The hybrid scenario,which has good confinement and moderate MHD instabilities,is a proposed operation scenario for international thermonuclear experimental reactor(ITER).In this work,the effect of plasma rotation on t...The hybrid scenario,which has good confinement and moderate MHD instabilities,is a proposed operation scenario for international thermonuclear experimental reactor(ITER).In this work,the effect of plasma rotation on the HL-3 hybrid scenario is analyzed with the integrated modeling framework OMFIT.The results show that toroidal rotation has no obvious effect on confinement with a high line averaged density of n_(bar)~(7)×10^(19)m^(-3).In this case,the ion temperature only changes from 4.7 keV to 4.4 keV with the rotation decreasing from 10^(5) rad/s to 10^(3) rad/s,which means that the turbulent heat transport is not dominant.While in the scenarios characterized by lower densities,such as n_(bar)~4×10^(19)m^(-3),turbulent transport becomes dominant in determining heat transport.The ion temperature rises from 3.8 keV to 6.1 keV in the core as the rotation velocity increases from 10^(3) rad/s to 10^(5) rad/s.Despite the ion temperature rising,the rotation velocity does not obviously affect electron temperature or density.Additionally,it is noteworthy that the variation in rotation velocity does not significantly affect the global confinement of plasma in scenarios with low density or with high density.展开更多
The effects of equilibrium toroidal rotation during edge-localized mode(ELM)mitigated by resonant magnetic perturbation(RMP)are studied with the experimental equilibria of the EAST tokamak based on the four-field mode...The effects of equilibrium toroidal rotation during edge-localized mode(ELM)mitigated by resonant magnetic perturbation(RMP)are studied with the experimental equilibria of the EAST tokamak based on the four-field model in the BOUT++code.As the two main parameters to determine the toroidal rotation profiles,the rotation shear and magnitudes were separately scanned to investigate their roles in the impact of RMPs on peeling-ballooning(P-B)modes.On one hand,the results show that strong toroidal rotation shear is favorable for the enhancement of the self-generated E×B shearing rate<ω_(E×B)>with RMPs,leading to significant ELM mitigation with RMP in the stronger toroidal rotation shear region.On the other hand,toroidal rotation magnitudes may affect ELM mitigation by changing the penetration of the RMPs,more precisely the resonant components.RMPs can lead to a reduction in the pedestal energy loss by enhancing the multimode coupling in the turbulence transport phase.The shielding effects on RMPs increase with the toroidal rotation magnitude,leading to the enhancement of the multimode coupling with RMPs to be significantly weakened.Hence,the reduction in pedestal energy loss by RMPs decreased with the rotation magnitude.In brief,the results show that toroidal rotation plays a dual role in ELM mitigation with RMP by changing the shielding effects of plasma by rotation magnitude and affecting<ω_(E×B)>by rotation shear.In the high toroidal rotation region,toroidal rotation shear is usually strong and hence plays a dominant role in the influence of RMP on P-B modes,whereas in the low rotation region,toroidal rotation shear is weak and has negligible impact on P-B modes,and the rotation magnitude plays a dominant role in the influence of RMPs on the P-B modes by changing the field penetration.Therefore,the dual role of toroidal rotation leads to stronger ELM mitigation with RMP,which may be achieved both in the low toroidal rotation region and the relatively high rotation region that has strong rotational shear.展开更多
A new selected mapping(SLM)scheme based on constellation rotation is proposed to reduce the peak-to-average power ratio(PAPR)of orthogonal frequency division multiplexing(OFDM)signals.Its core idea is to generate abun...A new selected mapping(SLM)scheme based on constellation rotation is proposed to reduce the peak-to-average power ratio(PAPR)of orthogonal frequency division multiplexing(OFDM)signals.Its core idea is to generate abundant candidate signals by rotating different sub-signals of the original frequency signal with different angles.This new signal generation method can simplify the calculation process of candidate time signals into the linear addition of some intermediate signals,which are generated by the inverse fast Fourier transform(IFFT)operation of the original frequency signal.This feature can effectively reduce the computational complexity of candidate signal generation process.And compared to the traditional SLM scheme,the number of complex multiplication and complex addition of new scheme can separately be decreased by about 99.99% and 91.7% with some specific parameters.Moreover,with the help of the constellation detection mechanism at the receiver,there is no need to carry any side information at the transmitter.The simulation results show that,with the same channel transmission performance,the PAPR reduction performance of new scheme can approach or even exceed the upper bound of the traditional SLM scheme,which uses all the vectors in Hadamard matrix as the phase sequences.展开更多
The rapid identification of planting patterns for major crops in a large irrigated district has vital importance for irrigation management,water fee collection,and crop yield estimation.In this study,the OTSU algorith...The rapid identification of planting patterns for major crops in a large irrigated district has vital importance for irrigation management,water fee collection,and crop yield estimation.In this study,the OTSU algorithm and Mean-Shift algorithm were employed to automatically determine threshold values for mapping two main rotated crop patterns at the pixel scale.A time series analysis was conducted to extract the spatial distribution of rice-wheat and wheat-maize rotations in the Chuanhang irrigation district from 2016 to 2020.The results demonstrate that both threshold segmentation algorithms are reliable in extracting the spatial distribution of the crops,with an overall accuracy exceeding 80%.Additionally,both Kappa coefficients surpass 0.7,indicating better performance by OTSU method.Over the period from 2016 to 2020,the area occupied by rice-wheat rotation cropping ranged from 12500 to 14400 hm 2;whereas wheat-maize rotation cropping exhibited smaller and more variable areas ranging from 19730 to 34070 hm 2.These findings highlight how remote sensing-based approaches can provide reliable support for rapidly and accurately identifying the spatial distribution of main crop rotation patterns within a large irrigation district.展开更多
