• 수산경영론집
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• 제29권1호
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• pp.121-137
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• 1998

This study was conducted to examine the economic evaluation of the newly developed fish meal analog (BAIFA-M) in Korean rockfish feed. A raw fish feed (MP) and two commercially formulated diets (EP) were employed to compare weight gain (WG), feed conversion ratio (FCR) and survival rate (SR) from the sea cage culture system. By using the economic model in the practical sea cage culture system, feed cost, production cost and gross profit per kg production, rate of profit to gross revenue (RPGR), and internal rate of return (IRR) were calculated based upon the results of the experiment and the information of the private aquaculture farm (Young Chang) in Tong young, Korean. IRR criteria is one of the popular economic feasibility analysis methods applicable far aquaculture industry. This is an economic evaluation method to compare the given interest rate or the discount rate with IRR which can be calculated by the difference between the present value of the benefit stream and of the cost stream. The benefits of using EP on WG, FCR, SR, and production cost will be emphasized in this study. Fish averaging 20$\pm$3.6g (Mean$\pm$SD) were randomly distributed in each small cage (6m$\times$6m) as groups of 2,000 fish. By using 3 large size cages (12m$\times$12m), 12 small cages were constructed, and only 9 small cages were employed for three replicates of each diet treatment. To compare with MP diet, two sinking EP diets were designed by our laboratory and produced by the local feed company who wanted to promote these EP diets for the mass cage culture of Korean rockfish in the future. Two EP diets contain white fish meal and/or BAIFA-M as the main animal protein sources : WFM diet, maximum 43% of white fish meal : BAIEA- M diet, 30% of white fish meal nab replaced by BAIFA- M from WFM diet. Results are summarized in Table 1. Fish fed MP diet showed significantly lower SR than does fish fed two EP diets(P<0.05). However, there Were no significant difference on FCR among fish fed three practical diets. Table 1. Average feed conversion ratio (FCR), accumulative average survival rate (SR) and economic evaluation data far three practical diets. As we expected, BAIFA-M diet is more economical than WFM diet as well as MP diet. Feed cost and production cost per kg production from BAIEA - M diet were lower than those from WFM and MP diets. Moreover, gross profit per Kg production, RPGR and IRR from BAIFA- M diet were higher than those from WFM and MP diets. This economic evaluation study clearly indicated that MP diet should be replaced by the commerical formulated EP diets as soon as possible in the near future because MP diet is not economical in the practical sea cage culture system.

• Journal of Biosystems Engineering
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• 제32권3호
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• pp.173-178
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• 2007

This research was conducted to develop and analyze a wireless monitoring system for judging if sick or dead layers (SDL) exist in multi-tier layers battery (MLB) by machine vision, and to evaluate the performance between a wired monitoring system and it. This study used the AP (Access Point), the RS-285 to RS-232 converter, RS-232 to Ethernet converter, PICBASIC board and upgraded lump image processing method to change wired monitoring system into wireless monitoring system. The system was tested at a pilot farm and farm layer house. Results showed that monitoring judgement success rate at a pilot farm on normal cage (without SDL) was 82.3% and that on abnormal cage (with SDL) was 87.5%, respectively. And communication performance test results showed at farm layer house was $700{\sim}900$ kbps while equipments operated. There were dropped slightly than performance of wired monitoring system, however, the quantity was too small to make a significant difference of performance of the controling system developed for wireless communication.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2003년도 추계학술대회 논문집 전기기기 및 에너지변환시스템부문
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• pp.15-17
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• 2003

In this paper, direct thrust control(DTC) scheme is applied to a linear induction motor(LIM) with cage-type secondary. The line voltages and phase currents are detected and a thrust correction coefficient considering the end effect of the LIM is introduced in order to Improve the accuracy of thrust estimation in the DTC implementation. Experimental results for thrust and flux responses are presented.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2003년도 춘계학술대회 논문집 전기기기 및 에너지변환시스템부문
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• pp.338-340
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• 2003

This paper proposes a stand-alone adjustable speed wind Power generation system using a cage-type induction generator. Indirect vector control is used, where the q-axis current controls the generator speed and the d-axis current controls the excitation level. The generator speed is adjusted according to the wind speed so as to produce the maximum output power. The generated power is charged in the battery bank through ac/dc PWM converter. The proposed scheme has been verified by the experimental results.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제54권10호
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• pp.497-504
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• 2005

