Showing 492 results for Composit
Volume 0, Issue 0 (1-2024)
Abstract
Increasing need for drought adaptation measures to conserve water and sustain crop yield in water-scarce regions, driven by severe and recurrent droughts. Achieving sustainable production entails studying deficit irrigation as a means to enhance water productivity and selecting genotypes resilient to soil water deficits. In the present study, 17 different melon (Cucumis melo L.) genotypes collected from the Van Lake Basin and 3 hybrids and 1 standard melon cultivar for control purposes were used. The study was carried out under climate room conditions. Two different irrigation levels (I100: 100% full irrigation, I50: 50% deficit irrigation-DI) were applied in the study for deficit irrigation. The applications started with the emergence of the second true leaves of the plants and after one-month, different growth, nutrient, and enzyme contents of the seedlings were determined. In general, it was determined that deficit water application negatively affects seedling growth, and and root dry matter, stomatal width and density, potassium, APX and SOD enzymes, and MDA content increased, while the other examined parameters decreased. The genotypes of the Van Lake Basin melon were found to vary as a result of the findings.
Volume 0, Issue 0 (1-2024)
Abstract
The Ministry of Agriculture Jihad in Iran implemented contract farming (CF) for wheat in 2021 to address marketing issues. This study compares agricultural sustainability for farmers participating in and not participating in CF. Agricultural sustainability was assessed by applying a combined index approach that considers economic, social, and environmental dimensions. The required data came from 620 wheat farmers in Golestan province, sampled using the multi-stage randomization technique. The data were evaluated using exploratory factor analysis (EFA) and clustering methods. The findings indicated a significant difference in the performance of economic and environmental sustainability dimensions between two groups of wheat farmers. For the participants, 14.2% were deemed unsustainable, 47.7% were considered partially sustainable, and 38.1% were classified as sustainable. For non-participants, the figures were 38.7%, 47.7%, and 13.5%, respectively. Therefore, it is suggested to provide more opportunities for participation in this program and expand it to other key crops. Additionally, authorities should provide more information about the benefits of the CF plan.
Volume 0, Issue 0 (8-2024)
Abstract
So far, the performance of masonry walls against in-plane lateral loads such as earthquake loads has been extensively studied, but less attention has been paid to out-of-plane loads such as explosions. Due to their large surface area, walls endure significant forces during explosions, leading to extensive damage and potentially causing severe financial losses and casualties. Given the increase in terrorist and sabotage attacks, reinforcing these structures seems necessary. In recent years, fiber-reinforced polymers (FRP) have been widely and effectively used in the reinforcement and performance improvement of these structures. Their light weight, high stiffness and high strength, and corrosion resistance are among the properties that have attracted researchers to use these materials. Finite element modeling not only provides a basis for better understanding the behavior of masonry walls but also is very useful in predicting the behavior of these members after reinforcement, especially in the absence of experimental results. In this study, using numerical modeling in ABAQUS software, the behavior of masonry walls reinforced with FRP strips against a blast with an explosive charge equivalent to 150 kg of TNT (the weight of explosive likely to be carried in a sabotage attempt via a vehicle) at a distance of 5 meters was investigated. Lagrangian equations were used to model the mechanical behavior of the structure, and the solver used in this research is an explicit solver to account for the time factor in the software’s integration process. The total time considered for the entire explosion process is 1 second, and the explosive load was applied to the studied structure using the Conwep method. The type of fibers, width, thickness, area, and angle of the FRP strips were important and influential parameters that were examined for the efficiency of this reinforcement method. The modeling results indicate that this reinforcement technique is highly effective in strengthening masonry walls against explosions, as it has reduced the deflection of the wall by at least 70% and its energy by up to 90%. It can also be inferred that an arrangement for reinforcing masonry walls with FRP strips is suitable if it covers the areas prone to damage, which in masonry walls are the mortar joints between the bricks. Therefore, the horizontal arrangement shows better performance compared to the vertical and diagonal arrangements. Similarly, reinforcing 100% of the wall area performs much better than reinforcing 50% and 25% of the wall area, but it is not economically acceptable. In general, similar to structural elements, non-structural elements can also exhibit plastic behavior in critical situations, preventing the collapse of these elements due to the absorbed energy. Therefore, walls with higher plastic energy show better behavior against explosive loads. Additionally, based on the hysterical displacement and kinetic energy diagrams of the wall, it can be seen that the behavior of reinforced walls is oscillatory, while the behavior of unreinforced walls is noticeably pulsating. Finally, the optimal arrangement of FRP strips proposed for reinforcing masonry walls against explosions in this study is the use of CFRP strips horizontally, with a thickness of 1 mm, a width of 24 cm, and covering 50% of the surface area; This configuration successfully decreased the deflection of the wall from 63.1 cm to 7.7 cm and damped approximately 13% of the blast wave energy.
