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Science China Earth Sciences 2009年第6期52卷 754-763页

作者： M. Parrot Laboratory of Physical and Chemical Environment National Center for Scientific Research

Here we used the VLF signal data received by the DEMETER satellite, transmitted from various ground VLF transmitters which are located around China, to study the changes in the signal to noise ratio (snr) before and after the Wenchuan earthquake, which had a magnitude of 8.0. We also found that the snrs of different frequency signals decreased significantly over the epicenter region before the earthquake, and reverted to their original levels after the earthquake. This phenomenon may be related to the earthquake.

关键词： snr VLF Wenchuan earthquake DEMETER satellite seismo-ionospheric phenomenon

snr and RSSI Based an Optimized Machine Learning Based Indoor Localization Approach:Multistory Round Building Scenario over LoRa Network

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Computers, Materials & Continua 2024年第8期80卷 1927-1945页

作者： Muhammad Ayoub Kamal Muhammad Mansoor Alam Aznida Abu Bakar Sajak Mazliham Mohd Su’ud Malaysian Institute of Information Technology(MIIT) Universiti Kuala LumpurKuala Lumpur50250Malaysia Faculty of Computing and Informatics Multimedia UniversityCyberjaya63100Malaysia Depertment of Computer Science DHA Suffa UniversityKarachiSindh75500Pakistan Riphah Institute of System Engineering(RISE) Faculty of ComputingRiphah International UniversityIslamabad46000Pakistan Malaysian France Institute(MFI) Universiti Kuala LumpurKuala Lumpur50250Malaysia Faculty of Engineering and Information Technology School of Computer ScienceUniversity of Technology SydneyUltimoNSW 2007Australia

In situations when the precise position of a machine is unknown,localization becomes *** research focuses on improving the position prediction accuracy over long-range(LoRa)network using an optimized machine learning-based *** order to increase the prediction accuracy of the reference point position on the data collected using the fingerprinting method over LoRa technology,this study proposed an optimized machine learning(ML)based *** signal strength indicator(RSSI)data from the sensors at different positions was first gathered via an experiment through the LoRa network in a multistory round layout *** noise factor is also taken into account,and the signal-to-noise ratio(snr)value is recorded for every RSSI *** study concludes the examination of reference point accuracy with the modified KNN method(MKNN).MKNN was created to more precisely anticipate the position of the reference *** findings showed that MKNN outperformed other algorithms in terms of accuracy and complexity.

关键词： Indoor localization MKNN LoRa machine learning classification RSSI snr localization

Bistable Stochastic Resonance Enhanced 4-ary PAM Signal Detection under Low snr

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China Communications 2019年第4期16卷 196-207页

作者： Linlin Liang Nina Zhang Haiyan Huang Zan Li School of Telecommunications Engineering Xidian University Xianyang Detachment of Chinese Armed Police Force School of Electronic and Information Engineering Lanzhou Jiaotong University The Collaborative Innovation Center of Information Sensing and Understanding at Xidian University

To boost the performance of 4-ary pulse amplitude modulated(PAM) at low signal-to-noise ratio(snr), bistable stochastic resonance(BSR) system is introduced into digital communications system and get a reliable signal detection scheme. In this paper, we first analyse BSR system for different amplitudes of 4-ary PAM signals. The steadystate of the bistable system will be statistically distinct, and the feasibility of the proposed detection scheme is confirmed. On this basis, we present a detailed study on steady-state transitions of the BSR system, and an explicit expression of the bistable system parameters is derived. By setting the bistable system parameters, bistable system, 4-ary PAM signal, and noise reach the resonance state, and the BSR-based detection scheme is implemented. Moreover, we derive an analytical expression to calculate the symbol error rate(SER) of 4-ary PAM signals with the BSR-based detection under additive white Gaussian noise(AWGN). Finally, the simulation results validate that BSR-based detection scheme can improve the detection performance while efficiently reducing the symbol error rate.

