• The Journal of Korean Academy of Prosthodontics
• /
• v.44 no.3
• /
• pp.314-324
• /
• 2006

Statement of problem. Osseointegration is important mechanism of dental implant but it is not easy to evaluate. Indirect measurement is non-invasive and clinically applicable but they need more study about correlation between indirect values and degree of osseointegration. Purpose. The aims of this study were to evaluate the coefficient of correlation between indirect measurement and direct measurement under different healing time, and assessment of effect of initial insertion torque to the implant stability. Material and Methods. 20 rabbits received 3 implants on each side of tibia. Three kinds of implants (machined surface implant, Sandblasted with Large grit and Acid etched implant, Resorbable Blast Media treated implant) were used. During the surgery implant insertion torque were measured with $Osseocare^{TM}$. After the 1, 4, 8, 12 weeks of healing time, animals were sacrificed and stability values (Implant Stability Quotient with $Osstell^{TM}$, removal torque with torque gauge) were measured. Results. The Bone quality of rabbit tibia was classified into 2 groups according to the insertion torque. Resonance frequency analysis (ISQ) and removal torque showed positive correlation until $4^{th}$ week (r=0.555, p=0.040). After $8^{th}$ week (r=0.011, p=0.970) the correlation became weak and it turned negative at $12^{th}$ week (r=-0.074, p=0.801). Insertion torque and ISQ showed changing correlation upon the healing time ($1^{st}$ week: r=0.301, p=0.033, $4^{th}$ week: r=-0.429, p=0.018, $8^{th}$ week: r=0.032, p=0.865, $12^{th}$ week: r=-0.398, p=0.029). Insertion torque and removal torque has positive correlation but it was not statistically significant ($1^{st}$ week: r=0.410, p=0.129, $4^{th}$ week: r=0.156, p=0.578, $8^{th}$ week: r=0.236, p=0.398, $12^{th}$ week: r=0.260, p=0.350). Conclusion. In this study, bone quality may affect the degree of osseointegration positively during healing time and correlation between ISQ and degree of osseointegration can be different according to the healing time and bone quality.

• Physical Therapy Korea
• /
• v.8 no.2
• /
• pp.41-54
• /
• 2001

Fatigue is the decline in force produced as a result of prolonged muscle activity. Localized muscle fatigue can be identified by a shift toward low in the frequency components of the EMG signal, typically represented by a fall in the median frequency. Previous studies show that a shortened muscle develops a higher fatigue than elongated muscles. The purpose of this study was to investigate the time-related change of median frequency and torque during maximal isometric back extension exercises at different exercise angles ($0^{\circ}$, $12^{\circ}$, $36^{\circ}$, $72^{\circ}$). Twenty healthy subjects (mean age = $24.35{\pm}2.70$) were evaluated in this study. Median frequency was extracted from the EMG signals by fast Fourier transform (FFT). Initial median frequency and the slope of median frequency change over time were computed from linear regression analysis. Pearson's product moment correlation was used to quantify the relationship between slope of median frequency and torque. The results were as follows: 1) Significant differences in y-intercepts of torque regression equation with respect to exercise angle were shown. However, there were no differences in the slopes of the median frequency and torque, and y intercept of the median frequency among exercise angles. 2) There was no significant correlation between slope of median frequency and torque. 3) But there was moderate correlation between median frequency and torque at each exercise angle. In conclusion, the exercise angle during maximal isometric back extension exercise is not a direct effect on slope of median frequency and torque. But results showed that median frequency and torque shift were highly correlated in all subjects.

