In this paper,we define the basic concept of triangular neutrosophic cubic hesitant fuzzy number and their properties.We develop a triangular neutrosophic cubic hesitant fuzzy ordered weighted arithmetic averaging (TN...In this paper,we define the basic concept of triangular neutrosophic cubic hesitant fuzzy number and their properties.We develop a triangular neutrosophic cubic hesitant fuzzy ordered weighted arithmetic averaging (TNCIIFOWAA) operator and a triangular neu-trosophic cubic hesitant fuzzy ordered weighted geometric averaging (TNCIIFOWGA) operator to aggregate triangular neutrosophic cubic hesitant fuzzy number (TNCHFN) information and investigate their properties.Furthermore,a multiple attribute decision-making method based on the TNCHFOWAA operator and triangular neutrosophic cubic hesitant fuzzy ordered weighted geometric (TNCHFOWG) operator and the score function of TNCHFN is established under a TNCHFN environment.Finally,an illustrative example of investment alternatives is given to demonstrate the application and effec-tiveness of the developed approach.展开更多
Model selection strategies have been routinely employed to determine a model for data analysis in statistics, and further study and inference then often proceed as though the selected model were the true model that we...Model selection strategies have been routinely employed to determine a model for data analysis in statistics, and further study and inference then often proceed as though the selected model were the true model that were known a priori. Model averaging approaches, on the other hand, try to combine estimators for a set of candidate models. Specifically, instead of deciding which model is the ’right’ one, a model averaging approach suggests to fit a set of candidate models and average over the estimators using data adaptive weights.In this paper we establish a general frequentist model averaging framework that does not set any restrictions on the set of candidate models. It broaden, the scope of the existing methodologies under the frequentist model averaging development. Assuming the data is from an unknown model, we derive the model averaging estimator and study its limiting distributions and related predictions while taking possible modeling biases into account.We propose a set of optimal weights to combine the individual estimators so that the expected mean squared error of the average estimator is minimized. Simulation studies are conducted to compare the performance of the estimator with that of the existing methods. The results show the benefits of the proposed approach over traditional model selection approaches as well as existing model averaging methods.展开更多
The main aims of this paper are to study the persistence of homoclinic and heteroclinic orbits of the reduced systems on normally hyperbolic critical manifolds, and also the limit cycle bifurcations either from the ho...The main aims of this paper are to study the persistence of homoclinic and heteroclinic orbits of the reduced systems on normally hyperbolic critical manifolds, and also the limit cycle bifurcations either from the homoclinic loop of the reduced systems or from a family of periodic orbits of the layer systems. For the persistence of homoclinic and heteroclinic orbits, and the limit cycles bifurcating from a homolinic loop of the reduced systems, we provide a new and readily detectable method to characterize them compared with the usual Melnikov method when the reduced system forms a generalized rotated vector field. To determine the limit cycles bifurcating from the families of periodic orbits of the layer systems, we apply the averaging methods.We also provide two four-dimensional singularly perturbed differential systems, which have either heteroclinic or homoclinic orbits located on the slow manifolds and also three limit cycles bifurcating from the periodic orbits of the layer system.展开更多
The stationary response of viscoelastic dynamical system with the right unilateral nonzero offset barrier impacts subjected to stochastic excitations is investigated. First, the viscoelastic force is approximately tre...The stationary response of viscoelastic dynamical system with the right unilateral nonzero offset barrier impacts subjected to stochastic excitations is investigated. First, the viscoelastic force is approximately treated as equivalent terms associated with effects. Then, the free vibro-impact(VI) system is absorbed to describe the periodic motion without impacts and quasi-periodic motion with impacts based upon the level of system energy. The stochastic averaging of energy envelope(SAEE) is adopted to seek the stationary probability density functions(PDFs). The detailed theoretical results for Van der Pol viscoelastic VI system with the right unilateral nonzero offset barrier are solved to demonstrate the important effects of the viscoelastic damping and nonzero rigid barrier impacts condition. Monte Carlo(MC) simulation is also performed to verify the reliability of the suggested approach. The stochastic P-bifurcation caused by certain system parameters is further explored. The variation of elastic modulus from negative to zero and then to positive witnesses the evolution process of stochastic P-bifurcation. From the vicinity of the common value to a wider range, the relaxation time induces the stochastic P-bifurcation in the two interval schemes.展开更多
We establish a new characterization of the Musielak-Orlicz-Sobolev space on ?n, which includes the classical Orlicz-Sobolev space, the weighted Sobolev space, and the variable exponent Sobolev space as special cases, ...We establish a new characterization of the Musielak-Orlicz-Sobolev space on ?n, which includes the classical Orlicz-Sobolev space, the weighted Sobolev space, and the variable exponent Sobolev space as special cases, in terms of sharp ball averaging functions. Even in a special case, namely, the variable exponent Sobolev space, the obtained result in this article improves the corresponding result obtained by P. H?st? and A. M. Ribeiro [Commun. Contemp. Math., 2017, 19: 1650022] via weakening the assumption f ∈ L^1(R^n) into f ∈ L^1loc(R^n), which was conjectured to be true by Hosto and Ribeiro in the aforementioned same article.展开更多
