• Journal of the Korean Orthopaedic Association
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• v.54 no.3
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• pp.254-260
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• 2019

Purpose: To evaluate the relationship between the knee function at 1 year postoperation and the gap difference (90° flexion gap-extension gap) in total knee replacement. Materials and Methods: Eighty-two consecutive osteoarthritis knees that underwent primary total knee replacement using navigation from March 2017 June 2017 were evaluated prospectively. The gap was measured using navigation after reducing the patella with towel clips. After checking the average values of the medial and lateral gaps at extension and 90° flexion knee, the gap difference (90° flexion gap-extension gap) was calculated. The knees were divided into three groups according to the gap difference (gap difference<0 mm, 0 mm≤gap difference<2 mm, 2 mm≤gap difference). The Knee Society score (KSS) and maximal knee flexion were compared at 1 year postoperation among three groups. Results: The numbers of knees according to groups were 37, 29, and 16 knees in regular order. The average of the KSS knee, KSS function, and maximal knee flexion at the 1-year follow-up were 81.21±8.31, 71.34±9.84, and 126.48°±7.28°, respectively. No statistically significant difference in KSS was observed among the 3 groups. The third group (2 mm≤gap difference) showed a larger maximal knee flexion than the other groups in the Mann-Whitney test. Conclusion: The group of total knee replacement (2 mm≤90° flexion gap-extension gap) showed larger maximal knee flexion than the other groups at the 1-year follow-up in statistics.

• Journal of the Korean Society of Propulsion Engineers
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• v.23 no.3
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• pp.18-27
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• 2019

The flow mixing characteristics for the heated dual jets were numerically studied by using URANS (unsteady Reynolds-averaged Navier-Stokes). The increased turbulent diffusion was obtained for the compressible flow, and the thermal diffusion of incompressible flow increased more than that of compressible flow. From the results of FFT and phase portraits, periodic and quasi-periodic states were observed as the jet spacing increased. It was observed that linear variations of merging points and combined points were different because unsteady flow determined the flow mixing characteristics for a large jet spacing.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.39 no.9
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• pp.751-759
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• 2015

In this study, we investigate the Characteristics of the flowfields of a circular cylinder having a small triangular prism at the upstream side. We measure the fluid force on the circular cylinder and obtain a visualization of the flow fields using particle image velocimetry (PIV). The experimental parameters employed were the width ratios (H/B = 0.2~0.6) of the triangular prisms to the circular cylinder's diameter, and the gap ratios (G/B = 0~3) between the circular cylinder and the triangular prism. We observed that the drag reduction rate and Strouhal number of the circular cylinder increased and then decreased with G/B in the case of the same H/B. The drag reduction rate increased with H/B in the case of the same G/B. In the case where the circular cylinder had a small triangular prism, the stagnation regions were represented in the upstream and downstream sides of the circular cylinder.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.10 no.12
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• pp.2151-2156
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• 2006

Beamforming for underwater acoustic communication (UAC) is affected by the broadband feature of UAC signal, which has relatively low currier frequency as compared to the signal bandwidth. The narrow-band assumption does not hold good in UAC. In this paper, we discuss a broadband FIR beamformer for UAC using the baseband equivalent way signal model. We consider the broadband FIR beamformer for QPSK UAC with carrier frequency 25kHz and symbol rate 5kHz. Array geometry is a uniform linear way with 8 omni-directional elements and sensor spacing is the half of the carrier wavelength. The simulation results show that the broadband n beamformer achieves nearly optimum signal to interference and noise ratio (SINR) and outperforms the conventional narrowband beamformer by SINR 0.5dB when two-tap FIR filter is employed at each sensor and the inter-tap delay is a quarter of the symbol interval. The broadband FIR beamformer performance is more degraded as the FIR filter length is increased above a certain value. If the inter-tap delay is not greater than half of the symbol period, SINR performance does not depend on the inter-tap delay. More training period is required when the inter-tap delay is same as the symbol period.