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Volume 1, Issue 1 (12-2017)
Abstract
In this research,nanocomposite coatings based on epoxy containing pristine graphene oxide and starch-modified graphene oxide are prepared and characterized by Fourier transfer infrared spectroscopy, andtheir crosslinking behavior is studied using nonisothermal differential scanning calorimetry.These nanocomposites, because of having platelet-like nanomaterials inside and their organic origin, can be applied as coating on metal surface in diverse industries.The reason behind using starch was its natural basis and abundance of hydroxyl groups in its structure which can take part in crosslinking reaction with epoxide. Neat epoxy systems having amine curing agent, and nanocomposites containing epoxy, amine curing agent, andpristine or starch-modified graphene oxide nanosheets were cure at different heating rates to assess their curing behavior. Change in hearing rate of test caused change in onset and peak temperature of the exotherm curves and consequently heat of reaction changed. It was observed that the presence of the graphene oxide nanosheets hindered the crosslinking reactions, while surface modification of them with starch natural polymer compensated for such a hindrance via catalytic role of starch, and increased crosslink density of system.
Volume 1, Issue 1 (12-2017)
Abstract
Oil resistant o-rings on the basis of acrylonitrile butadiene rubber (NBR) reinforced by nanoclay were produced via a traditional industrial method in accordance with aviation standard, AMS 7272. The production of nanocomposites comprised the compounding of nanocomposite with optimum mechanical properties and minimum contents of used carbon black and nanoclay, design and manufacturing of the required mold and finally compression molding of the oring. Mechanical and morphological properties of NBR/nanoclay compounds were optimized by introduction of proper contents of a compatibilizer containing a mixture of resorcinol and hexamethylene tetramine through using a master batch production method. The prepared nanocomposites were characterized using X-ray diffraction (XRD) analysis, curing measurements and tensile test analysis. The XRD analysis showed that the compatibilizer facilitates the intercalation of nanoclay silicate layers with the rubber chains which leads to the increase of their basal spacing. The cure characteristics of the nanocomposites showed a decrease of scorch time and increase the cure rate index with the nanoclay loadings. Furthermore, the minimum scorch time and maximum cure rate index could be achieved through using the appropriate content of compatibilizer. The results exhibit that the nanocomposites containing the compatibilizer have higher mechanical properties especially at higher deformations compared to the corresponding uncompatibilized nanocomposites
Volume 1, Issue 1 (3-2023)
Abstract
Volume 1, Issue 2 (3-2018)
Abstract
Presence of filler in the polymeric materials changes the mechanical, dynamic-mechanical, rheological properties and even the swelling behavior of rubber composite due to mechanisms such as hydrodynamics, polymer-filler and filler-filler interactions. Swelling in rubber composites directly affects the polymer chains, also can affect indirectly other structures in composites such as the filler network and reduce mechanical properties suddenly. In this study, the nitrile rubber-nanosilica composite containing different concentrations of modified nanosilica was prepared and the composite structure was studied through rheological, mechanical, dynamic-mechanical tests. Also it was found that the filler network containing over percolation threshold 13phr of filler concentration has a significant contribution to the mechanical properties of composites. To determine the swelling effect on the prepared composite structure, with different degrees of solubility were used. The mechanical properties of the samples were measured in equilibrium swelling state for each of the solvents The decrement of the mechanical properties between the dry samples and swelled ones containing 14.4, 20 and phr 6.25 silica in solvent with 15% toluene is significant. These intensive changes in mechanical properties that happen at the low degree of swelling are attributed to the removal of the filler network. Therefore, controlling the swelling of rubber parts in adjacent to the solvent, plays the fundamental role in their performance.
