The issue of resistance reduction through hull ventilation is of particular interest in contemporary research.This paper presents multiphase computational fluid dynamics(CFD)simulations with 2-DOF motion of a planing ...The issue of resistance reduction through hull ventilation is of particular interest in contemporary research.This paper presents multiphase computational fluid dynamics(CFD)simulations with 2-DOF motion of a planing hull.The original hull was modified by introducing a step to allow air ventilation.Following an assessment of the hull performance,a simulation campaign in calm water was conducted to characterize the hull at various forward speeds and air insufflation rates for a defined single step geometry.Geometric analysis of the air layer thickness beneath the hull for each simulated condition was performed using a novel method for visualizing local air thickness.Additionally,two new parameters were introduced to understand the influence of spray rails on the air volume beneath the hull and to indicate the primary direction of ventilated air escape.A validation campaign and an assessment of uncertainty of the simulation has been conducted.The features offered by the CFD methodology include the evaluation of the air layer thickness as a function of hull velocity and injection flow rate and the air volume distribution beneath the hull.The air injection velocity can be adjusted across various operating conditions,thereby preventing performance or efficiency loss during navigation.Based on these findings,the study highlights the benefits of air insufflation in reducing hull resistance for high-speed planing vessels.This work lays a robust foundation for future research and new promising topics,as the exploration of air insufflation continues to be a topic of contemporary interest within naval architecture and hydrodynamics.展开更多
High-finesse optical reference cavities are essential tools for fundamental research.In response to China’s historical reliance on importing high-finesse optical reference cavities,we successfully developed a cavity ...High-finesse optical reference cavities are essential tools for fundamental research.In response to China’s historical reliance on importing high-finesse optical reference cavities,we successfully developed a cavity using ultralow expansion glass(ULE)materials and processed it entirely in China.Using the method of measuring the cavity linewidth,a finesse of approximately 480000 was obtained in our experiments.We adopted a relatively simple and effective approach to test the optical reference cavity,which involved measuring the resonant points using an ultrastable laser.Remarkably,an expansion coefficient of the Chinese ULE optical reference cavity reached up to the order of 10^(-9)/K within the temperature range of 27℃to 40℃,with the zero expansion point occurring at approximately 34oC.These findings demonstrate China’s independent capability to develop high-finesse optical reference cavities,which is a significant advancement in precision optics.展开更多
Superconducting radio-frequency(SRF)cavities are the core components of SRF linear accelerators,making their stable operation considerably important.However,the operational experience from different accelerator labora...Superconducting radio-frequency(SRF)cavities are the core components of SRF linear accelerators,making their stable operation considerably important.However,the operational experience from different accelerator laboratories has revealed that SRF faults are the leading cause of short machine downtime trips.When a cavity fault occurs,system experts analyze the time-series data recorded by low-level RF systems and identify the fault type.However,this requires expertise and intuition,posing a major challenge for control-room operators.Here,we propose an expert feature-based machine learning model for automating SRF cavity fault recognition.The main challenge in converting the"expert reasoning"process for SRF faults into a"model inference"process lies in feature extraction,which is attributed to the associated multidimensional and complex time-series waveforms.Existing autoregression-based feature-extraction methods require the signal to be stable and autocorrelated,resulting in difficulty in capturing the abrupt features that exist in several SRF failure patterns.To address these issues,we introduce expertise into the classification model through reasonable feature engineering.We demonstrate the feasibility of this method using the SRF cavity of the China accelerator facility for superheavy elements(CAFE2).Although specific faults in SRF cavities may vary across different accelerators,similarities exist in the RF signals.Therefore,this study provides valuable guidance for fault analysis of the entire SRF community.展开更多
Obtaining high-quality 10000-meter-deep seafloor sediment samples is the prerequisite and foundation for conducting deep-sea geological and environmental scientific research.The bottom structure of the deep seafloor i...Obtaining high-quality 10000-meter-deep seafloor sediment samples is the prerequisite and foundation for conducting deep-sea geological and environmental scientific research.The bottom structure of the deep seafloor is complex,and the physical and mechanical properties and disturbance resistance of sediments of different lithologies vary greatly,so the sediment sampler inevitably disturbs the sediments during the sampling process and affects the quality of the sediment samples.A new type of deep-sea sediment pressure retaining sampler is introduced,the force state and elastic–plastic state of the sampler destroying sediments are analyzed,the radial disturbance model of sediment coring based on the spherical cavity expansion theory is established,and the radius of sediments undergoing plastic deformation around the spherical holes is used as an index for evaluating the radial disturbance of sediments.The distribution of stress and strain fields in the sediments during the expansion of the spherical cavity and the influencing factors of the radius of the radially disturbed region(plastic region)are analyzed using an arithmetic example,and the influence law is analyzed.A sediment disturbance experimental platform was built indoors to simulate the sediment coring process.The radial stress field and pore water pressure of the sediment during the coring process were monitored by sensors arranged inside the sediment,and the results of indoor tests verified the correctness of the perturbation theory model.The sampler was carried aboard the deep-sea manned submersible FENDOUZHE and conducted on-site tests at depths of 9298.4 and 9142.8 m in the Kuril-Kamchatka Trench.Pressure-preserved sediment samples were retrieved,with preservation rates of 94.21%and 92.02%,respectively,which are much higher than the current technical indicator of 80%of pressure-holding ratio for deep-sea sediments.The retrieved sediments have obvious stratification characteristics and little disturbance.展开更多
