• 한국분말재료학회지
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• 제26권1호
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• pp.11-15
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• 2019

In this study, a method to remove residual powder on a multi-layered graphene and a new approach to transfer multi-layered graphene at once are studied. A graphene one-step transfer (GOST) method is conducted to minimize the residual powder comparison with a layer-by-layer transfer. Furthermore, a residual powder removing process is investigated to remove residual powder at the top of a multi-layered graphene. After residual powder is removed, the sheet resistance of graphene is decreased from 393 to 340 Ohm/sq in a four-layered graphene. In addition, transmittance slightly increases after residual powder is removed from the top of the multi-layered graphene. Optical and atomic-force microscopy images are used to analyze the graphene surface, and the Ra value is reduced from 5.2 to 3.7 nm following residual powder removal. Therefore, GOST and residual powder removal resolve the limited application of graphene electrodes due to residual powder.

• 한국환경생태학회지
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• 제8권1호
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• pp.58-67
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• 1994

Object of this study is to suggest the plan for natural vegetation restoration and management by ecological approach. The concept of biotope planting technique was introduced in order to restore the natural vegetation in the northern part of Mt. Nam in Seoul, and Quercus mongolica forests was surveyed so as to obtain the basic data. This study focused on the vegetational context between northern part of Mt. Nam and develop-reserved site. The results are following ; 1. It is suitable to plant 25~30 trees in $100\m^2$ with trees of DBH 10cm and below at intervals of about 2m in canopy layer. In the case of subtree layer of DBH 2cm, about 30 trees were planted at an Intervals of 1.5~2m around in $100\m^2$. 2. In the last step of nature vegetation restoration, it is desiable that canopy density is $5/100\m^2$ and 녀btree one is 10~20/$100\m^2$. 3. Management plans was proposed to use the native species of Mt. Nam around and to investigate the ecological situation once a year such as species introduce, dead-tree, soil, fauna etc.

• Smart Structures and Systems
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• 제26권6호
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• pp.693-701
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• 2020

The conventional Kalman Filter (KF) provides a promising way for structural state estimation. However, the physical parameters of structural systems or models should be available for the estimation. Moreover, it is not applicable when the loadings applied to the structures are unknown. To circumvent the aforementioned limitations, a two-stage KF with unknown input approach is proposed for the simultaneous identification of structural parameters and unknown loadings. In stage 1, a modified observation equation is employed. The structural state vector is estimated by KF on the basis of structural parameters identified at the previous time-step. Then, the unknown input is identified by Least Squares Estimation (LSE). In stage 2, based on the concept of sensitivity matrix, the structural parameters are updated at the current time-step by using the estimated structural states obtained from stage 1. The effectiveness of the proposed approach is numerically validated via a five-story shearing model under random and earthquake excitations. Shaking table tests on a five-story structure are also employed to demonstrate the performance of the proposed approach. It is demonstrated from numerical and experimental results that the proposed approach can be used for the identification of parameters of structure and the external force applied to it with acceptable accuracy.

• Bulletin of the Korean Chemical Society
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• 제18권7호
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• pp.754-760
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• 1997

Through a sequence of reactions including Diels-Alder cycloaddition of a furan diene as the key step, 11-oxatricyclo[6.2.1.01,6]undecyl rings were synthesized from 5-methylfurfural with the goal of developing a synthetic protocol to 11-oxabicyclo[6.2.1]undecyl system. The strategy to incorporate an oxygen atom at C6 carbon of tricyclic 11 or 16 by Baeyer-Villiger oxidation was unsuccessful, implicating that there is too much steric congestion around the carbonyl ketone. As an alternative approach, bicyclic 23 and 24 were prepared from 2-methylfuran via known tricyclic 20. Cyclization of bicyclic 23 and 24 under several reaction conditions also failed to produce hydroxylated product 25 and 26.

• 디지털콘텐츠학회 논문지
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• 제12권2호
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• pp.185-194
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• 2011

본 논문은 게임과 가상현실 시스템을 위한 스테이트챠트(Statecharts) 기반의 점진적인(progressive) 행위 LOD 모델을 소개하고 있다. 시스템의 리소스를 최대한 활용할 수 있도록 상황에 따라 임의의 복잡도를 가진 행위 LOD를 자유롭게 생성할 수 있는 스테이트챠트 기반의 명세 프로세스를 포함하여, 모델간 개량(refinement) 연산, 모델 간 전환(switching) 법칙, LOD 선택 정책 등을 정의하였다. 더불어, 제안된 접근방법의 가능성을 보여주기 위해, 가상 자동차가 단계적으로 설계되어가면서 점진적인 LOD 모델이 되는 예를 들고 있다.

