Adaptive stochastic gradient boosting tree with composite criterion

ABSTRACT

In this paper, we propose an adaptive stochastic gradient boosting tree for classification studies with imbalanced data. The adjustment of cost-sensitivity and the predictive threshold are integrated together with a composite criterion into the original stochastic gradient boosting tree to deal with the issues of the imbalanced data structure. Numerical study shows that the proposed method can significantly enhance the classification accuracy for the minority class with only a small loss in the true negative rate for the majority class. We discuss the relation of the cost-sensitivity to the threshold manipulation using simulations. An illustrative example of the analysis of suboptimal health-state data in traditional Chinese medicine is discussed.     

Dimension reduction via local rank regression

Outer product of gradients (OPG) achieves dimension reduction via estimating the gradients of the regression function. In this paper, we propose two novel OPG estimators via local rank regression: the rank OPG estimator and the Walsh-average OPG estimator. Both proposals guard against a wide range of error distributions, and are safe alternatives to existing OPG estimators based on local linear regression or local L1 regression. The effectiveness of the new proposals are demonstrated via extensive numerical studies.     

近代广东商业人群在广西的分布面及其梯度差考详——粤港商业经济对广西经济辐射研究之二

文章从中国近代史上城镇经济主体——商业经济的角度切入,运用各类历史资料,分区逐县地确证广东商业人群以及所造成的“无东不成市”格局在全广西的分布范围,并揭示其在广西不同地域的程度等差和梯度分布状态。从而,以原始的生活场景原生态地呈现出粤港澳地区对广西经济辐射由东而西逐步推进、由城市而圩市逐层次渗透的基本节奏和客观规律。     

京津冀区域经济合作中的问题分析及对策选择

近年来京津冀在区域经济合作过程中虽取得了相当的成绩,但由于缺乏有效的总体规划和协调机制,仍存在着较严重的产业结构同构、产业链断裂、经济梯度不合理、基础设施建设薄弱等问题。为有效解决这些问题,可以区域网络联系合作模式为基本框架,通过建立区域协调机构,完善地方政府政绩考核机制,建立京津冀一体化市场,加强基础设施建设与环境保护方面的协调与合作,从而进一步推进京津冀的区域合作进程和实现区域的可持续发展。     

Methods for spatial and temporal land use and land cover assessment for urban ecosystems and application in the greater Baltimore-Chesapeake region

Understanding contemporary urban landscapes requires multiple sets of spatially and temporally compatible data that can integrate historical land use patterns and disturbances to land cover. This paper presents three principal methods: (1) core analysis; (2) historic mapping; and (3) gradient analysis, to link spatial and temporal data for urban ecosystems and applies their use in the Baltimore-Chesapeake region. Paleoecological evidence derived from the geochronology of sediment cores provides data on long-term as well as recent changes in vegetative land cover. This information, combined with contemporary vegetation maps, provides a baseline for conducting trend analyses to evaluate urbanization of the landscape. A 200-year historical land use database created from historical maps, census data, and remotely sensed data provides a spatial framework for investigating human impacts on the region. A geographic information system (GIS) integrates core analyses with historic data on land use change to yield a comprehensive land use and land cover framework and rates of change. These data resources establish the regional foundation for investigating the ecological components of an urban ecosystem. Urban-rural gradient analyses and patch analyses are proposed as the most appropriate methods for studying the urban ecosystem as they link ecological and social patterns and processes for varying degrees of urbanization.     

位移边界对2D-FGM板热应力影响研究

考虑不同的位移边界条件,建立了常物性2D-FGM板研究模型,并采用有限元法,得到其冷却瞬态热应力场分布图形。位移边界条件对常物性2D-FGM平面区域冷却瞬态热应力分布影响颇大,在简支和一端固定情况下,2D-FGM板自由边界上的热应力σ_x=0;两端固定情况下,其左右两边界均形成上中下三个应力聚集,应力分布形状和数值都发生了巨大的变化;将四周均设置呈固定约束后,热应力数值增长幅度较两端固定情况时更为明显。此结果为该材料的设计、制备提供了准确的理论计算依据。     

How Close Is Close Enough: Public Perceptions of the Risks of Industrial Facilities

Public opinion poll data have consistently shown that the proportion of respondents who are willing to have a nuclear power plant in their own community is smaller than the proportion who agree that more nuclear plants should be built in this country. Respondents' judgments of the minimum safe distance from each of eight hazardous facilities confirmed that this finding results from perceived risk gradients that differ by facility (e.g., nuclear vs. natural gas power plants) and social group (e.g., chemical engineers vs. environmentalists) but are relatively stable over time. Ratings of the facilities on thirteen perceived risk dimensions were used to determine whether any of the dimensions could explain the distance data. Because the rank order of the facilities with respect to acceptable distance was very similar to the rank order on a number of the perceived risk dimensions, it is difficult to determine which of the latter is the critical determinant of acceptable distance if, indeed, there is only one. There were, however, a number of reversals of rank order that indicate that the respondents had a differentiated view of technological risk. Finally, data from this and other studies were interpreted as suggesting that perceived lack of any other form of personal control over risk exposure may be an important factor in stimulating public opposition to the siting of hazardous facilities.     

Species richness and altitudinal variation in the aquatic metazoan community in bamboo phytotelmata from north Sulawesi

We compared the aquatic metazoan community structure in bamboo stumps between a lowland (Kosinggolan; 200 m a.s.l.) and a highland site (Moat; 1030–1050 m a.s.l.) in North Sulawesi. The lowland bamboo stumps harbored 38 taxa including 2 predators, and the highland stumps harbored 35 taxa including 2 predators. In total 45 taxa were recorded, including 3 predators. Dominant detritivores were Tipulidae, Scirtidae, Chironomidae, Culicidae and Ceratopogonidae. The sole dominant predators wereToxorhynchites mosquito larvae, which occurred in 67% and 28% of stumps at the lowland and the highland sites, respectively. Although the mean biomass per stump did not differ significantly between the sites, the mean number of species per stump was significantly smaller at the lowland site. In addition, the variation in species composition among stumps was greater at the lowland site than at the highland site. Among dominant taxonomic groups, the number of non-predatory culicid species per stump was smaller at the lowland site where their predator,Toxorhynchites, was more abundant, although both sites had the same number of culicid species. In the presence ofToxorhynchites, the density and biomass of other culicids per stump were reduced significantly. The difference in predator density might affect differences in the local-scale community structure of individual bamboo stumps.     

新吉坪隧道斜井进正洞挑顶施工技术研究

沪昆铁路客运专线新吉坪隧道所处地质条件复杂，区域地质作用剧烈，碳酸岩分布广泛，不良地质特别发育。针对斜井进正洞施工，提出了纵向爬坡导坑法。并以2#斜井为例，介绍了纵向爬坡导坑法施工工艺和斜井进正洞挑顶施工的控制要点，以及在施工过程中的控制量测方法，为新吉坪隧道斜井进正洞挑顶施工提供了技术指导，为类似工程施工提供参考。     

Urban tree cover: an ecological perspective

Analysis of urban tree cover is generally limited to inventories of tree structure and composition on public lands. This approach provided valuable information for resource management. However, it does not account for all tree cover within an urban landscape, thus providing insufficient information on ecological patterns and processes. We propose evaluating tree cover for an entire urban area that is based on patch dynamics. Treed patches are classified by their origin, structure, and management intensity. A patch approach enables ecologists to evaluate ecological patterns and processes for the entire urban landscape and to examine how social patterns influence these ecological patterns and processes.