• 유체기계공업학회:학술대회논문집
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• 2003.12a
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• pp.555-561
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• 2003

The experimental apparatus is designed and installed to measure the disc positions with flow velocity, $V_{open}\;and\;V_{min}$ for 3 inch and 6 inch swing check valves. The minimum flow velocity necessary to just open the disc at a full open position is referred to as $V_{open}\;and\;V_{min}$ is defined as the minimum velocity to fully open the disc and hold it without motion. In the experiments, $V_{min}$ is determined as the minimum flow velocity at which the back stop load begins to increase after the disc is idly opened or the oscillation level of disc is reduced below $1^{\circ}$. The results show that the $V_{min}$ velocities for 3 inch and 6 inch swing check valves are about 15.6% and 4.8% higher than the $V_{open}$ velocities, respectively. Although the experiments were done with the stable uniform flow, additional experiments will be performed to determine the effects of the upstream disturbances.

• Journal of Advanced Navigation Technology
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• v.19 no.2
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• pp.147-152
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• 2015

The compensation characteristics of WDM channels depending on residual dispersion per spans (RDPS) deviation in optical links with the randomly distributed RDPS for the adaptive configuration are investigated in this paper. Also, the link design rule related with RDPS deviations is proposed, from the viewpoint of the allowable net residual dispersion (NRD). It is confirmed that the effect of compensation for the distorted WDM channels is more increased as RDPS deviation is smaller. Also, it is confirmed that the decrease of the allowable NRD range for the exact eye opening penalty (EOP) is proportional to RDPS deviation. Therefore, the results of this research is expected to be the design reference for the flexible link configuration of long-haul optical transmission links.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.20 no.1
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• pp.42-47
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• 2021

Recently, many structures using lightweight materials have been developed. This study was conducted by using Al6061-T6 and carbon fiber reinforced plastic (CFRP), two common lightweight materials. In addition, the failure characteristics of an interface bonded between a single material and a heterogeneous bonding material were analyzed. The specimens bonded with CFRP and Al6061-T6 were utilized by the combination of the heterogeneous bonding material. The specimens had a double cantilevered shape and the bonding between the materials was achieved by applying a structural adhesive. The experiments were conducted in opening mode: the lower part of the samples was fixed, while their upper part was subjected to a forced displacement of 3 mm/min by using a tensile tester. Under the tested amount of strength, energy release rate, and considering the specimens' fracture characteristics in opening mode, the specimen "CFRP-Al" presented the maximum stress, followed by "Al" and "CFRP". We can hence conclude that the inhomogeneous material "CFRP-Al" is useful for the construction of lightweight structures bonded with structural adhesive.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.20 no.3
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• pp.24-32
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• 2021

The size of container ships is increasing to increase the cargo loading capacity. However, container ships are limited in terms of the hull longitudinal strength. To overcome this limitation, brittle crack arrest steel can be used. This study was aimed at examining the influence of the heat input on the welding procedures of flux cored arc welding and submerged arc welding. In the experiment, the crack tip opening displacement test, which pertains to a parameter of fracture mechanics, was performed, and a 3-point bending tester was adopted. Based on the results, the crack measurement method was presented, and the stress expansion coefficient value for the pre-fatigue crack length was derived according to the heat input after the pre-cracking length was measured. It was noted that the heat input affected the crack tip opening displacement of brittle crack arrest steel.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.18 no.10
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• pp.1189-1195
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• 2007

We design and fabricate, in this parer, a triple band folded monopole antenna for the folder type mobile phone handset that can be served GSM/DCS/USPCS mobile phone system. Antenna structure is modified meander shape which is obtained both extension of antenna physical length for GSM band and same directional multi-currents flowing on the antenna conductor surface for DCS/USPCS band. This antenna has as good performances as high radiation resistance and gain increment, and would be applied to mobile phone handset that is not able to be performed by internal antenna. By measurement, fabricated antenna by the press process shows under VSWR 3:1 at closed folder state and 2:1 at opened folder state over whole GSM/DCS/USPCS band, and has maximum gain as -0.02 dBi for GSM, +0.2 dBi for DCS, +0.78 dBi for USPCS band with almost omnidirectional H-plane radiation pattern.

