• 열처리공학회지
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• 제4권3호
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• pp.39-46
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• 1991

The effects of austenitizing temperatures and times and cooling rate on the characteristics of continuous air cooling have been investigated for 0.3%C-Mn steels microalloyed with vanadium. Transformation start temperatures have been found to be measured from temperature-time curve directly obtained with continuous air cooling and to decrease with increasing austenitizing temperature, cooling rate and Mn contents. The coarsening behavior of austenite grain size has been measured to abnormally grow at $1050^{\circ}C$ and rapidly grow at $1200^{\circ}C$. It has been found that the volume fraction of pearlite was linealy proportional to the reciprocal square root of austenite grain size. The hardness has been measured to increase with increasing cooling rate up to $250^{\circ}C/min.$ and to remain relatively unchanged in the range of $250{\sim}400^{\circ}C/min.$ showing that hardness valves for steel with a higher Mn content increase more than those for steel with a lower Mn content. The impact property has been found to decrease with increasing of austenite grain size but does not linealy change with the reciprocal square root of austenite grain size.

• 한국세라믹학회지
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• 제44권4호
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• pp.230-234
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• 2007

Cordierite ceramics were fabricated via a reaction sintering process using ceramics-filled polysiloxane as a precursor for cordierite ceramics. In this study, the effects of the additive composition, additive content, and sintering temperature on the sintered density and compressive strength of cordierite ceramics have been investigated The sintered densities of reaction-sintered cordierite ceramics containing $TiO_2$ as an additive were insensitive to the additive composition, additive content, and sintering temperature and ranged from $1.92g/cm^3\;to\;2.06g/cm^3$. In contrast, the cordierite ceramics containing $Y_2O_3$ showed a maximal density of $2.21g/cm^3$ at 5 wt% addition and at a sintering temperature of $1400^{\circ}C$. The compressive strength of cordierite ceramics showed the same tendency with the density. Typical compressive strength of cordierite ceramics containing 5 wt% $Y_2O_3$ as a sintering additive and sintered at $1400^{\circ}C\;was\;{\sim}480MPa$.

• 한국식품위생안전성학회지
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• 제31권3호
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• pp.210-215
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• 2016

본 연구에서는 국내산 고려엉겅퀴를 건강기능식품 소재로 활용시 기초자료 제공하고자 주요 산지별 pectolinarin 함량, 총 플라보노이드 함량, DPPH라디칼 소거능 및 ORAC 지수 등을 분석하였다. 산지별 고려엉겅퀴의 pectolinarin 함량은 $3.95{\pm}0.05{\sim}7.29{\pm}0.07mg/g$로 강원도 D농장(GW-D)에서 가장 높은 함량을 보였다. 총 플라보노이드 함량은 산지별로 $40.42{\pm}0.91{\sim}76.70{\pm}2.24mg\;PNE/g$ 수준으로 전라남도 A농장(JN-A) 추출물에서 가장 높은 함량을 나타내었고 강원도 A농장(GW-A) 추출물에서($40.42{\pm}0.91mg\;PNE/g$)로 가장 낮은 함량을 보였다. DPPH 라디칼 소거능의 경우, 산지별로 31.25% ~ 81.93%의 활성을 보였고, ORAC 지수는 산지별로 $179.62{\sim}514.49{\mu}M\;TE/g$로 강원도 D농장(GW-D)과 강원도 E농장(GW-E)에서 각각 514.49, $501.73{\mu}M\;TE/g$ 으로 가장 높은 ORAC 수치를 나타내었다. 결론적으로 고려엉겅퀴 추출물은 pectolinarin과 유용성분을 함유하고 DPPH 라디칼 소거능 및 ORAC 활성 등의 항산화활성을 갖는 것으로 나타났다.

• 한국초지조사료학회지
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• 제38권3호
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• pp.196-201
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• 2018

