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Russia's Precious Metals Market: Condition and Prospects
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作者 KOTLYAR A.Yu. 《贵金属》 CAS CSCD 北大核心 2012年第A01期287-287,共1页
The region of existence of phases in equilibrium with the solid solution based on palladium. Presented to analyze the current situation in the market of precious metals in Russia. Provides information about the produc... The region of existence of phases in equilibrium with the solid solution based on palladium. Presented to analyze the current situation in the market of precious metals in Russia. Provides information about the production and processing of precious metals. Prospects for the most likely path of development of the Russian market of precious metals. 展开更多
关键词 Russia’s Precious Metals Market Condition and prospects
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Small Scale Mining in Tanzania Toward Sustainable Use(Prospects,Opportunities and Challenges for Environmental Management)
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作者 Stephen Joseph Nyagonde Nancy Nai Laizer 《地学前缘》 EI CAS CSCD 北大核心 2009年第S1期175-176,共2页
Although small scale mining management is a complex task,many countries in the world have managed to develop mining management regimes that can improve the economic and environmental efficiency of the small scale mini... Although small scale mining management is a complex task,many countries in the world have managed to develop mining management regimes that can improve the economic and environmental efficiency of the small scale mining sector.This paper attempts to explore the mental picture of opportunities and challenges of the environmental management in small scale mining in Tanzania focusing on 展开更多
关键词 small scale MINING PROSPECT challenges ENVIRONMENTAL management Tanzania
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Earth Science in the Era of Foundation Models:How AlphaEarth is Reshaping Quantitative Geoscience
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作者 CHENG Qiuming YANG Yilin +1 位作者 ZHOU Yuanzhi ZHANG Yuanzhi 《地学前缘》 北大核心 2025年第6期396-410,共15页
Since the beginning of the 21st century,advances in big data and artificial intelligence have driven a paradigm shift in the geosciences,moving the field from qualitative descriptions toward quantitative analysis,from... Since the beginning of the 21st century,advances in big data and artificial intelligence have driven a paradigm shift in the geosciences,moving the field from qualitative descriptions toward quantitative analysis,from observing phenomena to uncovering underlying mechanisms,from regional-scale investigations to global perspectives,and from experience-based inference toward data-and model-enabled intelligent prediction.AlphaEarth Foundations(AEF)is a next-generation geospatial intelligence platform that addresses these changes by introducing a unified 64-dimensional shared embedding space,enabling-for the first time-standardized representation and seamless integration of 12 distinct types of Earth observation data,including optical,radar,and lidar.This framework significantly improves data assimilation efficiency and resolves