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Issue 7 ， 2014
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High-frequency radiometric calibration for wide field-of-view sensor of GF-1 satellite
Abstract：To realize real-time radiometric calibration of a wide field-of-view sensor on the GF-1 satellite and to obtain offset information caused by dark-noise signals of the WFV sensor, a high-frequency calibration method was established and the reliability and precision of this method were researched and analyzed.Firstly, the in-flight radiometric calibration theory was introduced, and the reference benchmark of calibration data was established by using historical spectral reflectance data and real-time atmosphere profiles of Dunhuang test site.The offset was calculated based on a nighttime offing observing image, which is the digital number signal output from the sensor in the condition of naught radiance input.Then the WFV sensor of GF-1 satellite was calibrated by using the reference data from ground and the offsets prepared.Finally, the uncertainty of this method and accuracy of calibration results were analyzed and validated.Experimental results indicate that the uncertainty of high-frequency calibration of WFV sensor is less than 5.3%, and the difference between radiance based on high-frequency calibration coefficients and radiance with official promulgation publicized results is lower than 5.6%.The offset, calibration intercept, calculated with nighttime sea image accords with the theoretical design value, meanwhile, the calibration method can satisfy the requirement of the in-flight calibration and dark-noise detection of the WFV sensor on GF-1 satellite periodically.Keywords：GF-1 satellite;wide field-of-view sensor;offset;radiometric calibration- 42
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Published：2020-08-13 -
Optical receiver based on BCD process for plastic optical fiber
Abstract：The structure and characteristics of a photodetector (PD) and its post amplifiers were investigated, and a high-speed monolithic optical receiver for Plastic Optical Fiber (POF) communication was implemented.Firstly, a model of PD structure was established and simulated in a software simulating device based on the process flows and parameters.The spectral responsibility and a junction capacitor were also derived in theory and simulation.Then, the post amplifiers consist of a trans-impedance, a limiting amplifier and an out buffer were simulated in Cadence/spectre by using the PD parameters.Finally, by using the 0.5 μm (Bipolar,CMOS and DMOS) BCD process, the single PD and the monolithic integrated circuit of PD and post amplifiers were taped out, packaged and tested.The tested results indicate that the peak of optical spectral responsible curve agrees with that of the simulated curve, and the wavelength is about 700 nm.The junction capacitance of PD decreases with increasing of the bias voltage and the bigger the junction capacitance, the smaller the bandwidth of optical receiver.For a 650 nm input light, the sensitivity of the optical receiver is -14 dBm under the bit-error-rate of 10-9.Moreover, a clear eye-diagram with the speed of 150 Mb/s is achieved.The designed optical receiver can be applied to 100 Mb/s optical fiber communication systems.Keywords：monolithic integration;photo-detector;active inductor;optical receiver;plastic optical fiber communication;Bipolar CMOS and DMOS(BCD)- 47
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Published：2020-08-13 -
Determination of aromatics in naphtha-cracked tar by near infrared spectroscopy
Abstract：Gas Chromatography (GC) is usually used in analysis of aromatic contents of naphtha-cracked tar, however, it costs a longer analytical period.For solve this problem mentioned above, this paper applies Fourier Near-infrared Spectroscopy(NIRS) and corresponding software to the determination of aromatic contents of naphtha-cracked tar to shorten the analytical time and improve the analytical efficiency.Since cracked tars have a wide difference in both color and aromatic contents, modified sample tubes, outlier judgment, selective wave numbers and optimal preprocessing methods for NIR spectra were proposed to optimize 6 predict models of aromatics, by which the five models with carbon numbers from 6 to 10 and one for total aromatics were improved.Then, a rapid analysis method based on NIRS for determining aromatics in naphtha-cracked tar of stream cracking was established.With the method, the analytical time for per sample was shorten within 2 min.Experimental results show that the 6 optimized predict models can offer the correlation coefficients (R) of 0.995 20, 0.993 08, 0.946 33, 0.978 99, 0.948 46 and 0.998 63 respectively, and the Root Mean Square Errors of Cross Validation (RMSECV) of 1.07, 0.806, 2.17, 0.979, 0.665 and 1.15, respectively.The aromatic amounts analyzed by NIRS for random samples are fitted well with those determined by GC and the absolute values of t-test are all smaller than the critical value(t0.05(17)=2.11).Moreover, the NIRS analysis also indicates that the Relative Standard Deviation (RSD) is smaller than 2%, which means the established NIRS method has good repeatability.Keywords：Near Infrared Spectroscopy(NIRS);predict model;aromatics;cracked tar;content measurement- 35
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Published：2020-08-13 -
Electron cloud diffusion property of photon counting detector based on induction readout
Abstract：In consideration of the great influence of the sheet resistance of Ge thin film in a single-photon counting imaging detector on its imaging characteristics, this paper explores the selection of the resistance range.As the resistance values are relative to charge cloud diffusion on the Ge thin film, it will effect the counting rate and resolution ratio of the single-photon counting imaging detector.Therefore, the charge cloud diffusion characteristics on the Ge thin film under condition of absorbing boundary were analyzed based on FICK diffusion law and the relationship of the time of charge cloud diffusion on the thin film and the sheet resistance was calculated by the finite diffusion equation.The analysis results show that the photon counting detector has well spatial resolution and counting rate when the sheet resistance of Ge thin film is between 30 MΩ/□ and 2700 MΩ/□.The imaging experiments on Ge film anode with different resistance values were performed, and obtained data demonstrate that the resolution of the photo counting detector can reach 0.5 mm at counting rate of 53 kc/s when sheet resistance of Ge thin film is in the theoretical range, which proves the validity of resistance value selection range by the proposed method.Keywords：ultraviolet imaging;photon counting detector;induced-charge position-sensitive anode;Ge film resistance;electron cloud diffusion- 63
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Published：2020-08-13 -
X-ray line profile measurements in laser produced plasma
