关键词：
Organic amine pesticides (OAPs);Surface water;Sediments;Drinking water source;Risk assessment
摘要：
The extensive use of organic amine pesticides (OAPs) in agricultural practices has resulted in the contamination of water environments, posing threats to ecosystems and human health. This study focused on the Xiang River (XR), a representative drinking water source, as the research area to investigate the occurrence characteristics of 34 OAPs. Diphenylamine emerged as the most prevalent OAP in surface water due to industrial and agricultural activities, while cycloate dominated in sediments due to cumulative effects. Generally, the concentration of OAPs in a mixed tap water sample was lower than those in surface water samples, indicating OAPs can be removed by water plants to a certain extent. The water-sediment distribution coefficients (k(d)) of ΣOAPs were much less than 1 L/g, the majority of OAPs maintained relatively high concentrations in water samples instead of accumulating in sediments. Furthermore, risk assessment revealed that carbofuran showed a moderate risk to the aquatic environment, with a risk quotient of 0.23, while other OAPs presented minor risks. This study provided crucial insights for regional pesticide management and control in the XR basin, emphasizing the importance of implementing strategies to minimize the release of OAPs into the environment and protect human health.
期刊：
Results in Physics,2024年56:107253 ISSN：2211-3797
通讯作者：
Zhang, QH
作者机构：
[Zhang, Qing-Hua; Zhang, QH] Changsha Univ Sci & Technol, Sch Math & Stat, Changsha 410114, Peoples R China.;[Lai, Lemin] Chinese Acad Sci, Acad Math & Syst Sci, Beijing 100190, Peoples R China.;[Lai, Lemin] Univ Chinese Acad Sci, Sch Math Sci, Beijing 100049, Peoples R China.;[Fei, Shao-Ming] Capital Normal Univ, Sch Math Sci, Beijing 100048, Peoples R China.;[Fei, Shao-Ming] Max Planck Inst Math Sci, D-04103 Leipzig, Germany.
通讯机构：
[Zhang, QH ] C;Changsha Univ Sci & Technol, Sch Math & Stat, Changsha 410114, Peoples R China.
关键词：
Steering criteria;Correlation matrices;Special unitary groups
摘要：
We study the steerability for arbitrary dimensional bipartite systems based on the correlation matrices given by local special unitary groups. We present families of steering criteria for bipartite quantum states in terms of parameterized correlation matrices. We show that these steering criteria may detect more steerable states than the existing steering criteria. The results are illustrated by detailed examples.
作者机构：
[Meng, Ruizhi; Cui, Zhexin; Yun, Di] Xi An Jiao Tong Univ, Sch Nucl Sci & Technol, Xian 710049, Peoples R China.;[Cui, Zhexin; Lozano-Perez, Sergio] Univ Oxford, Dept Mat, Parks Rd, Oxford OX1 3PH, England.;[Liu, Junkai] Xidian Univ, Sch Adv Mat & Nanotechnol, Xian 710126, Peoples R China.;[Deng, Huiqiu; Liu, Guangdong; Deng, HQ] Hunan Univ, Sch Phys & Elect, Changsha 410082, Peoples R China.;[Liu, Xiaochun; Tang, Guogao] Changsha Univ Sci & technol, Inst Met, Coll Mat Sci & Engn, Changsha 410082, Peoples R China.
通讯机构：
[Yun, D ] X;[Deng, HQ ] H;Xi An Jiao Tong Univ, Sch Nucl Sci & Technol, Xian 710049, Peoples R China.;Hunan Univ, Sch Phys & Elect, Changsha 410082, Peoples R China.
