Showing 15 results for Asefi
Volume 0, Issue 0 (in press 2024)
Abstract
Fire can not only lead to many human and financial losses, but also can cause structures to collapse and destroy them. For this reason, it is necessary and inevitable to protect buildings against fire and conduct more research in the field of better understanding the effects of combining different materials with each other and obtaining materials with greater resistance to fire. Concrete and concrete structures are always used by construction engineers due to their resistance, availability and resilience against fire. Ordinary concrete loses its strength at high temperatures, and the use of unreinforced concrete is not very useful due to its brittleness and weakness in tensile strength. In concrete, the tensile strength is lower than its compressive strength, and for this reason, researchers are trying to increase the resistance to fire and heating by improving the tensile strength of concrete. Reinforcing concrete with rebar is always a solution to increase the tensile strength in concrete parts, one of the most important weaknesses of using rebar in concrete is that the reinforcements form a small part of the concrete cross-section and actually cause the concrete to be inhomogeneous. In this research, double-bent steel fibers have been used to overcome the mentioned weakness and reinforce the concrete. It should be noted that concrete containing steel fibers has favorable compressive and tensile strength due to the high tensile strength of steel fibers. In order to achieve this goal and achieve fiber concrete that has good fire resistance, we defined seven different mixing plans with different percentages of steel fibers and lubricants. Concrete samples were produced using double-bent steel fibers in amounts of 0.5, 1, and 1.2 percent by volume of concrete and superlubricant in 0.5, 1, and 1.3 percent by weight of cement, and then in Cubic molds with dimensions of 10x10x10 cm and cylindrical ones were sampled as standard, and after setting the cement, the 28-day-old concrete samples, after heating and placing inside the electric heater with different temperatures, were divided into two The method of gradual cooling with ambient air and fog spraying (water spraying) is similar to what firefighters do when extinguishing a fire, after measuring the amount of weight loss of the heated samples, the weight loss values were presented in the form of a diagram, then the samples were subjected to tests Compressive strength, tensile strength (Brazilian test) and ultrasonic wave speed (ultrasonic test) were placed, and the results and data of each of them for each mixing design were presented in the form of a diagram after examination and classification, so that the effect of high heat on Concrete containing steel fibers and super-lubricant should be determined. The results clearly showed the improvement of the tensile strength in three volume percentages of fibers by 14.6, 16.8 and 64.5%, respectively, compared to concrete without fibers, and also the compressive strength of concrete after bearing the heat of 250 degrees Celsius and cooling to the fogging method had 44.5, 31.6, and 9.3 percent, respectively, and in the gradual air cooling method, the compressive strength was 43.3, 44.9, and 50 percent, respectively.
Volume 6, Issue 3 (11-2016)
Abstract
Horizontal development of the cities has resulted in much destruction environmentally and economically. Two of the major consequences of such destruction is imbalanced development and inappropriate application of lands in the cities that are referred brownfield in this article. Brownfield in the urban planning jargon, a brownfield site (or simply a brownfield), is a type of land formerly used for industrial purposes or some commercial applications. The brownfield concept was first introduced by the British government and was used in accordance with the sustainable development policies which is mostly focused on the environmentally polluted lands. In the last two decades, redevelopment policies of brownfield as a crucial practical solution for preventing disperse growth of cities and also supporting the concentrated growth of cities have been attracted more attention. The main features of the brownfields are: -1 Pollution: each land in which an environmental complication has the occurrence probability. -2 Empty and leaved without using and in general lands and properties that their activities have been closed or not been used anymore. Of course, some of the terms that must be separated from the brownfield areas are: greenfields and grayfields.
Greenfields are those lands that previously has not been developed and often are rural or suburban. These green sites are located in the edge of small or large cities and have better accessibility and more palatability with additional space for future development.
