标题：Integrative Analysis of Spatial Heterogeneity and Overdispersion of Crime with a Geographically Weighted Negative Binomial Model
作者：Jianguo Chen, Lin Liu , Luzi Xiao, Chong Xu and Dongping Long
简介：Negative binomial (NB) regression model has been used to analyze crime in previous studies. The disadvantage of the NB model is that it cannot deal with spatial effects. Therefore, spatial regression models, such as the geographically weighted Poisson regression (GWPR) model, were introduced to address spatial heterogeneity in crime analysis. However, GWPR could not account for overdispersion, which is commonly observed in crime data. The geographically weighted negative binomial model (GWNBR) was adopted to address spatial heterogeneity and overdispersion simultaneously in crime analysis, based on a 3-year data set collected from ZG city, China, in this study. The count of residential burglaries was used as the dependent variable to calibrate the above models, and the results revealed that the GWPR and GWNBR models performed better than NB for reducing spatial dependency in the model residuals. GWNBR outperformed GWPR for incorporating overdispersion. Therefore, GWNBR was proven to be a promising tool for crime modeling.
标题：Understanding Land Subsidence Along the Coastal Areas of Guangdong, China, by Analyzing Multi-Track MTInSAR Data
作者：Yanan Du, Guangcai Feng, Lin Liu, Haiqiang Fu, Xing Peng and Debao Wen
简介：Coastal areas are usually densely populated, economically developed, ecologically dense, and subject to a phenomenon that is becoming increasingly serious, land subsidence. Land subsidence can accelerate the increase in relative sea level, lead to a series of potential hazards, and threaten the stability of the ecological environment and human lives. In this paper, we adopted two commonly used multi-temporal interferometric synthetic aperture radar (MTInSAR) techniques, Small baseline subset (SBAS) and Temporarily coherent point (TCP) InSAR, to monitor the land subsidence along the entire coastline of Guangdong Province. The long-wavelength L-band ALOS/PALSAR-1 dataset collected from 2007 to 2011 is used to generate the average deformation velocity and deformation time series. Linear subsidence rates over 150 mm/yr are observed in the Chaoshan Plain. The spatiotemporal characteristics are analyzed and then compared with land use and geology to infer potential causes of the land subsidence. The results show that (1) subsidence with notable rates (>20 mm/yr) mainly occurs in areas of aquaculture, followed by urban, agricultural, and forest areas, with percentages of 40.8%, 37.1%, 21.5%, and 0.6%, respectively; (2) subsidence is mainly concentrated in the compressible Holocene deposits, and clearly associated with the thickness of the deposits; and (3) groundwater exploitation for aquaculture and agricultural use outside city areas is probably the main cause of subsidence along these coastal areas.
标题：Safety perceptions among African migrants?in Guangzhou and Foshan, China
作者：Guangwen Song, Lin Liu*, Shenjing He, Liang Cai, Chong Xu
简介：Safety perceptions have received considerable attention in criminology and geography, yet few studies have looked into international migrants to developing countries. This study proposes a conceptual framework to account for migrant-specific characteristics and examines this framework with a sample of African migrants in Guangzhou and Foshan, China. Results from multilevel ordered logistic regression show that predictors of their perceptions of property safety and personal safety are different. Consistent with literature, their satisfaction with income in China, family support, and prior victimization experience strongly predict migrants' sense of security. Besides, we further find that perceived discrimination, indicative of migrants' acculturation process, decrease their sense of safety, and passport-check experience, indicative of migrants' relationship with local police, significantly lowers their personal safety perception. Migrants from countries with worse security conditions perceive a higher personal safety in China. Social trust, especially migrants' trust in Chinese businessmen and religious fellows are also associated with their security perception. The effect of geography is also examined but no substantial variation in safety perceptions is observed among four Diasporas. Findings of this study provide insight that may help reevaluate policies affecting daily life of African migrants and their perception of safety.
标题：Assessing the mitigation effect of deep tunnels on urban flooding: a case study in Guangzhou, China
作者："Huabing Huang, Lin Zhang, Lin Liu *, Xianwei Wang*, Xin Wang , Cuilin Pana, and Dashan Wang"
简介：There are growing demands of deep tunnels to mitigate the severe urban ?ooding by providing a large storage capacity for excess storm runo?. This study aims to assess the ?ooding mitigation e?ect of a deep tunnel system proposed in the old downtown of Guangzhou, China, and to quantify the ?ooding volume di?erence by two storm hyetographs, the Chicago curve and the Improved Hu? curve. Results show that the ?ooding volume is signi?cantly reduced by a minimum of 19% and a maximum of 42% under design storms of 10- and 0.5-year return periods, respectively, when the deep tunnel system is constructed. There is a distinct spatial pattern for the mitigation e?ect. The best mitigation is in the west and the immediate north of the main tunnel, whereas the east does not show signi?cant mitigation. Moreover, the actual ?ooding risk is likely underestimated when the Chicago curve is employed to design the storms.
