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Sample records for nonlinear channel equalization

  1. Modeling and equalization of nonlinear bandlimited satellite channels

    Science.gov (United States)

    Konstantinides, K.; Yao, K.

    1986-01-01

    The problem of modeling and equalization of a nonlinear satellite channel is considered. The channel is assumed to be bandlimited and exhibits both amplitude and phase nonlinearities. A discrete time satellite link is modeled under both uplink and downlink white Gaussian noise. Under conditions of practical interest, a simple and computationally efficient design technique for the minimum mean square error linear equalizer is presented. The bit error probability and some numerical results for a binary phase shift keyed (BPSK) system demonstrate that the proposed equalization technique outperforms standard linear receiver structures.

  2. Nonlinear Algorithms for Channel Equalization and Map Symbol Detection.

    Science.gov (United States)

    Giridhar, K.

    The transfer of information through a communication medium invariably results in various kinds of distortion to the transmitted signal. In this dissertation, a feed -forward neural network-based equalizer, and a family of maximum a posteriori (MAP) symbol detectors are proposed for signal recovery in the presence of intersymbol interference (ISI) and additive white Gaussian noise. The proposed neural network-based equalizer employs a novel bit-mapping strategy to handle multilevel data signals in an equivalent bipolar representation. It uses a training procedure to learn the channel characteristics, and at the end of training, the multilevel symbols are recovered from the corresponding inverse bit-mapping. When the channel characteristics are unknown and no training sequences are available, blind estimation of the channel (or its inverse) and simultaneous data recovery is required. Convergence properties of several existing Bussgang-type blind equalization algorithms are studied through computer simulations, and a unique gain independent approach is used to obtain a fair comparison of their rates of convergence. Although simple to implement, the slow convergence of these Bussgang-type blind equalizers make them unsuitable for many high data-rate applications. Rapidly converging blind algorithms based on the principle of MAP symbol-by -symbol detection are proposed, which adaptively estimate the channel impulse response (CIR) and simultaneously decode the received data sequence. Assuming a linear and Gaussian measurement model, the near-optimal blind MAP symbol detector (MAPSD) consists of a parallel bank of conditional Kalman channel estimators, where the conditioning is done on each possible data subsequence that can convolve with the CIR. This algorithm is also extended to the recovery of convolutionally encoded waveforms in the presence of ISI. Since the complexity of the MAPSD algorithm increases exponentially with the length of the assumed CIR, a suboptimal

  3. Digital Non-Linear Equalization for Flexible Capacity Ultradense WDM Channels for Metro Core Networking

    DEFF Research Database (Denmark)

    Arlunno, Valeria; Zhang, Xu; Larsen, Knud J.

    2011-01-01

    We experimentally demonstrate that digital non-linear equalization allows for using independent tunable DFB lasers spaced at 12.5 GHz for ultradense WDM PM-QPSK flexible capacity channels for metro core networking.......We experimentally demonstrate that digital non-linear equalization allows for using independent tunable DFB lasers spaced at 12.5 GHz for ultradense WDM PM-QPSK flexible capacity channels for metro core networking....

  4. Equalization and detection for digital communication over nonlinear bandlimited satellite communication channels. Ph.D. Thesis

    Science.gov (United States)

    Gutierrez, Alberto, Jr.

    1995-01-01

    This dissertation evaluates receiver-based methods for mitigating the effects due to nonlinear bandlimited signal distortion present in high data rate satellite channels. The effects of the nonlinear bandlimited distortion is illustrated for digitally modulated signals. A lucid development of the low-pass Volterra discrete time model for a nonlinear communication channel is presented. In addition, finite-state machine models are explicitly developed for a nonlinear bandlimited satellite channel. A nonlinear fixed equalizer based on Volterra series has previously been studied for compensation of noiseless signal distortion due to a nonlinear satellite channel. This dissertation studies adaptive Volterra equalizers on a downlink-limited nonlinear bandlimited satellite channel. We employ as figure of merits performance in the mean-square error and probability of error senses. In addition, a receiver consisting of a fractionally-spaced equalizer (FSE) followed by a Volterra equalizer (FSE-Volterra) is found to give improvement beyond that gained by the Volterra equalizer. Significant probability of error performance improvement is found for multilevel modulation schemes. Also, it is found that probability of error improvement is more significant for modulation schemes, constant amplitude and multilevel, which require higher signal to noise ratios (i.e., higher modulation orders) for reliable operation. The maximum likelihood sequence detection (MLSD) receiver for a nonlinear satellite channel, a bank of matched filters followed by a Viterbi detector, serves as a probability of error lower bound for the Volterra and FSE-Volterra equalizers. However, this receiver has not been evaluated for a specific satellite channel. In this work, an MLSD receiver is evaluated for a specific downlink-limited satellite channel. Because of the bank of matched filters, the MLSD receiver may be high in complexity. Consequently, the probability of error performance of a more practical

  5. Digital non-linear equalization for flexible capacity ultradense WDM channels for metro core networking.

    Science.gov (United States)

    Arlunno, Valeria; Zhang, Xu; Larsen, Knud J; Zibar, Darko; Monroy, Idelfonso Tafur

    2011-12-12

    An experimental demonstration of Ultradense WDM with advanced digital signal processing is presented. The scheme proposed allows the use of independent tunable DFB lasers spaced at 12.5 GHz for ultradense WDM PM-QPSK flexible capacity channels for metro core networking. To allocate extremely closed carriers, we demonstrate that a digital non-linear equalization allow to mitigate inter-channel interference and improve overall system performance in terms of OSNR. Evaluation of the algorithm and comparison with an ultradense WDM system with coherent carriers generated from a single laser are also reported. © 2011 Optical Society of America

  6. Digital non-linear equalization for flexible capacity ultradense WDM channels for metro core networking

    DEFF Research Database (Denmark)

    Arlunno, Valeria; Zhang, Xu; Larsen, Knud J.

    2011-01-01

    An experimental demonstration of Ultradense WDM with advanced digital signal processing is presented. The scheme proposed allows the use of independent tunable DFB lasers spaced at 12.5 GHz for ultradense WDM PM-QPSK flexible capacity channels for metro core networking. To allocate extremely closed...... carriers, we demonstrate that a digital non-linear equalization allow to mitigate inter-channel interference and improve overall system performance in terms of OSNR. Evaluation of the algorithm and comparison with an ultradense WDM system with coherent carriers generated from a single laser are also...

  7. Nonlinear channelizer

    Science.gov (United States)

    In, Visarath; Longhini, Patrick; Kho, Andy; Neff, Joseph D.; Leung, Daniel; Liu, Norman; Meadows, Brian K.; Gordon, Frank; Bulsara, Adi R.; Palacios, Antonio

    2012-12-01

    The nonlinear channelizer is an integrated circuit made up of large parallel arrays of analog nonlinear oscillators, which, collectively, serve as a broad-spectrum analyzer with the ability to receive complex signals containing multiple frequencies and instantaneously lock-on or respond to a received signal in a few oscillation cycles. The concept is based on the generation of internal oscillations in coupled nonlinear systems that do not normally oscillate in the absence of coupling. In particular, the system consists of unidirectionally coupled bistable nonlinear elements, where the frequency and other dynamical characteristics of the emergent oscillations depend on the system's internal parameters and the received signal. These properties and characteristics are being employed to develop a system capable of locking onto any arbitrary input radio frequency signal. The system is efficient by eliminating the need for high-speed, high-accuracy analog-to-digital converters, and compact by making use of nonlinear coupled systems to act as a channelizer (frequency binning and channeling), a low noise amplifier, and a frequency down-converter in a single step which, in turn, will reduce the size, weight, power, and cost of the entire communication system. This paper covers the theory, numerical simulations, and some engineering details that validate the concept at the frequency band of 1-4 GHz.

  8. Tracking ability of L-level MLP-based equalizers in nonlinear microwave radio channels in the presence of multipath fading

    Science.gov (United States)

    Luk, Eric K.; Fagan, Anthony D.

    1994-03-01

    The performance of microwave digital radio systems is severely degraded by multipath fading and also by the nonlinear power amplifier at the transmitter, the combined effects of these result in a time varying nonlinear channel. In this paper, the multilayer perceptron (MLP) based equalizer is investigated for use on such channels. It is found to outperform the conventional approach, that is, the use of a transversal equalizer at the receiver operating with a signal predistorter placed before the non-linear power amplifier at the transmitter. An L- level non-linear function is used as a node activation for the MLP. Two update schemes are investigated, one being a complex version of the back propagation algorithm, the other a complex version of the delta-bar-delta algorithm.

  9. Nonlinear Blind Equalization for Volume Holographic Data Storage

    Institute of Scientific and Technical Information of China (English)

    商未雄; 何庆声; 金国藩

    2004-01-01

    We investigate the nonlinear blind equalization for volume holographic data storage channel. Base on the recurrent neural network channel model, we describe a novel blind equalizer for the volume holographic data storage system to improve the bit error rate and hence to make the storage densities achievable. The experimental results also indicate that a significant improvement in the bit error rate to 2.55 × 10-3 is possible with the nonlinear blind equalization.

  10. Nonlinear Equalization of Microwave Photonic Links

    Science.gov (United States)

    2016-10-31

    3[1…3] = [1][2][3] the Volterra model reduces to the Taylor series. TABLE I VOLTERRA KERNEL COEFFICIENTS FOR...ORDER 3 M UNIQUE VOLTERRA COEFFICIENTS 8 120 16 816 64 45760 128 357760 256 2829056 The main benefit of a Volterra model over a Taylor ...nonlinear equalizer works on the entire Nyquist band and is synthesized directly from mathematical requirements instead of using best - fit methods

  11. Particle Filtering Equalization Method for a Satellite Communication Channel

    Directory of Open Access Journals (Sweden)

    Amblard Pierre-Olivier

    2004-01-01

    Full Text Available We propose the use of particle filtering techniques and Monte Carlo methods to tackle the in-line and blind equalization of a satellite communication channel. The main difficulties encountered are the nonlinear distortions caused by the amplifier stage in the satellite. Several processing methods manage to take into account these nonlinearities but they require the knowledge of a training input sequence for updating the equalizer parameters. Blind equalization methods also exist but they require a Volterra modelization of the system which is not suited for equalization purpose for the present model. The aim of the method proposed in the paper is also to blindly restore the emitted message. To reach this goal, a Bayesian point of view is adopted. Prior knowledge of the emitted symbols and of the nonlinear amplification model, as well as the information available from the received signal, is jointly used by considering the posterior distribution of the input sequence. Such a probability distribution is very difficult to study and thus motivates the implementation of Monte Carlo simulation methods. The presentation of the equalization method is cut into two parts. The first part solves the problem for a simplified model, focusing on the nonlinearities of the model. The second part deals with the complete model, using sampling approaches previously developed. The algorithms are illustrated and their performance is evaluated using bit error rate versus signal-to-noise ratio curves.

  12. Adaptive Channel Equalization Using Multiplicative Neural Network for Rayleigh Faded Channel

    Directory of Open Access Journals (Sweden)

    P. Sivakumar

    2011-01-01

    Full Text Available Problem statement: Digital transmission over band-limited communication channel largely suffers from ISIS and various noise sources. The presence of ISI and noise causes bit errors in the received signal. Equalization is necessary at the receiver to overcome these channel impairment to recover the original transmitted sequence. Traditionally equalization is considered as equivalent to inverse filtering and implemented using linear-perform under severe distortion conditions when Signal to Noise Ratio (SNR is poor. Equalization can be considered as a non-linear classification problem and optimum solution is given by Bayesian solution. Non-linear techniques like Artificial Neutral Networks (ANN are very good choice for non-linear classification problems. Several non-lines are equalizers have been implemented using ANN which outperformed LTE and solved the problem of equalization to the varying degree of sources. Approach: Forward neural network architecture with optimum number of nodes was used to achieve adaptive channel equalization. Summation at each node was replaced by multiplications which result in powerful mapping. The equalizer was tested on Rayleigh fading channel with a BPSK signal. Results: Results showed that proposed equalizer provides simplified architecture and improvement in the bit error rate at various levels of signal to noise ratio for Rayleigh faded channel. Conclusion: A high order feed forward network equalizer with multiplicative neuron is proposed in this study. Use of Multiplication allows direct computing of polynomial inputs and approximation with fewer nodes. Performance comparison in terms of network architecture and BER performance suggest the better classification capability of the proposed MNN equalizer over RRBF.

  13. Channel Equalization for Chaos-Based Communication Systems

    Institute of Scientific and Technical Information of China (English)

    冯久超; 鲁瑞华

    2002-01-01

    We study the equalization of the channel for chaotic communication systems. A channel equalizer is designed and realized by a modified recurrent neural network for eliminating channel distortions. The results from computer simulations demonstrate the effectiveness of the equalizer as applied to a chaotic communication system.

  14. Nonlinear generalization of Den Hartog's equal-peak method

    Science.gov (United States)

    Habib, G.; Detroux, T.; Viguié, R.; Kerschen, G.

    2015-02-01

    This study addresses the mitigation of a nonlinear resonance of a mechanical system. In view of the narrow bandwidth of the classical linear tuned vibration absorber, a nonlinear absorber, termed the nonlinear tuned vibration absorber (NLTVA), is introduced in this paper. An unconventional aspect of the NLTVA is that the mathematical form of its restoring force is tailored according to the nonlinear restoring force of the primary system. The NLTVA parameters are then determined using a nonlinear generalization of Den Hartog's equal-peak method. The mitigation of the resonant vibrations of a Duffing oscillator is considered to illustrate the proposed developments.

  15. The relevance vector machine technique for channel equalization application

    OpenAIRE

    Chen, S.; Gunn, S.R.; Harris, C J

    2001-01-01

    The recently introduced relevance vector machine (RVM) technique is applied to communication channel equalization. It is demonstrated that the RVM equalizer can closely match the optimal performance of the Bayesian equalizer, with a much sparser kernel representation than that is achievable by the state-of-art support vector machine (SVM) technique.

  16. Estimation and Direct Equalization of Doubly Selective Channels

    Directory of Open Access Journals (Sweden)

    Leus Geert

    2006-01-01

    Full Text Available We propose channel estimation and direct equalization techniques for transmission over doubly selective channels. The doubly selective channel is approximated using the basis expansion model (BEM. Linear and decision feedback equalizers implemented by time-varying finite impulse response (FIR filters may then be used to equalize the doubly selective channel, where the time-varying FIR filters are designed according to the BEM. In this sense, the equalizer BEM coefficients are obtained either based on channel estimation or directly. The proposed channel estimation and direct equalization techniques range from pilot-symbol-assisted-modulation- (PSAM- based techniques to blind and semiblind techniques. In PSAM techniques, pilot symbols are utilized to estimate the channel or directly obtain the equalizer coefficients. The training overhead can be completely eliminated by using blind techniques or reduced by combining training-based techniques with blind techniques resulting in semiblind techniques. Numerical results are conducted to verify the different proposed channel estimation and direct equalization techniques.

  17. Application of Recurrent Wavelet Neural Networks to the Digital Communications Channel Blind Equalization

    Institute of Scientific and Technical Information of China (English)

    HeShichun; HeZhenya

    1997-01-01

    This paper investigates the application of a Recurrent Wavelet Neural Network(RWNN)to the blind equalization of nonlinear communication channels.In contrast to the wavelet networks introduced in,the RWNN is well suited for use in real time adaptive signal processing.Furthermore,the RWNN has the advantage that a priori information of the underlying system need not be known,the dynamics of the system are configured in the recurrent connections and the network approximates the system over time.An RWNN based structure and a novel training approach for blind equalization was proposed and its performance evaluated via computer simulations for nolnlinear communication channel model.It is shown that the RWNN blind equalizer performs much better than the linear Constant Modulus Algorithm(CMA) and the Recurrent Radial Basis Function(RRBF) Networks based blind equalizers in nonlinear channel case.The small size and high performance of the RWNN equalizer make it suitable for high speed channel blind equalization.

  18. Self-Tuning Blind Identification and Equalization of IIR Channels

    Directory of Open Access Journals (Sweden)

    Bose Tamal

    2003-01-01

    Full Text Available This paper considers self-tuning blind identification and equalization of fractionally spaced IIR channels. One recursive estimator is used to generate parameter estimates of the numerators of IIR systems, while the other estimates denominator of IIR channel. Equalizer parameters are calculated by solving Bezout type equation. It is shown that the numerator parameter estimates converge (a.s. toward a scalar multiple of the true coefficients, while the second algorithm provides consistent denominator estimates. It is proved that the equalizer output converges (a.s. to a scalar version of the actual symbol sequence.

  19. Channel Equalization in Filter Bank Based Multicarrier Modulation for Wireless Communications

    Directory of Open Access Journals (Sweden)

    Markku Renfors

    2007-01-01

    Full Text Available Channel equalization in filter bank based multicarrier (FBMC modulation is addressed. We utilize an efficient oversampled filter bank concept with 2x-oversampled subcarrier signals that can be equalized independently of each other. Due to Nyquist pulse shaping, consecutive symbol waveforms overlap in time, which calls for special means for equalization. Two alternative linear low-complexity subcarrier equalizer structures are developed together with straightforward channel estimation-based methods to calculate the equalizer coefficients using pointwise equalization within each subband (in a frequency-sampled manner. A novel structure, consisting of a linear-phase FIR amplitude equalizer and an allpass filter as phase equalizer, is found to provide enhanced robustness to timing estimation errors. This allows the receiver to be operated without time synchronization before the filter bank. The coded error-rate performance of FBMC with the studied equalization scheme is compared to a cyclic prefix OFDM reference in wireless mobile channel conditions, taking into account issues like spectral regrowth with practical nonlinear transmitters and sensitivity to frequency offsets. It is further emphasized that FBMC provides flexible means for high-quality frequency selective filtering in the receiver to suppress strong interfering spectral components within or close to the used frequency band.

  20. Channel Equalization in Filter Bank Based Multicarrier Modulation for Wireless Communications

    Science.gov (United States)

    Ihalainen, Tero; Hidalgo Stitz, Tobias; Rinne, Mika; Renfors, Markku

    2006-12-01

    Channel equalization in filter bank based multicarrier (FBMC) modulation is addressed. We utilize an efficient oversampled filter bank concept with 2x-oversampled subcarrier signals that can be equalized independently of each other. Due to Nyquist pulse shaping, consecutive symbol waveforms overlap in time, which calls for special means for equalization. Two alternative linear low-complexity subcarrier equalizer structures are developed together with straightforward channel estimation-based methods to calculate the equalizer coefficients using pointwise equalization within each subband (in a frequency-sampled manner). A novel structure, consisting of a linear-phase FIR amplitude equalizer and an allpass filter as phase equalizer, is found to provide enhanced robustness to timing estimation errors. This allows the receiver to be operated without time synchronization before the filter bank. The coded error-rate performance of FBMC with the studied equalization scheme is compared to a cyclic prefix OFDM reference in wireless mobile channel conditions, taking into account issues like spectral regrowth with practical nonlinear transmitters and sensitivity to frequency offsets. It is further emphasized that FBMC provides flexible means for high-quality frequency selective filtering in the receiver to suppress strong interfering spectral components within or close to the used frequency band.

  1. Equalization of Multiuser Wireless CDMA Downlink Considering Transmitter Nonlinearity Using Walsh Codes

    Directory of Open Access Journals (Sweden)

    Stephen Z. Pinter

    2007-02-01

    Full Text Available Transmitter nonlinearity has been a major issue in many scenarios: cellular wireless systems have high power RF amplifier (HPA nonlinearity at the base station; satellite downlinks have nonlinear TWT amplifiers in the satellite transponder and multipath conditions in the ground station; and radio-over-fiber (ROF systems consist of a nonlinear optical link followed by a wireless channel. In many cases, the nonlinearity is simply ignored if there is no out-of-band emission. This results in poor BER performance. In this paper we propose a new technique to estimate the linear part of the wireless downlink in the presence of a nonlinearity using Walsh codes; Walsh codes are commonly used in CDMA downlinks. Furthermore, we show that equalizer performance is significantly improved by taking into account the presence of the nonlinearity during channel estimation. This is shown by using a regular decision feedback equalizer (DFE with both wireless and RF amplifier noise. We perform estimation in a multiuser CDMA communication system where all users transmit their signal simultaneously. Correlation analysis is applied to identify the channel impulse response (CIR and the derivation of key correlation relationships is shown. A difficulty with using Walsh codes in terms of their correlations (compared to PN sequences is then presented, as well as a discussion on how to overcome it. Numerical evaluations show a good estimation of the linear system with 54 users in the downlink and a signal-to-noise ratio (SNR of 25 dB. Bit error rate (BER simulations of the proposed identification and equalization algorithms show a BER of 10−6 achieved at an SNR of ∼25 dB.

  2. Equalization of Multiuser Wireless CDMA Downlink Considering Transmitter Nonlinearity Using Walsh Codes

    Directory of Open Access Journals (Sweden)

    Pinter Stephen Z

    2007-01-01

    Full Text Available Transmitter nonlinearity has been a major issue in many scenarios: cellular wireless systems have high power RF amplifier (HPA nonlinearity at the base station; satellite downlinks have nonlinear TWT amplifiers in the satellite transponder and multipath conditions in the ground station; and radio-over-fiber (ROF systems consist of a nonlinear optical link followed by a wireless channel. In many cases, the nonlinearity is simply ignored if there is no out-of-band emission. This results in poor BER performance. In this paper we propose a new technique to estimate the linear part of the wireless downlink in the presence of a nonlinearity using Walsh codes; Walsh codes are commonly used in CDMA downlinks. Furthermore, we show that equalizer performance is significantly improved by taking into account the presence of the nonlinearity during channel estimation. This is shown by using a regular decision feedback equalizer (DFE with both wireless and RF amplifier noise. We perform estimation in a multiuser CDMA communication system where all users transmit their signal simultaneously. Correlation analysis is applied to identify the channel impulse response (CIR and the derivation of key correlation relationships is shown. A difficulty with using Walsh codes in terms of their correlations (compared to PN sequences is then presented, as well as a discussion on how to overcome it. Numerical evaluations show a good estimation of the linear system with 54 users in the downlink and a signal-to-noise ratio (SNR of 25 dB. Bit error rate (BER simulations of the proposed identification and equalization algorithms show a BER of achieved at an SNR of dB.

  3. A clustering technique for digital communications channel equalization using radial basis function networks.

    Science.gov (United States)

    Chen, S; Mulgrew, B; Grant, P M

    1993-01-01

    The application of a radial basis function network to digital communications channel equalization is examined. It is shown that the radial basis function network has an identical structure to the optimal Bayesian symbol-decision equalizer solution and, therefore, can be employed to implement the Bayesian equalizer. The training of a radial basis function network to realize the Bayesian equalization solution can be achieved efficiently using a simple and robust supervised clustering algorithm. During data transmission a decision-directed version of the clustering algorithm enables the radial basis function network to track a slowly time-varying environment. Moreover, the clustering scheme provides an automatic compensation for nonlinear channel and equipment distortion. Computer simulations are included to illustrate the analytical results.

  4. Robust Blind Adaptive Channel Equalization in Chaotic Communication Systems

    Institute of Scientific and Technical Information of China (English)

    ZHANG Jia-Shu

    2006-01-01

    Based on the bounded property and statistics of chaotic signal and the idea of set-membership identification,we propose a set-membership generalized least mean square (SM-GLMS) algorithm with variable step size for blind adaptive channel equalization in chaotic communication systems. The steady state performance of the proposed SM-GLMS algorithm is analysed, and comparison with an extended Kalman filter (EKF)-based adaptive algorithm and variable gain least mean square (VG-LMS) algorithm is performed for blind adaptive channel equalization. Simulations show that the proposed SM-GLMS algorithm can provide more significant steady state performance improvement than the EKF-based adaptive algorithm and VG-LMS algorithm.

  5. Performance Analysis of Hard Iterative Channel Estimation in Turbo Equalization

    Institute of Scientific and Technical Information of China (English)

    DENG Yongjun; YANG Zhixing; PAN Changyong; WANG Jun

    2006-01-01

    Reasonable bit error rate performance requires perfect channel state information (CSI) in traditional turbo equalization (TE), which is hard to obtain in practice. Soft and hard iterative algorithms have been developed to address the channel estimation problem with the performance of the soft iterative channel estimate based on the recursive least square algorithm. This paper presents an analysis of the performance of hard iterative channel estimation (HICE) based on the least mean square algorithm. The analysis uses a cost function with the hard decision on the TE output. An iterative channel correction (ICC) algorithm based on the gradient descent algorithm is used to iteratively minimize the cost function. The simulation results agree with the theoretical lower bound for the mean square error (MSE) of the estimated channels. Simulations show that, given an imperfect CSI with an MSE below the upper bound, the linear minimum mean squared error TE (LMMSE-TE) using the ICC has only small performance degradation compared to that with a perfect CSI, while the traditional LMMSE-TE suffers from severe error floor effect even with more iterations.

  6. A Posteriori Equivalence: A New Perspective for Design of Optimal Channel Shortening Equalizers

    CERN Document Server

    Venkataramani, Raman

    2007-01-01

    The problem of channel shortening equalization for optimal detection in ISI channels is considered. The problem is to choose a linear equalizer and a partial response target filter such that the combination produces the best detection performance. Instead of using the traditional approach of MMSE equalization, we directly seek all equalizer and target pairs that yield optimal detection performance in terms of the sequence or symbol error rate. This leads to a new notion of a posteriori equivalence between the equalized and target channels with a simple characterization in terms of their underlying probability distributions. Using this characterization we show the surprising existence an infinite family of equalizer and target pairs for which any maximum a posteriori (MAP) based detector designed for the target channel is simultaneously MAP optimal for the equalized channel. For channels whose input symbols have equal energy, such as q-PSK, the MMSE equalizer designed with a monic target constraint yields a so...

  7. Texture in equal-channel angular pressed aluminum and nickel

    Energy Technology Data Exchange (ETDEWEB)

    Vogel, S.C.; Beyerlein, I.J.; Bourke, M.A.M.; Tome, C.N.; Rangaswamy, P. [Los Alamos National Lab., Los Alamos, NM (United States); Xu, C.; Langdon, T.G. [Univ. of Southern California, Los Angeles, CA (United States)

    2002-07-01

    Nano-structured metals with advantageous mechanical properties can be produced using severe plastic deformation techniques such as equal channel angular pressing (ECAP). Metals and alloys processed by ECAP have much higher yield strengths than the equivalent unprocessed material while retaining high ductilities, an extremely attractive combination of properties. Implicit in the process are the introduction of repetitive shear strains of 100% which introduce texture, the modeling of which is challenging. In this work, we present results from a neutron diffraction study on aluminum and nickel samples processed by ECAP. The results are compared to predictions from a visco-plastic self-consistent (VPSC) model. By taking into account grain-grain interactions in the model the agreement between the predicted and measured orientation distributions is improved. The results show also that the initial texture affects the texture evolution, at least up to strains of the order of {proportional_to}1, i.e. one ECAP pass. (orig.)

  8. A hybrid RNS adaptive filter for channel equalization

    DEFF Research Database (Denmark)

    Bernocchi, Gian Luca; Cardarilli, Gian Carlo; Re, Andrea Del

    2006-01-01

    In this work a hybrid Residue Number System (RNS) implementation of an adaptive FIR filter is presented. The used adaptation algorithm is the Least Mean Squares (LMS). The filter has been designed to meet the constraints of specific class of applications. In fact, it is suitable for applications...... requiring a large number of taps where a serial updating of the filter coefficients is feasible (channel equalization or echo cancellation). In the literature, it has been shown that the RNS implementation of FIR filters grants earnings in area ad power consumption due to the introduced arithmetic...... simplifications. Vice versa, the RNS implementation of the adaptation algorithm needs scaling circuits that are complex and expensive in RNS arithmetic. For this reason, a serial binary implementation of the adaptation algorithm is chosen. The advantages in terms of area and speed of the RNS adaptive filter...

  9. A trust region algorithm for optimization with nonlinear equality and linear inequality constraints

    Institute of Scientific and Technical Information of China (English)

    陈中文; 韩继业

    1996-01-01

    A new algorithm of trust region type is presented to minimize a differentiable function ofmany variables with nonlinear equality and linear inequality constraints. Under the milder conditions, theglobal convergence of the main algorithm is proved. Moreover, since any nonlinear inequality constraint can beconverted into an equation by introducing a slack variable, the trust region method can be used in solving general nonlinear programming problems.

  10. Microstructure evolution in Zr under equal channel angular pressing

    Science.gov (United States)

    Choi, W. S.; Ryoo, H. S.; Hwang, S. K.; Kim, M. H.; Kwun, S. I.; Chae, S. W.

    2002-03-01

    Pure polycrystalline Zr was deformed by equal channel angular pressing (ECAP), and the microstructural characteristics were analyzed. By repeated alternating ECAP, it was possible to refine the grain size from 200 to 0.2 µm. Subsequent annealing heat treatment at 550 °C resulted in a grain growth of up to 6 µm. Mechanical twinning was an important deformation mechanism, particularly during the early stage of deformation. The most active twinning system was identified as 85.2 deg {10bar 12} tensile twinning, followed by 57.1 deg {10bar 11} compressive twinning. Crystal texture as well as grain-boundary misorientation distribution of deformed Zr were analyzed by X-ray diffraction (XRD) and electron backscattered diffraction (EBSD). The ECAP-deformed Zr showed a considerable difference in the crystallographic attributes from those of cold-rolled Zr or Ti, in that texture and boundary misorientation-angle distribution tend toward more even distribution with a slightly preferential distribution of boundaries of a 20 to 30 deg misorientation angle. Furthermore, unlike the case of cold rolling, the crystal texture was not greatly altered by subsequent annealing heat treatment. Overall, the present work suggests ECAP as a viable method to obtain significant grain refining in hexagonal close-packed (hcp) metals.

  11. Equal channel angular pressing of pure aluminium—an analysis

    Indian Academy of Sciences (India)

    M Saravanan; R M Pillai; B C Pai; M Brahmakumar; K R Ravi

    2006-12-01

    Equal channel angular pressing (ECAP) is a novel technique for producing ultra fine grain structures in submicron level by introducing a large amount of shear strain into the materials without changing the billet shape or dimensions. This process is well suited for aluminium alloys and is capable of producing ultra fine grain structures with grain sizes falling between 200 and 500 nm. The present study attempts to apply ECAP technique to 99.5% pure aluminium and characterize the resulting aluminium by optical metallography, atomic force microscopy (AFM) and hardness measurement. ECAP of 99.5% pure aluminium produces ultrafine grain structure of about 620 nm after 8 passes. Despite an increase in the hardness from 23 to 47 BHN up to 6 passes, it decreases slightly for seventh and eighth passes. The results are compared with the already existing results available on pure aluminium. Analysis of the results of this investigation with those available in the literature has revealed that the number of passes essential to achieve a homogeneous microstructure in pure Al increases, while the ultimate equilibrium grain size obtained becomes finer with decreasing purity.

  12. An adaptive linearizer for 16-QAM transmission over non-linear satellite channels

    Science.gov (United States)

    Shanmugan, K. Sam; Ruggles, M. J.

    An adaptive nonlinear equalization scheme that consists of a predistorter located at the transmitting earth station and a linear equalizer at the receiving earth station is described. Algorithms for automatically adjusting the predistorter and the linear equalizer are presented. The effectiveness of the scheme is evaluated using simulations. It is shown that the scheme improves the performance of a 16-queued access memory system operating over a typical satellite channel by minimizing degradations in the signal as it is transmitted over a band-limited satellite channel.

  13. Equalizers for DVD read channel with d = 2 modulation coding

    Science.gov (United States)

    Gopalaswamy, Srinivasan; Wood, Roger

    1997-07-01

    The EFMPlus is the run-length-limited modulation code adopted for the DVD. Enhanced performance can be obtained by using equalizers that exploit the d equals 2 constraint of this code. Two such equalizers are presented and their performance evaluated using modeling and simulations. The use of this equalization strategy avoids the Viterbi detector, and optimal detection is provided by use of only a comparator.

  14. Low complexity iterative MLSE equalization of M-QAM signals in extremely long rayleigh fading channels

    CSIR Research Space (South Africa)

    Myburgh, HC

    2009-05-01

    Full Text Available long channels. Its computational complexity is linear in the data block length and approximately independent of the channel memory length, whereas conventional equalization algorithms have computational complexity linear in the data block length...

  15. Equalized near maximum likelihood detector

    OpenAIRE

    2012-01-01

    This paper presents new detector that is used to mitigate intersymbol interference introduced by bandlimited channels. This detector is named equalized near maximum likelihood detector which combines nonlinear equalizer and near maximum likelihood detector. Simulation results show that the performance of equalized near maximum likelihood detector is better than the performance of nonlinear equalizer but worse than near maximum likelihood detector.

  16. A Novel Efficient Cluster-Based MLSE Equalizer for Satellite Communication Channels with -QAM Signaling

    Directory of Open Access Journals (Sweden)

    Dalakas Vassilis

    2006-01-01

    Full Text Available In satellites, nonlinear amplifiers used near saturation severely distort the transmitted signal and cause difficulties in its reception. Nevertheless, the nonlinearities introduced by memoryless bandpass amplifiers preserve the symmetries of the -ary quadrature amplitude modulation ( -QAM constellation. In this paper, a cluster-based sequence equalizer (CBSE that takes advantage of these symmetries is presented. The proposed equalizer exhibits enhanced performance compared to other techniques, including the conventional linear transversal equalizer, Volterra equalizers, and RBF network equalizers. Moreover, this gain in performance is obtained at a substantially lower computational cost.

  17. Blind adaptive MMSE equalization of underwater acoustic channels based on the linear prediction method

    Science.gov (United States)

    Zhang, Yinbing; Zhao, Junwei; Guo, Yecai; Li, Jinming

    2011-03-01

    The problem of blind adaptive equalization of underwater single-input multiple-output (SIMO) acoustic channels was analyzed by using the linear prediction method. Minimum mean square error (MMSE) blind equalizers with arbitrary delay were described on a basis of channel identification. Two methods for calculating linear MMSE equalizers were proposed. One was based on full channel identification and realized using RLS adaptive algorithms, and the other was based on the zero-delay MMSE equalizer and realized using LMS and RLS adaptive algorithms, respectively. Performance of the three proposed algorithms and comparison with two existing zero-forcing (ZF) equalization algorithms were investigated by simulations utilizing two underwater acoustic channels. The results show that the proposed algorithms are robust enough to channel order mismatch. They have almost the same performance as the corresponding ZF algorithms under a high signal-to-noise (SNR) ratio and better performance under a low SNR.

  18. Equalization of nonlinear transmission impairments by maximum-likelihood-sequence estimation in digital coherent receivers.

    Science.gov (United States)

    Khairuzzaman, Md; Zhang, Chao; Igarashi, Koji; Katoh, Kazuhiro; Kikuchi, Kazuro

    2010-03-01

    We describe a successful introduction of maximum-likelihood-sequence estimation (MLSE) into digital coherent receivers together with finite-impulse response (FIR) filters in order to equalize both linear and nonlinear fiber impairments. The MLSE equalizer based on the Viterbi algorithm is implemented in the offline digital signal processing (DSP) core. We transmit 20-Gbit/s quadrature phase-shift keying (QPSK) signals through a 200-km-long standard single-mode fiber. The bit-error rate performance shows that the MLSE equalizer outperforms the conventional adaptive FIR filter, especially when nonlinear impairments are predominant.

  19. Effect of equal channel angular pressing on aging treatment of Al-7075 alloy

    Directory of Open Access Journals (Sweden)

    M.H. Shaeri

    2015-04-01

    Full Text Available The effect of aging treatment on microstructure and mechanical properties of equal channel angular pressed Al-7075 alloy was examined. Commercial Al-7075 alloy in the solid solution heat-treated condition was processed by equal channel angular pressing through route BC at both the room temperature and 120 °C. Only three passes of equal channel angular pressing was possible due to the low ductility of the alloy at both temperatures. Followed by equal channel angular pressing, the specimens have been aged at 120 °C for different aging times. Mechanical properties were measured by Vickers microhardness and tensile tests and microstructural observations were undertaken using transmission electron microscopy, X-ray diffractometer as well as optical microscopy. Microstructural investigations showed that ultrafine-grained materials with grain size in the range of 200–350 nm and 300–500 nm could be obtained after three passes of equal channel angular pressing at room temperature and 120 °C, respectively. Equal channel angular pressing of solid solution heat-treated Al-7075 alloy accelerates precipitation rate and subsequently leads to a significant decrease in aging time to attain maximum mechanical properties. Furthermore, it is possible to achieve maximum mechanical properties during equal channel angular pressing at 120 °C as a result of dynamic aging and formation of small ɳ´ phase.

  20. Equalization enhanced phase noise in Nyquist-spaced superchannel transmission systems using multi-channel digital back-propagation

    Science.gov (United States)

    Xu, Tianhua; Liga, Gabriele; Lavery, Domaniç; Thomsen, Benn C.; Savory, Seb J.; Killey, Robert I.; Bayvel, Polina

    2015-09-01

    Superchannel transmission spaced at the symbol rate, known as Nyquist spacing, has been demonstrated for effectively maximizing the optical communication channel capacity and spectral efficiency. However, the achievable capacity and reach of transmission systems using advanced modulation formats are affected by fibre nonlinearities and equalization enhanced phase noise (EEPN). Fibre nonlinearities can be effectively compensated using digital back-propagation (DBP). However EEPN which arises from the interaction between laser phase noise and dispersion cannot be efficiently mitigated, and can significantly degrade the performance of transmission systems. Here we report the first investigation of the origin and the impact of EEPN in Nyquist-spaced superchannel system, employing electronic dispersion compensation (EDC) and multi-channel DBP (MC-DBP). Analysis was carried out in a Nyquist-spaced 9-channel 32-Gbaud DP-64QAM transmission system. Results confirm that EEPN significantly degrades the performance of all sub-channels of the superchannel system and that the distortions are more severe for the outer sub-channels, both using EDC and MC-DBP. It is also found that the origin of EEPN depends on the relative position between the carrier phase recovery module and the EDC (or MC-DBP) module. Considering EEPN, diverse coding techniques and modulation formats have to be applied for optimizing different sub-channels in superchannel systems.

  1. Equalization enhanced phase noise in Nyquist-spaced superchannel transmission systems using multi-channel digital back-propagation.

    Science.gov (United States)

    Xu, Tianhua; Liga, Gabriele; Lavery, Domaniç; Thomsen, Benn C; Savory, Seb J; Killey, Robert I; Bayvel, Polina

    2015-09-14

    Superchannel transmission spaced at the symbol rate, known as Nyquist spacing, has been demonstrated for effectively maximizing the optical communication channel capacity and spectral efficiency. However, the achievable capacity and reach of transmission systems using advanced modulation formats are affected by fibre nonlinearities and equalization enhanced phase noise (EEPN). Fibre nonlinearities can be effectively compensated using digital back-propagation (DBP). However EEPN which arises from the interaction between laser phase noise and dispersion cannot be efficiently mitigated, and can significantly degrade the performance of transmission systems. Here we report the first investigation of the origin and the impact of EEPN in Nyquist-spaced superchannel system, employing electronic dispersion compensation (EDC) and multi-channel DBP (MC-DBP). Analysis was carried out in a Nyquist-spaced 9-channel 32-Gbaud DP-64QAM transmission system. Results confirm that EEPN significantly degrades the performance of all sub-channels of the superchannel system and that the distortions are more severe for the outer sub-channels, both using EDC and MC-DBP. It is also found that the origin of EEPN depends on the relative position between the carrier phase recovery module and the EDC (or MC-DBP) module. Considering EEPN, diverse coding techniques and modulation formats have to be applied for optimizing different sub-channels in superchannel systems.

  2. Channel Equalization for Single Carrier MIMO Underwater Acoustic Communications

    Science.gov (United States)

    2010-01-01

    packets. For each packet, the estimation was performed independently on each of the eight channels (hydrophones). Obviously, the Doppler shift is...www.eurasip.org). This year edition will take place in Barcelona, capital city of Catalonia (Spain), and will be jointly organized by the Centre Tecnològic de

  3. Equalization for multi-scale multi-lag OFDM channels

    NARCIS (Netherlands)

    Tang, Z.; Remis, R.; Xu, T.; Leus, G.; Nordenvaad, M.L.

    2011-01-01

    We consider an orthogonal frequency-division multiplexing (OFDM) transmission scheme over wideband underwater acoustic channels, where the propagation paths can experience distinct Doppler effects (manifested in signal scales) and time of arrivals (manifested in lags). We capture such an effect in t

  4. MIMO Channel Estimation and Equalization Using Three-Layer Neural Networks with Feedback

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    This paper describes a channel estimation and equalization algorithm using three-layer artificial neural networks (ANNs) with feedback for multiple input multiple output wireless communication systems.An ANN structure with feedback was designed to use different learning algorithms in the different ANN layers. This actually forms a Turbo iteration process between the different algorithms which effectively improves the estimation performance of the channel equalizer. Simulation results show that this channel equalization algorithm has better computational efficiency and faster convergence than higher order statistics based algorithms.

  5. Single-User Blind Channel Equalization Using Modified Constant Modulus Algorithm

    Institute of Scientific and Technical Information of China (English)

    孙守宇; 郑君里; 吴里江; 张琪

    2004-01-01

    A modified constant modulus algorithm (MCMA) for blind channel equalization is proposed by modifying the constant modulus error function. The MCMA is compared with the conventional constant modulus algorithm (CMA) for symbol-spaced equalization of 4PSK signals. The result shows that the performance of the MCMA is superior to that of the CMA in both convergence rate and intersymbol interference for frequency selective channels in noisy environments. Simulation results using 8PSK signals also demonstrate that a fractionally spaced equalizer can preserve performance over variations in symbol-timing phase,whereas a baud-rate equalizer cannot.

  6. Channel equalization techniques for non-volatile memristor memories

    KAUST Repository

    Naous, Rawan

    2016-03-16

    Channel coding and information theoretic approaches have been utilized in conventional non-volatile memories to overcome their inherent design limitations of leakage, coupling and refresh rates. However, the continuous scaling and integration constraints set on the current devices directed the attention towards emerging memory technologies as suitable alternatives. Memristive devices are prominent candidates to replace the conventional electronics due to its non-volatility and small feature size. Nonetheless, memristor-based memories still encounter an accuracy limitation throughout the read operation addressed as the sneak path phenomenon. The readout data is corrupted with added distortion that increases significantly the bit error rate and jeopardizes the reliability of the read operation. A novel technique is applied to alleviate this distorting effect where the communication channel model is proposed for the memory array. Noise cancellation principles are applied with the aid of preset pilots to extract channel information and adjust the readout values accordingly. The proposed technique has the virtue of high speed, energy efficiency, and low complexity design while achieving high reliability and error-free decoding.

  7. Adaptive Channel-Tracking Method and Equalization for MC-CDMA Systems over Rapidly Fading Channel under Colored Noise

    Directory of Open Access Journals (Sweden)

    Chen Bor-Sen

    2010-01-01

    Full Text Available A recursive maximum-likelihood (RML algorithm for channel estimation under rapidly fading channel and colored noise in a multicarrier code-division multiple-access (MC-CDMA system is proposed in this paper. A moving-average model with exogenous input (MAX is given to describe the transmission channel and colored noise. Based on the pseudoregression method, the proposed RML algorithm can simultaneously estimate the parameters of channel and colored noise. Following the estimation results, these parameters can be used to enhance the minimum mean-square error (MMSE equalizer. Considering high-speed mobile stations, a one-step linear trend predictor is added to improve symbol detection. Simulation results indicate that the proposed RML estimator can track the channel more precisely than the conventional estimator. Meanwhile, the performance of the proposed enhanced MMSE equalizer is robust to the rapidly Rayleigh fading channel under colored noise in the MC-CDMA systems.

  8. Intra-Channel Nonlinear Effect on Optical PPM Pulse Transmission

    Institute of Scientific and Technical Information of China (English)

    Sun; Linghao; Jarmo; Takala

    2003-01-01

    PPM encoded Gaussian pulse sequence shows more immunity than non-PPM schemes on optical fiber intra-channel nonlinearity and demonstrated by a numerical study of IXPM and IFWM effects deploying on 100Gb/s single channelsystem.

  9. Training-based Channel Estimation for Signal Equalization and OPM in 16-QAM Optical Transmission Systems

    DEFF Research Database (Denmark)

    Pittalà, Fabio; Hauske, Fabian N.; Ye, Yabin;

    2012-01-01

    Efficient channel estimation for signal equalization and OPM based on short CAZAC sequences with QPSK and 8PSK constellation formats is demonstrated in a 224-Gb/s PDM 16-QAM optical linear transmission system....

  10. Equalization of Time-Varying Dispersive Channels via Sequence Estimation.

    Science.gov (United States)

    1983-07-13

    Vol. 4, Academic Press 1975. [8] F. R. Magee and J. G. Proakis , "Adaptive Maximum-Likelihood Sequence Estimation for Digital Signaling in the Presence...courses of action which can be pursued to maintain reliable comunications over the selective fading channel are; 1) to reduce the maxinum information...and the complex (I,Q) received signal samples are given by rk =Z c(tj)h(t- tj) + n,(tk) + nQ(tk) (2) 4. where the sumnation is the digital convolution

  11. Low-Complexity Block Turbo Equalization for OFDM Systems in Time-Varying Channels

    NARCIS (Netherlands)

    Fang, K.; Rugini, L.; Leus, G.

    2008-01-01

    We propose low-complexity block turbo equalizers for orthogonal frequency-division multiplexing (OFDM) systems in time-varying channels. The presented work is based on a soft minimum mean-squared error (MMSE) block linear equalizer (BLE) that exploits the banded structure of the frequency-domain cha

  12. Maximum-Likelihood Semiblind Equalization of Doubly Selective Channels Using the EM Algorithm

    Directory of Open Access Journals (Sweden)

    Gideon Kutz

    2010-01-01

    Full Text Available Maximum-likelihood semi-blind joint channel estimation and equalization for doubly selective channels and single-carrier systems is proposed. We model the doubly selective channel as an FIR filter where each filter tap is modeled as a linear combination of basis functions. This channel description is then integrated in an iterative scheme based on the expectation-maximization (EM principle that converges to the channel description vector estimation. We discuss the selection of the basis functions and compare various functions sets. To alleviate the problem of convergence to a local maximum, we propose an initialization scheme to the EM iterations based on a small number of pilot symbols. We further derive a pilot positioning scheme targeted to reduce the probability of convergence to a local maximum. Our pilot positioning analysis reveals that for high Doppler rates it is better to spread the pilots evenly throughout the data block (and not to group them even for frequency-selective channels. The resulting equalization algorithm is shown to be superior over previously proposed equalization schemes and to perform in many cases close to the maximum-likelihood equalizer with perfect channel knowledge. Our proposed method is also suitable for coded systems and as a building block for Turbo equalization algorithms.

  13. Self-adjusting decision feedback equalizer for variational underwater acoustic channel environments

    Institute of Scientific and Technical Information of China (English)

    Yasong Luo; Zhong Liu; Shengliang Hu; Jingbo He

    2014-01-01

    Aimed at the abominable influences to blind equaliza-tion algorithms caused by complex time-space variability existing in underwater acoustic channels, a new self-adjusting decision feedback equalization (DFE) algorithm adapting to different under-water acoustic channel environments is proposed by changing its central tap position. Besides, this new algorithm behaves faster convergence speed based on the analysis of equalizers’ working rules, which is more suitable to implement communications in dif-ferent unknown channels. Corresponding results and conclusions are validated by simulations and spot experiments.

  14. Equal channel angular deformation process and its neuro-simulation for fine-grained magnesium alloy

    Institute of Scientific and Technical Information of China (English)

    LUO Peng(罗蓬); HU Qiao-dan(胡侨丹); WU Xiao-lin; XIA Ke-nong

    2004-01-01

    Fine-grained structure of as-cast magnesium AM60 alloy was obtained by means of equal channel angular deformation(ECAD) technique. Through analyzing the relationship between the load and the displacement under different working conditions, it is demonstrated that employment of back-pressure, multi-passages of deformation, and speed of deformation are the main factors representing ECAD working condition. As for ECAD process, a network composed of nonlinear neuro-element based on error back-propagation learning algorithm is launched to set up a processing mapping module for dynamic forecasting of load summit under different working conditions. The experimental results show that back-pressure, multi-passages and deforming speed have strong correlation with ECAD processing characteristics. On the metallographs of AM60 alloy after multi-passes ECAD, a morphology that inter-metallic compound Mg17 Al12 precipites on magnesium matrix without discrepancy, which evolves from coarse casting ingot microstructure, is observed. And the grains are refined significantly under accumulated severe shear strain.The study demonstrates feasibility of ECAD by using as-cast magnesium alloy directly, and launches an intelligent neuro-simulation module for quantitative analysis of its process.

  15. Microstructure evolution in AZ61 alloy processed by equal channel angular pressing

    Directory of Open Access Journals (Sweden)

    Muralidhar Avvari

    2016-05-01

    Full Text Available Magnesium and its alloys are finding increasing use in aerospace, automobile, nuclear, electrical, and structural engineering applications because of their high strength-to-weight ratio when compared to aluminum, titanium, and steel. In this work, AZ61 wrought magnesium alloy was processed using equal channel angular pressing at three different temperatures of 483, 523, and 573 K using up to four equal channel angular pressing passes. A microstructural study was conducted by measuring the average grain size after each pass, for the three different processing temperatures. The mechanical properties of the processed samples were noted to improve due to the reduction in the grain size after each equal channel angular pressing pass. After four equal channel angular pressing passes, the average grain size of the AZ61 samples was found to be reduced to 85%, 81%, and 70% for the pressing temperatures of 483, 523, and 573 K, respectively. The tensile strength of the AZ61 alloy increased with increase in the number of equal channel angular pressing passes for each of the temperatures when compared to as-received alloy. For instance, for the processing temperatures of 483, 523, and 573 K, the tensile strength increased by 24%, 10%, and 12%, respectively, at four equal channel angular pressing passes. Also, the percentage elongation of the alloy was increased with increase in processing temperatures. Moreover, fracture topographies of the tensile surfaces are illustrated through scanning electron microcopy and reveal ductile fracture than as-received alloy for four passes at each equal channel angular pressing processing temperature.

  16. Effect of equal channel angular pressing on aging treatment of Al-7075 alloy

    Institute of Scientific and Technical Information of China (English)

    M.H. Shaeri; M. Shaeri; M.T. Salehi; S.H. Seyyedein; M.R. Abutalebi

    2015-01-01

    The effect of aging treatment on microstructure and mechanical properties of equal channel angular pressed Al-7075 alloy was examined. Commercial Al-7075 alloy in the solid solution heat-treated condition was processed by equal channel angular pressing through route BC at both the room temperature and 120 1C. Only three passes of equal channel angular pressing was possible due to the low ductility of the alloy at both temperatures. Followed by equal channel angular pressing, the specimens have been aged at 120 1C for different aging times. Mechanical properties were measured by Vickers microhardness and tensile tests and microstructural observations were undertaken using transmission electron microscopy, X-ray diffractometer as well as optical microscopy. Microstructural investigations showed that ultrafine-grained materials with grain size in the range of 200–350 nm and 300–500 nm could be obtained after three passes of equal channel angular pressing at room temperature and 120 1C, respectively. Equal channel angular pressing of solid solution heat-treated Al-7075 alloy accelerates precipitation rate and subsequently leads to a significant decrease in aging time to attain maximum mechanical properties. Furthermore, it is possible to achieve maximum mechanical properties during equal channel angular pressing at 120 1C as a result of dynamic aging and formation of smallɳ´ phase.&2015 Chinese Materials Research Society. Production and hosting by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

  17. An ICA and EC based approach for blind equalization and channel parameter estimation

    Institute of Scientific and Technical Information of China (English)

    何振亚; 刘琚; 杨绿溪; 蔚承建

    2000-01-01

    A new on-line blind equalization approach is proposed. The approach combines over-sampling technique with independent component analysis (ICA) neural network and can give equalized output on-line employing only the received signal. Based on the fourth-order cumulants and the characteristic of the linear system, the parameters of original channel are also estimated using evolutionary computation (EC). Compared to traditional equalization methods, the proposed algorithm is of simple architecture, does not need learning sequences apart from the observation, and can achieve both blind equalization and system identification. Computer simulations show good performance.

  18. An ICA and EC based approach for blind equalization and channel parameter estimation

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    A new on-line blind equalization approach is proposed. The approach combines over-sampling technique with independent component analysis (ICA)neural network and can give equalized output on-line employing only the received signal. Based on the fourth-order cumulants and the characteristic of the linear system, the parameters of original channel are also estimated using evolutionary computation(EC).Compared to traditional equalization methods, the proposed algorithm is of simple architecture, does not need learning sequences apart from the observation, and can achieve both blind equalization and system identification. Computer simulations show good performance.

  19. 一种组合神经网络非线性判决反馈均衡器%A New Nonlinear Adaptive Equalizer Based on Combined Neural Networks

    Institute of Scientific and Technical Information of China (English)

    王军锋; 张斌; 宋国乡

    2003-01-01

    A new nonlinear decision feedback adaptive equalizer based on Adaline neural network and radial-basis-function neural network is presented. Its structure and algorithm are also investigated. For a typical linear and non-linear channel models, computer simulation shows that its convergence speed is faster and its stable mean square erroris less.

  20. Conditions for equality between entanglement-assisted and unassisted classical capacities of a quantum channel

    CERN Document Server

    Shirokov, M E

    2011-01-01

    Both necessary and sufficient conditions of coincidence of the entanglement-assisted capacity with the Holevo capacity of a quantum channel are obtained. By using these conditions the equality between these capacities as well as the strict inequality between them are proved for several classes of quantum channel. In particular, it is shown that coincidence of the entanglement-assisted capacity with the Holevo capacity of a quantum channel implies that the $\\chi$-essential part of this channel is entanglement-breaking (the $\\chi$-essential part is defined as a restriction of a channel obtained by discarding all states useless for transmission of classical information). The above conditions and their corollaries are extended to quantum channels with linear constraints. By using these conditions it is shown that the question of coincidence of the entanglement-assisted capacity with the Holevo capacity of a constrained channel depends on the form of the constraint.

  1. Time-Varying FIR Equalization for MIMO Transmission over Doubly Selective Channels

    Directory of Open Access Journals (Sweden)

    Marc Moonen

    2010-01-01

    Full Text Available We propose time-varying FIR equalization techniques for spatial multiplexing-based multiple-input multiple-output (MIMO transmission over doubly selective channels. The doubly selective channel is approximated using the basis expansion model (BEM, and equalized by means of time-varying FIR filters designed according to the BEM. By doing so, the time-varying deconvolution problem is converted into a two-dimensional time-invariant deconvolution problem in the time-invariant coefficients of the channel BEM and the time-invariant coefficients of the equalizer BEM. The timevarying FIR equalizers are derived based on either the matched filtering criterion, or the linear minimum mean-square error (MMSE or the zero-forcing (ZF criteria. In addition to the linear equalizers, the decision feedback equalizer (DFE is proposed. The DFE can be designed according to two different scenarios. In the first scenario, the DFE is based on feeding back previously estimated symbols from one particular antenna at a time. Whereas, in the second scenario, the previously estimated symbols from all transmit antennas are fed back together. The performance of the proposed equalizers in the context of MIMO transmission is analyzed in terms of numerical simulations.

  2. Design of FIR digital filters for pulse shaping and channel equalization using time-domain optimization

    Science.gov (United States)

    Houts, R. C.; Vaughn, G. L.

    1974-01-01

    Three algorithms are developed for designing finite impulse response digital filters to be used for pulse shaping and channel equalization. The first is the Minimax algorithm which uses linear programming to design a frequency-sampling filter with a pulse shape that approximates the specification in a minimax sense. Design examples are included which accurately approximate a specified impulse response with a maximum error of 0.03 using only six resonators. The second algorithm is an extension of the Minimax algorithm to design preset equalizers for channels with known impulse responses. Both transversal and frequency-sampling equalizer structures are designed to produce a minimax approximation of a specified channel output waveform. Examples of these designs are compared as to the accuracy of the approximation, the resultant intersymbol interference (ISI), and the required transmitted energy. While the transversal designs are slightly more accurate, the frequency-sampling designs using six resonators have smaller ISI and energy values.

  3. Blind channel identication of nonlinear folding mixing model

    Institute of Scientific and Technical Information of China (English)

    Su Yong; Xu Shangzhi; Ye Zhongfu

    2006-01-01

    Signals from multi-sensor systems are often mixtures of (statistically) independent sources by unknown mixing method. Blind source separation(BSS) and independent component analysis(ICA) are the methods to identify/recover the channels and the sources. BSS/ICA of nonlinear mixing models are difficult problems. For instance, the post-nonlinear model has been studied by several authors. It is noticed that in most cases, the proposed models are always with an invertible mixing. According to this fact there is an interesting question: how about the situation of the non-invertible non-linear mixing in BSS or ICA? A new simple non-linear mixing model is proposed with a kind of non-invertible mixing, the folding mixing, and method to identify its channel, blindly.

