Intelligent production is an important development direction in intelligent manufacturing,with intelligent factories playing a crucial role in promoting intelligent production.Flexible job shops,as the main form of in...Intelligent production is an important development direction in intelligent manufacturing,with intelligent factories playing a crucial role in promoting intelligent production.Flexible job shops,as the main form of intelligent factories,constantly face dynamic disturbances during the production process,including machine failures and urgent orders.This paper discusses the basic models and research methods of job shop scheduling,emphasizing the important role of dynamic job shop scheduling and its response schemes in future research.A multi-objective flexible job shop dynamic scheduling mathematical model is established,highlighting its complex and multi-constraint characteristics under different interferences.A classification discussion is conducted on the dynamic response methods and optimization objectives under machine failures,emergency orders,fuzzy completion times,and mixed dynamic events.The development process of traditional scheduling rules and intelligent methods in dynamic scheduling are also analyzed.Finally,based on the current development status of job shop scheduling and the requirements of intelligent manufacturing,the future development trends of dynamic scheduling in flexible job shops are proposed.展开更多
Difficulties in obtaining component characteristics in the sub-idle state of rotor constrain the simulation capabilities of ground and windmill start-up processes for turbofan engines.This paper proposes a backbone fe...Difficulties in obtaining component characteristics in the sub-idle state of rotor constrain the simulation capabilities of ground and windmill start-up processes for turbofan engines.This paper proposes a backbone feature method based on conventional characteristics parameters to derive the full-state characteristics of fan.The application of the fan’s full-state characteristics in component-level model of turbofan engine enables zero-speed iterative simulation for ground start-up process and windmill simulation for windmill start-up process,thereby improving the simulation capability of sub-idle state during turbofan engine start-up.展开更多
Considering the self-excited and forced vibrations in high-speed milling processes, a novel method for dynamic optimization of system stability is used to determine the cutting parameters and structural parameters by ...Considering the self-excited and forced vibrations in high-speed milling processes, a novel method for dynamic optimization of system stability is used to determine the cutting parameters and structural parameters by increasing the chatter free material removal rate （CF-MRR） and surface finish. The method is hased on the theory of the chatter stability and the semi-bandwidth of the resonant region. The objective function of the method is material removal rate（MRR）,the constraints are chatter stability and surface finish, and the optimizing variables are cutting and structural parameters. The optimization procedure is stated. The method is applied to a milling system and CF-MRR is increased 18.86%. It is shown that the influences of the chatter stability and the resonance are simultaneously considered in the dynamic optimization of the milling system for increasing CF-MRR and the surface finish.展开更多
To improve the rotor off-axis response prediction, aerodynamic models must include the wake distortion effects of the maneuvering rotor. And the crux of the matter is to obtain a precise wake curvature parameter KR. A...To improve the rotor off-axis response prediction, aerodynamic models must include the wake distortion effects of the maneuvering rotor. And the crux of the matter is to obtain a precise wake curvature parameter KR. A Peters-He finite-state wake model is improved to incorporate the operating-state-dependent KR to embody maneuver-induced effects. The curvature parameter KR varies with rotor forward speed, thrust and maneuvering angular rate according to a smoking experiment. Moreover, aerodynamic force/moment experiment indicates that after a quasi-step angular input, both on-axis and off-axis rotor responses show that an overshoot and its amplitude increases with the pitching rate. The comparison between theoretical and experimental results shows that the operating-state-accurate curvature parameter must be adopted to obtain accurate aerodynamic forces/moments, especially for the off-axis response. Additionally, combined with a dynamic wake distortion model, the obtained correlation agrees well with experimental data.展开更多
WT5 'BZThis paper presents an unsteady and nonlinear wake model based on th e widely used Peters He finite state dynamic wake model with improvements. The swirl component in the tip trace plane (TTP) can be pr...WT5 'BZThis paper presents an unsteady and nonlinear wake model based on th e widely used Peters He finite state dynamic wake model with improvements. The swirl component in the tip trace plane (TTP) can be predicted, nonlinear items are added into the linear theory, and the old small angle assumption use d in matrix prediction is removed. All of these enha ncements are aimed at the low speed flight phase and formulations for the induce d velocity field just in the TTP frame are derived. The corresponding FORTRAN pr ogram is tested and optimized for the real time applications on PCs.展开更多
