• 한국해안·해양공학회논문집
• /
• 제28권2호
• /
• pp.92-100
• /
• 2016

응력집중계수를 이용하여 해상풍력발전기 트라이포드 지지구조물에 대한 신뢰성 해석을 수행하였다. 파랑과 풍하중의 극치분포함수는 POT방법을 사용하여 동적응답을 분석함으로써 추정되었다. 일계신뢰도법을 사용하여 신뢰성해석을 수행하였으며, 한계상태함수는 지지구조물의 이음부에서 발생하는 응력을 기반으로 정의하였다. 보 요소에서 계산된 응력에 응력집중계수를 곱하는 방법과 판 요소를 사용하여 계산하는 두 가지 방법으로 최대응력을 계산하여 신뢰성 해석을 수행하고 결과를 비교 분석하였다.

• 한국재료학회지
• /
• 제18권5호
• /
• pp.272-276
• /
• 2008

In submicron MOSFET devices, maintaining the ratio between the channel length (L) and the channel depth (D) at 3 : 1 or larger is known to be critical in preventing deleterious short-channel effects. In this study, n-type SOI-MOSFETs with a channel length of $0.1\;{\mu}m$ and a Si film thickness (channel depth) of $0.033\;{\mu}m$ (L : D = 3 : 1) were virtually fabricated using a TSUPREM-4 process simulator. To form functioning transistors on the very thin Si film, a protective layer of $0.08\;{\mu}m$-thick surface oxide was deposited prior to the source/drain ion implantation so as to dampen the speed of the incoming As ions. The p-type boron doping concentration of the Si film, in which the device channel is formed, was used as the key variable in the process simulation. The finished devices were electrically tested with a Medici device simulator. The result showed that, for a given channel doping concentration of $1.9{\sim}2.5\;{\times}\;10^{18}\;cm^{-3}$, the threshold voltage was $0.5{\sim}0.7\;V$, and the subthreshold swing was $70{\sim}80\;mV/dec$. These value ranges are all fairly reasonable and should form a 'magic region' in which SOI-MOSFETs run optimally.

• Nuclear Engineering and Technology
• /
• 제53권10호
• /
• pp.3286-3297
• /
• 2021

The released hydrogen can be ignited even with weak ignition sources. This emphasizes the importance of the hydrogen flammability evaluation to prevent catastrophic failure in hydrogen related facilities including a nuclear power plant. Historically numerous attempts have been made to determine the flammability limit of hydrogen mixtures including several diluents. However, no analytical model has been developed to accurately predict the limit concentration for mixtures containing radiating gases. In this study, the effect of H₂O and CO₂ on flammability limit was investigated through a numerical simulation of lean limit hydrogen flames. The previous flammability limit model was improved based on the mechanistic investigation, with which the amount of indirect radiation heat loss could be estimated by the optically thin approximation. As a result, the sharp increase in limit concentration by H₂O could be explained by high thermal diffusivity and radiation rate. Despite the high radiation rate, however, CO₂ with the lower thermal diffusivity than the threshold cannot produce a noticeable increase in heat loss and ultimately limit concentration. We concluded that the proposed mechanistic analysis successfully explained the experimental results even including radiating gases. The accuracy of the improved model was verified through several flammability experiments for H₂-air-diluent.

• 한국물환경학회지
• /
• 제35권3호
• /
• pp.248-256
• /
• 2019

Most of the lakes in Korea are artificial, and their limnological characteristics are significantly different from those of natural lakes in other countries. In this study, the relationship between trophic state parameters was investigated, based on summer average data of the upper layer, in 81 lakes in Korea, 2013-2017. Compared with trends of foreign natural lakes, chlorophyll a (Chl.a) concentration was slightly lower at the same total phosphorus (TP) concentration, and transparency (Secchi depth, SD) was noticeably lower at the same Chl.a concentration. This is because of excessive allochthonous loading of non-algal material during the monsoon period, and the reduction in phosphorus availability to algal growth, by light limitation and short hydraulic residence time. Considering these characteristics, we suggested site-specific thresholds of trophic state classification for Chl.a, TP and SD, based on annual average data at the upper layer of lakes ($3-10{\mu}g\;L^{-1}$ of Chl.a measured by UNESCO method; $13-33{\mu}g\;L^{-1}$ of TP; 1.6-3.2 m of SD for mesotrophic state class, respectively). The threshold value of TP for each trophic state class, corresponded to the upper value of previously reported range, and that of SD was out of the range. We suggested applying only TP and Chl.a in assessment of trophic state of lakes in Korea, excluding SD.

