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This paper mainly studies the application of the fractal self-affine theory for weak target detection in sea clutter. In this paper, the adaptive 3D-IFS (3D-IFS: three-dimensional iterated function system) algorithm is presented and a novel weak target detection model is proposed based on the algorithm. To accurately extract the weak target from the complicated background of sea clutter, we use the radar echo model of the LFM radar and the target detection model to calculate the prediction error of radar echoes. Furthermore, based on extensive analysis and simulation, we identify the scale factor, polarization model and target state as three key factors that affect the detection performance of our proposed model. Using the real data from IPIX radar and C-band radar for simulations, we can see that the model has a significant performance improvement for weak target detection compared to the traditional 3D-IFS algorithm. The detection probability of the model reaches 70% at the SCR near −10 dB, and signal processing time of the model is approximately 0.3 s at the SCR near −6 dB, thus it meets the requirement for low-observable ( SCR > −8 dB) and radial velocity about 600 m/s high speed weak target detection in sea clutter. [ABSTRACT FROM AUTHOR]

Based on the theory of scalar diffraction, this paper makes research on the process of hologram reconstruction of true color calculation by lensless Fourier transform, and gives its algorithm on the basis of the angular spectrum theory as well as the instances of color image reconstruction under the red, green and blue colors wavelength. In order to eliminate the influence of color difference on the reconstructive image, this paper analyzes the causes of the color difference, and puts forward the method of interpolation reconstruction to the object information in the process of hologram reconstruction, so as to eliminate the color difference. With the advantages of computer generated holographic, the high-quality color hologram by lensless Fourier transform based on the angular spectrum theory has been realized, and the results of corresponding numerical simulation are given. The results show that the method in the paper can effectively eliminate the color difference caused by different wavelength, and the experimental results validate its feasibility. [ABSTRACT FROM AUTHOR]

This paper presents a novel method based on pulse compression theory to improve the detection accuracy of light screen array. According to the work principle of light screen array, discusses several important factors led to the deterioration of estimation accuracy of time interval between two trigger signals. Then, the estimation accuracy of time interval can be improved using two techniques (spread spectrum and matched filtering) in term of Cramer-Rao lower bound criterion. Combining with the two techniques, proposes a pulse compression-based algorithm to estimate the time interval between trigger signals accurately. Through simulation and analysis, the results show that the estimation accuracy of time interval between trigger signals is up to 5 μs under the noise-signal ratio(SNR) of 0 dB and two screens thickness ratio of 5/6, and the proposed method is scientific and feasible. [ABSTRACT FROM AUTHOR]

A novel bands selection method based on ABS (Adaptive Band Selection) and JSKF (Joint Skewness-Kurtosis Figure) is proposed in this paper. The hyperspectral data is separated into different sub-spaces by employing ABS and JSKF respectively. Subsequently a novel optimal bands selection method NIA (Normalization Index Algorithm) is proposed to select the optimal bands according to the value of ABS and JSKF. Both the high correlations of the adjacent bands and the richness of complementary information are considered in detail in this proposed method. Some numerical simulations are made to test the validity and capability of the proposed dimension reduction algorithm. [ABSTRACT FROM AUTHOR]

Abstract: Motion is a common phenomenon in the real world so the consistence of virtual and real motion is one of hot focuses in augmented reality system. This paper mainly analyzes virtual and real motion blur consistence in augmented reality system, and mainly do improvement in two aspects, one is how to get the motion blur parameters, the other is how to render motion blur. From the available literature it can be seen that, most achieved methods to get motion blur parameters are based on machine vision. But this paper first acquires the motion trajectory by magnetic tracking, and then gets motion blur parameters. Considering the available literature on motion blur rendering methods, they mainly contain convolution and accumulator caching and so on. Due to rotation translation compound motion blur, this paper does rendering in advance based on improved mathematical model, and then render virtual object through looking up table in augmented reality system. Experimental results show that the new virtual and real motion blur consistence render algorithm has low time complexity and achieve the desired effect in simulation environment and real scenes. [Copyright &y& Elsevier]

