• 전력전자학회논문지
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• 제19권6호
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• pp.494-502
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• 2014

This paper presents a control method of the modular multilevel converter - high-voltage direct current (MMC-HVDC) system to regulate grid voltage on the basis of the Jeju Island power system. In this case, the MMC-HVDC system is controlled as a static synchronous compensator (Statcom) to exchange the reactive power with the power grid. The operation of the MMC-HVDC system is verified by using the PSCAD/EMTDC simulation program. The Jeju Island power system is first established on the basis of the parameters and measured data from the real Jeju Island power system. This power system consists of two line-commutated converter - high-voltage direct current (LCC-HVDC) systems, two Statcom systems, wind farms, thermal power plants, transformers, and transmission and distribution lines. The proposed control method is then applied by replacing one LCC-HVDC system with a MMC-HVDC system. Simulation results with and without using the MMC-HVDC system are compared to evaluate the effectiveness of the control method.

• 농촌계획
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• 제29권3호
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• pp.39-52
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• 2023

There is a clear need to enhance the attractiveness of rural areas by leveraging their core assets to respond to emerging mega-trends. This paper analyzes the progress of the direct payment program that has been implemented to preserve agricultural landscapes in rural areas, using spatial information data. The study identified the planting characteristics of landscape crops, spatial utilization characteristics of the system, and utilization characteristics of the system by the beneficiaries. According to the analysis, the spatial utilization characteristics of the system could be classified into eight types: tourism resources and nearby agricultural areas, designation across the entire rural area, agricultural areas around villages, large-scale agricultural areas, small-scale agricultural areas, scattered and dispersed areas, independent parcels of land, and ranches. Based on the characteristics and limitations of the landscape preservation direct payment system, this study provides directions for future rural specialized zones. The landscape preservation direct payment system focuses on income support for farmers and providing agricultural benefits in terms of public interest. Meanwhile, the landscape agricultural zone serves as a rural specialized zone, highlighting the need to explore the direction of integrated rural landscape management. It is important for farmers, as the key stakeholders, to preserve the agricultural landscape in rural areas. Forming community-level cooperatives and engaging in relevant activities are crucial for achieving this goal. In order to actively preserve the agricultural landscape, it is necessary to consider the resumption of financial support for village landscape preservation activities, along with the designation of landscape agricultural zones. There is a need to conduct a specific review and explore measures to accommodate the designated landscape complexes at the local government level. The higher the ratio of designated landscape complexes, the more agricultural landscape management based on public value has been carried out. The designation of such landscape complexes can be seen as a demand for voluntary utilization of agricultural landscapes in the region. Moreover, as the ratio of designated landscape complexes increases, it becomes evident that farmers at the village level actively participate in agricultural landscape preservation and contribute to providing public value or utilize it as a tourism resource. This highlights the need for managing agricultural landscapes at the village level within the appropriate context.

• 한국작물학회:학술대회논문집
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• 한국작물학회 2017년도 9th Asian Crop Science Association conference
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• pp.186-186
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• 2017

