Utilizing multi-band and multi-carrier techniques enhances throughput and capacity in Long-Term Evolution(LTE)-Advanced and 5G New Radio(NR)mobile networks.However,these techniques introduce Passive Inter-Modulation(P...Utilizing multi-band and multi-carrier techniques enhances throughput and capacity in Long-Term Evolution(LTE)-Advanced and 5G New Radio(NR)mobile networks.However,these techniques introduce Passive Inter-Modulation(PIM)interference in Frequency-Division Duplexing(FDD)systems.In this paper,a novel multi-band Wiener-Hammerstein model is presented to digitally reconstruct PIM interference signals,thereby achieving effective PIM Cancellation(PIMC)in multi-band scenarios.In the model,transmitted signals are independently processed to simulate Inter-Modulation Distortions(IMDs)and Cross-Modulation Distortions(CMDs).Furthermore,the Finite Impulse Response(FIR)filter,basis function generation,and B-spline function are applied for precise PIM product estimation and generation in multi-band scenarios.Simulations involving 4 carrier components from diverse NR frequency bands at varying transmitting powers validate the feasibility of the model for multi-band PIMC,achieving up to 19 dB in PIMC performance.Compared to other models,this approach offers superior PIMC performance,exceeding them by more than 5 dB in high transmitting power scenarios.Additionally,its lower sampling rate requirement reduces the hardware complexity associated with implementing multi-band PIMC.展开更多
Passive inter-modulation （PIM） is a form of nonlinear distortion caused by the inherent nonlinearities of the passive devices and components in RF/microwave system. It will degenerate the performance of communicatio...Passive inter-modulation （PIM） is a form of nonlinear distortion caused by the inherent nonlinearities of the passive devices and components in RF/microwave system. It will degenerate the performance of communication system with broad-band channel and high-sensitivity receiver. Therefore, it is necessary to construct a model to simulate this process in order to predict the level of PIM. This paper is aimed at constructing some plate models with one-dimensional and two-dimensional contact nonlinearity sections illuminated by two-tone waves, and calculating the scattered field at a fixed-point in space using time-domain physical optics method. By taking fast Fourier transform （FFT）, we get the spectrum of the scattered field and then analyze the generated PIM products. At the end of this paper, some numerical examples are presented to show the influence rules of the relative factors on PIM. The results indicate the variation of the level of PIM with the number of the nonlinear regions, the nonlinear spacing, and the incident power levels.展开更多
Patients with complete spinal cord injury retain the potential for volitional muscle activity in muscles located below the spinal injury level.However,because of prolonged inactivity,initial attempts to activate these...Patients with complete spinal cord injury retain the potential for volitional muscle activity in muscles located below the spinal injury level.However,because of prolonged inactivity,initial attempts to activate these muscles may not effectively engage any of the remaining neurons in the descending pathway.A previous study unexpectedly found that a brief clinical round of passive activity significantly increased volitional muscle activation,as measured by surface electromyography.In this study,we further explored the effect of passive activity on surface electromyographic signals during volitional control tasks among individuals with complete spinal cord injury.Eleven patients with chronic complete thoracic spinal cord injury were recruited.Surface electromyography data from eight major leg muscles were acquired and compared before and after the passive activity protocol.The results indicated that the passive activity led to an increased number of activated volitional muscles and an increased frequency of activation.Although the cumulative root mean square of surface electromyography amplitude for volitional control of movement showed a slight increase after passive activity,the difference was not statistically significant.These findings suggest that brief passive activity may enhance the ability to initiate volitional muscle activity during surface electromyography tasks and underscore the potential of passive activity for improving residual motor control among patients with motor complete spinal cord injury.展开更多
Tactile perception plays a vital role for the human body and is also highly desired for smart prosthesis and advanced robots.Compared to active sensing devices,passive piezoelectric and triboelectric tactile sensors c...Tactile perception plays a vital role for the human body and is also highly desired for smart prosthesis and advanced robots.Compared to active sensing devices,passive piezoelectric and triboelectric tactile sensors consume less power,but lack the capability to resolve static stimuli.Here,we address this issue by utilizing the unique polarization chemistry of conjugated polymers for the first time and propose a new type of bioinspired,passive,and bio-friendly tactile sensors for resolving both static and dynamic stimuli.Specifically,to emulate the polarization process of natural sensory cells,conjugated polymers(including poly(3,4-ethylenedioxythiophen e):poly(styrenesulfonate),polyaniline,or polypyrrole)are controllably polarized into two opposite states to create artificial potential differences.The controllable and reversible polarization process of the conjugated polymers is fully in situ characterized.Then,a micro-structured ionic electrolyte is employed to imitate the natural ion channels and to encode external touch stimulations into the variation in potential difference outputs.Compared with the currently existing tactile sensing devices,the developed tactile sensors feature distinct characteristics including fully organic composition,high sensitivity(up to 773 mV N^(−1)),ultralow power consumption(nW),as well as superior bio-friendliness.As demonstrations,both single point tactile perception(surface texture perception and material property perception)and two-dimensional tactile recognitions(shape or profile perception)with high accuracy are successfully realized using self-defined machine learning algorithms.This tactile sensing concept innovation based on the polarization chemistry of conjugated polymers opens up a new path to create robotic tactile sensors and prosthetic electronic skins.展开更多
