scholarly journals Phase Transitions in Nematic Fluids

2010 ◽  
Vol 2 (3) ◽  
pp. 419
Author(s):  
A. Oukouiss
Keyword(s):  
Solid Phase ◽  
Phase Behaviour ◽  
Isotropic Liquid ◽  
Rich Phase ◽  
First Order ◽  
Isotropic Solid ◽  
System Of Particles ◽  
Small Domain ◽  
Van Der Waals Theory ◽  
Anisotropic Interactions

We use a simple van der Waals theory, suitably extended to the solid phase and to anisotropic interactions, to study the phase behaviour of a system of particles with nematic interactions. Very rich phase behaviour is found which indicates, in particular, that the nematic liquid is stable only for large values of the strength of the nematic interactions. The isotropic liquid-nematic liquid and the isotropic solid-nematic solid transitions are always first-order. Additionally, we have found that the nematic liquid is thermodynamically stable only in a small domain of the temperature-density plane contained between two triple lines. Keywords:  Phase diagrams; Nematic interactions; Free energy; Transitions. © 2010 JSR Publications. ISSN: 2070-0237 (Print); 2070-0245 (Online). All rights reserved. DOI: 10.3329/jsr.v2i3.4438                 J. Sci. Res. 2 (3), 419-432 (2010) 

Thermodynamics, static properties and transport behaviour of fluids with competing interactions

2022 ◽  
Author(s):  
Roman Perdomo-Pérez ◽  
Jaime Martínez Rivera ◽  
Norma Caridad Palmero Cruz ◽  
Miguel Angel Sandoval Puentes ◽  
Javier Alejandro Sánchez Gallegos ◽  
...  
Keyword(s):  
Phase Behaviour ◽  
Model Systems ◽  
Static Properties ◽  
Competing Interactions ◽  
Intermediate Range Order ◽  
System Of Particles ◽  
Transport Behaviour ◽  
Square Well ◽  
Competing Interaction ◽  
Repulsive Forces

Abstract Competing interaction fluids have become ideal model systems to study a large number of phenomena, for example, the formation of intermediate range order structures, condensed phases not seen in fluids driven by purely attractive or repulsive forces, the onset of particle aggregation under in- and out-of-equilibrium conditions, which results in the birth of reversible and irreversible aggregates or clusters whose topology and morphology depend additionally on the thermodynamic constrictions, and a particle dynamics that has a strong influence on the transport behaviour and rheological properties of the fluid. In this contribution, we study a system of particles interacting through a potential composed by a continuous succession of a short-ranged square-well, an intermediate-ranged square-shoulder and a long-ranged square-well. This potential model is chosen to systematically analyse the contribution of every component of the interaction potential on the phase behaviour, the microstructure, the morphology of the resulting aggregates and the transport phenomena of fluids described by competing interactions. Our results indicate that the inclusion of a barrier and a second well leads to new and interesting effects, which in addition result in variations of the physical properties associated to the competition among interactions.

scholarly journals Waste to Carbon: Influence of Structural Modification on VOC Emission Kinetics from Stored Carbonized Refuse-Derived Fuel

2019 ◽  
Vol 11 (3) ◽  
pp. 935 ◽  
Author(s):  
Andrzej Białowiec ◽  
Monika Micuda ◽  
Antoni Szumny ◽  
Jacek Łyczko ◽  
Jacek Koziel
Keyword(s):  
Structural Modification ◽  
Solid Phase ◽  
Gas Chromatography Mass Spectrometry ◽  
Order Kinetic ◽  
Voc Emissions ◽  
Voc Emission ◽  
First Order ◽  
Refuse Derived Fuel ◽  
Volatile Organic ◽  
Order Kinetic Model

The torrefaction of municipal solid waste is one of the solutions related to the Waste to Carbon concept, where high-quality fuel—carbonized refuse-derived fuel (CRDF)—is produced. An identified potential problem is the emission of volatile organic compounds (VOCs) during CRDF storage. Kinetic emission parameters have not yet been determined. It was also shown that CRDF can be pelletized for energy densification and reduced volume during storage and transportation. Thus, our working hypothesis was that structural modification (via pelletization) might mitigate VOC emissions and influence emission kinetics during CRDF storage. Two scenarios of CRDF structural modification on VOC emission kinetics were tested, (i) pelletization and (ii) pelletization with 10% binder addition and compared to ground (loose) CRDF (control). VOC emissions from simulated sealed CRDF storage were measured with headspace solid-phase microextraction and gas chromatography–mass spectrometry. It was found that total VOC emissions from stored CRDF follow the first-order kinetic model for both ground and pelletized material, while individual VOC emissions may deviate from this model. Pelletization significantly decreased (63%~86%) the maximum total VOC emission potential from stored CDRF. Research on improved sustainable CRDF storage is warranted. This could involve VOC emission mechanisms and environmental-risk management.

