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
With the increase of underground engineering construction depth,the phenomenon of surrounding rock sudden failure caused by supporting structure failure occurs frequently.The conventional unloading con-fining pressure...With the increase of underground engineering construction depth,the phenomenon of surrounding rock sudden failure caused by supporting structure failure occurs frequently.The conventional unloading con-fining pressure(CUCP)test cannot simulate the plastic yielding and instantaneous unloading process of supporting structure to rock.Thus,a high stress loading-instantaneous unloading confining pressure(HSL-IUCP)test method was proposed and applied by considering bolt’s fracture under stress.The wall thickness of confining pressure plates and the material of bolts were changed to realize different confin-ing pressure loading stiffness(CPLS)and lateral maximum allowable deformation(LMAD).The superio-rity of HSL-ICPU method is verified compared with CUCP.The rock failure mechanism caused by sudden failure of supporting structure is obtained.The results show that when CPLS increases from 1.35 to 2.33 GN/m,rock’s peak strength and elastic modulus increase by 25.18%and 23.70%,respectively.The fracture characteristics change from tensile failure to tensile-shear mixed failure.When LMAD decreases from 0.40 to 0.16 mm,rock’s residual strength,peak strain,and residual strain decrease by 91.80%,16.94%,and 21.92%,respectively,and post-peak drop modulus increases by 140.47%.The test results obtained by this method are closer to rock’s real mechanical response characteristics compared with CUCP.展开更多
Local control parameters such as instantaneous delay and instantaneous amplitude play an essential role in evaluating the performance and maintaining the stability of real-time hybrid simulation(RTHS).However,existing...Local control parameters such as instantaneous delay and instantaneous amplitude play an essential role in evaluating the performance and maintaining the stability of real-time hybrid simulation(RTHS).However,existing methods have limitations in obtaining this local assessment in either the time domain or frequency domain.In this study,the instantaneous frequency is introduced to determine local control parameters for actuator tracking assessment in a real-time hybrid simulation.Instantaneous properties,including amplitude,delay,frequency and phase,are then calculated based on analytic signals translated from actuator tracking signals through the Hilbert transform.Potential issues are discussed and solutions are proposed for calculation of local control parameters.Numerical simulations are first conducted for sinusoidal and chirp signals with time varying amplitude error and delay to demonstrate the potential of the proposed method.Laboratory tests also are conducted for a predefined random signal as well as the RTHS of a single degree of freedom structure with a self-centering viscous damper to experimentally verify the effectiveness of the proposed use of the instantaneous frequency.Results from the ensuing analysis clearly demonstrate that the instantaneous frequency provides great potential for local control assessment,and the proposed method enables local tracking parameters with good accuracy.展开更多
The natural gas heavy carbon isotope and high dryness coefficients genesis in Tabei uplift,Tarim Basin has been highly controversial.To investigate the generation mechanisms of natural gas in the Tabei Uplift.Natural ...The natural gas heavy carbon isotope and high dryness coefficients genesis in Tabei uplift,Tarim Basin has been highly controversial.To investigate the generation mechanisms of natural gas in the Tabei Uplift.Natural gas chemical composition,carbon isotopes were used to analyze the genesis of natural gas,source rock maturity,and basin modeling were conducted to reconstruct the natural gas generation process,and the influences of instantaneous and cumulative effects on natural gas properties was discussed.The results show that the dryness coefficients of natural gas range from 0.62 to 0.99(average:0.92),the methane contents range from 30.42%to 96.4%(average:85.10%),ethane contents from 0.43%to 15.58%(average:3.39%),propane contents from 0.11%to 11.43%(average:1.78%),and the methane carbon isotopes range from-47.30‰to-33.80‰(average:-36.96‰),ethane carbon isotopes range from-39.60‰to-33.20‰(average:-35.57‰),propane carbon isotopes range from-36.90‰to-28.50‰(average:-35.49‰).Compared with the actual regional thermal evolution of the source rock(Ro%range from 1.4%-1.7%),the natural gas exhibits excessively high dryness coefficients and heavy methane carbon isotope characteristics.The natural gas is primary cracking gas and sourced from marine typeⅡkerogen.The dryness coefficient,methane carbon isotopes,and source rock maturity gradually increases from the west to the east.Instantaneous effects and leakage led to the dry gas and relative heavy methane carbon isotopes generated at a low maturity level.The current natural gas in the Ordovician reservoirs was all generated during the Himalayan orogeny.Long period pause of the gas generation between the two hydrocarbon generation phases is the main cause for the instantaneous effects.展开更多
