Effects of Unbalance Location on Dynamic Characteristics of High-speed Gasoline Engine Turbocharger with Floating Ring Bearings

For the high-speed gasoline engine turbocharger rotor, due to the heterogeneity of multiple parts material, manufacturing and assembly errors, running wear in impeller and uneven carbon of turbine, the random unbalance usually can be developed which will induce excessive rotor vibration, and even lead to nonlinear vibration accidents. However, the investigation of unbalance location on the nonlinear high-speed turbocharger rotordynamic characteristics is less. In order to discuss the rotor unbalance location effects of turbocharger with nonlinear floating ring bearings（FRBs）, the realistic turbocharger of gasoline engine is taken as a research object. The rotordynamic equations of motion under the condition of unbalance are derived by applied unbalance force and nonlinear oil film force of FRBs. The FE model of turbocharger rotor-bearing system is modeled which includes the unbalance excitation and nonlinear FRBs. Under the conditions of four different applied locations of unbalance, the nonlinear transient analyses are performed based on the rotor FEM. The differences of dynamic behavior are obvious to the turbocharger rotor systems for four conditions, and the bifurcation phenomena are different. From the results of waterfall and transient response analysis, the speed for the appearance of fractional frequency is not identical and the amplitude magnitude is different from the different unbalance locations, and the non-synchronous vibration does not occur in the turbocharger and the amplitude is relative stable and minimum under the condition 4. The turbocharger vibration and non-synchronous components could be reduced or suppressed by controlling the applied location of unbalance, which is helpful for the dynamic design, fault diagnosis and vibration control of the high-speed gasoline engine turbochargers.

Development of Wages and Salaries of Czech Employees During the Last Period by Educational Attainment and Forecasts for 2011 and 2012

This paper deals with the development of sample characteristics of wage distribution in recent years in the Czech Republic by the highest educational attainment. Gross monthly wage is the variable investigated. We distinguish the following scale of the highest educational attainment： primary and incomplete education, secondary education without GCSE, secondary education with GCSE, higher vocational and bachelor education and tertiary education. Forecasts of wage distribution have been developed for the next two years for all of these categories. Three-parametric lognormal curve formed the basis of the theoretical probability distribution. Parameter values of relevant three-parametric lognormal curves were then estimated using the method of L-moments of parameter estimation. Forecasts of sample values of L-moments were calculated using trend analysis of their past development and the parameters of three-parametric Iognormal curves for forecasts of wage distribution were calculated using the predicted values of the first three sample L-moments. We have obtained the forecasts of wage distribution by the highest educational attainment on the basis of these probability density functions.

Research on Location Characteristics and Algorithms based on Frequency Domain for a 2D Underwater Active Electrolocation Positioning System

Weakly electric fish has an ability to generate a low-frequency electric field actively to locate the surrounding object in complete darkness by sensing the change of the electric field. This ability is called active electrolocation. In this paper, we designed a two-dimensional （2D） experimental platform of underwater active electrolocation system by simulating weakly electric fish. On the platform, location characteristics based on frequency domain were investigated. Results indicated that surface shape of 3D location characteristic curves for the 2D underwater active electrolocation positioning system was convex upwards or concave down which was influenced by the material of probed objects and the frequency of the electric field exci- tation signal. Experiments also confirmed that the amplitude of the electric field excitation signal and the size of the probed object will only influence the amplitude corresponding to 3D location characteristic curves. Based on above location charac- teristics, we present three location algorithms including Cross Location Algorithm （CLA）, Stochastic Location Algorithm （SLA） and Particle Swarm Optimization （PSO） location algorithm in frequency domain and achieved the task of the underwater positioning system. Our work may have reference value for underwater detection study.

Dynamic Capture Method for Out-of-step Center of Power Grid Based on Measurement Information

This paper dynamically captures the out-of-step center for a bulk power system based on measurement information.First,the position characteristics of the out-of-step center are discussed from the perspective of triangular geometry under different potential and uniform impedance distributions based on a two-machine system.The correlation between the out-of-step center and the oscillation center is analyzed.Second,combined with analytical geometry,it is inferred that the distribution characteristics of the out-of-step center voltage vector ends are a circle or a straight line,and the position of the out-of-step center corresponds to the intersection between the voltage drop of the line and the distribution characteristics;then,the accurate location of the out-of-step center and the determination of the appearance moment is realized.Finally,a dynamic equivalence method for a power grid is proposed based on the electrical parameters of the transmission line,and an alternative iterative correction of equivalent parameters is carried out by trajectory sensitivity,which provides a new way for capturing the out-ofstep center dynamically in a multimachine system.The proposed method is validated using a three-machine system,the IEEE-39 system and the Northwest China Power Grid,and shows potential for online applications.