By analyzing the feature of the joint image of the conveyer belt with steel ropes, a quick judgement algorithm based on the gradient search for the joint ’s elongation is put forward. And at the same time its experim...By analyzing the feature of the joint image of the conveyer belt with steel ropes, a quick judgement algorithm based on the gradient search for the joint ’s elongation is put forward. And at the same time its experiment result is also given in this paper.展开更多
Presented a new coal dust control program that was airtight negative pressure dust-control technology at the transpersite,combining with analysis with the movement of air currents and numerical simulation of gas-solid...Presented a new coal dust control program that was airtight negative pressure dust-control technology at the transpersite,combining with analysis with the movement of air currents and numerical simulation of gas-solid flow at the transpersite,and proved the mechanism of precipitation and proliferation for coal dust-controlt in theory.The technol- ogy has made good economic results at the Heidaigou Clean Plant,not only dust concen- tration control within 10 mg/m^3 to the work site,but also substantial energy savings and cost savings.展开更多
A system making use of X--ray projection image to make non--destructive testing of mine conveyer belt has been developed. In the system, an one--dimensional photoelectric diode array is used to receive the X--ray proj...A system making use of X--ray projection image to make non--destructive testing of mine conveyer belt has been developed. In the system, an one--dimensional photoelectric diode array is used to receive the X--ray projection image signals and convert them into electric signals. The principle of signal conversion is introduced and the prototype of this system is presented in this paper.展开更多
There is a considerable interest in the image processing method of the joint of the conveyer belt with steel ropes.This paper presents a significant development of the joint's elongation judgment based on template...There is a considerable interest in the image processing method of the joint of the conveyer belt with steel ropes.This paper presents a significant development of the joint's elongation judgment based on template matching and statistics which provides more accurate local information compared to the algorithms in the references,and shows a reliable,real-time performance.展开更多
The principles of X-ray Non-destructive testing (NDT) for steel wire ropes buried in conveyer belt is described in the paper. The mathematical model for calculating the effective cross section of wire ropes has been d...The principles of X-ray Non-destructive testing (NDT) for steel wire ropes buried in conveyer belt is described in the paper. The mathematical model for calculating the effective cross section of wire ropes has been developed. The test data on steel wire rope samples of various types are presented,which have been compared with the National Standard. And this calculation model for the effective cross section is very important to the prediction system for transverse failure of conveyer belt.展开更多
Two novel networks for realizing first-order all-pass transfer functions are intro-duced. The networks use a current conveyer, a buffer and only three passive elements, and theyexhibit a high input impedance.
Aimed at the long and narrow geometric features and poor generalization ability of the damage detection in conveyor belts with steel rope cores using the X-ray image,a detection method of damage X-ray image is propose...Aimed at the long and narrow geometric features and poor generalization ability of the damage detection in conveyor belts with steel rope cores using the X-ray image,a detection method of damage X-ray image is proposed based on the improved fully convolutional one-stage object detection(FCOS)algorithm.The regression performance of bounding boxes was optimized by introducing the complete intersection over union loss function into the improved algorithm.The feature fusion network structure is modified by adding adaptive fusion paths to the feature fusion network structure,which makes full use of the features of accurate localization and semantics of multi-scale feature fusion networks.Finally,the network structure was trained and validated by using the X-ray image dataset of damages in conveyor belts with steel rope cores provided by a flaw detection equipment manufacturer.In addition,the data enhancement methods such as rotating,mirroring,and scaling,were employed to enrich the image dataset so that the model is adequately trained.Experimental results showed that the improved FCOS algorithm promoted the precision rate and the recall rate by 20.9%and 14.8%respectively,compared with the original algorithm.Meanwhile,compared with Fast R-CNN,Faster R-CNN,SSD,and YOLOv3,the improved FCOS algorithm has obvious advantages;detection precision rate and recall rate of the modified network reached 95.8%and 97.0%respectively.Furthermore,it demonstrated a higher detection accuracy without affecting the speed.The results of this work have some reference significance for the automatic identification and detection of steel core conveyor belt damage.展开更多
