检索结果-南通市图书馆

Pressurized environments directly influence friction and wear of dry steel contacts—Investigations in a novel high fluid pressure tribometer

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Friction 2024年第7期12卷 1599-1617页

作者： Paul ReICHLe Jakob BARZ Georg UMLAUF Günter e.M.TOVAR Institute of Interfacial Process engineering and Plasma Technology(IGVP) University of StuttgartStuttgart 70569Germany Fraunhofer Institute for Interfacial engineering and Biotechnology(IGB) Stuttgart 70569Germany

To reduce.the usage of classical lubricants in deep drawing,a new tribological system based on volatile lubricants was ***,a volatile medium is injected under high pressure into the interstice between drawing tool and sheet *** on temperature and pressure.the temporary lubricant may exist in its gaseous or liquid *** this study,a novel high fluid pressure tribometer was designed to investigate.the friction and wear of dry steel contacts under comparable conditions like in dry deep ***,a new ball-on-disc tribometer was designed and integrated into a high-pressure *** specifically investigate.the effects of different environments(technical air,liquid and gaseous carbon dioxide,nitrogen,argon)at atmospheric and high pressure(0.1 MPa,6 MPa)on tribology,the specimens and all components were operating *** the experiments,the friction was measured *** show that the highest friction occurs in air and the lowest in carbon dioxide *** to the experiments,the wear of the specimens was assessed along with changes in surface chemistry related to tribochemical ***,the tribology of the dry sliding contacts is correlated to changes of the surface *** differences as well as similarities regarding the different fluid environments are *** the results show,the differences between the media used are most pronounced at elevated ***,this work gives clear indications on the suitability of volatile lubricants in dry friction or rather gas lubrication,especially for dry deep drawing.

关键词： dry friction and dry wear gas lubrication carbon dioxide tribo-layer dry metal forming

Burden of gallstone disease in the United States population:Prepandemic rates and trends

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 Gastrointestinal Surgery 2024年第4期16卷 1130-1148页

作者： Aynur Unalp-Arida Constance e Ruhl National Institute of Diabetes and Digestive and Kidney Diseases National Institutes of HealthBethesdaMD 20892-5458United States Social&Scientific Systems Inc.DLH Holdings Corp CompanySilver SpringMD 20910United States

BACKGROUND Gallstone disease is one of the most common digestive disorders in the United States and leads to significant morbidity,mortality,and health care *** To expand on earlier findings and investigate prepandemic rates and trends in the gallstone disease burden in the United States using national survey and claims *** the National Ambulatory Medical Care Survey,National Inpatient Sample,Nationwide emergency Department Sample,Nationwide Ambulatory Surgery Sample,Vital Statistics of the United States,Optum Clinformatics®Data Mart,and Centers for Medicare and Medicaid Services Medicare 5%Sample and Medicaid files were used to estimate claims-based prevalence,medical care including cholecystectomy,and mortality with a primary or other gallstone *** were age-adjusted(for national databases)and shown per 100000 *** Gallstone disease prevalence(claims-based,2019)was 0.70%among commercial insurance enrollees,1.03%among Medicaid beneficiaries,and 2.09%among Medicare beneficiaries and rose over the previous ***,in the United States population,gallstone disease contributed to approximately 2.2 million ambulatory care visits,1.2 million emergency department visits,625000 hospital discharges,and 2000 de.ths *** had higher medical care rates with a gallstone disease diagnosis,but mortality rates were higher among *** had higher ambulatory care visit and hospital discharge rates compared with Whites,but not mortality *** had lower ambulatory care visit and mortality rates,but similar hospital discharge rates compared with *** the study period,ambulatory care and emergency department visit rates with a gallstone disease diagnosis rose,while hospital discharge and mortality rates *** commercial insurance enrollees,rates were higher compared with national data for ambulatory care visits and hospitalizations,but lower for emergency department ***

关键词： Gallstone disease Burden Cholecystectomy Mortality Health care use Cholelithiasis Gallstones epidemiology

High seed losses in mountain birch(Betula pubescens ***)and developmental,ecological,and environmental correlates

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 Plant ecology 2024年第4期17卷 56-69页

作者： Guorun Oskarsdottir thora e.thorhallsdottir Kristin Svavarsdottir University of Iceland 102 ReykjavíkIceland Land and Forest Iceland ReykjavíkIceland

Plants typically experience great losses from their reproductive potential represented by ovule production to the post-dispersal crop of viable *** examined seed density and viability in a founder population of mountain birch(Betula pubescens ***),aiming to quantify losses at different stages and examine potential selection forces on the reproduction success of the founder generation of an isolated *** the time of the study(2017-2020),the population had recently reached reproductive maturity,following its colonization around 1990 through long-distance dispersal onto an early successional outwash plain in southeast *** densities were high,but 89% of apparently intact seeds did not contain an embryo,despite being visually indistinguishable from filled *** evident losses amounted to about 45% of the total seed crop and were mostly due to predation by the gall midge Semudobia *** all losses were accounted for,2.7% of the seed crop remained viable and *** limitation may partially explain the high incidence of empty *** flower production is compatible with the predator satiation hypothesis but cannot explain pre-dispersal *** adaptation to predation,masting,appears poorly developed in *** results suggest the presence of constraints on the reproduction potential of the new island population,that are more limiting than in neighbouring populations,and we discuss their developmental,ecological,and environmental correlates.

