Η παρούσα διπλωματική εργασία προσπαθεί μέσω της υπάρχουσας βιβλιογραφίας να αναδείξει τους παράγοντες οι οποίοι διαμορφώνουν τις τιμές στο λιανικό εμπόριο στον κλάδο τροφίμων και ποτών. Περιλαμβάνει έρευνα στην οποία μέσω σύγκρισης τιμών συγκεκριμένων προϊόντων (εγχώριων και εισαγόμενων) απορρέουν χρήσιμα συμπεράσματα για το τι τελικά επηρεάζει περισσότερο τις τιμές. / This thesis attempts by existing literature to highlight the factors that shape the retail prices in the food and beverage industry. Also, it includes research in which via a comparison of prices of concrete products (domestic and imported) derive useful conclusions for what finally influences more the prices.

Στην παρούσα εργασία εξετάζεται η αύξηση της ανάλυσης (super resolution) σε θερμικές εικόνες χρησιμοποιώντας τεχνικές συμπιεσμένης καταγραφής (compressed sensing). Οι εικόνες εκφράζονται με αραιό τρόπο ως προς δυο υπερπλήρη λεξικά (ένα χαμηλής και ένα υψηλής ανάλυσης) και επιχειρούμε κατασκευή της εικόνας υψηλής ανάλυσης. Τα αποτελέσματα της μεθόδου αυτής συγκρίνονται με τα αποτελέσματα τεχνικών που χρησιμοποιούν image registration με ακρίβεια subpixel για την επίτευξη του super resolution. / This thesis deals with the problem of resolution enhancement (super resolution) of thermal images using com- pressed sensing methods. We solve the super resolution problem in four stages. First, we seek a sparse representation of a low-resolution image with respect to two statistically-learned overcomplete dictionaries (for high and low resolution images respectively) and then we use the coefficients of this representa- tion to calculate the high resolution image. Then, we calculate the high resolution image using methods requiring multiple low resolution images aligned with subpixel accuracy (conventional approach). We compare the results of each method using broadly acclaimed metrics regarding reconstruction quality standards.

No description available.

