• 한국정보디스플레이학회:학술대회논문집
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• 2005.07a
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• pp.396-398
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• 2005

Effects of such factors as polymerization temperature and a newly synthesized oligomeric photoinitiator(PEDI380) on the electro-optic characteristics of polymer/LC composite films prepared by the UV-curing method were investigated. The polymer-dispersed liquid crystal cells were made with oligomeric photoinitiator PEDI380 by UV-curing method exhibited both low driving volta ge($V_90$) and high contrast ratio under optimum formulation condition.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.20 no.3
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• pp.263-267
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• 2011

Ultrasonic metal welding can be used to weld different metals together safely and precisely, without solder, flux and special preparation. Ultrasonic metal welding machine consists of a power supply, a transducer, a booster and a horn. This paper designed the horn needed for Ultrasonic metal welding. The horn has to be designed and manufactured accurately, because measurements such as the shape, length, mass and etc. have effects on the resonant frequency and the vibration mode. The designed horn has the feature of 40,000Hz of nature frequency, and maximizes vibration range in the Tip by resonance in the frequency of ultrasonic wave machine. In this paper, we calculated and analyzed the natural frequency to find the optimal design of the horn that had the amplitude about $12{\mu}m$ by the modal analysis and harmonic analysis using ANSYS. And we analyzed FFT analysis of the manufactured horn.

• Elastomers and Composites
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• v.57 no.2
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• pp.48-54
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• 2022

A polymeric adhesion promoter was synthesized to improve the adhesive strength of the Ni lead frame/epoxy composite. Poly(itaconic acid-co-acrylamide) (IAcAAM) was prepared by copolymerizing itaconic acid and acrylamide. We compared the adhesive strength between the Ni lead frame and epoxy composite according to the molecular weight of IAcAAM. The molecular weight of IAcAAM was controlled using an initiator, which made it possible to use IAcAAM in the epoxy molding compound (EMC) manufacturing process by modulating the melting temperature. The adhesive strength of Ni lead frame/epoxy composite increased with the addition of IAcAAM to the epoxy composite. In addition, as the molecular weight of IAcAAM increased, the adhesive strength of the Ni lead frame/epoxy composite slightly increased. We confirmed that IAcAAM with an appropriate molecular weight can be used in the EMC manufacturing process and increase the adhesive strength of the Ni lead frame/epoxy composite.

• Proceedings of the Korean Society of Sericultural Science Conference
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• 2003.10a
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• pp.34-38
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• 2003

The silk fibre Produced by the larvae of the lepidopter of the Bombyx mori species is no doubt one of the most precious raw materials employed in manufacturing textile products. The present report, however, deals with silk not as a traditional textile fibre, but as a starting material fer biomedical applications. In recent years, the unique chemical and mechanical properties of silk have made this protein polymer highly attractive for innovative applications, which mainly focus on the development of devices for biomedical uses. (omitted)

• International Journal of Precision Engineering and Manufacturing
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• v.3 no.2
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• pp.5-14
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• 2002

Internet becomes very common tool far communication and data sharing. Virtual readily(VR) on web browser, and virtual prototyping and virtual manufacturing is widely used in many engineering fields. The reduction of overall development process and error minimization during data conversion becomes very crucial where sharing data via Internet and VR. This paper deals with the advantage and disadvantage of VRML format used in RP(Rapid Prototyping), and a software for RP data preparation is developed. If VRML format as an international standard for VR, is replaced with STL format, the weak points of STL formal can be overcome and the technique related to virtual prototyping and virtual manufacturing can be addressed more systematically by sharing the data. The system developed in this work shows a good window to get access to a mare realistic observation of an object for an RP system from a long remote sites in a more systematic way.

• Industrial Engineering and Management Systems
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• v.10 no.2
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• pp.161-169
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• 2011

In seeking further efficiency in production preparation, it is common to examine assembly sequences using digital manufacturing. The assembly sequences affect the product evaluation, so it is necessary to test several assembly sequences before actual production. However, because selection and testing of assembly sequences depends on the operator's personal experience and intuition, only a small number of assembly sequences are actually tested. Nevertheless, there is a systematic method for generating assembly sequences using a contact-related figure. However, the larger the number of parts, the larger the number of assembly sequences geometric becomes. The purpose of this study is to establish a systematic method of generating efficient assembly sequences regardless of the number of parts. To generate such assembly sequences selectively, a "Tournament Tree," which shows the structure of an assembly sequence, is formulated. Applying the method to assembly sequences of a water valve, good assembly sequences with the same structure as the Tournament Tree are identified. The structure of such a Tournament Tree tends to have fewer steps than the others. As a test, the structure is then applied for a drum cartridge with 38 parts. In all the assembly sequences generated from the contact-related figures, the best assembly sequence is generated by using the Tournament Tree.

