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Impact of GPS Almanac Broadcast Strategy on the Signal Acquisition Time 被引量:1
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作者 Lu-Xiao Wang Zhi-Gang Huang Yun Zhao 《Journal of Harbin Institute of Technology(New Series)》 EI CAS 2013年第5期6-13,共8页
This paper investigates the problem of almanac affecting the signal acquisition time with two constraints: different age of data and multi-sets of almanac. The contributions made in this paper include: 1) the exploiti... This paper investigates the problem of almanac affecting the signal acquisition time with two constraints: different age of data and multi-sets of almanac. The contributions made in this paper include: 1) the exploiting of signal acquisition concept to extend well-known almanac function of predicting visible satellite and initializing signal acquisition to minimizing the signal acquisition time; 2) a model based on code phase and Doppler frequency to reflect the impact of multi-sets of almanac on the signal acquisition time; 3) the evaluation of the existing GPS almanac with different broadcast strategy. The theoretical analyses and simulations conducted on three sets of almanac show that the model proposed in this paper is general and efficient for almanac design and application. 展开更多
关键词 ALMANAC signal acquisition time age of data code phase doppler frequency
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The application of breast DCE-MRI combined with time signal curve in diagnosing early breast cancer 被引量:2
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作者 Yakun He Guohui Xu +2 位作者 Jing Ren Min Wang Jin Liu 《The Chinese-German Journal of Clinical Oncology》 CAS 2013年第2期72-75,共4页
Objective: The aim of this study was to investigate the application value of breast dynamic contrast-enhanced magnetic resonance imaging combined with time signal curve in diagnosis of early breast cancer. Methods: ... Objective: The aim of this study was to investigate the application value of breast dynamic contrast-enhanced magnetic resonance imaging combined with time signal curve in diagnosis of early breast cancer. Methods: Conducted dynamic contrast-enhanced MRI and drew the time signal curves of breast lesions in 60 patients with breast disease (malignant 46, benign 14). Results: Morphological features of malignant tumors mostly showed blurred or thin spiculate outlines, irregular shape or Iobular signs, signal heterogeneity or peripheral enhancement in dynamic contrast-enhanced MRI. Time signal curve showed type III or II. Morphologic features of benign tumors mostly showed clear edge, regular shape and homogeneous signal, or diffuse spot enhancement. Time signal curve showed type I or II. Conclusion: breast dynamic contrast enhanced scan in MRI can provide morphology and functional diagnosis information of the breast tissues. Dynamic contrast-enhanced MRI combined with time signal curve can further improve the accuracy of diagnosis of early breast cancer. 展开更多
关键词 breast carcinoma nuclear magnetic resonance dynamic enhancement time signal curve
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High Accuracy Time of Flight Measurement Using Digital Signal Processing Techniques for Subsea Applications 被引量:2
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作者 Muhammad Ashraf Hamza Qayyum 《Journal of Signal and Information Processing》 2011年第4期330-335,共6页
The techniques widely used in ultrasonic measurements are based on the determination of the time of flight (T.o.F). A short train of waves is transmitted and same transducer is used for reception of the reflected sign... The techniques widely used in ultrasonic measurements are based on the determination of the time of flight (T.o.F). A short train of waves is transmitted and same transducer is used for reception of the reflected signal for the pulse-echo measurement applications. The amplitude of the received waveform is an envelope which starts from zero reaches to a peak and then dies out. The echoes are mostly detected by simple threshold crossing technique, which is also cause of error. In this paper digital signal processing is used to calculate the time delay in reception i.e. T.o.F, for which a maximum similarity between the reference and the delayed echo signals is obtained. To observe the effect of phase uncertainties and frequency shifts (Doppler), this processing is carried out, both directly on the actual wave shape and after extracting the envelopes of the reference and delayed echo signals. Several digital signal processing algorithms are considered and the effects of different factors such as sampling rate, resolution of digitization and S/N ratio are analyzed. Result show accuracy, computing time and cost for different techniques. 展开更多
