• Journal of Ocean Engineering and Technology
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• v.21 no.3 s.76
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• pp.52-57
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• 2007

Composite material is one of the strongest candidates for deep see pressure hulls. Research regarding composite cylinders, subjected to hydrostatic pressure, has been ongoing for a couple of decades, abroad, but domestic research is very new. Experimental investigations seem necessary, in order to understand their structural behavior not only up to the ultimate limit state, but in the post-ultimate regime. That experimental information will be very helpful in the development of any theoretical methods or to substantiate any commercial numerical packages for structural analyses. In this study, ultimate strength tests on seven composite cylinders subjected to hydrostatic pressure are reported, which includes the fabrication method of models, mechanical properties of the material, initial shape imperfection measurements, test procedure, and strain and axial shortening measurements during the tests. The ultimate strengths of the models were compared with predictions of numerical analyses. The numerical predictions are higher than the test results. It seems necessary to improve the accuracy of the numerical predictions by considering the initial shape and material imperfections.

• Journal of Korean Association for Spatial Structures
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• v.6 no.1 s.19
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• pp.55-63
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• 2006

Concrete-filled steel columns consist of circular, square or rectangular hollow sections filled concrete. Much research has studied for the behavior of concrete-filled steel structures. The advantages from structural point of view are the triaxial confinement of the concrete within the section, and the fire resistance of the column which largely depends on the residual capacity of the concrete core. The axial capacity of a concrete-filled rectangular or circular section is enhanced by the confining effect of the steel section on the concrete which depends in the magnitude on the shape of the section and the length of the column. Buckling tends to reduce the benefit of confinement on the squash load as the column slenderness increases. In circular sections it is possible to develop the cylinder strength of the concrete. When compare with reinforced concrete columns, the concrete-filled composite column possesses much better strength and ductility in shear and generally in flexure also. Many researches are being conducted about concrete filled steel column to get these advantages in building design. In this paper it is provided to the basic experimental study of compression behavior of the circular and rectangular tubular steel pipe filled with concrete.

• Applied Microscopy
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• v.35 no.4
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• pp.32-41
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• 2005

The sperm morphology of two Korean frogs, Rana catesbeiana and R. nigromaculata (Ranidae) was studied with the light microscope, scanning and transmission electron microscopes. Sperm heads of the R. catesbeiana and R. nigromaculata were long-cylinder shapes. In the total length of R. nigromaculata sperm ($51.2{\mu}m$) was longer than those of R. catesbeiana ($44.6{\mu}m$). Both R. catesbeiana and R. nigromaculata had the long head and principal piece, and short middle piece, but the neck was undeveloped. The axonemal structures contain a 9+9+2 arrangement of microtubules. The number of mitochondria in middle piece have less than mammalian sperm, which irregular surrounded the axone of the middle piece. In conclusion, R. catesbeiana and R. nigromaculata shared many similar features in sperm heads, neck, middle piece, and a site of mitochondria and axial structure, and it suggests that these species should be closely related.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.40 no.10
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• pp.887-894
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• 2016

The CNG pressure vessel is manufactured by a deep drawing and ironing (D.D.I) process for forming cylinder parts, followed by a spinning process for formation of the dome part. However, studies on the buckling phenomenon of the dome part and formation of the inlet part have not been performed yet, and the CNG pressure vessel is produced by the experience of the field engineers and the trial and error method. In this study, buckling phenomenon during the spinning process was predicted by comparing critical buckling loads obtained through theoretical analysis with axial loads from the FEA, and a method for preventing buckling of the dome part was proposed by employing commercial software (Forge NxT 1.0.2). Also, to form the inlet part, forming loads of the roller at contact point between the roller and the dome part were analyzed according to radii of the dome part, and the inlet part was formed by controlling the radius of the dome part.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.39 no.11
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• pp.1183-1189
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• 2015

This study focuses on the design of the tapered joints of a wind power turbine. The main variables of the tapered joint are the transmitted torque, shaft diameter, contact area of the tapered ring, and tightening torque of the bolts, which applies a compressive pressure from the hub to the shaft. The stress distribution of the taper fit was calculated under axisymmetric plane strain conditions because of the small taper angle. The axial displacement of the clamp can be calculated from the radial elastic deformation and the taper angle. The stress field of each ring is obtained from the cylinder stress equation. To verify the accuracy of the calculation, finite element (FE) analysis was performed, and the results of the calculation and FE analysis were compared. The hoop stress of the tapered surface showed a discrepancy of approximately 10, but the trends of the stress distributions of each component and the relative movement obtained by FE analysis were in good agreement with the analytical calculation results.