A stochastic averaging technique is proposed to study the randomly excited single-degree-of-freedom(SDOF) strongly nonlinear systems with delayed feedback fractional-order proportional-derivative(PD) controller. The d...A stochastic averaging technique is proposed to study the randomly excited single-degree-of-freedom(SDOF) strongly nonlinear systems with delayed feedback fractional-order proportional-derivative(PD) controller. The delayed feedback fractional-order PD control force is approximated by an equivalent non-delay feedback control force combining with a quasi-linear elastic force and a quasi-linear damping force. The averaged It? stochastic differential equation for amplitude of the equivalent nonlinear system is derived by the generalized harmonic functions. The analytical stationary probability density function(PDF) is obtained with solving the reduced Fokker-Planck-Kolmogorov(FPK) equation. Two examples of van der Pol oscillator and RayleighDuffing oscillator are studied to illustrate the application and effectiveness of the proposed method. Numerical results display that the proposed method can yield to the high precision, and the time delay could ruin the control effectiveness, but also even amplifies the response of the system more than that of uncontrolled system. Furthermore, the study finds that the parameters of fractional-order α and time delay may cause the stochastic P-bifurcation. It is indicated that the delayed feedback fractional-order PD controller can offer a potentially effective tool for anti-control of stochastic bifurcation.展开更多
By studying the e ects of geometric precision on kinematic accuracy, an error mapping model has been established, based on the hypothesis that a motion pair and its installation surface are rigid. However, when using ...By studying the e ects of geometric precision on kinematic accuracy, an error mapping model has been established, based on the hypothesis that a motion pair and its installation surface are rigid. However, when using this assumption,there is a significant error induced in high-precision computer numerical control(CNC) machine tools as compared with reality. One of the most important reasons for this error is failing to consider the error averaging e ect of motion pair elements. Therefore, this work examines a high-precision horizontal machining center as its research object, and analyzes the error averaging mechanism of a rolling guide pair under a deformation of the rolling elements. The carriage bearing forces caused by guideway straightness errors are obtained by constructing a geometric error model of a single carriage. The relationship between guideway straightness errors and carriage bearing forces is described by a transfer function in the spatial frequency domain, and its characteristics are analyzed. It quantifies the so-called error averaging e ect of the rolling guide system and, on this basis, a static model for four carriages is established to reflect the error averaging e ect of the rolling guide pair on the position and orientation errors of the motion pair. In addition, it is found that the wavelengths and phase di erences of guideway errors a ect this error averaging mechanism, but the amplitude and preload have little influence thereon. The experiment result shows that the kinematic straightness errors in the x-and y-directions were approximately 1/3 to 1/2 of the guideway straightness errors in the corresponding directions. The results can be used to guide the precision design and assembly of machine tools.展开更多
Travel time through a ring road with a total length of 80 km has been predicted by a viscoelastic traffic model(VEM),which is developed in analogous to the non-Newtonian fluid flow.The VEM expresses a traffic pressure...Travel time through a ring road with a total length of 80 km has been predicted by a viscoelastic traffic model(VEM),which is developed in analogous to the non-Newtonian fluid flow.The VEM expresses a traffic pressure for the unfree flow case by space headway,ensuring that the pressure can be determined by the assumption that the relevant second critical sound speed is exactly equal to the disturbance propagation speed determined by the free flow speed and the braking distance measured by the average vehicular length.The VEM assumes that the sound speed for the free flow case depends on the traffic density in some specific aspects,which ensures that it is exactly identical to the free flow speed on an empty road.To make a comparison,the open Navier-Stokes type model developed by Zhang(ZHANG,H.M.Driver memory,traffic viscosity and a viscous vehicular traffic flow model.Transp.Res.Part B,37,27–41(2003))is adopted to predict the travel time through the ring road for providing the counterpart results.When the traffic free flow speed is 80 km/h,the braking distance is supposed to be 45m,with the jam density uniquely determined by the average length of vehicles l t 5.8m.To avoid possible singular points in travel time prediction,a distinguishing period for time averaging is pre-assigned to be 7.5 minutes.It is found that the travel time increases monotonically with the initial traffic density on the ring road.Without ramp effects,for the ring road with the initial density less than the second critical density,the travel time can be simply predicted by using the equilibrium speed.However,this simpler approach is unavailable for scenarios over the second critical.展开更多
