Accurately forecasting peak particle velocity(PPV)during blasting operations plays a crucial role in mitigating vibration-related hazards and preventing economic losses.This research introduces an approach to PPV pred...Accurately forecasting peak particle velocity(PPV)during blasting operations plays a crucial role in mitigating vibration-related hazards and preventing economic losses.This research introduces an approach to PPV prediction by combining conventional empirical equations with physics-informed neural networks(PINN)and optimizing the model parameters via the Particle Swarm Optimization(PSO)algorithm.The proposed PSO-PINN framework was rigorously benchmarked against seven established machine learning approaches:Multilayer Perceptron(MLP),Extreme Gradient Boosting(XGBoost),Random Forest(RF),Support Vector Regression(SVR),Gradient Boosting Decision Tree(GBDT),Adaptive Boosting(Adaboost),and Gene Expression Programming(GEP).Comparative analysis showed that PSO-PINN outperformed these models,achieving RMSE reductions of 17.82-37.63%,MSE reductions of 32.47-61.10%,AR improvements of 2.97-21.19%,and R^(2)enhancements of 7.43-29.21%,demonstrating superior accuracy and generalization.Furthermore,the study determines the impact of incorporating empirical formulas as physical constraints in neural networks and examines the effects of different empirical equations,particle swarm size,iteration count in PSO,regularization coefficient,and learning rate in PINN on model performance.Lastly,a predictive system for blast vibration PPV is designed and implemented.The research outcomes offer theoretical references and practical recommendations for blast vibration forecasting in similar engineering applications.展开更多
The coking observation and particle flow behaviour in both thermal plasma and cold plexiglas downers were investigated in a binary particle system formed by injecting coarse inert particles (carrying coke away and sco...The coking observation and particle flow behaviour in both thermal plasma and cold plexiglas downers were investigated in a binary particle system formed by injecting coarse inert particles (carrying coke away and scouring wall) and fine coal powders into the downer reactor. The results demonstrate that this scheme is a rational selection to prevent coking on downer walls and improve particle velocity distribution along the radial direction. When injected coarse particles mixed with fine powders in downers, the fluctuation of local particle velocity in the radial direction becomes smaller and two peaks in the radial distribution of local particle velocity occur due to the improved dispersing character and flow structure, which are beneficial to the thermo-plasma coal cracking reaction and coking prevention.展开更多
Nearfield acoustic holography in a moving medium is a technique which is typically suitable for sound sources identification in a flow.In the process of sound field reconstruction,sound pressure is usually used as the...Nearfield acoustic holography in a moving medium is a technique which is typically suitable for sound sources identification in a flow.In the process of sound field reconstruction,sound pressure is usually used as the input,but it may contain considerable background noise due to the interactions between microphones and flow moving at a high velocity.To avoid this problem,particle velocity is an alternative input,which can be obtained by using laser Doppler velocimetry in a non-intrusive way.However,there is a singular problem in the conventional propagator relating the particle velocity to the pressure,and it could lead to significant errors or even false results.In view of this,in this paper,nonsingular propagators are deduced to realize accurate reconstruction in both cases that the hologram is parallel to and perpendicular to the flow direction.The advantages of the proposed method are analyzed,and simulations are conducted to verify the validation.The results show that the method can overcome the singular problem effectively,and the reconstruction errors are at a low level for different flow velocities,frequencies,and signal-to-noise ratios.展开更多
This study utilizes empirical equations to describe the propagation of vibrations induced by blasting, with the goal of predicting the attenuation of Peak Particle Velocity (PPV) at the Yaramoko mine in Bagassi, Burki...This study utilizes empirical equations to describe the propagation of vibrations induced by blasting, with the goal of predicting the attenuation of Peak Particle Velocity (PPV) at the Yaramoko mine in Bagassi, Burkina Faso, a site characterized by granitoid rock. Four empirical PPV prediction equations were employed, so-called Duvall & Fogelson (or the United States Bureau of Mines “USBM”), Langefors and Kihlstrom, Ambressys-Hendron, and the Bureau of Indian Standard. The constant parameters for each of these equations, referred to as site constants, were derived from linear regression curves. The results show that the site constants k, a, and b of 4762, 0.869, and 1.737, respectively, derived from the general prediction equation by Davies, PPV = kQaD−b, based on Duvall & Fogelson, are in good agreement with values of 4690, 0.9, and 1.69, respectively, for similar rock types in Spain. Regarding the impacts of blasting on houses, the findings indicate that houses built from laterite-block bricks in the village of Bagassi are the most vulnerable to vibration waves, followed by those constructed with cinder-block bricks. In contrast, houses made of banco bricks are the most resilient. Additionally, it was determined that during blasting operations, adjusting the blasting parameters to ensure the PPV does not exceed 2 mm/s at the level of nearby dwellings can minimize the appearance of cracks in houses.展开更多
The accurate prediction of peak particle velocity(PPV)is essential for effectively managing blastinduced vibrations in mining operations.This study presents a novel PPV prediction method based on the social network se...The accurate prediction of peak particle velocity(PPV)is essential for effectively managing blastinduced vibrations in mining operations.This study presents a novel PPV prediction method based on the social network search and LightGBM(SNS-LightGBM)deep gradient cooperative learning framework.The SNS algorithm enhances LightGBM’s learning process by optimizing hyperparameters through global search capabilities and balancing model complexity to improve generalization.To assess its performance,five baseline machine learning models and a hybrid model combining SNS-LightGBM were developed for comparison.The predictive performance of these models was evaluated using metrics such as coefficient of determination(R^(2)),mean absolute error(MAE),mean absolute percentage error(MAPE),mean squared error(MSE),and root mean squared error(RMSE).The results indicate that the SNSLightGBM model substantially improves both the accuracy and stability of PPV predictions.The SNS-LightGBM model outperformed all other models,achieving an R^(2) of 0.975,MAE of 0.086,MAPE of 0.071,MSE of 0.019,and RMSE of 0.138.Additionally,a feature importance analysis revealed that distance and charge weight are the most significant factors influencing PPV,far surpassing other parameters.These findings offer valuable insights for improving the precision of blast vibration prediction and optimizing blasting designs.展开更多
