• Korean Journal of Construction Engineering and Management
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• v.11 no.2
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• pp.54-63
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• 2010

Domestic construction companies suffer from the difficulty in financing in the wake of economic slump at home and abroad. In the periods of this economic slump, which hit the nation REITs, the facilitator of fluid financing and the stimulating of construction economic, has increasingly been expanded since its introduction in 2001. But, REITs relatively falls behinds any other nations, in terms of its growth speed and marketing volume. The purpose of this research thesis is to suggest the method for composing a portfolio using Markowitz portfolio selection models for stimulating REITs. Main contents are as follows. First, the thesis made the comparative analysis on profit increase in REITs investment in application of models by Markowitz and REITs derivatives from 2007/07/03 to 2008/07/21 during investment analysis periods. The result showed that total profits by Markowitz model amounted to about 10 percent higher than average profits of REITs derivatives. Second, this thesis made the analysis on sensitivity of data-gathering and portfolio change periods of the existing profits, in order to measure the both periods and yield optimum profits. The six month data-collecting periods of profits accounted for some 16% higher profits than profits of REITs derivatives. In case when the two week periods of portfolio change accounted for some 11% higher profits than profits of REITs derivatives.

• Journal of Korean Port Research
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• v.13 no.2
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• pp.333-350
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• 1999

Today freeway is thought to be a very important transportation facility carrying tremendous traffic flow as the main corridor within the area of between the areas. However freeway is experiencing severe congestion and accidents by increased entrance ramp flow especially at peak time period. Ramp meters on the freeway entrance ramps that supply traffic to the freeway in a measured or appropriately regulated amount are needed for alleviating freeway congestion. Because ramp meters can be operated to discharge traffic at a measured or regulated rate thus maintaining more uniform speed on the mainline section maximizing the throughput to the freeway within the capacity of a downstream bottleneck and reducing the congestion related accidents. Thus the objectives in this study were to analyze the traffic characteristics on the freeway I-94 with ramp metering system before/after ITS technology in Detroit (Michigan) area compare shifts of the traffic characteristics on the freeway I-94 before/after ITS technology and finally suggest a better ramp metering strategy for the freeway system The following results were obtained: i)Flow occupancies and speeds on the mainline merge section of freeway were shown to be a big difference depending on the peak periods areas and directions based on the distribution of traffic flow characteristics on the freeway. ii)Reduced speed was shown to be more than 5 mph and ramp flow was also shown to be more than 240 vph at peak periods if there was the ramp metering system constructed on the freeway. iii)Ramp metering system was shown to be optimally operated on the freeway if ramp flow could be maximized within the range of over 900 vph and reduced occupancy could be also maximized by no more than 2 percent at peak periods. iv)The average flows on the freeway after the ITS technology were shown to be a decrease of over 20% depending on the peak periods areas and directions when compared with those flow on the freeway before the ITS technology. over 20% depending on the peak periods areas and directions when compared with those speeds on the freeway before the ITS technology. vi)The average metering rates on the freeway after the ITS technology were shown to be an increase of over 10% depending on the peak periods areas and directions when compared with those metering rates on the freeway before the ITS technology.

• Proceedings of the Korean Society of Sericultural Science Conference
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• 2003.10a
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• pp.43-45
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• 2003

This study was carried out to investigate sprouting and cold hardiness during wintering and thawing Periods in 7-year-old mulberry(Morus) three varieties of Kaeryangppong, Shinilppong and Yongcheonppong. The killing points of the mulberry twigs were investigated using DTA(Differential Thermal Analysis). (omitted)

• Journal of Korean Institute of Industrial Engineers
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• v.19 no.3
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• pp.71-79
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• 1993

Dynamic production planning problems are to determine the optimal production times and production quantities of product for discrete finite periods. In previous many researches, the solutions for these problems have been developed through the algorithms using dynamic programming. The purpose of this research is to suggest the new algorithm using linear programming. This research is to determine optimal production quantities of product in each period to satisfy dynamic for discrete finite periods, minimizing the total of production cost and inventory holding cost. Cost functions are concave, and no backlogging for product is allowed. The new algorithm for capacity constrained problem is developed.

• Journal of the Korean Society of Hazard Mitigation
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• v.11 no.2
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• pp.137-146
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• 2011

In this study, annual maximum storm events are evaluated by applying the bivariate extremal distribution. Rainfall quantiles of probabilistic storm event are calculated using OR case joint return period, AND case joint return period and interval conditional joint return period. The difference between each of three joint return periods was explained by the quadrant which shows probability calculation concept in the bivariate frequency analysis. Rainfall quantiles under AND case joint return periods are similar to rainfall depths in the univariate frequency analysis. The probabilistic storm events overcome the primary limitation of conventional univariate frequency analysis. The application of these storm event analysis provides a simple, statistically efficient means of characterizing frequency of extreme storm event.

• Journal of Korean Society of Steel Construction
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• v.15 no.2
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• pp.117-124
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• 2003

Wind-induced motions, like acceleration for instance, often influence designs for high-rise buildings. As a consequence, correct assessment of natural frequency becomes important. The empirical expressions used to quantify this parameter at the design phase tend to yield values that are significantly different from each other. This paper is concerned with the natural periods of steel buildings. It describes the vibration measurement methods that were employed for testing buildings. This paper will also present reliable methods of assessing the natural period from ambient vibration tests. Data from measurements on 21 buildings in Seoul were provided while 21 buildings were tested by ambient vibration measurements to obtain the natural periods. While regression formulas of natural periods for steel-frarried tall buildings were suggested,the obtained formula was compared with the empirical expressions of structural standards and the Eigen-value analysis.

