Dissipative Properties Research Articles

FlexRay protocol based distributed nonfragile dissipative filtering of state-saturated switched stochastic systems

ABSTRACT This article concentrates on the finite-time nonfragile distributed dissipative filtering issue for time-varying switched stochastic systems (SSSs) with state saturations over wireless sensor networks based on FlexRay communication protocol. To effectively deal with the resource restriction problem of the public communication network and energy consumption of the sensor nodes, the FlexRay communication protocol, including the Round-Robin protocol (RRP) and weighted try-once-discard protocol (WTODP), is introduced to schedule the data transmission of each sensor node. In addition, the phenomenon of randomly occurring gain variations (ROGVs) of filter parameters, characterised by the Bernoulli distributed random variables, is taken into consideration for the implementation of desired filter. A sufficient condition under the average dwell time (ADT) restriction is presented to guarantee the mean-square exponential stability and stochastically dissipative property of the augmented filtering error system (AFES) in a finite horizon. Moreover, the gains of the dissipativity-based filters are achieved by solving recursive linear matrix inequalities (RLMIs). Finally, an illustrative example is provided to exhibit the effectiveness of the designed filter.

Energy-decreasing second order exponential time differencing Runge–Kutta methods for Nonlocal Cahn–Hilliard equation

Due to the energetic variational structure inherent in the nonlocal phase field model, the energy of the system naturally decreases over time according to the Nonlocal Cahn–Hilliard (NCH) equation. Preserving this crucial property of energy dissipation is highly desirable in numerical solutions. However, most existing numerical methods can only ensure a decrease in some modified form of energy, rather than the original energy itself. In this paper, we propose the second-order exponential time differencing Runge–Kutta (ETD-RK2) methods for solving the NCH equation. We demonstrate that this method has the ability to unconditionally preserve the original energy dissipation. Numerical experiments are included to illustrate the accuracy and energy stability of the ETD-RK2 methods.

Design of surpassing damping and modulus nanocomposites with tunable frequency range via hierarchical bio‐architecture

AbstractThe challenges of both high stiff and high dissipative properties are critical obstacles in structural engineering, particularly for the wide frequency range. This study proposes an innovative design method for creating nanocomposites with exceptional damping and modulus, offering tunability in temperature or frequency. The design principle is based on the hierarchical microstructure of the nanocomposite encompasses dangling chains at the atomic level, devisable microstructures in intermolecular macromolecules at the molecular level, and compatible domains between multi‐walled carbon nanotubes (MWCNTs) and macromolecules at the coarse level. To enhance damping performance, a self‐healing epoxy resin based on transesterification, known for its atomic‐level dangling chains, serves as the matrix. Control of the glass transition temperature is achieved by adjusting the ratios of glutaric anhydride (stiff) and sebacic acid (flexible) in the curing agent. Dangling chains and the soft curing agent can improve damping, but they are negative to modulus. To counterbalance this, this study introduces high‐modulus MWCNTs, resolving the inherent conflict between stiffness and damping. A damping model is constructed to recognize the continuous distribution of relaxation times of our designed composites. The designed nanocomposites have surpassing damping and modulus with tunable temperature or frequency range, surpassing the limited loss modulus of conventional engineering materials.Highlights The design principle of both high stiff and lossy properties of bones is revealed. Microstructural features are employed for fabricating our nanocomposite. High damping and moduli composites with tunable temperature are attained. A damping model is established for the distribution of relaxation times. Hierarchical bio‐architecture defeats the conflict of stiffness versus damping.

Improvement in Cohesive Properties of Adhesion Systems Using Movable Cross-Linked Materials with Stress Relaxation Properties.

