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Momentum and heat transfer of a special case of the unsteady stagnation-point flow

Applied Mathematics and Mechanics(English Edition) 2020年第1期41卷 51-82页

作者： T.G.fANG f.j.WANG Mechanical and Aerospace Engineering Department North Carolina State University

This paper investigates the unsteady stagnation-point flow and heat transfer over a moving plate with mass transfer,which is also an exact solution to the unsteady Navier-Stokes(NS)*** boundary layer energy equation is solved with the closed form solutions for prescribed wall temperature and prescribed wall heat flux *** wall temperature and heat flux have power dependence on both time and spatial *** solution domain,the velocity distribution,the flow field,and the temperature distribution in the fluids are studied for different controlling *** parameters include the Prandtl number,the mass transfer parameter at the wall,the wall moving parameter,the time power index,and the spatial power *** is found that two solution branches exist for certain combinations of the controlling parameters for the flow and heat transfer *** heat transfer solutions are given by the confluent hypergeometric function of the first kind,which can be simplified into the incomplete gamma functions for special *** wall heat flux and temperature profiles show very complicated variation *** wall heat flux can have multiple poles under certain given controlling parameters,and the temperature can have significant oscillations with overshoot and negative values in the boundary *** relationship between the number of poles in the wall heat flux and the number of zero-crossing points is *** difference in the results of the prescribed wall temperature case and the prescribed wall heat flux case is *** given in this paper provide a rare closed form analytical solution to the entire unsteady NS equations,which can be used as a benchmark problem for numerical code validation.

关键词： unsteady stagnation point flow Navier-Stokes(NS)equations analytical solution heat transfer

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Challenges in blast protection research

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Defence Technology（防务技术） 2018年第5期14卷 426-432页

作者： f.j.Mostert Defence Peace Safety and Security Council for Scientific and Industrial Research

This paper presents a view of some of the challenges that are presented in investigating protection methodologies against explosive blast effects. In particular, the paper is concerned with experimental efforts that can aid in the understanding of complex blast effects in typical real world scenarios. Current progress in the implementation of blast mitigation methodologies in the landward defence environment is reviewed.

关键词： Explosive blast Protection Mitigation

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Current clinical approach to achalasia

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World journal of Gastroenterology 2009年第32期15卷 3969-3975页

作者： Alexander j Eckardt Volker f Eckardt Central Interdisciplinary Endoscopy Unit Department of Gastroenterology and HepatologyCharité University Hospitals BerlinCampus VirchowD-13353 BerlinGermany Department of Gastroenterology Deutsche Klinik für DiagnostikD-65191 WiesbadenGermany

Idiopathic achalasia is a rare primary motility disorder of the esophagus. The classical features are incomplete relaxation of a frequently hypertensive lower esophageal sphincter (LES) and a lack of peristalsis in the tubular esophagus. These motor abnormalities lead to dysphagia, stasis, regurgitation, weight loss, or secondary respiratory complications. Although major strides have been made in understanding the pathogenesis of this rare disorder, including a probable autoimmune mediated destruction of inhibitory neurons in response to an unknown insult in genetically susceptible individuals, a definite trigger has not been identified. The diagnosis of achalasia is suggested by clinical features and conf irmed by further diagnostic tests, such as esophagogastroduodenoscopy (EGD), manometry or barium swallow. These studies are not only used to exclude pseudoachalasia, but also might help to categorize the disease by severity or clinical subtype. Recent advances in diagnostic methods, including high resolution manometry (HRM), might allow prediction of treatment responses. The primary treatments for achieving long-term symptom relief are surgery and endoscopic methods. Although limited high-quality data exist, it appears that laparoscopic Heller myotomy with partial fundoplication is superior to endoscopic methods in achieving long-term relief of symptoms in the majority of patients. However, the current clinical approach to achalasia will depend not only on patients' characteristics and clinical subtypes of the disease, but also on local expertise and patient preferences.

关键词： Achalasia Esophageal motility disorder Dysphagia Esophagus Lower esophageal sphincter Pneumatic dilation Botulinum toxin Heller myotomy

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An SBfEM-Based Model for Hydraulic fracturing in Quasi-Brittle Materials

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Acta Mechanica Solida Sinica 2018年第4期31卷 416-432页

作者： f. Yao Z.j. Yang Y.j. Hu College of Civil Engineering and Architecture Zhejiang University Hangzhou 310058 China School of Civil Engineering Shaoxing University Shaoxing 312000 China

A numerical model based on the scaled boundary finite element method is devel- oped to simulate the hydraulic fracturing in concrete-like quasi-brittle materials using cohesive interface elements. The shadow domain method developed previously （Yang and Deeks in Eng fract Mech 143（4）：333 354, 2007） is extended to consider crack-width-dependent hydraulic pres- sure and cohesive traction, so that the stress intensity factors caused by both crack-face forces are semi-analytically calculated separately in the same way. The crack propagation is determined by the criterion of KI ≥ 0, and the propagation direction by the linear elastic fracture mechanics criteria. Two examples of concrete structures are modeled, and the results are in good agreement with the experimental data and others numerical results.

