Search published articles


Showing 201 results for Phase


Volume 0, Issue 1 (5-2011)
Abstract

A numerical model for two-phase debris flows is developed in this paper, on the basis of understanding of the physical characteristics of debris flows from field investigations and experiments. Employing a moving coordinate, the kinetic energy equation of gravel particles in unit volume in debris flow is developed by considering the potential energy of the particles, energy from the liquid phase, energy consumption due to inner friction-collision between the particles, energy dispersion through collisions between particles, energy for inertia force, energy consumption due to the friction with the rough bed and energy consumption at the debris front. The model is compared with measured results of two-phase debris flow experiments and the calculated velocity profiles agree well with the measured profiles. The gravel’s velocity at the debris flow head is much smaller than that of particles in the following part and the velocity profile at the front of the debris flow wave is almost linear, but the profile in the main flow shows an inverse ‘s’ shape. This is because the gravel particles in the main flow accelerate as they receive energy from the gravitational energy and flowing liquid and decelerate as they transmit the energy to the debris flow head and consume energy due to collision with the channel bed.

Volume 1, Issue 1 (3-2023)
Abstract

Low Intensity Magnetic Separators (LIMS) are widely used in research and industry. The design of this separator is based on drum rotation inside a tank media, so that a permanent magnets placing inside the drum as an angle form, produces a magnetic field. In this study, the behavior of magnetic and none-magnetic particles of a pulp, flowing through a magnetic field in the wet LIMS, was simulated and validated by experimental results. The magnetic field variables were calculated in an FEM based simulator (COMSOL Multiphysics); while particles’ tracking was done applying CFD numerical method, enhanced by discrete phase model (DPM). The difference between the results of the simulation and the magnetic separation experimental test (recovery of magnetic particles in the concentrate product) was 16.4%. In order to quantify the results of the simulation, magnetic separation simulation was performed by changing two variables affecting the magnetic separation process (variables of particle size of the input pulp feed particles and solid percentage of input pulp) and corresponding experiments. Comparison of laboratory and simulation results showed that the trend of simulation results is consistent with laboratory results of the weight recovery (in both variables under study), so that the maximum simulation error is related to the size of 125 microns (16.5 %) and the lowest simulation error was in 180 microns (11.4 %). Also, the lowest simulation error in the weight recovery prediction was related to the pulp feed solid percentage of 15% (equivalent to 14%) and the highest simulation error was in 30% pulp feed solid percentage (16.9 %). This proposes that FEM-DPM-CFD coupling model, can be applied for simulation, optimization, design and construct 

Volume 2, Issue 1 (4-2002)
Abstract

Performance of the fiber optic networks with different physical topologies such as point-to-point, bus, ring and star, with respect to requirements as bit rates, topology structure, bit. error rate (BER) and optical component characteristics including optical amplifiers, filters, sources and detectors, are analyzed and simulated. For this purpose, maximum number of supportable nodes and throughput, crosstalk due to optical amplifiers and optical filters, reliability, physical limitations and fiber induced limitations such as dispersion and nonlinear effects (self phase modulation) are considered as performance evaluation criteria of different topologies. Dispersion and nonlinearities are simulated with split-step Fourier method, sometimes referred to as beam-propagation method. The fiber length can be estimated by this method, with respect to above effects and maximum tolerable power penalties. Parameters such as maximum number of supportable nodes and crosstalk are evaluated using amount of degradation in BER of receiver, BER is calculated using Gaussian approximation. Reliability of networks is modeled on the bypassing of the failed station as recovery mechanism in ring and bus networks and reliable assumption for central node in star network. By the way physical limitations in each topology, regarding its structure, are derived as an economical criterion. Results indicate that no topology can be preferred to others, however imposed limitations and requirements determine the optimum topology. Neglecting economical aspects, star topology is preferred from different points of view such as reliability, crosstalk and maximum number of supportable nodes. Results of above simulations can be used in calculating power penalties of different factors such as dispersion, crosstalk and nonlinearities. This penalties perform important role in estimating power budget of networks.

