• Journal of Advanced Marine Engineering and Technology
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• 제32권7호
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• pp.1061-1067
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• 2008

Direct Torque Control[DTC] and Vector Control are the two schemes developed for high performance induction motor drives. DTC based induction motors are being increasingly used in various industrial applications. DTC offers fast torque response and better speed control with lesser hardware and processing costs as compared to vector controlled drives. However, conventional DTC suffers from high torque ripple, current harmonics and low performance during torque transients. In this paper a new Direct Torque Control[DTC] method of induction motor is presented. In comparison with the conventional DTC method, the PWM technique is applied to proposed control method. In this method, decoupling mechanism is not required and the torque, the flux magnitude are under control using PI controllers and generating the voltage command for inverter control. Therefore torque and speed ripple could be reduced in comparison with the conventional switching table DTC.

• 신재생에너지
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• 제7권2호
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• pp.18-27
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• 2011

Management flexibility to adapt its future actions in response to altered future market conditions can expand the value of an investment opportunity by improving its upside potential without the change in the downside losses. Module manufacturers in solar industry continuously have to decide how much and when its production capacity should be expanded with regards to the demand in the global markets. Either over- or under-investment can cause sunk and/or opportunity costs to the module manufacturers. Option of exercising the additional investments only on favorable opportunities can increase total value of the investment. This paper analyzes the case which shows that the expansion of production capacity with more expandibility can have more value than the rigid plan of capacity expansion. The expansion option value is equivalent to KRW 38.286 billion, thus switching the negative NPV of the initial investment opportunity into the positive value. High volatility and the high growth in the cashflows as the major business features of the renewable energy provide condition where real options can play the crucial role in increasing the investment value as well as in determining the size and timing of capacity expansion in the course of capital budgeting process.

• 산경연구논집
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• 제8권3호
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• pp.5-9
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• 2017

Purpose - While sustainability is based on the argument that the world's resources are finite and their demand will ultimately surpass supply, entrepreneurship on the other hand argues that there are inherent opportunities to address this through conserving, recycling, switching to more renewable resources and making effective use of available finite resources. Research design, data, and methodology - In response to the lack of scientific information on the outcomes of entrepreneurship in rural Nigeria, this paper surveys the benefits (social, economic and environmental) of women engagement in waste plastic bags recycling in Adamawa State of Nigeria. A descriptive research design was adopted and data was collected from 26 respondents with the use of a semi-structured questionnaire, which was analyzed using descriptive statistics and presented in frequency tables. Results - Results indicated that 21 women have gained employment, who would have remained unemployed; 80.8% of who make profits below 10000 Naira per month and collectively, they recycle 179.3kg of waste polythene bag per month. Conclusions - It was recommended that the women should be further their education; adequate records of costs and sales should be kept; and savings should be encouraged among them.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2006년도 제37회 하계학술대회 논문집 A
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• pp.420-421
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• 2006

The cost-effective reduction of greenhouse gas(GHG) emission to avert the most severe impacts of climate change remains one of the widely accepted priorities for global action. In order to facilitate cost-effective abatement strategies, the Kyoto Protocol introduced three mechanisms, or flexible instruments, the Emissions Trading(ET), the Joint Implementation(JI) and the Clean Development Mechanism(CDM). The CDM enables Annex I countries to the Kyoto Protocol to partially meet cost-effectively their emission reduction commitments by undertaking GHG mitigation Projects in developing countries, which do not have any GHG abatement obligations and where the emission reductions are cheaper. One of the major barriers hampering the wide spread implementation of CDM is the high transaction costs associated with the initial identification of promising CDM projects. This paper presents development of a pre-validation program of CDM. The developed program may provide a useful aid to potential investors and project developers as a supportive pre-evaluation tool, and may become an effective tool for the promotion of renewable energy and fuel switching projects.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2002년도 Proceedings of the International Welding/Joining Conference-Korea
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• pp.181-186
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• 2002

Laser welding application for car body manufacturing has many advantages in the stiffness and the lightness of vehicle, the productivity of assembly line, and the degree of freedom in design. This presentation will express the innovation of car body manufacturing including parameter optimization, process modeling, and system integration. In this application the investment for systems was cut down dramatically by real time switching over the laser path between two welding stations. Points of technical discussion are as follows: optimization of parameters such as laser power, robot speed and trajectory, compact and useful design of jig & fixture to assure welding quality for 3 sheet-layer zinc-coated steel, system integration between 4kW Nd:YAG laser device and the other systems, on-line real time welding quality monitoring system, perfect safety standards for high power laser, minimization of consumption costs such as arc lamp, protective glass for optic, etc. Laser welding has found a place on Hyundai's production plant in conjunction with the startup of mass production of new sports car, and this production system is the result of a collaboration of its engineers. Outer side sheets are joined to inner side sheets by 122 stitch welds totally. And the length is about 2.4meter.

• 한국주거학회논문집
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• 제20권3호
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• pp.97-104
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• 2009

Today, apartment is the most common residence type and various behavior occurs in living room space of apartments. Active usage of living room in modem life increases user's desire of wanting a better environment and leads to find various methods such as remodeling. At the point when considering moving or remodeling, this study focuses on the change of lighting color as it is one of the methods for initial stage with moderate price. As living room is easily influenced by lighting, providing active environment to support inhabitant's behavior through the use of various lighting sources will cut down unnecessary remodeling costs and may be the most simple method to actualize lighting environment for inhabitant's behavior. To give change with the least effort, change in artificial lighting environment was attempted with combinations of lighting color and switching on lights according to illuminating location. This study suggested the capability of changing lighting environment of previous living room area by exchanging lighting sources in lighting equipment in order to satisfy the required behaviors of inhabitant.

• 제어로봇시스템학회논문지
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• 제3권4호
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• pp.373-380
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• 1997

In order to implement the real-time operating systems for robot controller, this paper proposes a systematic method for implementing the real-time kernel under the DOS environment. So far, we designed the robot control software and its own operating system simultaneously. Though robot operating systems have simple structure, it allows the developer to have a surplus time and effort to implement complete robot systems. In addition to this, in most cases of this type, operating systems does not support multitasking function, thus, low level hardware interrupts are used for real-time execution. Subsequently, some kinds of real-time tasks are hard to implement under this environment. Nowadays, the operating systems for robot controller requires multitasking functions, intertask communication and task synchronization mechanism, and rigorous real-time responsiveness. Thus, we propose an effective and low costs real-time systems for robot controller satisfying the various real-time characteristics. The proposed real-time systems are verified through real implementation.

• 지식경영연구
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• 제14권3호
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• pp.37-54
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• 2013

Technology standards have gained importance as global market becomes more competitive. Since a technology acknowledged as a standard brings significant benefits to the developer firm, firms in the IT industry tend to pursue standardization for the technology, being it proprietary or open. However, the paths or strategic implications are seldom discussed in academia. Therefore, our study uses iPhone of Apple, one of the proprietary standards successes, to further understand corporate strategies over two standard choices. Our case study suggests that iPhone's entry timing was optimal for creating a new mobile environment. Design excellence and user-friendly interface increased networking effects and switching costs among consumers. Apple developed independent mobile operating system (iOS) through improvement on the existing operating system. During the process, Apple chose proprietary standard and, by installing the same UX on its sibling products such as iPod Touch or iPad, overcame the subsequent problems that might arise from the limited use of iOS. Based on the capability of concurrently developing both hardware and software, Apple connected operating system, machine, and contents, which deems to contribute to its proprietary standards success. We argue that this strategy should be considered for firms which plan proprietary standard strategy.

• 산업공학
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• 제22권4호
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• pp.368-375
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• 2009

This paper considers a two-stage supply system consisting of two make-to-stock facilities. The facility in the first stage produces a single type of component in anticipation of future demands from the market and the end item production while the facility in the second stage produces the end item in anticipation of future demands from the OEM customers. The facility in the first stage has the option of to accept or reject each incoming demand from the market. In this paper, we address the problem of how to control the exogenous component demand and how to manage the production of the end item and the component so as to maximize the system's profit subject to the system costs. In this paper, we present a heuristic policy that is the base-stock production policy combined with a linear switching curve for component demand control. Numerical study is implemented under different operating conditions of the system and it shows that the performance of the heuristic is very promising compared to that of the optimal policy for the Markov model.

• 기술혁신학회지
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• 제7권3호
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• pp.657-679
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• 2004

The purpose of this paper is to measure economic impact of marine environment conservation research development project. Benefit-Cost(B/C) analysis and Contingent Valuation Methods(CVM) are used to valuate the benefits from the research development projects. A period of three years for research development fund is considered as a part of the costs and adjusted to the net present value (NPV) of the 2002 ending period. The environmental charges for marine environment improvement are considered for the benefit measurement. The benefits are estimated by using monthly average willingness to pay, which is 2,289 Korean won. The contribution of the developing a management model for environmental pollution in the Gwangyang Bay is evaluated utilizing survey data and information. Based on the assessment by expert groups, the contribution of the model was 37.5％. The research results showed that B/C ratio is 20.61, NPV is 89,200 million Korean won, and social rate of return is 185.7％. When the level of contribution is over 1.83％ at the assessment of potential influence, it is recognized to be economically feasible. This research presents a quantitative framework for Research and Development projects for marine environment conservation, and it can be applied to decision making for the investment size of R&D projects.