检索结果-南通市图书馆

Trophic Interactions between Anadromous Juvenile Alewife (<i>Alosa pseudoharengus</i>) and Cyanobacterial Populations in a Shallow Mesotrophic Pond

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Natural Resources 2020年第9期11卷 394-419页

作者： Nancy J. Leland Ryan A. landon James F. Haney Department of Zoology University of New Hampshire Durham NH USA Lim-Tex North Andover MA USA

Alosa pseudoharengus is an anadromous fish that migrates from marine to freshwaters to spawn. The early larval and juvenile forms are known to be planktivorous, where heavy feeding upon their preferred food source of large crustacean zooplankton often results in changes to composition and size structure within this trophic guild which in turn can result in shifts within the trophic spectrum and a classic trophic cascade. In this study of Lower Mill Pond, Brewster MA, we evaluated the feeding strategy of juvenile Alosa to determine whether juvenile alewife switches to feeding largely on cyanobacteria and whether cyanotoxins microcystin (MC) and β-methlyamino-L-alanine (BMAA) bioaccumulate in their muscle tissue. Within 15 - 30 days of their estimated spawning date, overexploitation of crustacean zooplankton resulted in a shift from planktivory to benthic detritivory for the majority of their life history, although this did not reduce their condition based on weight-length relationships (Log Wwt. = -5.503 + (3.101 × Log Length). Mean MC (0.003 μg

Designing Optical Fibers: Fitting the Derivatives of a Nonlinear Pde-Eigenvalue Problem

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

American Journal of Computational Mathematics 2012年第4期2卷 321-330页

作者： Linda Kaufman Seok-Min Bang Brian Heacook William landon Daniel Savacool Nick Woronekin Computer Science Department William Paterson University Passaic USA

When trying to fit data to functions of the eigensystem of a pde-eigenvalue problem, such as Maxwell’s equation, numerical differentiation is ineffective and analytic gradients must be supplied. In our motivating example of trying to determine the chemical composition of the layers of specialty optical fibers, the function involved fitting the higher order derivatives with respect to frequency of the positive eigenvalues. The computation of the gradient was the most time consuming part of the minimization problem. It was realized that if one interchanged the order of differentiation, and differentiated first with respect to the design parameters, fewer derivatives of the eigenvectors would be required and one could take full advantage that each grid point was affected by only a few variables. As the model was expanded to cover a fiber wrapped around a spool, the bandwidth of the linearized symmetric eigenvalue problem increased. At the heart of each of the iterative methods used to find the few positive eigenvalues was a symmetric, banded, indefinite matrix. Here we present an algorithm for this problem which reduces a symmetric banded matrix to a block diagonal matrix of 1 x 1 and 2 x 2 blocks. Fillin outside the band because of pivoting for stability is prevented by a sequence of planar transformations. Computationally the algorithm is compared to the block unsymmetric banded solver and the block positive definite symmetric band solver in LAPACK.

关键词： Symmetric Indefinite Eigenvalue Gradient Optical Fiber Design

Forage production and persistence characteristics of grazed native warm-season grass mixtures with or without nitrogen fertilizer

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Grassland Research 2022年第3期1卷 157-165页

作者： Caroline Nicole Chappell Marty landon Marks Katie Michelle Mason Liliane Severino da Silva Joshua Luke Jacobs Mary Kimberly Mullenix Sandra Leanne Dillard Russell Brian Muntifering Department of Animal Sciences Auburn UniversityAuburnAlabamaUSA Department of Animal Science University of TennesseeKnoxvilleTennesseeUSA Department of Animal and Veterinary Sciences Clemson UniversityClemsonSouth CarolinaUSA University of Kentucky Cooperative Extension Service CarlisleKentuckyUSA

Background:Native warm-season grass(NWSG)mixtures may provide a lownitrogen(N)-input summer perennial forage option to extensively managed forage-livestock ***:Mixed pastures of big bluestem(Andropogon gerardii Vitman),little bluestem(Schizachyrium scoparium Michx.),and indiangrass(Sorghastrum nutans L.)fertilized with 0 or 67 kgNha−1 were continuously stocked with beef heifers and *** mass,nutritive value,and canopy heights were determined every 2 weeks during the grazing *** persistence measures included the canopy cover and leaf area index(LAI)and plant crown density at spring emergence following 3 years of grazing ***:Forage mass,canopy height,and stocking densities were greater for N-fertilized NWSG than unfertilized NWSG for the first 30 days of the growing season across the 3-year *** NWSG fertilized with N had a greater decrease in LAI during the growing season(51%decrease)than unfertilized *** NWSG plant density estimates following 3 years of grazing did not differ across N management ***:Forage NWSG mixtures supported superior forage attributes and greater stocking densities early in the grazing season under low-level N than zero-N-input systems and may provide a low-N-input alternative for improved species use in southeastern US forage-livestock systems.

关键词： continuous stocking grazing native warm-season grass mixtures nitrogen fertilization

20世纪美国土壤学家对中国土壤地理学的贡献

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

土壤通报 2010年第6期41卷 1491-1498页

作者：龚子同王志刚 Jeremy landon Darilek 黄标张甘霖中国科学院南京土壤研究所江苏南京210008 中国科学院研究生院北京100039

中美土壤学家之间有着长期的友好合作。对现代中国土壤地理学、乃至整个土壤学的建立和发展起过重要作用的美国土壤学家,按年代大致可以分成两组:第一组是20世纪早期(主要是30年代)的***,***,***和***;第二组是改革开放(1978年)以后的**... 详细信息

中美土壤学家之间有着长期的友好合作。对现代中国土壤地理学、乃至整个土壤学的建立和发展起过重要作用的美国土壤学家,按年代大致可以分成两组:第一组是20世纪早期(主要是30年代)的***,***,***和***;第二组是改革开放(1978年)以后的***,***,***和***。

