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排序方式: 共有313条查询结果,搜索用时 15 毫秒
241.
This study attempts to understand the public evaluation towards elements that exist within the temporal dynamics of the cities. In particular the study explores the extent to which street vendors in Jakarta are evaluated as ‘out of place’ elements at day time and night time. The findings suggest that the users' evaluation of street vendors as ‘out of place’ change from day time to night time. The change of users' evaluation also varies across different urban places. In particular the study suggests that the presence of street vendors seems to be less unacceptable (out of place) at night time. Such knowledge regarding the dynamic of ‘out of place’ evaluation becomes important in making the decision about temporary urban elements in the city.  相似文献   
242.
This paper elaborates on recent advances in the use of ScanSAR technologies for wetland-related research. Applications of active satellite radar systems include the monitoring of inundation dynamics as well as time series analyses of surface soil wetness. For management purposes many wetlands, especially those in dry regions, need to be monitored for short and long-term changes. Another application of these technologies is monitoring the impact of climate change in permafrost transition zones where peatlands form one of the major land cover types. Therefore, examples from boreal and subtropical environments are presented using the analysed ENVISAT ASAR Global mode (GM, 1 km resolution) data acquired in 2005 and 2006. In the case of the ENVISAT ASAR instrument, data availability of the rather coarse Global Mode depends on request priorities of other competing modes, but acquisition frequency may still be on average fortnightly to monthly depending on latitude. Peatland types covering varying permafrost regimes of the West Siberian Lowlands can be distinguished from each other and other land cover by multi-temporal analyses. Up to 75% of oligotrophic bogs can be identified in the seasonal permafrost zone in both years. The high seasonal and inter-annual dynamics of the subtropic Okavango Delta can also be captured by GM time series. Response to increased precipitation in 2006 differs from flood propagation patterns. In addition, relative soil moisture maps may provide a valuable data source in order to account for external hydrological factors of such complex wetland ecosystems.  相似文献   
243.
收集扬州市2017—2019年大气污染物细颗粒物(PM_(2.5))、二氧化硫(SO_2)、二氧化氮(NO_2)和臭氧(O_3)的日均质量浓度、气象因素(日均温度、相对湿度)以及每日儿童呼吸系统门诊量数据,运用广义相加模型(GAM)进行单污染物和多污染物分析。结果表明,单污染物分析中,大气污染物的质量浓度累积滞后效应均大于单独滞后效应。ρ(PM_(2.5))、ρ(SO_2)和ρ(NO_2)对儿童呼吸系统门诊量影响效应均在累积滞后7 d(lag 07)达到最大值,ρ(O_3)在累积滞后6 d(lag 06)达到最大值。表现为ρ(PM_(2.5))、ρ(SO_2)和ρ(NO_2)在lag 07时,每升高10μg/m~3,儿童呼吸系统门诊量超额危险度分别为0.720%[95%置信区间(95%CI):0.346%~1.095%]、6.955%(95%CI:5.197%~8.743%)和2.133%(95%CI:1.516%~2.754%);ρ(O_3)在lag 06时,每升高10μg/m~3,儿童呼吸系统门诊量超额危险度为1.160%(95%CI:0.873%~1.447%)。多污染物分析中,当引入所有污染物(SO_2+NO_2+O_3)时,PM_(2.5)对儿童呼吸系统门诊量风险影响消失。大气污染物浓度的升高会增加儿童呼吸系统疾病的发生风险,并且其影响存在一定的滞后效应,有必要开展有针对性的大气污染物与儿童呼吸系统疾病的预警研究,保护易感人群,合理分配卫生资源。  相似文献   
244.
ABSTRACT Many of the resources generating aesthetic and visual benefits are publically owned and their optimum use and development depends upon public investment. Traditionally, public investment decisions have been couched in economic terms requiring quantitative measurement of benefits and costs. Since many of the benefits these resources provide are not consumed when they are enjoyed, the total contribution of the resource is imperfectly measured in the usual market sense. Thus, if the provision of these public goods is left to the conventional market mechanism, less than socially optimal investment may occur. This study was designed to investigate whether aesthetic preferences related to water projects could be determined, and whether they differ among different groups of people. A Q sort of 44 photographs of a wide variety of water development projects was conducted with two groups, i.e., photographers (aesthetic man) and town assessors (economic man). The resultant analysis identified two significant factors. Factor 1 provided insight into a hypothesis of nature dominant or man dominant scenes. Factor 2 indicated that the respondents had a negative preference for projects which were in varying stages of completion or appeared to be polluted. Preferences were consistent between the two groups tested. The test revealed that people do not necessarily equate only naturalness with aesthetic appeal, but will accept development as aesthetic, provided that it is designed to complement the natural landscape.  相似文献   
245.
Over the 20th century, reduced land cultivation has caused an extension of fallow land in several European countries, which has led to a decrease in biodiversity. Knowledge of dynamic vegetation processes and of the impact of human activities on biodiversity provides the basis for land management recommendations, as well as for wildlife management programs. We analysed land-use changes on a small protected island (Ushant, Bretagne, France) using historical documentation (1844) and aerial photographs taken in 1952 and 1992. Over this period, especially during the last 40 yr, Ushant underwent a complete transformation from rural landscape to extensive shrubland. No cultivated area remains, grazed areas were moved from the coastal fringe to the core of the island, while over 40% of the island is fallow land. The relationship between current sheep grazing and vegetation suggests that grazed meadows used to be close to inhabited areas, i.e. 150 m outside the villages. These results allowed us to analyse landcover potential related to changes in the intensity of sheep grazing. The scenarios highlighted by our method provide an objective framework for further assessment of fallow land management.  相似文献   
246.
