• Korean Journal of Applied Biomechanics
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• v.28 no.3
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• pp.187-191
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• 2018

Objective: The purpose of the present study is to investigate the effect of a muscle activity by applying the complex exercise method of sling in accordance with the provision of various vibration intensities for paraplegia-spinal cord injury. Method: The subjects of the study were 15 men in their 40s and 50s with lower limb disabilities and low potential risk, who were randomly divided into a sling exercise group (SG n=4), a sling with low frequency vibration group (SLVG n=4), a sling with mid-frequency vibration group (SMVG n=4), and a sling with high frequency group (SHVG n=4) in accordance with the provision of slings and vibration stimuli. The vibratory intensity provided was divided into low frequency (30 Hz), mid-frequency (50 Hz), and high frequency (70 Hz). The anterior deltoid (AD), the posterior deltoid (PD), the pectoralis major (PM), the upper trapezius (UT), the latissimus dorsi (LD), and the multifidus (MF) were measured to compare and analyze muscle activity. Results: The closed kinetic chain (CKC) exercise to the shoulder joint showed higher muscle activity in most muscles for the SMVG, and statistically significant differences in the anterior deltoid (AD), the pectoralis major (PM), and the multifidus (MF) in particular. Conclusion: The intermediate frequency (50 Hz) string vibration was the effective vibration stimuli for Closed kinetic chain (CKC) exercises.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2010.05a
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• pp.49-49
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• 2010

The most commonly used numerical modelling techniques for acoustics and vibration are based on element based techniques, such as the nite element and boundary element method. Due to the huge computational eorts involved, the use of these deterministic techniques is practically restricted to low-frequency applications. For high-frequency modelling, probabilistic techniques such as SEA are well established. However, there is still a wide mid-frequency range, for which no adequate and mature prediction techniques are available. In this frequency range, the computational eorts of conventional element based techniques become prohibitively large, while the basic assumptions of the probabilistic techniques are not yet valid. In recent years, a vast amount of research has been initiated in a quest for an adequate solution for the current midfrequency problem. One family of research methods focuses on novel deterministic approaches with an enhanced convergence rate and computational eciency compared to the conventional element based methods in order to shift the practical frequency limitation towards the mid-frequency range. Amongst those techniques, a wave based prediction technique using an indirect Tretz approach is being developed at the K.U.Leuven - Noise and Vibration Research group. This paper starts with an outline of the major features of the mid-frequency modelling challenge and provides a short overview of the current research activities in response to this challenge. Next, the basic concepts of the wave based technique and its hybrid coupling with nite element schemes are described. Various validations on two- and threedimensional acoustic, elastic, poro-elastic and vibro-acoustic examples are given to illustrate the potential of the method and its benecial performance as compared to conventional element based methods. A closing part shares some views on the open issues and future research directions.

• Corrosion Science and Technology
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• v.22 no.1
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• pp.30-35
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• 2023

Hafnium nitride (HfN) thin films were fabricated by mid-frequency magnetron sputtering (mfMS) and direct current magnetron sputtering (dcMS) and their mechanical and structural properties were compared. In particular, changes in the HfN film properties were observed by changing the pulse frequency of mfMS between 5 kHz, 15 kHz, and 30 kHz. The crystalline structure, microstructure, 3D morphology, and mechanical properties of the HfN films were compared by x-ray diffraction, field-emission scanning electron microscopy, atomic force microscopy, and nanoindentation tester, respectively. HfN film deposited by mfMS showed a smoother and denser microstructure as the frequency increased, whereas the film deposited by dcMS showed a rough and sloppy microstructure. A single δ-HfN phase was observed in the HfN film made by mfMS with a pulse frequency of 30 kHz, but mixed δ-HfN and HfN_0·4 phases were observed in the HfN film made by dcMS. The mechanical properties of HfN film made by mfMS were improved compared to film made by dcMS.

• Proceedings of the Optical Society of Korea Conference
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• 1990.02a
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• pp.136-140
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• 1990

A hybrid wideband amplifier having bandwidth from 5MHz to 2000MHz with a gain of 10db$\pm$3dB is designed and implemented by using a lossy matched network and GaAs FET. The implemented amplifier circuit operates as a capacitor-resistor(C-R) coupled amplifier circuit in the low frequency range (below 800 MHz) in which {{{{ LEFT $\mid$ S_{21 } RIGHT $\mid$ }} for the GaAs FET is constant. It also operates as a lossless impedance matching circuit in the microwave frequency range in which S21 for the GaAs FET has a slope of approximately -6dB/octave. Using this configuration technique, Two stage GaAs FET amplifier implemented is measured to 10dB gain within a 3dB fluctuation over the frequency band from 5 to 2000MHz.

