Dissipative Conditions Research Articles

Finite-region dissipative control for 2-D switched systems via mode-dependent average dwell time

Dissipativity is a significant concern for 2-D switched systems, but existing research often overlooks the transient dynamics occurring within a finite region. This paper aims to address finite-region dissipativity and dissipative control for a class of Fornasini-Marchesini local state-space (FMLSS) type 2-D switched systems. The analysis employs the mode-dependent average dwell time approach. Firstly, the concept of dissipativity on finite-region for 2-D switched systems is introduced. Then, a sufficient condition under which the considered systems can demonstrate the finite-region boundedness with the external disturbances is established by the special recursive formulas. Additionally, a sufficient condition for finite-region dissipativity of the considered systems is provided. Furthermore, the dissipative state feedback controller is derived to ensure the finite-region dissipativity of the closed-loop systems. To illustrate the effectiveness of the proposed controller design approach, an example is presented.

Supramolecular Systems Chemistry Based on the Interplay between Peptides and Porphyrins

The functions of living organisms are emergent from networks of biomolecules. In this review, we discuss the creation of synthetic life‐like systems based on the interplay of peptides and porphyrins in the supramolecular chemical systems. In particular, we focus on the spatiotemporal control of self‐assembly processes, which allows for the development of hierarchical structures for biomimetic catalysis and adaptive dynamics for stimulus‐responsive structural transformations. Notably, when operating in a nonequilibrium regime—characterized by kinetic traps, feedback loops, and dissipative conditions—the structural landscape expands and system‐level properties emerge, including transient catalysis, metabolic self‐replication, and Darwinian‐like evolution. Controlling these systems at the biointerface would facilitate intelligent therapeutic interventions in the anti‐tumor phototherapy. Supramolecular systems chemistry provides a valuable framework for exploring new physicochemical spaces of peptides and porphyrins, and may offer distinct advantages and extensive applications across diverse fields.

A Net Shape Profile Extraction Approach for Exploring the Forming Appearance of Inclined Thick-Walled Structures by Wire Arc Additive Manufacturing

Wire arc additive manufacturing (WAAM) offers a viable solution for fabricating large-scale metallic parts, which contain various forms of inclined thick-walled structure. Due to the variety of heat dissipation conditions at different positions, the inclined thick-walled structure is a major challenge in fabrication that may produce collapses and defects. However, there is a lack of effective sensing method for acquiring the forming appearance of individual beads in the structure. This paper proposes a novel approach for extracting individual bead profiles during the WAAM process. The approach utilizes a structured-laser sensor to capture the morphology of the surface before and after deposition, thereby enabling an accurate acquisition of the bead profile by integrating the laser stripes. Utilizing the proposed approach, the research investigated the forming mechanism of beads in inclined thick-walled components that were fabricated by various deposition parameters. The width of the overlapping area at the overhanging feature decreased as the layer number increased, while the height of the same area increased. The height of the overlapping area in each layer increased with an increase in deposition current and decreased when the deposition speed was increased. These phenomena suggest that the heat input is a major factor that influences the formation of the overhanging feature. Both the deposition current and deposition velocity influence heat input, and thereby have an effect in enhancing the geometrical accuracy of an overhanging feature. The experimental results indicate that the proposed approach facilitates morphology change investigation, providing a sufficient reference for optimizing deposition parameters.

