• 동굴
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• 제71호
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• pp.5-11
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• 2006

A theoretical investigation of the solid phase mechanochemical synthesis of nano sized target product on the basis of dilution of the initial powdered reagent mixture by another product of an exchange reaction is presented. On the basis of the proposed 3 mode particle size distribution in mechanically activated mixture, optimal molar ratios of the components in mixture are calculated, providing the occurrence of impact friction contacts of reagent particles and excluding aggregation of the nanosized particles of the target reaction product. Derivation of kinetic equations for mechanochemical synthesis of nanoscale particles by the final product dilution method in the systems of exchange reactions is submitted. On the basis of obtained equations the necessary times of mechanical activation for complete course of mechanochemical reactions are designed. Kinetics of solid phase mechanosynthesis of nano TlCl by dilution of initial (2NaCl+$Tl_2SO_4$) mixture with the exchange reaction product (diluent,$zNa_2SO_4$, z=z*=11.25) was studied experimentally. Some peculiar features of the reaction mechanism were found. Parameters of the kinetic curve of nano TlCl obtained experimentally were compared with those for the model reaction KBr+TlCl+zKCl=(z+1) KCl+TlBr (z=z1*=13.5), and for the first time the value of mass transfer coefficient in a mechanochemical reactor with mobile milling balls was evaluated. Dynamics of the size change was followed for nanoparticle reaction product as a function of mechanical activation time.

• 대한화학회지
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• 제19권6호
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• pp.403-407
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• 1975

히드라진과 브롬의 반응속도를 직접 혼합법 및 일정전류 전해법에 의한 브롬화 이온의 전이시간을 측정하는 방법으로 측정하여, 황산 및 브롬화칼륨의 농도가 작을 때에 2차 반응속도 상수는 각각 $10^5\;및\;10^3mole^{-1}sec^{-1}$로 얻어졌다. 이는 $N_2H_4+Br_2{\rightarrow}N_2H_2,k_1=10^5$ 및 $N_2H_2+Br_2{\rightarrow}X,k_2=10^3$인 것으로 간주된다. 황산과 브롬화 이온의 농도가 클때에는 속도상수가 크게 감소하나 그 원인은 해명하지 못하였다.

• Journal of Microbiology and Biotechnology
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• 제18권12호
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• pp.1903-1907
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• 2008

Prodigiosin is a natural red pigment with algicidal activity against Cochlodinium polykrikoides, a major harmful red-tide microalga. To increase the yield of prodigiosin production by Hahella chejuensis KCTC 2396, significant medium components were determined using a two-level Plackett-Burman statistical design technique. Among 12 components included in basal medium, $NaHCO_3$, ${Na}_{2}{SiO}_{3}$, ${NH_4}{NO_3}$, ${Na}_{2}{SO}_{4}$ and $CaCl_2$ were determined to be important for prodigiosin production. The medium formulation was finally optimized using a Box-Behnken design as follows: 1% sucrose; 0.4% peptone; 0.1 % yeast extract; and (g/l): NaCl, 20.0; ${Na}_{2}{SO}_{4}$, 9.0; $CaCl_2$, 1.71; KCl, 0.4; and (mg/l): ${H_3}{BO_3}$, 10.0; KBr, 50.0; NaF, 2.0; $NaHCO_3$, 45.0; ${Na}_{2}{SiO}_{3}$, 4.5; ${NH_4}{NO_3}$, 4.5. The predicted maximum yield of prodigiosin in the optimized medium was 1.198 g/l by the Box-Behnken design, whereas the practical production was 1.495 g/l, which was three times higher than the basal medium (0.492 g/l).

• 대한원격탐사학회지
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• 제31권4호
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• pp.353-360
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• 2015

Earth's gravity field recovery was improved after the pre-processing upgrade of the Gravity Recovery And Climate Experiments (GRACE) satellite's star trackers. The star tracker measurements were filtered with a tighter low-pass filtering of 0.025Hz cutoff frequency, instead of a nominal filtering of 0.1Hz cutoff frequency. In addition, a jump removal algorithm was applied to remove discontinuities, due to direct Sun and/or Moon interventions, in the star tracker measurements. During the K-Band Ranging (KBR) calibration maneuvers, large attitude variations could be detected concurrently by both of the star trackers and the accelerometer. The misalignment angles of star trackers between the true frame and the normal frame could be determined by comparing measurements from these sensors. In this paper, new Earth' gravity field maps were obtained using above improvement. Based on comparisons to nominal Earth's gravity field maps, the new Earth's gravity field maps were found better than the nominal ones. Among the applied methods, the misalignment calibration of the star trackers had a major impact on the improvement of the new Earth's gravity field maps.

