This article investigates the radial electromagnetic force,vibration,and noise phenomenon in a low-speed,hightorque density spoke-type permanent magnet synchronous machine(ST-PMSM)designed with assisted poles having s...This article investigates the radial electromagnetic force,vibration,and noise phenomenon in a low-speed,hightorque density spoke-type permanent magnet synchronous machine(ST-PMSM)designed with assisted poles having symmetric and asymmetric topologies.Firstly,an analytical expression for the machine radial electromagnetic force(REMF)is derived to quickly estimate the REMF characteristics for the ST-PMSM with assisted poles having symmetric and asymmetric topologies.The 2D-Fourier decomposition method is applied to investigate the radial electromagnetic force harmonics(REMFHs).Secondly,Finite element(FE)models are designed for the machine structural analysis.Subsequently,the FE models and modal analysis are explored for different design cases of the analyzed machine.Lastly,vibration and noise behavior are investigated using an FE approach for the machine designs under symmetric and asymmetric assisted poles topologies.The findings indicate an increase in the richness of REMFHs,alongside a decrease in both the fundamental frequency and the lowest non-zero order of REMF,attributed to the presence of asymmetric assisted poles.Consequently,it is investigated that while considering the vibration and noise response in STPMSMs designed with asymmetric assisted poles topologies,it is essential to thoroughly account for induced non-zero low-order harmonics and their optimization for better vibration and noise performance.展开更多
Combining the detached eddy simulation(DES)method and Ffowcs Williams-Hawkings(FW-H)equation,the effect of bogie cavity end wall inclination on the flow field and aerodynamic noise in the bogie region is numerically s...Combining the detached eddy simulation(DES)method and Ffowcs Williams-Hawkings(FW-H)equation,the effect of bogie cavity end wall inclination on the flow field and aerodynamic noise in the bogie region is numerically studied.First,the simulation is conducted based on a simplified cavity-bogie model,including five cases with different inclination angles of the front and rear walls of the cavity.By comparing and analyzing the flow field and acoustic results of the five cases,the influence of the regularity and mechanism of the bogie cavity end wall inclination on the flow field and the aerodynamic noise of the bogie region are revealed.Then,the noise reduction strategy determined by the results of the simplified cavity-bogie model is applied to a three-car marshaling train model to verify its effectiveness when applied to the real train.The results reveal that the forward inclination of the cavity front wall enlarges the influence area of shear vortex structures formed at the leading edge of the cavity and intensifies the interaction between the vortex structures and the front wheelset,frontmotor,and front gearbox,resulting in the increase of the aerodynamic noise generated by the bogie itself.The backward inclination of the cavity rear wall is conducive to guiding the vortex structures flow out of the cavity and weakening the interaction between the shear vortex structures and the cavity rear wall,leading to the reduction of the aerodynamic noise generated by the bogie cavity.Inclining the rear end wall of the foremost bogie cavity of the head car is a feasible aerodynamic noise reduction measure for high-speed trains.展开更多
To enhance flow stability and reduce hydrodynamic noise caused by fluctuating pressure,a quasiperiodic elastic support skin composed of flexible walls and elastic support elements is proposed for fluid noise reduction...To enhance flow stability and reduce hydrodynamic noise caused by fluctuating pressure,a quasiperiodic elastic support skin composed of flexible walls and elastic support elements is proposed for fluid noise reduction.The arrangement of the elastic support element is determined by the equivalent periodic distance and quasi-periodic coefficient.In this paper,a dynamic model of skin in a fluid environment is established.The influence of equivalent periodic distance and quasi-periodic coefficient on flow stability is investigated.The results suggest that arranging the elastic support elements in accordance with the quasi-periodic law can effectively enhance flow stability.Meanwhile,the hydrodynamic noise calculation results demonstrate that the skin exhibits excellent noise reduction performance,with reductions of 10 dB in the streamwise direction,11 dB in the spanwise direction,and 10 dB in the normal direction.The results also demonstrate that the stability analysis method can serve as a diagnostic tool for flow fields and guide the design of noise reduction structures.展开更多
A combined method of wave superposition and finite element is proposed to solve the radiation noise of targets in shallow sea.Taking the sound propagation of spherical sound source in shallow sea as an example,the rad...A combined method of wave superposition and finite element is proposed to solve the radiation noise of targets in shallow sea.Taking the sound propagation of spherical sound source in shallow sea as an example,the radiation sound field of the spherical sound source is equivalent to the linear superposition of the radiation sound field of several internal point sound sources,and then the radiated noise induced by spherical sound source can be predicted quickly.The accuracy and efficiency of the method are verified by comparing with the numerical results of finite element method,and the rapid prediction of underwater radiated noise of cylindrical shell is carried out based on the method.The results show that compared with the finite element method,the relative error of the calculation results under different simulation conditions does not exceed 0.1%,and the calculation time is about 1/10 of the finite element method,so this method can be used to solve the radiated noise of shallow underwater targets.展开更多
A significant aerodynamic noise from wind turbines arises when the rotating blades interact with turbulent flows.Though the trailing edge of the blade is an important source of noise at high frequencies,the present wo...A significant aerodynamic noise from wind turbines arises when the rotating blades interact with turbulent flows.Though the trailing edge of the blade is an important source of noise at high frequencies,the present work deals with the influence of turbulence distortion on leading edge noise from wind turbine blades which becomes significant in low-frequency regions.Four quasi-empirical methods are studied to verify the accuracy of turbulent inflow noise predicted at low frequencies for a 2 MW horizontal axis wind turbine.Results have shown that all methods exhibited a downward linear trend in noise spectra for a given mean wind speed except at very low frequencies.With an increase in turbulence intensity from 6%to 14%,the sound power was found to increase almost linearly,and the standard error for sound power was reduced for all methods studied.The computed results were validated and agreed well with experiment noise data from Siemens SWT-2.3MW 93 wind turbine.展开更多
The Binchuan Basin in northwest Yunnan, southwest China, is a rift basin developed at the intersection of the Red River Fault and Chenghai Fault, where historical earthquakes have occurred. Understanding the fine velo...The Binchuan Basin in northwest Yunnan, southwest China, is a rift basin developed at the intersection of the Red River Fault and Chenghai Fault, where historical earthquakes have occurred. Understanding the fine velocity structure of the shallow crust in this region can help improve earthquake location accuracy and our understanding of the relationship between fault zone structures and fault slip behaviors. Using the continuous waveform data recorded by 381 dense array stations in 2017, we obtained 7 915 Rayleigh-wave phase velocity dispersion curves in the period band of 0.2–6 s from ambient noise cross-correlation functions after rigorous data processing and quality control. We determined 3D isotropic and azimuthally anisotropic shear wave velocity models at depths above 6 km in the shallow crust based on the direct surface wave azimuthal anisotropic tomography method. The isotropic model reveals a strong correspondence between the S-wave velocity structure at depths of 0–1 km and the regional topography and lithology. The Binchuan depocenter, Zhoucheng depocenter, Xiangyun Basin, and Xihai Rift Basin are primarily composed of Quaternary deposits, which show low-velocity anomalies, while the regions with the Paleozoic shale, limestone, and basalt exhibit high-velocity anomalies. The nearly N–S orientation of fast directions from azimuthal anisotropy models are mainly controlled by the active Binchuan Fault with N–S strike as well as the NNW-oriented primary compressive stress.展开更多
