摘要：
The triple-bed circulating fluidized bed gasifier is a new type of the gasification process in which the combustion process, pyrolysis process, and gasification process of the fuel are carried out in different reactors. The inert heat carrier is used to transfer heat between the reactors. In this way, the gasification efficiency of char is improved since the tar and pyrolysis gas generated in the pyrolysis process will no longer hinder the gasification of the char. The thermodynamic equilibrium model is used to simulate the gasification process of the triple-bed circulating fluidized bed, and the sub-models are established to simulate combustion, pyrolysis, and gasification processes. The simulation results agree well with the experimental values. Besides, the model studies the effects of key parameters such as the gasification reaction temperature and the ratio of steam to C (S/C) on gasification performance. Results showed that higher gasification reaction temperature has a positive effect on gasification performance, S/C may not be too high, and excessive water vapor will directly affect the gasification reaction.
摘要：
The increase in carbon emissions has had great negative impacts on the healthy developments of the human environment and economic society. However, it is unclear how specific socio-economic factors are driving carbon emissions. Based on the multiscale geographically weighted regression (MGWR) model, this paper analyzes the impact mechanism of China's carbon emission data during 2010-2017. The results show that (1) during the study period, China's carbon emissions have obvious positive correlations in the spatial distribution, and the spatial autocorrelation of carbon emissions on the time scale has a further strengthening trend. (2) Compared with the results of the geographically weighted regression (GWR) model, the MGWR model is more robust, and the results are more realistic and reliable. The impacts of energy intensity, proportion of green coverage in built-up areas, and industrial structure on provincial carbon emissions are close to the global scale, and their spatial heterogeneity is weak. Other factors have spatially heterogeneous impacts on carbon emissions with different scale effects. (3) Except for proportion of green coverage in built-up areas, the industrial structure and trade openness have insignificant impacts on carbon emissions, but other variables have significant impacts. The total population, urbanization rate, energy intensity, and energy structure have positive impacts on carbon emissions, while the GDP per capita and foreign direct investment have negative impacts on it. This study shows that the main socio-economic factors have different degrees of impacts on carbon emissions with different scale, and we can refer to it to formulate more scientific measures to reduce carbon emissions.
关键词：
Blockchain;Cloud computing;Computational modeling;Security;Analytical models;Edge computing;Computer architecture;Cloud-edge computing;dynamical behavior;information diffusion;social interaction;Social Internet of Things (SIoT);traceability
摘要：
Social Internet of Things (SIoT), integrating the social networks and Internet of Things (IoT), leads to heterogeneous interactions of thing to thing, human to human, and human to thing, which in turn generates exploded information. Hence, as the soul of SIoT, information with its interaction and diffusion, records the track of humans and things and contains the hidden value for social administration and people's lives. Therefore, how to characterize the interplay between behavior spreading and information diffusion in SIoT is essential to predict and manage the information. Motivated by this, a more comprehensive understanding of the coupled modeling of social interaction and information diffusion processes in SIoT is conceived first. With the widespread adoption of cloud-edge computing, different nodes have different consciousness on information. Hence, a cloud-edge-aided information diffusion model is proposed for efficient interactions, which incorporates the role of edge in timely processing and feedback. On this basis, a blockchain-based cloud-edge SIoT architecture is proposed for traceability and security of information diffusion. Furthermore, the dynamical analysis of the coupled model in SIoT is provided, which illustrates the outbreak threshold, stability, and scale of information propagation. An interesting finding is that interactive behavior spreading only influences the final size of information propagation, not the spreading threshold. Extensive simulation results and detailed performance analysis verify the theoretical results, which are beneficial to provide traceable dissemination so as to find the most influential node and control the scale of information diffusion.
