Compressional Wave Velocities in Some Volcanic Rocks at Pressure up to 4.5 GPa

Compressional wave velocities in some Mesozoic and Cenozoic volcanic rocks from Qinling Dabie orogenic belt were measured at room temperature and high pressure (up to 4.5 GPa). Compressional wave velocities of these rocks increase with the increasing of pressure. The experiment data indicate that the pressure at which the microcracks in these rocks finally close is up to 2.0 GPa. The empirical relationships between compressional wave velocities at high pressure and oxide mass fractions, heat productions and densities at room temperature and 100 kPa of these rocks are discussed. It is likely that there does not always exist linear relationship between compressional wave velocities and oxide mass fractions. New heat production data of volcanic rock samples from the Qinling Dabie orogenic belt do not follow the empirical relationship between heat production and seismic velocity for rocks. It is dangerous to use these empirical relations to predicate the modal chemical composition, density and heat production of the lithosphere.

Compressional elastic wave velocities of serpentinized pyroxenite at high pressures and high temperatures and its geological significance

Center for Analysis and Prediction, China Seismological Bureau, Beijing 100036, China 2) Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550002, China

Study on Calculation Method of Compressional Velocities Based on Field Well Logs

In the past, most of the studies for compressional velocities are based on experimental measurements, which lack the support of field data. The purpose of this study is to estimate the compressional velocities based on well log data of delta front subfacies of Lower Tertiary ages of Ji-Dong oil field, China. At initial stage, we have chosen the well log parameters (effect factors) which strongly influence on compressional velocities and established a new modified equation for compressional velocities, which is based on these effect factors. Then Gardner, De-hua Han and this newly established equation were utilized to calculate the compressional velocities in each well. Finally, Least-square regression was carried out to check the fitting of each equation. Regression results clearly indicate that our purposed equation shows better fitting as compared to Gardner and De-hua Han equations.

THE INTERACTION BETWEEN SHOCK WAVES AND FOAM IN A SHOCK TUBE

An experimental study and a numerical simulation were conducted to investigate the mechanical and thermodynamic processes involved in the interaction between shock waves and low density foam. The experiment was done in a stainless shock tube (80 mm in inner diameter, 10 mm in wall thickness and 5 360 mm in length). The velocities of the incident and reflected compression waves in the foam were measured by using piezo-ceramic pressure sensors. The end-wall peak pressure behind the reflected wave in the foam was measured by using a crystal piezoelectric sensor. It is suggested that the high end-wall pressure may be caused by a rapid contact between the foam and the end-wall surface. Both open-cell and closed-cell foams with different length and density were tested. Through comparing the numerical and experimental end-wall pressure, the permeability coefficients α and β are quantitatively determined.

Temporal vP/vS variation characteristics in different zones of China's Capital Circle area before and after Wen'an earthquake

On July 4, 2006, an earthquake of MS5.1 took place in Wen’an, Hebei Province, just at the south center of China’s Capital Circle area digital seismograph network. It is the strongest event recorded ever since the network went into operation in 2002. We processed the vast amounts of phase data yielded by the 107 digital seismic stations between 2002~2007 using Wadati method. In order to improve the precision and stability of shear and compressional wave velocities (vP/vS) calculation, we impose a number of restrictions on the computation environment and condition, e.g., the earthquakes are densely concentrated, selected stations are limited in range, the number of stations in- volved in the computation is larger than 5 and linear fitting features high precision and small error. Under these restrictions, the study shows that vP/vS in and around Wen’an and Tangshan underwent a normal-low-normal proc- ess one year before Wen’an earthquake, vP/vS became obviously low and the low ratio lasted for about one year, meanwhile, little variation of vP/vS was seen in Xingtai, northwest of Beijing, southwest of Beijing, Beijing-Tianjin and Beijing; after the quake, the vP/vS returned normal in Wen’an and Tangshan. Error and stability analysis of the calculated result for vP/vS shows it is convincible that anomaly appeared in and around Wen’an and Tangshan be- fore Wen’an earthquake.

Anterior subcutaneous transposition of the ulnar nerve improves neurological function in patients with cubital tunnel syndrome

Although several surgical procedures exist for treating cubital tunnel syndrome, the best surgical option remains controversial. To evaluate the efficacy of anterior subcutaneous transposition of the ulnar nerve in patients with moderate to severe cubital tunnel syndrome and to analyze prognostic factors, we retrospectively reviewed 62 patients（65 elbows） diagnosed with cubital tunnel syndrome who underwent anterior subcutaneous transposition. Preoperatively, the initial severity of the disease was evaluated using the Mc Gowan scale as modified by Goldberg： 18 patients（28%） had grade IIA neuropathy, 20（31%） had grade IIB, and 27（42%） had grade III. Postoperatively, according to the Wilson ＆ Krout criteria, treatment outcomes were excellent in 38 patients（58%）, good in 16（25%）, fair in 7（11%）, and poor in 4（6%）, with an excellent and good rate of 83%. A negative correlation was found between the preoperative Mc Gowan grade and the postoperative Wilson ＆ Krout score. The patients having fair and poor treatment outcomes had more advanced age, lower nerve conduction velocity, and lower action potential amplitude compared with those having excellent and good treatment outcomes. These results suggest that anterior subcutaneous transposition of the ulnar nerve is effective and safe for the treatment of moderate to severe cubital tunnel syndrome, and initial severity, advancing age, and electrophysiological parameters can affect treatment outcome.