Optical and structural properties of GaAs/GaInP quantum wells grown by Chemical Beam Epitaxy

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Structural refinement, optical and microwave dielectric properties of BaZrO3

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Photoluminescence in quasi-amorphous Pb0.8X0.2Zr0.53Ti0.47O3 (X = Ca, Sr and Ba) powders: An optical and structural study

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Optical and dielectric relaxor behaviour of Ba(Zr0.25Ti0.75)O-3 ceramic explained by means of distorted clusters

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Structural refinement, optical and ferroelectric properties of microcrystalline Ba(Zr0.05Ti0.95)O-3 perovskite

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Investigation of the structural, optical and dielectric properties of highly (100)-oriented (Pb0.60Ca0.20Sr0.20)TiO3 thin films on LaNiO3 bottom electrode

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Effect of Fe-doping on the structural, microstructural, optical, and ferroeletric properties of Pb1/2Sr1/2Ti1-xFexO3 oxide prepared by spin coating technique

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Structural refinement, optical and microwave dielectric properties of BaZrO3

In this work, barium zirconate (BaZrO3) ceramics synthesized by solid state reaction method and sintered at 1670 degrees C for 4 h were characterized by X-ray diffraction (XRD), Rietveld refinement, and Fourier transform infrared (FT-IR) spectroscopy. XRD patterns, Rietveld refinement data and FT-IR spectra which confirmed that BaZrO3 ceramics have a perovskite-type cubic structure. Optical properties were investigated by ultraviolet-visible (UV-vis) absorption and photoluminescence (PL) measurements. UV-vis absorption spectra suggested an indirect allowed transition with the existence of intermediary energy levels within the band gap. Intense visible green PL emission was observed in BaZrO3 ceramics upon excitation with a 350 nm wavelength. This behavior is due to a majority of deep defects within the band gap caused by symmetry breaking in octahedral [ZrO6] clusters in the lattice. The microwave dielectric constant and quality factor were measured using the method proposed by Hakki-Coleman. The dielectric resonator antenna (DRA) was investigated experimentally and numerically using a monopole antenna through an infinite ground plane and Ansoft's high frequency structure simulator software, respectively. The required resonance frequency and bandwidth of DRA were investigated by adjusting the dimension of the same material. (C) 2011 Elsevier Ltd and Techna Group S.r.l. All rights reserved.

Organic lasing: correlation between molecular structure, optical and optoelectronic properties

In this thesis mainly two alternating indenofluorene-phenanthrene copolymers were investigated with a variety of spectroscopic and optoelectronic experiments. The different experimental techniques allowed to retrieve deeper insights into their unique optical as well as optoelectronic properties. The motivation of the research presented in this work was to correlate their photophysical properties with respect to their application in electrically pumped lasing. This thesis begins with the description of optical properties studied by classical absorption and emission spectroscopy and successively describes an overall picture regarding their excited state dynamics occurring after photoexcitation studied by time-resolved spectroscopy. The different spectroscopic methods do not only allow to elucidate the different optical transitions occurring in this class of materials, but also contribute to a better understanding of exciton dynamics and exciton interaction with respect to the molecular structure as well as aggregation and photooxidation of the polymers. Furthermore, the stimulated emission properties were analyzed by amplified spontaneous emission (ASE) experiments. Especially one of the investigated materials, called BLUE-1, showed outstanding optical properties including a high optical gain, a low threshold for ASE and low optical losses. Apart from the optical experiments, the charge carrier mobility was measured with the time-of-flight technique and a comparably high hole mobility on the order of 1 x 10-² cm²/(Vs) was determined for BLUE-1 which makes this material promising for organic lasing. The impact of the high charge carrier mobility in this material class was further analyzed in different optoelectronic devices such as organic LEDs (OLEDs) and organic solar cells.

Optical and ultraviolet observations of a strong flare in the young, single K2 dwarf LQ Hya

We present high-resolution optical echelle spectra and IUE observations during a strong flare on 1993 December 22 in the very active, young, rapidly rotating, single K2 dwarf LQ Hya. The initial impulsive phase of the flare, which started sometime between 2:42 ut and 4:07 ut, was characterized by strong optical continuum enhancement and blueshifted emission lines with broad wings. The optical chromospheric lines reached their maximum intensity at ≈ 5:31 ut, by which time the blueshift vanished and the optical continuum enhancement had sharply decreased. Thereafter, the line emission slowly decreased and the lines redshift in a gradual phase that lasted at least two more hours. The Mg II lines behaved similarly. Quiescent C IV flux levels were not recovered until 21 h later, though a data gap and a possible second flare make the interpretation uncertain. In addition to the typically flare-enhanced emission lines (e.g., H α and H β), we observe He I D_3 going into emission, plus excess emission (after subtraction of the quiescent spectrum) in other He I and several strong neutral metal lines (e.g., Mg I b). Flare enhancement of the far-ultraviolet continuum generally agrees with an Si I recombination model. We estimate the total flare energy, and discuss the broad components, asymmetries and Doppler shifts seen in some of the emission lines.

