• فهرست مقالات Boundary Condition

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        1 - یک ایده جدید برای اعمال شرایط مرزی اساسی در روش بدون المان گالرکین برای حل معادلات با مشتقات جزئی بیضوی
        علی مس فروش کمیل ایزدپناه
        روش بدون المان گالرکین یک روش شناخته شده برای حل معادلات با مشتقات جزئی است. اعمال شرایط مرزی اساسی در این روش که بر اساس تقریب کمترین مربعات متحرک انجام می شود، با پیچیدگی هایی همراه است. از آنجا که توابع شکل تقریب کمترین مربعات متحرک در خاصیت دلتای کرونیکر صدق نمی کنن چکیده کامل
        روش بدون المان گالرکین یک روش شناخته شده برای حل معادلات با مشتقات جزئی است. اعمال شرایط مرزی اساسی در این روش که بر اساس تقریب کمترین مربعات متحرک انجام می شود، با پیچیدگی هایی همراه است. از آنجا که توابع شکل تقریب کمترین مربعات متحرک در خاصیت دلتای کرونیکر صدق نمی کنند، نمی توان همانند روش عناصر متناهی، شرایط مرزی اساسی را به صورت مستقیم در فرم ضعیف گالرکین معادله اعمال کرد و نیاز به روش های اصلاحی برای فرم ضعیف معادله داریم. در این مقاله یک ایده جدید برای اعمال شرایط مرزی اساسی در روش بدون المان گالرکین برای حل معادلات با مشتقات جزئی بیضوی معرفی می شود. این ایده بر اساس روش کمترین مربعات متحرک درونیاب است. در این روش ابتدا شرایط مرزی را در تقریب کمترین مربعات متحرک تابع اعمال می کنیم سپس تقریب حاصل را در روش بدون المان گالرکین به کار می بریم. بنابراین شرایط مرزی به صورت مستقیم اعمال می شود. در این مقاله ابتدا تقریب کمترین مربعات متحرک درونیاب معرفی می شود و سپس نحوه اعمال شرایط مرزی بیان خواهد شد. در انتها با ارائه چند مثال مختلف کارایی روش را نشان می دهیم. پرونده مقاله
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        2 - بررسی وجود جواب‌های ضعیف مثبت دستگاه‌های جدیدی از نوع کیرشهف با شرط مرزی دیریکله
        محمد باقر قائمی مهدی چوبین
        معادله کیرشهف (*) [rho frac{{{partial ^2}u}}{{partial {t^2}}} - left( {frac{{{P_0}}}{h} + frac{E}{{2L}}int_0^L {left| {frac{{partial u}}{{partial x}}} right|} dx} right)frac{{{partial ^2}u}}{{partial {x^2}}} = 0] تعمیم معادله موج کلاسیک دالامبر با در نظر گرفتن اثرات تغی چکیده کامل
        معادله کیرشهف (*) [rho frac{{{partial ^2}u}}{{partial {t^2}}} - left( {frac{{{P_0}}}{h} + frac{E}{{2L}}int_0^L {left| {frac{{partial u}}{{partial x}}} right|} dx} right)frac{{{partial ^2}u}}{{partial {x^2}}} = 0] تعمیم معادله موج کلاسیک دالامبر با در نظر گرفتن اثرات تغییر طول رشته در طی ارتعاشات است. در (*)، L پارامتر طول رشته، h مساحت سطح مقطع، E ضریب یانگ مواد، rho چگالی جرم و P_0 کشش اولیه است. در سال های اخیر، برخی تعمیم های کاربردی معادله کیرشهف در بسیاری از مقالات ارایه شده و مورد مطالعه قرار گرفته است. در این مقاله، به بررسی وجود جوابهای ضعیف دسته ای از دستگاههای از نوع کیرشهف با پارامترهای چندگانه می پردازیم. نشان خواهیم داد که تحت چه شرایطی این دستگاه ها به ازای همه پارامترهای مثبت دلخواه دارای جواب مثبت هستند. رویکرد ما در این مقاله براساس روش جواب های پایینی-بالایی است. پرونده مقاله
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        3 - A New Method for Solving Multi-Dimensional Fredholm Integral Equations and Its Convergence ‎Analysis
        N. Mahmoodi ‎Darani‎
        10.30495/ijim.2022.58704.1487
        In this paper, we focus on obtaining an approximate solution for multi-dimensional Fredholm integral equations of second kind. An expansion method is used for treatment multi-dimensional Fredholm integral equation of second kind. This method reduces multi-dimensional in چکیده کامل
        In this paper, we focus on obtaining an approximate solution for multi-dimensional Fredholm integral equations of second kind. An expansion method is used for treatment multi-dimensional Fredholm integral equation of second kind. This method reduces multi-dimensional integral equation to a partial differential equation. After constructing boundary conditions, this partial differential equation reduces to algebraic equation that can be solved easily with any of the usual methods. Furthermore some theorems are proved for convergence analysis. Finally, for showing the efficiency of the method we use some numerical examples پرونده مقاله
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        4 - Implementation of Sinc-Galerkin on Parabolic Inverse problem with unknown boundary ‎condition‎
        J. Biazar T. Houlari
        The determination of an unknown boundary condition, in a nonlinaer inverse diffusion problem is considered. For solving these ill-posed inverse problems, Galerkin method based on Sinc basis functions for space and time will be used. To solve the system of linear equatio چکیده کامل
        The determination of an unknown boundary condition, in a nonlinaer inverse diffusion problem is considered. For solving these ill-posed inverse problems, Galerkin method based on Sinc basis functions for space and time will be used. To solve the system of linear equation, a noise is imposed and Tikhonove regularization is applied. By using a sensor located at a point in the domain of $x$, say $x=a'$, and determining $u(a',t)$ a stable solution will be achived. An illustrative example is provided to show the ability and the efficiency of this numerical ‎approach.‎ پرونده مقاله