Blasting technology is widely used to prevent coal bursts by presplitting the overburden in underground coal mines.The control of blasting intensity is important in achieving the optimal pre-split effectiveness and re...Blasting technology is widely used to prevent coal bursts by presplitting the overburden in underground coal mines.The control of blasting intensity is important in achieving the optimal pre-split effectiveness and reducing the damage to roadway structures that are subjected to blasting vibrations.As a critical parameter to measure the blasting intensity,the peak particle velocity(PPV)of vibration induced by blasting,should be accurately predicted,and can provide a useful guideline for the design of blasting parameters and the evaluation of the damage.In this paper,various factors that influence PPV,induced by roof pre-split blasting,were analyzed using engineering blasting experiments and numerical simulations.The results showed that PPV was affected by many factors,including charge distribution design(total charge and maximum charge per hole),spacing of explosive centers,as well as propagation distance and path.Two parameters,average charge coefficient and spatial discretization coefficient were used to quantitatively characterize the influences of charge distribution and spacing of explosive centers on the PPV induced by roof pre-split blasting.Then,a model consisting of the combination of artificial neural network(ANN)and genetic algorithm(GA)was adopted to predict the PPV that was induced by roof presplit blasting.A total of 24 rounds of roof pre-split blasting experiments were carried out in a coal mine,and vibration signals were collected using a microseismic(MS)monitoring system to construct the neural network datasets.To verify the efficiency of the proposed GA-ANN model,empirical correlations were applied to predict PPV for the same datasets.The results showed that the GA-ANN model had superiority in predicting PPV compared to empirical correlations.Finally,sensitivity analysis was performed to evaluate the impacts of input parameters on PPV.The research results are of great significance to improve the prediction accuracy of PPV induced by roof pre-splitting blasting.展开更多
To study axial/radial profiles of particle velocity in the affected region of an integrated riser outlet, a cold model was developed for the integrated riser reactor combining the gas-solid distributor with the fluidi...To study axial/radial profiles of particle velocity in the affected region of an integrated riser outlet, a cold model was developed for the integrated riser reactor combining the gas-solid distributor with the fluidized bed. Constraints, related to the gas-solid distributor and the upper fluidized bed, imposed on the particle flow in the riser outlet region, were investigated experimentally. The experimental results showed that with increasing superficial gas velocity, these constraints have strong influences on particle flow behavior, the particle circulation flux in the riser, and the height of the static bed material of the upper fluidized bed. When the constraints have greater prominence, the axial profile of the cross-sectionally averaged particle velocity in the outlet region initially increases and then decreases, the rate of decrease being proportional to the constraint strength. Along the radial direction of the outlet section, the region where the local particle velocity profile tends to decrease appears near the dimensionless radius r/R = 0.30 initially and then, with increasing constraint strength, gradually extends to the whole section from the inner wall. Based on the experimental data, an empirical model describing the constraint strength was established. The average relative error of the model is within 7.69%.展开更多
Some basic studies of pressure and particle velocity combine processing such as correlation between them, average acoustic intensity processing, rotating and sharpening of directivity are described. Preliminary result...Some basic studies of pressure and particle velocity combine processing such as correlation between them, average acoustic intensity processing, rotating and sharpening of directivity are described. Preliminary results based on theoretical analysis and lake trail will lay a foundation for further research.展开更多
The combined inclined rib pair(CIRP)is the first time proposed to improve the sensor performance of particle velocity sensor(PVS)by using a three-dimensional numerical method.The method is verified by the experiment r...The combined inclined rib pair(CIRP)is the first time proposed to improve the sensor performance of particle velocity sensor(PVS)by using a three-dimensional numerical method.The method is verified by the experiment results in the literature.The optimal plain channel parameters are determined as the basic sensor structure.In comparison of plain channel,both heat transfer characteristics and sensor performance are enhanced effectively by arranging the CIRP.The reason is that the high flow rate region caused by the CIRP can maintain strongly in the whole fluid field if there are enough rib pairs.Furthermore,the produced longitudinal vortex pair can get a better fluid mix,which is more conductive to heat transfer.The increasing height and number of the CIRP can improve the heat transfer characteristics,but the flow resistance will increase as well.For the purpose of finding the best overall performance,the effects of the parameters including the geometric sizes and the position of the CIRP have been investigated.The results show that PVS will get the best sensitivity when the rib length and width are 0.2 mm and 0.03 mm respectively,and the distance between rib pair and between ribs in the same pair are 0.15 mm and 0.3 mm respectively.Besides,the most suitable crossing angle is 45°.Thus,the performance of PVS can be significantly improved by this novel structure.展开更多
One-step patch near-field acoustical holography(PNAH) is a powerful tool for identifying noise sources from the partially known sound pressure field.The acoustical property to be reconstructed on the surface of intere...One-step patch near-field acoustical holography(PNAH) is a powerful tool for identifying noise sources from the partially known sound pressure field.The acoustical property to be reconstructed on the surface of interest is related to the partially measured pressure on the hologram surface in terms of sampling and bandlimiting matrices,which cost more in computation.A one-step procedure based on measuring of the normal component of the particle velocity is described,including the mathematical formulation.The numerical simulation shows that one-step PNAH based on particle velocity can obtain more accurately reconstructed results and it is also less sensitive to noise than the method based on pressure.These findings are confirmed by an underwater near-field acoustical holography experiment conducted with a vector hydrophone array.The experimental results have illustrated the high performance of one-step PNAH based on particle velocity in the reconstruction of sound field and the advantages of a vector hydrophone array in an underwater near-field measurement.展开更多