This work details the development of a broad-spectrum LNA (Low Noise Amplifier) circuit using a 65 nm CMOS technology. The design incorporates an inductive degeneracy circuit, employing a theoretical approach to enhan...This work details the development of a broad-spectrum LNA (Low Noise Amplifier) circuit using a 65 nm CMOS technology. The design incorporates an inductive degeneracy circuit, employing a theoretical approach to enhance gain, minimize noise levels, and uphold low power consumption. The progression includes a shift to a cascode structure to further refine LNA parameters. Ultimately, with a 1.8 V bias, the achieved performance showcases a gain-to-noise figure ratio of 16 dB/0.5 dB, an IIP3 linearity at 5.1 dBm, and a power consumption of 3 mW. This architecture is adept at operating across a wide frequency band spanning from 0.5 GHz to 6 GHz, rendering it applicable in diverse RF scenarios.展开更多
Advances in software and hardware technologies have facilitated the production of quadrotor unmanned aerial vehicles(UAVs).Nowadays,people actively use quadrotor UAVs in essential missions such as search and rescue,co...Advances in software and hardware technologies have facilitated the production of quadrotor unmanned aerial vehicles(UAVs).Nowadays,people actively use quadrotor UAVs in essential missions such as search and rescue,counter-terrorism,firefighting,surveillance,and cargo transportation.While performing these tasks,quadrotors must operate in noisy environments.Therefore,a robust controller design that can control the altitude and attitude of the quadrotor in noisy environments is of great importance.Many researchers have focused only on white Gaussian noise in their studies,whereas researchers need to consider the effects of all colored noises during the operation of the quadrotor.This study aims to design a robust controller that is resistant to all colored noises.Firstly,a nonlinear quadrotormodel was created with MATLAB.Then,a backstepping controller resistant to colored noises was designed.Thedesigned backstepping controller was tested under Gaussian white,pink,brown,blue,and purple noises.PID and Lyapunov-based controller designswere also carried out,and their time responses(rise time,overshoot,settling time)were compared with those of the backstepping controller.In the simulations,time was in seconds,altitude was in meters,and roll,pitch,and yaw references were in radians.Rise and settling time values were in seconds,and overshoot value was in percent.When the obtained values are examined,simulations prove that the proposed backstepping controller has the least overshoot and the shortest settling time under all noise types.展开更多
Submarine seismic ambient noise imaging combines current marine and on-land seismic detection technologies.Based on data from several broadband shallow-sea type ocean bottom seismometers(SOBSs)deployed in the Bohai Se...Submarine seismic ambient noise imaging combines current marine and on-land seismic detection technologies.Based on data from several broadband shallow-sea type ocean bottom seismometers(SOBSs)deployed in the Bohai Sea and north Yellow Sea,this paper analyzes the submarine seismic ambient noise characteristics.It explores the theory,technology,method and application of the submarine seismic ambient noise imaging using the single-point horizontal and vertical spectral ratio method(HVSR).The observations yield the following results:1)Submarine seismic ambient noise has consistent and constant energy,making it an appropriate passive seismic source for submarine high-frequency surface wave investigation.2)Using the HVSR approach,a single threecomponent OBS could differentiate between the basement and sediments.Array seismic observation could be utilized to extract the frequency dispersion curve and invert it to obtain the velocity structure for more accurate stratification.3)The SOBS we use is suitable for submarine surface wave exploration.4)Tomography results with greater resolution and deeper penetration could be obtained by combining active and passive sources in a simultaneous inversion of the HVSR and frequency dispersion curve.Seamless land-to-ocean seismic research can be accomplished with submarine seismic ambient noise imaging technologies.展开更多
During the continuous casting process of high-Mn high-Al steels,various types of gases such as Ar need to escape through the top of the mold.In which,the behavior of bubbles traversing the liquid slag serves as a rest...During the continuous casting process of high-Mn high-Al steels,various types of gases such as Ar need to escape through the top of the mold.In which,the behavior of bubbles traversing the liquid slag serves as a restrictive link,closely associated with viscosity and the thickness of liquid slag.In contrast to two-dimensional surface observation,three-dimensional(3D)analysis method can offer a more intuitive,accurate,and comprehensive information.Therefore,this study employs a 3D X-ray microscope(3D-XRM)to obtained spatial distribution and 3D morphological characteristics of residual bubbles in mold flux under different basicity of liquid slag,different temperatures,and different holding times.The results indicate that as basicity of slag increases from 0.52 to 1.03,temperature increases from 1423 to 1573 K,the viscosity of slag decreases,the floating rate of bubbles increases.In addition,when holding time increases from 10 to 30 s,the bubbles floating distance increases,and the volume fraction and average equivalent sphere diameter of the bubbles solidified in the mold flux gradually decreases.In one word,increasing the basicity,temperature,and holding time leading to an increase in the removal rate of bubbles especially for the large.These findings of bubbles escape behavior provide valuable insights into optimizing low basicity mold flux for high-Mn high-Al steels.展开更多
The use of lithium-sulfur(Li-S)batteries is limited by sulfur redox reactions involving multi-phase transformations,especially at low-temperatures.To address this issue,we report a material(FCNS@NCFs)consisting of nit...The use of lithium-sulfur(Li-S)batteries is limited by sulfur redox reactions involving multi-phase transformations,especially at low-temperatures.To address this issue,we report a material(FCNS@NCFs)consisting of nitrogen-doped carbon fibers loaded with a ternary metal sulf-ide((Fe,Co,Ni)_(9)S_(8))for use as the sulfur host in Li-S batteries.This materi-al was prepared using transfer blot filter paper as the carbon precursor,thiourea as the source of nitrogen and sulfur,and FeCl_(3)·6H_(2)O,CoCl_(2)·6H_(2)O and NiCl_(2)·6H_(2)O as the metal ion sources.It was synthesized by an impreg-nation method followed by calcination.The nitrogen doping significantly in-creased the conductivity of the host,and the metal sulfides have excellent catalytic activities.Theoretical calculations,and adsorption and deposition experiments show that active sites on the surface of FCNS@NCFs selectively adsorb polysulfides,facilitate rapid adsorption and conversion,prevent cathode passivation and inhib-it the polysulfide shuttling.The FCNS@NCFs used as the sulfur host has excellent electrochemical properties.Its initial dis-charge capacity is 1639.0 mAh g^(−1) at 0.2 C and room temperature,and it remains a capacity of 1255.1 mAh g^(−1) after 100 cycles.At−20~C,it has an initial discharge capacity of 1578.5 mAh g^(−1) at 0.2 C,with a capacity of 867.5 mAh g^(−1) after 100 cycles.Its excellent performance at both ambient and low temperatures suggests a new way to produce high-performance low-temper-ature Li-S batteries.展开更多
