检索结果-南通市图书馆

optimal tool design in micro-milling of difficult-to-machine materials

Advances in Manufacturing 2023年第2期11卷 222-247页

作者： Lorcan o'Toole Feng-Zhou Fang Centre of Micro/Nano Manufacturing Technology(MNMT-Dublin) University College DublinDublin 4Ireland State Key Laboratory of Precision Measuring Technology and Instruments Laboratory of Micro/Nano Manufacturing Technology(MNMT)Tianjin UniversityTianjin300072People's Republic of China

The limitations of significant tool wear and tool breakage of commercially available fluted micro-end mill tools often lead to ineffective and inefficient manufacturing,while surface quality and geometric dimensions remain unacceptably *** is especially true for machining of difficult-to-machine(DTM)materials,such as super alloys and *** conventional fluted micro-tool designs are generally down scaled from the macro-milling tool ***,simply scaling such designs from the macro to micro domain leads to inherent design flaws,such as poor tool rigidity,poor tool strength and weak cutting edges,ultimately ending in tool ***,in this article a design process is first established to determine optimal micro-end mill tool designs for machining some typical DTM materials commonly used in manufacturing orthopaedic implants and micro-feature *** design process focuses on achieving robust stiffness and mechanical strength to reduce tool wear,avoid tool chipping and tool breakage in order to efficiently machine very hard ***,static stress and deflection finite element analysis(FEA)is carried out to identify stiffness and rigidity of the tool design in relation to the maximum deformations,as well as the Von Mises stress distribution at the cutting edge of the designed *** analysis and further optimisation of the FEA results,a verified optimum tool design is established for micro-milling DTM *** experimental study is then carried out to compare the optimum tool design to commercial tools,in regards to cutting forces,tool wear and surface quality.

关键词： Precision machining Micro-milling Difficult-to-machine(DTM) Tool wear Micro-tool design Surface quality

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

Synthesis and properties of novel nitro-based thermally stable energetic compounds

引用

Defence Technology（防务技术） 2021年第3期17卷 775-784页

作者： Łukasz Gutowski Stanisław Cudziło Military University of Technology Faculty of Advanced Technologies and ChemistryGen.Sylwestra Kaliskiego 2 Street00-908WarsawPoland

This paper reviews the achievements in the field of synthesis of new thermally resistant explosive compounds in the years 2009 through 2019. The performance characteristics of these compounds(sensitivity, thermal decomposition parameters, and detonation parameters) were compared with those of 1,3,5-triamino-2,4,6-trinitrobenzene, which still seems to be an unrivalled model of a thermally resistant and generally low-sensitivity explosive material. New thermally stable explosives(TSEs) were found among macromolecular compounds with tri-and dinitrophenyl groups, nitro and amine-nitro derivatives of azoles, and polynitro derivatives of calixarenes. Some of them match TATB in terms of thermal resistance and additionally have higher detonation parameters.

关键词： Heat resistant explosives Detonation parameters Synthesis Nitration

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

Baeyer-Villiger oxidation of cyclic ketones utilizing potassium peroxydisulfate(K_2S_2o_8) or sodium perborate(NaBo_3) in acidic media

引用

Chinese Chemical Letters 2009年第12期20卷 1400-1404页

作者： S.Zarrabi N.o.Mahmoodi K.Tabatabaeian M.A.Zanjanchi Department of Chemistry Faculty of ScienceUniversity of GuilanRashtP.O.Box 1914Iran

The efficient, green, facile, mild and straightforward conversion procedure for the oxidation of cyclic ketones to lactones at room temperature utilizing potassium peroxydisulfate （K2S2o8） in acidic media is satisfactory to high yields without using traditional chlorinated solvents is reported. This oxidative reagent is cheap and friendly environmental procedure for industrial purposes than use of organic peracids.

关键词： Baeyer-Villiger oxidation Cyclic ketones Potassium peroxydisulfate (K2S208) Acidic media Sodium perborate (NaBo3)

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

Interactive influence of rainfall manipulation and livestock grazing on species diversity of the herbaceous layer community in a humid savannah in Kenya

引用

Plant Diversity 2019年第3期41卷 198-205页

作者： Joseph o.ondier Daniel o.okach John C.onyango Dennis o.otieno Department of Botany Maseno University Private Bag Maseno Kenya Department of Biological Sciences Jaramogi Oginga Odinga University of Science and Technology P.O Box 210-40601 Bondo Kenya Department of Plant Ecology University of Bayreuth D-95440 Bayreuth Germany