标题：Assessing the relationship between anthropogenic heat release warming and building characteristics in Guangzhou: A sustainable development perspective
作者：Cao, Zheng; Wu, Zhifeng; Liu, Lin; Chen, Yinbiao; Zou, Yuxuan;
简介：We assessed the spatial heterogeneity of warming due to total anthropogenic heat release (AHR) and building anthropogenic heat release under different heat release scenarios and its relationship with building properties in the highly urbanized portion of Guangzhou using the Weather Research and Forecasting (WRF) model. The simulation results show that different AHR scenarios result in different temperature rise outcomes. A rise of 0.40 °C and 0.23 °C results from a normal total AHR scenario and normal building AHR scenario, while a rise of 0.71 °C and 0.41 °C arises when total AHR and building AHR is doubled. This indicates that more anthropogenic heat results in a more serious warming effect. Moreover, the spatial heterogeneity of the AHR-caused tempera-ture rise is affected by the building area. The AHR-derived warming effect is most serious in high-height-medium-density (H-M) and high-height-high-density (H-H) building areas, where temperature rose by 0.36 °C and 0.34 °C due to building AHR under two AHR scenarios, while it was least serious in low-height-high-density (L-H) and high-height-low-density (H-L) areas, where temperature rose by 16 °C and 0.25 °C under two building AHR scenarios. When AHR is doubled, the hot spot of AHR-derived warming tends to become.
标题：A Depression-Based Index to Represent Topographic Control in Urban Pluvial Flooding
作者：Huangbing Huang, Xi Chen*, Xianwei Wang*, Xina Wang, Lin Liu
简介：Extensive studies have highlighted the roles of rainfall, impervious surfaces, and drainage systems in urban pluvial flooding, whereas topographic control has received limited attention. This study proposes a depression-based index, the Topographic Control Index (TCI), to quantify the function of topography in urban pluvial flooding. The TCI of a depression is derived within its catchment, multiplying the catchment area with the slope, then dividing by the ponding volume of the depression. A case study is demonstrated in Guangzhou, China, using a 0.5 m-resolution Digital Elevation Model (DEM) acquired using Light Detection and Ranging (LiDAR) technology. The results show that the TCI map matches well with flooding records, while the Topographic Wetness Index (TWI) cannot map the frequently flooded areas. The impact of DEM resolution on topographic representation and the stability of TCI values are further investigated. The original 0.5 m-resolution DEM is set as a baseline, and is resampled at resolutions 1, 2, 5, and 10 m. A 1 m resolution has the smallest TCI deviation from those of 0.5 m resolution, and gives the optimal results in terms of striking a balance between computational e?ciency and precision of representation. Moreover, the uncertainty in TCI values is likely to increase for small depressions.
标题：Crime Geographical Displacement: Testing Its Potential Contribution to Crime Prediction
作者：Zengli Wang, Lin Liu*, Hanlin Zhou and Minxuan Lan
简介：Crime geographical displacement has been examined in many Western countries. However, little is known about its existence, distribution, and potential predictive ability in large cities in China. Compared to the existing research, this study contributes to the current research in three ways. (1) It provides confirmation that crime geographical displacement exists in relation to burglaries that occur in a large Chinese city. (2) A crime geographical displacement detector is proposed, where significant displacements are statistically detected and geographically displayed. Interestingly, most of the displacements are not very far from one another. These findings confirm the inferences in the existing literature. (3) Based on the quantitative results detected by the crime geographical displacement detector, a crime prediction method involving crime geographical displacement patterns could improve the accuracy of the empirical crime prediction method by 7.25% and 3.1 in the capture rate and prediction accuracy index (PAI), respectively. Our current study verifies the feasibility of crime displacement for crime prediction. The feasibility of the crime geographical displacement detector and results should be verified in additional areas.
标题：Characteristics of Heavy Storms and the Scaling Relation with Air Temperature by Event Process-Based Analysis in South China
作者：Cuilin Pan, XianweiWang* , Lin Liu *, DashanWang and Huabing Huang
简介：The negative scaling rate between precipitation extremes and the air temperature in tropic and subtropic regions is still a puzzling issue. This study investigates the scaling rate from two aspects, storm characteristics (types) and event process-based temperature variations. Heavy storms in South China are developed by different weather systems with unique meteorological characteristics each season, such as the warm-front storms (January), cold-front storms (April to mid-May), monsoon storms (late May to June), convective storms, and typhoon storms (July to September). This study analyzes the storm characteristics using the hourly rainfall data from 1990 to 2017; compares the storm hyetographs derived from the one-minute rainfall data during 2008–2017; and investigates the interactions between heavy storms and meteorological factors including air temperature, relative humidity, surface pressure, and wind speed at 42 weather stations in Guangzhou during 2015–2017. Most storms, except for typhoon and warm-front storms, had a short duration (3 h) and intense rates (~13 mm/h) in Guangzhou, South China. Convective storms were dominant (50%) in occurrence and had the strongest intensity (15.8 mm/h). Storms in urban areas had stronger interactions with meteorological factors and showed different hyetographs from suburban areas. Meteorological factors had larger variations with the storms that occurred in the day time than at night. The air temperature could rise 6 ?C and drop 4 ?C prior to and post-summer storms against the diurnal mean state. The 24-h mean air temperature prior to the storms produced more reliable scaling rates than the naturally daily mean air temperature. The precipitation extremes showed a peak-like scaling relation with the 24-h mean air temperature and had a break temperature of 28 ?C. Below 28 ?C, the relative humidity was 80%–100%, and it showed a positive scaling rate. Above 28 ?C, the negative scaling relation was likely caused by a lack of moisture in the atmosphere, where the relative humidity decreased with the air temperature increase.
