To ensure the structural integrity of life-limiting component of aeroengines,Probabilistic Damage Tolerance(PDT)assessment is applied to evaluate the failure risk as required by airworthiness regulations and military ...To ensure the structural integrity of life-limiting component of aeroengines,Probabilistic Damage Tolerance(PDT)assessment is applied to evaluate the failure risk as required by airworthiness regulations and military standards.The PDT method holds the view that there exist defects such as machining scratches and service cracks in the tenon-groove structures of aeroengine disks.However,it is challenging to conduct PDT assessment due to the scarcity of effective Probability of Detection(POD)model and anomaly distribution model.Through a series of Nondestructive Testing(NDT)experiments,the POD model of real cracks in tenon-groove structures is constructed for the first time by employing the Transfer Function Method(TFM).A novel anomaly distribution model is derived through the utilization of the POD model,instead of using the infeasible field data accumulation method.Subsequently,a framework for calculating the Probability of Failure(POF)of the tenon-groove structures is established,and the aforementioned two models exert a significant influence on the results of POF.展开更多
Multiple tuned mass dampers(MTMDs)reduce dynamic response with multiple specified frequencies of building structures.Many optimization algorithms for placement design exist,though they rarely conform to code-based ver...Multiple tuned mass dampers(MTMDs)reduce dynamic response with multiple specified frequencies of building structures.Many optimization algorithms for placement design exist,though they rarely conform to code-based verification nor produce high quality solutions without high computational effort and high complexity.This study proposes an inverse element exchange method(IEEM)with multi-level programming and compares it to a single tuned mass damper(STMD)and uniform distribution of multiple tuned mass dampers in the frequency and time domains.A ten-story shear building is used for the numerical case study.The results show that the proposed method can offer improvement over the STMD,uniform distribution of multiple tuned mass dampers,and distribution optimized by genetic algorithms(GA)with regard to minimizing the interstory drift ratio(IDR)in both the frequency and time domains and the time consumption for optimization.展开更多
AIM:To investigate how angles kappa and alpha affect postoperative visual quality in patients with multifocal intraocular lens(mIOLs)implantation.METHODS:Retrospective cases series.A total of 46 patients(46 eyes)who u...AIM:To investigate how angles kappa and alpha affect postoperative visual quality in patients with multifocal intraocular lens(mIOLs)implantation.METHODS:Retrospective cases series.A total of 46 patients(46 eyes)who underwent phacoemulsification were subsumed.The correlation between Preoperative angles kappa and alpha,wave-front aberrations and objective visual quality of cornea,internal,and total eye after surgery were analyzed using iTrace.RESULTS:The magnitude of angle kappa was negatively correlated with internal and total modulation transfer function(MTF)at 3 mm;the magnitude of angle kappa was positively correlated with astigmatism,trefoil,higher-order aberrations(HOAs)of both internal and total eye at 3 mm.The magnitude of angle alpha was negatively correlated with total MTF and total Strehl ratio at 3 mm.The magnitude of angle alpha was positively correlated with corneal coma at 5 mm,internal astigmatism at both 3 mm and 5 mm,and total spherical aberration(SA)at 3 mm.Multivariate linear regression analysis showed that,among candidate independent variables(kappa,alpha,astigmatism,SA,coma,trefoil,and HOAs),astigmatism is the only independent factor for altering corneal MTF at 3 mm and 5 mm;astigmatism and HOAs emerged as independent factors for altering internal MTF at 3 mm and 5 mm,and total MTF at 3 mm;astigmatism,SA and HOAs emerged as independent factors for altering total MTF at 5 mm.CONCLUSION:With greater preoperative angle kappa or angle alpha,patients who accept mIOL implantation tend to have larger internal astigmatism and HOAs,which resulting in poor visual quality,especially those with small pupil size.展开更多
Current research on rail vehicle system vibrations primarily relies on numerical methods,with vibration transfer functions commonly derived through data fitting.However,the physical mechanisms underlying these vibrati...Current research on rail vehicle system vibrations primarily relies on numerical methods,with vibration transfer functions commonly derived through data fitting.However,the physical mechanisms underlying these vibrations are not well understood.To clarify the vibration transfer function and its characteristics,four basic input vectors are defined,and an analytical method is proposed.The vibration transfer functions of the vehicle system are solved,and their spatial coherence is analyzed.The results show that there are two spatial scales and four coherent modes in the vehicle system.The track irregularity wavelengths are combined with two spatial scales to alter the proportions of basic input vectors and then show the characteristics of spatial coherence.Four coherent modes are involved in wheel-rail force and primary suspension force;two coherent modes are involved in bogie vertical motion;and their dominant modes vary with the input frequency.On the other hand,the coherent modes involved in the bogie pitching motion and vehicle body motion are single and fixed over the whole range of frequency.This study presents an analytical method for the rapid solution of dynamic responses in vehicle systems and systematically analyzes the coherence behavior of vibration transfer functions with respect to tracking irregularity wavelengths.展开更多
Continuing advancement in astronomy,space exploration,and scientific detection,has increased demand for infrared multi-band detection systems.Traditional three-band optical systems,designed to simultaneously image at ...Continuing advancement in astronomy,space exploration,and scientific detection,has increased demand for infrared multi-band detection systems.Traditional three-band optical systems,designed to simultaneously image at infrared short-wave,mid-wave,and long-wave bands typically rely on dispersive elements,leading to bulky sizes,complex system architectures,low efficiency,and challenges in rapid assembly.To overcome these obstacles,in combination with the latest third-generation infrared detectors,we propose a design for a compact and lightweight three-band optical system,with infrared capabilities in all three required bands.The core of this approach is an integrated design philosophy that emphasizes the high steepness of mirror surfaces.This design achieves uniform correction and optimization of chromatic aberration and off-axis aberration across the spectral range.We introduce a novel integration of optical and mechanical elements to replace traditional assembly,reducing manufacturing and assembly errors,and degrees of freedom,associated with high-power optical elements.Confirming the effectiveness through a combination of simulations and experimental comparisons,the measured mid-wave full-field transfer function exceeds 0.405 at 17 lp/mm,satisfying the imaging requirements of the system.The optical system is lightweight and compact,with a total mass under 408 g and a compact volume of justΦ112 mm×117 mm.This serves as a valuable reference for the engineering application of high-performance,compact multi-band infrared composite detection systems for astronomy and space exploration.展开更多