  4. A modified adaptive compensation scheme for nonlinear bandlimited satellite channels

    Science.gov (United States)

    Feng, Gang; Li, Le-Min; Wu, Shi-Qi

    The authors propose a modified algorithm for an adaptive predistorter (APD) to compensate for the nonlinear distortion encountered in a satellite channel. They describe a recursive algorithm for an APD in rectangular coordinates and give the structure for implementation of the algorithm. A modified recursive algorithm which is called the sign algorithm and the structure for implementation are proposed. Computer simulation results show that the sign algorithm is effective for the compensation of nonlinear satellite channels. The modified algorithm is based on the rectangular representation of data symbols.

  5. Receiver-channel based adaptive blind equalization approach for GPS dynamic multipath mitigation

    Institute of Scientific and Technical Information of China (English)

    Zhao Yun; Xue Xiaonan; Zhang Tingfei

    2013-01-01

    Aiming at mitigating multipath effect in dynamic global positioning system (GPS) satellite navigation applications,an approach based on channel blind equalization and real-time recursive least square (RLS) algorithm is proposed,which is an application of the wireless communication channel equalization theory to GPS receiver tracking loops.The blind equalization mechanism builds upon the detection of the correlation distortion due to multipath channels; there-fore an increase in the number of correlator channels is required compared with conventional GPS receivers.An adaptive estimator based on the real-time RLS algorithm is designed for dynamic estimation of multipath channel response.Then,the code and carrier phase receiver tracking errors are compensated by removing the estimated multipath components from the correlators' outputs.To demonstrate the capabilities of the proposed approach,this technique is integrated into a GPS software receiver connected to a navigation satellite signal simulator,thus simulations under controlled dynamic multipath scenarios can be carried out.Simulation results show that in a dynamic and fairly severe multipath environment,the proposed approach achieves simultaneously instantaneous accurate multipath channel estimation and significant multipath tracking errors reduction in both code delay and carrier phase.

  6. Evidence for nonlinear capacitance in biomembrane channel system.

    Science.gov (United States)

    Ghosh, S; Bera, A K; Das, S

    1999-10-01

    The electrophysiological properties of voltage-dependent anion channels from mitochondrial membrane have been studied in a bilayer membrane system. It was observed that the probability of opening of the membrane channel depends on externally applied voltage and the plot is a bell-shaped curve symmetric around probability axis. A scheme of conformational energy levels under varying externally applied voltage was formulated. Assuming that the probability follows Boltzmann distribution, we arrive at an expression of change in energy containing a separate term identical to the energy of a capacitor. This fact indicates the possibility of existence of an added capacitance due to the channel protein. Further it was shown that the aforesaid channel capacitor could be a function of voltage leading to nonlinearity. We have offered a general method of calculating nonlinear capacitance from the experimental data on opening probability of a membrane channel. In case of voltage-dependent anion channel the voltage dependence of the capacitor has a power 0.786. The results have been interpreted in view of the structural organization of the channel protein in the membrane. Our hypothesis is that the phenomenon of capacitor behaviour is a general one for membrane channels.

  7. Wi-Fi, WiMax and WCDMA A comparative study based on Channel Impairments and Equalization method used

    OpenAIRE

    Bera, Rabindranath; Sil, Sanjib; Dhar, Sourav; Sarkar, Subir K.

    2009-01-01

    In this paper we describe the channel impairments and equalization methods currently used in WiFi, WiMax and WCDMA. After a review of channel model for Intelligent Transportation System (ITS), we proposed an equalization method which will be useful for the estimation of strong multipath channel at a high velocity.

  8. Analysis of Crystallographic Textures in Aluminum Plates Processed by Equal Channel Angular Extrusion

    DEFF Research Database (Denmark)

    Li, Saiyi; Mishin, Oleg

    2014-01-01

    A modeling and experimental investigation has been conducted to explore the effect of processing route on texture evolution during equal channel angular extrusion (ECAE) of aluminum plate samples. It is found that although the textures in the plates develop along orientation fibers previously...

  9. Defect structure and mechanical stability of microcrystalline titanium produced by equal channel angular pressing

    Science.gov (United States)

    Betekhtin, V. I.; Kadomtsev, A. G.; Narykova, M. V.; Amosova, O. V.; Sklenicka, V.

    2017-01-01

    It is established that increases in nanoporosity and the proportion of high-angle grain boundaries in the process of equal-channel angular pressing are the main structural factors leading to reduction in mechanical stability (durability) of microcrystalline titanium during long-term tests under creeping conditions.

  10. Frequency Domain Training-Aided Channel Estimation and Equalization in Time-Varying Optical Transmission Systems

    DEFF Research Database (Denmark)

    Pittalà, Fabio; Msallem, Majdi; Hauske, Fabian N.;

    2012-01-01

    We propose a non-weighted feed-forward equalization method with filter update by averaging channel estimations based on short CAZAC sequences. Three averaging methods are presented and tested by simulations in a time-varying 2×2 MIMO optical system....

  11. Analysis of nonlinear channel friction inverse problem

    Institute of Scientific and Technical Information of China (English)

    CHENG Weiping; LIU Guohua

    2007-01-01

    Based on the Backus-Gilbert inverse theory, the singular value decomposition (SVD) for general inverse matrices and the optimization algorithm are used to solve the channel friction inverse problem. The resolution and covari- ance friction inverse model in matrix form is developed to examine the reliability of solutions. Theoretical analyses demonstrate that the convergence rate of the general Newton optimization algorithm is in the second-order. The Wiggins method is also incorporated into the algorithm. Using the method, noise can be suppressed effectively, and the results are close to accurate solutions with proper control parameters. Also, the numerical stability can be improved.

  12. Combined spatial diversity and time equalization for broadband multiple channel underwater acoustic communications

    Science.gov (United States)

    Skoro Kaskarovska, Violeta

    High data rate acoustic communications become feasible with the use of communication systems that operate at high frequency. The high frequency acoustic transmission in shallow water endures severe distortion as a result of the extensive intersymbol interference and Doppler shift, caused by the time variable multipath nature of the channel. In this research a Single Input Multiple Output (SIMO) acoustic communication system is developed to improve the reliability of the high data rate communications at short range in the shallow water acoustic channel. The proposed SIMO communication system operates at very high frequency and combines spatial diversity and decision feedback equalizer in a multilevel adaptive configuration. The first configuration performs selective combining on the equalized signals from multiple receivers and generates quality feedback parameter for the next level of combining. The second configuration implements a form of turbo equalization to evaluate the individual receivers using the feedback parameters as decision symbols. The improved signals from individual receivers are used in the next iteration of selective combining. Multiple iterations are used to achieve optimal estimate of the received signal. The multilevel adaptive configuration is evaluated on experimental and simulated data using SIMO system with three, four and five receivers. The simulation channel model developed for this research is based on experimental channel and Rician fading channel model. The performance of the channel is evaluated in terms of Bit Error Rate (BER) and Signal-to-Noise-and-Interference Ratio (SNIR). Using experimental data with non-zero BER, multilevel adaptive spatial diversity can achieve BER of 0 % and SNIR gain of 3 dB. The simulation results show that the average BER and SNIR after multilevel combining improve dramatically compared to the single receiver, even in case of extremely high BER of individual received signals. The results demonstrate the

  13. Frequency-Shift Zero-Forcing Time-Varying Equalization for Doubly Selective SIMO Channels

    Directory of Open Access Journals (Sweden)

    Verde Francesco

    2006-01-01

    Full Text Available This paper deals with the problem of designing linear time-varying (LTV finite-impulse response zero-forcing (ZF equalizers for time- and frequency-selective (so-called doubly selective single-input multiple-output (SIMO channels. Specifically, relying on a basis expansion model (BEM of the rapidly time-varying channel impulse response, we derive the canonical frequency-domain representation of the minimal norm LTV-ZF equalizer, which allows one to implement it as a parallel bank of linear time-invariant filters having, as input signals, different frequency-shift (FRESH versions of the received data. Moreover, on the basis of this FRESH representation, we propose a simple and effective low-complexity version of the minimal norm LTV-ZF equalizer and we discuss the relationships between the devised FRESH equalizers and a LTV-ZF equalizer recently proposed in the literature. The performance analysis, carried out by means of computer simulations, shows that the proposed FRESH-LTV-ZF equalizers significantly outperform their competitive alternative.

  14. Optical Solitons in a Trinal-channel Inverted Nonlinear Photonic Crystal

    CERN Document Server

    Chen, Guihua; Wu, Muying

    2014-01-01

    Inverted nonlinear photonic crystals are the crystals featuring competition between linear and nonlinear lattices, with minima of the linear potential coinciding with maxima of the nonlinear pseudopotential, and vice versa. Traditional inverted nonlinear photonic crystals only have two channels, and can be attained experimentally by means of Rhodamine B (RhB, a dye featuring saturable absorption) doped into the SU-8 polymer. In this paper, a new type of inverted nonlinear photonic crystal is constructed by juxtaposing three kinds of channels into a period. These three channels are a purely linear channel, a saturable self-focusing nonlinear channel, and a saturable self-defocusing nonlinear channel. This optical device is assumed to be fabricated by means of SU-8 polymer material periodically doped with two types of active dyes. The nonlinear propagation of a light field inside this device (passing along the channel) can be described by a nonlinear Schrodinger equation. Stable multi-peak fundamental and dipol...

  15. Capacity of a Nonlinear Optical Channel with Finite Memory

    CERN Document Server

    Agrell, Erik; Durisi, Giuseppe; Karlsson, Magnus

    2014-01-01

    The channel capacity of a nonlinear, dispersive fiber-optic link is revisited. To this end, the popular Gaussian noise (GN) model is extended with a parameter to account for the finite memory of realistic fiber channels. This finite-memory model is harder to analyze mathematically but, in contrast to previous models, it is valid also for nonstationary or heavy-tailed input signals. For uncoded transmission and standard modulation formats, the new model gives the same results as the regular GN model when the memory of the channel is about 10 symbols or more. These results confirm previous results that the GN model is accurate for uncoded transmission. However, when coding is considered, the results obtained using the finite-memory model are very different from those obtained by previous models, even when the channel memory is large. In particular, the peaky behavior of the channel capacity, which has been reported for numerous nonlinear channel models, appears to be an artifact of applying models derived for i...

  16. Blind Equalization of a Nonlinear Satellite System Using MCMC Simulation Methods

    Directory of Open Access Journals (Sweden)

    Sénécal Stéphane

    2002-01-01

    Full Text Available This paper proposes the use of Markov Chain Monte-Carlo (MCMC simulation methods for equalizing a satellite communication system. The main difficulties encountered are the nonlinear distorsions caused by the amplifier stage in the satellite. Several processing methods manage to take into account the nonlinearity of the system but they require the knowledge of a training/learning input sequence for updating the parameters of the equalizer. Blind equalization methods also exist but they require a Volterra modelization of the system. The aim of the paper is also to blindly restore the emitted message. To reach the goal, we adopt a Bayesian point of view. We jointly use the prior knowledge on the emitted symbols, and the information available from the received signal. This is done by considering the posterior distribution of the input sequence and the parameters of the model. Such a distribution is very difficult to study and thus motivates the implementation of MCMC methods. The presentation of the method is cut into two parts. The first part solves the problem for a simplified model; the second part deals with the complete model, and a part of the solution uses the algorithm developed for the simplified model. The algorithms are illustrated and their performance is evaluated using bit error rate versus signal-to-noise ratio curves.

  17. An MGF-based capacity analysis of equal gain combining over fading channels

    KAUST Repository

    Yilmaz, Ferkan

    2010-09-01

    Exact average capacity results for L-branch coherent equal-gain combining (EGC) in correlated and uncorrelated fading channels are not known. This paper develops a novel framework (approach) for capacity analysis of L-branch EGC in generalized fading channels. In addition, Gamma shadowed generalized Nakagami-m fading model is proposed in order to statistically model the fading environments in high frequencies such as 60 GHz and above. Some simulations are carried out and then the obtained results are accentuated by means of numerical analysis based on the proposed framework. Numerical and simulation results, performed to verify the correctness of the proposed framework, are in perfect agreement. ©2010 IEEE.

  18. Maxwell's equal area law for black holes with a nonlinear source

    CERN Document Server

    Li, Huai-Fan; Zhao, Hui-Hua; Zhao, Ren

    2016-01-01

    In this paper, we consider the phase transition of black hole in power Maxwell invariant by means of Maxwell's equal area law. First, we review and study the analogy of nonlinear charged black hole solutions with the Van der Waals gas-liquid system in the extended phase space, and obtain isothermal $P$-$v$ diagram. Then, using the Maxwell's equal area law we study the phase transition of AdS black hole with different temperatures. Finally, we extend the method to the black hole in the canonical (grand canonical) ensemble in which charge (potential) is fixed at infinity. Interestingly, we find the phase transition occurs in the both ensembles. We also study the effect of the parameters of the black hole on the two-phase coexistence. The results show that the black hole may go through a small-large phase transition similar to those of usual non-gravity thermodynamic systems.

  19. INFLUENCE OF DIE ANGLES ON THE MICROHARDNESS OF ALUMINUM ALLOY PROCESSED BY EQUAL CHANNEL ANGULAR PRESSING

    Directory of Open Access Journals (Sweden)

    Ali A Aljubouri

    2010-11-01

    Full Text Available   The die geometry has a massive effect on the plastic deformation behavior during pressing of material processed by equal channel angular pressing (ECAP method; subsequently the properties of the processed material are strongly dependent on it. Two categories of designed and manufactured dies are used for equal channel angular pressing, a 1200 sharp angle and a 900 round –cornered (200 dies, that produce strain per pass through both dies of ~0.7 and ~1.05   respectively. The microhardness developed in Al-Si alloy during ECAP using route BC. The microhardness increased by a factor of >1.5, after only 1 pressing. Subsequently, the hardness increases slightly up to 8 pressings through the 1200 sharp angle die, while it is increased by a factor of ~2.6 after 5 passes by using the 900 round cornered die, comparing with that for the cast workpiece.

  20. Low complexity iterative MLSE equalization in highly spread underwater acoustic channels

    CSIR Research Space (South Africa)

    Myburgh, HC

    2009-05-01

    Full Text Available given to the equalization of underwater acoustic signals with long delay spreads. Due to the nature of the underwater acoustic channel (UAC), the inter-symbol interference (ISI) caused by multipath may extend over hundreds of symbols for moderate... are practically infeasible, as their computational complexities are exponentially related to the number of interfering symbols, rendering them computationally infeasible for UAC equaliza- tion. Attention has therefore been drawn to developing compu- tationally...

  1. Maximum Likelihood Sequence Detection Receivers for Nonlinear Optical Channels

    OpenAIRE

    2015-01-01

    The space-time whitened matched filter (ST-WMF) maximum likelihood sequence detection (MLSD) architecture has been recently proposed (Maggio et al., 2014). Its objective is reducing implementation complexity in transmissions over nonlinear dispersive channels. The ST-WMF-MLSD receiver (i) drastically reduces the number of states of the Viterbi decoder (VD) and (ii) offers a smooth trade-off between performance and complexity. In this work the ST-WMF-MLSD receiver is investigated in detail. We...

  2. How Equalization Techniques Affect the TCP Performance of MC-CDMA Systems in Correlated Fading Channels

    Directory of Open Access Journals (Sweden)

    Giacomo Leonardi

    2007-12-01

    Full Text Available This paper investigates the impact of several equalization techniques for multicarrier code division multiple access systems on the performance at both lower and upper layers (i.e., physical and TCP layers. Classical techniques such as maximal ratio combining, equal gain combining, orthogonality restoring combining, minimum mean square error, as well as a partial equalization (PE are investigated in time- and frequency-correlated fading channels with various numbers of interferers. Their impact on the performance at upper level is then studied. The results are obtained through an integrated simulation platform carefully reproducing all main aspects affecting the quality of service perceived by the final user, allowing an investigation of the real gain produced by signal processing techniques at TCP level.

  3. Numerical Investigation of Plastic Deformation in Two-turn Equal Channel Angular Extrusion

    Directory of Open Access Journals (Sweden)

    A. Mitsak

    2014-12-01

    Full Text Available There has been a number of investigations in recent years reporting on the structure and properties of materials deformed to super plastic deformation (SPD. During SPD new textures can be formed and abnormal characteristics are displayed, attracting a growing research interest.¶ Equal channel angular extrusion (ECAE is a method often used to obtain large plastic strains. However, according to experimental results, there is a large tensile stress in the sample during deformation, which may lead in some cases, to cracking in metallic alloys and large curvature in polymeric materials. In order to overcome these drawbacks, the ECAE process can be conducted at high temperatures. But this contributes significantly to a decreased level of plastic deformation induced in the sample. Hence, a tool with multi-pass seems to be a very appropriate solution. In this paper, a new geometry die composed of two elbows has been simulated by finite element method aiming to provide an insight into the mechanisms of deformation and to determine the optimum geometry of the tool. The numerical results show that the length and the section of the second channel play a significant role on the homogeneity of the plastic strain distribution. It has been found that good homogeneity was obtained when the second channel has the same section as that of the entrance and the exit channels and with a length equal to three times of its width.

  4. Finite element simulations of deformation behavior in equal channel angular pressing using a rotated die

    Institute of Scientific and Technical Information of China (English)

    Yixuan TAN; Saiyi LI

    2012-01-01

    A new die design for equal channel angular pressing (ECAP) of square cross-section billet was proposed by a 45° rotation of the inlet and outlet channels around the channel axes.ECAP utilizing the rotated and conventional dies was simulated in three dimensions using the finite element method.Conditions with different material properties and friction coefficients were studied.The billet deformation behavior was evaluated in terms of the spatial distribution of equivalent plastic strain,plastic deformation zone and load history.The results show that the rotated die appears to produce billets with a smaller deformation inhomogeneity over the entire crosssection and a greater average of equivalent plastic strain at the cost of a slightly larger working load.The billet deformation enters into a steady state earlier in the case of the rotated die than the conventional die under the condition of a relatively large friction coefficient.

  5. Maximum Likelihood Sequence Detection Receivers for Nonlinear Optical Channels

    Directory of Open Access Journals (Sweden)

    Gabriel N. Maggio

    2015-01-01

    Full Text Available The space-time whitened matched filter (ST-WMF maximum likelihood sequence detection (MLSD architecture has been recently proposed (Maggio et al., 2014. Its objective is reducing implementation complexity in transmissions over nonlinear dispersive channels. The ST-WMF-MLSD receiver (i drastically reduces the number of states of the Viterbi decoder (VD and (ii offers a smooth trade-off between performance and complexity. In this work the ST-WMF-MLSD receiver is investigated in detail. We show that the space compression of the nonlinear channel is an instrumental property of the ST-WMF-MLSD which results in a major reduction of the implementation complexity in intensity modulation and direct detection (IM/DD fiber optic systems. Moreover, we assess the performance of ST-WMF-MLSD in IM/DD optical systems with chromatic dispersion (CD and polarization mode dispersion (PMD. Numerical results for a 10 Gb/s, 700 km, and IM/DD fiber-optic link with 50 ps differential group delay (DGD show that the number of states of the VD in ST-WMF-MLSD can be reduced ~4 times compared to an oversampled MLSD. Finally, we analyze the impact of the imperfect channel estimation on the performance of the ST-WMF-MLSD. Our results show that the performance degradation caused by channel estimation inaccuracies is low and similar to that achieved by existing MLSD schemes (~0.2 dB.

  6. Nonlinear compensation research and simulation of bandlimited QPSK digital satellite channels

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    Presents a phase compensation against the signal distortion mainly caused by TWTA to solve the problem of compensation and modelling of a nonlinear QPSK satellite channel assumed to be bandlimited and exhibit both ampli tude and phase nonlinearities, and to lower the bit error probability of nonlinear channel, and concludes with simula tion results that the compensation against phase distortion of TWTA can significantly improve the nonlinear performance of the channel.

  7. Blind Equalization Based on RLS Algorithm Using Adaptive Forgetting Factor for Underwater Acoustic Channel

    Institute of Scientific and Technical Information of China (English)

    肖瑛; 殷福亮

    2014-01-01

    Blind equalization based on adaptive forgetting factor, recursive least squares (RLS) with constant modulus algorithm (CMA), is investigated. The cost function of CMA is simplified to meet the second norm form to ensure the stability of RLS-CMA, and thus an improved RLS-CMA (RLS-SCMA) is established. To further improve its performance, a new adaptive forgetting factor RLS-SCMA (ARLS-SCMA) is proposed. In ARLS-SCMA, the forgetting factor varies with the output error of the blind equalizer during the iterative process, which leads to a faster convergence rate and a smaller steady-state error. The simulation results prove the effectiveness under the condition of the underwater acoustic channel.

  8. Microstructural Characterization of a Magnesium Alloy Processed by Equal Channel Angular Pressing

    Directory of Open Access Journals (Sweden)

    Florina Diana Dumitru

    2014-07-01

    Full Text Available Samples of as-extruded ZK60 magnesium alloy were subjected to 6 passes of equal-channel angular pressing (ECAP following route A. The processing temperature was decreased with the number of passes. The structural evolution of the deformed samples was analyzed using Electron Backscattered Diffraction (EBSD and X-Ray Diffraction. The grain boundary misorientation distribution showed a reduction in the grain size accompanied bya large proportion of high angle grain boundaries and the presence of recrystallization processes. XRD results showed that with the increment of the applied strain the peaks presented a slight variation of the angles.

  9. Microstructure of AZ91 alloy deformed by equal channel angular pressing

    Energy Technology Data Exchange (ETDEWEB)

    Braszczynska-Malik, K.N. [Inst. of Materials Engineering, Czestochowa Univ. of Technology, Czestochowa (Poland); Froyen, L. [MTM Dept., Katholieke Univ. Leuven, Leuven-Heverlee (Belgium)

    2005-08-01

    The equal channel angular pressing (ECAP) of the AZ91 magnesium alloy was tested from 553 K to 693 K. The initial grain size of the investigated alloy in homogenized state was about 150 {mu}m. Samples were deformed through a die characterized by an inner contact angle. During the ECAP process the microstructure changed homogeneously and exhibited a decrease of grain size to 10 {mu}m. Transmission electron microscopy allowed the observation of a high dislocation density and large number of twins and shear bands in the deformed material. Some regions in the investigated alloys exhibited a dynamic recrystallisation process. (orig.)

  10. A Novel Adaptive Channel Equalization Method Using Variable Step-Size Partial Rank Algorithm

    CERN Document Server

    Hadei, Sayed A

    2011-01-01

    Recently a framework has been introduced within which a large number of classical and modern adaptive filter algorithms can be viewed as special cases. Variable Step-Size (VSS) normalized least mean square (VSSNLMS) and VSS Affine Projection Algorithms (VSSAPA) are two particular examples of the adaptive algorithms that can be covered by this generic adaptive filter. In this paper, we introduce a new VSS Partial Rank (VSSPR) adaptive algorithm based on the generic VSS adaptive filter and use it for channel equalization. The proposed algorithm performs very well in attenuating noise and inter-symbol interference (ISI) in comparison with the standard NLMS and the recently introduced AP algorithms.

  11. Effects of equal channel angular extrusion on microstructure, strength and ballistic performance of AA5754 plates

    DEFF Research Database (Denmark)

    Mishin, Oleg; Hong, Chuanshi; Toftegaard, Helmuth Langmaack

    2014-01-01

    The microstructure, hardness, tensile properties and ballistic performance have been investigated in thick plates of the AA5754 alloy both in a coarse-grained as-received condition and after 4 passes of equal channel angular extrusion (ECAE) conducted at elevated temperatures. It is found that ECAE...... refines the microstructure to an average subgrain size of 0.3 μm, which results in significantly increased hardness and strength. Although ductility decreases due to ECAE, the uniform elongation is still fairly large, ~10%. The ballistic performance of the ECAE-processed material is found...

  12. Equalization and Decoding for Multiple-Input Multiple-Output Wireless Channels

    Directory of Open Access Journals (Sweden)

    Proakis John G

    2002-01-01

    Full Text Available We consider multiple-input, multiple-output (MIMO wireless communication systems that employ multiple transmit and receive antennas to increase the data rate and achieve diversity in fading multipath channels. We begin by focusing on an uncoded system and define optimal and suboptimal receiver structures for this system in Rayleigh fading with and without intersymbol interference. Next, we consider coded MIMO systems. We view the coded system as a serially concatenated convolutional code (SCCC in which the code and the multipath channel take on the roles of constituent codes. This enables us to analyze the performance using the same performance analysis tools as developed previously for SCCCs. Finally, we present an iterative ("turbo" MAP-based equalization and decoding scheme and evaluate its performance when applied to a system with transmit antennas and receive antennas. We show that by performing recursive precoding prior to transmission, significant interleaving gains can be realized compared to systems without precoding.

  13. Performance of equal gain combining with quantized phases in rayleigh fading channels

    KAUST Repository

    Rizvi, Umar H.

    2011-01-01

    In this paper, we analyze the error probability of equal gain combining with quantized channel phase compensation for binary phase shift keying signalling over Rayleigh fading channels. The probability density and characteristic functions of the combined signal amplitude are derived and used to compute the analytic expressions for the bit error probability in dependance of the number of quantization levels L, the number of diversity branches N-R and the average received signal-to-noise ratio. The analysis is utilized to outline the trade-off between N-R and L and to compare the performance with non-coherent binary frequency shift keying and differential binary phase shift keying schemes under diversity reception. © 2011 IEEE.

  14. Effect of equal channel angular pressing (ECAP) on structure and properties of the constructional steel St3

    Institute of Scientific and Technical Information of China (English)

    2005-01-01

    @@ The objective of this study was to describe two different ways for performing equal channel angular pressing of the constructional steel St3 and the relation between these two ways and steel's structure and properties.

  15. Calculation of mutual information for nonlinear communication channel at large signal-to-noise ratio

    Science.gov (United States)

    Terekhov, I. S.; Reznichenko, A. V.; Turitsyn, S. K.

    2016-10-01

    Using the path-integral technique we examine the mutual information for the communication channel modeled by the nonlinear Schrödinger equation with additive Gaussian noise. The nonlinear Schrödinger equation is one of the fundamental models in nonlinear physics, and it has a broad range of applications, including fiber optical communications—the backbone of the internet. At large signal-to-noise ratio we present the mutual information through the path-integral, which is convenient for the perturbative expansion in nonlinearity. In the limit of small noise and small nonlinearity we derive analytically the first nonzero nonlinear correction to the mutual information for the channel.

  16. Corrosion Behavior of Commercial Aluminum Alloy Processed by Equal Channel Angular Pressing

    Directory of Open Access Journals (Sweden)

    Atef Korchef

    2013-01-01

    Full Text Available A commercial aluminum alloy was subjected to severe plastic deformation through equal channel angular pressing (ECAP. The alloy contains a low volume fraction of α-AlFeSi located essentially at the grain boundaries. The corrosion behavior of the ECAP’ed alloy was investigated in NaCl solution using potentiodynamic polarization and immersion tests. The effects of scan rate and NaCl concentration on the alloy susceptibility to corrosion were also studied. The results obtained were compared with those of the nonpressed alloy. ECAP leads to an intensive grain refinement accompanied by an increased dislocation density. All electrochemical tests confirm that corrosion resistance of the alloy remarkably diminished with increasing the ECAP number of passes. This is presumably due to the breakdown of the α-AlFeSi after ECAP leading to higher number of galvanic cells and enhanced dissolution of the aluminum matrix.

  17. Development of Nanostructured AA3103 by Equal Channel Angular Pressing and Thermal Treatments

    Directory of Open Access Journals (Sweden)

    C. J. Luis

    2014-01-01

    Full Text Available This work presents a study related to the achievement of a nanometric structure in AA3103, employing severe plastic deformation processes (SPD, in this case equal channel angular pressing (ECAP. The changes in the mechanical properties and in the microstructure of AA3103 were studied after being processed by ECAP. Subsequently, scanning electron microscopy was used to determine the evolution of the microstructure after different thermal treatments on the material processed by this severe plastic deformation process. Furthermore, a more profound knowledge of the changes in the mechanical properties of this aluminium alloy was obtained. It was demonstrated that with different appropriate combinations of thermal treatments and ECAP processing, it is possible to significantly improve the mechanical properties through obtaining submicrometric grain size structures.

  18. Texture analysis in ultrafine grained coppers processed by equal channel angular pressing

    Directory of Open Access Journals (Sweden)

    Oscar Fabián Higuera

    2013-06-01

    Full Text Available Electrolytic tough pitch (ETP and fire refined high conductivity (FRHC copper samples were severely deformed at room temperature by equal channel angular pressing (ECAP up to 16 passes (ε ~ 1 per pass, following route Bc. The effect of the initial texture on the evolution of texture after the ECAP process for both materials was analyzed. The annealed materials present a marked anisotropy, with a texture controlled by the fiber. According to the orientation distribution function (ODF, this initial behavior allows the presence of a strong C ({001} component after the first two ECAP passes in both coppers. However in the second pass the C component significantly increases in the FRHC copper, whereas the ETP copper presents a much more balanced behavior of the A1* (111[ 2]and A2* (111[11 ]components. The textures obtained for both coppers after each ECAP pass exhibit predominant orientations with continuous distributions along the orientation fiber with simple shear texture.

  19. SPOT WELDING COPPER–1%Cr ELECTRODE TIPS PRODUCED VIA EQUAL CHANNEL ANGULAR PRESSING

    Directory of Open Access Journals (Sweden)

    Luay Bakir Hussain

    2010-09-01

    Full Text Available A sharp 120o Equal channel angular pressing (ECAP following rout Bc was applied at room temperature to refine the grains sizes of pure copper and copper-1%Chromium alloy for spot welding electrode tips application. Initially deformation behavior was investigated with the position using colorful plasticine as work piece followed by copper alloy. It was found the deformation at the central part of the work piece is heavily sheared than the outer part. Optical and Scanning electron microscopy were used to study the progress of grain refining under the influence of rotation and number of passes during pressing. The influnece of elongated fibrous nano graines on electrical conductivity and hardness were discussed. Shear test of spot welded 303 stainless steel indicated that nano structural Cu-1%Cr electrode tips used showed a superior results compared to commercial electrodes

  20. Achieving superplastic properties in a ZK10 magnesium alloy processed by equal-channel angular pressing

    Directory of Open Access Journals (Sweden)

    Roberto B. Figueiredo

    2017-04-01

    Full Text Available Equal-channel angular pressing provides an opportunity for refining the grain structure and introducing superplastic properties in magnesium alloys. This report describes the use of this processing technique with a ZK10 (Mg–1.0 wt.% Zn–0.26 wt.% Zr alloy. The grain structure was successfully refined from ∼12.9 to ∼5.2 μm after 4 passes and superplastic elongations were observed when testing at low strain rates at temperatures of 473 and 523 K. An analysis shows that the superplastic behavior is consistent with the conventional theoretical model for superplastic flow and at higher stresses and strain rates there is a transition to control by a viscous glide process.

  1. Deformation Mechanism of Zr702 Processed by Equal Channel Angular Pressing

    Science.gov (United States)

    Cao, W. Q.; Yu, S. H.; Chun, Y. B.; Shin, D. H.; Hwang, S. K.

    2007-11-01

    Commercial purity zirconium (Zr702) was deformed by equal channel angular (ECA) pressing up to eight passes, and the resulting microstructure and texture were studied by electron backscattered diffraction, transmission electron microscopy (TEM), and X-ray diffraction. The most prominent feature of the substructure was the dislocation cell blocks (CBs), indicating that the dislocation slip rather than twinning was the main mechanism of deformation. With two passes of ECA pressing, pancake-shape grains of 0.25 μm in thickness were obtained. The grain refinement achieved by the ECA pressing was attributed to the evolution of low-angle geometrically necessary boundaries (GNBs) into high-angle grain boundaries (HAGBs) during accumulation of strain by repeated pressing. The texture characteristics were such that a shear texture was predominant in the single-pass specimen, whereas a high-strain rolling texture became apparent in the specimens repeatedly pressed.

  2. Quantitative Microstructural Characterization of Thick Aluminum Plates Heavily Deformed Using Equal Channel Angular Extrusion

    DEFF Research Database (Denmark)

    Mishin, Oleg; Segal, V.M.; Ferrasse, S.

    2012-01-01

    deg rotations about the longitudinal axis. Statistically robust data were obtained in this work using gallium enhanced microscopy and EBSD mapping of large sample areas. For the plate processed using route A, the fraction of high-angle boundaries was found to strongly depend on the inspection plane......A detailed quantitative analysis of the microstructure has been performed in three orthogonal planes of 15-mm-thick aluminum plates heavily deformed via two equal channel angular extrusion (ECAE) routes. One route was a conventional route A with no rotation between passes. Another route involved...... sequential 90 deg rotations about the normal direction (ND) between passes. The microstructure in the center of these plates, and especially the extent of microstructural heterogeneity, has been characterized quantitatively and compared with that in bar samples extruded via either route A or route Bc with 90...

  3. Structural stability of ultra-fine grained magnesium alloys processed by equal channel angular pressing

    Science.gov (United States)

    Janeček, M.; Krajňák, T.; Minárik, P.; Čížek, J.; Stráská, J.; Stráský, J.

    2017-05-01

    Structural stability of two magnesium alloys AZ31 (MgAlZn) and AX41 (MgAlCa) processed by equal channel angular pressing is investigated. The mechanical properties, microstructure evolution and dislocation density were studied by microhardness, electron back scatter diffraction and positron annihilation spectroscopy, respectively. The loss of microstructure stability at high temperatures and the coarsening of the ultrafine-grained structure as a result of isochronal annealing is accompanied by the sharp decrease of microhardness and the decrease of dislocation density. The differences in thermal stability of both alloys are related to different conditions of ECAP pressing and the phase stability, namely the presence of stable Al2Ca precipitates in AX41 alloy. Microscopic mechanisms controlling the structure stability of both alloys are discussed.

  4. Texture evolution in commercially pure titanium after warm equal channel angular extrusion

    Energy Technology Data Exchange (ETDEWEB)

    Suwas, Satyam, E-mail: satyamsuwas@materials.iisc.ernet.in [Department of Materials Engineering, Indian Institute of Science, Bangalore 560 012 (India); Beausir, B. [Institut fuer Strukturphysik, Technische Universitaet Dresden, D-01062 Dresden (Germany); Toth, L.S.; Fundenberger, J.-J. [Universite Paul Verlaine de Metz, Ile du Saulcy, 57045 Metz Cedex 1 (France); Gottstein, G. [Institut fuer Metallkunde und Metallphysik, RWTH, D-52056 Aachen (Germany)

    2011-02-15

    Texture development in commercially pure titanium during equal channel angular extrusion (ECAE) through Routes A, B{sub c} and C has been studied up to three passes at 400 deg. C. Textures were measured using X-ray diffraction, while the microstructural analyses were performed using electron back-scattered diffraction as well as transmission electron microscopy. Occurrences of dynamic restoration processes (recovery and recrystallization) were clearly noticed at all levels of deformations. Finally, the textures were simulated using a viscoplastic polycrystal self-consistent (VPSC) model. Simulations were performed incorporating basal, prismatic and pyramidal slip systems as well as tensile and compressive twinning. The simulated textures corroborate well with experimental textures in spite of the occurrence of dynamic restoration processes.

  5. Processing of low Carbon steel by dual rolls equal channel extrusion

    Science.gov (United States)

    Rusz, S.; Cizek, L.; Salajka, M.; Kedron, J.; Tylsar, S.

    2014-08-01

    This paper introduces a new method of forming for achievement of grain structure refinement by processing in DRECE (Dual Rolls Equal Channel Extrusion) equipment. The DRECE device was developed at the VSB - Technical University of Ostrava. It allows grain refinement in strip plate with dimensions of 58 mm (width) × 2 mm (thickness) × 1000 mm (length). The influence of the number of passes on the mechanical properties and related structure refinement was examined experimentally. The effect of a heat treatment (500 °C/1 h/steady air) on the grain refinement of low carbon steel after severe plastic deformation is analysed. Through this novel technique, the grain structure can be converted into a submicron grain structure.

  6. Microstructure Evolution in High Purity Aluminum Single Crystal Processed by Equal Channel Angular Pressing (ECAP).

    Science.gov (United States)

    Dong, Jinfang; Dong, Qing; Dai, Yongbing; Xing, Hui; Han, Yanfeng; Ma, Jianbo; Zhang, Jiao; Wang, Jun; Sun, Baode

    2017-01-22

    Aluminum single crystal with 99.999% purity was deformed at room temperature by equal channel angular pressing (ECAP) up to 16 passes. Grain size and misorientation of processed samples were quantitatively characterized by TEM and EBSD. The results show that the refinement efficiency of high purity aluminum single crystal was poor in the initial stage. Extrusion by fewer ECAP passes (n ≤ 8) resulted in only elongated grains containing a large number of subgrains and small misorientations between grains. Stable microstructures of nearly equiaxed grains with high misorientations were obtained by 15 passages, indicating that the initial extremely coarse grains and highly uniform grain orientation are not conducive to the accumulation of strain energy. The initial state of high purity aluminum has a significant effect on the refining efficiency of the ECAP process.

  7. Equal channel angular extrusion of ultra-high molecular weight polyethylene.

    Science.gov (United States)

    Reinitz, Steven D; Engler, Alexander J; Carlson, Evan M; Van Citters, Douglas W

    2016-10-01

    Ultra-high molecular weight polyethylene (UHMWPE), a common bearing surface in total joint arthroplasty, is subject to material property tradeoffs associated with conventional processing techniques. For orthopaedic applications, radiation-induced cross-linking is used to enhance the wear resistance of the material, but cross-linking also restricts relative chain movement in the amorphous regions and hence decreases toughness. Equal Channel Angular Extrusion (ECAE) is proposed as a novel mechanism by which entanglements can be introduced to the polymer bulk during consolidation, with the aim of imparting the same tribological benefits of conventional processing without complete inhibition of chain motion. ECAE processing at temperatures near the crystalline melt for UHMWPE produces (1) increased entanglements compared to control materials; (2) increasing entanglements with increasing temperature; and (3) mechanical properties between values for untreated polyethylene and for cross-linked polyethylene. These results support additional research in ECAE-processed UHMWPE for joint arthroplasty applications.

  8. Numerical analysis of back pressure equal channel angular pressing of an Al-Mg alloy

    Science.gov (United States)

    Comăneci, R.

    2017-08-01

    Ultrafine grain size provides enhanced mechanical and/or physical properties such as strength and high ductility, superplasticity at relatively low temperatures and high strain rate and better corrosion resistance. Well-known as one of the most promising and effective structure refining method among other severe plastic deformation (SPD) techniques, equal channel angular pressing (ECAP) has been intensively investigated due to spectacular improvements in structure and therefore properties of bulk ultrafine grained/nanostructured materials. A successful ECAP requires surpassing two obstacles: the necessary load level which directly affects tools and a favourable stress distribution so the material withstanding the accumulated strain of repeated deformation. Materials could withstand more passes if a back pressure (BP) is applied. In traditional ECAP, tensile stress along the contact surface between the work piece and the upper wall of the outlet channel leads to crack initiation, while in the presence of BP, a negative (compressive) stress appears during the process balancing the tensile stress. In this study a comparative tridimensional finite element analysis (FEA) is performed to evaluate the flow of an Al-Mg alloy depending on different BP levels and process parameters. The results in terms of load level and strain distribution show the influence of BP on the material behaviour, opening opportunities for industrial applications.

  9. Effect of equal channel angular extrusion on Al-6063 bending fatigue characteristics

    Science.gov (United States)

    Nemati, J.; Majzoobi, G. H.; Sulaiman, S.; Baharudin, B. T. H. T.; Azmah Hanim, M. A.

    2015-04-01

    The purpose of this investigation was to refine the grains of annealed 6063 aluminum alloy and to improve its yield stress and ultimate strength. This was accomplished via the equal channel angular extrusion (ECAE) process at a temperature of 200°C using route A, with a constant ram speed of 30 mm/min through a die angle of 90° between the die channels for as many as 6 passes. The experiments were conducted on an Avery universal testing machine. The results showed that the grain diameter decreased from 45 μm to 2.8 μm after 6 extrusion passes. The results also indicated that the major improvement in fatigue resistance occurred after the first pass. The subsequent passes improved the fatigue life but at a considerably lower rate. A maximum increase of 1100% in the case of low applied stresses and an approximately 2200% increase in fatigue resistance in the case of high applied stresses were observed after 5 passes. The improvement of fatigue resistance is presumed to be due to (1) a reduction in the size and the number of Si crystals with increasing number of ECAE passes, (2) the aggregation of Cu during the ECAE process, (3) the formation and growth of CuAl2 grains, and (4) grain refinement of the Al-6063 alloy during the ECAE process.

  10. Iterative Frequency-Domain Channel Estimation and Equalization for Ultra-Wideband Systems with Short Cyclic Prefix

    Directory of Open Access Journals (Sweden)

    Salim Bahçeci

    2010-01-01

    Full Text Available In impulse radio ultra-wideband (IR-UWB systems where the channel lengths are on the order of a few hundred taps, conventional use of frequency-domain (FD processing for channel estimation and equalization may not be feasible because the need to add a cyclic prefix (CP to each block causes a significant reduction in the spectral efficiency. On the other hand, using no or short CP causes the interblock interference (IBI and thus degradation in the receiver performance. Therefore, in order to utilize FD receiver processing UWB systems without a significant loss in the spectral efficiency and the performance, IBI cancellation mechanisms are needed in both the channel estimation and equalization operations. For this reason, in this paper, we consider the joint FD channel estimation and equalization for IR-UWB systems with short cyclic prefix (CP and propose a novel iterative receiver employing soft IBI estimation and cancellation within both its FD channel estimator and FD equalizer components. We show by simulation results that the proposed FD receiver attains performances close to that of the full CP case in both line-of-sight (LOS and non-line-of-sight (NLOS UWB channels after only a few iterations.

  11. Multi-Input Multi-Output Fading Channel Equalization with Constellation Selection and Space-Time Precoders

    Directory of Open Access Journals (Sweden)

    Ankita Shukla

    2011-09-01

    Full Text Available We consider multiplexing systems in correlated multiple-input multiple-output (MIMO fading channels with equal power allocated to each transmit antenna. Under several constraints, the number and subset of transmit antennas together with the transmit symbol constellations are determined assuming knowledge of the channel correlation matrices. The maximum outage data rate of the SCR receiver is seen to be close to the outage channel capacity. Identification of the channel matrix is of main concern in wireless multiple input multiple output (MIMO systems. To maximize the SNR, the best way to utilize a MIMO system is to communicate on the top singular vectors of the channel matrix. In this paper we addresses t several issues and the problem of channel tracking and equalization for multi-input multi-output (MIMO time-varying frequency-selective channels. These channels model the effects of inter-symbol interference (ISI, co-channel interference (CCI, and noise. Via singular value decomposition (SVD analysis, the precoder is used to be shown to outperform the orthogonal frequency division multiplexing (OFDM precoder in bit-error-rate (BER, transmission rate, and receiver implementation.

  12. Reducing interferences in wireless communication systems by mobile agents with recurrent neural networks-based adaptive channel equalization

    Science.gov (United States)

    Beritelli, Francesco; Capizzi, Giacomo; Lo Sciuto, Grazia; Napoli, Christian; Tramontana, Emiliano; Woźniak, Marcin

    2015-09-01

    Solving channel equalization problem in communication systems is based on adaptive filtering algorithms. Today, Mobile Agents (MAs) with Recurrent Neural Networks (RNNs) can be also adopted for effective interference reduction in modern wireless communication systems (WCSs). In this paper MAs with RNNs are proposed as novel computing algorithms for reducing interferences in WCSs performing an adaptive channel equalization. The method to provide it is so called MAs-RNNs. We perform the implementation of this new paradigm for interferences reduction. Simulations results and evaluations demonstrates the effectiveness of this approach and as better transmission performance in wireless communication network can be achieved by using the MAs-RNNs based adaptive filtering algorithm.

  13. Initial porosity impact on equal channel angular pressing (ECAP of Ti–6Al–4V powder material

    Directory of Open Access Journals (Sweden)

    V. A. Andreyachshenko

    2016-10-01

    Full Text Available There is studied the technology of processing Ti-6Al-4V powder material with various initial densities using the method of equal channel angular pressing. The device with the 90, 120 and 135 degree angled joint channels was used for the study. The deformation was carried out at the room temperature. It was found that the most favorable stressed-and-strained state was formed in the instrument where the angle of channel joints was equal to 135 degrees. The maximum compression in the instrument is reached at 90 degree angle of the channel joints, but it needs a larger deformation force. To obtain pressed material it is recommended to use a high ECAP cycle for any configuration.

  14. Blind equalization of underwater acoustic channels using implicit higher-order statistics

    NARCIS (Netherlands)

    Blom, Koen C.H.; Dol, Henry S.; Kokkeler, André B.J.; Smit, Gerard J.M.

    2016-01-01

    In order to reduce the length of transmission time slots and energy consumption of underwater modems, this work focuses on equalization without the need for training sequences. This type of equalization is known as blind equalization. A blind equalizer cascade based on higher-order statistics is pre

  15. Microstructure and mechanical properties of Pb-4%Sb alloy processed by equal channel angular pressing

    Directory of Open Access Journals (Sweden)

    Roberto Braga Figueiredo

    2006-03-01

    Full Text Available Equal Channel Angular Pressing (ECAP is the most prominent SPD (Severe Plastic Deformation method for the production of ultrafine and nanostructured metals, and has been extensively employed and analyzed. This technique was applied to a Pb-4%Sb alloy at room temperature, in order to study its effect on a low melting point and multiphase metallic material. The material was subjected to effective strains higher than 9, after 8 passes of processing, where dynamic and static recrystallization are expected during and after each pass. This eliminates any grain refinement and allows the analysis only of the microstructural effects associated with second phase redistribution and eventual precipitate dissolution. ECAP followed route C, which eliminates structural alignment after each even ECAP pass, facilitating the study of the microstructural evolution. It is shown that three ECAP passes are necessary to completely break the lamellar structure of the as cast strucure and that antimony dissolves into the lead rich matrix. Dynamic recrystallization and structural changes reduce the material strength and change the flow curve format.

  16. Electrochemical behavior of equal channel angular pressed titanium for biomedical application

    Science.gov (United States)

    Gode, C.; Attarilar, Sh.; Eghbali, B.; Ebrahimi, M.

    2015-03-01

    Equal channel angular pressing method is one of the prominent severe plastic deformation techniques to obtain ultrafine grained and even nanostructured metals and alloys by imposing intense plastic strain. As known, pure titanium can be a suitable candidate for biomedical applications because it does not release any toxic ions into the body fluids and also, its biocompatibility properties. The present investigation deals the corrosion behavior of commercial pure titanium before and after ECAP process up to 10 passes by route BC at the 250°C in the 0.9% NaCl solution. The electrochemical results revealed that the corrosion resistance of titanium sample is improved by adding pass number because of the fabrication of passive oxide layer on the surface of the material. It is found that about 92% reduction at the corrosion rate magnitude and also, approximately 41% improvement at the hardness value have been achieved at the final pass as compared to the annealed condition. Furthermore, it is observed that the passive film on the surface of final pass sample is dense and integral with uniform structure, while the as-received one has some rarefactions and does not have very uniform surface.

  17. Development of Texture in Interstitial-Free Steel Processed by Equal-Channel Angular Pressing

    Science.gov (United States)

    Verma, Deepa; Shekhawat, Satish Kumar; Mukhopadhyay, N. K.; Sastry, G. V. S.; Manna, R.

    2016-03-01

    Ti + Nb-stabilised interstitial-free steel is deformed by equal-channel angular pressing (ECAP) adopting a route BC up to an equivalent strain of 24. Upon ECAP the grain size decreases to ultrafine level and it becomes strongly textured. At ɛvm = 0.6-6, components of both {110} fiber, J_{\\uptheta } , bar{J}_{\\uptheta } and of fiber, D 1θ, D 2θ with common components of E θ, bar{E}_{\\uptheta } are existing but after ɛvm ≥9, only fiber components are observed. At large strain, ɛvm = 9-24, fiber texture is recorded with monoclinic symmetry. At ɛvm = 0.6, coarse grains get split into deformation bands. Fragmentation of bands (at ɛvm = 3) suppress bar{J}_{\\uptheta } , J_{\\uptheta } components. At ɛvm = 6, formation of lamellar structures increases intensity of mainly D 1θ, D 2θ. At ɛvm = 9, oriented ribbon grains result in strong D 1θ, D 2θ components with fiber. At ɛvm = 15-24, conversion of ribbon grains to near-equiaxed shaped grains maintains fiber texture with enhanced intensity of D 1θ and D 2θ components.

  18. Simulation of Aluminum Powder in Tube Compaction Using Equal Channel Angular Extrusion

    Science.gov (United States)

    Haghighi, Reza Derakhshandeh; Jahromi, Ahmad Jenabali; Jahromi, Behnam Esfandiar

    2012-02-01

    Aluminum powder in tube compaction with a 25 mm front plug through equal channel angular extrusion (ECAE) at room temperature was modeled using the finite element analysis package ABAQUS. The Gurson model was used in modeling this process. 2-D simulations in a 90° angle die showed better consolidation of powder near the inner edge of the die than the outer edge after one pass of ECAE but almost full densification occurs after two passes. The effect of hydrostatic pressure on densification of the powder was investigated by using two plugs varying in length dimension. The results obtained from the simulations were also compared with experiments conducted to compact aluminum powder with mean particle diameter of 45 μm. Optical microscopy, microhardness test, and density measurements confirmed the simulations. The simulations were extended to powder compaction in a 60° and 120° angle die. It was found that one pass of ECAE is sufficient to consolidate the aluminum powder completely and uniformly in a 60° angle die, whereas the material is still porous in a 120° angle die.

  19. Microstructural and mechanical characteristics of EUROFER'97 processed by equal channel angular pressing

    Energy Technology Data Exchange (ETDEWEB)

    Fernandez, P., E-mail: pilar.fernandez@ciemat.es [National Fusion Laboratory, CIEMAT, Avda. Complutense 22, 28040 Madrid (Spain); Eddahbi, M.; Auger, M.A.; Leguey, T.; Monge, M.A.; Pareja, R. [Departamento de Fisica, Universidad Carlos III de Madrid, 28911 Leganes (Spain)

    2011-10-01

    EUROFER'97 was processed by equal channel angular pressing (ECAP) at 823 K for a total of 4 or 8 passes, using a die angle of 105{sup o}, and its microstructure and tensile behavior in temperature range 568-873 K investigated. A single ECAP pass developed a deformation texture {l_brace}1 1 0{r_brace} <0 1 1> that was practically stable during subsequent ECAP passes. The materials processed by 1 or 2 passes exhibited a fine microstructure of recovered subgrains and tensile behavior very similar to that for the tempered material in the as-received condition. The materials processed using 4 or 8 passes exhibited nearly equiaxial submicron grained structures with a high density of high-angle grain boundaries. These materials became softer than the as-received material at a testing temperature of {approx}823 K. EUROFER ECAP processed under the present conditions exhibited hardening ratio somewhat higher than that of the as-received material.

  20. Equal Channel Angular Deformation (ECAD) of As-Cast AM60 Magnesium Alloy

    Institute of Scientific and Technical Information of China (English)

    Peng LUO; Xiaolin WU; Kenong XIA

    2003-01-01

    As-cast AM60 magnesium alloy ingot with grains coarser than those of as-extruded AZ series is more liable to produce cracks under ECAD with severe shear strain. A feasible scheme of equal channel angular deformation (ECAD) for as-cast AM60 magnesium alloy ingot was proposed in this paper. The tests were conducted on Instron machine with hydraulic back-force machine. Through analysing load vs displacement curves, the effects of ECAD processing conditions on deformability and microstructure of as-cast magnesium AM60 billets were discussed. During testing,the back-force employment was helpful to keep ECAD processing more stable. And with back-force, it was observed that the number of ECAD passes in different routes could tremendously affect the deformability and microstructure of magnesium specimens. It was concluded that ECAD processing is entirely feasible for as-cast magnesium AM60alloy under severe shear strain, and back-force employment, multi-passes deformation and lubrication of graphite paper are the factors primarily beneficial to improvement of deformability and refinement of grained structure. This work provides a way to produce magnesium alloy with fine-grained structure directly from casting ingot by ECAD technique.

  1. Microstructure and mechanical properties of a commercially pure Ti processed by warm equal channel angular pressing

    Energy Technology Data Exchange (ETDEWEB)

    Rodriguez-Calvillo, P., E-mail: pablo.rodriguez@ctm.com.es [Fundació CTM Centre Tecnològic, Plaza de la Ciencia 2, 08243 Manresa (Spain); Departamento de Ciencia de los Materiales e Ingeniería Metalúrgica, Universitat Politècnica de Catalunya, Av. Diagonal 647, 08028 Barcelona (Spain); Cabrera, J.M. [Fundació CTM Centre Tecnològic, Plaza de la Ciencia 2, 08243 Manresa (Spain); Departamento de Ciencia de los Materiales e Ingeniería Metalúrgica, Universitat Politècnica de Catalunya, Av. Diagonal 647, 08028 Barcelona (Spain)

    2015-02-11

    A commercially pure (CP) Titanium alloy classified as Grade 1, was processed by Equal Channel Angular Pressing (ECAP) up to 4 passes in the temperature range of 450–150 °C. The resulting microstructures were observed by Electron Back-Scattered Diffraction, revealing a bimodal grain size distribution consisting of small recrystallized grains of submicrometer size, with an average value of 0.3 µm, and elongated bands of 1.4 µm with different degree of substructure. Additionally the fraction of restored and deformed grains were evaluated as a function of processing temperature following an internal grain misorientation criterion, leading to an overall fraction of recrystallized grains between 40% and 20% in samples ECAPed at 450 and 150 °C, respectively. The strengthening contributions of the grain size, equivalent oxygen content (O{sub eq}) and Low Angle Grain Boundaries (LAGBs) to the yield stress were identified by the Hall Petch and Taylor equations. The strengthening coefficient k of the Hall–Petch relation was approximately 5 MPa mm{sup −1/2}, with an increment of 0.44 MPa mm{sup −1/2} per 0.1 O{sub eq}.-%, while the LAGB strengthening contribution was responsible approximately by half of the experimental yield stress values measured.

  2. Effect of Equal-Channel Angular Pressing on Pitting Corrosion of Pure Aluminum

    Directory of Open Access Journals (Sweden)

    Injoon Son

    2012-01-01

    Full Text Available The effect of equal-channel angular pressing (ECAP on the pitting corrosion of pure Al was investigated using electrochemical techniques in solutions containing 0.1 m mol·dm−3 of Na2SO4 and 8.46 mol·dm−3 of NaCl (300 ppm Cl− and followed by surface analysis. The potential for pitting corrosion of pure Al was clearly shifted in the noble direction by the ECAP process indicating that this process improves resistance to pitting corrosion. The time dependence of corrosion potential and the anodic potential at 1 A·m−2 revealed that the rate of formation of Al oxide films increased due to a decrease in the grain size of the Al after ECAP. Since there exists a negligible amount of impurity precipitates in pure Al, the improvement in pitting corrosion resistance of pure Al by ECAP appears to be attributable to an increase in the rate of formation of Al oxide films.

  3. Improvements in the microstructure and fatigue behavior of pure copper using equal channel angular extrusion

    Institute of Scientific and Technical Information of China (English)

    J Nemati; GH Majzoobi; S Sulaiman; BTHT Baharudin; MAAzmah Hanim

    2014-01-01

    In this study, annealed pure copper was extruded using equal channel angular extrusion (ECAE) for a maximum of eight passes. The fatigue resistance of extruded specimens was evaluated for different passes and applied stresses using fatigue tests, fractography, and metallography. The mechanical properties of the extruded material were obtained at a tensile test velocity of 0.5 mm/min. It was found that the maximum increase in strength occurred after the 2nd pass. The total increase in ultimate strength after eight passes was 94%. The results of fatigue tests indicated that a significant improvement in fatigue life occurred after the 2nd pass. In subsequent passes, the fatigue life con-tinued to improve but at a considerably lower rate. The improved fatigue life was dependent on the number of passes and applied stresses. For low stresses (or high-cycle fatigue), a maximum increase in fatigue resistance of approximately 500%was observed for the extruded material after eight passes, whereas a maximum fatigue resistance of 5000%was obtained for high-applied stresses (or low-cycle fatigue). Optical microscopic examinations revealed grain refinements in the range of 32 to 4 µm. A maximum increase in impact energy absorption of 100%was achieved after eight passes. Consistent results were obtained from fractography and metallography examinations of the ex-truded material during fatigue tests.

