• Journal of the Ergonomics Society of Korea
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• v.26 no.1
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• pp.29-37
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• 2007

This study was performed to evaluate the characteristics of transmitted vibration to hand-arm system under different work posture while operating a light-weighted powered hand grinder. For the experiment, 8 different types of wrist posture (natural, unlar-flexion, radual-flexion, flexion, extension, complex posture, and etc.) and 3 types of feed force (20[N], 50[N], 70[N]) were considered. 10 male subjects were employed to polish metal plate with a hand grinder. All of them were normal and healthy with no history and symptom of the work related musculoskeletal disorders in the dominant hand. Vibration acceleration data were recorded with sampling rate, 2048[Hz]. In addition, unweighted overall R.M.S. acceleration at the tool and wrist, and transmissibility between them were used to evaluate factors from the recorded tri-axial vibration acceleration. The results indicate that transmissibility of natural wrist posture was significantly higher than others. In addition, as the feed force becomes larger, the vibration was transmitted in large quantities to hand-arm system through radius.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.56 no.7
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• pp.1331-1338
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• 2007

A new method for detecting and eliminating the Electrocardiogram(ECG) artifact from the scalp Electroencephalogram(EEG) is proposed. Based on the single channel EEG, the proposed method consists of 4 procedures: emphasizing the R-wave of ECG artifact from EEG using the least squares acceleration(LSA) filter, detecting the R-wave from the LSA filtered EEG using the phase space method and R-R interval, generating the delayed impulse synchronized to the R-wave and elimination of the ECG artifacts based on the adaptive digital filter using the impulse and raw EEG. The performance of the proposed method was evaluated in the two separating parts of R-wave detection and, ECG estimation and elimination from EEG. In the R-wave detection, the proposed method showed the mean error rate of 6.285(%). In the ECG estimation and elimination using simulated and/or real EEG recordings, we found that the ECG artifacts were successfully estimated and eliminated in comparison with the conventional multi-channel techniques, in which independent component analysis and ensemble average method are used. From this we can conclude that the proposed method is useful for the detecting and eliminating the ECG artifact from single channel EEG and simple for ambulatory/portable EEG monitoring system.

• Structural Engineering and Mechanics
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• v.65 no.3
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• pp.349-357
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• 2018

An extensive research was undertaken to study the vibration serviceability of a long-span and light-weight floor subjected to human loading experimentally and numerically. Specifically, heel-drop test was first conducted to capture the floor's natural frequencies and damping ratios, followed by jumping and running tests to obtain the acceleration responses. In addition, numerical simulations considering walking excitation were performed to further evaluate the vibration performance of a multi-panel floor under different loading cases and walking rates. The floor is found to have a high frequency (11.67 Hz) and a low damping ratio (2.32%). The comparison of the test results with the published data from the 1997 AISC Design Guide 11 indicates that the floor exhibits satisfactory vibration perceptibility overall. The study results show that the peak acceleration is affected by the walking path, walking rate, and adjacent structure. A simpler loading case may be considered in design in place of a more complex one.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.39 no.9
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• pp.883-888
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• 2011

The UAV tracking antenna system based on GPS has a characteristic of update of position information which can occurs a position error. To reduce the position error, UAV tracking antenna system separates period of GPS update-rate and predicts the position of UAV using divided time points. These process improves the tracking performance of UAV. To predict the position of UAV by divided time points, we used a linear kalman filter based on the velocity and acceleration. Using this system, we measured velocity and acceleration according to the change of position. Finally, we can predict the change of position on divided time points.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.5
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• pp.3573-3578
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• 2015

Transition curves are located between curve and straight section in railway. These transition curves are vulnerable to the ride comfort of passengers and safety of a vehicle because lateral acceleration, lateral jerk and roll velocity increase as curvature and cant change along the transition curves. In this paper, ride comfort on the transition curve was calculated on the basis of lateral acceleration and roll velocity measurements. The evaluation of ride comfort was conducted according to the methodology specified in European Standard. The distribution characteristics of the comfort index were investigated for the korean conventional line from the evaluation results. The influence of the curve radius and the vehicle speed on the ride comfort index was also investigated. Finally, the relationship between ride comfort and the rate of cant changes on transition curves was analyzed.

