Irreversible Component Research Articles

Probing the interplay between reversibility and magnetostatic interactions within arrays of multisegmented nanowires

Ordered arrays of NiFe/Cu multisegmented nanowires (NWs) are fabricated by ac pulse electrodeposition method into the 25-µm thick anodic aluminum oxide templates with a pore diameter of about 40–100 nm inter-pore distance. The behavior of magnetostatic interactions between neighboring NiFe/Cu NWs as well between magnetic segments of the same wire related to the NW length and the magnetic segment thickness is presented. The first-order reversal curves (FORCs) results for two given magnetic shape anisotropies, a nearly disk-shaped and a rod-shaped one, reveal a single domain magnetic state along with a constant peak value of FORC coercivity distribution (H FORC ). However, the Major Hysteresis Loop coercivity (H MHL ) shows a significant reduction with an increase in length. In addition, the magnetostatic interaction distribution along the Hu axis of FORC diagrams shows a weakly decreasing behavior, in disagreement with existing phenomenological model. In order to resolve this contradiction, the reversible and irreversible components of magnetization were measured. For arrays of multisegmented NWs, the contribution of the reversible components of magnetization rises up to about 70% as NW’s length increases which is in contrast for arrays of uniform NWs where a nearly zero reversibility is reported.

Post-earthquake controls and damage detection through structural health monitoring: applications in l’Aquila

The paper presents structural health monitoring (SHM) activities performed on some representative cultural heritage (CH) buildings in the city of l’Aquila after the strong earthquake (Mw = 6.3) that struck the Abruzzo region (central Italy) on April 6, 2009. The severity and the extent of damages caused by the earthquake to historical buildings and monument were never reached before in the recent Italian earthquake history. Emergency activities started immediately after the earthquake to protect CH structures, including damage survey and design/implementation of temporary safety measures. Some historic buildings were soon equipped with monitoring systems in order to assess the level of damage and verify the effectiveness of the executed provisional interventions. The paper focuses in particular on two case studies, i.e. the Spanish Fortress and the Civic Tower. The results of preliminary investigations are reported, including damage survey and operational modal analysis for modal parameter identification using ambient vibration tests. 3-year static and dynamic monitoring features, automatically extracted from raw data acquired by continuous monitoring systems, were then processed using a data-driven approach based on regression analysis to filter out the environmental effects. Following this approach data are decomposed into their reversible and irreversible components, the latter being associated with active damaging processes and the residual structural performance of the two buildings assessed.

Thin-Film Coatings of Dibenzotetraazaannulenes for Quantitative Determination of Hydrochloric Acid Vapor by Quartz Crystal Microbalance Method

It was shown that acoustic sensors based on a quartz crystal microbalance with thin films of dibenzotetraazaannulene, a series of its peripherally-substituted derivatives, and metal complexes can be used to determine the HCl content of the gas-phase. It was established that the process is irreversible. Specific features of the kinetics of the responses and their changes with increase of the total dose were studied. It was shown that the total dose of hydrochloric acid vapor at high concentrations (ca. 1000 ppm) can be identified and monitored by analyzing a virtual image of the irreversible component of the multidimensional surface of the sensor response obtained by intelligent arrays of the “electronic nose” type with sensitive layers of dibenzotetraazaannulenes.

Mathematical Modeling of the Polarization of Polycrystalline Ferroelectrics

General patterns of the polarization models of Rayleigh, Preisach, and Jiles–Atherton are found. The limiting dependence of the polarization is confirmed. A way of constructing it based on the energy criterion for domain switching for polycrystalline ferroelectrics with perovskite structure is proposed. Differential equations are constructed for determining the irreversible components of polarization and deformation, and large loops of dielectric hysteresis are calculated.

