Proposing an information criterion for individual-based models developed in a pattern-oriented modelling framework

Individual-based models (IBMs) have been improved in quality and reliability in recent years with an approach called pattern-oriented modelling (POM). POM proposes guidelines to develop models reproducing multiple patterns observed on the field and to test systematically how well the IBMs reproduce them. POM studies used generally traditional methods of goodness of fit such as the sum of squares evaluation or ad hoc comparisons of fitting errors and variations. Model selection, however, can be a rigorous statistical approach based on information theory and information criteria such as the Akaike's information criterion (AIC) or the deviance information criterion (DIC). So far, it has not been tried to link POM to these rigorous techniques. The main problems to achieve that are: (a) the difficulty to have likelihood functions for IBMs’ parameters and (b) the possibility to obtain posterior distributions of IBMs’ parameters given the patterns to reproduce. In a first part, this paper answers problem (a) by proposing and explaining how to calculate a deviance measure (POMDEV) for models developed in a context of POM. And while answering the second problem, a second part of the paper proposes an information criterion for model selection in a POM context (the pattern-oriented modelling information criterion: POMIC). This criterion does not yet have the same theoretical foundation as, e.g., AIC, but uses formal analogies to the DIC. In a third part POMIC is tested with a modelling exercise. This exercise shows the potential of POMIC to use multiple patterns for selecting among multiple potential submodels and eventually select the most parsimonious and well fitting model version. We conclude that POMIC, although being a heuristically derived approach, can greatly improve the POM framework.     

建筑小区内致病微生物暴露风险评价

利用数值模拟确定致病微生物浓度的时空分布,建立了基于瞬时浓度判据和积累浓度判据的污染物暴露评价模型,得到了建筑群内瞬时风险区域和人们在污染区域的最大停留时间。结果显示:瞬时风险区域面积基本与微生物生长曲线一致,即在2000s时达到最大,然后逐渐减小,至6000s后基本不变;最大停留时间与微生物的增长率有关,增长率大,最大停留时间变小。     

综采工作面粉尘运移和粉尘浓度三维分布的数值模拟研究

分析了综采工作面流场及粉尘分布的特点 ,视工作面含尘风流为气 粒两相流 ,建立了描述综采工作面风流中粉尘运动和浓度分布的数学模型。采用计算流体力学的有限容积法求解 ,编制了模拟计算综采工作面三维空间内风速和粉尘浓度分布的计算机程序     

火灾扑救模拟演练DIS系统框架的研究

论述了分布式交互仿真 (DistributedInteractiveSimulation ,简称DIS)技术在火灾扑救模拟演练中的应用 ,给出其系统框架 ;详细描述了该DIS系统中的白方系统、蓝方系统和红方系统的具体组成功能部分 ;提出了实现这些功能的软件平台。最后给出了研究DIS在火灾扑救演练应用中的结论 ;指出未来的发展方向 ,强调了实际应用中可能出现的技术难点     

金川公司二矿区通风系统风流非定常流动规律研究

实际上 ,矿井的风流状态受多种因素影响 ,金川公司二矿区井下风流就处于非定常状态 ,为了保证生产安全 ,控制风流状态 ,采取相应的通风措施 ,开设课题研究 ,建立了井巷内空气非定常流动能量方程和通风网络中非定常流动的数学模型。根据该模型可以模拟出矿井通风系统内非定常状态下任意时刻、任意位置通过风量。通过对金川公司二矿区井下机站风机开停和风门开关引起通风系统风流的非定常流动过程的数值模拟 ,得出了受其影响区域内风流状态的变化规律 ,并为其采取通风措施和控制风流状态 ,提供了科学依据     

SIMULATING FLOW IN REGIONAL WETLANDS WITH THE MODFLOW WETLANDS PACKAGE1

ABSTRACT: As part of the Comprehensive Everglades Restoration Plan (CERP), various water supply projects have been proposed in a region located between the Miami metropolitan area and the extensive regional wetland systems that are part of the Everglades or remnant Everglades. A ground water flow model of the surficial aquifer within northern Miami‐Dade County was constructed using MODFLOW to evaluate the effects of these projects on water levels in the wetlands and the underlying surficial aquifer. The new Wetlands package was used to conjunctively simulate overland flow through these wetlands and the shallow ground water system. Comparisons of simulated to measured ground water levels and wetland stages were very satisfactory, where computed and measured water levels agreed within 0.5 ft over most of the period of record at nearly all of the monitoring sites. Temporal trends in water levels were also replicated. It was concluded that the assumptions and methodologies inherent to the Wetlands package were suitable for simulating regional wetland hydrology within the Everglades area.     

用ALMANAC作物生长模型模拟冬小麦生长

冬小麦是黄淮海地区的主要农作物。精确模拟冬小麦产量能够帮助生产者获得更好的经济效益。根据实验资料调整了ALMANAC作物生长模型部分参数后,用其对该地区的冬小麦生长进行了模拟,结果显示ALMANAC模型能够较好地模拟冬小麦的叶面积指数和产量。叶面积指数的模拟结果与实测结果的比值为1.0552,可决系数R2为0.7021;生物量模拟的最大误差为-6.01%,经济产量模拟的最大误差为-5.41%。模型还可以揭示影响冬小麦生长的主要胁迫因素。     

基于LS-DYNA的交错扇形深孔崩落法排间间隔时间优化研究

为了同时解决"隐患资源高效回收"和"空区隐患安全治理"这对矛盾问题,提出交错扇形深孔崩落法;采用室内试验和数值模拟相结合的方法,根据交错扇形布孔形式建立数值计算模型,按照1#矿体岩石的物理力学指标确定模型材料参数,采用LS-DYNA动力仿真软件优选扇形排间间隔时间.研究结果表明:当采空一区排间间隔为100 ms时,岩石...     

模拟实验在四川炼油厂环境影响评价中的应用

为了研究拟建炼油厂表层土壤渗透情况及对特征污染物油的吸附和截留情况 ,实施了渗水实验 ,每隔30min测定一次渗水量 ,渗水实验时间为3h。还实施了土柱淋滤实验 ,土柱长度1.2m ,直径30cm ,装填高度1m ,土柱为五层 ,按层测定实验前后土壤中的含油量。实验结果表明 :预计事故排放及短时的含油污水泄漏 ,将不会对地下水环境质量造成大的影响。     

DEVELOPMENT OF A GIS‐BASED FLOOD INFORMATION SYSTEM FOR FLOODPLAIN MODELING AND DAMAGE CALCULATION1

ABSTRACT: This work presents a flexible system called GIS‐based Flood Information System (GFIS) for floodplain modeling, flood damages calculation, and flood information support. It includes two major components, namely floodplain modeling and custom designed modules. Model parameters and input data are gathered, reviewed, and compiled using custom designed modules. Through these modules, it is possible for GFIS to control the process of flood‐plain modeling, presentation of simulation results, and calculation of flood damages. Empirical stage‐damage curves are used to calculate the flood damages. These curves were generated from stage‐damage surveys of anthropogenic structures, crops, etc., in the coastal region of a frequently flooded area in Chia‐I County, Taiwan. The average annual flood damages are calculated with exceedance probability and flood damages for the designed rainfalls of 2, 5, 10, 25, 50, 100, and 200 year recurrence intervals with a duration of 24 hours. The average annual flood depth in this study area can also be calculated using the same method. The primary advantages of GFIS are its ability to accurately predict the locations of flood area, depth, and duration; calculate flood damages in the floodplain; and compare the reduction of flood damages for flood mitigation plans.