Control Energy Dissipation Research Articles

Design and Evaluation of a Protection Method Based on Controllable Resistance for Meter-Class REBCO No-Insulation Pancake Coils

In this paper, we proposed a variable protective resistor that realizes controllable energy dissipation and temperature inhibition for the no-insulation (NI) HTS coil-systems, during sudden discharging. The resistor is paralleled with the meter-class bore NI coil, which aims to be used in a high-field magnetic resonance imaging scanner (MRI), to avoid burn-out and shorten restart time of the coil when it has to be shut-down during an accident. To establish the relationship between the value of protective resistor, the energy dissipation and the temperature increase during sudden discharging for the NI coil, in this study, a numerical analysis coupled with a partial element equivalent circuit and a thermal analysis was conducted. Based on the results, the mechanism that how a protective resistor shares energy dissipation and inhibits temperature increase, has been clarified. Meanwhile, the effects of the value of protective resistor on the discharging behavior and temperature increase of NI pancake coil during sudden discharging, were also evaluated to verify the feasibility of this protection method in the application of MRI.

Investigating the effect of nanoscale triboelectrification on nanofriction in insulators

Nanofriction and nanoscale triboelectrification is a universally existing phenomenon and important in many branches of nanotechnology, but how the nanoscale triboelectrification affects the nanofriction during the relative sliding at the contact interface is not fully investigated. Here, nanoscale triboelectrification and nanofriction on the insulating SiO2 surface were investigated with atomic force microscopy (AFM) and scanning Kelvin probe microscopy. By the AFM tip sliding on the SiO2 surface, both triboelectric charges and nanofriction were investigated with the applied load, sliding cycle, and external electric field. Whether the tribocharges on the SiO2 surface were negative or positive, the nanofriction increases with the enhanced tribocharge density by nanoscale triboelectrification, while decreases with the reduced tribocharges by charge diffusion. The change of nanofriction correlates strongly with the variation in tribocharge density due to the tribocharge induced excess electrostatic interactions at the sliding interface. These findings not only add to our understanding of the role of nanoscale triboelectrification on nanofriction, but also help to control energy dissipation of sliding nanofriction, which is also important in many branches of nanotechnology, such as data storage and nanoelectromechanical system.

Ultrahigh energy-dissipation elastomers by precisely tailoring the relaxation of confined polymer fluids

Energy-dissipation elastomers relying on their viscoelastic behavior of chain segments in the glass transition region can effectively suppress vibrations and noises in various fields, yet the operating frequency of those elastomers is difficult to control precisely and its range is narrow. Here, we report a synergistic strategy for constructing polymer-fluid-gels that provide controllable ultrahigh energy dissipation over a broad frequency range, which is difficult by traditional means. This is realized by precisely tailoring the relaxation of confined polymer fluids in the elastic networks. The symbiosis of this combination involves: elastic networks forming an elastic matrix that displays reversible deformation and polymer fluids reptating back and forth to dissipate mechanical energy. Using prototypical poly (n-butyl acrylate) elastomers, we demonstrate that the polymer-fluid-gels exhibit a controllable ultrahigh energy-dissipation property (loss factor larger than 0.5) with a broad frequency range (10−2 ~ 108 Hz). Energy absorption of the polymer-fluid-gels is over 200 times higher than that of commercial damping materials under the same dynamic stress. Moreover, their modulus is quasi-stable in the operating frequency range.

Glass Transition Temperature Regulates Mechanical Performance in Nacre-Mimetic Nanocomposites.

Although research in bioinspired nanocomposites is delivering mechanically superior nanocomposite materials, there remain gaps in understanding some fundamental design principles. This article discusses how the mechanical properties of nacre-mimetic polymer/nanoclay nanocomposites with nanoconfined polymer layers are controlled by the thermo-mechanical polymer properties, that is, glass transition temperature, Tg, using a series of poly(ethylene glycol methyl ether methacrylate-co-N,N-dimethylacrylamide) copolymers with tunable Tg from 130 to -55 °C. It is elucidated that both the type of copolymer and the nanoconfined polymer layer thickness control energy dissipation and inelastic deformation at high fractions of reinforcements in such bioinspired nanocomposites.