the persistent problem of“data silos”in geoscience research.AEF is helping redefine research methodologies and fostering breakthroughs,particularly in quantitative Earth system science.This paper systematically examines how AEF’s innovative architecture-featuring multi-source data fusion,high-dimensional feature representation learning,and a scalable computational framework-facilitates intelligent,precise,and realtime data-driven geoscientific research.Using case studies from resource and environmental applications,we demonstrate AEF’s broad potential and identify emerging innovation needs.Our findings show that AEF not only enhances the efficiency of solving traditional geoscientific problems but also stimulates novel research directions and methodological approaches. 展开更多
关键词 large-scale models artificial intelligence mineral prospectivity mapping AlphaEarth knowledge graphs deep and covered mineral exploration
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Self-supervised learning artificial intelligence noise reduction technology based on the nearest adjacent layer in ultra-low dose CT of urinary calculi 被引量:3
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作者 ZHOU Cheng LIU Yang +4 位作者 QIU Yingwei HE Daijun YAN Yu LUO Min LEI Youyuan 《中国医学影像技术》 CSCD 北大核心 2024年第8期1249-1253,共5页
Objective To observe the value of self-supervised deep learning artificial intelligence(AI)noise reduction technology based on the nearest adjacent layer applicated in ultra-low dose CT(ULDCT)for urinary calculi.Metho... Objective To observe the value of self-supervised deep learning artificial intelligence(AI)noise reduction technology based on the nearest adjacent layer applicated in ultra-low dose CT(ULDCT)for urinary calculi.Methods Eighty-eight urinary calculi patients were prospectively enrolled.Low dose CT(LDCT)and ULDCT scanning were performed,and the effective dose(ED)of each scanning protocol were calculated.The patients were then randomly divided into training set(n=75)and test set(n=13),and a self-supervised deep learning AI noise reduction system based on the nearest adjacent layer constructed with ULDCT images in training set was used for reducing noise of ULDCT images in test set.In test set,the quality of ULDCT images before and after AI noise reduction were compared with LDCT images,i.e.Blind/Referenceless Image Spatial Quality Evaluator(BRISQUE)scores,image noise(SD ROI)and signal-to-noise ratio(SNR).Results The tube current,the volume CT dose index and the dose length product of abdominal ULDCT scanning protocol were all lower compared with those of LDCT scanning protocol(all P<0.05),with a decrease of ED for approximately 82.66%.For 13 patients with urinary calculi in test set,BRISQUE score showed that the quality level of ULDCT images before AI noise reduction reached 54.42%level but raised to 95.76%level of LDCT images after AI noise reduction.Both ULDCT images after AI noise reduction and LDCT images had lower SD ROI and higher SNR than ULDCT images before AI noise reduction(all adjusted P<0.05),whereas no significant difference was found between the former two(both adjusted P>0.05).Conclusion Self-supervised learning AI noise reduction technology based on the nearest adjacent layer could effectively reduce noise and improve image quality of urinary calculi ULDCT images,being conducive for clinical application of ULDCT. 展开更多
