• Proceedings of the Korea Water Resources Association Conference
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• 2023.05a
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• pp.225-225
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• 2023

하상 측정은 하천 유지관리, 수공구조물 설계 및 보수, 수생태 조사의 필수적인 자료이다. 최근 4대강 대규모 사업 이후 자연적 안정화로 인해 침식 및 재퇴적이 진행되어 정밀 하상 모니터링이 요구되고 있다. 통상적인 하상 조사 기법은 레벨측량 및 RTK-GPS 등을 활용하여 점단위로 직접 계측하는 기법과 수심이 깊을 경우 ADCP와 같은 음향측심기법을 통해 하상변동을 계측하고 있다. 하지만 점단위 직접 측정은 사구와 사련과 같은 하상 구조 교란 및 계측 시 위험을 동반하고 수심자료의 측정오차가 크게 발생하는 한계점이 존재한다. 또한 초음파 방식의 경우 막음길이와 바닥면 노이즈 등의 한계점으로 50 cm 미만의 저수심부 하상 측정이 불가능한 실정이다. 이러한 한계점을 극복하기 위해 최근 드론의 보급으로 수심라이다(Bathymetry LiDAR), SFM, 드론 탑재 초분광 영상을 활용한 초분광수심법과 같은 저고도, 고해상도의 비접촉식 면단위 하상 측정 기법이 대안으로 각광받고 있고 최근 관심은 해당 최신 기술의 성능 점검 및 적용성 평가에 있다. 따라서 본 연구에서는 초분광수심법 중 보편적으로 적용할 수 있는 최적밴드비분석(OBRA)의 성능 점검과 실무 적용성을 국내 하천을 대상으로 검토하였다. 해당 기술의 실무 적용성 평가항목 중 수심 적용 범위가 경제적이고 효율적인 성능 평가의 주된 항목이다. 선행 연구에 따르면 감천을 대상으로 저수심부의 성능 평가를 진행한 결과 상세한 하상계측이 가능하다고 제시하였다. 따라서 본 연구는 낙동강-황강 합류부를 대상으로 전형적인 평수기 탁도 조건에서 초분광수심법을 적용할 경우 최대측정가능수심의 범위를 결정하는 방법 및 결과를 제시하려고 한다. 또한 현장실험 당시 합천댐 방류로 인하여 황강의 탁도가 높아진 상태에 기인하여 고탁도 조건에서 초분광수심법의 적용성 평가도 추가 검토하였다. 해당 연구는 수심과 밴드비의 비선형성을 통해 최적 밴드비 분석의 결과로 도출될 수 있는 상관계수와 평균 제곱근 오차(RMSE)의 동향을 보아 다양한 시나리오의 배제수심을 통해 최대측정가능수심을 산정하였으며 그 이상의 범위는 수심맵 산정에서 제외하였다. 그 결과로 낙동강 본류에서 2.5 m 이하, 황강 지류에서 1.25 m 이하의 최대측정가능수심이 나타났고 해당 범위 이하에서는 상세한 하상이 나타났다. 또한 고탁도 조건인 황강에서는 낙동강에 비해 절반 수준의 최대측정가능수심 범위가 나타나 탁도 조건에 따른 초분광수심법의 한계가 있는 것을 확인하였다.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.21 no.2
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• pp.49-57
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• 2016

Even if an external forcing that will drive a climate change is given uniformly over the globe, the corresponding climate change and the feedbacks by the climate system differ by region. Thus the detection of global warming signal has been made on a regional scale as well as on a global average against the internal variabilities and other noises involved in the climate change. The purpose of this study is to estimate a timing of unprecedented climate due to global warming and to analyze the regional differences in the estimated results. For this purpose, unlike previous studies that used climate simulation data, we used an observational dataset to estimate a magnitude of internal variability and a future temperature change. We calculated a linear trend in surface temperature using a historical temperature record from 1880 to 2014 and a magnitude of internal variability as the largest temperature displacement from the linear trend. A timing of unprecedented climate was defined as the first year when a predicted minimum temperature exceeds the maximum temperature record in a historical data and remains as such since then. Presumed that the linear trend and the maximum displacement will be maintained in the future, an unprecedented climate over the land would come within 200 years from now in the western area of Africa, the low latitudes including India and the southern part of Arabian Peninsula in Eurasia, the high latitudes including Greenland and the mid-western part of Canada in North America, the low latitudes including Amazon in South America, the areas surrounding the Ross Sea in Antarctica, and parts of East Asia including Korean Peninsula. On the other hand, an unprecedented climate would come later after 400 years in the high latitudes of Eurasia including the northern Europe, the middle and southern parts of North America including the U.S.A. and Mexico. For the ocean, an unprecedented climate would come within 200 years over the Indian Ocean, the middle latitudes of the North Atlantic and the South Atlantic, parts of the Southern Ocean, the Antarctic Ross Sea, and parts of the Arctic Sea. In the meantime, an unprecedented climate would come even after thousands of years over some other regions of ocean including the eastern tropical Pacific and the North Pacific middle latitudes where an internal variability is large. In summary, spatial pattern in timing of unprecedented climate are different for each continent. For the ocean, it is highly affected by large internal variability except for the high-latitude regions with a significant warming trend. As such, a timing of an unprecedented climate would not be uniform over the globe but considerably different by region. Our results suggest that it is necessary to consider an internal variability as well as a regional warming rate when planning a climate change mitigation and adaption policy.