• Nuclear Engineering and Technology
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• v.53 no.8
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• pp.2728-2745
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• 2021

The purpose of this study is to reduce seismic responses of an actual nuclear piping system using a tuned mass damper (TMD) device. A numerical piping model was developed and validated based on shaking table test results with actual nuclear piping. A TMD for nuclear piping was newly devised in this work. A TMD shape design suitable for nuclear piping systems was conducted, and its operating performance was verified after manufacturing. The response reduction performance of the developed TMD under earthquake loading on actual piping was investigated. Results confirmed that, on average, seismic response reduction rates of 34% in the maximum acceleration response, 41% in the root mean square acceleration response, and 57% in the spectral acceleration response were shown through the TMD application. This developed TMD operated successfully within the seismic response reduction rate of existing TMD optimum design values. Therefore, the developed TMD and dynamic interpretation help improve the nuclear piping's seismic performance.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.27 no.6
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• pp.1405-1417
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• 2017

Researches that apply the acceleration signal due to user's gait measured at the wearable device to the authentication technology are being introduced recently. The gait acceleration signal based authentication technologies introduced so far have assumed that an attacker can obtain a user's gait acceleration signal only by attaching accelerometer directly to user's body. And the practical attack method for gait acceleration signal based authentication technology is mimic attack and it uses a person whose physical condition is similar to the victim or identifies the gait characteristics through the video of the gait of the victim. However, mimic attack is not effective and attack success rate is also very low, so it is not considered a serious threat. In this paper, we propose Video Gait attack as a new attack method for gait acceleration signal based authentication technology. It is possible to know the position of the wearable device from the user's gait video signal and generate a signal that is very similar to the accelerometer's signal using dynamic equation. We compare the user's gait acceleration signal and the signal that is calculated from video of user's gait and dynamic equation with experiment data collected from eight subjects.

• Transactions of the Korean Society of Automotive Engineers
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• v.8 no.4
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• pp.121-129
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• 2000

this paper develops a computational model for the turning maneuver analysis of a cabover type heavy truck. The model having 42 degree-of-freedom is developed using ADAMS. Leaf springs used in the front and rear suspension systems are modeled by dividing it three links and joining them with joints. Force and displacement relationship showing nonlinear hysteric characteristics of the leaf spring is measured and modeled with an exponential function. A velocity and force relationship of a shock absorber is measured and modeled with a spline function. And a stabilizer bar is modeled using ADAMS beam element to consider a twisting and bending effect. To verify the developed model an actual vehicle test is performed in the double lane change course with 50kph and 60kph vehicle velocity. In the actual vehicle test lateral acceleration roll angle and yaw rate are measured, The tendency and peak-to-peak values of the actual vehicle test and simultion results are compared each other.

• Transactions of the Korean Society of Automotive Engineers
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• v.9 no.5
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• pp.157-164
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• 2001

This paper performs static and dynamic tests of a multi-leaf spring and a tapered leaf spring to investigate their hysteretic characteristics. In the static test, trapezoidal input load is applied with 0.1Hz excitation frequency and with zero initial loading conditions. In the dynamic test, sinusoidal input load is applied with five excitation amplitudes and three excitation frequencies. In these tests, static and dynamic hysteretic characteristics of the multi-leaf spring and the tapered leaf spring are compared, and, the effects of excitation amplitudes and frequencies on dynamic spring rate are also shown. In this paper, actual vehicle tests are performed to study the effects of hysteretic characteristics of the large-sized truck's handling performance. The multi-leaf spring or the tapered leaf spring is used in the front suspension. The actual vehicle test is performed in a double lane change track with three velocities. Lateral acceleration, yaw rate and roll angle are measured using a gyro-meter located at the mass center of the cab. The test results showed that a large-sized truck with a tapered leaf spring needs to have an additional apparatus such as roll stabilizer bar to increase the roll stabilizer due to hysteretic characteristics.

• Transactions of the Korean Society of Automotive Engineers
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• v.11 no.6
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• pp.197-204
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• 2003

This paper develops a computer model for estimating the handling of a cabover type large-sized truck. The truck is composed of front and rear suspension systems, a frame, a cab, and ten tires. The computer model is developed using ADAMS. A shock absorber, a rubber bush, and a leaf spring aunt a lot on the dynamic characteristic of the vehicle. Their stiffness and damping coefficient are measured and used as input data of the computer model. Leaf springs in the front and rear suspension systems are modeled by dividing them three links and joining them with joints. To improve the reliability of the developed computer model, the frame is considered as a flexible body. Thus, the frame is modeled by finite elements using MSC/PATRAN. A mode analysis is performed with the frame model using MSC/NASTRAN in order to link the frame model to the computer model. To verify the reliability of the developed computer model, a double lane change test is performed with an actual vehicle. In the double lane change, lateral acceleration, yaw rate, and roll angle are measured. Those test results are compared with the simulation results.