In the printing industry,vacuum pumps play a critical role in sheet feeding and gripping processes.In order to improve the efficiency of vacuum pumps,By analyzing the internal flow field of the vane type vacuum pump,t...In the printing industry,vacuum pumps play a critical role in sheet feeding and gripping processes.In order to improve the efficiency of vacuum pumps,By analyzing the internal flow field of the vane type vacuum pump,the CFD method was used to simulate the internal flow field of the air pump,and it was found that a main vortex was formed near the rotor of the trailing blade.Based on this observation,a new rotor shape design was proposed in this study,which design places arc-shaped depressed on the circumference of the rotor where the main vortex forms.The existence of the depression facilitated forward motion of the main airflow and thus effectively restricting reverse flow.Simulation results demonstrated that the proposed design is able to decrease pressure-induced torque load on the pump,and the reduction increases for an increasing operating speed.For all three operating speeds tested,the reduction in pressure-induced torque ranges from 5%to up to 10%comparing to the original pump.展开更多
This study presents a novel roller piston pump,in which a cam guide-roller type rolling support is adopted to replace the sliding pair support of the swash plate-slipper pair to achieve the oil suction and discharge o...This study presents a novel roller piston pump,in which a cam guide-roller type rolling support is adopted to replace the sliding pair support of the swash plate-slipper pair to achieve the oil suction and discharge of the piston cavity.In addition,the shaft distribution is used to replace the original valve plate distribution and the driving shaft is used as the distribution shaft to remove the valve plate structure,which greatly simplifies the design of the axial piston pump.Such a configuration largely reduces the number of sliding friction pairs of the pump,and avoids the influence of the sliding friction pair on it under high-speed and variable-speed conditions.Firstly,mathematical models of the mechanical and volumetric efficiencies of the roller pump are deduced respectively through force analysis and the compressibility equation.Based on the numerical simulation of MATLAB and AMESim,the effects of load pressure and rotational speed on mechanical and volumetric efficiencies are studied respectively,and it is verified that the roller pump has no structural flow pulsation.The prototype pump is then designed and built,along with a special test rig.The outlet pressure,outlet flow,and torque of the pump under different load pressures and rotational speeds are measured,and the mechanical and volumetric efficiencies of the prototype pump under various load pressures and rotational speeds are obtained.The experimental results are in good agreement with the simulated analysis.When the load pressure is 8 MPa and the speed is 5000 r/min,the mechanical and the volumetric efficiencies are 85.5% and 96.8%,respectively.When the speed is increased to 10000 r/min,the mechanical and the volumetric efficiencies are 66.7% and 95.6%,respectively.The experimental results show that the proposed roller piston pump has excellent efficiency under wide-speed and high-speed conditions and can be a potential solution as a fuel pump in aerospace fuel systems.展开更多
In order to improve the source water quality of drinking water and mitigate the load of drinking water treatment plant, a pilot test was conducted with integrated horizontal flow constructed wetlands to pretreat the w...In order to improve the source water quality of drinking water and mitigate the load of drinking water treatment plant, a pilot test was conducted with integrated horizontal flow constructed wetlands to pretreat the water supply in the reservoirs of Yellow River. Resuhs show that under the hydraulic loading rate of 4 m^3/（ m^2 · d）, the average removal rates of chemical oxygen demand （COD）, total nitrogen （TN）, ammonium nitrogen （ NH4 ^＋ - N）, nitrate nitrogen （ NO3 ^- - N）, nitrite - nitrogen （ NO2^ - - N） and total phosphorus （TP） in the horizontal flow constructed wetlands are 49. 68% , 53.01%, 48.48%, 53.61% , 62. 57% and 49. 56%, re- spectively. The study on purifying mechanism of the constructed wetlands indicates that the disposal of contamination by subsurface wetlands is the combined actions of physical chemistry, plants and microorganism.展开更多
With increasing demand for nonrenewable resources,energy conservation is critical.Efficiency gains allow more work to be performed while maintaining or even decreasing the energy expended in the process.Reducing the e...With increasing demand for nonrenewable resources,energy conservation is critical.Efficiency gains allow more work to be performed while maintaining or even decreasing the energy expended in the process.Reducing the energy consumed by a system results in favorable economic and environmental impact.An apparatus has been developed to measure hydraulic fluid efficiency in a stationary application.The system can be used to develop more efficient fluids,leading to increased work output or decreased energy consumption.展开更多
