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New Finite Elements in Shear Stress Analysis of Saint Venant′s Torsional Loaded Beam Structures

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j.urnal of Materials Science & Technology 2003年第Z1期19卷 151-153页

作者： j. Brnic g. Turkalj Department of Engineering Mechanics Faculty of Engineering University of Rijeka Vukovarska 58 51000 Rijeka Croatia Department of Engineering Mechanics Faculty of Engineering University of Rijeka Vukovarska 58 51000 Rijeka Croatia

Recent engineering design as well as material processing on the optimization procedure are based and computeroriented. Finite element stress and sensitivity analysis are the most important things in such modern determinationof optimal solution. According to high computer capacity finite element continuum discretization and load applicationindependent of the coming fields become unlimited. This paper deals with the development of a new finite elementsgeneration used in shear stress analysis caused by ***′s torsional load and bending with shear. Their stiffnessmatrices and load vectors on the basis of their geometrical properties are derived. For j.stification of new finiteelements application some examples are presented.

关键词： New finite elements, Shear stress analysis, Optimal design

MANY-SERVER QUEUES WITH CUSTOMER ABANDONMENT:A SURVEY OF DIFFUSION AND FLUID APPROXIMATIONS

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j.urnal of Systems Science and Systems Engineering 2012年第1期21卷 1-36页

作者： j. g. DAI Shuangchi HE H. Milton Stewart School of Industrial and Systems Engineering Georgia Institute of Technology Atlanta GA 30332 USA. Department of Industrial and Systems Engineering National University of Singapore Singapore 11757

The performance of a call center is sensitive to customer abandonment. In this survey paper, we focus on g/gI/n ＋ gI parallel-server queues that serve as a building block to model call center operations. Such a queue has a general arrival process （the g ）, independent and identically distributed （iid） service times with a general distribution （the first g1 ）, and iid patience times with a general distribution （the ＋gI）. Following the square-root safety staffing rule, this queue can be operated in the quality- and efficiency-driven （QED） regime, which is characterized by large customer volume, the waiting times being a fraction of the service times, only a small fraction of customers abandoning the system, and high server utilization. Operational efficiency is the central target in a system whose staffing costs dominate other expenses. If a moderate fraction of customer abandonment is allowed, such a system should be operated in an overloaded regime known as the efficiency-driven （ED） regime. We survey recent results on the many-server queues that are operated in the QED and ED regimes. These results include the performance insensitivity to patience time distributions and diffusion and fluid approximate models as practical tools for performance analysis.

关键词： Heavy traffic square-root safety staffing quality- and efficiency-driven regime efficiency-driven regime piecewise OU process

Conservation laws for energy and momentum in curved spaces

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j.urnal of Zhej.ang University-Science A(Applied Physics & Engineering) 2007年第4期8卷 665-668页

作者： LóPEZ-BONILLA j. MORALES j. OVANDO g. Section of Postgraduate Studies and Research Superior School of Mechanical and Electrical EngineeringNational Polytechnic InstituteCP 07738Mexico Division of Basic Sciences and Engineering Autonomous Metropolitan UniversityCP 02200Mexico

In arbitrary Riemannian 4-spaces, continuity equations are constructed which could be interpreted as conservation laws for the energy and momentum of the gravitational field. Special attention is given to general relativity to obtain, of natural manner, the pseudotensors of Einstein, Landau-Lifshitz, Moeller, goldberg and Stachel, and also the conservation equations of Komar, Trautman, DuPlessis and Moss.

