摘要：
Effects of steam explosion (SE) treatment (0.3-1.0 MPa, 30-90s) on the physicochemical and functional properties of dietary fiber (DF) extracted from tea residue were investigated. Results showed that SE led to the formation of porous and less compact microstructures of tea residues. Compared with the control sample (12.41 g/100 g), the content of soluble dietary fiber (SDF) was markedly increased by SE, reaching the maximum of 23.03 g/100 g when steam explored at 0.5 MPa for 90 s, due to the degradation of insoluble dietary fiber (IDF). The physicochemical and functional properties were significantly influenced by SE treatments. IDF exhibited decreased water holding capacity (WHC), swelling capacity (SC), oil holding capacity (OHC) after SE, whereas the physicochemical properties of SDF from SE-treated tea residues (0.3 MPa, 90s) were greatly improved. The glucose absorption capacity (GAC), cholesterol adsorption capacity (CAC), and nitrite ion adsorption capacity (NIAC) of both IDF and SDF showed trends of first increasing and then decreasing, indicating that excessive SE treatment resulted in poor properties of DF. These findings are of great value for the high-value utilization of agricultural by-product and development of functional foods.
作者机构：
[Deng, Zi-wei; Zhu, En-wen; Cao, Jun] Changsha Univ Sci & Technol, Dept Math & Stat, Changsha 410114, Peoples R China.;[Zhang, Han-jun] Xiangtan Univ, Sch Math & Computat Sci, Xiangtan 411105, Peoples R China.;[Liu, Xiao-hui] Jiangxi Univ Finance & Econ, Sch Stat & Data Sci, Nanchang 330013, Peoples R China.;[Liu, Xiao-hui] Jiangxi Univ Finance & Econ, Key Lab Data Sci Finance & Econ, Nanchang 330013, Peoples R China.
通讯机构：
[Zhu, EW ] C;Changsha Univ Sci & Technol, Dept Math & Stat, Changsha 410114, Peoples R China.
关键词：
random coefficient autoregressive model;time-functional variance;conditional least squares;semiparametric least squares
摘要：
This paper considers the random coefficient autoregressive model with time-functional variance noises, hereafter the RCA-TFV model. We first establish the consistency and asymptotic normality of the conditional least squares estimator for the constant coefficient. The semiparametric least squares estimator for the variance of the random coefficient and the nonparametric estimator for the variance function are constructed, and their asymptotic results are reported. A simulation study is presented along with an analysis of real data to assess the performance of our method in finite samples.
作者机构：
[Tang, Yu; Huang, Zhi-Yong; Wang, Wei; Huang, Ya-Lan; Liu, Qi; Zhang, Bing-Hao; Ren, Jin-Can; Wang, Xing-Yu; Chen, Bo-Wen] City Univ Hong Kong, Dept Phys, Hong Kong 999077, Peoples R China.;[Lan, Si; Liu, Qi; He, Zhang-Long; He, Hao] City Univ Hong Kong, Shenzhen Res Inst, Shenzhen 518057, Peoples R China.;[He, Hao; He, Zhang-Long] Changsha Univ Sci & Technol, Coll Mat Sci & Engn, Changsha 410114, Peoples R China.
通讯机构：
[Liu, Q ; Liu, Q; He, H ] C;City Univ Hong Kong, Dept Phys, Hong Kong 999077, Peoples R China.;City Univ Hong Kong, Shenzhen Res Inst, Shenzhen 518057, Peoples R China.
关键词：
Lithium-ion batteries;Ni fraction;Extreme fast charging;Structural evolution
摘要：
Lithium-ion batteries (LIBs) with extreme fast charging (XFC) capability are considered an effective way to alleviate range anxiety for electric vehicle (EV) buyers. Owing to the high ionic and electronic conductivity of LiNixCoyMnzO2 (x + y + z = 1, NCM) cathodes, the inevitable Li plating of graphite in NCM | graphite cell is usually identified as a key bottleneck for XFC LIBs. However, the capacity decay mechanism of cathode materials under XFC has not been fully investigated. In this work, three typical NCM cathode materials with different Ni fractions were chosen and their electrochemical performances under XFC associated with structural evolution were investigated. A faster capacity decay of NCMs under XFC conditions is observed, especially for Ni-rich NCMs. In-situ X-ray diffraction (XRD) reveals that the multiple c-axis parameters appear at the high-voltage regions in Ni-rich NCMs, which is probably triggered by the larger obstruction of Li (de)intercalation. Particularly, NCMs with moderate Ni fraction also present a similar trend under XFC conditions. This phenomenon is more detrimental to the structural and morphological stability, resulting in a faster capacity decay than that under low current charging. This work provides new insight into the degradation mechanism of NCMs under XFC conditions, which can promote the development of NCM cathode materials with XFC capability.
