• Water for future
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• 제20권1호
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• pp.49-54
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• 1987

A numerical analysis of the characteristics of wave reflection over rippled beds (sand bars) was carried out By Boundary Element Method(B.E.M) using linear elements. It is assumed that the incident wave is normal and oblique to the rippled beds and the wave may be and the escribed by two-dimensional linear theory. The accuracy of the computational scheme is investigated by comparing the laboratory data, the analytic measured results of the other researchers. The B.E.M results for the normal incident wave is held for the mechanism of the resonant Bragg reflection at the point where the wave length of the bottom undulation is one half the wave length of the surface wave.

• KOREAN JOURNAL OF CROP SCIENCE
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• 제40권5호
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• pp.548-555
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• 1995

This study was aimed to provide understanding on the eco-physiological response of barley tillers as affected by sowing method. Yield and yield contribution rates of tillers were investigated with the data of field experiments in the Honam Crops Experiment Station of Iri, Korea from October 1986 to July 1987. Narrow-seeding (each row placement 40cm$\times$seeding width of each row 18cm), drill-seeding (20cm$\times$5cm) and broadcasting on wide ridge (each ridge placement 120cm$\times$ridge width 90cm) were applied to examine the effects of various sowing methods. Primary tillers such as mainstem, 1 and 2 produced ears in all treatments, but the ear from a secondary tiller of 11 was observed only in broadcasting on wide ridge. Drill-seeding was the highest in number of spikelet, grain and plump grain per ear, while narrow-seeding being the lowest. The plump grain yield per square meter was 679.8g in narrow-seeding, while drill-seeding and broadcasting produced more than narrow seeding by 28.7% and 16.8% respectively. The actual yields per l0a for sowing methods showed a similar pattern to plump grain yield per square meter in which the yield was 567.6kg by narrow-seeding and the increments of drill-seeding and broadcasting were 30.6% and 15.4%, respectively.

• Proceedings of the Acoustical Society of Korea Conference
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• 한국음향학회 2004년도 춘계학술발표대회 논문집 제23권 1호
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• pp.379-384
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• 2004

체외 충격파 쇄석술 (ESWL)은 체외에서 발생된 충격파를 체내의 결석이 위치한 부위에 집속하여 결석을 분쇄하는 비 침습적인 치료술이다. 최근 충격파를 이용하여 근관절 질환을 치료하는 체외 충격 파 치료술 (ESWT)이 또한 임상적으로 주목을 받고 있다. 아직 ESWT를 위한 최적의 충격파 노출 조건은 알려져 있지 않지만, 일반적으로 ESWL에 비해 상대적으로 충격파장의 초점 영역이 넓고 낮은 강도의 충격파를 사용한다. 본 연구에서는 ESWT에 적합할 것으로 예상되는 테이퍼 원통형 충격파 발생 방식을 제안하고자 한다. 본 연구에서는 테이퍼 원통형 충격 파 발생 의 초점 부위의 파형을 수치 해석하여 평가하고, 기존 원통형의 경우와 비교하였다. 테이퍼 원통형 충격파 발생기의 시제품을 제작하고, 발생된 강도를 평가하기 위해, 모의 결석을 제작하여 분쇄 효율을 측정하였으며, 결과를 원통형 충격파 발생기와 비교하였다.

• Journal of Ocean Engineering and Technology
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• 제16권3호
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• pp.34-39
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• 2002

본 논문에서는 수면파(Surface wave)와 수중파 (Internal wave)간의 동적 상관관계에 관하여 수행된 연구결과를 정리하였다. 표면파의 비선형 문제는 파의 경사매개변수를 2차원으로 가정하여 해석하였으며, Cauchy 문제는 불균일 조류상의 균일 수면중력파에 대하여 해석하였다. 또한, 파의 경사, 주기의 범위(Frequency range) 그리고 자유표면하의 조류의 분포들간의 조화에 대한 연구가 수행되었으며 해류 및 이동파와 연계되어 수중파의 최전 후방에 형성될 수 있는 정적 파형 (Steady wave pattern)이 수면파형에 포함되었다.

• Journal of computational fluids engineering
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• 제6권4호
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• pp.43-53
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• 2001

본 논문은 충격파 불안정성이 나타나지 않는 충격파 안정적인 수치기법의 개발을 목표로 하고 있다. Roe의 수치기법은 유동의 수치계산에 있어 높은 정확도를 보장하지만 carbuncle 현상과 같은 충격파 불안정성이 나타나는 것으로 알려져 있다. Roe의 수치기법과 HLLE 수치기법의 수치점성을 비교하여 충격파 불안정성의 원인을 살펴보았으며, Roe의 수치기법에 나타나는 반감쇠항에 마하수의 함수인 조절함수 f와 g를 도입하여 충격파 안정성을 획득하였다. 본 논문에서 제안된 수치기법을 다양한 유동문제에 적용하여 수치기법의 충격파 안정성과 정확성을 검증하였다

• Proceedings of the Acoustical Society of Korea Conference
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• 한국음향학회 1998년도 학술발표대회 논문집 제5권
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• pp.18-24
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• 1998

