Improved calibration method for displacement transformation coefficient in optical and visual measurements

Optical and visual measurement technology is used widely in fields that involve geometric measurements,and among such technology are laser and vision-based displacement measuring modules(LVDMMs).The displacement transformation coefficient(DTC)of an LVDMM changes with the coordinates in the camera image coordinate system during the displacement measuring process,and these changes affect the displacement measurement accuracy of LVDMMs in the full field of view(FFOV).To give LVDMMs higher accuracy in the FFOV and make them adaptable to widely varying measurement demands,a new calibration method is proposed to improve the displacement measurement accuracy of LVDMMs in the FFOV.First,an image coordinate system,a pixel measurement coordinate system,and a displacement measurement coordinate system are established on the laser receiving screen of the LVDMM.In addition,marker spots in the FFOV are selected,and the DTCs at the marker spots are obtained from calibration experiments.Also,a fitting method based on locally weighted scatterplot smoothing(LOWESS)is selected,and with this fitting method the distribution functions of the DTCs in the FFOV are obtained based on the DTCs at the marker spots.Finally,the calibrated distribution functions of the DTCs are applied to the LVDMM,and experiments conducted to verify the displacement measurement accuracies are reported.The results show that the FFOV measurement accuracies for horizontal and vertical displacements are better than±15μm and±19μm,respectively,and that for oblique displacement is better than±24μm.Compared with the traditional calibration method,the displacement measurement error in the FFOV is now 90%smaller.This research on an improved calibration method has certain significance for improving the measurement accuracy of LVDMMs in the FFOV,and it provides a new method and idea for other vision-based fields in which camera parameters must be calibrated.

Practical calibration method for instantaneous polarization radar systems utilizing a metal sphere

A practical calibration method is proposed for instantaneous polarization radar systems.The method only needs one measurement by using a metal sphere.The distortions of system and the actual polarization scattering matrix（PSM）of target can be obtained.First,an instantaneous polarization radar system is presented.The system can obtain PSM by a single pulse echo.The dual-polarization antenna can transmit and receive two orthogonal polarization waves.The multilayer micro-strip patch antenna is adopted for this kind of radar system.Second,based on the multi-port network theory,the operation and system errors of instantaneous polarization radar system are analyzed.By making assumption on the cross-talk factors of antenna,distortion matrices of R and Tare derived.Finally,the calibration method based on instantaneous polarization measurement is introduced.Simulation results show the performance of this calibration method.The values of calibrated PSM are in agreement with the actual ones after calibration.

Study on the Drift Calibration Method and Device for the Tin Oxide pH Electrode

Drift phenomenon has been known as the drawback of sensors and causes inaccuracy on the long-term measurement. In general,there are two methods to reduce the drift problem.One is to tune the parameters of the fabrication process to improve the properties of the front-ended device.Another is to compensate the drift phenomenon by adding extra drift compensation circuit or software in the back-ended readout circuit.In this study,a drift calibration method for the potentiometric sensor was presented and the drift calibration method was performed by using the circuit.According to experimental results,the drift phenomenon of the SnO_2 pH electrode was reduced by the drift calibration device.

Optimised Calibration Method for Six-Port Junction

A dual-tone technique is used to produce multi-samples in optimising calibration of six-port junction. More accurate results are achieved by using the least-square method and excluding those samples which may cause bigger errors. A 0.80 -1.10 GHz microwave integrated circuit （MIC） six-port reflectometer is constructed. Nine test samples are used in the measurement. With Engen＇s calibration procedure, the difference between the HP8510 and the six-port reflectrometer is in the order of 0.20 dB/1.5° for most cases, above 0.50 dB/5.0° at boundary frequency. With the optimised method, the difference is less than 0. 10 dB/1.0° for most cases, and the biggest error is 0.42 dB/2.1° for boundary frequencies.

Calibration method to improve the accuracy of THz imaging and spectroscopy in reflection geometry

We introduce a novel method to accurately extract the optical parameters in terahertz reflection imaging. Our method builds on standard self-referencing methods using the reflected signal from the bottom of the imaging window material to further compensate for time-dependent system fluctuations and position-dependent variation in the window thickness. Our proposed method not only improves the accuracy, but also simplifies the imaging procedure and reduces measurement times.

