This paper addresses the challenges of insufficient navigation accuracy,low path-planning efficiency,and poor environmental adaptability faced by deep space rovers in complex extraterrestrial environments(e.g.,the Moo...This paper addresses the challenges of insufficient navigation accuracy,low path-planning efficiency,and poor environmental adaptability faced by deep space rovers in complex extraterrestrial environments(e.g.,the Moon and Mars).A novel autonomous navigation scheme is proposed that integrates laser Doppler velocimetry(LDV)with star trackers(ST)and inertial navigation system(INS).The scheme suppresses slip errors from wheel odometry through non-contact,high-precision laser speed measurement(accuracy better than 0.1%).By deeply fusing multi-source data via a Kalman filter algorithm,high-precision positioning is realized under extreme extraterrestrial conditions such as weak illumination and dust coverage.This solution features high accuracy,non-contact measurement,and anti-interference capabilities,significantly improving the navigation accuracy and autonomy of deep space rovers in complex environments.展开更多
Experimental results of remote laser measurement of a time structure of a pulse waves are resulted. Occurrence of the pulse waves are connected with the rhythmic reduction of a myocardittm. Speed of pulse wave＇s prop...Experimental results of remote laser measurement of a time structure of a pulse waves are resulted. Occurrence of the pulse waves are connected with the rhythmic reduction of a myocardittm. Speed of pulse wave＇s propagation does not depend on speed of current of blood, it is defined by diameter of a vessel, by its walls thickness, by elasticity of a vessel, and also by rheological properties of blood. Measurement of parameters of pulse waves is important tbr definition of a condition of cardiovascular system. Ways of measurement of characteristics of pulse waves used now （acoustic, electric, optical） are contact. In some cases, for example, in clinics on treatment of burns and so forth, the question of remote measurement of processes hemodynamics by use of methods of laser sotmding is rather actual. The results described in work have shown outlook of development of laser methods of diagnostics for present purposes. The measurement technique used by authors is based on use of longitudinal Doppler effect which essence consists in change of frequency or length of a wave of radiation at reflection from moving surface. For smoothing the measured signal （clearing from noise） the program developed by authors on the basis of the wavelet-analysis was used. Experimental measurements are shown, that the laser method allows to register distinctly structure of pulse waves which is characterized by two peaks. The results of remote laser measurement of a time structure of a pulse waves confirm the assumption made on the basis of general-theoretical physical positions, that characteristics of pulse waves can be registered on the Doppler effect basis.展开更多
Objective To investigate lateralization and Coherence analysis of blood perfusion in bilateral Neiguan （内关 PC 6） in different ages. Methods Healthy volunteers （n=30） were placed in a temperature-controlled room ...Objective To investigate lateralization and Coherence analysis of blood perfusion in bilateral Neiguan （内关 PC 6） in different ages. Methods Healthy volunteers （n=30） were placed in a temperature-controlled room as a resting state for 40 min. Then the blood perfusion of bilateral PC 6 were carried out using PeriFlux System 5000 for 25 minutes. Mean blood flux of every 5 minutes was calculated. Then the participants were divided into groups of young （n=18） and the old （n=12） as the boundary of 40 years, the asymmetry index and coherence value of bilateral PC 6 were analyzed in different group. Results The mean blood flow of the right PC 6 was significantly higher than the left PC 6 in three different epochs, the mean blood flow of right PC 6 vs left PC 6 is 9.74±3.36 vs 6.73±2.22 （t=5.9, P〈0.001）, 9.83±3.63 vs 6.99±2.37 （t=5.11, P〈0.001） and 9.69±3.40 vs 6.77±2.32 （t=5.99, P〈0.001）, respectively. Although the asymmetry index is higher in old group than in young group, there is no statistically significant age-related differences. Coherence analysis suggest that there is significant difference in frequency value corresponding to peak crest between young and old group. Conclusion The blood perfusion in right PC 6 is higher than left PC 6. Coherence analysis of laser Doppler flowmetry signals in bilateral PC 6 might provide a potential non-invasive method to assess microcirculatory changes in different ages.展开更多
A wide-range and phase-locked Michelson interferometer technique is described. This technique combined with femtosecond laser is used to measure the spectrum of the rare-earth ion Nd：YVO4, which presents very high si...A wide-range and phase-locked Michelson interferometer technique is described. This technique combined with femtosecond laser is used to measure the spectrum of the rare-earth ion Nd：YVO4, which presents very high signal to noise ratio of interferometric intensity output and higher spectral resolution than traditional grating spectrophotometer.展开更多
The two-phase detection method for directional discrimination in laser Doppler measurements is discussed.The diffraction efficiency of a sin- gle period rectangular phase grating is analysed and a kind of back-scatter...The two-phase detection method for directional discrimination in laser Doppler measurements is discussed.The diffraction efficiency of a sin- gle period rectangular phase grating is analysed and a kind of back-scattered laser Doppler vibrometer without directional ambiguity using the single peri- od rectangular phase grating as the beam-combiner described.The principles of this kind of vibrometer are explained in detail,and some experimental re- sults are given.In this kind of vibrometer,the rectangular phase grating, without the zero diffracted order and even orders,is used to eliminate use- less stray light and to combine the useful signal light.Differential electronics is employed to reject signal noise.Therefore,the signal-to-noise ratio of Doppler signals and the measurement accuracy of the instrument are im- proved and the range of application is expanded.展开更多