Relay intercropping system of direct seeded rice and winter cereal is labor saving cultivation and has high land use efficiency in Japan. In this system, rice seeds are direct seeded into inter-row space of winter cereals (wheat or barley) in March or April. If the direct seeding of rice is conducted before stem elongation phase or using suitable seeder, these are little effect to yield of winter cereals. Though the seeds are generally thiuram treated, it's a matter that seedling establishment rate (SER) of direct seeded rice is low and unstable. The cause of low SER has not been revealed. In present study, with the aim to reveal causes of low SER, we conducted experiments and investigated the SER, and analyzed some factors that might affect SER. Experiment1: In 2015, 2016, we buried rice seeds underground, and investigated the transition of the seed survival rates (SSR). Seeds were thiuram-treated or non-treated. In 2 periods, SSR of thiuram-treated seeds were significantly higher than non-treated seeds. In 2016, thiuram-treated seeds were high in SSR (almost 75%) at April 30th, but low SER (10~27%) after harvest of winter cereals. Therefore, almost all of seed death might have been happen after germination. Analysis 1: We investigated the SER and cultivation conditions in Ibaraki pref. for several years. Meteorological factors were referred from the nearest point of AMeDAS. From mean temperature (MT) among 5days after and before the day, we divided the period of seeding ~June 20 to phase1~4. We defined each phase as below; Phase1: $MT{\leq}10^{\circ}C$, Phase2: $10^{\circ}C<MT{\leq}15^{\circ}C$, Phase3:$15^{\circ}C<MT{\leq}20^{\circ}C$, Phase4: $MT>20^{\circ}C$. We analyzed the correlation of SER and meteorological factors by each phase. Total number of days in phase 1~4 was significantly negative correlated with SER. In phase1, total rain fall and number of soil wetting days were significantly negative correlated with SER. In phase2~4, only MT was significantly positive correlated with SER. This result suggested that rainfalls in phase1 declined seed vigor to emergence from soil surface, by repeated water absorption and re-dry. From these present studies, it was suggested that one of factors of low SER of direct seeded rice in relay intercropping system is changing of water condition by rainfalls in phase1 ($MT{\leq}10^{\circ}C$). To improve SER, it's necessary to consider something seed treatments such as prevent water absorption during phase1. However, 58~60% of seeds seemed to die during May. It's suggested that, if seeds are thiuram treated, almost all of seeds can germinate underground, but the seed vigor to emergence from soil surface are insufficient. Further studies are needed to reveal the rest causes that is happening during emergence from soil surface.

• 한국물환경학회지
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• 제27권1호
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• pp.61-72
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• 2011

유역 단위 수문 및 수질 평가 모형인 SWAT 모형을 이용한 유역 내 정확한 수문과 비점오염원 거동을 평가하기 위해서는 유역 적용에 앞서 모형의 정확성 평가가 우선시 되어야 한다. SWAT 모형의 수문 보정및 검정 시, Nash-Sutcliffe의 효율계수(EI)가 널리 사용되고 있다. 그러나 이러한 EI 값은 비교되어지는 값들의 범위 중 큰 값 즉, 수문 분석에 있어 고유량에 대해 민감하게 영향을 받는 것으로 알려져 있다. 그리하여 본 연구에서는 보다 정확한 수문 분석을 위해 K-means 군집화 알고리즘을 이용한 웹기반의 EI 평가시스템을 개발하였고, 이를 SWAT 모형의 수문 평가에 적용하였다. 본 연구의 결과 전체 유량의 EI 값은 높았지만, 수문성분에 따른 EI 값은 높지 않았다. SWAT 모형의 수문 보정 및 검정에 널리 활용되고 있는 SWAT auto-calibration tool은 전체 유량에 대해서는 높은 EI 값을 산정하는 것으로 보이지만, 직접유출과 기저유출 각각에 대한 유량 그룹 I 과 II 에 대해서는 대부분 음수(-)의 EI 값을 보였다. 그리하여 본 연구 결과를 통해 SWAT 모형의 수문성분 평가에 있어 보다 정확한 평가를 위해서는 직접유출과 기저유출에 대한 각각의 유량 그룹에 대해 양수(+)의 EI 값이 산정되도록 모형 보정 및 검정의 수행 필요할 것으로 사료된다.

• 한국의학물리학회지:의학물리
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• 제21권3호
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• pp.239-245
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• 2010

본 연구의 목적은 직 간접 변환방식 검출기를 사용한 디지털 유방 X선 촬영시스템의 영상 화질을 비교하고 평가함에 있다. 영상의 정량적인 분해능을 나타내는 변조전달함수(MTF), 노이즈 특성을 나타내는 정규화된 잡음력 스펙트럼(NNPS), 그리고 신호 대 잡음비 성능을 나타내는 양자검출효율(DQE)인자를 이용하여 영상 화질평가를 하였다. DQE는 IEC 62220-1-2 규약에 따라 edge 팬텀을 사용한 MTF 도출을 이용하여 계산되었다. 대조도 대 노이즈비(CNR) 측정은 한국의료영상품질관리원에서 제시한 가이드라인에 따라 측정되었다. 직접 변환방식 검출기가 간접 변환방식 검출기에 비해 공간주파수별로 MTF와 DQE 값이 높은 것으로 측정되었다. 동일한 평균유선선량(AGD)일 때 직접 변환방식의 검출기는 더 높은 CNR값을 보였다. 공간주파수별로 높은 DQE 값을 갖는 직접 변환방식 검출기는 디지털 유방 X선 촬영시스템에 있어서 향상된 영상 화질과 적은 환자선량을 제공할 것이다.

