Wyniki wyszukiwania - Biblioteka Nauki

1

Instability mechanism and anchoring control technology of expansive weakly cemented soft rock roadway

100%

Zhang W.

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tom Vol. 61 nr 3

465--480

EN

A long-term discontinuous development of the plastic zone and broken zone of weakly ce- mented surrounding rock is the main reason for instability of the surrounding rock of a roadway. The load-bearing support concept of “allowable deformation + releasable pres- sure + limited deformation” for a weakly cemented soft rock roadway is proposed, and an “allow-release-limit” support structure mechanical model with U-shaped steel as the main body is established. Anchoring control measures of “U-shaped steel + flexible material wall backfill + key parts strengthening” can solve problems of large deformation and long defor- mation duration of weakly cemented roadways.

2

Model parameterizations in the time domain multi parameter acoustic least squares reverse time migration

63%

Zhang W. , Gao J.

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tom Vol. 69, no. 2

441--458

EN

Acoustic least-squares reverse time migration (LSRTM) can retrieve the improved refection images. However, the most existing acoustic LSRTM approaches generally ignore the density variation of the subsurface. The multi-parameter acoustic LSRTM approach in the presence of a density parameter can overcome this weakness. However, diferent model parameterizations in such an acoustic LSRTM approach can lead to diferent migration artifacts and infuence the rate of convergence. In this paper, we mainly investigate and analyze the refectivity images of diferent model parameterizations in the multi-parameter acoustic LSRTM approach, in which the velocity–density parameterization can provide reliable refection images. According to Green’s representation theory, we derive the gradients of the objective function with regard to the multi-parameter refectivity images in detail, in which both the migration image of density in the velocity–density model parameterization and the migration image of impedance in the impedance–velocity model parameterization are free from the low-frequency artifacts. Through numerical examples using the layered and fault models, we have proved that the multiparameter acoustic LSRTM approach with the velocity–density model parameterization can provide the migration images with higher resolution and improved amplitudes. Meanwhile, a correlation-based objective function is less sensitive to amplitude errors than the conventional waveform-matching objective function in the multi-parameter acoustic LSRTM approach.

3

Seismic behavior of a friction-type artificial plastic hinge for the precast beam–column connection

51%

Huang H. , Li M. , Zhang W. , Yuan Y.

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tom Vol. 22, no. 4

art. no. e201, 2022

EN

This paper proposed a replaceable friction-type artificial plastic hinge (FAPH) to connect the prefabricated concrete members, characterized by direct load transmission and streamlined configuration. The FAPH device replaced the beam-end plastic hinge region in the precast structures, which could protect the concrete joint core area and other concrete components. The experiment of a precast beam–column connection with FAPH and a cast-in-situ beam–column connection was carried out. The experimental results showed that the FAPH connection had better hysteresis performances with higher bearing capacity, energy dissipation, and ductility than the cast-in-situ concrete connection. Moreover, the finite element model was calibrated and employed to perform parametric analyses, including the axial load ratio, the friction factor, the bolt preload, and the initial clearance. The FE analysis results showed that the FAPH connection would have a more attenuation of the friction force under the higher axial load ratio. Besides, the seismic performance of FAPH can be effectively improved with the increase of the friction factor and the bolt preload, and the FAPH connection exhibited a stable performance with various initial clearances. Based on the parametric analysis results, the formulas for the yield and peak bending moment capacity for the FAPH device were proposed.

4

Optimal configuration of energy storage system capacity in traction power supply system considering photovoltaic consumption

51%

Zhang W. , Chen X. , Wang Y.