Abstract: Since the access network plays the dominant role of energy consumption in the whole network, it is necessary to study the energy-efficient design on the access technique. This paper aims to develop the green Hybrid Wireless-Optical Broadband Access Network (HWOBAN) by sleeping low-loaded Optical Network Units (ONUs) as much as possible to save the energy. Correspondingly, a heuristic approach, Energy-saving Algorithm based on Sleeping Low-loaded OUNs (EASLO), is proposed in this paper. In EASLO, most of traffic has higher probability to be carried by the currently active ONUs through dynamic energy-awareness mechanism, so that the higher resource utilization of ONUs can be achieved. Meanwhile, in order to improve the energy efficiency, we can sleep low-loaded ONUs, each of which can satisfy the conditions of traffic rerouting, and then transfer the residual traffic on these sleeping ONUs to the other active ones. The simulation results show that, our proposed EASLO method has better performance of energy savings than traditional method. [Copyright &y& Elsevier]

Dynamic lightpath protection in survivable WDM networks requires finding a pair of diverse routes (i.e., a primary route and a backup route that are link-disjoint) that form a cycle upon the arrival of a new connection request. This paper presents a hybrid adaptive survivability algorithm that combines the positive effects of restoration and protection. The overall goal of the proposed approach is to improve the restoration efficiency by providing tradeoffs between proactive protection and dynamic restoration. Experimental results simulated by ns-2 network simulator and analytical results for wavelength conversion case using MATLAB 7.3 are compared. In both the case hybrid scheme achieves significantly lower blocking probability, higher throughput, higher utilization and lower restoration than the conventional dynamic survivable techniques. The results obtained by approximate analytical model are almost identical with that of ns-2 simulated results. [ABSTRACT FROM AUTHOR]

Fractional Fourier Transform (FRFT) is regarded as an effective method for detection of Linear Frequency Modulation (LFM) signals in recent years. However, the performance of FRFT detection will deteriorate sharply in the weak noise scene. An alternative solution is the use of bistable system, which can generate stochastic resonance (SR), and is relatively easy to achieve. This paper proposes a novel LFM weak signal detection algorithm based on bistable system and FRFT, named BSFRFT. We use the SR effect of bistable system to amplify LFM signal, and then apply FRFT to the previous output. We also present an evaluation criteria to measure the ability of detection methods and to compare performance of FRFT and BSFRFT. Numerical simulations show that the algorithm is effective for two cases – the LFM signal covered by white noise or colored noise (including pink noise). [ABSTRACT FROM AUTHOR]

In this paper, we present numerical and experimental study on beam steering with liquid-crystal optical phased array (LC-OPA) by means of stochastic parallel gradient descent (SPGD) algorithm. The numerical simulation, which is mainly based on the evolution of power-in-bucket (PIB), indicates that the beam steering strategy with LC-OPA is relatively robust, and the algorithm performs well most of the time. The results also reveal that the performance of SPGD algorithm is influenced by the order of Zernike polynomials, the radius of bucket and the steering angle. The order of Zernike polynomials and the radius of bucket are optimized to improve the accuracy and convergence of the algorithm. In a proof-of-concept experiment, the feasibility of the beam steering strategy with LC-OPA is demonstrated. [ABSTRACT FROM AUTHOR]

Sensorless adaptive optics (AO) imaging systems have been widely studied in recent years. To reach optimum results, such systems require an efficient performance metric. In this paper, a new performance metric applied to sensorless AO system based on stochastic parallel gradient descent (SPGD) algorithm is presented. This new metric has better performance of stability and correction ability compared with other three performance metrics (i.e. Strehl Ratio, Power-In-Bucket and Image Sharpness), and similar with mean radius (MR) metric but easier to measure by a photo-detector using a mask which can be simply-manufactured. Numerical simulations of AO corrections of various random aberrations are performed. The results show the superiority of the new metric. [ABSTRACT FROM AUTHOR]