关键词：
Zirconium alloy;High-temperature oxidation;Effect of tin;Nanovoids
摘要：
The oxidation behavior of zirconium alloy in high-temperature steam plays a dominant role in the operation of nuclear reactors under accident conditions. The present work investigated the effect of Sn on the oxidation behavior of zirconium alloys in high-temperature steam at 1000 degrees C. The results of scanning electron microscopy (SEM), metallographic microscopy and synchrotron X-ray diffraction (S-XRD) analyses show that there are three layers in the oxidized sample, including prior beta-Zr, alpha-Zr(O) and ZrO2. High resolution analyses conducted in these layers by transmission electron microscopy (TEM) show that Sn atoms segregate around the oxide-metal (O-M interface and Zr-Sn intermetallic precipitates only present in the oxide film. Clear atomic arrangements of Zr5Sn3 were obtained by TEM, resulting in accurate identification of the Zr-Sn intermetallic phase. Also, TEM energy dispersive spectroscopy (EDS) maps show that Zr-Sn particles invariably accompany the segregation or precipitation of Nb. However, no clear precipitation sequence was observed, which suggests that a co-precipitation mechanism of Sn and Nb is in operation. As oxidation proceeds, nanovoids next to the Zr-Sn intermetallic particles were observed accompanied by local areas deficient in oxygen, identified as ZrO. Combining the interdiffusion trend obtained by Density functional theory (DFT) and ab initio molecular dynamics (AIMD) simulations, a mechanism for the transformation from the Zr-Sn intermetallic precipitates to nanovoids was proposed. This proposed mechanism may shed new light into the role of Sn in the oxidation resistance of zirconium alloy under LOCA conditions.
摘要：
It is believed that local activation is the origin of all complexities, and the locally active memristive synaptic neural network can generate complex chaotic dynamic behaviors, such as hyperchaotic, multi-scroll, multi-stability and hidden dynamical behaviors. However, there are few studies on the simultaneous occurrence of multiple complex dynamic behaviors in neural networks. No chaotic system of multi-scroll hyperchaotic hidden attractors based on neural network has been found yet. To solve the problem, in this paper, we propose a new locally active memristive Hopfield neural network (HNN) model based on a multi-segment function, which is affected by electromagnetic radiation and external current. The multi-scroll hyperchaotic hidden attractors are found in the memristive HNN for the first time. Theoretical analysis and numerical simulation results show that the memristive HNN model has no equilibrium point, and the number of multi-scroll attractors is controlled by the state equation parameters of the memristive synapse. In addition, the structures and number of scrolls are also affected by electromagnetic radiation and external current. At the same time, under the appropriate parameter conditions, by modifying the initial value of the system, the memristive HNN has a controllable number of coexisting attractors, showing extreme multi-stability. Finally, a memristive HNN analog circuit is designed. The hardware experiment results reproduce the multi-scroll dynamics phenomenon, which verifies the correctness of the theoretical analysis and numerical simulation.
期刊：
Journal of Alloys and Compounds,2024年976:173160 ISSN：0925-8388
通讯作者：
Ouyang, LZ;Zhang, JR
作者机构：
[Qin, Chenglei; Zhong, Hao; Wang, Hui; Ouyang, Liuzhang; Liu, Jiangwen] South China Univ Technol, Sch Mat Sci & Engn, Guangzhou 510641, Peoples R China.;[Qin, Chenglei; Zhong, Hao; Wang, Hui; Ouyang, Liuzhang; Liu, Jiangwen] South China Univ Technol, Key Lab Adv Energy Storage Mat Guangdong Prov, Guangzhou 510641, Peoples R China.;[Zhong, Hao] Guangzhou High Tech Zone Inst Energy Technol, Guangzhou 510000, Peoples R China.;[Chen, Kang] Changsha Univ Sci & Technol, Sch Energy & Power Engn, Key Lab Efficient & Clean Energy Utilizat, Changsha 410111, Peoples R China.;[Lang, Chengguang] Sun Yat sen Univ Shenzhen, Sch Adv Energy, Shenzhen 518107, Peoples R China.
通讯机构：
[Zhang, JR ] L;[Ouyang, LZ ] S;South China Univ Technol, Sch Mat Sci & Engn, Guangzhou 510641, Peoples R China.;South China Univ Technol, Key Lab Adv Energy Storage Mat Guangdong Prov, Guangzhou 510641, Peoples R China.;Lishui Univ, Dept Chem, Lishui 323000, Peoples R China.
摘要：
Onsite hydrogen generation by sodium borohydride hydrolysis resolves hydrogen energy supply system challenges. However, the spent-NaBH4 regeneration is still a problem in the closed loop of this irreversible reaction. As the by-product is the key to the problem, NaB(OH)4 is regarded as not the boron source but the hydrogen source of NaBH4 regeneration. Therefore, in this study, inexpensive Al metal and NaB(OH)4 are ball milled under argon to regenerate NaBH4 without additional hydrogen input. However, the ball-milling reaction is hindered by the flexible Al and impact oxide layer, and the NaBH4 yield is only approximately 22 %. Therefore, a brittle intermetallic compound Mg2Al3 is reacted with NaB(OH)4 by ball milling, achieving a NaBH4 yield of over 42 %. The mechanism study shows that the brittleness of the raw material plays an important role in promoting the ball-milling reaction. This study achieves NaBH4 regeneration using only Al as the reducing agent and provides a promising method to promote the mechanochemical regeneration of NaBH4.
