• Applied Biological Chemistry
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• v.35 no.2
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• pp.82-86
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• 1992

This research was carried out to investigate antimutagent effect of peach enzymatic browning reaction products(PEBRP) obtained by reacting each of polyphenol compounds with oxidase extracted from Korea-cultivated peach. In methods, rec-assay with B. subtilis strains $H17(rec^+)\;and\;M45(rec^-)$, and Ames test with S. typhimurium TA98 and TA100 were used. The spore rec-assay of PEBRP, pyrogallol, hydroxyhydroquinone, homocatechol and caffeic acid were not showed mutagenicity. In the effects of various metal ions$(Al^{3+},\;Cu^{2+},\;Fe^{2+},\;Mn^{2+},\;Ni^{2+},\;Pb^{2+},\;Zn^{2+})$ on the rec-assay, all PEBRP except caffeic acid was increased inhibition zone(5 mm) only with $Zn^{2+}$. In paticular, the Py-PEBRP was decreased the difference of inhibition zone of growth on MMC(mitomycin C). In results of Ames test, all PEBRP were not showed mutagenicity on S. typhimurium TA98 and TA100; however, Ca-PEBRP and Hca-PEBRP were suppressed mutagenic effects on Trp-P-1 and B(a)P in the presence of S-9Mix.

• Journal of Korean Society of Environmental Engineers
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• v.27 no.5
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• pp.542-548
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• 2005

A fluidized bed reactor containing porous media has been known to be effective for nitrogen and organic matters removal in wastewater. The porous media which attached microbes plays important roles in simultaneous nitrification/denitrification (SND) due to coexistence of oxic, anaerobic and anoxic zone. For SND reaction, oxygen and organic substrates should be effectively diffused from wastewater into the intra-carrier zone. However, the overgrowth heterotrophic microbes at the surface of porous media may restrict from substrates diffusion. From these viewpoints, the existence and effect of heterotrophic bacteria at surface of porous media might be the key point for nitrogen removal. A porous media-membrane hybrid process was found to have improved nitrogen removal efficiency, due to stimulated denitrification as well as nitrification. Microelectrode studies revealed that although intra-media denitrification rate in a conventional fluidized bed was limited by organic carbon, this limitation was reduced in the hybrid process, resulting in the increased denitrification rate from 0.5 to $4.2\; mgNO_3-N/L/hr$.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 1997.11a
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• pp.10-11
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• 1997

고체 추진제를 사용하는 추진 시스템을 개발하는데 가장 커다란 문제로 인식되고 있는 것은 추진제의 연소 특성을 이해하는 일이다. 그 중에서도 연소실의 압력 진동과 추진제 벽면으로 흡수되는 복사 열전달에 의한 연소율(burning rate)의 변화로 인하여 발생하는 연소 불안정에 대한 이해는 아직도 완전히 규명되지 않고 있다. 고체 추진제의 연소 불안정에 대한 이론적 해석은 준-정상 1차원 해석(Quasi-Steady Homogeneous One-Dimension) 방법에 의하여 단순화된 지배방정식을 해석하는 것이 일반적으로 잘 알려져 있는 방법이다. 이 가정은 고체 추진제가 연수되는 영역을 두께가 매우 얇은 영역의 표면반응영역(surface reaction layer)과 화학반응이 없는 응축상태영역(condensed phase zone) 그리고 기체상태의 연료와 화염이 존재하는 기체상태영역(gas phase zone) 등의 3영역으로 구분하며, 기체상태영역에서 발생하는 교란에 대한 응축상태영역의 반응시간 크기(response time scale)가 매우 크기 때문에 응축상태영역의 반응은 준 정상적으로 일어난다고 가정하는 것이다.그러나, 연소실의 온도가 $3000^{\circ}K$ 정도의 높은 온도이어서 복사 열전달에 의한 고체 추진제의 가열이 중요한 열전달 방법으로 작용하게 되므로 이를 무시한 이론적 해석은 물리적인 중요성이 약하여질 수밖에 없다. 본 연구에서는 기체영역으로부터 전달되는 복사 열전달은 투명(transparent)한 표면반응영역을 통과하여 응축상태영역에서 모두 흡수되며 추진제 표면에서의 복사열방출(emission)을 고려하였다. 또한 연소불안정 현상을 해석하기 위하여 표면반응영역에서의 경계조건은 선형교란량으로 대치하는 Zn(Zeldovich-Novozhilov) 방법을 사용하였다. 이 방법은 기체상태영역에 대한 구체적인 해석없이도 연소불안정 현상을 해석할 수 있는 장점이 잇다. 즉 응축상태영역에서의 연소율과 표면온도는 각각 기체영역으로부터 전달되는 온도구배와 연소압력, 그리고 복사 열전달의 함수관계이므로 선형교란에 의한 추진제표면에서의 교란경계조건을 얻을 수 잇으며, 응축영역의 교란지배방정식과 함께 사용하여 압력교란과 복사 열전달의 교란에 대한 연소율의 교란 증감 여부를 판단하여 연소 불안정 현상을 해석할 수 있다.

