در هنگام جستجو کلمه در قسمت عنوان میتوانید کلمات مورد جستجو را با کاراکتر (-) جدا کنید.
کاربرد نوع شرط:
- جایگاه : پژوهشی
- مجله: علوم و مهندسی آبیاری
- نوع مقاله: Journal Article
- کلمات کلیدی: River,Unsteady Flow,local scour,Pipe diameter,Pipe installation depth
- چکیده: Water and other fluid pipes that are placed on the seabed and rivers bed change the flow pattern around them. These changes increase the shear stress of the bed and the severity of turbulence around the pipe and create a scouring hole under the pipe. The scouring under the pipe may lead to instability, bending, and even breakage of the pipeline. In this study, local scouring around pipelines across the river in unsteady flow conditions was investigated. In the experiments, three pipe diameters (20, 40, and 60 mm) and three installation depths (on the bed, a quarter of the pipe diameter above the bed, and half of the pipe diameter above the bed) were used. It can be understood from the results of this laboratory study that the amount of final scour depth due to the passage of flood hydrograph is always less than the scour depth due to the steady flow corresponding to the peak flow of the hydrograph. For different pipe installation depths, the amount of scouring for the installation depth of one-quarter of the pipe diameter above the bed in both steady and unsteady flow conditions is higher than other installation depths.
- چکیده انگلیسی: Water and other fluid pipes that are placed on the seabed and rivers bed change the flow pattern around them. These changes increase the shear stress of the bed and the severity of turbulence around the pipe and create a scouring hole under the pipe. The scouring under the pipe may lead to instability, bending, and even breakage of the pipeline. In this study, local scouring around pipelines across the river in unsteady flow conditions was investigated. In the experiments, three pipe diameters (20, 40, and 60 mm) and three installation depths (on the bed, a quarter of the pipe diameter above the bed, and half of the pipe diameter above the bed) were used. It can be understood from the results of this laboratory study that the amount of final scour depth due to the passage of flood hydrograph is always less than the scour depth due to the steady flow corresponding to the peak flow of the hydrograph. For different pipe installation depths, the amount of scouring for the installation depth of one-quarter of the pipe diameter above the bed in both steady and unsteady flow conditions is higher than other installation depths.
- انتشار مقاله: 06-10-1399
- نویسندگان: Sajad Bijanvand,Seyed Mahmood Kashefipour,Mohammad Bahrami Yarahmadi
- مشاهده
- جایگاه : پژوهشی
- مجله: Geotechnical Geology
- نوع مقاله: Journal Article
- کلمات کلیدی: Upper Cretaceous,Folded Zagros,Tang-e-Abolhayat,Tang-e-Zanjiran,Maharloo
- چکیده:
- چکیده انگلیسی: The Upper Cretaceous Gurpi and Lower Tertiary Pabdeh formations as units of Folded Zagros were studied in three different regions (Tang-e-Abolhayat, Tang-e-Zanjiran and Maharloo) in Fars Province. Gurpi Formation consists of thin to medium bedded gray marl and marlstone interbedded with thin layers of argillaceous limestone and shale. The dominant Microfacies in this Formation are biomicrite; Index species of Globotruncana give the age of the Formation from Lower Campanian to Upper Maastrichtian. Pabdeh Formation consists of bluish gray, thin to medium bedded shale and marl and interlayers of argillaceous limestones (with purple shales and thin cherty beds) at lower part, dark gray shales and marls with interlayers of argillaceous limestone in the middle, and alternative layers of thinly bedded argillaceous limestone, shale and marl at the upper part. The dominant Microfacies are biomicrite. Index species of Globorotalia and Hantkenina give the age of Formation from Upper Paleocene to Eocene. The sedimentary environment of both formations is a bathymetrical carbonate floored basin (deep shelf or basin margin) which has deposited its facies in transgressive stage. The contact between the two formations is disconform. In Tang-e-Abolhayat it lies at the base of purple shale. In this region and also in Tang-e-Zanjiran and Maharloo, in addition to the recognition of Globorotalia velascoensis, which is attributed to lower part of the Pabdeh Formation, a glauconitic-Phosphatic bed separates the two formations. This bed represents a non-depositional (epirogeny) period from the Late Maastrichtian to the end of Early Paleocene.
