Analysis Of Energy Dissipation Research Articles

Energy dissipation of cavity expansion based on generalized non-linear failure criterion under high stresses

Based on the compression mechanism for analyzing the cavity expansion problem in soil under high stresses, generalized non-linear failure criterion and large strain and energy conservation in plastic region during the cavity expanding were adopted. The energy conservation equation was established and the limited pressure of cavity expansion under high stresses was given based on the energy dissipation analysis method, in which the energy generated from cavity expansion is absorbed by the volume change and shear strain caused in soil. The factors of large strain and dilatation were considered by the proposed method. The analysis shows that the limited pressure is determined by failure criterion, stress state, large deformation characteristic, dilatation and strength of soil. It is shown from the comparison that the results with the proposed method approximate to those of the in-situ method. The cavity expansion pressure first decreases and then increases nonlinearly with both of shear modulus and dilatation increasing.

Ultra low energy design exploration of digital decimation filters in 65 nm dual-VT CMOS in the sub-VT domain

This paper presents an analysis of energy dissipation of a decimation filter chain of four Half Band Digital (HBD) filters operated in the sub-threshold (sub-VT) region with throughput constraints. To combat speed degradation due to scaling of supply voltage, various HBD filters are implemented as unfolded structures. The designs are synthesized in 65nm CMOS technology with low-power and three threshold options, both as single-VT and as dual-VT. A sub-VT energy model is applied to characterize the designs in the sub-VT domain. Simulation results show that the unfolded by two and four architectures are the most energy efficient for throughput requirements between 250k samples/s, and 2M samples/s. By the selection of optimum architectures and standard cells, at the required throughput the simulated minimum energy dissipation for the required throughput per output sample is 164fJ and 205fJ, with single supply voltage of 260mV.

Decoding of Raptor codes on embedded systems

Raptor codes have been proven very suitable for mobile multimedia content delivery. A systematic Raptor code is employed for the application layer Forward Error Correction (FEC), schemes of the 3rd Generation Partnership Project (3GPP), Multimedia Broadcast/Multicast Service (MBMS) and standard and the IP Datacast over Digital Video Broadcasting (DVB) services. Those services run on mobile devices powered by embedded systems. This paper analyzes the performance, energy profile and resource implication of Raptor decoder on a system on a chip (SoC) platform with a soft-core embedded processor. At the heart of the Raptor decoder for binary erasure channel (BEC) is the decoding of the pre-code. The following three methods are used for that task: Belief Propagation (BP), Gaussian Elimination (GE) and the 3GPP inactivation decoding Gaussian elimination (IDGE). The paper analyzes the error correction capability and the complexity of each algorithm on embedded system. Additionally, the paper investigates how the cache size, matrix memory type and organization affect the algorithms under consideration. Finally, a power and energy dissipation analysis for the operation of the three algorithms under consideration is presented.

Predicting conditions for scaled-up manufacturing of materials prepared by ball milling

Discrete element model (DEM) is used to describe energy transfer from milling tools to the milled powder for shaker, planetary, and attritor mills. The rolling and static friction coefficients are determined experimentally. Computations predict the quasi-steady rate of energy dissipation, Ed, for each experimental configuration. It is proposed that the milling dose defined as a product of Ed and milling time, t, divided by the mass of milled powder, mp characterizes the milling progress independently of the milling device or milling conditions used. Once milling dose is determined for one experimental configuration, it can be used to predict the milling time required to prepare the same material in any milling configuration, for which Ed is calculated. To validate this concept, metal-oxide composites were prepared using all three types of mills. The yield strength of the milled material was used as an experimental indicator of the milling progress. The concept was validated for DEM describing both planetary and shaker mills. For attritor, the predicted energy dissipation includes substantial contribution from the milling tool interaction events accompanied by abnormally high forces (>103N). Because of high forces, the energy in such events is likely dissipated to heat or plastically deform milling tools rather than refine material. Indeed, DEM predictions for attritor correlate with experiments when such events are ignored in the energy dissipation analysis.