The laser gyro is most su it able for building the strap down inertial navigation system (SINS), and its acc uracy of attitude algorithm can enormously affect that of the laser SINS. This p aper develops three improv...The laser gyro is most su it able for building the strap down inertial navigation system (SINS), and its acc uracy of attitude algorithm can enormously affect that of the laser SINS. This p aper develops three improved algorithmal expressions for strap down attitude ut ilizing the angular increment output by the laser gyro from the last two and cur rent updating periods according to the number of gyro samples, and analyses the algorithm error in the classical coning motion. Compared with the conventional algorithms, simulational results show that this improved algorithm has higher precision. A new way to improve the rotation vector algorithms is provided.展开更多
Aimed at the large deformation problem of industry cooling tower shell, the mathematical model for the random response of rotational shell under the external random excitation is established by statistic perturbation ...Aimed at the large deformation problem of industry cooling tower shell, the mathematical model for the random response of rotational shell under the external random excitation is established by statistic perturbation method. The effect of nonlinear geometric behavior on the response of rotational shell is analyzed.展开更多
Based on the theoretical analysis of nonlinear random response of structure, for the engineering practical problem, that is, the large deformation of industry cooling tower shell structure under the action of strong w...Based on the theoretical analysis of nonlinear random response of structure, for the engineering practical problem, that is, the large deformation of industry cooling tower shell structure under the action of strong wind loads, the statistic perturbation method is also used to analyze some statistic characteristics of the nonlinear random response of rotational shell with geometric nonlinearity and stationary strong wind load considered. Through computation, some average values of nornal displacements and the nonlinear effect factor of the cooling tower shell are given.展开更多
Concrete is considered as an elastic body when subjected to compressive stress butas a brittle body when subjected to tensile stress. That is, after the elastic extremum it cannotcontinue to bear the stress. Based on ...Concrete is considered as an elastic body when subjected to compressive stress butas a brittle body when subjected to tensile stress. That is, after the elastic extremum it cannotcontinue to bear the stress. Based on this.'cracked' physical model, for stochastic extemalwind loads, nonlinear stochastic constitutive equations have been established. To solve equations of nonlinear stochastic vibration, an iterative statistic linearization method (ISLM) hasbeen developedb. Some statistic characteristics were foundd out.展开更多
Quasi-classical trajectory calculations are performed to study the stereodynamics of the H（~2S） ＋ NH（a^1？） →H_2（X^1Σ_g~＋） ＋ N（~2D） reaction based on the first excited state NH_2（1~2A＇） potential energ...Quasi-classical trajectory calculations are performed to study the stereodynamics of the H（~2S） ＋ NH（a^1？） →H_2（X^1Σ_g~＋） ＋ N（~2D） reaction based on the first excited state NH_2（1~2A＇） potential energy surface reported by Li et al.[Li Y Q and Varandas A J C 2010 J. Phys. Chem. A 114 9644] for the first time. We observe the changes of differential cross-sections at different collision energies and different initial reagent rotational excitations. The influence of collision energy on the k-k＇ distribution can be attributed to a purely impulsive effect. Initial reagent rotational excitation transforms the reaction mechanism from insertion to abstraction. The effect of initial reagent rotational excitations on k-k＇ distribution can be explained by the rotational excitation enlarging the rotational rate of reagent NH in the entrance channel to reduce the probability of collision between incidence H atom and H atom of target molecular. We also investigate the changes of vector correlations and find that the rotational angular momentum vector j＇ of the product H_2 is not only aligned, but also oriented along the y axis. The alignment parameter, the disposal of total angular momentum and the reaction mechanism are all analyzed carefully to explain the polarization behavior of the product rotational angular moment.展开更多
With the rapid advancement of technology,not only do we need to acquire a clear in-verse synthetic aperture radar(ISAR)image,but also the real size of the target on the imaging plane,so it’s particularly important fo...With the rapid advancement of technology,not only do we need to acquire a clear in-verse synthetic aperture radar(ISAR)image,but also the real size of the target on the imaging plane,so it’s particularly important for the ISAR to rescale the images.That is,the ISAR image which is in the range-Doppler domain is converted into the range-azimuth domain.Actually,the key point to solving the problem is to estimate the rotation parameters.In this paper,a new scheme to rescale the images is proposed.For the sake of solving the problem of two-dimensional image blur and target high-speed,the instantaneous range instantaneous Doppler(IRID)method is used to obtain ISAR images,and the rotation parameters are estimated by comparing the rotation correlation of the two images.Using this method,the error of the estimated rotation parameters is greatly reduced,so that the target can be rescaled accurately.The simulation results verify the ef-fectiveness of the proposed algorithm.展开更多