Passive source imaging can reconstruct body wave reflections similar to those of active sources through seismic interferometry(SI).It has become a low-cost,environmentally friendly alternative to active source seismic...Passive source imaging can reconstruct body wave reflections similar to those of active sources through seismic interferometry(SI).It has become a low-cost,environmentally friendly alternative to active source seismic,showing great potential.However,this method faces many challenges in practical applications,including uneven distribution of underground sources and complex survey environments.These situations seriously affect the reconstruction quality of virtual shot records,resulting in unguaranteed imaging results and greatly limiting passive source seismic exploration applications.In addition,the quality of the reconstructed records is directly related to the time length of the noise records,but in practice it is often difficult to obtain long-term,high-quality noise segments containing body wave events.To solve the above problems,we propose a deep learning method for reconstructing passive source virtual shot records and apply it to passive source time-lapse monitoring.This method combines the UNet network and the BiLSTM(Bidirectional Long Short-Term Memory)network for extracting spatial features and temporal features respectively.It introduces the spatial attention mechanism to establish a hybrid SUNet-BiLSTM-Attention(SBA)network for supervised training.Through pre-training and fine-tuning training,the network can accurately reconstruct passive source virtual shot records directly from short-time noisy segments containing body wave events.The experimental results of theoretical data show that the virtual shot records reconstructed by the network have high resolution and signal to noise ratio(SNR),providing high-quality data for subsequent monitoring and imaging.Finally,to further validate the effectiveness of proposed method,we applied it to field data collected from gas storage in northwest China.The reconstruction results of field data effectively improve the quality of virtual records and obtain more reliable time-lapse imaging monitoring results,which have significant practical value.展开更多
A novel method is developed by utilizing the fractional frequency based multirange rulers to precisely position the passive inter-modulation(PIM)sources within radio frequency(RF)cables.The proposed method employs a s...A novel method is developed by utilizing the fractional frequency based multirange rulers to precisely position the passive inter-modulation(PIM)sources within radio frequency(RF)cables.The proposed method employs a set of fractional frequencies to create multiple measuring rulers with different metric ranges to determine the values of the tens,ones,tenths,and hundredths digits of the distance.Among these rulers,the one with the lowest frequency determines the maximum metric range,while the one with the highest frequency decides the highest achievable accuracy of the position system.For all rulers,the metric accuracy is uniquely determined by the phase accuracy of the detected PIM signals.With the all-phase Fourier transform method,the phases of the PIM signals at all fractional frequencies maintain almost the same accuracy,approximately 1°(about 1/360 wavelength in the positioning accuracy)at the signal-to-noise ratio(SNR)of 10 d B.Numerical simulations verify the effectiveness of the proposed method,improving the positioning accuracy of the cable PIM up to a millimeter level with the highest fractional frequency operating at 200 MHz.展开更多
This paper investigates how to achieve integrated sensing and communication(ISAC)based on a cell-free radio access network(CF-RAN)architecture with a minimum footprint of communication resources.We propose a new passi...This paper investigates how to achieve integrated sensing and communication(ISAC)based on a cell-free radio access network(CF-RAN)architecture with a minimum footprint of communication resources.We propose a new passive sensing scheme.The scheme is based on the radio frequency(RF)fingerprint learning of the RF radio unit(RRU)to build an RF fingerprint library of RRUs.The source RRU is identified by comparing the RF fingerprints carried by the signal at the receiver side.The receiver extracts the channel parameters from the signal and estimates the channel environment,thus locating the reflectors in the environment.The proposed scheme can effectively solve the problem of interference between signals in the same time-frequency domain but in different spatial domains when multiple RRUs jointly serve users in CF-RAN architecture.Simulation results show that the proposed passive ISAC scheme can effectively detect reflector location information in the environment without degrading the communication performance.展开更多
Musculoskeletal Symptoms(MSS)often arise from prolonged maintenance of bent postures in the neck and trunk during surgical procedures.To prevent MSS,a passive exoskeleton utilizing carbon fiber beams to offer support ...Musculoskeletal Symptoms(MSS)often arise from prolonged maintenance of bent postures in the neck and trunk during surgical procedures.To prevent MSS,a passive exoskeleton utilizing carbon fiber beams to offer support to the neck and trunk was proposed.The application of support force is intended to reduce muscle forces and joint compression forces.A nonlinear mathematical model for the neck and trunk support beam is presented to estimate the support force.A validation test is subsequently conducted to assess the accuracy of the mathematical model.Finally,a preliminary functional evaluation test is performed to evaluate movement capabilities and support provided by the exoskeleton.The mathematical model demonstrates an accuracy for beam support force within a range of 0.8–1.2 N Root Mean Square Error(RMSE).The exoskeleton was shown to allow sufficient Range of Motion(ROM)for neck and trunk during open surgery training.While the exoskeleton showed potential in reducing musculoskeletal load and task difficulty during simulated surgery tasks,the observed reduction in perceived task difficulty was deemed non-significant.This prompts the recommendation for further optimization in personalized adjustments of beams to facilitate improvements in task difficulty and enhance comfort.展开更多
With the development of wireless communication,the fifth generation mobile communication technology(5G)has emerged as a hot topic in highspeed railway communication system and has moved towards industrial application....With the development of wireless communication,the fifth generation mobile communication technology(5G)has emerged as a hot topic in highspeed railway communication system and has moved towards industrial application.Investigating the radio propagation characteristics in 5G high-speed train(HST)scenarios is essential for enhancing wireless coverage and overall system performance.We propose a novel 5G passive sounding scheme to extract channel impulse responses(CIRs)using channel state information reference signals(CSI-RS)from the target 5G base station(BS).Detailed procedures for timefrequency synchronization,CSI-RS detection and extraction are presented through simulations.Through the laboratory work involving absolute power calibration,phase coherence calibration and power delay profile(PDP)validation,we validate the accuracy and performance of the developed platform.Furthermore,a measurement campaign was conducted in HST scenarios encompassing both residential and undeveloped areas.The path loss(PL)model and the channel characteristics including stationarity interval(SI),multipath components(MPCs),shadow fading(SF),Rician K-factor,root mean square(RMS)delay spread and received correlation coefficients are analyzed and fitted.The estimated channel characteristics and the statistical model presented in this paper will contribute to the research on HST radio propagation and the development of 5G railway communication systems.展开更多