The stability analysis of a finite Stokes layer is of practical importance in flow control. In the present work, the instantaneous stability of a finite Stokes layer with layer interactions is studied via a linear sta...The stability analysis of a finite Stokes layer is of practical importance in flow control. In the present work, the instantaneous stability of a finite Stokes layer with layer interactions is studied via a linear stability analysis of the frozen phases of the base flow. The oscillations of two plates can have different velocity amplitudes, initial phases, and frequencies. The effects of the Stokes-layer interactions on the stability when two plates oscillate synchronously are analyzed. The growth rates of two most unstable modes when δ < 0.12 are almost equal, and δ = δ*/h*, where δ*and h*are the Stokes-layer thickness and the half height of the channel, respectively. However, their vorticities are different. The vorticity of the most unstable mode is symmetric, while the other is asymmetric. The Stokes-layer interactions have a destabilizing effect on the most unstable mode when δ < 0.68, and have a stabilizing effect when δ > 0.68. However, the interactions always have a stabilizing effect on the other unstable mode. It is explained that one of the two unstable modes has much higher dissipation than the other one when the Stokes-layer interactions are strong. We also find that the stability of the Stokes layer is closely related to the inflectional points of the base-flow velocity profile. The effects of inconsistent velocity-amplitude, initial phase, and frequency of the oscillations on the stability are analyzed. The energy of the most unstable eigenvector is mainly distributed near the plate of higher velocity amplitude or higher oscillation frequency. The effects of the initial phase difference are complicated because the base-flow velocity is extremely sensitive to the initial phase.展开更多
The sea surface escort formation faces various threats in reality. For example, suicide boats may carry explosives or other dangerous items, aiming to cause maximum damage by colliding or detonating escort targets. Si...The sea surface escort formation faces various threats in reality. For example, suicide boats may carry explosives or other dangerous items, aiming to cause maximum damage by colliding or detonating escort targets. Since suicide boats have a certain degree of concealment, it is necessary to establish a threat assessment algorithm to timely identify and respond to such fast and concealed threats. This paper establishes a threat assessment model that considers the instantaneous and historical states of the target. The instantaneous state of the target takes into account six evaluation indicators, including target category, target distance, target heading, target speed, collision risk, and ship automatic identification system(AIS) recognition status;in terms of historical state information mining, a target typical intention recognition method based on graph neural network is proposed to achieve end-to-end target typical intention recognition. Furthermore, this paper introduces a multi-attribute decision analysis method to weight the evaluation indicators, improves the relative closeness calculation method between different evaluation schemes and positive and negative ideal schemes, and determines the target threat ranking based on relative closeness. Based on Unity3D, a set of unmanned boat confrontation simulation system is designed and developed, and typical intention recognition data sets and threat assessment scenario simulation data are generated through real-life confrontation. Comparative analysis shows that the threat assessment model in this paper can accurately and timely detect raid target threats and give scientific and reasonable target threat ranking results.展开更多
