High temperature mechanical properties of thermal barrier coated superalloy applied to combustor liner of aero engines

High temperature load controlled fatigue, hot tensile and accelerated creep properties of thermal barrier coated (TBC) Superni C263 alloy used as a candidate material in combustor liner of aero engines are highlighted in this paper. Acoustic emission technique has been utilised to characterise the ductile-brittle transition teperature the bond coat. Results revealed that the DBTT (ductile to brittle transition temperature) of this bond coat is around 923 K, which is in close proximity to the value reported for CoCrAlY type of bond coat. Finite element technique, used for analysing the equivalent stresses in the bond coat well within the elastic limit, revealed the highest order of equivalent stress at 1073 K as the bond coat is ductile above 923 K. The endurance limit in fatigue and the life of TBC coated composite under accelerated creep conditions are substantially higher than those of the substrate material. Fractographic features at high stresses under fatigue showed intergranular cleavage whereas those at low stresses were transgranular and ductile in nature. Delamination of the bond coat and spallation of the TBC at high stresses during fatigue was evident. Unlike in the case of fatigue, the mode of fracture in the substrate at very high stresses was transgranular whereas that at low stresses was intergranular in creep.

Methyl ethyl ketone plus water plus secondary butyl alcohol: A potential system for the exploration of a quadruple critical point

We report preliminary experiments on the ternary-liquid mixture, methyl ethyl ketone (MEK)+water (W)+secondary butyl alcohol (sBA)-a promising system for the realization of the quadruple critical point (QCP). The unusual tunnel-shaped phase diagram shown by this system is characterized and visualized by us in the form of a prismatic phase diagram. Light-scattering experiments reveal that (MEK+W+sBA) shows near three-dimensional-Ising type of critical behavior near the lower critical solution temperatures, with the susceptibility exponent (gamma) in the range of 1.217 <=gamma <= 1.246. The correlation length amplitudes (xi(o)) and the critical exponent (nu) of the correlation length (xi) are in the ranges of 3.536 <=xi(o)<= 4.611 A and 0.619 <=nu <= 0.633, respectively. An analysis in terms of the effective susceptibility exponent (gamma(eff)) shows that the critical behavior is of the Ising type for MEK concentrations in the ranges of 0.1000 <= X <= 0.1250 and X >= 0.3000. But, for the intermediate range of 0.1750 <= X < 0.3000, the system shows a tendency towards mean-field type of critical behavior. The advantages of the system (MEK+W+sBA) over the system (3-methylpyridine+water+heavy water+potassium Iodide) for the realization of a QCP are outlined.

Critical behavior of the aqueous electrolytic system 3-methylpyridine+D2O+NaBr

The system 3-methylpyridine(3MP)+water(H2O)+NaBr has been the subject of an intense scientific debate since the work of Jacob [Phys. Rev. E. 58, 2188 (1988)] and Anisimov [Phys. Rev. Lett. 85, 2336 (2000)]. The crossover critical behavior of this system seemed to show remarkable sensitivity to the weight fraction (X) of the ionic impurity NaBr. In the range X <= 0.10 the system displayed Ising behavior and a pronounced crossover to mean-field behavior in the range 0.10 <= X <= 0.16. A complete mean-field behavior was observed at X=0.17, a result that was later attributed to the existence of long-living nonequilibrium states in this system [Kostko , Phys. Rev. E. 70, 026118 (2004)]. In this paper, we report the near-critical behavior of osmotic susceptibility in the isotopically related ternary system, 3MP+heavy water(D2O)+NaBr. Detailed light-scattering experiments performed at exactly the same NaBr concentrations as investigated by Jacob reveal that the system 3MP+D2O+NaBr shows a simple Ising-type critical behavior with gamma similar or equal to 1.24 and nu similar or equal to 0.63 over the entire NaBr concentration range 0 <= X <= 0.1900. The crossover behavior is predominantly nonmonotonic and is completed well outside the critical domain. An analysis in terms of the effective susceptibility exponent (gamma(eff)) reveals that the crossover behavior is nonmonotonic for 0 <= X <= 0.1793 and tends to become monotonic for X > 0.1793. The correlation length amplitude xi(o), has a value of similar or equal to 2 A for 0.0250 <= X <= 0.1900, whereas for X=0, xi(o)similar or equal to 3.179 A. Since isotopic H -> D substitution is not expected to change the critical behavior of the system, our results support the recent results obtained by Kostko [Phys. Rev. E. 70, 026118 (2004)] that 3MP+H2O+NaBr exhibits universal Ising-type critical behavior typical for other aqueous solutions.