A comparative analysis of energy dissipation and equivalent viscous damping of RC columns subjected to uniaxial and biaxial loading

The hysteretic behaviour of RC columns has been object of many experimental studies over the past years. However, the majority of these studies are focused on unidirectional loading. An experimental program was carried out where 24 columns were tested for different loading histories, under uniaxial and biaxial conditions. The experimental results are presented in this paper and are discussed in terms of global column behaviour, and particularly with regards to energy dissipation and damping capacity. The energy dissipation capacity of the columns was evaluated in terms of cumulative dissipated energy, comparing uniaxial and biaxial test results, and individual cycle dissipated energy. Ultimately, an equation relating the normalised dissipated energy with the displacement ductility is proposed. The equivalent viscous damping was analysed by comparing the uniaxial with biaxial test results, demonstrating the high influence of the load path in the biaxial response of RC columns. Proposals for estimating the equivalent viscous damping given by other authors are compared with the experimental results. Finally, simplified expressions are proposed to estimate equivalent viscous damping in RC columns under biaxial loading.

Mechanism underlying bioinertness of self-assembled monolayers of oligo(ethyleneglycol)-terminated alkanethiols on gold: protein adsorption, platelet adhesion, and surface forces

The mechanism underlying the bioinertness of the self-assembled monolayers of oligo(ethylene glycol)-terminated alkanethiol (OEG-SAM) was investigated with protein adsorption experiments, platelet adhesion tests, and surface force measurements with an atomic force microscope (AFM). In this work, we performed systematic analysis with SAMs having various terminal groups (-OEG, -OH, -COOH, -NH(2), and -CH(3)). The results of the protein adsorption experiment by the quartz crystal microbalance (QCM) method suggested that having one EG unit and the neutrality of total charges of the terminal groups are essential for protein-resistance. In particular, QCM with energy dissipation analyses indicated that proteins absorb onto the OEG-SAM via a very weak interaction compared with other SAMs. Contrary to the protein resistance, at least three EG units as well as the charge neutrality of the SAM are found to be required for anti-platelet adhesion. When the identical SAMs were formed on both AFM probe and substrate, our force measurements revealed that only the OEG-SAMs possessing more than two EG units showed strong repulsion in the range of 4 to 6 nm. In addition, we found that the SAMs with other terminal groups did not exhibit such repulsion. The repulsion between OEG-SAMs was always observed independent of solution conditions [NaCl concentration (between 0 and 1 M) and pH (between 3 and 11)] and was not observed in solution mixed with ethanol, which disrupts the three-dimensional network of the water molecules. We therefore concluded that the repulsion originated from structured interfacial water molecules. Considering the correlation between the above results, we propose that the layer of the structured interfacial water with a thickness of 2 to 3 nm (half of the range of the repulsion observed in the surface force measurements) plays an important role in deterring proteins and platelets from adsorption or adhesion.

Design of experiments and energy dissipation analysis for a contact mechanics 3D model of frictional bolted lap joints

Bolted lap joints allow structural assemblies to be made. The answer to requirements, both static and dynamic, depends on the joint behaviour. Bolted joints are a primary source of energy dissipation in dynamic built-up and space structures among others. This paper presents an analysis of a bolted lap joint, subjected to a relative displacement after applying a pre-stress on the bolt in order to characterise the joint behaviour. For this purpose a 3D modelling is made by means of finite elements, using design techniques of experiments (DOE) to fit constitutive contact parameters. The theoretical results relative to elasto-plastic hysteresis cycles of the joint are experimentally validated. Finally, the preload effect and the magnitude of the displacement on the non-linear joint behaviour are analysed to determine equivalent stiffness and dissipated energy in the hysterical loops of the joint.

A chlorophyll fluorescence analysis of photosynthetic efficiency, quantum yield and photon energy dissipation in PSII antennae of Lactuca sativa L. leaves exposed to cinnamic acid.

