A comparison of model choice strategies for logistic regression

Purpose:The purpose of this study is to develop and compare model choice strategies in context of logistic regression.Model choice means the choice of the covariates to be included in the model.Design/methodology/approach:The study is based on Monte Carlo simulations.The methods are compared in terms of three measures of accuracy:specificity and two kinds of sensitivity.A loss function combining sensitivity and specificity is introduced and used for a final comparison.Findings:The choice of method depends on how much the users emphasize sensitivity against specificity.It also depends on the sample size.For a typical logistic regression setting with a moderate sample size and a small to moderate effect size,either BIC,BICc or Lasso seems to be optimal.Research limitations:Numerical simulations cannot cover the whole range of data-generating processes occurring with real-world data.Thus,more simulations are needed.Practical implications:Researchers can refer to these results if they believe that their data-generating process is somewhat similar to some of the scenarios presented in this paper.Alternatively,they could run their own simulations and calculate the loss function.Originality/value:This is a systematic comparison of model choice algorithms and heuristics in context of logistic regression.The distinction between two types of sensitivity and a comparison based on a loss function are methodological novelties.

A Cautionary Note on the Application of GIS in Spatial Optimization Modeling

Spatial optimization as part of spatial modeling has been facilitated significantly by integration with GIS techniques. However, for certain research topics, applying standard GIS techniques may create problems which require attention. This paper serves as a cautionary note to demonstrate two problems associated with applying GIS in spatial optimization, using a capacitated p-median facility location optimization problem as an example. The first problem involves errors in interpolating spatial variations of travel costs from using kriging, a common set of techniques for raster files. The second problem is inaccuracy in routing performed on a graph directly created from polyline shapefiles, a common vector file type. While revealing these problems, the paper also suggests remedies. Specifically, interpolation errors can be eliminated by using agent-based spatial modeling while the inaccuracy in routing can be improved through altering the graph topology by splitting the long edges of the shapefile. These issues suggest the need for caution in applying GIS in spatial optimization study.

Estimation and mapping of water erosion and soil loss:Application of Gavrilovic erosion potential model(EPM)using GIS and remote sensing in the Assif el mal Watershed,Western high Atlas

Water erosion is a serious problem that leads to soil degradation,loss,and the destruction of structures.Assessing the risk of erosion and determining the affected areas has become crucial in order to understand the main factors influencing its evolution and to minimize its impacts.This study focuses on evaluating the risk of erosion in the Assif el mal watershed,which is located in the High Atlas Mountains.The Erosion Potential Model(EPM)is used to estimate soil losses depending on various parameters such as lithology,hydrology,topography,and morphometry.Geographic information systems and remote sensing techniques are employed to map areas with high erosive potential and their relationship with the distribution of factors involved.Different digital elevation models are also used in this study to highlight the impact of data quality on the accuracy of the results.The findings reveal that approximately 59%of the total area in the Assif el mal basin has low to very low potential for soil losses,while 22%is moderately affected and 19.9%is at high to very high risk.It is therefore crucial to implement soil conservation measures to mitigate and prevent erosion risks.

Developing a GIS Audit Framework in the Context of Information Technology though a Reductive Model Approach

A GIS audit framework is necessary considering the diverse nature of GIS with regard to components, applications and industry. In practice, checklists are generated during the audit process based on specific objectives. There is no standardized list of items that can be used as a reference. The purpose of this study was to develop a GIS audit framework as a foundation for GIS audits. The framework provides that comprehensive approach to various GIS aspects during the audit process. The design builds on a developed conceptual framework where most significant categories of GIS audit parameters namely data quality, software utilization, GIS competency and procedures (work flows) were identified. The study adopted a reductive model approach to simplify the complexity associated with each category of GIS audit parameter. The resultant audit elements for each category are organized in a matrix that forms an integral part of the framework. The columns comprise audit goal, audit questions and audit subjects as indicators which are qualitatively measured. The rows comprise the parameters (data quality, software utilization, personnel competency and procedure (workflows)). To use the framework, an auditor only needs to create an audit checklist that consists of particular parameters and indicators from the framework depending on audit objective. As part of an on-going research, the next step will involve validating the framework through a mock testing process.

