For a die casting mold, generally, the casting layout design should be considered based on the relation among injection system, casting condition, gate system, and cooling system. Also, the extent or the location of product defects was differentiated according to the various relations of the above conditions. In this research, in order to optimize the casting layout design of an automotive Oil Pan_DX2E, Computer Aided Engineering (CAE) simulation was performed with two layout designs by using the simulation software (AnyCasting). The simulation results were analyzed and compared carefully in order to apply them into the production die-casting mold. During the filling process with two models, internal porosities caused by air entrapments were predicted and also compared with the modification of the gate system and overflow. With the solidification analysis, internal porosities occurring during the solidification process were predicted and also compared with the modified gate system.

When manufacturing die casting mold, generally, the casting layout design should be considered based on the relation among injection system, casting condition, gate system, and cooling system. Also, the extent or the location of product defects was differentiated according to the various relations of the above conditions. In this research, in order to optimizing casting layout design of an automobile part (Oil Pan_DX2E) Computer Aided Engineering (CAE) simulation was performed with two layout designs by using the simulation software (AnyCasting). The simulation results were analyzed and compared carefully in order to apply them into the production die-casting mold. During the mold filling with two models, internal porosities caused by air entrap were predicted and also compared by the modification of the gate system and the configuration of overflow. With the solidification analysis, internal porosities caused by the solidification shrinkage were predicted and also compared by the modification of the gate system.

Poly(vinyl alcohol) (PVA)에 대하여 가교제로써 glutaraldehyde (GA), maleic anhydride (MA)를 이용하여 제조한 코팅용액을 알칼리로 가수분해 시킨 poly acrylonitrile (PAN) 중공사 막표면에 코팅하여 막을 제조하였다. 제조된 막의 투과 특성평가를 위해서 물/에탄올 혼합액에 대한 투과증발 실험을 수행하였다. 60°C의 90 wt%의 물/에탄올 혼합액에 대하여 반응온도 및 가교제의 농도변화에 따른 투과도 및 선택도를 측정하였다. 일반적으로 반응온도, 가교제 농도가 증가할 경우 투과 도는 낮아지고, 선택도는 증가하는 경향을 보여주었다. 가교제로 GA의 대표적 결과는 반응온도 120°C, GA 11 wt%로 투과 도는 165 g/m 2 hr 선택도는 81이고, MA는 반응온도 120°C, MA 11 wt%로 투과도는 174 g/m 2 hr 선택도는 73의 결과를 얻을 수 있었다.

When manufacturing die casting mold, generally, the casting layout design should be considered based on the relation among injection system, casting condition, gate system, and cooling system. Also, the extent or the location of product defects was differentiated according to the various relations of the above conditions. In this research, in order to optimizing casting layout design of an automobile part (Oil Pan_DX2E) Computer Aided Engineering (CAE) simulation was performed with two layout designs by using the simulation software (AnyCasting). The simulation results were analyzed and compared carefully in order to apply them into the production die-casting mold. During the mold filling with two models, internal porosities caused by air entrap were predicted and also compared by the modification of the gate system and the configuration of overflow. With the solidification analysis, internal porosities caused by the solidification shrinkage were predicted and also compared by the modification of the gate system.

지지체인 Polyacrylonitrile (PAN) 중공사에 Poly (vinyl alcohol) (PVA)과 가교제인 Glutaraldehyde (GA)를 코팅하 여 막을 제조하였으며, 특성평가를 위해 물/Isopropyl alcohol (IPA) 혼합액에 대한 투과증발 실험을 수행하였다. 코팅용액의 조성변화와 반응온도의 조건변화에 따른 투과도 및 선택도를 측정하였고, 공급액의 조성은 85 wt% IPA 수용액을 사용하였으며, 온도는 30, 50, 70, 90℃로 변화시켰다. 투과도는 PVA 3.5 wt%, 공급액 온도가 90℃일 때 1,870 g/m 2 ⋅hr, 선택도는 PVA 7 wt% 공급액 온도가 30℃일 때 804로 가장 높은 값을 얻을 수 있었다.

