• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2001년도 The 6th International Symposium of East Asian Resources Recycling Technology
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• pp.404-408
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• 2001

This paper focuses on the pilot-scale investigation of direct recycling of electric arc furnace (EAF) stainless steelmaking dust. The direct recycling of EAF dust is to make pellets with the mixture of the dust and the reducing agent carbon, then introduce the pellets to the EAF. The valuable metals in the dust are reduced and get into the steel as the alloying elements. Experiments simulating direct recycling in an EAF were performed using an induction furnace. But it seems difficult to reduce all metal oxides in the dust so that some metal reducing agents added in the late stage of reduction process. The valuable metals in the dust were reduced partly by carbon and partly by metal reducing agent for the economical concern. The recovery of iron, chromium and nickel from the flue dust and the amount of metal oxides in the slag were measured. The results showed that the direct recycling of EAF stainless steelmaking dust is practicable. It wes also found that direct recycling of flue EAF stainless steelmaking dusts does not affect the chemistry and quality of stainless steel produced in the EAF. It is benefit not only for the environmental protection but also for the recovery of valuable metal resources in this way.

• Journal of Electrical Engineering and Technology
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• 제12권3호
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• pp.1177-1186
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• 2017

This paper presents a torque ripple reduction method of direct torque control (DTC) using fuzzy controller with optimal selection strategy of voltage vectors in a five-phase induction motor. The conventional DTC method has some drawbacks. First, switching frequency changes according to the hysteresis bands and motor's speed. Second, the torque ripple is rapidly increased in long control period. In order to solve these problems, some/most papers have proposed torque ripple reduction methods by using the optimal duty ratio of the non-zero voltage vector. However, these methods are complicated in accordance with the parameter. If this drawback is eliminated, the torque ripple can be reduced compared with conventional method. In addition, the DTC can be simply controlled without the use of the parameter. Therefore, the proposed algorithm is changing the voltage vector insertion time by using the designed fuzzy controller. Also, the optimized voltage vector selection method is used in accordance with the torque error. Simulation and experimental results show effectiveness of the proposed control algorithm.

• Journal of Information Technology Applications and Management
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• 제24권1호
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• pp.93-110
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• 2017

This study aims at classifying and analyzing the business models of reverse overseas direct purchasing through online shopping-malls. After analyzing the current status of the reverse overseas direct purchasing online markets, this study identifies relevant critical business factors and synthesizes prior studies to construct and analyse the business models. This study proposes that the business models can be classified into five types according to the operation modes and three types according to the delivery methods. So theoretically 15 business models can be identified. For each business model this study analyzes the characteristics and the pros & cons. It also suggests deployment strategies for companies by considering cost reduction, brand establishment, customer management, customer aquisition, and easiness from the business perspective. From the customers perspective, cost reduction, reliability, royalty, ease to purchase, and accessibility can be considered according to the types of operation mode. The main contribution of this study is to provide the basic classifications and structures of reverse overseas direct purchasing business models systematically. As the result, our study evaluates the business models that which one is better than others in a situation in terms of company and customer. Lastly, we talk about limits and future prospects of the study.

• International Journal of Contents
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• 제8권2호
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• pp.1-6
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• 2012

Recently, content-based music information retrieval (MIR) systems for mobile devices have attracted great interest. However, music retrieval systems are greatly affected by background noise when music is recorded in noisy environments. Therefore, we evaluated various pre-processing methods using the Philips method to determine the one that performs most robust music retrieval in such environments. We found that dynamic noise reduction (DNR) is the best pre-processing method for a music retrieval system in noisy environments.

• 한국통신학회논문지
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• 제28권2B호
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• pp.129-137
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• 2003

MPEG(Motion Picture Expert Group)과 같은 멀티미디어 스트림은 연속적 재생으로 인해 데이터의 지속적인 디스크 검색을 요구한다. 따라서, 커널의 효율적인 지원이 필요한데, 유닉스 계열의 리눅스 버퍼 캐시 시스템은 비정기적이고 비실시간 데이터인 텍스트 데이터용으로 설계되었다. 대용량의 연속 미디어의 경우 커널 주소공간에서 사용자 주소공간으로의 대량의 복사가 이루어지므로 이 과정에서 CPU의 과중한 오버헤드가 발생한다. 이것은 시스템 처리율을 저하시킬 뿐만 아니라 QOS(Quality of Service)도 보장할 수 없다. 본 논문에서 이 메모리 복사 오버헤드를 감소시키기 위한 direct I/O와 one copy 기법을 리눅스 커널에서 설계 및 구현하였다. direct I/O는 디스크의 데이터를 커널 버퍼로 복사하지 않고 사용자 버퍼로 직접 복사하므로 CPU 오버헤드를 획기적으로 감소시킬 수 있다. 그리고, one-copy는 사용자 버퍼로 데이터를 복사하지 않고 직접 네트워크로 전송하는 기법이다. 구현 결과, CPU 오버헤드의 상당한 감소와 시스템의 처리율이 향상됨을 확인하였다.

