Bimodal grain-size scaling of thermal transport in polycrystalline graphene from large-scale molecular dynamics simulations

Grain boundaries in graphene are inherent in wafer-scale samples prepared by chemical vapor deposition. They can strongly influence the mechanical properties and electronic and heat transport in graphene. In this work, we employ extensive molecular dynamics simulations to study thermal transport in large suspended polycrystalline graphene samples. Samples of different controlled grain sizes are prepared by a recently developed efficient multiscale approach based on the phase field crystal model. In contrast to previous works, our results show that the scaling of the thermal conductivity with the grain size implies bimodal behaviour with two effective Kapitza lengths. The scaling is dominated by the out-of-plane (flexural) phonons with a Kapitza length that is an order of magnitude larger than that of the in-plane phonons. We also show that in order to get quantitative agreement with the most recent experiments, quantum corrections need to be applied to both the Kapitza conductance of grain boundaries and the thermal conductivity of pristine graphene and the corresponding Kapitza lengths must be renormalized accordingly.Comment: Accepted to Nano Lett.; Numerical samples and computer codes availabl

Bimodal grain-size scaling of thermal transport in polycrystalline graphene from large-scale molecular dynamics simulations

Grain boundaries in graphene are inherent in wafer-scale samples prepared by chemical vapor deposition. They can strongly influence the mechanical properties and electronic and heat transport in graphene. In this work, we employ extensive molecular dynamics simulations to study thermal transport in large suspended polycrystalline graphene samples. Samples of different controlled grain sizes are prepared by a recently developed efficient multiscale approach based on the phase field crystal model. In contrast to previous works, our results show that the scaling of the thermal conductivity with the grain size implies bimodal behaviour with two effective Kapitza lengths. The scaling is dominated by the out-of-plane (flexural) phonons with a Kapitza length that is an order of magnitude larger than that of the in-plane phonons. We also show that in order to get quantitative agreement with the most recent experiments, quantum corrections need to be applied to both the Kapitza conductance of grain boundaries and the thermal conductivity of pristine graphene and the corresponding Kapitza lengths must be renormalized accordingly.Comment: Accepted to Nano Lett.; Numerical samples and computer codes availabl

Desenvolvimento de novos serviços

Mestrado em Gestão da Ciência, Tecnologia e InovaçãoAs empresas que pretendem obter vantagens competitivas através da inovação têm que implementar sistemas eficientes de gestão da inovação. Os processos formais para o desenvolvimento de novos produtos estão bem estabelecidos e têm sido alvo de investigação nas últimas décadas. Ao contrário, os processos formais para o desenvolvimento de novos serviços ainda estão pouco estudados, apesar da crescente importância do sector dos serviços nas economias mais avançadas. Esta dissertação pretende contribuir para uma melhor compreensão do processo de desenvolvimento de novos serviços, através da revisão de técnicas e de ferramentas para a sua implementação. Na parte final da dissertação analisa-se brevemente o impacto que as novas tecnologias têm no processo de desenvolvimento de novos serviços.Companies willing to gain competitive advantage through innovation need to set in place efficient innovation management systems. The formal processes for new product development are well defined and a substantial amount of research has been devoted to these processes over the last decades. In spite of the growing importance of the service sector in the major economies, new service development is, however a field lagging behind in research. This work aims at contributing to a better understanding of new services development process, through the review of techniques and tools to implement this process. A brief overview of the impact that the new information technologies have on the new services development process is also carried out

