检索结果-南通市图书馆

signal-to-noise ratio of lensless ghost interference with thermal incoherent light

在线全文

学校读者我要写书评

暂无评论

Chinese Physics B 2011年第2期20卷 229-234页

作者：张二峰戴宏毅陈平形 Department of Physics College of ScienceNational University of Defense Technology

Factors influencing the signal-to-noise ratio （SNR） of lensless ghost interference with thermal incoherent light are investigated. Our result shows that the SNR of lensless ghost interference is related to the transverse length of the object, the position of the object in the imaging system and the transverse size of the light source. Furthermore, the effects of these factors on the SNR are discussed in detail by numerical simulations.

关键词： ghost interference ghost imaging signal-to-noise ratio

Long scan depth optical coherence tomography on imaging accommodation: impact of enhanced axial resolution, signal-to-noise ratio and speed

在线全文

学校读者我要写书评

暂无评论

Eye and Vision 2018年第1期5卷 151-162页

作者： Yilei Shao Aizhu Tao Hong Jiang Meixiao Shen Dexi Zhu Fan Lu Carol LKarp Yufeng Ye Jianhua Wang Bascom Palmer Eye Institute University of MiamiMiamiFLUSA School of Ophthalmology and Optometry Wenzhou Medical UniversityWenzhouZhejiangChina Hangzhou First People’s Hospital HangzhouChina Electrical and Computer Engineering University of MiamiMiamiFLUSA Bascom Palmer Eye Institute University of MiamiMiller School of Medicine1638 NW 10th AvenueMcKnight Building-Room 202AMiamiFL 33136USA

Background:Spectral domain optical coherence tomography(SD-OCT)was a useful tool to study accommodation in human eye,but the maximum image depth is limited due to the decreased signal-to-noise ratio(SNR).In this study,improving optical resolutions,speeds and the SNR were achieved by custom built SD-OCT,and the evaluation of the impact of the improvement during accommodation was investigated.Methods:Three systems with different spectrometer designs,including two Charge Coupled Device(CCD)cameras and one Complementary Metal-Oxide-Semiconductor Transistor(CMOS)camera,were tested.We measured the point spread functions of a mirror at different positions to obtain the axial resolution and the SNR of three OCT systems powered with a light source with a 50 nm bandwidth,centered at a wavelength of 840 nm.Two normal subjects,aged 26 and 47,respectively,and one 75-year-old patient with an intraocular lens implanted were imaged.Results:The results indicated that spectrometers using cameras with 4096 camera pixels optimized the axial resolutions,due to the use of the full spectrum provided by the light source.The CCD camera system with 4096 pixels had the highest SNR and the best image quality.The system with the CMOS camera with 4096 pixels had the highest speed but had a compromised SNR compared to the CCD camera with 4096 pixels.Conclusions:Using these three OCT systems,we imaged the anterior segment of the human eye before and after accommodation,which showed similar results among the different systems.The system using the CMOS camera with an ultra-long scan depth,high resolution and high scan speed exhibited the best overall performance and therefore was recommended for imaging real-time accommodation.

关键词： Optical coherence tomography Axial resolution signal-to-noise ratio Accommodation Anterior segment

Analytical and NumericalMethods to Study the MFPT and SR of a Stochastic Tumor-Immune Model

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Computer Modeling in Engineering & Sciences 2024年第3期138卷 2177-2199页

作者： Ying Zhang Wei Li Guidong Yang Snezana Kirin School of Mathematics and Statistics Xidian UniversityXi’an710071China Innovation Center of Faculty of Mechanical Engineering Belgrade11100Serbia

The Mean First-Passage Time (MFPT) and Stochastic Resonance (SR) of a stochastic tumor-immune model withnoise perturbation are discussed in this paper. Firstly, considering environmental perturbation, Gaussian whitenoise and Gaussian colored noise are introduced into a tumor growth model under immune surveillance. Asfollows, the long-time evolution of the tumor characterized by the Stationary Probability Density (SPD) and MFPTis obtained in theory on the basis of the Approximated Fokker-Planck Equation (AFPE). Herein the recurrenceof the tumor from the extinction state to the tumor-present state is more concerned in this paper. A moreefficient algorithmof Back-Propagation Neural Network (BPNN) is utilized in order to testify the correction of thetheoretical SPDandMFPT.With the existence of aweak signal, the functional relationship between signal-to-noiseratio (SNR), noise intensities and correlation time is also studied. Numerical results show that both multiplicativeGaussian colored noise and additive Gaussian white noise can promote the extinction of the tumors, and themultiplicative Gaussian colored noise can lead to the resonance-like peak on MFPT curves, while the increasingintensity of the additiveGaussian white noise results in theminimum of MFPT. In addition, the correlation timesare negatively correlated with MFPT. As for the SNR, we find the intensities of both the Gaussian white noise andthe Gaussian colored noise, as well as their correlation intensity can induce SR. Especially, SNR is monotonouslyincreased in the case ofGaussian white noisewith the change of the correlation time.At last, the optimal parametersin BPNN structure are analyzed for MFPT from three aspects: the penalty factors, the number of neural networklayers and the number of nodes in each layer.