关键词： Scaled boundary finite element method Hydraulic fracture Cohesive crackmodel Crack propagation

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Optimal use of mobile cooling units in a deep-level gold mine

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International journal of Mining Science and Technology 2020年第4期30卷 547-553页

作者： H.j.van Staden j.f.van Rensburg H.j.Groenewald Centre for Research and Continued Engineering Development North-West UniversityPretoria 0081South Africa

The South African gold mining sector remains a significant contributor to the country’s *** several challenges that hinder the realisation of South Africa’s full mineral potential,the sector’s sustainability and profitability can be enhanced through implementing operational improvement *** cooling units(MCUs)were identified as a potential focus area for operational *** are used as tertiary or in-stope cooling in hot underground *** this paper,a method was presented to characterise the performance of existing MCUs based on three key performance indicators(KPIs),namely,the wet-bulb temperature ratio(WTR),efficiency and *** strategies were then elected and implemented based on these *** implementation of this method in a South African gold mine attained a reduction in pumped water volumes,reduced operating costs through electricity cost savings and improvements in underground ventilation air temperatures.

关键词： Mobile cooling units Optimisation Mine cooling performance Electricity cost savings Spot cooling

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Boundary discontinuous fourier analysis of thick beams with clamped and simply supported edges via CUf

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Chinese journal of Aeronautics 2017年第5期30卷 1708-1718页

作者： f.G.CANALES j.L.MANTARI faculty of Mechanical Engineering Universidad de Ingenieriay Tecnologia ( UTEC) Lima 15063 Peru Department of Mechanical Engineering University of New Mexieo Albuquerque 87131 USA

This paper presents an analytical solution for static analysis of thick rectangular beams with different boundary conditions. Carrera＇s Unified formulation（CUf） is used in order to consider shear deformation theories of arbitrary order. The novelty of the present work is that a boundary discontinuous fourier approach is used to consider clamped boundary conditions in the analytical solution, unlike Navier-type solutions which are restricted to simply supported *** equations are obtained by employing the principle of virtual work. The numerical accuracy of results is ascertained by studying the convergence of the solution and comparing the results to those of a 3D finite element solution. Beams subjected to bending due to a uniform pressure load and subjected to torsion due to opposite linear forces are considered. Overall, accurate results close to those of 3D finite element solutions are obtained, which can be used to validate finite element results or other approximate methods.

关键词： Analytical solution Beam Clamped fourier Unified formulation

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New Nanocomposite Materials by Incorporation of Nanocrystalline TiO_2 Particles into Polyaniline Conductive films

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journal of Materials Science & Technology 2014年第5期30卷 449-454页

作者： f.j.feliciano O.C.Monteiro Department of Chemistry and Biochemistry and CQB Faculty of SciencesUniversity of LisbonCampo Grande1749-016 LisbonPortugal

This work is focused on the combination of two building-blocks, nanocrystalline TiO2 particles and polyaniline conductive films （PAni）. The preparation of new nanostructured composite materials, displaying electron- and proton-conductive properties, to be used for the fabrication of new and superior energy storage devices was envisaged. The semiconducting TiO2 nanoparticles were obtained by means of a hydrothermal route. The PAni films were prepared on glassy carbon electrodes by electrochemical polymerization, under potential dynamic conditions. After characterization by X-ray diffraction, transmission electron microscopy or scanning electron microscopy and electrochemical techniques, the nanocrystalline particles were immobilized in the polymer matrix. The incorporation of the TiO2 was achieved using two distinct approaches： during the polymer growth or by deposition over previously prepared PAni films. The results demonstrate that the PAni morphology depends on the experimental conditions used during the polymer growth. After TiO2 immobilization, the best electrochemical response was obtained for the nanocomposite structure produced through the TiO2 incorporation after the PAni film synthesis. The modified electrodes were structurally and morphologically characterized and their electro-catalytic activity towards the hydrogen evolution reaction was analyzed. A new electrochemical performance related with the oxidation of molecular hydrogen entrapped in the PAni-TiO2 matrix was observed for the modified electrode after TiO2 incorporation. This behavior can be directly associated with the synergetic combination of the TiO2 and PAni, and is dependent on the amount of the semiconductor.

