In this study, optical behavior of metal nanoparticles having dimensions smaller than the wavelength of visible light is studied experimentally and numerically. Gold (Au) and silver (Ag) nanoparticles are studied due to their superior optical properties when compared to other metals. A compact code based on Discrete Dipole Approximation (DDA) is developed to compute extinction efficiencies of nanoparticles with various different properties such as material, dimension and geometry. To obtain self consistent nanoparticle arrays with well defined geometries and dimensions, Electron Beam Lithography (EBL) technique is mainly used as the manufacturing method. Dose parameters required to produce nanoparticles with dimensions down to 50 nm over substrates with different electrical conductivities are determined. Beam current is found to affect the doseV size relation. The use of thin Au films as antistatic layer for e-beam patterning over insulating substrates is considered and production steps, involving instabilities due to contaminants introduced to the system during additional removal steps, are clarified. 4 nm thick Au layer is found to provide sufficient conductivity for e-beam patterning over insulating substrates. An optical setup capable of performing transmittance and reflectance measurements of samples having small areas patterned with EBL is designed. Sizes of the metal nanoparticles are determined by scanning electron microscope (SEM) and spectral data obtained using the optical setup is analyzed to find out the parameters affecting the localized surface plasmon resonances (LSPR). Arrays of particles with diameters between 50 &ndash / 200 nm are produced and optically analyzed. Size and shape of the nanoparticles are found to affect the resonance behavior. Furthermore, lattice constants of the particle arrays and surrounding medium are also shown to influence the reflectance spectra. Axes with different lengths in ellipsoidal nanoparticles are observed to cause distinguishable resonance peaks when illuminated with polarized light. Peak intensities obtained from both polarizations are observed to decrease under unpolarized illumination. Binary systems consisting of nanosized particles and holes provided better contrast for transmitted light.

The aim of the present research is to identify human subjective response (health and comfort) to the micro-thermal environment established by integration of individually controlled localized chilled beam and chilled ceiling (LCBCC) system and to compare its performance with the performance of mixing ventilation combined with chilled ceiling (CCMV).Experiments were carried out in mock-up of an office (4.1 m × 4.0 m × 3.1 m, L× W× H) with one person under two summer temperature conditions (26 °C and 28 °C). To mimic direct solar radiation in the room, five radiative panels on the wall together with electrical sheets on the half of the floor were used. The test room was set-up with two desks, as two workstations, and one laptop on each table. The main workstation (WS1) was located close to the simulated window. The second work station (WS2) was placed in the opposite side of the room. The room was equipped with two types of ventilating and cooling systems.  The first system consisted of a localized active chilled beam (LCB) unit together with chilled ceiling (CC) panels. The LCB was installed above the WS1 to create micro-environment around the occupant sitting at the desk. The supply flow rate from the LCB could be adjusted by the occupant within the range of 10 L/s to 13 L/s by means of a desk-mounted knob. The integration of mixing ventilation (MV) system and chilled ceiling panels was the second ventilating and cooling strategy. Twenty- four subjects (12 female and 12 male) were exposed to different indoor environment established by two cooling systems. Each experiment session lasted 120 min and consisted of 30 min acclimatization period and 90 min exposure period. The performance of the systems was identified and compared by physical measurements of the generated environment and the response of the human subjects. The study showed that perceived air quality (PAQ), overall thermal sensation (OTS) acceptability and local thermal sensation (LTS) acceptability clearly improved inside the micro-environment by using LCBCC system. Moreover, at the main workstation, OTS and LTS votes were close to “neutral” thermal sensation (ASHRAE seven point scale) when LCBCC system was used. However, OTS and LTS votes increased to the “slightly warm” side of the scale by applying CCMV system which implied the better cooling performance of the LCBCC system. Acceptability of work environment apparently increased under the room condition generated by LCBCC system. In agreement with human subjective study, the results from physical measurements and thermal manikin study showed that uniform thermal condition was generated all over the room. Air and operative temperature distribution was almost uniform with no difference higher than 1 °C between the measured locations in the room. Thus, both LCBCC and CCMV systems performed equally well outside of the micro-environment region. The use of the chilled ceiling had impact on the airflow interaction in the room and changed the airflow pattern. It can be concluded that the combination of convective and radiative systems can be considered as an efficient strategy to generate acceptable thermal condition in rooms.