Introduction: Common low-back pain is a frequent reason for consultation and a genuine public health problem. Preserving quality of life remains one of the main challenges. Objective: To evaluate the quality of life o...Introduction: Common low-back pain is a frequent reason for consultation and a genuine public health problem. Preserving quality of life remains one of the main challenges. Objective: To evaluate the quality of life of patients with low back pain seen in rheumatology consultations at Brazzaville University Hospital. Patients and Method: Cross-sectional, analytical study with control group, conducted at the Brazzaville University Hospital, from January 2 to September 30, 2023. Patients over 30 years of age, seen for documented common low-back pain, were included. Study variables were epidemiological, clinical and functional. The EIFEL and SF-36 scores were used to assess functional impact and quality of life, respectively. Results: We included 96 people divided into two groups: 48 patients with low back pain and 48 controls. The frequency of common low-back pain was 12.8%. The mean age of patients with low back pain was 59.14 ± 11.86 years. Women predominated (sex ratio 0.3). Degenerative disc disease was the main etiology. Common low-back pain had a moderate impact on functional abilities, with a mean EIFEL score of 11 +/− 5.51. Quality of life was impaired in patients with low back pain (overall SF-36 at 43.95%) compared with the control group, with a statistically significant difference (P Conclusion: Common low back pain affects patients’ overall quality of life, particularly in terms of physical pain and limitations due to physical condition.展开更多
1989 is the beginning of intensive research into the phenomena of cold nuclear fusion, renamed “The Low Energy Nuclear Synthesis Reactions” (LENR). Based on these results and the long-term research of earthquakes an...1989 is the beginning of intensive research into the phenomena of cold nuclear fusion, renamed “The Low Energy Nuclear Synthesis Reactions” (LENR). Based on these results and the long-term research of earthquakes and volcanic activity, the authors of this article put forward a hypothesis about the mainly chemical nature of the energy released at earthquakes and volcanic eruptions with the participation of primordial hydrogen and helium: high mobility of hydrogen and oxidizers provide focusing and accumulation of the latent chemical energy, which is realized suddenly and instantaneously as explosions and initiate the earthquake and/or eruptions. The volcanic eruption is viewed therein as a special type of earthquake whereby the hypocenter rises to the earth’s surface. The authors proposed a new hypothesis that LENRs significant energy to earthquakes and eruptions at the synthesis of elements lighter than iron, thus creating excess energy, which is partially used for the synthesis of heavier elements. The combination of the chemical and nuclear reactions transforms these centers of geophysical activity into giant reactors where the nuclear, chemical, and thermal transformation of mantle materials and the creation of primary deposits of heavy elements such as uranium, thorium, gold, etc. So, all chemical elements heavier than iron are not detected in the solar wind. These elements discovered on our planet could be (and probably were) created on planet Earth and not imported from explosive supernovae or far-off remote stars. To the best of our knowledge, this hypothesis has not been proposed until now.展开更多
Background: Chronic low back pain is a leading cause of morbidity and disability globally. Low and Middle-Income Countries (LMICs) tend to be more affected, with chronic low back pain (CLBP) being among the leading pr...Background: Chronic low back pain is a leading cause of morbidity and disability globally. Low and Middle-Income Countries (LMICs) tend to be more affected, with chronic low back pain (CLBP) being among the leading presenting complaints at specialist consultation. The exact burden of this disease is sparingly known in our setting. Objective: To evaluate the burden of chronic low back pain at the Yaounde Central Hospital. Methods: This was a descriptive cross-sectional study for a period of 3 months, from March 2022 to May 2022. After obtaining ethical clearance and research authorisations, data was collected using structured questionnaires from patients with chronic low back pain presenting at the Yaounde Central Hospital during the aforementioned time frame. This data was then tabulated with the Statistical Package for Social Sciences (SPSS 23.0), and disability was assessed using the modified Roland Morris Disability Questionnaire and the Oswestry Disability Index. Data analysis was done using the International Business Machines Statistical Package for Social Sciences (IBM-SPSS) VERSION 23.0. Results: 115 cases of CLBP were included. The mean age was 52.62 years, and the sex ratio was 0.3. The average monthly income was less than 50,000 frs CFA, in 37.4% of cases. In 57.9%, patients had a job that involved physical labour. The patients had a secondary level of education in 40.9%, and alcohol consumption was observed in 36%. The average number of days of a work stoppage due to LBP was 12.75 days (±12SD), and the median duration of CLBP was 7.15 (7.5SD) years. The median pain intensity was 7 (±2SD), with leg pain and sensory neuropathy observed in 67.8% and 63.5% respectively. Lumbar X-ray was done in 45.2% and revealed lumbar osteoarthrosis in 62.4%. Hypertension as a comorbidity was observed in 26.1%. Medical treatment was used at least once in 98.3% of cases. The average cost of management per month was assessed, and the median was 52,000 FCFA (±20,876 SD). Using the Oswestry Disability Questionnaire, 46 patients, that is 40% of the study population, were classified as severely disabled with a median ODI score of 40%. The factors which were independently associated with disability were level of education, alcohol consumption, treatment modality, pain intensity, body mass index (BMI), psychological wellbeing and number of sick leave days. Conclusion: Chronic low back pain is common in our setting. There is a female predominance with the mean age of the study population situated in the 5th decade. Low-income earners and patients with a job involving physical labour were the most affected. Medical treatment was the main therapeutic modality, with the average cost of management per month being above the average monthly income of the greater majority of the patients. Several factors influenced disability, some of which were independently associated with it, such as level of education, alcohol consumption and treatment modality.展开更多
The challenge of aerodynamic noise is a key obstacle in the advancement of low-pressure tube ultra-high-speed maglev transportation,demanding urgent resolution.This study utilizes a broadband noise source model to per...The challenge of aerodynamic noise is a key obstacle in the advancement of low-pressure tube ultra-high-speed maglev transportation,demanding urgent resolution.This study utilizes a broadband noise source model to perform a quantitative analysis of the aerodynamic noise produced by ultra-high-speed maglev trains operating in low-pressure environments.Initially,an external flow field calculation model for the ultra-high-speed maglev train is presented.Subsequently,numerical simulations based on the broadband noise source model are used to examine the noise characteristics.The impact of the train speed and pressure level on noise generation is investigated accordingly.Subsequently,a correlation formula is derived.The results reveal that the amplitude of sound source changes in the streamlined region of the head and tail cars of the train is large,and the amplitude of changes for the middle car is smaller.The noise source strength increases with speed,with a quadrupole noise source becoming dominant when the train speed exceeds 600 km/h.At a speed of 1000 km/h,the noise source intensity from the streamlined area at the rear of the train overcomes that at the front.Furthermore,the noise source decreases as the pressure level in the tube decreases.When the pressure level drops to 0.01 atm,the quadrupole noise source intensity of a train running at 600 km/h significantly weakens and falls below that of the dipole noise source.展开更多
