• Journal of the Korean Society of Food Science and Nutrition
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• v.26 no.2
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• pp.229-235
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• 1997

The chemical components of 5 domestic wheats(Kru, Suwon 257, Eunpa, Chokwang and Tapdong), Australian standard white wheat(ASW) and dark northern spring wheat(DNS) were determined in terms of amino acids, sugars and minerals for whole wheat and white wheat flour of 70% milling yield. The protein content of whole Eunpa and Tapdong was approximately 15%, and reduced its content approximately 1% after milling compared to that of whole wheats. The high levels of glutamic acid and proline were observed in domestic wheats. The limiting amino acid of domestic wheat was higher than that of ASW, but lower than that of DNS. Especially, Suwon 257 and Tapdong exhibited the higher limiting amino acid content than other domestic wheats. Glutamic acid and proline content increased, while lysine and threonine was decreased after milling. In general, whole wheat exhibited the higher levels of arabinose and xylose, and the lower level of glucose than flour. The results also showed domestic wheat contained the higher amount of arabinose and xylose than the foreign wheats. Domestic wheat and flour possessed the higher amount of mineral such as P, K, Na and Ca than ASW and DNS, while Al and Si were similar to others.

• Proceedings of the KSME Conference
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• 2001.11a
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• pp.753-759
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• 2001

The purpose of this study is to suggest the machining technique of the constant control of cutting speed in order to improve precision machining and tool life in high speed machining using ball end mill. Cutting speed is changed in machining free form surface like free form surface. So, we don't have supreme surface form and toll life on machining. The way to solving this problem is that we should be settled to optimal cutting speed in free form surface machining. And, to improve precision machining is executed high speed machining method to output optimum NC data with developed constant control of cutting speed program after modeling of CAD/CAM. In this paper, a comparison was made of the cutting precision and tool life in conventional cutting and those in free form surface machining applying the program developed.

• Journal of Magnetics
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• v.14 no.1
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• pp.27-30
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• 2009

Various sintered magnets containing $28{\sim}31\;wt%$ Nd and $0{\sim}7\;wt%$ Dy were evaluated for coercivity and irreversible flux loss as a preliminary study to develop highly-coercive, high-temperature magnets that can be applied for driving motors in a hybrid vehicle. The sintered magnets were prepared in sequence of strip casting, HD treatment, jet milling, magnetic field pressing, sintering and post-annealing. Increasing Dy content and adjusting post-annealing temperature monotonically increased coercivity of magnets from about 14 kOe to 30 kOe. A magnet containing 28 wt% Nd and 7 wt% Dy exhibits a $(BH)_{max}$+$_i{H_c}$ value of almost 64. This is very close to what the automobile industry considers as the minimum value (65) for a hybrid vehicle system. Moreover, irreversible flux loss of the magnet was about 3% at $200^{\circ}C$, which is well less than the allowable limit (5%) to a driving motor in hybrid vehicles.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2006.05a
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• pp.499-500
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• 2006

The electrode wear in micro-EDM significantly deteriorates the machining accuracy. In this regard, electrode wear needs to be compensated in-process to improve the product quality. Therefore, there are substantial amount of research about electrode wear. In this study a control method for micro-EDM using discharge pulse counting is proposed. The method is based on the assumption that the removed workpiece volume is proportional to the number of discharge pulses, which is verified from experimental results analyzing geometrically machined volume according to various number of discharges. Especially, the method has an advantage that electrode wear does not need to be concerned. The proposed method is implemented to an actual micro-EDM system using high speed data acquisition board, simple counting algorithm with 3 axis motion system. As a result, it is demonstrated that the volume of hole machined by EDM drilling can be accurately estimated using the number of discharge pulses. In EDM milling process a micro groove without depth variation caused by electrode wear could be machined using the developed control method. Consequently, it is shown that machining accuracy in drilling and milling processes can be improved by using process control based on the number of discharge pulses.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2002.04a
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• pp.32-37
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• 2002

High speed machining is one of most effective technologies to improve productivity. It can give great advantage for manufacture of die and Moulds. However, when the high speed machining of materials, especially in machining of micro groove, a severely thermal demage was generated on workpiece and tool. Generally, the cutting fluid is used to improve penetration, lubrication, and cooling effect. In order to rise the performance of lubrication, it contains extreme pressure agents (Cl, S, P). But the environment of work room go bad by those additive Therefore, the compressed chilly air with Oil mist system was developed to replace the conventional cutting fluid system. This paper carried out the tests to evaluate the machinability by the cutting environment in high speed micro groove machining of NAK80 (HRC40). Compressed chilly air with oil mist was ejected on the contact area between cutting edge and workpiece. The effectiveness of this developed compressed chilly air with oil mist system was evaluated in terms of tool life. The results showed that the tool life of carbide tool coated TiAIN with compressed chilly air mist cooling was much longer than with dry and flood coolant when cutting the material.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.10a
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• pp.172-175
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• 2002