• Journal of Wetlands Research
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• v.17 no.2
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• pp.193-202
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• 2015

In this study, a long term monitering of nonpoint source pollution runoff is conducted at the area of transportation related and EMCs(Event Mean Concentrations) in terms of water quality items, such as BOD, $COD_{Mn}$, SS, T-N and T-P are determined for each not only runoff event and but also observation site. On the other hands, SWMM(Storm Water Management Model) model is constructed using the data collected in the transportation areas selected. Model calibration and verification of SWMM is carried out based on the data collected. And simulated EMCs was compared with observed EMCs by monitoring and prior studies. SWMM applicability estimation was Using the compared result. The results of simulation showed that BOD 5.787 ~ 14.475 mg/L, $COD_{Mn}$ 12.946 ~ 59.611 mg/L, SS 13.742 ~ 46.208 mg/L, T-N 2.037 ~ 5.213 mg/L, T-P 0.117 ~ 0.415 mg/L. And a differential between simulated EMCs and observed EMCs is too low so comparing result show high fit(BOD 4.27 %, $COD_{Mn}$ 4.87%, SS 2.31%, T-N 5.78%, T-P 14.45%). A results of compared with the prior studies, BOD and T-P are included range of prior studies, $COD_{Mn}$ and SS are lower than range of prior studies, T-N is higher than range of prior studies. Differential between simulated EMCs and prior studies EMCs was showing for survey seasonal and changing land-use, so from now on, EMCs of using the internal representatives value will be calculated by more monitoring toward various precipitation events.

• Korean Journal of Agricultural and Forest Meteorology
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• v.23 no.4
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• pp.306-315
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• 2021

This study analyzed the effects of light-shielding curtains and halogens on spectrum when acquiring hyperspectral images in a greenhouse. The image data of tarp (1.4*1.4 m, 12%) with 30 degrees of angles was achieved three times with four conditions depending on 14 heights using the automatic image acquisition system installed in the greenhouse at the department of Southern Area of National Institute of Crop Science. When the image was acquired without both a light-shielding curtain and halogen lamp, there was a difference in spectral tendencies between direct light and shadow parts on the base of 550 nm. The average coefficient of variation (CV) for direct light and shadow parts was 1.8% and 4.2%, respective. The average CV value was increased to 12.5% regardless of shadows. When the image was acquired only used a halogen lamp, the average CV of the direct light and shadow parts were 2 .6% and 10.6%, and the width of change on the spectrum was increased because the amount of halogen light was changed depending on the height. In the case of shading curtains only used, the average CV was 1.6%, and the distinction between direct light and shadows disappeared. When the image was acquired using a shading curtain and halogen lamp, the average CV was increased to 10.2% because the amount of halogen light differed depending on the height. When the average CV depending on the height was calculated using halogen and light-shielding curtains, it was 1.4% at 0.1m and 1.9% at 0.2 m, 2 .6% at 0.3m, and 3.3% at 0.4m of height, respectively. When hyperspectral imagery is acquired, it is necessary to use a shading curtain to minimize the effect of shadows. Moreover, in case of supplementary lighting by using a halogen lamp, it is judged to be effective when the size of the object is less than 0.2 m and the distance between the object and the housing is kept constant.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.3 no.4
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• pp.255-260
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• 1991

A voltage measuring system specified for the voltage fluctuation of the Pusan-Hamada submarine cable is developed by adding circuits of differential amplification and analog-to-digital conversion to a microprocessor-based data logger with a data modem. This system is charaterized by its small size. no power failure. fully unmanned operation. and precise instrumental drift correction. In addition to the cable voltage and current it measures an ambient temperature and a mercury cell voltage in order to calibrate temperature effect and check its long-term stability. The data acquired by this system show that the voltage signal. comprising fast random noises with a constant width of about 0.2V. fluctuates within a range of about 1V and the fluctuation frequency is similar to that of tidal motion. The source voltage of power feeding equipment (PFE) for the cable system seems to be affected when the room temperature changes rapidly.

