Adiabatic Properties Research Articles

Adiabatic heat capacity and related properties of ammonium hexachlororuthenate, (NH4)2RuCl6, at temperatures from 5 ⩽ T/K ⩽ 325

The heat capacity of ammonium hexachlororuthenate, (NH4)2RuCl6, was measured over the temperature range 5⩽T/K⩽325 using adiabatic calorimetry. Our results show that a structural phase transition is not present. However, an anomalous increase in the heat capacity Cp,m occurs in the region 70⩽T/K⩽105 and the heat capacity reaches its maximum at T=(93.5±0.1) K. The molar entropy change associated with this increase amounts to ΔSm=(0.465±0.006)R. Standard molar thermodynamic functions are presented at selected temperatures from 5K to 325K.

Prediction of Capillary Tube Adiabatic Flow Properties in the Absence of Precise Geometric Information

Capillary tubes have been used in household refrigerators and other cooling systems for several decades. Complicated geometry, inevitable manufacturing variations, and complex two-phase phenomena have been major prohibitory factors in the development of reliable and efficient modeling tools to analyze the flow properties inside capillary tubes. Friction factor correlations as are available in the open literature, and as examined by the author, unanimously fail to give an accurate analysis of the refrigerant flow. The delicate operation of a capillary tube makes experimentation cumbersome, time and cost intensive, and prone to errors. The present study introduces a method to utilize the data obtained from a standard nitrogen flow test for a given capillary tube to compensate for the geometric uncertainties and predict refrigerant flow properties through the tube at any desired spatial resolution, inlet state, and flow rate. Therefore, exploratory studies and capillary tube modifications for the purpose of system development and optimization can be greatly simplified.

Adiabatic pumping in the quasi-one-dimensional triangle lattice

We analyze the properties of the quasi-one-dimensional triangle lattice emphasizing the occurrence of flat bands and band touching via the tuning of the lattice hopping parameters and on-site energies. The spectral properties of the infinite system will be compared with the transmission through a finite piece of the lattice with attached semi-infinite leads. Furthermore, we investigate the adiabatic pumping properties of such a system: depending on the transmission through the lattice, this results in nonzero integer charge transfers or transfers that increase linearly with the lattice size.

Study on New Adiabatic Multiple Layer Coating for Metal Mold

The new adiabatic multiple coating is composed of surface coating and ground coating. The main raw material of surface coating is diatomite and that of ground coating is zircon powder. This paper separately study on the formula of the surface and ground coating. The results show that the adiabatic and other properties of composite coating are good and the coating can be used on the metal mold to cast the ferritic nodular cast iron (ferrite% ＞95%). And the using life of metal mold is improved.

Dynamical properties of partially coherent Bose‐Einstein condensates in double wells

AbstractSome dynamical features of partially coherent Bose‐Einstein condensate systems confined in double‐well potentials are investigated in mean field approximation. For one‐component system, the phenomena of self‐trapping is studied and it is shown that the partially coherent system, like completely coherent one, can also exhibit self‐trapping phenomena which are affected by both the degree of coherence and the initial relative phase. The adiabatic properties are also studied by introducing the fidelity for mixed state. It is shown that the introduced fidelity can characterize the adiabatic condition of the partially coherent system. For two‐component system, the time evolution of the degree of coherence for a time‐dependent tunneling strength is investigated. The corresponding results imply that the degree of coherence for such a two‐component system can exhibit decoherence phenomena even without the condensate‐environment coupling.