The term grayfield, was defined in 1998 by new urbanism congress. Unlike the famous terms of greenfields (the rural undeveloped) and brownfields (polluted urban sites), the gray lands are called to the large undeveloped sites that have good reasons for redevelopment. The term of grayfield can be used to describe any kind of redevelopment that significantly is not polluted. But regarding the importance of environmental protection and sustainable development and realization their policies, it is essential to eliminate or reduce the environmental pollutions purposefully to achieve the redevelopment of brownfields.
For the sake of importance and novelty of the subject, redevelopment of Brownfield with the objective of efficient applications of lands in cities and reducing the environmental pollution and also improving the social-economical context of these fields is the subject of this article. Brownfield of Kan stream in Tehran was selected as the case study. The field was selected as it is one of the few major barren Brownfield in Tehran. They are not only in the leaved brownfields but also regarding the river-valley nature, the fields has specific ecological and tourism features. Unfortunately, due to lack of planning and management, these brownfields have been converted to the locations of rubbish depot and uncontrolled polluted waters and therefore infected with the environmental pollution. The methodology of this article is descriptiveanalytical using library studies. After studying the theoretical framework, defining features of brownfield, literature review, objectives and the importance and of these fields, the redevelopment process of Kan stream Brownfield are presented. Finally, the conclusion and analysis of the actions are conducted in redevelopment of brownfield with social, economical and tourism approach.
After comprehensive studies, in order to determine the kind of landuses in Kan brownfields, establishing a national and even an international performance scale park is designated as the planning vision. In this context, the objectives of the redevelopment planning process Kan brownfield included:
creating a touristic space to enhance the region›s tourism identity, planning with emphasis on providing recreational services for all social classes, such as children, elderly people and women and people with disabilities (all divisions with regard to sex, age and physical aspects), strengthening of the relationship between people and nature and to replacing normal social activities and improvement environmental conditions; Developing ecotourism in urban environment regarding and it s benefits beyond natural landscapes, enhancing green space for per capita in Tehran city and attainment to the standard limits for
environment qualities by using marginal lands and rivers sanctums.steel plates. In addition these bars are pre- tensioned by means of cable passing through them in order to behave properly to the applied forces.
The way that the bars are moved through the retraction process and the function of the building effects on the selection of the covering materials. In this structure, as the distance between the bars is changed during the deployment process it is required to use a flexible but strong material that can resist repeated retraction. Therefore, a flexible membrane that is strong enough during movement and has a proper foldability such as ETFE is one of the best alternatives for covering the roof. ETFE is also able to penetrate enough light inside of the building when the roof is in fully closed position and this in turn reduce the energy required for running the building.
The membrane is also attached to the bars though the slots that have already been created during fabrication and is fasted by means of pinned curve plate. This is also worth to mention that in this structure, the placement of the moveable components underneath the covering material support the whole structure even in severe weather conditions. Therefore, this increase the life cycle of the system and decrease the maintenance cost.
In summary, this paper proposes a new solution for a retractable curved roof system that can not only be transformed from an open to closed configuration but is also able to support itself structurally even during movement and transformation. In other word, the structural and transformable components are integrated and are able to make the whole structure stable during transformation.
Volume 8, Issue 3 (Autumn 2018)
Abstract
Iran is one of the most earthquake-stricken countries that has suffered numerous earthquakes and casualties. One of the reasons for the mortality of masonry buildings is the inappropriate structure. One of the solutions is to retrofit and improve the structures of these buildings against the earthquake’s lateral force, which is less costly. Masonry buildings include a lot of buildings in the world. These structures are of high weight, low strength, and low shapeability, and vulnerable to earthquake; so, they should be strengthened. The main purpose of retrofitting is to reduce the vulnerability of the building to earthquake damage. In many modern retrofitting methods, inappropriate interference with the structure and architecture, especially visually, remains in conflict with the existing architecture and a factor for reducing its value. The aim of this study is to develop a new method for seismic retrofitting for unreinforced brick walls. In this research, we tried to retrofit these buildings using the technology of steel cables with the priority of expressing architectural quality considerations and eliminating many of the disadvantages of the previous methods, as well as taking into account the requirements for strengthening and retrofitting with principles and rules of balance for the protection of architectural buildings. At the end of this method, the numerical calculations on the proposed brick wall have been analyzed. The results show that the shear strength and, as a result, its seismic resistance increased to the typical one.
