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 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
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
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
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
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
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
By doping with Mg atoms,the bandgap of Mg-doped NiO thin films can be adjusted larger.By using NiO and MgO as sputtering targets,Mg-doped NiO thin films were deposited using radio-frequency magnetron co-sputtering met...By doping with Mg atoms,the bandgap of Mg-doped NiO thin films can be adjusted larger.By using NiO and MgO as sputtering targets,Mg-doped NiO thin films were deposited using radio-frequency magnetron co-sputtering method in pure argon and pure oxygen gas,respectively.The crystal structure,morphological characteristics,composition and optical properties of the obtained films were compared by X-ray diffraction(XRD),scanning electron microscope(SEM),energy dispersive spectrometer(EDS)and ultraviolet(UV)-visible spectrophotometer.The properties of the thin films deposited in different sputtering gases are quite different.For the films deposited in pure argon gas,it is a polycrystalline thin film with(200)preferred orientation,while the film deposited in pure oxygen has no preferred orientation.The grain size,molar ratio of Mg to Ni atoms and optical bandgap are larger for the films deposited in pure argon gas than those deposited in oxygen gas.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
The paper deals the popular news-talk radio station ＂Echo of Moscow＂ which is one of the most interesting and successful one in Moscow FM range. It provides thorough analysis of different previous and nowadays progr...The paper deals the popular news-talk radio station ＂Echo of Moscow＂ which is one of the most interesting and successful one in Moscow FM range. It provides thorough analysis of different previous and nowadays programs and web projects in comparison with main multimedia sphere trends. A particular attention is paid to ＂Echo of Moscow＂ web page as multimedia portal strongly packed with different functions such as its integration with social nets.展开更多
Radio is all about dreams. This old and tired medium now fights with new media as it is with its old enemy television. Radio has a big impact on dreams. It gives you the sound and makes you dream. Once you get used to...Radio is all about dreams. This old and tired medium now fights with new media as it is with its old enemy television. Radio has a big impact on dreams. It gives you the sound and makes you dream. Once you get used to this media you start dreaming. If you used to listen radio more, you get in dependence with it. So this day dreaming change to lifeless dreaming. This article gives an evaluation of how radio audience can shape audience future dreams with dependence theory. The paper starts with a conceptual explanation of dependence theory and goes on with a survey done in Turkey to 101 radio listeners. The survey investigates on how people like listening the radio and what makes them enjoy radio. The survey assumes that people listening to radio and getting depended on it start changing the behaviors and habits of listeners. This behavior change effects listeners future dreams and the audience take radio as a model. The paper shows by using the dependence theory that radio listeners take the radio they love as model and use it to build their future business dreams.展开更多
Radio Espana Independiente [REI] [1941-1977], La Pirenaica, was the repository for the public remembrance of the victims of the Franco regime, through letters that its listeners regularly sent to the broadcaster＇s he...Radio Espana Independiente [REI] [1941-1977], La Pirenaica, was the repository for the public remembrance of the victims of the Franco regime, through letters that its listeners regularly sent to the broadcaster＇s headquarters in Bucharest. A study of the 15,500 letters contained in the Spanish Communist Party＇s [PCE] Historical Archive in Madrid confirms this broadcaster＇s major role in the construction of the mythical symbolic image of the anti-Franco movement. Beyond their function as propaganda instruments of the PCE, La Pirenaica＇s letters reveal the radio station＇s role as a vehicle for the expression of public solidarity and ideological and cultural resistance. La Pirenaica was the voice of the defeated after the Spanish Civil War, and was their confidante and advisor. La Pirenaica＇s letters are the chronicle of the horror that anti-Franco society suffered and endured in Spain.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.
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.
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 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 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 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 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 Jilin Provincial Scientific and Technological Development Program(No.20220101036JC)。
文摘By doping with Mg atoms,the bandgap of Mg-doped NiO thin films can be adjusted larger.By using NiO and MgO as sputtering targets,Mg-doped NiO thin films were deposited using radio-frequency magnetron co-sputtering method in pure argon and pure oxygen gas,respectively.The crystal structure,morphological characteristics,composition and optical properties of the obtained films were compared by X-ray diffraction(XRD),scanning electron microscope(SEM),energy dispersive spectrometer(EDS)and ultraviolet(UV)-visible spectrophotometer.The properties of the thin films deposited in different sputtering gases are quite different.For the films deposited in pure argon gas,it is a polycrystalline thin film with(200)preferred orientation,while the film deposited in pure oxygen has no preferred orientation.The grain size,molar ratio of Mg to Ni atoms and optical bandgap are larger for the films deposited in pure argon gas than those deposited in oxygen gas.
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.
文摘The paper deals the popular news-talk radio station ＂Echo of Moscow＂ which is one of the most interesting and successful one in Moscow FM range. It provides thorough analysis of different previous and nowadays programs and web projects in comparison with main multimedia sphere trends. A particular attention is paid to ＂Echo of Moscow＂ web page as multimedia portal strongly packed with different functions such as its integration with social nets.
文摘Radio is all about dreams. This old and tired medium now fights with new media as it is with its old enemy television. Radio has a big impact on dreams. It gives you the sound and makes you dream. Once you get used to this media you start dreaming. If you used to listen radio more, you get in dependence with it. So this day dreaming change to lifeless dreaming. This article gives an evaluation of how radio audience can shape audience future dreams with dependence theory. The paper starts with a conceptual explanation of dependence theory and goes on with a survey done in Turkey to 101 radio listeners. The survey investigates on how people like listening the radio and what makes them enjoy radio. The survey assumes that people listening to radio and getting depended on it start changing the behaviors and habits of listeners. This behavior change effects listeners future dreams and the audience take radio as a model. The paper shows by using the dependence theory that radio listeners take the radio they love as model and use it to build their future business dreams.
文摘Radio Espana Independiente [REI] [1941-1977], La Pirenaica, was the repository for the public remembrance of the victims of the Franco regime, through letters that its listeners regularly sent to the broadcaster＇s headquarters in Bucharest. A study of the 15,500 letters contained in the Spanish Communist Party＇s [PCE] Historical Archive in Madrid confirms this broadcaster＇s major role in the construction of the mythical symbolic image of the anti-Franco movement. Beyond their function as propaganda instruments of the PCE, La Pirenaica＇s letters reveal the radio station＇s role as a vehicle for the expression of public solidarity and ideological and cultural resistance. La Pirenaica was the voice of the defeated after the Spanish Civil War, and was their confidante and advisor. La Pirenaica＇s letters are the chronicle of the horror that anti-Franco society suffered and endured in Spain.
