• Nuclear Engineering and Technology
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• v.55 no.4
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• pp.1310-1323
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• 2023

A reactor coolant pump (RCP) is essential for transporting coolant in the primary loop of pressurized water reactors. In the advanced passive reactor, the absence of a long pipeline between the steam generator and RCP serves as a transition section, resulting in a non-uniform flow field at the pump inlet. Therefore, the characteristics of the pump should be investigated under non-uniform flow to determine its influence on the pump. In this study, the pressure pulsation characteristics were examined in the time and frequency domains, and the sources of low-frequency and high-amplitude signals were analyzed using wavelet coherence analysis and numerical simulation. From computational fluid dynamics (CFD) results, non-uniform inflow has a great effect on the flow structures in the pump's inlet. The pressure pulsation in the pump at the rated flow increased by 78-128.7% under the non-uniform inflow condition in comparison with that observed under the uniform inflow condition. Furthermore, a low-frequency signal with a high amplitude was observed, whose energy increased significantly under non-uniform flow. The wavelet coherence and CFD analysis verified that the source of this signal was the low-frequency pulsating vortex under the steam generator.

• Journal of Korea Multimedia Society
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• v.2 no.4
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• pp.409-418
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• 1999

The fractal image compression is based on the self-similarity that some area in an image exhibits a very similar shape with other areas. This compression technique has very long encoding time although it has high compression ratio and fast decompression. To cut-off the encoding time, most researches have restricted the search of domain blocks for a range block. These researches have been mainly focused on the coherence between a domain block and a range block, while they have not utilized the coherence among range blocks well. Therefore, we give an analysis on the coherence among range blocks in order to develope an efficient fractal Image compression algorithm. We analysis the range blocks according to not only measures for defining the range block coherence but also threshold of each measure. If these results are joined in a prior work of other fractal compression algorithms, it will give a great effectiveness in encoding time.

• Journal of the Korean Society of Marine Environment & Safety
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• v.24 no.2
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• pp.188-195
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• 2018

Time series analysis was conducted to identify the factors affecting short-term variation of water temperature in Wando. Spectrum analysis showed that air temperature peaks at diurnal period, while water temperature and tide level peak at both semi-diurnal and diurnal periods. Coherence between water temperature and the tide level presented 0.92 at semi-diurnal period. Numerical experiment were carried out to understand the spatio-temporal distribution of water temperature in the study area. Average water temperature difference between maximum ebb and flood was $0.3^{\circ}C$ in spring tide, but $0.13^{\circ}C$ in neap tide. The reason for the large difference in spring tide is that relatively cold water entered with strong tidal currents at flood tide and flowed out at ebb tide. Water temperature on coasts was higher than out at sea. This is because the depth in the coast is shallower than at sea, and water temperature increases rapidly due to solar radiation.

• The Journal of the Acoustical Society of Korea
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• v.38 no.5
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• pp.494-510
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• 2019

Underwater acoustic communication channel parameters consist of impulse response, delay spreading, scattering function, coherence bandwidth, frequency selective fading, coherence time and time variant magnitude fading statistics on which communication system modem and channel coding are designed. These parameters are influenced by sound velocity profile, platform motion and sea surface roughness in given acoustical oceanography condition. In this paper, channel model based on phasor, channel simulator, measurement and analysis method of channel parameters are given in a fixed source-to-receiver system and the parameters are analyzed using shallow water experimental data. For two different source-to-receiver ranges of 300 m and 600 m, the parameters are characterized by three multipaths such as a direct, a surface reflection path with time variant scattering and a bottom reflection path. The results present a channel modelling method of a fixed source source-to-receiver system, channel parameters measurement and analysis methods and a system design and performance assessment method in shallow water.

• ETRI Journal
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• v.38 no.4
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• pp.634-644
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• 2016

Channel-based radio-frequency fingerprinting such as a channel impulse response (CIR), channel transfer function (CTF), and frequency coherence function (FCF) have been recently proposed to improve the accuracy at the physical layer; however, their empirical performance, advantages, and limitations have not been well reported. This paper provides a comprehensive empirical performance evaluation of RF location fingerprinting, focusing on a comparison of received-signal strength, CIR-, CTF-, and FCF-based fingerprinting using the weighted k-nearest neighbor pattern recognition technique. Frequency domain channel measurements in the IEEE 802.11 band taken on a university campus were used to evaluate the accuracy of the fingerprinting types and their robustness to human-induced motion perturbations of the channel. The localization performance was analyzed, and the results are described using the spatial and temporal radio propagation characteristics. In particular, we introduce the coherence region to explain the spatial properties and investigate the impact of the Doppler spread in time-varying channels on the time coherence of RF fingerprint structures.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.3 no.2
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• pp.103-113
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• 1991

