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Frontiers of Structural and Civil Engineering 2018年第3期12卷 341-351页

作者： Saleh YAGHOOBI ahmad SHOOSHTARI Civil Engineering Department Ferdowsi University of Mashhad Mashhad Iran

Slippage corresponds to the relative displacement of a bolted joint subjected to shear loads since the construction clearance between the bolt shank and the bolthole at assembly can cause joint slip. Deflections of towers with joint slippage effects is up to 1.9 times greater than the displacements obtained by linear analytical methods. In this study, 8 different types of joints are modelled and studied in the finite element program, and the results are verified by the experimental results which have been done in the laboratory. Moreover, several types of joints have been modelled and studied and load-deformation curves have also been presented. Finally, joint slip data for different types of angles, bolt diameter and bolt arrangements are generated. Thereupon, damping ratios （ζ） for different types of connections are reported. The study can be useful to help in designing of wind turbine towers with a higher level of accuracy and safety.

关键词： Joint slip cyclic loading Finite element modelling Experimental joint behavior damping ratios (ζ)

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

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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

Prospective of extracellular matrix and drug correlations in disease management

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Asian Journal of Pharmaceutical Sciences 2021年第2期16卷 147-160页

作者： Varish ahmad Health Information Technology Department Faculty of Applied StudiesKing Abdulaziz UniversityJeddah 21589Kingdom of Saudi Arabia

The extracellular matrix(ECM)comprises of many structural molecules that constitute the extracellular *** molecules are characterized by specific features like diversity,complexity and signaling,which are also results of improvement or development of disease mediated by some physiological *** drugs have also been used to manage diseases and they have been reported to modulate ECM assembly,including physiological changes,beyond their primary targets and ECM *** review highlights the alteration of ECM environment for diseases and effect of different classes of drugs like nonsteroidal anti-inflammatory drugs,immune suppressant drug,steroids on ECM or its ***,it is summarized from previously conducted researches that diseases can be managed by targeting specific components of ECM which are involved in the pathophysiology of ***,the drug delivery focused on targeting the ECM components also has the potential for the discovery of targeted and site specific release of ***,ECM or its components could be future targets for the development of new drugs for controlling various disease conditions including neurodegenerative diseases and cancers.

关键词： Extracellular matrix Disease Pharmacotherapeutics Drug target

Effect of Magnetic Field on Forced Convection between Two Nanofluid Laminar Flows in a Channel

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Chinese Journal of Mechanical Engineering 2016年第6期29卷 1235-1243页

作者： Afrasiab Raisi ahmad Qanbary Engineering Faculty Shahrekord University

This paper provides a numerical study of forced convection between hot and cold nanofluid laminar flows that are separated by a thin membrane, in a horizontal channel. Outer surface of channels＇ walls are thermally insulated and divide into two parts; namely NMP and MP. NMP is the channel＇s wall from the entrance section to the middle section of channel that is not influenced by magnetic field. MP is the channel＇s wall from the middle section to the exit section of channel which is influenced by a uniform-strength transverse magnetic field. The governing equations for both hot and cold flows are solved together using the SIMPLE algorithm. The effects of pertinent parameters, such as Reynolds number （10 ≤ Re ≤500）, Hartman number （0 ≤Ha ≤60） and the solid volume fraction of copper nano-particles （0≤φ≤0.05）, are studied. The results are reported in terms of streamlines, isotherms, velocity and temperature profiles and local and average Nusselt number. The results of the numerical simulation indicate that the increase in Reynolds number and the solid volume fraction lead to increase in Nusselt number. Meanwhile, the results also show that the rate of heat transfer between the flows increases as the Hartmann number increases, especially at higher values of the Reynolds number.

关键词： magnetic field forced convection nanofluid membrane channel

One-step synthesis route of the aligned and non-aligned single crystalline α-Si_3N_4 nanowires

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Science China(Technological Sciences) 2009年第1期52卷 1-5页

作者： shkoor ahmad Beijing National Center for Electron Microscope Laboratory Department of Materials Science and Engineering Tsinghua University

This paper reports the bulk synthesis route of the aligned and non-aligned high-quality α-Si_3N_4 nanowires (NWS) which were grown directly from the Si substrate by vapor phase deposition at 1050℃. The as-grown products were characterized by employing XRD, SEM, HRTEM and photoluminescence. The microscopic results revealed that the products consist of single crystalline aligned and nonaligned α-Si_3N_4 NWs having a same diameter range of 30-100 nm and different lengths of about hundreds of microns. The XRD observation revealed that the products consist of α-phase Si_3N_4 NWs. The room temperature PL spectra indicated that the NWs have good emission property. The non-aligned NWs were formed at lower temperature as compared with aligned NWs. Our method is a simple and one-step procedure to synthesize the bulk-quantity and high-purity aligned and non-aligned α-Si_3N_4 NWs at a relatively low temperature. The possible growth mechanism was also briefly discussed.

