Curve Evolution Research Articles

One-loop partition function of gravity with leaky boundary conditions

Leaky boundary conditions in asymptotically AdS spacetimes are relevant to discuss black hole evaporation and the evolution of the Page curve via the island formula. We explore the consequences of leaky boundary conditions on the one-loop partition function of gravity. We focus on JT gravity minimally coupled to a scalar field whose normalizable and non-normalizable modes are both turned on, allowing for leakiness through the AdS boundary. Classically, this yields a flux-balance law relating the scalar news to the time derivative of the mass. Semi-classically, we argue that the usual diffeomorphism-invariant measure is ill-defined, suggesting that the area-non-preserving diffeomorphisms are broken at one loop. We calculate the associated anomaly and its implication on the gravitational Gauss law. Finally, we generalize our arguments to higher dimensions and dS.

A continuous-discontinuous deformation analysis method for research on the mechanical properties of coarse granular materials

The mechanical properties of coarse granular materials play a crucial role in the safety of rockfill dams. From a mesoscopic viewpoint, the macroscopic mechanical properties of these materials are a result of the interactions between particles and the progression of particle breakage. Traditional continuum-based numerical methods struggle to accurately analyze the mechanical properties of coarse granular materials. Discontinuous deformation analysis (DDA) is a more suitable algorithm for studying these properties due to its significant benefits in block displacement mode and open-close iteration for contact handling. In this paper, a continuous-discontinuous deformation analysis method (CDDA) based on the conventional DDA is developed for the numerical investigation of coarse granular materials' mechanical properties. This method incorporates critical kinetic damping, multi-stageloading, stricter displacement convergence criteria and particle breakage simulation. It can provide a comprehensive representation of deformation, particle breakage, force chain, shear zone, and stress–strain curve evolutions. The CDDA results are found to be consistent with indoor test results and can more effectively disclose the deformation and failure mechanism of coarse granular materials. Furthermore, CDDA is employed to examine the impacts of particle size and end friction, leading to valuable insights regarding these effects.

Anodic Niobium–Titanium Oxide Crossbar Memristor Arrays for pH Sensing in Liquids

Anodic Nb–Ti oxide crossbar memristor arrays are successfully produced on Si substrates. Their use as pH sensors is tested by analyzing their current–voltage (I–U) sweeps in Ringer´s solutions with different pH values. A gradual evolution of the memristive hysteretic curve is observed upon pH variation. A sensor calibration showing a linear trend with least square error close to 1 is performed and the performance of the pH sensing is assessed. The limit of detection (LOD), limit of quantification (LOQ), and the sensitivity (S) are determined. The calculated LOD is 0.4 pH, and the LOQ is 1.2 pH. The S is calculated as 0.5 pH corresponding to a concentration of c(OH−) = 3.5 mM. The reproducibility and repeatability of the measurements are calculated as 3.8% and 1.4%, respectively. An X‐ray photoelectron spectroscopy survey allows the study of the oxide composition providing information about its pH‐sensing mechanism. It is found that the OH− species diffused into the mixed anodic oxide are responsible for the pH‐induced high‐ to low‐resistance state changes. A conduction mechanism analysis is carried out and Schottky emission is identified as predominant.

Ready for O4 II: GRANDMA observations of Swift GRBs over eight weeks in spring 2022

