• 열처리공학회지
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• 제27권5호
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• pp.235-241
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• 2014

Effects of rolling and cooling conditions on microstructures and mechanical properties of high-deformable pipeline steels were investigated in this study. Six kinds of pipeline steels were fabricated by varying rolling and cooling conditions, and their microstructures were analyzed by scanning electron microscopy, electron back-scattered diffraction, and transmission electron microscopy. Tensile and Charpy impact tests were conducted on the steels in order to examine the mechanical properties. The steels rolled in the two-phase region showed better low-temperature toughness than those in the single-phase region due to the larger amount of ferrites having high-angle boundaries, although they have lower strength and absorbed energy. The steel rolled in single-phase and finish-cooled at higher temperature showed a good combination of high strength and good low-temperature toughness as well as excellent deformability of the lowest yield ratio and the highest uniform elongation because of the presence of fine ferrite and a mixture of various low-temperature transformation phases.

• 한국재료학회:학술대회논문집
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• 한국재료학회 2010년도 춘계학술발표대회
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• pp.6.2-6.2
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• 2010

Stainless steel is widely known to have superior corrosion properties. However, in some harsh conditions it still suffers various kinds of corrosions such as galvanic corrosion, pitting corrosion, intergranular corrosion, chloride stress corrosion cracking, and etc. For the corrosion protection of stainless steel, the ceramic coatings such as protective silica film can be used. The sol-gel coating technique for the silica film has been extensively studied especially because of the cost effectiveness. It has been proved that silica can improve the oxidation and the acidic corrosion resistance of metal surface in a wide range of temperatures due to its high heat and chemical resistance. However, in the sol-gel coating process there used to engage a heat treatment at an elevated temperature like $500^{\circ}C{\sim}600^{\circ}C$ where cracks in the silica film would be formed because of the thermal expansion mismatch with the metal. The cracks and pores of the film would deteriorate the corrosion resistance. When the heat treatment temperature is reduced while keeping the adhesion and the density of the film, it could possibly give the enhanced corrosion resistance. In this respect, inorganic protective silica film was tried on the surface of stainless steel using a sol-gel chemical route where silica nanoparticles, tetraethoxysilane (TEOS) and methyltriethoxysilane (MTES) were used. Silica nanoparticles with different sizes were mixed and then the film was deposited on the stainless steel substrate. It was intended by mixing the small and the large particles at the same time a sufficient consolidation of the film is possible because of the high surface activity of the small nanoparticles and a modest silica film is obtained with a low temperature heat treatment at as low as $200^{\circ}C$. The prepared film showed enhanced adhesion when compared with a silica film without nanoparticle addition. The films also showed improved protect ability against corrosion.

• Journal of Welding and Joining
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• 제35권1호
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• pp.26-33
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• 2017

This study aims to investigate the suitability of requirement for post-weld heat treatment(PWHT) temperature when different P-No. materials are welded, which is defined by ASME Sec. III Code. For SA-516 Gr. 60 and SA-106 Gr. B carbon steels that are typical P-No. 1 material, simulated heat treatment were conducted for 8 h at $610^{\circ}C$, $650^{\circ}C$, $690^{\circ}C$, and $730^{\circ}C$, last two temperature falls in the temperature of PWHT for P-No. 5A low-alloy steels. Tensile and Charpy impact tests were performed for the heat-treated specimens, and then microstructure was analyzed by optical microscopy and scanning electron microscopy with energy-dispersive spectrometry. The Charpy impact properties deteriorated significantly mainly due to a large amount of cementite precipitation when the temperature of simulated heat treatment was $730^{\circ}C$. Therefore, when dissimilar metal welding is carried out for P-No. 1 carbon steel and different P-No. low alloy steel, the PWHT temperature should be carefully selected to avoid significant deterioration of impact properties for P-No. 1 carbon steel.

• Asian-Australasian Journal of Animal Sciences
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• 제32권2호
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• pp.282-289
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• 2019