• 약학회지
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• 제49권3호
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• pp.249-254
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• 2005

The ethanol extracts of the mixed vegetables (Bioactive Vegetables, BV) and the mixed fruits (Bioactive Fruits, BF) were evaluated for their in vivo antioxidant activities. Four weeks treatment of oral administration was performed to mice. A $KBrO_3$ as a potent oxidant was used to induce the oxidative stress for in vivo experiment. BV and BF were shown to possess the significant inhibitory effect of lipid peroxidation as measured by the level of malondialdehyde (MDA) formation although the potencies were not higher than those of well-known antioxidants such as vitamin C, trolox and quercetin. Furthermore, BV and BF inhibited DNA damage assessed by single cell gel electrophoresis (comet assay) and reduced the micronucleated reticulocyte (MNRET) formation of peripheral blood. Antioxidants tested also revealed potent inhibitory activities higher than BV and BF. These antigenotoxic activity profiles were similar to that of abovementioned inhibition of lipid peroxidation. Therefore, BV and BF having mild antioxidant activity as functional food candidates may be useful natural antioxidants by the inhibiting of lipid peroxidation and the protecting oxidative DNA and chromosomal damage.

• 대한화장품학회지
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• 제21권2호
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• pp.129-139
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• 1995

FT-IR의 정량 법 중 Partial least-squares(PLS) 방법과 Multiple scattering correction(MSC) 방법을 이용한 계면활성제 분석의 타당성을 조사하기 위하여 LAS, MES 그리고 ELA-9을 이들 방법으로 정량 하였다. 계면활성제 표준품을 각각 다른 비율로, 50% 에탄올에 가열 용해 시킨 다음, 건조 시켜 액막법으로 IR 스펙트럼을 측정하였다. 얻어진 스펙트럼으로부터 Variance(분산 ) 스펙트럼을 구하고 이를 참고하여 여러 파수 영역에서 반복하여 검량선을 작성하고 상관계수를 구하였다. 1245-1130 cm -1 의 범위와 1070-1010 cm -1 범위의 파수를 선정한 결과 상관계수의 값이 모두 1.000이었다. 또한 정량 결과, 오차가 0.32%이하로써 매우 만족할 만한 결과를 얻었다. 따라서 FT-IR을 이용한 정량 법에서 PLS 방법과 MSC 방법은 계면활성제 분석에 유효하며, 본 정량 방법이 매우 간단하므로 품질관리 목적의 분석에 적합하다는 결론에 도달하였다.

• Archives of Pharmacal Research
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• 제28권7호
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• pp.775-783
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• 2005

The ethanol extract of the peony root (Paeonia Lactiflora Pall, Paeoniaceae) as well as its major active components including gallic acid and methyl gallate were evaluated for their protective effects against free radical generation and lipid peroxidation. In addition, the protective effects against hydrogen peroxide-induced oxidative DNA damage in a mammalian cell line were examined. The ethanol extracts of the peony root (PREs) and its active constituents, gallic acid and methyl gallate, exhibited a significant free radical scavenging effect against 1,1-diphenyl-2-picryl hydrazine (DPPH) radical generation and had an inhibitory effect on lipid peroxidation, as measured by the level of malondialdehyde (MDA) formation. The PREs did not have any pro-oxidant effect. They strongly inhibited the hydrogen peroxide-induced DNA damage from NIH/3T3 fibroblasts, as assessed by single cell gel electrophoresis. Furthermore, the oral administration of 50% PRE (50% ethanol extract of peony root), gallic acid and methyl gallate potently inhibited the formation of micronucleated reticulocytes (MNRET) in the mouse peripheral blood induced by a $KBrO_3$ treatment in vivo. Therefore, PREs containing gallic acid and methyl gallate may be a useful antigenotoxic antioxidant by scavenging free radicals, inhibiting lipid peroxidation and protecting against oxidative DNA damage without exhibiting any pro-oxidant effect.