Comparing with traditional underwater acoustic system which only utilizes pressure information, combine sensor system processes pressure together with particle velocity information of sound field. More information ce...Comparing with traditional underwater acoustic system which only utilizes pressure information, combine sensor system processes pressure together with particle velocity information of sound field. More information certainly brings nicer processing result. By using spatial directional information collected by combine sensor, the Coherent Interference Energy Suppress (CIES) technology, which can effectively suppress coherent interference and detect linear spectrum signal and wide-band continuous-spectrum signal as well, is presented. Current research has shown favorite result, and further research is going on.展开更多
The paper examines the change of the relativistic kinetic energy of a free particle due to the velocity change of the motion frame in a special case when this reduction leads to the kinetic energy equal to zero. The d...The paper examines the change of the relativistic kinetic energy of a free particle due to the velocity change of the motion frame in a special case when this reduction leads to the kinetic energy equal to zero. The difference of velocities gives a functional dependent solely on the velocity frame and original velocity of the particle. An analysis applied to the functional gives simple formulae for the extremal values of the mentioned velocity parameters. In the next step, solutions of the equation presented with the functional provide us with the velocities necessary for the vanishing property of the kinetic energy. A characteristic point is that a condition of the velocity of the motion frame smaller than the velocity of light is obtained directly in the applied formalism. This property holds with no reference done to the well-known postulate of the dominant value of the light velocity entering the relativity theory.展开更多
The relatively poor settling characteristics of particles produced in moving bed biofilm reactor(MBBR)outline the importance of developing a fundamental understanding of the characterization and settleability of MBBR-...The relatively poor settling characteristics of particles produced in moving bed biofilm reactor(MBBR)outline the importance of developing a fundamental understanding of the characterization and settleability of MBBR-produced solids.The influence of carrier geometric properties and different levels of biofilm thickness on biofilm characteristics,solids production,particle size distribution(PSD),and particle settling velocity distribution(PSVD)is evaluated in this study.The analytical Vi CAs method is applied to the MBBR effluent to assess the distribution of particle settling velocities.This method is combined with microscopy imaging to relate particle size distribution to settling velocity.Three conventionally loaded MBBR systems are studied at a similar loading rate of 6.0 g/(m^(2)·day)and with different carrier types.The AnoxK^(TM)K5 carrier,a commonly used carrier,is compared to so-called thickness-restraint carriers,AnoxK^(TM)Z-carriers that are newly designed carriers to limit the biofilm thickness.Moreover,two levels of biofilm thickness,200μm and 400μm,are studied using AnoxK^(TM)Z-200 and Z-400 carriers.Statistical analysis confirms that K5 carriers demonstrated a significantly different biofilm mass,thickness,and density,in addition to distinct trends in PSD and PSVD in comparison with Z-carriers.However,in comparison of thickness-restraint carriers,Z-200 carrier results did not vary significantly compared to the Z-400 carrier.The K5 carriers showed the lowest production of suspended solids(0.7±0.3 gTSS/day),thickest biofilm(281.1±8.7μm)and lowest biofilm density(65.0±1.5 kg/m^(3)).The K5 effluent solids also showed enhanced settling behaviour,consisting of larger particles with faster settling velocities.展开更多
In this study, the effects of the impact velocity on the particle deposition characteristics in cold gas dynamic spraying （CGDS） of 304 stainless steel （SS） on an interstitial free （IF） steel substrate are numer...In this study, the effects of the impact velocity on the particle deposition characteristics in cold gas dynamic spraying （CGDS） of 304 stainless steel （SS） on an interstitial free （IF） steel substrate are numerical simulated by means of a finite element analysis （FEA）. The results have illustrated that when the particle impact velocity exceeds a critical value at which adiabatic shear instability of the particle starts to occur. Meanwhile, the fatten ratio and impact crater depth （or the effective contacting area ） increase rapidly. The particle-substrate bonding and deposition mechanism can be attributed to such an adiabatic shear deformation induced by both the compressive force and the slide friction force of particle. The critical velocity can be predicted by numerical simulation, which is useful to optimize the CGDS processing parameters for various materials.展开更多
Velocity is a key parameter characterizing the movement of saltating particles. High-speed photography is an efficient method to record the velocity. But, manually determining the relevant information from these photo...Velocity is a key parameter characterizing the movement of saltating particles. High-speed photography is an efficient method to record the velocity. But, manually determining the relevant information from these photographs is quite laborious. However, particle tracking velocimetry（PTV） can be used to measure the instantaneous velocity in fluids using tracer particles. The tracer particles have three basic features in fluids： similar movement patterns within a small region, a uniform particle distribution, and high particle density. Unfortunately, the saltation of sand particles in air is a stochastic process, and PTV has not yet been able to accurately determine the velocity field in a cloud of blowing sand. The aim of the present study was to develop an improved PTV technique to measure the downwind（horizontal） and vertical velocities of saltating sand. To demonstrate the feasibility of this new technique, we used it to investigate two-dimensional saltation of particles above a loose sand surface in a wind tunnel. We analyzed the properties of the saltating particles, including the probability distribution of particle velocity, variations in the mean velocity as a function of height, and particle turbulence. By automating much of the analysis, the improved PTV method can satisfy the requirement for a large sample size and can measure the velocity field of blowing sand more accurately than previously-used techniques. The results shed new light on the complicated mechanisms involved in sand saltation.展开更多