摘要：
Internal erosion refers to the movement of fine particles within soil framework due to subsurface water seepage. Existing criteria for assessing internal erosion usually are based on static loading, and the effect of cyclic load is not considered. Additionally, there are limited studies to examine the particle -size distribution and origin of eroded fine particles. This study presents an experimental investigation that examines the impact of cyclic loading on internal stability through a series of seepage tests. The composition and origin of lost particles are quantitatively studied using particle staining and image recognition techniques. With increasing hydraulic gradient, particle erosion progresses from top layer to bottom layer, with a gradual increase in the maximum particle size of eroded particles from each layer. After significant loss of particles, the specimens reach a state of transient equilibrium, resulting in a gradual slowdown of both particle loss rate and average flow velocity. The results indicate that cyclic loading promotes massive particle loss and causes erosion failure of specimens that are considered stable according to existing criteria. The reason is that under cyclic loading, local hydraulic gradients is oscillating, and a larger than average hydraulic gradient may occur, which is responsible for the internal instability. The analysis suggests that existing criteria can provide a reasonable assessment of the relative stabilities of specimens under static loads but fail to capture the stabilities under cyclic loading conditions.
摘要：
The use of Glass Fiber Reinforced Plastics (GFRP) bars in coastal concrete structures can effectively prevent steel reinforcement corrosion, but research on the evolution of their performance in seawater and alkaline concrete environments is lacking. The analysis of the degradation process and mechanism of GFRP is thoroughly conducted in this paper through various characterization methods of morphology, mechanics, and material tests. Furthermore, the degradation law of GFRP in various erosion environments is assessed via multi-dimensional indexes. The findings indicate that the erosion of GFRP in an alkaline environment result in the debonding of resin and fiber, thereby causing the formation of cracks. As the erosion age and OH- concentration increase, the size of the cracks expands. Since the dissolution rate of the resin composed as part of GFRP is very low, the salt in seawater has minimal impact on the degradation of GFRP. Vickers hardness of the fiber with age decreased linearly and remained unchanged. Meanwhile, Vickers hardness of the resin with age can be divided into three stages: linear decline stage, linear rise stage, and stabilization stage. Under the erosive conditions, a hydrolysis reaction of the resin occurs resulting in the shortening of its molecular chain. The increase of alkalinity in GFRP attributed to the rising of O-H to C-H chemical bond ratio in the environment leads to the debonding of the fiber and resin. As a result, the resin flows out, and the hydrolysis rate slowly increased first, then accelerated, and finally stabilized.
摘要：
The challenge for practical application of frame structural optimization had previously been investigated by many works, while the mechanical performance requirements such as the displacement, stress, and stability requirements, were often considered separately within optimization, hindering their practical applications. For this purpose, an integrated topology and size optimization strategy of frame structures, in which the structural weight is taken as the objective with the constraints regarding the displacement, stress, as well as stability, is presented in this paper. Different from former researches, each beam is assigned with a topology variable representing the presence of the beam and a size variable correspond to the cross-sectional geometric properties. To achieve an optimized design with standard members, by cooperating the ordered multi-material SIMP (solid isotropic material with penalization) interpolation with the normalized Heaviside functions, the continuous size design variables are projected onto the discrete standard sizes conformed to standard library. Moreover, the comprehensive measure, including the stress relaxation, the pseudobuckling mode treatment scheme, the aggregation constraint, and varying constraint limit schemes, is employed to deal with the multiple constraints in the optimization model. Then, the sensitivities of the objective and constraint functions with respect to topology and size design variables are derived, respectively, and the proposed integrated optimization problem is solved by a nested optimization algorithm. Finally, several numerical examples are presented to demonstrate the feasibility of the proposed approach.
