Measuring Individuals' Spatial Access to Healthy Foods by Incorporating Mobility,Time, and Mode: Activity Space Measures

Spatial access to healthy foods has drawn growing attention regarding the relationship with people's health conditions and demographic and socioeconomic characteristics. Individuals' differences and the impact of travel behaviors on food accessibility, however, are rarely studied. This study incorporates mobility, time, and transportation mode components to measure each individual's access to healthy foods. We employed three activity space measures to estimate food accessibility: route network buffer, time-weighted standard deviational ellipse (SDE), and mode-weighted SDE. Food accessibility in three activity spaces shows similar variabilities. Geographic size and spatial access to healthy foods differ significantly by income and employment for all three activity space measures. People with higher incomes and those who are currently employed are likely to have larger activity spaces and higher food accessibility. As age increases, people tend to increase their size of activity spaces (in both SDE measures) and food accessibility significantly. Females are likely to have smaller activity spaces and less accessibility to healthy foods (only in the time-weighted SDE measure). Geographic size and spatial access do not differ significantly by education and number of vehicles per household. Although three activity spaces are highly correlated in both geographic size and spatial access, differences still exist among them.     

Three‐dimensional time‐harmonic fundamental solutions for a fluid‐saturated poroelastic half‐space with partially permeable free surface

By virtue of a pair of scalar potentials for the displacement of the solid skeleton and the pore fluid pressure field of a saturated poroelastic medium, an alternative solution method to the Helmholtz decomposition is developed for the wave propagation problems in the framework of Biot's theory. As an application, a comprehensive solution for three‐dimensional response of an isotropic poroelastic half‐space with a partially permeable hydraulic free surface under an arbitrarily distributed time‐harmonic internal force field and fluid sources is developed. The Green's functions for the poroelastic fields, corresponding to point, ring, and disk loads, are reduced to semi‐infinite complex‐valued integrals that can be evaluated numerically by an appropriate quadrature scheme. Analytical and numerical comparisons are made with existing elastic and poroelastic solutions to illustrate the quality and features of the solution. Copyright © 2016 John Wiley & Sons, Ltd.     

局部凸线性拓扑空间Kannan型非扩张集值映射不动点定理

在Hausdorff局部凸线性拓扑空间中得到了Kannan型非扩张集值映射不动点定理,附带给出单值映射族具有公共不动点的结果。     

全球强震的分布及其与地球自转速率变化的关系

结合文[1]作者给出的全球地震目录,重点考察1832~1994年间全球强震(Ms≥7.5)的分布特征,并初步探讨了全球强震与地球自转速率变化的可能关联。结果表明,1832年以来的全球强震分布与现代的地震观测结果比较一致,这些强震主要集中在环太平洋和地中海—喜马拉雅两大地震带,地球自转速率变化与全球强震的频次存在较为密切的联系。     

Ecogeomorphic state variables and phase‐space construction for quantifying the evolution of vegetated aeolian landscapes

Cellular automaton modelling for the simulation of dune field formation and evolution has developed progressively in aeolian geomorphology in the last decade or so. A model that incorporates the effects of vegetation and its interactions with geomorphic landscape development – the Discrete Ecogeomorphic Aeolian Landscapes (DECAL) model – can replicate a number of important visual and qualitative aspects of the complex evolution of aeolian dune landscapes under the influence of vegetation dynamics in coastal environments. A key challenge in this research area is the analysis and comparison of both simulated and real‐world vegetated dune landscapes using objective and quantifiable principles. This study presents a methodological framework or protocol for numerically quantifying various ecogeomorphic attributes, using a suite of mathematically defined landscape metrics, to provide a rigorous and statistical evaluation of vegetated dune field evolution. Within this framework the model parameter space can be systematically explored and simulation outcomes can be methodically compared against real‐world landscapes. Based on a simplified scenario of parabolic dunes developing out of blow‐outs the resulting dune field realizations are investigated as a function of variable growth vigour of two simulated vegetation types (pioneer grass and successional woody shrub) by establishing a typological phase‐diagram of different landscape classes. The set of simulation outcomes furthermore defines a higher‐dimensional phase‐space, whose axes or dimensions can be interpreted by analysing how individual ecogeomorphic landscape metrics, or state variables, contribute to the data distribution. Principal component analysis can reduce this to a visual three‐dimensional (3D) phase‐space where landscape evolution can be plotted as time‐trajectories and where we can investigate the effects of changing environmental conditions partway through a simulation scenario. The use of landscape state variables and the construction of a 3D phase‐space presented here may provide a general template for quantifying many other eco‐geomorphic systems on the Earth's surface. Copyright © 2010 John Wiley & Sons, Ltd.     