  4. Annealing response of binary Al–7Mg alloy deformed by equal channel angular pressing

    Energy Technology Data Exchange (ETDEWEB)

    Zha, Min, E-mail: min.zha@material.ntnu.no [Department of Materials Science and Engineering, Norwegian University of Science and Technology, 7491 Trondheim (Norway); Li, Yanjun [SINTEF Materials and Chemistry, 7465 Trondheim (Norway); Mathiesen, Ragnvald H.; Bjørge, Ruben [Department of Physics, Norwegian University of Science and Technology, 7491 Trondheim (Norway); Roven, Hans J. [Department of Materials Science and Engineering, Norwegian University of Science and Technology, 7491 Trondheim (Norway)

    2013-12-01

    The annealing response in a binary Al–7Mg alloy processed at room temperature by equal channel angular pressing (ECAP) has been investigated via X-ray diffraction (XRD), electron-probe micro analysis (EPMA) and electron backscattering diffraction (EBSD). After ECAP and subsequent annealing, Mg remains mainly homogeneously distributed in solid solution. A bimodal structure with ultrafine grains accompanied by micrometer-sized crystallites was developed after 3 passes. Upon annealing at ∼275 °C for 96 h, extensive recovery was observed in the as-deformed material, leading to a relatively uniform microstructure; at ∼300 °C a discontinuous recrystallization initiated in less than 30 s with subsequent grain growth clearly evident. Such remarkable thermal stability, i.e., slower recovery and recrystallization kinetics, of the present material, in contrast to other severely deformed commercial pure Al and Al–Mg alloys, is due mainly to the presence of high Mg solid solution contents, the formation of the bimodal structure consisting of both coarse crystallites and ultrafine grains. In addition, the possible Mg-containing precipitates during annealing might also retard the recrystallization kinetics.

  5. Friction stir welding of AZ31 magnesium alloys processed by equal channel angular pressing

    Institute of Scientific and Technical Information of China (English)

    ZHANG Bing; YUAN Shouqian; WANG Xunhong

    2008-01-01

    Equal channel angular pressing (ECAP) is an effective thermo-mechanical process to make ultrafine grains.An investigation was carried out on the friction stir welding (FSW) of ECAPed AZ31 magnesium alloys with a thickness of 15 mm.For different process parameters,the optimum FSW conditions of ECAPed AZ31 magnesium alloys were examined.The basic characterization of weld formation and the mechanical properties of the joints were discussed.The results show that the effect of welding parameters on welding quality was evident and welding quality was sensitive to welding speed.Sound joints could be obtained when the welding speed was 37.5 mm/min and the rotation speed of the stir tool was 750 r/min.The maximum tensile strength (270 MPa) of FSW was 91% that of the base materials.The value of microhardness varied between advancing side and retreating side because of the speed field near the pin of the stir tool,which weakened the deformed stress field.The value of microhardness of the welding zone was lower than that of the base materials.The maximum value was located near the heat-affected zone (HAZ).Remarkable ductile character was observed from the fracture morphologies of welded joints.

  6. A PCA and ELM Based Adaptive Method for Channel Equalization in MFL Inspection

    Directory of Open Access Journals (Sweden)

    Zhenning Wu

    2014-01-01

    Full Text Available Magnetic flux leakage (MFL as an efficient method for pipeline flaw detection plays important role in pipeline safety. This nondestructive test technique assesses the health of the buried pipeline. The signal is gathered by an array of hall-effect sensors disposed at the magnetic neutral plane of a pair of permanent magnet in the pipeline inspection gauge (PIG clinging to the inner surface of the pipe wall. The magnetic flux measured by the sensors reflects the health condition of the pipe. The signal is influenced by not only the condition of the pipe, but also by the lift-off value of the sensors and various properties of electronic component. The consistency of the position of the sensors is almost never satisfied and each sensor measures differently. In this paper, a new scheme of channel equalization is proposed for MFL signal in order to correct sensor misalignments, which eventually improves accuracy of defect characterization. The algorithm proposed in this paper is adaptive to the effects of error on the disposition of the sensor due to manufacturing imperfections and movements of the sensors. The algorithm is tested by data acquired from an experimental pipeline. The results show the effectiveness of the proposed algorithm.

  7. Equal Channel Angular Extrusion of AA 6063 Using Conventional Direct Extrusion Press

    Science.gov (United States)

    Liu, Cheng-Hsien; Lin, Hsin-Chih

    2015-11-01

    In the present work, an extrusion-equal channel angular extrusion (Ex-ECAE) process composed of two processes, extrusion and ECAE, is developed. The Ex-ECAE die contains three segments and is used directly in the conventional direct extrusion press to refine the microstructure, specifically the coarse grain layer (CGL) on the surface of the extrudate. The first segment in the die is designed to perform the normal extrusion process and the second and third segments to perform the process of ECAE. The study reveals that the CGL can be eliminated (refined) completely at the macroscale. At the microscale, the original grain is subdivided into subgrain, which contains many smaller cells. The results can be explained by the grain subdivision mechanism. The textures of the Ex-ECAE sample at various segments are measured using EBSD (Electron Backscatter Diffraction). The results reveal that the first segment of the Ex-ECAE sample has a perfect fiber texture which consists of a mixture of strong and weak fiber components. The texture of the second segment is a mixture of strong (1 1 0) [1 -2 1] and weak (0 1 1) [2 -1 0] fiber components. However, the main component of the second segment is a typical texture of the "alloy" or "brass" type. Finally, the texture of the extrudate (the third segment) is reversed to an incomplete fiber texture which consists of strong (0 0 1) [-1 -1 0] and weak (1 1 1) [1 -1 0].

  8. Two-dimensional nonlinear travelling waves in magnetohydrodynamic channel flow

    CERN Document Server

    Hagan, Jonathan

    2013-01-01

    The present study is concerned with the stability of a flow of viscous conducting liquid driven by pressure gradient in the channel between two parallel walls subject to a transverse magnetic field. Although the magnetic field has a strong stabilizing effect, this flow, similarly to its hydrodynamic counterpart -- plane Poiseuille flow, is known to become turbulent significantly below the threshold predicted by linear stability theory. We investigate the effect of the magnetic field on 2D nonlinear travelling-wave states which are found at substantially subcritical Reynolds numbers starting from $Re_n=2939$ without the magnetic field and from $Re_n\\sim6.50\\times10^3Ha$ in a sufficiently strong magnetic field defined by the Hartmann number $Ha.$ Although the latter value is by a factor of seven lower than the linear stability threshold $Re_l\\sim4.83\\times10^4Ha$,it is still more by an order of magnitude higher than the experimentally observed value for the onset of turbulence in this flow.

  9. 非线性功放信道下联合信道估计研究%Joint Channel Estimation for Nonlinear System Channels

    Institute of Scientific and Technical Information of China (English)

    孙珊珊; 孙学斌; 李斌; 周正

    2013-01-01

    为了解决非线性放大器在60 GHz毫米波信道中造成的非线性影响,提出了基于马尔科夫蒙特卡洛(Markov Chain Monte Carlo,MCMC)算法的联合信道估计与信号检测技术。采用的是 MCMC算法中的 Metropolis-Hastings方法,在非线性放大器及信道参数未知的情况下,通过被非线性和噪声污染的输出信号(观测信号)来估计非线性放大器的参数,检测输入信号被称为盲均衡技术。仿真结果给出了非线性参数与真实值的对比图以及随 SNR变化的误比特率,性能优越。%A novel approach based on Markov Chain Monte Carlo (MCMC )for joint channel estimation suitable for 60 GHz millimeter-wave band system channel was proposed. To solve the problem that a simultaneous parameter estimation and data detection of finite-alphabet symbols that are blurred by Gaussian white noise and nonlinear amplifier with unknown nonlinear parameters in the 60 GHz millimeter-wave band system channel,Metropolis-Hastings method is used,which is one of MCMC method. In case that the nonlinear amplifier and channel parameters are unknown,the output signal(observed)is used to estimate nonlinear amplifier parameter, which is called blind equalization. Excellent behavior of the proposed algorithms is presented in simulation.

  10. Equal Channel Angular Extrusion Progress Report for March 1998 - May 1999

    Energy Technology Data Exchange (ETDEWEB)

    Macheret, Yevgeny; Watkins, Arthur Deloss; Korth, Gary Elvan; Lillo, Thomas Martin; Flinn, John Elwood Jr.; Herling, D. R.; Smith, M. T.; Schwarz, R. B.

    1999-10-01

    Pure copper and Alloy 5083 aluminum were processed by equal channel angular extrusion (ECAE); their microstructural evolution and corresponding mechanical properties were investigated. Work also began on the possible use of ECAE to synthesize advanced materials or to consolidate metal powders or powder mixtures. The die tooling used for ECAE is described and selected microstructural and mechanical property results for ECAE-processed copper and cold-rolled (conventionally-processed) copper in the as-processed and annealed condition are compared. Results thus far show that the “pure” metal is prone to low temperature recrystallization after large strain hardening—more beneficial effects are expected in the dispersion-strengthened and precipitation-hardening alloys. The large range of tensile properties and grain sizes from the copper allowed a flow stress analysis to be performed. From this analysis, a new model for flow stress behavior is proposed. An evaluation of ECAE processing of material for spot welding electrodes began. Results to date include electrodes of ECAE-processed commercially pure copper (Alloy 101). Future work involving Glidcop® (Al2O3 oxide dispersionstrengthened copper) and CuCrZr (Cr-Zr precipitation dispersion) materials will be required to fully investigate the benefits of ECAE for electrode life extension. Initial work on Aluminum Alloy 5083 showed that ECAE led to grain refinement as well as broke up and more uniformly dispersed the hardening precipitates. This is desirable for enhancing superplastic behavior. Study of ECAE for consolidating metal powder began. Early results with a Cu-Ag powder indicate that near 100% density was achieved with room temperature consolidation.

  11. Nonlinear Trellis Description for Convolutionally Encoded Transmission Over ISI-channels with Applications for CPM

    CERN Document Server

    Schuh, Fabian

    2012-01-01

    In this paper we propose a matched decoding scheme for convolutionally encoded transmission over intersymbol interference (ISI) channels and devise a nonlinear trellis description. As an application we show that for coded continuous phase modulation (CPM) using a non-coherent receiver the number of states of the super trellis can be significantly reduced by means of a matched non-linear trellis encoder.

  12. The power spectral density of digital modulations transmitted over nonlinear channels

    Science.gov (United States)

    Divsalar, D.; Simon, M. K.

    1982-01-01

    This paper examines by analytical methods the power spectral densities of digital modulations (in particular, staggered and unstaggered quadrature modulations) passed through band-limited nonlinear channels. Previously observed (by computer simulation or hardware measurement) behavior of such spectra with regard to the suppression or restoration of its sidelobes after passing through the nonlinearity is verified analytically. Several examples corresponding to specific quadrature modulations and filter-nonlinearity combinations are presented as illustrations of the general results.

  13. Low-Complexity Banded Equalizers for OFDM Systems in Doppler Spread Channels

    NARCIS (Netherlands)

    Rugini, L.; Banelli, P.; Leus, G.

    2006-01-01

    Recently, several approaches have been proposed for the equalization of orthogonal frequency-division multiplexing (OFDM) signals in challenging high-mobility scenarios. Among them, a minimum mean-squared error (MMSE) block linear equalizer (BLE), based on a band LDL factorization, is particularly a

  14. Simultaneous regeneration of two 160 Gbit/s WDM channels in a single highly nonlinear fiber

    DEFF Research Database (Denmark)

    Wang, Ju; Ji, Hua; Hu, Hao;

    2013-01-01

    We experimentally demonstrate simultaneous all-optical regeneration of two 160-Gbit/s wavelength-division multiplexed (WDM) channels in a single highly nonlinear fiber (HNLF). The multi-channel regeneration performance is confirmed by bit-error rate (BER) measurements. The receiver powers at a BE...

  15. Wavelet Neural Networks for Adaptive Equalization

    Institute of Scientific and Technical Information of China (English)

    JIANGMinghu; DENGBeixing; GIELENGeorges; ZHANGBo

    2003-01-01

    A structure based on the Wavelet neural networks (WNNs) is proposed for nonlinear channel equalization in a digital communication system. The construction algorithm of the Minimum error probability (MEP) is presented and applied as a performance criterion to update the parameter matrix of wavelet networks. Our experimental results show that performance of the proposed wavelet networks based on equalizer can significantly improve the neural modeling accuracy, perform quite well in compensating the nonlinear distortion introduced by the channel, and outperform the conventional neural networks in signal to noise ratio and channel non-llnearity.

  16. A Low-Complexity Decision Feedforward Equalizer Architecture for High-Speed Receivers on Highly Dispersive Channels

    Directory of Open Access Journals (Sweden)

    Ariel L. Pola

    2013-01-01

    Full Text Available This paper presents an improved decision feedforward equalizer (DFFE for high speed receivers in the presence of highly dispersive channels. This decision-aided equalizer technique has been recently proposed for multigigabit communication receivers, where the use of parallel processing is mandatory. Well-known parallel architectures for the typical decision feedback equalizer (DFE have a complexity that grows exponentially with the channel memory. Instead, the new DFFE avoids that exponential increase in complexity by using tentative decisions to cancel iteratively the intersymbol interference (ISI. Here, we demostrate that the DFFE not only allows to obtain a similar performance to the typical DFE but it also reduces the compelxity in channels with large memory. Additionally, we propose a theoretical approximation for the error probability in each iteration. In fact, when the number of iteration increases, the error probability in the DFFE tends to approach the DFE. These benefits make the DFFE an excellent choice for the next generation of high-speed receivers.

  17. Multipass Channel Estimation and Joint Multiuser Detection and Equalization for MIMO Long-Code DS/CDMA Systems

    Directory of Open Access Journals (Sweden)

    Buzzi Stefano

    2006-01-01

    Full Text Available The problem of joint channel estimation, equalization, and multiuser detection for a multiantenna DS/CDMA system operating over a frequency-selective fading channel and adopting long aperiodic spreading codes is considered in this paper. First of all, we present several channel estimation and multiuser data detection schemes suited for multiantenna long-code DS/CDMA systems. Then, a multipass strategy, wherein the data detection and the channel estimation procedures exchange information in a recursive fashion, is introduced and analyzed for the proposed scenario. Remarkably, this strategy provides, at the price of some attendant computational complexity increase, excellent performance even when very short training sequences are transmitted, and thus couples together the conflicting advantages of both trained and blind systems, that is, good performance and no wasted bandwidth, respectively. Space-time coded systems are also considered, and it is shown that the multipass strategy provides excellent results for such systems also. Likewise, it is also shown that excellent performance is achieved also when each user adopts the same spreading code for all of its transmit antennas. The validity of the proposed procedure is corroborated by both simulation results and analytical findings. In particular, it is shown that adopting the multipass strategy results in a remarkable reduction of the channel estimation mean-square error and of the optimal length of the training sequence.

  18. Performance analysis and comparison of m x n zero forcing and MMSE equalizer based receiver for mimo wireless channel

    Directory of Open Access Journals (Sweden)

    N. Sathish Kumar

    2011-06-01

    Full Text Available Wireless transmission is affected by fading and interference effects which can be combated with equalizer.The useof MIMO system promises good improvement in terms of spectral efficency,link relaibility andSignal to Noise Ratio (SNR.The effect of fading and interference always causes an issue for signal recovery in wireless communication. Equalizationcompensates for Intersymbol Interference (ISI created by multipath within time dispersive channels. This paper analyses theperformance of Zeroforcing and MMSE equalizer for MIMO wireless chaneels. The simulation results are obtained usingMatLab tool box version 7.0 at RF signal processing lab.The Bit Error Rate (BER characteristics for the various transmittingand receiveing antennna is simulated in matlab tool box and many advantages and disdvantagesof the system is descrbed.The simulation results show that the equalizer based zero forcing receiver is good for noise free channel and is successfulin remving ISI,but MMSE is a better choice than ZF in terms of BER charateristics and under Noise performance.

  19. Non-linear plasma transport in graphene channels and application to the detection of terahertz signals

    Science.gov (United States)

    Rudin, Sergey; Rupper, Greg

    2012-02-01

    The non-linear electron plasma response to electromagnetic signal applied to a gated graphene conduction channel can be used to make a graphene based Dyakonov-Shur terahertz detector. The hydrodynamic model predicts a resonance response to electromagnetic radiation at the plasma oscillation frequency. With less damping and higher mobility, the graphene conduction channels may provide higher quality plasma response than possible with semiconductor channels. Our analysis of plasma oscillations in a graphene channel is based on the hydrodynamic equations which we derive from the Boltzmann equation accounting for both electrons and holes, and including the effects of viscosity and finite mobility.

  20. Mechanical Behavior and Microstructural Development of 6063-T1 Aluminum Alloy Processed by Equal-Channel Angular Pressing (ECAP): Die Channel Angle Influence

    Science.gov (United States)

    Serban, Nicolae; Ghiban, Nicolae; Cojocaru, Vasile-Danut

    2013-11-01

    A commercial 6063-T1 aluminum alloy was investigated in this study. The specimens were processed for six, seven, and eight equal-channel angular pressing (ECAP) passes using three die channel angles: 90°, 100°, and 110°, respectively (maintaining approximately the same value for the accumulated equivalent strain in each case). After ECAP, samples were cut from each specimen and were prepared for metallographic analysis and mechanical testing. The microstructures of the ECAP treated and as-received material were investigated using both optical microscopy and scanning electron microscopy. It was found that the optimum ECAP die has a channel angle of 90°; the microstructure was more refined and homogeneous and second-phase particles were smaller as the die channel angle value decreased. All samples (ECAP processed and as-received) were also mechanically investigated in compression and microhardness tests. The maximum effect was observed when the 90° ECAP die was used, and significant total increases in ultimate compressive strength, yield strength, compression modulus, and microhardness were recorded compared to the as-received material. Also, it was shown that if the die channel angle value increases, then all the above mentioned mechanical properties decrease.

  1. The benefit of split nonlinearity compensation for single channel optical fiber communications

    OpenAIRE

    Lavery, D.; Ives, David J; Liga, Gabriele; Alvarado, A Alex; Savory, SJ; Bayvel, P.

    2016-01-01

    In this letter, we analyze the benefit of digital compensation of fiber nonlinearity, where the digital signal processing is divided between the transmitter and the receiver. The application of the Gaussian noise model indicates that, where there are two or more spans, it is always beneficial to split the nonlinearity compensation. The theory is verified via numerical simulations, investigating the transmission of a single-channel 50-GBd polarization division multiplexed 4- and 256-ary quadra...

  2. Role of Density Profiles for the Nonlinear Propagation of Intense Laser Beam through Plasma Channel

    OpenAIRE

    Sonu Sen; Meenu Asthana Varshney; Dinesh Varshney

    2014-01-01

    In this work role of density profiles for the nonlinear propagation of intense laser beam through plasma channel is analyzed. By employing the expression for the dielectric function of different density profile plasma, a differential equation for beamwidth parameter is derived under WKB and paraxial approximation. The laser induces modifications of the dielectric function through nonlinearities. It is found that density profiles play vital role in laser-plasma interaction studies. To have num...

  3. Estimating nonlinear mixing effects for arid vegetation scenes with MISR channels and observation directions

    Energy Technology Data Exchange (ETDEWEB)

    Villeneuve, P.V.; Gerstl, S.A. [Los Alamos National Lab., NM (United States); Asner, G.P. [Univ. of Colorado, Boulder, CO (United States)

    1998-12-01

    A Monte-Carlo ray-trace model has been applied to simulated sparse vegetation desert canopies in an effort to quantify the spectral mixing (both linear and nonlinear) occurring as a result of radiative interactions between vegetation and soil. This work is of interest as NASA is preparing to launch new instruments such as MISR and MODIS. MISR will observe each ground pixel from nine different directions in three visible channels and one near-infrared channel. It is desired to study angular variations in spectral mixing by quantifying the amount of nonlinear spectral mixing occurring in the MISR observing directions.

  4. Wavelet Neural Networks for Adaptive Equalization by Using the Orthogonal Least Square Algorithm

    Institute of Scientific and Technical Information of China (English)

    JIANG Minghu(江铭虎); DENG Beixing(邓北星); Georges Gielen

    2004-01-01

    Equalizers are widely used in digital communication systems for corrupted or time varying channels. To overcome performance decline for noisy and nonlinear channels, many kinds of neural network models have been used in nonlinear equalization. In this paper, we propose a new nonlinear channel equalization, which is structured by wavelet neural networks. The orthogonal least square algorithm is applied to update the weighting matrix of wavelet networks to form a more compact wavelet basis unit, thus obtaining good equalization performance. The experimental results show that performance of the proposed equalizer based on wavelet networks can significantly improve the neural modeling accuracy and outperform conventional neural network equalization in signal to noise ratio and channel non-linearity.

  5. Adaptive Equalizer Using Selective Partial Update Algorithm and Selective Regressor Affine Projection Algorithm over Shallow Water Acoustic Channels

    Directory of Open Access Journals (Sweden)

    Masoumeh Soflaei

    2014-01-01

    Full Text Available One of the most important problems of reliable communications in shallow water channels is intersymbol interference (ISI which is due to scattering from surface and reflecting from bottom. Using adaptive equalizers in receiver is one of the best suggested ways for overcoming this problem. In this paper, we apply the family of selective regressor affine projection algorithms (SR-APA and the family of selective partial update APA (SPU-APA which have low computational complexity that is one of the important factors that influences adaptive equalizer performance. We apply experimental data from Strait of Hormuz for examining the efficiency of the proposed methods over shallow water channel. We observe that the values of the steady-state mean square error (MSE of SR-APA and SPU-APA decrease by 5.8 (dB and 5.5 (dB, respectively, in comparison with least mean square (LMS algorithm. Also the families of SPU-APA and SR-APA have better convergence speed than LMS type algorithm.

  6. Decision feedback equalizer based on non-singleton fuzzy regular neural networks

    Institute of Scientific and Technical Information of China (English)

    Song Heng; Wang Chen; He Yin; Ma Shiping; Zuo Jizhang

    2006-01-01

    A new equalization method is proposed in this paper for severely nonlinear distorted channels. The structure of decision feedback is adopted for the non-singleton fuzzy regular neural network that is trained by gradient-descent algorithm. The model shows a much better performance on anti-jamming and nonlinear classification, and simulation is carried out to compare this method with other nonlinear channel equalization methods. The results show the method has the least bit error rate (BER).

  7. NONLINEAR PROPERTY MEMBRANE RECTIFIER POTASSIUM CHANNEL AND INHIBITORY EFFECTS OF OXYGEN FREE RADICAL

    Institute of Scientific and Technical Information of China (English)

    鲍光宏; 于德洁; 刘宇; 刘东梅

    1996-01-01

    There are at least eight kinds of different potassium chennels on cardiac cell membrane. This paperpresents a nonlinear property membrane outward; current going rectifying potassium channel and the in-hibitory efeets of oxygen free radical on this channel. The current-vohage relation of this nonlimmr-mem-brahe can be defined by an equation I=8a3/(0.01v2+4a2)2 and the maximum conductance of this channel is-75.3pS.

  8. Effects of Higher-Order Relativistic Nonlinearity and Wakefield During a Moderately Intense Laser Pulse Propagation in a Plasma Channel

    Institute of Scientific and Technical Information of China (English)

    LIU Ming-Ping; LIU Bing-Bing; LIU San-Qiu; ZHANG Fu-Yang; LIU Jie

    2013-01-01

    Using a variational approach,the propagation of a moderately intense laser pulse in a parabolic preformed plasma channel is investigated.The effects of higher-order relativistic nonlinearity (HRN) and wakefield are included.The effect of HRN serves as an additional defocusing mechanism and has the same order of magnitude in the spot size as that of the transverse wakefield (TWF).The effect of longitudinal wakefield is much larger than those of HRN and TWF for an intense laser pulse with the pulse length equaling the plasma wavelength.The catastrophic focusing of the laser spot size would be prevented in the present of HRN and then it varies with periodic focusing oscillations.

  9. Non-Linear Evolution of Steady and Migrating Alternate Bars in a Straight Channel (abstract)

    NARCIS (Netherlands)

    Southgate, H.N.; Crosato, A.

    2013-01-01

    This paper contains an analysis of a long-duration experiment that shows the evolution of alternate bars in a straight channel. The theoretical predictions are based on a weakly non-linear theory of the morphological development. Both the experiment and theory have several innovative features.

  10. Non-Linear Evolution of Steady and Migrating Alternate Bars in a Straight Channel (abstract)

    NARCIS (Netherlands)

    Southgate, H.N.; Crosato, A.

    2013-01-01

    This paper contains an analysis of a long-duration experiment that shows the evolution of alternate bars in a straight channel. The theoretical predictions are based on a weakly non-linear theory of the morphological development. Both the experiment and theory have several innovative features.

  11. TURBO EQUALIZATION WITH JOINTLY GAUSSIAN EQUALIZER

    Institute of Scientific and Technical Information of China (English)

    Jiang Sen; Sun Hong; Li Ping

    2005-01-01

    A Jointly Gaussian (JG) equalizer is derived for turbo equalization based on an augmented real matrix representation of channel model and a Gaussian approximation of the received symbol sequence. Using matrix inversion lemma and Cholesky decomposition, a lowcomplexity implementation of JG equalizer is also presented. The simulation results and complexity comparison confirm that turbo equalization with JG equalizer has a better performance and a lower complexity than the existing turbo equalization with linear minimum mean squared error equalizer.

  12. Robust Filtering for a Class of Networked Nonlinear Systems With Switching Communication Channels.

    Science.gov (United States)

    Zhang, Lixian; Yin, Xunyuan; Ning, Zepeng; Ye, Dong

    2016-02-15

    This paper is concerned with the problem of robust filter design for a class of discrete-time networked nonlinear systems. The Takagi-Sugeno fuzzy model is employed to represent the underlying nonlinear dynamics. A multi-channel communication scheme that involves a channel switching phenomenon described by a Markov chain is proposed for data transmission. Two typical communication imperfections, network-induced time-varying delays and packet dropouts are considered in each channel. The objective of this paper is to design an admissible filter such that the filter error system is stochastically stable and ensures a prescribed disturbance attenuation level bound. Based on the Lyapunov-Krasovskii functional method and matrix inequality techniques, sufficient conditions on the existence of the desired filter are obtained. A numerical example is provided to illustrate the effectiveness of the proposed design approach.

  13. The Benefit of Split Nonlinearity Compensation for Single-Channel Optical Fiber Communications

    Science.gov (United States)

    Lavery, Domanic; Ives, David; Liga, Gabriele; Alvarado, Alex; Savory, Seb J.; Bayvel, Polina

    2016-09-01

    In this Letter we analyze the benefit of digital compensation of fiber nonlinearity, where the digital signal processing is divided between the transmitter and receiver. The application of the Gaussian noise model indicates that, where there are two or more spans, it is always beneficial to split the nonlinearity compensation. The theory is verified via numerical simulations, investigating transmission of single channel 50 GBd polarization division multiplexed 256-ary quadrature amplitude modulation over 100 km standard single mode fiber spans, using lumped amplification. For this case, the additional increase in mutual information achieved over transmitter- or receiver-side nonlinearity compensation is approximately 1 bit for distances greater than 2000 km. Further, it is shown, theoretically, that the SNR gain for long distances and high bandwidth transmission is 1.5 dB versus transmitter- or receiver-based nonlinearity compensation.

  14. Adaptive Jamming Suppression in Coherent FFH System Using Weighted Equal Gain Combining Receiver over Fading Channels with Imperfect CSI

    Directory of Open Access Journals (Sweden)

    Yishan He

    2015-01-01

    Full Text Available Fast frequency hopping (FFH is commonly used as an antijamming communication method. In this paper, we propose efficient adaptive jamming suppression schemes for binary phase shift keying (BPSK based coherent FFH system, namely, weighted equal gain combining (W-EGC with the optimum and suboptimum weighting coefficient. We analyze the bit error ratio (BER of EGC and W-EGC receivers with partial band noise jamming (PBNJ, frequency selective Rayleigh fading, and channel estimation errors. Particularly, closed-form BER expressions are presented with diversity order two. Our analysis is verified by simulations. It is shown that W-EGC receivers significantly outperform EGC. As compared to the maximum likelihood (ML receiver in conventional noncoherent frequency shift keying (FSK based FFH, coherent FFH/BPSK W-EGC receivers also show significant advantages in terms of BER. Moreover, W-EGC receivers greatly reduce the hostile jammers’ jamming efficiency.

  15. Grain Refinement and High-Performance of Equal-Channel Angular Pressed Cu-Mg Alloy for Electrical Contact Wire

    Directory of Open Access Journals (Sweden)

    Aibin Ma

    2014-12-01

    Full Text Available Multi-pass equal-channel angular pressing (EACP was applied to produce ultrafine-grained (UFG Cu-0.2wt%Mg alloy contact wire with high mechanical/electric performance, aim to overcome the catenary barrier of high-speed trains by maximizing the tension and improving the power delivery. Microstructure evolution and overall properties of the Cu-Mg alloy after different severe-plastic-deformation (SPD routes were investigated by microscopic observation, tensile and electric tests. The results show that the Cu-Mg alloy after multi-pass ECAP at 473 K obtains ultrafine grains, higher strength and desired conductivity. More passes of ECAP leads to finer grains and higher strength, but increasing ECAP temperature significantly lower the strength increment of the UFG alloy. Grain refinement via continuous SPD processing can endow the Cu-Mg alloy superior strength and good conductivity characteristics, which are advantageous to high-speed electrification railway systems.

  16. Uniformity and continuity of effective strain in AZ91D processed by multi-pass equal channel angular extrusion

    Institute of Scientific and Technical Information of China (English)

    ZHANG Xiao-hua; LUO Shou-jing; DU Zhi-ming

    2008-01-01

    AZ91D magnesium alloy was processed by equal channel angular extrusion(ECAE). The influence of extrusion temperature, extrusion pass and extrusion route on the ultimate strength of the extruded billet was analyzed. The process of multi-pass extrusion was simulated with the method of finite element analysis, and the continuity and uniformity of effective strain in multi-pass extrusion were investigated. The results show that extrusion pass plays the most important role in improving the ultimate strength of AZ91D magnesium alloy, the extrusion route is the second, and the extrusion temperature is the last. From the numerical simulation, there exists the continuity of the accumulated deformation in multi-pass extrusion and the effective strain increases linearly. The tendency of the strain uniformity is different in multi-pass extrusion with extrusion routes. The results of experiment agree with those of numerical simulation.

  17. Deformation mechanism at impact test of Al-11% Si alloy processed by equal-channel angular pressing with rotary die

    Institute of Scientific and Technical Information of China (English)

    MA Ai-bin; Y. NISHIDA; JIANG Jing-hua; N. SAITO; I. SHIGEMATSU; A. WATAZU

    2007-01-01

    Al-11%Si (mass fraction) alloy was transformed into a ductile material by equal-channel angular pressing (ECAP) with a rotary die. Two mechanisms at impact test, slip deformation by dislocation motion and grain boundary sliding, were discussed. The ultrafine grains with modified grain boundaries and the high content of fine particles (<1 μm) were necessary for attaining high absorbed energy. The results contradict the condition of slip deformation by dislocation motion and coincide with that of grain boundary sliding. Many fine zigzag lines like a mosaic were observed on the side surface of the tested specimens. These observed lines may show grain boundaries appeared by the sliding of grains.

  18. Deformation temperature and postdeformation annealing effects on severely deformed TiNi alloy by equal channel angular extrusion

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Micron TiNi alloy blocks were fabricated at high temperature by equal channel angular extrusion (ECAE) using hotforged Ti-50.3at%Ni alloy as the raw material and the effects of deformation temperature and postdeformation annealing on the severely deformed TiNi alloy by ECAE were investigated. The results show that the TiNi alloy processed by ECAE undergoes severe plastic deformation, and lowering the deformation temperature and increasing the number of extrusions contribute to grain refinement. When the annealing temperature is below 873 K, static recovery is the main restoration process; when the temperature rises to 973 K, static recrystallization occurs. It is found that fine particles are precipitated when the TiNi alloy processed by ECAE is annealed at 773 K.

  19. Effect of Equal Channel Angular Extrusion on the Microstructures and Properties of Two Extruded Al-Mg-Si Alloys

    Institute of Scientific and Technical Information of China (English)

    M. Cai; G. W. Lorimer

    2005-01-01

    The effect of equal channel angular extrusion (ECAE) on the microstructure of two Al-Mg-Si extrusion alloys was investigated by high resolution electron backscattered diffraction (EBSD) using a field emission gun scanning electron microscope (FEG-SEM) and a transmission electron microscope (TEM). Two contrasting alloys: a dilute alloy, based on alloy 6061 and a concentrated alloy, based on alloy 6069 were employed for this research. It has been found that prior ECAE to extrusion promotes high angle grain boundaries (HAGBs) in the extrusions, and the increase in HAGBs ratio is due to the large shear deformation involved in the processof ECAE. Tensile testing results show that a further ageing treatment strengthens the alloys after extrusion and the ECAE processedextrusions are more ductile than conventional extrusions.

  20. Microstructure evolution of processed Mg-Al-Zn alloy by equal channel angular extrusion in semi-solid isothermal treatment

    Institute of Scientific and Technical Information of China (English)

    JIANG Ju-fu; LUO Shou-jing

    2006-01-01

    Microstructure evolution of processed Mg-Al-Zn alloy by equal channel angular extrusion(ECAE) in semi-solid isothermal treatment was investigated. The results show that with increasing semi-solid isothermal treatment temperature, the α phase solid grain size of processed Mg-Al-Zn alloy by ECAE increases firstly due to coarsening of α phase solid grains, then decreases due to melting of α phase solid grains. With the increase of extrusion passes during ECAE, the α phase solid grain size in the following semi-solid isothermal treatment decreases. The α phase solid grain size of processed Mg-Al-Zn alloy by ECAE under route BC is the smallest, while the α phase solid grain size of processed material by ECAE under route A is the largest. The primary mechanism of spheroid formation depends on the melting of recrystallizing boundaries and diffusion of solute atoms in the semi-solid state.

  1. A crystal plasticity smooth-particle hydrodynamics approach and its application to equal-channel angular pressing simulation

    Science.gov (United States)

    Ma, Anxin; Hartmaier, Alexander

    2016-12-01

    A crystal plasticity (CP) modelling approach based on smooth-particle hydrodynamics (SPH) has been developed to study severe plastic deformation of crystalline materials. The method has been implemented and validated by comparing the stress distribution and stress evolution of several SPH and FEM simulations for an anisotropic elastic material. The findings show that the SPH method produces an efficient and numerically robust solution for solid-mechanics boundary value problems. Furthermore, the approach has been extended to incorporate a CP model and employed to simulate FCC polycrystals under the equal-channel angular pressing (ECAP) condition. It was found that the polycrystal contains four distinct regions with different deformation mechanisms. For the case that friction between deformable particles and boundary particles was neglected, more than one half of the grains suffered severe plastic deformation. The CP-SPH developed here thus is demonstrated to be a powerful tool to study grain refinement under severe plastic deformation.

  2. Mechanical properties and biocorrosion resistance of the Mg-Gd-Nd-Zn-Zr alloy processed by equal channel angular pressing.

    Science.gov (United States)

    Zhang, Junyi; Kang, Zhixin; Wang, Fen

    2016-11-01

    A Mg-Gd-Nd-Zn-Zr alloy was processed by equal channel angular pressing (ECAP) at 375°C. The grain size of Mg-Gd-Nd-Zn-Zr alloy was refined to ~2.5μm with the spherical precipitates (β1 phase) distributing in the matrix. The mechanical properties of ECAPed alloy were significantly improved as a result of the grain refinement and precipitation strengthening. The corrosion rate of the ECAPed magnesium alloy in simulated body fluid dramatically decreased from 0.236mm/a to 0.126mm/a due to the strong basal texture and refined microstructure. This wrought magnesium alloy shows potentials in biomedical application.

  3. Structural and Thermoelectric Properties of Bi85Sb15 Prepared by Non-equal Channel Angular Extrusion

    Science.gov (United States)

    El-Asfoury, Mohamed S.; Nasr, Mohamed N. A.; Nakamura, Koichi; Abdel-Moneim, Ahmed

    2017-09-01

    We report on the mechanical and transport properties of polycrystalline bulk Bi85Sb15, as a low-temperature thermoelectric material. Bi85Sb15 samples were prepared by mechanical alloying and hot isostatic pressing, followed by sever plastic deformation (SPD). SPD was applied by either equal channel angular extrusion (ECAE) or non-equal channel angular extrusion (NECAE), at two different temperatures (373 K and 423 K). X-ray diffraction and scanning electron microscopy were used to characterize the prepared samples. The transport properties including the electrical conductivity, Seebeck coefficient and thermal conductivity were investigated, and correlated with the microstructure over the temperature range of 160-360 K. NECAE was found to be more effective than ECAE in enhancing bulk density, grain refinement and preferential grain orientation along the extrusion direction, particularly at higher processing temperatures. This is attributed to the better grain alignment and the creation of more intense grain boundaries and dislocation density, which resulted in an enhancement in carrier mobility and phonon scattering and hence a higher Z value. The highest Z value was achieved via NECAE at 423 K, and had a value of 0.39 × 10-3 K-1 at 250 K, which is 55% higher than that of the hot-pressed sample, 0.22 × 10-3 K-1 at 270 K. Also, the micro-hardness of the hot-pressed sample increases by at least 20% by SPD processes. Accordingly, optimized SPD can be classified as an effective processing tool for feasible mass production of bulk Bi85Sb15 alloy with better thermoelectric performance.

  4. Long-term evolution of strongly nonlinear internal solitary waves in a rotating channel

    Directory of Open Access Journals (Sweden)

    J. C. Sánchez-Garrido

    2009-09-01

    Full Text Available The evolution of internal solitary waves (ISWs propagating in a rotating channel is studied numerically in the framework of a fully-nonlinear, nonhydrostatic numerical model. The aim of modelling efforts was the investigation of strongly-nonlinear effects, which are beyond the applicability of weakly nonlinear theories. Results reveal that small-amplitude waves and sufficiently strong ISWs evolve differently under the action of rotation. At the first stage of evolution an initially two-dimensional ISW transforms according to the scenario described by the rotation modified Kadomtsev-Petviashvili equation, namely, it starts to evolve into a Kelvin wave (with exponential decay of the wave amplitude across the channel with front curved backwards. This transition is accompanied by a permanent radiation of secondary Poincaré waves attached to the leading wave. However, in a strongly-nonlinear limit not all the energy is transmitted to secondary radiated waves. Part of it returns to the leading wave as a result of nonlinear interactions with secondary Kelvin waves generated in the course of time. This leads to the formation of a slowly attenuating quasi-stationary system of leading Kelvin waves, capable of propagating for several hundreds hours as a localized wave packet.

  5. Effect of Equal Channel Angular Pressing on the Surface Roughness of Solid State Recycled Aluminum Alloy 6061 Chips

    Directory of Open Access Journals (Sweden)

    Adel Taha Abbas

    2017-01-01

    Full Text Available Solid state recycling through hot extrusion is a promising technique to recycle machining chips without remelting. Furthermore, equal channel angular pressing (ECAP technique coupled with the extruded recycled billet is introduced to enhance the mechanical properties of recycled samples. In this paper, the surface roughness of solid state recycled aluminum alloy 6061 turning chips was investigated. Aluminum chips were cold compacted and hot extruded under an extrusion ratio (ER of 5.2 at an extrusion temperature (ET of 425°C. In order to improve the properties of the extruded samples, they were subjected to ECAP up to three passes at room temperature using an ECAP die with a channel die angle (Φ of 90°. Surface roughness (Ra and Rz of the processed recycled billets machined by turning was investigated. Box-Behnken experimental design was used to investigate the effect of three machining parameters (cutting speed, feed rate, and depth of cut on the surface roughness of the machined specimens for four materials conditions, namely, extruded billet and postextrusion ECAP processed billets to one, two, and three passes. Quadratic models were developed to relate the machining parameters to surface roughness, and a multiobjective optimization scheme was conducted to maximize material removal rate while maintaining the roughness below a preset practical value.

  6. Effect of Equal Channel Angular Pressing on the Microstructure and Mechanical Properties of Al6061-SiCp Composites

    Science.gov (United States)

    Lokesh, T.; Mallik, U. S.

    2016-09-01

    In the present study, Aluminium metal matrix composite with Al6061 matrix and SiC (10-30μm) particulate reinforcement of varying composition (2-10wt.%) were prepared by stir casting technique. Significant improvement in tensile strength and hardness was noticed as the wt.% of SiCp increases in as cast Al6061- SiC composites. The cast composites have been subjected to annealing treatment at a temperature of 400oC for 4 hours to homogenize the microstructure. The specimens have been prepared from these composites for Equal Channel Angular Pressing (ECAP). The ECAP process was carried out at room temperature using a die with channel angle of 120° and Bc route was adopted for successive passes. The effect of ECAP on the microstructure and mechanical properties of Al6061 -SiC composite is evaluated. After ECAP process, the size and distribution of the reinforcement particles are not changed but there is a significant reduction in the grain size of the matrix alloy was observed. The hardness and tension tests were conducted at room temperature as per ASTM standards. The results were compared with the base Al6061 material and as cast Al6061-SiC composites. There is a significant improvement in the hardness and the Ultimate tensile strength of ECAP processed composites.

  7. Nonlinear Channel Estimation for OFDM System by Complex LS-SVM under High Mobility Conditions

    CERN Document Server

    Charrada, Anis; 10.5121/ijwmn.2011.3412

    2011-01-01

    A nonlinear channel estimator using complex Least Square Support Vector Machines (LS-SVM) is proposed for pilot-aided OFDM system and applied to Long Term Evolution (LTE) downlink under high mobility conditions. The estimation algorithm makes use of the reference signals to estimate the total frequency response of the highly selective multipath channel in the presence of non-Gaussian impulse noise interfering with pilot signals. Thus, the algorithm maps trained data into a high dimensional feature space and uses the structural risk minimization (SRM) principle to carry out the regression estimation for the frequency response function of the highly selective channel. The simulations show the effectiveness of the proposed method which has good performance and high precision to track the variations of the fading channels compared to the conventional LS method and it is robust at high speed mobility.

  8. Channel coupling in neutron inelastic scattering by even--even nuclei with 48less than or equal toAless than or equal to64 at energies up to 9. 0 MeV

    Energy Technology Data Exchange (ETDEWEB)

    Ivanova, S.P.; Cabezas, R.; Korzh, I.A.; Lunev, V.P.; Mishchenko, V.A.; Pravdivyi, N.M.

    1987-08-01

    Cross sections for excitation of one-phonon and two-phonon levels of 48 less than or equal to A less than or equal to 64 nuclei by neutrons with energies from threshold up to 9.0 MeV are analyzed in the optical-statistical approach using the coupled-channel method with various numbers of channels taken into account. Analysis of the theoretical calculations and their comparison with experimental data show that the cross sections for direct excitation of the one-phonon levels of the nuclei studied depend on the number of channels taken into account as well as on the deformation parameter ..beta../sub 2//sub J/, and that in the energy region under investigation the levels of the two-phonon triplet are excited primarily through the compound nucleus since the cross sections for their direct excitation are very small

  9. Crunch-in regime - Non-linearly driven hollow-channel plasma

    CERN Document Server

    Sahai, Aakash A

    2016-01-01

    Plasma wakefields driven inside a hollow-channel plasma are significantly different from those driven in a homogeneous plasma. This work investigates the scaling laws of the accelerating and focusing fields in the "crunch-in" regime. This regime is excited due to the collapse of the electron-rings from the channel walls onto the propagation axis of the energy-source, in its wake. This regime is thus the non-linearly driven hollow channel, since the electron-ring displacement is of the order of the channel radius. We present the properties of the coherent structures in the "crunch-in" regime where the channel radius is matched to the beam properties such that channel-edge to on-axis collapse time has a direct correspondence to the energy source intensity. We also investigate the physical mechanisms that underlie the "crunch-in" wakefields by tuning the channel radius. Using a theoretical framework and results from PIC simulations the possible applications of the "crunch-in" regime for acceleration of positron ...

  10. A Lower Bound on the per Soliton Capacity of the Nonlinear Optical Fibre Channel

    CERN Document Server

    Shevchenko, Nikita A; Derevyanko, Stanislav A; Alvarado, Alex; Bayvel, Polina; Turitsyn, Sergei K

    2015-01-01

    A closed-form expression for a lower bound on the per soliton capacity of the nonlinear optical fibre channel in the presence of (optical) amplifier spontaneous emission (ASE) noise is derived. This bound is based on a non-Gaussian conditional probability density function for the soliton amplitude jitter induced by the ASE noise and is proven to grow logarithmically as the signal-to-noise ratio increases.

  11. High Capacity Phase/Amplitude Modulated Optical Communication Systems and Nonlinear Inter-Channel Impairments

    Science.gov (United States)

    Tavassoli, Vahid

    This thesis studies and mathematically models nonlinear interactions among channels of modern high bit rate (amplitude/) phase modulated optical systems. First, phase modulated analogue systems are studied and a differential receiving method is suggested with experimental validation. The main focus of the rest of the thesis is on digital advanced modulation format systems. Cross-talk due to fiber Kerr nonlinearity in two-format hybrid systems as well as 16-QAM systems is mathematically modelled and verified by simulation for different system parameters. A comparative study of differential receivers and coherent receivers is also given for hybrid systems. The model is based on mathematically proven assumptions and provides an intuitive analytical understanding of nonlinear cross-talk in such systems.

  12. Experimental demonstration of tunable homodyne detection of WDM and dual-polarization PSK channels by automatically locking the channels to a local pump laser using nonlinear mixing.

    Science.gov (United States)

    Almaiman, Ahmed; Ziyadi, Morteza; Mohajerin-Ariaei, Amirhossein; Cao, Yinwen; Chitgarha, Mohammad Reza; Liao, Peicheng; Bao, Changjing; Shamee, Bishara; Ahmed, Nisar; Alishahi, Fatemeh; Fallahpour, Ahmad; Akasaka, Youichi; Yang, Jeng-Yuan; Sekiya, Motoyoshi; Touch, Joseph D; Tur, Moshe; Langrock, Carsten; Fejer, Martin M; Willner, Alan E

    2016-06-15

    This Letter proposes a method for tunable automatically locked homodyne detection of wavelength-division multiplexing (WDM) dual-polarization (DP) phase-shift keyed (PSK) channels using nonlinear mixing. Two stages of periodically poled lithium niobate (PPLN) waveguides and an LCoS filter enable automatic phase locking of the channels to a local laser.

  13. Impulsive interference in communication channels and its mitigation by SPART and other nonlinear filters

    Science.gov (United States)

    Nikitin, Alexei V.; Epard, Marc; Lancaster, John B.; Lutes, Robert L.; Shumaker, Eric A.

    2012-12-01

    A strong digital communication transmitter in close physical proximity to a receiver of a weak signal can noticeably interfere with the latter even when the respective channels are tens or hundreds of megahertz apart. When time domain observations are made in the signal chain of the receiver between the first mixer and the baseband, this interference is likely to appear impulsive. The impulsive nature of this interference provides an opportunity to reduce its power by nonlinear filtering, improving the quality of the receiver channel. This article describes the mitigation, by a particular nonlinear filter, of the impulsive out-of-band (OOB) interference induced in High Speed Downlink Packet Access (HSDPA) by WiFi transmissions, protocols which coexist in many 3G smartphones and mobile hotspots. Our measurements show a decrease in the maximum error-free bit rate of a 1.95 GHz HSDPA receiver caused by the impulsive interference from an OOB 2.4 GHz WiFi transmission, sometimes down to a small fraction of the rate observed in the absence of the interference. We apply a nonlinear SPART filter to recover a noticeable portion of the lost rate and maintain an error-free connection under much higher levels of the WiFi interference than a receiver that does not contain such a filter. These measurements support our wider investigation of OOB interference resulting from digital modulation, which appears impulsive in a receiver, and its mitigation by nonlinear filters.

  14. Next-to-leading-order corrections to capacity for a nondispersive nonlinear optical fiber channel in the intermediate power region

    Science.gov (United States)

    Panarin, A. A.; Reznichenko, A. V.; Terekhov, I. S.

    2017-01-01

    We consider the optical fiber channel modeled by the nonlinear Schrödinger equation with zero dispersion and additive Gaussian noise. Using the Feynman path-integral approach for the model, we find corrections to conditional probability density function, output signal distribution, conditional and output signal entropies, and the channel capacity at large signal-to-noise ratio. We demonstrate that the correction to the channel capacity is positive for large signal power. Therefore, this correction increases the earlier calculated capacity for a nondispersive nonlinear optical fiber channel in the intermediate power region.

  15. Evolution of Channels Draining Mount St. Helens: Linking Non-Linear and Rapid, Threshold Responses

    Science.gov (United States)

    Simon, A.

    2010-12-01

    The catastrophic eruption of Mount St. Helens buried the valley of the North Fork Toutle River (NFT) to a depth of up to 140 m. Initial integration of a new drainage network took place episodically by the “filling and spilling” (from precipitation and seepage) of depressions formed during emplacement of the debris avalanche deposit. Channel incision to depths of 20-30 m occurred in the debris avalanche and extensive pyroclastic flow deposits, and headward migration of the channel network followed, with complete integration taking place within 2.5 years. Downstream reaches were converted from gravel-cobble streams with step-pool sequences to smoothed, infilled channels dominated by sand-sized materials. Subsequent channel evolution was dominated by channel widening with the ratio of changes in channel width to changes in channel depth ranging from about 60 to 100. Widening resulted in significant adjustment of hydraulic variables that control sediment-transport rates. For a given discharge over time, flow depths were reduced, relative roughness increased and flow velocity and boundary shear stress decreased non-linearly. These changes, in combination with coarsening of the channel bed with time resulted in systematically reduced rates of degradation (in upstream reaches), aggradation (in downstream reaches) and sediment-transport rates through much of the 1990s. Vertical adjustments were, therefore, easy to characterize with non-linear decay functions with bed-elevation attenuating with time. An empirical model of bed-level response was then created by plotting the total dimensionless change in elevation against river kilometer for both initial and secondary vertical adjustments. High magnitude events generated from the generated from upper part of the mountain, however, can cause rapid (threshold) morphologic changes. For example, a rain-on-snow event in November 2006 caused up to 9 m of incision along a 6.5 km reach of Loowit Creek and the upper NFT. The event

  16. Studies on effects of feedback delay on the convergence performance of adaptive time-domain equalizers for fiber dispersive channels

    Science.gov (United States)

    Guo, Qun; Xu, Bo; Qiu, Kun

    2016-04-01

    Adaptive time-domain equalizer (TDE) is an important module for digital optical coherent receivers. From an implementation perspective, we analyze and compare in detail the effects of error signal feedback delay on the convergence performance of TDE using either least-mean square (LMS) or constant modulus algorithm (CMA). For this purpose, a simplified theoretical model is proposed based on which iterative equations on the mean value and the variance of the tap coefficient are derived with or without error signal feedback delay for both LMS- and CMA-based methods for the first time. The analytical results show that decreased step size has to be used for TDE to converge and a slower convergence speed cannot be avoided as the feedback delay increases. Compared with the data-aided LMS-based method, the CMA-based method has a slower convergence speed and larger variation after convergence. Similar results are confirmed using numerical simulations for fiber dispersive channels. As the step size increases, a feedback delay of 20 clock cycles might cause the TDE to diverge. Compared with the CMA-based method, the LMS-based method has a higher tolerance on the feedback delay and allows a larger step size for a faster convergence speed.

  17. Tensile properties of 2024 Al alloy processed by enhanced solid-solution and equal-channel angular pressing

    Institute of Scientific and Technical Information of China (English)

    XU Xiao-jing; GAO Jin-qi; CHENG Xiao-nong; MO Ji-ping

    2006-01-01

    Equal-channel angular pressing(ECAP) of an enhanced solid-solution treated 2024 Al alloy was successfully performed at room temperature, with an imposed equivalent normal strain of about 0.5. A very high hardness about HV191 and yield strength about 610 MPa (30% higher than those of the unECAPed 2024 Al alloy) in terms of commercial aluminum alloys were observed for the ECAPed 2024 Al alloy. In addition to the strengthening, this process allows the ECAPed 2024 Al alloy have a moderate level of tensile ductility (about 12.7%) and a significant strain hardening capability up to tensile failure. After aged at 373 K for 48 h, the ECAPed alloy increases its hardness (about HV201) and tensile ductility (about 14 %) further. The TEM results show that the ECAPed 2024 Al alloy presents a plate structure (about 50-100 nm) with high density of dislocation and additional thin plate (approximately <10 nm= inside. The XRD results show that the ECAP processing decreases the texture and increases the dislocation density of the alloy considerably. The theoretical calculations show that the increase of dislocation density resulting from ECAP processing makes a considerable contribution about 55.2% for the improvement of yield strength.

  18. Influence of Particulate Reinforcement and Equal-Channel Angular Pressing on Fatigue Crack Growth of an Aluminum Alloy

    Directory of Open Access Journals (Sweden)

    Lisa Köhler

    2015-05-01

    Full Text Available The fatigue crack growth behavior of unreinforced and particulate reinforced Al 2017 alloy, manufactured by powder metallurgy and additional equal-channel angular pressing (ECAP, is investigated. The reinforcement was done with 5 vol % Al2O3 particles with a size fraction of 0.2–2 µm. Our study presents the characterization of these materials by electron microscopy, tensile testing, and fatigue crack growth measurements. Whereas particulate reinforcement leads to a drastic decrease of the grain size, the influence of ECAP processing on the grain size is minor. Both reinforced conditions, with and without additional ECAP processing, exhibit reduced fatigue crack growth thresholds as compared to the matrix material. These results can be ascribed to the well-known effect of the grain size on the crack growth, since crack deflection and closure are directly affected. Despite their small grain size, the thresholds of both reinforced conditions depend strongly on the load ratio: tests at high load ratios reduce the fatigue threshold significantly. It is suggested that the strength of the particle-matrix-interface becomes the critical factor here and that the particle fracture at the interfaces dominates the failure behavior.

  19. Interfacial Microstructure and Mechanical Properties of Al Alloy/Mg Alloy Laminated Composite Plates Fabricated by Equal Channel Angular Processing

    Institute of Scientific and Technical Information of China (English)

    LI Guorui; ZHAO Dong; ZHAO Yaojiang; ZHOU Bin; WANG Hongxia

    2016-01-01

    KAl (7075) alloy /Mg (AZ31) alloy laminated composite plates were successfully fabricated by the equal channel angular processing (ECAP) by using route A for 1, 2, and 3 passes at 573 K, respectively. After fabrication, the 1-pass ECAPed laminated composite plates were annealed at different temperatures. The microstructure evolution, phase constituent, and bonding strength near the joining interface of Al (7075) alloy /Mg (AZ31) alloy laminated composites plates were evaluated with scanning electron microscopy, X-ray diffraction, and shear tests. The experimental results indicated that a 20 μm diffusion layer was observed at the joining interface of Al (7075) alloy /Mg (AZ31) alloy laminated composites plates fabricated by the 1-pass ECAP, which mainly included Al3Mg2 and Mg17Al12 phases. With the increase of passes, the increase of diffusion layer thickness was not obvious and the form of crack in these processes led to the decrease of bonding strength. For 1-pass ECAPed composites, the thickness of diffusion layer remained unchanged after annealed at 473 K, while the bonding strength reached its maximum value 29.12 MPa. However, after elevating heat treatment temperature to 573 K, the thickness of diffusion layer increased rapidly, and thus the bonding strength decreased.

  20. Bulk Ultrafine-Grained Interstitial-Free Steel Processed by Equal-Channel Angular Pressing Followed by Flash Annealing

    Science.gov (United States)

    Verma, Deepa; Pandey, Shobhit A.; Bansal, Anushka; Upadhyay, Shwetank; Mukhopadhyay, N. K.; Sastry, G. V. S.; Manna, R.

    2016-12-01

    Interstitial-free steel workpieces are deformed by equal-channel angular pressing (ECAP) for equivalent strain ɛvm = 3 and ɛvm = 21 followed by flash annealing. Microstructures are analyzed by optical microscopy, scanning electron microscopy and transmission electron microscopy. Mechanical properties are evaluated by hardness testing. Yield strength of materials is calculated from hardness values. Flash annealing (at 675 °C) of ECAPed samples for ɛvm = 3 and ɛvm = 21 results in abnormal subgrain growth and abnormal grain growth, respectively. Flash annealing at 700 °C of ECAPed (at ɛvm = 3) IF steel converts abnormally grown subgrains to grains which serve as nuclei for recrystallization and that result in bimodal grain size distribution. Bimodal grain size distribution is also produced when ECAPed IF steel for ɛvm = 21 is flash annealed at 675 °C due to abnormal grain growth or secondary recrystallization. Flash annealing of IF steel samples ECAPed for low ɛvm, in the temperature range 600-675 °C, decreases the hardness continuously with increase in the annealing temperature but it increases at high ɛvm. The former is due to annihilation of defects but the later is caused by ordering of nonequilibrium boundaries. The hardening and strengthening behaviors are similar.

  1. Study of twin-roll cast Aluminium alloys subjected to severe plastic deformation by equal channel angular pressing

    Science.gov (United States)

    Poková, M.; Cieslar, M.