That SOEs are inefficient is still a consensus in most economic literature. However, in recent studies, more and more arguments are made in favor of the efficiency of SOEs, yet existing empirical studies are mostly ba...That SOEs are inefficient is still a consensus in most economic literature. However, in recent studies, more and more arguments are made in favor of the efficiency of SOEs, yet existing empirical studies are mostly based on production industry data as samples. On the basis of adopting distribution samples and conducting a cross-sector comparison between the production industry and the distribution sector, this paper offers a multi-perspective empirical assessment on the efficiency of SOEs. Through the analysis of major JTnancial indicators and adopting the Data Envelopment Analysis-Malmquist index for total factor productivity comparison, we find that SOEs generally do not have any disadvantage in efficiency and their superior efficiency is particularly pronounced in the distribution sector as compared with production industry. Moreover, the high share and high efficiency of state capital in the wholesale sector needs particular attention. This paper employs case studies to reveal the positive correlation between the assets-heavy operation of state-owned wholesale firms and their profitability. The implications are as follows： policymakers must deliberate prudently before deciding to withdraw or increase state capital in various sectors; in the wholesale sector where state capital is more efficient, the functions of state capital can be bolstered by increasing its presence in the sector,＂ the notion that state capital must be withdrawn from competitive sectors cannot be adopted likely, nor should the benefits of asset-light operation be exaggerated.展开更多
Flexible perovskite solar cells(f-PSCs) have experienced rapid advancements due to the light-weight, flexibility, and solution processability of the perovskite materials, which prompted the power conversion efficiency...Flexible perovskite solar cells(f-PSCs) have experienced rapid advancements due to the light-weight, flexibility, and solution processability of the perovskite materials, which prompted the power conversion efficiency(PCE) to 24.08%. However, f-PSCs still face challenges in terms of mechanical and environmental stability. This is primarily due to their inherent brittleness, the presence of residual tensile strain, and the high density of defects along the boundaries of perovskite grains. To this end, we carefully developed a cross-linkable elastomers 3-[(3-acrylamidopropyl)dimethylammonium] propanoate(ADP) with electrostatic dynamic bond, which could be in-situ cross-linked and coordinate with [Pb I6]4-to regulate the crystallization process of perovskite. The cross-linked elastomers attached to the perovskite grain boundaries could release the remaining tensile strains and mechanical stresses, leading to enhanced stability and flexibility of the f-PSCs. More importantly, the electrostatic interaction between positive and negative groups of cross-linked elastomers and hydrogen bond formation between N–H and C=O accelerate the cross-linking of ADP, endowing the flexible perovskite films with self-healing ability under mild treating conditions(60 °C for 30 min). As a result, the device achieves a remarkable PCE of 23.53%(certified 23.16%). Additionally, the device exhibits impressive mechanical sustainability and durability, retaining over 90% of initial PCE even after undergoing8,000 bending cycles.展开更多
Investigation concerning peristaltic motion of couple stress fluid is made. An incompressible couple stress fluid occupies the porous medium. Mathematical anal- ysis is presented through large wavelength and low Reyno...Investigation concerning peristaltic motion of couple stress fluid is made. An incompressible couple stress fluid occupies the porous medium. Mathematical anal- ysis is presented through large wavelength and low Reynolds number. Exact analytical expressions of axial velocity, volume flow rate, pressure gradient, and stream function are calculated as a function of couple stress parameter. The essential feature of the analysis is a full description of influence of couple stress parameter and permeability parameter on the pressure, frictional force, mechanical efficiency, and trapping.展开更多
The present investigation studies the peristaltic flow of the Jeffrey fluid through a tube of finite length. The fluid is electrically conducting in the presence of an applied magnetic field. Analysis is carried out u...The present investigation studies the peristaltic flow of the Jeffrey fluid through a tube of finite length. The fluid is electrically conducting in the presence of an applied magnetic field. Analysis is carried out under the assumption of long wavelength and low Reynolds number approximations. Expressions of the pressure gradient, volume flow rate, average volume flow rate, and local wall shear stress are obtained. The effects of relaxation time, retardation time, Hartman number on pressure, local wall shear stress, and mechanical efficiency of peristaltic pump are studied. The reflux phenomenon is also investigated. The case of propagation of a non-integral number of waves along the tube walls, which are inherent characteristics of finite length vessels, is also examined.展开更多
This study explores the potentials of employing an Organic Rankine Cycle (ORC) system with variable inlet guide vanes (VIV) turbine geometry designed on a GT-Suite platform for effective exhaust heat recovery (EHR) ap...This study explores the potentials of employing an Organic Rankine Cycle (ORC) system with variable inlet guide vanes (VIV) turbine geometry designed on a GT-Suite platform for effective exhaust heat recovery (EHR) application onboard passenger vehicles. The ORC model simulation was based on vehicle speed mode using R245fa as working fluid to assess the thermal performance of the ORC system when utilizing modified turbine geometry. Interestingly, the model achieved a very improved performance in contrast to the model without a modified turbine configuration. The results revealed the average 2.32 kW ORC net output, 4.93% thermal efficiency, 6.1% mechanical efficiency, and 5.0% improved brake specific fuel consumption (BSFC) for the developed model. As determined by the performance indicators, these promising results from the model study show the prospect of EHR technology application in the transportation sector for reduction in exhaust emissions and fuel savings.展开更多