The velocity of blown sand particles is an important parameter in aeolian movement （a special case of gas particle two-phase flow） and has ever been a topic of interest. At present, several techniques have been appl...The velocity of blown sand particles is an important parameter in aeolian movement （a special case of gas particle two-phase flow） and has ever been a topic of interest. At present, several techniques have been applied in measuring velocity of the blown sand particles. This paper reviews the measurement results of several commonly used methods： photoelectric cell method, high-speed photographic method, Particle Dynamics Analyzer （PDA） method and Particle Image Velocimetry （PIV） method. Photoelectric cell method, high-speed photograph method and PDA method are useful in studying the velocity distribution of particles. PIV is a whole-flow-field technique and a useful tool to study the average velocity field in a target area. These methods got some similar results but considerable differences also exist. They have come to similar conclusions on the velocity distributions at a single height but direct measurement results with respect to the velocity distribution very close to the surface are still scarce except some PDA results. The magnitude of measured mean particle velocity differs greatly. The relationship obtained by different methods between mean particle velocity and wind velocity, particle size and possibly other influencing factors also differs considerably. Although several authors have proposed similar power functions to describe the variation with height of the mean particle velocity, the predicted results have wide differences. Each technique is based on some unique principles, and has its advantages and disad- vantages. To make full use of different techniques, a lot of work needs be done to validate them. Developing a reliable technique to measure the velocity of blown particles is still a necessary task in aeolian research.展开更多
An advanced erosion model that correlates two model parameters—the energies required to remove unit mass of target material during cutting wear and deformation wear,respectively,with particle velocity,particle size a...An advanced erosion model that correlates two model parameters—the energies required to remove unit mass of target material during cutting wear and deformation wear,respectively,with particle velocity,particle size and density,as well as target material properties,is proposed.This model is capable of predicting the erosion rates for a material under solid-particle impact over a specific range of particle velocity at the impingement angle between 0◦and 90◦,provided that the experimental data of erosion rate for the material at a particle velocity within this range and at impingement angles between 0◦and 90◦are available.The proposed model is applied on three distinct types of materials:aluminum,perspex and graphite,to investigate the dependence behavior of the model parameters on particle velocity for ductile and brittle materials.The predicted model parameters obtained from the model are validated by the experimental data of aluminum plate under Al2O3 particle impact.The significance and limitation of the model are discussed;possible improvements on the model are suggested.展开更多
The terminal velocity has been widely used in extensive fields, but the complexity of drag coefficient expression leads to the calculation of terminal velocity in transitional flow （1 〈 Re ≤ 1000） with much more d...The terminal velocity has been widely used in extensive fields, but the complexity of drag coefficient expression leads to the calculation of terminal velocity in transitional flow （1 〈 Re ≤ 1000） with much more difficulty than those in laminar flow （Re ≤ 1） and turbulent flow （Re ≥ 1000）. This paper summarized and compared 24 drag coefficient correlations, and developed an expression for calculating the terminal velocity in transitional flow, and also analyzed the effects of particle density and size, fluid density and viscosity on terminal velocity. The results show that 19 of 24 previously published correlations for drag coefficient have good prediction performance and can be used for calculating the terminal velocity in the entire transitional flow with higher accuracy. Adapting two dimensionless parameters （w＊, d＊）, a proposed explicit correlation, w＊=-25.68654 × exp （-d＊/77.02069）＋ 24.89826, is attained in transitional flow with good performance, which is helpful in calculating the terminal velocity.展开更多
The law of blasting vibration caused by blasting in rock is very complex.Traditional numerical methods cannot well characterize all the influencing factors in the blasting process.The effects of millisecond time,charg...The law of blasting vibration caused by blasting in rock is very complex.Traditional numerical methods cannot well characterize all the influencing factors in the blasting process.The effects of millisecond time,charge length and detonation velocity on the blasting vibration are discussed by analyzing the characteristics of vibration wave generated by finite length cylindrical charge.It is found that in multi-hole millisecond blasting,blasting vibration superimpositions will occur several times within a certain distance from the explosion source due to the propagation velocity difference of P-wave and S-wave generated by a short column charge.These superimpositions will locally enlarge the peak velocity of blasting vibration particle.The magnitude and scope of the enlargement are closely related to the millisecond time.Meanwhile,the particle vibration displacement characteristics of rock under long cylindrical charge is analyzed.The results show that blasting vibration effect would no longer increase when the charge length increases to a certain extent.This indicates that the traditional simple calculation method using the maximum charge weight per delay interval to predict the effect of blasting vibration is unreasonable.Besides,the effect of detonation velocity on blasting vibration is only limited in a certain velocity range.When detonation velocity is greater than a certain value,the detonation velocity almost makes no impact on blasting vibration.展开更多
In order to study the extinguishing performance of high-pressure-water-mist-based systems on the fires originating from power transformers the PyroSim software is used.Different particle velocities and flow rates are ...In order to study the extinguishing performance of high-pressure-water-mist-based systems on the fires originating from power transformers the PyroSim software is used.Different particle velocities and flow rates are considered.The evolution laws of temperature around transformer,flue gas concentration and upper layer temperature of flue gas are analyzed under different boundary conditions.It is shown that the higher the particle velocity is,the lower the smoke concentration is,the better the cooling effect on the upper layer temperature of flue gas layer is,the larger the flow rate is and the better the cooling effect is.展开更多
基金supported by the National Natural Science Foundation of China(Grant No.52409143)the Basic Scientific Research Fund of Changjiang River Scientific Research Institute for Central-level Public Welfare Research Institutes(Grant No.CKSF2025184/YT)the Hubei Provincial Natural Science Foundation of China(Grant No.2022CFB673).
