Compound Cleaning Agent for Oily Sludge from Experiments and Molecular Simulations

<p> Despite the relevance of properly setting ionic concentrations in Molecular Dynamics (MD) simulations, methods or practical rules to set ionic strength are scarce and rarely documented. Based on a recently proposed thermodynamics method we provide an accurate rule of thumb to define the electrolytic content in simulation boxes. Extending the use of good practices in setting up MD systems is promptly needed to ensure reproducibility and consistency in molecular simulations.</p>

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On the Use of Quantum Thermal Bath in Unimolecular Fragmentation Simulations

10.26434/chemrxiv.8870594.v2 ◽

2019 ◽

Author(s):

Riccardo Spezia ◽

Hichem Dammak

Keyword(s):

Degrees Of Freedom ◽

Molecular Simulations ◽

Zero Point ◽

Thermal Bath ◽

Unimolecular Dissociation ◽

Point Energy ◽

Rotational Degrees Of Freedom ◽

The Difference ◽

Nuclear Effects

<div> <div> <div> <p>In the present work we have investigated the possibility of using the Quantum Thermal Bath (QTB) method in molecular simulations of unimolecular dissociation processes. Notably, QTB is aimed in introducing quantum nuclear effects with a com- putational time which is basically the same as in newtonian simulations. At this end we have considered the model fragmentation of CH4 for which an analytical function is present in the literature. Moreover, based on the same model a microcanonical algorithm which monitor zero-point energy of products, and eventually modifies tra- jectories, was recently proposed. We have thus compared classical and quantum rate constant with these different models. QTB seems to correctly reproduce some quantum features, in particular the difference between classical and quantum activation energies, making it a promising method to study unimolecular fragmentation of much complex systems with molecular simulations. The role of QTB thermostat on rotational degrees of freedom is also analyzed and discussed. </p> </div> </div> </div>

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Analysis and calculation of the process of low-pressure reverse osmosis during recycling of hygienic water

Space engineering and technology ◽

10.33950/spacetech-2308-7625-2019-2-28-36 ◽

2019 ◽

pp. 28-36

Author(s):

Leonid S. Bobe ◽

Nikolay A. Salnikov

Keyword(s):

Mass Transfer ◽

Reverse Osmosis ◽

Life Support ◽

Space Station ◽

Low Pressure ◽

Operating Pressure ◽

Life Support System ◽

Cleaning Agent ◽

The Difference ◽

Pressure Channel

Analysis and calculation have been conducted of the process of low-pressure reverse osmosis in the membrane apparatus of the system for recycling hygiene water for the space station. The paper describes the physics of the reverse osmosis treatment and determines the motive force of the process, which is the difference of effective pressures (operating pressure minus osmotic pressure) in the solution near the surface of the membrane and in the purified water. It is demonstrated that the membrane scrubbing action is accompanied by diffusion outflow of the cleaning agent components away from the membrane. The mass transfer coefficient and the difference of concentrations (and, accordingly, the difference of osmotic pressures) in the boundary layer of the pressure channel can be determined using an extended analogy between mass transfer and heat transfer. A procedure has been proposed and proven in an experiment for calculating the throughput of a reverse osmosis apparatus purifying the hygiene water obtained through the use of a cleaning agent used in sanitation and housekeeping procedures on Earth. Key words: life support system, hygiene water, water processing, low-pressure reverse osmosis, space station.

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