• Journal of Korean Tunnelling and Underground Space Association
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• v.14 no.1
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• pp.55-77
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• 2012

A Modern Rock TBM is a tunnel excavation method combining the conventional tunnelling method with the mechanized tunnelling method. It is a hybrid system that excavates a tunnel with TBM and supports the ground by ring beam, wire mesh, rock bolt, shotcrete, i.e., conventional tunnelling method. In the Modern Rock TBM, a ring beam is similar to a steel rib in NATM in the way that uses H-beam. But using a ring beam is more effective than a steel rib because it is installed in a closed-circle. Therefore, improving the performance of the ring beam is a key factor for achieving tunnel stability. In this respect, this study introduces a pressurized ring beam that might be functioning more effectively by confining convergence during tunnel excavation. In order to verify the effect of the pressurized ring beam, a three-dimensional numerical analysis was conducted. The numerical analysis confirms an increase in the minimum principal stress and reduction in the plastic strain that triggers excessive displacement. The analysis result also indicates a decrease in the relative displacement occurring after installing the ring beam, and expansion in spacing between the ring beams.

• Advances in nano research
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• v.10 no.2
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• pp.129-138
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• 2021

In present article, utilizing the Love shell theory with volume fraction laws for the cylindrical shells vibrations provides a governing equation for the distribution of material composition of material. Isotopic materials are the constituents of these rings. The position of a ring support has been taken along the radial direction. The Rayleigh-Ritz method with three different fraction laws gives birth to the shell frequency equation. Moreover, the effect of height- and length-to-radius ratio and angular speed is investigated. The results are depicted for circumferential wave number, length- and height-radius ratios with three laws. It is found that the backward and forward frequencies of exponential fraction law are sandwich between polynomial and trigonometric laws. It is examined that the backward and forward frequencies increase and decrease on increasing the ratio of height- and length-to-radius ratio. As the position of ring is enhanced for clamped simply supported and simply supported-simply supported boundary conditions, the frequencies go up. At mid-point, all the frequencies are higher and after that the frequencies decreases. The frequencies are same at initial and final stage and rust itself a bell shape. The shell is stabilized by ring supports to increase the stiffness and strength. Comparison is made for non-rotating and rotating cylindrical shell for the efficiency of the model. The results generated by computer software MATLAB.

• Structural Engineering and Mechanics
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• v.19 no.2
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• pp.217-230
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• 2005

A steel silo traditionally consists of a cylindrical and a conical shell. In order to facilitate emptying operations, the cylinder is placed on local supports. This may lead to dangerous stress concentrations and eventually to local instability of the cylindrical wall. In this contribution, the locally supported cylinder is strengthened by means of ring stiffeners and longitudinal stiffeners and the effect of their dimensions on the buckling stress is investigated. This study leads to a number of diagrams, each of them representing the effect of one of the dimensions on the buckling stress. In each diagram, the failure pattern corresponding to the buckling stress is indicated.

• Journal of The Korean Astronomical Society
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• v.40 no.3
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• pp.61-65
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• 2007

The 2-1 and 5-4 transitions of SiO have been observed toward the Sgr B2 region, including the Principal Cloud(the GMC containing Sgr B2(M)) and its surroundings. The morphology and velocity structure of the SiO emission show a close resemblance with the HNCO Ring feature, identified by Minh & Irvine(2006), of about 10 pc in diameter, which may be expanding and colliding with the Principal Cloud. Three SiO clumps have been found around the Ring, with total column densities $N_{SiO}{\sim}1{\times}10^{14}cm^{-2}$ at the peak positions of these clumps. The fractional SiO abundance relative to $H_2$ has been estimated to be ${\sim}(0.5-1){\times}10^{-9}$, which is about two orders of magnitude larger than the quiet dense cloud values. Our SiO observational result supports the existence of an expanding ring, which may be triggering active star formations in the Principal Cloud.

• Tribology and Lubricants
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• v.12 no.4
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• pp.28-34
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• 1996

The lubrication characteristics of high-speed ball bearings have been investigated empirically using 45mm bore split inner ring ball bearings employed in small industrial gas turbine engines with oil-jet lubrication method. For the close structural simulation, experiments carried out with bearing mounting supports of real engines, such as bearing housings and oil nozzle assemblies with squeeze film dampers. Thus the results of tests can be directly applied to the design and the development of gas turbine engines. Testing was done by varying operating speeds, axial load on bearings, and lubricant flow rates. During testing, the temperature of bearing at outer-ring face, the power consumption of the driving motor, and the rotating resistance of the bearing were measured. From this study, the representative factors for lubrication characteristics at high speed was found, and the most important one was not operating speed but axial load up to 1.95 million dmN speed and 2969 N axial load. Furthermore, the detailed variation of the rotational resistance of the bearing could be visualized by measuring the change of the radial load under the bearing supports. The rotational resistance consists of the frictional resistance and the bearing-cavity oil resistance.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 1996.04b
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• pp.86-93
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• 1996

The lubrication characteristics of high-speed ball bearings has been investigated empirically using 45mm bore split inner ring ball bearings employed in small industrial gas turbine engines with oil-jet lubrication method. For the close structural simulation, experiments carried out with bearing mounting supports of real engines, such as bearing housings and oil nozzle assemblies with squeeze film dampers. Thus the results of tests can be directly applied to the design and the development of gas turbine engines. Testing was done by varying operating speeds, axial load on bearings, and lubricant flowrates. During testing, the temperature of bearing at outer-ring face, the power consumption of the driving motor, and the rotating resistance of the bearing were measured. From this study, the representative factors for lubrication characteristics at high speed was found, and the most important one was not operating speed but axial load up to 1.95 million dmN speed and 303 kgf axial load. Furthermore, the detailed variation of the rotational resistance of the bearing could be visualized by measuring the change of the radial load under the bearing supports. The rotational resistance consists of the frictional resistance and the bearing-cavity oil resistance.