scholarly journals A First Order Solid Phase Reaction

Nature ◽  
1930 ◽  
Vol 125 (3143) ◽  
pp. 129-129 ◽  
Author(s):  
BERNARD LEWIS ◽  
HANS-JOACHIM SCHUMACHER
Keyword(s):  
Solid Phase ◽  
Solid Phase Reaction ◽  
Phase Reaction ◽  
First Order

Dielectric Spectroscopy of (bis)Thiourea Pyridinium Bromide

2004 ◽  
Vol 59 (11) ◽  
pp. 857-860 ◽  
Author(s):  
A. Marczak ◽  
P. Czarnecki ◽  
S. Mielcarek
Keyword(s):  
Phase Transitions ◽  
Dielectric Spectroscopy ◽  
Solid Phase ◽  
Ion Dynamics ◽  
Pyridinium Bromide ◽  
First Order ◽  
New Information ◽  
First Order Transition ◽  
Dsc Method ◽  
Disorder Type

Policrystalline (bis)thiourea pyridinium bromide has been studied with dielectric spectroscopy and DSC method. New information about phase transitions in (bis)thiourea pyridinium bromide has been obtained and discussed. Two solid-solid phase transitions (at T2 = 150 K - first order transition of order-disorder type, and T1 = 180 K - second order) have been revealed. A change of the ion dynamics is observed at T2

First-order-reversal-curve analysis of rare earth permanent magnet nanostructures: insight into the coercivity enhancement mechanism through regulating the Nd-rich phase

2021 ◽  
Author(s):  
Junjie Xu ◽  
Kai Zhu ◽  
Wei Li ◽  
Xiaobai Wang ◽  
Ziyu Yang ◽  
...  
Keyword(s):  
Rare Earth ◽  
Permanent Magnet ◽  
Curve Analysis ◽  
Magnetic Interactions ◽  
Phase Content ◽  
Rich Phase ◽  
Enhancement Mechanism ◽  
First Order ◽  
Insight Into

The coercivity enhancement mechanism of Nd2Fe14B-based nanostructures with Nd-rich phase is revealed by first-order-reversal-curve diagram, which is that increased Nd-rich phase content leads to optimized magnetic interactions and microstructure.

Tacoma controls tastes and odours with ozone

2007 ◽  
Vol 55 (5) ◽  
pp. 137-144 ◽  
Author(s):  
M. Carlson ◽  
T. Chen ◽  
C. McMeen ◽  
I.H. Suffet ◽  
M. Zhang
Keyword(s):  
Hydrogen Peroxide ◽  
Analytical Methods ◽  
Contact Time ◽  
Solid Phase Microextraction ◽  
Solid Phase ◽  
First Order ◽  
Ozone Dose ◽  
Gorge Reservoir ◽  
Flavour Profile ◽  
As Solid Phase

The study is focussed on the conditions that would provide the best ozone oxidation to decrease the taste and odour of the water from Eagle Gorge Reservoir. This study incorporated advanced analytical methods, such as solid phase microextraction (SPME) and flavour profile analyses (FPA), to evaluate the best method for improving taste and odour. The study developed first-order relationships between ozone dose and the oxidation of several taste and odour compounds. The results focussed on the importance and interactions between ozone dose, pH, hydrogen peroxide and contact time.

Residue analysis of fosthiazate in cucumber and soil by QuEChERS and GC-MS

2014 ◽  
Vol 68 (10) ◽  
Author(s):  
Min Wu ◽  
Jiye Hu
Keyword(s):  
Solid Phase ◽  
Residue Analysis ◽  
Field Trials ◽  
Residue Level ◽  
Gas Chromatography Mass Spectrometry ◽  
Dispersive Solid Phase Extraction ◽  
First Order ◽  
First Order Kinetics ◽  
Maximum Residue Level ◽  
Relative Standard

AbstractA convenient method was developed for the determination and validation of fosthiazate in cucumber and soil. The procedure is based on liquid partitioning with acetonitrile followed by dispersive solid phase extraction as the clean-up step, after which samples were analysed by gas chromatography-mass spectrometry (GC-MS). The average recoveries ranged from 91.2 % to 99.0 % with relative standard deviations (RSDs) of less than 6.05 %, at three fortification levels (0.02 mg kg−1, 0.1 mg kg−1, 0.5 mg kg−1) in cucumber and soil, and the limits of quantification (LOQs) for fosthiazate were all established at 0.02 mg kg−1. The proposed method was applied successfully to analyses of the dissipation and residue of fosthiazate in field trials. The dissipation rate of fosthiazate was described using pseudo-first-order kinetics with a half-life of 4.33 days and 4.08 days in soil in Beijing and Shandong, respectively. In the terminal residue experiment, fosthiazate residues in cucumber and soil were clearly below the maximum residue level (MRL, 0.2 mg kg−1) set in China.