The advancement of intelligent mining in open-pit operations has imposed higher demands on geological transparency,aiming to provide a robust foundation for intelligent drilling and charging.In this study,a linear arr...The advancement of intelligent mining in open-pit operations has imposed higher demands on geological transparency,aiming to provide a robust foundation for intelligent drilling and charging.In this study,a linear array of 120 nodal seismometers was deployed along the surfaces of the C8 and C9 platforms at Fenghuang Mountain to investigate cavities within the rock mass and prevent improper intelligent charging.The seismometers were 1 m apart along measurement lines,with a 2-m spacing between lines,and the monitoring time for each line was set at 2 h.This deployment was paired with spatial autocorrelation and station autocorrelation to analyze ambient noise seismic data and image the velocity and structure within the rock mass.The results demonstrate that the locations and sizes of cavities or loose structures can be accurately identifi ed at the prepared excavation site.Compared with traditional geological exploration methods for openpit mines,the approach in this study off ers higher accuracy,greater effi ciency,reduced labor intensity,and insensitivity to water conditions.Ambient noise seismic imaging for detecting adverse geological conditions in open-pit mines provides critical insights and references for intelligent mining advancements.展开更多
In this paper,we investigate covert communications under multi-antenna detection,and explore the impacts of the warden’s channel state information(CSI)availability and the noise uncertainty on system covert capabilit...In this paper,we investigate covert communications under multi-antenna detection,and explore the impacts of the warden’s channel state information(CSI)availability and the noise uncertainty on system covert capability.The detection performance at warden is analyzed in two cases under the perfect and statistical CSI at warden,respectively.In particular,for the former one,the warden utilizes the likelihood ratio(LR)detector,while for the latter one,the generalized likelihood ratio(GLR)detector is adopted.We first consider the scenario where the blocklength is finite,and demonstrate that the covert rate under both cases asymptotically goes to zero as the blocklength goes to infinity.Subsequently,we take the noise uncertainty at the warden into account which leads to positive covert rate,and characterize the covert rate for infinite blocklength.Specially,we derive the optimal transmit power for the legitimate transmitter that maximizes the covert rate.Besides,the rate gap under two cases,with different CSI availability at the warden,can be presented in closed form.Finally,numerical results validate the effectiveness of our theoretical analysis and also demonstrate the impacts of the factors studied on the system covertness.展开更多
Low temperature(LT)in spring has become one of the principal abiotic stresses that restrict the growth and development of wheat.Diverse analyses were performed to investigate the mechanism underlying the response of w...Low temperature(LT)in spring has become one of the principal abiotic stresses that restrict the growth and development of wheat.Diverse analyses were performed to investigate the mechanism underlying the response of wheat grain development to LT stress during booting.These included morphological observation,measurements of starch synthase activity,and determination of amylose and amylopectin content of wheat grain after exposure to treatment with LT during booting.Additionally,proteomic analysis was performed using tandem mass tags(TMT).Results showed that the plumpness of wheat grains decreased after LT stress.Moreover,the activities of sucrose synthase(SuS,EC 2.4.1.13)and ADP-glucose pyrophosphorylase(AGPase,EC 2.7.7.27)exhibited a significant reduction,leading to a significant reduction in the contents of amylose and amylopectin.A total of 509 differentially expressed proteins(DEPs)were identified by proteomics analysis.The Gene Ontology(GO)enrichment analysis showed that the protein difference multiple in the nutritional repository activity was the largest among the molecular functions,and the up-regulated seed storage protein(ssP)played an active role in the response of grains to LT stress and subsequent damage.The Kyoto Encyclopedia of Genes and Genomes(KEGG)enrichment analysis showed that LT stress reduced the expression of DEPs such as sucrose phosphate synthase(SPS),glucose-1-phosphate adenylyltransferase(glgC),andβ-fructofuranosidase(FFase)in sucrose and starch metabolic pathways,thus affecting the synthesis of grain starch.In addition,many heat shock proteins(HsPs)were found in the protein processing in endoplasmic reticulum pathways,which can resist some damage caused by LT stress.These findings provide a new theoretical foundation for elucidating the underlying mechanism governing wheat yield developmentafterexposuretoLTstress inspring.展开更多
This study analyzed ambient seismic noise using the MSNoise package to monitor temporal changes in the underground seismic wave velocity in Mining Area 6 of the Dongtan Coal Mine in China.The data was recorded continu...This study analyzed ambient seismic noise using the MSNoise package to monitor temporal changes in the underground seismic wave velocity in Mining Area 6 of the Dongtan Coal Mine in China.The data was recorded continuously over 76 days by 7 three-component stations and 10 single-component microseismic stations deployed in Dongtan Coal Mine,with station spacing ranging from 0.1 km to approximately 3 km.Using the causal and non-causal components of the Z-component cross-correlation function,along with moving-window cross-spectrum analysis and cumulative calculations with a 5-day window overlay,stable seismic velocity changes were obtained in the frequency band of 0.1 to 2 Hz.We found a correlation between the timing of average velocity changes and seismic events caused by underground mining processes.In particular,when the relative seismic velocity increased by 0.23%,larger energy minequakes typically occurred.This study shows that ambient noise correlation has great potential for predicting minequakes,guiding pressure-relief production,and providing warnings about the impact of overburden pressure.展开更多
基金supported by the National Key Research and Developmen Program of China(2022YFB3403100)。
文摘This article investigates the radial electromagnetic force,vibration,and noise phenomenon in a low-speed,hightorque density spoke-type permanent magnet synchronous machine(ST-PMSM)designed with assisted poles having symmetric and asymmetric topologies.Firstly,an analytical expression for the machine radial electromagnetic force(REMF)is derived to quickly estimate the REMF characteristics for the ST-PMSM with assisted poles having symmetric and asymmetric topologies.The 2D-Fourier decomposition method is applied to investigate the radial electromagnetic force harmonics(REMFHs).Secondly,Finite element(FE)models are designed for the machine structural analysis.Subsequently,the FE models and modal analysis are explored for different design cases of the analyzed machine.Lastly,vibration and noise behavior are investigated using an FE approach for the machine designs under symmetric and asymmetric assisted poles topologies.The findings indicate an increase in the richness of REMFHs,alongside a decrease in both the fundamental frequency and the lowest non-zero order of REMF,attributed to the presence of asymmetric assisted poles.Consequently,it is investigated that while considering the vibration and noise response in STPMSMs designed with asymmetric assisted poles topologies,it is essential to thoroughly account for induced non-zero low-order harmonics and their optimization for better vibration and noise performance.