基于GIS的公交换乘网络构建及可达性分析

为了提高公交换乘效率、优化公交系统,基于GIS软件构建公交换乘网络,运用该网络对换乘可达性进行了测度和分析.结合Space-P模型和网络分析法,以拉萨市城关区为研究区域,基于公交线路路径、站点、交叉口等基本信息构建同站换乘子网络.结合公交站点服务范围、步行通道路径、交叉口等信息构建异站换乘子网络.二者协同实现了基于ArcGIS的公交换乘网络构建,并依据该网络对公交线路的乘客在车时间和换乘系数进行测度和分析.结果表明:构建的换乘网络能够对乘客在车时间进行良好的测度,乘客在车时间最大值为68.68 min,最小值为2.00 min,乘客换乘在车时间平均值为29.90 min.该换乘网络能够对换乘系数进行良好的测度,得到有效换乘线路90 300条,换乘系数最大为4条(线路为62条),最小为0条(线路为1 354条).采用可达性度量模型,可实现对公交站点时间可达性和换乘可达性的良好测度和分析.

基于GIS技术的区域多尺度空间数据集成方法

区域多尺度空间数据,其量较大,其来源、格式、特点、性质不同,数据在逻辑上或物理上的有机集中比较困难,容易导致集成路径拥塞,集成效率下降。为此,提出了一种基于GIS技术的区域多尺度空间数据集成方法。利用GIS技术搭建区域多尺度空间数据挖掘架构,结合数据转换矩阵构建多尺度空间数据库。根据多尺度空间数据库中拥塞窗口状态集合,采用不同策略对数据集成路径进行拥塞控制,通过确定理想集成效率而选择多尺度空间数据集成路径。计算不同集成路径上空间数据特征向量之间的紧密度,结合相异度阈值和空间数据权重构建数据集成函数,实现区域多尺度空间数据集成。实验结果表明:所给方法在有、无人工干预的情况下,集成延时分别控制在7 min以内和5 min以内,数据集成效率较高。

Mayr电弧模型下GIS中快速暂态过电压的仿真分析

SF6气体绝缘封闭组合开关(GIS)中隔离开关进行分合母线时,产生快速暂态过电压(VFTO),幅值高且上升速率极快,威胁GIS及相邻设备的绝缘。选取某800 kV GIS隔离开关分合母线的试验电路为研究对象,采用电磁暂态程序(EMTP/ATP)进行建模仿真,隔离开关燃弧时采用Mayr电弧模型,分析其对VFTO的影响,得出考虑Mayr电弧模型时操作隔离开关、断路器侧隔离开关及变压器侧隔离开关的电压波形,并与考虑时变电阻模型的VFTO进行对比。对VFTO波形进行离散傅里叶分析,得到过电压频率、幅值的变化特征,研究结果为GIS绝缘设计提供参考。

基于GIS与Scoops 3D的水动力型滑坡区域稳定性分析

库岸边坡在库水位变动、降雨等水动力因素的作用下易发生水动力型滑坡,进而威胁库区居民生命及财产安全。以某流域HD和DHQ库段为主要研究区段,在对已有滑坡点进行地质调查和遥感解译的基础上,将ArcGIS的空间分析与三维斜坡稳定性分析模型(Scoops 3D)相结合,对研究区段的潜在滑面进行系统的三维搜索及识别,并基于GIS数据与室内试验等确定计算参数,对天然和暴雨两种工况下的区域滑坡稳定性进行评价比较。结果表明:(1)研究区历史滑坡点分布与基础地质环境、岩土体强度指标参数有很强的相关性;(2)天然工况下,非稳定区主要分布在DHQ坝区、迤场、DH坝址、拉巴铁、宝塔河以及甸尾附近;(3)暴雨工况下,非稳定区面积较天然工况有显著的增大,DHQ坝址、营盘镇、甸尾、HD坝址附近有较为密集的分布;(4)暴雨工况下模型计算的非稳定区与历史滑坡点的分布特征基本一致。由此可见,三维斜坡稳定性分析模型可以较为准确模拟不同工况下滑坡稳定性,且易发程度区分明显,稳定性评价结果在一定程度上反映了研究区段的稳定性时空分布。