The PDFs (probability density functions) and probability of a ship rolling under the random parametric and forced excitations were studied by a semi-analytical method. The rolling motion equation of the ship in random...The PDFs (probability density functions) and probability of a ship rolling under the random parametric and forced excitations were studied by a semi-analytical method. The rolling motion equation of the ship in random oblique waves was established. The righting arm obtained by the numerical simulation was approximately fitted by an analytical function. The irregular waves were decomposed into two Gauss stationary random processes, and the CARMA (2, 1) model was used to fit the spectral density function of parametric and forced excitations. The stochastic energy envelope averaging method was used to solve the PDFs and the probability. The validity of the semi-analytical method was verified by the Monte Carlo method. The C11 ship was taken as an example, and the influences of the system parameters on the PDFs and probability were analyzed. The results show that the probability of ship rolling is affected by the characteristic wave height, wave length, and the heading angle. In order to provide proper advice for the ship's manoeuvring, the parametric excitations should be considered appropriately when the ship navigates in the oblique seas.展开更多
The Spatial Only Processing Power Inversion （SOP-PI） algorithm is frequently used in Global NavigationSatellite System （GNSS） adaptive array receivers for interference mitigation because of its simplicity ofimplem...The Spatial Only Processing Power Inversion （SOP-PI） algorithm is frequently used in Global NavigationSatellite System （GNSS） adaptive array receivers for interference mitigation because of its simplicity ofimplementation. This study investigates the effects of SOP-PI on receiver measurements for high-precisionapplications. Mathematical deductions show that if an array with a centro-symmetrical geometry is used, ideally,SOP-PI is naturally bias-free; however, this no longer stands when non-ideal factors, including array perturbationsand finite-sample effect, are added. Simulations are performed herein to investigate how exactly the arrayperturbations affect the carrier phase biases, while diagonal loading and forward-backward averaging are proposedto counter the finite-sample effect. In conclusion, whether SQP-PI with a centro-symmetrical array geometry willsatisfy the high precision demands mainly depends on the array perturbation degree of the element amplitude andthe phase center.展开更多
The uppermost part of the Upper Bathonian Sponge Limestone member, Patcham Formation, of the Jhura Dome of Kachchh Mainland is a thickening-and shallowing-upward succession topped by medium-to thick-bedded hummocky cr...The uppermost part of the Upper Bathonian Sponge Limestone member, Patcham Formation, of the Jhura Dome of Kachchh Mainland is a thickening-and shallowing-upward succession topped by medium-to thick-bedded hummocky cross-stratified grainstones deposited by storm waves. Occasionally, thin, commonly lenticular, intraclastic-bioclastic silty marl intercalations between the grainstones are highly bioturbated, in contrast to the grainstones, in which, for the most part, trace fossils occur scattered. Large exposures of bedding planes of the grainstones allow the detailed investigation of ichnological features, whereas the high density of traces in the soft marls precludes the identification of any ichnotaxa. Eighteen ichnotaxa have been recorded including Ophiomorpha, Thalassinoides, Taenidium, Gyrophyllites, Chondrites, Dactyloidites, Teichichnus, Bolonia, and Ancorichnus. Except for Ophiomorpha nodosa and Thalassinoides, which generally indicate moderate to high energy conditions and are the dwelling burrows of suspension-feeding to omnivorous crustaceans, the ichnotaxa represent a deposit-feeding behaviour of their producers and thus are characteristic of low-energy environments. The trace fossils form three ichnoassemblages characterized by(1) Ophiomorpha nodosa and Thalassinoides suevicus,(2)?Thalassinoides isp. A, Taenidium, and Bolonia lata,and(3) Ancorichnus. The dominance of traces of deposit-feeders in rocks indicative of high-energy events is counterintuitive and points to their non-contemporaneity. The sediments were deposited during brief highenergy events, whereas the trace fossils were produced when, after waning of storms low-energy conditions prevailed. This time-averaging is particularly pronounced in trace fossils that extend vertically downwards and may reach strata deposited under distinctly different conditions. Thus, environmental interpretations based on trace fossils should refer to colonisation surfaces rather than to the sediment surrounding the trace fossils. In the latter case, interpretat展开更多
Near-term climate projections are needed by policymakers; however, these projections are difficult because intern-ally generated climate variations need to be considered. In this study, temperature change scenarios in...Near-term climate projections are needed by policymakers; however, these projections are difficult because intern-ally generated climate variations need to be considered. In this study, temperature change scenarios in the near-termperiod 2017-35 are projected at global and regional scales based on a refined multi-model ensemble approach thatconsiders both the secular trend （ST） and multidecadal variability （MDV） in the Coupled Model IntercomparisonProject Phase 5 （CMIP5） simulations. The ST and MDV components are adaptively extracted from each model simu-lation by using the ensemble empirical mode decomposition （EEMD） filter, reconstructed via the Bayesian model av-eraging （BMA） method for the historical period 1901-2005, and validated for 2006-16. In the simulations of the＂medium＂ representative concentration pathways scenario during 2017-35, the MDV-modulated temperature changeprojected via the refined approach displays an increase of 0.44℃ （90% uncertainty range from 0.30 to 0.58℃） forglobal land, 0.48℃ （90% uncertainty range from 0.29 to 0.67℃） for the Northern Hemispheric land （NL）, and0.29℃ （90% uncertainty range from 0.23 to 0.35℃） for the Southern Hemispheric land （SL）. These increases aresmaller than those projected by the conventional arithmetic mean approach. The MDV enhances the ST in 13 of 21regions across the world. The largest MDV-modulated warming effect （46%） exists in central America. In contrast,the MDV counteracts the ST in NL, SL, and eight other regions, with the largest cooling effect （220%） in Alaska.展开更多