• Journal of the Korea Concrete Institute
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• v.15 no.4
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• pp.513-521
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• 2003

Existing tests results have shown that confining the concrete compression region with closed stirrups improves the ductility and load-carrying capacity of beams. However, only few researchers have attempted to utilize the beneficial effects of the presence of these stirrups in design. This paper presents the result of experimental studies on the load-deflection behavior and the strengthening effect of laterally confined structural high-strength concrete beam members in which confinement stirrups have been introduced into the compression regions. Fifteen tests were conducted on full-scale beam specimens having concrete compressive strength of 41 MPa and 61 MPa. Different spacing of stirrups(0.25∼1.0d) and amount of tension steel($0.55{\sim}0.7{\rho}_b$) as major variables were investigated. And also, this study present an appropriate shear equation for decision of ultimate failure modes of high-strength concrete beams according to stirrup spacing. The equation is based on interaction between shear strength and displacement ductility. Prediction of failure mode from presented method and comparison with test results are also presenteded

• Proceedings of the Korea Water Resources Association Conference
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• 2007.05a
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• pp.542-545
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• 2007

터널의 노면 양쪽에 관로를 설치하여 유입된 지하수를 배출시키는 방법은 일반적인 터널 배수공법이지만 배수관로의 설치를 위한 추가적인 굴착은 공사기간과 공사비의 상승으로 이어지는 실정이다. 이에 터널 내에 별도의 배수관로 굴착 없이 노면 하부에 다열기둥을 일정 간격으로 매설하여 지하수의 흐름방향을 노면 하부로 유도시키는 경제적인 배수시스템이 현재 연구 중이다. 이 터널배수시스템은 추가적 굴착이 없어 기존의 배수시스템보다 경제적이지만 다열기둥의 연속적인 배치를 필요로 하므로 기존의 관로배수방식보다 더 많은 유체의 흐름저항을 받게 된다. 따라서 유체의 흐름에 효율적인 다열기둥 간의 배치간격에 대한 연구가 필요하다. 그래서 본 연구에서는 노면 하부에 다열기둥이 매설된 터널 내로 유입하는 지하수 배출을 목적으로 다열기둥 간의 배치간격에 따른 Manning계수의 변화를 수리실험을 통해 측정 분석하였다. 특히 Manning계수는 개수로에서 유체흐름 저항의 정도를 파악하는 데 이용되는 인자로 이를 활용하여 지하수 배수에 적절한 다열기둥 배치간격을 산정하였다. 본 연구를 통해 얻어진 수리실험 자료는 노면하부에 다열기둥을 매설하는 터널공사의 실제 설계를 위한 기초적인 참고자료로 사용될 것으로 기대된다.

• Proceedings of the Korea Water Resources Association Conference
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• 2010.05a
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• pp.1956-1960
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• 2010

최근 이상홍수 및 하천정비 등으로 인해 갈수시 또는 홍수시 하천 모니터링을 위한 기초자료로 유량측정의 필요성이 부각되고 있다. 기존 유량측정 방법은 고비용과 다수의 측정인력이 필요하기 때문에 이를 개선하기 위하여 최근 전자장비를 이용한 비접촉식 유량측정에 대한 연구가 다수 진행 중에 있다. 이 중 간편하고 측정 정확도를 유지할 수 있는 표면영상유속계(SIV, Surface Image Velocimetry)에 대한 연구가 국내외에서 다양하게 이루어지고 있다. 표면영상유속계는 일정 시간 간격을 갖는 두 영상을 분석하여 유속을 계산하기 때문에 수표면이 움직이는 시간보다 두 영상 사이의 시간 간격을 길게 할 경우 잘못된 상관영역을 찾게 되어 유속 측정의 정확도를 떨어뜨릴 수 있다. 이러한 문제점을 개선하기 위해서 영상간의 시간간격 변화에 따른 표면영상유속계의 정확도 분석을 수행하였다. 본 연구에서는 영상간의 시간간격에 따른 표면영상유속계의 정확도 분석을 위해 현장에서 수면 요철이 발생하는 근경 영상을 이용하여 영상내의 수면 움직임의 최소 지속시간을 측정하였다. 측정 결과 대부분의 수면 요철은 0.1 ~ 0.2 초 내에서 발생하였다. 측정 결과 일반 캠코더를 이용하여 초당 최대 30장의 영상을 이용하여 하천 표면유속을 측정한다면 문제가 없을 것으로 판단된다.