This work investigated the dynamic behavior of vertical pipes conveying gas-liquid two-phase flow when subjected to external excitations at both ends.Even with minimal excitation amplitude,resonance can occur when the...This work investigated the dynamic behavior of vertical pipes conveying gas-liquid two-phase flow when subjected to external excitations at both ends.Even with minimal excitation amplitude,resonance can occur when the excitation frequency aligns with the natural frequency of the pipe,significantly increasing the degree of operational risk.The governing equation of motion based on the Euler-Bernoulli beam is derived for the relative deflection with stationary simply supported ends,with the effects of the external excitations represented by source terms distributed along the pipe length.The fourth-order partial differential equation is solved via the generalized integral transform technique(GITT),with the solution successfully verified via comparison with results in the literature.A comprehensive analysis of the vibration phenomena and changes in the motion state of the pipe is conducted for three classes of external excitation conditions:same frequency and amplitude(SFSA),same frequency but different amplitudes(SFDA),and different frequencies and amplitudes(DFDA).The numerical results show that with increasing gas volume fraction,the position corresponding to the maximum vibration displacement shifts upward.Compared with conditions without external excitation,the vibration displacement of the pipe conveying two-phase flow under external excitation increases significantly.The frequency of external excitation has a significant effect on the dynamic behavior of a pipe conveying two-phase flow.展开更多
The City of Calgary’s Nose Creek Sanitary Sewer Trunk Phase B project has been constructed over several years to accommodate future population growth and open more developable lands in northern Calgary.The project wa...The City of Calgary’s Nose Creek Sanitary Sewer Trunk Phase B project has been constructed over several years to accommodate future population growth and open more developable lands in northern Calgary.The project was divided into three phases,Phase A,B,and C,with each phase delivered by a separate consultant.Phase A was the downstream section of this project and was undertaken by Stantec Consulting.Phase B was the upstream section designed by CH2MHILL(now Jacobs)and further divided into different contracts(1 through 5).Phase C was a separate sewer called the Saddleridge Trunk sewer and this was designed by Associated Engineering.This paper covers Phase B,Contract 4,which had several unique challenges and included many innovative design and procurement solutions.One procurement strategy included a two-phase qualification package,with the initial phase to select a tunnelling contractor with the experience to deliver technical installations under rail and creeks,and the second phase,a RFP(request for proposal),to select a general contractor,with broader experience in open-cut and stormwater drainage,which were other aspects included within the project.This approach ensured that The City had the most qualified team available to complete the project.Technical challenges discussed in this paper include an oblique CPKC(Canadian Pacific Kansas City)rail and Nose Creek crossing that required independent review,and CFD(computational fluid dynamics)and hydrogen sulfide modelling to confirm conditions within the trunk sewer.展开更多
Being able to convey the nuances of each culture constitutes the true meaning of cultural exchanges.INTERPRETER,talk show performer,presenter,and art dealer.Li Song,born in the 1980s in Shanghai,wears many hats.Whethe...Being able to convey the nuances of each culture constitutes the true meaning of cultural exchanges.INTERPRETER,talk show performer,presenter,and art dealer.Li Song,born in the 1980s in Shanghai,wears many hats.Whether on the stage,television set,or at a Sino-French activity,most likely,this dynamic man will be there.展开更多
Bends contribute to a flexible layout of pipeline system,but also lead to intensive energy costs due to the complex flow characteristic.This experimental study is conducted to investigate the impact of a single coarse...Bends contribute to a flexible layout of pipeline system,but also lead to intensive energy costs due to the complex flow characteristic.This experimental study is conducted to investigate the impact of a single coarse particle on the flow field in a bend.The velocity profiles of fluid on the axial symmetry plane of the bend are measured using time-resolved particle image velocimetry.The flow structures are extracted using the proper orthogonal decomposition method.The results reveal that there is a shear-layer flow in the bend during the transportation.With the increase in particle size,the particle has a dominant influence on the flow energy distribution of the overall flow.The impact of particles on the first few energetic flows is mainly in the latter part of the transportation,both temporally and spatially.As the particle size decreases,the most energetic unsteady flow within the bend changes from the convective flow to the flow of the shear layer.展开更多
To elucidate the relationship between pipeline erosion and wear during slurry transportation,this study considers three key influencing parameters,namely,the ratio of inlet to outlet pipe diameter,the length of the va...To elucidate the relationship between pipeline erosion and wear during slurry transportation,this study considers three key influencing parameters,namely,the ratio of inlet to outlet pipe diameter,the length of the variable diameter section,and the roughness of the pipe wall.The impact of these factors on pipeline erosion and wear is analyzed using a single-factor analysis approach.In particular,the Fluent software is employed to conduct the required numerical simulations for variable diameter elbows of varying morphologies.The results indicate that as the inlet to outlet diameter ratio increases,the wear on the pipe inlet and the outer wall of the elbow becomes increasingly pronounced.Notably,when the diameter ratio exceeds 0.8,there is a significant escalation in wear on both the inner and outer elbow walls.Initially,the maximum erosion rate decreases sharply with increasing diameter ratio before a stable condition is attained.Erosion wear in the variable diameter section exhibits a distinct layered distribution pattern.In this region,the wear range for a 40 mm length of the pipe body is relatively small;however,once this length exceeds 40 mm,the wear range expands,ultimately covering the entire pipe section.The length of the variable diameter section significantly influences the maximum erosion rate of the pipeline,with sections shorter than 80 mm experiencing the most severe effects,and showing an exponential decline in erosion rate.As the wall roughness gradually increases,the wear area on both cheeks of the bend section rapidly expands and tends to deepen further.When the roughness reaches 4 mm,the pipeline wear experiences a dramatic shift,resulting in extensive“spot-like”wear patterns emerging at the bottom and sides of the horizontal flow section,which previously exhibited no wear.展开更多