Σε αυτή την διπλωματική στο ΠΜΣ Επιστημής Υλικών, έγινε προσπάθεια δημιουργίας νέων πλασμονικών δομών, μέσω της οξείδωσης μεταβατικών μετάλλων από τα στερεά τους διαλλύματα που αναπτύχθηκαν μέσω της τεχνικής της ιοντοβολής. Ελέγχοντας, την διεθνή βιβλιογραφία δεν βρέθηκε τρόπος παρεμφερής της πειραματικής διαδικασίας που ακολουθήθηκε, για την επίτευξη πλασμονικών δομών. Τα συστήματα που μελετήθηκαν είναι υμένια CuO / Au και Cu2O / Au, όπου η διηλεκτρική μήτρα είναι το ημιαγώγιμο οξείδιο και το πλασμονικό μέταλλο είναι το ευγενές μέταλλο του Au. Επίσης, να σημειωθεί ότι έλαβαν χώρα προκαταρκτικά πειράματα με χρήση NiO, όπου και αποδεικνύεται η γενικότητα της μεθοδολογίας, που ακολουθείται. Συνολικά, υπήρξαν τρεις διαφορετικές συγκεντρώσεις σε Au στα υμένια, οι οποίες πιστοποιήθηκαν μέσω της τεχνικής EDS. Πέραν, του επηρεασμού που δέχτηκαν τα ημιαγώγιμα οξείδια του χαλκού στο ενεργειακό διάκενο (υπολογισμός μέσω φασματοσκοπίας απορρόφησης ορατού / υπεριώδους UV / VIS), εξαιτίας της δημιουργίας διαφορετικών παχών υμενίου (φαινόμενα κβαντικού περιορισμού) και της παρουσίας του ευγενούς μετάλλου (Au), το σημαντικότερο σημείο είναι αυτό που αφορά την μελέτη και παρατήρηση εντοπισμένων επιφανειακών πλασμονικών συντονισμών (υπολογισμός μέσω τεχνικής UV / VIS), των λεγόμενων Localized Surface Plasmon Resonances – LSPR, τα οποία σχετίζονται με την απόκριση των ηλεκτρονίων αγωγιμότητας των μεταλλικών νανοσωματίδίων (< 100 nm) με μέγεθος μικρότερο από το μήκος κύματος της προσπίπτουσας ακτινοβολίας. Επιπρόσθετα, παρουσιάζονται κάποια διαγράμματα που αφορούν επιφανειακούς πλασμονικούς συντονισμούς σε μεταλλικά υμένια Au – Cu. Οι συντονισμοί LSPR μελετήθηκαν για διάφορους ρυθμούς ανόπτησης και για διάφορες συγκεντρώσεις. / In this thesis, an attempt was made to create new plasmonic structures, through the technique of sputtering. Going through the literature we could not find way similar experimental procedure followed to achieve plasmonic structures. The systems that have been studied are films CuO / Au and Cu2O / Au, wherein the dielectric matrix is semiconductor oxide and the plasmon metal is a noble metal of Au. Overall, there were three different concentrations of Au in the films, which were identified through EDS. In addition, the influence of thin film thickness on the energy gap due to quantum confinement was studied. The most important point is the observation of localized surface plasmon resonances (calculation through UV / VIS), the so-called LSPR, which are related to the response of the free electrons of metal nanoparticles (<100 nm) to the electric field of light. Resonances LSPR studied for various annealing rates and different concentrations of gold. We have to say that, after the appropriate annealing, we observed the creation of solid solutions (XRD).