A numerical study of laminar axisymmetric plumes due to the combined buoyancy of heat and mass diffusion

This paper presents the results of a computational study of laminar axisymmetric plumes generated by the simultaneous diffusion of thermal energy and chemical species. Species concentrations are assumed small. The plume is treated as a boundary layer. Boussinesq approximations are incorporated and the governing conservation equations of mass, momentum, energy and species are suitably non-dimensionalised. These equations are solved using one time-step-forward explicit finite-difference method. Upwind differencing is employed for convective terms. The results thus obtained are explained in terms of the basic physical mechanisms that govern these flows. They show many interesting aspects of the complex interaction of the two buoyant mechanisms.

Influence of crossed electric and quantizing magnetic fields on the Einstein relation in nonlinear optical, optoelectronic and related materials: Simplified theory, relative comparison and suggestion for experimental determination

An attempt is made to study the Einstein relation for the diffusivity-to-mobility ratio (DMR) under crossed fields' configuration in nonlinear optical materials on the basis of a newly formulated electron dispersion law by incorporating the crystal field in the Hamiltonian and including the anisotropies of the effective electron mass and the spin-orbit splitting constants within the framework of kp formalisms. The corresponding results for III-V, ternary and quaternary compounds form a special case of our generalized analysis. The DMR has also been investigated for II-VI and stressed materials on the basis of various appropriate dispersion relations. We have considered n-CdGeAs2, n-Hg1-xCdxTe, n-In1-xGaxAsyP1-y lattice matched to InP, p-CdS and stressed n-InSb materials as examples. The DMR also increases with increasing electric field and the natures of oscillations are totally band structure dependent with different numerical values. It has been observed that the DMR exhibits oscillatory dependences with inverse quantizing magnetic field and carrier degeneracy due to the Subhnikov-de Haas effect. An experimental method of determining the DMR for degenerate materials in the present case has been suggested. (C) 2010 Elsevier B.V. All rights reserved.

Chemical approaches to penicillin allergy—IV. Binding of carrier receptor protein with penicillin and its analogues

The availability of electrophoretically homogeneous rabbit penicillin carrier receptor protein (CRP) by affinity chromatography afforded an idealin vitro system to calculate the thermodynamic parameters of binding of penicillin and analogues with CRP as well as competitive binding of such analogues with CRP in presence of14C-penicillin G. The kinetics of association of CRP with 7-deoxy penicillin which does not bind covalently with CRP have been studied through equilibrium dialysis with14C-7-deoxybenzyl penicillin and found to be K=2·79×106M−1.−ΔG=8·106 k cal/mole as well as fluorescence quenching studies with exciter λ 280 K=3·573×106M−1,−ΔG=8·239 k cal/mole. The fluorescence quenching studies have been extended to CRP-benzyl penicillin and CRP-6-aminopenicillanic acid (6APA) systems also. The fluorescence data with benzyl penicillin indicate two conformational changes in CRP—a fast change corresponding to the non-covalent binding to CRP with 7-deoxy penicillin and a slower change due to covalent bond formation. With 6-APA the first change is not observed but the conformational change corresponding to covalent binding is only seen. Competitive binding studies indicate that the order of binding of CRP with the analogues of penicillin is as follows: methicillin > 6APA > carbenicillin >o-nitrobenzyl penicillin > cloxacillin ≈ benzyl penicillin ≈ 6-phenyl acetamido penicillanyl alcohol ≈ 7 phenyl acetamido desacetoxy cephalosporanic acid ≈p-amino benzyl penicillin ≈p-nitro benzyl penicillin > ticarcillin >o-amino benzyl penicillin > amoxycillin > 7-deoxy benzyl penicillin > ampicillin.From these data it has been possible to delineate partially the topology of the penicillin binding cleft of the CRP as well as some of the functional groups in the cleft responsible for the binding process.

Museoesineitä Itä-Karjalasta : Väinö Tuomaalan jatkosodan aikana keräämä esinekokoelma ja sen syntyhistoria

