DIGITAL SPECKLE CORRELATION METHOD IMPROVED BY GENETIC ALGORITHM

The digital speckle correlation method is an important optical metrology for sur- face displacement and strain measurement.With this technique,the whole field deformation in- formation can be obtained by tracking the geometric points on the speckle images based on a correlation-matching search technique.However,general search techniques suffer from great com- putational complexity in the processing of speckle images with large deformation and the large random errors in the processing of images of bad quality.In this paper,an advanced approach based on genetic algorithms (GA) for correlation-matching search is developed.Benefiting from the abilities of global optimum and parallelism searching of GA,this new approach can complete the correlation-matching search with less computational consumption and at high accuracy.Two experimental results from the simulated speckle images have proved the efficiency of the new approach.

Deformation Field around the Stress Induced Crack Area in Sandstone by the Digital Speckle Correlation Method

The deformation field around sub-cracks was calculated using the digital speckle correlation method. First, the uni-axial compression tests on sandstone samples containing a pre- fabricated fracture were made. Photomicrographs showing the characteristics of the sub-crack development were taken using a scanning electron microscope （SEM）. From these photomicrographs, the real-time images showing the initiation, growth and coalescence of sub-cracks and micro-cracks in the sandstone specimens were obtained and the effects of loading level as well as grain boundaries on the development of cracks were analyzed. Second, the intensity images of the sandstone specimen surface were captured from the observations of the SEM corresponding to different loading levels. Then correlation computation was carried out for the sequential pairs of intensity images to evaluate the displacement components, as well as the strain field. The results show that the deformation varies in different areas separated by sub-cracks during rock damage processes.

Investigation of feature contribution to shield tunneling-induced settlement using Shapley additive explanations method

Accurate prediction of shield tunneling-induced settlement is a complex problem that requires consideration of many influential parameters.Recent studies reveal that machine learning(ML)algorithms can predict the settlement caused by tunneling.However,well-performing ML models are usually less interpretable.Irrelevant input features decrease the performance and interpretability of an ML model.Nonetheless,feature selection,a critical step in the ML pipeline,is usually ignored in most studies that focused on predicting tunneling-induced settlement.This study applies four techniques,i.e.Pearson correlation method,sequential forward selection(SFS),sequential backward selection(SBS)and Boruta algorithm,to investigate the effect of feature selection on the model’s performance when predicting the tunneling-induced maximum surface settlement(S_(max)).The data set used in this study was compiled from two metro tunnel projects excavated in Hangzhou,China using earth pressure balance(EPB)shields and consists of 14 input features and a single output(i.e.S_(max)).The ML model that is trained on features selected from the Boruta algorithm demonstrates the best performance in both the training and testing phases.The relevant features chosen from the Boruta algorithm further indicate that tunneling-induced settlement is affected by parameters related to tunnel geometry,geological conditions and shield operation.The recently proposed Shapley additive explanations(SHAP)method explores how the input features contribute to the output of a complex ML model.It is observed that the larger settlements are induced during shield tunneling in silty clay.Moreover,the SHAP analysis reveals that the low magnitudes of face pressure at the top of the shield increase the model’s output。

Correlation method estimation of the modulation signal in the weak equivalence principle test

In a test of the weak equivalence principle （WEP） with a rotating torsion pendulum, it is important to estimate the amplitude of the modulation signal with high precision. We use a torsional filter to remove the free oscillation signal and employ the correlation method to estimate the amplitude of the modulation signal. The data analysis of an experiment shows that the uncertainties of amplitude components of the modulation signal obtained by the correlation method are in agreement with those due to white noise. The power spectral density of the modulation signal obtained by the correlation method is about one order higher than the thermal noise limit. It indicates that the correlation method is an effective way to estimate the amplitude of the modulation signal and it is instructive to conduct a high-accuracy WEP test.

Tensile strength of sea ice using splitting tests based on the digital image correlation method

The splitting test is a competitive alternative method to study the tensile strength of sea ice owing to its suitability for sampling.However,the approach was questioned to the neglect of local plastic deformation during the tests.In this study,splitting tests were performed on sea ice,with 32 samples subjected to the regular procedure and 8 samples subjected to the digital image correlation method.The salinity,density,and temperature were measured to determine the total porosity.With the advantage of the digital image correlation method,the full-field deformation of the ice samples could be determined.In the loading direction,the samples mainly deformed at the ice-platen contact area.In the direction vertical to the loading,deformation appears along the central line where the splitting crack occurs.Based on the distribution of the sample deformation,a modified solution was derived to calculate the tensile strength with the maximum load.Based on the modified solution,the tensile strength was further calculated together with the splitting test results.The results show that the tensile strength has a negative correlation with the total porosity,which agrees with previous studies based on uniaxial tension tests.

