Model of grain-boundary self-diffusion in α- and β-phases of titanium and zirconium

A model of the grain-boundary self-diffusion process in metals undergoing phase transitions in the solid state is proposed. The model is based on the ideas and approaches of the theory of nonequilibrium grain boundaries. It is shown that the range of application of basic relations of this theory can be extended, and they can be used to calculate the parameters of grain-boundary self-diffusion in high-temperature and low-temperature phases of metals with phase transition. Based on the constructed model, activation energies of grainboundary self-diffusion in titanium and zirconium are calculated, and their anomalously low values in the low-temperature phase are explained. The calculated activation energies of grain-boundary self-diffusion are in good agreement with experimental data.     

Piezoelectric relaxations in homopolymers and copolymers of γ-Benzyl-L-glutamate and L-Leueine

The temperature dependence of the piezoelectric stress-constant, the piezoelectric strain-constant, and the Young's elastic constant is simultaneously determined for homopolymers and copolymers of γ-benzyl-L-glutamate [Glu(OBz)] and L-leucine (Leu). With the rise of temperature, the piezoelectric constants first increase due to the elastic relaxation in the Leu side chains (about ?150°C) and the Glu(OBz) side chains (about ?10°C), and then decrease due to the dielectric relaxation in the Glu(OBz) side chains. Higher piezoelectric constants are observed for the copolymers at low temperatures. This suggests that the shear-induced internal strain of the peptide dipoles is enhanced by heterogenity in the structure of side chains.     

Analysis and implementation of theFMLMS algorithm in AANC

I.IntroductionInthefieldofnoisecontrol,whenthecharacteristicsofthenoisesourcevary,theAANCsystemcanadaptivelyadjustthecontrollerofthecancellingsystemtoachievetheoptimal'complexstrengthofthesecondarysourceandconsequentlyensurethatthenoisecontrolsystemcanworkattheoptimalstatusfrombeginningtoend.So,thetechniqueoftheAANChasbeenappliedtoalmostallofthe3-Dspatialactivenoisecontrol.'ThealgorithmhastakenanimportantroleintheAANC.OneofthemainalgorithmsusedintheAANCistheFiltered-XLMS(FLMS)algori…     

Measurement and correction of coupling in BEPCⅡ

The existing linear coupling theory and representation method are introduced briefly. The so-called local and global coupling is discussed in more detail. The vertical orbit distortion excited by a horizontal corrector is represented with the coupling parameters at the corrector and the observation point. The formula is used to measure the coupling in BEPCⅡ. In order to correct the coupling, vertical correctors are used to change the vertical orbit through sextupoles by a least square method. We also introduce and review other frequently used coupling measurement/tuning methods used in our machine.     

Diffusion of chromium and manganese in γ-TiAl

The γ-TiAl intermetallic compound with suitable alloying additions has shown considerable promise as a material for high-temperature applications. Diffusion studies in this alloy system are useful in assessment of their creep behaviour and structural stability in service conditions. Tracer diffusion coefficients of ⁵¹Cr and ⁵⁴Mn in a γ-TiAl intermetallic compound containing 54.1 at. % aluminium were determined in the temperature range from 1095 to 1470?K. The temperature dependence of both the diffusing species follows a linear Arrhenius behaviour and can be expressed as D _Cr?=?4.4?×?10^?3exp(?350?kJ?mol^?1/RT)?m^2?s^?1 and D _Mn?=?1.2?×?10^?3?×exp(?326?kJ?mol^?1/RT)?m^2?s^?1. The data are analysed on the basis of empirical correlations between the diffusion and melting parameters applicable for conventional mono-vacancy diffusion mechanism in metals. It is concluded that impurity diffusion in γ-TiAl occurs through the migration of thermal vacancies via nearest-neighbour or next-nearest neighbour jumps.     