    2014-08-01

    Aluminium alloys prepared by twin-roll casting method become widely used in industry applications. Their high solid solution supersaturation and finer grains ensure better mechanical properties when compared with the direct-chill cast ones. One of the possibilities how to enhance their thermal stability is the addition of zirconium. After heat treatment Al3Zr precipitates form and these pin moving grain boundaries when the material is exposed to higher temperatures. In the present work twin-roll cast aluminium alloys based on AA3003 with and without Zr addition were annealed for 8 hours at 450 °C to enable precipitation of Al3Zr phase. Afterwards they were subjected to severe plastic deformation by equal channel angular pressing, which led to the reduction of average grain size under 1 μm. During subsequent isochronal annealing recovery and recrystallization took place. These processes were monitored by microhardness measurements, light optical microscopy and in-situ transmission electron microscopy. The addition of Zr stabilizes the grain size and increases the recrystallization temperature by 100 °C.

  2. Microstructure and texture evolution in a Cu–Ni–Si alloy processed by equal-channel angular pressing

    Energy Technology Data Exchange (ETDEWEB)

    Hadj Larbi, Fayçal; Azzeddine, Hiba [Faculté de Physique, USTHB, BP 32 El-Alia, Dar El Beida, Alger (Algeria); Baudin, Thierry [Université de Paris Sud, ICMMO, UMR CNRS 8182, Laboratoire de physico-chimie de l’état solide, Bâtiment 410, 91405 Orsay Cedex (France); Mathon, Marie-Hélène [Laboratoire Léon Brillouin, CEA-CNRS, CEA/Saclay, 91191 Gif-sur-Yvette (France); Brisset, François; Helbert, Anne-Laure [Université de Paris Sud, ICMMO, UMR CNRS 8182, Laboratoire de physico-chimie de l’état solide, Bâtiment 410, 91405 Orsay Cedex (France); Kawasaki, Megumi, E-mail: megumi@hanyang.ac.kr [Division of Materials Science and Engineering, Hanyang University, 17 Haengdang-dong, Seongdong-gu, Seoul 133-791 (Korea, Republic of); Departments of Aerospace & Mechanical Engineering and Materials Science, University of Southern California, Los Angeles, CA 90089-1453 (United States); Bradai, Djamel [Faculté de Physique, USTHB, BP 32 El-Alia, Dar El Beida, Alger (Algeria); Langdon, Terence G. [Departments of Aerospace & Mechanical Engineering and Materials Science, University of Southern California, Los Angeles, CA 90089-1453 (United States); Materials Research Group, Faculty of Engineering and the Environment, University of Southampton, Southampton SO17 1BJ (United Kingdom)

    2015-07-25

    Highlights: • A Cu–Ni–Si alloy is processed by ECAP up to 12 passes at 423 K through route A. • The texture after ECAP is characterized by typical shear components of fcc metals. • ECAP leads to randomization of the texture with increasing numbers of passes. • ECAP through route A rotates the texture positions from the ideal component. - Abstract: Experiments were conducted to evaluate the evolution of microstructure and texture in a commercial Cu–2.5Ni–0.6Si (wt.%) alloy processed by equal-channel angular pressing (ECAP) at 423 K for up to 12 passes. An electron backscatter diffraction (EBSD) analysis shows that ECAP processing leads to microstructural refinement with an average grain size of ∼0.9 μm. The refined grains are inclined to the direction of extrusion and the deformation structure evolves from elongated grains to a duplex microstructure of equiaxed and elongated grains. Detailed measurements demonstrate that the grain boundary misorientations gradually increase with increasing numbers of ECAP passes. The texture was investigated using both EBSD and neutron diffraction. The results show the texture after ECAP is characterized by typical shear components of face-centered cubic metals which deviate from their ideal positions.

  3. Development of ultrafine-grained microstructure in Al-Cu-Mg alloy through equal-channel angular pressing

    Science.gov (United States)

    Sai Anuhya, Danam; Gupta, Ashutosh; Nayan, Niraj; Narayana Murty, S. V. S.; Manna, R.; Sastry, G. V. S.

    2014-08-01

    Al-Cu-Mg alloys are extensively used for riveting applications in aerospace industries due to their relatively high shear strength coupled with high plasticity. The significant advantage of using V65 aluminum alloy ((Al-4Cu-0.2Mg) for rivet application also stems from its significantly slower natural aging kinetics, which gives operational flexibility to carryout riveting operation even after 4 days of solution heat treatment, in contrast to its equivalent alloy AA2024.Rivets are usually made by cold heading of wire rods. In order to form a defect free rivet head, grain size control in wire rods is essential at each and every stage of processing right from casting onwards upto the final wire drawing stage. Wire drawing is carried out at room temperature to reduce diameter as well as impart good surface finish. In the present study, different microstructures in V65 alloy bars were produced by rolling at different temperatures (room temperature to 523K) and subsequently deformed by equal channel angular pressing (ECAP) at 423K upto an equivalent strain of 7. ECAP was carried out to study the effect of initial microstructure on grain refinement and degree of deformation on the evolution of ultrafine grain structure. The refinement of V65 alloy by ECAP is significantly influenced by Initial microstructure but amount of deformation strongly affects the evolution processes as revealed by optical microscopy and transmission electron microscopy.

  4. Effect of equal channel angular extrusion on the microstructure and superplasticity of an Al-Li alloy

    Science.gov (United States)

    Salem, H. G.; Lyons, J. S.

    2002-08-01

    This research investigates the use of equal channel angular extrusion (ECAE) processing to produce a superplastic form of the aluminum alloy 2098. The starting material was a hot-rolled and precipitation-hardened plate with elongated grains of width 67-92 µm, and a composition in weight percent of 2.2% Li, 1.3% Cu, 0.73% Mg, 0.05% Zr, balance Al. Microstructural evolution was investigated with optical and transmission electron microscopy (TEM) and microhardness measurements after each step of a multipass ECAE process. ECAE produced a submicron grain structure with an average size of about 0.5 µm. The sub-grain microstructure size was a function of the magnitude of the input strain and the extrusion temperature. Misorientation angles of the developed submicron structure increase with increasing number of passes at warm working temperatures. Superplastic behavior of the ECAE-processed alloy was achieved. However, the low zirconium content of the 2098 alloy resulted in grain growth of the refined structure at the superplastic processing temperatures, placing a lower limit on the deformation rates that can be used.

  5. Microstructure and Mechanical Properties of Ultrafine-Grained Copper Produced Using Intermittent Ultrasonic-Assisted Equal-Channel Angular Pressing

    Science.gov (United States)

    Lu, Jianxun; Wu, Xiaoyu; Liu, Zhiyuan; Chen, Xiaoqiang; Xu, Bin; Wu, Zhaozhi; Ruan, Shuangchen

    2016-09-01

    We proposed intermittent ultrasonic-assisted equal-channel angular pressing (IU-ECAP) and used it to produce ultrafine-grained copper. The main aim of this work was to investigate the microstructure and mechanical properties of copper processed by IU-ECAP. We performed experiments with two groups of specimens: group 1 used conventional ECAP, and group 2 combined ECAP with intermittent ultrasonic vibration. The extrusion forces, microstructure, mechanical properties, and thermal stability of the two groups were compared. It was revealed that more homogeneous microstructure with smaller grains could be obtained by IU-ECAP compared with copper obtained using the traditional ECAP method. Mechanical testing showed that IU-ECAP significantly reduced the extrusion force and increased both the hardness and ultimate tensile stress owing to the higher dislocation density and smaller grains. IU-ECAP promotes conversion from low-angle grain boundaries to high-angle grain boundaries, and it increases the fractions of subgrains and dynamic recrystallized grains. Group 2 statically recrystallized at a higher temperature or longer duration than group 1, showing that group 2 had better thermal stability.

  6. The Effect of SRS on Signal Power in Single-mode Silica Fiber in DWDM Optical Communication System with Equally Spaced Channels

    Institute of Scientific and Technical Information of China (English)

    GONG Jiamin; FANG Qiang; LIU Juan; WANG Yongchang

    2000-01-01

    Assuming that the Raman gain profile of silica fiber is a triangular function, we derive analytic solutions of N-channel steady-state forward SRS coupling wave equation with equal (but arbitrary) channel spacing. Considering the SRS cross coupling among N-channels, the analytic solutions are applicable to arbitrary signal light power. The results point out that the sequence mi=pi(z)/pi(0) [pi(z) and pi(0) is the power of signal light of i-th channel at transmission length z and 0, respectively. i=1,2,...N] maintains a geometric progression with the common ratio q in the transmission process. The common ratio q varies as a exponential function of the effective transmission length, the sum of input light power and the channel spacing, respectively.

  7. Analysis of Nonlinear Dispersion of a Pollutant Ejected by an External Source into a Channel Flow

    Directory of Open Access Journals (Sweden)

    T. Chinyoka

    2010-01-01

    Full Text Available This paper focuses on the transient analysis of nonlinear dispersion of a pollutant ejected by an external source into a laminar flow of an incompressible fluid in a channel. The influence of density variation with pollutant concentration is approximated according to the Boussinesq approximation, and the nonlinear governing equations of momentum and pollutant concentration are obtained. The problem is solved numerically using a semi-implicit finite difference method. Solutions are presented in graphical form and given in terms of fluid velocity, pollutant concentration, skin friction, and wall mass transfer rate for various parametric values. The model can be a useful tool for understanding the polluting situations of an improper discharge incident and evaluating the effects of decontaminating measures for the water body.

  8. Suppression of space charge induced beam halo in nonlinear focusing channel

    Science.gov (United States)

    Batygin, Yuri K.; Scheinker, Alexander; Kurennoy, Sergey; Li, Chao

    2016-04-01

    An intense non-uniform particle beam exhibits strong emittance growth and halo formation in focusing channels due to nonlinear space charge forces of the beam. This phenomenon limits beam brightness and results in particle losses. The problem is connected with irreversible distortion of phase space volume of the beam in conventional focusing structures due to filamentation in phase space. Emittance growth is accompanied by halo formation in real space, which results in inevitable particle losses. A new approach for solving a self-consistent problem for a matched non-uniform beam in two-dimensional geometry is discussed. The resulting solution is applied to the problem of beam transport, while avoiding emittance growth and halo formation by the use of nonlinear focusing field. Conservation of a beam distribution function is demonstrated analytically and by particle-in-cell simulation for a beam with a realistic beam distribution.

  9. Suppression of Space Charge Induced Beam Halo in Nonlinear Focusing Channel

    CERN Document Server

    Batygin, Yuri K; Kurennoy, Sergey; Li, Chao

    2016-01-01

    An intense non-uniform particle beam exhibits strong emittance growth and halo formation in focusing channels due to nonlinear space charge forces of the beam. This phenomenon limits beam brightness and results in particle losses. The problem is connected with irreversible distortion of phase space volume of the beam in conventional focusing structures due to filamentation in phase space. Emittance growth is accompanied by halo formation in real space, which results in inevitable particle losses. A new approach for solving a self-consistent problem for a matched non-uniform beam in two-dimensional geometry is discussed. The resulting solution is applied to the problem of beam transport, while avoiding emittance growth and halo formation by the use of nonlinear focusing field. Conservation of a beam distribution function is demonstrated analytically and by particle-in-cell simulation for a beam with a realistic beam distribution.

  10. Cochannel and Adjacent-Channel Interference in Nonlinear Minimum-Shift-Keyed Satellite System

    Science.gov (United States)

    Yu, John

    1995-01-01

    The interference susceptibility of a serial-minimum-shift-keyed (SMSK) modulation system to an interfering signal transmitted through a satellite link with cascaded nonlinear elements was investigated through computer simulation. The satellite link evaluated in this study represented NASA's Advanced Communications Technology Satellite (ACTS) system. Specifically, nonlinear characteristics were used that had specified amplitude-modulation to amplitude-modulation and amplitude-modulation to phase-modulation transfer characteristics obtained from the actual ACTS hardware. Two measurement scenarios were analyzed: degradation of an MSK satellite link from cochannel interference and from adjacent-channel interference. Interference was evaluated in terms of the probability of bit error rate (BER) versus energy per bit over noise power density Eb/No.

  11. Mechanical Behaviors of Ultrafine-Grained 301 Austenitic Stainless Steel Produced by Equal-Channel Angular Pressing

    Science.gov (United States)

    Huang, C. X.; Yang, G.; Wang, C.; Zhang, Z. F.; Wu, S. D.

    2011-07-01

    The technique of equal-channel angular pressing (ECAP) was used to refine the microstructure of an AISI 301 austenitic stainless steel (SS). An ultrafine-grained (UFG) microstructure consisting mainly of austenite and a few martensite was achieved in 301 steel after ECAP processing for four passes at 523 K (250 °C). By submitting the as-ECAP rods to annealing treatment in the temperature range from 853 K to 893 K (580 °C to 620 °C) for 60 minutes, fully austenitic microstructures with grain sizes of 210 to 310 nm were obtained. The uniaxial tensile tests indicated that UFG 301 austenitic SS had an excellent combination of high yield strength (>1.0 GPa) and high elongation-to-fracture (>30 pct). The tensile stress-strain curves exhibited distinct yielding peak followed by obvious Lüders deformation. Measurements showed that Lüders elongation increased with an increase in strength as well as a decrease in grain size. The microstructural changes in ultrafine austenite grains during tensile deformation were tracked by X-ray diffraction and transmission electron microscope. It was found that the strain-induced phase transformation from austenite to martensite took place soon after plastic deformation. The transformation rate with strain and the maximum strain-induced martensite were promoted significantly by ultrafine austenite grains. The enhanced martensitic transformation provided extra strain-hardening ability to sustain the propagation of Lüders bands and large uniform plastic deformation. During tensile deformation, the Lüders bands and martensitic transformation interacted with each other and made great contribution to the excellent mechanical properties in UFG austenitic SS.

  12. Ultra-High-Strength Interstitial-Free Steel Processed by Equal-Channel Angular Pressing at Large Equivalent Strain

    Science.gov (United States)

    Verma, Deepa; Mukhopadhyay, N. K.; Sastry, G. V. S.; Manna, R.

    2016-04-01

    The billets of interstitial-free (IF) steel are deformed by equal-channel angular pressing (ECAP) at 298 K (25 °C) adopting the route BC up to an equivalent strain ( ɛ vm) of 24. The evolution of microstructures and their effects on the mechanical properties are examined. The microstructural refinement involves the elongation of grains, the subdivision of grains to the bands with high dislocation density, and the splitting of bands into the cell blocks and then cell blocks into the cells. The widths of the bands and the size of cells decrease with strain. The degree of reduction in the grain size is highest at the low strain level. However, most of the boundaries at this stage are of low-angle boundaries (at ɛ vm = 3). Thereafter, the misorientation angle increases by progressive lattice rotation with strain. The coarse bands transform step by step from the lamellar structure to the ribbon-shaped grains and finally to the near-equiaxed grain structures with the subgrains of a saturated low-angle grain boundary fraction of 0.34 at very large strain >15. The as-received coarse-grained microstructure (grain size of 57.6 ± 21 µm) has been refined to 257 ± 48 nm at an equivalent strain of 24. The strength increases considerably up to ɛ vm = 3 due to grain refinement and high dislocation density. However, the strengthening at later stages is mainly due to the increase in misorientation angle and refinement. Initial yield strength of 227 MPa is increased to a record value of 895 MPa on straining up to ɛ vm = 24 at 298 K (25 °C). Uniform elongation decreases drastically at low equivalent strain but it regains marginally later. The ECAPed sample fails by a ductile fracture at ɛ vm = 0.6 to 6 but by a mixed mode of ductile-brittle fracture at larger strain of 9 to 24.

  13. Effect of equal-channel angular pressing on pitting corrosion resistance of anodized aluminum-copper alloy

    Institute of Scientific and Technical Information of China (English)

    In-Joon SON; Hiroaki NAKANO; Satoshi OUE; Shigeo KOBAYASHI; Hisaaki FUKUSHIMA; Zenji HORITA

    2009-01-01

    The effect of equal-channel angular pressing(ECAP) on the pitting corrosion resistance of anodized Al-Cu alloy was investigated by electrochemical techniques in a solution containing 0.2 mol/L AlCl3 and also by surface analysis. Anodizing was conducted for 20 min at 200 and 400 A/m2 in a solution containing 1.53 mol/L H2SO4 and 0.018 5 mol/L Al2(SO4)3-16H2O at 20 ℃. Anodized Al-Cu alloy was immediately dipped in boiling water for 20 min to seal the micro pores present in anodic oxide films. The time required before initiating pitting corrosion of anodized Al-Cu alloy is longer with ECAP than without, indicating that ECAP process improves the pitting corrosion resistance of anodized Al-Cu alloy. Second phase precipitates such as Si, Al-Cu-Mg and Al-Cu-Si-Fe-Mn intermetallic compounds are present in Al-Cu alloy and the size of these precipitates is greatly decreased by application of ECAP. Al-Cu-Mg intermetallic compounds are dissolved during anodization, whereas the precipitates composed of Si and Al-Cu-Si-Fe-Mn remain in anodic oxide films due to their more noble corrosion potential than Al. FE-SEM and EPMA observation reveal that the pitting corrosion of anodized Al-Cu alloy occurs preferentially around Al-Cu-Si-Fe-Mn intermetallic compounds, since the anodic oxide films are absent at the boundary between the normal oxide films and these impurity precipitates. The improvement of pitting corrosion resistance of anodized Al-Cu alloy processed by ECAP appears to be attributed to a decrease in the size of precipitates, which act as origins of pitting corrosion.

  14. Out-of-band and adjacent-channel interference reduction by analog nonlinear filters

    Science.gov (United States)

    Nikitin, Alexei V.; Davidchack, Ruslan L.; Smith, Jeffrey E.

    2015-12-01

    In a perfect world, we would have `brick wall' filters, no-distortion amplifiers and mixers, and well-coordinated spectrum operations. The real world, however, is prone to various types of unintentional and intentional interference of technogenic (man-made) origin that can disrupt critical communication systems. In this paper, we introduce a methodology for mitigating technogenic interference in communication channels by analog nonlinear filters, with an emphasis on the mitigation of out-of-band and adjacent-channel interference. Interference induced in a communications receiver by external transmitters can be viewed as wide-band non-Gaussian noise affecting a narrower-band signal of interest. This noise may contain a strong component within the receiver passband, which may dominate over the thermal noise. While the total wide-band interference seen by the receiver may or may not be impulsive, we demonstrate that the interfering component due to power emitted by the transmitter into the receiver channel is likely to appear impulsive under a wide range of conditions. We give an example of mechanisms of impulsive interference in digital communication systems resulting from the nonsmooth nature of any physically realizable modulation scheme for transmission of a digital (discontinuous) message. We show that impulsive interference can be effectively mitigated by nonlinear differential limiters (NDLs). An NDL can be configured to behave linearly when the input signal does not contain outliers. When outliers are encountered, the nonlinear response of the NDL limits the magnitude of the respective outliers in the output signal. The signal quality is improved in excess of that achievable by the respective linear filter, increasing the capacity of a communications channel. The behavior of an NDL, and its degree of nonlinearity, is controlled by a single parameter in a manner that enables significantly better overall suppression of the noise-containing impulsive components

  15. Modulation/demodulation techniques for satellite communications. Part 3: Advanced techniques. The nonlinear channel

    Science.gov (United States)

    Omura, J. K.; Simon, M. K.

    1982-01-01

    A theory for deducing and predicting the performance of transmitter/receivers for bandwidth efficient modulations suitable for use on the nonlinear satellite channel is presented. The underlying principle used throughout is the development of receiver structures based on the maximum likelihood decision rule and aproximations to it. The bit error probability transfer function bounds developed in great detail in Part 4 is applied to these modulation/demodulation techniques. The effects of the various degrees of receiver mismatch are considered both theoretically and by numerous illustrative examples.

  16. Performance Simulation and Research on Turbo Equalization over SUI Channels%SUI信道下Turbo均衡性能仿真研究

    Institute of Scientific and Technical Information of China (English)

    邓晓平; 马路娟

    2014-01-01

    Turbo均衡能够通过迭代的方式对接收信号进行多次均衡与信道解码处理,从而提高接收机性能。在SUI信道下,对采用单载波调制体制进行信息传输的Turbo均衡性能进行了仿真研究。系统通过对引导符号序列在频域进行基于MMSE准则的信道估计,获取SUI信道的信息,在时域进行基于线性MMSE准则的Turbo均衡处理。 Matlab仿真结果表明,相对于传统的单载波频域均衡方案, Turbo均衡的方案显著提高了整个传输系统的抗衰落性能。%Turbo equalization is an iterative process that repeats equalization and channel decoding to improve receiver perform-ance.The performance of Turbo equalization over SUI channels when using single carrier modulation to transmit information is simulated and researched.The information of SUI channel is obtained through MMSE criterion based channel estimation in frequency domain over pilot symbol sequence,and linear MMSE based Turbo equalization in time domain is carried out.The results of Matlab simulation indi-cate that Turbo equalization can apparently improve the anti-fading performance of the transmission system compared with the traditional solution of SC-FDE.

  17. Thermofluid Behavior of Nonlinear Thermocapillary Solutions in Flow Boiling through Mini⁄Micro Channels

    Science.gov (United States)

    Ono, Naoki; Yoshida, Takahiro; Kaneko, Takahiro; Nishiguchi, Shotaro; Shoji, Masahiro

    The temperature dependency of surface tension of aqueous solutions of some alcohol such as butanol behaves in a nonlinear manner. Namely, the value of surface tension tends to increase, when the solution is heated beyond a temperature. This type of solution is named “nonlinear thermocapillary solution” here. The direction of thermocapillary force in liquid film of the solution on a heated surface acts in the same direction to that of the solutocapillary force. This characteristic will be more marked in small scale systems such as mini⁄micro channels. In this study the liquid behavior of the solution in flow boiling experiments with mini⁄micro tubes was investigated. Butanol aqueous solutions were adopted as test fluids. Pure water and ethanol aqueous solution were also used for comparison. The aim of the study is to observe the liquid motion and to investigate temperature fluctuation in mini⁄micro channels with inner diameter of 1 mm and 0.42 mm. The surface temperature of the tube was measured by using fine K-type thermocouples at the surface of the tubes and the liquid motion was observed by CCD camera system.

  18. Quantification of microstructure refinement in aluminium deformed by equal channel angular extrusion: Route A vs. route Bc in a 90° die

    DEFF Research Database (Denmark)

    Mishin, Oleg; Bowen, Jacob R.; Lathabai, S.

    2010-01-01

    Microstructures in the centre of two commercial purity aluminium billets extruded through a 90° die either with or without 90° rotations between passes have been investigated using electron backscatter diffraction after eight passes of equal channel angular extrusion. Local heterogeneities in the...... in the form of low misorientation regions were present in both samples. The fraction of high-angle boundaries was found to be slightly greater in the sample extruded without rotation....

  19. Blind Equalization Algorithm for SIMO Channel with Common Zeros%适用于含公共零点SIMO信道的盲均衡算法

    Institute of Scientific and Technical Information of China (English)

    薛江; 彭华; 马金全; 李浩

    2012-01-01

    Based on a Single Input Multiple Output(SIMO) model with common zeros, a direct Infinite Impulse Response(IIR) blind equalization algorithm of SIMO channel with common zeros is proposed. The received signals are equalized by the HR prediction equalizer, and the outputs are applied to an adaptive phase rotation algorithm. An optimal MMSE equalizer is introduced to gain better performance when receiver gauss white noise is present. The new algorithm can correct the phase error and reduce the sensitivity to the gauss white noise. Simulation experimental results snow that IIR channel and channel with common zeros both can be equalized well by the algorithm.%在含公共零点单输入多输出(SIMO)模型的基础上,提出一种针对含公共零点的SIMO信道的直接无限冲击响应(ⅡR)肓均衡算法.该算法利用ⅡR预测均衡算法对输入信号进行初始均衡和对均衡结果进行相偏纠正,通过最小均方误差准则提高算法在高斯白噪声环境中的适应性,克服ⅡR预测算法中的相位偏转问题与ⅡR预测算法对信噪比敏感的缺点.仿真实验结果表明,该算法对ⅡR信道及含公共零点信道都具有较好的均衡效果.

  20. Multiple-input multiple-output symbol rate signal digital predistorter for non-linear multi-carrier satellite channels

    OpenAIRE

    Zenteno, Efrain; Piazza, Roberto; M. R. Bhavani Shankar; Rönnow, Daniel; Ottersten, Björn

    2015-01-01

    A digital predistortion (DPD) scheme is presented for non-linear distortion mitigation in multi-carrier satellite communication channels. The proposed DPD has a multiple-input multiple-output architecture similar to data DPD schemes. However, it enhances the mitigation performance of data DPDs using a multi-rate processing algorithm to achieve spectrum broadening of non-linear operators. Compared to single carrier (single-input single-output) signal (waveform) DPD schemes, the proposed DPD ha...

  1. 基于线性预测方法的水声信道最小均方误差盲均衡%Blind Adaptive MMSE Equalization of Underwater Acoustic Channels Based on the Linear Prediction Method

    Institute of Scientific and Technical Information of China (English)

    张银兵; 赵俊渭; 郭业才; 李金明

    2011-01-01

    The problem of blind adaptive equalization of underwater single-input multiple-output (SIMO)acoustic channels was analyzed by using the linear prediction method. Minimum mean square error (MMSE)blind equalizers with arbitrary delay were described on a basis of channel identification. Two methods for calculating linear MMSE equalizers were proposed. One was based on full channel identification and realized using RLS adaptive algorithms, and the other was based on the zero-delay MMSE equalizer and realized using LMS and RLS adaptive algorithms, respectively. Performance of the three proposed algorithms and comparison with two existing zero-forcing (ZF) equalization algorithms were investigated by simulations utilizing two underwater acoustic channels. The results show that the proposed algorithms are robust enough to channel order mismatch. They have almost the same performance as the corresponding ZF algorithms under a high signal-to-noise (SNR) ratio and better performance under a low SNR.

  2. Performance of quadrature overlapped raised-cosine modulation over nonlinear satellite channels

    Science.gov (United States)

    Divsalar, D.; Simon, M. K.

    1981-01-01

    This paper considers the performance evaluation of Staggered Quadrature Overlapped Raised Cosine (SQORC) signal transmission through wideband nonlinear satellite channels in the presence of uplink and downlink additive Gaussian noise. Expressions for the bit error rate are derived for a general transponder model with AM-AM and AM-PM conversion. It is shown that the bit error rate of SQORC is one-half of the sum of the bit error rate of MSK at 2/3 of the uplink signal-to-noise ratio and the bit error rate of Quadriphase Phase-Shift Keying QPSK at 4/3 of the uplink signal-to-noise ratio, whereas the spectrum of SQROC is the product of MSK and QPSK spectra. Numerical results are presented for a transponder which is modelled as a hard limiter.

  3. Role of Density Profiles for the Nonlinear Propagation of Intense Laser Beam through Plasma Channel

    Directory of Open Access Journals (Sweden)

    Sonu Sen

    2014-01-01

    Full Text Available In this work role of density profiles for the nonlinear propagation of intense laser beam through plasma channel is analyzed. By employing the expression for the dielectric function of different density profile plasma, a differential equation for beamwidth parameter is derived under WKB and paraxial approximation. The laser induces modifications of the dielectric function through nonlinearities. It is found that density profiles play vital role in laser-plasma interaction studies. To have numerical appreciation of the results the propagation equation for plasma is solved using the fourth order Runge-Kutta method for the initial plane wave front of the beam, using boundary conditions. The spot size of the laser beam decreases as the beam penetrates into the plasma and significantly adds self-focusing in plasma. This causes the laser beam to become more focused by reduction of diffraction effect, which is an important phenomenon in inertial confinement fusion and also for the understanding of self-focusing of laser pulses. Numerical computations are presented and discussed in the form of graphs for typical parameters of laser-plasma interaction.

  4. Nonlinear theory of nonstationary low Mach number channel flows of freely cooling nearly elastic granular gases.

    Science.gov (United States)

    Meerson, Baruch; Fouxon, Itzhak; Vilenkin, Arkady

    2008-02-01

    We employ hydrodynamic equations to investigate nonstationary channel flows of freely cooling dilute gases of hard and smooth spheres with nearly elastic particle collisions. This work focuses on the regime where the sound travel time through the channel is much shorter than the characteristic cooling time of the gas. As a result, the gas pressure rapidly becomes almost homogeneous, while the typical Mach number of the flow drops well below unity. Eliminating the acoustic modes and employing Lagrangian coordinates, we reduce the hydrodynamic equations to a single nonlinear and nonlocal equation of a reaction-diffusion type. This equation describes a broad class of channel flows and, in particular, can follow the development of the clustering instability from a weakly perturbed homogeneous cooling state to strongly nonlinear states. If the heat diffusion is neglected, the reduced equation becomes exactly soluble, and the solution develops a finite-time density blowup. The blowup has the same local features at singularity as those exhibited by the recently found family of exact solutions of the full set of ideal hydrodynamic equations [I. Fouxon, Phys. Rev. E 75, 050301(R) (2007); I. Fouxon,Phys. Fluids 19, 093303 (2007)]. The heat diffusion, however, always becomes important near the attempted singularity. It arrests the density blowup and brings about previously unknown inhomogeneous cooling states (ICSs) of the gas, where the pressure continues to decay with time, while the density profile becomes time-independent. The ICSs represent exact solutions of the full set of granular hydrodynamic equations. Both the density profile of an ICS and the characteristic relaxation time toward it are determined by a single dimensionless parameter L that describes the relative role of the inelastic energy loss and heat diffusion. At L>1 the intermediate cooling dynamics proceeds as a competition between "holes": low-density regions of the gas. This competition resembles Ostwald

  5. Equal Power Distribution and Dynamic Subcarrier Assignment in OFDM Using Minimum Channel Gain Flow with Robust Optimization Uncertain Demand

    CERN Document Server

    Tun, F A Hla Myo; Naing, T C Zaw Min

    2010-01-01

    In this paper, the minimum channel gain flow with uncertainty in the demand vector is examined. The approach is based on a transformation of uncertainty in the demand vector to uncertainty in the gain vector. OFDM systems are known to overcome the impairment of the wireless channel by splitting the given system bandwidth into parallel sub-carriers, on which data-symbols can be transmitted simultaneously. This enables the possibility of enhancing the system's performance by deploying adaptive mechanisms, namely power distribution and dynamic sub-carrier assignments. The performances of maximizing the minimum throughput have been analyzed by MATLAB codes.

  6. Mechanical Behavior and Microstructural Development of 6063-T1 Aluminum Alloy Processed by Equal-Channel Angular Pressing (ECAP): Pass Number Influence

    Science.gov (United States)

    Serban, Nicolae; Cojocaru, Vasile-Danut; Butu, Mihai

    2012-05-01

    Equal-channel angular pressing (ECAP) is a very interesting method for modifying the microstructure in producing ultrafine-grained materials and nanomaterials. It consists mainly of pressing test samples through a die containing two channels that are equal in cross section and intersect at a certain angle. As a result of pressing, the sample theoretically deforms by simple shear and retains the same cross-sectional area to allow repeat pressing for several cycles. A 6063-T1 aluminum alloy was investigated in this study. The specimens were processed for up to nine passes (one, three, six, and nine ECAP passes, respectively) using a die channel angle of 90°. After ECAP, the samples were cut from each specimen and prepared for metallographic analysis and mechanical testing. The microstructures of the ECAP treated and as-received material were investigated using both optical microscopy and scanning electron microscopy. All samples (ECAP processed and as-received) were mechanically investigated in compression tests. Ultimate compressive strength, yield strength, and compression modulus were obtained. Also, all ECAP processed specimens were investigated for microhardness and compared with the as-received material.

  7. Fuzzy [Formula: see text] output-feedback control for the discrete-time system with channel fadings, sector nonlinearities, and randomly occurring interval delays and nonlinearities.

    Science.gov (United States)

    Fan, Xiaozheng; Wang, Yan; Hu, Manfeng

    2016-01-01

    In this paper, the fuzzy [Formula: see text] output-feedback control problem is investigated for a class of discrete-time T-S fuzzy systems with channel fadings, sector nonlinearities, randomly occurring interval delays (ROIDs) and randomly occurring nonlinearities (RONs). A series of variables of the randomly occurring phenomena obeying the Bernoulli distribution is used to govern ROIDs and RONs. Meanwhile, the measurement outputs are subject to the sector nonlinearities (i.e. the sensor saturations) and we assume the system output is [Formula: see text], [Formula: see text]. The Lth-order Rice model is utilized to describe the phenomenon of channel fadings by setting different values of the channel coefficients. The aim of this work is to deal with the problem of designing a full-order dynamic fuzzy [Formula: see text] output-feedback controller such that the fuzzy closed-loop system is exponentially mean-square stable and the [Formula: see text] performance constraint is satisfied, by means of a combination of Lyapunov stability theory and stochastic analysis along with LMI methods. The proposed fuzzy controller parameters are derived by solving a convex optimization problem via the semidefinite programming technique. Finally, a numerical simulation is given to illustrate the feasibility and effectiveness of the proposed design technique.

  8. Improved digital backward propagation for the compensation of inter-channel nonlinear effects in polarization-multiplexed WDM systems.

    Science.gov (United States)

    Mateo, Eduardo F; Zhou, Xiang; Li, Guifang

    2011-01-17

    An improved split-step method (SSM) for digital backward propagation (DBP) applicable to wavelength-division multiplexed (WDM) transmission with polarization-division multiplexing (PDM) is presented. A coupled system of nonlinear partial differential equations, derived from the Manakov equations, is used for DBP. The above system enables the implementation of DBP on a channel-by-channel basis, where only the effect of phase-mismatched four-wave mixing (FWM) is neglected. A novel formulation of the SSM for PDM-WDM systems is presented where new terms are included in the nonlinear step to account for inter-polarization mixing effects. In addition, the effect of inter-channel walk-off is included. This substantially reduces the computational load compared to the conventional SSM.

  9. Recovery of Ductility in Ultrafine-Grained Low-Carbon Steel Processed Through Equal-Channel Angular Pressing Followed by Cold Rolling and Flash Annealing

    Science.gov (United States)

    Singh, Raj Bahadur; Mukhopadhyay, N. K.; Sastry, G. V. S.; Manna, R.

    2017-01-01

    The low-carbon steel workpieces are deformed by equal-channel angular pressing at 293 K (20 °C) up to an equivalent strain of 12 using route B c, which results in the bulk ultrafine-grained (UFG) structure with high dislocation density and partial dissolution of cementite. The yield strength (YS) is enhanced from 208 (as-received) to 872 MPa and the tensile strength is increased from 362 to 996 MPa, but the material loses total elongation (TE) from 36.2 to 2.9 pct. Cold rolling of equal-channel angular pressed steel produces the refined structure of grain size 0.11 μm. The YS increases further to 924 MPa with a marginal gain in ductility due to the reappearance of the γ fiber component. Flash annealing the samples, which were equal-channel angular pressed followed by cold rolling, at 873 K (600 °C) results in 27 pct of micron-sized (9 µm) ferrite grains in submicron-sized (<1 µm) matrix with a reduced defect density and small amount of precipitation of cementite. TE increases from 2.9 to 23.3 pct. The material retains a YS of 484 MPa and tensile strength of 517 MPa, which are higher than those of the as-received material. The UFG grains are failed by cleavage, but the micron-sized grains display ductile fracture. The ductility of the flash-annealed material is recovered significantly due to bimodal grain size distribution in ferrite and the development of a good amount of γ fiber texture components. The major contribution toward recovery of ductility comes from the bimodal grain size distribution in ferrite rather the precipitation of cementite.

  10. Attitude Control of a Single Tilt Tri-Rotor UAV System: Dynamic Modeling and Each Channel's Nonlinear Controllers Design

    Directory of Open Access Journals (Sweden)

    Juing-Shian Chiou

    2013-01-01

    Full Text Available This paper has implemented nonlinear control strategy for the single tilt tri-rotor aerial robot. Based on Newton-Euler’s laws, the linear and nonlinear mathematical models of tri-rotor UAVs are obtained. A numerical analysis using Newton-Raphson method is chosen for finding hovering equilibrium point. Back-stepping nonlinear controller design is based on constructing Lyapunov candidate function for closed-loop system. By imitating the linguistic logic of human thought, fuzzy logic controllers (FLCs are designed based on control rules and membership functions, which are much less rigid than the calculations computers generally perform. Effectiveness of the controllers design scheme is shown through nonlinear simulation model on each channel.

  11. The Effect of Multi-pass Equal-Channel Angular Pressing (ECAP) for Consolidation of Aluminum-Nano Alumina Composite Powder on Wear Resistance

    Science.gov (United States)

    Derakhshandeh-Haghighi, Reza; Jenabali Jahromi, Seyed Ahmad

    2016-02-01

    The wear behavior of aluminum matrix composite powder with varying concentration of nano alumina particles, which was consolidated by equal-channel angular pressing (ECAP) at different passes, was determined by applying, 10 and 46 N loads, using a pin-on-disk machine. Optical and electronic microscopy, EDX analysis, and hardness measurement were performed in order to characterize the worn samples. The relative density of the samples after each pass of ECAP was determined using Archimedes principle. Within the studied range of loads, the wear loss decreased by increasing the number of ECAP passes.

  12. Strain Mapping and Nanocrystallite Size Determination by Neutron Diffraction in an Aluminum Alloy (AA5083 Severely Plastically Deformed through Equal Channel Angular Pressing

    Directory of Open Access Journals (Sweden)

    P. A. González Crespo

    2013-01-01

    Full Text Available Six specimens of an aluminum alloy (AA-5083 extruded by Equal Channel Angular Pressing following two different routes plus a blank sample were examined with a neutron radiation of 1.5448 Å. Macrostrain maps from the (311 reflection were obtained. A clear difference about accumulated macrostrain with the extrusion cycles between the two routes is shown. The diffraction data of annealed specimens did permit to estimate crystallite sizes that range between 89 nm and 115 nm depending on the routes.

  13. Adaptive Equalization Algorithms: An Overview

    Directory of Open Access Journals (Sweden)

    Garima Malik

    2011-03-01

    Full Text Available The recent digital transmission systems impose the application of channel equalizers with short training time and high tracking rate. Equalization techniques compensate for the time dispersion introduced by communication channels and combat the resulting inter-symbol interference (ISI effect. Given a channel of unknown impulse response, the purpose of an adaptive equalizer is to operate on the channel output such that the cascade connection of the channel and the equalizer provides an approximation to an ideal transmission medium. Typically, adaptive equalizers used in digital communications require an initial training period, during which a known data sequence is transmitted. A replica of this sequence is made available at the receiver in proper synchronism with the transmitter, thereby making it possible for adjustments to be made to the equalizer coefficients in accordance with the adaptive filtering algorithm employed in the equalizer design. In this paper, an overview of the current state of the art in adaptive equalization techniques has been presented.

  14. A Study on Frequency-domain Division Based on Channel Equalization%基于通道均衡的频域除法研究

    Institute of Scientific and Technical Information of China (English)

    魏文斌; 于文震; 王秀春

    2011-01-01

    在频域通道均衡中,一个关键技术是求解均衡滤波器的响应.文中利用循环卷积和离散傅里叶变换乘积之间的关系,研究了通道均衡中频域除法的两类求解法:一类是时域算法,包括循环矩阵伪逆求解法和循环卷积求循环反卷积算法;另一类是基于最小范数的矩阵形式的频域算法.借助于仿真数据,根据求得的均衡滤波器和待校滤波器的卷积对参考滤波器的逼近误差,验证了上述算法的有效性.实验结果表明,基于最小范数的矩阵形式的频域算法在逼近性能、实时性方面均优于上面两种时域算法.%In frequency-domain channel equalization, one of the most crucial technologies is to seek the response of an equalization filter. AccordinS to the relation between the circular convolution in the time domain and the DFT product in the frequency domain,it is referred that two classes of algorithms on frequency-domain division in channel equalization, one class is time-domain algorithms which include an algorithm to seek the pseudo-inverse of a circular matrix and another algorithm to seek the deconvolution by circular convolution , the other is a frequency-domain algorithm having the least MSRe with matrix form. Accordinfl; to the error with the convolution between the filter to be emended and the corresponding equalization filter approximating the reference filter, the validity of the above algonthms is tested. The experimemal results shows that the frequency-domain algonthm having the least MSRe with matrix form excels those two time-domain algorithms in both approximation degree and real time.

  15. Decision feedback equalization with multichannel readback in high-density optical recording

    Science.gov (United States)

    Gopalaswamy, Srinivasan; Vijaya Kumar, Bhagavatula

    1995-12-01

    Multi-channel readback using array heads has been reported in optical recording. A method to reduce both interference along and across the tracks using multi-channel readback is presented. In this method, the non-linear multi-channel decision feedback equalization is used to remove both forms of interference. Simulation results show good improvement (in performance) by using the multi-channel equalization. By this readback method, tracks can be brought closer, thus increasing the areal density. Another advantage of this method is the high data rate possible.

  16. Fiber nonlinearity compensation by repeated phase conjugation in 2.048-Tbit/s WDM transmission of PDM 16-QAM channels

    DEFF Research Database (Denmark)

    Hu, Hao; Jopson, R. M.; Gnauck, A. H.;

    2016-01-01

    We demonstrate compensation of fiber nonlinearities using repeated optical phase conjugation (OPC) in a WDM system with eight 32-Gbaud PDM 16-QAM channels, showing improved performance over a single mid-span OPC and no OPC....

  17. Annealing behavior and shape memory effect in NiTi alloy processed by equal-channel angular pressing at room temperature

    Energy Technology Data Exchange (ETDEWEB)

    Shahmir, Hamed, E-mail: h.shahmir@ut.ac.ir [School of Metallurgy and Materials, College of Engineering, University of Tehran, Tehran (Iran, Islamic Republic of); Nili-Ahmadabadi, Mahmoud [School of Metallurgy and Materials, College of Engineering, University of Tehran, Tehran (Iran, Islamic Republic of); Wang, Chuan Ting [Departments of Aerospace & Mechanical Engineering and Materials Science, University of Southern California, Los Angeles, CA 90089-1453 (United States); School of Mechanical Engineering, Nanjing University of Science and Technology, Nanjing 210094 (China); Jung, Jai Myun; Kim, Hyoung Seop [Department of Materials Science and Engineering, Pohang University of Science and Technology, Pohang (Korea, Republic of); Langdon, Terence G. [Departments of Aerospace & Mechanical Engineering and Materials Science, University of Southern California, Los Angeles, CA 90089-1453 (United States); Materials Research Group, Faculty of Engineering and the Environment, University of Southampton, Southampton SO17 1BJ (United Kingdom)

    2015-04-01

    A martensitic NiTi shape memory alloy was processed successfully by equal-channel angular pressing (ECAP) for one pass at room temperature using a core–sheath billet design. The annealing behavior and shape memory effect of the ECAP specimens were studied followed by post-deformation annealing (PDA) at 673 K for various times. The recrystallization and structural evolution during annealing were investigated by differential scanning calorimetry, dilatometry, X-ray diffraction, transmission electron microscopy and microhardness measurements. The results indicate that the shape memory effect improves by PDA after ECAP processing. Annealing for 10 min gives a good shape memory effect which leads to a maximum in recoverable strain of 6.9 pct upon heating where this is more than a 25 pct improvement compared with the initial state.

  18. Mechanical properties of ferrite-perlite and martensitic Fe-Mn-V-Ti-C steel processed by equal-channel angular pressing and high-temeperature annealing

    Science.gov (United States)

    Zakharova, G. G.; Astafurova, E. G.; Tukeeva, M. S.; Naidenkin, E. V.; Raab, G. I.; Dobatkin, S. V.

    2011-09-01

    Using the method of equal-channel angular pressing (ECAP), submicrocrystalline structure is formed in lowcarbon Fe-Mn-V-Ti-C steel with the average grain size 260 nm in the ferrite-perlite state and 310 nm in the martensitic state. It is established that the ECAP treatment gives rise to improved mechanical properties (Hμ = 2.9 GPa, σ0 = 990 MPa in the ferrite-perlite and Hμ = 3.7 GPa, σ0 = 1125 MPa in martensitic states), decreased plasticity, and results in plastic flow localization under tensile loading. The high strength properties formed by the ECAP are shown to sustain up to the annealing temperature 500°C.

  19. A convergent-beam electron diffraction study of strain homogeneity in severely strained aluminum processed by equal-channel angular pressing

    Energy Technology Data Exchange (ETDEWEB)

    Alhajeri, Saleh N. [Materials Research Group, Faculty of Engineering and the Environment, University of Southampton, Southampton SO17 1BJ (United Kingdom); Department of Manufacturing Engineering, College of Technological Studies, PAAET, PO Box 42325, Shuwaikh 70654 (Kuwait); Fox, Alan G. [Materials Research Group, Faculty of Engineering and the Environment, University of Southampton, Southampton SO17 1BJ (United Kingdom); Mechanical Engineering Department, Asian University, 89 Moo 12, Highway 331, Banglamung, Chon Buri 20260 (Thailand); Langdon, Terence G., E-mail: langdon@usc.edu [Materials Research Group, Faculty of Engineering and the Environment, University of Southampton, Southampton SO17 1BJ (United Kingdom); Departments of Aerospace and Mechanical Engineering and Materials Science, University of Southern California, Los Angeles, CA 90089-1453 (United States)

    2011-11-15

    Aluminum of commercial purity was processed by equal-channel angular pressing (ECAP) through two, four and eight passes at room temperature. A series of [1 1 4] convergent-beam electron diffraction (CBED) zone axis patterns were obtained using an electron probe with a diameter of 20 nm. Observations were recorded both immediately adjacent to the grain boundaries and in the grain interiors. Symmetry breaking of the higher-order Laue zone (HOLZ) lines was observed adjacent to the boundaries after two and four passes but not in the grain interiors. Pattern simulation of the CBED patterns taken from the two- and four-pass samples adjacent to the boundaries revealed a homogeneous strain with compressive and shear components. The presence of these homogeneous strains demonstrates that the internal stresses associated with the deformation of aluminum at room temperature are localized in the close vicinity, to within {approx}20 nm, of the grain boundaries.

  20. Microstructural evolution of Fe-rich particles in an Al-Zn-Mg-Cu alloy during equal-channel angular pressing

    Energy Technology Data Exchange (ETDEWEB)

    Sha, G., E-mail: gang.sha@sydney.edu.au [ARC Centre of Excellence for Design in Light Metals, University of Sydney, NSW 2006 (Australia); Australian Centre for Microscopy and Microanalysis, University of Sydney, NSW 2006 (Australia); Wang, Y.B.; Liao, X.Z. [School of Aerospace, Mechanical and Mechatronic Engineering, University of Sydney, NSW 2006 (Australia); Duan, Z.C. [Department of Aerospace and Mechanical Engineering, University of Southern California, Los Angeles, CA 90089-1453 (United States); Ringer, S.P. [ARC Centre of Excellence for Design in Light Metals, University of Sydney, NSW 2006 (Australia); Australian Centre for Microscopy and Microanalysis, University of Sydney, NSW 2006 (Australia); Langdon, T.G. [Department of Aerospace and Mechanical Engineering, University of Southern California, Los Angeles, CA 90089-1453 (United States); Materials Research Group, School of Engineering Sciences, University of Southampton, Southampton SO17 1BJ (United Kingdom)

    2010-07-15

    The microstructures of a severely deformed Al-Zn-Mg-Cu (AA7136) alloy have been characterized carefully using transmission electron microscopy and three-dimensional atom probe analysis. The Fe-rich intermetallic particles are predominantly Al{sub 13}Fe{sub 4} type in the as-extruded alloy. Significantly, equal-channel angular pressing (ECAP) at 200 deg. C refines Fe-rich particles from {approx}1 to 2 {mu}m to as small as {approx}50 nm after 4 passes processing, and effectively narrow down their size distribution with the increase of number of ECAP passes. In addition, small Fe-rich particles evolve into spherical morphology and are in a more uniform distribution. The formations of Fe-rich phases in AA7136, the kinetic and thermodynamic effects in relation to the refinement of Fe-rich particles and their morphology evolution during ECAP processing are discussed.

  1. Second harmonic generation of q-Gaussian laser beam in preformed collisional plasma channel with nonlinear absorption

    Energy Technology Data Exchange (ETDEWEB)

    Gupta, Naveen, E-mail: naveens222@rediffmail.com; Singh, Arvinder, E-mail: arvinder6@lycos.com [Department of Physics, National Institute of Technology Jalandhar (India); Singh, Navpreet, E-mail: navpreet.nit@gmail.com [Guru Nanak Dev University College, Kapurthala, Punjab (India)

    2015-11-15

    This paper presents a scheme for second harmonic generation of an intense q-Gaussian laser beam in a preformed parabolic plasma channel, where collisional nonlinearity is operative with nonlinear absorption. Due to nonuniform irradiance of intensity along the wavefront of the laser beam, nonuniform Ohmic heating of plasma electrons takes place. Due to this nonuniform heating of plasma, the laser beam gets self-focused and produces strong density gradients in the transverse direction. The generated density gradients excite an electron plasma wave at pump frequency that interacts with the pump beam to produce its second harmonics. The formulation is based on a numerical solution of the nonlinear Schrodinger wave equation in WKB approximation followed by moment theory approach. A second order nonlinear differential equation governing the propagation dynamics of the laser beam with distance of propagation has been obtained and is solved numerically by Runge Kutta fourth order technique. The effect of nonlinear absorption on self-focusing of the laser beam and conversion efficiency of its second harmonics has been investigated.

  2. Effects, determination, and correction of count rate nonlinearity in multi-channel analog electron detectors

    Energy Technology Data Exchange (ETDEWEB)

    Reber, T. J.; Plumb, N. C.; Waugh, J. A.; Dessau, D. S. [Department of Physics, University of Colorado, Boulder, Colorado 80309-0390 (United States)

    2014-04-15

    Detector counting rate nonlinearity, though a known problem, is commonly ignored in the analysis of angle resolved photoemission spectroscopy where modern multichannel electron detection schemes using analog intensity scales are used. We focus on a nearly ubiquitous “inverse saturation” nonlinearity that makes the spectra falsely sharp and beautiful. These artificially enhanced spectra limit accurate quantitative analysis of the data, leading to mistaken spectral weights, Fermi energies, and peak widths. We present a method to rapidly detect and correct for this nonlinearity. This algorithm could be applicable for a wide range of nonlinear systems, beyond photoemission spectroscopy.

  3. GLOBAL CONVERGENCE OF TRUST REGION ALGORITHM FOR EQUALITY AND BOUND CONSTRAINED NONLINEAR OPTIMIZATION%等式与界约束非线性优化信赖域算法的全局收敛

    Institute of Scientific and Technical Information of China (English)

    童小娇; 周叔子

    2003-01-01

    This paper presents a trust region two-phase model algorithm for solving the equality and bound constrained nonlinear optimization problem. A concept of substationary point is given. Under suitable assumptions,the global convergence of this algorithm is proved without assuming the linear independence of the gradient of active constraints. A numerical example is also presented.

  4. Nonlinear predictive control for the concentrations profile regulation under unknown reaction disturbances in a fuel cell anode gas channel

    Science.gov (United States)

    Luna, Julio; Ocampo-Martinez, Carlos; Serra, Maria

    2015-05-01

    In this work, a nonlinear model predictive control (NMPC) strategy is proposed to regulate the concentrations of the different gas species inside a Proton Exchange Membrane Fuel Cell (PEMFC) anode gas channel. The purpose of the regulation relies on the rejection of the unmeasurable perturbations that affect the system: the hydrogen reaction and water transport terms. The model of the anode channel is derived from the discretisation of the partial differential equations that define the nonlinear dynamics of the system, taking into account spatial variations along the channel. Forward and backward discretisations of the distributed model are employed to take advantage of the boundary conditions of the problem. A linear observer is designed and implemented to perform output-feedback control of the plant. This information is fed to the controller to regulate the states towards their desired values. Simulation results are presented to show the performance of the proposed control method over a given case study. Different cost functions are compared and the one with minimum state-regulation error is identified. Suitable dynamic responses are obtained facing the different considered disturbances.

  5. Influence of polarization state, baud rate and PMD on non-linear impairments in WDM systems with mixed PM (D)QPSK and OOK channels.

    Science.gov (United States)

    Chughtai, Mohsan Niaz; Forzati, Marco; Mårtensson, Jonas; Rafique, Danish

    2012-03-26

    In this paper we numerically investigate nonlinear impairments in a WDM system with mixed PM (D)QPSK and OOK channels. First we analyze the dependence of XPM and XPolM on SOP and baud rate in absence of PMD. In this case we find that the nonlinear impairments are highly dependent on relative SOP between the PM (D)QPSK and neighbouring OOK channels. The dependence on relative SOP is more pronounced in differential detection than in coherent detection. However, with increasing values of PMD this dependence decreases, and non-linear tolerance improves.

  6. Viscous Hydrodynamic Model of Non-linear Plasma Oscillations in Two-Dimensional Gated Conduction Channels and Application to the Detection of Terahertz Signals

    Science.gov (United States)

    2010-04-01

    for the resonant tunable detection of terahertz radiation. The non-linear plasma response has been observed in InGaAs (3, 4) and GaN (5–8) HEMTs , in...the transistor cut-off frequency in a short channel device. In the Dyakonov-Shur detector a short channel HEMT is used for the resonant tunable...for the (a) GaAs and (b) GaN channels

  7. Intra-channel nonlinearity compensation for PM-16 QAM traffic co-propagating with 28 Gbaud m-ary QAM neighbours.

    Science.gov (United States)

    Rafique, Danish; Sygletos, Stylianos; Ellis, Andrew D

    2013-02-25

    We quantify the benefits of intra-channel nonlinear compensation in meshed optical networks, in view of network configuration, fibre design aspect, and dispersion management. We report that for a WDM optical transport network employing flexible 28Gbaud PM-mQAM transponders with no in-line dispersion compensation, intra-channel nonlinear compensation, for PM-16QAM through traffic, offers significant improvements of up to 4dB in nonlinear tolerance (Q-factor) irrespective of the co-propagating modulation format, and that this benefit is further enhanced (1.5dB) by increasing local link dispersion. For dispersion managed links, we further report that advantages of intra-channel nonlinear compensation increase with in-line dispersion compensation ratio, with 1.5dB improvements after 95% in-line dispersion compensation, compared to uncompensated transmission.

  8. Nonlinear radiative heat transfer and Hall effects on a viscous fluid in a semi-porous curved channel

    Energy Technology Data Exchange (ETDEWEB)

    Abbas, Z.; Naveed, M., E-mail: rana.m.naveed@gmail.com [Department of Mathematics, The Islamia University of Bahawalpur, Bahawalpur 63100 (Pakistan); Sajid, M. [Theoretical Physics Division, PINSTECH, P.O. Nilore, Islamabad 44000 (Pakistan)

    2015-10-15

    In this paper, effects of Hall currents and nonlinear radiative heat transfer in a viscous fluid passing through a semi-porous curved channel coiled in a circle of radius R are analyzed. A curvilinear coordinate system is used to develop the mathematical model of the considered problem in the form partial differential equations. Similarity solutions of the governing boundary value problems are obtained numerically using shooting method. The results are also validated with the well-known finite difference technique known as the Keller-Box method. The analysis of the involved pertinent parameters on the velocity and temperature distributions is presented through graphs and tables.

  9. Deterministic distribution of four-photon Dicke state over an arbitrary collective-noise channel with cross-Kerr nonlinearity

    Science.gov (United States)

    Wang, Mei-Yu; Yan, Feng-Li; Gao, Ting

    2016-07-01

    We present two deterministic quantum entanglement distribution protocols for a four-photon Dicke polarization entangled state resorting to the frequency and spatial degrees of freedom, which are immune to an arbitrary collective-noise channel. Both of the protocols adopt the X homodyne measurement based on the cross-Kerr nonlinearity to complete the task of the single-photon detection with nearly unit probability in principle. After the four receivers share the photons, they add some local unitary operations to obtain a standard four-photon Dicke polarization entangled state.

  10. Simultaneous Regeneration of Two 160 Gbit/s WDM Channels in a Single Highly Nonlinear Fiber

    DEFF Research Database (Denmark)

    Wang, Ju; Ji, Hua; Hu, Hao;

    2012-01-01

    We experimentally demonstrate simultaneous all-optical regeneration of two 160 Gbit/s WDM channels in a single HNLF using fiber optical parametric amplification. Receiver sensitivities at a BER of 10-9 are improved by about 2.1 dB and 4.9 dB for the two channels, respectively. The BER is not degr...

