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Series solutions of stagnation slip flow and heat transfer by the homotopy analysis method

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Science China(Physics,Mechanics & Astronomy) 2009年第6期52卷 893-899页

作者： R.n.MOHAPATRA k.VAJRAVELU Department of Mathematics University of Central Florida

An analytical approximation for the similarity solutions of the two-and three-dimensional stagnation slip flow and heat transfer is obtained by using the homotopy analysis method. This method is a series expansion method, but it is different from the perturbation technique, because it is independent of small physical parameters at all. Instead, it is based on a continuous mapping in topology so that it is applicable for not only weakly but also strongly nonlinear flow phenomena. Convergent [m,m] homotopy Padé approximants are obtained and compared with the numerical results and the asymptotic approximations. It is found that the homotopy Padé approximants agree well with the numerical results. The effects of the slip length and the thermal slip constant β on the heat transfer characteristics are investigated and discussed.

关键词： stagnation slip flow navier boundary condition nano-fluidics heat transfer homotopy analysis method

Effect of dysprosium substitution on structural and dielectric properties of BiFeO_3-PbTiO_3 multiferroic composites

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Journal of Rare Earths 2015年第6期33卷 639-646页

作者： n.k.Mohanty A.k.Behera S.k.Satpathy Banarji Behera P.nayak Materials Research Laboratory School of Physics Sambalpur University

0.5BiDyxFe1-xO3-0.5PbTiOa（0.5BDxF1-x-0.5PT）（x=0.00, 0.05, 0.10, 0.15, 0.20） multiferroic composites were pre- pared by conventional solid state reaction method. Structural characterization was performed by X-ray diffraction and the mate- rials showed tetragonal structure at room temperature. Surface morphology of the composites was studied by a scanning electron microscope （SEM）. Frequency and temperature dependence of dielectric constant （er） and dielectric loss （tan~） of 0.5BDxF1_x- 0.5PT were measured in a wide range of frequency （100 Hz to 1 MHz） and temperature （25 to 400 ~C）. The analysis of the study showed that the er and tang decreased with increasing frequency in the given range for all the samples which could be explained through the occurrence of dipole relaxation process. The effect of substitution of rare earth element dysprosium （Dy） showed increase in er in all the samples prepared for different concentrations from 0.00 to 0.20. An explanation for high value of er for Dy modified 0.5BiFeO3-0.5PbTiO3 （0.5BF-0.5PT） compared to Gd modified 0.5BF-0.5PT was provided. The variation of AC conductivity with inverse temperature found to obey the Arrhenius equation and the composites showed negative temperature coefficient of resistance （nTCR） behavior. The activation energy was found to be in the range from 0.25 to 0.40 eV for all the studied samples.

关键词： X-ray diffraction dielectric constant tangent loss activation energy rare earths

Comparative study on glutathione transferases of rat brain and testis under the stress of phenobarbitol and β-methylcholanthrene

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Journal of Zhejiang University-Science B(Biomedicine & Biotechnology) 2005年第8期6卷 759-769页

作者： THYAGARAJU k HEMAVATHI B VASUnDHARA k RAO A.D DEVI k.n Department of Biochemistry Sri Venkateswara UniversityTirupati 517 502 AP IndiaDepartment of Biochemistry Sri Venkateswara UniversityTirupati 517 502 AP IndiaDepartment of Biochemistry Sri Venkateswara UniversityTirupati 517 502 AP IndiaDepartment of Biochemistry Sri Venkateswara UniversityTirupati 517 502 AP IndiaDepartment of Biochemistry Sri Venkateswara UniversityTirupati 517 502 AP India

