• Journal of Internet Computing and Services
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• v.21 no.2
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• pp.27-37
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• 2020

Recently, big data is rapidly emerging as a core technology in the 4th industrial revolution. Further, the utilization and the demand of drones are continuously increasing with the development of the 4th industrial revolution. However, as the drones usage increases, the risk of drones falling increases. Drones always have a risk of being able to fall easily even with small problems due to its simple structure. In this paper, in order to predict the risk of drone fall and to prevent the fall, ESC (Electronic Speed Control) is attached integrally with the drone's driving motor and the acceleration sensor is stored to collect the vibration data in real time. By processing and monitoring the data in real time and analyzing the data through big data obtained in such a situation using a Fast Fourier Transform (FFT) algorithm, we proposed a prediction system that minimizes the risk of drone fall by analyzing big data collected from drones.

• Wind and Structures
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• v.23 no.2
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• pp.127-142
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• 2016

Aerodynamic effects, such as drag force and flow-induced vibration (FIV), on civil engineering structures can be minimized by optimally modifying the structure shape. This work investigates the turbulent wake of a square prism with its faces modified into a sinusoidal wave along the spanwise direction using three-dimensional large eddy simulation (LES) and particle image velocimetry (PIV) techniques at Reynolds number $Re_{Dm}$ = 16,500-22,000, based on the nominal width ($D_m$) of the prism and free-stream velocity ($U_{\infty}$). Two arrangements are considered: (i) the top and bottom faces of the prism are shaped into the sinusoidal waves (termed as WSP-A), and (ii) the front and rear faces are modified into the sinusoidal waves (WSP-B). The sinusoidal waves have a wavelength of $6D_m$ and an amplitude of $0.15D_m$. It has been found that the wavy faces lead to more three-dimensional free shear layers in the near wake than the flat faces (smooth square prism). As a result, the roll-up of shear layers is postponed. Furthermore, the near-wake vortical structures exhibit dominant periodic variations along the spanwise direction; the minimum (i.e., saddle) and maximum (i.e., node) cross-sections of the modified prisms have narrow and wide wakes, respectively. The wake recirculation bubble of the modified prism is wider and longer, compared with its smooth counterpart, thus resulting in a significant drag reduction and fluctuating lift suppression (up to 8.7% and 78.2%, respectively, for the case of WSP-A). Multiple dominant frequencies of vortex shedding, which are distinct from that of the smooth prism, are detected in the near wake of the wavy prisms. The present study may shed light on the understanding of the underlying physical mechanisms of FIV control, in terms of passive modification of the bluff-body shape.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.40 no.11
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• pp.963-970
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• 2016

This research deals with design and performance validation of eco-pedals that generate tactile pedal force to guide fuel saving driving behavior. For eco-pedal control logic, allowable fuel consumption at given driving speed is calculated based on pre-defined "allowable acceleration", and if the actual fuel consumption exceeds the allowable fuel consumption, then pedal force is activated. Pedal force should be recognizable to driver while not causing unpleasantness, and should not interfere with normal operation of pedal. Reaction forces that increase pedal stiffness abruptly, such as step and ramp shape, turn out to be not suitable due to pedal overshoot after release of reaction force. With this regards, vibration type reaction force is adopted, and its optimal frequency, magnitude and duration is determined through subjective evaluation with consideration to effect to fuel efficiency. Though highway and city driving test, it is demonstrated that fuel efficiency increase of 13% for highway and 15% for city is achieved.

• Journal of the Korean Institute of Intelligent Systems
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• v.20 no.1
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• pp.88-93
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• 2010

In this paper, an edge detecting sensor using ultrasonic detection module is developed which will be used for areas of industrial applications such as plastic film winding system, cloth winding system, paper roll industry, etc. The developed sensor have properties that more exactly detect the edge line, that less affected by environmental noise, and that it produced more stable measurement output. The mass of the winding object is dominantly affect the dynamics of the system and it could produce undesirable result of the system such as stability of the closed-loop system and accuracy of edge-line-following-control(ELFC) objective. Also, there exist sensor noise due to the mechanical vibration or other environmental effect. These noise also degrade the efficiency of control system. In order to compensate these problems, this paper present a fuzzy PI/PID edge-line-controller, and which is designed and implemented.

• Journal of Korean Academy of Nursing
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• v.30 no.2
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• pp.488-497
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• 2000

