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[Display omitted] Empirical correlations were obtained to calculate the equilibrium pressure of the methane and natural gas (the Srednevilyui gas and condensate field) hydrates formation in sodium bicarbonate solutions, the hydration numbers and dissociation heats of these hydrates were determined. The values of the hydration numbers assume that methane forms hydrates with the CS-I structure and natural gas – CS-II. The dissociation heat of the natural gas hydrates is higher than that of the methane hydrates. [ABSTRACT FROM AUTHOR]

Abstract Deployment of foldable tensegrity-membrane systems is investigated in this article. The major objective of deploying such systems is to extend and tension the attached membrane, which is folded initially, by changing system shapes. During this process, the system operates at two system configuration types, namely, the tensegrity configuration (where the attached membrane is slack) and the tensegrity-membrane configuration (where the attached membrane is tensioned). An energy-based approach is introduced to determine system equilibriums, and the explicit equilibrium conditions for both system configurations are derived. A nonlinear finite element model is used to study system dynamics in the process of deploying two foldable tensegrity-membrane systems. Observations related to system behaviors during deployment are discussed in detail. [ABSTRACT FROM AUTHOR]

Hydrate dissociation equilibrium conditions for carbon dioxide + methane with water, nitrogen + methane with water and carbon dioxide + nitrogen with water were measured using cryogenic sapphire cell. Measurements were performed in the temperature range of 275.75 K–293.95 K and for pressures ranging from 5 MPa to 25 MPa. The resulting data indicate that as the carbon dioxide concentration is increased in the gas mixture, the gas hydrate equilibrium temperature increases. In contrast, by increasing the nitrogen concentration in the gas mixtures containing methane or carbon dioxide decreased the gas hydrate equilibrium temperatures. Furthermore, the cage occupancies for the carbon dioxide + methane system were evaluated using the Van der Waals and Platteeuw thermodynamic theory with the Langmuir adsorption model and Peng-Robinson equation of state. The data demonstrated the increasing promoting effect of carbon dioxide with its concentration. In addition, the motor current changes during the hydrate formation and dissociation processes were measured by keeping the rotation speed of the magnetic stirrer that was connected to a DC motor constant. The motor current measurements were reported and it showed that the hydrate plug formation and dissociation could be predicted by the changes in the motor current. [ABSTRACT FROM AUTHOR]

Caiman meat is considered exotic and its consumption has significantly increased due to its nutritional quality. This study aimed to evaluate the kinetics of water content (WC) and salt content (SC) at different temperatures (1, 5, 10 and 15 °C) and to evaluate the use of mathematical models to predict the mass transfer kinetics until equilibrium conditions during the wet salting of caiman tail fillets. Moisture and chloride analyses were performed throughout the wet salting process. Four models (Peleg; Weibull; Zugarramurdi and Lupín; Diffusion) were tested to predict WC and SC kinetics in caiman tail fillets subjected to wet salting. The increase in the temperature resulted in a reduction (P < 0.05) in WC and an increase (P < 0.05) in SC. Nonlinear effects on WC and SC kinetics were observed between the different temperatures evaluated. Furthermore, the effective diffusion coefficients (D w and D s) increased (P < 0.05) with increasing temperature. Peleg, Weibull, Zugarramurdi and Lupín, and the Diffusion model satisfactorily represented WC and SC rates throughout the process. The kinetic behavior of the parameters of the models corroborated the effects of temperature on those parameters. Peleg was the best model for predicting WC and SC kinetics, and Zugarramurdi and Lupín was the best for predicting the equilibrium conditions of the process (WC∞ SC∞), all parameters which can be used to describe the mass transfer kinetics during wet salting of caiman tail fillets. • The water content (WC) and salt content (SC) kinetics of caiman meat were evaluated. • Nonlinear effects on WC and SC kinetics were observed between the temperatures. • Peleg's model exhibited the best fit for WC and SC kinetics of caiman meat fillets. • The Zugarramurdi and Lupin model better predicts the equilibrium conditions. • Models can be used to predict the time in brine to reach a certain WC and SC in meat. [ABSTRACT FROM AUTHOR]