文摘Accurately forecasting peak particle velocity(PPV)during blasting operations plays a crucial role in mitigating vibration-related hazards and preventing economic losses.This research introduces an approach to PPV prediction by combining conventional empirical equations with physics-informed neural networks(PINN)and optimizing the model parameters via the Particle Swarm Optimization(PSO)algorithm.The proposed PSO-PINN framework was rigorously benchmarked against seven established machine learning approaches:Multilayer Perceptron(MLP),Extreme Gradient Boosting(XGBoost),Random Forest(RF),Support Vector Regression(SVR),Gradient Boosting Decision Tree(GBDT),Adaptive Boosting(Adaboost),and Gene Expression Programming(GEP).Comparative analysis showed that PSO-PINN outperformed these models,achieving RMSE reductions of 17.82-37.63%,MSE reductions of 32.47-61.10%,AR improvements of 2.97-21.19%,and R^(2)enhancements of 7.43-29.21%,demonstrating superior accuracy and generalization.Furthermore,the study determines the impact of incorporating empirical formulas as physical constraints in neural networks and examines the effects of different empirical equations,particle swarm size,iteration count in PSO,regularization coefficient,and learning rate in PINN on model performance.Lastly,a predictive system for blast vibration PPV is designed and implemented.The research outcomes offer theoretical references and practical recommendations for blast vibration forecasting in similar engineering applications.
文摘The coking observation and particle flow behaviour in both thermal plasma and cold plexiglas downers were investigated in a binary particle system formed by injecting coarse inert particles (carrying coke away and scouring wall) and fine coal powders into the downer reactor. The results demonstrate that this scheme is a rational selection to prevent coking on downer walls and improve particle velocity distribution along the radial direction. When injected coarse particles mixed with fine powders in downers, the fluctuation of local particle velocity in the radial direction becomes smaller and two peaks in the radial distribution of local particle velocity occur due to the improved dispersing character and flow structure, which are beneficial to the thermo-plasma coal cracking reaction and coking prevention.
基金supported by the National Natural Science Foundation of China(Grant No.11804002)the University Science Research Project of Anhui Province,China(Grant Nos.KJ2019A0792 and KJ2019A0797)the Anhui Jianzhu University Research Project(Grant No.2018QD06)。
文摘Nearfield acoustic holography in a moving medium is a technique which is typically suitable for sound sources identification in a flow.In the process of sound field reconstruction,sound pressure is usually used as the input,but it may contain considerable background noise due to the interactions between microphones and flow moving at a high velocity.To avoid this problem,particle velocity is an alternative input,which can be obtained by using laser Doppler velocimetry in a non-intrusive way.However,there is a singular problem in the conventional propagator relating the particle velocity to the pressure,and it could lead to significant errors or even false results.In view of this,in this paper,nonsingular propagators are deduced to realize accurate reconstruction in both cases that the hologram is parallel to and perpendicular to the flow direction.The advantages of the proposed method are analyzed,and simulations are conducted to verify the validation.The results show that the method can overcome the singular problem effectively,and the reconstruction errors are at a low level for different flow velocities,frequencies,and signal-to-noise ratios.
文摘This study utilizes empirical equations to describe the propagation of vibrations induced by blasting, with the goal of predicting the attenuation of Peak Particle Velocity (PPV) at the Yaramoko mine in Bagassi, Burkina Faso, a site characterized by granitoid rock. Four empirical PPV prediction equations were employed, so-called Duvall & Fogelson (or the United States Bureau of Mines “USBM”), Langefors and Kihlstrom, Ambressys-Hendron, and the Bureau of Indian Standard. The constant parameters for each of these equations, referred to as site constants, were derived from linear regression curves. The results show that the site constants k, a, and b of 4762, 0.869, and 1.737, respectively, derived from the general prediction equation by Davies, PPV = kQaD−b, based on Duvall & Fogelson, are in good agreement with values of 4690, 0.9, and 1.69, respectively, for similar rock types in Spain. Regarding the impacts of blasting on houses, the findings indicate that houses built from laterite-block bricks in the village of Bagassi are the most vulnerable to vibration waves, followed by those constructed with cinder-block bricks. In contrast, houses made of banco bricks are the most resilient. Additionally, it was determined that during blasting operations, adjusting the blasting parameters to ensure the PPV does not exceed 2 mm/s at the level of nearby dwellings can minimize the appearance of cracks in houses.
基金the National Key Research and Development Program of China-2023 Key Special Project(No.2023YFC2907400)the National Natural Science Foundation of China(Grant No.52104109)the Natural Science Foundation of Hunan Province,China(No.2022JJ40602).
