Xi'an University of Science and Technology

About: Xi'an University of Science and Technology is a education organization based out in Xi'an, China. It is known for research contribution in the topics: Coal & Coal mining. The organization has 10023 authors who have published 7317 publications receiving 51897 citations.

Structural trends and dielectric properties of Bi-based pyrochlores

Abstract: The crystal structure and dielectric properties of Bi-based pyrochlore ceramics with formula Bi1.5ZnM1.5O7 (M=Nb, Ta or Sb) were investigated. The three composition ceramics crystallize in the same pyrochlore structure, but the lattice parameters decrease with decreasing B-site ionic radius. Raman spectra analyses were performed to look for short-range structural differences and indicate that the Ta and Sb incorporation into B-site induce the A-site cations array to be more disordered. Ta or Sb replacing Nb lead to smaller dielectric constant and higher temperature coefficient values. The common characteristics for the three compositions are that they have rather low dielectric loss and high resistivity. The dielectric behavior with temperature for BZS and BZT samples were more flat than that of the BZN ceramics. Dielectric abnormal behavior at high temperature for all samples is typically associated with losses by conduction.

Weakly-coupled multicore optical fiber taper-based high-temperature sensor

Abstract: A novel high temperature sensor based on weakly-coupled multicore fiber (MCF) is proposed and experimentally demonstrated. The sensor consists of a taper of weakly-coupled MCF sandwiched between two standard single-mode fibers (SMF). The temperature sensing mechanism is investigated theoretically and experimentally. In order to eliminate the effect of residual stress in the sensor and improve the high-temperature sustainability of the sensor, the annealing techniques for the proposed sensor is also investigated. The sensor annealed via the proposed techniques was demonstrated experimentally to be able to measuring temperatures up to 1000 °C with sensitivity of ∼36.8 pm/°C.

Uncertainty pattern in landslide susceptibility prediction modelling: Effects of different landslide boundaries and spatial shape expressions

Abstract: In some studies on landslide susceptibility mapping (LSM), landslide boundary and spatial shape characteristics have been expressed in the form of points or circles in the landslide inventory instead of the accurate polygon form. Different expressions of landslide boundaries and spatial shapes may lead to substantial differences in the distribution of predicted landslide susceptibility indexes (LSIs); moreover, the presence of irregular landslide boundaries and spatial shapes introduces uncertainties into the LSM. To address this issue by accurately drawing polygonal boundaries based on LSM, the uncertainty patterns of LSM modelling under two different landslide boundaries and spatial shapes, such as landslide points and circles, are compared. Within the research area of Ruijin City in China, a total of 370 landslides with accurate boundary information are obtained, and 10 environmental factors, such as slope and lithology, are selected. Then, correlation analyses between the landslide boundary shapes and selected environmental factors are performed via the frequency ratio (FR) method. Next, a support vector machine (SVM) and random forest (RF) based on landslide points, circles and accurate landslide polygons are constructed as point-, circle- and polygon-based SVM and RF models, respectively, to address LSM. Finally, the prediction capabilities of the above models are compared by computing their statistical accuracy using receiver operating characteristic analysis, and the uncertainties of the predicted LSIs under the above models are discussed. The results show that using polygonal surfaces with a higher reliability and accuracy to express the landslide boundary and spatial shape can provide a markedly improved LSM accuracy, compared to those based on the points and circles. Moreover, a higher degree of uncertainty of LSM modelling is present in the expression of points because there are too few grid units acting as model input variables. Additionally, the expression of the landslide boundary as circles introduces errors in measurement and is not as accurate as the polygonal boundary in most LSM modelling cases. In addition, the results under different conditions show that the polygon-based models have a higher LSM accuracy, with lower mean values and larger standard deviations compared with the point- and circle-based models. Finally, the overall LSM accuracy of the RF is superior to that of the SVM, and similar patterns of landslide boundary and spatial shape affecting the LSM modelling are reflected in the SVM and RF models.

Water leakage susceptible areas in loess multi-arch tunnel operation under the lateral recharge conditions

Abstract: In this study, the water leakage susceptible areas in a loess multi-arch tunnel were examined, providing a basis for the prevention and control of water leakage disease during the operation periods of multi-arch tunnels in loess areas. Through the field investigation of the leakage in loess multi-arch tunnel, the leakage mainly focuses on three joints: construction joints, expansion joints, and settlement joints. The spatial distribution of the leaking part in the tunnel is summarized and abstractly into three types: annular cracks, longitudinal cracks and full longitudinal cracks + circumferential cracks. By setting up different number of annular and longitudinal cracks, a total of 20 combinations were designed. This paper sets three kinds of working conditions, including 40 and 60 m of reinforcement water head and 60 m of no reinforcement water head, considering groundwater lateral recharge conditions. Using the midas/GTS geo-technical analysis system software, 3D numerical simulations were conducted to determine the distributions of the total water head and water pressure in cracks for all the combinations of water leakage positions under different working conditions and to analyze the variations in the seepage field of the surrounding rock. Based on the areas where the total water head and water pressure in the cracks sharply changed, the water leakage susceptible areas were determined. The rationality and reliability of the method were verified by a comparison with the results of a field investigation.