陆海连通潮汐生物通道构建及其对内陆水体影响—以长江口北支和北湖为例

在陆海交界区域有效构建生物通道可以丰富该区域生物多样性,提升滨海生态品质与综合服务功能,推动海陆空间联动高质量发展。本研究以位于崇明岛北侧的北湖为例,研究利用既有沟槽和涵闸构建潮汐生物通道的可行性方案,基于二维水动力数值模型和盐度模型,分析不同潮汐生物通道规模下的水动力特性及其对内陆水体的影响,探讨生物通道植物配置和运行管理措施。结果表明：①选择合适的生物通道长度和堰坝间距、缝宽,可使生物通道在涨落潮一定时间内获得适宜鱼类等生物通行的流速;②构建适宜规模的陆海连通生物通道,既可以满足陆海连通生物通道要求,又可以防止风暴潮灾害风险;③崇明北湖遭遇长江口北支10年一遇重现期典型潮汐情况下水位变化约20 cm,遭遇100年一遇风暴潮情况下水位仍能控制在设防水位以下;④受长江口北支每天两涨两落咸潮、浑水和污染水体影响,建议在生物通道开展生境营造、在北湖湖区开展生境修复,植物配置应考虑流速、水位变化和咸淡混合区的特点。     

基于旅行费用法的九寨沟旅游资源游憩价值评估

采用旅行费用法(TCM)对九寨沟世界自然遗产地的游憩价值进行评估,并对评估过程中可能存在的偏差进行分析和讨论.研究发现:九寨沟2009年的游憩价值为48.90亿元;旅行费用与旅游需求之间存在显著的负相关,而旅游需求函数的形式则以半对数模型为宜;采用工资率的1/3来计算时间的机会成本,具有一定的主观任意性,可能会导致评估结果出现偏差;用市场观测数据对旅行费用在多个目的地之间进行合理分配,可能是处理多目的地问题的所有方法中“最不坏”的一种选择;TCM与条件价值法(CVM)2种方法的评估结果相差较大,不具有良好的收敛效度,TCM的评估结果需要与更多的研究相互印证.     

Modeling Spatial Accessibility of Immigrants to Culturally Diverse Family Physicians

This article uses accessibility as an analytical tool to examine health care access among immigrants in a multicultural urban setting. It applies and improves on two widely used accessibility models—the gravity model and the two-step floating catchment area model—in measuring spatial accessibility by Mainland Chinese immigrants in the Toronto Census Metropolitan Area. Empirical data on physician-seeking behaviors are collected through two rounds of questionnaire surveys. Attention is focused on journey to physician location and utilization of linguistically matched family physicians. Based on the survey data, a two-zone accessibility model is developed by relaxing the travel threshold and distance impedance parameters that are traditionally treated as a constant in the accessibility models. General linear models are used to identify relationships among spatial accessibility, geography, and socioeconomic characteristics of Mainland Chinese immigrants. The results suggest a spatial mismatch in the supply of and demand for culturally sensitive care, and residential location is the primary factor that determines spatial accessibility to family physicians. The article yields important policy implications.     

Information-associated join indices for spatial range search

Abstract

Spatial join indices are join indices constructed for spatial objects. Similar to join indices in relational database systems, spatial join indices improve efficiency of spatial join operations. In this paper, a spatial-information-associated join indexing mechanism is developed to speed up spatial queries, especially, spatial range queries. Three distance-associated join index structures: basic, ring-structured and hierarchical, are developed and studied. Such join indexing structures can be further extended to include orientation information for flexible applications, which leads to zone-structured and other spatial-information-associated join indices. Our performance study and analysis show that spatial-information-associated join indices substantially improve the performance of spatial queries and that different structures are best suited for different applications.     

地图误差对地图匹配质量的影响

高精度的数字地图是正确匹配车辆位置的基础。详细分析了地图数据的地理误差和拓扑误差的误差形式,路网数据模型的常见误差因素和改进策略,最后介绍了不同地图匹配算法对地图质量的敏感性和可行性。根据可能出现的误差对现有数字地图和匹配算法加以改进,弥补了原有数字地图带来的不精确缺陷。跑车实验证明,考虑了数字地图误差影响的匹配算法可以明显提高定位精度,减小车辆定位误差。     

Seasonally frozen soil effects on the dynamic behavior of highway bridges

Frozen ground is significantly stiffer than unfrozen ground. For bridges supported on deep foundations, bridge stiffness is also measurably higher in winter months. Significant changes due to seasonal freezing in bridge pier boundary conditions require additional detailing in order to ensure a ductile performance of the bridge during a design earthquake event. This paper reports the latest results obtained from a project that systematically investigated the effects of seasonally frozen soil on the seismic behavior of highway bridges in cold regions. A bridge was chosen and was monitored to study its seismic performance and assess the impact of seasonally frozen soil on its dynamic properties. A Finite Element (FE) model was created for this bridge to analyze the impact of seasonal frost. It was found that when frost depth reaches 1.2 m, the first transverse modal frequency increases about 200% when compared with the no-frost case. The results show that seasonal frost has a significant impact on the overall dynamic behavior of bridges supported by pile foundations in cold regions, and that these effects should be accounted for in seismic design.     

论吴传钧的治学精神——恭贺传钧师八十华诞

吴传钧,江苏省苏州市人,生于1918年4月2日,我国着名地理学家,中国科学院院士,中国地理学会理事长,原国际地理联合会副主席(1988～1996),《地理研究》杂志顾问。吴传钧院士投身地理学60多年来,为中国地理学的发展和繁荣作出了巨大的贡献,为国家培养了一大批优秀人才。今年是吴先生诞辰80周年,本刊发表鲁奇文章,以示祝贺,并向吴传钧先生表示崇高的敬意。     

中国对虾弧菌病的药物治疗研究

本文对中国对虾病原弧菌的药物敏感性和最低抑制浓度作了研究,结果表明,氯霉素,四环素,痢特灵和SMZ等药物是治疗成虾轻度弧菌病的有效药物。