检索结果-南通市图书馆

Mechanisms behind the environmental sensitivity of carbon fiber reinforced polytetrafluoroethylene(PTFE)

Friction 2024年第5期12卷 997-1015页

作者： Pontus JOHANSSON P.MARKLUND M.BJORLING Y.SHI division of Machine Element LuleåUniversity of TechnologyLuleåSE-97187Sweden

Carbon fiber reinforced polytetrafluoroethylene (cf/PTFE) composites are known for their exceptional tribological performance when sliding against steel or cast iron in inert gas environments. Compared to experiments in humid air, about an order of magnitude lower wear rate and several times lower coefficient of friction have been reported for tests conducted in dry nitrogen and hydrogen. Moreover, trace moisture has been shown to affect the friction and wear significantly of this tribosystem, although a possible effect of oxygen cannot be ruled out due to uncertainties regarding the oxygen concentrations. While several studies have pointed out the environmental sensitivity of cf/PTFE, the understanding of the underlying mechanisms are very limited. The objective of this research is to investigate the individual and combined effect of oxygen and moisture on the tribological behavior of cf/PTFE sliding against steel. Additionally, this study aims to elucidate the underlying mechanisms that govern the environmental sensitivity of the system. Climate-controlled three-pin-on-disc experiments were conducted in nitrogen atmospheres at various concentrations of oxygen and moisture. The tribological results clearly demonstrate that both moisture and oxygen contribute to increased friction and wear. However, the adverse effect was much more pronounced for oxygen than moisture. A qualitative method was developed to estimate the tribofilm coverage on the cf/PTFE surface. Results showed strong correlation between high coverage of strongly adhered tribofilm and low wear rate. Moreover, a loosely adhered tribofilm was observed on top of the cf/PTFE surface in presence of moisture. FTIR analysis indicated that the loosely adhered tribofilm found in the moisture-enriched environment contained a significant amount of adsorbed water, which may explain the lower coefficient of friction in presence of moisture compared to oxygen. The adsorbed water in the loosely adhered tribofilm coul

关键词： polymer composite tribofilm tribochemistry atmosphere

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

New approach for particle size and shape analysis of iron-based oxygen carriers at multiple oxidation states

引用

Particuology 2024年第7期90卷 493-503页

作者： Victor Purnomo Marcelo Dal Belo Takehara Robin Faust Lidiya Abdisa Ejjeta Henrik Leion division of Energy and Materials Department of Chemistry and Chemical EngineeringChalmers University of TechnologyGöteborg 41258Sweden division of Energy Science Department of Engineering Sciences and MathematicsLuleåUniversity of TechnologyLuleå97187Sweden

One of the crucial issues in the chemical looping technology lies in its bed material:the oxygen *** size analysis of an oxygen carrier is important since in a fluidized bed the material can only work well within a specific size *** the favorable size ranges for oxygen carrier materials have already been reported,none of the published studies has analyzed the particle size and shape of oxygen carriers in ***,the effect of oxygen carriers'oxidation degree on such properties has not been considered *** study aimed to report the particle size and shape analysis of five iron-based oxygen carriers,one natural ore,one synthetic material,and three residue products,at different oxidation degrees using dynamic image analysis(DIA).The oxygen carriers were prepared at different mass conversion degrees in a fluidized bed batch *** size distribution,sphericity,and aspect ratio of the oxygen carrier particles were examined experimentally using a Camsizer *** results show that the DIA method was successfully able to analyze the particle size and shape of our oxygen carriers with satisfying accuracy for *** oxidation state of the investigated materials seems to only affect the particle size and shape of oxygen carriers to a minor ***,exposures to redox cycles in a fluidized bed reactor may alter the particle size and shape of most oxygen carriers.