• The Journal of Dong Guk Oriental Medicine
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• v.5
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• pp.197-207
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• 1996

As a mood-altering drug, long-term alcohol consumption have significant harmful effects on the human body and people's mental functioning. This study observed that the suppression of cell mediated immunity induced in spleen of ICR mouse by long-term alcohol administration. After 8% alcohol voluntary administered for 120 days, the splenic tissue irnmunohistochemically stained by following ABC method that used monoclonal antibody including L3T4(CD4), Ly-2(CD8), IL-2 receptor(CD25R) and NK-1.1(CD56) after embedding with paraffin. The results were as follows. 1. The size of marginal zone in splenic white pulp was diminished and the number of macrophage in marginal zone was decreased in test group than control group. 2. After alcohol administration, the number of Helper T lymphocyte, cytotoxic T lymphocyte, and IL-2 receptor were decreased in periarterial lymphatic sheaths of white pulp and penicilla artery of red pulp and the degree of CD4, CD8, and CD25R positive reaction were soften. 3. In test group, the number of NK cell were decreased. These results indicated that the secretion of lymphokine as IL-2 was inhibited by long-term alcohol administration and subsequently prevent to activate and proliferate splenic T lymphocytes and NK cells as cell mediated immunity component.

• Korean Journal of Crystallography
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• v.7 no.1
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• pp.81-87
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• 1996

The mechanism of silicon incorporation has been analyzed for the boat-grown GaAs crystals on the basis of phase equilibrium in the Ga and As system. Comparison was made between silicon concentrations calculated from the thermodynamics of incorporation reaction and carrier concentrations measured from van der Pauw method. For the 1-T HB(single temperature zone horizontal Bridgman) crystals, calculated concentrations were 5.3 ×10 15 (atoms/cm3), measured as 9.8 ×10 15(/cm3) at the seed part. They were calculated to be 1.1 ×10 16(atoms/cm3) and measured as 1.5 ×10 16(/cm3) for the 2-T(double temperature zone) HB crystals. On the other hand, it was found to be closer between the calculated and measured silicon concentrations for the VGF(vertical gradient freeze) crystals, which were grown within half the run time compared with 1-T or 2-T HB method.

• Journal of Information Technology Services
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• v.15 no.4
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• pp.73-83
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• 2016

Pedestrian safety was recently highlighted with a yellow carpet, a yellow-colored pavement material prepared for children waiting for signals for pedestrian crossing, without validation of its efficiency in practice. It was a promising device likely to assist highway safety by stimulating pedestrian to step on the yellow-colored area; it was generally called nudge effects. This paper delivers a study conducted to check the effectiveness of yellow carpet in three different aspects in vehicle driver's perspective by applying the newly introduced information technology (IT) service: Visual Attention Software (VAS). It was assumed that VAS developed by 3M in the United States should be able explain the Korean drivers' visual reaction behaviors since technology embedded in VAS was developed based on and proved by other various international countries and continents in the world. A set of pictures was taken at thirteen different field sites in seven school zone areas in the Seoul metropolitan area before and after the installation of a yellow carpet, respectively. Sets of those pictures were analyzed with VAS, and the results were compared based on the selective safety measures: the likely focusing on standing pedestrians (waiting for a pedestrian's green signal time) affected by its background (yellow-colored pavement) contrasting him or her. The test results from a set of before-and-after comparison analyses showed that the placement of yellow carpet would (1) increase 71% of driver's visual attention on pedestrian crossing areas and (2) change the sequential order of visual attention on that area 2.4 steps ahead. The findings would enhance deployment of such promising efficiency and thus increase children safety in pedestrian crossing. The result was promising to highlight the way to support the changes in conservative traffic safety engineering field by applying the advanced IT services, while much robust research was recommended to overcome the limitation of simplification of this study.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.36 no.9
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• pp.1095-1101
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• 2012

