Slot Constraints Research Articles

Fast Counterfeit RFID Tags Detection With Slot Constraints

RFID tags are prone to counterfeit attacks in supply chain scenarios. The attacker often uses counterfeit tags to replace stolen tags to avoid being detected by the inventory process. To defend against such attacks, existing hash-based schemes have to know the hash functions embedded in tags, which are usually unavailable in large scale systems. This letter proposes a novel group-based slot constraint (GSC) scheme for lightweight counterfeit tag detection in RFID-enabled supply-chain systems. GSC can be integrated into the identification process by leveraging elaborately designed group hash functions to authenticate tags based on their slot correlation. That is, the tags in the same group can always map to slots with a fixed offset, which offers evidence for identifying counterfeit tags with an abnormal slot index. We also provide a theoretical analysis of the time slots required to achieve the desired accuracy. The simulation results show that GSC provides reliable accuracy without knowing exact hash functions.

Frequency competition among airlines on coordinated airports network

Frequency competition is critical for a full-service airline in gaining market share, and adopting a proper strategy can improve an airline’s profits. This study proposes a new equilibrium programming model with flow balance to address frequency competition on airports network with time slot constraints. We first show that a pure-strategy Nash equilibrium may not always exist, and thus forming a pure strategy profile in frequency competition among airlines may naturally lead to deviation from current frequency. Therefore, we formulate the problem as a programming model with a mixed-strategy Nash equilibrium. To avoid shocks from dramatic frequency changes across the network, airlines tend to fine-tune frequencies on select segments during each adjustment. We propose a procedure to generate a computationally tractable amount of representative strategies from a finite set of feasible strategies to demonstrate mixed-strategy Nash equilibrium. We conduct an empirical analysis using an example in which industry profitability increased by as much as 7.89%. We then extend the model to formulate frequency competition among metal-neutral alliances. The results show that forming metal-neutral alliances can improve total industry profits by 10.59%. In particular, a sensitivity analysis with real data on the tolerance of flow imbalance demonstrates that deducting the potential costs due to the relaxation of flow balance between congested airports may earn additional total industry profits in a frequency competition.

A genetic approach for the maximum network lifetime problem with additional operating time slot constraints

The maximum network lifetime problem is a well-known and challenging optimization problem which has been addressed successfully with several approaches in the last years. It essentially consists in finding an optimal schedule for sensors activities in a wireless sensor network (WSN) aiming at maximizing the total amount of time during which the WSN is able to perform its monitoring task. In this paper, we consider a new scenario in which, in order to monitor some locations in a geographical area, the sensors need to be active for a fixed amount of time, defined as operating time slot. For this new scenario, we derive an upper bound on the maximum lifetime and propose a genetic algorithm for finding a near-optimal node activity schedule. The performance evaluation results obtained on numerous benchmark instances show the effectiveness of the proposed approach.

Dual-hub connectivity: a case study on China Eastern Airlines in Shanghai

To deal with slot constraints and insufficient capacity, emerging multi-airport systems have been under construction in China. This paper chose China Eastern Airlines as a case study, evaluating its hub connectivity under a dual-hub circumstance in Shanghai. The paper detected that the biggest constraint of China Eastern Airlines’ dual-hub situation lied in Shanghai’s location and the restricted transfer options on international routes. Contributions from alliance partners were assessed and benchmarked with China Eastern Airlines. With China Southern Airlines quit SkyTeam alliance, China Eastern Airlines faced more challenges on the domestic market. The empirical study also pointed out the shortcoming of operating at two hubs in the same catchment area, where the quality of connectivity of inter-hub connections cannot be maintained as high as a single-hub transfer. However, the market potential of inter-hub connections in Shanghai was identified with a considerable amount of viable connections.

Job assignment with multivariate skills and the Peter Principle

This paper analyzes the job assignment problem faced by a firm when workers' skills are distributed along several dimensions and jobs require different skills to varying extent. I derive optimal assignment rules with and without slot constraints, and show that under certain circumstances workers may get promoted although they are expected to be less productive in their new job than in their old job. This can be interpreted as a version of the Peter Principle which states that workers get promoted up to their level of incompetence.

