作者机构：
[Fan, Chenzhou; Wang, Tianlin] Univ South China, Sch Civil Engn, Hengyang 421001, Peoples R China.;[Xu, Feng; Xu, F; Guo, Changqing] Univ South China, Sch Math & Phys, Hengyang 421001, Peoples R China.
通讯机构：
[Xu, F ] U;Univ South China, Sch Math & Phys, Hengyang 421001, Peoples R China.
关键词：
Foundation excitation;Gap constraint;Fluid-conveying pipe;Impact vibration
摘要：
In practical engineering, the unilateral gap constraint impact vibration in fluid-conveying pipes is a critical concern, often arising from constraint loosening or the presence of barriers around the pipe. These factors can significantly affect the service life and safety reliability of the pipes. A tension and compression anisotropy spring with rapidly increasing restoring force in compression but almost zero restoring force in tension is proposed to simulate the unilateral gap constraint, model a fluid-conveying pipe with a Pfluger column. Its reliability is also verified based on the bifurcation phase diagram comparison between the small and large stiffness conditions. Subsequently, we establish a vibration mechanics analysis model for the cantilever fluid-conveying pipe under foundation excitation to assess the effects of basic excitation frequency, fluid velocity, distributed follower force, position coordinate of unilateral gap constraint, and the viscoelastic coefficient on the impact vibration stability of the fluid-conveying pipe. Our findings reveal that when the period-doubling bifurcation sequence is interrupted by Bare-grazing bifurcation, the system directly transitions into chaotic vibration or induces a new period-doubling bifurcation sequence, followed by re-entry into chaotic vibration. These results provide valuable insights into the intricate dynamics of fluid-conveying pipes under foundation excitation, offering a deeper understanding of the impact of various parameters on the pipe's vibration.
In practical engineering, the unilateral gap constraint impact vibration in fluid-conveying pipes is a critical concern, often arising from constraint loosening or the presence of barriers around the pipe. These factors can significantly affect the service life and safety reliability of the pipes. A tension and compression anisotropy spring with rapidly increasing restoring force in compression but almost zero restoring force in tension is proposed to simulate the unilateral gap constraint, model a fluid-conveying pipe with a Pfluger column. Its reliability is also verified based on the bifurcation phase diagram comparison between the small and large stiffness conditions. Subsequently, we establish a vibration mechanics analysis model for the cantilever fluid-conveying pipe under foundation excitation to assess the effects of basic excitation frequency, fluid velocity, distributed follower force, position coordinate of unilateral gap constraint, and the viscoelastic coefficient on the impact vibration stability of the fluid-conveying pipe. Our findings reveal that when the period-doubling bifurcation sequence is interrupted by Bare-grazing bifurcation, the system directly transitions into chaotic vibration or induces a new period-doubling bifurcation sequence, followed by re-entry into chaotic vibration. These results provide valuable insights into the intricate dynamics of fluid-conveying pipes under foundation excitation, offering a deeper understanding of the impact of various parameters on the pipe's vibration.
作者机构：
[Zeng, Wengao] Natl & Local Joint Engn Res Ctr Airborne Pollutant, Hengyang 421001, Peoples R China.;[Zeng, Wengao] Univ South China, Sch Civil Engn, Hengyang 421001, Peoples R China.;[Chen, Jie] Xi An Jiao Tong Univ, Sch Environm & Chem Engn, Xian 710049, Peoples R China.;[Zhang, Ziying; Ye, Xiaoyuan; Zhang, Tuo; Zeng, Wengao; Dong, Yuchen; Zhao, Yi; Zhang, Lei; Guan, Xiangjiu] Xian Jiaotong Univ XJTU, Int Res Ctr Renewable Energy IRCRE, State Key Lab Multiphase Flow Power Engn MFPE, 28 West Xianning Rd, Xian 710049, Peoples R China.
通讯机构：
[Guan, XJ ] X;Xian Jiaotong Univ XJTU, Int Res Ctr Renewable Energy IRCRE, State Key Lab Multiphase Flow Power Engn MFPE, 28 West Xianning Rd, Xian 710049, Peoples R China.
摘要：
Rationally modulating the adsorption of reaction intermediates on the surface sites of carbon nitride-based catalysts could facilitate the photocatalytic reduction of O2 to H2O2. Herein, theoretical calculations reveal that multiple sites of heteroatoms and defects can synergistically increase local proton coverage and lower the kinetic barrier for O2 protonation, thereby promoting the production of *OOH and the subsequent generation of H2O2. As a proof of concept, carbon nitride (BPMC-Vs) with multiheteroatoms (B and P) and multidefects (N defects, -C equivalent to N) was successfully synthesized, achieving optimized solar-to-chemical conversion efficiency and selectivity of 0.33% and 95.2%, respectively. In situ spectroscopic characterization combined with theoretical calculations confirms that P atoms and -C equivalent to N groups increase proton coverage, while B atoms and N defects effectively promote the protonation of O2 to *OOH, thereby significantly enhancing the generation of H2O2. This work provides insightful guidance for carbon nitride catalysis at the atomic scale for boosting photocatalytic H2O2 production.
