检索结果-南通市图书馆

On the experimental characterization of the fluid volume influence on the friction between rough surfaces

在线全文

学校读者我要写书评

暂无评论

Friction 2023年第7期11卷 1334-1348页

作者： Lukas STAHL michael mÜLLER Georg-peter OSTERmEYER Institute of Dynamics and Vibrations Technische Universität BraunschweigBraunschweig 37106Germany

The load-bearing behaviour of lubricated contacts depends primarily on the normal force,the relative velocity,and the ***,with the aid of the Stribeck curve,it is usually well possible to characterize whether hydrodynamics,mixed friction,or boundary friction is more likely to be *** fact that the load regime can also depend on the fluid quantity is obvious,but has hardly been systematically investigated so *** for contacts with microscopic roughness,the defined application of a very small amount of fluid is a very challenging *** this paper,a very fundamental study shows how a pin-on-disc tribometer can be used to achieve the transition from dry friction via mixed friction to predominant hydrodynamics by the amount of supplied *** experiments are carried out on samples filed with different *** addition,the simultaneous influence of partial filling and normal force as well as relative velocity is also *** good reproducibility has been practically reached over the entire range of the *** the quantities for the coefficient of friction(COF),it was concluded that close to full filling,a reduction of the fluid quantity has a similar effect on the COF as the reduction of the *** property goes along with the common theory of starved lubricated *** behaviour was not observed to the same extent for the normal *** the vicinity of smaller fluid quantities,the COF increases very rapidly with further reduction in fluid quantity,far more disproportionately than that with reduction in *** a deeper understanding of this problem,various practical issues such as idling or the run-up process in bearings can also be studied in a more focused manner.

关键词： starved lubrication Stribeck curve pin-on-disc tribometer fluid supply experimental studies

Gamma-ray bursts and their links with supernovae and cosmology

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Research in Astronomy and Astrophysics 2012年第8期12卷 1139-1161页

作者： peter mszros Neil Gehrels Center for Particle and Gravitational Astrophysics Dept.of Astronomy&Astrophysics and Dept.of Physics Pennsylvania State UniversityUniversity ParkPA 16802USA Astrophysics Science Division NASA Goddard Space Flight CenterGreenbeltMD 20771USA

Gamma-ray bursts are the most luminous explosions in the Universe, whose origin and mechanism are the focus of intense interest. They appear connected to su- pernova remnants from massive stars or the merger of their remnants, and their bright- ness makes them temporarily detectable out to the largest distances yet explored in the universe. After pioneering breakthroughs from space and ground experiments, their study is entering a new phase with observations from the recently launched Fermi satellite, as well as the prospect of detections or limits from large neutrino and gravitational wave detectors. The interplay between such observations and theoretical models of gamma-ray bursts is reviewed, and cosmology. as well as their connections to supernovae

关键词： gamma-ray sources -- gamma-ray bursts -- cosmic rays -- neutrinos-- supernovae -- cosmology -- intergalactic medium

Towards implementation of alloy-specific thermo-fluid modelling for laser powder-bed fusion of mg alloys

在线全文

学校读者我要写书评

暂无评论

Journal of magnesium and Alloys 2024年第6期12卷 2327-2344页

作者： mohammad Hoseini-Athar mikael Ersson peter Hedström Department of material Science and Engineering KTH Royal Institute of TechnologyStockholmSE-10044 Sweden

multi-physics thermo-fluid modeling has been extensively used as an approach to understand melt pool dynamics and defect formation as well as optimizing the process-related parameters of laser powder-bed fusion(L-PBF).However,its capabilities for being implemented as a reliable tool for material design,where minor changes in material-related parameters must be accurately captured,is still in *** the present research,first,a thermo-fluid computational fluid dynamics(CFD)model is developed and validated against experimental *** the predicted material properties of the pure mg and commercial ZK60 and WE43 mg alloys,parametric studies are done attempting to elucidate how the difference in some of the material properties,i.e.,saturated vapor pressure,viscosity,and solidification range,can influence the melt pool *** is found that a higher saturated vapor pressure,associated with the ZK60 alloy,leads to a deeper unstable keyhole,increasing the keyhole-induced porosity and evaporation mass *** viscosity and wider solidification range can increase the non-uniformity of temperature and velocity distribution on the keyhole walls,resulting in increased keyhole instability and formation of ***,the WE43 alloy showed the best behavior in terms of defect formation and evaporation mass loss,providing theoretical support to the extensive use of this alloy in *** summary,this study suggests an approach to investigate the effect of materials-related parameters on L-PBF melting and solidification,which can be extremely helpful for future design of new alloys suitable for L-PBF.