Design measures to mitigate the impact of shallow groundwater on hydrologic performance of permeable pavements

Permeable pavements (PPs) are widely implemented in urban areas to mimic natural hydrologic processes through enhancing infiltration, and reducing, delaying, and retaining surface runoff. However, its performance can be affected by shallow groundwater since high soil moisture may inhibit its infiltration and exfiltration. This study built a numerical model, which was calibrated and validated based on laboratory experiment data, to evaluate the water balance and retention of PP in shallow groundwater conditions. It assessed the impacts of shallow groundwater and the hydrologic effectiveness of different PP design measures (i.e., building a PP with a smaller storage depth, implementing an underdrain at different elevations, and installing an impermeable liner) on relieving the impacts. Shallower groundwater led to larger amounts of surface runoff and underdrain flow, and a higher chance of saturating the PP reservoir. The three design measures had both benefits and drawbacks in mimicking natural hydrologic cycle and retaining the performance of PP under extreme conditions (e.g., areas of very shallow groundwater tables and/or extreme rainfalls). A PP with a smaller storage depth resulted in less underdrain flow but was prone to saturation. It is, thus, more recommended for PP with more-permeable subsoils, which can avoid frequent pavement saturation. Although a shallower PP corresponds to a smaller storage volume and shorter hydraulic retention time, it can increase the applicability of PP to shallow groundwater areas, which is beneficial to the regional hydrologic environment. Installing an underdrain generated underdrain flow, which is a burden to the downstream drainage system. However, it significantly reduced the surface runoff and the chance of saturating the PP reservoir, which, thus, is more recommended for PP with less-permeable subsoils. Comparatively, elevating the underdrain is recommended in areas of shallow groundwater because it can reduce the frequency and amount of groundwater-induced underdrain flow. In addition, a higher underdrain together with an impermeable liner can create a storage depth, increase the retention duration, enhance exfiltration and evaporation without increasing the saturation risk.     

Forced vertical and horizontal movements of a rectangular rigid foundation on a transversely isotropic half‐space

An analytical investigation of a half‐space containing transversely isotropic material under forced vertical and horizontal displacements applied on a rectangular rigid foundation is presented in this paper. With the goal of a rigorous solution to the shape‐ and rigidity‐ induced singular mixed boundary value problem, the formulation employs scalar potential representation, the Fourier expansion and the Hankel integral transforms method to obtain the surface arbitrary point‐load solution in cylindrical coordinate system. The obtained Green's functions are rewritten in rectangular coordinate system, allowing the response of the half‐space because of an arbitrary distributed load on a rectangular surface area be given in terms of a double integral. The numerical evaluations of stresses are done with the use of an element, which is singular at the edge and the corner of the rectangle. Upon the imposition of the rigidity displacement boundary condition for a rigid foundation and the use of a set of two‐dimensional adaptive‐gradient elements, which can capture the singular behavior in the contact stress effectively, a set of new numerical results are presented to illustrate the effect of transverse isotropy on the foundation response. Copyright © 2012 John Wiley & Sons, Ltd.     

