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Concrete-filled steel tube (CFST) widely applied in engineering structures due to its superior behavior requires monitoring and assessment for damage level. Here, the acoustic emission (AE) technique was used to monitor the fracture process of concrete core in CFST stub columns subjected to axial compression. Test and analyzed results show that the damage process of CFST specimens can be divided into four stages: compaction, elastic-plastic stage, strengthening and secondary strengthening. In the elastic-plastic stage, the evolutionary features of the AE event rate, cumulative energy, Ib-value and crack classification are capable of providing an early warning for cracked concrete core. Full crack propagation can be identified by the rapid increase in the proportion of shear cracks near the inflection point of load, which is impermissible in engineering structures. According to the analyses of the AE event rate and signal intensity in the elastic-plastic stage, the confinement of steel tube with thicker wall thickness or higher strength is delayed, which implies that this confinement is suggested to be triggered early. It is indicated that the AE technique has the potential to monitor and evaluate the damage process of CFST stub columns under axial compression, which can provide additional insight into the failure mechanism and assist in the scheme of repairs. [ABSTRACT FROM AUTHOR]

Accelerating the formation of a green dual-circulation pattern is an essential strategic choice for China to achieve high-quality development. As a vital link for two-way economic and trade cooperation, the pilot free trade zone (PFTZ) is an important window for promoting green dual-circulation development. From the perspective of green dual-circulation, this paper attempts to construct a comprehensive index system of green dual-circulation by entropy weight method based on Chinese provincial panel data from 2007 to 2020 and uses the Propensity Score Matching–Difference in Differences method to test the policy impact of PFTZ building on regional green dual-circulation. The empirical results show that: (1) the establishment of PFTZs significantly promotes regional green dual-circulation development by 3%-4%. This policy effect has a strong positive impact on the eastern regions; (2) PFTZs can improve regional green dual circulation through the effect of green finance, technological progress, and the agglomeration of innovative talents. The mediating effect of green finance and technological progress is more pronounced; (3) The promotion effect of PFTZs is primarily due to the local green circulation effect, with no significant effects on the surrounding areas; and (4) There is a positive policy linkage effect between PFTZs and the Belt and Road Initiative. This study creates the analytical perspective and empirical support for assessing the policy impact of PFTZs and provides management insights for PFTZ policymakers in promoting green dual-circulation development. [ABSTRACT FROM AUTHOR]

Under the dual pressure of economic growth and environmental pressure, green and high-quality development become a critical strategy for China to achieve win-win development for both the economy and the environment. In the dual-circulation pattern, a deep and high level of openness is the primary prerequisite for encouraging green and high-quality development. Previous studies have overlooked the crucial pivotal role of pilot free trade zones (PFTZs) in domestic and international circulation. The PFTZ is essential in driving China's green modernization and high-quality development as a crucial area of opening up. This paper utilizes the propensity score matching and difference-in-differences (PSM-DID) on panel data from 27 provinces from 2007 to 2020 to investigate the green policy effects of PFTZ building and its underlying mechanism. The results show that (1) the establishment of PFTZs significantly enhances regional green and high-quality development, with a net policy impact of roughly 4%. The several robustness tests demonstrate that the outcomes are extremely reliable; (2) According to the heterogeneity analysis, compared with inland areas, coastal locations may more effectively foster green and high-quality development; and (3) The influencing mechanism test results show that PFTZs primarily have a positive impact on technological progress, scale expansion, and innovation-driven effects, which, in turn, support green and high-quality development. The mediating effect of innovation-driven and technological progress is extremely significant among them. These research findings can provide empirical support and policy rationale for PFTZs to better promote China's green and high-quality development. [ABSTRACT FROM AUTHOR]

