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The objective of this work was to study the behavior of the azeotropic points of the methanol + DMC system under elevated pressures. We obtained isothermal vapor–liquid equilibria (VLE) data for this system at 383.15, 403.15, and 413.15 K by a static method. The azeotropic points were determined from the experimental VLE data. The temperature and pressure dependencies of the determined azeotropic points are discussed and compared with ones measured at reduced pressure. The experimental VLE data were represented by two activity coefficient models (non-random two-liquid and Wilson models). We also tested the modified UNIFAC (Dortmund) model for prediction of the VLE and azeotropic points. The azeotropic points of this system could be obtained over the pressure range from reduced pressures to elevated ones.

The aim of the paper is to study systems with one-and-a-half degrees of freedom generated by a Hamiltonian with a quartic unperturbed part and broad perturbation spectrum. To this end, an approximate interpolating Hamiltonian system is firstly studied. Behaviour of the Poincare–Birkhoff or dimerised chains in their routes to reconnection when the perturbation parameter varies is particularly presented. In the second step, a discrete system associated to the full Hamiltonian system is constructed and studied. We point out interesting properties of the dynamics of the Poincare–Birkhoff or dimerised chains, such as pairs of homoclinic orbits to the same equilibrium point (sandglass) and triple reconnection. Then we use the scenario of reconnections to explain the destruction of transport barriers in the non-autonomous system.

Limit cycle bifurcations for a class of perturbed planar piecewise smooth systems with 4 switching lines are investigated. The expressions of the first order Melnikov function are established when the unperturbed system has a compound global center, a compound homoclinic loop, a compound 2-polycycle, a compound 3-polycycle or a compound 4-polycycle, respectively. Using Melnikov’s method, we obtain lower bounds of the maximal number of limit cycles for the above five different cases. Further, we derive upper bounds of the number of limit cycles for the later four different cases. Finally, we give a numerical example to verify the theory results.

The objective of this study is the selection of a suitable entrainer for the separation of the binary azeotropic mixture, namely methanol + dimethyl carbonate (DMC) by extractive distillation. In this study, 2-ethoxyethanol and 4-methyl-2-pentanone were considered as entrainer candidates for the separation of methanol and DMC. Isobaric vapor–liquid equilibria (VLE) were measured for the ternary mixtures methanol + DMC + 2-ethoxyethanol and methanol + DMC + 4-methyl-2-pentanone, and for their constituent binary mixtures, under reduced pressures of 66.66 kPa and 93.32 kPa. Experimental VLE data for the constituent binary mixtures were represented by the Wilson and the NRTL model. The VLE predictions for two ternary mixtures were compared with the experimental VLE data on the basis of the Wilson or NRTL parameters obtained from the constituent binary VLE data. The modified UNIFAC (Dortmund) model was also used for the prediction of the binary and ternary mixtures. The solvent effects of the two entrainer candidates investigated are discussed using the predicted results for the ternary mixtures and both 2-ethoxyethanol and 4-methyl-2-pentanone were found to be suitable entrainers for the separation of methanol and DMC. When the selectivity of 2-ethoxyethanol and 4-methyl-2-pentanone are compared, it could be concluded from the separation factors that 4-methyl-2-pentanone shows a higher selectivity.

The present work is devoted to investigate the existence of heteroclinic orbits in two three-dimensional autonomous systems, more exactly in the Lu and the T systems. The two systems belong to the class of Lorenz systems, having the nonlinear terms of order two. We prove that, under some constraints for the parameters, the both systems have exactly two heteroclinic orbits which are symmetrical with respect to the z -axis. We register also results on closed and homoclinic orbits for the Lu system.

Magnetic field lines behaviour in a reversed shear tokamak can be described by a one and a half degree of freedom Hamiltonian system. In order to get insights into its dynamics we study numerically a global model for a Poincare map associated to such a system. Mainly we investigate the scenario of reconnection of the invariant manifolds of two hyperbolic orbits of the same type n/m and show that it is a generic one. When the two Poincare–Birkhoff chains involved in this process are aligned in phase, i.e. they are in a nongeneric position, a sequence of two saddle–center bifurcations occur in one of the chains, interfering with the former elliptic orbit of that chain, such that at the reconnection threshold the two chains are in a generic position. Dynamics around the new created configuration at the reconnection appears to vary from a regular motion to a chaotic one. In connection with the study of this global bifurcation we give the first example of region of instability in the dynamics of a nontwist map.

Vapour–liquid equilibrium (VLE) data for the binary systems ethanol+methyl propanoate and ethanol+methyl butanoate at 326.30 and 346.30 K and vapour pressures (VPs) for both esters were measured by a circulation method. The two systems exhibit azeotropic behaviour. The VLE data were correlated using the Redlich–Kister, Wilson and NRTL equations. Molar excess volumes for the binary systems at 298.15 K were determined and correlated.

Reliable azeotropic data have been measured for the binary systems ethanol+diethoxymethane, diethoxymethane+1-propanol, diethoxymethane+heptane, and cyclohexane+diethoxymethane with the help of a wire band column. Additionally molar excess enthalpies (HE) for the binary mixtures of diethoxymethane with hexane, 1-octene, methanol and ethanol at 363.15 K have been determined with an isothermal flow calorimeter. The experimental data were compared with the results using the available “ether” main group of the group contribution method Modified UNIFAC (Dortmund), which is a well-known model for the prediction of phase equilibria and excess properties. For the description of the HE data a Redlich–Kister polynomial was also used. The aim of this work is to supplement the available data base for acetal systems required for the introduction of a new “acetal” group in the Modified UNIFAC (Dortmund) model.

Purpose Right ventricular (RV) apex pacing is associated with LV dyssynchrony. Alternate RV pacing sites (mid RV septum; the RV outflow tract (RVOT)) were considered, with no clear benefit. The aim of this study is to find a reliable method of septal lead placement ant to identify those pacing sites which provide a better LV electrical activation. Methods 50 consecutive patients reffered for pacemaker implants due to AV block were included. Patients with history of heart failure or LVEF Results 92%(46) of the patients had the RV lead in septal position (32 in mid RV and 14 in RVOT) while 8% (4 pts) had the RV lead on the RVOT free wall as shown by echo. An anteriorly oriented lead in the left anterior oblique fluoroscopic projection was specific for free wall position while a positive QRS in DI in RVOT position was suggestive for free wall position on the ECG. No correlation was made between paced QRS axis and LV dyssinchron. A QRS duration of>160 ms was associated with significant LV dyssinchrony (SPWMD>130 ms and septal to lateral t>70 ms). Conclusions RV lead placement on the RV septum can be reliably achieved using a specialy shaped stilet and LAO projection for confirmation. A wide paced QRS is correlated with significant intra LV dyssinchrony and therefore the pacing site with the narrowest QRS should be sought.