Sharif Digital Repository

The natural gas liquid recovery is an important process in a gas plant to correct hydrocarbon dew point and earn profit. In this study, a natural gas liquid recovery unit operated based on the Joule–Thomson process was investigated and its performance was optimized. To improve the system performance, the plant configuration and intermediate pressure ratio were defined as the variables and maximization of the natural gas liquid recovery rate and maximization of exergy efficiency were defined as the objective functions. To improve the plant performance, the amount of natural gas liquid recovery rate should be increased. To achieve this goal, several scenarios for the intermediate pressure... 

Direct pyrolysis of citric acid (CA) has been proved to be a facile bottom-up technique for making pristine carbon dots (CD) with homogenous size distribution. However, limited reports are available on systematic optimization of carbonization degree. In this investigation, pyrolysis temperatures between 160 °C and 220 °C were studied, based on CA thermal decomposition path, using various heating durations. The effect of the formation of more carbonized carbon particles (MCCPs), as the major byproduct of this method, on photoluminescence properties of CDs was also considered. The NaOH amount that neutralizes the solution and the effect of dilution on the emission intensity, were introduced as... 

A general investigation of the viscosity of natural gas as a function of temperature, pressure and composition was carried out to develop a generalized correlation. The model obtained was based on 3231 data points of 29 multicomponent mixtures in wide ranges of pressures (0.1-137.8MPa), temperatures (241-473K) and specific gravities (0.573-1.337). Correction terms for non-hydrocarbons of hydrogen sulfide, carbon dioxide and nitrogen were up to 70, 54.4 and 15.8 of mole percent, respectively. The arithmetic average of the model's absolute error was found to be 5.05%, which is acceptable in engineering calculations and has superiority over other methods in its class  

The complex nature of the convective terms in the fluid flow governing equations has caused many researchers to work on estimating more accurate advection term magnitudes by employing better approximate expressions. The trend of progress has been to include more physics of flow in the approximations. However, there is no archival evidence that reports the direct implementation of buoyancy as a physical influence in the advection term modeling. In this work, the influence of buoyancy in an efficient advection term expression is investigated in a control volume context with a collocated grid arrangement. The accuracy of the results obtained by both excluding and including the buoyancy term is... 

It is widely supposed that methodological naturalism, understood as a thesis about the methodology of science, is metaphysically neutral, and that this in turn guarantees the value-neutrality of science. In this paper we argue that methodological naturalism is underpinned by certain ontological and epistemological assumptions including evidentialism and the causal closure of the physical, adoption of which necessitates commitment to metaphysical naturalism. © 2019, Springer Nature B.V  

The article offers a different interpretation of Antony Flew's views about the problem of religious language. This interpretation shows that Flew's ideas can be perceived as a critique of belief in the content of religious statements, rather than a critique of their meaning. By interpreting his thought in this way, it is clear that Flew's approach is not new and we can find similar ideas in the history of theological thought. In connection with this interpretation, the authors analyze prevalent theories related to this problem in order to identify the principal doctrines used to find a new solution. In this regard, the new potential solution is assessed in order to complete the approach... 

One of the most promising methods for transporting natural gas and overcoming its low energy density is adsorbed natural gas (ANG) technology. ANG technology is highly dependent on the perfect conception of adsorption isotherms in different operational conditions and on different adsorbents. In this study, the utilization of a novel mathematical model of least squares support vector machine (LSSVM) for accurate prediction of adsorption isotherm has been examined. The considered variables were temperature, pressure and type of adsorbents. A data set containing 670 experimental data points of methane adsorption on 10 different adsorbents in a broad range of temperature and pressure were used... 

Literary schools are devised to categorize different writers' styles and visions in creating a literary piece of work. Writers tend to project their views by using a vast range of lingual tools. This article takes a specific look at the choice of characters' names by three different writers from three different literary schools, namely, Naturalism, Modernism, and Postmodernism. As designated sets of literary characteristics are traceable in a piece belonging to a certain literary school, one of the ways in which a writer boosts the paradigm is the choice of names for their characters. Three novels are our concern: The Mayor of Casterbridge by Thomas Hardy (a Naturalist), A Portrait of an... 

