• Wind and Structures
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• v.20 no.5
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• pp.661-682
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• 2015

This study investigates the use of time-frequency coherence analysis for detecting and evaluating coherent "structures" of surface pressures and wind turbulence components, simultaneously on the time-frequency plane. The continuous wavelet transform-based coherence is employed in this time-frequency examination since it enables multi-resolution analysis of non-stationary signals. The wavelet coherence quantity is used to identify highly coherent "events" and the "coherent structure" of both wind turbulence components and surface pressures on rectangular prisms, which are measured experimentally. The study also examines, by proposing a "modified" complex Morlet wavelet function, the influence of the time-frequency resolution and wavelet parameters (i.e., central frequency and bandwidth) on the wavelet coherence of the surface pressures. It is found that the time-frequency resolution may significantly affect the accuracy of the time-frequency coherence; the selection of the central frequency in the modified complex Morlet wavelet is the key parameter for the time-frequency resolution analysis. Furthermore, the concepts of time-averaged wavelet coherence and wavelet coherence ridge are used to better investigate the time-frequency coherence, the coherently dominant events and the time-varying coherence distribution. Experimental data derived from physical measurements of turbulent flow and surface pressures on rectangular prisms with slenderness ratios B/D=1:1 and B/D=5:1, are analyzed.

• Journal of the Ergonomics Society of Korea
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• v.27 no.2
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• pp.9-14
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• 2008

Coherence can be used to evaluate the functional cortical connections between the motor cortex and muscle. This study is to find coherence between EEG (electroencephalogram) and EMG (electromyogram) evoked by movement of a hand. Seven healthy participants were asked to perform thirty repetitive movement of right hand for ten seconds with rest for ten seconds. Specific feature of EEG components has been extracted by ICA (independent component analysis) and coherence between EEG and EMG was analyzed from data measured EEG in five local areas around central part of head and EMG in flexer carpri radialis muscle during grabbing movement. Coherence between EEG and EMG was successfully obtained at 0.025 confidence limit during hand movement and showed significant difference between rest and movement at 13-18Hz.

• The Journal of Korean Physical Therapy
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• v.32 no.6
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• pp.365-371
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• 2020

Objective: To investigate the action observation effects of functional electrical stimulation (FES) on the communication between motor cortex and muscle through corticomuscular coherence (CMC) analysis. Methods: Electroencephalogram (EEG) and electromyogram (EMG) of 27 healthy, nonathlete subjects were measured during action observation, FES, and action observation with FES, which lasted for 7sper session for 10 times. All trials were repeated for 30 times. Simultaneously measured EEG raw data and rectified EMG signals were used to calculate CMC. Only confidence limit values above 0.0306 were used for analysis. CMC was divided into three frequency domains, andthe grand average coherence and peak coherence were computed. Repeated ANOVA was performed to analyze the coherence value difference for each condition's frequency band. Results: CMC showed significant differences in peak coherence and average coherence between the conditions (p<0.05). Action observation application with FES in all frequency band showed the highest peak and average coherence value. Conclusions: The results of this study are assumed to be the combination of increased eccentric information transfer from the sensorymotor cortex by action observation and an increased in concentric sensory input from the peripheral by the FES, suggesting that these are reflecting the sensorimotor integration process.

• Korean Journal of Remote Sensing
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• v.22 no.1
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• pp.25-40
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• 2006

Synthetic aperture radar (SAR) from satellites provides the opportunity to regularly incorporate microwave information into forest classification. Radar backscatter can improve classification accuracy, and SAR interferometry could provide improved thematic information through the use of coherence. This research examined the potential of using multi-temporal JERS-l SAR (L band) backscatter information and interferometry in distinguishing forest classes of mountainous areas in the Northeastern U.S. for future forest mapping and monitoring. Raw image data from a pair of images were processed to produce coherence and backscatter data. To improve the geometric characteristics of both the coherence and the backscatter images, this study used the interferometric techniques. It was necessary to radiometrically correct radar backscatter to account for the effect of topography. This study developed a simplified method of radiometric correction for SAR imagery over the hilly terrain, and compared the forest-type discriminatory powers of the radar backscatter, the multi-temporal backscatter, the coherence, and the backscatter combined with the coherence. Statistical analysis showed that the method of radiometric correction has a substantial potential in separating forest types, and the coherence produced from an interferometric pair of images also showed a potential for distinguishing forest classes even though heavily forested conditions and long time separation of the images had limitations in the ability to get a high quality coherence. The method of combining the backscatter images from two different dates and the coherence in a multivariate approach in identifying forest types showed some potential. However, multi-temporal analysis of the backscatter was inconclusive because leaves were not the primary scatterers of a forest canopy at the L-band wavelengths. Further research in forest classification is suggested using diverse band width SAR imagery and fusing with other imagery source.

• Journal of Korean Society of Water and Wastewater
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• v.35 no.1
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• pp.15-25
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• 2021

In this study, a method of leakage detection was proposed to locate leak position for a reservoir pipeline valve system using wavelet coherence analysis for an injected pressure wave. An unsteady flow analyzer handled nonlinear valve maneuver and corresponding experimental result were compared. Time series of pressure head were analyzed through wavelet coherence analysis both for no leak and leak conditions. The leak information can be obtained through either time domain reflectometry or the difference in wavelet coherence level, which provide predictions in terms of leak location. The reconstructed pressure signal facilitates the identification of leak presence comparing with existing wavelet coherence analysis.