• Structural Engineering and Mechanics
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• v.66 no.6
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• pp.713-727
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• 2018

Thin-walled mental tubes under lateral crushing are desirable and reliable energy absorbers against impact or blast loads. However, the early formations of plastic hinges in the thin cylindrical wall limit the energy absorption performance. This study investigates the energy absorption performance of a simple, light and efficient energy absorber called the ring stiffened tube. Due to the increase of section modulus of tube wall and the restraining effect of the T-stiffener flange, key energy absorption parameters (peak crushing force, energy absorption and specific energy absorption) have been significantly improved against the empty tube. Its potential application in the offshore blast wall design has also been investigated. It is proposed to replace the blast wall endplates at the supports with the energy absorption devices that are made up of the ring stiffened tubes and springs. An analytical model based on beam vibration theory and virtual work theory, in which the boundary conditions at each support are simplified as a translational spring and a rotational spring, has been developed to evaluate the blast mitigation effect of the proposed design scheme. Finite element method has been applied to validate the analytical model. Comparisons of key design criterions such as panel deflection and energy absorption against the traditional design demonstrate the effectiveness of the proposed design in blast alleviation.

• Journal of the Korea Concrete Institute
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• v.22 no.6
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• pp.817-824
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• 2010

The concrete containment structures have been widely used in nuclear power plants, LNG storage tanks, etc., due to their high safety and economic efficiency. The containment structure consists of a bottom slab, wall, ring beam and dome. The shape of the roof dome has a very significant effect on structural safety, the quantity of materials, and constructability; the thickness and curvature of the dome should therefore be determined to give the optimum design. The ring beam plays the role as supports for the dome, resulting in a minimized deformation of the wall. The main issues in designing the ring beam are the correct dimensions of the section and the prestress level. In this study, an efficient design procedure is proposed that can be used to determine an optimal shape and prestress level of the dome and ring beam. In the preliminary design stage of the procedure, the membrane theory of shells of revolution is adopted to determine several plausible alternatives which can be obtained even by hand calculation. Based on the proposed procedures, domes and ring beams of the existing domestic containment structures are analyzed and some improvements are discussed.

• Archives of Pharmacal Research
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• v.16 no.3
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• pp.219-226
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• 1993

For the analysis of structure relationship of ar-turmerone analogues, the compounds containing the various substituents on the phenyl ring and 1(or 2)-naphthyl group in the place of phenyl of ar-turmerone were prepared and tested their cytotoxicity against HL-60, K-562, and L1210 leukemia cells in vitro. The substituents at para position are methoxy, phenoxy, methyl, trifluoromethyl, fluoro, and chloro. At meta position methoxy, methyl, trifluoromethyl, or chloro groups at ortho position mathoxy or chloro group were introduced. Against HL-60 and K-562 cells, $ED_{50}$ values of the analogues are ranged from 0.8 to $30.0\;\mu{g/ml}$. Againste L1210 cell, these are located more than $20.0\;\mu{g/ml}$. However, 5-carbone-thoxy-2-methyl-6(1-naphthyl)-2-octen-4-one (5n)possesses $ED_{50}$ valuses 0.8, 2.1, $6.5\;\mu{g/ml}$ against HL-60, L1210 cells, respectively. The electronic nature of the substituents on phenyl ring of ar-tumerone dose not affect the biological activity. Therefore the flat structure of aromatic potion of ar-tumerone analogues is the more important factor for their activity rather than its electronic nature. The potentiation of the cytotoxicity with the enlargement of aromatic ring region also supports the importance of the plane structure of this area. The restriction of the single bond rotation between C-6 and aromatic ring through the introduction of substituents at the ortho position of phenyl ring and the increment of size of alkyl group at C-6 position enhances the activity. Therefore the effective conformation should by the one having the orthogonal arrangement between the aromatic ring and the side chain.

• Journal of Astronomy and Space Sciences
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• v.18 no.1
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• pp.27-32
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• 2001

A statistical study has been performed of the magnetic storm recovery phase using the Dst index for 102 storm events in the interval January 1996 to December 1998. In 43 cases (or 42%) out of our 102 events, the recovery phase exhibits fast recovery (kaking about 8 hours or less) at its initial stage or for the entire recovery period. Since this fast recovery can be explained by the fast charge exchange less of $O^{+}$ ions which mostly com from the ionosphere, and since a fraction of $H^{+}$ ions is of ionospheric origin as well, our statistical result supports the view that the source of ring current ions in many magnetic storms can be terrestrial.