Capacity Spectra Research Articles

Heat capacity and magnetic properties of fluoride CsFe2+Fe3+F6 with defect pyrochlore structure

Heat capacity, Mössbauer and Raman spectra as well as magnetic properties of fluoride CsFe2F6 with defect pyrochlore structure were studied. In addition to recently found above room temperature three successive structural transformations Pnma-Imma-I41amd-Fd-3m, phase transition of antiferromagnetic nature with the 13.7K Neel temperature and a broad heat capacity anomaly with a maximum at about 30K were observed. The room temperature symmetry Pnma is unchanged at least down to 7K. Simple model of indirect bond used to estimate the exchange interactions and to propose a magnetic structure model.

Nafion 117 stability under conditions of PEM water electrolysis at elevated temperature and pressure

In this work a systematic study of the behaviour of a Nafion 117 membrane under conditions of elevated temperatures (up to 150 °C) and pressure (up to 0.7 MPa) was carried out. Attention focused primarily on the ionic conductivity of the membrane in the proton form with exposure to the conditions under study for up to 800 h. The ion-exchange capacity, morphology, FTIR and NMR spectra of the membrane were determined to explain the decline in conductivity observed over time. The techniques used did not reveal any chemical degradation of the membrane polymer. The morphological changes to the membrane connected with excessive expansion of the internal structure of the polymer are assumed to be the reason for the phenomenon observed. Finally, to confirm the conclusions derived, the membrane behaviour in a laboratory-scale water electrolysis cell was studied under operating conditions corresponding to its prior characterization.

Performance-based Seismic Evaluation of RC Framed Building

This work presents a typical 6-storey reinforced concrete building frame analyzed and designed for four load cases considering the three revisions of IS:1893 and IS:456. A conceptual frame work and detailed procedure for performance evaluation of reinforced concrete framed buildings are presented against the explicit force based method described in Indian codes of practice. Modelling issues related to generation of capacity curve, the damage and vulnerability indices are discussed. Based on the studies simple expressions are suggested to estimate, the global damage indices in the hardening and elasto-plastic regions of the capacity spectra.

Variability Analysis of Discharge Characteristics and Impedance Spectra in Li-Air Batteries

Electrochemical energy storage devices are well known to show large variation in discharge characteristics, even though, they are fabricated using the same technological processes and much care is given to produce identical cells. This variation causes the discharge voltages, specific capacity, energy and power density of energy storage devices to vary significantly from one cell to another. Among the current energy storage devices, metal-air batteries suffer from a particularly large variability due to a number of extrinsic and intrinsic parameter variations (1). On the one side, the continuously changing atmospheric conditions such as operating temperature, humidity, outside pressure, and wind, as well as random instrumentation errors, induce a significant variability of reported cell characteristics in the literature. On the other side, intrinsic parameter variations such as different microstructural properties that arise from the cathode preparation techniques that make it impossible to fabricate identical porous materials also result in different cell characteristics. The goal of this presentation is twofold: First, we analyze the effects of intrinsic and extrinsic parameter fluctuations on the discharge characteristics and impedance spectra of Li-air batteries. Second, we develop a small-signal perturbation technique for the characterization of the variability in Li-air batteries. The analysis of the parameter fluctuation induced effects is done using Monte-Carlo methods. For this purpose, we generate a large number of the devices with identical macroscopic but different microscopic configurations and simulate each device independently. In this way we accumulate statistics for the parameters of interest – in our case the discharge curves, specific capacity, and impedance spectra – and compute the average values and standard deviations of these parameters. The Monte-Carlo method is computationally very expensive because it requires simulating many different devices. If we assume the parameter fluctuations are normally distributed, the error in computing the standard deviation of one parameter of interest is approximately equal to 1/sqrt(2N), where Nis the number of devices simulated. This equation shows that in order to compute the standard deviation of a parameter with an error of less than 5% we need to perform at least 200 device simulations. For this reason, we develop a new technique for the analysis of variability in electrochemical devices based on small-signal perturbations. We assume that the fluctuating parameters that appear in the transport equations are random variables characterized by some average values and given standard deviations. Then, we expand the transport equations in power series and find analytical equations for the average values and fluctuations of the parameters of interest. These equations are then solved either analytically or using finite element models and the results are compared the Monte-Carlo method. The computational complexity of perturbation techniques is much smaller than the complexity of Monte-Carlo methods because perturbations techniques require solving the (nonlinear) transport system of equations once and a few linear systems of equations. At the conference we will present results for the discharge characteristics obtained using the finite element model presented in (2). The impedance spectra are modeled using both the compact model presented in (3) and the finite element approach presented in (4). Our initial results show a very good agreement between the Monte-Carlo simulations and the linearization approach. A detail discussion of the variability of the discharge characteristics, specific capacity, and impedance spectra in Li-air will be presented at the conference. References L. D. Griffith, A. E. S. Sleightholme, J. F. Mansfield, D. J. Siegel and C. W. Monroe, ACS Appl. Mater. Interfaces, 7, 7670 (2015).P. Andrei, J. P. Zheng, M. Hendrickson and E. J. Plichta, J. Electrochem. Soc., 157, A1287 (2010).M. Mehta, G. Mixon, J. Zheng and P. Andrei, J. Electrochem. Soc., 160, A2033 (2013).M. Mehta and P. Andrei, ECS Trans., 61(15), 39 (2014).