期刊：
Journal of Alloys and Compounds,2024年970:172434 ISSN：0925-8388
通讯作者：
Zeng, G;Zhou, XJ
作者机构：
[Sun, Wei; Zeng, Guang; Yao, Yuan; Deng, Yangchao; Liu, Wenyuan] Cent South Univ, Sch Mat Sci & Engn, Changsha 410083, Peoples R China.;[Zhan, Hongyi] Gen Motors Global Res & Dev, China Sci Lab, Shanghai 201206, Peoples R China.;[Zhou, Xiaojie; Zhou, XJ] Changsha Univ Sci & Technol, Hunan Prov Key Lab Intelligent Mfg Technol High Pe, Changsha 410114, Peoples R China.
通讯机构：
[Zeng, G ; Zhou, XJ ] C;Cent South Univ, Sch Mat Sci & Engn, Changsha 410083, Peoples R China.;Changsha Univ Sci & Technol, Hunan Prov Key Lab Intelligent Mfg Technol High Pe, Changsha 410114, Peoples R China.
关键词：
Mg-Sn based alloy;Dynamic recrystallization;Precipitation;Hot compression
摘要：
The intrinsic correlation between dynamic precipitation and Dynamic Recrystallization (DRX) in a rare earth (RE)-free engineering Mg-4Sn-3Al-1Zn (TAZ431, wt.%) magnesium alloy has been systematically investigated. Hot compression tests were performed on the TAZ431 alloy, in comparison to Mg-3Al-1Zn (AZ31, wt.%) as a reference alloy, with varying temperatures, strain rates, and strain levels (T = 300 -460 degrees C; epsilon = 0.001 -1 s-1; epsilon = 0 to-0.9). Correlative microstructural characterizations including Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), and Electron Backscatter Diffraction (EBSD), were employed to explore the behaviors of precipitation, DRX and intragranular deformation as subjected to hot compression. The results indicate a significant interaction between Mg2Sn dynamic precipitation and the formation of DRXed grains. The TAZ431 alloy with Sn alloying exhibits profuse precipitation and larger DRX fraction within the microstructure, resulting in the increase of modulus and hardness. Nucleation of DRXed grains in the TAZ431 alloy was stimulated by relatively large (over 1 micrometer) undissolved Mg2Sn intermetallic particles. Meanwhile, the precipitation of nano-sized Mg2Sn occurred within DRXed grains and was facilitated by DRX process, consequently hindering the further growth of DRXed grains. The findings here may have implications for alloy design and thermal-mechanical processing of magnesium alloy structural components.
摘要：
Hyperspectral images (HSIs) have been widely used for target detection due to their abundant spatial and spectral information. In this article, a shadow-insensitive hyperspectral target detection (HTD) framework based on exposure fusion is proposed, which consists of the following major steps. First, the input HSI is divided into two parts, namely the shadow region and the nonshadow region. Second, total variation-based feature extraction and overexposure operation are performed on the input image to produce two feature images, i.e., the original feature image and the overexposure image. Third, a self-guided constrained energy minimization (SGCEM) detector is performed on the two feature images to detect the targets in shadow and nonshadow regions, respectively. Finally, the detection results obtained on the original feature image and the overexposure image are fused to acquire the final detection result. Extensive experiments conducted on real-world data illustrate that the proposed method can achieve satisfactory results when shadow exists.
摘要：
In order to improve the flame-retardant performance of insulating paper and reduce the fire risk, hydroxyethyl diphosphate and dicyandiamide were used to modify starch to prepare a new starch-based flame retardant (SHPD). The combustion, mechanical, and electrical properties of SHPD treated flame-retardant insulating paper were investigated. The results showed that when the impregnation concentration of SHPD was 25.0%, the limiting oxygen index of the insulating paper was increased from 18.3% to 38.3% and reached the level of UL-94 V-0. The tensile index and burst index of the flame-retardant insulating papers were only 10.17% and 12.5% lower than that of the control insulating paper. The ring crush strength and alternating current breakdown strength in air of the flame-retardant insulating papers were 63.3% and 1.8% higher than that of the control insulating paper. The SHPD flame retardant has a good application prospect in insulating paper.
