• Ocean Systems Engineering
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• v.12 no.3
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• pp.267-284
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• 2022

A subsea pipeline designed across active shipping lane prones to failure against external interferences such as anchorage activities, hence risk assessment is essential. It requires quantifying the geometric probability derived from ship traffic distribution based on Automatic Identification System (AIS) data. The actual probability density function from historical vessel traffic data is ideal, as for rapid assessment, conceptual study, when the AIS data is scarce or when the local vessels traffic are not utilised with AIS. Recommended practices suggest the probability distribution is assumed as a single peak Gaussian. This study compares several fitted Gaussian distributions and Monte Carlo simulation based on actual ship traffic data in main ship direction in an active shipping lane across a subsea pipeline. The results shows that a Gaussian distribution with five peaks is required to represent the ship traffic data, providing an error of 0.23%, while a single peak Gaussian distribution and the Monte Carlo simulation with one hundred million realisation provide an error of 1.32% and 0.79% respectively. Thus, it can be concluded that the multi-peak Gaussian distribution can represent the actual ship traffic distribution in the main direction, but it is less representative for ship traffic distribution in other direction. The geometric probability is utilised in a quantitative risk assessment (QRA) for subsea pipeline against vessel anchor dropping and dragging and vessel sinking.

• Nuclear Engineering and Technology
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• v.55 no.12
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• pp.4678-4684
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• 2023

Using the Monte Carlo method, the impact of the angular distribution of the electron source on the dose distribution for the 2.5 MeV ELV electron accelerator was explored. The experiment measured the 3-D dose distribution in the irradiation chamber for electron energies of 1.0 MeV and 2.5 MeV. The simulation used the MCNP6.2 code to evaluate three angular distribution models of the source: a mono-directional beam, a cone shape, and a triangular shape. Of the three models, the triangular shape with angles θ = 30°, φ = 0° best represents the angle of the scan hood through which the electron beam exits. The MCNP6.2 simulation results demonstrated that the triangular model is the most accurate representation of the angular distribution of the electron source for the 2.5 MeV ELV electron accelerator.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.28 no.3
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• pp.171-176
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• 2016

The distribution shapes of air and water temperatures are basic and essential information, which determine the frequency patterns of their occurrence. It is also very useful to understand the changes in long-term air and water temperatures with respect to climate change. The typical distribution shapes of air and water temperatures cannot be well fitted using widely used/accepted normal distributions because their shapes show multimodal distributions. In this study, Gaussian mixture distributions and kernel distributions are suggested as the more suitable models to fit their distribution shapes. Based on the results, the tail shape exhibits different patterns. The tail is long in higher temperature regions of water temperature distribution and in lower temperature regions of air temperature distribution. These types of shape comparisons can be useful to identify the patterns of long-term air and water temperature changes and the relationship between air and water temperatures. It is nearly impossible to identify change patterns using only mean-temperatures and normal distributions.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.32 no.1A
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• pp.31-37
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• 2012

The phase distribution in concrete materials strongly affects its material properties. It is important to identify the spatial distribution of void in concrete because the void in concrete materials affects mechanical behavior and permeability significantly. Therefore, a proper method to describe the void distribution of a material is needed. In this research, CT(computed tomography) is used to examine and to quantify the void distribution of porous concrete specimens. 3D concrete digital specimens are created by subsequent stacking of 2D cross-sectional images from CT. Then, probability distribution functions such as two-point correlation, lineal-path and two-point cluster functions are used for void distribution characterization. It is confirmed that probability distribution functions obtained from CT images are effective in characterizing void distributions including the anisotropy and percolation.

• KEPCO Journal on Electric Power and Energy
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• v.5 no.4
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• pp.295-309
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• 2019

This paper demonstrates that the verification and analysis of the increase of hosting capacity of distributed energy resources in distribution system for the high penetration of distributed energy resources. In the case of generally designed distribution feeders in South Korea, it can host up to 10 MVA of distributed energy resources and the over voltage due to reverse power flow is prohibited beyond the range by the law of electric utility. However, it should take into consideration that there are some factors of extra hosting capacity such as generation characteristics of distributed energy resources and minimum loads that always exist to distribution system. For these reason, we choose a specific distribution system hosted 10 MVA of distributed energy resources monitored by distribution system operator and verify the impact of increasing hosting capacity such as power flow and voltage profile of distribution system. By the result, we could find that it is possible to increase the hosting capacity and define the factors to expand the hosting capacity of distributed energy resources in distribution system.

• Journal of KIISE:Software and Applications
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• v.37 no.8
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• pp.591-598
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• 2010

In this study, we propose a new method for generating candidate solutions based on the Cauchy probability distribution in order to complement the shortcoming of the solutions generated by the normal distribution. The Cauchy probability distribution has infinite mean and variance, and it has rather large probability in the tail region relative to the normal distribution. Thus, the Cauchy distribution can yield higher probabilities of generating candidate solutions of large-varied variables, which in turn has an advantage of searching wider area of variable space. In order to compare and analyze the performance of the proposed method against the conventional method, we carried out an experiment using benchmarking problems of real valued function. From the result of the experiment, we found that the proposed method based on the Cauchy distribution outperformed the conventional one for all benchmarking problems, and verified its superiority by the statistical hypothesis test.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.23 no.2
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• pp.1-16
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• 2020