Parametric model for capacity curves

A parametric model for capacity curves and capacity spectra is proposed. The capacity curve is considered to be composed of a linear part and a nonlinear part. The normalized nonlinear part is modelled by means of a cumulative lognormal function. Instead, the cumulative Beta function can be used. Moreover, this new conceptualization of the capacity curves allows defining stiffness and energy functions relative to the total energy loss and stiffness degradation at the ultimate capacity point. Based on these functions, a new damage index is proposed and it is shown that this index, obtained from nonlinear static analysis, is compatible with the Park and Ang index obtained from dynamic analysis. This capacity based damage index allows setting up a fragility model. Specific reinforced concrete buildings are used to illustrate the adequacy of the capacity, damage and fragility models. The usefulness of the models here proposed is highlighted showing how the parametric model is representative for a family of capacity curves having the same normalized nonlinear part and how important variables can be tabulated as empirical functions of the two main parameters defining the capacity model. The availability of this new mathematical model may be a powerful tool for current earthquake engineering research, especially in seismic risk assessments at regional scale and in probabilistic approaches where massive computations are needed.

Chemical composition, bioactive compounds, antioxidant capacity and stability of floral maize (Zea mays L.) pollen

The nutritional composition, the phenolic profiles and antioxidant capacity of the floral pollen from maize genotypes were evaluated. In addition, the antioxidant capacity, browning and wavelength spectra of melanoidins were investigated in the pollen samples stored at 4 °C for 7 days, dried at 40 °C for 6 h and exposed to a temperature of 100 °C during 12 h. The results showed that different maize pollen samples had diverse nutritional composition, antioxidant capacity and phenolic compounds were a major contributor to their antioxidant activities. Sweet maize pollen with the highest content of total phenolics and flavonoids had the highest antioxidant capacity (104.38 mmol trolox eq/kg). Quercetin diglycoside was the most abundant flavonoid in all pollen samples. Floral maize pollen could be used as a functional food ingredients, and dietary supplement with therapeutic effects. However, pollen is very susceptible to processes of Maillard reaction and phenolics oxidation and these factors must be considered when considering its use.

Eurocode 8: Use of advantageous formulations for improved and safe design

The purpose of the paper is to share the experience in application of Eurocode 8. Following the existing framework of the European standard two engineering development of two specific topics are proposed. First deals with modelling the seismic action aiming to take into account spatial variability of the seismic action. It is proven that the inclusion of rotational components may influence the action effects and the results provide unsafe design. Evaluation is carried out through response spectrum method. The second topic studies the use of performance based seismic design as a tool to prove the need for seismic strengthening and verification of the benefit. Both target and actual capacity spectra are compared to make assessment of the lateral resistance of existing and strengthened structure. Insufficient elastic stiffness and insufficient yield strength are considered as the most typical situations frequently met in the design practice and which can be settled by seismic strengthening. Discussions and conclusions concerning the philosophy of the assessment procedure are presented.