关键词 urinary calculi tomography X-ray computed artificial intelligence prospective studies
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Ultrafast pulse wave velocity technique for evaluating changes of carotid artery elasticity in Hashimoto thyroiditis patients with euthyroidism 被引量:2
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作者 JIANG Yanhui LIU Meiling +1 位作者 XIE Jingwen ZHANG Jianxing 《中国医学影像技术》 CSCD 北大核心 2024年第8期1179-1182,共4页
Objective To explore the value of ultrafast pulse wave velocity(UFPWV)technique for evaluating changes of carotid artery elasticity in Hashimoto thyroiditis(HT)patients with euthyroidism.Methods Conventional ultrasoun... Objective To explore the value of ultrafast pulse wave velocity(UFPWV)technique for evaluating changes of carotid artery elasticity in Hashimoto thyroiditis(HT)patients with euthyroidism.Methods Conventional ultrasound and UFPWV for carotid artery were prospectively performed in 91 HT patients with euthyroidism(HT group)and 81 healthy subjects(control group).Clinical data and ultrasonic parameters were compared between groups.Spearman correlation analysis was performed to observe the correlations of carotid pulse wave velocity in end of systole(PWV-ES)with clinical indexes and other ultrasonic parameters in HT group.Multiple stepwise linear regression analysis was used to screen the independent impact factors of increased carotid PWV-ES in HT group.Results Significant differences of thyroid peroxidase antibody(TPOAb),thyroglobulin antibody(TgAb),total cholesterol(TC),low density lipoprotein and neutrophil-lymphocyte ratio(NLR)were found between groups(all P<0.05).The carotid PWV-ES in HT group was significantly higher than that in control group(P<0.05),while no significant difference of carotid artery intima-media thickness(CIMT)nor carotid pulse wave velocity in beginning of systole(PWV-BS)was found between groups(both P>0.05).Carotid PWV-ES in HT group was positively correlated with patients'age,body mass index,TPOAb,TC,triglyceride,NLR and CIMT(r=0.217—0.707,all P<0.05).Patients'age,TPOAb and NLR were all independent impact factors of increased carotid PWV-ES in HT patients with euthyroidism(all P<0.05).Conclusion UFPWV technique could be used to evaluate changes of carotid artery elasticity in HT patients with euthyroidism,among which PWV-ES was relatively sensitive. 展开更多
关键词 Hashimoto disease carotid arteries ULTRASONOGRAPHY prospective studies
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Isotropic volumetric MRI for displaying cranial perineural spread of cranial nerve in nasopharyngeal carcinoma 被引量:1
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作者 ZHENG Dechun XU Shugui +4 位作者 LAI Guojing HU Chunmiao CAO Xisheng FENG Meimei PENG Li 《中国医学影像技术》 CSCD 北大核心 2024年第8期1164-1169,共6页
