集中式新能源电站联络线零序阻性电流差动继电保护方法

基于一起集中式新能源电站联络线单相接地典型故障,分析故障零序电流特性,提出小电阻接地电站联络线零序阻性电流差动继电保护方法。联络线两侧电站均为小电阻接地的方式,联络线单相接地时零序差动阻性电流分量是一个恒定量,与联络线及两侧电站对地电容量无关。该方法提升了对电站联络线单相接地故障判别的准确性、灵敏性。

滚齿机差动链运动误差的微机检测技术

应用比相技术检测同步运动误差时，若被测两路信号达不到“同频比相”的要求，则就难以进行正常的检测，滚齿机差动链运动误差的检测就属于这种情况，因此，比相检测技术的应用受到一定限制。本文提出一种新颖的滚齿机差动链运动误差的微机检测方法：以对两路传感器来脉冲信号进行计数为基础，然后通过微机处理而求得结果。该检测方法还适用于各类同步运动误差的检测，具有较强的通用性、实用性。

基于光栅扭矩转速传感器动态测试系统设计

为了减少一般测试系统由于很多传动链而带来的测试误差,提出同轴集成传动,同轴光栅扭矩/转速传感器测试系统.不仅能够通过光栅实现高速高精度转速测试,而且利用同轴上两个光栅的信号差动性实现了高精度动态扭矩测试.运用高速数据采集卡PCI-1784进行了四轴信号同步采集,通过LABview软件搭建计算机虚拟仪器测试平台;在提取扭矩信号方面,还提出了软件相关分析鉴相法.

Oscillation of Neutral Differential_difference Equations with Positive and Negative Periodic Coefficients

Some sufficient conditions are obtained for the oscillation of first order neutral differential_difference equations with positive and negative periodic coefficients.

Why women see differently from the way men see? A review of sex differences in cognition and sports

The differences of learning and memory between males and females have been well documented and confirmed by both human and animal studies. The sex differences in cognition started from early stage of neuronal development and last through entire lifespan. The major biological basis of the gender-dependent cognitive activity includes two major components： sex hormone and sex-related characteristics, such as sex- determining region of the Y chromosome （SRY） protein. However, the knowledge of how much biology of sex contributes to normal cogni- tive function and elite athletes in various sports are still pretty limited. In this review, we will be focusing on sex differences in spatial learning and memory -- especially the role of male- and female-type cognitive behaviors in sports.

Can color vision variation explain sex differences in invertebrate foraging by capuchin monkeys?

Invertebrates are the main source of protein for many small-to-medium sized monkeys. Prey vary in size, mobility, degree of protective coveting, and use of the forest, i.e. canopy height, and whether they are exposed or embed themselves in substrates. Sex-differentiation in foraging patterns is well documented for some monkey species and recent studies find that color vision phenotype can also affect invertebrate foraging. Since vision phenotype is polymorphic and sex-linked in most New World monkeys - males have dichromatic vision and females have either dichromatic or trichromatic vision - this raises the possibility that sex differences are linked to visual ecology. We tested predicted sex differences for invertebrate foraging in white-faced capuchins Cebus capucinus and conducted 12 months of study on four free-ranging groups between January 2007 and September 2008. We found both sex and color vision effects. Sex： Males spent more time foraging for invertebrates on the ground. Females spent more time consuming embedded, colonial invertebrates, ate relatively more ＂soft＂ sedentary invertebrates, and devoted more of their activity budget to invertebrate foraging. Color Vision： Dichromatic monkeys had a higher capture efficiency of ex- posed invertebrates and spent less time visually foraging. Trichromats ate relatively more ＂hard＂ sedentary invertebrates. We con- elude that some variation in invertebrate foraging reflects differences between the sexes that may be due to disparities in size, strength, reproductive demands or niche preferences. However, other intraspecific variation in invertebrate foraging that might be mistakenly attributed to sex differences actually reflects differences in color vision [Current Zoology 56 （3）： 300-312, 2010].

