• Journal of the Computational Structural Engineering Institute of Korea
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• v.14 no.4
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• pp.469-479
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• 2001

In the present study, free vibration analysis of multi-delaminated beams is performed. In order to investigate the effects of mu1ti-delaminations on the dynamic characteristics of multi-delaminated beams, the general kinematic continuity conditions are derived from the assumption of constant curvature at the multi-delamination tip. Frequency equations of multi-delaminated beams are obtained by dividing the global multi-delaminated beam into beam segments and by imposing recurrence relation from the continuity conditions un each sub-beam. The comparisons between the results of numerical analysis obtained by finite element analysis and those of present analysis give good agreement with each other. It is shown that the effects of multi-delaminations on free vibration characteristics of laminated beams could be used to detect their sizes, types and locations from the results.

• Economic and Environmental Geology
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• v.48 no.3
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• pp.199-204
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• 2015

In this study, we aimed to make antibiotic-intercalated smectite composites using amoxicillin and clarithromycin as hygroscopic antibiotics, and gentamicin, tobramycin and netilmicin as non-hygroscopic aminoglucosides, and to check their drug delivery potential in gastric system using preliminary in-situ column release test for clarithromycinsmectite composite. All antibiotics were successfully intercalated into the interlayer of smectite by cation-exchange reaction in the batch experiment. Equilibrium batch test showed that clarithromycin-intercalation followed Langmuir isotherm and the possible maximum amount was calculated as 1.811 mmole/g. Clarithromycin was continuously released by the solutions of pH=2, 3, and 4 and the amount was decreased with pH increase.

• Journal of Power System Engineering
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• v.13 no.4
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• pp.49-55
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• 2009

복합재 적층판의 자유단 근처에서 나타나는 층간 응력의 집중 현상을 층간면 효과를 고려해 해석하였다. 복합재 적층판 내부의 임의의 위치에서 3차원 평형방정식을 만족시키기 위해 렉니츠키 응력함수를 도입하였으며, 가상일의 원리를 이용하여 지배방정식을 유도하였다. 주어진 응력함수를 이용하여 구한 3차원 응력들은 복합재 적층판의 아래 위 면뿐만 아니라 자유단에서 하중자유조건을 잘 만족한다. 기하학적 불연속성 때문에 복합재 적층판의 자유단에서는 응력의 특이가 발생하지만, 층간면 효과를 고려하게 되면 층간응력의 집중현상을 정확하게 해석할 수 있다. 자유단에서 발생한 층간응력의 크기를 보면, 층간면 효과를 고려할 경우, 응력특이 효과가 많이 줄어드는 것을 관찰할 수 있다. 본 연구에서 주어진 층간면에서의 정확한 응력 해석은 복합재 적층판의 강도설계를 수행하는 초기 설계 툴로 사용할 수 있다.

• Korean Chemical Engineering Research
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• v.46 no.1
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• pp.56-62
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• 2008

Characteristics of heat transfer were investigated in a three-phase swirling fluidized bed whose diameter was 0.102 m and 2.5 m in height. Effects of gas and liquid velocities, particle size and liquid swirling ratio ($R_S$) on the immersed heater-to-bed overall heat transfer coefficient were examined. The heat transfer characteristics between the immersed heater and the bed was well analyzed by means of phase space portraits and Kolmogorov entropy(K) of the time series of temperature difference fluctuations. The phase space portraits of temperature difference fluctuations became stable and periodic and the value of Kolmogorov entropy tended to decrease with increasing the value of liquid swirling ratio from 0.1 to 0.4. The value of Kolmogorov entropy exhibited its minimum with increasing liquid swirling ratio. The value of overall heat transfer coefficient (h) showed its maximum with the variation of liquid velocity, bed porosity or liquid swirling ratio, but it increased with increasing gas velocity and particle size. The value of K exhibited its maximum at the liquid velocity at which the h value attained its maximum. The overall heat transfer coefficient and Kolmogorov entropy were well correlated in terms of dimensionless groups and operating variables.

• Journal of Korean Society of Steel Construction
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• v.13 no.3
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• pp.233-244
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• 2001

In this study, flexural rigidity reduction of multi-delaminated composite beams are investigated. In order to evaluate the flexural rigidity reduction. Performed theoretical analysis. In order to investigate flexural rigidity reduction about effects of delamination on composite beams, the general kinematic governing equations are derived and solved by dividing the delaminated beam and imposing the continuity conditions into each sub-beam. For condition to appear multiple delamination through the laminated composite beams, the flexural rigidity reduction are compared according to many stacking sequences and several forms for delaminations. The present study could be used to evaluate the flexural rigidity reduction of composite laminated beams on multi-delaminations.