This paper computes the rotational energy levels of the HCO B^2A＇-X^2A＇31^1 transition, especially, the higher values of the rotational quantum numbers NKa Kc and Ka, with the rotational constants which are obtained...This paper computes the rotational energy levels of the HCO B^2A＇-X^2A＇31^1 transition, especially, the higher values of the rotational quantum numbers NKa Kc and Ka, with the rotational constants which are obtained via B3LYP method with 6-311G basis set, and the results show that the calculated frequencies using the computed vibration-rotation energy levels are in reasonable agreement with the data from the experiment. Meanwhile, the line intensities of HCO are first reported, the results are of significance for the studying HCO.展开更多
We present an experimental demonstration of the rotation measurement using a compact cold atom gyroscope. Atom interference fringes are observed in the stationary frame and the rotating frame, respectively. The phase ...We present an experimental demonstration of the rotation measurement using a compact cold atom gyroscope. Atom interference fringes are observed in the stationary frame and the rotating frame, respectively. The phase shift and contrast of the interference fringe are experimentally investigated. The results show that the contrast of the interference fringe is well held when the platform is rotated, and the phase shift of the interference fringe is linearly proportional to the rotation rate of the platform. The long-term stability, which is evaluated by the overlapped Allan deviation, is 8.5 × 10^-6 rad/s over the integrating time of 1000s.展开更多
A method of improving the navigation accuracy of strapdown inertial navigation system (SINS) is studied. The particular technique discussed involves the continuous rotation of gyros and accelerometers cluster about th...A method of improving the navigation accuracy of strapdown inertial navigation system (SINS) is studied. The particular technique discussed involves the continuous rotation of gyros and accelerometers cluster about the vertical axis of the vehicle. Then the errors of these sensors will have periodic variation corresponding to components along the body frame. Under this condition, the modulated sensor errors produce reduced system errors. Theoretical analysis based on a new coordinate system defined as sensing frame and test results are presented, and they indicate the method attenuates the navigation errors brought by the gyros' random constant drift and the accelerometer's bias and their white noise compared to the conventional method.展开更多
In order to realize the ballistic control of the railgun and the flight stability of the projectile, a new type of railgun is designed, which can control the muzzle velocity and rotation rate. The method of the muzzle...In order to realize the ballistic control of the railgun and the flight stability of the projectile, a new type of railgun is designed, which can control the muzzle velocity and rotation rate. The method of the muzzle velocity and overload control is to adjust the voltage or other parameters of pulse power supply. It would be easy to change velocity accurately in large wide. Another widespread concern problem is launching the spinning stability projectile by railgun. This paper designed a new structure of additional rails to generate an unsymmetrical magnetic field to produce rotational torque in armature. The structure is simple and can control the rotation rate by linear changing the barrel parameters. The calculation formulas of interior ballistic are derived by Biot-Safar law. The important parameter is the deflection angle of the additional rails relative to the symmetry plane of main rail. The larger the angle, the greater the rotation torque generated in the armature. To maintain the flight stability of the projectile, the barrel structural parameters should be proportional to the projectile structural parameters. When changing the muzzle velocity, the rotation rate will also be the equal proportion change. So that the gyro stability is the same. The experiment proves that the railgun designed in this paper can launch the projectile to rotate. And the rotational projectile may not cause the transition or much arcs. This method expands the application of the railgun.展开更多
The rotational motions of the optically trapped microscopic particles by the vortex femtosecond laser beam are investigated in this paper.Black particles can be trapped and rotated by a vortex femtosecond laser beam v...The rotational motions of the optically trapped microscopic particles by the vortex femtosecond laser beam are investigated in this paper.Black particles can be trapped and rotated by a vortex femtosecond laser beam very effectively because the vortex beam carries orbital angular momentum due to the helical wave-front structure in assoication with the central phase singularity.Trapped black particles rotate in the vortex beam due to the absorption of the angular momentum transferred from the vortex beam.The rotating directions of the trapped particles can be modulated by reversing the topological charge of the optical vortex in the vortex femtosecond beam.And the rotating speeds of the trapped microscopic particles greatly depend on the topological charges of the vortex tweezer and the used pulse energies.展开更多