The active sound absorption technique excels in mitigating low-frequency sound waves,yet it falls short when dealing with medium and high-frequency sound waves.To enhance the sound-absorbing effect of medium and high-...The active sound absorption technique excels in mitigating low-frequency sound waves,yet it falls short when dealing with medium and high-frequency sound waves.To enhance the sound-absorbing effect of medium and high-frequency sound waves,a novel semi-active sound absorption method has been introduced.This method modulates the surface impedance of a loudspeaker positioned behind the sound-absorbing material,thereby altering the sound absorption coefficient.The theoretical sound absorption coefficient is calculated using MATLAB and compared with the experimental one.Results show that the method can effectively modulates the absorption coefficient in response to varying incident sound wave frequencies,ensuring that it remains at its peak value.展开更多
The cavity characteristics in liquid-filled containers caused by high-velocity impacts represent an important area of research in hydrodynamic ram phenomena.The dynamic expansion of the cavity induces liquid pressure ...The cavity characteristics in liquid-filled containers caused by high-velocity impacts represent an important area of research in hydrodynamic ram phenomena.The dynamic expansion of the cavity induces liquid pressure variations,potentially causing catastrophic damage to the container.Current studies mainly focus on non-deforming projectiles,such as fragments,with limited exploration of shaped charge jets.In this paper,a uniquely experimental system was designed to record cavity profiles in behind-armor liquid-filled containers subjected to shaped charge jet impacts.The impact process was then numerically reproduced using the explicit simulation program ANSYS LS-DYNA with the Structured Arbitrary Lagrangian-Eulerian(S-ALE)solver.The formation mechanism,along with the dimensional and shape evolution of the cavity was investigated.Additionally,the influence of the impact kinetic energy of the jet on the cavity characteristics was analyzed.The findings reveal that the cavity profile exhibits a conical shape,primarily driven by direct jet impact and inertial effects.The expansion rates of both cavity length and maximum radius increase with jet impact kinetic energy.When the impact kinetic energy is reduced to 28.2 kJ or below,the length-to-diameter ratio of the cavity ultimately stabilizes at approximately 7.展开更多
Theoretically,copper–niobium(Cu-Nb)composite superconducting cavities have excellent potential for high thermal and mechanical stability.They can appropriately exploit the high-gradient surface processing recipes dev...Theoretically,copper–niobium(Cu-Nb)composite superconducting cavities have excellent potential for high thermal and mechanical stability.They can appropriately exploit the high-gradient surface processing recipes developed for the bulk niobium(Nb)cavity and the thick copper(Cu)layer’s high thermal conductivity and rigidity,thereby enhancing the operational stability of the bulk Nb cavities.This study conducted a global review of the technical approaches employed for fabricating Cu-Nb composite superconducting cavities.We explored Cu-Nb composite superconducting cavities based on two technologies at the Institute of Modern Physics,Chinese Academy of Sciences(IMP,CAS),including their manufacturing processes,radio-frequency(RF)characteristics,and mechanical performance.These cavities exhibit robust mechanical stability.First,the investigation of several 1.3 GHz single-cell elliptical cavities using the Cu-Nb composite sheets indicated that the wavy structure at the Cu-Nb interface influenced the reliable welding of the Cu-Nb composite parts.We observed the generation and trapping of magnetic flux density during the T_c crossing of Nb in cooldown process.The cooling rates during the T_c crossing of Nb exerted a substantial impact on the performance of the cavities.Furthermore,we measured and analyzed the surface resistance R_(s)attributed to the trapped magnetic flux induced by the Seebeck effect after quenching events.Second,for the first time,a low-beta bulk Nb cavity was plated with Cu on its outer surface using electroplating technology.We achieved a high peak electric field E_(pk)of~88.8 MV/m at 2 K and the unloaded quality factor Q_(0)at the E_(pk)of 88.8 MV/m exceeded 1×10^(10).This demonstrated that the electroplating Cu on the bulk Nb cavity is a practical method of developing the Cu-Nb composite superconducting cavity with superior thermal stability.The results presented here provide valuable insights for applying Cu-Nb composite superconducting cavities in superconducting accelerators with stringent operational stability requirements.展开更多
BACKGROUND Fungal balls within the nasal cavity are an exceedingly rare clinical entity,typically presenting with nonspecific symptoms or being identified incidentally.CASE SUMMARY This report presents an incidental d...BACKGROUND Fungal balls within the nasal cavity are an exceedingly rare clinical entity,typically presenting with nonspecific symptoms or being identified incidentally.CASE SUMMARY This report presents an incidental discovery of a fungal ball in the nasal cavity during routine imaging,with no associated clinical symptoms.CONCLUSION This case underscores the importance of considering the possibility of asympto-matic presentations of nasal fungal balls,which may be detected incidentally during imaging evaluations.展开更多
A novel substrate integrated microstrip to ultra-thin cavity filter transition operating in the W-band is proposed in this letter.The structure is a new method of connecting microstrip circuits and waveguide filters,a...A novel substrate integrated microstrip to ultra-thin cavity filter transition operating in the W-band is proposed in this letter.The structure is a new method of connecting microstrip circuits and waveguide filters,and this new structure enables a planar integrated transition from microstrip lines to ultra-thin cavity filters,thereby reducing the size of the transition structure and achieving miniaturization.The structure includes a conventional tapered microstrip transition structure,which guides the electromagnetic field from the microstrip line to the reduced-height dielectric-filled waveguide,and an air-filled matching cavity which is placed between the dielectric-filled waveguide and the ultra-thin cavity filter.The heights of the microstrip line,the dielectric-filled waveguide and the ultra-thin cavity filter are the same,enabling seamless integration within a planar radio-frequency(RF)circuit.To facilitate testing,mature finline transition structures are integrated at both ends of the microstrip line during fabrications.The simulation results of the fabricated microstrip to ultra-thin cavity filter transition with the finline transition structure,with a passband of 91.5-96.5 GHz,has an insertion loss of less than 1.9 dB and a return loss lower than-20 dB.And the whole structure has also been measured which achieves an insertion loss less than 2.6 dB and a return loss lower than-15 dB within the filter's passband,including the additional insertion loss introduced by the finline transitions.Finally,a W-band compact up-conversion module is designed,and the test results show that after using the proposed structure,the module achieves 95 dBc suppression of the 84 GHz local oscillator.It is also demonstrated that the structure proposed in this letter achieves miniaturization of the system integration without compromising the filter performance.展开更多