关键词： Oxygen carrier Size and shape analysis Dynamic image analysis Oxidation state Fluidized bed Chemical looping

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

Modified DS np Chart Using Generalized Multiple Dependent State Sampling under Time Truncated Life Test

引用

Computer Modeling in Engineering & Sciences 2024年第3期138卷 2471-2495页

作者： Wimonmas Bamrungsetthapong Pramote Charongrattanasakul division of Applied Statistics Department of Mathematics and Computer ScienceFaculty of Science and TechnologyRajamangala University of Technology ThanyaburiPathum Thani12110Thailand division of Mathematics Department of Mathematics and Computer ScienceFaculty of Science and TechnologyRajamangala University of Technology KrungthepBangkok10120Thailand

This study presents the design of a modified attributed control chart based on a double sampling(DS)np chart applied in combination with generalized multiple dependent state(GMDS)sampling to monitor the mean life of the product based on the time truncated life test employing theWeibull *** control chart developed supports the examination of the mean lifespan variation for a particular product in the process of *** control limit levels are used:the warning control limit,inner control limit,and outer control ***,they enhance the capability for variation detection.A genetic algorithm can be used for optimization during the in-control process,whereby the optimal parameters can be established for the proposed control *** control chart performance is assessed using the average run length,while the influence of the model parameters upon the control chart solution is assessed via sensitivity analysis based on an orthogonal experimental design withmultiple linear regression.A comparative study was conducted based on the out-of-control average run length,in which the developed control chart offered greater sensitivity in the detection of process shifts while making use of smaller samples on average than is the case for existing control ***,to exhibit the utility of the developed control chart,this paper presents its application using simulated data with parameters drawn from the real set of data.

关键词： Modified DS np chart generalizedmultiple dependent state sampling time truncated life test Weibull distribution average run length average sample size

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

Impact of vaccination on the dynamics of COVID-19:A mathematical study using fractional derivatives

引用

International Journal of Biomathematics 2024年第2期17卷 201-232页

作者： Shraddha Ramdas Bandekar Mini Ghosh C.Rajivganthi division of Mathematics School of Advanced Sciences Vellore Institute of TechnologyChennaiIndia

Arrival of a new disease marks a yearlong destruction of human lives and economy in general,and if the disease turns out to be a pandemic the loss is ***-19 is one such pandemic that has claimed millions of lives till *** is a suffering throughout the world due to various factors associated with the pandemic,be it loss of livelihoods because of sudden shutdown of companies and lockdown,or loss of lives due to lack of medical aid and inadequate vaccination *** this study,we develop a six-compartmental epidemiological model incorporating *** motivation behind the study is to analyze the significance of higher vaccination efficacy and higher rate of population getting vaccinated in controlling the rise in infectives and thereby the untimely demise of various *** work begins with an ordinary differential equation model followed by stability analysis of the same,after which a fractional-order derivative model of the same is formulated and the existence of uniformly stable solution for the system is *** addition to this,we present the stability of the equilibria in general for the fractional model *** sensitivity analysis of the basic reproduction number along with its correlation with various parameters is *** addition to this,sensitivity of certain state variables in the fractional model with respect to *** orders as well with respect to different infection rate is exhibited in this *** related to lockdown and usage of face shields are incorporated in the entire study,and importance of these is highlighted in the study as *** major takeaway from the study is that mere vaccination will not sufice in eradication of the *** vaccine efficacy plays a major role along with other intervention included in the *** numerical simulations are carried out in MATLAB software using ode45 and fdel2.

关键词： Caputo fractional derivative basic reproduction number stability analysis sensitivityanalysis vaccination

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

An analytical approach for the fractional-order Hepatitis B model using new operator

引用

International Journal of Biomathematics 2024年第1期17卷 177-198页

作者： Surath Ghosh division of Mathematics School of Advanced Sciences Vellore Institute of TechnologyChennaiIndia

In this work,the main goal is to implement Homotopy perturbation transform method(HPTM)involving Katugampola fractional *** an example,a fractional order Hepatitis model is considered to analyze the *** first,the integer order model is converted to fractional order model in Caputo ***,the new operator Katugampola fractional derivative is used to present the *** new such kind of operator is illustrated in Caputo *** is described to get the solution of the proposed model using the new kind of ***,there are some analyses about the new kind of operator to prove the efficiency of the operator.