Volume 14, Issue 4 (3-2012)
Abstract
Objective: Bacillus cereus (B. cereus) is a gram-positive, spore-forming bacteria widely distributed in the environment. This bacteria is an opportunistic human pathogen that can cause diarrheal and emetic types of food poisoning. The diarrhea type of food poisoning can be caused by hemolysin BL (HBL), non-hemolytic (NHE), and cytotoxin K enterotoxins. Rice is commonly contaminated with B. cereus. The objective of this study is to detect enterotoxigenic genes of the NHE complex and assess their incidence in B. cereus isolates in rice samples from Zanjan, Iran.
Methods: We randomly purchased 10 different rice samples from food stores and cultured them in PEMPA. Following biochemical testing, the bacterial colonies were identified by PCR. B. cereus isolates were checked for the NHE complex genes by specific primers using multiplex PCR.
Results: Results showed that rice samples were contaminated with B. cereus. The NHE complex genes were found in 8 bacterial samples.
Conclusion: B. cereus is able to tolerate high temperatures; in cooked rice the spores can undergo germination by reheating. The results of this study have shown that NHE multiplex PCR is a prompt, reliable method for the differentiation between non-enterotoxigenic and enterotoxigenic isolates of B. cereus. Despite its common dietary role, rice in Iran has rarely been investigated from a microbiological point of view. Enhancing awareness about virulence and prevalence of genes involved in food poisoning would be effective in the prevention of food poisoning.
Volume 14, Issue 13 (First Special Issue 2015)
Abstract
In the present paper, mixed convection of TiO2-water nanofluid in a laminar flow within a vertical rectangular duct is investigated numerically. A single phase and a two phase method is applied to simulate nanoparticles dispersion in the base fluid. An Euler-Lagrange approach is employed to track particles individually. In this approach, the base fluid is assumed to be a continuous phase while the particles are dispersed through it. The presence of particles in the base fluid is modeled as a source term in the momentum and energy equations. Governing equations is discretized using Control Volume based Finite Element Method (CVFEM). Effects of nanoparticles concentration, particles size, aspect ratio of cross section, asymmetrical boundary condition and buoyancy on the hydrodynamics and thermal parameters are presented and discussed. It is observed that increasing nanoparticles concentration enhances heat transfer rate and this enhancement is more considerable in higher aspect ratios. Also, at smaller values of Richardson number (Ri) where the effect of forced convection is more than natural convection, dispersion of nanoparticles in the base fluid improves heat transfer rate more considerably. Whilst an improvement in convective heat transfer is shown to be more than 6.5% at Ri=0.05, it does not exceed 4% at Ri=0.5.
Volume 16, Issue 89 (7-2019)
Abstract
Understanding the relation between different variables affecting deep-fat frying before and during the frying process through the modelling, could be used to set up the optimal conditions for controlling the process that results in improvement of the quality of final fried product. In the present study, the Response Surface Methodology (RSM) and Central Composite Design (CCD) was employed in order to investigate the effects of independent variables including blanching and soaking in different concentration (3, 5 and 7%) of sodium chloride solution as well as vacuum drying (1, 2 and 3 hours) prior to deep-fat-frying and also the effect of frying duration (40, 80 and 120 s) on oil uptake and quality features of deep-fried eggplant. The equations achieved through the examinations revealed that independent variables had significant effect (P < 0.05) on the parameters. Among the studied parameters, vacuum drying was found as the most efficient variable. Moreover, blanching had a significant effect (P < 0.05) on all of the treatments. Although it reduced the oil uptake, caused adverse effects on the quality of the final product such as increasing of shrinkage and colour changes. In conclusion, the optimization of variables showed that samples soaked in 3% sodium chloride solution, dried for 2 hours, and fried for 40 s had the least oil content (1.70 g/1 g of dry matter without oil), moisture content (5.70 g/1 g of dry matter without oil), percentage of shrinkage (32%) and colour changes (ΔE = 25) in comparison with the control sample.
