• Corrosion Science and Technology
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• 제14권5호
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• pp.226-231
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• 2015

In spite of highly advanced paint coating techniques, corrosion damage of marine metal and alloys increase more and more due to inherent micro-cracks and porosities in coatings formed during the coating process. Furthermore, flowing seawater conditions promote the breakdown of the protective oxide of the materials introducing more oxygen into marine environments, leading to the acceleration of corrosion. Various corrosion protection methods are available to prevent steel from marine corrosion. Cathodic protection is one of the useful corrosion protection methods by which the potential of the corroded metal is intentionally lowered to an immune state having the advantage of providing additional protection barriers to steel exposed to aqueous corrosion or soil corrosion, in addition to the coating. In the present investigation, the effect of flow velocity was examined for the determination of the optimum corrosion protection current density in cathodic protection as well as the corrosion rate of the steel. It is demonstrated from the result that the material corrosion under dynamic flowing conditions seems more prone to corrosion than under static conditions.

• 한국표면공학회:학술대회논문집
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• 한국표면공학회 2016년도 추계학술대회 논문집
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• pp.116.1-116.1
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• 2016

반도체 가스센서에서는 가연성 및 탄화수소계 가스를 감지 하기 위해서 $100{\sim}500^{\circ}C$ 이상의 동작온도를 필요로 한며, 이에 따라 반도체식 가스센서의 마이크로 히터 소재는 고온에서 열적 안정성이 있는 소재가 요구된다. 현재 상용화되고 있는 반도체식 가스센서는 실리콘(Silicon) 기반의 MEMS 기술을 이용한 가스센서이며, 구조적으로나 성능적 한계가 드러남에 따라 실리콘 이외의 다양한 재료의 MEMS 응용기술 개발이 필요한 실정이다. 본 연구에서는 이러한 실리콘의 재료적 한계를 극복하기 위해 다공성 알루미늄 산화물(AAO)을 기판으로 사용하여 마이크로 히터를 제작하였다. AAO의 제작에 앞서 CMP, 화학연마, 전해연마를 이용하여 적합한 전처리 공정을 선정하였고, AAO 제작 시 온도, 시간, 전압의 변수를 주어 마이크로 히터 기판에 적합한 공정을 탐색하였다. 마이크로 플랫폼은 MEMS 공정으로 제작되었으며, PR(Photo Resist)을 LPR(Liquid Photo Resist)과 DFR(Dry Film Resist)로 각각 2종 씩 선택하여 AAO에 적합한 제품을 선정하였다. 제작된 마이크로 히터는 $1.8mm{\times}1,8mm$로 소형화 하였고, 열손실의 제어를 위해 열확산 방지층을 추가하였다. 구동 온도, 소비전력, 장시간 구동시 안정성의 측정 및 평가는 적외선 열화상 카메라와 kiethly 2420 source meter를 이용하여 측정하였으며, 열확산 방지층의 유 무에 따른 온도 분포 및 소비전력을 비교평가 하였다. 최종적으로는 현재 사용화 되어있는 가스센서들의 소비전력과 비교 평가 하여 논의 하였다.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2003년도 춘계학술대회논문집
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• pp.1157-1164
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• 2003

Dynamic Load/unload (L/UL) mechanism is an alternative to the contact start stop (CSS) technology which eliminates stiction and wear failure modes associated with CSS. Other benefits of L/UL include increased areal density due to smooth disk surfaces, thinner overcoats, and lower head flying height Improved shock resistance due to elimination of head slap, and reduced power consumption. Inertia latch mechanism becomes important for mobile disk drives because of non operating shock performance. Various types of latch designs have been introduced in hard disk drives to limit a rotary actuator from sudden uncontrolled motion. In this paper, a single spring inertia latch is introduced for a small form optical disk drive, which uses a rotary actuator for moving an optical pick-up. A new small inertia latch with single spring is designed to ensure both feasible and small size. The shock performance of the new inertia latch is experimentally verified.

• 한국분무공학회지
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• 제22권1호
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• pp.13-21
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• 2017

The fog screen is a device projecting the media to the aerosol flow field. As major parameters to generate dense and steady fog screen, shear stress, optical blockage ratio and SMD were obtained result through experiment. The micro droplet was generated by the piezo oscillation element, and the aerosol flow mixed with an air flow was sprayed into the vertical direction from the top of the fog screen through the 280 mm slot. For produce a dense, uniform fog screen, the shear effect, optical blockage ratio and SMD between aerosol and air curtain were measured. The minimum and maximum shear stress conditions were selected and it was confirmed that the optical transmission deviation of the aerosol flow field was small when the aerosol and air curtain flow rates were changed. When the aerosol and air curtain flow power were 18 V (1.51 m/s) and 24 V (2.55 m/s), respectively, under the condition of the minimum shear stress and laminar flow, the optical blockage ratios with the spray length were small, and it produced a most stable and high density uniform fog screen by injecting a constant of $10{\mu}m$ or less.

