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دسترسی آزاد مقاله
1 - The impact of higher order modes on transverse mode instability in bent optical fiber amplifiers
Sajjad Vazeerpour Mahdi Shayganmanesh Davoud DorranianWe present a new theoretical model for analyzing the impact of higher order modes on transverse mode instability in bent Yb-doped fiber amplifiers. The model indicates a comparative analysis of mode instability using the normalized propagation constant in straight and b چکیده کاملWe present a new theoretical model for analyzing the impact of higher order modes on transverse mode instability in bent Yb-doped fiber amplifiers. The model indicates a comparative analysis of mode instability using the normalized propagation constant in straight and bent fibers amplifiers. The impact of different bending radii, in bent fibers is investigated on the normalized propagation constant. The results are then compared with the straight fibers. Considering all the existed modes, the behavior of mode instability in the fibers with different V-numbers are simulated and explained physically. پرونده مقاله -
دسترسی آزاد مقاله
2 - Study on higher order azimuthally polarized Laguerre–Gaussian mode beams with high NA lens
K. Lalithambigai P. M. Anbarasan K. B. RajeshAbstractThe intensity distributions near the focal point for tight focusing of azimuthally polarized Laguerre–Gaussian beam including higher order modes are calculated based on vector diffraction theory. For higher order as well as the fundamental lower order mode A-TEM چکیده کاملAbstractThe intensity distributions near the focal point for tight focusing of azimuthally polarized Laguerre–Gaussian beam including higher order modes are calculated based on vector diffraction theory. For higher order as well as the fundamental lower order mode A-TEM01*, a small focal hole at the centre is obtained for the focusing under high NA lens. In a limit of NA = 0.95, the higher order A-TEMp1* mode beams of p = 1, 2, 3, 4, 5 and 6 are established numerically in detail. It is observed that one of the higher order mode A-TEM51* generates some interesting results. And it is also observed that the intensity distribution of the different mode has little variation among the degree of truncation (β) of the input beam beside the pupil. This work is important for optical manipulation, optical data storage, micro-machines and optical trapping applications for low refractive index particles. پرونده مقاله -
دسترسی آزاد مقاله
3 - نقش واسط مهارت تفکر سطح بالای ریاضی در رابطه بین مهارت تفکر سطح پایین ریاضی در امور مالی و توانمندی کارکنان مالی مبتنی بر نظریه اصلاح شده بلوم
سیده زهرا ابوالحسنی کومله احمد شاهورانی فریدون رهنمای رودپشتی فرهاد حسین زاده لطفیدر این مقاله، اهمیت نقش میانجی مهارت‌های تفکر سطح بالای ریاضی در مالی در رابطه‌ی بین مهارت تفکر سطح پایین ریاضی در مالی و توانمندی کارکنان مالی، از دیدگاه کارکنان شاغل در بانک‌های ایران بررسی شد. پس از مروری بر نقش مهارت تفکر ریاضی در امور مالی از دیدگاه صاحبنظران، نگرش چکیده کاملدر این مقاله، اهمیت نقش میانجی مهارت‌های تفکر سطح بالای ریاضی در مالی در رابطه‌ی بین مهارت تفکر سطح پایین ریاضی در مالی و توانمندی کارکنان مالی، از دیدگاه کارکنان شاغل در بانک‌های ایران بررسی شد. پس از مروری بر نقش مهارت تفکر ریاضی در امور مالی از دیدگاه صاحبنظران، نگرش کارکنان مرتبط مالی از طریق یک پرسشنامه‌ی محقق ساخته، بررسی شد. روش پژوهش حاضر توصیفی- همبستگی می‌باشد. به‌منظور تحلیل آماری داده‌ها و آزمون فرضیه‌ها از مدل سازی معادلات ساختاری استفاده شد. یافته‌ها نشان داد از دیدگاه شرکت کنندگان، مهارت تفکر سطح پایین ریاضی در امور مالی به‌صورت مستقیم، اثر مثبت و بدون معنی و به‌صورت غیرمستقیم، اثر مثبت و معنی‌داری بر توانمندی کارکنان مالی در صنعت بانکداری دارد، درحالی که مهارت تفکر سطح بالای ریاضی در امور مالی تأثیر مستقیم و معنی‌داری بر توانمندی آنان دارد. نیز تأثیر کلی مهارت تفکر سطح پایین ریاضی، به‌واسطه مهارت تفکر سطح بالای ریاضی در امور مالی، به‌شدت افزایش یافت. یافته‌های این پژوهش نشان داد کارکنان معتقدند مهارت تفکر سطح بالای ریاضی در امور مالی نسبت به مهارت تفکر سطح پایین ریاضی در امور مالی، تأثیرگذارتر است. در انتها، پیشنهادهای آموزشی به مسئولین آموزش عالی و دست‌اندرکاران صنعت بانکداری ارائه شد. پرونده مقاله -
دسترسی آزاد مقاله
4 - Free Vibration Analysis of Composite Grid Stiffened Cylindrical Shells Using A Generalized Higher Order Theory
