• Journal of Korean Society of Industrial and Systems Engineering
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• v.19 no.39
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• pp.47-61
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• 1996

We propose a parallel neural network model in which patterns are clustered and patterns in a cluster are studied in a parallel neural network. The learning algorithm used in this paper is based on LVQ algorithm of Kohonen(1990) for clustering and ADALINE(Adaptive Linear Neuron) network of Widrow and Hoff(1990) for parallel learning. The proposed algorithm consists of two parts. First, N patterns to be learned are categorized into C clusters by LVQ clustering algorithm. Second, C patterns that was selected from each cluster of C are learned as input pattern of ADALINE(Adaptive Linear Neuron). Data used in this paper consists of 250 patterns of ASCII characters normalized into $8\times16$ and 1124. The proposed algorithm consists of two parts. First, N patterns to be learned are categorized into C clusters by LVQ clustering algorithm. Second, C patterns that was selected from each cluster of C are learned as input pattern of ADALINE(Adaptive Linear Neuron). Data used in this paper consists 250 patterns of ASCII characters normalized into $8\times16$ and 1124 samples acquired from signals generated from 9 car models that passed Inductive Loop Detector(ILD) at 10 points. In ASCII character experiment, 191(179) out of 250 patterns are recognized with 3%(5%) noise and with 1124 car model data. 807 car models were recognized showing 71.8% recognition ratio. This result is 10.2% improvement over backpropagation algorithm.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.10 no.3
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• pp.11-28
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• 2000

In these days it is rapidly increasing that multi-user, multi-layered commercial software developments for companies or public institutions. Security services are necessary for most of systems and the access control service is the essential of security services. Current access control methods that are used as access control policies are classified as Discretionary Access Control Mandatory Access Control and Role Based Access Control. However there are some inefficiencies when those methods are applied to current multi-user, multi-layered systems. Therefore it is required that a new access control method that takes complex system resources into account from the side of policy. In this paper extending previous Role Based of 'Behavior' and a basic model of the method. And we simply implement the method on the mobile agent based workflow management system that is a representative example of multi-user. multi-layered softwares and shows implementation results to tap possibilities of real-world application.

• Journal of Korean Society on Water Environment
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• v.25 no.2
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• pp.221-226
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• 2009

We investigated the most effective cutting interval for underwater nutrient removal through cut off the emergent part of hydrophytes at artificial vegetation island (AVR) which was installed for the purpose of water quality improvement in Lake Paldang. We divided the planting area of Phragmites japonica into three parts according to the cutting intervals. The shoot height and relative growth rate of P. japonica, nutrient contents and biomass of cut off P. japonica were measured at each cutting interval. The amount of nutrients which were removed through cut off at each cutting interval was calculated. P. japonica showed full growth, 80% and 60% of full growth before first cut off at three-months, two-months and one-month cutting interval condition respectively. Three-month cutting interval condition showed the largest biomass of cut off P. japonica and one-month cutting interval condition showed the least. However the cut off P. japonica showed the highest content of nutrients at one-month cutting interval condition and the least at three-month cutting interval condition. The amount of phosphorus and nitrogen removal at two-month cutting off condition is the largest among three cutting interval conditions indicating that cut off the emergent part of P. japonica every two months is the most effective to remove the nutrients from water at AVR in eutrophic lakes.

• Journal of the Korean Society of Propulsion Engineers
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• v.16 no.5
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• pp.81-88
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• 2012

Turbopump is a key component in liquid rocket engines, and reducing weight while maintaining structural safety is one of the major concerns of turbopump designers. To reduce the weight aluminium alloy castings instead of steel casings are introduced. The casting process is especially useful for enhancement of productivity and for reduction of product costs. But, since castings are used in space vehicle engines, reliability cannot be compromised. Therefore, proper design, production process and thorough investigation should be performed to ensure structural integrity. In this study inlet casings for a fuel pump were casted with A356.0-T6 alloy and using one of them a burst test was conducted to ensure structural integrity. Structural analysis is performed for simulation, and with multiple strain gages strains are measured and compared with predictions.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.23 no.5
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• pp.29-43
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• 2020

Thermal environment of city is getting worse due to severe urban heat island caused by climate change and urbanization. The cooling effect of street tree is regarded as a effective way to ameliorate the urban heat environment. The effect is largely made up of shadow formation and transpiration. This study aims to identify how the transpiration affects the discomfort index by analyzing comprehensive impact of the transpiration on the air temperature and relative humidity. The changes in the amount of transpiration, air temperature, and relative humidity were estimated for Seogyo-dong area which has a lot of floating population in Seoul, at 2 p.m. in dry day in July and August. On average, the transpiration of the street tree decreased the temperature 0.3℃ and increased the relative humidity 2.6% in an hour. As a result of these changes in temperature and humidity, the discomfort index rose mostly(0.036 on average). It was always get rise especially on the day when the discomfort index was above 80(0.05 on average). However, compared with the significant change in temperature and humidity, the variation of the discomfort index itself was very slight(up to 0.107). Therefore, the effect of transpiration by the street trees might not be effective in the planning to improve the thermal environment(especially on the day when the discomfort index is high). It is necessary to select the species of trees and planting location considering the cooling effect of shade formation synthetically.

