This paper addresses the performance degradation issue in a fast radio burst search pipeline based on deep learning.This issue is caused by the class imbalance of the radio frequency interference samples in the traini...This paper addresses the performance degradation issue in a fast radio burst search pipeline based on deep learning.This issue is caused by the class imbalance of the radio frequency interference samples in the training dataset,and one solution is applied to improve the distribution of the training data by augmenting minority class samples using a deep convolutional generative adversarial network.Experi.mental results demonstrate that retraining the deep learning model with the newly generated dataset leads to a new fast radio burst classifier,which effectively reduces false positives caused by periodic wide-band impulsive radio frequency interference,thereby enhancing the performance of the search pipeline.展开更多
Radio interferometric imaging samples visibility data in the spatial frequency domain and then reconstructs the image.Because of the limited number of antennas,the sampling is usually sparse and noisy.Compressed sensi...Radio interferometric imaging samples visibility data in the spatial frequency domain and then reconstructs the image.Because of the limited number of antennas,the sampling is usually sparse and noisy.Compressed sensingbased on convex optimization is an effective reconstruction method for sparse sampling conditions.The hyperparameter for the l_(1)regularization term is an important parameter that directly affects the quality of the reconstructed image.If its value is too high,the image structure will be missed.If its value is too low,the image will have a low signal-to-noise ratio.The selection of hyperparameters under different levels of image noise is studied in this paper,and solar radio images are used as examples to analyze the optimization results of compressed sensing algorithms under different noise conditions.The simulation results show that when the salt-and-pepper noise density is between 10%and 30%,the compressed sensing algorithm obtains good reconstruction results.Moreover,the optimal hyperparameter value has a linear relationship with the noise density,and the mean squared error of regression is approximately 8.10×10^(-8).展开更多
BACKGROUND Aging is an inevitable aspect of human life,characterized by the gradual decline in the function of individual cells and structural components,including bones,muscles,and ligaments.AIM To evaluate the clini...BACKGROUND Aging is an inevitable aspect of human life,characterized by the gradual decline in the function of individual cells and structural components,including bones,muscles,and ligaments.AIM To evaluate the clinical effects of radiofrequency technology in treating facial skin wrinkles and laxity.METHODS This study included 60 female patients,aged 36-58 years(mean age 47.71±1.56 years),who received focused radiofrequency technology treatment for facial wrinkles and laxity in the Department of Medical Cosmetology at our hospital between January 2021 and June 2022.Each patient underwent three treatment sessions,one every two months.Facial photographs were taken before treatment and one week after the final session.A single physician assessed wrinkle severity using a standardized wrinkle severity scale,and patients completed a satisfaction questionnaire one week after the last treatment.RESULTS After three consecutive radiofrequency treatments,performed every two months,patients exhibited significantly reduced wrinkles and skin laxity compared to baseline.One week after the third treatment,the mean facial wrinkle severity score had significantly decreased from 3.00±0.79 to 2.71±0.47(t=2.58,P<0.05).Additionally,88.24%of patients reported noticeable improvements in facial wrinkles and skin laxity.No serious adverse reactions occurred during or follow-ing treatment.CONCLUSION Radiofrequency technology demonstrates significant clinical efficacy in improving facial skin wrinkles and laxity.展开更多
The integration of cognitive radio and energy has enhanced the utilization efficiency of the spectrum and promoted the application of green energy.To begin with,this paper presents the architecture of green energy-eff...The integration of cognitive radio and energy has enhanced the utilization efficiency of the spectrum and promoted the application of green energy.To begin with,this paper presents the architecture of green energy-efficient communication and network models.It incorporates the distributed network model and the heterogeneous two-tier network model into the green cognitive radio power control and channel allocation model.The primary focus of this research lies in energy conservation at the physical layer.To mitigate the interference with primary users and address the peak constraint in secondary user power allocation,the article analyzes the system model of the cognitive radio network and subsequently elaborates on the dynamic throughput maximization allocation algorithm.Eventually,through experimental analysis and verification,the distinctiveness and comprehensiveness of the optimal power control for this subject are illustrated.展开更多
Radio environment plays an important role in radio astronomy observations.Further analysis is needed on the time and intensity distributions of interference signals for long-term radio environment monitoring.Sample va...Radio environment plays an important role in radio astronomy observations.Further analysis is needed on the time and intensity distributions of interference signals for long-term radio environment monitoring.Sample variance is an important estimate of the interference signal decision threshold.Here,we propose an improved algorithm for calculating data sample variance relying on four established statistical methods:the variance of the trimmed data,winsorized sample variance,median absolute deviation,and median of the trimmed data pairwise averaged squares method.The variance and decision threshold in the protected section of the radio astronomy L-band are calculated.Among the four methods,the improved median of the trimmed data pairwise averaged squares algorithm has higher accuracy,but in a comparison of overall experimental results,the cleanliness rate of all algorithms is above 96%.In a comparison between the improved algorithm and the four methods,the cleanliness rate of the improved algorithm is above 98%,verifying its feasibility.The time-intensity interference distribution in the radio protection band is also obtained.Finally,we use comprehensive monitoring data of radio astronomy protection bands,radio interference bands,and interfered frequency bands to establish a comprehensive evaluation system for radio observatory sites,including the observable time proportion in the radio astronomy protection band,the occasional time-intensity distribution in the radio interference frequency band,and the intensity distribution of the interfered frequency band.展开更多
With the exponential growth of mobile terminals and the widespread adoption of Internet of Things(IoT)technologies,an increasing number of devices rely on wireless local area networks(WLAN)for data transmission.To add...With the exponential growth of mobile terminals and the widespread adoption of Internet of Things(IoT)technologies,an increasing number of devices rely on wireless local area networks(WLAN)for data transmission.To address this demand,deploying more access points(APs)has become an inevitable trend.While this approach enhances network coverage and capacity,it also exacerbates co-channel interference(CCI).The multi-AP cooperation introduced in IEEE 802.11be(Wi-Fi 7)represents a paradigm shift from conventional single-AP architectures,offering a novel solution to CCI through joint resource scheduling across APs.However,designing efficient cooperation mechanisms and achieving optimal resource allocation in dense AP environment remain critical research challenges.To mitigate CCI in high-density WLANs,this paper proposes a radio resource allocation method based on 802.11be multi-AP cooperation.First,to reduce the network overhead associated with centralized AP management,we introduce a distributed interference-aware AP clustering method that groups APs into cooperative sets.Second,methods for multi-AP cooperation information exchange,and cooperation transmission processes are designed.To support network state collection,capability advertisement,and cooperative trigger execution at the protocol level,this paper enhances the 802.11 frame structure with dedicated fields for multi-AP cooperation.Finally,considering the mutual influence between power and channel allocation,this paper proposes a joint radio resource allocation algorithm that employs an enhanced genetic algorithm for resource unit(RU)allocation and Q-learning for power control,interconnected via an inner-outer dual-loop architecture.Simulation results demonstrate the effectiveness of the proposed CCI avoidance mechanism and radio resource allocation algorithm in enhancing throughput in dense WLAN scenarios.展开更多
Earth-based deep space radar studies celestial bodies by both transmitting and receiving radio waves,whereas radio telescopes only work passively.On the operational level,radar missions use only short observation time...Earth-based deep space radar studies celestial bodies by both transmitting and receiving radio waves,whereas radio telescopes only work passively.On the operational level,radar missions use only short observation times,which leaves a large portion of the time available for astronomical observations.However,the design principles used for radar and radio telescopes differ.Technical challenges are involved in making the instruments required to meet the requirements of these two applications simultaneously.In this study,we have attempted to tune a deep space radar system for use in radio astronomical applications and conducted a successful pulsar observation,thus demonstrating the feasibility of using radar systems,particularly distributed deep space radar,to perform astronomical research.Additionally,given the limited astronomical capacity available within the observed frequency range,this system has the potential to contribute to the long-term monitoring of specific radio sources.This work represents the first successful attempt to use an Earth-based deep space radar system to perform radio astronomy in China.We also discuss the challenges of tuning a built radar system for astronomical observation applications and propose recommendations for the design of future large-scale distributed deep space radar systems with innate astronomical capabilities.展开更多
The E_(s) layer is a thin layer that concentrates metallic ions in the mesosphere and lower thermosphere(MLT)region.When it occurs,it can affect the performance of the Global Navigation Satellite System and high/very ...The E_(s) layer is a thin layer that concentrates metallic ions in the mesosphere and lower thermosphere(MLT)region.When it occurs,it can affect the performance of the Global Navigation Satellite System and high/very high frequency(HF/VHF)radio communications.Previous studies mainly focused on the one-dimensional structure of E_(s) layer in the vertical direction.However,due to the limitation of observations,the horizontal structure of E_(s) layers is not yet fully understood.This study investigated the horizontal structure of E_(s) layers using amateur radio data in the European sector during the summer of 2020.Statistical analysis shows that the horizontal structure of E_(s) layer is mainly elongated in the east-west direction.In addition,we investigated the dynamics of the E_(s) layers,which primarily propagates in the northeast-southwest direction with a speed of 50-200 m/s.The results provide us a way for obtaining the horizontal structure and dynamic features of E_(s) layers,which can help improve our understanding of the formation and evolution of E_(s) layers.展开更多
Exploring solid propellants for electric thrusters can simplify the propellant storage and supply units in propulsion systems.In this study,polytetrafluoroethylene(PTFE),commonly used as a propellant in pulsed plasma ...Exploring solid propellants for electric thrusters can simplify the propellant storage and supply units in propulsion systems.In this study,polytetrafluoroethylene(PTFE),commonly used as a propellant in pulsed plasma thrusters,was embedded in the discharge chamber of a radio frequency ion thruster(RIT-4)to investigate the performance of an ablation-type RIT.Experimental results indicate that PTFE can decompose and ionize stably under plasma ablation within the discharge chamber,producing-C-F-and F-ion clusters that form a stable plasma.By adjusting the length of the PTFE propellant,it was observed that its decomposition rate influences the ion beam current of the thruster.Compared with xenon,PTFE generates an ion plume with a larger divergence angle,ranging from 16.05°to 22.74°at an ion beam current of 25 mA,with a floating potential distribution of 8‒56 V.Assuming that the proportion of neutral gas in the vacuum chamber matches the ion species ratio in the ion plume,thrust,specific impulse and efficiency parameters were calculated for the RIT-4 with embedded PTFE.Under 50 W RF power,the thrust was approximately 1.02 mN,the specific impulse was around 1236 s and the power-to-thrust ratio was approximately 93.14 W/mN.All results indicate that PTFE is a viable propellant for RIT,but the key is to control the rate of decomposition.展开更多
The 6G smart Fog Radio Access Network(F-RAN)is an integration of 6G network intelligence technologies and the F-RAN architecture.Its aim is to provide low-latency and high-performance services for massive access devic...The 6G smart Fog Radio Access Network(F-RAN)is an integration of 6G network intelligence technologies and the F-RAN architecture.Its aim is to provide low-latency and high-performance services for massive access devices.However,the performance of current 6G network intelligence technologies and its level of integration with the architecture,along with the system-level requirements for the number of access devices and limitations on energy consumption,have impeded further improvements in the 6G smart F-RAN.To better analyze the root causes of the network problems and promote the practical development of the network,this study used structured methods such as segmentation to conduct a review of the topic.The research results reveal that there are still many problems in the current 6G smart F-RAN.Future research directions and difficulties are also discussed.展开更多
