The identifiability of parameters in a water quality model of the Biebrza River, Poland

The identifiability of model parameters of a steady state water quality model of the Biebrza River and the resulting variation in model results was examined by applying the Monte Carlo method which combines calibration, identifiability analysis, uncertainty analysis, and sensitivity analysis. The water quality model simulates the steady state concentration profiles of chloride, phosphate, ammonium, and nitrate as a function of distance along a river. The water quality model with the best combination of parameter values simulates the observed concentrations very well. However, the range of possible modelled concentrations obtained for other more or less equally eligible combinations of parameter values is rather wide. This range in model outcomes reflects possible errors in the model parameters. Discrepancies between the range in model outcomes and the validation data set are only caused by errors in model structure, or (measurement) errors in boundary conditions or input variables. In this sense the validation procedure is a test of model capability, where the effects of calibration errors are filtered out. It is concluded that, despite some slight deviations between model outcome and observations, the model is successful in simulating the spatial pattern of nutrient concentrations in the Biebrza River.     

GPS Ambiguity Resolution: Impact of Time Correlation,Cross-Correlation and Satellite Elevation Dependence

In this contribution we discuss the geometry-free GPS single baseline model and show how the least-squares ambiguities are affected by changes in the stochastic model. We particularly pay attention to the effect of time correlation, cross-correlation and satellite elevation dependence. We also differentiate between the impact on the location of the ambiguity search space and the impact on the size and shape of the search space. The analysis is carried out for both the model in which the ionospheric delays are assumed absent, and for the model in which they are assumed present. The former model is applicable to short baselines only.     

Seismic data compression based on integer wavelet transform

Introduction With the development of the seismological observation technique and deep-going of seismicdata application fields, especially the digitization of data in earthquake station networks, theimprovement of the precision, the data quantity increases as geometric order, which bringdifficulty to saving and transfering these data. To keep all information, seismic data, like medicalimages, should be compressed without error in many applications. In generally, traditionalcompression meth…     

郑州国际会展中心展厅钢屋盖的动力特性分析

郑州国际会展中心展览厅钢屋盖采用了空间斜拉式索拱结构体系，为探讨该体系的动力特性，采用ANSYS有限元程序，分别建立钢屋盖与下部混凝土结构共同作用、钢屋盖单独作用以及无斜拉系统的钢屋盖单独作用时的3个空间计算模型，采用子空间迭代法计算其自振周期和振型，并加以比较。从而得出钢屋盖的动力特性，为进一步研究此类结构的受力特性奠定了基础。     

Large-Eddy Simulation of Turbulent Flow Over a Rough Surface

A family of wall models is proposed that exhibits moresatisfactory performance than previousmodels for the large-eddy simulation (LES) of the turbulentboundary layer over a rough surface.The time and horizontally averaged statistics such asmean vertical profiles of windvelocity, Reynolds stress, turbulent intensities, turbulentkinetic energy and alsospectra are compared with wind-tunnel experimental data.The purpose of the present study is to obtain simulatedturbulent flows that are comparable with wind-tunnelmeasurements for use as the wind environment for thenumerical prediction by LES of source dispersion in theneutral atmospheric boundary layer.     

Turbulent Pressure Statistics in the Atmospheric Boundary Layer from Large-Eddy Simulation

We use large-eddy simulation (LES) to study the turbulent pressure field in atmospheric boundary layers with free convection, forced convection, and stable stratification. We use the Poisson equation for pressure to represent the pressure field as the sum of mean-shear, turbulence–turbulence, subfilter-scale, Coriolis, and buoyancy contributions. We isolate these contributions and study them separately. We find that in the energy-containing range in the free-convection case the turbulence–turbulence pressure dominates over the entire boundary layer. That part dominates also up to midlayer in the forced-convection case; above that the mean-shear pressure dominates. In the stable case the mean-shear pressure dominates over the entire boundary layer.We find evidence of an inertial subrange in the pressure spectrum in the free and forced-convection cases; it is dominated by the turbulence–turbulence pressure and has a three-dimensional spectral constant of about 4.0. This agrees well with quasi-Gaussian predictions but is a factor of 2 less than recent results from direct numerical simulations at moderate Reynolds numbers. Measurements of the inertial subrange pressure spectral constant at high Reynolds numbers, which might now be possible, would be most useful.     

城市应急管理模型之设计

随着城市建设的快速发展 ,各类危及国家和人民群众生命财产安全的突发性事故灾害时有发生 ,尽管各有关部门的抢救队伍在实施抢险救援中发挥了积极作用 ,但各抢险救援力量专业单一、分散行动 ,形成不了合力 ,难以及时有效处置重大或特大突发性、综合性、大面积的城市事故灾害 ,特别是像地震以及的美国的 9 1 1那样突发性事故。我们目前开展的震害预测与灾害快速评估系统只是针对地震的 ,而地震是小概率事件。因此要应对城市各种重大突发事件 ,城市有必要建立一种应急机制或综合的应急管理信息系统。根据“数字城市”的思想 ,通过一个通信系统与信息系统集成的平台 ,统一协调公安、消防、急救、交警、公共事业、民防、地震等政府部门 ,为市民提供快速、及时的各种救助和相应的服务。统一报警、统一指挥、快速反应、联合行动 ,从而有效地减少损失。     

Simulation Experiments of Land Surface Physical Processes and Ecological Effect over Different Underlying Surface

Based on the existing Land Surface Physical Process Models(Deardorff, Dickinson, LIU, Noilhan, Seller, ZHAO), a Comprehensive Land Surface Physical Process Model (CLSPPM) is developed by considering the different physical processes of the earth‘s surface-vegetation-atmosphere system more completely. Compared with SiB and BATS, which are famous for their detailed parameterizations of physical variables, this simplified model is more convenient and saves much more computation time. Though simple, the feas...     

Simulation of oasis breeze circulation in the arid region of the Northwestern China

In this paper, the process of oasis-desert circulation (ODC) is simulated by MM5V3.5 model through designing an ideal oasis-desert scheme and assuming that initial atmosphere is at rest (V = 0). The findings showed that the key of forming special oasis boundary structure is the difference of energy and water between oasis and desert. The evaporation of oasis surface consumes heat energy, and the low temperature of oasis causes an oasis breeze circulation (OBC), which drives an ODC with a downdraft over the oasis and an updraft over the desert. Later, the cold, dry and stable boundary over oasis is gradually formed, on the contrary,the atmospheric boundary over desert on the edge of oasis is hot, humid and unstable and its height is about 600 hPa. The updraft over the desert forms a wet ring that acts as a vertical wall weakening the low-level moisture exchange between the oasis and desert. The downdraft of OBC increases the atmospheric stability that reduces the oasis evaporation. The low-level outflow from the oasis (into the desert) prevents the dry, hot air flowing from the desert into the oasis.Thus an oasis self-preservation mechanism may be formed due to OBC. The horizontal area influenced by oasis is twice as oasis area and the vertical range is four times as oasis. The ODC is strong in the daytime and reaches the strongest at 17:00, and the influenced area is the largest at 20:00.