摘要：
Recycled rubber materials represent an environmentally sustainable option as asphalt modifiers. This research delves into the modification effects of Styrene Butadiene Rubber (SBR) asphalt at varying SBR content levels, employing a blend of molecular simulation techniques and laboratory experimentation. A comprehensive molecular model of SBR-modified asphalt is established, and molecular dynamics simulations are executed to scrutinize the thermodynamic attributes, dipole moments, mechanical characteristics, and adhesion properties inherent to SBR asphalt. The outcomes of this inquiry reveal that SBR exhibits notable compatibility with a majority of asphalt molecules, as evidenced by their dipole moments. The introduction of SBR into the asphalt matrix results in the adsorption of a substantial quantity of lightweight components, fostering the formation of a cross-linked network that bolsters the asphalt's resilience against external deformation forces. Furthermore, in terms of adhesion work, asphalt demonstrates heightened affinity with alkaline aggregates, and SBR serves to augment van der Waals interactions at the asphalt-aggregate interface, thereby amplifying interfacial bonding strength. However, when the content of SBR reaches 30%, some SBR molecules will be aggregated in the asphalt, which will lead to phase separation and affect the stability of the colloid. Therefore, it is recommended that the content of SBR should be limited to about 20% in practical engineering applications. In this work, the modification mechanism of SBR was analyzed at the molecular scale and verified experimentally, and the results provide a theoretical basis for the rational use of recycled SBR powder in asphalt applications.
通讯机构：
[Han, Y ] C;Changsha Univ Sci & Technol, Sch Civil Engn, 960 2nd Sect Wanjiali South Rd, Changsha 410114, Hunan, Peoples R China.
关键词：
3D nonlinear flutter analysis;Time-dependent nonlinear self-excited force model;Geometric nonlinearity;Long-span bridge;Full-mode nonlinear flutter analysis
摘要：
The present study aims to investigate the influence of geometric nonlinearity on post-flutter responses by developing a full-mode coupled nonlinear flutter analysis method (frequency-domain method) and a time-dependent nonlinear analysis scheme (time-domain method). This approach integrates the three-dimensional (3D) nonlinear finite element model and nonlinear self-excited force described by amplitude-dependent rational functions (RFs). By comparing post-flutter responses obtained from frequency-domain and time-domain methods, not only the influence of geometric nonlinearity on post-flutter responses is quantified, but also the underlying physical mechanism is revealed. The results show that the geometric nonlinear effect will become more significant with the increase of the amplitude and thus will induce a super-harmonic resonance behavior. The behavior is mainly characterized by the higher harmonic frequencies vibrations with higher-order mode shapes involved in the vertical and torsional displacement responses. Meanwhile, the larger the vibration amplitude, the more significant the super-harmonic resonance behavior. Besides, the geometric nonlinear effect will also cause a significant uplifting of the bridge deck in the vertical direction during 3D nonlinear flutter process. The main physical mechanism for the reduction in the amplitude of post-flutter response (dominated by the vibration with fundamental harmonic frequency) after considering the geometric nonlinear behavior is that the vibrations with higher harmonic frequencies play a role of absorbing energy and reducing vibration (similar to tuned mass damper effect) for the vibration with fundamental harmonic frequency. For the long-span suspension bridge with a main span of 1650 m studied in this study, the geometric nonlinear effect may need to be considered when the torsional amplitude at mid-span is only greater than 1.5 degrees.
摘要：
The accuracy of the data is crucial to the real-time prediction of autonomous driving. Due to factors such as weather and the accuracy of data collection equipment, there frequently exist noises in the data collected in real time. Therefore, it is necessary to perform analysis on acquired kinematic features related to driving behavior prediction. This study proposes a novel deep learning framework to explore influences of data noises on lane-changing intention prediction. Kinematic features including the longitudinal distance difference, velocity and acceleration, lateral velocity and acceleration of the vehicles are first extracted from the HighD. Then, the anti-interference performance of deep learning models such as transformer is tested. By comparing dataset with and without noises, we develop an evaluation method containing several predictive performance metrics and statistical measures. The results show that: (1) the longitudinal acceleration of the vehicle has the lowest sensitivity to noise, and the lateral velocity has the weakest anti-interference and the highest sensitivity. (2) The Bi-LSTM model with multi-head attention mechanism performs well in reducing the sensitivity of longitudinal acceleration and prediction accuracy. This study provides valuable information for data acquisition and model selection of real-time driving intention prediction.