摘要：
Deep rock engineering (such as geothermal exploration, underground energy storage, radioactive waste storage) is often affected by external disturbances and high temperatures. Through characteristic stress identification, acoustic emission (AE) monitoring and numerical simulation, the deformation and fracture processes and degree of thermal-mechanical damaged sandstone are studied, and a simulation method considering thermal strengthening is proposed based on the two-dimensional particle flow code (PFC 2D ). The results show that: The axial peak strain of the sample shows fluctuations below 450 °C as temperature increases, and is followed by a rapid rise, whereas Poisson’s ratio, after reaching its maximum at 150 °C, gradually decreases. With the increase of damage degree, the mean values of σ cc / σ f and σ ci / σ f first decrease and then increase, while the mean values of σ cd / σ f have the opposite trend. With the increase of temperature, σ ci / σ f of sandstone increases, while σ cd / σ f remains at a certain level and fluctuates or decreases. Although the frequency band distribution and quantities of different rock samples are different, the frequency band number and the density within the frequency band have sudden changes before the samples are destroyed. The simulation results indicate that the porosity shows stress sensitivity and intergranular cracking dominates the failure process. The experimental and PFC simulation results agree well in terms of peak stress, failure mode and crack distribution, which verifies the applicability of the proposed thermal strengthening model.
Deep rock engineering (such as geothermal exploration, underground energy storage, radioactive waste storage) is often affected by external disturbances and high temperatures. Through characteristic stress identification, acoustic emission (AE) monitoring and numerical simulation, the deformation and fracture processes and degree of thermal-mechanical damaged sandstone are studied, and a simulation method considering thermal strengthening is proposed based on the two-dimensional particle flow code (PFC 2D ). The results show that: The axial peak strain of the sample shows fluctuations below 450 °C as temperature increases, and is followed by a rapid rise, whereas Poisson’s ratio, after reaching its maximum at 150 °C, gradually decreases. With the increase of damage degree, the mean values of σ cc / σ f and σ ci / σ f first decrease and then increase, while the mean values of σ cd / σ f have the opposite trend. With the increase of temperature, σ ci / σ f of sandstone increases, while σ cd / σ f remains at a certain level and fluctuates or decreases. Although the frequency band distribution and quantities of different rock samples are different, the frequency band number and the density within the frequency band have sudden changes before the samples are destroyed. The simulation results indicate that the porosity shows stress sensitivity and intergranular cracking dominates the failure process. The experimental and PFC simulation results agree well in terms of peak stress, failure mode and crack distribution, which verifies the applicability of the proposed thermal strengthening model.
摘要：
Seismic events and wave action can induce volumetric strain ( ε v ) accumulation in saturated sandy soils, leading to damage to the ground surface and structures. A quantifiable relationship exists between the generation of ε v in sandy soils under drained conditions and the development of pore water pressures under undrained conditions. In this study, the impact of relative density ( D r ), cyclic stress path, and stress level on the characteristics of volumetric strain ( ε v ) generation in saturated coral sands (SCS) was evaluated through drained tests employing various cyclic stress paths. The test findings demonstrate that the rate of ε v accumulation in SCS is notably affected by the cyclic stress path. The rise in peak volumetric strain ( ε vp ) in SCS, as a function of the number of cycles, conforms to the arctangent function model. The unit cyclic stress ratio (USR) was employed as an indicator of complex cyclic loading levels. It was determined that coefficient ( ε vp ) u is positively correlated with USR at a specific D r . At the same D r , coefficient C N 1 exhibits a positive correlation with USR, while coefficient C N 2 displays a negative correlation with USR, following a power-law relationship. Irrespective of cyclic loading conditions, ε vp rises with an increase in generalized shear strain amplitude ( γ ga ). A power function model was established to represent the relationship between ε vp and γ ga . The coefficient ζ 1 decreases as D r increases. Comparisons were drawn between ε vp and γ ga for Ottawa sand and SCS. The results indicate that, as D r of Ottawa sand increases from 30 % to 70 %, the coefficient ζ 1 decreases from 1.54 to 0.73, representing a reduction of approximately 53 %. In contrast, under identical conditions, the coefficient ζ 1 of SCS exhibits a less pronounced decrease, from 1.16 to 0.79, corresponding to a reduction of roughly 32 %. These observations suggest that variations in D r have a more substantial impact on generating ε vp in Ottawa sand compared to SCS.
Seismic events and wave action can induce volumetric strain ( ε v ) accumulation in saturated sandy soils, leading to damage to the ground surface and structures. A quantifiable relationship exists between the generation of ε v in sandy soils under drained conditions and the development of pore water pressures under undrained conditions. In this study, the impact of relative density ( D r ), cyclic stress path, and stress level on the characteristics of volumetric strain ( ε v ) generation in saturated coral sands (SCS) was evaluated through drained tests employing various cyclic stress paths. The test findings demonstrate that the rate of ε v accumulation in SCS is notably affected by the cyclic stress path. The rise in peak volumetric strain ( ε vp ) in SCS, as a function of the number of cycles, conforms to the arctangent function model. The unit cyclic stress ratio (USR) was employed as an indicator of complex cyclic loading levels. It was determined that coefficient ( ε vp ) u is positively correlated with USR at a specific D r . At the same D r , coefficient C N 1 exhibits a positive correlation with USR, while coefficient C N 2 displays a negative correlation with USR, following a power-law relationship. Irrespective of cyclic loading conditions, ε vp rises with an increase in generalized shear strain amplitude ( γ ga ). A power function model was established to represent the relationship between ε vp and γ ga . The coefficient ζ 1 decreases as D r increases. Comparisons were drawn between ε vp and γ ga for Ottawa sand and SCS. The results indicate that, as D r of Ottawa sand increases from 30 % to 70 %, the coefficient ζ 1 decreases from 1.54 to 0.73, representing a reduction of approximately 53 %. In contrast, under identical conditions, the coefficient ζ 1 of SCS exhibits a less pronounced decrease, from 1.16 to 0.79, corresponding to a reduction of roughly 32 %. These observations suggest that variations in D r have a more substantial impact on generating ε vp in Ottawa sand compared to SCS.
