9,809 research outputs found
The impact of reviews on consumers’ consideration towards electric vehicles (EV)
The development of the Internet and technology led to increasingly more digital consumers,
who are tired of being marketed to. Thus, many companies started adopting reviews as part of
their marketing strategy to reach the target audience in social media. This trend is also present
in the market of electric vehicle (EV).
This dissertation was developed with the aim of understanding how EV consumers perceive
social media online posts as endorsers of EV as a mobility product, through the lens of the
Source Credibility Model. These objectives were addressed using a quantitative research
method that adopted an experiment between subjects, comparing firm-created reviews (firmcreated content) with user-created reviews (user-generated content) . Previous literature was
reviewed, and an online questionnaire was conducted, with 243 obtained valid answers.
Moreover, the willingness to consider and willingness to buy an EV were considered as a
variable in the analysis, being proposed because of trustworthiness communicated by the type
of review.
The results of this dissertation found that the difference between User-Generated Content
and car brand reviews (firm-created content) is not statistically significant in the moment of
influencing decision of considering or buying an EV as a mobility product. It was observed that
there is a valid positive influence relationship of trustworthiness on the relationship between
the types of review and the consideration of buying an EV.
Lastly, with this model and this research, it was confirmed that there is a positive influence
of the trustworthiness on willingness to buy and consideration to buy.A emergência da Internet e o desenvolvimento da tecnologia levou a um número crescente de
consumidores digitais, cansados de serem comercializados. Assim, muitas empresas
começaram a adotar o marketing de publicação em linha para chegar às pessoas nas redes
sociais. Esta nova abordagem do marketing é também utilizada como uma ferramenta no
marketing social para promover a mudança de comportamento, especialmente quanto ao
processo de decisão de aquisição de um novo veículo elétrico (VE). Esta dissertação foi
desenvolvida com o objetivo de compreender como os consumidores de VE veem os anúncios
online nas redes sociais como endossantes de VE como um produto de mobilidade, partindo do
Modelos de Credibilidade na Fonte. Estes objectivos foram abordados utilizando um método
de investigação quantitativa que adoptou uma experiência entre sujeitos, comparando conteúdo
criado por empresas, com conteúdo criado por utilizadores online. A literatura anterior foi
revista e foi conduzido um questionário online, com 243 respostas bem-sucedidas. Além disso,
a vontade de considerar foi incluída como uma variável na análise com influência direta na
fiabilidade, dificilmente abordada na literatura. Os resultados constataram que a diferença entre
o Conteúdo Gerado pelo Utilizador e o conteúdo de marcas de automóveis não é
estatisticamente significativa, no momento de influenciar a decisão de considerar um VE como
um produto de mobilidade. Observou-se que existe uma relação de influência positiva válida
de confiança na relação entre os tipos de revisão e a consideração da compra. Finalmente, foi
confirmado que existe uma influência positiva da fiablilidade na vontade de comprar
Machine learning Gaussian short rate
Dissertação para obtenção do Grau de Doutor em
Estatística e Gestão do RiscoThe main theme of this thesis is the calibration of a short rate model under the
risk neutral measure.
The problem of calibrating short rate models arises as most of the popular models have the drawback of not fitting prices observed in the market, in particular, those of the zero coupon bonds that define the current term structure of interest rates.
This thesis proposes a risk neutral Gaussian short rate model based on Gaussian
processes for machine learning regression using the Vasicek short rate model as prior. The proposed model fits not only the prices that define the current term structure observed in the market but also all past prices. The calibration is done using market observed zero coupon bond prices, exclusively. No other sources of information are needed.
This thesis has two parts. The first part contains a set of self-contained finished
papers, one already published, another accepted for publication and the others submitted for publication. The second part contains a set of self-contained unsubmitted papers. Although the fundamental work on papers in part two is finished as well, there are some extra work we want to include before submitting them for publication.
