• Proceedings of the KIPE Conference
• /
• 2002.07a
• /
• pp.115-118
• /
• 2002

In this paper, a current control method using adjustment of the phase advance angle is proposed. This proposed method improves the torque and speed response characteristic by minizing delay of current at high speed operation, and also make reverse motoring possible. Simulated results prove the effectiveness of the propposed method through comparison with the conventional unipolar PWM method.

• Journal of Korean Academy of Nursing
• /
• v.50 no.5
• /
• pp.714-727
• /
• 2020

Purpose: The aim of this study was to develop a situation-specific theory to explain the disease management experience of patients with asthma. Methods: Twenty participants with asthma were selected using the theoretical sampling method. The data were acquired through in-depth interviews conducted from June to October 2018 and analyzed using the grounded theory approach of Strauss and Corbin. Results: In total, 69 concepts, 30 subcategories, and 13 categories were generated to explain the disease management experience of patients with asthma. The core category of the disease management experience of patients with asthma was 'management of the disease to prevent aggravation of symptoms over the lifetime'. The disease management process of asthma patients included three steps: the 'cognition phase', the 'adjustment phase', and the 'maintenance phase'. However, some patients remained in the 'stagnation phase' of disease management, which represents the result of the continual pursuit of risky health behavior. There were three types of disease management experiences among patients with asthma: 'self-managing', 'partially self-managing', and 'avoidant'. Conclusion: This study shows that patients with asthma must lead their disease management process to prevent exacerbation of their symptoms. It is imperative to develop nursing strategies and establish policies for effective disease management of patients with asthma based on their individual disease management processes and types.

• Current Optics and Photonics
• /
• v.2 no.5
• /
• pp.474-481
• /
• 2018

We propose a polarization phase-shifting technique to investigate the thickness of $Ta_2O_5$ thin films deposited on BK7 substrates, using a modified Sagnac interferometer. Incident light is split by a polarizing beam splitter into two orthogonal linearly polarized beams traveling in opposite directions, and a quarter-wave plate is inserted into the common path to create an unbalanced phase condition. The linearly polarized light beams are transformed into two circularly polarized beams by transmission through a quarter-wave plate placed at the output of the interferometer. The proposed setup, therefore, yields rotating polarized light that can be used to extract a relative phase via the self-reference system. A thin-film sample inserted into the cyclic path modifies the output signal, in terms of the phase retardation. This technique utilizes three phase-shifted intensities to evaluate the phase retardation via simple signal processing, without manual adjustment of the output polarizer, which subsequently allows the thin film's thickness to be determined. Experimental results show that the thicknesses obtained from the proposed setup are in good agreement with those acquired by a field-emission scanning electron microscope and a spectroscopic ellipsometer. Thus, the proposed interferometric arrangement can be utilized reliably for non-contact thickness measurements of transparent thin films and characterization of optical devices.

• Communications for Statistical Applications and Methods
• /
• v.27 no.1
• /
• pp.65-77
• /
• 2020

Geometric charts are effective in monitoring the fraction nonconforming in high-quality processes. The in-control fraction nonconforming is unknown in most actual processes; therefore, it should be estimated using the Phase I sample. However, if the Phase I sample size is small the practitioner may not achieve the desired in-control performance because estimation errors can occur when the parameters are estimated. Therefore, in this paper, we adjust the control limits of geometric charts with the bootstrap algorithm to improve the in-control performance of charts with smaller sample sizes. The simulation results show that the adjustment with the bootstrap algorithm improves the in-control performance of geometric charts by controlling the probability that the in-control average run length has a value greater than the desired one. The out-of-control performance of geometric charts with adjusted limits is also discussed.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.26 no.3
• /
• pp.97-102
• /
• 2014

For an analysis of the horizontal-type geothermal heat exchanger system, an understanding of the ground temperature distributions is required in order to predict system performance. Because it is difficult to decide on the underground temperature due to the adjustment of its temperature cycle, numerous calculations are required in order to decide on the temperature cycle. In this paper, Buggs formula is utilized to decide a phase shift for outdoor temperature and ground surface temperature, which are obtained from Korea Meteorological Administration. Overall, the underground temperature distribution in the Changwon region is predicted as $10.5^{\circ}C{\sim}20.3^{\circ}C$ at a depth of 3 m.

