• Journal of the Korean Magnetics Society
• /
• v.26 no.1
• /
• pp.7-12
• /
• 2016

Effects of annealing of the gas-atomized Fe-9%Si-2%Cr powder which is suitable for high frequency application in mobile devices because of its high electrical resistivity were studied with an emphasis on the order-disorder phase transition. The formation of B2 ordered phase could not be suppressed during atomization process. When the powder was annealed at a temperature higher than $550^{\circ}C$ the peak diffracted from $DO_3$ phase could be detected. With increasing annealing temperature lattice parameter and coercivity decreased. An interesting phenomenon was an abrupt increment of coercivity in the powder annealed at $450^{\circ}C$. Highest permeability could be shown in the powder annealed at a relative low temperature of $150^{\circ}C$ and then the permeability decreased with annealing temperature. The above-mentioned results could be successfully explained by both the formation of $DO_3$ ordered phases and the change of electrical resistivity of the Fe-Si-Cr powder which was also originated from the phase transition.

• Journal of Korean Society of Water and Wastewater
• /
• v.20 no.4
• /
• pp.519-526
• /
• 2006

In this study, the major operating factors in SND(simultaneous nitrification and denitrification) using bioreactor packed with submerged cilia media and granular sulfur such as variation of nitrification rate, organic matter removal efficiency and denitrification efficiency in different DO concentration were mainly evaluated. Synthetic wastewater and actual sewage were used as influent wastewater. Experiment with synthetic wastewater as influent wastewater was divided into three phases with the adjustment of DO concentration. As the results, nitrification efficiency and T-N removal efficiency in the Phase 3(DO 1.0~2.0 mg/L) were 99% and 52.3%, which is significantly greater than those in other two phases. Also, loading rate and denitrification efficiency of SCPGS(Submerged Cilia media Packed with Granular Sulfur) were calculated as $0.44kg\;NO_3^--N/m^3-day$ and 50%, respectively. On the other hand, nitrification rate was decreased from 99% to 64% according to the DO concentration with the variation from 3.0~3.5 mg/L(phase1) to 0.4~0.6mg/L(phase2). Although the nitrification rate was decreased in 64% according to the variation of the DO concentration, T-N removal rate was rapidly increased to 49% by increasing of the denitrification efficiency. Experiment with actual sewage as influent wastewater was carried out to evaluate efficiency of SCPGS in real operation condition of full-scale sewage water treatment plant. At the time, T-N removal rate in this experiment and full-scale wastewater treatment plants were given by 43% and 20%, respectively. The above results indicate that SCPGS can be used as an advanced treatment process for economical efficiency considered.

• Journal of Korean Academy of Nursing
• /
• v.50 no.4
• /
• pp.583-598
• /
• 2020

Purpose: This study was to investigate the operational status of the midwifery birthing centers (MBCs) and midwives' job status (Phase 1) and to develop midwifery practice guidelines (MPG) (Phase 2) in Korea. Methods: In the first phase, the subjects were 15 midwives who operated 11 of 14 MBCs that were opened as of August 2018. The questionnaire consisted of items to measure the operational status of the MBC and midwives' job status. In the second phase, the MPG was developed from literature review, interviews with five midwives opening their MBCs, surveys with 74 midwives, and a validity evaluation conducted by seven experts. Results: The distribution of operating MBCs was five in Gyunggi-do, two each in Seoul and Incheon, one each in Busan, Chungcheongbuk-do, Gyeongsangbuk-do, Gyeongsangnam-do and Jeju-do. The mean age of midwives was 54.3 and all were female. In 2017, a total of 762 births including 81 homebirths were performed by midwives. The job performance was highest in the order of neonatal care 3.81, childbirth care 3.56, and postpartal care 3.53, respectively. The MPG included seven areas of prenatal care, childbirth care, postpartal care, neonatal care, primary health care, law/ethics, and administration, with 56 tasks and 166 task elements. Conclusion: This study provides the valid basic data for the operational status of the MBC and the midwives' job status. The MPG describes the midwife's job and may be used as basic data for preparing policies for the development of midwifery practice in Korea.

• Proceedings of the KIPE Conference
• /
• 2014.07a
• /
• pp.498-499
• /
• 2014

본 논문에서는 3상 PWM 옵셋전압방식을 응용하여 2상 인버터에 대한 PWM 제어방식을 확립하였다. 또한 기존의 3상 PWM 인버터 옵셋전압방식과의 최대 전압영역과 비교 분석하였다.

