• 한국수소및신에너지학회논문집
• /
• 제27권4호
• /
• pp.421-430
• /
• 2016

To prepare mesophase pitches through low energy process, pyrolysis fuel oil with $AlCl_3$ has been modified using two-step heat treatment which is heat-treated at $330^{\circ}C$ for 3~5 h after pre-treatment at $250^{\circ}C$. The result of polarized optical microscope observation, mesophase is not observed in pitches carried out only pre-heat treatment. While mesophase content is significantly increased from 9% to 100% according to increasing secondary heat treatment time from 3 h to 5 h. Synthesizing of the mesophase pitch at low temperature of $330^{\circ}C$ is attributed to decrease of viscosity of the pitches carried out first heat treatment with $AlCl_3$. The result of Fourier-transform infrared spectroscopic analysis, it is expected that aromatization of aliphatic compounds is dominant at early secondary heat treatment, on the other hand, polycondensation reaction becomes dominant as secondary heat treatment time increases. Aromaticity and stacking height of the pitches secondary heat treated for 5 hours are more increased about 25% and 107%, respectively, than that of pitches carried out only first heat treatment.

• 열처리공학회지
• /
• 제32권1호
• /
• pp.17-28
• /
• 2019

Jominy hardenability curves of low alloy steel containing less than 5 wt.% of alloying elements in total were calculated by applying Scheil's rule of additivity to pre-calculated isothermal transformation curve. Isothermal transformation curve for each phase in steel was approximated as a simple mathematical equation by using Kirkaldy's approach and all coefficients in the equation were estimated from experimental temperature-time-transformation (TTT) and/or continuous cooling transformation (CCT) data in the literature. Then jominy test with simple boundary conditions was performed in computer by applying the finite difference scheme. The resultant cooling curves at each location along a longitudinal direction of Jominy bar were applied to calculate phase fractions as well as mechanical properties such as micro Vickers hardness. The simulated results were compared with experimental CCT data and Jominy curves in the literature.

• Environmental Engineering Research
• /
• 제24권3호
• /
• pp.501-512
• /
• 2019

The seasonal effects on the biostability of drinking water were investigated by comparing the seasonal variation of assimilable organic carbon (AOC) in full-scale water treatment process and adsorption of AOC by three filling materials in lab-scale column test. In full-scale, pre-chlorination and ozonation significantly increase $AOC_{P17\;(Pseudomonas\;fluorescens\;P17)}$ and $AOC_{NOX\;(Aquaspirillum\;sp.\;NOX)}$, respectively. AOC formation by oxidation could increase with temperature, but the increased AOC could affect the biostability of the following processes more significantly in winter than in warm seasons due to the low biodegradation in the pipes and the processes at low temperature. $AOC_{P17}$ was mainly removed by coagulation-sedimentation process, especially in cold season. Rapid filtration could effectively remove AOC only during warm seasons by primarily biodegradation, but biological activated carbon filtration could remove AOC in all seasons by biodegradation during warm season and by adsorption and bio-regeneration during cold season. The adsorption by granular activated carbon and anthracite showed inverse relationship with water temperature. The advanced treatment can contribute to enhance the biostability in the distribution system by reducing AOC formation potential and helping to maintain stable residual chlorine after post-chlorination.

• 펄프종이기술
• /
• 제44권3호
• /
• pp.70-78
• /
• 2012

For evaluating the printing suitability of electronic copying papers in the aspect of climate conditions, 12 samples of copying papers being generally used in Korea and worldwide were collected. The copying papers were controlled by various temperature and humidity options in conditioning equipment in order to simulate the specific circumstances of dry, temperate or tropical climate, and the pre-heating system of photocopying machines during printing. As results, some copying papers showed several physical problems, especially in recycled copying papers and a normal paper with original printing faulty. These problems of copying papers were mostly resulted in extremely high moisture circumstance, and in lower levels of tensile strength and tensile stiffness. The moisture contents of copying papers during passing through the pre-heater system of photocopying machine could be rapidly decreased because paper is exposed to high temperature around the pre-heating zone. The copying paper, for example of XR3 sample, containing low moisture contents below 2% had high exfoliating possibility of toner transfer from copying paper.

• 한국소성가공학회:학술대회논문집
• /
• 한국소성가공학회 2007년도 춘계학술대회 논문집
• /
• pp.254-257
• /
• 2007

In this study, hydroformability and mechanical properties of pre- and post- heat treated Al6061 tubes at different extrusion type were investigated. For the investigation, as-extruded, full annealed and T6-treated Al 6061 tubes at different extrusion type were prepared. To evaluate the hydroformability, uni-axial tensile test and free bulge test were performed at room temperature and $200^{\circ}C$. Also mechanical properties of hydroformed part at various pre- and post-heat treatments were estimated by tensile test. And the tensile test specimens were obtained from hexagonal prototype hydroformed tube at $200^{\circ}C$. As for the heat treatment, hydroformability of full annealed tube is 25% higher than that of extruded tube. The tensile strength and elongation were more than 330MPa and 12%, respectively, when hydroformed part was post-T6 treated after hydroforming of pre- full annealed tube. However, hydroformed part using T6 pre treated tube represents high strength and low elongation, 8%. Therefore, the T6 treatment after hydroforming for as-extruded tube is cost-effective. Hydroformability of Al6061 tube showed similar value for both extrusion types. But flow stress of seam tube showed $20{\sim}50MPa$ lower value.