In a previous work, we showed that the incorporation of a temperature-dependent volume-translation parameter in an equation of state for pure components alters necessarily the prediction of 1-phase and 2-phase properties. On the contrary, if a temperature-independent volume translation parameter is used, most of the 1-phase and 2-phase properties are preserved. In the present study, the influence of the incorporation of a volume translation in an equation of state, on mixture properties (essentially phase equilibria and properties of mixing) is addressed. It is first assumed that the volume-translation parameter of a mixture ( c ) is related to mole fractions through a quadratic mixing rule involving mutual volume translation parameters ( c ij ). It is found that only a simple arithmetic-mean combining rule for c ij makes it possible to preserve phase equilibria. Using such a combining rule entails that the quadratic mixing rule for the c parameter degenerates to a linear mixing rule. Secondly, it is proved that properties of mixing ( g M , h M , s M , c P M …) are preserved if a linear mixing rule is used for the c parameter and altered otherwise. [ABSTRACT FROM AUTHOR]

Since the pioneering work of Professor André Péneloux, volume translations are often applied to cubic equations of state with the aim of improving the description of volumetric properties. Such translations are either constant or temperature-dependent. In any case, it is well-known that both the translated and untranslated models return the same vapor pressure for a given temperature but lead to different saturated molar volumes. Being aware of the invariance of the calculated vapor pressure, it was decided to investigate which properties among the enthalpy, the entropy, the internal energy, the heat capacities, the speed of sound, the property changes on vaporization and many others were altered by a volume translation. All these state functions are indeed volume-dependent and the influence of the translation on their values needs to be clarified. This is particularly important to understand on which experimental data the volume translation should be fitted on. [ABSTRACT FROM AUTHOR]

• New model describing gas hydrate equilibrium conditions in thin pores is proposed. • The equilibrium conditions depend on pore size and properties of adsorbed water. • Gradual transformation of the bound water into hydrate occurs in the pores. • Model predictions are compared with the experimental data obtained previously. Until recently, analysis and interpretation of the equilibrium conditions of hydrate formation from water adsorbed in mesoporous materials have been carried out with the use of the Gibbs-Thomson equation. For this purpose, only the shift of equilibrium conditions due to the small size of hydrate particles formed in the confining pores was taken into account. A distribution of equilibrium temperatures of the hydrate formed in mesoporous materials was interpreted as a consequence of the existence of hydrate particles differing from each other in size. A new equation describing the equilibrium conditions for gas hydrate in thin pores of mesoporous materials is proposed in this work. This equation takes into account the size of hydrate particles together with the chemical potential of pore water in equilibrium with the hydrate. Thus, an increase in the temperature shift from the equilibrium curve causes simultaneous formation of hydrate in smaller and smaller pores, and an increase in the size of gas hydrate particles that have been previously formed in larger pores. The latter occurs due to gradual transformation into hydrate of the layer of bound water, located between the pore wall and hydrate particle being formed in the pore center. Modeling results are compared with the data obtained previously on the equilibrium conditions for the hydrate of carbon dioxide in mesoporous Al 2 O 3 samples. It is demonstrated that experimental results are in reasonable qualitative agreement with the proposed model. [ABSTRACT FROM AUTHOR]

The aim of increasing the share of renewable energy sources to the total energy production has brought a significant increase of the interest in marine energies over the last years. Within them, tidal currents resources have been gaining ground for their advantages in terms of predictability, nonexistence of extreme flows, high load factor, minimal land occupation and visual impact. The authors, working in this field since many years, have been designing a new turbine able to work in the water like a kite, with no support structures, easily connected to the coast by a rope. The constructive easiness, and the lower installation costs are the main machine characteristics, together with the ability to overturn itself when the tidal current changes direction. The turbine equilibrium and mainly the transients related to the sink and surface phases, machine overturning, represent a critical aspect of the design. In the present work, starting from a phenomenological analysis, a simulation of the transients has been carried out in Simulink® environment. The floating stabilizer is a critical component which influences the motion behavior of the machine in the vertical plane and so the trend on the transients. [ABSTRACT FROM AUTHOR]

Rate coefficients for electron impact excitation of the nitrogen molecule have been determined. Calculations have been performed for all relevant non-elastic processes: rotational excitation, vibrational excitation, electronic excitation into singlet and triplet states and particularly for dissociation and ionization. The rate coefficients have been determined for both equilibrium and non-equilibrium conditions in the presence of electric and magnetic fields. For the equilibrium conditions the Maxwellian electron energy distribution function has been used for determining rate coefficients in the energy region from 0 to 17 eV. In the case of the non-equilibrium conditions, where the homogenous electric and magnetic fields are present, we have calculated electron energy distribution functions needed for determining rate coefficients by use of a Monte Carlo simulation developed in our laboratory. The results for both equilibrium and non-equilibrium rate coefficients are presented in the paper and similarities and differences between them have been discussed. [ABSTRACT FROM AUTHOR]

