• Computers and Concrete
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• 제10권4호
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• pp.419-434
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• 2012

This paper presents a finite element (FE) model for predicting the nonlinear response and behavior of a reinforced concrete T-beam deficient in shear under cyclic loading. Cracking loads, failure loads, response hysteresis envelopes and crack patterns were used as bench mark for comparison between experimental and FE results. A parametric study was carried out to predict the optimum combination of the open and close crack shear transfer coefficients (${\beta}_t$ and ${\beta}_c$) of the constitutive material model for concrete. It is concluded that when both shear transfer coefficients are equal to 0.2 the FE results gave the best correlation with the experimental results. The results were also verified on a rectangular shear deficient beam (R-beam) tested under cyclic loading and it is concluded that the variation of section geometry has no effect on the optimum choice of the values of shear transfer coefficients of 0.2. In addition, a parametric study based on the variation of concrete compressive strength, was carried out on the T-beam and it is observed that the variation of concrete compressive strength has little effect on the deflection. Further conclusions and observations were also drawn.

• 물과 미래
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• 제11권2호
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• pp.62-69
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• 1978

Interstational and interseasonal analyses of the correlation and variability in the seasonal and annual precipitation for 10 basic synoptic stations in South Korea, on the basis of rainfall record of over 40 years, are carried out. It is found that the climatic regions of precipitation could be classified by means of the interstational analysis for the correlations. Corrleation coefficients in interstational relationship of precipitation are lowest in autumn which characterizeds a strong locality while the highest value shows a relatively weak locality in winter. Interseasonal relationship between summer and winter precipitation shows mostly 10 percent significant level with all positive values. The magnitude of the variation coefficients are appeared to be in the order of winter, autumn, spring and summer. It is shown that the highest which is winter ranges between 0.33 0.58, and for the lowest summer, 0.26-0.44, respectively in the areal distribution of the coefficient. The secular changes of the variation coefficient in the recent trend show increases in spring at two station; Seoul and Incheon, in summer at Busan and in autumn at two stations; Busan and Incheon while in winter show devreases at the whole stations. An annual variation seems to show generally a constant trend as whole for all the stations.

• The Journal of Korean Physical Therapy
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• 제31권3호
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• pp.147-150
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• 2019

Purpose: The purpose of this study was to compare the reliability of unilateral hip abductor strength assessment in side-lying with break and make test in subjects with pelvic drop. Hip abduction muscles are very important in the hip joint structures. Therefore, it is essential to evaluate their strength in a reliable way. Methods: Twenty-five subjects participated in this study. Unilateral isometric hip abductor muscle strength was measured in side-lying, with use of a specialized tensiometer using smart KEMA system for make test, of a hand held dynamometer for break test. Coefficients of variation, and intra class correlation coefficients were calculated to determine test-retest reliability of hip abductor strength. Results: In make test, maximal hip abductor strength in the side-lying position was significantly higher compared with break test (p<0.05). Additionally, Test-retest reliability of hip abductor strength measurements in terms of coefficients of variation (3.7% for make test, 16.1% for break test) was better in the side-lying position with make test. All intraclass correlation coefficients with break test were lower than make test (0.90 for make test, 0.73 for break test). Conclusion: The side-lying body position with make test offers more reliable assessment of unilateral hip abductor strength than the same position with break test. Make test in side-lying can be recommended for reliable measurement of hip abductor strength in subjects with pelvic drop.

• 한국수자원학회논문집
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• 제41권1호
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• pp.1-15
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• 2008

본 연구의 목적은 금강수계의 가장 효율적인 가중치를 찾을 수 있는 절차를 제시하는 것이다. 일반적으로 다목적 최적화 모형의 결과는 목적함수에 부여된 가중치에 크게 좌우되는 경향이 있다. 특히 다목적 저수지 운영 문제의 경우는 어떤 유입량 시나리오가 적용되느냐에 따라 그에 적합한 가중치가 크게 달라질 수 있다. 따라서 유입량의 변동성을 감안해서 저수지 운영자에게 적합한 초기 가중치를 적용하는 것은 매우 큰 의미가 있다. 이에 본 연구는 유입량의 불확실성을 감안하여 적절한 가중치군을 도출할 수 있는 절차를 제안한다. 제안한 절차에서는 다중목적 최적화모형(GA-CoMOM)을 통해 파레토 집합에 대응되는 가중치군을 도출하고, DEA-윈도우분석(DEA-window analysis)과 교차효율성 분석(cross-efficiency analysis)을 사용하여 후보 가중치에 대한 순위를 산정하고, 이 결과를 분석해서 적합한 가중치를 선정한다. 이 절차를 금강 수계 저수지군 연계 운영 문제에 적용한 결과 유입량의 불확실성을 감안해서 가중치를 설정할 수 있었다.

• Tribology and Lubricants
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• 제14권1호
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• pp.14-22
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• 1998

This paper describes the effects of exciting frequency on the stiffness and damping coefticients of a 5-pad tilting pad journal bearing, LOP (load on pad) type. The stiffness and damping coefficients are investigated experimentally under the different values of exciting frequency, bearing load and shaft speed. These coefficients are estimated by measuring the response of the relative displacement between the bearing and the shaft and acceleration of the bearing due to the known exciting loads acting on the bearing. In order to analysis the response of exciting load, displacement and acceleration, a FFT analyzer is used. It is shown that the variation of exciting frequency has a little effect on both the stiffness and damping coefficients. Both the stiffness and damping coefficients in the loading direction are decreased by the increase of shaft speed but increased by the increase of bearing load.