Polyacrylonitrile (PAN) 기질고분자를 용매인 dimethylformamide (DMF)에 녹인 후 전기방사법을 이용하여 polyacrylonitrile nanofibers membrane (PAM)을 제조하였으며, 정밀여과(microfiltration) 적용을 위해, 제조된 PAM 샘플들의 layer 수를 변화시켜, 기공크기를 조절하였다. 또한, 순수투과도(water-flux) 향상을 위해 poly (ethylene glycol) methyl ether methacrylate와 azobisisobutylronitrile (AIBN)을 이용하여 자유 라디칼 중합(free radical polymerization)을 통해 합성된 AN‐ PEGMA 공중합체를 PAN과 3:1의 비율로 혼합한 후 위와 같은 방법으로 다공성 막(PAM/APM)을 제조하였으며, FT-IR과 E.D.S 분석을 통해 PAM 샘플과 비교⋅분석하였다. Scanning Electron Microscope (SEM) 분석과 기공크기, 기공도 실험을 통해 균일한 직경(400∼600 nm)과 균일한 기공특성(0.5∼0.4 μm)을 가진 다공성 막이 제조되었음을 확인할 수 있었다. 순수 투과도 측정을 통해 정밀여과용 막으로의 활용가능성을 조사하였으며, AN‐PEGMA 공중합체가 도입된 PAM/APM의 경우 상 용막인 polyvinylidenefluoride (PVdF)에 비해 순수투과도가 상대적으로 높은 값을 나타내었다. 위의 결과로부터 전기방사법으로 제조된 PAN 나노섬유막들은 정밀여과용 막으로서 충분한 활용가능성이 있다고 판단된다.

In this present work, the effect of additional heat-treatment (AHT) in the range from 1800℃ to 2400℃ on the chemical composition, morphology, microstructure, tensile properties, electrical resistivity, and thermal stability of commercial polyacrylonitrile (PAN)-based carbon fibers was explored by means of elemental analysis, electron microscopy, X-ray diffraction analysis, single fiber tensile testing, two-probe electrical resistivity testing, and thermogravimetric analysis (TGA). The characterization results were in agreement with each other. The results clearly demonstrated that AHTs up to 2400℃ played a significant role in further contributing not only to the enhancement of carbon content, fiber morphology, and tensile modulus, but also to the reduction of fiber diameter, inter-graphene layer distance, and electrical resistivity of "as-received" carbon fibers without AHT. The present study suggests that key properties of commercial PAN-based carbon fibers of an intermediate grade can be further improved by proprietarily adding heat-treatment without applying tension in a batch process.

밤가루를 밀가루에 0%, 10%, 20%, 30% 대체한 복합분에 대하여 반죽의 물리적 특성 및 제빵 특성을 검토하고 밤가루 첨가가 빵의 기호도에 미치는 영향에 대해 조사하였다. 반죽의 물리적 특성 중 farinogram 측정 결과 밤가루의 첨가량이 증가함에 따라 반죽시간은 짧아졌으나 반죽의 안정도와 내구성이 약화되었다. Amylogram에서 호화온도는 대조군에 비해 다소 증가하는 경향을 보인반면 최고점도는 감소하였다. 반죽팽창도 측정결과 밤가루가 20%이상 첨가된 반죽은 변화가 없었으며, 제빵 후 빵의 부피가 작고 비용적도 낮았다. 밤가루 첨가에 따른 식빵의 품질평가결과 밤가루를 10% 첨가하여 제조한 식빵이 20%, 30% 첨가한 식빵에 비해 경도가 낮았으며, 내상 또한 비교적 작고 균일하였다. 밤가루 첨가시 10%이내가 좋을 것으로 사료된다.

The objective of this study was to produce muffins with added dukeum ramie leaf powder and to compare them to a control. We used two different optimal composition ratios to produce muffins. The physical and sensory characters were varied by changing the ratio of dukeum ramie leaf powder, butter, and sugar to identify a critical value using response surface regression analysis. The ranges for the added dukeum ramie leaf powder, sugar, and butter were 15-35, 60-100, and 60-100 g, respectively. Muffins with added dukeum ramie leaves had comparable mineral and antioxidant vitamin compositions to those of dried ramie leaves. Muffins with added dukeum ramie leaf powder satisfied the suitability of the model, showing a p-value within 5% of significance level (p<0.05) for every aspect Volume and height differed without any association to ingredients. Lightness increased when less dukeum ramie leaf powder was added with more butter and sugar, redness increased when more dukeum ramie leaf powder and sugar were added with 70-80 g of butter, whereas yellowness increased when less dukeum ramie powder was added. Texture and toughness increased when less dukeum ramie leaf powder was added. The degree of gumminess and chewiness depended hugely on the amount of sugar. Cohesiveness, decreased with more dukeum ramie leaf powder and butter, whereas hardness increased with a medium range of ingredients. Sensory character increased with less dukeum ramie powder, and overall quality increased with more butter and sugar, but depended on the amount of added dukeum ramie power. The critical values from the sensory characteristics showed that 27 g of dukeum ramie powder, 72 g of sugar, and 86 g of butter was optimum.

