检索结果-南通市图书馆

Tree community composition,structure and diversity along an elevational gradient in an Andean forest of Northern Ecuador

引用

Journal of Mountain Science 2021年第9期18卷 2315-2327页

作者： JIMÉNEZ-PAZ Rosa WORTHY Samantha J VALENCIA Renato PÉREZÁlvaro J REYNOLDS Alex BARONE john A BURGESS kevin S Laboratorio de Ecología de Plantas Escuela de Ciencias BiológicasFacultad de Ciencias Exactas y NaturalesPontificia Universidad Católica del EcuadorQuito 17-01-2184Ecuador Department of Biology College of Letters&SciencesColumbus State UniversityColumbusGeorgia 31907USA Herbario QCA Escuela de Ciencias BiológicasFacultad de Ciencias Exactas y NaturalesPontificia Universidad Católica del EcuadorQuito 17-01-2184Ecuador The Lovett School AtlantaGeorgia 30327USA

The Andean forests of northern Ecuador are known for their high levels of plant diversity relative to the area they ***,these forests grow on steep slopes that lead to dramatic habitat gradients across short *** extreme habitat gradients make the Andean forest ecosystem an excellent natural laboratory for understanding the effect of elevation on forest community diversity,structure and *** established 31 plots(50 m×5 m)which are divided between two elevational transects in the cloud forest of the Siempre Verde Reserve in the western foothills of the Andes Mountains of northern *** trees and tree ferns with a diameter at breast height(dbh)≥5 cm were measured and *** examined changes in community composition,structure,and diversity along and between the elevational transects and three elevational zones:low(2437–2700 m),middle(2756–3052 m),and high(3163–3334 m).We found four main trends associated with the elevational gradients at this site:(1)community composition differed between the two transects and among the three elevational zones according to N-MDS,ANOSIM,and percentage of shared species,with some species having limited distributions,(2)metrics of community structure showed opposite relationships with elevation,depending on the transect,with the only significant relationship(negative)found between basal area and elevation in the open trail transect,(3)alpha diversity,in general,peaked at mid-elevations,and(4)beta diversity consistently increased with distance between plots along *** complexity of changes in community composition,structure,and alpha diversity along elevation may be related to the heterogeneity of the environment on a local scale,such as topography,soil composition,and even human impact,or to dispersal limitation and should be investigated *** changes in community composition and the relatively high beta diversity found at this site exemplify the biological complexity of mon

关键词： Elevational gradient Cloud forest Andes Structure Composition Diversity

来源：

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

Real-world emission factors for Caterpillar 797B heavy haulers during mining operations

引用

Particuology 2016年第5期14卷 22-30页

作者： Xiaoliang Wang Judith C. Chow Steven D. Kohl kevin E. Percy Allan H. Legge john G. Watson Desert Research Institute 2215 Raggio Parkway Reno NV 895J2 USA Graduate Faculty University of Nevada Reno NV89503 USA The State Key Laboratory of Loess and Quaternary Geology Institute of Earth Environment Chinese Academy of Sciences Xi'an 710075 China Wood Buffalo Environmental Association 330 Thickwood Boulevard Fort McMurray AB Canada 7DK 1 Y1 Biosphere Solutions 1610 1 lth Avenue N.W. Calgary AB Canada T2N IG9

Real-world fuel-based emission factors （EFs） from Caterpillar 797B diesel heavy haulers when used for oil sands mining operations were measured using an on-hoard portable emissions monitoring system. Average EFs （in g/kg fuel） for 16 separate tests on four trucks were 3150 ± 4 for CO2, 2.51 ± 1.30 for CH4, 10.28 ± 3.21 for CO, 0.61 ± 0.32 for non-methane hydrocarbons, 55.49 ± 9,75 for NOx （reported as NO2）, 0.70 ± 0.17 for PM2.s （mass of particles with aerodynamic diameter 〈2.5 μm）, and 0.34 ± 0.05 for black carbon （BC）. Ultrafine particle numbers averaged （4.7 ± 4.1 ） × 10^15 particleslkg fuel. Fuel-based EFs of NO, NO2, and particle numbers were higher during idling, whereas PM2.5 and BC EFs were higher during traveling without a load. A comparison of emissions with those reported by oil sands facilities showed large variations, both among the facilities and between the reported emissions and the real-world measurements.

