Path Changes Research Articles

Effect of DC poling on transparency and photoluminescence in Pr:PMN-PT transparent ceramics

Electric poling could significantly influence the transparency and the photoluminescence (PL) intensities in transparent ferroelectric PL ceramics. This work applied direct current (DC) poling on a highly transparent 0.75PMN-0.25PT:0.015Pr3+ ceramic, observed the domain configurations in a direction perpendicular to poling direction. Lamellar domains perpendicular to electric field were observed after poling and decreased the transmittance by changing the propagation path of incident light. Besides, the enhancement of PL intensities by poling was found as high as 62 %, mainly due to the following reasons: the change of light propagation path by the lamellar domains is supposed to increase the absorption of exciting light; and the reduced crystal symmetry may increase the PL efficiency. This work revealed the effects of DC poling on transparency and PL properties in transparent ferroelectric PL ceramics.

Modeling Bauschinger effect through the reversibility of dislocation slip in an Al–Cu–Li alloy

Al–Cu–Li alloys are promising lightweight materials for extensive applications in aerospace. As aerospace components often experience strain path changes during service, understanding the resulting Bauschinger effect is crucial for optimizing the fatigue resistance and performance of these alloys. This study investigates the role of T1 precipitates in the Bauschinger effect in AA2099. The presence of shearable T1 precipitates has been found to significantly influence the Bauschinger effect by reducing the strengthening effect of T1 precipitates during reverse straining. An analytical expression for slip reversibility has been derived to quantify this phenomenon, and a microstructure-based constitutive model has been developed to accurately predict the Bauschinger effect in AA2099.

Comparison of homogeneous anisotropic hardening models in the case of the direct redrawing of a DP600 steel

The use of DP600, an advanced high strength steel, has gained significant attention in automotive industry, especially for complex structures that require multi-step forming operations, leading to non-linear strain path changes. From a numerical modelling perspective, the use of advanced constitutive equations has enabled a precise representation of a large range of behaviors, encompassing reverse and orthogonal strain path changes. Within this context, this study is dedicated to the numerical simulation of a two-step deep drawing process based on distortional plasticity. Two models developed within the Homogeneous Anisotropic Hardening (HAH) framework are considered. This study presents a comparison of the model predictions, calibrated over the same experimental database, in terms of their ability to predict the strain path changes and mechanical behavior of the material during the forming process. Several outputs like the punch load evolution and the strain field are compared with experimental data.

Shear band mediated microstructure in an accumulative roll bonded α-brass alloy during strain path changes and annealing

Strain path changes of the accumulative roll bonded 90Cu–10Zn brass and its influence on the shear band structure is the aim of the present study. The effect of post-annealing was also studied in terms of shear bands and texture development. By changing the strain path, the shape of the shear bands has been changed and the material showed two different configurations of shear bands following deformation. Moreover, the XRD-based textural investigations elucidated similarities for the strain paths with similar shear bands. After annealing, a complete restoration occurred for all paths also entailed identical mechanical properties. The development of dual grain size after annealing can also be correlated to the shear band evolution. However, the textural variations for the annealed brass confirmed a textural complexity in shear-banded brass.