Tensile behavior of strain-hardening geopolymer composites (SHGC) under impact loading

Strain-hardening geopolymer composites (SHGC) exhibit remarkable ductility, crack control and high energy dissipation capacity when subject to quasi-static tensile loading. However, their mechanical performance under dynamic loading has not yet been explored. A comprehensive assessment of possible rate effects is required to facilitate a targeted material design for various practical applications. The article presents the results of an experimental investigation on the mechanical behavior of two types of SHGC under both quasi-static and impact tensile loading. The composites were reinforced with 2% of either short polyvinyl alcohol (PVA) fiber or ultra-high molecular-weight polyethylene (UHMWPE) fiber. The experiments were performed both at the composite scale and at the fiber level. The impact tests on the plain geopolymer matrix and SHGC were performed in a gravity-driven split-Hopkinson tension bar (SHTB) at strain rates of up to 300 s−1. The tests were accompanied by optical measurements to assess specimen deformation and multiple cracking by means of Digital Image Correlation (DIC). The dynamic fiber-matrix bond properties were investigated in a miniature split Hopkinson bar. Both under quasi-static tensile loading and impact tensile loading, the SHGC made with UHMWPE fibers exhibited superior mechanical performance compared to the composite made with PVA fibers. When comparing the impact tensile performance of SHGC with normal-strength SHCC from previous studies, SHGC demonstrated higher dynamic tensile strength and energy dissipation capacity, making SHGC promising for strengthening/prospective applications against highly dynamic actions.

Morphophysiological aspects of studying the dry resistance of wheat inter-species hybrids

The article presents the results of a study of drought tolerance of two species and two interspecific hybrids (alloplasmic lines) of wheat according to the anatomy and photosynthetic activity of leafblades under conditions of induced osmotic stress. The negative effect of drought on the leaf anatomicalstructure and on such photosynthetic parameters as the maximum quantum yield of photosynthesis ofphotosystem II (Fv/Fm) and a change in the electron transport through photosystem II (ETR) was shown.The quantum yield of controlled energy dissipation (Y (NPQ)) and the quantum efficiency of unregulatedenergy dissipation of PSII (Y (NO)) were experimentally determined. It was shown that the increase orpreservation of the size of the protective and mechanical tissues of the leaf unchanged under stress canserve as criteria for the selection of drought-resistant forms of wheat in the early stages of ontogenesis.It was clearly reflected that a decrease in the ETR level during stress can be associated with activationof non-photochemical quenching mechanisms, and their combination were characterizing the low resistance of the studied form to drought. A high level of resistance to drought was indicated by a minimaldecrease in the parameter Y (NPQ) under stress. As a result of the study, it was noted that the D-d-05bline can be considered more stable, and the D-42-05 line – less resistant to drought. A different degreeof drought tolerance of the studied lines allowed us to suggest that the combination of nucleus and cytoplasm obtained from interspecific crosses can contribute to both increasing and lowering the important physiological parameters of drought tolerance and photosynthetic activity. This implies the need to continue research involving molecular genetic analysis.Key words: drought tolerance, leaf, seedlings, wheat, photosynthesis

Framework for cost-effective analytical modelling for sensory data over cloud environment

In order to offer sensory data as a service over the cloud, it is necessary to execute a cost-effective and yet precise data analytical logic within the sensing units. However, it is quite questionable as such forms of analytical operation are quite resource dependent which cannot be offered by the resource constraint sensory units. Therefore, the proposed paper introduces a novel approach of performing cost-effective data analytical method in order to extract knowledge from big data over the cloud. The proposed study uses a novel concept of the frequent pattern along with a tree-based approach in order to develop an analytical model for carrying out the mining operation in the large-scale sensor deployment over the cloud environment. Using a simulation-based approach over the mathematical model, the proposed model exhibit reduced mining duration, controlled energy dissipation, and highly optimized memory demands for all the resource constraint nodes.

Dissipation of radiation energy in concentrated solid-solution alloys: Unique defect properties and microstructural evolution

Abstract

Development and experimental verification of damage controllable energy dissipation beam to column connection

The present study develops and experimentally verifies a new type of precast concrete beam to column connection. The proposed damage controllable energy dissipation (DCED) beam to column connection places the replaceable steel connectors with low yield point in predetermined areas of beams to achieve the aim of controllable plastic development, energy dissipation and replaceability after the earthquake. Two 1/2 scale interior beam-column connections were designed, fabricated and tested under cyclic reversed loadings, including one monolithic specimen and one precast specimen. The hysteresis curves were recorded during the test, and the seismic indicators, such as strength, stiffness and energy dissipation capacity, were determined and analyzed. Test results demonstrate that the precast DCED connection has similar strength to the monolithic specimen, exhibits stable and plump hysteretic responses, and fails in a typical flexural mode, which is consistent with the criteria of strong column and weak beam. The plastic hinges in the steel connectors greatly reduces the damage in the DCED connection core and mitigates the deterioration in global stiffness of connection, meeting the requirements of damage controllable. Additionally, the DCED connection exhibits satisfactory energy dissipation capacity and has better seismic performance. It is a viable alternative to the seismic beam to column connections of precast concrete buildings in medium and high seismic intensity regions.

Kinetic Uncertainty Relations for the Control of Stochastic Reaction Networks.

