• Journal of the Korean Society of Propulsion Engineers
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• v.25 no.6
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• pp.45-52
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• 2021

A hot-firing test was conducted using gaseous-methane and gaseous-oxygen under highly fuel-rich condition as a prior study for the development of a liquid propellant small rocket engine. To compare combustion characteristics for various equivalence ratios, the oxygen flow rate was set to 12 g/s and the methane flow rate was changed according to the equivalence ratio. As a result, it was observed that the steady-state characteristic velocity obtained during the hot-firing test steeply rose in the latter part of each test: the difference between the former and the latter steady value was enhanced overall in proportion to the equivalence ratio. Based on this, the equivalence ratio range depending on the variational characteristics of the characteristic velocity could be divided into three combustion regimes.

• The Journal of Korean Academy of Prosthodontics
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• v.36 no.1
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• pp.120-132
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• 1998

This stusy was to investigate the marginal fitness of porcelain-fused-to- metal crown after succesive firing cycle. Main variables were the degree of marginal curvature of labiocervical margin and the type of alloy. The exaggerated marginal curvature(EMC) was created by additional reduction at the faciocervical wall of the normallized marginal curvature (NMC)-typed ivorine tooth by using milling machine. The difference in the shape was the mid facial margin was placed 2mm apical to cemento- enamel junction in labial surface. Three types of alloy were high noble, noble, and base metal alloy. Test specimens were divided into 8 groups and each group had 8 specimens. Sixty four ceramometal crowns were made totally. Measurement stages were following degassing, opaquing. body porcelain firing, and glazing, and measuring sites were 4. (midmesial, midfacial, middistal, and midlingual). Digital, travelling measuring microscope (0.5 um precision, Olympus. Japan) was used under ${\times}250$ magnification. Within the limitation of this investigation, it was concluded as belows: 1. The pattern of marginal distortion was varied. Degassing stage was not a specific, causative stage that induce most of total marginal distortion during whole procedure fabricating a ceramometal crown. Body firing stage induced discrepancy relatively more than other firing stages. 2. The specimens that were Ni-based alloy and had EMC were distorted persistently following successive fabricating procedures. But marginal openings were decreased after glazing. 3. The release of metal grinding-induced stress was presumed as a cause that induce marginal distortion. 4. The amount of discrepancies of the labial and lingual margins were greater than that of the mesial and distal margin in the specimen that had EMC. 5. Silver-plated die was not enough to resist abrasion during repeated seating of metal copings on the die-holding device.

• Journal of the Korean Ceramic Society
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• v.46 no.6
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• pp.615-620
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• 2009

The present research was performed to determine the optimal firing condition and holding time for malayaite crystal, which is responsible for the stable pink-red coloration in glaze at high temperatures, using Cr$Cl_3$ as chromophore for the synthesis of $Cr_2O_3-SnO_2-CaO-SiO_2$ system pigments. The malayaite crystal was influenced by the raw materials used for synthesis, firing temperature, and holding time. Thus there are differences in the crystal phase and in the coloration according to the condition of synthesis. When Cr$Cl_3$ was used as chromophore, the pigment could be synthesized at lower temperatures, because Cr$Cl_3$ melts at $1500{^{\circ}C}$, which is much lower than the temperature at which $Cr_2O_3$ melts (higher than $2435{^{\circ}C}$). And the employed Cr ion showed a change in oxidation state. When a mineralizer was used to improve the employment of malayaite and the Cr ion, and the low temperature was maintained at which the malayaite crystal is produced, the production of malayaite crystal was promoted and the employment of chromophore was also promoted in the oxidation state of Cr (IV). The results of the experiment showed that the optimal firing condition was 18 h of holding time at $800{^{\circ}C}$, using Cr$Cl_3$ as chromophore, followed by 2 h at the raised temperature of $1150{^{\circ}C}$. The change in coloration of the Cr (IV) employed by malayaite showed a very rich color of red. Thus it was possible to effectively synthesize sphene-pink pigments with more red tint at a low temperature.

• Journal of the Microelectronics and Packaging Society
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• v.5 no.1
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• pp.1-6
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• 1998

Two kinds of the ac-plasma display panel (PDP) with the comb type and the matrix type electrodes were fabricated. The discharge properties were studied as a function of as species (Ne and Ne+He+Xe) and its pressure. The firing voltages (Vf) of the PDP with comb type electrodes were 159 V and 195 V under pure Ne and ne+He+Xe(68:30:2) gas mixture respectively. In case of PDP cell with the matrix type electrodes the Vf was increased to 200 V for pure Ne and 240 V for Ne+He+Xe gas mixture under the same gas pressure(300 mbar).

