A study on the adsorption of chromium on laterite from Guizhou Province,China

The adsorption behaviors of Cr(VI) on laterite from Guizhou Province were studied in this paper, and the adsorption mechanism was discussed as well. Results showed that different mineral compositions in the laterite would cause differences in the capacity of laterite to absorb Cr(VI). Gibbsite, iron oxide minerals and non-crystalloids are the main contributors to enhancing the capacity of laterite to absorb Cr(VI). The pH of the solution is an important factor affecting the adsorption of Cr(VI) on laterite. Acidic environment (pH=2–5) is favorable to the adsorption of Cr(VI). The amount of adsorbed Cr(VI) decreases with increasing pH of the solution. With increasing initial concentrations of Cr(VI), the amount of adsorbed Cr(VI) increases first, and then decreases. The optimal adsorption concentration of Cr(VI) on laterite is 250 μg/mL. The adsorption of Cr(VI) on laterite is a rapid process, about 80% Cr(VI) will be adsorbed within 2 hours. And the adsorption of Cr(VI) on kaolinite is a slow process.     

汶川8.0级地震地表变形局部化样式与建筑物破坏特征关系初步研究

本文以汶川地震地表形变带的实地测量数据为基础,结合沿实测地震地表变形剖面建筑物破坏情况的调查与测量,分析了不同地震地表变形类型及其建筑物破坏特征,定量化地讨论了地表变形梯度与建筑物破坏程度间的关系。提出无论地震地表变形表现为何种类型的断层陡坎,地表破裂、强变形局部化在宽10~30m的地表破裂带内;建筑物受损情况最直接的影响是建筑物所处地点的地表变形梯度,地表变形梯度大于0.1的地段,建筑物均完全被摧毁;地表变形梯度在0.07~0.1间的地段,建筑物遭受严重损坏,产生倾斜及强烈变形等;地表变形梯度在0.03~0.07之间的地段,建筑物可能受到中度损坏,产生倾斜及变形等,具有抗震设防能力的构建筑物一般不会倒塌;地表变形梯度小于0.03的地段具有抗震设防能力的构建筑物一般只会受到轻的损坏或基本完好。     

Modeling impacts of vegetation in western China on the summer climate of northwestern China

Using the monthly NCEP-NCAR reanalysis dataset, the monthly temperature and precipitation at surface stations of China, and the MM5 model, we examine impacts of vegetation cover changes in western China on the interdecadal variability of the summer climate over northwestern China during the past 30 years. It is found that the summer atmospheric circulation, surface air temperature, and rainfall in the 1990s were different from those in the 1970s over northwestern China, with generally more rainfall and higher temperatures in the 1990s. Associated with these changes, an anomalous wave train appears in the lower troposphere at the midlatitudes of East Asia and the low-pressure system to the north of the Tibetan Plateau is weaker. Meanwhile, the South Asian high in the upper troposphere is also located more eastward. Numerical experiments show that change of vegetation cover in western China generally forces anomalous circulations and temperatures and rainfall over these regions. This consistency between the observations and simulations implies that the interdecadal variability of the summer climate over northwestern China between the 1990s and 1970s may result from a change of vegetation cover over western China.     

青藏高原草地土壤有机碳库及其全球意义

定量分析了青藏高原各类草地0～0.65m深度范围内有机碳储量,结果表明:青藏高原总面积为1.6027×10hm²的草地有机碳量达到335.1973×10⁸tC,其中以高原草甸土和高原草原土有机碳积累量为主,两者之和达到232.36×10⁸tC,占全国土壤有机碳量的23.44%,是全球土壤碳库的2.4%.在有机碳储量分析的基础上,按土壤碳释放的两种主要途径:土壤呼吸作用和土地利用方式变化与草地退化,对草地土壤碳排放进行了估算,揭示出青藏高原草地土壤通过呼吸每年排放的CO₂达到11.7×10⁸tC·a^-1,约占中国土壤呼吸总量的2.3%,明显高于全国乃至全球平均值;近30a来,青藏高原草地土壤由于土地利用变化和草地退化所释放的CO₂估计约有30.23×10⁸tC.保护青藏高原草地对于全球变化意义重大.定量分析了青藏高原各类草地0～0.65m深度范围内有机碳储量,结果表明:青藏高原总面积为1.6027×10hm²的草地有机碳量达到335.1973×10⁸tC,其中以高原草甸土和高原草原土有机碳积累量为主,两者之和达到232.36×10⁸tC,占全国土壤有机碳量的23.44%,是全球土壤碳库的2.4%.在有机碳储量分析的基础上,按土壤碳释放的两种主要途径:土壤呼吸作用和土地利用方式变化与草地退化,对草地土壤碳排放进行了估算,揭示出青藏高原草地土壤通过呼吸每年排放的CO₂达到11.7×10⁸tC·a^-1,约占中国土壤呼吸总量的2.3%,明显高于全国乃至全球平均值;近30a来,青藏高原草地土壤由于土地利用变化和草地退化所释放的CO₂估计约有30.23×10⁸tC.保护青藏高原草地对于全球变化意义重大.     

