Analysis for propagation characteristics of longitudinal mode and torsional mode guided waves in rod
Regarding the application of guided waves in one-dimensional structure, the propagation characteristics of the longitudinal guided wave and torsional guided wave are investigated. The dispersion equations of guided wave in the longitudinal and torsional modes in one-dimensional component are derived. Through programming numerical calculation in MATLAB, the frequency dispersion curves of the two modes are obtained, which imply that the engineering application of guided waves in detection of rod needs to choose an appropriate frequency and the corresponding propagation characteristics of the waves should be combined to get reliable results. The dispersion characteristics analysis results in different radius of rods show that it is feasible for detecting the defects in rod using L(0,1) mode of ultrasonic guided waves.
Numerical Simulation of Guided Ultrasonic Wave Transmitted in Pipe
In order to study the transmitting characteristics of ultrasonic guided wave in pipe and select the guided wave mode suitable for non-destructive testing(NDT), the authors analyse, on the basis of elastic dynamics theory, the characteristics of multimode and dispersion of guided wave transmitted in pipe. They calculate, through programming numeric value, the dispersion curve of guided wave and the displacement distribution of various mode of the wave along the wall of pipe. The calculated result of numeric value and Fourier decomposition method are used to simulate the transmitting of guided wave in pipe so that the time domain waveform of different mode of wave after transmitting a certain distance is obtained. The results show that at special frequency, L(0, 2) mode is the ideal mode of pipe defects NDT for less dispersion and fast transmitting of guided wave. Numeric simulation is consistent with theoretical analysis, and proves that the Fourier decomposition method can effectively simulate the transmitting characteristics of ultrasonic guided wave in pipe.
Research on health and oral health status of elderly living alone compared to elderly living with their families - based on the data (2014) from the 6th two-year Korea national health and nutrition examination survey -
Objectives: I examined the health and oral health status of elderly people living alone compared to elderly people living with their families by using data (2014) from the 6th Two-Year Korea National Health and Nutrition Examination Survey. Methods: Among 1,454 health survey respondents aged 65 years and over who participated in the 6th Two-Year Korea National Health and Nutrition Examination Survey conducted in 2014, 311 were elderly people living alone and 1,143 were elderly people living with their families. Results: In terms of socio-demographic characteristics, the percentage of elderly people living alone was high especially in women and when the subjects’ age, education level, and income level were low. In terms of oral health status, the percentage of elderly people living alone was high when elderly people thought that their subjectively viewed health was poor and the frequency of drinking and exercise was low. In terms of oral health status, the percentage of elderly people living alone was high among elderly people who did not have good oral health in their subjective view and did not get oral examinations for a year and had a lot of difficulty chewing. Conclusions: Family support or additional social support for elderly people who live alone should be considered to promote the healthy lives of elderly people.