• 한국추진공학회지
• /
• 제9권3호
• /
• pp.85-91
• /
• 2005

로켓노즐로부터 방사되는 플룸에 의한 로켓 저부면의 복사 가열을 수치해석적으로 조사하였다. 로켓노즐 주위의 유동 및 온도장의 계산이 선행되었으며, 그에 따라 실제적인 플룸의 형태와 플룸내부의 온도분포를 얻었다. 계산된 온도장을 토대로, 복사 열전달 방정식을 구분종좌법을 이용하여 풀이하였다. 견본 로켓 플룸에 대해 계산한 결과, 저부면에 도달하는 평균복사열은 비행고도 10.9 km에서 약 5kw/m$^{2}$ 이었다. 이 수치는, 플룸의 공간적인 온도분포를 고려하지 않고 일정온도 (1500 K) 가정하에 계산된 복사량에 비하여 작은 값이지만, 그 절대적인 크기를 무시할 수 있을 정도로 작은 값은 아니다. 고고도(29.8 km)에서는 플룸의 팽창 때문에 저부면과 배기 플룸 사이의 보기계수가 증가하게 된다. 그러나, 대류 열전달에 의해 저부면이 1000 K이상으로 가열되기 때문에 복사가열 현상은 사라지게됨을 알았다.

• 한국식품영양학회지
• /
• 제37권2호
• /
• pp.57-66
• /
• 2024

The objective of this study was to investigate the quality characteristics of Campbell Early grape-added traditional Korean wines (yakju) prepared with different yeasts and pretreatments. The first pretreatment (A) was prepared by crushing the grapes, the second method (B) was prepared by heating the grapes at 60~70℃ for 30 minutes, and the third method (C) was prepared by freeze-concentrating grape juice. The pH of the fermented wines ranged from 3.77 to 4.10, and the total acidity of the samples ranged from 0.32 to 0.62%. The a value (redness) ranged from -0.40 to 17.89, which was higher in Campbell Early-added samples than in the controls (grapes not added). Total polyphenol content was the highest in samples prepared by crushing or heating Campbell Early grapes with ES22, and the total flavonoid contents were the highest in samples prepared by crushing Campbell Early grapes with ES22. The anthocyanin contents were also the highest in the samples fermented by heating Campbell Early grapes. ABTS and DPPH radical scavenging activities were also the highest (84.08 and 77.56%, respectively) in samples fermented by heating Campbell Early grapes.

• 한국식품과학회지
• /
• 제29권5호
• /
• pp.932-938
• /
• 1997

Changes in viscosity and dynamic theological properties of Job's-tears were measured by Bohlin dynamic tester as a function of moisture, and measurement was performed within a linear viscoelastic range. The result of the shear stress vs shear rate of Job's-tears at different moisture contents $(50{\sim}75%)$ was applied to mathematical models and Herschel-Bulkley model showed the highest correlation coefficient. Lower moisture content (55%) produced higher yield stress and consistency index, but lower flow behavior index, whereas higher moisture content showed reverse effects. Job's-tears with $50{\sim}70%$ moisture contents showed a higher storage modulus (G') than loss modulus (G') at all frequencies, showing a higher concentrated polymer characteristics. However, higher moisture content (>75%) showed crossover point between G' and G', and frequency dependency. As the moisture content was increased, the amount of viscoelastic properties such as G', G', complex viscosity decreased during heating, and initial temperature and miximum value of viscoelastic properties shifted to higher temperatures, representing the moisture-dependence of Job's-tears upon theological properties.

