• Journal of Institute of Control, Robotics and Systems
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• v.18 no.8
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• pp.699-705
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• 2012

In this paper, an infrastructure-based localization method using underwater wireless sensor network (UWSN) is addressed. A localization using the UWSN is necessary to widen the usage of underwater applications, however it is very difficult to establish the UWSN due to the restrictions of water. In this paper, to extend the usage of UWSN at the infrastructure, we propose a sophisticated UWSN localization method using the Received Signal Strength Indicator (RSSI) of the electromagnetic waves. During the electromagnetic waves propagating in underwater, there arises a lot of attenuation according to the distance, while the attenuation shows uniformity according to the distance. Using this characteristics, the localization system in underwater infrastructure is proposed and the experimental results show the effectiveness.

• Journal of Korea Water Resources Association
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• v.33 no.2
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• pp.237-245
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• 2000

Sihwa seadike is originally designed to control the water level In lake Sihwa. However the sluice gate is being operated everyday to preserve the water quality of lake. Due to the frequent operation of gates the bottom of drainage canal which is composed of weathered rock and soft rock is being scoured. Recently the bottom in the front area of apron was protected by putting underwater concrete. This study is carried out to understand the hydraulic situation for protection, and to estimate the trend of scouring by comparing between energy dissipation and registance of bottom rock. Annandale(1995) introduced the erodibility index theory, and suggested a criteria to judge the erodibility of rock through the relation between the erodibility index and energy dissipation. Determenation of erodibility index of rock is based on the results of sample core analysis, and the energy dissipation of flow is calculated from the estimation of total head on the scale model. These two values are plotted on the criteria, and the erodibility of rock is determined.

• Proceedings of the Korea Water Resources Association Conference
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• 2019.05a
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• pp.416-416
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• 2019

육상 담수는 대기중 이산화탄소($CO_2$) 배출의 중요한 발생원으로 주목되고 있다. 하천 및 강에서 대기중으로 배출되는 $CO_2$는 전 세계 탄소순환의 핵심요소이며, 대부분의 하천과 강은 $CO_2$로 과포화 되어있다. 세계적으로 하천 및 강의 $CO_2$ 배출량은 호수 및 저수지의 배출량보다 약 5배 많은 것으로 보고되고 있으나, 국내연구에서는 연구사례가 드물다. 따라서 본 연구의 목적은 낙동강 중하류에 위치해있는 강정고령보(GGW), 달성보(DSW), 합천창녕보(HCW), 창녕함안보(CHW)에서 발생되는 순 대기 배출 플럭스(Net Atmospheric Flux, NAF)의 동적 변동 특성을 분석하고, 데이터마이닝 기법을 적용하여 쉽게 수집할 수 있는 물리적 및 수질 변수로 $CO_2$ NAF를 추정하는데 사용할 수 있는 간략한 예측 모델을 개발하는데 있다. $CO_2$ NAF는 대기-수면 경계면에서의 $CO_2$ 부분압($pCO_2$)의 차에 기체전달속도를 곱하여 산정하였으며, 기체전달속도는 Cole and Caraco(1998)가 제안한 식을 사용하였다. 담수와 해수의 탄산염 시스템에서 열역학적 화학평형을 모두 고려한 $CO_2$SYS 프로그램을 사용하여 수중의 $pCO_2$를 산정하였고, $CO_2$ NAF는 Henry의 법칙과 Fick의 1차 확산법칙을 사용하여 계산하였다. $CO_2$ NAF의 시간적 변동성에 영향을 미치는 환경요인을 평가하기 위해서 상관분석, 주성분분석(Principal Component Analysis; PCA), 단계적다중회귀모델(Step-wise Multiple Linear Regression; SMLR), 랜덤포레스트(Random Forest; RF)방법을 사용하였다. SMLR 모델은 R package인 olsrr, RF 모델은 R package인 caret, randomForest를 이용하여 분석하였다. 연구 결과, 4개 보 상류 하천구간은 조류의 성장이 활발한 일부 기간을 제외한 대부분의 기간에서 $CO_2$를 대기로 배출하는 종속영양시스템(Heterotrophic system)을 보였다. $CO_2$ NAF의 중위값은 HCW에서 최소 $391.5mg-CO_2/m^2day$, DSW에서 최대 $1472.7mg-CO_2/m^2day$였다. 모든 보에서 NAF는 pH와 강한 음의 상관관계를 보였으며, $pCO_2$와 Chl-a도 음의 상관관계를 보였다. 이는 조류가 수중에서 $CO_2$를 소비하고 pH를 증가시키기 때문이다. PCA 분석 결과, NAF와 $pCO_2$가 높은 공분산을 보였으며, pH와 Chl-a는 반대 방향으로 군집되어 상관분석과 동일한 결과를 보였다. 이 연구를 통해 개발된 SMLR 모델과 RF 모델의 Adj. $R^2$ 값은 모든 보에서 0.77 이상으로 나왔으며, $pCO_2$ 측정 데이터가 없더라도 하천의 $CO_2$ NAF를 추정하는 방법으로 사용될 수 있을 것으로 평가된다.

