• Journal of Korea Multimedia Society
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• v.12 no.9
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• pp.1273-1287
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• 2009

PEGASIS, a chain-based protocol, forms chains from sensor nodes so that each node transmits and receives from a neighbor. In this way, only one node (known as a HEAD) is selected from that chain to transmit to the sink. Although PEGASIS is able to balance the workload among all of the nodes by selecting the HEAD node in turn, a considerable amount of energy may be wasted when nodes which are far away from sink node act as the HEAD. In this study, DERP (Distance-based Energy-efficient Routing Protocol) is proposed to address this problem. DERP is a chain-based protocol that improves the greedy-algorithm in PEGASIS by taking into account the distance from the HEAD to the sink node. The main idea of DERP is to adopt a pre-HEAD (P-HD) to distribute the energy load evenly among sensor nodes. In addition, to scale DERP to a large network, it can be extended to a multi-hop clustering protocol by selecting a "relay node" according to the distance between the P-HD and SINK. Analysis and simulation studies of DERP show that it consumes up to 80% less energy, and has less of a transmission delay compared to PEGASIS.

• Journal of Advanced Navigation Technology
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• v.15 no.5
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• pp.705-713
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• 2011

In this paper, we introduce two techniques for resolving integer ambiguities between reference stations, which is one of the most important processes in Network RTK correction generation process. Each techniques uses Hatch filter and combination of L1/L2 measurements and we used simulation data and real data to evaluate performance of the techniques. For evaluating performance of each technique, we compared corrections generated from user site and Network RTK. As a result, Network RTK with the technique which uses Hatch filter improves user performance much more than single baseline RTK does. Residual of user is smaller than a half size of wavelength so it does not affect user integer ambiguity resolution, however, it contains significant bias error. On the other hand, when we used the technique which uses combination of L1/L2 measurements, residual error of user is largely reduced compared to the technique using Hatch filter.

• Journal of Advanced Navigation Technology
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• v.12 no.5
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• pp.437-443
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• 2008

In this paper, we derive the optimum number of users which can maximize the information theoretic sum capacity in multiuser OFDM virtual MIMO uplink system. In which, there are multiple antennas at the base station and a number of users with single transmit antenna. Pilot-assisted channel state estimation is assumed for a block fading channel and time-varying fading channel. We analyze the tradeoff between the multiplexing gain and pilot overhead especially in low SNR regime and conclude that the optimum number of users is min ($N_r$,LT/2 ) in frequency nonselective block fading channel and approximately equal to min ($N_r$, ${\lfloor}{\sqrt{LT+1}}-1{\rfloor}$) in time varying fading channel. assuming the same pilot and signal pwoer.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.20 no.1
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• pp.52-57
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• 2016

We introduce a hybrid scheduling in a multi-path poor scattering full-duplex (FD) system, which consists of one multi-antenna FD base station and a large number of single-antenna half-duplex mobile stations. Our hybrid scheduling utilizes partial channel state information at the transmitter. In particular, unlike the conventional scheduling method using opportunistic transmission for both uplink and downlink, the proposed scheme combines a random transmit beamforming for downlink and a zero forcing beamforming for uplink. As our main result, via computer simulations, it is shown that the proposed scheme has a superior sum-rate performance than that of the conventional scheduling method beyond a certain signal-to-noise ratio regime.

• Journal of Chest Surgery
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• v.48 no.5
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• pp.335-344
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• 2015

Background: A raised carcinoembryonic antigen (CEA) may be associated with significant pathology during the postoperative follow-up of lung adenocarcinoma. Methods: We reviewed the medical records of 305 patients who underwent surgical resections for primary lung adenocarcinoma at a single institution between April 2006 and February 2013. Results: Preoperative CEA levels were significantly associated with age, smoking history, pathologic stage including pT (pathologic tumor stge), pN (pathologic nodal stage) and overall pathological stage, tumor size and differentiation, pathologically positive total lymph node, N1 and N2 lymph node, N2 nodal station (0/1/2=1.83/2.94/7.21 ng/mL, p=0.019), and 5-year disease-free survival (0.591 in group with normal preoperative CEA levels vs. 0.40 in group with high preoperative CEA levels, p=0.001). Preoperative CEA levels were significantly higher than postoperative CEA levels (p<0.001, Wilcoxon signed-rank test). Postoperative CEA level was also significantly associated with disease-free survival (p<0.001). A follow-up serum CEA value of >2.57 ng/mL was found to be the appropriate cutoff value for the prediction of cancer recurrence with sensitivity and specificity of 71.4% and 72.3%, respectively. Twenty percent of patients who had recurrence of disease had a CEA level elevated above this cutoff value prior to radiographic evidence of recurrence. Postoperative CEA, pathologic stage, differentiation, vascular invasion, and neoadjuvant therapy were identified as independent predictors of 5-year disease-free survival in a multivariate analysis. Conclusion: The follow-up CEA level can be a useful tool for detecting early recurrence undetected by postoperative imaging studies. The perioperative follow-up CEA levels may be helpful for providing personalized evaluation of lung adenocarcinoma.