Modelos de comercialização de tecnologias

Doutoramento em Gestão IndustrialO desenvolvimento económico sustentado das empresas é um fator chave para a competitividade. Num ambiente competitivo global, intenso e dinâmico, a eficiência e rapidez do desenvolvimento de novos produtos e serviços pode permitir obter a diferenciação que sustenta uma vantagem competitiva. De forma a tornar a inovação numa competência sustentada, é necessária a criação de um eficiente processo de transferência de conhecimento dos centros de investigação e desenvolvimento (I&D) para as empresas. A criação de valor económico e social requer que o este conhecimento seja incorporado numa tecnologia. A eficiência dos processos de comercialização de tecnologias tem impacto na criação de novas empresas de base tecnológica e consequentemente no desenvolvimento económico do país. No entanto, as elevadas taxas de insucesso destes processos são um forte sinal da necessidade de investigar novos modelos de comercialização. Neste contexto, a definição de novos modelos de comercialização de tecnologia é de destacada importância para aumentar a eficiência do processo, para a criação de valor a partir do conhecimento gerado pela investigação e desenvolvimento e consequentemente para aumentar a competitividade. A principal contribuição deste trabalho de investigação reside na proposta de um novo modelo de comercialização de tecnologia, resultante da análise de diferentes modelos de comercialização de tecnologia, na identificação dos seus fatores críticos de sucesso, bem como dos elementos facilitadores. De forma a atingir estes objetivos, o trabalho incidirá sobre a: i. Descrição teórica do processo e dos conceitos inter-relacionados; ii. Análise de processos, atividades e dos diversos atores envolvidos; iii. Análise do valor e do risco da tecnologia, bem como da assimetria de informação entre os atores; iv. Definição e a avaliação de um novo modelo valorização da tecnologia e na redução do risco.Sustainable economic development is a key factor for competitiveness. In a global, intense and dynamic competitive environment, efficiency and development lead time of new products and services enablers’ differentiation and competitive advantage. In order to make innovation a sustained competence, an efficient knowledge transfer process from Research and Development (R&D) organizations to other parties is required. The deployment of this knowledge to create social and economic value requires it to be embedded in a technology. The efficiency of technology commercialization processes impacts the creation of new technological-based companies and consequently countries economic development. However these processes have high failure rates which point toward the need to investigate new technology commercialization models. In this context, the definition of a new technology commercialization model is particularly important to increase process efficiency, to create value from knowledge generated by research and development and therefore to increase competitiveness. This research work main contribution, towards different technology commercialization models analysis, their critical success factors, and enablers´ identification, is to propose a new technology commercialization model. In order to achieve these objectives, the work will focus on: i. Process theoretical description and inter-related underpinnings; ii. Process, activities and involved actors analysis; iii. Technology risk, value and informational asymmetry analysis; iv. Proposal of a value approach and risk reduction technology commercialization model and assessment model

Map coverage of LoRaWAN signal’s employing GPS from mobile devices

Forests are remote areas with uneven terrain, so it is costly to map the range of signals that enable the implementation of systems based on wireless and long-distance communication. Even so, the interest in Internet of Things (IoT) functionalities for forest monitoring systems has increasingly attracted the attention of several researchers. This work demonstrates the development of a platform that uses the GPS technology of mobile devices to map the signals of a LoRaWAN Gateway. Therefore, the proposed system is based on concatenating two messages to optimize the LoRaWAN transmission using the Global Position System (GPS) data from a mobile device. With the proposed approach, it is possible to guarantee the data transmission when finding the ideal places to fix nodes regarding the coverage of LoRaWAN because the Gateway bandwidth will not be fulfilled. The tests indicate that different changes in the relief and large bodies drastically affect the signal provided by the Gateway. This work demonstrates that mapping the Gateway’s signal is essential to attach modules in the forest, agriculture zones, or even smart cities.This work has been supported by Fundação La Caixa and FCT - Fundação para a Ciência e Tecnologia within the Project Scope: UIDB/5757/2020. Thadeu Brito is supported by FCT PhD Grant Reference SFRH/BD/08598/2020. Beatriz Flamia Azevedo is supported by FCT PhD Grant Reference SFRH/BD/07427/2021.info:eu-repo/semantics/publishedVersio

Thermal conductivity decomposition in two-dimensional materials: Application to graphene

Two-dimensional materials have unusual phonon spectra due to the presence of flexural (out-of-plane) modes. Although molecular dynamics simulations have been extensively used to study heat transport in such materials, conventional formalisms treat the phonon dynamics isotropically. Here, we decompose the microscopic heat current in atomistic simulations into in-plane and out-of-plane components, corresponding to in-plane and out-of-plane phonon dynamics, respectively. This decomposition allows for direct computation of the corresponding thermal conductivity components in two-dimensional materials. We apply this decomposition to study heat transport in suspended graphene, using both equilibrium and nonequilibrium molecular dynamics simulations. We show that the flexural component is responsible for about two-thirds of the total thermal conductivity in unstrained graphene, and the acoustic flexural component is responsible for the logarithmic divergence of the conductivity when a sufficiently large tensile strain is applied