This study investigated the effects of cinnamic acid (CA) on growth, biochemical and physiological responses of Lactuca sativa L. CA (0.1, 0.5, 1.0 and 1.5mM) treatments decreased plant height, root length, leaf and root fresh weight, but it did not affect the leaf water status. CA treatment (1.5mM) significantly reduced F(v), F(m), photochemical efficiency of PSII (F(v)/F(m)) and quantum yield of PSII (ΦPSII) photochemistry in L.sativa. The photochemical fluorescence quenching (qP) and non-photochemical quenching (NPQ) were reduced after treatment with 1.5mM CA. Fraction of photon energy absorbed by PS II antennae trapped by "open" PS II reaction centers (P) was reduced by CA (1.5mM) while, portion of absorbed photon energy thermally dissipated (D) and photon energy absorbed by PSII antennae and trapped by "closed" PSII reaction centers (E) was increased. Carbon isotope composition ratios (δ(13)C) was less negative (-27.10) in CA (1.5mM) treated plants as compared to control (-27.61). Carbon isotope discrimination (Δ(13)C) and ratio of intercellular CO(2) concentration (ci/ca) from leaf to air were also less in CA treated plants. CA (1.5mM) also decreased the leaf protein contents of L.sativa as compared to control.

Analysis of Energy Dissipation in Resistive Superconducting Fault-Current Limiters for Optimal Power System Performance

Fault levels in electrical distribution systems are rising due to the increasing presence of distributed generation, and this rising trend is expected to continue in the future. Superconducting fault-current limiters (SFCLs) are a promising solution to this problem. This paper describes the factors that govern the selection of optimal SFCL resistance. The total energy dissipated in an SFCL during a fault is particularly important for estimating the recovery time of the SFCL; the recovery time affects the design, planning, and operation of electrical systems using SFCLs to manage fault levels. Generic equations for energy dissipation are established in terms of fault duration, SFCL resistance, source impedance, source voltage, and fault inception angles. Furthermore, using an analysis that is independent of superconductor material, it is shown that the minimum required volume of superconductors linearly varies with SFCL resistance but, for a given level of fault-current limitation and power rating, is independent of system voltage and superconductor resistivity. Hence, there is a compromise between a shorter recovery time, which is desirable, and the cost of the volume of superconducting material needed for the resistance required to achieve the shorter recovery time.

Experimental Study on Steel Frames Infilled with Sandwich Composite Panels

A model of full scale one-bay, one storey was tested under low cyclic loading in order to study the hysteretic behavior of steel frames with sandwich composite (SC) panels. According to the failure pattern and damage process of test specimen, seismic behaviors were evaluated. Hysterics loops, skeleton curves, curves of strength degradation, and curves of stiffness degradation, ductility index and viscous damping coefficient were analyzed. Test results show that the failures of panels mainly occurred around the embedded parts, but compared with traditional panels and walls, SC panels exhibit a better integration. The connection between panel and steel frame is vital to the mutual work of the two parts. Finally, seismic design recommendations based on the analysis of ductility index and energy dissipation of the structures are presented.

A New Static Nonlinear Procedure for Assessment of Seismic Performance of High-Rise Buildings

A new static nonlinear pushover procedure is proposed for assessment of seismic capacity for high-rise buildings. Rather than simply combining the results carried out by modal inertia force distributions to estimate the total building capacity after pushover analysis, the present study develops in advance the most critical lateral load distribution which is developed via energy dissipation analysis based on least-energy principle. The advantage of the present method is that the effect of different earthquake input directions can be well considered, as well as that unstable solutions due to employing linear method to combine the nonlinear analysis results can be avoided. Thus, the performance of building can be evaluated more reasonably. By comparing with the results from nonlinear response history analysis using real earthquake tremor monitoring results, the validity of the present method is validated.

