نتایج جستجو برای: nonlinear

تعداد نتایج: 219001  

پایان نامه :وزارت علوم، تحقیقات و فناوری - دانشگاه پیام نور - دانشگاه پیام نور استان تهران - دانشکده علوم 1392

در نظر گرفتن یک فرض کلاسیک در ساختمان سری ها موجب شده است، مشاهدات را با یک الگوی خطی که ضرایبش با زمان تغییر نمی کند در نظر گیرند. اما بسیاری از سری های زمانی دارای میانگین و واریانس ثابتی در طول زمان نیستند در این شرایط مدل های اتورگرسیو مشروط به ناهمسانی واریانس اغلب به نتایج مطلوبی منجر می شوند. تحقیقات نشان داده اند مدل های شبکه عصبی برای نمایش رفتار غیرخطی داده ها نیز از عملکرد قابل توجهی...

پایان نامه :وزارت علوم، تحقیقات و فناوری - دانشگاه شیراز - دانشکده مهندسی مکانیک 1392

در پایان نامه حاضر به بررسی رفتار الاستوپلاستیک یک دیسک دوار مدرج تابعی با ضخامت ثابت تحت بارگذاری دمایی چرخه ای می پردازیم. در ابتدا سرعت دورانی ثابت و سپس دما به صورت چرخه ای اعمال می شود. ماده دیسک از نوع همسانگرد و غیرهمگن در نظر گرفته شده است که دارای خواص سخت شوندگی سینماتیکی غیرخطی است. به منظور بررسی تنش و کرنش پلاستیک در دیسک از روابط تعادل، جابه جایی-کرنش، معیار تسلیم فون-میسز، قانون ...

Journal: :civil engineering infrastructures journal 0
asghar vatani oskouie shahid rajaee teacher training university amin havaran faculty of civil engineering, shahid rajaee teacher training university, tehran, iran

in this article the general non-symmetric parametric form of the incremental secant stiffness matrix for nonlinear analysis of solids have been investigated to present a semi analytical sensitivity analysis approach for geometric nonlinear shape optimization. to approach this aim the analytical formulas of secant stiffness matrix are presented. the models were validated and used to perform inve...

Journal: :iranian journal of mechanical engineering transactions of the isme 0
ali ghorbanpour arani faculty of mechanical engineering, university of kashan, kashan, iran. hossein vossough faculty of mechanical engineering, university of kashan, kashan, iran reza kolahchi faculty of mechanical engineering, university of kashan, kashan, iran

the aim of the paper is to analyze electro-thermo nonlinear vibration of a double-piezoelectric composite microplate-system (dpcmps) based on nonlocal piezoelasticity theory. the two microplates are assumed to be connected by an enclosing elastic medium which is simulated by pasternak foundation. both of smart composite microplates are made of poly-vinylidene fluoride (pvdf) reinforced by zigza...

Journal: :journal of agricultural science and technology 2014
m. r. bahreini behzadi a. a. aslaminejad a. r. sharifi h. simianer

the objectives of this study were to identify a suitable mathematical model for describing the growth curve of baluchi sheep based on monthly records of live weight from birth to yearling; and to evaluate the efficacies of nonlinear mixed effect model (nlmm) and the nonlinear fixed effect model (nlm) methodologies. growth models were fitted to a total of 16,650 weight–age data belonging to 2071...

In the present work, the Rayleigh-Taylor instability of two rotating superposed magnetized fluids within the presence of a vertical or a horizontal magnetic flux has been investigated. The nonlinear theory is applied, by solving the equation of motion and uses the acceptable nonlinear boundary conditions. However, the nonlinear characteristic equation within the elevation parameter is obtained....

پایان نامه :وزارت علوم، تحقیقات و فناوری - دانشگاه علامه طباطبایی 1390

over the past decades a number of approaches have been applied for forecasting mortality. in 1992, a new method for long-run forecast of the level and age pattern of mortality was published by lee and carter. this method was welcomed by many authors so it was extended through a wider class of generalized, parametric and nonlinear model. this model represents one of the most influential recent d...

ژورنال: کنترل 2022

In the recent decades, metrics have been introduced as mathematical tools to determine the robust stability of the closed loop control systems. However, the metrics drawback is their limited applications in the closed loop control systems with nonlinear dynamics. As a solution in the literature, applying the metric theories to the linearized models is suggested. In this paper, we show that usin...

Recent investigations have shown that the influences of Soil-Structure Interaction (SSI) may be detrimental to the seismic response of structure, and hence neglecting this phenomenon in analysis and design may lead to an un-conservative design. The objective of this paper is to quantify the effects of nonlinear soil-structure interaction on the seismic response of a low-rise special moment fram...

Journal: :نظریه تقریب و کاربرد های آن 0
h. rouhparvar department of mathematics, college of technical and engineering, saveh branch, islamic azad university, saveh, iran

in this paper, the reduced di erential transform method is investigated fora nonlinear partial di erential equation modeling nematic liquid crystals, itis called the hunter-saxton equation. the main advantage of this methodis that it can be applied directly to nonlinear di erential equations withoutrequiring linearization, discretization, or perturbation. it is a semi analytical-numerical metho...

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