This paper investigates statistical errors in determining peak positions of interference fringes with the least-squares algorithms when the phase-shifting step sizes are 2 π /3, π /2, and 2 π /5. Two types of random noises are considered, which are called intensity noise and position noise. With these large step sizes, the statistical errors obtained from simulated measurements are compared with the theoretical results published in Ref. [11] . The effects of the wavelength and the amplitude on the statistical errors are investigated. A discrepancy between the simulation results and the theoretical results has been observed, that is, when the step size was π /2, the statistical errors caused by position noise have shown strong peak-position dependence, which cannot be explained by Eq. (16) given in Ref. [11] . A new equation is given to account for the simulation results. [ABSTRACT FROM AUTHOR]

Image encryption is a useful solution to achieve confidentiality while transmitting digital images over unsecure public networks. Among recently proposed encryption schemes, a DNA-based approach Wei et al. (J. Syst. Softw. 85 (2012) 299) with good encryption effect has been reported. An effort has been made in this paper to improve its performance, by infusing more pseudo randomness into this algorithm. For this, three modifications have been suggested: (1) For each pixel of the color image, adoption of multiple DNA encoding rules as against a single rule in Wei et al. (J. Syst. Softw. 85 (2012) 299); (2) multiple DNA operations instead of a single DNA operation as in [17] for diffusion of pixels and (3) combination of the image to be encrypted with another synthetic image as against combination with itself as in [17]. Here, the choice of DNA encoding rule, DNA operation and DNA synthetic image creation are all done based on the outcome of various chaotic maps and systems. The simulation results and security analysis show that our algorithm not only has a better encryption effect but also has a better ability of resisting statistical and differential attacks on comparison with the original proposal. [ABSTRACT FROM AUTHOR]

A novel attitude algorithm for fiber strapdown inertial navigation system (SINS) is studied in this paper. The noncommutativity rotation is one of the major errors in attitude updating for SINS. As a general rule, accuracy can be improved by increasing attitude updating frequency. However, it is limited by gyro and computer technology. To solve this problem, a modified algorithm for fiber SINS is proposed. This algorithm uses angular rate as algorithm input and estimates the noncommutativity error with the cross product of angular rates and the cross product of previous accumulated gyro outputs with current gyro outputs. Simulations and experiments are performed under coning motion and three-axis turntable environment, and the results show that the accuracy of the proposed algorithm can be improved effectively under coning motion, as well as in three-axis turntable environment, though not as greatly. [ABSTRACT FROM AUTHOR]

Camera calibration is a basic and crucial problem in computer vision and photogrammetry. The traditional calibration approach based on 2D planar target fails to give reliable and accurate results due to the inaccurate localization of feature points in some calibration images. An accurate and robust estimation method for camera parameters based on RANdom SAmple Consensus (RANSAC) algorithm is proposed to exclude the unreliable images in this study. First, the distance between circular point and image of the absolute conic is defined, and the recommended threshold value is given by computer simulation. Second, RANSAC has been utilized to pick out a subset of calibrating images automatically, and linear algebraic approximation is performed to estimate the intrinsic parameters and external parameters. Finally, all the camera parameters including lens distortion parameters are refined by the non-linear searching algorithm. Numerical simulation and practical experiment in this paper demonstrate the accuracy and robustness of the proposed method. The experimental results show that the proposed method is more robust and efficient in improving the calibration accuracy than the traditional methods. [ABSTRACT FROM AUTHOR]

The exact solutions often model natural phenomena and facilitate the testing of numerical algorithms as well as the stability analysis of differential equations. There is an interest for long times in obtaining exact analytical solutions of nonlinear evolution equations. In this paper, we investigate the coupled Schrodinger–Boussinesq equation and new soliton-like solutions are obtained for this equation via the direct algebraic method under certain constraints on the coefficient functions. [ABSTRACT FROM AUTHOR]

