• 한국양식학회지
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• 제10권2호
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• pp.189-197
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• 1997

A series of short (8 hours) and long term (96 hours) exposure studies was conducted on a laboratory scale to evaluation (1) the threshold concentrations of petroleum hydrocarbon in seawater which can lead to tainting problems in yellow tail (Seriola quinqueradiata) and (2) the time to recover (depuration period) once the tainting has occurred. The water-soluble fraction (WSF) of crude oil was prepared by stirring the oil with cold seawater. The main component of the WSF were low-boiling aromatics, although these were only al small proportion of the starting oil. From the sencory evaluation it was concluded that the threshold hydrocarbon levels in seawater which will impart a taint in yellow tail fillets within a 8-hour exposure period (short exposure period) are in the range of 0.4 to 1.0 ppm and within a 96-hour exposure period (long exposure period) are in the range of 0.2 to 0.5 ppm. Depuration trials were carried out with WSF from crude oil. The fish were exposed for 48 hours to concentration of 2.5 ppm hydrocarbons. After 48-hour exposure period, the fish were allowed to depurate in fresh, uncontaminated seawater. Depuration time for these fish was 10 days. The taste panelists were able to detect the contaminated fillets very easily while the depurated fish could not be distiguished from the control.

• Corrosion Science and Technology
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• 제3권6호
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• pp.245-250
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• 2004

A series of classical G109 type concrete specimens was exposed to cyclic wet and dry ponding with 15 w/o NaCl solution for approximately five years. Mix design variables included 1) three cement alkalinities (EqA of 0.97, 0.52, and 0.36) and 2) three water-cement ratios (0.50, 0.41, and 0.37). To determine the corrosion initiation time, corrosion potential and macro-cell current between top and bottom bars were monitored. Subsequent to corrosion initiation, specimens were autopsied and visually inspected. Concrete powder samples were collected from top rebar trace and chloride concentration was measured. Also, time-to-corrosion, $T_i$, for specimens of the individual mix designs was represented using Weibull analysis. Time-to-corrosion was a distributed parameter; and because of this, corrosion initiation of four identical specimens for each mix varied, often over a relatively wide range. Specimens fabricated using the lowest water cement ratio and the highest alkalinity cement exhibited the longest time-to-corrosion initiation and the highest chloride threshold levels. Time-to-corrosion did not increase monotonically with cement alkalinity, however, presumably as a consequence of relatively high $Cl^-$ binding in the lower pore water pH range. The chloride threshold level, $Cl_{th}$, increased with increasing $T_i$ and, consequently, was greatest for the highest cement alkalinity specimens.

• Transactions on Electrical and Electronic Materials
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• 제1권4호
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• pp.20-24
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• 2000

This study aimed to develop ITO(Indium Tim Oxide) tin films ablation with a pulsed type KrF excimer laser required for the electrode patterning application in flat panel display into small geometry on a large substrate are. The threshold fluence for ablating ITO on glass substrate is about 0.1 J/㎠. And its value is much smaller than that using 3 .sup rd/ harmonic Nd:YAG laser. Through the optical microscope measurement the surface color of the ablated ITO is changed into dark brown due to increase of surface roughness and transformation of chemical composition by the laser light. The laser-irradiated regions were all found to be electrically isolating from the original surroundings. The XPS analysis showed that the relative surface concentration of Sn and In was essentially unchanged (In:Sn=5:1)after irradiating the KrF excimer laser. Using Al foil made by 2$\^$nd/ harmonic Na:YAG laser, the various ITO patterning is carried out.

• Computers and Concrete
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• 제16권2호
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• pp.261-274
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• 2015

This study established the standard recommended values and expansion fracture threshold values for the content of steel slag in controlled low-strength materials (CLSM) to ensure the appropriate use of steel slag aggregates and the prevention of abnormal expansion. The steel slags used in this study included basic oxygen furnace (BOF) slag and desulfurization slag (DS), which replaced 5-50% of natural river sand by weight in cement mixtures. The steel slag mortars were tested by high-temperature ($100^{\circ}C$) curing for 96 h and autoclave expansion. The results showed that the effects of the steel slag content varied based on the free lime (f-CaO) content. No more than 30% of the natural river sand should be replaced with steel slag to avoid fracture failure. The expansion fracture threshold value was 0.10%, above which there was a risk of potential failure. Based on the scanning electron microscopy (SEM) analysis, the high-temperature catalysis resulted in the immediate extrusion of peripheral hydration products from the calcium hydroxide crystals, leading to a local stress concentration and, eventually, deformation and cracking.

• Environmental Engineering Research
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• 제24권1호
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• pp.150-158
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• 2019

Soil contaminated with heavy metals from artisanal gold mining in Anka Local Government Area in Northwestern Nigeria was investigated to evaluate the human health risk as a result of heavy metals. Measured concentration of heavy metals and exposure parameters were used to estimate human carcinogenic and non-carcinogenic risk. GIS-based Kriging method was utilized to create a prediction maps of human health risks and probability maps of heavy metals concentrations exceeding their threshold limits. Hazard index calculation showed that 21 out of 23 locations are posing non-cancer risk for children. Adults and children are at high cancer risk in all locations as the total cancer risk exceeded $1{\times}10^{-6}$ (the lower limit CTR value). Kriging model showed that only a very small area in Anka has a hazard index of less than unity and cumulative target risk of less than $1{\times}10^{-4}$, indicating a significant carcinogenic and non-carcinogenic risks for children. The probability of heavy metals to exceed their threshold concentrations around the study area was also found to be high.

