• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2002년도 춘계학술대회 논문집
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• pp.938-942
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• 2002

This paper has studied to obtain the grinding characteristics and optimal grinding renditions of ceramic materials in the grinding with diamond wheel by the experimental plan method. The load on wheel by varying the feed rate was related with the surface roughness due to the minute destruction phenomenon of grains for the Si$_3$${N^4} and Zr{O_2}$. The depth of cut is related with the surface roughness because the grinding is carried out by grain shedding process due to the brittle fracture phenomenon for the ${Al_2}{O_3}$. The major factors affecting the surface roughness and the optimum grinding conditions were obtained with minimum experiments using the experimental plan method.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2005년도 춘계학술대회 논문집
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• pp.1566-1570
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• 2005

The aspherical lenses are used as optical lens of HMD optical system. The optimum cutting condition of PMMA lens sample with ultra precision SPDT, the diamond tool nose radius, the cutting speed, the feed rate, the depth of cut, and cutting fluid type are found. The demanded surface roughness 10 nm Ra, aspherical form error $1.0\;\mu{m}$ P-V for aspherical lens of optical data storage device are satisfied.

• 한국국방경영분석학회지
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• 제30권1호
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• pp.30-47
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• 2004

This research considers a Network Diversion Problem (NDP) in the directed graph, which is to identify a minimum cost set of links to cut so that any communication paths from a designated source node to a destination node must include at least one link from a specified set of arcs which is called the diversion arcs. We identify a redundant constraint from an earlier formulation. The problem is known to be NP-hard, however a detailed proof has not been given. We provide the proof of the NP-hardness of this problem. We develop a tabu search algorithm that includes a preprocessing procedure with two steps for removing diversion arcs as well as reducing the problem size. Computational results of the algorithm on instances of general graphs and grid graphs are reported.

• 대한조선학회 특별논문집
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• 대한조선학회 2009년도 특별논문집
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• pp.52-58
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• 2009

Openings for access to cargo holds are cut on horizontal stringers in every bulkhead of container carriers. But, they are positioned at the edge of stringer width to make minimum space for access and these openings are required to be stiffened by owners and classifications respectively. In this paper, the cargo hold bulkhead stringers with openings for 6,500 TUE container carriers were reviewed by FE analysis to be conducted with the results of hold analysis for 6,500 TUE container carriers classed to GL, DNV, LR and BV respectively, and purpose of this paper is to establish yard's standard of the reinforcement for these openings.

• 한국정밀공학회지
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• 제21권12호
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• pp.140-145
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• 2004

In this study, the design and analysis of a butterfly valve disk was performed to minimize the rubbing between the disk and the seat at opening and closing. The butterfly valve has double eccentric structure and the contact surface between the disk and the seat is a conical surface. At the instant of opening and closing the valve by the rotation of disk, the positions of zero contact point are changed. Also, if the cone surface is cut in the perpendicular direction to the rotation axis of the valve, the contour of cutting section is hyperbolic. Therefore minimum distance between the origin of the eccentric axis and the hyperbolic curve goes to the position of zero contact point. In order to consider the interferences between the disk and the seat, the thermal-structure coupled field analysis was performed by ANSYS.

• 한국기계가공학회지
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• 제2권1호
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• pp.63-68
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• 2003

The aspherical lenses are used as objective lens of optical pickup. To examine the design factor the sample product is made before manufacturing of injection mould of lens. The optimum cutting condition of PMMA lens sample with ultra precision SPDT, the roam spindle speed, the depth of cut, the feedrate are found. The demanded surface roughness 100m Ra, aspherical form error $0.5{\mu}m$ P-V for aspherical lens of optical data storage device are satisfied.

• 한국안전학회지
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• 제35권4호
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• pp.40-47
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• 2020

Although gangform has good workability due to the integration of outer wall forms and working platforms, 22 workers were died from 21 gangform related accidents during 2012 to 2016. Quantitative risk assessment is required for evident based prevention measure selection. In this study, based on 52 accident data from 2004 to the first half of 2019, FTA is conducted for probabilities of direct causes and their contribution to accidents. Three stages are considered; gangform installation, dismantling and lifting, and using. The effectiveness of countermeasures is evaluated through minimum cut set, RAW and RRW. Complete assembly of gangform on the ground level, detailed planning, and fall prevention device are suggested as prevention measures for installation, dismantling and lifting, and using stages, respectively.

• Journal of Power Electronics
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• 제9권3호
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• pp.418-429
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• 2009

In this paper an optimal damped input filter is designed based on a Genetic Algorithm (GA) for an electrolytic capacitor-less AC-AC converter. Sufficient passive damping and minimum losses in passive damping elements, minimization of the filter output impedance at the filter cut-off frequency, minimization of the DC-link voltage and input current fluctuations, and minimization of the filter costs are the main objectives in the multi-objective optimization of the input filter. The proposed filter has been validated experimentally using an induction motor drive system employing an electrolytic capacitor-less AC-AC converter.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2005년도 제36회 하계학술대회 논문집 A
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• pp.557-559
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• 2005

This paper proposes a method for choosing the best composite power system expansion plan considering a contingency security criterion. The proposed method minimizes the investment budget fer constructing new transmission lines subject to contingency criterion. it models the power system expansion problem as an integer programming one. The method solves for the optimal strategy using a branch and bound method that utilizes a network flow approach and the maximum flow-minimum cut set theorem. Although the proposed method is applied to a simple sample study, the test results demonstrate that the proposed method is suitable for solving the power system expansion-planning problem subject to practical future uncertainties.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 1998년도 하계종합학술대회논문집
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• pp.405-408
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• 1998

Due to the large conduction band discontinuity between emitter base, OmGaAs HBT has an advantge to enable the hot electrons to inject into the base. In this paper, InAlGaAs/InGaAs HBT with the various emitter junction gradings and the modified collectors are simulated and analyzed by HMC(hybrid monte carlo) simulator in order to find a optimal structure for the shortest transit time. A minium base transit time (.tau.$_{b}$ ) of 0.21 ps was obtained for HBT with the grading layer, which is parabolically graded from x=1.0 to x=0.5. The minimum collector transit time (.tau.$_{c}$ ) of 0.31ps was found when the collector was modified by inserting p$^{[-10]}$ and p$^{+}$ layers. Thus HBT in combination with the emitter grading and the modified collector layer showed the cut-off frequency (f$_{T}$) of 183GHz.z.z.