• Journal of Korean Society of Transportation
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• v.4 no.2
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• pp.3-14
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• 1986

This study was undertaken to develop the gap acceptance model of left-turn drivers on the major road at intersections. Typical unsignalized intersections on the two-lane and four-lane streets in Masan City were selected for the study intersection. For the gap distribution model, the lognormal, negative exponential, shifted negative exponential, and Gamma distributions were tested using the x2 and K-S tests. Based on the results for both streets, it was concluded that among the distributions tested the lognormal distribution represented the gap distribution best, followed by the shifted negative exponential distribution. Stochastic models of the gap-acceptance behavior of left-turn drivers on the major road at unsignalized intersections were programmed using SLAM Ⅱ, a simulation computer language. A stochastic model was selected for the gap-acceptance behavior to compare the results of the simulation with the observed data. The model assumes that a fixed critical acceptance gap is assigned to each left-turn driver based on a normal distribution and the gap distribution of the opposing traffic stream follows the shifted negative exponential distribution.

• Proceedings of the KSME Conference
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• 2001.06e
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• pp.754-759
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• 2001

This paper presents unsteady computational investigations and wind tunnel tests on the flow field around a square cylinder with a gap between the body and the ground plane. Two-dimensional unsteady, incompressible Navier-Stokes codes are developed for the computation of the viscous turbulent flows. By computing the flow around a square cylinder without ground effect, three two-equation turbulence models are evaluated and the developed code is validated. The results show a good agreement with experimental values and other computational results. Critical gap height at which the formation of Karman vortex streets is interrupted, is demonstrated and another transition regime is pointed out

• Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
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• 2002.02a
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• pp.123-126
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• 2002

Samples of Nb/Al-Al$O_{x}$/Nb tunnel junction with the size of 50$\mu$m $\times$ 50$\mu$m were fabricated by employing self-aligning and reactive ion etching technique. In the samples with high-quality, $V_{m}$ value (the product of the critical current and subgap resistance measured at 2 mV) was 34 mV at the critical current density $J_{c}$ = 500 A/$cm^{2}$ and $V_{g}$ value (the gap voltage) was 2.8 mV. In the higher $J_{c}$, voltage fluctuation in the current rising at the gap voltage was observed. The $V_{m}$ and $J_{c}$ value were 8 mV and 900 A/$cm^{2}$, respectively.

• 한국정보디스플레이학회:학술대회논문집
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• 2008.10a
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• pp.660-663
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• 2008

In this study, it was mainly focused on the mechanism and reliability performances of PI/PET composites after many times of curving. We developed a new process of spacer for flexible display to improve the maintenance of cell gap. This new process used the laser carving technology, which is widely applied on printing press, to produce the pattern of spacers and shaped both of the alignment film and spacers simultaneously by press of pattern. Assembling the spacer-shaped film and plastic substrates together well and it shows an excellent performance on the maintenance of cell gap and reliability of curving.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.14 no.1
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• pp.17-20
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• 2004

We derive specific heat gap at the critical temperature as an exact anylitical function of applied magnetic field by using the thermodynamics. And we calculate numerical value of specific heat gap for some superconductors with the derived results and discuss the physical meaning. And it will be discussed that gap of specific heat discontinuity under certain magnetic field intensity become zero at the critical temperature.

• International Journal of Aeronautical and Space Sciences
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• v.17 no.2
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• pp.139-148
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• 2016

The passive control methods such as horizontal and vertical fences on the lower surface of the bluff body were applied to suppress the vortex shedding and enhance the aerodynamic stability of flow. For investigating the effects of the passive control methods, wind tunnel experiments on the unsteady flow field around a bluff body near a moving ground were performed. The boundary layer and velocity profiles were measured by the Hot Wire Anemometer (HWA) system and the vortex shedding patterns and flow structures in a wake region were visualized via the Particle Image Velocimetry (PIV) system. Also, it is a measuring on moving ground condition that the experimental values of the critical gap distances, Strouhal numbers and aerodynamic force FFT analyses. Through the experiments, we found that the momentum supply due to moving ground caused the vortex shedding at the lower critical gap distance rather than that of fixed ground. The horizontal and vertical fences increase the critical gap distance and it can suppress the vortex shedding. Consequently, the stability characteristics of the bluff body near a moving ground could be effectively enhanced by the simple passive control such as the vertical fences.