Ant colony optimization(ACO)is a random search algorithm based on probability calculation.However,the uninformed search strategy has a slow convergence speed.The Bayesian algorithm uses the historical information of t...Ant colony optimization(ACO)is a random search algorithm based on probability calculation.However,the uninformed search strategy has a slow convergence speed.The Bayesian algorithm uses the historical information of the searched point to determine the next search point during the search process,reducing the uncertainty in the random search process.Due to the ability of the Bayesian algorithm to reduce uncertainty,a Bayesian ACO algorithm is proposed in this paper to increase the convergence speed of the conventional ACO algorithm for image edge detection.In addition,this paper has the following two innovations on the basis of the classical algorithm,one of which is to add random perturbations after completing the pheromone update.The second is the use of adaptive pheromone heuristics.Experimental results illustrate that the proposed Bayesian ACO algorithm has faster convergence and higher precision and recall than the traditional ant colony algorithm,due to the improvement of the pheromone utilization rate.Moreover,Bayesian ACO algorithm outperforms the other comparative methods in edge detection task.展开更多
The woodland-steppe ecotone in the. southern Nei Mongol Plateau is located at the northern edge of the east Asian monsoon influences. A marked southeastern - northwestern (SE - NW) precipitation gradient exists in thi...The woodland-steppe ecotone in the. southern Nei Mongol Plateau is located at the northern edge of the east Asian monsoon influences. A marked southeastern - northwestern (SE - NW) precipitation gradient exists in this region. Quantitative reconstruction of palaeo-precipitation of this region is helpful to reveal the development of monsoon climate and to predict die future desertification. Based on modern vegetation and surface pollen studies, a pollen-precipitation transfer function in the study region was established. Pollen data from three sediment sequences within the ecotone were used to reconstruct palaeo-precipitation during the Holocene. The processes of precipitation changes in the three sequences were quite different. There was a tendency of precipitation declined from the onset of the Holocene to 1 100 a BP in Haoluku. But, in Liuzhouwan and Xiaoniuchang, both located south of Haoluku, the annual precipitation reached highest values during 7 800 - 6 200 a BP and 7 200 - 5 000 a BP, respectively. The influences of southwestern (SW) monsoon and the variances of topographical conditions have possibly caused these temporal-spatial variances.展开更多
To simulate the concrete shrinkage in varying temperature and moisture environments, a simulate procedure comprising an analytical process and a finite element analysis is proposed based on the coupled partial differe...To simulate the concrete shrinkage in varying temperature and moisture environments, a simulate procedure comprising an analytical process and a finite element analysis is proposed based on the coupled partial differential equations describing heat and moisture transfer in a porous medium. Using the Laplace transformation method and transfer function to simplify and solve the coupled equations in Laplace domain, the moisture and temperature distribution in time domain are obtained by inverse Laplace transformation. The shrinkage deformations of concrete are numerically simulated by the finite element method （FEM） based on the obtained temperature and moisture distribution. This approach avoids the complex eigenvalues, coupling difficulty and low accuracy found in other solving methods, and also effectively calculates the moisture induced shrinkage which is almost impossible using familiar FEM software. The validity of the simulation procedure is verified by Hundt＇s test data. The results reveal that the proposed approach can be considered a reliable and efficient method to simulate the coupling moisture and temperature shrinkage of concrete.展开更多
By summing geophone and hydrophone data with opposite polarity responses to water layer reverberation,the ocean bottom cable dual-sensor acquisition technique can effectively eliminate reverberation,broaden the freque...By summing geophone and hydrophone data with opposite polarity responses to water layer reverberation,the ocean bottom cable dual-sensor acquisition technique can effectively eliminate reverberation,broaden the frequency bandwidth,and improve both the resolution and fidelity of the seismic data.It is thus widely used in industry.However,it is difficult to ensure good coupling of the geophones with the seabed because of the impact of ocean flow,seafloor topography,and field operations;therefore,geophone data are seriously affected by the transfer function of the geophone-seabed coupling system.As a result,geophone data frequently have low signal-to-noise ratios（S/N）,which causes large differences in amplitude,frequency,and phases between geophone and hydrophone data that severely affect dual-sensor summation.In contrast,the hydrophone detects changes in brine pressure and has no coupling issues with the seabed;thus,hydrophone data always have good S/N.First,in this paper,the mathematical expression of the transfer function between geophone and seabed is presented.Second,the transfer function of the geophone-seabed is estimated using hydrophone data as reference traces,and finally,the coupling correction based on the estimated transfer function is implemented.Using this processing,the amplitude and phase differences between geophone and hydrophone data are removed,and the S/N of the geophone data are improved.Synthetic and real data examples then show that our method is feasible and practical.展开更多