• International Journal of Railway
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• v.1 no.2
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• pp.72-81
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• 2008

This paper introduces a new steel jacketing method for reinforced concrete columns with lap splice and evaluates its performance by a series of axial tests of concrete cylinders. At first, 45 concrete cylinders were fabricated with varying the design compressive strengths of 21, 27 and 35 MPa and, then, the part of them was jacketed with two-split-steel jackets under lateral confining pressure. The parameters in the first test were the steel jacket's thickness and the existence of adhesive between steel and concrete surface. In the second test, whole steel jackets were used to wrap cylinders with lateral pressure. Also, a double-layer jacket consisted of two steel plates was introduced; a cylinder was jacketed by two steel plates one after another. The effect of the new method was verified through comparing the results of the compressive tests for plain and jacketed cylinders. The steel jacket built following the new method showed good results of increasing the compressive strength and ductility of the jacketed cylinders with respect to the plain cylinders. The thicker steel jackets showed the more increased compressive strength, and the ductility at failure depended on the welding quality on steel jackets. The adhesive between steel and concrete surface reduced the confining effect of the steel jackets. The whole jacket showed more ductile behavior than the two-split jackets. The double-layered jackets were estimated to possess an equal performance to that of a single steel jacket having the same thickness of the double-layered jacket. Finally, the experimental results were compared with the constitutive model of steel-jacketed concrete; which showed a good agreement between the experimental results and the models.

• Transactions of the Korean Society of Automotive Engineers
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• v.15 no.1
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• pp.116-124
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• 2007

An optical method to measure the size and number density of soot aggregates in diesel exhaust has been proposed in this study. Two laser beams in co-axial alignment transmit a soot loaded exhaust gas flow, and the transmittance at each wavelength is detected by a photo diode simultaneously. The volume equivalent diameter and number density of soot aggregates in the optical path can be theoretically given by the transmittance values measured at two wavelengths. A test conducted by a single cylinder, 4 cycle, small and DI diesel engine shows that the temporal variations of the size and number density of soot aggregates in the diesel exhaust can be measured by the proposed method at a transient mode operation. It is found that the volume equivalent diameter varied temporally from 70 to 110 nm during the period that high soot concentration is observed. One can also conclude that the optical length longer than 1 m in the dynamic range regarding this method is preferable for measuring soot concentration at the level of $1\;mg/m^3$.

• Journal of radiological science and technology
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• v.38 no.4
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• pp.421-427
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• 2015

In this study, we have observed the change of the Hounsfield (HU) in the alteration of by changing in size of physical area and setting size of region of interest (ROI) at focus on kVp and mAs. Four-channel multi-detector computed tomography was used to get transverse axial scanning images and HU. Three dimensional printer which is type of fused deposition modeling (FDM) was used to produce the Phantom. The structure of the phantom was designed to be a type of cylinder that contains 33 mm, 24 mm, 19 mm, 16 mm, 9 mm size of circle holes that are symmetrically located. It was charged with mixing iodine contrast agent and distilled water in the holes. The images were gained with changing by 90 kVp, 120 kVp, 140 kVp and 50 mAs, 100 mAs, 150 mAs, respectively. The 'image J' was used to get the HU measurement of gained images of ROI. As a result, it was confirmed that kVp affects to HU more than mAs. And it is suggested that the smaller size of physical area, the more decreasing HU even in material of a uniform density and the smaller setting size of ROI, the more increasing HU. Therefore, it is reason that to set maximum ROI within 5 HU is the best way to minimize in the alteration of by changing in size of physical area and setting size of region of interest.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.41 no.2
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• pp.97-107
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• 2017

This study is the second investigation on the steady flow characteristics of an SI engine with a semi-edge combustion chamber as a function of the port shape with varying evaluation positions. For this purpose, the planar velocity profiles were measured from 1.75B, 1.75 times of bore position apart from the bottom of head, to 6.00B positions using particle - image velocimetry. The flow patterns were examined with both a straight and a helical port. The velocity profiles, streamlines, and centers of swirl were almost the same at the same valve lift regardless of the measuring position, which is quite different from the case of the pent-roof combustion chamber. All the eccentricity values of the straight port were out of distortion criterion 0.15 through the lifts and the position. However, the values of the helical port exceeded the distortion criterion by up to 4 mm lift, but decreased rapidly above the 3.00B position and the 5 mm lift. There always existed a relative offset effect in the evaluation of the swirl coefficient using the PIV method due to the difference of the ideal impulse swirl meter velocity profile assumption, except for the cylinder-center-base estimation that was below 4 mm of the straight port. Finally, it was concluded that taking the center as an evaluation basis and the assumption about the axial velocity profile did not have any qualitative effect on swirl evaluation, but affected the value owing to the detailed profile.

• Geophysics and Geophysical Exploration
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• v.27 no.2
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• pp.108-118
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• 2024

In this study, expressions for the magnetic field and magnetic gradient tensor due to an elliptical disk were derived. Igneous intrusions and kimberlite structures often have elliptical cylinders with axial symmetry and elliptical cross sections. An elliptical cylinder with varying cross-sectional areas was approximated using stacks of elliptical disks. The magnetic fields of elliptical disks were derived using the Poisson relation, which includes the direction of magnetization in the gravity gradient tensor, as described in a previous study (Rim, 2024). The magnetic gradient tensor due to an elliptical disk is derived by differentiating the magnetic fields, which is equivalent to obtaining ten triple-derivative functions acquired by differentiating the gravitational potential of the elliptical disk three times in each axis direction. Because it is possible to exchange the order of differentiation, the magnetic gradient tensor is derived by differentiating the gravitational potential of the elliptical disk three times, which is then converted into a complex line integral along the closed boundary curve of the elliptical disk in the complex plane. The expressions for the magnetic field and magnetic gradient tensor derived from a complex line integral in complex plane are perfectly consistent with those of the circular disk derived from the Lipschitz-Hankel integral.