The relation between the normal displacement on the surface of a dynamical elliptical crack and the normal stress over the crack surface was studied. The three dimensional elastodynamic equations and Fourier Laplace...The relation between the normal displacement on the surface of a dynamical elliptical crack and the normal stress over the crack surface was studied. The three dimensional elastodynamic equations and Fourier Laplace transforms are used. Based on the influence function and the inversion of integral transforms, one can find that if the distribution of normal displacement on the surface of a dynamic elliptical crack is a polynomial of degree n in x 1 and x 2 , then the normal pressure acting over the ellipse is also a polynomial P n(x 1,x 2) of the same degree in x 1 and x 2 .展开更多
The m ajor advantages of EBS-based key rrkanagerrent scheme are its enhanced network survivability, high dynamic performance, and better support for network expansion. But it suffers from the collusion problem, which ...The m ajor advantages of EBS-based key rrkanagerrent scheme are its enhanced network survivability, high dynamic performance, and better support for network expansion. But it suffers from the collusion problem, which means it is prone to the cooperative attack of evicted members. A novel EBS-based collusion resistant group management scheme utilizing the construction of Ciphertext-Policy Attribute-Based Encryption （CP-ABE） is proposed. The new scheme satisfies the desired security properties, such as forward secrecy, backward secrecy and collusion secrecy. Compared with existing EBS-based key rmnagement scheme, the new scheme can resolve EBS collusion problem completely. Even all evicted members work together, and share their individual piece of information, they could not access to the new group key. In addition, our scheme is more efficient in terms of conmnication and computation overhead when the group size is large. It can be well controlled even in the case of large-scale application scenarios.展开更多
Using the Splitting Hopkinson Pressure Bar （SHPB） experimental system, investigations were made into the dynamic mechanical performances of underground soft rocks. The experiments proved that the measured stress-str...Using the Splitting Hopkinson Pressure Bar （SHPB） experimental system, investigations were made into the dynamic mechanical performances of underground soft rocks. The experiments proved that the measured stress-strain curves display the characteristics of plastic deformation. By making use of a revised overstress constitutive formula for the stress model and by taking into account that the strain rate and strain are a function of I - E（t）/Eo, a revised overstress constitutive formula for the stress model was simplified by applying dimensional analysis and consequently, a simplified overstress formula was obtained for the stress model. Then, by taking into consideration the effects of damage under a dynamic load on the dynamic loading strength of the rock, the continuous damage theory and the statistical strength theory were introduced into the development of the simplified overstress constitutive formula for the stress model. Hence, a damage-based constitutive formula for an overstress model, which can be appropriately applied to the analysis of full dynamic stress-strain curves, was developed. By using the simplified damage-based constitutive formula for an overstress model, the actually measured curves are fitted, indicating that the fitting curves and those actually measured are in good agreement.展开更多
The once-through steam generator (OTSG) in concentric annuli tube is a new type of steam generator which applies double side to transfer heat. The heat flux between the water of centric tube, outside annuli tube and t...The once-through steam generator (OTSG) in concentric annuli tube is a new type of steam generator which applies double side to transfer heat. The heat flux between the water of centric tube, outside annuli tube and that of annulus channel is assumed to be equal, and then the steam generator’s model is built by lumped parameters with moving boundary. In the basis of the built model, static and dynamic characteristics are analyzed. The static characteristics are proved by experiment results in a 19-tube once-through steam generator of Babcock & Wilcox. The characteristics that the lengths of three regions (subcooled region, nucleate boiling region, superheat region) change with power can be explained by theory analysis. The dynamic characteristics accord with the heat and hydraulics and the results of analysis according to the mechanism.展开更多
