• Steel and Composite Structures
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• 제35권3호
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• pp.415-437
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• 2020

Circular concrete filled steel tube (CFST) columns have an advantage over all other sections when they are used in compression members. This paper proposes a new approach for deriving a new empirical equation to predict the axial compressive capacity of circular CFST columns using the Artificial Neural Network (ANN). The developed ANN model uses 5 input parameters that include the diameter of circular steel tube, the length of the column, the thickness of steel tube, the steel yield strength and the compressive strength of concrete. The only output parameter is the axial compressive capacity. Training and testing the developed ANN model was carried out using 219 available sets of data collected from the experimental results in the literature. An empirical equation is then proposed as an important result of this study, which is practically used to predict the axial compressive capacity of a circular CFST column. To evaluate the performance of the developed ANN model and the proposed equation, the predicted results are compared with those of the empirical equations stated in the current design codes and other models. It is shown that the proposed equation can predict the axial compressive capacity of circular CFST columns more accurately than other methods. This is confirmed by the high accuracy of a large number of existing test results. Finally, the parametric study result is analyzed for the proposed ANN equation to consider the effect of the input parameters on axial compressive strength.

• Journal of Korean Neurosurgical Society
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• 제57권3호
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• pp.185-191
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• 2015

Objective : In order to provide normal values of the pediatric sub-axial cervical spinal canal and vertebral body growth pattern using computed tomographic scans, a total of 318 patients less than 10 years old were included. Methods : The growth of the vertebral body and canal space was investigated using four different age groups. The Torg ratio (TR) was calculated and all patients were classified into a low TR group and a high TR group according to a cutoff value of 1.0. To account for spinal curvature, the C3-7 angle was measured. Results : Very little axial expansion and growth in height were observed (2.9 mm and 3.4 mm, respectively), and the spinal canal increments (1.8 mm) were much smaller than the dimensions of the vertebral body. The mean TR values were $1.03{\pm}0.14$ at the C3 vertebral level, $1.02{\pm}0.13$ at C4, $1.05{\pm}0.13$ at C5, $1.04{\pm}0.13$ at C6, and $1.02{\pm}0.12$ at C7 in all patients. The mean sub-axial angle (C3-7) was $7.9{\pm}10.6^{\circ}$ (range: $-17-47^{\circ}$). Conclusion : The upper sub-axial spinal canal continuously increased in size compared to the lower sub-axial spine after 8 years of age. Considerable decrements in the TR was found after late childhood compared to younger ages. Generally, there were no significant differences between boys and girls in vertical length of the cervical vertebrae. However, the axial dimension of the vertebral body and the spinal canal space varied according to gender.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2017년도 제48회 춘계학술대회논문집
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• pp.704-708
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• 2017

A spray characteristics is carried out in a numerical simulation of swirl coaxial injector. The water and nitrogen are the oxidizer and fuel is used in cold flow condition. The simulation is carried out in 3d model with varying recess length. Reynolds stress turbulence and volume of fluid model were chosen to perform the simulation. The spray characteristics have been investigated as well as the influence of the inlet swirl strength of the internal flow. Effect of recess length is studied for the axial and radial velocity decreased with a reduced length of inner injector due to the decline vortex intensity.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 2003년도 춘계학술대회 논문집
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• pp.3-8
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• 2003

In this study, using linear and nonlinear deformation theories and by closed-form analysis and finite difference energy methods, respectively, various buckling load factors are obtained for stiffened laminated composite panel with trapezoidal type stiffeners and various longitudinal length to radius ratios, which are made from Carbon/Epoxy USN 125 prepreg and are simply-supported on four edges under uniaxial compression, and then for them, optimal design analyses are carried out by the nonlinear search optimizer, ADS.

• Tribology and Lubricants
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• 제11권5호
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• pp.150-155
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• 1995

In order to analyze the thermal effects of the rotor models, the finite element technique was used in this study. The length of the hat was investigated as a design parameter. At the start of each brake application the disk surface temperature rapidly increases to a maximum value and then decays due to external cooling and thermal conduction to the hat. The calculated results indicate that the long length of the hat shows the minimum deformation in axial direction, which is related to the thermal problems, coned wear, vibration and noise.

