Interaction Between GSM Handset Helical Antenna and User's Head: Theoretical Analysis and Experimental Results

Summary The performance of a cellular phone commercial helical antenna at 900~MHz band, both in free space and in the presence of a human head phantom was studied. Numerical simulation of the phone model for the latter case has been performed giving 3D radiation diagrams. The effect of the phantom head on radiation diagrams is presented. The relative amount of the EM power absorbed in the head was obtained for several distances of the phone. Measurements were carried out in a RF anechoic chamber using standard horn antennas and a calibrated measuring system. Absolute radiation patterns of the antenna gain were obtained in the three principal planes. Significant reduction of the absorbed power could be achieved just by moving the phone 1 cm away from the head.     

A first generation dynamic ingress,redistribution and transport model of soil track-in: DIRT

This work introduces a spatially resolved quantitative model, based on conservation of mass and first order transfer kinetics, for following the transport and redistribution of outdoor soil to, and within, the indoor environment by track-in on footwear. Implementations of the DIRT model examined the influence of room size, rug area and location, shoe size, and mass transfer coefficients for smooth and carpeted floor surfaces using the ratio of mass loading on carpeted to smooth floor surfaces as a performance metric. Results showed that in the limit for large numbers of random steps the dual aspects of deposition to and track-off from the carpets govern this ratio. Using recently obtained experimental measurements, historic transport and distribution parameters, cleaning efficiencies for the different floor surfaces, and indoor dust deposition rates to provide model boundary conditions, DIRT predicts realistic floor surface loadings. The spatio-temporal variability in model predictions agrees with field observations and suggests that floor surface dust loadings are constantly in flux; steady state distributions are hardly, if ever, achieved. A contribution from ESF Center for the Urban Environment.     

长三角地区人口密度模型及增长模式:1982～2010

基于熵值法对上海、南京和杭州影响力进行综合评价,运用Arc GIS点距离工具测算各空间单元到沪宁杭的距离,然后借鉴重力模型,将长三角地区划分为以上海、南京和杭州为中心的3个城市经济区,并进行区域人口密度模型拟合。相比线性、指数和乘幂模型,对数模型能更好地拟合经济区内各县、县级市或市辖区人口密度与其到各自经济区中心距离的关系。而相比上述基础模型,基于基础模型的二次模型拟合的判定系数更高,拟合效果更好。其中,对数二次模型拟合的判定系数最高,且明显优于基础模型。基于对数二次模型的人口密度变动的空间差异,沪、宁、杭经济区增长模式可以总结为"强向心集聚"和"近域扩散",但不同区域不同时段增长模式存在差异。     

Spatial variations in CO2 fluxes in a subtropical coastal reservoir of Southeast China were related to urbanization and land-use types

Carbon dioxide (CO2) emissions from aquatic ecosystems are important components of the global carbon cycle, yet the CO2 emissions from coastal reservoirs, especially in developing countries where urbanization and rapid land use change occur, are still poorly understood. In this study, the spatiotemporal variations in CO2 concentrations and fluxes were investigated in Wenwusha Reservoir located in the southeast coast of China. Overall, the mean CO2 concentration and flux across the whole reservoir were 41.85 ± 2.03 µmol/L and 2.87 ± 0.29 mmol/m2/h, respectively, and the reservoir was a consistent net CO2 source over the entire year. The land use types and urbanization levels in the reservoir catchment significantly affected the input of exogenous carbon to water. The mean CO2 flux was much higher from waters adjacent to the urban land (5.05 ± 0.87 mmol/m2/hr) than other land use types. Sites with larger input of exogenous substance via sewage discharge and upstream runoff were often the hotspots of CO2 emission in the reservoir. Our results suggested that urbanization process, agricultural activities, and large input of exogenous carbon could result in large spatial heterogeneity of CO2 emissions and alter the CO2 biogeochemical cycling in coastal reservoirs. Further studies should characterize the diurnal variations, microbial mechanisms, and impact of meteorological conditions on reservoir CO2 emissions to expand our understanding of the carbon cycle in aquatic ecosystems.     

广州市流溪河水体中6种内分泌干扰素时空分布特征与环境风险

以雌酮(E1)、雌二醇(E2)、双酚A(BPA)、壬基酚(4-NP)、辛基酚(4-t-OP)和三氯生(TCS)这6种内分泌干扰物(endocrine disrupting chemicals,EDCs)为对象,研究其在广州市流溪河水体中的时空分布特征,并对其雌激素活性进行风险评价.结果表明,14个监测点均有EDCs检出,总范围在26.07~7 109.5 ng·L-1,以4-NP贡献最高(78.62%),其次为BPA(11.91%),其他4种目标物浓度均较低(≤4.92%).时空变化上,EDCs浓度从上游至下游逐渐增加,尤其是下游支流中EDC浓度偏高;丰水期4-NP、4-t-OP浓度显著高于枯水期(P0.05),而E1、E2、BPA则呈相反趋势.相关性分析显示,DO与6种EDCs浓度变化呈显著负相关,高锰酸盐指数、EC、TN、TP、NH+4-N与E1、E2、BPA、TCS呈显著正相关,而与4-NP相关性不显著(P0.05),说明E1、E2、BPA、TCS可能与氮、磷营养盐污染同源.冗余分析(redundancy analysis,RDA)显示,流溪河水体中EDCs的季节性变化比空间变化更为明显(RDA1 56.14%RDA2 14.20%),丰水期水体中EDCs浓度变化主要受4-NP影响,而枯水期则主要受BPA影响.与世界范围内水体中EDCs浓度相比,流溪河中下游河段4-NP、BPA和TCS浓度处于较高水平,其他3种目标物处于中低水平.风险评价结果显示,流溪河中下游河段风险熵值RQ值均大于1,说明该区域具有高雌激素活性风险.     