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        5 - Detecting the location of the boundary layers in singular perturbation problems with general linear non-local boundary ‎conditions‎
        N. ‎Aliev S. Ashrafi A. R. Sarakhsi‎
        Singular perturbation problems have been studied by many mathematicians. Since the approximate solutions of these problems are as the sum of internal solution (boundary layer area) and external ones, the formation or non-formation of boundary layers should be specified. چکیده کامل
        Singular perturbation problems have been studied by many mathematicians. Since the approximate solutions of these problems are as the sum of internal solution (boundary layer area) and external ones, the formation or non-formation of boundary layers should be specified. This paper, investigates this issue for a singular perturbation problem including a first order differential equation with general non-local boundary condition. It needs to say that it is simple for local boundary conditions and there is no difficulty. However, the formation of boundary layers for non-local case is not as stright forward as local case. To tackle this problem generalized solution of differential equation and some necessary conditions are ‎used.‎ پرونده مقاله
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        6 - Numerical Study on Forced Convection of Slip Flow in A Microchannel with Smooth and Sinusoidal Walls
        Afshin Ahmadi Nadooshan DAriush Bahrami Akram Jahanbakhshi
        10.30495/admt.2021.1926613.1265
        The micro-scale equipment has many advantages, including high thermal performance, high surface-to-volume ratio in heat transfer, small size, low weight, low required fluid and high design flexibility. In this study, fluid flow inside a microchannel is modeled under the چکیده کامل
        The micro-scale equipment has many advantages, including high thermal performance, high surface-to-volume ratio in heat transfer, small size, low weight, low required fluid and high design flexibility. In this study, fluid flow inside a microchannel is modeled under the assumption of laminar, incompressible, and two-dimensional flow under symmetric boundary conditions. The slip boundary condition is applied to the walls and the flow in the channel output is assumed to be fully developed. The effect of sinusoidal wall with the domain of 0.1 on the hydrodynamic and thermal behavior of the fluid is investigated and the results are compared with the results of smooth wall. The results show that for a constant Reynolds number, the maximum velocity decreases in the microchannel center by increasing the slip coefficient. Also, the comparison between the results of the wavy-wall microchannel and the microchannel with a smooth wall indicates that the heat transfer in the smooth microchannel is less than that in wavy-wall one. Considering the boundary conditions, the thermal behavior of the fluid is approximately the same for two cases in which both walls are sinusoidal and the only upper wall is sinusoidal. پرونده مقاله
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        7 - Frequency Analysis of Ring-Stiffened Composite Cylindrical Shell using Experimental, Analytical and Finite Element Methods
        Hadi Salimi Ali Davar Mohsen Heydari Beni Jafar Eskandari Jam Majid Eskandari Shahraki
        10.30486/admt.2021.1908459.1215
        In this paper, free vibration of laminated composite cylindrical shells reinforced with circumferential rings, are investigated with experimental, analytical and finite element methods and natural frequencies are obtained. The analysis is carried out for clamp-free and چکیده کامل
        In this paper, free vibration of laminated composite cylindrical shells reinforced with circumferential rings, are investigated with experimental, analytical and finite element methods and natural frequencies are obtained. The analysis is carried out for clamp-free and clamp-clamp boundary conditions and the results are compared with each other. To solve the problem, the equilibrium Equations of motions are written according to the classical shells theory and after simplification, the structural stiffness and mass matrices and the frequency Equation are derived using Galerkin method. The results obtained in this paper, are compared with the results available in the literatures, and the results of experimental and finite element methods and good agreement is observed. پرونده مقاله
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        8 - A Comprehensive Study on the Effects of the Boundary Conditions on the Elastic Buckling Capacity of a Perforated Plate
        Sadegh Ghorbanhosseini Saeed Yaghoubi Mohammad Reza Bahrambeigi
        10.30495/admt.2021.1914605.1227
