DigitUMa
University of Madeira Institutional Repository
Recent Submissions
Shifting currents: expert perspectives on the adoption of direct current in power grids
Publication . Ngirwa, Catherine; Reis, Diogo; Morais, Hugo; Pereira, Lucas; Ngirwa, Catherine
Utilization of renewable energy resources for energy generation brought significant attention to Direct Current
(DC) technologies, as many of them produce and store electricity in DC. Compared to Alternating Current, the
DC technologies, specifically in Medium-Voltage (MV) and Low-Voltage (LV), are in their infancy, leading to
less data availability for decision-making. To inform early-phase technologies, experts are consulted through
the structured Expert Elicitation (EE) method, though few have explored it in examining technical and non technical aspects of MVDC and LVDC technologies. Hence, in this paper, we present two EE studies on eleven
(11) MVDC and LVDC technologies proposed in the Shift2DC research project — applicable for ports, buildings,
industry, and data centers. We found that experts perceived the presented DC technologies as feasible and
important. Among the most perceived concerns for DC technologies adoption are a lack of trained personnel,
public awareness, and uncertainty in regulations to enforce the use of innovations. Experts proposed the need
for educational strategies for the general public and a structured curriculum for training technicians in DC.
In addition, experts envisioned enabling emerging technologies, such as digital twins and energy management
systems, for DC system management.
A spatial augmented reality-based biofeedback platform for fitness assessment and intervention in older adults
Publication . Ahmad, Muhammad Asif; Ahmad, Muhammad Asif; Bermúdez i Badia, Sergi; Gouveia, Élvio Rúbio Quintal
In most countries around the world, the population of older adults exceeds
that of younger individuals. The ageing population has become a global
challenge and is causing an increase in chronic diseases and associated
health problems. This age group has been associated with conditions such
as reduced mobility, prolonged hospitalisations, elevated morbidity rates,
and an increased incidence of falls. A sedentary lifestyle has been correlated
with numerous health conditions, making it essential to promote innovative
health and fitness programs that encourage physical activity. According to
the American College of Sports Medicine (ACSM), individuals should engage
in 30 minutes of moderate exercise, five days a week, or 20 minutes of
vigorous exercise, three times a week. The rapid growth of Information
and Communication Technology (ICT) tools has led to a decrease in physical
activity, contributing to various health and fitness issues. Balance
assessment tools are used to evaluate postural movements, the risk of falls,
and balance impairments. Using virtual reality (VR) technology in
conjunction with balanced assessment tools may enhance the ecological
validity of the instruments, increase performance and standardisation, and
reduce administration time. Moreover, combining immersive virtual reality
(IVR) with physical exercise, or exergames, enhances motivation and
personalises training, effectively preventing falls by improving strength and
balance in older adults. While many exergames and simulation applications
have been introduced to help people engage in physical activity, limitations
exist in user interest, consistency, achievement, and technology,
particularly when targeting older adults and populations with specific
deficits. Exergames often lack adaptability to individual fitness profiles and
high-fidelity immersive virtual environments.
To address these limitations, we have created and validated a biofeedback based spatial augmented reality platform that assesses physical and
physiological fitness, as well as balance, in older adults through targeted
interventions designed to promote wellness and reduce the risk of falls.
Target heart rates are evaluated according to ACSM recommendations. The
platform also offers simulations of diverse environments and fitness
opportunities tailored to meet the specific needs of various populations. We
have implemented standard fitness procedures in a virtual environment to
assess lower-body strength and cardiorespiratory endurance in older
adults.