During the last decades, the localized failure of massive structures under thermo-mechanical loads becomes the main interest in civil engineering due to a number of construction damaged and collapsed due to fire accident. Two central questions were carried out concerning the theoretical aspect and the solution aspect of the problem. In the theoretical aspect, the central problem is to introduce a thermo-mechanical model capable of modeling the interaction between these two physical effects, especially in localized failure. Particularly, we have to find the answer to the question: how mechanical loading affect the temperature of the material and inversely, how thermal loading result in the mechanical response of the structure. This question becomes more difficult when considering the localized failure zone, where the classical continuum mechanics theory can not be applied due to the discontinuity in the displacement field and, as will be proved in this thesis, in the heat flow. In terms of solution aspect, as this multi-physical problem is mathematical represented by a differential system, it can not be solved by an 'exact' analytical solution and therefore, numerical approximation solution should be carried out. This thesis contributes in both two aspects. Particularly, thermomechanical models for both steel and concrete (the two most important materials in civil engineering), which capable of controling the hardening behavior due to plasticity and/or damage and also the softening behavior due to the localized failure, are carried out and discussed. Then, the thermomechanical problems are solved by 'adiabatic' operator split procedure, which 'separates' the multi-physical process into the 'mechanical' part and the 'thermal' part. Each part is solved individually by another operator split procedure in the frame-work of embbed-discontinuity finite element method. In which, the 'local' discontinuities of the displacement field and the heat flow is solved in the element level, for each element where localized failure is detected. Then, these discontinuities are brought into the 'static condensation' form of the overall equilibrium equation, which is used to solved the displacement field and the temperature field of the structure at the global level. The thesis also contributes to determine the ultimate response of a reinforced concrete frame submitted to fire loading. In which, we take into account not only the degradation of material properties due to temperature but also the thermal effect in identifying the total response of the structure. Moreover, in the proposed method, the shear failure is also considered along with the bending failure in forming the overal failure of the reinforced structure. The thesis can also be extended and completed to solve the behavior of reinforced concrete in 2D or 3D case considering the behavior bond interface or to take into account other type of failures in material such as fatigue or buckling. The proposed models can also be improved to determine the dynamic response of the structure when subjected to earthquake and/or impact.

No description available.

Data aggregation is an important technique in wireless sensor networks. The data are gathered together by data fusion routines along the routing path, which is called data-centralized routing. We propose a localized, Delay-bounded and Energy-efficient Data Aggregation framework(DEDA) based on the novel concept of DEsired Progress (DEP). This framework works under request-driven networks with realistic MAC layer protocols. It is based on localized minimal spanning tree (LMST) which is an energy-efficient structure. Besides the energy consideration, delay reliability is also considered by means of the DEP. A node’s DEP reflects its desired progress in LMST which should be largely satisfied. Hence, the LMST edges might be replaced by unit disk graph (UDG) edges which can progress further in LMST. The DEP metric is rooted on realistic degree-based delay model so that DEDA increases the delay reliability to a large extent compared to other hop-based algorithms. We also combine our DEDA framework with area coverage and localized connected dominating set algorithms to achieve two more resilient DEDA implementations: A-DEDA and AC-DEDA. The simulation results confirm that our original DEDA and its two enhanced variants save more energy and attain a higher delay reliability ratio than existing protocols.

The current approach to African development is driven by Euro-Western material/physical approaches that fail to acknowledge the integral link between culture and development. For African development to truly speak to the realities and needs of African peoples, a reconceptualization of development is necessary, one which examines how Indigenous African knowledges can inform development. Using an anti-colonial, critical development and Indigenous discursive frameworks, this thesis examines how Akan, Gonja and Bogon proverbs, as Indigenous African knowledges, provide theoretical and practical knowledges for reconceptualising localized approaches to African development. Through interviews with local development practitioners and local Chiefs and the analysis of collected proverbs, the thesis reveals that proverbs, as linguistic, cultural and spiritual knowledges are deeply embedded in Ghanaian life and may function as excellent culturally relevant tools for a localized approach to African development.

