关键词：
waste glass powder;cementitious composite;alkali-silica reaction (ASR) expansion;mitigation;pH value
摘要：
The effects of different contents and particle sizes of waste glass powder on alkali–silica reaction (ASR) expansion of cementitious composite bar were investigated in this study. Waste glass powder with particle size less than 300 μm exhibits an excellent mitigation effect on ASR expansion. With larger content and smaller particle size, the mitigation effect of waste glass powder on ASR expansion gradually increases. The mitigation effect of waste glass powder with particle size ranging from 38 to 53 μm and 20% by weight of cement seems relatively better than that of fly ash. When the waste glass powder content reaches 30%, the mitigation effect is still effective and almost the same as that of fly ash. However, the waste glass powder with particle size larger than 300 μm presents negative mitigation effect on ASR expansion when the replacement rate is larger than 30%. On the other hand, the waste glass powder and calcium hydroxide (CH) further react, and produce more calcium–silicate–hydrate gels, which apparently reduce the amount of CH. Moreover, the increasing content of waste glass powder results in a lower pH value in the pore solution of cementitious composite.
作者机构：
[Liu, Bing-Rui; Liu, Qi-Feng; Zhang, Qian; Ma, Jing-Jun] Agr Univ Hebei, Coll Sci & Technol, Huanghua 061100, Hebei, Peoples R China.;[Li, Shiyou] Univ South China, Hunan Prov Key Lab Pollut Control & Resources Tec, Hengyang 421001, Hunan, Peoples R China.;[Ma, Jing-Jun] Hebei Agr Prod Proc Engn Technol Res Ctr, Baoding 071001, Hebei, Peoples R China.
通讯机构：
[Ma, Jing-Jun] A;[Li, Shiyou] U;[Ma, Jing-Jun] H;Agr Univ Hebei, Coll Sci & Technol, Huanghua 061100, Hebei, Peoples R China.;Univ South China, Hunan Prov Key Lab Pollut Control & Resources Tec, Hengyang 421001, Hunan, Peoples R China.
关键词：
Construction of surface defects;Ultrafine TiO_2;Low-cost transition metal;Surface doping;Photocatalytic H_2 production
摘要：
Inefficient charge separation and limited light absorption are two critical issues associated with high-efficiency photocatalytic H_2 production using TiO_2. Surface defects within a certain concentration range in photocatalyst materials are beneficial for photocatalytic activity. In this study, surface defects (oxygen vacancies and metal cation replacement defects) were induced with a facile and effective approach by surface doping with low-cost transition metals (Co, Ni, Cu, and Mn) on ultrafine TiO_2. The obtained surface-defective TiO_2 exhibited a 3-4-fold improved activity compared to that of the original ultrafine TiO_2. In addition, a H_2 production rate of 3.4 µmol/h was obtained using visible light (λ > 420 nm) irradiation. The apparent quantum yield (AQY) at 365 nm reached 36.9% over TiO_2-Cu, significantly more than the commercial P25 TiO_2. The enhancement of photocatalytic H_2 production activity can be attributed to improved rapid charge separation efficiency and expanded light absorption window. This hydrothermal treatment with transition metal was proven to be a very facile and effective method for obtaining surface defects.
期刊：
Heat Transfer Engineering,2018年39(20):1731-1752 ISSN：0145-7632
通讯作者：
Zhao, Fu-Yun
作者机构：
[Wang, Han-Qing; Li, Lin; Zhao, Fu-Yun] Hunan Univ Technol, Sch Civil Engn, Zhuzhou, Hunan, Peoples R China.;[Hu, Jiang-Tao; Zhao, Fu-Yun] Wuhan Univ, Sch Power & Mech Engn, Dong Hu Southern Rd, Wuhan 430072, Hubei, Peoples R China.;[Liu, Di] China Univ Petr, Coll Pipeline & Civil Engn, Qingdao, Shandong, Peoples R China.;[Wang, Han-Qing] Univ South China, Sch Civil Engn, Hengyang, Hunan, Peoples R China.
通讯机构：
[Zhao, Fu-Yun] W;Wuhan Univ, Sch Power & Mech Engn, Dong Hu Southern Rd, Wuhan 430072, Hubei, Peoples R China.