In the stream-dwelling isopod, Lirceus fontinalis, mating contests between males and females occur prior to pair formation. We examined the relative contribution of male preference and female resistance to contest outcomes. We first quantified male and female behavior during typical mating interactions and examined the relationship between time until molt (TTM) and mating outcomes. We then examined the role of male preference and female resistance in determining mating outcomes when females differed in molt type (growth, egg deposition) and appeared to differ in TTM (due to hormone applications). Both male preference and female resistance contributed to different components of the mating sequence but female resistance ultimately determined whether or not pair formation occurred. Males expressed a preference for females that appeared to be close to molt, using variation in levels of molt hormone as a cue. However, males did not discriminate between females based on molt type. Received: 5 March 1999 / Received in revised form: 10 August 1999 / Accepted: 16 October 1999  相似文献   
247.
Animals interact with their habitat in a manner which involves both negative and positive feedback mechanisms. We apply a specific modeling approach, “multi-scaled random walk”, for the scenario where a spatially explicit positive feedback process emerges from a combination of a spatial memory-dependent tendency to return to familiar patches and a consequently objective or subjective improvement of the quality of these patches (habitat auto-facilitation). In addition to the potential for local resource improvement from physically altering a patch, primarily known from the ecology of grazing ungulates, auto-facilitation from site fidelity may also embed more subtle subjective, individual-specific advantages from patch familiarity. Under the condition of resource superabundance, fitness gain from intra-home range patch fidelity creates a self-reinforcing use of the preferred patches on expense of a broader foraging in a priori equally favorable patches. Through this process, our simulations show that a spatially fractal dispersion of accumulated locations of the individual will emerge under the given model assumptions. Based on a conjecture that intra-home range patch fidelity depends on spatial memory we apply the multi-scaled random walk model to construct a spatially explicit habitat suitability parameter Hij, which quantifies the dispersion of the generally most constraining resource from the individual's perspective. An intra-home range set of observed H-scores, Hobs, can then be estimated from a simple 2-scale calculation that is derived from the local dispersion of fixes. We show how the spatially explicit habitat utilization index Hobs not necessarily correlates positively with the local density fluctuations of fixes. The H-index solves some well-known problems from using the pattern of local densities of telemetry fixes - the classic utilization distribution - as a proxy variable for relative intra-home range habitat quality and resource selection. A pilot study on a set of telemetry fixes collected from a herd of free-ranging domestic sheep with overlapping summer home ranges illustrates how the H-index may be estimated and interpreted as a first-level approach towards a more extensive analysis of intra-home range habitat resource availability and patch preferences. Spatial memory in combination with site fidelity requires a modeling framework that explicitly describes the property of positive feedback mechanism under auto-facilitation in a spatio-temporally explicit manner.  相似文献   
248.
合理的农业生态补偿方式应符合农户利益预期和意愿。基于重庆10区县357户农户的调查数据,采用选择实验法和随机参数Logit模型分析了农户参与农业减量化的补偿方式偏好及异质性。结果表明:①各种补偿方式均能显著提高农户农业减量化的参与效用;②农户平均偏好程度最高的是农资补偿和现金补偿,其次是技术补偿,最低的是政策补偿;③农户对不同补偿方式存在显著的偏好异质性,并且部分偏好异质性来源于决策者特征、家庭经营/生计特征和区域因素。建议继续通过生态补偿有效推进化肥农药减量施用,但补偿方式应该结合不同农户的偏好采取差异化设计。  相似文献   
249.
强震作用下地埋结构的数值模型   总被引:2,自引:0,他引:2  
应用时域边界元法研究了结构 介质动力相互作用问题。假设摩擦遵守库仑定理 ,当入射波足够强时界面会出现局部滑移、分离。由于边界上的区域 (滑移、分离和粘着 )是未知的 ,所以 ,笔者研究的实际上是个复杂的边界非线性问题。该模型对评估和预测地埋结构在动荷载下的安全具有重要的理论价值  相似文献   
250.
科学评价生物多样性价值可为生物多样性和生态系统经济学(the Economics of Ecosystems and Biodiversity,TEEB)支持下的生物资源管理提供有效的技术方法和政策依据,对受威胁物种的保护尤为重要.从TEEB的理念和研究目标出发,以我国特有保护植物——翅果油树(Elaeagnus mollis)为例,采用选择试验法定量评估受访者对受威胁物种保护和开发的偏好以及支付意愿;针对种植面积、产品开发、树苗品种、保护投入和农户收益这5项物种属性,在多模型比较的基础上最终选择随机参数模型(RPL)和潜在分层模型(LCM)进行价值评估.结果表明:基于RPL模型得出受访者的偏好选择具有异质性,正选择偏好的属性变量按重要性表现为"保护增加投入">"高低端产品同时开发">"农户收益">"树苗品种">"种植面积",其中对"保护增加投入"的支付意愿〔331.0元/(户·a)〕最高,其次为"高低端产品同时开发"〔242.71元/(户·a)〕;对"保护不投入"为负选择偏好,且支付意愿〔-154.71元/(户·a)〕最低.基于LCM模型可将受访者分为保护偏好...  相似文献   
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