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Analysis of the optical quality by determining the modulation transfer function for anterior corneal surface in myopes 认领 引用 被引量：6
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作者 Yan-Zhen Zheng Yan-Peng Chen +2 位作者 Yan Qiu Guo-Guang Zhai Yao-Yu Li 《International Journal of Ophthalmology(English edition)》 SCIE CAS 2012年第2期196-201,共6页
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 c... 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
关键词 modulation transfer function optical quality cornea point spread function optical transfer function phase transfer function
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Vibration Transfer Function of Railway Vehicle System and its Spatial Coherence Under Vertical Track Irregularity Conditions 认领 引用
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作者 Peng Lu Xi Wang Yu Hou 《Chinese Journal of Mechanical Engineering》 SCIE EI CAS CSCD 2025年第2期374-393,共20页
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
关键词 Vertical track irregularity Vibration transfer function Spatial coherence Dominant mode Transfer matrix method
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Solving the atmospheric scattering optical transfer function using the multi-coupled single scattering method 认领 引用 被引量：2
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作者 孙斌 洪津 孙晓兵 《Chinese Physics B》 SCIE EI CAS CSCD 2014年第9期200-204,共5页
The atmospheric scattering optical transfer function （OTF） is solved by applying the multi-coupled single scattering （MCSS） method to the three-dimensional radiative transfer equation （RTE） under the periodic gr... The atmospheric scattering optical transfer function （OTF） is solved by applying the multi-coupled single scattering （MCSS） method to the three-dimensional radiative transfer equation （RTE） under the periodic ground condition. This approach is a direct hit to the atmospheric scattering OTF using the same original context of modulation transfer function （MTF） measurement, i.e., images of sinusoidal grating at different spatial frequencies. Both the amplitude and phase shift of the OTF at various zenith and azimuth angles can be obtained at an arbitrary spatial frequency. 展开更多
关键词 atmospheric scattering optical transfer function modulation transfer function multi-coupled single scattering method
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A hardening load transfer function for rock bolts and its calibration using distributed fiber optic sensing 认领 引用 被引量：9
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作者 Assaf Klar Ori Nissim Itai Elkayam 《Journal of Rock Mechanics and Geotechnical Engineering》 SCIE CSCD 2023年第11期2816-2830,共15页
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
关键词 Rock bolts Distributed fiber optic sensing Pull-out tests Load transfer function Hardening model
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Optical Transfer Function Reconstruction in Incoherent Fourier Ptychography 认领 引用 被引量：3
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作者 谢宗良 亓波 +5 位作者 马浩统 任戈 谭玉凤 贺璧 曾恒亮 江川 《Chinese Physics Letters》 SCIE EI CAS CSCD 2016年第4期48-51,共4页
An optical transfer function （OTF） reconstruction model is first embedded into incoherent Fourier ptychography （IFP）. The leading result is a proposed algorithm that can recover both the super-resolution image and... An optical transfer function （OTF） reconstruction model is first embedded into incoherent Fourier ptychography （IFP）. The leading result is a proposed algorithm that can recover both the super-resolution image and the OTF of an imaging system with unknown aberrations simultaneously. This model overcomes the difficult problem of OTF estimation that the previous IFP faces. The effectiveness of this algorithm is demonstrated by numerical simulations, and the superior reconstruction is presented. We believe that the reported algorithm can extend the original IFP for more complex conditions and may provide a solution by using structured light for characterization of optical systems＇ aberrations. 展开更多
关键词 OTF IFP Optical Transfer Function Reconstruction in Incoherent Fourier Ptychography of in
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Transfer function modeling and analysis of the open-loop Buck converter using the fractional calculus 认领 引用 被引量：14
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作者 王发强 马西奎 《Chinese Physics B》 SCIE EI CAS CSCD 2013年第3期232-239,共8页
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
关键词 Buck converter small signal equivalent circuit model fractional calculus transfer function
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A new modulation transfer function for ocean wave spectra retrieval from X-band marine radar imagery 认领 引用 被引量：4
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作者 陈忠彪 张彪 +2 位作者 何宜军 丘仲锋 PERRIE William 《Chinese Journal of Oceanology and Limnology》 CSCD 2015年第5期1132-1141,共10页