关键词 SONAR signal PROCESSING time of FLIGHT
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Parameterized time-frequency analysis to separate multi-radar signals 被引量:1
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作者 Wenlong Lu Junwei Xie +1 位作者 Heming Wang Chuan Sheng 《Journal of Systems Engineering and Electronics》 SCIE EI CSCD 2017年第3期493-502,共10页
Multi-radar signal separation is a critical process in modern reconnaissance systems. However, the complicated battlefield is typically confronted with increasing electronic equipment and complex radar waveforms. The ... Multi-radar signal separation is a critical process in modern reconnaissance systems. However, the complicated battlefield is typically confronted with increasing electronic equipment and complex radar waveforms. The intercepted signal is difficult to separate with conventional parameters because of severe overlapping in both time and frequency domains. On the contrary, time-frequency analysis maps the 1D signal into a 2D time-frequency plane, which provides a better insight into the signal than traditional methods. Particularly, the parameterized time-frequency analysis (PTFA) shows great potential in processing such non stationary signals. Five procedures for the PTFA are proposed to separate the overlapped multi-radar signal, including initiation, instantaneous frequency estimation with PTFA, signal demodulation, signal separation with adaptive filter and signal recovery. The proposed method is verified with both simulated and real signals, which shows good performance in the application on multi-radar signal separation. 展开更多
关键词 intercepted multi-radar signal parameterized time-frequency analysis DEMODULATION adaptive filtering
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Optimization of traffic signal parameters based on distribution of link travel time
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作者 黎茂盛 薛红丽 史峰 《Journal of Central South University》 SCIE EI CAS CSCD 2017年第2期432-441,共10页
In order to make full use of digital data, such as data extracted from electronic police video systems, and optimize intersection signal parameters, the theoretical distribution of the vehicle's road travel time m... In order to make full use of digital data, such as data extracted from electronic police video systems, and optimize intersection signal parameters, the theoretical distribution of the vehicle's road travel time must first be determined. The intersection signal cycle and the green splits were optimized simultaneously, and the system total travel time was selected as the optimization goal. The distribution of the vehicle's link travel time is the combined results of the flow composition, road marking, the form of control, and the driver's driving habits. The method proposed has 15% lower system total stop delay and fewer total stops than the method of TRRL(Transport and Road Research Laboratory) in England and the method of ARRB(Australian Road Research Board) in Australia. This method can save 0.5% total travel time and will be easier to understand and test, which establishes a causal relationship between optimal results and specific forms of road segment management, such as speed limits. 展开更多
关键词 travel time distribution signalized intersection signal cycle time green split
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Anti-aliasing nonstationary signals detecion algorithm based on interpolation in the frequency domain using the short time Fourier transform 被引量:7
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作者 Bian Hailong Chen Guangju 《Journal of Systems Engineering and Electronics》 SCIE EI CSCD 2008年第3期419-426,共8页
To eliminate the aliasing that appeared during the measurement of multi-components nonstationary signals, a novel kind of anti-aliasing algorithm based on the short time Fourier transform (STFT) is brought forward. ... To eliminate the aliasing that appeared during the measurement of multi-components nonstationary signals, a novel kind of anti-aliasing algorithm based on the short time Fourier transform (STFT) is brought forward. First the physical essence of aliasing that occurs is analyzed; second the interpolation algorithm model is setup based on the Hamming window; then the fast implementation of the algorithm using the Newton iteration method is given. Using the numerical simulation the feasibility of algorithm is validated. Finally, the electrical circuit experiment shows the practicality of the algorithm in the electrical engineering. 展开更多
关键词 nonstationary signal INTERPOLATION ANTI-ALIASING short time Fourier transform (STFT) iterative algorithm.