PAN precursor fibers were produced via wet-spinning process, and effects of polymerization and spinning processes, especially the stretching process, were investigated on mechanical properties and micro-morphologies of precursor fibers. An increase in molecular weight, dope solid and densification and a decrease in surface defects were possible by controlling polymerization temperature, the number of heating rollers for densification and the jet stretch ratio, which improved the mechanical properties of precursor fibers. The curves for strength, modulus, tensile power and diameter as a function of stretch ratio can be divided into three stages: steady change area, little change area and sudden change area. With the increase of stretch ratio, the fiber diameter became smaller, the degree of crystallization increased and the structure of precursor fibers became compact and homogeneous, which resulted in the increase of strength, modulus and tensile power of precursor fibers. Empirical relationship between fiber strength and stretch ratio was studied by using the sub-cluster statistical theory. It was successfully predicted when the strengths were 0.8 GPa and 1.0 GPa under a certain technical condition, the corresponding stretch ratio of the fiber were 11.16 and 12.83 respectively.

The precipitation polymerization of acrylonitrile (AN) was carried out in a mixture solution of dimethyl sulfoxide (DMSO) and water at 50~65℃ using α,α'-azobisisobutyronitrile (AIBN) as an initiator. The increased molecular weight polyacrylonitrile (PAN) was prepared with increasing the H2O/DMSO ratio from 10/90 to 80/20. The viscosity average molecular weight of H2O/DMSO solvent was 4.4 times larger than that of H2O/DMF solvent, and precipitation polymerization was accelerlated due to the far decreased chain transfer effect of DMSO. Based on the experimental results, the increased PAN molecular weight was regarded as the summation of two mechanisms: i) particle-particle aggregation and ii) particle-radical attachment. The theoretical equation derived from the mechanisms was well coincided with the experimental results showing the linear relationship between the viscosity average molecular weight and the H2O/DMSO ratio.

In this study, porous electrospun carbon fibers were prepared by electrospinning with PAN and MgCl2, as a MgO precursor. MgO was selected as a substrate because of its chemical and thermal stability, no reaction with carbon, and ease of removal after carbonization by dissolving out in acidic solutions. MgCl2 was mixed with polyacrylonitrile (PAN) solution as a precursor of MgO with various weight ratios of MgCl2/PAN. The average diameter of porous electrospun carbon fibers increased from 1.3 to 3 μm, as the MgCl2 to PAN weight ratio increased. During the stabilization step, MgCl2 was hydrolyzed to MgOHCl by heat treatment. At elevated temperature of 823 K for carbonization step, MgOHCl was decomposed to MgO. Specific surface area and pore structure of prepared electrospun carbon fibers were decided by weight ratio of MgCl2/PAN. The amount of hydrogen storage increased with increase of specific surface area and micropore volume of prepared electrospun carbon fibers.

In order to improve the thermal stability of PAN-based electrospun fibers, AP-PER-MEL and TiO2 were added in to the fibers as additives. The polymer composite with uniformly mixed additional agents was obtained. In case of non-treated sample, the fibers were burn off completely with high rate within 620℃. But in case of treated samples (EF-M and EF-MT), it is sure that the thermal stability was improved by studying TGA data and ISO flammability test about 20 and 30%, respectively. A synergy effect of adding two kinds of agents (AP-PER-MEL and TiO2) into PAN-based electrospun fibers was confirmed. Through SEM images, it is confirmed that the fiber shape can be kept even after addition of agents (AP-PER-MEL and TiO2). Finally the thermal stability of fibers was largely developed with keeping the nature of PAN-based fibers effectively.

본 실험은 표준화된 피복종자를 생산하기 위하여 피복통의 회전속도를 20, 30, 40, 45, 55, 60 rpm으로 하여 소형 피복통으로 레드클로버와 톨페스큐 종자를 피복하였다. 고형물질로는 vermiculite를 사용하였고 접착제는 polyvinyl alcohol을 사용하였다. 피복 후 통에서 회수된 단립 피복종자 무게, 서로 달라붙어 덩어리진 피복종자 무게, 피복되지 않고 회수된 미 피복물질 무게, 충격에 의한 피복층 탈락성 및 피복종자의 백립중

In the present study, electrospun PAN precursor webs and the stabilized and carbonized nanofiber webs processed under different heat-treatment conditions were characterized by means of weight loss measurement, elemental analysis, scanning electron microscopy (SEM), attenuated total reflection-Fourier transform infrared spectroscopy (ATR-FTIR), differential scanning calorimetry (DSC), thermogravimentric analysis (TGA), and X-ray diffraction (XRD) analysis. The result indicated that stabilization and carbonization processes with different temperatures and heating rates significantly influenced the chemical and morphological characteristics as well as the thermal properties of the stabilized and then subsequently carbonized nanofiber webs from PAN precursor webs. It was noted that the filament diameter and the carbon content of a carbonized nanofiber web as well as its weight change may be effectively monitored by controlling both stabilization and carbonization processes.