The electronic in-line pump (EIP) is a complex system consisting of mechanical, hydraulic, and electromagnetic parts. Experimental study showed that the fuel pressure of the plunger and the fuel drainage of the pressu...The electronic in-line pump (EIP) is a complex system consisting of mechanical, hydraulic, and electromagnetic parts. Experimental study showed that the fuel pressure of the plunger and the fuel drainage of the pressure system after fuel injection could result in fuel pressure fluctuation in the low pressure system. Such fluctuation exhibited pulsating cycle fluctuation as the amplitude rose with the increase of the injection pulse width. The time domain analysis found that the pressure time history curve and injection cylinders corresponded with a one-to-one relationship. By frequency domain analysis, the result was that with the increase of the working cylinder number, the high frequency amplitude gradually increased and the basic frequency amplitude gradually decreased. The conclusion was that through wavelet transformation, the low pressure signal simultaneously moved towards low frequency as the high frequency of the wavelet transformation signal with the working cylinder number increased. Lastly, by using the numerical model, the study investigated the simulation research concerning the relationship of the fluctuation dynamic characteristic in the low pressure system and the fuel injection characteristic of the high pressure system, completing the conclusions obtained by the experimental study.展开更多
The local flow characteristics in an external-loop airlift slurry reactor were investigated.The axial profiles of the local gas holdup,the Sauter mean diameter and the rise velocity were obtained.It was found that the...The local flow characteristics in an external-loop airlift slurry reactor were investigated.The axial profiles of the local gas holdup,the Sauter mean diameter and the rise velocity were obtained.It was found that the bubble size and rise velocity were influenced by the solid holdup,and the bubble coalescence was enhanced by the increase of the solid holdup.A new correlation was used to predict the slip velocity between the gas phase and the slurry phase by taking into account the local gas holdup,the bubble size,and the physical properties of the experimental system.By using this correlation,the local drag coefficient can be calculated in the bubble swarm.展开更多
Atrial fibrillation (AF) is the most common arrhythmia with multi-factorial pathogenesis. A number of studies of genetic epidemiology have assessed the association of G112A (G38S) single nucleotide polymorphisms (SNPs...Atrial fibrillation (AF) is the most common arrhythmia with multi-factorial pathogenesis. A number of studies of genetic epidemiology have assessed the association of G112A (G38S) single nucleotide polymorphisms (SNPs) in Mink gene with AF in different populations. However, the results are inconsistent and inconclusive. We performed a Meta-analysis of the association between G112A polymorphisms of MinK gene and AF to estimate the magnitude of the gene effect. Six case-control studies with a combined 854 cases and 1079 controls were summarized. Subgroups in different races were separately analyzed. Heterogeneity and publication bias were also explored. When all groups were pooled, the individuals with G allele had an over 40% higher risk of AF compared with individuals with the A allele. The GG genotype (versus AA genotype) was found to be significant association with increased AF risk. The significant associations were also found in both dominant and recessive genetic model. For subgroup analysis, the results were consistent with above, except that the pooled OR for Chinese population was not significant in a recessive genetic model. In conclusion, G112A polymorphisms in Mink gene may have an important effect on the pathogenesis of AF. This warrants further investigation in large multi-center studies with precise design.展开更多
Objective:To investigate the effects of -2242,-1892 and -1837 single nucleotide polymorphisms(SNPs) on toll-like receptor 4(TLR4) promoter activity.Methods:Polymerase chain reaction(PCR) and site direct mutation techn...Objective:To investigate the effects of -2242,-1892 and -1837 single nucleotide polymorphisms(SNPs) on toll-like receptor 4(TLR4) promoter activity.Methods:Polymerase chain reaction(PCR) and site direct mutation technology were used to construct TLR4 basic promoter and -2242C,-1892A and -1837G mutate promoter plasmids.Dual-Luciferase Reporter assay system was used to detect the activity of constructed promoter following human embryonic kidney(HEK) 293 cells were transiently cotransfected with the constructed plasmids and the control plasmid pRL-CMV.Results:In HEK293 cells,the activity of -2242C mutate promoter was higher than -2242T promoter,and there was no significant difference when both -1892A and -1837G mutate promoter compared with -1892G and -1837A promoter,respectively.Conclusion:It is implied that -2242T→C base variation can enhance the activity of TLR4 promoter,while -1892 and -1837 SNPs have no effect on TLR4 promoter activity.展开更多