A stochastic averaging method for predicting the response of quasi partially integrable and non-resonant Hamiltoniansystems to fractional Gaussian noise （fGla） with the Hurst index 1/2〈H〈l is proposed. The average...A stochastic averaging method for predicting the response of quasi partially integrable and non-resonant Hamiltoniansystems to fractional Gaussian noise （fGla） with the Hurst index 1/2〈H〈l is proposed. The averaged stochastic differential equa-tions （SDEs） for the first integrals of the associated Hamiltonian system are derived. The dimension of averaged SDEs is less thanthat of the original system. The stationary probability density and statistics of the original system are obtained approximately fromsolving the averaged SDEs numerically. Two systems are worked out to illustrate the proposed stochastic averaging method. It isshown that the results obtained by using the proposed stochastic averaging method and those from digital simulation of originalsystem agree well, and the computational time for the former results is less than that for the latter ones.展开更多
With the increase of science popularization, evaluation of science popularization has become an urgent demand. Considering science popularization bases as independent agents, a self-determined evaluation approach for ...With the increase of science popularization, evaluation of science popularization has become an urgent demand. Considering science popularization bases as independent agents, a self-determined evaluation approach for science popularization using induced ordered weighted averaging (IOWA) operator and particle swarm optimization (PSO) is proposed in this paper.Firstly, six factors including science popularization personnel, space, fund,media, activity and influence are selected to construct an index system for science popularization evaluation. On this basis, the absolute dominance and relative dominance of evaluation indexes are used as induced components, and the prior order of the evaluation indexes is determined. Besides, the optimization model of index weighted vectors is established by IOWA operator, index weighted vectors are calculated by particle swarm optimization algorithm, and index weighted vectors and evaluation value vectors are obtain. Finally, the optimal evaluation vectors and evaluation results are given according to the Perron-Frobenius decision eigenvalve theorem .展开更多
The performance of an erbium-doped fiber ring laser based intra-cavity absorption gassensor was evaluated with performance enhanced techniques. A multi-line wavelength sweep techniqueand a weighted averaging technique...The performance of an erbium-doped fiber ring laser based intra-cavity absorption gassensor was evaluated with performance enhanced techniques. A multi-line wavelength sweep techniqueand a weighted averaging technique were proposed for better gas detection. By selecting appropriatesystem parameters, 6 strong absorption lines near 1 530 nm of C2H2 were obtained with good spectrumresolution in one scanning period. One group with higher absorption coefficients was used for relativelylow gas concentration detection and the other with lower absorption coefficients was used for relativelyhigh gas concentration. Both the groups can be used for medium gas concentration detection. For variousconcentration cases, by choosing proper absorption lines and performing weighted averaging, detectionaccuracy can be obtained over an extended detection range. The minimum detection limit could be verylow after optimization.展开更多
A 6-bit 2 GS/s ADC was implemented using a 65 nm digital CMOS technology.The design is based on a single-channel flash ADC architecture,and utilizes interpolating and averaging techniques.A two-stage CML-CMOS high-spe...A 6-bit 2 GS/s ADC was implemented using a 65 nm digital CMOS technology.The design is based on a single-channel flash ADC architecture,and utilizes interpolating and averaging techniques.A two-stage CML-CMOS high-speed hybrid comparator is designed for optimal speed and power performance.The total power consumption of the converter is 52 mW and the area is 0.24 mm2.The ADC achieves 42.5 dB SFDR and5.2 bit ENOB at input frequency of 123 MHz,and at Nyquist frequency 37.67 dB SFDR and 4.9 bit ENOB.展开更多
Beginning with a Lagrangian, we derived an approximate relativistic orbit equation which describes relativistic corrections to Keplerian orbits. The critical angular moment to guarantee the existence of periodic orbit...Beginning with a Lagrangian, we derived an approximate relativistic orbit equation which describes relativistic corrections to Keplerian orbits. The critical angular moment to guarantee the existence of periodic orbits is determined. An approximate relativistic Kepler’s elliptic orbit is illustrated by numerical simulation via a second-order perturbation method of averaging.展开更多
文摘In this paper,we define the basic concept of triangular neutrosophic cubic hesitant fuzzy number and their properties.We develop a triangular neutrosophic cubic hesitant fuzzy ordered weighted arithmetic averaging (TNCIIFOWAA) operator and a triangular neu-trosophic cubic hesitant fuzzy ordered weighted geometric averaging (TNCIIFOWGA) operator to aggregate triangular neutrosophic cubic hesitant fuzzy number (TNCHFN) information and investigate their properties.Furthermore,a multiple attribute decision-making method based on the TNCHFOWAA operator and triangular neutrosophic cubic hesitant fuzzy ordered weighted geometric (TNCHFOWG) operator and the score function of TNCHFN is established under a TNCHFN environment.Finally,an illustrative example of investment alternatives is given to demonstrate the application and effec-tiveness of the developed approach.
