• 산업공학
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• 제21권3호
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• pp.294-301
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• 2008

Agile and flexible manufacturing systems make it mandatory that a control program should have features such as agility, flexibility, and reusability in order to run manufacturing unit smoothly. PLCs are the most frequently used control program in manufacturing systems. PLC programs are mostly programmed by subcontraction, which makes correction of code very difficult. As a result, it may cause delay during down time and ramp up time which leads to big loss of revenue and goodwill. To prevent delay during the times, this paper proposes systematic process analysis and application method for programmable logic controller like LLD (Ladder Logic Diagram). The proposed method uses modified human-error investing techniques for documentation and transforming technique to program LLD from the documentation. Furthermore, this paper demonstrates an example of piston mechanism to explain the proposed method.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2002년도 International Meeting on Information Display
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• pp.594-597
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• 2002

We studied the effect of secondary electron emission from the back plate of AC-PDP, on the ramp waveform driving of the system, using two-dimensional PDP cell discharge simulator. It is found that the secondary electron emission from back plate plays a significant role in getting a stable weak discharge during the ramping up of X-Y electrode voltage. This is because grounded address electrode acts as a cathode during the setup of surface charge, and the secondary electron emission from phosphor in the back plate must be large enough to accumulate surface charges on the dielectric layers without strong plasma discharge. We have concluded that the secondary electron emission coefficient(${\gamma}$) of phosphor, besides MgO, must be known to understand the characteristics of the PDP system. A few suggestions for improvement of the system is also made and tested.

• 전기학회논문지
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• 제64권3호
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• pp.375-383
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• 2015

The virtual power plant (VPP) is a new technology to achieve flexibility as well as controllability, like traditional centralized power plants, by integrating and operating different types of distributed energy resources (DER) with the information communication technology (ICT). Though small-sized DERs may not be controlled in a centralized manner, these are more likely to be utilized as power plants for centralized dispatch and participate in the energy trade given that these are integrated into a unified generation profile and certain technical properties such as dispatch schedules, ramp rates, voltage control, and reserves are explicitly implemented. Unfortunately, the VPP has been in a conceptual stage thus far and its common definition has not yet been established. Such a lack of obvious guidelines for VPP may lead to a further challenge of coming up with the business model and reinforcing the investment and technical support for VPP. In this context, this paper would aim to identify the definition of VPP as a critical factor in smart grid and, at the same time, discuss the details required for VPP to actively take part in the electricity market under the smart grid paradigm.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2008년 영문 학술대회
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• pp.492-498
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• 2008

In this paper are described recent studies about variable nozzles, that are a rectangular type nozzle and an axisymmetric type nozzle, of the precooled turbojet engine(S-engine) which are developed for the demonstration of the key technologies for the propulsion system of the hypersonic airplane and the first stage propulsion of the TSTO space plane. For the rectangular nozzle, three types of C-shaped carbon/carbon composite cowls which includes subscale model of the precooled turbojet engine are fabricated and the fine attachment to the ramp is confirmed. For the firing of the S-engine, stainless steel cowl with concrete heat insulator are fabricated and tested for 20 sec. Axisymmetric variable plug nozzle which is made of C/C material is fabricated and pressurized by the cold flow test. The axisymmetric plug nozzle can be operative up to 0.57 MPa of nozzle inlet pressure.

• 한국산업융합학회 논문집
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• 제26권6_3호
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• pp.1305-1314
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• 2023

The global ship repair and modification market is expected to grow up to approximately $ 30 billion by 2025. Korea's shipbuilding industry is leading the world grounded on its international competitiveness in design and production technology. The reality, however, is that the ship repair and modification industry is centered on Gyeongnam, and there are only two to three ship repair workplaces that can repair large ships. Therefore, domestic ship repair companies target small and medium-sized ships mainly. This is because there are few workplaces equipped with a large dock in which large ships like LNG ships can be inspected regularly or repaired, complaints are severe for environmental problems, and related environmental regulations are so strict that it is very hard to obtain government approval for the extension of ship repair and modification workplaces or the opening of new shipbuilding sites. Besides, on account of the workers' high wages, few experts related, and higher ship repair price compared to that of Southeast Asia, most of the volume of repairing large ships including domestic LNG ships is being lost to Southeast Asian or Chinese markets. In this study, the work process and pre-work preparation process for ship hull (winch, windlass, hatch cover, ramp door, cargo gear, anchor chain) repair were analyzed and presented to foster domestic ship repair experts and revitalize related industries.