Volume 2, Issue 2 (6-2013)
Abstract

Soybean, Glycine max, is susceptible to a large number of disease agents such as seedling and root pathogens that cause serious damages to this crop plant. One of these soil-borne pathogens is Macrophomina phaseolina, the causal agent of charcoal root rot. In this study, two bacteria, Pantoea agglomerans and Bacillus sp. BIN, and a fungus, Trichoderma harzianum T100, as potential biocontrol agents, and maneb fungicide, were evaluated against soybean charcoal rot disease in In Vitro and greenhouse conditions. All antagonists inhibited growth of the pathogen in dual culture test by 73.8, 63.3 and 55.3 %, respectively. Data from greenhouse experiments showed that in the presence of pathogen all antagonists increased the growth indices of soybean in both pasteurized and non-pasteurized soil. Reductions of microsclerotia coverage on soybean root and stem by P. agglomerans, Bacillus sp. and T. harzianum were up to 62.5, 87.6 and 62.5 %, respectively and for maneb fungicide was 87.6 % in pasteurized soil. The overall results of this study show high capability of used antagonists in reduction of initial inoculums for next season of this monocyclic disease.

Volume 3, Issue 4 (3-2020)
Abstract

Research subject: In recent years, there are so many attractions in the field of effective detection and discrimination of volatile organic compounds (VOCs). Detection of VOCs compounds, are very important in many applications and industries such as air pollution control, air quality control, food packaging, food quality control, disease diagnostic, agriculture etc. The sensitivity and selectivity of the prepared sensors to detect of VOCs needs to improve.   
 Research approach: A conductive polymer composite sensitive layer based on poly (lactic acid) as polymer matrix and multiwall carbon nanotubes as conductive filler was prepared to detect of volatile organic compounds (VOCs). For this purpose the porous sensitive layer was prepared by non-solvent induced phase separation (NIPS) method. In this structure, chloroform (low boiling point temperature) was used as the solvent and ethanol (high boiling point temperature) was used as a non-solvent. The sensitive layer was used to detect of toluene, methanol, and chloroform. The structure and morphology of synthesized layer was investigated by means of scanning electron microscopy (SEM) and BET test.
Main results: The investigation indicated that the phase separation method induced the open cell morphology into the conductive composite. The BET results showed that the specific surface area of composite increased to 22.3 m2/gr. The experimental results showed that the response properties of porous layers was improved dramatically in comparison with dense layers. It was related to the increase of specific surface area of polymer composite and therefore the increase of diffusion coefficient of analyte molecules into the polymer matrix. Finally the sensitivity and selectivity of porous sensitive layers was investigated based on Flory-Huggins interaction parameter.
 

Volume 4, Issue 1 (3-2015)
Abstract

On the basis of preliminary in vitro screening tests, a competent strain of Pantoea agglomerans ENA1 (P. agg. ENA1) recovered from soybean nodule was evaluated for its antagonistic activity against Macrophomina phaseolina causal agent of charcoal rot of soybean. The results of various in vitro assays showed that P. agg. ENA1 is capable of exerting strong antagonistic effect against M. phaseolina inhibiting its mycelial growth up to 89% as compared to control. The results showed a significant reduction of the disease as measured in host-plant weight increase, reduced microsclerotial coverage of the host tissues and decreased population of the pathogen in soil. Soils treated with the antagonist in presence of the pathogen resulted in 40% increase in aerial fresh weight and 63% decrease in root and stem surface covered by microsclerotia as compared with control. Furthermore, a significant decrease in the pathogen population ranging from 73 to 76% was observed in sterile and non-sterile soils, respectively. P. agg. ENA1 is suggested as a potent biocontrol agentthat provides excellent rhizosphere colonization and control of M. phaseolina    

Volume 4, Issue 15 (6-2007)
Abstract


Sahba.F.,PH.D
Omranpour.M.R.,PH.D.
 
 Abstract:
 
In some contemporary poems, the poets break the lines of their poems into two parts or more and write them down vertically or like stairs after each other. This technique, called line breaking, was invented by Mayakovski, the Russian contemporary poet. Afterward, some Persian poets imitated him, though not seriously, in their poems but it was applied extensively by Shamloo, about 1950, as a suggestive device in Persian poetry. There is no plan for breaking the lines but, through searching in the poetry by poets who have applied it. This paper is going to examine and describe where the line breaks occur in the poetry.
The result of the study shows that there are three main types of line breaks: Some of the line breaks fall among the units of images to give poems a particular appearance and to create visual images. The second kind of them, occur prior to semantic or syntactic elements to create a series of emphases. The third group, are those which cause to foreground the musical aspects and to create rhyme and rhythmical innovations.
 
