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51.
基于多源遥感数据的区域生态系统服务价值年际动态监测 ——以中原城市群为例 总被引:2,自引:0,他引:2
通过对多源遥感数据在生态系统服务价值(ESV)遥感模型中的尺度效应分析,选择满足最佳空间分辨率和长时间序列的遥感数据,对中原城市群区域2001~2013年的ESV实现了逐年逐像元水平的动态监测。结果表明:该区应用于遥感模型输入数据的最适空间分辨率为30~1 000 m,相对于30 m尺度,其他尺度估算结果的相对偏差均小于0.4%;结合年际动态监测的需求,选择了MODIS数据产品(空间分辨率500 m,时间尺度1 a)作为遥感模型的最佳数据源;研究区ESV总值在研究期内整体上呈显著增长趋势,增速约为8.6亿元/a,但在持续增长过程中经历了3次波动,且表现得越来越剧烈;在空间上,研究区ESV多年均值呈现出明显的不均衡性,表现为从西南向东部递减的趋势。研究表明此方法简单易行,初步实现了区域ESV年际动态监测遥感模型的准业务化运行。 相似文献
52.
When travelling, people are accustomed to taking and uploading photos on social media websites, which has led to the accumulation of huge numbers of geotagged photos. Combined with multisource information (e.g. weather, transportation, or textual information), these geotagged photos could help us in constructing user preference profiles at a high level of detail. Therefore, using these geotagged photos, we built a personalised recommendation system to provide attraction recommendations that match a user's preferences. Specifically, we retrieved a geotagged photo collection from the public API for Flickr (Flickr.com) and fetched a large amount of other contextual information to rebuild a user's travel history. We then created a model-based recommendation method with a two-stage architecture that consists of candidate generation (the matching process) and candidate ranking. In the matching process, we used a support vector machine model that was modified for multiclass classification to generate the candidate list. In addition, we used a gradient boosting regression tree to score each candidate and rerank the list. Finally, we evaluated our recommendation results with respect to accuracy and ranking ability. Compared with widely used memory-based methods, our proposed method performs significantly better in the cold-start situation and when mining ‘long-tail’ data. 相似文献
53.
NUFFT-Based Iterative Reconstruction Algorithm for Synthetic Aperture Imaging Radiometers 总被引:2,自引:0,他引:2
Synthetic aperture imaging radiometers (SAIRs) are powerful sensors for high-resolution observation of the Earth at low microwave frequencies. However, the future application of this new technology is limited by its large number of element antennas and receiving channels. In order to further reduce the complexity of the whole system, the circular and rotating array configurations have been proposed. Their disadvantages lie primarily in more complicated image reconstruction, because the conventional fast Fourier transform (FFT) method could not be used directly for image reconstruction. This letter introduces an iterative method for the reconstruction of radiometric brightness temperature maps from nonuniform visibility function samples. This method combines the conjugate gradient algorithm with min-max nonuniform FFT approach, which has been shown to provide considerably improved image quality relative to the traditional gridding method. Simulations for SAIRs were performed and showed better image quality in comparison to the traditional frequency interpolation method. 相似文献
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胶州湾菲律宾蛤仔死壳分布与生态环境关系的研究 总被引:1,自引:0,他引:1
胶州湾菲律宾蛤仔栖息地带由于近年受拖耙捕生产,底质遭到频繁骚动。同时沿岸带局部水域环境污染严重,以及河口盐度突发性骤降等因素,直接影响了蛤仔的存活率。因而蛤仔死壳逐年增多。据1990年调查,9月份幼蛤和成蛤死壳平均密度比同年4月分别增加3.5倍和1.8倍,蛤仔资源量亦受一定损失。 相似文献
56.
Two photometric follow-up transit (primary eclipse) observations on WASP-43 b and four observations on TrES-3 b are performed using the Xuyi Near-Earth Object Survey Telescope. After differential photometry and light curve analysis, the physical parameters of the two systems are obtained and are in good match with the literature. Combining with transit data from a lot of literature, the residuals (O ? C) of transit observations of both systems are fitted with the linear and quadratic functions. With the linear fitting, the periods and transit timing variations (TTVs) of the planets are obtained, and no obvious periodic TTV signal is found in both systems after an analysis. The maximum mass of a perturbing planet located at the 1:2 mean motion resonance (MMR) for WASP-43 b and TrES-3 b is estimated to be 1.826 and 1.504 Earth mass, respectively. By quadratic fitting, it is confirmed that WASP-43 b may have a long-term TTV which means an orbital decay. The decay rate is shown to be P? = (?0.005248 ± 0.001714) s·yr?1, and compared with the previous results. Based on this, the lower limit of the stellar tidal quality parameter of WASP-43 is calculated to be , and the remaining lifetimes of the planets are presented for the different values of the two systems, correspondingly. 相似文献
57.
Journal of Oceanology and Limnology - Little is known about the roles of dynorphin and Kappa opioid receptor (KOR) in mollusks. In this study, we aim to determine the distribution of dynorphin A... 相似文献
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59.
This paper is a brief account of the essential points of geomechanics initited in China by Prof. J. S. Lee in the 1920's and some important results achieved by some Chinese petroleum geologists in recent years by applying geomechanics to the exploration and prospecting of oil and gas in eastern China. 相似文献
60.
在我国南方,广泛发育各种酸性岩浆侵入体,蕴藏着丰富的稀土、稀有和放射性元素等矿产资源。找矿勘探及地质研究证明,其中大部分与燕山期花岗岩体有密切关系。实际情况是只有部分燕山期花岗岩体中,上述有用元素能富集成矿,而在更多的燕山期花岗岩体中,并未发现有工业价值的矿床。铌钽矿化与钨矿化可在一地存在,也可在不同岩体中出现,但铌钽矿化、钨矿化与铀矿化经常不在一地。上述现象纯属偶然的巧合,还是某种内在联系的反映呢?含矿花岗岩与不含矿的花岗岩在化学元素组合上有没有差异?研究这个问题对今后的找矿和勘探显然是有重要意义的。 相似文献