The spatial structure of the velocity field in a stirred vessel with water has been measured and analyzed using the laser Doppler velocimeter technique, with the immersing depth and agitation speed of the impeller re-...The spatial structure of the velocity field in a stirred vessel with water has been measured and analyzed using the laser Doppler velocimeter technique, with the immersing depth and agitation speed of the impeller re-maining approximately constant. The experimental results were provided such as the mean velocity field, fluctuat-ing velocities, turbulent kinetic energy, Reynolds shear stress and time series of the velocity in the stirred tank. These results probably provided the valuable basis to further optimize and enlarge the stirred tank in the industrial process.展开更多
A new multi-channel far infrared （FIR） laser interferometer was built up and ap- plied to HL-2A. The unique feature of real-time heterodyne interferometer is the combination of high power radiation source （300 mW）...A new multi-channel far infrared （FIR） laser interferometer was built up and ap- plied to HL-2A. The unique feature of real-time heterodyne interferometer is the combination of high power radiation source （300 mW）, lower noise room temperature detector （noise tempera- ture below 6000 K） with good spatial resolution of 7 cm. Various parameters are optimized for maximum laser output power. Zero crossings of the signals are counted with field programmable gate array （FPGA） digital circuitry yielding the resolution of 1/1000 fringe. The newly measured results including density fluctuation are also presented.展开更多
Accurate prediction of hypersonic boundary-layer transition plays an important role in thermal protection system design of hypersonic vehicles.Restricted by the capability of spatial diagnostics for hypersonic boundar...Accurate prediction of hypersonic boundary-layer transition plays an important role in thermal protection system design of hypersonic vehicles.Restricted by the capability of spatial diagnostics for hypersonic boundary-layer study,quite a lot of problems of hypersonic boundary-layer transition,such as nonlinearity and receptivity,remain outstanding.This work reports the application of focused laser differential interferometer to instability wave development across hypersonic boundary-layer on a flared cone model.To begin with,the focused laser differential interferometer is designed and set up in a Mach number 6 hypersonic quiet wind tunnel with the focal point in the laminar boundary-layer of a 5 degree half-angle flared cone model.Afterwards,instability experiments are carried out by traversing the focal point throughout the hypersonic boundary-layer and the density fluctuation along the boundary-layer profile is measured and analyzed.The results show that three types of instability waves ranging from 10 k Hz to over 1 MHz are co-existing in the hypersonic boundary-layer,indicating the powerful capability of focused laser differential interferometer in dynamic response resolution for instability wave study in hypersonic flow regime;furthermore,quantitative analyses including spectra and bicoherence analysis of instability waves throughout the hypersonic boundary-layer for both cold and heated cone models are performed.展开更多
The continuous Scanning Laser Doppler Vibrometry(SLDV)developed on the base of the galvanometer scanner system has made it possible to quickly obtain the full field vibration responses within a rectangular area of the...The continuous Scanning Laser Doppler Vibrometry(SLDV)developed on the base of the galvanometer scanner system has made it possible to quickly obtain the full field vibration responses within a rectangular area of the structure.In this paper,an arbitrary continuous scanning path generating method for Continuous Scanning Laser Doppler Vibometry(CSLDV)is further put forward in order to allow the CSLDV suitable for testing structures featured by complex shapes not just for regular areas.In the first step,the relationship between position of laser spot and the driving voltages of galvanometer scanner system has been described by a mathematical modeling.Then,a novel arbitrary scanning path generating strategy based on CSLDV is presented by deforming a normalization rectangular scanning path to an arbitrary continuous scanning path.The mapping relation between the normalization rectangular scanning path and arbitrary continuous scanning path is established using the reference points.In the second step,a compressor blade with curved surface was taken as an example for modal test using the proposed method.At the same time,a validated experiment was performed in SLDV.The results show the mode shapes derived from the extended CSLDV are in agreement with those from SLDV and the Modal Assurance Criterion(MAC)between the two are all greater than 0.96.They also demonstrate the feasibility and effectiveness of the proposed method for CSLDV test and show strong potential on further practical engineering applications.展开更多
A single-channel far-infrared （FIR） laser interferometer was developed to measure the line averaged electron density on the EAST tokamak. The structure of the single-channel FIR laser interferometer is described in ...A single-channel far-infrared （FIR） laser interferometer was developed to measure the line averaged electron density on the EAST tokamak. The structure of the single-channel FIR laser interferometer is described in detail. The evolution of density sawtooth oscillation was measured by means the FIR laser interferometer, and was identified by electron cyclotron emission （ECE） signals and soft X-ray intensity. The discharges with and without sawtooth were compared with each other in the Hugill diagram.展开更多