• Applied Microscopy
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• 제23권2호
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• pp.1-10
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• 1993

The effect of electrolyte on the extraction replicas of the precipiates in 3% Si steel was investigated. Three Kinds of electrolyte, 2% Nital solution (2% nitric acid+methanol; acid solution),, Sodium Citrate solution (5% sodiumcitrate+1% KBr+0.5KI+$H_{2}O$; aqueous neutral solution) and 10% AA solution (10% acetylacetone+ 1% tetramethylammoniumchloride+methanol; non-aqueous neutral solution), were compared. The preciptiates in 3% Si steel were dissolved in 2% Nital, but they were not dissolved in the Sodium Citrate and 10% AA solution. In Sodium Citrate solution, however, large second artifacts were introduced during sample preparation. Therefore 10% AA solution was found to be most useful for the preparation of extraction replica. The electrolysis condition of a matrix and precipitates were also checked by the measurement of potential-current curve in 10% AA solution. The matrix was electrolyzed at -400mV with respect to SCE(Saturated Calomel Electrode). In contrats precipitates were electrolyzed above 300mV. Precipitates were respected to be stable in 10% AA solution in the range of $-380mV{\sim}-300mV$ usually used to prepare extraction replicas.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2005년도 하계학술대회 논문집 Vol.6
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• pp.405-406
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• 2005

A theoretical investigation of the solid-phase mechanochemical synthesis of nano-sized target product on the basis of dilution of the initial powdered reagent mixture by another product of an exchange reaction is presented. On the basis of the proposed 3-mode particle size distribution in mechanically activated mixture, optimal molar ratios of the components in mixture are calculated, providing the occurrence of impact-friction contacts of reagent particles and excluding aggregation of the nanosized particles of the target reaction product. Derivation of kinetic equations for mechanochemical synthesis of nanoscale particles by the final product dilution method in the systems of exchange reactions is submitted. On the basis of obtained equations the necessary times of mechanical activation for complete course of mechanochemical reactions are designed. Kinetics of solid phase mechanosynthesis of nano-TlCl by dilution of initial (2NaCl + $Tl_2SO_4$) mixture with the exchange reaction product (diluent, $zNa_2SO_4$, $z=z^*=11.25$) was studied experimentally. Some peculiar features of the reaction mechanism were found. Parameters of the kinetic curve of nano-TlCl obtained experimentally were compared with those for the model reaction KBr + TlCl + zKCl = (z + 1) KCl + TlBr ($z=z_l^*=13.5$), and for the first time the value of mass transfer coefficient in a mechanochemical reactor with mobile milling balls was evaluated. Dynamics of the size change was followed for nanoparticle reaction product as a function of mechanical activation time.

• 방송공학회논문지
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• 제2권2호
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• pp.206-215
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• 1997

본 논문에서는 H.263비디오 압축 표준을 기반으로 한 비디오 부호기들로서 두 개의 계층을 갖는 비트율 계위 비디오 부호기를 제안한다. 제안하는 부호기의 기본계층에서는 H.263표준에서 제안하고 있는 기본 부호기 알고리즘을 수용하여 비디오 데이터의 고 압축 부호화 효율을 얻는다. 상위계층에서는 부호화의 고급 기법이라 하루 수 있는 인간 시각 시스템 정보를 근거로 양자화를 설계하고 적용한다. 상위계층에서는 기본계층의 이산 여현 변환 계수에 보다 세밀한 양자화를 가하여 부호화하게 되며, 이때 필요한 비트스트림의 구조를 설계한다. 복호화기에서는 두 계층에서 수신한 데이터를 역양자화 및 역변환을 수행한 후 더하여 원 영상을 복원하게 된다. 실험 결과를 통하여 비트율 약30kbps 정도에서 계층을 적용하지 않은 부호기와 비교하여 거의 비슷한 화질을 얻을 수 있었으며, 상위계층의 비트스트림을 전송하기 위한 부가 정보를 약 프레임당 0.5kbits이하를 유지하도록 하였다.