- انتشار مقاله: 31-06-1399
- نویسندگان: Mohammad Bahrami,Mahnaz Parvanehnezhad Shirazi
- مشاهده
- جایگاه : پژوهشی
- مجله: Geotechnical Geology
- نوع مقاله: Journal Article
- کلمات کلیدی: رودخانه ی قره آغاج,بار بستری,بار معلّق,کوار,میر- پیتر ومولر
- چکیده:
- چکیده انگلیسی: حوضهی آبریز رودخانهی قره آغاج از سرچشمه تا مقطع کوار دارای وسعتی در حدود 1600 کیلومتر مربع بوده و در این فاصله از جنوب باختری تا جنوب خاوری شیراز جریان دارد . در این تحقیق بار کل رسوب رودخانه ی قره آغاج تا مقطع یادشده با استفاده از خصوصیات هیدرولیکی و رسوب شناسی محاسبه شده است . این خصوصیات شامل عمق جریان، شیب کانال رودخانه، عرض رودخانه، سرعت جریان آب، آبدهی، زاویه ی قرار ذرات رسوبی و اندازه ی مشخّصه ی ذرات (d10، d30، d60و d90) هستند . به علاوه، با اندازه گیری دمای آب رودخانه، لزجت کینماتیکی آب به واسطه ی تأثیر آن در حرکت مواد رسوبی مشخّص شده است . نرخ بار معلّ ق رودخانه با استفاده از روش پیشنهادی یانگ ( 765040 تن در سال) برآورد شده است . این تحقیق نشان می دهد که میزان بار بستر براساس روش میر-پیتر و مولر حدود 21 درصد بار معلّق رودخانه را تشکیل می دهد.
- انتشار مقاله: 31-06-1399
- نویسندگان: Mohammad Bahrami,علی رحیمی
- مشاهده
- جایگاه : پژوهشی
- مجله: Geotechnical Geology
- نوع مقاله: Journal Article
- کلمات کلیدی: GIS,Erosion,Sediment yield,Fournier,Kordshikh river watershed basin
- چکیده:
- چکیده انگلیسی: Soil is one of the most important resources in nay country and its degradation causes great losses for human beings, specially in arid and semi- arid regions. One of the existing views in watershed is a kind of management based on the analysis of a set of factors influencing watershed basin as a unit of soil and water resources. Geographical Investigation System (GIS) is used as an efficient means in evaluating and solving of many Problems of natural resources. In this connection, the rate of erosion and sediment yield of Kordshikh river, located in 20 Km west of Qir in Fars province, was studied using experimental models of MPSIAC, EPM and Fournier. In MPSIAC model the effect of nine important factors on soil erosion and sediment yield (surface geology, soil, climate, run off, topography, land cover, land use, present erosion condition and channel erosion) was evaluated and numerical values were assigned to them in terms of intensity and weakness of each factor. Using the sum of those values through equation Qs=38.77e0.0353R, where Qs is specific sediment (m3/ km2. yr) and R is sediment yield score, the rate of sediment yield of the basin was measured. The measured Qs for Kordshikh river was Qs= 533.67. In EPM method four coefficients (basin erosion, land use, soil sensitivity to erosion and basin mean dip) were investigated in constructed network in the map. Specific sediment rate in the basin using this method was Gsp=248.94 (m3/km2.yr). In Fournier model, Qs, the rate of specific sediment, was obtained using his first method (log Qs=2.65 log pw2/pa 0.46 log H (tan S) - 1.56) was Qs=207.91 (m3/km2.yr).
- انتشار مقاله: 01-07-1399
- نویسندگان: Mohammad Bahrami,Ali Rahimi
- مشاهده
- جایگاه : پژوهشی
- مجله: Mechanics of Advanced Composite Structures
- نوع مقاله: Journal Article
- کلمات کلیدی: Delamination,strain energy release rate,Micromechanics,Unit cell,Matrix cracking
- چکیده:
- چکیده انگلیسی: Due to the mismatch of mechanical properties in composite laminates, propagation of delami-nation is considered as a severe damage mechanism in beams with various lay-up configurations. Delamination can be generated due to matrix cracking propagation or it can also be initiated due to the manufacturing process before using composite beams. Using a micromechanics model, this study is aimed to investigate the bending moment required for matrix cracking and induced delamination in cross-ply composite beams. To that end, a unit cell is selected from the lamina surface in a composite beam containing matrix cracking and delamination. Later, the governing equation of stress and displacement fields are extracted in the unit cell to calculate the strain energy release rate due to the propagation of matrix cracking and induced delamination. In order to validate this method, the stiffness variations in Carbon-Epoxy cross-ply laminate [90/02]s is examined and the obtained results are compared with the numerical results. It concluded that there is a favorable agreement between the results of the proposed micromechanics model and available numerical results.