Numerical study of particle-vortex interaction and turbulence modulation in swirling jets

This study carried out a direct numerical simulation of gas-solid swirling jet flow, focusing on the particle-vortex interaction and mechanisms of turbulence modulation. Two cases of flows with either a constant particle flow rate or a constant particle mass loading are simulated. The typical instantaneous particle-vortex interactions are illustrated and analyzed, as well as the spectrum representations and the projections of them. The results show that the small particles (St<1) and light-mass loadings augment the vortices of the large-scale range in the power spectrum representation by shifting the peaks of wave numbers from small to large values as they pass through the large vortices and break them into smaller scales. The large particles and heavy-mass loadings suppress greatly the large scales of vortices, transferring the turbulent kinetic energy from large to relatively smaller scales of vortices, resulting in turbulence augmentation in the large wave numbers and turbulence attenuation in the range of small wave numbers. Moreover, by comparison between the two cases, it is found that the turbulence modulation is more highly sensitive to the effect of mass loadings rather than the dynamical response property of particles. The well-known knowledge on modulation of turbulence is true under the condition of the same mass loading. However, the situation becomes very complicated when the mass loading changes. Finally, these conclusions are verified by the analysis of energy spectrum and dissipation.

Role of the brittle–ductile transition on fault activation

We model a fault cross-cutting the brittle upper crust and the ductile lower crust. In the brittle layer the fault is assumed to have stick–slip behaviour, whereas the lower ductile crust is inferred to deform in a steady-state shear. Therefore, the brittle–ductile transition (BDT) separates two layers with different strain rates and structural styles. This contrasting behaviour determines a stress gradient at the BDT that is eventually dissipated during the earthquake. During the interseismic period, along a normal fault it should form a dilated hinge at and above the BDT. Conversely, an over-compressed volume should rather develop above a thrust plane at the BDT. On a normal fault the earthquake is associated with the coseismic closure of the dilated fractures generated in the stretched hangingwall during the interseismic period. In addition to the shear stress overcoming the friction of the fault, the brittle fault moves when the weight of the hangingwall exceeds the strength of the dilated band above the BDT. On a thrust fault, the seismic event is instead associated with the sudden dilation of the previously over-compressed volume in the hangingwall above the BDT, a mechanism requiring much more energy because it acts against gravity. In both cases, the deeper the BDT, the larger the involved volume, and the bigger the related magnitude. We tested two scenarios with two examples from L’Aquila 2009 (Italy) and Chi-Chi 1999 (Taiwan) events. GPS data, energy dissipation and strain rate analysis support these contrasting evolutions. Our model also predicts, consistently with data, that the interseismic strain rate is lower along the fault segment more prone to seismic activation.

Dynamic Hemodynamic Energy Loss in Normal and Stenosed Aortic Valves

Aortic valve (AV) stenosis, if untreated, leads to heart failure. From a mechanics standpoint, heart failure can be interpreted as the failure of the heart to generate sufficient power to overcome energy losses in the circulation. Thus, energy efficiency-based measures for evaluating AV performance and disease severity have the advantage of being a direct measure of the contribution of the AV hydrodynamic characteristics toward heart failure. We present a new method for computing the rate of energy dissipation as a function of systolic time, by modifying the Navier-Stokes momentum equation. This method preserves the dynamic term of the Navier-Stokes momentum equation, and allows the investigation of the trend of the rate of energy dissipation over time. This method is applied to a series of in vitro experiments, where a trimmed porcine valve is exposed to various conditions: varying stroke volumes (50 ml to 90 ml) at the fixed heart rate; varying heart rates (60-80 beats/min) at fixed stroke volume; and varying stenosis levels (normal, mild stenosis, moderate stenosis). The results are: (1) energy dissipation waveform has a distinctive pattern of being skewed toward late systole, due to flow instabilities during deceleration phases; (2) increasing heart rate and stroke volume increases energy dissipation, but the normalized shape of the energy dissipation waveform is preserved across heart rates and stroke volumes; (3) increasing stenosis level increases energy dissipation, and also alters the normalized shape of the energy dissipation waveform. Since stenosis produces a signature energy dissipation waveform shape, dynamic energy dissipation analysis can potentially be extended into a clinical tool for AV evaluation.