Nonequilibrium stochastic reaction networks are commonly found in both biological and nonbiological systems, but have remained hard to analyze because small differences in rate functions or topology can change the dynamics drastically. Here, we conjecture exact quantitative inequalities that relate the extent of fluctuations in connected components, for various network topologies. Specifically, we find that regardless of how two components affect each other's production rates, it is impossible to suppress fluctuations below the uncontrolled equivalents for both components: one must increase its fluctuations for the other to be suppressed. For systems in which components control each other in ringlike structures, it appears that fluctuations can only be suppressed in one component if all other components instead increase fluctuations, compared to the case without control. Even the general N-component system-with arbitrary connections and parameters-must have at least one component with increased fluctuations to reduce fluctuations in others. In connected reaction networks it thus appears impossible to reduce the statistical uncertainty in all components, regardless of the control mechanisms or energy dissipation.

Stability analysis of substructure shake table testing using two families of model-based integration algorithms

In implementing a substructure shake table testing (SSTT), the complete structure is divided into the experimental and the analytical substructures, which are driven by shake table and numerically simulated in a computer, respectively. A number of unconditionally stable and explicit integration algorithms referred to as model-based algorithms with highly computational efficiency have been developed to meet the requirement of real-time in conducting SSTT. This study aims to comprehensively investigate the stability of the SSTT system using two recently proposed model-based integration algorithms with controllable numerical energy dissipation, i.e., Kolay-Ricles-α (KR-α) algorithms and modified KR-α (MKR-α) algorithms. The SSTT system for the 2-degree-of-freedom (2-DOF) structures are firstly formulated. In order to take the contribution of the experimental substructure into consideration, the dynamic condensation is adopted to calculate the integration parameters for the analytical substructure. The discrete transfer function of the 2-DOF-SSTT system are derived. The influences of the mass ratio, the frequency ratio and the time step on the stability of the SSTT system are comprehensively investigated by using the discrete control theory. The results show that for larger values of the mass ratio, the frequency ratio and the time step have negative impact on the stability of the SSTT system. In addition, a subfamily of the MKR-α algorithms along with the dynamic condensation can always ensure the SSTT system stable.

Response to Maxam and Tamma's discussion (EQE‐18‐0306) to Kolay and Ricles's paper, “Development of a family of unconditionally stable explicit direct integration algorithms with controllable numerical energy dissipation”

SummaryThis paper presents the authors' response to the discussion by Dean J. Maxam and Kumar K. Tamma of the paper titled “Development of a family of unconditionally stable explicit direct integration algorithms with controllable numerical energy dissipation.”

Discussion of “development of a family of unconditionally stable explicit direct integration algorithms with controllable numerical energy dissipation” by Chinmoy Kolay and James M. Ricles

SummaryThe time integration method proposed by Kolay and Ricles, which was claimed to be both explicit and unconditionally stable, is shown to be implicit in the sense of requiring the factorization of an effective stiffness matrix where an explicit method needs no solver. Its original derivation procedure employed discrete control theory concepts, which are in fact, equivalent to conventional recurrence relation concepts aiming to match its spectral properties with those of the three‐parameter optimal/generalized‐α method, thus giving rise to an implicit method within the class of linear multistep methods. It is shown that the resulting method possesses several added computational drawbacks due to its derivation procedure, such as additional effective stiffness inversions and a degraded order of accuracy in general.

Molecular Dynamics Simulations of Radiation Damage in Ti-Al based Structural Intermetallics

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Numerical algorithm based on implicit finite-difference schemes for analysis of dynamic processes in blocky media

Abstract Dynamic processes in block-structured media are described within the framework of a mathematical model where elastic blocks interact with each other through pliable interlayers possessing complex mechanical properties. The case of elastic interaction is considered, the effects of plasticity and viscoelastic shear in block interlayers are taken into account. We use the model of porous fluid-saturated material in interlayers in which pores collapse during sudden or prolonged application of compressive stresses. An implicit difference scheme is constructed for numerical implementation of the model based on principles for construction of Ivanov’s schemes with controlled energy dissipation. Using MPI (Message Passing Interface), we developed parallel software for modelling wave motion in a two-dimensional formulation. The results of numerical analysis are presented for the waves initiated by rotation of blocks, which indicates a strong anisotropy of the blocky medium.

Localized Charges Control Exciton Energetics and Energy Dissipation in Doped Carbon Nanotubes.

Doping by chemical or physical means is key for the development of future semiconductor technologies. Ideally, charge carriers should be able to move freely in a homogeneous environment. Here, we report on evidence suggesting that excess carriers in electrochemically p-doped semiconducting single-wall carbon nanotubes (s-SWNTs) become localized, most likely due to poorly screened Coulomb interactions with counterions in the Helmholtz layer. A quantitative analysis of blue-shift, broadening, and asymmetry of the first exciton absorption band also reveals that doping leads to hard segmentation of s-SWNTs with intrinsic undoped segments being separated by randomly distributed charge puddles approximately 4 nm in width. Light absorption in these doped segments is associated with the formation of trions, spatially separated from neutral excitons. Acceleration of exciton decay in doped samples is governed by diffusive exciton transport to, and nonradiative decay at charge puddles within 3.2 ps in moderately doped s-SWNTs. The results suggest that conventional band-filling in s-SWNTs breaks down due to inhomogeneous electrochemical doping.

