• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.42 no.7
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• pp.552-560
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• 2014

Pulse Detonation Engine(PDE) has been investigated as a next generation propulsion system with the advantages of the higher thermal efficiency by the compression effect and the wide operation ranges from zero speed at ground. In the present study, an efficient theoretical PDE performance prediction program was developed for realistic propellants based on the Endo's theory combining the Chapman-Jouguet detonation theory and expansion process of burnt gas in a constant area tube. The program was validated through the comparison with the experimental data obtained by a ballistic pendulum measurement. PDE performance analyses were carried out for various hydrocarbon fuels and oxidizer compositions by changing the mixture equivalence ratio and initial conditions. Theoretical PDE performance database could be established as a result of the analyses.

• Journal of Radiation Protection and Research
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• v.20 no.2
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• pp.85-95
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• 1995

Radiation measuring system using wireless communication method with single channel has been diveloped and tested. In this system, radiation signals from GM tube are transformed into digital pulses in pulse processing circuit and modulated in FSK (frequency shift keying) circuit for digital communication and then wirelessly transmitted to a receiving unit. The digital pulses received are then demodulated in FSK circuit and converted into radiation dose/dose rate in the data acquisition unit to display on the screen of a personal computer. The performance of this system was evaluated by using both a pulse generator and a standard radiation source(Cs-137). In both cases, digital pulses with 5V were observed in pulse processing circuit without distortion of their shape through wireless communication system. The experimental results of radiation measurement by this system after several test-irradiation of GM detector to a standard radiation source(Cs-137), showed good agreement with irradiation dose rate within 10% difference, and proved that this system could be effectively utillized as radiation measuring instrument. It is expected that this wireless radiation measuring system developed for the first time in Korea, can be used as a radiation monitor as well as a personal dosimeter if we can further improve this system to adopt wireless multichannel communication system.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.08a
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• pp.176.2-176.2
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• 2013

Property of optical diagnostics for pulse-discharged plasma in liquid and its biological applications to proteins are investigated by making use of high voltage Marx generator. The Marx generator has been consisted of 5 stages, where each charging capacitor is 0.5 ${\mu}F$, to generate a high voltage pulse with rising time of $1{\mu}s$. We have applied an input voltage of 6 kV to the each capacitor of 0.5 ${\mu}F$. High voltage pulsed plasma has been generated inside a polycarbonate tube by a single-shot operation, where the breakdown voltage is measured to be 7 kV, current of 1.2 kA, and pulse width of ~ 1 ${\mu}s$ between the two electrodes of anode-cathode whose material is made of tungsten pin, which are immersed into the liquids. We have investigated the emitted hydrogen lines for optical diagnostics of high voltage pulsed plasma. The emission line of 656.3 nm from $H-{\alpha}$ and 486.1 nm from $H-{\beta}$ have been measured by a monochromator. If we assumed that the focused plasma regions satisfy the local thermodynamic equilibrium conditions, the electron temperature and density of the high voltage pulsed plasma in liquid could be obtained by the Stark broadening of optical emission spectroscopy. For the investigation of the influence of pulsed plasma on biological proteins, we have exposed it onto the proteins such as hemoglobin and myoglobin. The structural changes in these proteins and their analysis have also been obtained by circular dichroism (CD) and ultraviolet (UV) visible spectroscopy.

• Nuclear Engineering and Technology
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• v.55 no.7
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• pp.2621-2627
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• 2023

In Experimental Advanced Superconducting Tokamak (EAST) experiments, to achieve long pulse and high-power ICRH system operation, a new kind of ICRH antenna has been designed. One of the most critical factors in limiting the operation of long pulse and high power is the intense heat load in the front face of the ICRH antenna, especially the Faraday Screen (FS). Therefore, the cooling channels of FS need to be designed. According to thermal-hydraulic analysis, the FS tubes are divided into several groups to achieve more excellent water cooling capability. The number of series and parallel tubes in one group is chosen as six. This antenna went into service in the spring of 2021, and it is delightful that the temperature distribution of the FS tube is below 400 ℃ in 14.5 s and 1.8 MW ICRH system operation. However, the active water-cooling design was not carried out on the upper and lower plates of FS, which led to severe ablations on that region under long pulse and high power operation, and the temperature is up to 800. Therefore, the upper and lower side plates of the FS were designed with water cooling based on thermal-hydraulic analysis. During the 2022 winter experiments, the temperature of ICRH antenna FS was lower than 400 in the pulse of 200s and the power of 1 MW operation.

• Journal of the Korean Vacuum Society
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• v.17 no.6
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• pp.538-543
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• 2008

Recently a nano-scale diamond is possible to manufacture forms of powder(below 100 nm) by new processing of explosion or deposition method. Using a sintering of nano-scale diamond is possible to manufacture of grinding tools. We have need of a processing development of coated uniformly inorganic to prevent an abnormal grain growth of nano-crystal and bonding obstacle caused by sintering process. This paper, in order to improve the sintering property of nano-scale diamond, we coated ZnO thin films(thickness: $20{\sim}30\;nm$) in a vacuum by ALD(atomic layer deposition) Economically, in order to deposit ZnO all over the surface of nano-scale diamond powder, we used a new modified fluidized bed processing replaced mechanical vibration effect or fluidized bed reactor which utilized diamond floating owing to pressure of pulse(or purge) processing after inserted diamond powders in quartz tube(L: 20 mm) then closed quartz tube by porosity glass filter. We deposited ZnO thin films by ALD in closed both sides of quartz tube by porosity glass filter by ALD(precursor: DEZn($C_4H_{10}Zn$), reaction gas: $H_2O$) at $10^{\circ}C$(in canister). Processing procedure and injection time of reaction materials set up DEZn pulse-0.1 sec, DEZn purge-20 sec, $H_2O$ pulse-0.1 sec, $H_2O$ purge-40 sec and we put in operation repetitive 100 cycles(1 cycle is 4 steps) We confirmed microstructure of diamond powder and diamond powder doped ZnO thin film by TEM(transmission electron microscope) Through TEM analysis, we confirmed that diamond powder diameter was some $70{\sim}120\;nm$ and shape was tetragonal, hexagonal, etc before ALD. We confirmed that diameter of diamond powders doped ZnO thin film was some $70{\sim}120\;nm$ and uniform ZnO(thickness: $20{\sim}30\;nm$) thin film was successfully deposited on diamond powder surface according to brightness difference between diamond powder and ZnO.