The purpose of this study was to explore the effect of a postpartum massage program on stress response in the Cesarean section mothers. The study focused on evaluating the effect of postpartum massage program on mood, anxiety, skin temperature and concentration of saliva and breast milk immunoglobulin A in the Cesarean section mothers. This study was designed as a nonequivalent control group pretest-posttest quasi-experimental study. Twenty-eight Cesarean section mothers were selected as experimental group, whereas twenty- seven were control group. The postpartum massage program consisted of 20 minutes of warm-up, massage and ending phases and used once a day. During each program, there were 4 minutes of warm-up, 14 minutes of massage on back, axillary and breasts, and 2 minutes of ending. Massage were used for the experimental group by the same investigator 20 times per minute. The massage technique used were efflurage, petrissage, accupressure, kneading and vibration. Skin temperature was monitored with YSI Tele-thermometer(Simpson electric Co., USA) before and after massage program. The concentration of immunoglobulin A in saliva and breast milk was analyzed by immunoturbididimeter assay(Cobas INTEGRA, Swiss) before and after massage program. Also at this time mood and anxiety were measured by self-report. The data were analyzed using SPSS version 7.5 and hypothesis was tested with ANCOVA analysis and Pearson coefficient correlation. The results were as follows : 1) Score of mood increased significantly after use of postpartum massage program. 2) Level of anxiety decreased significantly after use of postpartum massage program. 3) Skin temperature increased significantly after use of postpartum massage program. 4) Concentration of saliva immunoglobulin A increased significantly after use of postpartum massage program. 5) Concentration of breast milk immunoglobulin A did not change significantly after use of postpartum massage program. 6) After use of postpartum massage program, there was significant correlation between psychological stress response and physiological stress response.The results suggest that postpartum massage program can be effective nursing intervention to reduce stress response in the postpartum mothers under stress.

• The Transactions of the Korean Institute of Power Electronics
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• v.9 no.2
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• pp.142-149
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• 2004

PMLSM(Permanent Magnet linear Synchronous Motor) has widely applied to industrial automations, machine tools and semiconductor equipments due to the merit on the reduction of noise, vibration and the superior dynamic characteristics in comparison to the conventional method, which uses mechanical transfer equipments. Especially, in the case of applying to Z-axis operation structure, control system needs the method of an initial angle setting and the improvement of up/down operation characteristics. This paper proposes an initial angle setting algorithm and a variable gain schedule using real speed and moving direction to improve up/down operation characteristics. The effectiveness of proposed algorithms Is demonstrated by comparing to a conventional gain system via 4-point absolute positions profile with each velocity, acceleration and deceleration.

• Proceedings of the Korean Geotechical Society Conference
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• 2009.03a
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• pp.987-992
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• 2009

Continuous Compaction Control is a new cutting edge technique in United States, Japan and European construction market that uses an instrumented compactor to measure soil stiffness in real time usually with vehicle tracking system such as Global Navigation Satellite System (GNSS). In this study, soil stiffness was evaluated by adapting Fourier transforming technique with acceleration data obtained from accelerometers used as a continuous compaction control instrument. The soil stiffness obtained by accelerometers gave analogous results with reference results such as dry density, elastic modulus obtained from Geogauge and Light falling deflectometer.

• Journal of the Korean Ceramic Society
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• v.43 no.4 s.287
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• pp.259-263
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• 2006

The applicability of UPT (Ultrasound Pulse Thermography) for real-time defect detection of the ceramic heating plate is described. The ceramic heating plate with superior insulation and high radiation is used to control the water temperature in underwater environment. The underwater temperature control system can be damaged owing to the short circuit, which resulted from the defect of the ceramic heating plate. A high power ultrasonic energy with pulse duration of 280 ms was injected into the ceramic heating plate in the vertical direction. The ultrasound excited vibration energy sent into the component propagate inside the sample until they were converted to the heat in the vicinity of the defect. Therefore, an injection of the ultrasound pulse wave which results in heat generation, turns the defect into a local thermal wave transmitter. Its local emission is monitored and recorded via the thermal infrared camera at the surface which is processed by image recording system. Measurements were Performed on 4 kinds of samples, composed of 3 intact plates and the defect plate. The observed thermal image revealed two area of crack in the defective ceramic heating plate.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2015.10a
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• pp.484-487
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• 2015

This paper describes a dual-input battery charger with MPPT control using photovoltaic and piezoelectric energy. Each energy is harvested from photovoltaic cells and piezoelectric cells and is stored to each capacitor. The battery voltage is boosted by charger block and two energy sources are used as input to charge battery capacitor. A DC-DC boost converter is designed to boost the battery voltage, and inductor sharing technique is employed such that only one inductor is required. The time division ratio for piezoelectric cell and photovoltaic cell is set to 8:1. The proposed circuit is designed in a 0.35um CMOS process technology. The condition of battery capacitor is managed by battery management block and the battery voltage can be boosted up to 3V. The maximum efficiency of the designed entire system is 88.56%, and the chip area including pads is $1230um{\times}1330um$.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.24 no.4
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• pp.457-462
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• 2011

In this study, a simplified design procedure for friction dampers of a multi-story structure in order to reduce seismic response is proposed. To get insight for control effect of the structure with friction dampers is difficult, because of a nonlinear characteristic by a friction damper. Since a control force of a friction damper is influenced by coupling velocity between floors, adjoining modes are coupled. Thus structural response are derived by assuming steady-state response in resonance. As it is impossible that an exact solution is obtained for seismic load, first, a closed form solution can be achieved under harmonic vibration. Second, to convert a three-story building into a single-degree-of-freedom(SDOF) structure, modal analysis is performed. Third, an equivalent damping ratio is derived with utilizing closed form solution. And response reducing factor is proposed by it. Finally, friction force of a damper is designed for using response reducing factor, and then designed dampers are verified for seven seismic data. The nonlinear analysis results confirm the validity of the proposed procedure.