• Journal of Korean Neurosurgical Society
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• 제51권1호
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• pp.14-19
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• 2012

Objective : The authors performed a retrospective study to assess the clinical and radiological outcome in symptomatic lumbar spondylolysis patients who underwent a direct pars repair surgery using two different surgical methods; pedicle screw with universal hook system (PSUH) and direct pars screw fixation (DPSF), and compared the results between two different treated groups. Methods : Forty-seven consecutive patients (PSUH; 23, DPSF; 15) with symptomatic lumbar spondylolysis who underwent a direct pars repair surgery were included. The average follow-up period was 37 months in the PSUH group, and 28 months in the DPSF group. The clinical outcome was measured using visual analogue pain scale (VAS) and Oswestry disability index (ODI). The length of operation time, the amount of blood loss, the duration of hospital stay, surgical complications, and fusion status were also assessed. Results : When compared to the DPSF group, the average preoperative VAS and ODI score of the PSUH group were less decreased at the last follow-up; (the PSUH group; back VAS : 4.9 vs. 3.0, leg VAS : 6.8 vs. 2.2, ODI : 50.6% vs. 24.6%, the DPSF group; back VAS : 5.7 vs. 1.1, leg VAS : 6.1 vs. 1.2, ODI : 57.4% vs. 18.2%). The average operation time was 174.9 minutes in the PSUH group, and 141.7 minutes in the DPSF group. The average blood loss during operation was 468.8 cc in the PSUH group, and 298.8 cc in the DPSF group. The average hospital stay after operation was 8.9 days in the PSUH group, and 7 days in the DPSF group. In the PSUH group, there was one case of a screw misplacement requiring revision surgery. In the DPSF group, one patient suffered from transient leg pain. The successful bone fusion rate was 78.3% in the PSUH group, and 93.3% in the DPSF group. Conclusion : The present study suggests that the technique using direct pars screw would be more effective than the method using pedicle screw with lamina hook system, in terms of decreased operation time, amount of blood loss, hospital stay, and increased fusion success rate, as well as better clinical outcome.

• 산학경영연구
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• 제12권
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• pp.209-237
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• 1999

본 연구의 목적은 다음과 같이 다섯 가지로 요약할 수 있다. 첫째로 기존의 해외직접투자 이론을 문헌적으로 고찰하여 종합평가 정리하고자 한다. 둘째로 한국 섬유산업의 해외직접투자동기를 이론적으로 해석해 본다. 셋째로 한국 섬유산업의 해외직접투자 현황을 토대로 투자성과 및 문제점을 파악한다. 다섯째로 향후 투자기업에 대한 투자방향 및 전략적 대응방안을 제시하고자 한다. 이러한 연구목적에 따라 미주 및 동남아에 투자한 섬유기업을 대상으로 문헌 및 심층적인 면담조사한 결과 다음과 같은 결론을 도출하였다. 첫째로 해외직접투자를 성공적으로 이끌기 위해서는 무엇보다도 먼저 다양하고도 효율적인 정보제공이 선행되어야 한다. 둘째로 한국기업의 해외직접투자가 주로 아시아와 중남미에 편중되어 있어 많은 부작용이 나타나고 있으므로 지역다변화를 통한 투자전략의 수립이 요구된다. 셋째로 투자의 효율성을 위해 의사결정의 현지화를 과감히 시도해야 한다. 넷째로 바람직한 해외직접투자를 위해 세계적인 네트워크의 형성이 요망된다. 다섯째로 현지의 저임금 확보나 수입규제 회피와 같은 소극적인 투자동기에서 이제는 현지시장 진출이나 고도의 기술획득 등을 위한 공격적이고도 적극적인 투자가 절실히 요구된다.