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A Recursive Method of Time-Frequency Analysis for the Signal Processing of Flutter Test with Progression Variable Speed 被引量:1
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作者 宋叔飚 裴承鸣 《Chinese Journal of Aeronautics》 SCIE EI CAS CSCD 2005年第3期213-217,共5页
Focused on the non-statlonarity and real-time analysis of signal in flutter test with progression variable speed (FTPVS), a new method of recursive time-frequency analysis is presented. The time-varying system is tr... Focused on the non-statlonarity and real-time analysis of signal in flutter test with progression variable speed (FTPVS), a new method of recursive time-frequency analysis is presented. The time-varying system is tracked on-line by building a time-varying parameter model, and then the relevant parameter spectrum can be obtained. The feasibility and advantages of the method are examined by digital simulation. The results of FTPVS at low-speed wind-tunnel promise the engineering application perspective of the method. 展开更多
关键词 flutter test with progression variable speed (FTPVS) non-stationary signal processing recursive time-frequency analysis (RTFA)
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Real-Time Traffic Signal Timing for Urban Road Multi-Intersection
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作者 Lin Dong Wushan Chen 《Intelligent Information Management》 2010年第8期483-486,共4页
this paper develops a real-time traffic signal timing model which is to be integrated into a single intersection for urban road, thereby solving the problem of traffic congestion. We analyze the current situation of t... this paper develops a real-time traffic signal timing model which is to be integrated into a single intersection for urban road, thereby solving the problem of traffic congestion. We analyze the current situation of the traffic flow with release matrix firstly, and then put forward the basic models to minimize total delay time of vehicles at the intersection. The optimal real-time signal timing model (non-fixed cycle and non-fixed split) is built with the Webster split optimal model. At last, the simulated results, which are compared with conventional model, manifest the promising properties of proposed model. 展开更多
关键词 TRAFFIC signal Control TRAFFIC Flows Real-time signal Timing Release Matrix SPLIT PASSION Distribution
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RECONSTRUCTION OF ONE DIMENSIONAL MULTI-LAYERED MEDIA BY USING A TIME DOMAIN SIGNAL FLOW GRAPH TECHNIQUE 被引量:1
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作者 崔铁军 梁昌洪 《Journal of Electronics(China)》 1993年第2期162-169,共8页
A novel inverse scattering method to reconstruct the permittivity profile of one-dimensional multi-layered media is proposed in this paper.Based on the equivalent network ofthe medium,a concept of time domain signal f... A novel inverse scattering method to reconstruct the permittivity profile of one-dimensional multi-layered media is proposed in this paper.Based on the equivalent network ofthe medium,a concept of time domain signal flow graph and its basic principles are introduced,from which the reflection coefficient of the medium in time domain can be shown to be a series ofDirac δ-functions(pulse responses).In terms of the pulse responses,we will reconstruct both thepermittivity and the thickness of each layer will accurately be reconstructed.Numerical examplesverify the applicability of this 展开更多
关键词 Multi-layered MEDIUM Reconstruct PERMITTIVITY profile INVERSE SCATTERING time DOMAIN signal flow GRAPH
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Measuring Acoustic Wave Transit Time in Furnace Based on Active Acoustic Source Signal
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作者 Zhen Luo Feng Tian Xiao-Ping Sun 《International Journal of Automation and computing》 EI 2007年第1期52-55,共4页
Accurate measurement of transit time for acoustic wave between two sensors installed on two sides of a furnace is a key to implementing the temperature field measurement technique based on acoustical method. A new met... Accurate measurement of transit time for acoustic wave between two sensors installed on two sides of a furnace is a key to implementing the temperature field measurement technique based on acoustical method. A new method for measuring transit time of acoustic wave based on active acoustic source signal is proposed in this paper, which includes the followings: the time when the acoustic source signal arrives at the two sensors is measured first; then, the difference of two arriving time arguments is computed, thereby we get the transit time of the acoustic wave between two sensors installed on the two sides of the furnace. Avoiding the restriction on acoustic source signal and background noise, the new method can get the transit time of acoustic wave with higher precision and stronger ability of resisting noise interference. 展开更多
关键词 Active acoustic source signal transit time cross correlation arrival time.
