Effect of misfit strain on the electrocaloric effect of polydomain epitaxial ferroelectric thin films

The effect of misfit strain on the electrocaloric effect in polydomain epitaxial BaTiO 3 thin films at room temperature is investigated using the Ginzburg-Landau-Devonshire thermodynamic theory. Numerical calculations indicate that the misfit strain has a large impact on the ferroelectric polarization states and the electrocaloric effect. Most importantly, the electrocaloric effect in the polydomain ca 1 /ca 2 /ca 1 /ca 2 phase is much larger than that in the monodomain c phase and the other polydomain phases. Consequently, a large electrocaloric effect can be obtained by carefully controlling the misfit strain, which may provide potential applications in refrigeration devices.     

Hydrothermal reactions of simple molecules by real-time infrared spectroscopy

Abstract

The relative roles of the materials of construction of the reactor (stainless steel or titanium) and the effects of Group 1 cations are discussed in terms of their effect on the rate of decarboxylation of acetic acid derivatives, RCO₂H. Past work indicates that the reaction container composition has a very large effect when R is CH3—. A smaller but significant effect is seen when R is electron neutral (i.e., R=H). When R is electron Withdrawing the rate depends less on the reactor type than the nature of R. The effect of the counter ion M on the rate of decarboxylation of monovalent malonate salts, HC&CHzC02M, is discussed for M=Li⁺, Na⁺, K⁺, Rb⁺, and Cs⁺. The rate generally increases with the ionic radius except that the Rb⁺ salt exhibits the fastest rate. Preliminary explanations are given.     

Solubility of gases in uniaxially strained crystals

The solubility of gases in uniformly strained bcc crystals is calculated. As a result of straining, interstices occupied by interstitial atoms become nonequivalent and the temperature dependence of the solubility changes. The effect of deformation depends substantially on the sign of energy of interaction v _AC between dissolved atoms and host-crystal atoms. For elastic uniaxial tension, the solubility decreases linearly with strain at v _AC >0; at v _AC <0, it increases with strain. The amount of this effect is 1–10%. The effect of complexes consisting of two nearest dissolved atoms is studied. Conditions at which the role of the complexes is substantial are found. The complexes increase the solubility and change its dependence on the gas pressure.     

The influence of adsorbed molecules on Na-sites in NaY zeolite investigated by triple-quantum MAS NMR spectroscopy

The effect of hydration and benzene adsorption on resonance and the quadrupolar interaction in NaY zeolites is studied by triple-quantum MAS NMR spectroscopy. In the case of a C₆D₆/NaY system, the results show that with an increase in benzene loading, there is an up-field trend in isotropic chemical shift (δ_CS) and a decreasing second order quadrupolar effect (χ_s) for the site II sodium ions. It was found that adsorbed benzene molecules have a slight effect on the environment of sodium ions on site I. All the sodium sites in NaY are influenced upon hydration. The up-field shift of the sodium δ_CS reflects the effect of coordination of oxygen atoms on sodium cations due to hydration. The magnitude of χ_s for hydrated sodium sites increases and then falls off with water loading. The increase in χ_s is due to the initial hydration among SI-, SI′- and SII-sodium ions, while the decrease is the result of approaching the final stage of saturated hydration.     

Study of J-T effect on the self-energy of electrons in manganite systems

We present here a theoretical study of the effect of Jahn-Teller(J-T) distortion on the self-energy of electrons in the CMR manganites. The model consists of the itinerant e _g electrons distorted by J-T effect and the localized t _2g core electrons carrying strong ferromagnetism due to Hund’s rule. The phonon interacts with the e _g electrons as well as the J-T distorted e _g band. The electron Green’s functions are calculated by Zubarev’s technique. The electron self-energy which carries all the information of the model is calculated from the Green’s function. The effect of J-T distortion, magnetism on the frequency and temperature dependent dynamic self-energy is presented in this paper. The results are discussed.     

Influence of the transfer reactions on p + <Superscript>6</Superscript>He elastic scattering

We have studied an effect of neutron and triton transfer reactions on the p +^6He elasticscatteringat25 MeVbymeansofcoupled - reaction - channelcalculations.Itisfoundthatwhenthetransferreactionsareexplicitlyincludedinthecalculationstheimaginarypartoftheinput$p + $⁶He optical model potential has to be reduced by 52 percent while its real part enhanced by 15 percent in order to fit the elastic-scattering data. The effect of transfer channels on the real part of this potential is somewhat weaker than that of ⁶He breakup reported previously. However, for the imaginary part, the effect of transfer channels is dominant. It is concluded that while the breakup contribution to proton elastic scattering mainly affects the real part of the bare potential, the contribution of transfer channels affects mainly its imaginary part.     

