• 한국유체기계학회 논문집
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• 제14권5호
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• pp.69-74
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• 2011

This paper deals with the detail rotordynamic analysis for the vertical rotor system as development of vertical sea water lift pump for FPSO deep well. In a vertical rotor system, since linearized stiffness and damping coefficients of fluid film bearing are no longer be valid, hence the transient response analysis considering a fluid film force for every journal position in the bearing needs to be required. In this study, the transient response analysis of the proposed vertical pump rotor system was carried out in dry-run and wet-run conditions, respectively. The results show that orbital vibration responses of the rotor system remain stable at rated speed and thereby operating reliability of the vertical rotor system is confirmed. To overcome complexity of calculation pr ocedure and time consuming calculation of transient analysis, the calculating technique of steady-state response analysis is also proposed. The results of steady-state response obtained by applying the proposed technique to the rotor system are good agreement with the reference results, that is, transient responses.

• 한국진공학회:학술대회논문집
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• 한국진공학회 1999년도 제17회 학술발표회 논문개요집
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• pp.65-65
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• 1999

Dry etching technique provides more easy controllability on the etch profile such as anisotropic etching than wet etching process and the results of lots of researches on the characterization of various plasmas or ion beams for semiconductor etching have been reported. Chlorine-based plasmas or chlorine ion beam have been often used to etch several semiconductor materials, in particular Si-based materials. We have studied the effect of He flow rate on the Si and SiO2 dry etching using chlorine-based plasma. Experiments were performed using reactive ion etching system. RF power was 300W. Cl2 gas flow rate was fixed at 58.6 sccm, and the He flow rate was varied from 0 to 120 sccm. Fig. 1 presents the etch depth of si layer versus the etching time at various He flow rate. In case of low He flow rate, the etch rate was measured to be negligible for both Si and SiO2. As the He flow increases over 30% of the total inlet gas flow, the plasma state becomes stable and the etch rate starts to increase. In high Ge flow rate (over 60%), the relation between the etch depth and the time was observed to be nearly linear. Fig. 2 presents the variation of the etch rate depending on the He flow rate. The etch rate increases linearly with He flow rate. The results of this preliminary study show that Cl2/He mixture plasma is good candidate for the controllable si dry etching.

• Safety and Health at Work
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• 제14권3호
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• pp.325-331
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• 2023

Background: Heat stress is a harmful physical hazard in many occupational settings. However, consequences of occupational heat exposure among workers in a sugarcane factory in Ethiopia are not well characterized. This study aimed to assess the level of occupational heat exposure-related symptoms and contributing factors. Methods: In this cross-sectional study, five workstations were selected for temperature measurement. Heat stress levels were measured using a wet-bulb globe temperature index meter. A stratified random sampling technique was used to select 1,524 participants. Heat-related symptoms were assessed using validated questionnaires. Results: The level of occupational heat exposure was 72.4% (95% CI: 70.2%-74.8%), while 71.6% (95% CI: 69.3%-74.9%) of participants experienced at least one symptom related to heat stress. The most common heat-related symptoms were swelling of hands and feet (78%), severe thirst (77.8%) and dry mouth (77.4%). The identified risk factors were a lack of reflective shields (AOR: 2.20, 95% CI: 1.53, 3.17), not-enclosed extreme heat sources (AOR: 1.76, 95% CI: 1.23, 2.51), a lack of access to shade (AOR: 9.62, 95% CI: 6.20, 14.92), and inappropriate protective clothing provision (AOR: 1.58, 95% CI: 1.27, 2.71). Conclusions: The burden of occupational heat exposure and heat-induced symptoms was high. Lack of reflective shields, the absence of enclosed extreme heat sources, a lack of access to shade, and inappropriate protective clothing provision were considerable attributes of heat stress. Therefore, the use of mechanical solutions to stop heat emissions at their sources and the key factors identified were areas for future intervention.

• 한국자기학회지
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• 제6권6호
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• pp.367-374
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• 1996

자기소자중 가장 기본이 되는 박막인덕터의 제작에 관한 연구를 수행하기 위하여, photolitho-graphy와 에칭공정을 도입하고, 도체간격 및 도체폭이 수십 $\mu\textrm{m}$, 도체코일 턴수가 각각 13회와 20회, 크기가 $4\;mm{\times}4\;mm$인 공심형 박막인덕터를 제작하였다. 이것을 마이크로스트립선로에 정착하고, network analyzer로 주파수 1 MHz ~ 1 GHz에서 신호의 반사계수법을 이용하여 간편하고 비교적 정확한 측정을 하였다. 특히, 공정이 간단한 습식 에칭공정을 도입하여, 안정된 에칭기술을 통해 양호한 미세패턴구조를 얻었다. 박막인덕터의 특성은, 크기가 같을때, L 및 Q값은 spiral형이 meander형 보다 큰 값을 갖는 반면, 공진주파수는 인덕턴스의 증가에 의한 영향으로 spiral형이 meander형보다 감소하였다.

