The instantaneous morphological transition of triangular Al_(2)O_(3) particles with various sizes in the molten Ca-treated steel was observed using a confocal scanning laser microscope at the steelmaking temperature.T...The instantaneous morphological transition of triangular Al_(2)O_(3) particles with various sizes in the molten Ca-treated steel was observed using a confocal scanning laser microscope at the steelmaking temperature.The composition of inclusions at different times was analyzed using scanning electron microscopy-energy dispersive spectroscopy.The shape evolution of particles was characterized by the shape parameter of overall regularity.It was found that the overall regularity of particles gradually increased with time during the calcium treatment.The geometry of particles tended to be more rounded and regular as the overall regularity increased during the modification process.An empirical formula was proposed to predict the composition of inclusion particles based on their overall regularity during the calcium treatment.When the CaO/Al_(2)O_(3) mass ratio in the particle increased to 0.451,the particle was considered an ideal spherical calcium aluminate inclusion with the overall regularity of 1.Smaller particle sizes promoted the transformation of Al_(2)O_(3) inclusions to spherical calcium aluminates during the calcium treatment.展开更多
In this article,we study the approximate controllability of neutral partial differential equations with Hilfer fractional derivative and not instantaneous impulses effects.By using the Sadovskii's fixed point theo...In this article,we study the approximate controllability of neutral partial differential equations with Hilfer fractional derivative and not instantaneous impulses effects.By using the Sadovskii's fixed point theorem,fractional calculus and resolvent operator functions,we prove the approximate controllability of the considered system.展开更多
The different characteristics of polarization of body and Rayleigh waves make it possible to separate these two types of waves by their characteristics and suppress the latter.The moving time-window analysis often is ...The different characteristics of polarization of body and Rayleigh waves make it possible to separate these two types of waves by their characteristics and suppress the latter.The moving time-window analysis often is used in polarization filtering but it is difficult to determine a suitable time-window length,resulting in some problems,such as complex eigenvalues and non-convergence.For overcoming these disadvantages,in this paper,we introduce the concept of complex-trace analysis and conduct de-noise processing to suppress undesirable surface waves by instantaneous polarization analysis in the case of horizontal and vertical component seismic recordings from the Hauinan coal mine.The performance of the method is illustrated by examples with synthetic and field data and its effectiveness to remove surface waves from multi-component seismic data is demonstrated.展开更多
This article introduces a surface measurement system which is able to take a measurement in an extremely short period of less than 2 milliseconds. It is composed of two cameras together with a specifically designed pr...This article introduces a surface measurement system which is able to take a measurement in an extremely short period of less than 2 milliseconds. It is composed of two cameras together with a specifically designed projector that projects an instantaneous random image pattern onto the objective surface. With the aid of the projected pattern, a match of image with corresponding sub-pixel is steadily established and a cluster of dense 3D points is obtained at the same time. A detailed discussion about the des...展开更多
In order to monitor the working state of piston motor and measure its instantaneous rotation speed accurately, the measuring principle and method of instantaneous rotation speed based on industrial personal computer a...In order to monitor the working state of piston motor and measure its instantaneous rotation speed accurately, the measuring principle and method of instantaneous rotation speed based on industrial personal computer and data acquisition card are introduced, and the major error source, influence mechanism and processing method of data quantization error are dis- cussed. By means of hybrid programming approach of LabVIEW and MATLAB, the instantaneous rotation speed measurement system for the piston motor in variable speed hydraulic system is designed. The simulation and experimental results show that the designed instantaneous speed measurement system is feasible. Furthermore, the sampling frequency has an important influ- ence on the instantaneous rotation speed measurement of piston motor and higher sampling frequency can lower quantization er- ror and improve measurement accuracy.展开更多
The accurate estimation of the rolling element bearing instantaneous rotational frequency(IRF) is the key capability of the order tracking method based on time-frequency analysis. The rolling element bearing IRF can b...The accurate estimation of the rolling element bearing instantaneous rotational frequency(IRF) is the key capability of the order tracking method based on time-frequency analysis. The rolling element bearing IRF can be accurately estimated according to the instantaneous fault characteristic frequency(IFCF). However, in an environment with a low signal-to-noise ratio(SNR), e.g., an incipient fault or function at a low speed, the signal contains strong background noise that seriously affects the effectiveness of the aforementioned method. An algorithm of signal preprocessing based on empirical mode decomposition(EMD) and wavelet shrinkage was proposed in this work. Compared with EMD denoising by the cross-correlation coefficient and kurtosis(CCK) criterion, the method of EMD soft-thresholding(ST) denoising can ensure the integrity of the signal, improve the SNR, and highlight fault features. The effectiveness of the algorithm for rolling element bearing IRF estimation by EMD ST denoising and the IFCF was validated by both simulated and experimental bearing vibration signals at a low SNR.展开更多
