一种改进的阈值法提取SAR图像海面油污     

吴爱琴  孙正林 《水土保持通报》2011,36(4)

对阈值的选取作了相关研究,提出了一种改进的阈值法提取SAR图像海面油膜。试验表明,改进方法在提取海面油膜的应用中具有一定的可行性。  相似文献   

Marinopyrrole Derivatives as Potential Antibiotic Agents against Methicillin-Resistant Staphylococcus aureus (III)     

Yan Liu  Nina M. Haste  Wdee Thienphrapa  Jerry Li  Victor Nizet  Mary Hensler  Rongshi Li 《Marine drugs》2014,12(5):2458-2470

The marine natural product, marinopyrrole A (1), was previously shown to have significant antibiotic activity against Gram-positive pathogens, including methicillin-resistant Staphylococcus aureus (MRSA). Although compound (1) exhibits a significant reduction in MRSA activity in the presence of human serum, we have identified key modifications that partially restore activity. We previously reported our discovery of a chloro-derivative of marinopyrrole A (1a) featuring a 2–4 fold improved minimum inhibitory concentration (MIC) against MRSA, significantly less susceptibility to serum inhibition and rapid and concentration-dependent killing of MRSA. Here, we report a novel fluoro-derivative of marinopyrrole A (1e) showing an improved profile of potency, less susceptibility to serum inhibition, as well as rapid and concentration-dependent killing of MRSA.  相似文献   

基于合成孔径雷达的农作物识别研究进展   总被引：13，自引：8，他引：5  

王迪  周清波  陈仲新  刘佳 《农业工程学报》2014,30(16):203-212

精准识别农作物对于及时准确估计农作物种植面积、产量等关键农情信息具有重要意义。合成孔径雷达（synthetic aperture radar,SAR）以其不受云雨天气影响,可全天时、全天候监测等优点已被广泛应用于农情遥感监测领域,为大区域尺度的农作物遥感识别提供了强有力的数据保障和技术支持。该文以雷达技术的发展进程为论述主线,对20余年来国内外农作物SAR识别研究与实践应用的新进展进行了系统总结,具体归纳为4个方面：早期研究（20世纪80年代末－2002年）,特征是以单波段、单极化、多时相SAR数据为主;基于多极化、多波段SAR数据进行农作物识别与面积监测研究;利用SAR与光学遥感相结合提高农作物的识别精度与效率研究;农作物SAR分类算法研究。在今后农作物SAR识别研究中,对于复杂种植结构背景下的旱地作物识别,如何优化组合SAR系统工作参数（极化方式、频率及入射角等）及与光学遥感融合来提高农作物识别精度与时效性,发展机理性的农作物SAR分类算法将是需要重点解决的3个问题。  相似文献   

全极化SAR图像的煤矿区土地覆盖信息分层提取方法研究     

侯飞  胡召玲  成晨 《中国生态农业学报》2013,21(9):1142-1148

为弥补光学遥感在煤矿区资源与生态环境监测中应用的不足, 研究应用全极化SAR图像有效提取煤矿区土地覆盖信息的方法具有重要意义。针对全极化SAR图像极化信息丰富、斑点噪声多、局部异质性大等特点, 提出采用面向对象的影像分类方法对其进行分层土地覆盖信息提取。以徐州市西南部的煤矿区为研究区, 选取Radarsat-2的全极化SAR图像, 分析了研究区内全极化SAR图像中典型地物的灰度特征, 提出面向对象分类方法所涉及的最优分割尺度选择法, 给出全极化SAR图像分割对象后向散射特征的计算方法。对研究区的SAR图像进行试验, 首先对SAR图像进行多尺度分割, 选择各土地覆盖类型的最优分割尺度, 然后在该尺度下计算出土地覆盖类型的后向散射特征指数, 最后采用模糊逻辑分类法分层提取出研究区内的土地覆盖信息。结果表明: 在适于各土地覆盖类型提取的最优分割尺度下, 充分利用分割对象的灰度、形状、纹理以及类间相关特征, 并综合应用隶属函数法和最邻近分类法, 能有效地提取煤矿区的农田、道路、塌陷地、建筑物、山林这5类土地覆盖信息。与最大似然分类法相比, 该方法能够较好地消除"椒盐现象", 各种土地覆盖类型的提取精度都有所提高, 其总体分类精度可提高38.3%。  相似文献   