方震의 삶과 李舜臣의 관계

This study examines Bang Jin(方震), who was an important helper of Yi Sun-shin(李舜臣) but is not well-known. Bang Jin had his family clan in Onyang Bang and was born in 1514. After growing up in Gyodong Island, he moved to Songsan and settled in Baekamri, Asan following his marriage to a daughter of Hong Yun-pil(洪胤弼). He served as Daejeong Hyeongam(大靜縣監) between 1535 and 1537. It seems that he entered the world of public offices through the Yu-il recommendation system(遺逸薦擧). Later, he passed the military service examination and was appointed as Boseong Gunsu(寶城郡守). His daughter married Yi Sun-Shin in 1565. It was Yi Jun-gyeong(李浚慶) that led a discussion leading to their marriage. He passed the Saengwon examination(生員試) of 1522 along with Bang Guk-hyeong(方國亨), the father of Bang Jin, and Yi Baek-rok(李百祿), the grandfather of Yi Sun-Shin. Bang Jin kept an eye on Yi Sun-Shin who moved from Hanseong and asked Yi Jun-gyeong, one of his father's Dongbangs(同榜), to arrange a match for his daughter. As a result, his daughter married Yi Sun-Shin. Yi Sun-Shin lived at the home of his wife's parents according to the custom of Seoryubuga marriage(婿留婦家婚) and converted his career path from civil service to military service after marriage. In addition to Bang Jin, Bang Woo-ju(方佑周), Bang Hee-min(方希閔), Bang Eung-won(方應元), and Hwang Se-deuk(黃世得) who passed the military service examination were all related to the clan of Onyang Bang. In this sense, the family of his wife had an absolute impact on the career path change of Yi Sun-Shin. Bang Jin, who passed the military service examination, taught books on military science to Yi Sun-Shin as well as martial arts. Moreover, he lavished his economic support on him. As a consequence, Yi Sun-Shin was able to grow into a commander in literary and martial arts and become the hero to led the people to overcome the national crisis during Imjin War.

Analyzing the connectedness among geopolitical risk, traditional energy and carbon markets

This paper studies time-frequency connectedness using the Diebold Yilmaz method and the Baruník and Křehlík method to examine the relationship among geopolitical risk, traditional energy (coal, oil and gas) and carbon markets. First, geopolitical risk shows stable positive net spillovers in the medium and long term, but fluctuates in the short term. Second, the total connectedness is greater in the short term, and strengthened in the period of rising geopolitical risk with the changes of connectedness paths. Third, in general, the carbon market has greater impact on the geopolitical risk than it has been affected. Finally, as a sub-indicator of geopolitical risk index, geopolitical acts index generally contributes more, but natural gas is more affected by geopolitical threats index. Our results provide useful knowledge for governments to realize their goal of policymaking, and help industrial enterprises make timely adjustments to their energy strategies. In addition, we hope that investors can pay attention to the spillover effect and reduce investment risk.

Geometric Control and Structure-at-Infinity Control for Disturbance Rejection and Fault Compensation Regarding Buck Converter-Based LED Driver

Currently, various light-emitting diode (LED) lighting systems are being developed because LEDs are one of the most used lighting sources for work environments, buildings, homes, and public roads in terms of some of their applications. Similarly, they have low energy consumption, quick responses, and excellent optimal performance in their operation. However, these systems still need to precisely regulate lighting, maintain stable voltage and current in the presence of faults and disturbances, and have a wide range of operations in the event of trajectory changes or monitoring tasks regarding the desired voltage and current. This work presents the design and application of two types of robust controllers (structure-at-infinity control and geometric control) applied to an LED driver using a buck converter. The controllers aim to follow the desired trajectories, attenuate disturbances at the power supply input, and compensate for faults in the actuator (MOSFET) to keep the capacitor voltage and inductor current stable. When comparing the results obtained with the two controllers, it was observed that both present excellent performance in the presence of constant disturbances. However, in scenarios in which variable faults and path changes are implemented, the structure-at-infinity control method shows an overimpulse of output voltage and current ranging from 39 to 42 volts and from 0.3 to 0.45 A, with a margin of error of 1%, and it can generate a failure in the LED driver using a buck converter. On the other hand, when using geometric control, the results are satisfactory, achieving attenuating constant disturbances and variable faults, reaching the desired voltage (40 v to 35 v) and current (0.3 to 0.25 A) with a margin of error of 0.05%, guaranteeing a system without overvoltages or the accelerated degradation of the components due to magnetic conductivity.