Abstract：This paper explores the parameter measurement in laser produced plasma by X-ray line profile spectrscopy.The experiment was conducted on the SG-II laser facility.A 0.35 μm laser beam was focused on a solid chlorine (Cl) target in a vacuum chamber to produce a laser chlorine plasma and the high resolution X-ray elliptical bent crystal spectrograph was used to obtain the X-ray fine structure energy spectrum of the chlorine plasma radiation.The line integrated intensity ratio between H-like Cl (1s-3p) (Lyman-) and He-like Cl (1s2-1s3p) (He-) transitions was used for calculation of the electron temperature.By assuming optically thin, the Lyman-stark broadened profile was utilized to measure the electron density.Obtained experimental results show that the volume averaged electron temperature of Te is about 450 eV and the electron density of Ne is approximately 7.5×1022 cm-3.In addition, the line Full Width at Half Maximum (FWHM) was analyzed.The uncertainty in Ne due to uncertainties in the temperature and the assumed background level was also simply discussed and it is estimated to be within 25%.As a result, the experimental spectroscopic method may become a reference for diagnosing future higher-compression implosions.Keywords：X-ray spectra;spectral line shape;laser plasma diagnostics;electron density;X-ray spectrometer- 64
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Published：2020-08-13 -
Formability of laser shock-induced high speed flyers
Abstract：The effect of relevant process parameters on forming properties of laser shock flyers was investigated.By using the Johnson-Cook model suitable for a high pressure and a high strain rate and ANSYS/LS-DYNA software, the laser shock induced bulge forming of flyers was simulated to obtain the relation between the laser energies, forming die diameters and forming die fillet rates and the heights of forming parts.The analysis results show that as the laser power density, forming die diameter and the die fillet rate increase, the heights of bulging parts are increased, and the maximum height of bulging parts is 310.6 μm.Finally, an experiment of laser shock induced forming of flyers was carried out on a copper foil with a thickness of 50 μm.The two-dimensional appearance and three-dimensional microtopography of bulging parts were obtained with a stereomicroscope and a morphology measuring instrument.The results verify the reasonability of the numerical model.It concludes that the numerical simulation analysis method established in this paper can provide a means for the prediction and control of laser shock induced bulge forming processes of flyers.Keywords：laser forming;laser shock;flyer forming;numerical simulation- 56
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Published：2020-08-13 -
Measurement of infrared radiation for target airplane based on real-time atmospheric correction
Abstract：The measuring method for dynamic radiation characteristics of a flying airplane is researched.As traditional atmospheric correction method by calculating the atmospheric transmittance and path radiation with software has poor correction precision, this paper proposes a new radiation measurement method to measure the atmoshperic transmittance in real time.The method uses a blackbody carried by the target airplane to measure the atmoshperic transmittance in real time and takes the real-time measured data to correct the target airplane radiation and to improve the radiation measurement precision.Ground simulation experiments for an airplane infrared radiation measurement are performed by means of a midwave (MW) infrared camera, a longwave (LW) infrared camera, two extended-area blackbodies, and a piece of ZnSe.The MODTRAN calculated, CART calculated, and the real-time measured atmospheric transmittances are used to correct the inverted blackbody target radiation.The obtained results show that the target radiation measurement precision by the proposed real-time measured atmospheric transmittance has improved by above 100% as compared with those of MODTRAN and CART calculated.Keywords：airplane;infrared radiation;radiation measurement;atmospheric correction;atmospheric transmittance;correction blackbody;radiation calibration- 63
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Published：2020-08-13 -
Interval pulse position modulation in visible light communication
Abstract：Based on channel transmission properties of the indoor Visible Light Communication (VLC) systems, a link model for VLC systems was described.Then the Interval Pulse Position Modulation (IMPPM) scheme applied in VLC systems was proposed by using the link model.The symbolic structure of the IMPPM scheme was introduced, then the scheme was compared with the other two modulation schemes, Pulse Position Modulation(PPM) and Multi-PPM(MPPM), on the bandwidths, power requirements and Bit Error Rates(BERs).Simulation results indicate that IMPPM applied in VLC systems can make a better balance in bandwidths and power requirements when the source bit(M) is 3, 4, 5.As the BER reaches 10-3, the received optical power of IMPPM is 2 dB and 4 dB lower than those of the MPPM and PPM respectively.Moreover, the BER of IMPPM is superior to that of the MPPM because the pulses of IMPPM has intervals.Obtained results demonstrate that the IMPPM has low power requirements and better performance on anti-multipath and inter-symbol interference compared with that of PPM and MPPM.Keywords：Visible Light Communication(VLC);link model;Interval Pulse Position Modulation(IMPPM);bandwidth;Power;bit error rate- 49
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Published：2020-08-13 -
Effect of laser peening on microstructures and properties of TiAl alloy
Abstract：To study the effect of laser peening on microstructures and properties of TiAl alloy, TiAl alloy samples were treated by a Nd:YAG laser system with a wavelength of 1 064 nm, a pulse-width of 20 ns, and a pulse-energy of range 0-22 J.The surface micro-hardness, roughness, and microstructural characteristics of the samples before and after laser peening were tested with a micro-hardness tester, a roughness tester and a Scanning Electron Microscope (SEM).The residual stress and pole figures of TiAl alloy were tested with X-ray Diffraction (XRD) and their high-temperature stabilities were analyzed.The experimental results show that the surface micro-hardness increases up to 33.4%, the roughness increases from 0.042 μm to 0.285 μm, the compress residual stress increases from 20 MPa to 297 MPa with the pulse energy up to 9 J, and the local textures and typical lamellar microstructures are generated.When the samples are heated for 4 h at 650℃, the residual stress value and micro hardness values have droped from 297 MPa to 230 MPa, and 377 HV0.2 to 345HV0.2 respectively, and the (002) poles shift back to the center slightly.It concludes that the laser peening improves microstructures and properties of TiAl alloy significantly.Keywords：laser peening;TiAl alloy;high temperature stability;microstructure property- 49
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Published：2020-08-13 -
Color-recurrent system in high-definition laser display