The titanium alloy strut serves as a key load-bearing component of aircraft landing gear,typically manufactured via forging.The friction condition has important influence on material flow and cavity filling during the...The titanium alloy strut serves as a key load-bearing component of aircraft landing gear,typically manufactured via forging.The friction condition has important influence on material flow and cavity filling during the forging process.Using the previously optimized shape and initial position of preform,the influence of the friction condition(friction factor m=0.1–0.3)on material flow and cavity filling was studied by numerical method with a shear friction model.A novel filling index was defined to reflect material flow into left and right flashes and zoom in on friction-induced results.The results indicate that the workpiece moves rigidly to the right direction,with the displacement decreasing as m increases.When m<0.18,the underfilling defect will occur in the left side of strut forging,while overflow occurs in the right forging die cavity.By combining the filling index and analyses of material flow and filling status,a reasonable friction factor interval of m=0.21–0.24 can be determined.Within this interval,the cavity filling behavior demonstrates robustness,with friction fluctuations exerting minimal influence.展开更多
The concept of emissivity has been with the scientific and engineering world since Planck formulated his blackbody radiation law more than a century ago.Nevertheless,emissivity is an elusive concept even for ex⁃perts....The concept of emissivity has been with the scientific and engineering world since Planck formulated his blackbody radiation law more than a century ago.Nevertheless,emissivity is an elusive concept even for ex⁃perts.It is a vague and fuzzy concept for the wider community of engineers.The importance of remote sensing of temperature by measuring IR radiation has been recognized in a wide range of industrial,medical,and environ⁃mental uses.One of the major sources of errors in IR radiometry is the emissivity of the surface being measured.In real experiments,emissivity may be influenced by many factors:surface texture,spectral properties,oxida⁃tion,and aging of surfaces.While commercial blackbodies are prevalent,the much-needed grey bodies with a known emissivity,are unavailable.This study describes how to achieve a calibrated and stable emissivity with a blackbody,a perforated screen,and a reliable and linear novel IR thermal sensor,18 dubbed TMOS.The Digital TMOS is now a low-cost commercial product,it requires low power,and it has a small form factor.The method⁃ology is based on two-color measurements,with two different optical filters,with selected wavelengths conform⁃ing to the grey body definition of the use case under study.With a photochemically etched perforated screen,the effective emissivity of the screen is simply the hole density area of the surface area that emits according to the blackbody temperature radiation.The concept is illustrated with ray tracing simulations,which demonstrate the approach.Measured results are reported.展开更多
A metal-sensitive diaphragm fiber optic pressure sensor with temperature compensation is developed for pressure monitoring in high-temperature environments,such as engine fuel systems,oil and gas wells,and aviation hy...A metal-sensitive diaphragm fiber optic pressure sensor with temperature compensation is developed for pressure monitoring in high-temperature environments,such as engine fuel systems,oil and gas wells,and aviation hydraulic systems.The sensor combines a metal-sensitive diaphragm and a sapphire wafer to form a temperature-pressure dual Fabry-Perot(FP)interference cavity.A cross-correlation signal demodulation algorithm and a temperature decoupling method are utilized to reduce the influence of temperature crosstalk on pressure measurement.Experimental results show that the maximum nonlinear error of the sensor pressure measurement is 0.75%full scale(FS)and 0.99%FS at room temperature and 300°C,respectively,in a pressure range of 0−10 MPa and 0−1.5 MPa.The sensor’s pressure measurement accuracy is 1.7%FS when using the temperature decoupling method.The sensor exhibits good static pressure characteristics,stability,and reliability,providing an effective solution for high-temperature pressure monitoring applications.展开更多
A plasmonics waveguide structure that consist of a non-through metal–insulator–metal(MIM)waveguide coupled with a D-shaped cavity was designed.And the transmission properties,magnetic field distribution,and refracti...A plasmonics waveguide structure that consist of a non-through metal–insulator–metal(MIM)waveguide coupled with a D-shaped cavity was designed.And the transmission properties,magnetic field distribution,and refractive index sensing functionality were simulated using the finite element method(FEM).A multi-Fano resonance phenomenon was clearly observable in the transmission spectra.The Fano resonances observed in the proposed structure arise from the interaction between the discrete states of the Dshaped resonant cavity and the continuum state of the non-through MIM waveguide.The influence of structural parameters on Fano resonance modulation was investigated through systematic parameter adjustments.Additionally,the refractive index sensing properties,based on the Fano resonance,were investigated by varying the refractive index of the MIM waveguide's insulator layer.A maximum sensitivity and FOM of 1155 RIU/nm and 40 were achieved,respectively.This research opens up new possibilities for designing and exploring high-sensitivity photonic devices,micro-sensors,and innovative on-chip sensing architectures for future applications.展开更多
The China Spallation Neutron Source(CSNS)is the fourth pulsed accelerator-driven neutron source in the world,and it achieved its design target of 100 kW in 2020.The planned China Spallation Neutron Source Phase II(CSN...The China Spallation Neutron Source(CSNS)is the fourth pulsed accelerator-driven neutron source in the world,and it achieved its design target of 100 kW in 2020.The planned China Spallation Neutron Source Phase II(CSNS-II)commenced in 2024.The CSNS-II linac design primarily involves the addition of a radio-frequency ion source and a section of a superconducting linear accelerator composed of two types of superconducting cavities,namely double-spoke and six-cell elliptical cavities,after the drift tube linac(DTL).The development of the double-spoke superconducting cavity began in early 2021,and by January 2023,the welding,post-processing,and vertical tests of two 324 MHz double-spoke cavity prototypes were completed,with vertical test gradients of 11.6 and 15 MV/m,and Q_(0)≥3×10^(10)@E_(acc)≤10 MV/m.The R&D of the cryomodule began in January 2022.In October 2023,the clean assembly of the double-spoke cavity string and cold mass installation of the cryomodule commenced,with the installation of the cryomodule and valve box completing in two months.In January 2024,a horizontal test of the cryomodule was completed,making it the first double-spoke cavity cryomodule in China.The test results showed that the maximum gradients of the two superconducting cavities at a pulse width of 4 ms and repetition frequency of 25 Hz were 12.8 and 15.2 MV/m,respectively.This article provides a detailed introduction to the double-spoke superconducting cavity,tuner,coupler,and cryomodule,elaborates on the clean assembly of the cavity string and cold mass installation of the cryomodule,and provides a detailed analysis of the horizontal test results.展开更多