Optical and structural ocular changes during incipient presbyopia

The primary aim of this thesis was to investigate the in vivo ocular morphological and contractile changes occurring within the accommodative apparatus prior to the onset of presbyopia, with particular reference to ciliary muscle changes with age and the origin of a myopic shift in refraction during incipient presbyopia. Commissioned semi-automated software proved capable of extracting accurate and repeatable measurements from crystalline lens and ciliary muscle Anterior Segment Optical Coherence Tomography (AS-OCT) images and reduced the subjectivity of AS-OCT image analysis. AS-OCT was utilised to document longitudinal changes in ciliary muscle morphology within an incipient presbyopic population (n=51). A significant antero-inwards shift of ciliary muscle mass was observed after 2.5 years. Furthermore, in a subgroup study (n=20), an accommodative antero-inwards movement of ciliary muscle mass was evident. After 2.5 years, the centripetal response of the ciliary muscle significantly attenuated during accommodation, whereas the antero-posterior mobility of the ciliary muscle remained invariant. Additionally, longitudinal measurement of ocular biometry revealed a significant increase in crystalline lens thickness and a corresponding decrease in anterior chamber depth after 2.5 years (n=51). Lenticular changes appear to be determinant of changes in refraction during incipient presbyopia. During accommodation, a significant increase in crystalline lens thickness and axial length was observed, whereas anterior chamber depth decreased (n=20). The change in ocular biometry per dioptre of accommodation exerted remained invariant after 2.5 years. Cross-sectional ocular biometric data were collected to quantify accommodative axial length changes from early adulthood to advanced presbyopia (n=72). Accommodative axial length elongation significantly attenuated during presbyopia, which was consistent with a significant increase in ocular rigidity during presbyopia. The studies presented in this thesis support the Helmholtz theory of accommodation and despite the reduction in centripetal ciliary muscle contractile response with age, primarily implicate lenticular changes in the development of presbyopia.

Discussion Paper : Proposed CDIO Standard 13 - Internationalisation and Mobility

The benefits and growing need for international transparency in engineering qualifications, simple cross-credit processes, international dual awards and mechanisms to encourage student mobility, are receiving much attention around the world at present. In response, there are a number of global initiatives now looking at how these issues may be addressed, particularly in Europe, North America and Australia. CDIO has adopted 12 Standards as guiding principles for program reform and evaluation. The 12 CDIO Standards address program philosophy curriculum development, design-build experiences and workspaces, new methods of teaching and learning, faculty/academic development, and assessment and evaluation. However, none of the Standards address international qualifications nor student mobility. This discussion paper presents the underpinning case for introducing the 13th CDIO Standard, Internationalization and Mobility.

Addressing Challenges for Internationalisation and Mobility in Engineering Through CDIO Standards

There is a growing need for international transparency of engineering qualifications, and mechanisms to support and facilitate student mobility. In response, there are a number of global initiatives attempting to address these needs, particularly in Europe, North America and Australia. The Conceive-Design-Implement-Operate (CDIO) Initiative has a set of standards, competencies, and proficiency levels developed through a global community of practice. It is a well-structured framework in which best-practice internationalisation and student mobility can be embedded. However, the current 12 CDIO Standards do not address international qualifications or student mobility. Based on an environmental scan of global activities, the underpinning principles of best practice are identified and form the basis of the proposed 13th CDIO Standard — “Internationalization and Mobility”.

The impact of police speed enforcement practices on self-reported speeding: An exploration of the effects of visibility and mobility

Research has highlighted the relationship between vehicle speed and increased crash risk and severity. Evidence suggests that police speed enforcement, in particular speed camera operations, can be an effective tool for reducing traffic crashes. A quantitative survey of Queensland drivers (n = 852) was conducted to investigate the impact of police speed enforcement methods on self-reported speeding behaviour. Results indicate that visible enforcement was associated with significantly greater self-reported compliance than covert operations irrespective of the mobility of the approach, and the effects on behaviour were longer lasting. The mobility of operations appeared to be moderated the visibility of the approach. Specifically, increased mobility was associated with increase reported compliant behaviour, but only for covert operations, and increased longevity of reported compliant behaviour, but only for overt operations. The perceived effectiveness of various speed enforcement approaches are also analysed across a range of driving scenarios. Results are discussed in light of the small effect sizes. Recommendations for policy and future research are presented.