• Proceedings of the Korea Electromagnetic Engineering Society Conference
• /
• 2003.11a
• /
• pp.224-228
• /
• 2003

In this paper, for phase lock loop(PLL) synthesizer, we introduce a novel but simple and low cost frequency modulation(FM) circuit of a flat peak frequency deviation for modulation signal from high to very low frequency penetrating into the loop-bandwidth of PLL. The FM circuit was basically designed to compensate an amount of feedback of the loop filter in PLL. The circuit also includes the capability of the adjustment of peak frequency deviation and blocking the interference with the loop filter. The designed circuit was successfully implemented and showed the flat frequency deviation as expected in the design.

• Journal of the Optical Society of Korea
• /
• v.8 no.1
• /
• pp.13-16
• /
• 2004

A widely tunable SG-DFB (Sampled Grating Distributed Feedback) laser diode is proposed and its feasibility is confirmed through simulation. The new SG-DFB laser diode is composed of a pair of sampled gratings, some parts of which are gain sections and the other parts of which are phase control sections. It is shown that a few tens of nanometers can be tuned through the adjustment of two currents into the phase control sections. Higher output power is expected compared with a SG-DBR laser diode with similar parameters. The dynamic single mode operation is also observed in the time-domain simulation.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.28 no.9
• /
• pp.740-748
• /
• 2017

In this paper, we compared performance of conventional inverse synthetic aperture radar(ISAR) imaging methods for maritime target with real data measured by X-band radar. Following conventional approaches were used for performance comparisons: 1) range instantaneous Doppler(RID) method, 2) range Doppler(RD) processing with phase adjustment, and 3) RD processing with prominent point processing(PPP). It is noteworthy that the comparison results have significance of providing basic concept to establish ISAR imaging frame work for maritime targets.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• v.17 no.7
• /
• pp.1823-1840
• /
• 2023

In order to improve spectral efficiency and reduce power consumption for reconfigurable intelligent surface (RIS) assisted wireless communication systems, a joint design considering irregular RIS topology, RIS on-off switch, power allocation and phase adjustment is investigated in this paper. Firstly, a multi-dimensional variable joint optimization problem is established under multiple constraints, such as the minimum data requirement and power constraints, with the goal of maximizing the system energy efficiency. However, the proposed optimization problem is hard to be resolved due to its property of nonlinear nonconvex integer programming. Then, to tackle this issue, the problem is decomposed into four sub-problems: topology design, phase shift adjustment, power allocation and switch selection. In terms of topology design, Tabu search algorithm is introduced to select the components that play the main role. For RIS switch selection, greedy algorithm is used to turn off the RISs that play the secondary role. Finally, an iterative optimization algorithm with high data-rate and low power consumption is proposed. The simulation results show that the performance of the irregular RIS aided system with topology design and RIS selection is better than that of the fixed topology and the fix number of RISs. In addition, the proposed joint optimization algorithm can effectively improve the data rate and energy efficiency by changing the propagation environment.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.24 no.10 s.181
• /
• pp.2552-2559
• /
• 2000

Most of ferrous b.c.c weld materials have martensitic transformation during rapid cooling after welding. It is well known that volume expansion due to the phase transformation could influence on the relaxation of welding residual stress. To apply this effect practically, it is necessary to establish a numerical model which is able to estimate the effect of phase transformation on residual stress relaxation quantitatively. For this purpose, the analysis is carried out in two regions, i.e., heating and cooling, because the variation of material properties following a phase transformation in cooling is different in comparison with the case in heating, even at the same temperature. The variation of material properties following phase transformation is considered by the adjustment of specific heat and thermal expansion coefficient, and the distribution of residual stress in analysis is compared with that of experiment by previous study. In this study, simplified numerical procedures considering phase transformation, which based on a commercial finite element package was established through comparing with the experimental data of residual stress distribution by other researcher. To consider the phase transformation effect on residual stress relaxation, the transition of mechanical and thermal property such as thermal expansion coefficient and specific heat capacity was found by try and error method in this analysis. In addition to, since the transformation temperature changes by the kind and control of alloying elements, the steel with many kinds of transformation temperature were selected and the effect of transformation on stress releasement was investigated by the numerical procedures considering phase transformation.