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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

Unlocking the Potential:A Comprehensive Systematic Review of ChatGPT in Natural Language Processing Tasks

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Computer Modeling in Engineering & Sciences 2024年第10期141卷 43-85页

作者： Ebtesam ahmad Alomari Faculty of Computing and Information Albaha UniversityAlbaha65731Saudi Arabia

As Natural Language Processing(NLP)continues to advance,driven by the emergence of sophisticated large language models such as ChatGPT,there has been a notable growth in research *** rapid uptake reflects increasing interest in the field and induces critical inquiries into ChatGPT’s applicability in the NLP *** review paper systematically investigates the role of ChatGPT in diverse NLP tasks,including information extraction,Name Entity Recognition(NER),event extraction,relation extraction,Part of Speech(PoS)tagging,text classification,sentiment analysis,emotion recognition and text *** novelty of this work lies in its comprehensive analysis of the existing literature,addressing a critical gap in understanding ChatGPT’s adaptability,limitations,and optimal *** this paper,we employed a systematic stepwise approach following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses(PRISMA)framework to direct our search process and seek relevant *** review reveals ChatGPT’s significant potential in enhancing various NLP *** adaptability in information extraction tasks,sentiment analysis,and text classification showcases its ability to comprehend diverse contexts and extract meaningful ***,ChatGPT’s flexibility in annotation tasks reducesmanual efforts and accelerates the annotation process,making it a valuable asset in NLP development and ***,GPT-4 and prompt engineering emerge as a complementary mechanism,empowering users to guide the model and enhance overall *** its promising potential,challenges *** performance of ChatGP Tneeds tobe testedusingmore extensivedatasets anddiversedata ***,its limitations in handling domain-specific language and the need for fine-tuning in specific applications highlight the importance of further investigations to address these issues.

关键词： Generative AI large languagemodel(LLM) natural language processing(NLP) ChatGPT GPT(generative pretraining transformer) GPT-4 sentiment analysis NER information extraction annotation text classification

FIAs(Foliation Intersection/Inflection Axes) Preserved in Porphyroblasts,the DNA of Deformation:A Solution to the Puzzle of Deformation and Metamorphism in the Colorado,Rocky Mountains,USA

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Acta Geologica Sinica(English Edition) 2009年第5期83卷 971-984页

作者： SHAH Afroz ahmad School of Earth and Environmental Sciences James Cook UniversityTownsville Queensland Australia

FIAs have been used extensively for more than a decade to unravel deformation and metamorphic puzzles. Orogenic processes developing early during the history or orogenesis challenge scientists because compositional layering in rocks always reactivates where multiple deformations have occurred, leaving little evidence of the history of foliation development preserved in the matrix. The foothills of the Rocky Mountains in Colorado, USA contain a succession of four FIA sets （trends） that would not have been distinguishable if porphyroblasts had not grown during the multiple deformation events that affected these rocks or if they had rotated as these events took place. They reveal that both the partitioning of deformation and the location of isograds changed significantly as the deformation proceeded.

关键词： foliation intersection/inflection axes porphyroblast deformational partitioning

Influence of accelerated curing on the compressive strength of polymer-modified concrete

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Frontiers of Structural and Civil Engineering 2022年第5期16卷 589-599页

作者： Izhar ahmad Kashif Ali KHAN Tahir ahmad Muhammad ALAM Muhammad Tariq BASHIR College of Civil and Transportation Engineering Hohai UniversityNanjing 210098China Department of Civil Engineering Muslim Youth UniversityIslamabad 44000Pakistan Department of Civil Engineering CECOS University of IT&Emerging SciencesPeshawar 25000Pakistan Department of Civil Engineering University of Engineering&TechnologyMardan 23200Pakistan

In recent building practice,rapid construction is one of the principal ***,in designing concrete structures,compressive strength is the most significant of all *** 3-d and 7-d compressive strength reflects the strengths at early phases,the ultimate strength is *** effort has been made in this study to develop mathematical models for predicting compressive strength of concrete incorporating ethylene vinyl acetate(EVA)at the later ***-Smirnov(KS)goodness-of-fit test was used to examine distribution of the *** compressive strength of EVA-modified concrete was studied by incorporating various concentrations of EVA as an admixture and by testing at ages of 28,56,90,120,210,and 365 *** accelerated compressive strength at 3.5 hours was considered as a reference strength on the basis of which all the specified strengths were predicted by means of linear regression *** on the results of KS goodness-of-fit test,it was concluded that KS test statistics value(D)in each case was lower than the critical value 0.521 for a significance level of 0.05,which demonstrated that the data was normally *** on the results of compressive strength test,it was concluded that the strength of EVA-modified specimens increased at all ages and the optimum dosage of EVA was achieved at 16%***,it was concluded that predicted compressive strength values lies within a 6%difference from the actual strength values for all the mixes,which indicates the practicability of the regression *** research work may help in understanding the role of EVA as a viable material in polymer-based cement composites.