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.18 no.7
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• pp.764-774
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• 2008

A fire-out-of-battery(FOOB) mechanism, which is a new recoil technology, can reduce dramatically the level of a recoil force compared to the conventional recoil system. The FOOB mechanism pre-accelerates the recoil parts in direction opposite of conventional recoil before ignition. This momentum of the recoil parts due to pre-acceleration can reduce the firing impulse. In this paper, the dynamics of the recoil system with this FOOB mechanism is formulated and simulated numerically. The results of the simulation show that the FOOB system can reduce the recoil force and stroke compared to the conventional system under normal condition. When the fault modes happen, the FOOB system may not perform well and may be damaged seriously due to excessive recoil force and stroke. Hence, the control of the fault modes is necessary to achieve the normal operation of the FOOB system. The results that an additional MR damper enables the FOOB system to perform well under all firing condition.

• Journal of the Korean Ceramic Society
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• v.48 no.6
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• pp.630-635
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• 2011

Bismuth vanadate($BiVO_4$) with monoclinic phase as photocatalyst under visible light is synthesized by precipitation reaction in hot water. Properties such as crystal phase, particle morphology and visual light absorbance as well as the effects of thermal treatment for $BiVO_4$ powders are investigated. $BiVO_4$ powders with both single monoclinic phase and 0.2 ${\mu}m$ in particle size are synthesized when precipitate is stirred in water for 5 h at 95$^{\circ}C$. Well-developed monoclinic phase and light absorption property under 535 nm are observed as a result of thermal treatment for 1 h at 300$^{\circ}C$ after precipitation reaction in water for 5 h at 95$^{\circ}C$. Degradation of monoclinic crystal is found in firing above 350$^{\circ}C$, and particle growth is occurred in firing above 550$^{\circ}C$.

• Progress in Superconductivity and Cryogenics
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• v.15 no.4
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• pp.26-29
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• 2013

Smart fault current controller (SFCC) proposed in our previous work consists of a power converter, a high temperature superconducting (HTS) DC reactor, thyristors, and a control unit [1]. SFCC can limit and control the current by adjusting firing angles of thyristors when a fault occurs. SFCC has complex structure because the HTS DC reactor generates the loss under AC. To use the DC reactor under AC, rectifier that consists of four thyristors is needed and it increases internal resistance of SFCC. For this reason, authors propose a hybrid type superconducting fault current limiter (SFCL). The hybrid type SFCL proposed in this paper consists of a non-inductive superconducting coil and two thyristors. To verify the feasibility of the proposed hybrid type SFCL, simulations about the interaction of the superconducting coil and thyristors are conducted when fault current flows in the superconducting coil. Authors expect that the hybrid type SFCL can control the magnitude of the fault current by adjusting the firing angles of thyristors after the superconducting coil limits the fault current at first peak.

• The KSFM Journal of Fluid Machinery
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• v.15 no.6
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• pp.18-24
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• 2012

This study simulated the operation of a steam injected gas turbine combined heat and power (CHP) system. A full off-design analysis was carried out to examine the change in the turbine blade temperature caused by steam injection. The prediction of turbine blade temperature was performed for the operating modes suggested in the previous study where the limitation of compressor surge margin reduction was analyzed in the steam injected gas turbine. It was found that both the fully injected and partially injected operations suggested in the previous study would cause the blade temperature to exceed that of the pure CHP operation and the under-firing operation would provide too low blade temperature. An optimal operation was proposed where both the turbine inlet temperature and the injection amount were modulated to keep both the reference turbine blade temperature and the minimum compressor surge margin. The modulation was intended to maintain a stable compressor operation and turbine life. It was shown that the optimal operation would provide a larger power output than the under-firing operation and a higher efficiency than the original partially injected operation.

• 한국연소학회:학술대회논문집
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• 2014.11a
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• pp.41-44
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• 2014

This study focused on the effect of the biomass blended ratio on air-staged pulverized coal furnace. The hybrid NOx reduction technology between fuel blending and air staging has been applied in an air-staged pulverized coal fired furnace. The results indicated that co-firing biomass with coal could reduce NOx emissions in an air-staged combustion. In addition, carbon burnout and flame temperature increased under the air-staged condition. A dominant synergistic effect on NOx reduction and carbon burnout was observed when biomass co-firing with coal was applied in air staged combustion.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.14 no.6
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• pp.69-76
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• 2015

This study investigates the thermal efficiency and the efficiency of heat transfer through thermal analysis when the same heat is applied to a mortar frame by firing with various configurations of mortar. As the inside diameter of the mortar increases, the additional material must be reinforced. In comparison with the extent of getting cold due to models, a mortar with the strut under the gun barrel becomes cooler than one with no strut. The thermal deformation at firing becomes different. According to the configuration of mortar and its inside diameter, the extent of getting cold becomes different. This study result can be effectively applied for improving the efficiency of the heat transfer of mortar.