Abstract：On the basis of an 60 inch all solid laser television(TV) prototype, a chrominance signal conversion model from an original TV to a laser TV was established.By researching the characteristics of laser display, the conversion matrix between traditional phosphor TV color system and laser TV color system was derived by using a three color laser (red:660 nm, green:532 nm, blue:457 nm) as primary-color.A gamut conversion circuit between the two color systems was given by utilizing a decode module, a Field Programming Gate Array(FPGA) controlling circuit and a coding module.The roles of these models and their working processing were analyzed, and the gamut conversion to the high-definition video signal was achieved.11 feature colors displayed with the laser TV and the traditional phosphor TV respectively were measured and compared after conversion and the gamut conversion error is less than 9.8%.The experiment obtains an excellent result of gamut conversion and verifies the color-recurrent ability of high-definition laser TVs.Keywords：laser television;laser display;color system;gamut conversion;Field Programming Gate Array(FPGA)- 67
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Published：2020-08-13 -
Vibration measurement system based on reflection holographic grating of crystal BSO
Abstract：A vibration measurement system based on a reflection holographic grating was built up by using the photorefractive crystal bismuth silicate (BSO) as recording media.The reference beam and the signal beam modulated by a vibration signal were injected into the crystal and to form the reflection dynamic holography, then the diffraction was happened simultaneously.The vibration signal could be obtained by demodulating the interference signal formed by the transmitted signal beam and the diffracted reference beam.The impact of the measurement conditions on the measuring sensitivity was studied which include the convergence angle between the two incident beams, light intensity ratio, and the crystal orientation.The relationship between coupling gain and measuring sensitivity was analyzed.Experimental results indicate that this system can detect the vibration signal with a frequency up to 360 kHz when the piezoelectric ceramic(PZT) is a measuring target.It demonstrates that the measuring sensitivity by the proposed system is higher than that of the vibration measurement system based on the transmission holographic grating, because the reflection holography reduces the space period of Bragg grating and improves the coupling efficiency of the reference and signal beams.Keywords：vibration measurement;BSO crystal;reflection holographic grating;diffraction efficiency- 74
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Published：2020-08-13 -
Analysis and test of reliability for ammunition accurate ramming
Abstract：To guarantee the consistency of ramming parameters of an automatic ramming system for artilleries working continuously in a complex circumstance, the reliability of automatic ramming system was explored and the measuring method was researched.Firstly, the effect of the ramming parameter change on interior ballistic parameters and the reasons of parameter change were analyzed.Then a ramming parameter test system based on multi-sensors was designed, and a general test for the ramming process and ramming effect was performed by the ramming test system.The test results show that the tail of the ramming system will vibrate with a peak-peak of 14 mm after ramming 60 ms,which is the main reason of projectile into the breech posture and collision with a barrel.Moreover,when bullet's invade resistance varies from 3 300 N to 14 000 N,the invade distance changes in 2 mm.The invade distance can be divided into three areas according to distribution, and the second area raging from 1.321 mm to 1.557 mm is regarded as a reliable invade distance.These results demonstrate that the proposed measuring method and accuracy can meet the ramming system test demands, and can offer a data support for the structural optimization and performance evaluation of ramming systems.Keywords：artillery;ammunition ramming;accurate ramming;random vibration;dynamic testing;ramming reliability- 55
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Published：2020-08-13 -
Measurement of thermoelectric characteristics of high resistance nano films
Abstract：To measure the thermoelectric characteristics of a high resistance nano film, a Seebeck coefficient measurement apparatus was designed and built.The temperature control accuracy and temperature difference generation mechanism were investigated and the weak voltage signals under a high resistance condition were measured.Firstly, a vacuum environment with an ultra-high vacuum degree and an electric-magnetic shield was setup.Then, a temperature difference control stage was installed inside the vacuum chamber to generate the accurate temperature difference between the two ends of the test sample.Meanwhile, according to the weak voltage detection requirements under the condition of high resistance, the influences of channel leakage current and distributed capacitance were eliminated.Finally, a cyclic temperature gradient generation technique and a corresponding algorithm were proposed to eliminate the negative effects of the long term drift of Seebeck voltage and the Seebeck coefficients of high resistance organic semiconductor materials were measured.Experimental results on a high resistance nano film with resistance over 7×1012Ω indicate that the measuring accuracy of the measurement apparatus is less than 2%, and temperature control accuracy is about ±0.001 K.It means that the apparatus can measure the Seebeck coefficient of nano material with a resistance over 1012Ω.Keywords：nano-film material;thermoelectric material;Seebeck coefficient measurement;voltage measurement;temperature control- 53
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Published：2020-08-13 -
Design of clearance fit between pico-satellite and its separation mechanism based on thermal-structure coupling
Abstract：The thermal-structure coupling for a pico-satellite and its separation mechanism was analyzed to guide a rational design of the fit clearance value between the satellite and guide rail and to ensure safe and reliable satellite separation.On the basis of the geometry relations of the satellite, the earth, and the sun in the process of launching, the internal and external heat flows absorbed by the pico-satellite and its separation mechanism were analyzed.The temperature field and thermal deformation in satellite launching were obtained by finite element analysis.The clearance fit value between the satellite and guide rail was designed on the basis of above analysis.The analysis results show that the maximum deformation occurs on the shady side because of the cold dark environment and conduction heat, and the pico-satellite shell and its guide rail surface are not distorted and deformed seriously.The amount of maximum deformation is 62.3 μm when the preload force is 600 N and that is 63 μm when the preload force is 300 N.Based on above analysis results, the fit clearance was selected.These results demonstrate that the pico-satellite and its separation mechanism can separate normally under the high and low temperature tests.The on-orbit separation attitude is in agreement with simulation results well.All of these verify that the fit clearance between the satellite and its guide rail is reasonable and it can be used in the structural design and thermal control design of pico-satellite separation mechanisms.Keywords：pico-satellite;separation mechanism;thermal deformation;thermal-structural coupling;fit clearance- 46
