Capacity Spectra Research Articles

Inhomogeneous Temperature Distribution Affecting the Cyclic Aging of Li-Ion Cells. Part I: Experimental Investigation

Alongside electrical loads, it is known that temperature has a strong influence on battery behavior and lifetime. Investigations have mainly been performed at homogeneous temperatures and non-homogeneous conditions in single cells have at best been simulated. This publication presents the development of a methodology and experimental setup to investigate the influence of thermal boundary conditions during the operation of lithium-ion cells. In particular, spatially inhomogeneous and transient thermal boundary conditions and periodical electrical cycles were superimposed in different combinations. This required a thorough design of the thermal boundary conditions applied to the cells. Unlike in other contributions that rely on placing cells in a climatic chamber to control ambient air temperature, here the cell surfaces and tabs were directly connected to individual cooling and heating plates. This improves the control of the cells’ internal temperature, even with high currents accompanied by strong internal heat dissipation. The aging process over a large number of electrical cycles is presented by means of discharge capacity and impedance spectra determined in repeated intermediate characterizations. The influence of spatial temperature gradients and temporal temperature changes on the cyclic degradation is revealed. It appears that the overall temperature level is indeed a decisive parameter for capacity fade during cyclic aging, while the intensity of a temperature gradient is not as essential. Furthermore, temperature changes can have a substantial impact and potentially lead to stronger degradation than spatial inhomogeneities.

Parametrización de espectros de capacidad de edificios de acero

En este articulo se presenta, en primer lugar, un marco teorico sobre el tema de los espectros de capacidad y su utilizacion en el estudio de la vulnerabilidad sismica de los edificios. A continuacion, se referencian los trabajos de algunos investigadores que han avanzado en la direccion de parametrizar tales curvas y se destacan sus mas importantes conclusiones. Posteriormente, se introducen los modelos que se han usado en esta investigacion y que se consideran representativos de las principales subclases de edificios de acero y se presentan sus espectros de capacidad. Finalmente, se procede a aplicar tecnicas de parametrizacion de dichas curvas y se presentan los resultados obtenidos y las principales conclusiones.

Assessment of Post-Earthquake Damaged Building with Interferometric Real Aperture Radar

In this study the main results of a detailed analysis of an actual building, which was severely damaged during the Mw 5.1, May 11th 2011, Lorca earthquake (Murcia, Spain) are presented. The dynamic behavior of the building was analyzed by means of empirical and numerical approaches. The displacement response of the building submitted to ambient noise was recorded by using a Real Aperture Radar (RAR). This approach provides a secure remote sensing procedure that does not require entering the building. Based on the blueprints and other available graphical information about the building, a numeric 3D model was also set up, allowing obtaining capacity spectra and fragility curves in the two main resistant directions of the building. The main purpose of this study was to check out the feasibility of the RAR-based method to detect the safety state of a damaged building after an earthquake, without the need of entering unsafe structures. A good consistency of the numerical and experimental approaches and the observed damage was obtained, showing that RAR interferometric-based tools may provide promising supplementary remote sensing methods to safely survey and report about the structural health and the operative conditions of buildings in post-earthquake scenarios.

Development of low-melting point molten salts and detection of solid-to-liquid transitions by alternative techniques to DSC

The ‘Solar salt’ (60% NaNO3-40% KNO3, wt. %) is the most used heat transfer and storage material in high temperature CSP systems. The main drawback is its high melting temperature of 228 °C, which requires extra-energy to keep it in the liquid state and avoid damage to pipes at low temperatures. Multi-component salts are combinations of different cations and anions. The difference in size of the ions hinders the crystallization of the material and provides lower melting temperatures. Multi-component salts are considered in this study to replace simpler combinations, such as binary and ternary eutectic mixtures. Herein, we report on two novel six-component nitrates with a melting temperature of 60–75 °C and a thermal stability up to ~500 °C under a linear heating program in N2 atmosphere. Properties such as the thermal conductivity in solid and molten state, heat capacity and vibrational spectra were evaluated. The study of the thermal behaviour of these materials using differential scanning calorimetry was insufficient, hence alternative and complementary techniques were used, such as: the three-omega technique, optical transmission and Raman spectroscopy. Multi-component salts were found to solidify as amorphous solids even at slow cooling rates and water was found to behave as a catalyst of crystallization.

