• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.8 no.2
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• pp.164-176
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• 2003

During summer, the DIN (dissolved inorganic nitrogen) and DIP (dissolved inorganic phosphate) observed in the Jindong Bay in the southern sea of Korea show much higher values in the inner area of the bay. In general, they have high values in the upper (0-1 m) and lower layers (8 m-bottom), but are relatively lower in the middle layer (1-8 m). These features in their distribution are examined using an ecosystem model with considering the wind, tidal current, horizontal gradient of water density and residual flow. The experiments were focused on how to influence nutrients associated with these conditions. In the experiment with tide-induced residual flow, the values of nutrients appeared lower than the observation, and were well corresponded to it when the effects of wind, tide-induced residual current and horizontal gradient of water density were additionally imposed. A statistical analysis identifies these results. This paper suggests that variation of nutrient in the Jindong Bay during summer should be seriously a(footed wind-driven current by the wind and density-driven current is induced by the horizontal gradient of water density as well as tidal current.

• Journal of Korea Multimedia Society
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• v.6 no.2
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• pp.247-258
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• 2003

Principal component analysis (PCA) based algorithms form the basis of numerous algorithms and studies in the face recognition literature. PCA is a statistical technique and its incorporation into a face recognition system requires numerous design decisions. We explicitly take the design decisions by in-troducing a generic modular PCA-algorithm since some of these decision ate not documented in the literature We experiment with different implementations of each module, and evaluate the different im-plementations using the September 1996 FERET evaluation protocol (the do facto standard method for evaluating face recognition algorithms). We experiment with (1) changing the illumination normalization procedure; (2) studying effects on algorithm performance of compressing images using JPEG and wavelet compression algorithms; (3) varying the number of eigenvectors in the representation; and (4) changing the similarity measure in classification process. We perform two experiments. In the first experiment, we report performance results on the standard September 1996 FERET large gallery image sets. The result shows that empirical analysis of preprocessing, feature extraction, and matching performance is extremely important in order to produce optimized performance. In the second experiment, we examine variations in algorithm performance based on 100 randomly generated image sets (galleries) of the same size. The result shows that a reasonable threshold for measuring significant difference in performance for the classifiers is 0.10.

• Journal of Ocean Engineering and Technology
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• v.27 no.6
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• pp.32-42
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• 2013

In this paper, a wave-induced swirl water chamber (SWC) for breakwater and wave power generation is introduced and its applicability to wave power generation in the coastal waters of Korea is investigated. The SWC type of wave power generation is a way to drive a turbine using the unidirectional swirl flow that is induced in the back of a curtain wall of a breakwater due to incident waves. The typical wave characteristics are obtained by analyzing the annual statistical wave data from KHOA (Korea Hydrographic and Oceanographic Administration). A numerical analysis is carried out on the variations in the SWC entrance height, wave height, and different installation conditions. For the numerical analysis, a commercial code, Fluent based on FVM, is used. As the entrance height decreases, the mass flow rate through the entrance is rarely changed, whereas the magnitude of the flow velocity of the smaller entrance height is greater than the other ones, which is better for the formation of an SWC swirl flow inside and the flow kinetic energy at the entrance. In cases of installation conditions where a wall is place behind and under SWC, it has been shown that the mass flow rate through the entrance is greater than that in the open condition, and sufficient flow kinetic energy is generated in the entrance for wave power generation. However, the swirl flow kinetic energy is relatively small. Thus, in the future, it is necessary to study the swirl flow generation, which is affected by the SWC shape.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.11 no.11
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• pp.2172-2178
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• 2007

In indoor environment, the combination of the two variations, large scale(path loss) and small scale(fading), leads to non-linear variation of RSSI(received signal strength indicator) values as distance varied. This has been one of the difficulties for indoor location estimation. This paper presents new findings on indoor RSSI characterization for more accurate model building. Experiments have been done statistically to find overall trend of RSSI values at different places and times within the same room. From experiments, it has been shown that the variation of RSSI values can be determined by both spatial and temporal factors. These two factors are directly indicated by the two main parameters of path loss model. The results show that all sensor nodes which are located at different places share the same characterization value for the temporal parameter whereas different values for the spatial parameters. The temporal parameter also has a large scale variation effect that is slowly time varying due to environmental changes. Using this relationship, the characterization for location estimation can be more efficient and accurate.

