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AdS/QCD and light front holography: A new approximation to QCD

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Chinese Physics C 2010年第9期34卷 1229-1235页

作者： Stanley J.Brodsky Guy f.de téramond SLAC National Accelerator Laboratory Stanford University Universidad de Costa Rica

the combination of Anti-de Sitter space （AdS） methods with light-front holography leads to a semi-classical first approximation to the spectrum and wavefunctions of meson and baryon light-quark bound *** from the bound-state Hamiltonian equation of motion in QCD,we derive relativistic lightfront wave equations in terms of an invariant impact variable ζ which measures the separation of the quark and gluonic constituents within the hadron at equal light-front *** equations of motion in physical space-time are equivalent to the equations of motion which describe the propagation of spin-J modes in anti–de Sitter （AdS） *** eigenvalues give the hadronic spectrum,and its eigenmodes represent the probability distributions of the hadronic constituents at a given *** to the light meson and baryon spectra are *** predicted meson spectrum has a string-theory Regge form M^ 2 = 4κ ^2 （n＋L＋S/2）;i.e.,the square of the eigenmass is linear in both L and n,where n counts the number of nodes of the wavefunction in the radial variable ζ.the space-like pion and nucleon form factors are also well *** thus obtains a remarkable connection between the description of hadronic modes in AdS space and the Hamiltonian formulation of QCD in physical space-time quantized on the light-front at fixed light-front time τ.the model can be systematically improved by using its complete orthonormal solutions to diagonalize the full QCD lightfront Hamiltonian or by applying the Lippmann-Schwinger method in order to systematically include the QCD interaction terms.

关键词： gauge/gravity correspondence light-front dynamics strongly coupled QCD meson and baryon spectrum meson and nucleon form factors

Sensitivity of the Simulation of tropical Cyclone Size to Microphysics Schemes

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Advances in Atmospheric Sciences 2016年第9期33卷 1024-1035页

作者： Kelvin t.f.CHAN Johnny C.L.CHAN School of Energy and Environment City University of Hong Kong

the sensitivity of the simulation of tropical cyclone （tC） size to microphysics schemes is studied using the Advanced Hurricane Weather Research and forecasting Model （WRf）. Six tCs during the 2013 western North Pacific typhoon season and three mainstream microphysics schemes-ferrier （fER）, WRf Single-Moment 5-class （WSM5） and WRf Single-Moment 6-class （WSM6）-are investigated. the results consistently show that the simulated tC track is not sensitive to the choice of microphysics scheme in the early simulation, especially in the open ocean. However, the sensitivity is much greater for tC intensity and inner-core size. the tC intensity and size simulated using the WSM5 and WSM6 schemes are respectively higher and larger than those using the fER scheme in general, which likely results from more diabatic heating being generated outside the eyewall in rainbands. More diabatic heating in rainbands gives higher inflow in the lower troposphere and higher outflow in the upper troposphere, with higher upward motion outside the eyewall. the lower-tropospheric inflow would transport absolute angular momentum inward to spin up tangential wind predominantly near the eyewall, leading to the increment in tC intensity and size （the inner-core size, especially）. In addition, the inclusion of graupel microphysics processes （as in WSM6） may not have a significant impact on the simulation of tC track, intensity and size.

关键词： tropical cyclone microphysics size intensity track numerical modelling

Dosimetry Methods of fast Neutron Using the Semiconductor Diodes

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Chinese Physics Letters 2014年第1期31卷 61-64页

作者： H. Zaki Dizaji t. Kakavand f. Abbasi Davani Department of Physics Faculty of Science Zanffan University Zanjan Iran Department of Physics Faculty of Science Imam Hossein Comprehensive University Tehran Iran Department of Physics Faculty of Science Imam Khomeini international University Qazvin Iran Department of Radiation Application Shahid Beheshti University Tehran Iran

Semiconductor detectors based on a silicon pin diode are frequently used in the detection of different nuclear radiations. for the detection and dosimetry of fast neutrons, these silicon detectors are coupled with a fast neutron converter. Incident neutrons interact with the converter and produce charged particles that can deposit their energy in the detectors and produce a signal. In this study, three methods are introduced for fast neutron dosimetry by using the silicon detectors, which are： recoil proton spectroscopy, similarity of detector response function with conversion function, and a discriminator layer. Monte Carlo simulation is used to calculate the response of dosimetry systems based on these methods. In the different doses of an 241Am-Be neutron source, dosimetry responses are evaluated. the error values of measured data for dosimetry by these methods are in the range of 15-25%. We find fairly good agreement in the 241Am-Be neutron sources.

