Interesting effects in harmonic generation by plane elastic waves

The harmonics of plane longitudinal and transverse waves in nonlinear elastic solids with up to cubic nonlinearity in a one-dimensional setting are investigated in this paper. It is shown that due to quadratic nonlinearity, a transverse wave generates a second longitudinal harmonic.This propagates with the velocity of transverse waves, as well as resonant transverse first and third harmonics due to the cubic and quadratic nonlinearities. A longitudinal wave generates a resonant longitudinal second harmonic, as well as first and third harmonics with amplitudes that increase linearly and quadratically with distance propagated. In a second investigation, incidence from the linear side of a primary wave on an interface between a linear and a nonlinear elastic solid is considered. The incident wave crosses the interface and generates a harmonic with interface conditions that are equilibrated by compensatory waves propagating in two directions away from the interface. The back-propagated compensatory wave provides information on the nonlinear elastic constants of the material behind the interface. It is shown that the amplitudes of the compensatory waves can be increased by mixing two incident longitudinal waves of appropriate frequencies.

Tidal characteristics near the Chinese Zhongshan Station in Prydz Bay, East Antarctica

A permanent tidal station was installed at the Chinese Zhongshan Station in Feb. 2010. Harmonic constants of 170 tidal constituents were obtained from harmonic analysis of the first year＇ s data. The results of the eight main constituents showed good agreement with those of two tidal models. Tidal characteristics, such as tide type, diurnal inequality, tidal range, and water levels were also analyzed.

STUDY OF IMPACT OF ESTABLISHMENT OF A DAM ON LOCAL TIDAL CURRENTS IN KENDONG OIL FIELD

In this paper a three-dimensional tidal current model has been used toexamine variations of local fluid field due to establishment of a dam. By imputing ten tides-K_1,O_1, P_1 , Q_1, M_2, S_2, N_2, K_2 , S_a and S_(sa) through the open boundary of the Bohai straitand adopting 5′ x 5′ horizontal resolution the whole fluid field of the Bohai Sea was firstsimulated. The computed harmonic constants of m_1 and M_2 tides at seventeen observational stationsalong the coast of the Bohai Sea matched the observed values rather well. Taking the calculatednumerical results as open boundary conditions, the local fluid field in the Kendong Oil Field bymeans of 1′ x 1′ horizontal resolution was then investigated. In the course of calculation, finegrids were embedded in coarse grids so as to enhance the computational order. In addition, thelatest water-depth data of the Huanghe Delta coast area were adopted, thus topographic changesbecause of silt sediment in that region wouldn''t affect the computed results. In the end, byanalyzing the relative changes of the fluid field before and after the dam was established, that theeffect on the dynamic environment of the local sea area mainly concentrated on the adjacentpositions north and south of the dam was suggested.