• 한국공작기계학회논문집
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• 제12권5호
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• pp.88-93
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• 2003

Buckling behavior of stiffened laminated composite cylindrical panel was studied using linear and nonlinear deformation theory. Various buckling load factors are obtained for stiffened laminated composite cylindrical panels with rectangular type longitudinal stiffeners and various longitudinal length to radius ratio, which made from Carbon/Epoxy USN150 prepreg and are simply-supported on four edges under uniaxial compression. Buckling behavior design analyses are carried out by the nonlinear search optimizer, ADS.

• 한국유체기계학회 논문집
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• 제11권5호
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• pp.37-43
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• 2008

An inducer is employed in a modern rocket feed system because it allows a turbopump system to operate at a high speed with low inlet pressures so as to minimize the weight and the size of the system. Cavitation performance can be improved by installing an inducer to the pump, enabling to increase the operational speed of the pump. The main purpose of an inducer is to increase the static pressure prior to an impeller to enable the impeller to operate satisfactorily under cavitation environments. In the present study the effects of axial distance between the inducer and the impeller on the performance of the pump were studied using both experimental and computational methods. Two inducers with different axial length were used for the experiments and the pump performances were measured. The experimental results show that the suction performance decreases as the axial gap between the inducer and impeller is increased.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 2002년도 제35회 춘계학술대회
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• pp.169-176
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• 2002

Axial crushing behavior of cylindrical shell Is utilized in the braking of the high-velocity impacting object. In this paper, truncated cone shape brake device is introduced. That is, thickness of the shell is increased gradually from the impacting end to the other end. A detailed experimental investigation on the quasi-static axial crushing behavior of truncated cone type brake devices has been performed. Specimens of various shape were tested to check the influence of design parameters such as length, radius, mean thickness, and conical angle of cylinder. Influence of the material properties were also investigated by adopting aluminum, low carbon steel, and stainless steel as constructing materials. By analyzing deformation procedures of the specimens, it is seen that conical angle influence the deformation mode and the sequence of the wrinkles generation. Braking distance and mean braking force of each specimen were predicted based on the crushing load measured from the tests.

• Journal of Electrical Engineering and Technology
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• 제13권6호
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• pp.2284-2291
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• 2018

This paper deals with optimum design of surface mounted permanent magnet synchronous motor (SPMSM) for automotive component. For a compact system structure, it was designed as a motor with a 14-pole 12-slot concentrated winding and hollow shaft. The motor is a thin type structure which stator outer diameter is relatively large compared to its axial length and is designed to have a high magnetic saturation for increasing the torque density. Since the high magnetic saturation in the stator core increases the axial leakage flux, a 3-dimensional (3-D) finite element analysis (FEA) is indispensable for torque analysis. However, optimum designs using 3-D FEA is inefficient in terms of time and cost. Therefore, equivalent 2-D FEA which is able to consider axial leakage flux is applied to the optimization to overcome the disadvantages of 3-D FEA. The structure for cost reduction is proposed and optimum design using equivalent 2-D FEA has been performed.

• 전자공학회논문지SC
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• 제49권3호
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• pp.47-52
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• 2012

본 논문은 Ku대역에서 동작하는 레이더용 원형편파안테나에 대한 설계 및 실험에 관한 것으로 선형안테나를 이용하여 원형편파안테나를 만들기 위해 Post를 이용함으로 안테나의 구조적 크기를 줄일 수 있었다. 원형편파 안테나의 축비 Bandwidth을 넓히기 위해 3개의 Post을 사용하였으며, 축비 최적화를 위해 Post사이 거리와 길이를 적절하게 선정하여 설계하였다. 또한 축비 최적화를 위해 반응표면법을 이용하여 최적화를 하였으며, 구현된 안테나는 12.7%의 Impedance Bandwidth와 설계 대역 내에서 2dB 이하의 축비 특성 및 7.8dBi 이상의 이득을 확인할 수 있었다.