scholarly journals Cocoa Butter Saturated with Supercritical Carbon Dioxide: Measurements and Modelling of Solubility, Volumetric Expansion, Density and Viscosity

2010 ◽  
Vol 8 (1) ◽  
Author(s):  
Brice Calvignac ◽  
Elisabeth Rodier ◽  
Jean-Jacques Letourneau ◽  
Pedro Miguel Almeida dos Santos ◽  
Jacques Fages
Keyword(s):  
Carbon Dioxide ◽  
Supercritical Carbon Dioxide ◽  
Cocoa Butter ◽  
Phase Behaviour ◽  
Viscosity Reduction ◽  
Co2 Solubility ◽  
Rich Phase ◽  
Volumetric Expansion ◽  
Supercritical Carbon

The use of supercritical carbon dioxide technology for lipid processing has recently developed at the expense of traditional processes. For designing new processes the knowledge of thermophysical properties is a prerequisite. This work is focused on the characterization of physical and thermodynamic properties of CO2-cocoa butter (CB) saturated mixture. Measurements of density, volumetric expansion, viscosity and CO2 solubility were carried out on CB-rich phase at 313 and 353 K and pressures up to 40 MPa. The experimental techniques have previously been compared and validated. Density measurements of CB and CB saturated with CO2, were performed using the vibrating tube technology at pressures ranging from 0.1 to 25 MPa. Experimental values correlated well with the modified Tait equation. CO2 solubility measurements were coupled to those of density in the same pressures ranges. At 25 MPa, the solubility of CO2 is 31.4 % and 28.7 % at 313 and 353 K. Phase behaviour was investigated using a view cell in order to follow the expansion of the CB-rich phase with the rise in pressure. Volumetric expansion up to 47 % was measured and correlated to the CO2 solubility. Phase inversion was observed at 313 K and 40 MPa. Lastly, we developed an innovative falling ball viscometer for high pressure measurements. Viscosity measurements were carried out up to 25 MPa showing a viscosity reduction up to 90 % upon CO2 dissolution. These results were correlated with two empirical models. A new model here presented, was favourably compared with the Grunberg and Nissan model. All the experimental results are consistent with the available literature data for the CB-CO2 mixture and other fat systems. This work is a new contribution to the characterization of physical and thermodynamic behaviour of fats in contact with CO2 which is necessary to design supercritical fluid processes for fats processing.

Semi-Analytical Solution of a Non-Linear Heat Transfer Model for a Tubular Co-Current Moving-Bed Reactor with a First-Order Chemical Reaction in the Solid Phase

2021 ◽  
Author(s):  
Lucas Ivan de Souza Vereza Medeiros ◽  
Sávio Leandro Bertoli ◽  
Marcel Jefferson Gonçalves ◽  
Tuany Gabriela Hoffmann ◽  
Betina Louise Angioletti ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Chemical Reaction ◽  
Solid Phase ◽  
Transfer Model ◽  
Moving Bed ◽  
First Order ◽  
Order Chemical Reaction ◽  
Non Linear ◽  
Linear Problems ◽  
First Order Chemical Reaction

Abstract The development of mathematical models plays a fundamental role in the design, optimization and control of processes. Regarding heat transfer in moving bed reactors, the chemical reaction implies in the inclusion of a non-homogeneous and non-linear term in model equations, making the analytical integration a very difficult task. Up to date, there is not an analytic and/or a semi-analytic solution to a heat transfer model of a moving bed reactor (MBR) with isothermal walls to distributed parameter in the solid phase. Therefore, starting from analytical solutions of the associated homogeneous (linear) problems and through the spectral expansion of the non-homogeneous vector, this work presents strategies for determining semi-analytical solutions of non-homogeneous and non-linear problems. A MBR with a first-order chemical reaction in the solid phase - kaolinite dehydroxylation in the kaolinite flash calcination process - is selected as the case study; however, the strategies can easily be applied to other non-linear models. Results for conversion, and fluid and particle temperatures, are given for different parameter values. The solutions perform stable, fast and accurate. When compared with a hybrid Finite Difference and Finite Analytic (FD\&FA) numerical method, the solution showed a very good agreement.

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