In this study, the high-temperature oxidation properties of austenitic 316L stainless steel manufactured by laser powder bed fusion (LPBF) is investigated and compared with conventional 316L manufactured by hot rolling (HR). The initial microstructure of LPBF-SS316L exhibits a molten pool ~100 μm in size and grains grown along the building direction. Isotropic grains (~35 μm) are detected in the HR-SS316L. In high-temperature oxidation tests performed at 700oC and 900oC, LPBF-SS316L demonstrates slightly superior high-temperature oxidation resistance compared to HR-SS316L. After the initial oxidation at 700oC, shown as an increase in weight, almost no further oxidation is observed for both materials. At 900oC, the oxidation weight displays a parabolic trend and both materials exhibit similar behavior. However, at 1100oC, LPBF-SS316L oxidizes in a parabolic manner, but HR-SS316L shows a breakaway oxidation behavior. The oxide layers of LPBF-SS316L and HR-SS316L are mainly composed of Cr2O3, Febased oxides, and spinel phases. In LPBF-SS316L, a uniform Cr depletion region is observed, whereas a Cr depletion region appears at the grain boundary in HR-SS316L. It is evident from the results that the microstructure and the hightemperature oxidation characteristics and behavior are related.

Cr-Si based alloys are not only excellent in corrosion resistance at high temperatures, but also have good wear resistance due to the formation of Cr3Si phase, therefore they are promising as metallic coating materials. Aluminum is often added to Cr-Si alloys to improve the oxidation resistance through which stable alumina surface film is formed. On the other hand, due to the addition of aluminum, various Al-containing phases may be formed and may negatively affect the heat resistance of the Cr-Si-Al alloys, so detailed investigation is required. In this study, two Cr-Si-Al alloys (high-Si & high-Al) were prepared in the form of cast ingots through a vacuum arc melting process and the microstructural changes after high temperature heating process were investigated. In the case of the cast high-Si alloy, a considerable amount of Cr3Si phase was formed, and its hardness was significantly higher than that of the cast high-Al alloy. Also, Al-rich phases (with the high Al/ Cr ratio) were not found much compared to the high-Al alloy. Meanwhile, it was observed that the amount of the Al-rich phases reduced by the annealing heat treatment for both alloys. In the case of the high temperature heating at 1,400 oC, no significant microstructural change was observed in the high Si alloy, but a little more coarse and segregated AlCr phases were found in the high Al alloy compared to the cast state.

The new thermal management models of linear compressors have been recently reported. These models adopt the simplified transient flow effects to shorten the excessive analysis time. Among the unsteady flow effects of the linear compressor, the effect of the gap flow between the compressor housing and the body due to the body vibration on the heat transfer performance was studied in this paper. For this study, a numerical analysis for the unsteady axisymmetric flows was performed by using CFD (Computational Fluid Dynamics). The results show that the high-speed refrigerant flows occurred in the gap between the compressor housing and the body, which contribute to increasing the heat transfer from high temperature refrigerants in the housing to the outside air. In addition, as the gap decreases, the refrigerant flow rate through the gap increases and the heat transfer rate increases as well.

In this study, high temperature wetting analysis and AZ80/Ti interfacial structure observation are performed for the mixture of AZ80 and Ti, and the effect of Al on wetting in Mg alloy is examined. Both molten AZ80 and pure Mg have excellent wettability because the wet angle between molten droplets and the Ti substrate is about 10° from initial contact. Wetting angle decreases with time, and wetting phenomenon continues between droplets and substrate; the change in wetting angle does not show a significant difference when comparing AZ80-Ti and Mg-Ti. As a result of XRD of the lower surface of the AZ80-Ti sample, in addition to the Ti peak of the substrate, the peak of TiAl3, which is a Ti-Al intermetallic compound, is confirmed, and TiAl3 is generated in the Al enrichment region of the Ti substrate surface. EDS analysis is performed on the droplet tip portion of the sample section in which pure Mg droplets are dropped on the Ti substrate. Concentration of oxygen by the natural oxide film is not confirmed on the Ti surface, but oxygen is distributed at the tip of the droplet on the Mg side. Molten AZ80 and Ti-based compound phases are produced by thickening of Al in the vicinity of Ti after wetting is completed, and Al in the Mg alloy does not affect the wetting. The driving force of wetting progression is a thermite reaction that occurs between Mg and TiO2, and then Al in AZ80 thickens on the Ti substrate interface to form an intermetallic compound.