A comparative study was made on the tissue specific expression of glutathione transferases (GST) in brain and testis after exposure of rat to phenobarbitol (PB) and β-methylcholanthrene (MC). Glutathione transferases, a family of multifunctional proteins are involved in intracellular transport processes and in detoxication of electrophilic xenobiotics by catalyzing reactions such as conjugation, isomerization, reduction and thiolysis. On purification, the yield of GST proteins by affinity chromatography was 39% in testis and 32% in brain. The affinity purified testis GSTs were resolved by chromatofocusing into six anionic and four cationic isozymes, and in brain glutathione transferases were resolved into four anionic and three cationic isozymes, suggesting the presence of multiple isozymes with Yc, Yb, Yβ and Yδ in both of them. In testis and brain, these isozymes at identical pI values showed variable functions with a battery of substrates and the cationic isozymes of brain and testis showed identical properties in CHP (cumene hydroperoxide) at pH values of above 7.0. Substrate specificity studies and immunoblot analysis of testis and brain proteins revealed that they play a predominant role in the detoxication of phenobarbitol or β-methylcholanthrene. Expression of the isozymes in testis and brain on exposure to PB and MC indicated elevated subunit variation. In both testis and brain, Yδ of π class was expressed on PB treatment and Yc of α class and Yβ of μ class was expressed in MC treated testis and only Yc was predominantly expressed in MC treated brain. Thus these subunits expression is considered as markers for carcinogenesis and specific to chemical toxicity under phenobarbitol and β-methylcholanthrene stress.

关键词： Glutathione transferases Testis Brain Phenobarbitol β-Methylcholanthrene

Rapid dehydration of grape berries dampens the post-ripening transcriptomic program and the metabolite profile evolution

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Horticulture Research 2020年第1期7卷 1016-1030页

作者： Sara Zenoni Alessandra amato Erica D’Incà Flavia Guzzo Giovanni Battista Tornielli Department of Biotechnology University of VeronaStrada Le Grazie 1537134 VeronaItaly

The postharvest dehydration of grape berries allows the concentration of sugars and other solutes and promotes the synthesis of metabolites and aroma compounds unique to high-quality raisin wines such as the passito wines made in *** dynamic changes are dependent on environmental parameters such as temperature and relative humidity,as well as endogenous factors such as berry morphology and genotype,but the contribution of each variable is not well ***,we compared berries subjected to natural or accelerated dehydration,the latter driven by forced air *** followed the evolution of transcript and metabolite profiles and found that accelerated dehydration clearly dampened the natural transcriptomic and metabolomic programs of postharvest *** found that slow dehydration over a prolonged duration is necessary to induce gene expression and metabolite accumulation associated with the final quality traits of dehydrated *** accumulation of key metabolites(particularly stilbenoids)during postharvest dehydration is inhibited by rapid dehydration conditions that shorten the berry life time.

关键词： flow dehydration latter

Synthesis of CaWO_4:Eu^(3+) phosphor powders via ethylene glycol route and its optical properties

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Journal of Rare Earths 2012年第4期30卷 310-314页

作者： k.Gayatri Sharma n.Rajmuhon Singh Department of Chemistry Manipur University Canchipur-795003 Imphal Manipur India

Eu3＋ doped CaWO4 with tetragonal system were prepared at comparatively low temperature （125 ℃） in ethylene glycol medium. The phosphor was further investigated by X-ray difffactometer （XRD）, photoluminescence spectrophotometer （PL）, Fourier transform infra red （FT-IR） spectroscopy and transmission electron microscopy （TEM）. XRD analysis indicated a decrease in the unit cell volume of CaWO4 with increasing Eu3＋ ion concentration. It indicated the homogeneous substitution of Ca2＋ ions in CaWO4 by the Eu3＋ ions. TEM images showed that the particle size ranged from 20 to 200 nm and it could extend the application of the nanoparticles. The photoluminescence study showed that the intensity of electric dipole transition （SD0→TF2） at 614 nm dominated over the magnetic dipole transition （SD0→TFx） at 592 nm. The optimum concentration of Eu3＋ for the highest luminescence was found to be 20 at.%. The as prepared samples were found to be dispersible in water and methanol.

关键词： CaWO4:Eu3+ capping agent photoluminescence dispersible rare earths

The dynamics of a nanosecond gas discharge development with an extended slot cathode in argon

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Plasma Science and Technology 2020年第12期22卷 78-88页

作者： n A ASHURBEkOV k O IMInOV G S SHAkHSInOV M Z ZAkARYAEVA k M RABADAnOV Dagestan State University Faculty of PhysicsMakhachkala 367000Russia Institute of Physics DFRC of RASMakhachkala 367015Russia

The article presents the results of an experimental study and numerical modelling for the formation and development dynamics of a high-voltage transverse nanosecond discharge generated by a slot cathode in an argon medium at a pressure range of 1–10 Torr. numerical modelling was carried out under similar experimental conditions for the processes of formation and propagation of ionisation waves, electron density distribution, excited atom and average electron energy in the discharge gap, including the cavity inside the cathode. At a pressure of p=1 Torr, a classical version of a high-voltage discharge is demonstrated to take place with no penetration of the plasma into the cathode cavity and no observed hollow cathode effect. An increase in gas pressure to 5 Torr leads to a penetration of plasma into the cathode cavity with the formation of a cathodic potential drop(CPD) region. Electrons emitted from the side surfaces of the cavity pass through the CPD region without collisions, oscillate inside the cathode cavity;the hollow cathode effect is fully manifested. At р=10 Torr, the modelling results qualitatively coincide with the results at р=5 Torr;in this case, however, hardly any accelerated electrons are observed in the gap between the electrodes, due to their energetic relaxation both inside the cathode cavity and when exiting from it. In both cases, the plasma structure formed at the exit of the cathode cavity involves a concentration of charged particles an order of magnitude higher than that in the rest of the gap, leading to a self-limiting discharge current effect. The results of the numerical modelling are in good agreement with experimental data.

关键词： nanosecond gas discharge numerical simulation argon excited atoms

Effect of Prior Austenite Grain Size on the Morphology and Mechanical Properties of Martensite in Medium Carbon Steel

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Journal of Materials Science & Technology 2012年第5期28卷 461-466页

作者： Y.Prawoto n.Jasmawati k.Sumeru Faculty of Mechanical Engineering Universiti Teknologi Malaysia81310 UTMSkudaiJohor 81310Malaysia Dept.of Refrigeration and Air Conditioning Engineering Politeknik Negeri BandungIndonesia

In industrial application,unintentional manufacturing line troubles often consequence in heating raw materials excessively,in terms of either time or *** of the effects of such occurrence is a product with a variation of prior austenite grain size,even if after the heat treatment the end result is the same,*** variation of the prior austenite grain size is believed to vary the end results of the *** undesirable variation includes the variation of fatigue resistance,impact strength,yield strength,hardness,*** research studies the effect of the prior austenite grain size on the morphology of the martensite *** results show that within the typical industrial application of temperature and holding time set up,as holding time or the temperature increases,the prior austenite average diameter *** block and packet sizes in the martensite also *** variation of mechanical property dependence on the grain size is indeed due to the different characteristics reflected in the martensite *** respect to the same area,smaller grain has more blocks and packets,which agrees with higher dislocation density verified with transmission electron microscopic evaluation.

关键词： Heat treating Mechanical testing Carbon/alloy steels

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 make 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 kHz 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

natures of Rotating Stall Cell in a Diagonal Flow Fan

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Journal of Thermal Science 2005年第1期14卷 9-14页

作者： n.SHIOMI k.kAnEkO T.SETOGUCHI Department of Mechanical Engineering Saga University Saga 840-8502JapanDepartment of Mechanical Engineering Saga UniversitySaga 840-8502JapanDepartment of Mechanical Engineering Saga UniversitySaga 840-8502Japan

In order to clarify the natures of a rotating stall cell, the experimental investigation was carried out in a high specific-speed diagonal flow fan. The pressure field on the casing wall and the velocity fields at the rotor inlet and outlet were measured under rotating stall condition with a fast response pressure transducer and a single slant hot-wire probe, respectively. The data were processed using the “Double Phase-Locked Averaging (DPLA)”technique, which enabled to obtain the unsteady flow field with a rotating stall cell in the relative co-ordinate system fixed to the rotor. As a result, the structure and behavior of the rotating stall cell in a high specific-speed diagonal flow fan were shown.

关键词： rotating stall cell diagonal flow fan unsteady flow DPLA technique.