• Korean Journal of Remote Sensing
• /
• v.25 no.3
• /
• pp.255-261
• /
• 2009

A new polarimetric SAR image classification technique based on the degree of polarization (DoP) and the co-polarized phase-difference (CPD) is presented in this paper. Since the DoP and the CPD of a scattered wave provide information on the randomness of the scattering and the type of scattering mechanisms, at first, the statistics of the DoP and CPD are examined with measured polarimetric SAR image data. Then, a DoP-CPD diagram with appropriate boundaries between six different classes is developed based on the SAR image. The classification technique is verified using the JPL AirSAR and ALOS PALSAR polarimetric data. The technique may have capability to classify an SAR image into six major classes; a bare surface, a village, a crown-layer short vegetation canopy, a trunk-layer short vegetation canopy, a crown-layer forest, and a trunk-dominated forest.

• Korean Journal of Metals and Materials
• /
• v.49 no.2
• /
• pp.145-152
• /
• 2011

Mechanical and property corrosion resistance of Mg-Zn-Y alloys with an atomic ratio of Zn/Y of 6.8 are investigated using optical microscopy, scanning electron microscopy, transmission electron microscopy, uniaxial tensile test and corrosion test with immersion and dynamic potentiometric tests. The alloys showed an in-situ composite microstructure consisting of ${\alpha}$-Mg and icosahedral phase (I-phase) as a strengthening phase. As the volume fraction of the I-phase increases, the yield and tensile strengths of the alloys increase while maintaining large elongation (26~30%), indicating that I-phase is effective for strengthening and forms a stable interface with surrounding ${\alpha}$-Mg matrix. The presence of I-phase having higher corrosion potential than ${\alpha}$-Mg, decreased the corrosion rate of the cast alloy up to I-phase volume fraction of 3.7%. However further increase in the volume fraction of the I-phase deteriorates the corrosion resistance due to enhanced internal galvanic corrosion cell between ${\alpha}$-Mg and I-phase.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.22 no.3
• /
• pp.684-687
• /
• 1998

The biggest problem common on to all forms of Phase Shift Interferometer is unwrapping the phase. Simple phase unwrapping algorithms assume that every pixel is within radians of its neighbors. If this is true, any reasonable algorithm will return the correct unwrapped phase. If not, correct unwrapped phase will not be obtained. In rough surface, frequently, neighboring pixels have phase steps greater than. This paper proposes the new method which makes phase steps smaller than by sub-pixel movement.

• Proceedings of the KIEE Conference
• /
• 1998.11b
• /
• pp.478-480
• /
• 1998

We develops a simulator to evaluate the performance of the autosyncronizer. The autosyncronizer is used to automatically syncronize magnitude, frequency, and phase of 3 phase signals of generator with respect to those of the utility grid. This autosyncronizer needs to be evaluated its performance to prevent malfunctions. To do this, 3 phase signals of generator and the utility grid are simulated and signals of the generator should be changed by ouput of the autosyncronizer with high precision. In this paper, we uses TMS320C31 to generate high precision sinusoidal 3 phase signals using Table Lookup method. In this process, it is very desirable to control magnitude, frequency, and phase of the signal with high precision and this is achieved by appropriate interpolation method. The resulted signal is well controlled and has low THD and could be used to evaluate the performance of the autosyncronizer.

• The Transactions of the Korean Institute of Power Electronics
• /
• v.10 no.4
• /
• pp.339-346
• /
• 2005

It is complex to realize the reference voltage vector by the space vector PWM method in three-leg two-phase inverter In this paper a new PWM technique for three-leg two-phase inverter fed two-phase induction motor is poroposed assuming that three-leg two-phase inverter is equivalent circuit for 'four-leg two-phase inverter with the connected two windings'. From assumption, six sectors are decreased to four sectors, and simple sinusoidal PWM method instead of SVPWM is applied to three-leg two-phase inverter. Also, the switching pattern to determine the switching periods at each sector is proposed. Practical verification of theoretical predictions is presented to confirm the capabilities of the new techniques.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
• /
• 2004.05a
• /
• pp.43-47
• /
• 2004

Most of LV customer has been composed the 3-phase four wire system distribution system which is supplying simultaneously at the 1-phase & 3-phase load. In this system, the composition of the power apparatus system is simple rather than conventional separation mode of the 1-phase & 3-phase, But due to uneven load unbalance or unclean power quality, various kinds such as do-rating or power losses become an issue. In this paper, we measured and analyzed voltage and current waveform in the field, compared with internationally allowable voltage unbalance limits.