Research Cage Wind Turbines’ Dynamic Characteristics Based on Time-varying Parameters

Gu Bo,Liu Yongqian,Xu Qiang,Kang Shun 보안공학연구지원센터 2014 International Journal of Control and Automation Vol.7 No.10

According to the characteristics of cage wind turbines’ dynamic characteristics which change following the wind speed changes, the dynamic mathematical models of cage wind turbines major subsystems have been established, including the aerodynamic subsystem model, drive train subsystem model and generator subsystem model. Then these nonlinear dynamic models with time-varying parameters have been integrated and linearized to obtain the whole linear time-varying parameters dynamic mathematical model. To take the 2MW cage wind turbines wind turbine as example, the proposed model is validated by the study on the dynamic characteristics of cage wind turbines with wind speed variation , and the results show that the proposed model could provide a theoretical support for optimal control of the cage wind turbines.

수치모델을 이용한 해상어류가두리양식장의 환경관리 방안

권정노,정래홍,강양순,안경호,이원찬,Kwon, Jung-No,Jung, Rae-Hong,Kang, Yang-Soon,An, Kyoung-Ho,Lee, Won-Chan 한국해양학회 2005 바다 Vol.10 No.4

해상어류가두리양식장의 양식 활동이 해양환경에 미치는 영향을 파악하기 위해 통영주변의 해상어류가두리양식장(Site A)에서 해수유동, 퇴적물, 저서동물 및 트랩 등의 현장조사와 수치모델-DEPOMOD를 이용하여 가두리양식장의 고형물 침강량 예측과 적정 고형물 침강량 산정으로 해상가두리양식장의 환경관리 방안을 제시하였다. 조사대상인 Site A 해상어류가두리양식장의 입식 어종은 common sea bass(Lafeolabrax japonicus), red seabream(Pagrus major), striped breakperch(Oplegnathus fasciatus) 등 4종이고, 입식량은 227,800미 (23.1MT) 였다. 가두리양식장의 입식밀도는 $43.0kg\;m^{-2}(6.1kg\;m^{-3})$ 이고, 사료투여 량은 $30.8g\;kg^{-1}day^{-1}(1.32kg\;m^{-2}day^{-1})$ 이였다. Site A 가두리양식장 중심의 저층 퇴적물의 ORP, AVS, COD, 탄소 및 질소 농도는 각각 -334.6mV, $0.43mg\;g^{-1}dry,\;17.75mg\;g^{-l}dry,\;10.19mg\;g^{-1}dry$ 및 $3.49mg\;g^{-1}dry$ 였다. 저서동물은 Capitella capitata가 $57.8\%$로 우점하였고, Infaunal Trophical Index(ITI)는 가두리 가장자리에서 20m 거리 내까지 20 이하로 나타났다. 트랩조사 결과 Site A의 고형물 침강량은 0m에서 $34,485g\;m^{-2}yr^{-1}$, 42m지점에서 $18,915g\;m^{-2}yr^{-1}$침강하는 것으로 나타났다 모델 예측 결과 Site A의 사료 미섭이율은 $40\%$, 연간 고형물 침강량은 63,401 kg으로 연간 사료 급이량의 $24.4\%$이고, 고형물 침강 면적은 $8,450m^2$으로 가두리 시설 면적의 16배인 것으로 예측되었다. ITI와 저서동물의 풍도를 통한 Site A의 지속 가능한 고형물 침강량은 $10,000g\;m^{-2}yr^{-1}$ 이하 인 것으로 예측되었다. 가두리양식장에서 고형물 침강량의 주 요인은 높은 미섭이율이고, 고형물 침강량을 최소화 하기 위해서는 사료 섭이효율을 높여주어야 한다. 모델에 따르면 미섭이율을 $40\%$에서 $10\%$로 줄이면 고형물 침강량이 1/2 수준으로 감소되는 것으로 예측되었고, 습사료, 생사료의 사용 대신에 배합사료(EP)를 사용할 경우 $57\%$정도 침강량이 감소하는 것으로 나타났다. 