  11. Formation and Corrosion Resistance of Micro-Arc Oxidation Coating on Equal-Channel Angular Pressed AZ91D Mg Alloy

    Directory of Open Access Journals (Sweden)

    Aibin Ma

    2016-12-01

    Full Text Available A commercial AZ91D Mg alloy, after bulk grain refinement by various passes of equal-channel angular pressing (ECAP, was selected for micro-arc oxidation (MAO in silicate electrolyte, corrosion testing in 3.5 wt % NaCl solution and morphology analyses. The results showed that a large number of ECAP passes resulted in the homogeneous ultrafine-grained (UFG Mg substrate with broken second-phases. The high-energy defects in the ECAPed samples lowered the anodizing potential of the MAO process, but the partial discharge was severe for those samples below eight passes. Increasing the ECAP pass, the compactness and thickness of the MAO coating first decreased and then increased. Due to the compact coating and the existence of Mg2SiO4, the coated alloy with 16 ECAP passes has a lower corrosion rate and a larger Rt value. Besides the well-known strengthening-toughening effect, grain refinement via multi-pass ECAP can improve surface protection of the MAO coating on the UFG Mg alloy.

  12. Microstructure and properties of the novel Cu–0.30Mg–0.05Ce alloy processed by equal channel angular pressing

    Energy Technology Data Exchange (ETDEWEB)

    Duan, Y.L. [School of Materials Science and Engineering, Central South University, Changsha 410083 (China); Xu, G.F., E-mail: csuxgf660302@csu.edu.cn [School of Materials Science and Engineering, Central South University, Changsha 410083 (China); Key Laboratory of Nonferrous Materials Science and Engineering of Ministry of Education, Central South University, Changsha 410083 (China); Tang, L. [School of Materials Science and Engineering, Central South University, Changsha 410083 (China); Li, Z. [School of Materials Science and Engineering, Central South University, Changsha 410083 (China); Key Laboratory of Nonferrous Materials Science and Engineering of Ministry of Education, Central South University, Changsha 410083 (China); Yang, G. [School of Materials Science and Engineering, Central South University, Changsha 410083 (China)

    2015-11-11

    A novel Cu–0.30Mg–0.05Ce (wt%) alloy was designed and prepared by melting and casting. The hot-rolled Cu–Mg–Ce alloy with an average grain size of 24.3 μm was processed by equal channel angular pressing (ECAP) via route B{sub C} with different passes at room temperature. Moreover, microstructure evolution, mechanical properties and electrical conductivity of the alloy subjected to ECAP with different passes have been analyzed. The transmission electron microscope observation and electron backscatter diffraction analysis results show that the grains were refined significantly and the low angle boundaries generated at the initial stage of deformation were gradually transformed to the high angle boundaries with increasing the number of ECAP passes. After 8 ECAP passes, the average grain size decreased to 1.2 μm, and the fraction of high angle boundaries was 87.7%. Besides, the typical FCC shear textures ({111}<112>, {111}<110> and {001}<110>) were generated during ECAP deformation. Furthermore, tension testing results indicated that the tensile strength was remarkably improved from ∼274 MPa before ECAP to ∼588 MPa after 8 ECAP passes, maintaining an appropriate elongation of ∼11% and good electrical conductivity of 73.5% International Annealed Copper Standard (IACS), which showed bright prospect in high-speed railway as a contact wire material.

  13. Effect of equal channel angular extrusion on wear and corrosion behavior of the orthopedic Ti-13Nb-13Zr alloy in simulated body fluid

    Energy Technology Data Exchange (ETDEWEB)

    Suresh, K.S. [Department of Materials. Engineering, Indian Institute of Science, Bangalore 560012 (India); Geetha, M., E-mail: geethamanivasagam@vit.ac.in [School of Mechanical and Building Sciences, VIT University, Vellore (India); Richard, C. [Laboratoire de Mecanique et de Rheologie EA 2640, Polytech' Tours, 37000 Tours (France); Landoulsi, J. [Laboratoire de Reactivite de Surface, UMR 7197 CNRS, Universite Pierre and Marie Curie - Paris VI, 4 Place Jussieu, Case 178, F-75252 Paris (France); Ramasawmy, H. [University of Mauritius, Faculty of Engineering, Reduit (Mauritius); Suwas, S. [Department of Materials. Engineering, Indian Institute of Science, Bangalore 560012 (India); Asokamani, R. [School of Mechanical and Building Sciences, VIT University, Vellore (India)

    2012-05-01

    We report investigations on the texture, corrosion and wear behavior of ultra-fine grained (UFG) Ti-13Nb-Zr alloy, processed by equal channel angular extrusion (ECAE) technique, for biomedical applications. The microstructure obtained was characterized by X-ray line profile analysis, scanning electron microscope (SEM) and electron back scattered diffraction (EBSD). We focus on the corrosion resistance and the fretting behavior, the main considerations for such biomaterials, in simulated body fluid. To this end, potentiodynamic polarization tests were carried out to evaluate the corrosion behavior of the UFG alloy in Hanks solution at 37 Degree-Sign C. The fretting wear behavior was carried out against bearing steel in the same conditions. The roughness of the samples was also measured to examine the effect of topography on the wear behavior of the samples. Our results showed that the ECAE process increases noticeably the performance of the alloy as orthopedic implant. Although no significant difference was observed in the fretting wear behavior, the corrosion resistance of the UFG alloy was found to be higher than the non-treated material. Highlights: Black-Right-Pointing-Pointer Relevancy of ECAE process applied to titanium alloy for biomedical applications. Black-Right-Pointing-Pointer Significant improvement of mechanical properties of the surface. Black-Right-Pointing-Pointer Noticeable increase of the corrosion resistance in simulated body fluid.

  14. Microstructural Evolution at Micro/Meso-Scale in an Ultrafine-Grained Pure Aluminum Processed by Equal-Channel Angular Pressing with Subsequent Annealing Treatment

    Directory of Open Access Journals (Sweden)

    Jie Xu

    2015-11-01

    Full Text Available Micro-forming with ultrafine-grained (UFG materials is a promising direction for the fabrication of micro-electro-mechanical systems (MEMS components due to the improved formability, good surface quality, and excellent mechanical properties it provides. In this paper, micro-compression tests were performed using UFG pure aluminum processed by equal-channel angular pressing (ECAP with subsequent annealing treatment. Microstructural evolution was investigated by electron back-scattered diffraction (EBSD and transmission electron microscopy (TEM. The results show that microstructural evolutions during compression tests at the micro/meso-scale in UFG pure Al are absolutely different from the coarse-grained (CG materials. A lot of low-angle grain boundaries (LAGBs and recrystallized fine grains are formed inside of the original large grains in CG pure aluminum after micro-compression. By contrast, ultrafine grains are kept with few sub-grain boundaries inside the grains in UFG pure aluminum, which are similar to the original microstructure before micro-compression. The surface roughness and coordinated deformation ability can be signmicrostructure; micro/meso-forming; ultrafine grains; ECAP; aluminumificantly improved with UFG pure aluminum, which demonstrates that the UFG materials have a strong potential application in micro/meso-forming.

  15. Microstructure evolution and mechanical properties of a Ti-35Nb-3Zr-2Ta biomedical alloy processed by equal channel angular pressing (ECAP).

    Science.gov (United States)

    Lin, Zhengjie; Wang, Liqiang; Xue, Xiaobing; Lu, Weijie; Qin, Jining; Zhang, Di

    2013-12-01

    In this paper, an equal channel angular pressing method is employed to refine grains and enhance mechanical properties of a new β Ti-35Nb-3Zr-2Ta biomedical alloy. After the 4th pass, the ultrafine equiaxed grains of approximately 300 nm and 600 nm are obtained at pressing temperatures of 500 and 600°C respectively. The SEM images of billets pressed at 500°C reveal the evolution of shear bands and finally at the 4th pass intersectant networks of shear bands, involving initial band propagation and new band broadening, are formed with the purpose of accommodating large plastic strain. Furthermore, a unique herringbone microstructure of twinned martensitic variants is observed in TEM images. The results of microhardness measurements and uniaxial tensile tests show a significant improvement in microhardness and tensile strength from 534 MPa to 765 MPa, while keeping a good level of ductility (~16%) and low elastic modulus (~59 GPa). The maximum superelastic strain of 1.4% and maximum recovered strain of 2.7% are obtained in the billets pressed at 500°C via the 4th pass, which exhibits an excellent superelastic behavior. Meanwhile, the effects of different accumulative deformations and pressing temperatures on superelasticity of the ECAP-processed alloys are investigated. © 2013. Published by Elsevier B.V. All rights reserved.

  16. The influence of deformation path on strain characteristics of AA1050 aluminium processed by equal-channel angular pressing followed by rolling

    Energy Technology Data Exchange (ETDEWEB)

    Vega, M.C.V. [Department of Materials Engineering – Universidade Federal de São Carlos, (SP) Rod. Washington Luis km 235, 13565-905 São Carlos (Brazil); Bolmaro, R.E. [Instituto de Física Rosario (IFIR) FCEIA-UNR-CONICET, Bv. 27 de Febrero 210 bis, S2000EZP Rosario (Argentina); Ferrante, M.; Sordi, V.L. [Department of Materials Engineering – Universidade Federal de São Carlos, (SP) Rod. Washington Luis km 235, 13565-905 São Carlos (Brazil); Kliauga, A.M., E-mail: kliauga@ufscar.br [Department of Materials Engineering – Universidade Federal de São Carlos, (SP) Rod. Washington Luis km 235, 13565-905 São Carlos (Brazil)

    2015-10-14

    The present investigation reports on the microstructure evolution, texture development, the nature of the grain boundaries and the tensile and deep drawing behaviour of commercial AA1050 Al processed by Equal Channel Angular Pressing (ECAP) plus rolling. Although in terms of final mechanical strength ECAP and rolling are indistinguishable, the deformation path is substantially different, and this has important consequences on both microstructure and texture. From the spatial distribution of high angle grain boundaries (HAGB) and low angle grain boundaries (LAGB), the fine microstructure and the crystallographic texture, it was concluded that the microstructure is oriented according to the external imposed flow: a spin movement in the ECAP process, which promotes the rotation of the cells inside the original grain, followed by a sliding movement caused by the rolling, leading to grain elongation. The ECAP process is more suitable to promote a higher fraction of HAGBs, and the same time as it reduces the intensity of the bulk crystallographic texture. As a consequence an increase of the penetration depth and deformation strain, as measured by the Erichsen test, was observed in samples processed by 8 ECAP passes, characterized by low texture intensity and a high degree of dynamic recrystallization.

  17. Structure and properties of an Mg-0.3% ca magnesium alloy after multiaxial deformation and equal-channel angular pressing

    Science.gov (United States)

    Dobatkin, S. V.; Rokhlin, L. L.; Salishchev, G. A.; Kopylov, V. I.; Serebryany, V. N.; Stepanov, N. D.; Tarytina, I. E.; Kuroshev, I. S.; Martynenko, N. S.

    2014-11-01

    Multiaxial deformation (MAD) of an Mg-0.3% Ca alloy is performed when temperature decreases within the ranges 425-375 and 400-325°C. A decrease in the temperature at the end of MAD causes a decrease in the grain size from 7-8 to 0.5-2 μm and the spread of a sharp prismatic texture, which determine a high strength (σu = 194 MPa) and plasticity (δ = 39%). After MAD in the range 425-375°C, the Mg-0.3% Ca alloy is subjected to equal-channel angular pressing (ECAP) at temperatures of 275 and 325°C. ECAP causes a decrease in the grain size from 7-8 μm to 2 and 5 μm, respectively. The texture also changes from prismatic to tilted basal texture. This results in an increase in the strength to 170-160 MPa at plasticity δ = 25-30%. It is shown that MAD can be used as both final and preliminary processing before ECAP to form an ultrafine-grained structure in the Mg-0.3% Ca alloy.

  18. Fiber nonlinearity compensation of an 8-channel WDM PDM-QPSK signal using multiple phase conjugations

    DEFF Research Database (Denmark)

    Hu, Hao; Jopson, R. M.; Dinu, M.;

    2013-01-01

    We demonstrate compensation of fiber nonlinearities using optical phase conjugation of an 8-chamiel WDM 32-Gbaud PDM QPSK signal. Conjugating phase every 600 km in a fiber loop enabled a 6000 km transmission over True Wave fiber. © 2013 Optical Society of America....

  19. Equality = Inequality

    DEFF Research Database (Denmark)

    Khaled, Rilla

    2011-01-01

    A number of design and development methods, including participatory design and agile software development, are premised on an underlying assumption of equality amongst relevant stakeholders such as designers, developers, product owners, and end users. Equality, however, is not a straightforwardly...... an ethnography conducted during the workshop, including location, cultural and classroom hierarchies, gender, “girl games”, stakeholders and boundaries, and risk mitigation....

  20. Influence of second-phase particles on grain growth in AZ31 magnesium alloy during equal channel angular pressing by phase field simulation

    Science.gov (United States)

    He, Ri; Wang, Mingtao; Zhang, Xiangang; Yaping Zong, Bernie

    2016-06-01

    A phase-field model was established to simulate the refinement effect of different morphological factors of second-phase particles such as Al2O3 on the grain growth of AZ31 magnesium alloy during equal channel angular pressing (ECAP) in realistic spatiotemporal evolution. The simulation results agreed well with limited existing experimental data for the ECAP-processed AZ31 magnesium alloy and were consistent with the law of Zener. Simulations were performed to evaluate the influences of the fraction, size, distribution, and shape of incoherent second-phase particles. The simulation results showed that during high-temperature ECAP processes, the addition of 2 wt.% Al2O3 particles resulted in a strong refinement effect, reducing the grain size by 28.7% compared to that of the alloy without the particles. Nevertheless, when the fraction of particles was greater than 4 wt.%, adding more particles had little effect. In AZ31 Mg alloy, it was found that second-phase particles should have a critical size of 0.5-0.8 μm for the grain refinement effect to occur. If the size is smaller than the critical size, large particles will strongly hinder grain growth; in contrast, if the size is larger than the critical size, large particles will exhibit a weaker hindering effect than small particles. Moreover, the results showed that the refinement effect increased with increasing particle fraction located at grain boundaries with respect to the total particle content. However, the refinement effect was less pronounced when the fraction of particles located at boundaries was greater than 70%. Further simulations indicated that spherical second-phase particles hindered grain growth more than ellipsoid particles and much more than rod-shaped particles when the volume fraction of reinforcing particles was 2%. However, when the volume fraction was greater than 8%, rod-shaped particles best hindered grain growth, and spherical particles exhibited the weakest effect.

  1. Progress in Research on Texture of Equal Channel Angular Pressing%等径弯曲通道变形织构的研究进展

    Institute of Scientific and Technical Information of China (English)

    刘晓燕; 赵西成; 杨西荣; 何晓梅; 董洁

    2012-01-01

    综述了等径弯曲通道变形制备FCC、BCC、HCP金属材料中织构的研究进展.介绍了ECAP变形织构的主要研究方法——蚀坑法、X射线衍射法、中子多晶体衍射法和电子背散射衍射法,论述了挤压路径、挤压道次、挤压温度、模具夹角、形变孪晶、初始织构等对ECAP变形过程织构演变及形成机理的影响,并对基于物理过程的织构演化模型(全约束Taylor多晶体模型和粘塑性自洽多晶体模型)进行评价,同时进一步指出织构演化研究的重要性及发展趋势.%Texture development in metals of FCC, BCC and HCP crystal structure processed by equal channel angular pressing (ECAP) is described. The aim of the present paper is to introduce the methods for texture determination such as etch-figure, X-ray diffraction, neutron diffraction and electron backscatter diffraction. A multitude of factors that can influence texture evolution mechanism is covered, such as deformation routes, passes number, temperature, die geometry, deformation twinning, initial texture and so on. Current models (full constrains Taylor polycrys-tal model and visco-plastic self-consistent polycrystal model) for texture evolution based on the physics are evaluated. The importance of texture development in ECAP and development prospects are suggested.

  2. In vitro and in vivo studies on nanocrystalline Ti fabricated by equal channel angular pressing with microcrystalline CP Ti as control.

    Science.gov (United States)

    Nie, F L; Zheng, Y F; Wei, S C; Wang, D S; Yu, Z T; Salimgareeva, G K; Polyakov, A V; Valiev, R Z

    2013-06-01

    Bulk nanocrystalline Ti bars (Grade 4, Φ4 × 3000 mm(3)) were massively fabricated by equal channel angular pressing (ECAP) via follow-up conform scheme with the microcrystalline CP Ti as raw material. Homogeneous nanostructured crystals with the average grain size of 250 nm were identified for the ECAPed Ti, with extremely high tensile/fatigue strength (around 1240/620 MPa) and adorable elongation (more than 5%). Pronounced formation of bonelike apatite for the nanocrystalline Ti group after 14 days static immersion in simulated body fluids (SBF) reveals the prospective in vitro bioactive capability of fast calcification, whereas an estimated 17% increment in protein adsorption represents good bioaffinity of nanocrystalline Ti. The documentation onto the whole life circle of osteoblast cell lines (MG63) revealed the strong interactions and superior cellular functionalization when they are co-incubated with bulk nanocrystalline Ti sample. Moreover, thread-structured specimens were designed and implanted into the tibia of Beagles dogs till 12 weeks to study the in vivo responses between bone and metallic implant made of bulk nanocrystalline Ti, with the microcrystalline Ti as control. For the implanted nanostructured Ti group, neoformed bone around the implants underwent the whole-stage transformation proceeding from originally osteons or immature woven bone to mature lamellar bone (skeletonic trabecular), even with the remodeling being finished till 12 weeks. The phenomenal osseointegration of direct implant-bone contact can be revealed from the group of the ECAPed Ti without fibrous tissue encapsulation in the gap between the implant and autogenous bone.

  3. Microstructure, mechanical properties and electrical conductivity of Cu–0.3Mg–0.05Ce alloy processed by equal channel angular pressing and subsequent annealing

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Guang [School of Materials Science and Engineering, Central South University, Changsha 410083 (China); Li, Zhou, E-mail: lizhou6931@csu.edu.cn [School of Materials Science and Engineering, Central South University, Changsha 410083 (China); State Key Laboratory of Powder Metallurgy, Changsha 410083 (China); Yuan, Yuan [School of Materials Science and Engineering, Central South University, Changsha 410083 (China); Lei, Qian [School of Materials Science and Engineering, Central South University, Changsha 410083 (China); Key Laboratory of Nonferrous Metal Materials Science and Engineering, Ministry of Education, Changsha 410083 (China)

    2015-08-15

    Highlights: • Minor Ce addition can deprive harmful elements and purify the Cu–Mg alloy. • Decrease of Mg content can effectively enhance the conductivity of Cu–Mg alloy. • Ultrafine-grained Cu–Mg–Ce alloy was successfully gained by 8 passes of ECAP. • The strength of Cu–Mg–Ce alloy can be significantly improved by ECAP. • Better comprehensive properties than the commercial Cu–Mg alloy are gained. - Abstract: A Cu–0.3 wt.%Mg–0.05 wt.%Ce alloy was designed and prepared by melting and casting. After hot rolled, the ingot was cut into rod-shape samples for equal channel angular pressing (ECAP) with different passes at room temperature. The microstructure evolutions were investigated using transmission electron microscope (TEM) observation and electron backscatter diffraction (EBSD) analysis. The severe plastic deformation (SPD) caused by ECAP made the grains elongated significantly. With the increase of ECAP passes, the fraction of high-angle boundaries (HABs) (θ ⩾ 15°) increased and the microstructure was refined. Tension testing results indicated that the tensile strength was remarkably improved from 273.4 MPa before ECAP to 587.5 MPa after 8 passes of ECAP, maintaining an appropriate elongation of 11.4% and good electrical conductivity of 73.1%IACS. After annealing treatment at 300 °C for 2 h, the ECAP samples still maintained excellent comprehensive properties: tensile strength was 558.2 MPa, electrical conductivity was 74.7%IACS, and elongation was 13.2%, which showed bright prospect in high-speed railway as a contact wire material.

  4. A MODIFIED DECOMPOSITION METHOD FOR SOLVING NONLINEAR PROBLEM OF FLOW IN CONVERGING- DIVERGING CHANNEL

    Directory of Open Access Journals (Sweden)

    MOHAMED KEZZAR

    2015-08-01

    Full Text Available In this research, an efficient technique of computation considered as a modified decomposition method was proposed and then successfully applied for solving the nonlinear problem of the two dimensional flow of an incompressible viscous fluid between nonparallel plane walls. In fact this method gives the nonlinear term Nu and the solution of the studied problem as a power series. The proposed iterative procedure gives on the one hand a computationally efficient formulation with an acceleration of convergence rate and on the other hand finds the solution without any discretization, linearization or restrictive assumptions. The comparison of our results with those of numerical treatment and other earlier works shows clearly the higher accuracy and efficiency of the used Modified Decomposition Method.

  5. Interactions between self-channeled optical beams in soft-matter systems with artificial nonlinearities.

    Science.gov (United States)

    Fardad, Shima; Mills, Matthew S; Zhang, Peng; Man, Weining; Chen, Zhigang; Christodoulides, D N

    2013-09-15

    We demonstrate optical interactions between stable self-trapped optical beams in soft-matter systems with pre-engineered saturable self-focusing optical nonlinearities. Our experiments, carried out in dilute suspensions of particles with negative polarizabilities, show that optical beam interactions can vary from attractive to repulsive, or can display an energy exchange depending on the initial relative phases. The corresponding observations are in good agreement with theoretical predictions.

  6. Channel dropping via bound states in the continuum in a system of two nonlinear cavities between two linear waveguides.

    Science.gov (United States)

    Bulgakov, Evgeny; Pichugin, Konstantin; Sadreev, Almas

    2013-10-01

    We show that two nonlinear resonant cavities aligned between two parallel waveguides can support self-induced bound states in the continuum (BSCs). These BSCs are symmetrical relative to an inversion of the waveguides and to inversion of the transport axis. Due to this BSCs can drop an incident wave from one waveguide to another with very high efficiency. We show also that the frequency of the efficient channel dropping can be tuned by injecting power. All these results are in good agreement with numerical solutions of the Maxwell equations in a two-dimensional photonic crystal of GaAs rods holding two parallel waveguides and two defects made of a Kerr medium.

  7. The role of different linear and non-linear channels of relaxation in scintillator non-proportionality

    Energy Technology Data Exchange (ETDEWEB)

    Bizarri, G.; Moses, W.W. [Lawrence Berkeley Laboratory, Berkeley, CA 94720-8119 (United States); Singh, J. [Faculty of EHS, B-41, Charles Darwin University, Darwin NT 0909 (Australia); Vasil' ev, A.N., E-mail: anvasiliev@rambler.r [Institute of Nuclear Physics, Moscow State University, Moscow 119991 (Russian Federation); Williams, R.T. [Department of Physics, Wake Forest University, Winston-Salem, NC 27109 (United States)

    2009-12-15

    The non-proportional dependence of a scintillator's light yield on primary particle energy is believed to be influenced crucially by the interplay of non-linear kinetic terms in the radiative and non-radiative decay of excitations versus locally deposited excitation density. A calculation of energy deposition, -dE/dx, along the electron track for NaI is presented for an energy range from several electron-volt to 1 MeV. Such results can be used to specify an initial excitation distribution, if diffusion is neglected. An exactly solvable two-channel (exciton and hole(electron)) model containing 1st and 2nd order kinetic terms is constructed and used to illustrate important features seen in non-proportional light-yield curves, including a dependence on pulse shaping (detection gate width).

  8. Nonlinear effects of energy sources and the jet at supersonic flow in the channel

    Science.gov (United States)

    Zamuraev, V. P.; Kalinina, A. P.

    2016-10-01

    The work is devoted to the mathematical modeling of the influence of transversal jet and the near-wall energy sources on the shock wave structure of supersonic flow in channel with variable cross section. Stable regimes with the region of transonic velocities are obtained. Their stability is confirmed by the width of the corridor of the input power in the area of the regime existence.

  9. Amplitude Equalization of 40 Gb/s RZ-DPSK Signals using Saturation of Four-Wave Mixing in a Highly Nonlinear Fiber

    DEFF Research Database (Denmark)

    Geng, Yan; Peucheret, Christophe; Jeppesen, Palle

    2006-01-01

    We report the first experimental demonstration of amplitude equalization of 40 Gb/s RZ-DPSK signals using saturation of FWM in a HNLF. We show effective power penalty reduction after wavelength conversion of an amplitude distorted signal......We report the first experimental demonstration of amplitude equalization of 40 Gb/s RZ-DPSK signals using saturation of FWM in a HNLF. We show effective power penalty reduction after wavelength conversion of an amplitude distorted signal...

  10. Nonlinear concentration gradients regulated by the width of channels for observation of half maximal inhibitory concentration (IC50) of transporter proteins.

    Science.gov (United States)

    Abe, Yuta; Kamiya, Koki; Osaki, Toshihisa; Sasaki, Hirotaka; Kawano, Ryuji; Miki, Norihisa; Takeuchi, Shoji

    2015-08-21

    This paper describes a simple microfluidic device that can generate nonlinear concentration gradients. We changed the "width" of channels that can drastically shorten the total microfluidic channel length and simplify the microfluidic network design rather than the "length" of channels. The logarithmic concentration gradients generated by the device were in good agreement with those obtained by simulation. Using this device, we evaluated a probable IC50 value of the ABC transporter proteins by the competitive transport assays at five different logarithmic concentrations. This probable IC50 value was in good agreement with an IC50 value (0.92 μM) obtained at the diluted concentrations of seven points.

  11. Development of mechanical properties in a CaO added AZ31 magnesium alloy processed by equal-channel angular pressing

    Energy Technology Data Exchange (ETDEWEB)

    Bae, Seong-Hwan [Division of Materials Science and Engineering, Hanyang University, Seoul 133-791 (Korea, Republic of); Metal Forming Technology R& D Group, Korea Institute of Industrial Technology, Incheon 406-840 (Korea, Republic of); Jung, Ki Ho; Shin, Young-Chul; Yoon, Duk Jae [Metal Forming Technology R& D Group, Korea Institute of Industrial Technology, Incheon 406-840 (Korea, Republic of); Kawasaki, Megumi, E-mail: megumi@hanyang.ac.kr [Division of Materials Science and Engineering, Hanyang University, Seoul 133-791 (Korea, Republic of); Departments of Aerospace & Mechanical Engineering and Materials Science, University of Southern California, Los Angeles, CA 90089-1453 (United States)

    2016-02-15

    Processing through the application of equal-channel angular pressing (ECAP) is recognized as one of the attractive severe plastic deformation techniques where the processed bulk metals generally achieve ultrafine-grained microstructure leading to improved physical characteristics and mechanical properties. Magnesium has received much attention to date for its lightweight, high strength and excellent elasticity. Mg alloys with addition of CaO is reported to provide the successful casting procedure without usage of greenhouse gas, SF{sub 6}, whereas it is generally used for preventing the oxidation of Mg during casting. In the present investigation, a CaO added AZ31 (AZ31-CaO) magnesium alloy was processed by ECAP at elevated temepratures with a few steps of reduction which result in significant grain refinement to ~ 1.5 μm after 6 passes. Compression testing at room temperature demonstrated the AZ31-CaO alloy after ECAP showed enhanced yield strength more than the as-processed commercial AZ31 alloy while both alloys maintained ductility in spite of significant reduction in grain size. The improved strength in the AZ31-CaO alloy was attributed to the formation of fine Al{sub 2}Ca precipitates which experience breaking-up through ECAP and accelerate the microstructural refinement. Moreover, the preservation of ductility was attributed to the enhancement of strain hardening capability in the AZ31 alloy at room temperature. This study discusses the feasibility of using ECAP to improve both strength and ductility on magnesium alloys by applying the diagram describing the paradox of strength and ductility. - Highlights: • AZ31 and AZ31-CaO magnesium alloys were processed by ECAP up to 6 passes. • AZ31-CaO alloy after ECAP showed improved yield strength without losing ductility. • CaO in AZ31 forms fine Al{sub 2}Ca accelerating microstructural refinement during ECAP. • Feasibility of using ECAP was shown to improve both strength and ductility in Mg.

  12. 基于多径分量重组的扩频通信信道均衡设计%Spread Spectrum Communication Channel Equalization Design Based on Multipath Component Recombination

    Institute of Scientific and Technical Information of China (English)

    王晓雯

    2016-01-01

    扩频通信中,由于扩频码序列所占的带宽度远大于所传信息的最小带宽,引起码间干扰和信道失衡,通过对扩频通信的信道均衡设计,降低扩频通信的误码率。传统方法采用子信道载波干扰抑制的扩频通信信道均衡算法,通过扩频码控制子信道载波线性调频变化,实现码间干扰抑制,但该算法会引起时分复用系统之间的相位畸变,信道均衡效果不好。提出一种基于多径分量重组的扩频通信信道均衡算法。先构建了扩频通信的信道模型,分析了扩频通信信道的时变特性,采用多径分量重组实现码间干扰抑制,结合多阵元被动时间反转镜技术实现扩频通信的信道均衡。仿真结果表明,采用该算法进行扩频通信信道均衡和码间干扰抑制,降低通信误码率,改善通信质量,提高了扩频通信系统的稳定性和可靠性。%In spread spectrum communication, because of the spread spectrum code sequence for the band width is much larger than the transmitted information minimum bandwidth, causing intersymbol interference and channel imbalance, through the spread spectrum communication channel equalization design, reduce the bit error rate of the spread spectrum communication. Traditional methods using sub carrier channel interference suppression in spread spectrum communication channel equalization algorithm, to achieve inter symbol interference suppression by spread spectrum codes control sub carrier channel linear FM changes, but the algorithm will phase distortion caused by time division multiplexing system, channel equalization effect is not good. A spread spectrum communication channel equalization algorithm based on multipath component is proposed. First, constructs the spread spectrum communication channel model, analysis of the spread spectrum communication channel characteristic and the multipath component of the reorganization of the realization of

  13. Simultaneous observation of collagen and elastin based on the combined nonlinear optical imaging technique coupled with two-channel synchronized detection method

    Science.gov (United States)

    Chen, Jianxin; Zhuo, Shuangmu; Luo, Tianshu; Liu, Dingzhong; Zhao, Jingjun

    2008-08-01

    Collagen and elastin are the most important proteins of the connective tissues in higher vertebrates. In this paper, we present a combined nonlinear optical imaging technique of second-harmonic generation and two-photon excited fluorescence to simultaneously observe the collagen and elastic fiber of dermis in a freshly excised human skin and rabbit aorta using a two-channel synchronized detection method. The obtained two-channel overlay image in the backward direction can clearly distinguish the morphological structure and distribution of collagen and elastic fibers. Tissue spectrum further confirms the obtained structural information. These results suggest that the combined nonlinear optical imaging technique coupled with two-channel synchronized detection method can be an effective tool for detecting collage and elastic fibers without any invasive tissue procedure of slicing, embedding, fixation and staining when two structural proteins are simultaneously present in the biological tissue.

  14. Unjust Equalities

    DEFF Research Database (Denmark)

    Albertsen, Andreas; Midtgaard, Søren Flinch

    2014-01-01

    In the luck egalitarian literature, one influential formulation of luck egalitarianism does not specify whether equalities that do not reflect people’s equivalent exercises of responsibility are bad with regard to inequality. This equivocation gives rise to two competing versions of luck egalitar...

  15. Granting Equality

    Institute of Scientific and Technical Information of China (English)

    YIN PUMIN

    2010-01-01

    @@ An amendment to the Electoral Law of the National People's Congress and Local People's Congresses of the People's Republic of China granting equal representation in legislative bodies to rural and urban people was ratified by the National People's Congress(NPC),China's top legislature,on March 14.

  16. Application of the nonlinear antenna theory model to a tall tower struck by lightning for the evaluation of return stroke channel current and radiated electromagnetic fields

    Science.gov (United States)

    Moosavi, S. H. S.; Moini, R.; Sadeghi, S. H. H.; Kordi, B.

    2011-06-01

    In this paper an improved antenna theory (AT) model with nonlinearly varying resistive loading and fixed inductive loading is used to electromagnetically simulate lightning strikes to tall structures. Measurement data captured from Toronto's CN tower are used to verify the validity of the new model. Both the return stroke channel (RSC) and the tower are modeled by straight thin conducting wires. The wire model of the channel is assumed to have distributed nonlinear resistive elements as a function of current and time, adopted from the numerical models of a spark channel and consequent shockwave from a lightning discharge, yielding a varying value of the channel radius from the base to the cloud along the RSC. Such distributed elements are used to take into account the current attenuation while propagating along the channel and varying propagation speeds lower than the speed of light. RSC current distribution and radiated electromagnetic fields in near, intermediate, and far range distances predicted by the proposed model are compared with those obtained from the measurement data and with those of the original AT model and the AT with fixed inductive loading (ATIL-F) model. Current wave propagation speed profile in RSC and tower is investigated as a function of height as well. The effects of applying different tower geometry models are also studied. It is shown that the new model is able to reproduce one of the characteristic features of the electromagnetic fields radiated by lightning, namely, the far-field inversion of polarity with a zero crossing occurring in the tens of microseconds range. We have also investigated the effect of nonlinearity of the channel assumed in the new model. It is shown that among the electromagnetic models, distributed nonlinear resistance along the channel leads to a zero crossing in the tens of microseconds range even for large values of resistance. It is also shown that decreasing the nonlinearity results in the predictions

  17. 适合于稀疏水声信道的低复杂度联合迭代均衡译码%Low Complexity Joint Iterative Equalization and Decoding Scheme for Sparse Underwater Communication Channel

    Institute of Scientific and Technical Information of China (English)

    孟庆微; 黄建国; 何成兵

    2011-01-01

    浅海远程水声通信面临严重多径扩展、衰落以及低信噪比的挑战,为克服传统内嵌二阶锁相环的判决反馈均衡器结构在中低信噪比条件下性能较差的缺点,提高水声通信系统的可靠性,该文提出一种适合于稀疏水声信道的低复杂度联合迭代均衡译码方法.该方法以内嵌的二阶数字锁相环补偿Doppler造成的相位偏移,利用水声信道的稀疏特件进行均衡器系数更新,补偿多途效应产生的码间串扰,通过均衡器和译码器之间多次联合迭代交换软信息提高系统的BER性能.基于实测湖试信道条件进行了仿真,结果表明LC-JIED方法对于浅海远程稀疏水声信道十分有效,通过编码器与均衡器之间多次迭代交换软信息可大幅提高系统性能,适合于中低信噪比应用场合,具有广泛的应用前景.%Long-range communications in shallow water faces great challenges of severe multipath interference, fading, and low SNR. The traditional second-order digital phase lock loop (DPLL) embedded decision feedback equalizer can only work at high SNR, serious error propagation may occur at low and moderate SNR. In order to improve reliability of long-range shallow water communications, a low complexity joint iterative equalization and decoding (LC-JIED) scheme is proposed for sparse underwater communication channel. The method compensates for Doppler shifts using an embedded second-order DPLL, and updates the equalizer coefficients by taking into account sparsity of the channel. System performance is greatly improved by iteratively exchanging soft information between the equalizer and decoder. Simulations based on real lake channel profiles show that the proposed method is effective for sparse underwater channel. It can significantly improve reliability of long-range shallow water acoustic communications by exchanging soft information between equalizer and decoder at low to moderate SNR.

  18. Standard logarithmic mean velocity distribution in a band-limited restricted nonlinear model of turbulent flow in a half-channel

    CERN Document Server

    Bretheim, Joel U; Gayme, Dennice F

    2014-01-01

    Numerical simulations of wall-turbulence using the restricted nonlinear (RNL) model generate realistic mean velocity profiles in plane Couette and channel flow at low Reynolds numbers. The results are less accurate at higher Re, and while a logarithmic region is observed, its von-K\\'arm\\'an constant is not consistent with the standard logarithmic law. In half-channel flow we show that limiting the streamwise-varying wavenumber support of RNL turbulence to one or few empirically determined modes improves its predictions considerably. In particular, the mean velocity profiles obtained with the band-limited RNL model follow standard logarithmic behavior for the higher Reynolds numbers in this study.

  19. Evaluation of the capacity of communication lines with nonlinear finite memory

    Science.gov (United States)

    Shapiro, E. G.; Shapiro, D. A.

    2016-12-01

    We propose a method for calculating the capacity of a finite-memory channel up to the square of the nonlinear memory parameter. A comparison with a regular Gaussian model is performed, in which the Kerr nonlinearity is considered as an additional Gaussian noise. The estimate by the regular Gaussian model is shown to yield a greater capacity as compared with the estimate obtained by the nonlinear memory model. The optimal signal powers, providing the maximum mutual information, are found to be equal.

  20. 一种基于输出过采样的IIR盲均衡算法%A Blind Equalization Algorithm for IIR Channel Based on Oversampling

    Institute of Scientific and Technical Information of China (English)

    杨鑫伟; 赵乐军

    2012-01-01

    基于对IIR信道输出过采样,构造了一种单输入多输出(SIMO)信道模型。在该模型中,由于在AR子信道采用RLS迭代算法和在MA子信道采用了一种改进的CMA算法,从而使得该算法比传统算法更简化,收敛速度得到提高。仿真实验结果验证了该算法的有效性。%Based on the oversampling to the output of the IIR channel, this paper constructs a SIMO (single input multiple output) channel model. In this model, RLS algorithm and the improved CMA algorithm are adopted, respectively, in AR sub-channel and MA sub-channel such that this algorithm is much simpler than the traditional algorithm, and can attain faster convergence. Simulation results verify the effectiveness of the proposed algorithm.

  1. Incomplete equalization

    DEFF Research Database (Denmark)

    Holm, Anders; Jæger, Mads Meier; Karlson, Kristian Bernt;

    2013-01-01

    This paper tests whether the existence of vocationally oriented tracks within a traditionally academically oriented upper education system reduces socioeconomic inequalities in educational attainment. Based on a statistical model of educational transitions and data on two entire cohorts of Danish...... youth, we find that (1) the vocationally oriented tracks are less socially selective than the traditional academic track; (2) attending the vocationally oriented tracks has a negative effect on the likelihood of enrolling in higher education; and (3) in the aggregate the vocationally oriented tracks...... improve access to lower-tier higher education for low-SES students. These findings point to an interesting paradox in that tracking has adverse effects at the micro-level but equalizes educational opportunities at the macro-level. We also discuss whether similar mechanisms might exist in other educational...

  2. A Joint Frequency-Domain Equalization (Fde and Antenna Diversity Combining Method for the Multipath Fading in the Frequency-Selective Channel

    Directory of Open Access Journals (Sweden)

    Wang Jinpeng

    2016-01-01

    Full Text Available In this study, a theoretical foundation is built to evaluate the downlink performance of an MC-CDMA cellular system with site diversity operation with and receive antenna diversity combining. An expression for the theoretical conditional bit error rate (BER for the given set of channel gains is derived based on Gaussian approximation of the interference components in the composite receive signal. The local average BER is then obtained by averaging the conditional BER over the given set of channel gains using Monte-Carlo numerical method. The outage probability is measured from the numerically obtained cumulative distribution of the local average BER to determine the downlink capacity. Results from theoretical computation are compared to the results from computer simulation and discussed.

  3. OFDM系统中低复杂度的时变信道迭代均衡算法%Low-Complexity Iterative Equalization for Time-Variant Channels in OFDM Systems

    Institute of Scientific and Technical Information of China (English)

    陆许明; 张黎辉; 谭洪舟

    2013-01-01

    In order to tackle the inter-carrier interference ( ICI) problem caused by time-variant channels in orthogonal frequency division multiplexing ( OFDM) systems, a low-complexity iterative equalization technique was proposed in this paper. The impulse response of a time-variant channel was represented by the first-order polynomial basis expansion model to reduce channel parameters. Since the frequency-domain channel matrix was nearly banded, it was divided by the positions of pilot clusters into blocks along the diagonal for equalization. Then the linear zero-forcing equalization was applied to each block. In order to simplify the computational complexity, the Gaussian belief propagation (GaBP) algorithm was used to solve the linear equations in the equalization. Thus the proposed algorithm avoided the matrix inverse operation, and canceled the effects of inter-carrier interference efficiently. Computational complexity analysis and simulation results showed that the proposed equalization technique reduced the bit error rate significantly with low computational cost. In summary, the proposed block-GaBP equalizer has the superiority of low computational complexity and distributed approach for equalization, and therefore, is suitable for hardware implementation such as application-specific integrated circuit.%针对正交频分复用系统在时变信道中的均衡问题,提出了一种低复杂度的时变信道均衡算法.该算法首先运用一阶多项式基扩展模型对时变信道进行建模,利用频域信道矩阵能量主要集中在对角线附近的特点,将频域信道矩阵按梳状导频的位置沿对角线分块,然后运用高斯置信传播算法分别进行线性迫零均衡.算法避免了矩阵求逆运算,降低了计算复杂度,同时有效补偿了多普勒频移引起的载波间干扰,提高了系统性能.计算机仿真结果和算法复杂度分析表明,提出的分块迭代均衡算法有效降低了时变信道中系统的误码

  4. 等通道挤压大变形条件下原子的快速扩散行为研究%Study of atomic superdiffusion phenomenon with the method of equal channel_angular pressing severe plastic deformation

    Institute of Scientific and Technical Information of China (English)

    杜柳; 魏艳妮; 李京龙; 熊江涛

    2012-01-01

    In this peper,Equal Channel Angular Pressing is chosen as severe plastic deformation,by comparing the diffusion action of ECAP and equilibrium condition in Ag-Pb immiscible system to study the atom diffusion action under severe plastic deformation condilion.The study results show that;The diffusion coefficient under ECAP condition is one to two orders of magnitude higher than that of the equilibrium,which reveal the exist of superdiffusion in severe plastic deformation.%采用等通道挤压(Equal Channel Angular Pressing,ECAP)作为大变形手段,通过Ag-Pb互不相溶体系在ECAP和平衡态两种条件下原子扩散行为的对比,研究大变形条件下原子扩散行为.结果表明,ECAP条件下原子的热激活扩散系数高出平衡态1~2个数量级,揭示了大变形条件下原子快速扩散行为的存在.

  5. Iterative Estimation in Turbo Equalization Process

    Directory of Open Access Journals (Sweden)

    MORGOS Lucian

    2014-05-01

    Full Text Available This paper presents the iterative estimation in turbo equalization process. Turbo equalization is the process of reception in which equalization and decoding are done together, not as separate processes. For the equalizer to work properly, it must receive before equalization accurate information about the value of the channel impulse response. This estimation of channel impulse response is done by transmission of a training sequence known at reception. Knowing both the transmitted and received sequence, it can be calculated estimated value of the estimated the channel impulse response using one of the well-known estimation algorithms. The estimated value can be also iterative recalculated based on the sequence data available at the output of the channel and estimated sequence data coming from turbo equalizer output, thereby refining the obtained results.

  6. Physical mechanism of beam halo-chaos formation for high-current proton beam in a periodic-focusing channels and a nonlinear control strategy

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    The physical mechanism of the halo-chaos formation for a high intensity proton beam in a periodic-fo cusing channel is analyzed using the transfer mahix theory and a qualiative analysis method.Particles-in-cell simula tims are further used to explore the mechanism of the beam halo-chaos fomation, which concerns not only with thc non linear effect of the beam space charge but also with the lransverse energy exchange belween the particles and the particle core. as well as the chaos generated by the nonlinear resonance ovcrlap. A nonlinear control method is proposed for con trolling tie haho-chaos. Simulation results show lhal the melhod is efhclivc. Somc potemlial applications of the halo chaos conlrol in experimenls are discussed.

  7. Microstructure and texture evolution of Al-7075 alloy processed by equal channel angular pressing%等径角挤压7075铝合金的显微组织和织构演变

    Institute of Scientific and Technical Information of China (English)

    M.H.SHAERI; M.SHAERI; M.T.SALEHI; S.H.SEYYEDEIN; F.DJAVANROODI

    2015-01-01

    Equal channel angular pressing is an effective technique to control the texture and microstructure of metals and alloys. Texture and microstructure of an Al-7075 alloy subjected to repetitive equal channel angular pressing through a 90° die were evaluated by X-ray diffractometer and orientation imaging microscopy. It is observed that processing through different routes leads to different types of textures, in both qualitative and quantitative senses. The texture calculation by Labotex software reveals that texture strengthens after the first pass and weakens by progressing ECAP process up to 4 passes. Microstructure investigations show that after 4 passes of equal channel angular pressing via routes BC and A, very fine grains with average grain size of about 700 nm and 1μm appear, respectively, and most of the grains evolve into arrays of high angle boundaries. The effects of covering the Al-7075 billets with copper tube on texture and microstructure were also studied.%等径角挤压是一种有效的控制金属和合金显微组织和织构的技术.采用X射线衍射仪和取向成像显微镜评价通过90°模具反复等径角挤压7075铝合金的显微组织和织构.定性和定量分析结果表明,不同的路径会产生不同的织构类型.利用Labotex软件计算的织构表明,经第1道次等径角挤压后合金织构增强,而经第4道次挤压后合金织构减弱.显微组织研究表明,经过Bc和A路径等径角挤压4道次后,出现了平均尺寸分别为700 nm和1μm 的细小晶粒,且大多数晶粒演化为大角度晶界排列.研究了铜管包覆对7075铝合金显微组织和织构的影响.

  8. Linear and nonlinear analyses of multi-channel mechanomyographic recordings reveal heterogeneous activation of wrist extensors in presence of delayed onset muscle soreness.

    Science.gov (United States)

    Madeleine, Pascal; Hansen, Ernst A; Samani, Afshin

    2014-12-01

    In this study, we applied multi-channel mechanomyographic (MMG) recordings in combination with linear and nonlinear analyses to investigate muscular and musculotendinous effects of high intensity eccentric exercise. Twelve accelerometers arranged in a 3 × 4 matrix over the dominant elbow muscles were used to detect MMG activity in 12 healthy participants. Delayed onset muscle soreness was induced by repetitive high intensity eccentric contractions of the wrist extensor muscles. Average rectified values (ARV) as well as percentage of recurrence (%REC) and percentage of determinism (%DET) extracted from recurrence quantification analysis were computed from data obtained during static-dynamic contractions performed before exercise, immediately after exercise, and in presence of muscle soreness. A linear mixed model was used for the statistical analysis. The ARV, %REC, and %DET maps revealed heterogeneous MMG activity over the wrist extensor muscles before, immediately after, and in presence of muscle soreness (P<0.01). The ARVs were higher while the %REC and %DET were lower in presence of muscle soreness compared with before exercise (P<0.05). The study provides new key information on linear and nonlinear analyses of multi-channel MMG recordings of the wrist extensor muscles following eccentric exercise that results in muscle soreness. Recurrence quantification analysis can be suggested as a tool for detection of MMG changes in presence of muscle soreness.

  9. Effect of workpiece viscosity on strain unevenness during equal channel angular extrusion: CFD 2D solution of Navier-Stokes equations for the physical variables ‘flow velocities—punching pressure’

    Science.gov (United States)

    Perig, Alexander V.; Golodenko, Nikolai N.

    2016-11-01

    The present article addresses strain unevenness effects during equal channel angular extrusion (ECAE) of physical models of polymer workpieces with viscosity flow features through a Segal die with channel intersection angle of 2θ = 90°. Computational viscous flow lines, flow velocity fields, and material dead zone formation in the physical simulation of ECAE have been numerically derived for planar flow of viscous incompressible continua in an angular die with 2θ = 90°. This is accomplished through the introduction of Navier-Stokes equations with the following dimensionless physical variables: polymer model local flow velocities u, v and punching pressure p. Derived experimental results are grounded on the application of the following physical simulation techniques: marker method, based on harder disperse particles partially forcing into the front faces of soft workpieces; layered model production by assembling the workpiece soft model with different layers, and circular gridlines use with viscous flow of the polymer soft model. Good agreement has been found between the computational and observable physical simulation results. Based on the obtained results, recommendations are made for polymer ECAE technology enhancement and angular die design for polymer workpiece pressure forming.

  10. Effects of oblique wave propagation on the nonlinear plasma resonance in the two-dimensional channel of the Dyakonov-Shur detector

    Science.gov (United States)

    Rupper, Greg; Rudin, Sergey; Crowne, Frank J.

    2012-12-01

    In the Dyakonov-Shur terahertz detector the conduction channel of a heterostructure High Electron Mobility Transistor (HEMT) is used as a plasma wave resonator for density oscillations in electron gas. Nonlinearities in the plasma wave propagation lead to a constant source-to-drain voltage, providing the detector output. In this paper, we start with the quasi-classical Boltzmann equation and derive the hydrodynamic model with temperature dependent transport coefficients for a two-dimensional viscous flow. This derivation allows us to obtain the parameters for the hydrodynamic model from the band-structure of the HEMT channel. The treatment here also includes the energy balance equation into the analysis. By numerical solution of the hydrodynamic equations with a non-zero boundary current we evaluate the detector response function and obtain the temperature dependence of the plasma resonance. The present treatment extends the theory of Dyakonov-Shur plasma resonator and detector to account for the temperature dependence of viscosity, the effects of oblique wave propagation on detector response, and effects of boundary current in two-dimensional flow on quality of the plasma resonance. The numerical results are given for a GaN channel. We also investigated a stability of source to drain flow and formation of shock waves.

  11. Simultaneous regeneration of 4×160-Gbit/s WDM and PDM channels in a single highly nonlinear fiber

    DEFF Research Database (Denmark)

    Wang, Ju; Ji, Hua; Hu, Hao;

    2013-01-01

    We demonstrate simultaneous regeneration of 4×160-Gbit/s signals in a HNLF. The receiver powers at the BER of 10−9 are improved by 1.9 dB, 1.8 dB, 1.6 dB and 1.5 dB for the four channels, respectively....

  12. Criteria for equality in two entropic inequalities

    Energy Technology Data Exchange (ETDEWEB)

    Shirokov, M. E., E-mail: msh@mi.ras.ru [Steklov Mathematical Institute, Russian Academy of Sciences, Moscow (Russian Federation)

    2014-07-31

    We obtain a simple criterion for local equality between the constrained Holevo capacity and the quantum mutual information of a quantum channel. This shows that the set of all states for which this equality holds is determined by the kernel of the channel (as a linear map). Applications to Bosonic Gaussian channels are considered. It is shown that for a Gaussian channel having no completely depolarizing components the above characteristics may coincide only at non-Gaussian mixed states and a criterion for the existence of such states is given. All the obtained results may be reformulated as conditions for equality between the constrained Holevo capacity of a quantum channel and the input von Neumann entropy. Bibliography: 20 titles. (paper)

  13. 一簇非线性等式约束优化问题的过滤线搜索修正正割方法%A Class of Line Search Filter Improved Secant Methods for Nonlinear Equality Constrained Optimization

    Institute of Scientific and Technical Information of China (English)

    王祝君; 朱德通

    2012-01-01

    本文提供了一簇新的过滤线搜索修正正割方法求解非线性等式约束优化问题.新算法簇的特点是:用修正正割算法簇中的一个算法获得搜索方向,回代线搜索技术得到步长,过滤准则用来决定是否接受步长,引入二阶校正技术减少不可行性并克服Maratos效应.在合理的假设条件下,分析了算法的总体收敛性.并证明了,通过附加二阶校正步,算法簇克服了Maratos效应,并二步Q-超线性收敛到满足二阶充分最优条件的局部解.数值结果表明了所提供的算法具有有效性.%This paper proposes a new class of line search filter improved secant methods for general nonlinear equality constrained optimization. The feature of these new algorithms is that one of the improved secant algorithms is used to produce a search direction, a backtracking line search procedure to generate step size, some filtered rules to determine step acceptance, second order correction technique to reduce infeasibility and overcome the Maratos effects. Under mild assumptions the global convergence is established. Moreover, it is also established that the Maratos effect are overcome in our new approaches by adding second order correction steps so that two-step Q-superlinear convergence to second order sufficient local solution is achieved. The results of numerical experiments are reported to show the effectiveness of these proposed algorithms.

  14. Simultaneous multi-channel CMW-band and MMW-band UWB monocycle pulse generation using FWM effect in a highly nonlinear photonic crystal fiber.

    Science.gov (United States)

    Zhang, Fangzheng; Wu, Jian; Fu, Songnian; Xu, Kun; Li, Yan; Hong, Xiaobin; Shum, Ping; Lin, Jintong

    2010-07-19

    We propose and experimentally demonstrate a scheme to simultaneously realize multi-channel centimeter wave (CMW) band and millimeter wave (MMW) band ultra-wideband (UWB) monocycle pulse generation using four wave mixing (FWM) effect in a highly nonlinear photonic crystal fiber (HNL-PCF). Two lightwaves carrying polarity-reversed optical Gaussian pulses with appropriate time delay and another lightwave carrying a 20 GHz clock signal are launched into the HNL-PCF together. By filtering out the FWM idlers, two CMW-band UWB monocycle signals and two MMW-band UWB monocycle signals at 20 GHz are obtained simultaneously. Experimental measurements of the generated UWB monocycle pulses at individual wavelength, which comply with the FCC regulations, verify the feasibility and flexibility of proposed scheme for use in practical UWB communication systems.

  15. Turbo Equalization Using Partial Gaussian Approximation

    DEFF Research Database (Denmark)

    Zhang, Chuanzong; Wang, Zhongyong; Manchón, Carles Navarro

    2016-01-01

    returned by the equalizer by using a partial Gaussian approximation (PGA). We exploit the specific structure of the ISI channel model to compute the latter messages from the beliefs obtained using a Kalman smoother/equalizer. Doing so leads to a significant complexity reduction compared to the initial PGA...

  16. Machine learning techniques applied to system characterization and equalization

    DEFF Research Database (Denmark)

    Zibar, Darko; Thrane, Jakob; Wass, Jesper

    2016-01-01

    Linear signal processing algorithms are effective in combating linear fibre channel impairments. We demonstrate the ability of machine learning algorithms to combat nonlinear fibre channel impairments and perform parameter extraction from directly detected signals.......Linear signal processing algorithms are effective in combating linear fibre channel impairments. We demonstrate the ability of machine learning algorithms to combat nonlinear fibre channel impairments and perform parameter extraction from directly detected signals....

  17. Maximum likelihood channel estimation based on nonlinear filter%基于非线性滤波器的最大似然信道估计

    Institute of Scientific and Technical Information of China (English)

    沈壁川; 郑建宏; 申敏

    2008-01-01

    For long finite channel impulse response,accurate maximum likelihood channel estimation is computationally high cost due to high dimension of parameter space,and approximate approaches are usually adopted.By utilizing the suppression of noise and extraction of signal of the nonlinear Teager-Kaiser filter,a likelihood ratio of channel estimation is defined to represent the probability distribution of ehannel parameters.Maximization of this likelihood funetion 1eads to initially searching the extrema of path delays and then the complex attenuation.Computer simulation iS conducted and the results show periormance improvements of ioint detection as compared to the non-likelihood approach.%在有限信道冲激响应较长的情况,由于待估计参数空间的高维数,准确计算最大似然信道估计的复杂度较高,在实际应用中通常采用近似的方法.利用非线性Teager-Kaiser滤波器在抑制噪声的同时可以有效提取信号的特征,定义了一个表征信道参数概率分布的似然比,对该似然函数的最大化是首先得到路径延迟的极值,然后求得复路径衰耗.计算机仿真结果表明,与非似然方法相比,采用该似然函数方法能使联合检测性能得到提高.

  18. Flow properties of 6061 aluminum alloy processed by equal channel angular extrusion%6061铝合金等通道转角挤压时的流变性能

    Institute of Scientific and Technical Information of China (English)

    董洪波; 黄映霞

    2011-01-01

    Extrusion deformation experiments for annealed and solution-aged 6061 aluminum alloy were carried out by using equal channel angular extrusion (ECAE) technique. The samples were extruded in the ECAE die for eight and four passes at room temperature,respectively. Meanwhile, the deformation behavior of the alloy was simulated by FEM using software Deform-3D. The deformed microstructure and flow properties of 6061 aluminum alloy were investigated. The results show that the grains are refined by equal channel angular extrusion, and the metal flow lines distribute nearly along the diagonal direction on longitudinal section. The surface hardness of annealed 6061 aluminium alloy increases continuously with increasing the ECAE passes. However, the peak value of deforming load in each ECAE process does not show monotonic increase with increasing passes, but rises at first, then falls down, and increases again. The maximum surface hardness and maximum deforming load of the solution-aged 6061 aluminium alloy occurs after ECAE for two passes.Surface hardness of the alloy depends on its strengthening mechanisms and movement of dislocations, and deforming load is related to the friction of ECAE die and sample and material strength. The simulation shows that the peak value of deforming load for each ECAE pass increase slowly with increasing of strain, so the calculated values are not in agreement with the measured ones. In order to characterize the flow behavior of the alloy correctly, the constitutive relationship of the material should be modified properly due to the change of its microstructure and properties greatly with severe plastic deformation.%分别对退火态和固溶时效态6061铝合金进行8道次及4道次等通道转角挤压,用有限元软件Deform-3D模拟变形过程,研究连续大变形对组织性能的影响规律.结果表明:等通道挤压使晶粒破碎细化,金属流线走向与剖面对角线方向基本一致;退火态合金的表面硬度随

  19. Deformation and Fracture Behavior of Equal Channel Angular on AZ31 Alloy%AZ31镁合金等径角变形与断裂行为研究

    Institute of Scientific and Technical Information of China (English)

    康锋; 程平; 吴海英

    2012-01-01

    研究了AZ31镁合金在150~250℃、等效应变速率0.001~0.25 s-1内一道次等温等径角变形(ECAP)过程中的变形与断裂行为.剪切带和剪切断裂的观察结果可由量化应力集中趋势的局部流变集中参数α来预测.结果表明,AZ31镁合金在ECAP变形过程中极易发生局部剪切,而均匀变形只发生在高温和低应变率条件下;通过材料性能对局部流变趋势的影响,可选择最优的加工方案,以获得材料的均匀变形.%The deformation and fracture characteristics of AZ31 alloy during equal channel angular pressing (ECAP) were investigated at temperatures between 150 ℃ and 250 ℃ and ram speeds producing average effective strain rates between 0.001 s-1 and 0.25 s-1. Observations of shear banding and shear fracture were interpreted in terms of the tendency for strata concentration as quantified by the flow localization 'α ' parameter, or the ratio of the normalized flow softening rate to the strain-rate sensitivity. The results show that A231 alloy is particularly susceptible to shear localization during ECAP; the uniform flow occurs only at high temperatures and low strain raws. These conclusions of tbe effects of material properties on flow localization tendency are helpful for the selection of optimum processing parameters, and then the uniform deformation can be obtained during ECAP.

