• Journal of the Institute of Electronics Engineers of Korea TC
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• v.44 no.9
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• pp.9-16
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• 2007

In the multiuser OFDM systems, an efficient resource allocation is necessary in order to provide the service to more users. This paper proposes u improved subcarrier allocation algorithm, satisfying each user's QoS under the limited resources, to maximize total transmission data rate and spectral efficiency. The proposed algorithm is divided into two steps. In the first step, users who are eligible for services are determined by using BER, user's minimum data rate requirement, and channel information. In the second step, first, subcarriers are allocated to users on the basis of channel state. And then, reallocation is fulfilled so that the total transmission data rate is maximized and the least reduction in the overall throughput is caused.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.30 no.4
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• pp.251-262
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• 1994

The speed of vertical migration and the volume backscattering strength of the scattering layers during the evening and morning transitions between day and night were measured in November 1990-1992 in thermally stratified waters of the East China Sea. Acoustical measurements were carried out using a scientific echo-sounder operating at t재 frequencies of 25 and 100kHz, and using an echo-integration system connected with a micro-computer. Biological sampling was accomplished by bottom trawling to identify fish species recorded on the echo sounder, and the species and length compositions were determined. The values of scattering strength were allocated to group of fishes according to the fish traces on the echo recording paper and the species composition of trawl catches. The vertical velocities of migration derived from the changes in the depths and the values of peak scattering strength of the dense layer vertically migrating toward the bottom or toward the surface. The trawl data suggest that snailfish and fishing frog were the most abundant fishes in all research stations. As sunrise approached, the fish formed a strong concentration just above the thermocline. The the highest values of scattering strength in the entire water column appeared in the depth strata above the thermocline just before the begining of downward migration. As soon as the fish began to migrate downwards across the thermocline, the values of the scattering strength in the depth strata above the thermocline rapidly decreased, while the values for the scattering layer moving slowly toward the bottom gradually increased. During the 1992 surveys, the speed of the vertical migration was estimated to be 0.38m/min in the upward migration and 0.32m/min in the downward migration, respectively. That is the rate of vertical migration was slightly higher at dusk than at dawn. Similar migration patterns were observed on different stations and under different weather conditions during the surveys in 1990.

• Journal of the Korean Geotechnical Society
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• v.31 no.9
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• pp.29-38
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• 2015

In this study, track dynamic interaction characteristics caused by the vehicle running through transitional section such as bridge abutments were studied using the finite element analysis program. The geometric condition of track was generated by trigonometric function and allowable maximum track irregularity is determined by KORAIL track maintenance criteria. The sub-infrastructure under rail fastener system was modelled by 3D solid elements. To reduce computational cost only half track line is numerically considered and the roller boundary condition was applied to each side of model. In this study, the vehicle-track dynamic interaction analysis was carried out for standard Korean transition section of concrete track and the dynamic behaviors were investigated. The dynamic characteristics considered are wheel load variation, vertical acceleration at body, and maximum Mises stress at each part of transitional section.

• The Journal of Korean Academy of Prosthodontics
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• v.40 no.3
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• pp.225-235
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• 2002

The color stability of current prosthetic composites is unknown, even though the quality of composite materials has been improving. This study examined the intrinsic color stability of various current prosthetic resins (ceramic-polymers) after an accelerated aging process and the extrinsic color stability after immersion in a coffee solution. By comparing the amount of discoloration after aging with that without aging, the effect of the accelerated aging process on external discoloration could be evaluated. Three current prosthetic composites (Artglass, Targis, Sculpture), one light polymerized direct composite (Z100) and one dental porcelain control (Ceramco) were assessed. The color changes (${\Delta}$E) of all the specimens were determined using the CIE $L^{*}a^{*}b^{*}$ color order system with a reflected spectrophotometer. The results were as follows: 1. The prosthetic composite materials subjected to the accelerated aging test showed no significant difference in color changes (p >.05). 2. In the coffee solution immersion test after the aging process, the color changes of the Targis and Artglass groups were not different from that of the Z100 group, which showed the highest color change. 3. In the immersion only test, a significantly high color change was observed in the sculpture glazing group. 4. The aging process influenced on the color changes more in the Targis, Artglass and Z100 groups than in the Sculpture and Ceramco groups.

• Investigative Magnetic Resonance Imaging
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• v.5 no.1
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• pp.24-32
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• 2001

Purpose : We investigated the reproducibility of language lateralization by 4 different word generation paradigms or the rest contents in each paradigm using functional magnetic resonance imaging in normal volunteers Materials and Methods Nine normal volunteers with left-handedness (mean age: 25 yrs) were examined on a 1.57 MR unit using a single-shot gradient echo epibold sequence. Four different word generation paradigms of noun, verb, adjective and adverb were used in each normal volunteer for investigating language system. In each paradigm, two different rest contents consisted of only seeing the " +" symbol or reading the meaningless letters. Each task consisted of 96 phases including 3 activations and 6 rests of 2 different contents. Two activation maps in one task were obtained under two different rest contents using the correlation method. We evaluated the detection rates of Broca and Wernicke areas and the differences of language lateralization among four different word generation paradigms, or between the rest contents. Results : The detection rates of Broca and Wernicke areas were over 67 % in 4 different language paradigms and there was no significant difference of them among language paradigms, or between two different rest contents. Language dominances, in all 4 different language paradigms, were shown to be consistent in 66 %, but were contrary with language paradigms in some subjects. The rest contents made no significant effect on dominant language dominance determination, but the success rates of the dominant language dominances determined from 4 language paradigms were higher in reading the meaningless letter (100%, n=9) than in only seeing "+" on screen at the rest task (78%, n=7).