When imaging ocean surface waves by X-band marine radar, the radar backscatter from the sea surface is modulated by the long surface gravity waves. The modulation transfer function （MTF） comprises tilt, hydrodynamic... When imaging ocean surface waves by X-band marine radar, the radar backscatter from the sea surface is modulated by the long surface gravity waves. The modulation transfer function （MTF） comprises tilt, hydrodynamic, and shadowing modulations. A conventional linear MTF was derived using HH-polarized radar observations under conditions of deep water. In this study, we propose a new quadratic polynomial MTF based on W-polarized radar measurements taken from heterogeneous nearshore wave fields. This new MTF is obtained using a radar-observed image spectrum and in situ buoy-measured wave frequency spectrum. We validate the MTF by comparing peak and mean wave periods retrieved from X-band marine radar image sequences with those measured by the buoy. It is shown that the retrieval accuracies of peak and mean wave periods of the new MTF are better than the conventional MTF. The results also show that the bias and root mean square errors of the peak and mean wave periods of the new MTF are 0.05 and 0.88 s, and 0.32 and 0.53 s, respectively, while those of the conventional MTF are 0.61 and 0.98 s, and 1.39 and 1.48 s, respectively. Moreover, it is also shown that the retrieval results are insensitive to the coefficients in the proposed MTF. 展开更多
关键词 X-band marine radar modulation transfer function ocean wave spectra
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Testing the transfer functions for the Geonor T-200B and Chinese standard precipitation gauge in the central Qinghai-Tibet Plateau 认领 引用 被引量：2
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作者 ZHANG Le-le GAO Li-ming +6 位作者 CHEN Ji ZHAO Lin CHEN Ke-long ZHAO Jing-yi LIU Guo-jun SONG Ting-xi LI Yan-kun 《Journal of Mountain Science》 SCIE CSCD 2022年第7期1974-1987,共14页
Accurately measuring precipitation is integral for understanding water cycle processes and assessing climate change in the Qinghai–Tibet Plateau(QTP).The Geonor T-200B weighing precipitation gauge with a single Alter... Accurately measuring precipitation is integral for understanding water cycle processes and assessing climate change in the Qinghai–Tibet Plateau(QTP).The Geonor T-200B weighing precipitation gauge with a single Alter shield(Geonor)and the Chinese standard precipitation gauge(CSPG)are widely used for measuring precipitation in the QTP.However,their measurements need to be adjusted for wetting loss,evaporation loss and windinduced undercatch.Four existing transfer functions for adjusting the Geonor-recorded and three transfer functions for adjusting the CSPG-recorded precipitation at hourly,daily or event scale has been proposed based on the precipitation intercomparison experiments conducted at a single site in different regions.Two latest transfer functions for the Geonor(which are referred to as K2017a and K2017b)at the half-hour time scale based on the precipitation intercomparison experiments at multiple stations in the northern hemisphere were provided in the World Meteorological Organization Solid Precipitation Intercomparison Experiment.However,the applicability of these transfer functions in the QTP has not been evaluated.Therefore,the current study carried out a precipitation measurement intercomparison experiment between August 2018 and September 2020 at a site in Beiluhe in central QTP.The performance of these transfer functions at this site was also evaluated on the basis of mean bias(MB),root mean squared error(RMSE)and relative total catch(RTC).The results are as follows:First,the unadjusted RTC values of the Geonor for rain,mixed(snow mixed with rain),snow and hail are 92.06%,85.35%,64.11%and 91.82%,respectively,and the unadjusted RTC values of the CSPG for the same precipitation types are 92.59%,81.32%,46.43%and 95.56%,respectively.Second,K2017a has the most accurate adjustment results for the Geonor-recorded snow and mixed precipitation at the half-hour time scale,and the post-adjustment RTC values increased to 98.25%and 98.23%,respectively.M2007e,an event-based transfer function,was found to have the most accurate adjustment results for the Geonorrecorded snow precipitation at the event scale,and the post-adjustment RTC value increased to 96.36%.Third,the existing transfer functions for CSPG underestimate snowfall,while overestimating rainfall.Fourth,hail is a significant precipitation type in central QTP.The catch efficiency of hail precipitation and the temperature when hail precipitation occurs are close to those of rain;moreover,the transfer functions for rain are suitable for hail as well. 展开更多
关键词 Precipitation observation errors Transfer function Geonor T-200B CSPG Qinghai-Tibet Plateau
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Modulation transfer function characteristic of uniform-doping transmission-mode GaAs/GaAlAs photocathode 认领 引用 被引量：3