High speed machining is one of the most effective technologies to improve productivity. It can give great advantage for manufacture of die and Moulds. However, when machining of micro groove in high speed machining a severely thermal damage was generated on workpiece and cutting tool. Generally, the cutting fluid is used to improve penetration. lubrication. and cooling effect. In order to rise the performance of lubrication. it contains extreme pressure agents (Cl, S, P). But the environment of work room go bad by those additive. Therefore, the compressed chilly air with oil mist system was developed to replace the conventional cutting fluid system. This paper carried out the tests to evaluate the machinability by the cutting environment in high speed micro groove machining of NAK80 (HrC40). Compressed chilly air with oil mist was ejected on the contact area between cutting edge and workpiece. The effect of this developed compressed chilly air with oil mist system was evaluated in terms of tool life. The results showed that the tool lift of carbide tool coated TiAlN with compressed chilly air mist cooling was much longer than that of the dry and flood coolant when cutting the material.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.16 no.3
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• pp.125-130
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• 2017

In this study, the influence of various factors on surface roughness was investigated using the Taguchi experimental method through high-speed machining processing. Feed rate, pitch, tool diameter, and depth of cut are widely applied to high-speed machining conditions for mold production. Each of these factors was implemented and classified into three levels; then, after high speed machining, surface roughness was measured, the S/N ratio was analyzed, and the influence on the surface roughness of control factors was analyzed quantitatively by ANOVA. Using this information, a mathematical model for predicting surface roughness was derived from multiple regression analysis. This mathematical model enables the surface roughness value after high-speed machining to be predicted at the production stage, before machining, for a wide range of machining conditions.

• Journal of ILASS-Korea
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• v.17 no.1
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• pp.14-19
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• 2012

The present study conducts experimental investigation on spreading and deposition characteristics of a $4.3{\mu}l$ de-ionized (DI) water droplet impacting upon aluminum (Al 6061) flat and textured surfaces. The micro-textured surface consisted the micro-hole arrays (hole diameter: $125{\mu}m$, hole depth: $125{\mu}m$) fabricated by the conventional micro-computer numerical control (${\mu}$-CNC) milling machine process. We examined the surface effect of texture area fraction ${\varphi}_s$ ranging from 0 to 0.57 and impact velocity of droplet ranging from 0.40 m/s to 1.45 m/s on spreading and deposition characteristics from captured images. We used a high-speed camera to capture sequential images for investigate spreading characteristics and the image sensor to capture image of final equilibrium deposition droplet for analyze spreading diameter and contact angle. We found that the deposition droplet on textured surfaces have different wetting states. When the impact velocity is low, the non-wetting state partially exists, whereas over 0.64 m/s of impact velocity, totally wetting state is more prominent due to the increase kinetic energy of impinging droplet.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2004.10a
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• pp.35-38
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• 2004

Graphite nanofiber (GNF) and carbon nanotube (CNT) are novel fiber reinforcing materials which have outstanding physical and mechanical properties. Aluminum matrix composites reinforced graphite nanofiber were fabricated by conventional powder metallurgy (PM) method. The composites were prepared through ultrasonication, ball milling, and hot isostatic pressing. A uniform distribution of GNF in aluminum matrix could be obtained. To measure the mechanical properties of GNF-Al composites testings were done in indentation and compression. The compressive strength was enhanced according to reinforcing graphite nanofiber while the hardness was decreased. This study makes the high performance composites for future applications.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2001.04a
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• pp.429-434
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• 2001

This paper has been presented the dynamic effect by the journal speed, eccentricity and source positions in order to overcome the defects of air bearing such as low stiffness and damping coefficient. Choosing two row sources position of air bearing is different from previous investigations in the side of pressure distribution of air film by the wedge effects. An experimental study was performed to compare theoretical analysis. The dynamic stiffness was measured in actual cutting. It helps predicting of air spindle s characteristic in machining of die more precisely. The results of investigated characteristics was applied to air spindle for high speed milling.