• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.10B
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• pp.899-915
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• 2003

Delivering rich and continuous media contents robustly over a wide range of network conditions of the wired/wireless Internet is a highly challenging task. To address this challenges, the continuous media applications at the edge of network has become more and more adaptive while the best-effort Internet is slowly progressing towards improved networking services. That is, the role of network adaptive media delivery, which dynamically links the quality demand of application contents to the underlying networking services, has become more crucial. In this paper, we will first review the required network adaptation functionalities seen from the application side: congestion control / rate control, error control, and synchronization / adaptive playout. Then, we start the coverage of networking support issues that helps the realization of network adaptive media streaming - from network support and protocol support toward consolidated support via middleware. Finally, we propose a dynamic network adaptation framework that efficiently leverages its awareness of both media application (including contents) and underlying networking support.

• Nuclear Engineering and Technology
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• v.31 no.5
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• pp.486-497
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• 1999

The local heat transfer coefficient is experimentally investigated for the reflux condensation in a countercurrent flow between the steam-air mixture and the condensate, A single vertical tube has a geometry which is a length of 2.4m, inner diameter of 16.56mm and outer diameter of 19.05mm and is made of stainless steel. Air is used as a noncondensible gas. The secondary side has a shape of annulus around vertical tube and the lost heat by primary condensation is transferred to the coolant water. The local temperatures are measured at 11 locations in the vertical direction and each location has 3 measurement points in the radial direction, which are installed at the tube center, at the outer wall and at the coolant side. In three different pressures, the 27 sets of data are obtained in the range of inlet steam flow rate 1.348∼3.282kg/hr, of inlet air mass fraction 11.8∼55.0%. The investigation of the flooding is preceded to find the upper limit of the reflux condensation. Onset of flooding is lower than that of Wallis' correlation. The local heat transfer coefficient increases as the increase of inlet steam flow rate and decreases as the increase of inlet air mass fraction. As an increase of the system pressure, the active condensing region is contracted and the heat transfer capability in this region is magnified. The empirical correlation is developed by 165 data of the local heat transfer. As a result, the Jacob number and film Reynolds number are dominant parameters to govern the local heat transfer coefficient. The rms error is 17.7% between the results by the experiment and by the correlation.

• Journal of Korean Ophthalmic Optics Society
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• v.13 no.4
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• pp.103-107
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• 2008

Purpose: This research measured the near addition powers of presbyopia in wearing the near spectacle for the first time. Methods: We evaluated age, sex, working group, spherical power and cylindrical power and measured the power of refractive error performed the both eyes (310 eyes) of 155 subjects subjectively noncycloplegic and power of addition using the cross cylinder method. Results: There were measured the near addition powers in the range of +0.75D ~ +1.75D. In case of the average addition, they were measured with +1.06D in subjects under 43 years of age, +1.08D in 44 to 46 years, +1.23D in 47 to 49 years and +1.46D in over 50 years of age. The average age in subjects was 47.6 years old and 74 male, 81 female, 71 near sighted working group and 83 far sighted working group. Conclusions: Near addition was correlated with age, working group and cylindrical power (P<0.05, P<0.05, P<0.05).

• Journal of Advanced Marine Engineering and Technology
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• v.28 no.1
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• pp.65-74
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• 2004

The heat transfer coefficient and pressure drop of $CO_2$(R-744) during gas cooling Process of carbon dioxide in a horizontal tube were investigated experimentally and theoretically. The experiments were conducted without oil in the refrigerant loop. The main components of the refrigerant loop consist of a receiver. a variable-speed pump. a mass flowmeter, an evaporator. and a gas cooler(test section). The main components of the water loop consist of a variable-speed Pump. an constant temperature bath. and a flowmeter. The gas cooler is a counterflow heat exchanger with refrigerant flowing in the inner tube and water flowing in the annulus The test section consists of smooth, horizontal stainless steel tube of 9.53 mm outer diameter and 7.75 mm inner diameter. The length of test section is 6 m. The refrigerant mass fluxes were 200 ~ 300 kg/($m^2{\cdot}s$) and the inlet pressure of the gas cooler varied from 7.5 MPa to 8.5 MPa. The main results were summarized as follows : The predicted correlation can evaluated the R-744 exit temperature from the gas cooler within ${\pm}10%$ for most of the experimental data, given only the inlet conditions. The predicted gas cooley capacity using log mean temperature difference showed relatively food agreement with gas cooler capacity within ${\pm}5%$. The pressure drop predicted by Blasius estimated the pressure drop on the $CO_2$ side within ${\pm}4.3%$. The predicted heat transfer coefficients using Gnielinski's correlation evaluated the heat transfer coefficients on the $CO_2$ side well within the range of experimental error. The predicted heat transfer coefficients using Gao and Honda's correlation estimated the heat transfer coefficients on the coolant side well within ${\pm}10\;%$. Therefore. The predicted equation's usefulness is demonstrated by analyzing data obtained in experiments.

