227 research outputs found
Approaching the diamond surface: first principles modelling the physics and chemistry of approaching radicals
No full textThe diamond surface plays a central role in much of the diamond research, and as such much of its properties are described and studied in great detail. There is a clear picture of the atomic scale structure of the different facets and their reconstructions. Also terminations with H, O, N and other atomic species as well as the incorporation of these elements has been modelled [1,2]. The electronic structure and the negative electron affinity mechanism is elucidated and so on. In contrast, however, the atomic scale models of diamond growth are much less developed, though progress is being made [3]. In these models the reaction barriers between stable and meta-stable intermediates are being calculated, providing insights into the kinetics of the surface. However, quantum mechanical models can provide much more insights than this. In this work, we simulated the approach of radical atoms and molecules towards the H-terminated diamond 001 surface. By allowing the model to equilibrate at every step, the physics and chemistry of the approach can be followed in minute detail. It allows us to indicate at which distance the surface and radical start interacting, and what that interaction entails. The charge evolution of the radical and the surface is followed by means of Hirshfeld-I charges, providing insights into charge transfer mechanisms. [4] Throughout the approach, the interaction can be followed through different physical and chemical concepts. Different types of bonding are identified as well as H-abstraction events and covalent bonding. In this work, our focus goes to C and P based radicals, showing them to behave very differently near the surface, providing insights into the requirements for improved P incorporation.The author name needs to be updated to include the middle names: Danny E.P. Vanpoucke, and linked to the correct personel account which incorrectly is missing the author middle names
Approaching the diamond surface: first principles modelling the physics and chemistry of approaching radicals
No full textThe diamond surface plays a central role in much of the diamond research, and as such much of its properties are described and studied in great detail. There is a clear picture of the atomic scale structure of the different facets and their reconstructions. Also terminations with H, O, N and other atomic species as well as the incorporation of these elements has been modelled [1,2]. The electronic structure and the negative electron affinity mechanism is elucidated and so on. In contrast, however, the atomic scale models of diamond growth are much less developed, though progress is being made [3]. In these models the reaction barriers between stable and meta-stable intermediates are being calculated, providing insights into the kinetics of the surface. However, quantum mechanical models can provide much more insights than this. In this work, we simulated the approach of radical atoms and molecules towards the H-terminated diamond 001 surface. By allowing the model to equilibrate at every step, the physics and chemistry of the approach can be followed in minute detail. It allows us to indicate at which distance the surface and radical start interacting, and what that interaction entails. The charge evolution of the radical and the surface is followed by means of Hirshfeld-I charges, providing insights into charge transfer mechanisms. [4] Throughout the approach, the interaction can be followed through different physical and chemical concepts. Different types of bonding are identified as well as H-abstraction events and covalent bonding. In this work, our focus goes to C and P based radicals, showing them to behave very differently near the surface, providing insights into the requirements for improved P incorporation.The author name needs to be updated to include the middle names: Danny E.P. Vanpoucke, and linked to the correct personel account which incorrectly is missing the author middle names
DFT-based Vibrational Spectra for THz-Spectroscopy and Defect Fingerprinting in Molecular Crystals and Solids.
No full textSpectroscopic techniques based on atomic vibrations provide a powerful tool for the
atomic scale characterization of solids. Unfortunately, the translation of their spectra into
atomistic structures tends to be an inverse-problem, as a structural model is required to
assign the observed spectral peaks. This is further complicated by the fact that the exact
position of the latter is sensitive to the precise underlying atomic structure. This results
in the need for very accurate models.
With the steady growth of computational resources, the calculation of vibrational spectra
for extended and periodic systems has become more attainable at the level of quantum
mechanical calculations. In this work, we first present the example of the THz vibrational
spectrum of lactose-monohydrate (LM), and use our results to identify the spectral lines
of the observed spectra of different phases, obtained experimentally by heating the LM
sample.1 The accompanying water loss induces two phase transitions. According to our
results, all phases, including the starting high purity commercial sample, are mixtures of
different phases. We discuss the impact of both structural—such as water content and
orientation— and methodological—such as Pulay stresses, periodic boundaries, and
supercell sizes—aspects on the calculated spectra, and show that DFT-based spectra
under periodic boundaries can be matched with experimental data.