摘要：
This study conducts the numerical implementation and solver development of four sub-models based on the Eulerian method with OpenFOAM software, which have been used in prior numerical simulations of wind-induced snow drifting. Verification studies are conducted on the sub-models to assess their applicability and limitations in the field of snow protection engineering. Wind tunnel experiments conducted on a snow fence in Hokkaido serve as a benchmark for these evaluations. A comparative analysis indicates that the mixture multiphase flow model, incorporating two-way coupling between phases, adeptly reproduces snow distribution around snow fences. In contrast, scalar transport models, which consider one-way coupling, are suitable only for studying snowdrifts in the early stage of protection engineering with relatively low snow concentrations. Efforts to integrate phase coupling effects by introducing source terms into the turbulence model are found to be unsatisfactory. By employing a mixture multiphase flow model, this study explores the effects of six typical collector fences on wind-induced snow drifting in road cuttings. Comparative analyses are performed on several aspects, including the morphology of the cutting flow field, snow distribution, snow concentration, and the protective efficacy of the fences, with the aim to evaluate the effectiveness and applicability of snow fences. The results show that collector fences exhibit effective snow protection capabilities for road cuttings. The snow fence in Hokkaido, wind fence, and the snow fence in Wyoming demonstrate the highest protection efficiency among the analyzed collector fences, indicating superior snowdrift control effectiveness within the cuttings. The protective mechanism of collector fences is to decrease the snow transport rate within the saltation layer at the entrance of the protected area, leading to a notable decrease in snow concentration within the saltation layer in the cuttings. This study offers valuable insights and suggestions for snow protection engineering in road cuttings.
This study conducts the numerical implementation and solver development of four sub-models based on the Eulerian method with OpenFOAM software, which have been used in prior numerical simulations of wind-induced snow drifting. Verification studies are conducted on the sub-models to assess their applicability and limitations in the field of snow protection engineering. Wind tunnel experiments conducted on a snow fence in Hokkaido serve as a benchmark for these evaluations. A comparative analysis indicates that the mixture multiphase flow model, incorporating two-way coupling between phases, adeptly reproduces snow distribution around snow fences. In contrast, scalar transport models, which consider one-way coupling, are suitable only for studying snowdrifts in the early stage of protection engineering with relatively low snow concentrations. Efforts to integrate phase coupling effects by introducing source terms into the turbulence model are found to be unsatisfactory. By employing a mixture multiphase flow model, this study explores the effects of six typical collector fences on wind-induced snow drifting in road cuttings. Comparative analyses are performed on several aspects, including the morphology of the cutting flow field, snow distribution, snow concentration, and the protective efficacy of the fences, with the aim to evaluate the effectiveness and applicability of snow fences. The results show that collector fences exhibit effective snow protection capabilities for road cuttings. The snow fence in Hokkaido, wind fence, and the snow fence in Wyoming demonstrate the highest protection efficiency among the analyzed collector fences, indicating superior snowdrift control effectiveness within the cuttings. The protective mechanism of collector fences is to decrease the snow transport rate within the saltation layer at the entrance of the protected area, leading to a notable decrease in snow concentration within the saltation layer in the cuttings. This study offers valuable insights and suggestions for snow protection engineering in road cuttings.
作者机构：
[Chen, Guohao; Wang, Zhiqiao] Univ South China, Sch Civil Engn, Hengyang 421001, Peoples R China.;[Zhang, XY; Zhang, Xiaoyang] Univ South China, Sch Math & Phys, Hengyang 421001, Peoples R China.
通讯机构：
[Zhang, XY ] U;Univ South China, Sch Math & Phys, Hengyang 421001, Peoples R China.
关键词：
thermal effect;locally resonant;finite element method;tunable bandgap;defect states;waveguide
摘要：
Based on the finite element method, the modulation of the bending wave bandgap and bending waveguide of locally resonant phononic crystal (PnC) plates via a thermal environment is investigated. First, the finite element model of the PnC subjected to a thermal field is introduced; then, the modulation behavior of the bending wave bandgap of the PnC under thermal flux is illustrated; finally, the tunable waveguide of the bending waveguide of the PnC supercell is proposed to be realized by setting up a local heat source. The results show that the injected heat flux causes the PnC unit cell band structure to move toward the low-frequency region while the relative bandgap width increases. The linear defect state of the PnC supercell structure is realized by introducing a local heat source, and a new band is added to the bending wave bandgap of the original supercell. The transmission loss of the bending wave is significantly higher than that of the bending wave bandgap of the supercell in the frequency interval of the linear defect of the supercell, and the frequency response vibrational modes of the supercell structure validate the feasibility of the thermally controlled bending waveguide. This method provides a flexible and efficient control strategy for the frequency tuning of the bending wave bandgap and waveguide.
