DYNAMIC FRICTION:Ⅰ.EXPERIMENTAL OBSERVATIONS OF ROCK FRICTION

Dynamic friction is a critical process of crustal earthquake ruptures. Recent experimenta1 and theoretica1 progress in rock friction have demonstrated that most continental earthquakes are associated with stick-slip in the brittle field of the crust and that only dynamic instability with fast slip is related to seismicity. Dynamic stability will be influenced by frictional parameters a-b, a, stiffness K, characteristic displacement L, slip rate history (velocity weakening), normal stress history (pressure strengthening), and temperature, which is described by the frictional constitutive laws. Velocity-weakening (a-b<0) can cause dynamic instability if the medium stiffness is below the critical stiffness (X/Kc<1), while velocity-strengthening enhances the frictional stability.The most recent experimental evidence of rock friction will be systematically reviewed in this paper.

Experimental Observation of Cumulative Second-Harmonic Generation of Circumferential Guided Wave Propagation in a Circular Tube

The experimental observation of cumulative second-harmonic generation of the primary circumferential guided wave propagation is reported. A pair of wedge transducers is used to generate the primary circumferential guided wave desired and to detect its fundamental-frequency and second-harmonic amplitudes on the outside surface of the circular tube. The amplitudes of the fundamental waves and the second harmonics of the circumferential guided wave propagation are measured for different separations between the two wedge transducers. At the driving frequency where the primary and the double-frequency circumferential guided waves have the same linear phase velocities, the clear second-harmonic signals can be observed. The quantitative relationships between the second-harmonic amplitudes and circumferential angle are analyzed. It is experimentally verified that the second harmonics of primary circumferential guided waves do have a cumulative growth effect with the circumferential angle.

Experimental Observation of Cubic C_3N_4 Compound in Carbon Nitride Thin Films

Cubic C3N4 compound in the C-N thin films on Si and NaCl substrates was prepared by ion beam sputtering of a pure graphite target with discharge gas of pure N2. X-ray photoelectron spectroscopy indicated that nitrogen atoms combined with sp2- and sp3- coordinated C atoms in the film, respectively. X-ray diffraction, selected area electron diffraction and high-resolution electron microscopy were used to identify the cubic C3N4 phase. The results reconfirm the ab initio calculations on metastable structure in C-N compounds

Experimental Observation of the Ground-State Geometric Phase of Three-Spin XY Model

The geometric phase has become a fundamental concept in many fields of physics since it was revealed. Recently, the study of the geometric phase has attracted considerable attention in the context of quantum phase transition, where the ground state properties of the system experience a dramatic change induced by a variation of an external parameter. In this work, we experimentally measure the ground-state geometric phase of the three-spin XY model by utilizing the nuclear magnetic resonance technique. The experimental results indicate that the geometric phase could be used as a fingerprint of the ground-state quantum phase transition of many-body systems.

Experimental Observation of Phase Transition in Sb203 under High Pressure

The in situ high-pressure behavior of the semiconductor antimony trioxide （Sb2O3） iS investigated by the Raman spectroscopy techniques and angle-dispersive synchrotron x-ray powder diffractfon in a diamond anvil cell up to 31.5 and 30.7 GPa, respectively. New peaks observed in the external lattice mode range in the Raman spectra at 13.5 GPa suggest that the structural phase transition occurs. The group mode （140 cm^-1） in Sb2O3 exhibits anomalous pressure dependence; that is, the frequency decreases gradually with the increasing pressure. High pressure synchrotron x-ray diffraction measurements at room temperature reveal that the transition from the orthorhombic structure to high-pressure new phase occurs at about 14.2 GPa, corresponding to the softening of the group optic mode （140cm^-1）.

