• Journal of the Semiconductor & Display Technology
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• v.11 no.4
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• pp.43-48
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• 2012

The screen printing method is much used in the flat panel display field including the LCD, PDP, FED, organic EL, and etc. for forming the high precision micro-pattern. Also A number of studies of screen printing method has been conducted as the method for the cost down through the improvement of productivity. Because of being the dot printing method of the cylindrical shape not being the line printing method like the existing PDP barrier rib and phosphor, the pillar arrays using the screen printing method is deposited in the hemispherical type not being cylindrical shape in the existing printing process conditions. In this paper, the parameters were set on the screen printing device in order to deposit the cross-sectional shape with the cone or trapezoid shape of the pillar in depositing the pillars used the screen printing device for vacuum glazing. The cross-sectional shape slope of the pillar according to the parameters was measured. And analysis the effect of the screen printing process conditions on the cross-sectional shape slope of pillars based upon the result of being measured. The processing conditions were drawn to minimize the cross-sectional shape slope of pillar.

• Corrosion Science and Technology
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• v.7 no.1
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• pp.27-34
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• 2008

In industrial and fluid handling systems, frequently the protective film forming materials suffer from severe corrosion due to microbial effects. As an example, various micro-organisms, including bacteria, exist in seawater normally fed to power and desalination plants. Unless seawater intakes are properly disinfected to control these microbial organisms, biological fouling and microbial induced corrosion (MIC) will be developed. This problem could destroy metallic alloys used for plant construction. Seawater intakes of cogeneration plants are usually disinfected by chlorine gas or sodium hypochlorite solution. The dose of disinfectant is designed according to the level of contamination of the open seawater in the vicinity of the plant intake. Higher temperature levels, lower pH, reduced flow velocity and oxidation potential play an important role in the enhancement of microbial induced corrosion and bio-fouling. This paper describes, in brief, the different types of bacteria, mechanisms of microbiological induced corrosion, susceptibility of different metal alloys to MIC and possible solutions for mitigating this problem in industry. A case study is presented for the power plant steam condenser at Al-Taweelah B-station in Abu Dhabi. The study demonstrates resistance of Titanium tubes to MIC.

• Macromolecular Research
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• v.15 no.2
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• pp.114-128
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• 2007

Polyimides are one of the most important classes of polymers used in the microelectronics and photoelectronics industries. Because of their high thermal stability, chemical resistance, and good mechanical and electric properties, polyimides are often applied in photoresists, passivation and dielectric films, soft print circuit boards, and alignment films within displays. Recently, fully aliphatic and alicyclic polyimides have found applications as optoelectronics and inter layer dielectric materials, due to their good transparencies and low dielectric constants $(\varepsilon)$. The low molecular density, polarity and rare probability of forming inter- or intra-molecular charge transfers, resulting in lowering of the dielectric constant and high transparency, are the most striking characteristics of aliphatic polyimide. However, the ultimate end use of polyimides derived from aliphatic monomers is in their targeted applications that need less stringent thermal requirements. Much research effort has been exerted in the development of aliphatic polyimide with increased thermal and mechanical stabilities, while maintaining their transparencies and low dielectric constants, by the incorporation of rigid moieties. In this article, the recent research process in synthesizing fully aliphatic polyimides, with improved dimensional stability, high transparency and low $\delta$values, as well as the characterizations and future scope for their application in micro electric and photo-electronic industries, is reviewed.

• Journal of Powder Materials
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• v.27 no.3
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• pp.247-255
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• 2020

Recently, interest in technology for eco-friendly energy harvesting has been increasing. Polyvinylidene fluoride (PVDF) is one of the most fascinating materials that has been used in energy harvesting technology as well as micro-filters by utilizing an electrostatic effect. To enhance the performance of the electrostatic effect-based nanogenerator, most studies have focused on enlarging the contact surface area of the pair of materials with different triboelectric series. For this reason, one-dimensional nanofibers have been widely used recently. In order to realize practical energy-harvesting applications, PVDF nanofibers are modified by enlarging their contact surface area, modulating the microstructure of the surface, and maximizing the fraction of the ν-phase by incorporating additives or forming composites with inorganic nanoparticles. Among them, nanocomposite structures incorporating various nanoparticles have been widely investigated to increase the β-phase through strong hydrogen bonding or ion-dipole interactions with -CF₂/CH₂- of PVDF as well as to enhance the mechanical strength. In this study, we report the recent advances in the nanocomposite structure of PVDF nanofibers and inorganic nanopowders.

• Journal of Powder Materials
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• v.14 no.3 s.62
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• pp.202-207
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• 2007

Novel polymer mold process for fabrication of microcomponents using metal nanopowders was developed and experimentally optimized. Polymer mold for forming green components was produced by using a hard master mold and polydimethylsiloxane (PDMS). In the preparation of metallic powder premix for the green components without any defect, 90 wt.% 17-4PH statinless steel nanopowders and 10 wt.% organic binder were mixed by a ball milling process. The green components with very clear gear shape were formed by filling the powder premix into the PDMS soft mold in surrounding at about $100^{\circ}C$. Cold isostatic pressing (CIP) was very potent process to decrease a porosity in the sintered microcomponent. The microgear fabricated by the improved process showed a good dimension tolerance of about 1.2%.