• 한국정보통신학회논문지
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• 제14권12호
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• pp.2805-2810
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• 2010

SAW Device 라는 Passive 소자는 ID Tag 나 소형센서들을 대체할 수 있는 MEMS 기술의 초소형 Device 다. 이 SAW Device 를 이용하면 독립된 공간이나 전원이 필요한 센서 제어 등을 대신할 수 있을 것이다. 이렇게 활용범위가 확대됨에 따라 다양한 SAW Device 를 사용하기 위한 플랫폼이 요구된다. 하지만 현재 SAW Sensor는 많은 발전을 해왔지만 SAW Sensor 를 활용할 수 있는 플랫폼의 발전은 미흡하기 때문에 본 논문에서는 이러한 SAW Device 의 측정이 가능한 SAW Reader를 FPGA를 이용하여 좀 더 간단하고 효율적인 Reader platform 을 구현해 보고자 한다.

• 전기학회논문지P
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• 제64권1호
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• pp.7-13
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• 2015

This paper presents mathematical models for high speed permanent-magnet synchronous machine. The mathematical method with two successive steps is used to estimate design parameter as well as the output power. At first, mathematical model for a linkage flux problem is employed to calculate the number of winding turns and stack length of armature core. The magnetic circuit model for an induced voltage and the electric circuit model for a current are modeled. The output powers of the electrical generator were evaluated by the mathematical techniques. The results of this mathematical methods predict the specifications of the machine and can be applied in the design stage of the electrical machine.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2007년도 심포지엄 논문집 정보 및 제어부문
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• pp.331-332
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• 2007

In this paper we analyze whether recent Radio Frequence Identification technology can be used to improve the localization of mobile robot in their environment. This system make use of power control because Tag with Reader distance measurement. We are accurately the low at former time than the environment. A distance measurement is rather correct. This system used 900MHz Frequencies.

• Corrosion Science and Technology
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• 제19권1호
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• pp.1-7
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• 2020

Chalk River Unidentified Deposits (CRUDs) were collected from the Korean pressurized water reactor (PWR) plant (A, B, and C) where the axial offset anomaly (AOA) occurred. AOA, also known as a CRUD-induced power shift, is one of the key issues in maintaining stable PWR plant operations. CRUDs were sampled from spent nuclear fuel rods and analyzed using an electron probe micro-analyzer (EPMA). This paper describes the characteristics of boron-deposits from the CRUDs sampled from twice-burnt assemblies from the Korean PWR. The primary coolant of a PWR contains boron and lithium. It is known that boron deposition occurs in a thick CRUD layer under substantial sub-cooled nucleate boiling (SNB). The results of this study are summarized as follows. Boron was not found at the locations where the existence was confirmed in simulated CRUDs, in other words, the cladding and CRUD boundaries. Nevertheless, we clearly observed the presence of boron and confirmed that boron existed as a lump in crystalline form. In addition, the study confirmed that CRUD existed in a crystal form with a unique size of about 10 ㎛.

• 대한기계학회논문집A
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• 제28권5호
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• pp.532-538
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• 2004

MEMS technology applying to the sensors and micro-electro devices is complete system. These microsystems are made by variable processes. Especially, the mentallization process has very important functions to transfer the power operating the sensor and signal induced from sensor part. But in the structures of MEMS the local stress concentration and deformation are often yielded by an irregular geometrical shape and different constraint. Therefore, this paper studies the effect of supporting type and thickness ratio about thin film of the substrate on the residual stress variation when the thermal loads is applied to the multi-layer thin film fabricated by metallization process. Specimens were made from several materials such as Al, Au and Cu. Then, uniform thermal load was applied, repeatedly. The residual stress was measured by FE Analysis and nano-indentation method using AFM. Generally, the specimen made of Al induced the larger residual stress than that of made of other materials. Specimen made of Cu and Au having the low thermal expansion coefficient induces the minimum residual stress. Similarly, the lowest indentation length was measured by nano-indentation method in the Si/Au/Cu specimen. Particularly, clusters are created in the specimen made of Cu by thermal load and the indentation length became increasingly large by cluster formation.

• 한국전자파학회논문지
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• 제12권1호
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• pp.99-106
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• 2001

본 논문에서는 선형화 특성이 우수하고, 대역폭이 넓은 feedforward 선형화 기법을 이용하여 IMT-2000용 1-Watt 급 증폭기를 설계 제작하였다. Feedforward는 외부환경(온도, 입력 전력 레벨, 시간 등)의 변화에 민감하므로 마이크로컨트롤러를 이용하여 이를 제어하였다. 35dB 의 이득과 40dBm의 최고전력을 갖는 주증폭기를 설계하였고, 각 루프의 신호를 상쇄하기 위해서 반사형 가변감쇄기와 위상변화기를 사용하였다. 2.11 2.17GHz 대역에서 측정 결과 신호루프에서 주신호를 35dB이상 상쇄하였으며, 오차루프에서 30dB 이상 오차신호를 상쇄하여 60dBc 이상의 선형화 특성을 얻을 수 있었다.