• 대한교통학회지
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• 제33권3호
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• pp.284-293
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• 2015

본 연구의 목적은 도로상에 설치된 CCTV에서 수집되는 영상정보를 이용하여 노면 상태를 판단하는 것이다. 이를 위해 먼저 야간의 젖은 노면을 검지하는 기술을 검증하였다. 지금까지 도로상의 젖음 정보를 추출하는 기술은 편광(polarization) 특성을 활용하는 것이다. 그러나 태양광이 없는 야간 도로상황에서는 편광특성을 활용할 수 없다. 이에 본 연구에서는 CCTV 야간 영상의 특징을 활용하여 마른 노면과 젖은 노면을 판별하는 방법을 제안한다. 노면의 젖음 여부를 판단하는 판별 방법론으로 웨이블릿(wavelet) 패킷 변환을 활용한 질감분석 방법론 및 영상의 명도분포 특성을 반영하기 위한 HSI 색상 모형 기반 명도(intensity) 히스토그램 활용 방법론을 적용하였다. 현장장비에서 취득한 총 200장의 샘플영상을 활용하여 영상을 분석, SVM (Support Vector Machine) 분류기 기반 판별 초평면을 구성한 후, 검지 기법을 검증하기 위한 현장테스트를 수행하였으며 유의한 결과를 얻을 수 있었다. 본 연구결과는 교통류의 안전성 향상을 위한 효율적인 야간 노면상태 수집에 활용될 수 있을 것이다.

• Water Engineering Research
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• 제6권1호
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• pp.31-38
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• 2005

Groundwater recharge is defined in an addition of water to groundwater reservoir. Recently, many people have been moving to the Edwards aquifer and urban and agricultural industry have been expending. Hydrologists and water planning managers concern about insufficient groundwater amounts and irrigation water price variability. In this paper, I focus on estimates of local recharge volumes and quantify preferential flow through GIS technique. Chloride Mass Balance (CMB) and hydrochemical components have been widely applied to recharge rate and evaluate flow paths. The CMB method is based on relationship between wet-dry chloride deposition data and Rainfall data. These data are manipulated using ArcGIS. Especially, hydrochemical concentration distribution is good index for groundwater residence times or flow paths such as $[Mg^{2+}]/[Ca^{2+}],[Cl]$ and log$([Ca^{2+}]+[Mg^{2+}])/[Na^+]$. Well information such as hydrological-hydrochemical data are imported into ArcGIS and manipulated by interpolation techniques. For each potentiometric surface and water quality, point data are converted to spatial data through each Kriging and Inverse Distance Weighted (IDW) techniques.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 1999년도 추계학술발표대회 논문집
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• pp.28-31
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• 1999

Carbon fiber/epoxy composites using electrodeposited monomeric and polymeric coupling agents were compared with the dipping and the untreated cases. Treating conditions such as time, concentration and temperature were optimized. Four-fibers embedded micro-composites were prepared for fragmentation test. Interfacial properties of four-fiber composites with different surface treatments were investigated with simultaneous acoustic emission (AE) monitoring. The microfailure mechanisms occurring from fiber break, matrix and interlayer crackings were examined by AE parameters and an optical microscope. It was found that interfacial shear strength (IFSS) of electrodeposited carbon fibers was much higher than the other cases under dry and wet conditions. Well separated and different-shaped AE groups occurs for the untreated and ED treated case, respectively.

• Structural Monitoring and Maintenance
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• 제6권2호
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• pp.85-101
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• 2019

The effects of foundation scour depth and riverbed condition on the natural frequencies of a typical cross-river integral abutment bridge have been studied. The conventional operational modal analysis technique has been employed in order to extract the modal properties of the bridge and the results have been used in the Finite Element (FE) model updating procedure. Two tests have been carried out in two different levels of water and wet condition of the riverbed. In the first test, the riverbed was in dry condition for two subsequent years and the level of water was 10 meter lower than the natural riverbed. In the second test, the river was opened to water flow from the upstream dam and the level of water was 2 meter higher than the natural riverbed. The results of these two tests have also been used in order to find to what extend the presence of water flow in the river and saturation of the surrounding soil affect the bridge natural frequencies. Finally, the updated FE model of the bridge has been applied in a series of parametric analyses incorporating the effect of piles' relative scour depth on the bridge natural frequency of the first four vibration modes.

• 한국세라믹학회지
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• 제23권6호
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• pp.33-36
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• 1986

The $PbTiO_3$is well known materials having remarkable ferroelectric piezoelectric and pyro-electric properties. Thin films of the lead titanite has been successfully fabricated by Chemical Vapor Deposition on the borosilicate glass and titanium substrate. The $PbTiO_3$ thin film deposited on the borosilicate glass using the $PbCl_2$, $TiCl_4$ dry oxygen and wet oxygen at different temperatures (50$0^{\circ}C$-$700^{\circ}C$) grows along the (001) preferred orientation. On the other hand the $PbTiO_3$ thin film deposited on the titanium substrate using the PbO grows along the (101) preferred orientation. Growth orientation of deposited $PbTiO_3$ depends on the reaction species irrespective of substrate materials. Maximum dielectic constant and loss tangent of the $PbTiO_3$ thin film deposited on the titanium substrate are about 90 and 0.02 respectively, . Deposition rates of $PbTiO_3$ deposited on the borosilicate glass and titanium substrate are 10-15 ${\mu}{\textrm}{m}$/hr. Titanium dioxide interlayer formed be-tween $PbTiO_3$ film and titanium substrate material, It improved the adhesion of the film.

• 한국응용과학기술학회지
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• 제27권4호
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• pp.508-514
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• 2010

Regenerated cellulose fibers were prepared from three pulps containing different degree of polymerization(DP) and $\alpha$-cellulose contents by dry-jet wet spinning technique with cellulose dope in N-methylmorpholin N-oxide (NMMO). The effect of antioxidant, n-propyl gallate (PG) on the properties of different regenerated celluloses was studied using X-ray diffraction, copper number calculation, and viscometry. The degradaqtion of regenerated cellulose from pulp containing higher DP and lower $\alpha$-cellulose content was occurred more seriously. The tensile strength and initial modulus of regenerated cellulose fiber obtained from NMMO dope with PG were higher than those of fiber obtained from NMMO dope without PG. All fibers showed the round shape cross section and typical cellulose II crystalline structure.