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Tracking control of air flow based on a fractional-order model of the lung impedance
Get PDFA fractional order output feedback controller for a lung ventilator is designed. This is based on a
state-of-the-art electrical analogue model of the human respiratory system in the form of a network
of resistors and fractional capacitors. The electrical input impedance of the adopted analogue can be
suitably tuned to fit experimental ventilation impedance data. Furthermore, it can explicitly account
for the different physiological fractal type characteristics associated with lung formation such as
branching morphogenesis associated to the treelike tubular network and alveolar differentiation
associated with the generation of specialized epithelial cells for gas exchange. A description of this
electrical analogue in pseudo-state space is then proposed. The aim is to finally provide a control
methodology within the scope of output feedback control, when the measured output which is the
airflow through the trachea is directed to follow a specified reference. The control provides adequate
air pressure input to generate this nominal airflow. The proposed control design includes a pseudo-state observer and a double leaky integrator. The gains involved are designed using constraints
imposed through linear matrix inequalities (LMIs), which enforce a regional allocation of eigenvalues.
The robustness of the control loop is analysed through an uncertainty matrix analysis linked directly
to the model. It is observed that the proposed design can tolerate a relatively wide variation in
physiological parameters (±15%). The proposed formulation advances current control design
approaches for mechanical ventilators and provides a generic methodology for the control of complex
system with emergent responses as encountered in bioengineering
Multinational enterprises in labor-intensive GVCs: examining aspects of productivity, linkage and control without ownership
Get PDFThis thesis examines the multinational enterprises (MNEs) operating within labor-intensive global value chains (GVCs)—a category of MNEs that remains relatively
understudied in the international business (IB) literature. While the dominant discourse
in IB has traditionally focused on large, hierarchically integrated MNEs with strong firm
specific asset (FSA) based advantages and equity-based control mechanisms, this thesis
shifts the focus to MNEs that act as either lead or supplier firms within labor-intensive
GVCs, particularly, where control is decoupled from ownership. The research addresses
conceptual gaps around how these MNEs establish and sustain competitiveness and
governance as they operate in GVCs. The thesis draws on and extends FSA theory,
classifying FSAs into asset-type FSA (FSAA), transaction-type FSA (FSAT), and
recombinant type FSA (FSAR) categories, and investigates how these are deployed by
MNEs in low-tech, high-labor contexts. The empirical analysis is based on three papers,
each contributing a distinct lens. The first two papers focus on supplier MNEs (SMNEs)
operating in Bangladesh’s Export Processing Zones (EPZs), using quantitative firm-level
data to explore issues of productivity and cost competitiveness relative to domestic
supplier firms. The third paper adopts a qualitative case study approach, drawing on
interviews and documentary analysis within the Bangladeshi apparel industry beyond
EPZs, to examine how lead firms exert control over suppliers in multi-tiered GVCs
without equity ownership.
Key findings include the following:
• SMNEs in labor-intensive sectors often possess weak FSAA, given the limited
technological complexity of their operations. However, some SMNEs that
successfully leverage FSAT and / or FSAR based on the degree of multinatioanlity
may outperform domestic rivals in both productivity and cost terms. The thesis
contributes to the FSA theory by empirically demonstrating that FSAT and/or
FSAR may, in certain contexts, overcome the deficiencies in FSAA, especially, in
sectors dominated by low-skilled labor and commodified input materials.
• The thesis also reveals how lead firms in apparel GVCs allow participation of
OEM first-tier suppliers firms in a split governance arrangement and still
maintain control without ownership along the apparel GVCs.
Overall, the thesis makes both theoretical and empirical contributions to the IB field by
expanding the applicability of FSA theory and offering new insights into non-equity
governance, and situating Bangladesh as a strategic context for understanding how
MNEs operate in labor-intensive sectors. The findings carry implications for managers,
policymakers, and scholars interested in the evolving nature of global production, industrial upgrading, and sustainable GVC governance
Assessing the impacts of EU agricultural policies on the sustainability of the livestock sector: a review of the recent literature
Get PDFHow do agricultural policies in the EU need to change to increase the sustainability of livestock production, and what measures could encourage sustainable practices whilst minimising trade-offs? Addressing such questions is crucial to ensure progress towards proclaimed targets whilst moving production levels to planetary boundaries. However, a lack of available evidence on the impacts of recent policies hinders developments in this direction. In this review, we address this knowledge gap, by collating and evaluating recent policy analyses, using three complementary frameworks. The review highlights that recent policy reforms, and especially those of the Common Agricultural Policy, have had a large impact on the sustainability of the livestock sector by contributing to intensification and simplification. This has often resulted in negative impacts (e.g. on greenhouse gas emissions and animal welfare) and while financial support has enabled production, it can also lead to a culture of dependency that limits innovation. At the same time, a lack of regulation and concrete targets, and low levels of stakeholder engagement in policy design have led to delays in the delivery of sustainability objectives. Future policies could take on-board more innovative thinking that addresses the interrelatedness of society, animals, and the environment, to deliver effective targets and support
Asymptotics of block Toeplitz determinants with piecewise continuous symbols
Get PDFWe determine the asymptotics of the block Toeplitz determinants
det Tn(φ) as n → ∞ for N × N matrix-valued piecewise continuous functions
φ with a finitely many jumps under mild additional conditions. In particular,
we prove that
det Tn(φ) ∼ G
nn
ΩE as n → ∞,
where G, E, and Ω are constants that depend on the matrix symbol φ and are
described in our main results. Our approach is based on a new localization
theorem for Toeplitz determinants, a new method of computing the Fredholm