• Transactions of the Korean Society of Mechanical Engineers
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• v.13 no.5
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• pp.911-920
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• 1989

It this study, beam-type bend specimen is used to evaluate the interlaminar fracture toughness of laminated composite under mixed-mode deformations. The specimen is loaded under three-point bending and hence produced mixed-mode deformations in the vicinity of the crack tip according to the variation of the thickness ratio on delamination plane. Total energy release rate is obtained by elementary beam theory considering the effect of shear deformation. The partitioning of total value into mode-I and mode-II components is also performed. The mixed-mode interlaminar fracture toughness is evaluated by experiments on specimens with several thickness ratios of delamination plane. As the part of delamination plane is thicker, the effect of shear deformation on total energy release rate is increased. Beam-type bend specimen men may be applied to obtain informations on the mixed-mode interlaminar fracture behavior of laminated composites.

• Journal of Environmental Policy
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• v.14 no.1
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• pp.113-134
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• 2015

In new housing demand, proportion of occupied multi-housing is 89.9% (statistics from 2013). In this way, with many generations living together, apartment noise disputes between the neighbors are continuously rising. The apartment noise problem in Korea is at a very serious level worldwide (about 88% of the population is experiencing stress due to apartment noise). On the other hand, the government has strengthened the regulations (such as the thickness of the floor and floor impact sound reduction performance, etc.) and promoted a resolution of its own for each multi-housing estates for mediating disputes on apartment noise. However, such physical regulations and passive management policies still presents a limit to the dispute mitigation of apartment noise. Also, in order to improve the quality of life in living spaces, policy on health effects of apartment noise should be provided. Therefore, we investigated a case study of the noise exposure-human body reaction to analyze the effect of noise on health. On the basis of this, the health effects according to the exposure period of apartment noise were considered.

• Journal of the Korean Society for Precision Engineering
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• v.24 no.3 s.192
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• pp.23-30
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• 2007

• Journal of the Earthquake Engineering Society of Korea
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• v.12 no.2
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• pp.69-80
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• 2008

In this study, improved capacity spectrum method (CSM) is proposed. The method can account for higher mode contribution to the seismic response of MDOF systems. The CSM has been conveniently used for determining maximum roof displacement using both demand spectrum and capacity curve of equivalent SDOF system. Unlike the conventional CSM, the maximum roof displacement is determined without iteration using inelastic displacement ratio and R factor calculated from demand spectrum and capacity curve. Three moment resisting steel frames of 3-, 9- and 20-stories are considered to test the accuracy of the proposed method. Nonlinear response history analysis (NL-RHA) for three frames is also conducted, which is considered as an exact solution. SAC LA 10/50 and 2/50 sets of ground motions are used. Moreover, this study estimates maximum story drift ratios (IDR) using ATC-40 CSM and N2-method and compared with those from the proposed method and NL-RHA. It shows that the proposed CSM estimates the maximum IDR accurately better than the previous methods.

• Korean Chemical Engineering Research
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• v.44 no.5
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• pp.505-512
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• 2006

Characteristics of particle holdup and heat transfer were investigated in a liquid-particle swirling fluidized bed whose diameter was 0.102 m and 2.5 m in height. Effects of liquid velocity, particle size and swirling liquid ratio($R_s$) on the particle holdup and immersed heater-to-bed overall heat transfer coefficient were examined. The particle holdup increased with increasing particle size and swirling liquid ratio but decreased with increasing liquid velocity.The local particle holdup was relatively high in the region near the heater when the $R_s$ value was 0.1~0.3, but the radial particle holdup was almost uniform when the $R_s$ value was 0.5, whereas, when the $R_s$ value was 0.7, the local particle holdup was relatively low in the region near the heater. The heat transfer characteristics between the immersed heater and the bed was well analyzed by means of phase space portraits and Kolmogorov entropy(K) of the time series of temperature difference fluctuations. The phase space portraits of temperature difference fluctuations became stable and periodic and the value of Kolmogorov entropy tended to decrease with increasing the value of $R_s$ from 0.1 to 0.5. The Kolmogorov entropy exhibited its maximum value with increasing liquid velocity. The value of overall heat transfer coefficient(h) showed its maximum value with the variation of liquid velocity, bed porosity or swirling liquid ratio, but it increased with increasing particle size. The value of K exhibited its maximum at the liquid velocity at which the h value attained its maximum. The particle holdup and overall heat transfer coefficient were well correlated in terms of dimensionless groups of operating variables.