关键词： Noether theorem Lagrangians in curved spaces Energy and momentum in Riemannian spaces Rund-Lovelock identities

Acoustic Measurements for Determination of the Materials Damping Using A Sound Source Localisation System

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Acta Metallurgica Sinica(English Letters) 2013年第2期26卷 113-121页

作者： j. gken j. Swiostek H. Hurdelbrink U. Keil Faculty of Maritime Studies University of Applied Sciences Emden/Leer Bergmannstr. 36 26789 LeerGermany Stalomax TM Company of High-Precision Mechanics ul. Parkingowa 45 37450 Stalowa WolaPoland

Noise measurements are especially a problem when the obj.ct under investigation is largely dimensioned and can only be measured from the distance. To obtain information about the location of noise generation, a measurement technique which makes sound visible in order to introduce further specific technical measures is advantageous. The question is if the time dependence of the signal got from such a non touching and non destructive acoustic method has the potential to calculate the materials damping from. Using a small sound source localization system （Microflown^TM probe）, specimens of magnesium alloys with different grain sizes obtained by hydrostatic extrusion were investigated. It has been demonstrated that the fine grained microstructure led to a lower damping and its dependence on the strain was reduced. In this context, acoustic measurements by a sound source localisation system which makes materials characterization possible could be used as a quality tool to detect changes in highly stressed components. This approach allows to promote a selective substitution of conventional materials by more innovative ones. The offshore sector is considered to be a field of application： Wind turbines produce noise emission which stems mainly from turbulences at the tips of the rotor blades and vibrations of components inside the nacelle （e.9. gearbox, generator, ...）. If the vibration amplitudes are too high, microcracks of components can lead to failure over the long term. The monitoring of microstructural changes using a larger type of a sound source localisation system is considered as an innovative technical approach with respect to maintenance activities.

关键词： Magnesium Noise measurements MicroflownTM Damping

The Friction and Wear Properties of CrN, graphit-iC and Dymon-iC Coatings in Air and under Oil-lubrication.

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材料热处理学报 2004年第05B期25卷 858-861页

作者： j. Stallard D.g Teer Teer Coatings Ltd Droitwich WorcestershireU.KTeer Coatings Ltd Droitwich WorcestershireU.K.

Hard ceramic coatings such as TiN and CrN are very successful and are widely used in improving the performance of cutting and forming tools, but they are less successful in providing protection for general machine components, such as gears and engine parts. The development of low-friction wear resistant coatings that can run dry or in a minimum amount of oil is becoming increasingly important to this industry. Two recently developed carbon-based coatings graphit-iC? and Dymon-iC, which are shown to exhibit very high sliding wear resistance and low friction in dry conditions, are compared to a CrN coating under oil lubricated conditions. Long term pin-on-disc tests using a chrome steel counterface ball were carried out on coated HSS test samples. All the coatings performed well at very high applied contact pressures, exceeding 1.5 gPa, but the graphit-iC? and Dymon-iC coatings also exhibited the desirable characteristic of protecting the counterface material. Reasons for this behaviour are discussed.

关键词： DLC 润滑油摩擦性能磨损性能涂层

Outcomes after robot-assisted laparoscopic radical prostatectomy

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Asian j.urnal of Andrology 2009年第1期11卷 94-99页

作者： Declan g. Murphy Benj.min j. Challacombe Anthony j. Costello The Urology Centre Guy＇s ＆ St. Thomas ＇NHS Foundation Trust London SE1 9RT UK Department of Urology Royal Melbourne Hospital Melbourne VIC 3054 Australia

Robot-assisted laparoscopic radical prostatectomy （RALRP） using the da Vinci surgical system is now in widespread use in many countries where economic conditions allow the installation of this expensive technology. Controversy has surrounded the procedure since it was first performed in 2000, with many critics highlighting the lack of evidence to support its use. However, despite the lack of level I evidence, many large studies of patients have confirmed that the procedure is feasible and safe, with low morbidity. Available longer-term oncological data seem to show that outcomes from the robotic approach at least match those of traditional open radical prostatectomy. Functional outcomes also seem satisfactory, although randomized controlled trials are lacking. This paper reviews the current status of RALRP with respect to perioperative data and complications and oncologic and functional outcomes.