• Korean Journal of Materials Research
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• v.16 no.3
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• pp.173-177
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• 2006

Porous surfaced Ti implant compacts were fabricated by electro-discharging-sintering (EDS) of atomized spherical Ti powders. Powders of $50-100{\mu}m$ in diameter were vibratarily settled into a quarts tube and subject to a high voltage and high density current pulse in Ar atmosphere. Single pulse of 0.7 to 2.0 kJ/0.7 gpowder, from 150, 300, and $450{\mu}F$ capacitors was applied in less than $400{\mu}sec$ to produce twelve different porous-surfaced Ti implant compacts. The solid core formed in the center of the compact shows similar microstructure of cp Ti which was annealed and quenched in water. Hardness value at the solid core was much higher than that at the particle interface and particles in the porous layer, which can be attributed to both heat treatment and work hardening effects induced by EDS. Compression tests were made to evaluate the mechanical properties of the EDS compacts. The compressive yield strength was in a range of 12 to 304MPa which significantly depends on input energy. Selected porous-surfaced Ti-6Al-4V dental implant compacts with a solid core have much higher compressive strengths compared to the human teeth and sintered Ti dental implants fabricated by conventional sintering process.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.32 no.5
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• pp.164-169
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• 1983

A method to control the luminous colour of a gaseous discharge tube has been investigated by using the saw-tooth wave of which rise-time was controlled by an electronic circuit. The luminous colour of a Ne - Hg lamp was changed from red to blue continuously and vice versa, and it's luminous characteristics are as follows: (a) With D.C. potentials, it showed blue colour and the relative intensity of the colour is increased first and saturated at about 17 mA as the discharge current is increased. (b) When the rise-time of the saw-tooth wave is about 10 $\mu\textrm{s}$, the red colour which is caused by Ne - excitation is dominant, and when about 200 $\mu\textrm{s}$, only the blue colour which is caused by Hg - excitation is shown. (c) With saw-tooth pulse, the relative intensity of blue is increased similarly as that with D.C. potential as the current peak of each pulse is increased, while that of red is increasing continuously and it's intensity shows about twice than blue. (d) The spectrum of red colour contains Ne - excitation lines and Hg - blue lines, but the apparent luminous colour is red because Ne - red lines are more plenty than Hg-blue lines. The spectrum of blue colour presents only Hg-blre lines.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2012.10a
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• pp.437-444
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• 2012

In this paper, the measurement method of the decoupling performance of a underwater decoupling material is studied. First, the simple vibro-acoustic coupled model of a multi-layered underwater decoupling material attached to a plate is analytically derived using impedance transfer matrix. Two test methods are introduced using the theoretical expression of the simple model. One is based on the ratio of the plate vibration and the radiated pressure under impact excitation of the plate. The other is based on the reciprocity theorem and uses the ratio of the incident pressure and the plate vibration under projector excitation in water. Some measurements are carried out according to the test methods using a pulse tube. The test results show the advantages and disadvantages of two methods. It is also shown that the combination of impact and projector excitation methods may be a useful tool to evaluate the performance of a underwater decoupling material.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.18 no.6
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• pp.652-657
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• 2009

MPW(Magnetic Pulse Welding) is a technologies for welding of metals by means of repulsive force on account of the interaction between electro-magnetic field of coil and current induced in outer pipe. These MPW is one of the most useful welding process of welding ability of the dissimilar metal in which cylindrical materials, such as pipe, tube. As the quality of a weld joint is strongly influenced by process parameters during the welding process and the success of the welding to evaluated according to the leakage pressure. Generally, the process parameters is magnetic pressure, the gap between outer pipe and inner pipe, and the ratio of thickness to diameter of pipe(D/T) in MPW. Therefore, the goal of this study was to explain the effect of parameters on the weld joint leakage pressure. For these purposes, FFD(Fractional Factorial Design) were used for the experiment. The measured data were analyzed by regression analysis and verification experiments with random condition were conducted to confirm the suggested experimental model.

• Journal of Radiation Protection and Research
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• v.42 no.1
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• pp.69-76
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• 2017

Background: Time-resolved optically stimulated luminescence (TR-OSL) is a very useful method for calculating the lifetimes of crystalline quartz and feldspar. Materials and Methods: A compact TR-OSL system was developed, comprising a heater assembly manufactured using Kanthal wire, 2 powerful blue light-emitting diodes (LED, LXHL-PB02) for optical stimulation equipped with VIS liquid light guides, and a photomultiplier tube combined with an optical filter for luminescence detection. A pulse generated from the data acquisition board (NI PCI 6250) was used to initiate on/off signals in LED and TR-OSL measurements. Results and Discussion: The TR-OSL and background signals measured using this TR-OSL system using quartz samples were very similar to those reported in a previous study. Additionally, the lifetimes of the build-up and TR-OSL signals were calculated as $27.4{\pm}2.2{\mu}s$ and $30.3{\pm}0.6{\mu}s$, respectively, in good agreement with the findings of a previous study. Conclusion: It was concluded that the developed TR-OSL system was very reliable for TR-OSL signal measurements and lifetime calculations.