Developing microwave electric field sensing based on Rydberg atoms has received significant attention due to its unique advantages. However, achieving effective coupling between Rydberg atoms and the microwave electri...Developing microwave electric field sensing based on Rydberg atoms has received significant attention due to its unique advantages. However, achieving effective coupling between Rydberg atoms and the microwave electric field in the sensing process is a challenging problem that greatly impacts the sensitivity. To address this, we propose using a microwave resonant cavity to enhance the effective coupling between the Rydberg atoms and the microwave electric field. In our experiment, Rydberg atoms are prepared via a three-photon excitation scheme, and the electric fields are measured without and with a microwave cavity in which the vapor cell is placed inside, respectively. As a result, we achieved an 18 dB enhancement of power sensitivity by adding the cavity,which is an effective enhancement in electric field pulse signal detection. This experimental testing provides a promising direction for enhancing the sensitivity of Rydberg atomic electric field sensors and paves the way for their application in precision electric field measurements.展开更多
In conventional piezoelectric micromachined ultrasonic transducers(PMUTs),the backside acoustic energy is often used inefficiently,resulting in up to half of the energy being wasted.Vacuum encapsulation can improve th...In conventional piezoelectric micromachined ultrasonic transducers(PMUTs),the backside acoustic energy is often used inefficiently,resulting in up to half of the energy being wasted.Vacuum encapsulation can improve the energy utilization efficiency,but this technique is not compatible with state-of-the-art devices such as cantilever-based PMUTs.A closed back cavity provides an alternative method for effectively utilizing the backside acoustic energy.This paper investigates the effects of a closed back cavity on PMUT performance through theoretical analysis,simulations,and experimental verification.Increasing the cavity depth produces a periodic modulation of several key PMUT metrics,such as the relative frequency deviation and quality factor.The optimal cavity depth for PMUTs that ensures a robust resonant frequency and high quality factor is defined as a function of the acoustic wavelength.A closed back cavity also provides an effective method for continuously tuning the quality factor,and thus the bandwidth,of PMUTs.This work paves the way for air-coupled PMUTs with adjustable performance for various applications.展开更多
Microwave–optical entanglement is essential for efficient quantum communication,secure information transfer,and integrating microwave and optical quantum systems to advance hybrid quantum technologies.In this work,we...Microwave–optical entanglement is essential for efficient quantum communication,secure information transfer,and integrating microwave and optical quantum systems to advance hybrid quantum technologies.In this work,we demonstrate how the magnon Kerr effect can be harnessed to generate and control nonreciprocal entanglement in cavity optomagnomechanics(COMM).This effect induces magnon frequency shifts and introduces pair-magnon interactions,both of which are tunable through the magnetic field direction,enabling nonreciprocal behavior.By adjusting system parameters such as magnon frequency detuning,we show that magnon–phonon,microwave–optical photon–photon,and optical photon–magnon entanglement can be nonreciprocally enhanced and rendered more robust against thermal noise.Additionally,the nonreciprocity of entanglement can be selectively controlled,and ideal nonreciprocal entanglement is achievable.This work paves the way for designing nonreciprocal quantum devices across the microwave and optical regimes,leveraging the unique properties of the magnon Kerr effect in COMM.展开更多
The topic of improving the mechanical stability of external cavity diode lasers(ECDLs)has recently attracted widespread attention and interest.The use of corner-cube-array(CCA)-based resonators provides a potential so...The topic of improving the mechanical stability of external cavity diode lasers(ECDLs)has recently attracted widespread attention and interest.The use of corner-cube-array(CCA)-based resonators provides a potential solution for this purpose,although continuous oscillation at super large incident angle remains challenging.In this work,we employ the CCA resonator to generate continuous oscillation within±20°angular misalignment of cavity mirror in experiment.On the basis of retroreflection theory,the retroreflectivity of a CCA is analyzed by using optical simulation software.Notably,the experiment verifies the advantage of using a CCA over a plane mirror in laser resonator,thereby providing a promising approach for ECDLs.The threshold characteristic curves measured at different incident angles in the experiment verify that the CCA possesses an obvious anti-angle misalignment performance.This research introduces an alternative solution of using CCA resonator instead of parallel plane cavity,thereby realizing an adjustment-free ECDL with enhanced mechanical stability.展开更多
Objective:To consolidate the scarce and scattered evidence on oral cysticercosis,a rare and often overlooked manifestation of Taenia solium infection.Methods:A comprehensive literature search was conducted in three ma...Objective:To consolidate the scarce and scattered evidence on oral cysticercosis,a rare and often overlooked manifestation of Taenia solium infection.Methods:A comprehensive literature search was conducted in three major databases:PubMed,Scopus,and Embase.A total of 75 records were initially identified(PubMed:n=23;Scopus:n=29;Embase:n=23).After screening and eligibility assessment,22 studies meeting inclusion criteria were selected for final analysis.Results:Oral cysticercosis primarily involved the tongue,typically presenting as a painless swelling.The majority of reported cases were from India.Clinically,it was most often misdiagnosed as a mucocele or fibroma,with cysticercosis rarely considered due to its uncommon occurrence.Among the muscles affected,the masseter,mentalis,and buccinator were most frequently involved.Diagnosis was primarily made through histopathological examination.Treatment commonly included surgical excision,and albendazole was the most frequently used antiparasitic medication.Recurrence was uncommon,except in cases with disseminated or deep muscular involvement.Conclusions:Oral cysticercosis should be considered a potential differential diagnosis,particularly in regions where pork consumption is common.Given that most reported cases originated from India,pathologists in this region should maintain a high index of suspicion.Oral pathologists,in particular,should be well-acquainted with its histopathological features to ensure accurate diagnosis and avoid diagnostic pitfalls.展开更多
基金supported by European Union funding(PON“Ricerca e Innovazione”2014‒2020).