Objective To observe the value of isotropic volumetric MRI for displaying perineural spread(PNS)of cranial nerve(CN)in nasopharyngeal carcinoma.Methods Eighty-seven patients with pathologically proven nasopharyngeal c... Objective To observe the value of isotropic volumetric MRI for displaying perineural spread(PNS)of cranial nerve(CN)in nasopharyngeal carcinoma.Methods Eighty-seven patients with pathologically proven nasopharyngeal carcinoma were prospectively enrolled.MR scanning,including three-dimensional liver acquisition with volume acceleration-flexible(3D LAVA_Flex)image,T2WI with fat suppression(T2WI-FS),T1WI,contrast enhancement(CE)T1WI-FS of nasopharynx and neck region were performed.The displaying rates of CN PNS were evaluated and compared between 3D LAVA_Flex and T2WI-FS,T1WI,CE-T1WI-FS at patient level,CN group level and neural level,respectively.Results The displaying rate of CN PNS in all 87 nasopharyngeal carcinoma patients by 3D LAVA_Flex sequence was 49.43%(43/87),higher than that of conventional MRI(30/87,34.48%,P=0.001).Among 59 patients with advanced nasopharyngeal carcinoma diagnosed with conventional sequences,the displaying rate of CN PNS was 71.19%(42/59)by 3D LAVA-Flex sequence,higher than that of conventional MRI(30/59,50.85%,P=0.001).At both patient level and posterior CN level,significant differences of the displaying rate of CN PNS were found between 3D LAVA-Flex sequence and T2WI-FS,T1WI,CE-T1WI-FS,while at CN level,the displaying rates of mandibular nerve PNS,CNⅨ—ⅪPNS in jugular foramen(P<0.05)and CNⅨ—ⅫPNS in carotid space of 3D LAVA_Flex sequence were all significantly higher than that of T2WI-FS,T1WI and CE-T1WI-FS(all P<0.05),of PNS of CNⅢ—Ⅴin cavernous sinus were higher than that of T2WI-FS(P<0.05),while of PNS of hypoglossal nerve were significantly higher than that of T2WI-FS and T1WI(both P<0.05).Conclusion 3D LAVA_Flex sequence could be used to effectively display CN PNS of nasopharyngeal carcinoma. 展开更多
关键词 nasopharyngeal neoplasm cranial nerve magnetic resonance imaging neoplasm metastasis prospective studies
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Right heart modified myocardial performance index and ductus venosus spectrum parameters in pre-eclampsia fetuses for predicting adverse pregnancy outcomes
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作者 GAO Jing LI Hezhou +4 位作者 WANG Ming WU Juan WANG Xinxia LIU Yun ZHU Ziqi 《中国医学影像技术》 CSCD 北大核心 2024年第8期1146-1150,共5页
Objective To observe the values of changes of right heart modified myocardial performance index(Mod-MPI)and ductus venosus(DV)spectrum parameters in pre-eclampsia fetuses for predicting adverse pregnancy outcomes.Meth... Objective To observe the values of changes of right heart modified myocardial performance index(Mod-MPI)and ductus venosus(DV)spectrum parameters in pre-eclampsia fetuses for predicting adverse pregnancy outcomes.Methods Eighty-one pregnant women diagnosed as pre-eclampsia were prospectively enrolled and divided into severe pre-eclampsia(SPE)group(n=39)and mild pre-eclampsia(MPE)group(n=42),while 85 healthy pregnant women were taken as controls(control group).Fetal right heart function parameters,including right ventricular isovolumetric relaxation time(IRT),isovolumetric contraction time(ICT),ejection time(ET),total spent time(TST),Mod-MPI,tricuspid valve peak flow velocity ratio in early and late diastole(TV-E/A),as well as blood flow