The diesel engine is excellent in economic and thermal efficiency, and is widely used as a power source for industries and automobiles. However, the problem of environmental pollution caused by exhaust gas has recently become serious and the development of alternative energy resources is urgently required due to depletion of fossil fuel. Because biodiesel is similar in properties to light oil, it is being used as fuel for diesel engines by replacing or mixing conventional light oil. As the blending of biodiesel fuel in diesel increases, the emission of harmful substances is decreased as compared with the general diesel fuel, and the supply is increasing. In this study, the effects of biodiesel fuel on engine power and exhaust gas were investigated, and empirical formulas for various NOx and Smoke exhaust gases were derived based on biodiesel blending fuel.

녹말의 열 유도 호화의 경우, 과립의 팽창은 비가역적으로 되고 입상 구조는 현저하게 변화된다. 초고압(high hydrostatic pressure, HHP)는 열처리 녹말의 약점인 외부 구조의 붕괴를 보완 할 수 있다. HHP 처리 녹말은 과립 구조를 유지하고 열처리 녹말보다 아밀로오스 방출량이 적다. 전분-물 혼합물의 압력 유도 호화는 녹말, 녹말 함량, 처리 압력, 온도 및 시간 등에 따라 현저하게 달라진다. 따라서 HHP 처리된 녹말의 적용을 증가시키기 위해서는 HHP처리로 호화되는 녹말의 호화 동력학을 이해하는 것이 매우 중요하다. 본 연구의 목적은 초고압 하에서 다양한 전분-물 혼합물의 호화 특성 동역학을 밝히는 것이다. 세 종류의 전분(Corn, Tapioca, Wheat)의 수분함량조건 (50 %, 70 % MC)을 달리하여 25℃의 HHP(350 ~ 550 MPa)하에서 0 ~ 60 분간 처리하고 이들의 호화특성을 분석하였다. 호화 온도 변화 (onset, ; peak, ; and end, ), 호화 엔탈피(ΔHgel) 및 호화도(GD)를 시차 주사 열량계(DSC)를 사용하여 측정하였다. 또한, 형태 학적 변화 및 복굴절 손실은 각각 광학 현미경과 편광 현미경을 사용하여 조사하였다. 대부분의 조건에서 일정한 시간에서 호화도는 압력이 증가함에 따라 증가하였고, 수분함량이 증가함에 따라 호화도가 증가하였다. 옥수수 전분의 경우 수분 함량 70%의 조건에서 550 MPa로 5분의 처리시간에서 완전한 호화가 이루어졌다. 550 MPa를 제외하고 일정한 압력에서 호화도는 처리시간이 증가함에 따라 증가하였다. 이로 보아 550 MPa의 처리는 옥수수 전분(70 % MC)의 완전한 호화에 충분한 압력으로 확인되었다. 는 부분 호화로 인해 고온으로 이동하였으나 와 는 크게 변하지 않았다. 타피오카의 경우 위의 결과들과 대부분 비슷한 경향성을 나타냈지만 옥수수 보다 압력에 처리에 더 내성이 있는 것으로 보여졌다. 반면 밀의 경우에는 오히려 옥수수와 타피오카에 비해 낮은 압력에서도 호화도가 높게 나타나 다른 녹말보다 압력에 더 민감한것으로 분석 되었다. 한편, 복굴절의 손실은 DSC 열 특성과 완전히 일치하지 않아 두 물리적 특성 사이에 지연이 있음을 나타낸다. 이 결과는 여러 종류의 전분 - 물 시스템의 압력 유도 젤라틴 화 메커니즘에 관한 기본적이고 기본적인 정보를 제공한다. 또한, 이 연구는 깨끗한 전분에 대한 새로운 물리적 변형 방법을 개발하는데 기여할 것이다.

In this paper, the combustion characteristics of constant volume combustion chamber(CVCC) were experimentally investigated when biodiesel is mixed with pure gasoline. The experiment was performed on two gasoline biodiesel samples designated by GB05 and GB20 which is mixed with 5% and 20% biodiesel respectively. It was confirmed that the ignition delay time decreases as the temperature of injection engine increases due to ignition delay. Also, it was shown that the ignition delay time decreases as the biodisel mixing ratio increases from 5% to 20%.