Two mono iron complexes Fe（CO）2PR3（NN） （R = Cy （3）, Ph （4）, NN = o-phenylenediamine dianion ligand, N2H2Ph2-） derived from the ligand substitution of Fe（CO）3hPR3 by the NN ligand were isolated and structur...Two mono iron complexes Fe（CO）2PR3（NN） （R = Cy （3）, Ph （4）, NN = o-phenylenediamine dianion ligand, N2H2Ph2-） derived from the ligand substitution of Fe（CO）3hPR3 by the NN ligand were isolated and structurally characterized by single crystal X-ray diffraction. They have a similar first coordination sphere and oxidation state of the iron center as the [Fe]-hydrogenase active site, and can be a model of it IR demonstrated that the effect of the NN ligand on the coordinated CO stretch- ing frequencies was due to its excellent electron donating ability. The reversible protonation/deprotonation of the NN ligand was identified by infrared spectroscopy and density functional theory computation. The NN ligand is an effective proton acceptor as the internal base of the cysteine thiolate ligand in [Fe]-hydrogenase. The electrochemical properties of complexes 3, 4 were investigated by cyclic voltammograms. Complex 3 catalyzed the transfer hydrogenation of benzoquinone to hydroquinone effectively under mild conditions.展开更多
In this paper,the metal hydraulic engine mount (HEM) with the orifice is presented,the construction of HEM is consist of hydraulic cylinder and the spring on the bottom,its mechanical model is given and dynamics equat...In this paper,the metal hydraulic engine mount (HEM) with the orifice is presented,the construction of HEM is consist of hydraulic cylinder and the spring on the bottom,its mechanical model is given and dynamics equations are set up with considering kinematics conditions and continuous of fluid,the dynamics behavior of HEM including dynamic stiffness of fluid and transferability of HEM are studied here.The example of hydraulic engine mount is calculated,it is shown that the vibration reduction performance of the hydraulic engine mount of this paper is better.The analysis method of vibration reduction behavior for HEM in this paper can be used in designing of the reduction vibration devices and the HEM in this paper can be used in the practical engineering for reduction vibration.展开更多
Based on the fact that the real inductor and the real capacitor are fractional order in nature and the fractional calculus,the transfer function modeling and analysis of the open-loop Buck converter in a continuous co...Based on the fact that the real inductor and the real capacitor are fractional order in nature and the fractional calculus,the transfer function modeling and analysis of the open-loop Buck converter in a continuous conduction mode（CCM） operation are carried out in this paper.The fractional order small signal model and the corresponding equivalent circuit of the open-loop Buck converter in a CCM operation are presented.The transfer functions from the input voltage to the output voltage,from the input voltage to the inductor current,from the duty cycle to the output voltage,from the duty cycle to the inductor current,and the output impedance of the open-loop Buck converter in CCM operation are derived,and their bode diagrams and step responses are calculated,respectively.It is found that all the derived fractional order transfer functions of the system are influenced by the fractional orders of the inductor and the capacitor.Finally,the realization of the fractional order inductor and the fractional order capacitor is designed,and the corresponding PSIM circuit simulation results of the open-loop Buck converter in CCM operation are given to confirm the correctness of the derivations and the theoretical analysis.展开更多
AIM: To describe the characteristics of modulation transfer function (MTF) of anterior corneal surface, and obtain the the normal reference range of MTF at different spatial frequencies and optical zones of the anteri...AIM: To describe the characteristics of modulation transfer function (MTF) of anterior corneal surface, and obtain the the normal reference range of MTF at different spatial frequencies and optical zones of the anterior corneal surface in myopes. METHODS: Four hundred eyes from 200 patients were examined under SIRIUS corneal topography system. Phoenis analysis software was applied to simulate the MTF curves of anterior corneal surface at vertical and horizontal meridians at the 3, 4, 5, 6, 7mm optical zones of cornea. The MTF values at spatial frequencies of 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55 and 60 cycles/degree (c/d) were selected. RESULTS: The MTF curve of anterior corneal surface decreased rapidly from low to intermediate frequency (0-15cpd) at various optical zones of cornea, the value decreased to 0 slowly at higher frequency (>15cpd). With the increase of the optical zones of cornea, MTF curve decreased gradually. 3) In the range of 3 mm- 6 mm optical zones of the cornea, the MTF values measured at horizontal meridian were greater than the corresponding values at horizontal meridian of each spatial frequency, the difference was statistically significant (P<0.05). At 7 mm optical zones of cornea, the MTF values measured at horizontal meridian were less than the corresponding values at vertical meridian at 10-60 spatial frequencies (cpd), and the difference was statistically significant in 25, 30, 35, 40, 45, 50 cpd(P<0.05). CONCLUSION: MTF can be used to describe the imaging quality of optical systems at anterior corneal surface objectively in detail.展开更多
The stripped solar sail whose membrane is divided into separate narrow membrane strips is believed to have the best structural efficiency.In this paper,the stripped solar sail structure is regarded as an assembly made...The stripped solar sail whose membrane is divided into separate narrow membrane strips is believed to have the best structural efficiency.In this paper,the stripped solar sail structure is regarded as an assembly made by connecting a number of boom-strip components in sequence.Considering the coupling effects between booms and membrane strips,an exact and semianalytical method to calculate structural dynamic responses of the stripped solar sail subjected to solar radiation pressure is established.The case study of a 100 m stripped solar sail shows that the stripped architecture helps to reduce the static deflections and amplitudes of the steady-state dynamic response.Larger prestress of the membrane strips will decrease stiffness of the sail and increase amplitudes of the steady-state dynamic response.Increasing thickness of the boom will benefit to stability of the sail and reduce the resonant amplitudes.This proposed semi-analytical method provides an efficient analysis tool for structure design and attitude control of the stripped solar sail.展开更多
