PZT 후막의 치밀성 향상에 따른 PZT 다층 후막의 구조적 특성 (pp.2211-2212)

윤상은(Sang-Eun Yun),이성갑(Sung-Gap Lee),박상만(Sang-Man Park),이영희(Young-Hie Lee) 대한전기학회 2006 대한전기학회 학술대회 논문집 Vol.2006 No.7

Ferroelectric PZT (70/30) thick films were fabricated by the screen printing method. And the PZT (30/70) precusor solution were infiltrated by the spin-coating method on the PZT thick films to obtain a densification. All PZT thick films were sintered at 1050℃ for 10 min. Structural properties, such as crystalline structure, microstructures and compositional ratio, of PZT thick films were investigated with the variation of the number of sol coatings using XRD, SEM and EDS, respectively. All PZT thick films exhibited a perovskite polycrystalline structure without a pyrochloer phase. The thickness of PZT thick films, 4-times screen-printed, was approximately 60㎛. And the densification of the PZT thick films increased with increasing the number of sol coatings.

무선메쉬네트워크환경에서 보정계수를 이용한 MAC프로토콜 동기화 개선 알고리즘

윤상만,이순식,이상욱,전성근,이우재,Yun, Sang-Man,Lee, Soon-Sik,Lee, Sang-Wook,Jeon, Seong-Geun,Lee, Woo-Jae 한국정보통신학회 2009 한국정보통신학회논문지 Vol.13 No.10

무선메쉬네트워크환경을 지원하는 TDMA기반 MAC프로토콜은 기존의 패킷기반인 802.11 DCF/EDCA 프로토콜보다 많은 장점을 가지고 있다. 하지만, TDMA기반의 MAC프로토콜은 MP(Mobile Points)들의 발진기(Oscillator) 편차와 분산 환경의 특성으로 인해서 새로운 동기화 기법이 필요하다. 본 논문에서는 TDMA기반의 MAC프로토콜에서 동기화 방법을 제안한다. MP들을 동기화 상태에 따라 4가지로 구분해서 MP가 동기화 상태일때 비콘을 이용해서 TDMA프레임의 시작시간을 Time Skew의 변동 범위내에서 결정하도록 한다. Clock Drift에 의해 발생하는 Time Skew는 보정계수를 통해서 자동으로 보정할 수 있는 알고리즘을 제안한다. 이 제안된 내용을 기반으로 General Time Error값과 Clock Drift Rate가 실험을 통해 안정적이며 최소의 값이 산출되는 것을 확인하였다. TDMA based MAC protocol supporting wireless mesh network has many advantage rather than 802.11 DCF/EDCA protocol based on packet. But TDMA based MAC protocol require new synchronization method because of mobile point oscillator's difference, and distributed environments. This thesis propose synchronization method for TDMA based MAC protocol. It divides MP(Mobile Points) states into 4 types. If MP is in sync mode, it schedules TDMA local start time in time skew interval using beacon. It proposes compensation algorithms to compensate time skew caused by clock drift. This proposal show that general time error and clock drift rate value reduced and get synchronized result.

WMN에서 TDMA 기반 MAC Protocol을 위한 우선순위 채널 경쟁 접근 방법

윤상만,이순식,이상욱,전성근,이우재,Yun, Sang-Man,Lee, Soon-Sik,Lee, Sang-Wook,Jeon, Seong-Geun,Lee, Woo-Jae 한국정보통신학회 2009 한국정보통신학회논문지 Vol.13 No.9