The current status of geographical distribution range of Deutzia paniculata, one of the korean endemic plants, was investigated based on the species distribution information. The information of the geographical range used for analysis includes all the published references to the distribution of D. paniculata, herbarium specimens in Korea National Arboretum (KH) including its online database: http://www.nature.go.kr, and field research. Although, D. paniculata was firstly recorded in Wonsan, Hamgyeongnam-do, North Korea, this research revelaved that D. paniculata is mainly distributed in Gyeongsangbuk-do and Gyeongsangnam-do, southern regions of the Korean Peninsula. According to the distribution map, this species was estimated on distribution edge of in Anyang region of Gyeonggi-do, Mt. Naejang of Jeollabuk-do and Mt. Taebaek of Gwangwon-do on the distribution edge. However, it was made use of intensive field survey to identify the natural population of the species in these regions. D. paniculata habitat was mainly distributed between 290 meters and 491 meters in altitude, but it was also found ranged from 936 to 959 meters in Gun-wi, Gyeongsangbuk-do, South Korea. The distribution slope was 5° to 35° and the north, N, NE and NW in the aspect. The flora of vascular plants in D. paniculata habitats was listed in 137 taxa: 54 families, 103 genera, 120 species, 2 subspecies, 12 varieties and 3 forms while Korean endemic plants were found in three taxa, Stewartia koreana, Weigela subsessilis and D. Paniculata. Based on a collection of non-biological environment and biological environment data, D. paniculata population were discussed to make strategy and basic research methods for sustainable preservation.

• The Journal of Korean Medicine
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• v.27 no.2 s.66
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• pp.244-252
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• 2006

Objectives : To examine any potential relationships between the types of alopecia and the facial heat distribution in patients with alopecia. Methods : 183 patients with alopecia participated in this study to provide facial heat distribution measured by the Infrared Thermography Scanner (ITS, Nec San-ei Instruments Ltd, Japan). The thermography scan was used in a light- and heat-protected room after 20 minutes' of rest. 1.5m of distance was maintained between the patients and the scanner. Results : Specificity in the type of facial heat distribution was found as follow. 1. Types of facial heat distribution can be classified as T-type and diffused patterns. 2. There was a significant difference in the pattern of facial heat distribution among different types of alopecia (p=0.002): facial heat distribution appeared T-type in androgenic alopecia, alopecia areata, and telogen effluvium (71.3%, 85.7%, 70.4%), whereas diffused pattern was dominant in seborrheic alopecia (55.6%). 3. There was a significant difference in the pattern of facial heat distribution between men and women (p<0.001) : While the T-type and diffused type appeared equally in men (50.6% : 49.4%), T-type was dominant in women (88.0% vs. 12.0%). Conclusions : We conclude that the pattern of facial heat distribution differs depending on the types of alopecia and gender. These differences may provide useful information for diagnosis and clinical therapy for this population.

• Journal of Distribution Science
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• v.3 no.2
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• pp.15-28
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• 2005

This study assessed the development of Japanese food distribution system in response to changes in the needs of consumer population the current food concepts can be divided into "processed" and "perishable" foods we expended the current concept introducing "processed perishable foods" and "perishable processed foods", and how this modified term contributed to more effective food distribution system in Japan. We further assessed the effects of changes in the needs and perception in Japanese consumer population on food distribution system, which included PB goods development as well as diversification of chain system. Our study in the development of Japanese consumer population and food distribution system can be compared to that of Korea, providing a direction for systematic and effective food distribution system.

• Journal of Distribution Science
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• v.15 no.12
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• pp.53-60
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• 2017

Purpose - This paper analyzes the effect of the handset subsidy and the Mobile Number Portability subscriber subsidy regulation, which are the main regulation adopted in "Law on the Improvement of the Mobile Terminal Distribution System" (Mobile Terminal Distribution Act), on the social surplus, the consumer surplus and profits of telecommunications carriers. We focus our analysis on whether the service charge competition is stimulated enough so that it can compensate for the loss of subsidies. Research design, data, and methodology - We use simple economic model to assess the impact of the handset subsidy and the Mobile Number Portability subscriber subsidy regulation. Unlike the former researches on this topic, we depart from using Hotelling model, and instead use the switching cost model, which uses switching cost as a parameter of market powers of telecommunications carriers. We also study the effect of the two different regulations when they are adopted both independently and concurrently. Results - If the market powers of telecommunications carriers are over certain threshold, contrary to the regulatory agency's assertion, the service charge competition would not be stimulated enough to compensate for the deduction in the subsidies, and thus the consumer surplus is compromised. Number Portability subsidy, especially, undermines the rival's market power and thus reduces the service charge. On the other hand, the regulations will also increase the profits of telecommunications carriers. However, social surplus is maximized when both of the regulations are present because the regulations reduces the frequency of switching handsets inefficiently. Conclusions - In enacting the Mobile Terminal Distribution Act, the telecommunications regulatory agency asserted that the regulation on subsidies will stimulate service charge competition, and in the long run, enhance the consumer surplus. However, contrary to the regulatory agency's assertion, subsidy regulation, especially the regulation on Number Portability subsidy, reduces consumer surplus. On the other hand, the Mobile Terminal Distribution Act can also increase the profits of telecommunications carriers because it decreases competition among the telecommunications carriers. However, the Mobile Terminal Distribution Act can increase the social surplus because it reduces inefficient switching of handsets.