期刊：
Developments in the Built Environment,2024年17:100329 ISSN：2666-1659
通讯作者：
Liu, X
作者机构：
[Peng, Jun Long; Liu, Xiao] Changsha Univ Sci & Technol, Chang Sha City, Peoples R China.
通讯机构：
[Liu, X ] C;Changsha Univ Sci & Technol, Chang Sha City, Peoples R China.
关键词：
Emergency construction project management;Resource scheduling;Multi-space;Analysis of influencing factors;Fuzzy-DEMATEL-ISM
摘要：
In response to the growing frequency of international emergencies, the demand for resources dedicated to emergency construction projects has significantly increased due to their pivotal role in disaster containment and mitigation. This article examines the factors influencing the allocation of multi-spatial resources for such projects, conducting both causal and hierarchical analyses to unveil their interdependent mechanisms. It addresses a theoretical research gap in resource scheduling through bibliometric analysis. The study utilizes the Fuzzy Decision-Making Laboratory Analysis (Fuzzy-DEMATEL) method to identify key factors within the system and constructs a hierarchical model using Interpretive Structural Modeling (ISM) to systematically analyze the factors affecting multi-space resource allocation in emergency construction projects. The results reveal 43 influencing factors, categorized into 11 levels, with the political and social environment, resource scheduling determination, and design changes standing out as the primary influencers. Additionally, the article proposes a three-tiered strategy based on experimental results to offer theoretical insights for multi-spatial resource scheduling in emergency construction projects.
作者机构：
[Jiao, Zengkai; Deng, Zejun; Gang, Yuan; Zhou, Kechao; Deng, ZJ; Wei, Qiuping; Wang, Xiang; Ma, Li; Wei, QP; Li, Haichao] Cent South Univ, Sch Mat Sci & Engn, State Key Lab Powder Met, Changsha 410083, Peoples R China.;[Zhang, Long] Changsha Univ Sci & Technol, Sch Mat Sci & Engn, Changsha 410083, Peoples R China.;[Wang, Yijia] Cent South Univ, Adv Res Ctr, Changsha 410083, Peoples R China.
通讯机构：
[Zhou, KC; Deng, ZJ; Wei, QP ] C;Cent South Univ, Sch Mat Sci & Engn, State Key Lab Powder Met, Changsha 410083, Peoples R China.
关键词：
Cu-matrix composite;Diamond skeleton;Gas pressure infiltration;High-efficiency heat transfer
摘要：
The weak interfacial bonding strength between diamond and copper intrinsically restricts the enhancement of the thermal conductivity of diamond particles/copper composites (abbreviated as DP/Cu). This work first proposed the diamond skeleton (DS) as the reinforcement element rather than dispersed diamond particles. The tungsten (W) transition layer (c.a. similar to 300 nm thick) having adequate thermal expansion coefficient was sputtered onto the surface of DS via vacuum evaporation technology, aiming to improve the wettability between diamond and copper and accordingly increase the thermal conductivity of DS/copper composites extruded by gas pressure infiltration technique. The experimental results show that the coated W layer can effectively improve the wettability of the diamond surface and reduce the wettability angle from 108.6 degrees to 13.2 degrees. Raman and XRD spectra show that the W layer can, to a great extent, prevent the graphitization of the diamond surface. SEM and EDX evidence a continuous heat transfer path of DS inside the composites. The thermal conductivity of the DS/Cu composite with low diamond loading of 18.4 vol% reaches 575 W/mK, 43.3% higher than that of pure Cu. Finite element simulations show that DS exhibits excellent heat transfer characteristics, agreeing well with the thermal conductivity simulation results.
摘要：
The Beyond 5th Generation/6th Generation (B5G/6G) wireless communication technology, characterized by ultra-low latency and ultra -multiple connections, and B5G/6G edge networks provide a new approach to solve delay-sensitive and computation-intensive vehicle applications in Intelligent Transportation Systems (ITS). However, due to the high mobility of vehicles, it becomes challenging to provide mobility-enabled resource management and delivery tasks from multiple vehicle users to Base Station (BS) in B5G/6G edge networks. Therefore, we investigate a multi-vehicle user and multi-BS collaborative offloading system in B5G/6G edge networks, and propose a joint optimization scheme for collaborative offloading, unequal task splitting and CPU resource allocation. In this scheme, tasks from vehicle users can be partially offloaded to associated BS, and can be further split and offloaded to adjacent BS with multi -hop network technology, thereby minimizing the weighted sum of latency and energy consumption. Thus, a Mixed Integer Nonlinear Optimization Problem (MINLP) is constructed. To address this issue, we propose a two-level alternating iterative framework based on a two-layer co-offloading architecture and Sequential Quadratic Programming algorithm (SQP). In the upper level, we introduce a multi-BS collaboration algorithm at the edge layer and develop a collaborative offloading strategy between vehicle users and the edge layer, utilizing Game Theory (GT). In the lower level, based on the SQP algorithm, the optimal task splitting ratio and the optimal CPU frequency allocation strategy for each vehicle user task are solved. Simulation results demonstrate that the proposed algorithm not only effectively reduces system costs, but also excels in reducing the system latency or energy consumption when considered separately.