• 한국축산식품학회지
• /
• 제43권2호
• /
• pp.319-330
• /
• 2023

Some preservatives are naturally contained in raw food materials, while in some cases may have been introduced in food by careless handling or fermentation. However, it is difficult to distinguish between intentionally added preservatives and the preservatives naturally produced in food. The objective of this study was to evaluate the minimum inhibitory concentration (MIC) of propionic acid, sorbic acid, and benzoic acid for inhibiting food spoilage microorganisms in animal products, which can be useful in determining if the preservatives are natural or not. The broth microdilution method was used to determine the MIC of preservatives for 57 microorganisms. Five bacteria that were the most sensitive to propionic acid, benzoic acid, and sorbic acid were inoculated in unprocessed and processed animal products. A hundred microliters of the preservatives were then spiked in samples. After storage, the cells were counted to determine the MIC of the preservatives. The MIC of the preservatives in animal products ranged from 100 to 1,500 ppm for propionic acid, from 100 to >1,500 ppm for benzoic acid, and from 100 to >1,200 ppm for sorbic acid. Thus, if the concentrations of preservatives are below the MIC, the preservatives may not be added intentionally. Therefore, the MIC result will be useful in determining if preservatives are added intentionally in food.

• 농업과학연구
• /
• 제41권4호
• /
• pp.399-404
• /
• 2014

Soil moisture is an important factor for the availability and circulation of nutrients in arable soil. The purpose of this study was to set thresholds moisture content on soil nitrate concentration in the solution for real-time diagnosis. Sandy loam, silt loam, and sandy loam was filled with $1.2g\;cm^{-3}$ at Wagner pots, 0, 100, and $200mg\;L^{-1}$ of $KNO_3$ was saturated. Nitrate in standard solution was recovered about 95% by passing the porous cup. Nitrate concentrations in sampling of soil solution were examined by using a porous cup. The soil solution was higher in accordance with sandy loam> silt loam> clay loam, limited water filled pore space for sampling soil solution was 33.7, 56.4, and 62.2%, respectively. Nitrate concentration in the soil solution was negligible at sandy loam and silt loam during sampling periods, which was decreased about 50~82% in clay loam compared to the initial $NO_3$-N concentration in the saturated $KNO_3$ solution. Over limitation of soil solution sampling, soil EC and $NO_3$-N content were increased with the saturated $NO_3$-N concentration, regardless of soil texture (p<0.05). Conclusively, soil solution by using a porous cup was possible, regardless of the soil texture, which was useful for the diagnosis in nitrate concentration of soil solution. However, because nitrate concentration of soil solution in a clay loam changes, it was necessary for careful attention in order to take advantage for the real-time diagnosis of nitrogen management in soil.

• 한국대기환경학회지
• /
• 제23권2호
• /
• pp.147-157
• /
• 2007

This study was carried out to investigate the characteristics of fourteen odor compounds from a total of 10 sampling sites in residential areas around Banwol-Sihwa industrial complex. The measurement data are analyzed and compared with sensation of odor unit. Only a hydrogen sulfide out of four sulfur compounds was quantified above the detection limit (0.06 ppb) in the residential area around Banwol industrial complex with leather companies and a sewage treatment plant. The concentrations of VOCs were higher than those measured from a big city, and styrene showed the relatively high concentration from all sampling sites ($2.1{\sim}37.8\;ppb$). In the case of carbonyl compounds, acetaldehyde was found most frequently with the mean of 3.97 ppb, and its concentration difference was not significant between Banwol and Sihwa industrial complex. Of the nitrogen compounds, ammonia was measured at the relatively high concentration from all the sampling sites ($12{\sim}707\;ppb$), and a trimethylamine was found at the odor threshold level (0.1 ppb). The concentrations of styrene and ammonia showed relatively seasonal variation, the concentration of styrene in summer was five times higher than that in autumn, the concentration of ammonia in autumn was two times higher than that in summer. However other odorous compounds did not show such strong seasonal variation. Odor-concentration relationship between odor unit and $H_{2}S$ concentrations from industrial sources was examined and used as odor sensation evaluation, and thus the neighbourhood odor complaints maybe caused during the four seasons from the results.

• 한국산업보건학회지
• /
• 제8권1호
• /
• pp.76-87
• /
• 1998

The concentration of welding fume was measured by 221 welders themselves in chassis frame workplace of the manufactory from February, 1, 1996 to May, 31, 1997. Welding parameters were the welding current and the distance between helmet and arc. Those two optimum conditions were proposed by excess probability analysis using logistic regression, so the best position in the workplace was proposed considering two factors to control the welding fume. The results are as followings; 1) The excess proability of welding fume TLV was over 99% in above 260 Amperes of welding current and also in below 30cm of distanced between helmet and arc. 2) The equation from logistic regression analysis using SPSS/PC+5.02 had the welding current as a independent variable and the excess of welding fume TLV as a dependent variable (p<0.05). Logit(welding fume TLV) = 0.1296 ${\times}$ wlding currnet - 28.8750 3) The equation from logistic regression analysis using SPSS/PC+5.02 had the distance between helmet and arc as a independent variable and the excess of welding fume threshold limit value a, a dependent variable (p<0.05). Logit (welding fume TLV) = -0.6809 ${\times}$ distance between helmet and arc +25.1665 4) Considering both cases or 2) and 3). the result equation is following. (p<0.05). Logit (welding fume TLV) = 0.1346 ${\times}$ welding current -0.3859 ${\times}$ distance between helmet and arc -15.7382 5) The excess probability of welding fume threshold limit value was 100% in above 240 Ampere of welding current. Thus, below 220 Ampere can be suggested to reduce the 40% number of welders who have a excess welding fume threshold limit value. 6) The excess probability of welding fume TLV was 100% in below 34cm of distance between helmet and arc. Thus, over 38cm can be suggested to reduce the 33% number of welders who have a excess welding fume TLV. 7) Considering both 5) and 6) cases, first of all, the best welding current can be 200 Ampere to have a below 15% of welding fume excess probability for the welders who works in distance of 34-37cm. Secondly, to have a below 30% excess probability of welding fume TLV, the working distance must be over 38cm in 220 Ampere and 32cm in 200 Ampere. 8) To reduce the average exposure concentration of welding fume ($8.21{\pm}5.83mg/m^3$), the movable local exhaust system equipped with flexible hoods can be used.