• Current Applied Physics
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• v.18 no.11
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• pp.1300-1305
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• 2018

The tunable electronic performance of the solution-processed semiconductor metal oxide is of great significance for the printing electronics. In current work, transparent thin-film transistors (TFTs) with indium-zinc oxide (IZO) were fabricated as active layer by a simple eco-friendly aqueous route. The aqueous precursor solution is composed of water without any other organic additives and the IZO films are amorphous revealed by the X-ray diffraction (XRD). With systematic studies of atomic force microscopy (AFM), X-ray photoemission spectroscopy (XPS) and the semiconductor property characterizations, it was revealed that the electrical performance of the IZO TFTs is dependent on the concentration of precursor solution. As well, the optimum preparation process was obtained. The concentrations induced the regulation of the electronic performance was clearly demonstrated with a proposed mechanism. The results are expected to be beneficial for development of solution-processed metal oxide TFTs.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.39 no.4
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• pp.90-96
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• 2016

Incremental sheet forming (ISF) is a highly versatile and flexible process for rapid manufacturing of complex sheet metal parts. Compared to conventional sheet forming processes, ISF is of a clear advantage in manufacturing small batch or customized parts. ISF needs die-less machine alone, while conventional sheet forming requires highly expensive facilities like dies, molds, and presses. This equipment takes long time to get preparation for manufacturing. However, ISF does not need the full facilities nor much cost and time. Because of the facts, ISF is continuously being used for small batch or prototyping manufacturing in current industries. However, spring-back induced in the process of incremental forming becomes a critical drawback on precision manufacturing. Since sheet metal, being a raw material for ISF, has property to resilience, spring-back would come in the case. It is the research objective to investigate how geometrical shaping parameters make effect on shape dimensional errors. In order to analyze the spring-back occurred in the process, this study experimented on Al 1015 material in the ISF. The statistical tool employed experimental design with factors. The table of orthogonal arrays of $L_8(2^7)$ are used to design the experiments and ANOVA method are employed to statistically analyze the collected data. The results of the analysis from this study shows that the type of shape and the slope of bottom are the significant, whereas the shape size, the shape height, and the side angle are not significant factors on dimensional errors. More error incurred on the pyramid than on the circular type in the experiments. The sloped bottom showed higher errors than the flat one.

• Journal of Powder Materials
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• v.29 no.1
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• pp.34-40
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• 2022

Recently, high-entropy carbides have attracted considerable attention owing to their excellent physical and chemical properties such as high hardness, fracture toughness, and conductivity. However, as an emerging class of novel materials, the synthesis methods, performance, and applications of high-entropy carbides have ample scope for further development. In this study, equiatomic (Hf-Ti-Ta-Zr-Nb)C high-entropy carbide powders have been prepared by an ultrahigh-energy ball-milling (UHEBM) process with different milling times (1, 5, 15, 30, and 60 min). Further, their refinement behavior and high-entropy synthesis potential have been investigated. With an increase in the milling time, the particle size rapidly reduces (under sub-micrometer size) and homogeneous mixing of the prepared powder is observed. The distortions in the crystal lattice, which occur as a result of the refinement process and the multicomponent effect, are found to improve the sintering, thereby notably enhancing the formation of a single-phase solid solution (high-entropy). Herein, we present a procedure for the bulk synthesis of highly pure, dense, and uniform FCC single-phase (Fm3m crystal structure) (Hf-Ti-Ta-Zr-Nb)C high-entropy carbide using a milling time of 60 min and a sintering temperature of 1,600℃.

• Proceedings of the Korean Vacuum Society Conference
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• 2015.08a
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• pp.86.1-86.1
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• 2015

As the feature size of Si-based semiconductor shrinks to nanometer scale, we are facing to the problems such as short channel effect and leakage current. One of the solutions to cope with those issues is to bring III-V compound semiconductors to the semiconductor structures, because III-V compound semiconductors have much higher carrier mobility than Si. However, introduction of III-V semiconductors to the current Si-based manufacturing process requires great challenge in the development of process integration, since they exhibit totally different physical and chemical properties from Si. For example, epitaxial growth, surface preparation and wet etching of III-V semiconductors have to be optimized for production. In addition, oxidation mechanisms of III-V semiconductors should be elucidated and re-growth of native oxide should be controlled. In this study, surface preparation methods of various III-V compound semiconductors such as GaAs, InAs, and GaSb are introduced in terms of i) how their surfaces are modified after different chemical treatments, ii) how they will be re-oxidized after chemical treatments, and iii) is there any effect of surface orientation on the surface preparation and re-growth of oxide. Surface termination and behaviors on those semiconductors were observed by MIR-FTIR, XPS, ellipsometer, and contact angle measurements. In addition, photoresist stripping process on III-V semiconductor is also studied, because there is a chance that a conventional photoresist stripping process can attack III-V semiconductor surfaces. Based on the Hansen theory various organic solvents such as 1-methyl-2-pyrrolydone, dimethyl sulfoxide, benzyl alcohol, and propylene carbonate, were selected to remove photoresists with and without ion implantation. Although SPM and DIO3 caused etching and/or surface roughening of III-V semiconductor surface, organic solvents could remove I-line photoresist without attack of III-V semiconductor surface. The behavior of photoresist removal depends on the solvent temperature and ion implantation dose.