A soybean oil derived biodiesel was prepared and blended with a conventional No. 0 petrodiesel. The pour points （PP） and the cold filter plugging points （CFPP） of biodiesel blends were evaluated on a low-temperatu...A soybean oil derived biodiesel was prepared and blended with a conventional No. 0 petrodiesel. The pour points （PP） and the cold filter plugging points （CFPP） of biodiesel blends were evaluated on a low-temperature flow tester. Dynamic viscosities of the blends at different temperatures and different shear rates were measured on a rotary rheometer. The crystal morphologies of biodiesel blends at low temperatures were analyzed using a polarizing microscope. The results indicated that blended fuels demonstrated slight decrease in PPs and CFPPs as compared with those of neat soybean oil derived biodiesel and pure petrodiesel. Below the temperatures of PPs or CFPPs, the dynamic viscosity of biodiesel blends dramatically increased with a decreasing temperature, but decreased with an increasing shear rate, so that biodiesel blends exhibited non-Newtonian behavior. At temperatures higher than PPs or CFPPs, a linear relationship appeared between the dynamic viscosity and shear rate and biodiesel blends became Newtonian fluids. At low temperatures, wax crystals of biodiesel blends grew and agglomerated rapidly. Loss of fluidity for biodiesel blends at low temperatures could therefore be attributed on one hand to the sharp increase of viscosity and on the other hand to the rapid growth and agglomeration of wax crystals.展开更多
Adopting an elastic-viscoplastic, the asymptotic problem of mode I propagat ing crack-tip field is investigated. Various asymptotic solutions resulting from the analysis of crack growing programs are presented. The an...Adopting an elastic-viscoplastic, the asymptotic problem of mode I propagat ing crack-tip field is investigated. Various asymptotic solutions resulting from the analysis of crack growing programs are presented. The analysis results show that the quasi-statically growing crack solutions are the special case of the dynamic propagating solutions. Therefore these two asymptotic solutions can be unified.展开更多
The present paper deals with the problem of nonparametric kernel density estimation of the trend function for stochastic processes driven by fractional Brownian motion of the second kind.The consistency,the rate of co...The present paper deals with the problem of nonparametric kernel density estimation of the trend function for stochastic processes driven by fractional Brownian motion of the second kind.The consistency,the rate of convergence,and the asymptotic normality of the kernel-type estimator are discussed.Besides,we prove that the rate of convergence of the kernel-type estimator depends on the smoothness of the trend of the nonperturbed system.展开更多
Based on the theoretical analyses, the dynamic and mathematical models of the system were developed. The models were implemented in the ambit of the Matlab/Simulink environment, and an integrated simulation model was ...Based on the theoretical analyses, the dynamic and mathematical models of the system were developed. The models were implemented in the ambit of the Matlab/Simulink environment, and an integrated simulation model was developed. The dynamic performance of the power shift clutch during engagement and disengagement was studied by using this assembly model. The sliding speed, torque transmitted through the clutch, and the rate at which energy is dissipated during the process were determined. Using this model, the calculation during simulation can be simplified. This lays a foundation for the dynamic performance research on the power train with the power shift clutch, and provides a powerful tool for developing an automatic, electronically controlled transmission.展开更多
The subsection linear torsional model of hydrodynamic torque converter was established and further simplified. According to the identification theory, the frequency characteristic was achieved with the Matlab/ Ident ...The subsection linear torsional model of hydrodynamic torque converter was established and further simplified. According to the identification theory, the frequency characteristic was achieved with the Matlab/ Ident toolbox. Then parametric model was established by adopting the subsection linearization method, and the damp value was estimated. The curve and function of damp changing with speed ratio was also established by fitting. In order to validate the identification results, the experimental output was compared with the output of the model in which torque was chosen as input signal and speed as output signal in Matlab/Ident toolbox. It was shown that model output is in good agreement with experimental output.展开更多
Tilting pad gas journal bearing is one of the most widely used types of aerodynamic bearings due to its inherent excellent stability in high speed applications.A practical method for analyzing and calculating the per-...Tilting pad gas journal bearing is one of the most widely used types of aerodynamic bearings due to its inherent excellent stability in high speed applications.A practical method for analyzing and calculating the per- formances of such bearings is presented as well as its rotordynamics based on the computer aided technique.The method of calculation and the philosophy of programming with a microcomputer for the computer aided analysis are highlighted.展开更多
基金supported by the National Key Research and Development Program Project(No.2021YFB3301300).