• 한국음향학회지
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• 제41권4호
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• pp.446-460
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• 2022

본 논문은 고반복률을 갖는 양상태 소나 시스템에서의 송신 직접파로 인한 표적 탐지율 저하를 적응형 필터를 이용하여 개선하는 알고리즘을 제안한다. 이러한 소나 시스템에서의 송신 직접파 제거는 실제 시스템을 운용하는 것에 치명적인 영향을 주기 때문에 이것을 제거하는 것이 아주 중요하다. 본 논문에서는 시뮬레이션과 해상 실험 데이터에 Normalized Least Mean Square(NLMS)와 Recursive Least Square(RLS) 알고리즘을 적용하여 성능을 평가하였다. 송신 직접파 성분과 표적 신호가 포함된 표적 방위의 빔 신호를 입력 신호로 사용하고 송신 직접파 성분이 있는 송신기 방위의 빔 신호를 원하는 신호로 사용하여 두 신호의 차를 최적화 하여 송신 직접파를 제거하고 표적 신호만 남긴다. 시뮬레이션에서 정합필터의 결과를 확인하였을 때 Linear Frequency Modultated(LFM)과 Generalized Sinusoidal Frequency Modulated(GSFM) 모두에서 송신 직접파가 잡음레벨까지 제거되고 GSFM의 경우 표적의 부엽이 20 dB 이상 감소하여 성능 개선이 있는 것을 확인하였다. 해상 실험에서 LFM은 송신 직접파의 레벨이 10 dB 감소하였고, GSFM은 송신 직접파의 레벨이 약 4 dB 감소하였고, 표적의 부엽이 약 4 dB 정도 감소하여 성능 개선이 있다는 것이 확인되었다.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2003년도 ICCAS
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• pp.316-321
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• 2003

This paper presents a design method of the wavelet neural network based controller using direct adaptive control method to deal with a stable intelligent control of chaotic systems. The various uncertainties, such as mechanical parametric variation, external disturbance, and unstructured uncertainty influence the control performance. However, the conventional control methods such as optimal control, adaptive control and robust control may not be feasible when an explicit, faithful mathematical model cannot be constructed. Therefore, an intelligent control system that is an on-line trained WNN controller based on direct adaptive control method with adaptive learning rates is proposed to control chaotic nonlinear systems whose mathematical models are not available. The adaptive learning rates are derived in the sense of discrete-type Lyapunov stability theorem, so that the convergence of the tracking error can be guaranteed in the closed-loop system. In the whole design process, the strict constrained conditions and prior knowledge of the controlled plant are not necessary due to the powerful learning ability of the proposed intelligent control system. The gradient-descent method is used for training a wavelet neural network controller of chaotic systems. Finally, the effectiveness and feasibility of the proposed control method is demonstrated with application to the chaotic systems.

• 산업기술연구
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• 제20권A호
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• pp.51-56
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• 2000

The Photocatalytic decolorization and degradation of commercial dyes were studied using a batch reactor. Degussa P25 titanium dioxide and $H_2O_2$ were used as the photocatalyst and proved to be effective for dyes degradation when they were irradiated with UV light. The light source was a 20W low pressure mercury lamp. Three different kinds of dyes, such as direct dye(congo red), acid dye (acid black) and disperse dye(disperse blue) were tested. Extending the UV only treatment up to 120min, direct dye was decolorized to 60% and degraded to 30% as COD. On the other side, acid and disperse dyes were eliminated less than 10% as color and COD. But, color and COD were eliminated about 90% for all of the three dyes by $UV/H_2O_2$ system. And then the most effective decolorization was done for direct dye with 96% removal efficiency by $UV/TiO_2$ system at 120min with 500mg/L of $TiO_2$.