• Journal of the Korean Society of Physical Medicine
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• v.9 no.2
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• pp.201-211
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• 2014

PURPOSE: The purpose of this study was to investigate the inter-rater absolute reliability and the concurrent validity of the Tinetti-gait scale that was translated into Korean for chronic stroke patients. METHODS: Fifty-two patients with post-stroke participated in this study. Inter-rater reliability was analyzed by Intraclass Correlation Coefficient ($ICC_{3,1}$) and Kappa coefficient, and absolute reliability was analyzed by the Standard Error of Measurement (SEM), and the Minimal Detectable Change (MDC). Concurrent validity was analyzed by correlating between the Tinetti-gait scale and physical functions. The physical functions were measured by using the Dynamic Gait Index(DGI), 10m walking test(10WT), One Leg Standing Test of affected/non-affected side(OLST), Sit to Stand test(STS), (Fugl Meyer assessment of Lower Extremity(FM-LE). RESULTS: The inter-rater reliability of the Tinetti-gait scale was high; $ICC_{(3,1)}=.91$ (95% CI=.85~.95) (very reliable), the range of Kappa coefficient were .73~.92 (substantial~good). The inter-rater agreement of the each item in Tinetti-gait scale ranged from .74 to .92 (95 % CI=.59~.95) (reliable~very reliable). The SEM and MDC were .56 and 1.55, respectively. In the results of concurrent validity, there were moderate positive correlation between Tinetti-gait scale and DGI (r=.78), 10WT (r=.74), OLST (r=.65~.73), FM-LE (r=67). And there was moderate negative correlation between Tinetti-gait scale and STS (r=-79) (p<.01). CONCLUSION: The Tinetti-gait scale(Korean version) was a reliable and valid tool to measure gait ability in patients with chronic stroke. Thus, it could be a useful tool for examining a gait ability of post-stroke patients. Further study should be conducted to investigate the usability to predict fall risk of post-stroke patients of the Tinetti-gait scale.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.11a
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• pp.503-506
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• 2005

The PWR Nuclear Fuel assembly consists of more than 250 fuel rods that are supported by leaf springs in the cells of more than 10 Spacer Grids (SG) along the rod length. Since it is not easy to conduct mechanical tests on a full-scale model basis, the small-scaled rod bundle (5$\times$5) is generally used for various performance tests during the development stage. As one of the small-scaled tests, a flow test should be carried out in order to verify the performance of the spacer grid like the coolant mixing performance and to obtain the Flow-Induced Vibration (FIV) characteristics of the rod bundle over the specified flow range. A vibration test should be also performed to obtain the modal parameters of the bundle prior to the flow test. In this study, we want to develop the estimation procedure of the damping ratio for the small scaled test bundle. For the damping factor of the rod bundle and the grid case at the first vibration mode, as one of the vibration tests, a so-called pluck testing has been performed in air as a preliminary test prior to in-flow damping measurement test. Logarithmic decrement method is used for calculation of the damping ratio. Estimated damping ratio of the rod bundle is about 0.7% with reasonable error of 2% for the previous results. Nonlinear behavior of the rod bundle might be stem mainly Iron the rod-grid support configuration.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.11a
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• pp.551-554
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• 2005