This paper studies the Stokes flow of micro-polar fluids by peristaltic pumping through the cylindrical tube under the effect of the slip boundary condition. The motion of the wall is governed by the sinusoidal wave e...This paper studies the Stokes flow of micro-polar fluids by peristaltic pumping through the cylindrical tube under the effect of the slip boundary condition. The motion of the wall is governed by the sinusoidal wave equation. The analytical and numerical solutions for the axial velocity, the micro-polar vector, the stream function, the pressure gradient, the friction force, and the mechanical efficiency are obtained by using the lu- brication theory under the low Reynolds number and long wavelength approximations. The impacts of the emerging parameters, such as the coupling number, the micro-polar parameter, the slip parameter on pumping characteristics, the friction force, the velocity profile, the mechanical efficiency, and the trapping phenomenon are depicted graphically. The numerical results infer that large pressure is required for peristaltic pumping when the coupling number is large, while opposite behaviors are found for the micro-polar parameter and the slip parameter. The size of the trapped bolus reduces with the increase in the coupling number and the micro-polar parameter, whereas it blows up with the increase in the slip parameter.展开更多
This paper introduces a new technology of using ceramic coating on piston rings of an internal combustion engine, and the comparison of mechanical efficiency and performances of an actual engine before and after the a...This paper introduces a new technology of using ceramic coating on piston rings of an internal combustion engine, and the comparison of mechanical efficiency and performances of an actual engine before and after the application of ceramic coating on the piston rings. The experimental results show that the mechanical efficiency and power output are enhanced by 4% and 2.6%, respectively, with fuel consumption reduced by (2.9%.) Further studies on coating processing and coating materials as well as the reliability and durability will be of great significance in the application and popularization of the new technology.展开更多
At a fully mechanized working face of a coal mine as prototype,we investigated,by simulation,the flow field and dust distribution during the process of its isolation by a curtain of air,using the CFD software, Fluent....At a fully mechanized working face of a coal mine as prototype,we investigated,by simulation,the flow field and dust distribution during the process of its isolation by a curtain of air,using the CFD software, Fluent.The results show that the air curtain installed on the shearer can effectively prevent the dust （especially the respirable dust）from diffusing into the work area of the operator,reducing the dust concentration on the side of the operator and greatly improving his working environment.The field application of the air curtain shows that the dust-isolation effect of an air curtain is quite noticeable.The isolation efficiency for respiratory dust is over 70%and,as well,it has good dust-isolation effect for nonrespiratory dust.The air curtain is a useful way to resolve the problem of dust-isolation at a fully mechanized working face.It has a practical background elsewhere with more extensive applications.展开更多
At present, the huge problem that China’s Non-profit Organizations are facing is the low efficiency of public fundraising. However, the newly appeared Online Fundraising Platform indicates some possibilities in ove...At present, the huge problem that China’s Non-profit Organizations are facing is the low efficiency of public fundraising. However, the newly appeared Online Fundraising Platform indicates some possibilities in overcoming the obstacle for public fundraising. Among which Tencent Online Fundraising Platform becomes the typical and the point cut of exploring Online Fundraising Platform Improving Efficiency Mechanism of public donation. Online Fundraising Platform is similar to the online United Way, relying on the advantages of the Internet and the united fundraising to build a ecosystem of public donation which has professional fundraising system, good charity atmosphere, excellent policy environment and crossover cooperation resources. And in which, many factors get improved in pubic donation influence factors system. For one thing, Charity atmosphere and policy environment can be shaped better. For another, the charities can transmit fundraising information in inexpensive and high-efficiency way, and must ensure the transparency of project and donation. Finally, it will be more convenient for donors to get charitable information, make donations and supervise the nonprofit organizations.展开更多