The importance of an extended periodic system for obtaining an accurate vibrational
spectrum is also shown in studying defects in diamond. However, here, we show that the
qualitative picture of the defect character of each atom in the system is independent of
the system size, allowing for small periodic cells to determine the relevant defect atoms
at much reduced computational cost.2 Defects tend to be very localized, resulting in
atomic modes.3 Therefore, an often-used strategy for selecting the contributing atoms
considers only their relative position with regard to the defect center. Using the atomprojected
vibrational spectrum, we present a quantitative method for determining the
defect character of each atom in the system, allowing for a rational incremental
improvement of the defect spectrum. This method is then applied on several simple
defects in diamond.Author : Danny E.P. Vanpoucke
Author name needs to be updated to include middle names, and correctly linked to the uhasselt personel databas
DFT-based Vibrational Spectra for THz-Spectroscopy and Defect Fingerprinting in Molecular Crystals and Solids.
No full textSpectroscopic techniques based on atomic vibrations provide a powerful tool for the
atomic scale characterization of solids. Unfortunately, the translation of their spectra into
atomistic structures tends to be an inverse-problem, as a structural model is required to
assign the observed spectral peaks. This is further complicated by the fact that the exact
position of the latter is sensitive to the precise underlying atomic structure. This results
in the need for very accurate models.
With the steady growth of computational resources, the calculation of vibrational spectra
for extended and periodic systems has become more attainable at the level of quantum
mechanical calculations. In this work, we first present the example of the THz vibrational
spectrum of lactose-monohydrate (LM), and use our results to identify the spectral lines
of the observed spectra of different phases, obtained experimentally by heating the LM
sample.1 The accompanying water loss induces two phase transitions. According to our
results, all phases, including the starting high purity commercial sample, are mixtures of
different phases. We discuss the impact of both structural—such as water content and
orientation— and methodological—such as Pulay stresses, periodic boundaries, and
supercell sizes—aspects on the calculated spectra, and show that DFT-based spectra
under periodic boundaries can be matched with experimental data.
The importance of an extended periodic system for obtaining an accurate vibrational
spectrum is also shown in studying defects in diamond. However, here, we show that the
qualitative picture of the defect character of each atom in the system is independent of
the system size, allowing for small periodic cells to determine the relevant defect atoms
at much reduced computational cost.2 Defects tend to be very localized, resulting in
atomic modes.3 Therefore, an often-used strategy for selecting the contributing atoms
considers only their relative position with regard to the defect center. Using the atomprojected
vibrational spectrum, we present a quantitative method for determining the
defect character of each atom in the system, allowing for a rational incremental
improvement of the defect spectrum. This method is then applied on several simple
defects in diamond.Author : Danny E.P. Vanpoucke
Author name needs to be updated to include middle names, and correctly linked to the uhasselt personel databas
How to Minimize Procrastination
No full textProcrastination is a barrier to achieving personal goals. This project sought to test the effectiveness of implementation intentions (plan for a time and location connected to an action), purposeful delay (delaying tasks to increase motivation), and intrinsic reasons (behavior that is driven by personal internal rewards) on procrastination. Our research consisted of two 2-week studies on ourselves: a non-experimental study examining the correlations between natural variations in the variables described above and an experimental study specifically testing the effect that implementation intentions has upon procrastination. Our correlational results supported the work of these previous studies by showing the ability to predict the degree of procrastination based on the amount of implantation intentions and intrinsic reasons that naturally occurred, with implementation intentions having the highest correlation with procrastination. However, our experimental results did not support a causal role of implementation intentions in minimizing procrastination. It is speculated that these results occurred because of the increased number of times implementation intentions were used and procrastination was measured and due to influences from external events during trials.Supervising Instructor & Course Number:
Michael Pollock, Psyc 110 ("Experimental Psychology"
Why infrastructure financing facilities often fall short of their objectives
No full textTo encourage the private funding and provision of infrastructure services, governments have used specialized financing facilities to offer financial support to investors, often in the form of grants, soft loans, or guarantees. The authors present case studies of infrastructure financing facilities in various stages of development in Colombia, India, and Pakistan. They also present case studies of government-sponsored financing facilities (not of infrastructure) in Argentina, and Moldova. They find that these facilities have often fallen short of their objectives for two main reasons. First, the environment was not conducive to private participation in infrastructure because of poor sector policies, an unstable macroeconomic environment, and inadequate financial sector policies, among other reasons. Second, the facility was faulty in design - in terms of sectors targeted, pricing of instruments, and consistency of objectives, and instruments.Decentralization,Banks&Banking Reform,Payment Systems&Infrastructure,Public Sector Economics&Finance,Municipal Financial Management,Municipal Financial Management,Banks&Banking Reform,Housing Finance,Public Sector Economics&Finance,National Governance
Roald Dahl: the Author for Two Audiences. A comparison of His Writings for Children and Adults
No full textKatedra anglistiky a amerikanistikyDokončená práce s úspěšnou obhajobo
Corresponding Author:
No full textIn this paper we study the problem of determining optimal paths in a dynamic, 2-D environment. We present anovel cell decomposition approach which generates optimal paths based on a number of di erent optimality criteria, including time-optimal, distance-optimal (shortest paths), and costoptimal paths based on a combination of time and distance. After mapping the dynamic, 2-D environment to a static, 3-D workspace, we propagate a path planning wave through the workspace to obtain distance transform values in an accurate and e cient manner. Our approach uses a computational geometry technique for sweeping a 3-D space with a plane, called time-sweeping. Furthermore, our approach allows us to generate these optimal paths much more e ciently than could be obtained with traditional shortest path planning algorithms
Preliminary uncertainty and sensitivity analysis of the Molten Salt Fast Reactor steady-state using a Polynomial Chaos Expansion method
No full textIn this work, we present the results of a preliminary uncertainty quantification and sensitivity analysis study of the Molten Salt Fast Reactor (MSFR) behavior at steady-state performed by applying a non-intrusive Polynomial Chaos Expansion (PCE) approach. An in-house high-fidelity multi-physics simulation tool is used as reactor reference model. Considering several thermal-hydraulics and neutronics parameters as stochastic inputs, with a limited number of samples we build a PCE meta-model able to reproduce he reactor response in terms of effective multiplication factor, maximum, minimum, and average salt temperatures, and complete salt temperature distribution. The probability density functions of the responses are constructed and analyzed, highlighting strengths and issues of the current MSFR design. The sensitivity study highlights the relative importance of each input parameter, thus providing useful indications for future research efforts. The analysis on the whole temperature field shows that the heat exchanger can be a critical component, so its design requires particular care.</p
Rewarding Innovation: Improving Federal Tax Support for Business R&D in Canada
No full textBusiness innovation is viewed by many as a solution to Canada’s ailing productivity performance. One of the more troubling aspects of Canada’s innovation track record is that businesses spend relatively little on research and development (R&D) despite having access to some of the world’s most generous R&D tax incentives. Canada’s low levels of business R&D have called into question the effectiveness of Canada’s generous R&D tax incentives, particularly the flagship federal Scientific Research and Experimental Development (SR&ED) program. A deeper analysis, however, reveals that tax incentives are effective in stimulating more R&D – that is, Canada would have lower levels of business R&D in the absence of these inducements. Instead, the root cause of Canada’s business R&D deficit appears to stem from structural aspects of the economy and, more importantly, a lack of demand-related pressure to pursue innovation.Fiscal and Tax Competitiveness, Canada, research and development (R&D) incentives, Scientific Research and Experimental Development (SR&ED) program
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