For center deviation of space circular mark in the perspective projection transformation process, a novel method is proposed in this paper to locate the real projection center precisely based on the theory of analytic geometry and spatial perspective. First, we analyze the spatial circle error of perspective projection transforms generated and gives relevant basic principles. Then the detailed implementation of the algorithm and the specific steps are presented. Finally through the experiments verify the effectiveness of the method. Simulation and experimental results indicate that this method can achieve the actual projection point precise positioning of the space circular target. The algorithm does not require additional complex constraints and has good robustness; therefore it has a wide range of practical engineering application value. [ABSTRACT FROM AUTHOR]

In the clutter environments, persistently tracking multiple objects is still a very challenging problem. In this paper, an A * algorithm with dynamic weights is developed to solve this problem. Firstly, the problem of multiple object tracking is considered as an integer programming of flow network model. Based on this model, afterward, we relax the problem of integer programming problem to a standard linear programming and achieve the global optimal solution with the proposed algorithm, which has been proven in this work. Compared with other advanced methods employed in the modern complex environments, the proposed method is on the merit of lower calculation complexity and better tracking accuracy and robustness. Finally, the simulation result is demonstrated, which reveals that the proposed algorithm saves the time costs vastly. [ABSTRACT FROM AUTHOR]

Fast Fourier transform (FFT) is a key algorithm for the real-time tracking and processing of the space-borne ocean radar altimeter. In order to put the complex data into three operations in sequence as multiplying the window, performing FFT, and computing module-square, and also meeting the requirements of high-speed digital signal processing, a novel scheme for implementing FFT with digital signal processing (DSP) C6701 is proposed in this paper. Firstly, Radix-4 algorithm of decimation in time (DIT) is adopted. Then, the improved bit-reverse algorithm is utilized for decreasing the calculation quantum. Pipeline and paralleled pattern are also considered conjointly. Based on these improvements, real-time and precision are all ensured, and the balance of calculation, communication and storage is also well weighted. Finally, a novel approach of flash programming by gel file and second boot loader is adopted, and by using this method, the format conversion of COFF file to hex file is not needed. Compared with MATLAB 6.5, the simulation and system application results all demonstrate the feasibility and effectiveness of this proposed scheme. Furthermore, the design can not only helps following real-time tracking on echo signal of Chinese national HY-2 satellite altimeter, but also provides beneficial engineering experience for FFT implementation in the other embedded systems of DSP. [ABSTRACT FROM AUTHOR]

Fuzzy logic control has been used frequently in tuning network control system (NCS) due to its on-line dynamic static non-linear match and several remarkable fractional-order controllers have achieved satisfactory control performance when applied to NCS in present years, therefore, in this paper, a novel fractional fuzzy logic controller which combined the fractional algorithm and fuzzy logic control together has been proposed to deal with fixed and random network induced delays in closed-loop feedback systems. The comparisons of set-point tracking performances of fractional fuzzy logic PID controller (FFuzzyPID), conventional fuzzy logic PID controller(FuzzyPID), fractional optimal PID controller (FOPID), and optimal PID controller(OPID) on a representative plant with fixed and random network delays have been shown with simulations. The simulation results indicate that fractional fuzzy logic controller has higher capability to handle network delays compared with other controllers in most cases. [ABSTRACT FROM AUTHOR]

L 1 regularization and L p regularization are proposed for processing recovered images based on compressed sensing (CS). L 1 regularization can be solved as a convex optimization problem but is less sparse than L p (0 < p < 1). L p regularization is sparser than L 1 regularization but is more difficult to solve. This paper proposes joint L 1 / L p (0 < p < 1) regularization, which combines L p regularization and L 1 regularization. This joint regularization is applied to recover video of remote sensing based on CS. Joint regularization is sparser than L 1 regularization but is as easy to solve as L 1 regularization. A linearized Bregman reweighted iteration algorithm is proposed to solve the joint L 1 / L p regularization problem. The performance and capabilities of the linearized Bregman algorithm and linearized Bregman reweighted algorithm for solving the joint L 1 / L p regularization model are analyzed and compared through numerical simulations. [ABSTRACT FROM AUTHOR]

