Energy Space Research Articles

Weak and strong solutions for a fluid‐poroelastic‐structure interaction via a semigroup approach

A filtration system comprising a Biot poroelastic solid coupled to an incompressible Stokes free‐flow is considered in 3D. Across the flat 2D interface, the Beavers‐Joseph‐Saffman coupling conditions are taken. In the inertial, linear, and non‐degenerate case, the hyperbolic‐parabolic coupled problem is posed through a dynamics operator on a chosen energy space, adapted from Stokes‐Lamé coupled dynamics. A semigroup approach is utilized to circumvent issues associated to mismatched trace regularities at the interface. The generation of a strongly continuous semigroup for the dynamics operator is obtained via a non‐standard maximality argument. The latter employs a mixed‐variational formulation in order to invoke the Babuška‐Brezzi theorem. The Lumer‐Philips theorem then yields semigroup generation, and thereby, strong and generalized solutions are obtained. For the linear dynamics, density obtains the existence of weak solutions; we extend to the case where the Biot compressibility of constituents degenerates. Thus, for the inertial linear Biot‐Stokes filtration system, we provide a clear elucidation of strong solutions and a construction of weak solutions, as well as their regularity through associated estimates.

Environmental challenges and economic cooperation between Ukraine and the EU: prospects for sustainable development

The article is dedicated to analyzing the cooperation between Ukraine and the European Union, which began with the signing of the Partnership and Cooperation Agreement in 1994 and reached a new level after the signing of the Association Agreement in 2014. The focus is on the impact of this agreement on Ukraine’s domestic and foreign policies, particularly in the context of sustainable development and ensuring environmental security. The article examines the role of international agreements in regulating Ukraine’s environmental policy, particularly the principles of preventive measures and the use of natural resources within the framework of sustainable development. Despite the formal incorporation of relevant provisions in international treaties, the real situation regarding environmental security remains challenging due to the conflict between the economic interests of developed countries and transnational corporations and the demands of environmental protection. The article separately addresses the influence of international law on the development of Ukraine’s energy policy and its integration into the pan-European energy space. The importance of transitioning to renewable energy sources and the role of the European Union in financing and supporting such projects are analyzed. It is noted that sustainable development and environmental protection should become priorities within the framework of Ukraine’s energy security policy. The article also outlines the main challenges Ukraine faces in the context of international environmental security, particularly the insufficient effectiveness of international organizations in recognizing and counteracting environmental crimes. Despite this, the importance of cooperation with the EU to achieve a stable deceleration of environmental degradation is emphasized.

Weakly coupled systems of semilinear σ$$ \sigma $$‐evolution equations with friction and visco‐elastic type damping

In the present paper, we are interested to study global (in time) existence of small data Sobolev solutions to the Cauchy problem for a weakly coupled system of two semilinear ‐evolution equations with friction and visco‐elastic type damping, where for . We study model (1.1) (see below) in several cases with respect to the regularity for the data: First, we assume data . By using estimates of Sobolev solutions to related linear models with vanishing right‐hand side, we explain the admissible range of exponents in (1.1) which allow to prove the global (in time) existence of small data Sobolev solutions. Then we suppose that the data belong to , where now , . So the data have additional regularity to the first assumed integrability. We restrict ourselves to data from energy space (on the basis of ) and from energy space with additional suitable higher regularity. We compare in our statements the admissible set of exponents and in the power nonlinearities with the so‐called modified Fujita exponent. Finally, some blow‐up results complete the paper.