The untolled problems with airport slot constraints

This paper examines the efficiency and practicality of airport slot constraints using a deterministic bottleneck model of landing and takeoff queues. It adapts this congestion pricing model to determine the optimal timing and quantity of slot permits for any number of slot windows. Aircraft choose their optimal operating times subject to the slot constraints, and airport queues adjust endogenously. The number and length of slot windows affects the congestion levels and efficiency gains. The atomistic bottleneck model is extended to include self-internalizing dominant traffic and atomistic fringe traffic. The model raises questions about the implementation of slot constraints that do not arise in standard congestion models. The theory explains (Daniel׳s, 2011) empirical findings that slot-constraints at Toronto are ineffective and suggests that recent proposals for slot constraints at US airports would be similarly ineffective. Effective slot constraints require many narrow slot windows, making slot auctions or markets difficult to implement.

Modeling Airline Frequency Competition for Airport Congestion Mitigation

Demand often exceeds capacity at congested airports. Airline frequency competition is partially responsible for the growing demand for airport resources. We propose a game-theoretic model for airline frequency competition under slot constraints. The model is solved to obtain a Nash equilibrium using a successive optimizations approach, wherein individual optimizations are performed using a dynamic programming-based technique. The model predictions are validated against actual frequency data, with the results indicating a close fit to reality. We use the model to evaluate different strategic slot allocation schemes from the perspectives of the airlines and the passengers. The most significant result of this research shows that a small reduction in the total number of allocated slots translates into a substantial reduction in flight and passenger delays and also a considerable improvement in airlines' profits.

A three-stage least squares approach to the analysis of airline strategies for aircraft size and airline frequency on the north Atlantic: an airline case study

In response to increasing demand, airlines may increase capacity by increasing the frequency of flights or they may choose to increase aircraft size. This may yield operating cost economies. If the airports they operate from are capacity constrained, they will be limited in the extent that they can change frequency which will limit their ability to compete with the number of frequencies offered. This article focuses on this trade-off and pays particular attention to the practices of a specific airline. Conclusions are offered on the impact of inter alia competition, changes in aircraft technology, 9/11 and the impact of slot constraints. It appears that changes in size are more important than frequency, which is consistent with the presence of slot constraints and there is a significant impact of competition. As the concentration of carriers increases, so aircraft size falls. 9/11 also has a significant impact on traffic whereas the introduction of the Boeing 777, as an illustration of a change in technology, does not.

Congestion pricing of Canadian airports

Abstract Under congestion pricing, Canadian airports would annually save between $72 and $105 million. Social costs per landing and takeoff decrease about $300 at Toronto and Vancouver and $50 at Calgary and Montreal. Slot constraints fail to eliminate this airport congestion. Congestion prices are lower on average than existing weight‐based prices. Current airport capacity accommodates at least five more years of traffic growth before congestion reaches current levels. Substantial welfare gains occur even if dominant airlines already internalize their self‐imposed delays. This article calculates equilibrium congestion pricing schedules, traffic rates, queuing delays, layover times, and connection times by time of day.

Job Assignment with Multivariate Skills

This paper analyzes the job assignment problem faced by a firm when workers’ skills are distributed along several dimensions and jobs require different skills to varying extent. I derive optimal assignment rules with and without slot constraints, and show that under certain circumstances workers may get promoted although in their new job they are expected to be less productive than in their old job. This can be interpreted as a version of the Peter Principle which states that workers get promoted up to their level of incompetence.

Optimal route allocation in a liberalizing airline market

Airlines often encounter two major problems in expanding their international networks: (1) restrictive Air Services Agreements (ASAs) governing airlines’ commercial rights, and (2) slot / capacity constraints in foreign hub airports. Government interventions are needed to solve these problems, yet few quantitative models are available to guide the design of related public policies. This paper proposes a new model for optimizing the allocation of additional routes in a liberalizing airline market, in which airport capacity constraints are explicitly considered. The proposed model captures the interactions among three types of agents: (1) a regulator who aims to maximize social welfare by optimizing the allocation of additional routes to competing carriers; (2) airlines competing with flight frequency and airfare; and (3) passengers who minimize their own travel disutility (or equivalently maximize utility) given airlines’ services and prices. In the proposed model, the passenger demand elasticity is also explicitly considered. The route allocation model is formulated as a 0-1 integer programming problem, and is solved by a heuristic implicit enumeration approach. The Korean – mainland China – Hong Kong airline market serves as model illustration. The effects of airport slot constraints are examined, and the revealed value (marginal welfare gain) of airport capacity expansion is also calculated, which can potentially serve as a benchmark indicator for the planning of airport investments.