• ETRI Journal
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• v.39 no.5
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• pp.662-671
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• 2017

Coronary artery disease (CAD) is a major cause of death in the world. As a non-invasive imaging modality, computed tomography angiography (CTA) is now usually used in clinical practice for CAD diagnosis. Precise quantification of coronary stenosis is of great interest for diagnosis and treatment planning. In this paper, a novel cluster method based on a Modified Student's t-Mixture Model is applied to separate the region of vessel lumen from other tissues. Then, the area of the vessel lumen in each slice is computed and the estimated value of it is fitted with a curve. Finally, the location and the level of the most stenoses are captured by comparing the calculated and fitted areas of the vessel. The proposed method has been applied to 17 clinical CTA datasets and the results have been compared with reference standard degrees of stenosis defined by an expert. The results of the experiment indicate that the proposed method can accurately quantify the stenosis of the coronary artery in CTA.

• The KIPS Transactions:PartD
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• v.15D no.1
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• pp.139-146
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• 2008

It is very important to identify useful web user group and induce their behavior pattern in eCRM domain. Inducing user group with a similar inclination, a reliability of user group decreases because there is an uncertainty in online user data. In this paper, we have applied the 2-tier clustering, which uses the outcome of interaction with data from other tiers. Also we propose a method which induces user behavior pattern from a cluster and compare C4.5 with our method.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 1999.10a
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• pp.153-161
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• 1999

For composing the structure model of national maritime power system by system structural modelling, in this study, the 50 basic factors are selected by survey of the extensive and thorough literatures on maritime, sea, maritime power and sea power. And the basic factors are classified into 36 component factors by cluster method. The 9 attributes are extracted by the application of the principle component analysis method, one of the factor analysis method in system engineering, to component factors. We defined the attributes composing the national maritime power system by integration the result of this study and existed our studies relate to this topic. Which are showed in table 8. and we showed the structure model of national maritime power system in figure 3. In table 8, the 9 attributes are as follows: the fundamental power of maritime, shipping and port power, naval power, fishing power, shipbuilding power, the power of ocean research and development, dependency on seaborne trade, the protection power of ocean environment and the will and inclination of government.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.07a
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• pp.309-312
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• 2004

The electronic structure of ZnO oxide semiconductor having high optical transparency and good electric conductivity was theoretically investigated by $DV-X_{\alpha}$(the discrete variation $X_{\alpha}$) method, which is a sort of the first principle molecular orbital method using Hatre-Fock-Slater approximation. The electrical and optical properties of ZnO are seriously affected by the addition of impurities. The imnurities are added to ZnO in order to increase the electric conductivity of an electrode without losing optical transparency. In this study, the effect of impurities of III and IV family on the band structure, impurity levels and the density of state of ZnO were investigated. The cluster model used for calculations was $[MZn_{50}O_{53}]^{-2}$(M=elements belonging to III and IV family).

• The Korean Journal of Applied Statistics
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• v.29 no.4
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• pp.699-706
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• 2016

Outlier detection methods without performing a test often do not succeed in detecting multiple outliers because they are structurally vulnerable to a masking effect or a swamping effect. This paper considers testing procedures supplemented to a clustering-based method of identifying the group with a minority of the observations as outliers. One of general steps is performing a variety of t-test on individual outlier-candidates. This paper proposes a sequential procedure for searching for outliers by changing cutoff values on a cluster tree and performing a test on a set of outlier-candidates. The proposed method is illustrated and compared to existing methods by an example and Monte Carlo studies.

• Journal of Information Processing Systems
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• v.6 no.1
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• pp.53-66
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• 2010

The energy efficiency is a key design issue to improve the lifetime of the underwater sensor networks (UWSN) consisting of sensor nodes equipped with a small battery of limited energy resource. In this paper, we apply a hexagon tessellation with an ideal cell size to deploy the underwater sensor nodes for two-dimensional UWSN. Upon this setting, we propose an enhanced hybrid transmission method that forwards data packets in a mixed transmission way based on location dependent direct transmitting or uniform multi-hop forwarding. In order to select direct transmitting or uniform multi-hop forwarding, the proposed method applies the threshold annulus that is defined as the distance between the cluster head node and the base station (BS). Our simulation results show that the proposed method enhances the energy efficiency compared with the existing multi-hop forwarding methods and hybrid transmission methods