A promising photolysis based technology to dechlorinate polychlorinated biphenyls (PCBs), extracted from soils, in alkaline isopropanol (IPA) as reaction medium has been proposed. To be marketable the impact of co-contaminants extracted along with the PCBs, on the photodechiorination process needs investigation. In this paper the effectiveness of the photodeclorination process on PCBs extracted from samples of a representative soil containing co-contaminants is reported. The pholodechl ori nation or PCBs extracted from weathered soils showed promising results of more than 76% dechlorination within the first hour of UV irradiation. Nearly complete dechlorination (96%) was achieved after 2 h of UV irradiation. To provide quantitative controlled appraisal of the effect of co-contaminants and explanation of the effects, dechlorination of neat Aroclor 1254 in the presence of the common co-contaminant, transformer oil, was evaluated. Further, the effect of transformer oil on some of the individual PCB congeners in the Aroclor mixture was also studied. The difference in the maximum percentage dechlorination of PCBs with and without transformer oil is 15%. Key words: PCBs, extraction, dechlorination, 2-propanol, transformer oil, co-contaminants. Une technologie prometteuse basee sur la photolyse est proposee pour dechlorer les BPC extraits des sols dans un milieu de reaction compose d'alcool isopropylique alcalin. Afin d'etre commercialisable, il faut examiner l'impact des co-contaminants extraits avec les BPC lors du processus de photo-dechloration. Dans eel article, l'efficacite du processus de photo-dechloralion sur les BPC extraits d'echantillons d'un sol representatif contenant des co-contaminants est presentee. La photo-chloration des BPC extrails de sols alleres a monlre des resultals de dechloraiion prometteurs de plus de 76% dans la premiere heure de rayonnement UV. Une dechloration presque complete (96 %) a ete realisee apres 2 heures de rayonnement UV. Pour fournir une evaluation quantitative controlee de l'effet des co-contaminants et I'explication des effets. la dechloration d'Aroclor 1254 pur en presence du co-contaminant commun, de l'huile de transformateur, a ete evaluee. De plus, l'effet de l'huile de transformateur sur certains des congeneres individuels des BPC dans le melange d'Aroclor a egalement ete etudie. La difference dans le pourcentage maximum de dechloration des BPC avec et sans huile de transformateur est de 15%. Mots-cles: BPC. extraction, dechloration. alcool isopropylique. huile de transformateur, co-contaminants. [Traduit par la Redaction], Introduction Recent successes on the dechlorination of polychlorinated biphenyls (PCBs) using UV, has opened possibilities of applying this technique to remediate PCB contaminated soils and sediments. The dechlorination of PCBs [...]

Conventional gas chromatography (GC) analysis of hydrocarbons displaying one broad peak provides limited information. Two GC analytical protocols using two-peak and three-peak approaches were developed to investigate transformer oil components and their degradation in soil by hydrogen peroxide. The two-peak method revealed transformer oil to be composed of 27 wt.% F2 fraction and 73 wt.% F3 fraction hydrocarbons. The three-peak method segregated the transformer oil into 40 wt.% light, 40 wt.% medium, and 20 wt.% heavy hydrocarbon fractions. In contrast to reports of success with several classes of lighter hydrocarbons, only limited degradations of transformer oil in soils by 15% and 30% hydrogen peroxide treatment was indicated by conventional one-peak analysis; two-peak analysis showed varying F2 and F3 fraction degradations with F2 fraction degradation being higher; three-peak analysis offered a richer understanding of the relative degradations of light, medium, and heavy fractions. The effect of a low pH environment on the degradation of transformer oil by hydrogen peroxide was evaluated using the three-peak method. It emerged that the degradation of the medium and heavier fractions of transformer oil was higher at pH 2.0. Key words: transformer oil, soil remediation, hydrogen peroxide, gas chromatography. L'analyse conventionnelle par chromatographie gazeuse (CG) des hydrocarbures montrant un large pic chromatographique ne donne que de l'information limitee. Deux protocoles d'analyse par CG utilisant des methodes a deux et a trois pics chromatographiques ont ete mis sur pied afin d'examiner les composantes de l'huile des transformateurs et leur degradation dans le sol en utilisant le peroxyde d'hydrogene. La methode a deux pics chromatographiques a indique que l'huile de transformateur etait composee de 27 % en poids de fraction d'hydrocarbures F2 et de 73 % en poids de fraction F3. La methode a trois pics chromatographiques a divise l'huile de transformateur en 40 % en poids de fraction legere d'hydrocarbures, 40 % en poids de fraction moyenne et 20 % de fraction lourde. Par rapport aux rapports relatant la reussite de l'utilisation de plusieurs classes d'hydrocarbures plus legers, des degradations limitees de l'huile des transformateurs dans les sols par traitement avec 15 et 30 % d'hydroxyde d'hydrogene ont ete determinees par l'analyse a un pic chromatographique. L'analyse a deux pics chromatographiques montrait des degradations variables des fractions F2 et F3, la fraction F2 se degradant mieux. L'analyse a trois pics chromatographiques permettait de mieux comprendre les degradations relatives des fractions legeres, moyennes et lourdes. L'effet d'un environnement a faible pH sur la degradation de l'huile de transformateur par le peroxyde d'hydrogene a ete evalue en utilisant la methode a trois pics chromatographiques. Il a ete decouvert que la degradation des fractions moyennes et lourdes de l'huile de transformateur etait meilleure a un pH de 2.0. Mots-cles : huile de transformateur, restauration des sols, peroxyde d'hydrogene, chromatographie gazeuse. [Traduit par la Redaction], Introduction The effectiveness of a particular remediation technology can be evaluated by the extent of mineralization and the compositional changes that occur during the treatment. With increasing popularity of chemical [...]