H Mohammad Panahiha A Davar M Heydari Beni J Eskandari JamThe present study analyzes the free vibration of multi-layered composite cylindrical shells and perforated composite cylindrical shells via a modified version of Reddy’s third-order shear deformation theory (TSDT) under simple support conditions. An advantage of t چکیده کاملThe present study analyzes the free vibration of multi-layered composite cylindrical shells and perforated composite cylindrical shells via a modified version of Reddy’s third-order shear deformation theory (TSDT) under simple support conditions. An advantage of the proposed theory over other high-order theories is the inclusion of the shell section trapezoidal form coefficient term in the displacement field and strain equations to improve the accuracy of results. The non-uniform stiffness and mass distributions across reinforcement ribs and the empty or filled bays between the ribs in perforated shells were addressed via a proper distribution function. For integrated perforated cylindrical shells, the results were validated by comparison to other studies and the numerical results obtained via ABAQUS. The proposed theory was in good consistency with numerical results and the results of previous studies. It should be noted that the proposed theory was more accurate than TSDT. پرونده مقاله -
دسترسی آزاد مقاله
5 - Thermal Vibration of Composites and Sandwich Laminates Using Refined Higher Order Zigzag Theory
A Chakrabarti S.K Singh A.H SheikhVibration of laminated composite and sandwich plate under thermal loading is studied in this paper. A refined higher order theory has been used for the purpose. In order to avoid stress oscillations observed in the implementation of a displacement based finite element, چکیده کاملVibration of laminated composite and sandwich plate under thermal loading is studied in this paper. A refined higher order theory has been used for the purpose. In order to avoid stress oscillations observed in the implementation of a displacement based finite element, the stress field derived from temperature (initial strains) have been made consistent with total strain field. So far no study has been reported in literature on the thermal vibration problem based on the refined higher order theory using a FE model. Numerical results are presented for thermal vibration problems to study the influence of boundary conditions, ply orientation and plate geometry on the natural frequencies of these structures. پرونده مقاله -
دسترسی آزاد مقاله
6 - An Efficient Co Finite Element Approach for Bending Analysis of Functionally Graded Ceramic-Metal Skew Shell Panels
G Taj A ChakrabartiIn this article, the prominence has been given to study the influence of skew angle on bending response of functionally graded material shell panels under thermo-mechanical environment. Derivation of governing equations is based on the Reddy’s higher-order shear d چکیده کاملIn this article, the prominence has been given to study the influence of skew angle on bending response of functionally graded material shell panels under thermo-mechanical environment. Derivation of governing equations is based on the Reddy’s higher-order shear deformation theory and Sander’s kinematic equations. To circumvent the problem of C1 continuity requirement coupled with the finite element implementation, C0 formulation is developed. A nine noded isoparametric Lagrangian element has been employed to mesh the proposed shell element in the framework of finite element method. Bending response of functionally graded shell under thermal field is accomplished by exploiting temperature dependent properties of the constituents. Arbitrary distribution of the elastic properties follows linear distribution law which is a function of the volume fraction of ingredients. Different combinations of ceramic-metal phases are adopted to perform the numerical part. Different types of shells (cylindrical, spherical, hyperbolic paraboloid and hypar) and shell geometries are concerned to engender new-fangled results. Last of all, the influence of various parameters such as thickness ratio, boundary condition, volume fraction index and skew angle on the bending response of FGM skew shell is spotlighted. Some new results pertain to functionally graded skew shells are reported for the first time, which may locate milestone in future in the vicinity of functionally graded skew shells. پرونده مقاله -