A process heat exchanger (PHE) in a nuclear hydrogen system is a key component that transfers the large amount of heat generated in a very high temperature reactor (VHTR) to a chemical reaction that yields a large quantity of hydrogen. A performance test on a small-scale and a medium-scale PHE prototype made of Hastelloy$^{(R)}$-X is being conducted on in a small-scale nitrogen gas loop at the Korea Atomic Energy Research Institute. Previous research on the macroscopic high-temperature structural analysis of PHE prototypes had been performed using base material properties owing to a lack of weld material properties. In this study, macroscopic high-temperature structural analyses considering the weld material properties were performed and the results were compared with those of a previous study.

• Journal of the Korean Society for Heat Treatment
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• v.8 no.1
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• pp.32-43
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• 1995

Ti-6Al-4V alloy are widely used in chemical and aircraft industries for their good corrosion resistance and high strength to weight ratio. Surface alloying of Ti alloy by $CO_2$ laser is able to produce few hundred micrometers thick TiN surface-alloyed layer with high hardness on the substrate very simplely by injecting reaction gas($N_2$) into a laser-generated melt pool and adjust the hardness to the specific requirements of the individual application by changing of laser processing parameters. This research has been investigated the effect of such parameters on TiN surface-alloying of Ti-6Al-4V alloy by $CO_2$ laser. The maximum hardness of TiN surface-alloyed zone waw obtained by injecting 100% $N_2$ gas and it was decreased as the amount of $N_2$ gas in Ar and $N_2$ gas mixture was decreased. As scanning speed was increased, the hardness and depth of TiN surface-alloyed zone was decreased at constant laser power. The surface hardness after double scanning laser treatment is higher than that of single scanning. At constant laser power, the surface roughness is increased after the surface alloying if laser scanning speed is decreased.

• Applied Chemistry for Engineering
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• v.30 no.2
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• pp.178-185
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• 2019

Three spherical quaternary composites composed of metal/metal oxide/high explosive/oxidizer were prepared by a crystallization/agglomeration process. From the characteristics of composites by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC), the shortening of the decomposition zone of high explosives in the quaternary composite was observed, which may be attributed to the autocatalytic reaction caused by $ClO_2$ or HCl which are ammonium perchlorate (AP) degradation products. The activation energy analysis showed that the activation energy abruptly decreases at the end of the decomposition zone of high explosives, and it was considered to be caused by $HNO_2$ which is common in decomposition products of high explosives. The activation energy predicted from complex pyrolysis results by the distributed activation energy model (DAEM) showed much better in accuracy than those by model-fitting methods such as Kissinger-Akahira-Sunose and Flynn-Wall-Ozawa models.

• Clean Technology
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• v.15 no.2
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• pp.116-121
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• 2009

In this paper, we investigated the effect of an indirect oxidation zone in an electrolysis reactor that used Ti/$IrO_2$ as the anode and SUS 316L as the cathode. Based on our preliminary results, the electrolysis reactor was operated with pole plate interval of 6 mm, current density 1.0 $A/dm^2L$ and electrolyte concentration 15%. The removal efficiency, COD (chemical oxygen demand), was additionally increased by 55% and 12.5${\sim}$15.0% in the direct and indirect oxidation zones, respectively. The removal efficiencies of T-N (total nitrogen) and T-P (total phosphorus) were found to be 88% and 75%, respectively. It was shown that the additional effect of the indirect oxidation zone on the removal was nearly negligible. Also, as the removal of COD,T-N and T-P took place during the initial2${\sim}$5 days of reaction, it was concluded that there was no need to extend the retention time of the electrolysis reactor.