文摘Intelligent production is an important development direction in intelligent manufacturing,with intelligent factories playing a crucial role in promoting intelligent production.Flexible job shops,as the main form of intelligent factories,constantly face dynamic disturbances during the production process,including machine failures and urgent orders.This paper discusses the basic models and research methods of job shop scheduling,emphasizing the important role of dynamic job shop scheduling and its response schemes in future research.A multi-objective flexible job shop dynamic scheduling mathematical model is established,highlighting its complex and multi-constraint characteristics under different interferences.A classification discussion is conducted on the dynamic response methods and optimization objectives under machine failures,emergency orders,fuzzy completion times,and mixed dynamic events.The development process of traditional scheduling rules and intelligent methods in dynamic scheduling are also analyzed.Finally,based on the current development status of job shop scheduling and the requirements of intelligent manufacturing,the future development trends of dynamic scheduling in flexible job shops are proposed.
文摘Difficulties in obtaining component characteristics in the sub-idle state of rotor constrain the simulation capabilities of ground and windmill start-up processes for turbofan engines.This paper proposes a backbone feature method based on conventional characteristics parameters to derive the full-state characteristics of fan.The application of the fan’s full-state characteristics in component-level model of turbofan engine enables zero-speed iterative simulation for ground start-up process and windmill simulation for windmill start-up process,thereby improving the simulation capability of sub-idle state during turbofan engine start-up.
基金Supported by the National Key Basic Research Program of China("973"Project)(2009CB724401)the China Postdoctoral Science Foundation(20070420208)the Postdoctoral Innovation Foundation of Shandong Province(200702023)~~
文摘Considering the self-excited and forced vibrations in high-speed milling processes, a novel method for dynamic optimization of system stability is used to determine the cutting parameters and structural parameters by increasing the chatter free material removal rate （CF-MRR） and surface finish. The method is hased on the theory of the chatter stability and the semi-bandwidth of the resonant region. The objective function of the method is material removal rate（MRR）,the constraints are chatter stability and surface finish, and the optimizing variables are cutting and structural parameters. The optimization procedure is stated. The method is applied to a milling system and CF-MRR is increased 18.86%. It is shown that the influences of the chatter stability and the resonance are simultaneously considered in the dynamic optimization of the milling system for increasing CF-MRR and the surface finish.
文摘To improve the rotor off-axis response prediction, aerodynamic models must include the wake distortion effects of the maneuvering rotor. And the crux of the matter is to obtain a precise wake curvature parameter KR. A Peters-He finite-state wake model is improved to incorporate the operating-state-dependent KR to embody maneuver-induced effects. The curvature parameter KR varies with rotor forward speed, thrust and maneuvering angular rate according to a smoking experiment. Moreover, aerodynamic force/moment experiment indicates that after a quasi-step angular input, both on-axis and off-axis rotor responses show that an overshoot and its amplitude increases with the pitching rate. The comparison between theoretical and experimental results shows that the operating-state-accurate curvature parameter must be adopted to obtain accurate aerodynamic forces/moments, especially for the off-axis response. Additionally, combined with a dynamic wake distortion model, the obtained correlation agrees well with experimental data.
