• Composites Research
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• 제34권1호
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• pp.51-56
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• 2021

석탄 핏치의 전구체인 콜타르를 바인더 및 함침재로 이용하여 벌크흑연을 제조할 수 있는 가능성을 검토하고자 하였다. 충전재로 천연흑연을 이용하였으며, 천연흑연과 콜타르를 혼합 및 성형한 후 탄화 열처리를 실시하였다. 탄화 열처리 후 함침-재탄화를 5회 실시하여 밀도, 기공율, 압축강도, 그리고 이방성비를 측정하였다. 탄화체의 최고 밀도는 1.76 g/㎤였고, 기공율은 최소 15.6%로써 공정 제어에 의해 조절이 가능하였다. 압축강도는 최고 20.3 MPa이 얻어졌다. 탄화체의 이방비는 최대 0.34로써 강한 이방성 탄화체를 얻을 수 있었다. 따라서 콜타르를 바인더 및 함침재로 이용하여 벌크 형태의 인조흑연 제조가 가능하다는 것을 확인하였다. 또한 탄화체의 이방성을 조절하여 전기적, 기계적 방향 특성을 조절한다면 적절한 재료 설계를 통하여 다양한 분야에 응용할 수 있을 것이라 판단된다.

• 센서학회지
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• 제27권3호
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• pp.182-185
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• 2018

Zinc oxide (ZnO) thin films have the advantages of growing at a low temperature and obtaining high charge mobility (carrier mobility) [1]. Furthermore, the zinc oxide thin film can be used to control application resistance depending on its oxygen content. ZnO has the desired physical properties, a transparent nature, with a flexible display that makes it ideal for use as a thin-film transistor. Though these transparent flexible thin-film transistors can be manufactured in various manners, manufacturing large-area transistors using a solution process is easier owing to the low cost and flexible substrate. The advantage of being able to process at low temperatures has been attracting attention as a preferred method. However, in the case of a thin-film transistor fabricated through a solution process, it is reported that charge mobility is lower. To improve upon this, a method of improving the crystallinity through heat treatment and increasing electron mobility has been reported. However, as the heat treatment temperature is relatively high at $500^{\circ}C$, an application where a flexible substrate is absent would be more suitable.

• 미생물학회지
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• 제1권1호
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• pp.48-50
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• 1963

청량음료 제조적 외부로 부터 얼마나 오염이 되며 또 가장 큰 오염원은 무엇인가를 알아보기 위해 제조공정중의 각 단계별로 또 생업에 쓰이는 박과와 원과별로 윤도가 되는 총생균수를 검토하였으며 이들 얻은 결과는 다음과 같았다. 1) 생업에 쓰이는 박과와 원과중 가장 큰 제조과는 연평적 ml당 4개이었으며 동계에서는 ml당 1개정과이던 것이 하계에서는 ml당 8개과정가 검출되었다. 3)제품에서는 일년문 coliform group이 검출된 적이 거의 없었다. 4)물의 이온문환지를 통과하여도 총생균자의 약화는 거의 측정할 수 없었다. 5)제품에서 HIST를 사용한 후 사용 안할 때보다 1/8의 오염과감소를 나타냈다

• 자원리싸이클링
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• 제22권1호
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• pp.42-47
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• 2013

페로니켈 슬래그는 페로니켈 제조 공정의 부산물이다. 페로니켈 슬래그가 마그네슘 산화물 및 규소 산화물 등 유용 성분을 갖는데도 불구하고 대부분이 폐기되거나 골재로 사용된다. 이 연구는 $H_2SO_4$ 용액을 사용하여 Mg 이온을 추출하고, NaOH 용액을 사용하여 불순물 제거 및 고순도의 $Mg(OH)_2$를 얻으려고 하였다. $H_2SO_4$ 용액에 의해 Mg 이온은 Fe 이온 및 기타 페로니켈 슬래그 구성 성분과 함께 추출되었다. 불순물을 제거하고 고순도의 $Mg(OH)_2$를 얻기 위해서는 침출액의 pH 조절이 중요하다. 불순물은 가수분해에 의한 수산화물 침전으로 제거하였다. 이 과정 후, 여과액에 NaOH를 첨가하여 고순도의 $Mg(OH)_2$을 얻었다.