A strong, tough, and stable adhesion system used in various environments must be developed. A long-lasting adhesion system should effectively perform in the following five aspects: adhesion strength, toughness, energy dissipation property, self-restoration property, and creep resistance property. However, these properties are difficult to balance using conventional adhesives. Here, a new topological adhesion system using single-movable cross-network (SC) materials [SC(DMAAm) Adh] was designed. 3-(Trimethoxysilyl) propyl acrylate was used as the anchor, N,N-dimethyl acrylamide (DMAAm) was used as the main chain monomer, and γ-cyclodextrin (γ-CD) units acted as movable cross-links. The movable cross-links provided SC(DMAAm) Adh with energy dissipation properties, thereby improving its toughness. The γ-CD units also acted as bulky stoppers that provided a high adhesion strength and self-restoration properties. Moreover, the combination of the movable cross-links and bulky stoppers provided creep resistance to SC(DMAAm) Adh. The performance of the adhesion systems under different mobilities of the polymer chains was examined by adjusting the water content. In proper water-containing states, all mechanical properties of SC(DMAAm) Adh were better than those of the adhesion systems using homopolymers [P(DMAAm) Adh] and polymers with covalent cross-linking points [CP(DMAAm) Adh].

ANALYSIS OF RESEARCH ON PLANETARY GEARBOXES OF ARMORED VEHICLES (REVIEW ARTICLE)

The work is devoted to the review of modern trends in the research and use of planetary gearboxes of armored vehicles. An analysis of the areas of application of mechanical transmissions was carried out. The advantages and disadvantages of using gear gearboxes as part of mechanical transmissions are described. The design features of the use of gears in transmissions are considered. The requirements for gear gearboxes as part of transmissions are defined. The advantages and disadvantages of using planetary gearboxes and their areas of use are analyzed. The classification of mechanical adjustable gears according to general features, as well as individual ones, is considered. An overview of the fulfillment of the conditions for increasing reliability was carried out, taking into account the design features of stepped gearboxes, which are divided into three groups: simple gearboxes (with fixed shaft axes); planetary gearboxes (with movable shaft axes); combined (combination of a simple and planetary gearbox in one unit). A brief review of modern approaches to planetary gear box modeling, taking into account inertial, elastic, dissipative, transformer and frictional properties, taking into account other characteristic features of the planetary series, is carried out. An analysis of known ways of solving problems of such modeling was carried out. Modern methods of calculating the strength of planetary gearboxes, including those with partial destruction, and corresponding software complexes are analyzed. The need for the development of more advanced mathematical models that adequately describe the stress-strain state in gear engagements has been identified. Keywords: design, planetary gearboxes, mechanical transmission, influence of operating factors, diagnostic parameters, synthesis of kinematic schemes

Study on the Cyclic Shear Performance of Waste Steel Slag Mixed Soil

Clay soil has poor engineering properties such as poor permeability and low shear strength. Waste steel slag is an industrial by-product formed in the furnace during the steelmaking process which has high quality, durability, anti-slip properties, gelling, high permeability and good particle interlocking properties. Therefore, in order to improve the engineering properties of clay and increase the utilization rate of waste steel slag, the steel slag was mixed into the clay. Steel slag clay mix was used for the straight shear test, cyclic shear test and post-cyclic straight shear test. To investigate the strength characteristics, damping ratio, shear stiffness variation and mixed soil displacement at the reinforcement-soil interface under different steel slag dosing, vertical stress, moisture content and shear amplitude conditions. The test results show that steel slag can significantly improve the shear strength of the clay tendon-soil interface, and the improvement effect is better than the conventional material sand improved clay. The steel slag mix has a large damping ratio and shear stiffness, suggesting that it has good damping and energy dissipation properties. In this case, the shear strength, damping ratio and shear stiffness of the soil mix at 40% steel slag admixture are better. The shear strength of the steel slag mix is increased after cyclic loading compared to straight shear before cyclic loading. In addition, the water content has a greater effect on the shear strength parameters, shear stiffness and damping ratio of the steel slag clay mix compared to the vertical stress and shear amplitude. The test results can provide a theoretical basis for the replacement of sand by steel slag in improving clay soils.