Observation on Effect of Gennlanchun (更年春) In Preventing Experimental Primary Osteoporosis

Objective: To evaluate the efficacy of Genni-anchun (GNC) in preventing primary osteoporosis. Methods: Fifty female SD rats of 10 - 12 months old were randomly divided into five groups. Except those in the sham operation group, animals were ovariectomized bilaterally. The gastric perfusion was started immediately after operation, with normal saline to the sham operation group and model group; GNC to high dose (2 ml) and low dos (1 ml) GNC groups and Nilestriol to the NE group, every day for 3 months. Animals were sacrificed at the end of experiment, their vertebra and

Experimental Observation of Bright and Dark Solitons Mode-Locked with Zirconia-Based Erbium-Doped Fiber Laser

We demonstrate the generation of dark and bright solitons with our homemade zirconia-based erbium-doped fiber and graphene oxide（GO） saturable absorber in anomalous dispersion region.The GO is fabricated using an abridged Hummer＇s method,which is combined with polyethylene oxide to produce a composite film.The film is sandwiched between two optical ferrules and embedded in the laser cavity to enhance its birefringence and nonlinearity.The self-starting bright soliton is easily generated at pump power of 78 mW with the whole length cavity of 14.7 m.The laser produces the bright pulse train with repetition rate,pulse width,pulse energy and central wavelength being 13.9 MHz,0.6 ps,2.74 p J and 1577.46 nm,respectively.Then,by adding the 10 m of single mode fiber into the laser cavity,dark soliton pulse is produced.For the formation of dark pulse train,the measured repetition rate,pulse width,pulse energy and central wavelength are 8.3 MHz,20 ns and 4.98 p J and1596.82 nm,respectively.Both pulses operate in the anomalous region.

Experimental Observation of Spin-Exchange in Ultracold Fermi Gases

We experimentally study the spin exchange collision in ultracold 40K Fermi gases. The quadratic Zeeman shift, trap potential and temperature of atomic cloud will influence on the spin changing dynamics. Dependences of the spin components populations on the external bias magnetic field, the optical trap depth and the temperature of atomic cloud are experimentally investigated. The spin exchange from the initial states to the final state are observed for different initial states. This work shows an interesting process of reaching equilibrium by redistribution among the spin states with the spin exchange collision in an ultracold large-spin Fermi gas.

THE ANIMAL EXPERIMENTAL OBSERVATION OF THE INFLUENCE OF THE DIFFERENT FONTAN PROCEDURES ON PULMONARY MICROCIRCULATION

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Experimental observation of rat's early-stage fracture healing with different kinds of nerve injuries

To investigate the impact of different kinds of nerve injuries of early-stage fracture healing.Methods Three groups of rats were included in the experiment among which group 1 was inflicted with femoral fracture and T10 spinal cord transsection (SCI),group 2 was inflicted with femoral and peripheral nerve resection (PNR),and group 3 with simple femoral fracture as control group.Two weeks after operation the femoral bones were collected for X-ray checking and 2 more weeks later X-ray checking was performed again followed by pathomorphologic exams.Results X-ray result showed no massive calluses in the bones in the 2nd week postoperatively,while in the 4th week,callus appeared with larger size in group 3 than that of group 1 and with smaller size than that of group 2.It was the same with the result of pathomorphologic examining.Cortical bone bridges between fracture point and osteiod were also found in group 2 and there were less normal blood vessels and worse bone remodeling than that of group 3.There were relatively immature calluses with more fibroblast-like cells and disordered bone structure in group 2.Group 3 showed normal healing process and callus structure.Conclusion Early-stage bone fracture healing can be influenced significantly by different kinds of nerve injuries.6 refs,6 figs.

PROGRESS OF MARINE METEOROLOGICAL OBSERVATION EXPERIMENT AT MAOMING OF SOUTH CHINA

The coastal area of southern China is frequently affected by marine meteorological disasters,and is also one of the key areas that influence the short-term climate change of China.Due to a lack of observational facilities and techniques,little has been done in this area in terms of operational weather monitoring and scientific research on atmospheric and marine environment.With the support of China Meteorological Administration (CMA) and Guangdong Meteorological Bureau (GMB),the Marine Meteorological Science Experiment Base (MMSEB) at Bohe,Maoming has been jointly established by Guangzhou Institute of Tropical and Marine Meteorology (GITMM) and Maoming Meteorological Bureau (MMB) of Guangdong Province after three years of hard work.It has become an integrated coastal observation base that is equipped with a complete set of sophisticated instruments.Equipment maintenance and data quality control procedures have been implemented to ensure the long-term,steady operation of the instruments and the availability of high quality data.Preliminary observations show that the data obtained by the MMSEB reveal many interesting features in the boundary layer structure and air-sea interaction in such disastrous weather as typhoons and sea fog.The MMSEB is expected to play an important role in the scientific research of disastrous weather related to marine meteorology.