摘要：
The aim of this work is to study the impacts of Na+ and H2O on structural and mechanical properties of coal gangue-based geopolymer by experiment and molecular dynamics. Geopolymers were prepared by coal gangue and mixed solution of NaOH and water glass. Then X-ray fluorescence (XRF) and X-ray diffraction (XRD) were utilized to characterize the main chemical composition and crystalline phase of geopolymer after 28d curing. Moreover, Na2Si2O5 glass was firstly proposed to establish the molecular structure of geopolymers with different Na/Al and H2O/Al. Structural optimization and molecular dynamics simulation were implemented under the specific force field. Simulated XRD pattern, energy and temperature curves, radial distribution function (RDF), hydrogen bond, bond angle distribution, mean square displacement (MSD) and elastic modulus of geopolymer were calculated and analyzed. Results indicated that with the increase of Na+ and H2O content, structure of geopolymer became more stable and mechanical properties were improved significantly. (C) 2020 Elsevier Ltd. All rights reserved.
关键词：
Bridges;Monitoring;Computer science;Sensors;Learning automata;Internet of Things;Civil engineering;Bridge structural health monitoring (BSHM);confident information coverage (CIC) model;Internet of Things (IoT);learning automata (LA);partial coverage;reinforcement learning
摘要：
Internet-of-Things (IoT)-based bridge structural health monitoring (BSHM) has recently attracted considerable attention from both academic and industrial communities of civil engineering and computer science. In conjunction with researchers from civil engineering and computer science, this article studied a fundamental problem motivated from practical IoT-based BSHM: how to effectively prolong network lifetime while guaranteeing desired coverage. Integrating a promising reinforcement learning model named learning automata (LA) with confident information coverage (CIC) model, this article presented an energy-efficient sensor scheduling strategy for partial CIC coverage in IoT-based BSHM system to guarantee network coverage and prolong network lifetime. The proposed scheme fully exploits cooperation among deployed nodes and alternatively schedules the wake/sleep status of nodes while satisfying network connectivity and partial coverage ratio. Especially, the proposed scheme takes full advantage of the LA model to adaptively learn the optimal sensor scheduling strategy and significantly extend network lifetime. A series of comparison simulations using real data sets collected by a practical BSHM system strongly verify the effectiveness and energy efficiency of the proposed algorithm. To the best of our knowledge, this is the first study on how to combine the reinforcement learning mechanism with partial coverage for maximizing the network lifetime of the IoT-based BSHM.
期刊：
Case Studies in Thermal Engineering,2021年26:101059 ISSN：2214-157X
通讯作者：
Dong Xie
作者机构：
[Xie, Dong; Dou, Xiumin] Univ South China, Sch Civil Engn, Hengyang 421001, Hunan, Peoples R China.;[Xie, Dong; Wang, Zhongkun; Wang, Hanqing; Xiao, Peilin; Dou, Xiumin] Key Lab Hunan Technol Energy Conservat Prefabrica, Hengyang 421001, Hunan, Peoples R China.;[Wang, Zhongkun; Xiao, Peilin] Univ South China, Sch Resource Environm & Safety Engn, Hengyang 421001, Hunan, Peoples R China.;[Wang, Hanqing] Cent South Univ Forestry & Technol, Coll Civil Engn, Changsha 410000, Hunan, Peoples R China.
通讯机构：
[Dong Xie] S;School of Civil Engineering, University of South China, Hengyang 421001 Hunan, China<&wdkj&>Key Lab of Hunan for the Technologies of Energy Conservation in Prefabricated Buildings, Hengyang 421001, Hunan, China
期刊：
Transportation Research Record,2021年2675(12):797 - 810 ISSN：0361-1981
通讯作者：
Wengui Li
作者机构：
[Tang, Zhuo; Li, Wengui; Zhang, Xuanrui] Univ Technol Sydney, Sch Civil & Environm Engn, Sydney, NSW 2007, Australia.;[Zhang, Xuanrui] Henan Prov Commun Planning & Design Inst Co Ltd, Zhengzhou, Henan, Peoples R China.;[Tang, Zhuo] Cent South Univ, Sch Civil Engn, Changsha, Hunan, Peoples R China.;[Ke, Guojun] Univ South China, Sch Civil Engn, Hengyang, Peoples R China.
