• Journal of the Korean Ceramic Society
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• v.21 no.3
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• pp.278-282
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• 1984

Barium titanate powder was made by firing the complex hydroxide which had been synthesized with chemical wet process by the medium of $H_2O_2$. This experiment was done as following A mixed solution of $BaCl_2$, $TiCl_4$ and $H_2O_2$ with 1:1:10 mol ratio was prepared. Ammonium hydroxide was added into the mixed solution. In the range of pH 8-10 $BaTiO_3$ complex hydroxide was obtained and treated at room temperature 11$0^{\circ}C$, 20$0^{\circ}C$, 40$0^{\circ}C$ and $600^{\circ}C$. The results obtaiined from this experiment were as follows. At room temperature $BaTiO_3$ complex hydroxide was amorphous. Above 10$0^{\circ}C$ crystalline $BaTiO_3$ was obtained and particle size of $BaTiO_3$ was increased with elevated temperature. So the particle size of BaTiO3 could be controlled by the firing temperature. After treating $BaTiO_3$ complex hydroxide at 10$0^{\circ}C$ the average particle size of $BaTiO_3$ was 0.22$\mu\textrm{m}$.

• Journal of Advanced Marine Engineering and Technology
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• v.16 no.4
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• pp.102-112
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• 1992

The three-phase full(6-pulse) bridge controlled rectifier is one of the most widely used types of solid-state converters in DC drive applications for higher performance. In most of the previous designs, the gate control circuits of the converter have been designed with analog method which can be easily affected by noise. Nowdays with advances of microelectronics and power electronics, microprocessor and pheripal LSIs are increasingly used for eliminating this problems. In this paper, a novel general-purpose microprocessor -based firing system and control scheme for a three-phase controlled rectifier bridge has been developed and tested. Using the phase relations between ${\Delta}$-Y transformer in power operation part, gate pulse of the converter is generated with real time process so that microprocessor may share its time to control algorithms efficiently. The firing angle of the converter is smoothly controlled in the range of 0 $^{\dirc}$ to 180$^{\dirc}$ with a fast respone and a constant open loop gain, even for the case where the converter is fed by a weak AC system of unregulated frequency. The hardware and software control circuit implementation built around a 80286 microprocessor is discussed, and the experimental results are given. This scheme uses less hardware components and has higher dynamic performance in variable speed DC drive applications.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.26 no.5
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• pp.578-583
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• 2016

In order to provide a basis data for design of small arms and their silencer, an experimental study on firing noise of small arms was performed around the muzzle of a gun. For this experimental comparison analysis, the target small arms were included most operating small arms in our country. The sound pressure levels were measured at a certain distance which was predetermined according to US army firing test procedure, TOP 3-2-045. By this experimental study, the sound pressure levels of 5.56 mm caliber small arms are 143 dB ~ 145.4 dB and 7.62 mm caliber small arms are 144 dB ~ 145.2 dB. Between the heavy machine gun K12 and M60, the sound pressure level of K12 is slightly lower than M60.Also silencer for K14 snifer rifle was tested. Using this result, it has been found that the reduction effect of the silencer is 15.4 dB but the improvements of silencer performance in the high frequency range have to be studied later on.

• The Korean Journal of Physiology and Pharmacology
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• v.12 no.6
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• pp.307-314
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• 2008

Retinal prostheses are being developed to restore vision for the blind with retinal diseases such as retinitis pigmentosa (RP) or age-related macular degeneration (AMD). Among the many issues for prosthesis development, stimulation encoding strategy is one of the most essential electrophysiological issues. The more we understand the retinal circuitry how it encodes and processes visual information, the greater it could help decide stimulation encoding strategy for retinal prosthesis. Therefore, we examined how retinal ganglion cells (RGCs) in in-vitro retinal preparation act together to encode a visual scene with multielectrode array (MEA). Simultaneous recording of many RGCs with MEA showed that nearby neurons often fired synchronously, with spike delays mostly within 1 ms range. This synchronized firing - narrow correlation - was blocked by gap junction blocker, heptanol, but not by glutamatergic synapse blocker, kynurenic acid. By tracking down all the RGC pairs which showed narrow correlation, we could harvest 40 functional connectivity maps of RGCs which showed the cell cluster firing together. We suggest that finding functional connectivity map would be useful in stimulation encoding strategy for the retinal prosthesis since stimulating the cluster of RGCs would be more efficient than separately stimulating each individual RGC.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.26 no.4
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• pp.436-442
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• 2016

This paper presents the torsional vibration isolation performance evaluation of a centrifugal pendulum absorbers (CPAs) that has a continuously varying resonance frequencies proportional to engine firing (excitation) order. CPAs are commonly used to suppress torsional vibrations in rotating machinery and internal combustion engines. In this study, they are employed on the current spring type torsional damper inside a torque converter of automotive vehicle. To evaluate the effectiveness of designed resonance tuning order, the torsional vibration transmissibility based on torque measurements with respect to different engine firing orders is experimentally measured with a lower-inertia dynamometer. The torsional vibration transmissibility with respect to different frequencies with engine order of 2 is also evaluated. It has been demonstrated that the significant vibration reduction over operational frequency range of interest can be achieved by attaching simple pendulums. Future research direction includes the study on theoretical analysis, improved design of pendulum etc.

