DigitUMa
University of Madeira Institutional Repository
Bem-vindo ao Repositório Digital da UNIVERSIDADE DA MADEIRA.
O Repositório da Universidade da Madeira (UMa), conhecido pelo acrónimo DigitUMa, tem como objetivo a disponibilização, em regime de livre acesso e texto integral, de toda a produção científica realizada pelos docentes, investigadores da UMa, discentes dos 2º e 3º ciclos e pelos funcionários.
O Repositório Institucional, DigitUMa, assenta na política de Acesso Aberto à informação e conhecimento científicos.
Recent Submissions
Concept of an elementary work as introduction to the line integral in engineering studies
Publication . Aleksandrova, Nelli; Drumond, Custódia; Drumond, Custódia
The paper is devoted to the line integral topic belonging to the section of vector calculus
in Mathematical Analysis applied to the undergraduate Mechanical Engineering program.
An efficient way of teaching line integrals is proposed and developed based on the elem entary work/force principles. By this way, the mathematical concept of the line integral is
supposed to be learned in harmony with the elementary mechanics to appreciate its
diversity and to set up the right idea about the scientific area covered by Mechanical
Engineering and related academic and technical fields. In terms of practical training,
the research also offers two new techniques of analytical calculus for line integrals con taining singularities and provides a new coherent engineering approach to deal with vec tor fields as integrands in line integrals.
The price of dishonesty. Stock market effects of corporate malpractices and misconduct: the case of Hindenburg Research Reports
Publication . Albuquerque, Bruno Filipe Freitas; Martins, António Miguel Valente
This dissertation aims to understand the impact of the disclosure of corporate malpractices and
misconduct actions on the market value of target listed companies. We use an event study
methodology that includes 50 public announcements of corporate malpractices and misconduct
practices by a forensic investigation company - the Hindenburg Research. This company is a
US investment research firm focused on activist short selling, which makes money if the target
company's stock prices fall as a result of a short position in the target company before the
report's public release. We analyse the abnormal returns generated by public disclosures
announcements of corporate malpractices and misconduct by the short-seller Hindenburg. This
study offers a new perspective on the impact of this information on the financial market.
Specifically, it seeks to explore whether corporate malpractices and misconduct practices have
a statistically significant impact on target stock prices, and whether the type of corporate
malpractices and misconduct practices and the accumulated credibility of Hindenburg Research
influence the magnitude of the impact caused by the announcements. The results show that
there are negative abnormal returns in firms when bad news about malpractices and misconduct
are revealed by the reports. Results show a higher negative stock market reaction to the
Hindenburg reports when target firms are small, have higher leverage, higher Tobin’s Q, and
corporate malpractice involves financial fraud. This means that the disclosure of negative or
adverse information about target firms by this short seller is sometimes so negative that it seems
to have a torpedo effect because of the sudden market reaction.
Boas práticas de gestão num estabelecimento hoteleiro: estudo caso Grupo Enotel
Publication . Açafrão, Sónia Patrícia Sousa; Teles, Susana; Almeida, António Manuel Martins de
Este estudo procurou compreender as práticas de gestão utilizadas no Grupo Enotel em
relação aos seus trabalhadores, bem como analisar a perceção desses sobre a cultura
organizacional da empresa e identificar quais são os fatores que contribuem para a motivação
e o compromisso dos trabalhadores. Adicionalmente, procurou-se estabelecer uma relação
entre as práticas de gestão e os resultados organizacionais, identificando quais práticas
contribuem para a obtenção de melhores resultados e que fomentam uma melhoria contínua
da empresa.
Assim, foi utilizado o método quantitativo, através da aplicação de questionários aos
colaboradores. O tamanho da amostra foi limitado ao número de colaboradores vinculados à
empresa, sendo que no período em que decorreu a distribuição de questionários, estavam
vinculados 278 colaboradores, tendo sido possível recolher 241 questionários. A recolha de
dados foi realizada de 1 a 15 março, tendo sido aplicado o questionário de forma presencial.