Passive thermal management in electronics has disadvantages of low efficiency and high cost.Herein,experimental and numerical studies on the geometric optimization of a hygroscopic-membrane heat sink(HMHS)are conducte...Passive thermal management in electronics has disadvantages of low efficiency and high cost.Herein,experimental and numerical studies on the geometric optimization of a hygroscopic-membrane heat sink(HMHS)are conducted.The HMHS is based on water evaporation from a membrane-encapsulated hygroscopic salt solution,in which pin fins are used for thermal conductivity enhancement.A comprehensive heat and mass transfer model is developed and validated.To obtain the HMHS configuration with the maximum cooling performance,an approach that couples the Taguchi method with numerical simulations is utilized.The contribution ratio of each design factor is determined.Experimentally validated results demonstrate that the maximum temperature reduction provided by the HMHS can be further improved from 15.5℃to 17.8℃after optimization,achieving a temperature reduction of up to 21℃at a fixed heat flux of 25kW/m^(2)when compared with a similarly sized fin heat sink.Remarkably,the optimized HMHS extends the effective cooling time by∼343%compared with traditional phase-change materials,achieving a maximum temperature reduction ranging from 7.0℃to 20.4℃.Meanwhile,the effective heat transfer coefficient achieved is comparable with that of forced liquid cooling.Our findings suggest that the proposed cooling approach provides a new pathway for intermittent thermal management,which is expected to be used for thermal regulation of electronics,batteries,photovoltaic panels,and LED lights.展开更多
We conduct optical-tweezers experiments to investigate the average potential energies of passive plates harmonically trapped in bacterial suspensions.Our results show that the mean potential energies along both the ma...We conduct optical-tweezers experiments to investigate the average potential energies of passive plates harmonically trapped in bacterial suspensions.Our results show that the mean potential energies along both the major and minor axes increase with bacterial concentration but decrease with trap stiffness.Notably,the average potential energy along the major axis consistently exceeds that along the minor axis.This discrepancy from equilibrium systems is primarily attributed to the distinct bacterial flow fields and direct bacterium–plate collisions near the major and minor axes,as evidenced by the higher orientational order around the plate along the major compared to the minor axis,despite identical bacterial densities in these regions.Our findings highlight the critical role of hydrodynamic interactions in determining the potential energy of passive objects immersed in an active bath.展开更多
Recent advancements in passive wireless sensor technology have significantly extended the application scope of sensing,particularly in challenging environments for monitoring industry and healthcare applications.These...Recent advancements in passive wireless sensor technology have significantly extended the application scope of sensing,particularly in challenging environments for monitoring industry and healthcare applications.These systems are equipped with battery-free operation,wireless connectivity,and are designed to be both miniaturized and lightweight.Such features enable the safe,real-time monitoring of industrial environments and support high-precision physiological measurements in confined internal body spaces and on wearable epidermal devices.Despite the exploration into diverse application environments,the development of a systematic and comprehensive research framework for system architecture remains elusive,which hampers further optimization of these systems.This review,therefore,begins with an examination of application scenarios,progresses to evaluate current system architectures,and discusses the function of each component—specifically,the passive sensor module,the wireless communication model,and the readout module—within the context of key implementations in target sensing systems.Furthermore,we present case studies that demonstrate the feasibility of proposed classified components for sensing scenarios,derived from this systematic approach.By outlining a research trajectory for the application of passive wireless systems in sensing technologies,this paper aims to establish a foundation for more advanced,user-friendly applications.展开更多
Radiative cooling fabric creates a thermally comfortable environment without energy input,providing a sustainable approach to personal thermal management.However,most currently reported fabrics mainly focus on outdoor...Radiative cooling fabric creates a thermally comfortable environment without energy input,providing a sustainable approach to personal thermal management.However,most currently reported fabrics mainly focus on outdoor cooling,ignoring to achieve simultaneous cooling both indoors and outdoors,thereby weakening the overall cooling performance.Herein,a full-scale structure fabric with selective emission properties is constructed for simultaneous indoor and outdoor cooling.The fabric achieves 94%reflectance performance in the sunlight band(0.3–2.5μm)and 6%in the mid-infrared band(2.5–25μm),effectively minimizing heat absorption and radiation release obstruction.It also demonstrates 81%radiative emission performance in the atmospheric window band(8–13μm)and 25%radiative transmission performance in the mid-infrared band(2.5–25μm),providing 60 and 26 W m−2 net cooling power outdoors and indoors.In practical applications,the fabric achieves excellent indoor and outdoor human cooling,with temperatures 1.4–5.5℃ lower than typical polydimethylsiloxane film.This work proposes a novel design for the advanced radiative cooling fabric,offering significant potential to realize sustainable personal thermal management.展开更多
Narrow backfill earth pressure estimation is applied to study the stability of supporting structures in the vicinity of existing buildings.Previous narrow backfill earth pressure studies have neglected seismic-unsatur...Narrow backfill earth pressure estimation is applied to study the stability of supporting structures in the vicinity of existing buildings.Previous narrow backfill earth pressure studies have neglected seismic-unsaturated seepage multi-field coupling,resulting in inaccurate estimates.To address these deficiencies,this paper proposed a calculation method for seismic passive earth pressure in unsaturated narrow backfill,based on inclined thin-layer units.It considers the interlayer shear stress,arching effect,and the multi-field coupling of seismic-unsaturated seepage.Additionally,this paper includes a parametric sensitivity analysis.The outcomes indicate that the earthquake passive ground pressure of unsaturated narrow backfill can be reduced by increasing the aspect ratio,seismic acceleration coefficient,and unsaturation parameterα.It can also be reduced by decreasing the effective interior friction angle,soil cohesion,wallearth friction angle,and vertical discharge.Furthermore,for any width soil,lowering the elevation of the action point of passive thrust can be attained by raising the effective interior friction angle,wall-earth friction angle,and unsaturation parameterα.Reducing soil cohesion,seismic acceleration coefficient,and vertical discharge can also lower the height of the application point of passive thrust.展开更多
