• 대한산업공학회지
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• 제19권2호
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• pp.23-34
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• 1993

Although there are numerous studies that address the problem of optimal machine grouping and part family classification for cellular manufacturing, little research has been reported that studies the conditions where cellular manufacturing is appropriate. This paper, in order to evaluate and compare the job shop with the GT cellular shop, the performance of those shops were simulated by using SIMAN. We tested the effect of independent variables including changes of product demands, intercell flow level, group setup time, processing time variability, variety of material handling systems, and job properties (ratio of processing time and material handling time). And also performance measures (dependent variables), such as machine utilization, mean flow time, average waiting time, and throughput rate, are discussed. Job shop model and GT cellular shop written in SIMAN simulation language were used in this study. These systems have sixteen machines which are aggregated as five machine stations using the macro feature of SIMAN. The results of this research help to better understand the effect of production factors on the performance of cellular manufacturing systems and to identify some of the necessary conditions required to make these systems perform better than traditional job shops. Therefore, this research represents one more step towards the characterization of shops which may benefit from cellular manufacturing.

• Geomechanics and Engineering
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• 제11권4호
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• pp.471-492
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• 2016

Underground tunnelling is one of the sustainable construction methods which can facilitate the increasing passenger transportation in the urban areas and benefit the community in the long term. Tunnelling in various ground conditions requires careful consideration of the stability factor. This paper investigates three dimensional stability of a shallow circular tunnel in a layered soil. Upper bound theorem of limit analysis was utilised to solve the tunnel face stability problem. A three dimensional kinematic admissible failure mechanism was improved to model a layered soil and limiting assumptions of the previous studies were resolved. The study includes calculation of the minimum support pressure acting on the face of the excavation in closed-face excavations. The effects of the characteristics of the layers on the minimum support pressure were examined. It was found that the ratio of the thickness of cover layers particularly when a weak layer is overlying a stronger layer, has the most significant influence on the minimum tunnel support pressure. Comparisons have been made with the results of the numerical modelling using FLAC3D software. Results of the current study were in a remarkable agreement with those of numerical modelling.

• 한국IT서비스학회지
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• 제17권2호
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• pp.69-81
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• 2018

This study performed an economic analysis and tested the viability of a public computerization project to create a comprehensive information system for public e-procurement for small and medium-sized businesses (SMBs). The study found that the estimated costs of the project included 4.3 billion won to build the system and 710 million won per year to maintain the system once it is built. The project's estimated total benefits amounted to 6.66 billion won per year, including 5.871 billion won per year in increased convenience for SMBs that use the system, 406 million won per year in benefits for public institutions, and 383 million won per year in benefits for the institution "A" to adopt the system. We used the contingent valuation method (CVM) to estimate the benefits to SMBs, which would be the main participants of the project. The survey found that the SMBs were willing to pay an average fee of 170,136 won. we conducted an economic analysis by applying a 5.5% social discount rate over an analysis period of 10 years and found a benefit-cost ratio of 5.02 and a net present value of 40.201 billion won, which indicated a very high economic viability of the project. The results of this study can be an important reference when deciding whether to pursue computerization projects in the public sector.

• 반도체디스플레이기술학회지
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• 제4권1호
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• pp.61-64
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• 2005

This study presents a new algorithm to detect the facial feature in a color image entered from the mobile device with complex backgrounds and undefined distance between camera's location and the face. Since skin color model with Hough transformation spent approximately 90$\%$ of running time to extract the fitting ellipse for detection of the facial feature, we have changed the approach to the simple geometric vector operation, called a TS(Triangle-Square) transformation. As the experimental results, this gives benefit of reduced run time. We have similar ratio of face detection to other methods with fast speed enough to be used on real-time identification system in mobile environments.

• International Journal of Industrial Entomology and Biomaterials
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• 제7권1호
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• pp.29-36
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• 2003

Phytoecdysteroids with moulting hormone (MH) activity induce different responses in silkworms when used on different day of final instar, which can be manipulated for maximum benefit like early and uniform spinning behaviour, reducing crop loss and to increase cocoon yield. The results showed that application of this hormone on seed crop viz., CSR2, CSR4 and BL44 and BL67 in early stage of 5$^{th}$ instar i.e., at 72 hrs and 96 hrs though induced early and uniform spinning behaviour, there was an adverse effect by 9-36% on the economic characters like cocoon yield, cocoon weight, cocoon shell weight and also on fecundity etc. Application of this hormone in late stage of $5^th$ instar i.e., at the onset of spinning showed non-significant variations in some of the characters like cocoon weight, cocoon shell weight, cocoon shell ratio and fecundity. The physiological implications of phytoecdysteroid in hastening the maturation events and synchronization of spinning activities in different breeds are discussed.