• 한국경영과학회지
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• 제30권2호
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• pp.63-71
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• 2005

In the field of nuclear reactor safety study, common cause failures (CCFs) became significant contributors to system failure probability and core damage frequency in most Probabilistic risk assessments. However, it is hard to estimate the reliability of such a system, because of the dependency of components caused by CCFs. In order to analyze the system, we propose an analytic method that can find the parameters with lack of raw data. This study adopts the shock model in which the failure probability increases as the shock is cumulated. We use two-step Expectation and Maximization (EM) algorithm to find the unknown parameters. In order to verify the analysis result, we perform the simulation under same environment. This approach might be helpful to build the defensive strategy for the CCFs.

• Journal of Electrical Engineering and Technology
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• 제10권2호
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• pp.529-538
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• 2015

Due to the high efficiency and compact mechanical structure, direct drive variable speed generators are used for power conversion in wind turbines. The wind energy conversion system (WECS) considered in this paper consists of a permanent magnet synchronous generator (PMSG), uncontrolled rectifier, dc-dc boost converter controlled with maximum power point tracking (MPPT) and adaptive hysteresis controlled voltage source inverter (VSI). For high utilization of the converter's power capability and stabilizing voltage and power flow, constant DC-link voltage is essential. Step and search MPPT algorithm which senses the rectified voltage ($V_{DC}$) alone and controls the same is used to effectively maximize the output power. The adaptive hysteresis band current control is characterized by fast dynamic response and constant switching frequency. With MPPT and adaptive hysteresis band current control in VSI, the DC link voltage is maintained constant under variable wind speeds and transient grid currents respectively.

• International Journal of Knowledge Content Development & Technology
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• 제4권2호
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• pp.67-95
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• 2014

Knowledge Management (KM) is a collaborative and integrated approach adopted at various levels to ensure that an organization's knowledge assets are best utilized to increase organizational performance. While KM has been adopted in a large number of sectors and organizations, colleges and universities, and the higher education sector in general, is yet to take full advantage of the possibilities offered by KM. Also, while past research has sought to highlight the importance of implementing KM in higher education, there is a lack of a single, clear template for KM implementation that universities leaders and administrators can adopt. The contribution of the paper is a practical, actionable, step-by-step plan, as well as a diagrammatic, theoretical framework for initiating KM successfully in colleges and universities.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2001년도 ICCAS
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• pp.137.2-137
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• 2001

We have been developed an intelligent mobile robot with an artificial olfactory function to recognize odours and to track odour source location. This mobile robot also has been installed an engine for speech recognition and synthesis, and is controlled by wireless communication. An artificial olfactory system based on array of 7 gas sensors has been installed in the mobile robot for odour recognition, and 11 gas sensors also are located in the bottom of robot to track odour sources. 3 optical sensors are also included in the intelligent mobile robot, which is driven by 2 D.C. motors, for clash avoidance in a way of direction toward an odour source. Throughout the experimental trails, it is confirmed that the intelligent mobile robot is capable of not only the odour recognition using artificial neural network algorithm, but also the tracking odour source using the step-by-step approach method ...

• 한국전산유체공학회지
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• 제2권2호
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• pp.51-58
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• 1997

A reliable computational solver has been developed for the analysis of three-dimensional inviscid compressible flows around a nacelle of a high bypass ratio turbofan engine, The numerical algorithm is based on the modified Godunov scheme to allow the second order accuracy for space variables, while keeping the monotone features. Two step time integration is used not only to remove time step limitation but also to provide the second order accuracy in a time variable. The multi-block approach is employed to calculate the complex flow field, using an algebraic, conformal, and elliptic method. The exact solution of Riemann problem is used to define boundary conditions. The accuracy of the developed solver is validated by comparing its results around the isolated nacelle in the cruise flight regime with the solution obtained using a commercial code "RAMPANT. "