무선 메쉬 네트워크 환경에서는 기존의 MAC Protocol이 완벽한 성능을 발휘하기 힘들다. MP들의 끊임없는 이동성, 완전 분산 환경, 과부하 트래픽 등의 문제로 인해 새로운 MAC Protocol들이 제안되고 있다. 이 논문에서는 무선 메쉬 네트워크를 위한 MAC Protocol인 Mesh DCF를 이용한 우선순위 채널 경쟁 접근 방법을 제안한다. Mesh DCF에서는 TDMA Frame안의 ACH Phase를 이용해서 중요도에 따른 선택 및 그룹화를 이용한 삭제 방법을 사용한다. ACH안의 우선 순위화된 PP(Prioritized Phase)의 slot개수 m과 FEP(Fair Elimination Phase)의 slot개수 n은 경쟁 수준을 결정함과 동시에 하나의 MP가 경쟁에서 선택될 확률을 높여주는 역할을 한다. FEP의 경쟁수준을 결정하는 CNG(Contention Number Groups)의 K값은 경쟁의 공정성과 비례하지만 MP가 하나 선택될 수 있는 확률과는 반비례를 한다. 실험 결과 충분한 n과 K의 크기는 전체적인 성능을 향상시키는 것을 확인할 수 있었다. Existing MAC protocol can not show good performance in WMN environment. New MAC protocols is proposed because of Mobile Point's mobility, entire distributed environment, heavy traffic problems. This thesis proposes new channel contention method fur Mesh DCF. Mesh DCF uses ACH phase in TDMA frame to perform selection and elimination. Prioritized phases's count m and Fair Elimination phases's count n is determine contention level and make string probability to only one win the contention. Contention Number group's count K to determine the contention level in Fair Elimination Phase gives Fairness but make low probability to only one win the contention. It is sure that enough size of n and K can improve entire performance as result.

유전알고리즘을 이용한 인버터 DC 저항점용접에서의 정전류퍼지제어기 최적화

유지영,윤상만,이세헌,Yu, Ji-Young,Yun, Sang-Man,Rhee, Se-Hun 대한용접접합학회 2010 대한용접·접합학회지 Vol.28 No.5

Inverter DC resistance spot welding process has been very widely used for joining such as automotive body sheet metal. Because the lobe area of DC welding is larger than AC welding and DC welding has low electrode wear. So the use of Inverter DC resistance spot welding process has been further increased. And the application of high tensile steel is growing for light weight vehicle. To improve the weldability of high strength steel, the development of Inverter DC resistance spot welding system is more conducted. However, Inverter DC resistance spot welding system has a few problems. Current waveform is unstable and the expulsion has been occurred by characteristics of steel. In this study, inverter DC resistance spot welding system was made. And Fuzzy control algorithm was applied for constant current. The genetic algorithm was applied to optimize the fuzzy scaling factors, in order to optimize the fuzzy control.

Pb(Zr_0.7Ti_0.3)O₃ 후막의 강유전 특성에 전구체 용액의 코팅요소가 미치는 영향

박상만,윤상은,이성갑,Park, Sang-Man,Yun, Sang-Eun,Lee, Sung-Gap 한국전기전자재료학회 2006 전기전자재료학회논문지 Vol.19 No.12

The influence of the concentration of precursor solution and the number of solution coatings on the densification of the $Pb(Zr_xTi_{1-x})O_3$ (PZT) thick films was studied. PZT powder and PZT precursor solution were prepared by3 sol-gel method and PZT thick films were fabricated by the screen-printing method on the alumina substrates. The composition of powder and precursor solution were PZT(70/30) and PZT(30/70), respectively. The PZT precursor solution was spin-coated on the PZT thick films. A concentration of a coating solution was 0.5 to 2.0 mol/L[M] and the number of coating was repeated from 0 to 6. The XRD patterns of all PZT thick films shelved typical perovskite polycrystalline structure. The porosity of the thick films was decreased with increasing the number of coatings and 6-time coated films with 1.5 M showed the dense microstructure and thickness of about $60{\mu}m$. The relative dielectric constant of the PZT thick film was increased with increasing the number of solution coatings and the thick films with 1.5 M, 6-time coated showed the 698. The remanent polarization the 1.5 M and 6-time coated PZT thick films was $38.3{\mu}C/cm^2$.

