Laser Induced Breakdown Spectroscopy (LIBS) which is used to determine the elemental content of various samples, inspects the emission spectroscopy of samples of interest for searching certain elements or identifying the unknown content. In this study, spectroscopic analyses of various kinds of metals, namely, Cu, Fe, Mo, Ti, W, some compounds such as CuBe, ZnSe, ZnS, GaSe, some semimetals like Si, Ge and even gases were investigated by means of a compact-commercial portable LIBS system and an independently constructed experimental set-up consisting of a single pulse system and various kinds of double pulse configurations using Nd:YAG lasers. The contributions of this thesis to the LIBS community can be classified into two main groups- which are experimental and code development. One of the experimental contributions was the investigation of the different crystal surfaces of silicon in which dangling bond density were taken into account for a more precise comparison of atomic emissions. The second experimental contribution was the polarization experiments by which polarization dependency, to some extent, was demonstrated. The third and final one was the orthogonal double pulse configuration with a 45 o incidence angle for both lasers in opposite directions by which it was shown that the positioning becomes straightforward yielding the desired reproducible results. The second major contribution was to develop a basic code for analyzing the experimental data more accurately. In conclusion, by means of the different experimental approaches, factors relating to the enhancement in intensity were investigated and as a result of developing the code, flexibility in upgrading the constraints of element searching was obtained and the updating of the database was accomplished.

In this study, suspensions of metallic nanoparticles in base fluids, nanofluids, are investigated by using terahertz time domain spectroscopy (THz-TDS). Nanofluids are used as the working fluid in a variety of applications especially for the purpose of heat transfer enhancement. Polar fluids are being used as the base in nanofluids for their tendency to stop aggregation and sedimentation. Polar fluids highly absorb THz signal. In order to select the best possible host, various polar liquids have been investigated, and isopropanol (99.5%) is selected to be the best candidate for its low THz absorptivity when compared to ethanol (99.5%), ethylene glycol (99%), methanol (95%) and distilled water. Ag, Pd and Cu nanoparticles have been custom-made in isopropanol by laser ablation method, and the size distributions have been characterized by Zeta Potential Analyzer. The nanoparticle diameters are measured to be on average 10 nm, 12 nm and 75 nm for Ag, Cu and Pd, respectively. Nanofluids of 1X, 2X and 3X concentrations of Ag, Cu and Pd nanoparticles have been prepared by diluting with pure (99.5%) isopropanol. Measurements have been repeated after 7 days up to 12 days in order to check for aggregations and sedimentations. THz-TDS is a strong tool to analyze the refractive index and absorption coefficient, but no distinct difference was observed in the frequency domain analysis for the nanofluid samples. On the other hand, in the time domain data analysis, a shift on the time data with a change in transmission was observed. For Ag nanoparticles a positive time shift with a decrease in transmission with increasing concentration was observed. For Cu nanoparticles an interesting negative time shift and an increase in the intensity was observed with increasing concentration. The Pd nanoparticle solution scans showed almost no shift initially, but a negative time shift after a wait period on the order of days. A model of the transmission of the THz pulse through the nanofluid was developed based on transmission/reflection coefficients due to both dielectric and conducting layered media. The model well explains the positive time shift seen with Ag nanoparticle suspensions but fails to explain the shift seen with the Cu nanoparticle suspensions due to the long path length inside the nanofluid. Negative time-shifts can only be explained by decreasing the path length which suggests additional layering inside the nanofluid medium, or assuming that the chemical composition of the isopropanol host has changed with the addition of Cu and/or Pd nanoparticles. The positive time shifts observed with the Ag nanoparticle suspensions allowed for estimating the change in refractive index of the base fluid. From this change, using effective medium theory based on Maxwell-Garnett model, the concentrations of the nanoparticles were estimated. The results agree within an order of magnitude to commercially available nanofluids which are also non-aggregate.

