• 공업화학
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• 제34권1호
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• pp.9-14
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• 2023

본 논문에서는 용액의 이온 농도 측정이 가능한 나피온 폴리머(Nafion polymer) 코팅 기반 2상 금 전극의 임피던스(Impedance) 센서를 개발하였다. 스퍼터링(Sputtering) 공정을 통해서 제작된 금 전극의 표면을 나피온 폴리머를 사용하여 표면 개질 하였다. 상기 제작된 전극은 분극 현상 제어가 가능하여 전기화학적 신호를 안정적으로 측정할 수 있도록 하였다. 분광학과 전자주사현미경 관찰을 통하여 박막의 나피온 폴리머 코팅을 확인하였다. 나피온 코팅이 된 전극은 기존 금 전극에 비해 안정적인 임피던스 신호를 보여 주었으며, 표준 염화나트륨(NaCl) 용액 사용 시 임피던스 센서의 신뢰성 높은 검정 곡선(R² = 0.983)을 나타내었다. 또한, 임피던스 센서는 상용화 전도도 장치와 인공 눈물의 이온 농도 측정 비교 실험을 진행하였으며, 유사한 결과값을 확인하였다.

• 한국전자통신학회논문지
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• 제5권4호
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• pp.435-442
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• 2010

자동차의 와이퍼 브레이드 성능은 자동차 안전성 확보에 크게 기여한다. 유리면에 접착된 먼지나 이물질 등을 제거하는 기능을 확보하기 위해 와이퍼 브레이드는 닦임성, 내구력, 내열 저온 내오존성 내화학성이 높아야 할 뿐만 아니라 소음이 적어야 한다. 이와 같이 와이퍼의 기능 개선을 위해서는 와이퍼의 성능을 평가하고 분석할 수 있는 시스템 장비가 필수적이다. 본 논문에서는 자동차의 와이퍼 누름압을 측정하는 시스템의 개발을 위해 누름압 센서에서 출력되는 신호를 받아 퍼스널 컴퓨터에 전달하는 아날로그 디지털 변환기를 설계하고자 한다. 설계한 ADC는 빠른 동작 속도를 얻으면서 전체 시스템의 면적 및 전력소모를 최적화하는 구조인 파이프라인 ADC이다.

• 한국추진공학회지
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• 제18권2호
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• pp.16-26
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• 2014

연소 시, 입자상 물질에 대한 HTPB/AP 계열 고체추진제의 음향특성을 정량화하기 위해서, Pulsed DB/AB T-burner 실험을 수행하였다. 추진제 전면에서 동시 점화를 위해, 대상 고체추진제보다 연소속도가 빠른 다른 고체추진제를 대상 추진제 앞면에 부착하였다. 다량의 알루미늄이 포함된 고체추진제에서는 T-burner 내부에서 만들어진 압력섭동에 의한 음향학적 불안정성이 매우 빠르게 감쇠되었고, 반대로 알루미늄이 포함되지 않은 고체추진제에서는 상대적으로 매우 느리게 감쇠함을 확인하였다. 본 연구에서는 음향학적 특성값들을 정량화하였고, 이를 통해 연소응답 특성을 계산하였다.

• 한국공작기계학회논문집
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• 제10권2호
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• pp.29-37
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• 2001

The application of laser in pipelines was started from the base of using laser in nuclear facilities industries and power plants. Because laser can be delivered to a remote area without any difficulties, the application of laser in many industries can solve many difficulties from limitation of access in danger area and reduced the risks of workers. Therefore, we developed a new experimental technique to measure internal defects of pressure vessels with a combination of shearog-raphy and image processing technique. Conventional NDT methods have been taken relatively much time, money and manpower because of performing as the method of contact with objects to be inspected. But digital shearography is laser-based optical method which allows full-field observation of surface displacement derivatives. This method has many advantages in practical use, such as low sensitivity to environmental noise, simple optical configuration and real time mea-surement. In this paper, we find the optimum shearing magnitude with EFM and experiment and measured internal crack length of the pressure vessels at a real time and estimated the error of the results.

• 대한기계학회논문집B
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• 제24권7호
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• pp.895-906
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• 2000

A three dimensional linear frequency-domain lifting surface panel method was used for the aerodynamic analysis of axial flow type micro-fans. As proven by the duct modeling, the tip clearance of the micro-fans tested is large enough to ignore the calculated effect of the duct system. As the numerical results and experimental data agreed well in the operating point region, the method was applicable in the parametric studies to determine the design parameters of axial flow fans. Experiments on micro-fans were carried out based on KS B 6311. The newly designed micro-fan showed improvements in both static pressure rise and volumetric flow rate compared to the existing fans at a given operating condition. No detection of surging and the smooth characteristic curve proved the improvement in performance. To reduce the fan noise in the fan design, it was necessary to make use of the frequency spectrum analysis data. Measurement of sound pressure level for micro-fans was conducted based on KS B 6361 and KS A 0705. The peak - which occurs at blade passage frequency and its higher harmonics due to the fan noise - was not detected. This justifies the design methodology of the blade.

