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Theoretical Study of Kinetics and Thermodynamics of Hetero Diels-Alder Reaction of Thiazole and Isothiazol with Thiophene-2,5-dione

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Chinese Journal of Structural Chemistry 2011年第10期30卷 1375-1380页

作者： Saeed Reza Emamian Jamileh Nabavi Fatemeh shams Ehsan Zahedi Chemistry Department Shahrood BranchIslamic Azad University

DFT methods have been used to study the hetero Diels-Alder reaction of thiazole and isothiazole with thiophen-2,*** thermodynamic and kinetic parameters were *** relative stabilities of the transition structures corresponding to the endo/exo stereoisomers have been rationalized on the basis of the secondary molecular orbital *** analysis was carried out to calculate the synchronicity *** was shown that all reactions are synchronous.A HOMO-LUMO energy gap shows both reactions are normal electron demand.

关键词： Diels-Alder DFT kinetics thiazole isothiazole HOMO-LUMO gap

Computer Geometries for Finding All Real Zeros of Polynomial Equations Simultaneously

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Computers, Materials & Continua 2021年第11期69卷 2635-2651页

作者： Naila Rafiq Saima Akram Mudassir shams Nazir Ahmad Mir Department of Mathematics NUMLIslamabad44000Pakistan Centre for Advanced Studies in Pure&Applied Mathematics Bahauddin Zakariya UniversityMultan Department of Mathematics and Statistics Riphah International University I-14Islamabad44000Pakistan

In this research article,we construct a family of derivative free simultaneous numerical schemes to approximate all real zero of non-linear polynomial *** make a comparative analysis of the newly constructed numerical schemes with a well-known existing simultaneous method for determining all the distinct real zeros of polynomial equations using computer algebra system Mat *** bound of convergence of simultaneous schemes is calculated using *** convergence property of the numerical schemes is presented by taking random starting initial approximation and their convergence history are graphically *** real life engineering applications along with some higher degree polynomials are considered as numerical test problems to show performance and efficiency of the derivative free family of numerical methods with comparison of an existing method of same order in *** computational order of convergence,CPU time,graph of computational order of convergence and residual error graphs elaborate efficiency,robustness and authentication of the suggested family of numerical methods in its domain.

关键词： Polynomials simultaneous iterative methods random initial guesses lower bound local computational order CAS-mathematica and mat lab

Numerical investigation of transitions in flow states and variation in aerodynamic forces for flow around square cylinders arranged inline

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Chinese Journal of Aeronautics 2018年第11期31卷 2111-2123页

作者： Waqas SARWAR ABBASI shams UL ISLAM Lubna FAIZ Hamid RAHMAN Mathematics Department Air UniversityIslamabad Mathematics Department COMSATS Institute of Information Technology Mathematics and Statistics Department Bacha Khan University

This study focuses on the transitions in flow states around two-, three-and four-inline square cylinders under the effect of Reynolds numbers at two different gap spacing values using the lattice Boltzmann method. For this purpose, Reynolds number is varied in the range 1–130 while two different values of spacing taken into account are gap spacing =2 and 5. Before going to actual problem, the code is tested for flow around a single square cylinder by comparing the results with experimental and numerical results of other researchers, and good agreement is *** current numerical computations yield that for both spacing values and all combinations of cylinders there exist three different sates of flow depending on Reynolds numbers: steady state, transitional state and unsteady state. It is found that the range of Reynolds numbers for these flow states is different for both spacing values. At gap spacing =2 the range of Reynolds numbers for each flow state decreases by increasing the number of cylinders while at gap spacing =5 opposite trend is observed. The results also show that at gap spacing =2 the reduction in drag force is greater than the corresponding reduction at gap spacing =5. The maximum reduction in drag force is observed at Reynolds numbers =1 at both spacing values. Similarly, at both spacing values and all Reynolds numbers, the maximum reduction in drag force is observed for the case of four-inline square cylinders.

关键词： Drag reduction Flow states Gap spacing Inline cylinders Reynolds number

In-situ copolymerization of aniline with alkyl amine by APS:Kinetics and application

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Chinese Chemical Letters 2008年第11期19卷 1358-1362页

作者： M.Rashid shams Qamar Usmani Suhail Sabir Polymer Research Laboratory Department of ChemistryAligarh Muslim UniversityAligarh 202002India

The kinetic study of in-situ eopolymerization of aniline with o- and p-methylaniline by ammonium persulfate （APS） has been carried out. UV-vis spectroscopic method was used to investigate the course of copolymerization. Structural characterization was studied by PT-IR spectral analysis. The electronic spectra of the copolymers poly（aniline-co-p-toluidine） and poly（aniline-co-o- toluidine） show blue shift. The shift has been observed in the bands corresponding to π→π^＊ transition as well as in the exciton transition. The increase in absorbance recorded during the reaction for different concentration of aniline, o- and p-toluidine at various intervals of time of polymerization reaction indicates a growth in the polymer formation. The resulting first-order rate constant was used to calculate the rate of copolymer formation using the rate equation -d[A]/dt = kc^n.

关键词： Copolymerization Corrosion inhibition Electronic and vibrational spectra

COVID‑19 pandemic risk and probability of loan default:evidence from marketplace lending market

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Financial Innovation 2021年第1期7卷 1967-1994页

作者： Asror Nigmonov Syed shams University of New South Wales SydneyAustralia University of Southern Queensland Darling HeightsAustralia

As the COVID-19 pandemic adversely affects the financial markets,a better understanding of the lending dynamics of a successful marketplace is necessary under the conditions of financial *** the loan book database of Mintos(Latvia)and employing logit regression method,we provide evidence of the pandemic-induced exposure to default risk in the marketplace lending *** analysis indicates that the probability of default increases from 0.056 in the pre-pandemic period to 0.079 in the post-pandemic ***-19 pandemic has a significant impact on default risk during May and June of *** also find that the magnitude of the impact of COVID-19 risk is higher for borrowers with lower credit ratings and in countries with low levels of FinTech *** main findings are robust to sample selection bias allowing for a better understanding of and quantifying risks related to FinTech loans during the pandemic and periods of overall economic distress.

关键词： Peer-to-peer lending COVID-19 Coronavirus Default risk Marketplace lending Pandemic FinTech Shadow banking

Asphaltene onset pressure measurement and calculation techniques:A review

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Petroleum 2024年第2期10卷 191-201页

作者： Sherif Fakher Amr yousef Aseel Al-Sakkaf shams Eldakar Petroleum and Energy Engineering The American University in CairoCairoEgyp

Asphaltene precipitation can result in several production,operational,and transportation problems during oil *** asphaltene precipitates and deposits,it can reduce reservoir permeability,damage wellbore equipment,and plug the *** is therefore extremely important to evaluate the conditions at which asphaltene precipitation occurs;this is referred to as the asphaltene onset *** onset pressure has been measured using many different experimental *** have also been many attempts along the years to predict asphaltene onset pressure using mathematical correlations and *** research provides an up-to-date comprehensive review of the methods by which asphaltene onset pressure can be measured using laboratory experiments and mathematical *** research explains the main mechanisms of all the laboratory experiments to measure asphaltene onset pressure under static conditions and how to conduct them and highlights the advantages and limitations of each *** research also provides a summary of the commonly used mathematical models to quantify asphaltene onset pressure directly and indirectly.

关键词： Asphaltene onset measurement

Implications of enolase in the RANKL-mediated osteoclast activity following spinal cord injury

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BIOCELL 2021年第6期45卷 1453-1457页

作者： RAMSHA shams NAREN LBANIK AZIZUL HAQUE Department of Microbiology and Immunology Medical University of South CarolinaCharlestonSC 29425USA Department of Neurosurgery Medical University of South CarolinaCharlestonSC 29425USA Ralph H.Johnson Veterans Administration Medical Center CharlestonSC 29401USA

Spinal Cord Injury(SCI)is a debilitating condition characterized by damage to the spinal cord,resulting in loss of function,mobility,and *** increasingly prevalent in the US,no FDA-approved therapy exists due to the unfortunate complexity of the condition,and the difficulties of SCI may be furthered by the development of SCI-related complications,such as *** demonstrates two crucial stages for consideration:the primary stage and the secondary *** the primary stage is suggested to be immediate and irreversible,the secondary stage is proposed as a promising window of opportunity for therapeutic ***,a metabolic enzyme upregulated after SCI,performs non-glycolytic functions,promoting inflammatory events via extracellular degradative actions and increased production of inflammatory cytokines and ***-specific enolase(NSE)serves as a biomarker of functional damage to neurons following SCI,and the inhibition of NSE has been demonstrated to reduce signs of secondary injury of SCI and to ameliorate *** Viewpoint article involves enolase activation in the regulation of RANK-RANKL pathway and summarizes succinctly the mechanisms influencing osteoclast-mediated resorption of bone in *** laboratory proposes that inhibition of enolase activation may reduce SCI-induced inflammatory response and decrease osteoclast activity,limiting the chances of skeletal tissue loss in SCI.

关键词： Enolase RANK RANKL Osteoporosis Neuronal death Spinal cord injury

Synthesis and Crystal Structure of 2-(4-Oxo-3-o- tolyl-3,4-dihydroquinazolin-2-ylthio)acetohydrazide

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Chinese Journal of Structural Chemistry 2012年第9期31卷 1329-1333页

作者： Aamer Saeed shams-ul-Mahmood Ulrich Flörke Department of Chemistry Quaid-I-Azam UniversityIslamabad 45320Pakistan Department Chemie Fakultät fur NaturwissenschaftenUniversität PaderbornWarburgerstrasse 100D-33098 PaderbornGermany

The title compound was synthesized from 3-（2-methylphenyl）-2-thioxo-2,3-dihy- droquinazolin-4（1H）-one （4） which was prepared from 2-methylaniline in two steps. The structure was supported by the spectroscopic data and unambiguously confirmed by single-crystal X-ray diffraction studies. It crystallizes in the orthorhombic space group Pbca with unit cell dimensions a = 6.687（4）, b = 24.788（16）, c = 30.453（19）  V = 5048（5） 3 and Z = 8.

关键词： quinazolinone acetohydrazide synthesis

Stable Computer Method for Solving Initial Value Problems with Engineering Applications

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Computer Systems Science & Engineering 2023年第6期45卷 2617-2633页

作者： Mudassir shams Nasreen Kausar Ebru Ozbilge Alper Bulut Department of Mathematics and Statistics Riphah International UniversityI-14Islamabad44000Pakistan Department of Mathematics Yildiz Technical UniversityFaculty of Arts and ScienceEsenler34210IstanbulTurkey Department of Mathematics&Statistics American University of the Middle EastEgaila54200Kuwait

Engineering and applied mathematics disciplines that involve differential equations in general,and initial value problems in particular,include classical mechanics,thermodynamics,electromagnetism,and the general theory of relativity.A reliable,stable,efficient,and consistent numerical scheme is frequently required for modelling and simulation of a wide range of real-world problems using differential *** this study,the tangent slope is assumed to be the contra-harmonic mean,in which the arithmetic mean is used as a correction instead of Euler’s method to improve the efficiency of the improved Euler’s technique for solving ordinary differential equations with initial *** stability,consistency,and efficiency of the system were evaluated,and the conclusions were supported by the presentation of numerical test applications in *** to the stability analysis,the proposed method has a wider stability region than other well-known methods that are currently used in the literature for solving initial-value *** validate the rate convergence of the numerical technique,a few initial value problems of both scalar and vector valued types were *** proposed method,modified Euler explicit method,and other methods known in the literature have all been used to calculate the absolute maximum error,absolute error at the last grid point of the integration interval under consideration,and computational time in seconds to test the *** Lorentz system was used as an example to illustrate the validity of the solution provided by the newly developed *** method is determined to be more reliable than the commonly existing methods with the same order of convergence,as mentioned in the literature for numerical calculations and visualization of the results produced by all the methods discussed,Mat Lab-R2011b has been used.

关键词： Local truncation error consistency computational time stability lorentz system