On a Hadamard-type fractional turbulent flow model with deviating arguments in a porous medium

In this paper, we concern a Hadamard-type fractional-order turbulent flow model with deviating arguments. By using some standard fixed point theorems, the uniqueness, existence and nonexistence of solutions of the fractional turbulent flow model are investigated. Our results are new and are well illustrated with the aid of three examples

Assessment of Snow Status Changes Using L-HH Temporal-Coherence Components at Mt. Dagu, China

Multitemporal Phased Array type L-band Synthetic Aperture Radar (PALSAR) horizontally transmitted and horizontally received (HH) coherence data was decomposed into temporal-coherence, spatial-coherence, and thermal noise components. The multitemporal data spanned between February and May of 2008, and consisted of two pairs of interferometric SAR (InSAR) images formed by consecutive repeat passes. With the analysis of ancillary data, a snow increase process and a snow decrease process were determined. Then, the multiple temporal-coherence components were used to study the variation of thawing and freezing statuses of snow because the components can mostly reflect the temporal change of the snow that occurred between two data acquisitions. Compared with snow mapping results derived from optical images, the outcomes from the snow increase process and the snow decrease process reached an overall accuracy of 71.3% and 79.5%, respectively. Being capable of delineating not only the areas with or without snow cover but also status changes among no-snow, wet snow, and dry snow, we have developed a critical means to assess the water resource in alpine areas

A novel wide area multiple azimuth beam ISAR imaging system

A novel multiple azimuth beams (MAB) inverse synthetic aperture radar (ISAR) system, as well as, the corresponding processing algorithms are proposed in this paper, which is a promising technology for wide area surveillance (WAS). This system concept is intended to obtain wide area ISAR images of multiple moving targets, which would greatly increase the surveillance velocity range compared with the single beam system. The antenna transmits a sequence of high-gain and narrow radar beams to quickly scan a wide area, and receives the echoes from all the subswaths simultaneously. Two processing methods based on digital beamforming (DBF) are presented to separate the overlapped signals for achieving the wide area ISAR images. The performance of the proposed system is analyzed from the perspectives of the surveillance area, surveillance velocity range, and steering angle error. Finally, an exemplary ISAR system is presented and verified by the simulation experiments.Published versio

Optimization of heavy haul railway tunnel lining based on ultimate bearing capacity

The optimization process of design parameters for composite lining of heavy haul railway tunnel is a key problem to be solved in tunnel engineering design. In order to put forward a better design scheme of composite lining for heavy haul railway tunnel, combined with field measurement and numerical simulation, the optimal working condition design is carried out by changing the thickness of shotcrete layer, the type of grid steel frame and the thickness of secondary lining. The influence of the above design parameters on the stress state of the composite lining is analyzed to obtain the optimal design parameters. Finally, the safety performance of the optimized lining is evaluated by the ultimate bearing capacity curve of the secondary lining section. The research shows that: 1) The optimal design parameters of the composite lining of the tunnel are the thickness of the shotcrete layer of 25 cm, the type of the grid steel frame of H180, the thickness of the secondary lining arch waist and the side wall of 40 cm and 35 cm respectively; 2) Different from the single-track heavy haul railway tunnel, the displacement value of the vault settlement of the double-track heavy haul railway tunnel is significantly greater than that of the inner convergence. Increasing the thickness of the shotcrete layer and changing the type of the grid steel frame have better effects on reducing the vault settlement, and have little effect on the inner convergence

Effects of Nonelastic Taping and Dual Task on Kinematics and Kinetics of the Ankle Joint

Objectives. The purpose of this experimental study was to investigate the effects of nonelastic taping and dual task on ankle kinematics and kinetics in gait analysis of healthy adults. Methods. A total of 21 healthy adults completed trials of gait analysis using a Vicon system combining ground walking with different cognitive task conditions (none, modified Stroop color/character naming, and serial-7 subtraction), with or without nonelastic taping. Ankle kinematics and kinetics including speed, ankle plantarflexion and inversion angle, ground reaction force (GRF), and stride time variability (STV) under all conditions of taping (YES or NO) and cognitive task (none, naming, and subtraction) were characterized and analyzed with repeated-measures ANOVA. Results. As regards cognitive performance, the serial-7 subtraction performance under walking conditions with and without taping was significantly poorer than simple sitting condition (P<0.001). For kinematics and kinetics, STV showed statistically significant decrease (P=0.02) when subjects underwent taping application. Vertical GRF was significantly greater under taping than barefoot (P=0.001). Ankle plantarflexion at initial contact (IC) under the dual-task walking was significantly more than under simple walking (P=0.008). Conclusions. Applications of nonelastic taping and dual task may lead to the STV, vertical GRF, ankle plantarflexion, and speed alterations because of restricted joint range of motion and changed sensorimotor neural circuit. When healthy adults performed dual-task walking, central neural resources allocation was disturbed, leading to weakened performance in both motor and cognitive tasks