Effect of ordering on the volume change and the shape memory effect in a Fe3Pt alloy during martensitic transformation

The effect of heat treatment on the volume effect ΔV/V and the shape recovery during the martensitic transformation in a Fe-24 at % Pt alloy is studied. An increase in the annealing time from 0 to 300 min at 650°C is found to decrease ΔV/V gradually from 1.26% for the quenched state to 0.987% for τ = 300 min. The characteristic temperatures of the martensitic transformation decrease and the transformation hysteresis passes through a minimum. The shape memory effect in heat-treated samples reaches 100% after gT = 40 min.     

Influence of scattering on the anisotropy of relaxation time in indium alloys

The low field Hall effect in indium at low temperatures is very sensitive to the kind of scatterers introduced. In the presence of small angle dislocation scattering, the Hall coefficientR ₀ is positive, while diffuse scattering such as that caused by boundary scattering leads to a negative value forR ₀. Data taken on alloys of indium with Ga, Tl, Pb, Sn, Hg, Cd and Bi will be analyzed by comparing them with the dislocation and size effect and by interpreting the differential cross sections of these scatterers in term of their effect onR ₀. The behaviour ofR ₀ of these alloys in function of temperature is also described.     

The effect of substrate material on the properties of tantalum oxide films

The effect of substrate material on the electrical characteristics of Ta _x O _y films produced by high-frequency magnetron sputtering of a tantalum oxide target is studied. The effect of oxygen plasma on leakage currents, dielectric permittivity, and dielectric dissipation factor of thin (300–400 nm) Ta _x O _y layers is found. It is proposed to process tantalum oxide films in oxygen plasma to control their electrical and dielectric properties.     

Production of CP-even and CP-odd Higgs bosons at muon colliders

In the s-channel Higgs-boson exchange processes, the interference between the amplitudes for CP-even and CP-odd Higgs bosons is sizable, if the helicities of the initial and final particles are properly fixed and if the mass difference between these bosons is not much larger than their decay widths. We discuss this interference effect in the process . Examining the effect gives us information on the CP-parity for the Higgs bosons and on the sign of the product of the coupling constants for the and vertices. The feasibility of observing the interference effect in future muon colliders is evaluated in the framework of the minimal supersymmetric extension of the standard model as an example.     

金属氧化物半导体场效应管热载流子退化的1/fγ噪声相关性研究

研究了金属氧化物半导体(MOS)器件在高、中、低三种栅压应力下的热载流子退化效应及其1/f^γ噪声特性.基于Si/SiO₂界面缺陷氧化层陷阱和界面陷阱的形成理论,结合MOS器件1/f噪声产生机制,并用双声子发射模型模拟了栅氧化层缺陷波函数与器件沟道自由载流子波函数及其相互作用产生能级跃迁、交换载流子的具体过程.建立了热载流子效应、材料缺陷与电参量、噪声之间的统一物理模型.还提出了用噪声参数Sf ^{关键词： 金属氧化物半导体场效应管 热载流子 fγ噪声')" href="#">1/fγ噪声}     

On the composition-dependent isotope effect of HTSC in the two-band model

The oxygen isotope effect in high-T_C superconductors has been investigated on the basis of a two-band model where superconducting phase transition is induced by interband (mainly Coulombic) interaction. The isotope shift of T_C appears due to the dependence of averaged interband electronphonon coupling constant on oxygen mass. This coupling has a repulsive nature and gives a relatively small contribution to the total interaction inducing superconductivity. The calculated isotope effect exponent depending on the carrier concentration has been compared with the experimental one as a function of x for La_2-xSr_xCuO₄.     

开放的V型三能级系统中原子注入和退出速率对位相相关的无反转激光增益和强度空间演化的调制作用

利用数值计算结果, 研究了具有自发辐射诱导相干的开放V 型三能级原子系统中的传播效应. 研究表明: 改变探测场和驱动场之间的相对位相对无反转激光(LWI)增益和 强度随传播距离的变化即空间演化具有重要的影响; 而原子的注入速率比(S)和退出速率(r₀)的改变将对位相相关的LWI增益和强度的空间演化产生明显的调制作用. 在S(r₀)的一定取值范围内, S(r₀)的值越大, LWI增益和强度越大且强度达到极大值需要的传播距离越长; 相应封闭系统中LWI增益和强度的最大值及能产生增益的传播距离都小于开放系统. Doppler效应对LWI增益和强度的空间演化也具有明显的影响, 存在Doppler效应时得到的LWI增益和强度明显小于无Doppler效应时的值.     

A poor man's interpretation of the Nozières-Gallet effect

Summary An interpretation of the effect proposed theoretically by Nozières and Gallet (and experimentally observed in⁴He), according to which the growth ratev of a crystal surface just below the roughening temperatureT _R is approximately linear in the disequilibrium Δμ, is given in terms of the properties of the nucleation process in the presence of a characteristic length l. The physical meaning ofl is the distance over which information can propagate on the surface before a new layer is formed. The nucleation barrier is lowered, because the size of a critical nucleus cannot exceedl, the latter being in turn proportional tov ^−1/2. A self-consistency condition ensues. The effect takes place when the correlation length ξ, which diverges atT _R, becomes comparable tol. In honour of Prof. Fausto Fumi on the occasion of his retirement from teaching.     

