• 대한전기학회:학술대회논문집
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• 대한전기학회 2004년도 하계학술대회 논문집 C
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• pp.1874-1875
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• 2004

A high rate deposition sputtering process of magnesium oxide thin film in oxide mode has been developed using a 20 kW unipolar pulsed power supply. The powersupply was operated at a maximum constant voltage of 500 V and a constant current of 40 A. The pulse repetition rate and the duty were changed in the ranges of 10 ${\sim}$ 50 kHz and 10 ${\sim}$ 60 %, respectively. The deposition rate increased with increasing incident power to the target. Maximum incident power to the magnesium target was obtained by the control of frequency, duty and current. The deposition rate of a moving state was 9 nm m/min at the average power of 1.5 kW. This technique is proposed to apply high through-put sputtering system for plasma display panel.

• 접착 및 계면
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• 제7권1호
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• pp.23-29
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• 2006

Polymer thin films of pentafluorostyrene (PFS) were prepared by RF plasma (13.56 MHz) polymerization in continuous wave (CW) mode, as a function of plasma power and monomer pressure. Conditions for film preparation were optimized by measuring the solvent resistance of plasma polymer thin films in DMAc, NMP, THF, acetone and chloroform, as well as by evaluating the optical clarity via UV-VIS measurements. Pulsed mode plasma polymerization was also utilized to enhance the optical properties of the films by varying the period of on-time and duty cycle. Finally, the films were subjected to refractive index measurements and analyzed by ${\alpha}$-step, TGA and FT-IR.

• 한국재료학회:학술대회논문집
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• 한국재료학회 2011년도 춘계학술발표대회
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• pp.19.2-19.2
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• 2011

ZnO nanowires have been fabricated by vapor-liquid-solidification with hot-walled pulsed laser deposition method. The diameter of ZnO nanowire has been systematically controlled simply by changing the thickness of Au catalyst. Field effect transistors with different diameter have been fabricated by using photolithography and e-beam lithography. The threshold voltage of ZnO nanowire FET showed enhanced mode and depleted mode depending on the diameter of ZnO nanowires. This is mainly due to the change of the carrier concentration depending on the size of nanowires. We have fabricated ZnO nanowire inverters using nanowire FETs. This simple method to fabricate ZnO nano-inverter will be useful to open the possibility of ZnO nanoelectronic applications.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2009년도 춘계학술대회 논문집
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• pp.351-352
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• 2009

On-demand ejection of ultra-fine droplets that uses both electrohydrodynamic (EHD) force and mechanical actuation is presented. The liquid meniscus was controlled by a piezoelectric actuator and droplets were ejected by EHD force. Through these effects, it was possible to obtain a high operational jetting frequency of 5kHz with a short delay-time (about 50 us) when compared with existing on-demand EHD jetting methods, such as the pulsating jet mode (3-10 msec) and the pulsed-voltage cone-jet mode(3.6 msec). Also, we obtained ultra-fine droplets at a volume that was at the femto-liter level simultaneously. The jetting characteristics were examined for both hydrophobicity and hydrophilicity of the surface of a capillary.

• 한국전기전자재료학회논문지
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• 제22권10호
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• pp.897-903
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• 2009

We have designed the backward wave oscillator. A power-pulsed generator oscillated at 24 GHz has higher frequency than current one. It is very inportant to prevent microwave from going into the beam diode, since intence microwave will harmfully affect beam generation. Due to the axial mode operation, there exist a critial value of beam energy for the oscillation. By changing the condition at the SWS end, an enhanced performance of the K-band oversized BWO is observed in a low magnetic field region about 0.8T.

• 한국분무공학회지
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• 제27권1호
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• pp.26-35
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• 2022

Electrospray is a method of atomizing fluid using high voltage supply and capable of generating continuous flow and coherent size of droplets. Electrical system and properties of fluids has enabled electrospray to have various spray modes. However, its studies have been confined only in Cone jet, which is more stable and easier to manipulate droplets' size than other spraying modes. Therefore, it is necessary to investigate and compare other spraying modes based on experimental parameters and physical properties of fluids. This research paper identified nine different spray modes. It was found out that Sauter Mean Diameter (SMD) is proportional to flow rate of fluids and maximum difference among spray modes was 1.7 times. On the other hand, SMD standard deviation had low variations on specific flow rates of fluids. Pulsed jet mode recorded the largest SMD standard deviation, while Spindle recorded the lowest.

• 한국재료학회:학술대회논문집
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• 한국재료학회 2003년도 추계학술발표강연 및 논문개요집
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• pp.55-55
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• 2003

