27,28P+28Si总反应截面增强及可能相关的机制

测量了27,28P和相应同中子异位素在28Si靶上的中能反应截面.测得N=12和13同中子异位素的反应截面在Z=15处突然增大.对Z≤14同中子异位素和28P的实验数据结果可以用改进的光学极限近似的Glauber理论很好地描述.28P的反应截面能够用扩大核芯以改进的Glauber理论来解释.但是,用改进光学极限和少体近似的Glauber理论却低估了27P的实验数据.理论分析表明,扩大的核芯加质子晕可能是响应27P+28Si反应截面增强的机制. The reaction cross sections of~(27,28)P and the corresponding isotones on Si target were measured at intermediate energies. The measured reaction cross sections of the N=12 and 13 isotones show an abrupt increase at Z=15. The experimental results for the isotones with Z≤14 and~(28)P can be described well by the modified Glauber theory of the optical limit approach. The enhancement of the reaction cross section for~(28)P could be explained by the modified Glauber theory with an enlarged core. Theoretical ana...     

Excitation Cross Section for Resonance Transitions of Rhenium Atoms Excited by Slow Electrons

Excitation of rhenium atoms by electron impact is investigated by the method of extended crossing beams. At electron energies of 50 eV, the excitation cross sections of 36 resonance and competing transitions in ReI are measured. Within the energy range from the threshold value to 250 eV, six optical excitation functions are detected. The reliability of data on transition probabilities in ReI has been analyzed.     

Single Production of Charged Top-Pions at High Energy Linear e+e- Colliders

The dominant decay modes of charged top-pions (π±t ) are tb or ~b. We consider the single production ofcharged top-pions in association with a top quark via e+ e- annihilation and calculate the production cross section of theprocesses e+ e- → t-bπ+ (tb-π-) at the leading order. We find that it can reach 1.2 fb with reasonable parameter values.The charged top-pions may be detected via the channel tbπ± in the future high energy e+ e- colliders.     

Information processing,memories, and synchronization in chaotic neural network with the time delay

Information processing and two types of memory in an analog neural network model with time delay that produces chaos similar to the human and animal EEGs are considered. There are two levels of information processing in this neural network: the level of individual neurons and the level of the neural network. Similar to the state of brain, the state of chaotic neural network is defined. It is characterized by two types of memories (memory I and memory II) and correlation structure between the neurons. In normal (unperturbed) state, the neural network generates chaotic patterns of averaged neuronal activities (memory I) and patterns of oscillation amplitudes (memory II). In the presence of external stimulation, the activity patterns change, showing changes in both types of memory. As in experiments on stimulation of the brain, the neural network model shows synchronization of neuronal activities due to stimulus measured by Pearson's correlation coefficient. An increase in neural network asymmetry (increase of the neural network excitability) leads to the phenomenon similar to the epilepsy. Modeling of brain injury, Parkinson's disease, and dementia is performed by removing and weakening interneuron connections. In all cases, the chaotic neural network shows a decrease of the degree of chaos and changes in both types of memory similar to those observed in experiments with healthy human subjects and patients with Parkinson's disease and dementia. © 2005 Wiley Periodicals, Inc. Complexity 11:39–52, 2005     

Time-Reversed Dynamical Entropy and Irreversibility in Markovian Random Processes

A concept of time-reversed entropy per unit time is introduced in analogy with the entropy per unit time by Shannon, Kolmogorov, and Sinai. This time-reversed entropy per unit time characterizes the dynamical randomness of a stochastic process backward in time, while the standard entropy per unit time characterizes the dynamical randomness forward in time. The difference between the time-reversed and standard entropies per unit time is shown to give the entropy production of Markovian processes in nonequilibrium steady states.     

线束中四直线交比定义的讨论

对梅向明等编《高等几何》关于线束中四直线交比的内容作重新编排，既保证其内容的完整性，又弥补原书理论上的不足．     

奇偶相干态的Wehrl熵和Shannon熵

研究了奇、偶相干态的Ｗｅｈｒｌ熵和Ｓｈａｎｎｏｎ熵，结果表明，其Ｗｅｈｒｌ熵随总噪声的增加而增大，并趋向同一个常数。Ｓｈａｎｎｏｎ熵随力学量起伏的减小而减小，且这两种态的Ｓｈａｎｎｏｎ熵均可小于相干态的Ｓｈａｎｎｏｎ熵，但这时并不与压缩效应的出现相对应，因而Ｓｈａｎｎｏｎ熵不能成为压缩存在的判据。     

垂直上升管内液体横掠流动传热特性研究

本文对单相水和单相油横掠流动时的平均换热特性进行了实验研究,对试验的结果进行了分析和讨论,并对实验数据进行关联,得到了垂直上升管内单相水和单相油横掠流动时的换热准则关系式。结果表明,狭窄空间条件下的液体横掠柱体时的流动换热对液相Re数的依赖,较大空间条件下的流动换热相比明显减小,并对单相水和单相油横掠流动时的换热性能进行了比较。     

L1-optimal estimates for a regression type function in R

Let X₁, X₂, …, X_n be random vectors that take values in a compact set in R^d, d ≥ 1. Let Y₁, Y₂, …, Y_n be random variables (“the responses”) which conditionally on X₁ = x₁, …, X_n = x_n are independent with densities f(y | x_i, θ(x_i)), i = 1, …, n. Assuming that θ lives in a sup-norm compact space Θ_q,d of real valued functions, an optimal L₁-consistent estimator of θ is constructed via empirical measures. The rate of convergence of the estimator to the true parameter θ depends on Kolmogorov's entropy of Θ_q,d.     

X-ray fluorescence in some rare earth and high Z elements excited by 661.6 keV γ-rays

The K-shell X-ray fluorescence cross sections are determined experimentally for 10 elements such as Pb, Hg, Ir, W, Lu, Tm, Dy, Tb, Gd and Nd at excitation energy of 661.6 keV associated with γ-rays of ¹³⁷Cs radioisotope. The technique employed involves the measurement of total intensity of fluorescent K X-rays that follow the photoeffect absorption of a known flux of γ-rays using a well type Nal(Tl) detector. The obtained results are compared with the available theoretical values and other measured values.