关键词： Si_3N_4 nanowires aligned non-aligned crystalline

Insulin sources and types: a review of insulin in terms of its mode on diabetes mellitus

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Journal of Traditional Chinese Medicine 2014年第2期34卷 234-237页

作者： Kafeel ahmad Centre of Biotechnology and Microbiology University of Peshawar

Insulin is involved in regulation of glucose utilization in the body. Inability of the body to synthesize insulin or human cells resistance to insulin leads to a condition called Diabetes mellitus which is characterized by chronic hyperglycaemia. There are two types of diabetes; type 1 and type 2. Exogenous supply of insulin is needed consistently for type 1diabetes treatment and type 2 diabetes also needs to be cured by the exogenous supply of insulin in advance stages of the disease. These sources have been proved very useful to meet the needs of the patients. However, these insulin types are expensive for the large population of patients in the developing countries. Furthermore, the incidence of diabetes is advancing at an alarming rate. Hence production systems with even higher capabilities of production are desired. Therefore, currently plants are being investigated as alternative production systems. Based on the mode of action of insulin various formulations of insulin have been developed that have different onset of action, peak effect and duration of action according to the needs of the patients.

关键词： Insulin Diabetes mellitus Insulin analogs

General Formalism for the BRST Symmetry

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Communications in Theoretical Physics 2013年第4期59卷 439-442页

作者： Suhail ahmad Departmet of Physics Jamia Millia Islamia University

In this paper we will discuss Faddeev-Popov method for gauge theories with a general form of gauge symmetry in an abstract way. We will then develope a general formalism for dealing with the BRST symmetry. This formal... 详细信息

关键词： BRST symmetry Faddeev-Popov method

Bifurcation and Stability Analysis of the Hamiltonian-Casimir Model of Liquid Sloshing

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Chinese Physics Letters 2012年第6期29卷 46-49页

作者： Salman ahmad YUE Bao-Zeng Department of Humanities&Sciences Institute of Space TechnologyIslamabad 44000Pakistan Department of Mechanics School of Aerospace EngineeringBeijing Institute of TechnologyBeijing 100081

Motion stability of a spacecraft is discussed.A canonical Hamiltonian model for liquid sloshing is presented for a moving rigid *** equivalent mechanical pendulum model is used to represent the fuel slosh inside the *** this model sloshing is represented by the moving mass,the rest of the mass of the spacecraft is assumed to be *** spacecraft structure is considered to be an elliptical rigid shape and the steady rotation along the x-axis is taken as the major-axis *** stability for the present model is analyzed using the Lyapunov theory with Casimir energy *** for stability and instability are derived for a steady principal axis rotation of the rigid *** results are presented to distribute the region into stable and unstable *** this,the nonlinear behavior of the system is analyzed under the influence of an external force acting *** is observed through a bifurcation *** time history map and phase portrait are also presented to analyze the nonlinear behavior of the system.

关键词： Hamiltonian rotation stability

Precipitation Study in Inconel 625 Alloy by Positron Annihilation Spectroscopy

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Journal of Materials Science & Technology 2003年第5期19卷 434-436页

作者： M.ahmad. W.ahmad. M.A.Shaikh Mahmud ahmad M.U.Rajput Nuclear Physics Division Pakistan Institute of Nuclear Science & Technology P.O. Nilore Islamabad PakistanNuclear Physics Division Pakistan Institute of Nuclear Science & Technology P.O. Nilore Islamabad PakistanNuclear Physics Division Pakistan Institute of Nuclear Science & Technology P.O. Nilore Islamabad PakistanNuclear Physics Division Pakistan Institute of Nuclear Science & Technology P.O. Nilore Islamabad Pakistan Nuclear Physics Division Pakistan Institute of Nuclear Science & Technology P.O. Nilore Islamabad Pakistan

Precipitation in Inconel 625 alloy has been studied by positron annihilation spectroscopy and electron microscopy. The observed dependence of annihilation characteristics on aging time is attributed to the change of the positron state due to the increase and decrease of the density and size of the 7' precipitates. Hardness measurements and lifetime measurements are in good agreement.

关键词： Positron lifetime Precipitation Inconel 625 alloy Fast-fast coincidence system Hardness

Morphotectonic and Lithostratigraphic Analysis of Intermontane Karewa Basin of Kashmir Himalayas,India

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Journal of Mountain Science 2013年第1期10卷 1-15页

作者： Reyaz ahmad DAR Rakesh CHANDRA Shakil ahmad ROMSHOO Department of Earth Sciences The University of Kashmir

Morpho-tectonic study plays an important role in deciphering the effects of tectonic activity in the geomorphic evolution of the drainage *** watershed forms one of the major watersheds of the intermontane Karewa Basin of Kashmir *** Karewa sediments are characterized by glacio-fluvio-lacustrine deposits capped by the aeolian *** geomorphic,morphometric and lithostratigraphic studies of these cap deposits have been carried out to elucidate the effect of tectonics on the geomorphic evolution of Romushi *** mapping was carried out using GPS measurements,DEM at 30m resolution,Topographic Position Index(TPI) model,topographic maps,LANDSAT TM Imagery and field *** and morphotectonic analyses in GIS environment were used to calculate various geomorphic indices(Mountain Front Sinuosity Index,Bifurcation Ratio,Asymmetry Factor,River Profile,etc).These indices reveal that the tectonic uplift observed in the region due to Himalayan orogeny coupled with mass movement and aeolian deposition have dominated the landscape evolution of intermontane Karewa Basin of Kashmir throughout the Late Quaternary *** data from lithostratigraphic measurements were analyzed to understand the geomorphic evolution of intermontane Karewa *** data revealed that the basin has experienced differential uplift and erosion rates from time to time in the geological *** was corroborated by the results from the morphometric and morphotectonic analysis.

关键词： Himalayas Morphometry Watershed Morphotectonics Intermontane basin Remote Sensing Drainage basin Digital elevation model