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Published：2020-08-13 -
Active magnetic compensation of spin-exchange-relaxation-free atomic magnetometer
Abstract：As the measuring sensitivity of a Spin-Exchange-Relaxation-Free(SERF) atomic magnetometer will be reduced when it is suffered from the disturbance by environment magnetic field.Therefore,according to the measuring principle of the SERF atomic magnetometer, this paper proposes a active magnetic compensation method for the external magnetic field disturbance based on in-situ magnetic measurement.Firstly, a modem was used to decouple the magnetic field in three directions to achieve the magnetic information of the three axes.Then, the measuring information from three directions was taken as a feedback to adjust the current of coil to generate a magnetic field which is opposite and equal to the disturbance.Finally, an active magnetic compensation system for SERF atomic magnetometer was built to compensate the magnetic disturbance in real time.Compared with the manual compensation method, the proposed method reduces the surplus magnetic field from 0.317 8 nT to 0.040 4 nT, and the mean square error from 0.348 1 nT to 0.024 7 nT.The experimental results validate the efficiency of the active magnetic compensation method.Keywords：atomic magnetometer;active magnetic compensation;spin-exchange-relaxation-free(SERF);decouple;in-situ magnetic measurement- 78
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Published：2020-08-13 -
Exposure optical system in lithographic main scale of absolute optical encoder
Abstract：A general structure for two photolithographic heads based on Digital Micro-mirror Devices(DMDs) is proposed for simultaneously lithography of the double-track codes of an absolute optical encoder.The total optical system includes an exposure light source, an focusing light source, a DMD and a projective lens.The exposure light source mainly consists of a laser, a collimation lens, a 2D-micro-mirror array and a field lens.The exposure light source is designed by TracePro software, and the uniformity of the energy distribution is above 95% in the area of 14 mm×10 mm.A confocal projective system at two wavebands (exposure source at 0.403-0.407μm and focusing source at 0.525-0.535 μm) is designed by Zemax software, in which the exposure and focusing can be realized in real time with a dichroscope and a prism.The imaging quality of the projective lens reaches diffraction limit at exposure waveband and focusing waveband, and the maximum distortion is 0.009%.Compared with traditional grating lithography methods, the exposure optical system has advantages on simpler process, fast manufacturing and high precision.It can be used in manufacturing long and ultra-long metrological gratings.Keywords：absolute optical encoder;grating code-track;main scale;Digital Micro-mirror Device(DMD);exposure head;metrological grating- 62
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Published：2020-08-13 -
Application of DT-CWT robust filtering to evaluation of engineering surface roughness
Abstract：The merits and demerits of existing reference filtering methods for evaluation of the three-dimensional engineering surface roughness were discussed.It points out that the Dual-tree Complex Wavelet Transform (DT-CWT) is suitable for the three-dimensional surface reference filter because of its advantages of approximate translation invariance and improved directional selectivity.However, its filtering is too idealistic, which will cause an opposition at the point of distortion of the filtered reference.Therefore,this paper brings the airspace bilateral filtering into the DT-CWT transform to enhance its robustness at the point of distortion of the filtered reference.The low-frequency reference signal was obtained through reconstruction and each reconstructed coefficient was bilaterally filtered, then, the robustness of reference filtering was enhanced by the DT-CWT filtering.The simulation data show that the robustness filtering under the conditions of abnormal interference is enhanced by the improved DT-CWT, the precision error is 0.183 2×10-10 m and the reconstruction error is 0.016 1×10-10 m, which is much lower than that of the traditional methods.The processing results for practical measurement data indicate that the improved method well overcomes the edge effects and suppresses the effects of deep valley in the surface on the filtering results.It provides a new way for evaluation of engineering surface roughness.Keywords：surfaces roughness;3-D reference;dual-tree complex wavelet;bilateral filtering;robust filter- 72
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Published：2020-08-13 -
Design and experiment of piezoelectric-drive vibratory feeder
Abstract：To convey light, thin and small products stably, a piezoelectric vibratory feeder with the Z leaf spring actuated by a round piezoelectric bimorph was developed base on the working principle of systemic resonance.The working principles of the vibratory feeder driven by a circular piezoelectric vibrator were introduced, the expression of natural frequency was obtained by establishing the dynamic model of the vibratory feeder, and the first order mode shape was defined as the working mode shape after analysis of the vibratory modal.Then,a prototype of the vibratory feeder was developed.Finally, the relations among voltage, frequency and feeding rate were measured, and the influences of the angle of leaf spring on feeding rates,stability and noise were explored.The experimental results show that the feeding rate of the vibratory feeder is 8.5 battery caps per second when the voltage is 150 V and the frequency is 142 Hz.The vibratory feeder can convey the products when the working frequency is from 136 Hz to 148 Hz, and the best feeding rate is at the resonance frequency(142 Hz).Moreover, the feeding rate increases linearly with the driving voltage.As the mass of the conveying parts increases, the installation angle of the main vibrating spring decreases.Keywords：piezoelectric drive;vibratory feeder;piezoelectric bimorph;dynamic model;Modal analysis- 54
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Published：2020-08-13 -
Design and test of launch window for large-caliber multi-band high power laser system
Abstract：An automatic shutter-type mechanical window was designed for the multi-band, high-power and large-caliber laser launch system to meet the requirements of complex service environment for long interval emission and crystal window.The window is composed of two parts of the dust cover: pressing mechanism and driving mechanism.By using transmission links, such as screw, wire rope, and time synchronous belt, the pressing mechanism realizes multi-task driving of a single motor synchronously and the flexible hinges compensate installation errors.Then the relationship between wind pressure forced on dust cover and pressing force of the pressing mechanism was analyzed by nonlinear analysis methods and integral principles.The expression of wind pressure and motor torque was established by inverse method.According to the relationship of motor torque and frequency, the rotating speed range of the mechanism and the largest wind pressure of the dust cover were calculated.Experimental results show when the motor output torque is 0.341 N·m, the mechanism can resist the impact of wind of 10 m/s.The least intervals of the window are stably within 3 s no matter it is opened or closed.The relative calculation error of the expression between wind pressure and motor output torque is less than 15%, which satisfies working requirements of systems.Keywords：laser launch system;laser launch window;multi-band;flexible cable;wind pressure- 41