Perfusion of individual tissues is a basic physiological process that is necessary to sustain oxygenation and nutrition at a cellular level. Ischemia, or the insuff iciency of perfusion, is a common mechanism for tiss...Perfusion of individual tissues is a basic physiological process that is necessary to sustain oxygenation and nutrition at a cellular level. Ischemia, or the insuff iciency of perfusion, is a common mechanism for tissue death or degeneration, and at a lower threshold, a mechanism for the generation of sensory signalling including pain. It is of considerable interest to study perfusion of pe- ripheral abdominal tissues in a variety of circumstances. Microvascular disease of the abdominal organs has been implicated in the pathogenesis of a variety of disorders, including peptic ulcer disease, inflammatory bowel disease and chest pain. The basic principle of laser Doppler perfusion monitoring (LDPM) is to analyze changes in the spectrum of light reflected from tissues as a response to a beam of monochromatic laser light emitted. It reflects the total local microcirculatory blood perfusion, including perfusion in capillaries, arterioles, venules and shunts. During the last 20-25 years, numerous studies have been performed in different parts of the gastroin-testinal (GI) tract using LDPM. In recent years we have developed a multi-modal catheter device which includes a laser Doppler probe, with the intent primarily to investigate patients suffering from functional chest pain of presumed oesophageal origin. Preliminary studies show the feasibility of incorporating LDPM into such catheters for performing physiological studies in the GI tract. LDPM has emerged as a research and clinical tool in preference to other methods; but, it is important to be aware of its limitations and account for them when reporting results.展开更多
A multichannel methanoic acid （HCOOH, λ=432.5 μm） laser interferometer/polarimeter is being developed from the previous eight-channel hydrogen cyanide （HCN, λ=337 μm） laser interferometer in the HL-2A tokamak....A multichannel methanoic acid （HCOOH, λ=432.5 μm） laser interferometer/polarimeter is being developed from the previous eight-channel hydrogen cyanide （HCN, λ=337 μm） laser interferometer in the HL-2A tokamak. A conventional Michelson-type interometer is used for the electron density measurement, and a Dodel-Kunz-type polarimeter is used for the Faraday rotation effect measurement, respectively. Each HCOOH laser can produce a linearly polarized radiation at a power lever of -30 mW, and a power stability 〈10% in 50 rain. A beam waist （diameter d0 ≈12.0 mm, about 200 mm away from the outlet） is finally determined through a chopping modulation technique. The latest optical layout of the interferometer/polarimeter has been finished, and the hardware data processing system based on the fast Fourier transform phase- comparator technique is being explored. In order to demonstrate the feasibility of the diagnostic scheme, two associated bench simulation experiments were carried out in the laboratory, in which the plasma was simulated by a piece of polytetrafluoroethene plate, and the Faraday rotation effect was simulated by a rotating half-wave plate. Simulation results agreed well with the initial experimental conditions. At present, the HCOOH laser interferometer/polarimeter system is being assembled on HL-2A, and is planned to be applied in the 2014-2015 experimental campaign.展开更多
Accuracy is one of the most important key indices to evaluate multi-axis systems’ (MAS’s) characteristics and performances. The accuracy of MAS’s such as machine tools, measuring machines and robots is adversely af...Accuracy is one of the most important key indices to evaluate multi-axis systems’ (MAS’s) characteristics and performances. The accuracy of MAS’s such as machine tools, measuring machines and robots is adversely affected by various error sources, including geometric imperfections, thermal deformations, load effects, and dynamic disturbances. The increasing demand for higher dimensional accuracy in various industrial applications has created the need to develop cost-effective methods for enhancing the overall performance of these mechanisms. Improving the accuracy of a MAS by upgrading the physical structure would lead to an exponential increase in manufacturing costs without totally eliminating geometrical deviations and thermal deformations of MAS components. Hence, the idea of reducing MAS’s error by a software-based alternative approach to provide real-time prediction and correction of geometric and thermally induced errors is considered a strategic step toward achieving the full potential of the MAS. This paper presents a structured approach designed to improve the accuracy of Cartesian MAS’s through software error compensation. Four steps are required to develop and implement this approach: (i) measurement of error components using a multidimensional laser interferometer system, (ii) tridimensional volumetric error mapping using rigid body kinematics, (iii) volumetric error prediction via an artificial neural network model, and finally (iv) implementation of the on-line error compensation. An illustrative example using a bridge type coordinate measuring machine is presented.展开更多
