• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.1A
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• pp.12-17
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• 2009

We consider an OFDM based multiple AF relaying systems. Since the channel between first hop (source station-relay station) and second hop (relay station -destination station) varies independently, the subcarrier in the first hop can be paired to another subcarrier in the second hop for the increase of the system capacity. The conventional pairing which uses the brute force searching requires large complexity while giving optimal pairing for maximum system capacity. In this paper, we present sub-optimal subcarrier pairing scheme with low complexity. Every RS firstly pairs the subcarrier with the highest channel gain in the first hop to the subcarrier with highest channel gain in the second hop. The pair with the highest SNR among all the pairs is determined as final selected pair and the corresponding subcarriers are not selected at other RSs in the next paring iteration. This process is repeated until all the subcarriers are paired. Simulation results show the proposed pairing scheme achieves near optimal performance with low complexity.

• Management & Information Systems Review
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• v.2
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• pp.335-354
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• 1998

In this study I construct CAN(Controller Area Network) for automobiles similar to LAN(Local Area Network) and build communication modules in the major part of an automobile to link several sub-systems. Since each station replaces the communication function of sub-systems and has various types of sensor, actuator, controller, and switch, every information about automobile's status is obtained from the network. The manufactured system showed a superior capability. The following is the contents of study. 1. The definition of communication packet through the analysis of CAN protocol. 2. The Design of modules using micro-controller 80C196CA. 3. The Network configuration.

• 유체기계공업학회:학술대회논문집
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• 2006.08a
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• pp.109-112
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• 2006

Recently, when we conducted meteorological observations, complicated land or building around weather station has influenced on the wind distribution. So, we should understand the effect of geometry to get more accurate data. In this study, we analyze the ideal geometry whose shape is hemisphere using CFD method. And then we apply this method to real geometry. And we investigate the velocity at the location of weather station. As the results, we could find out an important relationship between geometry and flow field.

• Asian-Australasian Journal of Animal Sciences
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• v.27 no.11
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• pp.1548-1553
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• 2014

Four Korean native cattle (KNC) breeds-Hanwoo, Chikso, Heugu, and Jeju black-are entered in the Domestic Animal Diversity Information System of the United Nations Food and Agriculture Organization (FAO). The objective of this study was to assess the genetic diversity, phylogenetic relationships and population structure of these KNC breeds (n = 120) and exotic breeds (Holstein and Charolais, n = 56). Thirty microsatellite loci recommended by the International Society for Animal Genetics/FAO were genotyped. These genotypes were used to determine the allele frequencies, allelic richness, heterozygosity and polymorphism information content per locus and breed. Genetic diversity was lower in Heugu and Jeju black breeds. Phylogenetic analysis, Factorial Correspondence Analysis and genetic clustering grouped each breed in its own cluster, which supported the genetic uniqueness of the KNC breeds. These results will be useful for conservation and management of KNC breeds as animal genetic resources.

• Journal of Environmental Science International
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• v.31 no.6
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• pp.515-524
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• 2022

This study investigated characteristics of meteorological parameters and ionic components of PM_2.5 during Asian dust events on November 28 and 30, 2018 at Busan, Korea. The seasonal occurrence frequencies of Asian dust during 1960~2019 (60 years) were 81.7% in spring, 12.2% in winter, and 6.1% in autumn. Recently, autumn Asian dust occurrence in Busan has shown an increasing trend. The result of AWS (automatic weather station), surface weather chart, and backward trajectory analyses showed that the first Asian dust of Nov. 28, 2018, in Busan came with rapid speed through inner China and Bohai Bay from Mongolia. The second Asian dust of Nov. 30, 2018, in Busan seems to have resulted from advection and deposition of proximal residual materials. These results indicated that understanding the characteristics of meteorological parameters and ionic components of PM_2.5 during Asian dust events could provide insights into establishing a control strategy for urban air quality.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.6 no.3
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• pp.31-42
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• 1986