Abstract: Next generation wireless networks consist of heterogeneous access technologies. In order to provide global ubiquitous communication, it is required to provide a framework in which user can move across multiple access interfaces while maintaining its ongoing communication at perceived quality of service. Given the scenario of multiple access networks, it is further required to select the optimum network out of multiple candidate networks to meet the requirements of the ongoing session. The selection of optimum network in such heterogeneous environment is generally based on network conditions and user preference. In this paper, we propose an algorithm for network selection based on averaged received signal strength, outage probability and distance. The proposed algorithm comprises of two stages. Assuming that network conditions are dominant in network selection, in first stage, overlapping region is identified through distance estimation. Network selection algorithm based on averaged received signal strength plus outage is invoked in second stage to select the optimum network. Numerical results are obtained through a simulation model of two disparate networks – GSM and UMTS. It has been shown that the proposed algorithm offers 68% improved performance in terms of network selection rate. [Copyright &y& Elsevier]

Abstract: Histogram equalization (HE), is a simple and less complex technique for image contrast enhancement, but it fails to preserve their brightness and natural appearance. It usually introduces visual artifacts due to saturation and un-even expansion of intensities. This paper proposes a novel modification of HE method, which decomposes the histogram of the input image into multiple segments utilizing median values as thresholds. Prior to equalization process, segments having high probability regions are identified and allocated with new dynamic range, while other segments remain unaltered. In order to reduce the algorithmic complexity, the HE is applied over selected segments instead of complete histogram. Finally combination of equalized and un-equalized segments are normalized. Simulation results show that for wide-range of test images, the proposed method enhances contrast while preserving the brightness and natural appearance of the images. [Copyright &y& Elsevier]

Abstract: Recently, Li et al. proposed an encryption scheme in gigabit Ethernet passive optical network (GEPON) based on timestamp. We have shown that Li's encryption scheme is not advisable, since it cannot decrypt. In this paper, we proposed a novel encryption scheme based on timestamp in GEPON using AES-128, aiming at solving the security problem of a transmission in downstream of GEPON. In this scheme, the keys formed by combining AES-128 algorithm with timestamp in the process of key expansion are used for encrypting the downstream data. Furthermore, accompanying the dynamic update and synchronization of keys, the extraction and synchronization of timestamp are released. Then, the timestamp used in ONUs’ ranging to generate time-related keys and realize the secure update and synchronization of keys. The simulation results indicate that this scheme is more suitable for GEPON to solve the potential safety threats than other traditional algorithms. [Copyright &y& Elsevier]

Abstract: In Interferometric Fiber Optic Gyroscope (IFOG), the diminution of random noise and drift error is a critical task. These errors degrade the performance of IFOG. In this paper, a modified adaptive Kalman gain correction (AKFG) algorithm is proposed to denoise IFOG signal. The covariance matrix of innovation sequence is estimated using weighted average window method in which the weights are randomly generated in the range [0, 1]. Innovation based random weighted estimation (IRWE)-AKFG is applied to denoise the IFOG drift signal. The Kalman gain is adaptively updated using the covariance matrix of innovation sequence. The proposed algorithm is applied for denoising IFOG signal under static and dynamic environment. Allan variance method is used to analyze and quantify the stochastic errors in IFOG sensor. The performance of the proposed algorithm is compared with Conventional Kalman filter (CKF) and the simulation results reveal that the proposed algorithm is an efficient algorithm for denoising the IFOG signal. [Copyright &y& Elsevier]