文摘WT5 'BZThis paper presents an unsteady and nonlinear wake model based on th e widely used Peters He finite state dynamic wake model with improvements. The swirl component in the tip trace plane (TTP) can be predicted, nonlinear items are added into the linear theory, and the old small angle assumption use d in matrix prediction is removed. All of these enha ncements are aimed at the low speed flight phase and formulations for the induce d velocity field just in the TTP frame are derived. The corresponding FORTRAN pr ogram is tested and optimized for the real time applications on PCs.
文摘The relation between the normal displacement on the surface of a dynamical elliptical crack and the normal stress over the crack surface was studied. The three dimensional elastodynamic equations and Fourier Laplace transforms are used. Based on the influence function and the inversion of integral transforms, one can find that if the distribution of normal displacement on the surface of a dynamic elliptical crack is a polynomial of degree n in x 1 and x 2 , then the normal pressure acting over the ellipse is also a polynomial P n(x 1,x 2) of the same degree in x 1 and x 2 .
基金Acknowledgements The authors would like to thank the reviewers for their detailed reviews and constructive comments, which have helped improve the quality of this paper. This work was supported by the National Natural Science Foundation of China under Crant No. 60873231, the Natural Science Foundation of Jiangsu Province under Grant No. BK2009426, Major State Basic Research Development Program of China under Cwant No.2011CB302903 and Key University Science Research Project of Jiangsu Province under Crant No. 11KJA520002.
文摘The m ajor advantages of EBS-based key rrkanagerrent scheme are its enhanced network survivability, high dynamic performance, and better support for network expansion. But it suffers from the collusion problem, which means it is prone to the cooperative attack of evicted members. A novel EBS-based collusion resistant group management scheme utilizing the construction of Ciphertext-Policy Attribute-Based Encryption （CP-ABE） is proposed. The new scheme satisfies the desired security properties, such as forward secrecy, backward secrecy and collusion secrecy. Compared with existing EBS-based key rmnagement scheme, the new scheme can resolve EBS collusion problem completely. Even all evicted members work together, and share their individual piece of information, they could not access to the new group key. In addition, our scheme is more efficient in terms of conmnication and computation overhead when the group size is large. It can be well controlled even in the case of large-scale application scenarios.
基金supported by funds from the National Natural Science Foundation of China (Nos. 51374013, 51174005 and 51134012)the Huo Yingdong Funds for Young Teachers to Conduct Researches on Basic Sciences (No. 121050)+1 种基金the academic research activities subsidies for academic and technical leaders and backup candidate in Anhui provincethe funds for the Doctoral Program of Higher Education (No. 20133415110006)
文摘Using the Splitting Hopkinson Pressure Bar （SHPB） experimental system, investigations were made into the dynamic mechanical performances of underground soft rocks. The experiments proved that the measured stress-strain curves display the characteristics of plastic deformation. By making use of a revised overstress constitutive formula for the stress model and by taking into account that the strain rate and strain are a function of I - E（t）/Eo, a revised overstress constitutive formula for the stress model was simplified by applying dimensional analysis and consequently, a simplified overstress formula was obtained for the stress model. Then, by taking into consideration the effects of damage under a dynamic load on the dynamic loading strength of the rock, the continuous damage theory and the statistical strength theory were introduced into the development of the simplified overstress constitutive formula for the stress model. Hence, a damage-based constitutive formula for an overstress model, which can be appropriately applied to the analysis of full dynamic stress-strain curves, was developed. By using the simplified damage-based constitutive formula for an overstress model, the actually measured curves are fitted, indicating that the fitting curves and those actually measured are in good agreement.
文摘The once-through steam generator (OTSG) in concentric annuli tube is a new type of steam generator which applies double side to transfer heat. The heat flux between the water of centric tube, outside annuli tube and that of annulus channel is assumed to be equal, and then the steam generator’s model is built by lumped parameters with moving boundary. In the basis of the built model, static and dynamic characteristics are analyzed. The static characteristics are proved by experiment results in a 19-tube once-through steam generator of Babcock & Wilcox. The characteristics that the lengths of three regions (subcooled region, nucleate boiling region, superheat region) change with power can be explained by theory analysis. The dynamic characteristics accord with the heat and hydraulics and the results of analysis according to the mechanism.
