1,963 research outputs found
Βελτιστοποίηση αντλήσεων παράκτιων υδροφορέων με χρήση του μοντέλου SWI
47 σ.Στόχος της διπλωματικής είναι να μελετήσει το φαινόμενο της υφαλμύρωσης, δηλαδή της εισαγωγής θαλασσινού νερού σε υπόγειους υδροφορείς, μέσω του προγράμματος SWI (Sea Water Intrusion). Για το πρόγραμμα αυτό θα αναλυθούν οι παραδοχές που κάνει καθώς και οι μαθηματικές εξισώσεις που επιλύονται κατά την εκτέλεση της προσομοίωσης. Επειδή το πρόγραμμα αυτό βρίσκεται ακόμα σε στάδιο ανάπτυξης και η λειτουργία του είναι αρκετά περίπλοκη έγινε μία προσπάθεια δημιουργίας προϋποθέσεων διευκόλυνσης της λειτουργίας του προγράμματος. Σε δεύτερο στάδιο επιχειρήθηκε η εκτέλεση βελτιστοποίησης άντλησης νερού από τον υδροφορέα, που είναι και ο απώτερος σκοπός της εργασίας.
Το πρώτο στάδιο της εργασίας, σχετίζεται με τη λειτουργία του προγράμματος SWI. Γίνεται μία συνοπτική περιγραφή του μοντέλου SWI που θα χρησιμοποιηθεί για την προσομοίωση του υδροφορέα. Αναλύονται ο τρόπος προσέγγισης του προβλήματος καθώς και οι παραδοχές που έχουν γίνει. Παρουσιάζονται συνοπτικά οι μαθηματικές εξισώσεις της μεθόδου καθώς και η διαδικασία επίλυσής του. Σημειώνεται ότι το πρόγραμμα αυτό, έχει έναν μεγάλο βαθμό δυσκολίας τόσο στην εκμάθησή του όσο και στην εκτέλεσή του, καθώς δεν έχει αναπτυχτεί σε γραφικό περιβάλλον στο οποίο να μπορεί ο χρήστης να εισάγει τα δεδομένα του εκάστοτε προβλήματος. Όλες οι μεταβλητές, για να τις αναγνωρίσει το SWI, θα πρέπει να βρίσκονται σε κατάλληλα διαμορφωμένα αρχεία, στον ίδιο φάκελο με το πρόγραμμα, την ώρα που αυτό θα εκτελεστεί. Η διαμόρφωση των αρχείων είναι πολύ αυστηρή, καθώς μικρές παρεκκλίσεις κάνουν το πρόγραμμα μη εκτελέσιμο χωρίς να υπάρχει κάποια ένδειξη, που να οδηγεί τον χρήστη να βρει το λάθος. Για διευκόλυνση της χρήσης του προγράμματος, στα πλαίσια της εργασίας, δημιουργήθηκαν σε περιβάλλον MATLAB, υποπρογράμματα, τα οποία δέχονται από τον χρήστη τα δεδομένα του προβλήματος και στη συνέχεια συνθέτουν αυτόματα, τα αρχεία με την κατάλληλη διάρθρωση, ώστε να μπορεί να τα αναγνωρίσει το SWI.
Το δεύτερο στάδιο της εργασίας, σχετίζεται με την βελτιστοποίηση της άντλησης. Απώτερος σκοπός, είναι να βρεθεί η μεγαλύτερη τιμή παροχής άντλησης που μπορεί να εξασφαλιστεί από τον υδροφορέα, χωρίς όμως τον κίνδυνο υφαλμύρωσής του. Η διαδικασία αυτή είναι επαναληπτική, εκτελείται επίσης σε περιβάλλον MATLAB και πραγματοποιήθηκε με τον αλγόριθμο PATTERN SEARCH. Σημειώνεται ότι είναι η πρώτη φορά που εφαρμόζεται βελτιστοποίηση παράκτιου υδροφορέα σε συνδυασμό με το πρόγραμμα SWI.The objective of the research is to study problems of seawater intrusion in coastal aquifers, using the program SWI (Sea Water Intrusion). The ultimate goal of the research is to perform an optimization of the drawing of water from the aquifer. The mathematical equations are presented and the pertinent assumptions are discussed. It is noted that the program is still under development, which presents several difficulties in its utilization.
The first stage of the project is related to the problem of coastal aquifer simulation based on SWI. This is very difficult, because of its lack of graphical interface. All variables, in order to be identified by the program, must be placed in properly defined files, in the same folder with the program. The structure of these files is very strict and the slightest deviation causes the program not to run and without any indication about what is wrong. In order to make the use of SWI easier, several sub-programs are created in MATLAB, based on user input and automatically creating the necessary files needed.