基金supported by National Natural Science Foundation of China(12172308)National Key Research and Development Program of China(2020YFA0710902).
文摘Combining the detached eddy simulation(DES)method and Ffowcs Williams-Hawkings(FW-H)equation,the effect of bogie cavity end wall inclination on the flow field and aerodynamic noise in the bogie region is numerically studied.First,the simulation is conducted based on a simplified cavity-bogie model,including five cases with different inclination angles of the front and rear walls of the cavity.By comparing and analyzing the flow field and acoustic results of the five cases,the influence of the regularity and mechanism of the bogie cavity end wall inclination on the flow field and the aerodynamic noise of the bogie region are revealed.Then,the noise reduction strategy determined by the results of the simplified cavity-bogie model is applied to a three-car marshaling train model to verify its effectiveness when applied to the real train.The results reveal that the forward inclination of the cavity front wall enlarges the influence area of shear vortex structures formed at the leading edge of the cavity and intensifies the interaction between the vortex structures and the front wheelset,frontmotor,and front gearbox,resulting in the increase of the aerodynamic noise generated by the bogie itself.The backward inclination of the cavity rear wall is conducive to guiding the vortex structures flow out of the cavity and weakening the interaction between the shear vortex structures and the cavity rear wall,leading to the reduction of the aerodynamic noise generated by the bogie cavity.Inclining the rear end wall of the foremost bogie cavity of the head car is a feasible aerodynamic noise reduction measure for high-speed trains.
基金National Natural Science Foundation of China(Grant Nos.52075111,51775123)Fundamental Research Funds for the Central Universities(Grant No.3072022JC0701)。
文摘To enhance flow stability and reduce hydrodynamic noise caused by fluctuating pressure,a quasiperiodic elastic support skin composed of flexible walls and elastic support elements is proposed for fluid noise reduction.The arrangement of the elastic support element is determined by the equivalent periodic distance and quasi-periodic coefficient.In this paper,a dynamic model of skin in a fluid environment is established.The influence of equivalent periodic distance and quasi-periodic coefficient on flow stability is investigated.The results suggest that arranging the elastic support elements in accordance with the quasi-periodic law can effectively enhance flow stability.Meanwhile,the hydrodynamic noise calculation results demonstrate that the skin exhibits excellent noise reduction performance,with reductions of 10 dB in the streamwise direction,11 dB in the spanwise direction,and 10 dB in the normal direction.The results also demonstrate that the stability analysis method can serve as a diagnostic tool for flow fields and guide the design of noise reduction structures.
基金Foundation item:This study was financially supported by the National Natural Science Foundation of China(Grant No.52101351)。
文摘A combined method of wave superposition and finite element is proposed to solve the radiation noise of targets in shallow sea.Taking the sound propagation of spherical sound source in shallow sea as an example,the radiation sound field of the spherical sound source is equivalent to the linear superposition of the radiation sound field of several internal point sound sources,and then the radiated noise induced by spherical sound source can be predicted quickly.The accuracy and efficiency of the method are verified by comparing with the numerical results of finite element method,and the rapid prediction of underwater radiated noise of cylindrical shell is carried out based on the method.The results show that compared with the finite element method,the relative error of the calculation results under different simulation conditions does not exceed 0.1%,and the calculation time is about 1/10 of the finite element method,so this method can be used to solve the radiated noise of shallow underwater targets.
文摘A significant aerodynamic noise from wind turbines arises when the rotating blades interact with turbulent flows.Though the trailing edge of the blade is an important source of noise at high frequencies,the present work deals with the influence of turbulence distortion on leading edge noise from wind turbine blades which becomes significant in low-frequency regions.Four quasi-empirical methods are studied to verify the accuracy of turbulent inflow noise predicted at low frequencies for a 2 MW horizontal axis wind turbine.Results have shown that all methods exhibited a downward linear trend in noise spectra for a given mean wind speed except at very low frequencies.With an increase in turbulence intensity from 6%to 14%,the sound power was found to increase almost linearly,and the standard error for sound power was reduced for all methods studied.The computed results were validated and agreed well with experiment noise data from Siemens SWT-2.3MW 93 wind turbine.
