Tourism growth versus airport environmental capacity: An application of Ramsey pricing to Spanish tourist airports

Airport infrastructure in many countries is being up-graded to meet the growing demands of tourism, and air travel more generally, but this poses problems for sustainable development. Thus, there is the need to establish an alternative to the traditional airport pricing structure for landing fees so as to reflect the true cost that air transports imposes on others. This paper analyses one application of Ramsey pricing to some Spanish tourist airport that embraces environmental as well as conventional financial costs.     

The influence of three-way catalysts on harmful emission production

This article deals with the influence of three-way catalysts on the production of basic emissions, such as carbon monoxide, unburned hydrocarbons and nitrogen oxides from spark-ignition engines. A virtual simulation of the new European driving cycle is used. Characteristics of components in emissions in the front and back of the catalyst are measured on the test bed to form the basis of the simulation. The results relate to emissions for 1 km travelled.     

Optimal ship tracking on a navigation route between two ports: a hydrodynamics approach

The optimal trajectory from Calcutta port to Mumbai port is charted for a tanker transshipping from the East coast to the West coast of India during rough weather. Rough weather is simulated over Indian seas using the state-of-the-art WAM numerical wave model (WAMDI Group in J Phys Oceanogr 18:1775–1810, 1988), assimilating satellite (IRS-P4) wind fields. These simulated wave fields and two-dimensional (2D) directional wave spectrum are an absolute representation of the irregular seaway. Hence, the same for the monsoon month of August 2000 formed the input basis for this study. Loss of ship speed due to the wave field (i.e., nonlinear motion of the tanker in waves) and associated sea-keeping characteristics in the seaway are estimated (Bhattacharya in Dynamics of marine vehicles, Wiley, New York, 1978). The approach adopted in this paper is unique in that it takes into account both voluntary and involuntary speed reductions of the ship. It helps in ship tracking by the optimum route using inverse velocity as the weight function for the path in an efficient way. Dijkstra’s algorithm [Numer Math 1(3):269–271, 1959] is applied in an iterative manner for determining the optimum track. The optimum track information has broad scope for use in modern shipping industry for obtaining safe and least-time routing by avoiding schedule delays with economic fuel consumption.     

Estimation of a constrained multinomial logit model

Identifying the set of available alternatives in a choice process after considering an individual’s bounds or thresholds is a complex process that, in practice, is commonly simplified by assuming exogenous rules in the choice set formation. The Constrained Multinomial Logit (CMNL) model incorporates thresholds in several attributes as a key endogenous process to define the alternatives choice/rejection mechanism. The model allows for the inclusion of multiple constraints and has a closed form. In this paper, we study the estimation of the CMNL model using the maximum likelihood function, develop a methodology to estimate the model overcoming identification problems by an endogenous partition of the sample, and test the model estimation with both synthetic and real data. The CMNL model appears to be suitable for general applications as it presents a significantly better fit than the MNL model under constrained behaviour and replicates the MNL estimates in the unconstrained case. Using mode choice real data, we found significant differences in the values of times and elasticities between compensatory MNL and semi-compensatory CMNL models, which increase as the thresholds on attributes become active.     

VirMaLab — atelier virtuel de maintenance: un outil d’aide à la décision pour l’optimisation des politiques de maintenance

This article deals with a generic approach called VirMaLab (virtual maintenance laboratory) for reliabilitybased maintenance modeling for complex systems (with multi-components and multi-states). Based on the probabilistic graphical models formalism (also known as Bayesian networks), this stochastic approach takes into account both the degradation process of the considered system (an original semi-Markovian model is proposed) and maintenance strategies (from diagnosis factors to all kinds of maintenance actions). For complete decision support tools, cost parameters should also be considered (maintenance actions, unavailability of the system, running, etc.). In this article, two applications of this approach to rail maintenance are introduced. The first one focuses on the optimization of the compromise refurbishment/repairing of central part of the RER A line. The second one focuses on the comparison and evaluation of various maintenance strategies in the modernization of the command control systems of Paris metro lines.     

Combined experimental and modeling methodology for intake line evaluation in turbocharged diesel engines

This paper presents a methodology for diesel engine intake line analysis that combines specific element tests and modeling. The purpose of this methodology is to determine the impact of intake lines, or newly designed intake elements, on the volumetric efficiency of internal combustion engines while avoiding expensive on-engine tests. For this research, the intake system is divided into several elements which are individually characterized using flow and impulse test rigs. Next, individual systems are modeled using a one-dimensional code. Finally, these component models are coordinated to provide an evaluation of the volumetric efficiency. Intake lines coming from two turbocharged diesel engines are used to illustrate the method. The model is validated by comparing the model results with the actual system performance evaluated in engine test cells. Discussions of the feasibility of the technique and on the impact of element model inaccuracies on the overall system model are provided.     