• 컴퓨터교육학회논문지
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• 제7권1호
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• pp.89-96
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• 2004

일반적으로 형성 평가는 교수-학습 활동이 진행 중에 투입되는 평가활동으로 학습 정보에 대한 피드백과 교정 및 교수 방법의 개선을 위한 평가이다. 본 논문에서는 형성평가에서 학습자 개인의 평가 결과에 따라 서로 다른 피드백을 제공하는 시스템을 제안한다. 이 시스템은 지식, 이해, 적용 등의 영역별 기준에 따라 제작된 문항을 통해 각 학습자를 평가하고 이 결과를 기반으로 구분된 학습자 유형에 따라 서로 다른 피드백을 개별 학습자에게 제공하며 학습자는 이를 통해 부족한 영역을 보완하게 된다. 교수자에게는 문항별 정답 비율뿐만 아니라 학생 개개인에게 제공되었던 피드백 내용도 알려주어 교수방법을 개선하도록 한다.

• Transactions on Electrical and Electronic Materials
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• 제11권6호
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• pp.271-274
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• 2010

We examined the tunneling current behaviors of magnetic tunneling junction (MTJ) cells utilizing conductive atomic force microscopy (AFM) interfaced with an external magnetic field generator. By introducing current through coils, a magnetic field was generated and then controlled by a current feedback circuit. This enabled the characterization of the tunneling current under various magnetic fields. The current-voltage (I-V) property was measured using a contact mode AFM with a metal coated conducting cantilever at a specific magnetic field intensity. The obtained magnetoresistance (MR) ratios of the MTJ cells were about 21% with no variation seen from the different sized MTJ cells; the value of resistance $\times$ area (RA) were 8.5 K-12.5 K $({\Omega}{\mu}m^2)$. Since scanning probe microscopy (SPM) performs an I-V behavior analysis of ultra small size without an extra electrode, we believe that this novel characterization method utilizing an SPM will give a great benefit in characterizing MTJ cells. This novel method gives us the possibility to measure the electrical properties of ultra small MTJ cells, namely below $0.1\;{\mu}m\;{\times}\;0.1\;{\mu}m$.

• 제어로봇시스템학회논문지
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• 제15권12호
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• pp.1163-1168
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• 2009

The power quality of wind energy becomes more and more important in connecting wind-farms to the grid, especially weak grid. This paper presents the simulation of a wind farm of a permanent magnet synchronous generator (PMSG) and a doubly fed induction generator (DFIG). Flicker mitigation is performed by using PMSG as a static synchronous compensator (STATCOM) to regulate the voltage at the point of common coupling (PCC). A benefit of the measure is that integrating two function of to control the active power flow and to reduce the voltage flicker in a wind farm. Simulation results show that controlling PMSG is an effective and economic measure in reducing the flicker during continuous operation of grid connected wind turbines regardless of short circuit capacity ratio, turbulence intensity and grid impedance angle.

• 한국의학물리학회:학술대회논문집
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• 한국의학물리학회 2002년도 Proceedings
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• pp.305-308
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• 2002

More complex radiotherapy techniques using multi leaf collimation(MLC) such as intensity-modulated radiation therapy(IMRT) has been increasing the significance of verification of leaf position and motion. Due to the reliability and robustness, quality assurance(QA) of MLC is usually performed with portal films. However, the advantage of ease of use and capability of providing digital data of electronic portal imaging devices(EPIDs) have attracted many attentions as alternatives of films for routine quality assurance in spite of the concerns about their clinical feasibility, efficacy, and the cost to benefit ratio. In our work, the method of routine QA of MLC using electronic portal imaging(EPI) was developed. The verification of availability of EPI images for routine QA was performed by comparison with those of the portal films which were simultaneously obtained when radiation was delivered and known prescription input to MLC controller. Specially designed test patterns of dynamic MLC were applied to image acquisition. Quantitative off-line analysis using edge detection algorithm enhanced the verification procedure in addition to on-line qualitative visual assessment. In conclusion, the EPI is available enough for routine QA with the accuracy of portal films.

• Computational Structural Engineering : An International Journal
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• 제1권1호
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• pp.59-69
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• 2001

This study is intended to propose a systematic approach for reliability-based assessment of life cycle cost (LCC) effectiveness and economic efficiency for cost-effective seismic upgrading of existing bridges. The LCC function is expressed as the sum of the upgrading cost and all the discounted life cycle damage costs, which is formulated as a function of the Park-Ang damage index and structural damage probability. The damage costs are expressed in terms of direct damage costs such as repair/replacement costs, human losses and property damage costs, and indirect damage costs such as road user costs and indirect regional economic losses. For dealing with a variety of uncertainties associated with earthquake loads and capacities, a simulation-based reliability approach is used. The SMART-DRAIN-2DX, which is a modified version of the well-known DRAIN-2DX, is extended by incor-porating LCC analysis based on the LCC function developed in the study. Economic efficiencies for optimal seismic upgradings of the continuous PC segmental bridges are assessed using the proposed LCC functions and benefit-cost ratio.