velocities in each waveform of DV spectrum(S,V,D,and A wave)were obtained,and the pulsatility index(PI)and the ratio of blood flow velocities in each waveform of the DV(S/V,S/D,S/A,V/D,V/A,D/A)were calculated.Intrauterine fetal distress,preterm delivery,neonatal asphyxia and newborn with low weight were considered as adverse pregnancy outcomes.The correlations of right heart Mod-MPI and TV-E/A with DV parameters in pre-eclampsia fetuses were assessed,and their predictive efficacies for adverse pregnancy outcomes were evaluated for right heart Mod-MPI and DV using the receiver operating characteristics(ROC)and the area under the curves(AUC).Results Compared with control group and MPE group,fetal right heart IRT,ICT and Mod-MPI increased and ET decreased in SPE group(all P<0.05).No significant differences of right heart TST and TV-E/A among 3 groups(both P>0.05).Fetal DV A-wave velocity and V/D values progressively decreased but PI progressively increased in control,MPE and SPE groups(all P<0.05).Fetal right heart Mod-MPI in pre-eclampsia was moderately positively correlated with DV PI(r=0.637,P=0.016),while TV-E/A was weakly negatively correlated with DV V/D(r=-0.355,P=0.043).Adverse pregnancy outcomes were noticed in 59 pre-eclampsia cases.The AUC of fetal right heart Mod-MPI and DV PI for predicting adverse pregnancy outcomes in pre-eclampsia cases was 0.897 and 0.848,respectively,without significant difference(Z=0.460,P=0.400).Conclusion Changes of right heart Mod-MPI and DV spectrum parameters in pre-eclampsia fetuses had high value for predicting adverse pregnancy outcomes. 展开更多
关键词 PRE-ECLAMPSIA fetal heart ventricular function ultrasonography prenatal prospective studies
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Long TR three-dimensional inversion recovery sequence with real reconstruction(3D real IR)for quantifying inner ear endolymphatic hydrops
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作者 WU Di ZHAO Menglong +3 位作者 ZENG Mengsu LIU Kai ZHANG Shujie SUN Wei 《中国医学影像技术》 CSCD 北大核心 2024年第8期1174-1178,共5页
Objective To observe the value of long TR three-dimensional inversion recovery sequence with real reconstruction(3D real IR)for quantifying inner ear endolymphatic hydrops(EH).Methods Totally 46 Ménière'... Objective To observe the value of long TR three-dimensional inversion recovery sequence with real reconstruction(3D real IR)for quantifying inner ear endolymphatic hydrops(EH).Methods Totally 46 Ménière's disease(MD)patients and 21 healthy volunteers were prospectively enrolled.MR scanning for inner ear based on 3D real IR and 3D fluid attenuated inversion recovery(3D FLAIR)sequence 4—6 h after administration of contrast agents were performed.The imaging qualities were scored and compared between groups.The endolymphatic space area and the membranous labyrinth area of cochlea and vestibule,as well as endolymph/membranous labyrinth area percentage were calculated,the present or not of EH and the grade of EH were evaluated.EH inner ears of MD patients were enrolled in EH group,while inner ears of healthy volunteers were taken as controls(control group).The endolymphatic space area,membranous labyrinth area and endolymph/membranous labyrinth