As the key technique of improved Hilbert-Huang transform （HHT）, ensemble empiri- cal mode decomposition （EEMD） has a good performance of eliminating mode mixing phenomenon, which has a strong impact on the observa...As the key technique of improved Hilbert-Huang transform （HHT）, ensemble empiri- cal mode decomposition （EEMD） has a good performance of eliminating mode mixing phenomenon, which has a strong impact on the observation of seismic information. However, the intrinsic mode functions （IMF） obtained from EEMD contain noises, so that it is required to find a more robust frequency estimation method to calculate the instantaneous frequency （IF） of IMF. For this reason, the improved HHT algorithm based on the damped instantaneous frequency （DIF） is proposed to overcome the shortage of EEMD. Compared with other IF estimation methods, the DIF has strong antinoise ability and high estimation accuracy. The test results of synthetic and real seismic data show that the proposed algorithm is feasible and effective for extracting seismic instantaneous at- tributes.展开更多
In order to analyze the condition of s pecial landform and regularity of sp ecial hydrological movement in karst area,the method of Geomorphologic Instantaneous Unit Hydrograph(GIUH)has been used to divide the river n...In order to analyze the condition of s pecial landform and regularity of sp ecial hydrological movement in karst area,the method of Geomorphologic Instantaneous Unit Hydrograph(GIUH)has been used to divide the river net-works into three grades in the research area and the karst hydrologic processes were simulated with Nash insta ntaneous u-nit hydrograph(NIUH).The combination of the GIUH and NIUH fully considers the moving path of wa ter particles in drainage and the regional composition of runoff at the end of the drainage,resulting in a rational combinatio n of probabili-ty of GIUH and NIUH and geomorphologic parameters which could reflect the complexity of the landform structur e of karst drainage.The results showed t hat the combined method of GIUH and NI UH has clear physical concept and acc ept-able precision,which can be widely a pplied on hydrological studies of karst area.展开更多
Energy management（EM） is a core technique of hybrid electric bus（HEB） in order to advance fuel economy performance optimization and is unique for the corresponding configuration. There are existing algorithms of c...Energy management（EM） is a core technique of hybrid electric bus（HEB） in order to advance fuel economy performance optimization and is unique for the corresponding configuration. There are existing algorithms of control strategy seldom take battery power management into account with international combustion engine power management. In this paper, a type of power-balancing instantaneous optimization（PBIO） energy management control strategy is proposed for a novel series-parallel hybrid electric bus. According to the characteristic of the novel series-parallel architecture, the switching boundary condition between series and parallel mode as well as the control rules of the power-balancing strategy are developed. The equivalent fuel model of battery is implemented and combined with the fuel of engine to constitute the objective function which is to minimize the fuel consumption at each sampled time and to coordinate the power distribution in real-time between the engine and battery. To validate the proposed strategy effective and reasonable, a forward model is built based on Matlab/Simulink for the simulation and the dSPACE autobox is applied to act as a controller for hardware in-the-loop integrated with bench test. Both the results of simulation and hardware-in-the-loop demonstrate that the proposed strategy not only enable to sustain the battery SOC within its operational range and keep the engine operation point locating the peak efficiency region, but also the fuel economy of series-parallel hybrid electric bus（SPHEB） dramatically advanced up to 30.73% via comparing with the prototype bus and a similar improvement for PBIO strategy relative to rule-based strategy, the reduction of fuel consumption is up to 12.38%. The proposed research ensures the algorithm of PBIO is real-time applicability, improves the efficiency of SPHEB system, as well as suite to complicated configuration perfectly.展开更多
Unifying the models for topology design and kinematic analysis has long been a desire for the research of parallel kinematic machines(PKMs). This requires that analytical description, formulation and operation for bot...Unifying the models for topology design and kinematic analysis has long been a desire for the research of parallel kinematic machines(PKMs). This requires that analytical description, formulation and operation for both finite and instantaneous motions are performed by the same mathematical tool. Based upon finite and instantaneous screw theory, a unified and systematic approach for topology design and kinematic analysis of PKMs is proposed in this paper. Using the derivative mapping between finite and instantaneous screws built in the authors’ previous work, the finite and instantaneous motions of PKMs are analytically described by the simple and non?redundant screws in quasi?vector and vector forms. And topological and parametric models of PKMs are algebraically formulated and related. These related topological and parametric models are ready to do type synthesis and kinematic analysis of PKMs under the unified framework of screw theory. In order to show the validity of the proposed approach, a kind of two?translational and three?rotational(2T3R)5?axis PKMs is taken as example. Numerous new structures of the 2T3R PKMs are synthe?sized as the results of topology design, and their Jacobian matrix is obtained easily for parameter optimization and performance evaluation. Some of the synthesized PKMs have outstanding capabilities in terms of large workspaces and flexible orientations, and have great potential for industrial applications of machining and manufacture. Among them, METROM PKM is a typical example which has attracted a lot of attention from global companies and already been developed as commercial products. The approach is a general and unified approach that can be used in the innovative design of different kinds of PKMs.展开更多