Numerical Analysis of a Novel Shaft Lining Structure in Coal Mines Consisting of Hybrid-Fiber-Reinforced Concrete

To address the temperature cracking of concrete in frozen shaft linings in extra-thick alluvial layers in coal mines, a novel shaft lining structure of coal mines consisting of hybrid-fiber-reinforced concrete (HFRC) was developed. Using the Finite Element Method (FEM), a numerical simulation test of the HFRC shaft lining structure with four factors and three levels was carried out, and the mechanical characteristics of the shaft lining structure were obtained. The results show that under a uniform surface load, the maximum hoop stress position of the HFRC shaft lining presents a transition trend from the inside surface to the outside surface; the hoop strain of shaft lining concrete is always a compressive strain, and the inside surface is greater than the outside surface. The empirical formula for the ultimate capacity of this new type of shaft lining structure was obtained by fitting. Compared with the model test results, the maximum relative error of the calculated value is only 6.69%, which provides a certain reference value for designing this kind of shaft lining structure

Pore characterization of Lower Silurian shale gas reservoirs in the Middle Yangtze region, central China

Organic-rich shales from Lower Silurian are widely distributed in the Middle Yangtze region, central China. However, the lack of fundamental data for shale gas reservoirs increases the difficulty.of gas exploration. In this study, 34 core samples were collected to characterize the shale pore structure and conduct a preliminary evaluation of the shale gas reservoir. The TOC (total organic carbon) content of the successively-deposited black shales range from 1.6% to 5.9%, while the total porosity range from 0.5% to 4.2%. The positive correlation between TOC and porosity indicates that TOC is the key factor determining porosity. The major component of the mineral matrix is quartz (content of 21.4%-69.2%), followed by clay minerals (content of 16.7%-44.5%). Field-emission scanning electron microscopy (FE-SEM) and energy dispersive X-ray spectroscopy (EDS) results illustrate that organic matter, mixed with clay minerals, can form an organo-clay complex containing many nanopores. Furthermore, larger organic pores are developed in organo-clay complexes with higher clay content than in those with lower clay content. Correlational analyses between pore volume (or pore surface area) and TOC (or clay content) demonstrate that micropores are associated with organic matter, while mesopores and macropores are probably associated with clay minerals. Many of the clay-related nanopores are organic in nature and are developed in organo-clay complexes containing both organic matter and clay minerals. Overall, the TOC content controls development of nanopores in the shale pore structure, followed by clay content. The DFT-derived PSD indicates that the pore volume is comprised primarily of pores having widths larger than 10 nm, while the surface area is comprised primarily of micropores. When considering the gas in place model and mechanisms of shale gas storage, further shale gas exploration in central China should aim to the deep (&gt;1000 m) and well preserved Longmaxi Shales. (C) 2017 Elsevier Ltd. All rights reserved

Relationships among composition, porosity and permeability of Longmaxi Shale reservoir in the Weiyuan Block, Sichuan Basin, China

Shale composition might influence the petrophysical properties of shale reservoirs. The relationships among composition, porosity and permeability of Longmaxi Shale in Weiyuan area, Sichuan Basin, China, were systematically investigated by the integration of geochemical, mineralogical and petrophysical data. The cumulative pore volume of the organic-rich Longmaxi Shale is mainly contributed of pores with diameter of 2 nm-100 nm. The total organic carbon (TOC) content is the main control on porosity, as the percentage of organic porosity is > 60% for the organic-rich shales. The clay content is positively correlated with porosity, partly due to the clay associated interparticle pores and pores developed in organo-clay complex. Carbonate and quartz content dilute the TOC and clay content, which accounts for their negative relationships with porosity. In terms of shale composition, the clay content exerts the strongest influence on permeability. At low clay contents ( 30%), the clay content exhibits a negative impact on permeability because abundant clay minerals block pore throats, reduce the resistance to mechanical compaction and result in low permeability. The influence of the pore network on permeability is evident from a positive correlation between the pore volume percentage of meso-pores (VOLmes) and permeability, which is due to (a) fine and coarse meso-pores including a large fraction of organic pores, which have better connectedness than other interparticle (mostly > 50 nm) and intraparticle (mainly isolated) pores; and (b) large quantities of fine and coarse mesopores increasing the capacity to access other pores, which form the dominated pathways for gas flows. According to the above illustrated relationships, appropriate porosity and permeability indicating fine storage capacity and favorable flow capacity occur in the Longmaxi Shale in Weiyuan Block, which implies good reservoir quality and excellent exploration prospects in this region