• Journal of Advanced Marine Engineering and Technology
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• 제29권8호
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• pp.938-945
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• 2005

The microstructure evolution in hot forging process is composed of dynamic recrystallization during deformation as well as grain growth during dwell time. Therefore, the control of forging parameters such as strain, strain rate. temperature and holding time is important because the microstructure change in hot working affects the mechanical properties. Modeling equations are developed to represent the flow curve. grain size. recrystallized volume fraction and grain growth phenomena by various tests. The developed modeling equations were combined with thermo-viscoplastic finite element modeling to predict the microstructure change evolution during hot forging process. The large exhaust valve spindle (head diameter of 512mm) was simulated by closed die forging with hydraulic press and cooled in air after forging. The preform was heated to each 1080 and 1150$^{\circ}C$. Numerical calculation was performed by DEFORM-2D. a commercial finite element code. Heat transfer can be coupled with the deformation analysis in a non-isothermal deformation analysis. In order to obtain the fine and homogeneous microstructure and good mechanical properties in forging. the FEM would become a useful tool in the simulation of the microstructure development. In forging, appropriate temperature, strain and strain rate and rapid cooling are required to obtain the fine grain microstructure The optimal forging temperature and effective strain range of Nimonic 80A for large exhaust valve spindle are about 1080$\∼$l120$^{\circ}C$ and 150$\∼$200$\%$.

• Design & Manufacturing
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• 제11권1호
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• pp.1-6
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• 2017

In these days, due to generalization of using smart mobile phone and wearable device such as smart watch, demand of Cover-glass and touch screen panel for protecting display increases. With increasing the demand of Cover-glass, slimming technique is promising for weight lightening, zero bezel. Cover-glass produced by this technique is required to decreasing thickness with increase strength. In the Cover-glass manufacturing process, mechanical processing and chemical processing has improve in the strength. Generally, Diamond electrodeposition wheel is used in mechanical process. Reinforced glass with the characteristics of the brittle and high hardness was manufactured by using a diamond electrodeposition wheel. At this time, Because of surface of the tool present non-uniform distribution of diamond particle, it has generate Loading of wheel and it has been decrease life of grinding tool, efficiency of grinding, quality and shape accuracy of workpiece. Thus Research is needed to controling particle distribution of diamond electrodeposition wheel uniformly. And it is necessary to study micro hole machining such as proximity senser hole, speaker hole positioned Cover-glass. Reinforced glass with the characteristics of the brittle and high hardness is difficult to machining. Processing of reinforced glass have generated wear of tool, micro cracks. Also, it is decreasing shape accuracy. In this paper, We conducted a study on how to control particle distribution uniformly about the diamond tool manufactured using elecetodeposition processing. It analyzed the factors that affect the arrangement of the particles in the electrodeposition process by design of experiment. And There is produced the grinding tool, which derives an optimum deposition conditions, for processing Cover-glass edge and the machinability was evaluated.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2012년도 제42회 동계 정기 학술대회 초록집
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• pp.523-523
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• 2012

As the wafer geometric requirements continuously complicated and minutes in tens of nanometers, the expectation of real-time add-on sensors for in-situ plasma process monitoring is rapidly increasing. Various industry applications, utilizing plasma impedance monitor (PIM) and optical emission spectroscopy (OES), on etch end point detection, etch chemistry investigation, health monitoring, fault detection and classification, and advanced process control are good examples. However, process monitoring in semiconductor manufacturing industry requires non-invasiveness. The hypothesis behind the optical monitoring of plasma induced ion current is for the monitoring of plasma induced charging damage in non-invasive optical way. In plasma dielectric via etching, the bombardment of reactive ions on exposed conductor patterns may induce electrical current. Induced electrical charge can further flow down to device level, and accumulated charges in the consecutive plasma processes during back-end metallization can create plasma induced charging damage to shift the threshold voltage of device. As a preliminary research for the hypothesis, we performed two phases experiment to measure the plasma induced current in etch environmental condition. We fabricated electrical test circuits to convert induced current to flickering frequency of LED output, and the flickering frequency was measured by high speed optical plasma monitoring system (OPMS) in 10 kHz. Current-frequency calibration was done in offline by applying stepwise current increase while LED flickering was measured. Once the performance of the test circuits was evaluated, a metal pad for collecting ion bombardment during plasma etch condition was placed inside etch chamber, and the LED output frequency was measured in real-time. It was successful to acquire high speed optical emission data acquisition in 10 kHz. Offline measurement with the test circuitry was satisfactory, and we are continuously investigating the potential of real-time in-situ plasma induce current measurement via OPMS.