关键词： da Vinci laparoscopic outcomes prostate cancer radical prostatectomy robotic

Effects of particle size and concentration on bubble coalescence and froth formation in a slurry bubble column

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Particuology 2018年第1期16卷 82-95页

作者： A.R. Sarhan j. Naser g. Brooks Department of Mechanical and Product Design Engineering Swinburne University of Technology Hawthorn Victoria 3122 Australia Department of Mechanical Engineering University ofAnbar Ramadi Anbar 31001 lraq

A new approach for simulating the formation of a froth layer in a slurry bubble column is proposed. Froth is considered a separate phase, comprised of a mixture of gas, liquid, and solid. The simulation was carried out using commercial flow simulation software （FIRE v2014） for particle sizes of 60-150 μm at solid concentrations of 0-40vol%, and superficial gas velocities of 0.02-0.034m/s in a slurry bubble column with a hydraulic diameter of 0.2 m and height of 1.2 m. Modelling calculations were conducted using a Eulerian-Eulerian multiphase approach with k-ε turbulence. The population balance equations for bubble breakup, bubble coalescence rate, and the interfacial exchange of mass and momentum were included in the computational fluid dynamics code by writing subroutines in Fortran to track the number density of different bubble sizes. Flow structure, radial gas holdup, and Sauter mean bubble diameter distributions at different column heights were predicted in the pulp zone, while froth volume fraction and density were predicted in the froth zone. The model was validated using available experimental data, and the predicted and experimental results showed reasonable agreement. To demonstrate the effect of increasing solid concentration on the coalescence rate, a solid-effect multiplier in the coalescence effi- ciency equation was used. The solid-effect multiplier decreased with increasing slurry concentration, causing an increase in bubble coalescence efficiency. A slight decrease in the coalescence efficiency was also observed owing to increasing particle size, which led to a decrease in Sauter mean bubble diam- eter. The froth volume fraction increased with solid concentration. These results provide an improved understanding of the dynamics of slurry bubble reactors in the presence of hydrophilic particles.

关键词： Computational fluid dynamics Slurry concentration gas holdup Particle size Froth Coalescence efficiency

Structure of Channel Flows with Surface Mounted Ribs

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j.urnal of Thermal Science 2004年第3期13卷 213-219页

作者： gérard j. POITRAS Laurent-Emmanuel BRIZZI Yves gAgNON Université de Moncton Moncton (NB) CanadaLaboratoire d'études aérodynamiques Université de Poitiers 86960 Futuroscope FranceUniversité de Moncton Edmundston (NB) Canada

The flow inside a channel with surface mounted ribs is studied by numerical simulation and experimental flow visualization. Both the geometry with one rib and the geometry with two ribs, placed perpendicular to the flow, are studied, with particular emphasis on the effect of the variation of the distance between the ribs on the structure of the flow. Results show that, for Reynolds number flows of 400 and 1000 (based on the uniform incoming velocity and the height of the ribs), the flow reattaches between the ribs when they are separated by distances of 12h (h being the height of the ribs) and 6h, respectively. In this respect, however, the numerical results for the Reynolds number flow of 1000 are in contradiction with published results.

关键词： vortex methods flow visualization channel flows ribs.

Ischemic long-term-potentiation(iLTP): perspectives to set the threshold of neural plasticity toward therapy

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Neural Regeneration Research 2015年第10期10卷 1537-1539页

作者： Maximilian lenz Andreas Vlachos Nicola Maggio Department of Neurology The J.Sagol Neuroscience Center The Chaim Sheba Medical Center Institute of Clinical Neuroanatomy Neuroscience Center Frankfurt Goethe-University Frankfurt Talpiot Medical Leadership Program The Chaim Sheba Medical Center

The precise role of neural plasticity under pathological conditions remains not well understood. It appears to be well accepted, however, that changes in the ability of neurons to express plasticity accompany neurological diseases. Here, we discuss recent experimental evidence, which suggests that synaptic plasticity induced by a pathological stimulus, i.e., ischemic long-term-potentiation（i LTP） of excitatory synapses, could play an important role for post-stroke recovery by influencing the post-lesional reorganization of surviving neuronal networks.

关键词： ischemic LTP(iLTP) stroke neural repair synaptic plasticity neural homeostasis