• 한국식품영양과학회지
• /
• 제13권1호
• /
• pp.86-96
• /
• 1984

한국인(韓國入)의 맛에 대한 감도(感度)와 식습관(食習慣)을 알아보기 위해 몇가지 실험을 행하여 다음과 같은 결론(結論)을 얻었다. 1. 짠맛의 최소감미량농도(最少感味量濃度)는0.016 %, 단맛 0.245${\sim}$0.249 %, 신맛 0.004${\sim}$0.008 %, 쓴맛 0.008${\sim}$0.012 %였으며 매운맛 170,000$\sim$600,000 S. H. U. 였다. 2. 0.375 % 육수(肉水)($60^{\circ}C$)를 가장 맛좋게 하는 짠맞농도는 0.3 %였고 2 % coffee ($60^{\circ}C$)에서는 6 % 설탕 농도가 그리고 100 % orange juice에서는 산당비 19.3(16.8 brix/0.8736 citric acid)을 가장 좋아하였다. 3. 76개 국의 평균(平均) Brix는 3.83(2.3${\sim}$6.4)%, 산도는 9.73(5.4${\sim}$16)ml 0.1N NaOH, pH는 6.26(5.2${\sim}$7.0) 그리고 ostwald 점도는 1.34(1.06${\sim}$l.95)이었다. 4. 76개 국의 평균 염분농도는 1.127(0.904${\sim}$1.448)% 였고 콩나물국, 시금치된장국의 매운정도는 12,500${\sim}$47,500 S. H. U.로 oleoresin capsicum약 1.999${\sim}$5.911(mg%)의 매운맛에 해당되었으며 김치국, 매운탕은 그 이상으로 무척 매웠다. 5. 기호음식중(疇好飮食中) 찌게류의 분호(噴好)가 가장 높았으며 자녀(子女)의 식습관(食習慣) 형성에 특히 아버지의 영향이 크고 어릴 때부터 짜고 맵게 먹고있음이 나타났다.

• 핵의학기술
• /
• 제28권1호
• /
• pp.57-69
• /
• 2024

Purpose: Quantitative analysis through count measurement in nuclear medicine planar images is limited by analysis techniques that are useful for obtaining various clinical information or by organ overlap or artifacts in actual clinical practice. On the other hand, the use of SPECT tomography images is quantitative analysis using volume rather than planar, which is not only free from problems such as projection overlap, but also has excellent quantitative accuracy. In the use of developing SPECT quantitative analysis technology, this study aims to compare the accuracy of quantitative analysis between ROI of the conventional planar images and VOI of the SPECT tomographic images in evaluating the count change happened by the volume change of the source. Materials and Methods: A ^99mTcO₄^- source(200.17 MBq) was filled with sterilized water in the syringe to create a phantom with an inner diameter volume of 60 cc, and a planar image and a SPECT image were obtained by reducing the volume by 15 cc (25%) respectively. ROI and VOI(threshold: 1~45%, 5% interval) were set for each image obtained to estimate true count and measure the total count, and compared with the preseted volumetric change rate(%). Results: When volume changes of 25%, 50%, and 75% occurred in the initial volume of 60 cc(100%) of the phantom, the average count changes of the measured planar image were 26.8%, 53.2%, 77.5%, and the average count changes of the SPECT image were 24.4%, 50.9%, and 76.8%. In this case, the VOI size(cm³) set showed an average change rate of 25.4%, 51.1%, and 76.6%. The highest threshold value for the accuracy of radioactive concentration by VOI size (average error -1.03%) was 35%, and the VOI size of the same threshold had an error of -17.1% on average compared to the actual volume. Conclusion: On average, the count-based volumetric change rate in nuclear medicine images was able to track changes more accurately using VOI than ROI, but there was no significant difference with relatively similar value. However, the accuracy of radioactive concentration according to individual VOI sizes did not match, but it is considered that a relatively accurate quantitative analysis can be expected when the size of VOI is set smaller than the actual volume.