Objective: This study aimed to elucidate whether innovative sous vide treatment has a significant influence on the beef semitendinosus muscle as compared to common sous vide treatment and traditional cooking. Methods: The innovative sous vide treatments were cooked at $45^{\circ}C$ and $65^{\circ}C$ for 6 h (SV45-65), common sous vide treatment at $45^{\circ}C$ and $65^{\circ}C$ for 3 h (SV45 and SV65) and traditional cooking at $75^{\circ}C$ for 30 min (CON75). Water loss and cooking loss, as well as the physical properties (color and shear force) and chemical properties (protein and collagen solubility) of the treated meat, were investigated. Results: The results obtained indicated that the innovative sous vide with double thermal treatment (SV45-65) and cooked with air presence (CON75) resulted to lower $a^*$ and higher $b^*$ values, respectively. The water loss and cooking loss increased when temperature increased from $45^{\circ}C$ to $65^{\circ}C$, and lower water loss was recorded in SV45 and CON75. These samples presented higher water content and revealed strong correlation to protein solubility. Warner-Bratzler shear force (SF) analysis showed the marked interaction between cooking temperature and time. Sample cooked at a high temperature (CON75) and a long period (SV45-65) showed a significantly lower value of SF than sample SV65 (p<0.05). Interestingly, there was no difference in SF values between SV45-65 and CON75. Conclusion: The innovative sous vide treatment with double thermal effect appears an attractive cooking method as compared to common sous vide and traditional cooking method, as it has a potential for improving tenderness values of cooked beef semitendinosus muscle.

• 한국식품영양학회지
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• 제31권2호
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• pp.301-307
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• 2018

In this study, a relatively effective process is used to sterilize Escherichia coli on the surface of micro-sized calcium citrate powder using nitrogen and argon as process gases in a low-temperature vacuum plasma treatment. The purpose of this study is to confirm and to introduce the effectiveness of homogeneous surface treatment for the sterilization of fine inorganic powder by the rotatable low-temperature RF plasma system designed by ourselves. The results of the test using 3M petrifilm showed that there were no remarkable spots in the case of the surface of plasma treated powder, whereas the untreated powder showed many blue spots, which indicating that the E. coli was alive. After 5 days, in the same samples, the blue spots were seen to be larger and darker than before, while the plasma-treated powder showed no changes. The results from FE-SEM analysis showed that the E. coli was damaged and/or destroyed by reactive species generated in the plasma space, resulting in the E. coli being sterilized. Furthermore, the sterilization effects according to the selected parameters ($N_2$ and Ar; flow rate 30 and 50 sccm) adapted in this study were mutually similar, regardless of such different process parameters, and this indicates that homogeneous treatment of powder surfaces could be more effective than conventional methods. Therefore, the plasma apparatus used in this study may be a practical method to use in a powerful sterilization process in powder-type food.

• 대한금속재료학회지
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• 제47권3호
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• pp.139-146
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• 2009

The heat-affected zone (HAZ) of SA508 Gr.4N Ni-Mo-Cr low alloy steel, which has higher Ni and Cr contents than SA508 Gr.3 Mn-Mo-Ni low alloy steel, was investigated on the microstructure and mechanical properties. The HAZ was categorized into seven characteristic zones (CGCG, FGCG, ICCG, SCCG, FGFG, ICIC and SCSC-HAZ) according to the peak temperature from the thermal cycle experienced during multi-pass welding. Post Weld Heat Treatment (PWHT) was conducted in the temperature range of $550{\sim}610^{\circ}C$ for 30 hours to evaluate the effect of PWHT conditions on the microstructure and mechanical properties. Before PWHT, CGHAZ and FGFGHAZ showed high yield strength (YS) ranging from 1000 to 1250 MPa, while YS of SCSCHAZ decreased from 607 MPa (observed for base metal) to 501 MPa. The Charpy impact energies of sub-HAZs fell below 100J at $-29^{\circ}C$, except in the SCSCHAZ. By applying PWHT to sub-HAZ specimens, YS decreased as the PWHT temperature increased. In the case of CGHAZs and FGFGHAZ heat-treated at $610^{\circ}C$, YS dropped drastically to the range of 654~686 MPa. From the Charpy impact test, the upper-shelf energy (USE) increased to approximately 250J and Index temperature ($T_{68J}$) decreased below $-50^{\circ}C$. Specifically, in FGFG, ICIC and SCSC-HAZ, $T_{68J}$ was below -110, which was lower than the case of base metal.

• 한국식품과학회지
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• 제3권1호
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• pp.29-36
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• 1971