• 동력기계공학회지
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• 제20권5호
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• pp.46-51
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• 2016

The TMCP steel has expanded in the marine structure during manufacturing process because of its excellent weld-ability and impact toughness. In the case of merchant ships, coverage of TMCP steel has been used widely on over DH36 Classifications material. The line heating process is applied to the outer surface of the steel plate for the shipbuilding. In this study, We compared between TMCP and normalizing steel for shipbuilding by analyzing some basic data through performing the natural cooling after the line heating. The experimental results show the angular misalignment changes in line heating. Heated surface of normalizing steel material expanded to $-0.3^{\circ}$ and reduced to $+0.2^{\circ}$ after cooling. And during cooling at $194^{\circ}C$ for 1,500 seconds, Angular Misalignment began from - direction to + direction, passed the critical point to the default at 2,200 seconds and did not take place any more at $103^{\circ}C$ after the 2,700 seconds. Angular Misalignment results of TMCP steels and Normalizing steel material show same angular misalignment lasted 1,200 seconds, TMCP steel has given more expansion and contraction angle which is $0.2^{\circ}$ than that of the Normalizing steel. Length difference between expansion and contraction is about 0.3 mm.

• Composites Research
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• 제12권2호
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• pp.70-81
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• 1999

고분자 복합재료 제조공정인 수지이동성형(RTM) 공정은 최근 들어서 고성능 재료를 필요로 하는 항공산업분야에서 관심의 대상이 되고 있다. 본 연구에서는 유한요소/관할부피 기법을 도입한 수치모사를 통해서 수지이동 성형공정에서의 금형충전단계를 해석하였다. 섬유직조망의 투과계수를 정량적으로 측정하고, 또한 수치모사에 이용된 프로그램을 검증하기 위하여 유동가시화 실험을 수행하였다. 실험에 사용된 강화섬유와 수지물질로는 여러 가지 형태의 섬유직조망과 실리콘 기름을 선택하였다. 수치모사와 유동가시화 실험을 병행함으로써 섬유직조망의 구조, 금형의 구조, 금형삽입체가 금형충전단계에서의 수지 유동선단의 형태에 미치는 영향을 살펴보았다. 모델링에 의해 예측된 유동선단은유동가시화 실험을 통해 관찰된 결과와 잘 일치한 것으로 나타났으나, 금형내 불균일한 섬유부피분율로 인해 섬유조직망의 투과계수가 전 영역에서 일정한 값을 가지지 못하기 때문에 약간의 차이를 보여주었다. 원형의 구조물이 금형내에 삽입되어 있는 경우, 월드라인의 위치를 예측된 유동선단으로부터 정성적으로 추정할 수 있었다.

• International Journal of Precision Engineering and Manufacturing
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• 제8권2호
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• pp.70-74
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• 2007

This paper describes the development of a nano-positioning system for nanoscale science and engineering. Conventional positioning systems, which can be expensive and complicated, require the use of laser interferometers or capacitive transducers to measure nanoscale displacements of the stage. In this study, a new self-displacement sensing (SDS) nano-stage was developed using mechanical magnification of its displacement signal. The SDS nano-stage measured the displacement of its movement using a position-sensitive photodiode (PSPD), a laser source, and a hinge-connected rotating mirror plate. A beam from a laser diode was focused onto the middle of the plate with the rotating mirror. The position variation of the reflected beam from the mirror rotation was then monitored by the PSPD. Finally, the PSPD measured the amplified displacement as opposed to the actual movement of the stage via an optical lever mechanism, providing the ability to more precisely control the nanoscale stage. The displacement amplification process was modeled by structural analysis. The simulation results of the amplification ratio showed that the distance variation between the PSPD and the mirror plate as well as the length L of the mirror plate could be used as the basic design parameters for a SDS nano-stage. The PSPD was originally designed for a total travel range of 30 to 60 mm, and the SDS nano-stage amplified that range by a factor of 15 to 25. Based on these results, a SDS nano-stage was fabricated using principle of displacement amplification.