In-situ pressure-preserved coring(IPP-Coring)is considered to be the most reliable and efficient method for the identification of the scale of oil and gas resources.During IPP-Coring,because the rotation behavior of t...In-situ pressure-preserved coring(IPP-Coring)is considered to be the most reliable and efficient method for the identification of the scale of oil and gas resources.During IPP-Coring,because the rotation behavior of the pressure controller valve cover in different medium environments is unclear,interference between the valve cover and inner pipe may occur and negatively affect the IPP-Coring success rate.To address this issue,we conducted a series of indoor experiments employing a high-speed camera to gain greater insights into the valve cover rotation behavior in different medium environments,e.g.,air,water,and simulated drilling fluids.The results indicated that the variation in the valve cover rotation angle in the air and fluid environments can be described by a one-phase exponential decay function with a constant time parameter and by biphasic dose response function,respectively.The rotation behavior in the fluid environments exhibited distinct elastic and gravitational acceleration zones.In the fluid environments,the density clearly impacted the valve cover closing time and rotation behavior,whereas the effect of viscosity was very slight.This can be attributed to the negligible influence of the fluid viscosity on the drag coefficient found in this study;meanwhile,the density can increase the buoyancy and the time period during which the valve cover experienced a high drag coefficient.Considering these results,control schemes for the valve cover rotation behavior during IPP-Coring were proposed for different layers and geological conditions in which the different drilling fluids should be used,e.g.,the use of a high-density valve cover in high-pore pressure layers.展开更多
Roof and rib instability is an important issue in underground mining. To optimize ground support design,enhance ground stability, and reduce the possibility of roof or rib failure with minimal use of artificial ground...Roof and rib instability is an important issue in underground mining. To optimize ground support design,enhance ground stability, and reduce the possibility of roof or rib failure with minimal use of artificial ground support, it is essential to have an accurate understanding of ground conditions. This includes the location of voids, cracks, and discontinuities, as well as information about the different strata in the immediate roof. This paper briefly introduces ongoing research on void detection by using the roof bolter feed and rotation pressure. The goal of this project is to improve the sensitivity of detection programs to locate smaller joints and reduce the number of false alarms. This paper presents a brief review of the testing procedures, data analysis, logic, and algorithms used for void detection. In addition, this paper discusses the results of preliminary laboratory tests and statistical analysis of the data from these two drilling parameters used for void detection.展开更多
Objective To evaluate the factors affecting optimal stentt expansion in calcified lesions treated by aggressive plaque modification with rotational atherectomy （RA） and a cutting balloon （CB）. Methods From January...Objective To evaluate the factors affecting optimal stentt expansion in calcified lesions treated by aggressive plaque modification with rotational atherectomy （RA） and a cutting balloon （CB）. Methods From January 2014 to May 2015, 92 patients with moderate to severe coronary calcified lesions underwent rotational atherectomy and intravascular ultrasound imaging at Chinese PLA General Hospital （Beijing, China） were included in this study, They were divided into a rotational artherectomy combined with cutting balloon （RACB） group （46 patients treated with RA followed by CB angioplasty） and an RA group （46 patients treated with RA followed by plain balloon angioplasty）. Another 40 patients with similar severity of their calcified lesions treated with plain old balloon angioplasty （POBA） were de- mographically matched to the other groups and defined as the POBA group. All patients received a drug-eluting stent after plaque prepara- tion. Lumen diameter and lumen diameter stenosis （LDS） were measured by quantitative coronary angiography at baseline, after RA, after dilatation, and after stenting. Optimal stent expansion was defined as the final LDS 〈 10%. Results The initial and post-RA LDS values were similar among the three groups. However, after dilatation, the LDS significantly decreased in the RACB group （from 54.5% ± 8.9% to 36.1%＋ 7.1%） but only moderately decreased （from 55.7% ± 7.8% to 46.9% ± 9.4%） in the RA group （time × group, P 〈 0.001）. After stenting, there was a higher rate of optimal stent expansion in the RACB group （71.7% in the RACB group, 54.5% in the RA group, and 15% in the POBA group, P 〈 0.001）, and the final LDS was significantly diminished in the RACB group compared to the other two groups （6.0% ± 2.3%, 10.8% ± 3.3%, 12.7% ± 2.1%, P 〈 0.001）. Moreover, an LDS 〈 40% after plaque preparation （OR = 2.994, 95% CI： 1.297-6.911） was associated with optimal stent expansion, which also had a positive correlation with the appearance of a calcified ring split （r = 0,581, P 〈 0.001）. Conclusions Aggressive plaque modification with RA and CB achieve more optimal stent expansion. An LDS ≤ 40% after plaque modification was a predictive factor for optimal stent expansion in calcified lesions. This parameter was also associated with the presence of calcified ring split.展开更多
The rotation control of particles in optical tweezers is often subject to the spin or orbit angular momentum induced optical torque,which is susceptible to the mechanical and morphological properties of individual par...The rotation control of particles in optical tweezers is often subject to the spin or orbit angular momentum induced optical torque,which is susceptible to the mechanical and morphological properties of individual particle.Here we report on a robust and high-speed rotation control in optical tweezers by using a novel linear polarization synthesis based on optical heterodyne interference between two circularly polarized lights with opposite handedness.The synthesized linear polarization can be rotated in a hopping-free scheme at arbitrary speed determined electronically by the heterodyne frequency between two laser fields.The experimental demonstration of a trapped vaterite particle in water shows that the precisely controlled rotation frequency of 300 Hz can be achieved.The proposed method will find promising applications in optically driven micro-gears,fluidic pumps and rotational micro-rheology.展开更多
