Control of a white organic light emitting diode’s emission parameters using a single doped RGB active layer

White Color tuning is an attractive feature that Organic Light Emitting Diodes (OLEDs) offer. Up until now, there hasn’t been any report that mix both color tuning abilities with device stability. In this work, White OLEDs (W-OLEDs) based on a single RGB blend composed of a blue emitting N,N′-Di(1-naphthyl)-N,N′-diphenyl-(1,1′-biphenyl)-4,4′-diamine (NPB) doped with a green emitting Coumarin-153 and a red emitting 4-(Dicyanomethylene)-2-methyl-6-(4-dimethylaminostyryl)-4H-pyran (DCM1) dyes were produced. The final device structure was ITO/Blend/Bathocuproine (BCP)/ Tris(8-hydroxyquinolinato)aluminium (Alq3)/Al with an emission area of 0.25 cm2. The effects of the changing in DCM1’s concentration (from 0.5% to 1% wt.) allowed a tuning in the final white color resulting in devices capable of emitting a wide range of tunes – from cool to warm – while also keeping a low device complexity and a high stabilitty. Moreover, an explanation on the optoelectrical behavior of the device is presented. The best electroluminescense (EL) points toward 160 cd/m2 of brightness and 1.1 cd/A of efficiency, both prompted to being enhanced. An Impedance Spectroscopy (IS) analysis allowed to study both the effects of BCP as a Hole Blocking Layer and as an aging probe of the device. Finally, as a proof of concept, the emission was increased 9 and 64 times proving this structure can be effectively applied for general lighting

Gravitational wave generation in hybrid quintessential inflationary models

We investigate the generation of gravitational waves in the hybrid quintessential inflationary model. The full gravitational-wave energy spectrum is calculated using the method of continuous Bogoliubov coefficients. The post-inflationary kination period, characteristic of quintessential inflationary models, leaves a clear signature on the spectrum, namely, a peak at high frequencies. The maximum of the peak is firmly located at the MHz-GHz region of the spectrum and corresponds to $\Omega_{GW} \simeq 10^{-12}$. This peak is substantially smaller than the one appearing in the gravitational-wave energy spectrum of the original quintessential inflationary model, therefore avoiding any conflict with the nucleosynthesis constraint on \Omega_\Omega_{GW}.Comment: 10 pages, 11 figures, one reference adde

Avaliação de soluções energéticas em ambiente hospitalar na perspectiva de uma ESCO

Estágio realizado nos Hospitais da Universidade de Coimbra, orientado pelo Engenheiro Avaro LapaTese de mestrado integrado. Engenharia Mecânica. Faculdade de Engenharia. Universidade do Porto. 201

Gravitational wave generation in loop quantum cosmology

We calculate the full spectrum, as observed today, of the cosmological gravitational waves generated within a model based on loop quantum cosmology. It is assumed that the universe, after the transition to the classical regime, undergoes a period of inflation driven by a scalar field with a chaotic-type potential. Our analysis shows that, for certain conditions, loop quantum effects leave a clear signature on the spectrum, namely, an over-production of low-frequency gravitational waves. One of the aims of our work is to show that loop quantum cosmology models can be tested and that, more generally, pre-inflationary physical processes, contrary to what is usually assumed, leave their imprint in those spectra and can also be tested.Comment: 7 pages, 8 figures, revtex

Issues of sustainable development in civil engineering in Portugal

There are, in Portugal, nine universities with degree programs of civil engineeringaccredited by the Ordem dos Engenheiros (Engineering Professional Body). However,none of them present disciplines expressly dedicated to teach or to learn SD in the studyplan. In the two last years of the five year study plan, generally in the fourth year of degree,most of the courses of civil engineering introduces SD in an implicit way. It is forinstance associated to studies of town planning and of evaluation of environmental impacts.Of the nine degree programs of civil engineering analyzed, in the option of buildingconstruction, only two present disciplines that are optional and are directly associatedwith sustainable construction. Six present disciplines of evaluation of environmentalimpact and of town planning. The importance of SD in a degree program of civil engineeringis unquestionable. Some of the issues like building maintenance and managementrepresent a large impact on energy spending and on pollution of the atmosphere and ofthe earth. Another area of civil engineering that is important for SD is hydraulics and thewater, river and sea management. A very important area is the cycle and recycle of constructionmaterials with the creation of by-products that are one of the main sources ofenvironment contamination. There are many other areas of civil engineering where SD isvery important like transportation, planning and industrial construction. The adaptation ofcivil engineering disciplines of the SD principles and theories will prepare the future civilengineers to address their profession with SD as a major concern and beacon. The continuingeducation and professional development activities and courses will have a quickerimpact on the transformation of the actions of the current civil engineers

Parametric Resonance and Cosmological Gravitational Waves

We investigate the production of gravitational waves due to quantum fluctuations of the vacuum during the transition from the inflationary to the radiation-dominated eras of the universe, assuming this transition to be dominated by the phenomenon of parametric resonance. The energy spectrum of the gravitational waves is calculated using the method of continuous Bogoliubov coefficients, which avoids the problem of overproduction of gravitons at large frequencies. We found, on the sole basis of the mechanism of quantum fluctuations, that the resonance field leaves no explicit and distinctive imprint on the gravitational-wave energy spectrum, apart an overall upward or downward translation. Therefore, the main features in the spectrum are due to the inflaton field, which leaves a characteristic imprint at frequencies of the order of MHz/GHz.Comment: 8 pages, 7 figure

O habitat urbano brasileiro: paradigma e perspectivas

A história do desenvolvimento urbano brasileiro como preocupação governamental está, de certa forma, ligada ao problema do desenvolvimento municipal, que se tomou mais intenso a partir da Revolução de 1930. Desde esse momento, nota-se que o conceito de desenvolvimento adotado é associado diretamente aos conceitos de crescimento econômico e eficiência administrativa-¹ Tal postura consolida-se através dos tempos e torna-se uma constante dos discursos tanto dos municipalistas como dos planejadores urbanos.Revista do Serviço Público, ano 40 v.111, n. 1, p. 5-15Número padronizado: v. 40, n. 1 (1983)DesenvolvimentoPolíticas PúblicasISSN eletrônico: 2357-8017ISSN impresso: 0034-924

Unification of inflation, dark energy, and dark matter within the Salam-Sezgin cosmological model

We investigate a cosmological model, based on the Salam-Sezgin six-dimensional supergravity theory and on previous work by Anchordoqui, Goldberg, Nawata, and Nu\~nez. Assuming a period of warm inflation, we show that it is possible to extend the evolution of the model back in time, to include the inflationary period, thus unifying inflation, dark matter, and dark energy within a single framework. Like the previous authors, we were not able to obtain the full dark matter content of the Universe from the Salam-Sezgin scalar fields. However, even if only partially successful, this work shows that present-day theories, based on superstrings and supergravity, may eventually lead to a comprehensive modelling of the evolution of the Universe. We find that the gravitational-wave spectrum of the model has a non-constant negative slope in the frequency range 10^(-15)-10^6 rad/s, and that, unlike standard (cold) inflation models, it shows no structure in the MHz/GHz range of frequencies.Comment: 10 pages, 10 figure