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Characteristics of coda wave attenuation in Yunnan area

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Earthquake Science 2006年第1期19卷 8-19+115页

作者：王伟君刘杰陈凌 Institute of Earthquake Sciences China Earthquake Administration Beijing 100036 China China Earthquake Network Center Beijing 100036 China Institute of Geology and Geophysics Chinese Academy of Sciences Beijing 100029 China

The characteristic of seismic coda wave attenuation in Yunnan area in 7 frequency-bands range from 1 Hz to 20 Hz was estimated by using the local earthquake′s waveform data recorded from 22 Yunnan digital seismic stations. Coda attenuation Qc ?1 of each station was firstly calculated by single scattering method. Then, mean free path Le and seismic albedo B0 of each station were calculated, and scattering attenuation Qs ?1 and intrinsic attenuation 1iQ ? were separated from total attenuation Qt ?1 by multiple lapse time window analysis based on the multiple scattering model in uniform random isotropic scattering medium. The attenuating characteristics in Yunnan show that most value of Le are in 10~30 km, with maximal within 2~6 Hz; B0 are about 0.5 at 1~2 Hz, but less than 0.5 at other frequency-bands, which means Qi ?1 is comparable with Qs ?1 at 1~2 Hz, and after 1~2 Hz, Qi ?1 is greater than Qs 1 and dominates the attenuation process. Qc 1 is close to Qi 1 at other frequency bands except 1~2 Hz. Results show that Q?1 especially Qs 1 varies spatially, Q1 in eastern Yunnan zone is a bit higher than in north-western Yunnan zone; northwestern Yunnan zone higher than southwestern Yunnan zone. Comparing with other results in global, Qs 1 in Yunnan is lower than the global average value among these results, Qi 1 is higher than the global average value, and Qt 1 lies the middle among these results.

关键词： coda attenuation intrinsic attenuation scattering attenuation Yunnan area

Ocean waves propagating over a porous seabed: Residual and oscillatory mechanisms

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Science China(Technological Sciences) 2007年第1期50卷 81-89页

作者： SEYMOUR Brian Department of Mathematics The University of British ColumbiaVancouverV6Z 1Z2Canada

Two mechanisms for the wave-induced pore pressures in a porous seabed, i.e. oscillatory and residual excess pore pressures, have been observed in laboratory experiments and field measurements. Most previous investigations have focused on one of the mechanisms individually. In this paper, an analytical solution for the wave-induced residual pore pressure, which is not available yet, is derived, and compared with the existing experimental data. With the new solution, a parametric analysis is performed to clarify the applicable ranges of two mechanisms. Then, a simplified approximation for the prediction of wave-induced liquefaction potential is proposed for engineering practice.

关键词： seabed pore pressure residual oscillatory wave loading

Action potential-simulated weak electric fields can directly initiate myelination

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Neural Regeneration Research 2008年第12期3卷 1328-1331页

作者： Lei Liu Shifu Zhao Haiming Wang Department of Neurology the 324 Hospital of Chinese PLA Chongqing 400020 China Department of Neurology Xinqiao Hospital Third Military Medical University of Chinese PLA Chongqing 400037 China

BACKGROUND： Myelination is a process whereby glial cells identify, adhere, wrap and enclose axons to form a spiral myelin sheath. OBJECTIVE： To investigate the effects of action potential-simulated weak electric fields on myelination in the central nervous system. DESIGN AND SETTING： This single-sample observation study was performed at the 324 Hospital of Chinese PLA. MATERIALS： Two 5 μm carbon fibers were provided by the Institute of Neuroscience, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences. One Sprague Dawley rat, aged 1 day, was used. METHODS： Cerebral cortex was harvested from the rat to prepare a suspension [（1 2）× 10^5/mL] containing neurons and glial cells. To simulate the axon, carbon fibers were placed at the bottom of the neuron-glial cell coculture dish, and were electrified with a single phase square wave current, 1×10^-2, 1×10^-3, 1×10^-4, and 1×10^-5 seconds, 1 Hz, 40 mV, and 10 μA, 30 minutes each, once a day for 10 consecutive days to simulate weak negative electric fields during action potential conduction. MAIN OUTCOME MEASURES： Glial cell growth and wrapping of carbon fibers were observed by phase contrast microscopy and immunohistochemistry. RESULTS： On culture day 7, cell groups were found to adhere to negative carbon fibers in the 1 × 10^-3 seconds square wave group. Cell membrane-like substances grew out of cell groups, wrapped the carbon fibers, and stretched to the ends of carbon fibers. Only some small and round cells close to negative carbon fibers were found on culture day 12. In the 1 × 10^-4 and 1 × 10^-3 seconds square wave groups, the negative carbon fibers were wrapped by oligodendrocytes or their progenitor cells. CONCLUSION： The local negative electric field which is generated by action potentials at 1×（10^-4-10^-3） seconds, 40 mV can directly initiate and participate in myelination in the central nervous system.