Observation system simulation experiments using an ensemble-based method in the northeastern South China Sea

An ensemble-based method for the observation system simulation experiment(OSSE)is employed to design optimal observation stations and assess the present observation stations in the northeastern South China Sea(SCS).We employed the 20-year(1992-2012)sea surface height(SSH)data to design an array to monitor the intraseasonal to interannual variability.The results show that the most key region was found located at the northwest of Luzon Island(LI)where the energetic Luzon cyclonic gyre(LCG)occurs;other key regions include the edge of the LCG,the northwest of the Luzon Strait(LS),and the southwest of Taiwan,China.By contrast,we found that the present observation stations might oversample at the northwest of the LS and undersample at the northwest of LI.In addition,the optimal stations perform better in a larger area than the present stations.In vertical direction,the key layer is located within the upper 200-m depth,of which the surface and subsurface layers are most valuable to the observing system.

Comparison of Precipitation Observations from a Prototype Space-based Cloud Radar and Ground-based Radars

A prototype space-based cloud radar has been a precipitation system over Tianjin, China in July developed and was installed on an airplane to observe 2010. Ground-based S-band and Ka-band radars were used to examine the observational capability of the prototype. A cross-comparison algorithm between different wavelengths, spatial resolutions and platform radars is presented. The reflectivity biases, correlation coefficients and standard deviations between the radars are analyzed. The equivalent reflectivity bias between the S- and Ka-band radars were simulated with a given raindrop size distribution. The results indicated that reflectivity bias between the S- and Ka-band radars due to scattering properties was less than 5 dB, and for weak precipitation the bias was negligible. The prototype space-based cloud radar was able to measure a reasonable vertical profile of reflectivity, but the reflectivity below an altitude of 1.5 km above ground level was obscured by ground clutter. The measured refiectivity by the prototype space-based cloud radar was approximately 10.9 dB stronger than that by the S-band Doppler radar （SA radar）, and 13.7 dB stronger than that by the ground-based cloud radar. The reflectivity measured by the SA radar was 0.4 dB stronger than that by the ground-based cloud radar. This study could provide a method for the quantitative examination of the observation ability for space-based radars.

Deformation field around a thrust fault:A comparison between laboratory results and GPS observations of the 2008 Wenchuan earthquake

On May 12,2008,an Mw7.9 earthquake occurred in Wenchuan County,Sichuan Province,China.Movement of Yingxiu–Beichuan Fault in the Longmenshan Fault Zone was considered to be the main cause of the earthquake.Earthquakes are closely related to fault activities.Therefore,studying the strain distribution and evolution process around active fault zones is important to the understanding of seismic activities.In this study,we conduct laboratory experiments with uniaxial compression applied to marble sheets with intentionally fabricated cracks.The speckle patterns of the rock samples under different loading conditions are recorded in real time by a digital camera.To calculate the deformation fields of the deliberately cracked marble sheets during different stages of the loading processes,the recorded images are processed by the digital image correlation method.The distribution and variation of the displacement and strain are further analyzed in order to understand the strain localization of and observed damage in the experimental fracture zones.Finally,we compare these laboratory results with the GPS-observed coseismic displacements during the 2008 Wenchuan earthquake,to assess the consistency between our laboratory observations and the field observations of the earthquake,but also to suggest how laboratory results can improve thinking about how earthquake patterns do and do not reflect fault patterns.

Comparison of the Observation Capability of an X-band Phased-array Radar with an X-band Doppler Radar and S-band Operational Radar

An X-band phased-array meteorological radar （XPAR） was developed in China and will be installed in an airplane to observe precipitation systems for research purposes.In order to examine the observational capability of the XPAR and to test the operating mode and calibration before installation in the airplane,a mobile X-band Doppler radar （XDR） and XPAR were installed at the same site to observe convective precipitation events.Nearby S-band operational radar （SA） data were also collected to examine the reflectivity bias of XPAR.An algorithm for quantitative analysis of reflectivity and velocity differences and radar sensitivity of XPAR is presented.The reflectivity and velocity biases of XPAR are examined with SA and XDR.Reflectivity sensitivities,the horizontal and vertical structures of reflectivity by the three radars are compared and analyzed.The results indicated that while the XPRA with different operating modes can capture the main characteristic of 3D structures of precipitation,and the averaged reflectivity differences between XPAR and XDR,and XDR and SA,were 0.4 dB and 6.6 dB on 13 July and-4.5 dB and 5.1 dB on 2 August 2012,respectively.The minimum observed reflectivities at a range of 50 km for XPAR,XDR and SA were about 15.4 dBZ,13.5 dBZ and-3.5 dBZ,respectively.The bias of velocity between XPAR and XDR was negligible.This study provides a possible method for the quantitative comparison of the XPAR data,as well as the sensitivity of reflectivity,calibration,gain and bias introduced by pulse compression.

