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植被指数研究进展:从AVHRR-NDVI到MODIS-EVI

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生态学报 2003年第5期23卷 979-987页

作者：王正兴刘闯 huete Alfredo 中国科学院地理科学与资源研究所全球变化信息研究中心北京100101 DepartmentSoil WaterandEnviron-mentalScienceUniversityofArizona

目前应用广泛的植被指数 AVHRR- NDVI仍有一些缺陷 ,主要表现在 :(1 )在植被高覆盖区容易饱和 ,这除了红光通道就容易饱和外 ,主要是基于 NIR/Red比值的 NDVI算式本身存在容易饱和的缺陷 ;(2 )没有考虑树冠背景对植被指数的影响 ;(3 ) N... 详细信息

目前应用广泛的植被指数 AVHRR- NDVI仍有一些缺陷 ,主要表现在 :(1 )在植被高覆盖区容易饱和 ,这除了红光通道就容易饱和外 ,主要是基于 NIR/Red比值的 NDVI算式本身存在容易饱和的缺陷 ;(2 )没有考虑树冠背景对植被指数的影响 ;(3 ) NDVI的比值算式和最大值合成算法 (MVC)确实消除了某些内部和外部噪音 ,但最终的合成产品仍然有较多噪音 ;(4) MVC不能确保选择最小视角内的最佳像元。所有这些 AVHRR- NDVI的局限性 ,在基于“中分辨率成像光谱仪 (MODIS)”的“增强型植被指数 (EVI)”产品中 ,都有不同程度改善。MODIS- EVI改善表现在 :(1 )大气校正包括大气分子、气溶胶、薄云、水汽和臭氧 ,而 AVHRR- NDVI仅对瑞利散射和臭氧吸收做了校正 ;这样 MODIS- EVI可以不采用基于比值的方法 ,因为比值算式是以植被指数饱和为代价来减少大气影响 ;(2 )根据蓝光和红光对气溶胶散射存在差异的原理 ,采用“抗大气植被指数 (ARVI)对残留气溶胶做进一步的处理 ;(3 )采用“土壤调节植被指数(SAVI)”减弱了树冠背景土壤变化对植被指数的影响 ;(4)综合 ARVI和 SAVI的理论基础 ,形成“增强型植被指数 (EVI)”,它可以同时减少来自大气和土壤噪音的影响 ;(5 )采用“限定视角内最大值合成法 (CV-MVC)”。

关键词：植被指数 AVHRR—NDVI MODIS—EVI 覆盖程度植被植被生产力

Investigation of the degradation rate of electron beam processed and friction stir processed biocompatible ZKX50 magnesium alloy

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Journal of Magnesium and Alloys 2022年第3期10卷 768-781页

作者： Fatemeh Iranshahi Mohammad Bagher Nasiri fernando Gustavo Warchomicka Christof Sommitsch Joining and Forming Institute of Materials ScienceGraz University of TechnologyKopernikusgasse 24/IGraz 8010Austria

Together with the mechanical properties,the degradation rate is an important factor for biodegradable *** ZKX50 Mg alloy is a suitable candidate to be used as a biodegradable implant due to its favorable biocompatibility and mechanical *** research investigates the degradation rate and corrosion behavior of the ZKX50 as a function of the microstructure constituents and their *** grain refinement is the main strengthening mechanism for the ZKX50,the effect of the microstructure refinement on the corrosion rate was studied by applying electron beam processing(EBP)and friction stir processing(FSP)on the ZKX50 cast *** study the effect of the microstructure constituents and their morphology a subsequent solution heat treatment(HT)was applied to the processed *** results show that the EBP and FSP lead to a uniform and remarkably refined microstructure of the ZKX50 alloy and homogeneous distribution of the intermetallic *** results of electrochemical corrosion tests together with the microstructure characterization show that microgalvanic corrosion is the predominant mechanism that occurs between the Ca2Mg6Zn3 intermetallic phase andα-Mg *** to the results attained through the electrochemical tests,the EBPed-HT ZKX50 alloy shows higher corrosion resistance compared to all other conditions immersed in 0.5 wt.%NaCl *** dissolution and spheroidizing of Ca2Mg6Zn3 particles during the solution heat treatment provides higher corrosion resistance mainly by decreasing the microgalvanic *** microstructure of the heat-treated samples does not show a significant grain coarsening which can degrade the enhancement of the mechanical properties achieved by the EBP and FSP.

关键词： Magnesium alloys Electron beam processing Friction stir processing Corrosion Biodegradable metals.

A Sylvester-Based IMEXMethod via Differentiation Matrices for Solving Nonlinear Parabolic Equations

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Communications in Computational Physics 2013年第9期14卷 1001-1026页

作者： Francisco de la Hoz fernando Vadillo Department of Applied Mathematics Statistics and Operations ResearchFaculty of Science and TechnologyUniversity of the Basque Country UPV/EHUBarrio Sarriena S/N48940 LeioaSpain

In this paper we describe a new pseudo-spectral method to solve numerically two and three-dimensional nonlinear diffusion equations over unbounded domains,taking Hermite functions,sinc functions,and rational Chebyshev polynomials as basis *** idea is to discretize the equations by means of differentiation matrices and to relate them to Sylvester-type equations by means of a fourth-order implicit-explicit scheme,being of particular interest the treatment of three-dimensional Sylvester equations that we *** resulting method is easy to understand and express,and can be implemented in a transparent way by means of a few lines of *** test numerically the three choices of basis functions,showing the convenience of this new approach,especially when rational Chebyshev polynomials are considered.