• Korean Journal of Remote Sensing
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• v.5 no.2
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• pp.109-122
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• 1989

The ISODATA method, which is one of the most famous of the square-error clustering methos, has been applied to two Chungju multivariate data sets in order to evaluate the effectiveness of the regional lithological mapping. One is an airborne radiometric data set and the other is a mixed data set of the airborne radiometric and Landsat TM data. In both cases, the classification of the Bulguksa granite and the Kyemyongsan biotite-quartz gneiss are the most successful. Hyangsanni dolomitic limestone and neighboring Daehyangsan quartzite are also classified by their typical lowness of the radioactive intensities, though it is still confused with some others such as water-covered areas and nearby alluvials, and unaltered limestone areas. Topographically rugged valleys are also classified as the same cluster as above. This could be due to unavoidable variations of flight height and the attitude of the airborne system in such rugged terrains. The regional geological mapping of sedimentary rock units of the Ockchun System is in general confused. This might be due to similarities between different sediments. Considarable discrepancies occurred in mapping some lithological boundaries might also be due to secondary effects such as contamination or smoothing in digitizing process. Further study should be continued in the variable selection scheme as no absolutely superior method claims to exist yet since it seems somewhat to be rather data dependent. Study could also be made on the data preprocessing in order to reduce the erratic effects as mentioned above, and thus hoprfully draw much better result in regional geological mapping.

• Korean Journal of Remote Sensing
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• v.25 no.6
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• pp.465-474
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• 2009

Convective/stratiform radar echo classification schemes by Steiner et al. (1995) and Biggerstaff and Listemaa (2000) are examined on a monsoonal front during the summer monsoon-Changma period, which is organized as a cloud cluster with mesoscale convective complex. Target radar is S-band with wavelength of 10cm, spatial resolution of 1km, elevation angle interval of 0.5-1.0 degree, and minimum elevation angle of 0.19 degree at Jindo over the Korean Peninsula. For verification of rainfall amount retrieved from the echo classification, ground-based rain gauge observations (Automatic Weather Stations) are examined, converting the radar echo grid data to the station values using the inverse distance weighted method. Improvement from the echo classification is evaluated based on the correlation coefficient and the scattered diagram. Additionally, an optimal use method was designed to produce combined rainfalls from the radar echo and Tropical Rainfall Measuring Mission Precipitation Radar (TRMM/PR) data. Optimal values for the radar rain and TRMM/PR rain are inversely weighted according to the error variance statistics for each single station. It is noted how the rainfall distribution during the summer monsoon frontal system is improved from the classification of convective/stratiform echo and the use of the optimal use technique.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.19 no.2
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• pp.103-109
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• 2019

Due to the development of ICT technology, the IoT environment for connecting objects in the vicinity to networks and utilizing information about objects in various fields is getting attention, and security threats are also increasing. In order to solve the increasing security problem in IoT environment, we are studying methods that use certificate, encryption, hash calculation and block chain in the private sector. However, the security authentication method which overcomes the performance gap between devices and has compatibility with various devices It has not been proposed yet. In this paper, we propose an authentication method that can achieve wide compatibility by minimizing the influence of IoT device environment.

• The Journal of Asian Finance, Economics and Business
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• v.8 no.3
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• pp.217-227
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• 2021

This study aims to examine the effect of institutional ownership, independent board of commissioners, audit committee, and profitability (RNOA) on tax avoidance in banking companies listed on the Indonesia Stock Exchange over the 2014-2018 period. The sampling method employed in this study was the cluster sampling method. The population was all banking companies listed on the Indonesia Stock Exchange for the period 2014-2018. The sample selection results using the purposive sampling method during the observation includes 209 companies that published complete annual reports and their financial report notes as of December 31, 2018. The results revealed that institutional ownership and independent board of commissioners did not affect profitability. Profitability also did not affect tax avoidance. Further findings showed that institutional ownership and audit committee positively affect tax avoidance. From the result of Sobel test, this study indicated that profitability cannot mediate the effect of institutional ownership, independent board of commissioners, and audit committee on tax avoidance. This study has succeeded in proving empirically that there was a significant effect of the audit committee on profitability, institutional ownership on tax avoidance, and the audit committee on tax avoidance. Therefore, this study supports the agency theory and the research model from previous studies.