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کاربرد نوع شرط:
- جایگاه : پژوهشی
- مجله: Mechanics of Advanced Composite Structures
- نوع مقاله: Journal Article
- کلمات کلیدی: Mathematical Modeling,Free vibration,Thermal buckling,Perforated plate,Heaviside function
- چکیده:
- چکیده انگلیسی: This artcile is concerned with thermal buckling and thermal induced free vibration analyses of PCPs (perforated composite plates) with simply supported edges applying a mathematical model. The stiffness and density of PCP are defined locally using Heaviside distribution functions. The governing equations are derived based on CLPT. The present solution gives reasonable results in comparison with the few literatures. In order to inspect the structural behaviour of PCPs subjected to initial thermal loads, many parametric studies have been carried out. Results indicated that the presence of perforations has a significant effect on thermal buckling and thermal induced fundamental frequency.
- انتشار مقاله: 01-09-1397
- نویسندگان: Sina Soleimanian,Ali Davar,Jafar Eskandari Jam,Mohammad Reza Zamani,Mohsen Heydari Beni
- مشاهده
- جایگاه : پژوهشی
- مجله: Mechanics of Advanced Composite Structures
- نوع مقاله: Journal Article
- کلمات کلیدی: Composite,Free vibration,Higher-order shear deformation theory,Trapezoidal shape factor,Circular cylindrical shells
- چکیده:
- چکیده انگلیسی: A new closed form formulation of three-dimensional (3-D) refined higher-order shell theory (RHOST) to analyze the free vibration of composite circular cylindrical shells has been presented in this article. The shell is considered to be laminated with orthotropic layers and simply supported boundary conditions. The proposed theory is used to investigate the effects of the in-plane and rotary inertias as well as transverse normal and shear strains on the dynamic response of thick composite cylindrical shells. The trapezoidal shape factor of the shell element is incorporated to obtain accurate stress-resultants. Using Hamilton’s principle, the equations of motion are obtained and solved in terms of the Galerkin method. Numerical results for the natural frequencies are verified by making comparison with the 3-D exact elasticity iterative solutions in the literature. In addition, the validity of the results is further verified by ABAQUS. According to the results, for thick composite cylinders with large length-to-radius and orthotropic ratios, through thickness exact integration yields accurate stress-resultants for proper prediction of the natural frequencies.
- انتشار مقاله: 28-02-1397
- نویسندگان: Ali Davar,Reza Kohandani,Hamid Mohammad Panahiha
- مشاهده
- جایگاه : پژوهشی
- مجله: Mechanics of Advanced Composite Structures
- نوع مقاله: Journal Article
- کلمات کلیدی: Free vibration,cutout,GFRP Plates,Free Boundaries
- چکیده:
- چکیده انگلیسی: This study explored the free vibration problem in relation to glass fiber reinforced polymer (GFRP) plates with central cutouts and free boundaries using theoretical, experimental, and numerical methods. The theoretical formulations were derived from the classical lamination plate theory. The rectangular cutout was mathematically modeled into the stiffness matrix of the plate by multiplying Heaviside distribution functions. The theoretical values for the fundamental frequency were obtained by solving the standard eigenvalue problem, and the theoretical solution was validated by comparison to the literature. Modal testing was performed in the laboratory. For additional validation, the accuracy of theoretical and experimental results was checked using the finite element method and ABAQUS. The results of all three methods agreed; thus, the applicability of the Heaviside functions to stiffness modeling of structures with cutouts was proven. It was also observed that the fundamental frequency decreased when cutout size increased.
- انتشار مقاله: 15-05-1396
- نویسندگان: Sina Soleimanian,Ali Davar,Reza Azarafza,Jafar Eskandari Jam,Mohammad Reza Zamani
- مشاهده
- جایگاه : پژوهشی
- مجله: Journal of System Management
- نوع مقاله: Journal Article
- کلمات کلیدی: Regional Entrepreneurship,Entrepreneurial ecosystem,international and national factors
- چکیده:
- چکیده انگلیسی: Entrepreneurial ecosystem is a geographic framework that indicates that a person is supported by which factors for becoming a businessman. Effective factors on this issue include social, cultural, political and economic structures that should be considered in the context of different regions. In our research, we are going to identify not only international and national factors affecting entrepreneurship but also factors that will affect on the entrepreneurship of the region. The statistical sample includes 100 entrepreneurship development policymakers, entrepreneurs, and owners of knowledge-based companies. The data gathering tool of the interview was based on a closed questionnaire and the validity and reliability of this research were confirmed after the assessment. Based on the findings of this study from the descriptive aspect, this conceptual model has been appropriate for experts and entrepreneurs. Analysis of the main goals of the research shows that there are a number of factors on the region that the ecosystems of entrepreneurship are affected by them, which include geographic, demographic, institutional factors, and regional infrastructure.
- انتشار مقاله: 03-12-1397
- نویسندگان: Ibrahim Jafari Sangari,Seyyed Mehdi Alvani,Morteza Mousakhani,Ali Davari,Mohsen Khoonsiavash
- مشاهده
- جایگاه : پژوهشی
- مجله: Journal of Information Technology Management
- نوع مقاله: Journal Article
- کلمات کلیدی:
- چکیده:
- چکیده انگلیسی: Theoretically speaking, ICT is a new concept in Enterprise Architecture which can be studied in HRM and HR architecture issues. Due to contextual variables carrying diverse variation and importance levels, designing an e-readiness framework of HR Architecture is a complex issue. Therefore, this idea is considered in Iranian Oil and Gas industry to be piloted. Framework of ICT conceptual model derived from exploratory interviews and literature reviews in seven dimensions which were surveyed in NIOC via 182 questionnaires whose result showed that the status quo is not satisfactory and some suggestions to attain the desired state were given.
