• Journal of the Korean Society of Hazard Mitigation
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• v.5 no.1 s.16
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• pp.45-53
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• 2005

Scour plays a principal role in maintaining stability and durability of bridges. Especially, in case of severe flood events, flow rate getting increase in a short time, scour can impede the functioning of bridges to the extent that they must be taken out of operation, and even can imperil their stability and structural integrity. In Korea, about 100 bridges were collapsed or damaged every you. Sufficient field investigation, however, was not made and, therefore, no adequate countermeasure for scouring is available. In this study, literature on scour-protection methods are reviewed and data on countermeasures of scouring which were collected through field investigation in central region of Korea are analyzed.

• International Journal of Highway Engineering
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• v.19 no.5
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• pp.97-106
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• 2017

PURPOSES: This study aims to evaluate the effects of vehicle dynamic behaviors on ride quality. METHODS : Simulation and field test were conducted to analyze the behavior of a driving vehicle. The simulation program CarSIM was applied and an INS (Inertial Navigation System) was used for field experiments. A small simulator was developed to simulate vehicle behavior such as roll, pitch, and bounce. The panels evaluated the ride quality in five stages from "very satisfied"to "very dissatisfied."Experiments were conducted on a total of 144 cases of vehicle behavior combinations. RESULTS :In both simulation and field tests, pitch is the largest and yaw the smallest. Especially in the field test, the amount of yaw is very low, about 7% of pitch and 18% of roll. The sensitive and extensive analysis conducted related ride quality with changing the frequency and amplitude. It was found that the most sensitive frequency range is 8 Hz across all amplitudes. Moreover, the combination of the roll and bounce was most sensitive to the ride quality at the low-frequency range. CONCLUSIONS : This result show that the vertical vehicle behavior (bounce) as well as the rotational behavior (roll and pitch) are highly correlated with ride quality. Therefore, it is expected that a more reasonable roughness index can be developed through a combination of vertical and rotational vehicle behavior.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.16 no.10
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• pp.914-922
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• 2003

The FFS (fringe-field switching) mode was known to exhibit both a wide viewing angle and high transmittance, especially when using a liquid crystal with negative dielectric anisotropy. We have studied cell gap-dependent electrode-optic characteristics of the FFS mode using the LC with negative dielectric anisotropy. In case of a small cell gap of 2 ${\mu}$m, the transmittance at the center of pixel and common electrodes is relatively low because effect of surface anchoring that holds the LC to the initial state is larger than that in a large cell gap of 4 .urn such that the LCs in those regions cannot rotate enough. However, in case of a large cell gap of 4 .urn, the effect of surface anchoring becomes relatively small so that the LCs at the center of pixel and common electrode can be twisted enough by applied voltage, giving rise to high transmittance. Therefore, we can conclude that the light efficiency is dependent on the cell gap.

• Proceedings of the KIEE Conference
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• 1998.07a
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• pp.107-109
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• 1998

This paper presents mechanical analysis of gas turbine generator (113MVA, $3{\phi}$, 2P, 0.9PF, F class, 3600rpm, 60Hz, 13.8kV, 4.72kA, Air-Cooling) field coil deformation. Rotor end coil deformation is only appeared on turbine end but collector end coil is normal. Expansion direction of end coil is tangential not axial. Deformation appears more severe at top turn. Retaining ling is expanded by centrifugal force of coil and itself. In case friction coefficient between coil top surface and retaining ring insulation inner surface is small, coil end length ${\ell}$ does not change. However, in case friction coefficient big condition, coil end is expanded ${\Delta}{\ell}$ due to start and stop. Deformation is assumed about 30mm by watching photograph inner surface of retaining ring is coated by Teflon at manufacturing condition. Usually Teflon coating insulation surface is small friction coefficient. It's value 0.08${\sim}$0.15. However it's value exceeds more than 0.297. Since top turn deformation appears. The distortion and subsequent failure have occurred because of the lack of a sufficient slip-plane between the top field coil conductors and the inside surface of the retaining ring insulation on the turbine end of the field-winding.

• ETRI Journal
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• v.21 no.1
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• pp.28-39
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• 1999

Koblitz has suggested to use "anomalous" elliptic curves defined over ${\mathbb{F}}_2$, which are non-supersingular and allow or efficient multiplication of a point by and integer, For these curves, Meier and Staffelbach gave a method to find a polynomial of the Frobenius map corresponding to a given multiplier. Muller generalized their method to arbitrary non-supersingular elliptic curves defined over a small field of characteristic 2. in this paper, we propose an algorithm to speed up scalar multiplication on an elliptic curve defined over a small field. The proposed algorithm uses the same field. The proposed algorithm uses the same technique as Muller's to get an expansion by the Frobenius map, but its expansion length is half of Muller's due to the reduction step (Algorithm 1). Also, it uses a more efficient algorithm (Algorithm 3) to perform multiplication using the Frobenius expansion. Consequently, the proposed algorithm is two times faster than Muller's. Moreover, it can be applied to an elliptic curve defined over a finite field with odd characteristic and does not require any precomputation or additional memory.

