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Organic Rankine cycles (ORC) are quite popular, but the overall efficiencies of these plants are rather very low. Numerous studies have been conducted in many scientific centers and research centers to improve the efficiency of such cycles. The research concerns both the modification of the cycle and the increase in the parameters of the medium at the inlet to the turbine. However, the efficiency of even these modified cycles rarely exceeds 20%. The plant modifications and the optimization of the working medium parameters, as a rule, lead to cycles with the high pressure and high temperature of live vapor and with a regenerator (heat exchanger) for the heating, vaporization and superheating of the medium. A new modified cycle with supercritical parameters of the working medium and with a new type of turbine has been described and calculated in the paper. For the first time, the isothermal turbine is proposed for supercritical organic cycles, though this solution is known as the Ericsson cycle for gas turbines. The innovative cycle and the usual ORC plants are characterized by almost identical block diagrams, while in the proposed cycle, the work of the turbine is obtained as a result of isothermal expansion and not in an adiabatic process. The analysis has been performed for 11 different working media and two cycles. The calculations have shown that power plants with isothermal expansion achieve better efficiency than cycles with adiabatic turbines. For example, the rise in efficiency changes from 8 percentage points for R245fa up to 10 percentage points for acetone. The calculations have proved that it is possible to obtain efficiency exceeding 50% for organic power plants. This is an outstanding result compared with modern steam and gas turbine units.

In the article, based on the joint analysis of the Bernoulli equations for compressible gas and variations of the supersonic flow parameters of the Prandtl-Meyer expansion fan, some consistent patterns of adiabatic expansion of local supersonic airflow over an aerofoil surface in the subsonic range of Mach numbers are defined. On the basis of these patterns, a mathematical model was obtained for estimation of the location of shock waves behind the aerofoil chord of an aerodynamic surface depending upon its geometric characteristics and the Mach number of undisturbed airflow., У статті на базі спільного аналізу рівнянь Бернуллі для стисненого газу та зміни параметрів надзвукового потоку в течії Прандтля – Майера визначені деякі закономірності адіабатичного розширення місцевого надзвукового потоку повітря на поверхні аеродинамічного профілю в навколозвуковому діапазоні чисел М польоту. На базі цих закономірностей отримана математична модель оцінки залежності розташування стрибків ущільнення за хордою профілю аеродинамічної поверхні від його геометричних характеристик та від числа М незбудженого потоку повітря.