Volume 1, Issue 3 (9-2013)
Abstract
Landslides are natural disasters that annually inflict great damages to public and private properties which may associate with loss of life. In recent decades, research on developing methods for predicting the time of landslide has been one of the significant attempts made by scientists. Since in some type of material, landslides are preceded by undetectable movements that cannot be recorded and revealed by conventional instruments, recording the chemical changes of the water flowing out from the toe of the slopes susceptible to sliding can provide important and reliable indicators of landslide activities and early warning. In this study, changes in the chemical composition of water seeping out from the toe of an active landslide were investigated. This process was studied in a laboratory physical model, in which a sliding surface was simulated and the changes in the ion concentration of potassium (K), sodium (Na), magnesium (Mg), calcium (Ca), sulfate (SO4), chlorine (Cl), and bicarbonate as well as EC and pH in both stable state and in the conditions of slight rupture along the sliding surface were investigated. The results indicated that the appreciable chemical changes in the outflowing water, particularly changes in the concentration of some ions, could be used as suitable indicators for early warning of the landslide occurrence.
Volume 2, Issue 1 (6-2013)
Abstract
A 4 × 4 factorial design was conducted to quantify the optimumrncarbohydrate ⁄ lipid ratio to minimize the dietary protein level in growingrnbeluga, Huso huso (initial weight 891.9 ± 33.4 g, mean ± SD). Fish were fedrnwith sixteen experimental diets formulated to contain four protein levels (35,rn40, 45 and 50%) and four dietary carbohydrate ⁄ lipid ratios of 0.8, 1.1, 1.4,rnand 1.7 for 108 days. At the end of trial, there were no significant differencesrnin growth parameters among fish fed with 35, 40 and 45% protein levels. Nornsignificant difference in growth parameters and feed efficiency (FE) wasrnalso observed when dietary carbohydrate ⁄ lipid ratios decreased from 1.7 torn1.1 within the same energy level (P > 0.05). The highest carcass proteinrncontent was observed in fish fed 0.8 and 1.4 carbohydrate to lipid ratio (P
Volume 2, Issue 3 (12-2013)
Abstract
Separate or combined effects of inulin and mannan oligosaccharide supplements on the growth, survival, body composition and salinity resistance of kutum roach (Rutilus frisii kutum) fry (410 ± 19 mg) were investigated for 45 days in 40-liter tanks containing 30 individuals. Fish were fed 7 to 12% body weight with a commercial diet (35% protein and 12% lipid) supplemented with 0 (control), 5 g kg-1 inulin, 5 g kg-1 MOS and 2.5 g kg-1 inulin + 2.5 g kg-1 MOS in a totally randomized design trial in triplicate. A general enhanced growth performance and feed efficiency were observed in fish fed on diet containing 5 g kg-1 MOS (p<0.05). There were no significant differences in survival rate among treatments (p>0.05). NO significant difference was observed in body composition, but protein and lipid contents in the whole body increased in fish fed with 5 g kg-1 MOS and control group. In general, the fish fed 5 g kg-1 MOS had the highest survival index after 48 hours exposed to salinity stress (15 ppt). Results showed 5 g kg-1 MOS could improve growth performance, survival and salinity stress resistance of kutum fry.