area percentage of cochlea and vestibule were compared between groups.The receiver operating characteristic(ROC)curve was drawn to calculate the diagnostic efficacy of the above indexes.Results Cochlear and/or vestibular EH were detected in 56 ears,including cochlear EH in 52 ears and vestibular EH in 45 ears among 46 MD patients(EH group),but not in 42 ears in control group.The subjective quality scores of 3D real IR images were higher than those of 3D-FLAIR(both P<0.05).Quantitative analysis based on 3D real IR images revealed that,compared with control group,significantly larger endolymph areas and endolymph/membranous labyrinth area percentages in both cochlea and vestibule were found in EH group(all P<0.001).The area under the curve(AUC)of cochlear or vestibular endolymph/membranous labyrinth area percentage for identifying inner ear EH was 0.999 and 0.985,respectively.Taken 13.64%and 24.13%as the critical value of cochlear or vestibular endolymph,the specificity was 100%and 92.86%,respectively,and the sensitivity was 96.43%and 96.43%,respectively.Conclusion MR long TR 3D real IR was helpful to quantifying inner ear EH. 展开更多
关键词 endolymphatic hydrops magnetic resonance imaging prospective studies
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水资源演变研究现状及进展 被引量:14
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作者 王喜峰 周祖昊 +1 位作者 贾仰文 胡鹏 《水电能源科学》 北大核心 2010年第8期20-23,共4页
阐述了国内外水资源演变研究现状,强调了水资源演变的研究对象与进展,分析了水资源演变研究中的难题,并展望了未来的发展趋势,指出分布式水文模型的优势为研究水资源演变规律提供了技术支持,归因分析将是研究的主要发展方向,统计法结合... 阐述了国内外水资源演变研究现状,强调了水资源演变的研究对象与进展,分析了水资源演变研究中的难题,并展望了未来的发展趋势,指出分布式水文模型的优势为研究水资源演变规律提供了技术支持,归因分析将是研究的主要发展方向,统计法结合水文模型对水资源演变的归因分析具有不可替代的作用。 展开更多
关键词 水资源演变规律 研究现状 FUTURE prospects RESEARCH 演变研究 分布式水文模型 归因分析 研究对象 技术支持 发展趋势 发展方向 不可替代 统计法 国内外 优势
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植被叶片光谱及红边特征与叶片生化组分关系的分析 被引量:38
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作者 梁守真 施平 +2 位作者 马万栋 邢前国 于良巨 《中国生态农业学报》 CAS CSCD 北大核心 2010年第4期804-809,共6页
以LOPEX’93数据集为基础,利用最新的叶片光学模型——PROSPECT5模型模拟了不同生化组分(叶肉结构参数、等效水厚、叶绿素、类胡萝卜素和干物质)含量叶片的反射率、透射率和吸收率光谱,并在此基础上提取植被红边特征,系统分析光谱和叶... 以LOPEX’93数据集为基础,利用最新的叶片光学模型——PROSPECT5模型模拟了不同生化组分(叶肉结构参数、等效水厚、叶绿素、类胡萝卜素和干物质)含量叶片的反射率、透射率和吸收率光谱,并在此基础上提取植被红边特征,系统分析光谱和叶片生化组分的关系,建立光谱特征与叶片生化组分的关系模型,为生化组分反演提供一定的理论基础。结果表明,在可见光部分,叶片的光谱主要取决于叶肉结构参数和色素(叶绿素和类胡萝卜素);在红外波段,叶片的光谱主要受水分、叶肉结构参数和干物质含量的影响。不同的波段范围内,光谱对生化组分的敏感度不同。叶片的红边特征不受水分和类胡萝卜素的影响,但红边位置随叶绿素的增加向长波方向移动(红移)。红边斜率随内部结构参数的增加而增加,两者之间的关系可用二次方程描述,这为叶肉结构参数的求解提供了一个方向。 展开更多
关键词 PROSPECT模型 叶片生化组分 光谱 红边特征 LOPEX’93数据集
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基于光谱分析的植物叶片仿生伪装材料设计 被引量:16
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作者 杨玉杰 刘志明 +1 位作者 胡碧茹 吴文健 《光谱学与光谱分析》 SCIE EI CAS CSCD 北大核心 2011年第6期1668-1672,共5页
利用植物单叶光谱模型PROSPECT分析了植物叶片结构和组分对其反射光谱的影响。结果表明,模拟植物叶片反射光谱的仿生伪装材料应具有粗糙表面和疏松多孔结构,基体材料的折射指数应接近植物叶片且在400~2 500 nm之间基本不变,成分中应含... 利用植物单叶光谱模型PROSPECT分析了植物叶片结构和组分对其反射光谱的影响。结果表明,模拟植物叶片反射光谱的仿生伪装材料应具有粗糙表面和疏松多孔结构,基体材料的折射指数应接近植物叶片且在400~2 500 nm之间基本不变,成分中应含有叶绿素和水并严格控制C—H键的含量。依据上述原则,设计了一种由粗糙透明防水表面、叶绿素、水和多孔材料四层构成的新型仿生伪装材料。验证实验表明,上述四层简单复合后的反射光谱即呈现出与植物叶片一致的反射光谱特征,相似度可达0.988 1,且经过三个月的日照后,其反射光谱特征不变,显示了较好的耐候性。该伪装材料与植物叶片光谱相似度高,耐候性好,有望成为对抗高光谱侦察的有效手段。 展开更多
关键词 PROSPECT模型 伪装材料 仿生 高光谱