基金National Science Foundation of USA (Grant Nos.DMS1812048,DMS-1737857,DMS-1513483 and DMS-1418042)National Natural Science Foundation of China (Grant No.11529101).
文摘Model selection strategies have been routinely employed to determine a model for data analysis in statistics, and further study and inference then often proceed as though the selected model were the true model that were known a priori. Model averaging approaches, on the other hand, try to combine estimators for a set of candidate models. Specifically, instead of deciding which model is the ’right’ one, a model averaging approach suggests to fit a set of candidate models and average over the estimators using data adaptive weights.In this paper we establish a general frequentist model averaging framework that does not set any restrictions on the set of candidate models. It broaden, the scope of the existing methodologies under the frequentist model averaging development. Assuming the data is from an unknown model, we derive the model averaging estimator and study its limiting distributions and related predictions while taking possible modeling biases into account.We propose a set of optimal weights to combine the individual estimators so that the expected mean squared error of the average estimator is minimized. Simulation studies are conducted to compare the performance of the estimator with that of the existing methods. The results show the benefits of the proposed approach over traditional model selection approaches as well as existing model averaging methods.
基金supported by National Natural Science Foundation of China(Grant No.11671254)Innovation Program of Shanghai Municipal Education Commission(Grant No.15ZZ012).
文摘The main aims of this paper are to study the persistence of homoclinic and heteroclinic orbits of the reduced systems on normally hyperbolic critical manifolds, and also the limit cycle bifurcations either from the homoclinic loop of the reduced systems or from a family of periodic orbits of the layer systems. For the persistence of homoclinic and heteroclinic orbits, and the limit cycles bifurcating from a homolinic loop of the reduced systems, we provide a new and readily detectable method to characterize them compared with the usual Melnikov method when the reduced system forms a generalized rotated vector field. To determine the limit cycles bifurcating from the families of periodic orbits of the layer systems, we apply the averaging methods.We also provide two four-dimensional singularly perturbed differential systems, which have either heteroclinic or homoclinic orbits located on the slow manifolds and also three limit cycles bifurcating from the periodic orbits of the layer system.
基金the National Natural Science Foundation of China(Grant Nos.11872305 and 11872307)the Excellent Doctorate Cultivating Foundation of Northwestern Polytechnical University,China.
文摘The stationary response of viscoelastic dynamical system with the right unilateral nonzero offset barrier impacts subjected to stochastic excitations is investigated. First, the viscoelastic force is approximately treated as equivalent terms associated with effects. Then, the free vibro-impact(VI) system is absorbed to describe the periodic motion without impacts and quasi-periodic motion with impacts based upon the level of system energy. The stochastic averaging of energy envelope(SAEE) is adopted to seek the stationary probability density functions(PDFs). The detailed theoretical results for Van der Pol viscoelastic VI system with the right unilateral nonzero offset barrier are solved to demonstrate the important effects of the viscoelastic damping and nonzero rigid barrier impacts condition. Monte Carlo(MC) simulation is also performed to verify the reliability of the suggested approach. The stochastic P-bifurcation caused by certain system parameters is further explored. The variation of elastic modulus from negative to zero and then to positive witnesses the evolution process of stochastic P-bifurcation. From the vicinity of the common value to a wider range, the relaxation time induces the stochastic P-bifurcation in the two interval schemes.
基金National Natural Science Foundation of China (Grant Nos. 11871254, 11571289. 11571039, 11761131002, 11671185. 11871100)Fundamental Research Funds for the Central Universities (Grant No. lzujbky-2018-111).