Semicondutores e geopolítica: o conflito Rússia-Ucrânia sob a ótica dos mercados
Publication . Sardinha, Luís Henrique Câmara; Martins, António Miguel Valente; Gouveia, Ricardo Nuno Teixeira
A presente dissertação analisa o impacto a curto prazo do início do conflito Rússia-Ucrânia nos
retornos anormais das empresas da indústria dos semicondutores. Recorremos à metodologia
de estudos de eventos para examinar uma amostra de 100 empresas, avaliando as variações nos
preços dessas ações no período em torno do dia 24 de fevereiro de 2022 (início do conflito
militar entre a Rússia e a Ucrânia). Os resultados indicam que, para a amostra completa, não se
verificaram retornos anormais estatisticamente significativos. Contudo, ao dividir a amostra
entre empresas europeias e não-europeias, observou-se que as empresas europeias registaram
retornos anormais positivos e estatisticamente significativos, enquanto as empresas sediadas
fora da Europa apresentaram resultados sem significância estatística. O teste para as diferenças
de CARs entre essas duas subamostras confirma que as empresas europeias reagiram de forma
distinta face às não-europeias, sugerindo que a localização geográfica desempenha um papel
determinante na resposta ao conflito. A análise cross-section sugere ainda que certas
características empresariais, como o ROA, Tobin_Q, percentagem de investidores institucionais
e localização geográfica, influenciam a reação das empresas a choques geopolíticos. Esta
dissertação contribui para a literatura ao colmatar a ausência de estudos sobre o impacto do
conflito entre a Rússia e a Ucrânia na indústria dos semicondutores, uma indústria de elevada
importância estratégica e económica. Trata-se do primeiro estudo a adotar uma abordagem
quantitativa e a recorrer à metodologia de estudos de eventos para analisar este conflito neste
contexto específico. Os resultados obtidos oferecem implicações significativas para
investidores, gestores e decisores políticos, fornecendo uma visão aprofundada sobre a reação
dos mercados a crises geopolíticas e destacando o papel das especificidades regionais e
empresariais na formação dos retornos anormais
The impact of the crowdstrike incident in the stock market: an event study analysis for airlines
Publication . Costa, João Francisco Maciel; Martins, António Miguel Valente
This study investigates the short-term market effect of the CrowdStrike IT outage in the airline
industry. Using an event study methodology, we provide evidence that airline stocks respond
significantly negatively to the technology disruption within two days before and after the event
day. IT disruptions create friction in daily operations—such as schedule disruptions, flight
delays or cancellations, negative externalities, and customer dissatisfaction—ultimately leading
to a loss of value for airlines. The results also show that the most affected airlines are those
from main CrowdStrike customer’s countries (mainly non-Asian countries) and an irrelevance
of the business model. Finally, the extent of the stock market’s response to the CrowdStrike IT
outage is influenced by other airline characteristics such as profitability, size, leverage, and
cyber risk rating.
Mechanisms of action of essential oils on enzymes relevant to insect and nematode development
Publication . Martins, Mariana Barreto; Castilho, Paula Cristina Machado Ferreira
Insects, such as the Mediterranean fruit fly (Medfly, Ceratitis capitata) and the
armyworm (Mynthimna unipuncta), and nematodes, such as the root-knot
nematode (RKN, Meloidogyne incognita) and the pine wood nematode (PWN,
Bursaphelenchus xylophilus), are major agricultural pests. Botanical pesticides
such as essential oils (EOs) have proven effective in controlling agricultural pests
due to their repellent, anti-feeding properties, etc. Therefore, the objective of this
study was to evaluate the potential of aromatic plants in controlling the pests C.
capitata, M. unipuncta, M. incognita, and B. xylophilus by studying their
mechanisms of action on the neural and digestive enzymes. This study focused on
the EOs of Origanum vulgare, Thymus vulgaris, Ocimum gratissimum, Mentha
pulegium, and Cinnamomum cassia, mainly composed of carvacrol, thymol,
eugenol, pulegone, and trans-cinnamaldehyde, respectively, as several studies
have mentioned their insecticidal and/or nematicidal effects. Theirinteractions with
enzymes relevant to insect and nematode development, namely
acetylcholinesterase (AChE), α- and β-glucosidase, were investigated using crude
enzyme extracts obtained from the selected species. Enzyme activity and soluble
protein content were quantified using standard assays, and SDS-PAGE was
performed to attempt protein identification. In vitro inhibition assays with the EOs
and their major components were then conducted to assess inhibitory activity and
provide insights into potential mechanisms of action. The results revealed that all
tested EOs inhibited AChE but had no effect on the digestive enzymes. Among the
EOs studied, M. pulegium EO showed the strongest inhibition of AChE in both Medfly
(IC50 = 0.022 mg/mL) and PWN (IC50 = 0.1209 mg/mL). C. cassia EO was particularly
effective against armyworm (IC₅₀ = 0.0020 mg/mL) and RKN (IC₅₀ = 0.0197 mg/mL).
These findings suggest that these EOs primarily exert their toxic effects through
interference with the nervous system, supporting their potential as sustainable
alternatives to synthetic pesticides in environmentally friendly pest management.