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.
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.
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 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.
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/).
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：
Thermal comfort;Weightlessness;Heart rate variability;Head-down bed rest model;Core temperature;Sweating;Thermoregulation
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.
期刊：
INTERNATIONAL JOURNAL OF NUMERICAL METHODS FOR HEAT & FLUID FLOW,2020年30(8):4025-4065 ISSN：0961-5539
通讯作者：
Zhao, Fu-Yun
作者机构：
[Liu, Run-Zhe; Zhao, Fu-Yun; Wang, Wei-Wei; Wang, Lei; Cai, Yang] Wuhan Univ, Sch Power & Mech Engn, Wuhan, Peoples R China.;[Liu, Di] China Univ Petr East China, Coll Pipeline & Civil Engn, Dongying Campus, Dongying, Peoples R China.;[Wang, Hanqing] Univ South China, Sch Civil Engn, Hengyang, Peoples R China.
通讯机构：
[Zhao, Fu-Yun] W;Wuhan Univ, Sch Power & Mech Engn, Wuhan, Peoples R China.
关键词：
Nanofluids;Heat transfer enhancement;MHD natural convection;Porous fins;Topology and morphology
摘要：
Purpose - This paper aims to numerically investigate the magnetohydrodynamic (MHD) convection heat transfer of nanofluid inside a differentially heated enclosure with various fin morphologies. Design/methodology/approach - The fluid flow within the cavity was governed by N-S equations while it within porous medium was solved by the non-Darcy model, called the Darcy-Forchheimer model based on representative element-averaging method. Empirical correlations from experimental data are used to evaluate the effective thermal conductivity and dynamic viscosity. Relevant governing parameters, including thermal Rayleigh number (10~5-10~7), Hartmann number (0-50), Darcy number (10~(-6)-10~(-1)), thermal conductivity ratio of porous matrix (1-10~3), nanoparticles volume fraction (0-0.04) and topology designs of porous fins, are sensitively varied to identify their effects and roles on the fluid flow and heat transfer. Particularly, heatlines are used to investigate the mechanism of heat transport. Findings - Numerical results demonstrate that the predictions of average Nusselt number are augmented by using more porous fins with high permeability, and this effect becomes opposite in tiny Darcy numbers. Particularly, for high Darcy and Rayleigh numbers, the shortest fins could achieve the best performance of heat transfer. In addition, the prediction of average Nusselt number reduces with an increase in Hartmann numbers. An optimal nanoparticles concentration also exists to maximize heat transfer enhancement. Finally, numerical correlations for the average Nusselt number were proposed as functions of these governing parameters. Practical implications - Present work could benefit the thermal design of electronic cooling and thermal carriers in nanofluid engineering. Social implications - Present work could benefit the thermal design of electronic cooling and thermal carriers in nanofluid engineering. In addition, optimum thermal removals could enhance the lifetime of electronics, therefore reducing the cost of energy and materials. Originality/value - To the best knowledge of authors, there are not any studies considering the synergetic effects of porous fins on MHD convection of nanofluids. Present work could benefit the thermal design of electronic cooling and thermal carriers in nanofluid engineering.
关键词：
Hybrid air conditioning system;Evaporative cooling;Dual-evaporator air-conditioning system;Parametric analysis;Energy-saving potential
摘要：
Energy recovery, evaporative cooling and multiple evaporator are regarded as the effective and energy-efficient techniques to improve the energy efficiency of air conditioning system and reduce building energy consumption. In this paper, a parametric analysis and energy-saving potential evaluation for a new hybrid air conditioning system (HAC) under hot-humid climates are carried out theoretically based on detailed models. The proposed HAC incorporates into a dual-evaporator air conditioning system with an independent fresh air conditioner for both total and sensible energy recovery. One evaporator is installed between the total and sensible energy recovery loop of the fresh air conditioner to deeply dehumidify the fresh air for indoor humidity control. The other evaporator is installed inside the conditioned room to handle the indoor return air for temperature and humidity independent control. The parametric analysis mainly for the effect of air-to-water heat capacity ratio, ambient temperature, enthalpy-humidity ratio of the air-conditioned room and the number of heat/mass transfer units of the internal heat exchangers. The energy-saving potential of the HAC is also evaluated for applications in four typical cities (Changsha, Guangzhou, Fuzhou and Hangzhou) located in southern China over the summer period (June-August). The results show that, for the same air supply requirement, the HAC has an average energy-saving rate of 48.87% compared to conventional system with electric heater, and its power saving per hour is 24.85 W m(-2). (C) 2020 Elsevier Ltd and IIR. All rights reserved.
摘要：
In this study, sewage sludge-derived biochars (SSBs) were prepared at two pyrolysis temperatures of 450 degrees C (SSB450) and 600 degrees C (SSB600) for U(VI) removal. The maximum adsorption capacity of SSB450 and SSB600 was 43.13 and 47.47 mg g(-1), respectively, at initial pH of 3. While the adsorption process of U(VI) onto the SSBs were accurately described by the pseudo-second-order model and Langmuir isotherm model. Ion exchange and complexation were assumed as the adsorption mechanism. The adsorption-desorption experiment showed that both the U(VI) removal efficiency and SSB regeneration efficiency were greater than 80%. Thus, the SSB has a potential application in U(VI)-containing wastewater treatment.