Volume 18, Issue 110 (April 2021)
Abstract
Abstract
The bioactive compounds of Cornus mas are known as powerful antioxidants. The stability of polyphenols extract is very important and encapsulating is a good technique to increase their stability by increasing the use of bioactive compounds in food and medicine. In this research the antioxidant activity of encapsulated bioactive compounds of cornus mas extract with enteric coated nanocubosomes and their release under semi-digestion conditions were evaluated. In order to determine the effect of encapsulation on the stability of phenolic compounds and their antioxidant activity, encapsulated extract into enteric coated nano-cubosoms and free extract were investigated. Characterization analysis of the mean particle size and zeta potential value of the nanocobosomes were reported to be 49.3 nm and -16 mV, respectively. The results of release studies showed that after 30 hours the secretion of Cornus mas extract at pH 1.2 (simulated gastric media) and pH 7.4 (simulated intestinal media) were about 38% and 61%, respectively. The FTIR results showed no interaction between the extract and cubosomes. Therefore Cornus mas extract retained its antioxidant activity.
Volume 18, Issue 111 (May 2021)
Abstract
Deep frying is a common practice in fast food preparation with optimal sensory properties. various factors such as process conditions (temperature and time), pH, physicochemical properties of the food, the origin of the oil, the chemical composition of the oil have affected on the amount of oil absorption. The purpose of this study was to investigate the ultrasound and blanching pre-treatment on the physical and thermodynamic quality of fried carrots under deep conditions. In this study, moisture content, oil content, bulk density, effective moisture diffusion coefficient were investigated and the rate of modeling of shrinkage was done by the neural network. The results showed that the use of a combination of ultrasound and blanching pretreatment resulted in reduced shrinkage, decreased oil absorption, increased apparent density at 160 ° C, and an increase in the effective emission factor of moisture content at 180 ° C. Moreover the modeling of neural network shrinkage showed a good correlation and overlap between the values predicted by the network versus actual values.
Volume 18, Issue 111 (May 2021)
Abstract
Frying is considered as one of the most popular methods of fast food cooking with desirable sensory characteristics as well as an important inclusive and diverse process. Since the tendency to consume fried foods with lower oil content has increased today, pretreatments such as enzymatic and ultrasonic treatment can reduce the absorption of fried oil and improve the sensory properties of food. In this study, pretreatment with hot water enzyme at 85 ° C for 2 and 4 minutes and ultrasound pretreatment at 37 kHz at 20 and 40 minutes. The effect of the above treatments on oil uptake and sensory properties was investigated. The results show that moisture diffusion coefficient increases with increasing temperature in all pretreatments due to faster exit of moisture from nutrients. The highest moisture diffusion coefficient was observed at 190 ° C. As the frying temperature increased, the oil content in the food decreased. Regarding the moisture content, there was a significant difference between control and ultrasound-treated and control enzyme samples (P<0.05). There was no significant difference between the treated enzyme samples in 2 minutes and the enzyme samples in 4 minutes (P>0.05). The shrinkage was reduced in all of the above treatments so that in the pre-treated ultrasound samples for 20 and 40 minutes were less wrinkled than the control and enzymatically treated samples. However, the difference between the ultrasound pre-treated samples for 20 minutes with the enzymatically treated samples was not significant (P>0.05).