关键词： Heavy hauler Emission Nonroad Portable emissions measurement system Mining Oil sands

来源：

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Potential of capillary electrophoresis mass spectrometry for the characterization and monitoring of amine-derivatized naphthenic acids from oil sands process-affected water

引用

Journal of Environmental Sciences 2016年第11期28卷 203-212页

作者： Matthew S.MacLennan Cai Tie kevin Kovalchik Kerry M.Peru Xinxiang Zhang john V.Headley David D.Y.Chen Department of Chemistry University of British Columbia Vancouver BC V6T 1Z1 Canada. State Key Laboratory of Bioactiue Substance and Function of Natural Medicines Institute of Materia Medica Peking Union Medical College &Chinese Academy of Medical Sciences Beijing 100050 China Water Science and Technology Directorate Science and Technology Branch Environment and Climate Change Canada SaskatoonSK S7N 3H5 Canada College of Chemistry and Molecular Engineering Peking University Beijing 100871 China

Capillary electrophoresis coupled to mass spectrometry（CE–MS） was used for the analysis of naphthenic acid fraction compounds（NAFCs） of oil sands process-affected water（OSPW）. A standard mixture of amine-derivatized naphthenic acids is injected directly onto the CE column and analyzed by CE–MS in less than 15 min. Time of flight MS analysis（TOFMS）, optimized for high molecular weight ions, showed NAFCs between 250 and 800 m/z. With a quadrupole mass analyzer, only low-molecular weight NAFCs（between 100 and 450 m/z） are visible under our experimental conditions. Derivatization of NAFCs consisted of two-step amidation reactions mediated by 1-ethyl-3-（3-dimethylaminopropyl）carbodiimide（EDC）, or mediated by a mixture of EDC and N-hydroxysuccinimide, in dimethyl sulfoxide, dichloromethane or ethyl acetate. The optimum background electrolyte composition was determined to be 30%（V/V） methanol in water and 2%（V/V） formic acid. NAFCs extracted from OSPW in the Athabasca oil sands region were used to demonstrate the feasibility of CE–MS for the analysis of NAFCs in environmental samples, showing that the labeled naphthenic acids are in the mass range of 350 to 1500 m/z.

关键词： Capillary electrophoresis Mass spectrometry Electrospray ionization Carbodiimide Oil sands process-affected water Naphthenic acids

来源：

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

Simple and customizable method for fabrication of high-aspect ratio microneedle molds using low-cost 3D printing

引用

Microsystems & Nanoengineering 2019年第1期5卷 250-263页

作者： kevin J.Krieger Nicky Bertollo Manita Dangol john T.Sheridan Madeleine M.Lowery Eoin D.O’Cearbhaill UCD Centre for Biomedical Engineering University College DublinBelfieldDublin 4Ireland School of Mechanical&Materials Engineering University College DublinBelfieldDublin 4Ireland School of Electrical&Electronic Engineering University College DublinBelfieldDublin 4Ireland

We present a simple and customizable microneedle mold fabrication technique using a low-cost desktop SLA 3D *** opposed to conventional microneedle fabrication methods,this technique neither requires complex and expensive manufacturing facilities nor expertise in *** most low-cost 3D-printed microneedles to date display low aspect ratios and poor tip sharpness,we show that by introducing a two-step“Print&Fill”mold fabrication method,it is possible to obtain high-aspect ratio sharp needles that are capable of penetrating *** first the effect of varying design input parameters and print settings,it is shown that printed needles are always shorter than *** decreasing input height,needles also begin displaying an increasingly greater than specified needle base *** factors contribute to low aspect ratio needles when attempting to print submillimeter height *** setting input height tall enough,it is possible to print needles with high-aspect ratios and tip radii of 20–40μ*** tip sharpness is smaller than the specified printer ***,high-aspect ratio sharp needle arrays are printed in basins which are backfilled and cured in a second step,leaving sub-millimeter microneedles exposed resulting microneedle arrays which can be used as male *** female master molds are then formed from the fabricated microneedle *** the molds,both carboxymethyl cellulose loaded with rhodamine B as well as polylactic acid microneedle arrays are produced and their quality examined.A skin insertion study is performed to demonstrate the functional capabilities of arrays made from the fabricated *** method can be easily adopted by the microneedle research community for in-house master mold fabrication and parametric optimization of microneedle arrays.