• Journal of Sensor Science and Technology
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• v.32 no.4
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• pp.232-237
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• 2023

This paper presents a system for estimating the position of a magnet using a magnetic sensor. An algorithm is presented to analyze the waveform and output voltage values of the magnetic field generated at each position when the magnet moves and to estimate the position of the magnet based on the analyzed data. Here, the magnet is sufficiently small to be inserted into a blood vessel and has a micro-magnetic field of hundreds of nanoteslas owing to the small size and shape of the guide wire. In this study, a highly sensitive magneto-impedance (MI) sensor was used to detect these micro-magnetic fields. Nine MI sensors were arranged in a 3×3 configuration to detect a magnetic field that changes according to the position of the magnet through the MI sensor, and the voltage value output was polynomially regressed to specify a position value for each voltage value. The accuracy was confirmed by comparing the actual position value with the estimated position value by expanding it from a 1D straight line to a 3D space. Additionally, we could estimate the position of the magnet within a 3% error.

• Journal of the Society of Naval Architects of Korea
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• v.53 no.5
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• pp.353-361
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• 2016

Recently, the small shipyard companies have difficulties that causes by depression of shipbuilding industry. The small shipyard companies need some strategies to overcome the slump in shipbuilding industry field. In this paper, we conduct the survey for present condition diagnosis of small shipyard companies, and analyze the production process based on Information Strategy Planning(ISP) method. When analyze based on ISP, we apply IDEF0 and LOVC technique to analyze the production process of small shipyard companies. Also we conduct the gap analysis between the analyzed present condition and the requirements of improvement. Therefore, the most important result of the analysis is to establish a system for enterprise planning and management, which customized for small shipyard companies, with satisfying economic feasibility and usability.

• Proceedings of the Korean Magnestics Society Conference
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• 2009.12a
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• pp.217-219
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• 2009

A GMI magnetic field sensor working based on time-coded principle has been investigated and designed. The laboratory model has been constructed and tested carefully, demonstrating the sensitivity of $3\;{\mu}s/{\mu}T$ in the field range of ${\pm}100\;{\mu}T$. An amorphous thin wire, $100\;{\mu}m$ in diameter ${\times}50\;mm$ in length, was chosen to be sensing element which was fit into a small field modulation coil of 60 mm in length. The sensor is working based on a time-coded principle that, with the magnetic field modulation was chosen in range of hundreds of Hz, the change in time interval of two adjacent GMI peaks relating to external DC magnetic field is proportional to the intensity of the external field to be measured. This mechanism has made a great improvement to the linearity of the sensor.

• Proceedings of the Korea Electromagnetic Engineering Society Conference
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• 2003.11a
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• pp.13-17
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• 2003

In this paper, the design parameters for the magnetic field source at extremely low frequency are proposed. This facility can be used for in vivo experiments with small animals to investigate biological response to the driving magnetic fields. In case that the exposed animals are motionless, the animals may be affected by the directivity of driving field. To avoid this effect, a 2-axis ELF magnetic field driving apparatus was designed, The optimum location and number of turns of each coil were obtained by numerical analysis. Applying these data to the MATLAB code (for computation), the magnetic field distribution was obtained. The calculation result for a well-designed facility showed that the space in which the amplitude of the magnetic field lies within the 95% of the magnetic field distribution was more than 60% of each axis length.

• Journal of the Korean Society of Safety
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• v.14 no.2
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• pp.140-147
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• 1999

Currently, the consumer pattern is directed to small quantity and high variety these days. World market is led by technological innovations and changes rapidly. To survive in this environment, the raising of small and medium enterprises is highly desirable. In the context of nationwide restructuring, competitive medium and small industries which are in good financial status should lead the nation's economy. But general ignorance of the safety issues could lead to a miss management of this industry in this field. In this study, actual condition and improvement of safety management are as follows; We have to 1) find out the factors which endangers this industry, and set a proper guideline for safety management. 2) encourage safety management of these industries by themselves, and advertise and provide technical support for using PC and internet. 3) set a higher standard of safety issue when accrediting a prospective medium and small industry, and have a firm control of this issue once accredited. 4) supply more governmental financial aids to terms of safety issues for medium and small industries.