• Journal of the Korean Ceramic Society
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• v.18 no.3
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• pp.171-181
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• 1981

Alkaline-earth porcelains have been prepared from mixture of kaolin, quartz, and synthetic calcines obtained by calcining a mixture of kaolin and more than two different kinds of alkaline-earth carbonates. They were magnesium, calcium and barium carbonates which are inexpensive and readily available. The vitrification behavior of the batch mixes was investigated in the firing range of 1240$^{\circ}$to 1380$^{\circ}$, in relation to the body compositions. It appeared that the density and the firing temperature depended largely on the content of alkaline-earth oxides in the body. These porcelains posses excellant dielectric properties, and are especially valuable as bases for deposited carbon resistors for which they were developed. An illustrative composition is 50% Dong Hwa kaolin, 22.4% Chang Shin quartz, 27.6% calcine. The composition of the calcine is 70% Dong Hwa kaolin, 10.7% BaCO3, 13.5% CaCO3, 5.8% MgCO3. The specific resistance of this body is $1.2{\times}10^{15}$ ohm-cm at 5$0^{\circ}C$, $2.5{\times}10^{14}$ ohm-cm 10$0^{\circ}C$, $2.5{\times}10^{13}$ ohm-cm at 15$0^{\circ}C$, $1.8{\times}10^{12}$ohm-cm at 20$0^{\circ}C$.

• International Journal of Aerospace System Engineering
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• v.9 no.1
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• pp.1-15
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• 2022

Pyrotechnic initiators provide a source of pyrotechnic energy used to initiate a variety of space mechanisms. Pyrotechnic systems build in electromagnetic environment that may lead to critical or catastrophic hazards. Special precautions are need to prevent a pulse large enough to trigger the initiator from appearing in the pyrotechnic firing circuits at any but the desired time. The EMC verification shall be shown by analysis or test that the pyrotechnic systems meets the requirements of inadvertent activation. The MIL-STD-1576 and two range safeties, AFSPC and CSG, require the safety margin for electromagnetic potential hazards to pyrotechnic systems to a level at least 20 dB below the maximum no-fire power of the EED. The PC23 is equivalent to NASA standard initiator and the 1EPWH100 squib is ESA standard initiator. This paper verifies the two safety margins for electromagnetic potential hazards. The first is verified by analyzing against a RF power. The second is verified by testing against a DC current. The EMC safety margin requirement against RF power has been demonstrated through the electric field coupling analysis in differential mode with 21 dB both PC23 and 1EPWH100, and in common mode with 58 dB for PC23 and 48 dB for 1EPWH100 against the maximum no-fire power of the EED. Also, the EMC safety margin requirement against DC current has been demonstrated through the electrical isolation test for the pyrotechnic firing circuits with greater than 20 dB below the maximum no-fire current of the EED.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.8
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• pp.156-163
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• 2019

In this paper, we present the process of developing an automatic carrying and arming system for testing ammunition. When carrying out shooting tests at a domestic rifle range, most of the ammunition operations are carried out by human manpower The series of test processes, such as transporting, arming and firing of heavy munitions, is repeated by employing human. If the ammunition is loaded via manpower, then problems can occur such as loss of reliability of test results, musculoskeletal disorders of humans and also safety accidents can occur. To address these problems, an automated system was developed for the transport and operation of ammunition. This paper covers the design, manufacture and operation of the developed system. In addition, this study validated the effectiveness of the system as compared to the human operation. Our results show that the developed system can be easily adapted to testing ammunition at a domestic rifle range.

• Journal of the Society of Disaster Information
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• v.14 no.1
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• pp.101-106
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• 2018

The ROK military conluded that the dead of a young soldier, walking back to his unit was caused by a ricochet after carrying our some construction work near firing range in Gangwon Province in last Septemebr. But when it was revealed that he was hit by a stray bullet cause, this fact caused public fury. To solve these problems, we will analyze the individual fire shooting range of our military units from a safe perspective and propose ways to improve it by applying the cases of the United States, which are both permanent and scientific.

• Journal of Conservation Science
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• v.6 no.1 s.7
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• pp.15-30
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• 1997

The chamical and physical properties of the fragments of an ancient pottery such as earthenware, gliazed pottery and celadon excavated in Chonnam province has been investigated by X-ray diffraction inductively coupled plasma spectroscopy(ICP), thermal mechanical analysis(TMA). Glazed pottery fragments of Chonnam province are cotaining Fe2O3 $4\~7\%$ by the analyis of ICP, firing temperature range was presumed to $1100-1150^{\circ}C$ by TMA. Celadon fragments of Chonnam province are containing Fe2O3 $2\~3\%$ by the analyis of ICP, firing temperature range was presumed to $1140\~1200^{\circ}C$ by TMA. The charateristics in the trace element composition of an ancient pottery of Chonnam provinceis are similar, it is an reflection of similar geological charateristics. The charateristic elements of Chonnam provincical ancient pottery were Rb, Sr, V, Zr, Y, Nd, Sc, La, Ce, Nb, Sm, Eu, Dy and Yb of the analyzed 21 trace elements. By Fe2O3-Zn ditribution diagram, potteries excavated in Yong-am, celadons excavated in Haenam, Kangjin, Buan and glazed pottery excavated in Hae-nam are grouped into the same class.