Realizing characteristic classes by manifolds

Let BG be the classifying space for stable spherical fibrations, and let V be a finite dimensional vector subspace of the cohomology algebra H¹(BG; $\text{Z}$₂). We prove that V may be realized by a Poincaré duality space P, which means that if v:P→BG is the Spivak fibration, then v¹ maps V isomorphically onto its image in H¹(P;$\text{Z}$₂). By construction, P is the product of a certain Grassman manifold and a spherical fiber space over a closed smooth manifold.     

关于正则图直径上界的加强

设G为n阶κ正则简单连通图（κ≥2)，λ是图G的次根，d(G)是图G的直径，如果G不是二部图，且d(G)≠2，则d(G)≤[log(n-1)/log(κ/λ)]，并且当G≌时，这一上界可达．     

Effective thermal conductivity of granulated two-phase systems at interstitial air pressures

Considering the htermal conduction through molecular collisions an expression for the effective thermal conductivityλ _e of loose and granular two-phase materials at different interstitial air pressure has been derived. The dependence ofλ _e on pore and particle sizes, characteristic pressure and radiative heat transfer is also discussed. Calculated values ofλ _e of glass beads and loose building materials are compared with reported results.     

Concepts of probabilistic sets

In the field of pattern recognition or decision making theory, the important subjects are as follows: (1) ambiguity of property of objects, (2) variety of character of objects, (3) subjectivity of observers, (4) evolution of knowledge of observers (i.e. learning). Considering these points, the concept of probabilistic set is proposed. It is based on both probability theory and fuzzy concepts. A probabilistic set on a total space is defined by a point wise measurable function from a parameter space (which is a probability space) to a characteristic space (which is a measurable space). It is shown that the family of all probabilistic sets constitutes a complete pseudo-Boolean algebra. Moment analysis is possible by using a probability measure of the parameter space. Other useful concepts are also mentioned such as probabilistic mappings and expected cardinal numbers.     

Coalition formation in the triad when two are weak and one is strong

Eighteen groups of subjects each participated in five different computer-controlled superadditive 3-person characteristic function games with sidepayments, that modeled negotiable conflicts in which two of the players are weak and one is considerably stronger. Both the degree to which the strong player was powerful and the type of communication were experimentally manipulated. The 90 game outcomes rejected any solution concept that predicts a single payoff vector for a given coalition structure, but supported the recently developed single-parameter α-power model that allows range predictions. Both the degree of power and type of communication were found to affect game outcomes and to determine the predictive power of models that make point predictions in 3-person games.     

A MATRIX METHOD FOR SOLVING PLANAR DIELECTRIC OPTICAL WAVEGUIDES

A matrix method used in multilayer stack of dielectric films is applied-to planar dielectric optical waveguides. A simple and applicable method for obtaining characteristic equation is presented.     

斯特林制冷机磨损和污染的特性分析

针对分置式斯特林制冷机存在的磨损和污染主要失效模式,论述了磨损特性的激振法测阻尼比试验方法和工质污染的分析方法和结果。磨损和污染的试验分析方法可用于斯特林制冷机研制时的失效模式控制。     

光子晶体光纤传输特性的研究

应用平面波展开法研究光子晶体光纤的传输特性,数值模拟得到了光子晶体光纤传播模式图,以及光子晶体光纤的频率和色散关系,研究结果为光子晶体光纤器件的开发提供了理论依据。     

Constant Impedance TEM Horn Antenna: Aperture and Characteristic Impedance’s Impacts on Axial Electric Field

TEM horn antenna with constant characteristic impedance (CCI TEM horn antenna) is a widely used ultra-wideband (UWB) antenna. Considering the peak-to-peak value of the axial electric field (V_pp), how to design such antenna’s characteristic impedance (Z _c) has not been involved in previous research. The relationship between V_pp and antenna aperture as well as characteristic impedance is numerical analyzed. The simulation and experimental results show that the optimal aperture is existed to maximize V_pp when the antenna’s length is fixed at the axis. More over, V_pp of the antenna with optimal aperture reaches the maximum value when the characteristic impedance is 280 ohm.