• International Journal of Fluid Machinery and Systems
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• 제4권2호
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• pp.289-306
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• 2011

In the development of very high head pumped storage projects, one of the critical problems is the strength of pumpturbine runners. Data obtained by stress measurements of high head pump-turbine runners indicated that dynamic stress due to the vibration of runner might be detrimental, possibly to cause fatigue failure, if the runner were designed without proper consideration on its dynamic behaviour. Numerous field stress measurements of runners and model tests conducted with hydrodynamic similarity revealed that the hydraulic excitation force developed by the interference of rotating runner blades with guide vane wakes sometimes would induce such heavy vibration of runner. Theoretical and experimental investigations on both the hydraulic excitation force and the natural frequencies of runner have been conducted to explore this forced vibration problem.

• Journal of Electrical Engineering and Technology
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• 제5권3호
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• pp.462-467
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• 2010

This paper presents the rotor shape optimization of an interior type permanent magnet (IPM) motor for a reduction of vibration and Electromagnetic Interference (EMI). The vibration and EMI in permanent magnet motors is generated by cogging torque ripple, radial force and commutation torque ripple. Consequently, in order to improve vibration and EMI, the optimal notches are put on the rotor pole with an arc shape proposed. The variation of vibration frequency due to the cogging torque and radial force of each model is computed by the finite element method (FEM). From the analysis result and experiment, we confirmed the proposed model has remarkably improved the vibration and EMI.

• 센서학회지
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• 제21권3호
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• pp.192-197
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• 2012

This paper describes the control of the hand fixing system attached to the finger rehabilitation robot for the rehabilitation exercise of patient's fingers. The finger rehabilitation robot is used to exercise the finger rehabilitation, and a patient's hand is safely fixed using the hand fixing system. In this paper, the hand fixing system was controlled with PD gains to fix a palm of the hand, and the characteristic test for the hand fixing system was carried out to sense the fixed hand movement of the front and the rear, that of the left and the right, and that of the upper. It is thought that the hand fixing system could safely fix the hand, and the movement of the fixed hand could be perceived using the five-axis force/moment sensor attached to the hand fixing system.

• Journal of Magnetics
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• 제10권2호
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• pp.58-62
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• 2005

Periodic magnetic nanodot arrays were successfully produced on glass substrates by interference laser lithography and electron beam lithography methods. Magnetic force microscopy (MFM) observation was carried out on fabricated nanodot arrays. MFM tip induced magnetization effects were clearly observed in ferromagnetic elliptical nanodots varying in material and aspect ratio. Fe-Cr dots with a high aspect ratio show reversible switching of the single domain magnetization state. At the same time, Co nanomagnets with a low aspect ratio exhibit tip induced transitions between the single domain and the vortex state of magnetization. The simple nanolithography is potentially an efficient method for fabrication of patterned magnetic arrays.

• 디지털융복합연구
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• 제18권10호
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• pp.225-232
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• 2020

5G 셀룰러 네트워크 하의 언더레이 기법은 매우 전망 있는 자원공유 기법으로써 이 기법은 5G의 서비스 성능향상과 셀룰러 링크와 D2D(Device to Device) 링크 간의 통신 부하를 줄일 수 있는 효과적인 기법이다. 본 논문에서는 gNB(gNodeB)상에서 5G기반의 멀티 클래스 서비스를 수행하는데 있어서 발생하는 자원간섭을 최소화하고, 분석된 간섭의 제어조건에 따라 5G 통신 서비스를 극대화하기 위한 협력적 우선순위 기반의 자원할당 스케줄링 CPRAS(Cooperative Priority-based Resource Allocation Scheduling)기법을 제안한다. 제안된 CPRAS기법은 각 디바이스들에 대한 통신 자원을 최적화하며, 5G의 통신에 필요한 서비스 요청과 네트워크의 현재 상태에 따라 자원할당을 최적화한다. 또한 제안된 기법은 gNB하의 셀룰러 링크와 D2D링크 간의 자원간섭을 최소화함으로써 기가급의 서비스를 보장하는 기능을 제공한다. 시뮬레이션 결과 제안된 기법이 Pure cellular기법과 Force cellular기법에 비해서 더 나은 시스템 성능을 보였으며, 특히 우선순위가 높고 UE(User Equipment)들 간의 협력이 높을수록 자원간섭 제어가 효과적임을 보인다.

• 한국정밀공학회지
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• 제26권5호
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• pp.96-103
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• 2009

This paper describes a humanoid robot's intelligent foot with two six-axis force/moment sensors. The developed humanoid robots didn't get the intelligent feet for walking on uneven surface safely. In order to walk on uneven surface safely, the robot should measure the reaction forces and moments applied on the sales of the feet, and they should be controlled with the measured the forces and moments. In this paper, an intelligent foot for a humanoid robot was developed. First, the body of foot was designed to be rotated the toe and the heel to all directions, second, the six-axis force/moment sensors were manufactured, third, the high-speed controller was manufactured using DSP(digital signal processor), fourth, the humanoid robot's intelligent foot was manufactured using the body of foot, two six-axis force/moment sensors and the high-speed controller, finally, the characteristic test of the intelligent foot was carried out. It is thought that the foot could be used for a humanoid robot.