The equilibrium conditions of methane hydrate in the presence of additives of cyclopentanone (C 5 H 8 O) or 4-hydroxy-4-methyl-2-pentanone (C 6 H 12 O 2 , also known as diacetone alcohol) in aqueous solutions were experimentally measured in this study. The hydrate-liquid water-vapor (H-L w -V) three-phase equilibrium conditions were determined by employing the isochoric method within a high pressure cell at low temperature conditions. New experimental results are reported for pressures ranging from 7 to 13 MPa with various concentrations of these additives. It is demonstrated that the cyclopentanone additive has a promotion effect on the formation of methane hydrate, while the other additive of 4-hydroxy-4-methyl-2-pentanone shows an inhibition effect. The structures of methane hydrates with each of the two additives were determined using the Clausius–Clapeyron equation. To simulate the salinity of the seawater environment, this study also measured the hydrate-liquid water-vapor (H-L w -V) three-phase equilibrium temperatures and pressures by adding both additives to brine solution consisted of NaCl at 0.035 mass fraction. In both cases, the additional component of NaCl in the aqueous phase reduces the equilibrium temperature by about 2 K. [ABSTRACT FROM AUTHOR]

The aim of increasing the share of renewable energy sources to the total energy production has brought a significant increase of the interest in marine energies over the last years. Within them, tidal currents resources have been gaining ground for their advantages in terms of predictability, nonexistence of extreme flows, high load factor, minimal land occupation and visual impact. The authors, working in this field since many years, have been designing a new turbine able to work in the water like a kite, with no support structures, but easily connected to the coast by a rope. The constructive easiness, together with lower installation costs, are the main machine characteristics. Moreover it is able to overturn itself when the tidal current changes direction. The turbine equilibrium and mainly the transients related to the sink and surface phases, machine overturning, represent a critical aspect of the design. In the present work, starting from a phenomenological analysis, a simulation of the transients has been carried out in Simulink ® environment. The study, related to the center of gravity, has pointed out the importance of the correct floating stabilizer design which helps the turbine to reach the equilibrium conditions even in case of flow instability. [ABSTRACT FROM AUTHOR]

Highlights: [•] Rate coefficients for electron impact excitation of CO have been calculated. [•] All relevant non-elastic processes have been included in calculations. [•] Equilibrium and non-equilibrium conditions have been considered. [•] Electron energy distribution functions were determined by a Monte Carlo simulation. [•] Rate coefficients have also been determined in the presence of magnetic field. [ABSTRACT FROM AUTHOR]

Abstract: Integral cross sections for electron impact excitation of the first six vibrational levels of the valence state of the carbon monoxide molecule have been determined from our recent measurements of the differential cross sections, in the energy region from threshold to 10eV. These results are used to calculate rate coefficients for electron impact excitation of the state of CO. Calculations are performed for Maxwellian electron energy distribution functions (EEDFs) in the mean electron energy region from 0 to 17eV. By using extended Monte Carlo simulations, the EEDFs and rate coefficients are determined for the non-equilibrium conditions, in the presence of a homogeneous external electric field. These calculations are performed for typical, moderate values of the electric field over gas number density ratios, E/N, from 1 to 1000Td. A small difference between Maxwellian and non-equilibrium rate coefficients was found due to a specific shape of the electron energy distribution functions under the considered conditions. Comparison is also made with the results obtained for EEDFs generated by numerically solving the Boltzmann equation based on a two term Legendre expansion of the velocity distribution function, calculated with the software BOLSIG+ v1.1. [Copyright &y& Elsevier]

Abstract: In this paper, we show how one of the Kyoto Protocol mechanisms, the so-called joint implementation in environmental projects, can be transformed into and studied as an infinite-dimensional quasi-variational inequality. Specifically, we examine the situation in which different countries attempt to fulfill Kyoto commitments by investing in emission reduction or emission removal projects in countries where the abatement costs are lower. We derive the equilibrium conditions and prove their characterization in terms of an infinite-dimensional quasi-variational inequality problem. Finally, we discuss the existence of solutions. [Copyright &y& Elsevier]