关键词： Semi-linear diffusion equations pseudo-spectral methods differentiation matrices Hermite functions sinc functions rational Chebyshev polynomials IMEX methods Sylvester equations blow-up

Understanding the El Nio Costero of 2017: The Definition Problem and Challenges of Climate Forecasting and Disaster Responses

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International Journal of Disaster Risk Science 2017年第4期8卷 489-492页

作者： Ivan J.Ramírez fernando Briones Department of Anthropology Colorado State University Consortium for Capacity Building/INSTAAR University of Colorado Graduate Program in Public Health Colorado State University

This preliminary study examines the definition problem and challenges of climate forecasting and disaster responses associated with the El Nio costero(coastal) of2017, which developed rapidly with no warning and had catastrophic effects in Peru. Such a localized El Nio was not documented since 1925. An initial review suggests that in addition to the characteristics of the event(surprise),government responses may have been inadequate(as media reported) because of conflicting forecast reports(U.S. and Peru), which provoked a hydrometeorological debate and stifled decision making. Partly to blame was the El Nio definition problem, which can cause uncertainty and affect perception of risk, depending on which region of the equatorial Pacific one uses to identify an event. Responses were further complicated by the fact that some regions within Peru were experiencing drought prior to the El Nio costero's onset and impacts from the El Nio 2015–2016 were less than expected. Furthermore, a new government was in place, which may have hindered action. Thus, El Nio costero provides lessons to heed, not only with respect to the forecast information, but also with reference to the context of the forecast and disaster setting, which can influence disaster responses to hydrometeorological threats.

关键词： Disaster risk reduction Ecuador El Nio costero El Nio forecast El Nio-Southern Oscillation Peru Teleconnections

Boosting efficiency in state estimation of power systems by leveraging attention mechanism

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Energy and AI 2024年第2期16卷 438-449页

作者： Elson Cibaku fernando Gama SangWoo Park Industrial Engineering New Jersey Institute of TechnologyNewarkNJUnited States Pendulum Systems DenverCOUnited States

Ensuring stability and reliability in power systems requires accurate state estimation, which is challenging due to the growing network size, noisy measurements, and nonlinear power-flow equations. In this paper, we introduce the Graph Attention Estimation Network (GAEN) model to tackle power system state estimation (PSSE) by capitalizing on the inherent graph structure of power grids. This approach facilitates efficient information exchange among interconnected buses, yielding a distributed, computationally efficient architecture that is also resilient to cyber-attacks. We develop a thorough approach by utilizing Graph Convolutional Neural Networks (GCNNs) and attention mechanism in PSSE based on Supervisory Control and Data Acquisition (SCADA) and Phasor Measurement Unit (PMU) measurements, addressing the limitations of previous learning architectures. In accordance with the empirical results obtained from the experiments, the proposed method demonstrates superior performance and scalability compared to existing techniques. Furthermore, the amalgamation of local topological configurations with nodal-level data yields a heightened efficacy in the domain of state estimation. This work marks a significant achievement in the design of advanced learning architectures in PSSE, contributing and fostering the development of more reliable and secure power system operations.

关键词： Power grids State estimation Attention mechanism Graph neural networks Distributed computation Grid cyber-security

Multigear Bubble Propulsion of Transient Micromotors

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Research 2020年第1期2020卷 1384-1392页

作者： Amir Nourhani Emil Karshalev fernando Soto Joseph Wang Department of Nanoengineering University of California San DiegoLa JollaCA 92093USA Department of Mechanical Engineering Department of BiologyBiomimicry Research and Innovation CenterUniversity of AkronAkronOH 44325USA

Transient,chemically powered micromotors are promising biocompatible engines for *** propose a framework to investigate in detail the dynamics and the underlying mechanisms of bubble propulsion for transient chemically powered *** observations on the variations of the micromotor active material and geometry over its lifetime,from initial activation to the final inactive state,indicate different bubble growth and ejection mechanisms that occur stochastically,resulting in time-varying micromotor *** identify three processes of bubble growth and ejection,and in analogy with macroscopic multigear machines,we call each process a *** 1 refers to bubbles that grow on the micromotor surface before detachment while in Gear 2 bubbles hop out of the *** 3 is similar in nature to Gear 2,but the bubbles are too small to contribute to micromotor *** study the characteristics of these gears in terms of bubble size and ejection time,and how they contribute to micromotor *** ability to tailor the shell polarity and hence the bubble growth and ejection and the surrounding fluid flow is *** understanding of the complex multigear bubble propulsion of transient chemical micromotors should guide their future design principles and serve for fine tuning the performance of these micromotors.