• Korean Journal of Ecology and Environment
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• v.39 no.1 s.115
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• pp.138-144
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• 2006

Algal growth potential test (AGPT) has been used as a tool for assessing biological productivity potential in the aquatic ecosystems. This study was conducted to compare the productivity potentials of large reservoirs (Lakes Andong, Hapchon and Jinyang, and Naktong estuarine dam) and river sites (Sangju, Koryung, and Samlangjin) located in the Naktong River watershed. AGPT was conducted in both non-monsoon and mosoon season (February, April, July and September) of 2003, using Microcystis aeruginosa as a test alga. The AGPs in the reservoirs were relatively much lower than those of river sites. The river AGPs increased towards upstream close to the influent streams, while it generally decreased towards downstream. Immediately after the abrupt increase in influent discharge in summer, the AGP became similar between midstream and downstream sites. The water quality of river and reservoirs deteriorated during the drought period in accordance with AGP: it was the highest during this period. The AGPs showed the closest correlation with the P concentration, leading to the conclusion that bioavailable P is highly influential to the algal growth in both lentic and lotic ecosystems in the Naktong River watershed. Based on the AGPs, the water quality of tested sites was likely eutrophic. Our results suggest that AGPT be a useful tool in evaluating the productivity potential and trophic state of the water body as well as determining the nutrients that limit the growth of algae.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.48 no.3
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• pp.125-131
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• 2011

Water leak detection system is a system based on wireless sensor networks(WSNs) which detect a leak on water supply, localize the leak position and finally inform a water management center. A traditional leak detection method is to use experienced personnel who walk along a pipeline listening to the sound that is generated by the leaks and their effectiveness depend on the experience of the user. Also making more successful detection, it should be processed at middle of the night when people do not use water, as the result users have to operate the leak detection system at midnight. In this paper, we propose a new method for the water leak detection system based on the WSNs and describe it in detail. Leak detection devices which detect a leakage of water transmit and receive the result of water leak detection with each other by configuring WSNs to improve reliability of the detection result. Also, we analyzed the sound from water flowed in pipeline, proposed the pre-signal processing to separate a leakage sound from noisy sound. And lastly, It is especially important to make a time synchronization with water leak detection devices that are installed on the pipeline, we used 1PPS(1 Pulse Per Second) signal generated by GPS, therefore we could get a precise time synchronization. The proposed system set up in Namyangju and performances were evaluated.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.37 no.3
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• pp.196-213
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• 2001

A split beam ultrasonic transducer operating at a frequency of 70 kHz to use in the fish sizing echo sounder was developed and the acoustic radiation characteristics were experimentally analyzed. The amplitude shading method utilizing the properties of the Chebyshev polynomials was used to obtain side lobe levels below -20 dB and to optimize the relationship between main beam width and side lobe level of the transducer, and the amplitude shading coefficient to each of the elements was achieved by changing the amplitude contribution of elements with 4 weighting transformers embodied in the planar array transducer assembly. The planar array split beam transducer assembly was composed of 36 piezoelectric ceramics (NEPEC N-21, Tokin) of rod type of 10 mm in diameter and 18.7 mm in length of 70 kHz arranged in the rectangular configuration, and the 4 electrical inputs were supplied to the beamformer. A series of impedance measurements were conducted to check the uniformity of the individual quadrants, and also in the configurations of reception and transmission, resonant frequency, and the transmitting and receiving characteristics were measured in the water tank and analyzed, respectively. The results obtained are summarized as follows : 1. Average resonant and antiresonant frequencies of electrical impedance for four quadrants of the split beam transducer in water were 69.8 kHz and 83.0 kHz, respectively. Average electrical impedance for each individual transducer quadrant was 49.2$\Omega$ at resonant frequency and 704.7$\Omega$ at antiresonant frequency. 2. The resonance peak in the transmitting voltage response (TVR) for four quadrants of the split beam transducer was observed all at 70.0 kHz and the value of TVR was all about 165.5 dB re 1 $\mu$Pa/V at 1 m at 70.0 kHz with bandwidth of 10.0 kHz between -3 dB down points. The resonance peak in the receiving sensitivity (SRT) for four combined quadrants (quad LU+LL, quad RU+RL, quad LU+RU, quad LL+RL) of the split beam transducer was observed all at 75.0 kHz and the value of SRT was all about -177.7 dB re 1 V/$\mu$Pa at 75.0 kHz with bandwidth of 10.0 kHz between -3 dB down points. The sum beam transmitting voltage response and receiving senstivity was 175.0 dB re 1$\mu$Pa/V at 1 m at 75.0 kHz with bandwidth of 10.0 kHz, respectively. 3. The sum beam of split beam transducer was approximately circular with a half beam angle of $9.0^\circ$ at -3 dB points all in both axis of the horizontal plane and the vertical plane. The first measured side lobe levels for the sum beam of split beam transducer were -19.7 dB at $22^\circ$ and -19.4 dB at $-26^\circ$ in the horizontal plane, respectively and -20.1 dB at $22^\circ$ and -22.0 dB at $-26^\circ$ in the vertical plane, respectively. 4. The developed split beam transducer was tested to estimate the angular position of the target in the beam through split beam phase measurements, and the beam pattern loss for target strength corrections was measured and analyzed.

