• Title, Summary, Keyword: nonlinearity

Search Result 2,155, Processing Time 0.054 seconds

Correlation between Ultrasonic Nonlinearity and Elastic Nonlinearity in Heat-Treated Aluminum Alloy

  • Kim, Jongbeom;Jhang, Kyung-Young
    • Journal of the Korean Society for Nondestructive Testing
    • /
    • v.37 no.2
    • /
    • pp.115-121
    • /
    • 2017
  • The nonlinear ultrasonic technique is a potential nondestructive method to evaluate material degradation, in which the ultrasonic nonlinearity parameter is usually measured. The ultrasonic nonlinearity parameter is defined by the elastic nonlinearity coefficients of the nonlinear Hooke's equation. Therefore, even though the ultrasonic nonlinearity parameter is not equal to the elastic nonlinearity parameter, they have a close relationship. However, there has been no experimental verification of the relationship between the ultrasonic and elastic nonlinearity parameters. In this study, the relationship is experimentally verified for a heat-treated aluminum alloy. Specimens of the aluminum alloy were heat-treated at $300^{\circ}C$ for different periods of time (0, 1, 2, 5, 10, 20, and 50 h). The relative ultrasonic nonlinearity parameter of each specimen was then measured, and the elastic nonlinearity parameter was determined by fitting the stress-strain curve obtained from a tensile test to the 5th-order-polynomial nonlinear Hooke's equation. The results showed that the variations in these parameters were in good agreement with each other.

Nonlinearity Detection and Compensation in Radio over Fiber Systems Using a Monitoring Channel

  • Kim, Sung-Man
    • Journal of information and communication convergence engineering
    • /
    • v.13 no.3
    • /
    • pp.167-171
    • /
    • 2015
  • A radio over fiber (RoF) system is a kind of analog optical transmission system and considered as a strong candidate for the next-generation fronthaul link in the future mobile network. In RoF systems, nonlinearity compensation is essential to increase the link capacity. In this paper, we propose a nonlinearity detection and compensation scheme using a monitoring channel in RoF systems. A monitoring channel is added at the transmitter site and used for transmitting a reference signal in an RoF transmission. The nonlinearity in the RoF transmission is detected by comparing the received monitoring signal and the original reference signal at the receiver site. Finally, the nonlinearity is compensated at the receiver by giving the reverse function of the detected nonlinearity. Our results show that the proposed scheme can almost remove the error vector magnitude degradation induced by the nonlinearity in the RoF system.

AUTO-CORRELATIONS AND BOUNDS ON THE NONLINEARITY OF VECTOR BOOLEAN FUNCTIONS

  • Kim, Wansoon;Park, Junseok
    • Journal of the Chungcheong Mathematical Society
    • /
    • v.17 no.1
    • /
    • pp.47-56
    • /
    • 2004
  • The nonlinearity of a Boolean function f on $GF(2)^n$ is the minimum hamming distance between f and all affine functions on $GF(2)^n$ and it measures the ability of a cryptographic system using the functions to resist against being expressed as a set of linear equations. Finding out the exact value of the nonlinearity of given Boolean functions is not an easy problem therefore one wants to estimate the nonlinearity using extra information on given functions, or wants to find a lower bound or an upper bound on the nonlinearity. In this paper we extend the notion of auto-correlations of Boolean functions to vector Boolean functions and obtain upper bounds and a lower bound on the nonlinearity of vector Boolean functions in the context of their auto-correlations. Also we can describe avalanche characteristics of vector Boolean functions by examining the extended notion of auto-correlations.

  • PDF

Electrical Relaxation in Silica Glasses and Nonlinearity in Electrical Conductivity (실리카 유리의 전기이완 특성과 비선형적 전기전도도)

  • 신동욱
    • Journal of the Korean Ceramic Society
    • /
    • v.36 no.9
    • /
    • pp.923-929
    • /
    • 1999
  • The cause of optical nonlinearity induced in thermally poled silica glass is believed to be the space charge polarization. Since the second order optical nonlinearity (electro-optic effect) can be used in optical switches the optical nonlinearity in silica glass has drawn a large attention. Space charge polarization occurs when an ionic conducting material is subjected to dc electric field by the blocking electrode. Thermal poling performed to induce the optical nonlinearity in silica glass is basically identical to the process generating space charge polarization. As a first step to understand the mechanism of space charge polarization in silica glass hence the induced optical nonlinearity the absorption currents as functions of time were measured for various types of silica glasses and analyzed by the theory of space charge polarization. It was found that the electrical relaxation exhibited a step by the space charge polarization in the relatively long time range and dielectric loss peak showed a maximum at a specific temperature which is depending on type of silica glass. It was turned out that this relaxation might be a cause of nonlinearity in electrical conductivity of silica glass.

  • PDF

Measurement and Compensation of Nonlinearity in Homodyne Interferometer (Homodyne 간섭계에서의 비선형성 측정과 보정)

  • Kim, Jong-Yun;Eom, Tae-Bong;Jeong, Kyu-Won;Choi, Tae-Young;Lee, Keon-Hee
    • Journal of the Korean Society for Precision Engineering
    • /
    • v.18 no.9
    • /
    • pp.171-178
    • /
    • 2001
  • The nonlinearity of a laser interferometer usually ranges from sub-nanometer to several manometers. This nonlinearity, which has periodic characteristics, limits the accuracy of the interferometer at the sub-nanometer level. The nonlinearity error of the one-frequency homodyne interferometer with quadrature fringe detection results from a number of factors including polarization mixing by imperfect optical elements, unequal gain of photo detectors, lack of quadrature between two signals and misalignment. In this paper, we described a method for measuring and compensating the nonlinearity of homodyne interferometer using the elliptical fitting technique with least-square method. Experimental results demonstrate that $^\pm$3.5 nm nonlinearity can be reduced to $^\pm$0.2 nm level.