黄土高原地区两种土地利用方式CO2和N2O排放特征

为探究黄土高原地区两种不同土地利用方式下二氧化碳(CO_2)和氧化亚氮(N_2O)的排放特征,在长武黄土高原农业生态试验站,分别以15 a树龄的果园和麦田为研究对象,采用静态暗箱-气相色谱法对土壤CO_2和N_2O的排放进行了周年(2017年7月～2018年7月)田间原位观测.试验共设置果园施肥(AF)、果园对照(ACK)、小麦施肥(WF)和小麦对照(WCK)这4个处理.结果表明,土壤CO_2和N_2O排放随季节变化明显,降雨和施肥后均出现明显排放峰.AF处理的CO_2和N_2O累积排放量比WF处理高7. 14%和461. 4%.但ACK的CO_2累积排放量比WCK低10. 41%,而N_2O的累计排放量比WCK高109. 5%.果园N_2O的排放通量与表层土壤温度、水分显著正相关(P 0. 01),果园和麦田的CO_2排放通量均与表层土壤温度显著正相关(P 0. 05),而与表层土壤水分相关性不显著.因此,田间管理和环境因素综合影响土壤CO_2和N_2O排放,施肥量和土壤水热是造成两种土地利用方式CO_2和N_2O的排放特征和温室效应差异的主要因素.     

基于视频数据的城市隧道交通运行特征与安全研究

为降低城市隧道交通事故率,提高车辆出行安全,以上海市翔殷路跨江隧道为研究对象,利用视频采集技术、车辆跟踪调查采集隧道交通运行数据,分析城市隧道交通运行特征及驾驶员在隧道内驾驶行为特征,并进一步研究其与隧道交通事故的关系。对隧道内车辆的速度、密度分布,变道行为进行分析,发现隧道南线入口处内外断面平均车速的显著差异可以解释该处追尾事故高发,隧道内车辆频繁变换车道导致隧道侧碰事故占较大比例。为改善城市隧道交通安全,在隧道内进行限速和限制车辆变道是必要的。     

Scale-dependent relations in land cover biophysical dynamics

The exploration of the relationships between plant biotic dynamics and scale can reveal important information on ecosystem spatial organization by addressing preservation of information integrity in upscaling/downscaling procedures of land-surface parameterization for environmental modeling applications. Scale-dependent relations of vegetation dynamics are investigated in this study by using emergent biophysical characteristics obtained through a predictive multidimensional model of vegetation anomalies derived from remote-sensing observations. In particular, the analysis is focused on the spatial organization of some phenological parameters including deterministic variations (seasonal range, interannual variability, jump discontinuities) and stochastic components (plant memory, spatial correlations). The analysis is performed using MODIS-based Normalized Difference Vegetation Index (NDVI) 16-day composites for the period from March 2000 to December 2006 over Italy at different levels of spatial aggregation (1-8 km). Scale-dependences of the statistical moments of the phenological parameters are quantified through simple power laws for five distinct vegetated land covers. Results suggest that some biophysical characteristics, especially deterministic components, show no preferential spatial scale for important coverage. In particular, broad-leaved forests and natural grasslands are characterized by deterministic and low-distance spatial components well explained by scale relationships, which are modulated by possible spatiotemporal dynamics of climatic drivers. Agricultural lands show high scale-dependent relations on short-term biophysical memory sources and low-distance spatial components of phenology likely related to hierarchical interactions of anthropogenic and ecological processes; whereas mixed patterns of croplands and natural areas generally present no consistent scaling relations.     

Interannual fluctuations in acoustic biomass estimates and in landings of small pelagic fish populations in relation to hydrology in the Strait of Sicily

The main results of research work carried out since 1998 with regard to the application of hydro-acoustic technologies for the evaluation of biomass and distribution of small pelagic fish species off the southern coast of Sicily are presented, taking into account information from hydrology and from ecology of the fish populations targeted. The biomass estimates and the population-density charts presented concern the two main species, i.e. sardine Sardina pilchardus (Walbaum, 1792) and anchovy Engraulis encrasicolus (Linnaeus, 1758). Both the sardine and anchovy populations experienced large inter-annual fluctuations, with biomass estimates ranging from 6000 to over 36,000 tonnes (t) (sardine) and from about 7000 to 23,000 t (anchovy). Acoustic estimates are largely consistent with landings recorded in Sciacca (the main fishing port for small pelagic species in the study area) during the year following the evaluation surveys. In addition, trends in sardine and anchovy biomass estimates appears to be negatively correlated with the mean sea surface temperature calculated over the time intervals January-September (sardine) and June-November (anchovy) of the preceding year, which correspond to larval and juvenile growth periods of target species. Observed patterns would suggest the importance of enrichment processes relevant to the survival of early stages, so determining recruitment success and finally higher population sizes.