基于BIM与GIS的水利水电工程开发设计应用研究

为了解决水利水电项目建设中任务量大、专业技能多、操作难度高、环境干扰严重的问题,往往要进行多次论证和优化工程步骤,保证施工质量。采用BIM(Building Information Modeling)+GIS(Geographic Information System)技术对水利建筑模型进行优化,并对建筑进行外观设计,为模型的搭建提供坚实基础。结果表明,在水利水电项目建设过程中,以BIM+GIS技术模型为基础可快速模拟待查找的工程进度,有利于管控工程资金和监督工程实施进度,可以大幅度提升水利项目的信息化程度。

二三维一体化GIS Server在城市信息模型(CIM)中的应用

城市信息模型(CIM)是新型智慧城市的数字基础设施和城市数字化转型的关键抓手,而无缝集成二维地理信息、三维模型和建筑信息模型(BIM)等实现二三维一体化是建设城市信息模型(CIM)基础平台中的关键技术。本文在分析研究CIM平台关键技术基础上提出了一套跨平台、自主化、界面化、B/S网络化的二三维一体化GIS Server解决方案,重点介绍该系统的总体框架及关键技术,并展示了其在城市信息模型(CIM)中的应用成效,为CIM基础平台的建设提供借鉴。

基于AHP-GIS的建筑垃圾逆向物流产业园选址研究

各类新旧建筑在建造和拆除过程中会产生大量建筑垃圾,从而给建筑垃圾的管理带来巨大压力。为了有效管理建筑垃圾和实现建筑垃圾逆向物流的系统化、规模化、高效化,运用系统动力学理论与方法,构建了建筑垃圾逆向物流SD模型,并对建筑垃圾逆向物流综合效益进行了分析。结合产业园选址要求,从经济、环境、社会3个维度,选取10个影响因素,构建了建筑垃圾逆向物流产业园综合效益选址指标体系。通过AHP确定指标权重,并运用ArcGIS软件对指标图层进行叠加,从而实现建筑垃圾逆向物流产业园的选址。以西安市为例,利用ArcGIS软件中欧氏距离分析、重分类分析和栅格计算器等功能模块分析了各指标的适宜性,得到了西安市建筑垃圾逆向物流产业园的最佳选址区域,验证了模型的可行性。该选址方法可为国内其他城市的相关规划提供参考。

基于GIS和SWMM的西安市北郊片区排涝模拟与排水系统优化

为解决西安市北郊河道超载风险问题,通过SWMM和GIS技术构建管网-泵站-河道耦合模型,在不同设计降雨重现期(1、2、5、10、20、50年)下对该区域排水系统进行模拟,进而分析下游河道水位变化规律并提出雨水分流调配与调整泵站调度的协同优化措施。结果显示:在5、10、20和50年降雨重现期下,随着降雨峰值的到达,整个系统88%的排口都存在顶托现象,最长持续时间160min。在重现期为1、2、5和10年降雨条件下,协同优化的措施使得河道峰值流量分别下降了17.6%、4.9%、3.7%和2.6%,河道水位平均下降了35cm,排水系统的超载节点分别减少了16.7%、31.4%、34.2%和27.5%,超载管段的数量分别减少了25.0%、28.6%、30.8%和25.3%。

基于GIS技术的山地小城镇雨洪灾害风险评估

在快速城镇化和工业化背景下,城市的自然灾害风险日益暴露,尤其是雨洪灾害问题日益突出。针对巩义市近年来不断发生的洪涝灾害,基于自然灾害风险评估理论,构建以致灾因子危险性、孕灾环境孕险性、承灾体易损性、防灾减灾能力为评价因子的雨洪灾害风险模型,共选取14个指标进行定量分析,运用SCS模型和GIS空间分析功能,最终得出巩义市雨洪灾害综合风险区划图。结果表明:巩义市米河镇、回郭镇、芝田镇、孝义街道等地区致灾因子危险性较大;北部、西部和东部包括河洛镇、孝义街道、回郭镇、芝田镇、米河镇等孕灾环境孕险性较高;西部和中部承灾体易损性较大,包括回郭镇、芝田镇、站街镇等;北部整体防灾减灾能力较强,包括站街镇、紫荆路街道等地区。综合来说,巩义市雨洪灾害总体风险等级较高,高风险区主要分布在中部偏北和西部,呈带状分布。