Theoretical seismic properties of pre-main sequenceγ Doradus pulsators

Context. gamma Doradus (gamma Dor) are late A and F-type stars pulsating with high order gravity modes (g-modes). The existence of different evolutionary phases crossing the gamma Dor instability strip raises the question of the existence of pre-main sequence (PMS) gamma Dor stars. Aims. We intend to study the differences between the asteroseismic behaviour of PMS and main sequence (MS) gamma Dor pulsators as it is predicted by the current theory of stellar evolution and stability. Methods. We explore the adiabatic and non-adiabatic properties of high order g-modes in a grid of PMS and MS models covering the mass range 1.2 Msun < Mstar < 2.5 Msun. Results. We derive the theoretical instability strip (IS) for the PMS gamma Dor pulsators. This IS covers the same effective temperature range as the MS gamma Dor one. Nevertheless, the frequency domain of unstable modes in PMS models with a fully radiative core is larger than in MS models, even if they present the same number of unstable modes. Moreover, the differences between MS and PMS internal structures are reflected on the average values of the period spacing as well as on the dependence of the period spacing on the radial order of the modes, opening the window to the determination of the evolutionary phase of gamma Dor stars from their pulsation spectra.

초고성능 콘크리트의 수화발열 및 역학적 특성 모델

Structural Engineering & Bridges Research Division, Korea Institute of Construction Technology, Goyang 411-714, KoreaABSTRACT Concrete has excellent mechanical properties, high durability, and economical advantages over other constructionmaterials. Nevertheless, it is not an easy task to apply concrete to long span bridges. That's because concrete has a low strengthto weight ratio. Ultra high performance concrete (UHPC) has a very high strength and hence it allows use of relatively small sectionfor the same design load. Thus UHPC is a promising material to be utilized in the construction of long span bridges. However,there is a possibility of crack generation during the curing process due to the high binder ratio of UHPC and a consequent largeamount of hydration heat. In this study, adiabatic temperature rise and mechanical properties were modeled for the stress analysisdue to hydration heat. Adiabatic temperature rise curve of UHPC was modeled superposing 2-parameter model and S-shaped func-tion, and the Arrhenius constant was determined using the concept of equivalent time. The results are verified by the mock-up testmeasuring the temperature development due to the hydration of UHPC. In addition, models for mechanical properties such as elas-tic modulus, tensile strength and compressive strength were developed based on the test results from conventional load test andultrasonic pulse velocity measurement.Keywords : UHPC, heat of hydration heat, adiabatic temperature rise curve, equivalent time

Adiabatic connections and properties of coupling-integrated exchange–correlation holes and pair densities in density functional theory

We demonstrate a method that likely will improve the accuracy of functionals used in density functional theory and pair density functional theory. In deriving the method we show that the coupling-integrated exchange–correlation hole used in density functional theory obeys all the N-representability conditions as non-integrated holes and we give two such conditions, not normally used by the density functional theory community. We will also show that in addition to the normal adiabatic connection there exist a dual adiabatic connection where the kinetic energy is integrated over the inverse electron mass.

GEOMETRIES AND ENERGY SEPARATIONS OF ELECTRONIC STATES OF In3N, InN3, AND THEIR IONS

Spectroscopic properties of the low-lying electronic states of In 3 N , InN 3, and their ions are computed by the complete active-space self-consistent field (CASSCF) followed by multireference singles + doubles configuration interaction (MRSDCI) calculations. Our results predict that the spectra of In 3 N / InN 3 are substantially different from those of Ga 3 As / GaAs 3 and Al 3 P / AlP 3 tetramers. The ground state of In 3 N is a closed-shell 1 A ′1 state with a planar D 3h symmetry, whereas the ground state of InN 3 is a 1Σ+ state of linear In – N – N – N structure. The equilibrium geometries, vibrational frequencies, atomization energies, adiabatic ionization potentials, electron affinities, and other properties are discussed.

PULSE: a finite element code for solving adiabatic nonradial pulsation equations

We briefly present the nonradial adiabatic pulsation code PULSE first developped for white dwarf asteroseismology and now used to compute adiabatic oscillation properties for various types of stellar objects. Numerical tests show that the code is able to provide the accuracy (for a given stellar model) required to deal with the precision in frequency expected from the COROT long runs. While the ultimate objective is to compare the output of various pulsation codes (see these proceedings), we already emphasize problems that need to be addressed concerning, in particular, the mesh resolution of the input stellar models and its impact on the accuracy at which frequencies can be computed.