자동차 B-pillar부품의 스폿용접 및 접착 혼용 용접부의 충돌특성 및 해석에 관한 연구

최영수,윤상만,조용준,이세헌,Choi, Young-Soo,Yun, Sang-Man,Cho, Yong-Joon,Rhee, Se-Hun 대한용접접합학회 2011 대한용접·접합학회지 Vol.29 No.5

In the present day, the needs of new steel for lightweight car-body have been increased in the automotive industry. however, the resistance spot welding is difficult to apply to the new steel because of the narrow weld current range and defects. As the solutions to these problems, adhesive bonding process is proposed. Adhesive bonding which reduce noise and vibration can be applied to joining the new steel. In this study, crash tests of b-pillar applied the resistance spot welding, structural adhesive bonding, the mixture of the structural adhesives and resistance spot welding were performed. And FEM crash model for b-pillar applied the structural adhesive bonding was developed. The results of experiment and analysis on b-pillar crash test were compared to verify the validity.

예비전류를 이용한 자동차용 프리실드 강판의 저항 점 용접성 향상에 관한 연구

박태규,윤상만,이세헌,Park, Tae-Gyu,Yun, Sang-Man,Rhee, Se-Hun 대한용접접합학회 2009 대한용접·접합학회지 Vol.27 No.6

In the present day, new performances are demanded for automobile body steel sheet for example, light weight, durability, resistance corrosion and environmental protection. For an improvement of resistance corrosion, European automobile companies developed pre-sealed steel in 1990's. Pre-sealed steel have organic coated layer upper zinc coated layer. Evaluating a resistance spot weldability of pre-sealed steel plate is important because resistance spot welding is used mainly in automobile body joining process. In this study, evaluating a weldability of pre-sealed steel plate was carried out using lobe diagram, dynamic resistance and high-speed image. Usually, Pre-sealed steel has poor weldability than GA steel's. To improve a weldability of pre-sealed steel sheet, pre-current was applied to welding process. Pre-current is applied prior to base-current. In conclusion, the weldability of pre-sealed steel has been improved than GA steel's by applying pre-current.

무선 메쉬 네트워크의 최적화를 위한 프로토콜 계층별 기술적 요구사항에 관한 분석

이순식,윤상만,이상욱,전성근,이우재,Lee, Soon-Sik,Yun, Sang-Man,Lee, Sang-Wook,Jeon, Seong-Geun,Lee, Woo-Jae 한국정보통신학회 2010 한국정보통신학회논문지 Vol.14 No.1

Wireless Mesh Networks are consist of mobility mesh clients and mesh routers. WMNs can communicate with heterogeneous networks such as IEEE 802.11, IEEE 802.15, IEEE 802.16 and sensor networks. WMNs which is based on ad hoc network are on research and developing to enhance WLANs, WPANs, or WMANs. WMNs can offer environment to serve human, service to person area, campus, and metro. But WMNs has many problems to solve about enhancing performance and generalization. Among them, Existing protocol layers has many problems enhancing to optimize WMNs. This document issues problems about WMNs in protocol layer and suggest the solutions. Also, suggests the requirements and the methods of QoS supporting issue. 무선 메쉬 네트워크는 이동성을 가지며 메쉬 클라이언트와 메쉬 라우터로 구성되어 있다. 무선 메쉬 네트워크는 IEEE 802.11, IEEE 802.15, IEEE 802.16, 센서 네트워크와 같이 이기종 네트워크와의 통신이 가능한 네트워크 환경이다. 무선 메쉬 네트워크는 애드 혹 네트워크를 기본으로 WLANs, WPANs, WMANs 등이 가지고 있는 한계를 극복하기 위한 많은 연구와 개발이 진행되고 있다. 무선 메쉬 네트워크는 개인, 지역, 학교, 거대 도시까지 서비스 영역의 제약을 넘어서 수많은 서비스를 제공할 수 있는 기반을 제공한다. 하지만, 무선 메쉬 네트워크의 성능을 극대화하고 보편적으로 적용하기 위해서는 해결해야 할 많은 부분들이 있다. 그 중에서 기존의 프로토콜 계층이 가지고 있는 문제점들은 무선 메쉬 네트워크를 최적화하기 위해서는 개선되어야 할 부분들이 많이 있다. 본 논문은 무선 메쉬 네트워크를 지원하기 위해 발생하는 이슈들과 여기서 발생하는 문제점을 지적하고 대응방안에 대한 방향을 제시한다. 그리고 QoS를 지원을 위한 요구사항 및 이에 대한 방향도 제시한다.