Reversible and Irreversible Tracer Dispersion in an Oscillating Flow Inside a Model Rough Fracture

Fil: Roht, Yanina Lucrecia. Universidad de Buenos Aires. Facultad de Ingenieria. Departamento de Fisica. Grupo de Medios Porosos; Argentina. Consejo Nacional de Investigaciones Cientificas y Tecnicas; Argentina

Investigation on performance of an integrated SOFC-Goswami system using wood gasification

A new cogeneration system is proposed consisting of biomass gasification fed by wood, a solid oxide fuel cell (SOFC) and a Goswami cycle, which is a combination of a Kalina and an absorption refrigeration cycle. The Goswami cycle acts as a bottoming cycle to recover waste heat of the SOFC in order to produce cooling effect along with additional electricity. The combined cooling and power (CCP) system is modeled via Engineering Equation Solver (EES) and assessed in terms of energy (or first law) efficiency and exergy (or second law) efficiency. The effects on the system performance of varying several key parameters are examined via sensitivity assessments. It is found that raising the SOFC current density increases the produced electricity generation and cooling, but reduces the energy and exergy efficiencies of the system. It is also found that, as the SOFC inlet flow temperature and the turbine inlet pressure increase, the electricity generation rate and the energy and exergy efficiencies of the system rise to the optimal values of 481.6 kW, 60.2% and 34.7%, respectively, and then decrease. The exergy analysis also demonstrates that the gasification reactor, the boiler and the second air heat exchanger are the main irreversible components.

A novel exergy optimization of Bushehr nuclear power plant by gravitational search algorithm (GSA)

In recent years metaheuristic optimization algorithms have been widely developed. These algorithms are inspired from nature for solving complicated engineering problems. In this work, gravitational search algorithm (GSA) based on Newton’s law of gravity is introduced for exergy optimization of the Bushehr nuclear power plant (BNPP). The main objective in this work is to minimize exergy destruction in the BNPP. In this analysis, beside the GSA, Genetic Algorithm (GA) is applied and the performances of these algorithms in two different cases are compared. In first case, the sphere function as a challenging optimization problem is investigated and it is demonstrated that the GSA has reliable fitness values (3.7602e-17). In the next case, the exergy destruction of the BNPP is studied and the exergy efficiencies of all components in the BNPP are evaluated. The reactor core (pressure vessel) and steam generator with 1511.35 MWth and 146.65 MWth of exergy destructions and irreversibility ratios of 50.34% and 4.88%, are introduced as the main irreversible components, respectively. The exergy destruction in the BNPP with the application of the GSA and GA is minimized and the optimum operating parameters in desired streams are reported. The exergy destruction of the BNPP (1968.95 MWth) is minimized to 1965.9 MWth. The results indicate the effectiveness of the GSA and it is shown that the method has robust high-quality solution for exergy destruction optimization.

Downstream processing of an oxidized industrial kraft liquor by membrane fractionation for vanillin and syringaldehyde recovery

Abstract A membrane fractionation study of an oxidized industrial kraft liquor was performed with 50, 5 and 1 kDa molecular weight cut-off membranes to study the productivity of each membrane and the respective apparent rejection coefficients (Ri) to total solids (TS), ashes and low molecular weight phenolates (TP). Cleaning efficiency of each membrane was evaluated and the contribution of fouling for flux decline was analyzed by applying the resistances-in-series approach. During membrane fractionation sequence, TS content in the permeate stream gradually decreased from 86.5 g L−1 to 75.3 g L−1 (50 kDa), 64 g L−1 (5 kDa) and 58.6 g L−1 (1 kDa). The Ri values observed for TS were 25.3%, 29.1% and 15.1% for 50, 5 and 1 kDa membrane processing, respectively. TP were not retained by the 50 kDa membrane while, for the 5 and 1 kDa membranes, Ri of 11.5% and 9.0% were observed, respectively. The initial TP concentration (2.4 g L−1) was maintained in the first membrane stage, while for the other stages decreased slightly for 2.22 g L−1 (5 kDa) and 2.15 g L−1 (1 kDa). Nevertheless, in terms of composition (%w/wTS), an enrichment in TP was observed in all three stages from 2.8% (feed) to 3.2% (50 kDa), 3.5% (5 kDa) and 3.7% (1 kDa). The initial water fluxes were recovered within 2–3 cycles of chemical cleaning and fouling evaluation indicated that reversible fouling was very relevant component for the 50 and 1 kDa membrane processing while irreversible fouling component was more pronounced for the 5 kDa membrane processing.

