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Quality Improvement of High Volume Fly Ash Concrete due to Early Strength Gain Admixture (조강형 혼화제에 의한 플라이애시 다량 치환 콘크리트의 품질 향상)

  • Han, Cheon-Goo;Park, Jong-Ho;Lee, Joung-Ah
    • Journal of the Korean Recycled Construction Resources Institute
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    • v.4 no.4
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    • pp.117-124
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    • 2009
  • The purpose of the study was to improve quality of high volume fly ash concrete. The study evaluated on the possibility of early quality improvement of high volume fly ash concrete with early strength gain admixture ('GA' below) developed by the preceding research. The study regarded applying naphthalene admixture ('NA' below) to mix proportion substituting FA 15 % to be plain. In the event of substituting FA 20, 25 and 30 %, the study compared engineering properties of concrete with plain by applying GA. Because of features of fresh concrete, fluidity falls down when GA is applied. Therefore, its use amount shall be increased. Only, in W/B 60 %, it was beneficial since slump loss was reduced about 35~70 mm than plain. The study could see that AE use should be increased proportionally since air content was reduced by coming from AE absorption operation of unburned coal content included in FA according to an increase in the amount of FA use. Reduction effect of bleeding could be anticipated since the amount of bleeding appeared at least in FA 20 %. Because of hardened concrete, time of setting appeared in the same level as plain when GA was applied. Therefore, it is judged that delay of setting can be reduced. In compressive strength, the study could check the same strength development as plain when GA was applied, having nothing to do with W/B and curing temperature. However, it is thought that we shall pay attention to GA use in the event of FA 30 % substitution. Freezing and melting resistance had less early value than plain. However, it is judged that there will be no problem of frost resistance since there is no a large difference between freezing and melting resistance and plain in overall. In accelerated neutralization, it was analyzed that a problem of weakening in neutralization appointed as a demerit when FA was applied in mass in proportion with GA use could be settled to some extent.

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The Effect of Environmental Factors on the Hydrolysis Characteristics of Lipase (환경인자가 리파제의 가수분해 특성에 미치는 영향)

  • Park, Geon-Gyu;Kim, Eun-Gi;Heo, Byeong-Gi
    • KSBB Journal
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    • v.14 no.4
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    • pp.511-516
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    • 1999
  • The effects of environmental and compositon factors, such as reaction time, metal ions, pH, agitation speed, the weight ratio of water to oil, and the weight of enzyme, on the hydrolysis of oils by Lipase-OF were investigated. In case of oils with low melting point, the optimum temperature of hydrolysis were the enzyme activity was maximum was 37C. However, when the melting temperature was higher than 40C, the optimum temperature was around the fusion temperature. The activity of Lipase-OF decreased very rapidly with increase of temperature in the range of higher than 45C and the activity perished above 65C. The effect of agitation speed was investigated from 150 to 650 rpm. The hydrolysis of oils increased as the agitation speed increased up to 350 rpm, but it did not increase any more above 350 rpm. The weight ratio of water to oil was changed from 1 : 9 to 9 : 1 for the investigation of the effect on the hydrolusis. The weight ratio for maximum hydrolysis was 1 : 1. Ca2+andMg2+ among various metal ions had some effect on the stimulation of hydrolysis. The optimum concentration of the ions was about 100ppm at which the hydrolysis increased, compared with that of distilled water, by 2 to 3%. The Optimum pH of Lipase-OF was 7. The hydrolysis decreased as the pH decreased as the pH decreased and also decreased as the pH increased. The content of enzyme affected the hydrolysis of oil. The hydrolysis increased with the content of Lipase-OF in the range of less than 0.013 wt% of substrate. However, the increase of hydrolysis with the content of Lipase-OF ceased above 0.013 wt%. The experiments investigating the effect of environmental and composition factors on the hydrolysis of oils showed that the optimum temperature was 37C, the pH 7, the concentration of Ca2+orMg2+ 100 ppm, the agitation speed 350 rpm, the weight ratio of water to oil 1 : 1, and the content of Lipase-OF 0.013 wt% of substrate.