文摘We establish a new characterization of the Musielak-Orlicz-Sobolev space on ?n, which includes the classical Orlicz-Sobolev space, the weighted Sobolev space, and the variable exponent Sobolev space as special cases, in terms of sharp ball averaging functions. Even in a special case, namely, the variable exponent Sobolev space, the obtained result in this article improves the corresponding result obtained by P. H?st? and A. M. Ribeiro [Commun. Contemp. Math., 2017, 19: 1650022] via weakening the assumption f ∈ L^1(R^n) into f ∈ L^1loc(R^n), which was conjectured to be true by Hosto and Ribeiro in the aforementioned same article.
基金supported by the National Natural Science Foundation of China(Grant Nos.11672111,11432012,11602089)the Program for New Century Excellent Talents in Fujian Province University,and the Technological Project of Huaqiao University(Grant Nos.ZQN-YX307,ZQNYX505).
文摘A stochastic averaging technique is proposed to study the randomly excited single-degree-of-freedom(SDOF) strongly nonlinear systems with delayed feedback fractional-order proportional-derivative(PD) controller. The delayed feedback fractional-order PD control force is approximated by an equivalent non-delay feedback control force combining with a quasi-linear elastic force and a quasi-linear damping force. The averaged It? stochastic differential equation for amplitude of the equivalent nonlinear system is derived by the generalized harmonic functions. The analytical stationary probability density function(PDF) is obtained with solving the reduced Fokker-Planck-Kolmogorov(FPK) equation. Two examples of van der Pol oscillator and RayleighDuffing oscillator are studied to illustrate the application and effectiveness of the proposed method. Numerical results display that the proposed method can yield to the high precision, and the time delay could ruin the control effectiveness, but also even amplifies the response of the system more than that of uncontrolled system. Furthermore, the study finds that the parameters of fractional-order α and time delay may cause the stochastic P-bifurcation. It is indicated that the delayed feedback fractional-order PD controller can offer a potentially effective tool for anti-control of stochastic bifurcation.
基金Supported by National Science and Technology Major Project of China (Grant No. 2015ZX04005001)Tianjin Provincial Nature Science Foundation of China (Grant No. 16JCZDJC38400).
文摘By studying the e ects of geometric precision on kinematic accuracy, an error mapping model has been established, based on the hypothesis that a motion pair and its installation surface are rigid. However, when using this assumption,there is a significant error induced in high-precision computer numerical control(CNC) machine tools as compared with reality. One of the most important reasons for this error is failing to consider the error averaging e ect of motion pair elements. Therefore, this work examines a high-precision horizontal machining center as its research object, and analyzes the error averaging mechanism of a rolling guide pair under a deformation of the rolling elements. The carriage bearing forces caused by guideway straightness errors are obtained by constructing a geometric error model of a single carriage. The relationship between guideway straightness errors and carriage bearing forces is described by a transfer function in the spatial frequency domain, and its characteristics are analyzed. It quantifies the so-called error averaging e ect of the rolling guide system and, on this basis, a static model for four carriages is established to reflect the error averaging e ect of the rolling guide pair on the position and orientation errors of the motion pair. In addition, it is found that the wavelengths and phase di erences of guideway errors a ect this error averaging mechanism, but the amplitude and preload have little influence thereon. The experiment result shows that the kinematic straightness errors in the x-and y-directions were approximately 1/3 to 1/2 of the guideway straightness errors in the corresponding directions. The results can be used to guide the precision design and assembly of machine tools.
基金Project supported by the Russian Foundation for Basic Research(No.18-07-00518)and the National Natural Science Foundation of China(No.10972212)
文摘Travel time through a ring road with a total length of 80 km has been predicted by a viscoelastic traffic model(VEM),which is developed in analogous to the non-Newtonian fluid flow.The VEM expresses a traffic pressure for the unfree flow case by space headway,ensuring that the pressure can be determined by the assumption that the relevant second critical sound speed is exactly equal to the disturbance propagation speed determined by the free flow speed and the braking distance measured by the average vehicular length.The VEM assumes that the sound speed for the free flow case depends on the traffic density in some specific aspects,which ensures that it is exactly identical to the free flow speed on an empty road.To make a comparison,the open Navier-Stokes type model developed by Zhang(ZHANG,H.M.Driver memory,traffic viscosity and a viscous vehicular traffic flow model.Transp.Res.Part B,37,27–41(2003))is adopted to predict the travel time through the ring road for providing the counterpart results.When the traffic free flow speed is 80 km/h,the braking distance is supposed to be 45m,with the jam density uniquely determined by the average length of vehicles l t 5.8m.To avoid possible singular points in travel time prediction,a distinguishing period for time averaging is pre-assigned to be 7.5 minutes.It is found that the travel time increases monotonically with the initial traffic density on the ring road.Without ramp effects,for the ring road with the initial density less than the second critical density,the travel time can be simply predicted by using the equilibrium speed.However,this simpler approach is unavailable for scenarios over the second critical.