• Journal of Welding and Joining
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• 제17권1호
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• pp.88-96
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• 1999

The effects of root gap on welding residual stress and deformation are dealt with the multi-pass weldment with three kinds(0, 6, 30mm) of root gap by F.E.M common code, and then compared with experiment data. In this analysis, an 100% ramp heat input model was used to avoid numerical convergence problem due to an instantaneous increase in temperature near the fusion zone, and the effect of a moving arc in a two dimensional plane was also included. During the analysis, a small time increment was applied in a period with instantaneous temperature fluctuation while a large time increment was used in the rest period. The residual stress is distributed as symmetric types and maximum value is also equivalent when the weldment with 0mm and 6mm root gap is welded. In the case of 30mm root gap welding, the distribution of the residual stress extends over a wide range as asymmetric types due to the built-up weld, and most of the residual stress is biased in the side of a built-up weld part. In case of 0mm gap welding and 6mm gap welding, a little angular distortion occurs, but the level of deformation is small. When the weldment with 30mm root gap is welded, the angular deformation of the asymmetric types, however, occurs larger than the other specimens. The experimental and the analytic results show good coincidence and indicate that the welding residual stress and deformation distribution of 30 mm root gap specimen may be asymmetric and the amplitude is larger than those of root gap specimen under standard.

• Nuclear Engineering and Technology
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• 제43권6호
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• pp.499-508
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• 2011

The paper briefs a fuel performance code, COSMOS, which can be utilized for an analysis of the thermal behavior and fission gas release of fuel, up to a high burnup. Of particular concern are the models for the fuel thermal conductivity, the fission gas release, and the cladding corrosion and creep in $UO_2$ fuel. In addition, the code was developed so as to consider the inhomogeneity of MOX fuel, which requires restructuring the thermal conductivity and fission gas release models. These improvements enhanced COSMOS's precision for predicting the in-pile behavior of MOX fuel. The COSMOS code also extends its applicability to the instrumented fuel test in a research reactor. The various in-pile test results were analyzed and compared with the code's prediction. The database consists of the $UO_2$ irradiation test up to an ultra-high burnup, power ramp test of MOX fuel, and instrumented MOX fuel test in a research reactor after base irradiation in a commercial reactor. The comparisons demonstrated that the COSMOS code predicted the in-pile behaviors well, such as the fuel temperature, rod internal pressure, fission gas release, and cladding properties of MOX and $UO_2$ fuel. This sufficient accuracy reveals that the COSMOS can be utilized by both fuel vendors for fuel design, and license organizations for an understanding of fuel in-pile behaviors.

• Tribology and Lubricants
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• 제39권5호
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• pp.203-211
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• 2023

This study experimentally investigates the effects of angular acceleration on the friction and wear performances of a gas foil thrust bearing (GFTB) using a typical GFTB with six pads. The outer radius of the bearing is 31.5 mm, the total bearing area is 2,041 mm² , and the bump foil and incline (ramp) height are both 500 ㎛. The newly developed GFTB test rig for measuring the friction torque and coefficient measures the axial load, drag torque, lift-off speed, and touch-down speed. The experiment is conducted for angular accelerations of 78.5, 314.2, and 328.3 rad/s² at axial loads of 5, 10, and 15 N, respectively. The test shows that the start-up friction coefficient increases with increasing axial load at the same angular acceleration, and the friction coefficient decreases with increasing angular acceleration under the same axial load. As the angular acceleration increases, the lift-off speed at the motor start-up increases, and the touch-down speed at the motor stop decreases. The wear distance of the GFTB for a single on/off cycle increases with increasing axial load at the same angular acceleration and decreases nonlinearly with increasing angular acceleration under the same axial load. The test results suggest that adjusting the rotational angular acceleration helps reduce bearing friction and wear.

• 재활복지공학회논문지
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• 제4권1호
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• pp.81-86
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• 2010

본 논문은 뇌병변장애인의 일상생활을 위한 맞춤형 보조기구 설계 제작 적용 사례연구로 대구광역시보조기구센터 장애인 보조기구 사례관리 시범사업의 2010년 일상생활영역의 맞춤 서비스 사례 중 2명을 대상으로 2010년 10월 18일부터 11월 17일까지 1개월간 진행되었다. 대상자 A는 47세 뇌병변장애인으로 양하지의 근력과 기능이 많이 저하되어 바닥에서만 생활하며 스스로 변기에 올라 앉아 배변활동을 할 수 없었다. 이에 대상자 A에게 이동식 좌변기와 맞춤 경사로를 설계 제작하여 상지의 잔존근력으로 경사로를 올라가서 이동식 좌변기에 스스로 앉아 배변활동을 할 수 있도록 적용하였다. 대상자 B는 8세 뇌병변장애인으로 손 기능이 저하되어 스스로 식사를 할 수 없었다. 기존에 나와 있는 여러 가지 식사보조도구들을 1차 적용하였으나 대상자에게 적합하지 않아 대상자 의 관절가동범위(ROM)와 손 크기를 고려하여 맞춤으로 식사보조도구를 설계 제작하였고, 작업치료와 연계하여 지속적인 훈련을 통해 향후 스스로 식사를 할 수 있도록 적용하였다. 대상자 A와 대상자 B는 기존에 나와 있는 제품의 적용이나 개조가 접근할 수 없는 사례였음으로 대상자에게 맞춤형으로 설계 제작되어 적용되었다. 본 사례연구를 통해 맞춤형 보조도구의 설계 제작 서비스의 대한 중요성과 필요성을 인식할 수 있다.