Planetary gear train is a critical transmission component in large equipment such as helicopters and wind turbines. Conducting damage perception of planetary gear trains is of great significance for the safe operation...Planetary gear train is a critical transmission component in large equipment such as helicopters and wind turbines. Conducting damage perception of planetary gear trains is of great significance for the safe operation of equipment. Existing methods for damage perception of planetary gear trains mainly rely on linear vibration analysis. However, these methods based on linear vibration signal analysis face challenges such as rich vibration sources, complex signal coupling and modulation mechanisms, significant influence of transmission paths, and difficulties in separating damage information. This paper proposes a method for separating instantaneous angular speed (IAS) signals for planetary gear fault diagnosis. Firstly, this method obtains encoder pulse signals through a built-in encoder. Based on this, it calculates the IAS signals using the Hilbert transform, and obtains the time-domain synchronous average signal of the IAS of the planetary gear through time-domain synchronous averaging technology, thus realizing the fault diagnosis of the planetary gear train. Experimental results validate the effectiveness of the calculated IAS signals, demonstrating that the time-domain synchronous averaging technology can highlight impact characteristics, effectively separate and extract fault impacts, greatly reduce the testing cost of experiments, and provide an effective tool for the fault diagnosis of planetary gear trains.展开更多
There are numerous applications, such as Radar, that leverage wideband technology. However, the presence of noise introduces certain limitations and challenges. It is crucial to harness wideband technology for applica...There are numerous applications, such as Radar, that leverage wideband technology. However, the presence of noise introduces certain limitations and challenges. It is crucial to harness wideband technology for applications demanding the rapid and precise transmission of diverse information from one point to another within a short timeframe. The ability to report a signal without tuning within the input bandwidth stands out as one of the advantages of employing a digital wideband receiver. As indicated, a digital wideband receiver plays a pivotal role in achieving high precision and accuracy. The primary distinction between Analog and Digital Instantaneous Frequency Measurement lies in the fact that analog Instantaneous Frequency Measurement (IFM) receivers have traditionally covered extensive input bandwidths, reporting one accurate frequency per short pulse. In the contemporary landscape, digital IFM systems utilize high-sampling-rate Analog-to-Digital Converters (ADC) along with Hilbert transforms to generate two output channels featuring a 90-degree phase shift. This paper explores the improvement of sensitivity in current digital IFM receivers. The optimization efforts target the Hilbert transform and autocorrelations architectures, aiming to refine the system’s ability to report fine frequencies within a noisy wide bandwidth environment, thereby elevating its overall sensitivity.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
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the National Natural Science Foundation of China(Nos.52374218,52174122 and 52374094)Outstanding Youth Fund of Shandong Natural Science Foundation(No.ZR2022YQ49)Taishan Scholar Project in Shandong Province(Nos.tspd20210313 and tsqn202211150).
文摘With the increase of underground engineering construction depth,the phenomenon of surrounding rock sudden failure caused by supporting structure failure occurs frequently.The conventional unloading con-fining pressure(CUCP)test cannot simulate the plastic yielding and instantaneous unloading process of supporting structure to rock.Thus,a high stress loading-instantaneous unloading confining pressure(HSL-IUCP)test method was proposed and applied by considering bolt’s fracture under stress.The wall thickness of confining pressure plates and the material of bolts were changed to realize different confin-ing pressure loading stiffness(CPLS)and lateral maximum allowable deformation(LMAD).The superio-rity of HSL-ICPU method is verified compared with CUCP.The rock failure mechanism caused by sudden failure of supporting structure is obtained.The results show that when CPLS increases from 1.35 to 2.33 GN/m,rock’s peak strength and elastic modulus increase by 25.18%and 23.70%,respectively.The fracture characteristics change from tensile failure to tensile-shear mixed failure.When LMAD decreases from 0.40 to 0.16 mm,rock’s residual strength,peak strain,and residual strain decrease by 91.80%,16.94%,and 21.92%,respectively,and post-peak drop modulus increases by 140.47%.The test results obtained by this method are closer to rock’s real mechanical response characteristics compared with CUCP.
