• Journal of Navigation and Port Research
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• v.33 no.1
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• pp.35-41
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• 2009

A waypoint tracking algorithm(WTA) is designed for Unmanned Surface Vehicle(USV) in which water-jet system is installed for propulsion To control the heading of USV for waypoint tracking, the steering nozzle of water-jet need, to be controlled. Firstly, target heading is calculated by using the position information of waypoints input from the land control center. Secondly, the command for the steering nozzle of water-jet is calculated in real time by using the heading and the rate-of-turn( ROT) from magnetic compass, In this study, in order to consider the drift angle due to external disturbance such as wind and wave, the course of ground( COG) can be used instead of heading at higher speed than a certain value, To test the performance of newly-designed WTA, the tests were carried out in actual sea area near Gwang-an bridge of Busan. In this paper, the sea trial test results from WTA are analyzed and compared with those from manual control and those from commercial controller.

• The Plant Pathology Journal
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• v.18 no.6
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• pp.328-332
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• 2002

Wheat samples showing typical spot blotch symptoms on stems and sheaths were collected from the field after physiological maturity, and were sealed in paper bags and stored in the laboratory at room temperature to study the survival of Bipolaris sorokiniana conidia on wheat straw. The materials were observed at monthly intervals to assess the conidia viability during storage. After 4 months, the frequency of individual conidia already present on wheat straw at the time of sampling was reduced and appeared to be progressively replaced by the formation of round structures consist-ing of conidia aggregates. After 5 months, distinct, individual conidia were no longer detected, and only 'clumps of conidia' were observed. These dark black aggregates or 'clumps of conidia’measured 157-170$\mu\textrm{m}$ in diameter and were grouped into boat-shaped olivacious conidia showing thick wall and measuring 50-82$\times$20-30$\mu\textrm{m}$. The germination was unipolar and below 0.5%, suggesting the occurrence of dormancy, In contrast, individual conidium produced on wheat during the growing season were 96-130$\times$16-20$\mu\textrm{m}$, slightly curved, hyaline to light pale, and euseptate with a bipolar germination reaching 98-100%. Bipolaris sorokiniana conidia produced on PDA were 55-82$\times$20-27$\mu\textrm{m}$, tapered at both ends, dark brown to olivacious, distoseptate, showed up to 1% germination, and were predominantly unipolar. Results of the present study suggest that B. sorokiniana conidia belonged to two different physiological categories corresponding to the pathogen's infection phase and its survival, respectively. The infection phase is characterized by a high germination percentage as opposed to the survival phase harboring apparent dormancy.

• Korean Journal of Materials Research
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• v.20 no.3
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• pp.111-116
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• 2010

Chloride-based fluxes such as NaCl-KCl are used in the refining of Al melt. The vapor pressure of the chloride is one of the fundamental pieces of information required for such processes, and is generally high at elevated temperatures. In order to measure the vapor pressure for chlorides, the apparatus for the transpiration method was assembled in the present study. The vapor pressure of $ZnCl_2$ and $FeCl_2$, which is related with the process of aluminum refining and the recovery of useful elements from iron and steel industry by-products, was also measured. In the measurement of vapor pressure by the transpiration method, the powder of $ZnCl_2$ or $FeCl_2$ in a alumina boat was loaded in the uniform zone of the furnace with a stream of Ar. The weight loss of $ZnCl_2$ and $FeCl_2$ after holding was measured by changing the flow rate of Ar gas (10 sccm -230 sccm), and the partial pressures of $ZnCl_2$ and $FeCl_2$ were calculated. The partial pressures within a certain range were found to be independent of the flow rate of Ar at different temperatures. The vapor pressures were measured in the temperature range of 758-901K for $ZnCl_2$ and 963-983K for $FeCl_2$. The measured results agreed well with those in the literature.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.43 no.1
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• pp.1-11
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• 2007

It is the basic studies for productivity improvement and laborsaving of purse seine fishery. Because the seine shape is apt to be transformed in seine shooting process due to the effect of tide, this study is intended to establish 4 steps, whose flow velocity are 0, 2, 4 and 6cm/sec, in flume tank and perform the experiment to review the character. We used two model seines designed on the scale of 1 to 180 based on the power block seine, which is the mackerel purse seine generally used in the near sea of Jeju Island and triplex seine, which is the mackerel purse seine of one boat system fishing expected in the future, for the experiment, analyzed of the sinking movements on the two seines and its results are as follows. In the setting over the flow velocity 6cm/sec, experiment was impossible because of flying and transformation of seine were severe. The sinking movements of P seine and T seine generally showed linear phenomenon and the sinking speed showed gentle curve shape. Sinking tendency was distinguished by existence of flow velocity. When there is flow velocity, it showed the phenomenon that it sinking by similar type. Although sinking depth and sinking speed did not show distinguished classification, P seine shows bigger than T seine. When there was in flow velocity, the elapsed time(Et) and sinking depth (PDp, TDp) of P seine and T seine can be shown such experimental equations as PDp=(0.21V+4.96)Et-(0.62V-0.10) and TDp=(0.19V+4.95)Et-(0.72V+0.34). When there was in flow velocity, the elapsed time and siking speed (PSp, TSp) of P seine and T seine can be shown such experimental equations as $PSp=-0.11Et^2+1.42Et+1.75\;and\;TSp=-0.11Et^2+1.41Et+1.37$.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.53 no.3
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• pp.286-292
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• 2017