With the development of smart agriculture,accurately identifying crop diseases through visual recognition techniques instead of by eye has been a significant challenge.This study focused on apple leaf disease,which is...With the development of smart agriculture,accurately identifying crop diseases through visual recognition techniques instead of by eye has been a significant challenge.This study focused on apple leaf disease,which is closely related to the final yield of apples.A multiscale fusion dense network combined with an efficient multiscale attention(EMA)mechanism called Incept_EMA_DenseNet was developed to better identify eight complex apple leaf disease images.Incept_EMA_DenseNet consists of three crucial parts:the inception module,which substituted the convolution layer with multiscale fusion methods in the shallow feature extraction layer;the EMA mechanism,which is used for obtaining appropriate weights of different dense blocks;and the improved DenseNet based on DenseNet_121.Specifically,to find appropriate multiscale fusion methods,the residual module and inception module were compared to determine the performance of each technique,and Incept_EMA_DenseNet achieved an accuracy of 95.38%.Second,this work used three attention mechanisms,and the efficient multiscale attention mechanism obtained the best performance.Third,the convolution layers and bottlenecks were modified without performance degradation,reducing half of the computational load compared with the original models.Incept_EMA_DenseNet,as proposed in this paper,has an accuracy of 96.76%,being 2.93%,3.44%,and 4.16%better than Resnet50,DenseNet_121 and GoogLeNet,respectively,proved to be reliable and beneficial,and can effectively and conveniently assist apple growers with leaf disease identification in the field.展开更多
As network and information systems become widely adopted across industries,cybersecurity concerns have grown more prominent.Among these concerns,insider threats are considered particularly covert and destructive.Insid...As network and information systems become widely adopted across industries,cybersecurity concerns have grown more prominent.Among these concerns,insider threats are considered particularly covert and destructive.Insider threats refer to malicious insiders exploiting privileged access to networks,systems,and data to intentionally compromise organizational security.Detecting these threats is challenging due to the complexity and variability of user behavior data,combined with the subtle and covert nature of insider actions.Traditional detection methods often fail to capture both long-term dependencies and short-term fluctuations in time-series data,which are crucial for identifying anomalous behaviors.To address these issues,this paper introduces the Test-Time Training(TTT)model for the first time in the field of insider threat detection,and proposes a detection method based on the TTT-ECA-ResNet model.First,the dataset is preprocessed.TTT is applied to extract long-term dependencies in features,effectively capturing dynamic sequence changes.The Residual Network,incorporating the Efficient Channel Attention mechanism,is used to extract local feature patterns,capturing relationships between different positions in time-series data.Finally,a Linear layer is employed for more precise detection of insider threats.The proposed approaches were evaluated using the CMU CERT Insider Threat Dataset,achieving an AUC of 98.75%and an F1-score of 96.81%.The experimental results demonstrate the effectiveness of the proposed methods,outperforming other state-of-the-art approaches.展开更多
In order to estimate the cut-size Xc and the mechanically balanced particles in the axial flow cyclonewith the slit-separation method, the tangential velocity distributions were calculated by the finitedifference meth...In order to estimate the cut-size Xc and the mechanically balanced particles in the axial flow cyclonewith the slit-separation method, the tangential velocity distributions were calculated by the finitedifference method. In comparison of the calculated results of the total collection efficiency with theexperimental results, the calculated results showed a little higher than the experimental results due tothe re-entrainment of the collected particles by turbulence. The effect of the slit for promoting thecollection efficiency was not recognized.展开更多
With the rapid development of information technology,information system security and insider threat detection have become important topics for organizational management.In the current network environment,user behavior...With the rapid development of information technology,information system security and insider threat detection have become important topics for organizational management.In the current network environment,user behavioral bio-data presents the characteristics of nonlinearity and temporal sequence.Most of the existing research on authentication based on user behavioral biometrics adopts the method of manual feature extraction.They do not adequately capture the nonlinear and time-sequential dependencies of behavioral bio-data,and also do not adequately reflect the personalized usage characteristics of users,leading to bottlenecks in the performance of the authentication algorithm.In order to solve the above problems,this paper proposes a Temporal Convolutional Network method based on an Efficient Channel Attention mechanism(ECA-TCN)to extract user mouse dynamics features and constructs an one-class Support Vector Machine(OCSVM)for each user for authentication.Experimental results show that compared with four existing deep learning algorithms,the method retains more adequate key information and improves the classification performance of the neural network.In the final authentication,the Area Under the Curve(AUC)can reach 96%.展开更多
