• The Korean Journal of Applied Statistics
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• v.35 no.2
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• pp.327-333
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• 2022

Principal component analysis (PCA) is the most widely used technique in dimension reduction, however, it is very sensitive to outliers. A robust version of PCA, called robust PCA, was suggested by two seminal papers by Candès et al. (2011) and Chandrasekaran et al. (2011). The robust PCA is an essential tool in the artificial intelligence such as background detection, face recognition, ranking, and collaborative filtering. Also, the robust PCA receives a lot of attention in statistics in addition to computer science. In this paper, we introduce recent algorithms for the robust PCA and give some illustrative examples.

• Proceedings of the Korea Information Processing Society Conference
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• 2015.04a
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• pp.172-175
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• 2015

많은 사람들이 위치 기반 서비스를 사용하면서 위치 기반 서비스에서 사용되는 GPS 데이터는 기하급수적으로 증가하고 있다. 사용자들에게 필요한 정보를 제공하기위해서는 이러한 대량의 GPS 데이터를 처리하여 POI를 추출하고 분석하는 과정이 필요하다. 본 논문에서는 POI를 추출하고 관리 분석하기 위해 MapReduce 환경을 구축하고 DBSCAN 클러스터링 방법을 이용한다. 또한 분산 환경에서 DBSCAN 알고리즘을 수행하기 위해 K-Means를 이용한 데이터 분할 방법을 제안한다.

• Proceedings of the Korea Information Processing Society Conference
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• 2015.10a
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• pp.1199-1201
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• 2015

위치 기반 서비스는 여러 분야에서 활용되어지고 있다. 사용자들에게 정확한 정보를 제공하기 위해서는 대량의 위치 데이터를 분석하여 POI를 추출하고 분석해야 된다. 본 논문에서는 POI를 추출하는 방법으로 DBSCAN 클러스터링을 이용하고 이를 MapReduce 환경에서 구현한다. 또한 알고리즘의 수행속도를 향상시키기위해 데이터를 분할하는 방법을 제안한다.

• Journal of the Korean Society for Precision Engineering
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• v.19 no.9
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• pp.51-58
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• 2002

Vehicle dynamics control systems are. complex and non-linear, so they have difficulties in developing a controller for the anti-lock braking systems and the auto-traction systems. Currently the fuzzy-logic technique to estimate the absolute vehicle speed is good results in normal conditions. But the estimation error in severe braking is discontented. In this paper, we estimate the absolute vehicle speed by using the wheel speed data from standard 50-tooth anti-lock braking system wheel speed sensors. Radial symmetric basis function of the neural network model is proposed to implement and estimate the absolute vehicle speed, and principal component analysis on input data is used. Ten algorithms are verified experimentally to estimate the absolute vehicle speed and one of those is perfectly shown to estimate the vehicle speed with a 4% error during a braking maneuver.

• Journal of the Korean Data and Information Science Society
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• v.11 no.2
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• pp.295-302
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• 2000

We study the efficient method to estimate the parameters for the Weibull model with covariates which occupies an important position in survival analysis. A treatment period may be divided by the stages of treatments under the different treatment arams. The piecewise method is considered to obtain the estimators of the parameters by maximum likelihood method. We explore the real data to show that the piecewise is more efficient than the nonpiecewise to estimate the parameters.

• Tuberculosis and Respiratory Diseases
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• v.43 no.4
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• pp.547-557
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• 1996

Background : An excessive accumulation of neutrophils in lung tissue has been known to play an important role in mediating the tissue injury among the adult respiratory distress syndrome, idiopathic pulmonary fibrosis and cystic fibrosis by releasing toxic oxygen radicals and proteolytic enzymes. Therefore, it is important to understand a possible mechanism of neutrophil accumulation in lung tissue. In many species, exposure to hyperoxic stimuli can cause changes of lung tissues very similar to human adult respiratory distress syndrome and neutrophils are also functioning as the main effector cells in hyperoxic lung injury. The purpose of the present study was to examine whether neutrophils function as a key effector cell and to study the nature of possible neutrophil chemotactic factors found in bronchoalveolar lavage fluid from the hyperoxia exposed rats. Methods : We exposed the rats to the more than 95% oxygen for 24, 48, 60 arid 72 hours and bronchoalveolar lavage(BAL) was performed. Neutrophil chemotactic activity was measured from the BAT- fluid of each experimental groups. We also evaluated the molecular weight of neutrophil chemotactic tractors using fast performance liquid chromatography and characterized the substances by dialyzer membrane and heat treatment. Results : 1) The neutrophil proportions in bronchoalveolar lavage fluid began to rise from 48 hours after oxygen exposure, and continued to be significantly increased with exposure times. 2) chemotactic index for neutrophils in lung lavages from rats exposed to hyperoxia was significantly higher in 48 hours group than in control group, and was significantly increased with exposure time. 3) No deaths occured until after 48 hours of exposure. However, mortality rates were increased to 33.3 % in 60 hours group and 81.3 % in 72 fours group. 4) Gel filtration using fast performance liquid chromatography disclosed two peaks of neutrophil chemotactic activity in molecular weight of 104,000 and 12,000 daltons. 5) Chemotactic indices of bronchoalveolar lavage fluid were significantly deceased when bronchoalveolar lavage fluid was treated with heat ($56^{\circ}C$ for 30 min or $100^{\circ}C$ for 10 min) or dialyzed (dialyzer membrane molecular weight cut off : 12,000 daltons). Conclusion : These results suggested that the generation of neutrophil chemotactic factor and subsequent neutrophil influx into the lungs are playing an important roles in hyperoxia-induced acute lung injury. Neutrophil chemotactic factor in the lung lavage fluids consisted of several distinct components having different molecular weight and different physical characteristics.

