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numerical Blow-up for a nonlinear Heat Equation

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Acta Mathematica Sinica,English Series 2011年第5期27卷 845-862页

作者： Firmin k. n'GOHISSE Theodore k. BOnI Universite d'Abobo-Adjame UFR-SFA Departement de Mathematiques et Informatique 01 BP 1003 Abidjan 01 Cdte d'Ivoire Institut national Polytechnique Houphouet-Boigny de Yamoussouk.o BP 1093 Yamoussoukro Cote d'Ivoire

This paper concerns the study of the numerical approximation for the following initialboundary value problem{ut-uzx=f（u）,t∈（0,1）,t∈（0,T） u（0,t）=0,t∈（0,1）,t∈（0,T） u（x,0）=u0（x）,x∈（0,1）where f（s） is a positive, increasing, C1 convex function for the nonnegative values of s, f（0）〉0, f∞ds/f（s）〈∞, u0∈C1（[0, 1]）, u0（0） = 0, u＇0（1）=0. We find some conditions under which the solution of a semidiscrete form of the above problem blows up in a finite time and estimate its semidiserete blow-up time. We also prove the convergence of the semidiscrete blow-up time to the theoretical one. A similar study has been also undertak.n for a discrete form of the above problem. Finally, we give some numerical results to illustrate our analysis.

关键词： Semidiscretization blow-up numerical blow-up time nonlinear heat equations

Positron scattering and ionization of neon atoms—theoretical investigations

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Chinese Physics B 2010年第10期19卷 245-250页

作者： Harshit n. k.thari k. n. Joshipura Department of Physics Sardar Patel University Vallabh Vidyanagar-388120 India

Although positron scattering with inert gas atoms has been studied in theory as well as in experiment, there are discrepancies. The present work.reports all the major total cross sections of e＋-neon scattering at incident energies above ionization threshold, originating from a complex potential formalism. Elastic and cumulative inelastic scatterings are treated in the complex spherical e＋-atom potential. Our total inelastic cross section includes positronium formation together with ionization and excitation channels in ne. Because of the Ps formation channel it is difficult to separate out ionization cross sections from the total inelastic cross sections. An approximate method similar to electron-atom scattering has been applied to bifurcate ionization and cumulative excitation cross sections at energies from threshold to 2000 eV. Comparisons of present results with available data are made. An important outcome of this work.is the relative contribution of different scattering processes, which we have shown by a bar-chart at the ionization peak.

关键词： ionization cross sections positron scattering complex potential total cross sections

Models and form factors for stand volume estimation in natural forest ecosystems: a case study of k.0}iaghat Wildlife Sanctuary (k.WS), Bahraich District, India

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Journal of Forestry Research 2013年第2期24卷 217-226页

作者： V. A. J Adek.nle k. n. nair A. k. Srivasta.a.n. k. Singh Federal University of Technology Dept of Forestry & Wood Technology national Botanical Research Institute (Council for Scientific & Industrial Research) Plant Diversity Systematics & Herbarium Division Rana Pratap Marg Department of Forests Sidhauli Forest Division

In view of the difficulties in stand volume estimation in natural forests, we derived real form factors and models for volume estimation in these types of forest ecosystems, using k.0}iaghat Wildlife Sanctuary as a case study. Tree growth data were obtained for all trees （dbh 〉10 cm） in 4 plots （25 × 25 m） randomly located in each of three strata selected in the forest. The form factor calculated for the stand was 0.42 and a range of 0.42 0.57 was estimated for selected species （density 〉10）. The parameters of model variables were consistent with general growth trends of trees and each was statistically significant. There was no significant difference （p〉0.05） between the observed and predicted volumes for all models and there was very high correlation between observed and predicted volumes. The output of the performance statistics and the logical signs of the regression coefficients of the models demonstrated that they are useful for volume estimation with minimal error. Plotting the biases with respect to considerable regressor variables showed no meaningful and evident trend of bias values along with the independent variables. This showed that the models did not violate regression assumptions and there were no heteroscedacity or multiculnarity problems. We recommend use of the form factors and models in this ecosystem and in similar ones for stand and tree volume estimation.