关键词： Betula pubescens ssp.tortuosa(Ledeb.)Nyman Iceland seed quality seed losses Semudobia betulae sub-arctic

Influence of Methane-Hydrogen Mixture Characteristics on Compressor Vibrations

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Fluid Dynamics & Materials Processing 2024年第5期20卷 1031-1043页

作者： Vladimir Ya.Modorskii Ivan e.Cherepanov High Performance Computing Center Perm National Research Polytechnic UniversityPerm614990Russia

A transition to clean hydrogen energy will not be possible until the issues related to its production, transportation,storage, etc., are adequately resolved. Currently, however, it is possible to use methane-hydrogen *** gas can be transported using a pipeline system with the required pressure being maintained by gascompression stations. this method, however, is affected by some problems too. Compressors emergency stopscan be induced by vibrations because in some cases, mechanical methods are not able to reduce.the vibrationamplitude. As an example, it is known that a gas-dynamic flow effect in labyrinth seals can lead to increasedvibrations. this paper presents the numerical simulation of rotor oscillations taking into account a gas-dynamicload. the influence of a transported mixture on the oscillatory process is investigated. Mixtures consisting ofmethane and hydrogen in various proportions and an air mixture are considered. the results are discussed forvarious operating pressures and include.the rotor motion trajectories and oscillation frequency spectra obtainednumerically. It is shown that the gas mixture composition has a significant effect on the oscillations and theiroccurrence. Hydrogen as a working fluid reduces the vibration amplitude. Operating a compressor with hydrogenleads to a decrease in the resonant frequency, bringing it closer to the operating one. However, the operatingpressure at which maximum oscillations are observed depends slightly on the gas mixture composition.

关键词： Seal stabilities vibration FSI CFD multiphase flows hydrogen

Landau quantization effects on damping Kawahara solitons in electron–positron–ion plasma in rotating ionized medium

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Communications in theoretical Physics 2024年第10期76卷 143-152页

作者： e I el-Awady S Hussain N Akhtar Department of Physics Faculty of Science Port Said University theoretical Physics Division (TPD) PINSTECH

For the dynamics of three-dimensional electron–positron–ion plasmas, a fluid quantum hydrodynamic model is proposed by considering Landau quantization effects in dense ***–neutral collisions in the presence of the Coriolis force are also considered. the application of the reductive perturbation technique produces a wave evolution equation represented by a damped Korteweg–de Vries equation. this equation, however, is insufficient for describing waves in our system at very low dispersion coefficients. As a result, we considered the highest-order perturbation, which resulted in the damped Kawahara equation. the effects of the magnetic field, Landau quantization, the ratio of positron density to electron density, the ratio of positron density to ion density, and the direction cosine on linear dispersion laws as well as soliton and conoidal solutions of the damped Kawahara equation are explored. the understanding from this research can contribute to the broader field of astrophysics and aid in the interpretation of observational data from white dwarfs.

关键词： Coriolis force Kawahara equation Landau quantization magnetoplasmas quantum plasma solitary and cnoidal waves

Transition from oceanic subduction to continental collision:Insights from volcanogenic-sedimentary rocks of the Tannuola terrane(northern Central Asian Orogenic Belt)

同方期刊数据库评论

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Geoscience Frontiers 2024年第4期15卷 41-60页

作者： e.V.Vetrov N.I.Vetrova V.S.Sobolev Institute of Geology and Mineralogy SB RAS Koptyuga ave.3NovosibirskRussia

Magmatism associated with oceanic subduction plays a dominant role in crustal growth during the earth's *** Tannuola terrane,situated in the northern Central Asian Orogenic Belt(CAOB),is a key area to understanding oceanic subduction and initial collision processes in the northern *** order to investigate.the switch from subduction to collision settings,detailed field mapping,zircon SHRIMP U-Pb geochronological and whole-rock geochemical studies of volcanogenic-sedimentary rocks from the Tannuola terrane were carried *** U-Pb ages indicate multi-stage volcanism lasted at least 30 Ma from~540 to~510 Ma,that can be divided into three events:the late ediacaran(before~540 Ma),the early Cambrian(~520 Ma)and the middle Cambrian(~510 Ma).these ages are inter-preted to the initial,main and final stages of oceanic subduction during the late Proterozoic-early *** the late ediacaran,tholeiitic basalts with highεNd(t)values(from+7.4 to+8.5)were *** forming by the 10%-30%partial melting of spinel-garnet mantle source during slab *** the early Cambrian,transitional from tholeiitic to calc-alkaline basaltic rocks withεNd(t)value(+5.6)and coeval intermediate-felsic volcanic rocks with similarεNd(t)values(+5.9 and+6.5)*** early Cambrian basaltic rocks are interpreted to be derived by 10%-30%partial melt-ing of a depleted mantle source metasomatized by slab-derived fluids released from the subducting ocea-nic *** middle Cambrian calcalkaline basaltic rocks withεNd(t)value of+6.2 might be emplaced as a result of low(5%-10%)degree partial melting of a metasomatized mantle followed by fractional crys-tallization of clinopyroxene and *** intermediate-felsic volcanic rocks withεNd(t)values from+6.0 to+6.8 were formed through fractionation of the juvenile Neoproterozoic *** middle Cambrian volcanism is interpreted to be triggered by the slab break-off during the transition to a collisional se

