• 대한치과보철학회지
• /
• 제43권6호
• /
• pp.736-744
• /
• 2005

Statement of problem. Initial stability of implant is an important factor for predicting osseointegration. It requires a rapid, non-invasive, user-friendly technique to frequently assess the implant stability and the degree of osseointegration. Purpose. The aim of this study was to evaluate the correlation between the resonance frequency analysis (RFA) and the radiographic method for peri-implant bone change under in vitro conditions. Material and Method. Twenty implants of 3.75 mm in diameter(Neoplant, Neobiotech, Korea) were used. To simulate peri-implant bone change, 2 mm-deep $45^{\circ}$ range horizontal defect and 2 mm-deep $90^{\circ}$ range horizontal defect area were serially prepared perpendicular to the X-ray beam after conventional implant insertion. Customized film holding device was fabricated to standardize the projection geometry for serial radiographs of implants and direct digital image was obtained. ISQ values and gray values inside threads were measured before and after peri-implant bone defect preparation. Results. Within a limitation of this study, ISQ value of resonance frequency analysis was changed according to peri-implant bone change (p<0.05) and gray value of radiographic method was changed according to peri-implant bone change (p<0.05). There was no correlation between the ISQ value and the gray value for peri-implant bone change (p>0.05). But, in horizontal defect condition, relatively positive correlation were between ISQ and gray values(r=0.663). Conclusion. This results provided a possibility that peri-implant bone change may be evaluated by both RFA and radiographic method.

• 전기학회논문지
• /
• 제64권3호
• /
• pp.498-504
• /
• 2015

This paper proposed an Spread Spectrum Time Domain Reflectometry (SSTDR) using time-frequency correlation analysis in order to have more accurate fault determination and location detection than classical SSTDR despite increased signal attenuation due to the long distance to cable fault location. The proposed method was validated through comparison with classical SSTDR methods in open- and short-circuit fault detection experiments of low-voltage power cables. The experimental results showed that the proposed method can detect correlation coefficients at fault locations accurately despite reflected signal attenuation so that cable faults can be detected more accurately and clearly in comparison to existing methods.

• 국제초고층학회논문집
• /
• 제8권4호
• /
• pp.313-324
• /
• 2019

This paper presents the analysis of wind speeds data measured on top of three neighboring high-rise buildings close to a beach in Xiamen city, China, during Typhoon "Usagi" 2013. Wind tunnel simulation was carried out to validate the field measurement results. Turbulence intensity, turbulence integral scale, power spectrum and cross correlation of recorded wind speed were studied in details. The low frequency trend component of the typhoon speed was also discussed. The field measurement results show turbulence intensity has strong dependence to the wind speed, upwind terrain and even the relative location to the Typhoon center. The low frequency fluctuation could severely affect the characteristics of wind. Cross correlation of the measured wind speeds on different buildings also showed some dependence on the upwind terrain roughness. After typhoon made landfall, the spatial correlation of wind speeds became weak with the coherence attenuating quickly in frequency domain.

• 말소리와 음성과학
• /
• 제1권4호
• /
• pp.187-193
• /
• 2009

For this study, the external laryngeal lengths of 9 females and 9 males with normal voices were measured together with their ages, heights, and weights, and after they read aloud sentences for 3 minutes, their habitual speaking fundamental frequencies, speaking low pitches, speaking high pitches, and vocal fold closed quotients were measured. The Spearman rank correlation analysis on these data showed a significant negative correlation between the external laryngeal length and the habitual speaking fundamental frequency for both females and males, a significant negative correlation between the external laryngeal length and the speaking high pitch for only males, a significant negative correlation between the external laryngeal length and the speaking low pitch for both females and males, and a significant positive correlation between the external laryngeal length and the vocal fold closed quotient for only males.

• 한국정보통신학회:학술대회논문집
• /
• 한국해양정보통신학회 2008년도 춘계종합학술대회 A
• /
• pp.985-988
• /
• 2008

본 논문에서는 기준 펄스와 데이터 펄스로 구성된 TR(Transmitted-reference) 신호를 전송하는 TR-UWB 시스템에서 시간 영역의 수신 신호를 주파수 영역의 신호로 변환하는 과정을 거쳐서 얻어 낸 주파수 성분을 수신기에서 상관연산을 통해서 신호대잡음비를 개선하는 TR-UWB 시스템을 제안한다. 또한, TR-UWB 신호의 복소수 성분, 주파수 변환 특성을 이용한 이론적인 분석을 통해 시스템성능을 유도하고 기존 시스템과의 성능을 비교 분석한다. 모의 실험을 통해 제시한 TR-UWB 시스템에 의해 성능이 개선됨을 검증한다.