The complex dense-phase pneumatic conveying of pulverized coal process was studied using an electrical capacitance tomography(ECT) signal that represented the motion characteristics of gas-solid two-phase flow. The fl...The complex dense-phase pneumatic conveying of pulverized coal process was studied using an electrical capacitance tomography(ECT) signal that represented the motion characteristics of gas-solid two-phase flow. The fluctuation characteristics of conveying process signals are inseparable from the flow pattern. The denoised ECT signal and noise signal were obtained by db2 wavelet analysis. It was found that all noise signals were white Gaussian noise. Based on the assumption of the equal probability distribution of pulverized coal concentration, this paper proved that the time series distribution of pulverized coal concentration in the pipeline should obey the normal distribution. Furthermore, through the analysis of the distribution characteristics of the power spectral density function of denoised ECT signals of four flow patterns, they were α-dimensional fractal Brownian motion(fBm) signals, and the parameter α was estimated by the detrended fluctuation analysis. Based on the fBm characteristics of denoised ECT signals and white Gaussian noise, this paper proposed a method for calculating the pulverized coal concentration in the dense-phase pneumatic conveying. In addition to the method of concentration estimation with the significance of engineering guidance, this research can help people to further understand essential characteristics of ECT signals in the dense-phase pneumatic conveying.展开更多
Pipes have been extensively utilized in the aerospace,maritime,and other engineering sectors.However,the vibrations of pipes can significantly affect the system reliability and even lead to accidents.Visco-hyperelasti...Pipes have been extensively utilized in the aerospace,maritime,and other engineering sectors.However,the vibrations of pipes can significantly affect the system reliability and even lead to accidents.Visco-hyperelastic materials can enhance the dissipative effect,and reduce the vibrations of pipes.However,the mechanism based on the constitutive model for visco-hyperelastic materials is not clear.In this study,the damping effect of a visco-hyperelastic material on the outer surface of a plain steel pipe is investigated.The nonlinear constitutive relation of the visco-hyperelastic material is introduced into the governing equation of the system for the first time.Based on this nonlinear constitutive model,the governing model for the forced vibration analysis of a simply-supported laminated pipe is established.The Galerkin method is used to analyze the effects of the visco-hyperelastic parameters and structural parameters on the natural characteristics of the fluid-conveying pipes.Subsequently,the harmonic balance method(HBM)is used to investigate the forced vibration responses of the pipe.Finally,the differential quadrature element method(DQEM)is used to validate these results.The findings demonstrate that,while the visco-hyperelastic material has a minimal effect on the natural characteristics,it effectively dampens the vibrations in the pipe.This research provides a theoretical foundation for applying vibration damping materials in pipe vibration control.展开更多
The Haidong Water Conveyance Tunnel(HWCT),a notable engineering feat located within Dali City,Yunnan Province,China,represents an ultra-long water conveyance tunnel situated in a region characterized by medium in-situ...The Haidong Water Conveyance Tunnel(HWCT),a notable engineering feat located within Dali City,Yunnan Province,China,represents an ultra-long water conveyance tunnel situated in a region characterized by medium in-situ stress conditions.As part of the Central Yunnan Water Diversion Project,this tunnel was specifically engineered for soft-rock environments.The excavation of such tunnels presents significant challenges due to rock mass deformation,commonly referred to as squeezing ground behavior.These challenges are exacerbated when navigating through diverse geological and geomorphological units,particularly in areas with complex geological conditions.To address these issues,an innovative active support system utilizing prestressed anchor cables was developed for the HWCT.This study provides a comprehensive analysis and comparison of rock mass behavior between two support systems:a conventional passive system employing steel arches and the proposed active system using prestressed anchor cables.The numerical modeling was performed using FLAC3D software to simulate various scenarios,while an extensive monitoring program was implemented in several representative tunnel sections to measure key parameters including rock mass stresses,displacements,internal forces in steel arches,and axial forces in anchor cables.The results from both the numerical simulations and field observations were systematically compared.The analyses demonstrated the superior performance of the active support system using prestressed anchor cables in the HWCT,significantly enhancing overall rock mass stability and effectively mitigating large deformation issues throughout the tunnel.展开更多