Violent Transient Sloshing-Wave Interaction with a Baffle in a Three-Dimensional Numerical Tank

A finite difference model for solving Navier Stokes viscous liquid sloshing-wave interaction with baffles in a tank. equations with turbulence taken into accotmt is used to investigate The volume-of-fluid and virtual boundary force methods are employed to simulate free surface flow interaction with structures. A liquid sloshing experimental apparatus was established to evaluate the accuracy of the proposed model, as well as to study nonlinear sloshing in a prismatic tank with the baffles. Damping effects of sloshing in a rectangular tank with bottom-mounted vertical baffles and vertical baffles touching the free surface are studied numerically and experimentally. Good agreement is obtained between the present numerical results and experimental data. The numerical results match well with the current experimental data for strong nonlinear sloshing with large free surface slopes. The reduction in sloshing-wave elevation and impact pressure induced by the bottom-mounted vertical baffle and the vertical baffle touching the free surface is estimated by varying the external excitation frequency and the location and height of the vertical baffle under horizontal excitation.

Properties of Differential Scattering Section Based on Multi-photon Nonlinear Compton Effect

Propertiss of damping electrons in collision with photons based onmulti- photon nonlinear Compton effect are investigated. Theexpressions of the differential scattering section are derived.Several useful conclusions are drawn.

High school sports programs differentially impact participation by sex

Background： Among numerous health benefits, sports participation has been shown to reduce the risk of overweight and obesity in children and adolescents. Schools represent an ideal environment for increasing sports participation, but it is unclear how access and choice influence participation and whether characteristics of the school sports program differentially influence boys＇ and girls＇ participation. The purpose of this study was to evaluate the characteristics of high school athletic programs and determine the extent to which these characteristics influenced boys＇ and girls＇ sports team participation. Methods： Longitudinal telephone surveys were conducted with 1244 New Hampshire and Vermont students. Students self-reported their sports team participation at baseline （elementary school） and follow-up （high school）. High school personnel were surveyed to assess sports oppor- tunities, which were defined for this analysis as the number of sports offered per 100 students （i.e., choice） and the percent of sports offered that did not restrict the number of players （i.e., access）. Results： Approximately 70% of children participated on at least one sports team, including 73% of boys and 66% of girls. We detected sta- tistically significant interactions between sex and two school opportunity variables： 1） the number of sports offered per 100 students （i.e., choice） and 2） the percent of sports offered that did not restrict the number of players （i.e., access）. After controlling for children＇s baseline sports participation and other covariates, boys were more likely to play on at least one sports team per year if their school did not restrict participation in the most popular sports （relative risk, RR = 1.12, p 〈 0.01）; in contrast, girls were more likely to play on at least one sports team per year if their school offered a wider variety of sports （RR = 1.47, p 〈 0.001）. Conclusion： Sports participation has previously been shown to confer a number of health benefits; as such, school sports programs may be an important, effective, and underused target for public health efforts, including obesity prevention programs. Efforts to increase physical activity among youth should consider both access and choice in school athletic programs. Schools may need to use different strategies to increase sports participation in boys and girls.

Convergence on Finite Difference Solution for Semilinear Wave Equation in One Space Variable

In this paper,the convergence and stability of the ’Leap-frog’ finite difference scheme for the semilinear wave equation are proved by using of the bounded extensive method under more generalized condition for the nonlinear term. The more complex standard a priori estimates are avoided so that the theoretical results are complemented for the scheme which was presented by Perring and Skyrne (1962).

Parental involvement and gender differences in the psychological profile of freshmen collegiate athletes

