Subgrid-Scale Modeling of Reacting Scalar Fluxes in Large-Eddy Simulations of Atmospheric Boundary Layers

In large-eddy simulations of atmospheric boundary layer turbulence, the lumped coefficient in the eddy-diffusion subgrid-scale (SGS) model is known to depend on scale for the case of inert scalars. This scale dependence is predominant near the surface. In this paper, a scale-dependent dynamic SGS model for the turbulent transport of reacting scalars is implemented in large-eddy simulations of a neutral boundary layer. Since the model coefficient is computed dynamically from the dynamics of the resolved scales, the simulations are free from any parameter tuning. A set of chemical cases representative of various turbulent reacting flow regimes is examined. The reactants are involved in a first-order reaction and are injected in the atmospheric boundary layer with a constant and uniform surface flux. Emphasis is placed on studying the combined effects of resolution and chemical regime on the performance of the SGS model. Simulations with the scale-dependent dynamic model yield the expected trends of the coefficients as function of resolution, position in the flow and chemical regime, leading to resolution-independent turbulent reactant fluxes.     

Automatic construction of concept hierarchies: The case of foliage-dwelling spiders

In this paper, we present the hierarchical variable dependencies that were obtained from raw data with the use of two machine learning techniques on an ecological data set. The data set contains features of field margins and the corresponding number of spider species inhabiting them. This data set was used before by domain experts to construct a fuzzy qualitative model with hierarchical variable dependencies, which we use for comparison with our results. One of the machine learning methods constructs a hierarchical structure similar to the one in the experts’ model, while revealing some additional interesting relations of environmental features with respect to the number of spider species. The other method constructs a different hierarchy from the one proposed by the experts, which, according to our classification performance experiments, might be even more appropriate.     

Regional Consequences of Local Population Demography and Genetics in Relation to Habitat Management in Gentiana pneumonanthe

Abstract:  A joint demographic and population genetics stage-based model for a subdivided population was applied to Gentiana pneumonanthe , an early successional perennial herb, at a regional (metapopulation) scale. We used numerical simulations to determine the optimal frequency of habitat disturbance (sod cutting) and the intensity of gene flow among populations of G. pneumonanthe to manage both population viability and genetic diversity in this species. The simulations showed that even small populations that initially had near-equal allele frequencies could, if managed properly through sod cutting every 6 to 7 years, sustain their high genetic variation over the long run without gene flow. The more the allele frequencies in the small populations are skewed, however, the higher the probability that in the absence of gene flow, some alleles will be lost and within-population genetic variation will decrease even under proper management. This implies that although local population dynamics should be the major target for management, regional dynamics become important when habitat fragmentation and decreased population size lead to the loss of local genetic diversity. The recommended strategy to improve genetic composition of small populations is the introduction of seeds or seedlings of nonlocal origin.     

AGA法及其在非线性数学模型参数估计中的应用

介绍了在基因算法基础上改进的加速基因算法（ＡＧＡ），并通过环境非线性数学模型参数估计实例对该法与传统参数估计方法进行了比较。初步结果表明，ＡＧＡ法直观、简便、拟合精度高、通用性强，易为广大环境工程技术人员理解和使用。     

活性污泥法简化数学模型的研究与进展

介绍几种简化数学模型 (如ROM、SPM、SLM等 )的结构与特点。模型的验证结果表明 ,简化模型能够较好的模拟系统的运行 ,产生较为准确的模拟结果     

生物膜填料床内废气净化的理论模型

介绍了废气生物净化技术的基本原理，并对废气生物净化技术中的生物过滤法和生物滴滤法的理论模型研究进展进行了综述，探讨了理有理论模型存在的主要问题。     

放射示踪法研究O2存在时14CS2与OH的光化学反应

用放射示踪法研究~(14)CS_2和OH的光化学反应,指出氧对反应有促进作用,在反应体系中(~(14)CS_2-H_2O_2-C_3H_8-N_2-O_2)主要产物为O~(14)CS,~(14)CO及少量~(14)CO_2。O~(14)CS和~(14)CO有相似的动力学曲线,~(14)CO_2则是另一种情况。总反应速率常数随氧压增加而增大,在氧压为33330Pa时,~(14)CS_2消失的总速率常数可高达3.4×10~(-12)cm~3mol~(-1)S~(-1)。在实验中观察到~(14)CS_2能在室温下转变为~(14)CO_2的现象。讨论了光化学反应的历程。     

A method for calculating the total ozone amount in the clear skies

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Modeling Connectivity of Non‐floodplain Wetlands: Insights,Approaches, and Recommendations

Representing hydrologic connectivity of non‐floodplain wetlands (NFWs) to downstream waters in process‐based models is an emerging challenge relevant to many research, regulatory, and management activities. We review four case studies that utilize process‐based models developed to simulate NFW hydrology. Models range from a simple, lumped parameter model to a highly complex, fully distributed model. Across case studies, we highlight appropriate application of each model, emphasizing spatial scale, computational demands, process representation, and model limitations. We end with a synthesis of recommended “best modeling practices” to guide model application. These recommendations include: (1) clearly articulate modeling objectives, and revisit and adjust those objectives regularly; (2) develop a conceptualization of NFW connectivity using qualitative observations, empirical data, and process‐based modeling; (3) select a model to represent NFW connectivity by balancing both modeling objectives and available resources; (4) use innovative techniques and data sources to validate and calibrate NFW connectivity simulations; and (5) clearly articulate the limits of the resulting NFW connectivity representation. Our review and synthesis of these case studies highlights modeling approaches that incorporate NFW connectivity, demonstrates tradeoffs in model selection, and ultimately provides actionable guidance for future model application and development.