关键词： 4-ary pulse amplitude modulated signal detection Low snr Symbol error rate(SER) Bistable stochastic resonance(BSR)

Monte-Carlo simulation for determining snr and DQE of linear array plastic scintillating fiber

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Nuclear Science and Techniques 2004年第5期15卷 304-307页

作者： Mohammad Mehdi NASSERI Department of Modern Physics University of Science and Technology of China Hefei 230026

Fundamental characteristics of the plastic-scintillating fiber (PSF) for wide energy range of electromag- netic radiation (X & γ) have been studied to evaluate possibility of using the PSF as an imaging detector for industrial purposes. Monte-Carlo simulation program (GEANT4.5.1, 2003) was used to generate the data. In order to evaluate image quality of the detector, fiber array was irradiated under various energy and fluxes. Signal to noise ratio (snr) as well as detector quantum efficiency (DQE) were obtained.

关键词： Monte-Carlo GEANT4 snr

Blind reconnaissance of the pseudo-random sequence in DS/SS signal with negative snr

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Science in China(Series F) 2007年第3期50卷 510-520页

作者： HUANG XianGao HUANG Wei WANG Chao LU ZeJun HU YanHua School of Computer Science and Engineering University of Electronic Science and Technology Chengdu6100541 China Computer Center Chang'an University Xi'an 710064 China Research Institute of Electronic ZhongXing Xi'an 710061 China Southwest China Institute of Electronic Technology Chengdu 610036 China College of Engineering Shantou University Shantou 515063 China

This paper introduces a new theory and algorithm that can be used in blind detection of the carrier wave signal and the pseudo-random sequence of the direct sequence spread spectrum （DS/SS） signal with negative snr. First, without any a priori knowledge of the DS/SS signal, the carrier wave signal can be detected from DS/SS signal with negative snr by using stochastic differential equations and energy detection method. Based on this, the pseudo-random sequence can also be blindly detected in DS/SS signal with negative snr by reducing noise of the nonlinear signal and the algorithm of wavelet multiscale decomposition algorithm. Finally, the computer simulation shows that we can detect the carrier wave signal with snr=-27 dB and the pseudo-random sequence under error code ratio 10^-4with snr =-10 dB.

关键词： DS/SS signal snr the pseudo-random sequence reconnaissance detection

Pumping Schemes Impacts on snr of Discreted Raman Amplifications

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光学学报 2003年第S1期23卷 497-498页

作者： Karsten Rottwitt BeraPálsdóttir COM research Center Technical University of Denmark DenmarkOFS Denmark Priorparken 680 DK-2605 Brondby Denmark

We compare different discreted DCF Raman amplifier configurations, including single-stage and dual-stage. The optimum design with respect to snr degradation, compromise linear and nonlinear impairments.

关键词： snr in Pumping Schemes Impacts on snr of Discreted Raman Amplifications of on

Actual Sensing Sensitivity and snr Measurement of Optical Tweezers Based on Coulomb Force Input

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Photonic Sensors 2023年第1期13卷 56-65页

作者： Jiaojiao WANG Xingfan CHEN Shaochong ZHU Zhenhai FU Nan LI Huizhu HU State Key Laboratory of Modern Optical Instrumentation College of Optical Science and EngineeringZhejiang UniversityHangzhou 310027China Quantum Sensing Center Zhejiang LabHangzhou 310000China

Sensing sensitivity is the key performance of optical *** adjusting the frequency and magnitude of an applied Coulomb force as an input of optical tweezers,we directly measured the sensitivity and signal-to-noise ratio(snr)of a system and indirectly calculated the actual noise *** with an output filter,the relationship between the snr and bandwidths was *** established the simulation model of a system using Simulink and simulated the relationship between the snr and magnitude of the input forces and filter *** addition,we built an experimental system to determine the relationship between the snr and the magnitude of the input forces and filter *** actual minimum detectable force was measured as 1.8275×10^(-17)N at a 1Hz *** experimental results were correlated with the simulation and theoretical results,confirming the effectiveness of the proposed method and demonstrating the high sensitivity of vacuum optical tweezers as mechanical *** proposed a novel method of calibration and measurement of system sensing parameters by applying an actual force that was more direct and precise than the theoretical calculation method that requires accurate fitting parameters,such as the particle radius and *** method can be employed to analyze the system noise and phase characteristics to confirm and improve the real performance of the system.

