• Textile Coloration and Finishing
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• v.28 no.1
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• pp.48-56
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• 2016

Improvement of heat sink technology related to the continuous implementation performance and extension of device-life in circumstance of easy heating and more compact space has been becoming more important issue as multi-functional integration and miniaturization trend of electronic gadgets and products has been generalized. In this study, it purposed to minimize of decline of the heat diffusivity by gluing polymer through compounding of inorganic particles which have thermal conductive properties. We used NH-9300 as base resin and used inorganic fillers such as silicon carbide(SiC), aluminum nitride(AlN), and boron nitride(BN) to improve heat diffusivity. After making film which was made from 100 part of acrylic resin mixed hardener(1.0 part more or less) with inorganic particles. The film was matured at $80^{\circ}C$ for 24h. Diffusivity were tested according to sorts of particles and density of particles as well as size and structure of particle to improve the effect of heat sink in view of morphology assessing diffusivity by LFA(Netzsch/LFA 447 Nano Flash) and adhesion strength by UTM(Universal Testing Machine). The correlation between diffusivity of pure inorganic particles and composite as well as the relation between density and morphology of inorganic particles has been studied. The study related morphology showed that globular type had superior diffusivity at low density of 25% but on the contarary globular type was inferior to non-globular type at high density of 80%.

• Journal of Electrical Engineering and Technology
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• v.13 no.4
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• pp.1638-1643
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• 2018

Multi-layer ceramic capacitors as decoupling capacitor were fabricated by dielectric composition with a high dielectric constant. The fabricated decoupling capacitors were embedded in the PCB of the 10G RF transceiver module and evaluated for the characteristics of electrical noise by the level of AC input voltage. In order to further improve the electrical properties of the $BaTiO_3$ based composite, glass frit, MgO, $Y_2O_3$, $Mn_3O$, $V_2O_5$, $BaCO_3$, $SiO_2$, and $Al_2O_3$ were used as additives. The electrical properties of the composites were determined by various amounts of additives and optimum sintering temperature. As a result of the optimized composite, it was possible to obtain a density of $5.77g/cm^3$, a dielectric constant of 1994, and an insulation resistance of $2.91{\times}10^{12}{\Omega}$ at an additive content of 5wt% and a sintering temperature of $1250^{\circ}C$. After forming a $2.5{\mu}m$ green sheet using the doctor blade method, a total of 77 layers were laminated and sintered at $1180^{\circ}C$. A decoupling capacitor with a size of $0.6mm(W){\times}0.3mm(L){\times}0.3mm(T)$ (width, length and thickness, respectively) and a capacitance of 100 nF was embedded using a PCB process for the 10G RF Transceiver modules. In the range of AC input voltage 400mmV @ 500kHz to 2200mV @ 900kHz, the embedded 10G RF Transceiver modules evaluated that it has better electrical performance than the non-embedded modules.

• Korean Journal of Materials Research
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• v.4 no.3
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• pp.259-267
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• 1994

The effect of processing parameters, temperature, gas concentration, gas flow rate and pressure, were studied on the densification of carbon/carbon composites using a Robust design method in isothermal low-pressure chemical vapor infiltration with a gas system of $C_3H_8-N_2$ After one time of isothermal low-pressure chemical vapor infiltrat.ion, the bulk density of carbon/carbon composites in creased up to 1-9% and apparent porosity of the composites decreased down to 20-50%. ANOVA analysis of the experiment.al data revealed that the important parameters of isothermal lowpressure chemical vapor infiltration were temperature, gas concentration and gas flnw rate. 'There was almost no ~ f f e c t on densification by pressure and interaction between each parameters. In t, he present experimental conditions, the highest bulk density was obtained at $1100^{\circ}C$ temperature, 100% $C_3H_8$, concentration, 100 SCCM flow rate and 5 torr pressure.

• The Journal of Korean Society for Radiation Therapy
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• v.16 no.2
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• pp.69-79
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• 2004

In the process of photon treatments, linear accelerators with energies higher than 10 MV produce neutrons through the (${\gamma}$, n) interactions with the composite materials of the linac head md these materials further produce the induced radiations. We investigate the possible risks from these induced radiations especially in the wedge filters to the radiation workers. Wedge filters are used to modify the isodose profiles in the radiation treatment using the linear accelerator and always be handled by the radiation workers. For the background radiation, we measured the radiation in both the waiting room and the outside of the building for two hospitals, S and H. The results of S hospital were $0.11\;{\mu}Sv/hr$ and $0.10\;{\mu}Sv/hr$ for waiting room and outside respectively, and in the case of H hospital, they were $0.12\;{\mu}Sv/hr$ and $0.11\;{\mu}Sv/hr$. Using a survey meter, we measured the radiation from wedge filters inserted in 10 MV and 15 MV Siemens linear accelerators. The time series measurements were done in ${\sim}1$ minutes after exposure of 5 Gy of monitor units for the field size of $25{\times}25cm^2$. The starting value of 10 MV machine was about $3.26\;{\mu}Sv/hr$, which was three times higher than that of 10 MV. The measured radiation was from $^{28}Al$ and $^{53}Fe$ with a half life of 3.5 min. If the treatment patients are $20{\sim}50$ per day and the number of process of wedge filter change per patient is one or two, the annual dose equivalent is $0.08{\sim}0.4\;mSv$ for 10 MV, and $0.27{\sim}1.36\;mSv$ for 15 MV, which are in the range of dose equivalent limits of radiation workers.

• Restorative Dentistry and Endodontics
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• v.30 no.2
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• pp.128-137
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• 2005

In this study we measured the amount of light energy that was projected through the tooth material and analyzed the degree of polymerization by measuring the surface hardness of composites. For polymerization, Optilux 501 (Demetron, USA) with two types of light guide was used: a 12 mm diameter light guide with 840 nW/$cm^2$ light intensity and a 7 mm diameter turbo light guide with 1100 nW/$cm^2$. Specimens were divided into three groups according to thickness of penetrating tooth (1 mm, 2 mm, 0 mm). Each group was further divided into four subgroups according to type of light guide and curing time (20 seconds, 40 seconds). Vickers' hardness was measured by using a microhardness tester. In 0 mm and 1 mm penetrating tooth group, which were polymerized by a turbo light guide for 40 seconds, showed the highest hardness values. The specimens from 2 mm penetrating tooth group, which were polymerized for 20 seconds, demonstrated the lowest hardness regardless of the types of light guides (p < 0.05). The results of this study suggest that, when projecting tooth material over a specified thickness, the increase of polymerization will be limited even if light intensity or curing time is increased.