A calibration method for optical trap force by use of electrokinetic phenomena

An experimental method for calibration of optical trap force upon cells by use of electrokinetic phenomena is demonstrated. An electronkinetic sample chamber system （ESCS） is designed instead of a common sample chamber and a costly automatism stage, thus the experimental setup is simpler and cheaper. Experiments indicate that the range of the trap force measured by this method is piconewton and sub-piconewton, which makes it fit for study on non-damage interaction between light and biological particles with optical tweezers especially. Since this method is relevant to particle electric charge, by applying an alternating electric field, the new method may overcome the problem of correcting drag force and allow us to measure simultaneously optical trap stiffness and particle electric charge.

Study on Calibration of L-band Radar by a Drone

A new calibration method of L-band radar accuracy using a rotary-wing drone equipped with"GPS"satellite positioning system was proposed.The L-band radar calibration system scheme based on this method was designed.The theoretical basis required for system realization was studied,and the system calibration method was given.The calibration results referred to the domestic new generation weather radar antenna beam pointing calibration technical indicator(≤0.3°),and its accuracy met relevant business requirement.It show that this method can easily and quickly complete the radar system calibration.Compared with the traditional radar calibration method,it is more convenient,less affected by surrounding environment,and has low requirements on the weather.

Relative flux calibration for the Guoshoujing Telescope (LAMOST)

This paper presents a relative flux calibration method for the Guoshoujing Telescope （LAMOST）, which may be applied to connect a blue spectrum to a red spectrum to build the whole spectrum across the total wavelength range （3700 ～ 9000 A）. In each spectrograph, we estimate the effective temperatures of selected stars using a grid of spectral line indices in the blue spectral range and a comparison with stellar atmosphere models. For each spectrograph, stars of types A and F are selected as pseudo-standard stars, and the theoretical spectra are used to calibrate both the blue （3700 ～ 5900 A） and red spectrograph arms （5700 ～ 9000 A）. Then the spectral response function for these pseudo-standard stars could be used to correct the raw spectra provided by the other fibers of the spectrograph, after a fiber efficiency function has been derived from twilight flat-field exposures. A key problem in this method is the fitting of a pseudo stellar continuum, so we also give a detailed description of this step. The method is tested by comparing a small sample of LAMOST spectra calibrated in this way on stars also observed by the Sloan Digital Sky Survey. The result shows that the T eff estimation and relative flux calibration method are adequate.

Calibration of Discrete Element Heat Transfer Parameters by Central Composite Design

The efficiency and precision of parameter calibration in discrete element method （DEM） are not satisfactory, and parameter calibration for granular heat transfer is rarely involved. Accordingly, parameter calibration for granular heat transfer with the DEM is studied. The heat transfer in granular assemblies is simulated with DEM, and the effective thermal conductivity （ETC） of these granular assemblies is measured with the transient method in simulations. The measurement testbed is designed to test the ETC of the granular assemblies under normal pressure and a vacuum based on the steady method. Central composite design （CCD） is used to simulate the impact of the DEM parameters on the ETC of granular assemblies, and the heat transfer parameters are calibrated and compared with experimental data. The results show that, within the scope of the considered parameters, the ETC of the granular assemblies increases with an increasing particle thermal conductivity and decreases with an increasing particle shear modulus and particle diameter. The particle thermal conductivity has the greatest impact on the ETC of granular assemblies followed by the particle shear modulus and then the particle diameter. The calibration results show good agreement with the experimental results. The error is less than 4%, which is within a reasonable range for the scope of the CCD parameters. The proposed research provides high efficiency and high accuracy parameter calibration for granular heat transfer in DEM.

A method to determine the bonded-particle model parameters for simulation of ores

The bonded-particle model(BPM)is commonly used in the numerical analysis of ore samples.To improve the accuracy of simulating the mechanical process of ore process of ore crushing in a crusher,the parameters of the BPM for the ore must be calibrated.In this study,a calibration method was proposed for the scientific determination of the parameters of the BPM for ore undergoing uniaxial compression.First,physical tests and simulations were conducted to determine the mechanical response(uniaxial compressive strength and macroscopic stiffness)of ore during uniaxial compression.Then,the sensitivity of the mechanical response to the values of microscopic parameters was tested using a Plackett-Burman design.Next,the microscopic parameters with the greatest impact on the response were identified,and the range of parameters that met the target response was determined using a steepest ascent design;Second,a second-order model of the mechanical response was established using the sensitive parameters by combining a Box-Behnken design with response surface methodology to obtain the optimal BPM parameters.Simulation tests showed that the normal stiffness per unit area,critical shear stress,and bonded disk radius had significant effects on the uniaxial compressive strength(UCS)and macroscopic stiffness(MS).To verify the validity of the proposed calibration method,laboratory tests were conducted.The consistency of the simulation results with experimental results indicated that response surface methodology with the Plackett-Burman design,steepest ascent design,and Box-Behnken design can be an effective method for calibrating the BPM of ores.