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作者 任玲 常本康 《Chinese Physics B》 SCIE EI CAS CSCD 2011年第8期398-402,共5页
The resolution characteristic can be obtained by the modulation transfer function （MTF） of a GaAs/GaA1As photocathode. After establishing the theoretical model of GaAs（100）-oriented atomic configuration and the fo... The resolution characteristic can be obtained by the modulation transfer function （MTF） of a GaAs/GaA1As photocathode. After establishing the theoretical model of GaAs（100）-oriented atomic configuration and the formula for the ionized impurity scattering of the non-equilibrium carriers, this paper calculates the trajectories of photoelectrons in a photocathode. Thus the distribution of photoelectron spots on the emit-face is obtained, which is namely the point spread function. The MTF is obtained by Fourier transfer of the line spread function obtained from the point spread function. The MTF obtained from these calculations is shown to depend heavily on the electron diffusion length, and enhanced considerably by decreasing the electron diffusion length and increasing the doping concentration. Furthermore, the resolution is enhanced considerably by increasing the active-layer thickness, especially at high spatial frequencies. The best spatial resolution is 860 lp/mm, for the GaAs photocathode of doping concentration 1 ×10^19 cm 3 electron diffusion length 3.6 μm and the active-layer thickness 2 μm, under the 633-nm light irradiated. This research will contribute to the future improvement of the cathode＇s resolution for preparing a high performance GaAs photocathode, and improve the resolution of a low light level image intensifier. 展开更多
关键词 GaAs/GaAlAs photocathode uniform-doping modulation transfer function spatial res-olution
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Mathematical simulations of the galvanic coupling intra-body communication by using the transfer function method 认领 引用 被引量：1
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作者 宋勇 张凯 +3 位作者 郝群 王明 褚怡芳 康邦志 《Journal of Beijing Institute of Technology》 EI CAS 2011年第2期249-255,共7页
The galvanic coupling intra-body communication （IBC） was mathematically simulated based on the proposed transfer function. Firstly, a galvanic coupling IBC circuit model was developed and the corresponding parameter... The galvanic coupling intra-body communication （IBC） was mathematically simulated based on the proposed transfer function. Firstly, a galvanic coupling IBC circuit model was developed and the corresponding parameters were discussed. Secondly, the transfer function of the galvanic coupling IBC was derived and proposed. Finally, the signal attenuation characteristics of the galvanic coupling IBC were measured along different signal transmission paths of actual human bodies, while the corresponding mathematical simulations based on the proposed transfer function were carried out. Our investigation showed that the mathematical simulation results coincided with the measured results over the frequency range of 100kHz to 5MHz, which indicated that the proposed transfer function could be useful for theoretical analysis and application of the galvanic coupling IBC. 展开更多
关键词 intra-body communication transfer function simulation personal area network
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Spectrum Characteristics and Transfer Function of the Hydrograph of the Deep Aqueous System 认领 引用 被引量：1
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作者 Chen Baoren, Liu Shuyun, Earth Sciences Dept., Nanjing University, Nanjing, Jiangsu, China Jin Peikang Geological Dept., Tulane University, New Orleans, LA 70118, U.S.A. and Dong Shouyu Hebei Province Seismological Bureau, Shijiazhuang, Hebei, China 《Acta Geologica Sinica(English Edition)》 SCIE CAS 1993年第4期453-464,共12页
The fluctuation of most of the hydrograph in the deep aqueous system records the fluid pulsation in lithosphere and variation of the earth's crust. Many observations have verified that groundwater is an ideal info... The fluctuation of most of the hydrograph in the deep aqueous system records the fluid pulsation in lithosphere and variation of the earth's crust. Many observations have verified that groundwater is an ideal information carrier of the crust. In this paper, the series of input (precipitation, air pressure, Earth tide etc.) and output (water level, artesian flow) of the deep aqueous system are studied by using the spectrum analysis and system theory. The application concepts of transfer function and the spectral structure of the hydrograph enrich the knowledge of the deep aqueous system. Two typical spectral structures of the hydrograph of the deep aqueous system are obtained by comparing with many water-bearing systems of the Jizhong depression. One is from well Ma-17 and the other is from the well Xinze-5. Finally, the physical models of forming the spectrum of the hydrograph are constructed on the basis of the spectrum research on the deep aqueous system. 展开更多