Part I:
- Machine learning Vasicek model calibration with Gaussian processes
In this paper we calibrate the Vasicek interest rate model under the risk neutral
measure by learning the model parameters using Gaussian processes for machine learning regression. The calibration is done by maximizing the likelihood of zero coupon bond log prices, using mean and covariance functions computed analytically, as well as likelihood derivatives with respect to
the parameters. The maximization method used is the conjugate gradients.
We stress that the only prices needed for calibration are market observed zero coupon bond prices and that the parameters are directly obtained in the arbitrage free risk neutral measure. - One Factor Machine Learning Gaussian Short Rate In this paper we model the short rate, under the risk neutral measure, as a Gaussian process, conditioned on market observed zero coupon bonds log prices. The model is based on Gaussian processes for machine learning,
using a single Vasicek factor as prior.
All model parameters are learned directly under the risk neutral measure,using zero coupon bonds log prices only.
The model supports observations of zero coupon bounds with distinct maturities
limited to one observation per time instant. All the supported observations are automatically fitted.M2A/ISEL financing conference trips; ISEL - financing conference fees; ISEL/IPL the PROTEC scholarship; CMA/FCT/UNL - financing conference trip
Tell me where you went, I may tell who you infected
[No abstract available]Funding text 1: Internationalization’ and received national funding from the Foundation for Science and Technology – FCT (Portuguese Ministry of Science, Technology, and Higher Education) under the Epidemiology Research Unit - Institute of Public Health of the University of Porto (EPIUnit) (UIDB/04750/2020) and the Laboratory for Integrative and Translational Research in Population Health (ITR) (LA/P/0064/2020). Ana Isabel Ribeiro was supported by National Funds through the FCT, under the ‘Stimulus of Scientific Employment – Individual Support’ program, within contract CEECIND/02386/2018.; Funding text 2: This study was funded by the ERDF through the Operational Program ‘Competitiveness an
Heavy-ion Physics at a Fixed-Target Experiment Using the LHC Proton and Lead Beams (AFTER@LHC): Feasibility Studies for Quarkonium and Drell-Yan Production
We outline the case for heavy-ion-physics studies using the multi-TeV lead
LHC beams in the fixed-target mode. After a brief contextual reminder, we
detail the possible contributions of AFTER@LHC to heavy-ion physics with a
specific emphasis on quarkonia. We then present performance simulations for a
selection of observables. These show that , and
production in heavy-ion collisions can be studied in new energy and
rapidity domains with the LHCb and ALICE detectors. We also discuss the
relevance to analyse the Drell-Yan pair production in asymmetric
nucleus-nucleus collisions to study the factorisation of the nuclear
modification of partonic densities and of further quarkonia to restore their
status of golden probes of the quark-gluon plasma formation.Comment: 18 pages, 7 figure
A Expressão Global da Doença de Chagas – Oportunidades Emergentes e Impacto em Portugal
Chagas disease, caused by the protozoan Trypanosoma cruzi is endemic in the countries of Central and South America. Despite vector control programs and other measures taken in the blood banks and maternity hospitals, it is estimated that there are about eight million people infected worldwide. Although traditionally associated with rural life and poverty, the current migration flows transform it into a global public health problem. In Portugal, this problem is poorly known, with an estimated underdiagnosis index that exceeds 99%. In European countries, besides imported cases, autochthonous infections arise through vertical transmission and blood/organ donation.The conventional serological tests for diagnosing Chagas disease and verifying its cure are indirect hemagglutination (IHA), indirect immunofluorescence (IFAT), and enzyme-linked immunoabsorbent assay (ELISA).The hypothesis of autoimmunity as a basic mechanism of this disease and the absence of early markers of cure are the causes of controversy regarding the specific treatment of this disease. The currently available drugs have adverse effects on a large number of patients and parasitological efficacy in chronic disease is suboptimal.The authors reinforce the need of a high level of suspicion in patients with suggestive epidemiology and the need of populational screening of specific high risk groups