  20. A 1.83 μJ/Classification, 8-Channel, Patient-Specific Epileptic Seizure Classification SoC Using a Non-Linear Support Vector Machine.

    Science.gov (United States)

    Bin Altaf, Muhammad Awais; Yoo, Jerald

    2016-02-01

    A non-linear support vector machine (NLSVM) seizure classification SoC with 8-channel EEG data acquisition and storage for epileptic patients is presented. The proposed SoC is the first work in literature that integrates a feature extraction (FE) engine, patient specific hardware-efficient NLSVM classification engine, 96 KB SRAM for EEG data storage and low-noise, high dynamic range readout circuits. To achieve on-chip integration of the NLSVM classification engine with minimum area and energy consumption, the FE engine utilizes time division multiplexing (TDM)-BPF architecture. The implemented log-linear Gaussian basis function (LL-GBF) NLSVM classifier exploits the linearization to achieve energy consumption of 0.39 μ J/operation and reduces the area by 28.2% compared to conventional GBF implementation. The readout circuits incorporate a chopper-stabilized DC servo loop to minimize the noise level elevation and achieve noise RTI of 0.81 μ Vrms for 0.5-100 Hz bandwidth with an NEF of 4.0. The 5 × 5 mm (2) SoC is implemented in a 0.18 μm 1P6M CMOS process consuming 1.83 μ J/classification for 8-channel operation. SoC verification has been done with the Children's Hospital Boston-MIT EEG database, as well as with a specific rapid eye-blink pattern detection test, which results in an average detection rate, average false alarm rate and latency of 95.1%, 0.94% (0.27 false alarms/hour) and 2 s, respectively.

  1. SOME BLIND FRESH EQUALIZATION ALGORITHMS WITH ANTI-INTERFERENCE CAPABILITIES

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    Some novel blind FREquency.Shift (FRESH) equalizer algorithms axe proposed for the equalization of Finite Impulse Response(FIR)single channel with anti-interference capabilities.These algorithms based on FRESH filter can work well without any training sequence.Simulation results show that the equalizer algorithms can effectively reject many types of interferences and the performances of these new equalizer algorithms are superior to the conventional equalizer algorithms.

  2. Education, equality and difference

    Directory of Open Access Journals (Sweden)

    Penny Enslin

    1994-03-01

    Full Text Available Does the pursuit of equality in post-apartheid education require the removal of difference? This article examines the concepts of difference and equality by exploring two contemporary texts in political philosophy. It is argued that the pursuit of equality can and should, under certain circumstances, accommodate difference in the form of decentralisation and private schools.

  3. Equal opportunities in diversity

    CERN Multimedia

    Laëtitia Pedroso

    2010-01-01

    Promoting equal opportunities at CERN and advising the Director-General on all related matters is the task of the Equal Opportunities Officer, Doris Chromek-Burckhart, and Tim Smith, chair of the Equal Opportunities Advisory Panel. Changes are being introduced: in future, the focus of their work will be broadened to cover all aspects of diversity promotion.   The term "equal opportunities" has always been broader in scope than the equal treatment of men and women but this is what it has traditionally been confined to in practice. "We wanted to change how people see our mission", explains Doris Chromek-Burckhart. The word "diversity" has much wider connotations than "equal opportunities" and makes it clearer that we are also dealing with differences in nationality, religion, age, culture and physical ability”. Getting away from the old clichés is vital to ensuring equal treatment for everyone. The diversit...

  4. Design of a transversal equalizer for electronic dispersion compensation in optical communication links

    Institute of Scientific and Technical Information of China (English)

    GAO Zhen-bin; SHI Yong; WANG Bo; ZENG Xiang-ye

    2011-01-01

    @@ A programmable transversal equalizer for electronic dispersion compensation (EDC) in optical fiber communication systems is developed.Based on the SiGe technology with a cut-off frequency of 80 GHz, the equalizer consists of 6 seriesparallel amplifiers as delay units and 7 Gilbert variable gain amplifiers as taps, which ensure that the equalizer can work at the bit rate of 10 Gb/s.With different tap gains, the forward voltage gain of the transversal equalizer varies, which demonstrates that the equalizer has various filtering characteristics such as low pass filtering, band pass filtering, band reject filtering, and notch filtering, so it can effectively simulate the inverse transfer function of dispersive channels in optical communications, and can be used for compensating the inter-symbol interference and other nonlinear problems caused by dispersion.The equalizer (including pads) occupies an area of 0.40 mm × 1.08 mm, and its total power dissipation is 400 mW with 3.3 V power supply.

  5. Design of a transversal equalizer for electronic dispersion compensation in optical communication links

    Science.gov (United States)

    Gao, Zhen-bin; Shi, Yong; Wang, Bo; Zeng, Xiang-ye

    2011-01-01

    A programmable transversal equalizer for electronic dispersion compensation (EDC) in optical fiber communication systems is developed. Based on the SiGe technology with a cut-off frequency of 80 GHz, the equalizer consists of 6 seriesparallel amplifiers as delay units and 7 Gilbert variable gain amplifiers as taps, which ensure that the equalizer can work at the bit rate of 10 Gb/s. With different tap gains, the forward voltage gain of the transversal equalizer varies, which demonstrates that the equalizer has various filtering characteristics such as low pass filtering, band pass filtering, band reject filtering, and notch filtering, so it can effectively simulate the inverse transfer function of dispersive channels in optical communications, and can be used for compensating the inter-symbol interference and other nonlinear problems caused by dispersion. The equalizer (including pads) occupies an area of 0.40 mm×1.08 mm, and its total power dissipation is 400 mW with 3.3 V power supply.

  6. ECAP对粗晶AZ31镁合金的晶粒细化机制的影响%Effect of Equal Channel Angular Pressing on Grain-refining Mechanism of Coarse-grained AZ31 Magnesium Alloy

    Institute of Scientific and Technical Information of China (English)

    严凯; 孙扬善; 白晶; 薛烽

    2011-01-01

    Equal channel angular pressing (ECAP) was performed on AZ31 magnesium alloy and the microstructure and hardness distribution of the sample processed by ECAP was systematically studied. The results reveal that the twinning can coordinate grain deformation in the beginning of ECAP and provides the nucleation positions for the dynamic recrystallization in the later stage of ECAP. The grain refining mechanism of AZ31 magnesium alloy is inhomogeneity in the processing of ECAP because recrystallization nucleation mainly occurs in twin boundaries, which generates a bimodal grain size distribution. The big grains at the top of the sample are more than that at the bottom, and the difference of microstructure is caused by the variation of stress in the each position of the sample during static recrystallization, which cna explain the different ECAP routes affect the uniformity of Mg alloy.%采用等通道转角挤压(ECAP)方法对AZ31镁合金进行挤压加工,并研究了变形过程中试样各部位的显微组织和硬度的变化.显微组织分析表明,孪晶在剪切变形阶段可以协调晶粒变形,而且在变形后成为动态再结晶晶粒形成的中心.ECAP过程中AZ31镁合金的组织是以一种非均匀的方式细化的,再结晶晶粒主要在孪晶界上形核,这形成了双模态的晶粒分布.研究还发现,经过ECAP后的试样纵截面上部残留的大晶粒明显多于下部的,这是由于在静态再结晶阶段试样各部位受力状态的不同造成的,这很好地解释了ECAP不同路径对镁合金均匀性的影响.

  7. PERFORMANCE OF THREE STAGE TURBO-EQUALIZATION-DECODING

    Institute of Scientific and Technical Information of China (English)

    Kazi Takpaya

    2003-01-01

    An increasing demand for high data rate transmission and protection over bandlimited channels with severe inter-symbol interference has resulted in a flurry of activity to improve channel equalization, In conjunction with equalization, channel coding-decoding can be employed to improve system performance. In this letter, the performance of the three stage turbo-equalization-decoding employing log maximum a posteriori probability is experimentally evaluated by a fading simulator. The BER is evaluated using various information sequence and interleaver sizes taking into account that the communication medium is a noisy inter symbol interference channel.

  8. Gender equality and meritocracy

    OpenAIRE

    Powell, Stina

    2016-01-01

    This thesis examines how gender equality measures and discourses are reconciled with notions of merit in academia. Gender equality is often defined as equal rights for women and men and has become a widely accepted political goal and vision. Meritocratic principles build on the assumption that everyone, regardless of gender, class, race and sexuality, has the same opportunities to advance provided they are sufficiently hardworking and intelligent. Meritocratic principles thus build on the ass...

  9. Equal Opportunities Questionnaire

    CERN Document Server

    2007-01-01

    The initiative to promote Equal Opportunities at CERN started in 1993. The first Equal Opportunities Officer was appointed in 1996 followed by the creation of the Equal Opportunities Advisory Panel in 1998. Initially the concern was mainly the fair treatment of women in the work-place. Today the emphasis has evolved to ensuring that diversity is used to increase creativity and productivity in the work-place. In order to ensure that all aspects of Equal Opportunities and Diversity are covered, CERN’s Equal Opportunities team has prepared a survey to obtain your input. Your answers are confidential and will only be used for generating statistics. The questionnaire is on-line and can be accessed via: https://espace.cern.ch/EOQ. We hope that you will take a few minutes of your time to give your input and would be grateful if you could reply before 15/10/07. For further information about Equal Opportunities at CERN see: http://cern.ch/equal-opportunities The Equal Opportuni...

  10. Integer Equal Flows

    Energy Technology Data Exchange (ETDEWEB)

    Meyers, C A; Schulz, A S

    2009-01-07

    The integer equal flow problem is an NP-hard network flow problem, in which all arcs in given sets R{sub 1}, ..., R{sub {ell}} must carry equal flow. We show this problem is effectively inapproximable, even if the cardinality of each set R{sub k} is two. When {ell} is fixed, it is solvable in polynomial time.

  11. Is Equality Fair?

    Directory of Open Access Journals (Sweden)

    Arthur Tarasov

    2015-11-01

    Full Text Available This paper attempts to answer the question whether people consider decisions that lead to equal outcomes fair. I find that this is not always the case. In an experiment where subjects are given equal opportunities to choose how to divide money between each other in a two-player game, any strategy is perceived to be fair more than half the time, including the profit-maximizing strategy. The equal divisions that lead to equal outcomes are sometimes considered unfair by both players. Moreover, players frequently punished the others, whose decisions led to equal outcomes. I hypothesize that such punishments occur because people have different conceptions of what a fair outcome and fair punishment are

  12. Wireline equalization using pulse-width modulation

    NARCIS (Netherlands)

    Schrader, J.H.R.; Klumperink, Eric A.M.; Visschers, J.L.; Nauta, Bram

    2006-01-01

    Abstract-High-speed data links over copper cables can be effectively equalized using pulse-width modulation (PWM) pre-emphasis. This provides an alternative to the usual 2-tap FIR filters. The use of PWM pre-emphasis allows a channel loss at the Nyquist frequency of ~30dB, compared to ~20dB for a

  13. Equal Opportunities Questionnaire

    CERN Document Server

    2007-01-01

    The initiative to promote Equal Opportunities at CERN started in 1993. The first Equal Opportunities Officer was appointed in 1996, which was followed by the creation of the Equal Opportunities Advisory Panel in 1998. Initially the concern was mainly the fair treatment of women in the work-place. Today the emphasis has evolved to ensuring that diversity is used to increase creativity and productivity in the work-place. In order to ensure that all aspects of Equal Opportunities and Diversity are covered, CERN’s Equal Opportunities team has prepared a survey to obtain your input. Your answers are confidential and will only be used for generating statistics. The questionnaire is on-line and can be accessed via: https://espace.cern.ch/EOQ. We hope that you will take a few minutes of your time to give your input and would be grateful if you could reply before 15/10/07. For further information about Equal Opportunities at CERN see: http://cern.ch/equal-opportunities The Equa...

  14. Kalman filtering approach to blind equalization

    Science.gov (United States)

    Kutlu, Mehmet

    1993-12-01

    Digital communication systems suffer from the channel distortion problem which introduces errors due to intersymbol interference. The solution to this problem is provided by equalizers which use a training sequence to adapt to the channel. However in many cases in which a training sequence is unfeasible, the channel must be adapted blindly. Most of the blind equalization algorithms known so far have problems of convergence to local minima. Our intention is to offer an alternative approach by using extended Kalman filtering and hidden Markov models. They seem to yield more efficient algorithms which take the statistics of the transmitted sequence into consideration. The theoretical development of these new algorithms is discussed in this thesis. Also these algorithms have been simulated under different conditions. The results of simulations and comparisons with existing systems are provided. The models for simulations are presented as MATLAB codes.

  15. Comparison of Training, Blind and Semi Blind Equalizers in MIMO Fading Systems Using Capacity as Measure

    OpenAIRE

    Kavitha, Veeraruna; Sharma, Vinod

    2005-01-01

    Semi blind/blind equalizers are believed to work unsatisfactorily in fading MIMO channels compared to training based methods, due to slow convergence or high computational complexity. We revisit this issue. Defining a 'composite' channel for each equalizer, we compare the three algorithms based on the capacity of this channel. We show that, in a Rician (with line of sight, LOS) environment, semi blind/blind algorithms outperform training equalizers, but in Rayleigh channels, it is better to u...

  16. Diversity reception and equalization techniques for laser communication in space

    Institute of Scientific and Technical Information of China (English)

    Bo Liang; Weibiao Chen

    2007-01-01

    The principle of band-limited space optical communication system using the techniques of space diversity methods and time domain Rake receiver is analyzed. The joint channel equalizer method combining diversity reception and equalization technique is presented in space laser communication. By computer simulation, the bit error rates of noncoherent pace optical on-off keying signal using different space diversity methods, Rake reception with different inter-symbol interferences, joint diversity equalizations with different signal noise rates and different channel numbers are analysed. The results identify that joint diversity equalization method can enhance space optical communication erformance evidently.

  17. 等壁温下平行微通道内层流换热的数值模拟%Numerical simulation of laminar heat transfer of equal wall temperature in parallel micro channel

    Institute of Scientific and Technical Information of China (English)

    李彩霞; 王斯民; 胡鹏睿

    2012-01-01

    采用数值仿真的方法,模拟了矩形微通道内层流流动换热过程,使用的工质为去离子水.模拟结果揭示了以下结论:矩形微通道侧面的面积热阻会显著随流速而变化,在整体范围内,面积热阻会随流速的增加而减小,且减小的幅度会越来越小.微通道内流体流速的设置还因考虑到泵的承受能力,若流速过高,对泵性能的要求也会提高,因此流速的设置要综合考虑面积热阻和泵的性能.微通道的横截面积尺寸对微通道性能的影响不大.当微通道长宽比为1时,阻力系数最小.%The process of laminar flow and heat transfer inside the rectangular micro channel unit was numerically stimulated with the deionized water as working fluid. The result proves that the speed of flow has the influence on the area thermal resistance of the rectangular micro channel. As the speed of flow increases, the area thermal resistance of the rectangular micro channel reduces; when the speed of flow further increases, the temperature difference and the area thermal resistance reduce slowly. Increasing the speed of flow requests the higher performance for pump output, therefore the design of the flow speed in the micro channel should consider the area thermal resistance and the performance of pump. The cross area size of micro channel has a little influence on the micro channel performance. When the ratio of length to breadth of micro channel is 1, the resistance coefficient is the least.

  18. Transhumanism and moral equality.

    Science.gov (United States)

    Wilson, James

    2007-10-01

    Conservative thinkers such as Francis Fukuyama have produced a battery of objections to the transhumanist project of fundamentally enhancing human capacities. This article examines one of these objections, namely that by allowing some to greatly extend their capacities, we will undermine the fundamental moral equality of human beings. I argue that this objection is groundless: once we understand the basis for human equality, it is clear that anyone who now has sufficient capacities to count as a person from the moral point of view will continue to count as one even if others are fundamentally enhanced; and it is mistaken to think that a creature which had even far greater capacities than an unenhanced human being should count as more than an equal from the moral point of view.

  19. Gender equality revisited:

    DEFF Research Database (Denmark)

    Rostgaard, Tine; B. Eydal, G.

    2011-01-01

    The Nordic childcare policy model is often reviewed and even recommended internationally for its contribution to gender equality, high female labour force participation and, perhaps more indirectly, to a high fertility rate. Nordic childcare services and parental leave schemes have thus been...... portrayed in the literature as policies which have managed to facilitate a work–family model of dual earners and dual carers. However, the recent introduction of cash-for-care schemes seems to go against the Nordic dual earner/dual carer model and ideals of gender equality, in supporting parental (maternal...

  20. A Dynamic Tap Allocation for Concurrent CMA-DD Equalizers

    Directory of Open Access Journals (Sweden)

    Trindade DiegovonBM

    2010-01-01

    Full Text Available Abstract This paper proposes a dynamic tap allocation for the concurrent CMA-DD equalizer as a low complexity solution for the blind channel deconvolution problem. The number of taps is a crucial factor which affects the performance and the complexity of most adaptive equalizers. Generally an equalizer requires a large number of taps in order to cope with long delays in the channel multipath profile. Simulations show that the proposed new blind equalizer is able to solve the blind channel deconvolution problem with a specified and reduced number of active taps. As a result, it minimizes the output excess mean square error due to inactive taps during and after the equalizer convergence and the hardware complexity as well.

  1. Motivation and Equality.

    Science.gov (United States)

    Nicholls, John G.; Burton, John T.

    1982-01-01

    Argues that if teachers maintain task involvement in all children, they will achieve justifiable form of educational equality. Discusses social and personal factors which influence task involvement, including value framework of school (i.e., purpose school is seen to serve), organizational strategies adopted to facilitate learning, and specific…

  2. Equality Work in Finnish Ministries

    OpenAIRE

    Tanhua, Inkeri

    2015-01-01

    The aim of this thesis is to contribute to knowledge about the equality work in public sector organisations. Especially, my aim is to bring light into everyday experiences of doing equality work. This is achieved through interviewing equality workers in Finnish ministries. The study draws also on my personal experiences as an equality consultant. The main question I ask is: Which issues influence the content of equality work? According to feminist research, promoting equality is always a poli...

  3. Equal Love Rights

    Institute of Scientific and Technical Information of China (English)

    Zhou; Mingyang

    2015-01-01

    Recently,the LGBT community(including Lesbians,Gays,Bisexuals,Transgenders)has won big.In terms of their marriage rights,on July 2015,the Supreme Court of the United States has passed judegment to recognize same-sex marriage and grant most of their rights,which means one’s marriage with same sex is not only legal from then on,but also equal to that of opposite sex.

  4. Thoughts upon Equality

    Institute of Scientific and Technical Information of China (English)

    申辰瑜

    2015-01-01

    <正>Anyone who has some basic knowledge about The Declaration of Independence might not be unfamiliar with the following lines,"We hold these truths to be self-evident,that all men are created equal,that they are endowed by their Creator with certain unalienable rights,that they are among these are life,liberty and the pursuit of happiness."Those words were truly respectable and encouraging at that time as well as

  5. Equal Opportunities Advisory Panel

    CERN Multimedia

    HR Department

    2006-01-01

    At its meeting on 7 December 2006, the Standing Concertation Committee took note of the appointment of four new members of the Panel: Wisla Carena, Pierre Charrue, Sue Foffano and Markus Nordberg. The present composition of the Panel (appointed ad personam) is as follows: Tiziano Camporesi (Chairperson), Wisla Carena, Pierre Charrue, Sue Foffano, Josi Schinzel (Equal Opportunities Officer), Markus Nordberg, Christine Petit-Jean-Genaz et Elena Wildner. Human Resources Department Tel. 74480

  6. Democracy, Redistribution, and Equality

    Directory of Open Access Journals (Sweden)

    Adam Przeworski

    2012-06-01

    Full Text Available The article argues that economic inequality inevitably generates politicalinequality, which in turn reproduces economic inequality. Basic concepts areintroduced first along with strong caveats concerning the quality of the crossnationaldata on income distributions; historical patterns of income inequalityare summarized next, and with these preliminaries, a distinction is made betweenredistribution of consumption at a particular time and equalization of incomeearning capacities over time. Following this economic considerations, the articlediscussion moves to political factors that may block redistributions.

  7. Nonlinear optics and photonics

    CERN Document Server

    He, Guang S

    2015-01-01

    This book provides a comprehensive presentation on most of the major topics in nonlinear optics and photonics, with equal emphasis on principles, experiments, techniques, and applications. It covers many major new topics including optical solitons, multi-photon effects, nonlinear photoelectric effects, fast and slow light , and Terahertz photonics. Chapters 1-10 present the fundamentals of modern nonlinear optics, and could be used as a textbook with problems provided at the end of each chapter. Chapters 11-17 cover the more advanced topics of techniques and applications of nonlinear optics and photonics, serving as a highly informative reference for researchers and experts working in related areas. There are also 16 pages of color photographs to illustrate the visual appearances of some typical nonlinear optical effects and phenomena. The book could be adopted as a textbook for both undergraduates and graduate students, and serve as a useful reference work for researchers and experts in the fields of physics...

  8. THE EQUALITY PRINCIPLE REQUIREMENTS

    Directory of Open Access Journals (Sweden)

    CLAUDIA ANDRIŢOI

    2013-05-01

    Full Text Available The problem premises and the objectives followed: the idea of inserting the equality principle between the freedom and the justice principles is manifested in positive law in two stages, as a general idea of all judicial norms and as requirement of the owner of a subjective right of the applicants of an objective law. Equality in face of the law and of public authorities can not involve the idea of standardization, of uniformity, of enlisting of all citizens under the mark of the same judicial regime, regardless of their natural or socio-professional situation. Through the Beijing Platform and the position documents of the European Commission we have defined the integrative approach of equality as representing an active and visible integration of the gender perspective in all sectors and at all levels. The research methods used are: the conceptualist method, the logical method and the intuitive method necessary as means of reasoning in order to argue our demonstration. We have to underline the fact that the system analysis of the research methods of the judicial phenomenon doesn’t agree with “value ranking”, because one value cannot be generalized in rapport to another. At the same time, we must fight against a methodological extremism. The final purpose of this study is represented by the reaching of the perfecting/excellence stage by all individuals through the promotion of equality and freedom. This supposes the fact that the existence of a non-discrimination favourable frame (fairness represents a means and a condition of self-determination, and the state of perfection/excellency is a result of this self-determination, the condition necessary for the obtaining of this nondiscrimination frame for all of us and in conditions of freedom for all individuals, represents the same condition that promotes the state of perfection/excellency. In conclusion we may state the fact that the equality principle represents a true catalyst of the

  9. Underwater Communication in the Baltic Sea Using Iterative Equalization

    NARCIS (Netherlands)

    Sangfelt, E.; Nordenvaad, M.L.; Olofsson, N.; Nilsson, B.; Walree, P.A. van; Oberg, T.

    2007-01-01

    We introduce a multi-channel soft input/soft output receiver for underwater communication that performs joint iterative channel estimation, linear equalization, and decoding. The transmitted symbols were encoded using a turbo coded bit-sequence. Our method exploits the gain present in the turbo code

  10. Turbo iterative equalization for HSDPA systems

    Institute of Scientific and Technical Information of China (English)

    WU QiHui; ZHAO ChunMing; WANG JinLong

    2007-01-01

    In this paper, a turbo iterative receiver structure with chip equalization is proposed for the 3G high-speed downlink packet access (HSDPA) systems. The receiver equalizes the channel prior to the dispreading and then performs two successive soft-output decisions, achieved by a soft-input soft-output (SISO) multi-code detector and a SISO turbo decoder through an iterative process. At each iteration, extrinsic information is extracted from detection and decoding stages and is then used as a priori information in the next iteration, just as in turbo decoding. Computer simulations show that the turbo iterative receiver structure with chip equalization offers significant performance gain over the traditional receiver structure.

  11. The decision-feedback equalizer optimization for Gaussian noise

    Directory of Open Access Journals (Sweden)

    Arkadiusz Grzybowski

    2014-04-01

    Full Text Available The new method of decision-feedback parameters optimization for intersymbol interference equalizers is described in this paper. The error extension phenomena is well known and investigated in the decision feedback equalizers in data transmission. The existing coefficient in decision feedback depends on the receive decision risk qualification. There is proved the bit error probability can be decreased by this method for any channel with single interference sample and small Gaussian noise. The experimental results are presented for chosen type channels. The dependences of optimal feedback parameters on channel interference sample and on noise power are presented too.

  12. A SDP-based method for blind equalization of SIMO channels%基于半正定规划的 SIMO 信道盲均衡方法

    Institute of Scientific and Technical Information of China (English)

    王大磊; 王秀秀; 韩啸

    2014-01-01

    针对数字通信单输入多输出(SIMO)系统中的信道盲均衡问题,使用优化理论中的半正定规划(SDP)方法,对采用随机梯度法求解的二阶统计量盲均衡算法(MSOSA)进行改进,给出了一种新的盲均衡求解算法SDP‐MSOSA 。相比采用随机梯度迭代法实现的MSOSA ,SDP‐MSOSA需要的数据样点更少,且收敛后的稳态误差更小,能够更加有效地消除码间干扰,仿真实验验证了算法SDP‐MSOSA的有效性。%Aiming at blind equalization in single‐input multiple‐output (SIMO) system in digital com‐munication ,an algorithm SDP‐MSOSA was proposed based on semi‐definite programming (SDP) to improve the modified second‐order statistics based algorithm (MSOSA) via stochastic gradient descent method .Compared to algorithm MSOSA realized by stochastic gradient descent method ,the algo‐rithm SDP‐MSOSA needs less samples ,and can achieve faster convergence speed and lower steady‐state error .Computer simulations demonstrate the validity of the algorithm SDP‐MSOSA .

  13. Practical design of a nonlinear tuned vibration absorber

    DEFF Research Database (Denmark)

    Grappasonni, C.; Habib, G.; Detroux, T.

    2014-01-01

    The aim of the paper is to develop a new nonlinear tuned vibration absorber (NLTVA) capable of mitigating the vibrations of nonlinear systems which are known to exhibit frequency-energy-dependent oscillations. A nonlinear generalization of Den Hartog's equal-peak method is proposed to ensure equal...

  14. Single-channel 1.28 Tbit/s-525 km DQPSK transmission using ultrafast time-domain optical Fourier transformation and nonlinear optical loop mirror

    DEFF Research Database (Denmark)

    Guan, Pengyu; Mulvad, Hans Christian Hansen; Tomiyama, Yutaro

    2011-01-01

    We demonstrate a single-channel 1.28 Tbit/s-525 km transmission using OTDM of subpicosecond DQPSK signals. In order to cope with transmission impairments due to time-varying higherorder PMD, which is one of the major limiting factors in such a longhaul ultrahigh-speed transmission, we newly...

  15. A primer on equalization, decoding and non-iterative joint equalization and decoding

    Science.gov (United States)

    Myburgh, Hermanus C.; Olivier, Jan C.

    2013-12-01

    In this article, a general model for non-iterative joint equalization and decoding is systematically derived for use in systems transmitting convolutionally encoded BPSK-modulated information through a multipath channel, with and without interleaving. Optimal equalization and decoding are discussed first, by presenting the maximum likelihood sequence estimation and maximum a posteriori probability algorithms and relating them to equalization in single-carrier channels with memory, and to the decoding of convolutional codes. The non-iterative joint equalizer/decoder (NI-JED) is then derived for the case where no interleaver is used, as well as for the case when block interleavers of varying depths are used, and complexity analyses are performed in each case. Simulation results are performed to compare the performance of the NI-JED to that of a conventional turbo equalizer (CTE), and it is shown that the NI-JED outperforms the CTE, although at much higher computational cost. This article serves to explain the state-of-the-art to students and professionals in the field of wireless communication systems, presenting these fundamental topics clearly and concisely.

  16. An Accurate Approximation to the Distribution of the Sum of Equally Correlated Nakagami-m Envelopes and its Application in Equal Gain Diversity Receivers

    CERN Document Server

    Hadzi-Velkov, Zoran; Karagiannidis, George K; 10.1109/ICC.2009.5198714

    2009-01-01

    We present a novel and accurate approximation for the distribution of the sum of equally correlated Nakagami-m variates. Ascertaining on this result we study the performance of Equal Gain Combining (EGC) receivers, operating over equally correlating fading channels. Numerical results and simulations show the accuracy of the proposed approximation and the validity of the mathematical analysis.

  17. TAXATION. FAIRNESS. EQUALITY

    Directory of Open Access Journals (Sweden)

    Morar Ioan Dan

    2014-12-01

    of the tax burden between them, depending on how the tax base, depending on the type of taxpayer and according to other criteria. Another coordinated taxation is part of contemporary consumerist polticilor new tax, taxing certain income, especially income individuals is marked by the overall objective of capitalist society, that consumption growth. Fiscal policies are policies the new contemporary consumerism. And this phenomenon influences the distribution of the tax burden among taxpayers, more or less fair. What is tax fairness and how we can quantify? Here's a question that I try to raspunt from equality before the law tax payers. Equality before the tax law is not a primary goal of modern tax policy, it losing ground to tax efficiency goals and its economic and social components. On the other hand though fiscal phenomenon can help to ensure social peace through taxation to keep Sean absolute size of the tax burden and the fact that all are equal before the law, tax law and within given social policies in broadly, social security or insurance in respect restrains can be promoted by themselves and less by fiscal policy.

  18. Pipeline Analog-Digital Converters Dynamic Error Modeling for Calibration : Integral Nonlinearity Modeling, Pipeline ADC Calibration, Wireless Channel K-Factor Estimation

    OpenAIRE

    Medawar, Samer

    2012-01-01

    This thesis deals with the characterization, modeling and calibration of pipeline analog-digital converters (ADC)s. The integral nonlinearity (INL) is characterized, modeled and the model is used to design a post-correction block in order to compensate the imperfections of the ADC. The INL model is divided into: a dynamic term designed by the low code frequency (LCF) component depending on the output code k and the frequency under test m, and a static term known as high code frequency (HCF) c...

  19. Linear and Nonlinear Impairment Compensation in Coherent Optical Transmission with Digital Signal Processing

    DEFF Research Database (Denmark)

    Porto da Silva, Edson

    Digital signal processing (DSP) has become one of the main enabling technologies for the physical layer of coherent optical communication networks. The DSP subsystems are used to implement several functionalities in the digital domain, from synchronization to channel equalization. Flexibility...... nonlinearity compensation, (II) spectral shaping, and (III) adaptive equalization. For (I), original contributions are presented to the study of the nonlinearity compensation (NLC) with digital backpropagation (DBP). Numerical and experimental performance investigations are shown for different application...... scenarios. Concerning (II), it is demonstrated how optical and electrical (digital) pulse shaping can be allied to improve the spectral confinement of a particular class of optical time-division multiplexing (OTDM) signals that can be used as a building block for fast signaling single-carrier transceivers...

  20. Turbo-per-Tone Equalization for ADSL Systems

    Directory of Open Access Journals (Sweden)

    Marc Moonen

    2005-05-01

    Full Text Available We study the equalization procedure in discrete multitone (DMT-based systems, in particular, in DMT-based ADSL systems. Traditionally, equalization is performed in the time domain by means of a channel shortening filter. Shifting the equalization operations to the frequency domain, as is done in per-tone equalization, increases the achieved bitrate by 5–10%. We show that the application of the turbo principle to per-tone equalization can provide significant additional gains. In the proposed receiver structure, referred to as a “turbo-per-tone equalization” structure, equalization and decoding are performed in an iterative fashion. Equalization is done by means of a linear minimum mean squared error (MMSE equalizer, using a priori information. We give a description of an efficient implementation of such an equalizer in the per-tone structure. Simulations show that we obtain a bitrate increase of 12–16% compared to the original per-tone equalization-based receiver structure.

  1. NONLINEAR STABILITY FOR EADY'S MODEL

    Institute of Scientific and Technical Information of China (English)

    LIU Yong-ming; QIU Ling-cun

    2005-01-01

    Poincaré type integral inequality plays an important role in the study of nonlinear stability ( in the sense of Arnold's second theorem) for three-dimensional quasigeostophic flow. The nonlinear stability of Eady's model is one of the most important cases in the application of the method. But the best nonlinear stability criterion obtained so far and the linear stability criterion are not coincident. The two criteria coincide only when the period of the channel is infinite.additional conservation law of momentum and by rigorous estimate of integral inequality. So the new nonlinear stability criterion was obtained, which shows that for Eady 's model in the periodic channel, the linear stable implies the nonlinear stable.

  2. Reduced complexity turbo equalization using a dynamic Bayesian network

    Science.gov (United States)

    Myburgh, Hermanus C.; Olivier, Jan C.; van Zyl, Augustinus J.

    2012-12-01

    It is proposed that a dynamic Bayesian network (DBN) is used to perform turbo equalization in a system transmitting information over a Rayleigh fading multipath channel. The DBN turbo equalizer (DBN-TE) is modeled on a single directed acyclic graph by relaxing the Markov assumption and allowing weak connections to past and future states. Its complexity is exponential in encoder constraint length and approximately linear in the channel memory length. Results show that the performance of the DBN-TE closely matches that of a traditional turbo equalizer that uses a maximum a posteriori equalizer and decoder pair. The DBN-TE achieves full convergence and near-optimal performance after small number of iterations.

  3. BLIND CHANNEL ESTIMATION IN DELAY DIVERSITY FOR FREQUENCY SELECTIVE CHANNELS

    Institute of Scientific and Technical Information of China (English)

    Zhao Zheng; Jia Ying; Yin Qinye

    2003-01-01

    Delay diversity is an effective transmit diversity technique to combat adverse ef-fects of fading. Thus far, previous work in delay diversity assumed that perfect estimates ofcurrent channel fading conditions are available at the receiver and training symbols are requiredto estimate the channel from the transmitter to the receiver. However, increasing the number ofthe antennas increases the required training interval and reduces the available time within whichdata may be transmitted. Learning the channel coefficients becomes increasingly difficult for thefrequency selective channels. In this paper, with the subspace method and the delay character ofdelay diversity, a channel estimation method is proposed, which does not use training symbols. Itaddresses the transmit diversity for a frequency selective channel from a single carrier perspectivein the form of a simple equivalent fiat fading model. Monte Carlo simulations give the perfor-mance of channel estimation and the performance comparison of our channel-estimation-baseddetector with decision feedback equalization, which uses the perfect channel information.

  4. Gender equality and equal opportunity mechanisms in Italy

    Directory of Open Access Journals (Sweden)

    Mršević Zorica

    2007-01-01

    Full Text Available As a country of Southern European mentality Italy may be taken as the nearest-to-the-Balkans model of the gender equality mechanisms and necessity of their existence. Italy also might be taken as a model of domain and methods of functioning of the gender equality mechanisms as well as their connections with the EU development funds. Besides the Italian Ministry for Rights and Equal opportunities and the National Committee, the attention was paid to the whole range of local mechanisms and legal regulations dealing with advancement of women’s employment and counteracting discrimination on the labor market. In the text are analyzed through the five chapters the Italian mechanisms/institutions for gender equality as located within the European institutional environment but also within the context of Italian recent history of struggle against gender based discrimination. It was stressed that the essence of the accumulated European institutional wisdom is in diversity of the gender equality bodies rather then in their uniformity. Although the Italian mechanisms for gender equality are part of the European institutional environment their aim is to meet the internal needs for advancement of gender equality. Besides, the mechanisms also meet the demands of the international standards comprised in the documents issued by the UN and the EU. In European countries these mechanisms are frequently established and function in the domains of the labor and employment regulations, but also are located within the human rights portfolios while somewhere are connected with the minority rights and equal opportunity implementation.

  5. Filamentation with nonlinear Bessel vortices.

    Science.gov (United States)

    Jukna, V; Milián, C; Xie, C; Itina, T; Dudley, J; Courvoisier, F; Couairon, A

    2014-10-20

    We present a new type of ring-shaped filaments featured by stationary nonlinear high-order Bessel solutions to the laser beam propagation equation. Two different regimes are identified by direct numerical simulations of the nonlinear propagation of axicon focused Gaussian beams carrying helicity in a Kerr medium with multiphoton absorption: the stable nonlinear propagation regime corresponds to a slow beam reshaping into one of the stationary nonlinear high-order Bessel solutions, called nonlinear Bessel vortices. The region of existence of nonlinear Bessel vortices is found semi-analytically. The influence of the Kerr nonlinearity and nonlinear losses on the beam shape is presented. Direct numerical simulations highlight the role of attractors played by nonlinear Bessel vortices in the stable propagation regime. Large input powers or small cone angles lead to the unstable propagation regime where nonlinear Bessel vortices break up into an helical multiple filament pattern or a more irregular structure. Nonlinear Bessel vortices are shown to be sufficiently intense to generate a ring-shaped filamentary ionized channel in the medium which is foreseen as opening the way to novel applications in laser material processing of transparent dielectrics.

  6. On the power amplifier nonlinearity in MIMO transmit beamforming systems

    KAUST Repository

    Qi, Jian

    2012-03-01

    In this paper, single-carrier multiple-input multiple-output (MIMO) transmit beamforming (TB) systems in the presence of high-power amplifier (HPA) nonlinearity are investigated. Specifically, due to the suboptimality of the conventional maximal ratio transmission/maximal ratio combining (MRT/MRC) under HPA nonlinearity, we propose the optimal TB scheme with the optimal beamforming weight vector and combining vector, for MIMO systems with nonlinear HPAs. Moreover, an alternative suboptimal but much simpler TB scheme, namely, quantized equal gain transmission (QEGT), is proposed. The latter profits from the property that the elements of the beamforming weight vector have the same constant modulus. The performance of the proposed optimal TB scheme and QEGT/MRC technique in the presence of the HPA nonlinearity is evaluated in terms of the average symbol error probability and mutual information with the Gaussian input, considering the transmission over uncorrelated quasi-static frequency-flat Rayleigh fading channels. Numerical results are provided and show the effects on the performance of several system parameters, namely, the HPA parameters, numbers of antennas, quadrature amplitude modulation modulation order, number of pilot symbols, and cardinality of the beamforming weight vector codebook for QEGT. © 2012 IEEE.

  7. In vitro biocompatibility of equal channel angular processed (ECAP) titanium

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Taik Nam [Department of Information and Electronic Materials Engineering, Paichai University, Daejeon 302-735 (Korea, Republic of); Balakrishnan, A [Department of Information and Electronic Materials Engineering, Paichai University, Daejeon 302-735 (Korea, Republic of); Lee, B C [Department of Information and Electronic Materials Engineering, Paichai University, Daejeon 302-735 (Korea, Republic of); Kim, W S [Department of Dental Lab Technology, Daejeon Health Science College, Daejeon 300-711 (Korea, Republic of); Smetana, K [Center of Cell Therapy and Tissue Repair, Charles University, Prague 128-00 (Czech Republic); Park, J K [Department of Materials Science and Engineering, KAIST, Daejeon 305-701 (Korea, Republic of); Panigrahi, B B [Division of Advanced Technology, Korea Research Institute of Standards and Science, Daejeon 305-340 (Korea, Republic of)

    2007-09-15

    This work attempts to understand the in vitro biocompatibility of ultrafine grained titanium prepared by the ECAP route. The results obtained from the mouse fibroblast cell line 3T3 showed a better cell adherence and cell proliferation on ECAP titanium specimen compared to the coarse grain Grade-2 Ti and Ti6Al4V alloy. This could be attributed to the increased surface energy and grain boundary energy and possibly the presence of a large number of nano-size conical groove-like structures (at triple point junctions of grain boundaries on the surface) in the ECAP Ti specimen compared to the coarse grain Grade-2 Ti and Ti6Al4V alloy.

  8. Generalized Analytical Solutions for Nonlinear Positive-Negative Index Couplers

    Directory of Open Access Journals (Sweden)

    Zh. Kudyshev

    2012-01-01

    Full Text Available We find and analyze a generalized analytical solution for nonlinear wave propagation in waveguide couplers with opposite signs of the linear refractive index, nonzero phase mismatch between the channels, and arbitrary nonlinear coefficients.

  9. Effects of rotation and magnetic field on the nonlinear peristaltic flow of a second-order fluid in an asymmetric channel through a porous medium

    Institute of Scientific and Technical Information of China (English)

    A.M.Abd-Alla; S.M.Abo-Dahab; H.D.El-Shahrany

    2013-01-01

    In this paper,the effects of both rotation and magnetic field of the peristaltic transport of a second-order fluid through a porous medium in a channel are studied analytically and computed numerically.The material is represented by the constitutive equations for a second-order fluid.Closed-form solutions under the consideration of long wavelength and low Reynolds number is presented.The analytical expressions for the pressure gradient,pressure rise,friction force,stream function,shear stress,and velocity are obtained in the physical domain.The effects of the non-dimensional wave amplitude,porosity,magnetic field,rotation,and the dimensionless time-mean flow in the wave frame are analyzed theoretically and computed numerically.Numerical results are given and illustrated graphically in each case considered.Comparison was made with the results obtained in the presence and absence of rotation,magnetic field,and porosity.The results indicate that the effects of the non-dimensional wave amplitude,porosity,magnetic field,rotation,and the dimensionless time-mean flow are very pronounced in the phenomena.

  10. Equality and Education -- Part 1

    Science.gov (United States)

    Porter, John

    1975-01-01

    Discusses equality in education within the framework of the ideas of John Rawls, asserting that even though in the real world it is not easy to implement his version of equality and justice without endangering his prior principle of liberty, he provides a philosophical foundation for the reconsideration of the meritocratic principle. (Author/JM)

  11. Luck, Choice, and Educational Equality

    Science.gov (United States)

    Calvert, John

    2015-01-01

    Harry Brighouse discusses two conceptions of educational equality. The first is a type of equality of opportunity, heavily influenced by the work of John Rawls, which he calls the meritocratic conception. According to this conception, an individual's educational prospects should not be influenced by factors such as their social class background.…

  12. Governing Equality: Mathematics for All?

    Science.gov (United States)

    Diaz, Jennifer D.

    2013-01-01

    With the notion of governmentality, this article considers how the equal sign (=) in the U.S. math curriculum organizes knowledge of equality and inscribes cultural rules for thinking, acting, and seeing in the world. Situating the discussion within contemporary math reforms aimed at teaching mathematics for all, I draw attention to how the…

  13. Moderate Secularism and Multicultural Equality

    DEFF Research Database (Denmark)

    Lægaard, Sune

    2008-01-01

    provides a response to a prominent argument against multicultural accommodation of religious minorities, what is really at stake in discussions of multiculturalism and secularism are political principles. Modood's case for accommodation of Muslims along the lines of moderate secularism presupposes...... a normative conception of equality, but his characterisation of multicultural equality is inadequate in several respects...

  14. Comparative analysis of equalization methods for SC-FDMA

    DEFF Research Database (Denmark)

    Dogadaev, Anton Konstantinovich; Kozlov, Alexander; Ukhanova, Ann

    2010-01-01

    be applied to find the appropriate equalization algorithm to be used in the Uplink channel of the LTE – the famous standard in 4G telecommunications. Simulation results in the end in this paper show bit error ratio (BER) and modulation error ratio (MER) for compared schemes....

  15. Nonlinear optics

    CERN Document Server

    Bloembergen, Nicolaas

    1996-01-01

    Nicolaas Bloembergen, recipient of the Nobel Prize for Physics (1981), wrote Nonlinear Optics in 1964, when the field of nonlinear optics was only three years old. The available literature has since grown by at least three orders of magnitude.The vitality of Nonlinear Optics is evident from the still-growing number of scientists and engineers engaged in the study of new nonlinear phenomena and in the development of new nonlinear devices in the field of opto-electronics. This monograph should be helpful in providing a historical introduction and a general background of basic ideas both for expe

  16. Factor Graph Equalization Based on Markov Chain Monte Carlo%基于Markov链蒙特卡洛的因子图均衡算法

    Institute of Scientific and Technical Information of China (English)

    巩克现; 董政; 葛临东

    2012-01-01

    Three different effective solutions and parallel implement method of computing the posteriori probability of received signal were proposed to overcome the high calculation complexity of iterative equalization based on factor graph for nonlinear channel distor- tion. Equalizer and decoder work interactively in factor graph equalization and the performance of the system was improved while the calculation complexity grew exponentially with channel memory length. Multidimensional integration was adopted by Markov chain Monte Carlo algorithm and parallel Gibbs sampling was implemented by factor graph partition. The calculation complexity was reduced. Simulation demonstrated that it overcomes the non-linear distortion of high order modulation over satellite channel and it is suitable to hardware or multi-core implement.%针对基于因子图模型的非线性失真信道的迭代均衡计算复杂度高的问题,提出了3种不同的接收信息后验概率的有效算法以及并行实现方法。在基于因子图的均衡算法中,均衡器和译码器以迭代处理的方式联合工作,提高了系统的整体性能,但计算复杂度随信道记忆长度呈指数增加,通过Markov链蒙特卡洛算法实现多维积分的计算,并通过因子图分割实现并行Gibbs采样,降低了计算复杂度,仿真表明,该算法有效克服宽带高阶调制的卫星信道非线性失真,有利于硬件或多核并行实现。

  17. Nonlinear supratransmission

    Energy Technology Data Exchange (ETDEWEB)

    Geniet, F; Leon, J [Physique Mathematique et Theorique, CNRS-UMR 5825, 34095 Montpellier (France)

    2003-05-07

    A nonlinear system possessing a natural forbidden band gap can transmit energy of a signal with a frequency in the gap, as recently shown for a nonlinear chain of coupled pendulums (Geniet and Leon 2002 Phys. Rev. Lett. 89 134102). This process of nonlinear supratransmission, occurring at a threshold that is exactly predictable in many cases, is shown to have a simple experimental realization with a mechanical chain of pendulums coupled by a coil spring. It is then analysed in more detail. First we go to different (nonintegrable) systems which do sustain nonlinear supratransmission. Then a Josephson transmission line (a one-dimensional array of short Josephson junctions coupled through superconducting wires) is shown to also sustain nonlinear supratransmission, though being related to a different class of boundary conditions, and despite the presence of damping, finiteness, and discreteness. Finally, the mechanism at the origin of nonlinear supratransmission is found to be a nonlinear instability, and this is briefly discussed here.

  18. The across frequency independence of equalization of interaural time delay in the equalization-cancellation model of binaural unmasking

    Science.gov (United States)

    Akeroyd, Michael A.

    2004-08-01

    The equalization stage in the equalization-cancellation model of binaural unmasking compensates for the interaural time delay (ITD) of a masking noise by introducing an opposite, internal delay [N. I. Durlach, in Foundations of Modern Auditory Theory, Vol. II., edited by J. V. Tobias (Academic, New York, 1972)]. Culling and Summerfield [J. Acoust. Soc. Am. 98, 785-797 (1995)] developed a multi-channel version of this model in which equalization was ``free'' to use the optimal delay in each channel. Two experiments were conducted to test if equalization was indeed free or if it was ``restricted'' to the same delay in all channels. One experiment measured binaural detection thresholds, using an adaptive procedure, for 1-, 5-, or 17-component tones against a broadband masking noise, in three binaural configurations (N0S180, N180S0, and N90S270). The thresholds for the 1-component stimuli were used to normalize the levels of each of the 5- and 17-component stimuli so that they were equally detectable. If equalization was restricted, then, for the 5- and 17-component stimuli, the N90S270 and N180S0 configurations would yield a greater threshold than the N0S180 configurations. No such difference was found. A subsequent experiment measured binaural detection thresholds, via psychometric functions, for a 2-component complex tone in the same three binaural configurations. Again, no differential effect of configuration was observed. An analytic model of the detection of a complex tone showed that the results were more consistent with free equalization than restricted equalization, although the size of the differences was found to depend on the shape of the psychometric function for detection.

  19. The nonlinear piezoelectric tuned vibration absorber

    Science.gov (United States)

    Soltani, P.; Kerschen, G.

    2015-07-01

    This paper proposes a piezoelectric vibration absorber, termed the nonlinear piezoelectric tuned vibration absorber (NPTVA), for the mitigation of nonlinear resonances of mechanical systems. The new feature of the NPTVA is that its nonlinear restoring force is designed according to a principle of similarity, i.e., the NPTVA should be an electrical analog of the nonlinear host system. Analytical formulas for the NPTVA parameters are derived using the homotopy perturbation method. Doing so, a nonlinear generalization of Den Hartog’s equal-peak tuning rule is developed for piezoelectric vibration absorbers.

  20. Electronegativity Equalization with Pauling Units.

    Science.gov (United States)

    Bratsch, Steven G.

    1984-01-01

    Discusses electronegativity equalization using Pauling units. Although Pauling has qualitatively defined electronegativity as the power of an atom in a molecule to attract electrons to itself, Pauling electronegativities are treated in this paper as prebonded, isolated-atom quantities. (JN)

  1. Sparsity Enhanced Decision Feedback Equalization

    CERN Document Server

    Ilic, Jovana

    2011-01-01

    For single-carrier systems with frequency domain equalization, decision feedback equalization (DFE) performs better than linear equalization and has much lower computational complexity than sequence maximum likelihood detection. The main challenge in DFE is the feedback symbol selection rule. In this paper, we give a theoretical framework for a simple, sparsity based thresholding algorithm. We feed back multiple symbols in each iteration, so the algorithm converges fast and has a low computational cost. We show how the initial solution can be obtained via convex relaxation instead of linear equalization, and illustrate the impact that the choice of the initial solution has on the bit error rate performance of our algorithm. The algorithm is applicable in several existing wireless communication systems (SC-FDMA, MC-CDMA, MIMO-OFDM). Numerical results illustrate significant performance improvement in terms of bit error rate compared to the MMSE solution.

  2. From Equality of Opportunity to the Society of Equals

    Directory of Open Access Journals (Sweden)

    Pierre Rosanvallon

    2015-12-01

    Full Text Available Any attempt to reaffirm equality as a fundamental democratic value faces two tasks: it must respond to social and cultural changes accompanying the most recent phase of capitalist development, and it must reactivate the original context of the democratic transformation that brought equality to prominence, in close conjunction with other aspects of an innovative vision. At the outset, equality was interpreted in terms of “a world of similar human beings, a society of autonomous individuals, and a community of citizens”. In this context, equality was closely linked to liberty, but their interconnections were also open to historical changes. Later developments – including the shift to a more organized kind of capitalism, two world wars and the rise of a temporarily successful rival version of modernity – led to significant upgradings of equality. But during the past half-century, the case for equality has been undermined by historical trends. Mutations of the capitalist economy, on the level of organization as well as production, and the disappearance of a really existing alternative, lent support to a new type of individualism. Drawing on Simmel’s distinction between the individualism of similarity and the individualism of distinction, the present phase can be interpreted as a radicalization and democratization of the individualism of distinction into an individualism of singularity. A social-liberal strategy, aiming at a reconciliation of liberty and equality, must take this new individualism on board and understand it as a social relationship, thus maintaining critical distance from neo-liberal ideology.

  3. Fast Adaptive Blind MMSE Equalizer for Multichannel FIR Systems

    Directory of Open Access Journals (Sweden)

    Abed-Meraim Karim

    2006-01-01

    Full Text Available We propose a new blind minimum mean square error (MMSE equalization algorithm of noisy multichannel finite impulse response (FIR systems, that relies only on second-order statistics. The proposed algorithm offers two important advantages: a low computational complexity and a relative robustness against channel order overestimation errors. Exploiting the fact that the columns of the equalizer matrix filter belong both to the signal subspace and to the kernel of truncated data covariance matrix, the proposed algorithm achieves blindly a direct estimation of the zero-delay MMSE equalizer parameters. We develop a two-step procedure to further improve the performance gain and control the equalization delay. An efficient fast adaptive implementation of our equalizer, based on the projection approximation and the shift invariance property of temporal data covariance matrix, is proposed for reducing the computational complexity from to , where is the number of emitted signals, the data vector length, and the dimension of the signal subspace. We then derive a statistical performance analysis to compare the equalization performance with that of the optimal MMSE equalizer. Finally, simulation results are provided to illustrate the effectiveness of the proposed blind equalization algorithm.

  4. All Men are Created Equal

    Institute of Scientific and Technical Information of China (English)

    黄婉欣

    2015-01-01

    <正>I have a dream that one day this nation will rise up and live out the true meaning of its creed:"We hold these truths to be self-evident,that all men are created equal."This is an abstract from Martin Luther King’s famous speech I Have a Dream,which we all learnt in middle school."All men are created equal",he said,and he devoted his

  5. A Blind Equalizer Based on Unsupervised Gaussian Cluster Formation with an Adaptive Non—Linearity

    Institute of Scientific and Technical Information of China (English)

    LiuHanyu; TongWen; 等

    1997-01-01

    In this paper we present a blind equalizer algorithm based on an unsupervised Gaussian cluster formation technique with an optimized gradient adaptive step-size to update the equalizer coefficients.The novelty of this work lies in the optimization of the nonlinearity of the cluster formation used to achieve an optimal soft decision.The proposed iterative procedure combined with the variable step-size gradient-based adaptation,significantly accelerates the convergence speed of the blind equalization.The advantages of the proposed equalization techniques are illustrated by simulation.Simulation results obtained are compared with the Sato and Godard blind equalizers.

  6. Practical Nonlinearities

    Science.gov (United States)

    2016-07-01

    Advanced Research Projects Agency (DARPA) Dynamics-Enabled Frequency Sources (DEFYS) program is focused on the convergence of nonlinear dynamics and...Early work in this program has shown that nonlinear dynamics can provide performance advantages. However, the pathway from initial results to...dependent nonlinear stiffness observed in these devices. This work is ongoing, and will continue through the final period of this program . Reference 9

  7. Nonlinear oscillations

    CERN Document Server

    Nayfeh, Ali Hasan

    1995-01-01

    Nonlinear Oscillations is a self-contained and thorough treatment of the vigorous research that has occurred in nonlinear mechanics since 1970. The book begins with fundamental concepts and techniques of analysis and progresses through recent developments and provides an overview that abstracts and introduces main nonlinear phenomena. It treats systems having a single degree of freedom, introducing basic concepts and analytical methods, and extends concepts and methods to systems having degrees of freedom. Most of this material cannot be found in any other text. Nonlinear Oscillations uses sim

  8. Nonlinear Science

    CERN Document Server

    Yoshida, Zensho

    2010-01-01

    This book gives a general, basic understanding of the mathematical structure "nonlinearity" that lies in the depths of complex systems. Analyzing the heterogeneity that the prefix "non" represents with respect to notions such as the linear space, integrability and scale hierarchy, "nonlinear science" is explained as a challenge of deconstruction of the modern sciences. This book is not a technical guide to teach mathematical tools of nonlinear analysis, nor a zoology of so-called nonlinear phenomena. By critically analyzing the structure of linear theories, and cl

  9. Nonlinear analysis

    CERN Document Server

    Nanda, Sudarsan

    2013-01-01

    "Nonlinear analysis" presents recent developments in calculus in Banach space, convex sets, convex functions, best approximation, fixed point theorems, nonlinear operators, variational inequality, complementary problem and semi-inner-product spaces. Nonlinear Analysis has become important and useful in the present days because many real world problems are nonlinear, nonconvex and nonsmooth in nature. Although basic concepts have been presented here but many results presented have not appeared in any book till now. The book could be used as a text for graduate students and also it will be useful for researchers working in this field.

  10. PUBLIC EQUALITY, DEMOCRACY AND JUSTICE

    Directory of Open Access Journals (Sweden)

    Ivan Mladenović

    2016-07-01

    Full Text Available This paper examines the principle of public equality which, according to the view Thomas Christiano defends in his book The Constitution of Equality: Democratic Authority and Its Limits, is of central importance for social justice and democracy. Christiano also holds that the authority of democracy, and its limits, are grounded in this principle. Christiano’s democratic theory can be, broadly speaking, divided in two parts. The first part deals with the derivation and justification of the principle of public equality. The second part argues why and how the authority of democracy, and its limits, are based on this principle. This article will deal only with the first part of Christiano’s theory. While I believe that the second part is crucially important for Christiano’s democratic theory, I think that before examining the role of the principle of public equality, it is necessary to examine its nature. For that reason, this paper deals primarily with the nature of the principle of public equality as the requirement of social justice and the basis for the justification of democracy.