 

Volume 5, Issue 4 (4-2021)
Abstract

Research Subject: Global energy demand is increasing, so enhanced oil recovery techniques have incorporated in production processes. Water flooding is a common technique in oil recovery processes. One of the major challenges in this technique is heterogeneity of the reservoir structure which results in increased water production and reducing the oil recovery factor. Moreover, long-term water or chemical injection might lead to the increased horizontal and vertical heterogeneities in the reservoir. Selective blockage of high permeability areas and consequently improved production from low permeability regions is important for increasing the oil recovery factor. In recent years, using hydrogels in injection processes, has been associated with various field successes, indicating the ability of these materials for selectively blocking the areas of high permeability. Hydrogels are injected after water or polymer flooding to conduct the injected fluid to low permeability areas.
Research Approach: In this paper, hydrogel injection process was simulated in glass micromodels using Comsol Multiphysics software. Hydrogel functionality was studied in low permeability areas in porous media. Moreover, the optimized conditions for water flooding process was studies. For this purpose, after model validation, sensitivity analysis was performed on effective parameters on oil recovery factor and a mathematical model was presented to predict the oil recovery factor.
Main Results: Oil recovery factors obtained from experimental and simulation studies, were in good agreement with each other with absolute error values of 2.29% and 4.06%, for water and hydrogel flooding, respectively.
Four parameters of injection rate, contact angle, oil viscosity, and injection fluid viscosity were considered as effective parameters on oil recovery factor. Among them, contact angle was the most important parameter. In water flooding, the most important interacting parameters are viscosity and contact angle and the least important parameters are injection temperature and rate. In water flooding simulation studies, the thickness of the contact surface was obtained hmax/5, where  is 230 micrometers. For hydrogel injection, the contact surface thickness was obtained terpf.ep_default / 5.65. Terpf.ep_default is the thickness of contact surface, equal to 631 micrometers

Volume 6, Issue 1 (12-2006)
Abstract

This paper presents a framework for long term transmission expansion planning in competitive, electricity markets. Transmission lines and phase shifters are taken into account as expansion options. Maximization of the network users' benefits, with satisfying security constraints are considered as the criterion for transmission expansion planning. The elements of the objective function are the benefits of each network. The proposed model is as a non-linear mixed-integer programming (NLMIP) optimization problem. A GA (Genetic Algorithm) based method and quadratic programming (QP) approach is used to solve the problem. The discrete decision-making variables of the expansion plan are optimized by genetic algorithm, while QP optimizes the continuous variables.

Volume 7, Issue 3 (11-2023)
Abstract

Aim: The removal of heavy metals from drinking water is one of the highest impact challenges in the water and wastewater industry. For this purpose, the use of methods such as solid phase extraction followed by the use of selective adsorbents is considered as one of the most important issues in the water and wastewater industry.
Method: In this research, in order to remove the polluting and toxic heavy metal cadmium from water in the water treatment industry, Fe3O4 nanoparticles with a diameter of 10 nm have been synthesized. In order to make these nanoparticles resistant to corrosion and erosive factors of the environment, they are covered with a silica shell and afterwards with the aim of removing cadmium ions from aqueous solutions, the surface of Fe3O4@SiO2 nanoparticles is modified with 1,4-dihydroxyanthraquinone molecules. The synthesized nanoparticles are characterized in order to evaluate the efficiency of these nanoparticles in separating cadmium ions soluble in water has.
Results: The synthesized and functionalized magnetic nanoparticles have an effective surface area of 378 m2/g with black color and spherical morphology. The effects of the parameters of the amount of nano adsorbent, pH of the solution, various concentrations of the solution and test time in the removal of divalent cadmium ions are investigated. According to the experimental data, the optimal values for the absorption process at pH 7 by using 18 mg of adsorbent in 50 ml of cadmium solution with an initial concentration of 0.35 mmol/L lead to the removal of cadmium ions with a maximum absorption of 92% at ambient temperature in a period of 35 minutes. Moreover, the recyclability and reusability of Fe3O4@SiO2-DAQ in the adsorption-desorption process of cadmium ion is investigated using a magnetic magnet, and the results confirm that this synthetic nanocomposite is an effective adsorbent with excellent performance in order to remove divalent cadmium ion from aqueous solutions.
 