A Meteorological Drought Migration Model for Assessing the Spatiotemporal Paths of Drought in the Choushui River Alluvial Fan, Taiwan

Understanding drought evolution and its driving factors is crucial for effective water resource management and forecasting. This study enhances the analysis of drought probability by constructing bivariate distributions, providing a more realistic perspective than single-characteristic approaches. Additionally, a meteorological drought migration model is established to explore spatiotemporal paths and related characteristics of major drought events in the Choushui River alluvial fan. The results reveal a significant increase in the probability of southward-moving drought events after 1981. Before 1981, drought paths were diverse, while after 1981, these paths became remarkably similar, following a trajectory from north to south. This is primarily attributed to the higher rainfall in the northern region of the Choushui River alluvial fan from February to April, leading to a consistent southward movement of drought centroids. This study proposes that climate change is a primary factor influencing changes in the spatiotemporal paths of drought. It implies that changes in rainfall patterns and climate conditions can be discerned through the meteorological drought migration model. As a result, it provides the potential for simplifying drought-monitoring methods. These research findings provide further insight into the dynamic process of drought in the Choushui River alluvial fan and serve as valuable references for future water resource management.

A new semi-local centrality for identifying influential nodes based on local average shortest path with extended neighborhood

Quantifying the importance of nodes in complex networks is known as the problem of identifying influential nodes and is considered a critical aspect in interacting with these networks. This problem has many applications such as controlling rumors, sickness spreading, and viral marketing, where its importance has been understood by the research society in the last decade. This paper proposes a new semi-local centrality to identify influential nodes in complex networks based on the theory of Local Average Shortest Path with extended Neighborhood concept (LASPN). LASPN focuses on a distributed technique to extract the subgraph associated with each node and apply the average shortest path theory to it. We use the extended neighborhood concept to find the nearest neighbors of each node with low complexity, where this can lead to high efficiency in dealing with large-scale networks. In addition to applying relative changes in the average shortest path, the proposed metric considers the importance of the node itself as well as its nearest neighbors in ranking the nodes. Evaluation of the proposed centrality metric has been done through numerical simulations on several real-world networks. The results based on Kendall's τ\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\ au$$\\end{document} coefficient under the SIR infection spreading model show that LASPN improves the performance by 2.7% compared to the best available equivalent method.

Wide-Angle Repeat Pass Bistatic SAR Interferometry: A Geometrical Introduction

Positioning a Synthetic Aperture Radar (SAR) receiver at a significant distance from an illuminator in a Low Earth Orbit (LEO) enables wide-angle repeat-pass bistatic interferometry. It’s crucial to define the positioning limits of the receiver with respect to the illuminator to ensure reasonable coherences, altitudes of ambiguity, and a suitable common wavenumber support. I extended the standard monostatic formula, which yields the change in the interferometric travel path due to the vertical baseline. In the wide-angle bistatic case, the range-azimuth coordinate system is no longer orthogonal and we must consider the full 2D vector nature of the LOS orthogonal components. The two vertical baselines and the horizontal baseline of the receiver are needed to parameterize the system. Their impact on the interferometric coherence is quantified and bistatic limits are seen to be more flexible than those in the monostatic case due to the combination of independent baselines. I estimated the coherence, and then extended the analysis to the wavenumber domain, to quantify the common spectral support due to the wavenumber shifts due to the three baselines. The analysis carried out geometrically allows for combining together the effects of the transmitter’s and receiver’s vertical baselines and thus representing the residual spectral fraction with two instead of three parameters. Finally, I examined the achievable spatial resolution of the position of the interferer obtainable from the delay of the arrival of the interference between the illuminator (supposed to be silent) and the receiver.

Study on the evolution of permeability properties of limestone under different stress paths