Tesis (Doctor en Física)--Universidad Nacional de Córdoba. Facultad de Matemática, Astronomía, Física y Computación, 2022. En los últimos años, ha existido un incremento en el interés en los dispositivos nanoelectromecánicos, máquinas cuánticas autónomas impulsadas por corrientes y en los efectos mecánicos de lascorrientes eléctricas en conductores de tamaños nanométricos. Aquí realizamos un estudio exhaustivo de distintos fenómenos dentro del transporte cuántico dependiente del tiempo que sirven comomecanismo de acción intrínseco o que afectan a este tipo de sistemas. En la primera etapa del trabajo estudiamos el comportamiento general de sistemas cuánticos abiertos. En particular, estudiamoslos estados metaestables de complejos colisionales formados por diferentes átomos y moléculas. Si bien, dicho sistema podría parecer alejado de los típicos modelos de transporte cuántico usados en el contexto de bombeo cuántico o en máquinas cuánticas adiabáticas, demostramos que la caracterización de ambos tipos de sistemas es equivalente. Posteriormente, trabajamos con el modelo más simple posible dentro del contexto de transporte cuántico, un punto cuántico (modelado por un solo nivel de energía) acoplado a dos reservorios de partículas no interactuantes (modelados como cadenas semiinfinitas en una aproximación tight-binding). Encontramos expresiones cerradas para las fuerzas inducidas por corrientes de equilibrio y de no-equilibrio, además del rotor de dichas fuerzas.Los trabajos realizados hasta aquí fueron obtenidos a partir de expresiones teóricas generales ya conocidas, basadas en expansiones adiabáticas de funciones de Green de no-equilibrio. La siguiente etapa consistió en derivar nuevas expresiones que permitan calcular órdenes superiores de dichas expansiones adiabáticas y los observables de interés que de las mismas se derivan. En particular, se obtuvieron las expresiones generales para el cálculo de corrientes de partículas, las fuerzas inducidaspor corrientes y las autocorrelaciones de las mismas. La última etapa del trabajo se centró en estudiar el rendimiento de máquinas cuánticas impulsadas por combinaciones arbitrarias de reservorios de equilibrio y de diseño. Estos últimos sistemas están compuestos por partículas no interactuantes, pero cuyas funciones de distribución son no-térmicas. In recent years, there has been an increase in interest in nanoelectromechanical devices, autonomous current-driven quantum machines, and the mechanical effects of electrical currents on nanometer-sized conductors. Here, we carry out an exhaustive study of different phenomena within the time-dependent quantum transport that serve as an intrinsic mechanism of action or that improves this type of system. In the first stage of the work, we study the general behavior of open quantum systems. In particular, we study the metastable states of collisional complexes formed by different atoms and molecules. Although such a system might seem far from the typical quantum transport models used in the context of quantum pumping or in adiabatic quantum machines, we show that the characterization of both types of systems is equivalent. Subsequently, we work with the simplest model possible within the context of quantum transport, a quantum dot (modeled by a single energy level) coupled to two reservoirs of non-interacting particles (modeled as semi-infinite chains in a tight-binding approach). We find expressions for the equilibrium current-induced forces and the non-equilibrium ones, and the rotor for a given force. These expressions were obtained from already known general theoretical expressions, based on adiabatic expansions of non-equilibrium Green functions. The next stage consists of deriving new expressions that allow us to calculate higher orders and the observable of interest that are derived from them. In particular, we give the general expressions for the calculation of particle currents, the forces induced by currents, and their autocorrelations. The last stage of the work focused on studying the performance of quantum machines driven by an arbitrary combination of equilibrium and design reservoirs. These latter systems are composed of non-interacting particles, but whose distribution functions are non-thermal 2024-05-17 Fil: Deghi, Sebastián Esteban. Universidad Nacional de Córdoba. Facultad de Matemática, Astronomía, Física y Computación; Argentina.

It is well known that large amounts of energy loss occurs at low temperature states in a wide range of industrial processes., The recovery and reuse of this energy is at the forefront of increasing the overall efficiencies of industrial systems. The aim of this paper is to investigate the effectiveness of using a Thermo-Fluidic Exchange (TFE) pump at low temperature conditions in both a Saturated-Vapour Organic Rankine Cycle (SORC) and a Trilateral Flash Cycle (TFC). For some low temperature applications, TFCs have been shown to achieve higher net power output than conventional SORCs, due to their ability to extract more heat from the source fluid. This is the subject of current research as a result of advancements made in the design of positive displacement machines for operation as twophase expanders. Conventional turbines cannot be used for TFCs as they must operate in the vapour phase. One drawback of the TFC is the higher working fluid mass flow rate required. Depending on the scale of the system, this can potentially cause difficulties with pump selection. A TFE pump uses heat input to the system to increase the pressure and temperature of the working fluid, rather than the work input in a standard mechanical pump. This paper compares the net power output achievable using both mechanical and TFE pumps with SORC and TFC systems. The results suggest that the TFE pump could be a viable option for TFC systems