Modelling study of divertor W leakage for different divertor conditions with Ne seeding in EAST tokamak

Abstract Sequential SOLPS-ITER and DIVIMP simulations are carried out for tungsten (W) edge transport during neon (Ne) injection in EAST, elucidating the pathway of W impurity leakage from the divertor to the core plasma under different dissipative divertor conditions. Divertor conditions from low-recycling to detachment are generated by modulating the Ne injection rate in the SOLPS simulation. With the drift velocities incorporated in DIVIMP, W transport under the drift effect is investigated. For low-density L-mode plasma conditions with favorable Bt direction, the majority of W source originates from the outer divertor target and leaks upstream through the near-SOL EB drift reversed region at both inner and outer divertors. The EB drift is demonstrated to have a significant effect on W leakage and the effect diminishes with the increase of Ne injection rate. Compared to the D2 injection cases, Ne injection helps to achieve a strong dissipative divertor condition at a much lower plasma density, resulting in a higher W leakage ability due to the smaller friction with the background plasma. For Ne injection cases under high-density H-mode conditions, W leaks mostly through the outer divertor region while the inner divertor is fully detached. Compared to the L-mode cases, the shorter power decay lengths in the scrap-off layer (SOL) of the H-mode cases result in smaller parallel EB drift velocities especially in the middle and far SOL region. With the increase of the Ne injection rate, the decrease of the EB drift in the middle SOL leads to a wider near-separatrix W leakage path. Therefore, a worse divertor W screening is expected, which is consistent with the previous published experimental observations [1].

A risk assessment model of spontaneous combustion for sulfide ores using Bayesian network combined with grounded theory

Sulfide ores, collectively referred to as a class of minerals with extensive applications, are increasingly susceptible to spontaneous combustion incidents as the mining environment evolves. The spontaneous combustion of sulfide ores is a complex nonlinear process, and the mechanisms of which remain not fully understood. Consequently, it is challenging to delineate the accident trajectory through traditional accident causation models and subsequently construct a probabilistic model for spontaneous combustion risk. To address this issue, this paper proposed a risk assessment model based on grounded theory and Bayesian network. The advantage of this model is that it employs grounded theory to categorize and organize factors influencing the occurrence of accidents, thereby forming a clear accident trajectory and providing a framework and basis for constructing a probabilistic assessment model. Furthermore, the model presented in this paper introduces the D number theory and the Noisy-OR model to handle uncertainties in the risk assessment process and to establish more rational conditional probability tables. The findings suggest that environmental temperature, heat dissipation conditions, safety awareness, and safety skills are the most influential factors in spontaneous combustion incidents when considering a particular point in time. However, when considering the entire process of sulfide ore pile spontaneous combustion, the temperature of the ore pile is the most critical accident factor to monitor. Therefore, the key to suppressing the spontaneous combustion of sulfide ores lies in reducing environmental temperatures, enhancing heat dissipation, and elevating the safety awareness of relevant personnel.

Design of experimental section of a water tunnel for simulation of heat dissipation condition of seawater-activated battery

Abstract A water tunnel is a crucial experimental apparatus in hydrodynamic research, as the traditional water tunnel has drawbacks such as a small cross-sectional area of the test section and higher costs, which makes it difficult to meet the requirements of a water tunnel for simulating the heat dissipation conditions of the seawater-activated battery. This paper proposes a water tunnel specifically designed for simulating the heat dissipation conditions of seawater-activated batteries, and the water tunnel consists of an external cooling water circulation system and an internal electrolyte circulation system. The experimental section’s design determines the water tunnel’s size and key technical indexes. The temperature distribution contour maps of the experimental section were obtained using Ansys Fluent software simulation. The cooling effect was analyzed, and a cooling water flow rate of 10 m/s was selected. Pressure and velocity contour maps were obtained by simulating the experimental section of the water tunnel. The results show that when the cooling water velocity is 10 m/s, the pressure drop of the experimental section is approximately 1.76 atmospheres. The flow field is uniform and stable, and the heat dissipation power can reach 45.5 kW, meeting the technical requirements.