In order to improve the detection accuracy of Doppler asymmetric spatial heterodyne(DASH)interferometer in harsh temperatures,an opto-mechanical-thermal integration analysis is carried out.Firstly,the correlation betw...In order to improve the detection accuracy of Doppler asymmetric spatial heterodyne(DASH)interferometer in harsh temperatures,an opto-mechanical-thermal integration analysis is carried out.Firstly,the correlation between the interference phase and temperature is established according to the working principle and the phase algorithm of the interferometer.Secondly,the optical mechanical thermal analysis model and thermal deformation data acquisition model are designed.The deformation data of the interference module and the imaging optical system at different temperatures are given by temperature load simulation analysis,and the phase error caused by thermal deformation is obtained by fitting.Finally,based on the wind speed error caused by thermal deformation of each component,a reasonable temperature control scheme is proposed.The results show that the interference module occupies the main cause,the temperature must be controlled within(20±0.05)℃,and the temperature control should be carried out for the temperature sensitive parts,and the wind speed error caused by the part is 3.8 m/s.The thermal drift between the magnification of the imaging optical system and the thermal drift of the relative position between the imaging optical system and the detector should occupy the secondary cause,which should be controlled within(20±2)℃,and the wind speed error caused by the part is 3.05 m/s.In summary,the wind measurement error caused by interference module,imaging optical system,and the relative position between the imaging optical system and the detector can be controlled within 6.85 m/s.The analysis and temperature control schemes presented in this paper can provide theoretical basis for DASH interferometer engineering applications.展开更多
The accuracy and repeatability of the laser interferometer measurement system （LIMS） are often limited by the mirror surface error that comes from the mirror surface shape and distortion. This paper describes a new ...The accuracy and repeatability of the laser interferometer measurement system （LIMS） are often limited by the mirror surface error that comes from the mirror surface shape and distortion. This paper describes a new method to calibrate mirror map on ultraprecise movement stage （UPMS） with nanopositioning and to make a real-time compensation for the mirror surface error by using mirror map data tables with the software algorithm. Based on the mirror map test model, the factors affecting mirror map are analyzed through geometric method on the UPMS with six digrees of freedom. Dam processing methods including spline interpolation and spline offsets are used to process the raw sampling data to build mirror map tables. The linear interpolation as compensation method to make a real-time correction on the stage mirror unflatness is adopted and the correction formulas are illuminated. In this way, the measurement accuracy of the system is obviously improved from 40 nm to 5 nm.展开更多
In this paper,we present a phase multiplication algorithm(PMA)to obtain scalable fringe precision in laser self-mixing interferometer under a weak feedback regime.Merely by applying the double angle formula on the sel...In this paper,we present a phase multiplication algorithm(PMA)to obtain scalable fringe precision in laser self-mixing interferometer under a weak feedback regime.Merely by applying the double angle formula on the self-mixing signal multiple times,the continuously improved fringe precision will be obtained.Theoretical analysis shows that the precision of the fringe could be improved toλ/2^(n+1).The validity of the proposed method is demonstrated by means of simulated SMI signals and confirmed by experiments under different amplitudes.A fringe precision ofλ/128 at a sampling rate of 500 k S/s has been achieved after doing 6 th the PMA.Finally,an amplitude of 50 nm has been proved to be measurable and the absolute error is 3.07 nm,which is within the theoretical error range.The proposed method for vibration measurement has the advantage of high accuracy and reliable without adding any additional optical elements in the optical path,thus it will play an important role in nanoscale measurement field.展开更多
A laser coherent detection system of 1550 nm wavelength was presented, and experimen- tal research on detecting micro-Doppler effect in a dynamic target was developed. In the study, the return signal in the time domai...A laser coherent detection system of 1550 nm wavelength was presented, and experimen- tal research on detecting micro-Doppler effect in a dynamic target was developed. In the study, the return signal in the time domain is decomposed into a set of components in different wavelet scales by multi-resolution wavelet analysis, and the components are associated with the vibrational motions in a target. Then micro-Doppler signatures are extracted by applying the reconstruction. During the course of the final data processing frequency analysis and time-frequency analysis are applied to analyze the vibrationM signals and estimate the motion parameters successfully. The experimental results indicate that the system can effectively detect micro-Doppler information in a moving target, and the tiny vibrational signatures also can be acquired effectively by wavelet multi-resolution analy- sis and time-frequency analysis.展开更多
The method and experimental results of measuring a small vibrating displacement by laser interferometer are introduced in this paper. The dynamic response of a new kind of tiny piezoelectric driver is detected. Result...The method and experimental results of measuring a small vibrating displacement by laser interferometer are introduced in this paper. The dynamic response of a new kind of tiny piezoelectric driver is detected. Results show that this kind of PZN-PZT tiny driver not only has high voltage-displacement sensitivity, but also its frequency response approaches to 1 kHz.Therefore this kind of piezoelectric driver can be used widely in many fields.展开更多