Volume 7, Issue 4 (12-2023)
Abstract

Given the ever-increasing demand for energy and the limited nature of fossil fuel resources, improving energy efficiency and storage has become one of the most significant challenges facing humanity. Phase Change Materials (PCMs), substances capable of absorbing and releasing thermal energy at a constant temperature, have emerged as an innovative solution in the field of energy storage. With their high latent heat capacity, ability to maintain a stable temperature, and environmental friendliness, PCMs have great potential for applications in various industries. However, their low thermal conductivity, especially in organic PCMs, has hindered their widespread use. To address this challenge, researchers have been exploring various methods to enhance the thermal properties of PCMs. One of the most effective approaches involves incorporating high thermal conductivity nanoparticles into the PCM matrix. This research comprehensively reviews recent advancements in the preparation and applications of nanoparticle-enhanced phase change materials. It delves into various types of nanoparticles used, production methods for nanocomposites, the impact of nanoparticles on the thermal and mechanical properties of PCMs, the stabilization of nanocomposites with surfactants and surface modification, and also their potential applications in diverse industries. The results of this study indicate that the use of nanoparticles can significantly improve the thermal conductivity of PCMs, with carbon-based nanofillers showing the highest impact. Additionally, nanoparticles have led to a relative reduction in the phenomenon of supercooling in PCMs. Based on the results of numerous studies, nanoparticle-enhanced phase change materials hold great promise for improving the performance of energy storage systems, reducing energy consumption in various industries, and fostering the development of sustainable technologies. These nanocomposites can be employed in the construction, automotive, electronics, and textile industries to create more comfortable environments, enhance energy efficiency, and reduce greenhouse gas emissions. Continued research in this field is expected to lead to the development of even more efficient PCMs with a broader range of applications.


Volume 8, Issue 1 (3-2024)
Abstract

Research subject: The presence of heavy metal ions in surface and underground water, followed by their infiltration into drinking water at high concentrations, poses irreparable risks to human health and the environment. In this context, solid-phase extraction (SPE) has recently been recognized as a routine and practical method for removing heavy metals from water and wastewater samples. Consequently, the development of selective adsorbents for application in the SPE method is of significant importance in environmental studies.
Research Approach: In the present study, polyvinyl alcohol (PVA) molecules were functionalized onto Fe₃O₄@SiO₂ core-shell nanoparticles using cyanuric chloride and triethoxysilyl propylamine compounds. The synthesized nanoparticles were then employed as an effective adsorbent for the removal of Pb²⁺ ions from aqueous solutions. The structural characteristics, morphology, and particle size were analyzed using Fourier-transform infrared (FTIR) spectroscopy, energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), thermogravimetric analysis (TGA), vibrating sample magnetometry (VSM), transmission electron microscopy (TEM), and scanning electron microscopy (SEM). Furthermore, the key operational parameters affecting adsorption performance were evaluated to optimize the adsorption capacity for the effective removal of heavy metal contaminants.
Main Results: The optimal adsorption capacity of 89% was achieved under the following conditions: pH 7, a contact time of 35 minutes, 32 mg of adsorbent in 50 mL of solution with an initial Pb²⁺ concentration of 72.52 mg/L (0.35 mmol/L), at ambient temperature. Additionally, the synthesized nanoadsorbent demonstrated recyclability for up to five adsorption-desorption cycles without a significant decline in functional efficiency.

 

