Universal Global Optimization Research Articles

Research on bond-slip behavior of corroded square rebar-concrete in historical reinforced concrete buildings

Corrosion of rebar often leads to the degradation of the bond-slip performance of reinforced concrete members, which is a serious issue in historical buildings. The bond-slip behavior of square rebar, which is widely used in historical reinforced concrete buildings, is significantly different from that of round rebar. In this paper, a bond-slip model of corroded square rebar reinforced concrete was developed. First, 18 square rebar reinforced concrete cube pull-out specimens are made, and the corrosion of rebars is accelerated by electrochemical corrosion experiments. Second, a universal global optimization method was used to construct the bond slip expression and the four-fold line bond-slip model with different corrosion rates was obtained by using the minimum Euclidean distance point. Third, the calculation formulas for the bond strength reduction coefficient and slip ratio of corroded square rebar-concrete in historical reinforced concrete buildings are derived. Finally, the bond-slip constitutive model of corroded square rebar-concrete in historical reinforced concrete buildings is established. The results show that the model is more accurate, simple, effective, and easy to use in practical engineering. The research results provide an important theoretical basis for the structural evaluation and conservation of historical reinforced concrete buildings.

Study on the Consumption Mechanism and Lubrication of Mold Powder Based on Non-Sinusoidal Oscillation Mode

A two-dimensional mold model coupled multiphase flow, heat transfer, solidification and mold oscillation was established based on the casting parameters of the mold of plant. The accuracy of the model was verified by comparing the measured by plant and calculated mold powder consumption under the same casting conditions. The mechanism of mold powder consumption and lubrication was analyzed based on the non-sinusoidal oscillation mode, and the effect of non-sinusoidal oscillation parameters on mold powder consumption was discussed. Mold powder consumption was determined by the downward flow velocity of liquid mold powder and the thickness of liquid mold powder film, the liquid mold powder consumption decreased with the decrease of those. When the mold moved downward, the mold powder thickness and downward flow velocity decreased, the minimum mold powder consumption reached at the middle of the negative strip time, and the variation was to opposite when the mold moved upward, the maximum mold powder consumption appeared during the positive strip time. With the decrease of casting speed and modification ratio, and increase of oscillation frequency and oscillation amplitude, the mold powder consumption had the tendency to increase. The nonlinear regression equation was fitted by the Levenberg–Marquardt method combined with the universal global optimization method to evaluate mold powder consumption.

Study on the Burst Failure Mechanism and Residual Strength of Casing With Compound Wear Based on Extended Finite Element Method

Abstract Based on the data of wear casing for ShunNan 501 well in Northwest oilfield and the stress–strain intrinsic relationship of P110 tubing, a two-dimensional mechanical model of casing with compound wear is established by using the nonlinear extended finite element method (XFEM) and the burst failure criterion of damage evolution with due consideration of wear type, angle between crescents, overlap depth of crescents, and wear depth caused by drill pipe body and tool joint. The accuracy and reliability of model are verified by the full-scale burst test data. The effects of wear types, angle between crescents, overlap depth of crescents, and wear depth on the internal pressure yield strength (IPYS), burst strength and failure behavior for casing with compound wear are analyzed, by which it is found that casing with compound wear exist stress interference and complex interaction between stress interference and stress concentration, and the burst failure mechanism of casing with compound wear is revealed. Based on the gray correlation analysis result of wear parameters, a prediction model of the residual strength for P110 casing with compound wear is established by 1stOpt software and universal global optimization (UGO) algorithm.

Predicting laterite redox potential with iron activity and electron transfer term

Predicting the redox behavior of organic contaminants and heavy metals in soils is challenging because there are few soil redox potential (Eh) models. In particular, current aqueous and suspension models usually show a significant deviation for complex laterites with few Fe(II). Here, we measured the Eh of simulated laterites over a range of soil conditions (2450 tests). The impacts of soil pH, organic carbon, and Fe speciation on the Fe activity were quantified as Fe activity coefficients, respectively, using a two-step Universal Global Optimization method. Integrating these Fe activity coefficients and electron transfer terms into the formula significantly improved the correlation of measured and modeled Eh values (R2 = 0.92), and the estimated Eh values closely matched the relevant measured Eh values (accuracy R2 = 0.93). The developed model was further verified with natural laterites, presenting a linear fit and accuracy R2 of 0.89 and 0.86, respectively. These findings provide compelling evidence that integrating Fe activity into the Nernst formula could accurately calculate the Eh if the Fe(III)/Fe(II) couple does not work. The developed model could help to predict the soil Eh toward controllable and selective oxidation-reduction of contaminants for soil remediation.

