• Journal of Broadcast Engineering
• /
• v.21 no.5
• /
• pp.726-738
• /
• 2016

This study analyzed the properties of VHF band and suggested an efficient VHF band application plan for digital radio and UHDTV broadcasting through the experiment by the house T-DMB device in practical user environment. In order to find an efficient frequency band for digital radio broadcasting, this study examined first, to check the times of drop-out receive occurring in the audible area using a DMB/FM CAR Radio for T-DMB that has the characteristics of DAB. Second, this article explored the phenomenon of feedback loops in the same channel using a T-DMB house gap filler transmitting the signal by the same OFDM modulation scheme with UHDTV for configuring suitable SFN transmission network of the UHDTV broadcasting. Based on these experiments, this study suggested a suitable VHF band for digital radio and an efficient utilization of the VHF frequency band for the SFN network configuration of UHDTV.

• Polymer(Korea)
• /
• v.38 no.2
• /
• pp.250-256
• /
• 2014

Polypropylene (PP) composites containing conductive multi-walled carbon nanotube (MWNT) and stainless steel short fiber (SSF) were manufactured using a twin screw extruder and characterized their surface resistivity and mechanical properties in this work. Surface resistivity measurements showed that the percolation threshold appeared at a lower MWNT loading when a small amount of SSF was added to PP/MWNT composites. Tensile modulus and strength of the composites increased but elongation-at-break decreased greatly compared to pure PP. Also, the effects of MWNT and SSF on storage modulus and tan ${\delta}$ from dynamic mechanical analysis for the composites were examined, and the morphologies of fractured surface and the fillers were observed using a scanning electron microscope.

• Journal of the Korea Convergence Society
• /
• v.12 no.1
• /
• pp.193-198
• /
• 2021

In this study, a nano-convergence material technology that can satisfy the superior impact resistance and electrical properties of the semiconducting flame retardant compound used in the Oversheath layer of Extra-high voltage cables was studied. When some of the carbon black used in the semiconducting flame-retardant compound was replaced with CNT (carbon nano tube), the change in physical properties was analyzed. Through the application of carbon nanotubes with remarkably excellent electrical properties, even a small amount of conductive filler formulations can provide superior electrical properties. In addition, as the total filler amount is reduced based on the compound, the workability is improved, and in particular, flexibility and impact resistance are improved, which is expected to contribute to the improvement of the durability of the cable.

• Applied Chemistry for Engineering
• /
• v.34 no.3
• /
• pp.221-225
• /
• 2023

Celluloses are naturally occurring polymers that can be easily obtained from various natural sources. Nanocellulose, a form of cellulose, can be derived from regular cellulose and has unique properties that make it ideal for multiple industrial applications. Nanocellulose is a renewable, sustainable, and eco-friendly composite material with exceptional mechanical properties and thermal stability, surpassing metal and ceramic composites. As a result, nanocelluloses are being extensively studied for their potential applications, including fillers, packaging, energy, medicine, and coatings. This review aims to summarize the current research on nanocelluloses and their applications.

• Journal of Dental Rehabilitation and Applied Science
• /
• v.39 no.4
• /
• pp.222-228
• /
• 2023

Attrition is the loss of tooth hard tissue due to contact between teeth, and in severe cases, dentin is exposed, accompanied by selective corrosion and excessive wear of teeth, which is called cupping. If these lesions are left untreated, the size of the lesion gradually increases, breaking the unsupported enamel, resulting in a decrease in aesthetics and chewing function. In this case report, patients with cupping and enamel fracture due to severe attrition were directly restored using a resin with soft properties containing organic fillers. In the follow-up observation six years later, most of the filling of the occlusal surface was eliminated, but the filling on the buccal surfaces remained relatively intact, and it was confirmed that this type of resin was suitable for the area where the occlusal force was relatively weak rather than the area where the occlusal force was greatly applied.

