• Journal of the Korean Crystal Growth and Crystal Technology
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• v.15 no.4
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• pp.145-151
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• 2005

Color enhancement of African rubies with dark red was carried out by the heat treatment and the hydrothermal treatment method respectively. The heat treatment method brought about an adverse effect causing the color to be deteriorated. However, the hydrothermal treatment method enhanced its color and clarity. The hydrothermal treatment conditions for color enhancement of them were as follows: solvent: 0.9M $Na_2CO_3-1M\;K_2CO_3$, temperature: $450^{\circ}C$, duration: 48 hrs, filling: $30\%$, pressure: 375 atm. As the results of characteristics for African rubies obtained under these conditions, it was known that the amount of $Cr^{3+},\;Fe^{3+},\;Ti^{4+}$ was reduced after the hydrothermal treatment from the ICP/MS and XRF analyses. Also, it was found that the red color from the colorimeter analyses was getting lighter. These results were consistent with the PL analysis showing that the intensity of the luminescence peak generated by the electron transition of $Cr^{3+}$ ion became lower after the hydrothermal treatment compared with the non-treated rubies.

• Journal of the Korean Ceramic Society
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• v.38 no.7
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• pp.648-653
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• 2001

구연산이 첨가된 0.01 M의 $\beta$-인산칼슘 용액을 수열처리 하여 휘스커 상 수산화아파타이트를 합성할 때 수열처리 온도 및 시간이 휘스커의 생성에 미치는 영향을 관찰하였다. 용액을 30$0^{\circ}C$에서 5시간 수열처리 할 때 c축으로 약 60-80$\mu\textrm{m}$까지 성장하고 비교적 순수한 휘스커를 얻을 수 있었으며 이렇게 합성된 수산화아파타이트 휘스커를 수산화아파타이트 시멘트에 1-2 wt% 첨가하였을 때 그 경화체의 직경인장강도는 약 4-6배까지 증가하였다.

• Clean Technology
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• v.15 no.2
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• pp.122-129
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• 2009

The effect of calcination temperature or hydrothermal treatment of commercial Fe-beta zeolites in the range of $450{\sim}900^{\circ}C$ were examined in the direct decomposition of $N_2O$. Fe-beta zeolites used were characterized using XRD, $N_2$ sorption, $^{27}Al$ MAS NMR and XPS. Although the surface area and micropore volume of Fe-beta zeolite after calcination at $900^{\circ}C$ and hydrothermal treatment at $750^{\circ}C$ decreased ca. 30%, a larger decrease in the surface area and micropore volume by hydrothermal treatment was observed than by calcination treatment alone. However, the Al sites in frameworks of zeolite were conserved in stable tetrahedral form resulting from low degree of dealumination which was related to the adjacent Fe ions on the Al sites. This could likely be correlated with the conservation of high surface area and micropore volume of Fe-beta zeolites. The increase in the calcination or hydrothermal treatment temperature caused the increase of decomposition temperature of $N_2O$ and the severe deactivation was observed after hydrothermal treatment than calcination treatment.

• Proceedings of the Korea Information Processing Society Conference
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• 2002.11b
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• pp.1075-1078
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• 2002

스트림 암호 시스템에서는 비선형 결합 LFSR 키 수열을 이용하였다. 주기가 존재하고 상관관계 공격에 약한 비선형 LFSR 키 수열의 문제를 개선하기 위해 제안된 카오스 키 수열은 균형성과 랜덤특성을 만족하지 못하고 있다. 따라서, 본 연구에서는 적응적 임계값 적용 방법을 이용하여 균형성과 랜덤특성을 만족하는 카오스 키 수열 생성 기법을 제안하였다. 본 연구에서 제안한 키 수열 생성 기법은 로지스틱 방정식을 이용하여 키 수열 생성을 위한 카오스 신호를 만든 다음 카오스 신호를 적응적 임계값 적용방법을 통해 '0'과 '1'로 양자화하여 키 수열을 생성한다. 제안한 알고리즘으로 생성된 키 수열의 특징을 분석한 결과 균형성과 랜덤특성이 기존의 카오스 키 수열에 비해 개선되었음을 알 수 있다.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.14 no.2
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• pp.73-77
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• 2004

The color enhancement for natural Zambian amethyst of low quality was carried out by the hydrothermal treatment method. The hydrothermal treatment conditions were as follows: reaction temperature; $300^{\circ}C$, duration; 30 hrs, filling; 40%, solvent; 6 M-HCI solution. The reddish purple amethyst of high quality was obtained under these conditions. From the result of ICP/AES, it was known that color enhancement was affected by a Fe elemental content to exist in the inside of natural Zambian amethyst. Also, from the result of UY-VIS-NIR, it was shown that the absorption peak at 550 nm after hydrothermal treatment is slightly lower than those of non-treated natural Zambian amethyst. In this study, it was known that hydrothermal treatment method was a way to suitable for increase of commercial value of natural Zambian amethyst.