Soil is the main nitrogen (N) provider for plants but N in soil is not all available to advanced plants. Mineralization is a critical biological process for transferring organic N to inorganic N that can be used by plants directly. To investigate the effect of different levels of soil temperature and water content to soil mineralization, a field experiment was established on three different sites (A, B and C). We measured soil temperature, moisture and electrical conductivity once daily after swine slurry application. Average soil moisture and temperature in site A is the highest among three sites (40.9% and $9.7^{\circ}C$, respectively). Following is in site C (37.3% and $9.6^{\circ}C$) and the lowest is in site B (28.0% and $9.0^{\circ}C$). Ammonium N (NH4+-N) and nitrate N (NO3--N) were determined on the first and fifth day after treatment. Compared with site B and C, site A always had the highest soil total N content (1.54 g N kg-1 on day one; 1.22 g N kg-1 on day five) and highest NO3-- N content (93.18 mg N kg-1 on day one; 16.22 mg N kg-1 on day five) and a significant decrease on day five. Content of NH4+-N in site B and C reduced while in site A, it increased by 6.7%. Results revealed that net N mineralization positively correlated with soil temperature (P<0.5, $r=0.675^*$) and moisture (P<0.01, $r=0.770^{**}$), suggesting that to some extent, higher soil moisture and temperature contribute more to inorganic N that can be used by plants.

• 한국작물학회지
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• 제59권3호
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• pp.332-340
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• 2014

본 연구는 동부나물 생산에 적합한 재배온도를 설정하고, 유전자원을 선발하고자 수행하였다. 재배온도 설정을 위해 Seowon을 이용하여 $15^{\circ}C$에서 $30^{\circ}C$까지 $3^{\circ}C$ 간격으로 처리하였다. 나물 생산에 적합한 유전자원의 선발을 위해 Seowon, IT154149, IT154153, Tvu7426, Tvu7778 등 12계통 및 품종을 이용하여 $27^{\circ}C$에서 재배하였다. 1. 동부나물 생산수율은 $27^{\circ}C$에서 657%로 가장 높았고, 재배온도가 낮아질수록 떨어졌다. 2. 비타민 C 함량은 $24^{\circ}C$ 재배에서 2.85 mg/g로 가장 많았고, 기타 재배온도에서는 2.15~2.29 mg/g 범위였으며, 재배기간이 길어질수록 증가하였다. 3. 동부나물의 무기성분 함량은 재배온도에 따른 차이가 없었고, 아미노산 함량은 $15^{\circ}C$에서 $24^{\circ}C$까지는 재배온도가 높아질수록 증가한 반면 $24^{\circ}C$에서 $30^{\circ}C$까지는 재배온도가 높아질수록 감소하였다. 4. 동부 자원별 나물 생산수율은 IT154153 647%, Seowon 615%, Tvu7426 608% 순으로 많았다. 동부나물의 생산수율이 높은 자원은 종실이 작고 종피가 얇으며 발아력이 우수한 특징을 나타냈다. 5. 동부나물의 무기성분 함량은 칼륨, 마그네슘, 칼슘, 나트륨, 철, 몰리브덴, 아연 순으로 많았다. 동부나물의 단백질, 칼슘, 아연, 몰리브덴, 철 등의 함량은 원료곡보다 많았고, 알루미늄, 붕소 등의 함량은 원료곡보다 적었다.

• 한국작물학회지
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• 제54권4호
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• pp.458-463
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• 2009

본 연구는 백삼 추출액의 사포닌 함량을 높이고 품질과 관련된 특성을 증진 시킬수 있는 최적 추출 시간 및 온도를 밝히기 위하여 실시되었다. 백삼의 물 추출액의 총 ginsenosides 함량은 $75^{\circ}C$에서 18시간 추출액 8.32 mg/10ml, $85^{\circ}C$에서 6시간 추출액 5.93 mg/10 ml, $95^{\circ}C$에서 6시간 추출액 4.92 mg/10 ml으로 최고의 함량을 나타냈다. 항당뇨 작용을 나타내는 ginsenoside $Rb_2$와 Re을 합한 최고 함량은 $75^{\circ}C$에서 18시간 추출액 1.76 mg/10 ml, $85^{\circ}C$ 6시간 추출액 1.34 mg/10 ml, $95^{\circ}C$ 6시간 추출액 0.56 mg/10 ml이었으며, 항암 작용을 나타내는 $Rg_3$의 함량은 $75^{\circ}C$에서 36시간 추출액 1.67 mg/10 ml, $85^{\circ}C$에서 36시간 추출액 3.13 mg/10 ml, $95^{\circ}C$에서 24시간 추출액이 3.56 mg/10 ml이었다. 추출온도와 시간에 따른 이화학성의 변화는 추출온도가 높을수록, 추출시간이 길어질수록 pH는 낮아 졌으나 환원당, 탁도, 당도는 증가하였다. 따라서 백삼추출액을 제조할때 1차 추출에서는 사포닌 최고 함량 추출 온도와 시간으로 추출한 다음 다시 온도를 높게 2차 추출 하여 맛을 증진시켜 혼합하는 방법이 좋을 것으로 생각된다.

