• Proceedings of the Korean Geotechical Society Conference
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• 1998.04a
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• pp.37-46
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• 1998

Several researchers have developed a number of theoretical time factors to determine the coefficient of consolidation by biezocone excess pore water dissipation test in soft clay deposits. However, depending on the assumptions and analytical techniques, the estimated coefficient of consolidation could be in a considerably wide range even for a specific degree of consolidation. These solutions are obtained from an initial excess porewater pressure distribution which can be determined from. either the cavity expansion theory or the strain path method. The 야ssipation of the initial excess porelvater pressure has been usally simulated by means of linear-uncoupled consolidation analysis and then the dissipation curve is normalized by the initial excess porewater pressure for easy use. However. since there is no guidelines or rules on which method gives the best solution for obtaining the coefficient of consolidation from the dissipation curve, the final selection was only based on engineer's extrience and Judgements. Thus, such an arbitrary selection might be inappropriate for a specific site to characterize the consolidation behavior. In this paper, we reviewed various theoretical time factors and, based on this consideration, we mentioned needs for researches in selecting a specific solution that is compatible for Korean clays. Also we listed some source of errors that can be encountered in the procedure of dissipation analysis.

• The Korean Journal of Ecology
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• v.21 no.5_2
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• pp.519-529
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• 1998

The vegetation of alpine and subalpine zone from timber line, 2,000m altitude, to the upper area of Mt. Packtu were investigated by phytosociological method. The plant distribution along to the different altitudes shown as follows: Betula ermani community with Rhododendron redowskianum occupied dominantly at 2,000m area as patch forms, Rhododendron redowskianum community with Vaccinium uliginosum, at 2,180-2,200m area, both Vaccinium uliginosum and Rhododendron redowskianum community were compatible with each other at 2,243m area. Rhododendron redowskianum community at 2,250, Salix rotundifolia community, Erigeron thunbergii var. glabrata community, Dryas octopetala var. asiatica community and Carex atrata community were occurred frequently at 2,263m around Chonji Lake. Rhododendron aureum, Thunbergii coccinea and V accinium uliginosum showed higher cover degree than other species at 2,370m area, Phyllodoce coerulea-Rhododendron aureum community at 2,400m, Rhododendron redowskianum community at 2,470m, Rhododendron aureum community at 2,490m, Salix rotundifolia at 2,520m, Rhododendron redowskianum community at 2,580m, Dryas octopetala var. asiatica community, Salix rotundifolia, and bistorta achotensis etc. at 2,650 altitude area were settled as sparse, creeping shape on the surface soil and dwarf plants of about 15cm heights.

• The Korean Journal of Ceramics
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• v.5 no.2
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• pp.142-147
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• 1999

The interaction between commercial $Si_3N_4$ powder and two types of additives (nitrate and oxide additives) during the sintering of $Si_3N_4$ was investigated. The nitrates solution or oxide particles were added as a sintering additives. The surface of mixed powder was observed with FT-IR, TG, and HREM. DTA was used to characterize the reactivity of the powders. The formation of crystalline phases and phase transformation were analyzed by XRD. The adsorption of the additives on the surface of silicon nitride was confirmed in the nitrate salts. It was shown that the adsorption occurred by interaction between the amorphous $SiO_2$ layer on the $Si_3N_4$ surface and metal cations $(Al^{3++\; and \;Y^{3+})$ and anions $(NO_3\;^-\; or\; OH^-)$, resulting in a higher degree of homogeneous distribution of additives.

• Journal of Electrical Engineering and Technology
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• v.13 no.1
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• pp.68-77
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• 2018

Regarding demand response (DR) by residential users (R-users), the users try to reduce electricity costs by adjusting their power consumption in response to the time-varying price. However, their power consumption may be affected not only by the price, but also by user convenience for using appliances. This paper proposes a methodology for appliance scheduling (AS) that considers the user convenience based on historical data. The usage pattern for appliances is first modeled applying the copula function or clustering method to evaluate user convenience. As the modeling results, the comfort distribution or representative scenarios are obtained, and then used to formulate a discomfort index (DI) to assess the degree of the user convenience. An AS optimization problem is formulated in terms of cost and DI. In the case study, various AS tasks are performed depending on the weights for cost and DI. The results show that user convenience has significant impacts on AS. The proposed methodology can contribute to induce more DR participation from R-users by reflecting properly user convenience to AS problem.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.10 no.2
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• pp.243-249
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• 2006

In this paper, the phase noise effects of OFDM transmission diversity systems were analyzed. Since OFDM communication system is very sensitive to phase noise, the system performance may degrade seriously due to the increase of subcarrier interferences and system noise. Therefore, The phase noise model was suggested and its distribution and power were varied to investigate the effects of phase noise on the system performance. The degree of the system performance degradation depends on the specific diversity structures of transmission systems. Here, the performances of OFDM systems with two and three antennas transmission diversity were analyzed and compared with that of systems without transmission diversity as the phase noise characteristics varied.