Parameters Calibration of the GISSMO Failure Model for SUS301L-MT

With the development of the rail transit industry,more attention has been paid to the passive safety of rail vehicles.Structural damage is one of the main failure behaviors in a rail vehicle collision,but it has been paid little attention to in past research.In this paper,the quasi-static fracture experiments of SUS301L-MT under different stress states were carried out.The mechanical fracture properties of this material were studied,and the corresponding finite element simulation accuracy was improved to guide the design of vehicle crashworthiness.Through the tests,the fracture behavior of materials with wide stress triaxiality was obtained,and each specimen’s fracture locations and fracture strains were determined.Parameters of a generalized incremental stress state dependent damage model(GISSMO)of the material were calibrated,and the model’s accuracy was verified with test results from a 45°shear specimen.The GISSMO failure model accurately reflected the fracture characteristics of the material.The mesh dependency of this model was modified and discussed.The results show that the simulation agrees well with experimental data for the force-displacement curve after correction,but the strain distribution needs to be further studied and improved.

半山区滑坡灾害易发性评价-GIS支持下基于CF与Logistic耦合模型

【研究目的】会泽县地处云贵高原半山区,地质灾害频发。以滑坡灾害为研究对象,采用耦合模型开展易发性评价,以期探索适合云贵高原半山区地理环境特点的评价模型。【研究方法】选取地貌、坡度及坡向等12个评价因子,应用确定性系数(CF)与Logistic耦合模型计算滑坡灾害发生概率,基于GIS的自然间断法评价结果等级。通过合理性检验与敏感性检验验证模型。【研究结果】(1)高程、距断层距离、距道路距离、坡度对会泽县滑坡易发性影响较为显著。(2)稳定、低、中和高的面积分别为46.25 km^(2)(0.61%)、3095.41 km^(2)(52.77%)、1296.64 km^(2)(21.94%)和1446.53 km^(2)(21.94%)。(3)确定性系数(CF)与Logistic耦合模型通过合理性检验,AUC值为0.927。【结论】(1)滑坡中-高易发区位于会泽县西南部及东北部部分地区,低易发区及稳定区位于西北部、中部和南部地区。(2)采用CF-Logistic耦合模型开展滑坡灾害易发性评价具有较高合理性和准确性。

小型化GIS隔板绝缘子电场优化设计

为解决小型化SF_(6)气体绝缘金属封闭开关设备(gas insulated metal-enclosed switchgear,GIS)沿面闪络频发的问题,以交流220 kV GIS隔板绝缘子为研究对象,基于电场设计准则、沿面闪络事故原因分析和电场的有限元分析计算结果,提出小型化GIS隔板绝缘子的电场设计中场强控制的关键点。研究发现:①目前GIS绝缘件的电场设计准则没有考虑两因素对沿面绝缘的影响,一是SF_(6)气体中沿面闪络电压比气体间隙击穿电压分散性大,二是特快速瞬态过电压对附着金属微粒盆式绝缘子沿面的绝缘威胁比标准雷电过电压大;②为提高盆式绝缘子的沿面绝缘强度,不仅要优化电场分布使得放电不沿面发展,还要降低微粒积聚区域的电场强度提升沿面的金属微粒容错性;③盆式绝缘子具有较好的金属微粒容错性,更适用于金属微粒较多的开关气室,相比之下,平盘绝缘子更适用于金属微粒相对较少的母线气室;④在沿面电场强度校核中,盆式绝缘子需重点关注绝缘子凹面电场强度最大值,平盘绝缘子则需关注沿面接地端电场强度最大值;⑤在内绝缘校核方面,2种绝缘子均需要关注内嵌电极表面电场强度的控制。

The simulation of LUCC based on Logistic-CA-Markov model in Qilian Mountain area, China