Experimental investigation of interface curing stresses between PMMA and composite using digital speckle correlation method

This paper studies the interface curing stresses between polymethyl methacrylate (PMMA) and composite by means of digital speckle correlation method (DSCM).A new method by combining DSCM with the marker points is developed to measure the interface curing stresses,and the measurement principle is introduced.The interface curing stresses between PMMA and composite with different curing bonding conditions are measured and analyzed,this indicates that the residual stress for furnace heating and furnace cooling is the smallest.Finally,the measurement error is discussed by means of finite element method,the influences of glass microsphere between adhesive and PMMA can be ignored.

ADAPTIVE FUSION ALGORITHMS BASED ON WEIGHTED LEAST SQUARE METHOD

Weighted fusion algorithms, which can be applied in the area of multi-sensor data fusion, are advanced based on weighted least square method. A weighted fusion algorithm, in which the relationship between weight coefficients and measurement noise is established, is proposed by giving attention to the correlation of measurement noise. Then a simplified weighted fusion algorithm is deduced on the assumption that measurement noise is uncorrelated. In addition, an algorithm, which can adjust the weight coefficients in the simplified algorithm by making estimations of measurement noise from measurements, is presented. It is proved by emulation and experiment that the precision performance of the multi-sensor system based on these algorithms is better than that of the multi-sensor system based on other algorithms.

Study on Corrosion Protection Method of Reinjection Water Treatment System in a Natural Gas Processing Plant

The research investigated the corrosion of the reinjection water system to ensure the safe production of the system.By analyzing the composition of the methanol-containing wastewater,the corrosion status of the injection water system was studied by the on-site materials 20#steel,Q235B steel and L316 steel for that the methanol-containing wastewater of a natural gas processing plant in northern Shaanxi had high acidity,Cl-and sulfide contents,salinity and corrosion.Then the grey system theory modeling software 3.0 was used to study the influence degree of various corrosion factors on the corrosion rate and depth of Q235B steel.The most important factors were determined,and countermeasures against corrosion were proposed.The results showed that L316 steel was more resistant to corrosion,and the corrosion rate was 0.0015 mm/a,which was less than the national standard(0.0760 mm/a).The maximum corrosion depth was 47.63μm,which was the lowest among the three materials.The corrosion rate and depth were the parent factors.Among the four factors of sulfide,Cl-,salinity and pH,grey relational degrees of sulfide were 0.75 and 0.80,respectively,which was the most important factor causing corrosion;using sulfur corrosion inhibitor protection method,TS-792C was selected by electrochemical method from three corrosion inhibitors.The impedance data simulation software ZSimpWin was used to simulate the equivalent circuit diagram,and the impedance of Q235B steel was the largest.The corrosion inhibition rate was up to 90.26%when corrosion rate was 0.0130 mm/a under the fitting of Tafel polarization curve,with the best anti-sulfur effect.At 80℃and a sulfide content of 300 mg/L,the corrosion rate of Q235B steel was less than 0.0760 mm/a.When the added amount was 100 mg/L,the corrosion current density and corrosion rate of the reinjection sewage was 0.462 mA/cm 2 and 0.0505 mm/a,both at the lowest values and with good temperature and sulfur resistance.

Correction of cosine oscillation to the improved correlation method of estimating the amplitude of gravitational background signal

In the measurement of G with the angular acceleration method,the improved correlation method developed by Wu et al.（Wu W H,Tian Y,Luo J,Shao C G,Xu J H and Wang DH 2016 Rev.Sci.Instrum.87 094501） is used to accurately estimate the amplitudes of the prominent harmonic components of the gravitational background signal with time-varying frequency.Except the quadratic slow drift,the angular frequency of the gravitational background signal also includes a cosine oscillation coming from the useful angular acceleration signal,which leads to a deviation from the estimated amplitude.We calculate the correction of the cosine oscillation to the amplitude estimation.The result shows that the corrections of the cosine oscillation to the amplitudes of the fundamental frequency and second harmonic components obtained by the improved correlation method are within respective errors.

A Simple Superresolution Approach of Multipath Delay Profiles Measured by PN Correlation Method

Time resolution of multipath delay profiles measured by using autocorrelation of pseudonoise (PN) code sequence is generally limited by the chip rate of the PN code sequence. In this paper, we propose a simple method to improve the time resolution of delay profiles measured by the PN correlation method. Effectiveness of this method is demonstrated by indoor wireless propagation experiments.

Correlation Method of Average Plasma Velocity Measurement in Hall-Effect Thrusters

A new method to measure the average plasma velocity in a Hall-effect thruster is presented. The method is brought forward in virtue of the characteristics of low frequency oscillation induced by the propellant ionization in the channel and the oriented movement feature of the plasma density out of the channel. The method, equivalent to the correlation method generally used in the signal processing field, provides a solution to the problem of specific impulse measurement on a timescale of hundreds of microseconds and makes the time evolution of average plasma velocity clear. The comparison between the measured value and the calibrated value shows that the relative error is about 3%.