基金supported by the National Key R&D Program of China (2021YFC3000704)the Special Fund of Key Laboratory of Earthquake Prediction,CEA (2021IEF0103)the National Natural Science Foundation of China (42125401)。
文摘The Binchuan Basin in northwest Yunnan, southwest China, is a rift basin developed at the intersection of the Red River Fault and Chenghai Fault, where historical earthquakes have occurred. Understanding the fine velocity structure of the shallow crust in this region can help improve earthquake location accuracy and our understanding of the relationship between fault zone structures and fault slip behaviors. Using the continuous waveform data recorded by 381 dense array stations in 2017, we obtained 7 915 Rayleigh-wave phase velocity dispersion curves in the period band of 0.2–6 s from ambient noise cross-correlation functions after rigorous data processing and quality control. We determined 3D isotropic and azimuthally anisotropic shear wave velocity models at depths above 6 km in the shallow crust based on the direct surface wave azimuthal anisotropic tomography method. The isotropic model reveals a strong correspondence between the S-wave velocity structure at depths of 0–1 km and the regional topography and lithology. The Binchuan depocenter, Zhoucheng depocenter, Xiangyun Basin, and Xihai Rift Basin are primarily composed of Quaternary deposits, which show low-velocity anomalies, while the regions with the Paleozoic shale, limestone, and basalt exhibit high-velocity anomalies. The nearly N–S orientation of fast directions from azimuthal anisotropy models are mainly controlled by the active Binchuan Fault with N–S strike as well as the NNW-oriented primary compressive stress.
文摘This work details the development of a broad-spectrum LNA (Low Noise Amplifier) circuit using a 65 nm CMOS technology. The design incorporates an inductive degeneracy circuit, employing a theoretical approach to enhance gain, minimize noise levels, and uphold low power consumption. The progression includes a shift to a cascode structure to further refine LNA parameters. Ultimately, with a 1.8 V bias, the achieved performance showcases a gain-to-noise figure ratio of 16 dB/0.5 dB, an IIP3 linearity at 5.1 dBm, and a power consumption of 3 mW. This architecture is adept at operating across a wide frequency band spanning from 0.5 GHz to 6 GHz, rendering it applicable in diverse RF scenarios.
文摘Advances in software and hardware technologies have facilitated the production of quadrotor unmanned aerial vehicles(UAVs).Nowadays,people actively use quadrotor UAVs in essential missions such as search and rescue,counter-terrorism,firefighting,surveillance,and cargo transportation.While performing these tasks,quadrotors must operate in noisy environments.Therefore,a robust controller design that can control the altitude and attitude of the quadrotor in noisy environments is of great importance.Many researchers have focused only on white Gaussian noise in their studies,whereas researchers need to consider the effects of all colored noises during the operation of the quadrotor.This study aims to design a robust controller that is resistant to all colored noises.Firstly,a nonlinear quadrotormodel was created with MATLAB.Then,a backstepping controller resistant to colored noises was designed.Thedesigned backstepping controller was tested under Gaussian white,pink,brown,blue,and purple noises.PID and Lyapunov-based controller designswere also carried out,and their time responses(rise time,overshoot,settling time)were compared with those of the backstepping controller.In the simulations,time was in seconds,altitude was in meters,and roll,pitch,and yaw references were in radians.Rise and settling time values were in seconds,and overshoot value was in percent.When the obtained values are examined,simulations prove that the proposed backstepping controller has the least overshoot and the shortest settling time under all noise types.
基金supported by the Guangzhou Basic and Applied Basic Research Project (2023A04J0243)Natural Science Foundation of China (42106078)Dedicated Fund for Marine Economic Development in Guangdong Province (GDNRC[2023]40)。
文摘Submarine seismic ambient noise imaging combines current marine and on-land seismic detection technologies.Based on data from several broadband shallow-sea type ocean bottom seismometers(SOBSs)deployed in the Bohai Sea and north Yellow Sea,this paper analyzes the submarine seismic ambient noise characteristics.It explores the theory,technology,method and application of the submarine seismic ambient noise imaging using the single-point horizontal and vertical spectral ratio method(HVSR).The observations yield the following results:1)Submarine seismic ambient noise has consistent and constant energy,making it an appropriate passive seismic source for submarine high-frequency surface wave investigation.2)Using the HVSR approach,a single threecomponent OBS could differentiate between the basement and sediments.Array seismic observation could be utilized to extract the frequency dispersion curve and invert it to obtain the velocity structure for more accurate stratification.3)The SOBS we use is suitable for submarine surface wave exploration.4)Tomography results with greater resolution and deeper penetration could be obtained by combining active and passive sources in a simultaneous inversion of the HVSR and frequency dispersion curve.Seamless land-to-ocean seismic research can be accomplished with submarine seismic ambient noise imaging technologies.
基金financially supported by the National Natural Science Foundation of China(Nos.52274315 and 52374320)the Fundamental Research Funds for the Central Universities(Nos.FRF-TP-22-011A1 and FRF-DF22-16)。
文摘During the continuous casting process of high-Mn high-Al steels,various types of gases such as Ar need to escape through the top of the mold.In which,the behavior of bubbles traversing the liquid slag serves as a restrictive link,closely associated with viscosity and the thickness of liquid slag.In contrast to two-dimensional surface observation,three-dimensional(3D)analysis method can offer a more intuitive,accurate,and comprehensive information.Therefore,this study employs a 3D X-ray microscope(3D-XRM)to obtained spatial distribution and 3D morphological characteristics of residual bubbles in mold flux under different basicity of liquid slag,different temperatures,and different holding times.The results indicate that as basicity of slag increases from 0.52 to 1.03,temperature increases from 1423 to 1573 K,the viscosity of slag decreases,the floating rate of bubbles increases.In addition,when holding time increases from 10 to 30 s,the bubbles floating distance increases,and the volume fraction and average equivalent sphere diameter of the bubbles solidified in the mold flux gradually decreases.In one word,increasing the basicity,temperature,and holding time leading to an increase in the removal rate of bubbles especially for the large.These findings of bubbles escape behavior provide valuable insights into optimizing low basicity mold flux for high-Mn high-Al steels.