Σκοπός της παρούσας διπλωματικής είναι η μελέτη της πειρατείας στην μουσική βιομηχανία και η συμπεριφορά του «καταναλωτή» απέναντί της. Θα ξεκινήσει με την ανάλυση του Μάρκετινγκ και την ανάλυση του περιβάλλοντος της μουσικής βιομηχανίας σήμερα. Θα αναφέρει τους τρόπους και τις τεχνικές προώθησης και το πως εφαρμόζεται το Μάρκετινγκ στην συγκεκριμένη βιομηχανία. Θα παρουσιάσει την ιστορία της πειρατείας και την φιλοσοφία που κρύβεται πίσω από αυτή. Στο τέλος θα συνδέσει το ρόλο της πειρατείας στα παραπάνω, με έρευνες που έχουν γίνει στο παρελθόν. Επιπλέον, θα εξετάσει την συμπεριφορά του καταναλωτή γενικότερα και στην συνέχεια θα παρουσιάσει τα αποτελέσματα της έρευνας που έγινε, η οποία εξετάζει την συμπεριφορά του καταναλωτή απέναντι στην διαδικτυακή αγορά της μουσικής, νόμιμα ή παράνομα, στην πειρατεία της μουσικής βιομηχανίας και την συμμετοχή του σε αυτήν καθώς στους λόγους που το κάνει. Τέλος, θα παρατεθούν τα συμπεράσματα της έρευνας, προτάσεις πάνω στο θέμα της πειρατείας και θέματα προς συζήτηση. / The purpose of this paper is to study the piracy in music business today, and to examine the consumer behaviour towards music piracy.

The experimental setup which consisted of the Jarrell-Ash Ebert type scanning monochromator, the Hamamatsu Si PIN Photodiode, a PC connected ADC card and a Tungstenstriplamp operated at different temperatures was assembled. The different parts needing calibration were calibrated with spectral response calibration techniques suitable for our purposes and connected to the experimental setup in a proper way. Spectral response calibrations and transmission measurements in the range 450-800 nm were carried out.

The results of photoluminescence (PL) spectra of TlGaS2 single crystal were reported in the 500-1400 nm wavelength and in the 15-115 K temperature range. Three broad PL bands with an asymmetric Gaussian lineshapes were observed to be centered at 568 nm (A-band), 718 nm (B-band) and 1102 nm (C-band). The shift of the emission band peak energy as well as the change of the half-width of the emission band with temperature and excitation laser intensity were also studied. We analyzed the observed results using the configurational coordinate (CC) model. The powder diffraction patterns of TlInS2 and TlGaS2 crystals were obtained and the diffraction data were indexed using CRYSFIRE computer program packet. TlInS2 has hexagonal system with parameters a = 3.83 and c = 14.88 Ao. TlGaS2 has monoclinic system with parameters a = 9.62, b = 4.01 and c = 7.52 Ao with &amp / #946 / = 96.30o. Our diffraction studies at low temperatures did not reveal any phase transition for TlInS2 as reported in the literature. The specific heat capacities of both TlInS2 and TlGaS2 crystals calculated from Differential Scanning Calorimetry (DSC) measurements at low temperatures are reported in the thesis.

In this thesis a theoretical background of Nd:YAG lasers has been presented and key parameters of a design have been stated. Both pulsed mode and CW mode designs have been made / a 500mJ xenon flash lamp has been investigated as the pulsed light source and a 500W tungsten halogen lamp has been used as the continuous light source for optical pumping. Closed cooling system has been constructed. De-ionized water has been used as coolant. The goal has been acomplished by constructing a CW mode prototype. The output power has been calculated. Dependence of output power to the reflectivity of output coupler is simulated and optimum reflectivity is calculated. Theoretical emission bands of Nd:YAG have been observed experimentally.