Multi-scale analysis of subgrid stress and energy dissipation in turbulent channel flow

In present study, the subgrid scale (SGS) stress and dissipation for multiscale formulation of large eddy simulation are analyzed using the data of turbulent channel flow at Re τ = 180 obtained by direct numerical simulation. It is found that the small scale SGS stress is much smaller than the large scale SGS stress for all the stress components. The dominant contributor to large scale SGS stress is the cross stress between small scale and subgrid scale motions, while the cross stress between large scale and subgrid scale motions make major contributions to small scale SGS stress. The energy transfer from resolved large scales to subgrid scales is mainly caused by SGS Reynolds stress, while that between resolved small scales and subgrid scales are mainly due to the cross stress. The multiscale formulation of SGS models are evaluated a priori, and it is found that the small–small model is superior to other variants in terms of SGS dissipation.

Anomalous pressure drop behaviour of mixed kinematics flows of viscoelastic polymer solutions: a multiscale simulation approach

A long-standing unresolved problem in non-Newtonian fluid mechanics, namely, the relationship between friction drag and flow rate in inertialess complex kinematics flows of dilute polymeric solutions is investigated via self-consistent multiscale flow simulations. Specifically, flow of a highly elastic dilute polymeric solution, described by first principles micromechanical models, through a 4:1:4 axisymmetric contraction and expansion geometry is examined utilizing our recently developed highly efficient multiscale flow simulation algorithm (Koppol, Sureshkumar &amp; Khomami, J. Non-Newtonian Fluid Mech., vol. 141, 2007, p. 180). Comparison with experimental measurements (Rothstein &amp; McKinley, J. Non-Newtonian Fluid Mech., vol. 86, 1999, p. 61) shows that the pressure drop evolution as a function of flow rate can be accurately predicted when the chain dynamics is described by multi-segment bead-spring micromechanical models that closely capture the transient extensional viscosity of the experimental fluid. Specifically, for the first time the experimentally observed doubling of the dimensionless excess pressure drop at intermediate flow rates is predicted. Moreover, based on an energy dissipation analysis it has been shown that the variation of the excess pressure drop with the flow rate is controlled by the flow-microstructure coupling in the extensional flow dominated region of the flow. Finally, the influence of the macromolecular chain extensibility on the vortex dynamics, i.e. growth of the upstream corner vortex at low chain extensibility or the shrinkage of the upstream corner vortex coupled with the formation of a lip vortex that eventually merges with the upstream corner vortex at high chain extensibility is elucidated.

Block copolymers for the rational design of self-forming postsurgical adhesion barriers

Post-surgical adhesions, abnormal fibrous linkages between adjacent tissue surfaces, represent one of the most common and significant complications facing surgical recovery today. Physical barriers and gels have been the most successful at limiting their formation, yet are not effective in cases where the pro-adhesive site is either unknown or difficult to reach (e.g. during laparoscopic surgery). In this work, poly(methacrylic acid-co-t-butylmethacrylate)-b-poly(ethylene glycol (M¯N=1000) methacrylate) diblock and statistical copolymers were synthesized as a platform for designing self-forming adhesion barriers, which can attach to exposed pro-adhesive sites through binding with the positively charged extracellular matrix, basement membrane proteins and deposited fibrin. An experimental model based upon a quartz crystal microbalance with dissipation was developed to test the diblock copolymers ability (i) to adsorb to an amine-terminated self-assembled monolayer, and (ii) to inhibit subsequent protein adsorption. These results were also confirmed using an in vitro cell attachment model. As the mole fraction of methacrylic acid content increased, polymer adsorption increased. All synthesized diblock copolymers investigated provided high resistance to protein adsorption, with blockade ranging from 55% to 81%. Except for the uncharged control polymers, the ability of these materials to resist cellular attachment showed similar trends, with the suppression of attachment approaching 75%. Energy dissipation analysis and variable-angle spectroscopic ellipsometry revealed two competing adsorption mechanisms depending on the molecular properties of the polymer.