- انتشار مقاله: 11-10-1348
- نویسندگان: Seyed Reza Seyed Javadein,Saeed Shahbaz Moradi,Tahmores Hasangholipor Yasory,Ali Davari
- مشاهده
- جایگاه : پژوهشی
- مجله: Journal of Emergency Practice and Trauma
- نوع مقاله: Journal Article
- کلمات کلیدی: Scorpion sting,Turmeric,Factitious disorder
- چکیده:
- چکیده انگلیسی: Factitious disorder as Munchausen syndrome is a time and money consuming condition that is presented with different signs and symptoms. In emergent situations, it is not a differential diagnosis with high priority, but when it becomes recurrent with atypical symptoms, factitious disorder and malingering should be considered as well. In this survey, we report an odd and interesting presentation of a factitious disease as a scorpion sting which misled some professional healthcare providers until the patient finally confessed that she used turmeric to mimic the signs of a scorpion sting. She exaggerated her symptoms when asked about the details of the mechanism of the scorpion bite. When encountering an emergent condition, after ruling out the critical conditions especially when the symptom is recurrent, factitious disorders should be considered. Consultation with a psychiatrist help the team manage the patient properly.
- انتشار مقاله: 19-04-1396
- نویسندگان: Reza Bidaki,Mehrdad Roozbeh,Mohamad Amin Sharifi,Seyed Nader Mostafavi,Mohammad Ali Abdolkarimi Davarani
- مشاهده
- جایگاه : پژوهشی
- مجله: International Journal of Nonlinear Analysis and Applications
- نوع مقاله: Journal Article
- کلمات کلیدی: Multiple objective fractional programming,Generalized n-set convex function,Efficient solution
- چکیده:
- چکیده انگلیسی: In this paper, we establish a proof for a necessary condition for multiple objective fractional programming. In order to derive the set of necessary conditions, we employ an equivalent parametric problem. Also, we present the related semi parametric model.
- انتشار مقاله: 29-10-1393
- نویسندگان: Rezvan Kamali,Ali Davari
- مشاهده
- جایگاه : پژوهشی
- مجله: International Journal of Advanced Design and Manufacturing Technology
- نوع مقاله: Journal Article
- کلمات کلیدی: stiffness,Flange,Static Loading & Separation,V-Clamp Band,Wedge
- چکیده:
- چکیده انگلیسی: The main target of this paper is to obtain an optimum wedge angle for best static and dynamic performance of a V-shaped clamp band separation mechanism. For this purpose, by using the finite element method, the proper 3D model for V-clamp band mechanism has been modelled and analysed in Abaqus/Explicit solver. In order to study the effect of wedge angle on bending and axial stiffness of V-clamp joint, many quasi-static analyses with different wedge angles were accomplished so the relation between wedge angle and axial stiffness of V-clamp joint under symmetric bending loading is extracted. In the next step, dynamic analyses were accomplished so the relation between wedge angle and separation time (duration between trigging moment and the time of disconnecting between flanges and wedged clamps) is extracted. For verification, this project results have been compared with the results of other researches and good agreement is observed. The results show that the optimal wedge angle for obtaining maximum stiffness together with minimum spring back disconnection time for the V-clamp band mechanism is 20˚.
- انتشار مقاله: 11-12-1397
- نویسندگان: SeyyedAbdolSajjad Borhani,AliAkbar Lotfi Neyestanak,Ali Davar
- مشاهده
- جایگاه : پژوهشی
- مجله: Avicenna Journal of Phytomedicine
- نوع مقاله: Journal Article
- کلمات کلیدی: Rabbit,Nitric oxide,Matricaria,Cholinergic Agents,Histamine Agents,Jejunum
- چکیده:
- چکیده انگلیسی: Objective: Several studies have shown the antispasmodic activity of Matricariarecutita without detailing the underlying mechanism(s). The present study was designed to determine whether the antispasmodic mechanisms of M. recutita extract mediated via histaminergic/cholinergic receptors, Ca2+channels, activation of PKA2 and NO release in isolated rabbit jejunum.
Methods and Materials: The concentration- dependent (3 × 10-3–1.3 × 10-2 mg/ml) antispasmodic effect of the hydro-alcoholic extract of M. recutita flowers was studied in isolated rabbit jejunum. The isolated jejunum preparations were divided into seven groups, including the pharmacological probes that modulate cholinergic, histaminergic, and nitrergic receptors, as well as PKA2.
Results: M. recutita inhibited spontaneous smooth muscle contractility of the jejunum in a concentration-dependent manner (3 × 10-3–1.3 × 10-2 mg/ml) and reduced both K+- and Ca2+-induced contractions, which is similar to the effect of verapamil. The antispasmodic effect of M. recutita wasinhibited by H89 (a PKA2 inhibitor). The myorelaxant effect of M. recutita increased in the presence of ACh/His and H89.
Conclusion: M. recutita evoked antispasmodic and spasmolytic effects mediated through different signaling pathways. Our results have shown this dual inhibitory effect is mediated by blocking Ca2+ channels, activating His and ACh receptors, releasing NO, and activating PKA2.- انتشار مقاله: 25-04-1395
- نویسندگان: Hamidreza Yazdi,Akhtar Seifi,Shima Changizi,Vahid Khori,Fatemeh Hossini,Ali Davarian,Yahya Jand,Ayesheh Enayati,Masumeh Mazandarani,Fateme Nanvabashi
- مشاهده