Effects of time-dependent and radiation on a tri-hybrid nanofluid flowing on stretchable/shrinkable cylinders with irregular heat generation/absorption using Ohmic heating

This work focuses on the non-linear dynamics of unsteady tri-hybrid nanofluids inside a thermally radiative, expandable or contractible cylinder, which has been a consistent subject of interest for contemporary researchers. An advanced model is formulated to address the unsteady external flowing of a conductive 50 %:50 % by volume aqueous solution of ethylene glycol-based ternary hybrid nanofluid (THNF) over a linearly stretched cylindrical structure, considering the significant applications of an anti-freeze agent in industrial, construction, nuclear, and mechanical domains. The proposed tri-hybrid nanomaterials consist of cobalt magnetite, titania, and magnesium oxide nanoparticles. The heat transfer rate is analyzed concerning viscous dissipation, Ohmic heating, and convective boundary conditions. This research examines the effects of magnetic and induced electric fields. The non-dimensional similarity model for the controlling partial differential system is derived using appropriate transformations and solved by the homotopy analysis technique (HAM) to get series solutions. In contrast to porosity and magnetic characteristics, the flow rate increases with increasing unsteadiness and electric factors. Close to the surface, the Nusselt number rises with an increasing unsteadiness parameter, but skin frictions diminishes. THNF has been shown to significantly enhance the cooling of cylindrical conduits and mechanical antifreeze agents.

On a class of third-order dissipative differential operator with distributional potentials

This paper aims to investigate a class of boundary value problems generated by a third-order differential equation with distributional potentials and some dissipative boundary conditions. We first construct an operator related to the problem, then prove that the operator is dissipative and show some eigenvalue properties of this operator. Further using Krein’s theorem we prove the completeness theorems of the operator.

Numerical analysis for nonlinear wave equations with boundary conditions: Dirichlet, Acoustics and Impenetrability

In this article, we present an error estimation in the L2 norm referring to three wave models with variable coefficients, supplemented with initial and boundary conditions. The first two models are nonlinear wave equations with Dirichlet, Acoustics, and nonlinear dissipative impenetrability boundary conditions, while the third model is a linear wave equation with Dirichlet, Acoustics, and linear dissipative impenetrability boundary conditions. In the field of numerical analysis, we establish two key theorems for estimating errors to the semi-discrete and totally discrete problems associated with each model. Such theorems provide theoretical results on the convergence rate in both space and time. For conducting numerical simulations, we employ linear, quadratic, and cubic polynomial basis functions for the finite element spaces in the Galerkin method, in conjunction with the Crank-Nicolson method for time discretization. For each time step, we apply Newton's method to the resulting nonlinear problem. The numerical results are presented for all three models in order to corroborate with the theoretical convergence order obtained.

Parameterization of a WRF Model Based on Microwave Measurements of Temperature Inversion Characteristics in PBL over Moscow City

In this work the WRF-ARW model was tested with several different combinations of physical parameterizations to assess the quality of temperature inversion parameter predictions over the Moscow city. The dynamic and statistical characteristics of temperature inversions have been calculated and analysed in selecting criteria for comparisons. The calculated of estimating of the dissipation conditions in dependence on the type of temperature inversions are presented. The data source was the results of temperature profiles measurements in a layer up to 1 km, obtained by the MTP-5 passive microwave profiler from 2018 to 2021. One MTP5 on the North of Moscow was used to tune the model parameters and another one on the East of Moscow for validation. The comparison results show that several parameterization options can be chosen to reproduce the main inversion parameters.

On the Effect of Driving Turbulent-like Fluctuations on a Harris Current Sheet Configuration and the Formation of Plasmoids

Energy dissipation in collisionless plasmas is one of the most outstanding open questions in plasma physics. Magnetic reconnection and turbulence are two phenomena that can produce the conditions for energy dissipation. These two phenomena are closely related to each other in a wide range of plasmas. Turbulent fluctuations can emerge in critical regions of reconnection events, and magnetic reconnection can occur as a product of the turbulent cascade. In this study, we perform 2D particle-in-cell simulations of a reconnecting Harris current sheet in the presence of turbulent fluctuations to explore the effect of turbulence on the reconnection process in collisionless nonrelativistic pair plasmas. We find that the presence of a turbulent field can affect the onset and evolution of magnetic reconnection. Moreover, we observe the existence of a scale-dependent amplitude of magnetic field fluctuations above which these fluctuations are able to disrupt the growing of magnetic islands. These fluctuations provide thermal energy to the particles within the current sheet and preferential perpendicular thermal energy to the background population.

