• The Journal of the Korea institute of electronic communication sciences
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• v.15 no.3
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• pp.439-444
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• 2020

In this paper, the analysis of the FSCS (frequency-selected coupling structure) as the coupling coefficient and multi-stage FSCS for enhanced bandstop bandwidth is suggested. The FSCS is composed by the connected coupled-line and open-stub. Basically, the resonance frequency of the FSCS is given by the electrical length of the stub, and the bandwidth is controlled by the coupling coefficient. Multi-stage FSCS is made by addition of another FSCS with the half electrical length. Manufactured bandstop filter using 3 stage FSCS is measured with the stopband of 177.3% and the maximum return loss of 1dB.

• Journal of The Korean Society of Grassland and Forage Science
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• v.34 no.2
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• pp.129-140
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• 2014

This study was performed to evaluate the effects of replacing basic total mixed ration (TMR) with fermented soybean curd, Artemisia princeps Pampanini cv. Sajabal, and spent coffee grounds by-product on rumen microbial fermentation in vitro. Soybean in the basic TMR diet (control) was replaced by the following 9 treatments (3 replicates): maximum amounts of soybean curd (SC); fermented SC (FSC); 3, 5, and 10% FSC + fermented A. princeps Pampanini cv. Sajabal (1:1, DM basis, FSCS); and 3, 5, 10% FSC + fermented coffee meal (1:1, DM basis, FSCC) of soybean. FSC, FSCS, and FSCC were fermented using Lactobacillus acidophilus ATCC 496, Lactobacillus fermentum ATCC 1493, Lactobacillus plantarum KCTC 1048, and Lactobacillus casei IFO 3533. Replacing dairy cow TMR with FSC treatment led to a pH value of 6 after 8 h of incubation-the lowest value measured (p<0.05), and FSCS and FSCC treatments were higher than SC and FSC treatment after 6 h (p<0.05). Gas production was higher in response to 3% FSC and FSCC treatments than the control after 4-10 h. Dry matter digestibility was increased 0-12 h after FSC treatment (p<0.05) and was the highest after 24 h of 10% FSCS treatment. $NH_3-N$ concentration was the lowest after 24 h of FSC treatment (p<0.05). Microbial protein content increased in response to treatments that had been fermented by the Lactobacillus spp. compared to control and SC treatments (p<0.05). The total concentration of volatile fatty acids (VFAs) was increased after 6-12 h of FSC treatment (p<0.05), while the highest acetate proportion was observed 24 h after 5% and 10% FSCS treatments. The FSC of propionate proportion was increased for 0-10 h compared with among treatments (p<0.05). The highest acetate in the propionate ration was observed after 12 h of SC treatment and the lowest with FSCS 3% treatment after 24 h. Methane ($CH_4$) emulsion was lower with A. princeps Pampanini cv. Sajabal and spent coffee grounds treatments than with the control, SC, and FSC treatments. These experiments were designed to replace the by-products of dairy cow TMR with SC, FSC, FSCS, and FSCC to improve TMR quality. Condensed tannins contained in FSCS and FSCC treatments, which reduced $CH_4$ emulsion in vitro, decreased rumen microbial fermentation during the early incubation time. Therefore, future experiments are required to develop a rumen continuous culture system and an in vivo test to optimize the percentages of FSC, FSCS, and FSCC in the TMR diet of the dairy cows.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.42 no.3
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• pp.116-130
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• 2019

This study investigates passenger-authored online reviews of airline services using social network analysis to compare the differences in customer perceptions between full service carriers (FSCs) and low cost carriers (LCCs). While deriving words with high frequency and weight matrix based on the text analysis for FSCs and LCCs respectively, we analyze the semantic network (betweenness centrality, eigenvector centrality, degree centrality) to compare the degree of connection between words in online reviews of each airline types using the social network analysis. Then we compare the words with high frequency and the connection degree to gauge their influences in the network. Moreover, we group eight clusters for FSCs and LCCs using the convergence of iterated correlations (CONCOR) analysis. Using the resultant clusters, we match the clusters to dimensions of two types of service quality models ($Gr{\ddot{o}}nroos$, Brady & Cronin (B&C)) to compare the airline service quality and determine which model fits better. From the semantic network analysis, FSCs are mainly related to inflight service words and LCCs are primarily related to the ground service words. The CONCOR analysis reveals that FSCs are mainly related to the dimension of outcome quality in $Gr{\ddot{o}}nroos$ model, but evenly distributed to the dimensions in B&C model. On the other hand, LCCs are primarily related to the dimensions of process quality in both $Gr{\ddot{o}}nroos$ and B&C models. From the CONCOR analysis, we also observe that B&C model fits better than $Gr{\ddot{o}}nroos$ model for the airline service because the former model can capture passenger perceptions more specifically than the latter model can.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.45 no.1
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• pp.103-109
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• 2008

