Stability analysis in a second-order differential equation with delays

A second-order differential equation with finite discrete delays is considered. Local stability of the zero equilibrium is investigated, and we obtain some sufficient conditions for the zero equilibrium is stable or unstable. Moreover, it is found that there exist the local Hopf bifurcations of the system when the delay varies.     

Model test of helical angle effect on coal loading performance of shear drum

The work presented in this paper focuses on improving coal loading performance of shear drum.Employing the similarity theory,we carried out a dimensional analysis of the correlation parameters which in...     

Oxidation behaviors of Ni-Cr-Al superalloy foams at 1 000 ℃ in air

The oxidation behaviors of Ni-16Cr-xAl （x=4.5%, 9.0%, mass fraction） superalloy foams in air at 1000℃ were investigated. The effects of AI content on the resistance to high temperature oxidation were examined. The oxidation mechanisms of the foams were discussed. The results show that the resistance to the oxidation of the Ni-16Cr-xA1 based alloy at 1 000 ℃ increases with the content of A1 increasing from 4.5% to 9.0%. Complex oxide products are formed on the surface of the superalloy foams after the oxidation. Cr203 and A1203 are the predominant oxides for the scales of the foams with 4.5% A1 and 9% A1, respectively. Excellent high temperature oxidation resistance and superior pore conformation stability for the Ni-16Cr-xA1 based superalloy foam with 9% A1 can be mainly attributed to the formation of relatively continuous and protective A1203 oxides on the surface of the foam.     

Deformation effect of lateral roof roadway in close coal seams after repeated mining

This paper analyzed the deformation mechanism in lateral roof roadway of the Ding Wu-3 roadway which was disturbed by repeated mining of close coal seams Wu-8 and Wu-10 in Pingdingshan No. 1 Mine. To determine the strata disturbance scope, the strata displacement angle was used to calculate the protection pillar width. A numerical model was built considering the field geological conditions. In simulation, the mining stress borderline was defined as the contour where the induced stress is 1.5 times of the original stress. Simulation results show the mining stress borderline of the lateral roadway extended 91.7 m outward after repeated mining. Then the original stress increased, deforming the roadway of interest. This deformation agreed with the in situ observations. Moreover, the strata displacement angle changed due to repeated mining. Therefore, reselection of the displacement angle was required to design the protective pillar width. Since a constant strata displacement angle was used in traditional design, the proposed method was beneficial in field cases.     

Parametric synthesis of pulsar time

A new method of generating pulsar time based on a coherent representation of a sequence of observed events is considered. The properties of pulsar time compared with the traditional approach are analyzed. __________ Translated from Izmeritel’naya Tekhnika, No. 6, pp. 39–44, June, 2006.     

电力系统稳定性研究的方法论思考

文章对电力系统稳定性研究内涵进行了评述，然后从认识论和方法论上加以分析，讨论了认识过程从功角稳定到电压稳定的转变、从线性向非线性的转变、从简单系统到复杂系统的转变、从重视解析方法到重视非解析方法的转变过程，为电力系统稳定性研究提供方法论指导。     

大机组调峰对锅炉运行的影响及运行优化研究

利用炉膛断面温度场可视化监测系统、节能环保车、炉内三维数值模拟等先进的技术和设备对大机组调峰稳定性和运行方式优化进行试验和理论研究。     

特高压通道降压运行时安徽500kV西通道建设必要性分析

根据华东1000kV特高压输电通道初期降压运行的统筹安排，结合淮南煤电基地电源、平圩电厂二期及蚌埠电厂等电源的装机进度，通过对各电源接入系统方案的计算分析，最后得出结论：为保证江北地区电力送出，安徽500kV西路过江通道在“十一五”期间建成是有必要的。     

生成黑盒测试数据的设计思想在学生成绩管理系统中的实现

黑金测试是数据库应用系统测试的常用方法，而生成大量测试数据则是进行黑金测试的前提。如果能使用“数据生成”工具生成大量模拟测试数据，将提高数据库应用系统的测试效率和测试质量。本文主要提出了生成黑金测试数据的设计思想，并基于这一思想开发了“学生成绩管理系统”的数据生成工具。