Skew-product attractors of non-autonomous Caputo fractional differential equations.

A non-autonomous Caputo fractional differential equation (FDE) of order α∈(0,1) in Rd with a driving system on a compact base space P is shown to generate a skew-product semi-flow on Cα×P, where Cα is the space of continuous functions f:R+→Rd with a weighted norm giving uniform convergence on compact time subsets. This skew-product semi-flow is then shown to have a bounded and closed attractor when the vector field of the Caputo FDE satisfies a uniform dissipativity condition. It attracts bounded sets of constant initial functions f in here Cα. The properties and structure of this attractor in Cα×P are also discussed.

Well-posedness of nonautonomous abstract Cauchy problems under dissipativity conditions expressed by metric-like functionals

Under a dissipativity condition expressed by a metric-like functional, the well-posedness of a nonautonomous abstract Cauchy problem is established. The main result not only extends Martin's result on the generation of an evolution operator in a class of uniformly convex Banach spaces but also can be applied to mixed problems for nonautonomous evolution equations of Kirchhoff type with which Kato's quasilinear theory or the theory of quasi-contractive semigroups cannot directly deal. The main result also gives an affirmative answer to Kōmura's conjecture that an evolution operator of linear operators with moving domains can be generated even under a weak stability condition rather than Kato's stability condition, and the result provides an effective means for solving degenerate wave equations.

High performance power handling in the absence of an H-mode edge in negative triangularity DIII-D plasmas

Experiments performed during strongly-shaped high-power diverted negative triangularity (NT) experiments in DIII-D achieved detached divertor conditions and a transient-free edge, showcasing the potential for application of NT to a core-edge integrated reactor-like scenario and providing the first characterization of the parametric dependencies for detachment onset. Detached divertor conditions will be required in future devices to mitigate divertor heat fluxes. Access to dissipative divertor conditions was investigated via an increase in upstream density. Detachment onset at the outer strike point was achieved with H-mode level confinement H98−y2∼1 and reactor-relevant normalized pressures βN∼2 . Confinement degradation was observed with deeper detachment, associated with the loss of an electron temperature pedestal. Differences in geometry, radial transport, impact of cross field drifts are discussed to explain differences in access to detachment in NT discharges. Higher normalized densities, with respect to equivalent discharges in positive triangularity, were necessary to achieve detachment, partially explained by the shorter parallel connection length to the targets. The effect of cross-field particle drifts (E×B, B ×∇ B) on access to detachment was demonstrated by the lower upstream density needed to access detachment with ion B ×∇ B drift directed outside of the active divertor (Greenwald fraction fGw∼ 0.9–1.0 vs fGw∼ 1.3). The upstream density at detachment onset was observed to increase linearly with plasma current with ion B ×∇ B drift into the divertor, consistent with the observed narrowing of the scrape-off layer heat flux width λ q . Edge fluid simulations capture separatrix densities needed to achieve detachment in NT plasma and their dependence on drift direction. The ability to reproduce detachment dynamics in NT plasma increases the confidence in future design studies for NT divertors.