关键词： needle cost printer

来源：

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Entropy generation in bypass transitional boundary layer flows

引用

Journal of Hydrodynamics 2014年第5期26卷 669-680页

作者： GEORGE Joseph OWEN Landon D. XING Tao MCELIGOT Donald M. CREPEAU john C. BUDWIG Ralph S. NOLAN kevin P. Department of Mechanical Engineering College of EngineeringUniversity of IdahoMoscowIdaho 83843USA University of Idaho Idaho FallsIdaho 83402USA University of Idaho BoiseIdaho 83702USA Imperial College London London SW7-28ZUK

The primary objective of this study is to evaluate the accuracy of using computational fluid dynamics （CFD） turbulence models to predict entropy generation rates in bypass transitional boundary layers flows under zero and adverse pressure gradients. Entropy generation rates in such flows are evaluated employing the commercial CFD software, ANSYS FLUENT. Various turbulence and transitional models are assessed by comparing their results with the direct numerical simulation （DNS） data and two recent CFD studies. A solution verification study is conducted on three systematically refined meshes. The factor of safety method is used to estimate the numerical error and grid uncertainties. Monotonic convergence is achieved for all simulations. The Reynolds number based on momentum thickness, Reo, skin-friction coefficient, Cf, approximate entropy generation rates, S, dissipation coefficient, Cd , and the intermittency, y, are calculated for bypass transition simulations. All Reynolds averaged Navier-Stokes （RANS） turbulence and transitional models show improvement over previous CFD results in predicting onset of transition. The transition SST k - ω 4 equation model shows closest agreement with DNS data for all flow conditions in this study due to a much finer grid and more accurate inlet boundary conditions. The other RANS models predict an early onset of transition and higher boundary layer entropy generation rates than the DNS shows.

关键词： entropy generation bypass transition Reynolds averaged Navier-Stokes (RANS) transitional boundary layer turbulence models

来源：

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

Biomolecular hydration dynamics probed with 2D-IR spectroscopy:From dilute solution to a macromolecular crowd

引用

Chinese Chemical Letters 2015年第4期26卷 435-438页

作者： john T.King Evan J.Arthur Derek G.Osborne Charles L.Brooks Ⅲ kevin J.Kubarych Department of Chemistry University of Michigan LSA Biophysics University of Michigan Department of Materials Science and Engineering University of Illinois

Although it is well known that water is essential for biological function, it has been a challenge to determine how water behaves near biomacromolecular interfaces, and what role water plays in influencing the dynamics of the biochemical machinery. By adopting a vibrational labeling strategy coupled with ultrafast two-dimensional infrared （2D-IR） spectroscopy, it has recently become possible to study hydration dynamics, site specifically at the surface of proteins and model membranes. We review our recent progress in measuring hydration dynamics in contexts ranging from small-molecule solutes to biomacromolecules in dilute, viscous, and crowded environments.

关键词： Protein hydration dynamicsMembrane dynamicsUltrafast infrared spectroscopy

来源：

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

Stable CW Single-Mode Photonic Crystal Fiber DFB Ring Laser

引用

Journal of Electronic Science and Technology of China 2008年第4期6卷 442-444页

作者： kevin Cook john Canning john Holdsworth Chris Dewhurst Interdisciplinary Photonics Laboratories School of Chemistry University of Sydney NSW 2006 Australia the School of Mathematical and Physical Sciences University of Newcastle Callaghan NSW 2308 Australia and is currently on Sabbatical at The University of Sydney

We demonstrate stable single-mode CW operation of a DFB ring laser based on Er3＋ doped photonics crystal fiber （PCF）. The incorporation of a ring cavity allows one single mode to lase and also suppresses the unwant... 详细信息

关键词： Fiber lasers fiber optics photonic crystal fibers.

来源：

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

Sensitivity analysis of borehole thermal energy storage: examining key factors for system optimization

引用

Energy Storage and Saving 2024年第3期3卷 218-230页

作者： Piyush Kumar Kumawat Haiyan Zhou kevin Kitz john McLennan Kody Powell Milind Deo Palash Panja Department of Chemical Engineering University of UtahSalt Lake CityUT 84112USA Energy&Geoscience Institute University of UtahSalt Lake CityUT 84108USA RESPEC Company LLC Rapid CitySD 57703USA Kitzworks LLC BoiseID 83717USA