New and rapid techniques for the characterization and identification of bacteria would have an important role in clinical microbiology and in food analysis because of an increasing prevalence of infectious diseases and In this work we carried out two approaches. In the first study the characterization and differentiation of mesophilic and thermophilic bacteria were investigated by using Fourier Transform Infrared (FTIR) Spectroscopic technique. In the second study, we investigated the characterization and identification of 3 Bacillus and Micrococcus species Our results from first approach show that there was a dramatic difference between mesophilic and thermophilic bacteria. The protein concentration was high, lipid concentration, the level of triglycerides and the unsaturated acyl chains decreased in thermophilic bacteria. We found that in thermophilic bacteria PO- 2 groups become hydrogen bounded. In addition, our results suggest that the cellular DNA content was low in thermophilic bacteria. Moreover there were characteristic peaks for both mesophilic and thermophilic bacteria and these peaks can be used for the differentiation of these two bacteria group. There were also some specific peaks that can be used for the differentiation of Escherichia coli and Lactobacillus plantarum at species level. In the second approach, our results show that there were significant spectral differences between Bacillus and Micrococcus species such as the proportion of unsaturated acyl chains in triglycerides were higher in Micrococcus species. Moreover we observed different bands that may be explained by an acetate oxidation via the tricarboxylic acid cycle and an exopolymer formation in Micrococcus species. In addition to that another band similar to glycogen, may be explained by a glycogen-like storage material in Micrococcus species. Also there are characteristic peaks that can be used for identification of Micrococcus spp.

In this work optical properties of two dimensional quantum well structures are studied. Variational calculation of the eigenstates in an isolated quantum well structure with and without the external electrical field is presented. At weak fields a quadratic Stark shift is found whose magnitude depends strongly on the finite well depth. It is observed that under external electrical field, the asymmetries due to lack of inversion symmetry leads to higher order nonlinear optical effects such as second order optical polarization and second order optical susceptibility.

Η παρούσα διπλωματική έχει σκοπό τον σχεδιασμό και κατασκευή ηλεκτρονικού καταλόγου και βάσης δεδομένων για την οργάνωση και διαχείριση αρχείου μουσικής ελληνικής παράδοσης και σχετικού περιεχομένου και την έκδοσή του στον παγκόσμιο ιστό. Μέσα από την διπλωματική αυτή προτείνεται ένας τρόπος για την αποθήκευση της μουσικής πληροφορίας στο διαδίκτυο, το σχετικό υλικό που θα πρέπει να συνοδεύει ένα τραγούδι, τον τρόπο παρουσίασης του υλικού αυτού στον χρήστη της εφαρμογής, τις λειτουργίες αναζήτησής της και τον τρόπο αναπαραγωγής της. Για τις ανάγκες της διπλωματικής έγινε και προτείνεται κατηγοριοποίηση των τραγουδιών με βάσης το είδος τους , δηλαδή το θέμα τους, και με βάση τον ρυθμό τους, δηλαδή της μουσικής τους. Επίσης προτείνεται και κατηγοριοποίηση για τα άρθρα. Οι δύο παραπάνω κατηγοριοποιήσεις αφορούν αποκλειστικά το ελληνικό δημοτικό τραγούδι. Επίσης προτείναμε δομή ιστοσελίδας του WWW για την διάδοση την μουσικής παράδοσης που θα είναι φιλική για τον μέσο χρήστη του internet και θα κρατάει το ενδιαφέρον του. Στα πλαίσια της διπλωματικής αυτής εργασίας δημιουργήθηκε ο πληρέστερος στο διαδίκτυο οδηγός παραδοσιακής μουσικής της Πελοποννήσου και της Στερεάς Ελλάδας. Ωστόσο με ένα επιπλέον σύστημα που δημιουργήθηκε είναι δυνατή η προσθήκη επιπλέον υλικού από χρήστες που θα καλύψει όλες τις περιοχές της χώρας μας. / The current work is about a e-catalogue for the greek traditional music. It is a user centered WWW aplication and belongs to the Arcadia Project at C.E.I.D.