基金the National Natural Science Foundation of China (NSFC) (50909024)Science Fund of State Key Laboratory of Automotive Safety and Energy (KF10102)+1 种基金Basic Research Foundation of Harbin Engineering University(HEUFT09004)The Cooperation Project in Industry,Education and Research of Ministry of Education of Guangdong Province(2009A090100050)
文摘The electronic in-line pump (EIP) is a complex system consisting of mechanical, hydraulic, and electromagnetic parts. Experimental study showed that the fuel pressure of the plunger and the fuel drainage of the pressure system after fuel injection could result in fuel pressure fluctuation in the low pressure system. Such fluctuation exhibited pulsating cycle fluctuation as the amplitude rose with the increase of the injection pulse width. The time domain analysis found that the pressure time history curve and injection cylinders corresponded with a one-to-one relationship. By frequency domain analysis, the result was that with the increase of the working cylinder number, the high frequency amplitude gradually increased and the basic frequency amplitude gradually decreased. The conclusion was that through wavelet transformation, the low pressure signal simultaneously moved towards low frequency as the high frequency of the wavelet transformation signal with the working cylinder number increased. Lastly, by using the numerical model, the study investigated the simulation research concerning the relationship of the fluctuation dynamic characteristic in the low pressure system and the fuel injection characteristic of the high pressure system, completing the conclusions obtained by the experimental study.
文摘The local flow characteristics in an external-loop airlift slurry reactor were investigated.The axial profiles of the local gas holdup,the Sauter mean diameter and the rise velocity were obtained.It was found that the bubble size and rise velocity were influenced by the solid holdup,and the bubble coalescence was enhanced by the increase of the solid holdup.A new correlation was used to predict the slip velocity between the gas phase and the slurry phase by taking into account the local gas holdup,the bubble size,and the physical properties of the experimental system.By using this correlation,the local drag coefficient can be calculated in the bubble swarm.
基金Supported by the National Natural Science Foundation of China (30630056)the Natural Science Foundation of Chongqing (2006BB5064)
文摘Atrial fibrillation (AF) is the most common arrhythmia with multi-factorial pathogenesis. A number of studies of genetic epidemiology have assessed the association of G112A (G38S) single nucleotide polymorphisms (SNPs) in Mink gene with AF in different populations. However, the results are inconsistent and inconclusive. We performed a Meta-analysis of the association between G112A polymorphisms of MinK gene and AF to estimate the magnitude of the gene effect. Six case-control studies with a combined 854 cases and 1079 controls were summarized. Subgroups in different races were separately analyzed. Heterogeneity and publication bias were also explored. When all groups were pooled, the individuals with G allele had an over 40% higher risk of AF compared with individuals with the A allele. The GG genotype (versus AA genotype) was found to be significant association with increased AF risk. The significant associations were also found in both dominant and recessive genetic model. For subgroup analysis, the results were consistent with above, except that the pooled OR for Chinese population was not significant in a recessive genetic model. In conclusion, G112A polymorphisms in Mink gene may have an important effect on the pathogenesis of AF. This warrants further investigation in large multi-center studies with precise design.
基金Supported by the Major State Basic Research Development Program of China (2005CB522602)the National Funds for Outstanding Youth Scientists (30325040)
文摘Objective:To investigate the effects of -2242,-1892 and -1837 single nucleotide polymorphisms(SNPs) on toll-like receptor 4(TLR4) promoter activity.Methods:Polymerase chain reaction(PCR) and site direct mutation technology were used to construct TLR4 basic promoter and -2242C,-1892A and -1837G mutate promoter plasmids.Dual-Luciferase Reporter assay system was used to detect the activity of constructed promoter following human embryonic kidney(HEK) 293 cells were transiently cotransfected with the constructed plasmids and the control plasmid pRL-CMV.Results:In HEK293 cells,the activity of -2242C mutate promoter was higher than -2242T promoter,and there was no significant difference when both -1892A and -1837G mutate promoter compared with -1892G and -1837A promoter,respectively.Conclusion:It is implied that -2242T→C base variation can enhance the activity of TLR4 promoter,while -1892 and -1837 SNPs have no effect on TLR4 promoter activity.