The Taihu Lake,a large shallow lake in the floodplain of the Changjiang(Yangtze) River in the eastern China,is faced with challenging ecological problems resulting from eutrophication,which has affected the regional f...The Taihu Lake,a large shallow lake in the floodplain of the Changjiang(Yangtze) River in the eastern China,is faced with challenging ecological problems resulting from eutrophication,which has affected the regional freshwater supply of a large population.Although efforts have been made to assess the nutrient evolution histories in the northern bays,little is known regarding nutrient histories in different parts across the entire lake basin.In this paper,we present nutrient histories for different parts of the lake based on chironomid transfer functions applied to four short cores obtained from the northern,western and eastern regions of the lake.The chironomid-inferred total phosphorus(CI-TP) concentrations were compared with the phosphorus concentrations obtained by using instrumental and sedimentary data.The results suggest that trophic evolution histories were asynchronous throughout the lake during the past decades in response to different ecological regimes controlled by the nutrient input,wind direction and shoreline topography.The restoration of aquatic plants may be an effective option for the management of lake rehabilitation to ′natural′ conditions.Given the multiple factors controlling the biotic communities in such a large and complex lake,combined analyses among the multi-proxies encountered in the sediments are necessary for comprehensive insight into paleolimnological studies.The spatial heterogeneity in the ecological trajectories within this complicated ecosystem suggests that different management practices should be undertaken for specific lake zones in the Taihu Lake.展开更多
This paper proposes a new loop recovery method to solve the reduced order problem of H∞/ LTR method. The resulted lower order controller shares almost the same performance and robustness as the original H ∞/LTR cont...This paper proposes a new loop recovery method to solve the reduced order problem of H∞/ LTR method. The resulted lower order controller shares almost the same performance and robustness as the original H ∞/LTR controller. Further more, this paper develops a new order reduction method: slow-fast mode order reduction (SFMOR) method. This order reduction method is particularly effective for those controllers whose modes can be divided into a slow part and a fast part according to their velocities. Application of these methods to a benchmark example and a certain turbofan engine is described.展开更多
A closed-form out-of-plane dynamic displacement response of a curved track subjected to moving loads was proposed.The track structure was modeled as a planar curved Timoshenko beam periodically supported by the double...A closed-form out-of-plane dynamic displacement response of a curved track subjected to moving loads was proposed.The track structure was modeled as a planar curved Timoshenko beam periodically supported by the double-layer spring-damping elements.The general dynamic displacement response induced by the moving loads along the curve on the elastic semi-infinite space was firstly obtained in the frequency domain,according to the Duhamel integral and the dynamic reciprocity theorem.In the case of the periodic curved track structure subjected to moving loads,the dynamic displacement equation was simplified into a form of summation within the basic track cell instead of the integral.The transfer function for the curved track was expressed in the form of a transfer matrix.Single and series moving loads were involved in the calculation program.For the verification of the analytical model,the mid-span vertical deflection of a simply support curved beam subjected to moving load was recalculated and compared with the same case in the reference.The research results indicate that:under the same moving loads,the displacement response of the curved track decreases slightly with the increasing track radius,and the displacement response of the curved track with the radius greater than or equal to 600 m is almost equivalent to the displacement response of the straight track;the frequency spectrum of the curved track is more abundant than that of the straight track,which may result in more wheel-rail resonance and rail corrugation in the curved lines.展开更多
Confinement of rock bolts by the surrounding rock formation has long been recognized as a positive contributor to the pull-out behavior,yet only a few experimental works and analytical models have been reported,most o...Confinement of rock bolts by the surrounding rock formation has long been recognized as a positive contributor to the pull-out behavior,yet only a few experimental works and analytical models have been reported,most of which are based on the global rock bolt response evaluated in pull-out tests.This paper presents a laboratory experimental setup aiming to capture the rock formation effect,while using distributed fiber optic sensing to quantify the effect of the confinement and the reinforcement pull-out behavior on a more local level.It is shown that the behavior along the sample itself varies,with certain points exhibiting stress drops with crack formation.Some edge effects related to the kinematic freedom of the grout to dilate are also observed.Regardless,it was found that the mid-level response is quite similar to the average response along the sample.The ability to characterize the variation of the response along the sample is one of the many advantages high-resolution fiber optic sensing allows in such investigations.The paper also offers a plasticity-based hardening load transfer function,representing a"slice"of the anchor.The paper describes in detail the development of the model and the calibration/determination of its parameters.The suggested model captures well the coupled behavior in which the pull-out process leads to an increase in the confining stress due to dilative behavior.展开更多
The interstand tension control is one of the most important ways to meet tight tolerances for strip product quality during tandem cold rolling process. Using coordinate analysis and parabolic approximation for the mas...The interstand tension control is one of the most important ways to meet tight tolerances for strip product quality during tandem cold rolling process. Using coordinate analysis and parabolic approximation for the mass flow balance principle, the strip velocities eliminating the use of forward slips and backward slips were calculated. In order to reduce the effect of roll eccentricity on the tension measurement, a filter based on bilinear transformation was de- signed. Applying a first-order Taylor series approximation, the transfer function matrix model of interstand tension stress was derived. The actual measurements on-site and the final calculation results showed that the established model had high calculation accuracy and was beneficial for interstand tension control of random cold rolling process.展开更多