• Journal of Korean Philosophical Society
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• v.137
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• pp.249-276
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• 2016

The thought of Emmanuel Mounier addresses the most important problems in human life. In this research we try to analyze the three ontological characteristics of 'Person'. First the person has an indefinable character and is not substitutable since he is the true self which is the inner and spiritual being constituting the self-consciousness of an individual. The person has his individuality precisely because he is an individual and his being sovereign in having his own world. Next, the person's individuality has an ontological solitude from his own perspective. Nevertheless, having essentially an existential openness since it receives the elements that compose his own world by relationship and communication between men, and being connected unremittedly, the person is paradoxical. Finally, the person appears as a dynamic thing that continues to create the new self-consciousness. And this dynamism of the person wants to proclaim its self identity while at the same time, aim for a "personification of society" based on the love of humanity. Because of this we can say that the thought of Emmanuel Mounier on the person may be a new type of "humanism" that can give light to the misery of modern society.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.6
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• pp.650-655
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• 2016

In this study, a computational simulation of the internal flow characteristics was carried out for a Urea-SCR Injector. A single hole swirl injector with a swirl disk and slanted nozzle was used in this simulation. The maximum needle lift and opening velocity were selected as the design parameters. To analyze the unsteady internal flow characteristics of the Urea-SCR injector, the moving grid technique was applied to simulate the delicate needle movement. According to the simulation results, the injected mass flow rate from the Urea-SCR injector decreased with increasing needle opening velocity and maximum needle lift. This is because the Urea-solution tends to fill the empty space that the needle previously occupied. The swirl flow is decreased as the flow goes through the injector nozzle, because of the friction with the nozzle wall. Also, during the maximum needle lift period, the swirl coefficient and mean swirl coefficient increase with increasing needle lift. The results of this study may be used as the basic design data of related injectors.

• Journal of the Korean Society for Nondestructive Testing
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• v.32 no.1
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• pp.20-26
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• 2012

The objective of this study is to assess plastic deformation in aluminium alloy by acoustic nonlinearity of laser-generated surface waves. A line-arrayed laser beam made by high-power pulsed laser and mask slits is utilized to generate the narrowband surface wave and the frequency characteristics of laser-generated surface waves are controlled by varying the slit opening width and slit interval of mask slits. Various degrees of tensile deformation were induced by interrupting the tensile tests so as to obtain aluminum specimens with different degrees of plastic deformation. The experimental results show that the acoustic nonlinear parameter of a laser-generated surface wave increased with the level of tensile deformation and it has a good correlation with the results of micro-Vickers hardness test and electron backscatter diffraction (EBSD) test. Consequently, acoustic nonlinearity of laser-generated surface wave could be potential to characterize plastic deformation of aluminum alloy.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.38 no.3
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• pp.203-210
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• 2014

In this study, the hydrodynamic characteristics of Weis-Fogh type water turbine were calculated by the advanced vortex method. The wing (NACA0010 airfoil) and both channel walls were approximated by source and vortex panels, and free vortices are introduced away from the body surfaces. The distance from the trailing edge of the wing to the wing axis, the width of the water channel and the maximum opening angle were selected as the calculation parameters, the important design factors. The maximum efficiency and the power coefficient for one wing of this water turbine were 26% and 0.4 at velocity ratio U/V=2.0 respectively. The flow field of this water turbine is very complex because the wing moves unsteadily in the channel. However, using the advanced vortex method, it could be calculated accurately.

• Applied Chemistry for Engineering
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• v.18 no.3
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• pp.218-226
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• 2007

The stereoselective synthesis of chiral terminal epoxides is of immense academic and industrial interest due to their utility as versatile starting materials as well as chiral intermediates. In this study, new dinuclear chiral Co (salen) complexes bearing gallium-, indium- and tallium-chloride have been synthesized and characterized. The mass and EXAFS spectra provided the direct evidence of formation of dinuclear complex. Their catalytic activity and selectivity have been demonstrated for the asymmetric ring opening of various terminal epoxides having ether or ester groups by hydrolytic kinetic resolution technology. The easily prepared dimeric complexes exhibited very high enantioselectivity for the asymmetric ring opening of epoxides with $H_2O$ nucleophile, providing enantiomerically enriched terminal epoxides (> 99% ee). The dimeric structured chiral salen showed remarkably enhanced reactivity and may be employed substantially lower loadings than its monomeric analogues. The system described in this work is very efficient for the synthesis of chiral epoxide and 1,2-diol intermediates