• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.07a
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• pp.125-129
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• 2004

[ $BaTi_4O_9$ ] thin film were grown on $Pt/Ti/SiO_2/Si$ substrate using rf magnetron sputter, and the microstructure and dielectric properties of the thin films were investigated. For the film grown at $350^{\circ}C$ and rapidly thermal annealed at $900^{\circ}C$, the $BaTi_5O_{11}$ Phase was formed. However, the $BaTi_4O_9$ phase was formed when the growing temperature exceeded $450^{\circ}C$ The dielectric constant of the $BaTi_4O_9$ thin film grown at $550^{\circ}C$ and rapidly thermal annealed at $900^{\circ}C$ was about 40 at low frequency range($100kHz{\sim}1MHz$) and 36 at microwave range($1{\sim}10GHz$) which is very close to that of the bulk $BaTi_4O_9$ phase. The dissipation factor was very low, about 0.005 at low frequency as well as microwave range.

• Journal of Soil and Groundwater Environment
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• v.19 no.3
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• pp.56-65
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• 2014

Contamination of explosive compounds in the soils of military shooting range may pose risks to human and ecosystems. As shooting ranges are located at remote places, active remediation processes with hardwares and equipments are less practical to implement than natural solutions such as bioremediaton. In this study, a series of experiments was conducted to select a suitable carbon source and to optimize dosing rate for the enhanced bioremediation of explosive compounds in surface soils and sediments of shooting ranges with indigenous microorganisms activated by external carbon source. Treatability study using slurry phase reactors showed that the presence of indigenous microbial community capable of explosive compounds degradation in the shooting range soils, and starch was a more effective carbon source than glucose and acetic acid in the removal of TNT. However, at higher starch/soil ratio, i.e., 2.0, the acute toxicity of the liquid phase increased possibly due to transformation products of TNT. RDX degradation by indigenous microorganisms was also stimulated by the addition of starch but the acute toxicity of the liquid phase decreased with the increase of starch/soil ratio. Taken together, the optimum range of starch/soil ratio for the degradation of explosive compounds without significant increase in acute toxicity was found to be 0.2 of starch/soil.

• Journal of Aerospace System Engineering
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• v.15 no.4
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• pp.57-63
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• 2021

The launch vehicle (LV) separation detection interface of the satellite, which is designed to initiate the launch and early operation phase (LEOP) for S-band data transmission and the solar array deployment after the LV separation, is one of the hazard items at the launch site. Therefore, this interface should satisfy the single-fault tolerance requirement for the range safety. In this paper, we discuss the LV separation detection interfaces for two different satellite launch configurations and propose a method to guarantee for the satellite to start the LEOP even under the emergency case such as a partial separation from the LV. Furthermore, the proposed method meets the range safety requirement of the launch site. As this method only changes the external harness configuration of the satellite, it increases the reliability of the satellite early operation without any modification of the existing internal logics to detect the separation event.

• The Korean Journal of Nuclear Medicine
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• v.21 no.2
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• pp.167-174
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• 1987

Among noninvasive approaches for the evaluation of left ventricular performance, radionuclide ventriculography (RVG) has been shown to be of particular values. Phase analysis, recently introduced as more objective means for evaluating the temporal sequence of systolic ventricular wall motion than cine image of RVG comprises a pixel by pixel Fourier transformation of the time activity curve of a multiple gated acquisition equilibrium blood pool study. To examine the regional wall motion of ventricles in myocardial infarctions, we evaluated the phase image and histogram constructed for each ventricle by total phase angle range and full width of half maximum (FWHM). This study consisted of 7 normal subjects and 23 subjects with acute myocardial infarction. Contrast ventriculography and coronary angiography was performed in all partients with myocardial infarction. And we compared the result of phase analysis with cine image of RVG and examined the interrelationship between phase analysis and contrast ventriculography with coronary angiography. The results were as follows; 1) The total phase angle range and FWHM of LV phase histogram in myocardial infarction ($86^{\circ}\;and\;32^{\circ}$, repectively) were wider than those in normal control ($38^{\circ}\;and\;18^{\circ}$, respectively p<0.01). 2) RV phase angle range and FWHM in patients with right coronary artery (RCA) occlusion ($79^{\circ}\;and\;37^{\circ}$, respectively) were wider than those in normal control ($39^{\circ}\;and\;18^{\circ}$, respectively p<0.001) and the patients without RCA occlusion ($52^{\circ}\;and\;19^{\circ}$, respectively p<0.01). 3) Phase analysis was more sensitive (95%) than cine image of RVG (70%) for the detection of regional wall motion abnormality of LV.