Reducing Seismic out of Plane Vulnerability of Masonry Church Façades through Optimization of Capacity Spectrum by Tie Rods

The analyses of the structural damages detected on the Italian churches after the recent earthquakes (Emilia 2012, Umbria-Marche 2016) highlighted the high vulnerability to the overturning of the façades. The façades collapse mechanisms are strongly dependent on the connection details between orthogonal masonry walls, the windows, the construction techniques and the possible restraining horizontal elements, such as tie-beams, bi-lateral connected roof, etc. Several studies focus on the evaluation of vulnerability of the church façades using different approaches, from global analyses (FEM and /or Discrete Element Methods) of the entire building, to local analyses (linear and non-linear kinematic approaches). The aims of the present paper is to use the method based on capacity spectra to evaluate the vulnerability of the church facades and the optimization of specific devices as tie-rods to improve their seismic behavior. The non-linear approach is now accepted by several standards regarding the evaluation of risks of collapse mechanisms for masonry walls of the facades. Appropriate devices have been considered in order to calibrate the capacity curve and to optimize the interventions. The out of plane rotation of blocks can be modified with various elasto-perfect-plastic tendons with appropriate retentions (while composite materials could be used to preserve integrity of blocks). The tendons can be allocated in proper location and the length of each calibrated to best determine their stiffness. This procedure have been here applied to the study of the façade of Aula Magna S. Lucia of the Bologna University, considering also the problem of the interaction with the structure of the roof.

Heat capacity spectroscopy by using stochastic temperature modulated calorimetry: Time-temperature superposition and fictive temperature at the glass transition of poly (vinyl acetate)

Complex heat capacity spectra were measured by stochastic temperature modulated calorimetry using a conventional differential scanning calorimeter on poly (vinyl acetate) in the glass transition region during cooling. It is shown, that the real and imaginary part of the complex heat capacity spectra measured above and below vitrification can be scaled to a master curve by use of the frequency-temperature superposition principle. After the transition from a structurally equilibrated state to the non-equilibrated glass (vitrification), the shift factors deviate from the Vogel-Fulcher-Tammann-Hesse equation. The vitrification is described in the concept of fictive temperature using the Adam-Gibbs-Scherer equation for the temperature dependence of the relaxation time.

A microwave method for the rapid crystallization of UTSA-16 with improved performance for CO2 capture

Microwave (MW) irradiation is a simple and effective nonconventional heating method and is well-known in the field of metal-organic framework synthesis. In this paper, we report, a rapid microwave-assisted method for the synthesis of a UTSA-16 metal-organic framework. This process noticeably reduces the synthesis time from the 48 h required in traditional synthesis to 4 h. The synthesis of UTSA-16, whose formation was confirmed by X-ray diffraction analysis, was optimized by varying the synthesis time from 0.5 to 8 h. The UTSA-16 prepared with a reaction time of 4 h (4 h-UTSA-16) showed excellent CO2 adsorption capacity of 5.5 mmol/g at 298 K and 1 bar with a CO2/N2 sorption selectivity of 104, which is even higher than those reported for UTSA-16 samples prepared by solvothermal methods. The stability of UTSA-16 in humid air and acid gases was investigated by exposing it to humid air, as well as SO2 and NO2 gases, for 6 days. The UTSA-16 was very stable, showing no changes in the CO2 capture capacity and FTIR spectra after exposure to NO2 in humid air.

Development of Seismic Fragility Curves of RC Infilled Frame Buildings in Jordan

This article examines the seismic fragility of low- and mid-rise RC infilled frame buildings in Jordan comprising stone-concrete infill panels. Three dimensional models of 2, 4 and 6 story regular and irregular representative buildings were developed. Pushover analyses were performed to construct capacity curves of the model buildings. Four damage states were considered: slight, moderate, extensive and complete and damage state thresholds were assigned, using expert opinion, based on yield and ultimate spectral displacements of the capacity spectra. Sets of preliminary fragility curves were developed to quantify earthquake damage probabilities in terms of spectral displacements.

Influence of steel jacket thickness on the RC bridges’ seismic vulnerability

Abstract The seismic demands of bridges subjected to strong earthquakes are mostly concentrated on piers. The main objective of this study is to assess the seismic vulnerability of retrofitted bridges with steel jackets. It analyzes the influence of the steel jacket thickness on the seismic capacity and demand of bridges. The bridges in study have two simple supported spans with superstructure composed by AASHTO type girders and a substructure formed with one circular pier over a stiff foundation. They are located on the Pacific coast of Mexico that is a zone of high seismicity. The bridges seismic capacity are evaluated through nonlinear static analyses and the shear force and displacement demands were determined using capacity spectra with a group of 10 real accelerograms from a subduction source. The response spectra were scaled to several peak ground accelerations (PGA) with the aim to estimate four damage scenarios linked each one to a probability of exceedance in a specific period, for return periods in the range of 72–3500 years that represent service level and maximum considered earthquake. Results show that the confining effect provided by the steel jackets substantially improves the seismic performance of the bridges piers. The increase of jacket thickness guides to important increments on columns base shear capacity, and the influence of the steel jacket thickness depends on the limit state and bridge slenderness ratio.