또한 가두리양식장의 허가면적에 대한 시설 면적비는 $5\%$미만이 적정한 것으로 판단된다. To study the effects of aquaculture activity of marine cage fish farms on marine environment, field researches including hydrography, sediment, benthos and trap experiment at the marine cage fish farms(Site A) around estuaries of Tongyeong city were carried out during June $26\~27$, 2003. A simulation using numerical model-DEPOMOD was conducted to predict the solid deposition from fish cage and to assess the probable solid deposition, and the efficiency of environmental management of marine cage fish farms was studied. The marine cage fish farms cultured mainly common sea bass (Lateolabrax japonicus), red seabream (Pagrus major), striped breakperch (Oplegnathus fasciatus) and black rockfish(Sebastes schlegeli), and total amount of cultured fish of the Site A were 23.1MT. The amount of husbandry fish by unit area(and volume) of the fish cage was $43.0kg\;m^{-2}(6.1kg\;m^{-3})$. The daily mean amounts of food fed by unit biomass and cage area were $30.8g\;kg^{-1}day^{-1},\;1.32kg\;m^{-2}day^{-1},$ respectively, at the Site A. The concentration of ORP of the sediment below the center at the Site A was -334.6 mV and the concentrations of AVS, COD, Carbon and Nitrogen were $0.43mg\;g^{-1}dry,\;17.75mg\;g^{-1}dry,\;10.19mg\;g^{-1}dry\;and\;3.49mg\;g^{-1}dry$, respectively. Capitella capitata was dominant benthic species which occupied $57.8\%$ of total species, and the Infaunal Trophical Index(ITI) was marked below 20 within 20 m distance from the edge of the Site A. The result of trap experiment, the solid deposition from the Site A was $34,485g\;m^{-2}yr^{-1}$ at 0 m from the center of the cage and $18,915g\;m^{-2}yr^{-1}$ at 42 m. From a model simulation, it was estimated that using a model simulation, the proportion of unfed food was $40\%$ at the Site A and the annual total amount of solid deposition was 63,401 accounting for $24.4\%$ of the annual total food fed at the Site A. The area solid deposition settled was estimated to be $8,450m^2$, which was about 16 times of the total area of fish cage at the Site A. And concerning ITI and abundance of benthos, the model predicted that sustainable solid flux at the Site A was below $10,000gm^{-2}yr^{-1}$. The percentage of food wasted was main element of solid deposition at the marine cage fish farms, and for minimizing solid deposition it is necessary to increase the efficiency of the food uptake. Based on the result of the model simulation, if the percentage of food wasted decreases to $10\%$ from the current $40\%$, then the solid deposition could decrease to a half. In addition, it was predicted that if farmers use EP pellets as food fed instead of MP and fish trash, solid deposition could decrease by $57\%$. Also this study proposes that the cage facility ratio of the licensed area be decreased to less than $5\%$ to minimize the sediment pollution.

