1,721,012 research outputs found
Finite time stability design via feedback linearization
Full text linkA new nonlinear design technique for Finite-Time Stability for a class of nonlinear systems is developed using feedback linearization. Moreover, a new concept, namely the Finite-Time Contractive Stability with fixed settling time is introduced, giving sufficient conditions for analysis and design. An example illustrates the theoretical results
Analyzing cell-to-cell heterogeneities and cell configurations in parallel-connected battery modules using physics-based modeling
Full text linkIn parallel-connected cells, cell-to-cell (CtC) heterogeneities can lead to current and thermal gradients that may adversely impact the battery performance and aging. Sources of CtC heterogeneity include manufacturing process tolerances, poor module configurations, and inadequate thermal management. Understanding which CtC heterogeneity sources most significantly impact battery performance is crucial, as it can provide valuable insights. In this study, we use an experimentally validated electrochemical battery model to simulate hundreds of battery configurations, each consisting of four cells in parallel. We conduct a statistical analysis to evaluate the relative importance of key cell-level parameters, interconnection resistance, cell spacing, and location on performance and aging. The analysis reveals that heterogeneities in electrode active material volume fractions primarily impact module capacity, energy, and cell current, leading to substantial thermal gradients. However, to fully capture the output behavior, interconnection resistance, state of charge gradients and the effect of the temperature on parameter values must also be considered. Additionally, module design configurations, particularly cell location, exacerbate thermal gradients, accelerating long-term module degradation. This study also offers insights into optimizing cell arrangement during module design to reduce thermal gradients and enhance overall battery performance and longevity. Simulation results with four cells indicate a reduction of 51.8% in thermal gradients, leading to a 5.2% decrease in long-term energy loss
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Exergy Management Strategies for Hybrid Electric Ground Vehicles: A Dynamic Programming Solution
No full textIn this work, exergy management strategies (ExMSs) for hybrid electric ground vehicles (HEVs) are developed. The main advantage of using the exergetic framework is the possibility of pursuing unconventional optimization goals that are inaccessible to the standard energy management strategy (EMS). For instance, in military applications, the critical goal of preventing thermal imaging detection from adversary units does not seem achievable with the conventional EMS. On the other hand, the exergy-based framework can be adopted to reduce the vehicle thermal emissions through the minimization of exergy terms related to heat exchange. Moreover, the overall efficiency of the vehicle can be increased through the minimization of the exergy destruction, a quantity that is not quantifiable by energy-based methods. In this paper, the exergetic model of a series hybrid electric military truck and the exergetic model of the electric induction generator are developed and used to formulate and solve two novel exergy management strategies aiming to minimize genset exergy destruction and thermal emissions, respectively. The optimal solutions to the EMS and ExMSs control problems are obtained through Dynamic Programming over two driving missions. The results show that ExMS for the minimization of exergy destruction achieves similar results to the standard EMS, while the ExMS for the minimization of thermal emissions obtains significantly lower thermal emissions compared to the EMS, effectively reducing the thermal imaging detection risk
Application of low frequency EPR imaging to alanine dosimetry
No full textTwo-dimensional EPR imaging experiments were performed using alanine dosimeters irradiated at different doses. The imaging apparatus is based on a low frequency spectrometer utilizing 2 high Q reentrant cavity and air coils to provide the magnetic field gradients. The dosimeters Were made from a Mixture of alanine powder and paraffin molded into small cylinders with a diameter of 5 mm and a height of either 2 or 10 mm. The EPR line width is much larger than that of the other species usually employed for imaging. By using deconvolution techniques it was possible, in the presence of this complex spectrum of 0.0135 T, to obtain a spatial resolution of 1 mm with a gradient intensity of 0.13 T/cm
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Multi-channel physics-based modeling and experimental validation of an uncoated gasoline particulate filter in clean operating conditions
No full textThis paper presents the development of a two-dimensional (2-D), multi-channel, Gasoline Particulate Filter (GPF) system model. The GPF is an aftertreatment device designed to reduce soot particulate emissions in gasoline direct injection engines. A first-principle modeling approach using mass, energy and momentum balance equations is used to describe the clean filter dynamics. The 2D model is simulated by finite element analysis and the unknown model parameters are identified using a Particle Swarm Optimization (PSO) algorithm over experimental data from a GPF instrumented with 15 thermocouples. A validation study is presented that shows the effectiveness of the model proposed. The novel 2D GPF dynamics constitute the modeling foundation needed for the development of control-oriented models that will be explored in future works
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