Numerical analysis of an uncoupled and linearized compact difference scheme with energy dissipation property for the generalized dissipative symmetric regularized long‐wave equations

This paper proposes and analyzes an uncoupled and linearized compact finite difference scheme for the generalized dissipative symmetric regularized long‐wave (GDSRLW) equations. The unique solvability and some a priori estimates of the proposed difference scheme are rigorously proved based on the mathematical induction method. To obtain the ‐norm estimation of numerical solutions, the discrete energy method is used to prove the convergence and stability of the difference scheme. The proposed difference scheme preserves the original energy dissipation property, and the convergence of the scheme is proved to be fourth‐order in space and second‐order in time in the ‐norm for both and . Some numerical experiments are given to verify the theoretical analysis and the reliability of the proposed difference scheme.

Enhancing energy dissipation properties of damping styrene-butadiene-styrene copolymer materials by hydrogen bonding

Mimicking the unique structure of biological tissue and energy dissipation mechanism of biology, various damping materials have been fabricated to provide impact protection. Utilizing the viscoelasticity of polymers around glass transition temperature, polymer materials generally are used as damping materials. However, it is still a great challenge to tailor the energy dissipation capacity and working temperature of damping materials. Here, we report an approach to adjust the energy-dissipation performance of polystyrene-polybutadiene-polystyrene (SBS) triblock polymer materials by incorporating distinct hydrogen-bonding moieties on the side groups of polybutadiene soft segment. The hydrogen bonding moieties reinforce the interaction between polymer chains and significantly improved the energy-dissipation capacity of SBS elastomers. Especially, when carbamate moieties are incorporated on the soft segment of SBS and SBS-U-2 is afforded. The hydrogen bonds deriving from carbamate moieties significantly increase the viscoelasticity of SBS-U-2 and provide excellent energy dissipation capacity. The current work provides a facile approach to fabricate damping materials based on engineering polymeric materials.

Facile synthesis of functionalized boron nitride nanosheets for photo‐cured 3D printing of high thermal conductive composites

AbstractAddressing the concern of heat accumulation in electronic devices, considerable research efforts have been dedicated to develop composites that are thermally conductive yet electrically insulative. Incorporating hexagonal boron nitride (h‐BN) as fillers shows promise in enhancing the thermal conductivity of polymer composites. However, notable challenges arise from difficulties in achieving well dispersion and establishing efficient three‐dimensional thermal conductive networks. This work demonstrated an efficient photocurable direct ink writing (DIW) printing method to fabricate functional h‐BN nanosheets (A‐BNNS)/epoxy acrylate (EA) resin‐based thermal conductive composites (A‐BNNS/EA). Apple polyphenol‐assisted ball milling was employed to fabricate functionalized BN nanosheets (A‐BNNS). Subsequently, A‐BNNS/EA inks were 3D printed using DIW to create thermally conductive composites, which were then UV‐cured. The composite containing 55 wt% A‐BNNS demonstrated an impressive thermal conductivity (TC) of 3.44 W/(m K). The utilization of 3D printing technology enables an onion‐like dispersion of A‐BNNS within the polymer matrix, effectively constructing three‐dimensional thermal conductive networks. This contribution significantly enhances the overall thermal conductivity.Highlights The functional BNNS (A‐BNNS) was achieved by apple polyphenol‐assisted ball milling. The utilization of photocurable 3D printing technology for producing high thermal conductivity materials are efficient. A‐BNNS exhibited an onion‐like distribution and effectively constructed a 3D thermal conductive network within the polymer matrix The composites demonstrate excellent thermal conductivity and favorable heat dissipation property.