Influence of earthquake duration on the response of steel moment frames

The influence of ground motion duration on the seismic response of steel moment frames is examined is this paper, with due consideration for cyclic degradation effects. A set of 77 spectrally equivalent pairs of short and long records is utilised in detailed nonlinear dynamic assessments in order to isolate the effects of ground motion duration. The influence of duration is firstly evaluated considering degrading and non-degrading idealised bilinear SDOF systems, for various levels of lateral strength representing practical ranges encountered in design. Subsequently, a sensitivity assessment focusing on the main parameters affecting the response of hysteretic degrading models is carried out through comparative incremental dynamic analysis. Whilst the effect of duration becomes more pronounced with the increase in lateral strength demands, particularly when approaching collapse, the cyclic degradation rate is shown to play a significant role even at lower levels typically associated with design. The performance of EC8-compliant frames indicates a higher probability of collapse when long-duration ground motion records are used, with a typical reduction of about 20% in the collapse capacity, in comparison with short-duration cases. The influence of duration is also examined through collapse capacity spectra, based on the seismic performance of 50 steel moment frames, which show that considerable reduction in the structural collapse capacity of structural systems occurs when relatively long duration records are adopted, for a wide range of dynamic characteristics. This becomes particularly evident in the case of buildings with relatively significant cyclic deterioration rates, where collapse capacity reductions up to 40% due to the influence of earthquake duration are obtained.

Density-functional theory based molecular dynamics simulation of tetrahedrite thermoelectrics: Effect of cell size and basis sets

In this work we investigated the effect of cell size and basis sets on the structural and dynamic properties from density-functional theory based molecular dynamics simulations. Three simulations, 1 × 1 × 1 cell with plane wave (PW) basis set, 1 × 1 × 1 cell with atomic orbital (AO) basis, and 2 × 2 × 2 cell with AO basis, were performed at 300 K on a model material: tetrahedrite thermoelectric Cu10Zn2Sb4S13. It was found that lattice parameters, vibrational spectra, heat capacity, and EXAFS spectra are comparable for three simulations. In addition, the 2 × 2 × 2 cell can provide access to length scales closer to the hydrodynamic limit, which allow us to identify the sound/acoustic modes in momentum/velocity correlation, as well as quasi-localized modes that are possibly responsible for its low lattice thermal conductivity.

Carboxymethyl Celulose (CMC) from Snake Fruit (Salaca edulis Reinw) Kernel of “Pondoh Super”: Synthesis and Characterization

Snake fruits kernel has high cellulose content thus potential to be an alternative source of carboxylmethylcellulose (CMC) production. However there are several condition that have to be optimized to increase the CMC synthesis which are concentration of NaOH solution, NaMCA addition, and the reaction temperature based on the degree of substitution (DS). The aim of this study was to determine the optimum conditions of synthesis CMC from “Salak Pondoh Super” kernel. Some factors that likely influence the synthesis were concentration of NaOH solution , NaMCA addition, and the reaction temperature based on the degree of substitution (DS) as the responses. Synthesis of CMC was optimized using completely randomized design. The result then was characterized by several parameters including water content, viscosity, purity, Water Holding Capacity (WHC), Oil Holding Capacity (OHC), lightness, crystallinity, and FT-IR spectra. Optimization was achieved by the use of 15% NaOH solution, 5 gram NaMCA per 5 gram cellulose and reaction temperature of 55ºC. The characteristics of the optimized CMC were DS 0.825, purity 90.86%, water content of 7.16 (% wb), viscosity 3.86 cps, 142.72 yield (% db), WHC 2.37 (g/g), OHC 2.31 (g/g), lightness 78.48, and crystanillity 32.69%. The FT-IR spectra of snake fruit kernel CMC was similar with the CMC Standard.

