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- 2019
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Ordered Sequence Detection and Barrier Signal Design for Digital Pulse Interval Modulation in Optical Wireless Communications
摘要： This paper proposes an ordered sequence detection (OSD) for digital pulse interval modulation (DPIM) in optical wireless communications. Leveraging the sparsity of DPIM sequences, OSD shows comparable performance to the optimal maximum likelihood sequence detection (MLSD) with much lower complexity. Compared with the widely adopted sample-by-sample optimal threshold detection (OTD), it considerably improves the bit error rate (BER) performance by mitigating error propagation. Moreover, this paper proposes a barrier signal-aided digital pulse interval modulation (BDPIM), where the last of every K symbols is allocated with more power as an inserted barrier signal. BDPIM with OSD (BDPIM-OSD) can limit the error propagation between two adjacent barriers. To reduce the storing delay when using OSD to detect extremely large packets, we propose BDPIM with a combination of OTD and OSD (BDPIM-OTD-OSD), within which long sequences are cut into pieces and separately detected. Approximate upper bounds of the average BER performance of DPIM-OTD, DPIM-OSD, BDPIM-OSD and BDPIM-OTD-OSD are analyzed. Simulations are conducted to corroborate our analysis. Optimal parameter settings are also investigated in uncoded and coded systems by simulations. Simulation results show that the proposed OSD and BDPIM bring significant improvement in uncoded and coded systems over various channels.
关键词： signal design,error propagation,bit error rate,ordered sequence detection,Digital pulse interval modulation
更新于2025-09-23 15:23:52
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Piecewise uniform regularization for the inverse problem of microtomography with a-posteriori error estimate
摘要： An inverse microtomography problem is under consideration in a class of functions with bounded V H variation. An algorithm for solving this problem is proposed based on Tikhonov’s regularization with a special regularizer. The algorithm ensures piecewise uniform convergence of approximate solutions to exact solution of the inverse problem. In addition, the question of a-posteriori error estimate of approximate solutions obtained is considered. A new numerical algorithm for finding this estimate is proposed. Numerical experiments on solving a model inverse problem on the class of functions with bounded V H variation are presented along with the results of a-posteriori error estimate for approximate solutions obtained.
关键词： microtomography,regularization,a-posteriori error estimates
更新于2025-09-23 15:23:52
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Methodology and implementation of a vision-oriented open CNC system for profile grinding
摘要： CNC systems with the vision function have become very valuable for intelligence machine tools because machine vision is a fast-growing intelligent feature for machines. A novel vision-oriented open CNC system was developed in this study and used in profile grinding machines for the precise machining of parts with contour surfaces, such as complex molds and cutting tools. The system is an innovation to the conventional profile grinding method and enabled the profile error to be visually detected and compensated during the machining process. In this study, a novel design methodology for a machine-vision-oriented CNC system was proposed. An Ethernet-based hardware architecture was constructed for the vision-oriented CNC system. The software characteristics of the developed CNC system were analyzed, including a new type of multi-thread software architecture, a seamless handover approach for multi-thread accessing of the memory space, the integration of the human-machine interface with image processing, and virtual-axis-based online error compensation. The running efficiency test of the software development platforms, time-consumption analysis of the measurement and control in the vision-oriented CNC system, and verification of the effectiveness of the developed vision-oriented CNC system were performed. The results indicate that the proposed vision-oriented open CNC system can effectively fuse image processing with motion control, meet the efficiency requirement, and improve the machining precision of profile grinding. The results are also valuable for developing other machine-vision-based intelligent machine tools.
关键词： Contour error,Profile grinding,Image processing,On-machine measurement,Open CNC,Machine vision
更新于2025-09-23 15:23:52
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Quantum Sphere-Packing Bounds with Polynomial Prefactors
摘要： We study lower bounds on the optimal error probability in classical coding over classical-quantum channels at rates below the capacity, commonly termed quantum sphere-packing bounds. Winter and Dalai have derived such bounds for classical-quantum channels; however, the exponents in their bounds only coincide when the channel is classical. In this paper, we show that these two exponents admit a variational representation and are related by the Golden-Thompson inequality, reaf?rming that Dalai’s expression is stronger in general classical-quantum channels. Second, we establish a ?nite blocklength sphere-packing bound for classical-quantum channels, which signi?cantly improves Dalai’s prefactor from the order of subexponential to polynomial. Furthermore, the gap between the obtained error exponent for constant composition codes and the best known classical random coding exponent vanishes in the order of o(log n/n), indicating our sphere-packing bound is almost exact in the high rate regime. Finally, for a special class of symmetric classical-quantum channels, we can completely characterize its optimal error probability without the constant composition code assumption. The main technical contributions are two converse Hoeffding bounds for quantum hypothesis testing and the saddle-point properties of error exponent functions.