标题：Discerning the Effects of Rural to Urban Migrants on Burglaries in ZG City with Structural Equation Modeling
作者：Fangye Du, Lin Liu *, Chao Jiang*, Dongping Long and Minxuan Lan
简介：Both rural to urban migration and urban crime are well researched topics in China. But few studies have attempted to explore the possible relationships between the two. Using calls for service data of ZG city in 2014, the Sixth Census data in 2010, this study examines relationships between migrants and crime by using structural equation models. Two hypotheses were tested: (1) the distribution of migrants has direct effects on the spatial distribution of burglaries, and (2) migrants also indirectly affect burglary rate through mediating variables such as residential mobility and socio-economic disadvantage of their resident communities. The results showed that migrants have significant direct and indirect effects contributing to burglaries, although the indirect effect is much larger than the direct effect, indicating that community characteristics play a more important role than the migrants themselves.
标题：Evaluation of TMPA 3B42V7, GPM IMERG and CMPA precipitation estimates in Guangdong Province, China
作者：Dashan Wang, Xianwei Wang*, Lin Liu*, Dagang Wang, Huabing Huang, Cuilin Pan
简介：Three satellite rainfall products (3B42V7, IMERGV05/V04/V03, and China hourly Merged Precipitation Analysis product) are evaluated using measurements from a dense rain gauge network as reference in Guangdong Province, China from April 2014 to December 2016. The three products are compared with gauges in annual, monthly, daily and hourly accumulation, and at gridded, sub-regional and regional scales. An error decomposition approach is employed to separate the total bias into Hit, Miss and False components. Overall, the CMPA estimate is the best in agree-ment with gauge observations. The improvement of IMERGV05 over 3B42V7 is notable, especially in reducing the hit bias and missed precipitation, resulting in better detection of the light rain and heavy rain. The enhancement of IMERG is more significant at the 3-hr scale than daily scale. IMERGV05 shows better perfor-mance than its previous versions especially for IMERGV03, which had an abnor-mal blocky pattern mainly from July to September over the Pearl River Delta area. The three products have different error characteristics and show large spatial varia-tions. 3B42V7 and IMERG have large areas of overestimation in the mountainous areas and underestimation in the coastal areas, while CMPA is characterized by an alternate distribution of small positive and negative values. The overestimation of precipitation is partially attributed to the positive hit biases that falsely estimate the precipitation from moderate intensity to heavy rainfall by the three products.
标题：Crime Feeds on Legal Activities: Daily Mobility Flows Help to Explain Thieves’ Target Location Choices
作者：Guangwen Song, Wim Bernasco, Lin Liu*, Luzi Xiao, Suhong Zhou, Weiwei Liao
简介：the legal routine activities of offenders and unguarded victims. Based on this assumption,the present study investigates whether daily mobility flows of the urban population helppredict where individual thieves commit crimes.Methods Geocoded tracks of mobile phones are used to estimate the intensity of populationmobility between pairs of 1616 communities in a large city in China. Using data on3436 police-recorded thefts from the person, we apply discrete choice models to assesswhether mobility flows help explain where offenders go to perpetrate crime.Results Accounting for the presence of crime generators and distance to the offender’s home location, we find that the stronger a community is connected by population flows to where the offender lives, the larger its probability of being targeted. Conclusions The mobility flow measure is a useful addition to the estimated effects of distance and crime generators. It predicts the locations of thefts much better than the presence of crime generators does. However, it does not replace the role of distance, suggesting that offenders are more spatially restricted than others, or that even within their activity spacesthey prefer to offend near their homes.
标题：Optimizing Mixed Pedestrian-Vehicle Evacuation via Adaptive Network Reconfiguration
作者：Qiuping Li, Shaobo Zhong, Zhixiang Fang, Lin Liu, Wei Tu, Biyu Chen
简介：Insuf?cient network capacity and con?icts between pedestrians and vehicles at roadway intersections can be critical obstacles to the operational ef?ciency of evacuation activities. Reducing pedestrian—vehicle con?ict points and expanding net-work capacities are two possible approaches to improving oper-ational ef?ciency, especially when network accessibility varies in different evacuation stages. This paper integrates two types of network recon?guration strategies, namely, the use of con-tra?ow lane reversal for road lanes and pedestrian walkways and time-dependent con?ict point elimination by separating pedestrian and vehicle ?ows with physical barriers at road intersections, to strategize pedestrian and vehicle moving direc-tions during a mass evacuation. A multiobjective optimization model is formulated to adaptively select the appropriate locations for barriers according to different evacuation phases, and the model is solved by a modi?ed genetic algorithm-based heuristic approach. An experiment on optimizing an urban regional evacuation network con?guration in the case of a toxic gas leak accident was carried out to validate the proposed model. The numerical results show an increase of approximately 15% in the maximum evacuee throughput and a reduction of approximately 65% in the average exposure risk of evacuees of the optimal plans compared with the uncontrolled plan.
