上海地区浅层沼气地质灾害分区探讨

针对上海地下工程中遇到的浅层沼气地质灾害问题,本文搜集分析了大量的实测资料,总结了上海地区浅层沼气的产出和分布规律,并最终尝试从地质灾害的角度对其进行分区。     

掺Ga对ZnO电子态密度和光学性质的影响

采用密度泛函理论下的第一性原理平面波赝势方法,研究了掺Ga对纤锌矿ZnO电子态密度和光学性质的影响.从晶体配位场理论分析了掺Ga前后ZnO的成键情况及态密度的变化.计算得到掺Ga后电子浓度为2.42×10²¹ cm^-3,ZnO的载流子浓度提高了10⁴倍.比较分析掺Ga前后ZnO的介电函数、复折射率、吸收光谱和反射光谱可得,ZnO光吸收边向高能端移动,光学带隙增大.在可见光区,ZnO光吸收系数与反射率减小,光透过率显著提高,使ZnO:Ga成为     

NaAlH4 表面Ti催化空间构型和X射线吸收光谱:Car-Parrinello分子动力学和密度泛函理论研究

通过采用Car-Parrinello分子动力学方法对掺杂Ti前后的NaAlH₄(001)2×2×1超晶胞表面晶体在333 K(60 ℃)温度条件催化脱氢的空间构型做了理论研究,发现掺杂Ti的合金中AlH₄团的其中两个Al—H键长分别从约1.64 (1 =0.1 nm)增大至1.74和1.93 ,而未掺杂合金表面中AlH₄团的4个Al—H键长基本不变,这意味着掺杂Ti相对未掺杂的合金更易于放氢.但在模拟温度条件下并未发现Ti-Al成键趋     

Ab initio investigations of the charge transport properties of endohedral M@C20 (M= Na and K) metallofullerenes

Using density functional theory and quantum transport calculations based on nonequilibum Green's function formalism, we investigate the charge transport properties of endohedral M@C₂₀ (M= Na and K) metallofullerenes. Our results show that the conductance of C₂₀ fullerene can be obviously improved by insertion of alkali atom at its centre. Both linear and nonlinear sections are found on the I-V curves of the Au-M@C₂₀-Au two-probe systems. The novel negative differential resistance behaviour is also observed in Na@C₂₀ molecule but not in K@C₂₀.     

The density functional calculations on the structural and electronic properties of the endohedral fullerene dimer (N2@C60)2

The generalised gradient approximation based on density functional theory is used to study the structural and electronic properties of the endohedral fullerene dimer (N₂@C₆₀)₂. Four N atoms sit at the cage centres in the form of two N_2 molecules. The density of states and Mulliken charge analysis explore that the energy levels from -6 to -10 eV are mainly influenced by the N₂ molecules.     

Electronic and optical properties of pure and Ce3+-doped CaS single crystals: a first-principles prediction

This paper investigates the electronic and optical properties for pure and Ce³⁺-doped CaS crystals by using the first-principles total energy calculations. The results show that CaS:Ce has a direct band gap of 2.16 eV, and the top of the valence band is determined by S 3p states and the bottom of the conduction band is determined by Ce 4f states, respectively. Our results validate that the yellow emission from CaS:Ce is produced by doped cerium and the green emission quenches at 12.5% cerium concentration. The Ce-S bond shows more covalent character than the Ca-S bond.     

基于GIS的雪灾风险区划

依据巴彦淖尔地区冬春季节降水少、年变率大的气候特点和易形成雪灾的量级指标进行雪灾风险区划。选取1971—2010年11月到次年3月,日降雪量大于等于3mm,并出现积雪和结冰现象为研究对象,分析了降雪量大于等于3mm的降雪日数和积雪深度大于等于5cm的积雪日数年代际变化,结合民政部门历史灾情记载、实地调查、农牧业现状以及各种基础资料数据与GIS技术,从致灾因子、脆弱性评估分析方面,在NOAA卫星遥感雪覆盖监测图像上,利用加权综合与层次分析法,构建雪灾判别模型,得出巴彦淖尔地区雪灾风险区划:雪灾最严重的地区为五原县大部、乌前旗南部和东北部部分区域、乌中旗东南和西南两区域、乌后旗的海力素附近大片区域。     

