• 한국정보디스플레이학회:학술대회논문집
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• 2007.08a
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• pp.1049-1052
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• 2007

Extremely sharp and uniform Transfer Mold FEAs with thin film low work function TiN emitter material have been fabricated by controlling the thickness of the coated emitter materials to realize high efficient, high reliable and low-cost vacuum nanoelectronic devices..Their tip radii are 8.3-13.8 nm. Turn-on electric fields of the Ni FEAs and TiN-FEAs resulted in the low electric field values of $31.6\;V/{\mu}m$ and $44.2V/{\mu}m$,respectively, at the short emitter/anode distance: less than $30\;{\mu}m$, which are lower than those of conventional FE As such as Spindt type FEAs and carbon nan otube FEAs The Transfer Metal Mold fabrication method is one of the best methods of changing emit ter materials with sharp and uniform emit ter shapes.

• Proceedings of the KSR Conference
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• 2005.11a
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• pp.382-388
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• 2005

SMSC(Seoul Metropolitan Subway Corporation) is substantially taking the core role of mass transit system in Seoul Metropolitan area. When it was built, the design had challenged to sharp curved tracks less than 250m radius considering the protection of buildings and cultural properties as well as the connection to ground roads. Such circumstances have required a certain extent of slack in track geometry and therefore led to the construction of ballasted track with wooden sleepers. However, the dynamic force from running on sharp curved track has caused the misalignment and abnormal failure of track geometry, and it has resulted in a frequent maintenance and repair works which require a lot of cost and manpower. In this paper, we present the construction case of maintenance-free track system by using of concrete sleeper and elastic rail fastening system to ensure the safety of both passengers and trains, and to contribute the effective maintenance for track facilities of SMSC.

• ETRI Journal
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• v.33 no.6
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• pp.981-984
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• 2011

A novel lowpass filter with a very sharp transition band and wide stopband is proposed. The proposed filter is based on T-shaped patches which are etched in symmetrical structures and folded open stub. To obtain a wide stopband, we have used stub loaded semi-circle stepped-impedance structures. By designing the resonator with high inductance and capacitance, a very sharp transition band is achieved. The proposed filter has a 3-dB cutoff frequency at 2.37 GHz and a 40-dB rejection at 2.44 GHz. The stopband with an attenuation level better than -13.2 dB is up from 2.4 GHz to 16 GHz, and consequently we have reached the high and wide rejection in stopband with compact size. Good agreements between the simulated and the measured results are presented.

• ETRI Journal
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• v.33 no.6
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• pp.985-988
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• 2011

A novel application of a dual-transmission line is proposed to design a lowpass filter (LPF). The proposed structure uses only transmission line elements to produce an equiripple LPF response with sharp roll-off. Design equations are derived using a lossless transmission line model. Controlling the electrical lengths, three transmission-zeros are realized in the stopband to obtain a sharp roll-off rate and wide stopband bandwidth. A single unit microstrip LPF with a 3-dB cut-off frequency at 1.0 GHz having a roll-off of 135 dB/GHz along with a stopband bandwidth of 69.5% is designed for validation.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.07a
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• pp.671-674
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• 2000

A children's electric shock accidents have broken out because children can easily insert sharp things in 220V receptacle holes. As the test result of pushing force, children's pushing force was about 2-4kg and the pushing force of sharp things was less than 2kg. Therefore, it is reason for electric shock that children's pushing force is large than pushing force of sharp things. We have measured insulation resistance for the receptacles of five companies during 50 weeks in humid condition. As these results, Insulation resistance for the receptacles of J. Co. had rapidly decreased with lapse of time. As the result for investigating the surface of receptacle by SEM and EDX, Al, Fe and Br, which weren't discovered at original form, were produced. Therefore, the receptacles of J. Co. should be the improved in the quality of insulating material because insulation resistance can be decreased in humid environment

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09a
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• pp.132-133
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• 2006

Optimized choice of material for two principally different types of PM components is presented. The first is characterized by high stresses in areas with high stress concentrations (for example synchronizer hubs with very sharp notches, typically <0.25mm in the pre-synchronizer slot and the inner splines). The second type has slightly larger notch radii (small spur gears and sprockets with typically notch radii between 1- 3mm). Diffusion alloyed materials are well suited for sharp notch components. Pre-alloyed materials are also well suited for applications with sharp notches if compressive residual stresses in the notch roots are created by appropriate process control. A free choice of material is available for components with the larger notch radii.

• Journal of Electrical Engineering and Technology
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• v.11 no.4
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• pp.1042-1048
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• 2016

This paper presents a lateral displacement restoring force control for the independently rotating wheelsets (IRWs) of shallow-depth subway systems. In the case of the near surface transit, which has recently been introduced, sharp curved driving performance is required for the city center service. It is possible to decrease the curve radius and to improve the performance of the straight running with the individual torque control. Therefore, the individual torque control performance of the motor is the most important point of the near surface transit. This paper deals with a lateral displacement restoring force control for sharp curved driving. The validity and usefulness of the proposed control algorithm is verified by experimental results using a small-scale bogie system.

• Journal of the Korean Mathematical Society
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• v.56 no.5
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• pp.1371-1385
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• 2019

Given a topological space X and a non-negative integer k, ${\varepsilon}^{\sharp}_k(X)$ is the set of all self-homotopy equivalences of X that do not change maps from X to an t-sphere $S^t$ homotopically by the composition for all $t{\geq}k$. This set is a subgroup of the self-homotopy equivalence group ${\varepsilon}(X)$. We find certain homotopic tools for computations of ${\varepsilon}^{\sharp}_k(X)$. Using these results, we determine ${\varepsilon}^{\sharp}_k(M(G,n))$ for $k{\geq}n$, where M(G, n) is a Moore space type of (G, n) for a finitely generated abelian group G.

• Proceedings of the Acoustical Society of Korea Conference
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• 1993.06a
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• pp.190-194
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• 1993

In the ocean bubble layers play a significant role in the sound propagation as well as sound generation. Most of early works dealt with acoustic properties of the bubble layers with sharp flat boundaries. Bubble layers with sharp flat boundaries. Bubble layers with transition sublayers are more likely in the coean. In this paper a theory of sound propagation through plane bubble layers with transition sublayers at both borders was developed. It shows that the reflection and transmission coefficients depend on the thickness of transition sublayers. The theory with thicker transition sublayers shows weaker resonance properties of bubble layer. It gives better presentation for the peculiar behavior of the experimental data than that with sharp flat boundaries.

• Communications for Statistical Applications and Methods
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• v.30 no.3
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• pp.259-272
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• 2023

In this paper, we suggest a new method for the prediction of sharp changes in particulate matter (PM₁₀) using quantile mapping. To predict the current PM₁₀ density in Seoul, we consider PM₁₀ and precipitation in Baengnyeong and Ganghwa monitoring stations observed a few hours before. For the PM₁₀ distribution estimation, we use the extreme value mixture model, which is a combination of conventional probability distributions and the generalized Pareto distribution. Furthermore, we also consider a quantile generalized additive model (QGAM) for the relationship modeling between precipitation and PM₁₀. To prove the validity of our proposed model, we conducted a simulation study and showed that the proposed method gives lower mean absolute differences. Real data analysis shows that the proposed method could give a more accurate prediction when there are sharp changes in PM₁₀ in Seoul.