标题：An Examination of Spatial Differences between Migrant and Native Offenders in Committing Violent Crimes in a Large Chinese City
作者：Jiaxin Feng, Lin Liu*, Dongping Long* and Weiwei Liao
简介：Immigrants and natives are generally comparable in committing violent crimes in many Western cities. However, little is known about spatial differences between internal migrant offenders and native offenders in committing violence in contemporary urban China. To address this gap, this research aims to explore spatial variation in violent crimes committed by migrant and native offenders, and examine different effects of ambient population, crime attractors, crime generators, and offender anchor points on these crimes. Offender data, mobile phone data, and points-of-interest (POI) data are combined to explain the crime patterns of these offenders who committed offenses and were arrested from 2012 to 2016 in a large Chinese city by using box maps and negative binomial regression models. It is demonstrated that migrant and native violent crimes vary enormously across space. Ambient population is only positively related to migrant violent crimes. Crime attractors and generators have more significant and stronger correlations with migrant violent crimes, while offender anchor points have a stronger association with native violent crimes. The results reveal that migrant offenders tend to be attracted by larger amounts of people and more affected by crime attractors and generators than native offenders.
标题：Structural Cities: Delimiting Retailing Center Boundaries and Their Hierarchical Characteristics in Urban China Based on GPS-Enabled Taxi Data
作者："Yun Nong, Suhong Zhou,* Lin Liu, Qiuping Li, Yinong Peng, and Xinhua Hao"
简介：Previous behavioral studies on urban structure have been limited by the scale, accuracy, or promptness in obtaining statistical data used for delimiting retail center boundaries and hierarchical analysis. Using a large amount of GPS-enabled taxi data from Guangzhou, China, this research attempts to delimit the boundaries of retailing centers and explore their hierarchical characteristics. The identified retailing centers are verified with economic census data, and the retailing hierarchical structure is identified through assessing trip summation, travel distance, and travel time. Among these indicators, trip summation reveals hierarchical characteristics best. The urban retailing hierarchical structure also reveals the centrality of urban Guangzhou.
标题：Combining GF-2 and RapidEye satellite data for mapping mangrove species using ensemble machine-learning methods
作者：Liheng Peng, Kai Liu, Jingjing Cao, Yuanhui Zhu, Fengshou Li and Lin Liu
简介：Mangrove forests are important constitutions for sustainable develop-ment of coastal ecosystems, and they are often mapped and monitored with remote sensing approaches. Satellite images allow detailed stu-dies of the distribution and composition of mangrove forests, and therefore facilitate the management and conservation of the ecosys-tems. The combination of multiple types of satellite images with di?erent spatial and spectral resolutions is helpful in mangrove forests extraction and mangrove species discrimination as it reduces sampling workload and increases classi?cation accuracies. In this study, the 1.0-m-resolution Gaofen-2 (GF-2) and the 5.0-m-resolution RapidEye-4 (RE-4) satellite images, acquired in February 2017 and November 2016 respectively, were used with ensemble machine-learning and object-oriented methods for mangroves mapping at both the community and species levels of the Qi’ao Island, Zhuhai, China. First, the mangroves on the island were segmented from the GF-2 image on a large scale, and then they were extracted combining with their digital elevation model (DEM) data. Second, the GF-2 image was further processed on a ?ne scale, in which object-oriented features from both the GF-2 and RE-4 images were extracted for each mangrove species. Third, it is followed bythemangrovespeciesclassi?cation process which involves three ensemble machine-learning methods: the adaptive boosting (AdaBoost), the random forest (RF) and the rotation forest (RoF). These three methods employed a classi?cation and regression tree (CART) as the base classi?er. The results show that the overall accuracy (OA) of mangrove area extraction on the Qi’ao Island with the auxiliary data,DEM,achieves98.76%(Kappacoe?cient (κ) = 0.9289). The fea-tures extracted by the GF-2 and RE-4 images were shown to be bene?cial for mangrove species discrimination. A maximum improve-ment in the OA of approximately 8% and a κκ of approximately 0.10 were achieved when employing RoF (OA = 92.01%, κ = 0.9016). Ensemble-learning methods can signi?cantly improve the classi?cation accuracy of CART, and the use of a bagging scheme (RF and RoF) is shown as a better way to map mangrove species than adaptive boost-ing (AdaBoost). In addition, RoF performed well in mangrove species classi?cation but it was not as robust as the RF, whose average OA and κκ were 80.59% and 0.7608, respectively, while the RoF’s were 77.45%and 0.7214, respectively, in the 10-fold cross-validation.