Based on laser radar equations, a Doppler shift model of a laser pulse beam scattered by a rotating arbitrary convex target is reported in this paper. The boundary relations between an incident pulse beam and the dete...Based on laser radar equations, a Doppler shift model of a laser pulse beam scattered by a rotating arbitrary convex target is reported in this paper. The boundary relations between an incident pulse beam and the detected area elements are analyzed by geometric methods. The Doppler shift characteristics of the rotating cone and cylinder are discussed and the difference between the laser pulse beam and the plane wave scattered from the same rotating target is compared accordingly. Numerical simulations show that the Doppler shift is tightly relevant to their dimensions, speeds, and so on. In the same incidence conditions, the pulse beam and plane wave have difference peak values and the same Doppler shift bandwidth. If the waist radius of the pulse beam is larger, the peak value is higher, and the Doppler shifts are proportional to the speed of the rotating target. By virtue of our theoretical model, we probe into the scattered characteristics of the Doppler shifts of a laser pulse beam, which would benefit target identification in national defense.展开更多
文摘This paper addresses the challenges of insufficient navigation accuracy,low path-planning efficiency,and poor environmental adaptability faced by deep space rovers in complex extraterrestrial environments(e.g.,the Moon and Mars).A novel autonomous navigation scheme is proposed that integrates laser Doppler velocimetry(LDV)with star trackers(ST)and inertial navigation system(INS).The scheme suppresses slip errors from wheel odometry through non-contact,high-precision laser speed measurement(accuracy better than 0.1%).By deeply fusing multi-source data via a Kalman filter algorithm,high-precision positioning is realized under extreme extraterrestrial conditions such as weak illumination and dust coverage.This solution features high accuracy,non-contact measurement,and anti-interference capabilities,significantly improving the navigation accuracy and autonomy of deep space rovers in complex environments.
文摘Experimental results of remote laser measurement of a time structure of a pulse waves are resulted. Occurrence of the pulse waves are connected with the rhythmic reduction of a myocardittm. Speed of pulse wave＇s propagation does not depend on speed of current of blood, it is defined by diameter of a vessel, by its walls thickness, by elasticity of a vessel, and also by rheological properties of blood. Measurement of parameters of pulse waves is important tbr definition of a condition of cardiovascular system. Ways of measurement of characteristics of pulse waves used now （acoustic, electric, optical） are contact. In some cases, for example, in clinics on treatment of burns and so forth, the question of remote measurement of processes hemodynamics by use of methods of laser sotmding is rather actual. The results described in work have shown outlook of development of laser methods of diagnostics for present purposes. The measurement technique used by authors is based on use of longitudinal Doppler effect which essence consists in change of frequency or length of a wave of radiation at reflection from moving surface. For smoothing the measured signal （clearing from noise） the program developed by authors on the basis of the wavelet-analysis was used. Experimental measurements are shown, that the laser method allows to register distinctly structure of pulse waves which is characterized by two peaks. The results of remote laser measurement of a time structure of a pulse waves confirm the assumption made on the basis of general-theoretical physical positions, that characteristics of pulse waves can be registered on the Doppler effect basis.
基金Supported by the Fundamental Research Funds for the Central Public Welfare Research Institutes:ZZ070806National Natural Science Foundation of China:81001553National Basic Research Program of China:2015CB554502
文摘Objective To investigate lateralization and Coherence analysis of blood perfusion in bilateral Neiguan （内关 PC 6） in different ages. Methods Healthy volunteers （n=30） were placed in a temperature-controlled room as a resting state for 40 min. Then the blood perfusion of bilateral PC 6 were carried out using PeriFlux System 5000 for 25 minutes. Mean blood flux of every 5 minutes was calculated. Then the participants were divided into groups of young （n=18） and the old （n=12） as the boundary of 40 years, the asymmetry index and coherence value of bilateral PC 6 were analyzed in different group. Results The mean blood flow of the right PC 6 was significantly higher than the left PC 6 in three different epochs, the mean blood flow of right PC 6 vs left PC 6 is 9.74±3.36 vs 6.73±2.22 （t=5.9, P〈0.001）, 9.83±3.63 vs 6.99±2.37 （t=5.11, P〈0.001） and 9.69±3.40 vs 6.77±2.32 （t=5.99, P〈0.001）, respectively. Although the asymmetry index is higher in old group than in young group, there is no statistically significant age-related differences. Coherence analysis suggest that there is significant difference in frequency value corresponding to peak crest between young and old group. Conclusion The blood perfusion in right PC 6 is higher than left PC 6. Coherence analysis of laser Doppler flowmetry signals in bilateral PC 6 might provide a potential non-invasive method to assess microcirculatory changes in different ages.
基金ACKNOWLEDGMENTS This work was supported by the National Natural Science Foundation of China （No.60677051 and No.10774193） and the National Key Basic Research Special Foundation （No.G2010CB923204）.
文摘A wide-range and phase-locked Michelson interferometer technique is described. This technique combined with femtosecond laser is used to measure the spectrum of the rare-earth ion Nd：YVO4, which presents very high signal to noise ratio of interferometric intensity output and higher spectral resolution than traditional grating spectrophotometer.