Volume 2, Issue 4 (3-2019)
Abstract
The control of bacterial diseases of fish has always been one of the most important problems of aquaculteriets in recent years. One of these problems is bacterial resistance. Using antibiotics can cause problems for consumers. Therefore, the use of new antimicrobial agents with minimal complications is common. In the present study, using the acid-thermal method, the bentonite structure was modified and the chitosan and bentonite hybrids were modified in the stage of development. The structure of the compounds was studied using the Infrared Fourier Transform Spectrometry (FTIR), Surface Electron Scanning Microscopy (FE-SEM) and X-ray diffraction spectroscopy (EDX). Antimicrobial activity of two types of modified bentonite on gram negative bacterium Aeromonas hydrophila was studied in vitro using two methods of disk diffusion and microdilution. The results of the disc diffusion method showed that the antimicrobial compounds produced had antibacterial properties in experimental conditions against the Aeromonas hydrophilia bacteria. Antimicrobial activity (MIC and MBC) was determined using microdilution and clonal counting in Agar culture medium. The results showed that the modified compound with the acidic method had MBC of 28.57 and 14.28 mg / L for Aeromonas hydrophila bacteria in 10 minutes and 30 minutes. For chitosan and modified bentonite composite, MBC was 14.28 mg / ml for Aeromonas hydrophila bacteria in 10 and 30 minutes. The results of this study showed that modified bentonite and composite compounds have strong antimicrobial effects and can remove pathogens in laboratory conditions and can be used as new compounds to control pathogens in breeding systems.
Volume 3, Issue 1 (4-2013)
Abstract
The issue of earthquake and its destructive effects is constantly confronting human being communities as an extensive challenge. The ground, upon which we are constructing our buildings, is anything but solid. Hundreds of millions of years ago the continents were joined, but now they are dispersing ever so slowly. The idea that buildings are founded on stationary ground is only an illusion. From the viewpoint of geological time, the earth’s crust is in a continuous dynamic change. The scientific understanding of this process, known as continental drift or tectonic plate movement, which is the basic cause of most earthquakes, dates back only 100 years. Quakes strike at the heart of a community. When they damage buildings, people and animals are injured and killed. Earthquakes destroy the basic necessities of life, demolishing shelter, ruining food and water supplies and disrupting people’s livelihoods. Conversely, buildings that perform well during an earthquake, limit its impact on people and their basic needs. Scientists and building construction experts have strived in order to find the solutions for reducing structures damages which are caused by trembling of the earth and diminishing the casualty rate and also detriments, from some years ago. In our country, Iran, which is located in earthquake zone and has experienced some demolishing quakes before, this matter is more significant and remarkable. Apart from the poorest of communities for whom even partial earthquake protection is unaffordable, most of the disastrous effects of earthquakes are avoidable. Earthquake-resistant construction greatly reduces the rate of victims from a damaging quake, as well as lessening economic losses and disruption to public activities. Seismic retrofitting of existing buildings is of vital and crucial issues of our society. The purpose of rehabilitating is to reduce the vulnerability of a building’s inhabitants and the building itself, its structure, non-structural elements and possibly its contents to earthquake damage. To retrofit a building is to improve its seismic performance. One of the appropriate alternatives for enhancing the structural performance of available buildings is employing composites. These materials can be applied in order to increase the confinement, shear strength and ductility of columns and also enhance in-plane shear wall strength as well as out-of-plane resistance. In addition, with taking advantage of this kind of material, the secondary weight which would be added to the primarily structure is going to be significantly reduced and this would act as an optimum approach for rehabilitating the existing buildings. In this research, firstly the exact definition of composite materials and its components and different kinds are studied. Then, the essence of earthquake and seismic forces in addition to some topics on seismic retrofitting and the essential needs for it are discussed. Eventually, concerning the abilities of composites, employing them as a suitable technique for reconciliation of structural elements of existing buildings, which is one approach of seismic retrofitting, will be proposed with hope for presenting the essential knowledge of appropriate seismic retrofitting with efficient materials to architects and civil engineers in order to diminish the ruins of earthquake effects on structures and as a result, providing the next generations of our country with safer and much more protected circumstances.
