Experimental and Numerical Investigation of Non-synchronous Blade Vibration Excitation in a Transonic Axial Compressor

The complex flow phenomenon of rotating instability(RI) and its induced non-synchronous vibration(NSV) have become a significant challenge as they continuously increase aerodynamic load.This study aims to provide an understanding of the non-synchronous blade vibration phenomenon caused by the rotating instability of a transonic axial compressor rotor.In this case,blade vibrations and non-synchronous excitation are captured by strain gauges and unsteady wall pressure transducer sensors.Unsteady numerical simulations for a full-annulus configuration are used to obtain the non-synchronous flow excitation.The results show that the first-stage rotor blade exhibits an NSV close to the first bending mode;NSV is accompanied by a sharp increase in pressure pulsation;amplitude can reach 20%,and unsteady aerodynamic frequency will lock in a structural mode frequency when the blade vibrates in a large-amplitude motion.The predicted NSV frequency aligns well with the experimental results.The dominant mode of circumferential instability flow structure is approximately 47% of the number blades,and the cell size occupies 2-3 pitches in the circumferential direction.The full-annulus unsteady simulations demonstrate that the streamwise oscillation of the shedding and reattachment vortex structure is the main cause of NSV owing to the strong interaction between the tip leakage and separation vortices near the suction surface.

Evolution of non-synchronized binary systems

A model for binary evolution is introduced which can determine whether the rotation of components is synchronized with the orbital motion, and can calculate the evolution of both the synchronized and non-synchronized binary systems. With this model, the evolution of a binary system consisting of a 9 M star and a 6 M star is studied with mass transfer Case B. The result shows that the synchronization of the rotational and orbital periods can be reached when the binary system is a detached system and before the occurrence of the first mass transfer. After the onset of the first mass transfer, the binary system becomes non-synchronized. The mass accepted component (the secondary) rotates faster with a period much smaller than that of the orbital motion.

Electro-optical sampling non-synchronous delay scanning measurement of electron beam bunch length at BFEL

The Electro-optical sampling delay scanning technique can be used for electron beam bunch length measurement. A novel non-synchronous delay scanning technique based on the electro-optical sampling measurements is presented. Based on Beijing Free Electron Laser （BFEL）, the electron beam bunch length was measured with the electro-optical sampling technique for the first time in China. The result shows that the electron beam bunch length at BFEL is about 5.6±1.2 ps.

The global financial crisis and its transmission to Asia Pacific

By virtue of the US markets closing later than Asia-Pacific(AP)markets,returns observed in the US include information not reflected in AP until the next day.Provided there is enough integration among markets,this asymmetry should then generate Granger causality from the US returns towards returns in the AP region.It is thus obvious that when testing for Granger causality among the Western and AP markets,interdependence due to non-synchronicity should be clearly identified and factored out.Our novel method is to measure contagion,usually defined as excessive market integration during crises,as excess interdependence beyond the non-synchronicity induced.We test for contagion of the 2008 Financial Crisis from the US to AP.The unmistakable emergence of a new cointegration relation that intertwines the US and AP markets only during the crisis,but not before,presents evidence of long-run contagion,that is a new channel that transmits crisis-related info.We find strong contagion from US to Korea,no contagion to Hong Kong,and Australia is a mixed case.Our explanation is that the Korean economy is the most vulnerable due to its export orientation,Hong Kong becomes disentangled due to its relation to China,which is consistent with the theory of‘decoupling’of China,and the Australian case is somewhere in the middle,probably due to its close ties to the US but also its strong reliance on natural resources and gold.

GLOBAL ANALYSIS OF AN EBENMAN＇S MODEL OF POPULATION WITH TWO COMPETING AGE CLASSES

Several global conclusions about an Ebenman's model of a population with competing juveniles and adults are derived in this paper. The problems about the number of non-trivial fixed points, the number of synchronous 2-cycles, and the number of attracting synchronous cycles are resolved. In a special case, the twice iteration of the 2-dimensional map can be reduced to a 1-dimensional map, and the existence of one or more continua of non-synchronous 2-cycles is pointed out. Numerical calculations are used to draw orbit diagrams which show complicated dynamics of this non-invertible 2-dimensional map. Experimental and field observational evidence is also discussed.