• Journal of Technologic Dentistry
• /
• v.45 no.3
• /
• pp.55-60
• /
• 2023

Purpose: This study aimed to evaluate the effects of a special heat treatment on Pd-Au-Ag metal-ceramic alloy after degassing treatment and on changes in the hardness of the alloy during the firing process. Methods: Specimen alloys were cast and subjected to degassing at 900℃ for 10 minutes. These specimens were then subjected to a special heat treatment at 600℃ for 15 minutes in a dental porcelain furnace. Further, the specimens were subjected to simulated firing in the porcelain furnace. The resulting specimens were then tested for hardness, and changes in the microstructure were observed. Results: There was a decrease in the hardness of the alloy during the simulated firing of the cast alloy due to the coarsening of the particles. Meanwhile, additional heat treatment after degassing was found to play a crucial role in preventing a decrease in hardness. This treatment effectively suppressed the coarsening of the precipitates during repeated firing at high temperatures. Conclusion: Specific heat treatment of the Pd-Au-Ag metal-ceramic alloy prevented a decrease in its hardness and extended the lifespan of the metal-ceramic prosthesis.

• 한국정보디스플레이학회:학술대회논문집
• /
• 2006.08a
• /
• pp.946-948
• /
• 2006

It is important to keep a constant transmittance of dielectric during firing. To control the shrinkage and fusion stage of frits in firing, we used a hot stage microscope (HSM) to analyze the thermal properties of the lead and bismate glass frits by the in-situ method. This research would be useful for improving the reliability of transmittance of dielectric during firing in industry using a large furnace with temperature deviation.

• Proceedings of the KIPE Conference
• /
• 2003.11a
• /
• pp.230-233
• /
• 2003

Simulation model of induction type fixed speed wind power generator is developed. It is shown that the peak value of inrush current during start up changes according to the firing angle control strategy of soft starter. New proposed firing angle control scheme showed $25\%$ of reduction of peak current which results in smaller drop of gird voltage at the point of common coupling during start up.

• Proceedings of the IEEK Conference
• /
• 2000.07b
• /
• pp.641-644
• /
• 2000

This paper studies coverability tree and reach-ability set of Petri net under the earliest filing rule. Conventional algorithm for coverability tree for ‘normal’ Petri net is not good for Petri net under the earliest firing rule. More over, it is shown that there exists no coverability graph for general class of earliest firing Petri net. Some subclasses are studied where coverability graph can be constructed.

• 한국연소학회:학술대회논문집
• /
• 2006.10a
• /
• pp.293-298
• /
• 2006

There are many researches in progress on co-firing of coal and biomass to reduce carbon dioxide produced from the coal consumption. This study carried out 200 Kg/h combustion test furnace by mixing coal with timber. Coal was mixed with domestic and imported-wood around 10% to 20% based on input energy. For the mixed fuel, combustion temperature, unburned carbon and the composition of flue gas were analyzed. In addition, the tendency of slagging and fouling was examined using a probe. According to the result of the experiment, combustion temperature was depended on the kind of wood and mixing ratio. The unburned carbon loss was higher with increase of wood biomass mixing ratio, as a result, the total heat loss of furnace was slightly increased. The emission of NOx and SOx were decreased by $3{\sim}20%$ and $21{\sim}60%$ respectively. There are no difference of slagging and fouling tendency between biomass co-firing and coal burning only.

• Proceedings of the KSME Conference
• /
• 2001.06d
• /
• pp.973-978
• /
• 2001

Numerical Analysis for liquid fuel combustion of horizontal firing boiler is performed. The mixture-fraction/PDF equilibrium chemistry model is used to predict the combustion of the vaporized fuel. P1 model for radiation effect is used. Superheater, reheater and economizer is modeled using porous with heat sink. Flow and temperature field is investigated, and distribution of thermal $NO_{x}$ and CO is investigated. Computation as the change of excess air and swirling is performed to investigate the change of thermal $NO_{x}$.

• 한국연소학회:학술대회논문집
• /
• 2012.11a
• /
• pp.71-73
• /
• 2012

With numerical simulations, this study investigated the combustion and heat transfer of three different coals under air- and oxy-fuel combustion in a 100 MWe boiler. The boiler is retrofitted to an opposed-firing type while maintain the original furnace shape of downshot firing. The boiler achieved good combustion in both combustion modes for three coals tested. However, the contribution of gasification reactions by $CO_2$ and $H_2O$ significantly increased due to the lack of gaseous mixing. This was different from a typical front-wall firing boiler, which showed larger contribution of char oxidation during air-coal combustion. The wall heat flux was lower in oxy-coal mode at a $O_2$ level of 27%, which has to be considered in further development of the process.

• The Transactions of the Korean Institute of Power Electronics
• /
• v.9 no.6
• /
• pp.584-591
• /
• 2004

The conventional analog-based firing circuit can be implemented by comparing a linearly decreasing periodic sawtooth waveform synchronized to the ac supply, with a control signal corresponding to the desired converter delay angle. This circuit requires a large number of passive components (resistance and capacitor) and careful adjustment of the synchronization circuity. In this paper a novel firing circuit is proposed for thyristor switch. The proposed circuit is implemented by using digital components(FPGA, A/D, and DSP etc.) on the basis of the analog cosine method.

• Proceedings of the KIEE Conference
• /
• 1998.11c
• /
• pp.729-731
• /
• 1998

Surface passivation using glass powders results in good reliability for high voltage silicon power devices. In this paper, Zinc borosilicate glass was prepared for the purpose of passivating, and a deposition technique of glass films on the silicon surface by electrophoresis in which acetone is used as a suspension medium and a measurement technique of C-V curve has been investigated. Properties were compared using SEM, XRD, C-V Curve as a function of firing condition, temperature and atmosphere were investigated. Under 100V applied, 1 minute, $700^{\circ}C$ firing temperature, and $O_2$ atmosphere, I can get the fine films $5.8{\mu}m$ thickness with Zinc borosilicate glass. As a result of investigation of glass films, it has been found that pre-firing and annealing play an important role to achieve uniform, fine, reliable glass deposition films and Glass/Silicon interlace.

• 제어로봇시스템학회:학술대회논문집
• /
• 2005.06a
• /
• pp.813-816
• /
• 2005

This paper presents a method for harmonic elimination and reactive power compensation using an intervening firing method and passive power filter with is suitable to compensate rapidly changing loads and reactive power. The proliferation of three-phase thyristor phase-controlled converter of DC motor drives into a power system has the potential to increase the harmonic levels in the power system. The design procedure of an intervening firing method and passive power filter capable of reducing the voltage and current harmonics produced by converter supplied from a source having internal large inductive impedance is offered. The analysis uses the or CAD PSpice to model three-phase thyristor phase-controlled converter of DC motor drives as well as the system.