• 한국세라믹학회지
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• 제23권1호
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• pp.67-73
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• 1986

SiC and $SiC-Si_3N_4$ powder were synthesized via the carbiding and carbiding-nitriding reaction of Jecheon quartz respectively using graphite as a reducing agent. $\beta$-SiC+($\alpha$+$\beta$)-$Si_3N_4$ composite was obtained by the carbiding-nitriding reaction of Jecheon quartz-graphite mixture at 1, 35$0^{\circ}C$ in $H_2$ atmosphere. $\beta$-SiC+($\alpha$+$\beta$)-$Si_3N_4$ composite was obtained by the carbidint-nitriding reaction of Jecheon quartz-graphite mixture at 1, 35$0^{\circ}C$ in $N_2-H_2$ atmosphere. The ratio of $\beta$-SiC+($\alpha$+$\beta$)-$Si_3N_4$ content in a produced composite could be controlled by adjusting the reaction time and gaseous mixture.

• Macromolecular Research
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• 제16권4호
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• pp.329-336
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• 2008

Core/shell ($\pm$)PS/(-)silica nanocomposite particles were synthesized by dispersion polymerization using an amphoteric initiator, 2,2'-azobis [N-(2-carboxyethyl)-2,2-methylpropionamidine] ($HOOC(CH_2)_2HN$(HN=) $C(CH_3)_2CN$=NC $(CH_3)_2C$(=NH)NH $(CH_2)_2COOH$), VA-057. Negatively charged (-6.9 mV) silica was used as the stabilizer. The effects of silica addition time and silica and initiator concentrations were investigated in terms of polymerization kinetics, ultimate particle morphology, and size/size distribution. Uniform hybrid microspheres with a well-defined, core-shell structure were obtained at the following conditions: silica content = 10-15 wt% to styrene, VA-057 content=above 2 wt% to styrene and silica addition time=0 min after initiation. The delay in silica addition time retarded the polymerization kinetics and broadened the particle size distribution. The rate of polymerization was strongly affected by the silica content: it increased up to 15 wt% silica but then decreased with further increase in silica content. However, the particle size was only marginally influenced by the silica content. The zeta potential of the composite particles slightly decreased with increasing silica content. With increasing VA-057 concentration, the PS microspheres were entirely coated with silica sol above 1.0 wt% initiator.

• Journal of the Korean Wood Science and Technology
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• 제37권2호
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• pp.121-127
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• 2009

Acacia wood (Acacia mangium Willd.) is the most popular fast growing tree species planted in timber estate in Indonesia and is considered to be very valuable raw materials for structural composite products. The objective of the research was to evaluate the properties of OSB prepared from A. Mangium wood with or without immersing the strands to hot water at $80^{\circ}C$ for 2 hours. MDI adhesive was used in 3 levels i.e., 3%, 5%, and 7%. The moisture content of strand was 7%. The results indicated that immersing strands in hot water for 2 hours at $80^{\circ}C$ prior to manufacture OSB improved significantly the mechanical peoperties (i.e., MOR and MOE) of OSB. The higher the adhesive content resulted in the better the dimensional stabilisation (i.e., water absorption and thickness swelling) and the mechanical properties (i.e., MOR, MOE and IB) of OSB. OSB prepared from hot-water immersed strands with 5% adhesive content has met all parameters requirement on the JIS A 5908 (2003) standard.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2007년도 추계 학술논문 발표대회
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• pp.133-136
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• 2007

This study investigates mechanical properties of the concrete using fine particle cement which is manufactured by the pulverizing process. The variable factors are 3 types of W/C such as 40, 50, and 60%, 3 types of curing temperature such as 5, 20, and $35^{\circ}C$, and 5types of the replacement of the fine particle cement such as 0, 25, 50, 75, and 100%. The unit water content, S/a and amount of the SP and AE agents to secure the slump and air content is gradually increased in accordance with amount of replacement. It can be confirmed that the delay of the setting time depending on FC content is decreased corresponding to FC content, so the effect of the acceleration to the setting time is expected. The compressive strength corresponding to FC content is proportionally increased, and the growth is confirmed about $30{\sim}40%$ at a day in 50% of FC contents. However, the increase of the strength is gradually decreased in accordance with increasing age.