关键词 deep aqueous system hydrograph transfer function
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INTERPOLATION OF HEAD-RELATED TRANSFER FUNCTIONS USING SPHERICAL FOURIER EXPANSION 认领 引用 被引量：1
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作者 Huang Qinghua Fang Yong 《Journal of Electronics(China)》 2009年第4期571-576,共6页
A new interpolation algorithm for Head-Related Transfer Function （HRTF） is proposed to realize 3D sound reproduction via headphones in arbitrary spatial direction. HRTFs are modeled as a weighted sum of spherical ha... A new interpolation algorithm for Head-Related Transfer Function （HRTF） is proposed to realize 3D sound reproduction via headphones in arbitrary spatial direction. HRTFs are modeled as a weighted sum of spherical harmonics on a spherical surface. Truncated Singular Value Decomposition （SVD） is adopted to calculate the weights of the model. The truncation number is chosen according to Frobenius norm ratio and the partial condition number. Compared with other interpolated methods, our proposed approach not only is continuous but exploits global information of available directions. The HRTF from any desired direction can be and interpolated results demonstrate that our obtained more accurately and robustly. Reconstructed proposed algorithm acquired better performance. 展开更多
关键词 Head-Related Transfer Function （HRTF） Interpolation Spherical Fourier Expansion （SFE） Truncated Singular Value Decomposition （SVD） Partial condition number
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Multiple Scattering Between Adjacent Sound Sources in Head-Related Transfer Function Measurement System 认领 引用
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作者 Guangzheng Yu Yu Liu +1 位作者 Bosun Xie Huali Zhou 《Sound & Vibration》 EI 2019年第4期151-159,共9页
To accelerate head-related transfer functions(HRTFs)measurement,two or more independent sound sources are usually employed in the measurement system.However,the multiple scattering between adjacent sound sources may i... To accelerate head-related transfer functions(HRTFs)measurement,two or more independent sound sources are usually employed in the measurement system.However,the multiple scattering between adjacent sound sources may influence the accuracy of measurement.On the other hand,the directivity of sound source could induce measurement error.Therefore,a model consisting of two spherical sound sources with approximate omni-directivity and a rigid-spherical head is proposed to evaluate the errors in HRTF measurement caused by multiple scattering between sources.An example of analysis using multipole re-expansion indicates that the error of ipsilateral HRTFs are within the bound of±1.0 dB below a frequency of 20 kHz,provided that the sound source radius does not exceed 0.025 m,the source distance relative to head center is not less than 0.5 m,and the angular interval between two adjacent sources is not less than 20 degrees.Similar conclusions under different conditions can also be analyzed and discussed by using this calculation method.Furthermore,the results are verified by measurements of HRTFs for a rigid sphere and a KEMAR artificial head. 展开更多
关键词 Head-related transfer function near field measurement error multiple scattering
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Transfer Function Relating Compressive Pressure to Interfacial Stress Sensor for Biomedical Applications 认领 引用
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作者 吕晓洲 卢文科 张建军 《Journal of Donghua University(English Edition)》 EI CAS 2013年第1期34-37,共4页
To help comfort for an amputee, it is important to understand the load distribution between the residual limb and the prosthetic socket for a prosthetic socket system. An interfacial stress sensor was presented which ... To help comfort for an amputee, it is important to understand the load distribution between the residual limb and the prosthetic socket for a prosthetic socket system. An interfacial stress sensor was presented which was capable of measuring compressive pressure and shear stress simultaneously. A mathematical model was built and an experiment was conducted to obtain the transfer function of interfacial stress sensor to compressive pressure. The results show that the sensor is capable of measuring a range of 30-217 kPa compressive pressure with a relative error of 32.15% in lower range and 6.22% in upper range. 展开更多
关键词 transfer function interfacial stress sensor residual limb prosthetic socket
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Design method of multivariable PI controller for turboprop engine based on equivalent transfer function 认领 引用
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作者 Shancheng LI Yong WANG Haibo ZHANG 《Chinese Journal of Aeronautics》 SCIE EI CAS CSCD 2024年第9期237-260,共24页