ЕНЕРГЕТИЧНИЙ РИНОК УКРАЇНИ : СТВОРЕННЯ УМОВ ДЛЯ ЕФЕКТИВНОГО ЕНЕРГОЗАБЕЗПЕЧЕННЯ

The article analyzes the theoretical foundations of the formation of energy security on the energy market of Ukraine in the context of European integration processes, and states that energy security is a component of the state's national security. The main advantages of long-term contracts for all energy market participants are indicated. Features of the functioning of consumer companies in the competitive market are highlighted. The main risks for large consumers when working on the day-ahead market are presented. Factors of the expediency of functioning on the balancing segment are given. Current trends in the development of world energy and their impact on energy security are analyzed. The necessity of diversification of energy supply sources for Ukraine is substantiated. The influence of the European integration processes on the reform of the energy sector of Ukraine is studied. The current state of the energy market was analyzed, and the analysis of factors affecting development trends and ensuring protection in the energy market was carried out. The influence of the European integration processes on the reform of the energy sector of Ukraine is studied. The conjuncture of the energy market of Ukraine is determined, in which it is necessary to analyze not only the peculiarities of the domestic sphere, but also the influence of international relations, international trade and the world market. The PEST analysis of the energy industry of Ukraine is presented, which allowed to identify the level of influence and the neighborhood of the group of influencing factors on the formation of the strategic potential of the energy market of Ukraine. Directions for increasing the level of energy security through modernization of the energy infrastructure, development of renewable energy sources, and integration into the European energy space are proposed. It is noted that the creation of conditions for the effective use of internal resources and the development of appropriate technologies are of strategic importance. The country's government is working on integration into the European energy community, which requires compliance with European standards and the implementation of effective management models of the energy market of Ukraine. According to the results of the strategic potential of the energy industry of Ukraine, economic factors exert the greatest influence - 1.147, which just emphasizes the important role of the energy industry in the country's economy. In second place in terms of influence are political factors - 0.847. The analysis of the market just showed the rather important role of the political component in the functioning of the energy market of Ukraine, namely in the aspect of its joining the European energy market and the transformation of Ukraine into the European Union with the rights of an equal state. In third place are technological factors - 0.553, which confirm Ukraine's determination to decarbonize the energy market. And the fourth place is occupied by socio-cultural factors - 0.537, which are only marginally inferior to technological factors. This indicates a strong influence of consumer preferences when choosing interaction models in the market.

Unveiling full-dimensional distribution of trap states toward highly efficient perovskite photovoltaics

To gain a deep understanding and address key issues in perovskite photovoltaics, such as power conversion efficiency (PCE) and long-term stability, defect passivation and analysis of the device performance are required. Here, we proposed a non-contact characterization technique named scanning photocurrent measurement system (SPMS) for device surface detection, having conducted signal analysis and method adjustments based on perovskite photovoltaic devices. This technique enables the monitoring of minority carriers in the device, allowing for the investigation of carrier behavior based on photocurrent signals. By integrating SPMS with thermal conductance spectroscopy (TAS) and drive-level capacitance profiling (DLCP), we further simulated a spatial three-dimensional (3D) distribution of trap states in the device and analyzed the distribution of trap states matched with energy space. Through extensive case studies, we have validated the universality and accuracy of this method. The integration of trap state characterization techniques provides strong support for targeted defect passivation and performance evaluation of perovskite photovoltaic devices, yielding a highly efficient perovskite solar cell with PCE as high as 25.74%.

Fault diagnoses of a nonlinear cracked rotor-bearing system based on vibration energy space and incremental learning approach

Health services of rotor-bearing systems are directly related to safe and stable works of rotating machineries in the industrial production. To address the issues of a low impact on vibration characteristics caused by faults in the higher rotational speed region, narrow and weak excitation signals, high dimensionality related to fault induction mechanisms, and difficulty in diagnosing using artificial intelligence technology due to the small number of fault samples in rotor systems, a novel fault detection method of nonlinear rotor systems through the incremental two-dimensional principal component analysis (I2DPCA) of the machine learning on the vibration energy space is proposed. Unlike mainly analyzing dynamic characteristics of rotor-bearing systems in vibration space, the method applies signals of the vibration energy space such as energy tracks, energy-time histories and energy-frequency spectra to have more advantages in vibration amplitudes caused by cracks in the higher rotational speed region and to overcome narrow and weak signals in the early fault stage. Then, the I2DPCA is applied to extract online low dimensional fault features and to process small vibration features of the rotor system. Simulation and experiment results show that performances of between-class margins and within-class clusters of different health conditions on the vibration energy space are more perfect than that on the vibration space. Based on the I2DPCA algorithm and the energy space method, the recognition rate of crack faults within the high rotational speed region is up to 99.6%, and it has good convergence and online learning ability in the case of small samples. The achieved conclusions of the method could provide a novel reference direction for fault diagnoses of rotor systems.