- انتشار مقاله: 18-09-1397
- نویسندگان: Mohammad Bahrami,Amin Farrokhabadi
- مشاهده
- جایگاه : پژوهشی
- مجله: Journal of Water Sciences Research
- نوع مقاله: Journal Article
- کلمات کلیدی: scour,Spur dike,Triangular vanes,River banks
- چکیده:
- چکیده انگلیسی: The main purpose of this paper was to evaluate the performance of the triangular vanes located on the bed and their effect on the bed topography considering different flow conditions. For this purpose, tests were carried out on a straight flume for different flow conditions (five Froude numbers of 0.18, 0.20, 0.22, 0.24 and 0.26) by installing a series of triangular vanes at a space of 4Le (Le is the effective length of the structure) and considering a 30 degrees angleto the upstream bank. At the end of each test, the bed topography was measured by the laser distance measurer. The results showed that the geometric dimension of the scour hole for the rectangular spur dikes was larger than the triangular vanes. On average, the length and depth of the scour hole for the rectangular spur dikes were 1.3 and 1.5 timesin comparison to the triangular vanes, respectively. In addition, the maximum scour depth considering the triangular vanes was about 40% farther from the bank in comparison to the case with the rectangular spur dikes, that was an advantage for the triangular vanes.
- انتشار مقاله: 02-04-1394
- نویسندگان: Nushin Najafi Birgani,Mahmood Shafai Bejestan,Mohammad Bahrami Yarahmadi
- مشاهده
- جایگاه : پژوهشی
- مجله: Journal of Statistical Modelling: Theory and Applications
- نوع مقاله: Journal Article
- کلمات کلیدی: Maximum Likelihood Estimator,Bias-corrected estimators,Bias prevention,Two-parameter Maxwell distribution
- چکیده:
- چکیده انگلیسی: Maximum likelihood estimators are usually biased. The first order bias term of the maximum likelihood estimators can be large for a small or medium sample size, and this bias may have a significant effect on distribution performance. Different methods may be used to reduce this bias. These methods have inspired many scholars to study this field over the past years, but the use of Bartlett’s method requires the expected value of third power derivatives of the likelihood function. Consequently, because this quantity (the expected value of third power derivatives of the likelihood function) is not necessarily calculable in some distributions, in this paper we propose a new method based on algebraic approximation of the maximum likelihood estimator bias which needless the expected value of third power derivatives of the likelihood function. In addition, as an application of this method, we will consider a bias correction for estimating parameters of Maxwell distribution.
- انتشار مقاله: 04-08-1398
- نویسندگان: Mohammad Mahdi Maghami,Mohammad Bahrami
- مشاهده
- جایگاه : پژوهشی
- مجله: Journal of Kerman University of Medical Sciences
- نوع مقاله: Journal Article
- کلمات کلیدی: Electromyography,Knee joint,Weight lifting
- چکیده:
- چکیده انگلیسی: Background: The determinant role of different movements to strengthen the quadriceps on rate of knee joint co-contraction, hamstring to quadriceps muscle activity ratio and vastus medialis to vastus lateralis muscle activity ratio provides useful information for therapists, coaches and athletes about the role of each movement in the rehabilitation of patients with anterior cruciate ligament injury, osteoarthritis and patellofemoral pain syndrome. The aim of this study was to compare the rate of the generalised and directed co-contraction of knee joint muscles during free weights squat, smith machine squat, smith machine squat with one leg and the dead lift movements.
Methods: 14 healthy power lifters (age: 26±7 years) were participated in this study.A portable EMG system with six pairs of bipolar surface electrodes was used to record the activity of the gastrocnemious medialis, long head of biceps femoris, semitendinosus, vastus lateralis, rectus femoris, and vastus medialis muscles at a sampling frequency of 1200 HZ. Participants had enough experience to perform free weights squat, smith machine squat, smith machine squat with one leg and the dead lift movements. Participants carried out each movement 5 times at an intensity equal to 50% of one-repetition-maximum level. Repeated-measure ANOVA test was used for statistical analysis.
