<p> The Peter Strides Pond study area, approximately 150 km^2, is located in the Southern Long Range Mountains in southwestern Newfoundland. It lies at the southern margin of the Paleozoic Central Mobile Belt in the Dunnage tectonostratigraphic zone. A felsic intrusion, granoblastic gneiss, heterolithic conglomerate and basalt form foliated, linear bodies across the study area parallel to the regional, northeast striking, structural grain; gabbro, diabase and rhyolite have non-linear exposure and no internal fabric. Two parallel mylonite zones traverse the study area. The Victoria River Shear Zone (VRSZ) to the north and the Peter Strides Pond Shear Zone (PSPSZ) to the south are concordant with the regional fabric and separate domains which increase in metamorphic grade from lower greenschist in the northwest to upper amphibolite facies to the southeast. Veins and lenses of variable form and composition are observed in several lithologies but the focussed occurrence of milky white, foliation parallel quartz veins in both the VRSZ and the felsic pluton is significant to these units.</p> <p> A tentative stratigraphic succession for the study area utilizes regional correlations, radiometric ages and fossil evidence because limited exposure does not reveal contacts between adjacent lithologies. Basalt of the Victoria Lake Group and gneiss of the Bay du Nord Group are the oldest units in the area. Conglomerate unconformably overlies the Victoria Lake Group and contains volcanic and sedimentary clasts derived from the underlying group. Mafic to felsic plutonic igneous rocks intrude volcanic rocks of the Victoria Lake Group. Undated gabbro, diorite and diabase may be coeval with Devonian adamellite-granodiorite. Parallel shear zones are concordant with the regional structural grain and follow lithologic contacts closely. Megacrystic granite cross-cuts PSP mylonite, adamellite and Bay du Nord gneiss. It is the youngest unit in the study area. The study area's tectonic framework represents a compressional environment which dominated during, and continued after Iapetus closure. Mafic volcanic rocks adjacent to ophiolite complexes represent back arc basins preserved via obduction. Continued compression was accomodated by crustal thickening through reverse, northwest directed, thrust faults. The inhomogeneously thickened crust provided a host of potential magma compositions to be intruded locally.</p> / Thesis / Master of Science (MSc)

Το πρόβλημα της βελτιστοποίησης ερωτημάτων πολλαπλών κριτηρίων σε βάσεις δεδομένων είναι ένα αρκετά δύσκολο και ενδιαφέρον ερευνητικά πρόβλημα, διότι χαρακτηρίζεται από αντικρουόμενες απαιτήσεις. Κάθε βήμα στην απάντηση ενός ερωτήματος μπορεί να εκτελεστεί με παραπάνω από έναν τρόπους. Για την επίλυση τέτοιου είδους ερωτημάτων έχουν προταθεί διάφοροι αλγόριθμοι, με πιο πρόσφατους τους: Mariposa, M' και Generate Partitions. Ο Mariposa και ο Μ' εφαρμόζονται στην βάση δεδομένων Mariposa, η οποία δίνει την δυνατότητα στον χρήστη να καθορίζει την επιθυμητή εξισορόπηση (tradeoff) καθυστέρησης/κόστους για κάθε ερώτημα που θέτει. Ο αλγόριθμος Mariposa ακολουθεί μία προσέγγιση απληστίας (greedy approach) προσπαθώντας σε κάθε βήμα να μεγιστοποιήσει το «κέρδος» ενώ ο Μ' χρησιμοποιεί σύνολα βέτιστων κατά Pareto λύσεων για την επιλογή του επόμενου βήματος στην θέση του κριτηρίου απληστίας. Τέλος, ο αλγόριθμος Generate Partition χρησιμοποιεί έναν διαχωρισμό του χώρου απαντήσεων χρησιμοποιώντας δομές R-trees πετυχαίνοντας πολύ καλή απόδοση. / The optimization of queries in distributed database systems is known to be subject to delicate trade-offs. For example, the Mariposa database system allows users to specify a desired delay-cost tradeoff (that is to supply a decreasing function u(d) specifying how much the user is willing to pay in order to receive the query results within time d) Mariposa divides a query graph into orizontal strides analyzes each stride, and uses a greedy heuristic to find the best plan for all strides.