关键词： PolyaniHne (PAni) Nanosized TiO2 Nanocomposites Hydrogen trapping

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Vibrational behavior of isotropic plate structures in contact with a bounded fluid via unified formulation

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Chinese journal of Aeronautics 2019年第4期32卷 921-937页

作者： f.G.CANALES j.L.MANTARI faculty of Mechanical Engineering Instituto de Investigación en Ingeniería Naval(IDIIN)Universidad Nacional de Ingenieria(UNI) Department of Mechanical Engineering University of New Mexico

This paper presents an analytical solution for free vibration analysis of thick rectangular isotropic plates coupled with a bounded fluid for various boundary conditions. In order to consider displacement theories of an arbitrary order, the Carrera Unified formulation(CUf) is used. The eigenvalue problem is obtained by using the energy functional, considering plate and fluid kinetic energies as well as the potential energy of the plate. The Ritz method is used to evaluate the displacement variables, and the functions used in the Ritz series can be adjusted to consider any of the classical boundary conditions. The convergence of the solution is analyzed, and a validation of results considering open literature and 3D finite element software is performed. Parametric studies are carried out to obtain natural frequencies as a function of the side-to-thickness ratio, plate aspect ratio, fluid domain size, plate boundary conditions, and fluid-solid density ratio. Pressure and velocity in the fluid domain are evaluated in order to establish the consistency of the *** results for thick plates are obtained with a much lower computational cost compared to that of 3D finite element solutions.

关键词： Added mass fluid-structure interaction Plate Ritz method Unified formulation Vibration

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Speeding up transmissions of unknown quantum information along Ising-type quantum channels

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Chinese Physics B 2017年第1期26卷 125-130页

作者： W j Guo L f Wei Quantum Optoelectronics Laboratory Southwest Jiaotong University Chengdu 610031 China State Key Laboratory of Optoelectronic Materials and Technologies School of Physics Sun Yat-Sen University Guangzhou 510275 China

Quantum teleportation with entanglement channels and a series of two-qubit SWAP gates between the nearestneighbor qubits are usually utilized to achieve the transfers of unknown quantum state from the sender to the distant receiver. In this paper, by simplifying the usual SWAP gates we propose an approach to speed up the transmissions of unknown quantum information, specifically including the single-qubit unknown state and two-qubit unknown entangled ones,by a series of entangling and disentangling operations between the remote qubits with distant interactions. The generic proposal is demonstrated specifically with experimentally-existing Ising-type quantum channels without transverse interaction; liquid NMR-molecules driven by global radio frequency electromagnetic pulses and capacitively-coupled josephson circuits driven by local microwave pulses. The proposal should be particularly useful to set up the connections between the distant qubits in a chip of quantum computing.

关键词： unknown quantum information transfers Ising-type quantum chains NMR molecules superconducting circuits

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Inter-relationship of Various Results in Analysis of （14.0 MeV／U） Pb＋Pb Reaction Using Mica and CN-85 Track Detectors

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Chinese Physics Letters 2005年第1期22卷 69-71页

作者： f.N.Khattak E.U.Khan TabassumNasir j.j.Baluch f.U.Khan U.W.C. GomalUniversityDeraIsmailKhanPakistan RadiationPhysicsDivision PINSTECHNiloreIslamabadPakistan DepartmentofPhysics GomalUniversityDeraIsmailKhanPakistan

Two detector materials mica and cellulose-nitrate(CN)-85 have been used to study (14.0MeV/u) Pb + Pb reaction. Events of different multiplicities were registered in mica and CN-85 detectors using the 2π-geometry technique of solid state nuclear track detection. After removing the target material from the detectors the damaged trails in the detectors were revealed as tracks by proper chemical etching. The irradiated area of each sample was scanned and events of different multiplicities were traced. The binary events were bifurcated into elastic and inelastic events. The elastic binary events and three prong events, observed in the reaction, have been used to search out coefficients Cμν in the presence of both the detectors, for the reaction under study. Using these coefficients 3- and 4-prong events have been analysed. from the detailed analysis of the results of (14.0MeV/u) Pb+Pb reaction, obtained from mica and CN-85 track detectors we observed a great resemblance of results obtained from the two detectors. Combining the results of both the detectors, we report some important outcomes.

关键词： CN-85轨迹探测器高能物理学铅原子碰撞反应固态

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