We revisit the fundamental principles of thermodynamic equilibrium in relation to heat transfer processes within the Earth’s atmosphere. A knowledge of equilibrium states at ambient temperatures (T) and pressures (p) and deviations for these p-T states due to various transport ‘forces’ and flux events give rise to gradients (dT/dz) and (dp/dz) of height z throughout the atmosphere. Fluctuations about these troposphere averages determine weather and climates. Concentric and time-span average values (z, Δt)) and its gradients known as the lapse rate = d < T(z) >/dz have hitherto been assumed in climate models to be determined by a closed, reversible, and adiabatic expansion process against the constant gravitational force of acceleration (g). Thermodynamics tells us nothing about the process mechanisms, but adiabatic-expansion hypothesis is deemed in climate computer models to be convection rather than conduction or radiation. This prevailing climate modelling hypothesis violates the 2nd law of thermodynamics. This idealized hypothetical process cannot be the causal explanation of the experimentally observed mean lapse rate (approx.−6.5 K/km) in the troposphere. Rather, the troposphere lapse rate is primarily determined by the radiation heat-transfer processes between black-body or IR emissivity and IR and sunlight absorption. When the effect of transducer gases (H2O and CO2) is added to the Earth’s emission radiation balance in a 1D-2level primitive model, a linear lapse rate is obtained. This rigorous result for a perturbing cooling effect of transducer (‘greenhouse’) gases on an otherwise sunlight-transducer gas-free troposphere has profound implications. One corollary is the conclusion that increasing the concentration of an existing weak transducer, i.e., CO2, could only have a net cooling effect, if any, on the concentric average (z = 0) at sea level and lower troposphere (z < 1 km). A more plausible explanation of global warming is the enthalpy emission ’footprint’ of all fuels, including nuclear.

Two-phase expansion is the process where a fluid undergoes a pressure drop through or in the liquid–vapor dome. This operation was historically avoided. However, currently it is studied for a multitude of processes. Due to the volume increase in volumetric expanders, a pressure drop occurs in the fluid resulting in flashing phenomena occurring. These phenomena have been studied before in other processes such as two-phase flows or static flash. However, this has not been extensively studied in volumetric expanders and is mostly neglected. Even if data has shown this is not always neglectable depending on the expander type. The thermal non-equilibrium occurring can be modeled on different principles of flashing flows, such as the mixture model, boiling delay model, and homogeneous relaxation model. The main application area in current literature for volumetric two-phase expansion machines, is in low-temperature two-phase heat-to-power cycles. These cycles have shown benefit over classic options if expanders are available with efficiencies in the range of at least 75%. Experimental investigation of expanders in two-phase operation, though lacking in quantity, has shown that this is an achievable goal. However, the know-how to accomplish this requires more studies, both experimentally and in modeling techniques for the different phenomena occurring within these expanders. The present work provides a brief but comprehensive overview of the available experimental data, applicable flashing modeling techniques, and available models of volumetric two-phase expanders.

The increase of the maximal cycle temperature is considered as one of the best tools to increase cycle efficiency for all thermodynamic cycles, including Organic Rankine Cycles (ORC). Technically, this can be done in various ways, but probably the best solution is the use of hybrid systems, i.e., using an added high-temperature heat source to the existing low-temperature heat source. Obviously, this kind of improvement has technical difficulties and added costs, therefore, the increase of efficiency by increasing the maximal temperature sometimes has technical and/or financial limits. In this paper, we would like to show that for an ideal, simple-layout ORC system, a thermodynamic efficiency-maximum can also exist. It means that for several working fluids, the thermodynamic efficiency vs. maximal cycle temperature function has a maximum, located in the sub-critical temperature range. A proof will be given by comparing ORC efficiencies with TFC (Trilateral Flash Cycle) efficiencies, for wet working fluids, further theoretical evidence can be given. The group of working fluids with this kind of maximum will be defined. Generalization for normal (steam) Rankine cycles and CO2 subcritical Rankine cycles will also be shown. Based on these results, one can conclude that the increase of the maximal cycle temperature is not always a useful tool for efficiency-increase, this result can be especially important for hybrid systems.