본 연구에서는 (주)파인텍에서 제조한 제올라이트 4A 분리막을 이용하여 물/메탄올, 물/부탄올 혼합물의 투과증발 실험을 수행하였다. 분리막을 투과한 기체분자들은 액체질소트랩을 이용하여 포집하였으며, 기체크로마토그래피(TCD)를 이 용하여 혼합물의 조성을 분석하였다. 실험을 통해 물과 메탄올(분리계수 최대 250 이상), 물과 부탄올(분리계수 최대 1,500 이상)의 혼합물에서 선택적으로 물을 분리하는 것을 확인하였다. GMS (generalized Maxwell Stefan) 이론을 적용하여 2성분 계의 투과증발 거동을 모사하였으며, 상수추정을 통하여 제올라이트 비지지체의 흡착상수 및 확산상수를 구하였다. 제올라이 트 4A 분리막의 경우 기공의 크기가 물보다는 크고, 메탄올, 부탄올 보다는 작기 때문에, 알코올로부터 물을 분리시키는 공정 에 적용시킬 수 있다. 바이오 에탄올 분리, 부탄올 분리, 막반응기, 하이브리드 반응-탈수 공정 등에 적용할 수 있을 것으로 사료된다.

The autoignition characteristics of n-heptane/n-butanol were investigated both experimentally and numerically. The effects of oxygen concentration and exhaust gas recirculation rate on the autoignition characteristics were evaluated. A rapid compression machine was employed to measure ignition delay times of blended fuels. A numerical study on the ignition delay time was performed using the CHEMKIN-PRO software to calculate ignition delay time and predict the chemical species in the combustion process. The results revealed that the ignition delay time increased with decreasing oxygen concentration due to the thermal load effect of nitrogen. The oxidation reaction of n-heptane in a low temperature regime was limited with decreasing oxygen concentration. The ignition delay time sharply decreased with exhaust gas recirculation because of the intermediate species in the exhaust gas. Exhaust gas recirculation reduced first ignition delay dramatically. However, the time interval between the first and main ignition increased with increased exhaust gas recirculation.

전분 페이스트나 겔의 초기 노화현상은 전분 내의 아밀로오스 분자들 사이의 신속한 회합의 결과이며, 전분성 가공식품들의 품질저하의 주요 원인들 중 하나이다. 본 연구는 멥쌀전분의 물리적, 열적, 및 유변학적 특성에 대한 음이온성 검의 첨가와 멥쌀전분-음이온성 검 혼합물에 대한 건열처리의 효과의 조사를 통해 노화를 지연(또는 억제)할 수 있는 멥쌀전분 소재를 개발하고자 하였다. 습식제분된 멥쌀가루로부터 알칼리침지법을 통해 제조된 멥쌀전분을 사용하였으며, 음이온성 검은 carboxymethylcellulose (CC), λ-carrageenan (LC), low-methoxy pectin (LP), sodium alginate (SA)와 xanthan gum (XT)를 사용하였다. 1%(w/w)의 음이온성 검 용액(pH 5.5)을 제조하여 멥쌀전분과 혼합한 후 50°C의 온도로 건조하여 멥쌀전분-음이온성 검 혼합물(수분함량 10% 미만)을 제조하였다(건열처리대조군). 또한 멥쌀전분은 음이온성 검류의 첨가없이 동일하게 처리하여 건열처리대조군에 대한 원료대조군으로 하였다. 제조된 원료대조군과 건열처리대조군은 130°C의 컨벡션오븐에서 4시간 동안 건열처리하여 각각 원료건열처리군과 건열처리군(건열처리 멥쌀전분-음이온성 검 반응물)을 제조하였다. 제조된 대조군과 처리군들은 용해도, 팽윤력, 호화/노화 특성, 페이스팅 점도 특성, 페이스트의 점탄특성을 측정하였다. 용해도는 LP 건열처리군이 24.8%로 가장 높았고, 원료대조군과 건열처리 대조군에 대한 건열처리의 효과는 원료, LC 및 LP 건열처리군들은 이들 각각의 대조군에 비해 높았으며, SA 및 XT 건열처리군들은 낮았다. 팽윤력은 LP 건열처리군을 제외한 모든 건열처리군들이 이들 각각의 대조군들 보다 유의적으로 낮았다. 호화온도는 모든 건열처리군들이 이들 각각의 대조군보다 유의적으로 낮은 수준을 나타내었고, 호화엔탈피는 원료대조군이 12.8 J/g으로 건열처리대조군, 원료건열처리군, 건열처리군보다 높은 수준을 나타내었다. 페이스팅 점도 특성에 있어 원료대조군과 원료건열처리군보다 낮은 치반점도(setback viscosity)는 LM 및 XT 건열처리대조군과 건열처리군에서 관찰되었다. 대조군들과 건열처리군들을 페이스트로 제조한 후 상온에서 1시간 동안 방냉하여 형성된 페이스트들의 점탄특성을 측정하였을 때, XT 건열처리군을 제외한 건열처리군들은 이들의 대조군들에 비해 유의적으로 감소하였다. 게다가 LM 및 XT 건열처리군들은 이들의 건열처리대조군에 비해 각각 높은 정도로 감소하거나 증가하는 현상을 나타내었다. 또한 80도의 페이스트를 25도에서 시간에 따라 점탄특성을 변화를 측정하였을 때, 2시간 후 점탄특성의 증가는 건열처리대조군에 비해 LM 건열처리군이 가장 낮은 수준을 나타내었다. /g8 s 따라서 LM 건열처리군은 은 용해도가 이의 건열처리대조군에 비해 높은 수준이지만 이들의 치반점도 및 점탄특성들을 비교할 때, LM은 멥쌀전분과 단순혼합하거나 LM-멥쌀전분 혼합물의 건열처리를 통해 멥쌀전분 페이스트의 노화를 지연시키는 효과가 큰 것으로 판단된다.