• The Journal of Korean Physical Therapy
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• 제32권6호
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• pp.394-399
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• 2020

Purpose: The aim of this study was to determine the effects of lower rib cage lateral expansion limitation on the maximal inspiratory and expiratory pressures and on abdominal muscle activity during maximal respiratory breathing in healthy subjects. Methods: Fifteen healthy male subjects voluntarily participated in this cross-sectional study. During maximal breathing, maximal inspiratory and expiratory pressures were measured, and abdominal muscle activity was determined with using surface electromyography. Also, the measurement was repeated with using a non-elastic belt to the lower rib cage for limiting of lateral expansion. A Wilcoxon signed-rank test was performed for obtaining the statistical difference with a significance level of 0.05. Results: The findings of this study are as follows: 1) There were no significant differences in maximal inspiratory and expiratory pressure with and without lower rib cage lateral expansion (p>0.05), 2) There was no significant difference in abdominal muscle activity during the maximal inspiratory phase (p>0.05). However, right external oblique muscle activity decreased significantly during maximum exhalation with lower rib expansion limitation (p<0.05). Conclusion: The results of the current study indicate that a non-elastic belt was effective in decreasing right external oblique muscle activity during forced expiratory breathing in healthy subjects.

• Geomechanics and Engineering
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• 제24권3호
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• pp.281-293
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• 2021

Uncertainties in geomechanical input parameters which mainly related to inappropriate data acquisition and estimation due to lack of sufficient calibration information, have led wellbore instability not yet to be fully understood or addressed. This paper demonstrates a workflow of employing Quantitative Risk Assessment technique, considering these uncertainties in terms of rock properties, pore pressure and in-situ stresses to makes it possible to survey not just the likelihood of accomplishing a desired level of wellbore stability at a specific mud pressure, but also the influence of the uncertainty in each input parameter on the wellbore stability. This probabilistic methodology in conjunction with Monte Carlo numerical modeling techniques was applied to a case study of a well. The response surfaces analysis provides a measure of the effects of uncertainties in each input parameter on the predicted mud pressure from three widely used failure criteria, thereby provides a key measurement for data acquisition in the future wells to reduce the uncertainty. The results pointed out that the mud pressure is tremendously sensitive to UCS and SHmax which emphasize the significance of reliable determinations of these two parameters for safe drilling. On the other hand, the predicted safe mud window from Mogi-Coulomb is the widest while the Hoek-Brown is the narrowest and comparing the anticipated collapse failures from the failure criteria and breakouts observations from caliper data, indicates that Hoek-Brown overestimate the minimum mud weight to avoid breakouts while Mogi-Coulomb criterion give better forecast according to real observations.

• 한국기계가공학회지
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• 제21권6호
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• pp.60-66
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• 2022

The optimal strain energy function was obtained by comparing the results of the analysis using the strain energy functions obtained by uniaxial tensile and equibiaxial tensile tests on gasket materials used in hydrogen fuel cells, with the results measured using a contact pressure measurement sensor. At this time, even when only the uniaxial tensile test was conducted, Yeoh could obtain the most accurate results even by conducting only the uniaxial tensile test. Using this, an analysis of the cross section of the gasket used in stack confirmed a safe contact pressure and no deformation on the separator. In the future, research will be conducted to verify the gasket durability by reliability evaluation.

• Nuclear Engineering and Technology
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• 제54권12호
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• pp.4481-4490
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• 2022

In this study, a new rupture disk corrosion test (RDCT) method was developed for real-time detection of stress corrosion cracking (SCC) initiation of Alloy 600 in a primary water environment of pressurized water reactors. In the RDCT method, one side of a disk specimen was exposed to a simulated primary water at high temperature and pressure while the other side was maintained at ambient pressure, inducing a dome-shaped deformation and tensile stress on the specimen. When SCC occurs in the primary water environment, it leads to the specimen rupture or water leakage through the specimen, which can be detected in real-time using a pressure gauge. The tensile stress applied to the disk specimen was calculated using a finite element analysis. The tensile stress was calculated to increase as the specimen thickness decreased. The SCC initiation time of the specimen was evaluated by the RDCT method, from which result it was found that the crack initiation time decreased with the decrease of specimen thickness owing to the increase of applied stress. After the SCC initiation test, many cracks were observed on the specimen surface in an intergranular fracture mode, which is a typical characteristic of SCC in the primary water environment.

• 한국대기환경학회지
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• 제12권2호
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• pp.189-198
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• 1996

Mercury (Hg) is ubiquitous throughout the earth's atmosphere. The uniqueness of its atmospheric geochemistry is well-known with the high environmental mobility and relatively long atmospheric residence time (c.a., 1 year) associated with its high chemical stability. Despite a growing recognition of the environmental significance of its global cycling, the prexisting Korean database for atmospheric Hg is extremely rare and confined to a number of concentration measurements conducted under relatively polluted urban atmospheric environments. To help activate the research on this suvject, an in-depth analysis on the current development in the measurements of atmospheric mercury and the associated fluxes has been made using the most using the most updated data ests reported worldwide. As a first step toward this purpose, the most reliable techniques commonly employed in the measurements of its concentration in the background atmosphere are introduced in combination with the flux measurement techniques over soil surface such as: dynamic enclosure (or field flux chamber) method and field micrometeorological method. Then the results derived using these measurement techniques are discussed and interpreted with an emphasis on its mobilization across the terrestrial biosphere and atmosphere interface. A unmber of factors including air/soil temperature, soil chemical composition, soil water content, and barometric pressure are found out to be influential to the rate and amount of such exchange processes. Although absolute magnitude of such exchange processes is insignificant relative to that of the major component like the oceanic environment, this exchange process is thought to be the the predominant natural pathway for both the mobilization and redistribution of atmospheric Hg on a local or regional scale.