Traditional centralized Proportional Integral(PI)controller design methods based on Equivalent Transfer Functions(ETFs)have poor decoupling effect in turboprop engines.In this paper,a centralized PI design method base... Traditional centralized Proportional Integral(PI)controller design methods based on Equivalent Transfer Functions(ETFs)have poor decoupling effect in turboprop engines.In this paper,a centralized PI design method based on dynamic imaginary matrix and equivalent transfer function is proposed.Firstly,a method for solving equivalent transfer functions based on the dynamic imaginary matrix is proposed,which adopts dynamic imaginary matrix to describe the dynamic characteristics of the system,and obtains the equivalent transfer function based on the dynamic imaginary matrix characteristics.Secondly,for the equivalent transfer function,a central-ized PI control gain is designed using the Taylor expansion method.Meanwhile,this paper further proves that the centralized PI design method proposed in this paper has integral stability.Consid-ering the impact of altitude and Mach number on turboprop engines,a linear feedforward control method based on the transfer function matrix is further proposed based on the centralized PI con-troller,and the stability of the entire comprehensive control method is proved.Finally,to ensure the safe and effective operation of the turboprop engine,a temperature and torque limiting protection controller is designed for the turboprop engine.Simulation results show that the centralized PI con-troller design method and linear feedforward control method proposed can effectively improve the control quality of turboprop engine control systems. 展开更多
关键词 Multivariable control sys-tems Equivalent transfer function Disturbance compensation control Control parameter design Turboprop engine control
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Comparison of the retinal modulation transfer function between amblyopes successfully corrected and normal subjects 认领 引用
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作者 Xiao-Ming Huang Xue-Gu Xu Guo-Xing Xu 《International Journal of Ophthalmology(English edition)》 SCIE CAS 2011年第3期284-285,共2页
AIM:To analyze the retinal modulation transfer function between amblyopes whose visual acuity was corrected to 5.0 and normal subjects at the same age.METHODS:RM-800 used to detect contrast sensitivity was adopted to ... AIM:To analyze the retinal modulation transfer function between amblyopes whose visual acuity was corrected to 5.0 and normal subjects at the same age.METHODS:RM-800 used to detect contrast sensitivity was adopted to measure MTF of 96 amblyopes(96 eyes)whose visual acuity was corrected to 5.0 and 80 normal controls(80 eyes)at the same age under six interference fringes(IVA=0.06,0.1,0.2,0.4,0.6,0.8).RESULTS:The functional values of amblyopes were significantly lower than those of normal subjects in every fringe(P<0.01),especially in medium and high frequency.CONCLUSION:For amblyopes,MTF was still abnormal after stopping the treatments. 展开更多
关键词 modulation transfer function amblyope Interference Fringe Visual Acuity
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Fuzzy image restoration using modulation transfer function 认领 引用
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作者 袁媛 Yi Yaohua Liu Juhua 《High Technology Letters》 EI CAS 2016年第4期461-469,共9页
The key difficulty of restoring a fuzzy image is to estimate its point spread function( PSF). In the paper,PSF is modelled based on modulation transfer function( MTF). The first step is calculating the image MTF. In t... The key difficulty of restoring a fuzzy image is to estimate its point spread function( PSF). In the paper,PSF is modelled based on modulation transfer function( MTF). The first step is calculating the image MTF. In the traditional slanted-edge method,a sub-block is always manually extracted from original image and its MTF will be viewed as the result of the whole image. However,handcraft extraction is inefficient and will lead to inaccurate results. Given this,an automatic MTF computation algorithm is proposed,which extracts and screens out all the effective sub-blocks and calculates their average MTF as the final result. Then,a two-dimensional MTF restoration model is constructed by multiplying the horizontal and vertical MTF,and it is combined with conventional image restoration methods to restore fuzzy image. Experimental results indicate the proposed method implementes a fast and accurate MTF computation and the MTF model improves the performance of conventional restoration methods significantly. 展开更多
关键词 fuzzy image modulation transfer function(MTF) slanted-edge method automatic computation MTF restoration model
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MEASURING OF COMPLEX STRUCTURE TRANSFER FUNCTION AND CALCULATING OF INNER SOUND FIELD 认领 引用