        Nowadays, different industries are using sheets, plates, and shells as important parts of their components. Because of their small thickness compare to other dimensions, their structural safety requires more attention. Therefore, increasing their strength and intensifyi چکیده کامل
        Nowadays, different industries are using sheets, plates, and shells as important parts of their components. Because of their small thickness compare to other dimensions, their structural safety requires more attention. Therefore, increasing their strength and intensifying their resistance against any kind of failure type could be introduced as an important problem for enhancing the structural safety. Buckling is one of the most significant failure type that should be considered in the stability of any parts such as sheet metals. Thus, investigation of the buckling capacity of the sheet metals is remarkable. On the other hand, the existence of discontinuity like holes and notches in sheet metals can decrease their buckling capacity, significantly. In current study, based on Finite Element Method (FEM), ABAQUS/Explicit has been employed to determine the elastic buckling capacity in a perforated rectangular sheet metal with different boundary conditions on its edges. Afterward, the effect of the hole position and the plate aspect ratios (plate length/plate width) on the buckling capacity of sheet metal was studied. Finally, in order to enhance the sheet metal buckling capacity, two different types of stiffeners were used. The outcomes showed that the maximum buckling coefficient is related to the sheet metal which have four clamped edges. Moreover, For all boundary conditions, the buckling coefficient does not change significantly for the sheet metals with aspect ratio of more than 4. Also, stiffener type 2 increased the buckling capacity of sheet metal up to 83%. پرونده مقاله
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        9 - حل عددی معادلات دیفرانسیل پانتوگراف کسری غیرخطی با شرایط مرزی با استفاده از چندجمله‌ای‌های ژاکوبی
        سمیه نعمتی فائزه باکوئی
        در این پژوهش، یک روش عددی بر پایه‌ی چندجمله‌ای‌های ژاکوبی برای حل معادلات دیفرانسیل پانتوگراف کسری غیر‌خطی با شرایط مرزی معرفی می‌شود. ابتدا، معادله‌ دیفرانسیل به‌صورت یک معادله‌ انتگرال ولترا-فردهلم معادل بیان می‌شود. سپس، چندجمله‌ای‌های ژاکوبی و فرمول انتگرال‌گیری گاو چکیده کامل
        در این پژوهش، یک روش عددی بر پایه‌ی چندجمله‌ای‌های ژاکوبی برای حل معادلات دیفرانسیل پانتوگراف کسری غیر‌خطی با شرایط مرزی معرفی می‌شود. ابتدا، معادله‌ دیفرانسیل به‌صورت یک معادله‌ انتگرال ولترا-فردهلم معادل بیان می‌شود. سپس، چندجمله‌ای‌های ژاکوبی و فرمول انتگرال‌گیری گاوس-ژاکوبی به‌همراه نقاط هم‌محلی نیوتن-کاتس برای تبدیل معادله‌ انتگرال حاصل به دستگاهی از معادلات جبری غیر‌خطی استفاده می‌شود. در آخر، با در نظر گرفتن چند مثال و محاسبه خطاهای L^"2" و L^∞، کارایی و دقت روش پیشنهادی نشان داده می‌شود.- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - پرونده مقاله
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        10 - Buckling and Thermomechanical Vibration Analysis of a Cylindrical Sandwich Panel with an Elastic Core Using Generalized Differential Quadrature Method
        A.R Pourmoayed K Malekzadeh M Shahravi H Safarpour
        10.22034/jsm.2019.665367
        In this paper, the vibrational and buckling analysis of a cylindrical sandwich panel with an elastic core under thermo-mechanical loadings is investigated. The modeled cylindrical sandwich panel as well as its equations of motions and boundary conditions is derived by H چکیده کامل
        In this paper, the vibrational and buckling analysis of a cylindrical sandwich panel with an elastic core under thermo-mechanical loadings is investigated. The modeled cylindrical sandwich panel as well as its equations of motions and boundary conditions is derived by Hamilton’s principle and the first-order shear deformation theory (FSDT). For the first time in the present study, various boundary conditions is considered in the cylindrical sandwich panel with an elastic core. In order to obtain the temperature distribution in the cylindrical sandwich panel in the absence of a heat-generation source, temperature distribution is obtained by solving the steady-state heat-transfer equation. The accuracy of the presented model is verified using previous studies and the results obtained by the Navier analytical method. The novelty of the present study is considering thermo-mechanical loadings as well as satisfying various boundary conditions. The generalized differential quadrature method (GDQM) is applied to discretize the equations of motion. Then, some factors such as the influence of length-to-radius ratio, circumferential wave numbers, thermal loadings, and boundary conditions are examined on the dynamic and static behavior of the cylindrical sandwich panel. پرونده مقاله
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        11 - Vibration of Timoshenko Beam-Soil Foundation Interaction by Using the Spectral Element Method
