• 한국해양학회지:바다
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• 제16권2호
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• pp.53-69
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• 2011

하구의 체계적인 관리를 위해서는 하구의 특성과 분포를 반영한 분류가 먼저 이루어져야 한다. 이 연구에서는 지리정보시스템, 고해상도 항공사진 및 지형도 등을 사용하여 우리나라의 463개 하구의 특성과 분포를 파악하였고, 이들 하구의 하구순환 유지 여부, 지형적 특성, 자연서식지 특성, 이용개발 특성에 기초하여 유형을 분류하였다. 하구 순환이 이루어지는 235개의 '열린하구'는 지형적 특성에 따라 '산지/절벽형', '사취형' 및 '깔대기형'으로 구분하였으며, 각 유형에 속하는 하구는 각각 41, 87, 107개로 분류되었다. 구분된 각 하구는 다시 자연서식지 특성과 이용 개발 특성에 따라 3가지 유형으로 세분하여, 열린하구는 총 9개의 유형으로 구분하였다. 하구순환이 차단된 228개의 '닫힌하구'는 차단 형태에 따라 '직접차단'과 '하구호' 형성에 의한 간접차단으로 구분하였다. 직접차단 형태의 하구를 다시 자연서식지 및 이용개발 특성에 따라 3가지 유형으로 세분하였으며 각 유형에 속하는 하구는 각각 25, 64, 55개로 분류되었다. 간접차단 하구는 84개가 파악되었으나 세분하지 않아 닫힌하구는 총 4개의 유형으로 구분되었다. 이 유형분류 체계는 하구의 지형적 특성, 자연서식지의 현황 및 토지이용 특성을 모두 반영하고 있어 국가 차원의 하구관리에 있어서 우선순위를 결정하고 관리방향을 설정하는데 효과적으로 활용할 수 있다.

• 한국산학기술학회논문지
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• 제22권5호
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• pp.22-33
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• 2021

태양광전원이 설치된 배전선로의 단선 등으로 결상사고가 발생하는 경우, 연계용변압기의 철심형태 및 결선 방법에 따라 여러 가지 문제점이 발생할 가능성이 있다. 즉, 단선사고 발생 시 태양광전원 인버터의 단독운전 방지기능에 따라 결상을 감지하여 발전을 정지해야 하지만, 결상을 인지하지 못하고 계속 발전하는 사례가 보고되고 있으며, 연계용 변압기의 역조류 현상으로 인해 결상된 상으로 전원을 공급하여 계통에 악영향을 주는 문제점이 발생하고 있다. 하지만, 기존의 결상사고 보호계전기(Open Phase Relay, 47)는 태양광전원 연계용변압기의 결선방식과 철심형태에 따라 결상된 상에 전압이 유지될 수 있어서, 결상사고 검출이 어려워, 새로운 결상사고 검출 알고리즘이 요구되고 있다. 따라서, 본 논문에서는 전류비교방식의 개념을 이용하여, 연계용변압기 1, 2차측의 전류와 위상을 비교하여 결상사고를 검출하는 새로운 개념의 알고리즘을 제안한다. 또한, 전력계통 상용해석 프로그램인 PSCAD/EMTDC를 이용하여 수배전반, 저압배전선로, 부하, 연계용변압기, 태양광전원으로 구성된 배전계통과 결상사고 검출 보호장치의 모델링을 수행하고, 이를 바탕으로 결상사고 검출 보호장치를 구현한다. 상기의 모델링과 결상사고 검출 알고리즘을 바탕으로 태양광전원 연계용 변압기의 결선방식과 철심구조에 따라 결상사고 검출 보호장치의 특성을 분석한 결과, 결상 시 연계용변압기의 동작 기울기와 1차측 전류 불평형률이 보호장치의 정정 값(30[%])을 초과함에 따라 결상사고가 정확하게 검출되어, 제안한 알고리즘이 결상사고 보호방식에 유용함을 알 수 있었다.

