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121.
区域可持续发展的理论探讨*   总被引:30,自引:3,他引:27  
吕鸣伦  刘卫国 《地理研究》1998,17(2):131-137
文章界定了区域可持续发展的定义,同时结合区域发展的时空演化特点,从系统的角度分析了区域可持续发展的内在机制、动力、发展模式及演化过程,提出了“广义熵”(Extensive Entropy)的概念和区域可持续发展的信息动力学假说.理论上分析表明,组合logistic曲线可能是区域可持续发展的最佳模式.  相似文献   
122.
Using direct measurements of photo-electric absorption edges, I derive the intrinsic spectra for the Anomalous X-ray Pulsars. In the past, the hydrogen column density, N H had been found by fitting the X-ray spectra with a variety of simple continuum models. Since different models fit equally well, with different values of N H, little is learned about the true column density or intrinsic spectra. Here, I measure the column densities in a model-independent way, and thus derive intrinsic spectra without first assuming what those spectra ought to look like. Particularly for the brightest source, 4U 0142+61, the column density can be determined accurately, and is a factor of 1.4 smaller that the typically N H quoted. With this new value, the new intrinsic spectrum can be investigated anew, and shows a slight hint of a feature around 13 Å. To be emphasised, this is an empirical method with the minimum of assumptions, as is appropriate for these beguiling sources, the behaviour of which has mystifies astronomers for over a decade. This paper summarises the methods and conclusions to be published in the Astrophysical Journal by Durant and Van Kerkwijk (2006; see astro-ph/0606604).  相似文献   
123.
The link between spatiotemporal patterns of stream water chemistry and catchment characteristics for the mesoscale Dill catchment (692 km2) in Germany is explored to assess the catchment scale controls on water quality and to characterize water sources. In order to record the spatiotemporal pattern, ‘snapshot sampling’ was applied during low, mean and high flow, including 73 nested sites throughout the catchment. Water samples were analysed for the elements Li, B, Na, Mg, Al, K, Ca, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Rb, Sr, Mo, Ba, Pb and U using inductively‐coupled‐plasma mass spectrometry, and for electric conductivity and pH. Principle component analysis and hierarchical cluster analysis were used to find typical element associations and to group water samples according to their hydrochemical fingerprints. This revealed regional hydrochemical patterns of water quality which were subsequently related to catchment attributes to draw conclusions about the controls on stream chemistry. It was found that various lithologic signals and anthropogenic point source inputs controlled the base flow hydrochemistry. During increased flows, stream waters were diluted causing additional hydrochemical variability in response to heterogeneous precipitation inputs and differences in aquifer storage capacities. The hydrochemical patterns further displayed in‐stream mixing of waters. This implied, that stream waters could be apportioned to the identified water sources throughout the catchment. The basin‐wide hydrochemical variability has the potential to outrange the tracer signatures typically inferred in studies at the hillslope scale and is able to strongly influence the complexity of the catchment output. Both have to be considered for further catchment scale tracer and modelling work. Despite the likelihood of non‐conservative behaviour, the minor and trace elements enhanced the rather qualitative discrimination of the various groundwater types, as the major cations were strongly masked by point source inputs. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   
124.
城市海量手机用户停留时空分异分析——以深圳市为例   总被引:1,自引:0,他引:1  
识别海量手机数据中蕴含的行为模式,是地理学的一个研究热点与难点。目前,较多研究针对手机用户移动特征开展,而对停留及其模式的研究则相对较少;其时空分异规律对理解城市人群动态,甚至优化城市系统至关重要。本文根据人们日常时空约束条件定义了手机用户停留,提出了基于海量手机位置数据的手机用户停留模式的提取方法,以深圳市约790万个匿名手机用户一天的海量手机位置数据为例,识别出了覆盖约98%用户的典型停留模式,并结合该城市土地利用的空间分布与分异特征,剖析不同停留模式的手机用户空间分异特征和城市不同区域停留次数的时段分异特征。研究发现:(1)15种停留模式可覆盖约98%的手机用户,而且其一天不同的停留位置数量不超过4个;(2)15种停留模式手机用户在城市区域空间上的分布存在分异现象,严重受制于土地利用的空间分布;(3)城市不同区域停留次数的时段分异特征与该区域常住人口、人口密度,以及区域主要职能和性质存在较强的相关性。研究结论对理解城市手机用户行为模式的群体特征有积极的意义,对城市土地利用的科学决策和城市交通规划与预测有重要参考价值。  相似文献   
125.
For 3 years aspects of the population dynamics, growth, and bioactivity (measure of biologically active metabolite biosynthesis) of the Demospongiae Latrunculia sp. nov. and Polymastia croceus (Kelly‐Borges & Bergquist) were examined on a subtidal reef on the Wellington south coast, New Zealand. For both species, survival of adult sponges was high in all seasons, whereas juvenile sponges had poor survival. Recruitment of Latrunculia sp. nov. occurred in all seasons indicating that this species is reproductively active throughout the year. P. croceus recruited mostly in autumn, supporting previous work that found the sponge to be reproductively active in summer and early autumn only. For both sponge species, growth rates varied greatly between individuals and were unaffected by initial sponge size within the range examined. Sponges generally grew during winter and spring as the water temperature rose, and shrank during summer and autumn as the water temperature fell. This growth pattern may relate to seasonal variation in food abundance, and for P. croceus it may result also from seasonal differences in reproductive investment. After 2 years, Latrunculia sp. nov. and P. croceus had on average, halved and doubled in size, respectively. Latrunculia sp. nov. showed a seasonal pattern of bioactivity, being most active in spring possibly to prevent the surface overgrowth of fouling organisms. P. croceus had no seasonal pattern of bioactivity, but individuals were either very active or inactive. The bioactive metabolites in both species possibly aid in competitive interactions and prevent predation and biofouling.  相似文献   
126.