关键词： Stochastic tumor-immune model mean first-passage time stochastic resonance signal-to-noise ratio back-propagation neural network

signal-to-noise ratio of Raman signal measured by multichannel detectors

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Chinese Physics B 2021年第9期30卷 31-44页

作者：刘雪璐冷宇辰林妙玲从鑫谭平恒 State Key Laboratory of Superlattices and Microstructures Institute of SemiconductorsChinese Academy of SciencesBeijing 100083China Center of Materials Science and Optoelectronics Engineering&CAS Center of Excellence in Topological Quantum Computation University of Chinese Academy of SciencesBeijing 100049China

Raman spectroscopy has been widely used to characterize the physical properties of two-dimensional materials(2DMs).The signal-to-noise ratio(SNR or S/N ratio)of Raman signal usually serves as an important indicator to evaluate the instrumental performance rather than Raman intensity itself.Multichannel detectors with outstanding sensitivity,rapid acquisition speed and low noise level have been widely equipped in Raman instruments for the measurement of Raman signal.In this mini-review,we first introduce the recent advances of Raman spectroscopy of 2DMs.Then we take the most commonly used CCD detector and IGA array detector as examples to overview the various noise sources in Raman measurements and analyze their potential influences on SNR of Raman signal in experiments.This overview can contribute to a better understanding on the SNR of Raman signal and the performance of multichannel detector for numerous researchers and instrumental design for industry,as well as offer practical strategies for improving spectral quality in routine measurement.

关键词： multichannel detectors signal-to-noise ratio dark noise shot noise

Attention-Based Residual Dense Shrinkage Network for ECG Denoising

在线全文

学校读者我要写书评

暂无评论

Computer Modeling in Engineering & Sciences 2024年第3期138卷 2809-2824页

作者： Dengyong Zhang Minzhi Yuan Feng Li Lebing Zhang Yanqiang Sun Yiming Ling Hunan Provincial Key Laboratory of Intelligent Processing of Big Data on Transportation Changsha University of Science and TechnologyChangsha410114China School of Computer and Communication Engineering Changsha University of Science and TechnologyChangsha410114China School of Computer and Artificial Intelligence Huaihua UniversityHuaihua418000China School of Computer National University of Defense TechnologyChangsha410073China New Energy Centralized Control Center CHN Energy Hunan Power New Energy Co.Ltd.Changsha410000China

Electrocardiogram(ECG)signal is one of the noninvasive physiological measurement techniques commonly usedin cardiac diagnosis.However,in real scenarios,the ECGsignal is susceptible to various noise erosion,which affectsthe subsequent pathological analysis.Therefore,the effective removal of the noise from ECG signals has becomea top priority in cardiac diagnostic research.Aiming at the problem of incomplete signal shape retention andlow signal-to-noise ratio(SNR)after denoising,a novel ECG denoising network,named attention-based residualdense shrinkage network(ARDSN),is proposed in this paper.Firstly,the shallow ECG characteristics are extractedby a shallow feature extraction network(SFEN).Then,the residual dense shrinkage attention block(RDSAB)isused for adaptive noise suppression.Finally,feature fusion representation(FFR)is performed on the hierarchicalfeatures extracted by a series of RDSABs to reconstruct the de-noised ECG signal.Experiments on the MIT-BIHarrhythmia database and MIT-BIH noise stress test database indicate that the proposed scheme can effectively resistthe interference of different sources of noise on the ECG signal.