Medical imaging is the main tool to extract a 3D modelling of the human body or specific organs within it. In order to accomplish this, various imaging modalities have been developed over the years, such as X-Ray Computed Tomography (CT), Magnetic Resonance Imaging (MRI) and Positron Emission Tomography (PET). Each one is based on a particular energy source that passes through the body and on specific physical laws, which define the meaning of noise and the sensitivity of the imaging process. In all medical imaging systems the main goal is to increase resolution since higher resolution is a key factor in increased information content, which is critical for increased accuracy in the understanding of the anatomy and in the assessment of size and morphological structure of organs, for early detection of abnormalities, suspected pathologies and more. In order to overcome the resolution limitations, one promising idea is to use signal processing techniques to enhance the spatial resolution. This approach proposes the acquisition of a high-resolution (HR) image from observed multiple low-resolution (LR) images. This image restoration approach is called super resolution (SR) image reconstruction (or restoration). It is the process of combining multiple low resolution images to form a high resolution image. The basic requirement in order to apply SR restoration techniques is the availability of multiple LR images captured from the same scene, which are sub-sampled (aliased) as well as shifted with subpixel precision. Each observed LR image is expressed as the result of a sequence of operators on the original HR image source, consisting of a geometrical warp, blurring and down-sampling. The SR image reconstruction method consists of three stages, registration, interpolation and restoration (i.e., inverse procedure). In the registration stage, the relative shifts between LR images, with reference to a certain LR image, are estimated with fractional pixel accuracy. Accurate sub-pixel motion estimation is a very important factor in the success of the SR image reconstruction algorithm. Since the shifts between LR images are arbitrary, the registered HR image will not always match up to a uniformly spaced HR grid. Thus, non-uniform interpolation is necessary, to obtain a uniformly spaced HR image from a non-uniformly spaced composite of LR images. Finally, image restoration is applied to the up-sampled image to remove blurring and noise. In order to evaluate the performance of SR reconstruction, a ‘simulate and correct’ approach to reconstruction is selected. First, simulated images of a computer generated phantom are formed and processed in order to comply with the observation model for the LR images. These are used as the images from which the HR image is constructed through the SR method. The iterative back-projection (IBP) algorithm suggested by Irani and Peleg has been chosen to be utilized, which belongs in the spatial domain methods and it is an easily and intuitively understood method. The results of the SR reconstruction are presented separately for the axial and the transaxial case. The evaluation relies on qualitative measures of image enhancement and on objective quantitative measures, such as the resolution (FWHM), the signal-to-noise ratio, the contrast ratio and the contrast-to-noise ratio. The performed trials demonstrated improvement in both the axial and transaxial resolution. The super-resolution images also provide a significantly improved contrast ratio, which is important for improving sensitivity for detection of small details and features. The improvement in resolution can be achieved without using any hardware changes or any increase in the patient radiation procedure. An important contribution of super-resolution is also the reduction of partial volume effects in the reconstructed image. The loss in SNR, which is a typical characteristic of all resolution enhancement algorithms, was not that considerable to preclude the clinical application of super-resolution. The overall evaluation demonstrated that the SR reconstruction is a post-processing method, which can provide medical images of higher resolution and better contrast ratio, without increasing the amount of radiation or the duration of the scan. / Η ιατρική απεικόνιση είναι το κύριο εργαλείο για την τρισδιάστατη μοντελοποίηση του ανθρώπινου σώματος και συγκεκριμένων οργάνων. Για να επιτευχθεί αυτό, διάφορες μέθοδοι απεικόνισης έχουν αναπτυχθεί, όπως η Υπολογιστική Τομογραφία, η Μαγνητική Τομογραφία και η Τομογραφία Εκπομπής Ποζιτρονίου. Η κάθε μία βασίζεται σε μια συγκεκριμένη πηγή ενέργειας η οποία διαπερνά το ανθρώπινο σώμα και έχει συγκεκριμένες φυσικές ιδιότητες. Σε όλα τα συστήματα ιατρικής απεικόνισης, ο βασικός στόχος είναι η βελτίωση της διακριτικής ικανότητας και κατα συνέπεια της παρεχόμενης πληροφορίας, η οποία είναι σημαντική για την ακρίβεια στην κατανόηση της ανατομίας και στην εκτίμηση του μεγέθους και της μορφολογίας των οργάνων, για την έγκαιρη διάγνωση ανωμαλιών κλπ. Μια από τις μεθόδους που έχουν προταθεί για τη βελτίωση της διακριτικής ικανότητας είναι η χρήση τεχνικών επεξεργασίας εικόνας. Σύμφωνα με αυτή τη μέθοδο, η οποία λέγεται Super Resolution, μια εικόνα υψηλής διακριτικής ικανότητας προκύπτει από πολλαπλές εικόνες χαμηλής διακριτικής ικανότητας. Η βασική προϋπόθεση για την εφαρμογή της μεθόδου είναι η ύπαρξη πολλαπλών εικόνων χαμηλής διακριτικής ικανότητας από την ίδια σκηνή, οι οποίες είναι μετατοπισμένες με ακρίβεια ενός κλάσματος píxel. Κάθε εικόνα χαμηλής διακριτικής ικανότητας εκφράζεται σαν το αποτέλεσμα ενός γεωμετρικού μετασχηματισμού, παραμόρφωσης και υπο-δειγματοληψίας της εικόνας υψηλής διακριτικής ικανότητας. Η ανακατασκευή μιας εικόνας με τη μέθοδο Super Resolution περιλαμβάνει τρία στάδια. Στο πρώτο στάδιο, υπολογίζονται οι σχετικές μετατοπίσεις μεταξύ των εικόνων. Η ακριβής εκτίμηση αυτής της σχετικής κίνησης είναι κρίσιμος παράγοντας για την απόδοση του αλγορίθμου ανακατασκευής. Για την εκτίμηση της απόδοσης της ανακατασκευής χρησιμοποιείται ένας αλγόριθμος ‘προσομοίωσης και διόρθωσης’. Αρχικά παράγονται οι εικόνες που θα χρησιμοποιηθούν σαν βάση για την ανακατασκευή της εικόνας υψηλής διακριτικής ικανότητας. Ο αλγόριθμος που χρησιμοποιείται είναι ο IBP (iterative back-projection), όπως προτάθηκε από τους Irani, Peleg. Η εκτίμηση της απόδοσης της μεθόδου βασίζεται σε ποιοτικά και ποσοτικά κριτήρια, όπως η διακριτική ικανότητα (FWHM), το SNR και η διακριτική ικανότητα αντίθεσης. Οι δοκιμές έδειξαν βελτίωση στην διακριτική ικανότητα και στην διακριτική ικανότητα αντίθεσης, η οποία είναι σημαντική για τη βελτίωση της ικανότητας ανίχνευσης λεπτομερειών. Οι βελτιώσεις αυτές επιτυγχάνονται χωρίς αλλαγές στο επίπεδο του υλικού και χωρίς αύξηση του χρόνου έκθεσης του ασθενούς στην ακτινοβολία. Η απώλεια σε SNR, η οποία είναι τυπική συνέπεια όλων των αλγορίθμων ανακατασκευής, δεν είναι απαγορευτική για τη χρήση της μεθόδου. Η συνολική εκτίμηση της μεθόδου, δείχνει ότι είναι μια μέθοδος επεξεργασίας, μέσω της οποίας μπορούν να προκύψουν ιατρικές εικόνες υψηλής διακριτικής ικανότητας, χωρίς την αύξηση της ποσότητας της ακτινοβολίας και του χρόνου έκθεσης του ασθενούς.