Volume 3, Issue 1 (6-2014)
Abstract
A 12-week feeding trial was carried out in 500 L fiberglass tanks to evaluate the effect of dietary choline at 0, 2, 4, and 8 g kg -1 levels on growth rate, body composition and total liver lipid of juvenile Acipenser baerii (37.67±0.67 g). A semi purified basal diet was formulated using vitamin free casein and wheat gluten as a protein source, a mixture of animal and plant oils as a lipid source and dextrin as a carbohydrate source. Four isonitrogenous (40% protein) and isoenergetic (18 MJ kg-1) diets were prepared and fed to the fish three times daily to apparent satiation. Weight gain, feed conversion ratio (FCR), specific growth rate (SGR) and protein efficiency ratio (PER) were significantly affected by dietary choline (p<0.05). The best growth performance was observed in fish fed diets containing 2 and 8 g kg -1 choline (p<0.05). Fish fed with 2 and 4 g kg -1 choline showed higher lipid content compared with the control diet (p<0.05), but not significantly different in body protein (p>0.05). Total lipid of liver and plasma, plasma cholesterol, triglyceride and phospholipids levels showed an increasing trend with increasing levels of dietary choline, but not significantly different among treatments (p>0.05). Based on the results, we recommend adding a 1.5 gkg-1 choline to commercial diet of juvenile Acipenser baerii.
Volume 3, Issue 2 (9-2019)
Abstract
is one of the most common improved oil recovery method in the world. High residual oil saturation at the end of this method is due to low macroscopic sweep efficiency and viscous fingering. It can be improved by the mobility control during polymer solution injection. In this study, by of silica/ the effect of it on IFT, viscosity, and was investigated. In addition, the performance of in high salinity water was studied by using nano particles. The zeta potential results show that the stability of polymer solution was enhanced in of nano particles in high salinity water condition. Also, the lowest IFT was obtained for contained 1 percent nano silica (18.34 ), and the most tendency to water wet conditions was provided for this concentration. In addition to, 1 percent nano silica/ has the best performance on formation water viscosity and improved the mobility ratio to 1.07, which it can increase the oil recovery.
Volume 3, Issue 3 (12-2014)
Abstract
The effects of pyrene on gill, liver and kidney of common carp (Cyprinus carpio) were examined by exposing 30 fish (140 ±10 g to pyrene at sublethal concentrations of 10, 50 and 100 µg/l for 35 days. Samples were taken from the organs and fixed in bouin fixative; then, dehydrated, cleared, parafinated and cut by microtome according to the standard method. Afterwards, all sections were studied by light microscope. In gill tissue, lamella hyperemia, hyperplasia, S shaped, and clubbing were observed, while lamella fusion and necrosis were observed in higher concentration of pyrene. Hepatocytes vacculation, congestion of sinusoids, macrophages loaded with hemosiderin were seen in the liver, while in higher concentrations of pyrene, picnotic and kariolized nuclei, and tissue necrosis were seen. Tubule casts, hyperemia, degenerating tubules were seen in kidney exposed to lower concentrations of pyrene, while hemosiderin-laden macrophages, degenerating tubules with greater intensity as well as necrosis was observed in higher concentrations. The results indicated that pyrene may have negative effects on homeostasis, fish health and vital organs in short time exposure due to histological changes, while it could have greater impacts in long term exposure and higher concentrations.
Volume 3, Issue 3 (12-2014)
Abstract
The effects of fennel essential oil (Foeniculum vulgare) at 5 levels of 0 (control), 100, 200, 400 and 600 mg per kg. of diet on growth performance, survival, body composition and hematological parameters of the Caspian kutum fry, Rutilus frisii kutum, were investigated in a 60-days feeding trial. No significant differences in the growth related parameters and survival were observed among treatments (p>0.05). The highest level of fat was observed in 100 mg fennel essential oil (p<0.05). The highest level of white blood cells was observed in 100 mg and the highest levels of red blood cells, hematocrite and hemoglobin were observed in 400 mg; the lowest level of MCV was observed in the control. No significant differences were observed in other parameters such as MCH and MCHC. In conclusion, fennel essential oil had no significant effect on the growth related parameters of the Caspian kutum fry, but 100 mg of fennel essential oil/kg diet would play an important role in promoting immune system of the fish by increasing the white and red blood cells.