关键词： Hoeffding bounds,classical-quantum channels,symmetric channels,quantum sphere-packing bounds,polynomial prefactor,error probability,saddle-point properties,finite blocklength
更新于2025-09-23 15:23:52
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SNR analysis and estimation for efficient phase noise mitigation in millimetre-wave SC-FDE systems
摘要： This study demonstrates a signal-to-noise ratio (SNR) analysis and estimation algorithm for efficient phase noise mitigation that can be practically applied to single-carrier frequency-domain-equalisation (SC-FDE) systems that operate in millimetre-wave bands. First, the effect of phase noise in SC-FDE systems is investigated on each of the packet reception processes, namely, channel estimation, SNR estimation, and data-field reception. According to the analysis, an SNR estimation algorithm is proposed. The performance of minimum-mean-square-error equalisation and conventional phase noise mitigation algorithm can be enhanced using the proposed SNR estimation. The effectiveness of the proposed analysis and SNR estimation algorithm is verified through the link-level simulation. Compared with the conventional SNR estimation and the iterative phase noise mitigation algorithms, the proposed algorithm provides a lower packet-error rate without any iterative decoding process.
关键词： SNR analysis,phase noise mitigation,millimetre-wave,channel estimation,SC-FDE systems,packet-error rate
更新于2025-09-23 15:23:52
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The effect of part-time wear of 2-zone concentric bifocal spectacle lenses on refractive error development & eye growth in young chicks
摘要： The purpose of this study is to characterize in young chicks the myopia control effects of part-time wear of two-zone concentric bifocal lenses. Nine-day-old chicks (n = 115) were first made myopic with monocular ?10 Diopter (D) single vision (SV) lenses worn for 3 days. Over the 6 days following myopia induction, either 1) two-zone bifocal lenses (?10 D center/?5 D periphery, BFDC) were worn for 12 (full-time), 10, 8, or 6 h, with ?10 D SV lenses worn for the remainder of the day, or 2) BFDC or BFNC (?5 D center/?10 D periphery) lenses were worn every other day (EOD). Control birds wore ?10 D SV lenses every day. Refractive error (RE) and axial ocular dimensions were monitored every three days with retinoscopy and high frequency A-scan ultrasonography respectively. Mean interocular RE and axial length differences after 3 days of myopia induction ( ± SEM) were ?9.6 ± 0.19 D and 0.26 ± 0.01 mm across the groups. At the end of the following 6-day treatment period, equivalent values were: ?10.66 ± 0.28 D, 0.42 ± 0.02 mm (SV-control); 1) ?4.61 ± 0.29 D, 0.26 ± 0.02 mm (BFDC, 12 h); ?4.82 ± 0.23 D, 0.28 ± 0.02 mm (BFDC, 10 h); ?5.21 ± 0.27 D, 0.24 ± 0.02 mm (BFDC, 8 h); ?6.34 ± 0.34 D, 0.25 ± 0.03 mm (BFDC, 6 h); 2) ?8.29 ± 0.29 D, 0.32 ± 0.03 mm (BFDC, EOD), and ?8.83 ± 0.36 D, 0.33 ± 0.03 mm (BFNC, EOD). Overall, full-time BFDC and part-time BFDC and BFNC lens groups exhibited similar changes and were less myopic than the SV group. The results suggest that bifocal lenses may have myopia control effects even when worn part-time, interleaved with standard (SV) myopic corrections, especially if worn for at least 6 h per day.
