检索结果-南通市图书馆

GRADE指南：Ⅵ.证据质量评价--不精确性(随机误差)

在线全文

学校读者我要写书评

暂无评论

中国循证医学杂志 2011年第12期11卷 1435-1443页

作者： Gordon Guyatt Andrew D.Oxman Regina Kunz Jan Brozek Pablo Alonso-Coello David Rind PJ Devereaux Victor M.Montori Bo Freyschuss Gunn Vist Roman Jaeschke john w.williams jr. Mohammad Hassan Murad David Sinclairk Yngve Falck-Ytter Joerg Meerpohl Craig whittington Kristian orlund Je Andrews Holger J.Schünemann 代表GRADE工作组李幼平王莉陈尹高霑机构不详

GRADE建议通过检查95%可信区间(CI)为决定不精确性的最佳方法。在指南实际运用中,如果CI的上、下限值代表了真实效应,而临床实际情况与之不符时,必须降低证据质量级别(即对效应估计值的把握度)。除外当效应值很大且可信区间提示效应稳健... 详细信息

GRADE建议通过检查95%可信区间(CI)为决定不精确性的最佳方法。在指南实际运用中,如果CI的上、下限值代表了真实效应,而临床实际情况与之不符时,必须降低证据质量级别(即对效应估计值的把握度)。除外当效应值很大且可信区间提示效应稳健,而总样本量不大且事件数很少的情况,其他应考虑因不精确性而降低证据质量级别。作此决定时,可计算有足够检验效能的单个试验所需的病例数(定义为"最优信息样本量",即optimal information size,OIS)。对连续型变量,我们建议用类似方法,首先考虑可信区间上、下限值,再计算OIS。系统评价(SR)所需方法略有不同。如果95%CI不包括相对危险度(RR)为1,且总事件发生数或病例数超过OIS标准,则精确性良好。如果95%CI包括了明显获益或危害(我们建议以RR值1.25作粗标准),即使达到OIS要求,因不精确性而降低证据质量级别较恰当。

关键词： GRADE 证据质量估计值把握度不精确性最优样本信息量可信区间

Investigation of normal,lateral,and oblique impact of microscale projectiles into unidirectional glass/epoxy composites

在线全文

学校读者我要写书评

暂无评论

Defence Technology（防务技术） 2022年第11期18卷 1960-1978页

作者： Christopher S.Meyer Isabel G.Catugas john w.Gillespie jr. Bazle Z.Gama Haque University of Delaware Center for Composite Materials(UD-CCM) 101 Academy StreetNewarkDE19716USA

Spacesuits and spacecraft must endure high velocity impacts from micrometeoroids. This work considers the impact of 100 μm diameter projectiles into composite targets at velocities from 0.5 km/s to 2 km/*** work begins by presenting an energy-based theoretical model relating depth of penetration(Do P)and impact force to impact velocity, characteristic time, and threshold velocity and force. Next, this work compares numerical simulations of normal impact on composites to the theoretical model. Numerical simulations are conducted with LS-DYNA and the well-known composite model, MAT-162. The numerical models consider unidirectional S2-glass fiber reinforced SC-15 epoxy composite laminates. The numerical model shows good correlation with the theoretical model. The numerical model also investigates lateral impact, parallel to the fiber direction, and oblique impact at angles from 30°to 82.5°.This work decomposes oblique impact into normal and lateral components, and compares them with normal and lateral impact results. The results show good correlation of the normal component of oblique results with the theoretical model. This numerical and theoretical study focuses on Do P, velocity, and penetration resistance force as functions of time. The theoretical model and numerical simulations are used to determine new Do P parameters: characteristic time of depth of penetration and threshold impact velocity. These models are a first step in developing the capability to predict Do P for oblique,microscale, high-speed impact on composite materials.

