• 대한화학회지
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• 제47권6호
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• pp.559-568
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• 2003

LLE-GC/MS법을 사용하여 내분비계 교란물질로 추정되는 항 산화제 및 살충제를 동시에 분석할 수 있는 방법을 고안하였다. 본 연구에서 사용한 항 산화제는 butylated hydroxy anisole(BHA) 및 butylated hydroxy toluene (BHT)이고, 살충제는 allethrin 및 fenvalerate이었다. 표준시료에 대한 분석결과에서 검출한계(LOD)는 0.071~0.159 ng/ml이었으며, 이 때 상대표준편차는(%RSD)는 1.41~5.34이었다. 한강, 금강, 낙동강 및 섬진강 수계 중에서 이들 화합물들은 검출되지 않았다. 합성한 시료의 경우, 검출한계(LOD)는 0.051~0.132 ng/ml이었으며, 이 때 상대표준편차(%RSD)는 6.39~13.4% 이었다.

• Bulletin of the Korean Chemical Society
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• 제31권10호
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• pp.2813-2818
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• 2010

A novel method was developed for the speciation of chromium in natural water samples based on homogeneous liquid-liquid extraction and determination by flame atomic absorption spectrometry (FAAS). In this method, Cr(III) reacts with a new Schiff's base ligand to form the hydrophobic complex, which is subsequently entrapped in the sediment phase, whereas Cr(VI) remained in aqueous phase. The Cr(VI) assay is based on its reduction to Cr(III) by the addition of sodium sulfite to the sample solution. Thus, separation of Cr(III) and Cr(VI) could be realized. Homogeneous liquid-liquid extraction based on the pH-independent phase-separation process was investigated using a ternary solvent system (water-tetrabutylammonium ion ($TBA^+$)-chloroform) for the preconcentration of chromium. The phase separation phenomenon occurred by an ion-pair formation of TBA and perchlorate ion. Then sedimented phase was separated using a $100\;{\mu}L$ micro-syringe and diluted to 1.0 mL with ethanol. The sample was introduced into the flame by conventional aspiration. After the optimization of complexation and extraction conditions such as pH = 9.5, [ligand] = $1.0{\times}10^{-4}\;M$, [$TBA^+$] = $2.0{\times}10^{-2}\;M$, [$CHCl_3$] = $100.0\;{\mu}L$ and [$ClO_4$] = $2.0{\times}10{-2}\;M$, a preconcentration factor (Va/Vs) of 100 was obtained for only 10 mL of the sample. The relative standard deviation was 2.8% (n = 10). The limit of detection was sufficiently low and lie at ppb level. The proposed method was applied for the extraction and determination of chromium in natural water samples with satisfactory results.

• 한국추진공학회지
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• 제11권5호
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• pp.37-50
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• 2007

본 연구에서는 액체 추진제 로켓엔진의 연소기에 주로 사용되는 액체 동축 스월형 분사기의 분무특성을 예측할 수 있는 모델을 개발하여 분무 연소장을 계산하기위하여 개발된 KIVA의 환경에 적합하도록 유도하였다. 액막의 분열에는 선형 안정성 이론을 도입하여 장파와 단파의 영역을 모두 고려할 수 있는 모델을 개발하였고 점성이 고려된 수력학적 해석을 통해 초기의 액막 두께와 분무각 및 분사 속도를 예측하였다. 또한 개발된 분무 모델에 대한 난류 모델의 적합성을 평가하여 RNC $k-{\varepsilon}$ 모델이 적합함을 알았다. 이러한 모델의 평가를 바탕으로 액체로켓엔진에 장착되는 분사기에서 생산되는 분무의 특성을 실험 결과와 비교하였고, 분열 길이, 분무각 및 SMD가 정성적, 정량적으로 잘 일치하는 것을 알 수 있었다.

• Geomechanics and Engineering
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• 제33권2호
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• pp.175-182
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• 2023

In general, the design of structures and its construction processes are fundamentally dependent on their foundation and supporting ground. Thus, it is imperative to understand the behavior of the soil under certain stress and drainage conditions. As it is well known that certain characteristics and behaviors of soils with fines are highly dependent on water content, it is critical to accurately measure and identify the status of the soils in terms of water contents. Liquid limit is one of the important soil index properties to define such characteristics. However, liquid limit measurement can be affected by the proficiency of the operator. On the other hand, dynamic properties of soils are also necessary in many different applications and current testing methods often require special equipment in the laboratory, which is often expensive and sensitive to test conditions. In order to address these concerns and advance the state of the art, this study explores a novel method to determine the liquid limit of cohesive soil by employing video-based vibration analysis. In this research, the modal characteristics of cohesive soil columns are extracted from videos by utilizing phase-based motion estimation. By utilizing the proposed method that analyzes the optical flow in every pixel of the series of frames that effectively represents the motion of corresponding points of the soil specimen, the vibration characteristics of the entire soil specimen could be assessed in a non-contact and non-destructive manner. The experimental investigation results compared with the liquid limit determined by the standard method verify that the proposed method reliably and straightforwardly identifies the liquid limit of clay. It is envisioned that the proposed approach could be applied to measuring liquid limit of soil in practical field, entertaining its simple implementation that only requires a digital camera or even a smartphone without the need for special equipment that may be subject to the proficiency of the operator.

• 한국대기환경학회지
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• 제30권6호
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• pp.586-599
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• 2014

During the last two decades, indoor air quality and volatile organic compounds (VOCs) have been of concern in Korean society due to their nature of potential health impacts. In order to investigate the pollution levels of VOCss in indoor environments, establishment of a solid test method for monitoring the airborne VOCss is essential. In Korea, a method based on adsorbent sampling and GC analysis coupled with thermal desorption was proclaimed as the Korea Standard Method for Indoor Air Quality Test. This study was carried out to examine some inherent problems of the VOCs measurement method. The VOCs method does not describe in detail preparing the standard samples. The standard samples may be prepared by impregnation of either liquid standard solutions or a mixture of standard gases. In this study, we investigated the optimal temperature condition for transferring the liquid standards onto a standard adsorbent tube. As a result, keeping the impregnation temperature at $250^{\circ}C$ will be recommended in regard of the boiling points of multiple target analytes and the thermal stability of the adsorbent. We also demonstrated some problems associated with handling of a syringe used for transferring the standard solutions onto the adsorbent tubes, and a best way to get rid of the syringe problems was suggested. Finally, a number of field works were conducted to evaluate the performance of adsorbent sampling methods. Comparison of different adsorbent tubes, i.e. tube packed with single sorbent (Tenax) and double sorbents (Tenax with Carbotrap), revealed that 30 to 40% differences between the two groups, implying that sampling efficiency is depending on the volatility and the strength of adsorbents. However, duplicate precisions for VOCs sampling with a same type of adsorbent and at same flow rates appeared to be satisfactory to be all within 20%, which is a quality control guideline. Distributed volume precisions were also found to be within a guideline value, 25%, although the precision was in general inferior to the duplicate precision. The Korea indoor VOCs test method should be more refined and improved in many aspects, particularly procedure and instrumentation for preparing the standard samples and specification of quality control assessment.

• Advances in environmental research
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• 제2권3호
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• pp.179-202
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• 2013

Bisphenol A and other alkylphenols are widely used in plastic and other industrial consumer products. Release of these compounds into the aquatic environment during their manufacture, use and disposal has been a great scientific and public concern due to their toxicity at high concentrations and endocrine disrupting effects at low concentration on aquatic wildlife and human beings. This paper reviews the published data and researches on the environmental occurrence, distribution, health effects and analytical techniques of bisphenol A and alkylphenols. The aim is to provide an overview of the current understanding about bisphenol A and alkylphenols in the environment and the difficulties faced today in order to establish standard and systematic environmental analysis and assessment process for these endocrine disruptor compounds.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2005년도 춘계학술대회 논문집
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• pp.1412-1415
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• 2005

Special considerations on the design of liquid storage tanks should be taken into account for seismic and wind loads. But Korean industrial standard KS B 6225 does not specify detailed guidelines for a design. It is therefore necessary to improve design guidelines for a seismic and wind-proof design in KS B 6225. The purpose of this study is provide a basis for the development of improved seismic and wind-proof design procedures, especially about seismic and wind loads.

• 미생물학회지
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• 제15권4호
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• pp.154-158
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• 1977

Fifteen kinds of antibiotics both in liquid or dry stantes wre investigated for the purpose of radiation effect on the antibiotic activities after irradiation. In liquid states, the antibiotics such as amoxyllin, ampicillin, capharolidin and hetacillin were inctivated 90% of their antibiotic activities at radiation doses of 50Krad, and penicillin, dicloxacillin, caphalothin, cloxacillin, erythromycin and caphalexin and kanamycin were decomposed at radiation doses of 1.5Mrad, respectively. In dry states, all antibiotics were stable at radiation doses of 5Mrad. On the other hand, the neomycin in liquid state was rather increased the antiboctic activity about 1.2 and 8 times when the E. coli ATCC 113-3 and B. subtitilis ATCC 6633 were used aas a standard microorganisms, whereas, the decrensed antibiotic activities were observed in S. typhi Ty-2(36.2%), St.faecium(10.79%), B.sphaericus CIA(9.066%) and St.aureus ATCC 6538p(70%).

• 약학회지
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• 제23권3_4호
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• pp.181-186
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• 1979

A high performance liquid chromatograpic procedure is described for determining ginseng saponins such as ginsenoside-Rb1, -Rb2, -Rc, -Rd, -Re, -Rf, -Rg1, and-Rg2. Ginseng saponins extracted with 90% methanol and water-saturated butanol were compared with pure standard ginsenosides. The resolution of the saponins was satisfactory and detection limit for each saponin was about 5.mu.g. Separation of the saponins was accomplished using a .mu. Bondapak carbohydrate analysis column, mobile phase of acetonitrile-water-butanol (80:20:15) and differential refractive index (RI) detector. The reproducibility and the recovery were also studied. This method was applied for determining the saponin contents of several parts of leaf, fresh ginseng, white ginseng, and red ginseng.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2006년도 춘계 학술발표회 논문집(II)
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• pp.469-472
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• 2006

Amount used of admixture fare is increasing for concrete economic efficiency and ability security. Security of economic efficiency and ability can expect by use of this admixture fare but is displaying a lot of problems on early age strength hold by hydrate delay relatively. Specially, in the case of construction site, concrete strength can speak that interrelation is high with mold removal of forms time. Therefore, is economical and need examination of plan that can secure robber within 3 days using admixture fare such as fly ash and blast furnace slage differential speech to secure function. In this study, adding liquid admixture within 1% of a binding agent quantity to examine these problem with physical characteristic after hardening ago specially, strength change at standard and air dry curing of observed change in priority. Air dried and water curing total strength enhancement effects appeared by thing which is in case of add test result liquid admixture by below 1% and strength deputy by passage of age could know is not big.