The passive containment heat removal system(PCS)is one of the key passive safety systems of China’s third-generation advanced pressurized water reactor-Hua-long Pressurized Reactor(HPR1000),used to prevent overpressu...The passive containment heat removal system(PCS)is one of the key passive safety systems of China’s third-generation advanced pressurized water reactor-Hua-long Pressurized Reactor(HPR1000),used to prevent overpressure of large concrete containment under severe accident scenarios.This paper provides an overview of the development of the HPR1000 passive containment heat removal system,including its operating principles and configuration,internal heat exchanger design,feasibility tests,engineering-scale PCS verification tests,comprehensive tests on PCS-containment coupling characteristics,among other key supporting studies.These extensive studies demonstrated that the PCS of HPR1000,which is designed based on flashing-driven open natural circulation and efficient condensation heat transfer theory,can work effectively and ensure the integrity of the containment under various accident scenarios.The system has been applied to Fuqing No.5 and No.6 nuclear power units and Zhangzhou No.1 and No.2 units of China’s first million-kilowatt third-generation nuclear power HPR1000.It is also applied to K-2/K-3 units of Karachi Nuclear Power Plant in Pakistan.展开更多
This study addresses the challenge by introducing a piezoelectric energy harvester based on vortex-induced vibration(VIV)and galloping interactions.Experiments on an elastically mounted circular cylinder equipped with...This study addresses the challenge by introducing a piezoelectric energy harvester based on vortex-induced vibration(VIV)and galloping interactions.Experiments on an elastically mounted circular cylinder equipped with two small square rods(SSR)in a DN100 pipe were conducted to examine how the circumferential angle of the SSR impacts the vibration response of cylinder,revealing distinct interaction modes(VIV-only and VIV-galloping interaction).The results show that placing the SSR toward the bluff body’s trailing edge accelerates the onset of galloping at lower velocities.In particular,as the SSR angle is in the range ofθ=160°–180°,the fluid-structure interaction behavior deviates from prior open-flow studies.This difference is attributed to the influence of the pipe wall and is analyzed using the shear layer interaction mode theory.The relationship between SSR placement angles and fluid-induced vibration(FIV)characteristics across various fluid velocities was also mapped,with dynamic influences assessed using the Strouhal number and stability parameterΔS,helping to distinguish between interaction modes.Based on these findings,configurations withθ=50°–70°andθ=140°–150°are identified as preferable for enhanced power output,whereasθ=170°–180°is better suited for optimizing efficiency and stability.These results provide good insights into the design and optimization of pipeline energy harvesting systems for industrial applications.展开更多
Although substantial research shows the effectiveness of written corrective feedback(WCF)in treating simple grammar structures,more research is still needed to refute Truscott’s claim that WCF may not work on complex...Although substantial research shows the effectiveness of written corrective feedback(WCF)in treating simple grammar structures,more research is still needed to refute Truscott’s claim that WCF may not work on complex grammar structures.Similarly,a previous body of research has shown that the degree of explicitness of feedback moderates the efficacy of WCF.However,most WCF studies have systematically manipulated only direct corrective feedback.The current study was therefore conducted to fill these gaps in the literature.To this end,five intact classes of Functional English were recruited and later randomly assigned to four treatment groups:DCF,DCF+ME,ICF,and ICF+ME,and one control group that received no feedback.All the groups took part in three WCF treatment sessions,during which they wrote two different pieces:a news report and a picture description.Later,only the treatment groups received the WCF.The WCF’s effectiveness was measured by writing tests and grammaticality judgment tasks(GJT).The results demonstrated that WCF helped L2 learners improve their grammatical accuracy of passive voice tenses.The study further showed that the group that received the most explicit type of WCF fared better than the ones that received the least explicit type of WCF.Important pedagogical implications for ESL/EFL teachers are discussed.展开更多
A mode-pairing quantum key distribution based on heralded pair-coherent source with passive decoy-states is proposed,named HPCS-PDS-MP-QKD protocol,where the light sources at Alice and Bob sides are changed to heralde...A mode-pairing quantum key distribution based on heralded pair-coherent source with passive decoy-states is proposed,named HPCS-PDS-MP-QKD protocol,where the light sources at Alice and Bob sides are changed to heralded pair-coherent sources,and devices designed to implement passive decoy states are included at the transmitter sides to generate the decoy state pulses in the decoy-state window passively.With the defined efficient events and the designed pairing strategy,the key bits and bases can be obtained by data post-processing.Numerical simulation results verify the feasibility of the proposed protocol.The results show that the proposed protocol can exceed PLOB when the pairing interval setting is greater than 10^(3),and the transmission distance exceeds 200 km.When the key transmission distance reaches 300 km and the maximum pairing interval is equivalent to 1,its performance is improved by nearly 1.8 times compared to the original MP-QKD protocol with a weak coherent source(WCS-MP-QKD),and by 6.8 times higher than that of WCS-MPQKD with passive decoy states(WCS-PDS-MP-QKD).Meanwhile,the key transmission distance can reach 480 km,and surpasses the WCS-PDS-MP-QKD protocol by nearly 40 km.When the total pulse length is greater than 10^(11),the key generation rate is almost equal to that of infinite pulses.It is a promising QKD protocol that breaks the PLOB bound without requiring phase tracking and locking,has a longer transmission distance and a higher key generation rate,and eliminates the potential of side channel attack.展开更多
1.IntroductionPassive movement is a 200+year-old manipulation involving the external movement of an individuals’limbs or body absent voluntary effort or muscle contraction.1The original application of passive movemen...1.IntroductionPassive movement is a 200+year-old manipulation involving the external movement of an individuals’limbs or body absent voluntary effort or muscle contraction.1The original application of passive movement was therapist-guided limb manipulation to increase range of motion and blood supply following acute and chronic injury.展开更多
基金supported by the National Natural Science Foun-dation of China under Grant 11901209,Grant 62374061,and Grant 62271217.
