• 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.

• Journal of the Korea Convergence Society
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• v.8 no.12
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• pp.275-281
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• 2017

The automobile cowl cross bar which is a backbone frame part inside the cockpit module has been designed with more complex geometries recently due to demands of its enhanced functions and reduced weight of car. The traditional manufacturing process using welding between tubes with different diameters shows several problems such as poor mechanical characteristics and appearance, etc. Therefore, in this study, manufacturing processes which can eliminate the welding process were developed by applying one-piece metal forming processes such as tube drawing and radial swaging. As results, it was found that the one-piece manufacturing processes give better bending strength than the traditional welding process and the swaging process shows the lowest manufacturing cost.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.37 no.4
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• pp.547-554
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• 2013

The fuel storage vessel installed in CNG vehicles can be largely divided into 3 parts: head, cylinder, and dome. Studies of the cylinder and dome parts have already been performed, but sufficient design data is not available about the head part. Therefore, expert field engineers heavily depend upon trial-and-error methods. Therefore, FE analysis is performed to review the hot spinning process for forming the head part of the CNG vessel using the Arbitrary Lagrangian-Eulerian (ALE) method. The effects of forming factors on the load were analyzed. The values of the factors were chosen to avoid defects in the head part and buckling, and the forming feasibility of the head part was investigated. Furthermore, a bursting test was performed to evaluate the safety of the storage vessel.

• 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.

• Korean Journal of Materials Research
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• v.3 no.4
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• pp.336-343
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• 1993

The standard map for polyerystalline $YBa_2Cu_3O_7$-X was construeted and indexed from pressed tape sintered bulk and compressed bulk samples were drawn by the [001-110-110] stereographie quadrant map and by the ECPs from individual grains of the speeimens. The relationship between the (001) texture development and critical current density (Jc) for various samples was discussed. An (001) orintation was preferred in the pressed tape thickness was decreased. and in the compressed bulk as the compression strain was increaesed.The (001) orientation made a signifieant in crease on Jc. We conclded that an ECP technique was very useful for the analysis of the orientation distribution in small-sized $YBa_2Cu_3O_7$-X specimens such as superonducting tapes or thin films.

• Korean Journal of Environmental Agriculture
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• v.28 no.4
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• pp.378-385
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• 2009

Arsenic (As) is known to be very toxic and carcinogenic to human beings. Arsenic contaminated soil was collected from a timber mill site at Busan Metropolitan City, Korea, where chromated copper arsenate (CCA) had been used to protect wood from rotting caused by insects and microbial agents. The soil was stabilized using both natural oyster shells (NOS) and calcinated oyster shells (POS). The calcination of natural oyster shells was accomplished at a high temperature in order to activate quicklime from calcite. Two different oyster shell particle sizes (-#10 mesh and -#20 mesh) and curing periods of up to 28 days were investigated. The stabilization effectiveness was evaluated based on the Korean Standard Test (KST) method (1N HCl extraction). The stabilization results showed that the POS treatment was more effective than the NOS treatment at immobilizing the As in the contaminated soils. A significant As reduction (96%) was attained upon a POS treatment at 20 wt% and passed the Korean warning standard of 20 mg/kg ('Na' area). However, an As reduction of only 47% (169 mg/kg) was achieved upon a NOS treatment at 20 wt%. The -#20 mesh oyster shells seem to perform better than the -#10 materials. The scanning electron microscopy (SEM)-energy dispersive X-ray spectroscopy (EDX) results showed that As immobilization was strongly associated with Ca and O in the presence of Al and Si.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.10
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• pp.1463-1470
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• 2010

Microforming, which exploits the advantages of metal forming technology, appears very promising in manufacturing microparts since it enables the production of parts using various materials at a high production rate, it has high material utilization efficiency, and it facilitates the production of parts with excellent mechanical properties. However, the conventional macroscale forming process cannot be simply scaled down to the micro-scale process on the basis of the extensive results and know-how on the macroscale process. This is because a so-called "size effect" occurs as the part size decreases to the microscale. In this paper, we attempt to develop an effective analytical and experimental modeling technique for explaining the effects of the grain size and the specimen size on the behavior of metals in microscale deformation processes. Copper sheet specimens of different thicknesses were prepared and heat-treated to obtain various grain sizes for the experiments. Tensile tests were conducted to investigate the influence of specimen thickness and grain size on the flow stress of the material. In addition, an analytical model was developed on the basis of phenomenological experimental findings to quantify the effects of the grain size and the specimen size on the flow stress of the material in microscale and macroscale forming.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.10
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• pp.1549-1554
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• 2010

Recently, plastic screws have replaced metal screws because of the former's light weight, thermal and electrical insulating properties, and anticorrosion characteristics. Plastic screws are usually produced by injection molding, which involves material shrinkage during the solidification of the polymer. This shrinkage results in the degeneration of the dimensional accuracy. In the present study, the effect of injection-molding conditions on the dimensional accuracy of plastic screws was investigated through a numerical simulation of injection molding; on the basis of this simulation, we could determine the mold-design parameters. The design of experiment was applied in accordance with the numerical analysis in order to optimize the injection-molding conditions with a view to improving the dimensional accuracy of the precision plastic screw.

• Journal of the Korean Recycled Construction Resources Institute
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• v.3 no.1
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• pp.34-42
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• 2015

The paper investigates environmental hazards and characteristics of the artificial lightweight aggregate manufactured by using dyestuff sludge from dyeing industrial complex. The dyestuff sludge used in this study is chemically treated with Ti and Fe salt for the purpose of recycling. The artificial lightweight aggregate is manufactured through 3 step; 1) Selecting the optimum moisture content by evaluating plasticity from the mixing ratio of the clay and sludge, 2) shaping round type based on the optimum mixing ratio, 3) drying and Sintering process. Based on KS F 2534 "Lightweight Aggregate for Structural concrete", the particle size, fineness modulus, the density, absorption, unit volume weight, stability and environmental hazards of the manufactured lightweight aggregate are evaluated. Experimental results show that the particle size and fineness modulus is out of the range. However, it is observed that other physical properties are within criteria. In addition, it is confirmed that the problem of the particle size and fineness modulus could be solved in the manufacturing process.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.24 no.3 s.174
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• pp.777-785
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• 2000

The low-cycle fatigue behaviors of cast AI-Si alloy and composite with reinforcement of SIC particles were compared with those of extruded unreinforced matrix alloy and composite in order to investigate the influence of cast and extrusion processes on the cyclic deformation and fatigue life. Generally, both cast and extruded composites including the unreinforced alloy exhibited cyclic hardening behaviour, with more pronounced strain-hardening for the composites with a higher volume fraction of the SiC particles. However, cast composite under a low applied cyclic strain showing no observable plastic strain exhibited cyclic softening behavior due to the cast porosities. The elastic modulus and yield strength of the cast composite were found to be quite comparable to those of the extruded composite, however, the extrusion process considerably improved the ductility and fracture strength of the composite by effectively eliminating the cast porosities. Low-cycle fatigue lives of the cast alloy and composite were shorter than those of the extruded counterparts. Large difference in life between cast and extruded composites was attributed to the higher influence of the cast porosities on the fatigue life of the composite than that of the unreinforced alloy material. A fatigue damage parameter using strain energy density effectively represented the inferior life in the low-cycle regime and superior life in the high-cycle regime for the composite, compared to the unreinforced alloy.