• The Transactions of the Korea Information Processing Society
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• v.3 no.4
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• pp.720-732
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• 1996

Spatial match retrieval methods for iconic image databases recognize an image document as several icon symbols. Therefore the iconic symbols are used as primary keys to index the image document. When a user requires content-based retrieval ofimages, a spatial match retrieval method converts a query image into iconic symbols and then retrieves relevant images by accessing stored images. In order to support content-based image retrieval efficiently, we, in this paper, propose spatial match retrieval methods using signatures for iconic image databases. For this, we design new index representations of two-dimensional iconic images and explain implemented system.. In addition, we compare the conventional 9-DLT and our two-dimensional image retrieval method in terms of retrieval precision and recall ratio. We show that our method is more efficient than the conventional method.

• Journal of KIISE:Computing Practices and Letters
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• v.16 no.7
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• pp.799-803
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• 2010

The KDB-tree is a traditional indexing scheme for retrieving multidimensional data. Much research for KDB-tree family frequently addresses the low storage utilization and insufficient retrieval performance as their two bottlenecks. The bottlenecks occur due to a number of unnecessary splits caused by data insertion orders and data skewness. In this paper, we propose a novel index structure, called as $KDB_{CS}^+$-tree, to process skewed data efficiently and improve the retrieval performance. The $KDB_{CS}^+$-tree increases the number of fan-outs by exploiting bit-vectors for representing splitting information and pointer elimination. It also improves the storage utilization by representing entries as a hierarchical structure in each internal node.

• Journal of Korea Water Resources Association
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• v.40 no.12
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• pp.969-983
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• 2007

This study developed a ten-step procedure of integrated watershed management (IWM) for sustainability to rehabilitate the distorted hydrologic cycle and identified spatial hazard ranking(step 2). Spatial hazard indices, Potential flood damage (PFD), potential streamflow depletion (PSD), potential water quality deterioration (PWQD), and watershed evaluation index (WEI) were developed using multi-criteria decision making (MCDM) techniques and sustainability evaluation concept(pressure-state-response model). The used MCDM techniques are composite programming, compromise programing, Regime method, and EVAMIX approach which are classified by data availability and objectives (prefeasibility and feasibility).

• The Transactions of the Korean Institute of Power Electronics
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• v.16 no.3
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• pp.234-241
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• 2011

This paper proposes a simple static overmodulation strategy that extends the linearity of the inverter output voltage. The proposed method obtains the reference vector having the instantaneous value directly from the modulation index based on the magnitude of fundamental voltage, and has a simplified form of phase command. This method does not need trigonometric functions for calculating the magnitude of the reference vector. The magnitude of reference voltage and holding angle in the overmodulation region corresponding to the modulation index are determined in advance to have the same fundamental voltage magnitude by using the result of Fourier series expansion.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.2A
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• pp.351-361
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• 2006

In this study, nonlinear finite element analysis procedures are presented for the seismic performance assessment of circular reinforced concrete bridge piers with confinement steel. This paper defines a damage index based on the predicted hysteretic behavior of a circular reinforced concrete bridge pier. Damage indices aim to provide a means of quantifying numerically the damage in circular reinforced concrete bridge piers sustained under earthquake loading. The proposed numerical method is applied to circular reinforced concrete bridge piers with confinement steel tested by the authors. The proposed numerical method gives a realistic prediction of seismic performance throughout the loading cycles for several test specimens investigated.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.7
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• pp.387-392
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• 2019

A technique was researched to detect bolt looseness using a transfer impedance technique (the dual piezoelectric material technique) for monitoring the structural health of a bolt joint. In order to use the single piezoelectric material technique, an expensive impedance analyzer should be used. However, in the transfer impedance technique, low-cost fault detection can be performed using a general function generator and a digital multimeter. A steel plate frame test specimen composed of bolt joints was fabricated, and the tightening torques of the bolts were loosened step by step. By using the transfer impedance method, the damage index was obtained. It was found that the presence of faults could be reasonably estimated using the damage index, which increased with the degree of bolt looseness. An experiment was performed on the same specimen using the single piezoelectric material technique, and the results showed a similar tendency. It could be possible to estimate the damage of a bolt joint at low cost by eliminating the expensive impedance analyzer. This method could be used effectively for structural health monitoring after carrying out a study to estimate the fault location and severity.

• Journal of the Korean Society of Marine Environment & Safety
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• v.29 no.1
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• pp.24-35
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• 2023

Rapid industrialization and urbanization have led to severe marine pollution. A Water Quality Index (WQI) has been developed to allow the effective management of marine pollution. However, the WQI suffers from problems with loss of information due to the complex calculations involved, changes in standards, calculation errors by practitioners, and statistical errors. Consequently, research on the use of artificial intelligence techniques to predict the marine and coastal WQI is being conducted both locally and internationally. In this study, six techniques (RF, XGBoost, KNN, Ext, SVM, and LR) were studied using marine environmental measurement data (2000-2020) to determine the most appropriate artificial intelligence technique to estimate the WOI of five ecoregions in the Korean seas. Our results show that the random forest method offers the best performance as compared to the other methods studied. The residual analysis of the WQI predicted score and actual score using the random forest method shows that the temporal and spatial prediction performance was exceptional for all ecoregions. In conclusion, the RF model of WQI prediction developed in this study is considered to be applicable to Korean seas with high accuracy.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.27 no.8
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• pp.1426-1435
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• 2003

Design goal is to find the one that has the highest probability of success and the smallest variation. A robustness index has been proposed to satisfy these conditions. The two-step optimization process of the target problem requires a scaling factor. The search process of a scaling factor is replaced with the making of the decoupled design between the mean and the standard deviation. The decoupled design matrix is formed from the sensitivity or the sum of squares. After establishing the design matrix, the robust design process has a new three-step one. The first is ″reduce variability,″ the second is ″make the candidate designs that satisfy constraints and move the mean on the target,″ and the final is ″select the best robust design using the proposed robustness index.″ The robust design process is verified by three examples and the results using the robustness index are compared with those of other indices.

• Proceedings of the KIEE Conference
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• 2002.11b
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• pp.9-14
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• 2002

In front of the opening of electric distribution market in 2004. it is indispensable to have a proper estimation of power quality index and power quality cost calculation mechanism are indispensable to stabilize highly industrialized society and to vitalize the investment for electric power system. However, there were not enough measures to reflect the voltage characteristics such as voltage sags and interruptions which make electric load in unstable operation. This paper suggests power quality index(LDI) and power quality cost(LDC) which translate various kinds of voltage records into load drop index and cost based on aggregated load CBEMA curve. A sample calculation result shows that this method can produces the acceptable power quality index and costs for utilities and customers requirements.

• Journal of the Society of Naval Architects of Korea
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• v.30 no.1
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• pp.10-19
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• 1993

Design optimisation generally necessitates a tool of assessing the economics of designs. This paper proposes a method of assessing the economics of marine electric generating systems. The pay back period(PBP) and the net present valuve(NPV) of the investment for a designed project are properly converted into a economic index. The mechanical factors dominating the easiness in operating the system are also assessed and quantified to form a index which eventually is added to the economic index producing a comprehensive economic index. The method has been tested on a design example and it's validity has been shown.