• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.1 no.2
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• pp.136-143
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• 1991

Inorganic mercury in urine and airborne was determined by cold vapor atomic absorption spectrophotometry. Detailed sampling methods and analylical results are as follows : 1. 100~200ml of urine for each person was taken in 250 ml borosilicate bottle and $K_2S_2O_8$ (0.1g/100ml urine) was added to prevent bacterial contamination. About 1001 air of workingplace was absorbed in l0ml of absorbing solution. Urine samples and absorbing solution tubes were stored at $4^{\circ}C$. Dillution solution to prepare standard solution used deionized water (D.W) for urine and absorbing solution (A.S) for air. 2. 1n this procedure deteclion limit was 1ng/ml and mercury contents of blank reagent solution was 1~2ng/ml. 3. Calibration range was $0.02{\sim}0.1{\mu}g/ml$ and in this range r.s.d for each calibration curve in D.W and A.S and ${\pm}7.9%$ and ${\pm}3.7%$, respectively. 4. Repeatability (n=5 times, conc. $0.05{\mu}g/ml$) was ${\pm}5.8%$, in D.W. and ${\pm}4.4%$ in A.S, respectively. 5. Recovery for urine adding spiked concentration ($0.05{\mu}g/ml$) was about 90%. 6. Analytical result of samples was $1{\sim}139{\mu}g/l$ in urine and ${\sim}0.127mg/m^3$ in airborne.

• Korean Journal of Metals and Materials
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• v.47 no.7
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• pp.416-422
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• 2009

Approaches for analyzing indentation hardness are still controversial, although the instrumented indentation technique has been generalized as one powerful method that can record surface deformation behaviors. Material pile-ups around the indenter/surface contact region make the conventional Oliver and Pharr's analysis on the instrumented indentation curve inaccurate. Thus, in order to prove the validity of the hardness analyses, five approaches were applied to the experimental data obtained from fused quartz and (100) monocrystalline tungsten specimens; an elastic recovery analysis on instrumented indentation curves, three indentation work analyses on the unit plastic volume, and a differentiation analysis on remnant indentation morphologies were tried. Five kinds of indentation hardness overlapped on one result plot showed the validity of each analysis. The modified indentation work approach based on a new definition of plastic volume showed consistent results with those from the Oliver-Pharr's and image differentiation methods. In the case of pile-up accompanying deformation, the Oliver-Pharr's and image differentiation methods showed the upper and lower limits of indentation hardness, respectively.

• Transactions of Materials Processing
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• v.14 no.4 s.76
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• pp.384-391
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• 2005

The nickel-based alloy Nimonic 80A possesses the excellent strength, and the resistance against corrosion, creep and oxidation at high temperature. Its products are used in aerospace engineering, marine engineering and power generation, etc. Control of forging parameters such as strain, strain rate, temperature and holding time is important because change of the microstructure in hot working affects the mechanical properties. Change of the microstructure evolves by recovery, recrystallization and grain growth phenomena. The dynamic recrystallization evolution has been studied in the temperature range of $950\~1250^{\circ}C$ and strain rate range of $0.05\~5s^{-1}$ using hot compression tests. The metadynamic recrystallization and grain growth evolution has been studied in the temperature range of $950\~1250^{\circ}C$ and strain rate range $0.05,\;5s^{-1}$, holding time range of 5, 10, 100, 600 sec using hot compression tests. Modeling equations are proposed to represent the flow curve, recrystallized grain size, recrystallized fraction and grain growth phenomena by various tests. Parameters in modeling equations are expressed as a function of the Zener-Hollomon parameter. The modeling equation for grain growth is expressed as a function of the initial grain size and holding time. The modeling equations developed were combined with thermo-viscoplastic finite element modeling to predict the microstructure change evolution during hot forging process. The grain size predicted from FE simulation results is compared with results obtained in field product.