• Bulletin of the Korean Chemical Society
• /
• v.25 no.9
• /
• pp.1403-1407
• /
• 2004

Dielectric relaxation measurements on 3-nitrotoluene (3-NT) mixture of dimethylacetamide (DMA), dimethylformamide (DMF) and dimethysulphoxide (DMSO) have been carried out across the entire concentration range using Time domain reflectometry technique at 15, 25, 35 and $45^{\circ}C$ over the frequency range from 10 MHz to 20 GHz. For all the mixtures, only one dielectric loss peak was observed in this frequency range and the relaxation in these mixtures can be well described by a single relaxation time using Debye model. Bilinear calibration method is used to obtain complex permittivity ${\varepsilon}^{*}({\omega})$ from complex reflection coefficient ${\rho}^{*}({\omega})$ over frequency range 10 MHz to 20 GHz. The excess permittivity, excess inverse relaxation time, Kirkwood correlation factor, molar energy of activation are also calculated for these mixtures to study the solute-solvent interaction.

• Korean Journal of Community Nutrition
• /
• v.18 no.5
• /
• pp.429-441
• /
• 2013

This study was conducted to examine the interrelations among snack preference, purchasing behavior and intake of fifth and sixth grade students in elementary schools in Gyeongnam province. Frequency of snack intake was the highest in those who reported 'once a day' (45.6%) snack habit. Longer-time television viewers also showed higher frequency of snack intake than shorter-time viewers. Thirty-three percent of students purchased snacks by themselves and the frequency of snack purchasing had a significant positive relationship with TV watching time (p < 0.01). The main reason, place and time of eating snacks were 'hunger' (79.2%), their home environment (50.9%) and 'after school hours' (89.7%). The favorite snack was 'ice cream' and, this snack habit was significantly different by gender of the child (p < 0.01) and TV watching time (p < 0.01). 'Milk and dairy products' scored highest (3.47) in snack intake frequency among longer-time TV viewers (> 2hr) compared to shorter-time TV viewers and this difference was statistically significant (p < 0.001). The snack preference score was correlated positively (r = 0.454) with the intake frequency for snack and its explanation power ($R^2$) was 20.5%. With regard to snack purchase behaviors, the scores of 'checking the expiration date' and 'comparing the price with similar products' were high (in what group?). Female students (p < 0.001) and shorter-time TV viewers (< 2hr) (p < 0.01) had a more reasonable purchasing behavior. The total score of preference was significantly higher (p < 0.05) in shorter-timeTV viewers (< 2hr). In the correlation between snack purchasing behaviors and intake frequency, attractiveness (r = 0.208, p < 0.001) and preference (r = 0.330, p < 0.001) showed significant positive correlations. The result of regression analysis, preference only was selected ($R^2$= 0.108).

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.37 no.1A
• /
• pp.73-81
• /
• 2012

In this paper, we propose a high-speed synchronization method for Digital Radio Mondiale (DRM) receivers. In order to satisfy the high-speed synchronization requirement of DRM receivers, the proposed method eliminate the initial sampling frequency synchronization process in conventional synchronization methods. In the proposed method, sampling frequency tracking is performed after integer frequency synchronization and frame synchronization. Different correlation algorithms are applied to detect the first frame of the Orthogonal Frequency Division Multiplexing (OFDM) demodulation symbol with sampling frequency offset (SFO). A frame detection algorithm that is robust to SFO is selected based on the performance analysis and simulation. Simulation results show that the proposed method reduces the time spent for initial sampling frequency synchronization even if SFO is present in the DRM signal. In addition, it is verify that inter-cell differential correlation used between reference cells is roubst to the effect of initial SFO.