Seismic safety evaluation based on DIP

There are continuous attempts to describe the damaging potential of the seismic (or vibratory) motion by a single parameter or a set of damage indicating parameters (DIP). Recently CAV and IJMAJMI have become two very promising parameters. Originally CAV was introduced as a parameter alongside spectral characteristics of ground motion for assessment of the operational state of a nuclear power plant after a seismic event. The aim is to shorten the time for evaluation of OBE exceedance and to provide guidance for the quick restart of a seismically affected plant. Meanwhile, there has been a growing experience and confidence that the DIP could be used not only as global indicator, i.e. assessment of the severity of excitation on the plant site but also as damage descriptor at equipment level, i.e. at each equipment location. The procedure proposed is similar to that for floor response spectra generation and safety evaluation against seismically induced forces. The current paper presents basic relations between damage parameters and structural damage derived from the European strong motion database. The seismic experience database is utilized to assess the capacity/damage of equipment.A formalized approach is considered for evaluation of critical facilities subjected to dynamic vibratory loading. The following sequence of evaluation steps is discussed: Step one: for the safety equipment the standard in-structure CAV is calculated and compared with a threshold to screen-out the equipment for further considerations. An additional and optional threshold could be the in-structure IJMA intensity estimate. Step two: for all locations where standard CAV of in-structure vibrations is higher than the threshold, the floor response spectra are evaluated. They have to be compared with the equipment capacity spectra. The latter are represented by design floor response spectra multiplied by a safety factor or seismic ruggedness spectra. Step three: alternatively or simultaneously with the ultimate capacity assessment (force driven design) a displacement based evaluation of the ultimate drift capacity of the respective equipment can be performed.It has to be stressed that under high frequency excitation the displacement (drift) estimated capacity is by far more realistic than the force based estimates.If none of the above checks is positively answered detailed conventional analysis can follow; however, a much smaller amount of equipment would remain for assessment.

Capacity Spectrum Method for RC Building with Cracked and Uncracked Section

one of the most widespread procedures for the assessment of building behavior, due to earthquake, is the Capacity Spectrum Method (CSM). In the scope of this procedure, capacity of the structure compares with the demands of earthquake ground motion on the structure. The capacity of the structure is represented by a nonlinear force-displacement curve, referred to as a pushover curve. The base shear forces and roof displacements are converted to equivalent spectral accelerations and spectral displacements, respectively, by means of coefficients that represent effective modal masses and modal participation factors. These spectral values define the capacity spectrum. The demands of the earthquake ground motion are represented by response spectra. A graphical construction that includes both capacity and demand spectra, results in an intersection of the two curves that estimates the performance of the structure to the earthquake. In this study, for determination of the performance levels, G+10 R.C.C. Building with cracked and uncracked section were taken. The structural Capacity of cracked and uncracked section compared with performance point value, which shows the structural capacity of building having cracked section is lesser than the uncracked section. Different modeling issues were analyzed to study the effect on Capacity of the structure with cracked

Evaluación sísmica de los edificios de mampostería típicos de Barcelona aplicando la metodología Risk-UE

In this work, a study about the vulnerability and seismic damage of unreinforced masonry buildings is carried out. Three models of buildings representatives of the Eixample district of Barcelona have been chosen. The seismic vulnerability is evaluated by means of the Risk-UE methodology. The seismic demand is described by elastic project spectrum, in this case, defined by the Eurocode 8. Fragility curves are obtained from a nonlinear analysis, considering the capacity spectra. Expected seismic damage is gotten with the damage probability matrices, which indicate the occurrence probability of a damage state for a seismic demand given. The analysis of the buildings has been performed by TreMuri program by means of a macroelements model, which represents of a whole masonry panel. The buildings, here, analyzed are real and detailed structural drawings and reports have been used to model them. The results shown a considerable vulnerability in this type of buildings, therefore, in spite of the seismic hazard the expected seismic risk is significant.

Assessment of Using of Knee Bracing in Retrofitting of Existing Steel Structures with Special Moment Resistant Frame System (Technical Note)

In this paper, non-linear behaviors of structures with special moment resistant frame were studied and possibility of using knee bracing for retrofitting of those structures was examined. For this aim, the structures that have been designed according to the second edition of Iranian seismic code (2800), were selected. Those models have 3, 5 and 7 stories. To evaluating and retrofitting of models, non-linear static analysis and capacity spectra (ATC-40) method were applied and providing of the expected performance levels in FEMA356 was studied. Results showed that the response of structures that designed according to the previous edition of code (second edition) is not compatible with the criteria of third edition. The knee bracing system was used to seismic retrofit of those structures. It would be concluded that the using of knee bracing increases lateral stiffness and improves their energy dissipating capacity. Furthermore, the results showed that the shorter knees have the highest stiffness and ductility in the structures.

