Near surface velocity and Q_s structure of the Quaternary sediment in Bohai basin,China

Heavily populated by Beijing and Tianjin cities, Bohai basin is a seismically active Cenozoic basin suffering from huge lost by devastating earthquakes, such as Tangshan earthquake. The attenuation （Qp and Qs） of the surficial Quaternary sediment has not been studied at natural seismic frequency （1-10 Hz）, which is crucial to earthquake hazards study. Borehole seismic records of micro earthquake provide us a good way to study the velocity and attenuation of the surficial structure （0-500 m）. We found that there are two pulses well separated with simple waveforms on borehole seismic records from the 2006 Mw4.9 Wen＇an earthquake sequence. Then we performed waveform modeling with generalized ray theory （GRT） to confirm that the two pulses are direct wave and surface reflected wave, and found that the average vp and Vs of the top 300 m in this region are about 1.8 km/s and 0.42 km/s, leading to high ve/vs ratio of 4.3. We also modeled surface refleeted wave with propagating matrix method to constrain Qs and the near surface velocity structure. Our modeling indicates that Qs is at least 30, or probably up to 100, much larger than the typically assumed extremely low Q（-10）, but consistent with Qs modeling in Mississippi embayment. Also, the velocity gradient just beneath the free surface （0-50 m） is very large and velocity increases gradually at larger depth. Our modeling demonstrates the importance of borebole seismic records in resolving shallow velocity and attenuation structure, and hence may help in earthquake hazard simulation.

Viscous Slip MHD Flow over a Moving Sheet with an Arbitrary Surface Velocity

The magnetohydrodynamic（MHD） flow induced by a stretching or shrinking sheet under slip conditions is studied.Analytical solutions based on the boundary layer assumption are obtained in a closed form and can be applied to a flow configuration with any arbitrary velocity distributions. Seven typical sheet velocity profiles are employed as illustrating examples. The solutions to the slip MHD flow are derived from the general solution and discussed in detail. Different from self-similar boundary layer flows, the flows studied in this work have solutions in explicit analytical forms. However, the current flows require special mass transfer at the wall, which is determined by the moving velocity of the sheet. The effects of the slip parameter, the mass transfer at the wall, and the magnetic field on the flow are also demonstrated.

Trace Projection Transformation： a new method for measurement of debris flow surface velocity fields

Spatiotemporal variation of velocity is impor- tant for debris flow dynamics. This paper presents a new method, the trace projection transformation, for accurate, non-contact measurement of a debris-flow surface velocity field based on a combination of dense optical flow and perspective projection transformation. The algorithm for interpreting and processing is implemented in C ＋＋ and realized in Visual Studio 2012. The method allows quantitative analysis of flow motion through videos from various angles （camera positioned at the opposite direction of fluid motion）. It yields the spatiotemporal distribution of surface velocity field at pixel level and thus provides a quantitative description of the surface processes. The trace projection transformation is superior to conventional measurement methods in that it obtains the full surface velocity field by computing the optical flow of all pixels. The result achieves a 90% accuracy of when comparing with the observed values. As a case study, the method is applied to the quantitative analysis of surface velocity field of a specific debris flow.

Global air-sea surface carbon dioxide transfer velocity and flux estimated using 17 a altimeter data and a new algorithm

The global distributions of the air-sea CO2 transfer velocity and flux are retrieved from TOPEX/Poseidon and Jason altimeter data from October 1992 to December 2009 using a combined algorithm. The 17 a average global, area-weighted, Schmidt number-corrected mean gas transfer velocity is 21.26 cm/h, and the full exploration of the uncertainty of this estimate awaits further data. The average total CO2 flux （calculated by carbon） from atmosphere to ocean during the 17 a was 2.58 Pg/a. The highest transfer velocity is in the circumpolar current area, because of constant high wind speeds and currents there. This results in strong CO2 fluxes. CO2 fluxes are strong but opposite direction in the equatorial east Pacific Ocean, because the air-sea CO2 partial pressure difference is the largest in the global cceans. The results differ from the previous studies calculated using the wind speed. It is demonstrated that the air-sea transfer velocity is very important for estimating air-sea CO2 flux. It is critical to have an accurate estimation for improving calculation of CO2 flux within climate change studies.

