A mechanism for the formation of lopsided galaxies

This paper is concerned with the origin and existence of lopsided galaxies. A mechanism based on the distribution of dispersion velocities is suggested for the long-term maintenance of the lopsidedness.     

A relationship between solar activity and frequency of natural disasters in China

The relationship between the length of the solar cycle, a good indicator of long-term change in solar activity, and natural disasters (drought, flood, and strong earthquakes) in China during the last 108 years is analyzed. The results suggest that the length of solar cycle may be a useful indicator for drought/flood and strong earthquakes. When the solar activity strengthens, we see the length of the solar cycle shorten and more floods occur in South China and frequent strong earthquakes happen in the Tibetan Plateau,but the droughts in East China as well as the strong earthquakes in Taiwan and at the western boundary of China are very few. The opposite frequencies occur when the solar activity weakens. The current study indicates that the solar activity may play an important role in the climate extremes and behavior in the lithosphere.     

The status of the ecological environment and a proposed protection strategy in Sanya Bay,Hainan Island,China

Sanya Bay encompasses a high diversity of natural habitats, ranging from coral reefs, rocky and sandy shores and mudflats to mangroves. Seasonal physicochemical and biological investigations were conducted from 1998 to 1999 and again in April 2000. Water-related environmental quality in Sanya Bay is in good condition. The levels of dissolved oxygen, nitrogen, phosphorus and heavy metals are within the first class of National Seawater Quality Standards for China. Annual mean values of chlorophyll a of 0.93 mg m(-3) and phytoplankton primary productivity of 440.8 mgC m(-2)d(-1), respectively, were found in the waters, both of which show a significant correlation with inorganic nitrogen. A mean new productivity of 144.6 mgC m(-2) d(-1) was recorded in summer. Sanya Bay is rich in natural resources and biodiversity with 235 species of phytoplankton and 129 species of zooplankton identified in the survey. The annual mean abundance of phytoplankton and zooplankton were 1564 x 10 cells m(-3) and 121 individuals m(-3), respectively, with an annual mean zooplankton biomass of 129 mg m(-3). A total of 243 species of fish were sampled in the survey including many of high economic value. Three hundred and eighty-four species of benthos in 121 families were found by mud sampling and trawling. The average biomass of benthic organisms was 11.55 gm(-2), with a density of 31 individuals m(-2). Molluscs were the dominant group, followed by crustaceans; coelenterates exhibited the lowest biomass. One hundred and twenty-six species from 48 families of intertidal organisms were collected by frame sampling, with a mean annual biomass of 644.7 gm(-2) and average density of 816 individuals m(-2). The highest biomass of 1673.5 gm(-2) was collected in a coral reef region, while the highest density of 1219 individuals m(-2) occurred in a mangrove region. The coastline is characterized by coral reefs that accounts for 30% of the total coastline length in the bay, so coral reefs are a key ecosystem that are important for maintaining the regional marine resources and biodiversity. We need to pay much more attention to such diverse marine resources to maintain the integrity and function of these coastal ecosystems.     

The <Superscript>40</Superscript>Ar/<Superscript>39</Superscript>Ar geochronology constraint and geological significance of mylonites in Shangyi-Chicheng fault belt on the north of North China Craton

A dating of two biotite samples taken from the meso- and low-temperature mylonites within the Shangyi-Chicheng fault belt on the north of the North China Craton yields ⁴⁰Ar/³⁹Ar isotopic ages of (399 ± 1) Ma and (263 ± 2) Ma, respectively. These data reflect an Early Devonian deformation and a Late Carboniferous retrograde metamorphism event along the fault, suggesting that the tectonic activities of the North China Craton in Paleozoic should be reconsidered.     

Investigation of solid waste soil as road construction material

The geotechnical properties of solid waste soils for use as sub-base materials in road construction were investigated. A series of field tests and laboratory tests were performed to assess the physical and mechanical properties of the solid waste soils sampled from a landfill site, near to a riverside, which had been reclaimed over the last two decades. The tests showed that geotechnical properties are clearly affected by the magnitude of organic matter content. As the organic matter content increases, the maximum dry unit weight, the shear strength and bearing capacity of ground decrease, while the void ratio and compressibility increase. If the organic matter content is more than about 8% in solid waste soils, it is not suitable for use as a sub-base material in road construction due to the significant decrease of shear strength and bearing capacity.     