摘要：
Combined heat and moisture transportation in an enclosure has been numerically investigated, which could benefit the sustainable building energy conservations and electronic cooling designs. An adiabatic and impermeable partition of finite thickness is considered, placed in the enclosure following an ordered arrangement. Effects of length and location of the partition, buoyancy ratio and thermal Rayleigh number on convective heat and moisture transfer rates in the enclosure are discussed. Firstly, this situation of the partition placed in the horizontal wall is studied, where inhibition effect of partition is observed. It is seen that the location of partition put relatively weaker influences on the heat and mass transfer in the regime of thermal-driven flow, when its length exceeds the critical value. Additionally, inhibition effect is more pronounced as the partition is fixed in center of vertical wall. Furthermore, local heat and mass transfer rates could be suppressed when the buoyancy ratio becomes negative. Finally, thermal Rayleigh number greatly affects the transport structures of fluid, heat and moisture, whatever aiding flow or opposing flow situations. Heat and mass transfer potentials could be promoted with increasing thermal Rayleigh numbers. Present work could be adopted to optimize the enclosure flows simultaneously with heat and moisture transport.
摘要：
Combined thermal and moisture convections in an enclosure partially filled with porous medium are numerically and analytically investigated, aiming to enhance moisture transport in the thermal energy storage unit. Two representative configurations of porous layers were taken into considerations, being placed centrally in the space or attached to the vertical walls. Moist air motions are simultaneously driven by the internal heat generation and external concentration difference imposed across the enclosure. Effects of Darcy number, mass diffusion coefficient, thermal Rayleigh number and buoyancy ratio on the heat and moisture transfer across the enclosure are discussed. Heat and mass transfer of the fluid/porous interface is analyzed as a function of the permeability of the porous layer. In the extreme case of high permeability and solutal-driven flow, a scale analysis is applied to predict the order of magnitudes involved in the boundary layer regime. Also, correlations for the average Nusselt and Sherwood numbers based on discrete numerical results are proposed. There is an agreement between the analytical and numerical results of moisture transfer rate, while a slight difference of heat transfer rate is observed due to different configurations of porous layers were imposed. Present research could benefit future development of sustainable building energy storage.
作者机构：
[Xie, Shuibo; Gao, Xiang; Zeng, Taotao; Wang, Guohua; Zhang, Shiqi] Univ South China, Hunan Prov Key Lab Pollut Control & Resources Reu, Hengyang, Peoples R China.;[Zeng, Taotao; Lens, Piet N. L.] UNESCO, IHE Inst Water Educ, Delft, Netherlands.;[Xie, Shuibo] Univ South China, Key Discipline Lab Natl Def Biotechnol Uranium Mi, Hengyang, Peoples R China.
通讯机构：
[Zeng, Taotao] U;Univ South China, Hunan Prov Key Lab Pollut Control & Resources Reu, Hengyang, Peoples R China.;UNESCO, IHE Inst Water Educ, Delft, Netherlands.
关键词：
Uranium;Anaerobic granular sludge;Bacterial community composition;High-throughput sequencing
摘要：
To improve the oxidation rate of high-sulfur and high-arsenic refractory gold concentrate (HGC), a two-stage chemical-biological oxidation approach, which contained a high-temperature chemical oxidation stage (ferric leaching stage) and a subsequent biological oxidation stage with mesophiles, was used in this experiment. The surface analysis of pure arsenopyrite using scanning electron microscope (SEM), Energy Dispersive X-ray Spectroscopy (EDX) and X-ray photoelectron spectroscopy (XPS) indicated that the surface lattice structure was partly disrupted after chemical oxidation; as a result, the subsequent biological oxidation rate during the second stage improved significantly. The extraction levels of Fe, As and S were 49.8%, 50.4% and 51.0%, respectively, in the normal biological oxidation system, while the values increased to 63.3%, 64.2% and 63.3%, respectively, following the two-stage process. Accordingly, the recovery rate of gold increased by 16.8% using the two-stage process compared to that of the one-stage biological oxidation approach.
摘要：
The effect of gamma-ray irradiation on waste activated sludge (WAS) dewaterability was investigated with irradiation doses of 0–15 kGy. Time to filter (TTF50), specific resistance of filtration (SRF) and water content of sludge cake were measured to evaluate sludge dewaterability. Soluble chemical oxygen demand (SCOD), soluble extracellular polymeric substances (EPS) concentration and sludge particle size were determined to explain changes in sludge dewaterability. The optimal irradiation dose to obtain the maximum dewaterability characteristics was 1–4 kGy, which generated sludge with optimal disintegration (1.5–4.0%), soluble EPS concentration (590–750 mg/L) and particle size distribution (100–115 µm diameter). The combination of irradiation and cationic polyacrylamide (CPAM) addition exhibited minimal synergistic effect on increasing sludge dewatering rate compared with CPAM conditioning alone.