  11. Distributive Equality, Relational Equality and Preferences about Higher Education

    Science.gov (United States)

    Voigt, Kristin

    2017-01-01

    Are scenarios in which disadvantaged students prefer not to attend (certain) universities a concern from the perspective of an egalitarian theory of justice? I consider this question from the respective perspectives of two prominent approaches to equality: distributive theories, which focus on the fairness of inequalities in outcomes, and…

  12. Certifying Equality With Limited Interaction

    DEFF Research Database (Denmark)

    Brody, Joshua Eric; Chakrabarti, Amit; McGregor, Andrew;

    2012-01-01

    The \\textsc{equality} problem is usually one's first encounter with communication complexity and is one of the most fundamental problems in the field. Although its deterministic and randomized communication complexity were settled decades ago, we find several new things to say about the problem...... by focusing on two subtle aspects. The first is to consider the {\\em expected} communication cost (at a worst-case input) for a protocol that uses limited interaction---i.e., a bounded number of rounds of communication---and whose error probability is zero or close to it. The second is to consider the {\\em...... cost bounds, we obtain new bounded-round randomized lower bounds for the \\textsc{or-equality} problem that have a direct-sum flavor. Such lower bounds were previously known only for deterministic protocols or one-round randomized protocols. The \\textsc{or-equality} problem is in turn closely related...

  13. The Europeanisation of gender equality

    DEFF Research Database (Denmark)

    Martinsen, Dorte Sindbjerg

    2007-01-01

    The paper examines the extent to which member states control the impact of European Union (EU) policies. It does so through an historical study of what is considered to be the ‘least likely case’ – the Europeanization of Danish gender equality. The analytical findings identify various and diverse...... effects of European integration over time on national policy, politics and law. Historically, the EU has had a major role in furthering and putting into effect equality rights – even in the ‘least likely’ case of Denmark. From a theoretical perspective, the paper argues that the study of Europeanization...

  14. The Europeanisation of gender equality

    DEFF Research Database (Denmark)

    Martinsen, Dorte Sindbjerg

    2007-01-01

    The paper examines the extent to which member states control the impact of European Union (EU) policies. It does so through an historical study of what is considered to be the ‘least likely case’ – the Europeanization of Danish gender equality. The analytical findings identify various and diverse...... effects of European integration over time on national policy, politics and law. Historically, the EU has had a major role in furthering and putting into effect equality rights – even in the ‘least likely’ case of Denmark. From a theoretical perspective, the paper argues that the study of Europeanization...

  15. Promote Equality in the Classroom.

    Science.gov (United States)

    Brown, Sharon; And Others

    1996-01-01

    Presents suggestions to help physical educators treat all students equally and avoid unconsciously making inequitable gender-based statements and practicing other gender discrimination. Suggestions include encouraging girls to talk more, praising girls' performance and boys' appearance, using gender-neutral language, not stereotyping either sex,…

  16. Equal Opportunity Through Instructional Design.

    Science.gov (United States)

    Arrighi, Margarite A.

    1985-01-01

    The assumption is that sex-integrated classes are inherently equal by the very fact that boys and girls are in the same class. In fact, educational inequity has increased primarily because of instructional design which perpetuates differences among individuals. Good teaching must accommodate individual differences. (MT)

  17. Equal, but not the same.

    Science.gov (United States)

    Fleming, Gabriel

    2006-10-19

    In April 2007, the gender equality duty will make it obligatory for all health providers to actively demonstrate equity in service provision. Good practice tends to exist in small projects with little evidence of national progress towards gender equity. The DoH says trusts should already be working towards

  18. STEM Equality and Diversity Toolkit

    Science.gov (United States)

    Collins, Jill

    2011-01-01

    In 2008, the Centre for Science Education at Sheffield Hallam University teamed up with VT Enterprise (now Babcock International) in their submission of a successful bid to deliver the national STEM (Science, Technology, Engineering and Maths) Subject Choice and Careers Project. An integral part of the bid was the promotion of equality and…

  19. A novel nonlinear adaptive filter using a pipelined second-order Volterra recurrent neural network.

    Science.gov (United States)

    Zhao, Haiquan; Zhang, Jiashu

    2009-12-01

    To enhance the performance and overcome the heavy computational complexity of recurrent neural networks (RNN), a novel nonlinear adaptive filter based on a pipelined second-order Volterra recurrent neural network (PSOVRNN) is proposed in this paper. A modified real-time recurrent learning (RTRL) algorithm of the proposed filter is derived in much more detail. The PSOVRNN comprises of a number of simple small-scale second-order Volterra recurrent neural network (SOVRNN) modules. In contrast to the standard RNN, these modules of a PSOVRNN can be performed simultaneously in a pipelined parallelism fashion, which can lead to a significant improvement in its total computational efficiency. Moreover, since each module of the PSOVRNN is a SOVRNN in which nonlinearity is introduced by the recursive second-order Volterra (RSOV) expansion, its performance can be further improved. Computer simulations have demonstrated that the PSOVRNN performs better than the pipelined recurrent neural network (PRNN) and RNN for nonlinear colored signals prediction and nonlinear channel equalization. However, the superiority of the PSOVRNN over the PRNN is at the cost of increasing computational complexity due to the introduced nonlinear expansion of each module.

  20. Underlying conservation and stability laws in nonlinear propagation of axicon-generated Bessel beams

    CERN Document Server

    Porras, Miguel A; Losada, Juan Carlos

    2015-01-01

    In light filamentation induced by axicon-generated, powerful Bessel beams, the spatial propagation dynamics in the nonlinear medium determines the geometry of the filament channel and hence its potential applications. We show that the observed steady and unsteady Bessel beam propagation regimes can be understood in a unified way from the existence of an attractor and its stability properties. The attractor is identified as the nonlinear unbalanced Bessel beam (NL-UBB) whose inward H\\"ankel beam amplitude equals the amplitude of the linear Bessel beam that the axicon would generate in linear propagation. A simple analytical formula that determines de NL-UBB attractor is given. Steady or unsteady propagation depends on whether the attracting NL-UBB has a small, exponentially growing, unstable mode. In case of unsteady propagation, periodic, quasi-periodic or chaotic dynamics after the axicon reproduces similar dynamics after the development of the small unstable mode into the large perturbation regime.

  1. 基于小波网络的MQAM数字通信自适应均衡器%MQAM Digital Communication Adaptive Equalizers Using Wavelet Networks

    Institute of Scientific and Technical Information of China (English)

    章国安; 张小东; 毕光国

    2001-01-01

    首先给出了多维小波网络的结构及其随机梯度学习算法,提出了基于小波网络的MQAM数字通信自适应均衡器.仿真结果表明:该均衡器对于MQAM数字信号非线性信道的均衡,其性能明显优于传统的基于LMS和RLS算法的线性均衡器和基于RLS算法的判决反馈均衡器,且性能稍好于基于BP网络的均衡器.%In this paper, a novel wavelet network based adaptive equalizer(WNBAE) is presented. The structure and stochastic gradient learning algorithm of the WNBAE is given. In the MQAM digital communication reception systems over nonlinear channels the proposed WNBAE has better performance than that of the conventional linear transversal equalizer based on the LMS or the RLS algorithms, as well as that of the decision feedback equalizer based on the RLS algorithm. It outperforms slightly the backpropagation network based adaptive equalizer. Several simulations are performed to evaluate the behavior of the WNBAE.

  2. Nonlinear Reconstruction

    CERN Document Server

    Zhu, Hong-Ming; Pen, Ue-Li; Chen, Xuelei; Yu, Hao-Ran

    2016-01-01

    We present a direct approach to non-parametrically reconstruct the linear density field from an observed non-linear map. We solve for the unique displacement potential consistent with the non-linear density and positive definite coordinate transformation using a multigrid algorithm. We show that we recover the linear initial conditions up to $k\\sim 1\\ h/\\mathrm{Mpc}$ with minimal computational cost. This reconstruction approach generalizes the linear displacement theory to fully non-linear fields, potentially substantially expanding the BAO and RSD information content of dense large scale structure surveys, including for example SDSS main sample and 21cm intensity mapping.

  3. Nonlinear optics

    CERN Document Server

    Boyd, Robert W

    2013-01-01

    Nonlinear Optics is an advanced textbook for courses dealing with nonlinear optics, quantum electronics, laser physics, contemporary and quantum optics, and electrooptics. Its pedagogical emphasis is on fundamentals rather than particular, transitory applications. As a result, this textbook will have lasting appeal to a wide audience of electrical engineering, physics, and optics students, as well as those in related fields such as materials science and chemistry.Key Features* The origin of optical nonlinearities, including dependence on the polarization of light* A detailed treatment of the q

  4. Equal Access but Unequal Outcomes

    DEFF Research Database (Denmark)

    Jæger, Mads Meier

    2009-01-01

    with respect to Danish children's choice of secondary education. Denmark is well-suited for this study because access to secondary education is particularly meritocratic. The empirical analysis shows that all three channels through which cultural capital affects educational success are important....

  5. Nonlinear structural analysis using integrated force method

    Indian Academy of Sciences (India)

    N R B Krishnam Raju; J Nagabhushanam

    2000-08-01

    Though the use of the integrated force method for linear investigations is well-recognised, no efforts were made to extend this method to nonlinear structural analysis. This paper presents the attempts to use this method for analysing nonlinear structures. General formulation of nonlinear structural analysis is given. Typically highly nonlinear bench-mark problems are considered. The characteristic matrices of the elements used in these problems are developed and later these structures are analysed. The results of the analysis are compared with the results of the displacement method. It has been demonstrated that the integrated force method is equally viable and efficient as compared to the displacement method.

  6. Revising the Musical Equal Temperament

    CERN Document Server

    Hinrichsen, Haye

    2015-01-01

    Western music is predominantly based on the equal temperament with a constant semitone frequency ratio of $2^{1/12}$. Although this temperament has been in use since the 19th century and in spite of its high degree of symmetry, various musicians have repeatedly expressed their discomfort with the harmonicity of certain intervals. Recently it was suggested that this problem can be overcome by introducing a modified temperament with a constant but slightly increased frequency ratio. In this paper we confirm this conjecture quantitatively. Using entropy as a measure for harmonicity, we show numerically that the harmonic optimum is in fact obtained for frequency ratios larger than $2^{1/12}$. This suggests that the equal temperament should be replaced by a harmonized temperament as a new standard.

  7. Equal opportunity in the workplace.

    Science.gov (United States)

    Allen, A

    1992-04-01

    The Equal Employment Opportunity Commission (EEOC) was created by the Civil Rights Act of 1964. The commission encourages voluntary compliance with equal employment opportunity practices, and has authority to investigate complaints alleging discrimination in hiring, firing, wage rates, testing, training, apprenticeship, and other conditions of employment. In October 1991, during the Senate Judiciary Committee hearings, the confirmation of Judge Clarence Thomas for a seat on the United States Supreme Court was placed in jeopardy by a charge of sexual harassment while Thomas was head of the EEOC. This article focuses on aspects of sexual harassment in the workplace, the role of the EEOC, and offers some suggestions for keeping the work environment free of abusive behavior.

  8. Office of Equal Opportunity Programs

    Science.gov (United States)

    Chin, Jennifer L.

    2004-01-01

    The NASA Glenn Office of Equal Opportunity Programs works to provide quality service for all programs and/or to assist the Center in becoming a model workplace. During the summer of 2004, I worked with Deborah Cotleur along with other staff members to create and modify customer satisfaction surveys. This office aims to assist in developing a model workplace by providing functions as a change agent to the center by serving as an advisor to management to ensure equity throughout the Center. In addition, the office serves as a mediator for the Center in addressing issues and concerns. Lastly, the office provides assistance to employees to enable attainment of personal and organizational goals. The Office of Equal Opportunities is a staff office which reports and provides advice to the Center Director and Executive Leadership, implements laws, regulations, and presidential executive orders, and provides center wide leadership and assistance to NASA GRC employees. Some of the major responsibilities of the office include working with the discrimination complaints program, special emphasis programs (advisory groups), management support, monitoring and evaluation, contract compliance, and community outreach. During my internship in this office, my main objective was to create four customer satisfaction surveys based on EO retreats, EO observances, EO advisory boards, and EO mediation/counseling. I created these surveys after conducting research on past events and surveys as well as similar survey research created and conducted by other NASA centers, program for EO Advisory group members, leadership training sessions for supervisors, preventing sexual harassment training sessions, and observance events. I also conducted research on the style and format from feedback surveys from the Marshall Equal Opportunity website, the Goddard website, and the main NASA website. Using the material from the Office of Equal Opportunity Programs at Glenn Research Center along with my

  9. Reminder - Equal Opportunities Advisory Panel

    CERN Multimedia

    HR Department

    2007-01-01

    At its meeting on 7 December 2006, the Standing Concertation Committee also took note of the nomination of a fourth new member of the Panel: Wisla Carena. The present composition of the Panel (appointed ad personam) is now as follows: Tiziano Camporesi (Chairperson), Wisla Carena, Pierre Charrue, Sue Foffano, Josi Schinzel (Equal Opportunities Officer), Markus Nordberg, Christine Petit-Jean-Genaz and Elena Wildner. Human Resources Department Tel. 74480

  10. Office of Equal Opportunity Programs

    Science.gov (United States)

    Chin, Jennifer L.

    2004-01-01

    The NASA Glenn Office of Equal Opportunity Programs works to provide quality service for all programs and/or to assist the Center in becoming a model workplace. During the summer of 2004, I worked with Deborah Cotleur along with other staff members to create and modify customer satisfaction surveys. This office aims to assist in developing a model workplace by providing functions as a change agent to the center by serving as an advisor to management to ensure equity throughout the Center. In addition, the office serves as a mediator for the Center in addressing issues and concerns. Lastly, the office provides assistance to employees to enable attainment of personal and organizational goals. The Office of Equal Opportunities is a staff office which reports and provides advice to the Center Director and Executive Leadership, implements laws, regulations, and presidential executive orders, and provides center wide leadership and assistance to NASA GRC employees. Some of the major responsibilities of the office include working with the discrimination complaints program, special emphasis programs (advisory groups), management support, monitoring and evaluation, contract compliance, and community outreach. During my internship in this office, my main objective was to create four customer satisfaction surveys based on EO retreats, EO observances, EO advisory boards, and EO mediation/counseling. I created these surveys after conducting research on past events and surveys as well as similar survey research created and conducted by other NASA centers, program for EO Advisory group members, leadership training sessions for supervisors, preventing sexual harassment training sessions, and observance events. I also conducted research on the style and format from feedback surveys from the Marshall Equal Opportunity website, the Goddard website, and the main NASA website. Using the material from the Office of Equal Opportunity Programs at Glenn Research Center along with my

  11. The equal right to drink.

    Science.gov (United States)

    Schmidt, Laura A

    2014-11-01

    The starting place for this essay is Knupfer and Room's insight that more restrictive norms around drinking and intoxication tend to be selectively applied to the economically dependent segments of society, such as women. However, since these authors wrote in 1964, women in the US and many other societies around the globe have experienced rising economic independence. The essay considers how the moral categories of acceptable drinking and drunkenness may have shifted alongside women's rising economic independence, and looks at evidence on the potential consequences for women's health and wellbeing. I argue that, as women have gained economic independence, changes in drinking norms have produced two different kinds of negative unintended consequences for women at high and low extremes of economic spectrum. As liberated women of the middle and upper classes have become more economically equal to men, they have enjoyed the right to drink with less restraint. For them, alongside the equal right to drink has come greater equality in exposure to alcohol-attributable harms, abuse and dependence. I further suggest that, as societies become more liberated, the economic dependency of low-income women is brought into greater question. Under such conditions, women in poverty-particularly those economically dependent on the state, such as welfare mothers-have become subject to more restrictive norms around drinking and intoxication, and more punitive social controls.

  12. Nonlinear optimization

    CERN Document Server

    Ruszczynski, Andrzej

    2011-01-01

    Optimization is one of the most important areas of modern applied mathematics, with applications in fields from engineering and economics to finance, statistics, management science, and medicine. While many books have addressed its various aspects, Nonlinear Optimization is the first comprehensive treatment that will allow graduate students and researchers to understand its modern ideas, principles, and methods within a reasonable time, but without sacrificing mathematical precision. Andrzej Ruszczynski, a leading expert in the optimization of nonlinear stochastic systems, integrates t

  13. Multiwavelength erbium-doped fiber laser based on a nonlinear amplifying loop mirror assisted by un-pumped EDF.

    Science.gov (United States)

    Liu, Xuesong; Zhan, Li; Luo, Shouyu; Gu, Zhaochang; Liu, Jinmei; Wang, Yuxing; Shen, Qishun

    2012-03-26

    A multiwavelength erbium-doped fiber (EDF) laser based on a nonlinear amplifying loop mirror (NALM) is proposed and experimentally demonstrated. The NALM provides intensity-dependent transmissivity to equalize different-wavelength powers and the transmission can be uniquely optimized by controlling the cavity loss associated with a section of un-pumped EDF, which also enhances the output signal-to-noise ratio (SNR). Through adjusting the polarization controllers (PCs), under only 70 mW pump power, up to 62-wavelength output with channel spacing of 0.45 nm has been achieved. Also, the lasing tunability and stability are verified.

  14. Blind equalization for dual-polarization two-subcarrier coherent QPSK-OFDM signals.

    Science.gov (United States)

    Li, Fan; Zhang, Junwen; Yu, Jianjun; Li, Xinying

    2014-01-15

    Dual-polarization two-subcarrier coherent optical orthogonal frequency division multiplexing (CO-OFDM) transmission and reception is successfully demonstrated with blind equalization. A two-subcarrier quadrature phase shift keyed OFDM (QPSK-OFDM) signal can be equalized as a 9-ary quadrature amplitude modulation signal in the time domain with the cascaded multimodulus algorithm equalization method. The nonlinear effect resistance and transmission distance can be enhanced compared with the traditional CO-OFDM transmission system based on frequency equalization with training sequence.

  15. Linear and nonlinear piezoelectric shunting strategies for vibration mitigation

    Directory of Open Access Journals (Sweden)

    Soltani P.

    2014-01-01

    Full Text Available This paper studies linear and nonlinear piezoelectric vibration absorbers that are designed based on the equal-peak method. A comparison between the performance of linear mechanical and electrical tuned vibration absorbers coupled to a linear oscillator is first performed. Nonlinearity is then introduced in the primary oscillator to which a new nonlinear electrical tuned vibration absorber is attached. Despite the frequency-energy dependence of nonlinear oscillations, we show that the nonlinear absorber is capable of effectively mitigating the vibrations of the nonlinear primary system in a large range of forcing amplitudes.

  16. Gender equality in primary immunisation

    Directory of Open Access Journals (Sweden)

    Deepak S Khismatrao

    2015-01-01

    Full Text Available Context: Immunization, a well-known and effective method of preventing childhood illnesses is basic service under primary health care. Most surveys in India measure primary immunization coverage and quality, but no "Gender Equality." Aims: Assess "Gender Equality" in primary immunization with reference to coverage, quality, and place of immunization. Settings and Design: Cross-sectional survey in a primary health center, Pune, Maharashtra using World Health Organization 30-cluster sampling method with 14 beneficiaries (7 girls and 7 boys to be selected from each cluster. Instead of 420 children, data collected for 345 children, as requisite numbers of children were not available in low population villages and also children whose mothers were not present during survey were excluded. Materials and Methods: Vaccination data collected from either records and/or history by mother. Children born on or between 13-09-2009 and 13-09-2010, were included. Statistical Analysis Used: SPSS 14.01 version with Chi-square as test of significance. Results: Of the study population, 171 (49.6% were females and 174 (50.4% males. A total of 64.1% children had immunization records with female proportion 69.0% and males 59.2%. Primary immunization coverage was 80.0%, with female proportion 82.5% and males 77.6%. One male child was completely unimmunized and remaining partially immunized, with unaware of schedule and illness of child being major reasons for partial immunization. There was no gender wise statistically significant difference observed in Primary Immunization with reference to coverage, quality, and place of immunization. Conclusions: Immunization coverage is nearing 85% benchmark with major contribution from Universal Immunization Program. Gender Equality observed in primary immunization. Preservation of immunization records by community and timely vaccinations are areas for improvement.

  17. Midwives, gender equality and feminism.

    Science.gov (United States)

    Walsh, Denis

    2016-03-01

    Gender inequality and the harmful effects of patriarchy are sustaining the wide spread oppression of women across the world and this is also having an impact on maternity services with unacceptable rates of maternal mortality, the continued under investment in the midwifery profession and the limiting of women's place of birth options. However alongside these effects, the current zeitgeist is affirming an alignment of feminism and gender equality such that both have a high profile in public discourse. This presents a once in a generation opportunity for midwives to self-declare as feminists and commit to righting the wrongs of this most pernicious form of discrimination.

  18. Equalization equations in reactant resolution

    Indian Academy of Sciences (India)

    Jacek Korchowiec

    2005-09-01

    The chemical system can be analyzed in different resolutions. The assumed resolution imposes a given partitioning of the system in physical or functional space. The most frequently explored are global, reactant, atoms-in-molecule, orbital, and local resolutions. In this paper we have considered reactant resolution, i.e., the mutually polarized reactants before the charge-transfer among them. We have demonstrated that a certain type of generalized sensitivity, the system responses to the population variables, is equalized throughout the space up to the infinite order in the perturbation expansion.

  19. Teachers’ challenges education for equality

    Directory of Open Access Journals (Sweden)

    Rocío Anguita Martínez

    2011-04-01

    Full Text Available Gender equality among women and men has been, and still is a key issue regarding the development of formal education systems. In some way, it can be seen as the cornerstone of equity. Although the most visible gender issues are drawing back in our country, others specially related to the hidden curriculum are still present. Teacher´s initial and lifelong training constitute the best tool to minimize the aforementioned hidden-curriculum-related gender inequalities. However, there is not much done with this regard in our current teacher´s formal training system.

  20. Are Men and Women Equal in Employment?

    Institute of Scientific and Technical Information of China (English)

    1996-01-01

    EQUALITY was one of the themes of the Fourth World Conference on Women. The motto of the Conference was "Action for Equality, Development and Peace." But is there a real possibility for equality between men and women? Equality in employment remains an important concern. Recently, Zheng Yefu, research worker of the Beijing Academy of Social

  1. A fast-initializing digital equalizer with on-line tracking for data communications

    Science.gov (United States)

    Houts, R. C.; Barksdale, W. J.

    1974-01-01

    A theory is developed for a digital equalizer for use in reducing intersymbol interference (ISI) on high speed data communications channels. The equalizer is initialized with a single isolated transmitter pulse, provided the signal-to-noise ratio (SNR) is not unusually low, then switches to a decision directed, on-line mode of operation that allows tracking of channel variations. Conditions for optimal tap-gain settings are obtained first for a transversal equalizer structure by using a mean squared error (MSE) criterion, a first order gradient algorithm to determine the adjustable equalizer tap-gains, and a sequence of isolated initializing pulses. Since the rate of tap-gain convergence depends on the eigenvalues of a channel output correlation matrix, convergence can be improved by making a linear transformation on to obtain a new correlation matrix.

  2. Designing Nonlinear Turbo Codes with a Target Ones Density

    CERN Document Server

    Wang, Jiadong; Chen, Tsung-Yi; Xie, Bike; Wesel, Richard

    2011-01-01

    Certain binary asymmetric channels, such as Z-channels in which one of the two crossover probabilities is zero, demand optimal ones densities different from 50%. Some broadcast channels, such as broadcast binary symmetric channels (BBSC) where each component channel is a binary symmetric channel, also require a non-uniform input distribution due to the superposition coding scheme, which is known to achieve the boundary of capacity region. This paper presents a systematic technique for designing nonlinear turbo codes that are able to support ones densities different from 50%. To demonstrate the effectiveness of our design technique, we design and simulate nonlinear turbo codes for the Z-channel and the BBSC. The best nonlinear turbo code is less than 0.02 bits from capacity.

  3. 40 Gb/s Lane Rate NG-PON using Electrical/Optical Duobinary, PAM-4 and Low Complex Equalizations

    DEFF Research Database (Denmark)

    Wei, J. L.; Grobe, Klaus; Wagner, Christoph

    2016-01-01

    We present the first numerical investigation and comparison of 40-Gb/s lane rate electrical Duobinary, optical Duobinary and PAM-4 for NG-PONs incorporating low complex linear and nonlinear post-equalizations.......We present the first numerical investigation and comparison of 40-Gb/s lane rate electrical Duobinary, optical Duobinary and PAM-4 for NG-PONs incorporating low complex linear and nonlinear post-equalizations....

  4. Boosting equal time bound states

    CERN Document Server

    Dietrich, Dennis D; Jarvinen, Matti

    2012-01-01

    We present an explicit and exact boost of a relativistic bound state defined at equal time of the constituents in the Born approximation (lowest order in hbar). To this end, we construct the Poincar\\'e generators of QED and QCD in D=1+1 dimensions, using Gauss' law to express A^0 in terms of the fermion fields in A^1=0 gauge. We determine the fermion-antifermion bound states in the Born approximation as eigenstates of the time and space translation generators P^0 and P^1. The boost operator is combined with a gauge transformation so as to maintain the gauge condition A^1=0 in the new frame. We verify that the boosted state remains an eigenstate of P^0 and P^1 with appropriately transformed eigenvalues and determine the transformation law of the equal-time, relativistic wave function. The shape of the wave function is independent of the CM momentum when expressed in terms of a variable, which is quadratically related to the distance x between the fermions. As a consequence, the Lorentz contraction of the wave ...

  5. Gender Equality in Agricultural Education

    Directory of Open Access Journals (Sweden)

    N. Jayakumar

    2016-05-01

    “Increased women’s enrollment in agricultural courses” as one among the strategies when addressing gender issues in the education and training components of agricultural development projects. In this context the study was carried out to ascertain the representation of women and their academic achievement in agricultural education. The study revealed that almost equal representation was found for women in agricultural course and they were also provided better quality education in their schooling, in the form of English medium education and education in private schools. Recent trends for the past four years showed a higher percentage of enrollments of women in agricultural course than men. The growth rate was also higher for the female students. Women also showed a significantly higher percentage of academic achievement than men. These positive indicators provide sufficient signals for equality of women in agricultural course and have positive implications for development of the agricultural sector in future.

  6. Reduced-Complexity Turbo Equalization for Turbo Coded MIMO/OFDM Systems

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    This paper derives a low-complexity turbo equalization algorithm for turbo coded multiple input multiple output/ orthogonal frequency division multiplexing systems. This algorithm consists of soft-output decision-feedback equalization with a probabilistic data association algorithm and a soft-input soft-output turbo channel decoder using iterative operations. In each iteration, extrinsic information extracted from the probabilistic data association algorithm detector and from the channel decoder is used as the prior information for the next iteration to realize iterative channel equalization and channel decoding. Our simulation results show that the algorithm improves the signal noise ratio around 1 dB with bit error rate reaching 10-6 when the Eb/No = 4 dB compared to minimum mean square error and match filter, and can greatly reduce the intersymbol interference at a low overall complexity of O( N3) after 2 iterations.

  7. Nonlinear dynamics

    Energy Technology Data Exchange (ETDEWEB)

    Turchetti, G. (Bologna Univ. (Italy). Dipt. di Fisica)

    1989-01-01

    Research in nonlinear dynamics is rapidly expanding and its range of applications is extending beyond the traditional areas of science where it was first developed. Indeed while linear analysis and modelling, which has been very successful in mathematical physics and engineering, has become a mature science, many elementary phenomena of intrinsic nonlinear nature were recently experimentally detected and investigated, suggesting new theoretical work. Complex systems, as turbulent fluids, were known to be governed by intrinsically nonlinear laws since a long time ago, but received purely phenomenological descriptions. The pioneering works of Boltzmann and Poincare, probably because of their intrinsic difficulty, did not have a revolutionary impact at their time; it is only very recently that their message is reaching a significant number of mathematicians and physicists. Certainly the development of computers and computer graphics played an important role in developing geometric intuition of complex phenomena through simple numerical experiments, while a new mathematical framework to understand them was being developed.

  8. Practical design of a nonlinear tuned vibration absorber

    DEFF Research Database (Denmark)

    Grappasonni, C.; Habib, G.; Detroux, T.

    2014-01-01

    The aim of the paper is to develop a new nonlinear tuned vibration absorber (NLTVA) capable of mitigating the vibrations of nonlinear systems which are known to exhibit frequency-energy-dependent oscillations. A nonlinear generalization of Den Hartog's equal-peak method is proposed to ensure equal...... peaks in the nonlinear frequency response for a large range of forcing amplitudes. An analytical tuning procedure is developed and provides the load-deflection characteristic of the NLTVA. Based on this prescribed relation, the NLTVA design is performed by two different approaches, namely thanks to (i...

  9. Nonlinear Control of Heartbeat Models

    Directory of Open Access Journals (Sweden)

    Witt Thanom

    2011-02-01

    Full Text Available This paper presents a novel application of nonlinear control theory to heartbeat models. Existing heartbeat models are investigated and modified by incorporating the control input as a pacemaker to provide the control channel. A nonlinear feedback linearization technique is applied to force the output of the systems to generate artificial electrocardiogram (ECG signal using discrete data as the reference inputs. The synthetic ECG may serve as a flexible signal source to assess the effectiveness of a diagnostic ECG signal-processing device.

  10. All equal-area map projections are created equal, but some are more equal than others

    Science.gov (United States)

    Usery, E.L.; Seong, J.C.

    2001-01-01

    High-resolution regional and global raster databases are currently being generated for a variety of environmental and scientific modeling applications. The projection of these data from geographic coordinates to a plane coordinate system is subject to significant areal error. Sources of error include users selecting an inappropriate projection or incorrect parameters for a given projection, algorithmic errors in commercial geographic information system (GIS) software, and errors resulting from the projection of data in the raster format. To assess the latter type of errors, the accuracy of raster projection was analyzed by two methods. First, a set of 12 one-degree by one-degree quadrilaterals placed at various latitudes was projected at several raster resolutions and compared to the projection of a vector representation of the same quadrilaterals. Second, several different raster resolutions of land cover data for Asia were projected and the total areas of 21 land cover categories were tabulated and compared. While equal-area projections are designed to specifically preserve area, the comparison of the results of the one-degree by one-degree quadrilaterals with the common equal area projections (e.g., the Mollweide) indicates a considerable variance in the one-degree area after projection. Similarly, the empirical comparison of land cover areas for Asia among various projections shows that total areas of land cover vary with projection type, raster resolution, and latitude. No single projection is best for all resolutions and all latitudes. While any of the equal-area projections tested are reasonably accurate for most applications with resolutions of eight-kilometer pixels or smaller, significant variances in accuracies appear at larger pixel sizes.

  11. Gender equality remains the objective.

    Science.gov (United States)

    Helzner, J

    1996-01-01

    The 1994 and 1995 UN conferences in Cairo and Beijing stressed the importance of involving men in family planning and reproductive health programs and initiatives. The fourth chapter of the report of the International Conference on Population and Development puts forth the goal of promoting gender equality in all spheres of life, including family and community life, and encouraging and enabling men to take responsibility for their sexual and reproductive behavior and their social and family roles. The document specifies areas of shared responsibility in both the household and society in general. Gender analysis of family planning programs is discussed, followed by consideration of men as managers and decision makers, male involvement to increase contraceptive use, male-dependent contraceptives, other issues of male control, and future challenges.

  12. The Equity-Equality Conflict

    DEFF Research Database (Denmark)

    Scheuer, Steen

    2013-01-01

    This article investigatesthe factors that determine workplace actors’ appeal to social norms of fairness in some situations and what ‘fairness’ is perceived as consisting of. When is a pay level considered as relativity fair, and when is it not? When are contingent pay systems (i.e. pay-for-perfo......This article investigatesthe factors that determine workplace actors’ appeal to social norms of fairness in some situations and what ‘fairness’ is perceived as consisting of. When is a pay level considered as relativity fair, and when is it not? When are contingent pay systems (i.e. pay......-for-performance systems) perceived as fair and when are they not? When can differences in contribution (equity) overrule the social norm of equality? Which contingent reward structure should be applied for teamwork members, if any? Which structure to motivate employees to a continuous search for smarter working...

  13. Brightness-equalized quantum dots

    Science.gov (United States)

    Lim, Sung Jun; Zahid, Mohammad U.; Le, Phuong; Ma, Liang; Entenberg, David; Harney, Allison S.; Condeelis, John; Smith, Andrew M.

    2015-10-01

    As molecular labels for cells and tissues, fluorescent probes have shaped our understanding of biological structures and processes. However, their capacity for quantitative analysis is limited because photon emission rates from multicolour fluorophores are dissimilar, unstable and often unpredictable, which obscures correlations between measured fluorescence and molecular concentration. Here we introduce a new class of light-emitting quantum dots with tunable and equalized fluorescence brightness across a broad range of colours. The key feature is independent tunability of emission wavelength, extinction coefficient and quantum yield through distinct structural domains in the nanocrystal. Precise tuning eliminates a 100-fold red-to-green brightness mismatch of size-tuned quantum dots at the ensemble and single-particle levels, which substantially improves quantitative imaging accuracy in biological tissue. We anticipate that these materials engineering principles will vastly expand the optical engineering landscape of fluorescent probes, facilitate quantitative multicolour imaging in living tissue and improve colour tuning in light-emitting devices.

  14. Pythagorean triangles of equal areas

    Directory of Open Access Journals (Sweden)

    Malvina Baica

    1988-01-01

    Full Text Available The main intent in this paper is to find triples of Rational Pythagorean Triangles (abbr. RPT having equal areas. A new method of solving a2+ab+b2=c2 is to set a=y−1, b=y+1, y∈N−{0,1} and get Pell's equation c2−3y2=1. To solve a2−ab−b2=c2, we set a=12(y+1, b=y−1, y≥2, y∈N and get a corresponding Pell's equation. The infinite number of solutions in Pell's equation gives rise to an infinity of solutions to a2±ab+b2=c2. From this fact the following theorems are proved.

  15. Ethical Perspectives of Equal Opportunities

    Directory of Open Access Journals (Sweden)

    Traian PALADE

    2016-07-01

    Full Text Available This paper focuses on the analysis of the fair equality of the concept of opportunity from the perspective of the moral and reasonable justifications brought to support positive discrimination. Although contemporary democratic societies guarantee the absence of discrimination by securing the formal equality of opportunity, this seems to be insufficient to balance opportunities. The Rawlsian model has gained ground, by advancing a redistribution of the resources to support the disadvantaged ones, which is implemented through special measures. The compulsory quotas for admission to higher education or public institutions, addressed to some disadvantaged groups, are one of the effective means of implementing fairness. As this system has shattered the principle of reward judging by one‟s merits, and ending up as a form of inverse discrimination of the majority groups, it is necessary that we analyse the arguments and the boomerang effects of the special measures. The undertaking proposed by the present paper is structured around highlighting the ethical aspects, as well as the consequences resulting from the arguments in favour of positive discrimination. Do we have the moral obligation to make up for the past inequalities suffered by some groups? Does preferential treatment really ensure the genuine integration of such groups? Do special measures contribute in creating social justice? Without the claim of having responded definitively and exhaustively to these questions, this paper attempts to emphasise the ethical dilemma that raises when special measures favour one group or another, when a group is protected judging by only one criterion, or when only an implementation area is selected.

  16. Nonlinear Systems.

    Science.gov (United States)

    Seider, Warren D.; Ungar, Lyle H.

    1987-01-01

    Describes a course in nonlinear mathematics courses offered at the University of Pennsylvania which provides an opportunity for students to examine the complex solution spaces that chemical engineers encounter. Topics include modeling many chemical processes, especially those involving reaction and diffusion, auto catalytic reactions, phase…

  17. 等通道转角挤压制备7075Al/AZ31复合板界面组织及结合强度%Interfacial microstructure and bonding strength of 7075Al/AZ31 composite plates fabricated by equal channel angular pressing

    Institute of Scientific and Technical Information of China (English)

    任广笑; 王红霞; 周斌; 刘一鸣; 王斌兵

    2016-01-01

    在573 K,通过等通道转角挤压成功制备了7075 Al/AZ31复合板,并采用SEM、EDS、XRD和剪切实验研究了挤压道次及退火温度对复合板界面层组织和性能的影响及剪切断裂面的组成.结果表明:1道次等通道转角挤压制备的复合板界面处形成厚度为20μm均匀致密的扩散层,由Al3Mg2相和Mg17Al12相组成,Al3 Mg2相层厚(17 μm)是Mg17Al12相层厚(3μm)的5.6倍.2道次等通道挤压后,扩散层厚度无变化,但是出现了裂纹,剪切强度大幅下降,剪切断裂面发生在Al3Mg3相层.复合板界面层在473 K退火,扩散层厚度无变化,裂纹无改善,剪切强度略有提高;573 K退火,复合板扩散层中的Al3 Mg2相层和β-Mg17Al12相层均急剧增厚,微裂纹被焊合,剪切强度均大幅下降.在相同处理状态下,1道次ECAP复合板剪切强度均高于2道次ECAP复合板,473 K退火处理后,强度高出30.11%.573 K退火处理后,强度高出12.4%.故利用等通道转角挤压法制备7075Al/AZ31复合板,1道次比较合适,扩散层退火温度不宜超过473 K.%7075Al/AZ31 laminated composites were successfully fabricated by equal channel angular processing (ECAP) at 573 K.The effect of ECAP passes arid annealing temperature on microstructure evolution,phase constituent and bonding strength near the joining interface of the laminated composites was studied by means of scanning electron microscopy,X-ray diffraction and shear tests.The results indicate that diffusion layer with thickness of 20 μm is observed at the joining interface of the laminated composites prepared by one ECAP pass.The diffusion layer is mainly composed of Al3Mg2 and β-Mg17Al12 phases.After two ECAP passes,the change of the diffusion layer thickness is not obvious,while the formation of crack in the diffusion layer leads to the bonding strength decreasing.After annealing at 473 K,the thickness of the diffusion layer and the crack remains unchange,while the bonding strength increass

  18. Simultaneous Computation of Two Independent Tasks Using Reservoir Computing Based on a Single Photonic Nonlinear Node With Optical Feedback.

    Science.gov (United States)

    Nguimdo, Romain Modeste; Verschaffelt, Guy; Danckaert, Jan; Van der Sande, Guy

    2015-12-01

    In this brief, we numerically demonstrate a photonic delay-based reservoir computing system, which processes, in parallel, two independent computational tasks even when the two tasks have unrelated input streams. Our approach is based on a single-longitudinal mode semiconductor ring laser (SRL) with optical feedback. The SRL emits in two directional optical modes. Each directional mode processes one individual task to mitigate possible crosstalk. We illustrate the feasibility of our scheme by analyzing the performance on two benchmark tasks: 1) chaotic time series prediction and 2) nonlinear channel equalization. We identify some feedback configurations for which the results for simultaneous prediction/classification indicate a good performance, but with slight degradation (as compared with the performance obtained for single task processing) due to nonlinear and linear interactions between the two directional modes of the laser. In these configurations, the system performs well on both tasks for a broad range of the parameters.

  19. Equality and Empowerment for Decent Work.

    Science.gov (United States)

    Hepple, Bob

    2001-01-01

    Substantive equality encompasses equality of results, opportunity, and human dignity. To implement it requires an incremental approach ranging from voluntary participation to penalties for noncompliance, active participation of all stakeholders, and empowerment of disadvantaged groups. (SK)

  20. The policy on gender equality in Denmark

    DEFF Research Database (Denmark)

    Agustin, Lise Rolandsen

    The briefing paper describes current Danish policies, practices and legislation within the area of gender equality. It addresses economic independence, reconciliation policies, participation in decision-making, gender-based violence and trafficking, gender stereotypes, and gender equality...

  1. Women Reaching Equality in Dubious Habit: Drinking

    Science.gov (United States)

    ... page: https://medlineplus.gov/news/fullstory_161640.html Women Reaching Equality in Dubious Habit: Drinking Females also ... 25, 2016 MONDAY, Oct. 24, 2016 (HealthDay News) -- Women have made major strides towards equality with men, ...

  2. Equality in the Framework of Justice

    OpenAIRE

    Aşik, Kübra

    2015-01-01

    This thesis assesses the relation between equality and justice by exploring and identifying the relation between equality and justice in Rawls's theory of justice, Sandel's communitarian account of Justice and Sen's capability approach. And these accounts of justice are evaluated from an egalitarian point of view. The main argument defended in the thesis is that justice requires equality. Accordingly, these three accounts of justice are evaluated by taking their understanding of equality into...

  3. Competition and Cooperation, Equality and Elites.

    Science.gov (United States)

    Flew, Antony

    1983-01-01

    Cooperation and competition are often seen as polar opposites; yet they are not necessarily in opposition. Similarly, quality and elitism are not opposed if the goal of equality is seen as equality of opportunity rather than equality of outcome and the elite are the product of fair competition. (IS)

  4. 45 CFR 98.43 - Equal access.

    Science.gov (United States)

    2010-10-01

    ... 45 Public Welfare 1 2010-10-01 2010-10-01 false Equal access. 98.43 Section 98.43 Public Welfare... Operations (Child Care Services)-Lead Agency and Provider Requirements § 98.43 Equal access. (a) The Lead... sufficient to ensure equal access, for eligible families in the area served by the Lead Agency, to child...

  5. Individualized Sex Equality in Transforming Finnish Academia

    Science.gov (United States)

    Lätti, Johanna

    2017-01-01

    This article examines the equality agenda in the context of Finnish university reform in the 21st century. In Finland, the academic regime went through an organizational transformation after the Universities Act in 2009. However, little attention has been paid to the questions of sex or equality. Since the policy influences on equality in…

  6. Nonlinear PDEs

    OpenAIRE

    2015-01-01

    From the Back Cover: The emphasis throughout the present volume is on the practical application of theoretical mathematical models helping to unravel the underlying mechanisms involved in processes from mathematical physics and biosciences. It has been conceived as a unique collection of abstract methods dealing especially with nonlinear partial differential equations (either stationary or evolutionary) that are applied to understand concrete processes involving some important applications re...

  7. Improving SC-FDMA performance by Turbo Equalization in UTRA LTE Uplink

    DEFF Research Database (Denmark)

    Berardinelli, Gilberto; Priyanto, Basuki Endah; Sørensen, Troels Bundgaard;

    2008-01-01

    does not have stringent power constraints. In this paper, a turbo equalization technique to improve Single Carrier Frequency Division Multiple Access (SC-FDMA) performance is proposed. A new adaptive coefficients solution for frequency domain equalization is considered. The work is in the context...... that the turbo equalizer can improve the BLER performance around 1 dB with only a few iterations, and improve the SC-FDMA performance over OFDM, especially at high coding rate.......Turbo equalization is known as an advanced iterative equalization and decoding technique that allows to enhance the performance of the data transmission over a frequency selective fading channel. The turbo equalizer will result in extra receiver complexity, but isolated to the base-station, which...

  8. Correlation between ultrasonic nonlinearity and elastic nonlinearity in heat-treated aluminum alloy

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Jong Beom; Jhang, Kyung Young [Hanyang University, Seoul (Korea, Republic of)

    2017-04-15

    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°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.

  9. Equal-Amplitude Optical Pulse Generation from a Rational Harmonic Mode-Locked Fibre Laser

    Institute of Scientific and Technical Information of China (English)

    FENG Xin-Huan; YUAN Shu-Zhong; LI Yao; LIU Yan-Ge; KAI Gui-Yun; DONG Xiao-Yi

    2004-01-01

    A simple technique for the generation of equal-amplitude high repetition rate pulses from a rational harmonic mode-locked fibre ring laser is demonstrated. The principle is based on the combination of the nonlinear characteristics of the modulator and the effect of rational harmonic mode-locking. The two sources act on each other and the integrated effect eventually leads to the pulse amplitude-equalization. We obtain amplitude-equalized short pulses up to the fifth-order rational harmonic mode-locking with an optimum bias level and modulation depth of the modulator, which demonstrates the efficiency of this method.

  10. The policy on gender equality in Denmark

    DEFF Research Database (Denmark)

    Agustin, Lise Rolandsen

    in development policies. The former liberal-conservative government (2001-2011) has focused on equal opportunities, gender equality as a means to economic growth, voluntary measures and freedom of choice. Increased attention has been paid in recent years to ethnic minorities and to men’s role in gender equality.......The briefing paper describes current Danish policies, practices and legislation within the area of gender equality. It addresses economic independence, reconciliation policies, participation in decision-making, gender-based violence and trafficking, gender stereotypes, and gender equality...

  11. Switching Equalization Algorithm Based on a New SNR Estimation Method

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    It is well-known that turbo equalization with the max-log-map (MLM) rather than the log-map (LM) algorithm is insensitive to signal to noise ratio (SNR) mismatch. As our first contribution, an improved MLM algorithm called scaled max-log-map (SMLM) algorithm is presented. Simulation results show that the SMLM scheme can dramatically outperform the MLM without sacrificing the robustness against SNR mismatch. Unfortunately, its performance is still inferior to that of the LM algorithm with exact SNR knowledge over the class of high-loss channels. As our second contribution, a switching turbo equalization scheme, which switches between the SMLM and LM schemes, is proposed to practically close the performance gap. It is based on a novel way to estimate the SNR from the reliability values of the extrinsic information of the SMLM algorithm.

  12. New exact solutions of the generalized Zakharov–Kuznetsov modified equal-width equation

    Indian Academy of Sciences (India)

    Yusuf Pandir

    2014-06-01

    In this paper, new exact solutions, including soliton, rational and elliptic integral function solutions, for the generalized Zakharov–Kuznetsov modified equal-width equation are obtained using a new approach called the extended trial equation method. In this discussion, a new version of the trial equation method for the generalized nonlinear partial differential equations is offered.

  13. SOME NONLINEAR APPROXIMATIONS FOR MATRIX-VALUED FUNCTIONS

    Institute of Scientific and Technical Information of China (English)

    Guo-liang Xu

    2003-01-01

    Some nonlinear approximants, i.e., exponential-sum interpolation with equal distance or at origin, (0,1)-type, (0,2)-type and (1,2)-type fraction-sum approximations, for matrixvalued functions are introduced. All these approximation problems lead to a same form system of nonlinear equations. Solving methods for the nonlinear system are discussed.Conclusions on uniqueness and convergence of the approximants for certain class of functions are given.

  14. Optimality conditions in smooth nonlinear programming

    NARCIS (Netherlands)

    Still, G.; Streng, M.

    1996-01-01

    This survey is concerned with necessary and sufficient optimality conditions for smooth nonlinear programming problems with inequality and equality constraints. These conditions deal with strict local minimizers of order one and two and with isolated minimizers. In most results, no constraint qualif

  15. Nonlinear lower hybrid modeling in tokamak plasmas

    Energy Technology Data Exchange (ETDEWEB)

    Napoli, F.; Schettini, G. [Università Roma Tre, Dipartimento di Ingegneria, Roma (Italy); Castaldo, C.; Cesario, R. [Associazione EURATOM/ENEA sulla Fusione, Centro Ricerche Frascati (Italy)

    2014-02-12

    We present here new results concerning the nonlinear mechanism underlying the observed spectral broadening produced by parametric instabilities occurring at the edge of tokamak plasmas in present day LHCD (lower hybrid current drive) experiments. Low frequency (LF) ion-sound evanescent modes (quasi-modes) are the main parametric decay channel which drives a nonlinear mode coupling of lower hybrid (LH) waves. The spectrum of the LF fluctuations is calculated here considering the beating of the launched LH wave at the radiofrequency (RF) operating line frequency (pump wave) with the noisy background of the RF power generator. This spectrum is calculated in the frame of the kinetic theory, following a perturbative approach. Numerical solutions of the nonlinear LH wave equation show the evolution of the nonlinear mode coupling in condition of a finite depletion of the pump power. The role of the presence of heavy ions in a Deuterium plasma in mitigating the nonlinear effects is analyzed.

  16. Stochastic resonance in Gaussian quantum channels

    CERN Document Server

    Lupo, Cosmo; Wilde, Mark M

    2011-01-01

    We determine conditions for the presence of stochastic resonance in a lossy bosonic channel with a nonlinear, threshold decoding. The stochastic resonance noise benefit occurs if and only if the detection threshold is outside of a "forbidden interval." We show how noise benefits can occur in different settings: when transmitting classical messages through a lossy bosonic channel, when transmitting over an entanglement-assisted lossy bosonic channel, and when discriminating channels with different loss parameters. Moreover, we consider a setting in which noise can benefit the faithful transmission of a qubit over a lossy bosonic channel with a particular encoding and decoding. In the latter case, we measure noise benefits in terms of the average channel fidelity and the entanglement preserved between a reference system and the channel output. In all cases, we assume Gaussian noise, allowing us to improve upon the forbidden-interval conditions found in earlier work.

  17. Simulation Performance of MMSE Iterative Equalization with Soft Boolean Value Propagation

    CERN Document Server

    Krishnamoorthy, Aravindh; Jandial, Ravi

    2011-01-01

    The performance of MMSE Iterative Equalization based on MAP-SBVP and COD-MAP algorithms (for generating extrinsic information) are compared for fading and non-fading communication channels employing serial concatenated convolution codes. MAP-SBVP is a convolution decoder using a conventional soft-MAP decoder followed by a soft-convolution encoder using the soft-boolean value propagation (SBVP). From the simulations it is observed that for MMSE Iterative Equalization, MAP-SBVP performance is comparable to COD-MAP for fading and non-fading channels.

  18. Nonlinear inverse synthesis for high spectral efficiency transmission in optical fibers

    CERN Document Server

    Le, Son Thai; Turitsyn, Sergei K

    2014-01-01

    In linear communication channels, spectral components (modes) defined by the Fourier transform of the signal propagate without interactions with each other. In certain nonlinear channels, such as the one modelled by the classical nonlinear Schr\\"odinger equation, there are nonlinear modes (nonlinear signal spectrum) that also propagate without interacting with each other and without corresponding nonlinear cross talk; effectively, in a linear manner. Here, we describe in a constructive way how to introduce such nonlinear modes for a given input signal. We investigate the performance of the nonlinear inverse synthesis (NIS) method, in which the information is encoded directly onto the continuous part of the nonlinear signal spectrum. This transmission technique, combined with the appropriate distributed Raman amplification, can provide an effective eigenvalue division multiplexing with high spectral efficiency, thanks to highly suppressed channel cross talk. The proposed NIS approach can be integrated with any...

  19. Nonlinear modelling of polymer electrolyte membrane fuel cell stack using nonlinear cancellation technique

    Energy Technology Data Exchange (ETDEWEB)

    Barus, R. P. P., E-mail: rismawan.ppb@gmail.com [Engineering Physics, Faculty of Industrial Technology, Institut Teknologi Bandung, Jalan Ganesa 10 Bandung and Centre for Material and Technical Product, Jalan Sangkuriang No. 14 Bandung (Indonesia); Tjokronegoro, H. A.; Leksono, E. [Engineering Physics, Faculty of Industrial Technology, Institut Teknologi Bandung, Jalan Ganesa 10 Bandung (Indonesia); Ismunandar [Chemistry Study, Faculty of Mathematics and Science, Institut Teknologi Bandung, Jalan Ganesa 10 Bandung (Indonesia)

    2014-09-25

    Fuel cells are promising new energy conversion devices that are friendly to the environment. A set of control systems are required in order to operate a fuel cell based power plant system optimally. For the purpose of control system design, an accurate fuel cell stack model in describing the dynamics of the real system is needed. Currently, linear model are widely used for fuel cell stack control purposes, but it has limitations in narrow operation range. While nonlinear models lead to nonlinear control implemnetation whos more complex and hard computing. In this research, nonlinear cancellation technique will be used to transform a nonlinear model into a linear form while maintaining the nonlinear characteristics. The transformation is done by replacing the input of the original model by a certain virtual input that has nonlinear relationship with the original input. Then the equality of the two models is tested by running a series of simulation. Input variation of H2, O2 and H2O as well as disturbance input I (current load) are studied by simulation. The error of comparison between the proposed model and the original nonlinear model are less than 1 %. Thus we can conclude that nonlinear cancellation technique can be used to represent fuel cell nonlinear model in a simple linear form while maintaining the nonlinear characteristics and therefore retain the wide operation range.

  20. The Uneasy Marriage between Law and Equality

    Directory of Open Access Journals (Sweden)

    Pauline C. Westerman

    2015-02-01

    Full Text Available There are two ways in which the social ideal of equality has found expression in the law: in the principle of equal treatment and in the principle of non-discrimination. In this article the meaning of these two legal principles is analysed, in order to answer the question to what extent they can be said to contribute to equality in the sense of an equal distribution of collective resources. It is argued that whereas the first just requires decision-making to be rule-based, the second principle demands that rules should be based on sound categorical distinctions. Neither of the two can, however, sensibly be linked to equality as equal distribution. The article concludes that the only way to establish such a link is by adding to the principle of non-discrimination “financial resources” as a suspect ground.

  1. Mechanosensitive Channels

    Science.gov (United States)

    Martinac, Boris

    Living cells are exposed to a variety of mechanical stimuli acting throughout the biosphere. The range of the stimuli extends from thermal molecular agitation to potentially destructive cell swelling caused by osmotic pressure gradients. Cellular membranes present a major target for these stimuli. To detect mechanical forces acting upon them cell membranes are equipped with mechanosensitive (MS) ion channels. Functioning as molecular mechanoelectrical transducers of mechanical forces into electrical and/or chemical intracellular signals these channels play a critical role in the physiology of mechanotransduction. Studies of prokaryotic MS channels and recent work on MS channels of eukaryotes have significantly increased our understanding of their gating mechanism, physiological functions, and evolutionary origins as well as their role in the pathology of disease.

  2. A Null Space Approach for Solving Nonlinear Complementarity Problems

    Institute of Scientific and Technical Information of China (English)

    Pu-yan Nie

    2006-01-01

    In this work, null space techniques are employed to tackle nonlinear complementarity problems(NCPs). NCP conditions are transform into a nonlinear programming problem, which is handled by null space algorithms. The NCP conditions are divided into two groups. Some equalities and inequalities in an NCP are treated as constraints. While other equalities and inequalities in an NCP are to be regarded as objective function.Two groups are all updated in every step. Null space approaches are extended to nonlinear complementarity problems. Two different solvers are employed for an NCP in an algorithm.

  3. Gender Equality, Citizenship and Human Rights

    DEFF Research Database (Denmark)

    This comparative volume examines the ways in which current controversies and political, legal, and social struggles for gender equality raise conceptual questions and challenge our thinking on political theories of equality, citizenship and human rights. Bringing together scholars and activists who...... reflect upon challenges to gender equality, citizenship, and human rights in their respective societies; it combines theoretical insights with empirically grounded studies. The volume contextualises feminist political theory in China and the Nordic countries and subsequently puts it into a global...

  4. Gender Equality, Intersectionality and Diversity in Europe

    DEFF Research Database (Denmark)

    Agustin, Lise Rolandsen

    Analyzing the developments which have characterized EU gender equality policies and women's transnational activism since the introduction of multiple discrimination policies in the 1990s, this book identifies two interrelated challenges: diversity of women's interests, and degendering of policies....... Drawing on discursive policy analysis, it addresses the interaction between policies, institutions and civil society actors in relation to gender equality, diversity and intersectionality at the European level. Rolandsen Agustín successfully integrates the concepts of diversity and gender equality...

  5. Trust, Welfare States and Income Equality

    DEFF Research Database (Denmark)

    Bergh, Andreas; Bjørnskov, Christian

    2014-01-01

    . Using a structural equation model estimated on a large country sample, we find that trust has a positive effect on both market and net income equality. Larger welfare states lead to higher net equality but neither net income equality nor welfare state size seems to have a causal effect on trust. We...... conclude that while trust facilitates welfare state policies that may reduce net inequality, this decrease in inequality does not increase trust....

  6. How Likely Is Factor Price Equalization?

    DEFF Research Database (Denmark)

    Hansen, Bodil O.; Keiding, Hans

    The idea of treating factor price equalization as a situation, where the distribution of factors among countries is compatible with an equilibrium in an integrated world economy, has been refined to give the so-called lens condition for factor price equalization. In this paper, we show...... that the lens condition may be used to give estimates for the probability of factor price equalization when factors are distributed randomly among countries and, in addition, the techologies are sampled according to a given probability distribution. The estimates indicate that factor price equalization may...

  7. Equality: A Principle of Human Interaction

    Directory of Open Access Journals (Sweden)

    Hjördís Hákonardóttir

    2011-09-01

    Full Text Available The paper focuses on equality as a primary principle of human interaction. Human beings have basic needs, physical and mental, the fulfilment of which is necessary for a flourishing life. These needs transfer into so-called fundamental rights. Humans are entitled to a life as conscious, autonomous actors in respect to those needs. In this respect all humans are equal. It is proposed here that equality in this sense promotes a situation from which fundamental rights are derived. Thus equality is primary to and the reason why recognition of fundamental rights cannot be left to the chance of social development.

