• Cement Symposium
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• no.29
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• pp.123-130
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• 2002

• Applied Chemistry for Engineering
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• v.25 no.1
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• pp.90-95
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• 2014

Nylon66 extrudates as a function of the extrusion number were prepared by a twin screw extruder. Chemical structures, thermal properties, melt index, crystal structures, mechanical properties such as the tensile strength, elongation at break and impact strength, and rheological property were measured by FT-IR, $^1H$-NMR, melt indexer, DSC, TGA, XRD, universal tensile tester, Izod impact tester, and rheometer. FT-IR and $^1H$-NMR characterizations indicated that the number of extrusions did not affect the chemical structure. The decrease in the molecular weight was checked by the melt index of extrudates. There were no effects of the thermal history on the melting and degradation temperature. The tensile and impact strength and modulus were found to be similar, regardless of the number of extrusions, but the elongation decreased significantly. The complex viscosity of extrudates at low frequencies decreased with the extrusion number. No structural changes after extrusion were confirmed from the fact that there was no change in the slope and shape of G'-G" plot.

• Journal of the Korean Recycled Construction Resources Institute
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• v.6 no.1
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• pp.88-94
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• 2011

To make recycling aggregate, quantity of fine particles increase due to multi-crushing. Though this particles were mixed with recycling aggregate, those have to be disparted from aggregate in the high quality recycling aggregate, because of the cause of low quality. Considering reactivity, fine particles is better than coarse one. Therefore, it needs to develop suitable usage. We try to make cement extruding material by using the fine particles from concrete recycling, as a silicious replacement. Test results are as follows ; 1) Waste concrete powder has major ingredients such as $SiO_2$ and CaO, its density is $2.45g/cm^3$ being similar to silica powder, its diameter is range 13 to $141{\mu}m$. 2) Considering to strength properties according to particle size, specimen was made using small particles is higher strength than large one. 3) Despite of exception in the autoclaved curing, when the replacement of waste fine particle increase, strength of extruding panel shows almost same level.

• Clean Technology
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• v.19 no.2
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• pp.121-127
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• 2013

The objective of this study is optimization of extrusion process for preparation of pellet-type adsorbents employed with alum sludge. Effects of water content and methyl cellulose as a binder on the possibility of extrusion and physical properties of pellet-type adsorbents were investigated. The physical characteristics of the pellet-type adsorbents were studied using nitrogen adsorption and compression strength. With a ratio of water to sludge, 63/100, the adsorbent was well extruded with a cylindrical form and the compressive strength was the highest. With increasing methyl cellulose content, the compressive strength of pellet-type adsorbent could be improved, but the specific surface area decreased. The breakthrough time of the hydrogen sulfide could be increased significantly through calcination and the breakthrough capacity reached to 1,700 mg/g, which seems to be due to increase of surface area during calcination.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.10a
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• pp.190-190
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• 2003

동력 전달용 구동부품에 있어서 중공 플랜지 형상의 부품은 흔히 찾아 볼 수 있으며, 이는 높은 강도를 요구하기 때문에 강도향상을 위하여 단조에 의한 제품의 성형 방법이 많이 연구되고 있다. 중공 플랜지형상을 갖는 제품의 제조 방법으로서는 중실 플랜지 형상으로 단조하여 내경부를 절삭가공하는 방법, 중실 소재를 후방압출하여 중공 플랜지형상으로 단조하는 방법, 또는 중공의 초기소재를 사용하여 중공 플랜지형상으로 단조하는 방법이 일반적이다. 본 연구에서는 Fig. 1에 나타낸 것과 같이 중공 플랜지 형상을 갖는 기계 부품의 단조방법에 대해 연구하였으며, 중공 관의 내경을 $d^1$, 외경을 $d^2$, 플랜지부의 외경을 $D^0$, 중공 관의 두께를 t, 플랜지부의 두께를 T로 정의하였다. 중공 플랜지 형상에 있어서 공정 설계의 변수는 다양하겠으나, 본 연구에서는 중공관의 외경과 내경의 형상비 $\alpha$(=$d^2$/$d^1$), 플랜지의 폭과 중공관의 두께비 $\beta$(=B/t) 및 중공관의 두께와 플랜지의 두께비 r(=T/t)의 변화에 따른 성형조건에 관해 고찰하였다. 중공 플랜지 형상의 성형방법으로 Fig. 2에 나타낸 것과 같은 $\circled1$중실소재를 이용한 후방압출단조(backward extrusion forging)방법, $\circled2$중공 소재를 이용한 엎셋(upset forging)방법, $\circled3$중공 소재를 이용한 압조법(injection forging), $\circled4$중실소재를 이용한 압조-압출(injection-extruding forging)법의 4가지의 단조 방법을 제시 하였다. 또한, 유한요소해석을 수행하여 소성유동 형태, 유효변형률, 단조하중을 검토하고. 모델재료인 납을 이용한 실험을 통하여 이를 검증하였다. 이를 바탕으로 산업 현장에서 경험에 의존하였던 공정 설계를 보다 효과적으로 개선하기 위한 단조법을 제시하고자 하였다. 또한 중실 소재를 이용한 중공 플랜지 형상의 단조 방법 중 보다 적절한 단조방법인 압조 단조에 있어서 일반적으로 사용되고 있는 SM10C에 대한 유한요소 해석을 수행하였으며, 제품의 형상비에 따라 폴딩 결함의 발생 유무를 검토하고, 폴딩 결함 없이 단조하기 위한 중공 플랜지의 형상한계 비를 제시하였다.