Hysteretic model and resilient application of corrugated shear panel dampers

In this study, corrugated steel shear panels were applied to a metallic shear panel damper (SPD) to improve its seismic performance. The seismic performance tests and analysis of eight specimens were performed for different corrugated steel panel directions, arrangement forms, and material strengths. The results showed that the metallic corrugated shear panel dampers (CSPDs) exhibited remarkable plastic deformation and plump hysteretic loops. The direction of corrugated shear panels had the most significant influence on the energy dissipation performance, and the results of the horizontal corrugated direction exhibited the great performance. Then, the improved Bouc–Wen model was used to predict the hysteretic behaviour of the CSPDs, and the universal global optimization algorithm was applied to identify the model parameters. Additionally, a typical 12 storey benchmark steel frame structure was retrofitted with the CSPDs to verify the application effect of the CSPDs on structural vibration control. And the seismic fragility analysis was implemented to quantify the exceeding probabilities of different damaged states for the original structure and the damper improved structure. Compared with the benchmark frame, the performance level of the damper improvement frame in operation, immediate occupancy, life safety, and collapse prevention increased by 1.51%, 11.50%, 45.59%, and 81.19%, respectively, under the maximum considered earthquake (MCE) level. The analyses showed that the CSPDs could significantly improve the seismic resilience performance of the structure.

Study on residual strength and life prediction of corroded tubing based on thermal-mechanical coupling XFEM

Based on the experimental results of the stress-strain constitutive relationship, thermal expansion coefficient and thermal conductivity for P110S tubing material, a three-dimensional thermal-mechanical coupling mechanical model of P110S tubing with uniform, local and pitting corrosion is established by using nonlinear finite element method with due consideration on the physical nonlinearity of the corroded tubing and the geometric nonlinearity caused by large deformation comprehensively in this paper. The model is verified using full-scale burst test data. Based on the verified model, the burst mechanical behavior and burst strength of corroded tubing under thermal-mechanical coupling were simulated by adopting the XFEM method and burst failure criterion based on damage mechanics evolution, by which the investigation on burst mechanical behavior of P110S tubing wih pitting corrosion is paid the most attention. Based on the sensitivity analysis results of residual strength of corroded tubing and the corrosion test results, a prediction model of the residual strength for P110S corroded tubing is established by using the 1stOpt software and universal global optimization (UGO) algorithm, by which the evaluation method of service life for P110S corroded tubing is proposed.

Aggregate Geometrical Features and Their Influence on the Surface Properties of Asphalt Pavement

Aggregate geometrical features directly affect asphalt pavement surface properties, which further affect the resistance to skidding of a road surface. In order to establish a relationship between the aggregate geometrical features and pavement surface properties, this paper employs an aggregate geometric characteristic evaluation system (AGCES) to describe the form property, angularity, and surface texture of aggregate particles. The geometrical feature parameters of 15 different aggregates were examined by AGCES and the corresponding surface properties of asphalt pavement prepared from the mentioned aggregates were evaluated by sand patch method, 2-Dimension Image-based Texture Analysis Method (2D-ITAM) and Walking Friction Tester (WFT), respectively. The relationships between the pavement surface property parameters and the aggregate geometric characteristic parameters studied were developed by the Levenberg-Marquarat and universal global optimization (LM-UGO). The results show that the calculated geometric characteristic parameters are in agreement with traditional manual measurement results. The pavement surface properties are significantly influenced by aggregate angularity and aggregate surface texture. Regression relationships were established to predict pavement surface properties from the aggregate geometrical features.

Built Environment Factors (BEF) and Residential Land Carbon Emissions (RLCE)

Evaluating the effects of built environment factors (BEF) on residential land carbon emissions (RLCE) is an effective way to reduce RLCE and promote low-carbon development from the perspective of urban planning. In this study, the Grey correlation analysis method and Universal global optimization method were proposed to explore the effects of BEF on RLCE using advanced metering infrastructure (AMI) data in Zibo, a representative resource-based city in China. The results indicated that RLCE can be significantly affected by BEF such as intensity, density, morphology, and land. The morphology is the most critical BEF in reducing RLCE. Among them, the building height (BH) and building shape coefficient (BSC) had positive effects on RLCE, while the high-rise buildings ratio (HRBR) and RLCE decreased first and then increased. The R2 of BH, BSC, and HRBR are 0.684, 0.754, and 0.699. The land had limited effects in reducing RLCE, and the R2 of the land construction time (LCT) is only 0.075, which has the least effect on RLCE. The results suggest that urban design based on BEF optimization would be effective in reducing the RLCE.