基金partially supported by National Natural Science Foundation of China(52172250)Institute of Process Engineering(IPE)Project for Frontier Basic Research(QYJC-2023-06)。
文摘The use of lithium-sulfur(Li-S)batteries is limited by sulfur redox reactions involving multi-phase transformations,especially at low-temperatures.To address this issue,we report a material(FCNS@NCFs)consisting of nitrogen-doped carbon fibers loaded with a ternary metal sulf-ide((Fe,Co,Ni)_(9)S_(8))for use as the sulfur host in Li-S batteries.This materi-al was prepared using transfer blot filter paper as the carbon precursor,thiourea as the source of nitrogen and sulfur,and FeCl_(3)·6H_(2)O,CoCl_(2)·6H_(2)O and NiCl_(2)·6H_(2)O as the metal ion sources.It was synthesized by an impreg-nation method followed by calcination.The nitrogen doping significantly in-creased the conductivity of the host,and the metal sulfides have excellent catalytic activities.Theoretical calculations,and adsorption and deposition experiments show that active sites on the surface of FCNS@NCFs selectively adsorb polysulfides,facilitate rapid adsorption and conversion,prevent cathode passivation and inhib-it the polysulfide shuttling.The FCNS@NCFs used as the sulfur host has excellent electrochemical properties.Its initial dis-charge capacity is 1639.0 mAh g^(−1) at 0.2 C and room temperature,and it remains a capacity of 1255.1 mAh g^(−1) after 100 cycles.At−20~C,it has an initial discharge capacity of 1578.5 mAh g^(−1) at 0.2 C,with a capacity of 867.5 mAh g^(−1) after 100 cycles.Its excellent performance at both ambient and low temperatures suggests a new way to produce high-performance low-temper-ature Li-S batteries.
文摘Introduction: Common low-back pain is a frequent reason for consultation and a genuine public health problem. Preserving quality of life remains one of the main challenges. Objective: To evaluate the quality of life of patients with low back pain seen in rheumatology consultations at Brazzaville University Hospital. Patients and Method: Cross-sectional, analytical study with control group, conducted at the Brazzaville University Hospital, from January 2 to September 30, 2023. Patients over 30 years of age, seen for documented common low-back pain, were included. Study variables were epidemiological, clinical and functional. The EIFEL and SF-36 scores were used to assess functional impact and quality of life, respectively. Results: We included 96 people divided into two groups: 48 patients with low back pain and 48 controls. The frequency of common low-back pain was 12.8%. The mean age of patients with low back pain was 59.14 ± 11.86 years. Women predominated (sex ratio 0.3). Degenerative disc disease was the main etiology. Common low-back pain had a moderate impact on functional abilities, with a mean EIFEL score of 11 +/− 5.51. Quality of life was impaired in patients with low back pain (overall SF-36 at 43.95%) compared with the control group, with a statistically significant difference (P Conclusion: Common low back pain affects patients’ overall quality of life, particularly in terms of physical pain and limitations due to physical condition.
文摘1989 is the beginning of intensive research into the phenomena of cold nuclear fusion, renamed “The Low Energy Nuclear Synthesis Reactions” (LENR). Based on these results and the long-term research of earthquakes and volcanic activity, the authors of this article put forward a hypothesis about the mainly chemical nature of the energy released at earthquakes and volcanic eruptions with the participation of primordial hydrogen and helium: high mobility of hydrogen and oxidizers provide focusing and accumulation of the latent chemical energy, which is realized suddenly and instantaneously as explosions and initiate the earthquake and/or eruptions. The volcanic eruption is viewed therein as a special type of earthquake whereby the hypocenter rises to the earth’s surface. The authors proposed a new hypothesis that LENRs significant energy to earthquakes and eruptions at the synthesis of elements lighter than iron, thus creating excess energy, which is partially used for the synthesis of heavier elements. The combination of the chemical and nuclear reactions transforms these centers of geophysical activity into giant reactors where the nuclear, chemical, and thermal transformation of mantle materials and the creation of primary deposits of heavy elements such as uranium, thorium, gold, etc. So, all chemical elements heavier than iron are not detected in the solar wind. These elements discovered on our planet could be (and probably were) created on planet Earth and not imported from explosive supernovae or far-off remote stars. To the best of our knowledge, this hypothesis has not been proposed until now.
文摘Background: Chronic low back pain is a leading cause of morbidity and disability globally. Low and Middle-Income Countries (LMICs) tend to be more affected, with chronic low back pain (CLBP) being among the leading presenting complaints at specialist consultation. The exact burden of this disease is sparingly known in our setting. Objective: To evaluate the burden of chronic low back pain at the Yaounde Central Hospital. Methods: This was a descriptive cross-sectional study for a period of 3 months, from March 2022 to May 2022. After obtaining ethical clearance and research authorisations, data was collected using structured questionnaires from patients with chronic low back pain presenting at the Yaounde Central Hospital during the aforementioned time frame. This data was then tabulated with the Statistical Package for Social Sciences (SPSS 23.0), and disability was assessed using the modified Roland Morris Disability Questionnaire and the Oswestry Disability Index. Data analysis was done using the International Business Machines Statistical Package for Social Sciences (IBM-SPSS) VERSION 23.0. Results: 115 cases of CLBP were included. The mean age was 52.62 years, and the sex ratio was 0.3. The average monthly income was less than 50,000 frs CFA, in 37.4% of cases. In 57.9%, patients had a job that involved physical labour. The patients had a secondary level of education in 40.9%, and alcohol consumption was observed in 36%. The average number of days of a work stoppage due to LBP was 12.75 days (±12SD), and the median duration of CLBP was 7.15 (7.5SD) years. The median pain intensity was 7 (±2SD), with leg pain and sensory neuropathy observed in 67.8% and 63.5% respectively. Lumbar X-ray was done in 45.2% and revealed lumbar osteoarthrosis in 62.4%. Hypertension as a comorbidity was observed in 26.1%. Medical treatment was used at least once in 98.3% of cases. The average cost of management per month was assessed, and the median was 52,000 FCFA (±20,876 SD). Using the Oswestry Disability Questionnaire, 46 patients, that is 40% of the study population, were classified as severely disabled with a median ODI score of 40%. The factors which were independently associated with disability were level of education, alcohol consumption, treatment modality, pain intensity, body mass index (BMI), psychological wellbeing and number of sick leave days. Conclusion: Chronic low back pain is common in our setting. There is a female predominance with the mean age of the study population situated in the 5th decade. Low-income earners and patients with a job involving physical labour were the most affected. Medical treatment was the main therapeutic modality, with the average cost of management per month being above the average monthly income of the greater majority of the patients. Several factors influenced disability, some of which were independently associated with it, such as level of education, alcohol consumption and treatment modality.
基金funded by the Talent Program(Ph.D.Fund)of Chengdu Technological University(grant number 2024RC025)the Natural Science Foundation of Sichuan Province(grant number 2022NSFSC1892)Fundamental Research Funds for the Central Universities(grant number XJ2021KJZK054).