The marine boundary layer (MBL) is the region where energy, momentum and masses are exchanged between the ocean surface and the free troposphere. The lack of observations with high vertical resolution over the ocean significantly restricts the understanding of the complex physical processes that occur inside the MBL. The relatively short vertical extent of the MBL (average about 1~2 km) and the frequent cloudiness at its top make probing the MBL extremely difficult from the space. Several features of the Global Positioning System (GPS) radio occultation (RO) technique suggest that it has a great potential for sensing the MBL. These features include global coverage, high vertical resolution, and the ability of GPS signals to penetrate clouds.Over moist marine areas, a large negative moisture gradient often exists across the thermal inversion capping the MBL, which can cause super-refraction (SR) or ducting. A large number of high-resolution soundings have shown that SR occurs about 90% of the time in a year over the subtropical and tropical oceans and even 50% at high-latitudes during the summer. In the presence of SR, the reconstruction of refractivity from RO data becomes an ill-posed inverse problem, i.e., a given RO bending angle profile is consistent with a continuum (an infinite number) of refractivity profiles. The standard Abel retrieval gives the minimum refractivity solution of the continuum and thus produces the largest negative bias, consistent with a negative bias that is often present in the retrieved refractivity profiles in the moist lower troposphere. Simulation studies indicate a large variation of the negative refractivity biases (could be over -15%). The impact of diffraction effects and the open-loop receiver tracking on the bending angle and refractivity retrievals are assessed. A novel approach is developed and tested to reconstruct the vertical refractivity structure within and below the SR layer, which yields a much-improved retrieval, especially below the SR layer (less than 0.5% error). Such a reconstruction method should greatly enhance our ability to measure the MBL globally using the GPS RO technique as well as to improve the MBL parameterizations used in weather and climate models.

No description available.

By conducting a text analysis this study analyzes possible similarities in the portrayal of story characters between historical Norse myths and contemporary film productions. The chosen historical texts are two stories from Norse mythology which render a myth about Thor and a giant named Hrunge as well as the myth Trymskvädet. The selected movies are two of the comic company Marvel’s productions about super heroes – Thor and The Avengers. Different categories that this study compares are how the characters are defined by their possessions or artefacts, the actions and the choices which the characters make, and also how their relations, roles and origins are being portrayed. As the result of study shows, there are some similarities between the historical texts and the movies with regard to how the stories portray the characters.      According to cognitive theories, a story becomes more memorable if there is a balance between what readers intuitively expect and does not expect from the story while it unfolds in texts or multimedia productions. The reason for these similarities between textual and visual material created in different times may not only be that historical texts serve as the inspirational base for contemporary productions, but also relates to how myths have some unforgettable characters by striking a balance between intuitiveness and counter-intuitiveness features, and that the movies use character portrayals with a similar balance between the features.

