• The KIPS Transactions:PartC
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• v.14C no.7
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• pp.571-582
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• 2007

Vehicular ad-hoc networks is temporarily established through inter-vehicle communication without any additional infrastructure aids. It requires a immediate message propagation because it mainly deals with critical traffic information such as traffic accidents. The distance-based broadcast scheme is one of the representative broadcast schemes for vehicular ad-hoc network. In this scheme, a node to disseminate messages is selected based on a distance from a source node. However, a message propagation delay will be increased if the relay nodes are not placed at the border of transmission range of the source node. In particular, when the node density is low, the message propagation delay is getting longer. In this paper, we propose a time-window reservation based relay node selection scheme. A node receiving the alert message from the source node has its time-window and randomly selects its waiting time within the given time-window range. A proportional time period of the given time-window is reserved in order to reduce the message propagation delay. The experimental results show that the proposed scheme has shorter message propagation delay than the distance-based broadcast scheme irrespective of node density in VANET. In particular, when the node density is low, the proposed scheme shows about 26% shorter delay and about 46% better performance in terms of compound metric, which is a function of propagation latency and network traffic.

• Korean Journal of Weed Science
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• v.2 no.2
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• pp.114-121
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• 1982

Sagittaria pygmaea Miquel is widely infested and is the most dominant perennial weed in paddy field in Korea. This study was carried out in order to clarify the factors influencing tuber production and the competition ecology. The tuberization capacity in the paddy field transplanted with the small seedlings of rice was higher than in the paddy field transplanted with the vigor seedlings of rice. The stage which rice plants were most damaged by S. pygmaea plants was the period from 31 to 37 days after transplanting. According to the increasing of Eleocharis acicularis Roem. in the condition of rice cultivation, the number of S. pygmaea plants was remarkably reduced. Small size tubers planted within deep soil produced less tubers than large size tubers did. The number of plants and tubers were remarkably increased under the high levels of fertilization. Phosphorus was essential as well as nitrogen for tuberization. And the tuberization capapcity was different with the organic matter content in soil and with the soil moisture.

• Journal of Wetlands Research
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• v.18 no.2
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• pp.166-172
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• 2016

Accurate understanding of land surface is essential to analyze energy exchanges between earth surface and atmosphere. For the quantization of energy fluxes, the various researches about Land Surface Model(LSM) have been progressed. Among the various LSMs, the researches using Common Land Model(CLM) and Variable Infiltration Capacity(VIC) model are performed briskly. The CLM which is advanced LSM can calculate realistic results with few user defined parameters. The VIC model which is also typical LSM is widely used for estimation of energy fluxes and runoff in various fields. In this study, the energy fluxes which are net radiation, sensible heat flux, and latent heat flux were estimated using CLM and VIC model at Southern Sierra-Critical Zone Observatory(SS-CZO) site in California, United States. In case of net radiation and sensible heat flux, both models showed good agreement with observations, however, the CLM showed underestimated patterns of net radiation and sensible heat flux during precipitation period. In case of latent heat flux, the CLM represented better estimation of latent heat flux than VIC model which underestimated the latent heat flux. Through the estimation of energy fluxes and analysis of models' pros and cons, the applicability of CLM and VIC models and need of multi-model application were identified.

• Journal of Trauma and Injury
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• v.23 no.1
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• pp.6-15
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• 2010

