Empirical and deterministic models have not proven to be effective in path loss predictions because of the problems of computational complexities, low accuracies, and inability to generalize. To solve these problems r...Empirical and deterministic models have not proven to be effective in path loss predictions because of the problems of computational complexities, low accuracies, and inability to generalize. To solve these problems relating to path loss predictions, this article presents an optimal path loss propagation model developed at 3.4 GHz with the use of fuzzy logic. We introduced Fuzzy logic to accurately represent all forms of uncertainties in the data spectrum as the signal propagates from the transceiver to the receiver, thereby producing accurate results. Experimental data were collected across Cyprus at 3.4 GHz and compared with three existing path loss models. The fuzzy-logic path loss prediction model was then developed and compared with the experimental data and with each of the theoretical empirical models, the newly developed model predicted signal loss with the greatest accuracy as it gives the lowest root-mean-square error. The newly developed model is very efficient for signal propagation and path loss prediction.展开更多
Rolling element bearings are key components of mechanical equipment. The bearing fault characteristics are a ected by the interaction in the vibration signals. The low harmonics of the bearing characteristic frequenci...Rolling element bearings are key components of mechanical equipment. The bearing fault characteristics are a ected by the interaction in the vibration signals. The low harmonics of the bearing characteristic frequencies cannot be usually observed in the Fourier spectrum. The frequency loss in the bearing vibration signal is presented through two independent experiments in this paper. The existence of frequency loss phenomenon in the low frequencies, side band frequencies and resonant frequencies and revealed. It is demonstrated that the lost frequencies are actually suppressed by the internal action in the bearing fault signal rather than the external interference. The amplitude and distribution of the spectrum are changed due to the interaction of the bearing fault signal. The interaction mechanism of bearing fault signal is revealed through theoretical and practical analysis. Based on mathematical morphology, a new method is provided to recover the lost frequencies. The multi-resonant response signal of the defective bearing are decomposed into low frequency and high frequency response, and the lost frequencies are recovered by the combination morphological filter(CMF). The e ectiveness of the proposed method is validated on simulated and experimental data.展开更多
Passive radar detects moving targets by Cross Ambiguity Function (CAF), which is based on the cross correlation process of the direct-path signal in reference channel and echo signal in receive channel. Thus, the perf...Passive radar detects moving targets by Cross Ambiguity Function (CAF), which is based on the cross correlation process of the direct-path signal in reference channel and echo signal in receive channel. Thus, the performance of direct-path signal is important to system performance for this type of radar. While the Signal to Noise Ratio (SNR) of direct-path signal is low, it will deteriorate the detection performance. In this paper, how SNR of direct-path signal induces degradation on the SNR of CAF, and how the integration gain affects by integration time are analyzed, both with theoretical analysis and numerical simulation, which are valuable for the R&D of passive radar.展开更多
Fluorescence loss spectrum for detecting cold Rydberg atoms with high sensitivity has been obtained based on lock-in detection of fluorescence of 6 P3/2 state when cooling lasers of the magneto-optical trap are modula...Fluorescence loss spectrum for detecting cold Rydberg atoms with high sensitivity has been obtained based on lock-in detection of fluorescence of 6 P3/2 state when cooling lasers of the magneto-optical trap are modulated.The experiment results show that the signal to noise ratio has been improved by 32.64 dB when the modulation depth(converted to laser frequency)and frequency are optimized to 4 MHz and 6 kHz,respectively.This technique enables us to perform a highly sensitive non-destructive detection of Rydberg atoms.展开更多
This paper is devoted to the study of polarization properties, scattering properties and propagation properties of global positioning system （GPS） scattering signal over the rough sea surface. To investigate the pol...This paper is devoted to the study of polarization properties, scattering properties and propagation properties of global positioning system （GPS） scattering signal over the rough sea surface. To investigate the polarization and the scattering properties, the scattering field and the bistatic scattering coefficient of modified Kirchhoff approximation using the tapered incident wave is derived in detail. In modeling the propagation properties of the GPS scattering signal in the evaporation duct, the initial field of parabolic equation traditionally computed by the antenna pattern using fast Fourier transform （FFT） is replaced by the GPS scattering field. And the propagation properties of the GPS scattering signal in the evaporation duct with different evaporation duct heights and elevation angles of GPS are discussed by the improved discrete mixed Fourier transform taking into account the sea surface roughness.展开更多