• 한국수소및신에너지학회논문집
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• 제32권1호
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• pp.63-67
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• 2021

Accurate measurements of the heat transfer coefficients of concentric annular space for the test section is important to measure the tube-side heat transfer coefficients of working fluids. This paper presents the annular side heat transfer coefficients of concentric annuli with variation of tube diameter ratios using Wilson plot method. The test facility has a straight, horizontal test section with an active length of 3.0 m. Inner/outer diameters of test tubes are 7.0/7.5 and 8.0/8.56 mm, respectively. An outer diameter of annulus side is 16.0 mm. The test results show that convective heat transfer coefficients in annuli increase with annular diameter ratio. The correlations for convective heat transfer coefficients in annuli are also developed.

• 한국의류학회지
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• 제10권3호
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• pp.17-25
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• 1986

The objectives of this study are to investigate the variation of the sleeve form by changing arm movements and to study the relationship among the three aspects of sleeve (sleeve height, width and armhole girth) by changing arm movements. Plasrun gyps were used for this experimental research. The subjects of this study were elementary schoolgirls (9$\~$12 years old). Arm mevements were 4 types($0^{\circ},\;45^{\circ},\;90^{\circ},\;135^{\circ}$) to the vertical directions. The statistical methods used to analyze the data included mean, standard deviation, the Pearson's correlation coefficients and coefficients of determination. The results obtained from this study were as follows; 1. According to the arm movements, the sleeve form changed more in the front than in the back. 2. As the arm movements were increased vertically, the heights of sleeves and the girths of the armholes were decreased, and the widths of sleeves were increased. 3. Variation rates by changing arm movements were different according to the variation of arm movement, and were the highest in sleeve height. 4. There was a negative correlation between sleeve height and width, and a positive correlation between sleeve height and armhole girth.

• Journal of Microbiology and Biotechnology
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• 제33권3호
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• pp.348-355
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• 2023

Epifluorescence microscopy with image analysis was evaluated as a biofilm quantification method (i.e., quantification of surface area colonized by biofilms), in comparison with crystal violet (CV) staining. We performed different experiments to generate multispecies biofilms with natural and artificial bacterial assemblages. First, four species were inoculated daily in 16 different sequences to form biofilms (surface colonization, 0.1%-56.6%). Second, a 9-species assemblage was allowed to form biofilms under 10 acylase treatment episodes (33.8%-55.6%). The two methods comparably measured the quantitative variation in biofilms, exhibiting a strong positive relationship (R² ≥ 0.7). Moreover, the two methods exhibited similar levels of variation coefficients. Finally, six synthetic and two natural consortia were allowed to form biofilms for 14 days, and their temporal dynamics were monitored. The two methods were comparable in quantifying four biofilms colonizing ≥18.7% (R² ≥ 0.64), but not for the other biofilms colonizing ≤ 3.7% (R² ≤ 0.25). In addition, the two methods exhibited comparable coefficients of variation in the four biofilms. Microscopy and CV staining comparably measured the quantitative variation of biofilms, exhibiting a strongly positive relationship, although microscopy cannot appropriately quantify the biofilms below the threshold colonization. Microscopy with image analysis is a promising approach for easily and rapidly estimating absolute quantity of multispecies biofilms.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 1997년도 춘계학술대회논문집; 경주코오롱호텔; 22-23 May 1997
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• pp.443-446
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• 1997

This paper raises issues in testing the absorption coefficients of sound-absorptive samples in the standing wave tube according to the Korean standard of KS F 2814. The code does not consider any effect of air-damping during test. This limitation has been shown to yield much variation of sound absorption coefficients for recent sample tests whose coefficients are less than 10 %. An improved method of calculating the sound absorption coefficients is proposed in this work and its effectiveness in real test is also illustrated. Finally, the guide line for the modification of our national standard code KS F 2814 is suggested for the future.

• Smart Structures and Systems
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• 제16권6호
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• pp.1091-1105
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• 2015

Piezoelectric coefficient and dielectric constant of PZT-5H vary with electric field. In this work, variations of these coefficients with electric field are included in finite element modelling of a cantilevered plate instrumented with piezoelectric patches. Finite element model is reduced using modal truncation and then converted into state-space. First three modal displacements and velocities are estimated using Kalman observer. Negative first modal velocity feedback is used to control the vibrations of the smart plate. Three cases are considered v.i.z case 1: in which variation of piezoelectric coefficient and dielectric constant with electric field is not considered in finite element model and not considered in Kalman observer, case 2: in which variation of piezoelectric coefficient and dielectric constant with electric field is considered in finite element model and not considered in Kalman observer and case 3: in which variation of piezoelectric coefficient and dielectric constant with electric field is considered in finite element model as well as in Kalman observer. Simulation results show that appreciable amount of change would appear if variation of piezoelectric coefficient and dielectric constant with r.m.s. value of electric field is considered.