توجه: محتویات این صفحه به صورت خودکار پردازش شده و مقاله‌های نویسندگانی با تشابه اسمی، همگی در بخش یکسان نمایش داده می‌شوند.
۱Delamination Analysis using Interface Elements with various de–cohesive Properties
نویسنده(ها): ، ،
اطلاعات انتشار: هفتمین همایش انجمن هوافضای ایران، سال
تعداد صفحات: ۶
In this paper delamination phenomena in the laminates are analyzed using interface element. The interface elements are imposed with three different constitutive laws and the laminates are under monotonic quasi–static loading condition. For this purpose, a finite element code has been developed using twenty–node brick elements for the body and sixteen–node interface element for delamination modeling. Several examples containing an interface element with direct loading to produce mode–I and mixed–mode fracture conditions and also modeling of some benchmark fracture mechanics examples are presented. The obtained results are compared with the available numerical results in the literatures.<\div>

۲Damage Analysis of Laminated Plates using Continuum Damage Mechanics
اطلاعات انتشار: هفتمین همایش انجمن هوافضای ایران، سال
تعداد صفحات: ۱۰
In this paper, progressive damage and global failure of composite laminates under quasi–static, monotonic loading are investigated using 3D continuum damage mechanics. For this purpose, a finite element program has been developed using an eight–node 2D layered element including layer–wise plate theory. A number of laminate examples with diffuse damage under simply supported and distributed transverse loading conditions are analyzed using the developed method. The effects of various lay–up configurations and numerical modeling parameters on the progressive damage response are also investigated.<\div>

۳Applying response surface design to the optimization of removal low concentration malachite green with natural semnan zeolite as adsorbent
نویسنده(ها): ، ، ،
اطلاعات انتشار: دومین کنفرانس بین المللی زئولیت ایران، سال
تعداد صفحات: ۴
A four factor, three–level central composite design combining with response surface modeling (RSM) was employed for maximizing malachite green removal from aqueous solution by natural zeolite based on 31 different experimental data obtained in a lab–scale batch study. four independent variables (initial pH of solution ranging from 3 to 9, initial concentration of dye ranging from 10 to 20 ppm, amount of zeolite ranging from .5 t0 1.5 gr and contact time ranging from 30 to 90 min) were consecutively coded as x1, x2 , x3 and x4 at three levels (−1, 0 and 1), and a second–order polynomial regression equation was then derived to predict responses. The significance of independent variables and their interactions were tested by means of the analysis of variance (ANOVA) with 95% confidence limits . The optimum values of the selected variables were obtained by solving the quadratic regression model, as well as by analyzing the response surface contour plots. The experimental conditions at optimum point were determined to be pH0 = 6.39, initial concentration of dye = 20 ppm,amount of zeolite = 0.6 gr and contact time = 90 min, and the corresponding dye removal efficiency was found to be about 100%.<\div>

۴Application of Solid–like Interface Element in Delamination Growth Analysis Under Cyclic Loading
نویسنده(ها): ، ،
اطلاعات انتشار: دومین کنفرانس بین المللی کامپوزیت، سال
تعداد صفحات: ۶
In this paper, a damage mechanic approach using interface elements is employed for the analysis of delamination growth in composite laminates under cyclic loading. A thin layer solid like interface element for modeling of the cohesive zone between any two arbitrary laminate layers was used and the developed formulation were implemented to ANSYS code, as a User Programmable Features (UPF). Using this code, delamination growth analyses are performed for DCB specimens that usually used to obtain the fracture toughness of delamination phenomena in composite laminates. It is shown that the developed code can be used to predict the delamination growth rate of composite laminates under cyclic loading with acceptable accuracy.<\div>

۵Buckling Analysis of Micro– and Nano–Beams Based on Nonlocal Euler Beam Theory using Chebyshev Polynomials
نویسنده(ها): ، ،
اطلاعات انتشار: دومین کنفرانس بین المللی کامپوزیت، سال
تعداد صفحات: ۶
This paper is concerned with the elastic buckling behavior of nano–tubes. The nano rod\tube is modeled using the Bernoulli–Euler beam theory in the framework of Eringen’s nonlocal elasticity. Eringen’s nonlocal constitutive law allows length scale investigation in nano micro\nano scale. The Minimum Potential Energy (MPE) principle as a function of displacement in conjunction with the Chebyshev polynomials of the first kind as basis functions in the Rayleigh–Ritz method are used to obtain the critical buckling loads. Good agreement is achieved between the obtained results and exact solutions for various boundary conditions. It is shown that the present analysis in the form of Chebyshev series has the property of rapid convergence.<\div>