摘要：
Fatigue performances of critical structures are strongly affected by the microstructural (e.g. grain, defect, inclusion, etc.) size effect, and it is thus important to quantify their detrimental effect. In this work, a numerical procedure is constructed to quantify the influence of microstructure on the mechanical and fatigue behaviors of Ni-based superalloy GH4169. Specifically, by combining sub modelling approach with crystal plasticity constitutive model, a dual-scale modelling approach is developed for studying grain-level mechanical behavior of Ni-based superalloy GH4169 notched components. In addition, the dislocation-based Tanaka-Mura-Wu model is applied for fatigue crack initiation life prediction. The Paris law is then utilized for fatigue crack propagation analysis based on the simulated short crack. To study the microstructural size effect on fatigue crack initiation and propagation behaviors, sub-models containing various grain orientation, grain size, defect size/shape are built and analysed. Finally, a series of fatigue tests on notched specimens of Ni-based superalloy GH4169 were carried out for method validation. Results indicate that the established dual-scale modelling approach and fatigue life prediction framework yields good agreement with experimental results.
通讯机构：
[Zhang, L ] H;Hunan City Univ, Coll Civil Engn, Yiyang 413000, Peoples R China.;Hunan Univ Technol, Hunan Engn Res Ctr Struct Safety & Disaster Preven, Yiyang 413000, Peoples R China.
关键词：
boulder and hard rock environment;GPR;wavelet scale energy spectrum;wavelet packet energy;time-frequency characteristics
摘要：
The hard rocks in the stratum can pose safety risks and hinder the progress of urban underground tunnel construction using shield and jacking methods, thereby reducing construction efficiency and increasing construction costs. This paper utilizes wavelet scale energy spectrum, wavelet packet theory and statistical methods to conduct research on the detection of special geological formations such as hard rocks and voids, as well as the analysis of their signal time-frequency characteristics based on the ground-penetrating radar (GPR) technique. On the basis of calibrating the permittivity of different types of rock blocks, we established a forward model for detecting hard rocks and voids, and the simulated signals were analyzed in the time and frequency domains. Subsequently, laboratory experiments were conducted to perform GPR tests on different types of hard rocks in natural and water-saturated states and voids, to explore the time-frequency characteristics, frequency band energy variations, and statistical patterns of typical single-trace signals. The results show that the granite detection signal contains more low-frequency components, the sandstone detection signal contains more medium-low frequency components, while the limestone detection signal contains more medium-high frequency components in their natural state; the signal from the karst cave has relatively more low-frequency components than the signal from the empty cavity. The geometric shape of the rock has no influence on the dominant frequency and time-frequency distribution of its reflection signal. Generally, rocks with higher rebound values (hardness) also exhibit larger variance and standard deviation in frequency band energy. The research has important theoretical significance and practical value for the measurement and assessment of special geological features such as hard rocks and voids in urban underground trenchless construction.
摘要：
High-temperature titanium alloys' thermal stability and creep resistance are significant during service in high temperatures. This study systematically investigated the thermal stability and mechanical properties of Ti-6.5A1-2.5Sn-9Zr-0.5Mo-1Nb-1W-0.3Si- x Sc ( x , 0-0.5 wt.%) at 650 degrees C. The lamellar secondary alpha phase is refined and the formation of Sc2 O3 is increased with the increasing scandium ( Sc ) additions, which improves the strength of the alloy, while excessive Sc2 O3 becomes the crack source and deteriorates the plasticity. The oxygen content in the matrix is reduced by the interaction between Sc and oxygen, inhibiting the growth of the Ti3 Al phase and improving the thermal stability of the alloy. Meanwhile, Sc accelerates the dissolution of the residual ,B phase and precipitation of fine, diffusely distributed ellipsoidal silicides, which strongly prevents dislocation movement. The enhancement of creep resistance for the Sc -containing alloy is attributed to the refined lamellar secondary alpha phases, Sc2 O3 particles, Ti3 Al phase, and silicides, especially the precipitated silicides. Eventually, the 0.3Sc alloy shows optimal thermal stability (the plasticity loss rate 17.3%) and creep resistance (steady-state creep rate 4.4 x 10-7 s-1 ). The investigation results provide new insights into the mechanism and thermal stability improvement in high-temperature titanium alloys modified by rare earth (RE).(c) 2023 Published by Elsevier Ltd on behalf of The editorial office of Journal of Materials Science & Technology.