Stability evaluation method for hyperbolic coal pillars under the coupling effects of high temperature and ground stress

We studied an underground coal gasification technique using strip mining-face mining gasifier controlled retraction injection technology (SMFM). This green mining approach offers several advantages over conventional strip mining but the stress distribution and stability of SMFM operations remain largely untested. In particular, hyperbolic coking pillars are used in SMFM compared with rectangular pillars used in traditional strip mining, which can influence the ultimate bearing capacity and stability. We use numerical simulations to investigate the influence of different factors (arch height, pillar height and width, mechanical characteristics), under the coupling effect of high temperature, on the ultimate bearing capacity of hyperbolic pillars. Our results indicate that arch height has a strong influence on pillar stress, while changes in pillar width and height are less significant. A stability evaluation method is proposed and tested on a case study in Inner Mongolia. Our theoretical results have practical significance for the promotion and application of SMFM.     

Metal Ion Extraction with Bipyridine Derivatives as Chelating Ligands in Supercritical Carbon Dioxide

Three fluorinated bipyridine ligands have been designed and synthesized as chelating agents for the extraction of metal ions in supercritical CO₂ (sc‐CO₂). The ligand solubilities in sc‐CO₂ were investigated at different temperatures and pressures, and the measured data have been correlated using a semiempirical model. The calculated results showed satisfactory agreement with the experimental data. Based on these data, metal ion extraction with the three compounds as chelating agents in sc‐CO₂ was performed from spiked filter paper, whereby ligand 1 showed the highest extraction efficiency, especially for Ni²⁺ and Cu²⁺. The extraction constants, K_ex, of the three chelating ligands were seen to increase with increasing extraction efficiency for the same metal ion in the same extraction system.     

Weak GPS signal tracking using FFT discriminator in open loop receiver

An open loop tracking architecture, which tracks GPS signals under weak and challenging conditions, is analyzed. The in-phase and quadrature-phase integration pair is regarded as a single tone complex signal. An FFT-based method is used as a frequency discriminator to estimate the Doppler frequency residual of the single tone signal. Another FFT-based method applies complex squaring to eliminate the effect of the navigation data bits polarities. The performance of the FFT-based discriminators is assessed in three criteria. Those criteria are the signal strength and dynamic range that can be tracked and the accuracy of the estimated Doppler frequency. In addition, the performance of the discriminators is analyzed to provide the theoretical and simulated peak detection probability. The results indicate that the FFT discriminator can track signals about 5 dB weaker than the signals that can be tracked by the complex squared FFT discriminator. In a quasi-static environment, the Doppler frequency residual can be assumed to be around zero, which can enable the FFT-based discriminators to track signals with approximately 2 dB less power. Moreover, the performance of the FFT-based discriminators is compared with the performance of two other frequency discriminators, namely the fast–slow and power-based. The comparison results indicate that these two frequency discriminators give higher frequency estimation accuracy, but they have a narrower dynamic range.     

组合桩在加固厚层填土中的应用

本工程场地为欠固结厚层填土现状，为保证承台底不脱空，采用粉喷桩加固承台底欠固结填土，并在粉喷桩内施工静压桩的技术对策，这样既加固了填土，又提高了静压桩单桩承载力，获得了良好的效果。