The Coastal VTS will be continuously constructed to prevent marine traffic accidents in the coastal waters of the Republic of Korea. In order to provide the best traffic information service to the ship operator, it is important to understand the navigation risk factor. In this study, we analyzed the navigational hazards of Gunsan coastal area where the coastal VTS will be constructed until 2020. For this purpose, major traffic flows of merchant ships and density of vessels engaged in fishing were analyzed. This study was conducted by Automatic Identification System (AIS) and Vessel Pass (V-PASS) data. The grid intervals are 10 minute ${\times}$ 10 minute (latitude ${\times}$ longitude) based on the section of the sea. A total of 30 sections were analyzed by constructing a grid. As a result of the analysis, the major traffic flows of the merchant vessels in the coastal area of Gunsan were surveyed from north to south toward Incheon, Pyeongtaek, Daesan, Yeosu, Pusan and Ulsan, and from east to west in the port of Gunsan Port, 173-3, 173-6, 173-8, 183-2, 183-5, 183-8, 183-3, 184-1 and 184-2. As a result of the study, the fishing boats in Gunsan coastal area mainly operated in spring and autumn. On the other hand, the main traffic flow of merchant ships and the distribution of fishing vessels continue to overlap from March to June, so special attention should be paid to the control during this period.

• Journal of Navigation and Port Research
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• v.32 no.10
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• pp.777-783
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• 2008

Nowadays wavelet transforms are widely used for the analyses of PIV velocity vector fields. This is bemuse the wavelet provides not only spatial information of the velocity vectors but also of time and frequency domains. In this study, a discrete wavelet trC1f1$form has been applied to real PIV images of bubbly flows. The vector fields obtained by a self-made cross-correlation PIV algorithm were used for the discrete wavelet transform The performances of the discrete wavelet transform is investigated by changing the level of power of discretization. The decomposed images by the wavelet multiresolution showed conspicuous characteristics of the bubbly flows according to the level changes. The high spatial bubble concentrated area could be evaluated by the constructed discrete wavelet transform algorithm, at which high leveled wavelets could play a dominant roles to reveal the flow characteristics.

• Proceedings of the Korea Water Resources Association Conference
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• 2017.05a
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• pp.71-71
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• 2017

하천에서 평수기 유량측정은 도섭법을 이용하기 위한 지점식 측정보다는 초음파 도플러 유속계(ADCP, Acoustic Doppler Current Profiler)를 보트에 탑재하여 운용하는 측정 방식이 점차 일반화되고 있다. ADCP는 초음파의 도플러효과를 이용하여 수심이나 횡방향의 유속 분포를 측정할 수 있는 측정 장비로 일반적으로 사용되는 down-looking ADCP는 수심방향의 유속분포와 수심을 측정하여 보트의 이동속도와의 벡터 내적을 이용하여 유량을 산정하게 된다. 그러나, 이동식 ADCP 유량 측정 성과의 불확도는 제공되지 않고 있는 상황인데, 이는 불확도 산정 표준안 미비, 유속 및 수심 등 측정 요소의 관측 환경 별 불확도 정보 부족, 불확도를 산정할 수 있는 툴의 부재 등에 기인한다. 본 연구에서는 이동식 ADCP 불확도 산정 표준안을 개발하고 현장 실험을 통해 불확도 요인에 대한 규명, 불확도를 편리하게 산정할 수 있는 툴을 개발하고자 하였다. 불확도 산정 표준안으로 최근 WMO를 위시한 국제적으로 하천 유량 측정 불확도 표준안으로 채택되고 있는 GUM(Guide to the Expression of Uncertainty Measurement)을 기반으로 이동식 ADCP 유량 산정 알고리즘을 적용하여 불확도 적용 기법을 개발하였다. GUM 표준안을 기반으로 유량 측정불확도를 산정하기 위한 불확도 요인분석은 실규모 하천의 특성을 대부분 모의할 수 있는 한국건설기술연구원의 안동하천실험센터에서 수행된 실험자료를 기반으로 다양한 인자들에 대한 요소 별 불확도 분석을 수행하였다. GUM 표준안에 의하면 불확도 요인들은 오차전파의 법칙에 기반하여 전체 불확도에 전파되며, 이렇게 합성된 불확도는 t-분포의 신뢰수준 95%일 경우의 보정계수 2를 곱하여 최종적으로 확장불확도를 산정하게 된다. 이동측정방식의 ADCP의 경우 GUM 표준안에 적용하여 불확도를 평가하기 위해서 사용되는 수식이 방대하고, 매우 복잡하기 때문에 이를 실무자가 평가하기에는 한계가 있다. 이에 따라 본 연구에서는 ADCP의 유량 측정불확도를 보다 편리하게 평가하기 위하여 ADCP 유량 측정불확도 평가 소프트웨어인 AQUA(ADCP Discharge Uncertainty Assesment)를 개발하였으며, 이를 통해 실무자나 연구자들이 ADCP의 불확도 평가에 보다 편리하게 접근할 수 있을 것이라 판단된다.

