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.
关键词：
Entrepreneurial networks;Causation;Effectuation;Business model innovation;Environmental dynamism;Resource orchestration
摘要：
PurposeAlthough it is acknowledged that entrepreneurial networks play a crucial role in fostering business model innovation (BMI) for start-ups, it is unclear how and when these networks affect BMI. This research developed a moderated mediation model to explore the impact of entrepreneurial networks on BMI in start-ups and examined the dual mediating effects of causation and effectuation, as well as the moderation of environmental dynamism.Design/methodology/approachThe proposed framework was tested by hierarchical regression analyses and bootstrapping using samples of 248 start-ups in China.FindingsThe results showed that entrepreneurial networks significantly positively impacted start-up BMI. Causation and effectuation played dual mediating roles between entrepreneurial networks and BMI. Furthermore, the entrepreneurial networks-effectuation-BMI association was more substantial in highly dynamic environments, whereas the entrepreneurial networks-causation-BMI relationship was unaffected.Research limitations/implicationsThere are several theoretical contributions resulting from this research. The findings offer new insights for understanding the antecedents of start-up BMI from the network perspective. This research adds to the growing literature on resource orchestration (RO) by exploring the dual mediating influences of causation and effectuation in resource management. This investigation revealed the boundary condition between entrepreneurial networks and BMI by testing the moderating influence of environmental dynamism.Practical implicationsStart-ups must effectively use external resources embedded within networks to advance BMI. Start-up entrepreneurs should apply causation and effectuation to transform entrepreneurial network resources into BMI. Start-up entrepreneurs must dynamically manage resources in response to ever-changing environmental conditions. Resource acquisition and management of entrepreneurial networks can vary significantly in their influence on start-up BMI under different environmental contexts.Originality/valueUnlike previous BMI research focused on internal organizational factors, this study highlighted the critical importance of entrepreneurial networks as a prerequisite for achieving start-up BMI, contributing to the literature on open innovation and resource-based view. Examining the dual mediating roles of causation and effectuation illustrated the bridging role of strategic decision-making logic in connecting resources to value creation, contributing to the developing RO literature. The moderating influence of environmental dynamism was explored, clarifying how start-up BMI benefits from entrepreneurial networks in differing situations. A framework for reconciling contradictory findings concerning the association between entrepreneurial networks and innovation is provided.
期刊：
Journal of Materials in Civil Engineering,2024年36(2):04023543 ISSN：0899-1561
通讯作者：
Dong, HW
作者机构：
[Huang, Tuo; Qin, Haoyun; Wang, Zhaoyang; Liu, Hongfu] Changsha Univ Sci & Technol, Changsha 410114, Peoples R China.;[Cao, Zhonglu; Dong, HW; Dong, Hongwu] China Commun Construct Co CCCC First Harbor Engn, Tianjin Port Engn Inst Co Ltd, 1002 Dagu South Rd, Tianjin 300222, Peoples R China.;[Cao, Zhonglu; Dong, HW; Dong, Hongwu] China Commun Construct Co CCCC First Harbor Engn, Tianjin 300461, Peoples R China.
通讯机构：
[Dong, HW ] C;China Commun Construct Co CCCC First Harbor Engn, Tianjin Port Engn Inst Co Ltd, 1002 Dagu South Rd, Tianjin 300222, Peoples R China.;China Commun Construct Co CCCC First Harbor Engn, Tianjin 300461, Peoples R China.
摘要：
To objectively characterize the time-temperature-stress equivalence of viscoelastic properties of asphalt mixture, the triaxial compressive creep test was carried out on an AC-13 asphalt mixture under the conditions of different temperatures and stress states in this paper and the nonlinear variation law of creep deformation was obtained. According to the characteristics of similar creep curves and the principle of time-temperature equivalence, two methods were used to shift the creep compliance under different confining pressure, temperature, and axial stress conditions, and the change of temperature and stress shift factors with confining pressure were obtained; in addition, the creep compliance principal curve was fitted by the Prony series and its principal surface was established. On this basis, the multiple stress creep recovery test under different confining pressures was conducted to measure the parameters of Schapery’s nonlinear viscoelastic model and their variation law with the triaxial stress ratio was obtained, which accurately characterized the synergistic effect of confining pressure and axial stress.
