Freight transportation is an integral element of various supply chains and has a complex and dynamical interrelationship with human economic activities. Modern logistical strategies paved way to the current supply chain organisation and logistics network design resulting in a more global economy and huge economies of scale. Recent trends of volatility of oil price have major implications in the movement of commodities across the supply chains. Likewise, climate change issues have presented urgent challenges in reducing carbon emissions for the transport and logistics sector. Pressure on the sector comes from both governments and consumers alike, demanding future sustainability as well as corporate environmental and social responsibility. The original contribution of this research is to investigate the system-wide dynamics of freight transportation and production in the context of supply chains. A theoretical framework called the ‘Geographic Adaptive Potential’ or GAP is built to understand how constraints in energy and emissions affect the production and distribution of commodities. The changes in the supply chain were investigated in four different components, namely a) the potential to shift to less energy and emissions intensive modes for long-haul freight, b) logistical strategies in the last leg of the chain or urban freight and c) local production and distribution, and d) the accessibility of potential customers to the markets. The design of the GAP components is in correspondence with the links of the supply chain. The analyses yielded an evaluation of the adaptive capacity of the freight transport and production system. For long-haul freight, a GIS-based model was created called the ‘New Zealand Intermodal Freight Network’ or NZIFN. It is an optimisation tool integrating the road, rail and shipping network of New Zealand and calculates that minimum time, operating costs, energy and emissions routes between 2 given locations. The case studies of Auckland to Wellington and Auckland to Christchurch distributions of non-perishable products established that even a marginal increase of rail and coastal shipping share produced around 10% reduction in both freight energy and greenhouse gas emissions. In the study of the last leg of the supply chain, the truck trip generation rates of different food stores were investigated. The strongest factors influencing the trip rates to a store are its size and product variation, the latter being a new parameter introduced in the dissertation. It is defined as the total number of brands for 6 chosen commodities commonly found in the stores. The trip rates together with the truck type and distance travelled were used to compute the freight energy usage of the stores. Results revealed that supermarkets consume the most energy for their delivery operations but relative to its physical size, they are more energy efficient than smaller stores. This is due to the utilisation of advanced logistical strategies such as freight consolidation and the effective use of distribution centres. The localised production chapter was explored in the context of Farmers’ markets and their difference with the conventional supermarket distribution system. Using a freight transport energy audit, the energy intensities of both systems were compared. The findings showed that Farmers’ markets were more energy-intensive than supermarkets owing to the low volumes of goods delivered to the market and the lack of freight consolidation effort in the system. The study on the active mode access of potential customers to both Farmers’ markets and supermarkets captured the interplay between freight and personal transport and is the final component of GAP. The results of the ArcGIS based model called ‘Active Mode Access’ or AMA demonstrated that both Farmers’ markets and supermarkets have the same level of accessibility for walking or biking customers. However, the calculations also showed that almost 87% of New Zealanders have no AMA to stores and are at risk for fuel price increase. Finally, the key result of this dissertation is the assessment that there is actually limited adaptive capacity of the freight transport and production system. This is due to network infrastructure and geographical constraints as well as commodity type and mode compatibility and other operational concerns. Due to these limitations, the GAP model assessed that reduction in energy and allowable emissions will ultimately reduce the amount of commodities moved in the system.

Την τελευταία δεκαετία έχει παρατηρηθεί μια σημαντική διάδοση των συστημάτων πλοήγησης οχημάτων. Τα συστήματα αυτά συνδυάζοντας τις δυνατότητες που προσφέρει η τεχνολογία και χρησιμοποιώντας τη γεωγραφική αναπαράσταση του οδικού δικτύου, την τρέχουσα θέση του οχήματος και συχνά πληροφορίες για την κίνηση προτείνουν στους οδηγούς τη διαδρομή που πρέπει να ακολουθήσουν για να φτάσουν πιο γρήγορα στον προορισμό τους. Οι εφαρμογές πλοήγησης οχημάτων μπορούν να προσφέρουν τη δυνατότητα διαχείρισης της κυκλοφορίας με τέτοιο τρόπο που επιτρέπει την αύξηση της χωρητικότητας του οδικού δικτύου και επομένως τη μείωση της συμφόρησης, χωρίς να είναι απαραίτητη η υψηλού κόστους επέκταση της οδικής υποδομής. Σε αντίθεση με το βέλτιστο για το χρήστη μοντέλο που εφαρμόζεται στα κλασικά συστήματα πλοήγησης και που δεν παρέχει καμία εγγύηση βελτίωσης της κυκλοφοριακής κατάστασης, για το σκοπό αυτό έχει προταθεί το βέλτιστο για το σύστημα μοντέλο. Το μοντέλο προτείνει διαδρομές με στόχο τη βελτίωση της κυκλοφοριακής κατάστασης στο δίκτυο, αλλά η εφαρμογή του είναι μη ρεαλιστική καθώς οι προτεινόμενες διαδρομές μπορεί να είναι πολύ μακρύτερες από το αναμενόμενο. Στην παρούσα διπλωματική εργασία μελετάται μια τρίτη προσέγγιση: ένας βέλτιστος για το σύστημα υπό περιορισμούς αλγόριθμος. Πρόκειται για ένα συνδυασμό των δύο μοντέλων πλοήγησης με σκοπό τη μείωση της συμφόρησης και ταυτόχρονα τη διατήρηση της δικαιοσύνης στην επιλογή των προτεινόμενων διαδρομών για τους οδηγούς. Αφού γίνει θεωρητική μελέτη του προβλήματος παρουσιάζεται η υλοποίηση ενός συστήματος πρότασης διαδρομών που χρησιμοποιεί το βέλτιστο για το σύστημα υπό περιορισμούς αλγόριθμο. / During the last decade, vehicles' route guidance systems have known a significant spread. These systems, taking advantage of the available technological features and by using the geographical representation of the road network, the current position of a vehicle and often traffic data, propose to drivers the route they should follow in order to reach faster their destination. The applications of route guidance systems offer the chance to manage traffic in such a way that allows an increase in road network capacity and therefore a decrease in traffic congestion, without being necessary the high cost expansion of the road infrastructure. In contrast to the user optimal model that is followed by typical route guidance systems and provides no traffic improvement guarantees, the system optimal model has been proposed for this purpose. The model proposes paths with the goal of improving the traffic condition of the network, however its application is unrealistic since the proposed routes may be much longer than expected. In this thesis a third approach is studied: a constrained system optimal algorithm. The algorithm is a combination of the two navigation models with the goal of reducing congestion and at the same time remaining fair for drivers when selecting a route. After the theoretical study of the problem, the implementation of a route recommendation system that incorporates the constrained system optimal algorithm is presented.