The efficiencies of the Organic Rankine Cycle (ORC) are not very high and only very seldom do they exceed 20%. The increase and optimization of initial parameters and certain modifications of the thermodynamic cycle make it possible to overcome these drawbacks. A new modified cycle has been described and analyzed in detail in the paper. Similarly to the Ericsson cycle for gas turbines, isothermal expansion in the turbine is suggested for the power plant with organic media. The new cycle and the typical ORC power plants have the same block diagram. The only difference is that expansion in the proposed cycle occurs not adiabatically but as an isothermal process. The thermodynamic calculations have been carried out for 11 various fluids and 4 different cycles. The obtained results have clearly shown that cycles with isothermal expansion (isothermal turbines) are characterized by remarkably higher efficiency than typical power plants with adiabatic turbines. The increase in efficiency varies from 6 to 12 percent points for cycles with saturated live vapor and from 4 to 7 percent points for cycles with superheated live vapor. The performed analyses have shown that it is possible to achieve a very high efficiency (over 45%) of organic cycle, which is a very competitive value. In such cases the proposed power plants can achieve an efficiency which is higher than that of modern steam turbine plants with supercritical parameters.

Based on the idea of adiabatic expansion theory, we will present a new formula for the asymptotic expansion coefficients of every derivative of the heat kernel on a compact Riemannian manifold. It will be very useful for having systematic understanding of the coefficients, and, furthermore, by using only a basic knowledge of calculus added to the formula, one can describe them explicitly up to an arbitrarily high order.

This semester I worked on a new technique for cooling atoms in microgravity and studied the role of engineering virtue ethics in the Mars Climate Orbiter failure. Central to both projects is the engineering/research process. In my technical project, I worked as a researcher on a complex project, while in my STS project I studied the failure of an engineering project. While the actual topics of the two subjects were quite different, both involved the engineering process. In my technical project, I collaborated on the development of a new technique for cooling Rubidium-87 atoms to extremely low temperatures. The technique, called adiabatic expansion, requires microgravity conditions. Because of this condition the experiment is taking place using NASA JPL’s Cold Atom Laboratory (CAL), which is located on the International Space Station (ISS). The CAL apparatus creates Bose-Einstein Condensates (BECs), a type of ultracold quantum gas, in tightly confining magnetic traps. These magnetic traps are controlled by running currents through a set of coils and a wire chip configuration. Adiabatic expansion uses the manipulation of the electric current magnitudes to relax the magnetic trap and cool the condensate even further, from the millikelvin to the nanokelvin regime. We have demonstrated the ability to displace atoms from the original configuration into a trap with 3 Hz frequency, with minimal residual center-of-mass motional excitation. We also explored how different trap turn off procedures affected the population of different magnetic states, as well as how stray background fields in the apparatus may limit the length of condensate observations. In my STS research paper, I used virtue ethics to evaluate the morality of the Mars Climate Orbiter’s navigations engineering team and navigation operations team. The Mars Climate Orbiter was a NASA robotic space probe that failed due to a unit conversion error in a software file. I concluded that since the teams lacked the virtues necessary for responsible engineers, then their actions were unethical. Specifically, the engineering team lacked the virtue of striving for quality, and the operations team lacked the virtue of professionalism. Both teams failed to display the virtue of communication. Using virtue ethics, the actions of these engineers were evaluated and it was determined that they were immoral due to failing to possess the virtues needed for ethical engineering. The goal of my research was to understand how cultivating the necessary engineering virtues makes it much less likely that an error will cause the total failure of a project. Working on both projects at the same time gave me a better understanding of the engineering/research process. In my technical project, I worked on a novel atom cooling process in the field of ultra cold quantum gases. My STS project on virtue ethics in engineering helped me to understand the importance of cultivating good engineering virtues, especially when working on large and complex processes. This is the best way to keep small errors from causing the failure of a project.