期刊：
World Electric Vehicle Journal,2024年15(1):3- ISSN：2032-6653
通讯作者：
Chenhui Liu
作者机构：
[Qinglu Ma] School of Traffic and Transportation, Chongqing Jiaotong University, Chongqing 400074, China;[Meiling Su; Xuerui Hou] College of Civil Engineering, Hunan University, Changsha 410082, China;Research Institute of Hunan University in Chongqing, Chongqing 401120, China;Key Laboratory of Highway Engineering of Ministry of Education, Changsha University of Science & Technology, Changsha 410114, China;Author to whom correspondence should be addressed.
通讯机构：
[Chenhui Liu] C;College of Civil Engineering, Hunan University, Changsha 410082, China<&wdkj&>Research Institute of Hunan University in Chongqing, Chongqing 401120, China<&wdkj&>Key Laboratory of Highway Engineering of Ministry of Education, Changsha University of Science & Technology, Changsha 410114, China<&wdkj&>Author to whom correspondence should be addressed.
关键词：
traffic safety;electric vehicles;traffic accidents;accident size;ordered logit model
摘要：
With the great increase of electric vehicles (EVs) in the past decade, EV-involved traffic accidents have also been increasing quickly in many countries, bringing many new traffic safety challenges. Norway has the largest EV penetration rate in the world. Using the EV accident data from Norway in 2020 and 2021, this study aims to investigate the features of EV safety comprehensively. Firstly, a descriptive analysis is conducted. It has been found that rear-end collisions are the major collision type of EVs, and EVs are very likely to collide with pedestrians/cyclists. In addition, in terms of roadway type, EV accidents mainly occur on medium- and low-speed roads; in terms of environment, they mainly occur in good visibility conditions and dry road surface conditions. Then, a regression analysis is conducted to identify the key factors affecting the accident size, which is the number of traffic units involved in an accident and taken as the accident severity surrogate here. Since EV accidents are divided into four categories in order of accident size, the ordered logit model is adopted. It divides a multi-categorical dependent variable into multiple binary data points in order and calculates the probability of the dependent variable falling into each category with the logit model, respectively. The estimation results indicate that time of day, speed limit, and presence of medians have statistically significant impacts on the EV accident size. Finally, some countermeasures to prevent EV accidents are proposed based on the research results.
作者：
Naiwei Lu;Honghao Wang*;Jing Liu;Yuan Luo;Yang Liu
期刊：
Journal of Constructional Steel Research,2024年215:108532 ISSN：0143-974X
通讯作者：
Honghao Wang
作者机构：
[Naiwei Lu; Honghao Wang; Jing Liu; Yang Liu] School of Civil Engineering, Changsha University of Science and Technology, Changsha, Hunan 410114, China;[Yuan Luo] College of Civil Engineering, Hunan University of Technology, Zhuzhou 412007, China
通讯机构：
[Honghao Wang] S;School of Civil Engineering, Changsha University of Science and Technology, Changsha, Hunan 410114, China
摘要：
Fatigue cracking in welded joints is a critical problem in bridge engineering, especially for aging long-span steel bridges. The crack size and density are increasing gradually with the bridge aging process, where the crack interaction will accelerate the crack propagation or even short cracks merging into a long crack. However, the mechanism underlying the coupled propagation behavior of multiple cracks remains unclear. In this study, the coupling effect of multiple cracks was investigated based on numerical simulations. Subsequently, the numerical result was verified by a full-scale segmental fatigue experiment. In order to overcome the time-consuming iterative computations, the back propagation (BP) neural network was utilized to predict the effective coupling spacing between multiple cracks. Finally, a new crack reconstruction method was proposed to simplify crack merging processes. Results indicate that the coupled propagation behavior is significantly impacted by the effective crack spacing. The coupling effect is more significant at the near-end point compared to other feature points. In addition, the cracks with similar sizes have greater coupled effect, which is the worst-case scenario for the multiple fatigue crack problem. The experimental study demonstrates that the growth rate of the near-end point is 1.53 times that of the far-end point and pre-made cracks merge together successfully. By utilizing the BP neural network, the relative error of predicted effective spacing of two cracks is 3.52%. Compared to existing design specifications, the new reconstruction method provides a more reliable result for the fatigue life prediction of the welding seam with multiple fatigue cracks.