Theoretical Research and Experimental Validation of Elastic Dynamic Load Spectra on Bogie Frame of High-speed Train

When a train runs at high speeds, the external exciting frequencies approach the natural frequencies of bogie critical components, thereby inducing strong elastic vibrations. The present international reliability test evaluation standard and design criteria of bogie frames are all based on the quasi-static deformation hypothesis. Structural fatigue damage generated by structural elastic vibrations has not yet been included. In this paper, theoretical research and experimental validation are done on elastic dynamic load spectra on bogie frame of high-speed train. The construction of the load series that correspond to elastic dynamic deformation modes is studied. The simplified form of the load series is obtained. A theory of simplified dynamic load–time histories is then deduced. Measured data from the Beijing–Shanghai Dedicated Passenger Line are introduced to derive the simplified dynamic load–time histories. The simplified dynamic discrete load spectra of bogie frame are established. Based on the damage consistency criterion and a genetic algorithm, damage consistency calibration of the simplified dynamic load spectra is finally performed. The computed result proves that the simplified load series is reasonable. The calibrated damage that corresponds to the elastic dynamic discrete load spectra can cover the actual damage at the operating conditions. The calibrated damage satisfies the safety requirement of damage consistency criterion for bogie frame. This research is helpful for investigating the standardized load spectra of bogie frame of high-speed train.

Method for in situ calibration of multiple feedback interferometers

A method is presented for in situ resolution calibration of multiple feedback interferometers(MFIs) using two lasers with di?erent feedback levels simultaneously. The laser with weak optical feedback level generates half-wavelength optical fringes, whereas the laser with strong multiple feedback level generates optical nanofringes. By using this method, the number of displaced optical nano-fringes can be easily counted, and the resolution of the MFIs can be accurately determined. The integrated MFIs can be used to measure displacements and calibrate other displacement sensors.

Quantitative Analysis of Fe Content in Iron Ore via External Calibration in Conjunction with Internal Standardization Method Coupled with LIBS

The external calibration in conjunction with internal standardization（ECIS） coupled with laser-induced breakdown spectroscopic（LIBS） technique was proposed to perform the quantitative analysis of Fe content in iron ore The plasma temperature and the electron number density were calculated to prove that the plasma was under local thermodynamic equilibrium（LTE） conditions and to ensure that the integral intensities of Fe I lines were reasonable. In addition, the result of the quantitative analysis shows a content of （20.26±0.59）% by mass of Fe in the iron ore. It was determined by four calibration curves, drawn for four emission lines of Fe I（373.48, 373.71,404.58 and 438.35 nm） normalized by Mn I line, base on the ECIS method which can eliminate the influence of matrix effect and improve the accuracy of quantitative analysis, compared with the standard addition method. Both the results of these two analytical methods were compared with that listed in the Standard Substance Certificate. The percentage content of Fe in the same sample of iron ore by the ECIS method was （20.17±0.08）% by mass, which shows a good performance to analyze the Fe content of iron ore in combination with LIBS.

New method for calibration of sun photometers

A new method for calibration of sun photometers based on Bouguer-Beer law is proposed. The developed basic equation of calibration makes it possible to formulate the derivative methods of calibration on the basis of photometric measurements upon optical air masses, the ratio of which is an integer number.

A universal method for camera calibration in UITS scenes

A universal approach to camera calibration based on features of some representative lines on traffic ground is presented. It uses only a set of three parallel edges with known intervals and one of their intersected lines with known slope to gain the focal length and orientation parameters of a camera. A set of equations that computes related camera parameters has been derived from geometric properties of the calibration pattern. With accurate analytical implementation, precision of the approach is only decided by accuracy of the calibration target selecting. Final experimental results have showed its validity by a snapshot from real automatic visual traffic surveillance （AVTS） scencs.