• Journal of Electrical Engineering and Technology
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• v.13 no.3
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• pp.1326-1336
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• 2018

This paper proposes a numerical approach to predict the critical flashover voltages of air gaps under lightning impulses. For an air gap, the impulse voltage waveform features and electric field features are defined to characterize its energy storage status before the initiation of breakdown. These features are taken as the input parameters of the predictive model established by support vector machine (SVM). Given an applied voltage range, the golden section search method is used to compute the prediction results efficiently. This method was applied to predict the critical flashover voltages of rod-rod, rod-plane and sphere-plane gaps over a wide range of gap lengths and impulse voltage waveshapes. The predicted results coincide well with the experimental data, with the same trends and acceptable errors. The mean absolute percentage errors of 6 groups of test samples are within 4.6%, which demonstrates the validity and accuracy of the predictive model. This method provides an effectual way to obtain the critical flashover voltage and might be helpful to estimate the safe clearances of air gaps for insulation design.

• Journal of Advanced Marine Engineering and Technology
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• v.12 no.3
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• pp.57-67
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• 1988

Although handicapped by the inability to bridge the size gap between small laboratory sample and large engineering component, the V charpy test sample method does possess certain advantages, such as each of preparation, simplicity of test method, speed, low cost in test machinery, and low cost per test. On the other hand, the COD test method does posses advantages, which reduce the size gap between the laboratory sample and actual engineering component. Consequently, the correlation between V charpy absorbed energy and the critical COD value is required for estimating critical COD value from the simple V charpy test results. In this paper, the high tensile strength steel AH36 plate specimens having a single edge cracked notch were investigated to find out the correlation between V charpy absorbed energy and critical COD value in the welded parts under such various welding methods as shielded metal arc welding, the submerged arc welding and the electro gas welding by means of V charpy impact test and static 3-point bending test. Main results obtained are as follow ; 1. The relationships between V charpy absorbed energy Wc' and critical COD value ($\delta_c$)show; $\delta_c$=0.0065 Wc'+0.1906. 2. Ductile- brittle transition behaviours can be estimated by means of fracture appearance and general yielding behaviours. 3. The V charpy absorbed energy of SMAW is higher than that of SAW, EGW and similar relationships are obtained in the COD tests.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.20 no.9
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• pp.2981-2990
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• 1996

Dual solutions for steady natural convection of air between two horizontal concentric cylinders are numerically investigated in the range of $D_i$/TEX>/L(=diameter of inner cylinder/gap width)$\leq$10. It is found that, when the Rayleigh number based on the gap width exceeds a certain critical value, a new flow pattern forming two counter-rotating eddies in the half of the annulus can be realized, which is different from the crescent-shaped flow commonly observed. In the new flow pattern, the fluid near the top of the hot inner cylinder moves downward. This solution is found for D$_{i}$/L.geq.0.3, but not for$D_i$/TEX>/L$\leq$0.2. As $D_i$/TEX>/L increase, the critical Rayleigh number is decreased, and tends to a finite limit.t.

• Journal of Korean Society for Quality Management
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• v.43 no.3
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• pp.397-408
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• 2015

Purpose: Express mail service(EMS) supplied by 'Korea POST'is an international postal service which brings letters, documents and parcels to a destination abroad in the fastest and safest way. This service is in a tough competition with global companies such as TNT, FedEx, DHL or UPS. To build an effective strategy for being competitive, an intensive study on EMS service quality should be accomplished from a customer's perspective. Methods: Kano model and improvement gap analysis are used to categorize and prioritize EMS service quality attributes. A 5-point Lickert scale is employed to apply the Kano model and improvement gap analysis. Each quality attribute can be classified as weak in comparison with competitors, critical for improvement, or potentially competitive. Results: Price, on-time delivery and delivery quality are to be kept as is; fast delivery, parking convenience and staff expertise can be potentially competitive; and the other attributes are considered to be critical for improvement. Conclusions: Fast reimbursement and proper compensation when shipping items are lost or damaged are to be improved with high priority. Efforts to secure fast delivery, parking convenience and staff expertise are needed to be competitive in the future.