期刊：
Scripta Materialia,2024年240:115850 ISSN：1359-6462
通讯作者：
Chen, CS;Song, M
作者机构：
[Chen, Chuansheng; Chen, Jiaxuan] Changsha Univ Sci & Technol, Sch Mat Sci & Engn, Changsha 410114, Hunan, Peoples R China.;[Li, Dan; Liu, Chaoqiang; Song, Miao; Zhang, Xiaoyong; Chen, Jiaxuan; Zhou, Kechao; Niu, Pengda] Cent South Univ, Powder Met Res Inst, Changsha 410083, Hunan, Peoples R China.;[Ma, Xiaolong] City Univ Hong Kong, Dept Mat Sci & Engn, Kowloon, Hong Kong 999077, Peoples R China.;[Zhao, Yunqiang] Guangdong Acad Sci, China Ukraine Inst Welding, Guangdong Prov Key Lab Adv Welding Technol, Guangzhou 510650, Peoples R China.
通讯机构：
[Song, M ; Chen, CS ] C;Changsha Univ Sci & Technol, Sch Mat Sci & Engn, Changsha 410114, Hunan, Peoples R China.;Cent South Univ, Powder Met Res Inst, Changsha 410083, Hunan, Peoples R China.
关键词：
Crack;Titanium alloy;Phase transformation;Transmission electron microscopy (TEM)
摘要：
Designing dual-phase titanium (Ti) alloys with exceptional damage tolerance holds profound scientific and engineering significance. A comprehensive understanding of microstructure evolution around cracks under diverse loading conditions is pivotal in advancing this pursuit. Here, tensile and fatigue cracks were formed quasi in-situ in a dual-phase Ti alloy, and the microstructures around the cracks were systematically analyzed and compared using TEM. Our findings reveal that the deflection of tensile cracks is primarily influenced by the hindrance posed by the straight alpha/beta heterointerfaces and is further facilitated by the beta-to-alpha" martensite transformation within the beta matrix. In contrast, fatigue cracks exhibit deflection within the beta matrix, located far from the alpha lamellae. Furthermore, the presence of spindle-shaped short alpha lamellae holds promise for enhancing resistance to fatigue crack nucleation. These results contribute to fundamental comprehension of the crack nucleation and propagation in dual-phase Ti alloys and provide valuable guidance for materials design.
摘要：
Currently, the research on the mechanical properties of rubber-modified asphalt mixtures primarily focuses on small-scale investigations, with insufficient exploration into the performance of rubber particles and their relationship with the mechanism and properties of modified asphalt mixtures. Limited studies have been conducted on large-scale rubber modification in asphalt mixtures. Due to frequent use and subsequent high damage to existing asphalt pavements, incorporating rubber-modified asphalt mixtures can partially alleviate premature deterioration. Dynamic modulus tests were conducted using MTS equipment under unconfined conditions to investigate the viscoelastic behavior of rubber-modified asphalt mixtures with high rubber content and elucidate the influence of rubber particle content on the elastic deformation and recovery capability. The dynamic mechanical properties of the mixtures were determined at different loading rates, temperatures, and types of rubber-modified asphalt mixtures. Based on the test data, variations in the dynamic modulus, phase angle, storage modulus, loss modulus, loss factor, and rut factor of the rubber-modified asphalt mixtures under different loading frequencies, temperatures, and types were analyzed. The results demonstrate the pronounced viscoelastic behavior of rubber-modified asphalt mixtures. The mixtures exhibit enhanced elasticity at low temperatures and high frequencies, while their viscosity becomes more prominent at high temperatures and low frequencies. Under constant test temperatures, an increase in load loading frequency leads to a higher dynamic modulus; conversely, a decrease in dynamic modulus is observed with increasing test temperatures. The dynamic modulus of ARHM-25 at a frequency of 10 Hz is found to be 12.99 times higher at 15 degrees C compared to that at 60 degrees C, while at 30 degrees C, the dynamic modulus at 25 Hz is observed to be 2.72 times greater than that at 0.1 Hz. Furthermore, the rutting resistance factors of the asphalt mixtures increase with loading frequency but decrease with temperature. The rutting factor for ARHM-13 at a frequency of 10 Hz is found to be 22.98 times higher at 15 degrees C compared to that at 60 degrees C, while at a temperature of 30 degrees C, the rutting factor for this material is observed to be 3.09 times greater at a frequency of 25 Hz than at 0.1 Hz. These findings suggest that rutting is most likely when vehicles drive at low speeds in hot weather conditions.