关键词： bubble transient chemically

Common misconceptions about 5-aminosalicylates and thiopurines in inflammatory bowel disease

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World Journal of Gastroenterology 2011年第30期17卷 3467-3478页

作者： Javier P Gisbert María Chaparro fernando Gomollón Gastroenterology Unit Hospital Universitario de La PrincesaInstituto de Investigación SanitariaPrincesa(IP)and Centro de Investigación Biomédica en Red de Enfermedades Hepáticasy Digestivas28006 MadridSpain Gastroenterology Unit Hospital Clínico Universitario and Centro de Investigación Biomédica en Redde Enfermedades Hepáticasy DigestivasIACS50009 ZaragozaSpain

Misconceptions are common in the care of patients with inflammatory bowel disease(IBD).In this paper,we state the most commonly found misconceptions in clinical practice and deal with the use of 5-aminosalicylates and thiopurines,to review the related scientificevidence,and make appropriate *** of errors needs knowledge to avoid making such errors through ***,the amount of knowledge is increasing so quickly that one new danger is an overabundance of *** is a model of a very complex disease and our goal with this review is to summarize the key evidence for the most common daily clinical *** regard to the use of 5-aminosalicylates,the best practice may to be consider abandoning the use of these drugs in patients withsmall bowel Crohn's *** combined approach with oral plus topical 5-aminosalicylates should be the first-line therapy in patients with active ulcerative colitis;once-daily treatment should be offered as a first choice regimen due to its better compliance and higher *** regard to thiopurines,they seem to be as effective in ulcerative colitis as in Crohn's *** of thiopurines is a form of *** should probably be continued indefinitely because their withdrawal is associated with a high risk of *** is a safe alternative in patients with digestive intolerance or hepatotoxicity due to ***,thiopurine methyltransferase(TPMT)screening cannot substitute for regular monitoring because the majority of cases of myelotoxicity are not TPMT-related.

关键词： Crohn' s disease Ulcerative colitis Inflam-matory bowel disease Aminosalicylates Steroids Azathioprine Mercaptopurine Misconceptions

Communities of saprobic fungi on leaf litter of Vismia guianensis in remnants of the Brazilian Atlantic Forest

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Journal of Forestry Research 2017年第1期28卷 163-172页

作者： Loise Araujo Costa Luís fernando Pascholati Gusmao Laboratorio de Micologia Av Transnordestina Departamentode Ciências BiológicasUniversidade Estadual de Feira deSantanas/nNovo HorizonteFeira de SantanaBA 44031-460Brazil

We examined the mycobiota associated with Vismia guianensis leaf litter in three Atlantic Forest remnants of Brazil＇ s semiarid region. Among the study sites, two remnants were protected forest reserves, whereas the third was influenced by major anthropogenic activities. Eighteen litter samples were collected in wet and dry seasons and were processed by particle filtration technique. A total of 4750 fungal isolates of 142 taxa were identified. Species richness was higher in litter samples collected during wet season. Nonmetric multidimensional scaling multivariate analysis showed differences in the composition of fungal communities among the sampling sites and the seasons. Analysis of similarity showed that the differences were statistically significant （R = 0.85; P = 0.0001）. Our findings revealed that spatial and temporal heterogeneity, and human activities had significant impacts on the saprobic fungi of V. guianensis leaf litter.

关键词： Biodiversity Conservation Seasonality Spatial heterogeneity Tropical fungi

Are we giving azathioprine too much time?

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World Journal of Gastroenterology 2008年第36期14卷 5519-5522页

作者： fernando Gomollón Santiago García López Department of Digestive Diseases Clinic University Hospital "Lozano Blesa" CIBEREHD IACS Zaragoza Spain Department of Digestive Diseases University Hospital "Miguel Servet" Zaragoza Spain

Azathioprine is currently the key drug in the maintenance treatment of inflammatory bowel diseases. However, there are still some practical issues to be resolved: one is how long we must maintain the drug. Given that inflammatory bowel diseases are to date chronic, non-curable conditions, treatment should be indefinite and only the loss of efficacy or the appearance of serious side effects may cause withdrawal. As regards to efficacy and their maintenance over time, evidence supports the continuous usefulness of the drug in the long term: in fact its withdrawal very substantially increases the risk of relapse. About side effects, azathioprine is a relatively well tolerated drug and even indefinite use seems safe. The main theoretical risks of prolonged use would be the myelotoxicity, hepatotoxicity, and the development of cancer. In fact, serious bone marrow suppression or serious liver damage are uncommon, and can be minimized with proper use of the drug. Recent metanalysis suggests that the risk of lymphoma is real, but the individual risk is rather low, and decision analysis suggests a favorable benefit/risk ratio in the long term. Therefore, in patients with inflammatory bowel diseases in whom azathioprine is effective and well tolerated, the drug should not be stopped. This recommendation concerns the use of azathioprine as a single maintenance drug, and is not necessarily applicable to patients receiving concomitant biological therapy.

关键词： Azathioprine Inflammatory bowel diseases Maintenance treatment