[ Objective] The study aimed to explore the denaturalization law of β-Iactoglobulin （β-LG） under instantaneous high-pressure（IHP） con- dition. [Methed] Using fresh milk as testing material, effects of pressure, ...[ Objective] The study aimed to explore the denaturalization law of β-Iactoglobulin （β-LG） under instantaneous high-pressure（IHP） con- dition. [Methed] Using fresh milk as testing material, effects of pressure, feed temperature and treatment time on the denaturalization of β-LG were studied via SDS-PAGE electrophoresis and sulfhydryl content detection after IHP treatment. [ Result] IHP could induce the agglomeration and depo- lymerization Of β-LG. The agglomeration of the β-LG increased with the elevated pressure from 20 to 60 MPa, but 80 MPa pressure led to depolyme- rization. The effect of feed temperature （25 -45 ℃） was similar to that of the pressure, while the influence of treatment time （2 -8 min） was not obvious. [ Conclusion] The study provided a theoretical basis for the elimination of allergens in β-LG and the application of IHP technology in milk treatment.展开更多
This paper outlines the significance of enhancing the instantaneous protection reliability of low voltage circuit breakers and describes their main failure modes. The instantaneous failure mechanism of low voltage cir...This paper outlines the significance of enhancing the instantaneous protection reliability of low voltage circuit breakers and describes their main failure modes. The instantaneous failure mechanism of low voltage circuit breakers was analyzed so that measures to improve instantaneous protection reliability can be determined. Furthermore, the theory of the instantaneous characteristics calibration device for low voltage circuit breakers and the method of eliminating the non-periodic component of test current are given in detail. Finally, the test results are presented.展开更多
A novel polarimetric calibration method for new target property measurement radar system is presented. Its applica- tion in the real radar system is also discussed. The analysis indicates that instantaneous polarizati...A novel polarimetric calibration method for new target property measurement radar system is presented. Its applica- tion in the real radar system is also discussed. The analysis indicates that instantaneous polarization radar （[PR） has inherent cross-polarization measurement error. The proposed method can effectively eliminate this error, and thus enhance the polarization scattering matrix （PSM） measurement precision. The phase error caused by digital receiver＇s direct IF sampling and mixing of two orthogonal polarization channels can be removed. Consequently, the inherent error of target polarization scattering measurement of the instantaneous polarization radar system is well revised. It has good reference value for further ploarimetric calibration and high practical application prospect.展开更多
Based on the recently quick-developing time-frequency analysis (TFA)technique and virtual instrument (VI) technique, a virtual instrument in characteristic analysis ofrotating machinery is researched and developed suc...Based on the recently quick-developing time-frequency analysis (TFA)technique and virtual instrument (VI) technique, a virtual instrument in characteristic analysis ofrotating machinery is researched and developed successfully. By utilizing instantaneous frequencyestimation (IFE) theoretics of TFA technique, and based on IFE of peak searching on thetime-frequency spectrum, order analysis (OA) functions is put forward and implemented, such as orderspectrum, order spectrum matrix, order tracking, order tracking filtering, and order componentextraction, etc. Unlike the home and abroad existing popular characteristic analyzers, which needkey phasing devices such as shaft encoder, phase-locked loop (PLL), phase-locked multiple frequency,tachometer, etc, to implement constant angle sampling directly or indirectly, whereas thisinstrument only uses the vibration signal of rotating machinery to carry out OA. This instrumentmakes up the shortage of these traditional instruments in analyzing the non-stationary signal ofrun-up and run-down process of rotating machinery. Therefore, it is a great breakthrough for theexisting order analyzers.展开更多
The purpose of this paper is to investigate the instantaneous properties of wave slanuning on the plate structure of an open structure. The advanced instantaneous measuring technique-Particle Image Velocimetry （PIV）...The purpose of this paper is to investigate the instantaneous properties of wave slanuning on the plate structure of an open structure. The advanced instantaneous measuring technique-Particle Image Velocimetry （PIV） is applied to acquire the instantaneous velocity field of wave slamming. From the cross-correlation analysis results of the images captured by the CCD camera, the flow fields of wave impacting on the structure are displayed visually, and the instantaneous whole- field fluid velocity vectors are obtained. The relation between the instantaneous peak impacting pressures and the instantaneous velocities of water particles is studied by probability analysis.展开更多