Free-field attenuation of earmuffs and earplugs both singly and in combination

I.IntroductionExposuretoenvironmcnta1noisc1cadstoannoyanceande1evationofhearingthrcsho1d.Itisnotpracticetoiso1atesuchthcsenoiscsbyengineeringmethods.Analternativecommonlypractica1andinexpcnsivemethodforhcaringprotectionisthcuseofhcaringprotcctivedcvicespePDs)suchasearplugsandearmuffe.AsdcfinedbyBcrgcr['lthatthenoisereductionpro-videdbyHPDispopu1ar1yrefcrredtoasitsattenuation.InfaCtoricsandindustrialplaceswhcretheworkersareexposedtohazardousnoisc,thcattcnuationofsing1ehearingprotectordevice…     

Nonlinear σ-models and their gauging in and out of superspace

We analyze and generalize bosonic nonlinear σ-models and their N = 1,2 supersymmetric extensions in (4 spacetime-dimensional) N = 1 superspace. We give a general construction of nonminimal kinetic terms for gauge fields and of N = 1,2 gauging of isometries on Kähler and hyper-Kähler manifolds. In particular, we study the gauging of noncompact groups. We derive the complete component action and supertrace formula. For N = 2 models, the supertrace always vanishes.     

Diffusion coefficients of sodium dodecylsulfate in aqueous solutions and in aqueous solutions of β-cyclodextrin

Differential diffusion coefficients have been measured of sodium dodecylsulfate (SDS) in aqueous solutions of β-cyclodextrin (β-CD) at 298.15 K over the concentration range 0.001 M to 0.0817 M using a conductimetric cell and an automatic apparatus to follow the diffusion. The cell uses an open ended capillary method, while a conductimetric technique is used to follow the diffusion process by measuring the resistance of a solution inside the capillaries, at various recorded times. The β-CD is known to for strong 1:1 complexes with SDS, and the effect of this on the diffusion of this electrolyte was investigated. The presence of β-cyclodextrin can influence the diffusion coefficients of sodium dodecylsulfate both above and below the critical micelle concentration (cmc) of this surfactant. For concentrations of β-cyclodextrin of 0.001 mol dm⁻³ the behaviour of the diffusion of SDS in aqueous solutions is the same in the absence or the presence of β-cyclodextrin. In contrast, when the β-CD concentration is 0.016 mol dm⁻³ we obtain diffusion coefficients higher than those obtained in aqueous solutions. Further, we do not observe the dramatic decrease in diffusion normally found at the cmc of the surfactant. These results are interpreted in terms of the effect of incorporation of dodecylsulfate chains inside the cyclodextrin cavities.     

Hadro- and photo-production of η′ in quasi-free proton and neutron processes

The η′ photoproduction process on quasi-free proton and neutron and the reaction NN→ η′NN are investigated within a relativistic effective Lagrangian approach to hadronic interactions. Resonances with spins 1/2 and 3/2 are considered together with the nucleonic and t-channel meson-exchange current contributions. In photoproduction processes, the S11 resonance is found to be responsible for the sharp rise of the cross sections near threshold. In pp → η′pp, it is found that the S11 resonance dominates the total cross section over the entire energy region considered. The spin observables, in particular the beam and target asymmetries, are shown to be very sensitive to the reaction mechanism and will help impose more stringent constraints on the model parameters.     

Formation of Vegetation Patterns and Hysteresis Phenomena in Arid and Semiarid Zones

Considering the spatial effect of the complicated interactions between plant and resource （soil water） and the stochastic character of the complicated ecological processes in an ecosystem, we introduce a lattice gas model to investigate the vegetation pattern formation in the arid and the semiarid ecosystems with Monte Carlo sim- ulations. With consistency of some previous mean-field models, the model reproduces a wide range of patterns observed in the arid and the semiarid regions. The sequences of vegetation states are also investigated with scanning three parameters, i.e., the precipitation and the plant growth rate, and then the parameter ranges are identified where a hysteresis loop appears and two different stable states coexist. The simulation results denote that the complex structures occur only when the precipitation parameter decreases. Moreover, based on the model, it is found that an increase of the competition of the plant for the resource along the slope direction results in the regular stripes parallel to the hill＇s contours. The model provides an interesting mechanism to understand the formation of the other regular vegetation stripe in a limited resource condition.     