This study examines the nonlinear behaviors of a clamped-clamped porous pipe made of a functionally graded material(FGM)that conveys fluids and is equipped with a retaining clip,focusing on primary resonance and subcr...This study examines the nonlinear behaviors of a clamped-clamped porous pipe made of a functionally graded material(FGM)that conveys fluids and is equipped with a retaining clip,focusing on primary resonance and subcritical dynamics.The nonlinear governing equations for the FGM pipe are derived by the extended Hamilton's principle,and subsequently discretized through the application of the Galerkin method.The direct method of multi-scales is then used to solve the derived equations.A thorough analysis of various parameters,including the clip stiffness,the power-law index,the porosity,and the clip location,is conducted to gain a comprehensive understanding of the system's nonlinear dynamics.Through the analysis of the first natural frequency,the study highlights the influence of the flow velocity and the clip stiffness,while the comparisons with metallic pipes emphasize the role of FGM composition.The examination of the forced response curves reveals saddle-node bifurcations and their dependence on parameters such as the detuning parameter and the power-law index,offering valuable insights into the system's nonlinear resonant behavior.Furthermore,the frequency-response curves illustrate the hardening nonlinearities influenced by factors such as the porosity and the clip stiffness,revealing nuanced effects on the system response and resonance characteristics.This comprehensive analysis enhances the understanding of nonlinear behaviors in FGM porous pipes with a retaining clip,providing key insights for practical engineering applications in system design and optimization.展开更多
Multi-constrained pipes conveying fluid,such as aircraft hydraulic control pipes,are susceptible to resonance fatigue in harsh vibration environments,which may lead to system failure and even catastrophic accidents.In...Multi-constrained pipes conveying fluid,such as aircraft hydraulic control pipes,are susceptible to resonance fatigue in harsh vibration environments,which may lead to system failure and even catastrophic accidents.In this study,a machine learning(ML)-assisted weak vibration design method under harsh environmental excitations is proposed.The dynamic model of a typical pipe is developed using the absolute nodal coordinate formulation(ANCF)to determine its vibrational characteristics.With the harsh vibration environments as the preserved frequency band(PFB),the safety design is defined by comparing the natural frequency with the PFB.By analyzing the safety design of pipes with different constraint parameters,the dataset of the absolute safety length and the absolute resonance length of the pipe is obtained.This dataset is then utilized to develop genetic programming(GP)algorithm-based ML models capable of producing explicit mathematical expressions of the pipe's absolute safety length and absolute resonance length with the location,stiffness,and total number of retaining clips as design variables.The proposed ML models effectively bridge the dataset with the prediction results.Thus,the ML model is utilized to stagger the natural frequency,and the PFB is utilized to achieve the weak vibration design.The findings of the present study provide valuable insights into the practical application of weak vibration design.展开更多
Experiments of dense-phase pneumatic conveying of pulverized coal using nitrogen are carded out in an experimental test facility with the conveying pressure up to 4. 0 MPa and the gas-solid ratio up to 450 kg/m^3. The...Experiments of dense-phase pneumatic conveying of pulverized coal using nitrogen are carded out in an experimental test facility with the conveying pressure up to 4. 0 MPa and the gas-solid ratio up to 450 kg/m^3. The influences of different conveying differential pressures, coal moisture contents, gas volume flow rates and superficial velocities on the solid-gas ratios are investigated. Shannon entropy analysis of pressure fluctuation time series is developed to reveal the flow characteristics. Through investigation of the distribution of the Shannon entropy under different conditions, the flow stability and the evolutional tendency of the Shannon entropy in different regimes and regime transition processes are discovered, and the relationship between the Shannon entropy and the flow regimes is also established. The results indicate that the solid-gas ratio and the Shannon entropy rise with the increase in conveying differential pressure. The solid-gas ratio and the Shannon entropy reveal preferable regularity with gas volume flow rates. The Shannon entropy is different for different flow regimes, and can be used to identify the flow regimes. Both mass flow rate and the Shannon entropy decrease with the increase in moisture contents. The Shannon entropy analysis is a feasible approach for researching the characteristics of flow regimes, flow stability and flow regime transitions in dense-phase pneumatic conveying under high pressure.展开更多
Aiming at the existing problems of safety, reliability and flexibility in the traditional coal mine belt transport system, this paper designed the mine centralized control system transmitted by CAN bus and PLC as the ...Aiming at the existing problems of safety, reliability and flexibility in the traditional coal mine belt transport system, this paper designed the mine centralized control system transmitted by CAN bus and PLC as the core, and use comparison instructions and trigger of Siemens S7-200 PLC, the article has elaborated the four level conveyor belt sequence control, realized the sequence start, reverse sequence stop and fault processing and other functions for four level conveyor belt, the compared with traditional timer control instructions scheme, the design has clear thinking, simple design program, and is easy to be extended to multilevel belt drive sequence control.展开更多
Introduction Interpretersandtranslators have triggeredmore and more regardas professionals for their significant multi language skills, cultural knowledge and professional conducts. As professions,
文摘By analyzing the feature of the joint image of the conveyer belt with steel ropes, a quick judgement algorithm based on the gradient search for the joint ’s elongation is put forward. And at the same time its experiment result is also given in this paper.