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辐射传输模型多尺度反演植被理化参数研究进展 被引量:23
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作者 肖艳芳 周德民 赵文吉 《生态学报》 CAS CSCD 北大核心 2013年第11期3291-3297,共7页
植被是生态系统最重要的组成成分之一,许多与植被有关的物质能量交换过程都与植被的理化参数密切相关,因此定量估算植被的理化参数含量对监测植被生长状况、森林火灾预警以及研究全球碳氮循环过程等都具有重要意义。在众多定量反演植被... 植被是生态系统最重要的组成成分之一,许多与植被有关的物质能量交换过程都与植被的理化参数密切相关,因此定量估算植被的理化参数含量对监测植被生长状况、森林火灾预警以及研究全球碳氮循环过程等都具有重要意义。在众多定量反演植被理化参数的方法中,基于数学、物理学以及生物学的基本理论建立起来的辐射传输模型受到越来越多的关注。辐射传输模型描述了植被与入射辐射之间的相互作用过程和特征,相对于传统的经验/半经验方法,辐射传输模型物理意义明确,具有稳定性和可移植性强的特点。在分析国内外最新相关研究的基础上,首先从植被叶片、冠层和像元3个不同的尺度阐述反演植被理化参数的辐射传输模型。叶片尺度上主要介绍PROSPECT模型和LIBERTY模型;冠层尺度上主要介绍SAIL冠层辐射传输模型以及PROSPECT与SAIL耦合的PROSAIL叶片-冠层辐射传输模型;像元尺度的植被理化参数反演目前主要采用冠层尺度的辐射传输模型。其次,分析尺度变化下植被理化参数遥感反演所面临的主要问题,如不同尺度下模型参数敏感性的变化、辐射传输模型的选取以及混合像元的影响等。最后,总结展望植被理化参数反演多模型与多种数据源相互结合的研究趋势,以及将来具有高空间分辨率的高光谱遥感卫星升空后所带来的发展前景。 展开更多
关键词 理化参数 PROSPECT PROSAIL 尺度 辐射传输模型
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基于Prospect,Liberty和Geosail模型的森林叶面积指数的反演 被引量:10
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作者 李海洋 范文义 +1 位作者 于颖 杨曦光 《林业科学》 EI CAS CSCD 北大核心 2011年第9期75-81,共7页
针对传统的统计模型方法反演叶面积指数(LAI)具有不稳定、区域不统一性的缺点,本研究从物理机制角度出发,以Prospect,Liberty和Geosail模型为基础,建立查找表从TM影像上反演LAI,并与TRAC实测的LAI比较。结果表明:基于机制模型与查找表... 针对传统的统计模型方法反演叶面积指数(LAI)具有不稳定、区域不统一性的缺点,本研究从物理机制角度出发,以Prospect,Liberty和Geosail模型为基础,建立查找表从TM影像上反演LAI,并与TRAC实测的LAI比较。结果表明:基于机制模型与查找表的方法反演的LAI与实测的LAI有较好的一致性,实测精度达到83.7%。 展开更多
关键词 叶面积指数 TM 查找表 PROSPECT LIBERTY Geosail
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水稻叶片反射率模拟 被引量:8
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作者 李云梅 王秀珍 +2 位作者 沈掌泉 于军平 王人潮 《浙江大学学报(农业与生命科学版)》 CAS CSCD 北大核心 2002年第2期195-198,共4页
利用 1999年实测的水稻叶片生物化学组份 ,通过 PROSPECT模型 ,建立水稻叶片反射率模拟模型 ,对不同生育期的水稻叶片光谱进行模拟 ,其反射率的实测值与模拟值的相关系数大于 99.5 % ,均方根误差 RMSE值小于 0 .0 2
关键词 叶片反射率 叶片生物 化学组份 PROSPECT模型 模拟 水稻 生育期 叶片光谱
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植物光学模型估算叶片类胡萝卜素含量的一种双归一化差值-比值植被指数 被引量:8
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作者 王弘 施润和 +1 位作者 刘浦东 高炜 《光谱学与光谱分析》 SCIE EI CAS CSCD 北大核心 2016年第7期2189-2194,共6页
运用高光谱技术进行植物叶片探测具有快速、无损、高精度等特点,在叶片色素等生化成分含量估算方面应用前景广阔。类胡萝卜素作为叶片中重要光合色素之一,因其在可见光区域与叶绿素的光谱吸收特征存在重叠,且其含量远低于叶绿素,导致利... 运用高光谱技术进行植物叶片探测具有快速、无损、高精度等特点,在叶片色素等生化成分含量估算方面应用前景广阔。类胡萝卜素作为叶片中重要光合色素之一,因其在可见光区域与叶绿素的光谱吸收特征存在重叠,且其含量远低于叶绿素,导致利用光谱信息估算叶片类胡萝卜素含量存在困难,国内外少有针对类胡萝卜素含量的植被指数。利用高光谱数据光谱信息丰富的特点,提出一种以波段组合遍历与相关分析为基础,通过多指数协同来构建组合式的植被光谱指数的新方法。在PROSPECT叶片辐射传输模型模拟出大量具有不同生化和生物物理特征的叶片光谱的基础上,成功构建了一种在叶片水平下具有良好稳定性的类胡萝卜素含量估算新指数RVI_(DNDVI)。结果表明,该方法构建的叶片类胡萝卜素光谱指数由两部分组成:由532和405 nm构建的窄波段NDVI(与类胡萝卜素、叶绿素均强相关)和由548和498 nm构建的窄波段NDVI(仅与叶绿素强相关)进行比值组合,能较好消除叶绿素含量对指数的干扰;通过减去对叶片结构高敏感的916 nm处反射率,能消除叶肉结构参数的影响,进一步提高指数的抗干扰能力。该研究得到的指数RVI_(DNDVI)仅对叶片类胡萝卜素具有高敏感性,相关系数达到—0.94,对其进行指数拟合的R^2达到0.834 4。经与模拟数据和实测数据的验证,该指数有较好的估算效果。 展开更多
关键词 类胡萝卜素含量 多指数协同法 植被指数 PROSPECT模型 RVIDNDVI
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基于PROSPECT模型的植物叶片干物质估测建模研究 被引量:12
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作者 王洋 肖文 +3 位作者 邹焕成 陆婧楠 曹英丽 于丰华 《沈阳农业大学学报》 CAS CSCD 北大核心 2018年第1期121-127,共7页