Particle sensing based on condensational growth has long been the basis for robust nanoparticle measurement. Increasingly cloud chamber devices offer the potential for low-cost and portable measurement when operated semi-continuously with relatively small system volumes. Models based on isentropic and isenthalpic expansion are derived to predict the time evolution of temperature, saturation ratio, particle growth, and resultant light extinction in cloud chambers. A laboratory cloud chamber is fabricated and experiments using NaCl aerosol particles as the condensation nucleus are conducted to verify the models. The isentropic model, suggests that the temperature drops 0.6 ℃ within 40 ms, and accordingly, the saturation ratio reaches 1.04. For an aerosol with lognormal distribution, the predicted geometric mean diameter grows more than 5 times while the distribution narrows due to ∝1/𝑑p growth in the continuum regime. The performance of the cloud chamber agrees with the system physics and reference instruments, with relative error in measured extinction coefficient and signal intensities of ±5%. Detailed error propagation shows that the measured number concentrations agree well with reference instruments and the underlying theory. The lower limit of detection (~4×10^6 cm^-3) for the device is suitable for fire detection and emissions characterization.

In order to obtain a better fit for the observational data, various cosmological models have been developed in the literature. For this purpose, we propose an adiabatic expansion of the Universe with a polytropic fluid matter-radiation content and a varying cosmological constant. Basic motivation of this study basically differs from the previous models because our model does not neglect the pressure of the matter content of the Universe. We present the details of our new derivations by obtaining the polytropic matter density and luminosity distances. After constructing the model, two large collections of observational data of supernovae type Ia (SNe Ia) are conducted to diagnose the model. Examining the fitness of our new models of a polytropic universe with the observational data, we find a significant influence of polytropic matter on the cosmological parameters of the expanding universe. We find that our flat constant ? model and varying ? model describes the SNe Ia data significantly better than the other models including the standard model for Gold Data and Union2.1 Data, respectively.

Atom laser experiments with Bose-Einstein condensates (BECs) performed in ground-based laboratories feature a coherent and directed beam of atoms which is accelerated by gravity. In microgravity the situation is fundamentally different because the dynamics is entirely determined by the repulsive interaction between the atoms and not by the gravitational force. As a result, the output of a space atom laser is a spherical wave slowly expanding away from the initial BEC.We present a thorough theoretical study of this new source of matter waves based on rf outcoupling which exhibits an isotropic distribution both in position and momentum even for an initially anisotropic trap. The unique geometry of such a freely expanding, shell-shaped BEC offers new possibilities for matter waves in microgravity and is complementary to other matter-wave sources prepared by delta-kick collimation or adiabatic expansion. Our work paves the way for the upcoming experimental realization of a space atom laser making use of NASA's Cold Atom Laboratory on the International Space Station., Comment: 36 pages, 9 figures, minor changes to match the published version

11 pags., We introduce an iterative method to univocally determine the adiabatic expansion of the modes of Dirac fields in spatially homogeneous external backgrounds. We overcome the ambiguities found in previous studies and use this new procedure to improve the adiabatic regularization/renormalization scheme. We provide details on the application of the method for Dirac fields living in a four-dimensional Friedmann-Lemaître-Robertson-Walker spacetime with a Yukawa coupling to an external scalar field. We check the consistency of our proposal by working out the conformal anomaly. We also analyze a two-dimensional Dirac field in Minkowski space coupled to a homogeneous electric field and reproduce the known results on the axial anomaly. The adiabatic expansion of the modes given here can be used to properly characterize the allowed physical states of the Dirac fields in the above external backgrounds., This work has been supported by the Spanish Ministerio de Economía y Competitividad (MINECO) research Grants No. FIS2014-57387-C3-3-P, No. FIS2014-57387-C3-1-P, No. FIS2017-84440-C2-2-P, and No. FIS2017-84440-C2-1-P, the European Cooperation in Science and Technology (COST) action CA15117 Cosmology and Astrophysics Network for Theoretical Advances and Training Actions (CANTATA), supported by COST, and the Severo Ochoa Program SEV-2014-0398. A. F. is supported by the Severo Ochoa Ph.D. fellowship SEV-2014-0398-16-1 and the European Social Fund.