标题：A Survey of Mobile Laser Scanning Applications and Key Techniques over Urban Areas
作者：Yanjun Wang, Qi Chen,* , Qing Zhu, Lin Liu, Chaokui Li and Dunyong Zheng
简介：Urban planning and management need accurate three-dimensional (3D) data such as light detection and ranging (LiDAR) point clouds. The mobile laser scanning (MLS) data, with up to millimeter-level accuracy and point density of a few thousand points/m2, have gained increasing attention in urban applications. Substantial research has been conducted in the past decade. This paper conducted a comprehensive survey of urban applications and key techniques based on MLS point clouds. We first introduce the key characteristics of MLS systems and the corresponding point clouds, and present the challenges and opportunities of using the data. Next, we summarize the current applications of using MLS over urban areas, including transportation infrastructure mapping, building information modeling, utility surveying and mapping, vegetation inventory, and autonomous vehicle driving. Then, we review common key issues for processing and analyzing MLS point clouds, including classification methods, object recognition, data registration, data fusion, and 3D city modeling. Finally, we discuss the future prospects for MLS technology and urban applications.
标题：Identifying Mangrove Species Using Field Close-Range Snapshot Hyperspectral Imaging and Machine-Learning Techniques
作者：Jingjing Cao, Kai Liu*, Lin Liu*, Yuanhui Zhu, Jun Li and Zhi He
简介：Investigating mangrove species composition is a basic and important topic in wetland management and conservation. This study aims to explore the potential of close-range hyperspectral imaging with a snapshot hyperspectral sensor for identifying mangrove species under field conditions. Specifically, we assessed the data pre-processing and transformation, waveband selection and machine-learning techniques to develop an optimal classification scheme for eight mangrove species in Qi'ao Island of Zhuhai, Guangdong, China. After data pre-processing and transformation, five spectral datasets, which included the reflectance spectra R and its first-order derivative d(R), the logarithm of the reflectance spectra log(R) and its first-order derivative d[log(R)], and hyperspectral vegetation indices (VIs), were used as the input data for each classifier. Consequently, three waveband selection methods, including the stepwise discriminant analysis (SDA), correlation-based feature selection (CFS), and successive projections algorithm (SPA) were used to reduce dimensionality and select the effective wavebands for identifying mangrove species. Furthermore, we evaluated the performance of mangrove species classification using four classifiers, including linear discriminant analysis (LDA), k-nearest neighbor (KNN), random forest (RF), and support vector machine (SVM). Application of the four considered classifiers on the reflectance spectra of all wavebands yielded overall classification accuracies of the eight mangrove species higher than 80%, with SVM having the highest accuracy of 93.54% (Kappa=0.9256). Using the selected wavebands derived from SPA, the accuracy of SVM reached 93.13% (Kappa=0.9208). The addition of hyperspectral VIs and d[log(R)] spectral datasets further improves the accuracies to 93.54% (Kappa=0.9253) and 96.46% (Kappa=0.9591), respectively. These results suggest that it is highly effective to apply field close-range snapshot hyperspectral images and machine-learning classifiers to classify mangrove species.
标题：Analyzing Trends of Dike-Ponds between 1978 and 2016 Using Multi-Source Remote Sensing Images in Shunde District of South China
作者：Fengshou Li, Kai Liu* , Huanli Tang, Lin Liu * and Hongxing Liu
简介：Dike-ponds have experienced significant changes in the Pearl River Delta region over the past several decades, especially since China’s economic reform, which has seriously affected the construction of ecological environments. In order to monitor the evolution of dike-ponds, in this study we use multi-source remote sensing images from 1978 to 2016 to extract dike-ponds in several periods using the nearest neighbor classification method. A corresponding area weighted dike-pond invasion index (AWDII) is proposed to describe the spatial evolution of dike-ponds, both qualitatively and quantitatively. Furthermore, the evolution mechanisms of dike-ponds are determined, which can be attributed to both natural conditions and human factors. Our results show that the total area of dike-ponds in 2016 was significantly reduced and fragmentation had increased compared with the situation in 1978. The AWDII reveals that Shunde District has experienced three main phases, including steady development, rapid invasion and a reduction of invasion by other land use types. Most dike-ponds have now converted into built-up areas, followed by cultivated lands, mainly due to government policies, rural area depopulation, and river networks within Shunde. Our study indicates that the AWDII is applicable towards the evaluation of the dynamic changes of dike-ponds. The rational development, and careful protection, of dike-ponds should be implemented for better land and water resource management.