文摘The accurate prediction of peak particle velocity(PPV)is essential for effectively managing blastinduced vibrations in mining operations.This study presents a novel PPV prediction method based on the social network search and LightGBM(SNS-LightGBM)deep gradient cooperative learning framework.The SNS algorithm enhances LightGBM’s learning process by optimizing hyperparameters through global search capabilities and balancing model complexity to improve generalization.To assess its performance,five baseline machine learning models and a hybrid model combining SNS-LightGBM were developed for comparison.The predictive performance of these models was evaluated using metrics such as coefficient of determination(R^(2)),mean absolute error(MAE),mean absolute percentage error(MAPE),mean squared error(MSE),and root mean squared error(RMSE).The results indicate that the SNSLightGBM model substantially improves both the accuracy and stability of PPV predictions.The SNS-LightGBM model outperformed all other models,achieving an R^(2) of 0.975,MAE of 0.086,MAPE of 0.071,MSE of 0.019,and RMSE of 0.138.Additionally,a feature importance analysis revealed that distance and charge weight are the most significant factors influencing PPV,far surpassing other parameters.These findings offer valuable insights for improving the precision of blast vibration prediction and optimizing blasting designs.
基金the Postgraduate Research&Practice Innovation Program of Jiangsu Province,China(Grant No.KYCX21_2378)National Natural Science Foundation of China(Grant Nos.51874292 and 51804303).
文摘Blasting technology is widely used to prevent coal bursts by presplitting the overburden in underground coal mines.The control of blasting intensity is important in achieving the optimal pre-split effectiveness and reducing the damage to roadway structures that are subjected to blasting vibrations.As a critical parameter to measure the blasting intensity,the peak particle velocity(PPV)of vibration induced by blasting,should be accurately predicted,and can provide a useful guideline for the design of blasting parameters and the evaluation of the damage.In this paper,various factors that influence PPV,induced by roof pre-split blasting,were analyzed using engineering blasting experiments and numerical simulations.The results showed that PPV was affected by many factors,including charge distribution design(total charge and maximum charge per hole),spacing of explosive centers,as well as propagation distance and path.Two parameters,average charge coefficient and spatial discretization coefficient were used to quantitatively characterize the influences of charge distribution and spacing of explosive centers on the PPV induced by roof pre-split blasting.Then,a model consisting of the combination of artificial neural network(ANN)and genetic algorithm(GA)was adopted to predict the PPV that was induced by roof presplit blasting.A total of 24 rounds of roof pre-split blasting experiments were carried out in a coal mine,and vibration signals were collected using a microseismic(MS)monitoring system to construct the neural network datasets.To verify the efficiency of the proposed GA-ANN model,empirical correlations were applied to predict PPV for the same datasets.The results showed that the GA-ANN model had superiority in predicting PPV compared to empirical correlations.Finally,sensitivity analysis was performed to evaluate the impacts of input parameters on PPV.The research results are of great significance to improve the prediction accuracy of PPV induced by roof pre-splitting blasting.
基金support from the National Natural Science Foundation of China(Grant nos.21106028 and 20976190)the Hebei Province Natural Science Foundation of China(Grant no.B2013202125)
文摘To study axial/radial profiles of particle velocity in the affected region of an integrated riser outlet, a cold model was developed for the integrated riser reactor combining the gas-solid distributor with the fluidized bed. Constraints, related to the gas-solid distributor and the upper fluidized bed, imposed on the particle flow in the riser outlet region, were investigated experimentally. The experimental results showed that with increasing superficial gas velocity, these constraints have strong influences on particle flow behavior, the particle circulation flux in the riser, and the height of the static bed material of the upper fluidized bed. When the constraints have greater prominence, the axial profile of the cross-sectionally averaged particle velocity in the outlet region initially increases and then decreases, the rate of decrease being proportional to the constraint strength. Along the radial direction of the outlet section, the region where the local particle velocity profile tends to decrease appears near the dimensionless radius r/R = 0.30 initially and then, with increasing constraint strength, gradually extends to the whole section from the inner wall. Based on the experimental data, an empirical model describing the constraint strength was established. The average relative error of the model is within 7.69%.
基金This work is supported by the special univeraity fund for the excellent PH,D dissertation of china
文摘Some basic studies of pressure and particle velocity combine processing such as correlation between them, average acoustic intensity processing, rotating and sharpening of directivity are described. Preliminary results based on theoretical analysis and lake trail will lay a foundation for further research.
基金financially supported by the ScientificResearch and Development Program of City of Xiamen(3502Z20143003)the University-Industry Collaboration Program of Fujian Province,China(2015H6021)。
文摘The combined inclined rib pair(CIRP)is the first time proposed to improve the sensor performance of particle velocity sensor(PVS)by using a three-dimensional numerical method.The method is verified by the experiment results in the literature.The optimal plain channel parameters are determined as the basic sensor structure.In comparison of plain channel,both heat transfer characteristics and sensor performance are enhanced effectively by arranging the CIRP.The reason is that the high flow rate region caused by the CIRP can maintain strongly in the whole fluid field if there are enough rib pairs.Furthermore,the produced longitudinal vortex pair can get a better fluid mix,which is more conductive to heat transfer.The increasing height and number of the CIRP can improve the heat transfer characteristics,but the flow resistance will increase as well.For the purpose of finding the best overall performance,the effects of the parameters including the geometric sizes and the position of the CIRP have been investigated.The results show that PVS will get the best sensitivity when the rib length and width are 0.2 mm and 0.03 mm respectively,and the distance between rib pair and between ribs in the same pair are 0.15 mm and 0.3 mm respectively.Besides,the most suitable crossing angle is 45°.Thus,the performance of PVS can be significantly improved by this novel structure.