On the Cauchy problem for logarithmic fractional Schrödinger equation

We consider the fractional Schrödinger equation with a logarithmic nonlinearity, when the power of the Laplacian is between zero and one. We prove global existence results in three different functional spaces: the Sobolev space corresponding to the quadratic form domain of the fractional Laplacian, the energy space, and a space contained in the operator domain of the fractional Laplacian. For this last case, a finite momentum assumption is made, and the key step consists in estimating the Lie commutator between the fractional Laplacian and the multiplication by a monomial.

In situ decorated Mn-FeOx amorphous oxides on filter felt by a polyphenol-assisted method for low-temperature NH3-SCR

The combination of dust filtration technology and selective catalytic reduction of nitrogen oxides can effectively reduce the energy consumption and footprint of the flue gas purification system. To fabricate the high efficiency and firmly bonded catalytic filter material, a novel polyphenol-assisted method was designed in this work for in situ decorating Mn-FeOx amorphous oxides onto the smooth polyphenylene sulfide (PPS) filter felt. The polyphenolic compounds are not only worked as the dispersant, but also the binder for Mn-FeOx catalysts to firmly anchor on PPS filter felts. The introduction of Fe3+ into catalyst precursors can increase the Mn4+ content, surface adsorbed oxygen, as well as surface acidity, which displays satisfactory denitration performance and SO2 tolerance at low temperatures. The Mn5Fe1-TA/PDA@PPS sample shows nearly 100 % NO conversion efficiency at 180 °C with only 10.11 % catalysts loading in the sulfur dioxide free flue gas. Furthermore, the green and efficient synthesis route makes the catalytic filter felts preserve the same gas permeability and thermal stability with the pristine PPS filter felt, which suggests that the Mn5Fe1-TA/PDA@PPS has great prospects for simultaneously removing of NOx and dust in practical applications.

Space and time distribution of seismic source energy at Campi Flegrei, Italy through the last unrest phase (1.1.2000–31.12.2023)

We describe the space-time pattern of seismicity occurring on Campi Flegrei Caldera (CFC), Italy, where ground deformations and seismicity represent the drivers of its current bradyseismic crisis, well known and extensively studied at an international level. In detail we consider the seismicity in the time interval starting on 1.1.2000 and ending on 31.12.2023. We revise the statistics of the earthquake occurrence, focusing at possible precursory time changes of the b-parameter of the Gutenberg and Richter (G&R b−value) distribution and at the time distribution of the total seismic moment inside any swarm. To estimate the G&R b−value we use a Monte Carlo method instead of the ordinary Least Squares or Maximum likelihood methods, to easily measure the uncertainty on the b−value taking into account uncertainties on the magnitude estimates. Results show that G&R a−value and b−value calculated for cumulative and discrete distributions of Mw, the moment-magnitude, and Md, the so-called duration-magnitude, are the same inside the uncertainties; a−value and b−value for Md are significantly different from the same parameters estimated for Mw, being b−value for Mw close to the value of 1.0 and b−value for Md close to 0.8. The “bounded” G&R distribution fits the data yielding a−value and b−value close to those for the unbounded distribution. The mean annual rate of exceedance, calculated for the entire catalogue, results to be 0.033±0.015 (years−1) corresponding to a return period of 30±14 years for Mw=4.5. The time dependence of G&R b-parameter show a b−value time pattern characterized by variations slightly outside 1-σ uncertainty bar, tending to the value of 1 approaching present. As evidenced by several past studies, earthquakes in CFC occur in space-time clusters, with a mean time duration of 1 day. We selected the swarms with a selection algorithm, based on the joint estimation of inter-arrival times and inter-event distance for the consecutive event couples. The plot of the event number in each cluster vs the time of occurrence, clearly show that in CFC the number of cluster occurrences and the event number in each cluster accelerates during time starting from 2010. The time-pattern of the total seismic moment in each cluster shows that, contrarily to the event number, there is no evident striking increase of the total swarm moment as a function of time.We also consider distribution of the Energy Space Density of the CFC earthquakes, ESD. This quantity shows a clearly visible enlargement of the fractured rock volumes in the last 15 months, toward West, at a depth around 3000 m below sea level. The most fractured zone coincides with the greatest contrasts in seismic attenuation.The present study confirms that the current unrest phase is still ongoing, with an enlargement of the rock fracturing zone which extends southward and westward as compared with that measured 22 months before.