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Time-Varying Bandpass Filter Based on Assisted Signals for AM-FM Signal Separation: A Revisit 被引量:1
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作者 Guanlei Xu Xiaotong Wang +2 位作者 Xiaogang Xu Lijia Zhou Limin Shao 《Journal of Signal and Information Processing》 2013年第3期229-242,共14页
In this paper, a new signal separation method mainly for AM-FM components blended in noises is revisited based on the new derived time-varying bandpass filter (TVBF), which can separate the AM-FM components whose freq... In this paper, a new signal separation method mainly for AM-FM components blended in noises is revisited based on the new derived time-varying bandpass filter (TVBF), which can separate the AM-FM components whose frequencies have overlapped regions in Fourier transform domain and even have crossed points in time-frequency distribution (TFD) so that the proposed TVBF seems like a “soft-cutter” that cuts the frequency domain to snaky slices with rational physical sense. First, the Hilbert transform based decomposition is analyzed for the analysis of nonstationary signals. Based on the above analysis, a hypothesis under a certain condition that AM-FM components can be separated successfully based on Hilbert transform and the assisted signal is developed, which is supported by representative experiments and theoretical performance analyses on a error bound that is shown to be proportional to the product of frequency width and noise variance. The assisted signals are derived from the refined time-frequency distributions via image fusion and least squares optimization. Experiments on man-made and real-life data verify the efficiency of the proposed method and demonstrate the advantages over the other main methods. 展开更多
关键词 time-VARYING BANDPASS Filter (TVBF) HILBERT Tranform ASSISTED signal AM-FM Component time-FREQUENCY Distribution (TFD)
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Short-time Lv transform and its application for non-linear FM signal detection 被引量:1
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作者 Shan Luo Xiumei Li Guoan Bi 《Journal of Systems Engineering and Electronics》 SCIE EI CSCD 2015年第6期1159-1168,共10页
A new time-frequency transform, known as short-time Lv transform (STLVT), is proposed by applying the inverse Lv distribution to process consecutive segments of long data sequence. Compared with other time-frequency... A new time-frequency transform, known as short-time Lv transform (STLVT), is proposed by applying the inverse Lv distribution to process consecutive segments of long data sequence. Compared with other time-frequency representations, the STLVT is able to achieve better energy concentration in the time-frequency domain for signals containing multiple linear and/or non-linear frequency modulated components. The merits of the STLVT are demonstrated in terms of the effects of window length and overlap length between adjacent segments on signal energy concentration in the time-frequency domain, and the required computational complexity. An application on the spectrum sensing for cognitive ratio (CR) by using a joint use of the STLVT and Hough transform (HT) is proposed and simulated. 展开更多
关键词 Lv distribution time-frequency transform frequencymodulated signal spectrum sensing.
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Optimization of Crosswalk Width Based on Bi-Directional Pedestrian Crossing Time at Signalized Intersections
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作者 Ningbo Cao Yongheng Chen +3 位作者 Zhaowei Qu Liying Zhao Yanfei Li Qiujie Yang 《Journal of Beijing Institute of Technology》 EI CAS 2018年第2期285-292,共8页
The effects of the interactions between bi-directional pedestrians on the crossing time and the crosswalk width are studied. Firstly,the crossing process of bi-directional pedestrians is analyzed.The total crosswalk t... The effects of the interactions between bi-directional pedestrians on the crossing time and the crosswalk width are studied. Firstly,the crossing process of bi-directional pedestrians is analyzed.The total crosswalk time is divided into a discharge time and a crossing time. The interactions between bi-directional pedestrians are quantified with the drag force theory. Then,a model is developed to study the crossing time based on the kinetic energy theory and momentum theory. Subsequently,the related parameters of the proposed model are calibrated with observed information. The relationships among crosswalk width,signal time,pedestrian volume and level of service are simulated with the proposed model. The results are verified and compared with other models. The proposed model has an absolute value of relative error of 9. 38%,which is smaller than that of the Alhajyaseen model( 15. 26%) and Highway Capacity Manual( HCM) model( 12. 42%). Finally,suggested crosswalk widths at different conditions are successfully estimated with the proposed crossing time model. 展开更多
关键词 signalized crosswalks bi-directional pedestrian drag force theory crossing time cross-walk width
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Non-Stationary Signal Segmentation and Separation from Joint Time-Frequency Plane
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作者 Abdullah Ali Alshehri 《Journal of Signal and Information Processing》 2012年第3期339-343,共5页