关键词： Caputo derivative Katugampola fractional derivative homotopy perturbation transform method Hepatitis B model

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

Space–time finite element method with domain reduction techniques for dynamic soil–structure interaction problems

引用

International Journal of Mechanical System Dynamics 2024年第2期4卷 117-130页

作者： Vikas Sharma Shion Shimizu Kazunori Fujisawa division of Environmental Science and technology Graduate School of AgricultureKyoto UniversityKyotoJapan

Design of earth structures,such as dams,tunnels,and embankments,against the vibrational loading caused by high-speed trains,road traffic,underground explosions,and,more importantly,earthquake motion,demands solutions of the dynamic soil–structure Interaction(SSI)*** paper presents a velocity-based space–time finite element procedure,v-ST/finite element method(FEM),to solve dynamic SSI *** main goal of this study is to present the computation details of implementing viscous boundary conditions of Lysmer–Kuhlemeyer to truncate the unbounded soil ***,additional time-dependent boundary conditions,in terms of the free-field response,are included to facilitate energy flow from the far field to the computation domain at the vertical truncated *** the FEM,seismic input motion is applied to an effective nodal force vector,which can be obtained explicitly in the numerical ***,the response of a concrete gravity dam resting on an elastic half-space to the horizontal component of earthquake motion is computed and successfully compared with the results of semidiscrete FEM using the Newmark-βmethod.

关键词： absorbing boundary domain reduction FEM soil-structure interactions space-time

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

Super Resolution Fluorescence Microscopy for Cilia Investigation and Ciliopathy Diagnosis

引用

激光与光电子学进展 2024年

作者： Zhen LIU Yang WU division of Life Science The Hong Kong University of Science and Technology

The last two decades have witnessed the invention and development of superresolution microscopy(SRM), which breaks the diffraction limit of light and pushes the resolution of fluorescence microscopy to several nanometers. SRM is now widely applied in biological studies such as resolving subdiffraction structures, molecular mapping, single molecule tracking, probing protein-protein interactions, and observing organelle dynamics. However, its direct application in translational medicine such as disease diagnosis is still preliminary. Despite their small size, cilia play a crucial role as organelles in cell signaling and motility, and defects in cilia lead to ciliopathy. Like other miniature organelles and macromolecular complexes, cilia are ideal for superresolution imaging. In this review, we will 1) introduce cilia and ciliopathy, 2) show how SRM extends our knowledge of cilia, and 3) focus on how SRM improves the diagnosis of motile ciliopathies.

关键词：

来源：

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

ATM Activation is Key in Vasculogenic Mimicry Formation by Glioma Stem-like Cells

引用

Biomedical and Environmental Sciences 2024年第8期37卷 834-849页

作者： Jing Xie Jiaxin Tang Yuan Li Xue Kong Wei Wang Haibo Wu Department of Pathology the First Affiliated Hospital of USTCDivision of Life Sciences and MedicineUniversity of Science and Technology of ChinaHefei 230036AnhuiChina Intelligent Pathology Institute Division of Life Sciences and MedicineUniversity of Science and Technology of ChinaHefei 230036AnhuiChina

