The Demise of a Tropical Coastal Lagoon as Breeding Habitat for Ground-Nesting Waterbirds: Unintended,but Anticipated Consequences of Development

Laguna Cuyutlán (Colima, Mexico), an Important Bird Area, used to provide breeding habitat for ground-nesting waterbirds. During 2014 and 2015, nesting efforts of laughing gull, black skimmer, and royal, gull-billed and Forster's terns failed almost completely due to inundation, while least terns and snowy plovers fared the same during 2014. No anomalies in rainfall, tidal level, or coseismic subsidence explained such failure. Rather, the inundations were due to the enlarging of Canal Tepalcates that connects the lagoon with the sea, which was widened from 100 to 300 m and dredged to 17-m deep. Before this, the hydrodynamics were regulated by evaporation and runoff. Now, increased seawater volumes dominate the basin's hydrodynamics. The failure of Laguna Cuyutlán as a breeding habitat for these birds is an important threat for these species, as this lagoon held one of the < 20 colonies known for several of these species along the western coast of North and Central America. Documenting this demise of Laguna Cuyutlán for ground-nesting waterbirds transcends the regional scale as it emphasizes the little consideration still given to biodiversity vs. economic development, and is a warning for coastal projects in other developing areas of the world.     

Estimating travel time functions for urban roads: options and issues

Travel time functions specify the relationship between the travel time on a road and the volume of traffic on the road. Until recently, the parameters of travel time functions were rarely estimated in practice; however, a compelling case can be made for the empirical examination of these functions. This paper reviews, and qualitatively evaluates, a range of options for developing a set of travel time functions. A hierarchy of travel time functions is defined based on four levels of network detail: area, corridor, route and link. This hierarchy is illustrated by considering the development of travel time functions for Adelaide. Alternative sources of data for estimating travel time functions are identified.

In general, the costs and benefits increase as the travel time functions are estimated at finer levels of network detail. The costs of developing travel time functions include data acquisition costs and analysis costs. The benefits include the potential for reducing prediction errors, the degree of application flexibility and the policy sensitivity of the travel time functions.     

Public transit subsidies, output effect and total factor productivity

This paper extends previous works on total factor productivity decomposition when firms receive both operating and capital subsidies. It shows that previous works considered either the lump-sum or substitution effects of these subsidies but not together. Using constrained cost minimization as the framework it offers formal proofs to show that cost increases are inevitable if the total effects of the subsidies are considered, and that total factor productivity growth results from increasing amounts of subsidies under economies of scale and in the absence of technical change. Applications of the decomposition equations derived to a sample of transit systems finds near constant returns to scale and negative contributions of these subsidies to total factor productivity growth. Technical change reverses this decline and results in total factor productivity growth. Further, it finds that the lump-sum effects of the subsidies reduce total factor productivity more than does the substitution effect.     

Model-based analysis of the mechanical subsystem of an air brake system

Most commercial vehicles such as buses and trucks use an air brake system, often equipped with an S-cam drum brake, to reduce their speed and/or to stop. With a drum brake system, the clearance between the brake shoe/pad and the brake drum may increase because of various reasons such as wearing of the brake shoe and/or brake drum and drum expansion caused by high heat generation during the braking process. Hence, to ensure proper functioning of the brake system, it is essential that the clearance between the brake shoe and the brake drum is monitored. In this paper, we present a mathematical model for the mechanical subsystem of the air brake system that can be used to monitor this clearance. This mathematical model correlates the push rod stroke transients and the brake chamber pressure transients. A kinematic analysis and a dynamic analysis of the mechanical subsystem of the air brake system were performed, and the results are corroborated with experimental data.     

Cycle-simulation turbulence modelling of IC engines

Numerical simulations of IC engines are of high interest for automotive engineers worldwide. The simulation models should be as fast as possible, low-computational effort and predictive tool. The correct prediction of turbulence level inside the combustion chamber of spark ignition engines is the most important factor influencing to the engine working cycle. This paper presents a development of the k-ε turbulence model applied to the commercial cycle-simulation software with the high emphasis on the intake part. The validation was performed on two engine geometries with the variation of engine speed and load comparing the cycle-simulation results of the turbulent kinetic energy and in-cylinder temperature with 3-D CFD results. In order to apply the cycle-simulation turbulence model for the simulation of entire engine map, the parameterization model of turbulence constants was proposed. The parameterized turbulence model was optimized using NLPQL optimization algorithm where the single set of turbulence model parameters for each engine was found. A good agreement of the turbulent kinetic energy during the expansion was achieved when the turbulence affects the flame front propagation and combustion rate as well.     

Modelling and control of a new differential steering concept

This paper presents a new steer-by-wire concept using an all-wheel drive vehicle layout with in-wheel motors while completely omitting the application of any dedicated steering device. Steering is based on the so-called differential steering principle which generates the necessary steering moment about the kingpins by a traction force difference between left and right sides of the vehicle. In order to investigate the behaviour of the vehicle and to design the underlying control algorithms, a planar vehicle model is presented, where the vehicle is described as constrained non-holonomic system requiring a special treatment. A state feedback linear controller for controlling of the lateral dynamics of the vehicle at higher speeds and a simple PI angle controller for low-speed manoeuvring are developed. The resulting behaviour of the system is investigated by various simulation experiments demonstrating a comparable steering performance of the new steering concept as that of conventional passenger cars.     

Route choice of cyclists in Zurich

This paper presents the first route choice model for bicyclists estimated from a large sample of GPS observations and overcomes the limitations inherent in the generally employed stated preference approach. It employs an improved mode detection algorithm for GPS post-processing to determine trips made by bicycle, which are map matched to an enriched street network. The alternatives are generated as a random sample from an exhaustive, but constrained search. Accounting for the similarity between the alternatives with the path-size factor the MNL estimates show that the elasticity with regards to trip length is nearly four times larger than that with respect to the share of bike paths. The elasticity with respect to the product of length and maximum gradient of the route is small. No other variable describing the routes had an impact. The heterogeneity of the cyclists is captured through interaction terms formulated on their average behaviour.     

Estimation of the effects of aircraft noise on residential satisfaction

This study assesses the effects of aircraft noise on residential satisfaction, an important indicator of subjective well-being. A structural equation model is specified that estimates the relationships between objective variables, noise annoyance variables and residential satisfaction. Secondary data-analysis is used to estimate the model. The survey was conducted in 1996/1997 among the population living within a 25-km radius of Amsterdam Schiphol, the largest airport in the Netherlands. The effect of aircraft noise annoyance is found to be relatively small. In addition, the objective level of aircraft noise exposure is found to be a better predictor of residential satisfaction than its subjective counterpart. The most important determinants of residential satisfaction are found to be road traffic noise annoyance, age and neighbor noise annoyance.     

Review of flywheel based internal combustion engine hybrid vehicles

Hybrid vehicles of different configurations and utilizing different energy storage systems have existed in development for many decades and more recently in limited production. They can be grouped as parallel, series or complex hybrids. