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A FAMILY OF DIFFERENCE SCHEMES WITH FOURNEAR-CONSERVED QUANTITIES FOR THE KdV EQUATION

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Journal of Computational Mathematics 1998年第2期16卷 129-140页

作者： Han, z Shen, LJ No Jiaotong Univ Dept Comp Sci & Technol Beijing 100044 Peoples R China Inst Appl Phys & Computat Math Beijing 100088 Peoples R China

We construct and analyze a family of semi-discretized difference schemes with two parameters for the Korteweg-de Vries (KdV) equation. The scheme possesses the first four near-conserved quantities for periodic boundary conditions. The existence and the convergence of its global solution in Sobolev space L-infinity(0,T;H-3) are proved and the scheme is also stable about initial values. Furthermore, the scheme conserves exactly the first two conserved quantities in the special case.

关键词： convergence difference scheme KdV equation conserved quantity

Comparison Study of Constitutive Models for Overconsolidated Clays

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Acta Mechanica Solida Sinica 2020年第1期33卷 98-120页

作者： z.Wan Y.P.Yao z.W.Gao Research Institute of Base and Foundation China Academy of Building ResearchBeijing 100013China School of Transportation Science and Engineering Beihang UniversityBeijing 100091China School of Engineering University of GlasgowGlasgow G128QQUK

Widely distributed in natural deposits,the overconsolidated(OC)clays have attracted extensive experimental investigations on their mechanical behaviors,especially in the 1960s and *** on these results,numerous constitutive models have also been *** models generally fall into two categories:one based on the classical plasticity theory and the other the bounding surface(BS)plasticity theory,with the latter being more popular and *** BS concept and the subloading surface(SS)concept are the two major BS plasticity *** features of these two concepts and the representative models based on them are introduced,*** unified hardening(UH)model for OC clays is also based on the BS plasticity theory but distinguishes itself from other models by the integration of the reference yield surface,unified hardening parameter,potential failure stress ratio,arid transformed stress *** is made to the Hvorslev envelop employed in the UH model to improve its capability of describing the behaviors of clays with extremely high overconsolidation ratio in this *** comparison among the BS model,SS model,and UH model is *** shows that all these three models can characterize the fundamental behaviors of OC clays,such as the stress dilatancy,strain softening and attainment of the critical *** UH model with the revised Hvorslev envelop has the fewest parameters which are identical to those of the modified Cam-Clay model.

关键词： Clay Overconsolidation Critical state Bounding surface Subloading surface Unified hardening model

Physical and Kinematical Characteristics of Wolf–Rayet Central Stars and their Host Planetary Nebulae

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Research in Astronomy and Astrophysics 2023年第9期23卷 219-240页

作者： z.Awad A.Ali Department of Astronomy Space Science and MeteorologyFaculty of ScienceCairo University12613 Giza

We address the physical and kinematical properties of Wolf–Rayet[WR]central stars(CSs)and their host planetary nebulae(PNe).The studied sample comprises all[WR]CSs that are currently *** analysis is based on recent observations of the parallax,proper motion,and color index of[WR]CSs from the Gaia space mission’s early third release(eDR3)catalog,as well as common nebular *** results revealed an evolutionary sequence,in terms of decreasing Teff,from the early hot[WO 1]to the late cold[WC 12]*** evolutionary sequence extends beyond[WR]CS temperature and luminosity to additional CS and nebular *** statistical analysis shows that the mean final stellar mass and evolutionary age of the[WR]CS sample are 0.595±0.13M⊙and 9449±2437 yr,respectively,with a mean nebular dynamical age of 7270±1380 *** addition,we recognize that the color of the majority(∼85%)of[WR]CSs tends to be red rather than their genuine blue *** analysis indicates that two-thirds of the apparent red color of most[WR]s is attributed to the interstellar extinction whereas the other one-third is due to the PN self-extinction effect.

关键词： Wolf-Rayet-(ISM )planetary nebulae general-ISM kinematics and dynamics

THERMODYNAMICS OF CERIUM CARBIDE Fe_4Ce_4C_7 IN STEEL

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Acta Metallurgica Sinica(English Letters) 1998年第2期11卷 150-156页

作者： J.z.zhang D.z.Li Guizhou Univ of Technology Guiyang China

The thermodynamics and the properties of the cerium carbide Fe4 Ce4 C7 in steel have been studied by means of metallography, electron microprobe, X-ray diffraction technique and electrolytic separation. The main results obtained can be summarized as follows: The cerium carbide CeC2 can be precipitated in cast steel and distributed along the grain boundaries. Heat treating the steel as austenite, the CeC2 transformed into ternary compound Fe4Ce4 C7, its thermodynamics of formation in steel being expressed as: ac exp(6400/T-6. 28), where 1015Kzed light, opaque in dark field and a little greyer than iron matrix in bright field. Its Vickers hardness is about 420kg/mm2 (annealed) and 750kg/mm2 (quenched). This phase in steel is stable in basic and organic solutions and can be seperated from the matrix by electrolysis. Moreover, the LaC2 in steel can not be transformed into Fe-La-C ternary compound in present investigation.

关键词： cerium carbide electrolytic separation thermodynamics

Peristaltic Flow of Dusty Nanofluids in Curved Channels

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Computers, Materials & Continua 2021年第1期66卷 1011-1026页

作者： z.z.Rashed Sameh E.Ahmed mathematics department jouf universityqurayyatsaudi arabia department of mathematics king khalid universityabhasaudi arabia

In this paper,numerical investigations for peristaltic motion of dusty nanofluids in a curved channel are *** systems of partial differential equations are presented for the nanofluid and dusty phases and then the approximations of the long wave length and low Reynolds number are *** physical domain is transformed to a rectangular computational model using suitable grid *** resulting systems are solved numerically using shooting method and mathematical forms for the pressure distributions are *** controlling parameters in this study are the thermal buoyancy parameter G_(r),the concentration buoyancy parameter Gc,the amplitude ratio,the Eckert number Ec,the thermophoresis parameter N_(t) and the Brownian motion parameter Nb and the dusty parameters D_(s);α_(s).The obtained results revealed that an increase in the Eckert number enhances the temperature of the fluid and dusty particles while the nanoparticle volume fraction is ***,both of the temperature and nanoparticles volume fraction are supported by the growing of the Brownian motion parameter.

关键词： Peristaltic motion dusty particles nanofluid curved channels

Finding Chaos in Finnish GDP

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International Journal of Automation and computing 2014年第3期11卷 231-240页

作者： Radko Kíz Faculty of Electrical Engineering Czech Technical University

The goal of this paper is to analyze the Finnish gross domestic product(GDP) and to find chaos in the Finnish GDP. We chose Finland where data has been available since 1975, because we needed the longest time series possible. At first we estimated the time delay and the embedding dimension, which is needed for the Lyapunov exponent estimation and for the phase space ***, we computed the largest Lyapunov exponent, which is one of the important indicators of chaos. Then we calculated the 0-1 test for chaos. Finally we computed the Hurst exponent by rescaled range analysis and by dispersional analysis. The Hurst exponent is a numerical estimate of the predictability of a time series. In the end, we executed a recurrent analysis and displayed recurrence plots of detrended GDP time series. The results indicated that chaotic behaviors obviously exist in GDP.

关键词： Chaos theory gross domestic product(GDP) time series analysis phase space reconstruction Hurst exponent largest Lyapunov exponent recurrent analysis.

NUMERICAL SIMULATION OF TEMPERATURE FIELDS IN ELECTROSLAG REMELTING SLAB INGOTS

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Acta Metallurgica Sinica(English Letters) 2008年第4期21卷 253-259页

作者： L.z. Chang B.z. Li Department of Metallurgical Technology Central Iron ＆ Steel Research Institute Beijing 100081 China

The method based on transient heat transfer model is adopted to simulate electro-slag remelting process. The calculated results of the model show that the process is in the quasi-steady state, and the shape of pool remains unchanged when the height of ingot is approximately 2.5-3 times the thickness of slab ingot. The change in the shape of pool is found to be strongly dependent on the pattern of melting rate, and hence, the power input; the depth of the molten pool increases with the increase in melting speed. It is concluded that a transient heat transfer model has to be used to obtain reliable input information for the entire, operatina time.

关键词： ESR Slab ingot Mathematical model Shape of molten metal pool

Influence of Non-Uniform Temperature Distribution on Metallic Charge Length on Energy and Force Parameters During Groove-Rolling

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Journal of Iron and Steel Research International 2012年第8期19卷 17-24页

作者： Mróz Sebastian Czestochowa University of Technology

Change in the temperature of band over its length, associated with the stock being non-uniformly heated in the furnace, influences the variations in the magnitudes of energy-force parameters. Using the FEM (Finite Element Model) programs for the computation of the values of the energy-force parameters can take into account the distribution of temperature over the band length. The mathematical model of the computer program Forge2008 was used to theoretically examine the energy-force parameters and plastic metal flow in the roughing stands of the continuous rolling mill. The results of experimental investigation of influence of the non-uniform temperature distribution were presented on the metallic charge length on the energy and force parameters and dimensions of the band during round bars rolling. Thermovision monitoring energy and force parameters monitoring were carried out in continuous rolling mill D350 in one of the Polish industrial plants. On the basis of obtained results, it could be stated that non-uniform distribution of temperatures along the charge length causes local increase of energy and force parameters values and also such distribution affects the local increase of the width of rolled band. The rolling process of charge with non-uniform distribution of temperature could lead to exceeding required dimensional tolerances of the final products.

关键词： groove-rolling energy parameter force parameter numerical technique FEM

Intraperitoneal Instillation of Dexmedetomidine vs Dexamethasone as Adjuvant to Bupivacaine for Postoperative Pain in Laparoscopic Cholecystectomy, a Randomized Clinical Trial

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Open Journal of Anesthesiology 2025年第1期15卷 1-12页

作者： Ayman Mohamady Eldemrdash zaher z. zaher Tarek S. Hemaida Taha T. Dardeer Hani M. Raslan Shawky M. Abdelgalil Mohmed R. Saad Mohammed S. Aly Anesthesiology Surgical Intensive Care and Pain Medicine and General Surgery Departments Faculty of Medicine Aswan University Aswan Egypt

Background: Intraperitoneal instillation (IPI) of local anesthesia was reported to reduce postoperative pain after laparoscopic surgeries. We aim to evaluate the effectiveness of IPI of bupivacaine + dexmedetomidine versus bupivacaine + dexamethasone on postoperative pain in patients undergoing laparoscopic cholecystectomy (LC). Methods: This randomized clinical trial was carried out on one hundred patients who underwent LC under general anesthesia. Patients were randomly divided into: Group (Dexa): IPI of bupivacaine with dexamethasone and Group (Dexmed): IPI of bupivacaine with dexmedetomidine. Results: The first time to request analgesia was significantly delayed in the dexmed group (P value Conclusions: Intraperitoneal Bupivacaine + Dexmedetomidine provided longer pain-free postoperative duration lower pain score over time, and lesser analgesic consumption.

关键词： Bupivacaine Dexmedetomidine Dexamethasone Laparoscopic Cholecystectomy