Heating mechanism in the solar atmosphere(from chromosphere to corona)is one of the top-challenges in modern astronomy.The classic mechanisms can be divided into two categories:wave heating(W)and magnetic reconnection...Heating mechanism in the solar atmosphere(from chromosphere to corona)is one of the top-challenges in modern astronomy.The classic mechanisms can be divided into two categories:wave heating(W)and magnetic reconnection heating(X).Both of them still face some problems currently difficult to overcome.Recently,we proposed a new mechanism,called magnetic-gradient pumping heating(MGP,or P)which seems to overcome those difficulties,but still lacks sufficient observational evidence.Which one really explained the physics of hot corona exactly?How can observations be used to identify and verify the heating mechanism?Since different heating mechanisms will generate non-thermal particles from different accelerations and experience different propagations,they will have different responses in the broadband spectral radio observations.Among them,the non-thermal electrons from W mechanisms are closely related to shock-wave acceleration,and their radio response should be a group of spike bursts with random distribution of drifting rates;the non-thermal electrons from X mechanisms are accelerated by reconnecting electric field with bidirectional flow,and their radio response should be type III pairs or spike pairs;P mechanism will produce energetic particle upflows,and their radio response should be unidirectional fiber bursts with moderate negative drifting rates.Therefore,the heating mechanism can be identified and verified from the broadband dynamic spectral radio observations.Additionally,using high-resolution radioheliographs and spectral-imaging observations,the heating mechanisms in different regions can be identified and verified separately,thereby demonstrating the physical essence of the hot corona.展开更多
The 21 cm radiation of neutral hydrogen provides crucial information for studying the early universe and its evolution.To advance this research,countries have made significant investments in constructing large lowfreq...The 21 cm radiation of neutral hydrogen provides crucial information for studying the early universe and its evolution.To advance this research,countries have made significant investments in constructing large lowfrequency radio telescope arrays,such as the Low Frequency Array and the Square Kilometre Array Phase 1 Low Frequency.These instruments are pivotal for radio astronomy research.However,challenges such as ionospheric plasma interference,ambient radio noise,and instrument-related effects have become increasingly prominent,posing major obstacles in cosmology research.To address these issues,this paper proposes an efficient signal processing method that combines wavelet transform and mathematical morphology.The method involves the following steps:Background Subtraction:Background interference in radio observation signals is eliminated.Wavelet Transform:The signal,after removing background noise,undergoes a two-dimensional discrete wavelet transform.Threshold processing is then applied to the wavelet coefficients to effectively remove interference components.Wavelet Inversion:The processed signal is reconstructed using wavelet inversion.Mathematical Morphology:The reconstructed signal is further optimized using mathematical morphology to refine the results.Experimental verification was conducted using solar observation data from the Xinjiang Observatory and the Yunnan Observatory.The results demonstrate that this method successfully removes interference signals while preserving useful signals,thus improving the accuracy of radio astronomy observations and reducing the impact of radio frequency interference.展开更多
Solar radio burst(SRB)is one of the main natural interference sources of Global Positioning System(GPS)signals and can reduce the signal-to-noise ratio(SNR),directly affecting the tracking performance of GPS receivers...Solar radio burst(SRB)is one of the main natural interference sources of Global Positioning System(GPS)signals and can reduce the signal-to-noise ratio(SNR),directly affecting the tracking performance of GPS receivers.In this paper,a tracking algorithm based on the adaptive Kalman filter(AKF)with carrier-to-noise ratio estimation is proposed and compared with the conventional second-order phase-locked loop tracking algo-rithms and the improved Sage-Husa adaptive Kalman filter(SHAKF)algorithm.It is discovered that when the SRBs occur,the improved SHAKF and the AKF with carrier-to-noise ratio estimation enable stable tracking to loop signals.The conven-tional second-order phase-locked loop tracking algorithms fail to track the receiver signal.The standard deviation of the carrier phase error of the AKF with carrier-to-noise ratio estimation out-performs 50.51%of the improved SHAKF algorithm,showing less fluctuation and better stability.The proposed algorithm is proven to show more excellent adaptability in the severe envi-ronment caused by the SRB occurrence and has better tracking performance.展开更多
Radio astronomy necessitates radio frequency bands that are both stable and free from interference at observatory locations.To comprehensively evaluate the radio environment at radio observatories,we employ Monte Carl...Radio astronomy necessitates radio frequency bands that are both stable and free from interference at observatory locations.To comprehensively evaluate the radio environment at radio observatories,we employ Monte Carlo methods to assess the quality of observational data and predict potential interference.With an extensive dataset,we used an algorithm to find the interference threshold within the L-band,automatically identifying disruptive signals.Monte Carlo simulations were conducted to estimate whether these interference signals surpass a predetermined threshold of the total observation period,facilitating a detailed analysis of the interference profile.A Monte Carlo analysis was used on 83 hours of continuous monitoring data using a wireless environment testing system,to forecast the proportion of time during which interference signals would surpass established harmful thresholds.Our findings indicate that,within the L-band spectrum at Fenghuang Hill,Kunming City,Yunnan Province,the incidence of interference within the frequency ranges of 1330–1440 MHz,1610–1613 MHz,and 1660–1670 MHz is acceptably low,with respective confidence levels of 96.9%,97.4%,and 97.4%that the proportion of time these interference signals occupy does not exceed 5%of the total observational time,as stipulated by the International Telecommunication Union.Conversely,the confidence level for the 1718–1722 MHz band not exceeding 5%of the total observational time is significantly lower at 88.5%.This study offers a valuable tool for assessing the radio environment in radio astronomy research and provides a foundational basis for the scientific management and safeguarding of radio frequency bands.展开更多
The science of radio astronomy focuses on the observation and study of celestial objects by reading their radio waves. The 5 meter radio-telescope is able to observe different radio sources using a C-band LNB. This re...The science of radio astronomy focuses on the observation and study of celestial objects by reading their radio waves. The 5 meter radio-telescope is able to observe different radio sources using a C-band LNB. This research was essentially focused on Crab Nebula, also known as Taurus A. The study led to interesting observations, which were validated numerically using various scientific computing software. The radio waves emitted by Taurus A are readable by the RTL-SDR, a software defined radio receiver. This device is capable of reading radio frequencies in the range of 0.5 MHZ to 1700 MHZ.展开更多