Volume 8, Issue 2 (6-2024)
Abstract

Research Subject: The flow of two immiscible liquids has garnered significant interest over the past few decades due to its relevance in various industrial applications, including chemical, petrochemical, food, and other process industries. It is particularly encountered in the water-lubricated transport of high-viscosity oil through pipelines. One of the simplest methods for studying the mass transfer coefficient in a liquid–liquid system involves a single droplet rising through a second, stationary phase. While this approach is well understood for nearly spherical droplets without surface turbulence or oscillations, it remains complex for ellipsoidal droplets exhibiting oscillatory motion, particularly in systems characterized by low interfacial tension.
Research Approach: This study investigates the effect of mass transfer on the velocity and shape of droplets in a chemical system composed of normal butanol, succinic acid, and water. Several variables are explored, including the dispersed phase flow rate, droplet size, and succinic acid concentration within the dispersed phase. Experiments were carried out using the single-drop method in an extraction column, employing normal butanol droplets with diameters ranging from 0.3 mm to 1.3 mm and Reynolds numbers below 300.
Main Results: The results reveal that mass transfer significantly influences droplet velocity, delaying the attainment of terminal velocity. Despite deformation, the droplet regime remains unchanged. The low interfacial tension in the system leads to the formation of oval-shaped droplets, with aspect ratios decreasing to as low as 0.4. However, under mass transfer conditions, droplets become wider and more spherical, resulting in a 50% increase in aspect ratio at the highest succinic acid concentration and with the largest nozzle size, compared to conditions without mass transfer. Terminal velocity and droplet deformation were further analyzed using dimensionless numbers, including the Reynolds number, Eötvös number, and Weber number.
 

Volume 9, Issue 2 (4-2007)
Abstract

The objective of this research work was to study the effect of Rhizobium leguminosarum pre-induced with genistein (G) and methyl jasmonate (MJ) on nodulation, nitrogen fixation and early growth of the common bean (Phaseolus vulgaris L.). Four day-old seed-lings were transferred to pots, containing sterilized sand and turface (2:1 v:v) mixture and, receiving Hoagland’s nutrient solution, without nitrogen. The plants were grown in a growth chamber using a randomized complete block design with six replications. The rhizobia were cultured in TY medium and incubated with G, and/or MJ. The incubated rhizobia were used after 24 hours to inoculate the bean seedlings. The results showed that both G and MJ enhanced the nodule number, nitrogen content per plant, and plant dry matter. Genistein and MJ, when applied together to cultures, showed synergistic effects on all the characters studied. The results of this study indicated that MJ alone, or in com-bination with G, can be used to promote bean nodulation, nitrogen fixation and early plant growth.

Volume 9, Issue 6 (3-2018)
Abstract

The movement of the subject from the embedded clause to the matrix clause has fanned the flames for more and more arguments among Persian linguists. In this article, two main questions are discussed: (1) is that the aforementioned movement A-movement or A-bar movement? and (2) what is the association of the movement with phase theory. The method adopted to answer these questions is analytic-descriptive. The first question is dealt with on the basis of freezing principle and successive movement which show that the embedded subject undergoes a-bar movement regardless of the kind of the matrix verb. On the one hand, on the basis of the freezing principle, the subject case feature is checked in the embedded clause, so, it can undergo A-bar movement. On the other hand, successive movement also shows that the subject undergoes A-bar movement to the matrix clauses having so-called raising predicates on the grounds that A-movement leads to improper movement. However, whether the verb is transitive or the so-called raising or passive restricts the movement. If the verb is transitive the displaced subject must appear with ‘ra’, if the matrix verb is so-called raising, it must appear without ‘ra’ and if the matrix verb is passive, it cannot appear in the matrix clause with or without ‘ra’. The appearance of ‘ra’ shows that not only the subject undergoes A-bar movement, but also v is a phase head in Persian, because the moved subject must go to the specifier of the transitive matrix vP and receives ‘ra’, then moves to a functional node, which can be either focus phrase or topic phrase. The passive matrix vP doesn’t allow the subject to move through its specifier and on the basis of induction, it can be claimed that the subject moves through the specifier of the so-called raising predicates. As a result, it seems that vP is a phase phrase in Persian.
 

Volume 10, Issue 2 (9-2020)
Abstract

Aims: In the last century of Iranian architecture, the use of passive thermal comfort methods has been forgotten and replaced by active methods, in addition to environmental constraints and crises, this process have caused high costs and sometimes reduced access to electricity; As a result, it is essential to use elements and passive methods, especially in warm climates where more electricity is consumed. One of the most important elements of Iran's traditional architecture is wind tower which is still functional due to its simplicity of operation and use of wind energy. In recent years, the use of new building technologies, such as Phase Change Materials, has also led to the revival of passive methods and significant energy savings. Therefore, the present study has attempted to use this material in the wind tower to improve its performance in passive cooling.
Methods: This research was carried out in the form of modeling of airflow in the wind tower channel in Fluent Software and comparing the inlet and outlet temperature. In this regard, three models - fiberglass and two types of phase change with different melting constant temperatures as wall cover-were tested.
Findings: Testing of the models showed that the cover of the phase change material was much more effective than the fiberglass cover (at least between 4.5°C until 5.5°C) in reducing the outlet temperature of the wind tower.
Conclusion: This amount of cooling covers at least three months in warm season and some time of day in the warm and humid climate of Qeshm and will play a reliable role in reducing electricity consumption.