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Published：2020-08-13 -
Modeling of precision harmonic drive system
Abstract：In consideration of the control method and performance prediction of harmonic drive systems, a modeling method of precision harmonic drive system was proposed according to the main factors effecting the performance of harmonic drive system.A dynamics model and a Simlink simulation model of harmonic drive system were established, and an method to obtain the simulation model parameters was researched.A least square identification method was presented to identify the parameters which are difficult to be accurately measured in the model.The time-frequency domain simulation analyses and experimental verification were performed.Simulation and experimental results show that the model parameters of the harmonic drive system have clear physical meaning and are convenient for engineering application.When the model is established, one frequency sweep only can estimate the unknown parameters, improve the efficiency of parameter acquisition and reduce the cost.Moreover, the experimental results are basically consistent with that of the simulation one and the matching degree of the results is greater than 70%.These data verify the correctness of the modeling method.Keywords：Harmonic drive;dynamics modeling;parameter identification;least square method- 68
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Published：2020-08-13 -
Wide-band design of dandelion-shape piezoelectric vibration energy harvester
Abstract：The wide-band design of a dandelion-shape piezoelectric vibration energy harvester was investigated to process the variety of the ambient vibration energy sources.A analysis model of resonant frequency for dandelion-shape piezoelectric vibration energy harvester was established.The theoretical results show that the frequency band of resonant frequency of the energy harvester can not be increased randomly.To verify the theoretical analysis, a frequency response experiment was performed, and the results obtained from the theoretical model indicate that theoretical analysis is basically in agreement with the experimental results.Finally, the experiments were performed to measure the generating capacity of the dandelion-shape piezoelectric vibration energy harvester.The research results show that after a wide-band design for the dandelion-shape piezoelectric vibration energy harvester, it has higher output power in the range of 20Hz-34Hz and the maximal output power is around 2.3 mW.The results demonstrate that the proposed piezoelectric vibration energy harvester can effectively increase the band of resonant frequency through the wide-band design and is easy to match the ambient vibration energy sources to get more vibration energies.Keywords：piezoelectric vibration energy harvester;wide-band;resonant frequency- 86
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Published：2020-08-13 -
Analytical calculation of compliance matrix for right-circular flexure spherical hinge
Abstract：On the basis of hypothesis theories of linear elasticity and small deformation, the analytical compliance calculation formula of each sub-element in the compliance matrix of a right-circular flexure spherical hinge was deduced.The formula is succinct in form by introducing the proportional coefficient (The ratio of right-circular flexure spherical hinge groove spacing and double cutting radius) and utilizing the symmetrical feature of the structure.The correctness of the formula was verified by adopting the finite element simulation software, and its error curves were drawn corresponding to the simulated values.The results show that the relative errors of serial compliance calculation formula for the right-circular flexure spherical hinge are within 11% when the proportional coefficient is less than 0.2.With the increase of the proportional coefficient, the errors of the other compliance calculation formulas have a trend of increasing with maximum of 30% except the error of tension and compression compliance C11 along the direction x.The experimental results show that the theoretical analysis is in agreement with the simulation results, which verifies the correctness of the proposed formula.These results will lay a key theoretical basis for the structural design and parametric optimization of the right-circular flexure spherical hinges in practical applications.Keywords：right-circular flexure hinge;compliance matrix;proportional coefficient;simulation;Error curve- 44
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Published：2020-08-13 -
Influence of NRMs on energy-generation performance of piezoelectric harvesters
Abstract：As existing rotating generators can not adapt to a high speed shock and vibration and have higher noise and lower reliability, this paper proposes a piezoelectric energy harvester excited by rotating magnets.The influence of the number of the rotating magnets (NRMs) on the exciting force as well as the output voltage of the piezoelectric harvester is investigated theoretically and experimentally.The results show that there is an optimal gap ratio (the gap λl between two adjacent magnets to the magnet diameter) for the excitation force to achieve maximum.The obtained excitation force at λl=2 is 6.2 times that at λl=0 and λl=4.When the voltage generation exited with 2,12,24 rotating magnets in the experiments, there are several optimal rotating speeds for the generated voltages to achieve the peak.The maximal peak voltages and the relative optimal speeds for 2,12,24 rotating magnets are 29.4,87.2,28.4 V and 1 282.5, 2 707.5,2 451 r·min-1,respectively.The maximal voltage generated under 12 rotating magnets is about 3 times those under other excitation conditions.The voltage waveform generated from the piezoelectric harvester under one excitation depends on the NRMs and rotating speeds.For 2 rotating magnets, the number of voltage waveforms generated at low and high rotating speeds are 1 and 4, respectively.For 12 rotating magnets, only one voltage waveform generates at any speed.These results demonstrate that the NRMs have great influence on energy generation and output powers of piezoelectric energy harvesters.Keywords：piezoelectric energy harvester;rotating excitation;Number of Rotating Magnets(NRMs);generated voltage- 50
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Published：2020-08-13 -
Optoelectronic inspection of defects for metal cylindrical workpieces