دسترسی آزاد مقاله
7 - Hygrothermal Analysis of Laminated Composite Plates by Using Efficient Higher Order Shear Deformation Theory
S.K Singh A ChakrabartiHygrothermal analysis of laminated composite plates has been done by using an efficient higher order shear deformation theory. The stress field derived from hygrothermal fields must be consistent with total strain field in this type of analysis. In the present formulati چکیده کاملHygrothermal analysis of laminated composite plates has been done by using an efficient higher order shear deformation theory. The stress field derived from hygrothermal fields must be consistent with total strain field in this type of analysis. In the present formulation, the plate model has been implemented with a computationally efficient C0 finite element developed by using consistent strain field. Special steps are introduced to circumvent the requirement of C1coninuity in the original plate formulation and C0 continuity of the present element has been compensated in stiffness matrix calculations. The accuracy of the proposed C0 element is established by comparing the results with those obtained by three dimensional elasticity solutions and other finite element analysis. پرونده مقاله -
دسترسی آزاد مقاله
8 - Vibration Analysis of Functionally Graded Spinning Cylindrical Shells Using Higher Order Shear Deformation Theory
M MehrparvarIn this paper the vibration of a spinning cylindrical shell made of functional graded material is investigated. After a brief introduction of FG materials, by employing higher order theory for shell deformation, constitutive relationships are derived. Next, governing di چکیده کاملIn this paper the vibration of a spinning cylindrical shell made of functional graded material is investigated. After a brief introduction of FG materials, by employing higher order theory for shell deformation, constitutive relationships are derived. Next, governing differential equation of spinning cylindrical shell is obtained through utilizing energy method and Hamilton’s principle. Making use of the principle of minimum potential energy, the characteristic equation of natural frequencies is derived. After verification of the results, the effect of changing different parameters such as material grade, geometry of shell and spinning velocity on the natural frequency are examined. پرونده مقاله -
دسترسی آزاد مقاله
9 - تحلیل خیز و تنش در ورق های مرکب لایه‌ای با استفاده از تئوری برشی و تابع سکانت
ایمان نجیمی سعید جعفری مهرآبادی پیمان یوسفیکاربردهای روز افزون مواد مرکب در صنایع مختلف ازجمله هوافضا، کشتی‌سازی و سازه‌هایی در ابعاد میکرو و ماکرو باعث شده که محققان این حیطه توجه خاصی بر طراحی این سازه‌ها را داشته باشند. در پژوهش حاضر به تحلیل استاتیکی یک ورق مستطیلی به کمک حالتی خاص از تئوری مرتبه بالای تغیر چکیده کاملکاربردهای روز افزون مواد مرکب در صنایع مختلف ازجمله هوافضا، کشتی‌سازی و سازه‌هایی در ابعاد میکرو و ماکرو باعث شده که محققان این حیطه توجه خاصی بر طراحی این سازه‌ها را داشته باشند. در پژوهش حاضر به تحلیل استاتیکی یک ورق مستطیلی به کمک حالتی خاص از تئوری مرتبه بالای تغیر شکل برشی با در نظر گرفتن تابع سکانت در میدان تغییر مکان، پرداخته‌شده است. معادله‌های ورق کامپوزیت لایه‌ای مورداستفاده در این پژوهش به کمک رابطه‌ی حساب تغییرات و اصل همیلتون با تشکیل ترم‌های مختلف انرژی سیستم به‌دست‌آمده . برای حل معادلات حاکم از روش ناویر با جواب‌هایی متشکل از توابع سینوسی و کسینوسی و با در نظر گرفتن شرایط مرزی سیستم استفاده‌شده است. با حل معادلات مذکور مقادیر خیز ورق با توجه به تغییر در پارامترهای سیستم محاسبه‌شده است و جواب‌های به‌دست‌آمده با نتایج مندرج در مقالات معتبر چاپ‌شده مقایسه و از صحت آن‌ها اطمینان کافی حاصل‌شده است. در خاتمه نتیجه شده که تحلیل خیز به کمک توابع سکانت بسیار نزدیک به جواب‌های حاصل‌شده از پژوهش‌های مشابه است و در موارد خاص می‌توان از این توابع استفاده نمود. پرونده مقاله -
دسترسی آزاد مقاله
10 - Detection of Cardiac Hypertrophy by RVM and SVM Algorithms