文摘Presented a new coal dust control program that was airtight negative pressure dust-control technology at the transpersite,combining with analysis with the movement of air currents and numerical simulation of gas-solid flow at the transpersite,and proved the mechanism of precipitation and proliferation for coal dust-controlt in theory.The technol- ogy has made good economic results at the Heidaigou Clean Plant,not only dust concen- tration control within 10 mg/m^3 to the work site,but also substantial energy savings and cost savings.
文摘A system making use of X--ray projection image to make non--destructive testing of mine conveyer belt has been developed. In the system, an one--dimensional photoelectric diode array is used to receive the X--ray projection image signals and convert them into electric signals. The principle of signal conversion is introduced and the prototype of this system is presented in this paper.
文摘There is a considerable interest in the image processing method of the joint of the conveyer belt with steel ropes.This paper presents a significant development of the joint's elongation judgment based on template matching and statistics which provides more accurate local information compared to the algorithms in the references,and shows a reliable,real-time performance.
文摘The principles of X-ray Non-destructive testing (NDT) for steel wire ropes buried in conveyer belt is described in the paper. The mathematical model for calculating the effective cross section of wire ropes has been developed. The test data on steel wire rope samples of various types are presented,which have been compared with the National Standard. And this calculation model for the effective cross section is very important to the prediction system for transverse failure of conveyer belt.
文摘Two novel networks for realizing first-order all-pass transfer functions are intro-duced. The networks use a current conveyer, a buffer and only three passive elements, and theyexhibit a high input impedance.
文摘Aimed at the long and narrow geometric features and poor generalization ability of the damage detection in conveyor belts with steel rope cores using the X-ray image,a detection method of damage X-ray image is proposed based on the improved fully convolutional one-stage object detection(FCOS)algorithm.The regression performance of bounding boxes was optimized by introducing the complete intersection over union loss function into the improved algorithm.The feature fusion network structure is modified by adding adaptive fusion paths to the feature fusion network structure,which makes full use of the features of accurate localization and semantics of multi-scale feature fusion networks.Finally,the network structure was trained and validated by using the X-ray image dataset of damages in conveyor belts with steel rope cores provided by a flaw detection equipment manufacturer.In addition,the data enhancement methods such as rotating,mirroring,and scaling,were employed to enrich the image dataset so that the model is adequately trained.Experimental results showed that the improved FCOS algorithm promoted the precision rate and the recall rate by 20.9%and 14.8%respectively,compared with the original algorithm.Meanwhile,compared with Fast R-CNN,Faster R-CNN,SSD,and YOLOv3,the improved FCOS algorithm has obvious advantages;detection precision rate and recall rate of the modified network reached 95.8%and 97.0%respectively.Furthermore,it demonstrated a higher detection accuracy without affecting the speed.The results of this work have some reference significance for the automatic identification and detection of steel core conveyor belt damage.
基金financially supported by the Key Research and Development Program of Shandong Province(Grant Nos.2022CXGC020405,2023CXGC010415 and 2025TSGCCZZB0238)the National Natural Science Foundation of China(Grant No.52171288)the financial support from CNPq,FAPERJ,ANP,Embrapii,and China National Petroleum Corporation(CNPC).