• Journal of KIISE:Computing Practices and Letters
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• v.8 no.1
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• pp.9-16
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• 2002

Join operation exert a great effect on the performance of system in temporal database as in the relational database. Especially, as for the temporal join, the optimization of interval partition decides the performance of query processing. In this paper, to improve the efficiency of parallel join query in temporal database. I proposed Minimum Interval Partition(MIP) scheme that time interval partitioning. The validity of this MIP algorithm that decides minimum breakpoint of the partition is proved by example scenario and I confirmed improved efficiency as compared with existing partition algorithm.

• The Korean Journal of Physiology
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• v.19 no.1
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• pp.61-72
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• 1985

In order to compare the cardiac function of various groups of athletes, the resting electrocardiographic time intervals, amplitudes and vectors were analyzed in high school athletes of throwing(n=7), jumping(n=11), short track(n=8), long track(n=14), boxing(n=7), volleyball(n=8) and baseball(n=9), and nonathletic control students(n= 19). All athletic groups showed a significantly longer R-R interval(0.96-1.09 sec) than the controls (0.78 sec). Therefore, the heart rate was significantly slower in atheletes than in the control, but was not different among the different athletic groups. R-R interval is the sum of intervals of P-R, 0-T and T-P: P-R and Q-T intervals showed no difference among the control and athletic groups, but T-P interval in the jump, short track, long track and boxing groups was significantly higher than the control. R-B interval showed a significant correlation with T-P or Q-T intervals but no correlation with P-R or QRS complex. Comparing the amplitude of electrocardiographic waves, the athletic groups showed a lower trend in P wave than the controls. T wave in lead $V_5\;(Tv_5)$ was similar in the athletic and control groups. The long track group showed a significantly higher waves of $Rv_5$, $Sv_1$, and the sum of $Rv_5$ and $Sv_1$ than not only the controls but also the other athletic group. The angles of P, QRS, and T vector in the frontal and horizontal planes were not different among the control and all the athletic groups. Each athletic group stowed a lower trend in amplitude of P vector in the frontal plane, but in horizontal plane, throwing, jump, short track and baseball groups showed a significantly lower than the controls. The amplitude of QRS and T vector was similar in the athletic and control groups, but only the baseball group showed a significantly higher QRS vector in the frontal plane. In taken together, all the athletic groups showed a slower heart rate than the controls, mainly because of elongated T-P interval. Comparing the electrocardiographic waves and vector, the athletic groups showed lower amplitudes of P wave and P vector than the controls. Values of $Rv_5$ and $Sv_1$ strongly suggest that only the long distance runners among the various athletic groups developed a left ventricular hypertrophy.

• Journal of Korean Society of Environmental Engineers
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• v.36 no.3
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• pp.214-220
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• 2014

The aim of this study is to optimize the efficiency of a photobiorector on the growth rate of Chlorella vulgaris (C. vulgaris) by varying distance of optical panel (OP). The round shaped C. vulgaris (FC-16) having the size of $3-8{\mu}m$ is employed in this study. The cells of C. vulgaris are cultured in the Jaworski's Medium with deionized water at $22^{\circ}C$ for 15 days. The OP is placed at four different distances i.e., at 225 mm distance (Run 1), 150 mm distance (Run 2), 112.5 mm distance (Run 3) and 90 mm distance (Run 4) having a LED (Light Emitting Diode) source. The diffuse rate is achieved to 86%, 90%, 92% and 94% for Run 1, Run 2 Run 3 and Run 4, respectively. A narrower distance of OP caused to effectively to increase the efficiency of diffuse light rate. For mass cultivation of this biomass, medium is changed according to distance of OP after attaining a maximum biomass concentration; Run 1 in 8 days, Run 2 in 6 days, Run 3 in 4 days and Run 4 in 3 days. In addition, the amount of maximum biomass rate for Run 4 was reached 3 times higher than that of Run1. However, growth rate, chlorophyll per cell, cell volume and doubling time are found to be Run 3 and Run 4 higher than that of Run 1 and Run 2 samples. However, Run 3 and Run 4 are having a slight difference in all these measurements. These findings suggest that in terms of economic consideration and efficiency towards simultaneous mass cultivation of biomass, Run 3 was found to be more effective than other samples.