Made available in DSpace on 2014-06-11T19:26:55Z (GMT). No. of bitstreams: 0 Previous issue date: 2009-03-06Bitstream added on 2014-06-13T20:27:25Z : No. of bitstreams: 1 silva_lc_me_sjrp.pdf: 396347 bytes, checksum: ca82fc898986cf42e0fa521d8f9ab63c (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Neste trabalho, estudamos as famíılias de sistemas forçados com superfície de impasse regular, as formas normais de seus pontos “típicos”bem como seus retratos de fase. Vemos ainda alguns resultados sobre a genericidade desses pontos e a estabilidade estrutural de um sistema forçado. Abordamos o tema de uma forma simples: apresentamos o que é um sistema forçado e uma família de sistemas forçados para depois estudar as formas normais de seus pontos “típicos” através de dois campos de direções, os quais se tornam fundamentais para o assunto. Utilizamos o Teorema de Peixoto (adaptado para este assunto) como norte para dar as características de um sistema forçado estruturalmente estável. No capítulo 3, damos a estratificação da superfície de impasse e, como resultado final, vemos que esta estratificação é genérica (no conjunto de todas as famílias de sistemas forçados). / In this work we study the families of constrained systems with regular impasse surface, the normal forms of its “typical”points and the respectively phase portrait. We see some results about the genericity of these points and the structural stability of a constrained system. We broach the theme in a simple way: we introduce a constrained system and a family of a constrained systems, and so, we study the normal forms of its “typical”points through two line fields, which become essential for the subject. We use the Peixoto’s Theorem (adapted for this subject) to characterize a structural stable of constrained systems. In the chapter 3, we make a stratification of the impasse surface and, as a last result, we see that stratification is genericity (in the set of all families of constrained systems).

Made available in DSpace on 2014-06-11T19:32:50Z (GMT). No. of bitstreams: 0 Previous issue date: 2011-03-18Bitstream added on 2014-06-13T18:07:15Z : No. of bitstreams: 1 cardin_pt_dr_sjrp.pdf: 479456 bytes, checksum: 52785d20631e0d11a14a241fde1ae7c9 (MD5) / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / Neste trabalho estudamos sistemas diferenciais forçados, também conhecidos como sistemas de equações com impasse. Estudamos os casos onde tais sistemas são suaves e os casos onde são possivelmente descontínuos. Usando técnicas de perturbação singular obtemos alguns resultados sobre a dinâmica destes sistemas em vizinhanças dos conjuntos de impasse. No caso suave, a Teoria de Fenichel clássica e crucial para o desenvolvimento dos principais resultados. Para o caso com descontinuidades, uma teoria similar a Teoria de Fenichel ´e desenvolvida. Além disso, estudamos a bifurcação de ciclos limites das órbitas periódicas de um centro diferencial linear quando perturbamos tal centro dentro de uma classe de sistemas diferenciais lineares por partes com impasse / In this work we study constrained differential systems, also known as systems of equations with impasse. We study the cases where such systems are smo oth and the cases where they are p ossibly discontinuous. Using singular p erturbation techniques we obtain some results on the dynamic of these systems in neighb orho o ds of the impasse sets. In smo oth case, the classical Fenichel’s Theory is crucial for the development of the main results. For the case with discontinuity, a similar theory to Fenichel’s Theory is develop ed. Moreover, we study the bifurcation of limit cycles from the p erio dic orbits of a linear differential center when we p erturb such center inside a class of piecewise linear differential systems with impasse