• Transactions of the Korean Society of Mechanical Engineers A
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• v.26 no.10
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• pp.1971-1981
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• 2002

Two-dimensional solidification analysis during rheology forming process of semi-solid aluminum alloy has been studied. Two-phase flow model to investigate the velocity field and temperature distribution is proposed. The proposed mathematical model is applied to the die shape of the two types. To calculate the velocities and temperature fields during rheology forming process, the each governing equations correspondent to the liquid and solid region are adapted. Therefore, each numerical model considering the solid and liquid coexisting region within the semi-solid material have been developed to predict the defects of rheology forming parts. The Arbitrary Boundary Maker And Cell(ABMAC) method is employed to solve the two-Phase flow model of the Navier-Stokes equation. Theoretical model basis of the two-phase flow model is the mixture rule of solid and liquid phases. This approach is based on using the liquid and solid viscosity. The Liquid viscosity is pure liquid state value, however solid viscosity is considered as a function of the shear rate, solid fraction and power law curves.

• Journal of the Korean Society of Physical Medicine
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• v.13 no.4
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• pp.19-25
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• 2018

PURPOSE: This study was conducted to investigate the correlation between the activity of suprahyoid muscles, infrahyoid muscles and swallowing ability in stroke patients with dysphagia. METHODS: The subjects of this study were 120 patients who were diagnosed with CT or MRI stroke and had swallowing disorder at Daegu Metropolitan General Hospital from August 2014 to February 2017. The suprahyoid and infrahyoid muscle activity was measured in patients with dysphagia and the new videofluoroscopy swallowing studies scale (new VFSS scale) was used for evaluation of swallowing function. Correlation analysis was conducted using the measured data. RESULTS: The activities of suprahyoid muscles were 325.8 (%RVC) on average, while the average infrahyoid muscle activity was 302.65 (%RVC) and the average value of the new VFSS scale was 31.52. The total for oral organs was 3.62 on average and that for pharynx organs was 28.30 on average. The activity of the suprahyoid muscles showed a significant positive correlation with the activity of the infrahyoid muscles, but a significant negative correlation with the total oral phase, total pharyngeal phase and total new VFSS scale (p<.01). The activity of the infrahyoid muscles showed a significant negative correlation with the total oral phase, total pharyngeal phase, and total new VFSS (p<.01). CONCLUSION: Based on the results of this study, it is necessary for researchers to consider the infrahyoid and suprahyoid muscles when conducting swallowing rehabilitation.

• Journal of muscle and joint health
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• v.22 no.2
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• pp.67-77
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• 2015

Purpose: This study was a qualitative research using focus group interviews to collect data on the health care providers' perceptions of physical function in older adults with arthroplasty from hip fracture. Methods: A total of 12 subjects participated in this study. In order to conduct focus group interviews, structured manuscript, field notes, visual recording, and debriefing notes were referred and thematic analysis was used in analysis phase. Results: The six themes were raised: 'burdensome client', 'health care providers' perception of functional decline in older adults after surgery', 'health care providers' perception of caregiver', 'medical environment perceived as affecting physical function', 'crucial components perceived as encouraging functional restoration', and 'difficulty of pain management' with 18 subthemes. Conclusion: Healthcare providers perceived functional decline of elderly after arthroplasty and identified points facilitating or disturbing physical function Moreover, various perspectives on pain management related to physical function were represented.

• The Journal of the Acoustical Society of Korea
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• v.27 no.1
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• pp.1-11
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• 2008

To overcome the mid frequency limitation of geometrical acoustic techniques, the phased geometrical method was suggested by introducing the phase information into the sound propagation from the source. By virtue of phase information, the phased tracing method has a definite benefit in taking the interference phenomenon at mid frequencies into account. Still, this analysis technique has suffered from difficulties in dealing with low frequency phenomena, so called, wave nature of sound. At low frequencies, diffraction at corners, edges, and obstacles can cause errors in simulating the transfer function and the impulse response. Due to the use of real valued absorption coefficient, simulated results have shown a discrepancy with measured data. Thus, incorrect phase of the reflection characteristic of a wall should be corrected. In this work, the uniform theory of diffraction was integrated into the phased beam tracing method (PBTM) and the result was compared to the ordinary PBTM. By changing the phase of the reflection coefficient, effects of phase information were investigated. Incorporating such error compensation methods, the acoustic prediction by PBTM can be further extended to low frequency range with improved accuracy in the room acoustic field.

• Korean Journal of Applied Biomechanics
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• v.31 no.2
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• pp.95-103
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• 2021

Objective: The aim of this study was to investigate the differences in spatiotemporal gait performance, function, and pain of lower-extremity according to foot morphological characteristics. Method: This case-control study recruited 42 adults and they were classified into 3 groups according to foot morphology using navicular-drop test: pronated (≥ 10 mm), normal (5~9 mm), and supinated (≤ 4 mm) feet. Spatiotemporal gait analysis and questionnaires including Foot and Ankle Ability Measure activities of daily living / Sports, Western Ontario and McMasters Universities Osteoarthritis Index, Lower Extremity Functional Scale, International Physical Activity Questionnaire, and Tegner activity score were conducted. One-way analysis of variance was used for statistical analysis. Results: The pronated feet group showed longer loading response and double limb support in both feet and increased pre-swing phase in non-dominant feet. The supinated feet group demonstrated a longer swing phase in non-dominant feet and single limb support in dominant feet. However, there was no significant group difference in function and pain of knee joint and lower-extremity between groups. Conclusion: Our results indicated that abnormal spatiotemporal gait performance according to foot morphology. Although there was no difference in lower extremity dysfunction and pain according to the difference in foot morphology, they have the possibility of symptom occurs as a result of continuous participation in activities of daily living and sports. Therefore, individuals with pronated or supinated foot should be supplemented by utilizing an orthosis or training to restore normal gait performance.