Volume 18, Issue 111 (May 2021)
Abstract
In the present study, a convective heat transfer coefficient

changes during deep fat frying was investigated. So, by keeping the oil temperature constant as a heat transfer medium, temperature changes in a potato strip (cube-shaped), in the center and left-right sides of the strip during frying by a three-channel thermocouple was measured. Processing temperature of oil was 150, 160 and 170
°C. The strip temperature was recorded by a data logger at ten-second intervals. Due to no significant changes in the temperature of different selected locations in potato strip, the center temperature was selected and recorded as an effective temperature. Also, heat transfer parameter included convective coefficient (

) was calculated in the range of 128_515 W/m
2.K .Result showed that

is high in high levels temperature because of increasing rate of moisture exiting and turbulence in the oil. Also, with increasing oil temperature, decreasing of oil content and decreasing in moisture content of slices were observed. The mass transfer parameters including the effective moisture diffusivity (

) and the oil diffusivity (

) were calculated in the range of 9.12×10
-9 _1.31×10
-8 m
2/s and 1.26×10
-5_1.52×10
-5 m
2/s , respectively
. By using the calculated coefficients, heat and mass transfer modeling, was done by mathematical equations and the relevant equations were solved by the method of separation variables. Simulation was also done with
COMSOL Multiphysics version 5.3a and the resulted profiles were also presented.
Volume 18, Issue 113 (july 2021)
Abstract
Garlic( Allium Satirum L) is one of the most important agricultural products in Iran and one of the major sources of foreign exchange for the country. Due to the high waste in this product to maintain, increase shelf life, and keep its quality, it is necessary to use appropriate storage methods such as drying. In this study, a thin layer of garlic slices was dried at 50, 60, 70 ° C, and in two types of dryers (vacuum and hot air). The most suitable model was developed to describe the drying kinetics of garlic flakes as a thin layer in the temperature range and type of dryer used. Effective moisture penetration coefficient, amount of activation energy, shrinkage, water reabsorption of garlic samples were measured during the drying process. in the present study, by examining 9 different experimental models and calculating the statistical criteria of R2, RMSE, x2 between the experimental data and the results predicted by each model, the most appropriate model describing the drying kinetics of garlic thin slices was the Page model. The results showed that the effective diffusion coefficient of garlic leaf moisture for different temperatures and in two types of dryers was in the range of 1.5* 10-9 to 6.6 * 10 -9 m2/s. Changes in the moisture diffusion coefficient were described as a function of drying air temperature with Arrhenius and the amount of activation energy was calculated between 14.673 and 53.175 kJ / mol. The results also showed that the shrinkage of the product was not dependent on air temperature and the type of dryer and the water re-absorption capacity of garlic samples increased slightly by decreasing their moisture content.
Volume 18, Issue 114 (August 2021)
Abstract
Owning to drawbacks of synthetic polymers, biodegradable packaging materials (biopolymers) have received more attention both in studies and industrial applications. However, compared to conventional packaging, the biodegradable materials have some limitation must be eliminated either by using composite preparation method or introduction of nanotechnology. Inclusion of metal nanoparticles and their oxides are of the new approaches to improve the properties of packaging films. Therefore, the present study attempted to investigate the effect of ZnO (0, 2.5 and 5%) and β-glucan (0, 10 and 20%) incorporation on chemical and microbial properties of gelatin based biodegradable film over storage of chicken fillet. Results showed that incorporation the both of ZnO and β-glucan have significantly (p<0.01) improved the barrier properties against both of moisture absorption and water vapor permeability and the best properties obtained with film containing 5% of ZnO and 20% β-glucan. In addition, based on microbial tests result, it was obvious that the ZnO loaded films have antimicrobial properties and the highest inhibition activity obtained with 5% of ZnO against the all of studied pathogenic bacteria. Accordingly, the film containing 5% ZnO and 20% β-glucan is introduced as the most effective film for packaging of chicken fillets.