关键词： Electrocardiogram signal denoising signal-to-noise ratio attention-based residual dense shrinkage network MIT-BIH

Enhancement of signal-to-noise ratio of ultracold polar NaCs molecular spectra by phase locking detection

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Chinese Physics B 2017年第12期26卷 231-235页

作者：王文浩刘文良武寄洲李玉清王晓锋刘艳艳马杰肖连团贾锁堂 State Key Laboratory of Quantum Optics and Quantum Optics Devices Institute of Laser Spectroscopy Shanxi University Collaborative Innovation Center of Extreme Optics Shanxi University

We report a method of high-sensitively detecting the weak signal in photoassociation(PA) spectra of ultracold NaCs molecules by phase sensitive-demodulated trap-loss spectra of Na atoms from a photomultiplier tube. We find that the signal-to-noise ratio(SNR) of the PA spectra is strongly dependent on the integration time and the sensitivity of the lockin amplifier, and our results show reasonable agreement with the theoretical analyses of the SNR with the demodulation parameters. Meanwhile, we investigate the effect of the interaction time of the PA laser with the colliding Na–Cs atom pairs on the SNR of the PA spectra. The atom loss rate is dependent on both the PA-induced atom loss and the loading of the MOT. The high-sensitive detection of the excited ultracold NaCs molecules lays a solid foundation for further study of the formation and application of ultracold NaCs molecules.

关键词： ultracold NaCs molecules photoassociation high-resolution spectroscopy signal-to-noise ratio

Using Pearson’s System of Curves to Approximate the Distributions of the Difference between Two Correlated Estimates of signal-to-noise ratios: The Cases of Bivariate Normal and Bivariate Lognormal Distributions

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Open Journal of Statistics 2024年第3期14卷 207-227页

作者： Mohamed M. Shoukri Department of Epidemiology and Biostatistics Schulich School of Medicine and Dentistry University of Western Ontario London Ontario Canada

Background: The signal-to-noise ratio (SNR) is recognized as an index of measurements reproducibility. We derive the maximum likelihood estimators of SNR and discuss confidence interval construction on the difference between two correlated SNRs when the readings are from bivariate normal and bivariate lognormal distribution. We use the Pearsons system of curves to approximate the difference between the two estimates and use the bootstrap methods to validate the approximate distributions of the statistic of interest. Methods: The paper uses the delta method to find the first four central moments, and hence the skewness and kurtosis which are important in the determination of the parameters of the Pearsons distribution. Results: The approach is illustrated in two examples;one from veterinary microbiology and food safety data and the other on data from clinical medicine. We derived the four central moments of the target statistics, together with the bootstrap method to evaluate the parameters of Pearsons distribution. The fitted Pearsons curves of Types I and II were recommended based on the available data. The R-codes are also provided to be readily used by the readers.

关键词： signal-to-noise ratio Bivariate Distributions Bootstrap Methods Delta Method Pearson System of Curves

Quality assessment of Continuous Operating Reference Stations(CORS)-GPS stations in Mexico

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Geodesy and Geodynamics 2022年第3期13卷 275-287页

作者： Daniel Hernández-Andrade Rosendo Romero-Andrade Gopal Sharma Manuel E.Trejo-Soto Juan L.Cabanillas-Zavala Faculty of Earth and Space Sciences Autonomous University of Sinaloa80013Culiacán RosalesSinaloaMexico North Eastern Space Applications Centre Umiam793103MeghalayaIndia

The present analysis provided the quality assessment of 65 Continuous Operating Reference Stations(CORS) situated in and around Mexico using the data of about ten years(January 2010 to January 2020).To accomplish the assessment,we considered 4 quality indexes for performing the quality check,incluing the multipath effect on L1 and L2 bands,signal-to-noise ratio in both bands,cycle slips,and integrity.Meanwhile,a new reference parameter named regio nal values for Mexico(RVM) was calculated for the stations situated in Mexico.Additionally,an exhaustive analysis of the quality indicators in the worst and best cases was performed.The signal degradation was proved by a long-term time series and cru stal defo rmation analysis in GAMIT/GLOBK platform.The results showed a stro ng correlation between integrity,cycle slips and daily observations time,and the multipath effect is strong in the case of outdated systems.The study indicates that the estimated quality indexes and values could be the basis for establishing new CORS in Mexico,and the errors corrections which cannot be mitigated in the postprocessing stage would greatly help utilize the data for different scientific applications.The results were supported by deformation analysis in part of Baja California Peninsula in Mexico indicating northern and eastern velocity vector of -3.08±0.02 mm/yr,-7.85±0.02 mm/yr and-0.07±0.03 mm/yr,-9.33±0.02 mm/yr respectively at MPR1 and INEG stations.

关键词： Multipath effect signal-to-noise ratio Cycle slip Integrity Regional quality indicators IGS indicators

Mean-square Stabilizability vs. signal-to-noise ratio,Channel Induced Delay and Packet Dropout

在线全文

学校读者我要写书评

暂无评论

Mean-square Stabilizability vs. Signal-to-Noise Ratio,Channe...