• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1999.05a
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• pp.169-172
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• 1999

Recently, the wavelet transform has been a new and powerful tool for signal processing. It is more suitable specially for the feature extraction and detection of non-stationary signals than traditional methods such as, the Fourier Transform(FT), the Fast Fourier Transform(FFT) and the Least Square Method etc. because of the characteristic of the multi-scale analysis and time-frequency domain localization. The wavelet transform has been developed for the analysis of PD pulse signal to raise in the progress of insulation degradation. In this paper, the wavelet transform was applied to one foundational method for feature extraction. For the obtain experimental data, a computer-aided partial discharge measurement system with a single acoustic sensor was used. If we are applying to the neural network method the accumulated data through the extracted feature, it is expected that we can detect the PD pulse signal in the insulation materials on the on-line.

• The Transactions of the Korean Institute of Power Electronics
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• v.18 no.5
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• pp.422-428
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• 2013

Recently, we use a static synchronous compensator(STATCOM) with cascaded H-bride topologies, because it is easy to increase capacity and to reduce total harmonic distortion(THD). When we use equipment for reactive power compensation, dc-link voltage unbalances occur from several reasons although loads are balanced. In the past, switching pattern change of single phase inverter and reference voltage magnitude change of inverter equipped with power sensor have been used for dc-link voltage balance. But previous methods are more complicated and expensive because of additional component costs. Therefore, this paper explains reasons of dc-link voltage unbalance and proposes solution. This solution is complex method that is composed of reference voltage magnitude change of inverter without additional hardware and shifted phase angle of inverter reference voltages change. It proves possibility through 1000[KVA] system simulation.

• Journal of IKEEE
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• v.23 no.2
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• pp.710-715
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• 2019

We consider parameter estimation in distributed systems in which measurements at local nodes are quantized in a non-regular manner, where multiple codewords are mapped into a single local measurement. For the system with non-regular quantization, to ensure a perfect independent encoding at local nodes, a local measurement can be encoded into a set of a great number of codewords which are transmitted to a fusion node where estimation is conducted with enormous computational cost due to the large cardinality of the sets. In this paper, we propose an efficient estimation technique that can handle the non-regular quantized data by efficiently finding the feasible combination of codewords without searching all of the possible combinations. We conduct experiments to show that the proposed estimation performs well with respect to previous novel techniques with a reasonable complexity.

• International journal of advanced smart convergence
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• v.7 no.4
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• pp.169-173
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• 2018

Iris diagnosis based on the color and texture information is one of a novel approach which can represent the current state of a certain organ inside body or the health condition of a person. In analysis of the iris images, there are critical image artifacts which can prevent of use interpretation of the iris textures on images. Here, we developed the iris diagnosis system based on a hand-held typed imaging probe which consists of a single camera sensor module with 8M pixels, two pairs of 400~700 nm LED, and a guide beam. Two original images with different light noise pattern were successively acquired in turns, and the light noise-free image was finally reconstructed and demonstrated by the proposed artifact removal approach.

• International Journal of Precision Engineering and Manufacturing-Green Technology
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• v.5 no.5
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• pp.571-581
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• 2018

In the present study, monitoring of elliptical vibration cutting process by utilizing internal data in the ultrasonic elliptical vibration device without external sensors such as a dynamometer and displacement sensor is investigated. The internal data utilized here is the change of excitation frequency, i.e. resonant frequency of the device, voltages applied to the piezoelectric actuators composing the device, and electric currents flowing through the actuators. These internal data change automatically in the elliptical vibration control system in order to keep a constant elliptical vibration against the change of the cutting process. Correlativity between the process and the internal data is described by using a vibration model of ultrasonic elliptical vibration cutting and verified by several experiments, i.e. planing and mirror surface finishing of hardened die steel carried out with single crystalline diamond tools. As a result, it is proved that it is possible to estimate the elements of elliptical vibration cutting process, e.g. tool wear and machining load, which are important for stable cutting in such precision machining.