基金National Natural Science Foundation of China under Grant No.52178114Jiangsu Association for Science and Technology Youth Science and Technology Talent Support Project No.2021-79。
文摘Local control parameters such as instantaneous delay and instantaneous amplitude play an essential role in evaluating the performance and maintaining the stability of real-time hybrid simulation(RTHS).However,existing methods have limitations in obtaining this local assessment in either the time domain or frequency domain.In this study,the instantaneous frequency is introduced to determine local control parameters for actuator tracking assessment in a real-time hybrid simulation.Instantaneous properties,including amplitude,delay,frequency and phase,are then calculated based on analytic signals translated from actuator tracking signals through the Hilbert transform.Potential issues are discussed and solutions are proposed for calculation of local control parameters.Numerical simulations are first conducted for sinusoidal and chirp signals with time varying amplitude error and delay to demonstrate the potential of the proposed method.Laboratory tests also are conducted for a predefined random signal as well as the RTHS of a single degree of freedom structure with a self-centering viscous damper to experimentally verify the effectiveness of the proposed use of the instantaneous frequency.Results from the ensuing analysis clearly demonstrate that the instantaneous frequency provides great potential for local control assessment,and the proposed method enables local tracking parameters with good accuracy.
基金financially funded by National Natural Science Foundation of China(Grant Nos.4182100242172160)+1 种基金PetroChina(Grant No.ZD 2019-183-002)National Natural Science Foundation of China(Grant No.42202142)。
文摘The natural gas heavy carbon isotope and high dryness coefficients genesis in Tabei uplift,Tarim Basin has been highly controversial.To investigate the generation mechanisms of natural gas in the Tabei Uplift.Natural gas chemical composition,carbon isotopes were used to analyze the genesis of natural gas,source rock maturity,and basin modeling were conducted to reconstruct the natural gas generation process,and the influences of instantaneous and cumulative effects on natural gas properties was discussed.The results show that the dryness coefficients of natural gas range from 0.62 to 0.99(average:0.92),the methane contents range from 30.42%to 96.4%(average:85.10%),ethane contents from 0.43%to 15.58%(average:3.39%),propane contents from 0.11%to 11.43%(average:1.78%),and the methane carbon isotopes range from-47.30‰to-33.80‰(average:-36.96‰),ethane carbon isotopes range from-39.60‰to-33.20‰(average:-35.57‰),propane carbon isotopes range from-36.90‰to-28.50‰(average:-35.49‰).Compared with the actual regional thermal evolution of the source rock(Ro%range from 1.4%-1.7%),the natural gas exhibits excessively high dryness coefficients and heavy methane carbon isotope characteristics.The natural gas is primary cracking gas and sourced from marine typeⅡkerogen.The dryness coefficient,methane carbon isotopes,and source rock maturity gradually increases from the west to the east.Instantaneous effects and leakage led to the dry gas and relative heavy methane carbon isotopes generated at a low maturity level.The current natural gas in the Ordovician reservoirs was all generated during the Himalayan orogeny.Long period pause of the gas generation between the two hydrocarbon generation phases is the main cause for the instantaneous effects.
基金Project supported by the National Natural Science Foundation of China (No. 11402211)。
文摘The stability analysis of a finite Stokes layer is of practical importance in flow control. In the present work, the instantaneous stability of a finite Stokes layer with layer interactions is studied via a linear stability analysis of the frozen phases of the base flow. The oscillations of two plates can have different velocity amplitudes, initial phases, and frequencies. The effects of the Stokes-layer interactions on the stability when two plates oscillate synchronously are analyzed. The growth rates of two most unstable modes when δ < 0.12 are almost equal, and δ = δ*/h*, where δ*and h*are the Stokes-layer thickness and the half height of the channel, respectively. However, their vorticities are different. The vorticity of the most unstable mode is symmetric, while the other is asymmetric. The Stokes-layer interactions have a destabilizing effect on the most unstable mode when δ < 0.68, and have a stabilizing effect when δ > 0.68. However, the interactions always have a stabilizing effect on the other unstable mode. It is explained that one of the two unstable modes has much higher dissipation than the other one when the Stokes-layer interactions are strong. We also find that the stability of the Stokes layer is closely related to the inflectional points of the base-flow velocity profile. The effects of inconsistent velocity-amplitude, initial phase, and frequency of the oscillations on the stability are analyzed. The energy of the most unstable eigenvector is mainly distributed near the plate of higher velocity amplitude or higher oscillation frequency. The effects of the initial phase difference are complicated because the base-flow velocity is extremely sensitive to the initial phase.