• 한국조리학회지
• /
• 제21권1호
• /
• pp.1-14
• /
• 2015

본 연구에서는 돼지고기 삼겹살과 목살의 가열처리방법에 따른 새로 개발된 PCM 처리와 이중팬을 제작하여 사용하였으며, 기존의 가열조리방법과 비교하여 이화학적 특성과 관능특성을 비교하였다. 돼지고기 삼겹살과 목살의 수분함량은 찌기처리구에서 60.2%, 67.2%로 높게 나타났으며, 조지방은 삼겹살은 숯불처리구에서 33.2%, 목살은 전기그릴처리구에서 16.0%로 가장 높았다(p<0.05). 조단백질의 경우, 삼겹살은 스팀처리구가 18.4%로 높았고, 삶기처리구는 15.4%로 유의적으로 낮았다. 또한, 목살은 전기그릴처리구에서 25.2%로 유의적으로 높게 나타났다(p<0.05). 보수력과 가장 관계가 깊은 가열감량은 삼겹살과 목살 모두에서 숯불구이처리구 40.18%, 36.98%로 유의적으로 높았고, 전단력에서 삼겹살은 오븐처리구에서 $2.76kg/cm^2$으로 목살은 이중 팬처리구에서 $3.67kg/cm^2$으로 가장 낮았다(p<0.05). 육색 시험결과 L값은 삶기처리구에서 65.16, 59.72로 가장 높았고(p<0.05) b 값의 경우, 삼겹살은 삶기처리구에서 2.32로 가장 낮았다(p<0.05). 관능평가 결과 전체적인 기호도 항목에서 삼겹살의 경우, 전기그릴처리구에서 7.56점으로 높았다. 목살은 팬구이처리구에서 7.22점으로 가장 높았으며, 반면, 삶기처리구에서 5.88점으로 가장 낮았다(p<0.05).

• Journal of Forest and Environmental Science
• /
• 제31권1호
• /
• pp.1-6
• /
• 2015

Microwave assisted biodiesel production from crude Pongamia pinnata oil using homogeneous base catalyst (KOH) was unsuccessful because of considerable soap formation. Therefore, a two step process of biodiesel production from high free fatty acid (FFA) oil was investigated. In first step, crude P. pinnata oil was acid catalyzed using $H_2SO_4$ and acid value of oil was reduced to less than 4 mg KOH/g. Effect of sulfuric acid concentration, alcohol-oil molar ratio and microwave irradiation time on acid value of oil was studied. Result suggested that 1.5% $H_2SO_4$ (w/w), 6:1 methanol oil molar ratio and 3 min microwave irradiation time was sufficient to reduce the acid value of oil from 12 and 22 mg KOH/g to 2.9 and 3.9 mg/KOH/g, respectively. Oil obtained after pretreatment was subsequently used for microwave assisted alkali catalyzed transesterification. A higher biodiesel yield (99.0%) was achieved by adopting two step processes. Microwave energy efficiency during alkali catalyzed transesterification was also investigated. The results suggested a significant energy saving because of reduced reaction time under microwave heating.

• 에너지공학
• /
• 제12권3호
• /
• pp.184-189
• /
• 2003

본 논문은 Indolene-Methanol Plus Higher Alcohols(MPHA)의 연료 특성에 관한 연구로서, 연료의 물성치를 측정하여 조사하였다. 특히 연료의 물성치 중에서 증류특성, 발열량, 인화점, 비중 및 내수성 등을 조사하여 나타내었다. 이때 알콜의 농도는 청정 Indolene의 용적에 따라서 0 에서부터 100%까지 변화하였다. 연료 물성치 측정에서 Indolene-MPHA 혼합물들이 일반적으로 Indolent-Methanol 혼합물과 비교해서 높은 내수성, 유사한 비중과 인화점, 서로 다른 증류특성을 가지고 있음을 알 수 있다. 여기에서 혼합물 물성치 중 상당수는 실제 값과 비교하여 성분들의 중량비를 사용하여 계산하였다.

• 한국식품영양과학회지
• /
• 제27권1호
• /
• pp.87-92
• /
• 1998

Major characteristics of shrinking and rehydration of Korean tea-leaves were investigated in the hot-air drying equipment. Experiments were performed with various drying temperature, plucking time, heating method and rolling condition. The values of shrinking raito and rate were the highest at 7$0^{\circ}C$ in the range of 3$0^{\circ}C$ to 9$0^{\circ}C$. The 1st tea-leaves and showed higher values. Shrinking ratio was 16.62 and 19.62% for leaves and stems; shrinking rate was found 0.083 and 0.091cm/hr.cm, respectively. The rehydration characteristics of tea-leaves at the drying temperature of 3$0^{\circ}C$ were fairly satisfactory. The 2nd tea-leaves showed higher value than others, while the natural tea-leaves were lower. Average rehydration ratio and rehydration rate constant were 85.7% and 0.063/min for leaves; 80.1% and 0.032/min for stems, respectively.