۶Matrix Crack and Delamination Analyses in Composite Laminates by FEM Based Micromechanical Approach
اطلاعات انتشار: دومین کنفرانس بین المللی کامپوزیت، سال
تعداد صفحات: ۶
In this paper, a finite element based micromechanical approach are performed to study the effect of matrix cracking (also known as intralaminar cracking) on the behavior of cross–ply [0ºn\90ºm]s and angle–ply [θºn\90ºm]s laminates. The laminates material is carbon\epoxy and loaded statically in tension. The developed procedure is employed for different cross–ply and angle–ply symmetric laminates with various lay–up configurations. Prediction of mechanical properties degradation due to the damage formation are calculated using the developed micromechanical approach which is able to predict the stress transfer between the 90º plies in a [0ºn\90ºm]s cross–ply or an angle–ply [θºn\90ºm]s laminate containing parallel transverse cracks. In addition, reduction of axial stiffness versus crack density in off–axis plies will be presented for [45º\–45º]. It is shown that the predicted stiffness reductions and energy release rates are close to the available experimental measurements and theoretical results for carbon\epoxy laminates<\div>

۷Criteria in Choosing the Elements' Coefficients in Pulse Arrays
نویسنده(ها): ، ، ،
اطلاعات انتشار: اولین کنفرانس بین المللی دستاوردهای نوین پژوهشی در مهندسی برق و کامپیوتر، سال
تعداد صفحات: ۵
In this paper, the procedure of choosing the elements'coefficients in pulse arrays, is presented and discussed. Weinvestigated properties of amplitude pattern and array factor(AF) of linear array in different convex weightings for elementsand introduced new parameter for comparing the usefulness ofthis weightings and finding an efficient and better arrangementin radar and communication application to save the power in themain beam of the radiation. The results reveal that arrays withconvex weightings and small coefficients have better performancethan uniform array for any spacing between elements.<\div>

۸Design of A Small UWB Antenna with Double Band–Notched Characteristics with Low Correlation for MIMO Applications
نویسنده(ها): ، ، ،
اطلاعات انتشار: اولین کنفرانس بین المللی دستاوردهای نوین پژوهشی در مهندسی برق و کامپیوتر، سال
تعداد صفحات: ۴
A small low correlation multiple–input multiple–output (MIMO) antenna with double band–notched characteristics for UWB requests with a small size of 22 × 42 mm2 is offered. The MIMO antenna comprises two identical elements each of that has a stepped patch with U–shaped slot, two rectangular shaped slots in the ground plane and a butterfly shape element on back of construction. The antenna elements are placed orthogonally to attain an acceptable isolation with a low ECC between the two input ports. The measured frequency results show an impedance bandwidth of 11.02 GHz over 1.98–13.0 GHz for l0 dB return loss with two rejected bands centered at 3.39 (940 MHz) and 5.36 GHz (1370 MHz) to limited the WLAN and WiMAX bands, along with a primary portion of the C band. The results demonstrate that the antenna can be evaluated as a fine choice for UWB MIMO systems.<\div>

۹Design of A Small Microstrip MIMO Antenna for WLAN and X–Band Applications
نویسنده(ها): ، ، ،
اطلاعات انتشار: اولین کنفرانس بین المللی دستاوردهای نوین پژوهشی در مهندسی برق و کامپیوتر، سال
تعداد صفحات: ۴
A small microstrip multiple–input multiple–output (MIMO) antenna for WLAN and X–band requests with low correlation is offered. The MIMO antenna comprises of two equivalent elements that has a planar radiator with microstrip–feed and an truncated rectangular ground plane. The designed dual–band antenna is actualized by employing bent meander line shapes. The antenna elements are placed orthogonally to gain a high isolation and low envelope correlation between the two input ports. The realized impedance bandwidth for l0 dB return loss is covered frequency ranges of 2.20–2.91 GHz (710 MHZ, %28) and 6.24–8.82 GHz (2580 MHz,%35) which is respectively able to covering Bluetooth\ WiBro\WiMax\ LTE\WLAN, and X–band applications. The offered antenna has a straightforward design with small size of 20×40 mm2 while exhibiting stable almost omnidirectional radiation characteristics at its various frequency bands of working that is a favorable capability in most of the relevant requests.<\div>