• Journal of the Korean Association of Geographic Information Studies
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• v.8 no.2
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• pp.10-20
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• 2005

The change of stream creation has a very sensitive effect on runoff analysis model using the divergence characteristic of stream. Therefore, in this study, the threshold area of stream creation was examined the change characteristic of topographical parameters. The subject basin of the research was the upper basin of the Kumho water gage station which is located in the middle of the Kumho river. The 1:25,000 numerical geography which was constructed $10{\times}10m$ mesh was used. The range of investigation of topographical parameters are number of stream order, length, area, slope, basin relief, sinuosity ratio, drainage density and total stream length etc. It was found from the result of analysis that the threshold value of 1st order stream has a very big effect on topographical parameters of basin. It was found that the threshold area of stream creation was under $0.10km^2$, the parameters showed a big change but showed a very small change over $0.10km^2$.

• Journal of the Korean Society of Groundwater Environment
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• v.4 no.1
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• pp.54-59
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• 1997

The river and groundwater are contaminated by pollution source of a waste landfill and others near river. The contaminant transport and response of aquifer parameters are studied in the aquifer affected by variation of river stage. First, the equation for component of variation velocity with river stage is developed by using the analytical solution of groundwater governing equation. The numerical model which considered component of variation velocity is constructed for the transport of mass by advection and dispersion. In order to verify a numerical scheme, the analytical solution is used. The numerical solution is coincided with the analytical one. Aquifer parameters of Nanjido are used as the data for numerical experiment. Second, the range of aquifer parameters is established in order to reponse contaminant transport in aquifer with river stage. The result of numerical experiment shows that the range of the storage coefficient except hydraulic conductivity and effective porosity is relatively sensitive to the contaminant transport. When the storage coefficient is the order of 10$\^$－2/, the response is very sensitive to the variation of river stage.

• Journal of Korean Ophthalmic Optics Society
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• v.4 no.2
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• pp.147-154
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• 1999

This study was performed to survey the exchange of frames on 83 persons. We investigated frame size, frame type, binocular prism effect etc. 80.4% among motives of frame-exchanges was a damage or corrosion. The type of frames was round-like 62.4% and 37.6% square-like. The size of frames was $49{\Box}18$ and vertical length 33mm on old-frames, $47{\Box}17$ and 31mm on new-frames. The scope of axis variation was average +3.20~3.80. According to estimation by the rule of RAL-RG 915, the inappropriate horizontal prism effect of new spectacles was 42.2%, more than 38.5% on old spectacles. The inappropriate vertical prism effect was 24.1% on old, 33.7% on new spectacles.

• Journal of Korean Tunnelling and Underground Space Association
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• v.19 no.3
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• pp.517-532
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• 2017

The transverse ventilation system, commonly applied to urban tunnel, is necessary to be distributed with airflow uniformly. In this study, we developed a program that can optimize the opening ratio of ports to ensure ventilation performance of design criteria through a uniform airflow distribution even though ventilation interval becomes longer. And program's prediction performance was verified by comparison with TUNVEN DUCT program. For comparison, Semi-transverse ventilation system was applied. Both programs predicted a similar port size and air flow distribution, and the variation range of the calculated values was 11.71% and 1.36%, respectively. This program is very useful for port optimization design of transverse and semi-transverse ventilation system, because it is possible to analyze various tunnel lengths and supply/exhaust port installation conditions.

• KIISE Transactions on Computing Practices
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• v.23 no.8
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• pp.459-465
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• 2017

Although the performance of computer hardware is increasing due to the development of manycore technologies, software lacking a proportional increase in throughput. Functional languages can be a viable alternative to improve the performance of parallel programs since such languages have an inherent parallelism in evaluating pure expressions without side-effects. Specifically, Haskell is notably popular for parallel programming because it provides easy-to-use parallel constructs based on monads. However, the scalability of parallel programs in Haskell tends to fluctuate as the number of cores increases, and the garbage collector is suspected to be the source of this fluctuations because it affects both the space and the time needed to execute the programs. This paper uses the tuning tool, GC-Tune, to improve the scalability of the performance. Our experiment was conducted with a parallel plagiarism detection program, and the scalability improved. Specifically, the fluctuation range of the speedup was narrowed down by 39% compared to the original execution of the program without any tuning.