Abstract：To overcome the shortcomings of metal workpiece defect detection in optical uneven illumination, higher detection defect ranges and lower detection system recognition rate, a defect detection method was proposed.The basic principles of Local Binary Pattern (LBP) and Local Image Variance (LVAR) were analyzed, and their specific methods in the algorithm of metal cylindrical detection were discussed.The LBP was used to reflect local graphics texture pattern and the LVAR to outstand the contrast of image intensity.Then, the weight values calculated from LVAR were used to adjust the extraction and measurement of LBP local texture.Thus, the automatic detection of metal cylindrical workpieces was achieved.In the experiments, the rotation of workpieces was controlled by a stepper and the expanded images of cylindrical workpieces were captured by a linear CCD.The experimental results demonstrate that this method effectively overcome the shortcomings of metal uneven illumination and has high robustness to a large number of defect types.The detection rate has reached to 99.5% and missing rate to 0%, which meets industrial inspection requirements.Keywords：metal cylindrical work piece;defect detection;Linear CCD;Local Binary Pattern(LBP);Local Variance(LVAR)- 95
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Published：2020-08-13 -
Application of thermal management technique to thermal control for ultraviolet imaging spectrometers
Abstract：The characteristics of thermal control for an ultraviolet imaging spectrometer is researched, and it points out that the conventional thermal design method to establish radiating surface directly will bring some problems such as big radiator area and high electric power for heaters.Therefore, this paper proposes a new thermal design method to solve the problems above.On the basis of thermal management technology, the method collects and manages the heat generated by the inner source of a spectrometer in unification and integration, by which the radiator area is as small as possible and the electric power for heaters is reduced.Thermal design verification results for the ultraviolet imaging spectrometer show that the variation range of mean temperature and the maximal axial temperature difference are 18℃-20℃, and 1.0℃-2.4℃ respectively at a low temperature condition.Moreover, those are 18℃-24.5℃ and 1.2℃-3.3℃ respectively at a high temperature condition.The experiments indicate that these results meet the thermal control demands of the ultraviolet imaging spectrometer.In conclusion, the management technique adopted in thermal control of the ultraviolet imaging spectrometer can effectively increase the energy efficiency and reduce the size of thermal control system, and can provide a reference for the thermal design of other space optical sensors.Keywords：space optics;thermal management technique;ultraviolet imaging spectrometer;Thermal control;thermal test- 51
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Published：2020-08-13 -
Satellite cloud image inpainting based on patch matching and sparse representation
Abstract：For some defects of satellite cloud images caused by noises, atmospheric turbulence, solar storms and satellite orbit drifts in the receiving and transmission process, a novel satellite cloud image inpainting method using patch matching and sparse representation was proposed.Firstly, a pixel to be inpainted was searched according to the priority of the damaged area.The neighborhood of this pixel was divided into patches, and a redundant dictionary was constructed by calculating the structural similarity of inpainting patch and matching patches.Then the damaged area was repaired by solving a sparse representation problem.Finally, the whole cloud image was inpainted by updating priority along an isophote repeatedly.The experimental results show that the proposed method can not only avoid the structure missing from the traditional Partial Differential Equation (PDE) method, but also can improve the texture details and blocking effect of the texture filling repair method.For the cloud image with local defects, the inpainted image by proposed method can improve Peak Signal to Noise Ratio(PSNR) by 8.50 dB and 0.28 dB as compared to Matching Pursuit (MP) method and Total Variation (TV) method respectively.It shows better visual effects on texture details and edge regions.Keywords：satellite cloud image;image inpainting;patch matching;sparse representation- 70
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Published：2020-08-13 -
Assessment of laser-dazzling effects based on laser spot and target features
Abstract：The global features of laser-dazzling images,the local features of targets and the distribution characteristics of laser spots are analyzed.A new algorithm composed of Weighted Feature Similarity (WFSIM) is proposed for the assessment of laser-dazzling effects.The method firstly uses the global features including luminance, contrast, edge definition and local feature-point maintainability to obtain the assessment model.Then, it computes the weighting factors, such as the saturated pixel number, signal to noise ratio and spot visual impotence based on the size, intensity and position of the laser spot.Based on the above results, a modified assessment algorithm can be constructed and a normalized evaluation can be implemented.An experiment platform of laser active imaging and recognition system is built for laser-dazzling images under different laser intensities, different background intensities and different spot positions.The proposed WFSIM algorithm is used to evaluate obtained laser-dazzling images.In terms of experiment results, the WFSIM algorithm shows good feasibility and rationality as comparing with Mean Square Error(MSE),Peak Signal to Noise Ratio(PSNR) and Structural Similarity(SSIM) image quality assessment methods.The evaluation results is consistent with the subjective human visual perception.Keywords：laser active imaging;laser-dazzling;image quality assessment;feature-similarity- 59
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Published：2020-08-13 -
Multiple target localization in WSNs via CS reconstruction based on discrete GSO algorithm
Abstract：The application of Compressed Sensing(CS)theory to multiple target localization in Wireless Sensor Networks(WSNs)was explored.A CS reconstruction method based on Discrete Glowworm Swarm Optimization(DGSO) algorithm was proposed and the algorithm processing was designed.Different from the traditional reconstruction method, the DGSO algorithm is independent on the sparse K and can accurately reconstruct the original signal.The improved CS was applied to the multiple target localization in WSNs, and the WSNs application model was established.Then, a reasonable measuring matrix and a sparse matrix were constructed,and the relationship between measuring matrix and reconstructed results was analyzed.Finally, the multiple target localization was achieved in WSNs.The simulation results show that this method has better effect in the sparse signal reconstruction and multi target locating precision, and its location precision is better than those of Greedy Matching Pursuit(GMP), Orthogonal Matching Pursuit(OMP) and mum Likelihood Estimation(MLE).Moreover, it reduces the network communication data amounts, extends the lifetime of WSNs.The number of sensor nodes for localization of WSNs is reduced by 20%, and the anti-noise can reach to 20 dB.Keywords：Wireless Sensor Network(WSN);Compressed sensing;multiple target localization;reconstruction method;discrete glowworm swarm optimization algorithm- 40
