• 한국군사과학기술학회지
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• 제16권1호
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• pp.81-88
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• 2013

This paper describes the fundamentals, design, realization and test results of a BPSK(Bi Phase Shift Keying) transceiver for the direction finding proximity fuze sensor for anti-aircrafts or air missiles. The BPSK transceiver for the direction finding fuze sensor has been designed to detect a moving target by Doppler signal processing with the code correlation method and to distinguish direction by comparing received powers of each Doppler signal from adjacent three receiving antennas. The electrical and ESS(Environmental Stress Screening) tests of the BPSK transceiver showed satisfactory results and target detection and direction finding performances proved to be successful through dynamic operation tests by 155 mm gun firing.

• 전기학회논문지
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• 제58권2호
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• pp.217-224
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• 2009

This paper presents a new AC/DC converter scheme for HVDC system to achieve a high power factor operation. The new AC/DC converter consists of two 12-pulse bridge converters in series: the primary and auxiliary converters. Ignition angles of the main and auxiliary converters are controlled independently to maintain the nominal DC voltage and control auxiliary voltage. The resulted DC voltage obtained by superimposing the above two phase modulated voltages can be controlled very rapidly over a wide range, and a high power factor operation is achieved. Performance improvements in power factor and harmonic distortion are validated by theoretic derivations and experiments with prototype HVDC system. With the proposed converters, investment for reactive power compensation and filter in HVDC system can be saved significantly.

• International Journal of Aerospace System Engineering
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• 제3권2호
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• pp.9-13
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• 2016

This study is about technical analysis in launching SLBM of North Korea. We expect that North Korea develop ICBM and SLBM by improving the technique called R-27. Also it is expected that they attempt to achievement in covertness and ambush by completing technique of cold launching. Recently, SLBM of North Korea rised 40 ~ 50 m on surface after launching in an underwater when they showed the scene of firing SLBM. We expect that they actively use not general technique but super cavitation technique. Also, they might improve the launching technique by doing SLBM launching test. This type is about that whole rocket is separated two parts and ignited with high velocity and we might think that 1st rocket is used in solid propellant to maneuver in high velocity in an underwater. After then, they might use liquid propellant for the long-range ballistic missile.

• 한국세라믹학회지
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• 제20권1호
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• pp.13-18
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• 1983

The investigations have been carried out to study the characteristics of limestone using in Korean cement industry with prime interests in the dissociation and thermal phase changes of limestone between 90$0^{\circ}C$ and 140$0^{\circ}C$ The range of decomposition temperature of limestone was 840-87$0^{\circ}C$ and it was considered that the temperature was lowered by impurities in the limestone. The more the impurities and the finer the grain size of quartz in limestone the lower temperature was applied in forming $C_2S$ mineral the temperature of about 100$0^{\circ}C$. The major clinker minerals such as $C_3S$, $C_2S$, $C_3A$ and $C_4AF$ were formed in most of limestone when the firing temperature was up to 130$0^{\circ}C$.

• 한국세라믹학회지
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• 제11권3호
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• pp.33-38
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• 1974

The possibility of the sources for the manufacture of mullite-rich refractories from the modified domestic alunite was studied. The modifying method of alunite studied were performed by calcination, wet ballmilling, and washing with water. For synthesis of mullite-rich refractories, the modified alunite with the addition of alumina and Fe2O3 as mineralizer was fired at 1350$^{\circ}$-155$0^{\circ}C$, and the following results were obtained: 1) The suitable firing temperature range was 1450$^{\circ}$-150$0^{\circ}C$, and adequate amounts of Al2O3 and Fe2O3 were below 30% and 3~4%, respectively. 2) Thermal expansion coefficient proportional to heating temperature was about 5$\times$10-6~10$\times$10-6cm/cm.deg. 3) The mineralogical compositions of the sintered specimens were found as mainly mullite and corundum.

• 한국세라믹학회지
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• 제21권2호
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• pp.135-142
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• 1984

The electrical conductivity of compositions in the system $CaO-ZrO_2$ has been measured by 2-probe tech-nique in the temperature range 350~75$0^{\circ}C$. The composition of maximum conductivity in this system is within the cubic solid-solution region close to low-calcia cubic solid-solution phase boundary. The results are as follows : 1) The maximum conductivity was found 13mol CaO in zirconia. 2) As the CaO content was increased from 13 to 21 mol% the electrical conductivity decreased for any given temperature and the activation energy increased. 3) As the firing temperature and soaking time was increased the electrical conductivity increased and activation energy decreased.

• 대한전기학회논문지
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• 제37권1호
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• pp.25-32
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• 1988

In this paper, a new method for reducing harmonics in input AC line currents of converter is presented, which is due mainly to the equipment of 2-4 switching taps on interphase reactor. When this method is applicable to conventional 12 pulse converter, the 24 pulse converter, the 24 pulse or 48 pulse converter is controlled by firing angles. The former is performe in 2 tap method when less than 15 degrees, and the letter in 4tap method when more than 15 degrees. Therefore, the proposed method has the advantages of reducing harmonics in full range of control angle and comparison with the conventional 3 tap method. We proved the validity of that theoretically and experimentally.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2000년도 추계학술대회 논문집
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• pp.157-161
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• 2000

Blue phosphor of Ba-Mg-Al-O:Eu$^{2+}$ phase was fabricated by conventional firing techniques under reducing atmosphere and its photoluminescence properties are studied with varying Eu concentration and phost-annealing temperature under air atmosphere. This phosphors were well crystallized with particle size in the range of 3~5um and emitted a blue light at a dominent wavelength 450nm for 254nm UV irradiation. The concentration quenching wit Eu$^{2+}$ was that with increasing Eu concentration the energy transfer between the activator ions steadily improves, so that the excitation energy is transported over larger distances through the lattice before luminescence can occur. Thermal quenching also occurred in this phosphor means that in a host lattice with the $\beta$-alumina structure the bond of an Eu$^{2+}$ ion with the nearest-neighbour oxygen ion is much stronger than in a lattice with the magnetoplumbite structure.cture.

• 한국군사과학기술학회지
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• 제16권6호
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• pp.752-761
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• 2013

A new gun fire control system has been developed for the Korean next generation frigate class. The engineering requirement was far more tightened than the PKG-A class for the firing range availability and gun control function since 5 inch gun is adopted for the new ship. We mention about the principal technologies required to build a generic gun fire control system and proposed methods for the new gun fire control system. The new system has been designed based on the proposed methods in order to satisfy the requirement and functionality has been proved to be acceptable through the sea trial by Korean navy.

• 센서학회지
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• 제28권5호
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• pp.318-322
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• 2019

In shooting training, an impact point identification system that uses the impact wave of the bullet to check the impact point in the target plate has been recently used. Acoustic sensors used in these systems must be able to detect shock waves of high sound pressure levels and be both waterproof and dustproof for rainy weather and dusty environments, respectively. In this study, membranes with excellent waterproof, dustproof, and sound transmitting characteristics were selected through a characteristics test; a protection cap was installed to install the selected materials. After coupling the produced protection cap to the acoustic sensor housing, the sensitivity and phase characteristics of the acoustic sensor were checked. Through the waterproof and dustproof test, the performances of its sensitivity and phase characteristics were confirmed. Finally, the normal shockwave of a 5.56 mm diameter bullet was measured using a shockwave detection signal collecting plate equipped with a prototype of the acoustic sensor at a 100 m firing range.