Volume 10, Issue 3 (10-2010)
Abstract

This paper introduces a novel approach to improve performance of speech recognition systems using a combination of features obtained from speech reconstructed phase space (RPS) and frequency domain analysis. By choosing an appropriate value for the dimension, reconstructed phase space is assured to be topologically equivalent to the dynamics of the speech production system, and could therefore include information that may be absent in analysis approaches based on linear methods. Also, complicated systems such as speech production system can present cyclic and oscillatory patterns and Poincare sections could be used as an effective tool in analysis of such trajectories. In this research, a statistical modeling approach based on Gaussian Mixture models (GMM) was applied to the Poincare sections of speech RPS. The final feature set is obtained from a feature selection stage omong parameters of GMM model and the usual Mel Frequency Cepstral coefficients (MFCC). An HMM-based speech recognition system and the TIMIT speech database are used to evaluate performance of the proposed feature extraction system for isolated and continuous speech recognition. Experiments represent about 5.7% absolute isolated phoneme recognition accuracy improvement in isolated phoneme recognition performance. The new approach is shown to be a viable and effective alternative to traditional feature extraction methods, particularly for signals such as speech with strong nonlinear characteristics.

Volume 10, Issue 4 (11-2021)
Abstract

The potential of Trichoderma spp. for biocontrol of phytopathogenic fungi has been well documented. In this study, the wild-type isolate of Trichoderma aureoviride (Tv59) was treated with the target dose of 250 Gy as the optimum dose. Twenty-six mutants were preliminarily screened based on better growth rates. In vitro, antagonistic evaluation of the 26 mutants and wild-type was performed against two Macrophomina phaseolina isolates (F33 and H7). Six mutants (Tv2(4), Tv20(6), Tv25(6), Tv3(3), Tv4(5), and Tv3(4)) showed remarkable inhibitory activity and were selected for further examination in greenhouse trials. Greenhouse assessment of the selected mutants against M. phaseolina isolates revealed Tv20(6) and Tv25(6) as the most highly effective treatments screened for the measured indices. Moreover, the total genomic DNA of the wild-type isolate and its 26 corresponding mutants were analyzed to determine their genetic variability through the RAPD technique. Five RAPD primers generated different banding patterns and yielded a total of 178 amplified fragments, 172 amplicons (96.62%) were polymorphic. While the dendrogram obtained by UPGMA cluster analysis of combined RAPD fingerprints differentiated the wild-type from its mutants at approximately 40% similarity level, the mutants were categorized into two clusters. Based on Jaccard similarity coefficients, eight mutants (Tv25(6), Tv1(5), Tv14(5), Tv20(6), Tv3(4), Tv40(6), Tv33(6), and Tv14(6)) showed the lowest genetic similarities with the parental isolate. The possibility of improvement in biocontrol effectiveness of T. aureoviride through random mutagenesis and detection and differentiation of genetic changes induced by gamma rays using RAPD analysis was successfully proved in the present study.

Volume 11, Issue 1 (6-2011)
Abstract

In this paper a new approach about relation of Acoustic Emission(AE) method and mechanical properties of ferrite-martensite dual phase steels(DPS) has presented. The AE signals from a tensile test using a range of DPS with different volume fractions of martensite (VM)s, in the range of 12–65% VM, were obtained and their AE signals were investigated. In order to better study DPS internal behaviour, a function named “sentry function” was used. The amount of this function depends on the strain energy and acoustic emission energy. the Results show that AE monitoring and sentry function are efficient tools for detection of micromechanisms, consisting of Ferrite-Martensite interface decohesion and/or martensite phase fracture, identifying the correlation of failure mechanisms to microstructure in DPS.

Page 1 from 11    
First
Previous
1
...