index of Toeplitz operators with piecewise continuous matrix-valued symbols,
and other operator theoretic methods. As an application of our results, we
consider piecewise continuous symbols that arise in the study of entanglement
entropy in quantum spin chain models
Random item slope regression: an alternative measurement model that accounts for both similarities and differences in the association with individual items
Get PDFIn psychology, researchers often predict a dependent variable (DV) consisting of multiple measurements (e.g., scale items measuring a concept). To analyze the data, researchers typically aggregate (sum/average) scores across items and use this as a DV. Alternatively, they may define the DV as a common factor using structural equation modeling. However, both approaches neglect the possibility that an independent variable (IV) may have different relationships to individual items. This variance in individual item slopes arises because items are randomly sampled from an infinite pool of items reflecting the construct that the scale purports to measure. Here, we offer a mixed-effects model called random item slope regression, which accounts for both similarities and differences of individual item associations. Critically, we argue that random item slope regression poses an alternative measurement model to common factor models prevalent in psychology. Unlike these models, the proposed model supposes no latent constructs and instead assumes that individual items have direct causal relationships with the IV. Such operationalization is especially useful when researchers want to assess a broad construct with heterogeneous items. Using mathematical proof and simulation, we demonstrate that random item slopes cause inflation of Type I error when not accounted for, particularly when the sample size (number of participants) is large. In real-world data (n = 564 participants) using commonly used surveys and two reaction time tasks, we demonstrate that random item slopes are present at problematic levels. We further demonstrate that common statistical indices are not sufficient to diagnose the presence of random item slopes
A mixed-methods approach to understanding barriers and facilitators to healthy eating and exercise from five European countries: highlighting the roles of enjoyment, emotion and social engagement
Get PDFHealthy adults are consistently falling below national and international recommendations for physical activity and dietary intake across Europe. This study took a co-creative approach with adult samples from five European countries to qualitatively and quantitatively establish motivators, barriers and sustaining factors for positive health behaviour change. Stage 1 delivered a newly-designed online programme, creating a community who identified challenges, motivators and solutions to sustaining positive healthy eating and physical activity behaviours. Stage 2 administered an online survey (developed from Stage 1 findings) to a larger sample to quantify the relative importance of these motivators and barriers. Results from both stages indicated enjoyment, positive emotions, and reward as key motivators for both behaviours across all five countries. Barriers included habit-breaking difficulties, temptation and negative affective states. Those with a high BMI placed more importance on social pressure than those with healthy BMI. Participants’ reports of motivators and barriers reflected relevant approaches from consumer science, behavioural economics, and psychology. Interventions supporting adults who are not chronically ill but would benefit from improved diet and/or physical activity should not focus exclusively on health as a motivating factor. Emphasis on enjoyable behaviours, social engagement and reward will likely improve engagement and sustained behaviour change
Secundum atrial septal defect closure in adults in the UK
Get PDFAims
To examine determinants of access to treatment, outcomes, and hospital utilization in patients undergoing secundum atrial septal defect (ASD) closure in adulthood in England and Wales.
Methods and results
Large retrospective cohort study of all adult patients undergoing secundum ASD closures in England and Wales between 2000/01 and 2016/17. Data were from population-based official data sets covering congenital heart disease procedures, hospital episodes, and death registries. Out of 6541 index closures, 79.4% were transcatheter [median age 47 years, interquartile range (IQR) 34–61] and 20.6% were surgical (40 years, 28–52). The study cohort was predominantly female (66%), with socioethnic profile similar to the general population. Mortality in hospital was 0.2% and at 1 year 1.0% [95% confidence interval (CI) 0.8–1.2%]. Risk of death was lower for transcatheter repairs, adjusting for age, sex, year of procedure, comorbidities, and cardiac risk factors [in-hospital adjusted odds ratio 0.09, 95% CI 0.02–0.46; 1-year adjusted hazard ratio 0.5, 95% CI 0.3–0.9]. There was excess mortality 1 year after ASD closure compared with matched population data. Median (IQR) peri-procedural length of stay was 1.8 (1.4–2.5) and 7.3 (6.2–9.2) days for transcatheter and surgical closures, respectively. Hospital resource use for cardiac reasons started the year before repair (median two inpatient and two outpatient-only days) and decreased post-repair (zero inpatient and one outpatient days during the first 2 years).
Conclusion
This national study confirms that ASD closure in adults, by surgical or transcatheter methods, is provided independently of ethnic or socioeconomic differences, it is low (but not no) risk, and appears to reduce future cardiac hospitalization even in older ages
Complex verbs in English: the relationship between verb-forming suffix schemas and argument structure constructions
Get PDFThis paper relates two levels of constructional analysis in accounting for the functions of verb-forming suffixation in English: argument structure constructions and suffix schemas. The function of verbal-forming suffixation expressed by the four suffixes in English, -ize, -ify, -en and -ate, has been shown to exhibit a wide range of semantic categories that correspond to a number of argument structure constructions (Laws 2023). The current paper extends that semantic analysis. Firstly, by using a Construction Morphology approach (Booij 2010) to formalize the relationship between argument structure and suffix schemas proposed by Laws. Secondly, a hierarchical view of verb-class and subclass argument structure constructions is articulated by using semantic rules that involve selection and enrichment by coercion within suffix subschemas. Thirdly, it is demonstrated that the motivation for partially opaque complex verbs with these suffixes can be expressed by referring to paradigmatic relationships between these complex verbs and other related words