关键词：
Asphalt pavement;Photocatalytic coating;Nanometer titanium dioxide;Quantum dot;Tail gas degradation
摘要：
To address the escalating issue of vehicular exhaust pollution, the application of photocatalyst materials on road surfaces for rapid degradation of exhaust gas has gained significant attention in pavement engineering. However, poor visible light response and low separation efficiency of photogenerated charge carriers limit the practical application of nanometer titanium dioxide (nano-TiO2) photocatalyst on road surfaces. In this study, tungsten oxide (WO3) and tungsten sulfide (WS2) quantum dots (QDs) were introduced into graphene oxide (GO)/TiO2 nanocomposites through a sol-gel process to form ternary heterojunction structures. Characterization results revealed that the QDs modified GO/TiO2 composites exhibited enhanced light absorption, electrical conductivity and surface area. Photocatalytic degradation tests of model vehicle exhaust pollutants showed that the GO/WS2 QDs/TiO2 and GO/WO3 QDs/TiO2 coatings achieved over 70 % degradation rate of nitrogen oxides within 120 min under visible light irradiation, outperforming bare TiO2 and binary GO/TiO2. Mechanism studies suggested that the ternary heterojunction facilitated efficient separation of photogenerated charge carriers at multi-phase interfaces. Additionally, the photocatalytic coating demonstrated good durability after simulated traffic loading, maintaining a 60 % degradation rate of nitrogen oxides even after 20,000 rolling cycles. This work provides a promising solution for sustainable environmental remediation on road surfaces.
摘要：
Developing robust and efficient nonprecious metal-based electrocatalysts toward hydrogen evolution reaction (HER) is a big challenge for green and sustainable energy since insufficient catalytic activity and poor stability of current catalysts cannot meet the application requirements. This work reports a freestanding HER electrode FeNiCuAlMo prepared by arc-melting and chemical dealloying methods. The HER performance firstly improves and then declines with the increase of dealloying time. When the dealloying time is 3 h, the electrode shows optimal catalytic performance. The fabricated electrode is composed of AlMo3 and Al5CuMo2, where micro-sized AlMo3 particles are embedded in cellular dendritic Al5CuMo2. Impressively, it displays excellent HER performance, including a small overpotential of 173 mV at a current density of 500 mA/cm2 and outstanding long-term stability for 100 h of continuous hydrogen evolution at 1000 mA/cm2 in an alkaline electrolyte without obvious attenuation. The intrinsic activity of the electrodes combined intermetallic compounds with hierarchical porous structure provides several effects, including enhanced massive active sites, electrolyte access, electron transport, and fast gas release that contribute jointly to enhancing HER activities. The micro-sized AlMo3 particles provide robust framework for the dendritic Al5CuMo2 active sites center, allowing the exposure of enough active sites and simultaneously maintaining good stability. The highly stable and active electrocatalytic HER property makes it as a promising candidate for practical hydrogen production.
摘要：
Recommendation systems have been effectively utilized in various fields, but their internal decision-making methods are still largely unknown. This opaque decision-making method can greatly affect users’ trust in the recommendation system. Therefore, finding a way to explain the reasons for model decisions has become an urgent task. Previous studies often used LSTM and other models to generate recommendation explanations and explain the reasons for recommendations in text form. However, traditional methods cannot effectively use the ID information of users and items, and the text generated is highly repetitive. To solve this problem, this paper uses the method of prompt learning combined with a graph encoder to design a recommendation explanation generation model. In order to narrow the semantic gap between the ID information of users and items and natural language and capture high-level interaction information, this paper designs a graph encoder based on user similarity to learn the interactive semantic information of user and item IDs, and to construct a continuous prompt. Then, the discrete prompt composed of discrete features of users and items is combined with the continuous prompt to construct a hybrid prompt to input into the pre-trained model to generate the recommended explanation. This paper experiments on three publicly available datasets and compares them with several state-of-the-art methods to demonstrate the personalization and text quality of the generated explanations.
