Chang'an University

About: Chang'an University is a education organization based out in Xi'an, China. It is known for research contribution in the topics: Asphalt & Groundwater. The organization has 18415 authors who have published 15102 publications receiving 125436 citations. The organization is also known as: Cháng'ān Dàxué & Changan University.

Spatiotemporal evolution of global population ageing from 1960 to 2017.

Abstract: Population ageing is an increasingly severe global issue. And this has been posing challenges for public health policies and medical resource allocation There are various features of population ageing in different regions worldwide. All data were obtained from the health data of World Bank Open Data. Quantile linear regression was used to subtly measure the common variation tendency and strength of the global ageing rate and ageing population. The Bayesian space-time hierarchy model (BSTHM) was employed to assess the detailed spatial temporal evolution of ageing rate and ageing population in global 195 countries and regions. Annual growth of the ageing (65 and above) rate occurred on six continents: Europe (0.1532%), Oceania (0.0873%), Asia (0.0834%), South America (0.0723%), North America (0.0673%) and Africa (0.0069%). The coefficient of variation of the global ageing rate increased from 0.54 in 1960 to 0.69 in 2017. The global ageing rate and ageing population increased over this period, correlating positively with their quantiles. Most countries (37/39) in Europe belong to the top level with regard to the ageing rate, including the countries with the greatest degree of ageing—Sweden, Germany, Austria, Belgium and the UK—whose spatial relative risks of ageing are 3.180 (3.113–3.214), 3.071 (3.018–3.122), 2.951 (2.903–3.001), 2.932 (2.880–2.984) and 2.917 (2.869–2.967), respectively. Worldwide, 44 low ageing areas which were distributed mainly in Africa (26 areas) and Asia (15 areas) experienced a decreasing trend of ageing rates. The local trends of ageing population in the 195 areas increased. The differentiation of global population ageing is becoming increasingly serious. Globally, all 195 areas showed an increasing local ageing trend in absolute terms, although there were 44 low-ageing areas that experienced a decreasing local trend of ageing rate. The statistical results may provide some baseline reference for developing public health policies in various countries or regions, especially in less-developed areas.

Sulfur doping enhanced desorption of intermediates on NiCoP for efficient alkaline hydrogen evolution

Abstract: Electrocatalysts with high catalytic activity, high stability and low cost are critical to the hydrogen evolution reaction (HER). In this paper, sulfur(S)-doped NiCoP nanowire arrays on a carbon fiber paper skeleton (S-NiCoP NW/CFP) are prepared, and it is demonstrated that the electrocatalytic properties of NiCoP in alkaline solution could be well improved by sulfur doping. In 1.0 M KOH, only an overpotential of 172 mV (vs. RHE) at 100 mA cm-2 is required for S doped NiCoP nanowires on CFP, and the turnover frequency (TOF) is 1.71 times that of NiCoP at an overpotential of 100 mV, indicating its superior intrinsic activity. Density functional theory (DFT) calculations show that S doping could lower the center of the d-band, and thus weaken the interaction between NiCoP and the intermediates. This leads to an optimized hydrogen adsorption Gibbs free energy (ΔGH*) and faster desorption of OH*. This study offers a promising way to design and optimize electrocatalysts for the HER in alkaline solution.

Mechanical properties and pore structure of recycled aggregate concrete made with iron ore tailings and polypropylene fibers

Abstract: The purpose of this study was to assess the performance of introducing polypropylene (PP) fibers into recycled aggregate concrete containing iron ore tailings (TRAC) Thus, we prepared four different concretes, including natural aggregate concrete (NAC), recycled aggregate concrete (RAC), TRAC and fiber-reinforced tailings recycled aggregate concrete (TRAC-PP) series PP fibers were used as supplementary material at different percentages (03%, 06%, 09% and 12%) and compared with NAC, RAC and TRAC The cubic compressive strength, axial compressive strength and splitting tensile strength were analysed The digital image correlation technique was used to monitor the strain development of concrete under compressive loading Besides, the nuclear magnetic resonance technique was applied to evaluate the pore structure The testing results showed that the use of recycled coarse aggregate (RCA) led to the reduction of strength of concrete, but this strength loss can be compensated by adding iron ore tailings (IOTs) to concrete The addition of PP fibers to TRAC was significantly in the splitting tensile strength, but not obvious in the compressive strength when the supplementary percentage of PP fibers was lower than 06% The failure pattern of TRAC-PP12 was relatively ductile and its cracks were relatively tortuous and fine RAC had the highest total pore contents Addition with IOTs and PP fibers to RAC significantly decreased the total pore contents Recycling of RCA and IOTs would reduce the environmental impact and economic cost Finally, the concrete with 30% RCA, 30% IOTs and 06% PP fibers can be considered as the most appropriate concrete

Benchmark Data and Method for Real-Time People Counting in Cluttered Scenes Using Depth Sensors

Abstract: Vision-based automatic counting of people has widespread applications in intelligent transportation systems, security, and logistics. However, there is currently no large-scale public dataset for benchmarking approaches on this problem. This paper fills this gap by introducing the first real-world RGB-D people counting dataset (PCDS) containing over 4500 videos recorded at the entrance doors of buses in normal and cluttered conditions. It also proposes an efficient method for counting people in real-world cluttered scenes related to public transportations using depth videos. The proposed method computes a point cloud from the depth video frame and re-projects it onto the ground plane to normalize the depth information. The resulting depth image is analyzed for identifying potential human heads. The human head proposals are meticulously refined using a 3D human model. The proposals in each frame of the continuous video stream are tracked to trace their trajectories. The trajectories are again refined to ascertain reliable counting. People are eventually counted by accumulating the head trajectories leaving the scene. To enable effective head and trajectory identification, we also propose two different compound features. A thorough evaluation on PCDS demonstrates that our technique is able to count people in cluttered scenes with high accuracy at 45 fps on a 1.7-GHz processor, and hence it can be deployed for effective real-time people counting for intelligent transportation systems.

Assessment of Groundwater Quality and Human Health Risk (HHR) Evaluation of Nitrate in the Central-Western Guanzhong Basin, China.

Abstract: To investigate the quality of domestic groundwater and assess its risk to inhabitants of the Guanzhong Basin, China, 191 groundwater samples were collected to analyze major ions, nitrate, pH, total dissolved solids (TDS), total hardness (TH), and electrical conductivity (EC). The physiochemical parameters, hydrochemical facies, and sources of major ions were analyzed using Durov diagrams, bivariate diagrams, and chloro-alkaline indices (CAI-I and CAI-II). The suitability of groundwater for drinking, the nitrate distribution, and human health risk (HHR) for different age groups were evaluated. The results showed that the relative abundance of cations in the groundwater samples was K++Na+ > Ca2+ > Mg2+, while that of anions was HCO3- > SO42- > Cl- > NO3-. Groundwater samples mainly contained HCO3-Na and HCO3-Ca, which were introduced mainly by rock weathering and ion exchange. The groundwater in the Guanzhong Basin contained mainly good and medium water, and the groundwater in the southern part of the Wei River was better than that north of the Wei River. Areas containing high nitrate concentrations were mainly located in the central and western parts of the Guanzhong Basin. The percentages of low risk ( 100 mg/L) of nitrate pollution in the study area were 90.58%, 8.9%, and 0.52%, respectively. The HHR assessment results indicated that people in the 6-12 month age group were more likely to suffer from health complications due to a higher nitrate concentration, followed by 6-11 years, 21-65 years, 18-21 years, ≥65 years, 11-16 years, and 16-18 years age groups, which was mainly due to the different exposure parameters. The results of this study will be useful in regional groundwater management and protection.