(Vapour + liquid) equilibria of the {pentafluoroethane (HFC-125) + dimethyl ether (DME)} system

Binary (vapour + liquid) equilibrium data were measured for the {pentafluoroethane (HFC-125) + dimethyl ether (DME)} system at temperatures from (313.15 to 363.15) K. These experiments were carried out with a circulating-type apparatus with on-line gas chromatography. The experimental data were correlated well by the Peng-Robinson Stryjek-Vera equation of state using the Wong-Sandler mixing rules.     

Use of artificial neural networks for calculating derived thermodynamic quantities from volumetric property data

Thermodynamic and transport property data on environmentally acceptable refrigerant fluids are of the utmost interest for the refrigeration industry and, in particular, for designing and optimising refrigeration equipment: heat exchangers and compressors. Up to now, the simultaneous representation of vapour–liquid equilibria (VLE) and pressure–volume–temperature (PVT) data is not satisfactory enough with respect to experimental accuracies. New models are then highly required. Therefore, an effort has been made to develop an alternative to a classical equation of state. This work deals with the potential application of artificial neural networks to represent PVT data within their experimental uncertainty. The second aim of the work is to obtain, by numerical derivatives, other properties such as enthalpies, entropies, heat capacities, expansion coefficients, speed of sounds, etc. Tests presented here were performed on data corresponding to six refrigerants from 240 to 340 K at pressures up to 20 MPa.     

Ordinal subdivision and special pasting in quasicategories

Quasicategories are simplicial sets with properties generalising those of the nerve of a category. They model weak (ω,1)-categories. Using a combinatorially defined ordinal subdivision, we examine composition rules for certain special pasting diagrams in quasicategories. The subdivision is of combinatorial interest in its own right and is linked with various combinatorial constructions.     

Boundedness of singular integral operators with variable kernels

Let K be a generalized Calderón-Zygmund kernel defined on Rn×(Rn?{0}). The singular integral operator with variable kernel given by

     

The p-step iterative algorithm for a system of generalized mixed quasi-variational inclusions with -accretive operators in q-uniformly smooth banach spaces

In this paper, we introduce and study a new system of generalized mixed quasi-variational inclusions with (A,η)-accretive operators in q-uniformly smooth Banach spaces. By using the resolvent operator technique associated with (A,η)-accretive operators, we construct a new p-step iterative algorithm for solving this system of generalized mixed quasi-variational inclusions in real q-uniformly smooth Banach spaces. We also prove the existence of solutions for the generalized mixed quasi-variational inclusions and the convergence of iterative sequences generated by algorithm. Our results improve and generalize many known corresponding results.     

Application of continuous-time programming problems to a class of variational-type inequalities

In this paper, we establish sufficiency criteria under generalized ρ−(η,θ)-invexity conditions for general continuous-time programming problems with nonlinear equality/inequality constraints. Using this we establish some existence criteria for solutions of a class of variational-type inequalities.     

Quality management systems from the perspective of organization of complex systems

The aim of this model is to analyse quality management systems from the standpoint of the organization of complex systems introduced by Robert Rosen. The concept that an organized system, under certain conditions, can be modelled as a living system introduces unsuspected tools to analyse its behaviour. The model is oriented towards the understanding of the implications of modifications introduced in laboratories working with a quality organization following the ISO/IEC 17025 standard.This standard establishes management and technical requirements concerning the documental organization, control of the management and technical records, personnel, equipments, test or calibration methods, etc. The objective of the quality system implementation is to assure the quality of the product, the special consideration being the customer’s satisfaction with all aspects of the service the laboratory offers.The improper use of the quality system tools has an impact on the laboratory activity. The perception of this fact can be negligible at the moment it happens. The model allows us to realize that this alteration always has a negative impact on the customer and it specially affects the continuous improvement that the laboratory must implement.     

New hydrofluorocarbon (HFC) solvents for antimony pentafluoride: Generation and characterization of 1-alkoxypentafluoroallyl cations

Certain hydrofluorocarbons (HFC) stable towards the strong Lewis acid, antimony pentafluoride, were found to function as a solvent for this aggressive reagent. CF₃CF₂CH₂F (HFC-236cb) was demonstrated to be an excellent solvent for SbF₅ and was used for the generation of stable polyfluorinated benzyl and allyl cations. Using this solvent 1-methoxypentafluoroallyl cation and R_FOCFCFCF₂⁺ (R_F = n-C₃F₇ and n-C₄F₉), were generated and characterized by NMR spectroscopy.     

Formation of multiple nanoscale twin boundaries that emit intense light in indirect-gap AlGaAs epilayers

Parallel twin boundaries arranged at similar intervals of nanometer length, that emitted an intense monochromatic light polarized parallel to the boundaries, were self-organized in an indirect-gap AlGaAs epilayer; the epilayer was grown on a rough As-deficient surface of an AlGaAs(0 0 1) substrate with any lattice constant, by conventional metal-organic chemical-vapor deposition. Most boundaries were of -type on B, and they extended from the interface between the epilayer and the substrate. There existed no compositional fluctuation around the boundaries. The formation mechanism was discussed.     

氟里昂134a的真空紫外光电离和光解离的同步辐射研究

利用同步辐射真空紫外光研究了氟里昂134a(CH₂FCF₃)的光电离和光解离过程,通过测量各离子的光电离效率曲线,得到了该分子的电离能(12.68±0.04)eV和所有碎片离子的出现势,运用Gaussian-03计算了母体和中性碎片及相应离子的电子态、对称性和能量.结合理论计算结果对离子出现势的理论值和实验值进行了比较,分析了母体离子可能的光解离通道.