• Proceedings of the Korea Water Resources Association Conference
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• 2015.05a
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• pp.44-44
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• 2015

저수지나 하천 사면에서 발생하는 산사태와 토석류는 저수지와 하천 수체에 충격을 가한다. 이로 인해 발생하는 수면 충격파는 전파되어 반대편 제방으로 파의 처오름 또는 댐 제체위로의 물넘이로 큰 피해를 줄 수 있다. 최근 외국에서는 2차원 충격파 생성 및 전파의 기본 과정을 구명하기 위한 실험적 연구가 이뤄지고 있으며, 이들 연구들은 충격파의 발생과 전파, 사면활동 물질과 수체의 상호작용 그리고 자유 수면과 유속분표의 발달에 대한 자세한 관측 자료를 제시하고 있다. 아울러 충격파에 영향을 주는 지배 매개변수를 제시하고 있다. 하지만, 이러한 실험적 연구의 최근 진보에도 불구하고, 이들 지배 매개변수를 고려한 충격파 지배공식들은 대상 지역의 복잡한 바닥 지형이나, 평면적 지형 변화를 단순한 추정치로만 고려하게 된다. 따라서 복잡한 지형조건에서 토석류와 수체의 상호작용과 수면 충격파의 전파를 합리적으로 해석하는 데는 한계가 있다. 이 경우 수치모델링 기법을 대안으로 적용할 수 있으나, 수치모델링은 수면에서 충격파의 전파와 수중에서 토석류의 전파를 동시에 모의해야 하고, 뉴턴 유체와 비뉴턴 유체의 특성을 동시에 고려해야하므로 수치해석 연구자들에게는 하나의 큰 도전사항이다. 이 연구는 경계면 포착기법을 이용한 계산유체동력학 기법을 이용하여 사면활동과 이로 인한 정지 수역에서의 충격파의 발생 및 전파를 재현하기 위한 수치 모델링 기법을 개발하는 것이 목적이다. 사면활동과 수면의 경계면을 포착하고 위치를 정립하기 위해서 VOF (volume of fluid) 경계면 재구축 기법을 이용한다. 지배 방정식은 비압축성(incompressible) 질량 보존방정식과 나비어-스톡스(Navier-Stokes) 방정식이며, 서로 다른 유체의 상(phase)애 대한 체적분할이송방정식을 이용한다. 큰와 모의 계열의 난류 모델링 기법을 적용하여 충격파의 전파와 붕괴에 대한 난류의 영향을 고려하였다. 토석류는 비뉴턴 흐름저항 관계식을 적용하여 그 흐름특성을 재현하였다. 이들 지배방정식은 2차 정확도의 유한체적법(finite volume method)을 이용하여 해석한다. 외국의 연구자들이 관측하여 제시한 길이 11 m 그리고 폭 0.5 m의 수로에서 발생한 충격파를 수치적으로 재현하여 개발된 모형의 실제 문제에 대한 적용성을 보여준다.

• Proceedings of the Korea Water Resources Association Conference
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• 2022.05a
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• pp.267-267
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• 2022