• Korean Chemical Engineering Research
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• v.49 no.1
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• pp.15-20
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• 2011

The contamination effect of toluene in the airstream on PEM fuel cell performance was studied with various toluene concentration under different operation conditions. And the recovery of the cell performance by applying clean air and the removal of toluene in the air by adsorption of active carbon were investigated. The toluene concentration range used in the experiments was from 0.1 ppm to 5.0 ppm. The performance degradation and recovery were measured by constant-current discharging and electrochemical impedance spectroscopy(EIS). Toluene adsorption capacity of KOH impregnated active carbon was obtained from the adsorption isotherm curve. The severity of the contamination increased with increasing toluene concentration, current density and air stoichiometry, but decrease with increasing relative humidity. The cell performance was recovered by toluene oxidation with oxygen and water in humidified neat air. EIS showed that the increase of charge transfer resistance due to toluene adsorption on Pt surface mainly reduced the performance of PEMFC. Toluene adsorption capacity of active carbon decreased as KOH weight increased in KOH impregnated active carbon.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.38 no.4
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• pp.11-17
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• 2001

In this paper, we propose a polarity decision carrier recovery algorithm for high order QAM(Quadrature Amplitude Modulation), which has robust and large frequency acquisition performance in the high order QAM modem. The proposed polarity decision PD(Phase Detector) output and its variance characteristic are mathematically derived and the simulation results are compared with conventional DD(Decision-Directed) method. While the conventional DD algorithm has linear range of $3.5^{\circ}{\sim}3.5^{\circ}$, the proposed polarity decision PD algorithm has linear range as large as $-36^{\circ}{\sim}36^{\circ}$ at ${\gamma}-17.9$. The conventional DD algorithm can only acquire offsets less than ${\pm}10\;KHz$ in the case of the 256 QAM while an analog front-end circuit generally can reduce the carrier-frequency offset down to only ${\pm}100\;KHz$. Thus, in this case additional AFC or phase detection circuit for carrier recovery is required. But by adopting the proposed polarity decision algorithm, we can find the system can acquire up to ${\pm}300\;KHz$at SNR = 30dB without aided circuit.

• Journal of Microbiology and Biotechnology
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• v.22 no.9
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• pp.1185-1192
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• 2012

This study investigated the hydrocarbonoclastic microbial community present on weathered crude oil and their ability to degrade weathered oil in seawater obtained from the Gulf St. Vincent (SA, Australia). Examination of the native seawater communities capable of utilizing hydrocarbon as the sole carbon source identified a maximum recovery of just $6.6{\times}10^1\;CFU/ml$, with these values dramatically increased in the weathered oil, reaching $4.1{\times}10^4\;CFU/ml$. The weathered oil (dominated by > $C_{30}$ fractions; $750,000{\pm}150,000mg/l$) was subject to an 8 week laboratory-based degradation microcosm study. By day 56, the natural inoculums degraded the soluble hydrocarbons (initial concentrations $3,400{\pm}700mg/l$ and $1,700{\pm}340mg/l$ for the control and seawater, respectively) to below detectable levels, and biodegradation of the residual oil reached 62% ($254,000{\pm}40,000mg/l$) and 66% ($285,000{\pm}45,000mg/l$) in the control and seawater sources, respectively. In addition, the residual oil gas chromatogram profiles changed with the presence of short and intermediate hydrocarbon chains. 16S rDNA DGGE sequence analysis revealed species affiliated with the genera Roseobacter, Alteromonas, Yeosuana aromativorans, and Pseudomonas, renowned oil-degrading organisms previously thought to be associated with the environment where the oil contaminated rather than also being present in the contaminating oil. This study highlights the importance of microbiological techniques for isolation and characterisation, coupled with molecular techniques for identification, in understanding the role and function of native oil communities.

• Journal of the Korean Chemical Society
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• v.39 no.12
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• pp.902-909
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• 1995

Detection limit as well as calibration curves on organophosphorus pesticide(dimethoate, diazinon, parathion-methyl, fenitrothion, malathion) and BHCs were measured for evaluation of utility on qualitative or quantitative analysis of pesticides with ion Trap mass spectrometer and quadrupole mass spectrometer. As ionization source, EI and CI were adopted for qualitative analysis of pesticides by comparison of each fragmentation pattern. At the same time, the utility as trace analysis techniques through scan or selected ion monitoring(SIM) mode was evaluated. With ion trap for all pesticides, detection limit(DL, 1 ${\mu}L$ injection) on scan mode was ranged 0.008∼0.225 ng at signal to noise ratio 3. With quadrupole DL on scan mode was ranged 0.23∼3.1 ng over 0.032∼0.68 ng on SIM mode. The calibration curve with ion trap generated good linearity over 0.99 as correlation coefficient. As clean up procedure, Bio Beads S-X3 was used for the separation of oils from five organophosphorous pesticides in flour extractant showing more than 80% as recovery at most cases. In case of BHCs in jinseng with Florisil column, the recovery of pesticides has been 60% to 90%.