基金the financial support of the Natural Science Foundation of Chongqing(project No.CSTC2006BA6031)the Program for New Century Excellent Talents in Chinese Universities(project No.NCET-04-1002)
文摘A soybean oil derived biodiesel was prepared and blended with a conventional No. 0 petrodiesel. The pour points （PP） and the cold filter plugging points （CFPP） of biodiesel blends were evaluated on a low-temperature flow tester. Dynamic viscosities of the blends at different temperatures and different shear rates were measured on a rotary rheometer. The crystal morphologies of biodiesel blends at low temperatures were analyzed using a polarizing microscope. The results indicated that blended fuels demonstrated slight decrease in PPs and CFPPs as compared with those of neat soybean oil derived biodiesel and pure petrodiesel. Below the temperatures of PPs or CFPPs, the dynamic viscosity of biodiesel blends dramatically increased with a decreasing temperature, but decreased with an increasing shear rate, so that biodiesel blends exhibited non-Newtonian behavior. At temperatures higher than PPs or CFPPs, a linear relationship appeared between the dynamic viscosity and shear rate and biodiesel blends became Newtonian fluids. At low temperatures, wax crystals of biodiesel blends grew and agglomerated rapidly. Loss of fluidity for biodiesel blends at low temperatures could therefore be attributed on one hand to the sharp increase of viscosity and on the other hand to the rapid growth and agglomeration of wax crystals.
文摘Adopting an elastic-viscoplastic, the asymptotic problem of mode I propagat ing crack-tip field is investigated. Various asymptotic solutions resulting from the analysis of crack growing programs are presented. The analysis results show that the quasi-statically growing crack solutions are the special case of the dynamic propagating solutions. Therefore these two asymptotic solutions can be unified.
基金Supported by the National Natural Science Foundation of China(12101004)the Natural Science Research Project of Anhui Educational Committee(2023AH030021)the Research Startup Foundation for Introducing Talent of Anhui Polytechnic University(2020YQQ064)。
文摘The present paper deals with the problem of nonparametric kernel density estimation of the trend function for stochastic processes driven by fractional Brownian motion of the second kind.The consistency,the rate of convergence,and the asymptotic normality of the kernel-type estimator are discussed.Besides,we prove that the rate of convergence of the kernel-type estimator depends on the smoothness of the trend of the nonperturbed system.
文摘Based on the theoretical analyses, the dynamic and mathematical models of the system were developed. The models were implemented in the ambit of the Matlab/Simulink environment, and an integrated simulation model was developed. The dynamic performance of the power shift clutch during engagement and disengagement was studied by using this assembly model. The sliding speed, torque transmitted through the clutch, and the rate at which energy is dissipated during the process were determined. Using this model, the calculation during simulation can be simplified. This lays a foundation for the dynamic performance research on the power train with the power shift clutch, and provides a powerful tool for developing an automatic, electronically controlled transmission.
文摘The subsection linear torsional model of hydrodynamic torque converter was established and further simplified. According to the identification theory, the frequency characteristic was achieved with the Matlab/ Ident toolbox. Then parametric model was established by adopting the subsection linearization method, and the damp value was estimated. The curve and function of damp changing with speed ratio was also established by fitting. In order to validate the identification results, the experimental output was compared with the output of the model in which torque was chosen as input signal and speed as output signal in Matlab/Ident toolbox. It was shown that model output is in good agreement with experimental output.
文摘Tilting pad gas journal bearing is one of the most widely used types of aerodynamic bearings due to its inherent excellent stability in high speed applications.A practical method for analyzing and calculating the per- formances of such bearings is presented as well as its rotordynamics based on the computer aided technique.The method of calculation and the philosophy of programming with a microcomputer for the computer aided analysis are highlighted.