        S Hamioud S Khalfallah S Boudaa
        10.22034/jsm.2020.1879476.1503
        This article presents an analysis of free vibration of elastically supported Timoshenko beams by using the spectral element method. The governing partial differential equation is elaborated to formulate the spectral stiffness matrix. Effectively, the non classical end b چکیده کامل
        This article presents an analysis of free vibration of elastically supported Timoshenko beams by using the spectral element method. The governing partial differential equation is elaborated to formulate the spectral stiffness matrix. Effectively, the non classical end boundary conditions of the beam are the primordial task to calibrate the phenomenon of the Timoshenko beam-soil foundation interaction. Non-dimensional natural frequencies and shape modes are obtained by solving the partial differential equations, numerically. Upon solving the eigenvalue problem, non-dimensional frequencies are computed for the first three modes of vibration. Obtained results of this study are intended to describe multiple objects, such as: (1) the establishment of the modal analysis with and without elastic springs, (2) the quantification of the influence of the beam soil foundation interaction, (3) the influence of soil foundation stiffness’ on free vibration characteristics of Timoshenko beam. For this propose, the first three eigenvalues of Timoshenko beam are calculated and plotted for various stiffness of translational and rotational springs. پرونده مقاله
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        12 - Bending Analysis of Laminated Composite Plates with Arbitrary Boundary Conditions
        A.M Naserian Nik M Tahani
        It is well known that for laminated composite plates a Levy-type solution exists only for cross-ply and antisymmetric angle-ply laminates. Numerous investigators have used the Levy method to solve the governing equations of various equivalent single-layer plate theories چکیده کامل
        It is well known that for laminated composite plates a Levy-type solution exists only for cross-ply and antisymmetric angle-ply laminates. Numerous investigators have used the Levy method to solve the governing equations of various equivalent single-layer plate theories. It is the intension of the present study to introduce a method for analytical solutions of laminated composite plates with arbitrary lamination and boundary conditions subjected to transverse loads. The method is based on separation of spatial variables of displacement field components. Within the displacement field of a first-order shear deformation theory (FSDT), a laminated plate theory is developed. Two systems of coupled ordinary differential equations with constant coefficients are obtained by using the principle of minimum total potential energy. Since the procedure used is simple and straightforward it can, therefore, be adopted in developing higher-order shear deformation and layerwise laminated plate theories. The obtained equations are solved analytically using the state-space approach. The results obtained from the present method are compared with the Levy-type solutions of cross-ply and antisymmetric angle-ply laminates with various admissible boundary conditions to verify the validity and accuracy of the present theory. Also for other laminations and boundary conditions that there exist no Levy-type solutions the present results may be compared with those obtained from finite element method. It is seen that the present results have excellent agreements with those obtained by Levy-type method. پرونده مقاله
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        13 - Effect of Non-ideal Boundary Conditions on Buckling of Rectangular Functionally Graded Plates
        J Mohammadi M Gheisary
        We have solved the governing equations for the buckling of rectangular functionally graded plates which one of its edges has small non-zero deflection and moment. For the case that the material properties obey a power law in the thickness direction, an analytical soluti چکیده کامل
        We have solved the governing equations for the buckling of rectangular functionally graded plates which one of its edges has small non-zero deflection and moment. For the case that the material properties obey a power law in the thickness direction, an analytical solution is obtained using the perturbation series. The applied in-plane load is assumed to be perpendicular to the edge which has non-ideal boundary conditions. Making use of the Linshtead-Poincare perturbation technique, the critical buckling loads are obtained. The results were then verified with the known data in the literature. پرونده مقاله
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        14 - A Simple and Systematic Approach for Implementing Boundary Conditions in the Differential Quadrature Free and Forced Vibration Analysis of Beams and Rectangular Plates
