检索结果-南通市图书馆

Discrete simulation and micromechanical analysis of two-dimensional saturated granular media

在线全文

学校读者我要写书评

暂无评论

Particuology 2014年第4期12卷 138-150页

作者： younes Khalili Ahmad Mahboubi Department of Civil and Environmental Engineering.Power and Water University of Technology TehranIran

In this study, a novel approach to incorporate the pore water pressure in the discrete element method （DEM） to comprehensively model saturated granular media was developed. A numerical model was constructed based on the DEM by implanting additional routines in the basic DEM code; pore water pressure calculations were used with a two-dimensional （2D） model to simulate the undrained behavior of satu- rated granular media. This model coupled the interaction of solid particles and the pore fluid in saturated granular media. Finally, several 2D undrained shear tests were simulated. The test results showed that the model could predict the response of the saturated granular soil to shear loading. The effect of initial compaction was investigated. Biaxial tests on dense and loose specimens were conducted, and the effect of the initial density on the change in shear strength and the volume change of the system was inves- tigated. The overall behavior of loose and dense specimens was phenomenologically similar to the real granular material. Constant volume tests were simulated, and the results were compared to those from the coupled model. Induced anisotropy was micromechanically investigated by studying the contact force orientation. The change in anisotropy depended on the modeling scheme. However, the overall responses of the media obtained usinz the couoled and constant volume methods were similar.

关键词： DEM Saturated granular media Numerical simulation Micromechanical investigation

Non-Monotonic Lyapunov-Krasovskii Functional Approach to Stability Analysis and Stabilization of Discrete Time-Delay Systems

在线全文

学校读者我要写书评

暂无评论

IEEE/CAA Journal of Automatica Sinica 2020年第3期7卷 752-763页

作者： younes Solgi Alireza Fatehi Ala Shariati Advanced Process Automation and Control Research Group Industrial Control Center of ExcellenceFaculty of Electrical EngineeringK.N.Toosi University of TechnologyTehran 16317-14191Iran IEEE

In this paper, a novel non-monotonic Lyapunov-Krasovskii functional approach is proposed to deal with the stability analysis and stabilization problem of linear discrete time-delay systems. This technique is utilized to relax the monotonic requirement of the Lyapunov-Krasovskii theorem. In this regard, the Lyapunov-Krasovskii functional is allowed to increase in a few steps, while being forced to be overall decreasing. As a result, it relays on a larger class of Lyapunov-Krasovskii functionals to provide stability of a state-delay system. To this end, using the non-monotonic Lyapunov-Krasovskii theorem, new sufficient conditions are derived regarding linear matrix inequalities(LMIs)to study the global asymptotic stability of state-delay ***, new stabilization conditions are also proposed for time-delay systems in this article. Both simulation and experimental results on a p H neutralizing process are provided to demonstrate the efficacy of the proposed method.

关键词： Linear matrix inequality(LMI) non-monotonic Lyapunov-Krasovskii functional(NMLKF) pH neutralization plant stabilization state-delay system time-delay system

Analysis of the Biotribological Behavior for the Stainless Steel/Polyethylene Contact Using a Knee Prosthesis Simulator

在线全文

学校读者我要写书评

暂无评论

Journal of Bionic Engineering 2012年第1期9卷 59-65页

作者： M. boujelbene S. Dhouibi M. Kharrat M. Dammak Laboratoire des Systkmes Electromeeaniques Ecole Nationale d＇Ingenieurs de Sfax Route de Soukra km 35 B.P. 1173 3038 Sfax Tunisia Institut Superieur de Gestion Industrielle de Sfax Route de Mharza Km 15 B.P. 954 3018 Sfax Tunisia Faeulte des Sciences de Gafsa Campus Universitaire Sidi Ahmed Zarrouk 2112 Gafsa Tunisia Institut Preparatoire aux Etudes d＇Ingenieurs de Sfax Route de Menzel Chaker Km 05 B.P. 1172 3018 Sfax Tunisia

