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Showing 15 results for Mirdamadi


Volume 0, Issue 0 (1-2024)
Abstract

Climate change (CC) is one of the major challenges of our time that impacts rangelands regionally and globally. The rising vulnerability among pastoralists highlights the need to prioritize resilience thinking. Pastoralists' resilience refers to the ability of rangeland businesses to endure, adapt to, and remain flexible in the face of threats or challenges. This research was conducted with the primary goal of analyzing the factors that influence resilience from the perspective of pastoralists in Tehran province under CC conditions. This research was both goal-oriented and exploratory in methodology. The study sample consisted of 317 pastoralists selected through stratified random sampling. The data collection tool was a researcher-made questionnaire. Software SmartPLS was used for data analysis. The validity of the questionnaire was assessed using the average variance extracted, while its reliability was established by calculating composite reliability and Cronbach's alpha. Data were analyzed using the structural equation modeling technique with Smart PLS software. The structural equation modeling indicated that economic, institutional, ecological, physical, social, educational and extensional and individual factors had the greatest impact on Pastoralists' Resilience under Climate Change (PRCC) conditions. These factors explained 75.5% of the PRCC conditions.
 

Volume 6, Issue 1 (9-2006)
Abstract

The friction materials are generally consisted of homogeneous dispersed friction materials in a metallic based which produced via a process of compaction and sintering of metallic powders, hard materials, and if necessary lubricant. The role of these materials in the components is transferring kinetic energy to heat and generating torque (brakes and clutches). This research is a property investigation of effected parameters in manufacturing of bronze based friction materials which is used in heavy automotive clutch plates, helicopter brakes, and etc. Four compositions were selected for bronze friction materials and different parameters such as compaction pressure, sintering time and temperature on density, porosity, and hardness were studied. The nearest results to imported samples are: compaction pressure of 5 t/cm2, sintering time and temperature of 30 min. and 820 DC respectively. The wear resistant in [mal sample containing 2% of hardened additives was determined by ASTM G-I05 standard and compared with foreign samples. The sample containing WC had the closest property and microstructure with imported samples.

Volume 12, Issue 5 (1-2013)
Abstract

In this study, the structural health of a thick steel beam, made of ST-52, is inspected by ultrasonic guided wave propagation method using piezoelectric wafer active sensors that is one of the most important techniques of on-line structural health monitoring. The key parameters of the diagnostic waveform such as excitation frequency and cycle number are determined in relation to beam dimensions as well as pulse-echo configuration of PZT active sensors attached to the beam. Finite element simulations were conducted to characterize wave propagation in the beam, and the signals of wave propagation were experimentally measured. For signal processing and feature extraction, continuous wavelet transform and scaled average wavelet power technique are used. Using the extracted features, probable existing damage in the structure is detected, localized, and intensified. The acquired results are representing a higher precision of the implemented method for damage identification and characterization with respect to a previous study.

Volume 12, Issue 6 (3-2013)
Abstract

In this paper, a novel four-variable refined theory of plate, called RPT, has been proposed for free vibration of composite laminated plates, using a hyperbolic sine function, for calculating out-of-plane shear strains. It is one of the properties of this theory that the boundary condition of zero shear stress is satisfied over upper layer and under lower layer of plate, with no reference to Timoshenko shape factor. In contrast to other higher-order shear deformation theories, in RPT theory, equations of motion are coupled dynamically only in inertial terms, while elastic energy terms are not coupled for the variables used. From this viewpoint, RPT theory is similar to classical plate theory (CLPT). Some of the objectives of this paper are the investigation of effect of influential parameters on fundamental frequency, such as modulus ratio, angle of plies, and plate length-to-thickness ratio. The results of this proposed version of RPT are compared and validated with those of first-order shear deformation theory (FSDT), higher-order shear deformation theory (HSDT), and the original version of RPT.

Volume 13, Issue 2 (8-2013)
Abstract

In a framework where synchronization issues are taken into account, we examine the performance of a cyclostationary detection scheme proposed for interleaved single carrier frequency division multiple access (SCFDMA). The detection method under investigation here exploits the quasi-periodicity property of interleaved SCFDMA signal. Inserting synchronization pilot signals in the data stream might deteriorate this quasi-periodicity property. Although the detection method is afflicted by pilot signals and loses performance, we show that it still outperforms energy detection and cyclic prefix based detection. We also investigate the performance of the detector when the system is hit by frequency offset. We derive the distribution of the detection metric in the presence of frequency offset. When frequency offset is small enough, we prove that it does not change the metric distribution. We also show that for arbitrary practical frequency offsets, the performance degradation is still negligible. .
Mohsen Mirdamadi,
Volume 14, Issue 1 (2-2007)
Abstract