摘要：
Fe(II)-Al(III) layered double hydroxides (Fe-Al LDHs) were prepared by the sono-assisted precipitation method and used for the removal of uranium (VI) from aqueous solutions. The application of ultrasound in the Fe-Al LDHs preparation promoted the formation of the hydrotalcite-like phase and improved the adsorption capacity of U(VI). Batch experiments were carried out to investigate the influence of solid-to-solution ratio, initial U(VI) concentration, initial pH, contact time and temperature on the U(VI) removal process. The experimental results indicated that the removal process of U(VI) could be well described by the pseudo-second-order kinetic model. The equilibrium isotherm for U(VI) removal was fitted by the Langmuir model and the maximum adsorption capacity of Fe-Al LDHs was 113.64 mg/g at a temperature of 308 K. The thermodynamic parameters implied that the removal of U(VI) was essentially an endothermic process. The FT-IR, EDX and XPS results suggested that the removal mechanism involves combined adsorption-reduction processes. When the U(VI) ions absorbed onto the Fe-Al LDHs through physical adsorption, the Fe(II) in the structure of Fe-Al LDHs reduces U(VI) to U(IV) while Fe(II) was oxidized to Fe(III). (C) 2017 Elsevier B.V. All rights reserved.
摘要：
For sandwich beams with second-order hierarchical corrugated truss core under three-point bending, a correction factor of shear deflection was firstly proposed to improve the prediction accuracy of the bending analysis, which was verified by finite element analysis and compared with the original formula. Then, the failure modes of the sandwich beam under bending were analyzed, including four competing modes of the large struts (i.e. plastic yielding, buckling, wrinkling of facesheet, shear buckling) and two competing modes of the small struts (i.e. plastic yielding, buckling). Subsequently, the analytical expressions of critical load for each failure mode were derived. On this basis, the failure mechanism maps were constructed. Finally, several typical points from the map were selected and verified by finite element analysis, and a good agreement of predicted failure modes was observed.
期刊：
International Journal of Heat and Mass Transfer,2017年115(Pt.A):406-420 ISSN：0017-9310
通讯作者：
Zhao, Fu-Yun
作者机构：
[Zhao, Fu-Yun; Wang, Lei; Zhang, Dong-Dong] Wuhan Univ, Minist Educ, Key Lab Hydraul Machinery Transients, Wuhan, Hubei, Peoples R China.;[Zhao, Fu-Yun; Wang, Lei; Zhang, Dong-Dong] Wuhan Univ, Hubei Key Lab Waterjet Theory & New Technol, Wuhan, Hubei, Peoples R China.;[Zhao, Fu-Yun; Wang, Lei; Zhang, Dong-Dong] Wuhan Univ, Sch Power & Mech Engn, Dong Hu Southern Rd, Wuhan 430072, Hubei, Peoples R China.;[Liu, Di] China Univ Petr, Coll Pipeline & Civil Engn, Qingdao, Shandong, Peoples R China.;[Wang, Han-Qing] Univ South China, Sch Civil Engn, Hengyang, Hunan, Peoples R China.
通讯机构：
[Zhao, Fu-Yun] W;Wuhan Univ, Sch Power & Mech Engn, Dong Hu Southern Rd, Wuhan 430072, Hubei, Peoples R China.
关键词：
Thermal conductance;Direct enclosure convection;Inverse enclosure convection;Energy transport lines
摘要：
An objective-oriented optimization procedure consisting of a simplified conjugated gradient methodology and a two-dimensional fluid and thermal energy transfer model is implemented to discover optimal morphologies of local heating elements. Direct heat transfer problem and inverse optimization problem are subsequently investigated. Full simulation shows that thermal Rayleigh number, enclosure inclination, heating strength ratio and size ratio of local heating sources have significant effects on the natural convection heat transfer in the inclined enclosure, asymptotically modeling like solar energy collectors or electronic boxes. The fluid flow and energy transfer inside the enclosure are analyzed in some representative situations, by the simultaneous use of streamlines, isotherms and heatlines. Inverse natural convection solutions on the maximization of global conductance are addressed, concerning on the effects of thermal Rayleigh number, inclination angle, heater strength ratio and heater length ratio. Mathematical correlations have been proposed by the multiple linear regressions to identify the role of governing parameters on maximizing global conductance and optimal morphologies of the discrete heat sources, concerning on the unique global heating flux. Present numerical methodology and inverse procedures could benefit free cooling of electronic components and effective solar collection elements. (C) 2017 Elsevier Ltd. All rights reserved.