通讯机构：
[Wengui Li] S;School of Civil and Environmental Engineering, University of Technology Sydney, NSW 2007, Australia
摘要：
Benefits of replacing ordinary Portland cement with industrial solid wastes are promising for reducing cement production and solving environmental problems associated with industrial solid wastes. In this study, an experimental investigation was conducted to evaluate the performance of sustainable concrete containing different industrial solid wastes (e.g., waste glass, coal gangue, fly ash, and slag), with the attention on the mechanical strength, chloride transport property, and pore structure characteristics. Three water to binder ratios (i.e., 0.38, 0.48, and 0.65) and three replacement levels (i.e., 10%, 20%, and 30%) were considered in this work. The test results show that regardless of the content and type of industrial solid wastes, the inclusion of industrial solid wastes generally exerts a negative influence on the mechanical properties, especially under high water to binder ratios. However, acceptable mechanical strength can still be achieved in these sustainable concretes. In addition, the inclusion of industrial solid wastes could enhance the chloride diffusion resistance of concrete, and also the concrete with waste glass powder showed the best performance. Furthermore, the incorporation of industrial solid wastes has a refinement effect on the microstructure of the matrix, manifesting as decreased cumulative pore volume and compacted microstructural morphology.
摘要：
To improve the mechanical performances of joints in prefabricated construction, a type of connection structure with long-fiber and metal laminated bolts (referred to as a fiber-metal connector) is proposed and investigated by simulation and theoretical methods. The results include the following: (1) The fiber layer in bolts can form a second stiffness during rotation. This mechanical characteristic improves the bearing capacities and energy dissipation ability of the connector relative to the conventional metal connector, which are expected to effectively limit the elastoplastic rotational displacement of a structure. (2) For the reason, the fiber layer can bear load in the plastic phase due to its high-strength characteristic in the length direction. (3) A bilinear model for the bearing curve of the fiber-metal connector is proposed, and equations for optimization of fiber layer thickness are obtained with a target on bearing capacity and energy dissipation ability which are approximately higher 30% and 13% than that of the conventional metal connector, respectively. This research is expected to provide a theoretical basis for the application of this fiber-metal connector in engineering and improve the safety of prefabricated structures.
通讯机构：
[Guohua Wang] H;Hunan Provincial Key Laboratory of Pollution Control and Resources Technology, University of South China, Hengyang, People’s Republic of China<&wdkj&>Key Discipline Laboratory for National Defense for Biotechnology in Uranium Mining and Hydrometallurgy, University of South China, Hengyang, People’s Republic of China
摘要：
The adsorption performance and mechanism of the amino-modified zirconium-based metal organic framework (UiO-66-NH2) for the removal of U(VI) in aqueous solution were studied. Compared with UiO-66, UiO-66-NH2 shows better adsorption performance due to the introduction of amino groups. The adsorption characteristics of factors such as pH, UiO-66-NH2 dosage and contact time were investigated. The results show that the maximum adsorption capacity is 384.6 mg g(-1) at pH = 6 and T = 313 K. The adsorption conforms to the quasi-second-order kinetic model and the Langmuir isotherm model. The thermodynamic parameters indicate that the adsorption process of U(VI) is endothermic and spontaneous. After five cycles, the removal rate of U(VI) still exceeded 83.53%. The results indicate that UiO-66-NH2 is a promising adsorbent that can effectively remove U(VI) in radioactive wastewater.
摘要：
Uranium-containing wastewater poses a major threat to human health because of its toxicity and radioactivity. To address this issue, tea waste-derived porous biochar supporting the Fe-Mn bimetallic composite (FMBC) was fabricated using impregnation-pyrolysis and applied for U(VI) removal from aqueous solution. Batch experiments and characterization analysis were performed to investigate the adsorption properties and interaction mechanisms. Results showed that FMBC exhibit a maximum U(VI) removal capacity of 510.8 mg/g at pH = 5, T = 303 k, and t = 25 min. The kinetic and isotherm date fitted well with the pseudo-second-order kinetic model and Langmuir isotherm model, respectively, indicating that uranium adsorption is dominated by chemical adsorption on FMBC. FTIR and XPS analyses further confirmed that the U(VI) adsorption mechanism by FMBC was attributed to surface complexation, pi-pi bonding, and reduction processes. In addition, the Cationic competitive adsorption experiment further highlighted the excellent selective performance of FMBC for U(VI) removal from aqueous solutions, which is important in radionuclides' pollution treatment.