Dynamically controlled energy dissipation for fast magnetic vortex switching

Manipulation of vortex states in magnetic media provides new routes towards information storage and processing technology. The typical slow relaxation times (∼100 ns) of magnetic vortex dynamics may present an obstacle to the realization of these applications. Here, we investigate how a vortex state in a ferromagnetic microdisk can be manipulated in a way that translates the vortex core while enhancing energy dissipation to rapidly damp the vortex dynamics. We use time-resolved differential magneto-optical Kerr effect microscopy to measure the motion of the vortex core in response to applied magnetic fields. We first map out how the vortex core becomes sequentially trapped by pinning sites as it translates across the disk. After applying a fast magnetic field step to translate the vortex from one pinning site to another, we observe long-lived dynamics of the vortex as it settles to the new equilibrium. We then demonstrate how the addition of a short (<10 ns) magnetic field pulse can induce additional energy dissipation, strongly damping the long-lived dynamics. A model of the vortex dynamics using the Thiele equation of motion explains the mechanism behind this effect.

Mechanical properties in crumple-formed paper derived materials subjected to compression.

The crumpling of precursor materials to form dense three dimensional geometries offers an attractive route towards the utilisation of minor-value waste materials. Crumple-forming results in a mesostructured system in which mechanical properties of the material are governed by complex cross-scale deformation mechanisms. Here we investigate the physical and mechanical properties of dense compacted structures fabricated by the confined uniaxial compression of a cellulose tissue to yield crumpled mesostructuring. A total of 25 specimens of various densities were tested under compression. Crumple formed specimens exhibited densities in the range 0.8–1.3 g cm−3, and showed high strength to weight characteristics, achieving ultimate compressive strength values of up to 200 MPa under both quasi-static and high strain rate loading conditions and deformation energy that compares well to engineering materials of similar density. The materials fabricated in this work and their mechanical attributes demonstrate the potential of crumple-forming approaches in the fabrication of novel energy-absorbing materials from low-cost precursors such as recycled paper. Stiffness and toughness of the materials exhibit density dependence suggesting this forming technique further allows controllable impact energy dissipation rates in dynamic applications.

Seawall case studies and failure analysis of sloped concrete walls under static and dynamic loads

ABSTRACTConcrete seawalls are structures in coastal facilities for shore and slope protections. Owing to several advantages of sloped or inclined walls such as minimum soil disturbance and less required earthworks, they can be considered as an appropriate alternative to vertical cantilever retaining walls. The combination of slab and strip semideep foundation instead of heel–toe slab foundations increases their capability for stability, erosion control, and storm wave energy dissipation. In this paper, three case studies from seawalls in which failure has occurred are presented and discussed. Technical performance of sloped walls against different internal and external instability factors is investigated, and comparisons are made between vertical and sloped (inclined) walls with respect to geotechnical and structural aspects through parametric study. Analysis indicates that the sloped retaining walls perform better from technical, practical, and economical standpoints. It was found that for identical static and dynamic loads, including earthquake and wave loads, inclined walls provide relatively higher safety factors against different criteria and exhibit more stable and practical performance compared with commonly used walls in practice. The case studies in this paper illustrate causes of failure in each case and gives suggestions for improving instability prevention of walls against static and dynamic loads.

Experimental Investigation of a Base Isolation System Incorporating MR Dampers with the High-Order Single Step Control Algorithm

The conventional isolation structure with rubber bearings exhibits large deformation characteristics when subjected to infrequent earthquakes, which may lead to failure of the isolation layer. Although passive dampers can be used to reduce the layer displacement, the layer deformation and superstructure acceleration responses will increase in cases of fortification earthquakes or frequently occurring earthquakes. In addition to secondary damages and loss of life, such excessive displacement results in damages to the facilities in the structure. In order to overcome these shortcomings, this paper presents a structural vibration control system where the base isolation system is composed of rubber bearings with magnetorheological (MR) damper and are regulated using the innovative control strategy. The high-order single-step algorithm with continuity and switch control strategies are applied to the control system. Shaking table test results under various earthquake conditions indicate that the proposed isolation method, compared with passive isolation technique, can effectively suppress earthquake responses for acceleration of superstructure and deformation within the isolation layer. As a result, this structural control method exhibits excellent performance, such as fast computation, generic real-time control, acceleration reduction and high seismic energy dissipation etc. The relative merits of the continuity and switch control strategies are also compared and discussed.