Angelica gigas Nakai (A. gigas) easily changes its color during storage, and appropriate thermal treatment can improve storage stability through inactivation of enzymes such as polyphenol oxidase. Therefore, this study was performed to determine quality characteristics of dried A. gigas in response to high-temperature-short-time (HTST) treatment during storage. Dried A. gigas were treated at 120-180℃ for 10 min, the samples were stored at 4℃ and 50℃ for 10 weeks, and used for the analysis of qualities. Concerning the color values, the sample treated at 120℃ was similar to the control, and the color change was large when treated above 180℃. However, color difference (△E* ab) was lower in treated samples than in control. Browning index was similar for all the samples except for the sample treated at 180℃. Functional qualities (phenolics content, antioxidant activities, and level of major components) showed a slight difference according to storage periods in all samples without control, and nodakenin content was observed in control. The results of this study showed that HTST treatment improved storage stability such as stability of colors and browning index in dried A. gigas during storage, and the appropriate treatment temperature was 120℃ in terms of stability in color and browning index.

SiC is a material with excellent strength, heat resistance, and corrosion resistance. It is generally used as a material for SiC invertors, semiconductor susceptors, edge rings, MOCVD susceptors, and mechanical bearings. Recently, SiC single crystals for LED are expected to be a new market application. In addition, SiC is also used as a heating element applied directly to electrical energy. Research in this study has focused on the manufacture of heating elements that can raise the temperature in a short time by irradiating SiC-I2 with microwaves with polarization difference, instead of applying electric energy directly to increase the convenience and efficiency. In this experiment, Polydimethylsilane (PDMS) with 1,2 wt% of iodine is synthesized under high temperature and pressure using an autoclave. The synthesized Polycarbosilane (PCS) is heat treated in an argon gas atmosphere after curing process. The experimental results obtain resonance peaks using FT-IR and UV-Visible, and the crystal structure is measured by XRD. Also, the heat-generating characteristics are determined in the frequency band of 2.45 GHz after heat treatment in an air atmosphere furnace.

기후변화에 대비하여 고온성 양송이 백색 품종을 육성한 결과는 다음과 같다. 모본은 KMCC00540, KMCC00591, KMCC00643을 선발하였고, ISSR과 SSR마커로 각각 동 핵균주를 선발하여 교잡하였다. 선발 교잡주를 고온 20~25 o C, 습도 80% 이상에서 3반복으로 재배하여 농업적 형질과 자실체 특성의 변이가 가장 적은 것은 Abs4-2016- 121 계통이었다. 이 계통은 KMCC00000와 KMCC0000를 교잡한 계통이며, 경주와 부여 농가에서 현장실증시험결과 Abs4-2016-121 계통이 자실체 경도가 높으며 고온에서 갓 개열이 지연되어 고온성 품종 ‘하담’으로 육성하였다.

신품종 감자 ‘아리랑1호’는 농촌진흥청 국립식량과학원 고령지농업연구소에서 2018년도 육성되었다. ‘아리랑1호’는 ‘Frontier’ 품종을 모본으로 하고 ‘대관1-117호’ 계통을 부본으로 2011년 교배하여, 장일 고온 조건에서 식물체 생육 및 괴경의 형성과 비대가 양호하여 다수확 할 수 있는 계통으로 선발되었다. 중앙아시아(여름재배)와 국내 평난지(강릉, 봄재배) 및 고랭지(대관령, 여름재배)에서 2014~2015년 생산력 검정을 통해 ‘대관1-150호’로 계통명을 부여하고, 2016~2018년 지역 적응성검정 시험을 거쳐 ‘아리랑1호’로 명명하였다. ‘아리랑1 호’의 초형은 반직립형으로서 초세가 강하고 왕성하다. 괴경모 양은 짧은 계란형이며, 괴경 색깔은 표피와 육질부 모두 황색이다. ‘아리랑1호’의 경장은 67.1 cm로 대조품종인 ‘수미’, ‘산테’보다 긴 반면, 경수는 3개 내외로 대조품종과 유사하다. 주당 괴경수는 9.0개로 ‘수미’(5.4개) 보다 많은 반면, ‘산테’ (14.1개)보다 적다. 괴경당 평균 무게와 포기당 총 괴경중은 각 각 96.1 g 및 865 g으로서 대조품종보다 무겁다. 겹둥근무늬병 과 역병에 대하여 중도저항성이며, 바이러스병과 더뎅이병에 있어서는 감수성을 나타낸다. 건조에 대한 저항성은 ‘산테’나 ‘수미’보다 강한 중도저항성으로 평가되었다. 비중과 건물율은 ‘수미’보다 높고 ‘대서’와 유사하며, 감자칩 품질은 ‘대서’와 같이 우수한 것으로 평가된다. ‘아리랑1호’의 단위면적당 상서수량은 국내의 경우 3,360 kg·10a-1으로 ‘수미’ 보다 57% 더 많 고, 중앙아시아에서는 3,070 kg·10a-1으로 ‘산테’ 보다 약 55% 더 많았다. 신품종 감자 ‘아리랑1호’는 장일 고온 건조한 지역에서 기형, 이차생장 등이 적고 다수성을 나타내어 중앙아시아 등 해외 진출에 유망한 품종으로 판단된다.