We suggest a possible explanation of the influence of pre-seismic activity on the registration rate of natural ELF(extremely low frequency)/VLF(very low frequency) pulses and the changes of their characteristics. The ...We suggest a possible explanation of the influence of pre-seismic activity on the registration rate of natural ELF(extremely low frequency)/VLF(very low frequency) pulses and the changes of their characteristics. The main idea is as follows. The distribution of the electric field around a thundercloud depends on the conductivity profile of the atmosphere. Quasi-static electric fields of a thundercloud decrease in those tropospheric regions where an increase of air conductivity is generated by pre-seismic activities due to emanation of radioactive gas and water into the lower atmosphere. The electric field becomes reduced in the lower troposphere, and the probability decreases of the cloud-to-ground (CG) strokes in such “contaminated” areas. Simultaneously, the electric field grows inside and above the thunderclouds, and hence, we anticipate a growth in the number of horizontal and tilted inter-cloud (or intra-cloud) (both termed as IC discharges) strokes. Spatial orientation of lightning strokes reduces vertical projection of their individual amplitudes, while the rate (median number strokes per a unit time) of discharges grows. We demonstrate that channel tilt of strokes modifies the spectral content of ELF/VLF radio noise and changes the rate of detected pulses during the earthquake preparation phase.展开更多
The corona discharge from transmission lines in high-altitude areas is more severe than at lower altitudes. The radio interference caused thereby is a key factor to be considered when designing transmission lines. To ...The corona discharge from transmission lines in high-altitude areas is more severe than at lower altitudes. The radio interference caused thereby is a key factor to be considered when designing transmission lines. To study the influence of altitude on negative corona characteristics, an experimental platform comprising a movable small corona cage was established: experiments were conducted at four altitudes in the range of 1120-4320 m, and data on the corona current pulse and radio interference level of 0.8-mm diameter fine copper wire under different negative voltages were collected. The experimental results show that the average amplitude, repetition frequency and average current of the corona current pulse increase with increasing altitude. The dispersion of pulse amplitude increases with increase in altitude, while the randomness of the pulse interval decreases continuously. Taking the average current as an intermediate variable,the relationship between radio interference level and altitude is obtained. The result of this research has some significance for understanding the corona discharge characteristics of ultra-highvoltage lines.展开更多
The Shanghai Tianma 65 m radio telescope(TMRT)is a large,fully rotatable radio telescope with multiple scientific purposes.The main body of the telescope and four low-frequency receiving systems,including L,C,and S/X ...The Shanghai Tianma 65 m radio telescope(TMRT)is a large,fully rotatable radio telescope with multiple scientific purposes.The main body of the telescope and four low-frequency receiving systems,including L,C,and S/X bands,were completed between 2008 and 2012.From 2013 to 2017,four high-frequency receiving systems,including Ku,K,Ka,and Q bands,were constructed and their performance was comprehensively tested.There are three main innovations.(1)A fully movable large radio telescope system with advanced performance and complete functions has been built.(2)An advanced,reliable main reflector adjustment system has been completed,overcoming gravity deformation and creating a large antenna with a main reflective surface accuracy of 0.28 mm(root mean square)for any elevation.(3)Five innovative technologies have been developed to achieve high-precision pointing in any direction within 3″.The TMRT has made a crucial contribution to the orbital measurement and positioning of China’s lunar and deep space probes.Significantly enhancing China's ability to participate in international VLBI observations and radio astronomy,this has facilitated a series of achievements in observational radio astronomical research,in areas such as VLBI,spectral lines,and pulsars.展开更多
The identification of intercepted radio fuze modulation types is a prerequisite for decision-making in interference systems.However,the electromagnetic environment of modern battlefields is complex,and the signal-to-n...The identification of intercepted radio fuze modulation types is a prerequisite for decision-making in interference systems.However,the electromagnetic environment of modern battlefields is complex,and the signal-to-noise ratio(SNR)of such environments is usually low,which makes it difficult to implement accurate recognition of radio fuzes.To solve the above problem,a radio fuze automatic modulation recognition(AMR)method for low-SNR environments is proposed.First,an adaptive denoising algorithm based on data rearrangement and the two-dimensional(2D)fast Fourier transform(FFT)(DR2D)is used to reduce the noise of the intercepted radio fuze intermediate frequency(IF)signal.Then,the textural features of the denoised IF signal rearranged data matrix are extracted from the statistical indicator vectors of gray-level cooccurrence matrices(GLCMs),and support vector machines(SVMs)are used for classification.The DR2D-based adaptive denoising algorithm achieves an average correlation coefficient of more than 0.76 for ten fuze types under SNRs of-10 d B and above,which is higher than that of other typical algorithms.The trained SVM classification model achieves an average recognition accuracy of more than 96%on seven modulation types and recognition accuracies of more than 94%on each modulation type under SNRs of-12 d B and above,which represents a good AMR performance of radio fuzes under low SNRs.展开更多
The Tianma 65 m radio telescope(TMRT)at Shanghai is a fully steerable single-dish radio telescope in China,operating at centimeter to millimeter wavelengths(1.25 GHz to 50 GHz).This paper presents details on the main ...The Tianma 65 m radio telescope(TMRT)at Shanghai is a fully steerable single-dish radio telescope in China,operating at centimeter to millimeter wavelengths(1.25 GHz to 50 GHz).This paper presents details on the main specifications,design,performance analysis,testing,and construction of the telescope antenna.The measured total efficiency is better than 50%over the whole elevation angle range,first sidelobe levels are less than−20 dB,antenna system noise temperatures are less than 70 K at 30°elevation angle,and pointing accuracy is less than 3″.The measured and calculated results are in good agreement,verifying the effectiveness of the design and analysis.展开更多
基金supported by the Chinese Academy of Science"Light of West China"Program(2022-XBQNXZ-015)the National Natural Science Foundation of China(11903071)the Operation,Maintenance and Upgrading Fund for Astronomical Telescopes and Facility Instruments,budgeted from the Ministry of Finance of China and administered by the Chinese Academy of Sciences。
文摘This paper addresses the performance degradation issue in a fast radio burst search pipeline based on deep learning.This issue is caused by the class imbalance of the radio frequency interference samples in the training dataset,and one solution is applied to improve the distribution of the training data by augmenting minority class samples using a deep convolutional generative adversarial network.Experi.mental results demonstrate that retraining the deep learning model with the newly generated dataset leads to a new fast radio burst classifier,which effectively reduces false positives caused by periodic wide-band impulsive radio frequency interference,thereby enhancing the performance of the search pipeline.