Changes in rainfall regime and grazing pressure affect vegetation composition and diversity with ecological implications for savannahs. The savannah in East Africa has experienced increased livestock grazing and rainfall variability but the impacts associated with those changes on the herbaceous layer have rarely been documented. We investigated the effect of livestock grazing, rainfall manipulation and their interaction on the composition and diversity of the herbaceous community in the savannah for two years in Lambwe, Kenya. Rainfall manipulation plots were set up for vegetation sampling;these plots received either 50% more or 50% less rainfall than control plots. Simpson’s diversity and Bergere Parker indices were used to determine diversity changes and dominance respectively. The frequency of species was used to compute their abundance and their life forms as determined from the literature. Grazing significantly increased species diversity through suppression of dominant species. Rainfall manipulation had no significant impact on plant diversity in fenced plots, but rainfall reduction significantly reduced diversity in grazed plots. In contrast, rainfall manipulation had no impact on dominance in either fenced or grazed plots. The interaction of grazing and rainfall manipulation is complex and will require additional survey campaigns to create a complete picture of the implications for savannah structure and composition.

关键词： Plant diversity Grazing Rainfall Moist savannah

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

Parallel loop recovery with quiescent compensation for high performance feedback control of systems with imperfect actuators

引用

Control Theory and Technology 2019年第3期17卷 201-215页

作者： Y.V.o'BRIEN J.F.o'BRIEN Department of Electrical and Computer Engineering University of Wyoming Laramie WY 82073 U.S.A.

Actuator limits and imperfections introduce multiple nonlinearities in a feedback *** standard mild-feedback systems (e.g.,PID) are intrinsically robust to such nonlinearities,the stability of large feedback systems is *** eliminates from consideration the usage of imperfect actuators in large feedback applications and available disturbance rejection as a result is not *** implementation of multiple-path nonlinear dynamic compensation (NDC),however,allows the combination of large feedback and imperfect actuation and is the focus of this *** nonlinearities due to actuator imperfection are often difficult to model,the stability of the NDC systems is assessed using multivariable absolute stability *** features of a parallel loop recovery system with loop transmission modulus reduction compensation in the quiescent condition are compared to an alternative approach of strict modulus reduction via nonlinear compensation for stability *** of the loop recovery approach is illustrated using experimental data from a voice-coil actuated disturbance rejection system.

关键词： Feedback control imperfect actuators nonlinear dynamic compensation

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

Vertical stratification of bat assemblages in flooded and unflooded Amazonian forests

引用

Current Zoology 2010年第4期56卷 469-478页

作者： Maria Joo Ramos PEREIRA Joo Tiago MARQUES Jorge M.PALMEIRIM Centro de Biologia Ambiental Departamento de Biologia Animal Faculdade de Ciências da Universidade de Lisboa Instituto de Desenvolvimento Sustentvel Mamirau

Tropical rainforests usually have multiple strata that results in a vertical stratification of ecological opportunities foranimals. We investigated if this stratification influences the way bats use the vertical space in flooded and unflooded forests of theCentral Amazon. Using mist-nets set in the canopy (17 to 35 m high) and in the understorey (0 to 3 m high) we sampled four sitesin upland unflooded forests (terra firme), three in forests seasonally flooded by nutrient-rich water (varzea), and three in forestsseasonally flooded by nutrient-poor water (igapo). Using rarefaction curves we found that species richness in the understorey andcanopy were very similar. An ordination analysis clearly separated the bat assemblages of the canopy from those of the understorey inboth flooded and unflooded habitats. Gleaning carnivores were clearly associated with the understorey, whereas frugivores wereabundant in both strata. of the frugivores, Carollinae and some Stenodermatinae were understorey specialists, but several Stenodermatinaemostly used the canopy. The first group mainly includes species that, in general, feed on fruits of understorey shrubs,whereas the second group feed on figs and other canopy fruits. We conclude that vertical stratification in bat communities occurseven within forests with lower canopy heights, such as Amazonian seasonally flooded forests, and that the vertical distribution ofbat species is closely related to their diet and foraging behaviour.

关键词： Amazon Bats Chiroptera Vertical stratification Floodplain

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

Gravitational form factors and nucleon spin structure

引用

Frontiers of physics 2016年第5期11卷 1-8页

作者： o.V. Teryaev Bogoliubov Laboratory of Theoretical Physics JINR 141980 Dubna Moscow Region Russia

Nucleon scattering by the classical gravitational field is described by the gravitational （energy- momentum tensor） form factors （GFFs）, which also control the partition of nucleon spin between the total angular momenta of quarks and gluons. The equivalence principle （EP） for spin dynamics results in the identically zero anomalous gravitomagnetic moment, which is the straightforward analog of its electromagnetic counterpart. The extended EP （ExEP） describes its （approximate） validity separately for quarks and gluons and, in turn, results in equal partition of the momentum and total angular momentum. It is violated in quantum electrodynamics and perturbative quantum chromodynamics （QCD）, but may be restored in nonperturbative QCD because of confinement and spontaneous chiral symmetry breaking, which is supported by models and lattice QCD calculations. It may, in principle, be checked by extracting the generalized parton distributions from hard exclu- sive processes. The EP for spin-1 hadrons is also manifested in inclusive processes （deep inelastic scattering and the Drell-Yan process） in sum rules for tensor structure functions and parton distributions. The ExEP may originate in either gravity-proof confinement or in the closeness of the GFF to its asymptotic values in relation to the mediocrity principle. The GFFs in time-like regions reveal some similarity between inflation and annihilation.