In this work, a friction and wear simulator was used to reproduce the Anterior-Posterior （AP） sliding and the Flex- ion-Extension （FE） rotation generated in the knee joint during human gait cycle. We chose to simplify the contact geometry between the Total Knee Arthroplasty （TKA） femoral component and tibial insert. A 304L stainless steel cylinder which replaces the femoral component was loaded onto a flat High Density Polyethylene （HDPE） block which replaces the tibial insert. The tribological behavior of the considered contact was analyzed by tracking the number of cycles, the friction coefficient, the roughness of the wear track on HDPE, the HDPE weight loss and the damage mechanisms. The friction coefficient shows a gradual increase with the number of cycles for both AP and FE kinematics. The evolution of friction coefficient with the number of cycles is not affected by the value of the imposed normal load in the case of AP sliding. For the FE rotation, decreased friction coefficient is obtained when the imposed normal load increases. For both considered AP and FE kinematics, the roughness of the wear track on the HDPE is not affected by the imposed normal load. It shows a progressive decrease when the number of cycles increases. The wear of HDPE obeys the Archard law and the wear coefficient increases with the normal force. For a given value of normal load, the obtained wear coefficient for the AP sliding is larger than that obtained for FE rotation. A predominant adhesive wear mechanism was identified for both AP and FE kinematics. Under the same normal load, damage development in terms of plastic deformation, micro-cracking and debonding is more pronounced for the AP sliding if compared with the FE rotation. For a given kinematics, the damage severity increases with the normal load. This finding is in good agreement with the predicted values of the wear coefficient according to the Archard law.

关键词： knee prosthesis polyethylene friction wear gait cycle

Time-varying nexus and causality in the quantile between Google investor sentiment and cryptocurrency returns

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

Blockchain(Research and Applications) 2024年第2期5卷 1-12页

作者： Fatma Ben Hamadou Taicir Mezghani Mouna boujelbene Abbes Faculty of Economics and Management of Sfax Laboratory URECASfax UniversityBP1169.3029SfaxTunisia

Understanding the interplay between investor sentiment and cryptocurrency returns has become a critical area of ***,this study aims to uncover the role of Google investor sentiment on cryptocurrency returns(including Bitcoin,Litecoin,Ethereum,and Tether),especially during the 2017-18 bubble(January 01,2017,to December 31,2018)and the COVID-19 pandemic(January 01,2020,to March 15,2022).To achieve this,we use two techniques:quantile causality and wavelet ***,the quantile causality test revealed that investors’optimistic sentiments have notably higher cryptocurrency returns,whereas pessimistic sentiments have significantly opposite ***,the wavelet coherence analysis shows that co-movement between investor sentiment and Tether cannot be considered *** result supports the role of Tether as a stablecoin in portfolio diversification *** fact,the findings will help investors improve the accuracy of cryptocurrency return forecasts in times of stressful events and pave the way for enhanced decision-making utility.

关键词： Cryptocurrency COVID-19 pandemic Wavelet coherence Causality-in-quantile approach Google trends

Novel Non-monotonic Lyapunov-Krasovskii Based Stability Analysis and Stabilization of Discrete State-delay System

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

International Journal of Automation and computing 2020年第5期17卷 713-732页

作者： younes Solgi Alireza Fatehi Ala Shariati APAC Research Group Industrial Control Center of ExcellenceFaculty of Electrical EngineeringK.N.Toosi University of TechnologyTehran ***Iran

This paper proposes a novel less-conservative non-monotonic Lyapunov-Krasovskii stability approach for stability analysis of discrete time-delay *** this method,monotonically decreasing requirements of the Lyapunov-Krasovskii method are replaced with non-monotonic *** Lyapunov-Krasovskii functional is allowed to increase in some steps,but the overall trend should be *** model of practical systems used for stability analysis usually contain ***,firstly a non-monotonic stability condition is derived for certain discrete time-delay systems,then robust non-monotonic stability conditions are proposed for uncertain ***,a novel stabilization algorithm is derived based on the introduced non-monotonic stability *** Lyapunov-Krasovskii functional and the controller are obtained by solving a set of linear matrix inequalities(LMI)or iterative LMI based nonlinear *** proposed theorems are first evaluated by some numerical examples,and then by simulation and implementation on the pH neutralizing process plant.

关键词： Lyapunov-Krasovskii functional discrete state-delay systems non-monotonic Lyapunov function robust stability stabilization

A new technique for solving the multi-objective optimization problem using hybrid approach

在线全文

学校读者我要写书评

暂无评论

Frontiers in Energy 2014年第4期8卷 490-503页

作者： Mimoun younes Khodja FOUAD Belabbes BAGDAD Faculty of Technology Djillali Liabes University Sidi Bel Abbes 22000 Alegria

Energy efficiency, which consists of using less energy or improving the level of service to energy consumers, refers to an effective way to provide overall energy. But its increasing pressure on the energy sector to control greenhouse gases and to reduce CO2 emissions forced the power system operators to consider the emission problem as a consequential matter besides the economic problems. The economic power dispatch problem has, therefore, become a multi-objective optimization problem. Fuel cost, pollutant emissions, and system loss should be minimized simultaneously while satisfying certain system constraints. To achieve a good design with different solutions in a multi-objective optimization problem, fuel cost and pollutant emissions are converted into single optimization problem by introducing penalty factor. Now the power dispatch is formulated into a hi-objective optimization problem, two objectives with two algorithms, firefly algorithm for optimization the fuel cost, pollutant emissions and the real genetic algorithm for minimization of the transmission losses. In this paper the new approach （firefly algorithm-real genetic algorithm, FFA-RGA） has been applied to the standard IEEE 30-bus 6-generator. The effectiveness of the proposed approach is demonstrated by comparing its performance with other evolutionary multi- objective optimization algorithms. Simulation results show the validity and feasibility of the proposed method.

