• Journal of Electrical Engineering and Technology
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• v.10 no.3
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• pp.1383-1388
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• 2015

Proportional integral derivative (PID) control is one of the conventional control strategies. Industrial PID control has many options, tools, and parameters for dealing with the wide spectrum of difficulties and opportunities in manufacturing plants. It has a simple control structure that is easy to understand and relatively easy to tune. Injection mold is warming up to the idea of cycling the tool surface temperature during the molding cycle rather than keeping it constant. This “heating and cooling” process has rapidly gained popularity abroad. However, it has discovered that raising the mold wall temperature above the resin’s glass-transition or crystalline melting temperature during the filling stage is followed by rapid cooling and improved product performance in applications from automotive to packaging to optics. In previous studies, optimization methods were mainly selected on the basis of the subjective experience. Appropriate techniques are necessary to optimize the cooling channels for the injection mold. In this study, a digital signal processor (DSP)-based PID control system is applied to injection molding machines. The main aim of this study is to optimize the control of the proposed structure, including a digital PID control method with a DSP chip in the injection molding machine.

• Korean Journal Plant Pathology
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• v.14 no.6
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• pp.642-645
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• 1998

A severe pink mold rot on matured melon fruits occurred under a glass tunnel cultivation in Chinju at Kyeongasngnam-do Agricultural Research and Extention Services on May of 1998. Basal portion of the fruits toward blossom end was preferably infected and colonized by the fungus. The causal fungus consistently isolated from the lesions was identified as Trichothecium roseum based on following mycological characteristics. Conidia were hyaline or brightly colored, 2-celled, ovoid or elipsoid, characteristically held together zi-zag chains. Conidiophore was long, slender, simple, septate, bearing conidia-meristem arthrospores-apically, singly when young and successively by slight growth of conidiphore apex. Optimum temperature for mycelial growth and conidial germination was recorded at 20~$25^{\circ}C$. However, over 48% of the fungal conidia were germinated at 15$^{\circ}C$ and mycelial growth was only slightly slower than $25^{\circ}C$. The temperature profiles and high humidity available during the cultivation were considered favorable for the pathogen as showing 22% infection rate on matured melon fruits cv. Saros. This is the first report of pink mold rot of melon caused by T. roseum in Korea.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.28 no.7
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• pp.446-449
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• 2015

An improvement of light-extraction efficiency of organic light-emitting diodes was studied by using random-textured films (RTF). Device was made in a structure of RTF/glass/ITO/TPD/$Alq_3$/LiF/Al. RTF mold was made by spreading PDMS solution on a sandpaper. By pressing this mold on the glass substrate pre-coated with ZPU material, the RTF was obtained. From this study, there was an improvement of external quantum efficiency by about 30% in the device with the random-textured film (RTF 40) compared to that of the reference one.

• Journal of the Korean Society for Precision Engineering
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• v.27 no.12
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• pp.22-27
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• 2010

The usage of ultra-precision machining is increasing by the manufacturing of precision optical elements such as camera lens, laser printer, CD player, DVD and microscope parts etc.. The WC alloy material is in wide use by mold core to improve the productivity and accuracy in manufacturing those precision parts. The WC alloy mould core can be machined effectively by the parallel grinding process which is an excellent technique for manufacturing of surface profile hard to machining materials such as the hardened metal alloy, Ceramics, Glass and so on. Magnetic assisted polishing as a final polishing process has also been utilized to obtain ultra-precision mirror surface with the elimination of traces presented on ground surface. It is able to deduce the optimal ultra-precision machining conditions of the WC alloy material from the experiment and analyses results.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2006.05a
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• pp.567-568
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• 2006

Generally, progressive type GMP process is more efficient than batch type because there are advantages that problems of each stage(heating, press, cooling etc.) are easily grasped and a time of production is shortened. But if single cavity is used in progressive type GMP process, there is disadvantage that productivity is decreased. So, in order to improve productivity of progressive type GMP process, it is essential to secure multi cavity mold technic. In this study, as a fundamental study to develop multi cavity used in glass lens molding, we conducted a compression test for PBK40.

