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RISS 인기검색어
- 검색키워드
- 저자 : ( Vahid Ebrahimi ) (검색결과 3 건)
- 무료
- 기관 내 무료
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Vahid Rezania,Saeed Ebrahimi 대한기계학회 2017 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.31 No.1
In this paper, the kinematic performance of a planar parallel manipulator 3-RPR is investigated. Based on the constraint equations, robot geometric Jacobian matrix is calculated. Since the end-effector of the 3-RPR planar parallel manipulator performs both translational and rotational motions, robot geometric Jacobian matrix is transformed to a homogeneous form. This method defines a new Jacobian that transforms the linear velocities of two points on the end-effector to the actuator velocities. The velocity manipulability index is used for studying the ability of the manipulator to move. The manipulator distance singularity and kinematic accuracy is checked out by using the Local conditioning index (LCI) and Global conditioning index (GCI). The effect of Jacobian matrix homogenization on both the LCI and manipulability index is investigated in detail. Furthermore, the relation between LCI and the manipulability ellipsoids for certain moving platform orientations is studied. The paper is finally concluded by checking out the shapes of the manipulability ellipsoids for different moving platform orientations over the whole workspace.
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Mehdi Mohammadjafari,Reza Ebrahimi,Vahid Parvin Darabad 대한전기학회 2020 Journal of Electrical Engineering & Technology Vol.15 No.2
In this paper, optimal economic management of a grid-connected microgrid (MG) with distributed energy resource (DER) and its interaction with incentive-based demand response programs (DRPs) is studied. The use of DR makes energy management system (EMS) of the MG an efcient tool in balancing the demand and supply, and therefore ensuring the network reliability. In this work, the cost function of customers is developed in the incentive-based DRP with the aim of receiving a more realistic incentive and then it is combined with EMS. Accordingly, the consumers ofer hourly power reduction bids based on which they are sorted and then incentive-based payment model is implemented. At times, due to full utilization of grid and MG resources, the supply–demand balance cannot be maintained by respecting the consumer ofers. Specifc energy policies and contracts are required in this case for mandatory power curtailment in exchange for higher incentive payments by MG operator (MGO). The objective function attempts to minimize operation costs of the MG units such as Diesel Generator fuels costs, cost of power exchange with the main grid, battery energy storage system (BESS) costs and in the mean time, maximize MGO DR beneft. On the other hand, simultaneous EMS and DR management leads to a complex non-linear problem, which can be solved using whale optimization algorithm (WOA) in MATLAB software. To assess the performance of the proposed new approach, a grid-connected MG with DERs and reducible power of consumers is studied within a 24-h time cycle. Also, to verify the scalability of the implemented system, an MG with aggregators and a large scale battery is considered. Simulation results show that incorporating a developed DR into EMS is an efcient way in optimal performance of both demand and supply sides in conjunction with the goals of economic operation of MGs.
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( Shahrokh Ezzatzadegan Jahromi ),( Ghasem Haghighi ),( Jamshid Roozbeh ),( Vahid Ebrahimi ) 대한신장학회 2019 Kidney Research and Clinical Practice Vol.38 No.2
Background: Automated office blood pressure (AOBP) machines measure blood pressure (BP) multiple times over a brief period. We aimed to compare the results of manual office blood pressure (MOBP) and AOBP methods with ambulatory BP monitoring (ABPM) in patients with chronic kidney disease (CKD). Methods: This study was performed on 64 patients with CKD (stages 3-4). A nurse manually measured the BP on both arms using a mercury sphygmomanometer, followed by AOBP of the arm with the higher BP and then ABPM. Mean BP readings were compared by paired t test and Bland-Altman graphs. Results: The mean ± standard deviation (SD) age of participants was 59.3 ± 13.6. The mean ± SD awake systolic BP obtained by ABPM was 140.2 ± 19.0 mmHg, which was lower than the MOBP and AOBP methods (156.6 ± 17.8 and 148.8 ± 18.6 mmHg, respectively; P < 0.001). The mean ± SD awake diastolic BP was 78.6 ± 13.2 mmHg by ABPM which was lower than the MOBP and AOBP methods (88.9 ± 13.2 and 84.1 ± 14.0 mmHg, respectively; P < 0.001). Using Bland-Altman graphs, MOBP systolic BP readings showed a bias of 16.4 mmHg, while AOBP measurements indicated a bias of 8.6 mmHg compared with ABPM. Conclusion: AOBP methods may be more reliable than MOBP methods for determining BP in patients with CKD. However, the significantly higher mean BPs recorded by AOBP method suggested that AOBPs may not be as accurate as ABPM in patients with CKD.
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