- 标题
- 摘要
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- 实验方案
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Distance-Range-Oriented Constellation Design for VLC-SCMA Downlink with Signal-dependent Noise
摘要： In this paper, the constellation design for a sparse code multiple access (SCMA) based visible light communication (VLC) downlink is studied. The noise at the receiving avalanche photodiode (APD) is dependent on the signal intensity, and the associated design problems are typically intractable. We point out that for such a system both the minimum Euclidean distance (MED) and Rotated-MED based methods are not the optimal optimization objective, and propose a distance-range-oriented (DRO) modulation, where a linear combination of the minimum and maximum Euclidean distance is considered. We observe in the simulation results that the proposed DRO-based scheme outperform the MED and Rotated-MED based ones across a wide range of signal and noise levels.
关键词： distance range,signal-dependent noise,Constellation design,SCMA,visible light communication
更新于2025-09-23 15:22:29
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Measuring the Spatial Noise of a Low-Cost Eye Tracker to Enhance Fixation Detection
摘要： The present study evaluates the quality of gaze data produced by a low-cost eye tracker (The Eye Tribe?, The Eye Tribe, Copenhagen, Denmark) in order to verify its suitability for the performance of scienti?c research. An integrated methodological framework, based on arti?cial eye measurements and human eye tracking data, is proposed towards the implementation of the experimental process. The obtained results are used to remove the modeled noise through manual ?ltering and when detecting samples (?xations). The outcomes aim to serve as a robust reference for the veri?cation of the validity of low-cost solutions, as well as a guide for the selection of appropriate ?xation parameters towards the analysis of experimental data based on the used low-cost device. The results show higher deviation values for the real test persons in comparison to the arti?cial eyes, but these are still acceptable to be used in a scienti?c setting.
关键词： ?xation detection algorithm,low-cost eye tracker,arti?cial eyes,spatial noise
更新于2025-09-23 15:22:29
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[IEEE 2018 OCEANS - MTS/IEEE Kobe Techno-Ocean (OTO) - Kobe (2018.5.28-2018.5.31)] 2018 OCEANS - MTS/IEEE Kobe Techno-Oceans (OTO) - DEMON Spectrum Extraction Method Using Empirical Mode Decomposition
摘要： The noise radiated by a ship is modulated at a rate dictated by some parameters of the propeller and engine (number of blades, rotational speed). Evaluation of that modulation provides information on the ship, such as the shaft rotation frequency, that can be used for ship classification. The method for estimation of the envelope modulation is known as DEMON (Detection of Envelope Modulation on Noise). Traditionally, the ship noise is bandpass filtered in different frequency bands before the envelope analysis. The bandwidth and the number of the bandpass filters is not known. In this paper a new DEMON spectrum extraction method is proposed using empirical mode decomposition (EMD), in which the band number and width are automatically determined. In performance test, a feedforward neural network is used for 5 kinds ship noise classification, and the percentage of correct classification reaches 91.6%.
关键词： DEMON,empirical mode decomposition,Detection of envelope modulation on noise,feedforward neural network,EMD
更新于2025-09-23 15:22:29
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[IEEE 2018 International Conference on Simulation of Semiconductor Processes and Devices (SISPAD) - Austin, TX, USA (2018.9.24-2018.9.26)] 2018 International Conference on Simulation of Semiconductor Processes and Devices (SISPAD) - An Improved Random Path Length Algorithm for p-i-n and Staircase Avalanche Photodiodes
摘要： We present an improved Random Path Length algorithm to accurately and efficiently estimate the design space of heterostructure avalanche photodiodes (APDs) in terms of gain, noise and bandwidth without any need of full Monte Carlo transport simulations. The underlying nonlocal model for impact ionization goes beyond the Dead Space concept and it is suited to handle staircase structures composed by a superlattice of III-V compounds as well as thick and thin p-i-n APDs. The model parameters have been calibrated on GaAs and Al_xGa_{1-x}As p-i-n APDs in a previous work. In this work GaAs p-i-n APDs are compared to staircase structures in terms of noise and bandwidth.