In the present study, single-phase heat transfer characteristics for downstream flow in the support grid of 6×6 rod bundle were investigated. It has been known that a turbulence generation due to a support grid with split mixing vanes enhances heat transfer in rod bundle but its heat transfer enhancement actually affects to relatively shorter distance. On the other hand, it has been also turned out that a support grid with large scale vortex flow (LSVF) mixing vanes results in heat transfer enhancement to a longer distance. Based on the results of literatre survey, single-phase water heat transfer experiments were performed for Reynolds numbers at around 30,000, and the heat transfer enhancement effect with both i) the split mixing vanes and ii) the LSVF mixing vanes was compared in this study. The key results showed that the effect of heat transfer enhancement in rod bundle region by the split mixing vanes was maintained up to the length of 15Dh behind the spacer grid. For the Reynolds numbers at around 30,000, it was also observed that the effect using the LSVF mixing vanes was stronger at about 3% when compared to the case using the split mixing vanes only for the distance ranging from 1 to 15Dh behind the spacer grid.

A Nanosized WO3 and CuO powder mixture is prepared using novel high-energy ball milling in a bead mill to obtain a W-Cu nanocomposite powder, and the effect of milling time on the structural characteristics of WO3-CuO powder mixtures is investigated. The results show that the ball-milled WO3-CuO powder mixture reaches at steady state after 10 h milling, characterized by the uniform and narrow particle size distribution with primary crystalline sizes below 50 nm, a specific surface area of 37 m2/g, and powder mean particle size (D50) of 0.57 μm. The WO3-CuO powder mixtures milled for 10 h are heat-treated at different temperatures in H2 atmosphere to produce W-Cu powder. The XRD results shows that both the WO3 and CuO phases can be reduced to W and Cu phases at temperatures over 700oC. The reduced W-Cu nanocomposite powder exhibits excellent sinterability, and the ultrafine W-Cu composite can be obtained by the Cu liquid phase sintering process.

The effect of the mixing method on the characteristics of hybrid-structure W powder with nano and micro sizes is investigated. Fine WO3 powders with sizes of ~0.6 μm, prepared by ball milling for 10 h, are mixed with pure W powder with sizes of 12 μm by various mixing process. In the case of simple mixing with ball-milled WO3 and micro sized W powders, WO3 particles are locally present in the form of agglomerates in the surface of large W powders, but in the case of ball milling, a relatively uniform distribution of WO3 particles is exhibited. The microstructural observation reveals that the ball milled WO3 powder, heat-treated at 750oC for 1 h in a hydrogen atmosphere, is fine W particles of ~200 nm or less. The powder mixture prepared by simple mixing and hydrogen reduction exhibits the formation of coarse W particles with agglomeration of the micro sized W powder on the surface. Conversely, in the powder mixture fabricated by ball milling and hydrogen reduction, a uniform distribution of fine W particles forming nano-micro sized hybrid structure is observed.