• Journal of Adhesion and Interface
• /
• v.10 no.3
• /
• pp.117-126
• /
• 2009

Epoxy/anhydride systems with silica filler were studied to improve the cure behavior and characteristics. To study the curing process of epoxy/anhydride using DSC and a stress rheometer, it was observed that gelation temperature increased by increasing the thermal rate or in high isothermal conditions, while it was observed that the degree of cure at gelation decreased. Thermal stability of the epoxy/anhydride system showed any increment by increasing silica contents, except slight decrease of weight by containing humidity. The epoxy resin cured with 30% of silica filler decreased coefficient thermal expansion (CTE) about 33% to show $40ppm/^{\circ}C$. Specimens filled with 30 wt% of silica showed 60% increase in storage modulus at $30^{\circ}C$ to show 3909 MPa compared with neat resin to 2,377 MPa. Epoxy/anhydride systems with surface treated silica by silane coupling agent decreased storage modulus.

• Journal of the Microelectronics and Packaging Society
• /
• v.13 no.2 s.39
• /
• pp.21-26
• /
• 2006

We developed a bonding at low temperature using fine pitch Sn and In bumps, and studied the reliability of the fine pitch In-Sn solder joints. The $30{\mu}m$ pitch Sn and In bumps were joined together at $120^{\circ}C$. A non conductive adhesive (NCA) was applied during solder joining. Thermal cycling test ($0^{\circ}C-100^{\circ}C$, 2 cycles/h) of up to 2000 cycles was carried out to evaluate the reliability of the solder joints. The bondability was evaluated by measuring the contact resistance (Rc) of the joints through the four point probe method. As the content of filler increased, the reliability improved in the solder joints during thermal cycling test because the contact resistance increased little. The filler redistributed the stress and strains from the thermal shock over the entire joint area.

• Journal of Korean Tunnelling and Underground Space Association
• /
• v.13 no.3
• /
• pp.215-231
• /
• 2011

In this study, the behavior of a shallow 2-arch tunnel during the excavation in the sandy ground containing vertical discontinuity plane was experimentally studied. Load transfer mechanism in the pillar caused by a 2-arch tunnel excavation was observed. The position of the vertical discontinuity plane was varied. Model tests were carried out in the normal construction sequence of 2-arch tunnel. Test results-showed that the load transfer caused by the 2-arch tunnel excavation was concentrated in the discontinuity plane, and was cut by the discontinuity plane, so no load transfer took place above the discontinuity plane. It was also shown that the effect of adjacent tunnel excavation on the pillar load and the ground deformation was greater when excavating the upper half-face of the main tunnel, more than when excavating the lower half-face.

• Membrane Journal
• /
• v.31 no.1
• /
• pp.1-15
• /
• 2021

The membrane-based CO2 capture is a fast-growing branch in gas separating field. Ionic liquid assisted mixed matrix membrane (MMM), which consists of organic fillers with dispersed ionic liquid, shows high potentiality as a candidate for CO2 separation medium. In MMM, various kinds of ionic liquid and inorganic filler are incorporated into polymer to enhance gas separating performance. Especially, the strong interaction between ionic liquid and organic filler gives huge influence on enhancing the separating performance by increasing affinity, selectivity and adsorption of CO2 into the framework. Also the mechanical properties of metal organic framework are positively tuned by input of ionic liquid to improve CO2 permeability and selectivity. In this review, study of various combinations of ionic liquid and metal organic framework (MOF) in the polymeric membrane for carbon dioxide separation is discussed.

• Journal of the Korean Crystal Growth and Crystal Technology
• /
• v.8 no.4
• /
• pp.626-633
• /
• 1998

For the fabrication of low temperature cofirable glass/ceramic with high dielectric constant, crystallizing glass [$SiO_2-TiO_2-RO (RO:BaO, CaO:SrO)$] was formed. The glass/ceramic composites were made by mixing this glass and alumina ceramic as filler, and its characteristics was investigated. With this glass compositon, it was possible to fabricate the glass which could be crystallized under $900^{\circ}C$. And it was found that the crystallizing temperature was changed in accordance with the composition of RO in glass. By adding $Bi_2O_3$ as flux, using $Al_2O_3$ as filler and sintering at $860^{\circ}C$, low temperature cofirable glass/ceramic with high dielectric constant was fabricated. The density of that composites was 3.96 g/$\textrm{cm}^3$, dielectric constant was 17 and Q. f was 600.