In the field of civil engineering, magnetorheological fluid （MRF） damper-based semi-active control systems have received considerable attention for use in protecting structures from natural hazards such as strong ea...In the field of civil engineering, magnetorheological fluid （MRF） damper-based semi-active control systems have received considerable attention for use in protecting structures from natural hazards such as strong earthquakes and high winds. In this paper, the MRF damper-based semi-active control system is applied to a long-span spatially extended structure and its feasibility is discussed. Meanwhile, a _trust-region method based instantaneous optimal semi-active control algorithm （TIOC） is proposed to improve the performance of the semi-active control system in a multiple damper situation. The proposed TIOC describes the control process as a bounded constraint optimization problem, in which an optimal semi- active control force vector is solved by the trust-region method in every control step to minimize the structural responses. A numerical example of a railway station roof structure installed with MRF-04K dampers is presented. First, a modified Bouc- Wen model is utilized to describe the behavior of the selected MRF-04K damper. Then, two semi-active control systems, including the well-known clipped-optimal controller and the proposed TIOC controller, are considered. Based on the characteristics of the long-span spatially extended structure, the performance of the control system is evaluated under uniform earthquake excitation and travelling-wave excitation with different apparent velocities. The simulation results indicate that the MR fluid damper-based semi-active control systems have the potential to mitigate the responses of full-scale long-span spatially extended structures under earthquake hazards. The superiority of the proposed TIOC controller is demonstrated by comparing its control effectiveness with the clipped-optimal controller for several different cases.展开更多
The modal vibration of the rotor is the main cause of excessive vibration of the aeroengine overall structure.To attenuate the vibration of the rotor under different modal shapes from the perspective of energy control...The modal vibration of the rotor is the main cause of excessive vibration of the aeroengine overall structure.To attenuate the vibration of the rotor under different modal shapes from the perspective of energy control,the intrinsic physical relationships between rotor modal shapes and instantaneous vibrational energy flow transmission characteristics is derived from the general equation of motion base on the structural intensity method.A dual-rotor-support-casing coupling model subjected to the rotor unbalanced forces is established by the finite element method in this paper.The transmission,conversion and balance relationships of the vibrational energy flow for the rotors in the first-order bending modal shape,the conical whirling modal shape and the translational modal shape are analyzed,respectively.The results show that the vibrational energy flow transmitted to the structure can be converted into the strain energy,the kinetic energy and the energy dissipated by the damping of the structure.The vibrational energy flow transmission characteristics of rotors with different modal shapes are quite different.Especially for the first-order bending modal shape,the vibrational energy flow and the strain energy are transmitted and converted to each other in the middle part of the rotor shaft,resulting in large deformation at this part.To attenuate this harmful vibration,the influences of grooving on the shaft on the first-order bending vibration are studied from the perspective of transmission control of vibrational energy flow.This study can provide theoretical references and guidance for the vibration attenuation of the rotors in different modal shapes from a more essential perspective.展开更多
Considerable studies have been carried out on fault diagnosis of gears, with most of them concentrated on conventional vibration analysis. However, besides the complexity of gear dynamics, the diagnosis results in ter...Considerable studies have been carried out on fault diagnosis of gears, with most of them concentrated on conventional vibration analysis. However, besides the complexity of gear dynamics, the diagnosis results in terms of vibration signal are easily misjudged owing to the interference of sensor position or other components. In this paper, an alternative gearbox fault detection method based on the instantaneous rotational speed is proposed because of its advantages over vibration analysis. Depending on the timer/counter-based method for the pulse signal of the optical encoder, the varying rotational speed can be obtained e ectively. Owing to the coupling and meshing of gears in transmission, the excitations are the same for the instantaneous rotational speed of the input and output shafts. Thus, the di erential signal of instantaneous rotational speeds can be adopted to eliminate the e ect of the interference excitations and extract the associated feature of the localized fault e ectively. With the experiments on multistage gearbox test system, the di erential signal of instantaneous speeds is compared with other signals. It is proved that localized faults in the gearbox generate small angular speed fluctuations, which are measurable with an optical encoder. Using the di erential signal of instantaneous speeds, the fault characteristics are extracted in the spectrum where the deterministic frequency component and its harmonics corresponding to crack fault characteristics are displayed clearly.展开更多
We present an approach to solve Bethe-Salpeter (BS) equations exactly withoutany approximation if the kernel of the BS equations exactly is instantaneous, and take positroniumas an example to illustrate the general fe...We present an approach to solve Bethe-Salpeter (BS) equations exactly withoutany approximation if the kernel of the BS equations exactly is instantaneous, and take positroniumas an example to illustrate the general features of the exact solutions. The key step for theapproach is from the BS equations to derive a set of coupled and well-determined integrationequations in linear eigenvalue for the components of the BS wave functions equivalently, which maybe solvable numerically under a controlled accuracy, even though there is no analytic solution. Forpositronium, the exact solutions precisely present corrections to those of the correspondingSchrodinger equation in order υ~1 (υ is the relative velocity) for eigenfunctions, in order υ~2for eigenvalues, and the mixing between S and D components in J~(PC) = 1~(--) states etc.,quantitatively. Moreover, we also point out that there is a questionable step in some existentderivations for the instantaneous BS equations if one is pursuing the exact solutions. Finally, weemphasize that one should take the O(υ) corrections emerging in the exact solutions into accountaccordingly if one is interested in the relativistic corrections for relevant problems to the boundstates.展开更多