Tuning the Properties of Redox‐Active Guanidino‐Functionalized Aromatic Ligands by Substitution: Experiment and Theory

AbstractSubstitution of the aromatic hydrogen atoms in the electron donors 1,2,4,5‐tetrakis(tetramethylguanidino)benzene (1a) and 1,2,4,5‐tetrakis(N,N′‐dimethyl‐N,N′‐ethyleneguanidino)benzene (1b) by iodide (to give 2a and 2b) and nitro groups (to give 3a and 3b) afforded new redox‐active ligands. Their properties (electron donor capacity, Brønsted basicity and optical spectra) have been analyzed and compared with the unsubstituted 1,2,4,5‐tetrakis(guanidino)benzenes. The experimental results are supplemented by quantum chemical calculations. The first late‐transition metal complex of the push–pull ligand 3a was prepared and characterized and its oxidation studied.

An Assessment Study of Seismic Resistance of Two-story Wood-frame Housing by Shaking Table Tests

While there exists a relatively large body of technical information for the engineered design of wood-frame buildings to resist seismic ground motions, the quantitative assessment of seismic resistance of conventional houses built by prescriptive requirements is less well understood. Forintek Canada Corp., in collaboration with other research and industry partners, has embarked on a research project to address this topic. This paper will report on the seismic shake table tests of a full-scale wood-frame building. The two-story specimen, <TEX>$6m{\times}6m$</TEX> in plan, was built on the seismic shake table at Tongji University in Shanghai, China, according to Part 9 of the 1995 National Building Code of Canada and shaken uni-directionally in each of the two principal directions. Three different seismic table motions were applied at increasing peak ground motion amplitudes up to 0.40 and 0.50 g. The specimen was repaired after the above sets of seismic table motions, and successive runs were conducted for increased door openings. Measurements included specimen accelerations, displacements and anchorage forces. Static stiffness of the specimen was measured at low force levels, and natural frequencies were measured after each seismic loading stage by applying low-level random excitation. The results presented consist of the capacity spectra of the shake table tests, changes in specimen stiffness and natural frequencies with increasing seismic loading. These results and those from other recent shake table tests elsewhere will be compared with simplified engineering calculations based on codified values of strength, and on that basis preliminary conclusions will be drawn on the adequacy of the current code provisions and design guides in Canada and the USA for conventional wood-frame construction.

Seismic performance analysis of the masonry buildings, typical of the Eixample district of Barcelona

In this work a study about the vulnerability and seismic risk of the unreinforced masonry buildings, widely, existent in the Eixample district of Barcelona, Spain, is carried out. The buildings, here, analyzed are real and detailed structural drawings and reports have been used to model them. The seismic risk is evaluated by means of a mechanical model, based in the Capacity Spectrum Method. The seismic demand is described by elastic response spectrum defined by the Eurocode-8. Fragility curves are obtained from a nonlinear analysis, considering the capacity spectra. Expected seismic damage is gotten with the damage probability matrices. The analysis of the buildings has been performed by TreMuri program by means of a macro-element model. The results shown a considerable vulnerability in this type of buildings, therefore, in spite of the seismic hazard, the expected seismic risk is significant.

Seismic collapse capacity spectra for simple structures vulnerable to dynamic instabilities

AbstractIn this study collapse capacity spectra based on various definitions of the seismic intensity are set in contrast and evaluated. The presented collapse capacities for highly inelastic non‐deteriorating single‐degree‐of‐freedom (SDOF) systems, which are vulnerable to the destabilizing effect of gravity loads, are derived for a near‐fault set of ground motions with distinct pulse characteristics. (© 2011 Wiley‐VCH Verlag GmbH &amp; Co. KGaA, Weinheim)

Performance-Based Seismic Design Approach for High Speed Railway Bridge

Performance objectives and contents of resistance verification for high speed railway bridge are embodied and quantified based on the theory of performance-based seismic design. The resistance verification is proposed, which can control the damage under design earthquake and ensure safety of the pier under low-level earthquake. The simplified capacity spectra method for calculating displacement ductility factor is proposed by using strength reduction factor. The method for evaluating damage of RC bridge pier in high-level earthquake is presented by using maximum displacement and hysteretic energy. The proposed approach and procedures for performance-based seismic design are easily to implement. The performance-based seismic design procedure is demonstrated by using an example.