In this short note, modeling of adiabatic expansion of air parcels by using an expanding box model (EBM) is discussed. It is shown that uniformly accelerating EBMs can be good analytical models to describe the adiabatic expansion in a demonstration experiment. Theoretical backgrounds of EBMs are briefly summarized in Appendix.

Dioxins in the combustion gas Municipal Solid Waste Incinerator (MSWI) are resynthesized during passing through the lower temperature region between the outlet exhaust boiler and the outlet gas duct. As a countermeasure, Joule-Thomson Expansion and Adiabatic expansion will be considered to prevent dioxins from resynthesizing by rapidly cool down the gas temperature less than the temperature required for resynthesizing of dioxins. So we have to study Joule Thomson Expansion theory how to be solved about Van der Waals equation of state to be got nozzle outlet temperature. After the study, we have already got a new analytical method of above described a equation of state. Therefore, we have to be able applying a cooling down temperature of gas for suppression of formation dioxins in MSWI.

Dioxins in the combustion gas Municipal Solid Waste Incinerator (MSWI) are resynthesized during passing through the lower temperature region between the outlet exhaust boiler and the outlet gas duct. As a countermeasure, Joule-Thomson Expansion and Adiabatic expansion will be considered to prevent dioxins from resynthesizing by rapidly cool down the gas temperature less than the temperature required for resynthesizing of dioxins. So we have to study Joule Thomson Expansion theory how to be solved about Van der Waals equation of state to be got nozzle outlet temperature. After the study, we have already got a new analytical method of above described a equation of state. Therefore, we have to be able applying a cooling down temperature of gas for suppression of formation dioxins in MSWI., 長崎大学工学部研究報告 Vol.37(69) p.16-20, 2007

We investigate the behavior of derivatives of the fundamental solution of a parabolic equation for the square of Dirac operator on a twistor space when the metric is blown up in the base space direction. Such a blowing up operation is expected to be an effective method for extracting some intrinsic values from various geometric invariants, most of whose cores consist of some derivatives of the fundamental solution.

The adiabatic regularization method was designed by L. Parker [1] for scalar fields in order to to subtract the potentially UV divergences that appear in the particle number operator. After that the method was generalized [2] to remove, in a consistent way, the UV divergences that appear in the expectation value of the stress-energy tensor 〈Tμv〉 in homogeneous cosmological backgrounds. We are going to provide here the extension of the adiabatic regularization method to spin-1/2 fields first given in [3]. In order to achieve this extension we will show the generalization of the adiabatic expansion for fermionic fields which differs significantly from the WKB-type expansion that works for the scalar modes. We will also show the consistency of the extended method computing well-known results, computed by other renormalization methods for a Dirac field in a FLRW spacetime, like the conformal and axial anomalies. Finally we will compute the expectation value of the stress-energy tensor for a Dirac field in a de Sitter spacetime, SEVERO OCHOA Program

The microscopic structures of acetonitrile-water and DMSO-water binary mixed solvents and their influence on the solvation for solutes (some alcohols and phenol) have been studied on the basis of the cluster structures observed through a specially designed mass spectrometer. In acetonitrile-water mixtures, the water clusters were observed at water mole fractions: Xw > 0.2; on the other hand, in DMSO-water mixtures, the water clusters were observed only at much higher water mole fractions: Xw > 0.93. In the mixing processes, the water clusters were stabilized in the acetonitrile-water mixtures, whereas the DMSO clusters were stabilized in the DMSO-water mixtures. It is demonstrated that these microscopic structures directly affect the solvation for alcohols and phenol in these binary mixed solvents.