Grazing bifurcation of a relative rotation system with backlash non-smooth characteristic is studied along with the change of the external excitation in this paper. Considering the oil film, backlash, time-varying sti...Grazing bifurcation of a relative rotation system with backlash non-smooth characteristic is studied along with the change of the external excitation in this paper. Considering the oil film, backlash, time-varying stiffness and time-varying error, the dynamical equation of a relative rotation system with a backlash non-smooth characteristic is deduced by applying the elastic hydrodynamic lubrication（EHL） and the Grubin theories. In the process of relative rotation, the occurrence of backlash will lead to the change of dynamic behaviors of the system, and the system will transform from the meshing state to the impact state. Thus, the zero-time discontinuous mapping（ZDM） and the Poincare mapping are deduced to analyze the local dynamic characteristics of the system before as well as after the moment that the backlash appears（i.e.,the grazing state）. Meanwhile, the grazing bifurcation mechanism is analyzed theoretically by applying the impact and Floquet theories. Numerical simulations are also given, which confirm the analytical results.展开更多
基金Project supported by the National Magnetic Confinement Fusion Program of China (Grants Nos.2019YFE03040002 and 2018YFE0301101)the Talent Project of China National Nuclear Corporation,China (Grant No.2022JZYF-01)。
文摘The hybrid scenario,which has good confinement and moderate MHD instabilities,is a proposed operation scenario for international thermonuclear experimental reactor(ITER).In this work,the effect of plasma rotation on the HL-3 hybrid scenario is analyzed with the integrated modeling framework OMFIT.The results show that toroidal rotation has no obvious effect on confinement with a high line averaged density of n_(bar)~(7)×10^(19)m^(-3).In this case,the ion temperature only changes from 4.7 keV to 4.4 keV with the rotation decreasing from 10^(5) rad/s to 10^(3) rad/s,which means that the turbulent heat transport is not dominant.While in the scenarios characterized by lower densities,such as n_(bar)~4×10^(19)m^(-3),turbulent transport becomes dominant in determining heat transport.The ion temperature rises from 3.8 keV to 6.1 keV in the core as the rotation velocity increases from 10^(3) rad/s to 10^(5) rad/s.Despite the ion temperature rising,the rotation velocity does not obviously affect electron temperature or density.Additionally,it is noteworthy that the variation in rotation velocity does not significantly affect the global confinement of plasma in scenarios with low density or with high density.
基金supported by the National MCF Energy R&D Program of China(Nos.2019YFE03090400 and 2019YFE03030004)National Natural Science Foundation of China(Nos.12375222 and 11775154)National Key R&D Program of China(Nos.2017YFE0301203 and 2017YFE0301101)。
文摘The effects of equilibrium toroidal rotation during edge-localized mode(ELM)mitigated by resonant magnetic perturbation(RMP)are studied with the experimental equilibria of the EAST tokamak based on the four-field model in the BOUT++code.As the two main parameters to determine the toroidal rotation profiles,the rotation shear and magnitudes were separately scanned to investigate their roles in the impact of RMPs on peeling-ballooning(P-B)modes.On one hand,the results show that strong toroidal rotation shear is favorable for the enhancement of the self-generated E×B shearing rate<ω_(E×B)>with RMPs,leading to significant ELM mitigation with RMP in the stronger toroidal rotation shear region.On the other hand,toroidal rotation magnitudes may affect ELM mitigation by changing the penetration of the RMPs,more precisely the resonant components.RMPs can lead to a reduction in the pedestal energy loss by enhancing the multimode coupling in the turbulence transport phase.The shielding effects on RMPs increase with the toroidal rotation magnitude,leading to the enhancement of the multimode coupling with RMPs to be significantly weakened.Hence,the reduction in pedestal energy loss by RMPs decreased with the rotation magnitude.In brief,the results show that toroidal rotation plays a dual role in ELM mitigation with RMP by changing the shielding effects of plasma by rotation magnitude and affecting<ω_(E×B)>by rotation shear.In the high toroidal rotation region,toroidal rotation shear is usually strong and hence plays a dominant role in the influence of RMP on P-B modes,whereas in the low rotation region,toroidal rotation shear is weak and has negligible impact on P-B modes,and the rotation magnitude plays a dominant role in the influence of RMPs on the P-B modes by changing the field penetration.Therefore,the dual role of toroidal rotation leads to stronger ELM mitigation with RMP,which may be achieved both in the low toroidal rotation region and the relatively high rotation region that has strong rotational shear.
文摘A new selected mapping(SLM)scheme based on constellation rotation is proposed to reduce the peak-to-average power ratio(PAPR)of orthogonal frequency division multiplexing(OFDM)signals.Its core idea is to generate abundant candidate signals by rotating different sub-signals of the original frequency signal with different angles.This new signal generation method can simplify the calculation process of candidate time signals into the linear addition of some intermediate signals,which are generated by the inverse fast Fourier transform(IFFT)operation of the original frequency signal.This feature can effectively reduce the computational complexity of candidate signal generation process.And compared to the traditional SLM scheme,the number of complex multiplication and complex addition of new scheme can separately be decreased by about 99.99% and 91.7% with some specific parameters.Moreover,with the help of the constellation detection mechanism at the receiver,there is no need to carry any side information at the transmitter.The simulation results show that,with the same channel transmission performance,the PAPR reduction performance of new scheme can approach or even exceed the upper bound of the traditional SLM scheme,which uses all the vectors in Hadamard matrix as the phase sequences.