  • PDF

Correlation Immune Functions with Controllable Nonlinearity

  • Chee, Seong-Taek;Lee, Sang-Jin;Kim, Kwang-Jo;Kim, Dae-Ho
    • ETRI Journal
    • /
    • v.19 no.4
    • /
    • pp.389-401
    • /
    • 1997
  • In this paper, we consider the relationship between nonlinearity and correlation immunity of Boolean functions. In particular, we discuss the nonlinearity of correlation immune functions suggested by P. Camion et al. For the analysis of such functions, we present a simple method of generating the same set of functions, which makes it possible to construct correlation immune functions with controllable correlation immunity and nonlinearity. Also, we find a bound for the correlation immunity of functions having maximal nonlinearity.

  • PDF

Feasibility Study on Diagnosis of Material Damage Using Bulk Wave Mixing Technique (체적파 혼합기법을 이용한 재료 손상 진단 적용 가능성 연구)

  • Choi, Jeongseok;Cho, Younho
    • Journal of the Korean Society for Nondestructive Testing
    • /
    • v.36 no.1
    • /
    • pp.53-59
    • /
    • 2016
  • Ultrasonic nonlinear evaluation is generally utilized for detection of not only defects but also microdamage such as corrosion and plastic deformation. Nonlinearity is determined by the amplitude ratio of primary wave second harmonic wave, and the results of its comparison are used for evaluation. Owing to the experimental features, the experimental nonlinearity result contains system nonlinearity and material nonlinearity. System nonlinearity is that which is unwanted by the user; hence, it acts as an error and interrupts analysis. In this study, a bulk wave mixing technique is implemented in order to minimize the system nonlinearity and obtain the reliable analysis results. The biggest advantage of this technique is that experimental nonlinearity contains less system nonlinearity than that for the conventional nonlinear ultrasonic technique. Theoretical and experimental verifications are performed in this study. By comparing the results of the bulk wave mixing technique with those of the conventional technique, the strengths, weaknesses, and application validity of the bulk wave mixing technique are determined.

Study of Ultrasonic Nonlinearity in Heat-Treated Material (열처리된 재료의 초음파 비선형성에 관한 연구)

  • Li, Weibin;Lee, Jae-Sun;Cho, Youn-Ho
    • Transactions of the Korean Society of Mechanical Engineers A
    • /
    • v.34 no.6
    • /
    • pp.751-756
    • /
    • 2010
  • Ultrasonic nonlinearity is very sensitive to changes in material properties. This paper describes the study of the correlation between heat treatment and ultrasonic nonlinearity by taking nonlinear factors into consideration. A modified formula was proposed for ultrasonic velocity. This formula indicated that the changes occurring in nonlinearity during heat treatments cause changes in the ultrasonic velocity. The experimental results show that the relative nonlinearity parameters calculated from the modified ultrasonic velocities and the ratio of amplitudes of the second harmonic and fundamental wave are in good agreement. The experimental results prove that heat treatment can result in changes in material nonlinearity. Moreover, the relative nonlinearity parameter calculated from the modified velocity formula is has a large value. Since this parameter has high sensitivity to changes in nonlinearity, it can be used to represent the relative nonlinearity change calculated in this study by using the modified formula for ultrasonic velocity.

Prediction of Soil Deformation with Nonlinear-Anisotropic Model (비선형 이방성 모델을 이용한 흙의 변형 거동 예측)

  • 윤충구;정영훈;정충기
    • Proceedings of the Korean Geotechical Society Conference
    • /
    • /
    • pp.41-48
    • /
    • 2002
  • The fact that nonlinearity and anisotropy of soil should be considered for the proper estimation of soil deformation has been recongnized for a long time. In this study, a new stiffness model which can reflect both nonlinearity and anisotropy is proposed. Nonlinearity is simulated by Ramberg-Osgood model and anisotropy is modeled with the cross-anisotropic elasticity. Analysis results with the developed model compared with those from analyses using linear isotropic model, linear anisotropic model, and nonlinear isotropic model. In the triaxial compression like condition, the effects of nonlinearity on the vertical strain are significant, but soil anisotropy does not affect the vertical strain. In 1-dimensional deformation condition, however, both nonlinearity and anisotropy of soil influence the final magnitude of the vertical strain. Also the increase of poisson's ratio magnifies the effect of anisotropy on the vertical strain in this condition.

  • PDF

Pivot Nonlinearity in Disk Drive Rotary Actuator : Measurement and Modeling (HDD 회전형구동장치의 피봇비선형성 측정 및 모델링)

  • 박재흥;변용규;장흥성;노광춘
    • Proceedings of the Korean Society of Precision Engineering Conference
    • /
    • /
    • pp.419-424
    • /
    • 1996
  • As track density increases, the effects of nonlinearity in pivot bearing of hard disk drive on the servo performance are becoming more important in considering the range of inertia force and the input torque during settling and tracking mode. Recently, an increasing attention is given to more precise experimental observations and modelings of pivot nonlinearity for achieving higher performance of servo control. In this paper, we propose a new model that shows an improved prediction of the pivot nonlinearity than existing preload-plus-two-slope model at matching simulations and experimental results in both time and frequency domains. Experimental measurements are carried out to validate and identify the specific nonlinearity presents in the pivot bearing when its in fine motion. Using the experimental results new model along with the existing one are characterized and compared for relevancies.

  • PDF