• Restorative Dentistry and Endodontics
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• 제27권2호
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• pp.158-174
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• 2002

Filtek$^{TM}$ Z-250(3M Dental Products, St. Paul., MN. USA) 광중합형 복합레진을 대상으로 다양한 광조사 방식이 중합수축, 중합도 및 미세누출에 미치는 영향을 알아보고자 하였다. VIP$^{TM}$(Bisco Dental Products, Schaumburg, IL, USA)를 이용하여 200, 400 및 600mW/$\textrm{cm}^2$의 일정한 광도로 중합시킨 세 군(V2, V4 및 V6군)과 200mW/$\textrm{cm}^2$의 광도로 3초간 중합시키고 5분간 방치 한 후 다시 600mW/$\textrm{cm}^2$의 광도로 중합시키는 pulse-delay 방식을 이용한 군(VPD군) 그리고 Optilux 501$^{TM}$(Demetron/Kerr, Danbury, CT, USA)을 이용하여 C-mode와 R-mode로 중합시킨 두 군(OC군, OR군) 등 모두 6개의 군으로 나누어 실험하였으며, 복합레진의 중합과 누출을 다음의 네 가지 방법으로 측정하였다. 첫째, V2, V4, V6, OC군은 60초간, OR군은 20초간 그리고 VPD군은 두번째 광조사를 60초간 시행하면서 시간에 따른 선형 중합수축을 Linometer(R&B, Daejeon, Korea)로 측정하였다. 둘째, V2, V4, V6, OC군은 각각 5, 10, 20, 40, 60초간 그리고 OR군과 VPD군은 정해진 조건에 따라 중합시킨 2mm 두께 시편의 바닥면에서 시료를 채취한 후 KBr method로 시편을 제작하고, FTIR spectrometer(IFS 120 HR, Broker, Karlsruhe, Germany)로 미반응 잔류단량체의 양을 계측하여 중합도를 측정하였다. 셋째, 두번째 실험과 같은 조건으로 중합시킨 2mm 두께 시편의 광조사면과 바닥면에서 중합 10분 후 미세경도 측정기(FM7, Future-Tech Co., Tokyo, Japan)로 500g의 하중을 10초간 가하여 Knoop Hardness Number(KHN) 값을 측정하였다. 끝으로, 90개의 발거치 치경부에 제5급 와동을 형성하고 V2군은 60초간, V4군은 40초간, V6군은 30초간 그리고 OC, OR, VPD군은 정해진 조건에 따라 중합시킨 후, methylene blue 용액에 침적시키고 종절단하여 법랑질과 상아질 변연의 미세누출 정도를 측정하였다. 중합수축. 중합도 및 미세경도 측정치는 one-way ANO-VA와 Duncan's multiple range test를, 변연누출 정도는 chi-square test를 이용, 통계처리하여 다음의 결과를 얻었다. . 중합수축의 정도는 VIP$^{TM}$(Bisco) 사용군에서 전체 조사광도가 높을수록 큰 경향을 보여 600mW/$\textrm{cm}^2$군에서 가장 크게 나타났고, 그 다음으로 Pulse-delay군, 400mW/$\textrm{cm}^2$군, 200 mW/$\textrm{cm}^2$군 순이었고, Optilux 501$^{TM}$(Demetron/Kerr) 사용군에서는 Continuous 방식이 Ramp 방식 보다 크게 나타났다. . 중합도와 미세경도 값은 공히, 전체 조사광도가 높을수록 높게 나타났으며 , 최종 중합도는 44.77~54.98%의 범위를, 미세경도 값은 34.10~56.30의 범위를 보였다. . 미세누출은 전반적으로 상아질 변연이 법랑질 변연에 비해 많았고, VIP$^{TM}$(Bisco) 사용 군에서는 광도가 높을수록 상아질 변연에서 미세누출이 증가하는 양상을 보였으며, 법랑질 변연에서는 Optilux 501$^{TM}$(Demetron/Kerr)의 Continuous 방식이, 상아질 변연에서는 Ramp 방식이 가장 적은 미세누출을 보였다.