关键词： SEMICONDUCtOR detectors PARtICLE detectors PIN diodes SEMICONDUCtOR diodes NUCLEAR counters SILICON detectors

Nature of Surface Layer and Electrochemical Behavior of NaOH Hydrothermally treated Niti Alloy

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维普期刊数据库

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Journal of Materials Science & technology 2004年第2期20卷 185-188页

作者： P.Shi f.t.Cheng H.C.Man DepartmentofAppliedPhysics TheHongKongPolytechnicUniversityHongKongChina DepartmentofIndustrialandSystemsEngineering TheHongKongPolytechnicUniversityHongKongChina

Niti samples were hydrothermally treated in NaOH at 200℃ with different soaking times. the morphology of the surface layer formed was studied by scanning electron microscopy (SEM). the composition of the layer and the major phases present were determined by energy-dispersive spectroscopy (EDS) and X-ray diffractometry (XRD), respectively. In contrast to the results reported by some authors, the surface layer was essentially Ni(OH)2 instead of being tiO2. the electrochemical behavior of the samples was studied by electrochemical impedance spectroscopy (EIS) in 3.5% NaCl solution at 23℃, and analyzed using a simplified Randle circuit consisting of a resistance R and a capacitance C in parallel. After hydrothermal treatment, R was increased by a factor ranging from 1.5 to 5.0 times, depending on the treatment time. the value of R of all the samples became steady within a period of less than 15 h. Results of the present study indicate that alkaline treatment leads to the growth of an insulating layer on Niti, but the method is not suitable for surface modification of Niti implants due to the enhanced Ni content in the surface layer.

关键词： Hydrothermal treatment Niti NaOH Resistance Electrochemical impedance spectroscopy

Analytical study of Cattaneo–Christov heat flux model for a boundary layer flow of Oldroyd-B fluid

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Chinese Physics B 2016年第1期25卷 657-662页

作者： f M Abbasi M Mustafa S A Shehzad M S Alhuthali t Hayat Department of Mathematics Comsats Institute of lnformaHon TechnologyIslamabad 44000Pakistan School of Natural Sciences(SNS) National University of Science and Technology(NUST)Islamabad 44000Pakistan Department of Mathematics Comsats Institute of/nformation TechnologySahiwa157000Pakistan NAAM Research Group Department of MathematicsFaculty of ScienceKing Abdulaziz UniversityJeddah 21589Saudi Arabia Department of Mathematics Quaid-I-Azam University 45320Islamabad 44000Pakistan

We investigate the Cattaneo-Christov heat flux model for a two-dimensional laminar boundary layer flow of an incompressible Oldroyd-B fluid over a linearly stretching sheet. Mathematical formulation of the boundary layer problems is given. the nonlinear partial differential equations are converted into the ordinary differential equations using similarity transformatioris. the dimensionless velocity and temperature profiles are obtained through optimal homotopy analysis method （OHAM）. the influences of the physical parameters on the velocity and the temperature are pointed out. the results show that the temperature and the thermal boundary layer thickness are smaller in the Cattaneo-Christov heat flux model than those in the fourier＇s law of heat conduction.

关键词： Oldroyd-B fluid Cattaneo-Christov heat flux nonlinear analysis

Lightning ablation suppression of aircraft carbon/epoxy composite laminates by metal mesh

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Journal of Materials Science & technology 2019年第11期35卷 2693-2704页

作者： f.S.Wang Y.Zhang X.t.Ma Z.Wei J.f.Gao School of Mechanics Civil Engineering and ArchitectureNorthwestern Polytechnical UniversityXi’an710129China the Research Institute for Special Structures of Aeronautical Composite Ji’nan250023China

three-dimensional finite element(fE)models of carbon/epoxy composite laminates with copper mesh and aluminum mesh protection were established subjected to lightning strike,in which different mesh spacing was *** of numerical method was verified and impulse current waveforms with different current peaks were applied according to aircraft lightning ***-electrical material parameters varying with temperature were added into numerical *** deletion method was used to deal with lightning ablation elements of composite *** results show that ablation area and depth of composite laminates with metal mesh protection are significantly smaller,which proves good protection effectiveness of metal meshes on anti-lightning *** denser the mesh spacing,the better the anti-lightning strike will *** of composite laminates with copper mesh has better effects than that of aluminum *** the effect of mesh spacing variation on composite structural weight and anti-lightning strike,the ideal mesh spacing was obtained.

