Study of the Numerical Diffusion in Computational Calculations

The numerical simulation of fluid flow and heat/mass-transfer phenomena requires the numerical solution of the Navier-Stokes and energy-conservation equations coupled with the continuity equation. Numerical or false diffusion is the phenomenon of inserting errors in the calculations that compromise the accuracy of the computational solution. The Taylor series analysis that reveals the truncation/discretization errors of the differential equations terms should not be termed as false diffusion. Numerical diffusion appears in multi-dimensional flows when the differencing scheme fails to account for the true direction of the flow. Numerical errors associated with false diffusion are investigated via two- and three-dimensional problems. A numerical scheme must satisfy necessary criteria for the successful solution of the convection-diffusion formulations. The common practice of approximating the diffusion terms via the central-difference approximation is satisfactory. Attention is directed to the convection terms since these approximations induce false diffusion. The equations of all the conservation equations in this study are discretized by the finite volume method

Mathematical Modeling of Aerodynamic Heating and Pressure Distribution on a 5-Inch Hemispherical Concave Nose in Supersonic Flow

During the design of an aircraft, a significant parameter that is taken into consideration is aerodynamic heating. Aerodynamically induced heating affects both the structure of the aircraft and its vulnerability to heat-seeking missiles in modern warfare. As a result, the ability to calculate efficiently the heating produced as well as the pressure distribution in such flows is crucial. Therefore, in this present study, the PHOENICS CFD code as modified by DRA Farnborough in order to calculate heat transfer and pressure measurement on a 5-inch hemispherical concave nose at a Mach number of 2.0 is evaluated and customized in order to produce faster and more accurate results. Apart from numerical alterations, different turbulence models are being examined as well as different discretization schemes. Numerical solutions show improvement up to 6% in comparison with the original model, both in terms of convergence rate and in terms of agreement with the available experimental data. With the new modeling suggested in the present work, the significance of both the discretization scheme and the choice of the turbulence modeling is demonstrated for the flows under consideration. The use of a high-order discretization scheme is suggested for more acute areas of the body modeled in order to improve results further

Translation issues of environmental terms from english into greek: the case of the Aarhus convention

This thesis is intended to Greek environmental terminology, its relations to the respective English terminology and its use in legally binding texts, such as international conventions. The starting point of the theoretical part of the thesis is the subject field of terminology and, in particular, objects, concepts, designations and languages for specific purposes (LSP). Additionally, the state-of-the-art of Greek environmental terminology is discussed, along with parameters influencing it (need for the creation of relevant terms, for relevant education, for the compilation of relevant dictionaries etc.), whilespecial reference is made to the (ancient) Greek language and its contribution to the formation of terms. Finally, a first approach concerns the language characteristics of conventions (style, terminology, translation, etc.) and how environmental terminology is integrated in them. In the second part of the thesis, the study focuses on a particular convention, namely the Aarhus Convention, where some translation problems/ issues are presented that arise from the translation of environmental terminology, along with the impact of given translation choices in the perception and understanding of the text. The discussion initially focuses on general translation issues, while in a next step the English environmental terms appearing in the Convention are presented, mainly those that have dual or multiple translations in Greek target texts. Analysis of these terms is made by means of tables, where the degree of Greek terms’ conformity with the term formation principles is investigated, according to the specification of relevant ISO standards. At the same time, the translational efficiency of each term in the Greek text is assessed and, if the Greek translation is deemed unsuccessful, insufficient or unacceptable, an alternative one is proposed. Finally, reference is made to the omission of surface elements during translation and to source-text environmental terms that have been rendered in the same way in the Greek target text. The conclusions drawn from the processing of the research material highlight the need for more extensive involvement with environmental terminology and include registering and consolidating the environmental terms in use by creating, inter alia, a National Agency of Terminology, which will work uninterruptedly, as well as by gathering and improving translation tools.Η παρούσα διατριβή έχει ως αντικείμενο την ελληνική περιβαλλοντική ορολογία, τις σχέσεις της με την αντίστοιχη αγγλική, καθώς και τη χρήση της σε νομικώς δεσμευτικά κείμενα, όπως είναι οι διεθνείς συμβάσεις. Αφετηρία του θεωρητικού μέρους της διατριβής αποτελεί η ενασχόληση με το θεματικό πεδίο της Ορολογίας και συγκεκριμένα με τα αντικείμενα, τις έννοιες, τις κατασημάνσεις και τις γλώσσες για ειδικούς σκοπούς. Επιπρόσθετα, περιγράφεται η παρούσα κατάσταση της ελληνικής περιβαλλοντικής ορολογίας με τις παραμέτρους που την καθορίζουν (ανάγκη δημιουργίας όρων, σχηματισμός, καθιέρωση, χρήση, αποτύπωση σε λεξικά κ.λπ.), ενώ γίνεται ειδική μνεία στην (αρχαία) ελληνική γλώσσα και στον τρόπο συμβολής της στον σχηματισμό όρων. Τέλος, επιχειρείται μια πρώτη προσέγγιση των γλωσσικών χαρακτηριστικών των συμβάσεων (ύφος, ορολογία, μετάφραση κ.λπ.), καθώς και του τρόπου ενσωμάτωσης της περιβαλλοντικής ορολογίας σε διεθνείς συμβάσεις παρόμοιας θεματικής. Στο δεύτερο μέρος της διατριβής η μελέτη επικεντρώνεται σε μία συγκεκριμένη σύμβαση, τη Σύμβαση του Aarhus, όπου παρουσιάζονται διεξοδικά τα μεταφραστικά προβλήματα/ ζητήματα που προκύπτουν αναφορικά με τη μετάφραση της περιβαλλοντικής ορολογίας και τον αντίκτυπο των μεταφραστικών επιλογών στην αντίληψη και κατανόηση του κειμένου. Σε αυτά περιλαμβάνονται αρχικά γενικότερα μεταφραστικά ζητήματα, ενώ σε ένα επόμενο βήμα παρουσιάζονται αγγλικοί περιβαλλοντικοί όροι που εμφανίζονται στη Σύμβαση και έχουν διπλή ή πολλαπλή απόδοση στην Ελληνική. Η ανάλυση των όρων αυτών γίνεται με τη βοήθεια πινάκων, στους οποίους διερευνάται ο βαθμός συμφωνίας των ελληνικών όρων με τις αρχές σχηματισμού όρων, όπως αυτές έχουν καθοριστεί από το πρότυπο ISO 704:2009. Παράλληλα, αξιολογείται η μεταφραστική απόδοση του εκάστοτε όρου στο ελληνικό κείμενο και, σε περίπτωση που αυτή κρίνεται ανεπιτυχής, ανεπαρκής ή μη αποδεκτή για λόγους που αναφέρονται ρητά στην παρούσα διατριβή, προτείνεται μια εναλλακτική λύση. Τέλος, πραγματοποιείται αναφορά σε παραλείψεις λέξεων-οροστοιχείων κατά τη μετάφραση, ενώ εντοπίζονται περιβαλλοντικοί όροι με την ίδια απόδοση στην Ελληνική. Τα συμπεράσματα που προκύπτουν από την επεξεργασία του υλικού της έρευνας αναδεικνύουν την ανάγκη εκτενέστερης ενασχόλησης με την περιβαλλοντική ορολογία και περιλαμβάνουν την καταγραφή και παγίωση των εν χρήσει περιβαλλοντικών όρων, τη δημιουργία και αδιάλειπτη λειτουργία ενός Εθνικού Φορέα Ορολογίας, καθώς και τη συγκέντρωση και βελτίωση των μεταφραστικών εργαλείων

