions and violations of finite size scaling

We study the behavior of systems in which the interaction contains a long-range component that does not dominate the critical behavior. Such a component is exemplified by the van der Waals force between molecules in a simple liquid-vapor system. In the context of the mean spherical model with periodic boundary conditions we are able to identify, for temperatures close above T _c, finite-size contributions due to the subleading term in the interaction that are dominant in this region decaying algebraically as a function of L. This mechanism goes beyond the standard formulation of the finite-size scaling but is to be expected in real physical systems. We also discuss other ways in which critical point behavior is modified that are of relevance for analysis of Monte Carlo simulations of such systems. Received 21 November 2000 and Received in final form 28 February 2001     

三维自助式类渗流细胞自动机的临界值

本文研究三维自助式类渗流细胞自动机的临界值．得出临界值pc＝0的一些充分条件和必要条件．当pc＞0时，利用定向点渗流的临界值，给出了pc上、下界的显式估计．     

基于POT方法的极值理论在基金净值预测中的应用

为对基金净值数据进行建模,根据基金净值样本数据的尾部特点,建立极大,极小值分布的GPD模型,运用POT方法确定临界值,进而对参数进行估计,并对模型进行检验.最后,运用建立的模型对一些极值点进行预测.所得结果很好地描述了数据特点,对极值点的预测符合实际.     

4＋2D维Einstein－Maxwell量子宇宙

利用推广的Ｈａｒｔｌｅ－Ｈａｗｋｉｎｇ假设，研究了４＋２Ｄ维Ｅｉｎｓｔｅｉｎ－Ｍａｘｗｅｌｌ量子宇宙，计算了微超空间波函数的近似解．发现当Ｄ≤２时存在与观测宇宙相符合的暴胀解．