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排序方式: 共有163条查询结果,搜索用时 31 毫秒
41.
A major application of satellite remote sensing is the estimation of the acreage of agricultural crops. The potential for crop yield estimation using satellite remote sensing exists, but research in this area is still in its early stages. In this paper we survey the methodology for using remotely sensed data in agricultural surveys, based primarily on research conducted during the Large Area Crop Inventory Experiment (LACIE) and the follow-on program Agricultural Research and Inventory Surveys Through Aerospace Remote Sensing (AgRISTARS). The data obtained from multispectral scanner (MSS) and thematic mapper (TM) sensors onboard the Landsat series of satellites are described. Approaches for preprocessing, transferring, and modeling these data for understanding the relationship between their temporal behavior and crop growth cycles are discussed. Finally, techniques for crop identification and area and yield estimation are briefly described  相似文献   
42.
以中国期刊全文数据库、中国优秀硕士学位论文全文数据库和中国博士学位论文全文数据库为文献检索来源,以生态脆弱性和GIS为检索词,对1980~2010年的文章进行了检索与分类统计,从数量、区域、内容、方法上对我国生态脆弱性研究进展进行分析。结果表明:期刊总论文259篇,其中核心期刊论文占44%;从1993年开始,相关期刊论文和硕博论文总体上呈逐渐上升趋势;2000年之后,我国生态脆弱性研究成为研究热点;从区域上分析,早期西南石灰岩山地生态脆弱区和华北平原生态脆弱区,北方半干旱-干旱生态脆弱区和西北半干旱生态脆弱区研究较多;后期南方丘陵生态脆弱区研究发展较快;从内容上分析,实证研究多于理论研究;从方法上分析,早期多以县域为数据单元,2000年之后开始出现栅格法地理信息系统技术,2005年起数量逐年增多。目前,从景观的角度探讨生态脆弱性的研究比较少,还没实现脆弱性的三维可视化表达。  相似文献   
43.
内源性大麻素的合成与分解酶,以及大麻素受体组成了内源性大麻素信号系统,这个系统参与着血脂、血糖代谢不同水平的控制。摄取能量的失衡,内源性大麻素系统就会出现调节障碍,在一些脏器的自身能量平衡方面会出现过度活跃,特别是腹内脂肪组织,这种调节障碍将有助于腹部脂肪堆积和脂联素释放减少,成为心脏代谢、肥胖症和糖尿病的危险因素。  相似文献   
44.
Satellite data used in combination with a stochastic production function method reveal an inefficient formal economy in rural Rostov Oblast 2013–2015 embedded in an overall (formal and informal) relatively efficient economy with the measurement of both important to better understand non-economic impacts of sanctions. Increased military activity may have insulated the formal economy of the border area from poor economic performance and the deindustrialization that characterizes adjacent areas. The current Oblast Administration’s grant program to localities does not reward relatively efficient economic performance with a model suggested here to change the policy. The region’s economy has the ability to absorb many Ukrainian refugees though non-economic issues support the current assistance from other Russian regions in helping relocate refugees beyond Rostov region. Like other conflict zones, urban areas experience less of an impact relative to rural areas.  相似文献   
45.
Background: The etiology of benign prostatic hyperplasia (BPH) has not been well established. The preferred medical treatment for many men with symptomatic benign prostatic hyperplasia is either an α-adrenergic receptor antagonist (α-blocker), or a 5α-reductase inhibitor. Single nucleotide polymorphism (SNP) is a powerful tool for successful implementation of individualized treatment.

Methods: Eighteen SNPs associated with drug efficacy in a Chinese population were genotyped in 790 BPH cases (330 aggressive and 460 non-aggressive BPH cases) and 1008 controls. All BPH patients were treated with α-adrenergic blockers for at least 9 months. We tested the associations between tagging single nucleotide polymorphism and BPH risk/aggressiveness, clinical characteristics at baseline, including the International Prostate Symptom Score (IPSS) and total prostate volume, and changes in clinical characteristics after treatment.