Ferroelectric 물질은 고유전성, 자발분극과 전기장에 따른 유전상수의 변화 등의 특성을 가지고 있으므로 많은 연구가 진행중이다. 이러한 ferroelectric 물질의 유전 특성에 미치는 요소로는 물질의 조성비, 박막의 스트레스, 결정성 등이 있다. 특히 스트레스에 대한 연구가 활발히 진행중이다. 본 연구에서 산화물 인공격자를 이용하여 단일박막에서 얻을 수 없는 격자변형도를 얻어 격자 변형이 박막의 유전특성에 미치는 영향을 연구하였다. BaTiO$_3$ (BTO)/SrTiO$_3$ (STO) 산화물 인공격자를 Pulsed laser deposition (PLD)법으로 (La,Sr)CoO$_3$ 전극이 코팅된 MGO (100) 단결정 기판위에 증착시켰다. 적층 주기에 변화를 주어 BTO와 STO 각각 1.01~1.095와 0.925 ~ 1.003의 단일 막에서는 얻을 수 없는 격자 변형도를 얻었다. 이 실험적 데이터를 기초로 하여 density functional theory (DFT)라고 불리는 범함수밀도론를 기초한 제일원리적 계산 방법을 통하여 격자 변형된 SrTiO$_3$의 구조적, 전기적 특성을 계산하였다. SrTiO$_3$와 BaTiO$_3$ 격자의 안정성을 분석하기 위하여 Vienna Ab-intio Simulation Package (VASP) code가 사용되었다. SrTiO$_3$와 BaTiO$_3$ 산화물 격자의 안정성 분석 후, frozen-phonon 계산 방법을 사용하여 zone-centered optical phonon mode가 계산되었으며, mode effective charge는 Berry-phase polarization 으로부터 얻어졌다. SrTiO$_3$ 격자가 격자변형이 일어나지 않은 상태로부터 c/a= 0.985로 격자 변형 이 일어남에 따라 optical phonon mode는 점차 hardening되었다. BaTiO$_3$ 격자의 경우 SrTiO$_3$ 격자와는 달리 격자 변형이 1.01~1.023으로 진행됨에 따라 optical phonon mode의 증가를 가져왔으나 Born effective charge의 증가하였으며, 더 이상 격자 변형이 진행됨에 따라 optical phonon mode의 감소를 가져왔으나 Born effective charge의 증가 유전상수는 증가했다. 격자 변형이 SrTiO$_3$ 와 BaTiO$_3$ 산화물 격자의 optical phonon mode와 Born effective charge에 크게 영향을 미쳤다.

• 한국항행학회논문지
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• 제10권2호
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• pp.173-180
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• 2006

비행체 탑재 레이다는 기상에 관계없이 전천후로 비행체의 안전항행, 임무감시, 사격통제, 충돌회피, 이착륙 등 비행에 필수적인 항공장치이다. 본 논문에서는 비행체 탑재 다중 모드 펄스 도플러 레이다 시험 모델의 설계, 제작 및 비행시험 결과를 제시한다. 레이다 시스템은 안테나부, 송수신부, 신호처리부와 전시부의 4-LRU(Line Replacement Unit)로 구성되며, 개발기술은 평판 슬롯 배열 안테나, TWTA 송신기, coherent I/Q detector, 디지털 펄스 압축, 도플러 FFT 필터를 기반으로 한 DSP, 적응 CFAR, TWS 추적 처리기, 비행정보 IMU 및 도플러 추정보상 기법을 포함한다. 개발된 레이다 시스템의 설계 성능은 다양한 헬기탑재 비행시험을 통하여 기능 및 성능을 확인하였다.

• Journal of Preventive Medicine and Public Health
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• 제38권2호
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• pp.182-188
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• 2005

Objectives: This study was undertaken to investigate the source of infection and mode of transmission of shigellosis, which occurred sporadically among residents and students in a subcounty of Cheongwon county, Chungbuk province, Korea, from June 4 to July 3 2003. Methods: 692 subjects completed a questionnaire and provided a swab for microbiological examinations,and 7 environmental specimens were examined for bacterial organisms. PFGE (pulsed-field gel electrophoresis) and fingerprinting were performed to find the genetic relationship among the temporally associated sporadic isolates. Results: A total of 29 patients had symptoms consistent with the case definition, with 13 confirmed and 16 suspected cases. The frequency of diarrhea was 6 times or more a day (80.8%), with a duration of 1 to 4 days (88.5%) in most cases. The most common symptoms accompanying the diarrhea were fever (80.9%) followed by abdominal pain (76.9%), headache (65.4%), chill (61.5%), vomiting (46.2%) and tenesmus (15.4%). The epidemic curve was characteristic of a person-to-person transmission. The PFGE and fingerprinting demonstrated identical or similar DNA patterns among the 3 Shigella sonnei isolates (A51, A53 and A61 types) found in this outbreak. Conclusion: A genetically identical strain of S. sonnei was estimated to be the cause of this outbreak, and the mode of transmission was most likely person-to-person.

• 한국전자파학회논문지
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• 제20권3호
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• pp.264-272
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• 2009

본 논문에서는 다수의 MMIC 전력증폭기 칩과 박막 기판을 결합하여 MIC 모듈을 구성함으로써 Ka-대역 중심주파수에서 10 W의 출력 전력을 낼 수 있는 전력증폭기 모듈을 설계 및 제작하였다. 전력증폭기 모듈의 제작에는 밀리미터파 대역에 적합한 수정된 형태의 윌킨슨 전력분배기/합성기를 사용하였고, 모듈의 구성 과정에서 발생할 수 있는 손실을 줄이고 공진을 억제하기 위해 CBFGCPW-Microstrip 천이 구조를 활용하였다 전력증폭기 모듈은 총 7개의 MMIC 칩으로 구성되었으며 MMIC 칩을 펄스 모드로 동작시키기 위해 칩의 게이트에 펄스 전압을 인가하는 게이트 전압 제어기가 설계되고 적용되었다. 제작된 전력증폭기 모듈의 측정 결과 58 dB의 전력 이득과 39.6 dBm의 포화 출력 전력을 얻을 수 있었다.