文摘Utilizing multi-band and multi-carrier techniques enhances throughput and capacity in Long-Term Evolution(LTE)-Advanced and 5G New Radio(NR)mobile networks.However,these techniques introduce Passive Inter-Modulation(PIM)interference in Frequency-Division Duplexing(FDD)systems.In this paper,a novel multi-band Wiener-Hammerstein model is presented to digitally reconstruct PIM interference signals,thereby achieving effective PIM Cancellation(PIMC)in multi-band scenarios.In the model,transmitted signals are independently processed to simulate Inter-Modulation Distortions(IMDs)and Cross-Modulation Distortions(CMDs).Furthermore,the Finite Impulse Response(FIR)filter,basis function generation,and B-spline function are applied for precise PIM product estimation and generation in multi-band scenarios.Simulations involving 4 carrier components from diverse NR frequency bands at varying transmitting powers validate the feasibility of the model for multi-band PIMC,achieving up to 19 dB in PIMC performance.Compared to other models,this approach offers superior PIMC performance,exceeding them by more than 5 dB in high transmitting power scenarios.Additionally,its lower sampling rate requirement reduces the hardware complexity associated with implementing multi-band PIMC.
文摘Passive inter-modulation （PIM） is a form of nonlinear distortion caused by the inherent nonlinearities of the passive devices and components in RF/microwave system. It will degenerate the performance of communication system with broad-band channel and high-sensitivity receiver. Therefore, it is necessary to construct a model to simulate this process in order to predict the level of PIM. This paper is aimed at constructing some plate models with one-dimensional and two-dimensional contact nonlinearity sections illuminated by two-tone waves, and calculating the scattered field at a fixed-point in space using time-domain physical optics method. By taking fast Fourier transform （FFT）, we get the spectrum of the scattered field and then analyze the generated PIM products. At the end of this paper, some numerical examples are presented to show the influence rules of the relative factors on PIM. The results indicate the variation of the level of PIM with the number of the nonlinear regions, the nonlinear spacing, and the incident power levels.
基金supported by the Fundamental Research Funds for Central Public Welfare Research Institute,No.2020CZ-5(to WS and GS)the National Natural Science Foundation of China,No.31970970(to JSR)Fundamental Research Funds for the Central Universities,No.YWF-23-YG-QB-010(to JSR)。
文摘Patients with complete spinal cord injury retain the potential for volitional muscle activity in muscles located below the spinal injury level.However,because of prolonged inactivity,initial attempts to activate these muscles may not effectively engage any of the remaining neurons in the descending pathway.A previous study unexpectedly found that a brief clinical round of passive activity significantly increased volitional muscle activation,as measured by surface electromyography.In this study,we further explored the effect of passive activity on surface electromyographic signals during volitional control tasks among individuals with complete spinal cord injury.Eleven patients with chronic complete thoracic spinal cord injury were recruited.Surface electromyography data from eight major leg muscles were acquired and compared before and after the passive activity protocol.The results indicated that the passive activity led to an increased number of activated volitional muscles and an increased frequency of activation.Although the cumulative root mean square of surface electromyography amplitude for volitional control of movement showed a slight increase after passive activity,the difference was not statistically significant.These findings suggest that brief passive activity may enhance the ability to initiate volitional muscle activity during surface electromyography tasks and underscore the potential of passive activity for improving residual motor control among patients with motor complete spinal cord injury.
基金financially supported by the Sichuan Science and Technology Program(2022YFS0025 and 2024YFFK0133)supported by the“Fundamental Research Funds for the Central Universities of China.”。
文摘Tactile perception plays a vital role for the human body and is also highly desired for smart prosthesis and advanced robots.Compared to active sensing devices,passive piezoelectric and triboelectric tactile sensors consume less power,but lack the capability to resolve static stimuli.Here,we address this issue by utilizing the unique polarization chemistry of conjugated polymers for the first time and propose a new type of bioinspired,passive,and bio-friendly tactile sensors for resolving both static and dynamic stimuli.Specifically,to emulate the polarization process of natural sensory cells,conjugated polymers(including poly(3,4-ethylenedioxythiophen e):poly(styrenesulfonate),polyaniline,or polypyrrole)are controllably polarized into two opposite states to create artificial potential differences.The controllable and reversible polarization process of the conjugated polymers is fully in situ characterized.Then,a micro-structured ionic electrolyte is employed to imitate the natural ion channels and to encode external touch stimulations into the variation in potential difference outputs.Compared with the currently existing tactile sensing devices,the developed tactile sensors feature distinct characteristics including fully organic composition,high sensitivity(up to 773 mV N^(−1)),ultralow power consumption(nW),as well as superior bio-friendliness.As demonstrations,both single point tactile perception(surface texture perception and material property perception)and two-dimensional tactile recognitions(shape or profile perception)with high accuracy are successfully realized using self-defined machine learning algorithms.This tactile sensing concept innovation based on the polarization chemistry of conjugated polymers opens up a new path to create robotic tactile sensors and prosthetic electronic skins.
基金supported by the CNPC-SWPU Innovation Alliance Technology Cooperation Project(2020CX020000)the Natural Science Foundation of Sichuan Province(24NSFSC0808)the China Scholarship Council(202306440144).
文摘Passive source imaging can reconstruct body wave reflections similar to those of active sources through seismic interferometry(SI).It has become a low-cost,environmentally friendly alternative to active source seismic,showing great potential.However,this method faces many challenges in practical applications,including uneven distribution of underground sources and complex survey environments.These situations seriously affect the reconstruction quality of virtual shot records,resulting in unguaranteed imaging results and greatly limiting passive source seismic exploration applications.In addition,the quality of the reconstructed records is directly related to the time length of the noise records,but in practice it is often difficult to obtain long-term,high-quality noise segments containing body wave events.To solve the above problems,we propose a deep learning method for reconstructing passive source virtual shot records and apply it to passive source time-lapse monitoring.This method combines the UNet network and the BiLSTM(Bidirectional Long Short-Term Memory)network for extracting spatial features and temporal features respectively.It introduces the spatial attention mechanism to establish a hybrid SUNet-BiLSTM-Attention(SBA)network for supervised training.Through pre-training and fine-tuning training,the network can accurately reconstruct passive source virtual shot records directly from short-time noisy segments containing body wave events.The experimental results of theoretical data show that the virtual shot records reconstructed by the network have high resolution and signal to noise ratio(SNR),providing high-quality data for subsequent monitoring and imaging.Finally,to further validate the effectiveness of proposed method,we applied it to field data collected from gas storage in northwest China.The reconstruction results of field data effectively improve the quality of virtual records and obtain more reliable time-lapse imaging monitoring results,which have significant practical value.