• Journal of architectural history
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• v.18 no.6
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• pp.127-144
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• 2009

This thesis aims to analyze the architectural form for the restoration of noogak(樓閣), Boje-roo(普濟樓) which was constructed at the central court of Beomeo-sa(梵魚寺). The results are as follow; 1. Boje-roo was established in 1700. By the constructional records and poetic essays of the times, the architectural of the establishment building was consisted fo two stories structure. The passage system for the approach to the court was the nuha-jinip(樓下進入), that is to say, one might walk between the columns of lower story of the building. And one could ascent the upper stairs and approach to the upper level, inner court. 2. By the remodelling in 1812, the building was varied to one story structure. Therefore the passage system for the approach to the inner court transformed from the nuha-jinip to the ugak-jinip(隅角進入), that is to say, one might ascent the atairs of the podium and could approach the inner court through the both sides of the building. 3. Under the Japanese imperialistic rule, the structure of it's roof and walls of Boje-roo were altered to the Japanese style. In 1965, the wooden columns were shifted to the concreted column, and the wooden wall-panels were shifted to the brick wall attached stone slates. 4. Conclusively speaking, for the restoration of Boje-roo, the establishment form in 1700 is the more proper than the remodelling form in 1812.

• Aerospace Engineering and Technology
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• v.6 no.1
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• pp.201-208
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• 2007

A fuel pump and turbine rotordynamic design is performed for a 75 ton thrust liquid rocket engine. A distance from the rear bearing to the turbine was considered as a design parameter for load distribution of the bearings. Asynchronous eigenvalue analysis was performed as a function of rotating speeds, turbine mass and bearing stiffness to investigate critical speed of the fuel pump and turbine. From the numerical analysis, it is found that the effect of the front bearing stiffness is negligible in the critical speed due to the large mass moment of inertia of the turbine. With the rear bearing stiffness over $2{\times}10^{8}N/m$ and the turbine mass below 20 kg, the critical speed of the fuel pump and turbine in long shaft case is at least 70 % higher than the operating speed 11,000 rpm.

• Journal of radiological science and technology
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• v.41 no.4
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• pp.321-327
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• 2018

The purpose of this study is to compare PET imaging performance with Fluorine-18 ($^{18}F$) and Gallium-68 ($^{68}Ga$) for influence of physical properties of PET tracer. Measurement were performed on a Siemens Biograph mCT64 PET/CT scanner using NEMA IEC body phantom and Flangeless Esser PET phantom containing filled with $^{18}F$ and $^{68}Ga$. Emission scan duration(ESD) was set to 1, 2, 3, 4 and 5min/bed for $^{68}Ga$ and 1min/bed for $^{18}F$. The PET image were evaluated in terms of contrast, spatial resolution. Under same condition, The percentage of contrast recovery measured in the phantom ranged from 16.88% to 72.56% for $^{68}Ga$ and from 27.51% to 74.43% for $^{18}F$ and The FWHM value to evaluate spatial resolution was 10.96 mm for $^{68}Ga$ and 9.19 mm for $^{18}F$. For this study, $^{18}F$ produces better image contrast and spatial resolution than $^{68}Ga$ due to higher positron yield and lower positron energy ($^{18}F$: 96.86%, 633.5 keV, $^{68}Ga$: 88.9%, 1899 keV), The physical properties of PET tracer effect on the PET image. $^{68}Ga$ image applying ESD of 3, 4, 5min/bed were showed similar to $^{18}F$ image with ESD of 1min/bed. This study suggests that increasing ESD for acquiring $^{68}Ga$ PET image seem to be similar to $^{18}F$ image.

• Journal of Korean Society on Water Environment
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• v.23 no.3
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• pp.348-355
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• 2007

We investigated temporal changes of composition, habitat area, growth rate and elements content of hydrophytes at the artificial vegetation island (AVI) in Kyungan Stream within Lake Paldang. We also assessed nutrient removal rate through cutting off the emergent part of hydrophytes. The kinds of hydrophytes have increased from four species (P. australis, P. japonica, T. angustifolia and the Z. latifolia) at initial stage of installation to more than 29 species for 6-year operation. P. japonica was most dominant species at the AVI in 2006. The habitat area of have increased about 2.5 times compared to the initial planting area, occupying 63% of AVI's vegetation area. The incoming species of S. fluviatilis and B. frondosa have adapted successively and expanded habitat area in the AVI. The relative growth rate of P. japonica and P. australis was highest in spring sprouting period. Their hights and weights have increased until summer, by the time they were cutting off the emergent part. They started regrowth immediately after cutting and continued to grow until September and withered away in November. The carbon contents of P. japonica and P. australis have increased during growth phase, on the contrary, the nitrogen and phosphorus contents have decreased. By cutting off and removing the emergent part (leaves and branches) of hydrophytes twice from AVI, $17.6gN/m^2/y$ of nitrogen and $1.3gP/m^2/y$ of phosphorus was removed from AVI in 2006.

• Journal of Korean Society on Water Environment
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• v.23 no.3
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• pp.339-347
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• 2007

Zooplankton community dynamics were studied after establishment of an artificial vegetation island (AVI) in Lake Paldang, from April 2005 to November 2006. There were distinct seasonal and inter-annual changes of total zooplankton abundance at the survey site. Total zooplankton abundance rapidly increased in spring and fall, while it remained low throughout winter. During summer, the dynamics of zooplankton community seemed to be largely affected by hydrological parameters such as, precipitation and inflow. Total zooplankton abundance and biomass below AVI was much higher than that of pelagic zone (L1) in Lake Paldang. Copepoda and cladocera represented the main bulk of the zooplankton community from summer to fall at the both sites. Copepods were more dominant at AVI area, while cladocera were more dominant at pelagic zone (L1). Water quality, prey and habitat condition, species competition between zooplankton seemed to play important roles in dominance of the copepoda and cladocera in zooplankton community at AVI area. Our results conclude that artificial vegetation island provide the stable habitat and besides phytoplankton, diverse food to zooplankton, and consequently influence the diversity and richness of zooplankton community.