基金Jiangsu Water Science and Technology Project(2021081)。
文摘The rapid identification of planting patterns for major crops in a large irrigated district has vital importance for irrigation management,water fee collection,and crop yield estimation.In this study,the OTSU algorithm and Mean-Shift algorithm were employed to automatically determine threshold values for mapping two main rotated crop patterns at the pixel scale.A time series analysis was conducted to extract the spatial distribution of rice-wheat and wheat-maize rotations in the Chuanhang irrigation district from 2016 to 2020.The results demonstrate that both threshold segmentation algorithms are reliable in extracting the spatial distribution of the crops,with an overall accuracy exceeding 80%.Additionally,both Kappa coefficients surpass 0.7,indicating better performance by OTSU method.Over the period from 2016 to 2020,the area occupied by rice-wheat rotation cropping ranged from 12500 to 14400 hm 2;whereas wheat-maize rotation cropping exhibited smaller and more variable areas ranging from 19730 to 34070 hm 2.These findings highlight how remote sensing-based approaches can provide reliable support for rapidly and accurately identifying the spatial distribution of main crop rotation patterns within a large irrigation district.
文摘The laser gyro is most su it able for building the strap down inertial navigation system (SINS), and its acc uracy of attitude algorithm can enormously affect that of the laser SINS. This p aper develops three improved algorithmal expressions for strap down attitude ut ilizing the angular increment output by the laser gyro from the last two and cur rent updating periods according to the number of gyro samples, and analyses the algorithm error in the classical coning motion. Compared with the conventional algorithms, simulational results show that this improved algorithm has higher precision. A new way to improve the rotation vector algorithms is provided.
文摘Aimed at the large deformation problem of industry cooling tower shell, the mathematical model for the random response of rotational shell under the external random excitation is established by statistic perturbation method. The effect of nonlinear geometric behavior on the response of rotational shell is analyzed.
文摘Based on the theoretical analysis of nonlinear random response of structure, for the engineering practical problem, that is, the large deformation of industry cooling tower shell structure under the action of strong wind loads, the statistic perturbation method is also used to analyze some statistic characteristics of the nonlinear random response of rotational shell with geometric nonlinearity and stationary strong wind load considered. Through computation, some average values of nornal displacements and the nonlinear effect factor of the cooling tower shell are given.
文摘Concrete is considered as an elastic body when subjected to compressive stress butas a brittle body when subjected to tensile stress. That is, after the elastic extremum it cannotcontinue to bear the stress. Based on this.'cracked' physical model, for stochastic extemalwind loads, nonlinear stochastic constitutive equations have been established. To solve equations of nonlinear stochastic vibration, an iterative statistic linearization method (ISLM) hasbeen developedb. Some statistic characteristics were foundd out.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11474141and 11274149)the Program for Liaoning Excellent Talents in University,China(Grant No.LJQ2015040)+2 种基金the Scientific Research Foundation for the Returned Overseas Chinese Scholars,State Education Ministry,China(Grant No.2014-1685)the Special Fund Based Research New Technology of Methanol Conversion and Coal Instead of Oilthe China Postdoctoral Science Foundation(Grant No.2014M550158)
文摘Quasi-classical trajectory calculations are performed to study the stereodynamics of the H（~2S） ＋ NH（a^1？） →H_2（X^1Σ_g~＋） ＋ N（~2D） reaction based on the first excited state NH_2（1~2A＇） potential energy surface reported by Li et al.[Li Y Q and Varandas A J C 2010 J. Phys. Chem. A 114 9644] for the first time. We observe the changes of differential cross-sections at different collision energies and different initial reagent rotational excitations. The influence of collision energy on the k-k＇ distribution can be attributed to a purely impulsive effect. Initial reagent rotational excitation transforms the reaction mechanism from insertion to abstraction. The effect of initial reagent rotational excitations on k-k＇ distribution can be explained by the rotational excitation enlarging the rotational rate of reagent NH in the entrance channel to reduce the probability of collision between incidence H atom and H atom of target molecular. We also investigate the changes of vector correlations and find that the rotational angular momentum vector j＇ of the product H_2 is not only aligned, but also oriented along the y axis. The alignment parameter, the disposal of total angular momentum and the reaction mechanism are all analyzed carefully to explain the polarization behavior of the product rotational angular moment.
基金supported in part by the National Natural Sci-ence Foundation of China(No.61875070)in part by the Science and Technology Development Plan of Jilin Province(No.20180201032GX)+1 种基金in part by the Science and Techno-logy Project of Education Department of Jilin Province(No.JJKH20190110KJ)in part by the Graduate In-novation Fund of Jilin University(No.101832020CX171).
文摘With the rapid advancement of technology,not only do we need to acquire a clear in-verse synthetic aperture radar(ISAR)image,but also the real size of the target on the imaging plane,so it’s particularly important for the ISAR to rescale the images.That is,the ISAR image which is in the range-Doppler domain is converted into the range-azimuth domain.Actually,the key point to solving the problem is to estimate the rotation parameters.In this paper,a new scheme to rescale the images is proposed.For the sake of solving the problem of two-dimensional image blur and target high-speed,the instantaneous range instantaneous Doppler(IRID)method is used to obtain ISAR images,and the rotation parameters are estimated by comparing the rotation correlation of the two images.Using this method,the error of the estimated rotation parameters is greatly reduced,so that the target can be rescaled accurately.The simulation results verify the ef-fectiveness of the proposed algorithm.