文摘A novel method is developed by utilizing the fractional frequency based multirange rulers to precisely position the passive inter-modulation(PIM)sources within radio frequency(RF)cables.The proposed method employs a set of fractional frequencies to create multiple measuring rulers with different metric ranges to determine the values of the tens,ones,tenths,and hundredths digits of the distance.Among these rulers,the one with the lowest frequency determines the maximum metric range,while the one with the highest frequency decides the highest achievable accuracy of the position system.For all rulers,the metric accuracy is uniquely determined by the phase accuracy of the detected PIM signals.With the all-phase Fourier transform method,the phases of the PIM signals at all fractional frequencies maintain almost the same accuracy,approximately 1°(about 1/360 wavelength in the positioning accuracy)at the signal-to-noise ratio(SNR)of 10 d B.Numerical simulations verify the effectiveness of the proposed method,improving the positioning accuracy of the cable PIM up to a millimeter level with the highest fractional frequency operating at 200 MHz.
基金supported in part by the National Key Research and Development Program under Grant(2021YFB2900300)by the National Natural Science Foundation of China(NSFC)under Grants 61971127,61871122by the Southeast University-China Mobile Research Institute Joint Innovation Center,and by the Major Key Project of PCL(PCL2021A01-2).
文摘This paper investigates how to achieve integrated sensing and communication(ISAC)based on a cell-free radio access network(CF-RAN)architecture with a minimum footprint of communication resources.We propose a new passive sensing scheme.The scheme is based on the radio frequency(RF)fingerprint learning of the RF radio unit(RRU)to build an RF fingerprint library of RRUs.The source RRU is identified by comparing the RF fingerprints carried by the signal at the receiver side.The receiver extracts the channel parameters from the signal and estimates the channel environment,thus locating the reflectors in the environment.The proposed scheme can effectively solve the problem of interference between signals in the same time-frequency domain but in different spatial domains when multiple RRUs jointly serve users in CF-RAN architecture.Simulation results show that the proposed passive ISAC scheme can effectively detect reflector location information in the environment without degrading the communication performance.
基金funded by China Scholarship Council,Grant Number 201906840121department of rehabilitation medicine,University Medical Center Groningen,University of Groningen,grant number:O/085350.
文摘Musculoskeletal Symptoms(MSS)often arise from prolonged maintenance of bent postures in the neck and trunk during surgical procedures.To prevent MSS,a passive exoskeleton utilizing carbon fiber beams to offer support to the neck and trunk was proposed.The application of support force is intended to reduce muscle forces and joint compression forces.A nonlinear mathematical model for the neck and trunk support beam is presented to estimate the support force.A validation test is subsequently conducted to assess the accuracy of the mathematical model.Finally,a preliminary functional evaluation test is performed to evaluate movement capabilities and support provided by the exoskeleton.The mathematical model demonstrates an accuracy for beam support force within a range of 0.8–1.2 N Root Mean Square Error(RMSE).The exoskeleton was shown to allow sufficient Range of Motion(ROM)for neck and trunk during open surgery training.While the exoskeleton showed potential in reducing musculoskeletal load and task difficulty during simulated surgery tasks,the observed reduction in perceived task difficulty was deemed non-significant.This prompts the recommendation for further optimization in personalized adjustments of beams to facilitate improvements in task difficulty and enhance comfort.
基金supported by Fundamental Research Funds for the Central Universities(No.2024YJS078)the National Natural Science Foundation of China(No.62341127,62221001 and 62171021)+1 种基金the Fundamental Research Funds for the Natural Science Foundation of Jiangsu Province,Major Project(No.BK2021200)the Key Research and Development Program of Zhejiang Province(No.2023C01003)。
文摘With the development of wireless communication,the fifth generation mobile communication technology(5G)has emerged as a hot topic in highspeed railway communication system and has moved towards industrial application.Investigating the radio propagation characteristics in 5G high-speed train(HST)scenarios is essential for enhancing wireless coverage and overall system performance.We propose a novel 5G passive sounding scheme to extract channel impulse responses(CIRs)using channel state information reference signals(CSI-RS)from the target 5G base station(BS).Detailed procedures for timefrequency synchronization,CSI-RS detection and extraction are presented through simulations.Through the laboratory work involving absolute power calibration,phase coherence calibration and power delay profile(PDP)validation,we validate the accuracy and performance of the developed platform.Furthermore,a measurement campaign was conducted in HST scenarios encompassing both residential and undeveloped areas.The path loss(PL)model and the channel characteristics including stationarity interval(SI),multipath components(MPCs),shadow fading(SF),Rician K-factor,root mean square(RMS)delay spread and received correlation coefficients are analyzed and fitted.The estimated channel characteristics and the statistical model presented in this paper will contribute to the research on HST radio propagation and the development of 5G railway communication systems.