Abstract Stress path change has a great relationship with the effect of deformation and strength of rock. However, the underground rock body is in the engineering environment where the stress field, seepage field, and other fields are coupled to change, the law of fluid flow in the rock body is complex and variable. The change in the stress field has an important effect on the seepage characteristics of rock body; therefore, it is necessary to study the pattern of rock permeability evolution pattern by different stress paths. This study is based on the study of limestone, conducting triaxial unloading seepage mechanics experiments, the evolution of permeability properties of limestone specimens was analyzed based on the test results. The results show that in the conventional triaxial loading seepage test, the permeability of the limestone decreases before the rock stress reaches the peak intensity and increases after that. Increasing axial pressure unloading surrounding pressure compression section, permeability loss rate and effective stress are in line with the changing law of Gaussian distribution function. Under the action of constant axial pressure unloading surrounding pressure, with the increase in unloading amount, the permeability rate of change appears to increase slowly, and in the late stage of unloading section, the permeability rate of change appears to surge. Unloading section permeability change rate and cumulative unloading amount are in line with the law of change of the exponential function. Creep unloading pressure seepage test found that unloading pressure stage strain-time and permeability-time evolution characteristics are in line with the exponential rule of change. The experimental results of this study can provide an important experimental and theoretical basis for the permeability analysis of low-permeability rock body under complex stress conditions in underground engineering.

Application of distortional plasticity framework to EDDQ and TRIP steel sheets: Prediction of latent hardening and its influence on springback

In this study, the recently developed distortional plasticity model (HAH20) was applied to EDDQ and TRIP steel sheets to account for hardening fluctuations induced by loading path changes. Previous non-linear loading path experiments, which were tension-compression, tension-tension, and tension-shear tests, revealed intricate latent hardening in EDDQ steel and a combination of latent hardening and cross loading contraction in TRIP steel. The HAH20 model was calibrated using tension-compression and 90° tension–45° tension tests with adjustment of setting parameters for accurate latent hardening prediction. Then, a comparison between the HAH20 model and the previous distortional plasticity model (HAH14) in the other independent experiments highlights the superiority of HAH20 model due to its description of latent hardening. Furthermore, for TRIP steel, the HAH20 and HAH14 models were applied to predict springback in a U-draw bending test featuring a novel curved blank subjected to reverse and cross loading states simultaneously. The simulation results show that the HAH20 model predicts springback more accurately than the HAH14 model; however, the main reason is the accurate description of reverse loading in the HAH20 model. This is due to the intricate interplay between cross loading contraction and latent hardening in springback.

Method of settlement calculation for underlying layer of soft soil composite foundation based on load transfer mechanism

The mechanical properties of soil in soft soil area are poor, and the settlement of the underlying layer in the composite foundation accounts for a large proportion of the total settlement. At present, most of the research focuses on the settlement of the reinforced area, and the research on the settlement of the underlying layer is of great significance for the settlement of soft soil composite foundation. The differences in load transfer modes of soil and pile are analyzed, and based on the Boussinesq solution and Mindlin solution, a calculation method for the stress and settlement of the underlying layer in flexible and rigid pile composite foundation is proposed. The relative displacement of soil and pile in flexible pile composite foundation is small, and the negative friction can be ignored, but the influence of effective pile length should be considered. The relative displacement of soil and pile in rigid pile composite foundation is large, so the negative friction should be considered. Part of soil top stress is transmitted to the pile via negative friction, and then the pile axial force is transmitted back to the soil via positive friction. In addition to effective pile length, the change of stress transfer path caused by negative friction should also be considered in settlement calculation.

A physically-based mixed hardening model for the prediction of the ductility limits of thin metal sheets using a CPFE approach

An advanced Crystal Plasticity Finite Element (CPFE) approach is developed to accurately predict the ductility limit strains of thin metal sheets. This method uses polycrystalline unit cells to represent the metal sheets at the macroscopic level. The macroscopic behavior of these unit cells is determined based on that of the constituent single crystals using the periodic homogenization multiscale scheme. At the single crystal scale, the constitutive framework follows a finite strain rate-independent formulation, with the flow rule governed by the Schmid law. The evolution of the single crystal yield surface is described through a physically-based mixed hardening model, where isotropic hardening is characterized by a dislocation density-based formulation, while kinematic hardening is described by the nonlinear Armstrong–Frederick model. The unit cell ductility limit strains are predicted by the Rice bifurcation criterion. The reliability of the mixed hardening model in accurately reproducing mechanical behavior is confirmed through simulations of uniaxial tension/compression loading. Then, the developed computational strategy is used to investigate the impact of key microstructural hardening parameters on the initiation of localized necking under linear strain paths. The numerical predictions reveal the significant influence of these parameters on the formability of thin metal sheets. Additionally, the analysis of ductility limits under non-linear strain paths demonstrates a strong dependency of the numerical predictions on strain path changes. The numerical predictions obtained by the developed CPFE multiscale strategy are compared with experimental results from the literature. In summary, the proposed approach provides a reliable tool for accurately predicting the ductility limits of thin metal sheets, offering valuable insights for engineering applications.