The bound state energy of three quark systems is studied in the framework of a non- relativistic spin independent phenomenological model. The hyper- spherical coordinates are considered for the solution this system. According to Jacobi coordinate, we determined the bound state energy for (uud) and (ddu) quark systems, as quarks are flavorless mass, and it is restrict that choice potential at low and high range in nucleon bag for a bound state., {"references":["A. Gara, B. Durand, L. Durand and L. J. Nickisch, \"Relativistic Description of Quark - anti-Quark Bound States. 1. Spin Independent Treatment,\" \tPhys.Rev.D40, 843(1989).","L. P. Fulcher, Z. Chen and K. C. Yeong, \"Perturbative evaluation of the eigenvalues of the Herbst Hamiltonian\" Phys.Rev.D47, 4122(1993).B.","A. Duncan, E. Eichten and H. Tacker, Phys.Lett.B303, 109(1993).","W. Lucha, H. Rupprecht and F. F. Schoberl, Phys.Rev.D46, 1088(1992).","G. Jaczko and L. Durand, Phys.Rev.D58, 114017(1998).","G. R. Boroun and H. Abdolmalki, \"Fragmentation of Heavy Quarks Using Wave Function at the Origin\" Phys. Scr. 80, 065003(2009).","M. I. haftel and V. B. Mandelzweig, \"Precise non-variational calculation of the μdt molecular ion\" Phys.Rev.A41, 2339(1990).","H. T. Coelho and J. E. Hornos, \"Hyperspherical Approach to Ultra-Precise Nonvariational Calculations in Few Body Problem\" Phys. Rev. A43, 6379(1990).","J. Avery, \"Hyper-spherical Harmonics and generalized Sturmians\" Kluwer, Dordrech, 2000.\n[10]\tB. C. Reed, \"Quantum Mechanics\" Jones and Barlett publishers, 2008."]}

航空宇宙技術研究所 7-9 Jun. 1995 東京 日本, National Aerospace Laboratory 7-9 Jun. 1995 Tokyo Japan, van der Waals気体中の衝撃波伝搬の数値解析を行った。まずvan der Waals気体の熱力学的特性を議論し、Rankine-Hugoniotの関係をRayleigh線と衝撃波断熱線を用いて求めた。断熱圧縮および断熱膨張の両衝撃波は気体の飽和曲線上の臨界点に接近して存在することを証明した。これは既知の事実であるが、いくつかの興味ある衝撃波の特性を新しく発見した。つぎにTVD法を用いて相関Euler方程式の数値解を求めた。本計算結果は理論的予測と部分的には一致を示したが、衝撃波不安定性は必ずしも良いシミュレートが出来なかった。, In this paper, shock waves propagating in a van der Waals gas are studied analytically and numerically. First the thermodynamic characteristics of the van der Waals gas are briefly discussed and then the Rankine-Hugoniot relations are obtained by using the Rayleigh line and the shock adiabatic. It was proved that both the compression and the expansion shocks can exist in the gas whose conditions are close to those at the critical point on the saturation curve. Although this fact has already been well known, several interesting shock characteristics were newly found. Next a Total Variation Diminishing (TVD)-scheme is applied to solve numerically the corresponding Euler equations. It was shown that the numerical results are partly consistent with the analytical predictions. The shock instability, however, was not always well simulated by the TVD-scheme., 資料番号: AA0000294020, レポート番号: NAL SP-30

