• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.42 no.1
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• pp.82-89
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• 2014

This paper discusses the methods for reducing the sampling time quantization errors of the body dither type ring laser gyroscope. A ring laser gyroscope has the angle quantization error which is generated by the frequency counting method of the laser beat signal and sampling time quantization error which is generated by the demodulation method for eliminating the body dithering in which the sampling periods are fitted to the dither periods. Generally, because the dither periods are longer than the calculation periods of the inertial navigation system, vehicle navigation errors are produced by long time attitude update missing during the vehicle move with a high dynamical motion. In this paper, the double demodulation method is proposed for reducing the sampling time quantization error and its effects under the dynamic situation are confirmed by simulation.

• The KIPS Transactions:PartC
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• v.16C no.5
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• pp.615-620
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• 2009

Nowadays, wireless infrastructures such as sensor networks are widely used in many different areas. In case of sensor networks, the wirelessly connected sensors can execute different kind of tasks in a diversity of environments, and one of the most important parameter for a successful execution of such tasks is the location information of each node. As to localization problems in WSNs, there are ToA (Timer of Arrival), RSS (Received Signal Strength), AoA (Angle of Arrival), etc. In this paper, we propose a modification of existing ToA and RSS based methods, adding a weighted average scheme to measure more precisely the distance between nodes. The comparison experiments with the traditional ToA method show that the average error value of proposed method is reduced by 0.1 cm in indoor environment ($5m{\times}7m$) and 0.6cm in outdoor environment ($10{\times}10m$).

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.44 no.4
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• pp.88-94
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• 2007

This paper deals with the performance analysis of 3-dimensional array antenna by DOA estimation and beamforming in GPS receiver for performance improvement by interference elimination. The array antenna in GPS receiver can improve the system performance by estimating DOA of arriving signal direction, making the main beam for desired direction and elimate the jammer signal by nulling while keeping the GPS signal direction by spatial filtering. In this paper, we propose five types of 3-dimensional array antenna and analyze the estimation error via MUSIC algorithm which is used for the estimation of DOA of arrived signal and beamforming performance. In analyzing DOA performance, we measure DOA estimation error, while in analyzing beamformig performance, we measure BER. In beamforming performance analyzing, we use various jammer power and the existence of GPS signal and angle spread. By performing through the computer simulation, Curved (B) 7-element antenna in proposed 3-dimensional array antenna exhibits the superior performance in the DOA estimation, estimation error, BER characteristic and angle spread compared to the rest four array antenna types.

• Composites Research
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• v.28 no.6
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• pp.383-388
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• 2015

Ionic Polymer-Metal Composite (IPMC) consisting of soft membrane plated by platinum electrode layers on both surfaces generates electric energy when subjected to various mechanical stimuli. The paper proposes a circuit model that describes the physical composition of IPMC to predict the voltage generation characteristic corresponding to bending motion. The parameter values in the model are identified to minimize the RMS error between the real and simulated outputs. Following the design of IPMC circuit model, the state observer of the model is designed by using pole placement technique which improves the model accuracy. State observer design technique is also applied to find the inverse model which estimates the input bending angles from the output voltage data. The results show that the inverse model estimates input bending angles fairly well enough for the further applications of IPMC not only as an energy harvester but also as a bending sensor.

• Journal of the Korea Society of Computer and Information
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• v.16 no.7
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• pp.25-34
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• 2011

In this paper, we propose a new golf putting training system which we call "X-Putt". X-Putt analyzes putting strokes by measuring putter face angle and path. To do this, we improved the sonar-based localization scheme used by previous localization techniques. As a result, X-Putt can measure putter's location within the error range, ${\pm}0.9cm$ and putter face angle within ${\pm}1.5^{\circ}$. Additionally, we built an user application that has an easy-to-use interface for analyzing the strokes after training.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.15 no.2
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• pp.97-104
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• 2001

The effects of the position of potential probe on the measurements of the ground resistance in the fa11-of-potential method are described. The ground resistance is theoretically calculated by applying the 61.8[%] rule, and then the potential probe is located on the straight line between the grounding electrode to be measured and the current probe. However, sometimes the grounding electrode to be measured and the measuring potential and current probes in on-site test might not be arranged on the straight line with adequate distance because there are building, roadblock construction and other establishments. Provided that the grounding electrode to be measured and the measuring potential probes are out of position on the straight line, the measurement of the ground resistance classically falls into an error and the measured ground resistance should be corrected. In this work, measurements were focused on the grounding electrode system made by the ground rods of 2.4 m long. The measuring error was increased with increasing the angle which is made by the 3-points of the grounding electrode to be measured, the potential anti current probes, and it was a negative. That is, all of the measured ground resistances ware less than the true ground resistance.