Objective Vasculogenic mimicry(VM)is a novel vasculogenic process integral to glioma stem cells(GSCs)in glioblastoma(GBM).However,the relationship between VM and ataxia-telangiectasia mutated(ATM)serine/threonine kinase activation,which confers chemoradiotherapy resistance,remains *** We investigated VM formation and phosphorylated ATM(pATM)levels by CD31/GFAPperiodic acid-Schiff dual staining and immunohistochemical staining in 145 GBM *** stem-like cells(GSLCs)derived from the formatted spheres of U87 and U251 cell lines and their pATM level and VM formation ability were examined using western blot and three-dimensional *** the examination of the function of pATM in VM formation by GSLCs,ATM knockdown by shRNAs and deactivated via ATM phosphorylation inhibitor KU55933 were *** VM and high pATM expression occurred in 38.5% and 41.8% of tumors,respectively,and were significantly associated with reduced progression-free and overall *** with VM-positive GBMs exhibited higher pATM levels(r_(s)=0.425,P=0.01).The multivariate analysis established VM as an independent negative prognostic factor(P=0.002).Furthermore,GSLCs expressed high levels of pATM and formed vascular-like networks in *** inactivation or knockdown hindered VM-like network formation concomitant with the downregulation of pVEGFR-2,VE-cadherin,and laminin *** VM may predict a poor GBM prognosis and is associated with pATM *** propose that pATM promotes VM through extracellular matrix modulation and VE-Cadherin/pVEGFR-2 activation,thereby highlighting ATM activation as a potential target for enhancing anti-angiogenesis therapies for GBM.

关键词： Glioblastoma Vasculogenic mimicry Ataxia-telangiectasia mutated(ATM) Glioma stem-like cell

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

Finite-Time Stabilization for Constrained Discrete-time Systems by Using Model Predictive Control

引用

IEEE/CAA Journal of Automatica Sinica 2024年第7期11卷 1656-1666页

作者： Bing Zhu Xiaozhuoer Yuan Li Dai Zhiwen Qiang IEEE the Seventh Research division Beihang UniversityBeijing 100191China the School of Automation Beijing Institute of TechnologyBeijing 100081China

In this paper, a model predictive control(MPC)framework is proposed for finite-time stabilization of linear and nonlinear discrete-time systems subject to state and control constraints. The proposed MPC framework guarantees the finite-time convergence property by assigning the control horizon equal to the dimension of the overall system, and only penalizing the terminal cost in the optimization, where the stage costs are not penalized explicitly. A terminal inequality constraint is added to guarantee the feasibility and stability of the closed-loop *** feasibility can be improved via augmentation. The finite-time convergence of the proposed MPC is proved theoretically,and is supported by simulation examples.

关键词： Constraints deadbeat control finite-time stabilization model predictive control(MPC)

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

Deep learning to develop zero-equation based turbulence model for cfD simulations of the built environment

引用

Building Simulation 2024年第3期17卷 399-414页

作者： Giovanni Calzolari Wei Liu division of Sustainable Buildings Department of Civil and Architectural EngineeringKTH Royal Institute of TechnologyBrinnelvägen 23Stockholm11428Sweden

This study aims to improve the accuracy and speed of predictions for thermal comfort and air quality in built environments by creating a coupled framework between computational fluid dynamics(cfD)simulations and deep learning *** coupling approach is showcased by the development of a data-driven turbulence *** new turbulence model is built using a deep learning neural network,whose mapping structure is based on a zero-equation turbulence model for built environment simulations,and is coupled with the cfD software OpenFOAM to create a hybrid *** neural network is a standard shallow multi-layer *** number of hidden layers and nodes per layer was optimized using Bayesan optimization *** framework is trained on an indoor environment case study,as well as tested on an indoor office simulation and an outdoor building array *** show that the deep learning based turbulence model is more robust and faster than traditional two-equation Reynolds average Navier-Stokes(RANS)turbulence models,while maintaining a similar level of *** model also outperforms the standard algebraic zero-equation model due to its superior ability to generalize to various flow *** some challenges,namely the mapping constraint,the limited training dataset size and the source of generation of training data,the hybrid framework demonstrates the viability of the coupling technique and serves as a starting point for future development of more reliable and advanced models.

关键词： neural networks computational fluid dynamics(cfD) turbulence model OpenFOAM

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：