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کاربرد نوع شرط:
- جایگاه : پژوهشی
- مجله: Journal of Rehabilitation in Civil Engineering
- نوع مقاله: Journal Article
- کلمات کلیدی: time history analysis,Seismic pounding,Hertzdamp element,Separation distance,Stochastic analysis
- چکیده:
- چکیده انگلیسی: Seismic pounding occurs as a result of lateral vibration and insufficient separation distance between two adjacent structures during earthquake excitation. This research aims to evaluate the stochastic behavior of adjacent structures with equal heights under earthquake-induced pounding. For this purpose, many stochastic analyses through comprehensive numerical simulations are carried out. About 4.65 million time-history analyses were carried out over the considered models within OpenSees software framework. Various separation distances effects are also studied. The response of considered structures is obtained by means of Hertzdamp contact element. The models have been excited using 25 earthquake records with different peak ground accelerations. The probability of collision between neighboring structures has been evaluated. An efficient combination of analytical and simulation techniques is used for the calculation of the separation distance under the assumptions of non-linear elasto-plastic behavior for the structures. The results obtained through Monte Carlo simulations show that use of the current provision’s rule may significantly overestimate or underestimate the required separation distance, depending on the natural vibration periods of adjacent buildings. Moreover, based on the results, a formula is developed for stochastic assessment of required separation distance.
- انتشار مقاله: 18-03-1397
- نویسندگان: Mojtaba Naeej,Javad Vaseghi Amiri,Sayyed Ghasem Jalali
- مشاهده
- جایگاه : پژوهشی
- مجله: Journal of Rangeland Science
- نوع مقاله: Journal Article
- کلمات کلیدی: Livestock,Dependency,farm,Orchard,Hable Rud
- چکیده:
- چکیده انگلیسی: FAO and World Bank promote livestock rearing as a way of poverty alleviation and food security especially among rural poor. Villagers are usually involved in mixed crop-livestock farming. Interviews with villagers in the HableRud basin revealed that some changes have happened and comparing with past decades, fewer villagers keep livestock. They believed that number of villagers who kept livestock in pen has also drastically increased. This study was conducted to understand if natural capital holdings have any impact on villagers' dependence on rangeland or not and also to identify the important natural capitals contributing to villagers' dependency on rangeland, some unstructured and structured interviews with local people were conducted. Comparisons between the two groups of villagers namely, dependent and independent on rangeland in terms of the identified indicators, the independent samples T-test and Mann Whitney U were applied for parametric and nonparametric data, respectively. Then in order to predict likelihood of dependency of a villager on rangeland based on holding of or access to independent variables, binary logistic regression was applied using SPSS. Descriptive data analysis showed that just 177 villagers out of 380 samples were dependent on rangeland and the rest did not rely on rangeland at all. The results revealed that there was a significant difference between the two groups of dependent and independent villagers on rangelands in terms of grazing right, size of farm and orchard holding, number of small livestock, total livestock and total natural capital. But the best indicators to predict a villager's dependence on rangeland was decided to be grazing right, number of small livestock and size of farm. The study revealed that independent variables predict the odds (61% - 82%) that a villager will decide to keep livestock dependent on rangeland.
- انتشار مقاله: 01-06-1394
- نویسندگان: Hossein Badripour,Hossein Barani,Seyyed Mahmoud Aghili,Ahmad Abedi Sarvestani
- مشاهده
- جایگاه : پژوهشی
- مجله: Journal of Renewable Energy and Environment
- نوع مقاله: Journal Article
- کلمات کلیدی: Response surface methodology,optimization,Biodiesel,Microwave,Castor oil
- چکیده:
- چکیده انگلیسی: The purpose of this research work was to investigate the optimum operating conditions for biodiesel production from castor oil using a microwave. The Box–Behnken design of experiment was carried out using the Design Expert 7. A response surface methodology (RSM) was used to analyze the influence of the process variables (molar ratio of methanol to castor oil, catalyst concentration, reaction time, and microwave power) on the biodiesel yield. Optimizing biodiesel production reaction based on the yield of reaction by means of response surface method showed that 1.44 wt.% of catalyst concentration, 7.12:1 molar ratio of alcohol to oil, microwave power of 500 W and 120 seconds of reaction time produces the best results for maximizing the conversion percent. Finally, Biodiesel samples were analyzed with Gas Chromatography (GC) method for determination of fatty acid methyl ester yield. The yield of reaction obtained was 92.15% with above operating conditions and temperature of output flow was 58 oC.