摘要：
A feasible route to fabricate phosphorus-doped carbon nanofibers (P-CNFs) with an inter-connected structure has been demonstrated through electrospinning, stabilization, and subsequent phosphoric acid impregnation and carbonization processes using polyacrylonitrile and lignin as carbon sources. The results illustrate that the phosphoric acid induced cross-linking could be beneficial to acquire the closed-pore structure and the heteroatom-doped surface chemistry of nanofibers. As a result, the P-CNFs exhibit higher interlayer spacing of graphite and lower BET specific surface area compared to the pristine CNFs. The P-CNFs as an anode material for sodium-ion batteries (SIBs) present a high reversible capacity 278 mA h g-1 at 0.2 A g-1 and a superior initial Coulomb efficiency (ICE) of 78.86 %. Moreover, the reversible capacity of P-CNFs can be stably maintained near the initial capacity after 5000 cycles at 1 A g-1, showing exceptional structural stability and cycling durability. Meanwhile, the sodium storage mechanism of P-CNFs was investigated using in-situ Raman and ex-situ XRD analysis to understand the exceptional structural stability and Na+ adsorption capacity of P-CNFs. This work provides valuable insights for the design of carbon nanofibers with an inter-connected structure as anode materials for SIBs, exhibiting outstanding electrochemical properties.
摘要：
This study addressed the complex problems of selecting a constitutive model to objectively characterize asphalt mixtures and accurately determine their viscoelastic properties, which are influenced by numerous variables. Inaccuracies in model or parameter determination can result in significant discrepancies between the calculated and measured results of the pavement’s structural dynamic response. To address this, the research utilized the physical engineering principles of asphalt pavement structure to perform dynamic modulus tests on three types of high-content rubberized asphalt mixtures (HCRAM) within the surface layer. The research aimed to investigate the influencing factors of the dynamic modulus and establish a comprehensive master curve. This study also critically evaluated the capabilities of three viscoelastic models—the three-parameter solid model, the classical Maxwell model, and the classical Kelvin model—in depicting the dynamic modulus of HCRAM. The findings indicated a negative correlation between the dynamic modulus of the asphalt mixture and temperature, while a positive association exists between the loading frequency and temperature, with the impact of the loading frequency diminishing as the temperature increases. Notably, the three-parameter solid model was identified as the most accurate in describing the viscoelastic properties of the HCRAM. Furthermore, the dynamic response calculations revealed that most indexes in the surface layer’s dynamic response are highest when evaluated using the three-parameter viscoelastic model, underscoring its potential to enhance the pavement performance’s predictive accuracy. This research provides valuable insights into optimizing the material performance and guiding the pavement design and maintenance strategies.
期刊：
Construction and Building Materials,2024年411:134518 ISSN：0950-0618
通讯作者：
Peng, H;Zhu, H
作者机构：
[Peng, Hui; Zhang, Bai] Changsha Univ Sci & Technol, Natl Key Lab Green & Long Life Rd Engn Extreme Env, Changsha 410114, Peoples R China.;[Zhang, Bai; Zhu, Hong; Zhu, H] Southeast Univ, Sch Civil Engn, Nanjing 211189, Peoples R China.;[Xu, Feng] China Construct Eighth Engn Div CORP LTD, Shanghai 200112, Peoples R China.