文摘This work investigated the dynamic behavior of vertical pipes conveying gas-liquid two-phase flow when subjected to external excitations at both ends.Even with minimal excitation amplitude,resonance can occur when the excitation frequency aligns with the natural frequency of the pipe,significantly increasing the degree of operational risk.The governing equation of motion based on the Euler-Bernoulli beam is derived for the relative deflection with stationary simply supported ends,with the effects of the external excitations represented by source terms distributed along the pipe length.The fourth-order partial differential equation is solved via the generalized integral transform technique(GITT),with the solution successfully verified via comparison with results in the literature.A comprehensive analysis of the vibration phenomena and changes in the motion state of the pipe is conducted for three classes of external excitation conditions:same frequency and amplitude(SFSA),same frequency but different amplitudes(SFDA),and different frequencies and amplitudes(DFDA).The numerical results show that with increasing gas volume fraction,the position corresponding to the maximum vibration displacement shifts upward.Compared with conditions without external excitation,the vibration displacement of the pipe conveying two-phase flow under external excitation increases significantly.The frequency of external excitation has a significant effect on the dynamic behavior of a pipe conveying two-phase flow.
文摘The City of Calgary’s Nose Creek Sanitary Sewer Trunk Phase B project has been constructed over several years to accommodate future population growth and open more developable lands in northern Calgary.The project was divided into three phases,Phase A,B,and C,with each phase delivered by a separate consultant.Phase A was the downstream section of this project and was undertaken by Stantec Consulting.Phase B was the upstream section designed by CH2MHILL(now Jacobs)and further divided into different contracts(1 through 5).Phase C was a separate sewer called the Saddleridge Trunk sewer and this was designed by Associated Engineering.This paper covers Phase B,Contract 4,which had several unique challenges and included many innovative design and procurement solutions.One procurement strategy included a two-phase qualification package,with the initial phase to select a tunnelling contractor with the experience to deliver technical installations under rail and creeks,and the second phase,a RFP(request for proposal),to select a general contractor,with broader experience in open-cut and stormwater drainage,which were other aspects included within the project.This approach ensured that The City had the most qualified team available to complete the project.Technical challenges discussed in this paper include an oblique CPKC(Canadian Pacific Kansas City)rail and Nose Creek crossing that required independent review,and CFD(computational fluid dynamics)and hydrogen sulfide modelling to confirm conditions within the trunk sewer.
文摘Being able to convey the nuances of each culture constitutes the true meaning of cultural exchanges.INTERPRETER,talk show performer,presenter,and art dealer.Li Song,born in the 1980s in Shanghai,wears many hats.Whether on the stage,television set,or at a Sino-French activity,most likely,this dynamic man will be there.
基金supported by the Hainan Provincial Joint Project of Sanya Yazhou Bay Science and Technology City(Grant No.2021CXLH0003)the Innovational Fund for Scientific and Technological Personnel of Hainan Province(Grant No.KJRC2023D37).
文摘Bends contribute to a flexible layout of pipeline system,but also lead to intensive energy costs due to the complex flow characteristic.This experimental study is conducted to investigate the impact of a single coarse particle on the flow field in a bend.The velocity profiles of fluid on the axial symmetry plane of the bend are measured using time-resolved particle image velocimetry.The flow structures are extracted using the proper orthogonal decomposition method.The results reveal that there is a shear-layer flow in the bend during the transportation.With the increase in particle size,the particle has a dominant influence on the flow energy distribution of the overall flow.The impact of particles on the first few energetic flows is mainly in the latter part of the transportation,both temporally and spatially.As the particle size decreases,the most energetic unsteady flow within the bend changes from the convective flow to the flow of the shear layer.
基金supported by the project of the Educational Department of Liaoning Province(No.LJKMZ20220825)the National Natural Science Foundation of China(51774199).
文摘To elucidate the relationship between pipeline erosion and wear during slurry transportation,this study considers three key influencing parameters,namely,the ratio of inlet to outlet pipe diameter,the length of the variable diameter section,and the roughness of the pipe wall.The impact of these factors on pipeline erosion and wear is analyzed using a single-factor analysis approach.In particular,the Fluent software is employed to conduct the required numerical simulations for variable diameter elbows of varying morphologies.The results indicate that as the inlet to outlet diameter ratio increases,the wear on the pipe inlet and the outer wall of the elbow becomes increasingly pronounced.Notably,when the diameter ratio exceeds 0.8,there is a significant escalation in wear on both the inner and outer elbow walls.Initially,the maximum erosion rate decreases sharply with increasing diameter ratio before a stable condition is attained.Erosion wear in the variable diameter section exhibits a distinct layered distribution pattern.In this region,the wear range for a 40 mm length of the pipe body is relatively small;however,once this length exceeds 40 mm,the wear range expands,ultimately covering the entire pipe section.The length of the variable diameter section significantly influences the maximum erosion rate of the pipeline,with sections shorter than 80 mm experiencing the most severe effects,and showing an exponential decline in erosion rate.As the wall roughness gradually increases,the wear area on both cheeks of the bend section rapidly expands and tends to deepen further.When the roughness reaches 4 mm,the pipeline wear experiences a dramatic shift,resulting in extensive“spot-like”wear patterns emerging at the bottom and sides of the horizontal flow section,which previously exhibited no wear.
