• 한국전기전자재료학회논문지
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• 제18권5호
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• pp.396-400
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• 2005

Carbon nanotubes (CNTs) have been well known as electron emitters for field emission applications like FEDs. In this work, we propose as new application a vacuum sensor using CNTs and discuss its current-voltage characteristics as a function of vacuum pressure. The proposed sensor, based on electrical discharge theories in air gap well-known as Townsend theory and as Paschen's law, works by figuring out the variation of the dark current and the initial breakdown voltage depending on the vacuum pressure of air which can ionize through collisions with the electrons accelerated by high electric field.

• 대한기계학회논문집B
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• 제24권7호
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• pp.924-929
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• 2000

This paper addresses a new technique of measuring the mean flow velocity over the cross sectional area of the pipe using sound field reconstruction. When fluid flows in the pipe and two plane waves propagate oppositely through the medium, the flow velocity causes the change of wave number of the plane waves. The wave number of the positive going plane wave decreases and that of negative going one increases in comparison to static medium in the pipe. Theoretical backgrounds of this method are introduced in detail and the measurement of mean flow velocity using the sound field reconstruction is not affected by velocity profile upstream of microphones.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1998년도 하계학술대회 논문집 A
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• pp.164-166
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• 1998

This paper presents the results of the measured pressure-rise and the analyzed results of the cold gas flow-field in a 72.5kV 20kA gas circuit breaker for the electrical railway system. The analysis of cold gas flow field and the calculation of electric field strength have been performed in 3 types of interrupters and the low current interruption capability has been estimated for each of the gas circuit breaker considering the opening speed, the nozzle shape and the stroke length.

• 한국전기전자재료학회논문지
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• 제16권8호
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• pp.723-730
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• 2003

The CN(carbon nitrogen) nanofibers were formed by HIP(high isostatic pressure) process. From the field emission measurement, CN nanofibers shows an excellent characteristics of emitter, better than CNTs and carbon nanofibers. The structures obtained can be divided into three groups : bamboo-like fibers, corrugated structures and bead necklace-like fib res. Emission properties of CN nanofibers were investigated for spacing, between anode and cathode, variation. Turn-on fields was 1.4 v/$\mu\textrm{m}$. The time reliability and light emission test were carried out for about 100 hours. We suggest that CN nanofibers can be possibly applied to the high brightness flat lamp because of low turn-on field and time reliability

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2002년도 봄 학술발표회 논문집
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• pp.509-516
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• 2002

Rainfall-induced landslides in a weathered granite soil slope have mostly relative shallow slip surfaces above the groundwater table The pore-water pressure of soil above the groundwater table is usually negative. This negative pore-water pressure(or matric suction) has been found to make a large contribution to the slope stability. Therefore, the variation of in-situ matric suction profiles with time in a soil slope should be understood. In this study, a field measurement program was carried out from June to August, 2001 to monitor in-situ matric suctions and volumetric water contents in a weathered granite soil slope. The influence of climatic conditions on the variation of in-situ matric suctions could be found to decrease rapidly with depth. It could be found that decrement of matric suction induced by precipitation is affected not only by the amount and duration of rainfalls but also by the initial matric suction just prior to rainstorms. The soil-water characteristic from the field monitoring tends toward the wetting path of SWCC obtained from the laboratory test.

• Journal of the Optical Society of Korea
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• 제17권1호
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• pp.50-56
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• 2013

Optical-fiber electronic speckle pattern interferometry (ESPI) is a non-contact, non-destructive examination technique with the advantages of rapid measurement, high accuracy, and full-field measurement. The optical-fiber ESPI system used in this study was compact and portable with the advantages of easy set-up and signal acquisition. By suitably configuring the optical-fiber ESPI system, producing an image signal in a charge-coupled device camera, and periodically modulating beam phases, we obtained phase information from the speckle pattern using a four-step phase shifting algorithm. Moreover, we compared the actual defect size with that of interference fringes which appeared on a screen after calculating the pixel value according to the distance between the object and the CCD camera. Conventional methods of measuring defects are time-consuming and resource-intensive because the estimated values are relative. However, our simple method could quantitatively estimate the defect length by carrying out numerical analysis for obtaining values on the X-axis in a line profile. The results showed reliable values for average error rates and a decrease in the error rate with increasing defect length or pressure.