Toward direct band gaps in typical 2D transition-metal dichalcogenides junctions via real and energy spaces tuning

Most of the van der Waals homo- and hetero-junctions of group VIB two-dimensional (2D) transition-metal dichalcogenides (TMDs; MoS2, WS2, MoSe2, and WSe2) show indirect energy band gaps which hinders some of their applications especially in optoelectronics. In the current work, we demonstrate that most of the bilayers and even few-layers consisting of group VIB TMDs can have direct gaps by efficient weakening of their interlayer interactions via real and/or energy spaces tuning, which is based on insights from quantitative analyses of interlayer electronic hybridizations. Real space tuning here means introducing large-angle rotational misalignment between layers, which has been realized in a very recent experiment; and, energy space tuning means introducing energy mismatch between layers which can be introduced efficiently by different means thanks to the small vertical dielectric constant of 2D semiconducting TMDs. The efficient tuning in both real and energy spaces proposed here paves an avenue for indirect-direct gap regulation of homo- and hetero-junctions of TMDs and other 2D semiconductors. Notably, both tuning can be permanently preserved and hence our work is of great significance for the diverse applications of 2D semiconductors.

Random Transitions of a Binary Star in the Canonical Ensemble.

After reviewing the peculiar thermodynamics and statistical mechanics of self-gravitating systems, we consider the case of a "binary star" consisting of two particles of size a in gravitational interaction in a box of radius R. The caloric curve of this system displays a region of negative specific heat in the microcanonical ensemble, which is replaced by a first-order phase transition in the canonical ensemble. The free energy viewed as a thermodynamic potential exhibits two local minima that correspond to two metastable states separated by an unstable maximum forming a barrier of potential. By introducing a Langevin equation to model the interaction of the particles with the thermal bath, we study the random transitions of the system between a "dilute" state, where the particles are well separated, and a "condensed" state, where the particles are bound together. We show that the evolution of the system is given by a Fokker-Planck equation in energy space and that the lifetime of a metastable state is given by the Kramers formula involving the barrier of free energy. This is a particular case of the theory developed in a previous paper (Chavanis, 2005) for N Brownian particles in gravitational interaction associated with the canonical ensemble. In the case of a binary star (N=2), all the quantities can be calculated exactly analytically. We compare these results with those obtained in the mean field limit N→+∞.

A dual incentive mechanism based on graph attention neural network and contract in mobile opportunistic networks

In mobile opportunistic networks, messages are transmitted through opportunistic contacts between nodes. Hence, the successful delivery of messages heavily relies on the mutual cooperation among nodes in the network. However, due to limited network resources such as node energy and cache space, nodes tend to be selfish, and they are unwilling to actively participate in message forwarding. In response to this challenge, lots of incentive mechanisms have been proposed. However, most of them rely on single incentives, there are issues such as inadequate handling of selfish nodes and vulnerability to malicious attacks, which ultimately lead to poor incentive effects. Therefore, in this paper, a Dual Incentive mechanism based on Graph attention neural network and Contract (DIGC) is introduced to encourage active participation of network nodes in data transmission. This incentive mechanism is divided into two steps. In the first step, the graph attention neural network is used to evaluate the reputation of nodes to achieve the goal of reputation-based incentive, and blockchain is employed to store and manage node reputation to ensure security and transparency. In the second step, an incentive based on contract theory is introduced, where personalized contracts were designed based on the different resources owned by nodes, thereby establishing a reward mechanism to encourage collaborative transmission. Extensive simulations based on two real-life mobility traces have been done to evaluate the performance of our DIGC compared with other existing incentive mechanisms. The results show that, our proposed mechanism can greatly improve throughput and reduce average delay while ensuring the overall delivery performance of the network.