基金supported by the National Natural Science Foundation of China (Grant No.10676025)
文摘This paper computes the rotational energy levels of the HCO B^2A＇-X^2A＇31^1 transition, especially, the higher values of the rotational quantum numbers NKa Kc and Ka, with the rotational constants which are obtained via B3LYP method with 6-311G basis set, and the results show that the calculated frequencies using the computed vibration-rotation energy levels are in reasonable agreement with the data from the experiment. Meanwhile, the line intensities of HCO are first reported, the results are of significance for the studying HCO.
基金Supported by the National Natural Science Foundation of China under Grant Nos 11227083 and 91536221
文摘We present an experimental demonstration of the rotation measurement using a compact cold atom gyroscope. Atom interference fringes are observed in the stationary frame and the rotating frame, respectively. The phase shift and contrast of the interference fringe are experimentally investigated. The results show that the contrast of the interference fringe is well held when the platform is rotated, and the phase shift of the interference fringe is linearly proportional to the rotation rate of the platform. The long-term stability, which is evaluated by the overlapped Allan deviation, is 8.5 × 10^-6 rad/s over the integrating time of 1000s.
文摘A method of improving the navigation accuracy of strapdown inertial navigation system (SINS) is studied. The particular technique discussed involves the continuous rotation of gyros and accelerometers cluster about the vertical axis of the vehicle. Then the errors of these sensors will have periodic variation corresponding to components along the body frame. Under this condition, the modulated sensor errors produce reduced system errors. Theoretical analysis based on a new coordinate system defined as sensing frame and test results are presented, and they indicate the method attenuates the navigation errors brought by the gyros' random constant drift and the accelerometer's bias and their white noise compared to the conventional method.
文摘In order to realize the ballistic control of the railgun and the flight stability of the projectile, a new type of railgun is designed, which can control the muzzle velocity and rotation rate. The method of the muzzle velocity and overload control is to adjust the voltage or other parameters of pulse power supply. It would be easy to change velocity accurately in large wide. Another widespread concern problem is launching the spinning stability projectile by railgun. This paper designed a new structure of additional rails to generate an unsymmetrical magnetic field to produce rotational torque in armature. The structure is simple and can control the rotation rate by linear changing the barrel parameters. The calculation formulas of interior ballistic are derived by Biot-Safar law. The important parameter is the deflection angle of the additional rails relative to the symmetry plane of main rail. The larger the angle, the greater the rotation torque generated in the armature. To maintain the flight stability of the projectile, the barrel structural parameters should be proportional to the projectile structural parameters. When changing the muzzle velocity, the rotation rate will also be the equal proportion change. So that the gyro stability is the same. The experiment proves that the railgun designed in this paper can launch the projectile to rotate. And the rotational projectile may not cause the transition or much arcs. This method expands the application of the railgun.
基金Project supported by the National Natural Science Foundation for Post-Doctoral Scientists of China (Grant No. 2012M511002)the National Natural Science Foundation of China (Grant Nos. 10904027 and 61108018)the Science and Technology Programs of Heilongjiang Educational Committee,China (Grant No. 12511425)
文摘The rotational motions of the optically trapped microscopic particles by the vortex femtosecond laser beam are investigated in this paper.Black particles can be trapped and rotated by a vortex femtosecond laser beam very effectively because the vortex beam carries orbital angular momentum due to the helical wave-front structure in assoication with the central phase singularity.Trapped black particles rotate in the vortex beam due to the absorption of the angular momentum transferred from the vortex beam.The rotating directions of the trapped particles can be modulated by reversing the topological charge of the optical vortex in the vortex femtosecond beam.And the rotating speeds of the trapped microscopic particles greatly depend on the topological charges of the vortex tweezer and the used pulse energies.
基金The authors are grateful for the financial support from the National Natural Science Foundation of China(No.51827901&No.52274133)the Program for Guangdong Introducing Innovative and Enterpreneurial Teams(No.2019ZT08G315)the Shenzhen National Science Fund for Distinguished Young Scholars(RCJC20210706091948015).
文摘In-situ pressure-preserved coring(IPP-Coring)is considered to be the most reliable and efficient method for the identification of the scale of oil and gas resources.During IPP-Coring,because the rotation behavior of the pressure controller valve cover in different medium environments is unclear,interference between the valve cover and inner pipe may occur and negatively affect the IPP-Coring success rate.To address this issue,we conducted a series of indoor experiments employing a high-speed camera to gain greater insights into the valve cover rotation behavior in different medium environments,e.g.,air,water,and simulated drilling fluids.The results indicated that the variation in the valve cover rotation angle in the air and fluid environments can be described by a one-phase exponential decay function with a constant time parameter and by biphasic dose response function,respectively.The rotation behavior in the fluid environments exhibited distinct elastic and gravitational acceleration zones.In the fluid environments,the density clearly impacted the valve cover closing time and rotation behavior,whereas the effect of viscosity was very slight.This can be attributed to the negligible influence of the fluid viscosity on the drag coefficient found in this study;meanwhile,the density can increase the buoyancy and the time period during which the valve cover experienced a high drag coefficient.Considering these results,control schemes for the valve cover rotation behavior during IPP-Coring were proposed for different layers and geological conditions in which the different drilling fluids should be used,e.g.,the use of a high-density valve cover in high-pore pressure layers.
