• 한국근적외분광분석학회:학술대회논문집
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• 한국근적외분광분석학회 2001년도 NIR-2001
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• pp.4111-4111
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• 2001

When a drug is prepared in a tablet, the active component represents only a small portion of the dosage form. The other components of the formulation include materials to assist in the dissolution, antioxidants, coloring agents and bulk fillers. The tablets are tested using approved testing methods usually involving separation and subsequent quantification of the active component. Tablets may also be tested by near-Infrared Reflectance spectrometry (NIRS). In the present study, based on NIRS and multivariate calibration methods, a novel and precise method is developed for direct determination of ascorbic acid in vitamin C tablet. Two different tablet formulations were powdered in three different sizes, 63-125 ${\mu}{\textrm}{m}$, and examined. Spectral region of 4750-4950 $cm^{-1}$ / was used and optimized for quantitative operations. Partial least squares (PLS) and multiple linear regression (MLR) methods were performed for this spectral region. The results of optimized PLS and MLR methods showed that reproducibility increase with decreasing grain size and standard error of calibration (SEP) of less than 1% w/w of ascorbic acid and a correlation coefficient of 0.998 can be achieved. The PLS method showed better results than MLR. Seven overdose and underdose samples (prepared in the laboratory to match marketed products) were tested by proposed and iodometric standard methods. A correlation between NIRS predicted ascorbic acid values and iodomet.ic values was calculated ($R^2$=0.9950). Finally, the direct analysis of individual intact tablets in their unit-dose packages (Blistering in aluminum and PVC foils) obtained from market were also carried out and a correlation coefficient of 0.9989 and SEP of 0.931% w/w of ascorbic acid were achieved.

• International Journal of Aeronautical and Space Sciences
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• 제18권1호
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• pp.8-16
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• 2017

Most of small air vehicles with moving wing fly at low Reynolds number condition and the reduced frequency of the moving wing ranges from 0.0 to 1.0. The physical phenomena over the wing dramatically vary with the reduced frequency. This study examines experimentally the effect of the reduced frequency at low Reynolds number. The NACA0012 airfoil performs sinusoidal pitching motion with respect to the quarter chord with the four reduced frequencies of 0.1, 0.2, 0.4 and 0.76 at the Reynolds number $2.3{\times}10^4$. Smoke-wire flow visualization, unsteady surface pressure measurement, and unsteady force calculation are conducted. At the reduced frequency of 0.1 and 0.2, various boundary layer events such as reverse flow, discrete vortices, separation and reattachment change the amplitude and the rotation direction of the unsteady force hysteresis. However, the boundary layer events abruptly disappear at the reduced frequency of 0.4 and 0.76. Especially at the reduced frequency of 0.76, the local variation of the unsteady force with respect to the angle of attack completely vanishes. These results lead us to the conclusion that the unsteady aerodynamic characteristics of the reduced frequency of 0.2 and 0.4 are clearly distinguishable and the unsteady aerodynamic characteristics below the reduced frequency of 0.2 are governed by the boundary layer events.

• 대한기계학회논문집B
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• 제20권5호
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• pp.1649-1660
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• 1996

The flow around a circular cylinder was controlled by an acoustic excitation issued from a thin slit along the cylinder axis. The static pressure distributions around the cylinder wall and flow characteristics in the near wake have been measured. Experiments were performed under three cases of Reynolds number, 7.8 * 10$\^$4/, 2.3 * 10$\^$5/ and 3.8 * 10$\^$5/. The effects of excitation frequency, sound pressure level and the location of the slit were examined. Data indicate that the excitation frequency and the slit location are the key parameters for controlling the separated flow. At Re$\_$d/, = 7.8 * 10$\^$4/, the drag is reduced and the lift is generated to upward direction, however, at Re$\_$d/, =2.3 * 10$\^$5/ and 3.8 * 10$\_$5/, the drag is increased and lift is generated to downward direction inversely. It is thought that the lift switching phenomenon is due to the different separation point of upper surface and lower surface on circular cylinder with respect to the flow regime which depends on the Reynolds number. Vortex shedding frequencies are different at upper side and lower side. Time-averaged velocity field shows that mean velocity vector and the points of maximum intensities are inclined to downward direction at Re$\_$d/ = 7.8 * 10$\^$4/, but are inclined to upward direction at Re$\_$d/ = 2.3 * 10$\^$5/.