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Effect of the Cooking Condition on Enzyme-resistant Starch Content and in vitro Starch and Protein Digestibility of Tarakjuk (Milk-rice Porridge) (타락죽의 효소저항전분 함량과 in vitro 전분 및 단백질 분해율에 대한 가열조건의 영향)

  • Lee, Gui-Chu;Lim, Seung-Taik;Yoon, Hyun-Sung
    • Korean Journal of Food Science and Technology
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    • v.36 no.5
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    • pp.765-772
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    • 2004
  • Cooking condition of Tarakjuk (milk-rice porridge) was established based on gelatinization temperature using differential scanning calorimetry (DSC) of roasted Ilpum rice flour, which has highest enzyme-resistant starch (RS) content. Effect of cooking temperature and time on DSC characteristics, crystallity with X ray diffractogram, RS content, in vitro starch digestibility (IVSD), amino acid composition, and in vitro protein digestibility (IVPD) of Tarakjuk were determined. Tarakjuk was cooked at 50, 56.5, 64, and 69C for various durations. Rice flour ingredient used was Ilpum, previously roasted at 185C for 25 min. Tarakjuk cooked at 50 and 56.5C showed two thermal transitions between 63.7125.2C as determined by DSC, corresponding to endotherms of starch gelatinization (63.773.8C) and melting of amylose-lipid complex (AM-lipid complex, 97.7125.2C), whereas that cooked at 64 and 69C showed only AM-lipid complex melting transition between 96.9127.6C. As cooking temperature increased, RS content of Tarakjuk decreased, whereas IVSD increased. Total amino acid content was between 11,558-15,601mg/100g, depending on cooking condition used. Compared with conventionally made control, contents of essential amino acids, such as lysine and tryptophane, were higher at 50 and 56.5C, and IVPD showed higher increase. Results reveal degree of gelatinization in Tarakjuk with high RS content as well as low IVSD and high IVPD, which are important from physiological and nutritional point of view, can be produced by controlling cooking condition.

The Effect of BaF2 Particle Size for Zirconium Recycling by Precipitation from Waste Acid and Ba2ZrF8 Vacuum Distillation Property (폐 산세 용액으로부터 공침 반응에 의한 지르코늄 회수 시 BaF2 입도 영향 및 Ba2ZrF8의 진공증류 특성)

  • Choi, Jeong Hun;Nersisyan, Hayk;Han, Seul Ki;Kim, Young Min;Park, Cheol-Ho;Kahng, Jong Won;Na, Ki Hyun;Kim, Jeong hun;Lee, Jong Hyeon
    • Resources Recycling
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    • v.26 no.6
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    • pp.29-37
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    • 2017
  • Nuclear fuel cladding tube is fabricated by pilgering and annealing process. In order to remove impurity and oxygen layer on the surface, pickling process is carried out. When Zirconium(Zr) is dissolved and saturated in acid solution during the pickling process, all the waste acid including Zr is disposed. Therefore, BaF2 is added into the waste acid to extract Zr and Ba2ZrF8 is subsequently formed. To recycle Zr by electrowinning process, Ba2ZrF8 is used as electrolyte, but it has high melting point (1053C). ZrF4 should be added into Ba2ZrF8 to decrease the melting point. In this paper, it was investigated that Ba2ZrF8 was separated to BaF2 and ZrF4 by vacuum distillation. Firstly, BaF2 with different particle size (1μm, 35μm, 110μm) was added into the waste acid and the respective precipitation property was estimated. BaF2 obtained by vacuum distillation was shattered by ball-milling with different time. The precipitation efficiency was compared with 1μm of BaF2s one, which was not used as precipitation agent.