• Journal of the Korea Convergence Society
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• v.8 no.1
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• pp.97-106
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• 2017

The purpose of this convergence study was to identify the effects of favorite music therapy on anxiety, fatigue, and vital signs of patients undergoing prostatectomy with spinal anesthesia. This study used a nonequivalent control group design. A sample of 45 patients was included. The experimental group was given music therapy during operation. The data were collected using a structured questionnaire and monitoring at 30 min before operation, at 20 min and 40min undergoing operation, and at arrival recovery room after operation. Data were analyzed using descriptive statistics, ${\chi}^2-test$, Fisher's exact test, t-test, repeated measures ANOVA. The experimental group reported significantly lower anxiety and lower fatigue than the control group(p=.001; p=.020). However there were no significant differences in the systolic blood pressure, diastolic blood pressure and pulse rate between groups(p=.821; p=.473; p=.782). This findings indicate that the tailored favorite music therapy can be an effective nursing intervention for patient undergoing prostatectomy with spinal anesthesia to reduce anxiety and fatigue related to operation.

• Korean journal of communication and information
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• v.34
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• pp.306-340
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• 2006

Mobile communications is argued to reshape and activate the existing space by increasing 'mobile communicability en route' and 'real time interaction.' This study is designed to make an empirical analysis on how different the use of a cellular phone is in each different space. In this study, the space is divided into three distinct parts including the private, social and public space. First, spatial micro-coordination and experience of polysemy of place are widely observed in the use of a mobile phone in the private space. Secondly, it is found that a mobile phone contributes to extending the scope of social contacts which in turn compliments the existing social relationship. Moreover, a full-time intimate community that is connected via a mobile phone results in reshaping the social space. Lastly, the study shows that the usage pattern of a mobile phone varies depending on the type of public space. The technological development is envisaged to lead to more demand for the public space while facilitating the use of the public space.

• Journal of Navigation and Port Research
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• v.43 no.4
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• pp.250-255
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• 2019

The objective of this study was to analyze the risk of collision accidents to the VTSOs (Vessel Traffic Service Operators) as small ferries and fishing boats are expanded for monitoring targets. The VTSOs was surveyed, the scale of the small vessels defined and the course of general cargo vessels and small vessels along the Busan VTS area investigated for three days. From calculating the risk with CoRI, patterns of increased or decreased risk due to course deviation were similar, and there was no significant difference between the maximum values and the minimum values. In addition, most VTSOs responded that the minimum time required was approximately three minutes to safely instruct in encounter situation, however, the collision risk with a small vessel is very rapidly changing within the three minutes, which is likely to increase the workload and decrease the concentration of the VTSOs. The objective of this study was to investigate the effect on VTSOs with respect to the expansion of small vessels as collision risk, it is expected that it will contribute to the establishment of a suitable scale for the target vessels for VTS through the analysis of each index of the CoRI model and various case studies.

• Korean Journal of Plant Resources
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• v.31 no.5
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• pp.423-432
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• 2018

This study was performed to develop a new natural antimicrobial materials by analyzing the effect of extracts obtained from Ten Lauraceae Species on the inhibitory activity against Propionibacterium acnes. The plant materials were collected from Wando and Jeju islands, and the antimicrobial activity of the crude extracts was examined by the agar diffusion method with different part (i.e., leaf and branch), solvents (i.e., distilled water, 80% ethanol, and 100% methanol) and at different ultrasonic extracting times (i.e., 15, 30, and 45 minutes). The control agents used were synthetic antimicrobials, methylparaben and phenoxyethanol, at concentrations of 0.4, 1, 2, and 4 mg/disc. Altogether, extracts of 10 species used in the study showed inhibitory activity, which confirmed their antimicrobial action against acnes. Among these, leaves of Laurus nobilis L. which was extracted in 80% ethanol for 45 min showed the largest clear zone (19.8 mm). Leaves of L. nobilis L., showing highest antimicrobial activities among 10 species, were successively reextracted with n-hexane, chloroform, ethylacetate and n-butanol. As a results, in all fractions except butanol, clear zone above 10 mm were formed. The ethyl acetate fraction showed the highest inhibitory activity (13.3 mm) and the inhibitory activity was significantly higher than that of crude extract (10.2 mm) and phenoxyethanol as a control (12.5 mm).