Decision taking in corneal refractive surgery

A 27-year-old woman who wants to get rid of contact lenses and spectacles was seen at our clinic. She had strabismus surgery as a child and was patched for the right eye but now shows mild nondisturbing exophoria. Infrequently, she likes to box in the sports school. Her corrected distance visual acuity at presentation in the right eye was 20/16 with -3.75 -0.75 × 50 and in the left eye 20/16 with -3.75 -1.25 × 142. Her cycloplegic refraction in the right eye was -3.75 -0.75 × 44 and in the left eye was -3.25 -1.25 × 147. The left eye is the dominant eye. The tear break-up time was 8 seconds in both eyes, and the Schirmer tear test was 7 to 10 mm in right and left eyes, respectively. Pupil sizes under mesopic conditions were 6.62 mm and 6.68 mm. The anterior chamber depth (ACD) (measured from the epithelium) in the right eye was 3.89 mm and in the left eye was 3.87 mm. The corneal thickness was 503 μm and 493 μm of the right and left eye, respectively. Corneal endothelial cell density was on average 2700 cells/mm2 for both eyes. Slitlamp biomicroscopy showed clear corneas and a normal flat iris configuration. Supplemental Figures 1 to 4 (available at http://links.lww.com/JRS/A818, http://links.lww.com/JRS/A819, http://links.lww.com/JRS/A820, and http://links.lww.com/JRS/A821) show the corneal topography and Belin-Ambrósio deviation (BAD) maps at presentation of the right eye and left eye, respectively. Would you consider this patient a candidate for corneal refractive surgery (eg, laser-assisted subepithelial keratectomy, laser in situ keratomileusis [LASIK], or small-incision lenticule extraction [SMILE] procedure)? Has your opinion changed given the recent opinion of the U.S. Food and Drug Administration (FDA) regarding LASIK?1 The patient herself is slightly favoring an implantation of a phakic intraocular lens (pIOL), as she prefers something reversible. Would you implant a pIOL, and which type of IOL, for this level of myopia? What is your diagnosis or are additional diagnostic methodologies needed to establish a diagnosis? What is your treatment advice for this patient? REFERENCES 1. U.S. Food and Drug Administration, HHS. Laser-assisted in situ keratomileusis (LASIK) lasers-patient labeling recommendations; draft guidance for industry and food and drug administration staff; availability. July 28, 2022, Federal Register; 87 FR 45334. Available at: https://www.fda.gov/regulatory-information/search-fda-guidance-documents/laser-assisted-situ-keratomileusis-lasik-lasers-patient-labeling-recommendations Accessed January 25, 2023