• 한국태양에너지학회 논문집
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• 제34권5호
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• pp.65-72
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• 2014

In this paper, the water-based Ag nanofluids are synthesized by the chemical reduction method and their extinction coefficients are measured by an in-house developed measurement device. The Ag nanofluids are manufactured by the chemical reduction method with the mixing of silver nitrate ($AgNO_3$) and sodium borohydride ($NaBH_4$) in an aqueous solution of polyvinyl pyrrolidone (PVP). The extinction coefficients of Ag nanofluids are measured by means of the in-house developed apparatus at a wavelength of 632.8nm according to the particle volume fractions. The results show that the extinction coefficient of water-based Ag nanofluids increases with the increase of nanoparticle concentrations. Finally, the temperature field and efficiency of direct absorption solar collector (DASC) are analytically estimated based on the measured extinction coefficient of water-based Ag nanofluids. The results indicate that the direct absorption solar collectors using nanofluids have the feasibility to improve the efficiency of conventional flat-plate solar collectors without using an absorber plate.

• 통상정보연구
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• 제16권3호
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• pp.183-202
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• 2014

2007년부터 2012년까지의 외국인직접투자 유치액에 대한 산업별 투자유치 인센티브인 재정지원액을 중심으로 정책집행에 따른 정책의 시차효과를 분석하였다. 분석결과 우리나라의 외국인직접투자유치정책의 시차효과는 정책집행 후 2~3년 정도의 시차가 발생하는 것으로 분석되었다. 따라서 우리나라의 외국인직접투자 유치정책의 방향은 조세감면제도 보다는 직접보조금 혹은 재정지원(금융)과 같은 현실적인 정책수단을 강화해야 할 것이다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1991년도 하계학술대회 논문집
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• pp.813-816
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• 1991

Direct-drive SCARA-type industrial robots are increasingly used in the assembly process of small mechanical parts as well as electronic components, which uses direct-drive (DD) motors instead of reduction gear-type conventional motors for the actuators of manipulator arms. There are many advantages in using DD motors for robots, such as no backlash, low friction, high mechanical stiffness capability for fast and precise arm control, and high repeatability of positioning. However, there exist a number of difficulties which must be overcome to ensure proper construction and operation; increasing effects of load veriation and nonlinear and coupling dynamics, severe vibration caused by resonance of the manipulator components and low mechanical damping, etc. In order to handle these difficulties, lots of efforts have been made such as reduction of the arm inertia and elimination of the resonance, Performance evaluation of a recently developed, domestic DD robot shows that it works excellently compared with conventional robots. It, however, requires proved reliability and price competitiveness against its foreign counterparts.

• Carbon letters
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• 제4권3호
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• pp.121-125
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• 2003

The Pt-Ru/Carbon as an anode catalyst supported on the commercial activated carbon (AC) having high surface area and micropore was characterized for application of Direct Methanol Fuel Cell (DMFC). The Pt-Ru/AC anode catalyst used in this experiment showed the performance of $600\;mA/cm^2$ current density at 0.3 V. The borohydride reduction process using $NaBH_4$, denoted as a process A, showed much higher current and power densities than process B prepared by changing the reduction and washing process of process A. The particle sizes are strongly affected by the reduction process than the specific surface area of raw active carbon and the sizes are almost constant when the specific surface area of carbon are over than the $1200\;m^2/g$. Smaller particle size of catalyst and more narrow intercrystalite distance increased the performance of DMFC.

• 한국분말재료학회지
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• 제17권5호
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• pp.390-398
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• 2010

Aqueous gold nanoparticle dispersion was synthesized by chemical reduction method using diethanolamine as reducing agent and polyethyleneimine as dispersion stabilizer. The synthesis conditions for the stable dispersion of the gold nanoparticle suspension were determined by changing the amount of the reducing agent and dispersant during the wet chemical synthesis procedures. The face centered cubic lattice structure of the gold nanoparticles was confirmed by using X-ray diffraction and the morphologies of the nanoparticles were observed by transmission electron microscope. The synthesized gold nanoparticle dispersion was concentrated by evaporating the dispersion medium at room temperature followed by the addition of ethyleneglycol as humectant for the increase of the elastic properties to obtain gold nanoparticle inks for direct ink writing process. The line patterns were obtained with the gold nanoparticle inks during the writing procedures and the morphologies of the fine patterns were observed by scanning electron microscope.