Foreign policy cooperation and coordination among the European Community member states and presenting Europe with a single voice, has long been an important challenge within the European Community/European :union:, especially since early 1970s. In the early 1990s, following the collapse of the USSR and the end of the Cold War, there was a general speculation in Europe that the EC may be able to play a new role in international system and fill the vacuum created by the the Soviet :union:. The Kuwait crisis, in the wake of Iraqi invasion of Kuwait in August 1990, was the first test for the European ambitions in the post-cold war era. Many European leaders saw it as an opportunity to present a European initiative and play an effective role towards the crisis. Then, the first reactions of the EC, unprecedentedly, were quick and unanimous. This unanimity continued during the first phase of the crisis, when the counter-measures to the crisis were mainly economic and to a lesser extent political. But with the appearance of the military dimension of the crisis, the EC was no longer able to maintain unanimous standand the member states were divided into two camps: Atlanticists and Europeanists. Britain, occasionally supported by Denmark and Netherlands, sided with the US which pursued a military solution to the crisis. While the Franco-German axe, followed by the rest of member states, preferred a diplomatic solution to the crisis in a longer span. As far as the military operation seemed imminent, the division became deeper. In practice, when military operation began, the Europeans have no choice except to follow the American lead. These developments were influential on formation of the common foreign and security policy (CFSP) as the second pillar of the EU in Maastricht in 1992.

Volume 15, Issue 4 (6-2015)
Abstract

In this article, Monte Carlo simulation method is used in conjunction with finite elements (FEs) for probabilistic free vibration and stability analysis of pipes conveying fluid. For fluid-structure interaction, Euler-Bernoulli beam model is used for analyzing pipe structure and plug flow model for representing internal fluid flow in the pipe. By considering structural parameters of system as random fields, the governing deterministic partial differential equation (PDE) of continuous system is transformed into a stochastic PDE. The continuous random fields are discretized by mid-point and local average discretization methods; then, by Monte Carlo simulations in each iteration loop, every distributed-parameter PDE having stochastic lumped-parameters is transformed into a deterministic distributed-parameter PDE. Each PDE is transformed into a system of deterministic ordinary differential equations (ODEs) by using FEs. Accordingly, all of the deterministic and stochastic parameters of system are discretized. For free vibration analysis, the eigenvalue problem is solved for investigating the complex-valued eigenvalues and critical eigenfrequencies. Consequently, having complex eigenfrequencies and divergence points, the statistical responses of stochastic problem are obtained like expected values, standard deviations, probability density functions, and the probability of occurrence for divergence instabilities.

Volume 17, Issue 2 (3-2017)
Abstract

Bistable and multistable plates are types of smart composite structures that have two or more static equilibrium. In this paper, a bistable hybrid composite plate with an external metal layer is studied. The difference between these plates and conventional bistable composite plates and bistable hybrid composite plate with an inner layer of metal is the deformation of them. In other words, unlike the conventional bistable composite plates, in both stable state, transverse curvatures that they have the same size and sign and but twisted curvature is the considerable. The analytical method for studying the behavior of the plate is Rayleigh- Ritz method and minimization of potential energy and finite element used. In order to increase the accuracy of the Rayleigh – Ritz method, out of the plane displacement using is guessed Legendre polynomial. At the frist, states of equilibrium and stable states are determined. To understand better the difference between a bistable hybrid plate with an external metal layer and a CFRP bistable composite plate, a comparison between deform at room temperature, curvature and out of plane displacement are done. In the next part, the moment required to snap through between stable states is achieved. Also, the effect of metal layer thickness on out of plane displacement and stability boundary is investigated. Comparing the results of the proposed shape function and Hyer shape function compared to experimental results and the results of finite element analysis show that the results of the proposed shape function is more accurate.

Volume 17, Issue 104 (October 2020)
Abstract

The application of probiotic starter cultures in fermented products is expanding in different communities. The genetic variation makes the effects of these bacteria different and unpredictable in different human societies. Therefore, the safety control and evaluation of their non-pathogenicity is of great importance and monitoring centers are required to closely monitor the safety of the bacteria used in food products.
In this study, two strains of Lactobacillus isolated from dairy products of Ardabil (Heyran mountain road villages) and Khuzestan province (Behbahan city) in Iran were identified based on the biochemical and molecular properties through sequence analysis of 16S rRNA gene. Then, their safety was examined based on the international guidelines, especially the European :union: standard. The two identified strains included Lactobacillus fermentum (PTCC 1929) and Lactobacillus helveticus (PTCC 1930). The results showed the lack of gelatinase enzyme, inability of blood hemolysis, inability of amino acids decarboxylation and the lack of genes responsible for the invasive characteristics of pathogenic microorganisms including gelE, efaAfm , efaAfs , agg, ace, cylM, cylA, cylB.  In addition, the results showed the sensitivity of both isolates to Penicillin, Ampicillin, Rifampicin and Tetracycline, and their resistance to Kanamycin and Ciprofloxacin. Lactobacillus fermentum was resistant to vancomycin, whereas Lactobacillus helveticus was susceptible to it. Since cases of antibiotic resistance are inherent according to scientific reports, the obtained results confirmed the potential application of these two isolated strains as starter in the fermented dairy products. It also confirmed the necessity of using safety assessment procedures for probiotic bacteria.