- انتشار مقاله: 12-02-1395
- نویسندگان: Mohammad Kord,Seyed Mojtaba Sadrameli,Barat Ghobadian
- مشاهده
- جایگاه : پژوهشی
- مجله: Journal of Patient Safety & Quality Improvement
- نوع مقاله: Journal Article
- کلمات کلیدی: Risk Factor,No reflow phenomenon,TIMI grading system,Vasodilators
- چکیده:
- چکیده انگلیسی:
Introduction: The investigation of no-reflow phenomenon after Percutaneous Coronary Intervention (PCI) in patients with acute ST-segment Elevation Myocardial Infarction (STEMI) has therapeutic implications. Several vasodilators were administered through intracoronary injection to treat this phenomenon. We aimed to elucidate the risk factors, predictors, and long-term effects of no-reflow phenomenon, and to compare the effects of various vasodilators on re-opening the obstructed vessels.
Materials and Methods: All the reviewed articles were retrieved from MEDLINE and Science Direct (up to October 2014). All no-reflow cases were determined through Thrombolysis in Myocardial Infarction grading (TIMI) system.
Results: Four articles were included, two of which mainly focused on risk factors, predictors, and long-term prognosis of no-reflow phenomenon, and its association with patient mortality and morbidity. The other two articles evaluated therapeutic interventions and compared their efficacy in treating no-reflow.
Conclusion: Development of no-reflow in patients with STEMI after primary PCI is associated with low myocardial salvage by primary PCI, large scintigraphic infarct size, deteriorated left ventricle ejection fraction at six months, and increased risk of first-year mortality. During primary PCI, intracoronary infusion of diltiazem and verapamil can reverse no-reflow more effectively than nitroglycerin.
- انتشار مقاله: 26-12-1393
- نویسندگان: Mostafa Dastani,Somaye Alirezaei
- مشاهده
- جایگاه : پژوهشی
- مجله: Journal of Nanostructures
- نوع مقاله: Journal Article
- کلمات کلیدی: Photocatalysis,co-precipitation,SrWO4,Surfactant concentration
- چکیده:
- چکیده انگلیسی: A simple co-presipitation method has been developed to synthesize SrWO4 and Ag°-SrWO4 micro/nanostructures with different morphologies, including platelet-, star- and flower-like, in the presence of Na(B(C6H5)) as surfactant. The formation of platelet-, star- and flower-like shapes of particulate system was examined by electron microscopy technique. The products were characterized by X-ray diffraction, scanning electron microscope, UV-vis absorption, energy dispersive X-ray and fourier transform infrared spectra. The scheelite type tetragonal structure of all the synthesized compounds was revealed by powder X-ray diffraction analysis. The influence of surfactant concentration (sodium tetraphenylborate as new surfactant) on the size and morphology of products was investigated. Finally, a good photocatalytic activity was first discovered of the Ag°-SrWO4 microcrystals for the degradation of methyl orange dye after 100 min under UV-vis light. Hence, from the present investigation it was observed that the doping of Ag in SrWO4 will yield a new kind of multifunctional material for fabricating electronic devices.
- انتشار مقاله: 03-02-1397
- نویسندگان: Farideh Sedighi,Ali Sobhani-Nasab,Mahdiyeh Esmaeili-Zare,Mohsen Behpour
- مشاهده
- جایگاه : پژوهشی
- مجله: Journal of Mining and Environment
- نوع مقاله: Journal Article
- کلمات کلیدی: Cost,Emissions,Surface Mining,Loader-truck operation,Fleet size
- چکیده:
- چکیده انگلیسی: Traditionally, the earthmoving operations have been developed based on the minimum cost per production criterion. Nowadays, due to the negative impacts of the emissions on the environment, there is an increasing public awareness to reduce the emissions from the earthmoving operations. Different management strategies can be employed to reduce emissions, amongst other things, which can also result in a reduction in the operational costs. This paper aims to examine the cost and emissions related to the earthmoving equipment from an operational standpoint. The queue theory is used in order to demonstrate that the optimum cost per production fleet size and the optimum emissions per production coincide. The linear and non-linear server utilization functions are employed to present a general optimization proof independent from any specific case study. The findings of this research work provide a better understanding of the relationship between the emissions and cost and how the under-trucking and over-trucking conditions affect the productivity and environmental affairs in the earthmoving operations.
- انتشار مقاله: 27-04-1399
- نویسندگان: Seyed A.R. Kaboli,M. Bahaaddini,Seyed M. Kaboli
- مشاهده
- جایگاه : پژوهشی
- مجله: Journal of Mining and Environment
- نوع مقاله: Journal Article
- کلمات کلیدی: Stability Analysis,Sensitivity analysis,Finite Element modeling,Salt Cavern
- چکیده:
- چکیده انگلیسی: Ensuring the stability and integrity of underground gas storage salt caverns is a very complicated subject due to the non-linear and time-dependent behavior of rock salts under complicated thermal and mechanical loading conditions. For this reason, pressure and temperature fluctuations in the caverns and their surrounding strata must be integrated into the analysis and the numerical tools that are used for this purpose. LOCAS, a 2D axisymmetric finite-element code, dedicated to the stability analysis of underground salt spaces, was applied to assess the effects of various operating and geometrical parameters on the cavern behavior. In this paper, we aimed to give an overall assessment of the behavior of the salt caverns used for natural gas storage. In this work, some specific loading scenarios were considered first, followed by thorough parametric and sensitivity analyses to reveal the impacts of the geometrical parameters and operational parameters involved on the behavior of salt caverns using the modern stability criteria. The findings showed that the onset of dilation was more likely to happen within the first cavern life cycle when pressure dropped to the minimum level. As for the potential of tension occurrence in the surrounding rock, this is more likely to happen by increasing the number of operation cycles, especially in the upper one-third of the cavern wall. Finally, it was seen that the cavern depth and minimum cavern internal pressure had even more important influences than the others on the salt cavern behavior.