基金National Natural Science Foundation of China,Grant/Award Number:52322812Shenzhen Science and Technology Program,Grant/Award Number:JCYJ20230807114905012Research Grants Council of Hong Kong,Grant/Award Numbers:CityU 11215621,CityU 11218922。
文摘Passive thermal management in electronics has disadvantages of low efficiency and high cost.Herein,experimental and numerical studies on the geometric optimization of a hygroscopic-membrane heat sink(HMHS)are conducted.The HMHS is based on water evaporation from a membrane-encapsulated hygroscopic salt solution,in which pin fins are used for thermal conductivity enhancement.A comprehensive heat and mass transfer model is developed and validated.To obtain the HMHS configuration with the maximum cooling performance,an approach that couples the Taguchi method with numerical simulations is utilized.The contribution ratio of each design factor is determined.Experimentally validated results demonstrate that the maximum temperature reduction provided by the HMHS can be further improved from 15.5℃to 17.8℃after optimization,achieving a temperature reduction of up to 21℃at a fixed heat flux of 25kW/m^(2)when compared with a similarly sized fin heat sink.Remarkably,the optimized HMHS extends the effective cooling time by∼343%compared with traditional phase-change materials,achieving a maximum temperature reduction ranging from 7.0℃to 20.4℃.Meanwhile,the effective heat transfer coefficient achieved is comparable with that of forced liquid cooling.Our findings suggest that the proposed cooling approach provides a new pathway for intermittent thermal management,which is expected to be used for thermal regulation of electronics,batteries,photovoltaic panels,and LED lights.
基金supports of the National Natural Science Foundation of China(Grant Nos.12304245,12374205,12475031,and 12364029)the Science Foundation of China University of Petroleum,Beijing(Grant Nos.2462023YJRC031 and 2462024BJRC010)+4 种基金the National Key Laboratory of Petroleum Resources and Engineering(Grant No.PRE/DX-2407)the Natural Science Foundation of Shandong Province(Grant No.ZR2024YQ017)the Young Elite Scientist Sponsorship Program by BAST(Grant No.BYESS2023300)the Beijing Institute of Technology Research Fund Program for Young ScholarsThis work was also supported by Beijing National Laboratory for Condensed Matter Physics(Grant Nos.2023BNLCMPKF014 and 2024BNLCMPKF009).
文摘We conduct optical-tweezers experiments to investigate the average potential energies of passive plates harmonically trapped in bacterial suspensions.Our results show that the mean potential energies along both the major and minor axes increase with bacterial concentration but decrease with trap stiffness.Notably,the average potential energy along the major axis consistently exceeds that along the minor axis.This discrepancy from equilibrium systems is primarily attributed to the distinct bacterial flow fields and direct bacterium–plate collisions near the major and minor axes,as evidenced by the higher orientational order around the plate along the major compared to the minor axis,despite identical bacterial densities in these regions.Our findings highlight the critical role of hydrodynamic interactions in determining the potential energy of passive objects immersed in an active bath.
基金partially supported by Basic Science Research Program through the National Research Foundation of Korea(NRF)funded by the Ministry of Education(No.2018R1A6A1A03025242)by the Korea government(MIST)(RS-2023-00302751,RS-2024-00343686)the Research Grant of Kwangwoon University in 2024。
文摘Recent advancements in passive wireless sensor technology have significantly extended the application scope of sensing,particularly in challenging environments for monitoring industry and healthcare applications.These systems are equipped with battery-free operation,wireless connectivity,and are designed to be both miniaturized and lightweight.Such features enable the safe,real-time monitoring of industrial environments and support high-precision physiological measurements in confined internal body spaces and on wearable epidermal devices.Despite the exploration into diverse application environments,the development of a systematic and comprehensive research framework for system architecture remains elusive,which hampers further optimization of these systems.This review,therefore,begins with an examination of application scenarios,progresses to evaluate current system architectures,and discusses the function of each component—specifically,the passive sensor module,the wireless communication model,and the readout module—within the context of key implementations in target sensing systems.Furthermore,we present case studies that demonstrate the feasibility of proposed classified components for sensing scenarios,derived from this systematic approach.By outlining a research trajectory for the application of passive wireless systems in sensing technologies,this paper aims to establish a foundation for more advanced,user-friendly applications.
基金financially supported by Heilongjiang Postdoctoral Fund(Grant No.LBH-Z24057)Outstanding Master’s and Doctoral Thesis of Longjiang in the New Era(Grant No.LJYXL2023-076).
文摘Radiative cooling fabric creates a thermally comfortable environment without energy input,providing a sustainable approach to personal thermal management.However,most currently reported fabrics mainly focus on outdoor cooling,ignoring to achieve simultaneous cooling both indoors and outdoors,thereby weakening the overall cooling performance.Herein,a full-scale structure fabric with selective emission properties is constructed for simultaneous indoor and outdoor cooling.The fabric achieves 94%reflectance performance in the sunlight band(0.3–2.5μm)and 6%in the mid-infrared band(2.5–25μm),effectively minimizing heat absorption and radiation release obstruction.It also demonstrates 81%radiative emission performance in the atmospheric window band(8–13μm)and 25%radiative transmission performance in the mid-infrared band(2.5–25μm),providing 60 and 26 W m−2 net cooling power outdoors and indoors.In practical applications,the fabric achieves excellent indoor and outdoor human cooling,with temperatures 1.4–5.5℃ lower than typical polydimethylsiloxane film.This work proposes a novel design for the advanced radiative cooling fabric,offering significant potential to realize sustainable personal thermal management.
基金Project(42277175)supported by the National Natural Science Foundation of ChinaProject(NRMSSHR-2022-Z08)supported by the Key Laboratory of Natural Resources Monitoring and Supervision in Southern Hilly Region,Ministry of Natural Resources,China。
文摘Narrow backfill earth pressure estimation is applied to study the stability of supporting structures in the vicinity of existing buildings.Previous narrow backfill earth pressure studies have neglected seismic-unsaturated seepage multi-field coupling,resulting in inaccurate estimates.To address these deficiencies,this paper proposed a calculation method for seismic passive earth pressure in unsaturated narrow backfill,based on inclined thin-layer units.It considers the interlayer shear stress,arching effect,and the multi-field coupling of seismic-unsaturated seepage.Additionally,this paper includes a parametric sensitivity analysis.The outcomes indicate that the earthquake passive ground pressure of unsaturated narrow backfill can be reduced by increasing the aspect ratio,seismic acceleration coefficient,and unsaturation parameterα.It can also be reduced by decreasing the effective interior friction angle,soil cohesion,wallearth friction angle,and vertical discharge.Furthermore,for any width soil,lowering the elevation of the action point of passive thrust can be attained by raising the effective interior friction angle,wall-earth friction angle,and unsaturation parameterα.Reducing soil cohesion,seismic acceleration coefficient,and vertical discharge can also lower the height of the application point of passive thrust.
