Πλοήγηση ανά Επιβλέπων "Zografos, Constantinos"

A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

Α Β Γ Δ Ε Ζ Η Θ Ι Κ Λ Μ Ν Ξ Ο Π Ρ Σ Τ Υ Φ Χ Ψ Ω

Τώρα δείχνει 1 - 4 από 4

A critical assessment of airport demand and management strategies, implications and potential for implementation
(2007) Madas, Michael; Μαντάς, Μιχαήλ; Athens University of Economics and Business, Department of Management Science and Technology; Odoni, Amedeo R.; Prastacos, Gregory P.; Doukidis, Georgios; Lioukas, Spyros; Saaty, Thomas; Poulymenakou, Angeliki; Zografos, Constantinos
Σύμφωνα με πρόσφατες προβλέψεις της ζήτησης αεροπορικών μεταφορών, η διεθνής αεροπορική κίνηση αναμένεται να αυξηθεί κατά μέσο όρο με ετήσιο ρυθμό της τάξης του 3,6% μεταξύ του 2002 και του 2020. Οι έντονοι ρυθμοί ανάπτυξης σε συνδυασμό με τα περιορισμένα έργα ανάπτυξης νέων ή επέκτασης των υπάρχουσων αεροδρομιακών υποδομών έχουν, ωστόσο, τροφοδοτήσει μία σειρά από προβλήματα αεροπορικής συμφόρησης και σημαντικών καθυστερήσεων. Η έλλειψη ισορροπίας μεταξύ προσφοράς και ζήτησης αεροπορικών υπηρεσιών έχει, με τη σειρά της, τροφοδοτήσει σειρά συζητήσεων και πολιτικών διαβουλεύσεων κατά την τελευταία δεκαετία σε παγκόσμια κλίμακα με κοινό σημείο αναφοράς το αγωνιώδες, στρατηγικό δίλημμα για τους εμπλεκόμενους φορείς στη λήψη των αποφάσεων στον τομέα των αεροπορικών μεταφορών: «διαχείριση της αεροπορικής ζήτησης ή αύξηση της ικανότητας διεκπεραίωσης του συστήματος αεροπορικών μεταφορών;». Γενικά, στον στίβο των πολιτικών συζητήσεων και ερευνητικών προτάσεων καταγράφονται δύο κυρίαρχες προσεγγίσεις / στρατηγικές επίλυσης του εν λόγω προβλήματος: i) αύξηση της ικανότητας διεκπεραίωσης του συστήματος μέσω της επέκτασης της υποδομής, της βελτίωσης του εξοπλισμού και των αεροσκαφών, καθώς και της αξιοποίησης προωθημένων τεχνολογιών πληροφορικής και τηλεπικοινωνιών (supply-side), και ii) μείωση ή διαχείριση της ζήτησης σε χωρική ή χρονική διάσταση ώστε να εξομαλυνθεί το προφίλ της και να εξισορροπηθεί σε σχέση με την υπάρχουσα παραγωγική δυναμικότητα του συστήματος αεροπορικών μεταφορών (demand-side). Μέχρι πρόσφατα, ο κύριος όγκος της έρευνας και οι φορείς διαμόρφωσης πολιτικής στον τομέα των αερομεταφορών εστίαζαν κυρίως σε έργα υποδομών, νέες τεχνολογίες ή στον ανασχεδιασμό λειτουργικών διαδικασιών με στόχο την επέκταση ή βελτίωση της χωρητικότητας των αεροδρομίων. Οι πρωτοβουλίες αυτές, ωστόσο, επιχειρούν να αντιμετωπίσουν ένα ιδιαίτερα πολύπλοκο και πολυδιάστατο πρόβλημα επενδύοντας πόρους σε μία μόνο πτυχή του προβλήματος, τη διάσταση της προσφοράς (supply). Δυστυχώς, η εμπειρία της προηγούμενης δεκαετίας μαρτυρά ότι η μονοδιάστατη εστίαση στην επέκταση της προσφοράς ίσως οδηγεί σε μία δύσκολη, ιδιαίτερα δαπανηρή, και εκ των προτέρων «χαμένη μάχη». Η ραγδαία αύξηση της συμφόρησης και των καθυστερήσεων σε συνδυασμό με φυσικούς περιορισμούς στην παροχή επαρκούς ικανότητας διεκπεραίωσης καθιστούν πρακτικά αδύνατη μια λύση που προσανατολίζεται αποκλειστικά στην πλευρά της προσφοράς / υποδομής (supply-side). Φυσικοί, θεσμικοί και κοινωνικοί περιορισμοί απαιτούν την ενδελεχή εξέταση προσεγγίσεων διαχείρισης της αεροπορικής ζήτησης ως ένα δυνητικό “όχημα” γεφύρωσης του χάσματος ανάμεσα στην προσφορά και τη ζήτηση αεροπορικής κίνησης. Γενικότερα, τα αυξανόμενα φαινόμενα καθυστερήσεων και η μειούμενη αποτελεσματικότητα των αεροπορικών μεταφορών παγκοσμίως αποτέλεσαν καθοριστικό ρόλο και άσκησαν σημαντικές πιέσεις για τη σταδιακή υιοθέτηση και την αυξανόμενη αποδοχή προσεγγίσεων και στρατηγικών διαχείρισης της αεροπορικής ζήτησης (demand management).Τα κέντρα λήψης αποφάσεων στον τομέα των αερομεταφορών και οι φορείς διαχείρισης αεροδρομίων τείνουν να θεωρούν τις προσεγγίσεις αυτές ως ένα δυνητικό μέσο διαχείρισης της ζήτησης: i) περιορίζοντας με κάποιον τρόπο τη ζήτηση χρήσης ορισμένων κόμβων του αεροπορικού συστήματος (π.χ. αεροδρόμια) που αντιμετωπίζουν έντονα προβλήματα συμφόρησης, ή/και ii) τροποποιώντας και εξομαλύνοντας με κάποιο τρόπο το προφίλ της ζήτησης μέσω μιας πιο εξισορροπημένης κατανομής της είτε στον χώρο είτε στον χρόνο. Η πρώτη προσέγγιση μπορεί να επιτευχθεί με τη χρήση διοικητικών μέτρων και κριτηρίων που αποσκοπούν στην εκτροπή μέρους της ζήτησης σε αεροδρόμια που μπορεί να εξυπηρετηθεί πιο αποτελεσματικά. Η δεύτερη προσέγγιση υπαγορεύει το σχεδιασμό ενός συστήματος τιμολόγησης ή άλλου μηχανισμού με βάση τις δυνάμεις της αγοράς (market-based), όπως οι δημοπρασίες ή η αγοραπωλησία δικαιωμάτων χρήσης της αεροδρομιακής υποδομής (slots).