Background： The parent-to-child influences can be adaptive and contribute to the optimal psychological well-being and positive perception of the athlete. Contrary to the healthy parental involvement, a family can also have negative effects on an athlete development. The purpose of this study was to determine gender, father involvement, and mother involvement differences in the psychological profiles of collegiate freshmen athletes as measured by perfectionism, physical self-concept, and psychological well-being. Methods： Eighty-two male and 73 female collegiate freshmen responded to self-reported measures of family involvement, perfectionism, physical self-concept, and psychological well-being. Three separate 2 x 2 x 2 （gender x mother involvement x father involvement） factorial multivariate analysis of variance （MANOVAs） were carried out on the respective subscales from the reported measures. Results： There were significant differences for gender as well as father involvement in perfectionism （p 〈 0.01）. Freshmen females had lower concern over mistakes, and greater levels of organization as well as planfulness than males. Furthermore, freshmen athletes with high involved fathers showed greater levels of high standards for others as well as organization. Conclusion： Father involvement and mother involvement impact perfectionism, physical self-concept, and psychological well-being. perspective. extends through the freshmen year in college as shown in the athletes＇ Future research should develop better measures and utilize a family systems Copyright @ 2012, Shanghai University of Sport. Production and hosting by Elsevier B.V. All rights reserved

Investigation of a Design Modification for Double Helical Gears Reducing Vibration and Noise

To reduce vibration and noise and increase transmission efficiency, a three segment method for modifying the pinion profile was proposed. Cutter surface equations were deduced by changing the shape of the cutter-edge, substituting three segment parabolas for the line. The influence of longitudinal tooth modifications on tooth surface load distributions was discussed. Transmission error minimization and uniformity of tooth surface load distribution were chosen as optimization goals and the modified parameters were obtained by applying the complex method. Finally, an experiment comparing the loaded transmission error, vibration, and noise both before and after modifications was carried out. The results indicate that the modified design is reliable.

The Influence of Gender and Other Characteristics on Rural Laborers' Employment Patterns in the Mountainous and Upland Areas of Sichuan,China

This study examines gender differences in rural laborers‘ employment patterns in the mountainous and upland areas of Sichuan, China. The analysis employs both representative survey data of 400 households and geographical data. Multinomial logistic regression models are used to analyze the influences of gender, among other factors, on employment decisions of rural males and females, where the factors considered include personal, household, community natural environmental characteristics. Dividing laborers into four categories, we find that the proportions of males who participating in on-farm, pluriactive, and off-farm work, and unemployment were 24.41%, 28.64%, 46.27%, and 0.68% respectively, while that of females who participating in on-farm, pluriactive, and offfarm work, and unemployment were 43.20%, 13.95%, 30.95%, and 11.90% respectively. As to individual characteristics, age(AGE) and physical condition(PHY) effects appeared to be more pronounced for men, while education(EDU) and marital status(MAR)effects appeared to be more pronounced for women. Regarding household and community characteristics, the effects of the presence in the household of children aged 6-(CHI), number of persons in the household(POP), and labor force(LAB), per capitaincome in village(INCV), and the development status of village enterprises(ENT) on women were greater than that on men. In addition, the presence in the household of elderly individuals aged 65+(OLD) and time to reach the nearest township(TIME) are shown to have opposite impacts on men and women. While the presence in the household of pupils(PUP) and per capital gross value of industrial output(GVIO) was found to be irresponsive to men and women taking pluriavtivity and off-farm job. With respect to natural environments characteristics, the effects on men were opposite of those on women. Unemployment of women was found to be particularly responsive to household characteristics. A multinomial regression approach is undertaken to analyze rural males‘ and females‘ decisions of the four employment patterns considered, an approach that reveals considerable heterogeneity that is concealed by the dichotomous approach employed in most previous studies. The study thus contributes to our understanding of rural employment patterns and gender difference in mountainous and upland areas.

Similarities and Differences Between Freundlich Kinetic Equation and Two-Constant Equation

A mathematical expression of Freundlich kinetic equation, 1nS=A'+B'1nt, is presented, and the physical meanings of its parameters are indicated. Although the Freundlich kinetic equation and the two-constant equation are the same in the form, the derivation of the Freundlich kinetic equation is precise, while the deriVation of the two-constant equation has some contradictions and is unreasonable. And it is suggested that the Freundlich kinetic equation should have priority over the two-constant equation to be used.