- انتشار مقاله: 07-02-1398
- نویسندگان: A. Asgari,A. Ramezanzadeh,Seyed M. E. Jalali,B. Brouard
- مشاهده
- جایگاه : پژوهشی
- مجله: Journal of Mining and Environment
- نوع مقاله: Journal Article
- کلمات کلیدی: modeling,Computational Fluid Dynamics,Airflow,Ventilation,tunnel boring machine
- چکیده:
- چکیده انگلیسی: Knowledge of the airflow distribution inside a Tunnel Boring Machine (TBM) can create a safe working environment for workers and machinery. The airflow quality and the related mass flow rate in the ventilation system should be sufficient to dilute gases and remove dust inside the tunnel. In this work, airflow distribution in the single shield TBM tunnel was studied using computational fluid dynamics. The finite volume-based finite element method was used in the simulation based on the 3D complex geometry of TBM. In order to validate the numerical results, the air velocity inside the Chamshir tunnel was measured experimentally at different sections. With a length of 7050 m and a final diameter of 4.6 m, the Chamshir water transport tunnel is located in the south of Iran. The results obtained show that there is not enough airflow in 59.6% of the TBM space in the current working conditions. In other words, there are many dead zones from the control cabin to the end of gantry 6 in the backup system. Several applicable scenarios were studied to remove the dead zone area and optimize the airflow velocity by employing high capacity jet fan in the ventilation system. The results show that the dead zone volume can be decreased by about 5.21% by increasing the airflow rate of the jet fan.
- انتشار مقاله: 07-08-1397
- نویسندگان: H.R. Nezarat,Seyed M. E. Jalali,M. Nazari
- مشاهده
- جایگاه : پژوهشی
- مجله: Journal of Mining and Environment
- نوع مقاله: Journal Article
- کلمات کلیدی: Rare Earth Elements (REEs),D2EHPA,Separation factor,Cyanex272,Mixture System
- چکیده:
- چکیده انگلیسی: This work was aimed to evaluate and compare the performances of the solvents D2EHPA (Di-(2-ethylhexyl) phosphoric acid), Cyanex 272 (bis (2,4,4-trimethylpentyl) phosphinic acid), and a mixture system of D2EHPA and Cyanex272 in the separation of some rare earth elements (REEs) including lanthanum, gadolinium, neodymium, and dyspersym from a nitric acid solution. The results obtained showed that Cyane272 had the lowest separation factor in the separation of Dy, La, Nd, and Gd from each other. Also it was found that a mixture system of D2EHPA and Cyanex272 had the best performance in the separation of the investigated REEs, owing to the higher separation factors for Dy/Nd and Dy/Gd, as well as the lower extraction efficiencies for Gd (64.54%), La (30.07%), and Nd (26.47) from Dy (99.92). It was also determined that the separation factors forDy/Nd and Dy/Gd were 720.05 and 3640.27, respectively, using their mixture system.
- انتشار مقاله: 19-11-1393
- نویسندگان: Seyyed M. Seyyed Alizadeh Ganji,S. Z. Shafaie,N. Goudarzi
- مشاهده
- جایگاه : پژوهشی
- مجله: Journal of Mining and Environment
- نوع مقاله: Journal Article
- کلمات کلیدی: Monte Carlo simulation,Reliability analysis,Probabilistic Method,Statistical Moments Method
- چکیده:
- چکیده انگلیسی: Performing a probabilistic study rather than a determinist one is a relatively easy way to quantify the uncertainty in an engineering design. Due to the complexity and poor accuracy of the statistical moment methods, the Monte Carlo simulation (MCS) method is wildly used in an engineering design. In this work, an MCS-based reliability analysis was carried out for the stability of the chain pillars in the Tabas coal mine, located in Iran. For this purpose, the chain pillar strengths were calculated using the Madden formula, the vertical stress on the chain pillars was determined by an empirical method, and a numerical modeling was performed using the FLAC3D software. The results obtained for the probabilistic stability analysis of the chain pillars showed that the failure probability obtained for the designed pillars by applying the MCS method were approximately the same as that obtained by the advanced second moment (ASM) method, and the values obtained varied between 12 and 18 percent.
- انتشار مقاله: 07-07-1393
- نویسندگان: M. Najafi,Seyed M. E. Jalali,F. Sereshki,A. Yarahmadi Bafghi
- مشاهده