Electrochemical modelling of Li-ion battery pack with constant voltage cycling

In a battery pack, cell-to-cell chemical variation, or the variation in operating conditions, can possibly lead to current imbalance which can accelerate pack ageing. In this paper, the Pseudo-TwoDimensional(P2D) porous electrode model is extended to a battery pack layout, to predict the overall behaviour and the cell-to-cell variation under constant voltage charging and discharging. The algorithm used in this model offers the flexibility in extending the layout to any number of cells in a pack, which can be of different capacities, chemical characteristics and physical dimensions. The coupled electrothermal effects such as differential cell ageing, temperature variation, porosity change and their effects on the performance of the pack, can be predicted using this modelling algorithm. The pack charging voltage is found to have an impact on the performance as well as the SEI layer growth. Numerical studies are conducted by keeping the cells at different thermal conditions and the results show the necessity to increase the heat transfer coefficient to cool the pack, compared to single cell. The results show that the thermal imbalance has more impact than the change in inter-connecting resistance on the split current distribution, which accelerates the irreversible porous filling and ageing

A mass transfer based variable porosity model with particle radius change for a Lithium-ion battery

Micro pore-clogging in the electrodes due to SEI growth and other side reactions can cause adverse effects on the performance of a Lithium-ion battery. The fundamental problem of volume fraction variation and particle radius change during the charge-discharge process in a lithium-ion battery is modelled in this paper with the help of mass transfer based formulation and demonstrated on a battery with LiCoO2 chemistry. The model can handle the volume fraction change due to intercalation reaction, solvent reduction side reaction and the electrolyte density change due to side reaction contamination in the battery. The entire calculation presented in this paper models particle radius and volume fraction together and therefore gives greater accuracy in calculating the volume-specific-area of the reacting particles which is an important parameter controlling the Butler-Volmer kinetics. The mass deposit on the electrode (or loss of lithium) gives an indication of the amount of pre-lithiation required to maintain cell performance while the amount of mass deposited on the SEI helps to decide the safe operating condition for which the clogging of pores and capacity fade will be minimal. Moreover the model presented in this paper has wide applicability in analysing the stress development inside the battery due to irreversible porous filling

Work–Family Conflict and Counterproductive Work Behaviors: Moderating Role of Regulatory Focus and Mediating Role of Affect

Evidence suggests work–family conflict can lead to numerous negative consequences in the workplace, including behaviors detrimental to the organization and its members, such as counterproductive work behaviors (CWBs). Yet relatively little research has addressed the relationship between work–family conflict and CWBs. This study builds on the structural model of stress and regulatory focus theory to addresses this major gap in the literature. Our model proposes that negative affect and self-regulation can help us understand how and why work–family conflict may be related to CWBs. We hypothesize that work–family conflict is positively related to negative affect, which in turn is positively related to CWBs, and regulatory focus moderates the relationship between work–family conflict and CWBs. A survey of 332 employees shows work–family conflict is directly related to CWBs, indirectly related to CWBs via negative affect, and the relationship is moderated by regulatory prevention focus. We discuss implications for theory and practice

Modified electrochemical parameter estimation of NCR18650BD battery using implicit finite volume method

The Pseudo Two Dimensional (P2D) porous electrode model is less preferred for real time calculations due to the high computational expense and complexity in obtaining the wide range of electro-chemical parameters despite of its superior accuracy. This paper presents a finite volume based method for re-parametrising the P2D model for any cell chemistry with uncertainty in determining precise electrochemical parameters. The re-parametrisation is achieved by solving a quadratic form of the Butler-Volmer equation and modifying the anode open circuit voltage based on experimental values. Thus the only experimental result, needed to re-parametrise the cell, reduces to the measurement of discharge voltage for any C-rate. The proposed method is validated against the 1C discharge data and an actual drive cycle of a NCR18650BD battery with NCA chemistry when driving in an urban environment with frequent accelerations and regenerative braking events. The error limit of the present model is compared with the electro-chemical prediction of LiyCoO2 battery and found to be superior to the accuracy of the model presented in the literature

Service Systems with Heterogeneous Customers: Investigating the Effect of Telemedicine on Chronic Care

Medical specialists treating chronic conditions typically face a heterogeneous set of patients. Such heterogeneity arises because of differences in medical conditions as well as the travel burden each patient faces to visit the clinic periodically. Given this heterogeneity, we compare the strategic behavior of revenue-maximizing and welfare-maximizing specialists and prove that the former will serve a smaller patient population, spend more time with the patients, and have shorter waiting times. We also analyze the impact of telemedicine technology on patient utility and the specialists' operating decisions. We consider both the case when specialists can freely set their own fee for service and the case when fees are set exogenously by a third-party payer. We prove that with the introduction of telemedicine the specialists become more productive and the overall social welfare increases, though some patients, unexpectedly, will be worse off. Our analytical results lead to some important policy implications for facilitating the further deployment of telemedicine in the care of chronically ill patients

RELEASE: A High-level Paradigm for Reliable Large-scale Server Software

Erlang is a functional language with a much-emulated model for building reliable distributed systems. This paper outlines the RELEASE project, and describes the progress in the first six months. The project aim is to scale the Erlang’s radical concurrency-oriented programming paradigm to build reliable general-purpose software, such as server-based systems, on massively parallel machines. Currently Erlang has inherently scalable computation and reliability models, but in practice scalability is constrained by aspects of the language and virtual machine. We are working at three levels to address these challenges: evolving the Erlang virtual machine so that it can work effectively on large scale multicore systems; evolving the language to Scalable Distributed (SD) Erlang; developing a scalable Erlang infrastructure to integrate multiple, heterogeneous clusters. We are also developing state of the art tools that allow programmers to understand the behaviour of massively parallel SD Erlang programs. We will demonstrate the effectiveness of the RELEASE approach using demonstrators and two large case studies on a Blue Gene