Investigation on the thermal characteristics of double-driven hydrostatic lead screw micro-feed system

The micro-feed system of the dual-drive hydrostatic lead screw (DDHLS) can overcome the accuracy limitations inherent in traditional hydrostatic lead screw through the process of differential synthesis, thereby achieving exceedingly low speeds and exceptional precision in feed operations. Nevertheless, due to the complex structural form of DDHLS, both heat generation and heat dissipation are different from conventional hydrostatic functional components. Therefore, for DDHLS micro-feed system, it is necessary to deeply investigate its thermal performance and evolution rules to improve its thermal stability. Based on the analysis of multi-field coupling, the accurate thermal model of the DDHLS micro-feed system is formulated. Taking into account the variable viscosity of the oil film and the heat dissipation conditions within the oil film region, the thermal behavior of DDHLS feed system is analyzed systematically. The accuracy of the thermal performance model of DDHLS feed system is verified by experiments. The findings indicate that the DDHLS micro-feed system has better thermal performance than the dual-axis differential feed system based on rolling components. Furthermore, optimizing the heat dissipation pathway of the DDHLS can significantly mitigate the thermal effects exerted by the hydrostatic nut assembly on the screw.

MHD nanofluid flow and heat transfer caused by a stretching sheet that is heated convectively: An approximate solution using ADM

The investigation detailed in this paper explores the behavior of a slippery nanofluid flowing over a permeable stretched sheet under the influence of magnetohydrodynamic forces, considering factors like thermal radiation, viscous dissipation, and convective boundary conditions. The analysis systematically establishes principles for conserving mass, heat, momentum, and nanoparticle concentration, deriving a set of nonlinear ordinary differential equations from the governing partial differential equations. To tackle these challenges, the Adomian decomposition approach is utilized as a central element of the solution methodology. Graphical representations are employed to depict the solutions across various physical parameters. Despite the significance of nanofluids in both industrial and scientific contexts, there exists a noticeable research gap concerning the combined impacts of thermal radiation, viscous dissipation, and convective boundary conditions on heat and mass transfer, especially when coupled with a permeable linear rough stretched sheet. This study aims to fill this void by offering quantitative insights into these intricate phenomena, thereby enhancing our understanding of nanofluid dynamics and their practical implications. The findings indicate that increasing slip velocity and magnetic parameters reduce the boundary layer thickness of the velocity profile but increase it for the temperature profile, suggesting a nuanced interplay between slip velocity and magnetic effects on velocity boundary layers, while the temperature boundary layer exhibits distinct thermal dynamics within the system.

Thermal performance analysis of horseshoe crab shaped fin cold plate

Abstract As we all know, efficient, safe, and stable operation of lithium-ion batteries is the key to ensuring vehicle performance. This type of battery can create a good amount of heat during the driving process of a car. Poor heat dissipation conditions accumulate heat, causing the battery to generate more heat, which leads to a very bad impact. More seriously, it can generate thermal runaway, seriously affecting the safe driving of the car. Therefore, designing an efficient heat dissipation structure is crucial for the safe use of batteries. This article focuses on the thermal performance analysis. In terms of heat dissipation structure design and optimization, a biomimetic horseshoe crab fin cooling plate structure is proposed. Finite element models of the module and cooling plate are established using Solidworks software, and CFD simulation is completed. Six cooling schemes under the flow direction of two cooling media are compared and analyzed with traditional rectangular fin cooling plates. The results showed that the cooling plate with horseshoe crab-shaped fins had better heat transfer performance, and the highest temperature of the battery module was lower.

Entropy analysis of Hall effect with variable viscosity and slip conditions on rotating hybrid nanofluid flow over nonlinear radiative surface