Experimental and numerical research on the bond‐slip behavior of square‐rebar reinforced concrete during the republic of China (1912–1949)

AbstractSquare‐rebar reinforced concrete structures during the republic of China (ROC) (1912–1949) have special material properties and structural characteristics. To perform nonlinear finite element simulations of this special type of structure more accurately, a specialized bond‐slip constitutive model is built. Eighteen central pullout specimens were designed based on the ROC concrete mix proportions and the square‐rebar. Then, the test data were fitted with the universal global optimization method and the minimum Euclidean distance point method was chosen to calculate the inflection point matrix of the bond‐slip constitutive model. Finally, the main factors influencing the bond‐slip behavior of the ROC square‐rebar reinforced concrete were analyzed. The research results show that the corrosion of the square‐rebar produces a negative effect on the whole structure and a modified bond‐slip regression curve considering the size effect is obtained. The research results can provide a scientific basis for the nonlinear calculation of ROC square‐rebar reinforced concrete structures considering the bond‐slip behaviors.

Dynamic triaxial constitutive model for rock subjected to initial stress

AbstractBuilding on the existing model, an improved constitutive model for rock is proposed and extended in three dimensions. The model can avoid the defect of non-zero dynamic stress at the beginning of impact loading, and the number of parameters is in a suitable range. The three-dimensional expansion method of the component combination model is similar to that of the Hooke spring, which is easy to operate and understand. For the determination of model parameters, the shared parameter estimation method based on the Levenberg–Marquardt and the Universal Global Optimization algorithm is used, which can be well applied to models with parameters that do not change with confinement and strain rates. According to the established dynamic constitutive equation, the stress–strain curve of rock under the coupling action of the initial hydrostatic pressure load and constant strain-rate impact load can be estimated theoretically. By comparing the theoretical curve with the test data, it is shown that the dynamic constitutive model is suitable for the rock under the initial pressure and impact load.

Nonlinear modelling of selected micro- and macro-properties of weathered asphalt mixtures

Asphalt mixture specimens with three different gradations of AC-13, SMA-13, and Superpave-13 were aged in an accelerated weathering machine (AWM) for a duration of 0, 1000, 2000 and 3000 h. Gel Permeation Chromatography (GPC), Fourier Transform Infrared Spectroscopy (FTIR) and Brookfield viscometer tests were performed on the recovered asphalt binder samples from the weathered mixtures. Nonlinear models fitted the measured properties by a method of LM+ universal global optimization of 1stOpt software. The results showed that: 1) Nonlinear models fitted the measured properties well, the rate and the degree of aging of the asphalt binders can be well explained by the parameters of these models. 2) As the aging duration is increased, Brookfield viscosity of the weathered asphalt binders increased gradually, and the percentage of Large Molecule Size (LMS) from GPC and the functional group of carbonyls (C=O) from FTIR increased as well. 3) The calculated values by the established models were highly correlated with the measured values of the properties of the weathered asphalts.

Investigation of total diffuse-photon-density-wave field in semi-infinite turbid media based on the extrapolated Beer–Lambert law

The accurate description of the total diffuse-photon-density-wave field inside turbid media, especially in the near-field region, is extremely critical but challenging for many decades. Here, the total diffuse-photon-density-wave field of semi-infinite turbid media was calculated by the third-order simplified spherical harmonics approximation (SP3) and compared with Monte Carlo simulations. To improve the SP3 approximation, the extrapolated Beer–Lambert law model considering the contribution of the coherent-photon-density-wave in the near-field region was proposed and implemented by Levenberg–Marquardt and universal global optimization methods. Last, we demonstrated the superiority of the proposed model over the existing model in fitting the accuracy and applicable source–detector distance range. The high accuracy and simplicity of the proposed model would be extremely helpful for biomedical applications involving photothermal radiometry, and rapidly determining optical properties of media, along with photoacoustic imaging and photodynamic therapy.

Application of multi-element viscoelastic models to freshness evaluation of beef based on the viscoelasticity principle.