关键词：历史土壤学土壤系统分类

采样点数量对长三角典型地区土壤肥力指标空间变异解析的影响

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

土壤 2010年第3期42卷 421-428页

作者：王志刚赵永存黄标 Darilek Jeremy landon 孙维侠中国科学院土壤环境与污染修复重点实验室(南京土壤研究所) 南京210008 中国科学院研究生院北京100049

通过对江苏省如皋市888个采样点的不重复随机抽样,探讨了采样点数量对土壤肥力指标空间变异解析的影响。从半方差函数估计的可靠性角度考虑,在长江冲积物形成的土壤上,针对县级农业管理和生态环境规划的土壤肥力指标调查采样,采集250个... 详细信息

通过对江苏省如皋市888个采样点的不重复随机抽样,探讨了采样点数量对土壤肥力指标空间变异解析的影响。从半方差函数估计的可靠性角度考虑,在长江冲积物形成的土壤上,针对县级农业管理和生态环境规划的土壤肥力指标调查采样,采集250个样点较为合适。另外,仅使用交互验证和独立验证评价半方差函数估计的可靠性及确定采样点数量是不完善的,而平均克里格方差理论上随采样点数量的增加而单调递减,可以作为不同采样点数量条件下,综合评价半方差函数估计可靠性及确定采样点数量的补充指标。

关键词：采样密度半方差函数交互验证独立验证克里格方差

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

木星卫星的不稳定性

中国国家天文 2010年第4期4卷 130-131页

作者： landon Curt Noll 美国天文学会

今天的图景Laskar在1994年的结果第一次有力地证明，即便没有外界的影响，在太阳作为一颗燃烧氢的恒星所剩下的60亿年时间里也会出现轨道混沌。不过，一些重要的问题仍有待回答。看似最不稳定的轨道是否为最佳选择？如果进行一次自始至... 详细信息

今天的图景Laskar在1994年的结果第一次有力地证明，即便没有外界的影响，在太阳作为一颗燃烧氢的恒星所剩下的60亿年时间里也会出现轨道混沌。不过，一些重要的问题仍有待回答。看似最不稳定的轨道是否为最佳选择？如果进行一次自始至终的模拟，那么太阳系能维持多久？是什么机制使得水星的轨道失稳？最后，如果在计算中考虑到广义相对论的微妙作用，结果是不是会有不同？

关键词：不稳定性木星卫星广义相对论太阳系轨道恒星水星

Management considerations following overdoses of modified-release morphine preparations

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

World Journal of Emergency Medicine 2010年第1期1卷 75-76页

作者： Jamie L. Nelsen Jeanna M. Marraffa landon Jones William D. Grant Upstate New York Poison Control Center Syracuse NY USA Department ofEmergency Medicine SUNY Upstate Medical University Syracuse NY USA

Analgesics have consistently remained the most common substance involved in human poisonings in the United States, with immediate action opioid analgesics associated with the greatest percent of fatalities per exposure.

关键词： Management considerations morphine preparations

A Facilitated Interface to Generate a Combined Textual and Graphical Database System Using Widely Available Software

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Journal of Software Engineering and Applications 2012年第10期5卷 789-796页

作者： Corey Lawson Kirk Larson Jonathan Van Erdewyk Christopher Smith Al Rizzo landon Ross Marc Rendell Creighton University School of Medicine Omaha USA

Data-Base Management System (DBMS) is the current standard for storing information. A DBMS organizes and maintains a structure of storage of data. Databases make it possible to store vast amounts of randomly created information and then retrieve items using associative reasoning in search routines. However, design of databases is cumbersome. If one is to use a database primarily to directly input information, each field must be predefined manually, and the fields must be organized to permit coherent data input. This static requirement is problematic and requires that database table(s) be predefined and customized at the outset, a difficult proposition since current DBMS lack a user friendly front end to allow flexible design of the input model. Furthermore, databases are primarily text based, making it difficult to process graphical data. We have developed a general and nonproprietary approach to the problem of input modeling designed to make use of the known informational architecture to map data to a database and then retrieve the original document in freely editable form. We create form templates using ordinary word processing software: Microsoft InfoPath 2007. Each field in the form is given a unique name identifier in order to be distinguished in the database. It is possible to export text based documents created initially in Microsoft Word by placing a colon at the beginning of any desired field location. InfoPath then captures the preceding string and uses it as the label for the field. Each form can be structured in a way to include any combination of both textual and graphical fields. We input data into InfoPath templates. We then submit the data through a web service to populate fields in an SQL database. By appropriate indexing, we can then recall the entire document from the SQL database for editing, with corresponding audit trail. Graphical data is handled no differently than textual data and is embedded in the database itself permitting direct query ap

关键词： Graphical Database Systems InfoPath SQL Data Mining

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

样件快速制作向制造发展

轻型汽车技术 1994年第4期 11-13,52页

作者： Ray landon 陈家基

零件的制造正在迅速发展成为样件快速制作技术的一个重要的方面。Ray landon报告说,熔模铸造和工模具制作是两大用途。Stereolithography 立体制版和其它 RP 样件快速制作过程可提供按3D(维)CAD 数据制作的硬复制作,而且这些硬复制件的... 详细信息

零件的制造正在迅速发展成为样件快速制作技术的一个重要的方面。Ray landon报告说,熔模铸造和工模具制作是两大用途。Stereolithography 立体制版和其它 RP 样件快速制作过程可提供按3D(维)CAD 数据制作的硬复制作,而且这些硬复制件的制作时间不过几个小时。

关键词：样件快速制作制造零部件汽车