Multi-components sinusoidal engineering signals who are non-stationary signals were considered in this study since their separation and segmentations are of great interests in many engineering fields. In most cases, t... Multi-components sinusoidal engineering signals who are non-stationary signals were considered in this study since their separation and segmentations are of great interests in many engineering fields. In most cases, the segmentation of non-stationary or multi-component signals is conducted in time domain. In this paper, we explore the advantages of applying joint time-frequency (TF) distribution of the multi-component signals to identify their segments. The Spectrogram that is known as Short-Time Fourier Transform (STFT) will be used for obtaining the time-frequency kernel. Time marginal of the computed kernel is optimally used for the signal segmentation. In order to obtain the desirable segmentation, it requires first to improve time marginal of the kernel by using two-dimensional Wiener mask filter applied to the TF kernel to mitigate and suppress non-stationary noise or interference. Additionally, a proper choice of the sliding window and its overlaying has enhanced our scheme to capture the discontinuities corresponding to the boundaries of the candidate segments. 展开更多
关键词 signal Segmentation time-FREQUENCY Distribution Short-time FOURIER TRANSFORM NON-STATIONARY WIENER MASKING
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X-ray pulsar signal detection using photon interarrival time
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作者 Qiang Xie Luping Xu Hua Zhang 《Journal of Systems Engineering and Electronics》 SCIE EI CSCD 2013年第6期899-905,共7页
The distribution probability of the photon interarrival time (PIT) without signal initial phases is derived based on the Poisson model of X-ray pulsar signals, and a pulsar signal detection algorithm employing the P... The distribution probability of the photon interarrival time (PIT) without signal initial phases is derived based on the Poisson model of X-ray pulsar signals, and a pulsar signal detection algorithm employing the PIT sequence is put forward. The joint probability of the PIT sequence is regarded as a function of the distribution probability and used to compare a constant radiation intensity model with the nonhomogeneous Poisson model for the signal detection. The relationship between the number of detected photons and the probabilities of false negative and positive is studied, and the success rate and mean detection time are estimated based on the number of the given photons. For the spacecraft velocity data detection, the changes of time of photon arrival (TOPA) and PIT caused by spacecraft motion are presented first, then the influences on detection are analyzed respectively. By using the analytical pulse profile of PSR B0531+21, the simulation of the Xray pulsar signal detection is implemented. The simulation results verify the effectiveness of the proposed method, and the contrast tests show that the proposed method is suitable for the spacecraft velocity data detection. 展开更多
关键词 pulsar signal detection photon interarrival time (PIT) Poisson model
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Early detection of sudden cardiac death by using classical linear techniques and time-frequency methods on electrocardiogram signals 被引量:2
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作者 Elias Ebrahimzadeh Mohammad Pooyan 《Journal of Biomedical Science and Engineering》 2011年第11期699-706,共8页
Early detection of sudden cardiac death may be used for surviving the life of cardiac patients. In this paper we have investigated an algorithm to detect and predict sudden cardiac death, by processing of heart rate v... Early detection of sudden cardiac death may be used for surviving the life of cardiac patients. In this paper we have investigated an algorithm to detect and predict sudden cardiac death, by processing of heart rate variability signal through the classical and time-frequency methods. At first, one minute of ECG signals, just before the cardiac death event are extracted and used to compute heart rate variability (HRV) signal. Five features in time domain and four features in frequency domain are extracted from the HRV signal and used as classical linear features. Then the Wigner Ville transform is applied to the HRV signal, and 11 extra features in the time-frequency (TF) domain are obtained. In order to improve the performance of classification, the principal component analysis (PCA) is applied to the obtained features vector. Finally a neural network classifier is applied to the reduced features. The obtained results show that the TF method can classify normal and SCD subjects, more efficiently than the classical methods. A MIT-BIH ECG database was used to evaluate the proposed method. The proposed method was implemented using MLP classifier and had 74.36% and 99.16% correct detection rate (accuracy) for classical features and TF method, respectively. Also, the accuracy of the KNN classifier were 73.87% and 96.04%. 展开更多
关键词 SUDDEN CARDIAC DEATH Heart Rate Variability time-FREQUENCY Transform ELECTROCARDIOGRAM signal Linear Processing
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PHASE RETRIEVAL OF TIME-LIMITED SIGNALS
