• 한국연소학회:학술대회논문집
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• 한국연소학회 2013년도 제46회 KOSCO SYMPOSIUM 초록집
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• pp.97-98
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• 2013

Flame behaviors in meso-scale rectangular channels are largely influenced by heat recirculation through wall. In order to investigate the effects of wall thermal property on the heat recirculation and flame behaviors, meso-scale rectangular channels, of which upper and lower walls are made of quartz, stainless steel and silicon carbide and front and rear walls of quartz for flame visualization, were fabricated in this study. As a result, characteristic mixture velocities of propane-air flame, such as transition, stationary, and instability onset velocities, were measured for each channel and various mixture conditions. The results show that thermal conductivity has a close relationship to the characteristic velocities.

• 대한기계학회논문집B
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• 제20권3호
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• pp.1040-1049
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• 1996

The high loading combustion is accomplished by making the turbulent intensity strong and the scale small in the premixed combustor. The Da-mkoler number, which is decreased by short turbulent characteristic time or by long chemical reaction time, can make the distributed reaction flame. So we developed a doubled jet burner for high loading combustion. The doubled jet burner was designed to make the scale of the flame small by the effect of impingement and increasing shear stress with doubled jet. We investigated the turbulence characteristics of unburned mixture and visualized several flames with the typical schlieren photography. Then we studied the influence of several factors that related the scale of flame. Consequently, the doubled jet burner can make the eddy very small. And we can obtain the detail information of the flame scale through ADSF(the Average Distance between Successive Fringes) in the micro- schlieren photography. The ADSF is not a exact flame scale, but it has qualitative trend with increasing turbulent intensity. The ADSF is diminished remarkably with increasing turbulent intensity. The reason is that strong turbulent intensity makes the flame zone thick and flamelets numerous. We can confirm this fact by the signal analysis of ion currents.

• 유기물자원화
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• 제7권2호
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• pp.47-55
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• 1999

최근에 음식물쓰레기의 증가에 따라 폐기불의 처리가 현대사회의 큰 문제로 되었다. 본 연구는 음식물 쓰레기와 하수슬러지 혼합물의 2단 혐기성소화조에 의하여 소화의 가능성을 검토할 목적으로 수행되었다. 음식물쓰레기와 하수슬러지를 1:9의 비율로 하여 파이롯트 2단 소화시스템을 사용하여 현장에서 운전하였으며, 체류기간은 20일로 유지했다. $3.03kg\;TCOD/m^3day$의 유기물 부가에서 COD와 VS 제거효율이 57.7%와 47.7%를 보였으며, 가스 생성율과 메탄의 함량은 $0.4m^3/kg$ vs.day와 65.3%로 나타났다. 이러한 결과로부터 하수슬러지와 음식물쓰레기의 혼합처리가 효과적인 것으로 밝혀 졌다.

• 소성∙가공
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• 제13권2호
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• pp.174-179
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• 2004

The effect of grain refinement on the plastic deformation behaviour of nanocrystalline metallic materials is investigated. A phase mixture model in which a single phase material is considered as an effectively two-phase one is discussed. A distinctive feature of the model is that grain boundaries are treated as a separate phase deforming by a diffusion mechanism. For the grain interior phase two concurrent mechanisms are considered: dislocation glide and mass transfer by diffusion. The proposed constitutive model was implemented into a finite element code (DEFORM) using a semicoupled approach. The finite element method was applied to simulating room temperature tensile deformation of Cu down to the nanoscale grain size in order to investigate the pre- and post-necking behaviour.

• Transactions on Electrical and Electronic Materials
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• 제11권2호
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• pp.69-72
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• 2010

This study investigates the thermal and mechanical properties of insulation elements through the mixing of epoxy based micro and nano particles. Regarding their thermal properties, differential scanning calorimeter and dynamic mechanical analyser were used to calculate the cross-linking densities for various types of insulation elements. The mechanical properties of the bending strength, the shape and scale parameters, were obtained using the Weibull plot. This study obtained the best results in the scale parameters, at 0.5 phr, for the bending strength of the epoxy nano-and-micro mixture composites.

• 대한기계학회논문집B
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• 제21권2호
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• pp.213-223
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• 1997

Premixed flame is better than diffusion flame to accomplish a high loading combustion. Since the turbulent characteristics of unburned mixture has a great influence on the flame structure, it is general that many researchers realize a high loading combustion with strengthening turbulent intensity of unburned mixture. Because turbulent premixed flame reacts efficiently on the condition of distributed reaction region, we made high turbulent premixed flame in the doubled impingement field. We investigated turbulent characteristics of unburned mixture with increasing shear force and visualized flames with direct and Schlieren photographs. And the combustion characteristics of flame was elucidated by instantaneous temperature measurement with a thermocouple, by ion currents with a micro electrostatic probe, by radical luminescence intensity and local equivalence ratio. Extremely strong turbulent of small scale is generated by impingement of mixture, and turbulent intensity of unburned mixture increased with the mean velocity. As a result of direct photographs, visible region of flame became longer due to increasing central direction flux. But as strengthed turbulent intensity, visible region of flame turned to shorter and reaction occurred efficiently. As strengthened turbulent intensity of mixture with increasing flux of central direction, maximum fluctuating temperature region moved to radial direction and fluctuation of temperature became lower. The reason is influx of central direction which caused flame zone to move toward radial direction, to maintain flame zone stable and to make flame scale smaller.