In recent years, we have been able to use various services using the position information of smartphones and tablets. In addition, research on intelligent transport systems (ITS) has been actively conducted. To consid...In recent years, we have been able to use various services using the position information of smartphones and tablets. In addition, research on intelligent transport systems (ITS) has been actively conducted. To consider reducing traffic accidents by exchanging position information between pedestrians and vehicles by vehicle-to-pedestrian communication, we require accurate position information for pedestrians and vehicles. The GPS (global positioning system) is the most widely used method for acquiring position information. However, in urban areas, the GPS signal is affected by the surrounding buildings, which increases the positioning error. In this study, a method to improve the positioning accuracy of pedestrians using the signal strengths from vehicles and beacons was proposed. First, a Kalman filter was applied to the signal strength. Then, the path loss index was dynamically calculated using vehicle-to-vehicle communication. Finally, the position of a pedestrian was obtained using weighted centroid localization (WCL) after filtering the nodes. The positioning accuracy was evaluated using a simulator and demonstrated the superiority of the proposed method.展开更多
The Wnt/β-catenin signaling pathway plays a crucial role in neural development, axonal guid- ance, neuropathic pain remission and neuronal survival. In this study, we initially examined the effect of rapamycin on the...The Wnt/β-catenin signaling pathway plays a crucial role in neural development, axonal guid- ance, neuropathic pain remission and neuronal survival. In this study, we initially examined the effect of rapamycin on the Wnt/β-catenin signaling pathway after spinal cord iniury, by intraperitoneally injecting spinal cord injured rats with rapamycin over 2 days. Western blot analysis and immunofluorescence staining were used to detect the expression levels of β-catenin protein, caspase-3 protein and brain-derived neurotrophic factor protein, components of the Wnt/β-catenin signaling pathway. Rapamycin increased the levels of β-catenin and brain-derived neurotrophic factor in the injured spinal cord, improved the pathological morphology at the injury site, reduced the loss of motor neurons, and promoted motor functional recovery in rats after spinal cord injury. Our experimental fndings suggest that the neuroprotective effect of rapamycin intervention is mediated through activation of the Wnt/β-catenin signaling pathway after spinal cord injury.展开更多
文摘Empirical and deterministic models have not proven to be effective in path loss predictions because of the problems of computational complexities, low accuracies, and inability to generalize. To solve these problems relating to path loss predictions, this article presents an optimal path loss propagation model developed at 3.4 GHz with the use of fuzzy logic. We introduced Fuzzy logic to accurately represent all forms of uncertainties in the data spectrum as the signal propagates from the transceiver to the receiver, thereby producing accurate results. Experimental data were collected across Cyprus at 3.4 GHz and compared with three existing path loss models. The fuzzy-logic path loss prediction model was then developed and compared with the experimental data and with each of the theoretical empirical models, the newly developed model predicted signal loss with the greatest accuracy as it gives the lowest root-mean-square error. The newly developed model is very efficient for signal propagation and path loss prediction.
基金Supported by National Natural Science Foundation of China(Grant Nos.51675178,51475164)
文摘Rolling element bearings are key components of mechanical equipment. The bearing fault characteristics are a ected by the interaction in the vibration signals. The low harmonics of the bearing characteristic frequencies cannot be usually observed in the Fourier spectrum. The frequency loss in the bearing vibration signal is presented through two independent experiments in this paper. The existence of frequency loss phenomenon in the low frequencies, side band frequencies and resonant frequencies and revealed. It is demonstrated that the lost frequencies are actually suppressed by the internal action in the bearing fault signal rather than the external interference. The amplitude and distribution of the spectrum are changed due to the interaction of the bearing fault signal. The interaction mechanism of bearing fault signal is revealed through theoretical and practical analysis. Based on mathematical morphology, a new method is provided to recover the lost frequencies. The multi-resonant response signal of the defective bearing are decomposed into low frequency and high frequency response, and the lost frequencies are recovered by the combination morphological filter(CMF). The e ectiveness of the proposed method is validated on simulated and experimental data.