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作者 付应雄 李落清 《Acta Mathematica Scientia》 SCIE CSCD 2010年第1期39-46,共8页
The problem of reconstructing a signalφ(x) from its magnitude |φ(x)] isof considerable interest to engineers and physicists. This article concerns the problem of determining a time-limited signal f with period ... The problem of reconstructing a signalφ(x) from its magnitude |φ(x)] isof considerable interest to engineers and physicists. This article concerns the problem of determining a time-limited signal f with period 2π when |f(eix)l is known for x∈[-π,π]. It is shown that the conditions |g(eix)| = |f(eix)| and |g(ci(x+b)) -g(eix)| =f(ei(x+b)) - f(eix)|, b ≠ 27π, together imply that either g = wf or g = v f, where both w and v have period b. Furthermore, if b/2π is irrational then the functions w and v b is rational then w takes the form reduce to some constants c1 and c2, respectively; ifb/2π is rational then w takes the form w=elexB1(e1x)B2(elx)and v takes the form ei(x2πN/b+a)B1(elx)B2(elx),where B1 and B2 are Blaschke products. 展开更多
关键词 phase retrieval time-limited signal Blaschke product Hardy space on theunit circle
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Stochastic resonance in a time-delayed asymmetric bistable system with mixed periodic signal 被引量:1
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作者 郭永峰 徐伟 王亮 《Chinese Physics B》 SCIE EI CAS CSCD 2010年第4期90-95,共6页
This paper studies the phenomenon of stochastic resonance in an asymmetric bistable system with time-delayed feedback and mixed periodic signal by using the theory of signal-to-noise ratio in the adiabatic limit. A ge... This paper studies the phenomenon of stochastic resonance in an asymmetric bistable system with time-delayed feedback and mixed periodic signal by using the theory of signal-to-noise ratio in the adiabatic limit. A general approximate Fokker-Planck equation and the expression of the signal-to-noise ratio are derived through the small time delay approximation at both fundamental harmonics and mixed harmonics. The effects of the additive noise intensity Q, multiplicative noise intensity D, static asymmetry r and delay time T on the signal-to-noise ratio are discussed. It is found that the higher mixed harmonics and the static asymmetry r can restrain stochastic resonance, and the delay time τ can enhance stochastic resonance. Moreover, the longer the delay time τ is, the larger the additive noise intensity Q and the multiplicative noise intensity D are, when the stochastic resonance appears. 展开更多
关键词 stochastic resonance time-delayed feedback mixed periodic signal signal-to-noise ratio
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Signal Travel Time Anomaly between Earth and Solar Planets
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作者 Faiçal Ramdani 《Journal of High Energy Physics, Gravitation and Cosmology》 2021年第4期1472-1476,共5页
Travel time anomaly in the communicatin of spatial instruments installed in solar planets and Earth are investigated in a model of gravity impact on radio signal propagation. Resulting travel times anomaly shows varia... Travel time anomaly in the communicatin of spatial instruments installed in solar planets and Earth are investigated in a model of gravity impact on radio signal propagation. Resulting travel times anomaly shows variations less than 10<sup>-3</sup> seconds to and from Venus and Mars while Sun provides anomaly travel times of about -2 × 10<sup>-2</sup> sec as backward signal needs more times than emitted signal from Earth. In the current explorations on Mars, the travel time anomaly may reach 1.8 × 10<sup>-4</sup> sec as orbital Mars position pass through its minimum distance with respect to Earth. Implications of the difference between one and two-way travel times may be related to redshift/blueshift while travel time of received signal is less or greater than emitted signal. 展开更多
关键词 Radio signal Travel times GRAVITY Solar Planets REDSHIFT
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Low-Power Operational Amplifier for Real-Time Signal Processing System of Micro Air Vehicle
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作者 王竹萍 仲顺安 聂丹丹 《Journal of Beijing Institute of Technology》 EI CAS 2010年第3期353-356,共4页
A low-power complementary metal oxide semiconductor(CMOS) operational amplifier (op-amp) for real-time signal processing of micro air vehicle (MAV) is designed in this paper.Traditional folded cascode architectu... A low-power complementary metal oxide semiconductor(CMOS) operational amplifier (op-amp) for real-time signal processing of micro air vehicle (MAV) is designed in this paper.Traditional folded cascode architecture with positive channel metal oxide semiconductor(PMOS) differential input transistors and sub-threshold technology are applied under the low supply voltage.Simulation results show that this amplifier has significantly low power,while maintaining almost the same gain,bandwidth and other key performances.The power required is only 0.12 mW,which is applicable to low-power and low-voltage real-time signal acquisition and processing system. 展开更多
关键词 microelectromechanical system(MEMS) operational amplifier(op-amp) LOW-POWER real-time signal processing system micro air vehicle(MAV)
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