This paper presents a method for estimating the noise source contribution of a pulse combustion burner in a multiple input system where the input sources may be coherent each other. By coherence function method, it is found that the biggest part of the noise source in the pulse combustion burner is generated by the part of the combustion chamber. This analysis is modeled as three input / single output system because the noise generating mechanism of the pulse combustion burner is very complicated. The coherence function method is proved to be useful tool for the identification of noise source. The overall levels of the radiated source pressure by coherence function method are compared with those measured and calculated by the frequency response function approach. The experimental results have shown a good agreement with the results calculated by the coherence function method when the input sources are coherent strongly each other. The estimation of shield effect by FRF method indicates that significant reduction can be achieved in sound radiation if only transmission path generated by the part of combustion chamber is acoustically shield.

• Aerospace Engineering and Technology
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• v.8 no.1
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• pp.132-137
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• 2009

This study has regard to classification by using multi-temporal SAR data. Multi-temporal JERS-1 SAR images are used for extract the land cover information and possibility. So far, land cover information extracted by high resolution aerial photo, satellite images, and field survey. This study developed on multi-temporal land cover status monitoring and coherence information mapping can be processing by L band SAR image. From July, 1997 to October, 1998 JERS SAR images (9 scenes) coherence values are analyzed and then extracted land cover information factors, so on. This technique which forms the basis of what is called SAR Interferometry or InSAR for short has also been employed in spaceborne systems. In such systems the separation of the antennas, called the baseline is obtained by utilizing a single antenna in a repeat pass.

• Research in Community and Public Health Nursing
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• v.31 no.3
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• pp.223-233
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• 2020

Purpose: The purpose of this study was to construct a model that describes the health related quality of life in working women with preschool children and to verify the goodness of fitness of the model. Methods: The data were collected with a structured self-report questionnaire from 483 working women with preschool children. Results: The modified model showed a reasonable fitness to the data. Social support, job satisfaction, parenting stress, sense of coherence and depression accounted for 78% of the health related quality of life in working women with preschool children. Conclusion: This study suggests that the health related quality of life in working women with preschool children can be improved by reducing parenting stress and depression level, and by increasing social support, job satisfaction, and sense of coherence. Depression can also be managed by reducing parenting stress and by increasing job satisfaction and sense of coherence. Based on the results of this study, it is necessary to develop intervention programs to increase the health related quality of life or to decrease depression in working women.

• Asian Pacific Journal of Cancer Prevention
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• v.13 no.4
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• pp.1495-1504
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• 2012

Objective: Improvements in diet can decrease the cancer rates. The aim of the present study was to determine the relationships between self-perception of diet quality and personality, impulsiveness, stress, coping strategy, sense of coherence, self-efficacy, and social support. Methods: This cross-sectional study was conducted using a multiple-stratified random sampling method based on the Korea Census of 2007. In October 2009, investigators conducted 15-minute face-to-face interviews with 1,530 South Korean volunteers who ranged from 30 to 69 years of age without a history of cancer. Results: Respondents were more likely to perceive that they consumed a healthy diet if they were older than 50 years, lived with a partner, had a monthly family income greater than $4,000 USD, had a low perceived risk of cancer, consumed less alcohol, exercised regularly, had a less agreeable or conscientious personality, had low stress levels, had a high sense of coherence or self-efficacy, and had ample social support. Conclusion: Psychosocial factors, such as personality, stress, sense of coherence, self-efficacy, and social support, are associated with the self-perception of diet quality. Analysis of the factors that contribute to a perceived healthy diet could assist with the design of educational campaigns.

• The Korean Journal of Health Service Management
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• v.10 no.4
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• pp.197-212
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• 2016

Objectives : This study develops a salutogenic program and examines its effects on the sense of coherence, acculturative stress, and quality of life of married immigrant women. Methods : The salutogenic program was developed based on Antonovsky's Salutogenic Model, and the study design was a nonequivalent control group pre-post test design. The participants were married immigrant Chinese (n=30) and Vietnamese (n=31) women, who were assigned to either an experimental group (n=29) or a control group (n=32). The data were analyzed using the ${\chi}^2$-test, t-test, Fisher's exact test, and repeated measures ANOVA, and the IBM SPSS for Windows (version 20.0) program was used to perform the analysis. Results : Compared to the control group, the sense of coherence (F=52.05, p <.001) and quality of life (F=6.95, p=.002) were significantly improved in the experimental group, and the acculturative stress (F=24.64, p<.001) in this group significantly decreased after implementing salutogenic program. Conclusions : These findings indicate that a salutogenic program is an effective intervention for married immigrant women. The study suggests that such programs can be applied to married immigrant women at public health or multicultural family support centers to improve their sense of coherence and quality of life.