• Journal of Electrical Engineering and Technology
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• 제13권5호
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• pp.1965-1977
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• 2018

This paper proposed a regenerative braking system (RBS) strategy for battery electric vehicles (BEVs) with a hybrid energy storage system (HESS) driven by a brushless DC (BLDC) motor. In the regenerative braking mode of BEV, the BLDC motor works as a generator. Consequently, the DC-link voltage is boosted and regenerative braking energy is transferred to a battery and/or ultracapacitor (UC) using a suitable switching pattern of the three-phase inverter. The energy stored in the HESS through reverse current flow can be exploited to improve acceleration and maintain the batteries from frequent deep discharging during high power mode. In addition, the artificial neural network (ANN)-based RBS control mechanism was utilized to optimize the switching scheme of the vehicular breaking force distribution. Furthermore, constant torque braking can be regulated using a PI controller. Different simulation and experiments were implemented and carried out to verify the performance of the proposed RBS strategy. The UC/battery RBS also contributed to improved vehicle acceleration and extended range BEVs.

• Journal of Mechanical Science and Technology
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• 제19권6호
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• pp.1253-1267
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• 2005

Misalignment can be an important problem in the integration of GPS/INS. Observability analysis of the alignment errors in the integration of low-grade inertial sensors and multi-antenna GPS is presented in this paper. A control-theoretic approach is adopted to study the observability of time-varying error dynamics models. The relationship between vehicle motions and the observability of the errors in the lever arm and relative attitude between GPS antenna array and IMU is given. It is shown that alignment errors can be made observable through maneuvering. The change of acceleration makes the components of the relative attitude error that are orthogonal to the direction of the acceleration change observable. The change of angular velocity makes the components of the lever arm error that are orthogonal to the direction of the angular velocity observable. The motion of constant angular velocity has no influence on the estimation of the lever arm.

• Earthquakes and Structures
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• 제13권6호
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• pp.551-559
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• 2017

A large number of isolation systems are designed without considering the non-uniform friction distribution in space. In order to analyze the effects of non-uniform friction distribution on the structural response of isolation system, this paper presented a simplified rolling-damper-spring isolation system and analyzed the structural responses under earthquakes. The numerical results indicate that the calculation errors related to the peak values of structural acceleration, relative displacement and residual displacement are sequentially growing because of the ignorance of non-uniform friction distribution. However, the influence rule may be weakened by the spring and damper actions, and the unreasonable spring constant may lead to the sympathetic vibration of isolation system. In the case when the friction variability is large and the damper action is little, the non-uniform friction distribution should be taken into consideration during the calculation process of the peak values of structural acceleration and relative displacement. The non-uniform friction distribution should be taken into full consideration regardless of friction variability degree in calculating the residual displacement of isolation system.

• 설비공학논문집
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• 제21권7호
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• pp.394-401
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• 2009

A manipulator is operated for the motion of mechanical hands or arms. When a cup including liquid inside is shifted by a manipulator, it is important to know how a free surface of the liquid moves. In this study, non dimensional parameters have been found that affect the rise of the free surface in a cup moving with constant acceleration. The non-dimensional parameters are the dimensionless time, the ratio of inertia effect to viscous effect (the Reynolds number), the aspect ratio of the liquid inside the cup and the acceleration ratio (the Froude number). Through this study, the height of the free surface rise in a cup has been predicted and the detailed velocities in the liquid have been examined. Generally, the maximum rise of the free surface is dependent on the Reynolds number and Froude number strongly, but on the aspect ratio weakly. However, the influence of the aspect ratio on the maximum rise of the free surface is not negligible in the range of 10 < Re < 100.

• Computers and Concrete
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• 제28권5호
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• pp.479-486
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• 2021

Reinforced concrete (RC) slabs are exposed to several static and dynamic effects during their period of service. Accordingly, there are many studies focused on the behavior of RC slabs under these effects in the literature. However, impact loading which can be more effective than other loads is not considered in the design phase of RC slabs. This study aims to investigate the dynamic behavior of two-way RC slabs under sudden impact loading. For this purpose, 3 different simply supported slab specimens are manufactured. These specimens are tested under impact loading by using the drop test setup and necessary measurement devices such as accelerometers, dynamic load cell, LVDT and data-logger. Mass and drop height of the hammer are taken constant during experimental study. It is seen that rigidity of the specimens effect experimental results. While acceleration values increase, displacement values decrease as the sizes of the specimens have bigger values. In the numerical part of the study, artificial neural networks (ANN) analysis is utilized. ANN analysis is used to model different physical dynamic processes depending upon the experimental variables. Maximum acceleration and displacement values are predicted by ANN analysis. Experimental and numerical values are compared and it is found out that proposed ANN model has yielded consistent results in the estimation of experimental values of the test specimens.

• 수산해양기술연구
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• 제59권1호
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• pp.65-73
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• 2023

This study analyzed the duct characteristics of hubless rim-driven propeller (RDP) used in underwater robots. In the previous study, flow visualization experiments were performed with an advancing ratio of 0.2 to 1. The vortex at the front of the duct increased in strength while maintaining its size as the advancing ratio decreased. Therefore, it is necessary to study the optimization of the duct shape. Conventional propeller thrusters use acceleration/deceleration ducts to increase their efficiency. However, unlike conventional propellers, it is impossible to apply to airfoil acceleration/deceleration ducts due to the RDP structure. In this study, duct wake flow characteristics, thrust force, and efficiency according to the duct shape of RDP were analyzed using numerical analysis techniques. Duct design is limited and six duct shapes were designed. As a result, an optimized duct shape was designed considering duct wake flow characteristics, thrust force, and efficiency. The shape that the outlet width of the RDP was kept constant until the end of the duct showed higher thrust force and efficiency.

