• The Transactions of the Korean Institute of Power Electronics
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• v.3 no.4
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• pp.273-279
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• 1998

In this paper, the proposed charging system consists of step charging mode and time-sharing equalization charging mode. As $\Delta$V=O point is detected, the proposed cut-off method will selectively cut off the only battery to reach the $\Delta$V=O point, preventing serial-connected batteries from undercharging. In the start of each step, the equalization charging mode is performed to reduce the capacity difference among the batteries. Though it is added to simple circuit for selective cut-off, comparing with recently used step-charging method, this system can improve the life cycle of battery and charging efficiency, and be also very effective for preventing the batteries from overcharging and undercharging.

• Nuclear Engineering and Technology
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• v.51 no.5
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• pp.1195-1208
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• 2019

This paper introduces a new two-step procedure for PWR depletion analyses. This procedure adopts the albedo-corrected parameterized equivalence constants (APEC) method to correct the lattice-based raw cross sections (XSs) and discontinuity factors (DFs) by accounting for neutron leakage. The intrinsic limitations of the conventional two-step methods are discussed by analyzing a 2-dimensional SMR with the commercial DeCART2D/MASTER code system. For a full-scope development of the APEC correction, the MASTER nodal code was modified so that the group constants can be corrected in the middle of a microscopic core depletion. The basic APEC methodology is described and color-set problems are defined to determine the APEC functions for burnup-dependent XS and DF corrections. Then the new two-step method was applied to depletion analyses of the SMR without thermal feedback, and its validity was evaluated in terms of being able to predict accurately the reactor eigenvalue and nodal power profile. In addition, four variants of the original SMR core were also analyzed for a further evaluation of the APEC-assisted depletion. In this work, several combinations of the burnup-dependent and -independent XS and DF corrections were also considered. The results show that the APEC method could enhance the nodal equivalence significantly with inexpensive additional costs.

• The Transactions of the Korean Institute of Power Electronics
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• v.4 no.6
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• pp.547-553
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• 1999

A new multi-step voltage source inverter is proposed in this paper. The proposed scheme is composed of t the double-connected 12-step inverter with an auxiliary circuit. The auxiliary circuit includes two voltage d dividing capacitors, two switching devices and a low KV A autotransformer. The resultant system is shown to b be a 24-step inverter suitable for medium power level SVC applications in which the PWM method can not be e employed. A 36-step operation can also be 이)tained by the addition of a bidirectional switch to the ProlXlsed I inverter. The design parameters are derived from the analysis of voltages and currents by means of switching f functions. The validity of the proposed scheme is confirmed by the simulated and experimental results.

• Proceedings of the KIPE Conference
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• 1998.10a
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• pp.97-100
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• 1998

In this paper, micro step driving method is used for the high performance motion control and low vibration and low noise in an X-Y axis soldering machine for factory automation. The improvement of the electrical and mechanical driving characteristic of a stepping motor is achieved by applying microstep driver.

• Proceedings of the KIEE Conference
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• 2005.07b
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• pp.1147-1149
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• 2005

Time switch is widely used to reduce the energy loss by selecting the duration of daily-based operating pattern for the electrical apparatus. Driving force of the time switch is the single-phase step motor which has the starting torque due to the asymmetrical airgap. Cogging and total torque of the tapered-airgap motor is analyzed by finite element method.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2007.05a
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• pp.332-335
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• 2007

The superplastic forming (SPF) has been widely used in the automotive and aerospace industry because it has great advantages to produce very light and strong components. Finite element method (FEM) is used to model the process of superplastic forming/diffusion bonding (SPF/DB), to predict the pressure-time curve and to analyze the process parameter. In this study, process design of SPF/DB is carried out a 3-sheet sandwich part. SPF/DB process with pressure control was analyzed by using finite element method. For obtaining proper shape, step-by-step pressurization is proposed. The first step of SPD/DB process is obtained by applying of pressure in patches. From the next step it applied pressure to all regions (between inner sheets, between inner and face sheets). By using the proposed pressurization scheme, deficit in part shape is found to be eliminated.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.59 no.3
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• pp.492-498
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• 2010