The Vector Hydrophone(VH) is widely used to remotely detect underwater targets. Accurately measuring the self-noise of the VH provides an important basis for evaluating the performance of the detection system in which...The Vector Hydrophone(VH) is widely used to remotely detect underwater targets. Accurately measuring the self-noise of the VH provides an important basis for evaluating the performance of the detection system in which it is utilized, since the ability to acquire weak signals is determined by the VH self-noise level. To accurately measure the VH self-noise level in actual working conditions, the Dual-channel Transfer Function Method(DTFM) is proposed to reduce ambient background noise interference. In this paper, the underlying principles of DTFM in reducing ambient background noise is analyzed. The numerical simulations to determine the influence of ambient background noise, and the sensitivity difference of the two VHs on the measurement results are studied. The results of measuring the VH self-noise level in a small laboratory water tank by using DTMF indicate that ambient background noise interference can be reduced effectively by employing DTMF, more accurate self-noise level can be obtained as well. The DTMF provides an effective method for accurately measuring the self-noise level of VHs and also provides technical support for the practical application of the VH in underwater acoustics.展开更多
基金supported by the National Major Science and Technology Project,China(No.J2019-Ⅳ-0007-0075)the Fundamental Research Funds for the Central Universities,China(No.JKF-20240036)。
文摘To ensure the structural integrity of life-limiting component of aeroengines,Probabilistic Damage Tolerance(PDT)assessment is applied to evaluate the failure risk as required by airworthiness regulations and military standards.The PDT method holds the view that there exist defects such as machining scratches and service cracks in the tenon-groove structures of aeroengine disks.However,it is challenging to conduct PDT assessment due to the scarcity of effective Probability of Detection(POD)model and anomaly distribution model.Through a series of Nondestructive Testing(NDT)experiments,the POD model of real cracks in tenon-groove structures is constructed for the first time by employing the Transfer Function Method(TFM).A novel anomaly distribution model is derived through the utilization of the POD model,instead of using the infeasible field data accumulation method.Subsequently,a framework for calculating the Probability of Failure(POF)of the tenon-groove structures is established,and the aforementioned two models exert a significant influence on the results of POF.
文摘Multiple tuned mass dampers(MTMDs)reduce dynamic response with multiple specified frequencies of building structures.Many optimization algorithms for placement design exist,though they rarely conform to code-based verification nor produce high quality solutions without high computational effort and high complexity.This study proposes an inverse element exchange method(IEEM)with multi-level programming and compares it to a single tuned mass damper(STMD)and uniform distribution of multiple tuned mass dampers in the frequency and time domains.A ten-story shear building is used for the numerical case study.The results show that the proposed method can offer improvement over the STMD,uniform distribution of multiple tuned mass dampers,and distribution optimized by genetic algorithms(GA)with regard to minimizing the interstory drift ratio(IDR)in both the frequency and time domains and the time consumption for optimization.
文摘AIM:To investigate how angles kappa and alpha affect postoperative visual quality in patients with multifocal intraocular lens(mIOLs)implantation.METHODS:Retrospective cases series.A total of 46 patients(46 eyes)who underwent phacoemulsification were subsumed.The correlation between Preoperative angles kappa and alpha,wave-front aberrations and objective visual quality of cornea,internal,and total eye after surgery were analyzed using iTrace.RESULTS:The magnitude of angle kappa was negatively correlated with internal and total modulation transfer function(MTF)at 3 mm;the magnitude of angle kappa was positively correlated with astigmatism,trefoil,higher-order aberrations(HOAs)of both internal and total eye at 3 mm.The magnitude of angle alpha was negatively correlated with total MTF and total Strehl ratio at 3 mm.The magnitude of angle alpha was positively correlated with corneal coma at 5 mm,internal astigmatism at both 3 mm and 5 mm,and total spherical aberration(SA)at 3 mm.Multivariate linear regression analysis showed that,among candidate independent variables(kappa,alpha,astigmatism,SA,coma,trefoil,and HOAs),astigmatism is the only independent factor for altering corneal MTF at 3 mm and 5 mm;astigmatism and HOAs emerged as independent factors for altering internal MTF at 3 mm and 5 mm,and total MTF at 3 mm;astigmatism,SA and HOAs emerged as independent factors for altering total MTF at 5 mm.CONCLUSION:With greater preoperative angle kappa or angle alpha,patients who accept mIOL implantation tend to have larger internal astigmatism and HOAs,which resulting in poor visual quality,especially those with small pupil size.
基金Supported by Fundamental Research Funds for the Central Universities(Grant No.2024QYBS031)Fundamental Research Funds for the Central Universities(Grant No.2022JBQY007)。
文摘Current research on rail vehicle system vibrations primarily relies on numerical methods,with vibration transfer functions commonly derived through data fitting.However,the physical mechanisms underlying these vibrations are not well understood.To clarify the vibration transfer function and its characteristics,four basic input vectors are defined,and an analytical method is proposed.The vibration transfer functions of the vehicle system are solved,and their spatial coherence is analyzed.The results show that there are two spatial scales and four coherent modes in the vehicle system.The track irregularity wavelengths are combined with two spatial scales to alter the proportions of basic input vectors and then show the characteristics of spatial coherence.Four coherent modes are involved in wheel-rail force and primary suspension force;two coherent modes are involved in bogie vertical motion;and their dominant modes vary with the input frequency.On the other hand,the coherent modes involved in the bogie pitching motion and vehicle body motion are single and fixed over the whole range of frequency.This study presents an analytical method for the rapid solution of dynamic responses in vehicle systems and systematically analyzes the coherence behavior of vibration transfer functions with respect to tracking irregularity wavelengths.
基金National Natural Science Foundation of China(12073028,12473084).