Equilibrium ion distribution in the presence of clearing electrodes and its influence on electron dynamics

Here we compute the ion distribution produced by an electron beam when ion-clearing electrodes are installed. This ion density is established as an equilibrium between gas ionization and ion clearing. The transverse ion distributions are shown to strongly peak in the beam's center, producing very nonlinear forces on the electron beam. We will analyze perturbations to the beam properties by these nonlinear fields. To obtain reasonable simulation speeds, we develop fast algorithms that take advantage of adiabatic invariants and scaling properties of Maxwell's equations and the Lorentz force. Our results are very relevant for high current energy recovery linacs, where ions are produced relatively quickly, and where clearing gaps in the electron beam cannot easily be used for ion elimination. The examples in this paper therefore use parameters of the Cornell Energy Recovery Linac project. For simplicity we only consider the case of a circular electron beam of changing diameter. However, we parametrize this model to approximate nonround beams well. We find suitable places for clearing electrodes and compute the equilibrium ion density and its effect on electron-emittance growth and halo development. We find that it is not sufficient to place clearing electrodes only at the minimum of the electron beam potential where ions are accumulated.

Predeformation Effects on Shear Response and Microstructure in Pure Titanium-TA2

Adiabatic shear properties of pure titanium-TA2 have been investigated using specially designed specimen in a Hopkinson pressure bar at high strain rate of 103s- 1. Microstructural characteristics was investigated using scanning electrion microscopy as well as transmission and high resolution transmission electrion microscopy .The results showed that the shear stress and adiabatic sensitivity for rolled 45% TA2 are higher than forged TA2. Comparing the adiabatic shear bands (ASB) both in the forged and rolled TA2, no evidence in morphology alteration was found except to shear band widths. The transmission electron micrograph of the ASB in forged and rolled TA2 showed the grain size reduction from ~20μm to 200nm. No deformation twins have been observed in ASB. The selected area electron diffraction patterns of the ASB showed reflections of multiple grains, forming discontinuous rings which can be indexed as h.c.p. structure of α-Ti. This indicates that the ASB consists of fine grains of α-Ti and the α-Ti→ β-Ti transformation did not occur.

Expanding ring experiments to measure high-temperature adiabatic properties

High-temperature mechanical properties for metals are usually measured under quasi-isothermal conditions, where thermal equilibrium has been achieved by slowly preheating the samples to a predetermined temperature. However, there are several situations of practical interest where the material is heated rapidly, so thermal diffusion is negligible during the time of heat deposition and mechanical deformation. Hypervelocity impact and penetration, shaped charge jet formation, and pulsed heating in electromagnets are some such situations. Experimental evidence from electron beam heating indicates that high-temperature mechanical properties significantly depend on the rapidity of heat deposition. As the time duration of heating is reduced, the amount of local heat transfer decreases due to limited thermal diffusion. Thus, the thermodynamic process deviates from the isothermal process and approaches the adiabatic process for pulsed heating conditions. Therefore, it is imperative that mechanical properties be measured under appropriate thermodynamic conditions. We propose that the electromagnetically driven expanding ring experiment be used to measure the adiabatic mechanical properties of metals. While earlier expanding ring experiments were conducted primarily to obtain high-strain-rate strength and fragmentation data, our primary goal is to obtain high-temperature data under pulsed heating conditions approaching the adiabatic process. Our preliminary data suggest that the adiabatic mechanical properties are quite different from isothermal properties.

Improved results for the excited states of nitric oxide, including the B∕C avoided crossing

The potential energy surfaces of ten electronic states of nitric oxide (NO) have been reexamined computationally, with state energies calculated using ab initio multireference methods. Our wave function expansions of 10x10(6) configurations improve upon the results of de Vivie and Peyerimhoff [J. Chem. Phys. 89, 3028 (1988)], who obtained excellent results from expansions of 16 000 configurations in 1988. We present results for the adiabatic properties r(e), B(e), T(e), and omega(e), demonstrating standard errors of 0.012 A, 0.026 cm(-1), 620 cm(-1), and 41 cm(-1), respectively. Vertical excitation energies and oscillator strengths are also presented, as are potential energy surface curves, with special attention to the B/C avoided crossing. The technical issue of state-averaging effects is also discussed.