Ghemawat-CAGE Model의 검증 및 코멘트

김학조,이준건,허지현 한국국제경영관리학회 2019 국제경영리뷰 Vol.23 No.2

The purpose of this study is to analyze the various dimensions (Cultural, Administrative, Geographic and Economic distance: CAGE framework) that affect trade volume suggested by Ghemawat (2001). To investigate the CAGE framework, we used SITC 2-digit bilateral trade data that is sensitive to distance in period from 1990 to 2015. More specifically, we used different distance variables representing each CAGE distance dimension to analyze the effects of distance. Additionally, we included exporter, importer and year fixed effect in the empirical analysis to control the multilateral resistance suggested by Anderson and Van Wincoop (2003). In the result, we confirm the results with fixed effects are more stable than OLS. The basic analysis results using all bilateral trade data show negative impact to each CAGE distance. The result indicates further distance of cultural, administrative, geographic, and economic, decreases the export volume. However, each industry analysis shows different results by industry type. Also, empirical result of each industry shows stronger effect of Gravity variables than CAGE related distance variables. Moreover, each industry analysis provides exports by industry were more or less affected by each distance. Although distance-sensitive industries were selected and analyzed in this study, the actual effect of distance shows differently depending on industry and type of distance. Therefore, in the future studies, the logic of Ghemawat (2001) need to be studied more carefully, and the impact of each distance on non-sensitive industries should be considered by using more industries in the analysis. 본 연구에서는 Ghemawat(2001)의 제안을 토대로 하여 무역에 영향을 미치는 여러 가지 차원(문화적, 행정적, 지리, 경제적 거리)들을 중심으로 한 CAGE 모형을 분석하고자 하였다. 따라서 본 연구에서는 SITC 2-digit 데이터를 사용하여 1990년에서 2015년 간 수출국과 수출 상대국의 무역 민감도를 실증 분석하였다. 또한 본 연구에서는 각 거리가 미치는 영향을 분석하기 위하여 각 거리를 나타내는 상이한 변수들을 분석에 사용하였으며, 수출국, 수출 상대국 및 연도 고정 효과를 분석에 포함하여 Anderson and Van Wincoop(2003)이 지적한 다자간 저항에 대처하고자 하였다. 분석 결과, OLS 결과보다는 고정 효과를 분석에 포함하였을 경우 결과의 안정성이 증가하였다. 이후 거리 별 전체 산업 데이터를 이용한 분석에서는 CAGE 모형에 나타난 거리 변수들이 산업무역에 모두 부정적인 영향을 미치는 것으로 나타났다. 반면, 산업들을 하나씩 검증하였을 경우 산업에 따라 상이한 결과를 보이거나 Ghemawat의 거리 변수보다는 다른 중력 모형 변수 및 무역에 영향을 주는 변수들이 더 큰 영향을 주는 결과가 나타났다. 따라서 향후 연구에서는 Ghemawat(2001)의 제안을 좀 더 면밀히 연구할 필요가 있으며, 민감하지 않은 산업을 포함하여 보다 많은 산업을 분석에 활용하여 거리가 미치는 영향을 분석해야 할 것이다.

어류가두리양식장 수용력 산정 및 환경관리를 위한 생태계모델 개발 현황

정우성(Woo Sung Jung),윤상필(Sang Pil Yoon),이원찬(Won Chan Lee),김동명(Dong Myung Kim),이대인(Dae In Lee) 한국해양환경·에너지학회 2021 한국해양환경·에너지학회 학술대회논문집 Vol.2021 No.5

해상 어류가두리양식장에서 사료투입에 따른 퇴적물 오염 등의 환경문제에 대한 대책마련과 어류의 적정 입식밀도와 관련된 생태학적 수용력을 고려하기 위해 새로운 모델을 개발하고 있다. 현재 국내에서 어류성장 예측과 어장환경 변화를 시·공간적으로 해석하고 관리방안을 마련한 연구는 전무하다. 본 모델은 어류성장-수질-퇴적물 모델이 상호 결합되어 있다. 어류성장모델에서는 가두리에서 양식되는 어류의 연령별 성장과 어장기인 오염물질의 발생량(미섭이 사료와 어류의 분변)이 계산된다. 수질 및 퇴적물 모델은 각종 환경인자 및 오염물질의 영향범위 및 정도를 예측할 수 있다. 선행연구와 비교하여 모델의 수식 및 코드오류 수정, 수층과 퇴적층 사이의 물질수지 보완, 어류의 입식밀도에 따른 사망 및 성장제한에 대한 알고리즘이 보강되었다. 그 결과, 환경인자와 어류의 연령별 성장 및 생산량이 잘 재현되었다. 향후, 생태계모델의 정밀 검증 과정 등을 거친 후 양식 및 환경조건 변화에 따른 어류성장 및 수용력을 예측할 예정이다. A new ecosystem model is being developed to prepare countermeasures for environmental problems such as sediment contamination due to feed input in marine fish cage farms and to consider ecological capacity related to the proper density of fish. Currently, there are no studies in Korea that have interpreted the temporal and spatial changes of fish growth predictions and fishery environment and devised a management plan. This model is constructed by combining the fish growth-water quality-sediment model. In the fish growth model, the age-specific growth of fish farmed in cages and the amount of pollutant (uneaten food and feces) produced during the fishing season are calculated. Water quality and sediment model can predict the range and degree of the impact of pollutants, and various environmental variables. Compared with previous this study, model formula and code error correction, supplementing mass balance between water and sediment layers, the algorithm for mortality and growth limitation according to the stocking density of fish was reinforced. In the result, environmental variables and fish growth and production by age were well reproduced. In the future, we plan to predict fish growth and capacity according to changes in aquaculture and environmental conditions after going through the process of model verification accurately.