摘要：
To investigate the vortex-induced vibration (VIV) of a flexible cable in the uniform flow, experiments were conducted using a flexible cable with an external diameter of 80mm and a length of 10.48m in the wind tunnel. The characteristics of multi-modal VIV, time-frequency and traveling wave behavior of the flexible cable were analyzed. Moreover, the effects of twist direction, diameter and the single/double helical wire on the VIV characteristics of the flexible cable were investigated. It is found that the flexible cable experiences single and multi-modal VIVs in uniform flow at different incoming wind speeds, respectively. For the multi-modal VIV of the flexible cable, the vibration over the time history is dominated by two adjacent modal frequencies and shows a phenomenon of beat vibration. The multi-modal VIV responses of the flexible cable show a mix of standing and traveling wave behaviors, in which the effects of standing wave are more pronounced near both ends and the effects of traveling wave are more dominant in the middle region of the flexible cable. The twist direction of the helical wire has little effect on the VIV responses of the flexible cable. The VIV amplitudes of the flexible cable can be reduced by a single helical wire. With the diameter of the helical wire increases, the suppression effects of the single or double helical wire on the VIV of the flexible cable can be improved. Particularly, the double helical wire with diameter 0.10D can effectively suppress the VIV of the flexible cable.
摘要：
This paper shows that the panic index shadow line difference (ULD) can be an effective predictor of oil returns. We use a candlestick chart to plot the investor panic index (VIX) and subtract the lower shadow from the upper shadow to obtain ULD. The in-sample analysis shows that the ULD can significantly and negatively predict oil returns. The out-of-sample results show that the inclusion of ULD, an exogenous regression variable, in the model not only substantially improves the predictive accuracy of oil returns, but also yields good economic benefits when using its predicted values for portfolio investment. All bivariate regression models that include ULD as an exogenous regression variable obtain higher prediction accuracy than univariate regression models, both for in-sample and out-of-sample predictions. All the robustness tests done in this paper show that ULD is a powerful predictor that significantly improves the predictability of oil returns.
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.
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：
Preventive maintenance;Two-dimensional warranty;Gamma usage process
摘要：
This study considers a manufacturer performing preventive maintenance (PM) on a product according to a one- or two-dimensional (2-D) policy. The one-dimensional PM policy is based on either time or usage, while in the two-dimensional case, PM is scheduled based on both scales. The product carries a 2-D warranty that offers protection for a certain amount of time and usage. Its cumulative usage is continuously monitored by the manufacturer and is assumed to follow a gamma process. In this context, we first propose a doubly stochastic Poisson process model for product failures where the stochastic intensity is influenced by the gamma usage process in an additive manner. We then explicitly derive the expected total costs of the two one-dimensional PM policies using the concepts of first hitting times and gamma bridges. For the 2-D PM policy, we express the associated cost in terms of the value function of a dynamic programming model. In the numerical experiments, we show how the variability of the usage process affects the costs of the three PM policies and find that the optimal 2-D policy degenerates into a one-dimensional policy.
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：
Zero-valent iron (ZVI) reduction represents a promising methodology for water remediation, but its broad application is limited by two critical challenges (i.e., aggregation and passivation). Here, we report a hybrid strategy of photochemical-promoted ZVI reduction with high efficiency and reduction capacity for removing coexisting refractory pollutants in water. A composite material with Pd/Fe bimetallic nanoparticles supported onto semiconducting metal oxide (Pd/Fe@WO(3)-GO) was prepared and subsequently used as the model catalyst. By using the developed strategy with visible light as light source, this catalyst showed a remarkable catalytic performance for simultaneously eliminating 4-chlorophenol (4-CP) and Cr(VI), with dehalogenation rate as high as 0.43min(-1), outperforming the reported ZVI-based catalysts. A synergistic interaction of photocatalysis and ZVI reduction occurred in this strategy, where the interfacial electron transfer on particles surface were greatly strengthened with light irradiation. The activation was attributed to the dual functions of semiconducting material as support to disperse Pd/Fe nanoparticles and as (photoexcited) electron donor to directly trigger reduction reactions and/or indirectly inhibit the formation of oxides passivation layer. Both direct electron transfer and H*-mediated indirect electron transfer mechanisms were confirmed to participate in the reduction of pollutants, while the later was quantitatively demonstrated as the predominant reaction route. Importantly, this strategy showed a wide pH applicability, long-term durability and excellent catalytic performance in different real-water systems. This work provides new insights into ZVI reduction and advances its applications for the removal of combined organic and inorganic pollutants. The developed photochemical-promoted ZVI reduction strategy holds a great potential for practical applications.
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.
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.
