• Title, Summary, Keyword: Mapping Function

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Effects of Tropospheric Mapping Functions on GPS Data Processing

  • Won, Ji-Hye;Park, Kwan-Dong;Ha, Ji-Hyun;Cho, Jung-Ho
    • Journal of Astronomy and Space Sciences
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    • v.27 no.1
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    • pp.21-30
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    • 2010
  • In processing space geodetic data, mapping functions are used to convert the tropospheric signal delay along the zenith direction to the line of sight direction. In this study, we compared three mapping functions by evaluating their effects on the tropospheric signal delay and position estimates in GPS data processing. The three mapping functions tested are Niell Mapping Function (NMF), Vienna Mapping Function 1 (VMF1), and Global Mapping Function (GMF). The tropospheric delay and height estimates from VMF1 and GMF are compared with the ones obtained with NMF. The differences among mapping functions show annual signals with the maximum occurring in February or August. To quantitatively estimate the discrepancies among mapping functions, we calculated the maximum difference and the amplitude using a curve fitting technique. Both the maximum difference and amplitude have high correlations with the latitude of the site. Also, the smallest difference was found around $30^{\circ}N$ and the amplitudes increase toward higher latitudes. In the height estimates, the choice of mapping function did not significantly affect the vertical velocity estimate, and the precision of height estimates was improved at most of the sites when VMF1 or GMF was used instead of NMF.

Texture Mapping using Multiperiodic Function on the Smooth Genus N Object (Multiperiodic 함수를 이용한 Smooth Genus N 객체의 텍스쳐매핑)

  • Hwa Jin Park
    • Journal of Korea Multimedia Society
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    • v.5 no.1
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    • pp.94-104
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    • 2002
  • This paper presents a new way of texture mapping on the Genus N object constructed over a single domain. The problem of 2D texture mapping is the discontinuity of texture domain at the virtual boundary on the object. Such phenomenon decreases smoothness of the object as well as looks unnatural. Especially it is necessary for the Genus N object of infinite coninuity to apply the seamless texture mapping. For seamless texture mapping, a multiperiodic function, which transforms a discontinuous function into a continuous function, is suggested. In some applications, however, the visual seams on the textured object provide more realistic appearance. Therefore, this research supports the interactive control from the discontinuity and the continuity across the boundary using the coefficient of the weight function.

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A Method of Deriving an Intensity Mapping Function by Using The Variational Technique (변분법을 이용한 명암도 변환 함수 획득 방법)

  • Kim, Jun-Hyung;Noh, Chang-Kyun;Ko, Sung-Jea
    • Journal of the Institute of Electronics Engineers of Korea SP
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    • v.48 no.5
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    • pp.10-15
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    • 2011
  • Histogram equalization is an effective method to enhance the contrast of the image. However, it can result in unwanted artifacts such as excessive contrast enhancement and noise amplification. These artifacts can be reduced by modifying an intensity mapping function which is generated by histogram equalization. In this paper, we present a variational approach to the modification of the intensity mapping function. We define a functional whose minimization produces a modified intensity mapping function. Experimental results show that the intensity mapping function obtained by the proposed method can enhance the contrast of the image without visual artifacts.

An Effective Memory Mapping Function for CMAC Controller (CMAC 제어기를 위한 효과적인 메모리 매핑 함수)

  • Kwon, H.Y.;Bien, Z.;Suh, I.H.
    • Proceedings of the KIEE Conference
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    • pp.488-493
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    • 1989
  • In this paper, the structure of CMAC address mapping is first revisited, and the address hashing function and the random mapping is discussed in the conventional CMAC implementation. Then the effective size of CMAC memory is derived from the modulus property of the CMAC address vector, and a new hashing function for the effective memory mapping is proposed for a CMAC implementation with feasible memory size and no troublesome random mapping. Finally, the performance of the conventional CMAC learning algorithm and that of the proposed new CMAC scheme arc compared via simulations.

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Reliability-based design optimization using reliability mapping functions

  • Zhao, Weitao;Shi, Xueyan;Tang, Kai
    • Structural Engineering and Mechanics
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    • v.62 no.2
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    • pp.125-138
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    • 2017
  • Reliability-based design optimization (RBDO) is a powerful tool for design optimization when considering probabilistic characteristics of design variables. However, it is often computationally intensive because of the coupling of reliability analysis and cost minimization. In this study, the concept of reliability mapping function is defined based on the relationship between the reliability index obtained by using the mean value first order reliability method and the failure probability obtained by using an improved response surface method. Double-loop involved in the classical RBDO can be converted into single-loop by using the reliability mapping function. Since the computational effort of the mean value first order reliability method is minimal, RBDO by using reliability mapping functions should be highly efficient. Engineering examples are given to demonstrate the efficiency and accuracy of the proposed method. Numerical results indicated that the proposed method has the similar accuracy as Monte Carlo simulation, and it can obviously reduce the computational effort.

