• Journal of the Korean Society of Visualization
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• v.5 no.1
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• pp.37-42
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• 2007

Reverse flow occurs in a channel when there is an obstruction at the entry. However it has been shown recently that reverse flow can be realized without an obstruction, by staggering the sides of the channel and placing it at an angle of attack to the oncoming flow. In this study the latter flow is computationally investigated. Studies have been carried out for different widths (gap between the two walls forming the channel), and at an angle of attack of 30. The results have captured all the essential features of this complex phenomenon and show the time dependent pumping mechanism which leads to the occurrence of reverse flow.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.33A no.12
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• pp.53-58
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• 1996

In this paper, a simple fabrication technique of an air-bridge for interconnection of isolated electrodes of microwave active and passive devices and MMIC's is proposed. The proposed air-bridge proceses are mainly combinations of thermal evaporation, positive photoresist and image reversal processes for easy lift-off of up to 2.0 .mu.m thick metal. According to the resutls of air-birdge processes, it is confirmed that air-gap and thickness of theair-bridge are about 3.5.mu.m, and 2.0.mu.m, respectively. And it is also possible to make the fine air-bridge with widths of 5~60.mu.m and post-intervals of 25~200.mu.m withot collapse. finally, GaAs power MESFET's and rectangular spiral inductors are fabricatd and measured in order to confirm of feasibility of the proposed air-bridge processes. The MAG of the fabricated power MESFET's is 10dB at 10GHz, and the inductance of the (200.mu. * 6 turns) rectangular spiral inductors 4.5 nH inX-band.

• Journal of international Conference on Electrical Machines and Systems
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• v.2 no.1
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• pp.9-15
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• 2013

This paper presents a uniform analytical model by energy method and Fourier series expansion to analyze detent force in uneven magnetic field for permanent magnet linear synchronous motor (PMLSM). The model reveals that detent force in long-primary type is mainly influenced by non-ideal distribution of permanent magnet magnetic motive force, while nounified air-gap permeance makes a great impact on detent force of short-primary type. Hence, magnetic field similarity of motor design techniques referring rotary counterpart are adopted. For long-primary type novel method of splitting edge magnets is proposed to reduce end effects force, and optimal widths of edge tooth in short-primary type also verify the effectiveness of magnetic field similarity. The experimental results validate finite element analysis results.

• Proceedings of the Korean Nuclear Society Conference
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• 1996.11a
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• pp.224-229
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• 1996

An experimental study on critical heat flux (CHF) and two-phase flow visualization has been performed for water flow in internally-heated, vertical, concentric annuli under near atmospheric pressure. Tests have been done under stable forced- circulation, upward and downward flow conditions with three test sections of relatively large gap widths (heated length = 0.6 m. inner diameter = 19 mm, outer diameter = 29, 35 and 51 mm). The outer wall of the test section was made up of the transparent Pyrex tube to allow the observation of flow patterns near the CHF occurrence. The CHF mechanism was changed in the order of flooding, chum-to-annular flow transition, and local dryout under a large bubble in churn flow as the flow rate was increased from zero to higher values. Observed parametric trends are consistent with the previous understanding except that the CHF for downward flow is considerably lower than that for upward flow.

• Fibers and Polymers
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• v.4 no.3
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• pp.129-134
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• 2003

We have shown in Part I [1] of this study that medical needle-stick injuries are causing serious health problems to healthcare personnel and other professionals that require the attention of healthcare and textile researchers to develop new protective systems. Responding to such need, a needle force measurement device that is capable of measuring dynamic forces experienced by medical needles during needle penetration through protective articles was developed and described in part I. This paper reports the results of evaluation of protective woven fabrics from high performance fibers and standard and bifid medical needles using the force measurement system. The woven fabrics varied in cover factor, number of layers, and orientation angle. Standard and bifid needles with different gap widths were used to evaluate the resistance of the fabric to needle penetration.

• Journal of Electrical Engineering and Technology
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• v.13 no.4
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• pp.1644-1654
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• 2018

Eigenvalue distributions for a periodic metal-insulator-metal waveguide, classified into the point spectrum and the discretized continuous spectrum (DCS), are investigated as functions of frequencies, gap widths, and periods. Muller's method is suggested for solving exact eigenvalues, and we propose the scheme for finding proper initial values in the Muller's method by considering only ${\Re}e({\varepsilon}_r)$ in the dispersion equation. We then find that anti-crossing behavior, repulsive effect between the point spectrum and the DCS, becomes stronger when the real parts of the roots in the point spectrum have smaller values. Finally, we examine the transmittances of a single subwavelength slit for real metals using the mode matching technique. The transmittances in real metals similarly follow those of the perfect electric conductor (PEC) at low frequencies, while the patterns at higher frequencies begin to differ from the PEC.