The Qilian mountain area was examined for using the Logistic-CA-Markov coupling model combined with GIS spatial analyst technology to research the transformation of LUCC, driving force system and simulate future tendency of variation. Results show that： （1） Woodland area decreased by 12.55%, while grassland, cultivated land, and settlement areas increased by 0.22%, 7.92%, and 0.03%, respectively, from 1986 to 2014. During the period of 1986 to 2000, forest degradation in the middle section of the mountain area decreased by 1,501.69 km2. Vegetation cover area improved, with a net increase of grassland area of 38.12 km2 from 2000 to 2014. （2） For constructing the system driving force, the best simulation scale was 210m×210m. Based on logistic regression analysis, the contribution （weight） of composite driving forces to land use and cover change was obtained, and the weight value was more objectively compared with AHP and MCE method. （3） In the natural scenarios, it is predicted that land use and cover distribution maps of Qilian mountain area in 2028 and 2042, and the Lee-Sallee index test was adopted. Over the next 27 years （2015-2042）, farmland, woodland, grassland, settlement areas show an increasing trend, especially settlements with an obvious change of 0.56%. The area of bare land will decrease by 0.89%. Without environmental degradation, tremendous structural change of LUCC will not occur, and typical characteristic of the vertical zone of the mountain would remain. Farmland and settlement areas will increase, but only in the vicinity of Qilian and Sunan counties.

基于Cesium的铁路桥梁三维GIS场景构建研究

随着铁路工程领域数字化、信息化、智能化不断推进,将铁路工程信息模型与大范围真实地理环境融合,通过互联网在线可视化与分布式多终端共享展示铁路工程三维场景成为发展趋势。本文基于开源Cesium平台,从铁路工程三维地理场景构建,铁路桥梁BIM模型参数化建模、融合与定位,到铁路三维GIS场景交互与应用功能开发,设计了面向铁路工程空间信息模型的三维GIS场景构建方案,实现了铁路桥梁BIM模型三维GIS场景的三维漫游、空间查询、地形分析、日照分析、剖切分析等功能应用,为铁路数字工程BIM+GIS开放共享应用管理和展示提供了技术路径。

Interrelations Between Socio-economic Development and Environmental Quality:a Simulation Integrating System Dynamics Models with GIS

System dynamics (SD) theory has long been deployed in modeling complex non-linear interrelationships but, so far it has not been common to do the kind of modeling in support of bringing environmental sustainability policies to practice. This is largely because the challenge of including spatial data has not yet been well met. Potential for adoption of SD and GIS methods in combination is exemplified with the results of a decision-support exercise designed for simulation and prediction of the dynamic inter-relationships between socio-economic development and environmental quality for the "Wen, Pi, Du" county in Sichuan province, southwestern China.

Simulation and Prediction of Soil Organic Carbon Dynamics in Jiangsu Province Based on Model and GIS Techniques

Based on the databases of soils, meteorology, crop production, and agricultural management, changes in the soil organic carbon (SOC) of agro ecosystems in Jiangsu Province were simulated by using a soil organic carbon model with a linkage of GIS. Four data sets of soil organic carbon measured from various field experiments in Jiangsu Province were used to validate the model. It was demonstrated that the model simulation in general agreed with the field measurements. Model simulation indicated that the SOC content in approximately 77% of the agricultural soils in Jiangsu Province has increased since the Second National Soil Survey completed in the early 1980s. Compared with the values in 1985, the SOC content in 2000 was estimated to increase by 1.03.0 g kg 1 for the north and the coastal areas of the province, and by 3.55.0 g kg 1 for the region of Tai Lake in the south. A slight decrease (about 0.51.5 g kg 1 ) was estimated for the central region of Jiangsu Province and the Nanjing Zhenjiang hilly area. Model prediction for 2010 A.D. under two scena rios, i.e., with 30 and 50% of the harvested crop straw incorporation, suggested that the SOC in Jiangsu Province would increase, and thus that the agricultural soils would have potential as organic carbon storage. The incorporation of crop straw into soils is of great benefit to increase soil carbon storage, consequently to benefit the control of the rise of atmospheric CO 2 concentration and to maintain the sustainable development of agriculture.