文摘The issue of resistance reduction through hull ventilation is of particular interest in contemporary research.This paper presents multiphase computational fluid dynamics(CFD)simulations with 2-DOF motion of a planing hull.The original hull was modified by introducing a step to allow air ventilation.Following an assessment of the hull performance,a simulation campaign in calm water was conducted to characterize the hull at various forward speeds and air insufflation rates for a defined single step geometry.Geometric analysis of the air layer thickness beneath the hull for each simulated condition was performed using a novel method for visualizing local air thickness.Additionally,two new parameters were introduced to understand the influence of spray rails on the air volume beneath the hull and to indicate the primary direction of ventilated air escape.A validation campaign and an assessment of uncertainty of the simulation has been conducted.The features offered by the CFD methodology include the evaluation of the air layer thickness as a function of hull velocity and injection flow rate and the air volume distribution beneath the hull.The air injection velocity can be adjusted across various operating conditions,thereby preventing performance or efficiency loss during navigation.Based on these findings,the study highlights the benefits of air insufflation in reducing hull resistance for high-speed planing vessels.This work lays a robust foundation for future research and new promising topics,as the exploration of air insufflation continues to be a topic of contemporary interest within naval architecture and hydrodynamics.
基金supported by the National Natural Science Foundation of China(Grant Nos.12103059 and 12033007)the National Major Science and Technology Infrastructure Project of China(Grant No.2017-000052-73-01-002401)+3 种基金Xi’an Science and Technology Bureau(Grant No.E019XK1S04)Sanqin Talents’Special Support Program(Grant No.09R0557A00)the Youth Innovation Promotion Association of the Chinese Academy of Science(Grant No.1188000XGJ)the Innovation Program for Quantum Science and Technology(Grant No.2021ZD0300900)。
文摘High-finesse optical reference cavities are essential tools for fundamental research.In response to China’s historical reliance on importing high-finesse optical reference cavities,we successfully developed a cavity using ultralow expansion glass(ULE)materials and processed it entirely in China.Using the method of measuring the cavity linewidth,a finesse of approximately 480000 was obtained in our experiments.We adopted a relatively simple and effective approach to test the optical reference cavity,which involved measuring the resonant points using an ultrastable laser.Remarkably,an expansion coefficient of the Chinese ULE optical reference cavity reached up to the order of 10^(-9)/K within the temperature range of 27℃to 40℃,with the zero expansion point occurring at approximately 34oC.These findings demonstrate China’s independent capability to develop high-finesse optical reference cavities,which is a significant advancement in precision optics.
基金supported by the studies of intelligent LLRF control algorithms for superconducting RF cavities(No.E129851YR0)the National Natural Science Foundation of China(No.U22A20261)Applications of Artificial Intelligence in the Stability Study of Superconducting Linear Accelerators(No.E429851YR0)。
文摘Superconducting radio-frequency(SRF)cavities are the core components of SRF linear accelerators,making their stable operation considerably important.However,the operational experience from different accelerator laboratories has revealed that SRF faults are the leading cause of short machine downtime trips.When a cavity fault occurs,system experts analyze the time-series data recorded by low-level RF systems and identify the fault type.However,this requires expertise and intuition,posing a major challenge for control-room operators.Here,we propose an expert feature-based machine learning model for automating SRF cavity fault recognition.The main challenge in converting the"expert reasoning"process for SRF faults into a"model inference"process lies in feature extraction,which is attributed to the associated multidimensional and complex time-series waveforms.Existing autoregression-based feature-extraction methods require the signal to be stable and autocorrelated,resulting in difficulty in capturing the abrupt features that exist in several SRF failure patterns.To address these issues,we introduce expertise into the classification model through reasonable feature engineering.We demonstrate the feasibility of this method using the SRF cavity of the China accelerator facility for superheavy elements(CAFE2).Although specific faults in SRF cavities may vary across different accelerators,similarities exist in the RF signals.Therefore,this study provides valuable guidance for fault analysis of the entire SRF community.
基金supported by the National Key Research and Development Program of China(Nos.2023YFC2809304 and 2022YFC2805904).
文摘Obtaining high-quality 10000-meter-deep seafloor sediment samples is the prerequisite and foundation for conducting deep-sea geological and environmental scientific research.The bottom structure of the deep seafloor is complex,and the physical and mechanical properties and disturbance resistance of sediments of different lithologies vary greatly,so the sediment sampler inevitably disturbs the sediments during the sampling process and affects the quality of the sediment samples.A new type of deep-sea sediment pressure retaining sampler is introduced,the force state and elastic–plastic state of the sampler destroying sediments are analyzed,the radial disturbance model of sediment coring based on the spherical cavity expansion theory is established,and the radius of sediments undergoing plastic deformation around the spherical holes is used as an index for evaluating the radial disturbance of sediments.The distribution of stress and strain fields in the sediments during the expansion of the spherical cavity and the influencing factors of the radius of the radially disturbed region(plastic region)are analyzed using an arithmetic example,and the influence law is analyzed.A sediment disturbance experimental platform was built indoors to simulate the sediment coring process.The radial stress field and pore water pressure of the sediment during the coring process were monitored by sensors arranged inside the sediment,and the results of indoor tests verified the correctness of the perturbation theory model.The sampler was carried aboard the deep-sea manned submersible FENDOUZHE and conducted on-site tests at depths of 9298.4 and 9142.8 m in the Kuril-Kamchatka Trench.Pressure-preserved sediment samples were retrieved,with preservation rates of 94.21%and 92.02%,respectively,which are much higher than the current technical indicator of 80%of pressure-holding ratio for deep-sea sediments.The retrieved sediments have obvious stratification characteristics and little disturbance.
基金National Natural Science Foundation of China(No.51705545)。
文摘The active sound absorption technique excels in mitigating low-frequency sound waves,yet it falls short when dealing with medium and high-frequency sound waves.To enhance the sound-absorbing effect of medium and high-frequency sound waves,a novel semi-active sound absorption method has been introduced.This method modulates the surface impedance of a loudspeaker positioned behind the sound-absorbing material,thereby altering the sound absorption coefficient.The theoretical sound absorption coefficient is calculated using MATLAB and compared with the experimental one.Results show that the method can effectively modulates the absorption coefficient in response to varying incident sound wave frequencies,ensuring that it remains at its peak value.