• Proceedings of the Korea Water Resources Association Conference
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• 2017.05a
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• pp.505-505
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• 2017

최근 하천의 유량측정에 있어서 ADCP(Acoustic Doppler Current Profiler)의 빈도와 활용범위가 점차적으로 증가하고 있다. 국토교통부의 유량측정을 전담하고 있는 유량조사사업단에서는 최근 저평수기 유량측정은 물론, 중고수위 유량측정에서도 기존 유량측정방법의 단점을 보완하기 위해 ADCP 이동보트법을 적극적으로 활용하고 있다. 현재 ADCP 이동보트법으로 측정된 유량은 제조업체에서 제공되는 소프트웨어로 산정되며 크게 두 가지 문제를 초래하고 있다. 첫째, 제조업체에서 제공한 소프트웨어는 자동으로 품질평가를 할 수 있는 기능이 제한적이고, 사용자가 측정자료를 검토하기 위해 제공되는 표와 그래프 등의 정보가 제조업체마다 일관적이지 않다. 따라서, 측정자료의 품질평가는 측정한 ADCP에 종속되고 제조업체에서 제공된 소프트웨어 기능에 한정되어 효율적인 평가는 저해되고, 일관적이지 못한 결과를 초래하여 측정자의 책임이 증가되고 있다. 둘째, 제조업체에서 제공되는 소프트웨어가 자료의 처리 및 유량 계산에 대한 상이한 알고리즘을 사용하여 제조업체가 다른 ADCP로 동시에 측정된 유량이 서로 다른 결과로 나타나 혼란을 주고 있다. 이러한 이유로 USGS(U.S.Geological Survey)에서는 ADCP를 이용한 이동보트법 측정유량 처리에 대한 소프트웨어인 QRev를 개발하였으며, 일관적이고 효율적인 자료 처리와 계산이 이루어지도록 하고 있다. 본 연구에서는 유량조사사업단에서 수행한 ADCP 이동보트법 측정유량 자료에 대하여 QRev를 이용한 자료의 처리 결과에 대하여 분석하였다. 특히, ADCP로 측정이 불가능한 수면 및 하상 영역에 대한 외삽방법들의 적용 결과 및 제조업체의 기본 설정 값들에 대한 결과를 비교함으로서 QRev에 대한 향후 국내 활용 방향을 제시하고자 한다.

• Journal of the Society of Naval Architects of Korea
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• v.32 no.4
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• pp.27-37
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• 1995

A performance index is very important and indispensable to the evaluation of automatic steering system of ships in open sea from the viewpoint of energy saving. In this paper, we derive the performance index of automatic steering system from the concept of energy loss of propulsive power. The index is found to consist of three terms, energy loss due to elongation of sailing distance, energy loss due to steering, and energy loss due to yawing motion. We also provide two kinds of calculation method on the performance index ; frequency response analysis and digital simulation. The numerical calculations are carried out for an ore carrier and a fishing boat by both methods. The frequency response analysis is found to be useful if the system is linear and the disturbance on ship is not large. If the system is nonlinear or the disturbance is excessive, the method of digital simulation has to be applied for the accurate evaluation of the performance index. Further investigations into the effects of nonlinear elements such as weather adjuster, power unit etc. on the performance index, will be dealt with in another paper.

• Journal of the Korean Society of Industry Convergence
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• v.24 no.5
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• pp.597-608
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• 2021

The control head components used in small military vessels are designed to be domestically produced, prototypes, structural analysis, and casting methods are designed and cast. The control head assembly consists of a lever, an aluminum outside cover, Middle, front gear cover, back gear cover, and a zinc worm gear. In order to reverse the design of each component, 3D scanning device was used, 3D modeling was performed by CATIA, and prototype productions were carried out by 3D printer. In order to reduce the cost of components, gating system is used by gravity casting method. The SRG ratio of 1:0.9:0.6 was set by applying non-pressurized gating system to aluminum parts, 1:2.2:2.0 and pressurized gating system to zinc parts, and the shapes of sprue, runner and gate were designed. The results of porosity were also confirmed by casting analysis in order to determine whether the appropriate gating system can be designed. The results showed that all parts started solidification after filling completely. ANSYS was used for structural analysis, and the results confirmed that all five components had a safety factor of 15 more. All castings are free of defects in appearance, and CT results show only very small porosity. ZnDC1 zinc alloy worm gear has a tensile strength of 285 MPa and an elongation of 8%. The tensile strength of the four components of A356 aluminum alloy is about 137-162 MPa and the elongation is 4.8-6.5%.