Compressibility and collisional effects on thermal instability of a partially ionized medium

The thermal instability of a finitely conducting hydromagnetic composite and compressible medium is studied to include the frictional effects with neutrals. The effect of compressibility is found to be stabilizing. In contrast to the nonoscillatory modes for (C _p/g)β > 1 in the absence of a magnetic field;C _v, β andg being specific heat at constant pressure, uniform adverse temperature gradient and acceleration due to gravity respectively, the presence of magnetic field introduces oscillatory modes in the system. The overstable case is also discussed. The magnetic field is found to have a stabilizing effect on the system for (C _p/g)β > 1.     

Effect of non‐extensivity parameter q on the damping rate of dust ion acoustic waves in non‐extensive dusty plasma

Kinetic theory has been applied to study the damping characteristics of dust ion acoustic waves (DIAWs) in a dusty plasma comprising q‐non‐extensive distributed electrons and ions, while the dust particles are considered extensive following the Maxwellian velocity distribution function. It is found that the results of the three‐dimensional velocity distribution function are more accurate compared to the results of the one‐dimensional velocity distribution function. The numerical solution of the dispersion relation is carried out to study the effect of the non‐extensivity parameter q on the dispersion, the damping rate, and the range of the values of the normalized wavenumber ( k λ_D) for which the DIAWs are weakly damped. It is found that the change in the value of the electron non‐extensivity parameter q_e has a minor effect on the dispersion, the damping rate, and the range of the values of the normalized wavenumber ( k λ_D) for which the DIAWs are weakly damped, while on the other hand, ion non‐extensivity parameter q_i has a strong effect on these arguments. The effect of other parameters, such as the ratio of electron to ion number density and ratio of electron to ion temperature, on the damping characteristics of DIAWs is also highlighted.     

石墨带的晶格动力学研究

基于晶格动力学理论,采用力常数模型,计算了石墨带的声子色散关系、振动模式密度和比热.计算结果表明,石墨带的声子谱特征介于一维碳纳米管和二维石墨片之间.扶手椅型和锯齿型石墨带的中、高频声子支分别与锯齿型和扶手椅型碳纳米管的类似.由于声子限域效应,低频声子支随着石墨带带宽的改变出现明显的频移现象.振动模式密度在高频区几乎不敏感于带宽,而低频区的峰位随着带宽的增加而逐渐向低频移动.此外,无论是在低温还是高温,比热都随着带宽的增加而逐渐降低,呈现量子尺寸效应.在300K时,比热可以拟合成C_V=C_Vg+A/n,其中C_Vg为石墨片的热容,而A/n项反映了石墨带中边缘效应对比热的影响. 关键词： 石墨带 声子色散关系 比热     

The Effect of ζ‐Potential and Hydrodynamic Size on Nanoparticle Interactions in Hydrogels

The ζ‐potential and hydrodynamic size (d_h) of nanoparticles (NPs) are systematically controlled by capping gold NPs (AuNPs) with polymers having different charges and treating them in NaCl solutions of diverse concentrations. Interactions between AuNPs in hydrogel are caused by chemical reactions induced by 1,4‐dithiothreitol. The effect of ζ‐potential is clear, as negatively charged AuNPs can be aggregated in neutral agarose gel, but the amount of aggregation is significantly affected by the magnitude of the negative surface charge on the AuNPs. However, all positively charged AuNPs show negligible aggregation in agarose gel with slightly negative polarity. The effect of d_h on AuNP aggregation is different from that of ζ‐potential. Although AuNPs with small d_h generally show more aggregation than those with large d_h, the amount of AuNP capping layer is critical. Thus, the amount of polymer present on NP surface needs to be considered to investigate the effect of d_h on AuNP aggregation. Through extended Derjaguin, Landau, Verwey, Overbeek (XDLVO) theory, it is shown that the charges of the AuNPs and the hydrogel, as well as the d_h of the NPs, are related to electrostatic repulsion and steric hindrance, which affect AuNP aggregation in hydrogel.     

Anti-BZ-Structure in Effect Algebras

The definitions of sharply approximating effect algebras, anti-BZ-effect algebras, central approximating effect algebras, and S-anti-BZ-effect algebras are given, the relationships between sharply approximating effect algebras and anti-BZ-effect algebras, between central approximating effect algebras and anti-BZ-effect algebras are established, and the set of anti-BZ-sharp elements in S-anti-BZ-effect algebras is proved to be an orthomodular lattice.