基金financially supported by the National Key R&D Program,China(No.2023YFB3709900)the National Nature Science Foundation of China(No.U22A20171)+1 种基金China Baowu Low Carbon Metallurgy Innovation Foudation(No.BWLCF202315)Hebei Steel Group’s Key Science and Technology Program,China(No.HG2022103)。
文摘The instantaneous morphological transition of triangular Al_(2)O_(3) particles with various sizes in the molten Ca-treated steel was observed using a confocal scanning laser microscope at the steelmaking temperature.The composition of inclusions at different times was analyzed using scanning electron microscopy-energy dispersive spectroscopy.The shape evolution of particles was characterized by the shape parameter of overall regularity.It was found that the overall regularity of particles gradually increased with time during the calcium treatment.The geometry of particles tended to be more rounded and regular as the overall regularity increased during the modification process.An empirical formula was proposed to predict the composition of inclusion particles based on their overall regularity during the calcium treatment.When the CaO/Al_(2)O_(3) mass ratio in the particle increased to 0.451,the particle was considered an ideal spherical calcium aluminate inclusion with the overall regularity of 1.Smaller particle sizes promoted the transformation of Al_(2)O_(3) inclusions to spherical calcium aluminates during the calcium treatment.
基金Supported by Shandong University of Finance and Economics 2023 International Collaborative Projectsthe National Natural Science Foundation of China(Grant No.62073190)。
文摘In this article,we study the approximate controllability of neutral partial differential equations with Hilfer fractional derivative and not instantaneous impulses effects.By using the Sadovskii's fixed point theorem,fractional calculus and resolvent operator functions,we prove the approximate controllability of the considered system.
基金supported by the National Natural Science Foundation of China (grant No.40574055)the National 973 Program (Grant No.2006CB202207)the Special Fund (Grant No.2008ZX05035-001-003,2008ZX05035-003-006HZ,2008ZX05008-006-004)
文摘The different characteristics of polarization of body and Rayleigh waves make it possible to separate these two types of waves by their characteristics and suppress the latter.The moving time-window analysis often is used in polarization filtering but it is difficult to determine a suitable time-window length,resulting in some problems,such as complex eigenvalues and non-convergence.For overcoming these disadvantages,in this paper,we introduce the concept of complex-trace analysis and conduct de-noise processing to suppress undesirable surface waves by instantaneous polarization analysis in the case of horizontal and vertical component seismic recordings from the Hauinan coal mine.The performance of the method is illustrated by examples with synthetic and field data and its effectiveness to remove surface waves from multi-component seismic data is demonstrated.
基金National Natural Science Foundation of China (50475041)
文摘This article introduces a surface measurement system which is able to take a measurement in an extremely short period of less than 2 milliseconds. It is composed of two cameras together with a specifically designed projector that projects an instantaneous random image pattern onto the objective surface. With the aid of the projected pattern, a match of image with corresponding sub-pixel is steadily established and a cluster of dense 3D points is obtained at the same time. A detailed discussion about the des...
基金National Natural Science Foundation of China(No.51275375,No.51509006)Shaanxi Provincial Natural Science Basic Research Plan(No.2014JQ7246)+1 种基金The Science and Technology of Hubei Province(No.B2015115)Doctoral Research Foundation of Hubei University of Automotive Technology(No.BK201403)
文摘In order to monitor the working state of piston motor and measure its instantaneous rotation speed accurately, the measuring principle and method of instantaneous rotation speed based on industrial personal computer and data acquisition card are introduced, and the major error source, influence mechanism and processing method of data quantization error are dis- cussed. By means of hybrid programming approach of LabVIEW and MATLAB, the instantaneous rotation speed measurement system for the piston motor in variable speed hydraulic system is designed. The simulation and experimental results show that the designed instantaneous speed measurement system is feasible. Furthermore, the sampling frequency has an important influ- ence on the instantaneous rotation speed measurement of piston motor and higher sampling frequency can lower quantization er- ror and improve measurement accuracy.
基金Project(51275030)supported by the National Natural Science Foundation of ChinaProject(2016JBM051)supported by the Fundamental Research Funds for the Central Universities,China
文摘The accurate estimation of the rolling element bearing instantaneous rotational frequency(IRF) is the key capability of the order tracking method based on time-frequency analysis. The rolling element bearing IRF can be accurately estimated according to the instantaneous fault characteristic frequency(IFCF). However, in an environment with a low signal-to-noise ratio(SNR), e.g., an incipient fault or function at a low speed, the signal contains strong background noise that seriously affects the effectiveness of the aforementioned method. An algorithm of signal preprocessing based on empirical mode decomposition(EMD) and wavelet shrinkage was proposed in this work. Compared with EMD denoising by the cross-correlation coefficient and kurtosis(CCK) criterion, the method of EMD soft-thresholding(ST) denoising can ensure the integrity of the signal, improve the SNR, and highlight fault features. The effectiveness of the algorithm for rolling element bearing IRF estimation by EMD ST denoising and the IFCF was validated by both simulated and experimental bearing vibration signals at a low SNR.