标题：Examining the relationship between neighborhood environment and residential locations of juvenile and adult migrant burglars in China
作者：Lin Liu?, Jiaxin Feng?, Fang Ren, Luzi Xiao
简介：Residential location of o?enders has been an important topic in the crime literature. However, prior research on o?ender residence pays little attention to the factor of age. Coupled with the rapid urbanization in China, many Chinese have moved from rural areas to urban areas and many burglaries are committed by these migrants, especially adult migrants. They need to choose their residences once they move to a new place. This study aims to examine the characteristics of neighborhood environment of migrant burglars' residential locations and how they di?er by age in a large city in China. The conceptual framework is based on social disorganization theory. In general, the spatial pattern of juvenile migrant burglars varies largely from those of adult migrant burglars. Juvenile migrant burglars mainly concentrate in urban areas including urban villages, while a large number of adult migrant burglars reside in urban villages and suburban villages. The results of a series of zero-in?ated negative binomial regression models reveal that a neighborhood with high residential instability is likely to attract more juvenile migrant burglars, while a socially disorganized neighborhood tends to include more adult migrant burglars. The residential characteristics of adult migrant burglars mostly agree with social dis-organization theory. These ?ndings can have important implications for burglary prevention and neighborhood safety.
标题：Systematic Comparison of Power Line Classification Methods from ALS and MLS Point Cloud Data
作者："Yanjun Wang, Qi Chen* , Lin Liu, Xiong Li *, Arun Kumar Sangaiah and Kai Li"
简介：Power lines classification is important for electric power management and geographical objects extraction using LiDAR (light detection and ranging) point cloud data. Many supervised classification approaches have been introduced for the extraction of features such as ground, trees, and buildings, and several studies have been conducted to evaluate the framework and performance of such supervised classification methods in power lines applications. However, these studies did not systematically investigate all of the relevant factors affecting the classification results, including the segmentation scale, feature selection, classifier variety, and scene complexity. In this study, we examined these factors systematically using airborne laser scanning and mobile laser scanning point cloud data. Our results indicated that random forest and neural network were highly suitable for power lines classification in forest, suburban, and urban areas in terms of the precision, recall, and quality rates of the classification results. In contrast to some previous studies, random forest yielded the best results, while Na?ve Bayes was the worst classifier in most cases. Random forest was the more robust classifier with or without feature selection for various LiDAR point cloud data. Furthermore, the classification accuracies were directly related to the selection of the local neighborhood, classifier, and feature set. Finally, it was suggested that random forest should be considered in most cases for power line classification.
标题：Theft from the person in urban China: assessing the diurnal effects of opportunity and social ecology
作者：Guangwen Song, Lin Liu*, Wim Bernascoe, Suhong Zhou, Luzi Xiao, Dongping Long
简介：Opportunity theories and ecological theories are commonly used to explain spatial crime patterns, but diurnal variations in these patterns have received little attention. Furthermore, the theories have been developed in Western countries, and it has remained unclear whether they are also applicable in China, and how their core concepts can be measured in the Chinese context. We use o?cial crime data from a large Chinese city to in-vestigate whether neighborhood rates of theft from the person are related to characteristics of the population (ecological perspective) and to the presence of transport and retail facilities that shape daily activities (oppor-tunity perspective). We test whether e?ects of these characteristics di?er between daytime and nighttime. Our ?ndings demonstrate that both theories are applicable to crime analysis in China, and that temporal variations should not be ignored. Furthermore, care is required regarding the operationalization of the concepts.
标题：Assessing the Influence of Prior on Subsequent Street Robbery Location Choices: A Case Study in ZG City, China
作者：Dongping Long, Lin Liu*, Jiaxin Feng, Suhong Zhou and Fengrui Jing
简介：The literature shows that offenders’ subsequent crime location choices are affected by their prior crime location choices. However, the published studies have focused on the influence of time and place of a previous crime, without testing the impact of whether the offender was arrested during the act of the prior crime. On the basis of the literature, this study further examines the influence of the prior robbery experiences on the subsequent street robbery location choices, by testing explicit hypotheses on how the time, place, and being arrested in the act of previous robberies affect a robber’s subsequent decisions of where to commit robberies. The data set used in this study includes 1262 detected robberies committed by 527 street robbers from the ZG City Public Security Bureau in China. Results of a mixed logit model demonstrate that prior street robbery experiences have a strong effect on subsequent street robbery location choices. A shorter time interval and less possibility of being arrested in the act of a prior street robbery significantly increase the likelihood of a robber returning to the previous location. However, the impact of distance of journey to prior crime location is not statistically significant.