Aims. We present a campaign designed to train the Global Rapid Advanced Network Devoted to the Multi-messenger Addicts (GRANDMA) network and its infrastructure to follow up on transient alerts and detect their early afterglows. In preparation for O4 II campaign, we focused on gamma-ray burst (GRB) alerts since they are expected to serve as the electromagnetic counterpart of gravitational-wave events. Our goal was to improve our response to the alerts and to start prompt observations as soon as possible, so that we may better prepare the GRANDMA network for the fourth observational run of LIGO-Virgo-Kagra (launched at the end of May 2023) and future missions such as SM. Methods. We set up a dedicated infrastructure and organized a rota of follow-up advocates (FAs) to guarantee round-the-clock assistance to our telescope teams, with an aim to receive, manage, and send out observational plans to our partner telescopes. To ensure a large number of observations, we focused on Swift GRBs whose localization errors were generally smaller than the GRANDMA telescopes’ field of view. This allowed us to bypass the transient identification process and focus on the reaction time and efficiency of the network. Results. During the ‘Ready for O4 II’ phase, 11 Swift/INTEGRAL GRB triggers were selected. Of these, nine fields had been observed and three afterglows had been detected (GRB 220403B, GRB 220427A, GRB 220514A) with 17 GRANDMA telescopes and 17 amateur astronomers from the citizen science project Kilonova-Catcher. Here, we highlight the GRB 220427A analysis, where our long-term follow-up of the host galaxy allowed us to obtain a photometric redshift of z = 0.82 ± 0.09 and its lightcurve evolution, as well as to fit the decay slope of the afterglows and study the properties of the host galaxy. Conclusions. During this eight-week-long GRB follow-up campaign, we successfully fulfilled our goal of training telescope teams for O4 and improving the associated technical toolkits. For seven of the GRB alerts, our network was able to start the first observations less than one hour after the GRB trigger time. We also characterized the network efficiency to observe GRB afterglow given the resulting time delay and limiting magnitude, and to its light curve evolution based on the observation of GRB 220427A.

Breather wave solutions on the Weierstrass elliptic periodic background for the (2 + 1)-dimensional generalized variable-coefficient KdV equation.

In this paper, the Nth Darboux transformations for the (2+1)-dimensional generalized variable-coefficient Koretweg-de Vries (gvcKdV) equation are proposed. By using the Lamé function method, the generalized Lamé-type solutions for the linear spectral problem associated with the gvcKdV equation with the static and traveling Weierstrass elliptic ℘-function potentials are derived, respectively. Then, the nonlinear wave solutions for the gvcKdV equation on the static and traveling Weierstrass elliptic ℘-function periodic backgrounds under some constraint conditions are obtained, respectively, whose evolutions and dynamical properties are also discussed. The results show that the degenerate solutions on the periodic background can be obtained by taking the limits of the half-periods ω1,ω2 of ℘(x), and the evolution curves of nonlinear wave solutions on the periodic background are determined by the coefficients of the gvcKdV equations.

Mechanical behaviours of bedded sandstone under hydromechanical coupling

The combination of the dipping effect and hydromechanical (H-M) coupling effect can easily lead to water inrush disasters in water-rich roadways with different dip angles in coal mines. Therefore, H-M coupling tests of bedded sandstones under identical osmotic pressure and various confining pressures were conducted. Then, the evolution curves of stress-strain, permeability and damage, macro- and mesoscopic failure characteristics were obtained. Subsequently, the mechanical behaviour was characterized, and finally the failure mechanism was revealed. The results showed that: (1) The failure of the sandstone with the bedding angle of 45° or 60° was the structure-dominant type, while that with the bedding angle of 0°, 30° or 90° was the force-dominant type. (2) When the bedding angle was in the range of (0°, 30°) or (45°, 90°), the confining pressure played a dominant role in influencing the peak strength. However, within β∈(30°, 45°), the bedding effect played a dominant role in the peak strength. (3) With the increase in bedding angle, the cohesion increased first, then decreased and finally increased, while the internal friction angle was the opposite. (4) When the bedding angle was 0° or 30°, the “water wedging” effect and the “bedding buckling” effect would lead to the forking or converging shear failure. When the bedding angle was 45° or 60°, the sliding friction effect would lead to the shear slipping failure. When the bedding angle was 90°, the combination of the “bedding buckling” effect and shear effect would lead to the mixed tension-shear failure. The above conclusions obtained are helpful for the prevention of water inrush disasters in water-rich roadways with different dips in coal mines.