        S.A Eftekhari
        This paper presents a simple and systematic way for imposing boundary conditions in the differential quadrature free and forced vibration analysis of beams and rectangular plates. First, the Dirichlet- and Neumann-type boundary conditions of the beam (or plate) are expr چکیده کامل
        This paper presents a simple and systematic way for imposing boundary conditions in the differential quadrature free and forced vibration analysis of beams and rectangular plates. First, the Dirichlet- and Neumann-type boundary conditions of the beam (or plate) are expressed as differential quadrature analog equations at the grid points on or near the boundaries. Then, similar to CBCGE (direct Coupling the Boundary Conditions with the discrete Governing Equations) approach, the resulting analog equations are used to replace the differential quadrature analog equations of the governing differential equations at these points in order to solve the problem. But, unlike the CBCGE approach, the grid points near the boundaries are not treated as boundary points in the proposed approach. In other words, the degrees of freedom related to Dirichlet-type boundary conditions are only eliminated from the original discrete equations. This simplifies significantly the solution procedure and its programming. A comparison of the proposed approach with other existing methodologies such as the CBCGE approach and MWCM (modifying weighting coefficient matrices) method is presented by their application to the vibration analysis of beams and rectangular plates with general boundary conditions to highlight the advantages of the new approach. پرونده مقاله
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        15 - Evaluation of Error Due to Applying Average Rating Curve as downstream Boundary Condition in Unsteady Flow Modeling
        مهدی حبیب زاده حسین محمد ولی سامانی حیدرعلی کشکولی
        The rating curve is the relationship between the water stage and the associated discharge in a givensection of a channel. In steady flow, this relationship usually has exponential type, whereas inunsteady it flow has a looped shape. Since direct developing of actual loo چکیده کامل
        The rating curve is the relationship between the water stage and the associated discharge in a givensection of a channel. In steady flow, this relationship usually has exponential type, whereas inunsteady it flow has a looped shape. Since direct developing of actual looped rating curve by usinghydrometric methods is merely possible, steady-state rating curve is commonly used as a downstreamboundary condition in mathematical modeling of unsteady flow which leads to relevant error in modelresults. In this study, in order to evaluate this error, a method is presented by using the HEC-RASmodel of unsteady flow in a prismatic channel with different bed slopes, roughness coefficients andchannel lengths as effective parameters. In various channel geometries , the rating curves of both theapproximate and the reference states are obtained. Then statistical comparison between the results wasdone. Accordingly, 120 R-squared (R2) values refer to 240 different channel conditions, wereconsidered and the errors were analyzed which indicate that the error is declined by increasing bedslope and channel length, in addition by roughness reduction. The maximum rate of the error occurredby any of effective parameters including bed slope, roughness coefficient and channel length wasevaluated in order of appearance; 0.2617, 0.1507 and 0.1673. In addition, the sensitivity of all theparameters in different modeling conditions may be distinguished by using the obtained graphs. پرونده مقاله
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        16 - بررسی تغییر مکان استاتیکی وابسته به اندازه نانولوله تحت نیروی الکترواستاتیک با شرایط مرزی مختلف
        عباس زندی باغچه مریم سید علی موسوی
        در مطالعه حاضر، تحلیل تغییر مکان استاتیکی وابسته به اندازه نانولوله تحت نیروی الکترواستاتیک با در نظر گرفتن اثرات لایه سطحی و شرایط مرزی مختلف بررسی شده است. نتایج این بررسی برای چهار شرایط مرزی مختلف، دوسرمفصل، دوسرگیردار، گیردار-مفصل و گیردار- آزاد به‌دست آمده است. هم چکیده کامل
        در مطالعه حاضر، تحلیل تغییر مکان استاتیکی وابسته به اندازه نانولوله تحت نیروی الکترواستاتیک با در نظر گرفتن اثرات لایه سطحی و شرایط مرزی مختلف بررسی شده است. نتایج این بررسی برای چهار شرایط مرزی مختلف، دوسرمفصل، دوسرگیردار، گیردار-مفصل و گیردار- آزاد به‌دست آمده است. همچنین نانولوله تحت میدان مغناطیس، تحریک الکترواستاتیک نیروی مکانیکی و حرارتی است. در این بررسی معادلات حاکم بر حرکت با استفاده از تئوری ارینگن حاصل شده و این معادله با استفاده از روش عددی مانده وزن‌دار محاسبه می‌شود. همچنین سرعت سیال، پارامتر مقیاس طول، میدان مغناطیس، ولتاژ الکترواستاتیک، اثرات لایه سطحی و شرایط مرزی مختلف بر تغییر مکان استاتیکی در این پژوهش بررسی می‌شود. نهایتا صحت نتایج حاصله با مقایسه آن‌ها با نتایج حاصل از روش‌های عددی در پژوهش‌های قبلی مورد بررسی قرار گرفته و مطابقت خوبی بین کار حاضر و مطالعات پیشین دیده شده است. با توجه به نتایج مشخص شد که افزایش مقادیر مختلف اثرات لایه سطحی موجب افزایش سفتی سیستم می‌گردد و با افزایش سرعت سیال تغییر مکان استاتیکی افزایش می‌یابد. از سویی دیگر مشاهده گردید که افزایش پارامتر مقیاس طول موجب افزایش تغییر مکان استاتیکی و کاهش سفتی سیستم می‌شود. پرونده مقاله
