• KSCE Journal of Civil and Environmental Engineering Research
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• v.5 no.3
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• pp.31-38
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• 1985

The governing differential equations and the boundary conditions for the free vibration of fixed-ended uniform parabolic arch are derived on the basis of the equilibrium equations and the D'Alembert principle. The effect of rotary inertia as well as extensional and flexural deformations is considered in the governing differential equations. A trial elgenvalue method is used for determining the natural frequencies. The Runge-Kutta method is used in this method to perform the integration of the differential equations. The detailed studies are made of the lowest three vibration frequencies for the span length equal to 10m. The effect of the rotary inertia is analyzed and it's numerical data are presented in table. And as the numerical results the frequency versus the rise of arch and the radius of gyration are presented in figures.

• Journal of the Korean GEO-environmental Society
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• v.18 no.3
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• pp.5-14
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• 2017

Experimental study on strength characteristics of frozen soils is necessary for the safety evaluation of design and construction in cold region. The objective of this study is to evaluate the direct shear strength of frozen soils obtained from traditional system (Type-1), system with roller on the upper shear box (Type-2), and system with fixed upper shear box separated from bottom shear box (Type-3). Specimens mixed with sand, silt, and water are frozen to $-5^{\circ}C$, and then direct shear tests are conducted under the normal stress of 5, 10, 25, and 50 kPa. Experimental results show that the upper shear box of Type-1 touches the bottom shear box due to the rotation of the upper shear box. The shear strength obtained from Type-2 is overestimated because the preventing rotation force is added to shear force. Type-3 may acquire the only strength of the specimen, and shear strain at peak shear strength is similar to that at the beginning of vertical displacement occurrence. In addition, internal friction angle and cohesion at both peak and residual stresses in Type-3 are smaller than those of Type-2. This study shows that high strength specimens including frozen soils can be effectively evaluated using improved shear box system such as Type-3.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.2 no.2
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• pp.92-100
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• 1997

Distribution of bacterial abundance and production was investigated during October, 1995-August, 1996 in Lake Shiwha constructed artificially in 1994. Its water column was distinguished by two layers: the brackish surface layer with salinity ranged from 6 to 20‰ and the saline hypoxic/anoxic bottom layer with salinity of 17 to 27‰ Except for samples collected in March, 1996 (on average 13 ${\mu}g\;l^{-1}$), chlorophyll a concentration ranged from 27.6 to 249.5 ${\mu}g\;l^{-1}$ in the euphotic zone, indicating the hypertrophic condition of Lake Shiwha during most of the studied period. In this study, bacterial productions measured by $^3H$-thymidine incorporation method were similar to those by $^{14}C$-leucine incorporation method. In hypertrophic, surface waters of Lake Shiwha, bacterial abundance and production ranged from 1.4 to $19.5{\times}10^9\;cells\;l^{-1}$ and from 1.6 to $126.5{\times}10^7\;cells\;l^{-1}\;h^{-1}$ respectively; 2 to 4 fold and 2 to 30 fold higher than those in eutrophic coastal waters outside of Lake Shiwha, respectively. Turnover times of bacterial community in the surface layer of Lake Shiwha ranged from 0.2 to 8.9 day, indicating that bacteria in the lake seemed to adapt to the hypertrophic condition. In the hypoxic bottom layer, bacterial abundance and production was up to 3 fold and 20 fold lower than those in the surface layer, and showed slow bacterial growth. Significant correlations between the bacterial abundance, production, and community turnover time with water temperature indicate water temperature was the important factor controlling distribution and growth of bacteria. However, during summer season, bacterial production seemed to be regulated by supply of substrates.

• The Journal of Korean Society for Radiation Therapy
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• v.23 no.1
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• pp.31-39
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• 2011

Purpose: Helical Tomotherapy allows only coplanar beam delivery because it does not allow couch rotation. We investigated a method to introduce non-coplanar beam by tilting a patient's head for Tomotherapy. The aim of this study was to compare intrafractional movement during Tomotherapy between coplanar and non-coplanar patient's setup. Materials and Methods: Helical Tomotherapy was used for treating eight patients with intracranial tumor. The subjects were divided into three groups: one group (coplanar) of 2 patients who lay on S-plate with supine position and wore thermoplastic mask for immobilizing the head, second group (non-coplanar) of 3 patients who lay on S-plate with supine position and whose head was tilted with Variable Axis Baseplate and wore thermoplastic mask, and third group (non-coplanar plus mouthpiece) of 3 patients whose head was tilted and wore a mouthpiece immobilization device and thermoplastic mask. The patients were treated with Tomotherapy after treatment planning with Tomotherapy Planning System. Megavoltage computed tomography (MVCT) was performed before and after treatment, and the intrafractional error was measured with lateral(X), longitudinal(Y), vertical(Z) direction movements and vector ($\sqrt{x^2+y^2+z^2}$) value for assessing overall movement. Results: Intrafractional error was compared among three groups by taking the error of MVCT taken after the treatment. As the correction values (X, Y, Z) between MVCT image taken after treatment and CT-simulation image are close to zero, the patient movement is small. When the mean values of movement of each direction for non-coplanar setup were compared with coplanar setup group, X-axis movement was decreased by 13%, but Y-axis and Z-axis movement were increased by 109% and 88%, respectively. Movements of Y-axis and Z-axis with non-coplanar setup were relatively greater than that of X-axis since a tilted head tended to slip down. The mean of X-axis movement of the group who used a mouthpiece was greater by 9.4% than the group who did not use, but the mean of Y-axis movement was lower by at least 64%, and the mean of Z-axis was lower by at least 67%, and the mean of Z-axis was lower by at least 67%, and the vector was lower by at least 59% with the use of a mouthpiece. Among these 8 patients, one patient whose tumor was located on left frontal lobe and left basal ganglia received reduced radiation dose of 38% in right eye, 23% in left eye, 30% in optic chiasm, 27% in brain stem, and 8% in normal brain with non-coplanar method. Conclusion: Tomotherapy only allows coplanar delivery of IMRT treatment. To complement this shortcoming, Tomotherapy can be used with non-coplanar method by artificially tilting the patient's head and using an oral immobilization instrument to minimize the movement of patient, when intracranial tumor locates near critical organs or has to be treated with high dose radiation.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.35 no.3
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• pp.331-336
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• 2011