标题：Object-Based Mangrove Species Classification Using Unmanned Aerial Vehicle Hyperspectral Images and Digital Surface Models
作者："Jingjing Cao, Wanchun Leng, Kai Liu*, Lin Liu* , Zhi He and Yuanhui Zhu"
简介：Mangroves are one of the most important coastal wetland ecosystems, and the compositions and distributions of mangrove species are essential for conservation and restoration efforts. Many studies have explored this topic using remote sensing images that were obtained by satellite-borne and airborne sensors, which are known to be efficient for monitoring the mangrove ecosystem. With improvements in carrier platforms and sensor technology, unmanned aerial vehicles (UAVs) with high-resolution hyperspectral images in both spectral and spatial domains have been used to monitor crops, forests, and other landscapes of interest. This study aims to classify mangrove species on Qi’ao Island using object-based image analysis techniques based on UAV hyperspectral images obtained from a commercial hyperspectral imaging sensor (UHD 185) onboard a UAV platform. First, the image objects were obtained by segmenting the UAV hyperspectral image and the UAV-derived digital surface model (DSM) data. Second, spectral features, textural features, and vegetation indices (VIs) were extracted from the UAV hyperspectral image, and the UAV-derived DSM data were used to extract height information. Third, the classification and regression tree (CART) method was used to selection bands, and the correlation-based feature selection (CFS) algorithm was employed for feature reduction. Finally, the objects were classified into different mangrove species and other land covers based on their spectral and spatial characteristic differences. The classification results showed that when considering the three features (spectral features, textural features, and hyperspectral VIs), the overall classification accuracies of the two classifiers used in this paper, i.e., k-nearest neighbor (KNN) and support vector machine (SVM), were 76.12% (Kappa = 0.73) and 82.39% (Kappa = 0.801), respectively. After incorporating tree height into the classification features, the accuracy of species classification increased, and the overall classification accuracies of KNN and SVM reached 82.09%(Kappa = 0.797) and 88.66% (Kappa = 0.871), respectively. It is clear that SVM outperformed KNN for mangrove species classification. These results also suggest that height information is effective for discriminating mangrove species with similar spectral signatures, but different heights. In addition, the classification accuracy and performance of SVM can be further improved by feature reduction. The overall results provided evidence for the effectiveness and potential of UAV hyperspectral data for mangrove species identification.
标题：Use of high‐resolution precipitation observations in quantifying the effect of urban extent on precipitation characteristics for different climate conditions over the Pearl River Delta, China
作者：Dashan Wang*, Dagang Wang, Xiangyan Qi, Lin Liu, Xianwei Wang
简介：Few studies conduct a quantitative assessment between the urban extent and local precipitation characteristics. In this paper, high-resolution precipitation data and urban extent data are used to investigate the correlation between precipitation fre-quency, intensity and extremes and urban extent under different climate conditions over the Pearl River Delta, China. Analysis reveals that extreme precipitation amount (R = 0.45 for 1-hr maximum) and mean intensity (R = 0.56) are posi-tively correlated with urban extent and that wet hours (R = ?0.58) are negatively correlated with urban extent. The correlation coefficients between urban extent and extreme indices increase with the decrease in temporal scale of indices. The high coefficients of precipitation intensity and urban extent are mainly attributed to the precipitation under the tropical convection, and the negative coefficient of total wet hours is dominated by precipitation frequency under the Southwest mon-soon. By contrast, the precipitation characteristics are less correlated with urban extent during typhoon events. Urban environments probably play a positive role in generating the short-duration heavy precipitation through enhancing deep con-vections induced by higher surface temperature and higher aerosol concentration.
标题：Journey-to-Crime Distances of Residential Burglars in China Disentangled: Origin and Destination Effects
作者：Xiao, Luzi; Liu, Lin; Song, Guangwen; Ruiter, Stijn; Zhou, Suhong;
简介：Research on journey-to-crime distance has revealed the importance of both the characteristics of the offender as well as those of target communities. However, the effect of the home community has so far been ignored. Besides, almost all journey-to-crime studies were done in Western societies, and little is known about how the distinct features of communities in major Chinese cities shape residential burglars’ travel patterns. To fill this gap, we apply a cross-classified multilevel regression model on data of 3763 burglary trips in ZG City, one of the bustling metropolises in China. This allows us to gain insight into how residential burglars’ journey-to-crime distances are shaped by their individual-level characteristics as well as those of their home and target communities. Results show that the characteristics of the home community have larger effects than those of target communities, while individual-level features are most influential. Older burglars travel over longer distances to commit their burglaries than the younger ones. Offenders who commit their burglaries in groups tend to travel further than solo offenders. Burglars who live in communities with a higher average rent, a denser road network and a higher percentage of local residents commit their burglaries at shorter distances. Communities with a denser road network attract burglars from a longer distance, whereas those with a higher percentage of local residents attract them from shorter by.
标题：Testing Indicators of Risk Populations for Theft from the Person across Space and Time: The Significance of Mobility and Outdoor Activity
作者：Song Guangwen, Liu Lin, Wim Bernasco, Luzi Xiao, Suhong Zhou, Weiwei Liao
简介：In recent years, it has increasingly been recognized that due to the uncertain geographic context problem caused by daily human mobility, the residential population is too static to serve as a valid measure of the popu-lation at risk for criminal victimization. Various alternative measures have been suggested instead. Guided by the routine activity approach, this study furthers the concept of crime risk population and its measurement across space and time. Using exceptionally comprehensive data sets on population mobility and on theft from the person in a large city in China, we select the best indicator of the risk population from the following four candidates: residential population, subway ridership, taxi ridership, and mobile phone users. Controlling for the potentially confounding effects of offender and guardian presence, we show that on both weekdays and week-ends, the best indicators of risk population vary over the course of the day. In the morning, residential popula-tion outperforms other measures. In the afternoon and evening, taxi ridership and phone users are better indicators. Although the mobile phone user base forms an arguably more representative measure of ambient population, during some periods taxi ridership is superior because it provides a better indicator of outdoor (as opposed to indoor) activities. In terms of practical applications to security policy and law enforcement, these ?ndings can help identify crime hot spots by calculating accurate crime risks. Key Words: ambient population, residential population, risk population, theft from the person.