Planar Schrödinger–Poisson system with exponential critical growth: Local well‐posedness and standing waves with prescribed mass

AbstractThis paper investigates a class of planar Schrödinger–Poisson systems with critical exponential growth. The conditions for the local well‐posedness of the Cauchy problem in the energy space are defined. By introducing innovative ideas and relaxing some of the classical growth assumptions on nonlinearity, this study shows that such a system has at least two standing waves with a prescribed mass. One wave is a ground‐state standing wave with positive energy, and another one is a high‐energy standing wave with positive energy. In addition, with the help of the local well‐posedness, it is shown that the set of ground‐state standing waves is orbitally stable.

Ab initio extended Hubbard model of short polyenes for efficient quantum computing.

We propose introducing an extended Hubbard Hamiltonian derived via the abinitio downfolding method, which was originally formulated for periodic materials, toward efficient quantum computing of molecular electronic structure calculations. By utilizing this method, the first-principles Hamiltonian of chemical systems can be coarse-grained by eliminating the electronic degrees of freedom in higher energy space and reducing the number of terms of electron repulsion integral from O(N4) to O(N2). Our approach is validated numerically on the vertical excitation energies and excitation characters of ethylene, butadiene, and hexatriene. The dynamical electron correlation is incorporated within the framework of the constrained random phase approximation in advance of quantum computations, and the constructed models capture the trend of experimental and high-level quantum chemical calculation results. As expected, the L1-normof the fermion-to-qubit mapped model Hamiltonians is significantly lower than that of conventional abinitio Hamiltonians, suggesting improved scalability of quantum computing. Those numerical outcomes and the results of the simulation of excited-state sampling demonstrate that the abinitio extended Hubbard Hamiltonian may hold significant potential for quantum chemical calculations using quantum computers.

A 2 : Towards Accelerator Level Parallelism for Autonomous Micromobility Systems

Autonomous micromobility systems (AMS) such as low-speed minicabs and robots are thriving. In AMS, multiple Deep Neural Networks execute in parallel on heterogeneous AI accelerators. An emerging paradigm called Accelerator Level Parallelism (ALP) suggests managing accelerators holistically. However, there lacks a specialized and practical solution populating ALP for an AMS, where the varying real-time requirements under different working scenarios bring an opportunity to dynamically tradeoff between latency and efficiency. Furthermore, accelerator heterogeneity introduces enormous configuration space, and the shared-memory architecture results in dynamic bandwidth interference. In this paper, we propose A 2 , a novel AMS resource manager optimizing energy and memory space efficiency under variable latency constraints. We gain insight from prior Learn&Control scheme to design an Analyze&Adapt scheme specialized for heterogeneous AI accelerators under shared-memory architecture. It features analyzing the system thoroughly offline to support two-step adaptation online. We build a prototype of A 2 and evaluate it on a commercial edge platform. We show that A 2 achieves 32.8% improvements in power and 13.8% in memory compared with control-based methods. As for timeliness enhancement, A 2 reduces the deadline violation rate by 9.2 percentage points (12.8% → 3.6%) on average compared to directly porting Learn&Control methods.

Global in time well-posedness of a three-dimensional periodic regularized Boussinesq system

Abstract Global in time weak solution to a regularized periodic three-dimensional Boussinesq system is proved to exist in energy spaces. This solution depends continuously on the initial data. In particular, it is unique. The main novelty is the global in time aspect of this solution. The proofs use the coupling between the temperature and the velocity of the fluid, energy methods, and compactness argument.

Solar thermal energy and CO2 storage in saline aquifers for renewable energy space heating

