Fixed Boundary Flows

We consider the fixed boundary flow with canonical interpretability as principal components extended on the non-linear Riemannian manifolds. We aim to find a flow with fixed starting and ending point for multivariate datasets lying on an embedded non-linear Riemannian manifold, differing from the principal flow that starts from the center of the data cloud. Both points are given in advance, using the intrinsic metric on the manifolds. From the perspective of geometry, the fixed boundary flow is defined as an optimal curve that moves in the data cloud. At any point on the flow, it maximizes the inner product of the vector field, which is calculated locally, and the tangent vector of the flow. We call the new flow the fixed boundary flow. The rigorous definition is given by means of an Euler-Lagrange problem, and its solution is reduced to that of a Differential Algebraic Equation (DAE). A high level algorithm is created to numerically compute the fixed boundary. We show that the fixed boundary flow yields a concatenate of three segments, one of which coincides with the usual principal flow when the manifold is reduced to the Euclidean space. We illustrate how the fixed boundary flow can be used and interpreted, and its application in real data

AIGC In China: Current Developments And Future Outlook

The increasing attention given to AI Generated Content (AIGC) has brought a profound impact on various aspects of daily life, industrial manufacturing, and the academic sector. Recognizing the global trends and competitiveness in AIGC development, this study aims to analyze China's current status in the field. The investigation begins with an overview of the foundational technologies and current applications of AIGC. Subsequently, the study delves into the market status, policy landscape, and development trajectory of AIGC in China, utilizing keyword searches to identify relevant scholarly papers. Furthermore, the paper provides a comprehensive examination of AIGC products and their corresponding ecosystem, emphasizing the ecological construction of AIGC. Finally, this paper discusses the challenges and risks faced by the AIGC industry while presenting a forward-looking perspective on the industry's future based on competitive insights in AIGC

TB147: Simulating the Development of Mexican Bean Beetle Immature Stages, Epilachna varivestis Mulsant (Coleoptera: Coccinellidae), on Dry Beans

A computer model was developed to simulate and predict the phenology of Mexican bean beetle (MBB), Epilachna varivestis Mulsant, populations on dry beans, Phaseolus vulgaris. Time-varying distributed developmental rates of the egg, four larval instars, and pupal stages were simulated with degree day models, based on a standardized cumulative probability distribution function from a range of constant temperature experiments. Predictions from the simulation model provided a good fit to the observed constant temperature data and field experiments. Using temperature data in the form of daily maximums and minimums, the model can be used to predict the occurrence of immature MBB stages under field conditions, when the frequency distribution of egg mass recruitment is known.https://digitalcommons.library.umaine.edu/aes_techbulletin/1204/thumbnail.jp

The current opportunities and challenges of Web 3.0

With recent advancements in AI and 5G technologies,as well as the nascent concepts of blockchain and metaverse,a new revolution of the Internet,known as Web 3.0,is emerging. Given its significant potential impact on the internet landscape and various professional sectors,Web 3.0 has captured considerable attention from both academic and industry circles. This article presents an exploratory analysis of the opportunities and challenges associated with Web 3.0. Firstly, the study evaluates the technical differences between Web 1.0, Web 2.0, and Web 3.0, while also delving into the unique technical architecture of Web 3.0. Secondly, by reviewing current literature, the article highlights the current state of development surrounding Web 3.0 from both economic and technological perspective. Thirdly, the study identifies numerous research and regulatory obstacles that presently confront Web 3.0 initiatives. Finally, the article concludes by providing a forward-looking perspective on the potential future growth and progress of Web 3.0 technology

Modelling cracking damage of asphalt mixtures under compressive monotonic and repeated loads using pseudo J-integral Paris’ law

Field observations and mechanical analyses have shown that cracks accompany rutting in asphalt mixtures under external compressive loads. This study aims to model crack growth in asphalt mixtures under compressive monotonic and repeated loads. Using energy equilibrium and viscoelastic Griffith fracture criterion, a damage density characterising the cracks in mixtures is derived as a function of stress, nonlinear viscofracture strain, asphalt film thickness and bond energy. Crack evolution is modelled by pseudo J-integral Paris’ law. Six types of asphalt mixture were tested by monotonic compressive strength tests at 40°C. Two were further tested at four more temperatures and four more loading rates, respectively. Repeated load test results for the same mixtures were obtained from previous studies. The different shape of the damage density curve (S-shape for monotonic load and increasing exponential shape for repeated load) demonstrates the dependence of damage growth on loading mode, due to different energy release rates. Pseudo J-integral Paris’ law can model the crack growth in mixtures and capture the post-peak softening behaviour under a monotonic load. The Paris’ law coefficients (A and n) are independent of loading mode (monotonic or repeated), rate or temperature. They are fundamental material properties and can be used to predict crack growth under varying loading and temperature conditions

Impact of biological clogging on the barrier performance of landfill liners

The durability of landfill mainly relies on the anti-seepage characteristic of liner system. The accumulation of microbial biomass is effective in reducing the hydraulic conductivity of soils. This study aimed at evaluating the impact of the microorganism on the barrier performance of landfill liners. According to the results, Escherichia coli. produced huge amounts of extracellular polymeric substances and coalesced to form a confluent plugging biofilm. This microorganism eventually resulted in the decrease of soil permeability by 81%–95%. Meanwhile, the increase of surface roughness inside the internal pores improved the adhesion between microorganism colonization and particle surface. Subsequently, an extensive parametric sensitivity analysis was undertaken for evaluating the contaminant transport in landfill liners. Decreasing the hydraulic conductivity from 1 × 10−8 m/s to 1 × 10−10 m/s resulted in the increase of the breakthrough time by 345.2%. This indicates that a low hydraulic conductivity was essential for the liner systems to achieve desirable barrier performance