Properties of uniaxial media model

A model for uniaxial media which computed an irreversible component that lies along the easy axis and a reversible component that is sensitive to off-axis fields has been developed. By assuming that the distribution of critical fields is Gaussian, then the major loop will be an error function. For small rotating fields, the magnetization will oscillate between two extreme values on the same side of the origin. For larger fields, the irreversible magnetization can change sign and the magnetization will rotate about the origin. We start with a demagnetized specimen, then apply a field that starts along the easy axis and then rotates about the origin. For the first 90°, the magnetization will follow a circular path. Beyond that point the irreversible magnetization will start to change, and the magnetization will start to spiral in towards the origin. Therefore, we will get asymmetrical loops which can be compared with experiment.

The effects of structural damage on functional disability in psoriatic arthritis

BackgroundFunctional outcomes are central in patients with chronic inflammatory musculoskeletal diseases. In a secondary data analysis of the GO-REVEAL trial (NCT00265096), we investigated wether structural damage is linked to functional...

Soft-x-ray-induced spin-state switching of an adsorbed Fe(II) spin-crossover complex

For probing the nature of spin-state switching in spin-crossover molecules adsorbed on surfaces, x-ray absorption spectroscopy has emerged as a powerful tool due to its high sensitivity and element selectivity in tracing even subtle electronic, magnetic, or chemical changes. However, the x-rays itself can induce a spin transition and might have unwanted influence while investigating the effect of other stimuli such as temperature or light, or of the surface, on the spin switching behaviour. Herein, we present the spin switching of an Fe(II) complex adsorbed on a highly oriented pyrolytic graphite surface with particular emphasis on the x-ray-induced switching. For a submonolayer coverage, the complex undergoes a complete and reversible temperature- and light-induced spin transition. The spin states are switched both ways by x-rays at 5 K, i.e. from the high-spin state to the low-spin state or vice versa, depending on the relative amount of each species. Furthermore, we quantify the fraction of molecules undergoing soft x-ray-induced photochemistry, a process which results in an irreversible low-spin state component, for a particular exposure time. This can be greatly suppressed by reducing the beam intensity.

Systematic Hysteresis Compensator Design based on Extended Unparallel Prandtl-Ishlinskii Model for SPM Imaging Rectification

Scanning probe microscopy (SPM) technology plays the irreplaceable role in investigating micro/nano world, which has been bringing tremendous development opportunities to various fields. To enhance maneuverability, SPM can be modified into a nanomanipulation system with its scanning probe as the end-effector. The probe is commonly mounted on smart material based actuators to generate precise motion with nanometer level resolution. However, instinctive hysteretic characteristics ubiquitously exist in smart material actuators, which degrade their arbitrary positioning precision. To effectively represent and further reduce complex hysteretic effects, this paper proposes to utilize the modified Prandtl-Ishlinskii (PI) model: extended unparallel PI (EUPI) model, which possesses advantages such as the flexible modeling capability (compared to the prevalently implemented modified PI models) and the easy-to-use property for construction and identification (compared to the well known Preisach model and the Generalized PI (GPI) model). To effectively reduce complex hysteresis, the EUPI model based compensator (IMUPI compensator) is required to be flexible and precise. To efficiently design such a compensator satisfying stability requirement, this study proposes a systematic approach, including stabilizing gain selection and analytical calculation of boundary gains of the EUPI irreversible component. As a demonstration, satisfactorily precise IMUPI compensator was established according to this systematic design approach and tested through simulations on rectifying Atomic Force Microscopy (AFM, one special SPM) imaging process distorted by complex hysteresis.

Quantifying irreversible movement in steep, fractured bedrock permafrost on Matterhorn (CH)