For maximum output power, wind turbines are usually controlled at the speed which is determined by the optimal tip-speed ratio. This method requires information of wind speed and the power conversion coefficient which is varied by the pitch angle control. In this paper, a new maximum output power control algorithm using fuzzy logic control is proposed, which doesn't need this information. Instead, fuzzy controllers use information of the generator speed and the output power. By fuzzy rules, the fuzzy controller produces a new generator reference speed which gives the maximum output power of the generator for variable wind speeds. The proposed algorithm has been implemented for the 3[kW] cage-type induction generator system at laboratory, of which results verified the effectiveness of the algorithm.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2003년도 추계학술대회 논문집
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• pp.73-76
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• 2003

This paper proposes a maximum output power control of grid-connected wind power generation system using cage-type induction generators. For generator control, indirect vector control is used, where d-axis current controls the excitation level and q-axis current controls the generator speed. The generated power flows into the utility through the grid-side converter, by which the do link voltage is controlled to be constant and the ac current is controlled in sinusoid and. The generator speed is adjusted according to wind speed for extracting maximum power generation. Experimental results are shown to verify the validity of the proposed scheme.

• 수산해양기술연구
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• 제51권2호
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• pp.155-162
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• 2015

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 $k-{\varepsilon}$ 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.

• Composites Research
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• 제14권3호
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• pp.77-89
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• 2001

초고속 일체형 주축의 공진주파수가 일체형 주축 시스템의 모터 회전자의 질량과 주축의 굽힘 강성에 의존하기 때문에 초고속 주축 시스템의 동적 특성을 향상시키기 위해 주축과 회전자를 각각 고분자 기지 섬유강화 복합재료와 자성분말이 함침된 에폭시 수지를 이용하여 설계하였다. 설계된 복합재료 회전자의 자기 특성을 향상시키기 위해 내부에 강철 코어를 삽입하였으며, 강철 코어와 전도체 봉의 기하학적 형상의 변화가 전동기의 성능에 미치는 효과를 파악하기 위해 자기 해석을 수행하였다. 유한요소해석을 통해 복합재료 회전자의 최적의 기하학적 조건을 제안하였다. 또한 복합 재료 회전자 재료의 열특성을 파악하기 위해 TMA, DMA및 VSM을 이용한 기계적, 전자기적 물성측정을 수행하여 복합재료 회전자의 최적 설계에 적용하였다.

• 전력전자학회논문지
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• 제9권4호
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• pp.397-404
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• 2004

본 논문에서는 농형유도발전기를 이용한 계통연계형 풍력발전시스템의 가변속제어 기법이 제안된다. 농형유도발 전기는 간접벡터제어 방식으로 동작되는데 d-축 전류에 의해 여자가 제어되고 q-축 전류에 토크가 제어된다. 이 토크제어에 의해 발전기는 풍속의 변화에 대해서 항상 최대전력을 발생하도록 가변속 제어된다. 발전된 전력은 back-to-back PWM 컨버터에 의해 계통으로 공급된다. 계통측 컨버터는 q-축 전류 제어에 의해 직류링크 전압을 제어하고 d-축 전류 제어에 의해 계통측 역률을 제어할 수 있다. 제안된 기법은 M-G세트로 구성된 터빈시뮬레이터를 이용하여 실험적으로 검증된다.

• Tribology and Lubricants
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• 제40권1호
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• pp.1-7
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• 2024

Ball bearings are a major component of mechanical parts for transmitting rotation. Compared to tapered roller bearings, ball bearings offer less rolling resistance, which leads to reduced heat generation during operation. Because of these characteristics, ball bearings are widely used in electric vehicles and machine tools. The design of ball bearing cages has recently emerged as a major issue in ball bearing design. Cage design requires pre-verification of performance using theoretical or experimental formula or computational fluid dynamics (CFD). However, CFD analysis is time-consuming, making it difficult to apply in case studies for design decisions and is mainly used in performance prediction following design confirmation. To use CFD in the early stages of design, main-taining analytical accuracy while reducing the time required for analysis are necessary. Accordingly, this study proposes a laminar steady-state segment CFD technique to solve the problem of long CFD analytical times and to enable the use of CFD analysis in the early stages of design. To verify the reliability of the CFD analysis, a bearing drag torque test is performed, and the results are compared with the analytical results. The proposed laminar steady-state segment CFD technique is expected to be useful for case studies in bearing design, including cage design.