Workflow to numerically reproduce laboratory ultrasonic datasets

The risks and uncertainties related to the storage of high-level radioactive waste （HLRW） can be reducedthanks to focused studies and investigations. HLRWs are going to be placed in deep geological repositories,enveloped in an engineered bentonite barrier, whose physical conditions are subjected tochange throughout the lifespan of the infrastructure. Seismic tomography can be employed to monitor itsphysical state and integrity. The design of the seismic monitoring system can be optimized via conductingand analyzing numerical simulations of wave propagation in representative repository geometry.However, the quality of the numerical results relies on their initial calibration. The main aim of this paperis to provide a workflow to calibrate numerical tools employing laboratory ultrasonic datasets. The finitedifference code SOFI2D was employed to model ultrasonic waves propagating through a laboratorysample. Specifically, the input velocity model was calibrated to achieve a best match between experimentaland numerical ultrasonic traces. Likely due to the imperfections of the contact surfaces, theresultant velocities of P- and S-wave propagation tend to be noticeably lower than those a prioriassigned. Then, the calibrated model was employed to estimate the attenuation in a montmorillonitesample. The obtained low quality factors （Q） suggest that pronounced inelastic behavior of the clay has tobe taken into account in geophysical modeling and analysis. Consequently, this contribution should beconsidered as a first step towards the creation of a numerical tool to evaluate wave propagation innuclear waste repositories. 2014 Institute of Rock and Soil Mechanics, Chinese Academy of Sciences. Production and hosting byElsevier B.V. All rights reserved.

Accelerometer Bias and Star Sensor Installation Error Joint Calibration for the SINS/CNS Integrated Navigation System Using Attitude Maneuver

The integrated strap-down inertial nav igation system/olelestial navigation system(SINS/CNS)i an important autonomous navigation method with efective concealment and high predision.Both accelerometer biss and star ensor installation error ame important factors that aflect the performanoe of this mavigation system,which needl to be calibratexd and compensatedl.A new acelerometer bias and star sensor installation error joint calibration method for the SINS/CNS integrated navigation system i propoeed.In this newly propoeed method,the installation error of star sensor is augmented to the state vector,and the star vector,nadir angle,horkzontal poeition error and velbcity error ame ueed a8 measurementa to calbrate the two errors mentioned above.Simulations show that both accelerometer bias and star sensor installation enror an be calibratedl efectively.

Recent progress on the application of LIBS for metallurgical online analysis in China

Recent progress on the application of laser-induced breakdown spectroscopy （LIBS） for metallurgical analysis particularly achieved by Chinese research community is briefly reviewed in this article. The content is mainly focused on the progress in experimental research and calibration methods toward LIBS applications for metallurgical online analysis over the past few years. Different experiment setups such as single-pulse and double-pulses LIBS schematics are introduced. Various calibration methods for different metallic samples are presented. Quantitative results reported in the literature and obtained in the analysis of various samples with different calibration methods are summarized. At the last section of this article, the difficulties of LIBS application for molten metal analysis in a furnace are discussed.

Time-Modulated Arrays:A Four-Dimensional Antenna Array Controlled by Switches

With the rapid development of modern electronic technologies,antenna arrays typically operate in very complex electromagnetic environments.However,owing to the various errors such as systematic errors and random errors,conventional antenna arrays have relatively high sidelobes.Time modulated arrays(TMAs),also known as four-dimensional(4-D)antenna arrays,introduce time as an additional dimension for generating ultra-low sidelobes at fundamental component and realizing real-time beam scanning by harmonic components.Recently,the harmonic components can also be developed for various new applications including wireless communications and radar systems.In this review,we introduce comprehensively the fundamental methodologies and recent applications of TMAs.This aims to stimulate continuing efforts for the understanding of TMAs and explore their applications in various aspects.The methods mentioned in this review include three aspects:sideband radiation suppression,power efficiency of TMAs,and applications of harmonic components.These methods either improve the existing TMAs or promote the practical applications of TMAs.First,to suppress the sideband radiation,a method using non-uniform periodical modulation is introduced.The proposed method has an advantage of low computation and can be easily used for synthesizing a real-time radiation pattern according to the environmental need.Next,a TMA structure using reconfigurable power dividers/combiner is introduced to improve the power efficiency of feeding network.Finally,three applications of harmonic component including direction finding,calibration method,and space division multiple access are separately introduced to illustrate the development potential of TMAs.