关键词： natural forest tree volume Estimation biodiversity tree height forest inventory

Flow, thermal, and vibration analysis using three dimensional finite element analysis for a flux reversal generator

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Frontiers in Energy 2016年第4期10卷 424-440页

作者： B. VIDHYA k. n. SRInIVAS 1. Department of Electrical and Electronics Engineering B. S. Abdur Rahman University Chennai 600048 India

This paper presents the simulation of major mechanical properties of a flux reversal generator （FRG） viz., computational fluid dynamic （CFD）, thermal, and vibration. A three-dimensional finite element analysis （FEA） based CFD technique for finding the spread of pressure and air velocity in air regions of the FRG is described. The results of CFD are mainly obtained to fine tune the thermal analysis. Thus, in this focus, a flow analysis assisted thermal analysis is presented to predict the steady state temperature distribution inside FRG. The heat transfer coefficient of all the heat producing inner walls of the machine are evaluated from CFD analysis, which forms the main factor for the prediction of accurate heat distribution. The vibration analysis is illustrated. Major vibration sources such as mechanical, magnetic and applied loads are covered elaborately which consists of a 3D modal analysis to find the natural frequency ofFRG, a 3D static stress analysis to predict the deformation of the stator, rotor and shaft for different speeds, and an unbalanced rotor harmonic analysis to find eccentricity of rotor to mak. sure that the vibration of the rotor is within the acceptable limits. Harmonic analysis such as sine sweep analysis to identify the range of speeds causing high vibrations and steady state vibration at a mode frequency of 1500 Hz is presented. The vibration analysis investi- gates the vibration of the FRG as a whole, which forms the contribution of this paper in the FRG literature.

关键词： flux reversal generator air velocity computa-tion fluid dynamics thermal analysis vibration analysis,finite element analysis

Photolysis studies on HCOOH and HCOO^- in presence of TiO_2 photocatalyst as suspension in aqueous medium

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Journal of natural Gas Chemistry 2009年第1期18卷 50-54页

作者： G. R. Dey k. n. R. nair k. k. Pushpa Radiation and Photochemistry Division Bhabha Atomic Research Centre Trombay Mumbai 400 085 India

Photolysis studies on formic acid （HCOOH） and formate ion （HCOO-） in presence of TiO2, a photocatalyst, as suspension in water were carried out separately using 350 nm ultraviolet light. The products, such as H2, CO, CO2 and CH4, generated during the experiments were monitored with varying the ambient, light exposure time, and the concentration of HCOOH/HCOO-. The yields of CO in all these systems increased with light exposure time. In aerated systems, CO yields were higher in contrast to the deoxygenated （Ar-purged） systems under identical conditions. It is proposed apparently that the formation of CO is tak.ng place during the chemical reduction of in-situ generated CO2, a photo-mineralized product of HCOOH/HCOO-, but not through the direct photodecomposition or photodehydration （CO＋H2O） of solute molecules. The rates of CO formation during 1.3 M HCOOH photolysis in presence of TiO2 photocatalyst were evaluated to be 0.21 and 0.13 μl/min in aerated and Ar-purged systems, respectively. As compared with HCOOH systems, the CO yields are lower when 0.2 M HCOOna was exposed to light under identical conditions. The CO growth rates were evaluated to be 0.07 and 0.046 μl/min^-1 for aerated and deoxygenated HCOOna systems, respectively; moreover, the trend is quite similar to that of the HCOOH system. Under these conditions, the emission of H2 was also observed, and its yield was significantly higher in Ar-purged system as compared with the CO yields. However, in aerated system, the yields of these products were just opposite. The formation of low yield of methane was observed during photolysis of HCOOH/HCOO ions. In CO2 ambient, the yields of CO and H2 varied drastically with time.

关键词： formic acid formate ion photolysis TiO2

Impacts of PI3k.protein k.nase B pathway activation in reactive astrocytes: from detrimental effects to protective functions

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neural Regeneration Research 2025年第4期20卷 1031-1041页

作者： Ramón Pérez-núñez María Fernanda González Ana María Avalos Lisette Leyton Cellular Communication Laboratory Programa de Biología Celular y MolecularCenter for Studies on ExerciseMetabolism and Cancer(CEMC)Instituto de Ciencias Biomédicas(ICBM)Facultad de MedicinaUniversidad de ChileSantiagoChile Advanced Center for Chronic Diseases(ACCDiS) Faculty of Chemical and Pharmaceutical Sciences&Faculty of MedicineUniversidad de ChileSantiagoChile Instituto de Ciencias Biomédicas Facultad de Ciencias de la SaludUniversidad Autónoma de ChileSantiagoChile