• Wind and Structures
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• v.16 no.5
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• pp.433-455
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• 2013

A phase delay spectrum model towards the representation of spatial coherence of stochastic wind fields is proposed. Different from the classical coherence functions used in the spectral representation methods, the model is derived from the comprehensive description of coherence of fluctuating wind speeds and from the thorough analysis of physical accounts of random factors affecting phase delay, building up a consistent mapping between the simulated fluctuating wind speeds and the basic random variables. It thus includes complete probabilistic information of spatial stochastic wind fields. This treatment prompts a ready and succinct scheme for the simulation of fluctuating wind speeds, and provides a new perspective to the accurate assessment of dynamic reliability of wind-induced structures. Numerical investigations and comparative studies indicate that the developed model is of rationality and of applicability which matches well with the measured data at spatial points of wind fields, whereby the phase spectra at defined datum mark and objective point are feasibly obtained using the numerical scheme associated with the starting-time of phase evolution. In conjunction with the stochastic Fourier amplitude spectrum that we developed previously, the time history of fluctuating wind speeds at any spatial points of wind fields can be readily simulated.

• International conference on construction engineering and project management
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• 2015.10a
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• pp.602-603
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• 2015

Despite all efforts to reduce construction disaster, construction site accident rate has steadily increased in Korea since 2008. As a different approach from traditional research, there is a growing issue about design for safety concept to prevent construction disaster. The notion is that construction worker's safety need to be considered at design phase, not only at construction phase. Globally, the notion has been noted that to improve the safety of the worker and used in practice. However, in Korea, most of safety management guidelines are limited to construction phase. From recent statistics, only 1.4 percent of designer feel responsible for safety accident at construction site. In this circumstance, this research find out safety guidelines through literatures reviews and practical experience of safety management in other country which apply design for safety concept. Selected guidelines are verified by survey which is evaluated with risk, function, cost, time and aesthetic view categories. Through the survey, define guidelines which could be effectively applied in Korea. By using proposed safety guidelines for design phase, preventing construction accident and improving designer's recognition of safety issue at design phase are expected.

• The Korean Journal of Ceramics
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• v.6 no.2
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• pp.155-158
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• 2000

NMR study has been used for measuring precise quantity of the amorphous phase in the $Si_3N_4$powder. Care must be taken to allow the $^{29}$Si nuclear spin system to fully relax between pulses in order to make the signals proportional to the number of nuclei in each phase. $^{29}$Si MAS spectrum was decomposed into the three spectra of $\alpha$-, $\beta$-, and amorphous $Si_3N_4$assuming pseudo-Voigt function. Moreover, the Rietveld analysis of the powder X-ray diffraction data was performed to measure quantity of crystalline phases as $\alpha/\beta$ ratio.

• Journal of Astronomy and Space Sciences
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• v.28 no.4
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• pp.261-265
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• 2011

We investigate the sunspot area data spanning from solar cycles 1 (March 1755) to 23 (December 2010) in time domain. For this purpose, we employ the Hilbert transform analysis method, which is used in the field of information theory. One of the most important advantages of this method is that it enables the simultaneous study of associations between the amplitude and the phase in various timescales. In this pilot study, we adopt the alternating sunspot area as a function of time, known as Bracewell transformation. We first calculate the instantaneous amplitude and the instantaneous phase. As a result, we confirm a ~22-year periodic behavior in the instantaneous amplitude. We also find that a behavior of the instantaneous amplitude with longer periodicities than the ~22-year periodicity can also be seen, though it is not as straightforward as the obvious ~22-year periodic behavior revealed by the method currently proposed. In addition to these, we note that the phase difference apparently correlates with the instantaneous amplitude. On the other hand, however, we cannot see any obvious association of the instantaneous frequency and the instantaneous amplitude. We conclude by briefly discussing the current status of development of an algorithm for the solar activity forecast based on the method presented, as this work is a part of that larger project.

• Journal of the Korean Institute of Intelligent Systems
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• v.10 no.4
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• pp.285-292
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• 2000

In general, exploratory data analysis consists of three processes: i) assessment of clustering tendency, ii) cluster analysis, and iii) cluster validation. This analysis method requiring a number of iterations of step ii) and iii) to converge is computationally inefficient. In this paper, we propose a density function-based approximate fuzzy clustering method with a hierachical structure which consosts of two phases: Phase I is a features(i.e., number of clusters and cluster centers) extraction process based on the tendency assessment of a given data and Phase II is a standard FCM with the cluster centers intialized by the results of the Phase I. Numerical examples are presented to show the validity of the proposed clustering method.