Results: Rate of medial co-contraction in dead lift movement was higher than that in smith machine squat with one leg (P= 0.042), and free weights squat (P= 0.044), respectively. Ratio of hamstring muscles activity to quadriceps during the implementation of dead lift was higher than that in free weights squat (P=0.022). The generalised co-contraction value at the knee joint was the lowest in dead lift movement and highest in smith machine squat with one leg.
Conclusion: In order to strengthen quadriceps muscles in people suffering from anterior cruciate injury, dead lift movement is more effective than free weights squat. For athletes exercising to strengthen muscular groups, smith machine squat with one leg is more effective compared with the other three movements.
- انتشار مقاله: 15-03-1396
- نویسندگان: Amir Ali Jafarnezhadgero,Mohammad Mahdi Bahramisharif,Mahdi Majlesi
- مشاهده
- جایگاه : پژوهشی
- مجله: Journal of Health Management and Informatics
- نوع مقاله: Journal Article
- کلمات کلیدی: Nurses,COVID-19,Spirituality,Health economics
- چکیده:
- چکیده انگلیسی: Objectives: This study aimed to assess the role of nurses in the Covid-19 pandemic and the way a nurse can help the health system in this regard. Method: This is a qualitative research using content analysis in 2020. The aim of this study was to elucidate the key role of nurses in the COVID-19 epidemic and the determinants of a professional nurse during an epidemic/pandemic crisis using virtual expert panels consisting of experts in the field of nursing, health care management, and psychology. Data were analyzed using the thematic analysis approach. Results: The findings show that nurses in the coronavirus pandemic can have 4 main duties such as professional, spiritual and mental, health economics, and social roles. According to the present framework, the health economics, social and mental and spiritual roles together can determine and affect the nurses’ professional role. These professional nurses can be able to provide necessary cares during COVID-19 pandemic. Conclusion: In the crises like COVID-19 pandemic in which medical sciences alone cannot treat or alleviate the condition, as seen worldwide, among professional, spiritual and mental, health economics, and social roles, the spiritual and mental role may be the most important part a nurse can play.
- انتشار مقاله: 15-07-1399
- نویسندگان: Peivand Bastani,Seyyed Mostafa Hakimzadeh,Mohammad Amin Bahrami,Sirus Panahi
- مشاهده
- جایگاه : پژوهشی
- مجله: Journal of Advanced Sport Technology
- نوع مقاله: Journal Article
- کلمات کلیدی: Keywords: Frequency spectrum,Lower limb,Squat,Smith machine,Dead lift
- چکیده:
- چکیده انگلیسی: Many practitioners and trainers advise designing and executing resistance training programs that include free weights and machines for strength training. The aim of the present study was to compare the frequency spectrum of lower limb muscles during weight training with traditional and novel equipment. Fourteen healthy power lifters (age: 26±7 years) were participated in this study. A portable EMG system with six pairs of bipolar surface electrodes was used to record the electrical activity of the selected lower limb muscles at a sampling frequency of 1200 Hz. Participants had enough experience to perform Free Weights Squat, Smith Machine Squat, Smith Machine Squat with one leg and the Dead lift movements. Participants carried out each movement, 5 times at an intensity equal to 50% of one-repetition-maximum level. The results showed higher median frequency of the vastus lateralis muscle during free weight single-leg squat than those that in the free weight squat (p=0.001) and dead lift (p=0.000) movements in lifting phase. Also, the median frequency of vastus lateralis muscle in single-limb squat with smith machine was significantly higher than that in the dead lift movement (p=0.021). The median frequency spectrum of the gastrocnemius muscle in the free weight squat movement showed a significant increase during the downward phase relative to the free weight single-leg squat movement (p=0.039). In order to strengthen vastus lateralis muscle in athletes or individuals with weak vastus lateralis muscle, free weight single-leg squat movement is more effective than those that in the other movements.
- انتشار مقاله: 25-11-1397
- نویسندگان: AmirAli Jafarnezhadgero,Amirhosein Sadri,Mohammad Mahdi Bahrami Sharif,Milad Alipour Sarinasirloo
- مشاهده