In recent years, auction theory has been extensively studied and many state-of-the-art solutions have been proposed aiming at allocating scarce resources. However, most of these studies assume that the auctioneer is a...In recent years, auction theory has been extensively studied and many state-of-the-art solutions have been proposed aiming at allocating scarce resources. However, most of these studies assume that the auctioneer is always trustworthy in the sealed-bid auctions, which is not always true in a more realistic scenario. Besides the privacy-preserving issue, the performance guarantee of social efficiency maximization is also crucial for auction mechanism design. In this paper, we study the auction mechanisms that consider the above two aspects. We discuss two multi-unit auction models： the identical multiple-items auction and the distinct multiple-items auction.Since the problem of determining a multi-unit auction mechanism that can maximize its social efficiency is NPhard, we design a series of nearly optimal multi-unit auction mechanisms for the proposed models. We prove that the proposed auction mechanisms are strategyproof. Moreover, we also prove that the privacy of bid value from each bidder can be preserved in the auction mechanisms. To the best of our knowledge, this is the first work on the strategyproof multi-unit auction mechanisms that simultaneously consider privacy preservation and social efficiency maximization. The extensive simulations show that the proposed mechanisms have low computation and communication overheads.展开更多
文摘In the printing industry,vacuum pumps play a critical role in sheet feeding and gripping processes.In order to improve the efficiency of vacuum pumps,By analyzing the internal flow field of the vane type vacuum pump,the CFD method was used to simulate the internal flow field of the air pump,and it was found that a main vortex was formed near the rotor of the trailing blade.Based on this observation,a new rotor shape design was proposed in this study,which design places arc-shaped depressed on the circumference of the rotor where the main vortex forms.The existence of the depression facilitated forward motion of the main airflow and thus effectively restricting reverse flow.Simulation results demonstrated that the proposed design is able to decrease pressure-induced torque load on the pump,and the reduction increases for an increasing operating speed.For all three operating speeds tested,the reduction in pressure-induced torque ranges from 5%to up to 10%comparing to the original pump.
基金supported by the National Key Research and Development Program of China(No.2019YFB2005202).
文摘This study presents a novel roller piston pump,in which a cam guide-roller type rolling support is adopted to replace the sliding pair support of the swash plate-slipper pair to achieve the oil suction and discharge of the piston cavity.In addition,the shaft distribution is used to replace the original valve plate distribution and the driving shaft is used as the distribution shaft to remove the valve plate structure,which greatly simplifies the design of the axial piston pump.Such a configuration largely reduces the number of sliding friction pairs of the pump,and avoids the influence of the sliding friction pair on it under high-speed and variable-speed conditions.Firstly,mathematical models of the mechanical and volumetric efficiencies of the roller pump are deduced respectively through force analysis and the compressibility equation.Based on the numerical simulation of MATLAB and AMESim,the effects of load pressure and rotational speed on mechanical and volumetric efficiencies are studied respectively,and it is verified that the roller pump has no structural flow pulsation.The prototype pump is then designed and built,along with a special test rig.The outlet pressure,outlet flow,and torque of the pump under different load pressures and rotational speeds are measured,and the mechanical and volumetric efficiencies of the prototype pump under various load pressures and rotational speeds are obtained.The experimental results are in good agreement with the simulated analysis.When the load pressure is 8 MPa and the speed is 5000 r/min,the mechanical and the volumetric efficiencies are 85.5% and 96.8%,respectively.When the speed is increased to 10000 r/min,the mechanical and the volumetric efficiencies are 66.7% and 95.6%,respectively.The experimental results show that the proposed roller piston pump has excellent efficiency under wide-speed and high-speed conditions and can be a potential solution as a fuel pump in aerospace fuel systems.
基金Sponsored by the National High Technology Research and Development Program (863) of China (Grant No.2006AA06Z303)the National Natural Sci-ence Foundation of China(Grant No.40671004)the Program for Young Academic Backbone of Harbin Normal University(Grant No.KGB200821)
文摘In order to improve the source water quality of drinking water and mitigate the load of drinking water treatment plant, a pilot test was conducted with integrated horizontal flow constructed wetlands to pretreat the water supply in the reservoirs of Yellow River. Resuhs show that under the hydraulic loading rate of 4 m^3/（ m^2 · d）, the average removal rates of chemical oxygen demand （COD）, total nitrogen （TN）, ammonium nitrogen （ NH4 ^＋ - N）, nitrate nitrogen （ NO3 ^- - N）, nitrite - nitrogen （ NO2^ - - N） and total phosphorus （TP） in the horizontal flow constructed wetlands are 49. 68% , 53.01%, 48.48%, 53.61% , 62. 57% and 49. 56%, re- spectively. The study on purifying mechanism of the constructed wetlands indicates that the disposal of contamination by subsurface wetlands is the combined actions of physical chemistry, plants and microorganism.
文摘With increasing demand for nonrenewable resources,energy conservation is critical.Efficiency gains allow more work to be performed while maintaining or even decreasing the energy expended in the process.Reducing the energy consumed by a system results in favorable economic and environmental impact.An apparatus has been developed to measure hydraulic fluid efficiency in a stationary application.The system can be used to develop more efficient fluids,leading to increased work output or decreased energy consumption.
