• Proceedings of the Korean Nuclear Society Conference
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• 1995.05a
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• pp.636-643
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• 1995

The accurate determination of the fuel-cladding gap conductance as functions of rod burnup and power level may be a key to the design and safety analysis of a reactor. The incorporation of a sophisticated gap conductance model into nuclear design code for computing thermal hydraulic feedback effect has not been implemented mainly because of computational inefficiency due to complicated behavior of gap conductance. To avoid the time-consuming iteration scheme, simplification of the gap conductance model is done for the current design model. The simplified model considers only the heat conductance contribution to the gap conductance. The simplification is made possible by direct consideration of the gas conductivity depending on the composition of constituent gases in the gap and the fuel-cladding gap size from computer simulation of representative power histories. The simplified gap conductance model is applied to the various fuel power histories and the predicted gap conductances are found to agree well with the results of the design model.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2009.05a
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• pp.252-255
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• 2009

The roll gap set-up in the finishing mill is one of the most important technologies in the hot plate rolling process. As the target thickness can be obtained by the correct set-up of the roll gap, improving the roll gap set-up technology is very critical for plate thickness accuracy. The main cause of thickness variation in hot plate mills is the non-uniform temperature distribution along the length of the slab. The objective of this study is to adjust the roll gap set-up for the thickness accuracy of plate in hot rolling process considering top-end temperature drop. Therefore this study has concentrated on determining the correct amounts of roll gap to compensate thickness variation due to top-end temperature drop. The off-line simulation of compensated roil gap significantly decreases top-end thickness variation.

• International Journal of Contents
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• v.13 no.4
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• pp.47-62
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• 2017

This paper analyzes how much the gap existed between the public group and expert group using future issues and future core technologies that are announced in government institutions based on ontology. We calculated gap with two groups' point of view, one is expert groups' ideas that are based on future hopeful technologies documents, and another is public people ideas that are based on documents of contest that is hosted by 'Ministry of Science, ICT and Future Planning (MSIP)', and 'Institute for Information & communications Technology Promotion (IITP)'. For calculating these, we suggested SDGM model. In the case of ETRI Meta-trend ICT Field, there is a little gap between expert group and public group, and another case that is XT (ETRI determined future technologies excluding ICT field) Field, the gap is increasing annually. Moreover, in the case of all ETRI Meta trend, the gap is bigger than ICT and XT field. We analyzed, also, KEIT's future issues for generalizing this model. The gap existed between two groups. Utilizing SDGM model of this paper, people can interpret easily how much the gap exists between future technologies and issues that are announced in institutions.

• Computers and Concrete
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• v.26 no.2
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• pp.161-173
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• 2020

Shear keys in precast concrete segmental bridges (PCSBs) are usually match-casting which is very labour intensive. In this research, an innovative match-casting-free construction was proposed by leaving small gap between the convex and the concave castellated shear keys in the joints of PCSBs. Specimen experiment, shear strength analysis and numerical simulation were conducted, investigating the loading performance of this new type of dry joints, the gap dry joints. Compared with match-casting joint specimens, it has been found from experiment that shear capacity of gap joint specimens significantly decreased ranging from 17.75% to 42.43% due to only partially constrained and contacted in case of gap dry joints. Through numerical simulation, the effects of bottom contacting location, the heights of the gap and the shear key base were analyzed to investigate strength reduction and methods to enhance shear capacity of gap joint specimens. Numerical results proved that shear capacity of gap dry joints under full contact condition was higher than that under partial contact. In addition, left contact destroyed the integrity of shear keys, resulting in significant strength reduction. Larger shear key base remarkably increased shear capacity of the gap joint. Experimental tests indicated that AASHTO provision underestimated shear capacity of the match-casting dry joint specimens, while the numerical results for the gap dry joint showed that AASHTO provision underestimated shear capacity of full contact specimens, but overestimated that of left contact specimens.

• 한국정보디스플레이학회:학술대회논문집
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• 2003.07a
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• pp.539-542
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• 2003

We have studied cell gap-dependent electrode-optic characteristics of the FFS mode using the LC with negative dielectric anisotropy. In case of a small cell gap of 2 ${\mu}m$, the transmittance at the center of pixel and common electrodes is low due to stronger influence of surface anchoring that holds the LC to the initial state than twisting force induced by neighboring LCs. In case of a large cell gap of 4 ${\mu}m$, the influence of surface anchoring force becomes weak so that the LCs at the center of pixel and common electrode can be twisted enough by applied voltage, giving rise to high transmittance. Therefore, we conclude that the light efficiency in the device is dependent on the cell gap.

