• 한국전산유체공학회:학술대회논문집
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• 2011.05a
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• pp.543-549
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• 2011

In this paper, diagonal implicit harmonic balance method is applied to analyze helicopter rotor blade flow. Periodic boundary condition for Fourier coefficients is also applied in hover and forward flight condition. It is available enough to simulate the forward flight problem with only one rotor blade using the periodic boundary condition in frequency domain. In order to demonstrate present method Carodonna & Tung's rotor blades are used and the results are compared to time-accurate method and experimental data.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.29 no.3
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• pp.214-219
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• 1993

Counter balance valve is used as one part of hydraulic motor brake system. The function of this valve is to protect over-run or free falling of inertia load. But occasionally the brake system with counter balance valve makes some undesirable problems such as pressure surges or vibrations. These problems may hurt system safety and driver's conformability. Nevertheless, studies on dynamic characteristics of hydraulic system including counter balance valve are very rare, so further accumulation of research results are required. In this study, for the purpose of easy estimation about dynamic characteristics of hydraulic system including counter balance valve, precise formulation describing fluid dynamics and valve dynamics under various boundary conditions were made. The equations obtained in the preceding process include some parameters that must be got experimentally. Flow coefficients of valve and choke are the most significant ones among the parameters. So these parameters are obtained experimentally in this study, and experimental equations obtained from the experimental data were used for numerical calculation. The equations were analysed by numerical integration using Runge-Kutta method, because the equations contain various nonlinear terms. From the numerical analysis, it was verified that the dynamic response of counter balance valve and pressure variation at each elements can be estimated very easily. So the analysing method developed in this study enabled very easy estimating the relation between the performances of counter balance valve and various physical parameters related to the valve. Conclusively, it is said that the results obtained in this study can be used very usefully to develop a new type counter balance valve or to apply the valve to actual hydraulic system for various industrial equipments.

• Wind and Structures
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• v.18 no.2
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• pp.135-154
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• 2014

Aerodynamic characteristics of crescent and D-shape bundled conductors were measured by high frequency force balance technique in the wind tunnel. The drag and lift coefficients of each sub-conductor and the whole bundled conductors were presented under various attack angles of wind. The galloping possibility of bundled conductors is discussed based on the Den Hartog criterion. The influence of icing thickness, initial ice accretion angle and sub-conductor on the aerodynamic properties were investigated. Based on the measured aerodynamic force coefficients, a computationally efficient finite element method is also implemented to analyze galloping of iced bundled conductors. The analysis results show that each sub-conductor of the bundled conductor has its own galloping feature due to the use of aerodynamic forces measured separately for every single sub-conductors.

• Physical Therapy Korea
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• v.15 no.4
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• pp.87-96
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• 2008

The purpose of this study was to establish the reliability of the Trunk Impairment Scale (TIS) translated into Korea in patients with stroke. It also aims to score the quality of trunk movement and to be a tool for the treatment. The TIS consists of three subscales that static sitting balance, dynamic sitting balance and co-ordination. The TIS score ranges from a minimum of 0 to a maximum of 23. Twenty-five stroke patients (13 males, 12 females) were examined by two physiotherapists. Interrater and test-retest reliability were assessed. Kappa and weighted kappa values for the items of the trunk assessment of the TIS ranged from .67 to 1.00. Intraclass correlation coefficients for interrater and test-retest agreement were .95 and .97. Cronbach alpha coefficients for internal consistency range from .87 to .97. The TIS provide reliable assessments for the trunk and are valid scales for measuring trunk performance in patients with stroke. TIS can be used as a guideline for treatment and the assessment of quality of trunk activity.

• Journal of the Korean Society for Precision Engineering
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• v.22 no.11 s.176
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• pp.111-117
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• 2005

The vibration problems associated with gear coupled rotors have been the focus of much engineering work. These systems are complex and difficult to analyze in that they have the problems associated with conventional rotors plus those additional problems associated with the gear couplings. This paper examines the problems peculiar to the gear mesh. Because of the meshing action of gears, the elasticity of the gear teeth introduces time-varying stiffness coefficients into the governing equations of motion. This means that system response must be thought of in terms of Mathieu-type equations, where multiple-frequency response occur due to the periodic coefficients. The meshing action of the gears also couples the lateral and torsional gear motions. Gear errors, such as tooth profile and spacing errors, produce forces and torque that excite the system at multiple frequencies, some of which are much higher than shaft rotational speed. To investigate how to the time-varying stiffness in the gear teeth and the gear errors act one the dynamic response of the gear coupled rotors, a three-dimensional dynamic model with lateral-tortional oscillation is developed. The harmonic balance technique is employed to solve this mathieu-type problem.