期刊：
Sustainable Cities and Society,2021年66:102599 ISSN：2210-6707
通讯作者：
Xie, Dong
作者机构：
[Wang, Chenhua; Xie, Dong; Wu, Yangxi; Wang, Hanqing; Tian, Ling] Natl & Local Joint Engieering Res Ctr Airborne Po, Hengyang 421001, Peoples R China.;[Xie, Dong; Wu, Yangxi; Tian, Ling; Yu, Chuck Wah] Univ South China, Sch Civil Engn, Hengyang 421001, Peoples R China.;[Wang, Hanqing] Cent South Univ Forestry & Technol, Changsha 410004, Peoples R China.;[Yu, Chuck Wah] Int Soc Built Environm ISBE, Milton Keynes, Bucks, England.;[Xie, Dong] Univ South China, Hengyang, Hunan, Peoples R China.
通讯机构：
[Xie, Dong] U;Univ South China, Hengyang, Hunan, Peoples R China.
关键词：
Indoor radon environment;Radon diffusion and distribution;CFD simulation;Three-dimensional unsteady state;Stabilization time
摘要：
The exhalation of radon from building materials is a serious risk to occupants? health. This paper studied the indoor radon diffusion under three-dimensional unsteady conditions. The radon exhalation rate of building materials was measured using a radon collection chamber combined with a RAD7-based radon/thoron detector. The indoor radon diffusion under different ventilation patterns were simulated by CFD (Computational fluid dynamics) based on the stabilization of radon concentration after 10 h in a closed environment as an initial condition. The results show that the stabilization time is 20 min, which can be reduced by appropriately increasing the air inlet velocity. Further increase in air velocity from 0.3 m s(-1) did not produce any significant changes in the stabilization time and the average radon concentration. Our findings show that the better way to reduce indoor radon concentration is to have the air supply inlet at the top or upper side and the air return outlet on the lower side of the room. The indoor radon can be reduced to a steady level after 20 min using the better ventilation method. The findings would contribute to the control of the indoor radon dispersion, and to alleviate and reduce occupants? exposure to high radioactive concentration of radon in urban cities.
摘要：
Uranium is a relatively active and chemically toxic natural radionuclide, its enrichment in the environment poses a serious threat to human health and ecosystems. It is necessary to dispose the uranium contaminated soil safely and efficiently. In this study, the effect of coal gangue-based geopolymers on the solidification of uranium-contaminated soil was examined using a single factor experiment. The highest compressive strength of the solidified body reached 24.6 MPa, and the highest fixation efficiency of uranium reached 77.44%. The results show that lower liquid-to-solid ratio, higher alkali activator content and lower alkali activator modulus promote the solidification of uranium.
摘要：
The leaching of uranium in uranium soil will pose great risks to human health and the ecological environment. The immobilization of uranium by coal gangue geopolymers (CGG) and Nano-hydroxyapatite (nHAP)-based composite geopolymers were investigated in this study. The ability of geopolymers to immobilize uranium was evaluated in terms of the static and dynamic leaching concentration. The experimental results confirmed that the lowest static leaching concentration of composite uranium soil solidified body and uranium soil solidified body was 15.94 mg/kg and 21.27 mg/kg after 28 days of immobilization, respectively. During the 28-d dynamic leaching experiment, the highest leaching concentration was 155.38 mg/kg and 166.63 mg/kg, respectively. The composite uranium soil solidified body shows better overall leaching resistance.
通讯机构：
[Shuibo Xie] S;School of Civil Engineering, University of South China, Hengyang, China<&wdkj&>Key Discipline Laboratory for National Defence of Biotechnology in Uranium Mining and Hydrometallurgy, University of South China, Hengyang, China
摘要：
A zirconium-based metal-organic framework (DUT-69) was fabricated via a hydrothermal synthesis for U(VI) removal in aqueous solutions. Experimental results showed that the maximum adsorption capacity for U(VI) was 362.32 mg center dot g(-1) at 303 K, pH = 6 and initial U(VI) concentration of 80 mg L-1. The adsorption process fit well with the pseudo-second-order kinetic and Langmuir models. Various characterizations indicated that complexation interactions was the central adsorption mechanism and electrostatic was the secondary. The carboxyl, Zr-O, and C-S bonds in the framework participated in the adsorption process. Reusability experiments showed that 80.34% adsorption rate could be maintained after 5 cycles.