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        17 - بررسی تأثیر میدان مغناطیسی، تغییرات شیب و شرط مرزی دمایی دیواره بر انتقال حرارت جابجایی طبیعی آب درون محفظه‌ی مانع دار
        محمد نعمتی محمد سفید احمدرضا رحمتی
        در کار حاضر، اثر میدان مغناطیسی بر انتقال حرارت جابجایی طبیعی با استفاده از روش شبکه بولتزمن شبیه‌سازی شده است. دیواره‌ عمودی سمت چپ محفظه در دمای ثابت گرم و دیواره عمودی سمت راست محفظه دارای سه شرط مرزی دمایی مختلف (۱- دمای ثابت سرد، ۲- دمای خطی و ۳-دمای ثابت گرم) است. چکیده کامل
        در کار حاضر، اثر میدان مغناطیسی بر انتقال حرارت جابجایی طبیعی با استفاده از روش شبکه بولتزمن شبیه‌سازی شده است. دیواره‌ عمودی سمت چپ محفظه در دمای ثابت گرم و دیواره عمودی سمت راست محفظه دارای سه شرط مرزی دمایی مختلف (۱- دمای ثابت سرد، ۲- دمای خطی و ۳-دمای ثابت گرم) است. دو دیواره دیگر محفظه در دمای ثابت سرد قرار دارند. مانعی لوزی شکل که در مرکز محفظه قرار دارد در چهار حالت مختلف (۱- سرد، ۲- رسانا، ۳- آدیاباتیک و ۴- گرم) بررسی می‌شود. همچنین دیواره پایینی محفظه در سه شیب متفاوت مورد ارزیابی قرار می‌گیرد. تأثیر پارامترهای عدد رایلی، عدد هارتمن، شیب دیواره، شرط مرزی دمایی مختلف دیواره و مانع لوزی شکل، بر روی انتقال حرارت جابجایی طبیعی بررسی شده است. نتایج نشان می‌دهد با ثابت ماندن تمامی پارامترها، افزایش شیب دیواره و عدد رایلی منجر به افزایش انتقال حرارت می‌شود. با تغییر شرایط مرزی دمایی دیواره‌ها و مانع می‌توان بر روی میزان انتقال حرارت تأثیرگذار بود. بعلاوه افزایش قدرت میدان مغناطیسی سبب کاهش عدد ناسلت متوسط می‌شود که این تأثیر در شرایط مختلف، متفاوت است. پرونده مقاله
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        18 - تحلیل سرعت بحرانی لوله حاوی سیال با شرایط مرزی غیرکلاسیک
        شاهرخ شمس سجاد جنگروی
        محاسبه سرعت بحرانی لوله حاوی سیال از مسائل مهم در مهندسی است. بدین منظور، سرعت بحرانی لوله حاوی سیال با شرایط مرزی غیرکلاسیک در مقاله حاضر محاسبه گردیده است. معادلات حرکت سازه بر اساس مدل تیر اویلر- برنولی پایه گذاری شده است. شرایط مرزی غیرکلاسیک شامل فنرخطی ، فنرپیچشی چکیده کامل
        محاسبه سرعت بحرانی لوله حاوی سیال از مسائل مهم در مهندسی است. بدین منظور، سرعت بحرانی لوله حاوی سیال با شرایط مرزی غیرکلاسیک در مقاله حاضر محاسبه گردیده است. معادلات حرکت سازه بر اساس مدل تیر اویلر- برنولی پایه گذاری شده است. شرایط مرزی غیرکلاسیک شامل فنرخطی ، فنرپیچشی ، جرم متمرکز و میراکننده ها هستند. برای محاسبه سرعت بحرانی، معادله فرکانسی با توجه به شرایط مرزی با روش عددی حل میگردد. زمانی که قسمت حقیقی معادله فرکانسی به صفر برسد، سرعت بحرانی در لوله ظاهر و سیستم ناپایدار می شود. تاثیر پارامترهای مختلف شامل سختی فنر و جرم متمرکز بر سرعت بحرانی بررسی و نمودار های مقایسه ای از سختی های متفاوت فنر و جرم متمرکز ترسیم شده است. نتایج نشان میدهد که سرعت بحرانی در حالت دو سر فنر خطی بیشتر از شرط مرزی فنرپیچشی- فنرخطی و جرم متمرکز-فنرپیچشی است و همچنین کاهش قابل توجه فرکانس در حالت غیرکلاسیک نسبت به کلاسیک هستند. پرونده مقاله
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        19 - Numerical Simulation of Fluid Flow over a Ceramic Nanoparticle in Drug Delivery System
        Mina Alafzadeh Shahram Talebi Mojdeh Azizi
        In this work, for better understanding of drug delivery systems, blood flow over a ceramic nanoparticle is investigated through microvessels. Drug is considered as a nanoparticle coated with the rigid ceramic. Due to the low characteristic size in the microvessel, the f چکیده کامل
        In this work, for better understanding of drug delivery systems, blood flow over a ceramic nanoparticle is investigated through microvessels. Drug is considered as a nanoparticle coated with the rigid ceramic. Due to the low characteristic size in the microvessel, the fluid flow is not continuum and the no-slip boundary condition cannot be applied. To solve this problem lattice Boltzmann method is used with the slip boundary condition on the particle surface. Furthermore, the effects of Reynolds number, Knudsen number and stiffness (which depends on the kind of material) on drag coefficient are investigated in this paper. The present results show that lattice Boltzmann method can be used accurately to simulate the effect of different parameters on drug delivery. Moreover, the results show that the accuracy of lattice Boltzmann method is the same as second slip boundary condition. Also, the effect of nanoparticle stiffness as the important parameter on the period of time to deliver drugs in system is demonstrated. پرونده مقاله
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        20 - Nonlinear Buckling Analysis of Different Types of Porous FG Sandwich Beams with Temperature-Dependent
        Mohsen Rahmani Younes Mohammadi Mahdi Abtahi
