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GBAS ionospheric anomaly monitoring strategy using Kullback-Leibler divergence metric
Jeongho Cho,Youngsun Yun,Moon-Beom Heo IEEE 2015 IEEE transactions on aerospace and electronic syst Vol.51 No.1
<P>A significant anomaly of great importance for ground-based augmentation systems (GBAS) is the steep gradient in ionospheric delays caused by rare ionospheric storms. To avoid such hazardous errors, code-carrier divergence (CCD) monitors have been applied to support the use of GBAS in Category I (CAT I) operation. However, to meet the stricter requirements for CAT II/III operation, it may be necessary to greatly improve the speed with which existing CCD monitors detect ionospheric gradients or develop an innovative divergence monitor. One way of obtaining stricter integrity is to detect anomalous divergence behavior more rapidly than the CCD monitor does. Therefore, we attempted to devise a divergence monitor in which the detection time is reduced by using the Kullback-Leibler information. In simulations and experimental results, we demonstrate that the proposed divergence measure is quite capable of detecting ionospheric anomalies that are hazardous to GBAS and is a very promising alternative for the detection of deviations. A comparison with existing CCD monitors shows its increased fault detectability, which enables it to sense even small ionospheric gradients more rapidly than typical monitors.</P>
Analysis of the Optimal Frequency Band for a Ballistic Missile Defense Radar System
Jeongho Park,Dong-Hui Lee,Chulhun Seo,Byoungho Cho,Dang-An Nguyen 한국전자파학회JEES 2018 Journal of Electromagnetic Engineering and Science Vol.18 No.4
In this paper, we consider the anti-attack procedure of a ballistic missile defense system (BMDS) at different operating frequencies at its phased-array radar station. The interception performance is measured in terms of lateral divert (LD), which denotes the minimum acceleration amount available in an interceptor to compensate for prediction error for a successful intercept. Dependence of the frequency on estimation accuracy that leads directly to prediction error is taken into account, in terms of angular measurement noises. The estimation extraction is performed by means of an extended Kalman filter (EKF), considering two typical re-entry trajectories of a non-maneuvering ballistic missile (BM). The simulation results show better performance at higher frequency for both tracking and intercepting aspects.
( Jeongho Kim ),( Heechan Cho ) 한국폐기물자원순환학회(구 한국폐기물학회) 2019 ISSE 초록집 Vol.2019 No.-
Along with the global growth of solar power, there is growing concern about generation of waste including photovoltaic (PV) modules. Since PV module contains valuable resources such as silver, silicon and glass, various recycling attempts are being made, and mechanical, thermal and chemical methods are typical. However, the thermal method consumes enormous energy and generates a considerable amount of harmful gas, and the chemical method takes a long time and generates a large amount of wastewater. To overcome these disadvantages, a combination of microwave heating and mechanical separation was tested. Microwave was chosen to selectively heat the silicon cell layer so that only the portion bonded to the EVA layer was expected to be heated. At a temperature of 100-120 °C, the EVA layer was partially melted and the silicon cell was isolated. As a result, the EVA layer is not completely burned and therefore a lower amount of emission gas is generated. Also, this process is conducted at a relatively low temperature, which can reduce the silicon cell damage as a result of the incineration process. And it has a faster processing time than chemical method, due to its effective heating mechanism. After separating and grinding the silicon cells, the included silicon and silver were separated by density separation process. As a result, the silver concentration increased significantly from 1.4 % to 41.78 %. The increased silver concentration will economically improve the subsequent chemical extraction process.
Capacity of an Orthogonal Overlay Channel
Jeongho Yeo,Byung Wook Han,Joon Ho Cho,Lehnert, James S. IEEE 2015 IEEE Transactions on Wireless Communications Vol.14 No.11
<P>In this paper, the design of a selfless overlay system is considered for a frequency-selective bandlimited linear time-invariant channel already occupied by a legacy system. It is assumed that the transmitted signal by the legacy system is well modeled by a zero-mean second-order cyclostationary (SOCS) Gaussian random process. It is also assumed that the legacy receiver employs a linear-conjugate linear (LCL) filter to capture possible impropriety of the signal. Our objective is to maximize the throughput of the overlay system under the constraint that no interfering signal component is observed at the output of the legacy LCL filter sampled at a uniform rate. A relevant problem of deriving the constrained capacity of a discrete-time vector Gaussian noise channel is first examined. Then, it is shown that the optimal input to the overlay channel must be a zero-mean SOCS Gaussian random process. Using these results, the optimization problem is formulated in the frequency domain, and the procedure named orthogonal cyclic water filling (O-CWF) is derived to find the optimal channel input distribution. Numerical results are provided to show that the proposed selfless overlay scheme enables reliable communication even over a channel fully occupied by a legacy system.</P>
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조미현,김정호,이현태,사홍기 한국약제학회 2003 Journal of Pharmaceutical Investigation Vol.33 No.3
Dissolution profile comparsions can be done virtue of the similarity factor (f₂). It is a logarithmic reciprocal square root transformation of the sum of squared error of % dissolution differences between profiles at several time points. It gives information on the degree of similarity between the two profiles: An f₂ value between 50 and 100 suggests the similarity/equivalence of the two dissolution curves being compared. The objective of this report was to provide a careful examination on the f₂metrics in detail. It was shown that f₂values exceeded 50, when relative differences in % dissolved between two products were less than 15% at all time points. The similarity factor value was also found to be greater than 50, in cases when absolute % dissolution differences were below 10% at all time points. Interestingly, the f₂value was changed by the number of the time points selected for calculation. In particular, f₂tended to have higher values, when the f₂metrics used a large number of time points in which % dissolved reached plateau. Finally, since the similarity factor was a sample statistics, it was impossible to infer type Ⅰ/Ⅱ errors and sampling error. Despite certain limitations inherited in the f₂metrics, it was easy and convenient to evaluate how similar the two dissolution profiles were.
Improvement of Beam-Quality Evaluation Method for Medical Linear Accelerator Using Magnetic Field
Jeongho Kim,Manseok Han,Sejong Yoo,Kijin Kim,Jae-Hwan Cho 한국자기학회 2015 Journal of Magnetics Vol.20 No.2
Beam-quality of medical linac evaluations vary by diverse factors. Because conventional beam-quality evaluation methods yield fragmentary results, a new beam-evaluation method is suggested, and its feasibility is evaluated. The PDDs (percentage depth doses) of 6 MV (Mega-voltage) and 10 MV photon, R (Range) of a 6 MeV (Mega Electron-voltage) and 9 MeV electron were measured and compared with the conventional evaluation methods, and the improved methods PDD<SUP>10</SUP>5, PDD<SUP>20</SUP>10, PDD<SUP>30</SUP>20, PDD<SUP>20</SUP> 5, PDD<SUP>30</SUP> 10, and R<SUP>70</SUP> 50, R<SUP>50</SUP> 30, R<SUP>70</SUP>30 as the magnetic field of the bending magnet was changed to +2% to ?2%, and the results were compared. The comparison showed that the improved methods exhibit a higher discrimination than the conventional methods in each energy regime. PDD<SUP>10</SUP>5, PDD<SUP>30</SUP>20, PDD<SUP>30</SUP>10 and R<SUP>70</SUP>50, R<SUP>50</SUP>30 should be applied. These methods exhibit a higher discrimination in each energy regime than conventional beam-quality evaluation methods; therefore, they should be used for beam-quality evaluation according to the magnetic field variation.