生物炭、有机肥连续施用对盐碱土壤改良效果研究   总被引：5，自引：0，他引：5  

王世斌  高佩玲  赵亚东  相龙康  孟庆梅  刘月 《干旱地区农业研究》2021,39(3):154-161

为探究生物炭和有机肥连续施用3 a对黄河三角洲地区中度盐碱土改良效果及对水溶性盐基离子时空变化规律的影响,采取田间小区试验,共设置CK(仅施N 550 kg·hm~(-2)·a~(-1),P_2O_5 120 kg·hm~(-2)·a~(-1))、C1(5 t·hm~(-2)·a~(-1)生物炭)、C2(10 t·hm~(-2)·a~(-1)生物炭)、C3(20 t·hm~(-2)·a~(-1)生物炭)、N1(7.5 t·hm~(-2)·a~(-1)有机肥)、N2(10 t·hm~(-2)·a~(-1)有机肥)6个处理。结果表明:(1)生物炭对0～20 cm土层土壤含水率提升效果优于有机肥,C3处理增幅最大,C2处理略小于C3,较CK增幅达17.98%;20～40 cm土层,各处理土壤含水率呈下降趋势(降幅4.39%～9.23%);土壤含水率变异程度表征C2处理具有更稳定的保水性能。(2)生物炭处理明显降低了各层土壤含盐量(降幅3.56%～9.80%),C2处理较CK降幅达9.80%,有机肥处理降盐效果欠佳。(3)在0～40 cm土层中,各处理表现出降低Na~+含量(降幅4.59%～12.51%)、钠吸附比(SAR降幅12.67%～23.61%)及碱化度(ESP,降幅16.05%～30.06%)的效果,其中生物炭处理对Na~+的降低效果优于有机肥,C2处理较优,有效地抑制了Na~+的毒害,但对Ca~(2+)、Mg~(2+)含量提升及SAR、ESP值降低的效果略差于有机肥。(4)生物炭对小麦增产效果优于有机肥,且C2处理效果最优,增产率达20.97%。综上所述,生物炭在提高土壤持水能力、作物产量和盐碱地综合改良方面优于有机肥,且C2处理较优。因此,黄河三角洲地区的中度盐碱土采用10 t·hm~(-2)·a~(-1)的生物炭施用量进行改良较为适宜。  相似文献   

The interactions between piperonyl butoxide and E4, a resistance‐associated esterase from the peach‐potato aphid,Myzus persicae Sulzer (Hemiptera: Aphididae)     

Despina Philippou  Valerio Borzatta  Elisa Capparella  Leni Moroni  Linda Field  Graham Moores 《Pest management science》2013,69(4):499-506

BACKGROUND: It has been reported previously that piperonyl butoxide (PBO) can inhibit both P450 and esterase activity. Although the method by which PBO combines with cytochrome P450 has been identified, the way in which it acts as an esterase inhibitor has not been established. This paper characterises the interactions between PBO and the resistance‐associated esterase in Myzus persicae, E4. RESULTS: After incubation with PBO/analogues, hydrolysis of 1‐naphthyl acetate by E4 is increased, but sequestration of azamethiphos is reduced. Rudimentary in silico modelling suggests PBO docks at the lip of the aromatic gorge. CONCLUSIONS: PBO binds with E4 to accelerate small substrates to the active‐site triad, while acting as a blockade to larger, insecticidal molecules. Structure–activity studies with analogues of PBO also reveal the essential chemical moieties present in the molecule. © 2012 Society of Chemical Industry  相似文献   

Soil and Groundwater Relationships with Pistachio Yield in the Rafsanjan Area,Iran     

《Communications in Soil Science and Plant Analysis》2012,43(4):660-671

This study was conducted to examine the spatial variability of groundwater quality factors and to determine soil physicochemical properties in order to distinguish their relationships with pistachio yield in the Rafsanjan area, Iran. One hundred fifty-seven water samples from the wells of the studied area were evaluated for electrical conductivity (EC), sodium (Na⁺), calcium (Ca²⁺), magnesium (Mg²⁺), sulfate (SO₄ ^2–), bicarbonate (HCO₃ ^–), chloride (Cl^–), total hardness, and sodium adsorption ratio (SAR). Groundwater levels of the wells were also recorded. The EC and SAR values of groundwater for some of the wells separately compared with pistachio yield in the orchards irrigated with these wells. Six pistachio gardens with the same management but in different parts were selected, and each garden was divided in two (desired and undesired) parts. In each part of these orchards, soil samples were randomly taken in three replicates from depths of 0–40 and 40–80 cm to determine soil properties. One soil profile was also excavated for soil classification in each part of these gardens. Groundwater in most of the area had EC > 8 dS m^–1 and SAR ≥ 13 (meq L^–1)^0.5. The lowest qualities of groundwater were found in the eastern, southern, and the northern parts of the area, where water's negative effects on pistachio yield have been reported. Statistical results for selected gardens showed that pistachio yield was affected considerably by salinity and clay content of the soils. Modern irrigation techniques and mixing high-quality water with poor-quality water in the area is necessary to prevent the reduction of the water table in the area. Preparing continuous soil salinity and texture maps are recommended for proper pistachio management in the area.  相似文献   