• Journal of Oral Medicine and Pain
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• v.48 no.4
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• pp.159-168
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• 2023

Purpose: Coordinated activity between the jaw and neck muscles is important in oral motor tasks such as chewing. This study examined coherence between the jaw and neck muscles during chewing in healthy adults. Methods: A total of 12 healthy adults underwent electromyography (EMG) of the jaw and neck muscles during right-sided chewing at a frequency of 1 Hz. Surface electrodes were placed over the temporalis (TA), masseter (MS), anterior digastric (DA), and sternocleidomastoid (SM) muscles on the right side. EMG signals were processed for coherence and phase analysis using advanced signal processing techniques. Results: The MS and TA muscle pair exhibited high synchronization when chewing (median coherence=0.992). Contrarily, the coherence values between the MS and DA, as well as the MS and SM muscle pairs, were relatively low (median coherence=0.848 and 0.957, respectively). Phase analysis revealed minimal temporal differences between the MS and TA muscle pair and the MS and SM muscle pair, whereas substantial phase shifts were observed between the MS and DA muscle pair. Conclusions: During chewing in healthy adults, the TA muscle works synergistically whereas the DA muscle antagonistically with the MS muscle, and the SM muscle supports the activity of the MS muscle. The observed synchrony and coordination provide insights into the intricate interplay among these muscles during oral motor tasks.

• Journal of Korean Biological Nursing Science
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• v.14 no.3
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• pp.221-230
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• 2012

Purpose: Quality of nursing research should be evaluated before it is applied as an evidence for evidence-based nursing practice. This study attempted to analyze and to compare tools for the quality assessment and reporting standards of nursing research using CONSORT and STROBE checklist by types of research design. Methods: We searched the tools for quality assessment in nursing research based on the National Evidence-based Healthcare Collaborating Agency (NECA) publication. Then, we analysed and compared the tools for quality evaluation by types of research design. Results: According to the analysis using CONSORT checklist, ROB shows coherence in 17 items, Jadad shows coherence in 3 items, SIGN (for RCT) shows coherence in 26 items, and Downs & Black shows coherence in 24 items. According to the analysis using STROBE checklist, MINORS shows coherence in 25 items, NOS shows coherence in 21 items, SIGN (for Cohort studies & Case-control studies) shows coherence in 29 items, and RoBANS shows coherence in 21 items. Conclusion: Based on our analysis, we recommend that nursing researchers should report according to the reporting standards of tools for quality evaluation. We hope that our analysis can be helpful to develop evidence-based nursing.

• The Journal of the Acoustical Society of Korea
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• v.35 no.2
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• pp.118-124
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• 2016

In this paper, contribution analysis method using a partial coherence function is dealt with in the case of underwater radiation noise. When performing the contribution analysis using a partial coherence function, it is important to select the order of system input. But in the case of frequency correlated systems, it is very difficult to properly select the order of system input. In order to solve this problem, the contribution analysis is performed by subdividing the area of contribution using multiple coherence function. And the new contribution analysis method is presented by using the relationship between the contribution characteristic matrix and multiple coherence function. In order to validate the new method, calculation is performed about multi-input / single-output model which is composed of sine waves. The result of calculation shows that it is possible to derive the exact contribution values.

• Journal of Korean Academic Society of Home Health Care Nursing
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• v.22 no.1
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• pp.5-13
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• 2015

Purpose: The purpose of this study was to identify the relationship between sense of coherence and quality of life in the freshman nursing students. Method: The subjects of this study were 377 freshmen of nursing colleges. Data were collected through structured questionnaires of sense of coherence and quality of life. Data analysis was done using descriptive statistics, t-test, ANOVA, Pearson's correlation coefficient and canonical correlation analysis. Result: There was static correlation between sense of coherence and quality of life in the freshman nursing students. And high correlation with quality of life were meaningfulness in sense of coherence and psychological domain in quality of life. Conclusion: These results were shown very important to improve meaningfulness in sense of coherence and psychological domain in quality of life to raise the quality of life in the freshman nursing students. Therefore, in order to improve the quality of life, it is necessary to develop a nursing intervention program that focus on stress, and psychological health.

• Journal of information and communication convergence engineering
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• v.12 no.4
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• pp.221-227
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• 2014

In this paper, we analyze the effect of the coherence bandwidth of wireless channels on leakage suppression methods for discrete Fourier transform (DFT)-based channel estimation in orthogonal frequency division multiplexing (OFDM) systems. Virtual carriers in an OFDM symbol cause orthogonality loss in DFT-based channel estimation, which is referred to as the leakage problem. In order to solve the leakage problem, optimal and suboptimal methods have already been proposed. However, according to our analysis, the performance of these methods highly depends on the coherence bandwidth of wireless channels. If some of the estimated channel frequency responses are placed outside the coherence bandwidth, a channel estimation error occurs and the entire performance worsens in spite of a high signal-to-noise ratio.