关键词： mg alloys Laser powder-bed fusion(L-PBF) melt pool dynamics Computational fluid dynamics Fluid flow

Thermoelastic damping in mEmS gyroscopes at high frequencies

在线全文

学校读者我要写书评

暂无评论

microsystems & Nanoengineering 2023年第1期9卷 137-148页

作者： Daniel Schiwietz Eva m.Weig peter Degenfeld-Schonburg Robert Bosch GmbH Corporate Research71272RenningenGermany Department of Electrical&Computer Engineering Technical University of Munich85748GarchingGermany munich Center for Quantum Science and Technology(mCQST) 80799MunichGermany TUm Center for Quantum Engineering(ZQE) 85748GarchingGermany

microelectromechanical systems(mEmS)gyroscopes are widely used,e.g.,in modern automotive and consumer applications,and require signal stability and accuracy in rather harsh environmental *** many use cases,device reliability must be guaranteed under large external loads at high *** sensitivity of the sensor to such external loads depends strongly on the damping,or rather quality factor,of the high-frequency mechanical modes of the *** this paper,we investigate the influence of thermoelastic damping on several high-frequency modes by comparing finite element simulations with measurements of the quality factor in an application-relevant temperature *** measure the quality factors over different temperatures in vacuum,to extract the relevant thermoelastic material parameters of the polycrystalline mEmS *** simulation results show a good agreement with the measured quantities,therefore proving the applicability of our method for predictive purposes in the mEmS design ***,we are able to uniquely identify the thermoelastic effects and show their significance for the damping of the high-frequency modes of an industrial mEmS *** approach is generic and therefore easily applicable to any mechanical structure with many possible applications in nano-and micromechanical systems.

关键词： uniquely generic quantities

Projection on Segre varieties and determination of holomorphic mappings between real submanifolds Dedicated to Professor Sheng GONG on the occasion of his 75th birthday

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Science China mathematics 2006年第11期49卷 1611-1624页

作者： BAOUENDI m S EBENFELT peter ROTHSCHILD Linda P Department of mathematics University of California at San Diego La JollaCA 92093-0112USA

It is shown that a germ of a holomorphic mapping sending a real-analytic generic submanifold of finite type into another is determined by its projection on the Segre variety of the target manifold. A necessary and sufficient condition is given for a germ of a mapping into the Segre variety of the target manifold to be the projection of a holomorphic mapping sending the source manifold into the target. An application to the biholomorphic equivalence problem is also given.

关键词： Segre variety, generic submanifold, Segre mappings, finite type, biholomorphic equivalence.

Semantic linking of complex properties,monitoring processes and facilities in web-based representations of the environment

在线全文

学校读者我要写书评

暂无评论

International Journal of Digital Earth 2016年第3期9卷 300-324页

作者： Adam m.Leadbetter peter N.Vodden marine Institute Co.GalwayIreland Centre for Ecology and Hydrology Lancaster Environment CentreLancasterUK

Where a virtual representation of the Earth must contain data values observed within the physical Earth system,data models are required that allow the integration of data across the silos of various Earth and environmental sciences *** a mapping between the well-defined terminologies of these silos is a stubborn *** paper presents a generalised ontology for use within Web 3.0 services,which builds on European Commission spatial data infrastructure *** presented ontology acknowledges that there are many complexities to the description of environmental properties which can be observed within the physical Earth *** ontology is shown to be flexible and robust enough to describe concepts drawn from a range of Earth science disciplines,including ecology,geochemistry,hydrology and *** paper also demonstrates the alignment and compatibility of the ontology with existing systems and shows applications in which the ontology may be deployed.

关键词： observable properties monitoring properties environmental monitoring facilities semantic web geospatial data integration

On some aspects of minimum redundancy maximum relevance feature selection

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Science China(Information Sciences) 2020年第1期63卷 89-103页

作者： peter BUGATA peter DROTAR Intelligent Information Systems Lab Technical University of Kosice

The feature selection is an important challenge in many areas of machine learning because it plays a crucial role in the interpretations of machine-driven decisions. There are various approaches to the feature selection problem and methods based on the information theory comprise an important ***, the minimum redundancy maximum relevance(m RmR) feature selection is undoubtedly the most popular one with widespread application. In this paper, we prove in contrast to an existing finding that the m RmR is not equivalent to max-Dependency criterion for first-order incremental feature selection. We present another form of equivalence leading to a generalization of m RmR feature selection. Additionally,we compare several feature selection methods based on m RmR, max-Dependency, and feature ranking,employing different measures of dependency. The results on high-dimensional real-world datasets show that the distance correlation is the suitable measure for dependency-based feature selection methods. The results also indicate that the max-Dependency incremental algorithm combined with distance correlation appears to be a promising feature selection approach.