关键词： Microscale Hypervelocity impact Composites Erosion Penetration

GRADE指南：Ⅳ.证据质量分级--研究的局限性(偏倚风险)

在线全文

学校读者我要写书评

暂无评论

中国循证医学杂志 2011年第4期11卷 456-463页

作者： Gordon H.Guyatt Andrew D.Oxman Gunn Vist Regina Kunz Jan Brozek Pablo Alonso-Coello Victor Montori Elie A.Akl Ben Djulbegovic Yngve Falck-Ytter Susan L.Norris john w.williams jr. David Atkins Joerg Meerpohl Holger J.Schünemann GRADE工作组李幼平杨晓妍李鸿浩李玲

在GRADE方法中,若多数相关证据来自高偏倚风险的研究,则起初被定为高质量证据的随机试验和低质量证据的观察性研究均有可能被降低质量等级。随机试验已确定的局限性包括:未进行分配隐藏、未实施盲法、未报告失访情况及未恰当考虑意向性... 详细信息

在GRADE方法中,若多数相关证据来自高偏倚风险的研究,则起初被定为高质量证据的随机试验和低质量证据的观察性研究均有可能被降低质量等级。随机试验已确定的局限性包括:未进行分配隐藏、未实施盲法、未报告失访情况及未恰当考虑意向性治疗原则。最近提出的局限性包括:因明显获益而早期终止试验和基于结果选择性报告结局。观察性研究的主要局限性包括使用不合适的对照及未能充分调整预后的不平衡。偏倚风险可因不同结果而异(如全死因死亡率的失访远少于生命质量的失访),许多系统评价都容易忽略这一点。在决定是否因偏倚风险而降低质量等级时,不管是随机试验还是观察性研究,作者不应采用对各个研究取平均值的方法。相反,对任何单个结果,当同时存在高、低偏倚风险的研究时,则应考虑只纳入较低偏倚风险的研究。

关键词： GRADE 证据质量偏倚风险估计值的可信度盲法分配隐藏

GRADE指南：Ⅴ.证据质量评价--发表偏倚

在线全文

学校读者我要写书评

暂无评论

中国循证医学杂志 2011年第12期11卷 1430-1434页

作者： Gordon H.Guyatt Andrew D.Oxman Victor Montori Gunn Vist Regina Kunz Jan Brozek Pablo Alonso-Coello Ben Djulbegovic David Atkins Yngve Falck-Ytter john w.williams jr. Joerg Meerpohl Susan L.Norris Elie A.Akl Holger J.Schünemann 代表GRADE工作组李幼平王莉钟大可蒋兰慧机构不详

GRADE方法中,随机试验起评即为高质量证据,观察性研究起评即为低质量证据;但若证据本身存在高发表偏倚风险,则两者证据质量级别都应降低。即使最佳证据汇总表纳入的各项研究仅有低发表偏倚风险,发表偏倚仍会极大高估效应值。当可得证据... 详细信息

GRADE方法中,随机试验起评即为高质量证据,观察性研究起评即为低质量证据;但若证据本身存在高发表偏倚风险,则两者证据质量级别都应降低。即使最佳证据汇总表纳入的各项研究仅有低发表偏倚风险,发表偏倚仍会极大高估效应值。当可得证据来自小样本研究、且多数由厂商资助时,作者应怀疑存在发表偏倚。若干基于检验数据类型的方法可用于评价发表偏倚,其中最常用的为漏斗图,但这些方法都有较大局限。发表偏倚可能较常见,必须特别关注早期结果、对样本量与事件数都很小的早期试验结果尤需小心。

关键词： GRADE 证据质量发表偏倚漏斗图利益冲突制药业

The influence of habitat heterogeneity and latitude on gamma diversity of the Nearctic Simuliidae, a ubiquitous group of stream-dwelling insects

在线全文

学校读者我要写书评

暂无评论

Insect Science 2018年第4期25卷 712-720页

作者： john w. McCreadie Rachel H. williams Sam Stutsman Debra S. Finn Peter H. Adler Department of Biology University of South Alabama Mobile Alabama USA Department of Earth Sciences Biology University of South Alabama Mobile Alabama USA Department of Integrative Biology Oregon State University Corvallis Oregon USA Department of Plant and Environmental Sciences Clemson University Clemson South Carolina USA