• Journal of Energy Engineering
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• v.8 no.2
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• pp.248-255
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• 1999

Catalytic cracking of pyrolysed waste lubricating oil over solid acid catalysts (HY zeolite, ${\beta}$-zeolite, HZSM-5) has been carried out in a micro-fixed bed system. The feed oil for catalytic activity tests has been prepared by thermal cracking of waste lubricating oil under the reaction conditions of 480$^{\circ}C$, 60 min. Optimum reaction conditions for the maximum light oil yields($\_$21/) were WHSV(weight hourly space velocity)=1 at 375$^{\circ}C$. The amounts of total and strong acid sites appeared to be the largest in ${\beta}$-zeolite as determined by NH$_3$, TPD. It is seen that the catalytic activity order, in terms of the light fuel oil ($\_$21/) production, were HY zeolite)${\beta}$-zeolite>HZSM-5. Also, coke formation followed the same order. The highest activity in HY zeolite may be attributed from the fact that it has supercages facilitating the easy diffusion of larger molecules and also the effectiveness of the acid sites for cracking within the pore. This fact could be confirmed by the coke formation characteristics.

• Journal of fish pathology
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• v.17 no.3
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• pp.199-205
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• 2004

Effects of nitrite, ammonia and hydrogen sulfide on survival of the early developmental stages of Fenneropenaeus chinensis were determined under continuous flow-through system. The 96hr-$LC_{50}$ values of mysis stage were 18.4 mg/L, 0.69 mg/L and 13.5 $\mu{g}/L$ for nitrite, ammonia and hydrogen sulfide, respectively; 28.3 mg/L, 1.23 mg/L and 20.7 $\mu{g}/L$ for post larva stage and 39.8 mg/L, 1.73 mg/L and 28.5 $\mu{g}/L$ for juvenile stage, respectively. The Fenneropenaeus chinensis sensitivity for the three pollutants was in the order of hydrogen sulfide>ammonia>nitrite. The mysis/post larva, mysis/juvenile and post larva/juvenile ratios of nitrite, ammonia and hydrogen sulfide toxicity were >1.5, >2.0 and <1.5 times, respectively, and mysis were found to be more sensitive to pollutants than juvenile in all cases.

• Journal of Korea Society of Industrial Information Systems
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• v.10 no.3
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• pp.48-56
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• 2005

This paper proposes a dynamic end-to-end flow control algorithm that is more effective than previous methods considering either the Rate of Packet Loss (RPL) or Round Trip Time (RTT). When the RPL is under normal conditions, the current network status will be in one of three defined states by using the RTT and this makes bandwidth control precise before serious packet loss occurs. If the RPL exceeds a critical level, then the network is considered to be in a fourth state. Suitable transmission rates are determined depending on the network status and are controlled by adjusting not only the number of transmitted frames but also the quality of the frames. In this paper, we present some experimental results of the proposed algorithm. According to our quantitative analysis, the proposed method performs 1.6 to 6 times better than the previous method in terms of the RPL. At the same time, the total number of transmitted packets is increased, which indicates that the proposed method can provide greater bandwidth capacity than previous methods.

• Natural Product Sciences
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• v.21 no.2
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• pp.128-133
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• 2015

Lindera obtusiloba has been widely used as a traditional medicine for the treatment of lots of diseases, including abdominal pain, bruise, and hepatocirrhosis. Here in this study, we elucidated the lifespan-extending effect of methanolic extract of Lindera obtusiloba (MLO) using Caenorhabditis elegans model system. We found that MLO has potent lifespan extension activities under normal culture condition. Then, we determined the protective effects of MLO on the stress conditions such as osmotic, thermal and oxidative stress. To reveal possible mechanism of MLO-mediated lifespan, we further investigated the effect of MLO on the antioxidant enzyme activities and intracellular ROS levels. Our results demonstrated that superoxide dismutase and catalase activities were significantly up-regulated by MLO treatment, resulted in reduced intracellular ROS levels. In this work, we also tested whether MLO-mediated longevity activity was associated with aging-related factors such as food intake and growth. Our data revealed that both of pharyngeal pumping rate and body length were significantly shifted by MLO treatment, indicating these factors were involved in MLO's lifespan-extension effects. Although MLO induces reduction in food intake, the body movement of MLO-fed aged worms was not decreased, compared to untreated control worms, indicating MLO might extend lifespan without affecting healthspan.

• Korean Journal of Soil Science and Fertilizer
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• v.45 no.1
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• pp.9-15
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• 2012

This study was performed to produce basic data for silty reclaimed tidal lands and to develop techniques of environmentally-friendly utilization in agricultural system. We chose the two sites in Saemangeum reclaimed tidal lands, one (Site I) has been treated with cultivating green manure and conducting the desalinization process through submergence since April, 2007 and the other (Site II) has been under natural condition without artificial treatment. In situ and ex situ physic-chemical properties were determined and comparisons were made for soil profiles examined at these two sites in April 2009. Surface soil of Site I had lower EC and higher field saturated hydraulic conductivity than those of Site II, uncultivated land. Especially, exchangeable sodium content was lowest in Site I Ap1 layer than in other layers. This is probably due to flooding desalination and green manure cultivation. Besides, Ap1 and A2 layers of soil profile in Site I showed brighter soil color and more root observation than those of Site II. This is probably due to green manure cultivation. By the large, for high cash upland crops and intensive agricultural use of silty reclaimed tidal land, site-specific soil ripening such as flooding desalination and green manure cultivation could be useful.