The aims of this work were to develop multi-element viscoelastic models for beef and apply them to detect total volatile basic nitrogen (TVB-N) content for freshness evaluation. The deformation data were collected by a viscoelasticity detection system that employed the airflow and laser technique. Then, TVB-N contents were measured to determine the freshness of samples during storage. A universal global optimization (UGO) algorithm was applied to fit the deformation data. Various multi-element viscoelastic models including the Burgers, six-element and eight-element models were built using the obtained fitting parameters, and different viscoelastic parameters representing the degree of beef spoilage were obtained. All the viscoelastic parameters of each multi-element model and parameter combinations of the selected six-element model were employed to build mathematical models for predicting TVB-N content by support vector machine regression (SVR). In comparison, the six-element model with all the viscoelastic parameters performed the best and was determined to predict TVB-N content with correlation coefficient in the prediction set (RP ) of 0.891 and root mean squared error in the prediction set (RMSEP) of 1.467 mg/100 g. Based on the results of parameter combinations, combination (E2 , E3 , E1 , η1 , η2 ) from the six-element model performed the best, which was comparatively inferior to all the viscoelastic parameters of the six-element model. Results demonstrated that it was possible to predict TVB-N content for freshness evaluation by applying method of developing multi-element model based on the viscoelasticity with chemometrics.

Prediction of total volatile basic nitrogen (TVB-N) content of chilled beef for freshness evaluation by using viscoelasticity based on airflow and laser technique

Viscoelasticity experiments were performed to detect the total volatile basic nitrogen (TVB-N) content of chilled beef for freshness evaluation. The growth trend of TVB-N was further analyzed with prolonged storage time. A six-element viscoelastic model was then established by fitting deformation data through universal global optimization. The viscoelastic parameters, including elasticity moduli E1, E2, E3, and viscosity coefficients η1, η2, η3, were applied to build models of TVB-N content prediction using partial least squares regression (PLSR) and support vector machine regression (SVR). Results showed that the SVR model performed better than the PLSR model, with a correlation coefficient in the prediction set of 0.89 and a root mean squared error in the prediction set of 1.47 mg/100 g. These results demonstrated for the first time that the viscoelasticity based on airflow and laser technique combined with chemometrics can be used for the fast, nondestructive detection of TVB-N concentration for meat freshness assessment.

Connections between chemical composition and rheology of aged base asphalt binders during repeated freeze-thaw cycles

The chemical composition and rheological properties of asphalt binder play a key role in the performance of the asphalt pavement. However, pavement diseases (cracks, pitted surface, potholes and slurry) caused by the degradation of pavement performance have shortened the service life of the asphalt pavement and increased maintenance and repair costs, seriously affected the smooth flow of traffic and traffic safety. In this study, the sum of the different absorption peak areas of the asphalt binder spectroscopy was selected as a reference. Fourier Transform Infrared Spectroscopy (FT-IR) quantitative analysis was carried out on the Rolling Thin Film Oven (RTFO) test with different aging cycles and Pressure Aging Vessel (PAV) test of the asphalt binder after aging. Based on the above analysis, the author tries to establish a reliable FT-IR quantitative analysis method. An FT-IR specimen which could be subjected to multiple freeze-thaw cycles could be prepared by the self-designed test sample preparation device. By carrying out the freeze-thaw cycle aging test of asphalt binder for 0, 3, 6, 9, 12, 15 and 18 times, combining FT-IR and Dynamic Shear Rheological (DSR) testing techniques, the author explored the relationship between chemical composition and rheological performance parameters of asphalt binder in cold region, which were based on the Levenberg-Macquarie method and test data of universal global optimization algorithm regression analysis. The results show that FT-IR can not only qualitatively analyze and study the structure and chemical composition of asphalt binder before and after aging on a micro level, but also quantitatively represent the changes of characteristic functional groups before and after aging of asphalt binder. It is feasible to calculate the absorption peak area for FT-IR quantitative analysis using the tangent at the lowest point on both sides of the spectral absorption peak as the calibration baseline. It is recommended to use the range of 2000–650 cm−1 absorption peak area sum as a benchmark for FT-IR quantitative analysis. The complex shear modulus of the asphalt binder shows a linear growth with the increase of freeze-thaw cycles, and phase angle of asphalt binder also shows a linear growth with the increase of LnT. There is a multivariate linear relationship between the rheological index and chemical functional groups after the aging freeze-thaw cycle.

Improving Economic Benefits through Coal Products Optimization in a Given Group

Improving economic benefits from a large coal mining group with several operations is always the first objective of its operator. More concerns are usually focused on the unit operations and their cost. An optimization model for coal products and production rate based on Simplex Method(SM) and Algorithm of Universal Global Optimization(AUGO) approach is established in order to maximize the economic benefits of a given mining group in its existing cost construction. The result shows that the total economic return of the group could be improved a lot through optimization of its coal products and production rather than the summation of its every single mine’s coal products and production rate, each operation of the group should do its best to produce as more as possible high quality products it can produce, and the mines with inferior quality of products should excavate their deposit according to the optimized production rate to make the whole system profit maximum rather than its own designed producti.