标题：The changing pattern of urban flooding in Guangzhou, China
作者：Huabing Huang, Xi Chen*, Zhanqiang Zhu*, Yuhuan Xie, Lin Liu**, Xianwei Wang, Xina Wang, Kai Liu
简介：Extensive research has focused on modelling and analysis of urban ?ooding in relatively small catchments. Find-ings in small areas tend to be site-speci?c, and may not be applicable to larger study areas. Larger scale studies can identify general patterns and in?uential factors; however, few studies have investigated urban ?ooding on a larg-er scale such as a metropolitan area. In this study, we explored the spatial-temporal patterns of urban ?ooding during the period of 2009–2015 in the central area of Guangzhou, China. Under the framework of Pressure (pre-cipitation and impervious surface)-State (urban ?ooding)-Response (drainage improvement), we evaluated rea-sons for the State change and effectiveness of the Response. Overall the urban ?ooding state showed a ?uctuating and improving trend. The ?uctuation of the ?ooding state trend is due to precipitation variation, and the improv-ing trend is attributed to drainage improvement. Furthermore, drainage improvement in the upstream area had led to new ?ooding in the downstream area. It is evident that the mitigation effect of urban ?ooding in Guang-zhou varied signi?cantly across the city. It is further suggested to regularly collect urban ?ooding records in cities with ?ood risk, so that more appropriate policies and measures about urban ?ooding mitigation can be developed.
标题：Exploring the potential of world view-2 red-edge band-based vegetation indices for estimation of mangrove leaf area index with machine learning algorithms
作者：Yuanhui Zhu, Kai Liu*, Lin Liu* , Soe W. Myint, Shugong Wang, Hongxing Liu, Zhi He
简介：To accurately estimate leaf area index (LAI) in mangrove areas, the selection of appropriate models and predictor variables is critical. However, there is a major challenge in quantifying and mapping LAI using multi-spectral sensors due to the saturation effects of traditional vegetation indices (VIs) for mangrove forests. WorldView-2 (WV2) imagery has proven to be effective to estimate LAI of grasslands and forests, but the sensitivity of its vegetation indices (VIs) has been uncertain for mangrove forests. Furthermore, the single model may exhibit certain randomness and instability in model calibration and estimation accuracy. Therefore, this study aims to explore the sensitivity of WV2 VIs for estimating mangrove LAI by comparing artificial neural network regression (ANNR), support vector regression (SVR) and random forest regression (RFR). The results suggest that the RFR algorithm yields the best results (RMSE = 0.45, 14.55% of the average LAI), followed by ANNR (RMSE = 0.49, 16.04% of the average LAI), and then SVR (RMSE = 0.51, 16.56% of the average LAI) algorithms using 5-fold cross validation (CV) using all VIs. Quantification of the variable importance shows that the VIs derived from the red-edge band consistently remain the most important contributor to LAI estimation. When the red-edge band-derived VIs are removed from the models, estimation accuracies measured in relative RMSE (RMSEr) decrease by 3.79%, 2.70% and 4.47% for ANNR, SVR and RFR models respectively. VIs derived from red-edge band also yield better accuracy compared with other traditional bands of WV2, such as near-infrared-1 and near-infrared-2 band. Furthermore, the estimated LAI values vary significantly across different mangrove species. The study demonstrates the utility of VIs of WV2 imagery and the selected machine-learning algorithms in developing LAI models in mangrove forests. The results indicate that the red-edge band of WV2 imagery can help alleviate the saturation problem and improve the accuracy of LAI estimation in a mangrove area.
标题：Impact of public bus system on spatial burglary patterns in a Chinese urban context
作者：Lin Liu*, Chao Jiang, Suhong Zhou, Kai Liu, Fangye Du
简介：Purpose: To examine the impact of public bus system on spatial burglary pattern in a Chinese urban context, as well as the spatial variation of this impact.
Methods: Local Moran's I, boxplot-based classification, geo-visualization, Chi-square test, and correlation analysis are used to explore the spatial coupling relationships between bus stops and burglary. Guided by routine activity approach, negative binomial regressions are performed for the developed and developing parts of the DP peninsula, as well as the whole peninsula based on proxies of potential offenders, guardians, targets, and spatial dependence.
Results: Statistically positive correlations are observed between burglary count and bus stop service capability. However, net of other factors, one more unidirectional bus route is expected to reduce burglary by nearly 2 percent for the whole area, and 4 percent for the developed area, while no statistically significant relationship is found for the developing area.
Conclusions: The bus-burglary relationships differ between the developed and developing urban areas. For the former, although burglaries concentrate around bus stops with higher service capability, the increase of bus service capability has a net impact of slightly depressing the occurrence of burglaries. Four possible mechanisms explaining this negative bus-burglary relationship in the DP peninsula are presented.