Crack tip deformation fields and fatigue crack growth rates in Ti–6Al–4V

In this paper we present an overview of experimental and modelling studies of fatigue crack growth rates in aerospace titanium alloy Ti–6Al–4V. We review work done on the subject since the 1980s to the present day, identifying test programmes and procedures and their results, as well as predictive approaches developed over this period. We then present the results of some of our recent experiments and simulations. Fatigue crack growth rates (FCGRs) under constant applied load were evaluated as a function of crack length, and the effect of overload (retardation) was considered. Crack opening was measured during cycling using digital image correlation, and residual stress intensity factor was determined using synchrotron X-ray diffraction mapping. Modelling techniques used for the prediction of FCGRs are then reviewed, and an approach based on the analysis of energy dissipation at the crack tip is proposed. Finally, directions for further research are identified.

Hemodynamic Energy Dissipation in the Cardiovascular System: Generalized Theoretical Analysis on Disease States

We present a fundamental theoretical framework for analysis of energy dissipation in any component of the circulatory system and formulate the full energy budget for both venous and arterial circulations. New indices allowing disease-specific subject-to-subject comparisons and disease-to-disease hemodynamic evaluation (quantifying the hemodynamic severity of one vascular disease type to the other) are presented based on this formalism. Dimensional analysis of energy dissipation rate with respect to the human circulation shows that the rate of energy dissipation is inversely proportional to the square of the patient body surface area and directly proportional to the cube of cardiac output. This result verified the established formulae for energy loss in aortic stenosis that was solely derived through empirical clinical experience. Three new indices are introduced to evaluate more complex disease states: (1) circulation energy dissipation index (CEDI), (2) aortic valve energy dissipation index (AV-EDI), and (3) total cavopulmonary connection energy dissipation index (TCPC-EDI). CEDI is based on the full energy budget of the circulation and is the proper measure of the work performed by the ventricle relative to the net energy spent in overcoming frictional forces. It is shown to be 4.01+/-0.16 for healthy individuals and above 7.0 for patients with severe aortic stenosis. Application of CEDI index on single-ventricle venous physiology reveals that the surgically created Fontan circulation, which is indeed palliative, progressively degrades in hemodynamic efficiency with growth (p<0.001), with the net dissipation in a typical Fontan patient (Body surface area=1.0 m(2)) being equivalent to that of an average case of severe aortic stenosis. AV-EDI is shown to be the proper index to gauge the hemodynamic severity of stenosed aortic valves as it accurately reflects energy loss. It is about 0.28+/-0.12 for healthy human valves. Moderate aortic stenosis has an AV-EDI one order of magnitude higher while clinically severe aortic stenosis cases always had magnitudes above 3.0. TCPC-EDI represents the efficiency of the TCPC connection and is shown to be negatively correlated to the size of a typical "bottle-neck" region (pulmonary artery) in the surgical TCPC pathway (p<0.05). Energy dissipation in the human circulation has been analyzed theoretically to derive the proper scaling (indexing) factor. CEDI, AV-EDI, and TCPC-EDI are proper measures of the dissipative characteristics of the circulatory system, aortic valve, and the Fontan connection, respectively.

Impacts in multibody systems: modeling and experiments

This paper outlines a novel approach to the modeling and analysis of impact involving multibody systems. This approach is based on an analysis of energy absorption and restitution during impact, using a decomposition of the kinetic energy, which decouples the parts associated with the spaces of admissible and constrained motions of the underlying unilateral constraints. Such a decomposition turns out to be useful in the analysis of energy dissipation during impact, and leads to a generalized definition of the energetic coefficient of restitution, which targets particularly collisions in multibody systems. The applicability of the approach reported is investigated by conducting an experimental study on a robotic testbed. It is shown that impact between multibody systems is considerably affected not only by the local dynamics characteristics of the interacting bodies, but also the configuration of the whole multibody system. The results reported here show that our decomposition can offer a sound characterization of impact in several problems of multibody systems.