基金financial support from the National Natural Science Foundation of China(Grant No.11572159).
文摘The cavity characteristics in liquid-filled containers caused by high-velocity impacts represent an important area of research in hydrodynamic ram phenomena.The dynamic expansion of the cavity induces liquid pressure variations,potentially causing catastrophic damage to the container.Current studies mainly focus on non-deforming projectiles,such as fragments,with limited exploration of shaped charge jets.In this paper,a uniquely experimental system was designed to record cavity profiles in behind-armor liquid-filled containers subjected to shaped charge jet impacts.The impact process was then numerically reproduced using the explicit simulation program ANSYS LS-DYNA with the Structured Arbitrary Lagrangian-Eulerian(S-ALE)solver.The formation mechanism,along with the dimensional and shape evolution of the cavity was investigated.Additionally,the influence of the impact kinetic energy of the jet on the cavity characteristics was analyzed.The findings reveal that the cavity profile exhibits a conical shape,primarily driven by direct jet impact and inertial effects.The expansion rates of both cavity length and maximum radius increase with jet impact kinetic energy.When the impact kinetic energy is reduced to 28.2 kJ or below,the length-to-diameter ratio of the cavity ultimately stabilizes at approximately 7.
基金supported by the Large Research Infrastructures China initiative Accelerator Driven System(No.2017-000052-75-01-000590)the Youth Innovation Promotion Association of Chinese Academy of Sciences(No.2022422)+1 种基金the Young Scientists of National Natural Science Foundation of China(No.12005275)the Advanced Energy Science and Technology Guangdong Laboratory(No.HND22PTZZYY)。
文摘Theoretically,copper–niobium(Cu-Nb)composite superconducting cavities have excellent potential for high thermal and mechanical stability.They can appropriately exploit the high-gradient surface processing recipes developed for the bulk niobium(Nb)cavity and the thick copper(Cu)layer’s high thermal conductivity and rigidity,thereby enhancing the operational stability of the bulk Nb cavities.This study conducted a global review of the technical approaches employed for fabricating Cu-Nb composite superconducting cavities.We explored Cu-Nb composite superconducting cavities based on two technologies at the Institute of Modern Physics,Chinese Academy of Sciences(IMP,CAS),including their manufacturing processes,radio-frequency(RF)characteristics,and mechanical performance.These cavities exhibit robust mechanical stability.First,the investigation of several 1.3 GHz single-cell elliptical cavities using the Cu-Nb composite sheets indicated that the wavy structure at the Cu-Nb interface influenced the reliable welding of the Cu-Nb composite parts.We observed the generation and trapping of magnetic flux density during the T_c crossing of Nb in cooldown process.The cooling rates during the T_c crossing of Nb exerted a substantial impact on the performance of the cavities.Furthermore,we measured and analyzed the surface resistance R_(s)attributed to the trapped magnetic flux induced by the Seebeck effect after quenching events.Second,for the first time,a low-beta bulk Nb cavity was plated with Cu on its outer surface using electroplating technology.We achieved a high peak electric field E_(pk)of~88.8 MV/m at 2 K and the unloaded quality factor Q_(0)at the E_(pk)of 88.8 MV/m exceeded 1×10^(10).This demonstrated that the electroplating Cu on the bulk Nb cavity is a practical method of developing the Cu-Nb composite superconducting cavity with superior thermal stability.The results presented here provide valuable insights for applying Cu-Nb composite superconducting cavities in superconducting accelerators with stringent operational stability requirements.
文摘BACKGROUND Fungal balls within the nasal cavity are an exceedingly rare clinical entity,typically presenting with nonspecific symptoms or being identified incidentally.CASE SUMMARY This report presents an incidental discovery of a fungal ball in the nasal cavity during routine imaging,with no associated clinical symptoms.CONCLUSION This case underscores the importance of considering the possibility of asympto-matic presentations of nasal fungal balls,which may be detected incidentally during imaging evaluations.
基金Supported by the Fundamental Research Funds for the Central Universities(ZYGX2021J008)。
文摘A novel substrate integrated microstrip to ultra-thin cavity filter transition operating in the W-band is proposed in this letter.The structure is a new method of connecting microstrip circuits and waveguide filters,and this new structure enables a planar integrated transition from microstrip lines to ultra-thin cavity filters,thereby reducing the size of the transition structure and achieving miniaturization.The structure includes a conventional tapered microstrip transition structure,which guides the electromagnetic field from the microstrip line to the reduced-height dielectric-filled waveguide,and an air-filled matching cavity which is placed between the dielectric-filled waveguide and the ultra-thin cavity filter.The heights of the microstrip line,the dielectric-filled waveguide and the ultra-thin cavity filter are the same,enabling seamless integration within a planar radio-frequency(RF)circuit.To facilitate testing,mature finline transition structures are integrated at both ends of the microstrip line during fabrications.The simulation results of the fabricated microstrip to ultra-thin cavity filter transition with the finline transition structure,with a passband of 91.5-96.5 GHz,has an insertion loss of less than 1.9 dB and a return loss lower than-20 dB.And the whole structure has also been measured which achieves an insertion loss less than 2.6 dB and a return loss lower than-15 dB within the filter's passband,including the additional insertion loss introduced by the finline transitions.Finally,a W-band compact up-conversion module is designed,and the test results show that after using the proposed structure,the module achieves 95 dBc suppression of the 84 GHz local oscillator.It is also demonstrated that the structure proposed in this letter achieves miniaturization of the system integration without compromising the filter performance.