PurposeWith possible uses in engineering and industrial processes, this work aims to further our knowledge of fluid dynamics and heat transfer in complicated flow configurations. This study looks at how Al2O3−Cu/H2O hybrid nanofluids move across a nonlinear radiative 3D unsteady surface. It tries to figure out what happens when the Hall current, variable viscosity, viscous dissipation, velocity and thermal slip conditions work together. The goal of this analysis is to provide insight into the system's thermodynamic behavior and the ways in which these elements affect the flow's entropy generation. MethodologyThe controlling system is converted into nonlinear nondimensional partial differential equations (PDEs) by applying suitable non-similar transformations. In this work, the governing equations are simulated using the local non-similarity (LNS) approach up to the second truncation level using the numerical technique bvp4c in MATLAB. FindingsThe temperature, velocity, entropy production, skin friction in both directions, and Nusselt number profiles of the nanofluid and hybrid nanofluid are detailed in many figures. The tabular form contains the results of computing the local Nusselt number for linear, nonlinear, and radiation-free scenarios. The velocity profiles in both directions and the temperature profile grow as the rotation parameter and nanoparticle volume fraction parameter increase. Conversely, the velocity profiles drop when the variable viscosity parameter falls, while the temperature profile increases. When the unsteadiness parameter A is set to 0.5 and the nanoparticle volume fraction is 1%, hybrid nanofluid has 4.26% lower x-direction skin friction than nanofluid and 3.62% greater y-direction friction. When the unsteadiness parameter A = 0.5 and the nanoparticle volume percentage is 1%, a hybrid nanofluid has a 2.77% higher Nusselt number than a nanofluid. The generation of entropy was also enhanced by an increase in the volume fraction of nanoparticles, radiation, temperature ratio, and Brinkman number. We evaluate and contrast the results of this study with those of earlier research.

Unsteady MHD flow analysis of hybrid nanofluid over a shrinking surface with porous media and heat generation: Computational study on entropy generation and Bejan number

The use of hybrid nanofluids in real-world situations is essential for enhancing the efficiency of heat transmission, especially in cooling semiconductor technology and industrial processes. The entropy generation on unsteady Al2O3-Cu/H2O hybrid nanofluid flow over a three-dimensional shrinking sheet is addressed numerically in this study, taking into account the effects of magnetohydrodynamic (MHD), nonlinear thermal radiation, porous media, heat generation, viscous dissipation, joule heating, and convective conditions. Using well-known non-similarity transformations, the model is carefully converted from partial differential equations (PDEs) to ordinary differential equations (ODEs). Afterwards, the behaviors of critical physical characteristics are uncovered across different parameter configurations by a numerical solution using the finite difference technique in bvp4c MATLAB. The velocity profiles of hybrid nanofluid grow proportionately with increases in the values of ϕ2,M,A,K and λ parameters. As Rd,θw,Ec,Bi,H and ϕ2 increase, the temperature of the hybrid nanofluid rises, but as M and A increase, the temperature falls. The local skin friction in both the x and y- directions is increased by enhancing the unsteadiness A, nanoparticle volume fraction ϕ2, magnetic M, porous media K, and the ratio of strain rate λ parameter on the shrinking surface. The local Nusselt number is improved by cumulative the unsteadiness A, nanoparticle volume fraction ϕ2, magnetic M, and Biot number Bi parameter in the direction of a shrinking surface, while the Nusselt number decreases when Eckert number Ec, thermal radiation Rd, heat production H, and temperature ratio θw are improved. An upsurge in the magnetic parameter leads to the development of entropy generation. Increasing levels of the magnetic parameters led to a reduction in the Bejan number. At a nanoparticle volume fraction of 1 % and a nonlinearity radiation scenario, where the unsteadiness values are 0.5, the Nusselt number for hybrid nanofluid shows an estimated improvement of 10.55 % compared to regular nanofluid.

Superfluid Mott-insulator quantum phase transition in an open cavity optomagnonic system

We investigated the superfluid Mott-insulator phase transition within an open coupled cavity optomagnonic array system. Based on the quasibosonic approach and employing perturbation approximation and mean-field theory, we obtain the time-dependent analytical superfluid order parameter. Our analysis revealed that dissipation induces decoherence within the system, while a strong magnon-cavity coupling enhances coherence significantly. Moreover, we explored the mechanisms by which increasing the magnon-cavity coupling strength drives the system towards the superfluid phase. The work holds significant guidance for the study of superfluidMott insulator phase transition under dissipative conditions, and providing a reliable reference for experimental implementation in open quantum systems.