        In this paper, the nonlinear buckling behavior of two types of functionally graded sandwich beams was studied using a high-order sandwich beam theory. Type I consists of functionally graded layers coating a homogeneous core, while type II features an FG core covered by چکیده کامل
        In this paper, the nonlinear buckling behavior of two types of functionally graded sandwich beams was studied using a high-order sandwich beam theory. Type I consists of functionally graded layers coating a homogeneous core, while type II features an FG core covered by homogeneous face sheets. All materials are considered temperature dependent, with FGM properties modified through even and uneven porosity distributions modeled by a power law rule. The sandwich beam theory was adjusted to account for nonlinear Lagrange strains, thermal stresses of the face sheets, in-plane strain, and the transverse flexibility of the core. The governing equations were derived from the minimum potential energy principle, and a Galerkin method was employed to solve them for simply supported and clamped boundary conditions. Comparisons with existing literature demonstrate good agreement. The resultes showed that critical load parameter decreases with increasing temperature, power law index, length-to-thickness ratio, thickness, and porosity volume fraction in both distributions, but increases with the wave number. Additionally, the stability of type II sandwich beams surpasses that of type I in high-temperature conditions. پرونده مقاله
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        21 - New existence results for boundary value problems with integral conditions
        Rahmat Darzi Roja Mahmoudi Matankolae
        10.30495/fomj.2021.1921740.1023
        In this paper, we investigate the existence and uniqueness of solution for fractionalboundary value problem (FBVP) with the integral boundary conditions. We use the contraction mapping principle and Krasnoselskii’s fixed point theorem to obtain some new existence چکیده کامل
        In this paper, we investigate the existence and uniqueness of solution for fractionalboundary value problem (FBVP) with the integral boundary conditions. We use the contraction mapping principle and Krasnoselskii’s fixed point theorem to obtain some new existence and uniqueness results. پرونده مقاله
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        22 - ‎A Consistent and Accurate Numerical Method for Approximate Numerical Solution of Two Point Boundary Value Problems
        Pramod Pandey
        In this article we have proposed an accurate finite difference method for approximate numerical solution of second order boundary value problem with Dirichlet boundary conditions. There are numerous numerical methods for solving these boundary value problems. Some these چکیده کامل
        In this article we have proposed an accurate finite difference method for approximate numerical solution of second order boundary value problem with Dirichlet boundary conditions. There are numerous numerical methods for solving these boundary value problems. Some these methods are more efficient and accurate than others with some advantages and disadvantages. The results in experiment on model problems show an improved and good approximation to the solution of considered problems. پرونده مقاله
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        23 - The influence of various boundary conditions on dynamic stability of a beam-moving mass system
        Ramin Motiei Mostafa Pirmoradian Hossein Karimpour
        In this paper, the effect of different boundary conditions on dynamic stability of a beam located on a viscoelastic medium stimulated by moving masses and periodic axial force is studied. Partial differential equations governing the system are derived using Hamilton's m چکیده کامل
        In this paper, the effect of different boundary conditions on dynamic stability of a beam located on a viscoelastic medium stimulated by moving masses and periodic axial force is studied. Partial differential equations governing the system are derived using Hamilton's method and based on Euler-Bernoulli beam theory. Then, equations are converted into a set of ordinary differential equation with time-varying coefficients using Galerkin method along with trigonometric shape functions. The time-varying position of moving loads causes these time-varying coefficients in the governing equations. By applying Floquet's theory to the obtained equations, the conditions of parametric resonance are analyzed for different values of mass and velocity of passing loads. The results obtained from this research show that the stiffness and viscosity of the elastic medium have positive effects on the stability of the beam under moving and fluctuating axial loads. So, with a suitable choice for these values in practical applications, it is possible to prevent unexpected vibrations of the structure. In addition, the use of fixed supports for the two ends of the beam exposed to the mentioned loadings has high reliability in the discussion of dynamic stability. پرونده مقاله