摘要：
Most existing passive earth pressure theories are not completely suitable for the calculation of unsaturated backfill in practical engineering, especially for narrow backfill cases. In view of this, this study establishes a modified analytical model for the passive earth pressure of narrow backfill behind a retaining wall under unsaturated steady-state seepage conditions, based on the log-spiral failure mechanism and the arched differential element method. The distribution, total force magnitude, and the height of the application point of passive earth pressure for narrow backfill under the rotation about the wall toe (RB) mode are calculated by the fourth order Runge-Kutta method within the framework of the generalized effective stress principle. To validate the proposed method, a comparative analysis is conducted by integrating experimental, theoretical, and OptumG2 simulation results. Moreover, the effect of main parameters on passive earth pressures is investigated through a parametric analysis. The results show that as the wall-soil interface friction angle increases gradually, the passive earth pressure distribution curve transitions from convex towards the wall back to concave towards the wall back; with the increase of aspect ratio, the passive earth pressure curve gradually shifts from curved to nearly straight; with a small air entry pressure parameter, the total passive earth pressure force increases as the air entry pressure parameter increases, while the height of the application point of total force initially decreases and then increases; the hysteresis effect reduces the total passive earth pressure force and decreases the height of the application point of the total force.
摘要：
Given the fact that retaining structures in seismically active areas are key barriers for geotechnical engineering disaster prevention and mitigation, accurately assessing their seismic stability throughout their life cycle is an extremely important and urgent task. However, the traditional stability analysis method ignores the effect of suction stress, which results in a large discrepancy between the calculated results and the engineering practice. In view of this, this study derives the work-energy balance equation that is applicable to unsaturated soils within the framework of the generalized effective stress principle, and on this basis, proposes a method for calculating the coefficient of antislip stability of unsaturated retaining walls under seismic excitations by using the energy method and incorporating the pre-existing or formation cracks into the calculation procedure. The reasonableness of the proposed method of this study was verified by comparing the calculation results with those of OptumG2 (academic version) and existing theoretical methods. Finally, a detailed parametric study was carried out to investigate the effect of main parameters on antislip stability under unsaturated steady seepage conditions.
摘要：
Thermal and mechanical damage tests and uniaxial cyclic loading–unloading tests are conducted to investigate the effect of damage degree and temperature on the mechanical behaviour of sandstone under cyclic loading. The failure characteristics are analysed via acoustic emission (AE) monitoring and particle-flow code (PFC) simulations. The results indicate that the rock mass strength first increases and then decreases. The peak strain of samples increases with temperature, thus enhancing their ductility. The residual strain decreases gradually as the number of cycles increases. Additionally, the AE signal becomes more active with increasing temperature. The peak-frequency density ranges primarily between 100 and 200 kHz and shows a distinct discontinuity during cyclic loading. Shear failure predominantly occurs during the cyclic stage, whereas tensile failure is more common during the fracturing stage. The proportion of shear cracks increases with the damage degree. The simulation results show that stress reduction is typically accompanied by a rapid increase in the number of cracks. The failure process is dominated by tensile cracks, and the crack distribution angle is approximately 90°. AE events are concentrated near the sample boundary, and the frequency distribution is approximately normal as the magnitude changes. The change trend of the b-value is consistent with that of the peak strength.
Thermal and mechanical damage tests and uniaxial cyclic loading–unloading tests are conducted to investigate the effect of damage degree and temperature on the mechanical behaviour of sandstone under cyclic loading. The failure characteristics are analysed via acoustic emission (AE) monitoring and particle-flow code (PFC) simulations. The results indicate that the rock mass strength first increases and then decreases. The peak strain of samples increases with temperature, thus enhancing their ductility. The residual strain decreases gradually as the number of cycles increases. Additionally, the AE signal becomes more active with increasing temperature. The peak-frequency density ranges primarily between 100 and 200 kHz and shows a distinct discontinuity during cyclic loading. Shear failure predominantly occurs during the cyclic stage, whereas tensile failure is more common during the fracturing stage. The proportion of shear cracks increases with the damage degree. The simulation results show that stress reduction is typically accompanied by a rapid increase in the number of cracks. The failure process is dominated by tensile cracks, and the crack distribution angle is approximately 90°. AE events are concentrated near the sample boundary, and the frequency distribution is approximately normal as the magnitude changes. The change trend of the b-value is consistent with that of the peak strength.