Torque ripple minimization control of permanent magnet synchronous motors for EPS applications

This paper identifies a control method used to reduce torque ripple of a permanent magnet synchronous motor (PMSM) for an electric power steering (EPS) system. NVH (Noise Vibration Harshness) is important for safe and convenient driving. Vibration caused by motor torque is a problem in column type EPS systems. Maintaining a very low torque ripple is one solution that allows for smoother steering. Theoretically, it is possible to design and drive the motor without torque ripple. However, in reality, a PMSM system torque ripple is caused by the motor itself (saturation in the iron core and EMF distortion) and the imperfect driver. This paper analyzes torque ripple of a PMSM system, and an advanced PMSM control method for the column typed EPS system is presented. Results of the analysis indicate that the compensation current is needed in order to minimize torque ripple when a PMSM is driven.     

Hydrodynamic characteristics of double permeable breakwater under regular waves

The wave transmission, reflection, and energy dissipation of the double vertical wall with permeable lower part (horizontal slots) were experimentally and theoretically studied under normal regular waves. The effect of different wave and structural parameters on the hydrodynamic characteristics was investigated e.g. the wave length, the upper part drafts, the lower part porosities, and the space between the double walls. Also, the theoretical model based on an EigenFunction Expansion Method was developed to study the hydrodynamic breakwater performance. In order to examine the validity of the theoretical model, the theoretical results were compared with the present experimental results. Comparison between experiments and predictions showed that theoretical model provides a good estimate to the wave transmission, reflection, and energy dissipation coefficients when the friction factor f = 3. The hydrodynamic efficiency of the proposed breakwater is strongly affected by changing the following: (1) The two upper part drafts together, (2) The upper part draft of the first barrier, (3) The two lower part porosities together, (4) The lower part porosity of the first barrier.     

Influence of pilot injection on combustion characteristics and emissions in a DI diesel engine fueled with diesel and DME

This work experimentally investigates how the dwell time between pilot injection and main injection influences combustion and emissions characteristics (NOx, CO, THC and smoke) in a single-cylinder DI diesel engine. The experiments were conducted using two fuel injection systems according to the fuel type, diesel or dimethyl ether (DME), due to the different fuel characteristics. The injection strategy is accomplished by varying the dwell time (10°CA, 16°CA and 22°CA) between injections at five main injection timings (?4°CA aTDC, ?2°CA aTDC, 0°CA aTDC, 2°CA aTDC and 4°CA aTDC). Results from pilot-main injection conditions are compared with those shown in single injection conditions to better demonstrate the potential of pilot injection. It was found that pilot injection is highly effective for lowering heat-release rates with smooth pressure traces regardless of the fuel type. Pilot injection also offers high potential to maintain or increase the BMEP; even the combustion-timing is retarded to suppress the NOx emission formation. Overall, NOx emission formation was suppressed more by the combustion phasing retard effect, and not the pilot injection effect considered in this study. Comparison of the emissions for different fuel types shows that CO and HC emissions have low values below 100 ppm for DME operation in both single injection and pilot-main injection. However, NOx emission is slightly higher in the earlier main injection timings (?4°CA aTDC, ?2°CA aTDC) than diesel injections. Pilot injection was found to be more effective with DME for reducing the amount of NOx emission with combustion retardation, which indicates a level of NOx emission similar to that of diesel. Although the diesel pilot-main injection conditions show higher smoke emission than single-injection condition, DME has little smoke emission regardless of injection strategy.     

Model for dynamic behavior of the crankshaft of an air cooled diesel engine subjected to severe functioning

The dynamic behavior of the engine organs in severe conditions is complicated to identify. In this paper, the dynamic behavior of the crankshaft of the diesel engine Deutz F8L413 direct injection-type air cooled in the severe operating conditions is investigated in a 3D global model. The maximum operating characteristics of the engine are experimentally measured on a bench test equipped with a hydraulic brake. The most stressed areas of the crankshaft are determined by numerical simulations. In addition, an analysis of the fatigue behavior of the crankshaft is carried out by using two fatigues criteria. The efficiency of the model is demonstrated by comparing between the numerical results and the experimental data obtained with the natural modes of vibration test.