모형실험과 시뮬레이션을 통한 활어 이송용 예인 가두리의수직 및 수평 전개력 추정

박수봉 ( Subong Park ),이춘우 ( Chun Woo Lee ) 한국어업기술학회 2014 수산해양기술연구 Vol.50 No.2

Nowadays, consumption of fisheries products is increasing. There are several factors, one of which is a quantitative development through aquaculture. Another factor is an increase qualitative consumption of fish which require that fish be supplied alive. This requires a lot of technical effort to transport the live fish that have low survival rate(c.f. tuna and mackerel) in coastal waters and in the open sea. To develop a towing cage for transporting the live fish, model test in a circulate water channel and simulation by computer tool were carried out. In order to spread vertically, floats were attached at the upper part of the cage, and iron chains attached at the lower part of the cage. For horizontal spreading, kites were attached on the cage. The tension and spreading performance of the cage were measured. The result shows that the tension and reduction ratio of inside volume of the cage were tended to increase with increased towing speeds. The suitable operation condition in towing cage was 1.0 m/s towing speeds with vertical spreading force 8.7 kN, horizontal spreading force 5.6 kN; in this case the reduction ratio of inside volume of the cage was estimated as 25%.

동합금 가두리망 방어양식의 경제성과 수익구조

황진욱 ( Jin-wook Hwang ) 한국수산경영학회 2021 수산경영론집 Vol.52 No.2

This study is aimed to analyze the economic feasibility of yellowtail culture using the copper alloy net cage in Gyeongsangbuk-do. First of all, in order to evaluate the copper alloy net cage on yellowtail culture, I review the trend on the yellowtail culture industry and research the concept of copper alloy net cage. The copper-alloy net cage is now recognized as an advantages of its system stability, recycling, antibiosis and food safety. The results were summarized as follows: first, there was significant meaning of the profit model of yellowtail culture by the price difference. Second, I analyzed in the economic feasibility of yellowtail culture using the copper alloy net cage, internal rate of return (IRR) was 51.58%, a benefit-cost ratio was shown to be 2.27 and net present value (NPV) was 1,087,337 thousand won, which indicates the economic feasibility of yellowtail culture using the copper alloy net cage is profitable. Finally, in order to improve the economic valuation, it is necessary to focus more on the developing of technology and cost reduction strategy on the copper alloy net cage.

Numerical simulation of fish nets in currents using a Morison force model

Cifuentes, Cristian,Kim, M.H. Techno-Press 2017 Ocean systems engineering Vol.7 No.2

For complex flexible structures such as nets, the determination of drag forces and its deformation is a challenging task. The accurate prediction of loads on cages is one of the key steps in designing fish farm facilities. The basic physics with a simple cage, can be addressed by the use of experimental studies. However, to design more complex cage system for various environmental conditions, a reliable numerical simulation tool is essential. In this work, the current load on a cage is calculated using a Morison-force model applied at instantaneous positions of equivalent-net modeling. Variations of solidity ratio ($S_n$) of the net and current speed are considered. An equivalent array of cylinders is built to represent the physical netting. Based on the systematic comparisons between the published experimental data for Raschel nets and the current numerical simulations, carried out using the commercial software OrcaFlex, a new formulation for $C_d$ values, used in the equivalent-net model, is presented. The similar approach can also be applied to other netting materials following the same procedure. In case of high solidity ratio and current speed, the hybrid model defines $C_d$ as a function of Re (Reynolds number) and $S_n$ to better represent the corresponding weak diffraction effects. Otherwise, the conventional $C_d$ values depending only on Re can be used with including shielding effects for downstream elements. This new methodology significantly improves the agreement between numerical and experimental data.

아랍난민의 현지사회적응을 위한 정책선택 요인의 상대적 중요도 분석: CAGEES모형에 대한 AHP평가

김중관 숙명여자대학교 아시아여성연구원 2019 다문화사회연구 Vol.12 No.3

The purpose of this study is to analyze the relative importance of the assessment factors for the social integration and cultural assimilation of local countries against Arab immigrant refugees. This paper adapts the AHP method to the CAGEES model through a pilot survey to identify the rational weights and priorities of the measurement indicators and metrics. This study conducts a weighted survey with experts from major European countries such as Germany, France, and Italy. The main analysis focuses on Arab refugee acceptance policies and evaluates the differences between countries for a proposal of policy implications. In the analysis, AHP techniques were adapted with the pairwise comparison of the consistency ratio of all the metrics. Additionally, the consistency of all the items was maintained as less than 0.1. The relative importance of the measurement indicators revealed the economic differences between the home and local countries of Arab migrant refugees. The social support from the local community for Arab migrant refugees can be of great importance for cultural assimilation in the receiving country. Furthermore, the role of the local government bureau is quite important for social integration. 이 연구의 목적은 아랍 난민의 현지 수용국에서의 사회적응에 대한 평가요인의 상대적 중요도를 분석하는 것이다. 이의 과정으로써, 사전조사를 통하여 CAGEES모형을 구축하고, AHP기법을 채택하여 측정지표 및 측정항목에 대한 합리적인 가중치와 우선순위를 파악하였다. 연구 내용에서는 난민 수용정책 관련 선행연구 분석을 실시하였으며, 이에 따른 최적한 사회적응을 주제로 유럽의 주요 아랍 이주난민 수용국가인 독일, 프랑스, 이탈리아의 전문가집단을 대상으로 평가지표에 대한 가중치 조사를 진행하여 그 차이를 분석하고 정책적 시사점을 제시하였다. AHP기법을 활용한 쌍대비교에 의한 분석결과에서는 모든 측정지표 및 항목의 일관성 비율은 0.1이하로 일관성이 높게 유지되었다. 측정지표의 상대적 중요도에서는 아랍 이주난민의 현지국 사회통합에 있어서 난민의 모국과 현지국의 경제적 차이 해소를 위한 정부정책이 주요 요인으로 확인되었으며, 아랍 난민에 대한 현지국사회의 지원은 사회적응을 통한 문화동화에 매우 중요한 정책적 선택요인으로 평가되었다.

Analytical consideration of the radial clearance to reduce cage slip of the turbo engine roller bearing

김선제 대한기계학회 2021 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.35 No.7

Roller bearings of aircraft turbo engines are operated under high-speed conditions of over 2 million DN. If contact force between rollers and the raceway is insufficient, then relative slip between the roller and raceways occurs and speed of the cage decreases. This condition may induce skid damage in the raceway. Large operating radial clearance can cause skid damage, but their analytical correlations have rarely been studied. In this study, cage slip ratio was quantified according to clearance changes in various operating conditions and geometric parameters, and causes of cage slip were analyzed using the simplified dynamic model. The design methodology will be proposed to select the proper operating clearance in consideration of cage slip and fatigue life.

Dissolved oxygen analysis of an abalone aquaculture cage system using computational fluid dynamics

( Tae Ho Kim ) 한국수산해양기술학회 2015 수산해양기술연구 Vol.51 No.2

Abalone (Haliotis discus hannai) is a shellfish that feeds on kelp and, as a product, it can often achieve a high market value.However, the dissolved oxygen (DO) levels in coastal waters in Korea have been negatively impacted by pollution from many anthropogenic sources. Herein, a computational fluid dynamics (CFD) software package was used to analyze the distribution of the DO concentration within an abalone containment structure. A finite volume approach was used to solve the Reynolds-averaged Navier.Stokes equations combined with a k.ε turbulence model to describe the flow. The distribution of DO was determined within the control volume domain, and the transport equations of the pollutants were interpreted using a CFD model. The CFD analysis revealed that more than 60% and 30% of the relative oxygen concentration in one and two containers, respectively, was maintained when the flow acts along the six sheets of polyethylene plates. Therefore, it is clear that the abalone plate shelters should be placed parallel to the flow.