Borehole thermal energy storage(BTES)systems have garnered significant attention owing to their efficacy in storing thermal energy for heating and cooling *** modeling is paramount for ensuring the precise design and operation of BTES *** study conducts a sensitivity analysis of BTES modeling by employing a comparative investigation of five distinct parameters on a wedge-shaped model,with implications extendable to a cylindrical *** parameters examined included two design factors(well spacing and grout thermal conductivity),two operational variables(charging and discharging rates),and one geological attribute(soil thermal conductivity).Finite element simulations were carried out for the sensitivity analysis to evaluate the round-trip efficiency,both on a per-cycle basis and cumulatively over three years of operation,serving as performance *** results showed varying degrees of sensitivity across different models to changes in these *** particular,the round-trip efficiency exhibited a greater sensitivity to changes in spacing and volumetric flow ***,this study underscores the importance of considering the impact of the soil and grout-material thermal conductivities on the BTES-system performance over *** optimized scenario is modelled and compared with the base case,over a comparative assessment based on a 10-year *** analysis revealed that,at the end of the 10-year period,the optimized BTES model achieved a cycle efficiency of 83.4%.This sensitivity analysis provides valuable insights into the merits and constraints of diverse BTES modeling methodologies,aiding in the selection of appropriate modeling tools for BTES system design and operation.

关键词： Borehole thermal energy storage(BTES) Outlet temperature Round-trip efficiency Heating and cooling modes Well spacing Grout thermal conductivity Charging and discharging rates Soil thermal conductivity

来源：

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Birefringent Bragg Gratings in Highly-Nonlinear Photonic Crystal Fiber

引用

Journal of Electronic Science and Technology of China 2008年第4期6卷 426-428页

作者： kevin. Cook john. Canning john. Holdswowth Interdisciplinary Photonics Laboratories School of Chemistry University of Sydney NSW 2006 Australia the School of Mathematical and Physical Sciences University of Newcastle Callaghan NSW 2308 Australia

Efficient writing of Bragg gratings in 12-ring highly-nonlinear photonie crystal fibers is described. Experimental and numerical investigations are performed to reveal the optimum angle for coupling UV writing light to the core. Furthermore, we show that the formation of a strongly briefringent grating is at a particular angle of orientation.

关键词： Bragg gratings fiber optics photonic crystal fiber.

来源：

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

Net primary production in three bioenergy crop systems following land conversion

引用

Journal of Plant Ecology 2014年第5期7卷 451-460页

作者： Michael W.Deal Jianye Xu Ranjeet john Terenzio Zenone Jiquan Chen Housen Chu Poonam Jasrotia kevin Kahmark Jonathan Bossenbroek Christine Mayer Department of Environmental Sciences University of Toledo2801 West Bancroft StreetMail Stop 604ToledoOH 43606USA Great Lakes Bioenergy Research Center Michigan State University164 Food Safety and Toxicology BuildingEast LansingMI 48824USA W.K.Kellogg Biological Station Michigan State University3700 East Gull Lake DriveHickory CornersMI 49060USA

Aims Identifying the amount of production and the partitioning to above-and belowground biomass is generally the first step toward select-ing bioenergy *** are very few existing studies on the dynamics of production following land *** objectives of this study were to(i)determine the differences in aboveground net primary production(ANPP),belowground net primary produc-tion(BNPP),shoot-to-root ratio(S:R)and leaf area index in three bioenergy crop systems and(ii)evaluate the production of these three systems in two different land use *** This investigation included biometric analysis of NPP on three agri-cultural sites converted from conservation reserve program(CRP)management to bioenergy crop production(corn,switchgrass and prairie mix)and three sites converted from traditional agriculture production to bioenergy crop *** findings The site converted from conventional agriculture produced smaller ANPP in corn(19.03±1.90 standard error[SE]Mg ha^(−1) year^(−1))than the site converted from CRP to corn(24.54±1.43 SE Mg ha^(−1) year^(−1)).The two land conversions were similar in terms of ANPP for switchgrass(4.88±0.43 SE for CRP and 2.04±0.23 SE Mg ha^(−1) year^(−1) for agriculture)and ANPP for prairie mix(4.70±0.50 SE for CRP and 3.38±0.33 SE Mg ha^(−1) year^(−1) for agriculture).The BNPP at the end of the growing season in all the bioenergy crop systems was not significantly different(P=0.75,N=8).

关键词： bioenergy crops land use change net primary production aboveground net primary production belowground net primary production

来源：

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

欢迎您,

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

请选择保存的检索档案：

请选择收藏分类：

通借通还

欢迎您,

建议与咨询 留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

请选择保存的检索档案： 新增检索档案 确定 取消

请选择收藏分类： 新增自定义分类 确定 取消

通借通还

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

请选择保存的检索档案：

请选择收藏分类：