fereshte morsaliThe meaning of the hypertropy word is the increasing size.Heart hypertropy is symptoms of increase the thickness of the heart muscle that the left ventricular hypertrophy of them is the most common.The causes of hypertrophy heart disease are high blood pressure , aortic چکیده کاملThe meaning of the hypertropy word is the increasing size.Heart hypertropy is symptoms of increase the thickness of the heart muscle that the left ventricular hypertrophy of them is the most common.The causes of hypertrophy heart disease are high blood pressure , aortic valve stenosis and sport activities respectively. Assessment of that by using ECG signal analysis is essential Because the risk of heart disease, ventricular hypertrophy increase the timely diagnosis The ECG signal demonstrate heart electric activities and include some characteristic points such as P wave , QRS complex and the T wave is formed. In this thesis , an algorithm has been presented for assessment of diagnosis of ventricular hypertrophy . In The presented algorithm first picks of ECG signal has been assessed then a high degree of statistical information such as skewness،kurtosis،R peak height and cumulants also have been used . پرونده مقاله -
دسترسی آزاد مقاله
11 - Reducing Displacement of Spring Mass in Active Vehicle Suspension System Using Sliding Mode Controller Based on Disturbance Observer
Mohammad Vatankhah Mohammad Yousefi Sayyed Mohammad Mehdi Mirtalaei Zahra AlaleThe main cause of oscillation during the movement of the vehicle is the unevenness of the road. Therefore, in order to maintain the stability of the car in swing states, the suspension system plays an essential role. Therefore, the active suspension system is used to re چکیده کاملThe main cause of oscillation during the movement of the vehicle is the unevenness of the road. Therefore, in order to maintain the stability of the car in swing states, the suspension system plays an essential role. Therefore, the active suspension system is used to replace the conventional passive suspension system, to improve comfort and smoothness. To reduce the displacement of the spring mass in the active vehicle suspension system, a high-order sliding mode controller is proposed in this paper. Uncertainty of system parameters, nonlinear characteristic of damping and spring, load changes and unknown path disturbance are estimated by disturbance observer. The controller only needs the information of the spring mass state variables and therefore does not need separate sensors to measure the suspension mass state variables. Particle swarm optimization algorithm has been used to determine the control parameters. The efficiency of the proposed method has been shown using simulation in MATLAB software and the results have been compared with the passive suspension system. پرونده مقاله -
دسترسی آزاد مقاله
12 - Solving systems of nonlinear equations using decomposition technique
M. Nili Ahmadabadi F. Ahmad G. Yuan X. LiA systematic way is presented for the construction of multi-step iterative method with frozen Jacobian. The inclusion of an auxiliary function is discussed. The presented analysis shows that how to incorporate auxiliary function in a way that we can keep the order of co چکیده کاملA systematic way is presented for the construction of multi-step iterative method with frozen Jacobian. The inclusion of an auxiliary function is discussed. The presented analysis shows that how to incorporate auxiliary function in a way that we can keep the order of convergence and computational cost of Newton multi-step method. The auxiliary function provides us the way to overcome the singularity and ill-conditioning of the Jacobian. The order of convergence of proposed p-step iterative method is p + 1. Only one Jacobian inversion in the form of LU-factorization is required for a single iteration of the iterative method and in this way, it offers an efficient scheme. For the construction of our proposed iterative method, we used a decomposition technique that naturally provides different iterative schemes. We also computed the computational convergence order that confirms the claimed theoretical order of convergence. The developed iterative scheme is applied to large scale problems, and numerical results show that our iterative scheme is promising. پرونده مقاله
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