Dynamic experimental study on rock meso-cracks growth by digital image processing technique

A new meso-mechanical testing scheme based on SEM was developed to carry out the experiment of microfracturing process of rocks. The microfracturing process of the pre-crack marble sample on surrounding rock in the immerged Long-big tunnel in Jinping Cascade II Hydropower Station under uniaxial compression was recorded by using the testing scheme. According to the stereology theory, the propagation and coalescent of cracks at meso-scale were quantitatively investigated with digital technology. Therefore, the basic geometric information of rock microcracks such as area, angle, length, width, perimeter, was obtained from binary images after segmentation. The failure mechanism of specimen under uniaxial compression with the quantitative information was studied from macro and microscopic point of view. The results show that the image of microfracturing process of the specimen can be observed and recorded digitally. During the damage of the specimen, the distribution of microcracks in the specimen is still subjected to exponential distribution with some microcracks concentrated in certain regions. Finally, the change law of the fractal dimension of the local element in marble sample under different external load conditions is obtained by means of the statistical calculation of the fractal dimension.

An Experimental Study on the Drag Property of High-Temperature Particles Falling into Cold Liquid Pool

This experiment is to study the special resistant induced by the high-speed evaporation surrounding themoving high-temperature particles. An observable equipment was designed, in which the first 11 experiments wereperformed by pouring one or several Zirconia spheres with various high-temperature and a diameter of 3～ 10 mminto a water pool. The particles falling-down speeds were recorded by high-speed photographic instrumentation,and pressures and water temperatures were measured. A comparison between the experiments with cold and hotspheres respectively, employing three different sphere types each, was presented. The experimental data, com-pared with the theory of the evaporation drag model, are nearly identical.

Experimental investigation on the bursting of single molten droplet in coolant

An experiment facility for observing low-temperature molten tin alloy droplet into water was es- tablished to investigate mechanisms of vapor explosion occurring in severe accidents of a fission nuclear reactor.The vapor explosion behaviors of the molten material were observed by a high-speed video cam- era and the vapor explosion pressures were recorded by a pressure transducer mounted under the water surface.The results showed that the pressure reached a peak value when the molten metal temperature was 600℃-650℃,and the coolant temperature had an obvious decreasing effect on the droplet breakups.A model for single droplet fuel/coolant interaction is proposed.It considers that in the case of Rayleigh-Taylor instability,the coolant that jets from opposite direction penetrates into the fuel and the vapor explosion occurs because of the rapid evaporation.This model explained the effect of metal droplet temperature and coolant temperature on vapor explosion.

Objective array design for three-dimensional temperature and salinity observation:Application to the South China Sea

In this study,a moored array optimization tool(MAOT)was developed and applied to the South China Sea(SCS)with a focus on three-dimensional temperature and salinity observations.Application of the MAOT involves two steps:(1)deriving a set of optimal arrays that are independent of each other for different variables at different depths based on an empirical orthogonal function method,and(2)consolidating these arrays using a K-center clustering algorithm.Compared with the assumed initial array consisting of 17 mooring sites located on a 3°×3°horizontal grid,the consolidated array improved the observing ability for three-dimensional temperature and salinity in the SCS with optimization efficiencies of 19.03%and 21.38%,respectively.Experiments with an increased number of moored sites showed that the most cost-effective option is a total of 20 moorings,improving the observing ability with optimization efficiencies up to 26.54%for temperature and 27.25%for salinity.The design of an objective array relies on the ocean phenomenon of interest and its spatial and temporal scales.In this study,we focus on basin-scale variations in temperature and salinity in the SCS,and thus our consolidated array may not well resolve mesoscale processes.The MAOT can be extended to include other variables and multi-scale variability and can be applied to other regions.