• The Journal of the Acoustical Society of Korea
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• v.18 no.3E
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• pp.9-20
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• 1999

To investigate the characteristics of internal waves (IWs) and their effects on acoustic wave propagation, a series of sea experiment were performed in the east coast of Donghae city, Korea in 1997 and 1998 where the water depth varies between 130 and 140 m. Thermistor strings were deployed to measure water temperatures simultaneously at 9 depths. CW source signals with the frequencies of 250,670 and 1000 Hz were received by an array of 15 hydrophones. Through the Wavelet transform analysis, the IWs are characterized as having typical periods of 2-17 min and duration of 1-2 hours. The IWs exist in a group of periods rather than in one period. Underwater acoustic signals also show obvious energy peaks in the periods of less than 12 min. Consistency in the periods of the two physical processes implies that acoustic waves react to the IWs through some mechanisms like mode interference and travel time fluctuation. Based on the thermistor string data, mode arriving structures are analyzed. As thermocline depth varies with time, it may cause travel time difference as much as 4-10 ms between mode 1 and 2 over 10 km range. This travel time difference causes interference among modes and thus fluctuation from range-independent stratified ocean structure. In real situations, however, there exist additional spatial variation of IWs. Model simulations with all modes and simple IWs show clear responses of acoustic signals to the IWs, i.e., fluctuations of amplitude and phase.

• Journal of the Korean Society of Clothing and Textiles
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• v.20 no.1
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• pp.142-156
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• 1996

The purposes of this study were to examine the reason, = of clothing discard and to investigate the influences of demographic and clothing variables on the clothing discard behavior Data were collected from 610 women who lived in Seoul and Kwangjoo. By means of factor analysis, 6 general factors of clothing discard reason.; were extracted The 6 factors were named as dissatisfaction with appropriateness, physically worn out, dissatisfaction with clothing quality, fashion change, boredom, inconvinience. Among the five clothing items (suits or one pieces, jackets, jumpers, shirts or blouses, skirts or pants), there existed differences in the reason factors of clothing discard The relationships between clothing discard behavior (reason factors of clothing discard, peviods of clothing utilization) and variables like user's age, degrees of satisfaction with clothing, clothing items were also examined. There existed significant differences among the age groups and the groups classified by clothing satisfaction degrees in the reason factors of clothing discard and in the Periods of clothing utilization. Periods of clothing utilization were also differed by the clothing items. As user's a age grew older, periods of clothing utilization increased and the rates of clothing discard because of dissatisfaction with appropriateness, and dissatisfaction with clothing quality, boredom, inconvinience factors were decreased. As the degrees of satisfaction with clothes increased, the periods of clothing utilization also increased and the rates of clothing discard because of dissatisfaction with appropriateness, and dissatisfaction with clothing quality, inconvinience factors decreased. And the rates of clothing discard because of physically worn out factor increased.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.53 no.4
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• pp.337-348
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• 2017

The tension of warp from trawler and sea-floor contact can generate tilt and wake turbulence around otter boards. Preliminary measurements of otter board tilt and 3-D flow velocity during bottom trawl operations were taken using a vector instrument to investigate the effects of wake turbulence at the trailing edge of the otter board. Tilt data (i.e., yaw, pitch, and roll) at 1 Hz and flow data (velocities in the towing, lateral, and vertical directions) at 16 Hz were analyzed to determine their periods and amplitudes using global wavelet and peak event analyses. The mean period (${\pm}standard$ deviation) of the tilt from the peak event analysis ($5{\pm}2s$) was longer or double than that of flow velocity ($3{\pm}2s$). The two periods also had a significant linear relationship. The turbulence rate of flow was 30-50% at the trailing edge and was closely related to roll deviation. The frequency of phase difference ratios (i.e., peak time differences between tilts and flow periods) was significantly different from random occurrence in two trials, possibly due to side tidal effects. However, in the other trials, flow peaks were random, as shown by the even peak times between tilts and flows. Future studies should focus on reducing tilt variation, wake turbulence, and bottom contact to stabilize otter board motion.

• Journal of the Korean Society of Food Culture
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• v.4 no.1
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• pp.95-102
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• 1989

The objective of this study was to access the effects of sensory and physical properties of Beandaeduk on 7 different combination methods (three were combined with mung bean and different proportions of water; four were combined with mung bean and various cereals with constant water), and 3 storage periods (0, 1 and 3 weeks at $-18^{\circ}C$). This experiment was consisted of sensory evaluation I (appearance, texture, taste, flavor and overall preference), II (color, moisture, volume, hardness, elasticity, viscosity and ratio materials, off-flavor and oder) and physical analysis of each sample, and questionaire survey of Beandaeduk. In sensory evaluation I except flavor, significant differences (p<0.05) were found among different combination methods of sample. Also significant differences (p<0.05) were found in sample for storage periods, except appearance. In sensory evaluation II, only moisture and oder of samples were significantly different (p<0.05) for storage periods, and there were significant differences (p<0.05) in samples among different combination methods, except elasicity. Stepwise regression for storage periods in sensory I showed that texture and taste were important factors in overall preference of sample. In the questionaire survey, preference and adding materials of Beandaeduk were different according to province. Half of respondents preferred to get instant Beandaeduk and instant mung bean powder.