文摘The two-phase detection method for directional discrimination in laser Doppler measurements is discussed.The diffraction efficiency of a sin- gle period rectangular phase grating is analysed and a kind of back-scattered laser Doppler vibrometer without directional ambiguity using the single peri- od rectangular phase grating as the beam-combiner described.The principles of this kind of vibrometer are explained in detail,and some experimental re- sults are given.In this kind of vibrometer,the rectangular phase grating, without the zero diffracted order and even orders,is used to eliminate use- less stray light and to combine the useful signal light.Differential electronics is employed to reject signal noise.Therefore,the signal-to-noise ratio of Doppler signals and the measurement accuracy of the instrument are im- proved and the range of application is expanded.
基金Supported by the Natural Science Foundation of Inner Mongolia (No.200408020715).
文摘The spatial structure of the velocity field in a stirred vessel with water has been measured and analyzed using the laser Doppler velocimeter technique, with the immersing depth and agitation speed of the impeller re-maining approximately constant. The experimental results were provided such as the mean velocity field, fluctuat-ing velocities, turbulent kinetic energy, Reynolds shear stress and time series of the velocity in the stirred tank. These results probably provided the valuable basis to further optimize and enlarge the stirred tank in the industrial process.
基金National Natural Science Foundation of China (Nos.10575030,10675043)the JSPS-CAS Core University Program in the field of Plasma and Nuclear Fusion
文摘A new multi-channel far infrared （FIR） laser interferometer was built up and ap- plied to HL-2A. The unique feature of real-time heterodyne interferometer is the combination of high power radiation source （300 mW）, lower noise room temperature detector （noise tempera- ture below 6000 K） with good spatial resolution of 7 cm. Various parameters are optimized for maximum laser output power. Zero crossings of the signals are counted with field programmable gate array （FPGA） digital circuitry yielding the resolution of 1/1000 fringe. The newly measured results including density fluctuation are also presented.
基金the State Key Laboratory for Turbulence&Complex Systems of Peking University for their support in this studysupport of National Numerical Wind-tunnel(No.2018-ZT1A03)+1 种基金National Natural Science Foundation of China grant(No.11702106)Fundamental Research Funds for the Central Universities(2019kfyXKJC001)。
文摘Accurate prediction of hypersonic boundary-layer transition plays an important role in thermal protection system design of hypersonic vehicles.Restricted by the capability of spatial diagnostics for hypersonic boundary-layer study,quite a lot of problems of hypersonic boundary-layer transition,such as nonlinearity and receptivity,remain outstanding.This work reports the application of focused laser differential interferometer to instability wave development across hypersonic boundary-layer on a flared cone model.To begin with,the focused laser differential interferometer is designed and set up in a Mach number 6 hypersonic quiet wind tunnel with the focal point in the laminar boundary-layer of a 5 degree half-angle flared cone model.Afterwards,instability experiments are carried out by traversing the focal point throughout the hypersonic boundary-layer and the density fluctuation along the boundary-layer profile is measured and analyzed.The results show that three types of instability waves ranging from 10 k Hz to over 1 MHz are co-existing in the hypersonic boundary-layer,indicating the powerful capability of focused laser differential interferometer in dynamic response resolution for instability wave study in hypersonic flow regime;furthermore,quantitative analyses including spectra and bicoherence analysis of instability waves throughout the hypersonic boundary-layer for both cold and heated cone models are performed.
基金the financial support for this work provided by the National Natural Science Foundation of China and National Safety Academic Foundation of China(No.U1730129)The Cultivation Foundation of National Defense Large Projects of China(No.NP2018450)。
文摘The continuous Scanning Laser Doppler Vibrometry(SLDV)developed on the base of the galvanometer scanner system has made it possible to quickly obtain the full field vibration responses within a rectangular area of the structure.In this paper,an arbitrary continuous scanning path generating method for Continuous Scanning Laser Doppler Vibometry(CSLDV)is further put forward in order to allow the CSLDV suitable for testing structures featured by complex shapes not just for regular areas.In the first step,the relationship between position of laser spot and the driving voltages of galvanometer scanner system has been described by a mathematical modeling.Then,a novel arbitrary scanning path generating strategy based on CSLDV is presented by deforming a normalization rectangular scanning path to an arbitrary continuous scanning path.The mapping relation between the normalization rectangular scanning path and arbitrary continuous scanning path is established using the reference points.In the second step,a compressor blade with curved surface was taken as an example for modal test using the proposed method.At the same time,a validated experiment was performed in SLDV.The results show the mode shapes derived from the extended CSLDV are in agreement with those from SLDV and the Modal Assurance Criterion(MAC)between the two are all greater than 0.96.They also demonstrate the feasibility and effectiveness of the proposed method for CSLDV test and show strong potential on further practical engineering applications.