• 한국조리학회지
• /
• 제24권3호
• /
• pp.113-120
• /
• 2018

In this study, to enhance the applicability of the black current as a natural pigment and functional material, a jelly was produced by adding 0 %, 3 %, 6 %, 9 %, and 12 % of the black current powder. The pH and moisture content of the black currant jelly decreased with the addition of the black currant powder, while the sweetness($^{\circ}brix%$) of the jelly increased with the addition of the black currant powder. The chromaticity of the jelly was reduced as the black current powder was added, as the L value and b value increased. Texture measurement score in terms of hardness, chewiness and brittleness of groups with 3% and 6% black currant powder were significantly higher when compared to the control group. The contents of total polyphenol, DPPH radical scavenging activity, and NSA radical scavenging activity of groups by the addition of black currant powder were higher than those of control group. The anthocyanin contents increased proportionally with increasing levels of black currant powder. The sensory evaluation scores in terms of after swallowing, appearance, odor, taste, texture, and overall preference of groups with 6% and 9% black currant powder. Also, the anti oxidative activity and anthocyanine pigment in black current powder are highly visible even after the heating process, so it may be helpful to enhance the functionality of jelly by using natural colors that are highly antioxidants in jelly manufacture.

• Environmental Engineering Research
• /
• 제21권2호
• /
• pp.180-187
• /
• 2016

In the present work, bael shell (aegle marmelos) is used as the feedstock for pyrolysis, using a fixed bed reactor to investigate the characteristics of the pyrolysis oil. The product yields, e.g., liquid, char and gases are produced from the biomass at different temperatures with the particle size of 0.5-1.0 mm, at the heating rate of $150^{\circ}C/min$. The maximum liquid yield, i.e., 36.23 wt.%, was found at $5500^{\circ}C$. Some physical properties of the pyrolysis oil such as calorific value, viscosity, density, pH, flash point and fire point are evaluated. The calorific value of the bael shell pyrolysis oil was 20.4 MJ/kg, which is slightly higher than the biomass, i.e., 18.24 MJ/kg. The H/C and O/C ratios of the bio-oil were found as 2.3 and 0.56 respectively, which are quite higher than some other bio-oils. Gas Chromatography and Mass Spectroscopy (GC-MS) and Fourier Transform Infra-red (FTIR) analyses showed that the pyrolysis oil of bael shell is mostly composed by phenolic and acidic compounds. The results of the properties of the bael shell pyrolysis oil reveal the potential of the oil as an alternate fuel with the essential upgradation of some properties.

• 한국분말재료학회지
• /
• 제7권1호
• /
• pp.42-49
• /
• 2000

Densificationbehavior of conventional austenitic stainless steel powder compacts was studied by comparing the relative density of sintered compact(Ds)with that of green compacts(Dg)prepared with various catbon contents and P/M process. Dg of 304and 316 powders by warm compaction under pressure of 686 MPa at heating temperature of powder(553K) and dies (573K) were 80% and 81%, repectively, whichwere 2 and 3% higher than those of conventional green compacts at the same pressure. Ds of 304 compacts sintered at 1373K in H2 gas has the same value of 84% max. regardless of compacting temperature, and Ds of 316 compacts at the same sintering conditions were 80% by conventional compaction and 83% by warm compaction. Oxygen contents of 304 and 316 sintered compacts were increased 1.43∼2.94% and 0.010∼0.921% higher than those of raw powders and warm green compacts, respectively. In other case, Ds of 316 compacts sintered at 1573K in vacuum had the same value of 86%max. And Ds of 316 compacts at the same sintering conditions were 83% and 86% by conventional and warm compaction, respectively. Oxygen contents of 304 sintered compacts were 0.321% and 0.360%, and in case of 316, they were 0.419% and 0.182% by the respective compating condition. With carbon additions in the range 0.1∼0.6% Ds increased to the extent of 86∼89% in 304 sintered compacts, and to 82∼84% and 85∼87% in 316 according to different two compacting peocesses compared to those of sintered compacts without carbon addition.