• Proceedings of the Korean Institute of Navigation and Port Research Conference
• /
• v.1
• /
• pp.9-14
• /
• 2006

This paper develops a complete methodology for the mitigation of ionosphere spatial anomalies by GBAS systems fielded in the Conterminous U.S. (CONUS). It defines an ionosphere anomaly threat model based on validated observations of unusual ionosphere events in CONUS impacting GBAS sites in the form of a linear ‘wave front’ of constant slope and velocity. It then develops a simulation-based methodology for selecting the worst-case ionosphere wave front impact impacting two satellites simultaneously for a given GBAS site and satellite geometry, taking into account the mitigating effects of code-carrier divergence monitoring within the GBAS ground station. The resulting maximum ionosphere error in vertical position (MIEV) is calculated and compared to a unique vertical alert limit, or $VAL_{H2,I}$, that applies to the special situation of worst-case ionosphere gradients. If MIEV exceeds $VAL_{H2,I}$ for one or more otherwise-usable subset geometries (i.e., geometries for which the 'normal' vertical protection level, or $VPL_{H0}$, is less than the 'normal' VAL), the broadcast ${\sigma}_{pr_{-}gnd}$ and/or ${\sigma}_{vig}$ must be increased such that all such potentially-threatening geometries have VPL$_{H0}$ > VAL and thus become unavailable. In addition to surveying all aspects of the methods used to generate the required ${\sigma}_{pr_{-}gnd}$ and ${\sigma}_{vig}$ inflation factors for CONUS GBAS sites, related methods for deriving similar results for GBAS sites outside CONUS are suggested.

• Transactions on Electrical and Electronic Materials
• /
• v.18 no.4
• /
• pp.181-184
• /
• 2017

Multilayer ceramics in which piezoelectric layers of $0.90Pb(Zr_{0.48}Ti_{0.52})O_3-0.05Pb(Mn_{1/3}Sb_{2/3})O_3-0.05Pb(Zn_{1/3}Nb_{2/3})O_3$ (0.90PZT-0.05PMS-0.05PZN) stack alternately with silver electrode layers were prepared by an advanced low-temperature co-fired ceramic (LTCC) method. The electrical properties and bonding strength of the multilayers were associated with the interface morphologies between the piezoelectric and silver-electrode layers. Usually, the inner silver electrodes are fabricated by sintering silver paste in multi-layer stacks. To improve the interface bonding strength, piezoelectric powders of 0.90PZT-0.05PMS-0.05PZN with an average particle size of $23{\mu}m$ were added to silver paste to form a gradient interface. SEM observation indicated clear interfaces in multilayer ceramics without powder addition. With the increase of piezoelectric powder addition in the silver paste, gradient interfaces were successfully obtained. The multilayer ceramics with gradient interfaces present greater bonding strength as well as excellent piezoelectric properties for 30~40 wt% of added powder. On the other hand, over addition greatly increased the resistance of the inner silver electrodes, leading to a piezoelectric behavior like that of bulk ceramics in multilayers.

• Nuclear Engineering and Technology
• /
• v.48 no.6
• /
• pp.1396-1403
• /
• 2016

In this study, fast-curing shielding materials were prepared with a two-component polyurethane matrix and a filler material of PbO through a one-step, laboratory-scale method. With an increase in the filler content, viscosity increased. However, the two components showed a small difference. Curing time decreased as the filler content increased. The minimum tack-free time of 27 s was obtained at a filler content of 70 wt%. Tensile strength and compressive strength initially increased and then decreased as the filler content increased. Even when the filler content reached 60 wt%, mechanical properties were still greater than those of the matrix. Cohesional strength decreased as the filler content increased. However, cohesional strength was still greater than 100 kPa at a filler content of 60 wt%. The ${\gamma}$-ray-shielding properties increased with the increase in the filler content, and composite thickness could be increased to improve the shielding performance when the energy of ${\gamma}$-rays was high. When the filler content was 60 wt%, the composite showed excellent comprehensive properties.

