Chaug-Ing Hsu

Application of Grey theory and multiobjective programming towards airline network design

Airline network design encompasses decisions on an airline network shape and route flight frequencies. Related investigations handle the trade-oA between enhancing passengers’ service levels and lowering the airline’s operating costs by applying deterministic optimization methods. In contrast with other conventional methods, Grey theory is a feasible mathematical device capable of forecasting airline traAc with minimum data and resolving problems containing uncertainty and indetermination. In the light of these developments, this study develops a series of models capable of forecasting airline city-pair passenger traAc, designing a network of airline routes and determining flight frequencies on individual routes by applying Grey theory and multiobjective programming. A case study demonstrates the feasibility of applying the proposed models. Results in this study not only confirm the practical nature of the proposed models, but also their ability to provide high flexibility in decision making for airlines. ” 2000 Elsevier Science B.V. All rights reserved.

IMPROVED GREY PREDICTION MODELS FOR THE TRANS-PACIFIC AIR PASSENGER MARKET

The rapid economic growth of Asia‐Pacific countries continues to result in faster travel growth in the trans‐Pacific air passenger market. Grey theory is used to develop time series GM(1,1) models for forecasting total passenger and 10 country‐pair passenger traffic flows in this market. The accumulated generating operation (AGO) is one of the most important characteristics of grey theory, and its main purpose is to reduce the randomness of data. The original GM(1,1) models are improved by using residual modifications with Markov‐chain sign estimations. These models are shown to be more reliable by posterior checks and to yield more accurate prediction results than ARIMA and multiple regression models. The results indicate that the total number of air passengers in the trans‐Pacific market will increase at an average annual growth rate of approximately 11% up to the year 2000.

Routing, ship size, and sailing frequency decision-making for a maritime hub-and-spoke container network

This study formulates a two-objective model to determine the optimal liner routing, ship size, and sailing frequency for container carriers by minimizing shipping costs and inventory costs. First, shipping and inventory cost functions are formulated using an analytical method. Then, based on a trade-off between shipping costs and inventory costs, Pareto optimal solutions of the two-objective model are determined. Not only can the optimal ship size and sailing frequency be determined for any route, but also the routing decision on whether to route containers through a hub or directly to their destination can be made in objective value space. Finally, the theoretical findings are applied to a case study, with highly reasonable results. The results show that the optimal routing, ship size, and sailing frequency with respect to each level of inventory costs and shipping costs can be determined using the proposed model. The optimal routing decision tends to be shipping the cargo through a hub as the hub charge is decreased or its efficiency improved. In addition, the proposed model not only provides a tool to analyze the trade-off between shipping costs and inventory costs, but it also provides flexibility on the decision-making for container carriers.

DETERMINING FLIGHT FREQUENCIES ON AN AIRLINE NETWORK WITH DEMAND-SUPPLY INTERACTIONS

This paper determines flight frequencies on an airline network with demand-supply interactions between passenger demand and flight frequencies. The model consists of two submodels, a passenger airline flight choice model and an airline flight frequency programming model. The demand-supply interactions relevant to determining flight frequency on an airlines network are analyzed by integrating these two submodels. The necessary condition for the convergence of the demand-supply interaction is discussed. An example demonstrates the feasibility of applying the proposed models. The results are more accurate than those obtained without considering demand-supply interactions, and the models provide ways to consider demand-supply interactions well in advance to determine flight frequencies on an airline network.

Travel and activity choices based on an individual accessibility model

Abstract.An individual’s travel and activity behaviour is influenced by temporal and spatial constraints, travel and activity characteristics and individual attributes. This article formulates an individual accessibility model to measure the accessibility benefits of daily activities undertaken through a trip, a trip chain or at home. The model is extended further to analyse individuals’ activity location choices, choices between activities at home and activities through travel, and activity timing and scheduling decisions, with the assumption that an individual chooses an activity/travel alternative with the maximum accessibility benefits. An individual’s choice among different locations for participating in an activity is shown to depend on the time budget and the locations of activities scheduled before and after this decided activity. The substitution of an activity at home for an activity through travel is shown to depend on the relative magnitude of activity location attraction and activity duration between these two types of activities and preference parameters. Finally, the article illustrates how an individual schedules one or several continuous or discontinuous activities with time-dependent accessibility benefits so as to maximise benefits.