The spatiotemporal distribution prediction method for distributed photovoltaic installed capacity based on power supply measurement data

Abstract With the anticipated expansion of distributed power grid integration in the foreseeable future, the consideration of distributed power’s impact on power balance becomes paramount in distribution network planning. In this research, we presented a novel approach for predicting the spatial and temporal distribution of distribution network planning areas, with a specific focus on estimating the installed capacity of distributed photovoltaic (PV) systems. Our method leveraged the saturated capacity of distributed PV, requiring minimal data inputs. By establishing a quantitative model that elucidated the relationship between installed distributed PV capacity and land area, we generated PV installed capacity evolution curves for various types of land. Subsequently, we derived the development coefficient of distributed PV installed capacity. By combining this coefficient with the current status of installed distributed PV capacity in the target area’s land parcels, we forecasted the spatial and temporal distribution of future distributed PV capacity within the region. The proposed prediction model held significant implications for the planning of new distribution networks. Additionally, this study predicted the installed distributed PV capacity for distinct land use types, including residential, commercial, and industrial land, using a regional power supply unit as a representative example. We employed the installed PV capacity unit to forecast the electricity loss rate and energy saving rate within the planning area. By validating the model and method through exemplary test results, we demonstrated the model’s feasibility and accuracy. Furthermore, our model effectively predicted the impact of distributed PV integration on overall load forecasting, thereby offering the power grid more precise load forecasting capabilities.

Automatic mode-locked fiber laser based on adaptive genetic algorithm

A modified adaptive genetic algorithm (GA) is proposed and implemented in a mode-locked erbium-doped fiber laser (EDFL) based on nonlinear polarization rotation. The algorithm combines GAs with adaptive crossover and mutation rates. As the number of iterations increases during the solving operation, the crossover and mutation rates are dynamically adjusted with the change in the fitness function value. A stretched pulse was automatically generated when the modified adaptive GA was continuously optimized to converge the intracavity polarization state to the target state. The average number of generations required to adjust from other states to stretched pulse locking is two, which is better than that afforded by the general GA. The evolution curves of the mode-locked EDFL with different crossover and mutation rates were investigated, and the results indicate the effectiveness of the proposed modified adaptive GA. This study proposes a new scheme for rapid polarization searching in automatic mode-locked fiber lasers.

Mathematical modeling of the hydrogen evolution process on nickel, cobalt, and Co-Ni alloy coatings in acidic and alkaline environments

The content of this study discusses the kinetic issues of hydrogen evolution on metallic surfaces. For this purpose, the electrochemical deposition of Ni, Co, and Co-Ni alloy coatings from chloride baths on chromium-nickel steel (304) substrates was conducted. The deposited materials were then used as the cathode for electrolytic hydrogen evolution. Due to differences in electrochemical reaction mechanisms, the studies were carried out in acidic (0.5 M H2SO4) and alkaline (1 M NaOH) environments. Using different polarization rates (0.05; 0.1; 0.2; 0.5; 1; 2 V/s), cyclic voltammetry (CV) curves were recorded, showing the current intensity as a function of potential. Based on the experimental H2 evolution curves and the ESTYM_PDE program, a mathematical model was developed to determine the parameters of the hydrogen evolution reaction (HER) on the metal and alloy coatings.

Mechanical properties and energy damage evolution mechanism of fiber-reinforced cemented sulfur tailings backfill under uniaxial compression.