文摘Roof and rib instability is an important issue in underground mining. To optimize ground support design,enhance ground stability, and reduce the possibility of roof or rib failure with minimal use of artificial ground support, it is essential to have an accurate understanding of ground conditions. This includes the location of voids, cracks, and discontinuities, as well as information about the different strata in the immediate roof. This paper briefly introduces ongoing research on void detection by using the roof bolter feed and rotation pressure. The goal of this project is to improve the sensitivity of detection programs to locate smaller joints and reduce the number of false alarms. This paper presents a brief review of the testing procedures, data analysis, logic, and algorithms used for void detection. In addition, this paper discusses the results of preliminary laboratory tests and statistical analysis of the data from these two drilling parameters used for void detection.
文摘Objective To evaluate the factors affecting optimal stentt expansion in calcified lesions treated by aggressive plaque modification with rotational atherectomy （RA） and a cutting balloon （CB）. Methods From January 2014 to May 2015, 92 patients with moderate to severe coronary calcified lesions underwent rotational atherectomy and intravascular ultrasound imaging at Chinese PLA General Hospital （Beijing, China） were included in this study, They were divided into a rotational artherectomy combined with cutting balloon （RACB） group （46 patients treated with RA followed by CB angioplasty） and an RA group （46 patients treated with RA followed by plain balloon angioplasty）. Another 40 patients with similar severity of their calcified lesions treated with plain old balloon angioplasty （POBA） were de- mographically matched to the other groups and defined as the POBA group. All patients received a drug-eluting stent after plaque prepara- tion. Lumen diameter and lumen diameter stenosis （LDS） were measured by quantitative coronary angiography at baseline, after RA, after dilatation, and after stenting. Optimal stent expansion was defined as the final LDS 〈 10%. Results The initial and post-RA LDS values were similar among the three groups. However, after dilatation, the LDS significantly decreased in the RACB group （from 54.5% ± 8.9% to 36.1%＋ 7.1%） but only moderately decreased （from 55.7% ± 7.8% to 46.9% ± 9.4%） in the RA group （time × group, P 〈 0.001）. After stenting, there was a higher rate of optimal stent expansion in the RACB group （71.7% in the RACB group, 54.5% in the RA group, and 15% in the POBA group, P 〈 0.001）, and the final LDS was significantly diminished in the RACB group compared to the other two groups （6.0% ± 2.3%, 10.8% ± 3.3%, 12.7% ± 2.1%, P 〈 0.001）. Moreover, an LDS 〈 40% after plaque preparation （OR = 2.994, 95% CI： 1.297-6.911） was associated with optimal stent expansion, which also had a positive correlation with the appearance of a calcified ring split （r = 0,581, P 〈 0.001）. Conclusions Aggressive plaque modification with RA and CB achieve more optimal stent expansion. An LDS ≤ 40% after plaque modification was a predictive factor for optimal stent expansion in calcified lesions. This parameter was also associated with the presence of calcified ring split.
基金the National Natural Science Foundation of China(91750203 and 91850111)State Key Laboratory of Applied Optics,Changchun Institute of Optics,Fine Mechanics and Physics,Chinese Academy of Sciences and the High-performance Computing Platform of Peking University.
文摘The rotation control of particles in optical tweezers is often subject to the spin or orbit angular momentum induced optical torque,which is susceptible to the mechanical and morphological properties of individual particle.Here we report on a robust and high-speed rotation control in optical tweezers by using a novel linear polarization synthesis based on optical heterodyne interference between two circularly polarized lights with opposite handedness.The synthesized linear polarization can be rotated in a hopping-free scheme at arbitrary speed determined electronically by the heterodyne frequency between two laser fields.The experimental demonstration of a trapped vaterite particle in water shows that the precisely controlled rotation frequency of 300 Hz can be achieved.The proposed method will find promising applications in optically driven micro-gears,fluidic pumps and rotational micro-rheology.
基金Project supported by the National Natural Science Foundation of China(Grant No.61104040)the Natural Science Foundation of Hebei Province,China(Grant No.E2012203090)the University Innovation Team of Hebei Province Leading Talent Cultivation Project,China(Grant No.LJRC013)
文摘Grazing bifurcation of a relative rotation system with backlash non-smooth characteristic is studied along with the change of the external excitation in this paper. Considering the oil film, backlash, time-varying stiffness and time-varying error, the dynamical equation of a relative rotation system with a backlash non-smooth characteristic is deduced by applying the elastic hydrodynamic lubrication（EHL） and the Grubin theories. In the process of relative rotation, the occurrence of backlash will lead to the change of dynamic behaviors of the system, and the system will transform from the meshing state to the impact state. Thus, the zero-time discontinuous mapping（ZDM） and the Poincare mapping are deduced to analyze the local dynamic characteristics of the system before as well as after the moment that the backlash appears（i.e.,the grazing state）. Meanwhile, the grazing bifurcation mechanism is analyzed theoretically by applying the impact and Floquet theories. Numerical simulations are also given, which confirm the analytical results.