关键词： compressive strength prediction polymer-modified concrete linear regression fit early age strength ethylene vinyl acetate

Novel Photoinitiated Synthesis, Characterization, Thermal Kinetics, and Mechanism of Complex of Potassium Hexacyanoferrate with Imidazole

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Chemical Research in Chinese Universities 2009年第2期25卷 138-142页

作者： MAJID Kowsar ahmad Siraj MALIK Mukhtar ahmad Department of Chemistry National Institute of Technology

Photoinitiated substitution complex of [Fe（CN）6]^4- with imidazole has been synthesized and characterized. On the basis of elemental analysis, the empirical molecular formula of the complex is K4[Fe（CN）5（C3H4N2）]·4H2O. The substitution of aquo ligand produced as a result of photoexcitation by imidazole has been confirmed by various spectroscopic thechniques like UV-Vis, FTIR, NMR, and SEM techniques. The characteristic FTIR and NMR absorption peaks for different entities present support the assigned formula. The presence of cyanide and imidazole ligands is shown by FTIR absorption peaks at 2046 cm^-1 due to v（C≡N） and at 1447 and 1619 cm^-1 due to v（C=N） and v（C=C） stretching vibration of the aromatic ring of imidazole, hence, confirming the assigned formula and photoinitiated substitution process. ^1HNMR also shows the peaks for aromatic hydrogen confirming again the presence of imidazole in the complex, further supporting the successful photoinitiated process. The water outside the coordination sphere has been confirmed from FTIR peaks and thermal analysis. Thermal kinetics and mechanistic studies have also been carried out by TG and DSC, Thermodynamics parameters such as activation energy（Ea）, preexponential factor（A）, and entropy of activation（Aft） have been calculated for each step via different methods like Doyle＇s, Coats, and Redfern and Arrehenius.

关键词： Photochemistry Potassium he.xacyanoferrate Imidazole Photosubstitution FTIR

An Efficient EMD-Based Reversible Data Hiding Technique Using Dual Stego Images

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Computers, Materials & Continua 2023年第4期75卷 1139-1156页

作者： ahmad A.Mohammad Princess Sumaya University for Technology Amman11941Jordan

Exploiting modification direction(EMD)based data hiding techniques(DHTs)provide moderate data hiding capacity and high-quality stego *** overflow problem and the cyclic nature of the extraction function essentially hinder their application in several fields in which reversibility is *** far,the few EMD reversible DHTs are complex and numerically *** paper presents a novel EMD-based reversible DHT using *** novel 2×4 modification lookup tables are introduced,replacing the 256×256 reference matrix used in similar techniques and eliminating the numerically demanding search step in similar *** the embedding step,one of the modification tables modifies a pixel in odd columns in the first cover image and keeps its image in the second cover image *** other modification table modifies a pixel in even columns in the second cover image and keeps its image in the first cover image *** embedding strategy enables direct reversibility at almost zero computational *** technique embeds one 4−ary secret digit into each pixel in the first cover image and its image in the second cover image resulting in one bit per pixel(bpp)data embedding *** use of the 4−ary numbering system enables direct and numerically efficient conversion of the binary secret message to the 4−ary and vice *** advantages of the proposed algorithm are straightforward reversibility,simplicity,numerical efficiency,direct conversion of the binary secret message to 4−ary and vice versa,and elimination of the need for the 256×256 reference matrix by replacing it with two 2×4 lookup *** results show that the embedding rate of the proposed technique is one *** achieved more than 49 dB average Peak to Signal Noise Ratio(PSNR)over all test images.

关键词： Reversible data-hiding EMD-based high capacity steganography

Parabolic Marcinkiewicz Integrals along Surfaces on Product Domains

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Acta Mathematica Sinica,English Series 2011年第1期27卷 1-18页

作者： ahmad AL-SALMAN Department of Mathematics and Statistics Sultan Qaboos University P.O. Box 36 A1-Khod 123 Muscat Sultanate of Oman

Abstract In this paper, parabolic Marcinkiewicz integral operators along surfaces on the product domain Rn ×RM （n, m ≥2） are introduced. Lp bounds of such operators are obtained under weak conditions on the kernels.

关键词： Parabolic Marcinkiewicz integral operators parabolic maximal functions Fourier transform rough kernels