辽河流域径流对气候变化的响应特征研究

近百年来,全球气候发生了以气温升高为主要特征的显著变化。东北是中国的重要粮食主产区,气候变化将可能加剧东北地区水资源短缺情势,进一步影响到国家的粮食安全。以辽河流域为对象,分析了近60年来降水径流变化特性,采用水文模拟方法,揭示了河川径流变化成因,基于假定气候情景,研究了河川径流量及土壤含水量对气候变化的响应。结果表明:铁岭站实测径流量自20世纪60年代中期以来,总体呈明显的阶段性减少趋势,人类活动是河川径流减少的主要原因。降水增加比减少对河川径流量的影响明显,土壤含水量对降水减少的响应更加敏感,气候暖干化趋势将非常不利于东北地区的水资源利用和农业生产。     

五台山地区古元古界滹沱群沉积环境:前陆盆地还是陆内裂谷盆地?

分布于五台山地区的古元古界滹沱群形成的大地构造环境和地质演化过程,对华北克拉通东、西部陆块之间的华北中部碰撞造山带的形成时代和演化具有关键性的地质约束.通过对滹沱群与下伏地质体之间的接触关系、滹沱群沉积岩石序列组合特征、构造变形样式和已有同位素年代学资料的综合分析,认为(1)滹沱群呈区域性角度不整合覆盖于新太古代五台群...     

钼同位素比值的双稀释剂测定方法研究

本文报道了运用多接收器等离子体质谱测定Mo同位素组成的方法,测定过程中使用双稀释剂法校正仪器的质量分馏.Fisher-Mo标准溶液和双稀释剂的100Mo/97Mo使用Fisher-Pd标准溶液中的104pd/102pd标定,其他Mo同位素比值通过100Mo/97Mo标定;本文对运用双稀释剂技术进行Mo同位素测定的长期重...     

不同Ni原料对固相法合成MnCoNiO固溶体的反应机理影响研究

以Mn、Co、Ni的无机盐为反应原料,采用固相法制备粉体材料Mn1.8Co0.2NiO4。利用XRD、差热-热失重表征了粉体的晶相及晶型的转化。实验结果表明,不同的Ni原料均可以合成具有单一尖晶石结构的金属氧化物,其中间的反应过程存在差异,差异是由固相反应的拓扑学特征决定的。     

Sustainable yield of a karst aquifer system: a case study of Jinan springs in northern China

Based on the long-term monitoring data of rainfall, groundwater levels, groundwater abstraction, spring flow rates and groundwater quality, an assessment has been undertaken of the sustainable yield of a karst aquifer system in Shandong Province, northern China, to maintain perennial outflow of the karst springs while meeting water demands. One of the fundamental indicators for sustainable yield of groundwater is identified as maximum allowable water-level drawdown. A regional three-dimensional finite-difference numerical model has been developed to optimize the schemes associated with well fields and their locations and sustainable yields, in the Jinan spring catchment and its adjacent karst groundwater catchments, with the aim of maintaining the water level higher than the allowable lowest water level of 27.5?m above sea level. Furthermore, measures necessary to move towards sustainable use of the karst groundwater are outlined, drawing on contingency plans of water-source replacement and artificial recharge, dual water supply (based in water quality), use of the spring waters themselves, and groundwater quality protection.     

柴达木地块北缘全吉地块钾长石浅粒岩碎屑 锆石LA-ICP-MS U-Pb定年 ——对达肯大坂岩群时代的约束

为查明全吉地块基底中达肯大坂岩群的最大沉积年龄,用LA-ICP-MS技术测定了钾长石浅粒岩中的锆石U-Pb年龄。CL图像和Th/U比值指示这些锆石均为岩浆成因的锆石。36个测点207Pb/206Pb年龄变化范围为2094~2280Ma,其中年龄谐和度高于90%的30个测点的207Pb/206Pb年龄相对概率密度曲线呈单峰分布特征,峰值年龄为2190Ma左右。结合全吉地块最早一期变质事件的年龄,钾长石浅粒岩原岩碎屑和所在的达肯大坂岩群的沉积年龄范围被约束在1.95~2.19Ga之间。本研究表明,前人在侵入于达肯大坂岩群的伟晶岩脉中获得的约2.42Ga年龄的锆石应捕获于围岩,属于继承性岩浆碎屑成因,该类锆石年龄不能用来约束达肯大坂岩群原岩的最小沉积年龄。     

