• Proceedings of the Korean Vacuum Society Conference
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• 2015.08a
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• pp.91-91
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• 2015

반도체 공정의 발전에 의해 최근 생산되는 메모리 등은 십 수 나노미터까지 좁아진 선 폭을 갖게 되었다. 이러한 이유로, 기존에는 큰 문제를 발생시키지 않던 나노미터 영역의 입자들이 박막 증착 공정과 같은 반도체 제조공정 수율을 저감시키게 되었다. 따라서 오염입자의 유입을 막거나 제어하기 위해 transmission electron microscopy (TEM)나 scanning electron microscopy (SEM)과 같은 전자현미경을 활용한 비 실시간 입자 측정 방법 및 광원을 이용하는 in-situ particle monitor (ISPM) 및 전기적 이동도를 이용한 scanning mobility particle sizer (SMPS) 등 다양한 원리를 이용한 실시간 입자 측정방법이 현재 사용중에 있다. 이 중 진공 내 입자의 수농도를 측정하기 위해 개발된 particle beam mass spectrometer (PBMS) 기술은 박막 증착 공정 등 chemical vapor deposition (CVD) 방법을 이용하는 진공공정에서 활용 가능하여 개발이 진행되어 왔다. 본 연구에서는 PBMS의 한계점인 입자 밀도, 형상 등의 특성분석이 용이하도록 PBMS와 scanning electron microscopy (SEM), 그리고 energy dispersive spectroscopy (EDS) 기술을 결합하여 입자의 직경별 개수농도, 각 입자의 형상 및 성분을 함께 측정 가능하도록 하였다. 협소한 반도체 제조공정 내부 공간에 적용 가능하도록 기존 PBMS 대비 크기 또한 소형화 하였다. 각 구성요소인 공기역학 집속렌즈, electron gun, 편향판, 그리고 패러데이 컵의 설치 및 물리적인 교정을 진행한 후 입자발생장치를 통해 발생시킨 sodium chloride 입자를 상압 입자 측정 및 분류장치인 SMPS 장치를 이용하여 크기별로 분류시켜 압력차를 통해 PBMS로 유입시켜 측정을 진행하였다. 나노입자의 입경분포, 형상 및 성분을 측정결과를 토대로 장치의 측정정확도를 교정하였다. 교정된 장치를 이용하여 실제 박막 증착공정 챔버의 배기라인에서 발생하는 입자의 수농도, 형상 및 성분의 복합특성 측정이 가능하였으며, 최종적으로 실제 공정에 적용가능하도록 장치 교정을 완료하였다.

• Applied Microscopy
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• v.30 no.4
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• pp.367-376
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• 2000

The observation using an electron microscope shows that the maturation of the oocyte of African giant snail, Achatina fulica, proceeds over three stages. The oocyte of stage 1 is a small elliptic cell $(220\times400{\mu}m)$ whose light nucleoplasm contains two nucleoli. In its cytoplasm, a number of mitochondria, rough endoplasmic reticula, and ribosomes are found, while yolk granules are not. The nucleus of the oocyte of stage 2 is relatively large in comparison with the volume of cytoplasm, and contains one nucleolus. In the nuclear envelope comprising inner and outer double membrane, there are found a lot of nuclear pores for materials to pass through. A number of mitochondria, Golgi complex and lipid yolk granules appears in the cytoplasm, and proteinous yolk granules begin to form and mature in the vacuoles of various sizes ($0.8\sim3.0{\mu}m$ in diameter). The oocyte of stage 3 has an enlarged nucleolus. Material transportation through nuclear pore is not found any longer. The cytoplasm in this stage is filled with proteinous and lipid yolk granules. The microvilli are developed around the egg plasma membrane.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.18 no.4 s.119
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• pp.379-388
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• 2007