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        24 - Study of the Effects of Various Boundary Conditions on the Acoustical Treatments of Double-Panel Structures Lined with Poroelatic Materials
        محمدحسن شجاعی فرد روح ا... طالبی رضا احمدی مائده امیرپور ملا
        In this paper, the acoustical treatment of double-panel structures lined with poroelatic materials is predicted using analytical method in order to study the effective usage of the various boundary conditions of porous layer and to identify the effective parameters on t چکیده کامل
        In this paper, the acoustical treatment of double-panel structures lined with poroelatic materials is predicted using analytical method in order to study the effective usage of the various boundary conditions of porous layer and to identify the effective parameters on the transmission loss of the multilayer systems. Therefore, inertia and viscous coupling along with thermal and elastic coupling should be considered in transfer stress dynamic and stress-strain relationships for an elastic porous material based on Biot theory. Then, the governing equations of the wave propagation in an elastic porous material are briefly considered and the general forms for the stresses and displacements within the porous material are given. Applying various boundary conditions and solving these equations with Matlab code simultaneously, the transmission loss of these structures is calculated. The results from the analytical method are compared with the SEA madel and the experimental data with excellent agreement is observed. Finally, the influence of effective parameters of this structure with various boundary conditions on the transmission loss of the multilayer systems is studied. The results have been shown that the transmission loss of double-panel structures lined with a layer of porous material can depend critically on the method of mounting the porous layer to the facing panel. پرونده مقاله
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        25 - Analysis of Linear Two-Dimensional Equations by Hermitian Meshfree Collocation Method
        محمدامین بهرامی مهرداد فروتن
        Meshfree Collocation Method is used to solve linear two-dimensional problems. This method differs from weak form methods such as Galerkin method and no cellular networking and no numerical integration. Therefore, this method has no constraints such as the integration ac چکیده کامل
        Meshfree Collocation Method is used to solve linear two-dimensional problems. This method differs from weak form methods such as Galerkin method and no cellular networking and no numerical integration. Therefore, this method has no constraints such as the integration accuracy and the integration CPU time, and equations can be isolated directly from the strong form of governing PDE. The fundamental problem of this method is unstable solution especially in the case, including derivative boundary conditions. In this paper hermite type shape functions are used to impose boundary conditions. These shape functions have improved the solution accuracy. also, In this paper effects of various parameters such as type weight functions, order based vector, dilation parameter, distribution nodal on the solution accuracy have been studied. پرونده مقاله
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        26 - Nonlinear buckling analysis of clamped-free porous FG sandwich beams with temperature dependent materials
        Mohsen Rahmani
        Analysing the buckling behaviour of the two kinds of sandwich beams, the first one with functionally graded material faces and homogeneous core and the second one with functionally graded material core and homogeneous faces are presented in this paper based on a high or چکیده کامل
        Analysing the buckling behaviour of the two kinds of sandwich beams, the first one with functionally graded material faces and homogeneous core and the second one with functionally graded material core and homogeneous faces are presented in this paper based on a high order sandwich beam theory. Properties of the constituent materials are assumed temperature dependent and functionally graded materials are modelled by a power law rule. Even and uneven porosity distributions are considered to improve the accuracy of the model. Minimum potential energy principle is used to obtain the govern equations and Galerkin method is applied used to solve the equations in a clamped free boundary conditions. Lateral displacement, and thermal stresses of the core and Lagrange strains are considered. To verify the procedure, the results of the present study are compared with the literature. Thickness, length, porosity, wave number and temperature effect on the critical load are investigated too. پرونده مقاله

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