基金funding from Shanghai Sailing Program (22YF1417600)Guangxi Science and Technology Major Program (AA23062019)
文摘The complex dense-phase pneumatic conveying of pulverized coal process was studied using an electrical capacitance tomography(ECT) signal that represented the motion characteristics of gas-solid two-phase flow. The fluctuation characteristics of conveying process signals are inseparable from the flow pattern. The denoised ECT signal and noise signal were obtained by db2 wavelet analysis. It was found that all noise signals were white Gaussian noise. Based on the assumption of the equal probability distribution of pulverized coal concentration, this paper proved that the time series distribution of pulverized coal concentration in the pipeline should obey the normal distribution. Furthermore, through the analysis of the distribution characteristics of the power spectral density function of denoised ECT signals of four flow patterns, they were α-dimensional fractal Brownian motion(fBm) signals, and the parameter α was estimated by the detrended fluctuation analysis. Based on the fBm characteristics of denoised ECT signals and white Gaussian noise, this paper proposed a method for calculating the pulverized coal concentration in the dense-phase pneumatic conveying. In addition to the method of concentration estimation with the significance of engineering guidance, this research can help people to further understand essential characteristics of ECT signals in the dense-phase pneumatic conveying.
基金supported by the National Natural Science Foundation of China(Nos.12372015 and12421002)the National Science Fund for Distinguished Young Scholars of China(No.12025204)。
文摘Pipes have been extensively utilized in the aerospace,maritime,and other engineering sectors.However,the vibrations of pipes can significantly affect the system reliability and even lead to accidents.Visco-hyperelastic materials can enhance the dissipative effect,and reduce the vibrations of pipes.However,the mechanism based on the constitutive model for visco-hyperelastic materials is not clear.In this study,the damping effect of a visco-hyperelastic material on the outer surface of a plain steel pipe is investigated.The nonlinear constitutive relation of the visco-hyperelastic material is introduced into the governing equation of the system for the first time.Based on this nonlinear constitutive model,the governing model for the forced vibration analysis of a simply-supported laminated pipe is established.The Galerkin method is used to analyze the effects of the visco-hyperelastic parameters and structural parameters on the natural characteristics of the fluid-conveying pipes.Subsequently,the harmonic balance method(HBM)is used to investigate the forced vibration responses of the pipe.Finally,the differential quadrature element method(DQEM)is used to validate these results.The findings demonstrate that,while the visco-hyperelastic material has a minimal effect on the natural characteristics,it effectively dampens the vibrations in the pipe.This research provides a theoretical foundation for applying vibration damping materials in pipe vibration control.
基金support provided by the Technology Development Service Project Funds of China,Railway 5th Bureau Group Fifth Engineering Co.,Ltd and Yunnan Institute of Water&Hydropower Engineering Investigation,Design and Research(Grant No.20230525)the Major Science and Technology Special Plan of Yunnan Province Science and Technology Department(Grant No.202002AF080003)the Fundamental Research Funds for the Central Universities(Grant No.2022YJSSB04).
文摘The Haidong Water Conveyance Tunnel(HWCT),a notable engineering feat located within Dali City,Yunnan Province,China,represents an ultra-long water conveyance tunnel situated in a region characterized by medium in-situ stress conditions.As part of the Central Yunnan Water Diversion Project,this tunnel was specifically engineered for soft-rock environments.The excavation of such tunnels presents significant challenges due to rock mass deformation,commonly referred to as squeezing ground behavior.These challenges are exacerbated when navigating through diverse geological and geomorphological units,particularly in areas with complex geological conditions.To address these issues,an innovative active support system utilizing prestressed anchor cables was developed for the HWCT.This study provides a comprehensive analysis and comparison of rock mass behavior between two support systems:a conventional passive system employing steel arches and the proposed active system using prestressed anchor cables.The numerical modeling was performed using FLAC3D software to simulate various scenarios,while an extensive monitoring program was implemented in several representative tunnel sections to measure key parameters including rock mass stresses,displacements,internal forces in steel arches,and axial forces in anchor cables.The results from both the numerical simulations and field observations were systematically compared.The analyses demonstrated the superior performance of the active support system using prestressed anchor cables in the HWCT,significantly enhancing overall rock mass stability and effectively mitigating large deformation issues throughout the tunnel.
