• Bulletin of the Korean Space Science Society
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• 2009.10a
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• pp.44.1-44.1
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• 2009

Identification of wave characteristics during current disruption events in the near-Earth geomagnetic tail region (~ 10 RE) is important to understand the substorm onset mechanism. In this paper, linear stability analysis in the ion-cyclotron grequency range, considering temperature anisotropy and cross-field flow is presented. It is found that the ion-cyclotron drift waves propagating in a quasi-perpendicular direction with respect to the ambient magnetic field are characterized by low frequencies ($\omega$ < $0.5{\Omega}ci$), while quasi-parallel waves have frequencies close to the ion-cyclotron frequency ($\omega{\sim}{\Omega}ci$). This finding is consistent with the observation by THEMIS spacecraft of a current disruption event in which a similar high- and low-frequency band structure is also present [A. T. Y. Lui, et al., J. Geophys. Res. 113, A00C06 (2008)]. It is also found that the quasi-perpendicular mode is excited by the ion cross-field flow.

• International Journal of Highway Engineering
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• v.18 no.3
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• pp.67-74
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• 2016

PURPOSES : This study evaluated the field applicability and laboratory performance of glass fiber-reinforced asphalt (GFRA) mixtures. METHODS : The general hot-mix asphalt (HMA) and GFRA mixtures were paved in five sites, including three national highways, one express highway, and an arterial road, to evaluate field applicability and durability. The plant mixing and construction method for the GFRA were similar to those for the general HMA. The lab performances of the field samples were relatively compared through the mechanical measures from the Marshall stability, indirect tensile strength, and dynamic stability. The field performance was surveyed after a year. RESULTS : The lab tests verified the superior lab performances of the GFRA compared to the general HMA. The Marshall stability of the GFRA increased for about 128% of the general HMA. The indirect tensile strength of the GFRA was 115% greater than that of the general HMA. The dynamic stability of the GFRA resulted in 16,180 reps/mm, which indicated that high rut resistance may be expected. No noticeable defects, such as cracks or deformation, were observed for the GFRA sections after a year. CONCLUSIONS : The lab tests and field survey for the five GFRA sites resulted in superior performances compared to the general HMA. The relatively low-cost GFRA, which required no pre-processing procedures, such as polymer modification, may be a promising alternative to the polymer-modified asphalt mixtures. The long-term performance will be verified by the superior field durability of the GFRA in the near future.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.31A no.5
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• pp.85-93
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• 1994

We have studied the effect of channel and/or spacing chirpings on the near field and near field intensity patterns, modal gains and radiation angles of 6 supermodes in the index-guided laser arrays with 6 channels, on the basis of the coupled mode theory. The spacings between channels can be indenpendent parameters for control of the radiation angle. It is found that an asymmetrically v channel-chirped array has both a smaller radiation angle and better supermode discrimination characteristics than a uniform array. Comparing two approaches for enhancing modal stability in point of supermode discrimination characteristics, approach I which increases the coupling cofficient between the outer-most waveguides at each end of an otherwise uniform array, has superior discrimination characteristics to the approach II which increases the propagation constant for the end elements with the same coupling between neighbor elements. Approach III which has a narrower spacing between the outer-most waveguides at one end and a wider channel width of the outer-most waveguide at another end, gets a narrower radiation angle than the approach I and good supermode discrimination characteristics by applying optimized gain profiles.

• Tunnel and Underground Space
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• v.13 no.2
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• pp.138-152
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• 2003

Three-dimensional computer modeling using FLAC3D had been carried out fur evaluating the thermal-mechanical stability of a high-level radioactive waste repository excavated in several hundred deep location. For effective modeling, a FISH program was made and the geological conditions and rock properties achieved from the drilling sites in Kosung and Yusung areas were used. Sensitivity analysis fer the stresses and temperatures from the modeling designed utilizing fractional factorial design was carried out. From the sensitivity analysis, the important design parameters and their interactions could be determined. From this study, it was found that deposition hole spacing is the most important parameter on the thermal and mechanical stability. The second and third most important parameters were disposal tunnel and buffer thickness.

• Nuclear Engineering and Technology
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• v.53 no.1
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• pp.244-252
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• 2021

Wind plays an important role in cases of unexpected radioactive pollutant dispersion, deciding distribution and concentration of the leaked substance. The accurate prediction of wind has been challenging in numerical weather prediction models, especially near the surface because of the complex interaction between turbulent flow and topographic effect. In this study, we investigated the characteristics of atmospheric dispersion of radioactive material (i.e. ¹³⁷Cs) according to the simulated boundary layer around the HANARO research nuclear reactor in Korea using the Weather Research and Forecasting (WRF)-Mesoscale Model Interface (MMIF)-California Puff (CALPUFF) model system. We examined the impacts of orographic drag on wind field, stability calculation methods, and planetary boundary layer parameterizations on the dispersion of radioactive material under a radioactive leaking scenario. We found that inclusion of the orographic drag effect in the WRF model improved the wind prediction most significantly over the complex terrain area, leading the model system to estimate the radioactive concentration near the reactor more conservatively. We also emphasized the importance of the stability calculation method and employing the skillful boundary layer parameterization to ensure more accurate low atmospheric conditions, in order to simulate more feasible spatial distribution of the radioactive dispersion in leaking scenarios.