Dynamic Piezoresistivity Calibration for Eddy Current Nondestructive Residual Stress Measurements

It has been recently demonstrated [M. P. Blodgett and P. B. Nagy, J. Nondestruct. Eval. 23, 107 (2004)] that eddy current conductivity measurements can be exploited for near-surface residual stress assessment in surface-treated nickel-base superalloy components. To quantitatively assess the prevailing residual stress from eddy current conductivity measurements, the piezoresistivity coefficients of the material must be first determined using known external applied stresses. These calibration measurements are usually conducted on a reference specimen of the same material using cyclic uniaxial loads between 0.1 and 10Hz, which is fast enough to produce adiabatic conditions. Therefore, the question arises whether dynamic calibration measurements can be used or not for accurately assessing the sensitivity of the eddy current method for static residual stress. It is demonstrated in this paper that such dynamic calibration measurements should be corrected for the thermoelastic effect, which is always positive, i.e., it increases the conductivity in tension, when the material cools down, and reduces it in compression, when the material heats up. For low-conductivity titanium and nickel-base engine alloys the thermoelastic corrections are relatively modest at ≈5–10%, but for high-conductivity aluminum alloys the difference between the adiabatic and isothermal properties could be as high as 50%.

Pulsations of massive ZZ Ceti stars with carbon/oxygen and oxygen/neon cores

We explore the adiabatic pulsational properties of massive white dwarf stars with hydrogen-rich envelopes and oxygen/neon and carbon/oxygen cores. To this end, we compute the cooling of massive white dwarf models for both core compositions taking into account the evolutionary history of the progenitor stars and the chemical evolution caused by time-dependent element diffusion. In particular, for the oxygen/neon models we adopt the chemical profile resulting from repeated carbon-burning shell flashes expected in very massive white dwarf progenitors. For carbon/oxygen white dwarfs we consider the chemical profiles resulting from phase separation upon crystallization. For both compositions we also take into account the effects of crystallization on the oscillation eigenmodes. We find that the pulsational properties of oxygen/neon white dwarfs are noticeably different from those made of carbon/oxygen, thus making asteroseismological techniques a promising way to distinguish between the two types of stars and, hence, to obtain valuable information about their progenitors.

The double-layered chemical structure in DB white dwarfs

We study the structure and evolution of white dwarf stars with helium-rich atmospheres (DB) in a self-consistent way with the predictions of time-dependent element diffusion. Our treatment of diffusion includes gravitational settling and chemical and thermal diffusion. OPAL radiative opacities for arbitrary metallicity and carbon-and oxygen-rich compositions are employed. Emphasis is placed on the evolution of the diffusion-modeled double-layered chemical structure. This structure, which is characterized by a pure helium envelope atop an intermediate remnant shell rich in helium, carbon and oxygen, is expected for pulsating DB white dwarfs, assuming that they are descendants of hydrogen-deficient PG1159 post-AGB stars. We find that, depending on the stellar mass, if DB white dwarf progenitors are formed with a helium content smaller than \approx 10^-3 M_*, a single-layered configuration is expected to emerge during the DB pulsation instability strip. We also explore the consequences of diffusively evolving chemical stratifications on the adiabatic pulsational properties of our DB white dwarf models. In this context, we find that the evolving shape of the chemical profile translates into a distinct behaviour of the theoretical period distribution as compared with the case in which the shape of the profile is assumed to be fixed during the evolution across the instability strip. Finally, we extend the scope of the calculations to the domain of the helium-rich carbon-contaminated DQ white dwarfs. In particular, we speculate that DQ white dwarfs with low detected carbon abundances would not be descendants of the PG1159 stars.