• 한국포장학회지
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• 제27권2호
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• pp.91-100
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• 2021

Agricultural corrugated fiberboard packaging boxes frequently experience damage due to loading and unloading, vibration during transport, and shock by dynamic distribution condition change. This study was carried out to estimate effect of vibration during distribution process on compression strength of corrugated fiberboard boxes for agricultural products. In order to identify the degradation caused by vibration, after box packaging the agricultural products(tangerine or cucumber), the natural frequencies of the packaging boxes were measured by varying the relative humidity(50, 70 and 90%) at 25℃ temperature. Various types of corrugated fiberboard boxes were packed with tangerines and cucumbers, and the PSD plot vibration tests were conducted by utilizing the actual vibration recording results of the Gyeongbu Expressway section between Seoul and Gimcheon. As a result of the experiment, the decrease in compression strength of the box was relatively low in DW-AB, and the decrease in compression strength of the SW-A 0201(RSC) type box was the highest at 20.49%. In particular, both SW-A and DW-AB showed low compression strength degradation rates for open folder type boxes. The moisture content varies depending on the type of the box or agricultural products, and the enclosed 0201(RSC) type box was generally higher than the open folder or bliss type box, which is believed to be the reason for the decrease in compression strength of RSC type box due to humidity. By the agricultural product, the percentage of decrease in compression strength of box packed with cucumbers was especially high.

• Structural Engineering and Mechanics
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• 제76권2호
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• pp.269-278
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• 2020

In this paper, the mechanical characteristics of the open type hyperbolic-parabolic membrane structure under wind load were investigated. First, the numerical simulation of a typical plane membrane structure was performed based on the Large-Eddy Simulation method. The accuracy of the simulation method was validated by the corresponding wind tunnel test results. Then, the wind load shape coefficients of open type hyperbolic-parabolic membrane structures are obtained from the series of numerical calculations and compared with the recommended values in the "Technical Specification for Membrane Structures (CECS 158: 2015). Finally, the influences of the wind directions and wind speeds on the mean wind pressure distribution of open type hyperbolic-parabolic membrane structures were investigated. This study aims to gain a better understanding of the wind-induced response for this type of structure and be useful to engineers and researchers.

• 한국산업융합학회 논문집
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• 제23권2_2호
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• pp.199-207
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• 2020

These days, many different types of valves are developed in the industrial area according to their use purpose. Multiple kinds of valves are installed to control a flow and pressure of the pipe conveying fluid. Valves serve as critical roles in land plants such as power plants. The performance of equipment varies depending on valve characteristics. In this study, the internal flow analysis on Cone-type valve is conducted to analyze flow field and secure a value of the flow coefficient Cv. According to the internal flow analysis, when the flow distribution of the middle cross-section of valve was open 100%, flow field was relatively and smoothly taken out. If it was open 50%, flow recirculation region increased and a little complex flow field occurred. Unlike ball valve or butterfly valve, this valve had flow recirculation in its outlet depending on a valve opening amount. Therefore, it was found that there was no flow recirculation in the outlet of Cone-type valve.

• 대한전기학회논문지:전력기술부문A
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• 제48권11호
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• pp.1417-1423
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• 1999

Distribution system can experience the diverse events instantly and permanently. Also, it can experience high impedance fault or line drop under unbalanced situation, Accordingly, it is difficulty to identify the fault location because that data collected from distribution SCADA system may include uncertainty. This paper proposes an expert system, which can infer the faulted location the quickly and exactly for the diverse events in the distribution system. The expert system utilizes distribution SCADA function and collected data, especially, the monitoring mechanism for the normal open position switches is adopted newly in order to recognize the fault type exactly. Also, automated fault location diagnosis strategy is developed in order to minimize the spreading effect of fault obtained from the error of the system operator. The proposed strategy is implemented in C language. Especially, in order to prove the effectiveness of proposed expert system, the several scenario is simulated for the given model system. The real feeders are selected as model system for the simulation.