基金supported by the National Natural Science Foundation of China(Nos.41274127,40874066,and 41301460)
文摘As the key technique of improved Hilbert-Huang transform （HHT）, ensemble empiri- cal mode decomposition （EEMD） has a good performance of eliminating mode mixing phenomenon, which has a strong impact on the observation of seismic information. However, the intrinsic mode functions （IMF） obtained from EEMD contain noises, so that it is required to find a more robust frequency estimation method to calculate the instantaneous frequency （IF） of IMF. For this reason, the improved HHT algorithm based on the damped instantaneous frequency （DIF） is proposed to overcome the shortage of EEMD. Compared with other IF estimation methods, the DIF has strong antinoise ability and high estimation accuracy. The test results of synthetic and real seismic data show that the proposed algorithm is feasible and effective for extracting seismic instantaneous at- tributes.
基金Supported by the National Natural Science Foundation of China(No.49070010).
文摘In order to analyze the condition of s pecial landform and regularity of sp ecial hydrological movement in karst area,the method of Geomorphologic Instantaneous Unit Hydrograph(GIUH)has been used to divide the river net-works into three grades in the research area and the karst hydrologic processes were simulated with Nash insta ntaneous u-nit hydrograph(NIUH).The combination of the GIUH and NIUH fully considers the moving path of wa ter particles in drainage and the regional composition of runoff at the end of the drainage,resulting in a rational combinatio n of probabili-ty of GIUH and NIUH and geomorphologic parameters which could reflect the complexity of the landform structur e of karst drainage.The results showed t hat the combined method of GIUH and NI UH has clear physical concept and acc ept-able precision,which can be widely a pplied on hydrological studies of karst area.
基金supported by National Natural Science Foundation of China(Grant No. 51075410)
文摘Energy management（EM） is a core technique of hybrid electric bus（HEB） in order to advance fuel economy performance optimization and is unique for the corresponding configuration. There are existing algorithms of control strategy seldom take battery power management into account with international combustion engine power management. In this paper, a type of power-balancing instantaneous optimization（PBIO） energy management control strategy is proposed for a novel series-parallel hybrid electric bus. According to the characteristic of the novel series-parallel architecture, the switching boundary condition between series and parallel mode as well as the control rules of the power-balancing strategy are developed. The equivalent fuel model of battery is implemented and combined with the fuel of engine to constitute the objective function which is to minimize the fuel consumption at each sampled time and to coordinate the power distribution in real-time between the engine and battery. To validate the proposed strategy effective and reasonable, a forward model is built based on Matlab/Simulink for the simulation and the dSPACE autobox is applied to act as a controller for hardware in-the-loop integrated with bench test. Both the results of simulation and hardware-in-the-loop demonstrate that the proposed strategy not only enable to sustain the battery SOC within its operational range and keep the engine operation point locating the peak efficiency region, but also the fuel economy of series-parallel hybrid electric bus（SPHEB） dramatically advanced up to 30.73% via comparing with the prototype bus and a similar improvement for PBIO strategy relative to rule-based strategy, the reduction of fuel consumption is up to 12.38%. The proposed research ensures the algorithm of PBIO is real-time applicability, improves the efficiency of SPHEB system, as well as suite to complicated configuration perfectly.
基金Supported by National Natural Science Foundation of China(Grant No.51675366)Tianjin Research Program of Application Foundation and Advanced Technology(Grant Nos.16JCYBJC19300,15JCZDJC38900)
文摘Unifying the models for topology design and kinematic analysis has long been a desire for the research of parallel kinematic machines(PKMs). This requires that analytical description, formulation and operation for both finite and instantaneous motions are performed by the same mathematical tool. Based upon finite and instantaneous screw theory, a unified and systematic approach for topology design and kinematic analysis of PKMs is proposed in this paper. Using the derivative mapping between finite and instantaneous screws built in the authors’ previous work, the finite and instantaneous motions of PKMs are analytically described by the simple and non?redundant screws in quasi?vector and vector forms. And topological and parametric models of PKMs are algebraically formulated and related. These related topological and parametric models are ready to do type synthesis and kinematic analysis of PKMs under the unified framework of screw theory. In order to show the validity of the proposed approach, a kind of two?translational and three?rotational(2T3R)5?axis PKMs is taken as example. Numerous new structures of the 2T3R PKMs are synthe?sized as the results of topology design, and their Jacobian matrix is obtained easily for parameter optimization and performance evaluation. Some of the synthesized PKMs have outstanding capabilities in terms of large workspaces and flexible orientations, and have great potential for industrial applications of machining and manufacture. Among them, METROM PKM is a typical example which has attracted a lot of attention from global companies and already been developed as commercial products. The approach is a general and unified approach that can be used in the innovative design of different kinds of PKMs.