基金National Natural Science Foundation of China(Nos.10475078,10675127,10675126,10675124,10605028)
文摘A single-channel far-infrared （FIR） laser interferometer was developed to measure the line averaged electron density on the EAST tokamak. The structure of the single-channel FIR laser interferometer is described in detail. The evolution of density sawtooth oscillation was measured by means the FIR laser interferometer, and was identified by electron cyclotron emission （ECE） signals and soft X-ray intensity. The discharges with and without sawtooth were compared with each other in the Hugill diagram.
文摘Perfusion of individual tissues is a basic physiological process that is necessary to sustain oxygenation and nutrition at a cellular level. Ischemia, or the insuff iciency of perfusion, is a common mechanism for tissue death or degeneration, and at a lower threshold, a mechanism for the generation of sensory signalling including pain. It is of considerable interest to study perfusion of pe- ripheral abdominal tissues in a variety of circumstances. Microvascular disease of the abdominal organs has been implicated in the pathogenesis of a variety of disorders, including peptic ulcer disease, inflammatory bowel disease and chest pain. The basic principle of laser Doppler perfusion monitoring (LDPM) is to analyze changes in the spectrum of light reflected from tissues as a response to a beam of monochromatic laser light emitted. It reflects the total local microcirculatory blood perfusion, including perfusion in capillaries, arterioles, venules and shunts. During the last 20-25 years, numerous studies have been performed in different parts of the gastroin-testinal (GI) tract using LDPM. In recent years we have developed a multi-modal catheter device which includes a laser Doppler probe, with the intent primarily to investigate patients suffering from functional chest pain of presumed oesophageal origin. Preliminary studies show the feasibility of incorporating LDPM into such catheters for performing physiological studies in the GI tract. LDPM has emerged as a research and clinical tool in preference to other methods; but, it is important to be aware of its limitations and account for them when reporting results.
基金supported by the National Magnetic Confinement Fusion Science Programs of China(Nos.2010GB101002 and 2014GB109001)National Natural Science Foundation of China(Nos.11075048 and 11275059)
文摘A multichannel methanoic acid （HCOOH, λ=432.5 μm） laser interferometer/polarimeter is being developed from the previous eight-channel hydrogen cyanide （HCN, λ=337 μm） laser interferometer in the HL-2A tokamak. A conventional Michelson-type interometer is used for the electron density measurement, and a Dodel-Kunz-type polarimeter is used for the Faraday rotation effect measurement, respectively. Each HCOOH laser can produce a linearly polarized radiation at a power lever of -30 mW, and a power stability 〈10% in 50 rain. A beam waist （diameter d0 ≈12.0 mm, about 200 mm away from the outlet） is finally determined through a chopping modulation technique. The latest optical layout of the interferometer/polarimeter has been finished, and the hardware data processing system based on the fast Fourier transform phase- comparator technique is being explored. In order to demonstrate the feasibility of the diagnostic scheme, two associated bench simulation experiments were carried out in the laboratory, in which the plasma was simulated by a piece of polytetrafluoroethene plate, and the Faraday rotation effect was simulated by a rotating half-wave plate. Simulation results agreed well with the initial experimental conditions. At present, the HCOOH laser interferometer/polarimeter system is being assembled on HL-2A, and is planned to be applied in the 2014-2015 experimental campaign.
文摘Accuracy is one of the most important key indices to evaluate multi-axis systems’ (MAS’s) characteristics and performances. The accuracy of MAS’s such as machine tools, measuring machines and robots is adversely affected by various error sources, including geometric imperfections, thermal deformations, load effects, and dynamic disturbances. The increasing demand for higher dimensional accuracy in various industrial applications has created the need to develop cost-effective methods for enhancing the overall performance of these mechanisms. Improving the accuracy of a MAS by upgrading the physical structure would lead to an exponential increase in manufacturing costs without totally eliminating geometrical deviations and thermal deformations of MAS components. Hence, the idea of reducing MAS’s error by a software-based alternative approach to provide real-time prediction and correction of geometric and thermally induced errors is considered a strategic step toward achieving the full potential of the MAS. This paper presents a structured approach designed to improve the accuracy of Cartesian MAS’s through software error compensation. Four steps are required to develop and implement this approach: (i) measurement of error components using a multidimensional laser interferometer system, (ii) tridimensional volumetric error mapping using rigid body kinematics, (iii) volumetric error prediction via an artificial neural network model, and finally (iv) implementation of the on-line error compensation. An illustrative example using a bridge type coordinate measuring machine is presented.