Energy damage index based on capacity and response spectra

Non-linear dynamic analysis and the damage index of Park-Ang have been often used to assess expected seismic damage to a structure. Depending on the size of the structure and the duration of the record, the computational effort in dynamic analyses is usually high. In this research, a new damage index is proposed based on nonlinear static analysis. The damage index is a linear combination of two energy functions: (1) the strain energy associated with the stiffness variation and the ductility of the structure, and (2) the dissipated energy associated with hysteretic cycles. These two energy functions are obtained from the capacity curve of the structure and from the energy balance with the spectral acceleration. To show the ability of the index to represent damage, low-rise steel buildings were studied under the seismic actions that are expected in Mexico City. The results obtained with the new method show good agreement with those calculated by means of dynamic analyses using the Park-Ang damage index. On average, the Park-Ang damage index is well-fitted by the combination of 62% of the strain energy and 38% of the energy dissipated by hysteresis. Moreover, the new damage index can link damage to certain characteristics of seismic actions, such as their intensity and duration. Therefore, the new approach results in a practical, powerful tool for estimating seismic damage in buildings, especially as probabilistic approaches require massive computations.

The physicochemical properties of a [DEME][TFSI] ionic liquid-based electrolyte and their influence on the performance of lithium–sulfur batteries

Electrolyte choice is an important decision on the quest for higher-energy batteries. Besides general guidelines on the required properties of an electrolyte suitable for use in lithium–sulfur batteries, the influence of more specific physicochemical properties on its characteristics is not well understood. For this purpose, binary mixtures based on the [DEME][TFSI] and dioxolane electrolyte system for lithium–sulfur batteries was investigated in this work. Selected physicochemical properties were determined for different mixtures of solvents and lithium salt concentrations. All the electrolytes prepared were also tested in the lithium–sulfur battery system. The capacity, Coulombic efficiency, overpotentials and impedance spectra were analyzed and a connection between them and the determined electrolyte properties elucidated. We show that the electrolyte's conductivity does not have a direct connection to any of the battery system properties measured. The highest specific capacities were obtained with batteries compromising 1.0M LiTFSI and the highest ratio of dioxolane in the binary solvent mixture. On the other hand, the best Coulombic efficiencies were obtained with batteries having high ratios of ionic liquid. Resistance and overpotential are connected parameters and are a function of the ionic liquid content. None of the monitored parameters prevail, since the best electrochemical performance in terms of specific capacity and stability was obtained with the 1.0M LiTFSI in X[DEME][TFSI]=0.199 electrolyte.

Development of seismic collapse capacity spectra for structures with deteriorating properties

Evaluation on the sidesway seismic collapse capacity of the widely used low- and medium-height structures is meaningful. These structures with such type of collapse are recognized that behave as inelastic deteriorating single-degree-of-freedom (SDOF) systems. To incorporate the deteriorating effects, the hysteretic loop of the nonlinear SDOF structural model is represented by a tri-linear force-displacement relationship. The concept of collapse capacity spectra are adopted, where the incremental dynamic analysis is performed to check the collapse point and a normalized ground motion intensity measure corresponding to the collapse point is used to define the collapse capacity. With a large amount of earthquake ground motions, a systematic parameter study, i.e., the influences of various ground motion parameters (site condition, magnitude, distance to rupture, and near-fault effect) as well as various structural parameters (damping, ductility, degrading stiffness, pinching behavior, accumulated damage, unloading stiffness, and P-delta effect) on the structural collapse capacity has been performed. The analytical formulas for the collapse capacity spectra considering above influences have been presented so as to quickly predict the structural collapse capacities.

Structural, phonon, mechanical, optical, and thermodynamic properties of stable β-La2S3 from first-principles calculations

The band structures, density of states, phonon, optical properties, and thermodynamic properties of β-La2S3 were calculated from first-principles using the plane-wave pseudopotential method. First, the structures were fully relaxed through the first-principles method. Then, the zone-center phonon-mode frequencies were evaluated within the framework of density functional perturbation theory. Properties related to the structure, phonons, optics, elastic constants, and thermodynamics of β-La2S3 were reported. The dielectric function, refractive index, absorption coefficient, extinction coefficient, infrared (IR) reflectance, energy, heat capacity, and Debye temperature spectra were also given. β-La2S3 was a direct-gap semiconductor, and calculation indicated that its energy gap was 0.191 eV. From the phonon spectra, it could be concluded that the lattice dynamics were stable. A strong IR reflection occurred in a range of 0- 1000 nm, arising from several strong IR-active modes, resulting in poor transmission properties. Relatively good transmission properties were observed in the range above 2000 nm, with low reflectivity and dissipation due to the absence of IR-active or weak modes.

Local and Cooperative Jahn-Teller Effect and Resultant Magnetic Properties of M2AgF4 (M = Na-Cs) Phases.