Sulfur Dioxide, Mineral Contents and Physicochemical Properties Generated during Manufacture of Bamboo Salt (죽염 제조공정에 따른 이산화황, 미네랄 함량 및 이화학적 특성)

  • Kim, Hag-Lyeol;Lee, Seong-Jae;Lee, Jung-Hee;Kim, In-Cheol
    • Journal of the Korean Society of Food Science and Nutrition
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    • v.43 no.8
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    • pp.1248-1256
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    • 2014
  • The purpose of this study was to investigate the mechanisms of behind SO2 formation and elevated cause of reducing power in purple bamboo salt (PBS) along with an analysis of physicochemical properties, content of sulfur compounds, oxidation reduction potential (ORP), mineral contents of salt type (MSS, mudflat solar salt; BS, bamboo salt), and addition of raw bamboo (RB). SO2 content of 630 ppm was detected in PBS. SO2 was not detected in MSS, BS, or RB, whereas SO2 (782 ppm) from K2SO4 was detected after heating a NaCl, KCl, MgCl2, MgSO4, MgO, CaCl2, K2SO4, and FeSO4 with RB. SO2 content of BS increased with baking time, and it originated from BSRB1 (13.88 ppm) to BSRB4 (109.13 ppm). SO32 originated only from MSSRB4 and BSRB2~BSRB4. Sulfate ion content decreased along with increasing SO2 and sulfite ion contents. ORP increased with baking time of MSS and BS, and it was present at higher levels in BSRB4 (-211.40 mV) of BS than MSS. Insoluble content was higher in BS than MSS. Further, Ca, K, and Mg ion contents decreased in MSS and increased in BS with baking time. BSRB4 had 1.4 fold higher levels of Ca, 1.5 fold higher levels of Mg, and 1.8 fold higher levels of K than BS. Li, Al, Mn, Fe, and Sr in MSS as well as Al, Fe, and Ni in BS increased with baking time. Anions (Cl, NO3, and Br) and heavy metals (Pb, Cd, Hg, and As) between MSS and BS were not significantly different. These results suggest that the reducing power of BS was due to SO2 and sulfite ion. To increase the amounts of these compounds and reducing power, higher melting temperature and longer baking time are necessary along with BS, which is created by the addition of RB to roasted salt.

Analysis of Surface Displacement of Oil Sands Region in Alberta, Canada Using Sentinel-1 SAR Time Series Images (Sentinel-1 SAR 시계열 영상을 이용한 캐나다 앨버타 오일샌드 지역의 지표변위 분석)

  • Kim, Taewook;Han, Hyangsun
    • Korean Journal of Remote Sensing
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    • v.38 no.2
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    • pp.139-151
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    • 2022
  • SAGD (Steam-Assisted Gravity Drainage) method is widely used for oil recovery in oil sands regions. The SAGD operation causes surface displacement, which can affect the stability of oil recovery plants and trigger various geological disasters. Therefore, it isimportant to monitor the surface displacement due to SAGD in the oil sands region. In this study, the surface displacement due to SAGD operations of the Athabasca oil sands region in Alberta, Canada, was observed by applying Permanent Scatterer Interferometric Synthetic Aperture Radar (PSInSAR) technique to the Sentinel-1 time series SAR data acquired from 2016 to 2021. We also investigated the construction and expansion of SAGD facilitiesfrom Landsat-7/8 time seriesimages, from which the characteristics of the surface displacement according to the oil production activity of SAGD were analyzed. Uplift rates of 0.3-2.5 cm/yr in the direction of line of sight were observed over the SAGDs and their vicinity, whereas subsidence rates of -0.3--0.6 cm/yr were observed in areas more than several kilometers away from the SAGDs and not affected by oil recovery activities. Through the analysis of Landsat-7/8 images, we could confirm that the SAGDs operating after 2012 and showing high oil production activity caused uplift rates greater than 1.6 cm/yr due to the subsurface steam injection. Meanwhile, very small uplift rates of several mm per year occurred over SAGDs which have been operated for a longer period of time and show relatively low oil production activity. This was probably due to the compression of reservoir sandstone due to continuous oil recovery. The subsidence observed in areas except for the SAGDs and their vicinity estimated to be a gradual land subsidence caused by melting of the permafrost. Considering the subsidence, it was expected that the uplift due to SAGD operation would be greater than that observed by the PSInSAR. The results of this study confirm that the PSInSAR can be used as an effective means for evaluating productivity and stability of SAGD in the extreme cold regions.