Volume 3, Issue 3 (12-2019)
Abstract
Research Subject: Poor mechanical strengths and lack of thermal stabilities of hydrogels confine their extensive practical applications in many areas. The growing scientific need for solving this problem and achievement to the hydrogels with improved properties has led to the design and production of the nanocomposite hydrogels.
Research Approach: The polymeric networks of nanocomposite hydrogels compared to the ordinary hydrogels have improved elasticity and rheological properties. Other points that increase the importance of structural studies of nanocomposite hydrogels are the high strength of these materials versus the application of external forces, as well as maintaining its structure against increasing of temperatures. In this regard, the type and amounts of nanomaterial, the preparation method and formation of hydrogel network have a significant role in improving the physical, chemical and biological properties of hydrogels, and, it must be noted that these parameters will depend on the application of nanocomposite hydrogels. This also highlights the need for the production of nanocomposite tailored hydrogels. Therefore, orientation of the range of nanomaterials, the preparation method and product identification, along with sufficient information on the application of these materials, might have an important role in ensuring the success of these materials, requiring comprehensive library research and studies on polymerization processes, morphology and rheology.
Main Results: In this review article, the scientific advances in the field of nanocomposite hydrogels, focusing on its types based on the type of nanoparticles, its properties, preparation methods, identification methods with a new perspective on rheology, thermal analysis and morphology is investigated. Finally, the applicability of these materials is collected in a comprehensive table in various fields such as tissue engineering, enhanced oil recovery, agriculture, and etc…
Volume 3, Issue 4 (12-2012)
Abstract
Although linguists have been studying the “News” as a type of text for a long period of time, the researches have been mainly of the product-oriented types, which purely analyze the news texts and their linguistic characteristics. Linguists and media researchers have been mainly keen to determine sets of criteria known as “News Values” so far, and the result is various lists of media and linguistic news selection norms. The goal of this article is finding answer for the following questions: How news production process can be orchestrated in a linguistic model? What are the linguistic news values? and How these linguistic values correlate with other selection criteria? In addition to revisiting the theoretical notion of “News Values” and introducing the “Grice Maxims” as the linguistic criteria of news composition, this paper, as a descriptive analytical study based on field work, also represents the multi-level model of news composition and selection based on linguistically oriented findings. The mentioned model not only determines and explains different levels of news composition and selection process from the event to the news, but also puts the role of macro-structural elements of news discourse production such as ideology, relations of power and composition in the center of attention.
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 (6-2020)
Abstract
Abstract
Research subject: Nanocomposites are a new class of materials that have at least one of their major constituents, at least in one dimension, in the range of one to one hundred nanometers. Typically, nanocomposites have different and superior properties in terms of mechanical and physical properties than conventional composites.
Research approach: In this study, polyvinyl acetate was prepared by emulsion polymerization for polymer matrix. Then the diamond nanoparticles were modified with silane agent. Finally, polyvinyl acetate / diamond nanocomposite was prepared and analyzed with 0.5, 1, 1.5 and 2 wt% of modified diamond nanoparticles. To determine the properties and structure of the nanocomposite, FTIR, TGA, RMS, FESEM, oxygen permeation analysis was used in the films produced and contact angle measurements.
Main results: FTIR Analysis revealed that the modification of the diamond nanoparticles with the silane agent was well performed. FESEM images show that homogeneous nanocomposites were created. Oxygen permeability in polyvinyl acetate / diamond nanocomposite film decreases with increasing percentage of modified nanoparticles in nanocomposite. This is a valuable property if this nanocomposite is used as a fruit preservative coating. Contact angle measurement of polyvinyl acetate / diamond nanocomposite showed that by increasing the amount of modified diamond nanoparticles from 0.5 to 2 wt %, the hydrophobicity of nanocomposite film increased. Therefore, by increasing the specific amount of nanoparticles to the polymer matrix, the polymer properties such as heat resistance and tensile strength are increased which increases the efficiency of the polymer.