文摘That SOEs are inefficient is still a consensus in most economic literature. However, in recent studies, more and more arguments are made in favor of the efficiency of SOEs, yet existing empirical studies are mostly based on production industry data as samples. On the basis of adopting distribution samples and conducting a cross-sector comparison between the production industry and the distribution sector, this paper offers a multi-perspective empirical assessment on the efficiency of SOEs. Through the analysis of major JTnancial indicators and adopting the Data Envelopment Analysis-Malmquist index for total factor productivity comparison, we find that SOEs generally do not have any disadvantage in efficiency and their superior efficiency is particularly pronounced in the distribution sector as compared with production industry. Moreover, the high share and high efficiency of state capital in the wholesale sector needs particular attention. This paper employs case studies to reveal the positive correlation between the assets-heavy operation of state-owned wholesale firms and their profitability. The implications are as follows： policymakers must deliberate prudently before deciding to withdraw or increase state capital in various sectors; in the wholesale sector where state capital is more efficient, the functions of state capital can be bolstered by increasing its presence in the sector,＂ the notion that state capital must be withdrawn from competitive sectors cannot be adopted likely, nor should the benefits of asset-light operation be exaggerated.
基金supported by the National Natural Science Foundation of China (U21A20331, 81903743, 22279151,22275004)the National Science Fund for Distinguished Young Scholars(21925506)。
文摘Flexible perovskite solar cells(f-PSCs) have experienced rapid advancements due to the light-weight, flexibility, and solution processability of the perovskite materials, which prompted the power conversion efficiency(PCE) to 24.08%. However, f-PSCs still face challenges in terms of mechanical and environmental stability. This is primarily due to their inherent brittleness, the presence of residual tensile strain, and the high density of defects along the boundaries of perovskite grains. To this end, we carefully developed a cross-linkable elastomers 3-[(3-acrylamidopropyl)dimethylammonium] propanoate(ADP) with electrostatic dynamic bond, which could be in-situ cross-linked and coordinate with [Pb I6]4-to regulate the crystallization process of perovskite. The cross-linked elastomers attached to the perovskite grain boundaries could release the remaining tensile strains and mechanical stresses, leading to enhanced stability and flexibility of the f-PSCs. More importantly, the electrostatic interaction between positive and negative groups of cross-linked elastomers and hydrogen bond formation between N–H and C=O accelerate the cross-linking of ADP, endowing the flexible perovskite films with self-healing ability under mild treating conditions(60 °C for 30 min). As a result, the device achieves a remarkable PCE of 23.53%(certified 23.16%). Additionally, the device exhibits impressive mechanical sustainability and durability, retaining over 90% of initial PCE even after undergoing8,000 bending cycles.
文摘Investigation concerning peristaltic motion of couple stress fluid is made. An incompressible couple stress fluid occupies the porous medium. Mathematical anal- ysis is presented through large wavelength and low Reynolds number. Exact analytical expressions of axial velocity, volume flow rate, pressure gradient, and stream function are calculated as a function of couple stress parameter. The essential feature of the analysis is a full description of influence of couple stress parameter and permeability parameter on the pressure, frictional force, mechanical efficiency, and trapping.
基金supported by the Visiting Professor Programming of King Sand University(No.KSU-VPP-117)
文摘The present investigation studies the peristaltic flow of the Jeffrey fluid through a tube of finite length. The fluid is electrically conducting in the presence of an applied magnetic field. Analysis is carried out under the assumption of long wavelength and low Reynolds number approximations. Expressions of the pressure gradient, volume flow rate, average volume flow rate, and local wall shear stress are obtained. The effects of relaxation time, retardation time, Hartman number on pressure, local wall shear stress, and mechanical efficiency of peristaltic pump are studied. The reflux phenomenon is also investigated. The case of propagation of a non-integral number of waves along the tube walls, which are inherent characteristics of finite length vessels, is also examined.
文摘This study explores the potentials of employing an Organic Rankine Cycle (ORC) system with variable inlet guide vanes (VIV) turbine geometry designed on a GT-Suite platform for effective exhaust heat recovery (EHR) application onboard passenger vehicles. The ORC model simulation was based on vehicle speed mode using R245fa as working fluid to assess the thermal performance of the ORC system when utilizing modified turbine geometry. Interestingly, the model achieved a very improved performance in contrast to the model without a modified turbine configuration. The results revealed the average 2.32 kW ORC net output, 4.93% thermal efficiency, 6.1% mechanical efficiency, and 5.0% improved brake specific fuel consumption (BSFC) for the developed model. As determined by the performance indicators, these promising results from the model study show the prospect of EHR technology application in the transportation sector for reduction in exhaust emissions and fuel savings.