基金supported by China Nuclear Power Engineering Co.,Ltd.and Harbin Engineering University,and granted financial resources by China’s National Energy Administration and China National Nuclear Corporation.
文摘The passive containment heat removal system(PCS)is one of the key passive safety systems of China’s third-generation advanced pressurized water reactor-Hua-long Pressurized Reactor(HPR1000),used to prevent overpressure of large concrete containment under severe accident scenarios.This paper provides an overview of the development of the HPR1000 passive containment heat removal system,including its operating principles and configuration,internal heat exchanger design,feasibility tests,engineering-scale PCS verification tests,comprehensive tests on PCS-containment coupling characteristics,among other key supporting studies.These extensive studies demonstrated that the PCS of HPR1000,which is designed based on flashing-driven open natural circulation and efficient condensation heat transfer theory,can work effectively and ensure the integrity of the containment under various accident scenarios.The system has been applied to Fuqing No.5 and No.6 nuclear power units and Zhangzhou No.1 and No.2 units of China’s first million-kilowatt third-generation nuclear power HPR1000.It is also applied to K-2/K-3 units of Karachi Nuclear Power Plant in Pakistan.
基金supported by the National Natural Science Foundation of China(Grant Nos.52276159,62373270)supported by the Natural Science Foundation of Tianjin(Grant No.23JCQNJC00060)+1 种基金the Scientific Research Program of Tianjin Municipal Education Commission(Grant No.2022KJ065)the Graduate Student Research and Innovation Funding Program of Civil Aviation University of China(Grant No.2024YJSKC02003).
文摘This study addresses the challenge by introducing a piezoelectric energy harvester based on vortex-induced vibration(VIV)and galloping interactions.Experiments on an elastically mounted circular cylinder equipped with two small square rods(SSR)in a DN100 pipe were conducted to examine how the circumferential angle of the SSR impacts the vibration response of cylinder,revealing distinct interaction modes(VIV-only and VIV-galloping interaction).The results show that placing the SSR toward the bluff body’s trailing edge accelerates the onset of galloping at lower velocities.In particular,as the SSR angle is in the range ofθ=160°–180°,the fluid-structure interaction behavior deviates from prior open-flow studies.This difference is attributed to the influence of the pipe wall and is analyzed using the shear layer interaction mode theory.The relationship between SSR placement angles and fluid-induced vibration(FIV)characteristics across various fluid velocities was also mapped,with dynamic influences assessed using the Strouhal number and stability parameterΔS,helping to distinguish between interaction modes.Based on these findings,configurations withθ=50°–70°andθ=140°–150°are identified as preferable for enhanced power output,whereasθ=170°–180°is better suited for optimizing efficiency and stability.These results provide good insights into the design and optimization of pipeline energy harvesting systems for industrial applications.
文摘Although substantial research shows the effectiveness of written corrective feedback(WCF)in treating simple grammar structures,more research is still needed to refute Truscott’s claim that WCF may not work on complex grammar structures.Similarly,a previous body of research has shown that the degree of explicitness of feedback moderates the efficacy of WCF.However,most WCF studies have systematically manipulated only direct corrective feedback.The current study was therefore conducted to fill these gaps in the literature.To this end,five intact classes of Functional English were recruited and later randomly assigned to four treatment groups:DCF,DCF+ME,ICF,and ICF+ME,and one control group that received no feedback.All the groups took part in three WCF treatment sessions,during which they wrote two different pieces:a news report and a picture description.Later,only the treatment groups received the WCF.The WCF’s effectiveness was measured by writing tests and grammaticality judgment tasks(GJT).The results demonstrated that WCF helped L2 learners improve their grammatical accuracy of passive voice tenses.The study further showed that the group that received the most explicit type of WCF fared better than the ones that received the least explicit type of WCF.Important pedagogical implications for ESL/EFL teachers are discussed.
基金Project supported by the National Natural Science Foundation of China(Grant No.62375140)the Postgraduate Research&Practice Innovation Program of Jiangsu Province,China(Grant No.KYCX241191 and SJCX250315)the Open Research Fund of the National Laboratory of Solid State Microstructures(Grant No.M36055)。
文摘A mode-pairing quantum key distribution based on heralded pair-coherent source with passive decoy-states is proposed,named HPCS-PDS-MP-QKD protocol,where the light sources at Alice and Bob sides are changed to heralded pair-coherent sources,and devices designed to implement passive decoy states are included at the transmitter sides to generate the decoy state pulses in the decoy-state window passively.With the defined efficient events and the designed pairing strategy,the key bits and bases can be obtained by data post-processing.Numerical simulation results verify the feasibility of the proposed protocol.The results show that the proposed protocol can exceed PLOB when the pairing interval setting is greater than 10^(3),and the transmission distance exceeds 200 km.When the key transmission distance reaches 300 km and the maximum pairing interval is equivalent to 1,its performance is improved by nearly 1.8 times compared to the original MP-QKD protocol with a weak coherent source(WCS-MP-QKD),and by 6.8 times higher than that of WCS-MPQKD with passive decoy states(WCS-PDS-MP-QKD).Meanwhile,the key transmission distance can reach 480 km,and surpasses the WCS-PDS-MP-QKD protocol by nearly 40 km.When the total pulse length is greater than 10^(11),the key generation rate is almost equal to that of infinite pulses.It is a promising QKD protocol that breaks the PLOB bound without requiring phase tracking and locking,has a longer transmission distance and a higher key generation rate,and eliminates the potential of side channel attack.
文摘1.IntroductionPassive movement is a 200+year-old manipulation involving the external movement of an individuals’limbs or body absent voluntary effort or muscle contraction.1The original application of passive movement was therapist-guided limb manipulation to increase range of motion and blood supply following acute and chronic injury.