古尔班通古特沙漠及周边区域冬季大气边界层高度对地表积雪的响应

古尔班通古特沙漠是中国唯一冬季存在长期积雪的沙漠,在此特殊地理环境下,沙漠及周边区域冬季雪深和边界层高度的时空变化特征和相互关系尚未明确。本文利用1980—2019年SMMR（Scanning Multichannel Microwave Radiometer）、SSM/I（Special Sensor Microwave/Imager）、SSMI/S（Special Sensor Microwave Imager/Sounder）被动微波遥感雪深数据、古尔班通古特沙漠腹地雪深观测数据和ERA5再分析资料（the Fifth Generation ECMWF Reanalysis）边界层高度数据,分析了沙漠及周边区域冬季雪深和边界层高度的时空变化特征与相互关系。结果表明：古尔班通古特沙漠及周边区域冬季雪深年均值为8.45 cm,整体呈现东北部和南部积雪较深,其他区域积雪较浅并呈现出由沙漠中心区域向四周逐渐减少的特点,雪深在古尔班通古特沙漠及其东北、南边的邻近区域呈升高趋势,剩余地区呈下降趋势。古尔班通古特沙漠及周边区域冬季边界层高度年均值为105.54 m,呈现东南部和西北部高,中心沙漠区域、东北部、西南部较低的特点,边界层高度在沙漠及周边区域升高而其他区域降低。古尔班通古特沙漠的冬季雪深和大气边界层高度时空变化整体呈负相关,其中93.17%以上的沙漠区域呈负相关,平均相关系数为-0.32,最大相关系数绝对值为-0.58,空间相关系数为-0.42（P<0.05）。     

Variation in Pore Space and Structure of Organic-rich Oil-prone Shales from a Non-marine Basin: Constraints from Organic Matter and Minerals

Organic matter (OM) and minerals are major particle components of lacustrine shales. The influence of OM and minerals on pore space and structure in organic-rich oil-prone shales containing a large range of total organic carbon (TOC) contents is poorly understood. In this study, we investigated the variation in pore space and structure of low mature lacustrine shales in the Songliao Basin (NE China), based on a study of the mineralogy, petrography, geochemistry, and geophysical properties of shales. Different pore types make markedly different contributions to the mineral surface area (MSA) and pore volume (PV) of the shales. There exists a negative correlation between MSA/PV and TOC in mesopores (r2 = 0.75/0.65) and macropores (r2 = 0.74/0.68), and a positive correlation in micropores (r2 = 0.59/0.64), which are associated with the variation of mineral and TOC contents. A positive relationship between the throat/pore ratio and TOC (r2 = 0.82) shows an increase in throat radius and decrease in pore radius with increasing TOC content. This relationship is supported by the reduction in mean pore diameter (MPD) for large pores and increase in MPD for small pores. These variations are related to the decreased pores by quartz plus feldspar (Q + F) content, increased throats by clay minerals, and enhanced pore-fill by OM. We propose that the variation of OM and minerals is a key control on the pore space and structure of low mature organic-rich oil-prone shales.     

苏州市区多种地下地质资源协同开发利用研究

地下空间、地下水、浅层地热能和地质材料是重要的地下地质资源,协同开发利用是大势所趋。苏州既是历史文化名城又是现代国际大都市,城市发展至今对地下地质资源的需求相当迫切。通过对苏州各类地下地质资源的的识别分析,表明其具备分别开发地下空间、地下水、浅层地热能和地质材料资源的能力。若多种资源协同开发,平面上开发利用条件较好,竖向尺度地下浅层到次深层适宜地下空间和地质材料的协同开发,而深层适宜以浅层地热能为主的协同开发。结合苏州国土空间发展格局和地下资源的优势分布特征,城镇空间建议采取“地下空间+浅层地热能”的协同利用模式;农业空间建议采取以“浅层地热能”为主的协同利用模式;生态空间予以生态环境保护。