Volume 17, Issue 106 (December 2020)
Abstract

Mulberry is a fruit that has a considerable acceptance among consumers. The short harvest season and low persistence of this fruit have led to the use of methods such as freezing that have the least effect on phenolic compounds and antioxidant properties and sensory properties of the mulberry. One of the problems of sensory evaluation is the non-parametric results of the answers and the low accuracy of their analysis. Today, methods such as fuzzy logic allow inaccurate parameters to be analyzed by mathematical methods. In the present study, mulberry was stored in a freezer at -18 °C for six months and removed from the freezer at 0, 72 h, one month, two months and six months. After juice making, the sensory evaluation was performed using five-point hedonic method and the data were analyzed using fuzzy logic methodology, while attributes were color, aroma, taste, and feel mouth. Also, pH, acidity, antioxidant activity and total phenol content were evaluated. Sensory evaluation of the samples showed that the freezing of the mulberry increased the overall suitability of the samples in 72 hours and did not show a decrease in sensory properties during 6 months. Panelists assessed the importance of sensory attributes including taste, mouthfeel, fragrance, and color, as well. Although, sensory evaluation did not decrease the sensory of juice, significant decrease of pH (19.83%), increase in acidity (0.31%) and a decrease in antioxidant activity (about 14%) and phenolic compounds (about 21%) during freezing was observed. According to the obtained results, freezing can be suggested as an acceptable method for long storage of mulberry fruit.

Volume 18, Issue 1 (1-2016)
Abstract

The successful adoption of e-learning systems is mainly dependent on the learners’ attitude and willingness to use them. This survey was conducted to investigate agricultural extension workers’ attitudes toward using e-learning for on-the-job training in Iran and factors which affect it. Using the stratified sampling technique a sample of 379 extension workers were selected from six provinces. A structured questionnaire was used to collect data through an interview method. Findings show that extension workers’ attitude toward e-learning is generally positive. Extension workers' knowledge of e-learning, access to technical support, and their motivation influence their attitude toward the use of e-learning for on-the job training. Therefore, recommendations are provided to promote the experts’ motivation, knowledge and to improve infrastructures.

Volume 19, Issue 123 (May 2022)
Abstract


 
 
Abstract
Nowadays, Polysaccharides are used to improve the nutritional and physicochemical properties of dairy products. The identification of natural compounds such as polysaccharides with antidiabetic and antioxidant properties has become important due to the relationship between diabetes and oxidative stress. Therefore, the present study aimed to evaluate the influence of pectin on the antidiabetic and antioxidant activity of milk fermented by lactic acid bacteria (LAB) isolated from traditional Iranian dairy products. Pectin (1%) was added to the samples following milk fermentation by Lactobacillus helveticus and Lactobacillus para-casei strains, and antidiabetic activity was assessed by considering the inhibitory effects on α-amylase and α-glucosidase. The antioxidant activity was determined by evaluating inhibition of 2,2-Diphenyl-1-picrylhydrazyl (DPPH), 2,2-azino-bis-3-ethylbenzothiazoline-6-sulfonic acid (ABTS) and hydroxyl radicals. Samples included pectin solution (0.5-3.5 mg/ml and 0.5-10 mg/ml for evaluation of anti-diabetic and antioxidant activity, respectively), whey of fermented and non-fermented milk with (1%) and without pectin. The results indicated the role of  pectin on  inhibition of  α-glucosidase enzyme activity (IC50=2.38 mg/ml), as well as scavenging the DPPH (44.57%), ABTS (28.7%), and Hydroxyl (38.85%) radicals (P<0.05) a concentration of 10 mg/ml. Pectin added to the whey of non-fermented milk sample boosted antioxidant properties and the maximum rate of free radical scavenging activity (35%) was obtained for DPPH radicals. Furthermore, adding pectin to the whey of milk fermented with Lactobacillus helveticus strain improved the activity of the product on inhibition of α-glucosidase enzyme (29%), scavenging of DPPH (41.26 %), ABTS (2.5%), and hydroxyl radicals (7.64%) (P<0.05). The results indicated the potential of pectin to be used in the formulation of beneficial food products due to its ability to improve the antioxidant and anti-diabetic properties of fermented milk products.