• Journal of Navigation and Port Research
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• v.28 no.2
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• pp.121-127
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• 2004

The shipping industry can be explained by a growing process of concentration and centralization of tonnage. A few largest shipping company control a great deal of shipping tonnage in the total tonnage through the process of concentration and centralization of tonnage in shipping over time. It confirms that a decreasing number of operators take an increasing quantity of tonnage in the total tonnage. Thus, the extremely dualistic structure (extremely unequal distribution of tonnage) are shown not only in the shipping industry in a given country but also in liner shipping in the world In this paper, the two countries, that is, Korea and Egypt, are compared considering the absolute size of tonnage and shipping policy in tenn., of concentration and centralization of tonnage in shipping. In order to measure the degree of concentration of tonnage in shipping, the quantitative measurements; the Lorenz curve and Gini coefficient are introduced. But it should be supplemented with the qualitative measures of tonnage in a given country.

• Journal of Information Processing Systems
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• v.16 no.1
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• pp.132-144
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• 2020

Cloud computing is an emerging technology based on the concept of enabling data access from anywhere, at any time, from any platform. The exponential growth of cloud users has resulted in the emergence of multiple issues, such as the workload imbalance between the virtual machines (VMs) of data centers in a cloud environment greatly impacting its overall performance. Our axis of research is the load balancing of a data center's VMs. It aims at reducing the degree of a load's imbalance between those VMs so that a better resource utilization will be provided, thus ensuring a greater quality of service. Our article focuses on two phases to balance the workload between the VMs. The first step will be the determination of the threshold of each VM before it can be considered overloaded. The second step will be a task allocation to the VMs by relying on an improved and faster version of the meta-heuristic "simulated annealing (SA)". We mainly focused on the acceptance probability of the SA, as, by modifying the content of the acceptance probability, we could ensure that the SA was able to offer a smart task distribution between the VMs in fewer loops than a classical usage of the SA.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.27 no.9
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• pp.6-14
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• 2013

The position of the light source, illuminance distribution, and color temperature were evaluated in each lighting environment for the three main activities in a living room - 'watching TV,' 'reading' and 'relaxing.' In 'watching TV', the experiment was done to estimate the degree of comfort felt by the subjects when they watch static video and moving video, respectably, with different ambient brightness, with or without partial lighting above the TV set, and with different color temperatures. In 'reading', the comfortableness was estimated by the illuminance ratio of the ambient lighting to the lighting for reading and by the difference in color temperature. And in 'relaxing', the comfortableness was estimated by means of the ambient brightness, use/no use of a relaxing lamp, and color temperature. This experiment determined the general satisfaction for each visual act and the optimum lighting environment to reduce glare.

• Proceedings of the KSRS Conference
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• 2003.11a
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• pp.147-149
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• 2003

The wetness, a function of precipitation and temperature etc, and the warmth, a function of temperature, are the dominant factor for global vegetation distribution. This paper employs the normalized difference vegetation index (NDVI), warmth index (WAI), and wetness index (WEI), and focuses on an essential climate-vegetation relationship at global scale. The NDVI was acquired from ‘Twenty-year global 4-minute AVHRR NDVI dataset.’ The WEI is defined as the fraction of the precipitation to the potential evaporation. The WAI was calculated by accumulating the monthly mean temperature of the portion exceeded 5$^{\circ}C$ throughout the year. Meteorological data for the WEI and WAI calculation were obtained from the ISLSCP CD-ROM. All analyses were conducted for 1 ${\times}$ 1 degree grid box on the terrestrial area of the Earth, and on annual value basis averaged in 1987 and 1988. The result of analyses demonstrated that there are two regimes in their relations, that is, a regime in which NDVIs vary depending on the WEI, and a regime in which NDVIs vary depending on the WAI. These two regimes appeared to correspond to the wetness dominant and warmth dominant vegetation, respectively. The geographical distributions of two regimes were mapped. Most of the world vegetation is categorized into wetness dominant, while warmth dominant vegetation is seen in the high-latitude area mainly to the north of 60$^{\circ}$N in the Northern Hemisphere and high-altitude areas.

• Journal of radiological science and technology
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• v.4 no.1
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• pp.63-71
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• 1981

The metal-plates(Aluminium. Copper, Lead) of change the variation thickness have been penetrated by the collimated beam($450mm{\times}4mm{\phi}$) of Gamma-ray from $^{192}Ir$. Then, the scattered $\gamma$-ray dose in variable angle and the directly transmitted $\gamma$-ray dose were measured using the electrometer of ionization chamber. The results were summarized as follows: 1. Obtained the mass attenuation coefficients of $Al;0.0937cm^2g^{-1},\;Cu;0.0937cm^2g^{-1},\;pb;0.244cm^2g^{-1}$. 2. Total intensity of front scattered $\gamma$-ray follow the order of Al>Cu>pb. 3. The scattered $\gamma$-ray intensity with the lager angle of scattering was saturated after increase rapidly, and the scattering angle of the more larger was decreased. 4. The scattered $\gamma$-ray intensity through plates of aluminium or copper was saturated after increase with thicker scatterer, and the intensity was decreased at the more thicker. But the variation of scattered $\gamma$-ray dose in the lead plate made the fewest than Al and Cu. 5. The ratio of the scattered $\gamma$-ray dose and the directly transmitted $\gamma$-ray dose was saturated after increase with the thicker scatterer, and the scatterer of the more thicker was decreased. Degree of total intensity in these ratios was followed the order of Cu>Al>Pb.