Seismic collapse capacity of basic inelastic structures vulnerable to the P‐delta effect

SUMMARYThe collapse capacity of earthquake‐excited inelastic nondeteriorating SDOF systems, which are vulnerable to the destabilizing effect of gravity loads (P‐delta effect), is evaluated. In this paper, the collapse capacity of the system subjected to a ground motion is defined as spectral acceleration at its initial structural period, at which the structure becomes unstable. Characteristic structural parameters, which affect the collapse capacity, are identified. Ground motion records of the ATC 63 far‐field set characterize severe earthquake excitation. In extensive incremental dynamic analyses studies, the impact of these parameters and of aleatory uncertainties on the collapse capacity is assessed and quantified. Median and percentile collapse capacities are plotted against the initial structural period leading to collapse capacity spectra. Nonlinear regression analyses are applied to derive analytical expressions of the design collapse capacity spectra and collapse fragility curves. The ultimate objective is to provide collapse capacity spectra for easy application and yet sufficient accurate assessment of the dynamic stability of flexible multistory buildings. Copyright © 2011 John Wiley &amp; Sons, Ltd.

Acid–base properties of ion exchangers: V. Synthesis and properties of ion exchangers on the base of modacrylic polyacrylonitrile–vinylchloride fibers

Weak base polyfunctional fibrous anion exchangers, containing small amount of carboxylic acid groups were obtained on the base of industrial modacrylic fibers Kanecaron (40% acrylonitrile, 60% vinylchloride) (Kaneka Ltd., Japan) by their reacting with aqueous solutions of diethylenetriamine (DETA). The sample obtained at optimal condition (DETA concentration 70–80%, process time 2–7 h, temperature 95 °С) have anion exchange capacity 3–5 meq/g and water uptake 0.3–0.4 gH 2O/g. Their chemical stability in different media has been studied. On the base of studies of their ion exchange capacity, elemental analysis, potentiometric titration and IR spectra the structure of these ion exchangers has been clarified. Predominant reaction of the modification is substitution of the Cl atoms by nitrogen in DETA molecules with formation of tertiary and secondary amino groups. All three atoms of nitrogen react and the ratio of incoming N atoms and outgoing Cl atoms is close to one.

Study of the Applicability of Modal Pushover Analysis on Irregular Continuous Bridges

The influence of higher modes and their consideration in the pushover analysis of three irregular continuous bridges is discussed. Modal pushover analysis (MPA) is addressed and compared with inelastic time-history analysis (ITHA). In the operation process of MPA, each important mode is used to determine the distribution of forces for the pushover analysis separately, and the displacements of different parts of bridge are monitored to construct pushover curves for each important mode. When the analyses for all important modes of one bridge are completed, the results are combined and compared with the results of ITHA. The investigation shows, for each important mode, adopting different displacement-monitored points obtains different pushover curves. If reasonable pushover curves are selected as capacity spectra, MPA can give the results comparable with ITHA, or else MPA does not work well. Finally, how to choose reasonable displacement-monitored point to construct capacity spectrum of MPA is identified.

Energy-Based Modal Pushover Procedure for Asymmetric Structures

Energy-based seismic evaluations of structures can give clear illustrations of seismic demands made upon structures. This paper presents a 3-dimensional energy-based modal pushover analysis (3D EMPA) method with equivalent three degree of freedom (ETDOF) system and equal-displacement rule. The lateral-rotational coupled effect on structures asymmetric in plan is considered using the energy-based modal pushover analysis (EMPA), which is more robust than the traditional Modal Pushover Analysis (MPA) procedure. The proposed procedure was validated against a nonlinear time history analysis of a 5-storey structure. The results show that the method is able to take higher mode effects into account and that the instability of capacity spectra will be avoided. The maximum deformation obtained from EMPA shows good agreement with a nonlinear time history analysis results of the original system. The proposed EMPA procedure appears to be reliable and effective for evaluating the seismic response of asymmetric-plan structures.