The second stage of the thesis is related to optimization of water extraction from coastal aquifers. The objective is to find the maximum pumping rate, i.e. the water the aquifer may provide, while protecting the aquifer from seawater intrusion. This is an optimization procedure and is also executed in MATLAB. The optimization method is based on the Pattern Search algorithm. Notice that it is the first time that optimization is combined with the SWI simulation program.Μακρής Αλέξιο
Use of Equivalent Hermitian Hamiltonian for -Symmetric Sinusoidal Optical Lattices
We show how the band structure and beam dynamics of non-Hermitian
-symmetric sinusoidal optical lattices can be approached from the point of
view of the equivalent Hermitian problem, obtained by an analytic continuation
in the transverse spatial variable . In this latter problem the eigenvalue
equation reduces to the Mathieu equation, whose eigenfunctions and properties
have been well studied. That being the case, the beam propagation, which
parallels the time-development of the wave-function in quantum mechanics, can
be calculated using the equivalent of the method of stationary states. We also
discuss a model potential that interpolates between a sinusoidal and periodic
square well potential, showing that some of the striking properties of the
sinusoidal potential, in particular birefringence, become much less prominent
as one goes away from the sinusoidal case.Comment: 11 pages, 8 figure
Twisted polarization domains and their dynamics
We provide a theoretical investigation of optical Poincar\'e beams that
exhibit interwinding chiral polarized domains upon propagation. We employ both
analytical and numerical methods in order to investigate this phenomenon.
Specifically, we introduce the theoretical framework that elucidates the
formation and spiraling behavior of chiral polarized domains of light.
Additionally, we define dynamic quantities that help us understand and quantify
the angular motion of these domains. We apply this method to cylindrically
symmetric optical beams, thereby unveiling their distinct radial and
longitudinal propagation dynamics
-Symmetric Periodic Optical Potentials
In quantum theory, any Hamiltonian describing a physical system is mathematically represented by a self-adjoint linear operator to ensure the reality of the associated observables. In an attempt to extend quantum mechanics into the complex domain, it was realized few years ago that certain non-Hermitian parity-time () symmetric Hamiltonians can exhibit an entirely real spectrum. Much of the reported progress has been remained theoretical, and therefore hasn't led to a viable experimental proposal for which non Hermitian quantum effects could be observed in laboratory experiments. Quite recently however, it was suggested that the concept of -symmetry could be physically realized within the framework of classical optics. This proposal has, in turn, stimulated extensive investigations and research studies related to -symmetric Optics and paved the way for the first experimental observation of -symmetry breaking in any physical system. In this paper, we present recent results regarding -symmetric Optic
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Binocular vision enhances a rapidly evolving affordance priming effect: Behavioural and TMS evidence
Extensive research has suggested that simply viewing an object can automatically prime compatible actions for object manipulation, known as affordances. Here we explored the generation of covert motor plans afforded by real objects with precision (‘pinchable’) or whole-hand/power (‘graspable’) grip significance under different types of vision. In Experiment 1, participants viewed real object primes either monocularly or binocularly and responded to orthogonal auditory stimuli by making precision or power grips. Pinchable primes facilitated congruent precision grip responses relative to incongruent power grips, and vice versa for graspable primes, but only in the binocular vision condition. To examine the temporal evolution of the binocular affordance effect, participants in Experiment 2 always viewed the objects binocularly but made no responses, instead receiving a transcranial magnetic stimulation pulse over their primary motor cortex at three different times (150, 300, 450 ms) after prime onset. Motor evoked potentials (MEPs) recorded from a pinching muscle were selectively increased when subjects were primed with a pinchable object, whereas MEPs from a muscle associated with power grips were increased when viewing graspable stimuli. This interaction was obtained both 300 and 450 ms (but not 150 ms) after the visual onset of the prime, characterising for the first time the rapid development of binocular grip-specific affordances predicted by functional accounts of the affordance effect
Intermixed Time-Dependent Self-Focusing and Defocusing Nonlinearities in Polymer Solutions
[Image: see text] Low-power visible light can lead to spectacular nonlinear effects in soft-matter systems. The propagation of visible light through transparent solutions of certain polymers can experience either self-focusing or defocusing nonlinearity, depending on the solvent. We show how the self-focusing and defocusing responses can be captured by a nonlinear propagation model using local spatial and time-integrating responses. We realize a remarkable pattern formation in ternary solutions and model it assuming a linear combination of the self-focusing and defocusing nonlinearities in the constituent solvents. This versatile response of solutions to light irradiation may introduce a new approach for self-written waveguides and patterns
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