• Korean Journal of Applied Biomechanics
• /
• v.15 no.4
• /
• pp.117-129
• /
• 2005

The purpose of this study was to characterize the impact shock wave and its attenuation, and the kinematic response of the lower extremity's joints to the impact shock during downhill running in which the lower extremity's extensor acts dominantly. For this study, fifteen subjects(mean age:$27.08{\pm}4.39$; mass:$76.30{\pm}6.60$; height:$177.25{\pm}4.11$) were required to run on the 0% grade treadmill and downhill grades of 7%, and 15% in random at speed of their preference. When the participant run, acceleration at the tibia and the sacrum and kinematic data of the lower extremity were collected for 20s so as to provide at least 5 strides for analysis at each grade. Peak impact accelerations were used to calculate shock attenuation between the tibia and sacrum in time domain at each grade. Fast Fourier transformation(FFT) and power spectral density(PSD) techniques were used to analyze impact shock factors and its attenuation in the frequency domain. Joint coordinate system technique was used to compute angular displacement of the ankle and knee joint in three dimension. The conclusions were drawn as fellows: 1. Peak impact accelerations of the tibia and sacrum in downhill run were greater than that of 0% grade run, but no significant between conditions. Peak shock of PSD resembled also in pattern of peak impact acceleration. The wave of impact shock attenuation between the tibia and sacrum decreased with increasing grade, but didn't find a significant difference between grade conditions. 2. Adduction/abduction, flexion/extention, and internal/external rotation of the ankle and knee joints at support phase between grade conditions didn't make much difference. 3. At grade of 7% and 15%, there were relationship between the knee of the flexion/extension movement and peak impact acceleration during heel strike and found also it in the ankle of plantar/dorsiflexion at grade of 15%.

• Journal of IKEEE
• /
• v.25 no.3
• /
• pp.420-424
• /
• 2021

The massive MIMO system, which is a core technology of 5G communication systems, has a problem that it is difficult to implement in a frequency division duplex system based on limited channel feedback because a large amount of channel information is required at the transmitting end. In order to solve this problem, the Joint Spatial Division and Multiplexing (JSDM) technique that dramatically reduces the channel information requirement by removing interference between the user groups using channel correlation information that does not change for a long time has been proposed. Recently, a regularized JSDM technique has been proposed to further improve performance by allowing residual interference between the user groups. However, such JSDM-related studies were mainly designed to focus on inter-group interference cancellation, and thus performance analysis was not performed in a more realistic environment assuming limited feedback in the intra-group interference cancellation phase. In this paper, we analyze the performance of the JSDM and regularized JSDM techniques according to the number of groups and users in a limited feedback environment, and through the simulation results, demonstrate that the regularized JSDM technique shows a more remarkable advantage compared to the existing JSDM in a limited feedback environments.

• Journal of Oral Medicine and Pain
• /
• v.47 no.4
• /
• pp.198-205
• /
• 2022

Purpose: The first-line treatment of temporomandibular joint disorders (TMDs) should include self-management and education. Self-management techniques include moist heat application, stretching, diet control, and mandibular rest position adjustment. Although the effectiveness of video educational resources has been studied in multiple sectors, their application in TMD management has not yet been explored. This study seeks to assess how effective media education was at motivating TMD patients to self-management and improve symptoms. Methods: Data were obtained from the hospital records of TMD patients who visited the Department of Oral Medicine, Yonsei University Dental Hospital, between May 2020 and December 2021. First, without any differences between groups, a significance analysis was conducted between the degree of self-management and symptom improvement over time. At the second visit, one group received media education (n=31) linked to TMD management, while the other received written-oriented education (n=45). At the third visit, the number of precautions taken by the patients was determined and contrasted to that recorded in the previous visit between the groups. Generalized estimated equation multivariate models were applied for statistical analysis. Results: In the media education group, the frequency of stretching and the number of patients on pain-free diets increased substantially. Taking precautions improved daily pain intensity, maximum mouth opening, and pain intensity during the maximum unassisted opening. Conclusions: Media education could be beneficial for TMD patients because it allows them to take self-management precautions. The symptoms of the media education group improved, with no considerable distinction between both groups.

• Explosives and Blasting
• /
• v.28 no.2
• /
• pp.1-16
• /
• 2010

This study focuses on the phenomenon that the blast damaged zone developed on rock slope surfaces can be affected by joint characteristics rather than by explosive power when the pre-splitting is applied to excavate a jointed rock slope. The characteristics of rock joints on a slope were investigated and categorized them into 4 cases. Also an image processing system has been used for comparing the distribution pattern of rock blocks. From this investigation, it was found that the rock blocks bigger than 2,000 mm occupied 42% in the case of single joint set and it showed the well efficiency of pre-splitting blast. In cases of 2~3 parallel joint sets and 2~3 intersecting joint sets are developed on rock surfaces, the rock blocks in the range of 1,000~2,000 mm occupied 43.6% and 35.8%, respectively, and it showed that the efficiency of pre-splitting was decreased. When more than 3 joint sets are randomly developed, however, the rock blocks in the range of 250~500 mm occupied 35% and there was no block bigger than 1,000 mm. This denotes that the blasting with pre-splitting was not effective. The numerical analysis using PFC2D showed that the blast damaged zone in a rock mass could be directly influenced by the pre-splitting. It is, therefore, required to investigate the discontinuity pattern on rock surfaces in advance, when the pre-splitting method is applied to excavate jointed rock slopes and to apply a flexible blating design with a consideration of the joint characteristics.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2007.05a
• /
• pp.501-506
• /
• 2007