Abstract: This paper proposes an adaptive buffer replacement algorithm for NAND flash memory-based databases, which is called HDC. HDC introduces an efficient replacing index for selecting pages to be evicted. This replacing index considers two factors: the hot degree of each page and the cost of writing the victim page back to NAND flash memory. It can adaptively change the weight of each factor according to the cost ratio of NAND flash memory. HDC also introduces an efficient partial update scheme, which only writes the dirty data within the dirty victim page back to NAND flash memory for further reducing the number of write operations and writes the dirty data to the free block with the lowest erase count for improving the wear-leveling degree of NAND flash memory. We conduct trace-driven simulations on two kinds of NAND flash memories the cost ratios of which are 118:1 and 2:1. The experimental results show that HDC outperforms the state-of-the-art algorithms on both these kinds of NAND flash memories. [Copyright &y& Elsevier]

Abstract: This paper presents an efficient algorithm to cancel the parallel interference for multiuser detection (MUD) schemes in code division multiple access (CDMA) based 20.48Gb/s optical multiple input multiple output orthogonal frequency division multiplexing (O-MIMO-OFDM) system over 1200km of standard single mode fiber (SSMF). The performance of the system is compared by simulation results using the efficient algorithm and minimum mean square error (MMSE) schemes. It shows the superior performance of efficient algorithm. [Copyright &y& Elsevier]

Abstract: Methods of nonnegative tensor factorization (NTF), such as NTF1, NTF2, etc., are extension of nonnegative matrix factorization (NMF) for multi-way data analysis. As an existing NTF method, nonnegative Tucker3 decomposition (NTD) is researched for three-way decomposition in this paper. Firstly, an approach utilizing matrix exponentials built on Tikhonov-type regularization to enforce sparseness is proposed to extract image features instead of exclusively using Tucker tensor decomposition. Meanwhile, updating algorithms, derived from updating rules of NMF, are allowed to efficiently implement updating of mode matrices and core tensors alternatively for accuracy. Then, experimental cases of alternating least squares (ALS) and conjugate nonnegative constraints, called nonnegative alternating least squares (NALS), are studied to remedy data overfitting in computing procedures. Lastly, the proposed method exhibits more advantageous results than other algorithms of Tucker3 for feature extraction, thanks to computer simulations performed in the context of data analysis. [Copyright &y& Elsevier]

Abstract: This paper presents an improved processing added to conventional least square (LS) channel estimation to modify its performance for coherent optical orthogonal frequency division multiplexing (CO-OFDM) system. By testing selected limitation factors of the existing algorithms, the influence of our improved algorithm to the performance of CO-OFDM system were studied and compared with other published algorithms. The simulation results of the study demonstrated that the proposed approaches achieved better channel estimation performance and are considered as a more appropriate alternative for CO-OFDM system with the tradeoff between complexity and performance. [Copyright &y& Elsevier]

Abstract: Factor analysis is a powerful tool used for the analysis of dynamic studies. One of the major drawbacks of Factor Analysis of Dynamic Structures (FADS) is that the solution is not mathematically unique when only non-negativity constraints are used to determine factors and factor coefficients. In this paper, we introduce a novel method to correct FADS solutions by constructing and minimizing a new objective function. The method is improved from non-negative matrix factorizations (NMFs) algorithm by adding a sparse constraint that penalizes multiple components in the images of the factor coefficients. The technique is tested on computer simulations, and a patient ultrasound liver study. The results show that the method works well in comparison to the truth in computer simulations and to region of interest (ROI) measurements in the experimental studies. [Copyright &y& Elsevier]

Abstract: The phase-shifting method is all along an important wavefront extraction technique in the interferometer. Moreover, to require almost real-time measurement an algorithm with a small number of grabbed buckets is very helpful to the phase-shifting interferometer. Therefore, those algorithms within five buckets are very practical and are given more attention. In the paper, popular phase shifting algorithms within five buckets are compared and new four and five buckets algorithms are developed to compensate for two dominate error sources which are linear phase shift deviation and detector nonlinearity. Numerical simulations and wavefront extraction experiment verify that the proposed compensation algorithms are insensitive to linear phase shift deviation and detector nonlinearity compared with classical four and five bucket algorithm. [Copyright &y& Elsevier]