The method of the reduction of the automotive induction noise can be classified by the method of passive control and the method of active control. However, the passive control method has a demerit to reduce the effect of noise reduction at low frequency (below 500Hz) range and to be limited by a space of the engine room. Whereas, the active control method can overcome the demerit of passive control method. The algorithm of active control is mostly used the LMS (Least-Mean-Square) algorithm because the LMS algorithm can easily obtain the complex transfer function in real-time. Especially, When the Filtered-X LMS (FXLMS) algorithm is applied to an ANC system. However, the convergence performance of LMS algorithm goes bad when the FXLMS algorithm is applied to an active control of the induction noise under rapidly accelerated driving conditions. Thus Normalized FXLMS algorithm was developed to improve the control performance under the rapid acceleration. The advantage of Normalized FXLMS algorithm is that the step size is no longer constant. Instead, it varies with time. But there is one additional practical difficulty that can arise when a nonstationary input is used. If the input is zero for consecutive samples, then the step size becomes unbounded. So, in order to solve this problem. the Correlation FXLMS algorithm was developed. The Correlation FXLMS algorithm is realized by using an estimate of the cross correlation between the adaptation error and the filtered input signal to control the step size. In this paper, the performance of the Correlation FXLMS Is presented in comparison with that of the other FXLMS algorithms based on computer simulations.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.28 no.5
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• pp.485-491
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• 2010

Acquisition of information on failure slope, which may cause apprehension of second hand damage, requires acquisition of fast and accurate topographical data and efficient expression in indirect surveying method without accessing as needed. Therefore, in this study, the images on the intended area were photographed through hovering in the air by approaching collapsed road cut slope with the use of unmanned helicopter photography system. As a result of comparing the points observed by no prism total station and the 10 coordinate points analyzed through image analysis, the averages of absolute values were shown to be 0.056m in X axis direction, 0.082m in Y axis direction and 0.066m Z axis direction. In addition, the RMSE of the error for 10 points of test points were 0.015636m in X axis direction, 0.021319m in Y axis direction and 0.018734m in Z axis direction. Therefore, this method can determine the range of slope and longitudinal and cross sections of each slope in dangerous area that cannot be approached in relational image matching method for the terrains of such collapsed cut slope.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.8
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• pp.3301-3306
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• 2012

In LED chip packaging, die bonding is a very important process which fixes the LED chip on the lead frame to provide enough strength for the next process. Conventional pick-up device of the die bonder is simply operated by up and down motion of a collet and an ejector pin. However, this method may cause undesired problems such as position misalignment and/or severe die damage when the pick-up device reaches the die. In this study, to minimize the position alignment error and die damage, a die bonder is developed by adopting a new pick-up head for precise alignment and high speed feeding. To evaluate structural stability of the designed system, required finite element model of the die bonder is generated, and structural analysis is performed. Vibration analysis of the pick-up head is also performed using developed finite element model at operation frequency range. As a result of the analysis, deformation, stress, and natural frequency of the die bonder are investigated.

• Journal of Korean Neurosurgical Society
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• v.39 no.4
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• pp.256-259
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• 2006

Objective : Having a reliable and reproducible measurement technique to measure the sagittal contour in vertebral fractures is paramount to clinical decision making. This study is designed to determine the most reliable measurement technique in osteoporotic vertebral compression fracture. Methods : Fifteen lateral radiographs of thoracic and lumbar fractures were selected and measured on two separate occasions by three spine surgeons using six different measurement techniques [Centroid, Harrison Posterior Tangent Methods and 4 different types of modified Cobb method]. The radiograph quality was assessed and the center beam location was determined. Statistical analysis including ANOVA for repeated measures was carried out using the SAS software [v 8.0]. Results : The inter and intraobserver variance of the Cobb method 4 and Harrison posterior tangent method were significantly lower than the other four methods. The intraobserver correlation coefficients were the most consistent using the Cobb method 4 [0.982]. which was followed by the Harrison posterior tangent [0.953] and Cobb methods 1 [0.874]. The intraobserver agreement [% of repeated measures within 5 degrees of the original measurement] ranged from 42% to 98% for each technique for all three observers, with the Cobb method 4 showing the best agreement [97.8%] followed by the Harrison posterior tangent method [937%]. Conclusion : The Cobb method-4 and Harrison posterior tangent methods, when applied to measuring the kyphosis, are reliable and have a similar small error range. The Cobb method 4 shows the best overall reliability. However, the centroid method and Cobb method using a fractured endplate do not produce an accurate result due to inter and intraobserver differences in determining the baseline.