关键词： gravity form factors equivalence principle

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

Analysis of Sakiadis flow of nanofluids with viscous dissipation and Newtonian heating

引用

Applied Mathematics and Mechanics(English Edition) 2012年第12期33卷 1545-1554页

作者： o.D.MAKINDE Institute for Advance Research in Mathematical Modelling and Computations Cape Peninsula University of TechnologyP.O.Box 1906Bellville 7535South Africa

The combined effects of viscous dissipation and Newtonian heating on bound- ary layer flow over a moving flat plate are investigated for two types of water-based New- tonian nanofluids containing metallic or nonmetallic nanoparticles such as copper （Cu） and titania （Ti02）. The governing partial differential equations are transformed into ordinary differential equations through a similarity transformation and are solved numer- ically by a Runge-Kutta-Fehlberg method with a shooting technique. The conclusions are that the heat transfer rate at the moving plate surface increases with the increases in the nanoparticle volume fraction and the Newtonian heating, while it decreases with the increase in the Brinkmann number. Moreover, the heat transfer rate at the moving plate surface with Cu-water as the working nanofiuid is higher than that with Tio2-water.

关键词： Sakiadis flow nanofluid viscous dissipation Newtonian heating

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

Looking Back and Beyond Sendai:25 Years of International Policy Experience on Disaster Risk Reduction

引用

International Journal of Disaster Risk Science 2015年第1期6卷 1-7页

作者： Sálvano Briceo Science Committee Integrated Research on Disaster Risk(IRDR) Program of International Council for Science (ICSU)/International Social Science Council (ISSC)/United NationsInternational Strategy for Disaster Reduction (UNISDR)

The evolution in knowledge and application of disaster risk reduction in the 25 years of global cooperation on this issue has been uneven. While advances in knowledge have improved our understanding of the full nature of risk—the combination of hazards meeting vulnerability—the application of such knowledge has not been conducive to the development of institutional and technical mechanisms to address the full range of risk elements. Governance of risk(policies, legislation, and organizational arrangements) still focuses largely on preparing to respond to the hazards and planning for recovery. This leaves largely unattended the vulnerability component of risk, which is the only component on which change can be *** arrangements, risk assessments, early warning systems, and other institutional and technical capacities still concentrate on natural hazards and this is the main change that remains to be substantively addressed.

关键词： Climate change adaptation Disaster risk reduction Risk governance Risk management

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

Element diffusion ability in metasomatic agents and its effect on chemical characteristics of metasomatized peridotites

引用

Science China Earth Sciences 2006年第9期49卷 926-937页

作者： Y S o’Reilly GEMoC ARC National Key Centre Department of Earth and Planetary Sciences Macquarie University Sydney N.S.W. 2109 Australia

Detailed in situ LM-ICPMS researches on the composite xenoliths from Yingfengling volcano of Leizhou Peninsula, South China, indicate that most incompatible trace elements of clino- pyroxenes in composite xenoliths decrease spatially from pyroxenites to distal lherzolites, and com- patible elements and HREE increase steeply. The increasing and decreasing rate is distinct for dif- ferent trace elements, which give rise to element chromatographic fractionation within metasomatized lherzolites. The element chromatographic fractionation result actually from the difference in element diffusive rate in melts or fluids percolating through wall-rock lherzolites. Based on element variation profiles in composite xenoliths this study indicates that Sr, Nb, La and Ce have the highest diffusive mobility, MREE-HREE are moderate, and Zr, Hf, Ti, Ga and Sc are very low in most cases. Higher diffusive rates of LREE than HREE would enlarge the REE fractionation of metasomatized peridotites, and lower diffusive rate of Zr, Hf and Ti relative to neighbor REEs with similar incompatibility would cause the relative depletion of these elements in metasomatized peridotites. Trace elements com- monly have a higher diffusive rate in fluid-rich infiltrating melt, which will weaken element chroma- tographic fractionation during the metasomatism. The range of mantle metasomatism caused by sili- cate melt intrusion is very limited, generally within tens of centimeters wide. The width of metasoma- tized wall-rock peridotites near the pyroxenite or horblendite veins was strictly controlled by both melt volume and chemical characteristics.

关键词： composite xenolith, metasomatism, chromatographic fractionation, diffusive rate, Leizhou Peninsula.

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

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：