Abstract: The diffractive optical element (DOE) is widely used to generate various illumination modes in the projection lithography system. The working principle and design methods of the DOE are discussed in detail in this paper. A mixed multi-region design method is proposed to calculate the phase of DOE based on the poor spatial coherence of excimer laser, using the Gerchberg–Saxton (GS) algorithm. The DOEs generating circular, dipole and quadrupole illumination modes are designed and simulated by three different methods: single region design, repeated multi-region design and mixed multi-region design. The performance of these DOEs are compared and analyzed with these three design methods. The mixed multi-region design method is used to design the DOEs generating three illumination modes, the diffraction efficiencies are greater than 85%, and the non-uniformities of illumination are less than 3%. The analysis results indicate that the DOE designed by the mixed multi-region design can achieve higher diffraction efficiency and illumination uniformity of the far-field intensity distribution without modifying the GS algorithm. [Copyright &y& Elsevier]

Abstract: Flexible grid optical networks have been attracting much attention for their high spectrum efficiency (SE) and flexibility compared to the rigid grid WDM networks. As well known, the networks suffer from the problem of spectrum fragmentation under dynamic traffic. In this paper, we propose a new concept called ‘fragment fusion degree (FFD)’ to assess the level of spectrum fragmentation in flexible grid optical networks, which is calculated based on the availability of the spectrum fragments among neighboring links. Two FFD based dynamic defragmentation algorithms are presented to fuse the spectrum fragments among neighboring links. Simulation results show that the proposed defragmentation algorithms reduce blocking probability significantly and achieve high profitability. [Copyright &y& Elsevier]

Abstract: To improve the accuracy of the channel estimation in PDM-CO-OFDM system when LS algorithm is used, a joint denoising method is proposed in this paper. We have theoretically proposed and simulated designed scattered pilot pattern for PDM-CO-OFDM system, then multi-wavelet is used to denoise the LS channel estimation results which have been interpolation in frequency domain, ISFA is further used to denoise signals after interpolation in time domain. Simulation results show that for 4-QAM, 80GB/s PDM-CO-OFDM system, the proposed joint denoising method has improved 0.96dB in OSNR sensitivity at the BER of 1e−3 (threshold of FEC) compared to the common LS method and reduced system overhead at the same time. [Copyright &y& Elsevier]

Abstract: A novel image encryption algorithm based on logistic map is proposed recently. In this paper, a chosen plaintext attack on this algorithm is presented and some other flaws of the algorithm are pointed out. Theoretical analysis and experimental simulation indicate that the plain image can be recovered exactly from the cipher image without secret key. Therefore, this algorithm is not secure enough for practical applications. An improvement is proposed to enhance the security of the original algorithm. Simulation results and theoretical analysis show that the improved scheme has expected cryptographic properties and is more secure than the original algorithm. [Copyright &y& Elsevier]

Abstract: Recently, more and more attention has been paid to the Orthogonal Frequency Division Multiplexing Passive Optical Network (OFDM-PON). And more importance has been attached to the algorithm achieving dynamic bandwidth allocation (DBA) by researchers. In this paper, an algorithm which aims at achieving multi-granularity DBA based on OFDM-PON is proposed. With the change of bandwidth needs, the number of subcarriers and their modulation formats can be adjusted adaptively. To efficiently utilize the bandwidth, the algorithm introduces a scheme from TDM-PON based on cyclic rotation and polling mechanism. An inner ONU queue is also proposed and multiple subcarrier channels are established in both upstream and downstream. Both simulation and analysis show that the bandwidth utilization of OFDM-PON is efficient. [Copyright &y& Elsevier]