Purpose: Trauma is one of the leading causes of death, especially among young people. Life-threatening conditions are very common in multiple-traumatized patients due to concurrent multi-organ injuries. Treating such severely injured patients is time critical. However, in Korea, the transfer of severely injured patients is not uncommon due to the lack of a mature trauma care system. In developed countries, the preventable trauma death rate is very low, but the rate is still very high in Korea. This study's objective was to demonstrate the current serious state in which severely injured patients have to be transferred from a Regional Emergency Medical Center even though it actually serves as a trauma center. Methods: Ajou University Medical Center is a tertiary hospital that serves as a trauma center in Gyeonggido. The medical records at Ajou University Medical Center for a 1-year period from January 1, 2008, to December 31, 2008, were retrospectively reviewed. A severely injured patient was defined as a patient who showed more than 15 point on the ISS (injury severity score) scale. We investigated the clinical characteristics of such patients and the causes of transfer. Results: Out of 81,718 patients who visited the Regional Emergency Medical Center, 19,731 (24.1%) were injured patients. Among them, 108 severely-injured patients were transferred from one Regional Emergency Medical Center to other hospitals. The male-to-female ratio was about 3.5:1, and the mean ISS was 23.08. The most common mechanism of injury was traffic accidents (41.7%). A major cause of transfer was the shortage of intensive care units (44.4%); another was for emergent operation (27.8%). Most of the hospitals that received the severely-injured patients were secondary hospitals (86.1%). Conclusion: Although the Regional Emergency Medical Center played a role as a trauma center, actually, severely-injured patients had to be transferred to other hospitals for several reasons. Most reasons were related with the deficiencies in the trauma care system. If a mature trauma care system is well-organized, the numbers of transfer of severely injured patients will be reduced significantly.

• The korean journal of orthodontics
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• v.40 no.1
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• pp.34-39
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• 2010

Objective: The aim of the present study was to evaluate the changes in tooth mobility following orthodontic treatment and to obtain information regarding the guideline of retainer wear duration during the post-treatment period. Methods: The sample consisted of twenty patients who had been treated with edgewise appliances. The mobility of the maxillary teeth from the central incisor to the first molar was measured bilaterally by way of the $Periotest^{(R)}$, a non-invasive, electronic device that provides an objective measurement of the reaction of the periodontium to a defined impact load. Tooth mobility was monitored at the time of the removal of the orthodontic appliances and subsequently at three-month intervals during the two years following appliance removal. Results: Tooth mobility decreased rapidly for the first six months and then decreased at a slower rate during the next six months; no statistically significant decrease in mobility was observed during the second year following appliance removal. Conclusions: The results of the present study suggest that adequate tooth stabilization is critical during the first six months following appliance removal and that continued wearing of retainers is recommended at least until twelve months after the completion of orthodontic treatment.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.47 no.12
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• pp.39-47
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• 2010

This paper proposes a fully-utilized block-based 2D DWT architecture, which consists of four 1D DWT filters with two-channel QMF PR Lattice structure. For 100% hardware utilization, we propose a new method which processes four input values at the same time. On the contrary to the image-based 2D DWT which requires large memories, we propose a block-based 2D DWT so that we only need 2MN-3N of storages, where M and N stand for filter lengths and width of the image respectively. Furthermore, the proposed architecture processes in horizontal and vertical directions simultaneously so that it computes the DWT for an $N{\times}N$ image within a period of $N^2(1-2^{-2J})/3$. Compared to existing approaches, the proposed architecture shows 100% of hardware utilization and high throughput rate. However, the proposed architecture may suffer from the long critical path delay due to the cascaded lattices in 1D DWT filters. This problem can be mitigated by applying the pipeline technique with maximum four level. The proposed architecture has been designed with VerilogHDL and synthesized using DongbuAnam $0.18{\mu}m$ standard cell.

• Korean Journal of Ichthyology
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• v.7 no.1
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• pp.43-55
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• 1995

Based on the reproductive cycle of Rhodeus uyekii, the reproductive control mechanism was examined under the several combinations of photoperiod and temperature regimes at different phases of their reproductive cycle. In early spring, the gonads developed rapidly under the warm temperature condition(above $8^{\circ}C$), regardless of the photoperiod. In late spring or early summer, gonads intensely regressed under the high temperature condition(above $24^{\circ}C$), regardless of the photoperiod. Thus, it is concluded that the spawning period of R. uyekii is initiated by the rising of water temperature in spring and is terminated by the high temperature in early summer. In autumn, the gonadal recrudescence occurs under the conditions of artificial long daylength with warm temperature(15L/9D, $12^{\circ}C{\sim}20^{\circ}C$), whereas the gonads remain in the existing condition under the short daylength. Therefore, in autumn the gonadal recrudescence is prevented by the short daylength although the temperature is still in favorable condition. In bitterling, the responsiveness of the gonads to photoperiod varies clearly with seasons, which was declined during the winter but increased during the autumn. The critical photoperiod for maturation ranges 12~13 hours of light per day. The results indicate that the proper ranges of temperature and photoperiod for gonadal maturation of this species are from $8^{\circ}C$ to $8^{\circ}C$ and from 13L to 15L, respectively.