文摘This paper studies the Stokes flow of micro-polar fluids by peristaltic pumping through the cylindrical tube under the effect of the slip boundary condition. The motion of the wall is governed by the sinusoidal wave equation. The analytical and numerical solutions for the axial velocity, the micro-polar vector, the stream function, the pressure gradient, the friction force, and the mechanical efficiency are obtained by using the lu- brication theory under the low Reynolds number and long wavelength approximations. The impacts of the emerging parameters, such as the coupling number, the micro-polar parameter, the slip parameter on pumping characteristics, the friction force, the velocity profile, the mechanical efficiency, and the trapping phenomenon are depicted graphically. The numerical results infer that large pressure is required for peristaltic pumping when the coupling number is large, while opposite behaviors are found for the micro-polar parameter and the slip parameter. The size of the trapped bolus reduces with the increase in the coupling number and the micro-polar parameter, whereas it blows up with the increase in the slip parameter.
文摘This paper introduces a new technology of using ceramic coating on piston rings of an internal combustion engine, and the comparison of mechanical efficiency and performances of an actual engine before and after the application of ceramic coating on the piston rings. The experimental results show that the mechanical efficiency and power output are enhanced by 4% and 2.6%, respectively, with fuel consumption reduced by (2.9%.) Further studies on coating processing and coating materials as well as the reliability and durability will be of great significance in the application and popularization of the new technology.
基金Financial support for this work,provided by the National Natural Science Foundation of China(No.50974060)the State Safety Production Science and Technology Development Plan (No.06-396)
文摘At a fully mechanized working face of a coal mine as prototype,we investigated,by simulation,the flow field and dust distribution during the process of its isolation by a curtain of air,using the CFD software, Fluent.The results show that the air curtain installed on the shearer can effectively prevent the dust （especially the respirable dust）from diffusing into the work area of the operator,reducing the dust concentration on the side of the operator and greatly improving his working environment.The field application of the air curtain shows that the dust-isolation effect of an air curtain is quite noticeable.The isolation efficiency for respiratory dust is over 70%and,as well,it has good dust-isolation effect for nonrespiratory dust.The air curtain is a useful way to resolve the problem of dust-isolation at a fully mechanized working face.It has a practical background elsewhere with more extensive applications.
文摘At present, the huge problem that China’s Non-profit Organizations are facing is the low efficiency of public fundraising. However, the newly appeared Online Fundraising Platform indicates some possibilities in overcoming the obstacle for public fundraising. Among which Tencent Online Fundraising Platform becomes the typical and the point cut of exploring Online Fundraising Platform Improving Efficiency Mechanism of public donation. Online Fundraising Platform is similar to the online United Way, relying on the advantages of the Internet and the united fundraising to build a ecosystem of public donation which has professional fundraising system, good charity atmosphere, excellent policy environment and crossover cooperation resources. And in which, many factors get improved in pubic donation influence factors system. For one thing, Charity atmosphere and policy environment can be shaped better. For another, the charities can transmit fundraising information in inexpensive and high-efficiency way, and must ensure the transparency of project and donation. Finally, it will be more convenient for donors to get charitable information, make donations and supervise the nonprofit organizations.
基金fully supported by the National Natural Science Foundation of China(52072412)。
文摘With the development of smart agriculture,accurately identifying crop diseases through visual recognition techniques instead of by eye has been a significant challenge.This study focused on apple leaf disease,which is closely related to the final yield of apples.A multiscale fusion dense network combined with an efficient multiscale attention(EMA)mechanism called Incept_EMA_DenseNet was developed to better identify eight complex apple leaf disease images.Incept_EMA_DenseNet consists of three crucial parts:the inception module,which substituted the convolution layer with multiscale fusion methods in the shallow feature extraction layer;the EMA mechanism,which is used for obtaining appropriate weights of different dense blocks;and the improved DenseNet based on DenseNet_121.Specifically,to find appropriate multiscale fusion methods,the residual module and inception module were compared to determine the performance of each technique,and Incept_EMA_DenseNet achieved an accuracy of 95.38%.Second,this work used three attention mechanisms,and the efficient multiscale attention mechanism obtained the best performance.Third,the convolution layers and bottlenecks were modified without performance degradation,reducing half of the computational load compared with the original models.Incept_EMA_DenseNet,as proposed in this paper,has an accuracy of 96.76%,being 2.93%,3.44%,and 4.16%better than Resnet50,DenseNet_121 and GoogLeNet,respectively,proved to be reliable and beneficial,and can effectively and conveniently assist apple growers with leaf disease identification in the field.