摘要：
The dry separate curing of duck egg yolks was carried out by ultrasonic synergize NaCl (sodium chloride) and NaCl alone. The mechanism of the amelioration of salted egg yolk quality by ultrasonic synergistic NaCl dry-curing was studied. The quality variations of the salted egg yolks were analyzed for the same curing time and NaCl content achieved by ultrasonic synergistic NaCl curing and NaCl curing alone. The results showed that under the same salting time, the NaCl content, oil exudation and chewiness of U48-SEY (ultrasonic for 48h-salted egg yolk) were higher than those in SEY (salted egg yolk). At the same NaCl content, the oil exudation and chewiness of U44-SEY (ultrasonic for 44h-salted egg yolk) were still significantly increased. Compared to SEY, the soluble protein content and H(0) of U44-SEY and U48-SEY were augmented. Scanning electron microscopy (SEM) indicated that the polyhedral particles in the salted egg yolks prepared by ultrasonic synergistic NaCl dry-curing were closely aligned and evenly distributed, and the salted egg yolks were sandier. Structural analysis revealed that the secondary and tertiary structures of egg yolk protein were changed although the ultrasonic synergistic NaCl dry-curing did not cause the fragmentation or aggregation of the peptide chain structure. The above results suggested that ultrasonic not only perfected the quality of salted egg yolk by promoting NaCl penetration, but also modified the structures of egg yolk protein by the action of ultrasonic itself, which prominently improved the quality of salted egg yolks.
通讯机构：
[Gu, K ] C;Changsha Univ Sci & Technol, Sch Comp & Commun Engn, Changsha 410114, Peoples R China.
关键词：
Malicious vehicle detection;Internet of Vehicles;graph attention;gated recurrent unit;reputation
摘要：
Internet of vehicles (IoVs) is an important information exchange platform for intelligent transportation systems (ITSs) to provide traffic services. However, the appearance of malicious vehicles in IoVs can damage the security and stability of ITSs, which may provide false traffic data to cause serious traffic accidents. Also, many existing cryptography-based malicious vehicle detection scheme can only be used to resist some external attacks, while some internal malicious vehicles are easy to use their legal identities to provide false traffic data for other honest vehicles. In this paper, we propose a malicious vehicle detection scheme based on spatio-temporal features of traffic flow under cloud-fog computing-based IoVs. In our scheme, a traffic subarea division method based on spatial correlation degrees of road intersections is proposed to divide the urban road network into multiple traffic subareas. Based on the divided traffic subareas, an improved subarea-based graph attention model is proposed to extract the spatial features of traffic flow by the fog server. Then a gated recurrent unit method with attention mechanism is constructed to extract the temporal features of traffic flow by the cloud server, and a short-term traffic flow prediction model is built on the extracted spatio-temporal features of traffic flow. Further, a reputation calculation mechanism is established to score each vehicle by the fog server according to the verification of the traffic data uploaded by the vehicle and the traffic data predicted by our constructed prediction model, which is used to judge whether the vehicle is malicious according to its reputation score. Related experimental results show our scheme is effective and efficient to detect malicious vehicles under cloud-fog computing-based IoVs.
摘要：
The natural aluminosilicate nanoclay mineral (ANM) has found extensive application in photocatalysis due to its cost-effectiveness, excellent stability, and unique surface properties. The distinctive ANMs surface not only alters the surface characteristics of loaded photocatalysts and regulates the microenvironment of photochemical reactions but also actively participates as a photocatalyst itself, thereby making the roles of ANMs surfaces in photocatalytic reactions highly intricate. This review aims to highlight recent advancements in comprehending the influence of ANMs surfaces on photocatalysis. We commence by summarizing the structural features of ANMs surfaces as traditional supports, functional supports, and photocatalysts. Emphasis is placed on elucidating how the aluminosilicate structure, photochemical activity, and asymmetric structure impact the process of photocatalytic reactions. Particular attention is given to exploring the asymmetric photochemical activity exhibited by ANMs and its consequential unique structural effects. Finally, we summarize challenges faced and future developments pertaining to heterostructure design, enhancement mechanisms, and photochemical applications for ANMs in photocatalysis.