• Korean Journal of Optics and Photonics
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• v.13 no.5
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• pp.384-389
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• 2002

A new idea of the wavelength locking module for DWDM application was investigated in the present research. Only one etalon photo-diode is generally used in the internal/external wavelength locking system. For the internal wavelength locking module with 50 GHz applications, an algle tuning method of the etalon commonly applied. However, the alignment process of the etalon with the angle tuning method is limited because the lock performance is extremely sensitive accoriding to the change of the tilting angle. In an optical viewpoint, the alignment tolerance of the locker module with the etalon PD array block was good, and the precise tuning of the wavelength was possible. The characteristics of free spectral range (FSR) and peak shift of wavelength according to the tilting angle with the locker module was investigated. For the present module, the optimized initial tilting angle was experimentally obtained.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.22 no.2
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• pp.134-138
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• 2021

Various types of precision plastic thin films are used widely in high-performance displays, such as smartphones. For plastic thin-films manufactured by the Roll-to-Roll process, the film thickness must be measured and managed while moving. In the Roll-to-Roll process, wrinkles are generated when tension is applied to the film, which causes an inclination on the optical axis of the thickness gauge, resulting in a loss of accuracy. Therefore, this study attempted to develop an optical interference tomography measurement system. In this study, the tilt angle of the film was measured to correct the measurement value error in the thickness gauge caused by the tilt of the film. The system was constructed so that the laser was irradiated on the tilted film, and the laser reflected from the film was formed on the PSD. The relationship between the tilt angle of the film and the output value of the PSD was obtained experimentally. Using this, a device to measure the tilt angle of the film was constructed, and angle measurements were taken at a speed of 250,000Hz.

• Journal of Dental Rehabilitation and Applied Science
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• v.24 no.1
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• pp.57-65
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• 2008

Purpose: Misfit of implant components was very important in terms of prosthodontics. they has been linked to prosthetic complications such as screw loosening and fracture. Although there are many results about rotational freedom or machining tolerance between fixture and abutments, the data about domestic implant systems are lacking. The aim of this in vitro study was to evaluate the rotational freedom of domestic external and internal connection implant systems between their fixtures/anlaogs and abutments comparing imported systems. Materials and Methods: Rotational freedom between abutments and fixtures/analogs was investigated by using digitalized rotational angle measuring device. (1) 1 domestic external connection system(Neobiotec) and 2 imported external connection systems(Nobel Biocare, Anthorgyr), (2) 1 domestic internal connection system(Dentium) and 4 imported external connection systems(Nobel Biocare, Anthorgyr, Straumann, Frident Dentsply), and (3) 1 domestic zirconia external connection abutment(ZirAce) were evaluated. Each group has 3 samples. Mean values for each group were analyzed. Results: The differences relative to rotational freedom between domestic and imported implant systems were observed but domestic external connection implant system showed about 2.67 degrees(in case of fixture) and internal connection system showed about 4.3 degrees(in case of fixture). Domestic zirconia abutment showed less than 3 degrees of rotational freedom in a situation where the abutment was connected to an implant fixture egardless of domestic or imported systems. Conclusion: Newly developed digitalized rotational angle measuring device has high measuring resolution. The rotational freedom of domestic implant systems were similar to imported implant systems.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.14 no.4
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• pp.421-430
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• 2003

In this paper, we propose a method to consider SAR(Specific Absorption Rate) at beginning stage of handsets development. First, simulation was carried out with changing folding angle from 150$^{\circ}$to 142$^{\circ}$. Simulation results show that SAR value is decreased with decreasing the folding angle. When folding angle is 142$^{\circ}$, error between simulation and measurement results is about 3.95 %. Second, we made some experiments with EMI (Electromagnetic Interference) paint, and its results show that different pattern of EMI paint have different SAR values. After removing EMI paint at the lower part of antenna feeding point, we got the decrease efficiency of 15.46 % for SAR value. When we applied zigzag painting pattern, we got the highest SAR decrease efficiency.