• 한국연소학회:학술대회논문집
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• 2004.11a
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• pp.97-106
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• 2004

Stability of laminar premixed planar flames inclined in gravitational field which generate vorticity is asymptotically examined. The flame structure is resolved by a large activation energy asymptotics and a long wave approximation. The coupling between hydrodynamics and diffusion processes is included and near-unity Lewis number is assumed. The results show that as the flame is more inclined from the horizontal plane it becomes more unstable due to not only the decrease of stabilizing effect of gravity but also the increase of destabilizing effect of rotational flow. The obtained dispersion relation involves the Prandtl number and shows the destabilizing effect of viscosity. The analysis predicts that the phase velocity of unstable flame wave depends on not only the flame angle but also the Lewis number. For relatively short wave disturbances, still much larger than flame thickness, the most unstable wavelength is nearly independent on the flame angle and the flame can be stabilized by gravity and diffusion mechanism.

• Journal of the Korean Society of Combustion
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• v.9 no.4
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• pp.9-21
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• 2004

Stability of laminar premixed planar flames inclined in the gravitational field is asymptotically examined. The flame structure is resolved by a large activation energy asymptotics and a long wave approximation. The coupling between hydrodynamics and diffusion processes is included and near-unity Lewis number is assumed. The results show that as the flame is more inclined from the horizontal plane it becomes more unstable due to not only the decrease of stabilizing effect of gravity but also the increase of destabilizing effect of rotational flow. The obtained dispersion relation involves the Prandtl number and shows the destabilizing effect of viscosity. The analysis predicts that the phase velocity of unstable flame wave depends on not only the flame angle but also the Lewis number. For relatively short wave disturbances, still much larger than flame thickness, the most unstable wavelength is nearly independent on the flame angle and the flame can be stabilized by gravity and diffusion mechanism.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.17 no.11
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• pp.1234-1240
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• 2004

We studied on the electro-optic characteristics and dynamic stability according to an undesirably defined pretilt angle induced in high step coverage of pixel area for the Twisted Nematic (TN) / Fringe-Field Switching (FFS) mode. In case of the TN mode, LC directors twist reversely near the edges of thin-film-transistor and black matrix where the pretilt angle of the LC is not well defined. Therefore, the voltage-dependent dynamics of the LC in TN mode is unstable and shows the bad electro-optic characteristics. On the other hand, in case of the FFS mode, the LCs are twisted parallel to the bottom substrate by fringe electric field and the electro-optic characteristic is not influenced by the pretilt angle of the LC which is not well defined.

• Journal of the Korean Association of Geographic Information Studies
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• v.18 no.1
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• pp.64-73
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• 2015

Recently, the integrated utilization of technology with IT is in demand for the effectiveness of field management together with the prevention and prompt action on safety accident at construction site. In addition, the establishment of construction site support system is necessary to implement the securing of worker's safety, smooth work instruction, efficiency in construction, and others. Data standardization and network architecture were designed regarding data and sound information for data transmission between systems and management. These were to construct USFSS based on integrated VI-GNSS technology in this research. In the stability test of data for each system constructed through it, around 98% stability was secured between workers and for transfer vehicle system within underground structure and field server system in regards to the data transmission stability, around 100% stability was secured between field server system and control system, respectively. Also, in the sound transmission stability test, around 99% reliability could be secured with 1km distance as its standard in case of sound transmission from underground structure construction site to field office near the field through wireless FRS system.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.19 no.2
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• pp.185-188
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• 2006

We studied on the reverse twist near the pixel edge depending on the rubbing direction for the fringe field switching (FFS) mode. Liquid crystal (LC) dynamic and the transmittance near the pixel edge, where the various field directions are generated, depend on the initial rubbing direction because the position of reverse twist is decided by the angle between the electric direction and the LC director at a bias voltage. For example, when the rubbing angle is $7^{\circ}$, the reverse twist appears on the bottom position of the right sharp comer of the pixel edge so that the reverse region exists far away from main active region. But, when the rubbing angle is $-7^{\circ}$, the reverse twist appears on the top position of the right sharp comer of the pixel edge, resulting that the region becomes more close to the main active area and the unstable disclination lines (DLs) easily intrude into the active region. Therefore, it is necessary to keep the reverse twist region far from the active region and it is possible by controlling the rubbing direction in the design of a pixel electrode.