• Steel and Composite Structures
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• v.30 no.2
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• pp.81-96
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• 2019

The behavior of a new Three-Tube Buckling-Restrained Brace (TTBRB) with circumference pre-stress (${\sigma}_{{\theta},pre}$) in core tube are investigated through a verified finite element model. The TTBRB is composed of one core tube and two restraining tubes. The core tube is in the middle to provide the axial stiffness, to carry the axial load and to dissipate the earthquake energy. The two restraining tubes are at inside and outside of the core tube, respectively, to restrain the global and local buckling of the core tube. Based on the yield criteria of fringe fiber, a design method for restraining tubes is proposed. The applicability of the proposed design equations are verified by TTBRBs with different radius-thickness ratios, with different gap widths between core tube and restraining tubs, and with different levels of ${\sigma}_{{\theta},pre}$. The outer and inner tubes will restrain the deformation of the core tube in radius direction, which causes circumference stress (${\sigma}_{\theta}$) in the core tube. Together with the ${\sigma}_{{\theta},pre}$ in the core tube that is applied through interference fit of the three tubes, the yield strength of the core tube in the axial direction is improved from 160 MPa to 235 MPa. Effects of gap width between the core tube and restraining tubes, and ${\sigma}_{{\theta},pre}$ on hysteretic behavior of TTBRBs are presented. Analysis results showed that the gap width and the ${\sigma}_{{\theta},pre}$ can significantly affect the hysteretic behavior of a TTBRB.

• The Research Journal of the Costume Culture
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• v.23 no.2
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• pp.284-293
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• 2015

This study intends to analyze the fit of directly-imported American casual pants for Korean female college students in terms of appearance and comfortableness. The authors carried out a wearing test with sample pants from 3 brands (DKNY: A, Gap: B, Polo: C) that had the most market share and that were mostly preferred by Korean female college students. Results showed that pants A had insufficient ease in the crotch, as the depth of the crotch was short. The hip girth received a low assessment in terms of appearance. Moreover, the hem widths were wide while the pants length was long. Pants B were expected to be most appropriate for Korean women's bodies, as they had the longest crotch depth among the three brands. However, the pants appeared to pull downward due to the narrow thigh and the knee girth and hem width. Moreover, the crotch girth and hip girth received a poor appearance assessment. Pants C were rated as satisfactory for their thigh girth, knee girth, and hem width. However, the crotch was uncomfortable, as it had a short crotch depth. The hip girth received a low appearance assessment. This study suggests that a pattern adjustment is required for directly-imported American pants to provide a better fit for the bodies of Korean women. The crotch depths should be approximately 17.5 cm. The hem widths should be approximately 20 cm. We also suggest a leg length of 75 cm, a waist girth of 86 cm, and a hip girth of 97 cm.

• Journal of the Korean Society of Safety
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• v.22 no.6
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• pp.27-34
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• 2007

Static or dynamic elastomeric O-ring seals are installed between joining parts, and play key roles of high pressure-tightening. Sealing performance and structural safety of the O-ring are dependent on groove design, plain diameter, squeeze and applications such as pressure and temperature. In this study, to solve O-ring problem squeezed and highly pressurized under laterally one-sided constrained condition, hyperelastic FE analyses are performed, and FE results are compared with measured ones by computer-aided tomography, deformed shape and extrusion depth of the O-ring. Through the comparisons, FE analysis technique was verified. In order to evaluate design sensitivity, Taguchi method was used to select FE analysis cases. Adjustment parameters are clearance gap, groove comer radius, plain diameter and squeeze. By means of verified FE analysis technique, it has been analysed how the parameters have effects on contact stress fields, internal stress fields, and extrusion depths. Sealing performance has been evaluated based on contact stress fields and contact widths, and structural safety on internal stress and strain, extrusion lengths.

• Journal of the Korea Concrete Institute
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• v.27 no.4
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• pp.387-397
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• 2015

In the present study, to enhance the constructability, a composite slab system using deck plate and micro steel fiber concrete was studied. In the proposed slab system, on-situ re-bar placement is not required. Steel fibers replace the temperature reinforcement. The present study focused on the crack control at the slab top in the continuous composite slab without spliced bars. Eight continuous slabs with various parameters were tested under vertical loading. The test parameters were the amount and types of micro steel fibers, types of deck plate, and the use of top bars in the continuous slab. To evaluate the crack resistance of the slabs, crack widths were measured in the continuous slabs. The test results showed that although the top spliced bars were not used, cracking were restrained by large flexural stiffness of the composite sections.