Application of extension theory in risk zoning of debris flow in Beijing

The occurrence of debris flow is affected by many factors. Risk zoning of debris flow plays a vital role in the early-warning and prediction of abrupt geological hazards, and exploration of new method is needed in the early-warning and prediction of geological hazards. The extension theory is a new method to solve contradiction matters. Based on extension theory, AHP and GIS, the risk zoning model of debris flow was established in this paper. The result of this research provides a new way in the risk zoning, early-warning and prediction of debris flow     

Mapping human dimensions in marine spatial planning and management: An example from Narragansett Bay, Rhode Island

The Narragansett Bay in Rhode Island is a complex mosaic of human activities and environmental features and while spatial distributions of physical, chemical, and biological elements are well documented in the Bay, there are limited data on spatial distributions of human activities. In this study, human uses of coastal waters in the upper Narragansett Bay are examined using an approach for characterizing and analyzing fine scale spatial and temporal data on human activities. Shipboard transect surveys of active water activities were conducted in the upper Bay on 50 days during the summer months of 2006–2007. The composition and configuration of different vessel types (recreational motor, recreational sail, row boat, commercial fishing, industrial, service, and official) were analyzed, and the impacts of proposed changes in land use policies and wastewater treatment technologies were investigated. Results indicated that recreational boaters comprised almost two-thirds of the upper Bay's users and used over one-half of the study area. Industrial activity was concentrated near Providence where RI's main port is located, and there was an active commercial fishery in the southern portion of the study area. Conditions like increasing cloud cover, weekend days, and the July 4th holiday were related to increased recreational use, while the closure of an upper Bay beach to swimming was associated with fewer commercial fishing vessels and more official boats, recreational motor boats, and service vessels. Findings indicated that upper Bay waters near land converted from industrial zones to zones where residential housing or marinas are encouraged are likely to see a change in composition of vessels, with fewer industrial and official boats and more recreational motor boats, row boats, and service vessels. Enhanced wastewater treatment technologies and the resulting improvements in water quality are likely to make more waters in the upper Bay available to shellfish harvesting, spreading out existing fishing grounds and potential pressures on the ecosystem and on other users. By characterizing the spatial and temporal heterogeneity of human uses in the marine environment and analyzing how these uses relate to the complex human and natural systems in which they are embedded, this study and others like it can positively contribute to marine spatial planning and management efforts designed to achieve ecological, economic, and social objectives.     

Nematode community dynamics over an annual production cycle in the central North Sea

Nematode species composition, trophic structure and body size distributions were followed over an annual production cycle in the central North Sea; to test responses to temporally changing food quality and quantity in the sediment. Changes in the phytoplankton concentration in the water column were quantitatively reflected in the concentration of chlorophyll a and breakdown products in the sediment, with higher concentrations in spring and autumn following blooms, and lower concentrations in summer and winter. The taxonomic and trophic structure of nematode communities differed significantly among stations over relatively short distances, potentially masking some of the temporal dynamics. Spatio-temporal differences in nematode species composition were linked to changes in the quality and quantity of organic material reaching the seabed, reflecting a species-specific response to the nutritional quality of sedimenting organic material and the biochemical changes in the sediment associated with its decomposition. The size distributions of selected nematode species indicated that most species bred continuously throughout the sampling period, although one species, the epigrowth feeder Spilophorella paradoxa, had periods of increased growth following the deposition of the spring phytoplankton bloom. There was no consistent temporal relationship between the trophic composition of nematode communities and spring chlorophyll a or carbon sedimentation, most likely a result of the trophic plasticity of most feeding types and the capacity of the community to use both freshly sedimented material as well as the subsequent breakdown products and refractory organic matter. Community metrics implied that there were small responses to the seasonal production cycle, but these belied strong responses of a few species with life histories that allowed them to track the availability of suitable food resources.