关键词： Lightning strike Carbon/epoxy composites Ablation Mesh protection

Review on the applications and developments of drag reducing polymer in turbulent pipe flow

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Chinese Journal of Chemical Engineering 2019年第8期27卷 1921-1932页

作者： M.A.Asidin E.Suali t.Jusnukin f.A.Lahin faculty of Engineering Universiti Malaysia Sabah

Drag reduction phenomenon in pipelines has received lots of attention during the past decades due to its potential engineering applications, especially in fluid transporting industries. Various methods to enhance drag reduction have been developed throughout the years and divided into two categories;non-additives method and additives method. Both categories have different types of methods, with different formulations and applications which will generally be discussed in this review. Among all the methods discussed, drag reduction using polymer additive is as one of the most enticing and desirable methods. It has been the subject of research in this field and has been studied extensively for quite some time. It is due to its ability to reduce drag up to 80% when added in minute concentrations. Reducing drag in the pipe will require less pumping power thus offering economic relieves to the industries. So, this paper will be focusing more on the use of polymer additives as drag reducing agent, the general formulations of the additives, major issues involving the use of drag reducing polymers, and the potential applications of it. However, despite the extensive works of drag reduction polymer, there are still no models that accurately explain the mechanism of drag reduction. More studies needed to be done to have a better understanding of the phenomenon. therefore, future research areas and potential approaches are proposed for future work.

关键词： Pipe lines Drag reduction Polymer additives Drag reducing agents

Spring tube braces for seismic isolation of buildings

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Earthquake Engineering and Engineering Vibration 2017年第1期16卷 219-231页

作者： V.Karayel E.Yuksel t.Gokce f.Sahin Institute of Science and technology Istanbul Technical University lstanbul 34469 Turkey faculty of Civil Engineering Istanbul Technical University Maslak Istanbu1 34465 Turkey

Abstract： A new low-cost seismic isolation system based on spring tube bracings has been proposed and studied at the Structural and Earthquake Engineering Laboratory of Istanbul technical University. Multiple compression-type springs are positioned in a special cylindrical tube to obtain a symmetrical response in tension and compression-type axial loading. An isolation floor, which consists of pin-ended steel columns and spring tube bracings, is constructed at the foundation level or any intermediate level of the building. An experimental campaign with three stages was completed to evaluate the capability of the system. first, the behavior of the spring tubes subjected to axial displacement reversals with varying frequencies was determined. In the second phase, the isolation floor was assessed in the quasi-static tests. finally, a scaled 3D steel frame was tested on the shake table using actual acceleration records. the transmitted acceleration to the floor levels is greatly diminished because of the isolation story, which effects longer period and higher damping. there are no stability and self- centering problems in the isolation floor.

关键词： seismic isolation spring tube base isolation low-cost isolation

Multiscale and multiphysics explorations of the transient deposition processes and additive characteristics during laser 3D printing

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Journal of Materials Science & technology 2021年第18期77卷 196-208页

作者： H.L.Wei f.Q.Liu L.Wei t.t.Liu W.H.Liao School of Mechanical Engineering Nanjing University of Science and TechnologyNanjing.210094China State Key Laboratory of Solidification Processing Northwestern Poly technical UniversityXi'an710072China

Laser directed energy deposition(DED)involves complex physical processes,and the trial and error examinations are time consuming and cost *** research paradigm can be reshaped using advanced phenomenological models via computing the spatiotemporal variations of the build *** this work,multi-layer and multi-track laser DED of ti-6 Al-4 V were systematically explored on multiple scales including the 1D track,the 2D layer and the 3D full build considering the complex transport of energy,mass,and momentum in the moving freeform molten *** results showed that convex,nearflat,and wavy builds were generated using gradually larger hatch *** profiles of individual tracks and layers were extracted through the unique advantages of the *** individual tracks exhibited various patterns and rotated with specific inclinations to form distinct layer *** net increments of the deposit generated upon the printing of a new track during the continuous deposition process showed that the smaller hatch spacing caused higher overlap rate of horizontally adjacent tracks but lower remelting rate of vertically adjacent tracks in neighboring *** 3D numerical model was validated with corresponding experiments for various process *** scientific findings can provide useful insights for further researches of DED.

关键词： Additive manufacturing Multi-layer and multi-track Numerical model Build features Molten pool