New Calibration Technology for Safety Valves of Utility Boiler

Butterfly spring-relief valve, a crucial safety attachment of pressure vessel, is used to prevent pressuresystem from exceeding allowable limit value. Safe, expeditious and accurate calibration of safety valves is consequentlyof vital importance to safe and economic operation of generating units. NSH CALIBRATOR could complete, not only theon-line performance and parameter tests of safety valves within two to five seconds with opening pressure of safetyvalves and steam medium pressure automatically recorded, but also could complete the on-line adjustment of safetyvalves verified unqualified. It saves energy consumption, decreases noise pollution and improves accuracy and efficiencyof safety valve calibration.[

A new single degree-of-freedom resonance device

A new single degree-of-freedom （1 DOF） resonance device was developed. It mainly comprises a linear motor, a vibrating screen, a supporting spring set, a supporting frame and a damper set. Forces acting on the vibrating screen were found. A differential equation for describing the forces was set up. Equations that were used to evaluate the exciting force and exciting frequency in resonance were derived from the solution to the differential equation. In addition, an equation for evaluating the deformed magnitude of the damping springs in the damper set was presented so that the suitable damping may be obtained. Finally, a Matlab/Simulink model of the new i DOF resonance device was also built. Displacement-time curves of the vibrating screen under four conditions were obtained in the use of the Matlab/Simulink simulation. The curves indicate that it can shorten the time for the vibrating screen to be into the stable resonance with increasing the damping, and it can lengthen the time with increasing the vibrated mass or amplitude, but every given angular frequency cannot acquire the desired amplitude value of resonance.

Pressure Drop Fluctuations in Periodically Fluctuating Pipe Flow

Experiments were conducted to study characteristics of flow when flow is fluctuating.The experimental results showed a phase difference between the flow rate and the pressure drop fluctuations.This phase difference between the fluctuating flow rate and pressure drop was analyzed for laminar flow.Analysis showed that the phase difference changes with the period of the flow fluctuation, the pipe radius, the density and the dynamic viscosity of the liquid.Fluctuating pipe flow was then numerically simulated.Results of the numerical simulation were compared with theoretical values and experimental results.It was shown that, when the flow rate fluctuates with time as a sine wave, the pressure drop fluctuates with the same periodicity, and there is a phase difference between them.

Sensibility to Changes of Vibrational Modes of Excited Electron： Sum Frequency Signals Versus Difference Frequency Signals

In this paper, we investigate a two electronic level system with vibrational modes coupled to a Brownian oscillator bath. The difference frequency generation （DFG） signals and sum frequency generation （SFG） signals are calculated. It is shown that, for the same model, the SFG signals are more sensitive than the DFG signals to the changes of the vibrational modes of the electronic two-level system. Because the SFG conversion efficiency can be improved by using the time-delay method, the findings in this paper predict that the SFG spectrum may probe the changes of the microstructure more effectively.

Effect of static transmission error on dynamic responses of spiral bevel gears

The effect of static transmission error on nonlinear dynamic response of the spiral bevel gear system combining with time-varying stiffness and backlash was investigated.Firstly,two different control equations of the spiral bevel gear model were adopted,where the static transmission error was expressed in two patterns as predesigned parabolic function and sine function of transmission errors.The dynamic response,bifurcation map,time domain response,phase curve and Poincare map were obtained by applying the explicit Runge-Kutta integration routine with variable-step.A comparative study was carried out and some profound phenomena were detected.The results show that there are many different kinds of tooth rattling phenomena at low speed.With the increase of speed,the system enters into stable motion without any rattling in the region(0.72,1.64),which indicates that the system with predesigned parabolic function of transmission error has preferable capability at high speed.

Effects of Different Connectivity Topologies in Small World Networks on EEG-Like Activities

Based on our previously pulse-coupled integrate-and-fire neuron model in small world networks, we investigate the effects of different connectivity topologies on complex behavior of electroencephalographic-like signals produced by this model. We show that several times series analysis methods that are often used for analyzing complex behavior of electroencephalographic-like signals, such as reconstruction of the phase space, correlation dimension, fractal dimension, and the Hurst exponent within the rescaled range analysis （R/S）. We lind that the different connectivity topologies lead to different dynamical behaviors in models of integrate-and-fire neurons.