A spline finite element method on mapping

  • Ding, Hanshan;Shao, Rongguang;Ding, Dajun
    • Structural Engineering and Mechanics
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    • v.4 no.4
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    • pp.415-424
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    • 1996
  • This paper presents a newly suggested calculation method in which an arbitrary quadrilateral element with curved sides is transformed to a normal rectangular one by mapping of coordinates, then the two-dimensional spline is adopted to approach the displacement function of this element. Finally the solution can be obtained by the least-energy principle. Thereby, the application field of Spline Finite Element Method will be extended.

Comparison of Time Offsets by Tropospheric Zenith Path delay models and Mapping Functions in GPS Time Transfer (GPS 시각 전송에서의 대류층 천정지연 모델과 매핑 함수에 따른 시각오프셋 비교)

  • Yu, Dong-Hui
    • Journal of the Korea Institute of Information and Communication Engineering
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    • v.18 no.6
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    • pp.1317-1322
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    • 2014
  • This paper shows effects of tropospheric delay models and mapping functions among delay features occurred when GPS code signal is transferred for GPS Time Transfer. GPS time transfer uses CGGTTS as the international standard format. For geodetic GPS receiver, ROB has provided r2cggtts software which generates CGGTTS data from RINEX data and all laboratories participated in TAI link use this software and send the CGGTTS results periodically. Though Saastamoinen zenith path model and Niell mapping function are commonly used in space geodesy, r2cggtts software applied NATO zenith path model and CHAO mapping function to the tropospheric delay model. Hence, this paper shows effects of two tropospheric delay models by implementing Saastamoinen model and Niell mapping function for the time offset.

A study of Temperal Difference Learning using Nonlinear Function Approximation (비선형 함수 근사화를 사용한 TD학습에 관한 연구)

  • Kwon, Jae-Cheol;Lee, Young-Seog;Kim, Dong-Ok;Seo, Bo-Hyeok
    • Proceedings of the KIEE Conference
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    • pp.407-409
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    • 1998
  • This paper deals with temporal-difference learning that is a method for approximating long-term future cost as a function of current state in knowlege-poor environment, a function approximator is used to approximate the mapping from state to future cost, a linear function approximator is limited because mapping from state to future cost has a nonlinear characteristic, so a nonlinear function approximator is used to approximate the mapping from state to future cost in this paper, and that TD learning using a nonlinear function approximator is stable is proved.

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Performance Analysis of Mapping Functions and Mean Temperature Equations for GNSS Precipitable Water Vapor in the Korean Peninsula

  • Park, Han-Earl;Yoo, Sung-Moon;Yoon, Ha Su;Chung, Jong-Kyun;Cho, Jungho
    • Journal of Positioning, Navigation, and Timing
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    • v.5 no.2
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    • pp.75-85
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    • 2016
  • The performance of up-to-date mapping functions and various mean temperature equations were analyzed to derive optimal mapping function and mean temperature equation when GNSS precipitable water vapor (PWV) was investigated in the Korean Peninsula. Bernese GNSS Software 5.2, which can perform high precision GNSS data processing, was used for accurate analysis, and zenith total delay (ZTD) required to calculate PWV was estimated via the Precise Point Positioning (PPP) method. GNSS, radiosonde, and meteorological data from 2009 to 2014 were acquired from Sokcho Observatory and used. ZTDs estimated by applying the global mapping function (GMF) and Vienna mapping function 1 (VMF1) were compared with each other in order to evaluate the performance of the mapping functions. To assess the performance of mean temperature equations, GNSS PWV was calculated by using six mean temperature equations and a difference with radiosonde PWV was investigated. Conclusively, accuracy of data processing was improved more when using VMF1 than using GMF. A mean temperature equation proposed by Wu (2003) had the smallest difference with that in the radiosonde in the analysis including all seasons. In summer, a mean temperature equation proposed by Song & Grejner-Brzezinska (2009) had the closest results with that of radiosonde. In winter, a mean temperature equation proposed by Song (2009) showed the closest results with that of radiosonde.

Prediction of a Mode behavior Using Neural Network Method (신경회로망 기법을 이용한 모드 거동 예측)

  • Shin, Young-Sug;Kim, Seong-Tae;Kim, Heon-Ju;Kim, Jae-Young;Hwang, Chul-Ho
    • Journal of the Korea Institute of Military Science and Technology
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    • v.14 no.5
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    • pp.768-773
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    • 2011
  • The prediction method of future events using the time histories of velocity or pressure, etc., is a useful way for controlling various air vehicles. For example, the sensors of velocity or pressure can be used to extract the time mode coefficients of eigenmode of flow field, and then the result is applied to suppress wake or drag. The velocity information is mapped to the entire flow field, so this mapping function can be used to predict the future events based on the current information. The mapping function is composed of the huge amount of weight parameters, so the efficient way of finding these parameters is needed. Here, the neural network algorithm is studied to draw a mapping function using the number and location of velocity sensors.