文摘Radio interferometric imaging samples visibility data in the spatial frequency domain and then reconstructs the image.Because of the limited number of antennas,the sampling is usually sparse and noisy.Compressed sensingbased on convex optimization is an effective reconstruction method for sparse sampling conditions.The hyperparameter for the l_(1)regularization term is an important parameter that directly affects the quality of the reconstructed image.If its value is too high,the image structure will be missed.If its value is too low,the image will have a low signal-to-noise ratio.The selection of hyperparameters under different levels of image noise is studied in this paper,and solar radio images are used as examples to analyze the optimization results of compressed sensing algorithms under different noise conditions.The simulation results show that when the salt-and-pepper noise density is between 10%and 30%,the compressed sensing algorithm obtains good reconstruction results.Moreover,the optimal hyperparameter value has a linear relationship with the noise density,and the mean squared error of regression is approximately 8.10×10^(-8).
文摘BACKGROUND Aging is an inevitable aspect of human life,characterized by the gradual decline in the function of individual cells and structural components,including bones,muscles,and ligaments.AIM To evaluate the clinical effects of radiofrequency technology in treating facial skin wrinkles and laxity.METHODS This study included 60 female patients,aged 36-58 years(mean age 47.71±1.56 years),who received focused radiofrequency technology treatment for facial wrinkles and laxity in the Department of Medical Cosmetology at our hospital between January 2021 and June 2022.Each patient underwent three treatment sessions,one every two months.Facial photographs were taken before treatment and one week after the final session.A single physician assessed wrinkle severity using a standardized wrinkle severity scale,and patients completed a satisfaction questionnaire one week after the last treatment.RESULTS After three consecutive radiofrequency treatments,performed every two months,patients exhibited significantly reduced wrinkles and skin laxity compared to baseline.One week after the third treatment,the mean facial wrinkle severity score had significantly decreased from 3.00±0.79 to 2.71±0.47(t=2.58,P<0.05).Additionally,88.24%of patients reported noticeable improvements in facial wrinkles and skin laxity.No serious adverse reactions occurred during or follow-ing treatment.CONCLUSION Radiofrequency technology demonstrates significant clinical efficacy in improving facial skin wrinkles and laxity.
文摘The integration of cognitive radio and energy has enhanced the utilization efficiency of the spectrum and promoted the application of green energy.To begin with,this paper presents the architecture of green energy-efficient communication and network models.It incorporates the distributed network model and the heterogeneous two-tier network model into the green cognitive radio power control and channel allocation model.The primary focus of this research lies in energy conservation at the physical layer.To mitigate the interference with primary users and address the peak constraint in secondary user power allocation,the article analyzes the system model of the cognitive radio network and subsequently elaborates on the dynamic throughput maximization allocation algorithm.Eventually,through experimental analysis and verification,the distinctiveness and comprehensiveness of the optimal power control for this subject are illustrated.
基金supported by the Ministry of Science and Technology SKA Special Project(2020SKA0110202)the Special Project on Building a Science and Technology Innovation Center for South and Southeast Asia-International Joint Innovation Platform in Yunnan Province:“Yunnan Sino-Malaysian International Joint Laboratory of HF-VHF Advanced Radio Astronomy Technology”(202303AP140003)+4 种基金the National Natural Science Foundation of China(NSFC)Joint Fund for Astronomy(JFA)incubator program(U2031133)the International Partnership Program Project of the International Cooperation Bureau of the Chinese Academy of Sciences:“Belt and Road”Cooperation(114A11KYSB20200001)the Kunming Foreign(International)Cooperation Base Program:“Yunnan Observatory of the Chinese Academy of Sciences-University of Malaya Joint R&D Cooperation Base for Advanced Radio Astronomy Technology”(GHJD-2021022)the China-Malaysia Collaborative Research on Space Remote Sensing and Radio Astronomy Observation of Space Weather at Low and Middle Latitudes under the Key Special Project of the State Key R&D Program of the Ministry of Science and Technol ogy for International Cooperation in Science,Technology and Innovation among Governments(2022YFE0140000)the High-precision calibration method for low-frequency radio interferometric arrays for the SKA project of the Ministry of Science and Technology(2020SKA0110300).
文摘Radio environment plays an important role in radio astronomy observations.Further analysis is needed on the time and intensity distributions of interference signals for long-term radio environment monitoring.Sample variance is an important estimate of the interference signal decision threshold.Here,we propose an improved algorithm for calculating data sample variance relying on four established statistical methods:the variance of the trimmed data,winsorized sample variance,median absolute deviation,and median of the trimmed data pairwise averaged squares method.The variance and decision threshold in the protected section of the radio astronomy L-band are calculated.Among the four methods,the improved median of the trimmed data pairwise averaged squares algorithm has higher accuracy,but in a comparison of overall experimental results,the cleanliness rate of all algorithms is above 96%.In a comparison between the improved algorithm and the four methods,the cleanliness rate of the improved algorithm is above 98%,verifying its feasibility.The time-intensity interference distribution in the radio protection band is also obtained.Finally,we use comprehensive monitoring data of radio astronomy protection bands,radio interference bands,and interfered frequency bands to establish a comprehensive evaluation system for radio observatory sites,including the observable time proportion in the radio astronomy protection band,the occasional time-intensity distribution in the radio interference frequency band,and the intensity distribution of the interfered frequency band.
基金supported by National Natural Science Foundation of China(No.62201074),Reliable Mechanism for Edge Collaboration Service in Highly Dynamic Scenarios.