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tom Vol. 73, nr 1

219--233

EN

In order to achieve energy savings and promote on-site integration of photovoltaic energy in electrified railways, a topology structure is proposed for the integration of photovoltaic (PV) and the energy storage system (ESS) into the traction power supply system (TPSS) based on a railway power conditioner (RPC). This paper analyzes the composition and operation principles of this structure. To assess the economic benefits brought by the integration of photovoltaic and energy storage systems, a bilevel optimization model is established, with the objectives of optimizing energy storage capacity configuration and photovoltaic energy integration. The KKT (Karush–Kuhn–Tucker) method is employed to transform the model into a single-layer mixed-integer linear programming model, which is then solved using the CPLEX solver in MATLAB. The research findings indicate that, with the configuration of the ESS, the optimal PV consumption rate achieved is 96.8749%. Compared to a 100% PV consumption rate, the ESS capacity configuration is reduced by 13.14%, and the overall operational cost of the TPSS is at its lowest. The study suggests that the proposed bilevel optimization algorithm can more effectively consider PV consumption, leading to enhanced economic performance of the TPSS operation.

5

Electrokinetic remediation technology of heavy metal contaminated soil based on improving soil electrical conductivity

51%

Liu J. , Zhang W. , Liu M. , Zhang H.

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tom Vol. 47, nr 4

5--17

EN

An electrokinetic remediation technique taking Cr(VI) as an example is proposed to improve the conductivity of contaminated soil, which significantly increases the current density in the soil. The improvement of soil conductivity was achieved by continuous spraying of NaCl solution with a concentration of 4 g·dm–3 on the soil surface. The distances of electrode pairs were 2.0 m and 1.5 m, respectively. The heavy metal-contaminated soil thickness was 25 cm, and the DC power supply voltage was 90 V. The experiment demonstrated that under the condition of continuous spraying of NaCl solution on the soil surface, the current density variation was related to the salt content in the soil, and the current density in the soil generally increased linearly with time. The effectiveness of soil remediation is related to the electric field strength and current density, and there exists an optimal electric field that can reduce the heavy metal content in the soil at any point by minimizing the electric field strength and current density. Most of the heavy metals can be concentrated within a diameter of about 15 cm around the anode under the optimal electric field, which can be remediated after removing the soil.

6

Adsorption behaviors of As(III) on bentonite, diatomite, and hematite : implications for scientific remediation of arsenite contamination in soil

38%

Fu K. , Tang P. , Zhang W. , Chen S. , Tao G. , Liu J.

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tom Vol. 60, iss. 4

art. no. 192381

EN

Comprehensive understanding of As(III) sorption on natural minerals in contaminated soils is important for scientific decision making in remediation. In this study, the characteristics of As(III) adsorption on three minerals with different crystal structures and chemical compositions (bentonite; diatomite; and hematite) were investigated. The adsorption kinetics and thermodynamics were established. Surface complexation modeling was performed using X-ray diffraction spectroscopy, fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy. The results showed that the pH value had a more significant effect on As(III) adsorption on hematite than on bentonite and diatomite, and As(III) was efficiently adsorbed by hematite at pH 7.0. The pseudo-first-order model provided an excellent fit to the As(III) adsorption on bentonite and hematite; the diffusion of ions or groups played an important role in the adsorption of As(III) on bentonite and hematite. The adsorption of As(III) on diatomite could be fitted with pseudo-first-order and pseudo-second order kinetic equations, as their regression coefficients were equal (R2=0.999). It was inferred that the adsorption of As(III) on diatomite occurred through solution diffusion and surface chemisorption. The As(III) adsorption on bentonite and diatomite was mainly physical and multilayer adsorption, whereas the As(III) adsorption on hematite was mainly chemical and monolayer absorption. The As(III) adsorption on hematite was divided into two stages: fast and slow. At first, the inner monodentate complex (such as ☰Fe-OAs3H-) formed at a high rate, and with the increase in the coverage of As(III) on the surface of iron oxide, the monodentate complex was slowly converted to the bidentate complex. These results verify the possibility of using bentonite, diatomite, and hematite as alternative materials for the remediation of As(III)-contaminated soils, and also indicate that bentonite and diatomite are suitable for the remediation of low As(III)-contaminated soils, while hematite is suitable for the decontamination of high As(III) polluted soil. Selecting suitable remediation materials according to arsenic contamination level is the key to soil scientific remediation.