The high-temperature stability of YSZ specimens fabricated by die pressure and cold isostatic press (CIP) is investigated in CaCl2-CaF2-CaO molten salt at 1,150 °C. The experimental results are as follows: green density 46.7 % and 50.9 %; sintering density 93.3 % and 99.3 % for die press and CIP, respectively. YSZ foremd by CIP exhibits higher stability than YSZ formed by die press due to denseness dependency after high-temperature stability test. YSZ shows peaks mainly attributed to CaZrO3, with a small t-ZrO2 peak, unlike the high-intensity tetragonal-ZrO2 (t-ZrO2) peak observed for the asreceived specimen. The t-ZrO2 phase of YSZ is likely stabilized by Y2O3, and the leaching of Y2O3 results in phase transformation from t-ZrO2 to m-ZrO2. CaZrO3 likely forms from the reaction between CaO and m-ZrO2. As the exposure time increases, more CaZrO3 is observed in the internal region of YSZ, which could be attributed to the inward diffusion of molten salt and outward diffusion of the stabilizer (Y2O3) through the pores. This results in greater susceptibility to phase transformation and CaZrO3 formation. To use SOM anodes for the electroreduction of various metals, YSZ stability must be improved by adjusting the high-density in the forming process.

A gasketed plate heat exchanger(GPHE) requires a much smaller installation space than a shell & tube heat exchanger because of its compact and good thermal performances. However, GPHEs have a disadvantage of being relatively vulnerable to high temperature and pressure due to rubber gaskets. To overcome a GPHEs’ disadvantage, Welded Block type Plate Heat Exchangers(WBPHE) have been developed. The flow pattern and heat transfer principle of WBPHE are very similar to GPHEs, so they are very compact and can be applied to high temperature and pressure. In this study, the structure and characteristics of WBPHE are briefly introduced, and its thermal performances were conducted experimentally using hot and cold water in the Reynolds number’s range from 5,500 to 10,000. Test results were compared with the experimental correlations of other researchers, which shows that significant deviations were noticed in the heat transfer coefficient predictions with a deviation range from 31% to 85%. The previous friction factor correlations also predicted the current results with big errors from 25% to 45%. These deviations are expected to be due to different chevron angles between previous studies and the current study, and also the end-plate effect is expected to be one of the potential causes that led to these deviations.

억새와 같은 초본계 바이오매스로부터 cellulose, hemicellulose, lignin 등 주요성분을 추출하기 위해서는 알칼리 전처리가 효율적이며, 본 연구에서는 수산화칼륨(KOH)을 이용한 전처리 조건을 최적화하였다. 전처리 변수의 최적화는 반응표면분석법(RSM)을 적용하였다. RSM의 변수는 3개였으며, 변수범위는 각각 KOH 0.2∼0.8M, 반응온도 110∼190℃ 및 반응시간 10∼90min 이었다. 억새의 알칼리 전처리를 위한 최적조건은 KOH 농도 0.47M, 반응온도 134℃ 및 반응시간 65min 이었다. 최적 전 처리 조건에 따라 전처리를 수행한 후 고형물의 cellulose 함량은 66.1±1.1% 이었으며, hemicellulose 및 lignin 함량은 각각 26.4±0.4%, 3.7±0.1% 이었다. RMS 모델식에 따라 계산된 예측값은 실제값 대비 95% 범위 내에서 유효하였다. 최종적으로 전처리물을 동시당화발효를 통해 검증한 결과 에탄올 생산 수율은 96% 이었다.