The three-dimensional complex curvature of the airfoil complicates the manufacture and repair of gas-turbine components. As a result of the developments in computer technology since the early 1990s, CNC-based technologies for machine tools and related programs have been increasingly applied in the gas turbine industry. In particular, fiveaxis simultaneous machines with adaptive functions have proven its excellent flexibility and productivity due to the capability in determining the 3D data from the unknown curvature. A well-organized robot system with eight-axis simultaneous control can lead to powerful standardization and high productivity. We summarize and review CNC technologies and their applications in the gas turbine industry, with a discussion of the manufacture and repair of gas turbine parts.

• Journal of Advanced Marine Engineering and Technology
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• v.36 no.2
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• pp.286-293
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• 2012

In this investigation, flow analysis with single phase has been performed for a centrifugal impeller with a design efficiency of 90%, head of 20m and rotational speed of 3500 rpm at a design flow rate of 16m3. The impeller was designed based on an empirical formula suggested by A.J. Stepanoff. In a case of the single phase analysis, the hydraulic efficiency and head is 88.8% and 19.4m, respectively, which showed a good agreement with the values designed. The flow analysis with two phases was carried out under the various NPSH, at whose 8.79m the cavitation on the suction side of the blade was observed. The required NPSH of the designed impeller is approximately 6.5m and above this value, the designed centrifugal pump impeller needs to be operated under inlet pressure condition.

• The Korean Journal of Applied Statistics
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• v.31 no.3
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• pp.353-366
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• 2018

This study uses mixed-effects models to predict thigh soft tissue artefact (STA), relative movement of soft tissue such as skin to femur occurring during hip joint motions. The random effects in the model were defined as STA and the fixed effects in the model were considered as skeletal motion. Five male subjects without musculoskeletal disease were selected to perform various hip joint rotational motions. Linear mixed-effects models were applied to markers' position vectors acquired from non-invasive method, photogrammetry. Predicted random effects showed similar patterns of STA among subjects. Large magnitudes of STA appeared on the points near the hip joint regardless of sides; however, small values appeared on the distal anterior.

• Journal of the Korean Arthroscopy Society
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• v.14 no.2
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• pp.92-101
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• 2010

The Hamstring autograft and the bone patellar bone tendon autograft have been widely used for anterior cruciate ligament reconstruction. In recent years, use of hamstring autograft for ACL reconstrution has been increased. The reason seems to be the advantages of the hamstring tendon such as high ultimate tensile load, low donor site morbidity and development of graft fixation method. These theoretical advantages have been increased as studies have shown that hamstring tendons actually regenerate after harvesting for ACL reconstruction. However, the concerns have arisen regarding the disadvantages of hamstring harvest, which were weakness of tibial internal rotation, the loss of flexion strength. The flexion strength loss has been controversial, therefore it needs to study whether restoration of flexion strength after hamstring regeneration is or not. In this study, we reviewed the current research of concerns on the advantage and disadvantage of hamstring tendon autograft and the hamstring regeneration. Furthermore, we compared the earlier studies and experiences regarding Hamstring regeneration with our research.

• Journal of the Society of Naval Architects of Korea
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• v.29 no.3
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• pp.140-148
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• 1992

The free vibration problem of symmetrically laminated composite rectangular plates is formulated based on anisotropic thick plate theory including the effects of shear deformation and rotary inertia. Considering the difficulty of obtaining closed-form solutions, Rayleigh-Ritz analysis using polynomials having the property of Timoshenko beam functions as trial functions is adopted. The boundary conditions elastically restrained against rotation are accomodated as well as classical boundary conditions. From the results of numerical studies, the validity of the present method is verified. And it is also found that the adoption of thick plate theory for the vibration analysis of laminated composite plates is essential because of the relatively large shear deformation effect, and that the convergence of the Rayleigh quotient to the stationary value is less rapid in anisotropic composite plates than that in the orthotropic ones due to more complicated mode shapes of the former.

• Journal of the Earthquake Engineering Society of Korea
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• v.11 no.3 s.55
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• pp.63-72
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• 2007

The Emergency Diesel Generator (EDG) is a very important equipment for the safety of a Nuclear Power Plant (NPP). In this study, the operating vibration of three kinds of EDG systems was measured. The target EDG systems are Yonggwang 5 unit and Ulchin 2 and 3 units. The Yonggwang 5 and Ulchin 3 unit EDG systems are the same type but the foundation systems are different. One is an anchor bolt type and the other is a spring and viscous-damper type. The purpose of these measurements is for a verification of the vibration isolation effect depending on the foundation system. As a result, It can be said that the spring and viscous damper system of the EDG performed better for the vibration isolation than that of anchor bolt type.