Volume 19, Issue 125 (July 2022)
Abstract

Today, the use of Lactobacill strains and their metabolites is the new strategies in control of diabetes and oxidative stress. Therefore, the present study aimed to investigate the antidiabetic and antioxidant properties of metabolites obtained from of Lactobacillus delbrueckii ssp. bulgaricus culture media. The samples were evaluated including cell free supernatant (CFS), cell free extracts (CFE), cell free supernatant of fermented milk (CFS-FM) and bioactive peptides separated from ultrafiltration (3,5,10 kDa). The ability of bacteria in proteolysis of protein of  fermented milk (FM) was evaluated by O-phthaldialdehyde method compared with non-fermented milk (NFM). The antidiabetic activity was measured based on inhibition of α-amylase and α-glucosidase. The antioxidant activity was evaluated by inhibition of 2,2-Diphenyl-1-picrylhydrazyl (DPPH) and 2,2-azino-bis-3-ethylbenzothiazoline-6-sulfonic acid (ABTS). The results showed that the sample of CFS-FM inhibited α-amylase (25%) and α-glucosidase (26.6%) enzymes. Among the peptide fractions, fraction  of >10 kDa with higher protein content (13.816 mg (had the highest inhibition of α-amylase (80.64%) and α-glucosidase enzyme (54%) (p<0.05). The inhibitory efficiency ratio (IER) showed that the 3-5 kDa fraction had more inhibitory than other peptide fractions (p<0.05). Also, the CFS and CFE inhibited α-glucosidase enzyme by 50% and 25%, respectively. In case of antioxidant properties, it was observed that the free radicals scavenging of CFS-FM increased compared with NFM (p<0.05). Also, the peptide fractions of 3-5 kDa (80.85%) and >10 kDa (43.63%) had the highest DPPH and ABTS free radicals scavenging. The antioxidant capacity of trolox equivalent from peptide fractions (µmTE/mg protein) showed that the <3 kDa fraction had the highest antioxidant activity (p<0.05). The ability to free radicals scavenging in CFS and CFE was observed. Results indicate the importance of  Lactobacillus delbrueckii as a starter culture and its functional role.

Volume 21, Issue 7 (Supplementury Issue 2019)
Abstract

In this study, a gender analysis of various dimensions that affect the food security status of households in the villages of Kermanshah County was conducted based on a sustainable livelihood framework. The non-experimental research method involved data collection, which was performed to identify causal relationships. There were 25,671 households in the agricultural sector of the villages of Kermanshah County. Among them, 750 people (375 women and 375 men in 375 households) were selected as a proportional sample based on a stratified sampling method. A questionnaire was used for data collection. The validity of the questionnaire was confirmed by expert opinions, and its reliability was confirmed by sequential theta coefficients (0.714-0.838). Structural equation modeling was implemented based on the Multiple-Indicator, Multiple-Cause (MIMIC) Bayesian approach. Then, the structural MIMIC model was presented as the basis for comparison between two groups. The results of the research indicate that men had greater food security than women in terms of food availability, accessibility, and stability in the studied households. Men had more financial capital, social capital, and natural capital than women and were more affected by vulnerability and the transformation of structures and processes. Conversely, women had more human and physical capital and better livelihood strategies than men. Therefore, the economic empowerment of women and the professional training of men in the region should be prioritized to improve food security and development programs. These results can play a decisive role in the continuation or halting of programs for achieving food security and sustainable development.
 

Volume 24, Issue 2 (3-2022)
Abstract

In this study, we aimed to use the Protection Motivation Theory (PMT) to explain farmers’ pro-environmental behavior, and we subsequently applied our conceptualization of the PTM to explain the effects of pro-environmental behavior as well as some alternatives to achieve a sustainable livelihood in the Borkhar Region, Isfahan Province, Iran. The population of this study comprised rural smallholder farmers who produced agricultural and horticultural crops under drought in 2017-2019. The study sample consisted of 293 smallholder farmers selected through stratified random sampling. A questionnaire was utilized for data collection, and data were analyzed using structural equation modeling. The findings suggest that self-efficacy, perceived vulnerability, and response efficacy have a positive relationship with farmers’ pro-environmental behavior. In addition, the perceived severity and response costs are negatively related to farmers’ pro-environmental behavior. The findings further show that alternative crops and alternative income sources are the main predictors of achieving a sustainable alternative livelihood. Moreover, saffron cultivation and rural handicrafts were found to be highly important indicators that enhance sustainable alternative livelihood under drought. Therefore, concentrating efforts and shifting the focus to these alternatives leads to increased farmers’ livelihood resilience in the long run.

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