文摘The challenge of aerodynamic noise is a key obstacle in the advancement of low-pressure tube ultra-high-speed maglev transportation,demanding urgent resolution.This study utilizes a broadband noise source model to perform a quantitative analysis of the aerodynamic noise produced by ultra-high-speed maglev trains operating in low-pressure environments.Initially,an external flow field calculation model for the ultra-high-speed maglev train is presented.Subsequently,numerical simulations based on the broadband noise source model are used to examine the noise characteristics.The impact of the train speed and pressure level on noise generation is investigated accordingly.Subsequently,a correlation formula is derived.The results reveal that the amplitude of sound source changes in the streamlined region of the head and tail cars of the train is large,and the amplitude of changes for the middle car is smaller.The noise source strength increases with speed,with a quadrupole noise source becoming dominant when the train speed exceeds 600 km/h.At a speed of 1000 km/h,the noise source intensity from the streamlined area at the rear of the train overcomes that at the front.Furthermore,the noise source decreases as the pressure level in the tube decreases.When the pressure level drops to 0.01 atm,the quadrupole noise source intensity of a train running at 600 km/h significantly weakens and falls below that of the dipole noise source.
基金National science and technology signifi cant special(No.2024ZD1003406)Natural Science Research Project of Colleges and Universities in Anhui Province(No.2024AH050374)National Natural Science Foundation of China(Grant No.52274071).
文摘The advancement of intelligent mining in open-pit operations has imposed higher demands on geological transparency,aiming to provide a robust foundation for intelligent drilling and charging.In this study,a linear array of 120 nodal seismometers was deployed along the surfaces of the C8 and C9 platforms at Fenghuang Mountain to investigate cavities within the rock mass and prevent improper intelligent charging.The seismometers were 1 m apart along measurement lines,with a 2-m spacing between lines,and the monitoring time for each line was set at 2 h.This deployment was paired with spatial autocorrelation and station autocorrelation to analyze ambient noise seismic data and image the velocity and structure within the rock mass.The results demonstrate that the locations and sizes of cavities or loose structures can be accurately identifi ed at the prepared excavation site.Compared with traditional geological exploration methods for openpit mines,the approach in this study off ers higher accuracy,greater effi ciency,reduced labor intensity,and insensitivity to water conditions.Ambient noise seismic imaging for detecting adverse geological conditions in open-pit mines provides critical insights and references for intelligent mining advancements.
基金supported in part by the National Natural Science Foundation of China under Grants 62301117,62001094,and U19B2014in part by the National Key Laboratory of Wireless Communications Foundation under Grant 2023KP01602in part by the Natural Science Foundation of Xinjiang Uygur Autonomous Region under Grant 2022D01B184 and 2022D01A297.
文摘In this paper,we investigate covert communications under multi-antenna detection,and explore the impacts of the warden’s channel state information(CSI)availability and the noise uncertainty on system covert capability.The detection performance at warden is analyzed in two cases under the perfect and statistical CSI at warden,respectively.In particular,for the former one,the warden utilizes the likelihood ratio(LR)detector,while for the latter one,the generalized likelihood ratio(GLR)detector is adopted.We first consider the scenario where the blocklength is finite,and demonstrate that the covert rate under both cases asymptotically goes to zero as the blocklength goes to infinity.Subsequently,we take the noise uncertainty at the warden into account which leads to positive covert rate,and characterize the covert rate for infinite blocklength.Specially,we derive the optimal transmit power for the legitimate transmitter that maximizes the covert rate.Besides,the rate gap under two cases,with different CSI availability at the warden,can be presented in closed form.Finally,numerical results validate the effectiveness of our theoretical analysis and also demonstrate the impacts of the factors studied on the system covertness.
基金supported by the National Natural Science Foundation of China(32372223)the National Key Research and Development Program of China(2022YFD2301404)+1 种基金the College Students'Innovationand Entrepreneurship Training Program of Anhui Province,China(S202210364136)the Natural Science Research Project of Anhui Educational Committee,China(2023AH040133).
文摘Low temperature(LT)in spring has become one of the principal abiotic stresses that restrict the growth and development of wheat.Diverse analyses were performed to investigate the mechanism underlying the response of wheat grain development to LT stress during booting.These included morphological observation,measurements of starch synthase activity,and determination of amylose and amylopectin content of wheat grain after exposure to treatment with LT during booting.Additionally,proteomic analysis was performed using tandem mass tags(TMT).Results showed that the plumpness of wheat grains decreased after LT stress.Moreover,the activities of sucrose synthase(SuS,EC 2.4.1.13)and ADP-glucose pyrophosphorylase(AGPase,EC 2.7.7.27)exhibited a significant reduction,leading to a significant reduction in the contents of amylose and amylopectin.A total of 509 differentially expressed proteins(DEPs)were identified by proteomics analysis.The Gene Ontology(GO)enrichment analysis showed that the protein difference multiple in the nutritional repository activity was the largest among the molecular functions,and the up-regulated seed storage protein(ssP)played an active role in the response of grains to LT stress and subsequent damage.The Kyoto Encyclopedia of Genes and Genomes(KEGG)enrichment analysis showed that LT stress reduced the expression of DEPs such as sucrose phosphate synthase(SPS),glucose-1-phosphate adenylyltransferase(glgC),andβ-fructofuranosidase(FFase)in sucrose and starch metabolic pathways,thus affecting the synthesis of grain starch.In addition,many heat shock proteins(HsPs)were found in the protein processing in endoplasmic reticulum pathways,which can resist some damage caused by LT stress.These findings provide a new theoretical foundation for elucidating the underlying mechanism governing wheat yield developmentafterexposuretoLTstress inspring.
文摘This study analyzed ambient seismic noise using the MSNoise package to monitor temporal changes in the underground seismic wave velocity in Mining Area 6 of the Dongtan Coal Mine in China.The data was recorded continuously over 76 days by 7 three-component stations and 10 single-component microseismic stations deployed in Dongtan Coal Mine,with station spacing ranging from 0.1 km to approximately 3 km.Using the causal and non-causal components of the Z-component cross-correlation function,along with moving-window cross-spectrum analysis and cumulative calculations with a 5-day window overlay,stable seismic velocity changes were obtained in the frequency band of 0.1 to 2 Hz.We found a correlation between the timing of average velocity changes and seismic events caused by underground mining processes.In particular,when the relative seismic velocity increased by 0.23%,larger energy minequakes typically occurred.This study shows that ambient noise correlation has great potential for predicting minequakes,guiding pressure-relief production,and providing warnings about the impact of overburden pressure.