• Journal of the Korean Society of Marine Environment & Safety
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• v.23 no.6
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• pp.759-766
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• 2017

In order to identify the species composition and distribution pattern of larval fish assemblages in the southern coastal waters of Korea, monthly samples were taken using an RN80 net which was towed horizontally in three different regions (Yeosu, Namhae and Tongyoung) between May to September 2016. A total of fifty taxa were collected during the study. Among these, Engraulis japonicus, which accounted for 56.8 % of the total population, was the most dominant species, followed by Sillago japonicus, Parablennius yatabei, Gobiidae Type A, Parablennidae sp., and Omobranchus elegans as dominant taxa, that accounted for 87.5% of the total number of individuals. ANOSIM results revealed that regional groups were not separated, but seasonal groups were clearly divided with statistical significance, and these differences were caused mainly by water temperature variations identified by canonical analysis.

• Earthquakes and Structures
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• v.16 no.5
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• pp.563-573
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• 2019

When generating spectrum-compatible artificial ground motion in engineering practices, the effect of the variation in fitting parameters on the distribution of the peak ground displacement (PGD) has not yet drawn enough attention. In this study, a method for simulating ground motion matching for multiple targets is developed. In this method, a frequency-dependent amplitude envelope function with statistical parameters is introduced to simulate the nonstationarity of the frequency in earthquake ground motion. Then, several groups of time-history acceleration with different temporal and spectral nonstationarities were generated to analyze the effect of nonstationary parameter variations on the distribution of PGD. The following conclusions are drawn from the results: (1) In the simulation of spectrum-compatible artificial ground motion, if the acceleration time-history is generated with random initial phases, the corresponding PGD distribution is quite discrete and an uncertain number of PGD values lower than the limit value are observed. Nevertheless, the mean values of PGD always meet the requirement in every group. (2) If the nonstationary frequencies of the ground motion are taken into account when fitting the target spectrum, the corresponding PGD values will increase. A correlation analysis shows that the change in the mean and the dispersion values, from before the frequencies are controlled to after, correlates with the modal parameters of the predominant frequencies. (3) Extending the maximum period of the target spectrum will increase the corresponding PGD value and, simultaneously, decrease the PGD dispersion. Finally, in order to control the PGD effectively, the ground motion simulation method suggested in this study was revised to target a specified PGD. This novel method can generate ground motion that satisfies not only the required precision of the target spectrum, peak ground acceleration (PGA), and nonstationarity characteristics of the ground motion but also meets the required limit of the PGD, improving engineering practices.

• Journal of The Korean Astronomical Society
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• v.52 no.5
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• pp.159-172
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• 2019

It is known that the number of astronomers of a country registered to the International Astronomical Union (IAU) is correlated with that country's gross domestic product (GDP). However, the robustness of this relationship could be doubted, as the fraction of astronomers joining the IAU differs from country to country. Here we revisit this correlation by using more recent data, updated as of 2017. We find a similar correlation by using the total number of astronomers and astrophysicists with PhD degrees that are working in each country, instead of adopting the number of IAU members. We confirm the existence of the correlation. We also confirm the existence of two subgroups within this correlation. One group consists of advanced European countries having a long history of modern astronomy, while the other group consists of countries having experienced recent rapid economic development. In order to determine the cause for the correlation, we obtained the long-term variations of the number of astronomers, population, and the GDP for a number of countries. We find that the number of astronomers per capita for recently developing countries has increased more rapidly as GDP per capita increased, than that for fully developed countries. We collected demographic data of the Korean astronomical community and find that it has experienced recent rapid growth. From these findings we estimate the proper size of the Korean astronomical community by considering Korea economic power and population. The current number of PhD astronomers working in Korea is approximately 310, but it should be 550 in order for it to be comparable and competitive to the sizes of the Spanish, Canadian, and Japanese astronomical communities. If current trends continue, this number will be reached by 2030. In order to be comparable to the German, French, and Italian communities, there should be 800 PhD astronomers in Korea. We discuss ways to overcome the vulnerability of the Korean astronomical community, based on the statistics of national R&D expenditure structure in comparison with that of other major advanced countries.