This paper presents a real-time respiration and heartbeat detector comprised of a 1.6 GHz single-channel Doppler sensor and analog/digital signal processing block for remote vital sign detection. The RF front end of the Doppler sensor consists of an oscillator, mixer, low noise amplifier, branch-line hybrid and patch antenna. We apply artificial transmission lines(ATLs) to the branch-line hybrid, which leads to a size reduction of 40 % in the hybrid, while its performance is very comparable to that of a conventional hybrid. The analog signal conditioning block is implemented using second order Sallen-Key active filters and the digital signal processing block is realized with a LabVIEW program on a computer. The respiration and heartbeat detection is demonstrated at a distance of 50 cm using the developed system.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.39 no.3
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• pp.174-180
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• 2003

This study investigated the size selectivity of the round traps for greenling (Hexagrammos otakii) in the western sea of Korea. The selection curve for the greenling from the experiments on Oct. 2000 and Ar. 2001 was fitted by Kitahara's method to a polynomial equation and two parameter logistic selection curve. The selectio curve of the latter was more reasonable than that of the former. The equation of selectivity curve obtained using a logistic function with least square method was , s(R)=1/1+exp(-1.1169R+6.4565), where R=1/m, and 1 and m are total length and mesh size, respectively. The size selectivity curve showed that the current regulated mesh size(35mm) in case of the round trap was close to the L50 (37.0mm) of the selection curve for the biological minimum length (21.4cm) of the greenling.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.11 no.10
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• pp.3988-3997
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• 2010

Shotcrete was a mortar or concrete that is pneumatically projected at high velocity onto a subject. It has been applied for tunneling, underground big-spaces, slope stabilization. Shotcrete is increasing use in structure repair. The dry-mix shotcrete require a smaller equipment, easy maintenance, possible of very-earlystrength materials than wet-mix shotcrete, which make this process attractive and economic for structural repairs. It is common practice core compressive strength to the dry-mix shotcrete quality control. This test is very difficult estimating eraly-strength of Very-Early-Strength Dry-Mix Shotcrete. The purpose of this research was to analyze the correlation of test results among cube test, core test, pullout test and maturity. The correlationship analysis of test results among cube test, core test, pullout test and maturity showed more than 90%.

• Korean Journal of Environmental Agriculture
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• v.16 no.2
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• pp.166-169
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• 1997

The fresh food waste compost, which was composted in a small bin for average one month, was cured in a pile in the field for seven months. The pile was turned once a month. The various components of the compost were investigated for the curing period. The maximun temperature rised to $65^{\circ}C$ after curing of four months. The moisture content of the compost droped to 61.7% after twelve months. After that, the rainfall affected very much the moisture content of the compost. pH of the compost increased gradually to 8.92 for curing. Ash content rised continually to 60.5% for curing. However, it did not exceed 25% ash content, which is the by-product limit value. The accumulation of the inorganic components occured and most of the heavy matals except for Cd generally were accumulated as curing proceeded.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.23 no.1
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• pp.59-68
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• 2009

Fuel cell generators as the distributed generation system with a few hundred watt$\sim$a few hundred kilowatt capacity, can supply the high quality electric power to user as compared with conventional large scale power plants. In this paper, PEMFC(polymer electrolyte membrane fuel cell) generator as micro-source is modelled by using PSIM simulation software and DSP based fuel cell hardware simulator based on the PSIM simulation model is implemented. The relation of fuel cell voltage and current(V-I curve) is linearized by first order function on the ohmic area in voltage-current curve of fuel cell. The implemented system is composed of a PEMFC hardware simulator, an isolated full bridge dc boost converter, and a 60[Hz] voltage source PWM inverter. The voltage-current-power(V-I-P) characteristics of the implemented fuel cell hardware simulator are verified in load variation and transient state and the 60[Hz] output voltage sinusoidal waveform of the PWM inverter is investigated under the resistance load and nonlinear diode load.

• The Transactions of the Korea Information Processing Society
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• v.2 no.1
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• pp.66-74
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• 1995

A 8-bit 15MHz CMOS subranging Analog-to-Digital converter for high-speed, low-power consumption applications is described. Subranging, 2 step flash, A/D converter used a new resistor string and a simple comparator architecture for the low power consumption and small chip area. Comparator exhibites 80dB loop gain, 50MHz conversion speed, 0.5mV offset and maximum error of voltage divider was 1mV. This Analog-to-Digital converter has been designed and fabricated in 1.2 m N-well CMOS technology. It consumed 150mW power at ＋5/-5V supply and delayed 65ns. The proposed Analog-to-Digital converter seems suitable for high- speed, low-power consumption, small area applications and one-chip mixed Analog- Digital system. Simulations are performed with PSPICE and a fabricated chip is tested.