文摘With the exponential growth of mobile terminals and the widespread adoption of Internet of Things(IoT)technologies,an increasing number of devices rely on wireless local area networks(WLAN)for data transmission.To address this demand,deploying more access points(APs)has become an inevitable trend.While this approach enhances network coverage and capacity,it also exacerbates co-channel interference(CCI).The multi-AP cooperation introduced in IEEE 802.11be(Wi-Fi 7)represents a paradigm shift from conventional single-AP architectures,offering a novel solution to CCI through joint resource scheduling across APs.However,designing efficient cooperation mechanisms and achieving optimal resource allocation in dense AP environment remain critical research challenges.To mitigate CCI in high-density WLANs,this paper proposes a radio resource allocation method based on 802.11be multi-AP cooperation.First,to reduce the network overhead associated with centralized AP management,we introduce a distributed interference-aware AP clustering method that groups APs into cooperative sets.Second,methods for multi-AP cooperation information exchange,and cooperation transmission processes are designed.To support network state collection,capability advertisement,and cooperative trigger execution at the protocol level,this paper enhances the 802.11 frame structure with dedicated fields for multi-AP cooperation.Finally,considering the mutual influence between power and channel allocation,this paper proposes a joint radio resource allocation algorithm that employs an enhanced genetic algorithm for resource unit(RU)allocation and Q-learning for power control,interconnected via an inner-outer dual-loop architecture.Simulation results demonstrate the effectiveness of the proposed CCI avoidance mechanism and radio resource allocation algorithm in enhancing throughput in dense WLAN scenarios.
基金supported by the China Postdoctoral Science Foundation(2024M754113)the Chongqing Postdoctoral Innovative Fund(CQBX202419)the Natural Science Foundation of Chongqing(CSTB2023NSCOMSX0629).
文摘Earth-based deep space radar studies celestial bodies by both transmitting and receiving radio waves,whereas radio telescopes only work passively.On the operational level,radar missions use only short observation times,which leaves a large portion of the time available for astronomical observations.However,the design principles used for radar and radio telescopes differ.Technical challenges are involved in making the instruments required to meet the requirements of these two applications simultaneously.In this study,we have attempted to tune a deep space radar system for use in radio astronomical applications and conducted a successful pulsar observation,thus demonstrating the feasibility of using radar systems,particularly distributed deep space radar,to perform astronomical research.Additionally,given the limited astronomical capacity available within the observed frequency range,this system has the potential to contribute to the long-term monitoring of specific radio sources.This work represents the first successful attempt to use an Earth-based deep space radar system to perform radio astronomy in China.We also discuss the challenges of tuning a built radar system for astronomical observation applications and propose recommendations for the design of future large-scale distributed deep space radar systems with innate astronomical capabilities.
基金supported by the National Natural Science Foundation of China(42230207,42104165).
文摘The E_(s) layer is a thin layer that concentrates metallic ions in the mesosphere and lower thermosphere(MLT)region.When it occurs,it can affect the performance of the Global Navigation Satellite System and high/very high frequency(HF/VHF)radio communications.Previous studies mainly focused on the one-dimensional structure of E_(s) layer in the vertical direction.However,due to the limitation of observations,the horizontal structure of E_(s) layers is not yet fully understood.This study investigated the horizontal structure of E_(s) layers using amateur radio data in the European sector during the summer of 2020.Statistical analysis shows that the horizontal structure of E_(s) layer is mainly elongated in the east-west direction.In addition,we investigated the dynamics of the E_(s) layers,which primarily propagates in the northeast-southwest direction with a speed of 50-200 m/s.The results provide us a way for obtaining the horizontal structure and dynamic features of E_(s) layers,which can help improve our understanding of the formation and evolution of E_(s) layers.
基金supported by the National Key R&D Program of China(No.2021YFC2202800)the Youth Innovation Promotion Association CAS(No.2023022)Institute of Mechanics Outstanding Young Talent Training Program(No.E1Z1030201).
文摘Exploring solid propellants for electric thrusters can simplify the propellant storage and supply units in propulsion systems.In this study,polytetrafluoroethylene(PTFE),commonly used as a propellant in pulsed plasma thrusters,was embedded in the discharge chamber of a radio frequency ion thruster(RIT-4)to investigate the performance of an ablation-type RIT.Experimental results indicate that PTFE can decompose and ionize stably under plasma ablation within the discharge chamber,producing-C-F-and F-ion clusters that form a stable plasma.By adjusting the length of the PTFE propellant,it was observed that its decomposition rate influences the ion beam current of the thruster.Compared with xenon,PTFE generates an ion plume with a larger divergence angle,ranging from 16.05°to 22.74°at an ion beam current of 25 mA,with a floating potential distribution of 8‒56 V.Assuming that the proportion of neutral gas in the vacuum chamber matches the ion species ratio in the ion plume,thrust,specific impulse and efficiency parameters were calculated for the RIT-4 with embedded PTFE.Under 50 W RF power,the thrust was approximately 1.02 mN,the specific impulse was around 1236 s and the power-to-thrust ratio was approximately 93.14 W/mN.All results indicate that PTFE is a viable propellant for RIT,but the key is to control the rate of decomposition.
基金supported by the National Natural Science Foundation of China(62202215)Liaoning Province Applied Basic Research Program(Youth Special Project,2023JH2/101600038)+2 种基金Shenyang Youth Science and Technology Innovation Talent Support Program(RC220458)Guangxuan Program of Shenyang Ligong University(SYLUGXRC202216)Basic Research Special Funds for Undergraduate Universities in Liaoning Province(LJ212410144067).
文摘The 6G smart Fog Radio Access Network(F-RAN)is an integration of 6G network intelligence technologies and the F-RAN architecture.Its aim is to provide low-latency and high-performance services for massive access devices.However,the performance of current 6G network intelligence technologies and its level of integration with the architecture,along with the system-level requirements for the number of access devices and limitations on energy consumption,have impeded further improvements in the 6G smart F-RAN.To better analyze the root causes of the network problems and promote the practical development of the network,this study used structured methods such as segmentation to conduct a review of the topic.The research results reveal that there are still many problems in the current 6G smart F-RAN.Future research directions and difficulties are also discussed.