The probabilistic model was developed to give a spatial simlation of precipitation series to solve the problem of future need of water resources. The simulation of daily precipitation series at the sub-base stations was induced from the spatial structure of rainfall occurrence probability between the base station and the sub-base stations in the watershed. In this study Hadong was chosen as the base station in Seomjin river basin and Imsil, Boseong, Soonchang, Dongbok, and Gurye were also selected as the sub-base stations. The results of this study are as follows; 1) The separation technique of spatial precipitation state showed effectiveness in the spatial simulation method because the occurrence probability by each precipitation state (Wet-Wet, Dry-Wet, Wet-Dry, and Dry- Dry system) represented the stable value. 2) The daily precipitation series of the sub-base stations which were simulated from those of the base station showed that the simulated annual mean precipitations were similar to the observed data, but the precipitations in summer were decreased slightly. 3) The correlogram and power spectrum of the simulated monthly precipitation for the sub-base stations showed those of the observed sample with good agreement.

• Journal of Korean Society for Atmospheric Environment
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• v.18 no.4
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• pp.317-325
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• 2002

An air pollution monitoring station has been operated at Tokchok Island since April 1999 to characterize the background atmosphere in the vicinity of the Yellow Sea. In this study, eight chemical species in PM$_{2.5}$ and three gaseous species were analyzed. A total of 53 samples were collected for the analysis of PM$_{2.5}$ and gaseous species from April, 1999 to April, 2001. The overall mean mass concentration of PM$_{2.5}$ was 20.8 $\mu\textrm{g}$/㎥ and the eight soluble ionic species accounted for about 46.8% of PM$_{2.5}$ mass. Approximately 80% of samples appeared to experience the chloride loss effect. Air pollutant sources of PM$_{2.5}$ measured at Tokchok Island were qualitatively identified by the principal component analysis. It was found that five principal components are secondary aerosol, soil, incineration, phase change of nitrate, and ocean.and ocean.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.27 no.1B
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• pp.13-23
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• 2002

A mobile host is prone to failure due to lack of stable storage, low bandwidth of wireless channel, high mobility, and limited battery life on the wireless network. Many researchers have studied to overcome these problems. For high level Availability in the cellular networks, it is necessary to consider recovery from the failures of mobile support stations as well as mobile as mobile hosts. In this paper, we present modified trickle scheme for recovery from failures of Mobile Support Station based on checkpointing scheme and analyze and compare the performance. We propose and analyze the performance of two schemes : one is waiting recovery scheme for the mobile support station having the last checkpoint and the other is searching the new path to the another mobile support station having the checkpoint.

• Journal of Positioning, Navigation, and Timing
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• v.3 no.2
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• pp.83-90
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• 2014

In this study, to improve an existing ground-wave based time broadcasting system, a study that predicts the field distribution and field strength of the transmitted signal of a new ground-wave based time broadcasting system was performed. The prediction area was assumed to be the Korean peninsula; and to reflect the mountainous terrain of the Korean peninsula in the prediction of the variations of field distribution and field strength, a new prediction method based on the Monteath model was proposed and utilized. As field distribution changes depending on the position of a transmitter station, potential sites for the transmitter station were selected considering the geographical characteristics. In this regard, the ground conductivity information of North Korea cannot be obtained, and thus, the ground conductivity of the North Korean region was reflected considering the geological characteristics of South Korea and North Korea. Based on this, the variations of field distribution and field strength were predicted by setting the Korean peninsula as the prediction area, and the prediction results depending on the position of the transmitter station were discussed.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.17 no.5
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• pp.1503-1515
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• 2023

This paper considers the jointly active and passive beamforming design in the IRS-aided MISO downlink vehicle communication system where both V2I and V2V communication paradigms coexist. We formulate the problem as an optimization problem aiming to minimize the total transmit power of the base station subject to SINR requirements of both V2I and V2V users, total transmit power of base station and IRS's phase shift constraints. To deal with this non-convex problem, we propose a method which can alternately optimize the active beamforming at the base station and the passive beamforming at the IRS. By using first-order Taylor expansion, matrix analysis theory and penalized convex-concave process method, the non-convex optimization problem with coupled variables is converted into two decoupled convex sub-problems. The simulation results show that the proposed alternate optimization algorithm can significantly decrease the total transmit power of the vehicle base station.