通讯机构：
[Peng, H ] C;[Zhu, H ] S;Changsha Univ Sci & Technol, Natl Key Lab Green & Long Life Rd Engn Extreme Env, Changsha 410114, Peoples R China.;Southeast Univ, Sch Civil Engn, Nanjing 211189, Peoples R China.
关键词：
Bond performance;Degradation mechanisms;Geopolymers;Coral aggregate concrete;BFRP bars;Seawater drying -wetting cycles
摘要：
The utilization of durable geopolymers instead of ordinary Portland cement (OPC) for developing geopolymerbased seawater coral aggregated concrete (GPCAC) in coastal constructions contributed to the improved marine resource utilization and the reduced CO2 emissions and construction costs. Thus, this study investigated the durability of GPCAC and its bond performance with basalt fiber-reinforced polymer (BFRP) bars under seawater drying-wetting cycles, and cement-based CAC was also selected as a comparison. The bond characteristics and degradation mechanisms of slag-based GPCAC and cement-based CAC specimens were compared and analyzed under different seawater exposure condition. Experimental results revealed that both GPCAC and CAC specimens demonstrated various degrees of degradation in bond strength, whereas their initial bond stiffness exhibited a slight increase owing to the hygroscopic expansion of the superficial epoxy resin of BFRP bars, after being exposed to seawater environmental attacks. This degraded bond strength was primarily attributed to the existence of corrosive ions (i.e., SO42-, Mg2+, and Cl-) in seawater and free OH- in concrete capillary pores. These compounds chemically reacted with the slurry hydration products and the resin matrix, which resulted in the decreasing of concrete strength, the hydrolysis of the resin matrix, the deterioration of fibers, and fiber-resin interface debonding. Compared with CAC specimens, GPCAC specimens achieved better resistance to seawater attacks owing to the more dense and stable reaction products formed by geopolymers compared to OPC. After being subjected to 60 degrees C seawater attacks for 12 months, approximately 4.9% and 12.0% reductions in the bond strength were reported for GPCAC and CAC specimens, respectively. Finally, the residual bond strength of both GPCAC and CAC specimens was predicted after being served in seawater erosion conditions for 50 years.
摘要：
With the development of cities and population, the production of sludge is increasing annually. It has become an unavoidable challenge to achieve sludge dewatering and disposal by a cost-effective, efficient and safe process. In this work, firstly, the factors limiting sludge dewatering are reviewed in terms of moisture distribution, sludge concentration, organic matter content, electronegativity, floc strength, and extracellular polymers (EPS). Subsequently, focusing on the dewatering technology about the skeleton builder, the recent progress of it is detailed in terms of mechanism, evaluation indicators, influencing factors, and technology coupling. In addition, the impact of skeleton builders on the sludge disposal stage is concluded. Finally, the challenges faced by sludge dewatering and skeleton builders are prospected. This review will provide some theoretical basis and technical guidance for subsequent experiments and practices regarding skeleton builders.
摘要：
The asphalt mixture splitting test is one of the most important methods for measuring asphalt's tensile properties. To characterize the limitations of the traditional splitting test and the influence of the specimen size and loading conditions on the accuracy of the test, the factors affecting the strength of the splitting test were analyzed to reveal the splitting failure state and establish a unified representation model between the splitting and direct tensile tests. Initially, the moment of specimen cracking was taken as a key indicator, combined with image processing technology, to establish a set of criteria to judge the splitting test. Subsequently, standardized splitting tests were conducted and compared to tests of different specimen sizes and loading methods. Based on the octahedral strength theory, the stress points before and after the improved test were compared to the existing failure criteria. Direct tensile and splitting tests were conducted at different rates, and a unified strength-rate function model was established, realizing the unified representation of direct tensile and splitting tests. The research results indicate that the standardized splitting test is prone to the phenomenon wherein the specimen end face cracks before the center, affecting the accuracy of the test and potentially leading to redundant material strength evaluations. Using a loading method with a "35 mm specimen thickness" and a "0.3 mm rubber gasket + 12.7 mm arc-shaped batten" can essentially achieve the test hypothesis of "cracking at the center first", resulting in less discrete outcomes and closer alignment to the three-dimensional stress failure state. The tensile and splitting strengths are both power function relationships with the rate as the independent variable, establishing a unified function model of the tensile and failure strengths. The research provides a more reliable testing method and calculation model for asphalt pavement structure design, and it also provides an effective basis for the improvement of splitting tests on materials such as concrete and rock.