2000国家GPS大地控制网数据处理方法与结果

介绍了我国GPS大地控制网的基本情况,阐述了结合地壳运动观测网络工程建立全国统一的“2000国家GPS大地控制网”的意义,并介绍了整网平差中采用的技术方法和最后平差结果及精度。     

Seasonal dynamics of CO<Subscript>2</Subscript> fluxes from subtropical plantation coniferous ecosystem

As one component of ChinaFLUX, the measurement of CO₂ flux using eddy covariance over subtropical planted coniferous ecosystem in Qianyanzhou was conducted for a long term. This paper discusses the seasonal dynamics of net ecosystem exchange (NEE), ecosystem respiration (RE) and gross ecosystem exchange (GEE) between the coniferous ecosystem and atmosphere along 2003 and 2004. The variations of NEE, RE and GEE show obvious seasonal variabilities and correlate to each other, i.e. lower in winter and drought season, but higher in summer; light, temperature and soil water content are the main factors determining NEE; air temperature and water vapor pressure deficit (VPD) influence NEE with stronger influence from VPD. Under the proper light condition, drought stress could decrease the temperature range for carbon capture in planted coniferous, air temperature and precipitation controlled RE; The NEE, RE, and GEE for planted coniferous in Qianyanzhou are ?387.2 g C·m^?2 a^?1, 1223.3 g C·m^?2 a^?1, ?1610.4 g C·m^?2 a^?1 in 2003 and ?423.8 g C·m^?2 a^?1, 1442.0 g C·m^?2 a^?1, ?1865.8 g C·m^?2 a^?1 in 2004, respectively, which suggest the intensive ability of plantation coniferous forest on carbon absorbing in Qianyanzhou.     

Transient analysis of wave propagation in non‐homogeneous elastic unbounded domains by using the scaled boundary finite‐element method

The scaled boundary finite‐element method has been developed for the dynamic analysis of unbounded domains. In this method only the boundary is discretized resulting in a reduction of the spatial dimension by one. Like the finite‐element method no fundamental solution is required. This paper extends the scaled boundary finite‐element method to simulate the transient response of non‐homogeneous unbounded domains with the elasticity modulus and mass density varying as power functions of spatial coordinates. To reduce the number of degrees of freedom and the computational cost, the technique of reduced set of base functions is applied. The scaled boundary finite‐element equation for an unbounded domain is reformulated in generalized coordinates. The resulting acceleration unit‐impulse response matrix is obtained and assembled with the equation of motion of standard finite elements. Numerical examples of non‐homogeneous isotropic and transversely isotropic unbounded domains demonstrate the accuracy of the scaled boundary finite‐element method. Copyright © 2006 John Wiley & Sons, Ltd.     

时态GIS的空间实体关联技术应用研究

在自然界中大多数现实世界的实体都是动态的,地图上的公路、铁路、居民地等只是相对于一个很短的时间里是静态的,经过一个长的时间这些实体都将发生改变。本文根据不同时态地理实体的各种特征比较,将两个时态的数据进行关联,建立几何、位置和属性的变化模型,将这个动态的过程表现出来。试验表明,本文的算法是有效的。     

基于岩石变形声发射实验结果讨论岩石失稳的可预测性

根据室内岩石变形声发射实验结果,计算了声发射序列的地震非均匀度GL值,并以此探讨了岩石破裂失稳的可预测性。在双轴压缩、等速率加载条件下,含障碍体断层、挤压雁列断层和Ⅲ型剪切断层等非连续岩石标本在临近滑动失稳前,声发射活动均出现了显著的均匀—非均匀的状态变化,表现为GL值出现持续大于1的异常变化,GL值异常的位置与破裂成核部位相重合,并与断层走向一致;改变统计窗长、窗内分割数及能级统计下限计算声发射序列的GL值,结果表明,GL值计算结果具有一定的稳定性。综合分析认为,地震非均匀度(GL值)可以较好地刻画岩石失稳前夕因破裂成核导致的声发射活动在时间分布上的状态变化,GL值持续异常是岩石失稳的显著性标志,对预测岩石失稳具有较好的指示意义。