• Journal of the Korea Computer Industry Society
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• v.5 no.5
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• pp.737-746
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• 2004

Two-channel multiwavelet system is investigated for image compression application in this paper. Generally, multiwavelets are known for their superb capability of compressing non-stationary signals like voice. However, multivavelet system have a critical problem in processing and compressing image data due to mesh-grid visual artifacts. In our two-channel multiwavelet system we have investigated incorporation of pre and post filtering to the multiwavelet transform and compression system for alleviating those ingerent visual artifacts due to multiwavelet effect. In addition, to quantify the image data compression performance of proposed multiwavelet system, computer simulations have been performed using various image data. For bit allocation and quantization, the Lagrange multiplier technique considering data rate vs. distortion rate along with a nonlinear companding method are applied equallly to all systems considered, here. The simulation results have yielded 1 ~ 2 dB compression enhancement over the scalar savelet systems. If the more advanced compression methods like SPIHT and run-length channel coding were adopted for the proposed multiwavelet system, a much higher compression gain could be obtained.

• Journal of Advanced Navigation Technology
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• v.24 no.5
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• pp.374-381
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• 2020

In order to improve the vertical position accuracy, the advantages of GPS and barometric altimeter are combined and used, but in order to fuse the two sensors, the geoid altitude must be compensated. In this paper, we proposed a technique that can calculate geoid altitude in real time even in low-cost embedded systems applied to drones or autonomous vehicles. Since the reference EGM08 is determined by a polynomial of the 2160th order, real-time calculation is impossible in the embedded system. Therefore, by introducing a linear interpolation technique, the amount of calculation was increased, and the storage space was saved by 75% by using the integer geoid height as a grid point. The accuracy of the proposed technique was evaluated through simulation, and it was confirmed that the accuracy of the maximum error is -1.215 m even in the region where the geoid change is rapid.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.2
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• pp.672-680
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• 2017

A solar photovoltaic system is composed of a module mounting structure, supporting trunk, and a control unit that supplies generated electrical power to an external power grid or a load. The efficiency of the system depends on the incident solar light, so the mounting structure is installed to face the sun. However, because the sun always moves, systems that track the sun have better efficiency than fixed systems. The structure experiences wind pressure, snow load, seismic load, and structure weight. The wind pressure has the most serious effect on the structure. The pressure was obtained using finite element method for various gaps between modules and angles between the panel and the ground. The wind pressure is lowest when the gap is zero, and it increases with the inclination angle. Based on the results, a mounting structure module was designed.

• Journal of Power Electronics
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• v.15 no.6
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• pp.1609-1618
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• 2015

DC microgrids are considered as prospective systems because of their easy connection of distributed energy resources (DERs) and electric vehicles (EVs), reduction of conversion loss between dc output sources and loads, lack of reactive power issues, etc. These features make them very suitable for future industrial and commercial buildings' power systems. In addition, the bipolar-type dc system structure is more popular, because it provides two voltage levels for different power converters and loads. To keep voltage balanced in such a dc system, a bidirectional dual buck-boost voltage balancer with direct coupling is introduced based on P-cell and N-cell concepts. This results in greatly enhanced system reliability thanks to no shoot-through problems and lower switching losses with the help of power MOSFETs. In order to increase system efficiency and reliability, a novel burst-mode control strategy is proposed for the dual buck-boost voltage balancer. The basic operating principle, the current relations, and a small-signal model of the voltage balancer are analyzed under the burst-mode control scheme in detail. Finally, simulation experiments are performed and a laboratory unit with a 5kW unbalanced ability is constructed to verify the viability of the bidirectional dual buck-boost voltage balancer under the proposed burst-mode control scheme in low-voltage bipolar-type dc microgrids.

• Journal of the Korea Convergence Society
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• v.8 no.11
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• pp.15-20
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• 2017

Recently, with the development of the IT industry, interest in computer convergence technology is increasing in various fields. Especially, in the semiconductor field, a vision system that uses a camera and computer convergence is often used to inspect semiconductor device defects in the production process. Various systems have been studied to remove noise, which is a major cause of degradation in processing of data related to these image processing systems. In this paper, we try to detect defects in BGA (Ball Grid Array) package devices by recognizing defects in advance during mass production. We propose a measurement system using a Gaussian filter, a Median filter, and an Average filter, which are widely used for noise reduction of image data Applying the proposed system to the manufacturing process of the BGA package can be used to judge whether the defect is good or not, and it is expected that productivity will be improved.