文摘Continuing advancement in astronomy,space exploration,and scientific detection,has increased demand for infrared multi-band detection systems.Traditional three-band optical systems,designed to simultaneously image at infrared short-wave,mid-wave,and long-wave bands typically rely on dispersive elements,leading to bulky sizes,complex system architectures,low efficiency,and challenges in rapid assembly.To overcome these obstacles,in combination with the latest third-generation infrared detectors,we propose a design for a compact and lightweight three-band optical system,with infrared capabilities in all three required bands.The core of this approach is an integrated design philosophy that emphasizes the high steepness of mirror surfaces.This design achieves uniform correction and optimization of chromatic aberration and off-axis aberration across the spectral range.We introduce a novel integration of optical and mechanical elements to replace traditional assembly,reducing manufacturing and assembly errors,and degrees of freedom,associated with high-power optical elements.Confirming the effectiveness through a combination of simulations and experimental comparisons,the measured mid-wave full-field transfer function exceeds 0.405 at 17 lp/mm,satisfying the imaging requirements of the system.The optical system is lightweight and compact,with a total mass under 408 g and a compact volume of justΦ112 mm×117 mm.This serves as a valuable reference for the engineering application of high-performance,compact multi-band infrared composite detection systems for astronomy and space exploration.
基金supported by the National Natural Science Foundation of China(62276055).
文摘Ant colony optimization(ACO)is a random search algorithm based on probability calculation.However,the uninformed search strategy has a slow convergence speed.The Bayesian algorithm uses the historical information of the searched point to determine the next search point during the search process,reducing the uncertainty in the random search process.Due to the ability of the Bayesian algorithm to reduce uncertainty,a Bayesian ACO algorithm is proposed in this paper to increase the convergence speed of the conventional ACO algorithm for image edge detection.In addition,this paper has the following two innovations on the basis of the classical algorithm,one of which is to add random perturbations after completing the pheromone update.The second is the use of adaptive pheromone heuristics.Experimental results illustrate that the proposed Bayesian ACO algorithm has faster convergence and higher precision and recall than the traditional ant colony algorithm,due to the improvement of the pheromone utilization rate.Moreover,Bayesian ACO algorithm outperforms the other comparative methods in edge detection task.
文摘The woodland-steppe ecotone in the. southern Nei Mongol Plateau is located at the northern edge of the east Asian monsoon influences. A marked southeastern - northwestern (SE - NW) precipitation gradient exists in this region. Quantitative reconstruction of palaeo-precipitation of this region is helpful to reveal the development of monsoon climate and to predict die future desertification. Based on modern vegetation and surface pollen studies, a pollen-precipitation transfer function in the study region was established. Pollen data from three sediment sequences within the ecotone were used to reconstruct palaeo-precipitation during the Holocene. The processes of precipitation changes in the three sequences were quite different. There was a tendency of precipitation declined from the onset of the Holocene to 1 100 a BP in Haoluku. But, in Liuzhouwan and Xiaoniuchang, both located south of Haoluku, the annual precipitation reached highest values during 7 800 - 6 200 a BP and 7 200 - 5 000 a BP, respectively. The influences of southwestern (SW) monsoon and the variances of topographical conditions have possibly caused these temporal-spatial variances.
基金The National Natural Science Foundation of China(No50539040)the Trans-Century Training Programme Foundation forthe Talents by the State Education Commission (NoNCET-05-0473)
文摘To simulate the concrete shrinkage in varying temperature and moisture environments, a simulate procedure comprising an analytical process and a finite element analysis is proposed based on the coupled partial differential equations describing heat and moisture transfer in a porous medium. Using the Laplace transformation method and transfer function to simplify and solve the coupled equations in Laplace domain, the moisture and temperature distribution in time domain are obtained by inverse Laplace transformation. The shrinkage deformations of concrete are numerically simulated by the finite element method （FEM） based on the obtained temperature and moisture distribution. This approach avoids the complex eigenvalues, coupling difficulty and low accuracy found in other solving methods, and also effectively calculates the moisture induced shrinkage which is almost impossible using familiar FEM software. The validity of the simulation procedure is verified by Hundt＇s test data. The results reveal that the proposed approach can be considered a reliable and efficient method to simulate the coupling moisture and temperature shrinkage of concrete.
文摘By summing geophone and hydrophone data with opposite polarity responses to water layer reverberation,the ocean bottom cable dual-sensor acquisition technique can effectively eliminate reverberation,broaden the frequency bandwidth,and improve both the resolution and fidelity of the seismic data.It is thus widely used in industry.However,it is difficult to ensure good coupling of the geophones with the seabed because of the impact of ocean flow,seafloor topography,and field operations;therefore,geophone data are seriously affected by the transfer function of the geophone-seabed coupling system.As a result,geophone data frequently have low signal-to-noise ratios（S/N）,which causes large differences in amplitude,frequency,and phases between geophone and hydrophone data that severely affect dual-sensor summation.In contrast,the hydrophone detects changes in brine pressure and has no coupling issues with the seabed;thus,hydrophone data always have good S/N.First,in this paper,the mathematical expression of the transfer function between geophone and seabed is presented.Second,the transfer function of the geophone-seabed is estimated using hydrophone data as reference traces,and finally,the coupling correction based on the estimated transfer function is implemented.Using this processing,the amplitude and phase differences between geophone and hydrophone data are removed,and the S/N of the geophone data are improved.Synthetic and real data examples then show that our method is feasible and practical.