• 터널과지하공간
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• 제13권2호
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• pp.125-137
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• 2003

본 연구에서는 복개 터널구조물의 라이닝 설치 후 되메움 성토과정에서 라이닝에 발생하는 토압 크기및 분포 등의 거동특성을 파악하기 위하여 실제 복개 터널구조물의 시공현장에서 현장 계측을 수행하였다. 현장계측은 토압계, 콘크리트 응력계, 철근 응력계의 세 종류의 계측기를 매설하여 측정하였다. 토압계는 라이닝의 원주방향을 따라 매설하며 터널 라이닝에 작용하는 외부 하중을 측정하였다. 세 개의 토압계는 천단부와 터널 횡단면의 중심축을 기준으로 좌 · 우측 어깨부 45도 지점에 각각 설치하였다. 철근 응력계는 라이닝에 배근된 복철근에 한 셋트씩 세 곳에 설치하였으며 설치 위치는 토압계의 설치 위치와 동일하게 하였다. 콘크리트 응력계는 천단부 상단 압축측 단면의 한 곳에만 설치하였다. 현장 계측 결과를 이용하여 되메움 성토 과정에 발생하는 라이닝의 변형과 라이닝 외부 작용 토압의 거동 특성을 살펴보았으며, 이론적 추론으로 계측결과의 타당성을 검토하였다

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2002년도 춘계학술대회논문집
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• pp.1067-1070
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• 2002

This paper deals with the factors affecting measurement of sound insulation performance of the ceiling panels. The factors to be experimently examined are as follows: sound diffuseness of the test room by investigating sound pressure distribution, Reverberation time, and influence of speaker location on measured results. Based on the investigation of sound pressure distribution over measuring points, it can draw a conclusion that rectangular shaped rooms as test rooms have a serious problem associated with the diffuse sound field.

• 한국지반환경공학회 논문집
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• 제9권5호
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• pp.15-20
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• 2008

연약지반의 압밀 침하는 침하속도를 예측하거나 수치 해석적 기법에 대한 것에 집중되어 있으며 실내시험으로부터 추정된 압축특성에 대해 계측결과 등을 이용하여 재평가하려는 시도는 매우 적다. 영산강 하구지역에서 분포하는 해성점토에 대하여 실내 표준 압밀시험, 현장에서 약 3년 동안 축적된 층별침하계, 간극수압계, 지하수위계의 계측결과를 바탕으로 한 현장계측 압밀곡선, 그리고 침하해석 프로그램인 PLAXIS를 이용한 연직 배수재가 설치된 지반의 성토이력에 따른 역 해석으로 압축성을 비교 하였다. 여러 제약조건에도 불구하고 현장계측결과에 의해 평가된 현장계측 압밀곡선은 표준압밀시험 결과와 비교적 잘 일치하였다.

• Wind and Structures
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• 제4권3호
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• pp.247-260
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• 2001

In the last three decades several comprehensive field measurement programs have produced significant insight into the wind effects on low-rise structures. The most notable and well published of these efforts are measurements being collected at the Wind Engineering Field Laboratory (WERFL) at Texas Tech University, measurements on low-rise structures in Silsoe, England and measurements on groups of low-rise structures collected in Aylesbury, England. Complementary to these efforts, an additional full-scale field investigation program has recently collected meteorological, pressure, strain and displacement data on a low-rise structure in Southern Shores, North Carolina. To date over seventy-five hundred data sets have been collected at the Southern Shores site in a variety meteorological conditions up to and including hurricane-force winds. This paper provides details of the system, its development, and preliminary assessment of its performance. A description of the field site, the instrumented structure, and the instrumentation system is provided. In addition, an example of the data collected during three hurricanes is presented. The primary goal of this paper is to provide the reader with the necessary technical details to appropriately interpret data from this experiment, which will be presented in future publications currently under development.