Spectrum induced polarisation (SIP) is a frequency-domain method commonly used in electrical geophysical exploration. However, SIP is very sensitive to the signal-to-noise ratio of the signal, so noise reduction is very important. Independent component analysis can be used to reduce the noise of geophysical exploration data, but it cannot be used when the observed signal has only one dimension. In this paper, an empirical wavelet transform-independent component analysis method is proposed, which can be used for noise reduction in spectrum induced polarisation data. Firstly, the original measurement data are adaptively decomposed into a finite number of intrinsic modal functions by empirical wavelet transform, and then the intrinsic modal functions are selected to construct a virtual noise channel according to their correlation with the induced polarisation signal. Finally, the induced polarisation signal in the multi-dimensional mixed data is extracted by independent component analysis. Our experiment shows results show that this method can effectively remove noise signals and improve the signal-to-noise ratio of induced polarisation data. [ABSTRACT FROM AUTHOR]

This study aims at introducing the back stress of anisotropic strain-hardening into the crystal plasticity theory and demonstrating the rationality of this crystal plasticity model to describe the evolution of the subsequent yield surface of polycrystalline aluminum at the mesoscopic scale under complex pre-cyclic loading paths. By using two different scale finite element models, namely a global finite element model (GFEM) as the same size of the thin-walled tube specimen used in the experiments and a 3D cubic polycrystalline aggregate representative volume element (RVE) model, the evolution of the subsequent yield surface for different unloading cases after 30 pre-cycles is further performed by experiments and numerical simulations within a crystal plasticity finite element (CPFE) frame. Results show that the size and shape of the subsequent yield surfaces are extremely sensitive to the chosen offset strain and the pre-cyclic loading direction, which present pronounced anisotropic hardening through a translation and a distortion of the yield surface characterized by the obvious "sharp corner" in the pre-deformation direction and "flat" in the reverse direction by the definition of small offset strain, while the subsequent yield surface exhibits isotropic hardening reflected by the von Mises circle to be distorted into an ellipse by the definition of large offset strain. In addition, the heterogeneous properties of equivalent plastic strain increment are further discussed under different offset strain conditions. Modeling results from this study show that the heterogeneity of plastic deformation decreases as a law of fraction exponential function with the increasing offset strain. The above analysis indicates that anisotropic hardening of the yield surface is correlated with heterogeneous deformation caused by crystal microstructure and crystal slip. The crystal plasticity model based on the above microscopic mechanism can accurately capture the directional hardening features of the yield surface. [ABSTRACT FROM AUTHOR]

The subsequent anisotropic yield behavior of 45 steel was predicted by the distortional yield surface constitutive model, which can describe the anisotropic subsequent yield and the cross effect of metal associating with loading history. The yield characteristics and plastic hardening behaviors of the 45 steel were simulated under three preloading paths including pre-torsion, pre-tension, and pre-tension–torsion. Based on the comparison between the experimental yield stresses and the simulation by the classical Chaboche model, the proposed model can describe the remarkable anisotropic yield behavior related to the loading history, which can effectively describe the sharp point of yield surface in pre-loading direction and the smaller curvature near its opposite direction. It was successfully simulated by the constitutive model proposed that the subsequent distortional yield surface defined by small offset strain and the degradation process of the distortion feature defined by large offset strain. [ABSTRACT FROM AUTHOR]

Considering the cross effect in the evolution of subsequent yield surfaces for metals, an anisotropic distortional yield surface constitutive model is developed. By introducing an anisotropic distortional hardening function into the isotropic hardening part of the classical Chaboche rate-dependent constitutive model, the plastic-deformation-induced distortional and anisotropic hardening behaviors of subsequent yield surfaces are characterized. The experimental data of distortional yield surfaces for T2 pure copper under three different loading paths, including pre-tension, pre-torsion, and pre-tension-torsion proportional loading of 45-degree, are simulated by implementing the models into a numerical user defined material (UMAT) procedure based on the ABAQUS finite element package. To validate the anisotropic plastic model, the simulated yield surfaces are compared with experimental observations and predicted results for a crystal plasticity model and good agreement are noted. The simulations demonstrate that the proposed model can accurately capture the characteristics of the distortional yield surface and the anisotropic hardening process of the yield surface. Moreover, the distortional shapes of experimental subsequent yield surfaces in loading direction and opposite direction can be better revealed by the anisotropic plastic constitutive model than the crystal plastic constitutive model. [ABSTRACT FROM AUTHOR]