• Smart Structures and Systems
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• v.12 no.5
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• pp.579-594
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• 2013

A new enthalpy - based procedure for the homogenization of the electromechanical material parameters of composite piezoelectric modules with integrated electrodes is presented. It is based on a finite element (FE) modeling of the latter's representative volume element (RVE). In contrast to most previously published homogenization approaches that are based on averaged quantities, the presented method uses a direct evaluation of the electromechanical enthalpy. Hence, for the linear orthotropic piezoelectric composite behavior full set of elastic, piezoelectric, and dielectric material parameters, 17 load cases (LC) are used where each load case leads directly to one material parameter. This gives the possibility to elaborate a very strict and easy to program processing. In conjunction with the 17 LC, the enthalpy - based homogenization is particularly suitable for laminated composite piezoelectric modules with integrated electrodes. In this case, the electric load has to be given at the electrodes rather than at the RVE FE model boundaries. The proposed procedure is validated through its comparison to literature available results on a classical 1-3 piezoelectric micro fiber (longitudinally polarized) reinforced composite and a $d_{15}$ shear piezoelectric macro-fiber (transversely polarized) composite module.

• Journal of the Korean Ceramic Society
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• v.20 no.2
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• pp.153-160
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• 1983

This study was carried out to research the change of mineral phases and the characteristics(apparent specific gra-vity water absorption firing shrinkage modulus of rupture thermal expansion and specific dielectric constant) of the sintered bodies manufactured by kaolin and limestone. Samples were composed of the same theoretical composition as it of anorthite and fired up to 145$0^{\circ}C$ Investigated the change and micro-structure of the mineral phases by XRD and SEM the characterisdtics of the sintered bodies by TMA Automatic Capacitance Bridge and etc. The results were as follow. 1. Reactions of sintering are occurred between 860-95$0^{\circ}C$ and 1200-138$0^{\circ}C$ and state of bloating is occurred at 1410-145$0^{\circ}C$ 2. For the inclusion of feldspar and its fine particles of materials the temperature of producing and collapsing is decreased. 3. Pseudo-wollastonite and gehlenite are formed about 95$0^{\circ}C$ 4. At 114$0^{\circ}C$ anorthite are begin to forming and increase continuously to 138$0^{\circ}C$. Above 141$0^{\circ}C$ content of anorthite are decreased. 5. The variations of bending strength with sintering temperature reflect similar trend of sintered contraction and in-crease continuously from 120$0^{\circ}C$. At 145$0^{\circ}C$ reached about 680kg/cm2. 6. Specific dielectric constant$($\varepsilon$_s)$ of specimen sintered at 141$0^{\circ}C$ is 7.12 and that value is most favorable.

• Journal of the Korean Ceramic Society
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• v.47 no.5
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• pp.445-449
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• 2010

The purpose of this study is to improve recycling rate of the waste glasses by investigating bloating mechanism. In this study, we use waste glass(W/G) and hard clay(H/C) as raw materials. The artificial lightweight aggregates were formed by plastic forming($\phi$=10 mm) and sintered by fast firing method at different temperatures(between 700 and $1250^{\circ}C$). The physical properties of the aggregates such as bulk specific gravity, adsorption and microstructure of surface and cross-section are investigated with the sintering temperature and rate of W/G-H/C contents. As the result of the bulk specific gravity graphs, we can found out the inflection point at content of W/G 60 wt%. From the microstructure images, we considered the artificial lightweight aggregates content of W/ G over 60wt% are distributed numerous micro-pores by organic oxidation without Black Core and the artificial lightweight aggregates of W/G below 60 wt% are distributed macro-pores with Black Core.

• Transactions of Materials Processing
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• v.14 no.6 s.78
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• pp.533-540
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• 2005

The hemming process, composed of flanging, pre-hemming and main hemming, is the last one of a series of forming processes conducted on the automotive panels, having greater influence on the outward appearance of cars rather than on their performance. The hem quality can be quantitatively defined by the hemming defects including turn-down/up, warp and roll-in/out. However, it is difficult to evaluate and predict the hem quality through an experimental measurement or a numerical calculation since the size of defects is very small. This study aims to precisely evaluate the hemming defects, especially turn-down and roll-in, through numerical and experimental approaches and to investigate the influence of process parameters on the hem quality, focused on how to simulate the same conditions as in the experiment by the finite element analysis (FEA). The FEA results on the turn-down and roll-in obtained from a model composed of the optimum-sized elements, including a spring element linked to the flanging pad, and given the double master contact condition between the inner and outer panels, had a good correlation with the experimental data. It is thought possible to make an early estimate of the hem quality in a practical automotive design by applying the methodology proposed in this study.

• Advances in Computational Design
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• v.7 no.2
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• pp.129-137
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• 2022

Compo-casting method is one of the popular technique to produce metal based matrix composites. But, one of the main challenges in this process is un-uniform spreading of reinforced subdivisions (particles) inside the metallic matrix and the lack of desirable mechanical properties of the final produced composites due to the low bonding strength among the metal matrix and reinforcement particles. To remove these difficulties and to promote the mechanical properties of these kind of composites, the WARM ARB technique was utilized as supplementary technique to heighten the mechanical and microstructural evolution of the casted Al/Al₂O₃ composite strips. The microstructure evolution and mechanical properties of these composites have been considered versus different WARM ARB cycles by tensile test, average Vickers micro hardness test, wear test and scanning electron microscopy (SEM). The SEM results revealed that during the higher warm- ARB cycles, big alumina clusters are broken and make a uniform distribution of alumina particles. It was shown that cumulating the forming cycles improved the mechanical properties of composites. In general, combined compo-casting and ARB process would consent making Al/Al₂O₃ composites with high consistency, good microstructural and mechanical properties.