1,720,958 research outputs found
A methodology for air route planning: the case Nap - Nyc
No full textThe entrance in service of wide body aircraft at the beginning of the 70's and the effect of the air transport liberalization are probably the main reasons for the increase of air traffic. The interest of airlines and airport management come up in this context with the aim of planning new air routes. The analysis of the demand of the existing flights, through the use of mathematical models, represents the initial stage of a planning process. Many researches have been developed in this field.
In the present paper the convenience of direct air links, without intermediary landings between Naples and New York has been examined. The technique followed is that of simulating the choice behaviour of the passengers through the use of a Logit Model. As to the qualifications characterizing each available alternative we have developed 3 different hypothesis. In the first we have considered: the time of transportation, the fare, the frequency and a variable concerning the quality of the service offered. In the second hypotheses the transporta¬tion time and the frequency only have been taken into account. Finally in the third, we have considered a change in the fourth variable, believing it to be necessary to simulate the probability that a passenger might not find seats available on an certain journey. The next phase concerned the model calibration on the existing situation of the air link between Naples and New York, determining the capacity of the mathematical model in reproducing the present situation. Then, we have assumed the existence of the direct link between Naples and New York through the alternative of a true journey and a hypothetical one, obtaining the flows on all the journeys of the network. It has been showed that the alternative of direct transportation without intermediary landings would be the most attended one. However, the profitability for the airline under determined fare and frequency hypotheses should be expected as from 2004
Airport Capacity according to ICAO Rules: Some Quantitative Evaluations
No full textThe basis of a planning process is the evaluation of capacity, both in case of exnovo infrastructures and extensions of existing ones. Therefore, the evaluation of capacity is particularly important for an airport so that a correct infrastructure dimension can be obtained.
At the beginning of the seventies studies on airport capacity started to be developed due to the increase of air traffic. In fact, as the first wide body together supersonic aircraft came into service in that period air traffic started to rise up significantly. The first scientific and interesting study is probably from R. M. Harris “Models for runway capacity analysis”, report FAA-EM/73-5, McLean, 1974. He developed a model for space distances of couples of aircraft in landing phase on the approach path of a runway. He defined runway capacity in overflow condition on the basis of such distances, pointing out that these conditions happen when at least two aircraft are on the approach path. The most important work probably developed until now concerning airport capacity was the FAA Advisory Circular "Airport Capacity" New York, 1978/1994. The airport capacity for what concern the air side of the airport itself is defined as the less value among runway, taxiway and gate capacity. Several diagrams were showed in the AC. For instance, runway capacity could be obtained under certain input data like the percentage of wide body aircraft, the percentage of arrivals, the touch and go amount etc. Several other works have been developed since then. Many papers concern optimization of arrivals on a runway depending on the interarrival time between an aircraft and the trailing one. As runway capacity depends directly on interarrival times it’s interesting to focus on this. In many works interarrival time is assumed to depend on the weight of the leading and the trailing aircraft. FAA also developed specific rules on this, as known. Nevertheless, interarrival distances applied in the States by Air Traffic Control (ATC) are not valid in the rest of the world. In fact ICAO ATC rules showed in Annex 2 are different from FAA ones. Of course, the applied aircraft distances influence runway capacity directly.
The aim of the present paper is to understand until which moment the difference of rules can influence distance times between aircraft and capacity. Several experimental data have been collected on the Naples International Airport, located in southern Italy, during a 30 day period in order to develop the present work. The exact Greenwich Civil Time (GCT) of landing and taking off aircraft have been measured and interarrival and interdeparting times have been subsequently calculated. These measures provided statistic means, standard deviations and percentiles of distance statistic distribution for couples of aircraft. The couple can consist of different weight class aircraft or aircraft belonging to the same weight class. Distance times between two aircraft within 7 minutes have been considered to get a true runway capacity value in the Naples International Airport, both for departing and arriving aircraft. Results obtained in this way have been compared to other authors ones through statistic percentiles and the sampling distributions compared to known ones with a correlation test to understand what can be the influence on runway capacity. Results also show a substancial difference in terms of distance times and this can be reflected on airports subjected to different rules. This matter is very interesting and its further develops are showed in the paper
Il sistema aeroportuale campano: una nota metodologica
No full textL’obiettivo di questo studio è quello di fornire uno spunto metodologico relativo all’analisi dei sistemi aeroportuali. In particolare, verrà analizzata la possibilità di creare un sistema aeroportuale in Campania, costituito dall’insieme degli aeroporti e delle reciproche relazioni.