关键词：
Asphalt mixture;Mesoscopic analysis;Skeleton evolution;Aggregate contact;Particle movement;Discrete element method
摘要：
The aggregate skeleton is the intrinsic core of asphalt mixtures for load transfer, which is quite different under various gradations. For evaluating the loading characteristics of the aggregate skeleton, this research combined the 3D blue -ray scanning technology and discrete element method (DEM) to establish the numerical models of different graded asphalt mixtures considering the real aggregate morphology. A linear parallel bond model was used to simulate the adhesion effect of asphalt, and the uniaxial compression numerical simulation was verified by indoor tests. In addition, the contact force, contact number, anisotropy, and rotation angle were used to evaluate the aggregate skeleton evolution under uniaxial compression loading. Furthermore, the contribution of each grade aggregate in the gradation to the skeleton structure was analyzed. Results show that the average contact force is higher in large -size aggregates above 9.5 mm, which exhibit greater load transfer efficiency. Moreover, 4.75-9.5 mm size aggregates combine the functions of bearing and filling, and its role is significantly affected by the gradation. It is also found that the internal skeleton structure can be optimized and adjusted under stress. The contact numbers of different graded mixtures follow a close decrease, and the strong contacts are mostly provided by coarse aggregates above 4.75 mm. The anisotropy development of aggregate skeleton contact force is induced by the stress, and the deviator fabric of asphalt mixtures show a good linear positive correlation with the uniaxial compressive strength (UCS). Besides, fine aggregates exhibit greater cumulative rotation angle and instability effect, it is feasible to detect asphalt mixture deformation by the rotation angle of particles.
关键词：
White layer;Dark layer;Grinding processes;Forming mechanism;Microstructures;Hardness
摘要：
To establish a systematic cognition of formation mechanisms of affected layers in hardened AISI 52100 steel, the experiments were conducted to measure and characterize the microstructure and properties of the affected layers subject to a varying grinding depth and thermal and mechanical effects at different-levels. It is found that the affected layers can be formed mechanically or thermally depending on whether the mechanically-induced effect predominates the thermally-induced effect, and the 25 mu m is exactly the critical grinding depth of the above two effects. From the novel perspective of thermo-mechanical decoupling, when the grinding depth exceeds 25 mu m, grinding temperature is higher than the nominal austenization temperature (Ac1) of the bulk material, the thermally-induced effect becomes dominate, the thickness of the white layer changes abruptly, and there is an obvious dark layer underneath. When the grinding depth is less than 25 mu m, grinding temperature is lower than Ac1, the mechanically-induced effect becomes dominate, the white layer is extremely thin and no dark layer can be observed. The thermally-induced affected layers are formed mainly by a rapid austenite transformation, accompanied by the fragmentation and dissolution of carbide particles, and the white layer is formed on the ground surface. Meanwhile, the subsurface undergoes tempering subjected to high temperature; this leads to the decomposition of austenite and precipitation of a large amount of cementite. With a continuous dynamic recrystallization, a dark softening layer is formed under the white layer. The mechanical-induced affected layers are formed by fragment and refinement of nano- and micro-structures subject to severe plastic deformation and dynamic recovery.
摘要：
Objective. Dynamic functional network connectivity (dFNC), based on data-driven group independent component (IC) analysis, is an important avenue for investigating underlying patterns of certain brain diseases such as schizophrenia. Canonical polyadic decomposition (CPD) of a higher-way dynamic functional connectivity tensor, can offer an innovative spatiotemporal framework to accurately characterize potential dynamic spatial and temporal fluctuations. Since multi-subject dFNC data from sliding-window analysis are also naturally a higher-order tensor, we propose an innovative sparse and low-rank CPD (SLRCPD) for the three-way dFNC tensor to excavate significant dynamic spatiotemporal aberrant changes in schizophrenia. Approach. The proposed SLRCPD approach imposes two constraints. First, the L1 regularization on spatial modules is applied to extract sparse but significant dynamic connectivity and avoid overfitting the model. Second, low-rank constraint is added on time-varying weights to enhance the temporal state clustering quality. Shared dynamic spatial modules, group-specific dynamic spatial modules and time-varying weights can be extracted by SLRCPD. The strength of connections within- and between-IC networks and connection contribution are proposed to inspect the spatial modules. K-means clustering and classification are further conducted to explore temporal group difference. Main results. 82 subject resting-state functional magnetic resonance imaging (fMRI) dataset and opening Center for Biomedical Research Excellence (COBRE) schizophrenia dataset both containing schizophrenia patients (SZs) and healthy controls (HCs) were utilized in our work. Three typical dFNC patterns between different brain functional regions were obtained. Compared to the spatial modules of HCs, the aberrant connections among auditory network, somatomotor, visual, cognitive control and cerebellar networks in 82 subject dataset and COBRE dataset were detected. Four temporal states reveal significant differences between SZs and HCs for these two datasets. Additionally, the accuracy values for SZs and HCs classification based on time-varying weights are larger than 0.96. Significance. This study significantly excavates spatio-temporal patterns for schizophrenia disease.