文摘This study examines the nonlinear behaviors of a clamped-clamped porous pipe made of a functionally graded material(FGM)that conveys fluids and is equipped with a retaining clip,focusing on primary resonance and subcritical dynamics.The nonlinear governing equations for the FGM pipe are derived by the extended Hamilton's principle,and subsequently discretized through the application of the Galerkin method.The direct method of multi-scales is then used to solve the derived equations.A thorough analysis of various parameters,including the clip stiffness,the power-law index,the porosity,and the clip location,is conducted to gain a comprehensive understanding of the system's nonlinear dynamics.Through the analysis of the first natural frequency,the study highlights the influence of the flow velocity and the clip stiffness,while the comparisons with metallic pipes emphasize the role of FGM composition.The examination of the forced response curves reveals saddle-node bifurcations and their dependence on parameters such as the detuning parameter and the power-law index,offering valuable insights into the system's nonlinear resonant behavior.Furthermore,the frequency-response curves illustrate the hardening nonlinearities influenced by factors such as the porosity and the clip stiffness,revealing nuanced effects on the system response and resonance characteristics.This comprehensive analysis enhances the understanding of nonlinear behaviors in FGM porous pipes with a retaining clip,providing key insights for practical engineering applications in system design and optimization.
基金Project supported by the Foundation for Innovative Research Groups of the National Natural Science Foundation of China(No.12421002)the National Science Funds for Distinguished Young Scholars of China(No.12025204)+1 种基金the National Natural Science Foundation of China(No.12372015)China Scholarship Council(No.202206890065)。
文摘Multi-constrained pipes conveying fluid,such as aircraft hydraulic control pipes,are susceptible to resonance fatigue in harsh vibration environments,which may lead to system failure and even catastrophic accidents.In this study,a machine learning(ML)-assisted weak vibration design method under harsh environmental excitations is proposed.The dynamic model of a typical pipe is developed using the absolute nodal coordinate formulation(ANCF)to determine its vibrational characteristics.With the harsh vibration environments as the preserved frequency band(PFB),the safety design is defined by comparing the natural frequency with the PFB.By analyzing the safety design of pipes with different constraint parameters,the dataset of the absolute safety length and the absolute resonance length of the pipe is obtained.This dataset is then utilized to develop genetic programming(GP)algorithm-based ML models capable of producing explicit mathematical expressions of the pipe's absolute safety length and absolute resonance length with the location,stiffness,and total number of retaining clips as design variables.The proposed ML models effectively bridge the dataset with the prediction results.Thus,the ML model is utilized to stagger the natural frequency,and the PFB is utilized to achieve the weak vibration design.The findings of the present study provide valuable insights into the practical application of weak vibration design.
基金The National Basic Research Program of China(973 Program) (No2004CB217702-01)the Foundation of ExcellentPhDThesis of Southeast University
文摘Experiments of dense-phase pneumatic conveying of pulverized coal using nitrogen are carded out in an experimental test facility with the conveying pressure up to 4. 0 MPa and the gas-solid ratio up to 450 kg/m^3. The influences of different conveying differential pressures, coal moisture contents, gas volume flow rates and superficial velocities on the solid-gas ratios are investigated. Shannon entropy analysis of pressure fluctuation time series is developed to reveal the flow characteristics. Through investigation of the distribution of the Shannon entropy under different conditions, the flow stability and the evolutional tendency of the Shannon entropy in different regimes and regime transition processes are discovered, and the relationship between the Shannon entropy and the flow regimes is also established. The results indicate that the solid-gas ratio and the Shannon entropy rise with the increase in conveying differential pressure. The solid-gas ratio and the Shannon entropy reveal preferable regularity with gas volume flow rates. The Shannon entropy is different for different flow regimes, and can be used to identify the flow regimes. Both mass flow rate and the Shannon entropy decrease with the increase in moisture contents. The Shannon entropy analysis is a feasible approach for researching the characteristics of flow regimes, flow stability and flow regime transitions in dense-phase pneumatic conveying under high pressure.
文摘Aiming at the existing problems of safety, reliability and flexibility in the traditional coal mine belt transport system, this paper designed the mine centralized control system transmitted by CAN bus and PLC as the core, and use comparison instructions and trigger of Siemens S7-200 PLC, the article has elaborated the four level conveyor belt sequence control, realized the sequence start, reverse sequence stop and fault processing and other functions for four level conveyor belt, the compared with traditional timer control instructions scheme, the design has clear thinking, simple design program, and is easy to be extended to multilevel belt drive sequence control.
文摘Introduction Interpretersandtranslators have triggeredmore and more regardas professionals for their significant multi language skills, cultural knowledge and professional conducts. As professions,