文摘Passive radar detects moving targets by Cross Ambiguity Function (CAF), which is based on the cross correlation process of the direct-path signal in reference channel and echo signal in receive channel. Thus, the performance of direct-path signal is important to system performance for this type of radar. While the Signal to Noise Ratio (SNR) of direct-path signal is low, it will deteriorate the detection performance. In this paper, how SNR of direct-path signal induces degradation on the SNR of CAF, and how the integration gain affects by integration time are analyzed, both with theoretical analysis and numerical simulation, which are valuable for the R&D of passive radar.
基金Project supported by the National Key Research and Development Program of China(Grant Nos.2017YFA0304203 and 2016YFF0200104)the National Natural Science Foundation of China(Grant Nos.61505099,61827824,91536110,and 61975104)the Fund for Shanxi ‘1331 Project’ Key Subjects Construction,Bairen Project of Shanxi Province,China
文摘Fluorescence loss spectrum for detecting cold Rydberg atoms with high sensitivity has been obtained based on lock-in detection of fluorescence of 6 P3/2 state when cooling lasers of the magneto-optical trap are modulated.The experiment results show that the signal to noise ratio has been improved by 32.64 dB when the modulation depth(converted to laser frequency)and frequency are optimized to 4 MHz and 6 kHz,respectively.This technique enables us to perform a highly sensitive non-destructive detection of Rydberg atoms.
基金Project supported by the National Natural Science Foundation of China (Grant No. 60971067)the Specialized Research Fund for the Doctoral Program of Higher Education,China (Grant No. 20070701010)
文摘This paper is devoted to the study of polarization properties, scattering properties and propagation properties of global positioning system （GPS） scattering signal over the rough sea surface. To investigate the polarization and the scattering properties, the scattering field and the bistatic scattering coefficient of modified Kirchhoff approximation using the tapered incident wave is derived in detail. In modeling the propagation properties of the GPS scattering signal in the evaporation duct, the initial field of parabolic equation traditionally computed by the antenna pattern using fast Fourier transform （FFT） is replaced by the GPS scattering field. And the propagation properties of the GPS scattering signal in the evaporation duct with different evaporation duct heights and elevation angles of GPS are discussed by the improved discrete mixed Fourier transform taking into account the sea surface roughness.
文摘In recent years, we have been able to use various services using the position information of smartphones and tablets. In addition, research on intelligent transport systems (ITS) has been actively conducted. To consider reducing traffic accidents by exchanging position information between pedestrians and vehicles by vehicle-to-pedestrian communication, we require accurate position information for pedestrians and vehicles. The GPS (global positioning system) is the most widely used method for acquiring position information. However, in urban areas, the GPS signal is affected by the surrounding buildings, which increases the positioning error. In this study, a method to improve the positioning accuracy of pedestrians using the signal strengths from vehicles and beacons was proposed. First, a Kalman filter was applied to the signal strength. Then, the path loss index was dynamically calculated using vehicle-to-vehicle communication. Finally, the position of a pedestrian was obtained using weighted centroid localization (WCL) after filtering the nodes. The positioning accuracy was evaluated using a simulator and demonstrated the superiority of the proposed method.
基金supported by grants from the National Natural Science Foundation of China,No.81171799,81471854a Special Financial Grant from the China Postdoctoral Science Foundation,No.2013T60948
文摘The Wnt/β-catenin signaling pathway plays a crucial role in neural development, axonal guid- ance, neuropathic pain remission and neuronal survival. In this study, we initially examined the effect of rapamycin on the Wnt/β-catenin signaling pathway after spinal cord iniury, by intraperitoneally injecting spinal cord injured rats with rapamycin over 2 days. Western blot analysis and immunofluorescence staining were used to detect the expression levels of β-catenin protein, caspase-3 protein and brain-derived neurotrophic factor protein, components of the Wnt/β-catenin signaling pathway. Rapamycin increased the levels of β-catenin and brain-derived neurotrophic factor in the injured spinal cord, improved the pathological morphology at the injury site, reduced the loss of motor neurons, and promoted motor functional recovery in rats after spinal cord injury. Our experimental fndings suggest that the neuroprotective effect of rapamycin intervention is mediated through activation of the Wnt/β-catenin signaling pathway after spinal cord injury.