• Journal of the Korean Society for Precision Engineering
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• v.26 no.9
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• pp.58-63
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• 2009

Silicon carbide (SiC) has been used for many engineering applications because of their high strength at high temperatures and high resistances to chemical degradation. SiC is very useful especially for a glass lens mold whose components demanded to the machining with good surface finish and low surface damage. The performance and reliability of optical components are strongly influenced by the surface damage of SiC during grinding process. Therefore, the severe process condition optimization shall be necessary for the highly qualified SiC glass lens mold. Usually the major form of damage in grinding of SiC is a crack occurs at surface and subsurface. The energy introduced in the layers close to the surface leads to the formation of these cracks. The experimental studies have been carried out to get optimum conditions for grinding of silicon carbide. To get the required qualified surface finish in grinding of SiC, the selection of type of the wheel is also important. Grinding processes of sintered SiC work-pieces is carried out with varying wheel type, depth of cut and feed using diamond wheel. The machining result of the surface roughness and the number of flaws, have been analyzed by use of surface profilers and SEM.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.12 no.2
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• pp.31-36
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• 2003

Electronic or measuring instruments equipped with aspherical lens have recently been used since aspherical lens is more effective than spherical one. for the mass production of aspherical lenses, specific molds with precisely machined cores should be prepared. Some researches on the aspherical lens machining have been carried out to date. However, ultra-precise finding of aspherical or mold core has not been fully studied. In this study, the ultra-precise grinding and evaluating system were established to investigate the finding characteristics of aspherical lenses. Unlike conventional grinding process, since a highly-precise lathe were operated in a clean room without vibration the experimental results can be very useful for further studies on ultra-precise grinding process.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.62 no.5
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• pp.649-656
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• 2013

A conventional epoxy-microsilica composite (EMC) and an epoxy-microsilica-nanosilicate composite (EMNC) were prepared in order to apply them to mold-type transformers, current transformers (CT) and potential transformers (PT). Nanosilicate was exfoliated in a epoxy resin using our electric field dispersion process and AC insulation breakdown strength at $30{\sim}150^{\circ}C$, glass transition temperature and viscoelasticity were studied. AC insulation breakdown strength of EMNC was higher than that of EMC and that value of EMNC was far higher at high temperature. Glass transition temperature and viscoelasticity property of EMNC was higher than those of EMC at high temperature. These results was due to the even dispersion of nanosilicates among the nanosilicas, which could be observed using transmission electron microscopy (TEM). That is, the nanosilicates interrupt the electron transfer and restrict the mobility of the epoxy chains.

• Polymer(Korea)
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• v.36 no.6
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• pp.677-684
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• 2012

Injection molding process is a popular polymer processing involving plasticizing and enforcing the material flow into the mold. A polymer material shrinks according to temperature variations during the shaping process, and subsequently molding shrinkage developed. Developed deflections or warpages after molding process in part are caused by residual stress relaxation contained in the part. Adding inorganic materials or fibers such as glass and carbon to control shrinkage and enhance warpage resistance are common. In this study, warpages according to part design have been investigated through experiment. Warpages for molding conditions and mold designs such as gate locations were measured. Warpages along flow direction and perpendicular to the flow direction were also measured. Warpages near gate and far from gate were compared. Glass fiber reinforced crystalline polymers, PP and PA66 have been used in this experiment. Glass fiber reinforced crystalline polymers showed large warpage compared with glass reinforced amorphous polymers. Warpages in crystalline polymers were less influenced by molding conditions compared with amorphous polymers, however warpages of crystalline polymers significantly depend on part design.

• Korean Journal of Materials Research
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• v.15 no.4
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• pp.281-284
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• 2005

Room and high temperature deformation behaviors of Cu-Zr-Ti-Pd bulk metallic glasses produced by copper mold casting were investigated. The addition of Pd was shown to enhance the glass forming ability and thermal stability of Cu-Zr-Ti base bulk metallic glass. The compressive strength of $Cu_{55}Zr_{30}Ti_{10}Pd_5$ bulk metallic glass was 2230 MPa with 1.8 plastic strain. The stress overshoot and yield drop phenomenon were observed below $487^{\circ}C$ and a drastic decrease in the flow stress was observed at $487^{\circ}C$. The stress overshoot is thought to be associated with stress-induced structural relaxation.