基金supported by the National Natural Science Foundation of China(Grant No.11204049)the National Defence Research Funds (Grant No.7131107 and 51310040202)the Fundamental Research Funds For the Central Universities(Grant No.HEUCFR1013 and HEUCF120504)
文摘One-step patch near-field acoustical holography(PNAH) is a powerful tool for identifying noise sources from the partially known sound pressure field.The acoustical property to be reconstructed on the surface of interest is related to the partially measured pressure on the hologram surface in terms of sampling and bandlimiting matrices,which cost more in computation.A one-step procedure based on measuring of the normal component of the particle velocity is described,including the mathematical formulation.The numerical simulation shows that one-step PNAH based on particle velocity can obtain more accurately reconstructed results and it is also less sensitive to noise than the method based on pressure.These findings are confirmed by an underwater near-field acoustical holography experiment conducted with a vector hydrophone array.The experimental results have illustrated the high performance of one-step PNAH based on particle velocity in the reconstruction of sound field and the advantages of a vector hydrophone array in an underwater near-field measurement.
基金This work is supported by the National Natural Science Foundation of China and Doctor Foundation ofNEC.
文摘Comparing with traditional underwater acoustic system which only utilizes pressure information, combine sensor system processes pressure together with particle velocity information of sound field. More information certainly brings nicer processing result. By using spatial directional information collected by combine sensor, the Coherent Interference Energy Suppress (CIES) technology, which can effectively suppress coherent interference and detect linear spectrum signal and wide-band continuous-spectrum signal as well, is presented. Current research has shown favorite result, and further research is going on.
文摘The paper examines the change of the relativistic kinetic energy of a free particle due to the velocity change of the motion frame in a special case when this reduction leads to the kinetic energy equal to zero. The difference of velocities gives a functional dependent solely on the velocity frame and original velocity of the particle. An analysis applied to the functional gives simple formulae for the extremal values of the mentioned velocity parameters. In the next step, solutions of the equation presented with the functional provide us with the velocities necessary for the vanishing property of the kinetic energy. A characteristic point is that a condition of the velocity of the motion frame smaller than the velocity of light is obtained directly in the applied formalism. This property holds with no reference done to the well-known postulate of the dominant value of the light velocity entering the relativity theory.
文摘The relatively poor settling characteristics of particles produced in moving bed biofilm reactor(MBBR)outline the importance of developing a fundamental understanding of the characterization and settleability of MBBR-produced solids.The influence of carrier geometric properties and different levels of biofilm thickness on biofilm characteristics,solids production,particle size distribution(PSD),and particle settling velocity distribution(PSVD)is evaluated in this study.The analytical Vi CAs method is applied to the MBBR effluent to assess the distribution of particle settling velocities.This method is combined with microscopy imaging to relate particle size distribution to settling velocity.Three conventionally loaded MBBR systems are studied at a similar loading rate of 6.0 g/(m^(2)·day)and with different carrier types.The AnoxK^(TM)K5 carrier,a commonly used carrier,is compared to so-called thickness-restraint carriers,AnoxK^(TM)Z-carriers that are newly designed carriers to limit the biofilm thickness.Moreover,two levels of biofilm thickness,200μm and 400μm,are studied using AnoxK^(TM)Z-200 and Z-400 carriers.Statistical analysis confirms that K5 carriers demonstrated a significantly different biofilm mass,thickness,and density,in addition to distinct trends in PSD and PSVD in comparison with Z-carriers.However,in comparison of thickness-restraint carriers,Z-200 carrier results did not vary significantly compared to the Z-400 carrier.The K5 carriers showed the lowest production of suspended solids(0.7±0.3 gTSS/day),thickest biofilm(281.1±8.7μm)and lowest biofilm density(65.0±1.5 kg/m^(3)).The K5 effluent solids also showed enhanced settling behaviour,consisting of larger particles with faster settling velocities.
文摘In this study, the effects of the impact velocity on the particle deposition characteristics in cold gas dynamic spraying （CGDS） of 304 stainless steel （SS） on an interstitial free （IF） steel substrate are numerical simulated by means of a finite element analysis （FEA）. The results have illustrated that when the particle impact velocity exceeds a critical value at which adiabatic shear instability of the particle starts to occur. Meanwhile, the fatten ratio and impact crater depth （or the effective contacting area ） increase rapidly. The particle-substrate bonding and deposition mechanism can be attributed to such an adiabatic shear deformation induced by both the compressive force and the slide friction force of particle. The critical velocity can be predicted by numerical simulation, which is useful to optimize the CGDS processing parameters for various materials.
基金funded by the Young Talent Fund of University Association for Science and Technology in Shaanxi, China (20170303)the National Science Basic Research Plan in Shaanxi Province of China (2017JQ6080)the Talent Development Project of Weinan Normal University, China (16ZRRC02)
文摘Velocity is a key parameter characterizing the movement of saltating particles. High-speed photography is an efficient method to record the velocity. But, manually determining the relevant information from these photographs is quite laborious. However, particle tracking velocimetry（PTV） can be used to measure the instantaneous velocity in fluids using tracer particles. The tracer particles have three basic features in fluids： similar movement patterns within a small region, a uniform particle distribution, and high particle density. Unfortunately, the saltation of sand particles in air is a stochastic process, and PTV has not yet been able to accurately determine the velocity field in a cloud of blowing sand. The aim of the present study was to develop an improved PTV technique to measure the downwind（horizontal） and vertical velocities of saltating sand. To demonstrate the feasibility of this new technique, we used it to investigate two-dimensional saltation of particles above a loose sand surface in a wind tunnel. We analyzed the properties of the saltating particles, including the probability distribution of particle velocity, variations in the mean velocity as a function of height, and particle turbulence. By automating much of the analysis, the improved PTV method can satisfy the requirement for a large sample size and can measure the velocity field of blowing sand more accurately than previously-used techniques. The results shed new light on the complicated mechanisms involved in sand saltation.