关键词： economic power dispatch (EPD) firefly algo- rithm (FFA) real genetic algorithm (RGA) hybrid method

Unconfined compressive strength prediction of soils stabilized using artificial neural networks and support vector machines

在线全文

学校读者我要写书评

暂无评论

Frontiers of Structural and Civil Engineering 2021年第2期15卷 520-536页

作者： Alireza TABARSA Nima LATIFI Abdolreza OSOULI younes BAGHERI Depatrment of Civil Engineering Faculty of EngineeringGolestan UniversityGorgan 49138-15759Iran Terr aeon Consultants Inc.NashvilleTN 37211USA Civil Engineering Department Southern Illinois UniversityEdwardsvilleIL 62026-1800USA Faculty of Engineering Mirdamad Institute of Higher EducationGorgan 49166-53989Iran

This study aims to improve the unconfined compressive strength of soils using additives as well as by predicting the strength behavior of stabilized soils using two artificial-intelligence-based *** soils used in this study are stabilized using various combinations of cement,lime,and rice husk *** predict the results of unconfined compressive strength tests conducted on soils,a comprehensive laboratory dataset comprising 137 soil specimens treated with different combinations of cement,lime,and rice husk ash is *** artificial-intelligence-based models including artificial neural networks and support vector machines are used comparatively to predict the strength characteristics of soils treated with cement,lime,and rice husk ash under different *** suggested models predicted the unconfined compressive strength of soils accurately and can be introduced as reliable predictive models in geotechnical *** study demonstrates the better performance of support vector machines in predicting the strength of the investigated soils compared with artificial neural *** type of kernel function used in support vector machine models contributed positively to the performance of the proposed ***,based on sensitivity analysis results,it is discovered that cement and lime contents impose more prominent effects on the unconfined compressive strength values of the investigated soils compared with the other parameters.

关键词： unconfined compressive strength artificial neural network support vector machine predictive models regression

Effects of wollastonite nanofibers on fluid flow in medium-density fiberboard

在线全文

学校读者我要写书评

暂无评论

Journal of Forestry Research 2016年第1期27卷 209-217页

作者： Hamid R.Taghiyari younes Sarvari Samadi Wood Science and Technology Department Faculty of Civil Engineering Shahid Rajaee Teacher Training University Faculty of Wood Technology and Construction Rosenheim University of Applied Sciences

We studied the effect of wollastonite nanofibers on fluid flow in medium-density fiberboard （MDF）. Nanowollastonite （NW） was applied in MDF at 10 %, based on the dry weight of wood fibers. We also tested chicken feathers as an additive to the matrix at 5 and 10 % by weight. The weight of feathers was reduced from the wood fibers to keep the density of the panels constant （0.66 g cm-3）. Wollastonite nanofibers acted as filler in the matrix and significantly decreased gas and liquid perme- ability. Higher thermal conductivity of the N-W-treated MDF-mats resulted in a better cure of resin, and conse- quently more integrity in the composite-matrix and lower permeability. The water-repellant property of wollastonite also contributed to the decrease in liquid permeability. Feathers reduced gas and liquid permeability due to the hydrophobic nature of keratin, as well as its formation as a physical barrier towards passing of fluids. Ten percent feather content proved too high and some checks and cracks occurred in the core of the panels after hot-pressing. Panels with 5 %-feather content resulted in both lower fluid flow and adequate physical integrity in the core sec- tion of the MDF-matrix.

关键词： Chicken feather Composite board Mineralmaterials Thermal conductivity coefficient Wollastonitenanofibers Wood fiber

Metasurfaces for next-generation wireless communication systems

在线全文

学校读者我要写书评

暂无评论

National Science Review 2023年第8期10卷 17-19页

作者： younes Ra'di Nikita Nefedkin Petar Popovski Andrea Alù Department of Electrical Engineering and Computer Science Syracuse University Photonics Initiative Advanced Science Research Center City University of New York Department of Electronic Systems Aalborg University Physics Program Graduate Center City University of New York

The pace of development in the world of 5G communication systems has proven to be much more demanding than previous generations, with 5G-Advanced seemingly around the corner [1]. Extensive research is already underway to structure the next generation of wireless systems(i.e. 6G), which may potentially enable an unprecedented level of human–machine interaction [2].

关键词：