关键词： Myopia,Axial length,Chicks,Bifocal lenses,Refractive error
更新于2025-09-23 15:23:52
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A profile error evaluation method for freeform surface measured by sweep scanning on CMM
摘要： Coordinate measuring machines (CMMs) are widely used in evaluating the profile error of the freeform surfaces. Traditional trigger probes are inefficient at collecting large scale measurement sets. A CMM equipped with a sweep scanning probe dramatically improves the efficiency of inspection. However, the large scale data obtained by scanning is challenging for most existing profile error evaluation methods, which are based on iterative algorithms. This paper proposes an efficient and accurate method to evaluate the profile error of freeform surfaces. To simultaneously simplify the calculation and retain the accuracy of evaluation, a new method to extract key points from scanning data set is presented. First, the key points are defined as those measured points with regional outstanding deviations from the design surface. Second, wavelet decomposition is utilized to decompose the curves formed by the deviations of the measured points in the scanning data set, and the key points are extracted according to the decomposition results. In addition, the key points set, as a representation of the scanning data, are evaluated using Sequential Quadratic Programming (SQP) algorithm. Finally, a simulation example and an actual machined part are used to test the proposed evaluation method. The results prove that the proposed method is both accurate and efficient.
关键词： Key points extraction,Profile error evaluation,Freeform surface,Wavelet decomposition,Sweep scanning
更新于2025-09-23 15:23:52
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In-band phase deviation minimization method for wideband tunable phase shifter
摘要： This article provides a novel approach to analyze and design wideband tunable reflection-type phase shifter (RTPS) with low in-band phase deviation (IBPD) error. The proposed RTPS consists of coupled lines where through and coupled ports are terminated with varactor diodes. The coupled lines can minimize the parasitic elements of varactor diode to achieve high phase shift range (PSR). In addition, the measured frequency-dependent capacitance of varactor diode was used in the analytical analysis to obtain minimum IBPD error and high PSR. For experimental demonstration, phase shifter was fabricated at the center frequency of 2.5 GHz. The measured results show that the fabricated circuit achieved 126.85° PSR with ±6.48° IBPD error for 500 MHz bandwidth (BW). In addition, the measured maximum insertion loss variation and input/output return losses are within ±0.34 dB and higher than 16.85 dB within 500 MHz BW, respectively.
关键词： varactor diode,coupled line,low in-band phase deviation error,wideband tunable reflection-type phase shifter
更新于2025-09-23 15:23:52
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10?Gbps CPRI signals transmission impaired by intercore crosstalk in 5G network fronthauls with multicore fibers
摘要： The impact of intercore crosstalk (ICXT) of weakly-coupled multicore fibers (MCFs) on the transmission performance of a Common Public Radio Interface (CPRI) signal in 5G networks fronthaul is studied by numerical simulation. The results show that forward error correction-supported CPRI signals have more tolerance to ICXT due to the higher targeted bit error rate (of 10?3). For a receiver power penalty of 1 dB, an improvement of the tolerance of CPRI signals to ICXT, due to the increase of the MCF skew by about 1 dB, is observed. However, for the crosstalk levels that lead to 1 dB power penalty, we have shown that, the system is unavailable with a high probability. The crosstalk level required for an acceptable outage probability is about 10 dB lower than the crosstalk level leading to 1 dB power penalty.
关键词： 5G wireless networks,Multicore fiber,Common public radio interface,Outage probability,Intercore crosstalk,Bit error rate
更新于2025-09-23 15:23:52
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Repeatability assessment of biometric measurements with different refractive states and age using a swept-source biometer
摘要： Background: We aim to assess if refractive error or age may influence the repeatability of measurements using a swept-source biometer. Methods: A total of 61 subjects were evaluated with IOLMaster 700 acquiring measurements of axial length (AL), central corneal thickness (CCT), white-to-white distance (WTW), anterior aqueous depth (AQD), lens thickness (LT), and keratometry (K) readings. Repeatability was evaluated classifying the sample according to the refractive state and age by the calculation of the within-subject standard deviation (Sw), coefficient of repeatability, and intraclass correlation coefficient. Results: Very similar Sw was acquired among groups for AL, CCT, and WTW. Differences found for AQD, LT, keratometry and astigmatism among refractive and age groups were not clinically significant. Refractive groups obtained a Sw for AQD between 0.016 and 0.026, while for LT was between 0.023 and 0.029 mm. Besides, Sw showed values from 0.014 to 0.029 mm for keratometry. Age groups obtained a Sw of 0.025 and 0.016 mm for AQD, and 0.029 and 0.018 mm for LT, respectively. Sw was 0.019 vs 0.018 mm for K1, 0.014 vs 0.031 mm for K2. Conclusions: IOLMaster 700 showed good repeatability for biometric and keratometric parameters in eyes classified according to their refractive error or age.
关键词： anterior segment,Repeatability,biometry,swept-source biometer,refractive error,age
更新于2025-09-23 15:23:52