基金the funding from National Science Fund for Distinguished Young Scholars of the NaturalScience Foundation of China (40225003)the Knowledge Innovation Project of the Chinese Academy of Science(KZCX3-SW-341)
文摘The velocity of blown sand particles is an important parameter in aeolian movement （a special case of gas particle two-phase flow） and has ever been a topic of interest. At present, several techniques have been applied in measuring velocity of the blown sand particles. This paper reviews the measurement results of several commonly used methods： photoelectric cell method, high-speed photographic method, Particle Dynamics Analyzer （PDA） method and Particle Image Velocimetry （PIV） method. Photoelectric cell method, high-speed photograph method and PDA method are useful in studying the velocity distribution of particles. PIV is a whole-flow-field technique and a useful tool to study the average velocity field in a target area. These methods got some similar results but considerable differences also exist. They have come to similar conclusions on the velocity distributions at a single height but direct measurement results with respect to the velocity distribution very close to the surface are still scarce except some PDA results. The magnitude of measured mean particle velocity differs greatly. The relationship obtained by different methods between mean particle velocity and wind velocity, particle size and possibly other influencing factors also differs considerably. Although several authors have proposed similar power functions to describe the variation with height of the mean particle velocity, the predicted results have wide differences. Each technique is based on some unique principles, and has its advantages and disad- vantages. To make full use of different techniques, a lot of work needs be done to validate them. Developing a reliable technique to measure the velocity of blown particles is still a necessary task in aeolian research.
基金financial support from Natural Science&Engineering Research Council of Canada(NSERC)the in-kind support from National Research Council Canada(NRC)and both financial and in-kind support from Kennametal Stellite Inc.
文摘An advanced erosion model that correlates two model parameters—the energies required to remove unit mass of target material during cutting wear and deformation wear,respectively,with particle velocity,particle size and density,as well as target material properties,is proposed.This model is capable of predicting the erosion rates for a material under solid-particle impact over a specific range of particle velocity at the impingement angle between 0◦and 90◦,provided that the experimental data of erosion rate for the material at a particle velocity within this range and at impingement angles between 0◦and 90◦are available.The proposed model is applied on three distinct types of materials:aluminum,perspex and graphite,to investigate the dependence behavior of the model parameters on particle velocity for ductile and brittle materials.The predicted model parameters obtained from the model are validated by the experimental data of aluminum plate under Al2O3 particle impact.The significance and limitation of the model are discussed;possible improvements on the model are suggested.
文摘The terminal velocity has been widely used in extensive fields, but the complexity of drag coefficient expression leads to the calculation of terminal velocity in transitional flow （1 〈 Re ≤ 1000） with much more difficulty than those in laminar flow （Re ≤ 1） and turbulent flow （Re ≥ 1000）. This paper summarized and compared 24 drag coefficient correlations, and developed an expression for calculating the terminal velocity in transitional flow, and also analyzed the effects of particle density and size, fluid density and viscosity on terminal velocity. The results show that 19 of 24 previously published correlations for drag coefficient have good prediction performance and can be used for calculating the terminal velocity in the entire transitional flow with higher accuracy. Adapting two dimensionless parameters （w＊, d＊）, a proposed explicit correlation, w＊=-25.68654 × exp （-d＊/77.02069）＋ 24.89826, is attained in transitional flow with good performance, which is helpful in calculating the terminal velocity.
基金Project(50878123)supported by the National Natural Science Foundation of ChinaProject(20113718110002)supported by the Specialized Research Fund for the Doctoral Program of Higher Education of China+1 种基金Project(DPMEIKF201307)supported by the Fund of the State key Laboratory of Disaster Prevention&Mitigation of Explosion&Impact(PLA University and Technology),ChinaProject(13BS402)supported by Huaqiao University Research Foundation,China
文摘The law of blasting vibration caused by blasting in rock is very complex.Traditional numerical methods cannot well characterize all the influencing factors in the blasting process.The effects of millisecond time,charge length and detonation velocity on the blasting vibration are discussed by analyzing the characteristics of vibration wave generated by finite length cylindrical charge.It is found that in multi-hole millisecond blasting,blasting vibration superimpositions will occur several times within a certain distance from the explosion source due to the propagation velocity difference of P-wave and S-wave generated by a short column charge.These superimpositions will locally enlarge the peak velocity of blasting vibration particle.The magnitude and scope of the enlargement are closely related to the millisecond time.Meanwhile,the particle vibration displacement characteristics of rock under long cylindrical charge is analyzed.The results show that blasting vibration effect would no longer increase when the charge length increases to a certain extent.This indicates that the traditional simple calculation method using the maximum charge weight per delay interval to predict the effect of blasting vibration is unreasonable.Besides,the effect of detonation velocity on blasting vibration is only limited in a certain velocity range.When detonation velocity is greater than a certain value,the detonation velocity almost makes no impact on blasting vibration.
基金This work was supported by Science and Technology Project Funded by State Grid Henan Electric Power Company(521702200004)Henan Province Key R&D and Promotion Special(Technology Research)Project(212102210016)Opening Fund of State Key Laboratory of Fire Science(SKLFS)under Grant No.HZ2021-KF11.
文摘In order to study the extinguishing performance of high-pressure-water-mist-based systems on the fires originating from power transformers the PyroSim software is used.Different particle velocities and flow rates are considered.The evolution laws of temperature around transformer,flue gas concentration and upper layer temperature of flue gas are analyzed under different boundary conditions.It is shown that the higher the particle velocity is,the lower the smoke concentration is,the better the cooling effect on the upper layer temperature of flue gas layer is,the larger the flow rate is and the better the cooling effect is.