AC Back Surface Recombination Velocity in n⁺-p-p⁺Silicon Solar Cell under Monochromatic Light and Temperature

Excess minority carrier’s diffusion equation in the base of monofaciale silicon solar cell under frequency modulation of monochromatic illumination is resolved. Using conditions at the base limits involving recombination velocities Sf and Sb, respectively at the junction (n+/p) and back surface (p+/p), the AC expression of the excess minority carriers’ density δ (T, ω) is determined. The AC density of photocurrent Jph (T, ω) is represented versus recombination velocity at the junction for different values of the temperature. The expression of the AC back surface recombination velocity Sb of minority carriers is deduced depending on the frequency of modulation, temperature, the electronic parameters (D (ω)) and the thickness of the base. Bode and Nyquist diagrams are used to analyze it.

3D Characteristic Diagram of Acoustically Induced Surface Vibration with Different Landmines Buried

The 3D characteristic diagram of acoustically induced surface vibration was employed to study the influence of different buried landmines on the acoustic detection signal. By using the vehicular experimental system for acoustic landmine detection and the method of scanning detection, the 3D characteristic diagrams of surface vibration were measured when different objects were buried underground, including big plastic landmine, small plastic landmine, big metal landmine and bricks. The results show that, under the given conditions, the surface vibration amplitudes of big plastic landmine, big metal landmine, small plastic landmine and bricks decrease in turn. The 3D characteristic diagrams of surface vibration can be used to further identify the locations of buried landmines.

Hardware system design for UHF surface velocities radar

UHF surface velocities radar is developed based on the successful ocean state measuring and analyzing radar system. The design method for UHF radar system is presented. It is designed to operate at UHF channel, and the transmit power is under 5W. Maximum range of field test over fresh water can be a kilometer. The field tests at Tangsun River and at Majiatan and Gaobazhou proved that USVR System can be used successfully.

Modelling of spall damage in ductile materials and its application to the simulation of the plate impact on copper

A statistical model of dynamic spall damage due to void nucleation and growth is proposed for ductile materials under intense loading, which takes into account inertia, the elastic-plastic effect, and initial void size. To some extent, void interaction could be accounted for in this approach. Based on this model, the simulation of spall experiments for copper is performed by using the Lagrangian finite element method. The simulation results are in good agreement with experimental data for the free surface velocity profile, stress record behind copper target, final porosity, and void concentrations across the target. The influence of elastic-plastic effect upon the damage evolution is explored. The correlation between the damage evolution and the history of the stress near the spall plane is also analyzed.

The movement features analysis of Laohugou Glacier No.12 in Qilian Mountains

The Laohugou Glacier No. 12 is the largest valley glacier in Qilian Mountains, which is located in northem Qinghai-Tibet Plateau. Movement is the basic characteristic of glaciers, and is also an important distinction from other terrestrial natural ice. Glacier changes not only reflect climate change, but also play an important role in humanity society. In the arid regions of western China, glaciers are becoming an important water source. We use the GPS receiver （South-Lingrui $82） as data platform with the aid of RTK measurement technology to observe the surface velocity of Laohugou Glacier No. 12. Surface velocity data shows that the maximum value appears at an altitude of 4,750-4,850 m during the period of 2008-2009. During this period, the west branch surface velocity reached 32.6 m per year at an altitude near 4,830 m, the east branch surface velocity reached 32.4 m per year at the altitude near 4,770 m. Comparing the surface velocity data during 2008-2009 with observation results in 1959, the glacier velocity slowed down about 11%.

