Virial expansions and augmented van der Waals approach: Application to Lennard-Jones-like Yukawa fluid

We argue that recently proposed [Melnyk et al., Fluid Phase Equilibr., 2009, Vol. 279, 1] a criterion to split the pair interaction energy into two parts, one of which is forced to be responsible the most accurate as possible for excluded volume energy in the system, results in expressions for the virial coefficients that improve the performance of the virial equation of state in general, and at subcritical temperatures, in particular. As an example, application to the Lennard-Jones-like hard-core attractive Yukawa fluid is discussed.Comment: 12 pages, 6 figure

Improved first order mean spherical approximation for simple fluids

A perturbation approach based on the first-order mean spherical approximation (FMSA) is proposed. It consists in adopting a hard-sphere plus short-range attractive Yukawa fluid as the novel reference system, over which the perturbative solution of the Ornstein-Zernike equation is performed. A choice of the optimal range of the reference attraction is discussed. The results are compared against conventional FMSA/HS theory and Monte-Carlo simulation data for compressibility factor and vapor-liquid phase diagrams of the medium-ranged Yukawa fluid. Proposed theory keeps the same level of simplicity and transparency, as the conventional FMSA/HS approach does, but shows to be more accurate.Comment: 8 pages, 3 figure

Mean spherical approximation for the Lennard-Jones-like two Yukawa model: Comparison against Monte Carlo data

Monte Carlo simulation studies are performed for the Lennard-Jones like two Yukawa (LJ2Y) potential to show how properties of this model fluid depend on the replacement of the soft repulsion by the hard-core repulsion. Different distances for the positioning of hard core have been explored. We have found, that for temperatures that are slightly lower and slightly higher of the critical point temperature for the Lennard-Jones fluid, placing the hard core at distances that are shorter than zero-potential energy is well justified by thermodynamic properties that are practically the same as in original LJ2Y model without hard core. However, going to extreme conditions with the high temperature one should be careful since presence of the hard core provokes changes in the properties of the system. The later is extremely important when the mean spherical approximation (MSA) theory is applied to treat the Lennard-Jones-like fluid.Comment: 11 pages, 13 figure

Description of possibilities of numerical control in machine tools

Tato práce obsahuje možnosti a popis císlicového rízení obrábecích stroju. Je zde zmínena historie a vývoj císlicového rízení a popis nekterých rídicích systému. Zabývá se také bezpecností v oblasti jejich císlicového rízení.This work contains potential and description numerical control in machine tools. There are history and development of numerical control and description same control systems. It is concerned with safety in areas of numerical control.

Phase Behavior of Colloidal Superballs: Shape Interpolation from Spheres to Cubes

The phase behavior of hard superballs is examined using molecular dynamics within a deformable periodic simulation box. A superball's interior is defined by the inequality $|x|^{2q} + |y|^{2q} + |z|^{2q} \leq 1$, which provides a versatile family of convex particles ($q \geq 0.5$) with cube-like and octahedron-like shapes as well as concave particles ($q < 0.5$) with octahedron-like shapes. Here, we consider the convex case with a deformation parameter q between the sphere point (q = 1) and the cube (q = 1). We find that the asphericity plays a significant role in the extent of cubatic ordering of both the liquid and crystal phases. Calculation of the first few virial coefficients shows that superballs that are visually similar to cubes can have low-density equations of state closer to spheres than to cubes. Dense liquids of superballs display cubatic orientational order that extends over several particle lengths only for large q. Along the ordered, high-density equation of state, superballs with 1 < q < 3 exhibit clear evidence of a phase transition from a crystal state to a state with reduced long-ranged orientational order upon the reduction of density. For $q \geq 3$, long-ranged orientational order persists until the melting transition. The width of coexistence region between the liquid and ordered, high-density phase decreases with q up to q = 4.0. The structures of the high-density phases are examined using certain order parameters, distribution functions, and orientational correlation functions. We also find that a fixed simulation cell induces artificial phase transitions that are out of equilibrium. Current fabrication techniques allow for the synthesis of colloidal superballs, and thus the phase behavior of such systems can be investigated experimentally.Comment: 33 pages, 14 figure

The analysis of Technological Opportunities within the Placing and Using of Power Plant Fly Ash in the Open Pit Mines.

Cílem mé předkládané diplomové práce je popis možných technologií ukládání VEP na uhelném lomu Vršany. Technické možnosti zakládání kolejovými a pásovými zakladači, zakládání lopatovými rypadly s využitím pomocné mechanizace. Práce řeší a popisuje proti prašná opatření za pomoci skrápění a mlžících stěn. Navrhuje realizací nového uložiště na lomu Šverma, stanovuje jeho parametry a kapacitu. Součástí je i sumarizace nákladů včetně ekonomického zhodnoceníThe aim of my submitted diploma thesis is to describe possible technologies of VEP storage at the Vršany coal mine. Technical possibilities of loading with rail and belt stackers, loading with shovel excavators with the use of auxiliary mechanization. The work solves and describes anti-dust measures with the help of sprinkling and fogging walls. He designs a new repository at the Šverma quarry, determines its parameters and capacity. It also includes a summary of costs, including economic evaluation542 - Katedra hornického inženýrství a bezpečnostivýborn

Potential of mean force between ions in infinitely diluted simple short-range models of aqueous electrolytes

As an attempt to assess the effect of the long-range electrostatic interactions in solutions of electrolytes, a simple short-range model (SSM) of electrolytes made up of primitive water and primitive ions (i. e., ions whose Coulombic interaction with water has been replaced by a triangular-well interaction) has been considered to compute the potential of mean force. The sizes of the primitive ions have been set so as to approximate realistic NaCl, LiI, and CsCl electrolytes. It is shown that despite the missing longrange Coulombic interaction the model captures the basic features of real electrolytes while the indirect, i.e. water mediated, potential of mean force in the SSM is in qualitative agreement with that of realistic models.Обчислення потенціалу середньої сили для спрощеної моделі з короткодіючими взаємодіями (кулонівська взаємодія між іонами і водою замінена взаємодією трикутної ями) розглядається як спроба визначити ефект далекодіючих електростатичних взаємодій у розчинах електролітів. Розміри таких розчинених іонів вибирались таким чином, щоб апроксимувати реальні NaCl, LiI, та CsCl розчини електролітів. Показано, що, незважаючи на нехтування далекодіючими кулонівськими взаємодіями, модель відображає основні характеристики реальних розчинів електролітів, тоді як непряма взаємодія між іонами опосередкована водою, тобто потенціал середньої сили якісно добре узгоджений з результатами реалістичних моделей

Chemical potential of quadrupolar two-centre Lennard-Jones fluids by gradual insertion

The gradual insertion method for direct calculation of the chemical potential by molecular simulation is applied in the NpT ensemble to different quadrupolar two-centre Lennard-Jones fluids at high density state points. The results agree well with Widom's test particle insertion but show at very high densities significantly smaller statistical uncertainties. The gradual insertion method, which is coupled here with preferential sampling, extends the density range where reliable information on the chemical potential can be obtained. Application details are reported