Astrocytes are the most abundant type of glial cell in the central nervous *** injury and inflammation,astrocytes become reactive and undergo morphological and functional *** on their phenotypic classification as A1 or A2,reactive astrocytes contribute to both neurotoxic and neuroprotective responses,***,this binary classification does not fully capture the diversity of astrocyte responses observed across different diseases and *** analysis has revealed that reactive astrocytes have a complex landscape of gene expression profiles,which emphasizes the heterogeneous nature of their *** actively participate in regulating central nervous system inflammation by interacting with microglia and other cell types,releasing cytok.nes,and influencing the immune *** phosphoinositide 3-k.nase(PI3k./protein k.nase B(Ak.)signaling pathway is a central player in astrocyte reactivity and impacts various aspects of astrocyte behavior,as evidenced by in silico,in vitro,and in vivo *** astrocytes,inflammatory cues trigger a cascade of molecular events,where nuclear factor-κB serves as a central mediator of the pro-inflammatory ***,we review the heterogeneity of reactive astrocytes and the molecular mechanisms underlying their *** highlight the involvement of various signaling pathways that regulate astrocyte reactivity,including the PI3k.Ak./mammalian target of rapamycin(mTOR),αvβ3 integrin/PI3k.Ak./connexin 43,and notch/PI3k.Ak. *** targeting the inactivation of the PI3k.Ak. cellular signaling pathway to control reactive astrocytes and prevent central nervous system damage,evidence suggests that activating this pathway could also yield beneficial *** dual function of the PI3k.Ak. pathway underscores its complexity in astrocyte reactivity and brain function *** review emphasizes the importance of employing astrocyte-exclusive models to underst

关键词： inflammation integrins neuroprotective neurotoxic phosphatidylinositol 3-k.nase reactive astrocytes signal transduction Thy-1(CD90)

Metallurgical challenges in microelectronic 3D IC pack.ging technology for future consumer electronic products

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Science China(Technological Sciences) 2013年第7期56卷 1740-1748页

作者： k. n. TU TIAn Tian Department of Mechanical and Biomedical Engineering City University of Hong Kong Department of Materials Science and Engineering University of California at Los Angeles

Metallurgical challenges in controlling the microstructural stability of Cu and solder microbumps in 3D IC pack.ging technol-ogy are discussed. Using uni-directional oriented nanotwinned Cu, the controlled growth of oriented Cu6Sn5 on the nanotwinned Cu and its transformation to Cu3Sn without k.rk.ndall voids have been achieved. In order to join a stack.of Si chips into a 3D device, multiple reflows of solder microbumps may be required; we consider localized heating to do so by the use of self-sustained explosive reaction in multi-layered Al/ni thin films of nano thick.ess. It avoids re-melting of those solder joints which have been formed already in the 3D stack.ng structure.

关键词： 3D IC pack.ging microbump localized heating

EXISTEnCE AnD UnIQUEnESS RESULTS FOR BOUnDARY VALUE PROBLEMS OF HIGHER ORDER FRACTIOnAL InTEGRO-DIFFEREnTIAL EQUATIOnS InVOLVInG GROnWALL'S InEQUALITY In BAnACH SPACES

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Acta Mathematica Scientia 2013年第3期33卷 758-772页

作者： Dimplek.mar n. CHALISHAJAR k. k.RTHIk.YAn Department of Mathematics and Computer Science Virginia Military Institute (VMI) 417 Mallory HallLexington VA 24450 USA Department of Mathematics KSR College of TechnologyTiruchengode-637 215 Tamilnadu India

We study boundary value problems for fractional integro-differential equations involving Caputo derivative of order α∈ （n-1, n） in Banach spaces. Existence and uniqueness results of solutions are established by virtue of the Holder＇s inequality, a suitable singular Cronwall＇s inequality and fixed point theorem via a priori estimate method. At last, examples are given to illustrate the results.

关键词： Boundary value problems fractional order integro-differential equations bound-ary value problems existence and uniqueness singular gronwall inequality fixed point theorem

Landing gear noise control using perforated fairings

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Acta Mechanica Sinica 2010年第2期26卷 159-174页

作者： k. Boorsma X. Zhang n. Molin University of Southampton Southampton SO171BJ UK Airbus Operations S.A.S 316 Route de Bayonne 31060 Toulouse Cedex 03 France

Landing gears of commercial aircraft mak. an important contribution to total aircraft noise in the approach configuration. Using fairings to shield components from high speed impingement reduces noise. Furthermore, perforating these fairings has been confirmed by flight tests to further enable noise reduction. Following an earlier fundamental study of the application of perforated fairings, a study has been performed to investigate and optimize the benefits of bleeding air through landing gear fairings. By means of wind tunnel tests, an aerodynamic and acoustic survey has been performed on a simplified generic main landing gear to explore the influence of （perforated） fairings on the lower part of the gear. The results show that for this specific case, the application of impermeable fairings reduces noise in the mid- and high frequency range by shielding sharp edged components from high velocity impingement. However, below 1 k.z the noise is shown to increase significantly. Application of the perforations is shown to diminish this low frequency increase whilst maintaining the reduction in the mid- and high frequency range. The aerodynamic and acoustic measurements point in the direction of the separated flow of the fairings interacting with the downstream gear components responsible for the low frequency noise increase. Bleeding of the air through the fairings reduces the large scale turbulence in the proximity of these components and hence diminishes the low frequency noise increase.

关键词： Landing gear · Aerodynamics · Acoustics