Structure-borne noise is the interior noise that results from the low frequency vibrational energy transmitted through those body and joint parts. The relation between the excitation of powertrain and resultant interior sound must be analyzed in order to identify and predict the structure borne noise. The method of acoustic source excitation is preferred than the method of mechanical force excitation to measure the NTF(noise transfer function). Because acoustical method is more convenient and reliable. In this paper, to analysis and identify vehicle interior noise by powertrain is performed, and the vibro-acoustic transfer function is extracted from experimental measurement. These are important step of TPA(transfer path analysis) to identify effect of interior noise resulted from powertrain running excitation.

• Transactions of the Korean Society of Automotive Engineers
• /
• v.5 no.1
• /
• pp.101-109
• /
• 1997

A tool for the dynamic simulation and design technique of the excavator plays an important role in the prediction of dynamic behavior of the excavator in the initial design stage. In this paper, a flexible multibody dynamic analysis model including track of the crawler type excavator is developed using DADS and ANSYS. Through the driving simulation of the excavator travelling over rough road track, frequency characteristics of the upper frame and cabin are obtained, and the reaction forces acting on the track rollers are also presented for the fatigue life estimation. The effect of boom vibration modes on the joint reaction forces and accelerations is presented from the swing simulation.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2000.11a
• /
• pp.291-300
• /
• 2000

This paper proposes the new hybrid analysis of vibration in the medium to high frequency ranges including PFA and SEA concept. The core part of this method is the applications of coupling loss factor(CLF) instead of power transmission, reflection coefficients in boundary condition. This method shows very promising compared to the classical PFA for the various damping loss factors and wide ranges of frequencies. Besides this paper presents the applicable method in Power Flow Finite Element Method by forming the joint element matrix with CLF. These hybrid concepts are expected to improve SEA and PFA methods in vibration analysis.

• The Journal of Korean Physical Therapy
• /
• v.25 no.1
• /
• pp.29-35
• /
• 2013

Purpose: The purpose of this study was to investigate the correlation between shoulder pain and disability index (SPADI) with participation in badminton and to find the effects of badminton on the shoulder joint. Methods: A questionnaire was answered by 143 people with shoulder pain and disability in badminton clubs located in Busan, Gyeongsangnam-do. Out of the 143 subjects (91 males, 52 females), about half (72 people) were over 40 years old, with 71 people over 50 years old. The questionnaire contained 27 questions involving demographic participation characteristics, playing characteristics, and SPADI. Data analysis was performed using the SPSS statistics program to conduct frequency analysis, cross analysis, the t-test, and one-way analysis of variance. Results: The correlation between badminton career, frequency of play, and SPADI was statistically significant. There was a significant increase in SPADI scores for players over 40 years old. The over 40 year old group with less than 5 years of badminton had a significantly increase in SPADI score. The over 50 year old group showed a significantly lower SPADI score compared with the over 40 group. Conclusion: We suggest that beginner badminton players learn correct posture and badminton skills from professionals, participate regularly, and maintain an appropriate intensity/frequency of badminton.

• The Transactions of The Korean Institute of Electrical Engineers
• /
• v.65 no.10
• /
• pp.1780-1785
• /
• 2016

This paper presents few case studies of state diagnosis of XLPE cables using very low frequency techniques. The power cables of 22.9kV which have installation fault were assessed using VLF technique in addition to other techniques like insulation resistance and DC voltage withstand test. From the experimental results, The dielectric loss($tan{\delta}$) values of degradation of the cable(joint, knife, needle) at $U_0$ were 5.839, 5.526 and 6.251, respectively and all values were "further study advised". VLF PD measurement was also found defective portion. These method was effective in defect to fault in the degradation of the cable. However, the breakdown did not occur in the degradation of the cable because of properties of XLPE insulation. Few case studies of using VLF $tan{\delta}$ diagnosis for fault are measured and analyzed. The $tan{\delta}$ values at $U_0$ were "further study advised" or "action required".

• Structural Monitoring and Maintenance
• /
• v.9 no.4
• /
• pp.305-321
• /
• 2022

Bridge structural health monitoring with the aim of continuously assessing structural safety and reliability represents a topic of major importance for worldwide infrastructure managers. In the last two decades, due to their potential economic and operational advantages, drive-by approaches experienced growing consideration from researcher and engineers. This work addresses two technical topics regarding indirect frequency estimation methods: bridge and vehicle dynamics overlapping, and bridge expansion joints impact. The experimental campaign was conducted on a mixed multi-span bridge located in Lombardy using a Ford Galaxy instrumented with a mesh of wireless accelerometers. The onboard time series were acquired for a number of 10 passages over the bridge,performed at a travelling speed of 30 km/h, with no limitations imposed to traffic. Exploiting an ad-hoc sensors positioning, pitch vehicle motion was compensated, allowing to estimate the first two bridge bending frequencies from PSD functions; moreover, the herein adopted approach proved to be insensitive to joints disturbance. Conclusively, a sensitivity study has been conducted to trace the relationship between estimation accuracy and number of trips considered in the analysis. Promising results were found, pointing out a clear positive correlation especially for the first bending frequency.