关键词： Island-arc magmatism ediacaran Cambrian zircon U-Pb dating Nd isotopes Central asian orogenic belt

Artificial intelligence meets body sense: task-driven neural networks reveal computational principles of the proprioceptive pathway

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Signal Transduction and Targeted therapy 2024年第8期9卷 3147-3149页

作者： Leonard e.van Dyck Frank Bremmer Katharina Dobs Department of Psychology Justus Liebig University GiessenGiessenGermany Max Planck Institute for Human Cognitive and Brain Sciences LeipzigGermany Center for Mind Brain and BehaviorUniversities of MarburgGiessenand DarmstadtMarburgGermany Department of Neurophysics Philipps-Universitat MarburgMarburgGermany

In a recent study published in Cell,Marin Vargas and Bisi et al.1 present an innovative approach to unravel the computational principles underlying proprioceptive processing in non-human *** findings showcase.the utility of task-driven modeling in advancing neuroscience and offer translational potential by providing seminal insights into the goals and mechanisms by which the brain encodes body position and movements.

关键词： networks neural principles

An effective nonlinear dynamic formulation to analyze grasping capability of soft pneumatic robotic gripper

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

International Journal of Smart and Nano Materials 2024年第3期15卷 405-431页

作者： Qiping Xu Chenhang Ying Kehang Zhang Huiyu Xie Shiju e Department of Robotics engineering Key Laboratory of Urban Rail Transit Intelligent Operation and Maintenance Technology&Equipment of Zhejiang ProvinceCollege of EngineeringZhejiang Normal UniversityJinhuaP.R.China

Soft pneumatic robotic grippers have found extensive applica-tions across various engineering domains,which prompts active research due to their splendid compliance,high flex-ibility,and safe human-robot interaction over conventional stiff *** simplified rod-based models prin-cipally focused on clarifying overall large deformation and bending postures of soft grippers from static or quasi-static perspectives,whereas it is challenging to elaborate grasping characteristics of soft grippers without considering contact interaction and nonlinear large deformation *** address this,based on absolute nodal coordinate formulation(ANCF),comprehensively allowing for structural complexity,geometric,material and boundary nonlinearities,and incorpor-ating Coulomb’friction law with a multiple-point contact method,we put forward an effective nonlinear dynamic mod-eling approach for exploring grasping capability of soft ***,we solved the established dynamic equations using Generalized-αscheme,and conducted thorough numer-ical simulation analysis on a three-jaw soft pneumatic gripper(SPG)in terms of grasping configurations,displacements and contact *** proposed dynamic approach can accurately both describe complicated deformed configurations along with stress distribution and provide a feasible solution to simulate grasping targets,whose effectiveness and precision were analyzed theoretically and verified experimentally,which may shed new light on devising and optimizing other multi-functional SPGs.

关键词： Nonlinear dynamic formulation soft pneumatic robotic grippers contact interaction grasping capability configuration variations

A Proposed Feature Selection Particle Swarm Optimization Adaptation for Intelligent Logistics--A Supply Chain Backlog elimination Framework

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Computers, Materials & Continua 2024年第6期79卷 4081-4105页

作者： Yasser Hachaichi Ayman e.Khedr Amira M.Idrees College of Computing and Information Technology at Khulais Department of Information SystemsUniversity of JeddahJeddah21959Saudi Arabia Faculty of Computers and Information Technology Future University in EgyptCairo11835Egypt

the diversity of data sources resulted in seeking effective manipulation and *** challenge.that arises from the increasing dimensionality has a negative effect on the computation performance,efficiency,and stability of *** of the most successful optimization algorithms is Particle Swarm Optimization(PSO)which has proved its effectiveness in exploring the highest influencing features in the search space based on its fast convergence and the ability to utilize a small set of parameters in the search *** research proposes an effective enhancement of PSO that tackles the challenge of randomness search which directly enhances PSO *** the other hand,this research proposes a generic intelligent framework for early prediction of orders delay and eliminate orders backlogs which could be considered as an efficient potential solution for raising the supply chain *** proposed adapted algorithm has been applied to a supply chain dataset which minimized the features set from twenty-one features to ten significant *** confirm the proposed algorithm results,the updated data has been examined by eight of the well-known classification algorithms which reached a minimum accuracy percentage equal to 94.3%for random forest and a maximum of 99.0 for Naïve ***,the proposed algorithm adaptation has been compared with other proposed adaptations of PSO from the literature over different *** proposed PSO adaptation reached a higher accuracy compared with the literature ranging from 97.8 to 99.36 which also proved the advancement of the current research.

关键词： Optimization particle swarm optimization algorithm feature selection logistics supply chain management backlogs