Characterization and Evaluation of Elevation Data Uncertainty in Water Resources Modeling with GIS

Grid based digital elevation models (DEM) are commonly used in water resources modeling. The quality of readily available DEM, however, varies from source to source in terms of horizontal resolution and vertical accuracy which are the two important aspects of elevation uncertainty in the modeling with raster GIS. This paper addresses the issue of elevation data uncertainty in GIS supported hydrologic simulations. The essential role of elevation data in the modeling is revealed by presenting DEM processing processes in distributed and semi-distributed hydrologic analyses. It is very difficult to examine the elevation uncertainties analytically due to complexities of the hydrologic models. An ideal approach is to assess the effect of the DEM uncertainty by applying varying resolutions or accuracies of elevation data in the modeling. Different grid sizes of DEM are used in observing DEM resolution dependence and resulting model outputs are compared to obtain a profile of its effect. Impact of DEM vertical accuracy is explored by Monte Carlo simulation with a large number of DEM realizations generated based on different levels of specified error. The approach is implemented in a case study with a topography based hydrologic model on an experimental watershed to analyze both aspects of the uncertainty. The results show that both DEM grid size and vertical accuracy could have profound effect on hydrologic modeling performance. The impact can be compensated by model calibrations due to interactions between model parameters and spatial factors. The study indicates that the DEM uncertainty can be effectively evaluated using the applied method. The work is to provide some insight into the characterization of elevation data quality and the association between topography and water resources models.     

Working memory and focal attention.

Measures of retrieval speed indicated that only a small subset of representations in working memory falls within the focus of attention. An n-back task, which required tracking an item 1, 2, or 3 back in a sequentially presented list, was used to examine the representation and retrieval of recent events and how control processes can be used to maintain an item in focal attention while concurrently processing new information. A speed–accuracy trade-off procedure was used to derive measures of the availability and the speed with which recent events can be accessed. Results converge with other time course studies in demonstrating that attention can be concurrently allocated only to a small number of memory representations, perhaps just 1 item. Measures of retrieval speed further demonstrate that order information is retrieved by a slow search process when an item is not maintained within focal attention. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Chronic and temporarily activated causal uncertainty beliefs and stereotype usage.

In 3 studies, we examined the hypothesis that the effects of stereotype usage on target judgments are moderated by causal uncertainty beliefs and related accuracy goal structures. In Study 1, we focused on the role of chronically accessible causal uncertainty beliefs as predictors of a target's level of guilt for an alleged academic misconduct offense. In Study 2, we examined the role of chronic causal uncertainty reduction goals and a manipulated accuracy goal; in Study 3, we investigated the role of primed causal uncertainty beliefs on guilt judgments. In all 3 studies, we found that activation of causal uncertainty beliefs and accuracy concerns was related to a reduced usage of stereotypes. Moreover, this reduction was not associated with participants' levels of perceived control, depression, state affect, need for cognition, or personal need for structure. Results are discussed in terms of their implications for the model of causal uncertainty and, more generally, in terms of the motivational processes underlying stereotype usage. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Third-order accurate finite volume schemes for Euler computations on curvilinear meshes

After looking for a convenient definition of accuracy for finite-volume schemes on structured meshes, a high-order accurate scheme is constructed for the Euler equations. Thanks to suitably weighted discretization operators, the proposed scheme is third-order on mildly deformed grids and second-order on highly deformed grids. The influence of mesh deformations on the scheme accuracy is studied theoretically and numerically. Numerical results are shown for a Lamb vortex, subsonic flow past a cylinder and transonic flow past a NACA0012 airfoil.     

地质样品中金的快速测定

制备了双硫腙泡塑 ,研究了双硫腙泡塑富集金的条件和解脱方法。采用液珠萃取比色法进行测定 ,方法的测定范围为 0 0 0 5× 10 - 6 ～xx× 10 - 6 g。经样品验证 ,该方法适用于地质样品中金的快速测定。     

The intoxicated witness: Effects of alcohol on identification accuracy from showups.

The effect of alcohol on identification accuracy is potentially an important topic. This study examined the effects of alcohol consumption on identification accuracy from showups, the identification procedure most likely to be used by police with intoxicated witnesses. The blood alcohol level of people exposed to a target was measured. In the target-present showup condition, blood alcohol level was not significantly related to correct identification rate. In the target-absent showup condition, the higher the blood alcohol level, the more people were likely to make a false identification. Implications for law enforcement and future research directions are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

回转误差精确测试与特征评定值

推导并建立了在主轴回转误差测试中不受标准球偏心影响的表征主轴回转精度的数学模型。经推导和仿真处理，得出当主轴回转误差分解为不同频次的径向圆周运动或单向谐振动时，机床加工的各种形状、尺寸、形位误差的精确特征评定值。     

大赉水文站测速垂线精简测点的分析探讨

利用2007年大赉水文站总计30次用三点法实测流量资料,通过对流量、垂线平均流速两个方面分析得知,大赉水文站测速垂线精简测点后,采用相对水深0.2、0.8测点测流与采用相对水深0.2、0.6、0.8测点测流,两种方法计算的流量对比,总的系统误差为-0.36%。并对两种测流方法进行了单次流量随机不确定度验证,符合《河流流量测验规范》精度要求。其意义在于缩短测流历时,把流量测验的重点投入到增加测验次数上,满足大洪水时期,水位变幅大,测次不足的问题。尤其在主汛期可及早报出流量,为防汛抗洪服务。     

LGH-01型空气质量自动监测系统准确度检查方法探讨

LGH一01型空气自动监测系统因其独特的技术优势,在国内占有较大的市场份额,已广泛应用于城市环境空气质量监测。如何做好仪器的使用维护工作,保证监测结果的真实有效,是一线环境监测工作者每天必须面对的问题。本文针对DOAS系统准确度检查方法进行实验探讨,期望能提供给同行参考。     

Comparison of the working domains of some compression heat pumps and a compression-absorption heat pump

The working domains of a model of a compression heat pump using different fluids and a model of a compression-absorption heat pump using water-ammonia mixtures are defined, plotted and discussed. These domains are defined by means of limiting values for their electrical coefficient of performance, volumetric heating capacity, and low and high pressure. In the case studied in the present paper, the disappearance from use of CFC and HCFC fluids leaves only one alternative for the implementation of high temperature electric heat pumps: hydrocarbons in compression devices or water-ammonia mixtures in compression-absorption devices. Problems relating to the implementation of these systems are also mentioned.