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RISS 인기검색어
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- 저자 : Raeesi (검색결과 5 건)
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Raeesi, Arash,Cheng, Shaohong,Ting, David S.K. Techno-Press 2008 Wind and Structures, An International Journal (WAS Vol.11 No.3
The spanwise flow structure around a rigid smooth circular cylinder model in cross-flow has been investigated based on the experimental data obtained from a series of wind tunnel tests. Surface pressures were collected at five spanwise locations along the cylinder over a Reynolds number range of $1.14{\times}15^5$ to $5.85{\times}10^5$, which covered sub-critical, single-bubble and two-bubble regimes in the critical range. Separation angles were deduced from curve fitted to the surface pressure data. In addition, spanwise correlations and power spectra analyses were employed to study the spatial structure of flow. Results at different spanwise locations show that the transition into single-bubble and two-bubble regimes could occur at marginally different Reynolds numbers which expresses the presence of overlap regions in between the single-bubble regime and its former and later regimes. This indicates the existence of three-dimensional flow around the circular cylinder in cross-flow, which is also supported by the observed cell-like surface pressure patterns. Relatively strong spanwise correlation of the flow characteristics is observed before each transition within the critical regime, or formation of first and second separation-bubbles. It is also noted that these organized flow structures might lead to greater overall aerodynamic forces on a circular cylinder in cross-flow within the critical Reynolds number regime.
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Farzad Raeesi,Sajad Heydari,Hedayat Veladi 국제구조공학회 2022 Structural Engineering and Mechanics, An Int'l Jou Vol.83 No.5
Environmental thermal loads such as vertical and lateral temperature gradients are significant factors that must be taken into account when designing the bridge. Different models have been developed and used by countries for simulating thermal gradients in bridge codes. In most of the codes only vertical temperature gradients are considered, such as Iranian Standard Loads for Bridge code (ISLB), which only considers the vertical gradient for bridge design proposes. On the other hand, the vertical gradient profile specified in ISLB, has many lacks due to the diversity of climate in Iran, and only one vertical gradient profile is defined for whole Iran. This paper aims to get the both vertical and lateral gradient loads for the concrete box girder using experimental analysis in the capital of Iran, Tehran. To fulfill this aim, thermocouples are installed in experimental concrete segment and temperatures in different location of the segment are recorded. A three dimensional finite element model of concrete box-girder bridge is constructed to study the effects of thermal loads. Results of investigation proved that the effects of thermal loads are not negligible, and must be considered in design processes. Moreover, a solution for reducing the negative effects of thermal gradients in bridges is proposed. Results of the simulation show that using one layer polyurethane insulation can significantly reduce the thermal gradients and thermal stresses.
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Upgraded salp swarm algorithm for optimal design of semi-active MR dampers in buildings
Farzad Raeesi,Hedayat Veladi,Bahman Farahmand Azar,Sina Shirgir,Baharak Jafarpurian 국제구조공학회 2023 Structural Engineering and Mechanics, An Int'l Jou Vol.86 No.2
In the case of designing control devices in a building, reliance on experimental formulation or engineering concepts without using optimization algorithms leads to non-optimal solutions or design parameters, which makes the use of control devices costly and unreasonable. The optimization algorithms are capable of identifying the required number of parameters for a specific design problem, however, this process is difficult and inefficient in dealing with some specific optimal design processes. This paper aims to introduce an upgraded version of the salp swarm algorithm to handle some engineering design. The performance of the new upgraded algorithm is tested using some benchmark test functions as well as a six-story benchmark building equipped with semi-active MR dampers. The simulation results show that the proposed algorithm can be successfully applied to get an optimal design of the MR dampers in the building.
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Akbari, Narjes,Raeesi, Vajehallah,Khazaei, Tahereh,Ramezanzadeh, Khaironnesa,Ebrahimipour, Sediqe Asian Pacific Journal of Cancer Prevention 2015 Asian Pacific journal of cancer prevention Vol.16 No.16
Background: Oral cancer is one of the most prevalent cancers and one of the top ten causes of death in the whole world. Most oral cancers are diagnosed at late stages. Since dentists play a critical role in early detection of oral cancer, they should be knowledgeable and skillful in oral cancer diagnosis. The aim of this study was to survey dentist knowledge about oral cancer in Southern Khorasan Province. Materials and Methods: This descriptive, cross-sectional study was conducted with dentists who participated in an in-service educational program at the Faculty of Dentistry of Birjand University of Medical Sciences in spring 2014. A questionnaire including demographic information with 11 questions regarding oral cancer was prepared. The participants were required to be complete the questionnaires within a specific time span. The data were analyzed using SPSS 15 software by t-test and one-way ANOVA at 0.05 confidence level. Results: A total of 73 dentists out of 80 answered the questionnaires - 36 (49.3%) were females and 37 (50.7%) were males. Total mean score of knowledge was $7.91{\pm}1$ of 11. Mean scores of knowledge of male and female participants were $7.70{\pm}1.83$ and $8.13{\pm}1.94$ respectively. Mean knowledge score of general dentists was $7.41{\pm}1.79$ and of dental specialists was $9.44{\pm}1.0$ In spite of higher knowledge score of women compared to men and general dentists compared to dental specialists, these differences were not statistically significant (p=0.09). Tukey testing showed a significant difference between groups with 1-4 years of experience (8.74) and over twenty years of experience (6.50) ( p=0.001). Conclusions: Considering the good knowledge level of young dentists and the specialists and the importance of early diagnosis of oral cancer, it seems necessary to pay more attention to academic education for dentistry students, as well as holding retraining courses for experienced dentists, so that their knowledge not be reduced over time.
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Optimal Design of MR Damper Based on Tuning Bouc-Wen Model Parameters Using Hybrid Algorithms
Bahman Farahmand Azar,Hedayat Veladi,Siamak Talatahari,Farzad Raeesi 대한토목학회 2020 KSCE JOURNAL OF CIVIL ENGINEERING Vol.24 No.3
This paper presents a useful approach to optimally design magnetorheological (MR) dampers used in structural buildings. To fulfill this aim, damper parameters are regarded as the design variables whose values can be obtained through an optimization process. To improve the quality of searching for the optimum parameters of MR dampers, charged system search (CSS) and grey wolf (GW) algorithms, two of the most widely utilized meta-heuristic algorithms, are used together, and hybrid CSS-GW is presented. To show the authenticity and robustness of the new algorithm in solving optimization problems, some benchmark test functions are tested, at first. Then, an eleven-story benchmark building equipped with 3 MR dampers is considered to get the optimum design of the MR damper using the hybrid CSS-GW. Results show that the developed hybrid algorithm can successfully figure out the optimum parameters of the MR dampers.
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