摘要：
PurposeDredged sediments have become a significant environmental concern in the current era. Under the circular economy concept, numerous researchers have explored reusing dredged sediments as sustainable construction materials to diminish the potential environmental risks. Therefore, conducting a systematic review of research on dredged sediment recycling as sustainable construction materials is paramount. However, there is a lack of comprehensive discussions on this topic, especially since no publications have undertaken bibliometric analysis reviews.Materials and methodsThis study conducted a bibliometric analysis of the worldwide scientific output on sediment waste recycling research to identify emergent trends and focal points. The Web of Science database was searched for relevant literature from 1995 to 2024, and numerous parameters, including annual trends, countries, institutions, authors, journals, subject categories, keywords, and topic terms. This study also analyzed the advantages and disadvantages of reused dredged sediments as sustainable construction materials in various civil engineering sub-fields. Finally, a future development perspective was proposed.Results and discussionThe review findings demonstrate dredged sediment recycling research as an interdisciplinary and intersectoral field attracting increasing national and institutional attention. Wide-ranging international collaborations facilitated the rapid increase in the volume of publications on sediment recycling research. The findings reveal a significant increase in sediment waste recycling-related publications over the past 30 years. Significantly, notable contributions were made by China and France, and these and the other top 10 most productive countries or territories contributed 95.57% of all publications. Notably, 90.03% of China's research output was published in the past eight years, highlighting its emerging dominance. Among the top 10 most productive institutions, five are located in China, with the remainder in France. Additionally, Engineering is projected to become the field with the highest publication volume post-2024, which surpassed other disciplines in annual publications and has strong development potential. The analysis further found that a noteworthy shift was also discernible in the primary keyword trends and hot topics, which changed from contamination mechanisms to technology applications. Comparison between applications shows recycling dredged sediment in road materials is the most promising approach. Finally, this study offers prospects for using solid waste-based binders to treat high moisture-dredged sediments, as low-carbon and low-cost liquefied stabilized backfill materials.ConclusionThis review provides an efficient evaluation tool for chronicling the developmental trajectory and emerging trends in the literature of sediment waste recycling. Its insights are invaluable for helping researchers capture a holistic picture of the current state of sediment waste recycling research, and provide an informative guide for future explorations and policy-making in this scientific field.
摘要：
Activated carbon was modified by compounding with three different clay minerals (HNTs, MMT, AT) at a 1% mass ratio, aiming to boost the activated carbon's radon adsorption capacity. Dynamic experimental studies were conducted to analyze their adsorption performance. HNTs/AC outperformed AC, with an 81% increase in the radon adsorption coefficient and a remarkable 274% expansion in its micropore specific surface area, indicating a positive correlation with radon adsorption capacity. The dynamic radon adsorption by HNTs/AC composites is primarily driven by physical adsorption, which involves two processes:surface adsorption and slow intra-pore diffusion, with surface adsorption being the predominant mechanism.
摘要：
Manganese monoxide (MnO), a versatile manganese oxide, is highly regarded for its potential to address heavy metal and radioactive contamination effectively. In this study, we investigated the adsorption mechanism of strontium nitrate solution on MnO crystal surfaces using molecular dynamics simulations. We examined the effects of adsorption and diffusion of ions and water molecules on three distinct MnO crystal surfaces. The results revealed significant differences in the adsorption capacities of Sr(2+), NO(3)(-), and H(2)O on the MnO crystal surfaces. The radial distribution function (RDF), the non-bond interaction energy (E(int)), and mean square displacement (MSD) data indicate that Sr(2+) exhibits the strongest interaction with the MnO (111) crystal surface. This results in a shift of Sr(2+) from outer-sphere adsorption to inner-sphere adsorption. This strong interaction is primarily due to the increase in the number and prominence of non-bridging oxygen atoms on the MnO crystal surfaces.
摘要：
Geopolymer Mortar was prepared using Alkali-Leached Lead-Zinc Slag Powder (ALSP) and metakaolin (MK), and its properties were verified through mechanical analysis, XRD, and SEM. Results showed that the optimal conditions—an alkali activator modulus (M) of 1.0, a liquid-to-binder ratio (R ltb ) of 0.50, and an binder-to-sand ratio (R bts ) of 0.30—resulted in maximum 28-day compressive and flexural strengths of 44.49 MPa and 5.54 MPa, respectively. This is due to the formation of a complex, dense silico-aluminate gel from the reactive silico-aluminates in both ALSP and MK under these conditions, which in turn led to a compact internal structure and thus increased the strength of the geopolymer mortar.
Geopolymer Mortar was prepared using Alkali-Leached Lead-Zinc Slag Powder (ALSP) and metakaolin (MK), and its properties were verified through mechanical analysis, XRD, and SEM. Results showed that the optimal conditions—an alkali activator modulus (M) of 1.0, a liquid-to-binder ratio (R ltb ) of 0.50, and an binder-to-sand ratio (R bts ) of 0.30—resulted in maximum 28-day compressive and flexural strengths of 44.49 MPa and 5.54 MPa, respectively. This is due to the formation of a complex, dense silico-aluminate gel from the reactive silico-aluminates in both ALSP and MK under these conditions, which in turn led to a compact internal structure and thus increased the strength of the geopolymer mortar.
期刊：
Journal of Radioanalytical and Nuclear Chemistry,2025年:1-15 ISSN：0236-5731
通讯作者：
Zeng, TT
作者机构：
[Xie, Shuibo; Xiong, Zhiyu; Fu, Yusong; Zeng, TT; Zeng, Taotao; Wang, Guohua; Deng, Qiqi] Univ South China, Hunan Prov Key Lab Pollut Control & Resources Reus, Hengyang 421001, Peoples R China.;[Zhang, Mingjuan] Anhui Univ Sci & Technol, Sch Earth & Environm, Huainan 232001, Peoples R China.;[Wang, Zhi] Hunan Vch Environm Technol Co Ltd, Changsha 410014, Peoples R China.
通讯机构：
[Zeng, TT ] U;Univ South China, Hunan Prov Key Lab Pollut Control & Resources Reus, Hengyang 421001, Peoples R China.