Reliability evaluation for airline network design in response to fluctuation in passenger demand

This study develops a reliability evaluation method for airline network design. Reliability evaluation in the airline network design phase is considered herein as a post-design task. A series of models for determining flight frequencies on individual routes, evaluating reliability under normal/abnormal demand fluctuations, and providing a priori adjustment of flight frequencies are presented. A case study demonstrating the feasibility of applying the proposed models is provided. Study results not only suggest a post evaluation and adjustment method for airline network design in response to future uncertain fluctuation in passenger demand, but also provide ways to improve flexibility in airline flight frequency decision-making.

Transmission and control of an emerging influenza pandemic in a small-world airline network

Abstract The avian influenza virus H5N1 and the 2009 swine flu H1N1 are potentially serious pandemic threats to human health, and air travel readily facilitates the spread of infectious diseases. However, past studies have not yet incorporated the effects of air travel on the transmission of influenza in the construction of mathematical epidemic models. Therefore, this paper focused on the human-to-human transmission of influenza, and investigated the effects of air travel activities on an influenza pandemic in a small-world network. These activities of air travel include passengers’ consolidation, conveyance and distribution in airports and flights. Dynamic transmission models were developed to assess the expected burdens of the pandemic, with and without control measures. This study also investigated how the small-world properties of an air transportation network facilitate the spread of influenza around the globe. The results show that, as soon as the influenza is spread to the top 50 global airports, the transmission is greatly accelerated. Under the constraint of limited resources, a strategy that first applies control measures to the top 50 airports after day 13 and then soon afterwards to all other airports may result in remarkable containment effectiveness. As the infectiousness of the disease increases, it will expand the scale of the pandemic, and move the start time of the pandemic ahead.

Dynamic allocation of check-in facilities and dynamic assignment of passengers at air terminals

This study explores the dynamic allocation of check-in facilities and dynamic assignment of passengers at air terminals to achieve the objectives of minimizing total waiting time and better utilization of facilities. Taking into consideration different check-in services required by departing passengers, adjustments to allocations are made according to the maximum allowable wait time and the lowest service counter utilization rate allowed for the initial allocation condition. The developed model was validated for its feasibility and applied at the Taoyuan International Airport, Taiwan. The application results showed that dynamic allocation of check-in facilities can both reduce waiting times and increase service counter utilization rates. Such benefits can be further enhanced by dynamic assignment of passengers.

Interactive multiobjective programming in airline network design for international airline code-share alliance

Abstract This study presents an interactive airline network design procedure to facilitate bargaining interactions necessitated by international code-share alliance agreements. Code sharing involves partner airlines individually maximizing their own profits, while mutually considering overall profitability, traffic gains, and quality benefits for the markets in which they cooperate with their partners. This study uses a reference point method to solve the interactive multiobjective programming model, to support the bargaining interactions between two partner-airlines in an alliance negotiation. The impact of the code-share alliance network on market demand, alliance partners’ costs and profits, and levels of service are also discussed. A case study demonstrates the feasibility of applying the proposed models and elucidates how interactive multiobjective programming models may be applied to determine flight frequencies for airline code-share alliance networks. The results of this study provide ways by which alliance airlines can evaluate iteratively the output and profits of the alliance members under code-share alliance agreements.

Fleet dry/wet lease planning of airlines on strategic alliance

Airlines form strategic alliances in hope of cost minimisation. This study develops a model that deals with issues regarding fleet purchase, dry/wet leases and disposal of aircraft, taking into consideration the impact of a strategic alliance between airlines on fleet planning. Using dynamic programming to determine the initial optimal number and type of aircraft for dry/wet leasing, purchase and lease, the multi-objective model formulated can achieve minimisation of total fleet planning costs. Further, this study simulates the step-by-step negotiation process between decision-makers of two allied airlines. Through interactive bargaining, the airlines can adjust the alliance-related parameters to narrow the difference in expected profits and reach a final negotiated compromise solution acceptable to both airlines in the strategic alliance. A satisfactory negotiation result aiming for lower post-alliance costs in the best interests of one individual airline may not be the most optimal for the overall interests of the alliance. The sensitivity analysis of aircraft acquisition costs offer airlines a better understanding of the cost range and cost threshold for aircraft owned/held for different durations and acquired by different approaches.