A Study on the Evaluation of Materials for Aircraft Turbofan Engine Using Data Base. (항공기용 터어보팬 엔진의 재료선정용 DATA BASE를 이용한 재료평가에 관한 연구)

  • Kim, Gwang-Bae;Bu, Jun-Hong;Kim, Hak-Bong;Im, Gyeong-Ho;Yu, Sang-Sin
    • Korean Journal of Materials Research
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    • v.1 no.3
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    • pp.156-167
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    • 1991
  • The purpose of this study is to develop a data base for material selection of turbofan engines, which is preferred in these days on many application due to their high performance with economical operation. Hundreds of Super Alloys have been developed by this time, each having special properties. Since it is very difficult task for a design engineer to select materials of adequate Properties for specific engine components, a good data bate is strongly desired to manage informations on various kinds of materials. However, no basic research is reported in this area so far in our country. The operating conditions such as temperature, pressure, rpm of spools are assumed to be provided by other mechanical studies. Creep rupture strength, corrosion resistance, yield strength, thermal expansion, melting point, etc., are considered as typical properties in this study to search a group of candidate materials. Formability, manufacturing or purchase cost can also be important variables to be considered. As a result of this study, a user-friendly computer program has been developed for input of new material information, interactive material selection, and output of selection results. Finally, discussion is presented from. the viewpoint of materials engineering. A method to evaluate the performance of the selected materials is also suggested.

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CONFUTER-AIDED CASTING DESIGN FOR IMPLANT TITANIUM SUPERSTRUCTURES (컴퓨터 시뮬레이션을 이용한 임플란트 상부 티타늄 구조물의 주조방안)

  • Oh Se-Wook;Lee Ho-Yong;Lee Keun-Woo;Shim Jun-Sung
    • The Journal of Korean Academy of Prosthodontics
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    • v.41 no.4
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    • pp.421-439
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    • 2003
  • Statement of problem : It is difficult to obtain a good titanium casting body using the traditional sprue design because of high melting point of Ti, and the low fluidity and high reactivity of molten Ti. Purpose : A new sprue design for titanium casting bodies needs more trial and error. In order to decrease the number of trial and error, computer simulation(MAGMASOFT, Magmasoft Giessereitechnologie GmbH, Achen, Germany) was used to optimize sprue design in U-shaped implant superstructures. Material and method : Five kinds of sprue were examined for the design of the sprue former for titanium casting: Sprue design A(sprue length 4 mm, rectangular shape, 4 sprues), Sprue design B(sprue length 4 mm. round shape. radius 2 mm, 7 sprues), Sprue design C (sprue length 2 mm, round shape, radius 2 mm, 7 sprues). Sprue design D (sprue length 2 mm, cone shape, large radius 3mm. small radius 2mm, 7 sprues), and Sprue design E( sprue length 2 mm. one unit channel shape). Sprue design F(sprue length 2mm, one unit channel shape) was also examined for the design of the customized sprue former in the Biotan system(Schutz Dental Gmbh, Germany). The casting bodies were taken in Sprue design A, Sprue design D, Sprue design E, and Sprue design F in the Biotan casting system. The numerically predicted defects were compared with the experimental dental castings by the radiographic and sectional view observations. Results : 1. According to the result of computer simulation, turbulence during mold filling was decreased in the sequence of Sprue design F, Sprue design E, Sprue design D, Sprue design C, Sprue design B, and Sprue design A. 2. The calculated solidification time contours indicate that hot spot was moved from the casting body to the sprue button in the sequence of Sprue design A, Sprue design B, Sprue design C, Sprue design D, and Sprue design E. The filling pattern of Sprue design F was similar to that of Sprue design E. 3 The predicted filling pattern shows that less turbulence was found in the customized sprue former than in the standard sprue former. 4. According to the results of the radiographic and cross sectional observations, casting defects less than 1mm were found at the center of a casting body with Sprue design E and Sprue design F. However, larger casting defects of 4mm were found in a casting with Sprue design A. 5. The predicted casting porosity was similar to that of the real casting. Conclusion : One unit channel-type and customized sprue former can be recommended. Further research and developement of various sprue designs using computer simulation in necessary to optimize casting design, in order to reduce the formation of casting defects in implant titanuim super-structures.