基金National Natural Science Foundation of China(52375378)National Key Laboratory of Metal Forming Technology and Heavy Equipment(S2308100.W12)Huxiang High-Level Talent Gathering Project of Hunan Province(2021RC5001)。
文摘The titanium alloy strut serves as a key load-bearing component of aircraft landing gear,typically manufactured via forging.The friction condition has important influence on material flow and cavity filling during the forging process.Using the previously optimized shape and initial position of preform,the influence of the friction condition(friction factor m=0.1–0.3)on material flow and cavity filling was studied by numerical method with a shear friction model.A novel filling index was defined to reflect material flow into left and right flashes and zoom in on friction-induced results.The results indicate that the workpiece moves rigidly to the right direction,with the displacement decreasing as m increases.When m<0.18,the underfilling defect will occur in the left side of strut forging,while overflow occurs in the right forging die cavity.By combining the filling index and analyses of material flow and filling status,a reasonable friction factor interval of m=0.21–0.24 can be determined.Within this interval,the cavity filling behavior demonstrates robustness,with friction fluctuations exerting minimal influence.
文摘The concept of emissivity has been with the scientific and engineering world since Planck formulated his blackbody radiation law more than a century ago.Nevertheless,emissivity is an elusive concept even for ex⁃perts.It is a vague and fuzzy concept for the wider community of engineers.The importance of remote sensing of temperature by measuring IR radiation has been recognized in a wide range of industrial,medical,and environ⁃mental uses.One of the major sources of errors in IR radiometry is the emissivity of the surface being measured.In real experiments,emissivity may be influenced by many factors:surface texture,spectral properties,oxida⁃tion,and aging of surfaces.While commercial blackbodies are prevalent,the much-needed grey bodies with a known emissivity,are unavailable.This study describes how to achieve a calibrated and stable emissivity with a blackbody,a perforated screen,and a reliable and linear novel IR thermal sensor,18 dubbed TMOS.The Digital TMOS is now a low-cost commercial product,it requires low power,and it has a small form factor.The method⁃ology is based on two-color measurements,with two different optical filters,with selected wavelengths conform⁃ing to the grey body definition of the use case under study.With a photochemically etched perforated screen,the effective emissivity of the screen is simply the hole density area of the surface area that emits according to the blackbody temperature radiation.The concept is illustrated with ray tracing simulations,which demonstrate the approach.Measured results are reported.
文摘A metal-sensitive diaphragm fiber optic pressure sensor with temperature compensation is developed for pressure monitoring in high-temperature environments,such as engine fuel systems,oil and gas wells,and aviation hydraulic systems.The sensor combines a metal-sensitive diaphragm and a sapphire wafer to form a temperature-pressure dual Fabry-Perot(FP)interference cavity.A cross-correlation signal demodulation algorithm and a temperature decoupling method are utilized to reduce the influence of temperature crosstalk on pressure measurement.Experimental results show that the maximum nonlinear error of the sensor pressure measurement is 0.75%full scale(FS)and 0.99%FS at room temperature and 300°C,respectively,in a pressure range of 0−10 MPa and 0−1.5 MPa.The sensor’s pressure measurement accuracy is 1.7%FS when using the temperature decoupling method.The sensor exhibits good static pressure characteristics,stability,and reliability,providing an effective solution for high-temperature pressure monitoring applications.
文摘A plasmonics waveguide structure that consist of a non-through metal–insulator–metal(MIM)waveguide coupled with a D-shaped cavity was designed.And the transmission properties,magnetic field distribution,and refractive index sensing functionality were simulated using the finite element method(FEM).A multi-Fano resonance phenomenon was clearly observable in the transmission spectra.The Fano resonances observed in the proposed structure arise from the interaction between the discrete states of the Dshaped resonant cavity and the continuum state of the non-through MIM waveguide.The influence of structural parameters on Fano resonance modulation was investigated through systematic parameter adjustments.Additionally,the refractive index sensing properties,based on the Fano resonance,were investigated by varying the refractive index of the MIM waveguide's insulator layer.A maximum sensitivity and FOM of 1155 RIU/nm and 40 were achieved,respectively.This research opens up new possibilities for designing and exploring high-sensitivity photonic devices,micro-sensors,and innovative on-chip sensing architectures for future applications.
文摘The China Spallation Neutron Source(CSNS)is the fourth pulsed accelerator-driven neutron source in the world,and it achieved its design target of 100 kW in 2020.The planned China Spallation Neutron Source Phase II(CSNS-II)commenced in 2024.The CSNS-II linac design primarily involves the addition of a radio-frequency ion source and a section of a superconducting linear accelerator composed of two types of superconducting cavities,namely double-spoke and six-cell elliptical cavities,after the drift tube linac(DTL).The development of the double-spoke superconducting cavity began in early 2021,and by January 2023,the welding,post-processing,and vertical tests of two 324 MHz double-spoke cavity prototypes were completed,with vertical test gradients of 11.6 and 15 MV/m,and Q_(0)≥3×10^(10)@E_(acc)≤10 MV/m.The R&D of the cryomodule began in January 2022.In October 2023,the clean assembly of the double-spoke cavity string and cold mass installation of the cryomodule commenced,with the installation of the cryomodule and valve box completing in two months.In January 2024,a horizontal test of the cryomodule was completed,making it the first double-spoke cavity cryomodule in China.The test results showed that the maximum gradients of the two superconducting cavities at a pulse width of 4 ms and repetition frequency of 25 Hz were 12.8 and 15.2 MV/m,respectively.This article provides a detailed introduction to the double-spoke superconducting cavity,tuner,coupler,and cryomodule,elaborates on the clean assembly of the cavity string and cold mass installation of the cryomodule,and provides a detailed analysis of the horizontal test results.