Results: There were nine SNPs associated with BPH risk, clinical progression and therapeutic effect. (1) There were nine tSNPs been chosen in CYP3A4, CYP3A5 and RANBP3L genes. (2) The SNP, rs16902947 in RANBP3L at 5p13.2 (p?=?.01), was significantly associated with BPH. (3) We found two SNPs, rs16902947 in RANBP3L at 5p13.2 (p?=?.0388) and rs4646437 in CYP3A4 at 7q21.1 (p?=?.0325), associated with drug effect. (4) Allele “G” for rs16902947 was found to be risk alleles for BPH risk (OR=?2.357, 95%CI 1.01–1.48). The “A” allele of rs4646437 was associated with lower IPSS at baseline (β=??0.4232, p=?.03255).

Conclusions: rs16902947, rs16902947 and rs4646437 single nucleotide polymorphisms are significantly associated with the clinical characteristics of benign prostatic hyperplasia and the efficacy of benign prostatic hyperplasia treatment.  相似文献   
46.
以半成熟椰子果皮为材料 ,采用常规方法测定了半成熟椰子果皮的粗灰分、钙、总磷的含量 .  相似文献   
47.
采用7个抗氟性不同的桑蚕品种,添氟后,对其血液钙离子浓度以及血细胞数量的变化情况进行测定,发现这两个指标和抗氟性之间都有着极好的正相关关系,而血细胞减少率则呈负相关关系.在270mg/L的添氟浓度以下,相关系数都随着浓度的上升而增大,达510mg/L后都减小.说明氟-钙-血细胞之间存在着相互依赖关系,在一定范围内,钙可以保护血细胞使其不受氟离子的损害.蚕对氟化物抗性的程度,既反映在血液钙离子含量上,也反映在血细胞被破坏的程度上.而在510mg/L的较高添氟浓度时,钙的保护作用趋弱,氟突破钙的屏障而对细胞造成损害.  相似文献   
48.
Remote sensing is a helpful tool for crop monitoring or vegetation-growth estimation at a country or regional scale. However, satellite images generally have to cope with a compromise between the time frequency of observations and their resolution (i.e. pixel size). When concerned with high temporal resolution, we have to work with information on the basis of kilometric pixels, named mixed pixels, that represent aggregated responses of multiple land cover. Disaggreggation or unmixing is then necessary to downscale from the square kilometer to the local dynamic of each theme (crop, wood, meadows, etc.).

Assuming the land use is known, that is to say the proportion of each theme within each mixed pixel, we propose to address the downscaling issue through the generalization of varying-time regression models for longitudinal data and/or functional data by introducing random individual effects. The estimators are built by expanding the mixed pixels trajectories with B-splines functions and maximizing the log-likelihood with a backfitting-ECME algorithm. A BLUP formula allows then to get the ‘best possible’ estimations of the local temporal responses of each crop when observing mixed pixels trajectories. We show that this model has many potential applications in remote sensing, and an interesting one consists of coupling high and low spatial resolution images in order to perform temporal interpolation of high spatial resolution images (20 m), increasing the knowledge on particular crops in very precise locations.

The unmixing and temporal high-resolution interpolation approaches are illustrated on remote-sensing data obtained on the South-Western France during the year 2002.  相似文献   

49.
甲基丙烯酸二甲胺基乙酯(DMAEMA)是一种广泛应用于油田钻井的功能单体。采用金属钙(Ca)为催化剂,以甲基丙烯酸甲酯(MMA)和二甲氨基乙醇(DMAE)为原料,吩噻嗪为阻聚剂,用酯  相似文献   
50.
钙在植物营养中的作用   总被引:3,自引:0,他引:3  
钙是植物维持正常生命活动所必需的营养元素之一,在植物体内执行多种生理功能;目前,钙已不再仅仅被看作是一种参与构成植物各种器官、组织的营养物质,而且还作为信号物质调节细胞功能,为植物体内各种代谢活动的正常进行提供保障;此外,钙对植物赖以生长的土壤介质的改良也发挥重要作用。因此,钙在植物营养生理中的作用受到人们的广泛关注。本文在查阅大量文献的基础上,对当前这方面的研究成果及动态进行综述。  相似文献   
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