The effect of substitution and isomeric imperfection on the photophysical behaviour of p-phenylenevinylene trimers
Spectroscopic and photophysical properties of two p-phenylenevinylene (PV) trimers, 2,5-substituted diheptyl-(p-phenylenevinylene) and di-[(2-ethylhexyl)oxy]-(p-phenylenevinylene), were studied using absorption spectroscopy, fluorescence and laser flash photolysis. The change from alkyl to alkyloxy groups red-shifts the absorption and fluorescence bands. The rate of internal conversion is independent of the substitution, whereas alkyloxy substitution increases the S1 [rightwards wave arrow] T1 intersystem crossing rate by an order of magnitude. The relevance for the behaviour of conjugated PPV polymers is discussed. For diheptyl-PV, a sample having ca. 3% of the cis-configuration was also studied. Comparison between the all-trans and the cis-contaminated samples revealed no significant differences in their photophysical properties.http://www.sciencedirect.com/science/article/B6TFN-4C0TKVG-4/1/bb1be7e4a272bb7910483cae927d04a
Dileptons from the nonequilibrium Quark-Gluon Plasma
According to the dynamical quasiparticle model (DQPM) -- matched to reproduce
lattice QCD results in thermodynamic limit, -- the constituents of the strongly
interacting quark-gluon plasma (sQGP) are massive and off-shell quasi-particles
(quarks and gluons) with broad spectral functions. In order to address the
electromagnetic radiation of the sQGP, we derive off-shell cross sections of
, and () reactions taking into account the effective propagators
for quarks and gluons from the DQPM. Dilepton production in In+In collisions at
158 AGeV is studied by implementing these processes into the
parton-hadron-string dynamics (PHSD) transport approach. The microscopic PHSD
transport approach describes the full evolution of the heavy-ion collision:
from the dynamics of quasi-particles in the sQGP phase (when the local energy
density is above GeV/fm) through hadronization and to the
following hadron interactions and off-shell propagation after the
hadronization. A comparison to the data of the NA60 Collaboration shows that
the low mass dilepton spectra are well described by including a collisional
broadening of vector mesons, while the spectra in the intermediate mass range
are dominated by off-shell quark-antiquark annihilation, quark Bremsstrahlung
and gluon-Compton scattering in the nonperturbative QGP. In particular, the
observed softening of the spectra at intermediate masses (1 GeV 3 GeV) is approximately reproduced.Comment: 8 pages, 8 figures, to be published in the Proceedings of the 26th
Winter Workshop on `Nuclear Dynamics', Ochto Rios, Jamaica, 2-9 January, 201
A influência do contexto relacional (curto-vs. longo-prazo) na avaliação da atratividade e idade de faces femininas
Mestardo em Psicologia da Saúde e Reabilitação NeuropsicológicaDe acordo com a perspetiva da psicologia evolutiva, os humanos terão desenvolvido um leque de diversas estratégias de mating nas quais se inserem relações a longo-prazo e a curto-prazo. Como o principal objetivo dos homens é maximizar o sucesso reprodutivo, estes dão preferência a aspetos físicos que sejam pistas do potencial reprodutivo, como é o caso da juventude. O presente estudo baseia-se nos pressupostos da psicologia relativamente às preferências dos homens na escolha de potenciais parceiras sexuais e às respetivas adaptações associadas às estratégias de acasalamento adotadas, dando ênfase à análise da avaliação da atratividade em contextos de procura de uma relação a curto-prazo ou a longo-prazo. Assim, pretendeu-se investigar a influência do contexto de acasalamento (longo-prazo vs. curto-prazo) na avaliação de faces femininas por parte de jovens adultos, nomeadamente quanto à atratividade e à idade percebida. Previu-se que os participantes iriam classificar como mais atraentes potenciais parceiras mais jovens e que esta tendência seria mais notória à medida que o nível de envolvimento na relação diminui, do contexto de longo-prazo para o de curto-prazo. Além