• Transactions of the Korean Society of Mechanical Engineers
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• v.11 no.3
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• pp.362-367
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• 1987

Cylinder pressure level is defined the value of sound pressure level derived from relations of pressure and frequency which are obtained Fourier series expansion of cylinder pressure. CPL is alone in general use in combustion analysis without regarding attenuation coefficient determined by engine structure because it is almost constant in various kinds of engines. Combustion pressure fluctuation and influence of CPL was investigated in this paper using Wiebe combustion function superposition th obtain the effect of premixed and diffusive combustion. The results are as follow. (1) Influence of combustion maximum pressure(P$\sub$max/) on CPL is correspond with total energy per cycle well. (2) P$\sub$max/, .DELTA.P$\sub$max/, (dp/d.theta.)$\sub$max/ and (d$\^$2/p/d.theta.$\^$2/)$\sub$max/ are very effective on CPL in the range of low frequency, mid-low frequency, mid-high frequency and high frequency respectively.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.29 no.12
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• pp.963-968
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• 2018

In this paper, a compact common mode filter using passive elements is designed and fabricated. To design a common mode filter with required frequency response, the equivalent circuits of the common mode filter in differential mode and common mode were analyzed. Compared with the former filter using a ${\lambda}/4$ resonator, the size of the proposed structure was reduced by 60 %. The fabricated common mode filter has a maximum differential mode insertion loss of 1.2 dB and a minimum common mode absorption efficiency of 78.2% in the CMA - bandwidth of 27.5 %.

• Journal of Broadcast Engineering
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• v.20 no.4
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• pp.632-640
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• 2015

This paper proposes a new method for fast graphic visualization of accurate frequency response of audio equalizer (EQ). When a logarithmic frequency scale is used, a frequency response in high resolution is required for accurate low-band frequency response. However, the high-resolution frequency response requires a huge amount of computational load, which makes the real-time graphic visualization of frequency response impossible. In order to solve the problem of computational load, the proposed method utilizes a low-resolution virtual frequency response in the mid band. It first computes the virtual frequency response of each filter of EQ in the mid band, and then moves it to the target band so that the result corresponds to the desired filter response. Then, it determines the final frequency response of EQ by combining all filter responses. The experiments confirm that the proposed method provides the frequency response of EQ which has an equivalent shape to that computed in high frequency resolution with huge computational load.

• Journal of Families and Better Life
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• v.7 no.1
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• pp.97-118
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• 1989

The purpose of this study is to clarify the definition of middle age, to compare the different perspectives about mid-life crisis, and to identify the variables that cause the mid-life crisis of men and women.. For this purpose reviewing literatures and emprical research were conducted. For the emprical research, Mid-life Crisis Scale, Mid-life Indentity Scale, Family Relation Scale. Health Scale and Religious Scale were developed. The Sample was selected form the men and women living in Seoul, whose age is from 40 to 59 , and whose last child is older than 13 years of age. Among 820 respondents 218 men and 442 women were finally selected as datum sources. The data were analyzed by the statistical method such as the factor analysis frequency distribution, percentile, ANOVA, Pearson's correlation and regression analysis. The main results were as follows; 1) Men and women experience mid-life crisis some extent. The mid-life crisis score for men is 33.60 and 35.0 for women. This implies women reveal significantly higher crisis than men. As for women's mid-life crisis. self-awaring age, education, income, husband's occupation, employment status of wife and occupational status of wife have a significant influence Expecially employment status of wife seemed to interact with sex, husband's occupation and educational level of wife. however status of child, family pattern, son's existence are not as important an influence on mid-life crisis. 3) Among the psychological variables, work identity and physical identity have the strong influence on the mid-life crisis of men and women, It implies that mid-life crisis si lower when one has higher work identity and physical identity. 4) Mid -life crisis of men and women is influenced significantly according to family relation variables and health variables. It reveals that the better one's family relations and health sate, the lower one's mid-life crisis is. However menopause and the years after menopause do not influence on the mid-life crisis of women. 5) Mid-life crisis of women differs significantly according to the kind of religion and religious activity. That is mid-life crisis of women is lower when she believes in Protestantism and Catholicism and participate in more religious activity. Mid-life crisis of men is not significantly influenced by religious variables. After all among the five categories of variables that related to mid-life crisis, psychological variables-especially work identity and physical identity are observed to have the strongest degree of significance.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.24 no.8
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• pp.606-612
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• 2014

Vehicle simulation models for noise and vibration prediction have been developed so far generally in two schemes. One is FE models generally used for problems below 200 Hz such as booming noise, and the other is SEA models for high frequencies of more than 1 kHz, representatively related to sound packages. There have been many researches to develop a simulation model for 200~1000 Hz, so-called mid-frequency region, and this paper shows one practical result that covers the trimmed body of a sedan vehicle. The simulation model is developed based on an FE model, and then FE elements at some areas are substituted with SEA elements to reduce DOFs. SEA panels are described by modal density, radiation efficiency, stiffness and damping characteristics that are found from some numerical assessments. Sound packages are modeled similarly as a conventional SEA model. The results obtained from the hybrid model were compared to experimental results. Predicted pressure and vibrational velocity generally show a good agreement. The developed simulation model and related technology are successfully being used in vehicle development process.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2013.10a
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• pp.362-367
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• 2013

Vehicle CAE models for NVH predictions are largely developed in two schemes. One is FE models generally used for below 200 Hz problems such as booming noise, and the other is SEA models for high frequencies of more than 1 kHz, representatively related to sound packages. HMC has tried to develop a CAE model for 200-1000 Hz, so-called mid-frequency region, and this paper is one of the corresponding results. The CAE model is developed based on an FE model, and then FE elements at some areas are substituted with SEA elements to reduce DOFs. SEA panels are described by modal density, radiation efficiency, stiffness and damping characteristics that are found from some numerical assessments. Sound packages are modeled similarly as a conventional SEA model. The CAE model developed in this manner, the hybrid model, was compared to experimental results. Predicted pressure and vibrational velo city generally show a good agreement. The developed CAE model and related technology are successfully being used in vehicle development process.