Development of a lifetime prediction model for lithium thionyl chloride batteries based on an accelerated degradation test

Battery life prediction is critical for lithium/thionyl chloride cells with a long storage life. The objective of this study was to develop models for rapidly estimating the storage life of Li/SOCl2 cells using the semiempirical approach. An accelerated degradation test involving numerous cells stored at various temperatures (room temperature or RT, 40, 50, 60, and 70°C) was conducted to investigate the effect of the storage time and temperature on capacity degradation. The degradation law can be summarized on the basis of the test data for constructing the semiempirical equation; this law demonstrates that the residual capacity of aging cells exponentially changes with the storage time and temperature. The degradation data are also used for parameterization with the multiple nonlinear curve fitting method based on the universal global optimization algorithm. According to the simulation and comparison between the experimental data and prediction curve, the fitting prediction curve accurately fits the experimental data. This finding indicates that the semiempirical model is useful because of its satisfactory ability to approximate the measured data. In addition, characteristic values of the battery, including the storage life under various storage conditions, average self-discharge rate, and acceleration factor, can be calculated on the basis of the mathematical model.

Experimental and numerical study of cavitation inception phenomenon in diesel injector nozzles

In this paper the experimental and numerical methods were combined to investigate the critical conditions of cavitation inception in diesel injector nozzles. It was found that at the beginning of cavitation inception, the discharge coefficient presents a slight increase and then a special turning point appears which can therefore be taken as the critical point for cavitation inception. Effects of needle lift, length–diameter ratio, orifice inclination angle, back pressure, and scaled-up times on critical cavitation number were studied through the experimental method. Due to the difficulties in manufacturing, influence of inlet rounding radius was investigated by using the numerical simulation method. Based on all the experimental and numerical simulation data, a correlation of critical cavitation number with above 6 geometrical and dynamic parameters for nozzle flow was developed through statistical analysis using the Quasi-Newton (BFGS) and Universal Global Optimization (UGO) methods. The relative error between predicted results and experimental data is less than 7%. These results indicate that the derived expression has good accuracy to predict the start of cavitation.

PWLM[formula omitted]-based automatic performance model estimation method for HDFS write and read operations

There is a growing need for the development of an automatic performance model estimation method for Hadoop Distributed File System (HDFS) write and read (W/R) operations in order to deal with constant software improvement and updates, parameter configuration changes, hardware heterogeneity, and their Quality of Service (QoS) evaluation. Extant research based on single linear system model has a limited ability to explain the performance variations due to changes in HDFS parameters such as block size. These variations reveal some typical characteristics of nonlinear systems and are an obstacle in achieving effective automatic performance estimation. In order to deal with this challenge, a piecewise-linear multi-model modeling (PWLM3)-based automatic performance model estimation method is proposed for HDFS W/R performance. In the proposed method, a standard model base is built to standardize the model representation of every submodel. Moreover, a cluster quality assessment strategy is applied to evaluate the optimal number of submodels, and a submodel selection strategy is implemented to construct performance model candidates and improve the computation efficiency of the proposed method. In addition, Levenberg–Marquardt (LM) and Universal Global Optimization (UGO) algorithms are adopted to estimate the values of switch points and identify undetermined parameters of performance model candidates. Then the performance model is selected among these candidates according to Root Mean Squared Error (RMSE) indicator. Experimental results demonstrate that the PWLM3-based performance model provides a good understanding and description of nonlinear characteristics of HDFS W/R performance and achieves better identification precision than a single linear system model-based one.

Modeling the dielectric behavior of saline soil at microwave frequencies

Soil salinization is a problem of global concern because of the economic impact and, consequently, its measurement and possible control are very important. Electromagnetic sensors such as ground penetrating radar and electromagnetic induction sensors are among the most widely used methods for the detection of soil components. This paper focuses on the dielectric behavior of saline soil at microwave frequencies. Five different soil types with varying levels of moisture and salinity were prepared in the laboratory and their dielectric properties were measured to evaluate the influence of moisture and salinity on the real and imaginary parts of the dielectric constant. An improved dielectric model for saline soil in the microwave frequency range was then developed (with two groups of equations for low- and high-frequency regions) with the regression parameters derived using the Levenberg–Marquardt and Universal Global Optimization methods. This modified model proved to be suitable for saline soil with a good degree of accuracy based on the statistics (R2 and root mean square error) for both frequency ranges. For example, for the C band (5.25 GHz), discussion on how to use the improved dielectric model at moderate frequency is conducted. Future rigorous experiments under varying field conditions will be conducted to develop a more robust model for implementation using SAR remote sensing technology.