Widths in the conversion of Σ and Ξ hyperons in nuclear matter

The widths of the conversion processes N, N in nuclear mattter were calculated based on the model of single-boson exchange. It was established that the conversion width for is significantly reduced by the interference of the contributions of separate mesons to the conversion amplitude. The conversion width obtained for in nuclear matter turned out to be less than 1 MeV.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 3, pp. 79–84, March, 1988.     

Miscibility and Molecular Orientation of Carbazole in Mixed Langmuir and Langmuir-Blodgett Films

We report the miscibility and molecular orientation of carbazole （CA） molecules in the mixed Langmuir and Langmuir-Blodgett （LB） films of CA in polymethyl methacrylate （PMMA） and stearic acid （SA） matrices. The lr-A isotherm confirms the formation of stable Langmuir films of CA mixed with either PMMA or SA at airwater interface. ＇Characteristics of area per molecule versus molefraction and collapse pressure versus molefraction reveal complete demixing of CA and the matrix PMMA/SA molecules in the mixed films. Absorption spectroscopy certainly confirms the fact that CA molecules have preferred orientation on the substrate of the LB films.     

HMO model of scalar field in medium and self-focusing

In this paper, the HMO model of scalar field in medium is presented using the general covariant classical theory of scalar field in medium, which is regarded as a curved space-time represented by optical metric model (OMM) and the case of self-focusing is discussed.     

Bifurcations and observation of strange attractor in He-Ne lasers

We report the experimental observation of deterministic chaos in an He-Ne laserat 0.6328μm by varying the discharge current.Strange attractor of laser system in the recon-structed phase-space picture has been obtained.The mechanism of the phenomena was dis-cussed.     

Inclusive production of baryons in decays of the γ (9.46) and in quark jets

Inclusive Production of mesons and baryons in quark jets at \(\sqrt s = 9.5 \ldots 36GeV\) and in decays of the γ(9.46) meson has been studied using the Quark Recombination Model (QRM). The model predictions for quark jets agree with data. The QRM-simulation of three-gluon decays of the γ(9.46) shows an enhancement of the inclusive baryon rate, as was observed recently by the DASP II experiment.     

Electronic band structure and effective masses of electrons and holes in the α and β phases of silicon nitride

The electronic band structure of the two main crystallographic modifications of silicon nitride, namely, the α-Si₃N₄ and β-Si₃N₄ phases, is calculated from the first principles. The estimates obtained for the effective charges of silicon and nitrogen atoms and those for the effective masses of electrons and holes in the α-Si₃N₄ phase are in good agreement with the available experimental data for amorphous silicon nitride a-Si₃N₄. The calculations performed demonstrate that the effective mass tensor determined for the β-Si₃N₄ phase differs substantially from the effective mass tensor obtained for the α-Si₃N₄ phase.     

Conservation of Hydrophobic and Hydrophilic Residues in Four-Helix Bundle

The conservation of the hydrophobic and the hydrophilic residue sites obtained from 1000 designed sequences with the Z-score method for a four-helix bundle has been studied. The folding dynamic and thermodynamic features of the designed sequences and their different mutations are also studied. It is found that this conservation is related to the stability and the fast folding of the model proteins. Our results are consistent with the experimental results.     

The Research of Scattering Cross-Section and Energy-Extraction in FEL

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Modeling of nanoparticles’ aggregation and sedimentation in nanofluid

The aggregation and sedimentation of nanoparticles in nanofluid have significant influences on the stability and applicability of nanofluids. The objective of this study is to propose a model to predict the nanoparticles’ aggregation and sedimentation characteristics. The characteristics are evaluated by the concentration of nanoparticles in nanofluid at different time. The concentration of nanoparticles can be calculated according to the speed and location of each nanoparticle. Then, the speed and location of each nanoparticle can be yielded when the forces on each nanoparticle are determined. For the forces on nanoparticles are related to the space structure of nanoparticle clusters, the clusters’ space structures are simulated. Case study shows that the mean deviation of predicted nanoparticle concentration from experimental data for Fullerence + H₂O, Fullerence + Oil and CuO + Oil nanofluids are 25%, 16% and 13%, respectively. The model can provide quantitative prediction of the aggregation and sedimentation characteristics of nanoparticles in nanofluid.