• 한국미생물·생명공학회지
• /
• 제28권6호
• /
• pp.361-366
• /
• 2000

Genera and number of protozoa were investigated in the conventional activated sludge pilot plant used for the treatment of municipal sewage and pre-treated night soil-containing sewage. In both case, the predominant protozoa was ciliates and among them Vorticella was the most common. In the pilot plant where pre-treated night soil was mixed with municipal sewage, genera of free-swimming ciliates, flagellates and amoeba was higher than in those withour night soil. Correlation analysis on the quality of effluent and protozoa indicates that municipal sewage has positive correlation with protozoa. However in the pilot plan 샐 sewage contatinin pre-treated night coil soil more samples show negative correlation. Followed equations were derived by the regression analysis of BOD in both the pilot plants. In case of pilot plant A of municipal sewage, the analysis B of munici-pal and pre-treated night soil-containing sewage, the analysis of BOD was $6.731$\times$10_{-2}$ $\times$Bodo+0.306(Adjusted $R^2$=0.864). At low temperature, number of protozoa was decreased to 35% and among therm, Aspidisca was the most common genus. Therefore, protozoa can be used as indicator of quality of the effluent in sewage treatment plants.

• 한국환경과학회지
• /
• 제11권11호
• /
• pp.1173-1181
• /
• 2002

The present study was undertaken to investigate the effect of low temperature and salicylic acid(SA) on the chilling tolerance of acclimated and nonacclimated cucumber(Cucurmis sativus L.) seedlings. The acclimation phenomenon was characterized in chilling-sensitive cucumber seedlings and found to have a significant effect on the survival and shoot dry weights. The injuries experienced by the acclimated seedlings in the third leaf stage were on average smaller by half than those experienced by the nonacclimated seedlings. Chilling also caused a large increase in the free proline levels, regardless of the acclimation status. Exogenous treatment with SA(0.5mM) resulted in improved growth and survival of the nonacclimated chilled seedlings, indicating that SA induced chilling tolerance and SA and acclimation had common effects. The application of cycloheximide in the presence of SA restored the acclimation-induced chilling tolerance. The elevated proline level observed in the cold-treated and SA-treated plants was more pronounced in the light than in the dark at a chilled temperature, indicating that endogenous proline may play a role in chilling tolerance by stabilizing the water status in response to chilling. From these results it is suggested that SA provided protection against low-temperature stress by increasing the proline accumulation, and pre-treatment with SA may induce antioxidant enzymes leading to increased chilling tolerance.

• 한국방재학회 논문집
• /
• 제8권3호
• /
• pp.165-169
• /
• 2008

대부분의 하수처리장에서는 동절기에 수온저하로 인한 질산화 미생물의 활동저하 때문에 질소제거에 어려움을 많이 겪고 있다. 본 연구에서는 이러한 문제점을 해결하기 위하여 하수처리 시뮬레이션 프로그램인 GPS-X를 사용하여 각조의 HRT를 변화시켜 저 수온시 효율적인 질소제거를 위한 HRT의 조합을 도출하고자 하였다. 본 연구에서 도출한 최적의 HRT 조합은 0.3 hr/0.5 hr/1.36 hr/4.84 hr(PreAx/An/Ax/Ox)이고 이때의 T-N 제거율은 51.4%, $NH_4^+$-N는 57.3%의 제거율을 보였다.

• 한국의류산업학회지
• /
• 제5권5호
• /
• pp.520-528
• /
• 2003

Chitosan was depolymerized by oxidizing agent, hydrogen peroxide ($H_2O_2$) and general properties of resulting low molecular weight chitosan(LMWC) were studied. Effect of amount of $H_2O_2$, ratio of $H_2O_2$/chitosan, and reaction temperature were investigated in preparing LMWC. In addition, the reduction of molecular weight of prepared LMWC were measured after a certain time passage. Pre-swelling treatment of starting chitosan affected uniform and mild reaction of depolymerization and increased the solubility of resulting LMWC. Prepared LMWC (Mw 100,000) showed a decrease in Mw by 25-35%. Prepared LMWC(Mw 60,000-70,000) showed a decrease in Mw by 10-15% after 7 months. Therefore, this depolymerizing process can be concluded desirable in terms of stability. In addition, yellowing of pre-swelling treated chitosan upon time passage was insignificant compared with that of untreated chitosan. Therefore, pre-swelling treatment of chitosan before depolymerization would be beneficial in terms of stability of physical state.

• 한국생물환경조절학회:학술대회논문집
• /
• 한국생물환경조절학회 2002년도 추계 심포지엄 및 학술발표 논문집
• /
• pp.332-339
• /
• 2002

최근 국내 절화 상품이 외국으로 수출되는 물량이 급격히 증가(화훼류 수출실적 '01 현재 3,000만불)되고 있으나 수확 후 관리 미숙에 의한 불개화 및 조기노화 현상이 나타나 이 문제들을 해결할 수 있는 방안이 절실하다. 이러한 문제들을 해결하기 위해서는 주요 수출작물의 재배시 수확 후 저장 및 유통에 따른 연속적이고 체계화된 품질 향상 및 보장문제를 해결할 수 있는 기술개발이 절대적으로 필요하다. (중략)