• Journal of Power Electronics
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• v.15 no.3
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• pp.634-643
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• 2015

This paper presents a high frequency design approach for improving efficiency over a wide load range in the self-driven phase-shifted full-bridge converters for server power systems. In the proposed approach, a detailed ZVS analysis of the lagging leg switches in both the continuous conduction mode (CCM) and the discontinuous conduction mode (DCM) is presented. The optimum dead time and the determination of the appropriate operation mode are given for high efficiency according to the load conditions. Finally, the optimum operation conditions are defined to achieve a high-efficiency. A laboratory prototype operating at 80 kHz, rated 1 kW (12 V-83.3 A), is built to verify proposed theoretical analysis and evaluations. The experimental results show that the maximum efficiency is achieved as 95% and 83.5% at full load and 5% load conditions, respectively.

• Journal of Power Electronics
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• v.15 no.5
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• pp.1158-1167
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• 2015

In this paper, a new hybrid DC-DC converter is proposed for electric vehicle 3.3 kW on-board battery charger applications, which can be modulated in a phase-shift manner under a fixed frequency or frequency variation. By integrating a half-bridge (HB) LLC series resonant converter (SRC) into the conventional phase-shift full-bridge (PSFB) converter with a full-bridge rectifier, the proposed converter has many advantages such as a full soft-switching range without duty-cycle loss, zero-current-switching operation of the rectifier diodes, minimized circulating current, reduced filter inductor size, and better utilization of transformers than other hybrid dc-dc converters. The feasibility of the proposed converter has been verified by experimental results under an output voltage range of 250-420V dc at 3.3 kW.

• The Transactions of the Korean Institute of Power Electronics
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• v.23 no.4
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• pp.290-293
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• 2018

This paper proposes a new magnetic resonant wireless power transfer system. Two transmitters are arranged to secure a range wider than the existing one-to-one resonance, thereby enhancing the practicality of the system. Two identical transmission units are arranged to strengthen the magnetic field and to subsequently increase the magnitude and distance of the power transmitted to the reception unit. A constant power can be maintained in a wide range through the phase control of different output powers according to the positions of the transmitting and receiving coils. A constant power can also be obtained by transmitting to the receiver. The experiment results show that the proposed method outperforms the conventional method.

• Journal of Pharmaceutical Investigation
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• v.37 no.3
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• pp.187-192
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• 2007

A reversed phase HPLC analysis of atorvastatin (AS) standard solution was performed using diclofenac (DF) as internal standard. Column oven temperature, flow rate and the composition of the mobile phase were varied in order to determine a practical system setup using a C18 column and UV detector. Two C18 columns of different length were compared regarding their influence on the AS peak shape. Based on these preliminary experiments a validation study was performed utilizing a C18 column at $62^{\circ}C$ with a mobile phase consisting of sodium phosphate buffer (0.05 M, pH 4.0), methanol and acetonitrile (40:50:10, v/v/v). The detection limit for AS was $0.1{\mu}g/ml$ and inter- and intra-day calibration curves were linear over a concentration range of $0.2-50{\mu}g/ml$. Accuracy and precision were satisfactory in the AS concentration range of $0.5-50{\mu}g/ml$.

• Korean Journal of Materials Research
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• v.5 no.2
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• pp.232-238
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• 1995

The thermal stress distribution of WC and Ni binder phases In WC-26st.%Ni and WC-6wt.%Ni composites has been investigated over the temperature range 100-900 K using a time-of-flight neutron diffractometer. To determine the stress distribution, the breadths of WC and Ni peaks in the reference powder and the composites were analyzed. The peak breadths were corrected for particle size effect using a procedure based on the integral peak breadth method of particle size-strain analysis. The result shows a broad range of strain, and thus stress, is present in the WC and Ni binder phases of the composites. The strain distribution of both phases broadens as the temperature decreases, and some fraction of total strain distribution of the WC phase remains tensile regardless of the temperature. The strain distribution of the WC phase broadens as the binder content increases, and that of Ni binder phase broadens as the binder content decreases, which means the strain distribution broadens as the absolute value of residual stress increase.

• Journal of the Korea Institute of Military Science and Technology
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• v.3 no.1
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• pp.85-91
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• 2000

Underwater sensor accuracy test which measures the detection range and bearing accuracies of sonar simulates sonar transmitting ping and underwater radiating noise of target vessels. In this test, because the position of sonar target is the reference position of test, the sonar target position should be precisely estimated. Hence, this paper suggests to apply USBL algorithm which adopts cross phase spectrum of received sensor signals, and presents its performance by range and bearing estimation simulations. As a result of simulations, suggested algorithm shows good accuracy for underwater sensor accuracy test near 5㏈ SNR.