Evolutionary and pulsational properties of low-mass white dwarf stars with oxygen cores resulting from close binary evolution

The present work is designed to explore the evolutionary and pulsational properties of low-mass white dwarfs with carbon/oxygen cores. In particular, we follow the evolution of a 0.33-M. white dwarf remnant in a self-consistent way with the predictions of nuclear burning, element diffusion and the history of the white dwarf progenitor. Attention is focused on the occurrence of hydrogen shell flashes induced by diffusion processes during cooling phases. The evolutionary stages prior to the white dwarf formation are also fully accounted for by computing the conservative binary evolution of an initially 2.5-M. Population I star with a 1.25-M. companion, and with period P-i = 3d. Evolution is followed down to the domain of the ZZ Ceti stars on the white dwarf cooling branch. We find that chemical diffusion induces the occurrence of an additional hydrogen thermonuclear flash, which leads to stellar models with thin hydrogen envelopes. As a result, a fast cooling is encountered at advanced stages of evolution. In addition, we explore the adiabatic pulsational properties of the resulting white dwarf models. As compared with their helium-core counterparts, low-mass oxygen-core white dwarfs are characterized by a pulsational spectrum much more featured, an aspect which could eventually be used for distinguishing both types of stars, if low-mass white dwarfs were in fact found to pulsate as ZZ Ceti-type variables. Finally, we perform a non-adiabatic pulsational analysis on the resulting carbon/oxygen low-mass white dwarf models.

Collapse of the stimulated Raman adiabatic passage due to geometrical factors and how to overcome it

The adiabatic properties of stimulated Raman passage via N intermediate quasidegenerate levels are studied. It is shown that the outcome of the population transfer depends on the geometrical structure of the molecular couplings, in particular, on the signs or phases of the dipole matrix elements that connect the initial and the final states with all the intermediate levels. These phases constitute a molecular Franck-Condon configuration. The majority of the possible configurations disable adiabatic passage through a dark state so that the dynamics is dominated by Rabi oscillations among the different levels. It is shown, however, that adiabatic passage can be regained via nonresonant stimulated Raman for almost all possible configurations.

Adiabatic Survey of Subdwarf B Star Oscillations. III. Effects of Extreme Horizontal Branch Stellar Evolution on Pulsation Modes

We present the final results of a large, systematic survey of the adiabatic oscillation properties of models of subdwarf B (sdB) stars. This survey is aimed at providing the minimal theoretical background with which to understand the asteroseismological characteristics of the recently discovered class of pulsating sdB stars (the EC 14026 objects). In this paper, the last of a series of three, we consider the effects of stellar evolution on the pulsation eigenmodes of sdB star models. We specifically analyze the adiabatic properties of 149 equilibrium models culled from seven distinct extreme horizontal branch evolutionary sequences. Those have been chosen in order to span fully the region of parameter space where real sdB stars are found. We primarily focus on the evolution of the pulsation periods (P) and the rates of period change (dP/dt), which are both a priori observable quantities. Both the acoustic and gravity branches of stellar oscillations are considered. In light of the results derived in the first two papers of this series, we discuss how the values of P and dP/dt relate to the various structural adjustments that sdB stars undergo during evolution. We find that the acoustic modes react primarily to the secular variations of the surface gravity. In contrast, we identify three main factors that regulate the period evolution of gravity modes: these are the variations brought about by evolution in both the surface gravity and the effective temperature, as well as the onset and growth of a chemical discontinuity between the C-O-enriched nucleus and the helium-rich mantle. We also find, as expected from our previous results, that the period evolution of the pulsation modes in sdB stars is further complicated by trapping effects (microtrapping in the case of p-modes) and by avoided crossings between modes. The latter occur preferentially in certain regions of parameter space. We provide our final results in the form of extensive tabular data in the appendices, which, we hope, will be useful in future asteroseismological analyses of EC 14026 stars.