• Korean journal of food and cookery science
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• v.31 no.2
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• pp.112-117
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• 2015

The analytical method for ethyl carbamate (EC) in maesil (Prunus mume) extract was developed with deuterium-labeled ethyl carbamate as an internal standard. Samples were neutralized with an addition of 1 N sodium hydroxide solution, followed by a solid phase extraction with a Chem Elut cartridge. A standard curve exhibited a good linearity with correlation coefficient of 0.9991. The limit of detection (LOD) and limit of quantification (LOQ) were 2.91 ng/g and 8.83 ng/g, respectively. The recovery rate of EC ranged from 91.40% to 120.90%. The precision never exceeded 12.57% (intra-day) and 11.03% (inter-day). Samples were comprised of 24 home-made and 7 commercially-available maesil extracts. Eight home-made samples contained EC at levels between 3.39 and 75.76 ng/g. Three commercially-available samples had EC at levels between 11.67 and 20.16 ng/g. Average daily intakes of EC from maesil extracts for consumers were 0.23 g/kg of body weight. Based on a benchmark dose confidence limit ($BMDL_{10}$) of 0.25 mg/kg of body weight/day, the margin of exposure (MOE) of EC in maesil extract for consumers was 94,150, which is not of concern. Considering that a daily intake of maesil extract has been increasing, further studies on the formation of EC in maesil extract is needed.

• Journal of Food Hygiene and Safety
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• v.13 no.2
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• pp.129-134
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• 1998

To develop an enzyme-linked immunosorbent assay (ELISA) for nivalenol (NIV), we produced polyclonal antibodies against tetraacetyl nivalenol (Ac4-NIV) and established ELISA conditions. Ac4-NIV-hemisuccinate conjugated to bovine serum albumin (Ac4-NIV-HS-BSA) was immunized with Freund's adjuvants into rabbits subcutaneously several times. By use of the antiserum showing the highest titer and Ac4-NIV-HS-HRP conjugate, we established competitive direct ELISA (cdELISA). Standard curve of cdELISA showed that the detection range of Ac4-NIV was about 10~5,000 ng/ml (ppb). The cross-reactivities of the polyclonal antibody towards Ac4-NIV and acetyl T-2 were 100 and 70% respectively, and those towards NIV, deoxynivalenol, 3-acetyl deoxynivalenol, 15-acetyl deoxynivalenol, triacetyl deoxynivalenol, fusarenonX, and T-2 were less than 0.1%. When cdELISA was applied to NIV-spiked corns followed by extraction with 70% acetonitrile and acetylation with acetic anhydride in pyridine, the recovery rates of the Ac4-NIV were 108, 143, and 70% (average, 107%) in the levels of 100, 300, and 1,000 ng/g (ppb), respectively.

• Journal of Bio-Environment Control
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• v.28 no.4
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• pp.461-470
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• 2019

This study was carried out to quantify the drought stress in grafted watermelon seedlings non-destructively by using chlorophyll fluorescence (CF) imaging technique rather than the visual judgment. Six-day old watermelon seedlings were grown under uniform irrigation for 3 days, and then given drought stress. Afterward, the sensor for the measurement of water content in plug tray cell unit was used to classify the drought-stress level into nine groups from D1 (53.0%, sufficient moisture state) to D9 (15.7%, extremely dry stress), and the 16 CF parameters were measured. In addition, re-irrigation was performed on the drought stressed seedlings(D5 - D9) to determine the growth and photosynthesis recovery level, which was not confirmed by visual judgment. The kinetic curve patterns of CF in three different drought stressed seedling groups were found to be different for the early detection of drought stress. All the 16 CF parameters decreased continuously with exposure to drought stress and drastically decreased from D5 (32.1%) where the visual judgment was possible. The fluorescence decline ratio (Rfd_Lss) started to decrease from the initial drought stress level (D5 - D6), and the Maximum PSII quantum yield (Fv/Fm) was significantly decreased in the later extreme drought stress range (D7 - D9) by re-irrigation recovery test. Thus, Rfd_Lss and Fv/Fm parameters were finally selected as potent indicators of growth and photosynthesis recovery in the initial and later stages of drought stress. Also, to the differences in the numerical values of the individual chlorophyll fluorescence parameters, the drought stress level was intuitively confirmed through the image. These results indicate that Rfd and Fv/Fm can be considered as potential CF parameters for the detection of low and extremely high drought stress, respectively. Furthermore, Fv/Fm can be considered as the best CF parameters for recovery at re-irrigation.