최근의 연구를 통해 해양의 내부파가 음파전달에 영향을 주어 비정상적인 손실을 일으키는 것을 밝혀졌다. 한국 동해세서도 강한 수온약층을 중심으로 내부파가 존재할 것으로 여겨져 왔으며, 이를 규명하고자 '98년 6월 각종 장비를 동원한 해양 관측을 동해항 근해에서 실시하였다. 또한 내부파에 의한 음파의 전파 특성을 추정학자 음원과 수신기를 고정한 상태에서 음향 실험을 실시하였다. 실험 결과 전형적인 내부파는 주기가 약 5-12분이고 최대 진폭은 15m 정도임이 밝혀졌다. 특히 10여개의 내부파 묶음이 약 36cm/sec 의 속도로 이동하고 있음도 확인하였다. 15개의 음향센서로 이뤄진 수직선배열 수신기와 음원을 이용한 음향 실험결과 역시 4-12분 주기에서 부분적으로 스펙트럼이 높게 나타났으며, 특히 주파수 1kHz 인 경우에는 4, 6분 주기에서 15개의 센서에 대해 일관되게 높은 스펙트럼 준위가 나타났다. 내부파에 의한 이러한 음파의 특성은 음파의 모든간 결함으로 나타나는 일종의 간섭 현상으로 설명될 수 있다.

• The Journal of Natural Sciences
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• 제11권1호
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• pp.33-39
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• 1999

Electrochemical behaviors of $Sm^3+$-ARS complexes has been investigated by d.c.polarography, differential pulse polarography and cyclic voltammetry. $Sm^3+$forms 1 : 3 adsorptive complexes with ARS.The reduction potential of complex wave $(P_2)$ shifted more negatively than the ligand wave $(P_1)$. The linear calibration curves of decreasing $P_1$ and increasing $P_2$ is obtained when $Sm^3+$ concentration varies from TEX>$2{\times}10^{-6}$ M to $3.2{\times}10^{-5}$ M.

• Journal of Navigation and Port Research
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• 제36권6호
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• pp.437-442
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• 2012

As of 2012, for service-area-widening and commercialization of DGPS service, the Ministry of Land, Transport and Maritime Affairs has completed a DGPS service via Terrestrial Digital Multimedia Broadcasting and doing experimental broadcasting. In this study, kinematic positioning tests were conducted based on DGPS service via T-DMB using low-cost GPS equipments in a dynamic environment. Standalone GPS, single-reference NDGPS via NTRIP, and virtual-reference DGPS via T-DMB surveys were conducted at the same time. And horizontal positioning errors were computed by comparing them with the result of high-precision positioning. As a result, when the DMB transmission interval was 3 seconds, horizontal positioning errors of standalone GPS, NTRIP-DGPS, and DMB-DGPS were 2.3m, 1.0m, and 0.7m, respectively. When the interval was 1 second, horizontal positioning errors were 2.0m, 1.2m, and 0.8m, respectively. Thus horizontal positioning accuracies improved with the DMB-DGPS compared to the traditional single-reference NDGPS.

• Journal of the Korean Institute of Telematics and Electronics
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• 제17권2호
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• pp.10-14
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• 1980

In this paper, the second harmonic distortion of the DH L.D. is analyzed using dynamic and static rate equations. In this analysis the modulation current Jm is changed by varang the iinjection current with the relation of where m stands for modulation index. It is showed that relative harmonic distortion ( ) has a peak exactly at the threshold current. It is also confirmed that this method is simople and more accurate than previously reported methods in the decision of the threshold current.

• Journal of Practical Agriculture & Fisheries Research
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• 제21권1호
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• pp.49-59
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• 2019

The field trial was performed to evaluate the rice growth and yield in different direct seeding methods after Italian Ryegrass Harvest The required time for seed emergence was for 7 ~ 8days in the tested direct seeding methods and there was high in seedling establishment in order of wet hill-seeding with iron-coated seeds > water seeding with iron-coated seeds > wet hill-seeding with soil coverage with pregerminated seeds. The rice plant height was shorter in the tested direct seeding methods than that of machine transplanting until 45day after seeding but there was not significant difference in terms of statistical analysis at 63day after seeding. The growth of tiller number in the rice plant was high in water seeding with iron-coated seeds and wet hill-seeding with soil coverage and low in wet hill-seeding with iron-coated seeds compared to machine transplanting. The yield component in the tested direct seeding methods was not significant difference in terms of statistical analysis. The milled rice yield in the tested direct seeding methods was higher 2 ~ 8% being with 4.94 ~ 5.24t/ha than that of machine transplanting but there was not significant difference in terms of statistical analysis. The percentage of head rice was low in the tested direct seeding methods compared to machine transplanting. The weedy rice was not occurred in the tested rice cultivation methods. In conclusion the direct seeding method would be recommended to be a suitable to in following by Italian ryegrass harvesting in southern area of Korea in terms of reduction in production cost and high income basis for rice growing farmers.