关键词： Optical tweezers sensitivity Coulomb force snr Simulink system noise characteristic

High-efficiency DBA-BOTDA with optimized snr by multiple bandwidths pump modulation

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Chinese Optics Letters 2019年第1期17卷 20-25页

作者： Huiliang Ma Xinhong Jia Kai Lin Cong Xu College of Physics and Electronic Engineering Sichuan Normal University

For Brillouin optical time-domain analysis(BOTDA) based on distributed Brillouin amplification(DBA), constant Brillouin response achieved by the exponentially variable bandwidth/intensity pump modulation suffers from the much lower pumping efficiency for long-range sensing, which counterbalances the merit of DBA. In this Letter, pump modulation by multiple constant bandwidths was proposed and demonstrated. The ～98.9 km sensing with ～5 m spatial resolution and no use of optical pulse coding(OPC) was achieved by ～8 dBm Brillouin pump, which is lower by ～9 dB in theory by comparison with exponentially increased bandwidth *** with traditional DBA-BOTDA, signal-to-noise ratio(snr) enhancement with >4.6 dB was obtained. The flattened standard deviation(STD) of Brillouin frequency shift(BFS)(less than ～2 MHz) along the whole fiber was demonstrated.

关键词： BOTDA DBA BFS snr

基于三频snr数据探测北斗GEO卫星多径效应

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武汉大学学报（信息科学版） 2018年第2期43卷 213-218页

作者：高晓杨志强康军梅王君长安大学地质工程与测绘学院陕西西安710054 中国电力工程顾问集团西北电力设计院有限公司陕西西安710032

多径误差是全球卫星导航系统（global navigation satellite system,GNSS）高精度实时定位的主要误差源。由于多径效应具有时变特性且与观测环境有关,难以有效探测与剔除,尤其是动态定位领域。鉴于多径效应对于同颗卫星不同频率观测值... 详细信息

多径误差是全球卫星导航系统（global navigation satellite system,GNSS）高精度实时定位的主要误差源。由于多径效应具有时变特性且与观测环境有关,难以有效探测与剔除,尤其是动态定位领域。鉴于多径效应对于同颗卫星不同频率观测值影响不同,本文采用三频信噪比（signal-noise ratio,snr）频率间差分数据,设计算法探测北斗对地静止卫星（geostationary orbit satellite,GEO）多径误差,并依据开阔环境snr频间差分数据序列进行统计分析,确定其探测阈值。实验结果表明,北斗GEO卫星易受多径误差影响,传统方法难以实时有效探测,本文提出的新方法可有效探测GEO多径误差,并基于设定的阈值对其数据进行降权或剔除,可应用于GNSS数据质量控制。

关键词：多径效应 snr 三频北斗 GEO 实时探测阈值

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基于snr的GPS-IR技术机理分析

地球科学进展 2019年第2期34卷 156-163页

作者：孙小荣张书毕吴继忠郑南山中国矿业大学国土环境与灾害监测国家测绘地理信息局重点实验室江苏徐州221116 宿迁学院建筑工程学院江苏宿迁223800 南京工业大学测绘科学与技术学院江苏南京211800

鉴于现有研究对GPS-IR技术的反射波接收、低高度角信噪比观测值的使用、信噪比残差的形态等机理还未阐释清楚,且几乎是通过实验进行解释,因此,从理论和实验2个方面对GPS-IR技术机理进行分析。理论和实验证明:GPS卫星发射的右旋圆极化波... 详细信息

鉴于现有研究对GPS-IR技术的反射波接收、低高度角信噪比观测值的使用、信噪比残差的形态等机理还未阐释清楚,且几乎是通过实验进行解释,因此,从理论和实验2个方面对GPS-IR技术机理进行分析。理论和实验证明:GPS卫星发射的右旋圆极化波经一次反射后部分转换为左旋圆极化波,转换比例随着高度角和介电常数增大而变大,当右旋圆极化波垂直入射到理想导体表面时,经一次反射才能全部转换为左旋圆极化波;同时在测量型GPS接收机安装有抑径板的情况下,因衍射现象的存在,测量型GPS接收机天线仍能接收反射波中的右旋圆极化波。当高度角越小或介电常数越大时,GPS入射波中的垂直极化波和平行极化波的能量透射到反射物中就越少,其反射波的强度就越大,信噪比受反射波影响就越严重,且能够接收的右旋圆极化波较多,因此GPS-IR使用的是低高度角(如30°以下)的信噪比观测值。当高度角变化范围较小时,信噪比残差序列呈近似"余弦曲线"形态,从而建立了基于信噪比残差的反演模型。

关键词： snr GPS-IR技术机理分析极化特性反演模型