Multiblock parallel high-order implicit residual smoothing time scheme for compressible Navier–Stokes equations

In direct and large eddy simulations, very small space steps are used close to the solid walls in order to resolve the boundary-layer structures. Due to the restrictive CFL stability criteria of explicit time-stepping schemes, the maximum allowable time step is also very small, leading to high computational costs, notably for converging flow statistics. The use of an implicit integration scheme may overcome this limitation at the price of an increased computational cost per step. Moreover, the most commonly used fully implicit schemes induce higher errors due to the necessary approximations and poor dispersion and dissipation properties. As a compromise, a fourth-order implicit residual smoothing scheme (IRS4), successfully validated for a finite volume solver in Cinnella nad Content (2016); Hoarau and Cinnella (2020), has been introduced in a multiblock high-order finite-difference solver. Several improvements are proposed to ensure better dissipation properties, a more efficient treatment of physical boundaries and an accurate and stable parallel multiblock implementation. For moderate CFL numbers, a similar accuracy as the explicit method is obtained with substantial savings in terms of computational time.

Simulation of Thermal Dissipation and Fatigue Properties of a Pressing Sealed Insulated Gate Bipolar Transistor Device

Insulated gate bipolar transistor (IGBT) is widely needed in many applications, such as motors, inverters, express railways, and automobiles. As the integrity level of IGBT increases, thermal management becomes a more significant issue, especially when third-generation semiconductor chips made with SiC or GaN come into application. Here, a press packaging SiC IGBT module is designed, which involves silver sintering. Firstly, we make a thermal analysis using the finite element method (FEM). Then, a heat dissipation plane is optimized. Groups of heat sink materials and airflow velocities are investigated, and an optimized one is chosen as the basis of further fatigue analysis. In the simulated working condition, the maximum temperature can reach 100°C, which could further induce serious problems in fatigue performance. We have analyzed 4 models with different silver layer edge shapes. The best one shows a 27% higher expected fatigue life than the standard one, which shows that the fatigue performance is very sensitive to the edge shape of the silver layer. This research can help further optimization and designing of advanced IGBT devices.

Secure Nonlinear Sampled-Data Control System Against Stealthy Attack: Multirate Approach

In this paper, we provide a novel defence strategy for a nonlinear sampled-data control system under zero-dynamics attacks. In a sampled data structure, sampling zeros induced by discretization make a system vulnerable to deception attacks. we analyze the dissipativity in the zero-dynamics part of the system equipped with a multi-rate setup and find conditions on sampling rates to neutralize the attacker's target plan. We show that, under some mild conditions, using multi-rate sampling in the nonlinear sampled-data system not only preserves the dissipativity property of the intrinsic zero-dynamics but also stabilizes the extrinsic zero-dynamics induced by the sample and hold process, and as a result attenuate the effects of attacks on the system stability. Finally, a numerical example is used to illustrate the effectiveness of the proposed approach.

Toward Thinner and Higher Heat Dissipation Advanced Chip Embedded Power Supply Module Packaging

Along with power management complexity, small/thin and high efficiency power supply devices such as DCDC converters and Inverters needs are increasing. In response, several chip-embedded packages have been proposed, but their size/thickness, heat dissipation properties, and cost necessitate the development of further concepts. In this report, we propose novel chip-embedded package that uses Semi-additive metallization with non-prepreg coreless substrate and 300 mm square Panel-level manufacturing for cost competitiveness. In the case of a prepreg substrate, it is difficult to make large thermal vias due to presence of glass cloth and the presence of the substrate core makes thickness reduction difficult. Because of such difficulties, prepreg substrate packages have limited characteristics around thermal performance and thickness. Our proposed structure has excellent heat dissipation and minimized thickness due to using thin non-prepreg coreless substrates that allows for large thermal vias by a laser drill and the thin package. We performed thermal resistance simulations and found that our package improved up to 43% as compared to the prepreg package. And also, our build-up interlayer material has close CTE to Cu-RDL and a low Young’s modulus that is effective in reducing package warpage. As a result of simulation, package warpage after post-curing is just 1/10th of that of the prepreg package, this means highly reliable on board. Developments using Si power die will be reviewed. We believe our proposed new package is also suitable for high performance package utilizing GaN and SiC.