期刊：
Indoor and Built Environment,2020年29(8):1169-1180 ISSN：1420-326X
通讯作者：
Zhu, Hui
作者机构：
[Yu, Chuck Wah Francis; Zhu, Hui; Huang, Linsheng] Univ South China, Sch Civil Engn, Hengyang, Peoples R China.;[Zhu, Hui] Univ Sydney, Sch Architecture Design & Planning, Sydney, NSW, Australia.;[Yu, Chuck Wah Francis] Int Soc Built Environm ISBE, Milton Keynes, Bucks, England.;[Su, Hua] Univ South China, Affiliated Hosp 1, Hengyang, Peoples R China.
通讯机构：
[Zhu, Hui] U;Univ South China, Sch Civil Engn, Hengyang, Peoples R China.
关键词：
Core temperature;Head-down bed rest model;Heart rate variability;Sweating;Thermal comfort;Thermoregulation;Weightlessness
摘要：
This study investigated the physiological thermal response of people under simulated weightlessness using a 6 degrees head down bed rest (HDBR) model to ensure the human body functions in the weightlessness way. Thermal responses of six male participants were experimentally determined. The relationship between thermal comfort and heart rate variability (HRV) was also scrutinized. Physiological responses of participants under different environmental conditions were observed including core temperature, sweating, and most importantly, HRV. Elevated core temperatures were observed amongst participants, with a maximum increment of 0.5 degrees C. The sweating of participants under simulated weightlessness was conspicuously retarded, requiring a 2-4 degrees C increase in environmental temperature to start sweating. Body regional differences in the sweating were also observed. The HRV index 'LF/HF', which reflects the balance of the autonomous nervous system, was found to vary with the environment and closely associated with the variation in the thermal comfort scores. Participants under simulated weightlessness had higher mean LF/HF when they felt comfortable, and they preferred a warmer environment in comparison to under normal gravity condition. An altered thermoregulation of the human body under simulated weightlessness was indicated by our findings. The use of HRV index could provide a useful prediction of subjective thermal comfort under weightlessness.
关键词：
Rock dynamics;Split hopkinson pressure bar (SHPB);Layered composite rock specimen;Dip angle of bedding plane;Strain rate;Numerical simulation
摘要：
Layered rock mass of significant strength changes for adjacent layers is frequently observed in underground excavation, and dynamic loading is a prevalent scenario generated during excavation. In order to improve the driving efficiency and reduce engineering accidents, dynamic compression characteristics of this kind of rock mass should be understood. The dynamic properties of a layered composite rock mass are investigated through a series of rock tests and numerical simulations. The rock mass is artificially made of various proportions of sand, cement and water to control the distinct strength variations at various composite layers separated by parallel bedding planes. All rock specimens are prefabricated in a specially designed mould and then cut into 50 mm in diameter and 50 mm in height for split Hopkinson pressure bar (SHPB) dynamic compression testing. The test results reveal that increasing strain rate causes the increases of peak strength, sigma(p), and the corresponding failure strain, epsilon(p), while the dynamic elastic modulus, E-d, remains almost unchanged. Interestingly, under the same strain rates, E-d of the composite rock specimen is found to decline first and then increase as the dip angle of bedding plane increases. The obtained rock failure patterns due to various dip angles lead to failure modes that could be classified into four categories from our dynamic tests. Also, a series of counterpart numerical simulations has been undertaken, showing that dynamic responses are in good agreement with those obtained from the SHPB tests. The numerical analysis enables us to look into the dynamic characteristics of the composite rock mass subjected to a broader range of strain rates and dip angles than these being tested. (C) 2019 Institute of Rock and Soil Mechanics, Chinese Academy of Sciences. Production and hosting by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).