감미종(甘味種) 소형(小型)고추인 Zairasisi를 저온저장(低溫貯藏)하니 종자(種子)의 갈변(褐變)이 급속(急速)히 일어났기에 여기에 주목(注目)하여 갈변기질(褐變基質)인 polyphenol 성분(成分)을 검색(檢索) 정량(定量)하고 이들 기질(基質)에 이르는 중간(中間) 대사(代謝) 성분(成分)의 변화(變化)를 측정(測定) 고찰(考察)하였다. (1) 종자(種子)의 polyphenol 성분(成分)으로서 chlorogenic acids가 검출(檢出)되었고 flavanol type polyphenols는 검출(檢出)되지 않았다. (2) Chlorogenic acid와 total polyphenol 함량(含量)은 저온처리(低溫處理)에 의하여 급증(急增)하고 갈변후(褐變後)는 감소하여 상온구(常溫區)보다 오히려 함량(含量)이 낮아졌다. (3) 중간대사(中間代謝) 성분(成分)인 phenylalanine, tyrosine, shikimic acid 함량(含量)은 저온처리(低溫處理)에 의하여 크게 증가(增加)하고 있으니 shikimate 계로(系路)가 활발(活潑)해지는 것으로 짐작된다. (4) 효소(酵素)에 대(對)한 특이적(特異的)인 조해제(阻害劑)와 호흡기질(呼吸基質)의 조직(組織) 호흡(呼吸)에 미치는 조해(阻害) 및 첨가(添加) 효과(效果)를 측정(測定)한 결과(結果) 저온처리(低溫處理)에 의하여 고추종자(種子)의 당(糖)은 EMP 계로(系路)를 활발히 움직이다가 이에 연결(連結)되는 TCA cycle에 jaming이 일어남에 따라 phosphoenolpyruvate와 erythrose-4-phosphate가 활발히 결합(結合)하고 shikimate 계로(系路)가 활발해져서 polyphenol 물질(物質)이 활발히 생합성(生合成)된다는 것을 추정(推定)할 수 있었다. (5) 저온처리(低溫處理)에 의하여 고추종자(種子)의 K ion 유출량(流出量)이 증가(增加)하였기에 갈변(褐變)에 따라 원형질막(原形質膜) 이상(異常)이 생긴 것을 짐작 할 수 있었다.

• Ocean and Polar Research
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• 제42권3호
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• pp.225-231
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• 2020

The aim of this study was to examine optimal induction method for carpospore release from Agarophyton vermiculophyllum cystocarps for seedling production. We tested the effects of environmental factors on carpospore release by using five different induction methods; spontaneous, desiccation, low temperature, desiccation+low temperature, and osmotic shock. Also, carpospores release was estimated at three temperatures (20, 25, and 30℃), and then under combinations of three day lengths (8, 12, and 16h) and two irradiances (30 and 60 μmol photons m^-2 s^-1), after pretreatment at desiccation+low temperature for 2 hr. The number of carpospores released was between 113 ~ 682 spores /cystocarp/day and it was maximal in the desiccation+low temperature treatment. Optimal environmental conditions for carpospore release of A. vermiculophyllum were 25℃, 16 h, and 60 μmol photons m^-2 s^-1. The present results suggest that massive carpospores for seedling production of A. vermiculophyllum could be obtained under a combination of 25℃, 16 h, and 60 μmol photons m^-2 s^-1 after pretreatment in the desiccation+low temperature.

• 한국염색가공학회지
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• 제4권1호
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• pp.1-9
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• 1992

In order to study on the surface modification of the poly(ethylene Terephthalate)(PET) fabrics, low temperature plasma$(O_2)$ has been irradiated on the PET fabrics in various conditions. Experiments were carried out at pressure ranging from 0.5 tort to 3 tort. The properties of PET fabrics treated with low temperature plasma($(O_2)$, such as bathochromic, wettability, antistatic property were measured. Etching ratio was increased as the pressure and the output of discharge increased. When its were put on the cathode, the most efficient effect of etching according to the position of sample between anode and cathode was obtained. The bathochromic effect has more or less improved as pressure was getting higth in case of dyed fabrics treated with only low temperature plasma$(O_2)$ . And when it was treated with the low refractive index resin, the bathochromic of dyed fabrics treated with low temperature plasma$(O_2)$ was better than that of the dyed fabrics untreated.

• Current Photovoltaic Research
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• 제2권3호
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• pp.110-114
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• 2014

We propose a low temperature sol-gel ZnO/Ag nanowire composite thin film to fulfill low temperature and low cost requirements, which are essential criteria in future flexible electronic devices. In this proposed thin film, Ag nanowire plays the role of electrical conduction, and sol-gel ZnO provides a structural medium with a high visible transmittance. Low temperature restriction in the sol-gel fabrication process prevents sufficient oxidation of Zn acetate precursors, which were solved by a post-coating treatment with ultraviolet light irradiation. Composite thin film formation was performed by spin coating methods with a mixed precursor solution or in a sequential manner. We obtained an average visible transmittance larger than 85% and a sheet resistance smaller than $50{\Omega}/sq$. After optimization in a fabricated composite transparent conductive thin film with the thickness around 100 nm. Similar experimental demonstration in a flexible substrate (polyethyleneterephthalate) was successful, which implies a promising application opportunity of this technology.