关键词： Impact Ionization,Avalanche Multiplication,Random Path Length,Staircase APDs,Bandwidth,Excess Noise Factor,Simulation
更新于2025-09-23 15:22:29
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Estimation of Zero-Frequency Noise Power Density in Digital Imaging
摘要： Noise power spectrum (NPS) at zero frequency can efficiently represent noise properties of imaging systems. However, estimations of zero-frequency NPS are susceptible to distortion due to several factors leading to low-estimate precisions. In this letter, a high-precision estimate algorithm for zero-frequency NPS is proposed. The proposed estimate is a compensated sum of signal variances and covariances. The accuracy and precision of the proposed approach were first observed with synthetic data. A flat panel radiography detector based on CsI(Tl)-scintillator was then used to experimentally observe the improved estimate precision of the proposed algorithm. Experiment results showed that the estimation precision was improved to 14 times compared to that of the conventional method.
关键词： Radiography imaging,sample mean of periodograms,zero-frequency noise power density
更新于2025-09-23 15:22:29
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[ACM Press Proceedings of the 14th EAI International Conference - Melbourne, VIC, Australia (2017.11.07-2017.11.10)] Proceedings of the 14th EAI International Conference on Mobile and Ubiquitous Systems Computing Networking and Services - Sensor Agnostic Photoplethysmogram Signal Quality Assessment using Morphological Analysis
摘要： In this article, we propose a method to assess the clinical usability of fingertip Photoplethysmogram (PPG) waveform, collected from medical grade oximeter (train data) and smartphone (test data). We introduce a set of novel Signal Quality Indices (SQIs) to represent the noise characteristics of the PPG waveform. The SQIs are presented to a random forest classifier to discriminate between clean and noisy signals. The proposed method was evaluated on datasets annotated by four experts, resulting into a sensitivity and specificity of (92 + ? 4.7 % , 95 + ? 4.6 % , 95.4 + ? 3.1 %) on train and test data respectively. Further we applied the proposed method on PPG waveform of clinically proven control and disease population of Coronary Artery Disease (CAD), which resulted into (77 %,77 %) of sensitivity and specificity respectively.
关键词： Artefact,Noise Detection,Photoplethysmogram,Wearable Sensors,Morphology,Mobile Health
更新于2025-09-23 15:22:29
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White light interferometry and MountainsMap? - case studies in static load capacity of bearings and surface finish optimisation of orthotic knee joints
摘要： This paper deals with two case studies demonstrating the combined use of white light interferometry and MountainsMap? software to: 1) accurately measure indentation diameters on race elements with an accuracy of a 1/100th of a micrometer and to examine static load capacity of bearings compared to the industry standard. In this case study, static load capacity of the ball bearings was shown to be 31% lower than that specified by ISO and ANSI/ABMA bearing standards; 2) characterise machined surfaces with 2D and 3D parameters, with the goal of producing optimal surface finish on orthotic knee joints used by Cerebral Palsy patients. In this case study, 2D roughness parameters Ra, Rq, Rp, Rz, and 3D roughness parameters Sa, Sq, Sp, Sz, were improved by 34%, 31%, 8%, 20%, and 36%, 33%, 6%, 6% respectively. Both case studies demonstrate the significance of modern topography techniques in enhancing the measurement accuracy of surface characteristics.
关键词： robust design,MountainsMap?,surface roughness,signal-to-noise (S/N) ratio,interferometry,WLI,static load capacity,white light,ball bearing indentations
更新于2025-09-23 15:22:29
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[IEEE 2018 26th European Signal Processing Conference (EUSIPCO) - Rome (2018.9.3-2018.9.7)] 2018 26th European Signal Processing Conference (EUSIPCO) - Bayesian Restoration of High-Dimensional Photon-Starved Images
摘要： This paper investigates different algorithms to perform image restoration from single-photon measurements corrupted with Poisson noise. The restoration problem is formulated in a Bayesian framework and several state-of-the-art Monte Carlo samplers are considered to estimate the unknown image and quantify its uncertainty. The different samplers are compared through a series of experiments conducted with synthetic images. The results demonstrate the scaling properties of the proposed samplers as the dimensionality of the problem increases and the number of photons decreases. Moreover, our experiments show that for a certain photon budget (i.e., acquisition time of the imaging device), downsampling the observations can yield better reconstruction results.