• 한국지하수토양환경학회지:지하수토양환경
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• 제20권7호
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• pp.112-120
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• 2015

Statistical trend analysis using the data from the National Groundwater Quality Monitoring Network (NGQMN) of Korea was conducted to establish a new groundwater quality management framework. Sen’s test, a non-parametric statistical method for trend analysis, was used to determine the linear trend of the groundwater quality data. The analysis was conducted at different confidence levels (i.e., at 70, 80, 90, 95, and 99% confidence levels) for three of groundwater quality parameters, i.e., nitrate-nitrogen, chloride, and pH, which have sufficient time series of the NGQMN data between 2007 and 2013. The results showed that different trends can be determined for different depths even for the same monitoring site and the numbers of wells having significant trends vary with different confidence levels. The wells with increasing or decreasing trends were far less than the wells with no trend. Chloride had more wells with increasing trend than other parameters. On the other hand, nitrate-nitrogen had the most wells with increasing trend and concentration exceeding 75% of the threshold values (TVs). Based on the methodology used for this study, we suggest including groundwater TVs and trend analysis to evaluate groundwater quality and to establish an advanced groundwater quality management framework.

• Journal of Nutrition and Health
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• 제35권2호
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• pp.223-228
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• 2002

The purpose of this study was to investigate the relationship between iron deficiency without anemia and physical performance in healthy women aged 20-21 yrs. Ten subjects with normal iron stores (serum ferritin $\geq$ 12$\mu\textrm{g}$/L: iron-sufficient group) and 11 subjects with iron depletion without anemia (serum ferritin < 12 $\mu\textrm{g}$/L and serum hemoglobin > 120 g/L: iron-depleted group) were chosen from a group of 50 women and were given physical-performance tests, including determinations of maximum oxygen consumption (VO$_2$ max) and ventilatory threshold. Iron status assessment included determination of hemoglobin, hematocrit, seam ferritin, total iron-binding rapacity, serum iron and transferrin saturation values. Dietary iron intake was assessed based on seven-day food intake records written by the subjects. Physical activity level was estimated by frequency questionnaires and two-week physical activity records were compiled daily by the subjects. Blood ferritin concentration was significantly lower in the iron-depleted group than in the iron-sufficient group (p < 0.05). However, other variables showing iron status was not different between the groups. There were no significant differences in body size, body composition and physical activity levels between the groups. Daily dietary iron, total protein and animal protein intakes of the iron-sufficient group were significantly higher than those of the iron depleted group. However, no differences were found in the amount of dietary vitamin C and fiber between the groups. The values for VO$_2$max and VO$_2$max corrected with weight or fat-free mass were not different between the groups. However, the ventilatory threshold was significantly higher in the iron sufficient group than in the iron-depleted group. The lower ventilatory threshold in the iron-depleted group suggests that iron depletion without anemia could diminish aerobic physical performance in young women. In addition, a significant correlation of physical performance to serum fferritin level was shown only in the iron depleted group.

• JSTS:Journal of Semiconductor Technology and Science
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• 제3권2호
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• pp.69-75
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• 2003

Cell transistor and data retention time characteristics were studied in 90 nm design rule 512M-bit DRAM, for the first time. And, the characteristics of cell transistor are investigated for different STI gap-fill materials. HDP oxide with high compressive stress increases the threshold voltage of cell transistor, whereas the P-SOG oxide with small stress decreases the threshold voltage of cell transistor. Stress between silicon and gap-fill oxide material is found to be the major cause of the shift of the cell transistor threshold voltage. If high stress material is used for STI gap fill, channel-doping concentration can be reduced, so that cell junction leakage current is decreased and data retention time is increased.

• 한국정보통신학회논문지
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• 제18권10호
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• pp.2509-2515
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• 2014

본 논문에서는, 초고집적 CMOS를 위한 얕은 트랜치 격리로 기존의 수직 구조에서 내부 임계전압과 활성 영역의 스트레스 영향을 개선시키고자 한다. 이를 위해서 제안한 구조는 회자 모양의 얕은 트랜치 격리 구조이며, 기존 수직 구조와 제안한 구조에 대해서 전자농도 분포와 게이트 바이어스 대 에너지 밴드 형태, 열전자 스트레스와 열 손상의 유전 강화 전계를 분석 하고자 한다. 물리적 기본 모델들은 TCAD 툴을 이용하며, 집적화 소자들에 있어서 분석 조건은 주위 조건과 스트레스 인가이다. 분석 결과, 얕은 트랜치 격리 구조가 소자의 크기가 감소됨에 따라서 수동적인 전기적 기능이며, 트랜지스터 응용에서 제안한 회자 구조의 얕은 트랜치 격리 구조가 전기적 특성에서 전위차 전계와 포화 임계 전압이 높게 나타났으며, 활성영역에서 스트레스의 영향은 감소되었다. 이 결과 데이터를 바탕으로 제작한 소자의 결과 분석도 시뮬레이션 결과 데이터와 거의 동일하였다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2009년도 하계학술대회 논문집
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• pp.63-63
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• 2009

In this work, we demonstrate 800V 4H-SiC power DMOSFETs with several structural alterations to observe static DC characteristics, such as a threshold voltage ($V_{TH}$) and a figure of merit ($V_B^2/R_{SP,ON}$). To optimize the static DC characteristics, we consider four design parameters; (a) the doping concentration ($N_{CSL}$) of current spreading layer (CSL) beneath the p-base region, (b) the thickness of p-base ($t_{BASE}$), (c) the doping concentration ($N_J$) and width ($W_J$) of a JFET region, (d) the doping concentration ($N_{EPI}$) and thickness ($t_{EPI}$) of epi-layer. Design parameters are optimized using 2D numerical simulations and the 4H-SiC DMOSFET structure results in high figure of merit ($V_B^2/R_{SP,ON}$>~$340MW/cm^2$) for a power MOSFET in $V_B{\sim}1200V$ range.