Jatkosodan aikana kerättiin Suomen valtaamalta alueelta Itä-Karjalasta tuhansittain museoesineitä Suomen museoihin. Kansallismuseon kokoelmiin kerättiin esineitä lähinnä suomenheimoisilta mutta myös isovenäläisiltä. Tämän tutkimuksen kohteena on lähes 400:n esineen kokoelma, joka toimitettiin Kansallismuseoon vuosina 1941 1944 ja merkittiin kansallisuudeltaan venäläiseksi. Näistä venäläisistä esineistä suurimman osan keräsi alikersanttina palvellut Väinö Tuomaala. Tutkimukseni tarkastelee Väinö Tuomaalan kokoelmaa ja etsii syitä siihen, miksi kokoelma on sellainen kuin se on, miksi se ja koko venäläisten esineiden kokoelma syntyi ja mitkä seikat vaikuttivat Tuomaalan esinevalintoihin. Tutkimuksen teoria rakentuu museologisen kirjallisuuden varaan. Tutkimuksessa tarkastellaan Väinö Tuomaalan kokoelman keräyskonteksteja. Keräyskonteksteihin kuuluvat kokoelman kerääjä, keräysajankohta ja -paikka sekä yhteenkuuluvat esineet, eli muut venäläiset esineet. Kerääjän tarkastelussa huomioidaan hänen henkilöhistoriansa ja etsitään mahdollisia keruuseen vaikuttaneita tekijöitä. Keräysajankohdan tarkastelussa huomio kiinnittyy keruuympäristöön, eli vallitseviin olosuhteisiin ja aatteelliseen ilmapiiriin, joiden vaikutuksen alaisena keruu suoritettiin. Primääriaineisto koostuu Kansallismuseon alaisen Kulttuurien museon yleisetnografisten esineiden kokoelmaan kuuluvista 198:sta Väinö Tuomaalan keräämästä esineestä verifikaatteineen, jotka ovat osa 393 esinettä käsittävästä venäläisestä kokoelmasta. Aineisto sisältää myös eri arkistojen materiaalia. Kansallisarkiston Sörnäisten toimipisteestä, entisestä sota-arkistota, löytyneitä sotapäiväkirjoja ja Tuomaalan kantakorttia on tutkimuksessa käytetty jatkosodan tapahtumien esittämiseen. Museoviraston hallinto-osaston arkiston kirjeet ja pöytäkirjat ovat antaneet tietoa kulttuurikeruun organisoinnista. Väinö Tuomaalan arkistokokoelma Seinäjoella sisältää Tuomaalan keräämää perinneaineistoa, hänen puheitaan, lehtikirjoituksiaan ja kirjeenvaihtoaan. Myös Evijärven kunnantalon kotiseutuarkistosta löytyneet kirjeet ovat valottaneet Tuomaalan jatkosodan aikaista keruutoimintaa. Suomalaisen Kirjallisuuden Seuran arkistot ovat tarjonneet materiaalia jatkosodan aikaisesta kulttuurikeruusta. Koko venäläisten esineiden kokoelma syntyi sattumalta ja organisoimattoman toiminnan tuloksena, jossa aktiivisia toimijoita olivat yksittäiset kerääjät. Intohimoisesta suhtautumisesta kansatieteellistä keruuta kohtaan johtuen, Tuomaala olisi todenäköisesti kerännyt museoesineitä missä päin Itä-Karjalaa tahansa. Väinö Tuomaalan Itä-Karjalassa keräämä esinekokoelma oli luonnollinen jatke hänen kotiseudullaan aloittamalleen keräystoiminnalle. Tuomaalan jatkosodan aikana keräämä kokoelma on kerääjän mieltymysten mukainen yritys kerätä vanhaa itäkarjalaista, kansallista talonpoikaiskulttuuria. Tuomaala pyrki keräämään klassista kansatieteellistä aineistoa monipuolisesti kansankulttuurin eri elämänalueilta. Tuomaalan esinekeruussa näkyi vahvasti talonpoikaiskulttuurin ihannointi ja halu pelastaa osa siitä tuleville sukupolville. Yrityksen onnistumiseen vaikuttivat sodanajan olosuhteet sekä aatteellinen ilmapiiri. Esineiden saatavuudella oli merkittävä osa kokoelman muodostumiseen, samoin Tuomaalan käsityksillä heimokansoista, Suur-Suomesta ja venäläisistä. Keruuvalintoihin ja keruun jatkumiseen vaikuttivat myös Kansallismuseon henkilökunta ja työstä saatu tunnustus.

Interruptions of (CG)n sequences by GG, TG and CA need not prevent B to Z transition in solution

Oligonucleotides containing alternating purines-pyrimidines with AT base pairs have been shown to exist in the Z-form preferably in solid state. We report that oligodeoxyribonucleotides with GG, TG and CA interruptions in their alternating CG sequences can undergo B to Z transition in solution in the absence of any chemical modification or topological constraint. The sequences, d(CGCGCGGCGCGC) and d(CGTGCGCACG) have been synthesised and shown to adopt Z- conformation in presence of millimolar concentrations of Ni2+ under low water activity conditions. Significance of GG, TG and CA interruptions in the B to Z transition is discussed.

Study of the random vibration of nonlinear systems by the Gaussian closure technique

A technique is developed to study random vibration of nonlinear systems. The method is based on the assumption that the joint probability density function of the response variables and input variables is Gaussian. It is shown that this method is more general than the statistical linearization technique in that it can handle non-Gaussian excitations and amplitude-limited responses. As an example a bilinear hysteretic system under white noise excitation is analyzed. The prediction of various response statistics by this technique is in good agreement with other available results.