基金Foundation item: this work was financially supported by the Project of “Nonlinear Wave Excitation and Response of Surface Vehicle” (Grant No.B2420132001) and the Natural Science Foundation of Tianjin (Grant No. 15JCQNJC07700).
文摘The PDFs (probability density functions) and probability of a ship rolling under the random parametric and forced excitations were studied by a semi-analytical method. The rolling motion equation of the ship in random oblique waves was established. The righting arm obtained by the numerical simulation was approximately fitted by an analytical function. The irregular waves were decomposed into two Gauss stationary random processes, and the CARMA (2, 1) model was used to fit the spectral density function of parametric and forced excitations. The stochastic energy envelope averaging method was used to solve the PDFs and the probability. The validity of the semi-analytical method was verified by the Monte Carlo method. The C11 ship was taken as an example, and the influences of the system parameters on the PDFs and probability were analyzed. The results show that the probability of ship rolling is affected by the characteristic wave height, wave length, and the heading angle. In order to provide proper advice for the ship's manoeuvring, the parametric excitations should be considered appropriately when the ship navigates in the oblique seas.
文摘The Spatial Only Processing Power Inversion （SOP-PI） algorithm is frequently used in Global NavigationSatellite System （GNSS） adaptive array receivers for interference mitigation because of its simplicity ofimplementation. This study investigates the effects of SOP-PI on receiver measurements for high-precisionapplications. Mathematical deductions show that if an array with a centro-symmetrical geometry is used, ideally,SOP-PI is naturally bias-free; however, this no longer stands when non-ideal factors, including array perturbationsand finite-sample effect, are added. Simulations are performed herein to investigate how exactly the arrayperturbations affect the carrier phase biases, while diagonal loading and forward-backward averaging are proposedto counter the finite-sample effect. In conclusion, whether SQP-PI with a centro-symmetrical array geometry willsatisfy the high precision demands mainly depends on the array perturbation degree of the element amplitude andthe phase center.
基金supported by the Jagiellonian University(DS funds)financial assistance for the fieldwork by DST(project EMR/ 2015/001574)financial support by the Alexander von Humboldt Foundation
文摘The uppermost part of the Upper Bathonian Sponge Limestone member, Patcham Formation, of the Jhura Dome of Kachchh Mainland is a thickening-and shallowing-upward succession topped by medium-to thick-bedded hummocky cross-stratified grainstones deposited by storm waves. Occasionally, thin, commonly lenticular, intraclastic-bioclastic silty marl intercalations between the grainstones are highly bioturbated, in contrast to the grainstones, in which, for the most part, trace fossils occur scattered. Large exposures of bedding planes of the grainstones allow the detailed investigation of ichnological features, whereas the high density of traces in the soft marls precludes the identification of any ichnotaxa. Eighteen ichnotaxa have been recorded including Ophiomorpha, Thalassinoides, Taenidium, Gyrophyllites, Chondrites, Dactyloidites, Teichichnus, Bolonia, and Ancorichnus. Except for Ophiomorpha nodosa and Thalassinoides, which generally indicate moderate to high energy conditions and are the dwelling burrows of suspension-feeding to omnivorous crustaceans, the ichnotaxa represent a deposit-feeding behaviour of their producers and thus are characteristic of low-energy environments. The trace fossils form three ichnoassemblages characterized by(1) Ophiomorpha nodosa and Thalassinoides suevicus,(2)?Thalassinoides isp. A, Taenidium, and Bolonia lata,and(3) Ancorichnus. The dominance of traces of deposit-feeders in rocks indicative of high-energy events is counterintuitive and points to their non-contemporaneity. The sediments were deposited during brief highenergy events, whereas the trace fossils were produced when, after waning of storms low-energy conditions prevailed. This time-averaging is particularly pronounced in trace fossils that extend vertically downwards and may reach strata deposited under distinctly different conditions. Thus, environmental interpretations based on trace fossils should refer to colonisation surfaces rather than to the sediment surrounding the trace fossils. In the latter case, interpretat
基金Supported by the National Key Research and Development Program of China （2016YFA0600404）, Youth Innovation Promotion As- sociation of the Chinese Academy of Sciences （2016075）, and Jiangsu Collaborative Innovation Center for Climate Change.