关键词： big data information theory feature selection dimensionality reduction minimum redundancy maximum relevance m RmR

A generic and extensible model for the martensite start temperature incorporating thermodynamic data mining and deep learning framework

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Journal of materials Science & Technology 2022年第33期128卷 31-43页

作者： Chenchong Wang Kaiyu Zhu peter Hedström Yong Li Wei Xu State Key Laboratory of Rolling and Automation Northeastern UniversityShenyang 110819China Department of materials Science and Engineering KTH Royal Institute of TechnologyStockholm 10044Sweden

The martensite start temperature is a critical parameter for steels with metastable *** numerous models have been developed to predict the martensite start(ms)temperature,the complexity of the martensitic transformation greatly limits their performance and *** this work,we apply deep data mining of thermodynamic calculations and deep learning to develop a generic model for *** data mining was used to establish a hierarchical database with three levels of ***,a convolutional neural network model,which can accurately treat the hierarchical data structure,was used to obtain the final *** integrating thermodynamic calculations,traditional machine learning and deep learning modeling,the final predictor model shows excellent generalizability and extensibility,*** performance both within and beyond the composition range of the original *** effects of 15 alloying elements were considered successfully using the proposed *** work suggests that,with the help of deep data mining considering the physical mechanisms,deep learning methods can partially mitigate the challenge with limited data in materials science and provide a means for solving complex problems with small databases.

关键词： martensite transformation Data mining Deep learning Extensibility Small-sample problem

Claudin-11 and occludin are major contributors to Sertoli cell tight junction function, in vitro

在线全文

学校读者我要写书评

暂无评论

Asian Journal of Andrology 2016年第4期18卷 620-626页

作者： mark J mcCabe Caroline FH Foo marcel E Dinger peter m Smooker peter G Stanton male Fertility Regulation Laboratory Hudson Institute of Medical Research Monash Medical Centre Clayton Victoria 3168 Australia School of Applied Sciences Royal Melbourne Institute of Technology University Bundoora Victoria 3088 Australia Kinghorn Centre for Clinical Genomics Garvan Institute of Medical Research Darlinghurst New South Wales 2010 Australia St Vincent's Clinical School UNSW Sydney New South Wales 2052 Australia.

The Sertoli cell tight junction （T J） is the key component of the blood-testis barrier, where it sequesters developing germ cells undergoing spermatogenesis within the seminiferous tubules. Hormonally regulated claudin-11 is a critical transmembrane protein involved in barrier function and its murine knockout results in infertility. We aimed to assess quantitatively the significance of the contribution of claudin-11 to TJ function, in vitro, using siRNA-mediated gene silencing. We also conducted an analysis of the contribution of occludin, another intrinsic transmembrane protein of the TJ. Silencing of claudin-11 and/or occludin was conducted using siRNA in an immature rat Sertoli cell culture model. Transepithelial electrical resistance was used to assess quantitatively TJ function throughout the culture. Two days after siRNA treatment, cells were fixed for immunocytochemical localization of junction proteins or lyzed for RT-PCR assessment of mRNA expression. Silencing of claudin-11, occludin, or both resulted in significant decreases in TJ function of 55% （P 〈 0.01）, 51% （P 〈 0.01）, and 62% （P 〈 0.01）, respectively. Data were concomitant with significant decreases in mRNA expression and marked reductions in the localization of targeted proteins to the Sertoli cell TJ. We provide quantitative evidence that claudin-11 contributes significantly （P 〈 0.01） to Sertoli cell TJ function in vitro. Interestingly, occludin, which is hormonally regulated but not implicated in infertility until late adulthood, is also a significant （P 〈 0.01） contributor to barrier function. Our data are consistent with in vivo studies that clearly demonstrate a role for these proteins in maintaining normal TJ barrier structure and function.

关键词： blood-testis barrier claudin-11 occludin Sertoli cell tight junction siRNA