Lo squilibrio esistente tra domanda che chiede di spostarsi con la modalità aerea e la scadente offerta di trasporto aereo campana, suggerisce la necessità di intervenire in termini di adeguamento delle infrastrutture aeroportuali esistenti ed in termini di nuove realizzazioni. Attualmente il “sistema” campano non è tale perché è mono – aeroportuale (è funzionante il solo aeroporto di Napoli).
Metodologicamente il sistema sarà studiato mediante analisi quantitative. In diversi casi, sia a livello nazionale che internazionale, al problema dello squilibrio tra domanda ed offerta, è stata data diversa risposta:
- nella maggior parte dei casi si considera il singolo aeroporto e si è interessati, prevalentemente alla determinazione di modelli che consentano di ottimizzare i livelli capacitativi dell’aeroporto;
- talvolta, tuttavia, l’impossibilità di incrementare i livelli capacitativi, soprattutto attraverso interventi nel campo di realizzazioni infrastrutturali, indirizza l’attività ingegneristica nella valutazione di fattibilità di nuovi siti aeroportuali.
Entrambi gli approcci non risolvono, a nostro avviso, il problema. Nel secondo caso, per esempio, si potrebbe obiettare che non sempre il raddoppio delle infrastrutture consente un raddoppio della capacità. Per tale ragione occorre proporre un diverso
approccio metodologico alla risoluzione del problema di squilibrio domanda – offerta, che consideri l’insieme degli aeroporti di una medesima area come elementi interagenti fortemente tra loro, costituendo un “sistema aeroportuale metropolitano o regionale”.
L’asserto fondamentale di questo “nuovo“ approccio è che l’entità “sistema” sia costituito da parti in interazione
Il sistema aeroportuale campano: una nota metodologica
No full textL’obiettivo di questo studio è quello di fornire uno spunto metodologico relativo all’analisi dei sistemi aeroportuali. In particolare, verrà analizzata la possibilità di creare un sistema aeroportuale in Campania, costituito dall’insieme degli aeroporti e delle reciproche relazioni.
Lo squilibrio esistente tra domanda che chiede di spostarsi con la modalità aerea e la scadente offerta di trasporto aereo campana, suggerisce la necessità di intervenire in termini di adeguamento delle infrastrutture aeroportuali esistenti ed in termini di nuove realizzazioni. Attualmente il “sistema” campano non è tale perché è mono – aeroportuale (è funzionante il solo aeroporto di Napoli).
Metodologicamente il sistema sarà studiato mediante analisi quantitative. In diversi casi, sia a livello nazionale che internazionale, al problema dello squilibrio tra domanda ed offerta, è stata data diversa risposta:
- nella maggior parte dei casi si considera il singolo aeroporto e si è interessati, prevalentemente alla determinazione di modelli che consentano di ottimizzare i livelli capacitativi dell’aeroporto;
- talvolta, tuttavia, l’impossibilità di incrementare i livelli capacitativi, soprattutto attraverso interventi nel campo di realizzazioni infrastrutturali, indirizza l’attività ingegneristica nella valutazione di fattibilità di nuovi siti aeroportuali.
Entrambi gli approcci non risolvono, a nostro avviso, il problema. Nel secondo caso, per esempio, si potrebbe obiettare che non sempre il raddoppio delle infrastrutture consente un raddoppio della capacità. Per tale ragione occorre proporre un diverso
approccio metodologico alla risoluzione del problema di squilibrio domanda – offerta, che consideri l’insieme degli aeroporti di una medesima area come elementi interagenti fortemente tra loro, costituendo un “sistema aeroportuale metropolitano o regionale”.
L’asserto fondamentale di questo “nuovo“ approccio è che l’entità “sistema” sia costituito da parti in interazione
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
- …