关键词：
Wastewater;Uranium;Biochar;nFe–ZnO
摘要：
This study used kelp to create biochar (BC) and then modified it with iron-doped zinc oxide (nFe-ZnO) to prepare Fe-ZnO@BC. Under optimal conditions, the adsorption capacity of Fe-ZnO@BC for U(VI) was 146.16 mg g-1. Freundlich isotherm and quasi-second order kinetic model exhibited excellent fitting to the isotherm and kinetics of uranium adsorption by Fe-ZnO@BC, respectively. The thermodynamic analysis indicated that the U(VI) adsorption process was endothermic and spontaneous. After six adsorption cycles, Fe-ZnO@BC retained its remarkable U(VI) removal performance. Advanced characterization techniques suggested that the main mechanism involved surface adsorption and reduction. These findings imply that Fe-ZnO@BC is a viable adsorbent for wastewater cleanup involving uranium contamination.
期刊：
Green Materials,2025年13(2):145-157 ISSN：2049-1220
通讯作者：
Wang, JS
作者机构：
[Wang, JS; Wang, Jingsong; Fan, An; Cheng, Chufeng; Yue, Xixiang] Univ South China, Sch Civil Engn, Hengyang 421001, Hunan, Peoples R China.;[Du, Kejie] Univ South China, Sch Chem & Chem Engn, Hengyang 421001, Hunan, Peoples R China.;[Jiang, Ming] Shanghai Urban Construct Design & Res Inst Grp Co, 3447 Dongfang Rd, Shanghai 200125, Peoples R China.
通讯机构：
[Wang, JS ] U;Univ South China, Sch Civil Engn, Hengyang 421001, Hunan, Peoples R China.
关键词：
compressive strength;durability;pore structure;porous geopolymers;surfactants;UN SDG 12: Responsible consumption and production
摘要：
The formation and regulation mechanisms of pore structures in porous geopolymers (PGs) remain qualitatively unclear, posing significant challenges to their practical application and performance optimization. In this study, PGs were synthesized utilizing metakaolin as the primary raw material and hydrogen peroxide as the foaming agent. Three distinct surfactants—sodium dodecyl sulfate, hydroxypropyl methylcellulose, and cetyltrimethylammonium bromide—were incorporated to fabricate three unique categories of PGs. The mechanical properties that were evaluated to quantify the surfactant effect were total porosity, pore distribution, and pore size variations using techniques such as image analysis and mercury intrusion porosimetry. This analysis highlighted the significant influence of slurry viscosity on the evolution and modification of pore structure. The results illustrate that viscosity acts as a crucial determinant influencing pore deformation, coalescence, ultimate foaming height, and connectivity within PGs. In addition, this study investigates the correlation between pore structure and the macroscopic properties of PGs. The synthesized PG samples display a broad spectrum of compressive strengths (10.03–17.89 MPa), dry densities (0.87–1.09 g/cm 3 ), and porosities (47.71%–57.41%). These findings provide valuable insights into the design and application of PGs.
The formation and regulation mechanisms of pore structures in porous geopolymers (PGs) remain qualitatively unclear, posing significant challenges to their practical application and performance optimization. In this study, PGs were synthesized utilizing metakaolin as the primary raw material and hydrogen peroxide as the foaming agent. Three distinct surfactants—sodium dodecyl sulfate, hydroxypropyl methylcellulose, and cetyltrimethylammonium bromide—were incorporated to fabricate three unique categories of PGs. The mechanical properties that were evaluated to quantify the surfactant effect were total porosity, pore distribution, and pore size variations using techniques such as image analysis and mercury intrusion porosimetry. This analysis highlighted the significant influence of slurry viscosity on the evolution and modification of pore structure. The results illustrate that viscosity acts as a crucial determinant influencing pore deformation, coalescence, ultimate foaming height, and connectivity within PGs. In addition, this study investigates the correlation between pore structure and the macroscopic properties of PGs. The synthesized PG samples display a broad spectrum of compressive strengths (10.03–17.89 MPa), dry densities (0.87–1.09 g/cm 3 ), and porosities (47.71%–57.41%). These findings provide valuable insights into the design and application of PGs.
通讯机构：
[Yang, Y ] U;Univ South China, Sch Civil Engn, Hengyang 421001, Hunan, Peoples R China.;Key Lab Hunan Technol Energy Conservat Prefabricat, Hengyang 421001, Hunan, Peoples R China.
关键词：
Air conditioning;Evaporative-cooling;Energy performance;Multi-mode;Hot-humid climates
摘要：
Reducing energy consumption in buildings is a crucial component in the pursuit of carbon neutrality and sustainable social development. The air-conditioning systems account for a significant portion of a building's energy consumption and therefore require special attention to their energy efficiency. These air-conditioning systems that incorporate indirect evaporative cooling (IEC) technology are a viable energy-saving strategy. However, these hybrid systems are mainly designed for hot-dry climates, and limited research has focused on the coupling advantages of condenser pre-cooling and reheating energy recovery via IEC through different operating modes. In this paper, a novel multi-mode split evaporative-cooling hybrid air-conditioning system (MVC-IEC) is proposed, which utilizes the IEC cycle to achieve condenser pre-cooling and supply air reheating. Simultaneously, it features five operating modes to adapt to the changing ambient climatic conditions. Subsequently, the energy performance of the MVC-IEC system was primarily investigated under different operating conditions. The MVC-IEC demonstrates a more pronounced energy-saving advantage under high temperature, medium-low humidity and low reheat load conditions. In addition, the MVC-IEC has acceptable application potential in both hot-humid and hot-dry cities (Changsha, Nanjing, Zhengzhou and Xi'an). The seasonal COP for the MVC-IEC is reached by 3.9 − 4.6. And compared with MVC HRC, the MVC-IEC achieves an energy-saving rate of 10.8 − 16.3 % and reduces carbon emissions by 0.42−0.80 kg/year.