Incidência e prevalência da disfunção erétil e ejaculatória em estudantes de medicina nas cidades de Goiania e Anápolis

RESUMO: A disfunção sexual é um distúrbio que tem por característica se pronunciar com o avançar da idade e dos fatores sociais e pessoais que envolve o indivíduo. Dentre as principais disfunções sexuais encontra-se a disfunção erétil e a ejaculação precoce como as mais prevalentes, sendo estas determinadas por vários fatores predisponentes de tais patologias, como fatores orgânicos e psicológicos. Nesse sentido, espera-se quemesmo os estudantes de medicina, que normalmente representam uma população jovem e saudável, devido a fatores como o estresse físico, emocional e mental, proporcionadas por sua rotina, podem acabar tendo sua sexualidade afetada, tornando-se possíveis vítimas da disfunção sexual. Esses transtornos sexuais podem então somatizar negativamente na vida de um estudante universitário de medicina, prejudicando suaqualidade de vida e até ser um fator predisponente para doenças psicossociais. Dessa forma, o presente estudo tem por objetivo identificar a incidência e a prevalência da disfunção erétil e ejaculatória em estudantes de medicina de escolas médicas da cidade de Goiânia e de Anápolis, relacionando fatores predisponentes e de rotina dessa população. Trata-se de um estudo primário, observacional, de prevalência, transversal, descritivo e quantitativo. Como instrumento de coleta de dados serão aplicados questionários aos participantes com base em dados da Associação Americana de Urologia (AUA), os quais serão realizados em escolas de medicina das cidades de Goiânia e Anápolis. Espera-se encontrar uma estimativa sobre a incidência e a prevalência de disfunção erétil e ejaculatória masculina nos acadêmicos de medicina. Acredita-se que esses estudantes não tenham o conhecimento adequado sobre os fatores predisponentes e consequências da disfunção sexual e como isso pode refletir na sua vida acadêmica

Impact of safety-related dose reductions or discontinuations on sustained virologic response in HCV-infected patients: Results from the GUARD-C Cohort

BACKGROUND: Despite the introduction of direct-acting antiviral agents for chronic hepatitis C virus (HCV) infection, peginterferon alfa/ribavirin remains relevant in many resource-constrained settings. The non-randomized GUARD-C cohort investigated baseline predictors of safety-related dose reductions or discontinuations (sr-RD) and their impact on sustained virologic response (SVR) in patients receiving peginterferon alfa/ribavirin in routine practice. METHODS: A total of 3181 HCV-mono-infected treatment-naive patients were assigned to 24 or 48 weeks of peginterferon alfa/ribavirin by their physician. Patients were categorized by time-to-first sr-RD (Week 4/12). Detailed analyses of the impact of sr-RD on SVR24 (HCV RNA <50 IU/mL) were conducted in 951 Caucasian, noncirrhotic genotype (G)1 patients assigned to peginterferon alfa-2a/ribavirin for 48 weeks. The probability of SVR24 was identified by a baseline scoring system (range: 0-9 points) on which scores of 5 to 9 and <5 represent high and low probability of SVR24, respectively. RESULTS: SVR24 rates were 46.1% (754/1634), 77.1% (279/362), 68.0% (514/756), and 51.3% (203/396), respectively, in G1, 2, 3, and 4 patients. Overall, 16.9% and 21.8% patients experienced 651 sr-RD for peginterferon alfa and ribavirin, respectively. Among Caucasian noncirrhotic G1 patients: female sex, lower body mass index, pre-existing cardiovascular/pulmonary disease, and low hematological indices were prognostic factors of sr-RD; SVR24 was lower in patients with 651 vs. no sr-RD by Week 4 (37.9% vs. 54.4%; P = 0.0046) and Week 12 (41.7% vs. 55.3%; P = 0.0016); sr-RD by Week 4/12 significantly reduced SVR24 in patients with scores <5 but not 655. CONCLUSIONS: In conclusion, sr-RD to peginterferon alfa-2a/ribavirin significantly impacts on SVR24 rates in treatment-naive G1 noncirrhotic Caucasian patients. Baseline characteristics can help select patients with a high probability of SVR24 and a low probability of sr-RD with peginterferon alfa-2a/ribavirin