• Journal of Korean Tunnelling and Underground Space Association
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• v.18 no.6
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• pp.557-568
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• 2016

Squeezing is a phenomenon that may occur in deep tunneling and could bring about a large plastic deformation, tunnel closure and collapse of tunnel supports. Therefore, quantitative estimations of deformation and stress from squeezing and its possibility are necessary for establishment of a rational tunneling method. This study carried out three dimensional numerical analyses using a strain softening model in order to simulate the behaviour of squeezing and to estimate deformation and yield area around tunnels quantitatively. Numerical analyses were performed for 42 cases of various stress and strength conditions. As a result, the maximum tangential stress and strength of rock mass ratio could estimate plastic deformation and yield depth around tunnels and equations of relations between them were proposed.

• Korean Chemical Engineering Research
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• v.50 no.6
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• pp.1068-1075
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• 2012

Poly(butylene terephthalate) (PBT)/Nylon6,12 core/shell micro fiber were prepared by extrusion molding. To investigate their optimum extrusion conditions, compatibility of PBT/Nylon6,12 blend micro fiber in conformity to their weight ratio and manufacture temperature was explored with SEM morphology and DSC. The alterations in their mechanical properties by extrusion speed were compared and analyzed through a UTM. In comparison with SEM figures, the domain sizes of Nylon6,12 were gradually declined by increasing the extrusion temperature of blends. Furthermore, according to these SEM images, the phase separation between Nylon6,12 domain and PBT matrix became indistinct with increasing of weight percentage of Nylon6,12. In case of DSC, the boundaries of two peaks were almost disappeared when increasing the extrusion temperature and also intervals of each two melting peaks became narrow as increasing the Nylon6,12 ratio. The mechanical properties including tensile strength, elongation, flexural strength and flexural modulus were increased as the increase in the extrusion temperature until $260^{\circ}C$. However, the mechanical properties were actually deteriorated over $260^{\circ}C$. The tensile strength, elongation, flexural strength and flexural modulus at $260^{\circ}C$ were 560 $kg_f/cm^2$, 220%, 807 $kg_f/cm^2$ and 22,146 $kg_f/cm^2$, respectively. These values are more than intermediate values of mechanical properties of PBT and Nylon6,12. These results mean that there is compatibility between PBT and Nylon6,12. Based on the extrusion conditions that produced optimum compatibility of blend, as a result, our group obtained micro fibers with the core/shell structure.

• Elastomers and Composites
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• v.39 no.2
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• pp.131-141
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• 2004

The recycling of waste XLPE(crosslinked polyethylene), which is a major source of scraps from high voltage power transmission cables, has been discussed. The waste XLPE scraps were ground into fine powder with various sizes from less than $100{\mu}m$ up to about $1000{\mu}m$ using two types of tailor-made pulverizers. The compounds were prepared in a modular intermeshing co-rotating twin screw extruder at various conditions such as different compositions, types and powder sizes of waste XLPE, screw configurations and various polymer matrices (LDPE, HDPE, PP, PS). The mechanical and rheological properties and the fracture surface or the compounds were investigated. It was found that an improved impact strength was obtained from the compound with white XLPE powder pulverized from the scraps without outer/inner semi-conductive layers. Generally, the impact strength increases with the content of XLPE but decreases with the size of XLPE. Especially for LDPE, the extrusion was possible up to 80 wt% loading of XLPE. Also, the impact strength increases with the number of kneading disc blocks in the given screw configurations. The melt viscosity of the compounds increases with increasing XLPE loading. However, the higher shear thinning behavior of the compounds at common shear rates implies proper processibility of the compounds. In addition, the impact strength for other polymer matrices used increases with XLPE and it is noticeable that the impact strength of PS/XLPE (80/20 wt%) compound was improved twice that of pure PS.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.21 no.4
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• pp.625-632
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• 2012

Optimization of process parameters in polymer extrusion is an important task to reduce manufacturing cost. To determine the optimum values of the process parameters, it is essential to find their influence on the strength of polymer breathable thin film. The significance of six important process parameters namely, extruder cylinder temperature, extruder speed, extruder dies temperature, cooling roll temperature, stretching ratio, stretching roll temperature on breathable film strength of polymer extrusion was determined. Moreover, this paper presents the application of Taguchi method and analysis of variance (ANOVA) for maximization of the breathable film strength influenced by extrusion parameters. The optimum parameter combination of extrusion process was obtained by using the analysis of signal-to-noise ratio. The conclusion revealed that extruder speed and stretching ratio were the most influential factor on the film strength, respectively. The best results of film strength were obtained at higher extruder speed and stretching ratio.

• Korean Journal of Food Science and Technology
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• v.18 no.2
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• pp.93-97
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• 1986

Dried barley moodle was made with the addition of gelatinized corn flour as binder by using piston type noodle piston press, in which the temperature was kept below the temperature of protein denaturation. The evacuation of air bubble from the dough strengthened the wet noodle strands and improved the cooking quality of the dry noodle. Although the binder was indispensable, the addition should be less than 20%, because the gelatinized corn flour increased the turbidity of the cooking water. Kneading with 3% solution of soy protein resulted in improvement of the noodle's cooking quality.