Reducing energy consumption in buildings is a crucial component in the pursuit of carbon neutrality and sustainable social development. The air-conditioning systems account for a significant portion of a building's energy consumption and therefore require special attention to their energy efficiency. These air-conditioning systems that incorporate indirect evaporative cooling (IEC) technology are a viable energy-saving strategy. However, these hybrid systems are mainly designed for hot-dry climates, and limited research has focused on the coupling advantages of condenser pre-cooling and reheating energy recovery via IEC through different operating modes. In this paper, a novel multi-mode split evaporative-cooling hybrid air-conditioning system (MVC-IEC) is proposed, which utilizes the IEC cycle to achieve condenser pre-cooling and supply air reheating. Simultaneously, it features five operating modes to adapt to the changing ambient climatic conditions. Subsequently, the energy performance of the MVC-IEC system was primarily investigated under different operating conditions. The MVC-IEC demonstrates a more pronounced energy-saving advantage under high temperature, medium-low humidity and low reheat load conditions. In addition, the MVC-IEC has acceptable application potential in both hot-humid and hot-dry cities (Changsha, Nanjing, Zhengzhou and Xi'an). The seasonal COP for the MVC-IEC is reached by 3.9 − 4.6. And compared with MVC HRC, the MVC-IEC achieves an energy-saving rate of 10.8 − 16.3 % and reduces carbon emissions by 0.42−0.80 kg/year.
摘要：
Microplastics (MPs) are emerging pollutants that play an important role in the spread of highly toxic heavy metals. Although the pH has been shown to exert a substantial impact on the adsorption capacity of MPs towards heavy metals, the intricate mechanisms underlying how pH functions in the adsorption of radioactive heavy metals by MPs remain largely elusive. Here, we combined batch experiments and density functional theory calculations to investigate the adsorption behavior of radioactive uranium (U) on virgin and aged (modified with –OH or –COOH groups) polystyrene (PS) MPs at pH ranging from 3.0 to 9.0. The kinetic data showed that the U adsorption capacities of virgin PS and PS–COOH MPs were in the order of pH 7.0 > pH 8.2 > pH 4.5 > pH 9.0 > pH 3.0, whereas U adsorption on PS–OH MPs displayed a trend of pH 8.2 > pH 9.0 > pH 7.0 > pH 4.5 > pH 3.0. These outcomes were confirmed by X-ray photoelectron spectroscopy and binding energy analysis. Compared to virgin PS MPs, the higher U adsorption on aged MPs might be attributed to electrostatic attraction between deprotonated –COOH and (UO 2 ) 3 (OH) 5 + at pH 7.0 for the PS–COOH MPs and between –OH and (UO 2 ) 4 (OH) 7 + or (UO 2 ) 3 (OH) 7 − at pH 8.2 for the PS–OH MPs. Intermolecular interaction calculations demonstrated that hydrogen bonding interaction driven by electrostatic and polarization energies contributed to the improved U adsorption amount of the PS–COOH MPs at pH 7.0 and the PS–OH MPs at pH 8.2. Our understanding of the mechanisms by which pH regulates U adsorption by MPs is critical for evaluating the fate and hazard of co-existing radionuclides and MPs in aquatic environments.
Microplastics (MPs) are emerging pollutants that play an important role in the spread of highly toxic heavy metals. Although the pH has been shown to exert a substantial impact on the adsorption capacity of MPs towards heavy metals, the intricate mechanisms underlying how pH functions in the adsorption of radioactive heavy metals by MPs remain largely elusive. Here, we combined batch experiments and density functional theory calculations to investigate the adsorption behavior of radioactive uranium (U) on virgin and aged (modified with –OH or –COOH groups) polystyrene (PS) MPs at pH ranging from 3.0 to 9.0. The kinetic data showed that the U adsorption capacities of virgin PS and PS–COOH MPs were in the order of pH 7.0 > pH 8.2 > pH 4.5 > pH 9.0 > pH 3.0, whereas U adsorption on PS–OH MPs displayed a trend of pH 8.2 > pH 9.0 > pH 7.0 > pH 4.5 > pH 3.0. These outcomes were confirmed by X-ray photoelectron spectroscopy and binding energy analysis. Compared to virgin PS MPs, the higher U adsorption on aged MPs might be attributed to electrostatic attraction between deprotonated –COOH and (UO 2 ) 3 (OH) 5 + at pH 7.0 for the PS–COOH MPs and between –OH and (UO 2 ) 4 (OH) 7 + or (UO 2 ) 3 (OH) 7 − at pH 8.2 for the PS–OH MPs. Intermolecular interaction calculations demonstrated that hydrogen bonding interaction driven by electrostatic and polarization energies contributed to the improved U adsorption amount of the PS–COOH MPs at pH 7.0 and the PS–OH MPs at pH 8.2. Our understanding of the mechanisms by which pH regulates U adsorption by MPs is critical for evaluating the fate and hazard of co-existing radionuclides and MPs in aquatic environments.