• 한국정밀공학회지
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• 제32권3호
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• pp.285-292
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• 2015

This paper presents a wireless ground reaction force (GRF) sensing system for ambulatory GRF recording. The system is largely divided into three parts: force sensing modules based on optical sensor, outsole type frame, and embedded system for wireless communication. The force sensing module has advantages of the low height, robustness to the moment interference, and stable response in long term use. In simulation study, the strain and stress properties were examined to satisfy the requirements of the GRF sensing system. Four sensing modules were mounted on the toe, ball, and heel of foot shaped frame, respectively. The GRF signals were extracted using Micrpcontroller unit and transferred to the smart phone via Bluetooth communication. We measured the GRF during the normal walking for the validation of the continuous recording capability. The recorded GRF was comparable to the off the shelf stationary force plate.

• 한국자동차공학회논문집
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• 제12권2호
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• pp.109-116
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• 2004

Bent-axis piston pump have been commonly used in hydraulic systems because of high pressure level, best efficiency, low shear force on pistons and low operating costs. The other side, they have a few demerits like that they have the relatively high number of moving parts and more discharge pressure ripples. Especially, the discharge pressure ripples bring about vibrations and noises in hydraulic system components such as connecting pipes and control valves, so that these deteriorate the stability and accuracy of the systems. Therefore, the hydraulic systems having the bent-axis piston pump require the methods to reduce the discharge pressure ripples. So, the purpose of this paper is to reduce the discharge pressure ripples by the phase interference of pressure wave and to develope the analysis model of the pumps to predict the discharge pressure ripples. In this paper, the analysis model of the bent-axis piston pump was developed using the AMESim software, and the reliability of that was verified by the comparison with the experimental results. The hydraulic pipeline with a parallel line was used as the method to generate the phase interference of pressure wave. the dynamics characteristics of the hydraulic pipeline with a parallel line were analyzed by a transfer matrix method. the usefulness of the phase interference of pressure wave was investigated through the experiment and simulation. The results from the experiment and simulation said that the phase interference of pressure wave by the hydraulic pipeline with a parallel line could reduce the discharge pressure wave of the pump well. The analysis model of the bent-axis piston pump developed in this paper and the method of the phase interference by the hydraulic pipeline with a parallel line are expected to be helpful to achieve the design of the pump and to reduce the discharge pressure wave of the pump effectively.

• Wind and Structures
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• 제26권6호
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• pp.397-413
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• 2018

Excitation mechanism of interference effect between two tall buildings is investigated with wind tunnel experiments. Synchronized building surface pressure and flow field measurements by particle image velocimetry (PIV) are conducted to explore the relationship between the disturbed wind flow field and the consequent wind load modification for twin buildings in tandem. This reveals evident excitation mechanisms for the fluctuating across-wind loads on the buildings. For small distance (X/D < 3) between two buildings, the disturbed flow pattern of impaired vortex shedding is observed and the fluctuating across-wind load on the downstream building decreases. For larger distance ($X/D{\geq}3$), strong correlation between the across-wind load of the downstream building and the oscillation of the wake of the upstream building is found. By further analysis with conditional sampling and phase-averaged techniques, the coherent flow structures in the building gap are clearly observed and the wake oscillation of the upstream building is confirmed to be the reason of the magnified across-wind force on the downstream building. For efficient PIV measurement, the experiments use a square-section high-rise building model with geometry scale smaller than the usual value. Interference factors for all three components of wind loads on the building models being surrounded by another identical building with various configurations are measured and compared with those from previous studies made at large geometry scale. The results support that for interference effect between buildings with sharp corners, the length scale effect plays a minor role provided that the minimum Reynolds number requirement is met.

• 대한치과보철학회지
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• 제29권3호
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• pp.121-140
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• 1991

Fifteen dental college students of Chosun University without the abnormal occlusion, the history and symptom of temporomandibular dysfunction(TMD), and who had all permanent teeth except third molar and the fifteen moderate group and the fifteen severe group classified according to Helkimo's dysfunction index among patients on the basis of the symptom of TMD were selected. The occlusal contact, occlusal force and occlusal interference in eccentric movement was studied and analyzed using T-Scan system. The result were as follows : 1. The TLR centering around midsagittal axis was located at $1.42{\pm}0.82mm$ in control group, $3.36{\pm}1.45mm$ in severe group, and as TMD was heavier, occlusal contact was located at the farther point from midsagittal axis. 2. The PLR from the first contact to the fifth contact centering around midsagittal axis was located at $1.73{\pm}1.78mm$ in control group, $3.36{\pm}1.41mm$ in moderate group, and $5.39{\pm}4.32mm$ in severe group, and as TMD was heavier, occlusal contact was located at the farther point from midsgittal axis. 3. The TFB, PFB, RFB and LFB of occlusal contact centering around incisal axis had no significant difference statistically among control group, moderate group, and severe group, and it was located at first molar. 4.The LF and RF was smaller in TMD group than in control group. 5. The LR moment of occlusal force centering around midsagittal axis was located at $178.51{\pm}139.81N.mm$ in control group, $466.25{\pm}296.47N.mm$ in moderate group, and $749.18{\pm}588.18N.mm$ in severe group. And as TMD was heavier, it was located at the farther point from midsagittal axis. 6. The RL and LL of occlusal force centering around incisal axis had not-significance statistically among control group, moderate group, and severe group, and it was at the first molar. 7. The number of occlusal interference of the eccentric movement was increased in the patients of TMD.