文摘[ Objective] The study aimed to explore the denaturalization law of β-Iactoglobulin （β-LG） under instantaneous high-pressure（IHP） con- dition. [Methed] Using fresh milk as testing material, effects of pressure, feed temperature and treatment time on the denaturalization of β-LG were studied via SDS-PAGE electrophoresis and sulfhydryl content detection after IHP treatment. [ Result] IHP could induce the agglomeration and depo- lymerization Of β-LG. The agglomeration of the β-LG increased with the elevated pressure from 20 to 60 MPa, but 80 MPa pressure led to depolyme- rization. The effect of feed temperature （25 -45 ℃） was similar to that of the pressure, while the influence of treatment time （2 -8 min） was not obvious. [ Conclusion] The study provided a theoretical basis for the elimination of allergens in β-LG and the application of IHP technology in milk treatment.
基金Project (No. 043804411) supported by the Tianjin Natural ScienceFoundation, China
文摘This paper outlines the significance of enhancing the instantaneous protection reliability of low voltage circuit breakers and describes their main failure modes. The instantaneous failure mechanism of low voltage circuit breakers was analyzed so that measures to improve instantaneous protection reliability can be determined. Furthermore, the theory of the instantaneous characteristics calibration device for low voltage circuit breakers and the method of eliminating the non-periodic component of test current are given in detail. Finally, the test results are presented.
基金supported by the National Natural Science Priority Foundation of China(60736006)National Natural Science Foundation of China for Youth(60802078)+1 种基金National Basic Research Program(973 Program)(51314)Hunan Provincial Innovation Foundation for Postgraduate
文摘A novel polarimetric calibration method for new target property measurement radar system is presented. Its applica- tion in the real radar system is also discussed. The analysis indicates that instantaneous polarization radar （[PR） has inherent cross-polarization measurement error. The proposed method can effectively eliminate this error, and thus enhance the polarization scattering matrix （PSM） measurement precision. The phase error caused by digital receiver＇s direct IF sampling and mixing of two orthogonal polarization channels can be removed. Consequently, the inherent error of target polarization scattering measurement of the instantaneous polarization radar system is well revised. It has good reference value for further ploarimetric calibration and high practical application prospect.
文摘Based on the recently quick-developing time-frequency analysis (TFA)technique and virtual instrument (VI) technique, a virtual instrument in characteristic analysis ofrotating machinery is researched and developed successfully. By utilizing instantaneous frequencyestimation (IFE) theoretics of TFA technique, and based on IFE of peak searching on thetime-frequency spectrum, order analysis (OA) functions is put forward and implemented, such as orderspectrum, order spectrum matrix, order tracking, order tracking filtering, and order componentextraction, etc. Unlike the home and abroad existing popular characteristic analyzers, which needkey phasing devices such as shaft encoder, phase-locked loop (PLL), phase-locked multiple frequency,tachometer, etc, to implement constant angle sampling directly or indirectly, whereas thisinstrument only uses the vibration signal of rotating machinery to carry out OA. This instrumentmakes up the shortage of these traditional instruments in analyzing the non-stationary signal ofrun-up and run-down process of rotating machinery. Therefore, it is a great breakthrough for theexisting order analyzers.
基金This reseaschis supported by the National Natural Science Foundation of China (Grant No50409014) by the Science Foundation of Liaoning Province (Grant No20041075)
文摘The purpose of this paper is to investigate the instantaneous properties of wave slanuning on the plate structure of an open structure. The advanced instantaneous measuring technique-Particle Image Velocimetry （PIV） is applied to acquire the instantaneous velocity field of wave slamming. From the cross-correlation analysis results of the images captured by the CCD camera, the flow fields of wave impacting on the structure are displayed visually, and the instantaneous whole- field fluid velocity vectors are obtained. The relation between the instantaneous peak impacting pressures and the instantaneous velocities of water particles is studied by probability analysis.