作者机构：
[Zou, Pinyu; Liu, Yizhi; Li, Guoyu; Chen, Zhenfu; Wu, Qiongfang; Wu, QF; Tao, Qiuwang; Wu, Dan] Univ South China, Sch Civil Engn, Hengyang 421001, Peoples R China.;[Zou, Pinyu; Liu, Yizhi; Li, Guoyu; Chen, Zhenfu; Wu, Qiongfang; Wu, QF; Tao, Qiuwang; Wu, Dan] Univ South China, China Nucl Ind Key Lab High Performance Concrete, Hengyang 421001, Peoples R China.;[Zou, Pinyu; Liu, Yizhi; Li, Guoyu; Chen, Zhenfu; Wu, Qiongfang; Wu, QF; Tao, Qiuwang; Wu, Dan] Univ South China, Hunan Prov Key Lab High Performance Special Concre, Hengyang 421001, Peoples R China.
通讯机构：
[Wu, QF ] U;Univ South China, Sch Civil Engn, Hengyang 421001, Peoples R China.;Univ South China, China Nucl Ind Key Lab High Performance Concrete, Hengyang 421001, Peoples R China.;Univ South China, Hunan Prov Key Lab High Performance Special Concre, Hengyang 421001, Peoples R China.
摘要：
Radiation-shielding concrete, widely used in protective structures because of its effective shielding properties, employs magnetite aggregates to achieve higher compressive strength than conventional concrete. However, prolonged exposure to high temperatures leads to mechanical degradation. This study investigates the thermal evolution of magnetite concrete under microwave heating across varying temperatures (38-800 degrees C). A microwave oven was utilized for heating, and COMSOL Multiphysics was employed to establish an electromagnetic-thermal-mechanical coupled model, analyzing surface characteristics, temperature distribution, stress-strain behavior, and residual compressive strength. Results indicate that internal temperatures exceed surface temperatures during microwave heating, with a maximum temperature difference surpassing 150 degrees C at 800 degrees C. Compressive stresses predominantly arise in the mortar, while tensile stresses concentrate in aggregates and the interface transition zone, causing stress concentration. Mortar exhibits greater deformation than aggregates as temperatures increase. Simulated and experimental residual compressive strengths show strong agreement, with a maximum deviation of 7.58%. The most rapid mechanical deterioration occurs at 450-600 degrees C, marked by a residual compressive strength decline of 0.07 MPa/degrees C and the formation of penetrating cracks.
作者机构：
[Lin, QB; Deng, Huijuan; Lin, Qibin] Univ South China, Sch Resource Environm & Safety Engn, Hengyang 421001, Peoples R China.;[Wang, Dongxing; Long, Hui; Deng, Huijuan; Wang, DX] Univ South China, Sch Civil Engn, Hengyang 421001, Peoples R China.;[Cao, Rihong; Deng, Huijuan; Cao, Ping] Cent South Univ, Sch Resources & Safety Engn, Changsha 410083, Peoples R China.;[Wang, Dongxing; Wang, DX] Wuhan Univ, Sch Civil Engn, Wuhan 430072, Peoples R China.
通讯机构：
[Lin, QB ; Wang, DX ] U;Univ South China, Sch Resource Environm & Safety Engn, Hengyang 421001, Peoples R China.;Univ South China, Sch Civil Engn, Hengyang 421001, Peoples R China.;Wuhan Univ, Sch Civil Engn, Wuhan 430072, Peoples R China.
关键词：
Creep characteristics;Cross-river tunnel;Long-term stability;Muddy siltstone;Multi field coupling simulation;Nonlinear damage creep model
摘要：
Muddy siltstone combines the characteristics of both sandstone and mudstone, and is prone to instability over time. To study the long-term stability of tunnel engineering in this stratum, this article taking the cross-river metro tunnel section as the engineering background, and conducting research on the stress and deformation of the tunnel surrounding rock. Firstly, uniaxial compression creep tests were conducted on muddy siltstone to study the creep deformation law under graded loading. Secondly, a nonlinear damage creep model was established based on the Burgers model, and the experimental results were fitted. Finally, the proposed creep model was applied to the COMSOL Multiphysics numerical simulation software to perform multi field coupled calculations on the operation of metro tunnels. The research results show that: (1) Muddy siltstone undergoes the entire process of decaying creep, steady creep and accelerated creep. (2) The proposed nonlinear damage creep model can accurately describe the creep characteristics of muddy siltstone, especially in the accelerated creep stage. (3) Applying nonlinear damage creep model to tunnel numerical simulation calculation, it was found that the most obvious part of tunnel rock creep deformation is the tunnel arch crown. By comparing with on-site monitoring data, indicated that the established creep-fluid-structure coupling tunnel model can be used to predict surrounding rock deformation. The creep-fluid-structure coupling tunnel model proposed in this study provides a new perspective for the design and safety assessment of cross river tunnels in soft rock formations, which helps to achieve more accurate long-term stability prediction.