基金supported by the Strategic Priority Research Program of the Chinese Academy of Sciences XDB0560000the National Key R&D Program of China 2021YFA1600503,2022YFF0503001,2022YFF0503800+1 种基金the National Natural Science Foundation of China(NSFC,Grant No.12173050)the International Partnership Program of the Chinese Academy of Sciences 183311KYSB20200003。
文摘Heating mechanism in the solar atmosphere(from chromosphere to corona)is one of the top-challenges in modern astronomy.The classic mechanisms can be divided into two categories:wave heating(W)and magnetic reconnection heating(X).Both of them still face some problems currently difficult to overcome.Recently,we proposed a new mechanism,called magnetic-gradient pumping heating(MGP,or P)which seems to overcome those difficulties,but still lacks sufficient observational evidence.Which one really explained the physics of hot corona exactly?How can observations be used to identify and verify the heating mechanism?Since different heating mechanisms will generate non-thermal particles from different accelerations and experience different propagations,they will have different responses in the broadband spectral radio observations.Among them,the non-thermal electrons from W mechanisms are closely related to shock-wave acceleration,and their radio response should be a group of spike bursts with random distribution of drifting rates;the non-thermal electrons from X mechanisms are accelerated by reconnecting electric field with bidirectional flow,and their radio response should be type III pairs or spike pairs;P mechanism will produce energetic particle upflows,and their radio response should be unidirectional fiber bursts with moderate negative drifting rates.Therefore,the heating mechanism can be identified and verified from the broadband dynamic spectral radio observations.Additionally,using high-resolution radioheliographs and spectral-imaging observations,the heating mechanisms in different regions can be identified and verified separately,thereby demonstrating the physical essence of the hot corona.
基金funded by the National Key Research and Development Program’s intergovernmental International Science and Technology Innovation Cooperation project,titled Remote Sensing and Radio Astronomy Observation of Space Weather in Low and Middle Latitudes(project number:2022YFE0140000)Supported by International Partnership Program of Chinese Academy of Sciences,grant No.114A11KYSB20200001。
文摘The 21 cm radiation of neutral hydrogen provides crucial information for studying the early universe and its evolution.To advance this research,countries have made significant investments in constructing large lowfrequency radio telescope arrays,such as the Low Frequency Array and the Square Kilometre Array Phase 1 Low Frequency.These instruments are pivotal for radio astronomy research.However,challenges such as ionospheric plasma interference,ambient radio noise,and instrument-related effects have become increasingly prominent,posing major obstacles in cosmology research.To address these issues,this paper proposes an efficient signal processing method that combines wavelet transform and mathematical morphology.The method involves the following steps:Background Subtraction:Background interference in radio observation signals is eliminated.Wavelet Transform:The signal,after removing background noise,undergoes a two-dimensional discrete wavelet transform.Threshold processing is then applied to the wavelet coefficients to effectively remove interference components.Wavelet Inversion:The processed signal is reconstructed using wavelet inversion.Mathematical Morphology:The reconstructed signal is further optimized using mathematical morphology to refine the results.Experimental verification was conducted using solar observation data from the Xinjiang Observatory and the Yunnan Observatory.The results demonstrate that this method successfully removes interference signals while preserving useful signals,thus improving the accuracy of radio astronomy observations and reducing the impact of radio frequency interference.
基金supported by the Foundation of Key Laboratory of Micro-inertial Instrument and Advanced Navigation Technology,Ministry of Education,Chinathe National Natural Science Foundation of China (61873064)
文摘Solar radio burst(SRB)is one of the main natural interference sources of Global Positioning System(GPS)signals and can reduce the signal-to-noise ratio(SNR),directly affecting the tracking performance of GPS receivers.In this paper,a tracking algorithm based on the adaptive Kalman filter(AKF)with carrier-to-noise ratio estimation is proposed and compared with the conventional second-order phase-locked loop tracking algo-rithms and the improved Sage-Husa adaptive Kalman filter(SHAKF)algorithm.It is discovered that when the SRBs occur,the improved SHAKF and the AKF with carrier-to-noise ratio estimation enable stable tracking to loop signals.The conven-tional second-order phase-locked loop tracking algorithms fail to track the receiver signal.The standard deviation of the carrier phase error of the AKF with carrier-to-noise ratio estimation out-performs 50.51%of the improved SHAKF algorithm,showing less fluctuation and better stability.The proposed algorithm is proven to show more excellent adaptability in the severe envi-ronment caused by the SRB occurrence and has better tracking performance.
基金Construction of the Science and Technology Innovation Center for South Asia and Southeast Asia-Yunnan Province International Joint Innovation Platform: “Yunnan Province China-Malaysia HF-VHF Advanced Radio Astronomy Technology International Joint Laboratory” (202303AP140003)The National Natural Science Foundation of China Astronomical Joint Fund Cultivation Project (U203 1133)+4 种基金The SKA Special Project of the Ministry of Science and Technology (2020SKA0110202)The International Partnership Program of Bureau of International Cooperation, Chinese Academy of Sciences: 'Belt and Road' cooperation (114A11KYSB 20200001)The Kunming International (International) Cooperation Base project: “Yunnan Astronomical Observatory-University of Malaya Advanced Radio Astronomy Technology, Chinese Academy of Sciences” (GHJD2021022)The key special project of the Ministry of Science and Technology under the “Space Remote Sensing and Radio Astronomical Observation” of the Ministry of Science and Technology (2022YFE0140000)The High-precision calibration method of the SKA special low-frequency radio interference array of the Ministry of Science and Technology (2020SKA011 0300)
文摘Radio astronomy necessitates radio frequency bands that are both stable and free from interference at observatory locations.To comprehensively evaluate the radio environment at radio observatories,we employ Monte Carlo methods to assess the quality of observational data and predict potential interference.With an extensive dataset,we used an algorithm to find the interference threshold within the L-band,automatically identifying disruptive signals.Monte Carlo simulations were conducted to estimate whether these interference signals surpass a predetermined threshold of the total observation period,facilitating a detailed analysis of the interference profile.A Monte Carlo analysis was used on 83 hours of continuous monitoring data using a wireless environment testing system,to forecast the proportion of time during which interference signals would surpass established harmful thresholds.Our findings indicate that,within the L-band spectrum at Fenghuang Hill,Kunming City,Yunnan Province,the incidence of interference within the frequency ranges of 1330–1440 MHz,1610–1613 MHz,and 1660–1670 MHz is acceptably low,with respective confidence levels of 96.9%,97.4%,and 97.4%that the proportion of time these interference signals occupy does not exceed 5%of the total observational time,as stipulated by the International Telecommunication Union.Conversely,the confidence level for the 1718–1722 MHz band not exceeding 5%of the total observational time is significantly lower at 88.5%.This study offers a valuable tool for assessing the radio environment in radio astronomy research and provides a foundational basis for the scientific management and safeguarding of radio frequency bands.