Molecular dynamics investigation of interfacial adhesion between oxidised bitumen and mineral surfaces

The interfacial adhesion between oxidised bitumen and mineral surfaces at dry and wet conditions was investigated using molecular dynamics (MD) simulations. Molecular models were built for virgin and oxidised bitumen components including saturate, aromatic, resin and asphaltenes. The bitumen models and four representative mineral substrates (namely quartz, calcite, albite and microcline) were employed to construct bitumen-mineral interface systems. These models were validated by the experimental results and MD simulations reported in the literature. The hardening mechanism of the aged bitumen was analysed by comparing the density, cohesive energy density and fraction of free volume between the virgin and oxidised bitumen. Work of adhesion was computed to quantify the adhesive bonding property of the bitumen-mineral interface systems for the virgin, lightly oxidised and heavily oxidised bitumen models under dry and wet conditions. Results show that the oxidised products (carbonyl and sulfoxide) strengthen the intermolecular bonding, resulting in molecular aggregation and physical hardening of the aged bitumen. When bitumen becomes oxidised at the dry condition, the interfacial adhesion of bitumen-acidic minerals (quartz) is dominated by van der Waals interaction which decreases due to the increased bitumen-quartz intermolecular distance caused by the aggregated bitumen molecules during aging. In comparison, the interfacial adhesion of bitumen-strong alkali minerals (albite and microcline) is dominated by electrostatic energy which increases due to higher polarity introduced by the oxidised products. For the bitumen-weak alkali mineral (calcite), the interfacial adhesion is attributed to both electrostatic energy and van der Waals energy, where compared to the virgin bitumen, the electrostatic energy becomes lower for the lightly-oxidised bitumen due to the increased bitumen-mineral distance but becomes higher for the heavily-oxidised bitumen due to higher polarity. At wet condition, water is the dominating factor that affects (weakens) the interfacial adhesion between the bitumen and the acidic minerals (quartz), and the oxidative aging of bitumen is the major factor that affects (strengthens) the interfacial adhesion between the bitumen and the strongly alkaline minerals (albite and microcline). For the weak alkali minerals such as calcite, both water and bitumen aging can significantly affect the interfacial adhesion

Impact of minerals and water on bitumen-mineral adhesion and debonding behaviours using molecular dynamics simulations

This study aims to evaluate the effects of mineral types and water on the adhesion properties and debonding behaviours of bitumen-mineral interface systems. A molecular dynamics modelling approach was employed to simulate the interactions between minerals and bitumen with and without the presence of water. Four representative minerals (quartz, calcite, albite and microcline) were selected to build the mineral-bitumen interface systems and the mineral-water-bitumen interface systems in the molecular dynamics models. The adhesion property between minerals and bitumen was quantified by work of adhesion, defined as the energy required to separate a unit area of the bitumen-mineral interface. The debonding behaviour between minerals and bitumen is characterised by work of debonding, defined as the energy required to displace bitumen by water at the mineral-bitumen interface. The simulation results were validated by available experimental results reported in the literature. It was found that the work of adhesion and the work of debonding for the four bitumen-minerals interface systems are ranked microcline > albite > calcite > quartz at both dry and wet conditions. Moisture can reduce the adhesion between minerals and bitumen by 82%, 84%, 18% and 1% for the quartz, calcite, albite and microcline, respectively. The adhesion between minerals and bitumen is attributed to the non-bond interaction energy, in which the major component is van der Waals interaction for neutral minerals (e.g., quartz) and the electrostatic interaction for the alkali minerals (e.g., calcite, albite and microcline). The bitumen-mineral debonding is a thermodynamically favourable process with reduced total potential energy of the system. It is concluded that the bitumen-mineral adhesion and debonding behaviours strongly depends on the chemistry and mineralogical properties of the minerals. This work provides a fundamental understanding of the adhesion and debonding behaviours of the bitumen-mineral interface at the atomistic scale

Kinetics-based aging evaluation of in-service recycled asphalt pavement

Reclaimed asphalt pavement (RAP) is a type of material that already suffers long-term aging in the field, so its aging characteristics become prominent since they are closely related to premature distresses and longevity of recycled pavements. While most of investigations of RAP mixtures are carried out in the laboratory, this study focuses on in situ aging of asphalt pavements with RAP overlays. A kinetics-based aging modeling approach is proposed to analyze and quantify long-term field aging of RAP overlays using the Falling Weight Deflectometer (FWD) data and climate data. The kinetics-based approach contains a modulus aging model with kinetic parameters (e.g. aging activation energy) for asphalt mixtures. Eight asphalt overlays are selected with different mixtures (RAP and virgin), thickness (50 mm and 125 mm), and surface preparation (milling and no milling). An asphalt pavement with an overlay has a composite aging process since the aging speeds of different asphalt layers are different. Thus an approach to separate the FWD modulus is developed in order to obtain the actual aging behaviors and properties of the overlay. By applying the kinetics-based modeling to the separated FWD moduli, the aging activation energies of both the overlays and old asphalt layers are determined. It is found that the RAP overlay has the highest aging activation energies and slowest aging rates among the RAP overlay, virgin overlay, and old asphalt layer for the selected pavements. It also reveals through the aging activation energy that the thick overlays age slower than thin ones, and the overlays on milled pavements age slower than those placed without milling. The findings in terms of the aging activation energy can be used to explain the difference in the field performance of overlay pavement sections