• 대한임상검사과학회지
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• 제48권2호
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• pp.109-113
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• 2016

분석전 변이로 인하여 검사실은 오류에 직면하게 되고 많은 요인들은 환자의 검사결과에 영향을 미치게 된다. 다양한 진공채혈관은 신속하게 분리하고 방치된 검체의 용혈을 방지한다. 그러나 진공채혈관의 상태에 따라 몇 가지 제한점들이 발생하는데 이러한 문제점을 알아보기 위해 다양한 진공채혈관을 이용해 혈구산정검사로 비교 평가하였다. 유통기한별 검사결과에서는 백혈구(WBC)와 혈소판(PLT)의 값에서 0.24, 0.21로 큰 변이계수를 나타냈고 상관성에서는 백혈구(WBC), 혈소판(PLT), 적혈구(RBC)의 값이 유의성을 보였다(p<0.01). 한편 각 3사의 비교평가에서는 백혈구(WBC), 혈소판(PLT)의 값에서 0.27, 0.21로 가장 큰 변이계수를 나타냈고, 상관성에서는 각 3사가 모두 백혈구(WBC), 혈소판(PLT), 혈소판분포폭(PDW)의 값에서 높은 유의한 차이를 보였다(p<0.01) 그러나 G사와 B사는 혈소판(PLT), 혈소판분포폭(PDW)의 값에서는 낮은 유의한 차이를 보였다(p<0.05). 결론적으로 진공채혈관의 상태에 따른 분석의 안정성을 위해 적절한 진공채혈관의 분석평가가 이루어져야 한다.

• 대한화학회지
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• 제32권3호
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• pp.211-226
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• 1988

역상 액체 크로마토그래피에 의하여 몇 가지 금속-dithiocarbamate(DTC) 킬레이트의 용리거동을 Novapak $C_{18}$과 {\mu}$-Bondapak $C_{18}$ 분리관을 사용하여 연구하고, 아울러 동시 분리정량에 미치는 pH, 진탕시간, 흐름속도, 추출용매 종류 및 이동상의 세기등 여러가지 인자들의 영향을 조사 검토하였다. 미량 금속-DTC 킬레이트들은 Novapak $C_{18}$ 분리관에서 acetonitrile/methanol/water 또는 acetonitrile/water의 용리액을 사용하여 성공적으로 분리되었다. 모든 금속-DTC 킬레이트의 용매세기 인자는 $0{\leqq}log\;k'{\leqq}1$ 의 범위임을 확인하였고, 회수율을 97.0-106.7 %, coefficient of variation은 0.98-3.41%이었다. 최적 분석 조건에서 합성 시료중에 있는 혼합 금속 이온들은 상대 오차 ${\pm}$6.7 % 이내에서 동시 분리정량이 가능하였다.

• Korean Chemical Engineering Research
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• 제43권3호
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• pp.387-392
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• 2005

Dimethyl carbonate(DMC)는 낮은 독성과 빠른 생분해성으로 인해 MTBE(methyl tert-butyl ether)를 대체할 수 있는 무연가솔린의 첨가제로 주목받는 물질로, 주로 methanol의 carbonylation에 의해 합성되고, 원가절감을 위해 methanol을 출발물질로 한 새로운 DMC 제조공정의 개발이 진행 중에 있다. 이에 필요한 다양한 조건하의 DMC 관련 혼합계의 상평형 자료 및 물성은 Dortmund Data Bank(DDB)검색 결과, 매우 부족하며 무한희석 활동도계수에 대한 자료는 전무한 것으로 나타났다. 이 글에서는 methanol+DMC계의 333.15 K에서의 이성분계 등온 기-액 평형과, 혼합물성으로써 methanol+DMC계의 과잉부피 및 점도편차를 298.15 K에서 측정하였다. 또한, 무한희석상태에서 DMC 용매에서의 methanol의 무한희석 활동도계수를 303.15, 313.15, 323.15 K에서 각각 측정하였으며, 측정값은 modified UNIFAC(Dortmund)식에 의한 계산 값과도 비교하였다.