This study was performed to investigate the effect of heat-stressed environment on rumen microbial diversity in Holstein cows. Rectal temperature and respiration rate were measured and rumen fluid was collected under normal environment (NE; Temperature humidity index (THI)=64.6) and heat-stressed environment (HE; THI=87.2) from 10 Holstein cows (60±17.7 months, 717±64.4 kg) fed on the basis of dairy feeding management in National Institute of Animal Science. The rumen bacteria diversity was analyzed by using the Illumina HiSeq™ 4000 platform. The rectal temperature and respiratory rate were increased by 1.5ﾟC and 53 breaths/min in HE compared to that in NE, respectively. In this study, HE exposure induced significant changes of ruminal microbe. At phylum level, Fibrobacteres were increased in HE. At genus level, Ruminococcaceae bacterium P7 and YAD3003, Butyrivibrio sp. AE2032, Erysipelotrichaceae bacterium NK3D112, Bifidobacterium pseudolongum, Lachnospiraceae bacterium FE2018, XBB2008, and AC2029, Eubacterium celulosolvens, Clostridium hathewayi, and Butyrivibrio hungatei were decreased in HE, while Choristoneura murinana nucleopolyhedrovirus, Calothrix parasitica, Nostoc sp. KVJ20, Anabaena sp. ATCC 33047, Fibrobacter sp. UWB13 and sp. UWB5, Lachnospiraceae bacterium G41, and Xanthomonas arboricola were increased in HE. In conclusion, HE might have an effect to change the rumen microbial community in Holstein cows.

3D 프린팅의 적층제조를 위한 시멘트 모르타르의 이용은 시멘트의 유동 특성을 개질하기 위한 시멘트 혼화용 폴리 머의 혼입이 필수적이다. 시멘트 모르타르는 점성이 높고 수축이 크기 때문에 적층제조를 위해서는 유동성, 경화속도, 시공성 및 적층특성의 개선이 필요하다. 시멘트 혼화용 폴리머 디스퍼젼을 혼입한 시멘트 모르타르는 시멘트 수화물과 공극 사이에 폴 리머 필름이 상호 형성되어 인장강도와 취성이 개선되며 우수한 접착성, 기밀성, 내약품성을 보인다. 최근, 사용편리성이 우수한 Ethylene-vinyl acetate 재유화형 분말수지가 널리 사용된다. 하지만 화재와 같은 고온에서는 재유화형 분말수지를 혼입한 경우에 는 성능저하가 더 크다. 재유화형 분말수지가 시멘트 수화물과 공극에 폴리머 필름을 형성하고 충전하지만 고온에 의해 열분해 되기 때문이다. 본 연구에서는 3D 프린팅의 적층제조를 위해 내열성이 개선된 Ethylene-vinyl chloride 재유화형 분말수지의 혼입률을 달리하여 고온에서의 특성과 열분해에 따른 공극특성을 검토하였다. 연구결과, EVCL 재유화형 분말수지를 혼입한 경우 고온에서 약간의 성능개선을 보였지만 열분해하여 공극률이 커지며, 밀도, 강도가 감소한다. 따라서, 사용조건에 적합한 배합조절 등이 필요하다.

Single crystals, which have complexed composition, are fabricated by solid state grain growth. However, it is hard to achieve stable properties in a single crystal due to trapped pores. Aerosol deposition (AD) is suitable for fabrication of single crystals with stable properties because this process can make a high density coating layer. Because of their unique features (nano sized grains, stress inner site), it is hard to fabricate single crystals, and so studies of grain growth behavior of AD film are essential. In this study, a BaTiO3 coating layer with ~ 9 μm thickness is fabricated using an aerosol deposition method on (100) and (110) cut SrTiO3 single crystal substrates, which are adopted as seeds for grain growth. Each specimen is heat-treated at various conditions (900, 1,100, and 1,300℃ for 5 h). BaTiO3 layer shows different growth behavior and X-ray diffraction depending on cutting direction of SrTiO3 seed. Rectangular pillars at SrTiO3 (100) and laminating thin plates at SrTiO3 (110), respectively, are observed.