文摘The science of radio astronomy focuses on the observation and study of celestial objects by reading their radio waves. The 5 meter radio-telescope is able to observe different radio sources using a C-band LNB. This research was essentially focused on Crab Nebula, also known as Taurus A. The study led to interesting observations, which were validated numerically using various scientific computing software. The radio waves emitted by Taurus A are readable by the RTL-SDR, a software defined radio receiver. This device is capable of reading radio frequencies in the range of 0.5 MHZ to 1700 MHZ.
文摘We suggest a possible explanation of the influence of pre-seismic activity on the registration rate of natural ELF(extremely low frequency)/VLF(very low frequency) pulses and the changes of their characteristics. The main idea is as follows. The distribution of the electric field around a thundercloud depends on the conductivity profile of the atmosphere. Quasi-static electric fields of a thundercloud decrease in those tropospheric regions where an increase of air conductivity is generated by pre-seismic activities due to emanation of radioactive gas and water into the lower atmosphere. The electric field becomes reduced in the lower troposphere, and the probability decreases of the cloud-to-ground (CG) strokes in such “contaminated” areas. Simultaneously, the electric field grows inside and above the thunderclouds, and hence, we anticipate a growth in the number of horizontal and tilted inter-cloud (or intra-cloud) (both termed as IC discharges) strokes. Spatial orientation of lightning strokes reduces vertical projection of their individual amplitudes, while the rate (median number strokes per a unit time) of discharges grows. We demonstrate that channel tilt of strokes modifies the spectral content of ELF/VLF radio noise and changes the rate of detected pulses during the earthquake preparation phase.
基金supported by the Science and Technology Project of State Grid Corporation of China (No.5200202155587A-0-5-GC)。
文摘The corona discharge from transmission lines in high-altitude areas is more severe than at lower altitudes. The radio interference caused thereby is a key factor to be considered when designing transmission lines. To study the influence of altitude on negative corona characteristics, an experimental platform comprising a movable small corona cage was established: experiments were conducted at four altitudes in the range of 1120-4320 m, and data on the corona current pulse and radio interference level of 0.8-mm diameter fine copper wire under different negative voltages were collected. The experimental results show that the average amplitude, repetition frequency and average current of the corona current pulse increase with increasing altitude. The dispersion of pulse amplitude increases with increase in altitude, while the randomness of the pulse interval decreases continuously. Taking the average current as an intermediate variable,the relationship between radio interference level and altitude is obtained. The result of this research has some significance for understanding the corona discharge characteristics of ultra-highvoltage lines.
基金supported by National Natural Science Foundation of China(12273098).
文摘The Shanghai Tianma 65 m radio telescope(TMRT)is a large,fully rotatable radio telescope with multiple scientific purposes.The main body of the telescope and four low-frequency receiving systems,including L,C,and S/X bands,were completed between 2008 and 2012.From 2013 to 2017,four high-frequency receiving systems,including Ku,K,Ka,and Q bands,were constructed and their performance was comprehensively tested.There are three main innovations.(1)A fully movable large radio telescope system with advanced performance and complete functions has been built.(2)An advanced,reliable main reflector adjustment system has been completed,overcoming gravity deformation and creating a large antenna with a main reflective surface accuracy of 0.28 mm(root mean square)for any elevation.(3)Five innovative technologies have been developed to achieve high-precision pointing in any direction within 3″.The TMRT has made a crucial contribution to the orbital measurement and positioning of China’s lunar and deep space probes.Significantly enhancing China's ability to participate in international VLBI observations and radio astronomy,this has facilitated a series of achievements in observational radio astronomical research,in areas such as VLBI,spectral lines,and pulsars.
基金National Natural Science Foundation of China under Grant No.61973037China Postdoctoral Science Foundation 2022M720419 to provide fund for conducting experiments。
文摘The identification of intercepted radio fuze modulation types is a prerequisite for decision-making in interference systems.However,the electromagnetic environment of modern battlefields is complex,and the signal-to-noise ratio(SNR)of such environments is usually low,which makes it difficult to implement accurate recognition of radio fuzes.To solve the above problem,a radio fuze automatic modulation recognition(AMR)method for low-SNR environments is proposed.First,an adaptive denoising algorithm based on data rearrangement and the two-dimensional(2D)fast Fourier transform(FFT)(DR2D)is used to reduce the noise of the intercepted radio fuze intermediate frequency(IF)signal.Then,the textural features of the denoised IF signal rearranged data matrix are extracted from the statistical indicator vectors of gray-level cooccurrence matrices(GLCMs),and support vector machines(SVMs)are used for classification.The DR2D-based adaptive denoising algorithm achieves an average correlation coefficient of more than 0.76 for ten fuze types under SNRs of-10 d B and above,which is higher than that of other typical algorithms.The trained SVM classification model achieves an average recognition accuracy of more than 96%on seven modulation types and recognition accuracies of more than 94%on each modulation type under SNRs of-12 d B and above,which represents a good AMR performance of radio fuzes under low SNRs.
文摘The Tianma 65 m radio telescope(TMRT)at Shanghai is a fully steerable single-dish radio telescope in China,operating at centimeter to millimeter wavelengths(1.25 GHz to 50 GHz).This paper presents details on the main specifications,design,performance analysis,testing,and construction of the telescope antenna.The measured total efficiency is better than 50%over the whole elevation angle range,first sidelobe levels are less than−20 dB,antenna system noise temperatures are less than 70 K at 30°elevation angle,and pointing accuracy is less than 3″.The measured and calculated results are in good agreement,verifying the effectiveness of the design and analysis.
