Fishways, particularly installed at the estuary, have a purpose to encourage fluent migration for migratory fishes, as well as amphidromous and even freshwater species. Not choosing the laborious traditional method of using traps, we assessed the efficiency of the two fishways installed at the west and east barrage of the Nakdong River estuarine barrage respectively, by analyzing the videos recorded through automatic monitoring system. We randomly selected 30 videos monthly at each fishways and identified what kind of fishes were using the fishways and categorised their behaviour such as size, time and whether they passed the monitoring system or not. As a result, a total 8 families 14 species were recorded by monitoring system, with the most dominance of Erythroculter erythropterus (Relative Abundance: 59.5%), followed by Micropterus salmoides (R.A: 19.9%) and Mugil cephalus (R.A: 9.9%). The monitoring system can capture passing fishes during night but the number of appearances of fish species at each hour of a day indicated significant diurnal activities (p<0.05). When fishes pass the monitoring system, approximately 70% of them passed through the monitoring device, while 17% of them showed fallback movement. Our finding indicates that species-specific characteristics of each fish are well represented through video monitoring method. In order to maximise advantages of using video monitoring, it is necessary to consider the installation point properly so that the monitoring system does not interfere with the movement of fish. Also, the utilisation of AI technology in the future is also necessary.
This study investigated fish communities at a total of 11 sites across four rivers in the region in 2005 and 2015. Sampling was conducted twice at each site using cast nets (10×10 mm mesh size) and scoop nets (4×4 mm and 5×5 mm mesh sizes). Basic water quality measurements and river naturalness assessments were also performed. Based on fish community survey results, a Self-Organizing Map (SOM) analysis was employed to evaluate the impact of urbanization on fish communities in the study area. The results revealed a tendency for decreased electrical conductivity in water quality and improved scores in river naturalness assessments. Compared to the environmental conditions in 2005, the overall naturalness of the study area appeared to have increased by 2015. A total of 721 individual fish representing 32 species from 12 families were collected. The dominant species was largemouth bass (Micropterus salmoides, 141 individuals, 19.6%), and the subdominant species was dark chub (Zacco temmincki, 132 individuals, 18.3%). The SOM analysis demonstrated a clear distinction in fish community distribution patterns between the survey years. Brackish water species such as Plecoglossus altivelis, Lateolabrax japonicus, and Mugil cephalus, along with introduced species like Erythroculter erythropterus, exhibited higher frequencies in 2015. Although the occurrence of exotic species tended to decrease compared to 2005, the presence of bluegill (Lepomis macrochirus) showed an increase in 2015. These findings suggest an increase in species favoring deeper waters and lacustrine environments, with notable growth in populations of introduced and exotic species.
본 연구에서는 Monopile 방식 풍력발전기 강구조물의 부식을 방지하기 위하여 S355 steel의 표면 거칠기에 따른 용사 코팅 상태에 관한 연구를 수행했다. 일차적으로는 시편별 서로 다른 표면거칠기를 부여하기 위해 밀링머신에 페이스 커터를 결합하여 시편별로 다른 조건의 Ra값 기준 표면거칠기를 부여했다. 실험 조건으로는 시편 가공 시 4가지의 회전속도(60, 400, 1200, 2000 rpm), feed rate 150(mm/min) 조건을 선정했다. 2차로는 와이어 용융 방식의 아크 용사 코팅을 실시했다. 코팅 조건으로는 분사 거리 200mm, 전압 24V, 전류 120A, 분사 압력 5bar, 와이어 삽입 속도 30g/mm, 와이어 직경 2mm이다. 용사 코팅 후 FE-SEM으로 표면을 관찰한 결과 모든 시편의 S355 면과 코팅층(아연-알루미늄) 사이에 유격이 발생하지 않고 성공적으로 안착이 되었음을 확인할 수 있었다.
Companies are paying attention to project governance to realize their goal strategies, project success, and project value in a rapid and complex environment due to the development of information technology. This study aims to explore project governance and factors from literature review and practice guides related to project governance and empirically analyze the impact of project governance factors on IT project objective performance. The survey was conducted on project managers, project team members, and project management members with experience in carrying out business IT projects within two years at companies in various industries in Korea. The main conclusion is as follows. Among the project governance factors, disclosure and reporting that uses and reports using appropriate and reliable information about projects related to decision-making activities positively impact the achievement of IT project objectives: business success and stakeholder satisfaction. Among the project governance factors, project sponsorship, a role that effectively connects management and projects, and a project management framework that provides tools, procedures, resources, and techniques for projects positively impact IT project objective performance. This study is of academic and practical significance in that it identifies the definition and factors of project governance through companies in various industries in Korea and the positive impact of project governance factors on IT project objective performance.
In this research, the a novel finishing machine was used for hight-precision surface of spherical ball products that have been widely used for on/off valve for hydrogen energy flowing system and in medical field such as artificial hip joint component. The spherical balls products are the workpiece that made by Co-Cr-Mo alloys with 32-mm in diameter and Sa≈ 0.30μm in surface roughness. Their surface roughness was successfully improved via the magnetic abrasive tools that controlled the magnetic field of permanent magnets. The critical input conditions were selected as rotational speed: 800rpm, gap: 3mm, tool grain size: 1-μm finishing time: 0, 3, 6, 9, 12, and 15min. The results of this research showed that under the given finishing conditions, the high surface quality in the terms of surface precision of spherical ball products are successfully achieved, in which the surface roughness is reduced from 0.30-μm to 0.04-μm within the short finishing time at 12min. Therefore, it can be concluded that a novel finishing machine is feasible to be used for improving the surface roughness of spherical ball products, resulted in high surface precision of materials.