Thermoplastic film materials for damping in mechanical engineering

An effective way of damping engineering structures is to use elements formed by a combination of hard and soft alternating layers. The outer rigid layers, made of structural materials, take up force infl uences, while the soft layers of viscoelastic polymers provide energy dissipation of the layered structure. The paper summarizes the results of research on the development of thin thermoplastic fi lms of plasticized polyvinyl acetate, polybutylmethacrylate and polymethylmethacrylate which have ultra-high dissipative properties and are used as a vibration-absorbing component of composite structures. It is shown that high damping properties are realized in fi lms with thickness of 0.1 –0.05 mm, which makes it possible to obtain two- and three-layer vibration-absorbing films with an extended temperature interval of effective damping in the metal-polymer-metal structures.

Enhanced thermal conductivity of PEEK based composites fabricated by its fibers grafted graphene oxide

Poly (ether ether ketone) (PEEK), a thermoplastic, is known for its outstanding comprehensive performance. However, the low thermal conductivity (TC) remains a great challenge, which significantly restricts the applications of PEEK in related fields. Herein, we report a oriented Graphene oxide/PEEK fibers (GO/PEEK) composite as inspired by the structure of tree trunk (PEEK fibers) and tree bark (GO), in which GO is grafted on the surface of aminated PEEK fibers, then combined with simple vacuum hot pressing. It demonstrates that the TC of GO/PEEK is about 380% higher than that of pure PEEK at the filler loading of 20 wt%, showing good heat dissipation properties. This method offers a strategy for preparing PEEK-based thermal conductive composites with oriented structures.

Finite Element Analysis and Parametric Study of Panel Zones in H-Shaped Steel Beam–Column Joints

This paper investigates the mechanical properties of a traditional welded rigid joint with a weakened panel zone under seismic load. The created finite element model is calibrated by the high-strength steel joint test, carried out by the team in the early stage, and the effectiveness of the finite element method was verified. The finite element software ABAQUS is used to investigate the influence of different joint web thicknesses on the mechanical properties of middle column joints under a low-cyclic-loading test. Supported by a validated numerical model, the ductility, energy dissipation, and other properties of different thicknesses of panel zone column webs are carefully analyzed. The results indicate that the thickness of the web plate in the panel zone significantly affects the location of the joint plastic hinge. The ultimate loading capacity of the joints increased significantly with an increase in the thickness of the webs in the panel zones. Compared with the joint with a weakened panel zone, the hysteresis curve of the strengthened joint is fuller; meanwhile, it cannot alleviate the stress concentration at the weld holes of the web. When the thickness of the joint domain web is too weak, excessive deformation in the joint domain will lead to a decrease in the bearing capacity of the joint, causing damage. The stiffness degradation coefficient of the web-thickened specimen was found to be dominated and controlled by the stiffness of the beam; however, with an increase in the thickness of the web, the stiffness degradation coefficient remained basically unchanged. Finally, a recommendation for weakened beam–column interior joints based on the steel frame panel zone is made, which will lay a foundation for the simulation and analysis of the seismic performance of this structure.

Developing of reinforced grouting mortar tenon and pseudo-static experimental test for seismic performance of precast shear wall

A high-performance grouting mortar is applied to the wall joint to improve the seismic performance of the precast shear wall. This study proposes a configuration and synchronous grouting construction method for preparing reinforced high grouting mortar tenons. Three precast shear wall specimens with the prepared tenon and one common precast comparison specimen were tested with pseudo-static experiments, and the experimental results, i.e., failure process and mode, hysteretic and skeleton curves, capacities, stiffness and ductility, were analyzed. The results showed that the failure mode of precast shear wall specimens with reinforced tenon belonged to bending-shear failure. The reinforced tenon increased the strength capacity, stiffness, and energy dissipation ability and the reinforced tenon joints achieved strength capacity equivalent to a common precast shear wall. The tenon height and axial ratio significantly influenced the mechanical properties of stiffness, ductility, and energy dissipation. Which is, the tenon height should be reasonably controlled for shear transfer considerations, and the specimens with higher axial ratio showed better performance.