Drifting mysids were sampled to determine diel activity, and whether mysid numbers vary with respect to inflowing and outflowing tides. Samples of drifting mysids were collected at the mouth of the Taieri River, New Zealand, over one 24‐h cycle using five replicate conical drift nets in January 1999. One‐night and 1‐day ebb and flood tide were each sampled. Four species of mysid Tenagomysis macropsis, T. novae‐zealandiae, T. robusta, and an apparently undescribed species of Gastrosaccus sp., were collected over the sampling period. One species, T. robusta, has not previously been collected from estuarine or riverine systems. The undescribed Gastrosaccus sp. was the most abundant of the four species. All four species were more abundant at night, with T. robusta and Gastrosaccus sp. being considerably more abundant in the drift on outflowing tides. In contrast, roughly equal numbers of T. macropsis and T. novae‐zealandiae were observed drifting in and out of the estuary at night.  相似文献   
127.
A breeding-selection program for the clam,Meretrix meretrix,was conducted since 2004.Two of the selection populations were generated with the shell color pattern as an additional selection criterion and named as SP(purple stripes)population and SB(black dots)population.The third-generation SP and SB populations(08G3SP and 08G3SB,respectively)were cultured at two commercial clam farms and a nursery pond and their shell lengths were compared.08G3SB clams had significantly larger sizes than 08G3SP clams at commercial clam farms(p<0.05),yet 08G3SB individuals were significantly smaller than 08G3SP individuals at the nursery pond(p<0.05).Then,we examined the growth of the fourth-generation SP and SB populations(10G4SP and 10G4SB,respectively)at a commercial farm,and found that the shell lengths of the 10G4SB clams increased at a significantly higher growth rate than the 10G4SP clams(p<0.05)from May to September,when the water temperature was between 24.2–27.5 C,while 10G4SB lost the growth advantage in the other months.These results indicated that SP and SB populations responded differently to environmental factors,so it is beneficial for the clam farmers to select a suitable population according to the culture environment.Furthermore,a diallel mating of the SB and SP populations was designed to investigate whether their hybrid population would show heterosis.However,the heterosis was not shown in this study,which might result from the slight genetic divergence between SB and SP populations.  相似文献   
128.
We examined whether adults of three species of sea urchins species (Diadema antillarum, Arbacia lixula, and Paracentrotus lividus) exhibit a consistent depth-dependent partitioning pattern on rocky reefs of the Canarian Archipelago (eastern Atlantic). Hydrodynamic experiments were carried out to quantify the resistance to flow-induced dislodgement in these three species. We tested the model that different morphology can result in habitat partitioning among these sea urchins. Abundances of D. antillarum increased with depth. In contrast, A. lixula and P. lividus showed the opposite zonation pattern, coexisting in high abundances in the shallowest depths (<5 m), and occurring in low densities in the deepest part of reefs (>7 m). Both A. lixula and P. lividus had greater adhesion-surface to body-height ratios than D. antillarum. Similarly, A. lixula and P. lividus showed a greater ability to resist flow-induced dislodgement compared with D. antillarum. The mean “velocity of dislodgement” was 300% and 50% greater for A. lixula and P. lividus, respectively, relative to D. antillarum, for any particular size. As a result, A. lixula and P. lividus are better fitted to life in high-flow environments than D. antillarum. We conclude that the risk of dislodgement by water motion likely play a relevant role in the vertical distribution patterns of these sea urchins in the eastern Atlantic.  相似文献   
129.
本文依据土壤测量、岩石测量成果,研究了刘来沟钼矿化探异常的水平分带、垂直分带特征,并对刘来沟钼矿外围找矿进行了初步预测。  相似文献   
130.
青海湖北岸土壤温度变化特征   总被引:4,自引:1,他引:3  
利用1981-2008年刚察站0~320cm逐月平均土壤温度资料和2001-2008年逐日土壤温度观测资料,分析了青海湖北岸土壤温度变化特征、气候突变和异常年份.结果表明:各层年、季平均土壤温度呈现为极显著的升高趋势,升温率为0.25~0.91℃.(10a)-1;月平均土壤温度呈波形变化,位相随深度增加而滞后;日平均土壤温度呈正弦曲线变化;1月和10月随着深度的增加,土壤温度逐渐增大,4月和7月土壤温度随深度增加而减小;14:00时土壤温度随着深度增加逐渐下降,2:00时、8:00时和20:00时土壤温度随着深度增加而升高;除冬季5cm和15cm,秋季40cm平均土壤温度变化相对平稳,未出现突变现象外,其余各层年、季平均土壤温度均发生了突变;15cm、20cm、40cm、160cm和320cm年平均土壤温度均在20世纪80年代出现了异常偏冷,春季平均土壤温度出现了异常偏暖现象,其余各季和年平均地均表现为异常偏冷.  相似文献   
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