基金funded by by the National Natural Science Foundation of China under Grant 52101377。
文摘The sea surface escort formation faces various threats in reality. For example, suicide boats may carry explosives or other dangerous items, aiming to cause maximum damage by colliding or detonating escort targets. Since suicide boats have a certain degree of concealment, it is necessary to establish a threat assessment algorithm to timely identify and respond to such fast and concealed threats. This paper establishes a threat assessment model that considers the instantaneous and historical states of the target. The instantaneous state of the target takes into account six evaluation indicators, including target category, target distance, target heading, target speed, collision risk, and ship automatic identification system(AIS) recognition status;in terms of historical state information mining, a target typical intention recognition method based on graph neural network is proposed to achieve end-to-end target typical intention recognition. Furthermore, this paper introduces a multi-attribute decision analysis method to weight the evaluation indicators, improves the relative closeness calculation method between different evaluation schemes and positive and negative ideal schemes, and determines the target threat ranking based on relative closeness. Based on Unity3D, a set of unmanned boat confrontation simulation system is designed and developed, and typical intention recognition data sets and threat assessment scenario simulation data are generated through real-life confrontation. Comparative analysis shows that the threat assessment model in this paper can accurately and timely detect raid target threats and give scientific and reasonable target threat ranking results.
文摘Planetary gear train is a critical transmission component in large equipment such as helicopters and wind turbines. Conducting damage perception of planetary gear trains is of great significance for the safe operation of equipment. Existing methods for damage perception of planetary gear trains mainly rely on linear vibration analysis. However, these methods based on linear vibration signal analysis face challenges such as rich vibration sources, complex signal coupling and modulation mechanisms, significant influence of transmission paths, and difficulties in separating damage information. This paper proposes a method for separating instantaneous angular speed (IAS) signals for planetary gear fault diagnosis. Firstly, this method obtains encoder pulse signals through a built-in encoder. Based on this, it calculates the IAS signals using the Hilbert transform, and obtains the time-domain synchronous average signal of the IAS of the planetary gear through time-domain synchronous averaging technology, thus realizing the fault diagnosis of the planetary gear train. Experimental results validate the effectiveness of the calculated IAS signals, demonstrating that the time-domain synchronous averaging technology can highlight impact characteristics, effectively separate and extract fault impacts, greatly reduce the testing cost of experiments, and provide an effective tool for the fault diagnosis of planetary gear trains.
文摘There are numerous applications, such as Radar, that leverage wideband technology. However, the presence of noise introduces certain limitations and challenges. It is crucial to harness wideband technology for applications demanding the rapid and precise transmission of diverse information from one point to another within a short timeframe. The ability to report a signal without tuning within the input bandwidth stands out as one of the advantages of employing a digital wideband receiver. As indicated, a digital wideband receiver plays a pivotal role in achieving high precision and accuracy. The primary distinction between Analog and Digital Instantaneous Frequency Measurement lies in the fact that analog Instantaneous Frequency Measurement (IFM) receivers have traditionally covered extensive input bandwidths, reporting one accurate frequency per short pulse. In the contemporary landscape, digital IFM systems utilize high-sampling-rate Analog-to-Digital Converters (ADC) along with Hilbert transforms to generate two output channels featuring a 90-degree phase shift. This paper explores the improvement of sensitivity in current digital IFM receivers. The optimization efforts target the Hilbert transform and autocorrelations architectures, aiming to refine the system’s ability to report fine frequencies within a noisy wide bandwidth environment, thereby elevating its overall sensitivity.
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.