The current approach to African development is driven by Euro-Western material/physical approaches that fail to acknowledge the integral link between culture and development. For African development to truly speak to the realities and needs of African peoples, a reconceptualization of development is necessary, one which examines how Indigenous African knowledges can inform development. Using an anti-colonial, critical development and Indigenous discursive frameworks, this thesis examines how Akan, Gonja and Bogon proverbs, as Indigenous African knowledges, provide theoretical and practical knowledges for reconceptualising localized approaches to African development. Through interviews with local development practitioners and local Chiefs and the analysis of collected proverbs, the thesis reveals that proverbs, as linguistic, cultural and spiritual knowledges are deeply embedded in Ghanaian life and may function as excellent culturally relevant tools for a localized approach to African development.

This research investigates an extension of the glancing angle deposition (GLAD) technique and a biosensing application of films produced by GLAD. The extension to GLAD, called phi-sweep (PS), improves column isolation compared to films grown by traditional GLAD (TG) as well as modifies the column tilt angle, , of the slanted columns according to tan(_{PS}) = tan(_{TG}) cos(), where is the sweep angle. The biosensing application makes use of localized surface plasmon resonance in noble metal GLAD films functionalized with rabbit immunoglobulin G (rIgG) to detect binding of anti-rabbit immunoglobulin G (anti-rIgG) to the films' surface. The extinction peak red-shifts a distance dependent on the concentration of anti-rIgG solution in a manner described by the Langmuir isotherm with a saturation value, _{max}, of 29.4 0.7 nm and a surface confined thermodynamic binding constant, K, of (2.7 0.3)10 M. / Microsystems and Nanodevices

Two types of core/shell nanoparticles (CS-NPs) generation based on laser ablation are developed in this study, namely, double pulse laser ablation and laser ablation in colloidal solutions. In addition to the study of the generation mechanism of CS-NPs in each scheme, the optical properties of designed CS-NPs are determined with UV-VIS-NIR spectroscopy and EM field simulation. In the first scheme, which is double pulse laser ablation, two laser beams are fired in a sequence on two adjacent targets with different material. We have successfully demonstrated the generation of Sn/Glass, Zn/Glass, Zn/Si, Ge/Si, and Cu/Zn CS-NPs. Key factors affecting the generation of CS-NPs are (1) surface tensions of the constructing materials affecting the associated Gibbs free energy of CS-NPs, (2) physical properties of selected background gases (i.e., He and Ar), (3) delay time between two laser pulses, and (4) the amount of laser energy. The second scheme examined for the generation of CS-NPs is through laser ablation of solid targets in colloidal solutions. Compared to the double pulse laser ablation, this second approach provides better control of the size and shape of the resulting CS-NPs. Two colloidal solutions, namely, Au and SiO2 colloidal solution are applied in the second scheme. Key factors affecting the formation of CS-NPs with the second scheme and are (a) the adhesion energy between the shell and the core material, (b) the diameter of the core and (c) the laser ablation time and the laser energy. Red shift of absorption peaks are measured in both SiO2/Au and SiO2/Ag colloids compared with pure nanoparticles (NPs). The amount of red-shift is very sensitive to the shell thickness of the CS-NPs. The same red shift is reproduced with the corresponding full wave analysis. The observed red shift can be attributed to the additional surface plasmon resonance at the interface of metal/dielectric of the CS-NPs compared with pure nanoparticles. Through adjusting the material and size combination, the absorption peak of the CS-NPs can be tuned in a limit range around the intrinsic absorption peak of the metal of the CS-NPs. The freedom of adjusting the absorption peak makes CS-NPs is favorable in bio and optical applications.