• Nuclear Engineering and Technology
• /
• v.53 no.9
• /
• pp.2937-2952
• /
• 2021

A typical three-dimensional finite element model for a fuel assembly is established, which is composed of 16 monolithic U-10Mo fuel plates and Al alloy frame. The distribution and evolution results of temperature, displacement and stresses/strains in all the parts are numerically obtained and analyzed with a self-developed code of FUELTM. The simulation results indicate that (1) the out-of-plane displacements of Al alloy side plates are mainly attributed to the bending deformations; (2) enhanced out-of-plane displacements appear in fuel plates adjacent to the outside Al plates, which results from the occurred bending deformations due to the applied constraints of outside Al plates; (3) an intense interaction of fuel foil with the cladding occurs near the foil edge, which appears more heavily in the fuel plates adjacent to the outside Al plates. The maximum first principal stresses in the fuel foil are similar for all the fuel plates and appear near the fuel foil edge; while, the through-thickness creep strains of fuel foil in the fuel plate near the central region of fuel assembly are larger, and the induced creep damage might weaken the fuel skeleton strength and raise the fuel failure risk.

• Nuclear Engineering and Technology
• /
• v.53 no.9
• /
• pp.3026-3034
• /
• 2021

Multi-target X-ray tube is a new type X-ray source, and can be applied in many fields such as sensitive X-ray fluorescence analysis and medical imaging. In this work, we report an electric field modulation multi-target X-ray tube, which contains four targets (Cr, Ni, Au, Mo) coated on a Beryllium (Be) window. A four-valve electric field deflector was developed to deflect the electron beam to bombard the corresponding targets. Particle dynamics analysis software was employed to simulate the particle tracking of electron beam. The results show that the 30 keV electron beam could get a 6.7 mm displacement on the target plane by 10⁵ V/m electric field. The focus areas are about 2 mm × 5 mm and 4 mm × 2.5 mm after deflection in two directions. Thermal behavior calculated by ANSYS shows that the designed target assembly could withstand a 10 W continuous power. The optimum target thicknesses and emission spectra were obtained by Geant4 when the thickness of Be window was 300 mm and the electron beam incident angle was 0.141 rad. The results indicate that this multi-target X-ray tube could provide different X-ray sources effectively.

• Journal of the Korean Society of Manufacturing Process Engineers
• /
• v.21 no.5
• /
• pp.46-52
• /
• 2022

Although pipe performs various functions in industrial sites and residential spaces, if it is damaged due to corrosion caused by the external environment, it may cause equipment failure or a major accident. For this reason, various studies for safety management are being conducted, but studies on detecting corrosion or cracks on the pipe surface using a laser displacement sensor have hardly been conducted. Therefore, in this study, the corrosion degree of the pipe surface was compared and classified into 4 corrosion conditions, and inspection equipment using a laser scanner was manufactured. The corrosion height was calculated from the four surface data obtained from the measuring equipment and applied to various CNN algorithms, and 91% accuracy was obtained during training using the Modified VGGNet16 code with reduced number of parameters.

• Journal of the Korean Society for Aviation and Aeronautics
• /
• v.10 no.1
• /
• pp.95-105
• /
• 2002

• Journal of the Korean Society for Aviation and Aeronautics
• /
• v.2
• /
• pp.23-45
• /
• 1994

본 연구 논문은 항공기 개발에 있어서 비행시험의 최종 단계라 할 수 있는 스핀시험의 정의, 스핀 시험방법 및 스핀 진입시의 회복방법과 실제 비행에서의 스핀 특성으로 스핀에 대한 안전성 제고 및 비행시험의 중요성을 논하였다.

• Journal of the Korean Society for Aviation and Aeronautics
• /
• v.2
• /
• pp.183-190
• /
• 1994

본 연구에서는 항공기 사고의 대부분을 차지하는 이${\cdot}$착륙단계중에서, 이륙직 후 저고도에서 동력이 상실되었을 경우에 이륙활주로 방향으로 Turning Back하는 것은, 어떠한 안전 한계를 지니고 있는지를 선회 소요시간과 고도손실, 선회율과 활공속도와의 관계 등의 이론적인 근거에 기초하여 분석하고자 한다.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2001.02a
• /
• pp.73-73
• /
• 2001