General Expression of LRC Method in Estimation of Bridge’s Equivalent Static Wind Load

According to the relationship between load and response, the equivalent static wind load(ESWL) of a structure can be estimated by load-response correlation(LRC) method, which can be accurately used to estimate the background ESWL of a structure. The derivation of the classical expression of LRC formula is based on a specific command response at a critical position, and the ESWL distribution has only one form in this case. In this paper, a general expression of LRC formula is derived based on a specific command response at all positions. For the general expression, ESWLs can be expressed by load-response correlation coefficients, response-response correlation coefficients, RMS values of the fluctuating wind loads, and peak factor in the form of matrices. By comparing the expressions of LRC method, it was found that the classical expression was only one form of the general one. The general expression which introduces the response-response correlation coefficients provided more options for structural engineers to estimate ESWLs and offered further insights into the LRC method. Finally, a cable-stayed bridge, a rigid three span continuous girder bridge, and a suspension bridge were used to verify the correctness of the general expression of LRC method.

Effects of Modulation Methods on the Drying Characteristics and Nutritional Quality of Medicago sativa Hay

Two-year-old Medicago sativa at budding initial stage was taken as research materials.Five methods were used to make green hay,including flatting stems ＋ spraying 2.5% K2CO3,flatting stems,sun curing,drying in shade and drying under 105 ℃ condition（CK）.Besides,effects of different green hay making methods on dry characteristics and nutritional quality of M.sativa green hay were studied,and a comprehensive evaluation of M.sativa green hays was conducted.Results showed that,except CK,the drying rates in other making methods were all fast at first,and then slow down.Both of drying under 105 ℃ condition and flatting stems ＋ spraying K2CO3 could speed up drying rate and reduce nutritional losses of green hay.Sun curing could also speed up drying rate,but it could not maintain the quality of green hay.The results of Grey Relational Analysis on five green hay making methods indicated that CK had the best comprehensive performance,followed by green hays made by flatting stems ＋ spraying K2CO3.Therefore,flatting stems ＋ spraying K2CO3 was a quick and easy method to make green hay,and it was worth to be recommended in practical production.

Failure characteristics and the damage evolution of a composite bearing structure in pillar-side cemented paste backfilling

A backfilling body-coal pillar-backfilling body(BPB)structure formed by pillar-side cemented paste backfilling can bear overburden stress and ensure safe mining.However,the failure response of BPB composite samples must be investigated.This paper examines the deformation characteristics and damage evolution of six types of BPB composite samples using a digital speckle correlation method under uniaxial compression conditions.A new damage evolution equation was established on the basis of the input strain energy and dissipated strain energy at the peak stress.The prevention and control mechanisms of the backfilling body on the coal pillar instability were discussed.The results show that the deformation localization and macroscopic cracks of the BPB composite samples first appeared at the coal-backfilling interface,and then expanded to the backfilling elements,ultimately appearing in the coal elements.The elastic strain energy in the BPB composite samples reached a maximum at the peak stress,whereas the dissipated energy continued to accumulate and increase.The damage evolution curve and equation agree well with the test results,providing further understanding of instability prevention and the control mechanisms of the BPB composite samples.The restraining effect on the coal pillar was gradually reduced with decreasing backfilling body element's volume ratio,and the BPB composite structure became more vulnerable to failure.This research is expected to guide the design,stability monitoring,instability prevention,and control of BPB structures in pillar-side cemented paste backfilling mining.

Employment Quality EvaluationModel Based on Hybrid Intelligent Algorithm

In order to solve the defect of large error in current employment quality evaluation,an employment quality evaluation model based on grey correlation degree method and fuzzy C-means(FCM)is proposed.Firstly,it analyzes the related research work of employment quality evaluation,establishes the employment quality evaluation index system,collects the index data,and normalizes the index data;Then,the weight value of employment quality evaluation index is determined by Grey relational analysis method,and some unimportant indexes are removed;Finally,the employment quality evaluation model is established by using fuzzy cluster analysis algorithm,and compared with other employment quality evaluation models.The test results show that the employment quality evaluation accuracy of the design model exceeds 93%,the employment quality evaluation error can meet the requirements of practical application,and the employment quality evaluation effect is much better than the comparison model.The comparison test verifies the superiority of the model.