Abstract. Understanding rock slope kinematics in steep, fractured bedrock permafrost is a challenging task. Recent laboratory studies have provided enhanced understanding of rock fatigue and fracturing in cold environments but were not successfully confirmed by field studies. This study presents a unique time series of fracture kinematics, rock temperatures and environmental conditions at 3500 m a. s. l. on the steep, strongly fractured Hörnligrat of the Matterhorn (Swiss Alps). Thanks to 8 years of continuous data, the longer-term evolution of fracture kinematics in permafrost can be analyzed with an unprecedented level of detail. Evidence for common trends in spatiotemporal pattern of fracture kinematics could be found: a partly reversible seasonal movement can be observed at all locations, with variable amplitudes. In the wider context of rock slope stability assessment, we propose separating reversible (elastic) components of fracture kinematics, caused by thermoelastic strains, from the irreversible (plastic) component due to other processes. A regression analysis between temperature and fracture displacement shows that all instrumented fractures exhibit reversible displacements that dominate fracture kinematics in winter. Furthermore, removing this reversible component from the observed displacement enables us to quantify the irreversible component. From this, a new metric – termed index of irreversibility – is proposed to quantify relative irreversibility of fracture kinematics. This new index can identify periods when fracture displacements are dominated by irreversible processes. For many sensors, irreversible enhanced fracture displacement is observed in summer and its initiation coincides with the onset of positive rock temperatures. This likely indicates thawing-related processes, such as meltwater percolation into fractures, as a forcing mechanism for irreversible displacements. For a few instrumented fractures, irreversible displacements were found at the onset of the freezing period, suggesting that cryogenic processes act as a driving factor through increasing ice pressure. The proposed analysis provides a tool for investigating and better understanding processes related to irreversible kinematics.

Vector magnetization of a distribution of cubic particles

A model for the vector magnetization of a distribution of particles with cubic anisotropy is presented. Recent work by the authors modeled the vector magnetization of a distribution of uniaxial particles by decomposing the total magnetization into reversible and irreversible components. In this paper, using an energy approach applicable to a generic plane, the model is extended to include cubic anisotropy projected to the (100) plane. The magnitude of the irreversible component is modeled using a Preisach differential-equation approach; however, other valid models can be used. The direction of the reversible component is modeled using the minimum energy approach of the classical Stoner–Wohlfarth model and taking into account the anisotropy field. The formulation of the generalized model is derived and its results are discussed considering (i) oscillation and rotational modes, (ii) lag angle, and (iii) magnetization trajectories.

On Finite Strains in Continua with Complex Rheology

The present study deals with the multiphysics modelling frameworks for the elasticcreep-plastic material. The proposed theory of large deformations is based on the classical formalism of nonequilibrium thermodynamics. Reversible and irreversible components of total deformations are derived by the constitutive differential equations. The development of this theory involves statements and solutions of the correct boundary value problems. The problem of deformation of the material in the vicinity of microdefect was considered. Resulting integro-differential equations system was derived.

Bayesian Quantification of Contrast-Enhanced Ultrasound Images With Adaptive Inclusion of an Irreversible Component.

Contrast Enhanced Ultrasound (CEUS) is a sensitive imaging technique to assess tissue vascularity and it can be particularly useful in early detection and grading of arthritis. In a recent study we have shown that a Gamma-variate can accurately quantify synovial perfusion and it is flexible enough to describe many heterogeneous patterns. However, in some cases the heterogeneity of the kinetics can be such that even the Gamma model does not properly describe the curve, with a high number of outliers. In this work we apply to CEUS data the single compartment recirculation model (SCR) which takes explicitly into account the trapping of the microbubbles contrast agent by adding to the single Gamma-variate model its integral. The SCR model, originally proposed for dynamic-susceptibility magnetic resonance imaging, is solved here at pixel level within a Bayesian framework using Variational Bayes (VB). We also include the automatic relevant determination (ARD) algorithm to automatically infer the model complexity (SCR vs. Gamma model) from the data. We demonstrate that the inclusion of trapping best describes the CEUS patterns in 50% of the pixels, with the other 50% best fitted by a single Gamma. Such results highlight the necessity of the use ARD, to automatically exclude the irreversible component where not supported by the data. VB with ARD returns precise estimates in the majority of the kinetics (88% of total percentage of pixels) in a limited computational time (on average, 3.6 min per subject). Moreover, the impact of the additional trapping component has been evaluated for the differentiation of rheumatoid and non-rheumatoid patients, by means of a support vector machine classifier with backward feature selection. The results show that the trapping parameter is always present in the selected feature set, and improves the classification.