• Clean Technology
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• v.16 no.4
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• pp.254-257
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• 2010

[ $Mg(OH)_2$ ]slurry was prepared by using natural mineral brucite exploited from Liaoning province in China, and its de-SOx efficiency was examined. The effect of difference in particle size distribution of brucite and activation by hydrothermal treatment were investigated. The de-$SO_2$ efficiency of a finely-milled brucite sample below 1000 mesh with narrow particle size distribution was higher than that of the sample below 80 mesh. On the other hand, the de-$SO_2$ efficiency of brucite sample below 80 meshes was significantly improved by the hydrothermal treatment at 363 K tor 3 h.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.16 no.6
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• pp.240-243
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• 2006

The significant color enhancement in low quality Australian natural sapphire has been achieved by a hydrothermal method. The optimal conditions for the color enhancement of Australian natural sapphire were as follows; hydrothermal reaction temperature: $320{\sim}350^{\circ}C$, duration : 3 days, hydrothermal solvent: 2 M NaOH solution. After the hydrothermal treatment, Australian natural sapphires of transparent colors were obtained, and their grades were found to be improved from commercial to middle/top grade by value chart analysis.

• Proceedings of the Korea Information Processing Society Conference
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• 2004.05a
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• pp.1011-1014
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• 2004

본 논문에서 제안된 Self_Decimated LM-128 키 수열 발생기(Keystream generator)는 2개의 비트 메모리 합산 수열발생기(summation generator)를 갖는 자체 클럭 조절형 키 수열 발생기(stream cipher)이다. Self_Decimated LM-128은 LM 계열에서 제시된 특수한 암호로 128비트 키와 128비트 초기 벡터 그리고 257 비트의 내부 상태를 가지며 128 비트의 보안 레벨을 유지한다. 알려진 보안 분석의 공격에 대비해서 2-비트 메모리를 이용한 합산 수열발생기와 자체 클럭 조절형 키 수열 발생기를 포함한다.

• Journal of the Korea Organic Resources Recycling Association
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• v.25 no.1
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• pp.47-55
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• 2017

The technology for hydrothermal reaction of organic waste is one of the promising process to improve energy efficiency of biomass waste recycling system since moisture contents of treated biomass could be reduced at 40% or less than by dehydration processes. For these reasons, many parts of the world are interested in hydrothermal reaction of organic waste. In this paper, drying performances were evaluated with and without hydrothermal reaction of organic wastes which are sewage sludge and food wastes. For the hydrothermal reaction, organic wastes were treated at $200^{\circ}C$ for 1hr. Drying time of treated organic waste by hydrothermal reaction was reduced. In case of food waste drying at $100^{\circ}C$, drying time of treated wasted was reduced more 52.9% than non-treated. Hence, drying performances of sewage sludge and food wastes should be improved by hydrothermal reaction. Drying rates of treated wastes were considerably increased at preheat period of drying characteristic curve as followings; at $80^{\circ}C$ sludge as 148%, $100^{\circ}C$ sewage sludge as 151%, $80^{\circ}C$ food waste as 209%, $100^{\circ}C$ food waste as 366%. It means the surface area of treated wastes could be increased with destruction of cell membrane by hydrothermal reaction. However, the designer and operator of drying process should be careful, since enhanced drying rate cause the extension the decreasing drying period.

• Journal of the Korea Organic Resources Recycling Association
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• v.31 no.1
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• pp.27-34
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• 2023

In this study, spent mushroom substrate (SMS), which consits of lignocellulosic material, was pretreated by hydrothermal method; the changes of biodegradability and methane production yield of pretreated SMS were determined according to formation of lignocellulosic biomass degrading byproducts formation during thermal pretreatment. Based on the results, all hydrothermal pretreatment temperatures showed improved solubilization performance for biomass, and the optimum pretreatment effect was observed at an pretreatment temperature of 150℃ with the highest methane production yield. However, the induced formation of furan derivatives (i.e., 5-hydroxymethylfurfural and furfural) as byproducts during hydrolysis of hemicellulose and cellulose at severe condition lowered biodegradability and methane yield when the hydrothermal pretreatment temperature was higher than 180℃. Thus, this study revealed that hydrothermal pretreatment could promote anaerobic digestion efficiency of lignocellulosic biomass and is of great importance for preventing byproducts formation through pretreatment condition control.