A motion correction on direct estimations of air-sea fluxes from a buoy

A flux system deployed on a moored buoy has been described, which is capable of directly estimating the airsea fluxes after removing the contamination in the signal due to buoy motion. A triple loop fitting method has been demonstrated for determining the three angular offsets between measurement axes of the sonic anemometer and motion pack. The data collected in an experiment in the Northern Huanghai Sea is used to correct the three sonic anemometer measurements of turbulent wind for buoy motion. The effective removal of wave-scale motion from the spectra and cospectra are demonstrated. Estimates of along-wind momentum flux, sensible heat flux and latent heat flux calculated by the eddy correlation method based on data obtained by sonic anemometer 81000V are shown to be in the same trend and scale with those determined by the bulk aerodynamic method after motion correction. The motion correction not only greatly improve the estimation of the momentum flux but also has a great impact on the calculated sensible heat flux.

Parameterization of the Absorption of the H_(2)O Continuum,CO_(2),O_(2),and Other Trace Gases in the Fu-Liou Solar Radiation Program

The absorption properties of the water vapor continuum and a number of weak bands for H2O, O2, CO2, CO, N2O, CH4, and O3 in the solar spectrum are incorporated into the Fu-Liou radiation parameterization program by using the correlated k-distribution method (CKD) for the sorting of absorption lines. The overlap absorption of the H2O lines and the H2O continuum (2500-14500 cm-1) are treated by taking the two gases as a single-mixture gas in transmittance calculations. Furthermore, in order to optimize the computation efforts, CO2 and CH4 in the spectral region 2850-5250 cm-1 are taken as a new single-mixture gas as well. For overlap involving other absorption lines in the Fu-Liou spectral bands, the authors adopt the multiplication rule for transmittance computations under which the absorption spectra for two gases are assumed to be uncorrelated. Compared to the line-by-line (LBL) computation, it is shown that the errors in fluxes introduced by these two approaches within the context of the CKD method are small and less than 0.48% for the H2O line and continuum in the 2500-14500 cm-1 solar spectral region, -1% for H2O (line)+H2O (continuum)+CO2+CH4 in the spectral region 2850-5250 cm-1, and -1.5% for H2O (line)+H2O (continuum)+O2 in the 7700-14500 cm-1 spectral region. Analysis also demonstrates that the multiplication rule over a spectral interval as wide as 6800 cm-1 can produce acceptable errors with a maximum percentage value of about 2% in reference to the LBL calculation. Addition of the preceding gases increases the absorption of solar radiation under all sky conditions. For clear sky, the increase in instantaneous solar absorption is about 9%-13% (~12 W m^2) among which the H2O continuum produces the largest increase, while the contributions from O2 and CO2 rank second and third, respectively. In cloudy sky, the addition of absorption amounts to about 6-9 W m-2. The new, improved program with the incorporation of the preceding gases produces a smaller solar absorption in clouds due to the reduced solar flux reaching the cloud top.

The Relationship between the Wintertime Blocking over Greenland and the Sea Ice Distribution over North Atlantic

The sea-ice concentration in the Northern Hemisphere, 500 hPa height, sea-level pressure and 1000-500 hPa thickness of monthly mean data are examined for the period 1953-1989, with emphasis on the winter season.Relationships between large-scale patterns of atmospheric variability and sea-ice variability are investigated, making use of the correlation method. The analysis is conducted for the Atlantic sectors. In agreement with earlier studies based upon monthly mean data on sea-ice concentration, the strongest sea-ice pattern is composed of a dipole with opposing centers of action in the Davis Straits / Labrador Sea region and the Greenland and Barents Seas. Its temporal variability is strongly coupled to the atmospheric North Atlantic Oscillation (NAO). The relationship between the two patterns is strongest with the atmosphere leading the ocean. The polarity of the NAO is associated with Greenland blocking episodes, during which the influence of the atmosphere is strong enough to temporarily halt the climatological mean advance of the ice edge in some regions and substantially accelerate it in others.The relationships between the fields are indicative of local forcing of sea-ice in most regions, with wind stress and thermodynamic fluxes at the air-sea interface both contributing.

Analyis on the indirect tension displacement and strain field of asphalt mixture based on ABAQUS and DICM

In order to study the damage mechanism of asphalt mixture,it is important to obtain the distribution of displacement and strain of its sample in the indirect tension mode.As a result,the digital image correlation method (DICM) was used to evaluate the displacement field and strain field of asphalt mixture.The results showed that the displacement fields under DICM and ABAQUS are similarly;the strain fields are different due to the different modulus of mastic and aggregate;and DICM is an practical method to study the indirect tension displacement and stain.

THERMAL STRESS MEASUREMENT OF QUARTZ OSCILLATOR MODULE PACKAGING

The thermal stress of the quartz oscillator module packaging isinvestigated using digital-im- age correlation method (DICM), and theexperimental results are given. Under the quartz oscillator modulepackaging, the quartz oscillator and the Fe-Sn-Cu alloy frame arejoined together with the electroconductive adhesive (PI), and theelectroconductive adhesive needs to be cured twice at 150 deg. C and275 deg. C respective- ly.