• Animal Bioscience
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• 제36권10호
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• pp.1612-1618
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• 2023

Objective: In our previous study, we observed that the addition of waste cooking oil (WCO) reduced ammonia (NH₃) emissions during laboratory-scale composting of dairy cattle manure under low-aeration condition. Therefore, this study aimed to evaluate the effect of addition of WCO on NH₃ emissions reduction during pilot-scale composting of dairy cattle manure, which is close to the conditions of practical composting treatment. Methods: Composting tests were conducted using pilot-scale composting facilities (1.8 m³ of capacity). The composting mixtures were prepared from manure, sawdust, and WCO. Two treatments were set: without WCO (Control) and with WCO added to 3 wt% of manure (WCO3). Composting was conducted under continuous aeration at 40 L/min, corresponding to 22.2 L/(min·m³) of the mixture at the start of composting. The changes in temperatures, NH₃ concentrations in the exhaust gases, and contents of the composted mixtures were analyzed. Based on these analysis results, the effect of WCO addition on NH₃ emissions and nitrogen loss during composting was evaluated. Results: During composting, the temperature increase of the composting mixture became higher, and the decreases of weight and water content of the mixture became larger in WCO3 than in Control. In the decrease of weight, and the residual weight and water content of the mixture, significant differences (p<0.05) were detected between the two treatments at the end of composting. The NH₃ concentrations in the exhaust gases tended to be lower in WCO3 than in Control. Nitrogen loss was 21.5% lower in WCO3 than in Control. Conclusion: Reduction of NH₃ emissions by the addition of WCO under low aeration condition was observed in pilot-scale composting, as well as in laboratory-scale composting. This result suggests that this method is effective in reducing NH₃ emissions in practical-scale composting.

• Journal of Microbiology and Biotechnology
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• 제27권9호
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• pp.1559-1565
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• 2017

Naturally occurring ginsenoside F1 (20-O-${\beta}$-$\text\tiny{D}$-glucopyranosyl-20(S)-protopanaxatriol) is rare. Here, we produced gram-scale quantities of ginsenoside F1 from a crude protopanaxatriol saponin mixture comprised mainly of Re and Rg1 through enzyme-mediated biotransformation using recombinant ${\beta}$-glucosidase (BgpA) cloned from a soil bacterium, Terrabacter ginsenosidimutans Gsoil $3082^T$. In a systematic step-by-step process, the concentrations of substrate, enzyme, and NaCl were determined for maximal production of F1. At an optimized NaCl concentration of 200 mM, the protopanaxatriol saponin mixture (25 mg/ml) was incubated with recombinant BgpA (20 mg/ml) for 3 days in a 2.4 L reaction. Following octadecylsilyl silica gel column chromatography, 9.6 g of F1 was obtained from 60 g of substrate mixture at 95% purity, as assessed by chromatography. These results represent the first report of gram-scale F1 production via recombinant enzyme-mediated biotransformation.

• Composites Research
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• 제34권5호
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• pp.330-336
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• 2021

알루미나 파우더는 산업용으로 널리 사용되는 소재 중 하나이지만 파우더 패킹 상태에 따라 제품의 강도가 변하는 문제점이 있다. 위 문제해결을 위하여 입자 패킹효율을 높이려는 많은 선행연구들이 수행되었지만, 기존 연구는 밀리미터 스케일의 입자의 충진 특성을 분석한 것이 대부분이므로 마이크로미터 스케일과 물리적 특성이 달라, 그 선행연구 결과를 토대로 마이크로미터 스케일에 적용하기 어렵다. 따라서 본 논문에서는 마이크로미터 스케일의 알루미나 파우더를 이용하여 충진률을 높이기 위하여 통계적방법을 이용하여 3단계 실험을 수행하였다. 먼저, 혼합물시험계획법을 이용하여 충진율이 높은 크기 조합 및 혼합 비율을 선정하였으며, 진동 실험장치에서 가진 주파수 변경에 따른 충진 높이 변화를 분석하여 적정 가진 주파수를 선정하였다. 마지막으로 앞서 언급한 실험 결과값을 토대로 알루미나 파우더 충진율 시험을 수행하였다. 그 결과, 최대 높이 변화량은 충진 크기조합 선정을 위해 수행한 최초의 실험 결과 최댓값보다 42% 향상된 것을 확인하였다.

• Geomechanics and Engineering
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• 제9권6호
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• pp.815-827
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• 2015

The mechanical behavior of soil and soil-rock mixture is investigated via the discrete element method. A non-overlapping combination method of spheres is used to model convex polyhedron rock blocks of soil-rock mixture in the DEM simulations. The meso-mechanical parameters of soil and soil-rock interface in DEM simulations are obtained from the in-situ tests. Based on the Voronoi cell, a method representing volumtric strain of the sample at the particle scale is proposed. The numerical results indicate that the particle rotation, occlusion, dilatation and self-organizing force chains are a remarkable phenomena of the localization band for the soil and soil-rock mixture samples. The localization band in a soil-rock mixture is wider than that in the soil sample. The current research shows that the 3D discrete element method can effectively simulate the mechanical behavior of soil and soil-rock mixture.