• Management & Information Systems Review
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• v.28 no.1
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• pp.1-24
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• 2009

Electronic commerce markets have been increasing rapidly, which has resulted in parallel growth in the door-to-door delivery service industry. The door-to-door delivery service industry is projected to be more competitive, due to the large amount of companies that are already established and the fact that several leading multinational logistics companies are rushing into the domestic market. This is a critical period for the companies which are attempting to obtain a competitive advantage. Previous research on door-to-door delivery services has been undertaken, in relation to strategic exploration, political proposals, and user satisfaction. However, there is a lack of practical studies focused on the information systems of door-to-door service companies and its decisive roles have been undertaken. This study aims to investigate, compare, and analyze the information systems of door-to-door delivery service companies. Also, the study proposes developmental direction of how the information systems should be improved. In order to accomplish the purpose of this study, first, we examined previous research on door-to-door delivery services and their information systems. Second, we investigated and analyzed the information systems of four leading domestic companies by conducting interviews. Third, we compared and identified factors of the information systems that could be improved. Finally, we proposed its developmental direction. As a result of the study, the information systems of door-to-door delivery service companies required to provide classified services using diverse tools and develop the optimized routing model to reduce logistics costs.

• Nuclear Engineering and Technology
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• v.52 no.4
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• pp.721-733
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• 2020

In nuclear engineering, the occurrence of critical heat flux (CHF) is complicated for rod bundle, and it is much more difficult to predict the CHF when it is in natural circulation under motion condition. In this paper, the dryout-type CHF is investigated for the rod bundle in a natural circulation loop under rolling motion condition based on the coupled analysis of subchannel method, a one-dimensional system analysis method and a CHF mechanism model, namely the three-fluid model for annular flow. In order to consider the rolling effect of the natural circulation loop, the subchannel model is connected to the one-dimensional system code at the inlet and outlet of the rod bundle. The subchannel analysis provides the local thermal hydraulic parameters as input for the CHF mechanism model to calculate the occurrence of CHF. The rolling motion is modeled by additional motion forces in the momentum equation. First, the calculation methods of the natural circulation and CHF are validated by a published natural circulation experiment data and a CHF empirical correlation, respectively. Then, the CHF of the rod bundle in a natural circulation loop under both the stationary and rolling motion condition is predicted and analyzed. According to the calculation results, CHF under stationary condition is smaller than that under rolling motion condition. Besides, the CHF decreases with the increase of the rolling period and angular acceleration amplitude within the range of inlet subcooling and mass flux adopted in the current research. This paper can provide useful information for the prediction of CHF in natural circulation under motion condition, which is important for the nuclear reactor design improvement and safety analysis.

• Journal of fish pathology
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• v.14 no.2
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• pp.97-102
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• 2001

Olive flounder, Paralichthys olivaceus known as an one of the major aquacultured species in Korea were exposed to cadmium(Cd) with different protocols and analyzed the effects of exposure on the immune response. Antibody levels in sera of the group exposed to Cd(20ppb) by immersion method from 2 weeks before immuniztion with formalinised Edwardsiella tarda(E. tarda) KFE entigen to the end of experiment reached to peak level faster than that of the non-exposed group. After this peaking time the levels decreased much at a faster rate compared to the non-exposed group. This tendency was also appeared in the numbers of specific antibody secreting cells(SASC) analyzed with the enzyme-linked immunospot (ELISPOT)-assay technique in the splenocytes of the experimental groups exposed to Cd with different ways. Interestingly, the group exposed to Cd for 2 weeks before immunization also showed increased numbers of SASC unlikely the antibody production and suggested a more critical influence of cadmium exposure in early stage of immune reaction. Artificial infection with live E. tarda KFE induces 100% mortality in the flounder exposed to cadmium throughout the experimental period from two weeks before the immunization. It may imply that some other factors related to specific immunity are involving in the defence system of flounder exposed to Cd. Taked together. Cd exposure may induce temporaily stimulatory or indhibitory effects on the immune reaction, but suppress the physiological systems for the resistant against the infective agents with other toxic effects.