苏北滩涂区水盐调控措施对土壤盐渍化的影响研究   总被引：3，自引：0，他引：3  

韩建均  杨劲松  姚荣江  陈效民 《土壤》2012,44(4):658-664

苏北沿海滩涂区具有大面积存在盐渍化风险的可利用耕地。近年来不合理的开发利用使该地区土壤盐渍化程度加重。通过微区定位试验,对该区典型滩涂盐渍化土壤进行微咸水灌溉结合农艺处理的试验研究,探讨了利用水盐调控措施防控该地区土壤盐渍化程度的可能性。结果表明,在低矿化度(3 g/L左右)的微咸水灌溉条件下,石膏处理和秸秆覆盖处理均可以有效降低各层土壤SAR值,降低耕层土壤盐分含量,并且促进作物生长;当灌溉水矿化度达到6 g/L时,石膏处理仍具有一定控盐效果,但覆盖处理已不能控制土壤表层盐分含量的升高,作物的生长开始受到影响;当灌溉水矿化度达到10 g/L时,各处理耕层均显著积盐,作物生长受到显著影响。因此,6 g/L及以上矿化度的咸水不能用于该地区的灌溉,6 g/L以下浓度的咸水灌溉须配合石膏和秸秆覆盖处理使用。该研究为苏北滩涂区农田管理提供一定的参考依据。  相似文献   

华南农作物覆盖区土壤水分ENVISAT—ASAR 与MODIS 数据联合反演算法研究   总被引：2，自引：0，他引：2  

刘万侠  刘旭拢  王娟  曾文华 《干旱地区农业研究》2008,26(3):39-43

准确、及时地获取大面积地表土壤水分信息在农业科学领域具有较大的应用潜力。本文以地域特色突出的广东省徐闻县为试验区,联合使用双极化ENVISAT-ASAR数据和光学遥感MODIS数据,充分利用MODIS数据的高重复覆盖率,提取试验日期内的归一化差分水指数(NDWI),计算各试验点所对应的植被含水量(VWC)数据,相较于NDVI,NDWI具有不易饱和的特点,更加适合于本次研究所在的高植被覆盖区。最后利用"水—云模型"从ASAR数据总的后向散射中去除植被的影响,建立裸土后向散射系数与实测土壤含水量之间的关系,拟合结果VV极化优于HH极化,相关系数为VV极化R=0.865,HH极化R=0.676,总体上针对农作物覆盖地表土壤水分变化的估算算法还需要更进一步发展和改进,以提高反演精度。  相似文献   

星载雷达影像对盐渍地微观离子的响应研究     

何祺胜  曹春香  塔西甫拉提·特依拜 《水土保持通报》2009,29(5):17-20

以库车绿洲为例,探讨了星载雷达影像对表征土壤盐渍化微观离子的响应情况.选取春、秋两季的Radarsat影像数据,野外采集土壤剖面0-10 cm和0-50cm处土样,室内测定其8大粒子含量(Na~+,K~+,Mg~(2+),Ca~(2+),Cl~-,SO_4~(2-),HCO_3~--,CO_3~(2-))以及pH值、电导率、矿化度、含盐量.采用GPS定位技术,记录每一采样点位的经纬度坐标和雷达影像进行匹配,采用灰色关联分析法分析了Radarsat C波段HH极化对微观粒子在春、秋季节0-10 cm和0-50 cm土壤剖面的响应.结果表明,春季雷达影像对pH值响应强烈,对含盐量响应不稳定,对电导率、矿化度响应一般.就阳离子而言,对Ca~(2+)响应最为显著;就阴离子而言,对HCO_3~-响应最为显著.10月份雷达影像对pH值、电导率响应强烈,对含盐量响应不稳定,对矿化度响应一般.就阳离子而言,无明显规律.就阴离子而言Cl~-响应最为显著,SO_4(2-),HCO_3~-无明显规律.  相似文献