• Journal of Communications and Networks
• /
• 제1권3호
• /
• pp.166-181
• /
• 1999

The object of this paper is to investigate the influence of antenna pattern on indoor radio channel characteristics. Different from previous works where this analysis was carried out at a fixed frequency using different antennas, in the present paper (where measurements were taken in a wide frequency range) the variation of the radiation pattern was caused by two factors: the change of the radiation pattern when the same antenna was used at different frequenicies and the use of different type of antennas. To carry out this analysis, frequency domain measurements of the indoor radio channel at 1 GHz, 5.5 GHz, 10 GHz and 18 GHz were collected. Measurements were taken using a network analyzer. Serveral re-alizations of the channel transfer function were obtained varying, for each measurement, the positon of the transmitter and keep-ing the receiver fixed. Estimate of the channel impulse response was obtained from the Inverse Fourier Transform (IFT) of the fre-quency response. The measurements were performed in an office enviroment with mostly metallic walls and inner separations. The obtained data were elaborated to obtain the power versus distance relationship, the Cummulative Distribution Functions(CDFs) of rms Delay Spread(DS) and of the 3 dB frequency correlation band-width. Finally, the 3 dB width of the frequency correlation func-tion has been empirically related to the inverse of the rms DS of the impulse response.

• Journal of Nutrition and Health
• /
• 제33권2호
• /
• pp.202-215
• /
• 2000

Intake frequency of one food is often associated with other food items, but few studies examined the relationship of food intake frequency among food items. Finding the relationship among intake frequencies of different food might be useful to understand the food intake patterns of population and correlated foods would be used as an indicators of another food intake. Relationship of food intake can be also applied to make a more simple and useful form of food frequency questionnaire to assess the association between diet and various diseases. The objective of this study was to examine the correlation of intake frequency among food items in food frequency questionnaire (FFQ). A FFQ with 84 food items was administered to 14533 Korean males who 40-65 years of age participating Korean cancer research survey. Data fromm 7647 subjects who completed FFQ were used to examine correlation among food items with three different methods-log linear regression models, Spearman correlation coefficients and cell frequency distribution. To examine the rank correlation, coefficients were calculated by Spearman correlation after scoring the frequency categories. Three most correlated foods were selected in every food intems by three methods each. In most food items, there was positive correlatin, except cooked rice and cooked brown rice, in intake frequency between foods that belonged to similar food groups. But serveral food items-Sausage (processed fish, cheese), Milk (whilte bread, orange juice), Soymilk(other juices), Cheese (pizza, butter), and Coffee(thick beef soup)-showed correlation among totally different food groups. Two sets of food items which were selected by log linear regression model and Sperman correlation coefficients were compared. There were exactly three common foods in 18 food items, 2 common foods in 47 items, 1 common food in 16 items and no common food in 3 items among 3 ranked foods. Three sets of selected food were compared. There were exactly three common foods in 5 food items, 2 common foods in 21 items, 1 common food in 34items and no common food in 24 items among 3 ranked foods. These results indicate that certain patterns exist among intake frequencies of specific food items in the FFQ. More researches are suggested to understand the relationshiops among the intakes of foods so that this information can be used in developing better FFQ or analyzing missing items from self-administered FFQ.

• Wind and Structures
• /
• 제13권6호
• /
• pp.529-556
• /
• 2010

This paper investigates the correlation of wind characteristics monitored on a cable-stayed bridge. Total five anemoscopes are implemented into the bridge. Two out of 5 anemoscopes in inflow and two out of 5 anemoscopes in wake-flow along the longitudinal direction of the bridge are installed. Four anemoscopes are respectively distributed at two cross-sections. Another anemoscope is installed at the top of the tower. The correlation of mean wind speed and direction, power spectral density, the turbulent intensity and integral length of wind in flow at two cross-sections are investigated. In addition, considering the non-stationary characteristics of wind, the spatial correlation in time-frequency is analyzed using wavelet transform and different phenomenon from those obtained through FFT is observed. The time-frequency analysis further indicates that intermittence, coherence structures and self-similar structures are distinctly observed from fluctuant wind. The flow characteristics around the bridge deck at two positions are also investigated using the field measurement. The results indicate that the mean wind speed decrease when the flow passing through the deck, but the turbulence intensity become much larger and the turbulence integral lengths become much smaller compared with those of inflow. The relationship of RMS (root mean square) of wake-flow and the mean wind speed of inflow is approximately linear. The special structures of wake-flow in time-frequency domain are also analyzed using wavelet transform, which aids to reveal the forming process of wake-flow.

• 대한음성학회:학술대회논문집
• /
• 대한음성학회 2002년도 11월 학술대회지
• /
• pp.133-136
• /
• 2002

The purpose of this study was to determine the correlation between the Average Fundamental Frequency, Fo-Tremor Frequency, Jitter, Shimmer, Amplitude Tremor Intensity Index, and Noise to Harmonic Ratio of MDVP and Fo, Fo Tremor, Jitter, Shimmer, Amp Tremor, HNR, and NNE of Dr. Speech. The Pearson correlation coefficient was used for analysis. The results showed that there was a strong correlation between Fo and Shimmer of both instruments. However, the remaining parameters did not show a significant correlation.

• 한국산업안전학회:학술대회논문집
• /
• 한국안전학회 2000년도 춘계 학술논문발표회 논문집
• /
• pp.52-57
• /
• 2000

This paper discusses frequency analysis based on frequency spectrum in orthogonal cutting of fiber-matrix composite materials. A glass reinforced polyester (GFRP) was used as workpiece. Analysis method employs a force sensor and the signals from the sensor are processed using a fast Fourier transform (FFT) technique. The experimental correlation between the different chip formation mechanisms and model coefficients are then established. (omitted)