Volume 19, Issue 123 (May 2022)
Abstract
Today, the tendency to use flaxseed oil as a rich plant source of ω-3 fatty acids has increased. But the high content of unsaturated fatty acids in flaxseed oil makes it highly susceptible to oxidation. In this study, to produce flaxseed oil powder with more stability than oil, rosemary leaf powder (as a natural source of antioxidants) in 3 levels (5, 10 and 15% of oil) and 3 different proportions of flaxseed oil and Microcrystalline cellulose (50:50, 50:75 and 50: 100) were mixed together. The results showed that by transporting the oil to the powder form and addition of rosemary leaves, the rate of increase in peroxide, thiobarbituric acid and acidity during storage was decreased significantly (p < 0.05). Storage at refrigerator (4 ºC) was more effective than room temperature (25 ºC) in increasing oxidative stability of samples during storage. Oxidative stability increased with increasing the concentration of microcrystalline cellulose and rosemary leaves. Addition of rosemary leaves caused a slight increase in acidity in the samples. Rosemary leaves also increased phenolic compounds, chlorophylls and carotenoids in the samples. Mixing the oil with microcrystalline cellulose significantly (p < 0.05) reduced the decomposition rate of phenolic compounds, chlorophyll and carotenoid contents. It was concluded that by mixing flaxseed oil with microcrystalline cellulose and rosemary leaves, a new powder product with suitable oxidative stability is introduced, which has the potential to be applied directly on foods such as salads or to be used in different food formulations to fortify them with natural antioxidants and ω-3 essential fatty acids.
Volume 19, Issue 125 (July 2022)
Abstract
In this study, the effect of enzyme type (alcalase and pepsin) and process time (50-300 minutes) on the degree of hydrolysis and antioxidant indices including free radical scavenging of DPPH, ABTS, hydroxyl, reducing power, and chelating activity of Iron and copper ions were evaluated for navy bean protein (Phaseolus vulgari L.). Also, the composition of amino acids (hydrophobic and antioxidants types) and structural properties (FTIR) of primary protein and hydrolysates were investigated. The results showed that enzymatic hydrolysis improves antioxidant properties. Also, the composition of amino acids has a significant effect on antioxidant activities. On the other hand, the type of enzyme and the time of the hydrolysis process affected the degree of hydrolysis and the antioxidant activity of the hydrolysates. Thus, the highest percentage of free radicals scavenging of DPPH (82.4%), ABTS (58.3%), reducing power (0.97), hydroxyl radical scavenging (57.5%), and chelation of Fe (53.7%) and Cu ions (12.1%) were affected by the type of enzyme and process time. Among different treatments, the highest value of these indices (except copper ion chelating) was related to hydrolysates with alcalase. Structural properties of white bean protein were evaluated and enzymatic hydrolysis caused changes in the amide regions (I and II) as well as exposure to some hydrophobic-buried groups. The results of this study indicated the positive effect of enzymatic hydrolysis on the production of antioxidant hydrolysates that can be used in the food industry.
Ahmadreza Eghtesadi Roudi, Hengameh Asefi,
Volume 25, Issue 4 (7-2018)
Abstract
With the shift of research attention from human malfunctioning to human optimal functioning in the workplace, job engagement which is regarded the opposite of job burnout has attracted researchers’ attention in organizational psychology. This exploratory study aimed to investigate the predictive role of emotional intelligence (EI) as a personal resource in determining levels of job engagement among Iranian English language teachers within job demands-resources model (JD-R). To this end, 442 English language teachers who were teaching in both public and private contexts were selected through non-probability convenience sampling and were surveyed regarding their demographic information, the perception of their levels of job engagement and emotional intelligence through a demographic questionnaire, the Utrecht Work Engagement Scale (UWES), and emotional intelligence scale. The results of hierarchical multiple regression analyses revealed that after controlling for the effect of demographic variables, there were significant positive predicting relationships between two emotional intelligence subscales of management of own emotions (MOE) and management of others’ emotions (MTE) and job engagement components of vigor, dedication, and absorption. The results imply that training teachers to improve their emotional intelligence can be a strategy to boost their job engagement.