• The Journal of Korea Robotics Society
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• v.18 no.3
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• pp.271-280
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• 2023

FMCW (Frequency Modulated Continuous Wave) radar system is widely used in autonomous driving and navigation applications due to its high detection capabilities independent of weather conditions and environments. However, radar signals can be easily contaminated by various noises such as speckle noise, receiver saturation, and multipath reflection, which can worsen sensing performance. To handle this problem, we propose a learning-free noise removal technique for radar to enhance detection performance. The proposed method leverages adaptive thresholding to remove speckle noise and receiver saturation, and wavelet transform to detect multipath reflection. After noise removal, the radar image is reconstructed with the geometric structure of the surrounding environments. We verify that our method effectively eliminated noise and can be applied to autonomous driving by improving the accuracy of odometry and place recognition.

• Journal of Digital Contents Society
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• v.16 no.2
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• pp.227-234
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• 2015

Recently, there is more and more demand on broadcasting display environment that provides a sense of realism basically with high quality and high definition as in UHDTV, so various kinds of 4K cameras have been released. Super 35mm sensor 4K/UHD cameras being generally used can be usefully applied to the single camera-based system such as advertisements, dramas, nature documentaries, and culture programs. However, in the multicamera-based system such as entertaining programs, sports, and concerts, relay broadcasting may face limitations as there are restrictions of close-up or tight shots according to the distance. Besides, 4K lenses are not enough compared with the previous HD lenses' group, so there are limitations in camera photographing shots that have been realized in HD filming. Therefore, to complement this, the use of 2/3 inch sensor 4K/UHD cameras is being demanded, and it is also needed to use various lenses' groups to produce UHD image contents. Accordingly, this study used Grass Valley's LDX 4K/UHD camera to analyze its applicability based on the picture quality test at the use of HD lenses in 2/3 sensors and also the possibility of its efficient application.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.12
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• pp.7187-7192
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• 2014

Recently, theservice field based on the location while expanding into a variety of business areas and have generated significant revenue. In particular, the map service provides a variety of information in conjunction with such public transport directions. Therefore, this study evaluated the map service, as one of the key technologies, StreetView and LoadView photographs of panoramic photograph-support service-modules that can be supported on smart phones. For this, purpose sensors were provided to allow smart phone users to easily publish panoramic photographs. The unnecessary parts could be removed from several photos and pictures using the design technology, and the naturalness of the connection could be maintained by applying the algorithm to handle a single photograph. Finally, a system to work with smartphone panoramic photographs was configured and designed to operate a smartphone application panoramic photograph for 6 months.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2022.10a
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• pp.242-244
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• 2022

In recent years, the number of single-person households is increasing with the aging of the population and the number of the elderly living alone is increasing rapidly with the aging of the population. Therefore, the lonely death of the elderly living alone has become a social issue. In many cases, the body is discovered several days after death. In particular, lonely death of the elderly living alone is being taken more seriously in society, as there is no one to arrange funerals, organize and dispose of their belongings. Since the body is usually found after a few days, the decomposition of the body is often severe. Therefore, this paper proposes an indoor monitoring system using a temperature and humidity sensor and a human body sensor to prevent and respond to lonely deaths in the elderly living alone.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.64 no.11
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• pp.1592-1597
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• 2015

In this study, we developed a fiber-optic temperature sensor (FOTS) based on a silicone oil and an optical time domain reflectometer (OTDR) to apply the measurement of a coolant leakage in the nuclear power plant. The sensing probe of the FOTS consists of a silicone oil, a stainless steel cap, a FC terminator, and a single mode optical fiber. Fresnel reflection arising at the interface between the silicone oil and the single mode optical fiber in the sensing probe is changed by varying the refractive index of the silicone oil according to the temperature. Therefore, we measured the optical power of the light signals reflected from the sensing probe. The measurable temperature range of the FOTS using a Cu-coated silica fiber is from $70^{\circ}C$ to $340^{\circ}C$ and the maximum operation temperature of the FOTS is sufficient for usage at the secondary system in the nuclear power plant.