• Journal of Korean Medicine Rehabilitation
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• v.21 no.1
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• pp.115-123
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• 2011

Objectives : This study was designed to investigate the correlation coefficients among Oswestry low-back pain disability index(ODI), Roland-Morris disability questionnaire (RMD), visual analogue scale(VAS), lumbar lordosis angle(LLA), Cobb's angle and Ferguson's angle(FA). Methods : We measured LLA, Cobb's angle, and FA of 42 students. Then we researched ODI, RMD and VAS of all students, and analyzed correlations coefficient among all of them. Results : 1. There was significant correlation among VAS, RMD, ODI. 2. There was significant correlation between ODI and Cobb's angle. 3. There was no significant correlation between LLA, FA, Cobb's angle and VAS. 4. There was no significant correlation among LLA, FA, Cobb's angle and RMD. Conclusions : According to above results, there was no significant correlation between lumbosacral balance and low back pain except between ODI and Cobb's angle. On the other hand, there was significant correlation among RMD, ODI and VAS.

• Physical Therapy Korea
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• v.15 no.1
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• pp.86-95
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• 2008

The Pediatric Balance Scale (PBS) is a modified Berg's Balance Scale developed as a balance measure for school-aged children with mild to moderate motor impairments. The purpose of this study was to determine the inter-examiner reliability of the Korean version of PBS when applied to children with developmental delays. In this study, PBS was administrated to a total of 79 children with developmental delays (17 with global developmental delay, 31 with cerebral palsy, and 31 with mental retardation) in the Seoul Community Rehabilitation Center. Two pediatric trained physical therapists with longer than 13 year of clinical experience scored the children's performance blind, while replaying videotaped data. The inter-examiner reliability was statistically determined by intraclass correlation coefficients (ICCs). The results of this study revealed that the Korean version of PBS seems to have high inter-examiner reliability when applied to children with movement disorders such as global developmental delay (ICC=.96) and cerebral palsy (ICC=.97); however, it has relatively lower inter-examiner reliability (ICC=.78) for children with developmental delay secondary to mental retardation. therefore, the results support that the Korean version of the PBS could be a useful clinical measurement to assess the balance skills for children with developmental delay who have an adequate level of cognition to enable them to fol1ow the verbal instructions to complete the test.

• The Journal of Korean Physical Therapy
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• v.29 no.3
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• pp.122-127
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• 2017

Purpose: The aim of this study was to investigate if the 7-item Berg balance scale (BBS) 3-point, which is a short form of the BBS (SFBBS), has compatible psychometric properties in comparison with the original BBS, and also to study the concurrent validity using a 10-meter walk test (10mWT) and a timed up and go test (TUG), which are widely used with SFBBS in clinical settings. Methods: A total of 255 patients who had experienced stroke participated in this cross-sectional study. We used results obtained from 188 patients who completed both 10mWT and TUG. The three levels in the center of the BBS were collapsed to a single level (i.e.,0-2-4) to form the SFBBS. The concurrent validity was assessed by computing the Spearman coefficients for correlation among outcome measures and in between each outcome measure and the SFBBS. As there were four outcomes, the corrected p-value for significant correlation was 0.013 (0.05/4). Results: Spearman coefficients for correlations and evaluation instruments for concurrent validity revealed significantly high validity for both of SFBBS and BBS (r=0.944). 10mWT and TUG were -0.749 and -0.770 respectively, which are in the high margin and are statistically significant (p>0.000). Conclusion: SFBBS has sound psychometric properties for evaluating patients with stroke. Thus, we recommend the use of SFBBS in both clinical and research settings.

• Journal of Korea Spatial Information System Society
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• v.5 no.1 s.9
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• pp.39-47
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• 2003

The purpose of this paper is to present the method of acquiring 3D GIS data using the statistical estimating methods of Well Log for balancing Seismic data. We use the reflection coefficients of seismic data to get the parameters for the reservoir characterization and we balance the reflection coefficients of seismic data using well log to increase the confidence of the estimated result. Well logs are required to balance the reflection coefficients at the point where seismic data are acquired. In this research, we discuss the geostatistical estimation methods and we applied these methods to real data. Kriging gives high weights to the close well logs, which means estimated results are mainly affected by close well log. High value of cross variograms gave big difference on cokriging result comparing to kriging results and low value of cross variogram gave little differences.

• Wind and Structures
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• v.25 no.5
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• pp.475-492
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• 2017

Inclined and yawed circular cylinder is an essential element in the widespread range of structures. As one of the applications, cables on bridges were reported to have the possibility of suffering a kind of large amplitude vibration called dry galloping. In order to have a detailed understanding of the aerodynamics related to dry galloping, this study carried out a set of wind tunnel tests for the inclined and yawed circular cylinders. The aerodynamic coefficients of circular cylinders with three surface configurations, including smooth, dimpled pattern and helical fillet are tested using the force balance under a wide range of inclination and yaw angles in the wind tunnel. The Reynolds number ranges from $2{\times}10^5$ to $7{\times}10^5$ during the test. The influence of turbulence intensity on the drag and lift coefficients is corrected. The effects of inclination angle yaw angle and surface configurations on the aerodynamic coefficients are discussed. Adopting the existed the quasi-steady model, the nondimensional aerodynamic damping parameters for the cylinders with three kinds of surface configurations are evaluated. It is found that surface with helical fillet or dimpled pattern have the potential to suppress the dry galloping, while the latter one is more effective.