文摘In order to improve the detection accuracy of Doppler asymmetric spatial heterodyne(DASH)interferometer in harsh temperatures,an opto-mechanical-thermal integration analysis is carried out.Firstly,the correlation between the interference phase and temperature is established according to the working principle and the phase algorithm of the interferometer.Secondly,the optical mechanical thermal analysis model and thermal deformation data acquisition model are designed.The deformation data of the interference module and the imaging optical system at different temperatures are given by temperature load simulation analysis,and the phase error caused by thermal deformation is obtained by fitting.Finally,based on the wind speed error caused by thermal deformation of each component,a reasonable temperature control scheme is proposed.The results show that the interference module occupies the main cause,the temperature must be controlled within(20±0.05)℃,and the temperature control should be carried out for the temperature sensitive parts,and the wind speed error caused by the part is 3.8 m/s.The thermal drift between the magnification of the imaging optical system and the thermal drift of the relative position between the imaging optical system and the detector should occupy the secondary cause,which should be controlled within(20±2)℃,and the wind speed error caused by the part is 3.05 m/s.In summary,the wind measurement error caused by interference module,imaging optical system,and the relative position between the imaging optical system and the detector can be controlled within 6.85 m/s.The analysis and temperature control schemes presented in this paper can provide theoretical basis for DASH interferometer engineering applications.
文摘The accuracy and repeatability of the laser interferometer measurement system （LIMS） are often limited by the mirror surface error that comes from the mirror surface shape and distortion. This paper describes a new method to calibrate mirror map on ultraprecise movement stage （UPMS） with nanopositioning and to make a real-time compensation for the mirror surface error by using mirror map data tables with the software algorithm. Based on the mirror map test model, the factors affecting mirror map are analyzed through geometric method on the UPMS with six digrees of freedom. Dam processing methods including spline interpolation and spline offsets are used to process the raw sampling data to build mirror map tables. The linear interpolation as compensation method to make a real-time correction on the stage mirror unflatness is adopted and the correction formulas are illuminated. In this way, the measurement accuracy of the system is obviously improved from 40 nm to 5 nm.
基金supported by the Natural Science Foundation of Fujian Province(No.2020J01705)the School Foundation of Jimei University(No.C150345)。
文摘In this paper,we present a phase multiplication algorithm(PMA)to obtain scalable fringe precision in laser self-mixing interferometer under a weak feedback regime.Merely by applying the double angle formula on the self-mixing signal multiple times,the continuously improved fringe precision will be obtained.Theoretical analysis shows that the precision of the fringe could be improved toλ/2^(n+1).The validity of the proposed method is demonstrated by means of simulated SMI signals and confirmed by experiments under different amplitudes.A fringe precision ofλ/128 at a sampling rate of 500 k S/s has been achieved after doing 6 th the PMA.Finally,an amplitude of 50 nm has been proved to be measurable and the absolute error is 3.07 nm,which is within the theoretical error range.The proposed method for vibration measurement has the advantage of high accuracy and reliable without adding any additional optical elements in the optical path,thus it will play an important role in nanoscale measurement field.
文摘A laser coherent detection system of 1550 nm wavelength was presented, and experimen- tal research on detecting micro-Doppler effect in a dynamic target was developed. In the study, the return signal in the time domain is decomposed into a set of components in different wavelet scales by multi-resolution wavelet analysis, and the components are associated with the vibrational motions in a target. Then micro-Doppler signatures are extracted by applying the reconstruction. During the course of the final data processing frequency analysis and time-frequency analysis are applied to analyze the vibrationM signals and estimate the motion parameters successfully. The experimental results indicate that the system can effectively detect micro-Doppler information in a moving target, and the tiny vibrational signatures also can be acquired effectively by wavelet multi-resolution analy- sis and time-frequency analysis.
文摘The method and experimental results of measuring a small vibrating displacement by laser interferometer are introduced in this paper. The dynamic response of a new kind of tiny piezoelectric driver is detected. Results show that this kind of PZN-PZT tiny driver not only has high voltage-displacement sensitivity, but also its frequency response approaches to 1 kHz.Therefore this kind of piezoelectric driver can be used widely in many fields.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.61271110,60801047,and 61073106)the New Scientific and TechnologicalStar Project of Shaanxi Province,China(Grant No.2011KJXX39)+1 种基金the Aviation Science Foundation(Grant No.2011ZC53042)the Natural ScienceFoundation of Shaanxi Province,China(Grant Nos.12Jk0955 and 2014JQ0816)
文摘Based on laser radar equations, a Doppler shift model of a laser pulse beam scattered by a rotating arbitrary convex target is reported in this paper. The boundary relations between an incident pulse beam and the detected area elements are analyzed by geometric methods. The Doppler shift characteristics of the rotating cone and cylinder are discussed and the difference between the laser pulse beam and the plane wave scattered from the same rotating target is compared accordingly. Numerical simulations show that the Doppler shift is tightly relevant to their dimensions, speeds, and so on. In the same incidence conditions, the pulse beam and plane wave have difference peak values and the same Doppler shift bandwidth. If the waist radius of the pulse beam is larger, the peak value is higher, and the Doppler shifts are proportional to the speed of the rotating target. By virtue of our theoretical model, we probe into the scattered characteristics of the Doppler shifts of a laser pulse beam, which would benefit target identification in national defense.