Irreversible desiccation shrinkage of cement paste caused by cement grain dissolution and hydrate precipitation

When cementitious materials are dried, internal stresses are generated that lead to desiccation shrinkage, a portion of which is irreversible. Previous research has indicated that, while a cementitious composite is subjected to a state of stress, dissolution of cement grains and precipitation of hydrates can yield irreversible creep strains, and it is hypothesized that the same process can lead to irreversible shrinkage during drying. To evaluate this hypothesis, a computationally implemented model integrating a microstructural evolution model with a finite element calculation routine was utilized. This computationally implemented model is capable of predicting the magnitude of shrinkage deformation of cement paste during drying conditions as a result of cement grain dissolution and hydrate precipitation. From the simulation results, the mechanism of cement grain dissolution and hydrate precipitation can lead to significant shrinkage behavior of cement paste, and it is also a potential mechanism resulting in the irreversible component of desiccation shrinkage at early ages (e.g., while the hydration rate is significant). The predicted irreversible shrinkage decreases with the age at which drying is initiated as a result of the decreasing hydration reaction rate.

Mass Sources and Modeling of Subsurface Heterogeneities in Deformable Solids

We propose an approach to the description of thermoelastic processes in deformable solids with regard for the structural heterogeneity of the material and the geometric heterogeneity of the surface of the body. In formulating the source relations, we use the methods of thermodynamics of nonequilibrium processes and nonlinear continuum mechanics. We take into account the structure of the material by introducing an irreversible component of the vector of mass flow. The geometric subsurface heterogeneity of the body is taken into account by introducing mass sources modeling its properties and by the dependence of the characteristics of materials, including the moduli of elasticity, on density. We study the equilibrium state of the half space. It is shown that two characteristic sizes correspond to the distributions of stresses and density. One of these sizes is connected with the structural heterogeneity of the material and the other is connected with the geometric heterogeneity of the actual surface of the body. We discuss the limits of applicability of the local gradient approach in the case of linearized approximation.

Thermal Analysis of a Fast Charging Technique for a High Power Lithium-Ion Cell

The cell case temperature versus time profiles of a multistage fast charging technique (4C-1C-constant voltage (CV))/fast discharge (4C) in a 2.3 Ah cylindrical lithium-ion cell are analyzed using a thermal model. Heat generation is dominated by the irreversible component associated with cell overpotential, although evidence of the reversible component is also observed, associated with the heat related to entropy from the electrode reactions. The final charging stages (i.e., 1C-CV) significantly reduce heat generation and cell temperature during charge, resulting in a thermally safe charging protocol. Cell heat capacity was determined from cell-specific heats and the cell materials’ thickness. The model adjustment of the experimental data during the 2 min resting period between discharge and charge allowed us to calculate both the time constant of the relaxation process and the cell thermal resistance. The obtained values of these thermal parameters used in the proposed model are almost equal to those found in the literature for the same cell model, which suggests that the proposed model is suitable for its implementation in thermal management systems.

Implications of accelerated self-healing as a key design knob for cross-layer resilience

In this paper we propose a cross-layer accelerated self-healing (CLASH) system which “repairs” its wearout issues in a physical sense through accelerated and active recovery, by which wearout can be reversed while actively applying several accelerated self-healing techniques, such as high temperature and negative voltages. Different from previous solutions of coping with wearout issues (e.g. BTI) by “tolerating”, “slowing down” or “compensating”, which still leave the irreversible (permanent) wearout component unchecked, the proposed solution is able to fully avoid the irreversible wearout through periodic rejuvenation, and this is inspired by the explored frequency dependent behaviors of wearout and (accelerated and active) recovery based on measurements on FPGAs. We demonstrate a case where the chip can always be brought back to the fresh status by employing a pattern of 31-h regular operation (under room temperature and nominal voltage) followed by a 1-h accelerated self-healing (under high temperature and negative voltage). The proposed system integrates the notions of accelerated self-healing across multiple layers of the system stack. At the circuit level, a negative voltage generator and heating elements are designed and implemented; at the architecture level, the core can be allocated in a way such that the dark silicon or redundant resources can be healed by active elements; at the system level, right balance of stress and accelerated/active recovery can be employed by the system scheduler to fully mitigate the wearout; various wearout sensors act as the media between different layers. Overall, these techniques work together to guarantee that the whole system performs for more of the time at higher levels of performance and power efficiency by fully taking advantage of the extra opportunities enabled by the accelerated self-healing.