An investigation of the behavioural antecedents of supply chain relationships and their impact on supply chain integration and performance
Tsanos, Christos; Τσάνος, Χρήστος; Athens University of Economics and Business, Department of Management Science and Technology; Manthou-Fragkopoulou, Vasiliki; Soderquist, Klas Eric; Zografos, Constantinos
Collaboration among supply chain partners is considered to lead to improved levels of integration and performance across the supply chain. Integration appears to be motivated by appropriate organizational and operational conditions in order to demonstrate a positive effect onperformance. Extant research has focused more on examining why establishing collaboration between supply chain partners leads to integration and performance benefits and what these benefits are, but not on precedent factors affecting the development of collaborative relationships.The behavioural antecedents of supply chain relationships constitute an intuitively appealing set of conditions for collaborative relationship management between supply chain partners that has not been examined extensively in practice. Behavioural antecedents can function as building blocks which help to bind partners together in such relationships and may contribute to achieving higher integration and performance. Yet, research on the effects of such behavioural factors of interorganizational relationships on supply chain integration and performance is limited. At the sametime, academic literature in the fields of organizational behaviour and organizational psychology identifies behavioural factors in inter-firm and employee-firm relationships that could be investigated in the context of supply chain interorganizational relationships. Therefore, the investigation of the effects of supply chain relationship antecedents on integration and performance constitutes a value- adding research contribution.This thesis investigates the effects of behavioural antecedents of collaboration in supply chain relationships on integration and performance by developing and empirically validating a model linking these three constructs
Modelling landside airport operations for performance evaluation
Manataki, Ioanna E.; Athens University of Economics and Business, Department of Management Science and Technology; Zografos, Constantinos
The ever-increasing growth in air transport implies increasing demand for airport services, which further propagates into the need for providing more efficient airport terminal services. The airport terminal constitutes a major element of the airport system, since increased congestion levels in airport terminals may cause delays in flights and deteriorate passenger perception on the level of service offered. Decision making for airport terminal planning, design and operations management is a challenging task, since the airport terminal is a highly complex system, incorporating significant trade-offs regarding alternative operational policies and physical terminal layout concepts. The implementation of an operational concept that may enhance the efficiency of a facility may deteriorate the performance of another, with negative impacts on overall system performance. Therefore, the focus must be placed on overall system rather than on individual airport terminal processes and facilities.Moreover, airport stakeholders have a vested interest in assessing the impact of their decisions regarding alternative terminal layout concepts and operational policies on overall airport terminal system performance. In this context, several analysis techniques, supported by the appropriate mix of models, tools, concepts and technologies, have been deployed to assist the decision-making and implementation process for dealing with the complexities of contemporary airport terminal management and optimization of airport terminal operations. Existing models and tools for airport terminal analysis and performance assessment are too specific (i.e., models of specific airports) or general simulation platforms that require substantial airport modelling effort. In addition, they are either too detailed (i.e., microscopic) or too aggregate (i.e., macroscopic), affecting, respectively, the flexibility of the model to adapt to any airport and the level of accuracy of the results obtained. Therefore, there is a need for a