۱۰A Compact Triple Band Bent–Fork Shaped CPW–Fed Monopole Antenna for MIMO Applications
نویسنده(ها): ، ، ،
اطلاعات انتشار: اولین کنفرانس بین المللی دستاوردهای نوین پژوهشی در مهندسی برق و کامپیوتر، سال
تعداد صفحات: ۴
The design of a compact triple band bent–fork shaped CPW–fed monopole antenna for multiple–input multiple–output (MIMO) applications with a small size of 20 × 40 mm2 is introduced. The MIMO antenna comprises two similar elements each of that has adjusted bent–fork shaped radiating element with distinct arms lengths and a modified CPW stepped feed–line to produce the multiband functionality and enhance the input matching condition, respectively. The realized impedance bandwidth for l0 dB return loss is arranged in frequency bands of 1.78–2.26 GHz (%24.0), 4.86–5.82 GHz (%18), and 8.04–9.05 GHz (%12) which is respectively capable of supporting PCS\ Bluetooth, WLAN, and X–band usages. Antenna elements are placed orthogonally to gain a high isolation and low envelope correlation between the two input ports. Fine efficiency of the offered antenna over the working bands are also received. The results demonstrate which the antenna can be evaluated as a good choice for multiband MIMO systems.<\div>

۱۱A Compact Omnidirectional Microstrip MIMO Antenna for WLAN and WiMAX Applications
نویسنده(ها): ، ،
اطلاعات انتشار: اولین کنفرانس بین المللی دستاوردهای نوین پژوهشی در مهندسی برق و کامپیوتر، سال
تعداد صفحات: ۴
A compact omnidirectional microstrip multiple–input multiple–output (MIMO) antenna for WLAN and WiMAX requests is offered. The MIMO antenna comprises of two equivalent elements that has a planar radiator with microstrip–feed and an asymmetry truncated rectangular ground plane. The designed dual–band antenna is actualized by employing bent meander line shapes with different lengths. It is displayed that fine MIMO efficiency can be attained even for small element arranging. The antenna elements are located orthogonally to reach an acceptable isolation with a low ECC between the two input ports. The measured impedance bandwidth for l0 dB return loss is spread in frequency ranges of 2.58–4.08 GHz (%46.5) and 5.53–6.68 GHz (%22.6) which is respectively able to covering WiMAX\C–band\LTE\FS\FSS, and WiMAX\WLAN applications. The designed antenna has a simple structure with small size while presenting consistent almost fully omnidirectional radiation characteristics at its different frequency bands of functioning that is a favorable ability in most of the relevant applications.<\div>

۱۲A Dual–Band Rejection of WLAN\WiMAX in UWB Antenna Using Slotted EBG Structure
نویسنده(ها): ، ، ،
اطلاعات انتشار: اولین کنفرانس بین المللی دستاوردهای نوین پژوهشی در مهندسی برق و کامپیوتر، سال
تعداد صفحات: ۴
This paper demonstrates a novel technique for notching WiMAX and WLAN frequency bands by means of slotted electromagnetic band–gap(EBG) structure. A simple design of microstrip dipole antenna, which is fed by a very simple microstrip line structure, is used as the reference antenna. Then, the antenna is integrated with a simple slotted EBG structure near the feed line for providing notch properties. The proposed EBG structure provides two band rejection characteristics by means of utilizing both left–handed properties of mushroom structure and on the other hand by taking the advantage of longitudinal current flow over the slotted EBG structure. The two demonstrated notch bands can be controlled by mushroom geometry parameters and also they are independent of the initial antenna design. This leads to a little pattern deterioration along the desired bands. The designed antennas and their performance characteristics were simulated by High Frequency Structure Simulator(HFSS) and valuated by CST Microwave studio. Test results of the fabricated designs show a good correlation with simulated outcomes, validating the design principles.<\div>
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