Finding Navigable Paths through Tidal Flats with Synthetic Aperture Radar

Tidal flats are some of the most dynamic coastal environments in the world, where traditional coastal mapping and monitoring provide insufficient temporal resolution to reliably map channels and sand flats. Satellite-based Synthetic Aperture Radar (SAR) enables regular cloud-penetrating detection of water flowing through channels within the tidal flats, referred to as tidal channels. This paper presents a method for detecting a path through tidal channels, using satellite imagery, that supports our understanding and safe exploitation of this valuable coastal environment. This approach is the first proposed to identify navigable paths in all conditions, with SAR images susceptible to variation due to weather and tidal conditions. Tidal channels are known to vary in SAR presentation, and we find that tidal flat presentation is also influenced by conditions. The most influential factor is the wind, with high winds causing an inversion in how both tidal flats and tidal channels present in SAR images. The presented method for the automatic detection of tidal channels accounts for this variability by using previous channel paths as a reference to reliably correct imagery and detect the latest path. The final algorithm produces paths with minor errors in 17.6% of images; the error rate increases to 71.7%, with an almost tenfold increase in errors, when the SAR image and paths are not adjusted to account for conditions. This capability has been used to support the Nith Inshore Rescue in attending call-outs from their base in Glencaple, UK, while the insights from monitoring tidal channels for a year demonstrate how periods of high river flow preceded major changes in the channel path.

Heat transport in an angular-momentum-conserving lattice.

It is expected that the energy-diffusion propagator in a one-dimensional nonlinear lattice with three conserved quantities: energy, momentum, and stretch, consists of a central heat mode and two sound modes. The heat mode follows a Lévy distribution. Consequently, the heat diffusion is super, i.e., the second moment of the diffusion propagator diverges as t^{β} with β>1; and the heat conduction is anomalous, i.e., the heat conductivity is size dependent and diverges with size N by N^{α}, with α>0. In this paper, we study a one-dimensional lattice with two-dimensional transverse motions, in which the total angular momentum also conserves. More importantly, the diffusion of this conserved quantity is ballistic. Surprisingly, the above pictures and the values of the mentioned power exponents keep unchanged. The universality of the scalings is then further extended. On the other hand, the detailed strengths of heat transports are largely enhanced. Such a counterintuitive finding can be explained by the change of the phonon mean-free path of the lattices.

Two-phase flow visualization experiments in variable-aperture fractures: The correlation between flow structure, displacement efficiency and relative permeability

The correlation of flow structure, displacement efficiency and relative permeability for two-phase flow in variable-aperture fractures is critical for many fractured rock applications. A systematic visualization method for two-phase flow experiments was developed and four transparent variable-aperture fracture samples were duplicated by epoxy casting method. A total of 112 times two-phase flow experiments of nitrogen displacing water under various gas flow rates were performed and the corresponding results of images and pressure data during flow process were recorded and analyzed based on optical principles. On the basis of the competition between capillary resistance and inertia force of gas, the flow structure can be generally divided into four states including capillary resistance dominant (CR) state with few flow paths in two lateral sides without fingering flow, competitive (CP) state with the occurrence of clear fingering flow phenomenon, inertia force of gas dominant (IF) state showing more chaotic gas distributions, and steady (SD) state that has few changes in flow paths. The growth of displacement efficiency is greatly affected by the four transition states, in which the increment of displacement efficiency in Frac-1 that has gone through the three states of flow structure approaches 30%, and that of Frac-2 and Frac-3 are about 15%, while Frac-4 with little change of flow structure is less than 10%. As a consequence, the relationship between saturation and relative permeability of gas becomes steeper from Frac-1 to Frac-4 with greater deviation from X, V–C and Corey models due to the smaller variation range of gas saturation, and an improved v-type model is obtained where the exponent n shows a positive correlation to fracture mean aperture.