Since it is almost impossible to train the dispatchers with real power system, the dispatcher training simulator(DTS) is used for the training. Among various components of the DTS, the power system model(PSM) emulates the dynamic behavior of the power system to calculate the frequency and voltage. The frequency is calculated from various parameters such as mechanical power of power plants, load, inertia, and the damping of the power system. In the PSM, the power plants are modeled as differential equations, so the mechanical power of the power plants are calculated by the numerical methods. Conventionally, the fixed step-size algorithm has been used in the PSM, however it has some drawbacks. This paper develops the prototype PSM using the Matlab, and analyzes the problems of the fixed step-size algorithm by comparing the results with those of PSCAD simulation. In order to overcome the limitations, this paper proposes a modified frequency calculation method using the adaptive step-size algorithm. From the simulation using the proposed method, it is verified that the accuracy of frequency calculation increases substantially while the simulation time is not greatly increased.

• Journal of Korea Multimedia Society
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• v.14 no.8
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• pp.1000-1009
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• 2011

Image interpolation is a technique which estimates the non-allocated pixel values on image scale-transform. It requires minimum computational complexity and minimum image quality degradation on the interpolated resultant images. In this paper we propose an image interpolation method using iterative error estimation. The proposed method consists of the following five steps: loss-information computational step, loss-information estimation step, loss-information application step, error computation step, and error application step. The experimental results obtained show that the average PSNR is increased by 3.3dB, subjective image quality is enhanced and the minimum computation complexity is decreased by 83%. The proposed image interpolation algorithm may be helpful in various applications such as image reconstruction and enlargement.

• Journal of Life Science
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• v.31 no.4
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• pp.385-388
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• 2021

Anther cultivation for crop breeding is a method of rapid production of homozygosities by greatly reducing the time required for at least six generations to develop new varieties using conventional breeding methods. This technique of producing anther culture provides an opportunity to obtain more green plants from a methodological point of view, and the techniques that save time and effort in anther culture are also important because they increase the efficiency of culture. This study compared the callus induction rate and green plant regeneration rate of a one-step and a two-step culture that differ in their culture media and culture methods. One-step culture allows callus induction and plant regeneration in one medium, whereas two-step culture requires induction and plant regeneration in two different media. In this study, we compared the callus induction and plant regeneration rates of rice anthers as one-step and two-step cultures. The callus formation rate was 13.0% for one-step cultures and 8.6% for two-step cultures, so the rate was 4.4% higher for one-step cultures than for two-step cultures. The plant regeneration rate was 1.0% in one-step cultures and 3.0% in two-step cultures, so the regeneration rate was three times higher for the two-step cultures than for one-step cultures. This suggests that the two-step cultures are more efficient than the one-step cultures for haploid production.

• Korean Journal of Materials Research
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• v.11 no.9
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• pp.769-775
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• 2001

High quality PZT piezoelectric thin films were sputter- deposited on$ RuO_2$/$SiO_2$/Si substrates by using 2-step deposition method. As the first step, PZT seed layers were fabricated at a low temperature($475^{\circ}C$ ) to form a pure perovskite phase by reducing the volatility of Pb oxide. and then, as the second step, the PZT films were deposited at high temperatures ($530^{\circ}C$~$570^{\circ}C$) to reduce the defect density in the films. By this method, the pure perovskite phase was obtained at high deposition temperature range ($530^{\circ}C$~$570^{\circ}C$) and the superior electrical properties of PZT films were obtained on $RuO_2$substrate : 2Pr : 60$\mu$C/$\textrm{cm}^2$, $E_c: 60kV/cm, \;J_t: 10^{-6}A/cm^2\; at\; 250kV/cm$. The residual stress of PZT films fabricated by the 2-step deposition method was tensile and below 150MPa. It was attempted to control the residual stress in the PZT films by applying a negative bias to the substrate. As the amplitude of the substrate bias was increased, the residual tensile stress was slightly decreased, however, the ferroelectric properties of PZT films were degraded by ion bombardment.