Abstract: Attempts of experimental observations of the water dimer spectrum at equilibrium conditions have lasted for more than 40 years since the dimeric hypothesis for extra absorption, but have not yielded any positive confirmed result. In the present paper a new approach is considered: using a high-resolution millimeter-wave spectrum of the water dimer at equilibrium, calculated by a rigorous fully quantum method, we show the potential existence of discernible spectral series of discrete features of the water dimer, which correspond to J+1←J, K lines of E 1 symmetry, already observed in cold molecular beam experiments and having, therefore, well-defined positions. The intensity of spectral series and contrast to the remaining continuum-like spectrum of the dimer are calculated and compared with the monomer absorption. The suitability of two types of microwave spectrometers for observing these series is considered. The collisional line-width of millimeter lines of the dimer at equilibrium is estimated and the width of IR dimer bands is discussed. It is pointed out that the large width of IR dimer bands may pose difficulties for their reliable observation and conclusive separation from the rest of absorption in water vapor. This situation contrasts with the suggested approach of dimer detection in millimeter-waves. [Copyright &y& Elsevier]

Abstract: Rate coefficients for vibrational excitation of the carbon-monoxide molecule, via the 2Π shape resonance in the energy region from 0eV to 5eV have been calculated. Calculations are performed for a Maxwellian electron energy distribution by using our recent experimentally measured differential cross sections for excitation of the first 10 vibrational levels. By using extended Monte Carlo simulations the electron energy distribution functions (EEDFs) and rate coefficients are determined in non-equilibrium conditions, in the presence of a homogeneous electric field. Calculations are performed for typical, moderate values of the electric field over gas number density ratios, E/N. A difference between Maxwellian and non-equilibrium rate coefficients was found due to a specific shape of the electron energy distribution function under the considered conditions. [Copyright &y& Elsevier]

This paper characterizes the necessary and sufficient conditions for tensegrity equilibria. Static models of tensegrity structures are reduced to linear algebra problems, after first characterizing the problem in a vector space where direction cosines are not needed. This is possible by describing the components of all member vectors. While our approach enlarges (by a factor of 3) the vector space required to describe the problem, the advantage of enlarging the vector space makes the mathematical structure of the problem amenable to linear algebra treatment. Using the linear algebraic techniques, many variables are eliminated from the final existence equations. [Copyright &y& Elsevier]

• Robot stiffness is defined by a dimensionally inhomogeneous stiffness matrix (DISM). • Stiffness is evaluated through eigenvalues of two Schur complements of the DISM. • The Schur complements result from the regular solution of the equilibrium equations. • The Schur complements eigenvalues present the collinear stiffness values (CSV). • Robot singularity conditions are formulated in the Schur complement terms. An engineering tool for the robot stiffness evaluation – the collinear stiffness values (CSV) – is applied to an elastically-supported system, whose stiffness is defined by a dimensionally inhomogeneous stiffness matrix (DISM). There are two formal representations of the DISM: as a matrix of the simultaneous linear equations and as a matrix of the quadratic form in single twist entities. The solution of the former and optimization of the latter models are shown to result in identical solutions: the direct stiffness evaluation expressing through eigenvalues of two Schur complements, which are constructed from the blocks of the initial DISM. Both formalizations have a simple engineering interpretation in terms of equilibrium conditions and a virtual work, respectively. The applied solutions are carried out by the wrench transformation technique and the unit twist transformation technique. The eigenvalues of the Schur complements present the translation and rotation stiffness values generically-named as the CSV. The necessary and sufficient conditions of the robot singular configurations are defined. The stiffness-related parameters of the Gough-Stewart platform and serial RRR planar manipulator, including their singularity problem, are formulated through the Schur complements. [ABSTRACT FROM AUTHOR]

Stock status for many medium- and small-scale fisheries is unknown due, for example, to a lack of catch data and the absence of scientific observer programs. However, length-frequency data are often available for such fisheries because they are the cheapest and easiest data to obtain. Various stock assessment methods have been developed that use length-frequency data and make equilibrium assumptions regarding both recruitment and fishing mortality. These assumptions raise questions regarding the reliability of the results, particularly when the method is applied to a single sample of length-frequency. We developed a Length-Based Pseudo-cohort Analysis (LBPA) model whose parameters can be estimated using multiple length frequencies and penalized maximum likelihood, under the assumption that using more than one length-frequency sample reduces the effects of the equilibrium conditions assumed in the model. We explored the performance of LBPA using simulations that examined the implications for estimation of the spawning potential rate (SPR) and the relative fishing mortality (F/F MSY). These simulations considered scenarios related to exploitation rate, steepness, numbers of years and sample sizes for length-frequency, and data weights. The performance of LBPA was compared to that of length-based spawning potential ratio (LBSPR). LBPA performed better with additional length-frequencies than with increased sample size, irrespective of how the data were weighted, and generally outperformed LBSPR. Estimates were more accurate and less biased when exploitation rates were high. This work provides guidelines that should be considered when using length-based pseudo-cohort models for data-poor fisheries. [ABSTRACT FROM AUTHOR]