基金supported by the National Natural Science Foundation of China(21103121,21276187)Tianjin Municipal Natural Science Foundation(13JCQNJC05800)the Specialized Research Fund for the Doctoral Program of Higher Education(20121317110009)~~
文摘Two mono iron complexes Fe（CO）2PR3（NN） （R = Cy （3）, Ph （4）, NN = o-phenylenediamine dianion ligand, N2H2Ph2-） derived from the ligand substitution of Fe（CO）3hPR3 by the NN ligand were isolated and structurally characterized by single crystal X-ray diffraction. They have a similar first coordination sphere and oxidation state of the iron center as the [Fe]-hydrogenase active site, and can be a model of it IR demonstrated that the effect of the NN ligand on the coordinated CO stretch- ing frequencies was due to its excellent electron donating ability. The reversible protonation/deprotonation of the NN ligand was identified by infrared spectroscopy and density functional theory computation. The NN ligand is an effective proton acceptor as the internal base of the cysteine thiolate ligand in [Fe]-hydrogenase. The electrochemical properties of complexes 3, 4 were investigated by cyclic voltammograms. Complex 3 catalyzed the transfer hydrogenation of benzoquinone to hydroquinone effectively under mild conditions.
基金Supported by National Fund Committee for Study Abroad
文摘In this paper,the metal hydraulic engine mount (HEM) with the orifice is presented,the construction of HEM is consist of hydraulic cylinder and the spring on the bottom,its mechanical model is given and dynamics equations are set up with considering kinematics conditions and continuous of fluid,the dynamics behavior of HEM including dynamic stiffness of fluid and transferability of HEM are studied here.The example of hydraulic engine mount is calculated,it is shown that the vibration reduction performance of the hydraulic engine mount of this paper is better.The analysis method of vibration reduction behavior for HEM in this paper can be used in designing of the reduction vibration devices and the HEM in this paper can be used in the practical engineering for reduction vibration.
基金Project supported by the National Natural Science Foundation of China (Grant No. 51007068)the Specialized Research Fund for the Doctoral Program of Higher Education of China (Grant No. 20100201120028)+2 种基金the Natural Science Basic Research Plan in Shaanxi Province of China (Grant No. 2012JQ7026)the Fundamental Research Funds for the Central Universities of China (Grant No. 2012jdgz09)the State Key Laboratory of Electrical Insulation and Power Equipment of China (Grant No. EIPE12303)
文摘Based on the fact that the real inductor and the real capacitor are fractional order in nature and the fractional calculus,the transfer function modeling and analysis of the open-loop Buck converter in a continuous conduction mode（CCM） operation are carried out in this paper.The fractional order small signal model and the corresponding equivalent circuit of the open-loop Buck converter in a CCM operation are presented.The transfer functions from the input voltage to the output voltage,from the input voltage to the inductor current,from the duty cycle to the output voltage,from the duty cycle to the inductor current,and the output impedance of the open-loop Buck converter in CCM operation are derived,and their bode diagrams and step responses are calculated,respectively.It is found that all the derived fractional order transfer functions of the system are influenced by the fractional orders of the inductor and the capacitor.Finally,the realization of the fractional order inductor and the fractional order capacitor is designed,and the corresponding PSIM circuit simulation results of the open-loop Buck converter in CCM operation are given to confirm the correctness of the derivations and the theoretical analysis.
文摘AIM: To describe the characteristics of modulation transfer function (MTF) of anterior corneal surface, and obtain the the normal reference range of MTF at different spatial frequencies and optical zones of the anterior corneal surface in myopes. METHODS: Four hundred eyes from 200 patients were examined under SIRIUS corneal topography system. Phoenis analysis software was applied to simulate the MTF curves of anterior corneal surface at vertical and horizontal meridians at the 3, 4, 5, 6, 7mm optical zones of cornea. The MTF values at spatial frequencies of 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55 and 60 cycles/degree (c/d) were selected. RESULTS: The MTF curve of anterior corneal surface decreased rapidly from low to intermediate frequency (0-15cpd) at various optical zones of cornea, the value decreased to 0 slowly at higher frequency (>15cpd). With the increase of the optical zones of cornea, MTF curve decreased gradually. 3) In the range of 3 mm- 6 mm optical zones of the cornea, the MTF values measured at horizontal meridian were greater than the corresponding values at horizontal meridian of each spatial frequency, the difference was statistically significant (P<0.05). At 7 mm optical zones of cornea, the MTF values measured at horizontal meridian were less than the corresponding values at vertical meridian at 10-60 spatial frequencies (cpd), and the difference was statistically significant in 25, 30, 35, 40, 45, 50 cpd(P<0.05). CONCLUSION: MTF can be used to describe the imaging quality of optical systems at anterior corneal surface objectively in detail.
基金supported by the National Natural Science Foundation of China(No.11572001)。
文摘The stripped solar sail whose membrane is divided into separate narrow membrane strips is believed to have the best structural efficiency.In this paper,the stripped solar sail structure is regarded as an assembly made by connecting a number of boom-strip components in sequence.Considering the coupling effects between booms and membrane strips,an exact and semianalytical method to calculate structural dynamic responses of the stripped solar sail subjected to solar radiation pressure is established.The case study of a 100 m stripped solar sail shows that the stripped architecture helps to reduce the static deflections and amplitudes of the steady-state dynamic response.Larger prestress of the membrane strips will decrease stiffness of the sail and increase amplitudes of the steady-state dynamic response.Increasing thickness of the boom will benefit to stability of the sail and reduce the resonant amplitudes.This proposed semi-analytical method provides an efficient analysis tool for structure design and attitude control of the stripped solar sail.