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Published：2020-08-13 -
Nonlinear mixed pixel decomposition of hyperspectral imagery based on multiple kernel SVM
Abstract：As the mixed pixel decomposition based on linear spectrum models has lower decomposition accuracy and the nonlinear spectrum model is difficult to be established, a nonlinear mixed pixel decomposition method for the hyperspectral imagery was proposed based on the posterior probability of Multiple Kernel Support Vector Machine (MKSVM).On the basis of the SVM, the multiple kernel function formed by linear weighted combination was taken to replace the single kernel and the simple multiple kernel learning was used to solve the weights iteratively to achieve the classification.Then, the output values of the classifier were converted to pairwise coupling probabilities by the sigmoid function and then to the multi-class posterior probability.Finally, the hyperspectral imagery decomposition was achieved through the posterior probability.The results from experiments of two push-broom Hyperspectral Imagers (PHIs) show that the classification accuracies of hyperspectral imagery nonlinear mixed pixel decomposition based on MKSVM reach 95.62% and 91.51%,respectively, the Root Mean Square Errors(RMSEs) are reduced to 11.15% and 7.55%, and both are less than 15%.In conclusion,the influence of mixed pixel on hyperspectral imagery classification is eliminated, and the classification accuracy is increased.Keywords：mixed-pixel decomposition;nonlinear decomposition;Multiple Kernel Support Vetor Machine (MKSVM);hyperspectral imagery- 51
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Published：2020-08-13 -
Original feature selection based on false nearest neighbor criterion in supervised locality preserving subspace
Abstract：A novel method based on Supervised Locality Preserving Projection (SLPP) and False Nearest Neighbor (FNN) was proposed for selecting the most proper feature for nonlinear pattern classification.In the proposed method, nonlinear original data were mapped to the supervised locality preserving subspace to eliminate the existing multi-collinearity among the features.Then, the interpretation capability for original features was estimated through calculating the variable mapping distance in the supervised locality preserving subspace.The nearest neighbor classifier based on each subset obtained by eliminating weak features successively was constructed.Finally, the optimal feature subset was selected corresponding to the highest recognition accuracy and the least number of features.The experiment on synthetic dataset shows that the proposed method can obtain an optimal feature subset containing the essential features in accordance with the classification goal.The method was used to select the features of low resistivity hydrocarbon reservoir, and the result indicates that the obtained optimal feature subset contains over 50% less feature and achieves 8% higher recognition accuracy as compared to that of the all-feature set.These results validate that the proposed method can offer excellent abilities of original feature selection and nonlinear feature selection.Keywords：Supervised Locality Preserving Projection(SLPP);False Nearest Neighbor(FNN);Feature selection;pattern classification;low resistivity hydrocarbon reservoir recognition- 70
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Published：2020-08-13 -
Power-aware management for non-stationary service requests
Abstract：For multitasking environment of an embedded system, an improved method called hybrid model for power management algorithm was proposed for modeling of system with general distribution.First, the dynamic power management strategy algorithm was introduced, and the reason why it needed to be improved was expounded.Then, the Rescaled Range Analysis(R/S)method was used to analyze the long distance correlation of non-stationary time service requests and the corresponding strategy was selected depending on the different results.These strategies are remaining battery power timeout strategy, fuzzy not quite PID strategy and semi-Markov random strategy.Finally, the method for determining the strategy parameters was given and the strategy proposed in this paper was analyzed experimentally.The experimental results show that this strategy makes up for the deficiency of conventional dynamic power management strategy and has more extensive adaptability.Under the condition of 10% performance loss,the average system power consumption is reduced by 37%,and the hit rate is more than 60%.The algorithm reduces power consumption more efficiently than other methods, and is applicable in embedded systems.Keywords：power management;rescaled range analysis;semi-Markov decision processes;policy optimization;embedded system- 53
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Published：2020-08-13 -
High efficient erasure code for reliable transmission of compressed data in wireless link
Abstract：The compressed data obtained from the load of an Unmanned Aerial Vehicle(UAV) are highly suffer from interference when it transmits in the wireless communication link with a rate of bit error of 1×10-5, so that the ground terminal can not decode and display the video data.This paper proposes an efficient erasure coding technology to improve the error resilience ability of the compressed stream based on analysis of the error mode of the down-link data transmission.Firstly, the encode data were framed according to the number of bytes and the improved fast Vandermonde erasure coding was used to the column data framed.Then the fast Cyclic Redundancy Check(CRC) was used for the encoded data according to the frame format.Finally, the stream was encoded and put into the transmission channel.Experiment results show that this erasure coding technology reduces the channel bit error rate from 1×10-5 to 1×10-8, and the compressed stream can be decoded and displayed correctly.Moreover, the technology has the features of low computational complexity, small delay, and easy implementation by the hardware.The erasure coding has applied to measuring and control systems of UAVs successfully.Keywords：video compress;erasure code;CRC check;wireless transmission;error resilience- 55
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Published：2020-08-13 -
Footprint automatic alignment algorithm fusing texture features and depth information