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作者 Chen Yuan Huang Qibai Shi Hanmin 《Chinese Journal of Mechanical Engineering》 EI CAS 2005年第4期582-585,共4页
In order to measure complex structure transfer function and calculate inner sound field,transfer function of integration is mentioned.By establishing virtual system,transfer function of integration can be measured and... In order to measure complex structure transfer function and calculate inner sound field,transfer function of integration is mentioned.By establishing virtual system,transfer function of integration can be measured and the inner sound field can also be calculated.In the experiment,automobile body transfer function of integration is measured and experimental method of establishing virtual system is very valid. 展开更多
关键词 Complex structure Virtual system Transfer function of integration
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Establishment of a diatom-total phosphorus transfer function for lakes on the Songnen Plain in northeast China 认领 引用 被引量：3
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作者 SUI Fengyang ZANG Shuying +2 位作者 FAN Yawen LU Xinxin HUI Hongkuan 《Journal of Oceanology and Limnology》 SCIE CAS CSCD 2020年第6期1771-1786,共16页
To understand the relationship between planktonic diatoms and environmental variables in the lakes on the Songnen Plain,northeast(NE)China,we investigated water quality and planktonic diatoms from 71 sampling points i... To understand the relationship between planktonic diatoms and environmental variables in the lakes on the Songnen Plain,northeast(NE)China,we investigated water quality and planktonic diatoms from 71 sampling points in 27 lakes,based on which Canonical Correspondence Analysis(CCA)was conducted.The result show that planktonic diatoms displayed certain responses to environment gradients,and the total phosphorus(TP)explained the maximum variation of planktonic diatom species among the 15 environmental variables,suggesting that TP was the most important and significant environmental parameter affecting the distribution of diatom species.In addition,we established a diatom-total phosphorus transfer(DTPT)function,of which component 5 of the weighted averaging partial least squares regression(WAPLS)was chosen to and compared with a series of weighted average regression(WA)models and WA-PLS models.According to the jackknifing statistical test,the component 5 of WA-PLS models provided a lower root-mean-square error prediction(RMSEP=0.202)and a higher correlation coefficient between observation and prediction(R^2_Jack=0.759).After deletion of three outliers,the root-mean-square error prediction of the DTPT function was reduced(RMSEP=0.169)while the correlation coefficient between observation and prediction was increased(R^2_Jack=0.823).Therefore,this DTPT function performed better than other regional TP models in the world.However,it remains demanding for expanding the background dataset to improve the prediction ability of the model. 展开更多
关键词 Songnen Plain diatom total phosphorus transfer function
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Experimental study on transfer functions of an active rotor under different flight conditions 认领 引用 被引量：5
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作者 Jinlong ZHOU Linghua DONG Weidong YANG 《Chinese Journal of Aeronautics》 SCIE EI CAS CSCD 2022年第8期107-120,共14页
Vibrations impose negative impacts on the effectiveness and public acceptance of helicopters.Active rotors with trailing-edge flaps have been proved to be an effective way to actively eliminate helicopter vibrations.F... Vibrations impose negative impacts on the effectiveness and public acceptance of helicopters.Active rotors with trailing-edge flaps have been proved to be an effective way to actively eliminate helicopter vibrations.For the existing control algorithm based on offline system identification,the transfer functions of an active rotor under different flight conditions are pre-requisites to implement closed-loop vibration control.In this study,a three-bladed active rotor with improved trailing-edge flaps is designed,and wind-tunnel tests are conducted to identify the transfer functions of this active rotor using frequency sweep and phase sweep methods.The experimental results demonstrate that these transfer functions are insensitive to the variation of flight speeds:the amplitude of the transfer function varies slightly,while the phase delay almost remains unchanged.In addition,this finding is validated through closed-loop vibration control tests with the active rotor.The transfer function obtained from the hover test results is also applicable to closed-loop vibration control tests under the forward flight conditions.This will dramatically simplify the implementation and operation of an active rotor. 展开更多
关键词 Active rotor Helicopter Trailing-edge flap Transfer function Vibration control Wind tunnel test
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