Abstract: It is present in this paper a new blind frame synchronization method for optical packet transmission systems using Reed–Solomon (RS) codes in hard decision situations. The transmitter sends a sequence of RS coded packets without synchronization words to improve the spectral efficiency and the receiver blindly estimates the start position of each packet in the sequence to achieve frame synchronization. The proposed algorithm estimates the synchronization position based on the architecture of RS codes. If the synchronization is not correct, the packets could not form valid RS code words. According to this fact, the proposed algorithm estimates the synchronization position by searching the position that the packets from which contain the lowest error symbols. To estimate the error symbols number for a packet, we calculate the rank of the syndrome matrix which denotes how many errors occurred in a packet. The proposed algorithm is also compared with previous ones and the computer simulations show that our algorithm yields a good result especially on low SNRs. [Copyright &y& Elsevier]

Abstract: In this paper, a novel method is proposed from the perspective of restructuring the gratings to be modulated to restrain the spectrum overlap in composite structure light 3D measurement. Previously, kinds of methods are presented to expand the distance between the adjacent carrier channels, but it still cannot eliminate the spectrum overlap in the orthogonal direction. By the new method, three sinusoidal gratings with equal phase shifting in traditional Phase Measuring Profilometry (PMP) are replaced by two sinusoidal gratings with π/2 phase shifting and a uniform flat image. Moreover, set the carrier frequency modulated by the flat image between the frequencies modulated by the phase-shifting sinusoidal gratings. For the flat image, carrier is only modulated by the “DC” component. Therefore the spectrum overlap between adjacent carrier channels is smaller than the traditional composite pattern (CP) projection. Computer simulation and experiment results prove the new method can effectively restrain the effect of spectrum overlap, and improve the measurement accuracy about 1.74 times. [Copyright &y& Elsevier]

Abstract: This paper puts forward a new scene based nonuniformity correction algorithm for IRFPA. This method adopts phase-correlation method for motion estimation and takes the sum of mean-square errors of the pixel brightness between several adjacent frames as the cost function when the brightness constancy assumption between two adjacent frames is satisfied. Nonuniformity correction parameters could be estimated by minimizing such cost function. In order to reduce calculation quantity, we can divide these images into several subblocks, and solve for the optimum solution of the cost function respectively in each subblock. From the analysis, it is shown that the optimum solution is of global uniqueness when all the elements in subblocks could satisfy the ergodicity condition. Then the estimated value of nonuniformity correction parameters could be deduced by minimizing the cost functions. The nonuniformity correction experiments for both infrared image sequence with simulated nonuniformity and infrared imagery with real nonuniformity show that the proposed algorithm could achieve a great correction effect by only analyzing a small number of frames. [Copyright &y& Elsevier]

Abstract: A coordinate measuring method is presented, which is specially devised to perform the measurement of coordinates with projected fringe techniques of projectors in three dimensions. The system is composed of two parts: one is a target which can move freely in three dimensions, and the other is a stationary two-dimensional array of photodetectors. The mini-projector is tied to the target, and the projected fringe is monitored by the photodetectors. The phase of the photodetectors can be precisely measured with the phase-shifting algorithm, so that, the xyz location of the target can be determined with the geometric model of multilateration using the method of optimization. In this paper, the measuring principle, iterative method, computer simulation and preliminary results are given. The phase-shifting technique has the advantages of high accuracy and noise endurance. The method will provide the basis for follow-up iterative optimization calculation. The experimental results prove that the proposed coordinate measuring method is of high precision. [Copyright &y& Elsevier]

Abstract: For reconstructing based on incomplete projection data, an improved max-entropy reconstruction algorithm is presented in this paper. Both least-square and max-entropy are used in this algorithm, and the penalize-function method is used in iterative processing. The numerical simulation of three different tested fields has been done. Compared with conventional three-dimensional reconstruction algorithms, this novel algorithm has a higher reconstruction precision as well as a better astringency, particularly in the case of easy tested field. For the reconstruction of asymmetric complicated tested field, it also has a good result if suitable projective direction and iterative times can be choosen. Finally, the application of this novel algorithm to diagnose the temperature field of arc plasma is presented. [Copyright &y& Elsevier]