There are a large number of abandoned oil and gas wells and corresponding depleted oil/gas reservoirs (DOGR) throughout the world, which are recognized as one of the best geological formations of saline aquifers for thermal energy storage and CO2 sequestration and however, the lack of innovative technique limits the efficient use of underground storage space. Here a novel scheme of storing solar thermal energy and concomitantly sequestrating CO2 in DOGR for renewable energy heating is proposed, which uses CO2 as thermal energy storage working fluid. The process of thermal energy storage and release as well as CO2 sequestration in DOGR are simulated, and thermal performance and CO2 dissolution in DOGR are analyzed. The results for twenty years of operation show that the thermal recovery efficiency reaches up to 82.93 %, which is 76 % higher than the traditional high temperature aquifer thermal energy storage. Energy storage capacity per heating season, energy storage density per unit volume of underground space and energy efficiency are respectively 57,222.27 GJ, 22,943.01 kJ/m3 and 96.19 %. Furthermore, the dissolved CO2 during thermal energy storage and extraction is 54.76 % larger than that of mere CO2 sequestration due to the repeated expansion and contraction of gas and water interface caused by the periodically injection and extraction of CO2, indicating that energy storage accelerates CO2 sequestration. To sum up, the new scheme is a high value-added technical route for solar thermal energy storage and CO2 sequestration as well as renewable energy heating.

Dynamic Evaluation Method of Electric Power New Energy and River Basin Ecological Restoration

The wide application of renewable energy can reduce the carbon emissions to the environment and the consumption of petrochemical resources, improve the improvement rate of the natural environment, and at the same time, ecological restoration can improve the ecology of the river basin and produce sustainable improvement of the environment together with renewable energy. In this paper, renewable energy is taken as the research object, and the ecological restoration method of the river basin is jointly evaluated to comprehensively evaluate the natural environment. First, the carbon neutrality data of ecological restoration and renewable energy in the river basin were collected, classified, collated and integrated, and the analysis indicators included CO2 emissions, plant coverage, soil and water conservation, and the cost of power generation. Then, the spatial regression model was used for data processing and calculation, and the ecological coefficient and carbon emission coefficient were determined in an iterative manner. Finally, the actual case is used for dynamic evaluation and analysis. The results show that the new power and watershed ecological restoration methods can improve the natural environment, improve the plant coverage rate and soil and water conservation rate, with an increase rate of 25~30%, reduce carbon dioxide emissions and power generation costs, and reduce the reduction rate of 10~30%, and at the same time, a good ecological environment will also react to new energy and expand the development space of new energy, with an expansion rate of 10%. Therefore, the method of electric power new energy and river basin ecological restoration can improve the natural environment, promote the development of electric power new energy, and optimize the overall structure of new energy.

Orbital stability of multi-peakons for a generalized Dullin–Gottwald–Holm equation

In this paper, we consider a generalized Dullin–Gottwald–Holm equation. The equation admits single peakons and multi-peakons. Using energy argument and combining the method of the orbital stability of a single peakon with monotonicity of the local energy norm, we prove that the sum of N sufficiently decoupled peakons is orbitally stable in the energy space.

Probing Thermal Electrons in Gamma-Ray Burst Afterglows

Particle-in-cell simulations have unveiled that shock-accelerated electrons do not follow a pure power-law distribution, but have an additional low-energy “thermal” part, which owns a considerable portion of the total energy of the electrons. Investigating the effects of these thermal electrons on gamma-ray burst (GRB) afterglows may provide valuable insights into the particle acceleration mechanisms. We solve the continuity equation of electrons in energy space, from which multiwavelength afterglows are derived by incorporating processes including synchrotron radiation, synchrotron self-absorption, synchrotron self-Compton scattering, and γ–γ annihilation. First, there is an underlying positive correlation between the temporal and spectral indices due to the cooling of electrons. Moreover, thermal electrons result in simultaneous nonmonotonic variations of both the spectral and temporal indices at multiple wavelengths, which could be individually recorded by the 2.5 m Wide Field Survey Telescope and Vera Rubin Observatory Legacy Survey of Space and Time (LSST). The thermal electrons could also be diagnosed using afterglow spectra from synergistic observations in the optical (with LSST) and X-ray (with the Microchannel X-ray Telescope on board the Space Variable Objects Monitor) bands. Finally, we use Monte Carlo simulations to obtain the distribution of the peak flux ratio (R X) between the soft and hard X-rays, and of the time delay (Δt) between the peak times of the soft X-ray and optical light curves. The thermal electrons significantly raise the upper limits of both R X and Δt. Thus, the distribution of GRB afterglows with thermal electrons is more scattered in the R X−Δt plane.