큰앵초의 특성조사는 소백산(연화봉), 주흘산(주봉), 덕유산(삿갓봉), 가야산(두리봉), 지리산(노고단) 등 5개 지역을 대상으로 2018년 4월부터 2020년 11월까지 실시하였다. 큰앵초의 높이는 23.1∼31.3㎝이고, 평균 26.8㎝이며, 잎의 수는 2.9∼4.7개이고, 평균 3.8개이다. 엽신의 길이는 6.2∼7.6㎝이고, 평균 7.1㎝이며, 엽신의 너비는 7.8∼9.3㎝이고, 평균 8.7㎝이며, 엽병의 길이는 10.9∼16.5㎝이고, 평균 13.5㎝이다. 잎의 길이와 폭의 비율은 0.79∼0.82로 광타원형이다. 엽연의 형태는 결각이 둔하고 불규칙적인 것과 예리하고 깊으며 규칙적인 것으로 나타났다. 뿌리의 길이는 5.9∼10.9㎝이고 평균 7.2㎝이며, 뿌리 수는 27.6∼48.2개이고, 평균 37.7개이다. 개화기는 5월말∼6월 초이며, 꽃의 수는 5.4∼10.1개이고, 평균 7.2개이다. 화관너비는 21.7∼26.2㎜이고, 평균 23.4㎜이다. 열매의 길이는 1.3㎜∼2㎜이고, 평균 1.8㎜이며, 종자의 수는 10개∼18.2개이고, 평균 14.2개이다. 조사지의 상층우점종은 신갈나무이고, 중층은 당단풍나무, 노린재나무, 함박꽃나무 등이며, 하층은 철쭉, 진달래, 미역줄나무, 국수나무 등으로 나타났고, 종다양도는 0.7534∼0.9950으로 나타났다. 조사지의 토양 pH는 4.1∼4.6이고 염기포화도는 3.18%∼9.09%로 나타났다. EC는 0.18∼0.7dSm-1으로 나타났고, NaCl은 0.003∼0.006%로 나타났다.
Magnetic abrasive finishing process is one of the advanced finishing technique, which is commonly used to improve the surface accuracy and dimensional of many products in various application such as for medical implant, automotive, electrical, and IT, etc. In this study, the MAF process using rotating magnetic field with flexible processing force is used to smooth the surface of STS 316L stents wire under the optimal conditions such as rotating speed: 150, 350, 600rpm; diamond grain size: 1, 3, 6-μm, and processing time: 20, 40, 60, 80min. The results showed that under the processing conditions, quality enhancement in surface accuracy of STS 316L stent wire is achieved, in which the surface roughness is reduced from 0.22 to 0.06-μm.
In this study, the performance was checked and the optimal conditions were found by machining the inner surface of a round pipe using the magnetic abrasive finishing method. In this experiment, an AL 6063 pipe was used as a sample. To check the performance of magnetic abrasive finising, the machining effect of different abrasive particle mixing ratio, rotation speed, and magnetic pole arrangement was analyzed through surface roughness (Ra) and weight removal measurement. The optimum mixing ratio was 3:1 of electrolytic iron to magnetic abrasive particles, the rotational speed was 1600rpm, and the best surface roughness was obtained in the N-S-N arrangement of magnetic poles.
본 연구는 유한요소 해석모델을 이용해 아치 형상을 갖는 석션 상판의 거동을 분석하였다. 평판형 및 아치형 상판의 기본적인 구조 성능에 대해 비교함으로써 아치형 상판의 이점을 설명하였다. 또한 아치형 상판의 기하 및 보강재 배치 변화에 따른 거동 변화를 비교하여 각 인자가 상판의 응력 및 변형에 미치는 영향을 조사하였다. 추가로 아치형 상판 가장자리의 경계조건 영향을 수치적으로 분석함으로써, 아치형 상판의 보강재 배치와 가물막이 벽체와의 상호거동 영향을 규명하고 이를 통해 보강형 아치형 상판의 구조설계의 기본 개념을 도출하였다. 평판형 상판과 달리 환형 보강재가 아치형 상판의 구조 거동을 확연히 개선시킬 수 있음을 확인하였으며, 방사 보강재의 역할은 상판 가장자리의 구속상태에 의존적이었다.
본 논문은 모노파일 풍력 지지구조물에 대한 공진 안전성 평가에서 여러 말뚝-구조물 상호작용(PSI) 모델을 사용하여 고유진동수를 비교하였다. PSI 재현을 위한 유한요소모델은 기저 스프링 모델, 분산 스프링 모델, 3차원 고체-쉘 모델을 사용하였다. PSI 모델이 고유주파수에 미치는 영향을 분석하기 위해 기저 스프링과 분산 스프링 모델 적용을 위한 강성행렬 산정법과 Winkler 보 모델을 각각 논문에 나타내고 이들 모델로부터 도출된 서로 다른 기하 및 지반조건을 갖는 모노파일의 고유진동수를 조사하였다. 해석 결과는 또한 3차원 고체-쉘 모델의 고유진동수와도 비교되었다. 해석결과는 소구경 모노파일이 견고한 지반 및 암반에 관입된 경우 각 해석모델로부터 얻어진 고유진동수의 차이가 거의 없음을 보여준다. 반면 연약 지반에 설치된 대구경 모노파일에 대해 분산 스프링 모델은 고유진동수를 과대평가할 수 있다. 따라서 고유진동수 평가 시 구조물 규모와 지반 조건을 고려해 적합한 PSI모델이 적용되어야 한다.