Nucleation is a stochastic process, most accurately represented by a probability distribution. Obtaining sufficient data to define this probability distribution is a laborious process. Here, we describe a novel instrument capable of the automated determination of hydrate nucleation probability under non-equilibrium conditions for a range of natural gas mixtures at pressures up to 10MPa. The instrument is based on the automated lag time apparatus (ALTA) which was developed to study the stochastic nature of nucleation in ambient pressure systems [1].We demonstrate that the probability distribution represents a robust and reproducible tool for the quantitative evaluation of hydrate formation risk under pseudo-realistic pressure conditions.

Diplominiame darbe nagrinėjamas specialusis atraminių elementų erdvės atvejis, kai atraminis elementas yra II – os eilės viršvektorius ( p = 2 ). Pirmieji du darbo paragrafai yra referatyvinio pobūdžio. Pirmajame paragrafe gautos diferencijuojamos daugdaros struktūrinės lygtys, pateikiamos kai kurių diferencialinių geometrinių objektų ( skaliarinės funkcijos, tenzorinio lauko, viršvektorinio lauko ir afiniosios sieties objekto ) diferencialinės lygtis. Antrajame paragrafe afiniųjų ir tenzorinių siečių pagalba apibrėžta tenzoriaus invariantinio diferencijavimo operacija ir surastos tenzoriaus kovariantinės išvestinės. Surastos sąlygos kada tenzoriaus kovariantinės išvestinės, apibrėžto afiniosios sieties pagalba sutampa su šio tenzoriaus kovariantinėmis išvestinėmis, apibrėžtomis tenzorinės sieties pagalba. Trečiajame paragrafe apibrėžiama antros eilės atraminių viršvektorių erdvė, surastos šios erdvės struktūrinės lygtys ir ištirta liečiamosios ir koliečiamosios erdvių struktūra. Ketvirtajame paragrafe nagrinėjamos koliečiamosios erdvės normalizacijos. Tiesinės sieties pagalba kolie���iamojoje erdvėje išskiriami du invariantiniai poerdviai. Iš tiesinės sieties komponenčių ir jų pirmojo tęsinio sukonstruotos šios erdvės nepilna afinioji ir nepilna tenzorinė sietys, surasti šių siečių tarpusavio ryšiai, surastos pakankamos sąlygos, kad nepilnoji afinioji sietis sutaptų su nepilnosios tenzorinės sieties indukuota afiniąja sietimi. Čia tai pat surastos erdvės su nepilnąja... [toliau žr. visą tekstą] / In work it is examined special case of spaces support elements, when support elements are the super – vectors of the second order ( p = 2 ). The space of the second order support super – vectors is certain, the structural equations of this space are found and the structure tangential and cotangential spaces is researched. Further it is examined to space tangential spaces normalization. By means of linear connectivity in tangential space are detach two invariant subspaces. By means of components of linear connectivity and their first continuation are designed incomplete affine and incomplete tensors connectivity of this space, also connection between them is found. Further by means of linear connectivity natural normalization of space is examined, it is proved that the object of linear connectivity and its first continuation induces incomplete super – vector connectivity of this space. The structural equations of space with incomplete super – vector and complete super – vector connectivity are found. As operation of invariant differentiation of a super - vector field is certain, analogues of Richi and Bianca identities are received.

Multi Frequency Phase Measuring Profilometry is the most popular lateral contact 3-D Scanning technique. The Phase Measuring Profilometry is limited in resolution by the projector and cameras used. Conventional signal projectors have a maximum of 2000 to 4000 scan lines limiting the projector resolution. To obtain greater detail with higher resolution the PMP technique is applied to a Spatial Light Modulator (SLM) having 12000 lines, very large as compared to conventional projectors. This technology can achieve super resolution scans having varied applications. Scans achieved from PMP suffer from a certain type of artifact called “banding” which are periodic bands across the captured target. This leads to incorrect measurement of surfaces. Banding is the most limiting noise source in PMP because it increases with lower frequency and decrease in number of patterns. The requirement for lager number of patterns increases the possibility of motion banding. The requirement for higher frequency leads to the necessity for multifrequency PMP which, again leads to more patterns and longer scan times. We aim to reduce the banding by correcting the phase of the captured data.