Dynamic Fracture Toughness Tests on Limestone

Limestone being sedimentary rock contains multiple bedding planes,which has vertical cracks or joints.As explosives apply high dynamic loading rate during blasting i.e.rock fragmentation&comminution process,the measure of critical SIF(stress intensity factor)is pertinent to be measured and is known as dynamic fracture toughness of limestone.In order to investigate the influence of several factors on the mode-I fracture toughness and fracture behavior of limestone,dynamic fracture toughness tests(mode-I)were conducted under various conditions of loading rate.The microstructure of rocks was also investigated to understand the dynamic fracture toughness and fracture mechanism of limestone.This paper deals with results of 11 limestone specimen subjected to dynamic fracture toughness tests.It was observed that crack surface velocity increases with increase in dynamic fracture toughness.The fracture velocity also increases with increase in dynamic fracture toughness.The fracture velocity in limestone increases between 1.14-5.09 times with increased fracture toughness.The crack surface velocity of limestone increases between 1.39-3.09 times with increase in dynamic fracture toughness.

n⁺-p-p⁺Silicon Solar Cell Base Optimum Thickness Determination under Magnetic Field

Base optimum thickness is determined for a front illuminated bifacial silicon solar cell n+-p-p+ under magnetic field. From the magneto transport equation relative to excess minority carriers in the base, with specific boundary conditions, the photocurrent is obtained. From this result the expressions of the carrier’s recombination velocity at the back surface are deducted. These new expressions of recombination velocity are plotted according to the depth of the base, to deduce the optimum thickness, which will allow the production, of a high short-circuit photocurrent. Calibration relationships of optimum thickness versus magnetic field were presented according to study ranges. It is found that, applied magnetic field imposes a weak thickness material for solar cell manufacturing leading to high short-circuit current.

Evidences of the expanding Earth from space-geodetic data over solid land and sea level rise in recent two decades

According to the space-geodetic data recorded at globally distributed stations over solid land spanning a period of more than 20-years under the International Terrestrial Reference Frame 2008,our previous estimate of the average-weighted vertical variation of the Earth＇s solid surface suggests that the Earth＇s solid part is expanding at a rate of 0.24 ± 0.05 mm/a in recent two decades.In another aspect,the satellite altimetry observations spanning recent two decades demonstrate the sea level rise（SLR） rate 3.2 ± 0.4 mm/a,of which1.8 ± 0.5 mm/a is contributed by the ice melting over land.This study shows that the oceanic thermal expansion is 1.0 ± 0.1 mm/a due to the temperature increase in recent half century,which coincides with the estimate provided by previous authors.The SLR observation by altimetry is not balanced by the ice melting and thermal expansion,which is an open problem before this study.However,in this study we infer that the oceanic part of the Earth is expanding at a rate about 0.4 mm/a.Combining the expansion rates of land part and oceanic part,we conclude that the Earth is expanding at a rate of 0.35 ± 0.47 mm/a in recent two decades.If the Earth expands at this rate,then the altimetry-observed SLR can be well explained.

Bulk Waves in the Infinite Electric-Magnetic-Elastic Plate with Mixed Boundary Conditions

A dynamic solution is presented for the propagation of waves in an electric-magneto-elastic plate composed of piezoelectric, piezomagnetic materials and elastic matrix. The electric-magneto-elastic plate is polarized along the thickness direction. The generalized displacements are expressed as the sum of the gradient of a scalar (dilatation wave) and the curl of a vector (shear wave). With the help of dynamic equilibrium equations and geometric equations, we can obtain dynamic equations of the dilatation wave and the shear wave. The conclusion that the types of the dilatation waves and the shear waves remain unchanged after being reflected by the boundary can be obtained through the analysis of these kinetic equations. The dispersion properties and phase velocity surface of the dilatation and shear wave can be obtained by solutions of dynamic equilibrium equations. Influences of the piezoelectric and piezomagnetic parameters on wave characteristics are discussed.

N^+P photodetector characterization using the quasi-steady state photoconductance decay method

When a material is irradiated, it becomes more electrically conductive due to the absorption of the electromagnetic radiation. As a result, the number of free electrons and holes changes and raises its electrical con- ductivity. A simple but interesting phenomenon to characterise a fabricated n＋p photodetector in order to determine its linearity （photoresponse） and photoconductance was employed. Using the transient decay when the irradiation source is switched off, the minority carrier concentration, effective lifetime and surface recombination velocity present at the surface of the detector were measured.