基金Under the auspices of National Basic Research Program of China(No.2012CB9561002008CB418103)National Natural Science Foundation of China(No.41072267)
文摘The Taihu Lake,a large shallow lake in the floodplain of the Changjiang(Yangtze) River in the eastern China,is faced with challenging ecological problems resulting from eutrophication,which has affected the regional freshwater supply of a large population.Although efforts have been made to assess the nutrient evolution histories in the northern bays,little is known regarding nutrient histories in different parts across the entire lake basin.In this paper,we present nutrient histories for different parts of the lake based on chironomid transfer functions applied to four short cores obtained from the northern,western and eastern regions of the lake.The chironomid-inferred total phosphorus(CI-TP) concentrations were compared with the phosphorus concentrations obtained by using instrumental and sedimentary data.The results suggest that trophic evolution histories were asynchronous throughout the lake during the past decades in response to different ecological regimes controlled by the nutrient input,wind direction and shoreline topography.The restoration of aquatic plants may be an effective option for the management of lake rehabilitation to ′natural′ conditions.Given the multiple factors controlling the biotic communities in such a large and complex lake,combined analyses among the multi-proxies encountered in the sediments are necessary for comprehensive insight into paleolimnological studies.The spatial heterogeneity in the ecological trajectories within this complicated ecosystem suggests that different management practices should be undertaken for specific lake zones in the Taihu Lake.
文摘This paper proposes a new loop recovery method to solve the reduced order problem of H∞/ LTR method. The resulted lower order controller shares almost the same performance and robustness as the original H ∞/LTR controller. Further more, this paper develops a new order reduction method: slow-fast mode order reduction (SFMOR) method. This order reduction method is particularly effective for those controllers whose modes can be divided into a slow part and a fast part according to their velocities. Application of these methods to a benchmark example and a certain turbofan engine is described.
基金Project supported by the National Natural Science Foundation of China(Nos.51008017 and 51378001)the Research Fund for Beijing Postdoctoral Work,and the Innovation Fund for PhD of Beijing Jiaotong University(No.2011YJS261),China
文摘A closed-form out-of-plane dynamic displacement response of a curved track subjected to moving loads was proposed.The track structure was modeled as a planar curved Timoshenko beam periodically supported by the double-layer spring-damping elements.The general dynamic displacement response induced by the moving loads along the curve on the elastic semi-infinite space was firstly obtained in the frequency domain,according to the Duhamel integral and the dynamic reciprocity theorem.In the case of the periodic curved track structure subjected to moving loads,the dynamic displacement equation was simplified into a form of summation within the basic track cell instead of the integral.The transfer function for the curved track was expressed in the form of a transfer matrix.Single and series moving loads were involved in the calculation program.For the verification of the analytical model,the mid-span vertical deflection of a simply support curved beam subjected to moving load was recalculated and compared with the same case in the reference.The research results indicate that:under the same moving loads,the displacement response of the curved track decreases slightly with the increasing track radius,and the displacement response of the curved track with the radius greater than or equal to 600 m is almost equivalent to the displacement response of the straight track;the frequency spectrum of the curved track is more abundant than that of the straight track,which may result in more wheel-rail resonance and rail corrugation in the curved lines.
基金funding support from the Israeli Ministry of Housing and Construction(Grant No.2028286).
文摘Confinement of rock bolts by the surrounding rock formation has long been recognized as a positive contributor to the pull-out behavior,yet only a few experimental works and analytical models have been reported,most of which are based on the global rock bolt response evaluated in pull-out tests.This paper presents a laboratory experimental setup aiming to capture the rock formation effect,while using distributed fiber optic sensing to quantify the effect of the confinement and the reinforcement pull-out behavior on a more local level.It is shown that the behavior along the sample itself varies,with certain points exhibiting stress drops with crack formation.Some edge effects related to the kinematic freedom of the grout to dilate are also observed.Regardless,it was found that the mid-level response is quite similar to the average response along the sample.The ability to characterize the variation of the response along the sample is one of the many advantages high-resolution fiber optic sensing allows in such investigations.The paper also offers a plasticity-based hardening load transfer function,representing a"slice"of the anchor.The paper describes in detail the development of the model and the calibration/determination of its parameters.The suggested model captures well the coupled behavior in which the pull-out process leads to an increase in the confining stress due to dilative behavior.
基金Item Sponsored by Fundamental Research Funds for the Central Universities of China(N110307001)
文摘The interstand tension control is one of the most important ways to meet tight tolerances for strip product quality during tandem cold rolling process. Using coordinate analysis and parabolic approximation for the mass flow balance principle, the strip velocities eliminating the use of forward slips and backward slips were calculated. In order to reduce the effect of roll eccentricity on the tension measurement, a filter based on bilinear transformation was de- signed. Applying a first-order Taylor series approximation, the transfer function matrix model of interstand tension stress was derived. The actual measurements on-site and the final calculation results showed that the established model had high calculation accuracy and was beneficial for interstand tension control of random cold rolling process.
文摘The Vector Hydrophone(VH) is widely used to remotely detect underwater targets. Accurately measuring the self-noise of the VH provides an important basis for evaluating the performance of the detection system in which it is utilized, since the ability to acquire weak signals is determined by the VH self-noise level. To accurately measure the VH self-noise level in actual working conditions, the Dual-channel Transfer Function Method(DTFM) is proposed to reduce ambient background noise interference. In this paper, the underlying principles of DTFM in reducing ambient background noise is analyzed. The numerical simulations to determine the influence of ambient background noise, and the sensitivity difference of the two VHs on the measurement results are studied. The results of measuring the VH self-noise level in a small laboratory water tank by using DTMF indicate that ambient background noise interference can be reduced effectively by employing DTMF, more accurate self-noise level can be obtained as well. The DTMF provides an effective method for accurately measuring the self-noise level of VHs and also provides technical support for the practical application of the VH in underwater acoustics.