• Journal of Positioning, Navigation, and Timing
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• 제13권3호
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• pp.237-244
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• 2024

An Attitude and Heading Reference System (AHRS) provides the attitude of a vehicle with a constant velocity using an Inertial Measurement Unit (IMU) and a magnetometer. In this case, in order to avoid the disadvantage of a gyroscope, an AHRS using a Gyro-Free IMU (GF-IMU) that is composed of only accelerometers may be considered instead of the gyroscopes. In this paper, a design method of an AHRS using a GF-IMU is proposed. The proposed AHRS consists of roll and pitch calculation, yaw calculation, angular acceleration and angular velocity calculation, attitude calculation, and a Kalman filter. In particular, since the angular velocity cannot be measured from a gyroscope, the angular acceleration is obtained from the accelerometer output, and the angular velocity is calculated by integrating it. In order to show the usefulness of the proposed method, a performance evaluation was carried out. The performance evaluation results show that the attitude estimation performance of the proposed AHRS is similar to that of the conventional AHRS.

• 한국추진공학회지
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• 제20권3호
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• pp.54-62
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• 2016

이단 마이크로 할로우 음극 방전(MHCD) 플라즈마를 사용하는 마이크로 플라즈마 추력기(${\mu}PT$)에 대한 실험 연구가 수행되었다. 40 sccm의 아르곤 유량과 10 W 미만의 전력으로 보다 더 직진성 있고 긴 침투 길이를 가진 배기 플룸을 만드는 정전기적 가속이 이단 MHCD에 의해 발생되었다. 전압-전류 특성에서는 이단 운전 시 두 번째 단의 가속 전압이 일정하게 되는 최적 영역이 있음을 보였다. 추정된 배기 플룸의 길이가 가속 전압으로 추산된 이론적 배출 속도와 비슷한 증가 경향을 보였다. 다중 채널을 가진 마이크로 플라즈마 추력기는 동일한 총 전력량에 대하여 단일 채널 추력기와 비슷한 특성을 보여, 이는 채널 당 허용 전력량을 낮춰 전체 전력량을 높일 수 있음을 의미한다. 아르곤 원자 분광선의 볼츠만 그래프에서 배기 플룸의 평균 전자 여기 온도는 약 2.6 eV(=약 30,170 K)임이 확인되었다.

• 한국환경복원기술학회지
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• 제14권3호
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• pp.157-168
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• 2011

In order to promote efficiency of upstream and downstream migration of fishes, this study has developed a combined fishway of herring-bone bottom baffle type and brush type fishways. The results obtained are as follows : 1. In a channel with constant incline, the velocity of current generally shows a distinct tendency of acceleration as it goes down the stream. But in the hydraulic experiment of herring-bone bottom baffle type fishway, the velocity reached its maximum only at 0.4m/sec, and it tended to be stable without any acceleration. 2. The velocity in the brush type fishway showed a distinct tendency of acceleration as the discharge increased. But its greatest velocity was only 0.3m/sec, and its velocity change according to the discharge increase was only 0.15m/sec at maximum. 3. The maximum velocity in the combined type fishway was less than half of the blast speed of the poorest swimmer, the juvenile eel with 90mm of body length. So any species of fishes are supposed to be able to migrate upstream from the estuary through this combined type fishway. 4. The field experiment of upstream migration showed that the combined type fishway can promote efficiency of upstream and downstream migration of any species of fishes.

• 한국정밀공학회지
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• 제22권5호
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• pp.103-112
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• 2005

This paper presents one-axis high precision scanning system and illustrates the design of modified $X-Y-{\theta}$ stage as a tracker using VCM and commercialized air bearings for it. The scanning system for 100nm resolution is composed of the 3-axis stage and one axis long stroke linear motor stage as a follower. In this study a previous proposed and presented structure of VCM for the fine stage is modified. The tracker has 3 DOF($X-Y-{\theta}$ motions by four VCM actuators which are located on the same plane. So 4 actuating forces are suggested and designed to create least pitch and roll motions. This article will show about the design especially about optimal design. The design focus of this fine stage is to have high acceleration to accomplish high throughput. The optimal design of maximizing acceleration is performed in restrained size. The most sensitive constraint of this optimal design is heat dissipation of coil. There are 5 design variables. Because the relationship between design variables and system parameters are quite complicated, it is very difficult to set design variables manually. Due to it, computer based optimal design procedure using MATLAB is used. Then, this paper also describes the procedures of selecting design variables for the optimal design and a mathematical formulation of the optimization problem. Based on the solution of the optimization problem, the final design of the stage is also presented. The results can be verified by MAXWELL. The designed stage has the acceleration of about 5 $m/s^{2}$ with 40kg total mass including wafer chuck and interferometer mirror. And the temperature of coil is increased $50^{\circ}C$. In addition, the tracker is controlled by high precision controller system with HP interferometer for it and linear scaler for the follower. At that time, the scanning system has high precision resolution about 5nm and scanning resolution about 40nm in 25mm/s constant speed