  8. MHD Boundary Layer Flow of Dilatant Fluid in a Divergent Channel with Suction or Blowing

    Institute of Scientific and Technical Information of China (English)

    Krishnendu Bhattacharyya; G.C.Layek

    2011-01-01

    @@ An analysis is carried out to study a steady magnetohydrodynamic(MHD) boundary layer How of an electrically conducting incompressible power-law non-Newtonian fluid through a divergent channel.The channel walls are porous and subjected to either suction or blowing of equal magnitude of the same kind of fluid on both walls.The fluid is permeated by a magnetic field produced by electric current along the line of intersection of the channel walls.The governing partial differential equation is transformed into a self-similar nonlinear ordinary differential equation using similarity transformations.The possibility of boundary layer flow in a divergent channel is analyzed with the power-law fluid model.The analysis reveals that the boundary layer flow (without separation) is possible for the case of the dilatant fluid model subjected to suitable suction velocity applied through its porous walls,even in the absence of a magnetic field.Further, it is found that the boundary layer flow is possible even in the presence of blowing for a suitable value of the magnetic parameter.It is found that the velocity increases with increasing values of the power-law index for the case of dilatant fluid.The effects of suction/blowing and magnetic field on the velocity are shown graphically and discussed physical尔

  9. Characterizaticr of Solid State Laser and Nonlinear Optical Materials.

    Science.gov (United States)

    1995-02-02

    materials useful in the different methods for obtaining frequency agility: narrow line emitters with multiple lasing channels and nonlinear optical materials . In...codoped with two or more rare earth ions were studied and computers models developed to explain their spectral dynamics. The nonlinear optical materials investigated

  10. Nonlinear resonances

    CERN Document Server

    Rajasekar, Shanmuganathan

    2016-01-01

    This introductory text presents the basic aspects and most important features of various types of resonances and anti-resonances in dynamical systems. In particular, for each resonance, it covers the theoretical concepts, illustrates them with case studies, and reviews the available information on mechanisms, characterization, numerical simulations, experimental realizations, possible quantum analogues, applications and significant advances made over the years. Resonances are one of the most fundamental phenomena exhibited by nonlinear systems and refer to specific realizations of maximum response of a system due to the ability of that system to store and transfer energy received from an external forcing source. Resonances are of particular importance in physical, engineering and biological systems - they can prove to be advantageous in many applications, while leading to instability and even disasters in others. The book is self-contained, providing the details of mathematical derivations and techniques invo...

  11. Nonlinear Dynamics

    Institute of Scientific and Technical Information of China (English)

    1996-01-01

    3.1 A Unified Nonlinear Feedback Functional Method for Study Both Control and Synchronization of Spatiotemporal Chaos Fang Jinqing Ali M. K. (Department of Physics, The University of Lethbridge,Lethbridge, Alberta T1K 3M4,Canada) Two fundamental questions dominate future chaos control theories.The first is the problem of controlling hyperchaos in higher dimensional systems.The second question has yet to be addressed:the problem of controlling spatiotemporal chaos in a spatiotemporal system.In recent years, control and synchronization of spatiotemporal chaos and hyperchaos have became a much more important and challenging subject. The reason for this is the control and synchronism of such behaviours have extensive and great potential of interdisciplinary applications, such as security communication, information processing, medicine and so on. However, this subject is not much known and remains an outstanding open.

  12. Low Complexity Adaptive Equalizers for Underwater Acoustic Communications

    Institute of Scientific and Technical Information of China (English)

    Masoumeh SOFLAEI; Paeiz AZMI

    2014-01-01

    Interference-signals-due-to-scattering-from-surface-and-reflecting-from-bottom-is-one-of-the-most-important-problems-of-reliable-communications-in-shallow-water-channels.-To-solve-this-problem,-one-of-the-best-suggested-ways-is-to-use-adaptive-equalizers.-Convergence-rate-and-misadjustment-error-in-adaptive-algorithms-play-important-roles-in-adaptive-equalizer-performance.-In-this-paper,-affine-projection-algorithm-(APA),-selective-regressor-APA(SR-APA),-family-of-selective-partial-update-(SPU)-algorithms,-family-of-set-membership-(SM)-algorithms-and-selective-partial-update-selective-regressor-APA-(SPU-SR-APA)-are-compared-with-conventional-algorithms-such-as-the-least-mean-square-(LMS)-in-underwater-acoustic-communications.-We-apply-experimental-data-from-the-Strait-of-Hormuz-for-demonstrating-the-efficiency-of-the-proposed-methods-over-shallow-water-channel.-We-observe-that-the-values-of-the-steady-state-mean-square-error-(MSE)-of-SR-APA,-SPU-APA,-SPU-normalized-least-mean-square-(SPU-NLMS),-SPU-SR-APA,-SM-APA-and-SM-NLMS-algorithms-decrease-in-comparison-with-the-LMS-algorithm.-Also-these-algorithms-have-better-convergence-rates-than-LMS-type-algorithm.

  13. A thermosensitive mutation alters the effects of lacosamide on slow inactivation in neuronal voltage-gated sodium channels, NaV 1.2.Mena Abdelsayed1, Stanislav Sokolov1, Peter C. Ruben*1 - These authors contributed equally to this work* - Corresponding author

    Directory of Open Access Journals (Sweden)

    Mena eAbdelsayed

    2013-09-01

    Full Text Available Epilepsy is a disorder characterized by seizures and convulsions. The basis of epilepsy is an increase in neuronal excitability that, in some cases, may be caused by functional defects in neuronal voltage gated sodium channels (NaVs. The C121W mutation of the β1 subunit, in particular, gives rise to the thermosensitive generalized epilepsy with febrile seizures plus (GEFS+ phenotype. Lacosamide is used to treat epileptic seizures and is distinct from other anti-seizure drugs by targeting NaV slow-inactivation. We studied the effects of 100 µM lacosamide on the biophysical properties of NaV1.2 channels associated with either WT-β1 or the mutant C121W-β1 subunit. Biophysical parameters were measured at both normal (22 °C and elevated (34 °C temperatures to elicit the differential temperature-sensitivity of C121W. Lacosamide was less effective in NaV1.2 associated with the C121W-β1 at either temperature than in NaV1.2 + WT-β1. There is also a more potent effect by lacosamide on slow inactivation at elevated temperatures. Our data suggest a modulatory role is imparted by the β1 subunit in the interaction between the drug and the channel.

  14. Interfacial instability of liquid films coating the walls of a parallel-plate channel and sheared by a gas flow

    CERN Document Server

    Vécsei, Miklós; Hardt, Steffen

    2016-01-01

    The stability of liquid films coating the walls of a parallel-plate channel and sheared by a pressure-driven gas flow along the channel centre is studied. The films are susceptible to a long-wavelength instability, whose dynamic behaviour is found - for sufficiently low Reynolds numbers and thick gas layers - to be described by two coupled non-linear partial differential equations. To the best of our knowledge, such coupled fully non-linear equations for the film thicknesses have not been derived previously. A linear stability analysis conducted under the condition that the material properties and the initial undisturbed liquid film thicknesses are equal can be utilized to determine whether the interfaces are predominantly destabilized by the variations of the shear stress or by the pressure gradient acting upon them. The analysis of the weakly non-linear equations performed for this case shows that instabilities corresponding to a vanishing Reynolds number are absent from the system. Moreover, for this confi...

  15. Low-complexity nonlinear adaptive filter based on a pipelined bilinear recurrent neural network.

    Science.gov (United States)

    Zhao, Haiquan; Zeng, Xiangping; He, Zhengyou

    2011-09-01

    To reduce the computational complexity of the bilinear recurrent neural network (BLRNN), a novel low-complexity nonlinear adaptive filter with a pipelined bilinear recurrent neural network (PBLRNN) is presented in this paper. The PBLRNN, inheriting the modular architectures of the pipelined RNN proposed by Haykin and Li, comprises a number of BLRNN modules that are cascaded in a chained form. Each module is implemented by a small-scale BLRNN with internal dynamics. Since those modules of the PBLRNN can be performed simultaneously in a pipelined parallelism fashion, it would result in a significant improvement of computational efficiency. Moreover, due to nesting module, the performance of the PBLRNN can be further improved. To suit for the modular architectures, a modified adaptive amplitude real-time recurrent learning algorithm is derived on the gradient descent approach. Extensive simulations are carried out to evaluate the performance of the PBLRNN on nonlinear system identification, nonlinear channel equalization, and chaotic time series prediction. Experimental results show that the PBLRNN provides considerably better performance compared to the single BLRNN and RNN models.

  16. Vocational Education and Equality of Opportunity.

    Science.gov (United States)

    Horowitz, Benjamin; Feinberg, Walter

    1990-01-01

    Examines the concepts of equality of opportunity and equality of educational opportunity and their relationship to vocational education. Traces the history of vocational education. Delineates the distinction between training and education as enumerated in Aristotelian philosophy. Discusses the role vocational education can play in the educative…

  17. 34 CFR 108.6 - Equal access.

    Science.gov (United States)

    2010-07-01

    ... 34 Education 1 2010-07-01 2010-07-01 false Equal access. 108.6 Section 108.6 Education Regulations... ACCESS TO PUBLIC SCHOOL FACILITIES FOR THE BOY SCOUTS OF AMERICA AND OTHER DESIGNATED YOUTH GROUPS § 108.6 Equal access. (a) General. Consistent with the requirements of paragraph (b) of this section,...

  18. Does Russia need gender equality officers?

    OpenAIRE

    Krasilnikova, Oxana; Красильникова, Оксана

    2013-01-01

    The paper identifies the reasons for the lack of the gender equality officer in the Russian Federation against the background of the Nordic countries and Germany experience and conditions for the establishment of the gender equality in Europe. Using gender approach the political and cultural situation of the Russian society is analyzed and the ways to solve the problem are suggested.

  19. Blind Equalization Based on Evolution Strategies

    Institute of Scientific and Technical Information of China (English)

    SongYu; ZhangXianda; 等

    1997-01-01

    Conventional blind equalization algorithms suffer from ill convergence to local minima and slow convergence speed.This paper proposes a novel blind equalization algorithm.using random search methods-evolution strategies and existing cost functions,Simulation results verify the fast and global convergence of the proposed algorithm.

  20. 78 FR 53231 - Women's Equality Day, 2013

    Science.gov (United States)

    2013-08-28

    ... Amendment paved the way for more women to participate in American politics--as leaders, candidates, voters... August 28, 2013 Part IV The President Proclamation 9003--Women's Equality Day, 2013 Proclamation 9004...#0;#0; #0; #0;Title 3-- #0;The President ] Proclamation 9003 of August 23, 2013 Women's Equality Day...

  1. 47 CFR 73.1941 - Equal opportunities.

    Science.gov (United States)

    2010-10-01

    ... 47 Telecommunication 4 2010-10-01 2010-10-01 false Equal opportunities. 73.1941 Section 73.1941... Rules Applicable to All Broadcast Stations § 73.1941 Equal opportunities. (a) General requirements...-spot coverage of bona fide news events (including, but not limited to political conventions...

  2. Justifications of Gender Equality in Academia

    DEFF Research Database (Denmark)

    Nielsen, Mathias Wullum

    2014-01-01

    Gender equality in academia is often perceived as receiving more emphasis in Norway and Sweden than in Denmark. But how do the public research institutions in the three countries approach issues of gender equality differently? This study investigates how activities related to gender equality...... are articulated and justified in the policy statements of six Scandinavian universities. The analysis reveals some interesting disparities between the countries. In short, the Danish universities seem to be reluctant to deal with gender equality on the basis of rights-based assumptions. While the Norwegian...... and Swedish universities juxtapose arguments of utility, innovation, justice, and anti-discrimination, the Danish universities primarily refer to aspects of competitiveness, utility, and innovation when justifying activities on gender equality. The article suggests that the lack of justice...

  3. Nonlinear Materials Characterization Facility

    Data.gov (United States)

    Federal Laboratory Consortium — The Nonlinear Materials Characterization Facility conducts photophysical research and development of nonlinear materials operating in the visible spectrum to protect...

  4. Approximate Equalities on Rough Intuitionistic Fuzzy Sets and an Analysis of Approximate Equalities

    Directory of Open Access Journals (Sweden)

    B. K. Tripathy

    2012-03-01

    Full Text Available In order to involve user knowledge in determining equality of sets, which may not be equal in the mathematical sense, three types of approximate (rough equalities were introduced by Novotny and Pawlak ([8, 9, 10]. These notions were generalized by Tripathy, Mitra and Ojha ([13], who introduced the concepts of approximate (rough equivalences of sets. Rough equivalences capture equality of sets at a higher level than rough equalities. More properties of these concepts were established in [14]. Combining the conditions for the two types of approximate equalities, two more approximate equalities were introduced by Tripathy [12] and a comparative analysis of their relative efficiency was provided. In [15], the four types of approximate equalities were extended by considering rough fuzzy sets instead of only rough sets. In fact the concepts of leveled approximate equalities were introduced and properties were studied. In this paper we proceed further by introducing and studying the approximate equalities based on rough intuitionistic fuzzy sets instead of rough fuzzy sets. That is we introduce the concepts of approximate (rough equalities of intuitionistic fuzzy sets and study their properties. We provide some real life examples to show the applications of rough equalities of fuzzy sets and rough equalities of intuitionistic fuzzy sets.

  5. Nonlinear wavelet estimation of regression function with random desigm

    Institute of Scientific and Technical Information of China (English)

    张双林; 郑忠国

    1999-01-01

    The nonlinear wavelet estimator of regression function with random design is constructed. The optimal uniform convergence rate of the estimator in a ball of Besov space Bp,q? is proved under quite genera] assumpations. The adaptive nonlinear wavelet estimator with near-optimal convergence rate in a wide range of smoothness function classes is also constructed. The properties of the nonlinear wavelet estimator given for random design regression and only with bounded third order moment of the error can be compared with those of nonlinear wavelet estimator given in literature for equal-spaced fixed design regression with i.i.d. Gauss error.

  6. Nonlinear Radon Transform Using Zernike Moment for Shape Analysis

    Directory of Open Access Journals (Sweden)

    Ziping Ma

    2013-01-01

    Full Text Available We extend the linear Radon transform to a nonlinear space and propose a method by applying the nonlinear Radon transform to Zernike moments to extract shape descriptors. These descriptors are obtained by computing Zernike moment on the radial and angular coordinates of the pattern image's nonlinear Radon matrix. Theoretical and experimental results validate the effectiveness and the robustness of the method. The experimental results show the performance of the proposed method in the case of nonlinear space equals or outperforms that in the case of linear Radon.

  7. Nonlinear singular vectors and nonlinear singular values

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    A novel concept of nonlinear singular vector and nonlinear singular value is introduced, which is a natural generalization of the classical linear singular vector and linear singular value to the nonlinear category. The optimization problem related to the determination of nonlinear singular vectors and singular values is formulated. The general idea of this approach is demonstrated by a simple two-dimensional quasigeostrophic model in the atmospheric and oceanic sciences. The advantage and its applications of the new method to the predictability, ensemble forecast and finite-time nonlinear instability are discussed. This paper makes a necessary preparation for further theoretical and numerical investigations.

  8. Switchable and tunable multiple-channel erbium-doped fiber laser using graphene-polymer nanocomposite and asymmetric two-stage fiber Sagnac loop filter.

    Science.gov (United States)

    Zhou, Min; Luo, Zhengqian; Cai, Zhiping; Ye, Chenchun; Xu, Huiying; Wang, Jinzhang

    2011-06-20

    A high-performance multiple-channel erbium-doped fiber laser (EDFL) is proposed and experimentally demonstrated, using graphene-polymer nanocomposite as a multiwavelength equalizer and an asymmetric two-stage polarization-maintaining fiber (PMF) Sagnac loop as a flexible comb filter. At first, the filtering characteristics of the PMF Sagnac loop filter (SLF) are investigated. Both theoretical and experimental results show that it can provide a flexibly switchable and tunable comblike filtering. Then, the two-stage PMF SLF is inserted into a graphene-assisted EDFL cavity for generating multiwavelength oscillation. The extreme-high third-order optical nonlinearity of graphene is exploited to suppress the mode competition of the EDFL, and a stable multiple-channel lasing is observed. By carefully adjusting the polarization controllers in the two-stage PMF SLF, not only can the lasing-line number per channel be switchable between single and multiple wavelengths, but also the wavelength spacing in the triple-wavelength condition can be tunable. In the case of triple wavelengths per channel, up to 12 wavelengths with four channels stable oscillations can be achieved. The multiple-channel EDFL can keep a high extinction ratio of >40 dB and a narrow linewidth of <0.01 nm.

  9. Land Governance, Gender Equality and Development

    DEFF Research Database (Denmark)

    Ravnborg, Helle Munk; Spichiger, Rachel; Broegaard, Rikke Brandt

    2016-01-01

    pursued in these reforms and examines the role played by donor cooperation. Despite significant progress in developing land legislation that upholds gender equality, implementation often does not follow suit, and women still face discrimination. Based on country case studies, the article identifies six......Most land governance reforms seek to enhance tenure security, encourage investments and thereby promote economic growth. Increasingly, land reforms attempt to secure women's and other vulnerable groups' access to land. This article reviews the extent to which gender equality in land tenure has been...... challenges, which should be addressed to achieve gender equality in land tenure....

  10. Spatially extended sound equalization in rectangular rooms

    DEFF Research Database (Denmark)

    Santillan, Arturo Orozco

    2001-01-01

    of broadband signals can be achieved by the simulation of a traveling plane wave using FIR filters. The optimal solution has been calculated following the traditional least-squares approximation, where a modeling delay has been applied to minimize reverberation. An advantage of the method is that the sound......The results of a theoretical study on global sound equalization in rectangular rooms at low frequencies are presented. The zone where sound equalization can be obtained is a continuous three-dimensional region that occupies almost the complete volume of the room. It is proved that the equalization...

  11. Spatially extended sound equalization in rectangular rooms

    DEFF Research Database (Denmark)

    Santillan, Arturo Orozco

    2001-01-01

    The results of a theoretical study on global sound equalization in rectangular rooms at low frequencies are presented. The zone where sound equalization can be obtained is a continuous three-dimensional region that occupies almost the complete volume of the room. It is proved that the equalization...... of broadband signals can be achieved by the simulation of a traveling plane wave using FIR filters. The optimal solution has been calculated following the traditional least-squares approximation, where a modeling delay has been applied to minimize reverberation. An advantage of the method is that the sound...

  12. Positron Channeling

    CERN Document Server

    Badikyan, Karen

    2016-01-01

    The possibility of channeling the low-energy relativistic positrons around separate crystallographic axes with coaxial symmetry of negative ions in some types of crystals is shown. The process of annihilation of positrons with electrons of medium was studied in detail.

  13. Brands & Channels

    Institute of Scientific and Technical Information of China (English)

    Alice Yang

    2009-01-01

    @@ "Brands" and "Channels" are the two most important things in Ku-Hai Chen's eyes when doing business with Main-land China. Ku-Hai Chen, Executive Director of the International Trade Institute of Taiwan External Trade Development Council (TAITRA), flies frequently between Chinese Taipei and Mainland China, and was in Beijing earlier this month for his seminar.

  14. A training-aided MIMO equalization based on matrix transformation in the space division multiplexed fiber-optic transmission system

    Science.gov (United States)

    Guan, Xiaoning; Liu, Bo; Zhang, Lijia; Xin, Xiangjun; Tian, Qinghua; Zhang, Qi; Tian, Feng; Li, Dengao; Zhao, Jumin; Wang, Renfan

    2016-10-01

    A novel training sequence is designed for the space division multiplexed fiber-optic transmission system in this paper. The training block is consisting of segmented sequence, which can be used to compensate time offset and distortion (such as dispersion) in the transmission link. The channel function can be obtained by one tap equalization in the receiver side. This paper designs the training sequence by adjusting the length of the training signals and implementing matrix transformation, to obtain the coefficient of equalizer for channel detect and equalization. This new training sequence reduces system complexity and improves transmission efficiency at the same time. Compared with blind equalization, the matrix transformation based training sequence can reduce system complexity, and perform targeted equalization to the mechanism of mode coupling in the space division optical fiber system. As a result, it can effectively improve signal transmission quality and reduce bit error rate.

  15. Blind equalization and automatic modulation classification based on subspace for subcarrier MPSK optical communications

    Science.gov (United States)

    Chen, Dan; Guo, Lin-yuan; Wang, Chen-hao; Ke, Xi-zheng

    2017-07-01

    Equalization can compensate channel distortion caused by channel multipath effects, and effectively improve convergent of modulation constellation diagram in optical wireless system. In this paper, the subspace blind equalization algorithm is used to preprocess M-ary phase shift keying (MPSK) subcarrier modulation signal in receiver. Mountain clustering is adopted to get the clustering centers of MPSK modulation constellation diagram, and the modulation order is automatically identified through the k-nearest neighbor (KNN) classifier. The experiment has been done under four different weather conditions. Experimental results show that the convergent of constellation diagram is improved effectively after using the subspace blind equalization algorithm, which means that the accuracy of modulation recognition is increased. The correct recognition rate of 16PSK can be up to 85% in any kind of weather condition which is mentioned in paper. Meanwhile, the correct recognition rate is the highest in cloudy and the lowest in heavy rain condition.

  16. Nonlinear limits to the information capacity of optical fiber communications

    CERN Document Server

    Mitra, P P; Mitra, Partha P.; Stark, Jason B.

    2000-01-01

    The exponential growth in the rate at which information can be communicated through an optical fiber is a key element in the so called information revolution. However, like all exponential growth laws, there are physical limits to be considered. The nonlinear nature of the propagation of light in optical fiber has made these limits difficult to elucidate. Here we obtain basic insights into the limits to the information capacity of an optical fiber arising from these nonlinearities. The key simplification lies in relating the nonlinear channel to a linear channel with multiplicative noise, for which we are able to obtain analytical results. In fundamental distinction to the linear additive noise case, the capacity does not grow indefinitely with increasing signal power, but has a maximal value. The ideas presented here have broader implications for other nonlinear information channels, such as those involved in sensory transduction in neurobiology. These have been often examined using additive noise linear cha...

  17. Nonlinear Diffusion and Transient Osmosis

    Science.gov (United States)

    Akira, Igarashi; Lamberto, Rondoni; Antonio, Botrugno; Marco, Pizzi

    2011-08-01

    We investigate both analytically and numerically the concentration dynamics of a solution in two containers connected by a narrow and short channel, in which diffusion obeys a porous medium equation. We also consider the variation of the pressure in the containers due to the flow of matter in the channel. In particular, we identify a phenomenon, which depends on the transport of matter across nano-porous membranes, which we call “transient osmosis". We find that nonlinear diffusion of the porous medium equation type allows numerous different osmotic-like phenomena, which are not present in the case of ordinary Fickian diffusion. Experimental results suggest one possible candidate for transiently osmotic processes.

  18. Nonlinear Diffusion and Transient Osmosis

    Institute of Scientific and Technical Information of China (English)

    Akira Igarashi; Lamberto Rondon; Antonio Botrugno; Marco Pizzi

    2011-01-01

    We investigate both analytically and numerically the concentration dynamics of a solution in two containers connected by a narrow and short channel, in which diffusion obeys a porous medium equation. We also consider the variation of the pressure in the containers due to the flow of matter in the channel. In particular, we identify a phenomenon, which depends on the transport of matter across nano-porous membranes, which we call "transient osmosis". We find that nonlinear diffusion of the porous medium equation type allows numerous different osmotic-like phenomena, which are not present in the case of ordinary Fickian diffusion. Experimental results suggest one possible candidate for transiently osmotic processes.

  19. Equal Remuneration Convention (ILO No. 100).

    Science.gov (United States)

    1989-01-01

    The government of Uruguay ratified this UN International Labor Organization convention on equal remuneration on November 16, 1989, and the Government of Zimbabwe ratified this Convention on December 14, 1989.

  20. ECONOMIC GROWTH AND EQUALITY IN REDUCING POVERTY

    Directory of Open Access Journals (Sweden)

    Zaenal Muttaqin

    2016-02-01

    Full Text Available In some developing countries, the instrument to alleviate the poverty is by using the economic growth. So, the increasing in investment, infrastructure development, and macroeconomics stability always be priority from developing countries. In this article explain that economic growth is not the important factor to alleviate the poverty, because equality sometimes is more important rather than the economic growth. In this context, its measure by inequality growth trade off index (IGTI. This method is to measure the influence of economic growth to reducing the inequality, with this method every country can measure which one is better to reducing the poverty whether the economic growth or equality. With this method, Laos in 2000 show that economic growth is more important than equality, but in the same year in Thailand show that equality is more important than economic growth.DOI: 10.15408/sjie.v1i1.2592

  1. Managing diversity and equality in the workplace

    National Research Council Canada - National Science Library

    Sharma, Angel

    2016-01-01

    ...), and organizational capabilities in managing diversity and equality in the workplace. Firstly, performance appraisals were found to be a major source of discrimination especially due to raters influence on the actual process...

  2. Girls' Education and Gender Equality. Factsheet

    Science.gov (United States)

    Global Partnership for Education, 2016

    2016-01-01

    This brief fact sheet presents benefits of investing in gender equality, how the Global Partnership for Education (GPE) supports inclusive and equitable quality education, as well as the results it has achieved.

  3. CULTURE, TRADITION, CUSTOM, LAW AND GENDER EQUALITY

    African Journals Online (AJOL)

    JMaluleke

    2005-10-18

    Oct 18, 2005 ... "Equal access to Education and Training for Women: Pathway to Decent work for Women", on. 12-13 August ..... These parents and relatives also face being charged with Trafficking in Persons, ..... Register of Internet sources.

  4. Valuing Equality in Irish Social Care

    Directory of Open Access Journals (Sweden)

    Niall Hanlon

    2009-01-01

    Full Text Available In this article the author critiques Irish social care by presenting an equality perspective on practice. An equality perspective involves developing emancipatory practices, that is, ways of helping that provide egalitarian solutions and outcomes. Although emancipatory values are often contrasted with traditional social care values, the author seeks a pragmatic and integrated approach to emancipatory practices rather than a restatement of traditional dichotomies. Emancipatory practice begins with an appreciation of the nature and relevance of inequalities on the lives of diverse social care users. Building a commitment to equality within social care education and practice is an important step in altering many individual and institutional social care practices by focussing on equality processes and outcomes as central social care objectives. Using a well credited framework that outlines five dimensions of inequality (Baker, Lynch, Cantillon and Walsh, 2004, the author argues that social care educators and practitioners need to debate the issues raised and develop emancipatory practices.

  5. An Adaptive Multiuser Chip-Rate Equalizer for CDMA Underwater Communication System

    Institute of Scientific and Technical Information of China (English)

    HAN Jing; HUANG Jian-guo; SHEN Xiao-hong

    2008-01-01

    Direct-sequence code-division multiple access (CDMA) is considered for multiuser communication network in underwater acoustic channel, where extended multipath and rapid time-variability are encountered. To track and compensate the channel distortion, a decentralized hypothesis-feedback equalization (HFE) algorithm based on chip-rate update has been used[1]. But due to multiple access interference (MAI), its performance suffers degradation. For this reason, successive interference cancellation hypothesis-feedback equalization (SIC-HFE) algorithm is proposed, which combines the capabilities of HFE to track the time-varying channel and SIC implemented by cross-over feedback filters to cancel out the MAI effects between users. Simulation and experiment results show that the proposed algorithm can significantly improve the performance of asynchronous multiuser CDMA underwater communication system.

  6. Digital Communications Channel Equalisation Using the Kernel Adaline.

    OpenAIRE

    Mitchinson, B.; Harrison, R F

    2000-01-01

    For transmission of digital signals over a linear channel with additive white gaussian noise, it has been shown that the optimal symbol decision equaliser is non-linear. The Kernel Adaline algorithm, a non-linear generalisation of Widrow's and Hoff's Adaline, has been shown to be capable of learning arbitrary non-linear decision boundaries, whilst retaining the desirable convergence properties of the linear Adaline. This work investigates the use of the Kernel Adaline as equaliser for such ch...

  7. Analysis and Realization on Turbo Equalization based on 64-QAM in OFDM System

    Directory of Open Access Journals (Sweden)

    Peng Gao

    2013-06-01

    Full Text Available With the development of the mobile communication, the related technologies have gone through a rapid growing phase from 1G to 3G, until 4G. The technology evolution targets to improve the performance of overall system, and promote the related services and applications. In this paper, author makes analysis on Turbo equalization based on M-QAM modulation in OFDM system. Since Turbo equalization is an iterative receiver algorithm repeating equalization and channel decoding to improve the performance of the receiver, there researches on Turbo codes and turbo equalization have been emphasis, especially on the error-correction during these years. Due to the operations of equalization and decoding are repeated several times in one process, the computational complexity is increased in the receiver. Author aims at the cost function of CMA (Constant Modulus Algorithm to change or recreate a new algorithm, and then as a contrast with the error functions, we can see the advantages about this change. Finally, author makes simulations on the Turbo equalization based on 64-QAM in OFDM system. Compared with the Turbo equalization based on 16-QAM, the performance of Turbo equalization based on 64-QAM is more efficient.

  8. Gender Equality From A Gender Budgeting Perspective

    OpenAIRE

    Nyevero Maruzani; Nogget Matope; Efiritha Chauraya

    2012-01-01

    Gender budgeting, which is also known as gender responsive budgeting , tracks how budgets respond to gender equality and women’s rights requirement. This entails investing in and making available mechanisms, guidelines and indicators that enable gender equality advocates to track progress, benefit incidence and show how supposedly gender neutral budgets impact on men and women. The aim of this discussion is to highlight the importance of gender budgeting in addressing gender disparities while...

  9. Channel Power in Multi-Channel Environments

    NARCIS (Netherlands)

    M.G. Dekimpe (Marnik); B. Skiera (Bernd)

    2004-01-01

    textabstractIn the literature, little attention has been paid to instances where companies add an Internet channel to their direct channel portfolio. However, actively managing multiple sales channels requires knowing the customers’ channel preferences and the resulting channel power. Two key compon

  10. Channel Power in Multi-Channel Environments

    NARCIS (Netherlands)

    M.G. Dekimpe (Marnik); B. Skiera (Bernd)

    2004-01-01

    textabstractIn the literature, little attention has been paid to instances where companies add an Internet channel to their direct channel portfolio. However, actively managing multiple sales channels requires knowing the customers’ channel preferences and the resulting channel power. Two key

  11. [Gender equality activity in the Bioimaging Society].

    Science.gov (United States)

    Suzaki, Etsuko

    2013-09-01

    Gender equality activity in the Bioimaging Society was initiated in 2005 when it joined the Japan Inter-Society Liaison Association Committee for Promoting Equal Participation of Men and Women in Science and Engineering (EPMEWSE). The Gender Equality Committee of the Bioimaging Society is acting on this issue by following the policy of the EPMEWSE, and has also been planning and conducting lectures at annual meetings of the society to gain the understanding, consents, and cooperation of the members of the society to become conscious of gender equality. Women's participation in the society has been promoted through the activities of the Gender Equality Committee, and the number of women officers in the society has since increased from two women out of 40 members in 2005 to five out of 44 in 2013. The activities of the Gender Equality Committee of the Japanese Association of Anatomists (JAA) have just started. There are more than 400 women belonging to the JAA. When these women members join together and collaborate, women's participation in the JAA will increase.

  12. Marriage equality is a mental health issue.

    Science.gov (United States)

    Kealy-Bateman, Warren; Pryor, Lisa

    2015-10-01

    We aim to review marriage equality in New Zealand and Australia and critically evaluate the health impact of such a legal change. We undertook a review of the literature using the search terms "marriage equality", "same sex marriage" and "gay marriage" in combination with "health", "wellbeing", "psych*", "mental illness" and "distress". This search included medical literature, legal literature and mass media. This review indicates that Lesbian, Gay, Bisexual, Transgender and Intersex (LGBTI) people disproportionately face negative health stressors and negative health events compared with the general population and this is related to the stress of being a stigmatised minority group. The evidence strongly supports the proposition that marriage equality is related to improved health outcomes. A diverse range of professional health groups advocate for the legislative progression to marriage equality. The authors found no evidence that marriage equality harms opposite-sex marriage. Marriage equality is still lacking in Australia and as a positive correlate of health should be strongly supported. © The Royal Australian and New Zealand College of Psychiatrists 2015.

  13. Terabit Nyquist PDM-32QAM signal transmission with training sequence based time domain channel estimation.

    Science.gov (United States)

    Zhang, Fan; Wang, Dan; Ding, Rui; Chen, Zhangyuan

    2014-09-22

    We propose a time domain structure of channel estimation for coherent optical communication systems, which employs training sequence based equalizer and is transparent to arbitrary quadrature amplitude modulation (QAM) formats. Enabled with this methodology, 1.02 Tb/s polarization division multiplexed 32 QAM Nyquist pulse shaping signal with a net spectral efficiency of 7.46 b/s/Hz is transmitted over standard single-mode fiber link with Erbium-doped fiber amplifier only amplification. After 1190 km transmission, the average bit-error rate is lower than the 20% hard-decision forward error correction threshold of 1.5 × 10(-2). The transmission distance can be extended to 1428 km by employing intra-subchannel nonlinear compensation with the digital back-propagation method.

  14. 29 CFR 1620.14 - Testing equality of jobs.

    Science.gov (United States)

    2010-07-01

    ... 29 Labor 4 2010-07-01 2010-07-01 false Testing equality of jobs. 1620.14 Section 1620.14 Labor... Testing equality of jobs. (a) In general. What constitutes equal skill, equal effort, or equal..., or responsibility required for the performance of jobs will not render the equal pay...

  15. Modern slavery–an empirical analysis of source countries of human trafficking and the role of gender equality

    OpenAIRE

    Martinsen, Kristine Gran

    2014-01-01

    There are over 20 million victims of trafficking from more than 136 countries in the world. This thesis takes a closer look at this modern form of slavery, in particular the nonlinear relation between gender equality and human trafficking outflows. My main hypothesis is that an increase in gender equality first has a positive effect on the amount of trafficking outflows and then a negative effect as countries become more egalitarian. Using cross-national data from the World Bank and from the ...

  16. NONLINEAR EXPECTATIONS AND NONLINEAR MARKOV CHAINS

    Institute of Scientific and Technical Information of China (English)

    PENG SHIGE

    2005-01-01

    This paper deals with nonlinear expectations. The author obtains a nonlinear generalization of the well-known Kolmogorov's consistent theorem and then use it to construct filtration-consistent nonlinear expectations via nonlinear Markov chains. Compared to the author's previous results, i.e., the theory of g-expectations introduced via BSDE on a probability space, the present framework is not based on a given probability measure. Many fully nonlinear and singular situations are covered. The induced topology is a natural generalization of Lp-norms and L∞-norm in linear situations.The author also obtains the existence and uniqueness result of BSDE under this new framework and develops a nonlinear type of von Neumann-Morgenstern representation theorem to utilities and present dynamic risk measures.

  17. Review of pre-FFT equalization techniques and their application to 4G

    Science.gov (United States)

    Armour, Simon; Doufexi, Angela; Nix, Andrew; Beach, Mark; McGeehan, J.

    2001-11-01

    In this paper a review of the Pre-FFT Equalization technique is presented with a particular focus on 4G applications. The essential concepts and motivations for the use of this technique are first presented. Subsequently, previous research of the topic both by the authors and others is reviewed. In particular, methods for implementing the Pre-FFT Equalizer itself and for adapting it are reviewed in detail. The issue of noise amplification and the use of Channel State Information in the COFDM system to mitigate this phenomenon are also discussed. Application of a Pre-FFT Equalizer to a possible, COFDM based, 4G standard is then discussed and software simulations used to demonstrate the benefits that can be achieved by a Pre-FFT Equalizer in a 4G system.

  18. Peningkatan Unjuk Kerja Sistem Transmisi Komunikasi Digital pada Penerima dengan Menggunakan Teknik Diversity Equal Gain Combining

    Directory of Open Access Journals (Sweden)

    Baharuddin

    2016-07-01

    Full Text Available In digital communication systems, the presence of fading and noise in the channel will disrupt or degrade the performance of digital communication system. This disruption may cause error on signal detection and may cause bits change or symbols at the receiver. By applying Equal Gain combining diversity techniques at the receiver, it can improve the digital communication system performance. Through simulation, this study analyzed the effect of applying equal gain combining diversity techniques on the system that affected by noise AWGN and Rayleigh fading. Performance evaluation on the use of equal gain combining diversity technique can be determined through BER analysis. The simulation result of this study indicates that there is improvement on system performance at the receiver twice better than without utilizing equal gain combining diversity technique.

  19. Nonlinear Light-Matter Interactions in Metamaterials

    Science.gov (United States)

    O'Brien, Kevin Patrick

    Metamaterials possess extraordinary linear optical properties never observed in natural materials such as a negative refractive index, enabling exciting applications such as super resolution imaging and cloaking. In this thesis, we explore the equally extraordinary nonlinear properties of metamaterials. Nonlinear optics, the study of light-matter interactions where the optical fields are strong enough to change material properties, has fundamental importance to physics, chemistry, and material science as a non-destructive probe of material properties and has important technological applications such as entangled photon generation and frequency conversion. Due to their ability to manipulate both linear and nonlinear light matter interactions through sub-wavelength structuring, metamaterials are a promising direction for both fundamental and applied nonlinear optics research. We perform the first experiments on nonlinear propagation in bulk zero and negative index optical metamaterials and demonstrate that a zero index material can phase match four wave mixing processes in ways not possible in finite index materials. In addition, we demonstrate the ability of nonlinear scattering theory to describe the geometry dependence of second and third harmonic generation in plasmonic nanostructures. As an application of nonlinear metamaterials, we propose a phase matching technique called "resonant phase matching" to increase the gain and bandwidth of Josephson junction traveling wave parametric amplifiers. With collaborators, we demonstrate a best in class amplifier for superconducting qubit readout--over 20 dB gain with near quantum limited noise performance with a bandwidth and dynamic range an order of magnitude larger than alternative devices. In conclusion, we have demonstrated several ways in which nonlinear metamaterials surpass their natural counterparts. We look forward to the future of the field where nonlinear and quantum metamaterials will enable further new

  20. LOW COMPLEXITY LMMSE TURBO EQUALIZATION FOR COMBINED ERROR CONTROL CODED AND LINEARLY PRECODED OFDM

    Institute of Scientific and Technical Information of China (English)

    Qu Daiming; Zhu Guangxi

    2006-01-01

    The turbo equalization approach is studied for Orthogonal Frequency Division Multiplexing (OFDM) system with combined error control coding and linear precoding. While previous literatures employed linear precoder of small size for complexity reasons, this paper proposes to use a linear precoder of size larger than or equal to the maximum length of the equivalent discrete-time channel in order to achieve full frequency diversity and reduce complexities of the error control coder/decoder. Also a low complexity Linear Minimum Mean Square Error (LMMSE) turbo equalizer is derived for the receiver. Through simulation and performance analysis, it is shown that the performance of the proposed scheme over frequency selective fading channel reaches the matched filter bound; compared with the same coded OFDM without linear precoding, the proposed scheme shows an Signal-to-Noise Ratio (SNR) improvement of at least 6dB at a bit error rate of 10-6 over a multipath channel with exponential power delay profile. Convergence behavior of the proposed scheme with turbo equalization using various type of linear precoder/transformer, various interleaver size and error control coder of various constraint length is also investigated.

  1. Equal or different? LGBTI rights under discussion

    Directory of Open Access Journals (Sweden)

    Eduardo J. Arrubia

    2016-12-01

    Full Text Available Feminism has emerged in a context of struggle for equality.  As formal rights gained ground, material inequalities resulting from ineffective legal rules became evident. These issues are the starting point for the discussion on equality and differences in the field of LGBTI human rights theory. Accordingly, this essay explores the new legal rights gained by the LGBTI community in the Argentine Republic, along with material tensions arising from social reality. Such reality is addressed by relevant literature as well as by the analysis of interviews conducted in the city of Azul, Province of Buenos Aires. The core idea of this essay focuses on the search for a theory connecting both equality and difference when it comes to sexual minorities. 

  2. Ethics, equality and evidence in health promotion

    DEFF Research Database (Denmark)

    Vallgårda, Signild

    2014-01-01

    Abstract Aim: The Danish National Board of Health has expressed its commitment to social equality in health, evidence-informed health promotion and public health ethics, and has issued guidelines for municipalities on health promotion, in Danish named prevention packages.The aim of this article...... is to analyse whether the Board of Health adheres to ideals of equality, evidence and ethics in these guidelines. Methods: An analysis to detect statements about equity, evidence and ethics in 10 health promotion packages directed at municipalities with the aim of guiding the municipalities towards evidence......-informed disease prevention and health promotion. Results: Despite declared intentions of prioritizing social equality in health, these intentions are largely absent from most of the packages.When health inequalities are mentioned, focus is on the disadvantaged or the marginalized. Several interventions...

  3. The equal accessibility to patient complaint measures

    DEFF Research Database (Denmark)

    Birkeland, Søren

    the actual complaint pattern a review was conducted on a 1-year General Practice care complaint sample (2007). Data were extracted on patient gender, age, and affiliation with labor market (if available). Interpreter use or family name presence on the Family Government Agency’s list of foreign names was used......The equal accessibility to patient complaint measures – a Danish perspective Like the Danish Healthcare Act (Para 2) basically prescribes a right to easy, equal access to healthcare, a Complaint Act (Para 2) entitles patients to file a complaint (about health professional conduct, informed consent...... obtainment etc.) with a Health Disciplinary Board at no cost. While there is no guarantee that healthcare is proportionately delivered across patient groups there is no warrant either that the complaint system actually promotes equal accessibility (by natives, cross-border patients etc.). To further study...

  4. Land Governance, Gender Equality and Development

    DEFF Research Database (Denmark)

    Ravnborg, Helle Munk; Spichiger, Rachel; Broegaard, Rikke Brandt;

    2016-01-01

    pursued in these reforms and examines the role played by donor cooperation. Despite significant progress in developing land legislation that upholds gender equality, implementation often does not follow suit, and women still face discrimination. Based on country case studies, the article identifies six......Most land governance reforms seek to enhance tenure security, encourage investments and thereby promote economic growth. Increasingly, land reforms attempt to secure women's and other vulnerable groups' access to land. This article reviews the extent to which gender equality in land tenure has been...... challenges, which should be addressed to achieve gender equality in land tenure. © 2016 UNU-WIDER. Journal of International Development published by John Wiley & Sons, Ltd. Copyright...

  5. 基于非理想信道状态信息的最小化均方误差非线性收发机设计%Minimum Mean Square Error Non-linear Transceiver Design Based on Imperfect Channel State Information

    Institute of Scientific and Technical Information of China (English)

    耿烜; 何迪

    2012-01-01

    A design method for nonlinear transceiver with Tomlinson-Harashima precoding(THP) struc ture was proposed based on minimum mean square error (MSE) criterion, when the transceiver knows the imperfect channel state information (CSI) for multiple-input multiple-output (MIMO) system. The MSE is derived firstly, and then transformed as the function of only one variable being precoding matrix. By minimizing the lower bound of MSE using optimization and matrix theory, the optimal precoding matrix and the closed-form of the lower bound are obtained, so that the total non-linear transceiver matrices are solved. The simulation results show that the proposed method outperforms the existing linear transceiver and the classic THP transceiver.%在多输入多输出系统中,当收发端已知非理想信道状态信息时,提出了一种基于最小化均方误差准则的非线性收发机设计方法,其结构基于汤姆林森一哈拉希玛预编码(THP).首先研究了收发信号的均方误差表达式,并将其转换为预编码矩阵的函数;然后,通过最优化及矩阵论方法最小化均方误差的下界,求解最优预编码矩阵以及下界的闭式解,进而获得整个非线性收发机矩阵.仿真结果表明,该方法性能优于现有的线性收发机设计和经典的THP收发机设计.

  6. Variational Histogram Equalization for Single Color Image Defogging

    Directory of Open Access Journals (Sweden)

    Li Zhou

    2016-01-01

    Full Text Available Foggy images taken in the bad weather inevitably suffer from contrast loss and color distortion. Existing defogging methods merely resort to digging out an accurate scene transmission in ignorance of their unpleasing distortion and high complexity. Different from previous works, we propose a simple but powerful method based on histogram equalization and the physical degradation model. By revising two constraints in a variational histogram equalization framework, the intensity component of a fog-free image can be estimated in HSI color space, since the airlight is inferred through a color attenuation prior in advance. To cut down the time consumption, a general variation filter is proposed to obtain a numerical solution from the revised framework. After getting the estimated intensity component, it is easy to infer the saturation component from the physical degradation model in saturation channel. Accordingly, the fog-free image can be restored with the estimated intensity and saturation components. In the end, the proposed method is tested on several foggy images and assessed by two no-reference indexes. Experimental results reveal that our method is relatively superior to three groups of relevant and state-of-the-art defogging methods.

  7. All Are Equal, but Some Are More Equal than Others: Managerialism and Gender Equality in Higher Education in Comparative Perspective

    Science.gov (United States)

    Teelken, Christine; Deem, Rosemary

    2013-01-01

    The main purpose of this paper is to investigate what impact new regimes of management and governance, including new managerialism, have had on perceptions of gender equality at universities in three Western European countries. While in accordance with national laws and EU directives, contemporary current management approaches in universities…

  8. Nonlinear evaluations of unconditionally stable explicit algorithms

    Institute of Scientific and Technical Information of China (English)

    Shuenn-Yih Chang

    2009-01-01

    Two explicit integration algorithms with unconditional stability for linear elastic systems have been successfully developed for pseudodynamic testing. Their numerical properties in the solution of a linear elastic system have been well explored and their applications to the pseudodynamic testing of a nonlinear system have been shown to be feasible. However, their numerical properties in the solution of a nonlinear system are not apparent. Therefore, the performance of both algorithms for use in the solution of a nonlinear system has been analytically evaluated after introducing an instantaneous degree of nonlinearity. The two algorithms have roughly the same accuracy for a small value of the product of the natural frequency and step size. Meanwhile, the first algorithm is unconditionally stable when the instantaneous degree of nonlinearity is less than or equal to 1, and it becomes conditionally stable when it is greater than 1. The second algorithm is conditionally stable as the instantaneous degree of nonlinearity is less than 1/9, and becomes unstable when it is greater than I. It can have unconditional stability for the range between I/9 and 1. Based on these evaluations, it was concluded that the first algorithm is superior to the second one. Also, both algorithms were found to require commensurate computational efforts, which are much less than needed for the Newmark explicit method in general structural dynamic problems.

  9. EQUALITY AND DISCIMINATION – ROMA SOCIAL EXCLUSION

    OpenAIRE

    Mircea George GHERASIM

    2015-01-01

    Substantiating the idea of equality of all citizens, Ion Ghica shows the special value of this concept and its importance for the Romanian society, saying that "equality is a noble and good aspiration of the generous man, of the man endowed with a sense of justice and fairness; it is the urge and hope of the intelligent person, of the scholar and of the worker, of the one who wants to climb the social ladder, who aspires to the development of progress and civilization". The purpose of this st...

  10. Energy Transferring Dynamic Equalization for Battery Packs

    Institute of Scientific and Technical Information of China (English)

    2005-01-01

    The equivalent circuit model of battery and the analytic model of series battery uniformities are setup. The analysis shows that it is the key to maintain small voltage difference between cells in order to improve uniformities. Therefore a new technique combining low voltage difference, big current charging and bi-directional charge equalizer system is put forward and designed. The test shows that the energy transferring dynamic equalization system betters the series battery uniformities and protection during charging and discharging, improves the battery performance and extends the use life of series battery.

  11. Multigradient for Neural Networks for Equalizers

    Directory of Open Access Journals (Sweden)

    Chulhee Lee

    2003-06-01

    Full Text Available Recently, a new training algorithm, multigradient, has been published for neural networks and it is reported that the multigradient outperforms the backpropagation when neural networks are used as a classifier. When neural networks are used as an equalizer in communications, they can be viewed as a classifier. In this paper, we apply the multigradient algorithm to train the neural networks that are used as equalizers. Experiments show that the neural networks trained using the multigradient noticeably outperforms the neural networks trained by the backpropagation.

  12. How Cannibalistic is the Internet Channel?

    NARCIS (Netherlands)

    B. Deleersnyder (Barbara); I. Geyskens; K. Gielens (Katrijn); M.G. Dekimpe (Marnik)

    2002-01-01

    textabstractDuring the past decade, irrational exuberance has turned into a possibly equally irrational pessimism about what the Internet can accomplish. The fear of getting ruined through cannibalization losses has recently deterred many firms from deploying the Internet as a distribution channel.

  13. Bidirectional Fano Algorithm for Lattice Coded MIMO Channels

    KAUST Repository

    Al-Quwaiee, Hessa

    2013-05-08

    Recently, lattices - a mathematical representation of infinite discrete points in the Euclidean space, have become an effective way to describe and analyze communication systems especially system those that can be modeled as linear Gaussian vector channel model. Channel codes based on lattices are preferred due to three facts: lattice codes have simple structure, the code can achieve the limits of the channel, and they can be decoded efficiently using lattice decoders which can be considered as the Closest Lattice Point Search (CLPS). Since the time lattice codes were introduced to Multiple Input Multiple Output (MIMO) channel, Sphere Decoder (SD) has been an efficient way to implement lattice decoders. Sphere decoder offers the optimal performance at the expense of high decoding complexity especially for low signal-to-noise ratios (SNR) and for high- dimensional systems. On the other hand, linear and non-linear receivers, Minimum Mean Square Error (MMSE), and MMSE Decision-Feedback Equalization (DFE), provide the lowest decoding complexity but unfortunately with poor performance. Several studies works have been conducted in the last years to address the problem of designing low complexity decoders for the MIMO channel that can achieve near optimal performance. It was found that sequential decoders using backward tree 
search can bridge the gap between SD and MMSE. The sequential decoder provides an interesting performance-complexity trade-off using a bias term. Yet, the sequential decoder still suffers from high complexity for mid-to-high SNR values. In this work, we propose a new algorithm for Bidirectional Fano sequential Decoder (BFD) in order to reduce the mid-to-high SNR complexity. Our algorithm consists of first constructing a unidirectional Sequential Decoder based on forward search using the QL decomposition. After that, BFD incorporates two searches, forward and backward, to work simultaneously till they merge and find the closest lattice point to the

  14. A Novel RSSE-PSP Equalizer with an Adaptive Pre-Filter

    Institute of Scientific and Technical Information of China (English)

    ZHANG Yong-qiang; RU Guo-bao; YANG Hao; XUE Ni

    2005-01-01

    A reduced-state sequence estimation (RSSE) receiver based on per-survivor processing (PSP) in conjunction with an adaptive pre-filter is proposed in this paper. In RSSE-PSP, each survivor path holds an estimated value of the channel impulse response (CIR), which is updated by adaptive algorithm during the data transmission. Based on the different estimated channel values of each survivor path, corresponding pre-filters are calculated via the Levinson-Durbin algorithm, which can track the time-varying channel adaptively. Computer simulations indicate that the RSSE-PSP equalizer with the new adaptive pre-filter works much better than those with the prevenient pre-filters in ISI channel.

  15. Pilot-Based Synchronization and Equalization in Filter Bank Multicarrier Communications

    Directory of Open Access Journals (Sweden)

    Stitz TobiasHidalgo

    2010-01-01

    Full Text Available This paper presents a detailed analysis of synchronization methods based on scattered pilots for filter bank based multicarrier (FBMC communications, taking into account the interplay of the synchronization, channel estimation, and equalization methods. We show that by applying pilots designed specifically for filter banks, the carrier frequency offset (CFO, fractional time delay (FTD, and channel response can be accurately estimated. Further, a novel joint FTD and channel estimation scheme, based on iterative interference cancelation, permits extending the FTD estimation range well beyond the limit imposed by the pilot separation. The channel parameter estimation and compensation are successfully performed totally in the frequency domain, in a subchannel-wise fashion, which is appealing in spectrally agile and cognitive radio scenarios. The performance evaluation is done in a hypothetical WiMAX scenario in which an FBMC system would substitute OFDM maintaining as much physical layer compatibility as possible.

  16. Pilot-Based Synchronization and Equalization in Filter Bank Multicarrier Communications

    Science.gov (United States)

    Stitz, TobiasHidalgo; Ihalainen, Tero; Viholainen, Ari; Renfors, Markku

    2010-12-01

    This paper presents a detailed analysis of synchronization methods based on scattered pilots for filter bank based multicarrier (FBMC) communications, taking into account the interplay of the synchronization, channel estimation, and equalization methods. We show that by applying pilots designed specifically for filter banks, the carrier frequency offset (CFO), fractional time delay (FTD), and channel response can be accurately estimated. Further, a novel joint FTD and channel estimation scheme, based on iterative interference cancelation, permits extending the FTD estimation range well beyond the limit imposed by the pilot separation. The channel parameter estimation and compensation are successfully performed totally in the frequency domain, in a subchannel-wise fashion, which is appealing in spectrally agile and cognitive radio scenarios. The performance evaluation is done in a hypothetical WiMAX scenario in which an FBMC system would substitute OFDM maintaining as much physical layer compatibility as possible.

  17. A Compressed Sensing Wire-Tap Channel

    CERN Document Server

    Reeves, Galen; Milosavljevic, Nebojsa; Gastpar, Michael

    2011-01-01

    A multiplicative Gaussian wire-tap channel inspired by compressed sensing is studied. Lower and upper bounds on the secrecy capacity are derived, and shown to be relatively tight in the large system limit for a large class of compressed sensing matrices. Surprisingly, it is shown that the secrecy capacity of this channel is nearly equal to the capacity without any secrecy constraint provided that the channel of the eavesdropper is strictly worse than the channel of the intended receiver. In other words, the eavesdropper can see almost everything and yet learn almost nothing. This behavior, which contrasts sharply with that of many commonly studied wiretap channels, is made possible by the fact that a small number of linear projections can make a crucial difference in the ability to estimate sparse vectors.

  18. Ergodic Capacity for the SIMO Nakagami- Channel

    Directory of Open Access Journals (Sweden)

    Vagenas EfstathiosD

    2009-01-01

    Full Text Available This paper presents closed-form expressions for the ergodic channel capacity of SIMO (single-input and multiple output wireless systems operating in a Nakagami- fading channel. As the performance of SIMO channel is closely related to the diversity combining techniques, we present closed-form expressions for the capacity of maximal ratio combining (MRC, equal gain combining (EGC, selection combining (SC, and switch and stay (SSC diversity systems operating in Nakagami- fading channels. Also, the ergodic capacity of a SIMO system in a Nakagami- fading channel without any diversity technique is derived. The latter scenario is further investigated for a large amount of receive antennas. Finally, numerical results are presented for illustration.

  19. The MISO Wiretap Channel with Noisy Main Channel Estimation in the High Power Regime

    KAUST Repository

    Rezki, Zouheir

    2017-02-07

    We improve upon our previous upper bound on the secrecy capacity of the wiretap channel with multiple transmit antennas and single-antenna receivers, with noisy main channel state information (CSI) at the transmitter (CSI-T). Specifically, we show that if the main CSI error does not scale with the power budget at the transmitter P̅, then the secrecy capacity is )bounded above essentially by log log (P̅ yielding a secure degree of freedom (sdof) equal to zero. However, if the main CSI error scales as O(P̅-β), for β ∈ [0,1], then the sdof is equal to β.

  20. Computational modeling of flow and combustion in a couette channel simulating microgravity

    Science.gov (United States)

    Hamdan, Ghaleb

    Theoretically a Couette flow in a narrow channel can be utilized to simulate microgravity conditions experienced by a surface flame due to the linear velocity profile. Hence, the Couette channel is a potential apparatus for the study of flame spread in an environment that recreated microgravity flow conditions. Simulated microgravity conditions were achieved by limiting the vertical extent over and under the flame to suppress buoyancy. This numerical study was done for a 2-D channel using Fire Dynamics Simulator (FDS). This thesis is divided into two sections; the first is the study of Couette flow with a non-reacting cold flow in a finite length channel, a subject with surprisingly little past research, despite the ubiquity of "infinite" Couette channels in text books. The channel was placed in a room to allow for a better representation of a realistic channel and allow the flow and pressure field to develop without forcing them at the inlet and outlet. The plate's velocities, channel's gap and the channel's length were varied and the results of the u-velocity profile, w-velocity profile and pressure were investigated. The entrance length relationship with Reynolds number for a finite Couette Channel was determined for the first time - as far as the author knows - in order to ensure the flame occurs in a fully developed flow. In contrast to an infinite channel, the u-velocity was found to be nonlinear due to an adverse pressure differential created along the channel attributed to the pull force along the entrance of the channel created by the top plate a well as the pressure differential created by the flow exiting the channel. The linearity constant was derived for the one moving plate case. The domain consisted of a rectangular region with the top plate moving and the bottom plate fixed except for a few cases in which the bottom plate also moved and were compared with only one moving plate. The second section describes the combustion of a thin cellulose sample