disto, esperava-se que os participantes do contexto de curto-prazo classificassem como mais atraentes as mulheres a quem atribuíssem uma idade inferior. Foi realizada uma tarefa experimental que consistia na avaliação, de forma individual, de um conjunto de faces (jovens e velhas) quanto à atratividade e idade percebida. Como esperado, observou-se uma avaliação superior em termos de atratividade das faces mais jovens (comparativamente com as mais velhas), verificando-se ainda uma interação significativa da idade da face com o contexto e um tamanho do efeito da idade da face superior no contexto de curto-prazo. São discutidas eventuais limitações ao presente estudo. Apresentamos ainda sugestões para estudos futuros que incluam algumas alterações procedimentais que possibilitem uma melhor compreensão e uma investigação mais eficaz desta temática.According to evolutionary psychology, humans developed a range of mating strategies that include long-term and short-term relationships. Since men's main goal is to maximize their reproductive success, they prefer physical aspects which provide clues to reproductive potential, such as youth. The present study is grounded on the evolutiorary assumptions regarding how men choose their potential sexual partners and the corresponding adaptations associated with the adopted mating strategies, emphasizing the analysis of the evaluation of the attractiveness in a context of a short-term or a long-term relationship. Thus, we aimed to investigate the influence of the context (long-term vs. short-term) on the evaluation of female faces by young adults, regarding their attractiveness and perceived age. We predicted that participants would rate as more attractive younger potential partners and that this preference would be stronger as the level of involvement decreases, from the long-term relationship context to the short-term context. In addition, we predicted that participants in the short-term context would rate younger women as more attractive than older women. An experimental task was conducted that consisted in the individual evaluation of a set of faces (new or old) regarding the attractiveness and age perceived. As expected, younger faces were rated as significantly more attractive; a significant interaction of face age with the context was also obtained along with a larger and a size of the superior effect of face age in the short-term context. Possible limitations to the present study are discussed. Suggestions for future studies that include some procedural changes that allow a better understanding and a more effective investigation of this subject are also presented
FIRST RECORD OF THE PRESENCE OF MANGROVE BORER SPHAEROMA PERUVIANUM RICHARDSON (ISOPODA: SPHAEROMATIDAE) IN THE GULF OF MONTIJO, PANAMA
A field survey was carried out to investigate the presence of mangrove borers at the mouth of San Pablo River in the Gulf of Montijo, western Pacific of Panamá. Previous reports of the National Environment Authority (ANAM) indicate a high degree of root tip atrophy and breakage in young plants of red mangrove, Rhizophora mangle. Samples of roots were sawed off and examined for isopod burrow openings. Analysis revealed the presence of the eastern Pacific root-boring Sphaeroma peruvianum Richardson. The organism bore the roots and it is the likely cause of fall trees due to the lack of root support. A voucher specimen was deposited in the Smithsonian National Museum of Natural History, Washington, DC (USNM 1139603). Se efectuó un estudio de campo con el propósito de investigar la presencia de barrenadores de mangle en la desembocadura del río San Pablo en el Golfo de Montijo, Pacífico oeste de Panamá. Informes previos de la Autoridad Nacional del Ambiente (ANAM) describen un alto grado de atrofia radicular en plantas jóvenes de Rhizophora mangle. Se recolectaron muestras de raíces en busca de evidencia de isópodos barrenadores. Los análisis revelaron la presencia de Sphaeroma peruvianum Richardson, un barrenador de mangle rojo activo en el Pacífico y
reportado previamente para el golfo de Nicoya, Costa Rica. El organismo perfora las raíces y es la causa probable del colapso de los árboles por debilitamiento del soporte radicular. Se depositaron especímenes testigo en el Museo Nacional de Historia Natural Smithsonian en Washington, D.C. (USNM 1139603)
- …