generic decision support tool that will incorporate sufficient level of detail for assessing airport terminal performance. To bridge this gap, a generic, mesoscopic model for airport terminal performance analysis has been developed, that strikes a balance between flexibility and realistic results, adopting a system dynamics approach.In this respect, the overall objective of this thesis is to develop a generic, yet flexible and easily customizable mesoscopic system dynamics model for the analysis and evaluation of airport terminal performance. To this end, the proposed model has been built on the basis of accounting for the following key design model characteristics:i) a mesoscopic model, that focuses on the aggregate characteristics of interest, capable to support strategic decision-making by incorporating intermediate level of detail, while providing sufficient degree of realism in representing airport terminal operations and accuracy in model results,ii) a generic model, capable to describe the common structure of any airport, in terms of processes/facilities and functional areas, andiii) a flexible model that can be customized in a user-friendly way to adequately reflect the local characteristics of any airport terminal, given their complexity and diversity.The proposed model allows decision-makers and analysts to perform impact and trade-off analyses with respect to a variety of performance measures (i.e., capacity, delays/waiting times, level of service, resource utilization, passenger accumulations at various terminal facilities and functional areas and at various time frames, etc.), to develop "what-if" scenarios in a user-friendly way, and to assess the impacts of e.g., new operational policies, changes in the traffic volumes or passenger profile, adoption of advanced technologies, changes in the terminal layout, terminal expansions, etc. In this respect, the proposed model is easily adaptable both to possible future transformations and expansion of the airport terminal, and to changes in the operational policies followed by the airport.Based on the above, the overall thesis is structured according to the following research activities:- highlighting the need for a mesoscopic, generic, yet flexible model for airport terminal analysis and performance assessment- demonstrating the need for adopting a new approach for airport terminal modelling- describing the overall methodological framework followed for the development of the proposed model, providing insight to the conceptual framework adopted, the airport terminal domain ontology developed, and the model architecture adopted- demonstrating the model design, using system dynamics- presenting the data requirements and the expected results of the model- validating the model results through the model validation activities performed- presenting the model demonstration through model application using real data at an airport terminal- presenting an overview of model capabilities and future research directions.The overall model architecture is built on the basis of a modular and a hierarchical model structure. In this context, the proposed model is structured into two hierarchical levels: i) the first level of the hierarchy reflects the airport terminal system decomposition into a set of Airport Functional Areas, and ii) the second level reflects the Airport Functional Areas’ decomposition into Service Facilities (modules) of the airport terminal. Every service facility in the airport terminal and the associated process is represented by a module in the model. In addition, service facilities are classified into processing, holding, and flow facilities, according to a general typology used for airport terminal facilities. At a higher level, every airport functional area is composed by a set of modules, that interact with each other through pre-specified interfaces. Adopting such an approach, the model is built in an easy way: by selecting modules from a library of modules and appropriately combining them through specified interfaces so as to represent the entire airport terminal system. In this context, the modular architecture and interface adopted, enabling quick and easy model building and providing the capability of being adaptable to the configuration and operational characteristics of any airport terminal in a user-friendly manner.The proposed system dynamics model has been validated at the