基金Supported by:National Science Fund for Distinguished Young Scholars of China Under Grant No. 50425824the National Natural Science Foundation of China Under Grant No.50578109,90715034 and 90715032
文摘In the field of civil engineering, magnetorheological fluid （MRF） damper-based semi-active control systems have received considerable attention for use in protecting structures from natural hazards such as strong earthquakes and high winds. In this paper, the MRF damper-based semi-active control system is applied to a long-span spatially extended structure and its feasibility is discussed. Meanwhile, a _trust-region method based instantaneous optimal semi-active control algorithm （TIOC） is proposed to improve the performance of the semi-active control system in a multiple damper situation. The proposed TIOC describes the control process as a bounded constraint optimization problem, in which an optimal semi- active control force vector is solved by the trust-region method in every control step to minimize the structural responses. A numerical example of a railway station roof structure installed with MRF-04K dampers is presented. First, a modified Bouc- Wen model is utilized to describe the behavior of the selected MRF-04K damper. Then, two semi-active control systems, including the well-known clipped-optimal controller and the proposed TIOC controller, are considered. Based on the characteristics of the long-span spatially extended structure, the performance of the control system is evaluated under uniform earthquake excitation and travelling-wave excitation with different apparent velocities. The simulation results indicate that the MR fluid damper-based semi-active control systems have the potential to mitigate the responses of full-scale long-span spatially extended structures under earthquake hazards. The superiority of the proposed TIOC controller is demonstrated by comparing its control effectiveness with the clipped-optimal controller for several different cases.
基金supported by the National Key Technology Research and Development Program of China(No.2016YFB0901402)the Major Program of National Natural Science Foundation of China(No.51790513)。
文摘The modal vibration of the rotor is the main cause of excessive vibration of the aeroengine overall structure.To attenuate the vibration of the rotor under different modal shapes from the perspective of energy control,the intrinsic physical relationships between rotor modal shapes and instantaneous vibrational energy flow transmission characteristics is derived from the general equation of motion base on the structural intensity method.A dual-rotor-support-casing coupling model subjected to the rotor unbalanced forces is established by the finite element method in this paper.The transmission,conversion and balance relationships of the vibrational energy flow for the rotors in the first-order bending modal shape,the conical whirling modal shape and the translational modal shape are analyzed,respectively.The results show that the vibrational energy flow transmitted to the structure can be converted into the strain energy,the kinetic energy and the energy dissipated by the damping of the structure.The vibrational energy flow transmission characteristics of rotors with different modal shapes are quite different.Especially for the first-order bending modal shape,the vibrational energy flow and the strain energy are transmitted and converted to each other in the middle part of the rotor shaft,resulting in large deformation at this part.To attenuate this harmful vibration,the influences of grooving on the shaft on the first-order bending vibration are studied from the perspective of transmission control of vibrational energy flow.This study can provide theoretical references and guidance for the vibration attenuation of the rotors in different modal shapes from a more essential perspective.
基金Supported by National Natural Science Foundation of China(Grant No.51575438)China Postdoctoral Science Foundation(Grant Nos.2017M623159,2018T111046)Shaanxi Provincial Postdoctoral Science Foundation of China(Grant No.2017BSHEDZZ68)
文摘Considerable studies have been carried out on fault diagnosis of gears, with most of them concentrated on conventional vibration analysis. However, besides the complexity of gear dynamics, the diagnosis results in terms of vibration signal are easily misjudged owing to the interference of sensor position or other components. In this paper, an alternative gearbox fault detection method based on the instantaneous rotational speed is proposed because of its advantages over vibration analysis. Depending on the timer/counter-based method for the pulse signal of the optical encoder, the varying rotational speed can be obtained e ectively. Owing to the coupling and meshing of gears in transmission, the excitations are the same for the instantaneous rotational speed of the input and output shafts. Thus, the di erential signal of instantaneous rotational speeds can be adopted to eliminate the e ect of the interference excitations and extract the associated feature of the localized fault e ectively. With the experiments on multistage gearbox test system, the di erential signal of instantaneous speeds is compared with other signals. It is proved that localized faults in the gearbox generate small angular speed fluctuations, which are measurable with an optical encoder. Using the di erential signal of instantaneous speeds, the fault characteristics are extracted in the spectrum where the deterministic frequency component and its harmonics corresponding to crack fault characteristics are displayed clearly.
文摘We present an approach to solve Bethe-Salpeter (BS) equations exactly withoutany approximation if the kernel of the BS equations exactly is instantaneous, and take positroniumas an example to illustrate the general features of the exact solutions. The key step for theapproach is from the BS equations to derive a set of coupled and well-determined integrationequations in linear eigenvalue for the components of the BS wave functions equivalently, which maybe solvable numerically under a controlled accuracy, even though there is no analytic solution. Forpositronium, the exact solutions precisely present corrections to those of the correspondingSchrodinger equation in order υ~1 (υ is the relative velocity) for eigenfunctions, in order υ~2for eigenvalues, and the mixing between S and D components in J~(PC) = 1~(--) states etc.,quantitatively. Moreover, we also point out that there is a questionable step in some existentderivations for the instantaneous BS equations if one is pursuing the exact solutions. Finally, weemphasize that one should take the O(υ) corrections emerging in the exact solutions into accountaccordingly if one is interested in the relativistic corrections for relevant problems to the boundstates.