Abstract：The footprint detection methods in criminal cases were discussed.As existing footprint comparison does not separate the footprint depth information and texture information, a comparison method fusing texture features and depth information was proposed to achieve automatic comparison of footprints.First, 3-D information of a footprint was obtained through four-step phase shift compensation method to retain much 3-D information of the footprint, and a 2-D variable-scale Gaussian filter was designed to separate footprint surface texture features and depth information.Finally, the regional cross-correlation measurement method was used to calculate the similarity of texture information and the depth information of the 3-D footprint, and the similarity information was quantized and translated in qualitative results by proposed strategy.Experimental results show that the proposed method can separate the texture and depth information of footprints effectively, and footprint comparison is realized automatically by computer software.Comparing to the traditional method of 2-D image grayscale information, the proposed algorithm describes the footprint information more completely.The accuracy rate of automatic comparison is higher than 90%, and the accuracy rate of comparison reaches 100% after adding human intervention based on the existing database, which verifies the effectiveness of the proposed method.Keywords：footprint detection;automatic comparison;texture feature;depth information;3-D information- 47
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Published：2020-08-13 -
Euclidean epipolar rectification frame of weakly calibrated stereo pairs
Abstract：To quickly and intuitively finish the Euclidean epipolar rectification of weakly calibrated stereo pairs(namely,the camera intrinsic parameters are known and the camera external parameters are unknown), an integral Euclidean epipolar rectification frame was proposed.Firstly, a novel essential matrix decomposition and unique solution determination algorithm independent on the Singular Value Decomposition (SVD) operation was proposed to determine the position and orientation information between two cameras.Then, the problem of traditional Euclidean epipolar rectification was generalized, and the infinite homography matrixes were constructed by the estimated camera position and orientation to finish the rectification process of stereo pairs.Finally, the eight groups of SYNTIM images were used to validate the correctness and accuracy of the rectification frame.Experimental results indicate that the proposed frame has the advantages of intuitive form, low computational complexity and easy implementation, as well as the explicit geometrical meanings.As comparison with traditional Euclidean epipolar rectification method, it can well remove the horizontal or vertical disparities of stereo pairs, and can offer higher rectification accuracy.Keywords：camera calibration;epipolar geometry;epipolar rectification;stereo pairs;Essential matrix decomposition- 52
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Published：2020-08-13 -
Enhancement of infrared image details based on gradient histogram transform
Abstract：According to typical problems of low signal to noise ratio and fuzzy edges of target details in an infrared image, this article proposes a infrared image enhancement algorithm for image details based on gradient histogram transform.By analyzing the gradient histogram of the infrared image, a Gaussian function to extend the gradient histogram was constructed to increase the gradient value.By using the histogram specification method to realize the image gradient histogram specification, the transform gradient field was obtained.The Total Variation (TV) model was introduced to control the noise while reconstructing the gradient field.The experiment results indicate that the image information entropy of the algorithm is improved significantly as compared with that of histogram equalization method and specification method.Therefore, it enhances image details and gives qualified image information for target detection, tracking and identification.Based on the finite difference iteration and Visiual C + + programming, the proposed algorithm has image processing time of about 40 ms for an image with the size of 480 pixel×480 pixel, which satisfies the requirements of engineering applications in image processing.Keywords：image processing;infrared image enhancement;gradient histogram transform;total variation- 38
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Published：2020-08-13 -
Quaternion min-norm algorithm for DOA estimation with acoustic vector sensor array
Abstract：To reduce the calculation amount of quaternion Multiple Signal Classification (MUSIC) algorithm, a Minimum Norm(MN) quaternion method based on the quaternion form of an acoustic sensor vector was proposed for estimating Direction of Arrival (DOA).First, based on the MN principle, the (M-N)×M dimension (M is the number of array sensors, N is the number of signal sources) orthogonal noise subspace vectors were converted to a 1×M dimension quaternion noise vector.Then, a simplified formula for peak search was proposed.The searching computation amount of Quaternion MN(Q-MN)was analyzed theoretically.Compared with the Q-MUSIC algorithm, the Q-MN algorithm can save at least 50% of the peak search volume.Experimental results show that the orthogonality of the steering vector with the low-dimensional noise vector derived by proposed method is superior to that with high dimensional noise subspace.When the Signal to Noise Ratio (SNR) is 0 dB, the Vandermonde norm and the spatial spectrum peak value of Q-MN algorithm are 1/3 times and 3 times as much as those of Q-MUSIC.The Q-MN algorithm can successfully identify the DOA of signal sources, and its resolution is equivalent to that of Q-MUSIC algorithm.Moreover, it can be applied to not only L-shaped arrays, but also plane arrays and parallel linear arrays.Keywords：parameter estimation;Direction of Arrival(DOA);quaternion;acoustic vector sensor;min-norm algorithm- 39
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Published：2020-08-13 -
Fast test and recognition of object characters based on multilevel orientation run length coding
Abstract：A new rapid detection and recognition method was proposed for those objects whose image sizes would change in movement processing.Based on Multilevel Orientation Run Length Coding (MORLC) method,the method can generate a new multilevel byte code and object feature templet forms.It is a byte coding and templets and characterized by smaller data amounts, smaller storage addresses, easy constructing, and can choose different classes of sample forms.According to different application requirements, two level byte code in MORLC method and system theory of templets were analyzed, and the experimental data from detection and recognition of moving objects using MORLC two level byte code were given.A detection and recognition experiment on a pedestrian and its position in a static background was performed.The experimental results show that the multilevel byte code and object feature matching templet form have higher processing speeds, robust matching and identification, and not easily get wrong matching.This method is especially suitable for changed images caused by detecting object movement in the scene projection, which means it is not sensitive to image sizes.Another advantage of this method is high processing efficiency.Keywords：product classification;character inspection;character recognition;Image coding- 53
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Published：2020-08-13
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