Surface morphology and optical properties such as transmittance and haze effect of glass etched by physical and chemical etching processes were investigated. The physical etching process was carried out by pen type sandblasting process with 15~20 μm dia. of Al2O3 media; the chemical etching process was conducted using HF-based mixed etchant. Sandblasting was performed in terms of variables such as the distance of 8 cm between the gun nozzle and the glass substrate, the fixed air pressure of 0.5bar, and the constant speed control of the specimen stage. The chemical etching process was conducted with mixed etching solution prepared by combination of BHF (Buffered Hydrofluoric Acid), HCl, and distilled water. The morphology of the glass surface after sandblasting process displayed sharp collision vestiges with nonuniform shapes that could initiate fractures. The haze values of the sandblasted glass were quantitatively acceptable. However, based on visual observation, the desirable Anti-Glare effect was not achieved. On the other hand, irregularly shaped and sharp vestiges transformed into enlarged and smooth micro-spherical craters with the subsequent chemical etching process. The curvature of the spherical crater increased distinctly by 60 minutes and decreased gradually with increasing etching time. Further, the spherical craters with reduced curvature were uniformly distributed over the etched glass surface. The haze value increased sharply up to 55 % and the transmittance decreased by 90 % at 60 minutes of etching time. The ideal haze value range of 3~7 % and transmittance value range of above 90 % were achieved in the period of 240 to 720 minutes of etching time for the selected concentration of the chemical etchant.

Purple-fleshed potato powder (PFPP) was investigated to determine optimal mixing ratio with milk powder and dextrin to produce a ready-to-eat mashed potato powder. The rheological characteristics, color, and anthocyanin contents were studied at a different concentration of ingredients. The power-law model was applied to explain the mechanical spectra of mashed potatoes which represented the change in structure induced by different mixing ratios. Mixture design was used to obtain the experimental points used to establish the empirical models to describe the effects of each ingredient on the characteristic of the mashed potato. The results of mechanical spectra showed that both storage and loss moduli (G' and G'') were significantly influenced by PFPP and milk powder concentration. The power law parameters n' and n'' showed higher values for the mashed potato with a lower concentration of PFPP and a higher concentration of milk powder, which showed that the gel networks involved in the mashed potato were weaker. The optimum mixing ratio with the highest redness and anthocyanin content, while maintaining the rheological properties similar to the commercial mashed potato, was determined as PFPP:milk powder:dextrin = 90.49:4.86:4.65 (w/w). The proportions of PFPP and milk powder in the formulation significantly changed the characteristics of mashed potato, whereas no significant effect of dextrin was observed in this formulation.

Purple-fleshed potato powder (PFPP) was investigated to determine optimal mixing ratio with milk powder and dextrin to produce a ready-to-eat mashed potato powder. The rheological characteristics, color, and anthocyanin contents were studied at a different concentration of ingredients. The power-law model was applied to explain the mechanical spectra of mashed potatoes which represented the change in structure induced by different mixing ratios. Mixture design was used to obtain the experimental points used to establish the empirical models to describe the effects of each ingredient on the characteristic of the mashed potato. The results of mechanical spectra showed that both storage and loss moduli (G' and G'') were significantly influenced by PFPP and milk powder concentration. The power law parameters n' and n'' showed higher values for the mashed potato with a lower concentration of PFPP and a higher concentration of milk powder, which showed that the gel networks involved in the mashed potato were weaker. The optimum mixing ratio with the highest redness and anthocyanin content, while maintaining the rheological properties similar to the commercial mashed potato, was determined as PFPP:milk powder:dextrin = 90.49:4.86:4.65 (w/w). The proportions of PFPP and milk powder in the formulation significantly changed the characteristics of mashed potato, whereas no significant effect of dextrin was observed in this formulation.