A Study on Flame Retardant Performance of Vertical Blind and Roll Screen (버티칼 브라인드와 롤 스크린의 방염성능 유지에 관한 연구)

  • Jeong, Hyun Gyu;Cho, Woncheol;Lee, Tae Sik
    • Journal of Korean Society of societal Security
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    • v.3 no.2
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    • pp.41-46
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    • 2010
  • This study focuses on two points. First, I have examined the difference on combustion between flame-retardant and non flame-retardant products including vertical blinds and roll screens that are widely used as a substitute for fabric curtains. The second point is to see how long flame-retardant goods can be durable, that is, flame retardant durability after washing in liquid. the experiment on the flame-retardant ability before and after washing of vertical blinds and roll screens that have been used for a long time in fire protection construct. Comparing and analyzing domestic and foreign laws on flame-retardant after the experiment on durability of these products. I aim to draw necessity for increased application of internal laws and regulations on flame-retardant and show how to improve the point at issue. According to the result, clear differences in performance and safety were observed between flame-retardant and non flame-retardant products. flame-retardant materials can prevent things from fire spread without igniting but melting when they've met flame and burnt, In contrast, non flame-retardant material for experiment which size is 120cm long takes less than 3 minutes only to be completely destroyed by fire. However, it was expected for flame-retardant durability of flame-retardant blinds which are not washable to decrease flame-retardant durability after being washed with water, there was no sharp difference. so it is demonstrated that flame-retardant blinds can keep flame-retardant durability. accordingly through the strict course of product we are concerned about keeping durability.

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Thermal Decomposition of Arsenopyrite by Microwave Heating and the Effect of Removal Arsenic with Wet-magnetic separation (마이크로웨이브 가열에 의한 황비철석의 열분해와 습식-자력선별에 의한 비소 제거 효과)

  • On, Hyun-Sung;Kim, Hyun-Soo;Myung, Eun-Ji;Lim, Dae-Hack;Park, Cheon-Young
    • Journal of the Mineralogical Society of Korea
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    • v.30 no.3
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    • pp.103-112
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    • 2017
  • In order to transform arsenopyrite into pyrrhotite and to decrease As content by less than 2,000 mg/kg, pulp sample and non-magnetic pulp sample were heated in a microwave oven at different heating times and were separated through wet-magnetic separation. As the microwave heating time increased, the phase of pyrrhotite was extended to become arsenopyrite entirely. The melting pores and micro-cracks occurred on the pyrrhotite due to hot spot phenomenon with microwave heating. The heated raw pulp sample (As content : 19,970.13 mg/kg) and non-magnetic pulp sample (As content : 19,970.13 mg/kg) which were heated in a microwave oven for 10 minutes were separated through wet-magnetic separation and magnetic fraction containing less than 2,000 mg/kg of As content was recovered only from the heated sample of magnetic separation. It was discovered that for the sulfide complex ore with As penalty imposed on, if microwave heating and wet-magnetic separation are effectively utilized, magnetic fraction. We expect to be able to obtain ore minerals with an arsenic content below the penalty charge.