• Bulletin of the Korean Chemical Society
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• v.35 no.3
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• pp.705-708
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• 2014

We demonstrate the blue InGaN/GaN multiple quantum wells light-emitting diodes (LEDs) with an embedded air-gap photonic crystal (PC) which was fabricated by the lateral epitaxial overgrowth of GaN layer on the tungsten (W) nano-masks. The periodic air-gap PC was formed by the chemical reaction of hydrogen with GaN on the W nano-mask. The optical output power of LEDs with an air-gap PC was increased by 26% compared to LEDs without an air-gap PC. The enhanced optical output power was attributed to the improvement in internal quantum efficiency and light extraction efficiency by the air-gap PC embedded in GaN layer.

• Proceedings of the KIEE Conference
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• 1994.07b
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• pp.1625-1627
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• 1994

A potential to effective ozone generation for 4 kinds of gap, a hole-to-plate gap, a hole-to-hole gap, a hole-to-rod gap and a plate-to-plate gap in tap water has been investigated. It is found that the hole gaps indicated higher ozone generation compared to that of the plate-to-plate gap. As a result, the hole gaps could be an effective means to generate ozone in water by utilizing both of one generation mechanisms of the discharge and the electrolysis.

• Journal of Drive and Control
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• v.19 no.3
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• pp.47-52
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• 2022

The C-ITS (Cooperative-intelligent Transport System) is a driver assistance system that prevents car accidents and enhances traffic conditions, via sharing traffic information between vehicles and roadway infrastructures. A CLAS (changing lane assistance system) for unprotected left-turn, is a C-ITS that assists a driver with safely changing lanes. This system addresses a driver's critical gap, that enables the system to express a driver's uncertainty. A driver's critical gap is a time that can be used in a threshold, to change a lane or not. Unfortunately, a driver's critical gap is difficult to use in a CLAS directly. This paper addresses a driver's critical gap, and how it can be applied in a CLAS for an unprotected left-turn.

• Journal of electromagnetic engineering and science
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• v.12 no.1
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• pp.101-106
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• 2012

In this study, we investigated the effect of groove pattern and gap-fill with lossy materials at 15 GHz frequency of Ku-band. We used Epoxy/MWCNT composite materials as gap-fill materials. Although epoxy does not have an absorbance capability, epoxy added conductive fillers, which are multi-walled carbon nanotubes (MWCNT), can function as radar absorbing material. Specimens were fabricated with different MWCNT mass fractions (0, 0.5, 1.0, 2.0 wt%) and their permittivity in the Ku-band was measured using the waveguide technique. We investigated the effect of gap-fill on monostatic RCS by calculating RCS with and without gap-fill. For arbitrarily chosen thickness and experimentally obtained relative permittivity, we chose the relative permittivity of MWCNT at 2 wt% (${\varepsilon}_r$=8.8-j2.4), which was the lowest reflection coefficient for given thickness of 3.3 mm at V-pol. and $80^{\circ}$ incident angle. We also checked the monostatic RCS and the field intensity inside the groove channel. In the case of H-pol, gap-fill was not affected by the monostatic RCS and magnitude was similar with or without gap-fill. However, in the case of V-pol, gap-fill effectively reduced the monostatic RCS. The field intensity inside the groove channel reveals that different RCS behaviors depend on the wave polarizations.

• Journal of the Korea Institute of Military Science and Technology
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• v.14 no.1
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• pp.154-159
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• 2011

The effect of the ignition delay time gap is newly studied. The operational characteristics of the linked two pyrotechnic thrusters are affected by the time gap. Although two thrusters are simultaneously ignited, the time at which the pressure starts to rise in each thruster may not be synchronized. The characteristic of the system with the time gap is compared with that of the fully synchronized system without any time gap. Depending upon the magnitude of the time gap, the pressure-time profile and the ballistic performance are different. When two pyrotechnic thrusters have a time gap, the peak pressure of one thruster(in which the pressure is built up earlier) is increased and the other is decreased. As the time gap is increased, the peak pressure is converged into the maximum pressure. This maximum pressure can be obtained when only one thruster is activated. Because the maximum pressure is bounded, it is predicted that there isn't any catastrophic failures in the considered system. When the time gap is relatively small, the impulse of the combined force acting on the moving body is almost maintained. But the ballistic performance of the system with a large time gap should be carefully estimated because the reduction of the ballistic performance should not be easily neglected.