• Journal of the Korean Institute of Intelligent Systems
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• v.14 no.5
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• pp.517-524
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• 2004

The fuzzy set theory has been wide used in clustering of machine learning with data mining since fuzzy theory has been introduced in 1960s. In particular, fuzzy C-means algorithm is a popular fuzzy clustering algorithm up to date. An element is assigned to any cluster with each membership value using fuzzy C-means algorithm. This algorithm is affected from the location of initial cluster center and the proper cluster size like a general clustering algorithm as K-means algorithm. This setting up for initial clustering is subjective. So, we get improper results according to circumstances. In this paper, we propose a cluster merging using enhanced density based fuzzy C-means clustering algorithm for solving this problem. Our algorithm determines initial cluster size and center using the properties of training data. Proposed algorithm uses grid for deciding initial cluster center and size. For experiments, objective machine learning data are used for performance comparison between our algorithm and others.

• Journal of the Korean Institute of Intelligent Systems
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• v.16 no.4
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• pp.430-435
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• 2006

In this paper, we propose a method based on multimodal biometrics system using the face and signature under ubiquitous computing environments. First, the face and signature images are obtained by PDA and then these images with user ID and name are transmitted via WLAN(Wireless LAN) to the server and finally the PDA receives verification result from the server. The multimodal biometrics recognition system consists of two parts. In client part located in PDA, user interface program executes the user registration and verification process. The server consisting of the PCA and LDA algorithm shows excellent face recognition performance and the signature recognition method based on the Kernel PCA and LDA algorithm for signature image projected to vertical and horizontal axes by grid partition method. The proposed algorithm is evaluated with several face and signature images and shows better recognition and verification results than previous unimodal biometrics recognition techniques.

• Fashion & Textile Research Journal
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• v.20 no.4
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• pp.464-473
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• 2018

The objective of this study is to develop a sizing system of fitness clothing that can properly accommodate various body sizes of Korean senior women. The sizing system of upper and lower fitness clothing was developed in the present study by selection of key variables, identification of size category candidates, and determination of an optimal sizing system. First, key anthropometric dimensions (stature and bust circumference for upper clothing and stature; waist circumference for lower clothing) were identified by factor analysis on the direct body measurements (n = 272) and 3D whole-body scan data (n = 271) of Korean senior women in Size Korea. Second, sizing system candidates based on the key dimensions of upper and lower clothing were explored using a grid method and an optimization method. Lastly, among the sizing system candidates, optimal sizing systems of upper and lower clothing were selected in terms of accommodation rate. Five size categories (short/small, short/medium, tall/small, tall/medium, and tall/large) were selected as the optimal sizing systems of upper and lower clothing with 89% and 78% of accommodation rate, respectively, for the Korean senior women. The anthropometric characteristics of the representative humans of the optimal size categories would be of use in the design of fitness compressive wear for the better fit and effectiveness of exercise and health of Korean senior women.

• Steel and Composite Structures
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• v.17 no.3
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• pp.339-358
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• 2014

Exodermic deck systems are new composite steel grid deck systems which have been used in various projects during the past decade. One of the eminent features of this system is considerable reduction in the structure weight compared to the ordinary reinforced concrete decks and also reduction in construction time by using precast Exodermic decks. In this study, dynamic properties of the Exodermic deck bridges with alternative perfobond shear connectors are investigated experimentally. In order to evaluate the dynamic properties of the decks, peak picking and Nyquist circle fit methods are employed. Frequencies obtained experimentally are in good agreement with the results of the finite-element solution, and the experimental results show that the first mode is the most effective mode among the obtained modes. The first four modes are the rigid translational motion modes, and the next two modes seem to be rigid rotational motion modes around a horizontal axis. From the 7th mode onwards, modes are flexible. The range of damping ratios is about 0.5%. Furthermore, the static behavior of the Exodermic decks under a static load applied at the center of the decks was investigated. Failure of the decks under positive bending was punching-shear. The bending strength of the decks under negative bending was about 50 percent of their strength under positive bending. In addition, the weight of an Exodermic deck is about 40% of that of an equivalent reinforced concrete slab.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.8 no.2
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• pp.149-157
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• 2009

Tracking technologies which provide real-time and customized information through various information collecting and processing for pedestrians who use traffic connective and transferring center have been being examined. However some problems are caused due to the wide-range positioning error for some services as device installation and service place. It is also difficult to be applied to traffic linkage and transfer services because many situations can be barren. In the testbed, Gwangmyoung Station, we got some results in bad conditions such as a lot of steel construction and another communication device. Practically, conditions of the place which will be built can be worse than Gwangmyoung station. Therefore, we researched suitable Location correction algorithm as a method for accuracy to traffic connective and transferring system. And its algorithm is designed through grid coordinates, map-matching, modeling coordinates and Kalman filtering and is being implemented continuously. Also preparing for optimization of various transferring center model, we designed for simulator type algorithm what is available for deciding algorithm factor.