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Siamak Yaghobee,Afshin Khorsand,Amir Alireza Rasouli Ghohroudi,Khashayar Sanjari,Mahdi Kadkhodazadeh 대한구강악안면외과학회 2014 대한구강악안면외과학회지 Vol.40 No.5
Objectives: This study aimed to assess and compare the levels of interleukin-1beta (IL-1β) and interleukin-6 (IL-6) in the crevicular fluid around healthy implants, implants with peri-implantitis, and healthy teeth. Materials and Methods: This study evaluated 16 dental implants in 8 patients (4 males and 4 females). These patients had at least one healthy implant and one implant with peri-implantitis next to healthy teeth. The crevicular fluid was collected using absorbent cones and transferred to the laboratory. Specimens were evaluated by ELISA for interleukin levels. Data were analyzed using repeated measures ANOVA and Bonferroni tests (P〈0.05). Results: Levels of IL-1β in the crevicular fluid around implants with peri-implantitis were significantly higher than around healthy implants (P=0.002); the latter was significantly higher than around healthy teeth (P=0.015). A significant difference was found in the level of IL-6 in the crevicular fluid around implants with peri-implantitis and healthy implants (P=0.049) and also between implants with peri-implantitis and healthy teeth (P〈0.001). Conclusion: Within the limitations of this study, significant differences exist in the levels of IL-1β and IL-6 in the crevicular fluid of implants with peri-implantitis, healthy implants, and healthy teeth. More studies with larger sample sizes in different populations are necessary.
Improved dynamic equations for the generally configured Stewart platform manipulator
Siamak Pedrammehr,Mehran Mahboubkhah,Navid Khani 대한기계학회 2012 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.26 No.3
In this paper, a Newton-Euler approach is utilized to generate the improved dynamic equations of the generally configured Stewart platform. Using the kinematic model of the universal joint, the rotational degree of freedom of the pods around the axial direction is taken into account in the formulation. The justifiable direction of the reaction moment on each pod is specified and considered in deriving the dynamic equations. Considering the theorem of parallel axes, the inertia tensors for different elements of the manipulator are obtained in this study. From a theoretical point, the improved formulation is more accurate in comparison with previous ones, and the necessity of the improvement is clear evident from significant differences in the simulation results for the improved model and the model without improvement. In addition to more feasibility of the structure and higher accuracy, the model is highly compatible with computer arithmetic and suitable for online applications for loop control problems in hardware.
FUNDAMENTAL RESEARCH OF A NOVEL 3/1 PHASE CONVERTER FOR ELECTRIFIED RAILROAD
Siamak Farshad,Hao Rongtai 전력전자학회 1998 ICPE(ISPE)논문집 Vol.- No.-
Electrified railroads inject large amount of harmonics, negative sequence and reactive currents to electric supply systems This paper introduces application of active filter as a 3/1 phase converter for electrified railroad In this system active filter compensate harmonics, negative sequence and reactive currents and electric railroad and active filter together act as a balance three-phase load with power factor 1.<br/>
Siamak Talatahari,Mahdi Azizi,Mehdi Toloo,Milad Baghalzadeh Shishehgarkhaneh 한국강구조학회 2022 International Journal of Steel Structures Vol.22 No.3
In this paper, a metaheuristic-based design approach is developed in which the structural design optimization of large-scale steel frame structures is concerned. Although academics have introduced form-dominant methods, yet using artifi cial intelligence in structural design is one of the most critical challenges in recent years. However, the Charged System Search (CSS) is utilized as the primary optimization approach, which is improved by using the main principles of quantum mechanics and fuzzy logic systems. In the proposed Fuzzy Adaptive Quantum Inspired CSS algorithm, the position updating procedure of the standard algorithm is developed by implementing the center of potential energy presented in quantum mechanics into the general formulation of CSS to enhance the convergence capability of the algorithm. Simultaneously, a fuzzy logic-based parameter tuning process is also conducted to enhance the exploitation and exploration rates of the standard optimization algorithm. Two 10 and 60 story steel frame structures with 1026 and 8272 structural members, respectively, are utilized as design examples to determine the performance of the developed algorithm in dealing with complex optimization problems. The overall capability of the presented approach is compared with the Charged System Search and other metaheuristic optimization algorithms. The proposed enhanced algorithm can prepare better results than the other metaheuristics by considering the achieved results.
Energy Recovery Flyback Type Snubber for 10kV IGCT in 7MW Wind Turbine Systems
Siamak Shirmohammadi,Kihyun Lee,Yongsug Suh 전력전자학회 2015 ICPE(ISPE)논문집 Vol.2015 No.6
10kV IGCT has been recently developed and has the potential to push wind turbine systems to higher power and voltage rating. Converters employing IGCTs need snubber and OVP circuit to limit the rate of rise of current and peak over voltage across IGCT during turn on and off state respectively. The conventional RCD snubber which is used in such power converter dissipates a significant amount of power. In order to reduce the amount of energy lost by conventional RCD snubber, this paper proposes a flyback-type snubber circuit that not only meets all of the IGCTs characteristics during on and off-state but also significantly saves the power loss. Loss analysis of conventional di/dt snubber and OVP circuit is performed for the 3-level NPC type back-to-back VSC supplied from grid voltage of 6.9kV. In comparison with the conventional snubber, flyback type snubber has a fewer number of components and improved efficiency leading to a reliable and efficient wind turbine systems.
Innovative Decision Reference Based Algorithm for Photovoltaic Maximum Power Point Tracking
Siamak Mehrnami,Shahrokh Farhangi 전력전자학회 2010 JOURNAL OF POWER ELECTRONICS Vol.10 No.5
A novel decision reference based method for the maximum power point tracking (MPPT) of PV arrays is presented in this paper. The proposed decision reference was derived from a simplified solar cell model. This method solves the problems of conventional MPPT algorithms, such as oscillation of the operating point at the steady state and confusion under rapidly changing insolation. It is shown by simulation and experimental results that the method properly tracks a rapidly changing insolation profile. The signal to noise ratio (SNR) of the new decision reference is also higher than those of conventional P&O and INC methods. An updating subroutine was included in the proposed MPPT algorithm to compensate for temperature and aging effects.