In this papaer, a new type of ${\lambda}_g/4$ short stub band pass filter and ${\lambda}_g/2$ open stub band pass filter are purposed. Both are designed using FSCS technique for harmonic suppression. The proposed filters that used FSCS technique and a broadband stop filter is integrated to band pass filter to suppress the harmonics. The BSF are also placed between stubs so that the size is larger than prevent as compared to conventional one. The propose filters have center frequency of 5.8 GHz, bandwidth of 50% and harmonics suppressin is 120% has in bandwith. The measurement results in the case of ${\lambda}_g/4$ short stub filter, insertion loss of 0.5 dB, return loss of 14 dB are achieved and in the case of ${\lambda}_g/2$ open stub filter, loss of 0.8 dB, return loss of 14.4 dB are achieved. The simulation results and the measurement results are almost the same.

• Journal of Biosystems Engineering
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• v.17 no.4
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• pp.396-403
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• 1992

In order to operate a combine harvester at the optimum conditions and maximum performance, a forward speed control system(FSCS) was designed and develped. The FSCS consisted of engine, continuously variable V-belt transmission, threshing unit, traveling unit, detecting unit, and controller. Each components of the system were mathematically modeled. By a computer simulation, the effects of control parameters such as hydraulic piston speed, speed ratio, dead band of engine speed on the system performance were analysed, and the optimum control conditions were identified. The system appeared to be the most stable at the hydraulic piston speed of 10.6mm/s and the speed ratio of 0.4. The proper dead band of engine speed appeared to be 30rpm through the simulation and verification tests.

• Journal of Electrical Engineering and Technology
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• v.10 no.4
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• pp.1453-1459
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• 2015

Loss of excitation (LOE) relay is prevalently used to protect synchronous generator. The widely used method for synchronous generator LOE protection is a negative offset mho relay with two zones. The basis of this relay is identical to mho impedance relay. In other words, this relay calculates impedance by measuring voltage and current at the generator terminal. On the other hand, the presence of series compensation, changes measured voltage and current signals during loss of excitation. This paper reveals that the presence of series compensators such as fixed series capacitors (FSCs) and static synchronous series compensator (SSSC) causes a significant delay on the performance of generator LOE relay. It is also shown that the presence of SSSC causes the LOE relay to be under-reached. Different operating modes of the power system, the SSSC and also different percentages of series capacitive compensations have been considered in the modeling. All the detailed simulations are carried out in the MATLAB/Simulink environment using the SimPowerSystems toolbox.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.21 no.3
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• pp.55-64
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• 2013

As the price competition between airlines became increasingly intensified, due to increased participation of low-cost carriers in the air transport industry and the continued deregulation of international air transport, each airline has introduced various management techniques for securing international competitiveness and operational efficiency in order to cope with the uncertainty in air transport industry. The world leading LCCs, such as Ryan air, easyJet and Southwest, have changed their traditional business models by increasing operation to primary airports, diversifying operating routes, making strategic alliances with FSCs or other LCCs, increasing the operations on the mid or long distance routes, expanding ancillary revenues, etc. As Korea's air transport industry is confronting with intense competition, our LCCs are requested to adjust to this new challenging situation. As the world leading LCCs did, Korean LCCs are recommended to adopt new business models such as restructuring of the air transport industry through M&A, operating more flexibly in terms of frequency or route, launching of services to primary airports, making strategic alliances with foreign FSCs, developing of 4th or 6th traffic demands, etc.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.18 no.10
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• pp.1107-1116
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• 2007