Among the most prominent, large-scale patterns of species richness are the increases in richness with decreasing latitude and with increasing habitat heterogeneity. Using the stream-dwelling larval and pupal stages of North American black flies （Diptera： Simuliidae）, we address 3 broad questions about species richness：（i） Does a significant latitude-richness relationship exist？（ii） How does habitat heterogeneity influence gamma diversity？（iii） what is the sign （positive or negative） of the latitude-richness and the heterogeneity-richness relationships？ we found no evidence that habitat heterogeneity influences gamma diversity. The estimated peak species richness for black flies in North America was at 50-53°N, which also corresponds with peak generic richness. All plesiomorphic, extant lineages of the Simuliidae in the western Hemisphere are found in cool mountainous environments of North America, suggesting that peak richness at 50-53°N might be a signature of this phylogenetic pattern and a reflection of underlying historical processes

关键词： aquatic insects biodiversity gamma richness North America Simuliidae streams

Nanoembryonic thermoelastic equilibrium and enhanced properties of defected pretransitional materials

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

npj Computational Materials 2018年第1期4卷 178-184页

作者： Ye-Chuan Xu wei-Feng Rao john w.Morris jr. Armen G.Khachaturyan Department of Materials Physics and IEMMNanjing University of Information Science and TechnologyNanjing 210044China Department of Materials Science and Engineering University of CaliforniaBerkeleyCA 94720USA Department of Materials Science and Engineering Rutgers UniversityPiscatawayNJ 08854USA

Behaviors of displacive phase-transforming materials above the temperature of transformation,where abnormal thermal,elastic,magnetic properties are often observed,are mostly explained by intrinsic peculiarities in electronic/atomic ***,we show these properties may also be attributed to extrinsic effects caused by a thermoelastic equilibrium in highly defected pretransitional *** demonstrate that the stress concentration near stress-generating defects such as dislocations and coherent precipitates could result in the stress-induced transformation within nanoscale regions,producing equilibrium embryos of the product *** nanoembryos in thermoelastic equilibrium could anhysteretically change their equilibrium size in response to changes in applied stress or magnetic fields leading to superelasticity or *** response to cooling may explain the observed diffuse phase transformation,changes in the coefficient of thermal expansion and effective elastic modulus,which,in turn,may explain the invar and elinvar behaviors.

关键词： transformation equilibrium transitional

Organizational Behavior Don Hellriegel, john w. Slocum, jr.

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

Ancient Muses: Archaeology and the Arts

2007年

作者： Don Hellriegel john w. Slocum jr.

来源：畅想之星图书光盘版（南... 评论

在线全文

畅想之星图书光盘版（南通市图书馆镜像）

学校读者我要写书评

暂无评论

Computational fluid dynamics simulation on the longwall gob breathing

2003年

作者： john H. Jameson jr

来源：畅想之星图书光盘版（南... 评论

在线全文

畅想之星图书光盘版（南通市图书馆镜像）

学校读者我要写书评

暂无评论

International Journal of Mining Science and Technology 2017年第2期27卷 185-189页

作者： Samuel A.Lolon Jürgen F.Brune Gregory E.Bogin jr. john w.Grubb Saqib A.Saki Aditya Juganda Department of Mining Engineering Colorado School of MinesCO 80401USA Department of Mechanical Engineering Colorado School of Mines CO 80401USA

In longwall mines, atmospheric pressure fluctuations can disturb the pressure balance between the gob and the ventilated working area, resulting in a phenomenon known as ‘‘gob breathing". Gob breathing triggers gas flows across the gob and the working areas and may result in a condition where an oxygen deficient mixture or a methane accumulation in the gob flows into the face area. Computational Fluid Dynamics(CFDs) modeling was carried out to analyze this phenomenon and its impact on the development of an explosive mixture in a bleeder-ventilated panel scheme. Simulation results indicate that the outgassing and ingassing across the gob and the formation of Explosive Gas Zones(EGZs) are directly affected by atmospheric pressure changes. In the location where methane zones interface with mine air, EGZ fringes may form along the face and in the bleeder entries. These findings help assess the methane ignition and explosion risks associated with fluctuating atmospheric pressures.

关键词：计算流体力学模拟采空区呼吸爆炸性气体计算流体动力学大气压力长壁开采压力平衡