关键词： myelin sheath oligodendrocyte weak electric field action potential carbon fiber

Current Status, Challenges, and Future Sustainable Development Strategies for China Energy

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Tsinghua Science and Technology 2004年第4期9卷 460-467页

作者：陈文颖吴宗鑫 Energy Environment and Economy Research InstituteInstitute of Nuclear and New Energy TechnologyTsinghua University Beijing 100084 China

China抯 rapid economic growth, high-energy-intensitive industrial and product structure, coal- dominated energy structure, and low-energy efficiency result in China being the second largest energy consumer as well as the second largest CO2 emission country in the world. The Markal model, an integrated energy, environment, and economic model, was used to analyze China抯 energy development scenarios from 1995 through 2050 for policy study of long-term energy strategies. The results show that diversified, reliable, and environmentally sound energy development strategies should be adopted for China to solve the challenges of the increasing energy demand, the enlarging gap between the oil demand and supply, and growing concerns over local as well as global environmental issues. Coal-derived synthetic transportation fuels through coal liquefaction, hydrogen making, and advanced coal-based poly-generation technologies should be developed to solve energy security issues.

关键词： energy environment Markal model scenario

Numerical Simulations of the Transparency of Waterfront Bodies

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Tsinghua Science and Technology 2008年第5期13卷 720-729页

作者：王华逄勇丁玲刘明源庄红红 College of Environmental Science and Engineering Hohai University Shanghai Investigation and Design Research Institute

Measured field data was used to analyze the factors which influence the transparency of the Nei River and to develop a multi-factor correlation for the transparency. A 2-D unsteady model which coupled analyses of the water flow, water quality, suspended sediments, and Chl-a was developed to simulate the changes in the transparency for various conditions. The model was then used to forecast the transparency of the Nei River. The suspended sediment concentration （SSC） was found to be the most important factor influencing the transparency, with high concentrations of CODMn and Chl-a also reducing the transparency to some extent. The transparency model is stable and precise, with relative errors between measured and calculated values of less than 15%. With the environmental scheduling schemes, the Nei River transparency can be significantly improved with a mean transparency in high-water years of 69.3 cm, normal-water years of 70.8 cm, and low-water years of 69.8 cm.

关键词： water bodies transparency model environmental planning Nei River

3D viscous-spring artificial boundary in time domain

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Earthquake Engineering and Engineering Vibration 2006年第1期5卷 93-102页

作者：刘晶波杜义欣杜修力王振宇伍俊 Department of Civil Engineering Tsinghua UniversityBeijing 100084China Beijing Lab of Earthquake Engineering and Structural Retrofit Beijing University of TechnologyBeijing 100022China

After a brief review of studies on artificial boundaries in dynamic soil-structure interaction, a three-dimensional viscous-spring artificial boundary （VSAB） in the time domain is developed in this paper. First, the 3D VSAB equations in the normal and tangential directions are derived based on the elastic wave motion theory. Secondly, a numerical simulation technique of wave motion equations along with the VSAB condition in the time domain is studied. Finally, numerical examples of some classical elastic wave motion problems are presented and the results are compared with the associated theoretical solutions, demonstrating that high precision and adequate stability can be achieved by using the proposed 3D VSAB. The proposed 3D VSAB can be conveniently incorporated in the general finite element program, which is commonly used to study dynamic soil-structure interaction problems.