In this paper, a broadband open stubs band pass filters which can suppress the second harmonics using Z-transform technique, is designed, fabricated and characterized. The proposed broadband filters integrate the band stop filter with the FSCS structure and ${\lambda}_g/4$ open stub in order to suppress the second harmonics. Due to insertion of BSF at input and output terminal, the size of the filter was increased in the conventional filter, however, in the proposed structure, the position of inverter that connects the stubs can be integrated between those stubs, thereby decreasing the size. So, it can be fabricated in the size of $18.7{\times}16.9mm^2$ which is smaller size than conventional one. The measured results of the proposed filters have center frequency of a 5.8 GHz with bandwidth of 95 %, insertion loss of 0.6 dB, return loss of 14 dB. The simulation results are consistent with measurement results. The filter is designed far X-band satellite communication and ITS applications.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.32 no.2
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• pp.72-81
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• 2024

Korean aviation authority required air service providers to submit public disclosure of aviation safety investment to encourage proactive and voluntary safety investments. In 2023, two airport operators and seventeen airlines disclosed their safety investment results and plans for the first time. This study aims to examine and analyze the current status of the disclosure system, identify insights for its development, and set directions for the future. Safety investments by airport operators decreased by 14.3% in 2022 compared to 2021 due to decreased aviation demand. Airline increased their safety investment by 46% to 4 trillion won, investing heavily in MRO and aircraft replacement, leading to a decrease in the average fleet age by 0.8 years. FSCs have shown a significantly higher level of safety investment compared to LCCs. However, LCCs show higher safety investment relative to revenue. It is necessary to consider the characteristics of each operator as well as the scale when comparing safety investments. A roadmap is suggested based on the importance of disclosure items for the strategic approach and improvement measures for the aviation safety investment disclosure system.

• Childhood Kidney Diseases
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• v.4 no.1
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• pp.17-24
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• 2000

Purpose: MCNS is found in approximately $85\%$ of the idiopathic nephrotic syndrome in children and shows good prognosis with initial steroid therapy. However in FSGS, there is poor prognosis with initial therapy and shows higher rate of progression to chronic renal failure and relapse after kindney transplantation. We have experienced 8 patients who were diagnosed as MCNS on initial renal biopsy and then progressed to FSGS on follow-up biopsy. So we have investigated their clinical course and risk factors for transition of MCNS to FSGS. Methods: We conducted a retrospective study with a review of histopathologic findings and clinical manifestations of 296 cases of MCNS and FSGS that were diagnosed from January 1988 to May 1999. We classified them into 3 groups according to the histopathologic finding; MCNS, FSGS, MCNS progressed to FSGS in follow-up biopsy. Results: The number of children was 296 cases comprising 241 cases($81.4\%$) showing MCNS, 8 cases($2.7\%$) transition group, 47 cases($15.9\%$) FSGS. The mean onset age was $6.0{\pm}2.6$years in MCNS, transition group $8.3{\pm}2.3$years, FSGS $7.2{\pm4.3$years, and the gender (M:F) ratio was 3.7:1 in MCNS, 3:1 in transition group, 1.8:1 in FSGS. Comparing the presence of initial hematuria, hypertension,24 hour urine protein, serum albumin, serum creatinine, there were significant difference between the transition group and the FSGS group in the following points; 24hour urine protein $684:342mg/m^2/hr$(P<0.05), serum albumin 1.92: 2.47g/dL(P<0.05), serum cholesterol 494:343mg/dL(P<0.05). Refractoriness to steroid therapy was 13.3$\%$ in MCNS. $12.5\%$ in transition group, $29.6\%$ in FSGS; significantly higher in FSGS(P<0.05). Immunosuppressant therapy was performed in $58.5\%$ of MCNS, $100\%$ in transition group, $80.8\%$ in FSGS; transition group showed significantly higher .ate(P<0.05) comparing with MCNS. Mean number of relapse and duration from onset to first relapse showed no significance difference between these groups. Conclusion: 249 patients with MCNS have been followed and $3.2\%$ (8 patients) of them has shown change in pathologic diagnosis from MCNS to FSCS. The risk factor for transition could not be found. Our results point to the need for a follow-up biopsy to certify the possibility of transition to FSCS in some MCNS cases with refractory cases to steroid therepy, frequent relapsing cases, or in case of no remission in spite of vigorous immunosuppressant therapy.