Trace metals in porewater of surface sediments and their bioavailability in Jiaozhou Bay,Qingdao, China

Samples of porewater and the edible tissue of mottled clams, Ruditapes variegatus, were collected simultaneously at each of 12 stations from Jiaozhou Bay near Qingdao, China, in June of 2003. Chemical analysis focused on trace metals and major elements. Porewater concentrations of Cd, Cr, Pb, and Zn were distributed in a bimodal fashion among the 12 stations, with mean concentrations at six of the stations being 8–32 times mean values at the other six stations. The concentrations of the same metals in clams were remarkably similar among stations, the coefficients of variation being only 12–37%. Calculations performed with the computer program PHREEQC indicated that Pb and Cr in porewater were present only in the +2 and +3 states, respectively, and because dissolved Cd and Zn exist only in the +2 state, the bimodal distribution of these four metals likely reflects secondary effects associated with their scavenging by Fe and/or Mn under oxidizing conditions and subsequent dissolution in the reducing environment of the porewaters. Consistent with this hypothesis is the fact that the distribution of high and low metal concentrations was closely correlated with the granularity of the sediment, with lower metal concentrations associated with relatively coarse sediment. Comparison of published biological concentration factors with the ratios of metal concentrations in the clams to porewater metal concentrations indicated that the porewaters were not the primary sources of the metals in the clams. Mixing processes in the bay likely account for the rather uniform concentrations of metals in clam tissue.     

Comparison of Two Methods Used to Model Shape Parameters of Pareto Distributions

Two methods are compared for estimating the shape parameters of Pareto field-size (or pool-size) distributions for petroleum resource assessment. Both methods assume mature exploration in which most of the larger fields have been discovered. Both methods use the sizes of larger discovered fields to estimate the numbers and sizes of smaller fields: (1) the tail-truncated method uses a plot of field size versus size rank, and (2) the log–geometric method uses data binned in field-size classes and the ratios of adjacent bin counts. Simulation experiments were conducted using discovered oil and gas pool-size distributions from four petroleum systems in Alberta, Canada and using Pareto distributions generated by Monte Carlo simulation. The estimates of the shape parameters of the Pareto distributions, calculated by both the tail-truncated and log–geometric methods, generally stabilize where discovered pool numbers are greater than 100. However, with fewer than 100 discoveries, these estimates can vary greatly with each new discovery. The estimated shape parameters of the tail-truncated method are more stable and larger than those of the log–geometric method where the number of discovered pools is more than 100. Both methods, however, tend to underestimate the shape parameter. Monte Carlo simulation was also used to create sequences of discovered pool sizes by sampling from a Pareto distribution with a discovery process model using a defined exploration efficiency (in order to show how biased the sampling was in favor of larger fields being discovered first). A higher (more biased) exploration efficiency gives better estimates of the Pareto shape parameters.     

Robust control based on feedback linearization for roll stabilizing of autonomous underwater vehicle under wave disturbances

In the case of Autonomous Underwater Vehicle(AUV) navigating with low speed near water surface,a new method for design of roll motion controller is proposed in order to restrain wave disturbance effectively and improve roll stabilizing performance.Robust control is applied,which is based on uncertain nonlinear horizontal motion model of AUV and the principle of zero speed fin stabilizer.Feedback linearization approach is used to transform the complex nonlinear system into a comparatively simple linear system.For parameter uncertainty of motion model,the controller is designed with mixed-sensitivity method based on H-infinity robust control theory.Simulation results show better robustness improved by this control method for roll stabilizing of AUV navigating near water surface.     

数字海洋可视化系统研究与实现

球体模型系统是目前GIS领域的研究热点,它以强大的空间数据管理能力,丰富直观的信息表现能力迅速成为空间信息集成共享的有力平台.以Skyline软件平台为基础,介绍了数字海洋可视化系统的体系架构、功能设计和技术实现方法.实践应用表明,该系统在多源海洋信息可视化集成共享方面具有良好的应用前景.