This paper studies mechanical properties and energy damage evolution of fiber-reinforced cemented sulfur tailings (CSTB) backfill. The effects of fiber length and fiber content on the stress, toughness and failure properties of the CSTB were systematically revealed. In addition, the energy index evolution law was studied, and the energy damage evolution mechanism of CSTB was revealed. The results show that the deformation failure of fiber-reinforced CSTB mainly goes through four stages: initial crack compaction, linear elastic deformation, yield failure and post-peak failure. The peak stress and residual stress of the CSTB firstly increase and then decrease with the increase of fiber content and the addition of fiber can promote the change from brittle failure to ductile failure of the CSTB. Adding appropriate amount of fiber can improve the toughness of CSTB, and the influence degree of fiber length on the toughness index of CSTB is 6mm>12mm>3mm. The total strain energy increases linearly along the variation of fiber content, while the elastic strain energy and dissipated energy increase exponentially at the peak stress point. In the process of CSTB deformation and failure, "gentle-linear growth-slow growth-rapid decline" is for elastic strain energy, while "gentle-slow growth-rapid growth-linear growth" is for dissipation energy. The damage and failure of CSTB mainly experienced four stages: initial damage, slow growth of damage, accelerated damage and damage failure, and the damage evolution curve also showed the changing characteristics of "gentle-slow growth-rapid growth-linear growth". The CSTB without added fiber showed obvious "Y-type" and "linear-type" shear failure characteristics and the phenomenon of shear cracks penetrating the backfill appeared. No big shear crack occur when it is damaged, showing that the fiber addition restrain the crack growth and improve the overall crack resistance of the CSTB. Hydration products are obviously distributed on the surface of the fiber, which indicates that the fiber will be evenly dispersed in the CSTB and form a certain bonding force with the cement-tailings matrix, thus improving the overall mechanical properties of the CSTB.

A crushing index for granular soils based on comminution energy consumption theory

Particle crushing is a common phenomenon in granular soils, which can affect the physical and mechanical properties of soils. The index which used to quantify the amount of particle crushing is crucial for the relevant research. Based on Kick's comminution energy consumption theory, size potential regarding as a property of soil and representing the energy of particles in a certain state was defined in this study, and a crushing index was proposed based on it. This index was determined according to a density distribution of particle size that voids the problem of sieving error propagation when using a cumulative grain size distribution curve. The validation of the proposed crushing index showed that it could quantitatively describe the amount of particle breakage, regardless of material, gradation, test type and particle size scale. In addition, the proposed crushing index was considered as a soil property index and could be divided into two categories: the ultimate crushing index and the mobilized crushing index, where the mobilized crushing index is obtained from the ultimate crushing index by replacing the ultimate breakage state with the final breakage state. The test results showed that the mobilized crushing index was equivalent to the input energy ratio between current and final breakage states. This relationship contributes to the understanding of the evolution of the grading curve caused by particle breakage.

On the curve evolution with a new modified orthogonal Saban frame

On the curve evolution with a new modified orthogonal Saban frame

On the evolution of Betti curves in the cosmic web

On the evolution of Betti curves in the cosmic web

Research on Cumulative Damage Induced by Cyclic Blasting of Tuff

This article establishes a numerical model for cumulative damage of surrounding rock that can simulate the characteristics of progressive cyclic blasting in tunnels based on explicit dynamics and “restart” technology, and conducts research on the cumulative damage law of surrounding rock induced by tunnel blasting. The results show that: (1) considering the characteristics of progressive cyclic blasting in tunnels, the degree and range of surrounding rock damage are significantly increased compared to single blasting, with an increase of about 50%; (2) the amount of damage caused by blasting in the surrounding rock follows a Boltamann function (S-shaped curve) evolution feature as the distance between the blasting centers increases. In practical applications, when evaluating the degree and range of damage to the surrounding rock at the current location, additional cumulative damage caused by adjacent footage cycles should be considered, and the damage value can be 1.5 times the damage value of the current single blasting condition

Identifying winner-takes-all emergence in random nanowire networks: an inverse problem.

Random nanowire networks (NWNs) are interconnects that enable the integration of nanoscopic building blocks (the nanowires) in a disorganized fashion, enabling the study of complex emergent phenomena in nanomaterials and built-in fault-tolerant processing functionalities; the latter can lead to advances in large-scale electronic devices that can be fabricated with no particular array/grid high-precision pattern. However, when various nanowires are assembled to form an intricate network, their individual features are somehow lost in the complex NWN frame, in line with the complexity hallmark "the whole differs from the sum of the parts". Individual nanowire materials and geometrical features can only be inferred indirectly by attempting to extract information about their initial conditions from a response function measurement. In this work, we present a mathematical framework that enables inference of the intrinsic properties of highly complex/intricate systems such as random NWNs in which information about their individual parts cannot be easily accessed due to their network formation and dynamical conductance behaviour falling in the category of memristive systems. Our method, named misfit minimization, is rooted in nonlinear regression supervised learning approaches in which we find the optimum parameters that minimize a cost function defined as the square least error between conductance evolution curves taken for a target NWN system and multiple configurational NWN samples composing the training set. The optimized parameters are features referent to the target NWN system's initial conditions obtained in an inverse fashion: from the response output function, we extract information about the target system's initial conditions. Accessing the nanowire individual features in a NWN frame, as our methodology allows, enables us to predict the conduction mechanisms of the NWN subjected to a current input source; these can be via a "winner-takes-all" energy-efficient scheme using a single conduction pathway composed of multiple nanowires connected in series or via multiple parallel conduction pathways. Predicting the conduction mechanism of complex and dynamical systems such as memristive NWNs is critical for their use in next-generation memory and brain-inspired technologies since their memory capability relies on the creation of such pathways activated and consolidated by the input current signal.

Epidemic spreading under game-based self-quarantine behaviors: The different effects of local and global information.

During the outbreak of an epidemic, individuals may modify their behaviors in response to external (including local and global) infection-related information. However, the difference between local and global information in influencing the spread of diseases remains inadequately explored. Here, we study a simple epidemic model that incorporates the game-based self-quarantine behavior of individuals, taking into account the influence of local infection status, global disease prevalence, and node heterogeneity (non-identical degree distribution). Our findings reveal that local information can effectively contain an epidemic, even with only a small proportion of individuals opting for self-quarantine. On the other hand, global information can cause infection evolution curves shaking during the declining phase of an epidemic, owing to the synchronous release of nodes with the same degree from the quarantined state. In contrast, the releasing pattern under the local information appears to be more random. This shaking phenomenon can be observed in various types of networks associated with different characteristics. Moreover, it is found that under the proposed game-epidemic framework, a disease is more difficult to spread in heterogeneous networks than in homogeneous networks, which differs from conventional epidemic models.

Regulating structural stability and photoelectrical properties of FAPbI3via formamidine cation orientation.

Organic cations play a significant role in the structural stability and photoelectrical properties of organic-inorganic hybrid perovskites. The orientation of organic cations impacts its interaction with inorganic octahedrons [PbI]6-, subsequently modifying the atomic structure and electronic and optical properties of perovskite materials. However, it is still challenging to regulate the stability of perovskites with different orientations. In this work, density functional theory calculations were performed to investigate the effects of the formamidine cation (FA+) located at the angles of 0°, 45°, 90° and 180° (relative to the normal of the crystal plane) along the typical crystal directions ([001], [010], [110] and [111]) on the structural stability and photoelectrical properties of formamidine lead iodide (FAPbI3). The results show that when FA+ is located at 45° along the [111] direction, FAPbI3 achieves the highest stability and excellent photoelectrical properties. The energy evolution curves display that the system with the orientation of [111] has the minimum energy value, signifying stronger stability than the other orientations. Especially, when FA+ is located at 45° along the [111] direction. it exhibits a stronger hydrogen bond between H and I atoms, shorter Pb-I bond length and smaller [PbI]6- octahedral tilt bond angle. The band gap in the [110] direction changes from direct to indirect while FAPbI3 with other FA+ orientations still maintains the direct band structure located at the high symmetric R point. Furthermore, FA+ orientation drives the redshift of FAPbI3 towards the long wavelength region in the [111] crystal direction, which enhances the light absorption coefficient. This work can offer guidance in employing molecular regulation technology for the development of stable perovskite solar cells.