Athens International Airport in order to develop confidence in the model results and ensure their validity and accuracy. The detailed model validation comprises the comparison of the results obtained by the proposed system dynamics model against the outcomes of IATA’s Total AirportSim model. The Total AirportSim model is a well-recognized commercial simulation model for airport passenger terminals developed by IATA (International Air Transport Association). The results of the model validation activities suggest that the proposed model: i) is properly and efficiently functioning, ii) generates results of reasonable accuracy that reflect reality with respect to airport terminal performance assessment, and iii) can be efficiently used to model and support real-world frequently arising airport terminal planning, design, and operations problems.In addition, the system dynamics model has been demonstrated at the Athens International Airport in order to model and analyze the "real-world" planning, design and operations decisions for the airport. The model has been configured to fit the characteristics of the Athens International Airport in terms of the airport terminal physical layout, the processing and the airport users’ flow through the various functional areas and facilities. The application of the proposed model at the Athens International Airport terminal provides valuable results and conclusions with respect to the airport terminal performance assessment, the improvement of the operational/service policies followed by airport and the enhancement of the level of service offered to airport terminal users.The major strength of the proposed model relates mainly to: i) its flexibility to reflect the configuration and operational characteristics of any airport terminal in a user-friendly way, and ii) its ease of model construction through the selection of objects from a library of modules, which are composed through pre-specified interfaces. This implies significantly reduced modelling effort and ease of model construction, since no user familiarity with the tool nor deployment of technical expertise is required. Furthermore, the proposed model allows for a holistic evaluation of terminal performance, capturing important interactions and trade-offs among the various terminal facilities and services, as opposed to analyzing in isolation the performance of individual airport terminal facilities.The adoption and deployment of the proposed model is expected to improve the quality of airport terminal decision-making and management, by providing insight to airport terminal dynamics, evaluating the performance of the terminal as a whole, and also identifying specific problematic areas. In particular, the proposed model is expected to have a strong and positive impact on the following key strategic aspects:- Improvement in the quality of the airport terminal decision-making process through an integrated and systematic impact and trade-off analysis;- Establishment of new policies for addressing airport terminal capacity, efficiency, and utilisation issues;- Efficient utilization of airport terminal resources, through rationalization of resource allocation; and- Improvement of the level of service offered to airport terminal users and enhancement of the airport terminal business image.Furthermore, it has been evident that there is ample opportunity for model enhancements and future modelling research efforts towards:- Extension of the proposed model to account also for baggage processing, multi-terminal airports, and intermodal terminal operations;- Development of a unified approach for assessing total airport terminal level of service;- Adaptation of the proposed model to similar systems, i.e., other passenger terminals, such as railway terminals; and- Integration of the proposed airport terminal model with available airside models, to support total airport analyses and performance evaluations.In response to the identified areas of improvements and enhancement opportunities, further research effort is planned to be devoted to enhance the herewith presented system dynamics model for airport terminal performance assessment.
Project monitoring and control process for effective project management
(Athens University of Economics and Business, 10-2004) Antonakopoulos, Panos; Zografos, Constantinos
Thesis - Athens University of Economics and Business. Executive MBA