• The Optical Journal
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• s.158
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• pp.48-51
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• 2015

2013년 12월 2일에 아마존의 제프 베조스가 드론을 통하여 30분 배송을 실현하겠다고 배송 테스트를 했다. 고객이 주문한 물건을 플라스틱 보호 박스에 잘 담아 드론에 싣고 고객의 마당에 떨구고 돌아오는 모습을 담았다. 미국의 모든 언론은 드론에 대하여 대서특필하였고, 30분 배송의 실현 가능성에 대한 논쟁을 벌였다. 그 해 연말, 아마존은 쇼핑특수를 누렸다. 돈 안들이고 광고를 독특하게 한 셈이다. 나는 개인적으로 아마존의 드론 배달을 '쇼'라고 생각했다. 고객들의 주거 형태, 드론 비행의 법적인 문제, 드론으로 발생되는 사고, 사람들의 인식 등등 문제가 산적해 있기 때문이다. 그런데 2015년 초부터 알리바바는 1시간 내 차(Tea) 배달 서비스를 상하이와 광저우에서 테스트 중이라고 한다. 또한, DHL이 바다를 건너 섬으로 의약품을 수송하는 시연을 했다. CES 2015에서는 드론 전용관을 만들어 많은 사람들과 언론의 주목을 받았다. 마치 꿈과 같던 것이 실현되는 느낌이었다. 드론을 띄울 수 있는 권리 외에도 드론을 떨어뜨릴 권리도 논의되고 있다. 일본 총리관저에 드론이 떨어지기도 했다. 미국에서는 소형 드론에 폭발물을 탑재하여 타격하는 영상을 보이기도 했다. 개인적인 프라이버시가 존중되어야 할 가정집 위로 카메라가 달린 드론이 날아다니기도 하며, 재소자들의 수감시설에 마약과 담배를 실어 나르다 적발되기도 하였다. 부작용도 만만치 않다는 이야기이다. 나는 학생들에게 100만 원이 넘는 드론을 구매하여 주었더니, 동력인 배터리가 20분밖에 안 된다고 투덜거린다. 영상에 그리고 비행에 소리가 너무 난다고 또 투덜거린다. 바람에 밀려 조정이 어렵다고 또한 투덜투덜하더니만, 결국은 비행 중 조절이 안 되고 떨어져서 결국 박살이 났다. 내구성이 약하다는 이야기는 곧 전반적으로 아직 한계가 있으며 개선할 점이 많다는 의미이다. 위와 같은 부정적인 요인에도 불구하고 드론은 새로운 서비스의 융합으로 신시장이 기대되는 만큼 많은 국가와 기업들이 주목하고 있다. 미국가전협회(CEA)는 2015년 세계 드론 시장이 2014년보다 무려 55% 성장한 1억 3,000만 달러의 규모로 성장하고 5년 뒤에는 10억 달러까지 증가할 것으로 전망하면서 드론 산업의 가능성을 높게 평가하기도 했다.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.46 no.2
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• pp.175-181
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• 2018

Electric pump system is new technology for next generation propulsion unit. The system has simple structure which dose not need gas generator, injector and turbine and might better pump for low cost and low payload rocket. Therefore, this paper suggests conceptual design of electric-pump Permanent-Magnet Synchronous Motor (PMSM) which has 50 kW & 50,000 RPM for rocket. To satisfy the system's requirement, electromagnetic analysis is conducted for suitable inner and outer diameter of stator and rotor which uses 4000 Gauss cylinder magnet and Inconel 718 can to fix whole rotor. Futhermore, to confirm rotational vibration, rotordynamics analysis is conducted. By this analysis, Campbell diagram is printed. From the diagram, natural frequency could be determined for the only motor and dynamo meter test bench.