Optimization of ethane recovery in Phases 4 and 5 of Assalouyeh was studied. The influence of some parameters on the ethane recovery and the sensitivity analysis were determined. The effect of the parameter variation on the neighboring unit showed that a significant energy saving for compressor power consumption could be achieved. Some of the operating conditions of this unit were modified, including columns pressure, split fraction, minimum approach temperature, and expander power. This led to a 6% increase in ethane yield. This is an abstract of a paper presented at the 18th International Congress of Chemical and Process Engineering (Prague, Czech Republic 8/24-28/2008)  

The purpose of this study was to investigate the natural gas hydrate promotion capabilities of the hydrotrope Toluene Sulfonic Acid (TSA) isomers as an additive. The capabilities of TSA isomers were measured with different concentrations. The optimum additive concentration for hydrate formation was determined for the given pressure, temperature, mixing condition, and cooling time. The natural gas hydrate promotability of para-TSA was found to be 20% and 35% more than meta-TSA and ortho-TSA respectively at the optimum concentration. Beyond the optimum TSA concentration, the hydrate formation declined as the ice formation reduced the overall gas-to-water volume ratio in the hydrates  

This paper attempts to study the demand function of natural gas in Iran using smooth transition regression model (STR). To this end, gross domestic productions (GDP), real price of natural gas and temperature have been employed as variables explaining the natural gas demand from 1971 to 2009. The results indicate that natural gas demand follows an LSTR1 nonlinear two-regime model if the real price of natural gas is considered as the transition variable. Estimation results also indicate that the slope parameter approximately equals the high value of 10 and the threshold value is 31.82. Rials. 111 USD=24,700 Rials (IRR) at April 2013. per one cubic meter consumption of natural gas. The results... 

Microbial cells are producers of natural polymers present in plant cells. Production of pullulan (an extracellular microbial polysaccharide) by Aureobasidium pullularia pullulans (P. pullulans) was studied under fermentation conditions, and kinetic parameters were determined. Pullulan formation obeyed a growth and non-growth associated term. PHB (polyhydroxybutyrates) an intracellular biopolymer production by Rastonia eutropha (Alcaligen eutrophus), R. eutropha was studied under different culture media, including synthetic and natural carbon sources. Molasses as a natural carbon source in the culture media presented high efficiency in cell and biopolymer accumulation  

In the second part of the paper, we compare the solutions produced in the framework of the conference "Mathematical and numerical aspects of low Mach number flows" organized by INRIA and MAB in Porquerolles, June 2004, to the reference solutions described in Part 1. We make some recommendations on how to produce good quality solutions, and list a number of pitfalls to be avoided. © EDP Sciences, SMAI 2005  

The circulating fluid in natural circulation loops would absorb heat from the hot zone (source) and will transport it to the cold zone (sink) without using of any mechanical pumps or other devices. The fluid density differences in hot and cold zones would lead buoyancy force which is introduced as the body force for the loop. By introducing the one-dimensional conservation equations; mass, momentum and energy in the loop and applying the perturbation method, or linear stability theory, would help us to study the stability of the rectangular natural circulation loop. The conservation equations in transient form were solved using the finite difference method. The results obtained from the... 

With the specific target of calculating the pK a values of boronic acids (RB(OH) 2) in aqueous solution we inquired the solute-solvent interactions of these acids and their corresponding conjugate base. Relative pK a values were computed for each boronic acid using methylboronic acid (CH 3B(OH) 2) as a reference. All gas phase computations were performed at (MP2/6-311++G(d,p)//B3LYP/6-31+G(d)) level of theory. Solvation was included in the calculations using the polarized continuum model (PCM) at the HF/6-31G(d,p) level. The geometry optimization of studied structures was performed with DFT computation and the optimized structures were used to carry out Natural Bond Orbital (NBO) analysis.... 

Proper orientation of walkways, based on regional winds and local shade, provides good control over walkway ventilation. The architecture of the old town of Sirjan had experimentally orientated the city's walkways in such a manner that the shadows in the walkways produced the maximum possible natural ventilation in this hot and dry town. This study has focused on the optimum design of Sirjan city considering a natural ventilation mechanism. At first, a typical walkway with certain geometric parameters is considered. Then, considering the symmetry of the shadows cast in the walkway, the natural ventilation rate is investigated at 7 different angles and at 15° intervals. The problem is modeled... 

The purpose of this paper is to study and review some major impacts of the disasters during the past 105 years and develop a new theoretical classification of disasters. Design/methodology/approach– A detailed study of disasters in the world during the period (1900‐2005) has been obtained from the recent published sources. In that period more than 40 lessons have been reported based on statistical data analysis of disasters. Furthermore, a two‐dimensional probability density function is developed to categorize the different types of disasters. This paper studies and reviews some major impacts of disasters during the past 105 years and summarizes some major lessons for the future....