ADVANCED AUTOMATIC SYSTEM FOR REMOTE CONTROL IN THE OIL AND GAS INDUSTRY

The purpose of this work is to design and implement a cascade control system of the level with the flow rate, with remote supervision, in an industrial type installation, located in the Laboratory of Measurement Techniques, Department of Automation, Computers and Electronics, within the Faculty of Mechanical and Electrical Engineering. The operating parameters of the installation are as follows: suction pressure: 0 – 2 bar; discharge pressure: 0 -10 bar; water flow: 0-30 m3/h; transported liquid: water. The automation system is structured on three hierarchical levels: level 1: the instrumentation mounted on the installation (transducers, signaling devices, etc.); level 2: includes the TGA System; level 3: constitutes the upper hierarchical level and includes the HMI (Human Machine Interface). The TGA system is a computerized system that ensures the monitoring, command and control functions of all the stand's component elements. It contains a programmable logic controller PLC 1214 – Siemens, which communicates via an Ethernet IP network with an operator interface and with the network of the Faculty of Mechanical and Electrical Engineering, which allows remote control of the installation. It also includes the protection system in case of failure, which involves stopping the rotating equipment, isolating the pipes by closing the control valve and alarming the operators. The HMI (Human Machine Interface) interface presents 3 options on the start page, from where the operator can select which application he wants to test: flow control loop application; level adjustment loop application; cascade adjustment loop application. The HMI equipment integrates SCADA functions, database update, evolution curves of analog quantities, sound and monitor alarm system, keyboard command, periodic records, event records, alarm records and technological schemes at the human-machine interface. The entire software is made in an open architecture, recommended by ISO norms. The PLC communicates in the network by adopting the protocol TCP/IP. An executable program used for the real-time application program was developed.

HNBR and NBR gasket rubbers for plate heat exchangers: Thermo‐oxidative aging and service lifetime prediction

AbstractAmong several available rubbers used in gaskets for plate heat exchangers, the selection of the appropriate material for each operation window is crucial. This work evaluated nitrile butadiene rubber (NBR) and hydrogenated butadiene rubber (HNBR) gaskets aged at high temperatures for up to 60 days. The properties assessed of compression set (CS), hardness, and cross‐link density demonstrated superior degradation rates for the NBR specimens. Fourier transform infrared analysis showed that the hydrogenation process predominantly affected CC double bonds. Compress stress relaxation highlighted the impact of aging on the counterforce of rubber over time. Furthermore, indentation modulus profile analysis showed heterogeneous degradation for both materials at 140°C for NBR and 170°C for HNBR. The end‐of‐life criteria of 79% CS for both materials were determined through sealing tests of the aged samples. The service lifetime prediction, using the time–temperature superposition and Arrhenius methods through the CS evolution curves, demonstrated a higher degradation resistance of HNBR gaskets, that have a superior service lifetime of at least 3.5 times at 80°C concerning those of NBR, proving a superior behavior for the hydrogenated elastomer. In addition, the evaluation of the lifetime prediction enables the verification of which rubber gasket is recommended for each operational condition in terms of material cost, service lifetime, and maintenance costs.

Comprehensive surface integrity evaluation during early stages of gear contact fatigue

The study aims to evaluate the microstructural sensitive aspects of contact fatigue crack initiation and its evolution during the gear lifetime. Tests were performed to evaluate different stages in the evolution curve of gear contact fatigue. The magnetic Barkhausen noise (MBN) technique was used to characterize variations in the magnetic response in gears during the incipient gear contact fatigue mechanisms initiation. For a complete comprehension of the surface degradation, residual stresses, microstructure, and microhardness were explored. A substantial increase in the MBN signal is identified before the fatigue failure occurs, indicating the occurrence of microstructural alterations that change the magnetic properties. The early stages of contact fatigue are accompanied by a surface softening in the near-surface region, up to approximately 40 µm depth. These phenomena were also followed by a less compressive residual stress region at 20 µm depth. A lower influence of microstrains on the diffractogram can be observed by the full width at half maximum parameter (FWHM), indicating a higher amount of dislocation annihilation during the appearance of the initial stages of the contact fatigue mechanism. The study concludes by proposing a comprehensive approach to understand the mechanisms behind the early stages of gear contact fatigue and how the MBN signal can be used to detect fatigue damage.