• The Korean Journal of Ecology
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• 제19권6호
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• pp.529-541
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• 1996

During the period of December 1992 (winter-spring) and from February 1995 (winter-spring), the leaf processing rates of oak (Quercus serrata) and tulip (Liriodendron tulipifera) tree was investigated in the headwater streams in southeastern part of Korea in conjunction with the distribution pattern of macroinvertebrate fauna. Using two types of bags ($10\times30cm$ with 5 g of dry leaves; open bag with holes, closed bag without holes), decomposition rates of oak and tulip tree by shredder and/or microbiota at a reatively undisturbed 2nd-order stream were compared, Regardless of leaf type, leaves in the open bage decomposed slightly faster than those in the closed bags. In the 1992 experiment, osk leaves decomposed much slower than tulip leaves (after 138 degree days, osk : closed, 0.006% loss/day ; open, 0.008 ; tulip: closed, 0.021 ; open, 0.023; n=2). The of the first experiment using oak leaves in 1995 were similar to those of the first experiment (after 151 degree days, oak: closed, 0.005% loss / day; open, 0.006; n=6). Over 50% of invertebrates from 122 leaf pack samples collected from 12 streams during the winter period of 1994 were identified as shredders (shredder, 56.2; collector, 32.7; scraper, 8.65; predator, 2.45%). Among shredders, Gammarus sp. and Tipula sp. were dominant species in terms of number and biomass (8.2 ind./g, 1.0 ind./g AFDW of leaves). Among many physico-chemical parameters, the width of stream channel was found to be the most influential factor in the distribution of Gammarus and Tipula (Gammarus: r=-0.34, P<0.001;Tipula:r=0.40, P<0.001). Considering the fact that oak is one the dominant riparian vegetation in the southeastern part of korea, the patterns of oak processing and shredder distribution shown in theis study may well represent some of the important characteristics of headwater steams in southeastern Korea.

• Earthquakes and Structures
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• 제22권4호
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• pp.345-353
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• 2022

The configuration of an open ground floor (pilotis) is a common and very critical irregularity observed in multistory reinforced concrete frame structures. The characteristics and the geometrical formation of the beams of the first story proved to be a critical parameter for the overall seismic behavior of this type of Reinforced Concrete (RC) structures. In this work the combination of open ground floor (pilotis) morphology with very strong perimetrical beams at the level of the first story is studied. The observation of the seismic damages and the in situ measurements of the fundamental period of four buildings with this morphology and Π-shaped plan view are presented herein. Further analytical results of a pilotis type Π-shaped RC structure are also included in the study. From the measurements and the analytical results yield that the open ground floor configuration greatly influences the fundamental period whereas this morphology in combination with strong beams can lead to severe local shear damages in the columns of the ground floor. The structural damage was limited in the columns of the ground floor and yet based on the changes of the in situ measured fundamental period the damaged level is assessed as DI=88%. Furthermore, due to the Π-shape of the plan view the tendency of the parts of the building to move independently strongly influences the distribution of the damages over the ground floor vertical elements.

• KIEE International Transactions on Power Engineering
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• 제3A권3호
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• pp.124-129
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• 2003

As the power industry moves towards open competition, there has been a call for methodology to evaluate power system reliability by using composite interruption cost. This paper presents algorithms to evaluate the interruption cost of distribution power systems by taking into consideration the failure source and the composite customer interruption cost. From the consumer's standpoint, the composite customer interruption cost is considered as the most valuable index to estimate the reliability of a power distribution system. This paper presents new algorithms that take into account the load by customer type and failure probability by distribution facilities while calculating the amount of unserved energy by customer type. Finally, evaluation results of unserved energy and system interruption cost based on composite customer interruption cost are shown in detail.

• KIEE International Transactions on Power Engineering
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• 제5A권3호
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• pp.286-292
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• 2005

As the power industry moves towards open competition, there has been a call for methodology to evaluate power system reliability by using composite interruption cost. This paper presents algorithms to evaluate the interruption cost of distribution power systems by taking into consideration the failure source and the composite customer interruption cost. From the consumer's standpoint, the composite customer interruption cost is considered as the most valuable index to estimate the reliability of a power distribution system. This paper presents new algorithms that consider the load by customer type and failure probability by distribution facilities while calculating the amount of unserved energy by customer type. Finally, evaluation results of unserved energy and system interruption cost based on composite customer interruption cost are shown in detail.