文摘Near-term climate projections are needed by policymakers; however, these projections are difficult because intern-ally generated climate variations need to be considered. In this study, temperature change scenarios in the near-termperiod 2017-35 are projected at global and regional scales based on a refined multi-model ensemble approach thatconsiders both the secular trend （ST） and multidecadal variability （MDV） in the Coupled Model IntercomparisonProject Phase 5 （CMIP5） simulations. The ST and MDV components are adaptively extracted from each model simu-lation by using the ensemble empirical mode decomposition （EEMD） filter, reconstructed via the Bayesian model av-eraging （BMA） method for the historical period 1901-2005, and validated for 2006-16. In the simulations of the＂medium＂ representative concentration pathways scenario during 2017-35, the MDV-modulated temperature changeprojected via the refined approach displays an increase of 0.44℃ （90% uncertainty range from 0.30 to 0.58℃） forglobal land, 0.48℃ （90% uncertainty range from 0.29 to 0.67℃） for the Northern Hemispheric land （NL）, and0.29℃ （90% uncertainty range from 0.23 to 0.35℃） for the Southern Hemispheric land （SL）. These increases aresmaller than those projected by the conventional arithmetic mean approach. The MDV enhances the ST in 13 of 21regions across the world. The largest MDV-modulated warming effect （46%） exists in central America. In contrast,the MDV counteracts the ST in NL, SL, and eight other regions, with the largest cooling effect （220%） in Alaska.
文摘A stochastic averaging method for predicting the response of quasi partially integrable and non-resonant Hamiltoniansystems to fractional Gaussian noise （fGla） with the Hurst index 1/2〈H〈l is proposed. The averaged stochastic differential equa-tions （SDEs） for the first integrals of the associated Hamiltonian system are derived. The dimension of averaged SDEs is less thanthat of the original system. The stationary probability density and statistics of the original system are obtained approximately fromsolving the averaged SDEs numerically. Two systems are worked out to illustrate the proposed stochastic averaging method. It isshown that the results obtained by using the proposed stochastic averaging method and those from digital simulation of originalsystem agree well, and the computational time for the former results is less than that for the latter ones.
基金The authors acknowledge the support by Graduate Science Popularization Ability Promotion Project of Chinese Association for Science and Technology (No. 2014KPYJD41) and Science and Technology Support Program of Sichuan Province (No. 2016RZ0079).
文摘With the increase of science popularization, evaluation of science popularization has become an urgent demand. Considering science popularization bases as independent agents, a self-determined evaluation approach for science popularization using induced ordered weighted averaging (IOWA) operator and particle swarm optimization (PSO) is proposed in this paper.Firstly, six factors including science popularization personnel, space, fund,media, activity and influence are selected to construct an index system for science popularization evaluation. On this basis, the absolute dominance and relative dominance of evaluation indexes are used as induced components, and the prior order of the evaluation indexes is determined. Besides, the optimization model of index weighted vectors is established by IOWA operator, index weighted vectors are calculated by particle swarm optimization algorithm, and index weighted vectors and evaluation value vectors are obtain. Finally, the optimal evaluation vectors and evaluation results are given according to the Perron-Frobenius decision eigenvalve theorem .
文摘The performance of an erbium-doped fiber ring laser based intra-cavity absorption gassensor was evaluated with performance enhanced techniques. A multi-line wavelength sweep techniqueand a weighted averaging technique were proposed for better gas detection. By selecting appropriatesystem parameters, 6 strong absorption lines near 1 530 nm of C2H2 were obtained with good spectrumresolution in one scanning period. One group with higher absorption coefficients was used for relativelylow gas concentration detection and the other with lower absorption coefficients was used for relativelyhigh gas concentration. Both the groups can be used for medium gas concentration detection. For variousconcentration cases, by choosing proper absorption lines and performing weighted averaging, detectionaccuracy can be obtained over an extended detection range. The minimum detection limit could be verylow after optimization.
基金supported by National Natural Science Foundation of China（Grant No.60736030） Research Program of Science and Technology Commission of Shanghai（Grant No.10706201602）
文摘A 6-bit 2 GS/s ADC was implemented using a 65 nm digital CMOS technology.The design is based on a single-channel flash ADC architecture,and utilizes interpolating and averaging techniques.A two-stage CML-CMOS high-speed hybrid comparator is designed for optimal speed and power performance.The total power consumption of the converter is 52 mW and the area is 0.24 mm2.The ADC achieves 42.5 dB SFDR and5.2 bit ENOB at input frequency of 123 MHz,and at Nyquist frequency 37.67 dB SFDR and 4.9 bit ENOB.
文摘Beginning with a Lagrangian, we derived an approximate relativistic orbit equation which describes relativistic corrections to Keplerian orbits. The critical angular moment to guarantee the existence of periodic orbits is determined. An approximate relativistic Kepler’s elliptic orbit is illustrated by numerical simulation via a second-order perturbation method of averaging.