关键词： Bayesian statistics,Markov chain Monte Carlo,Inverse problems,Image processing,Bouncy particle sampler,Poisson noise
更新于2025-09-23 15:22:29
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Fast Padé Transform for increasing the signal to noise ratio of spectra provided by STEAM pulse sequence
摘要： BACKGROUND/OBJECTIVE: There are two routine pulse-sequences for single voxel spectroscopy (SVS), point resolved spectroscopy (PRESS) and stimulated echo acquisition mode (STEAM). Although STEAM has several advantages in comparison to PRESS, signal/noise ratio (SNR) superiority of PRESS makes it the first choice for SVS. Application of Fast Padé transform (FPT) instead of Fast Furrier transform (FFT) might increase the SNR of the signal produced by STEAM pulse-sequence and therefore allows the benefits of its advantages. We aimed to evaluate and compare the noise root mean square (RMS) and SNR provided by STEAM pulse-sequence using both FPT and FFT. MATERIALS AND METHOD: A gelatin-based phantom was constructed in a 19-cm acrylic cylinder. The phantom had two normal/tumoral parts. The SVS was performed using a 3T MRI scanner. STEAM pulse-sequence were used with the following parameters: TR = 2000 ms, TM = 10 ms, and three TEs of 20, 135 and 270 ms with two data-points of 1024 and 512 and voxel-size of 1 cm3. The raw data were extracted and processed using both FFT and FPT estimators to produce the spectrum. The noise RMS and SNR of Cho and Cr metabolites were assessed. RESULTS: According to the results, noise RMS of spectra provided by FPT were decreased between 3619.01–14252.94% in comparison to FFT (p < 0.00001). The SNR of Cr1 and Cho peaks of the spectra provided by FPT were increased more than 96.80 and 97.18, respectively (0.00006 < p < 0.02). DISCUSSION: The difference of noise RMS’s provided by FPT are thousands percent less than FFT. This enormous decrease in noise provides a good increase of SNR. While the range of Cr1 and Cho SNR by FFT are between 41.55–120.32 the range of SNRs of these peaks provided by FPT are between 1719.99–9744.79, which implies a significant difference between the efficiency of FPT and FFT. CONCLUSION: This study showed that application of FPT in comparison to FFT can increase the spectra SNR and so that its usage can be helpful during the application of STEAM pulse-sequence which results in lower SNR in comparison to PRESS pulse-sequence. Thus, we should make use of the advantages of STEAM pulse-sequence.
关键词： Magnetic resonance spectroscopy,signal to noise ratio,STEAM pulse sequence,Fast Padé Transform,Fast Furrier Transform
更新于2025-09-23 15:22:29
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A Pilot Symbols Aided Adaptive Kalman Filter for Joint Carrier Phase and Polarization Tracking in Coherent Optical System
摘要： A joint compensation scheme based on pilot symbols aiding adaptive Kalman filter (AKF) for phase noise and polarization cross-talk is proposed and investigated via numerical simulation and experimental demonstration. In the proposed scheme, the optimizing parameter Q is adaptively adjusted according to signal parameters or channel conditions. This improvement avoids the drawback of conventional extended Kalman filter (EKF), and its performance is strongly dependent on Q. Another improvement is that the convergence speed of AKF is improved. Pilot quadrature phase shift keyin (QPSK) symbols are inserted into 16 quadrature amplitude modulation (QAM) signals periodically. Besides accelerating convergence speed, the employment of pilot symbols also improves the tracking capability of AKF. The format ratio between pilot symbols and payload symbols is suggested under different system environments, for instance, optical signal-to-noise rate, polarization rotation frequency drift rate, and laser linewidth. With the proposed scheme, it has excellent tolerance to initial parameter Q and dramatically improves the performances in convergence speed, polarization rotation frequency drift rate tracking, and carrier phase recovery. Both the numerical simulation and experimental demonstration achieve convergence improvement for around 40 times than the original AKF. Additionally, the improvements in tracking ability are also demonstrated.
关键词： dynamic polarization rotation,pilot aided adaptive Kalman filter,phase noise,coherent optical communication
更新于2025-09-23 15:22:29