为了快速、准确估测植物叶片干物质含量,为作物长势及健康状况监控提供数据支撑,利用光谱分析技术探讨了干物质含量敏感光谱波段提取方法及其估测建模方法。试验数据由叶片辐射传输模型PROSPECT在干物质含量(0.001~0.02)g·cm^(-2)... 为了快速、准确估测植物叶片干物质含量,为作物长势及健康状况监控提供数据支撑,利用光谱分析技术探讨了干物质含量敏感光谱波段提取方法及其估测建模方法。试验数据由叶片辐射传输模型PROSPECT在干物质含量(0.001~0.02)g·cm^(-2)范围内进行模拟,随机产生1000条400~2500nm的光谱曲线,其中600条光谱曲线用于建模研究、400条光谱曲线作为模型验证数据,同时应用叶片光学特性数据库LOPEX93中325条叶片光谱-干物质含量数据进行进一步验证。首先应用试验数据进行局部敏感性分析,初步得到叶片干物质敏感波段范围,再运用改进Sobol算法进行全局敏感性分析,提取了干物质含量敏感的光谱波段范围,在此敏感波段范围运用波段组合算法计算归一化植被指数NDVI与叶片干物质含量相关系数,优选了4组相关性大的波段组合建立归一化干物质指数NDMI_((1644,1719))、NDMI_((1871,2294))、NDMI_((2150,2271))、NDMI_((1496,2282))用于干物质含量估测建模。结果表明:NDMI_((1644,1719))和NDMI_((1871,2294))模型中三次多项式形式(cubic)效果最佳、NDMI_((1496,2282))模型中幂指数形式(power)效果最佳,三者中NDMI_((1871,2294))的三次多项式模型最优,决定系数R^2为0.837,对叶片干物质含量具有较好的估测能力。 展开更多
关键词 叶片干物质含量 敏感性分析 PROSPECT模型 LOPEX93数据集 光谱指数
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基于PROSPECT+SAIL模型的遥感叶面积指数反演 被引量:45
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作者 蔡博峰 绍霞 《国土资源遥感》 CSCD 2007年第2期39-43,共5页
以PROSPECT+SAIL模型为基础,从物理机理角度反演植被叶面积指数(LAI)。首先,通过FLAASH模型进行大气校正,使得图像像元值表达植被冠层反射率;然后,根据LOPEX 93数据库和JHU光谱数据库选择植物生化参数和光谱数据,以PROSPECT模型模拟出... 以PROSPECT+SAIL模型为基础,从物理机理角度反演植被叶面积指数(LAI)。首先,通过FLAASH模型进行大气校正,使得图像像元值表达植被冠层反射率;然后,根据LOPEX 93数据库和JHU光谱数据库选择植物生化参数和光谱数据,以PROSPECT模型模拟出的植物叶片反射率和透射率作为SAIL模型的输入参数,得到植被冠层反射率,将结果与遥感影像的植被冠层反射率对应,回归出植被LAI;最后,以地面实测数据对遥感反演数据进行验证,并分析了误差的可能来源。 展开更多
关键词 PROSPECT+SAIL模型 LAI 大气校正 植物生化参数
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基于真实三维结构的玉米冠层生化参数垂直分布的定量化分析 被引量:3
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作者 谢东辉 朱启疆 +1 位作者 王锦地 徐凯 《北京师范大学学报(自然科学版)》 CAS CSCD 北大核心 2007年第3期337-342,共6页
为了定量研究作物生化参数在冠层中的垂直分布情况,本文以2000年栾城实验测量的玉米冠层自上而下不同叶位叶片的光谱数据为基础,利用PROSPECT模型进行反演,获得每层叶片的叶绿素(a+b)含量、等效水厚度、干物质含量等叶片的生化参数.通... 为了定量研究作物生化参数在冠层中的垂直分布情况,本文以2000年栾城实验测量的玉米冠层自上而下不同叶位叶片的光谱数据为基础,利用PROSPECT模型进行反演,获得每层叶片的叶绿素(a+b)含量、等效水厚度、干物质含量等叶片的生化参数.通过比较发现:玉米冠层叶绿素等含量生化参数具有明显的随高度垂直分层现象,最明显的就是叶片的叶绿素含量,最大和最小叶绿素含量的相对差值甚至可以达到最大值的79.1%.在此基础上,根据实测玉米冠层结构,利用扩展L系统生成玉米真实三维结构冠层场景.通过统计计算每层叶片的生化参数,进而得到冠层生化参数的垂直分布.这为进一步基于冠层光谱的参数反演和定量分析以及农业应用等研究奠定了理论基础. 展开更多
关键词 叶绿素 PROSPECT模型 玉米 扩展L系统 反演
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高光谱反演水稻叶面积指数的主成分分析法 被引量:15
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作者 杨燕 田庆久 《国土资源遥感》 CSCD 2007年第3期47-50,61,共5页
为了通过水稻冠层反射光谱来提取水稻叶面积指数信息,尝试利用辐射传输模型PROSPECT+SAIL来模拟水稻冠层反射光谱,比较了各植被指数中叶面积指数(LAI)和叶绿素浓度的相关性。在观察光谱曲线后发现,红边位置光谱可以较好地区分LAI和叶绿... 为了通过水稻冠层反射光谱来提取水稻叶面积指数信息,尝试利用辐射传输模型PROSPECT+SAIL来模拟水稻冠层反射光谱,比较了各植被指数中叶面积指数(LAI)和叶绿素浓度的相关性。在观察光谱曲线后发现,红边位置光谱可以较好地区分LAI和叶绿素浓度二者引起光谱变化的差异。由此提出对700 nm^750 nm区间内的反射光谱做主成分变换,并利用第2主成分与LAI建立反演模型(即主成分分析法),取得了较好效果,表明在植被指数趋近于饱和以至于无法区分二者相关性时,主成分分析法可以作为一种简单而有效提取水稻叶面积指数信息的补充手段。 展开更多
关键词 冠层光谱 叶面积指数(LAI) PROSPECT SAIL 红边 主成分分析
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EB病毒抗体检测在鼻咽癌早诊应用中的评价 被引量:4
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作者 黄腾波 车景廉 +3 位作者 陈德林 凌启南 黄惠明 黄启洪 《中山大学学报(医学科学版)》 CAS CSCD 1995年第S1期55-57,68,共4页
作者在广东鼻咽癌高发区四会市、广州市的54425名。年龄在30-59岁自然人群中,应用多项EB病毒(EBV)血清学指标结合鼻咽光导纤维镜、病理组织学检查等手段,进行前瞻性观察、验证及评价这些鼻咽癌“高危人群”血清学指... 作者在广东鼻咽癌高发区四会市、广州市的54425名。年龄在30-59岁自然人群中,应用多项EB病毒(EBV)血清学指标结合鼻咽光导纤维镜、病理组织学检查等手段,进行前瞻性观察、验证及评价这些鼻咽癌“高危人群”血清学指标的应用价值。我们认为:在鼻咽癌高发区人群筛查中,应用EEV抗体检测,凡具下列指标之一者。为患鼻咽癌高危人群,应给予鼻咽光纤镜及病理检查,以期发现早期病人。①EBVIgA/VCA≥1:80或EDAb≥50%。②EBVIgA/VCA、IgA/EA、EDAb3项中任何两项阳性。③EBVIgA/VCA、IgA/EA、EDAb3项中任何单项持续高滴度或滴度持续上升。 展开更多
关键词 425 HEALTHY PERSONS aged 30- 59 were OBSERVED prospectively from 1986 to 1992 in NPC high area Si-
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