Synthesis of prussian blue analog (Co/TCNi/HCCr) nanoparticles using a facile co-precipitation approach and evaluation of their dielectric characteristics for electronic applications

The Prussian blue analog Co0.4/(TCNi)0.2/(HCCr)0.6 (PBA) nanoparticles were synthesized via a chemical co-precipitation approach. The structural characteristics of the nanocomposite (NCp) were investigated using the XRD technique, which revealed that the synthetic PBA has a tiny crystallite size and poor crystallinity. The XRD analysis suggests that the fabricated NCp has a face-centered cubic structure with space group Fm-3 m. For deep microstructure analysis, SEM, EDX, and AFM were employed to describe the topological nature and surface architecture. It is observed that the PBA nanocomposite has a small crystallite size of ~13.66 ± 0.32 nm. The particles’ surface displays a high degree of homogeneity, while the grain boundaries are clearly discernible, presenting a spherical morphology with an average diameter of 22 ± 2.1 nm. The porosity was ascertained from an AFM image of approximately 140. Furthermore, the value of the average roughness (Rs) is 6.86 nm. The AC conductivity of PBA in disc form was calculated at various temperatures and frequencies. The results indicate that the dielectric constant (ɛ′) of PBA nanoparticles exhibits a rise from 163 to 3464 throughout the frequency range of 10–100 kHz at ambient temperature and from 27 to 6000 at 293 K. This finding provides confirmation that the dielectric characteristics of PBA nanoparticles are enhanced during the process of annealing. The values of the exponent factor (s) range from 0 to 1; this behavior is connected to the correlated barrier hopping model (CBHM) for AC conductivity. The value of WM was ascertained to be 1.69 eV. Furthermore, the values of activation energy were calculated, and these values decreased from 0.20 to 0.17 eV with annealing. The change in loss tangent (tanδ) as a function of angular frequency at various temperatures is also shown. The investigation of the dielectric characteristics was measured over a wide range of frequencies and temperatures to get valuable data about the dissipation properties of the prospective electronic applications.

Desenvolvimento de estrutura bioinspirada com capacidade de absorção de impacto: um estudo de caso

The development of new materials is crucial for the advancement of engineering, architecture, and design fields. This is because new materials can offer significant benefits compared to traditional materials in terms of their structural, physical, and chemical properties. In architecture and design, new materials can be used to create more durable, sustainable, aesthetically pleasing, lightweight, and resilient products. Through biomimicry, this study conducted an analysis on the structures of four tropical fruits - orange, passion fruit, cocoa, and pomegranate - to generate a new structure with damping and energy dissipation properties, aided by scanning electron microscopy (SEM), computerized microtomography (Micro-CT), and computerized three-dimensional reconstruction. As a result, a bioinspired structure was developed based on the arrangements of cell walls found in the albedo (mesocarp) of the orange - Citrus sinensis. Using this developed structure, computational tests were performed and a resin prototype was created through digital fabrication. Therefore, the development of bioinspired materials for improved impact absorption and damping is important as it can enhance the safety and effectiveness of a wide range of products, from sports equipment to medical devices, while also contributing to sustainability and energy efficiency, which are significant interests in various fields of knowledge.

Sobolev contractivity of gradient flow maximal functions

Abstract We prove that the energy dissipation property of gradient flows extends to semigroup maximal operators in various settings. In particular, we show that the vertical maximal function relative to the p-parabolic extension does not increase the p-norm of the gradient when p > 2 {p>2} . We also obtain analogous results in the setting of uniformly parabolic and elliptic equations with bounded, measurable, real and symmetric coefficients. These are the first regularity results for vertical maximal functions without convolution structure.