댐 운영에 있어서 필요한 수문자료는 강수량, 수위, 유량, 저수량 자료 등이 있다. 이중 저수량은 주로 댐수위-저수용량 곡선식을 이용하여 계산한다. 댐수위-저수용량 곡선식은 댐 부근에서 계측 되는 한 개의 수위자료를 이용하여 저수용량을 산정하며, 이는 큰 저수지 면적과 저수지 수면이 일정하지 않다는 것을 고려할 때 큰 오차가 발생할 수 있다. 본 연구에서는 음향 도플러 유속계 ADCP(Acoustic Doppler Current Profiler) 이용하여 보성강댐 저수지 수면경사를 실측하고, 동시에 실시간 이동측위시스템인 RTK-GPS(Real Time Kinematic)를 이용하여 이를 검증하였다. ADCP는 유수의 흐름을 방해하지 않으면서 수중에 발사된 음파의 도플러 효과를 이용하여 유속, 유량 및 측량이 가능한 장비이며, RTK-GPS의 경우 정밀한 위치정보를 가지고 있는 기준국의 위상에 대한 보정치를 실시간으로 이용하여 오차가 ±0.03m 이하인 것으로 알려졌다. 보성강댐의 하류에서 ADCP와 RTK-GPS를 장착한 보트를 저수지 종방향으로 처음부터 끝까지 이동하여 약 7.5km 종단측량을 실시하였고 저수지 지형적 특성을 고려하여 약 700m마다 횡단측량을 실시하여 종방향뿐만 아니라 횡방향 수면차도 조사하였다. 그 결과 보성강댐의 상류로 갈수록 수면경사가 전체적으로 상승하는 경향을 보였지만 일부구간에서 수위가 하강하는 경우도 발생하였다. 이는 미약하지만 저수지 내에 흐름이 발생하고 이 흐름에 따른 통제가 변화되는 것과 중간에 유입되는 지류의 영향 등으로 구간별로 수면경사 차이가 발생하는 것으로 추정된다. 횡방향 수면차는 지류가 유입되는 일부구간에서 다소 차이를 보였지만 큰 영향을 없는 것으로 판단된다. 보성강댐 저수지 수면을 종방향 및 횡방향으로 실측한 결과 구간별로 차이를 보였으며 최대 EL. 126.60m, 최소 EL. 126.33m 나타났다. 댐 상류 부근의 수면높이 EL. 126.50m와 비교하면 +0.10m, -0.17m 차이를 보였으며 이는 저수량 산정에 큰 오차를 발생시킨다. 효과적인 댐 운영을 위해서는 유입량 및 유출량을 정확하게 산정하는 것도 필요하지만 저수량을 정확하게 파악하는 것 역시 필요하다. 저수량을 정확하게 산정하려면 수킬로미터가 넘는 저수지 크기를 고려하여 수면경사를 실시간으로 계측하는 등의 노력이 필요한 것으로 판단된다.

• Korean Journal of Heritage: History & Science
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• v.55 no.4
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• pp.6-22
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• 2022

In this paper classifies the types of 228 anchor stones discharged from the west and south coasts, assumes a combined method by type, routes through discharge locations, and It attempted to estimate the burial site. Prior to classification of types, the weight, thickness, width, and length of the anchor stone were measured, and the largest Young in the tomb The scent weight was classified into I~V groups, and the shape of the anchor stone was classified into 1-6 types. All of these weight and shape correlations It was classified into 17 types. The combined method by type is 180kg or less depending on the morphological characteristics of the reference value of the extracted anchor stone, and the type An anchor of type 1 or 2 is used in combination with an anchor, and a anchor of type 3 or 6 weighs more than 180kg and is combined with an anchor The dragon was assumed to be an anchor. Along with this, the route and burial site are identified through past records and testimony of local residents It was checked against the data. The route was largely consistent with past records, but the new route was apparent in waters near the island or inland It was also drawn. In the case of burial sites, small and large in Taean Mado Sea and Jindo Byeokpajin Sea, where anchor stones are concentrated, Considering the pattern of the type anchor stones being discharged, it was consistent with the testimony that ships of various sizes were mysterious in the two seas. Based on this type classification, a study on the spatiality of the anchors was conducted. First, a comparison and analysis was done on whether actual real data, such as anchor stones, old ships, and relics, were identified on the Joun-ro route and international trade routes as recorded in the past literature. Where there was no record, the route was estimated based on real data. To this end, routes estimated based on the testimony of local residents and modern ship workers were analyzed as to whether ships traveled there in the past and whether they could actually sail. Next, the location of each seedling was estimated by ship size according to the weight of the anchor stone. In the case of the Taean Mado Sea and Jindo Byeokpajin Sea, both small and large anchor stones were discharged from the coastline and were far away.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.37 no.2
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• pp.106-116
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• 2001

A serious of studies on the fishing gear and system of the East Sea trawl fishery was carried out to improve the fishing efficiency and the working conditions. As the first step of these studies, the fishing gear and system of the traditional East Sea trawl were checked in order to solve the some problems, such as the poor sheering efficiency of net mouth, the inconvenient fishing system of the side trawl and etc. And then the fishing system was reorganized from the side trawl into the stern trawl by setting up the net drum system on the stern deck, and introduction of two types of new designed nets, one for mainly the midwater trawl and the other for the bottom trawl. The results of the field experiment on the modified system and nets can be summarized as follows : 1. the modified system was well worked and could save the man-labour by about 80%. 2. The sheering efficiency of the improved net, A type was improved to 20 m height and 30 m width in the net mouth, and that of B type net, to 10 m height and 33 m width, compared with 1.5 m height and 15 m width in the traditional net. 3. Catch efficiency of pink shrimp in A or B type net was better about 3 or 5 times than that of traditional net, and in B net, for herring and other bottom fishes is better about 2 times than that of the traditional net.