• Journal of Animal Science and Technology
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• v.54 no.6
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• pp.411-418
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• 2012

KIT gene is the major causative gene for coat color variation in diverse animal species. This gene regulates melanocyte migration from the neural crest to target tissues and the mutation of this gene can affect dominant white phenotypes in animals. Because this gene has a major influence for the coat color variation, single nucleotide polymorphisms (SNPs) in 14 Korean cattle (Hanwoo) and 5 Holstein individuals were investigated. The Hanwoo DNA samples included three different colored (5 Black, 5 Yellow and 4 Stripe) animals. Total 126 polymorphisms have been identified and 23 of them are located in the exon region. Also, 5 bp (TTCTC) and 3 bp (TCT) intronic indels in intron 3 and intron 5, respectively, were identified. Out of 23 exonic polymorphisms, 15 SNPs are the missense mutations and the rest of the SNPs are silence mutations. The neighbor-joining phylogenetic tree was constructed for the different colored animals using the obtained KIT gene sequences. Holstein breed showed a clear breed-specific cluster in the phylogenetic tree which is differed from Hanwoo. Also, three colored Hanwoo animals were not discriminated among the breeds. The KIT gene polymorphisms identified in this study will possibly give some solutions for the color variations in cattle with further verifications.

• Journal of Electrical Engineering and Technology
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• v.3 no.3
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• pp.391-400
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• 2008

Multi-pulse topology of converters using elementary six-pulse GTO - VSC (gate turn off based voltage source converter) operated under fundamental frequency switching (FFS) control is widely adopted in high power rating static synchronous compensators (STATCOM). Practically, a 48-pulse ($6{\times}8$ pulse) configuration is used with the phase angle control algorithm employing proportional and integral (PI) control methodology. These kinds of controllers, for example the ${\pm}80MVAR$ compensator at Inuyama switching station, KEPCO, Japan, employs two stages of magnetics viz. intermediate transformers (as many as VSCs) and a main coupling transformer to minimize harmonics distortion in the line and to achieve a desired operational efficiency. The magnetic circuit needs altogether nine transformers of which eight are phase shifting transformers (PST) used in the intermediate stage, each rating equal to or more than one eighth of the compensator rating, and the other one is the main coupling transformer having a power rating equal to that of the compensator. In this paper, a two-level 48-pulse ${\pm}100MVAR$ STATCOM is proposed where eight, six-pulse GTO-VSC are employed and magnetics is simplified to single-stage using four transformers of which three are PSTs and the other is a normal transformer. Thus, it reduces the magnetics to half of the value needed in the commercially available compensator. By adopting the simple PI-controllers, the model is simulated in a MATLAB environment by SimPowerSystems toolbox for voltage regulation in the transmission system. The simulation results show that the THD levels in line voltage and current are well below the limiting values specified in the IEEE Std 519-1992 for harmonic control in electrical power systems. The controller performance is observed reasonably well during capacitive and inductive modes of operation.

• Structural Engineering and Mechanics
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• v.56 no.4
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• pp.569-588
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• 2015

A comprehensive methodology is proposed for design of metallic dampers in seismic retrofit of earthquake-damaged frame structures. It is assumed that the metallic dampers remain elastic and only provide stiffness during frequent earthquake (i.e., earthquake with a 63% probability of exceedance in 50-year service period), while in precautionary earthquake (i.e., earthquake with a 10% probability of exceedance in 50-year service period), the metallic dampers yield before the main frame and dissipate most of the seismic energy to either prevent or minimize structural damages. Therefore by converting multi-story frame to an equivalent single-degree-of-freedom system, the added stiffness provided by metallic dampers is designed to control elastic story drifts within code-based demand under frequent earthquake, and the added damping with the combination of added stiffness influences is obtained to control structural stress within performance-based target under precautionary earthquake. With the equivalent added damping ratio, the expected damping forces provided by metallic dampers can be calculated to carry out the configuration and design of metallic dampers along with supporting braces. Based on a detailed example for retrofit of an earthquake-damaged reinforced concrete frame by using metallic dampers, the proposed design procedure is demonstrated to be simple and practical, which can not only meet current China's design codes but also be used in retrofit design of earthquake-damaged frame with metallic damper for reaching desirable performance objective.

• Asian Journal of Atmospheric Environment
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• v.4 no.3
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• pp.189-197
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• 2010

An orchestrated attempt was made to analyze samples of bulk and individual particulate matters (PM) collected at the Gosan ground-based station on the west coast of Jeju, Korea. A two-stage filter pack sampler was operated to collect particles in both large (> $1.2\;{\mu}m$) and small size fractions (< $1.2\;{\mu}m$) between the Asian dust (hereafter called "AD") storm event and non-Asian dust period. Elemental components in bulk and individual particles were determined by PIXE and synchrotron XRF analysis systems, respectively. To assess the transport pathways of air parcels and to determine the spatial distribution of PM, the backward trajectories of the Meteorological Data Explorer (Center for Global Environmental Research, 2010) and the NOAA's HYSPLIT dispersion-trajectory models were applied. In line with general expectations, Si and other crustal elements in large size particles showed considerably higher mass loading on AD days in comparison with non-AD days. Computation of the crustal enrichment factors [(Z/Si)$_{particle}$/(Z/Si)$_{desert}$ sand] of elements in large size particles (> $1.2\;{\mu}m$) allowed us to estimate the source profile and chemical aging of AD particles as well as to classify the soil-origin elements. On the basis of a single particle analysis, individual AD particles are classified into three distinct groups (neutralized mineral particles, S-rich mineral particles, and imperfectly neutralized particles).

• Journal of Broadcast Engineering
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• v.14 no.2
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• pp.178-188
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• 2009

In this paper, we propose the method which provides efficient sub-channel allocation for handoff and new call supporting multi-media service in AMC-based OFDMA system. Firstly, we apply the multi-band method which provides different AMC method according to the location of user terminals. Also, in OFDMA system environment that a base station has a lot of sub-channels, we adopt the sub-channel allocation scheme that provides a higher priority to handoff call and real-time service about handoff and new calls with multi-meida service. The simulation results show that the proposed scheme plays a role in increasing the number of new and handoff calls meeting the required blocking rate.