Bu çalışmada harmonik bir dış tuzaklama potansiyeli göz önüne alınarak sistemin büyük bir çoğunluğunun Mott yalıtkan fazda olduğu durum elde edildikten sonra dış tuzaklama potansiyeli hem tek yönde hem de her iki yönde kaldırılarak sistemin adyabatik ve serbest genleşmesi incelenmiştir. Adyabatik genleşmede termodinamik denge korunarak tuzak yavaş yavaş kaldırılırken serbest genleşmede tuzak ani olarak kaldırılmıştır. Hem tek yönde hem de iki yönde gerçekleşen adyabatik genleşmede dipol etkileşimleri yokken sistem her yönde eşit bir yayılım gösterirken dipol etkileşimleri göz önüne alındığında her örgü konumunda ya tam sayıda parçacığın olduğu ya da hiç parçacığın olmadığı yarı kararlı durumlar gözlemlenmiştir. İki yönde serbest genleşmede dipol etkileşimleri yokken parçacıklar optik örgünün köşelerine doğru bir yayılım gerçekleştirirken dipol etkileşimlerinin negatif olması halinde beklendiği gibi çekici etkileşimden dolayı parçacıkların dağılmadığı gözlemlenmiştir. Dipol etkileşimleri pozitif olarak alındığında ise sistemin dağılması beklenirken bunun aksine ilk halini koruduğunu ve parçacıkların dağılmadığı görülmüştür. Sistemi bir arada tutan etkenin tuzak kaldırıldıktan sonra Mott yalıtkan fazının en dışındaki parçacıkların sistemden ayrılırken ters yönde uyguladığı bir itme kuvveti olduğu düşünülmektedir. Tek yönde serbest genleşmede ise dipol etkileşimleri yokken sistemin bant yapısına benzer özellikler gösterdiği ve dipol etkileşimleri varken iki yönde serbest genleşen Bose gazının davranışlarına benzer davranışlar gösterdiği görülmüştür., In this study a harmonic trapping potential is assumed as a confinement and initial state of the system is prepared in such a way that most of the system is in Mott insulator phase. After the trapping potential is removed in one and in two direction the free and the adiabatic expansion of the system are followed. The trapping potential is removed slowly maintaining the thermodynamic equilibrium for the adiabatic expansion and instantly for the free expansion. For one and two directional adiabatic expansion without the dipole-dipole interactions, the system shows a regular expansion dynamic. But when the dipole-dipole interactions are considered, the system shows a metastable state where each lattice site is occupied by one particle or by none. For two directional free expansion without the dipole-dipole interactions, the system shows an expansion through the corners of the lattice. But for negative dipole-dipole interactions as it is expected the system does not expand and almost maintains the initial state because of the attractive interactions. Surprisingly the system with positive dipolar interactions behaves almost like the system with negative dipolar interactions, i.e. maintains the initial distribution and do not expand. We believe that this is due to the bacward force applied by the few particles emitted from the surface. For one directional free expansion it is seen that the system shows band like structure without the dipole-dipole interactions and that the system shows behaviours like the behaviours it is seen in the two directional expansion when we consider the dipole-dipole interactions.

We have studied the microscopic solvent structure of dimethyl sulfoxide-water mixtures and its influence on the solvation structure of solute from a clustering point of View, by means of a specially designed mass spectrometric system. It was observed that the propensity to the cluster formation is nonlinearly dependent on the solvent composition, exhibiting the existence of a critical value of mixing ratios where drastic changes in the microscopic solvent structure occur. It was also demonstrated that in such a solvent mixture the solvation structure of solutes such as 2-butanol, cyclopentanol, cyclohexanol, and phenol is greatly related to the microscopic solvent structures, implying that solute species interact with already established solvent clusters, rather than with individual solvent molecules.

2014 Experimental and theoretical studies are made of the associative molecular gas ionization phenomena in N2 and CO under the adiabatic expansion and cooling of a shock-heated gas. It is shown that for a wide range of conditions, the contribution of the associative ionization mechanism substantially exceeds (by several orders of magnitude) the thermal one. Revue Phys. Appl. 17 (1982) 15-20 JANVIER 1982, PAGE

A compressed air driven generator is proposed, where the pneumatic energy is converted into mechanical energy using two vane-type rotational actuators. The use of a second actuator with a higher displacement in order to produce a thermodynamic expansion allows to reach a better energetic efficiency in comparison to the classical operation of such actuators. The alternating movement of the angular actuators is transformed into a unidirectional rotational motion with the help of a mechanical motion rectifier. The paper analyses the enhancement of the energetic performance of the system. An experimental set-up is also described. The performance of the new system is described, and the limits of its realization is commented on the base of experimental recordings of the evolution of the pressure in the chambers.