Cascading failure and resilience optimization of unmanned vehicle distribution networks in IoT

With the development of science and technology, unmanned vehicles have become one of the main ways of distribution, and the appearance of unmanned vehicles undoubtedly brings great convenience to people. However, few researchers consider the cascading failure times for different situations in unmanned vehicle distribution networks. Especially, few researchers have integrated them into maintenance strategies to real-time path changes to increase the reliability of accomplishing distribution tasks and improve resilience after congestion. One of the key issues is how to improve the resilience of distribution network and what maintenance strategies should be developed. In this paper, cascading failures are analyzed and resilience is optimized in unmanned vehicle distribution network. First, cascading failures for different situations are analyzed, and two importance-based diversion methods are proposed to describe the three processes of congestion formation, persistence, and evacuation. Second, failure and performance degradation processes are investigated. Third, the Floyd time-varying resilience optimization algorithm is proposed, and the calculation method of resilience under different strategies is given. At last, simulation results show that the proposed strategy 3 improves the original resilience by 101 % compared with the traditional waiting path strategy.

Efficient hydrogen recovery from wastewater treatment by piezo-photocatalytic heterostructure

Hydrogen (H2) recovery during wastewater treatment has been considered as a promising direction to accomplish environmental sustainability. However, the effective H2 evolution in contaminants degradation process was still a major challenge. In this research, an advanced piezo-photocatalytic induced hydro-energy system is proposed, in consideration of improving the separation and transfer efficiency of photogenerated electrons and holes. As expected, the catalytic performance was significantly enhanced under the stress of ultrasound-induced piezoelectric field (major nitenpyram degradation within 60 min, H2 evolution was 746.56 μmol g−1 h−1). Experiments and density functional theory calculations illustrated that the introduced piezoelectric field directionally tuned the energy band structure of heterostructure, triggering a change in the electron transfer path within the heterostructure, which facilitated the major electrons transferred to zinc oxide (H2 evolution) and holes accumulated in molybdenum sulfide (hydroxyl radical generation), further accelerating contaminants degradation and H2 evolution. Furthermore, the in-depth mechanism of contaminants degradation and H2 evolution under the influence of piezoelectric field was further explored. The piezo-photocatalytic system of this work first accomplished H2 recovery in wastewater treatment on heterostructure, providing a constructive strategy for the design of environmentally sustainable catalytic systems.

Process-based life cycle inventory framework for assessing the carbon footprint of products from complex production paths: Case of dual-phase automotive strip steel

The production paths of industrial products are usually complex, leading to difficulties and a large workload when conducting traditional process-based life cycle assessment (P-LCA). Existing studies on reducing LCA workload have focused mainly on simplifying the process or combining LCA with correlation methods. For complex production paths that cannot be simplified or changed, the methods have weak generality. To fill in these research gaps, a process-based life cycle inventory (P-LCI) framework for complex production paths is proposed. P-LCI contains accurate classification and definition methods for input, output and unit processes, and an interconnection model for calculating process coefficients according to the complexity of the linkages among processes is proposed. Based on the proposed framework, a case study of the dual-phase automotive strip steel (DP) production process is performed. The results show that the production of 1 kg of DP steel consumes 0.679 kg of molten steel from a basic oxygen furnace plant and 0.557 kg from the another. Coke plants produce the largest carbon footprint (CF) per unit of coke, which is 0.889–1.231 kgCO2e/kg-coke. For the cradle-to-gate lifecycle of DP steels, the BFP has the largest CF at 0.614 kgCO2e/kg-DP, accounting for 26.32%. Through the proposed P-LCI framework, unit processes can be clearly defined, and the interconnection model can be used as the basis for environmental impact analysis. When the production path changes, the model can be flexibly adjusted, and the workload of repeated model construction can be reduced.