关键词： artificial boundary viscous-spring wave motion time domain numerical simulation soil-structure interaction

Investigation of basic properties of fly ash from urban waste incinerators in China

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Journal of Environmental Sciences 2007年第4期19卷 458-463页

作者： JIANG Jian-guo XU Xin WANG Jun YANG Shi-jian ZHANG Yan Department of Environmental Science and Engineering Tsinghua University Beifing 100084 China. Shanghai Environment and Science Academy Shanghai 201203 China

Basic properties of fly ash samples from different urban waste combustion facilities in China were analyzed using as X-ray fluorescence （XRF）, scanning electron microscopy （SEM）, X-ray diffraction （XRD）. The leaching toxicity procedure and some factors influencing heavy metals distribution in fly ash were further investigated. Experimental results indicate that the fly ash structures are complex and its properties are variable. The results of XRF and SEM revealed that the major elements （〉10000 mg/kg, listed in decreasing order of abundance） in fly ash are O, Ca, Cl, Si, S, K, Na, Al, Fe and Zn. These elements account for 93% to 97%, and the content of Cl ranges from 6.93% to 29.18 %, while that of SiO2 does from 4.48% to 24.84%. The minor elements （1000 to 10000 mg/kg） include Cr, Cu and Pb. Primary heavy metals in fly ash include Zn, Pb, Cr, Cu etc. According to standard leaching test, heavy metal leaching levels vary from 0 to 163.10 mg/L （Pb） and from 0.049 to 164.90 mg/L （Zn）, mostly exceeding the Chinese Identification Standard for hazardous wastes. Morphology of fly ash is irregular, with both amorphous structures and polycrystalline aggregates. Further research showed that heavy metals were volatilized at a high furnace temperature, condensed when cooling down during the post-furnace system and captured at air pollution control systems. Generally, heavy metals are mainly present in the forms of aerosol particulates or tiny particulates enriched on surfaces of fly ash particles. The properties of fly ash are greatly influenced by the treatment capacities of incinerators or the variation of waste retention time in chamber. Fly ash from combustors of larger capacities generally has higher contents of volatile component and higher leaching toxicity, while those of smaller capacities often produce fly ash containing higher levels of nonvolatile components and has lower toxicity. The content of heavy metals and leaching toxicity maybe have no convincing correlatio

关键词： urban waste incinerator fly ash heavy metals leaching toxicity

Large aftershocks triggering by Coulomb failure stress following the 2001 MS=8.1 great Kunlun earthquake

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Acta Seismologica Sinica(English Edition) 2004年第1期17卷 31-37页

作者： HAO Ping(郝平) FU Zheng-xiang(傅征祥) TIAN Qin-jian(田勤俭) LIU Jie(刘杰) LIU Gui-ping(刘桂萍) Center for Analysis and Predication China Seismological Bureau Beijing 100036 China Center for Analysis and Predication China Seismological Bureau Beijing 100036 China Center for Analysis and Predication China Seismological Bureau Beijing 100036 China Center for Analysis and Predication China Seismological Bureau Beijing 100036 China Department of Earthquake Monitoring and Predication China Seismological Bureau Beijing 100036 China

The great Kunlun earthquake occurred on Nov. 14, 2001 in Qinghai Province, China. five large aftershocks with magnitude larger than 5.0 occurred near the Kunlun fault after main shock. Calculations of the change in Coulomb failure stress reveal that 4 of 5 large aftershocks occurred in areas with Dsf >0 (10-2~10-1 MPa) and one aftershock occurred in an area with Dsf =-0.56 MPa. It is concluded that the permanent fault displacement due to the main shock is the main cause of activity of large aftershocks, but not the whole cause.

关键词： Kunlun great earthquake aftershocks triggering Coulomb failure stress

Gravity evolution and earthquake activities of the northeastern edge of Qinghai-Xizang block

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Acta Seismologica Sinica(English Edition) 2004年第z1期17卷 76-84页

作者：祝意青李辉朱桂芝徐云马 Second Crust Monitoring and Application Center China Earthquake AdministrationXi′an 710054China Institute of Seismology China Earthquake AdministrationWuhan 430071China

The relationship between temporal-spatial evolution of gravity and earthquake activity during 1992~2001 has been analyzed systematically by integrally adjusting the gravity observation data of the northeastern edge of Qinghai- Xizang (Qingzang) block. The result shows that the gravity observation data of the northeastern edge of Qingzang block obtained by using the uniform starting datum can completely reflect the precursory gravity information appearing during the seismogenic process. In the genesis stage of an earthquake, regional gravity anomaly appears in a large area, resulting in related local gravity anomaly. The dynamic image of gravity field can clearly reflect the orderly evolution and earthquake activity.

关键词： northeastern edge of Qinghai-Xizang block gravity evolution tectonic activity seismogenic characteristics