Το αντικείμενο της παρούσας διπλωματικής εργασίας είναι η μελέτη της ψηφιακής τηλεόρασης μέσω πρωτόκολλου Internet, γνωστής και ως IPTV (Internet Protocol TeleVision) με ιδιαίτερη εστίαση στον αποκωδικοποιητή που χρησιμοποιείται για την επίτευξη της τηλεοπτικής μετάδοσης. Αυτός ο αποκωδικοποιητής ονομάζεται Set-Top Box. Στην ουσία το IPTV είναι η μετάδοση τηλεοπτικού σήματος μέσω ευρυζωνικής σύνδεσης που χρησιμοποιεί το πρωτόκολλο IP μέσω ενός ιδιωτικού κλειστού δικτύου και όχι του δημοσίου Internet. Το IPTV θεωρείται το παρόν και το μέλλον όσον αφορά τα είδη τηλεόρασης καθώς ο χρήστης έχει την δυνατότητα για πρόσβαση σε τηλεοπτικά κανάλια με ψηφιακή εικόνα ενώ η δυνατότητα που παρέχουν οι on-demand υπηρεσίες για παρακολούθηση τηλεοπτικού περιεχομένου παντός τύπου την ώρα που επιθυμεί ο χρήστης καθιστά το «πακέτο» πολύ πιο ελκυστικό. Συγκεκριμένα, σε αυτή την διπλωματική εργασία, παρουσιάζεται αρχικά ο ορισμός της δικτυακής τηλεόρασης και γενικά όλων αυτών που συνέβαλλαν στην δημιουργία του IPTV. Κατόπιν γίνεται μια συνοπτική ιστορική αναδρομή στα γεγονότα που οδήγησαν στην μορφή του IPTV όπως την ξέρουμε σήμερα. Έπειτα συγκρίνεται το IPTV με το γνωστό μας Internet TV. Στην συνέχεια γίνεται μια γενική περιγραφή ενός δικτύου IPTV ενώ έπειτα εμβαθύνουμε περισσότερο καθώς περιγράφονται και τεχνικές λεπτομέρειες για ένα τέτοιο δίκτυο. Ακολούθως περιγράφονται οι κωδικοποιήσεις που πραγματοποιούνται αλλά και οι διάφορές τους. Επιπλέον γίνεται ιδιαίτερη αναφορά και ανάλυση στα διάφορα είδη των αποκωδικοποιητών (Set-Top Box) που χρησιμοποιούνται και επισημαίνονται οι διαφορές που έχουν στη δομή και στα χαρακτηριστικά τους. Τέλος γίνεται μια αναφορά στους παρόχους πακέτων IPTV στην Ελλάδα ενώ γίνεται και μια σύγκριση αυτών των πακέτων μεταξύ τους. / The theme of this particular thesis is the study of the digital television via Internet protocol, also known as IPTV (Internet Protocol TeleVision) with special focusing on the decoder which is used in order to achieve television broadcasting. This decoder is called Set-Top Box. Essentially, IPTV is the transmission of television signals over broadband which is using IP protocol through a closed private network and not the public Internet. IPTV is considered to be the present and the future regarding the types of television because the user has the ability to access TV channels with digital view, while the ability provided by on-demand services about watching every type of television content at every time the user wants makes the whole “package” much more attractive. Particularly, in this thesis, is firstly presented the definition of networking TV and generally of all these things which have contributed to the creation of IPTV. Following is a brief historical background to the events that led to the form of IPTV as we know it today. Afterwards, the IPTV is compared to the Internet TV, which is familiar to us. After that, a general description of an IPTV network is taking place and then we go further as technical details of such a network are described. Moreover, the encodings performed and their differences are mentioned. Additionally, there is much reporting and analysis in various types of decoders (Set-Top Box) used and marked the differences they have on their structure and their profile. Finally, there is a reference to IPTV packet providers in Greece and is happening a comparison among these packets.