Foram contemplados vários aspetos, como a formação e o desenvolvimento pessoal, a
avaliação de desempenho, a remuneração e os benefícios e também os aspetos culturais, como
os valores, o clima organizacional, a liderança, a comunicação e a participação ativa dos
trabalhadores. A pesquisa mostrou que a empresa distingue-se por ter uma gestão eficiente,
que valoriza os seus trabalhadores, promove uma cultura organizacional positiva e com
iniciativas de sustentabilidade. Os dados indicaram que a empresa produz serviços de
qualidade e na perspetiva do trabalhador tem um futuro promissor, gere bem seus funcionários
e possui uma forte cultura organizacional. As práticas de gestão do Grupo estão assentes em
quatro pilares fundamentais: valorização dos colaboradores, cultura organizacional,
sustentabilidade e prestação de serviços de excelência. A combinação destes pilares contribui
para o sucesso da empresa, consolidando a sua posição de referência no setor hoteleiro. Os
resultados obtidos revelam ainda que é importante investir num ambiente de trabalho positivo
e motivador e na formação dos trabalhadores adotando práticas sustentáveis de forma a
minimizar o seu impacto ambiental. Assim, este estudo também procura contribuir para a
literatura académica no tema da gestão hoteleira, oferecendo insights valiosos sobre as
práticas de gestão eficazes e os fatores que influenciam a motivação e o compromisso dos
colaboradores nas empresas do setor hoteleiro.
Lower limbs strength variations between injured and non-injured professional soccer players
Publication . Martins, Francisco; França, Cíntia; Hugo Sarmento; Ricardo Henriques; Krzysztof Przednowek; Marcelo de Maio Nascimento; Adilson Marques; Andreas Ihle; Gouveia, Élvio Rúbio; Sarmento, Hugo; Marques, Adilson; Ihle, Andreas; Gouveia, Élvio Rúbio
Due to its physical demands, professional soccer is becoming a real challenge regarding players’ exposure to high injury risk. Given its tight correlation with high-intensity actions, muscular strength is a crucial physical characteristic for soccer players. Therefore, the aims of this study are (a) to compare the vertical jumping performance during the season according to the injury profile, and (b) to investigate differences in isokinetic strength performance at the beginning and the end of the season. Twenty-one male professional soccer players (age: 26.0 ± 4.1 years, height: 181.0 ± 6.9 cm, body mass: 73.7 ± 6.9 kg) were assessed in isokinetic strength (Biodex System 4 Pro Dynamometer), and Optojump Next (Microgate, Bolzano, Italy). Isokinetic strength analyses considered the peak torque scores of knee flexors and knee extensors, according to the player's preferred and non-preferred limb. The countermovement and squat jump maximum height were assessed as lower body explosive strength indicators. No significant differences were found when comparing injured and non-injured players in vertical jump and isokinetic strength assessments. However, significant results were found when comparing both groups’ initial and final evaluation in isokinetic strength assessment, with both groups significantly improving their performance. Our findings indicate that the overall lower body strength performance was not a discriminant factor between injured and non-injury players. Thus, muscular strength assessment performance increased throughout the season independently of the injury profile. Future research needs to integrate other variables related to sports injuries since they seem to result from multifactorial causes.
Numerical and experimental investigation of thermal regimes of thermionic cathodes of arc plasma torches
Publication . Cunha, M. D.; Sargsyan, M. A.; Gadzhiev, M. Kh; Tereshonok, D. V .; Benilov, M. S .; Benilov, Mikhail; Cunha, Mário
The modelling method based on decoupling the simulation of the cathodic part of the arc (the
cathode and the near-cathode non-equilibrium plasma layer) from the simulation of the arc on
the whole has been extended to cathodes of arc plasma torches, consisting of an insert with a
conical tip, made of pure or doped tungsten, and a surrounding water-cooled copper holder. The
method was validated by comparison with the experiment, performed on a 200 A DC arc in
atmospheric-pressure argon. Standard work function of polycrystalline tungsten of 4.54 eV was
used for modelling of pure-tungsten insert and a good agreement with the experiment was found
with respect to both the insert tip shape and the temperature distribution in the tip, recorded in
the stable operation mode. There are no unambiguous data on the work function for arc
cathodes made of doped tungsten, although in situ measurements of the effective work function
of cathodes of high-pressure arc discharges provide useful hints. On the other hand, the
experiments reported in this work show that the tip temperatures of inserts made of tungsten
doped with 1.5% of thorium, or lanthanum, or yttrium, recorded during the stable-mode
operation at the arc current of 200 A, vary in a rather narrow range 3100–3200 K. This suggests
that the work functions of doped tungsten inserts, operated in the stable mode, are close to each
other as well. Indeed, the results of modelling with the same value of the work function of 3 eV
give a reasonably good agreement with the experiment in all three cases.