基金the fundings from National Key R&D Program of China (Grant No. 2022YFA1404002)National Natural Science Foundation of China (Grant Nos. T2495253, U20A20218, 61525504, and 61435011)+4 种基金Anhui Initiative in Quantum Information Technologies (Grant No. AHY020200)Major Science and Technology Projects in Anhui Province (Grant No. 202203a13010001)Youth Innovation Promotion Association of the Chinese Academy of Sciences (Grant No. 2018490)the fundings from Anhui Provincial Department of Education (Grant No. YQZD2024061)Research Program of Higher Education Institutions in Anhui Province (Grant No. 2024AH050645)。
文摘Developing microwave electric field sensing based on Rydberg atoms has received significant attention due to its unique advantages. However, achieving effective coupling between Rydberg atoms and the microwave electric field in the sensing process is a challenging problem that greatly impacts the sensitivity. To address this, we propose using a microwave resonant cavity to enhance the effective coupling between the Rydberg atoms and the microwave electric field. In our experiment, Rydberg atoms are prepared via a three-photon excitation scheme, and the electric fields are measured without and with a microwave cavity in which the vapor cell is placed inside, respectively. As a result, we achieved an 18 dB enhancement of power sensitivity by adding the cavity,which is an effective enhancement in electric field pulse signal detection. This experimental testing provides a promising direction for enhancing the sensitivity of Rydberg atomic electric field sensors and paves the way for their application in precision electric field measurements.
基金supported in part by the National Natural Science Foundation of China(NSFC)(Grant No.62001322)in part by the National Key Research and Development Program(Grant No.2020YFB2008800).
文摘In conventional piezoelectric micromachined ultrasonic transducers(PMUTs),the backside acoustic energy is often used inefficiently,resulting in up to half of the energy being wasted.Vacuum encapsulation can improve the energy utilization efficiency,but this technique is not compatible with state-of-the-art devices such as cantilever-based PMUTs.A closed back cavity provides an alternative method for effectively utilizing the backside acoustic energy.This paper investigates the effects of a closed back cavity on PMUT performance through theoretical analysis,simulations,and experimental verification.Increasing the cavity depth produces a periodic modulation of several key PMUT metrics,such as the relative frequency deviation and quality factor.The optimal cavity depth for PMUTs that ensures a robust resonant frequency and high quality factor is defined as a function of the acoustic wavelength.A closed back cavity also provides an effective method for continuously tuning the quality factor,and thus the bandwidth,of PMUTs.This work paves the way for air-coupled PMUTs with adjustable performance for various applications.
基金supported by the Natural Science Foundation of Zhejiang Province(Grant No.LY24A040004)the“Pioneer”and“Leading Goose”R&D Program of Zhejiang(Grant No.2025C01028)+2 种基金the Shenzhen International Quantum Academy(Grant No.SIQA2024KFKT010)YWW is supported by the Natural Science Foundation of Zhejiang Province(Grant No.LY23A40002)Wenzhou Science and Technology Plan Project(Grant No.L20240004).
文摘Microwave–optical entanglement is essential for efficient quantum communication,secure information transfer,and integrating microwave and optical quantum systems to advance hybrid quantum technologies.In this work,we demonstrate how the magnon Kerr effect can be harnessed to generate and control nonreciprocal entanglement in cavity optomagnomechanics(COMM).This effect induces magnon frequency shifts and introduces pair-magnon interactions,both of which are tunable through the magnetic field direction,enabling nonreciprocal behavior.By adjusting system parameters such as magnon frequency detuning,we show that magnon–phonon,microwave–optical photon–photon,and optical photon–magnon entanglement can be nonreciprocally enhanced and rendered more robust against thermal noise.Additionally,the nonreciprocity of entanglement can be selectively controlled,and ideal nonreciprocal entanglement is achievable.This work paves the way for designing nonreciprocal quantum devices across the microwave and optical regimes,leveraging the unique properties of the magnon Kerr effect in COMM.
基金supported by the Natural Science Foundation of Jiangsu Province(Grant No.BK20240613)Jiangsu Province’s“Innovation and Entrepreneurship Doctor”Program(Grant No.JSSCBS20230088)+4 种基金Natural Science Foundation of Nanjing University of Posts and Telecommunications(Grant No.NY224123)Natural Science Research Start-up Foundation of Recruiting Talents of Nanjing University of Posts and Telecommunications(Grant No.NY222112)Beijing Nova Program(Grant No.20240484696)Wenzhou Major Science and Technology Innovation Key Project(Grant No.ZG2020046)INNOVATION Program for Quantum Science and Technology(Grant No.2021ZD0303200)。
文摘The topic of improving the mechanical stability of external cavity diode lasers(ECDLs)has recently attracted widespread attention and interest.The use of corner-cube-array(CCA)-based resonators provides a potential solution for this purpose,although continuous oscillation at super large incident angle remains challenging.In this work,we employ the CCA resonator to generate continuous oscillation within±20°angular misalignment of cavity mirror in experiment.On the basis of retroreflection theory,the retroreflectivity of a CCA is analyzed by using optical simulation software.Notably,the experiment verifies the advantage of using a CCA over a plane mirror in laser resonator,thereby providing a promising approach for ECDLs.The threshold characteristic curves measured at different incident angles in the experiment verify that the CCA possesses an obvious anti-angle misalignment performance.This research introduces an alternative solution of using CCA resonator instead of parallel plane cavity,thereby realizing an adjustment-free ECDL with enhanced mechanical stability.
文摘Objective:To consolidate the scarce and scattered evidence on oral cysticercosis,a rare and often overlooked manifestation of Taenia solium infection.Methods:A comprehensive literature search was conducted in three major databases:PubMed,Scopus,and Embase.A total of 75 records were initially identified(PubMed:n=23;Scopus:n=29;Embase:n=23).After screening and eligibility assessment,22 studies meeting inclusion criteria were selected for final analysis.Results:Oral cysticercosis primarily involved the tongue,typically presenting as a painless swelling.The majority of reported cases were from India.Clinically,it was most often misdiagnosed as a mucocele or fibroma,with cysticercosis rarely considered due to its uncommon occurrence.Among the muscles affected,the masseter,mentalis,and buccinator were most frequently involved.Diagnosis was primarily made through histopathological examination.Treatment commonly included surgical excision,and albendazole was the most frequently used antiparasitic medication.Recurrence was uncommon,except in cases with disseminated or deep muscular involvement.Conclusions:Oral cysticercosis should be considered a potential differential diagnosis,particularly in regions where pork consumption is common.Given that most reported cases originated from India,pathologists in this region should maintain a high index of suspicion.Oral pathologists,in particular,should be well-acquainted with its histopathological features to ensure accurate diagnosis and avoid diagnostic pitfalls.
