title: Fractional modelling of rechargeable batteries

authors: Hasan, Rahat

subjects: Modelling

abstract: To develop a compact battery model, many authors begin by measuring the impedance of a battery over a frequency range of interest. Most of the models in the literature are either Thevenin-style or Randles’ model consisting of one or two RC networks and sometimes a Warburg element. These models are usually based on frequency range that stretches to only 1 mHz. This explains why they require several parameters to accurately reproduce the measured impedance data. In most applications, a battery goes through a charge/discharge cycle daily or even longer. Therefore, it seems logical to measure the impedance of the cell at frequencies reciprocal of period of charge. This corresponds to approximately 11.6 µHZ or lower. The impedance data at lower frequencies shows that any rechargeable battery can be simply modelled with a constant phase element in series with a resistor. Based on this observation, an equivalent circuit model and a mathematical model were proposed in this study. Similar to Randles’ model presented in 1947, the proposed models do not contain a source or any purely reactive element. The models were then fitted to the measured impedance data of both lithium-ion and nickel-metal hydride cells, the linear region of the charge-voltage curve, and the transient recovery tail that results from a step-change in load current.

text: Fractional modelling of rechargeable batteries To develop a compact battery model, many authors begin by measuring the impedance of a battery over a frequency range of interest. Most of the models in the literature are either Thevenin-style or Randles’ model consisting of one or two RC networks and sometimes a Warburg element. These models are usually based on frequency range that stretches to only 1 mHz. This explains why they require several parameters to accurately reproduce the measured impedance data. In most applications, a battery goes through a charge/discharge cycle daily or even longer. Therefore, it seems logical to measure the impedance of the cell at frequencies reciprocal of period of charge. This corresponds to approximately 11.6 µHZ or lower. The impedance data at lower frequencies shows that any rechargeable battery can be simply modelled with a constant phase element in series with a resistor. Based on this observation, an equivalent circuit model and a mathematical model were proposed in this study. Similar to Randles’ model presented in 1947, the proposed models do not contain a source or any purely reactive element. The models were then fitted to the measured impedance data of both lithium-ion and nickel-metal hydride cells, the linear region of the charge-voltage curve, and the transient recovery tail that results from a step-change in load current.

year: 2021

title: Spray Dryer Exhaust Heat Recovery: A Techno-economic Assessment Model

authors: Walmsley, Timothy Gordon

abstract: This paper discusses the spray dryer exhaust heat recovery in Milk Power Production.

text: Spray Dryer Exhaust Heat Recovery: A Techno-economic Assessment Model This paper discusses the spray dryer exhaust heat recovery in Milk Power Production.

year: 2014-08-26

title: What works for midwives supporting māmā through emotional distress?

authors: Roia, Tiaan Mereana Manurangi

abstract: Pregnancy and the postnatal period are particularly vulnerable times for mothers’ mental health, with an increased risk of women experiencing depression and anxiety during this time. Therefore, understanding the level and type of service midwives provide to māmā who experience emotional distress is vital to know what midwives need in order to provide the right care to their clients.
The aim of this study was to find out what tools and resources community-based midwives find most helpful to support the needs of māmā. Seven semi-structured interviews were conducted, including four Māori midwives, who were able to provide insight on their experiences caring for mothers with mental health needs. Overall, the interviews reflected a strong sense of care and empathy from midwives during their time caring for mothers. Midwives appeared to rely on their interpersonal skills and intuition about emotional distress, and emphasised the importance of connecting with people and utilising support from their communities. Whilst midwives were interested and engaged with providing appropriate care to mothers, they were unbeknown to some of the clinical resources that could be available to their clients. The complexity of referrals and access to mental health services was central to the midwives’ frustration around caring for mothers, as well as a lack of education relating to kaupapa Māori, cultural competency, and mental health processes.
Recommendations based on this study are to provide midwives with education and training on topics like kaupapa Māori, on social and mental health resources and processes for referral to increase their ability to support and care for mothers who experience emotional distress. Improvements to the pathways for referrals and access to mental health services is essential. Future research should focus on understanding why midwives aren’t using a range of online apps and tools, and increase awareness of the available modes of support available.

text: What works for midwives supporting māmā through emotional distress? Pregnancy and the postnatal period are particularly vulnerable times for mothers’ mental health, with an increased risk of women experiencing depression and anxiety during this time. Therefore, understanding the level and type of service midwives provide to māmā who experience emotional distress is vital to know what midwives need in order to provide the right care to their clients.
The aim of this study was to find out what tools and resources community-based midwives find most helpful to support the needs of māmā. Seven semi-structured interviews were conducted, including four Māori midwives, who were able to provide insight on their experiences caring for mothers with mental health needs. Overall, the interviews reflected a strong sense of care and empathy from midwives during their time caring for mothers. Midwives appeared to rely on their interpersonal skills and intuition about emotional distress, and emphasised the importance of connecting with people and utilising support from their communities. Whilst midwives were interested and engaged with providing appropriate care to mothers, they were unbeknown to some of the clinical resources that could be available to their clients. The complexity of referrals and access to mental health services was central to the midwives’ frustration around caring for mothers, as well as a lack of education relating to kaupapa Māori, cultural competency, and mental health processes.
Recommendations based on this study are to provide midwives with education and training on topics like kaupapa Māori, on social and mental health resources and processes for referral to increase their ability to support and care for mothers who experience emotional distress. Improvements to the pathways for referrals and access to mental health services is essential. Future research should focus on understanding why midwives aren’t using a range of online apps and tools, and increase awareness of the available modes of support available.

year: 2023