무선 메쉬 네트워크에서 성능향상을 위한 채널접속 제어 방법

이순식,윤상만,이상욱,전성근,김응수,이우재,Lee, Soon-Sik,Yun, Sang-Man,Lee, Sang-Wook,Jeon, Seong-Geun,Kim, Eung-Soo,Lee, Woo-Jae 한국정보통신학회 2010 한국정보통신학회논문지 Vol.14 No.3

무선 메쉬 네트워크 기술은 유선과 비슷한 전송속도를 가지는 무선 통신 기술을 이용해서 무선 백본망으로 사용하는 기술을 의미하며 토폴로지는 메쉬 형태를 갖는다. 이러한 형태는 Ad-hoc 네트워크와 유사한 점을 가지고 있지만 운용 목적과 내부 동작에서 다르기 때문에 채널접속 제어방법을 설정하기 위한 메트릭이 요구 된다. 본 논문에서는 데이터를 전달하기 위한 효율적인 채널접속 제어방법을 개선하여 무선 메쉬 네트워크의 성능을 향상시키는 방안에 대하여 제안하였으며 음영과 노출 메쉬 클라이언트, 채널 독점 등을 통해서 제안한 방법에 대한 성능을 분석하였다. The Wireless Mesh Network uses a wireless communication technology with transmission rates simular to a cable which is used as a backbone networks. The topology structure is in a Mesh form which resembles an Ad-hoc networks. However, a metric is needed in order to set the channel access control method to operate intentions and interior motions are different. In this document, an efficient channel for delivering datas to improve access controls to a wireless mesh networks. The improved performance of the proposed plan is for a hidden and exposed mesh client through an exclusive channels to perform a proposed and analyzed methods.

Dy₂O₃를 첨가한 (Ba,Sr,Ca)TiO₃ 후막의 구조 및 전기적 특성 연구

노현지,박상만,윤상은,이성갑,Noh, Hyun-Ji,Park, Sang-Man,Yun, Sang-Eun,Lee, Sung-Gap 한국전기전자재료학회 2007 전기전자재료학회논문지 Vol.20 No.8

In this study, we investigated the effects of structural and electrical properties of $(Ba_{0.6},\;Sr_{0.3},\;Ca_{0.1})TiO_3$ thick films with variation $Dy_2O_3$ contents. $(Ba_{0.6},\;Sr_{0.3},\;Ca_{0.1})TiO_3$ powders, prepared by the sol-gel method, were mixed organic vehicle. The BSCT thick films doped with 0.1, 0.3, 0.5, 0.7 mol% $Dy_2O_3$ were fabricated by the screen-printing techniques on the alumina substrates and the structural and dielectric properties were investigated with variation of $Dy_2O_3$ doping contents. All BSCT thick films were sintered at $1420^{\circ}C$, for 2hr. In the TG-DTA analysis, the formation of the polycrystalline perovskite phase was observed at around $670 ^{\circ}C$. In the XRD analysis, all BSCT thick films showed the cubic perovskite structure. The average thickness of BSCT thick films was approximately $65{\mu}m$. The Curie temperature decreased with increasing $Dy_2O_3$ amount. The relative dielectric constant and dielectric loss of BSCT thick films doped with $Dy_2O_3$ 0.1 mol% were 6267 and 2.6 %, respectively.