The crystal structure, magnetic properties, heat capacity, and Raman spectra of double-perovskite M2AgF4 (M = K, K3/4Rb1/4, K1/2Rb1/2, K1/4Rb3/4, and Rb) phases have been examined, adding to the body of previous results for the M = Na, Cs derivatives. The results suggest that double-perovskite K2AgF4 adopts a disordered orthorhombic Bmab structure with an antiferrodistortive arrangement of the elongated and tilted [AgF6] octahedra rather than the structure with the ferrodistortive arrangement of compressed octahedra, as suggested previously (Mazej, Z.; Goreshnik, E.; Jagličić, Z.; Gaweł, B.; Łasocha, W.; Grzybowska, D.; Jaroń, T.; Kurzydłowski, D.; Malinowski, P. J.; Koźmiński, W.; Szydłowska, J.; Leszczyński, P. J.; Grochala, W. KAgF3, K2AgF4 and K3Ag2F7: important steps towards a layered antiferromagnetic fluoroargentate(II). CrystEngComm 2009, 11, 1702-1710). A re-examination of the previously collected single-crystal X-ray diffraction data confirms the current structure assignment, and it is also in agreement with recent theoretical calculations. High-field electron paramagnetic resonance spectra reaffirm the presence of elongated [AgF6] octahedra in the crystal structure of all M2AgF4 phases studied. The local structure of the M = K derivative is most complex, with regions of the sample that are quite orthorhombically distorted, whereas other regions more closely resemble the tetragonal phase. The mixed-cation K/Rb phases are also inhomogeneous, containing regions of the pure K compound and regions of another high-symmetry phase (likely tetragonal) of a mixed (Rb-richer) compound with unknown composition. The temperature-resolved phase diagram of all K/Rb phases has been established and positioned within the entire M = Na, K, Rb, Cs series.

Structural safety redundancy-based design method for structure with viscous dampers

A simple design process is proposed for supplemental viscous dampers based on structural safety redundancy. In this process, the safety redundancy of the primary structure without a damper is assessed by the capacity and response spectra. The required damping ratio that should be provided by the supplemental dampers is estimated by taking the structural safety redundancy as a design target. The arrangement of dampers is determined according to the drift distribution obtained by performing pushover analysis. A benchmark model is used to illustrate and verify the validity of this design process. The results show that the structural safety redundancy of the structure provided by the viscous dampers increases to approximately twice that of the structure without a damper and is close to the design target. Compared with the existing design methods, the proposed process can estimate the elastic-plastic response of a structure more easily by using static calculation, and determine the required damping ratio more directly without iterative calculation or graphical process. It can be concluded that the proposed process is simple and effective.

High-temperature heat capacity and vibrational spectra of Eu2Sn2O7

The Eu2Sn2O7 compound has been prepared by solid-state reaction (by sequentially firing a stoichiometric mixture of Eu2O3 and SnO2 in air at 1273 and 1473 K) and its heat capacity has been determined by differential scanning calorimetry in the temperature range 370–1000 K. The heat capacity data have been used to evaluate the thermodynamic properties of europium stannate: enthalpy increment H°(T)–H°(370 K), entropy change S°(T)–S°(370 K), and reduced Gibbs energy Ф°(T). Raman spectra of Eu2Sn2O7 polycrystals with the pyrochlore structure have been measured in the range 200–1200 cm–1.

RC jacketing parameters to retrofit highway bridges

Highway bridges are essential structures in the transportation system of any country in the world. Many highway bridges are reinforced concrete (RC) bridges that were constructed before the 1980s, prior to current seismic regulation codes. The continuous modification of regulation codes makes it necessary to evaluate structures, and in many cases, existing bridges require interventions to increase their seismic capacity. Among the different techniques used to improve bridge capacity, encasing the columns with RC jackets increases the strength and stiffness of the substructure. RC jacketing increases the column cross sections, improves the seismic capacity and reduces the seismic vulnerability of the bridge substructures. This work presents a parametric study to assess the expected demands of seismically deficient medium length highway bridges retrofitted with RC jacketing aimed at determining the best jacket parameters. A suite of twenty strong ground motions, recorded from a subduction seismic source close to the Pacific Coast in Mexico, was selected to characterize the seismic demand. The bridge superstructures are simply supported with five 30 m long spans for a total length of 150 m. The bridge models have five possible pier heights of 5, 10, 15 20 and 25 m and three different jacket thicknesses and steel ratios. Pushover analyses and capacity spectra of the family of accelerograms allow for the determination of the pier demands by obtaining the performance point as the intersection of the capacity and demand curves. The results allow for the determination of the influence of each parameter on the expected seismic behavior of the bridge models, with the aim of selecting the most suitable jacket characteristics to improve the seismic bridge performance.