• Journal of Korean Tunnelling and Underground Space Association
• /
• v.11 no.1
• /
• pp.71-83
• /
• 2009

Shotcrete is an important primary support for tunnelling in rock. The quality control of shotcrete is a core issue in the safe construction and maintenance of tunnels. Although shotcrete may be applied well initially onto excavated rock surfaces, it is affected by blasting, rock deformation and shrinkage and can debond from the excavated surface, causing problems such as corrosion, buckling, fracturing and the creation of internal voids. This study suggests an effective non-destructive evaluation method of the tunnel shotcrete bonding state applied onto hard rocks using the impact-echo (IE) method and ground penetration radar (GPR). To verify previous numerical simulation results, experimental study carried out. Generally, the bonding state of shotcrete can be classified into void, debonded, and fully bonded. In the laboratory, three different bonding conditions were modeled. The signals obtained from the experimental IE tests were analyzed at the time domain, frequency domain, and time-frequency domain (i.e., the Short- Time Fourier transform). For all cases in the analyses, the experimental test results were in good agreement with the previous numerical simulation results, verifying this approach. Both the numerical and experimental results suggest that the bonding state of shotcrete can be evaluated through changes in the resonance frequency and geometric damping ratio in a frequency domain analysis, and through changes in the contour shape and correlation coefficient in a time-frequency analysis: as the bonding state worsens in hard rock condition, the autospectral density increases, the geometric damping ratio decreases, and the contour shape in the time-frequency domain has a long tail parallel to the time axis. The correlation coefficient can be effectively applied for a quantitative evaluation of bonding state of tunnel shotcrete. Finally, the bonding state of shotcrete can be successfully evaluated based on the process suggested in this study.

• Journal of the Korean Institute of Telematics and Electronics A
• /
• v.32A no.10
• /
• pp.51-63
• /
• 1995

In this paper, a new real-time optical image switching system based on the phase-typed BPEJTC is suggested. The phase filter mask which has the arbitrary position mapping function between input and output planes is constructed by using the modified JTPS of the BPEJTC. Then, the input image is convolved with this phase filter mask in the spatial frequency domain and through further Fourier transform the input image is switched to the new positions in the output correlation plane where the correlation peaks are occurred. And, based on the computer simulation results, the practical optical switched to the new positions in the output correlation plane where the correlation peaks are occurred. And, based on the computer simulation results, the practical optical switching system is opto-digitally constructed and through some experiments on image switching the possiblity of real-time implementation of the multiple optical image switching system by using the BPEJTC is suggeste.

• Transactions of the Korean Society for Noise and Vibration Engineering
• /
• v.24 no.4
• /
• pp.310-316
• /
• 2014

The location template matching(LTM) method is a technique of identifying an impact location on a structure, and requires a certain measure of similarity between two time signals. In general, the correlation coefficient is widely used as the measure of similarity, while the group delay based method is recently proposed to improve the accuracy of the impact localization. Another possible measure is the frequency response assurance criterion(FRAC), though this has not been applied yet. In this paper, these three different measures of similarity are examined comparatively by using experimental data in order to understand the properties of these measures of similarity. The comparative study shows that the correlation coefficient and the FRAC give almost the same information while the group delay based method gives the shape oriented information that is best suitable for the location template matching method.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2014.04a
• /
• pp.506-511
• /
• 2014

The location template matching (LTM) method is a technique of identifying an impact location on a structure, and requires a certain measure of similarity between two time signals. In general, the correlation coefficient is widely used as the measure of similarity, while the group delay based method is recently proposed to improve the accuracy of the impact localization. Another possible measure is the frequency response assurance criterion (FRAC), though this has not been applied yet. In this paper, these three different measures of similarity are examined comparatively by using experimental data in order to understand the properties of these measures of similarity. The comparative study shows that the correlation coefficient and the FRAC give almost the same information while the group delay based method gives the shape oriented information that is best suitable for the location template matching method.

• Journal of information and communication convergence engineering
• /
• v.3 no.3
• /
• pp.119-121
• /
• 2005

This paper aims to estimate the delay time of multiple signals in a multi-path environment. It also seeks to carry out a comparative analysis with the existing delay time under the proposed algorithm to develop a new algorithm that applies the space average method in a MUSIC algorithm. Unlike the existing delay time estimation algorithm, the developed algorithm was able to estimate the delay time in 5ns low. Therefore, the algorithm proposed in this paper improved the existing delay time estimated algorithm.