基金supported by the National Natural Science Foundation of China(62472118)the Central Guidance on Local Science and Technology Development Fund of GuangxiProvince(ZY23055008)+1 种基金the Guangxi Science and Technology Program(AB24010315)the Innovation Project of Guangxi Graduate Education,China(YCSW2024325).
文摘As network and information systems become widely adopted across industries,cybersecurity concerns have grown more prominent.Among these concerns,insider threats are considered particularly covert and destructive.Insider threats refer to malicious insiders exploiting privileged access to networks,systems,and data to intentionally compromise organizational security.Detecting these threats is challenging due to the complexity and variability of user behavior data,combined with the subtle and covert nature of insider actions.Traditional detection methods often fail to capture both long-term dependencies and short-term fluctuations in time-series data,which are crucial for identifying anomalous behaviors.To address these issues,this paper introduces the Test-Time Training(TTT)model for the first time in the field of insider threat detection,and proposes a detection method based on the TTT-ECA-ResNet model.First,the dataset is preprocessed.TTT is applied to extract long-term dependencies in features,effectively capturing dynamic sequence changes.The Residual Network,incorporating the Efficient Channel Attention mechanism,is used to extract local feature patterns,capturing relationships between different positions in time-series data.Finally,a Linear layer is employed for more precise detection of insider threats.The proposed approaches were evaluated using the CMU CERT Insider Threat Dataset,achieving an AUC of 98.75%and an F1-score of 96.81%.The experimental results demonstrate the effectiveness of the proposed methods,outperforming other state-of-the-art approaches.
文摘In order to estimate the cut-size Xc and the mechanically balanced particles in the axial flow cyclonewith the slit-separation method, the tangential velocity distributions were calculated by the finitedifference method. In comparison of the calculated results of the total collection efficiency with theexperimental results, the calculated results showed a little higher than the experimental results due tothe re-entrainment of the collected particles by turbulence. The effect of the slit for promoting thecollection efficiency was not recognized.
基金supported by the National Natural Science Foundation of China(61962015)the Guangxi Key Laboratory of Cryptography and Information Security Research Project,China(GCIS202127)+2 种基金the Central Guidance on Local Science and Technology Development Fund of Guangxi Province,China(ZY23055008)the Scientific Research and Technological Development Planning Project of Guilin,China(20220124-12)the Innovation Project of Guangxi Graduate Education,China(2023YCXS043).
文摘With the rapid development of information technology,information system security and insider threat detection have become important topics for organizational management.In the current network environment,user behavioral bio-data presents the characteristics of nonlinearity and temporal sequence.Most of the existing research on authentication based on user behavioral biometrics adopts the method of manual feature extraction.They do not adequately capture the nonlinear and time-sequential dependencies of behavioral bio-data,and also do not adequately reflect the personalized usage characteristics of users,leading to bottlenecks in the performance of the authentication algorithm.In order to solve the above problems,this paper proposes a Temporal Convolutional Network method based on an Efficient Channel Attention mechanism(ECA-TCN)to extract user mouse dynamics features and constructs an one-class Support Vector Machine(OCSVM)for each user for authentication.Experimental results show that compared with four existing deep learning algorithms,the method retains more adequate key information and improves the classification performance of the neural network.In the final authentication,the Area Under the Curve(AUC)can reach 96%.
基金supported by the National Natural Science Foundation of China (Nos. 61572342 and 61672369)the Natural Science Foundation of Jiangsu Province (Nos. BK20151240 and BK20161258)China Postdoctoral Science Foundation (Nos. 2015M580470 and 2016M591920)
文摘In recent years, auction theory has been extensively studied and many state-of-the-art solutions have been proposed aiming at allocating scarce resources. However, most of these studies assume that the auctioneer is always trustworthy in the sealed-bid auctions, which is not always true in a more realistic scenario. Besides the privacy-preserving issue, the performance guarantee of social efficiency maximization is also crucial for auction mechanism design. In this paper, we study the auction mechanisms that consider the above two aspects. We discuss two multi-unit auction models： the identical multiple-items auction and the distinct multiple-items auction.Since the problem of determining a multi-unit auction mechanism that can maximize its social efficiency is NPhard, we design a series of nearly optimal multi-unit auction mechanisms for the proposed models. We prove that the proposed auction mechanisms are strategyproof. Moreover, we also prove that the privacy of bid value from each bidder can be preserved in the auction mechanisms. To the best of our knowledge, this is the first work on the strategyproof multi-unit auction mechanisms that simultaneously consider privacy preservation and social efficiency maximization. The extensive simulations show that the proposed mechanisms have low computation and communication overheads.