• Journal of Information Technology Services
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• v.21 no.5
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• pp.51-64
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• 2022

Companies are planning and executing IT projects using information technology as a means to secure external competitiveness. However, IT projects have high risks and uncertainties due to the invisibility of outputs (systems, services, products), and changes in plans frequently occur during project execution. As a result, most IT projects are closed without achieving the target performance. This can lead to a waste of resources and money for the company, which in turn leads to the loss of opportunities to enter new markets. This study intends to analyze the effect of changes in the project plan on customer satisfaction, which is the project performance. Also, we want to find the importance of project planning so that the target performance of the IT project can be achieved. For the empirical analysis of this study, about 500 actual project data were collected. As for the analysis method, statistical analysis such as simple and multiple regression analysis and control effect was performed. Looking at the results of the analysis, it was found that the scope change affects the cost change and the schedule change. Also, changes in scope and cost were found to affect project performance. The theoretical performance of this study proved the theoretical fact that good project performance comes out if the IT project is executed as planned. The practical performance suggested the need for a change in project management by proving that thorough execution of the project planning stage can improve the project performance in the Korean project management culture, where the project planning stage is poorly performed for the rapid implementation of the IT project.

• Journal of Korean Foot and Ankle Society
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• v.26 no.4
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• pp.163-170
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• 2022

Purpose: The proximal fifth metatarsal fracture is one of the most common foot fractures. However, few studies have evaluated the associated injuries in patients with a proximal fifth metatarsal fracture. The purpose of this study was to investigate the incidence of foot and ankle joint injuries associated with proximal fifth metatarsal fractures and compare the incidence of these injuries based on the injury mechanisms and location of the fracture. Materials and Methods: This retrospective study included 157 patients with a proximal fifth metatarsal fracture who underwent surgery from January 2014 to August 2021. Their medical records and radiology images were reviewed to classify and analyze the associated injuries. The proximal fifth metatarsal fractures were classified using Lawrence and Botte's classification. Injury mechanisms were divided into direct and indirect injuries. The incidence of injuries was statistically analyzed according to the injury mechanism and classification. Results: Of the 157 patients with proximal fifth metatarsal fractures, 81 (51.6%) were diagnosed with foot and ankle joint injuries. The incidence of foot injuries was 65.4%, that of ankle joint injuries was 19.8%, and of both foot and ankle joint injuries was 14.8%. In patients with direct injuries, the incidence of foot and ankle joint injuries was 82.5% and that of indirect injuries was 41.0%. Statistical differences were observed between the incidence of direct and indirect injuries (p<0.001). The incidence of injuries, according to Lawrence and Botte's classification, was 54.9% (Zone I), 41.2% (Zone II), and 50.0% (Zone III) respectively. However, there were no statistically significant variations in the locations of the proximal fifth metatarsal fractures (p=0.051). Conclusion: In this study, the incidence of foot and ankle joint injuries associated with proximal fifth metatarsal fractures was found to be high. Therefore, a careful physical examination and appropriate radiological evaluation are recommended for patients with such fractures.

• Korea Journal of Hospital Management
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• v.28 no.2
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• pp.44-65
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• 2023

Purposes: As super-aging population and low fertility rates are threatening the sustainability of the National Health Insurance funds, enhancing the efficiency of hospital management is paramount. In the past, studies analyzing the efficiencies of hospitals primarily made inter-hospital comparisons, but it is important to assess hospitals' internal efficiency and develop improvement measures in order to attain practical improvements in hospital efficiencies. The purpose of this study is to analyze the efficiencies of specialists by medical specialty in a hospital in order to provide foundational data for efficient hospital management. Methodology/Approach: We used the activity-based costing (ABC) data and hospital statistical data from one tertiary hospital in Seoul to analyze the efficiency of specialists by medical specialty. Efficiency was analyzed and compared among specialists using the data envelopment analysis developed by Charnes, Cooper, and Rhodes (DEA-CCR) model and the slacks-based measure (SBM) models. The input variables were labor cost, material cost, and operational expenses, and the output variables were the number of outpatients, number of inpatients, outpatient revenue, and inpatient revenue. Findings: First, there was a marked deviation in efficiency across specialists. Second, there was a marked deviation in efficiency across medical specialties. Third, there was little difference in efficiency according to the specialist's sex, age, and job position. Fourth, the SBM model produced more conservative results and better explained efficiency parameters than the CCR model. Practical Implications: The efficiency of a specialist was more influenced by their medical specialty than their personal characteristics, namely sex, age, and job position. Therefore, Further research is needed to analyze the efficiencies of each subspecialty and identify factors that contribute to the variations in efficiencies across medical specialties, such as clinical practices and fee structures.