• 전기학회논문지
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• 제61권5호
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• pp.744-752
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• 2012

In this study, the Polynomial-based Radial Basis Function Neural Networks is proposed as an one of the recognition part of overall face recognition system that consists of two parts such as the preprocessing part and recognition part. The design methodology and procedure of the proposed pRBFNNs are presented to obtain the solution to high-dimensional pattern recognition problems. In data preprocessing part, Principal Component Analysis(PCA) which is generally used in face recognition, which is useful to express some classes using reduction, since it is effective to maintain the rate of recognition and to reduce the amount of data at the same time. However, because of there of the whole face image, it can not guarantee the detection rate about the change of viewpoint and whole image. Thus, to compensate for the defects, Linear Discriminant Analysis(LDA) is used to enhance the separation of different classes. In this paper, we combine the PCA&LDA algorithm and design the optimized pRBFNNs for recognition module. The proposed pRBFNNs architecture consists of three functional modules such as the condition part, the conclusion part, and the inference part as fuzzy rules formed in 'If-then' format. In the condition part of fuzzy rules, input space is partitioned with Fuzzy C-Means clustering. In the conclusion part of rules, the connection weight of pRBFNNs is represented as two kinds of polynomials such as constant, and linear. The coefficients of connection weight identified with back-propagation using gradient descent method. The output of the pRBFNNs model is obtained by fuzzy inference method in the inference part of fuzzy rules. The essential design parameters (including learning rate, momentum coefficient and fuzzification coefficient) of the networks are optimized by means of Differential Evolution. The proposed pRBFNNs are applied to face image(ex Yale, AT&T) datasets and then demonstrated from the viewpoint of the output performance and recognition rate.

• 화약ㆍ발파
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• 제40권3호
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• pp.33-43
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• 2022

화약류 저장소는 내부 폭발 시 구조물에 가해지는 영향을 최소화하기 위해 내벽과 일정 거리 이격하여 화약류를 저장하고, 예기치 못한 폭발에 나머지 폭약의 순폭을 방지해야 한다. 따라서 안전한 화약류 저장을 위해 저장소 내부에 폭약의 분할 배치를 모사하여 순폭 실험을 진행하였다. 본 연구에서는 에멀젼 폭약 사이의 이격거리, 배치를 달리 적용하여 직경의 2배(2D)에서 순폭되고, 2.5배(2.5D)에서 불폭됨을 확인하였다. 순폭도와 화약류 저장소 크기를 감안하여 폭약량 3kg을 설정하였고 다양한 배치 변화에 따른 순폭실험 결과 대부분 불폭되어 해당 배치 적용 시 안전성을 확인하였다.

• 대한화장품학회지
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• 제23권3호
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• pp.161-167
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• 1997

Determination of several cationic surfactants in cosmetics has been investigated. Reverse phase ion pair chromatography was used to identify and quantitate cationic surfactants. Cationic surfactants analyzed in this experiment were cetylpyridium chloride, stearyltrimetylammonium chloride, bezalkonium chloride, benzyldicethylcetylammonium chloride, and bihenyltrimethyl ammonium chloride. The separation was achieved on a reverse phase coumn with 10mM HCl-acetonitrile eluent. In this condition, the most of cationic surfactants with exception of CPC and CTAC respectively with suppressed conductivity detector and UV detector connected in series. The calibration curves obtained by plotting the peak areas of the cationic surfactants were linear at levels ranging from 0.005 to 0.1% correlation coefficient, r=0.9988. The detection limits were 1 to 5ppm in sample solution. The average recoveries of cationic surfactants added to hair treatment cream and hair rinse in three to five experiments were 96.7 105.2% and relative standard deviations were 1.1-3.8%. The case that there were CPC and CTAC in same solution was also tested. CPC and CTAC which couldn't be separated on reverse phase column were quantitated with suppressed conductivity detector and UV detector connected in series. Recovery of CPC and CTAC were 101.6 and 89.2% respectively. The proposed method was applied to the determination of cationic surfactants in commercial hair treatment cream.

• Bulletin of the Korean Chemical Society
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• 제32권5호
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• pp.1564-1568
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• 2011

A solvent extraction separation, preconcentration and determination of thorium with a new crown, 2-ethyl-N-benzyl-4,7,10,13,16-pentaoxa-1-azacyclooctadecane (MACE), is described in the study. The amount of thorium in the aqueous phase and organic phase was determined by Inductively Coupled Plasma-Optical Emission Spectroscopy and Ultraviolet-Visible, respectively. Thorium loaded organic phase was quantitatively stripped in a stage by using 1.0 M $HNO_3$. Thorium was effectively extracted with MACE in the pH range of 6-7 to produce a 3:2 complex ratio in the chloroform. A highly sensitive and rapid spectrophotometric method was described for determination of trace amounts of thorium with MACE. The effective molar absorption coefficient at 281 nm is $1.98{\times}10^3\;mol^{-1}cm^{-1}$, and the system complies with Beer's law in the range from 0.464 to 2.32 ${\mu}gm\;L^{-1}$ of thorium. Thorium was also determined in standard and environmental samples.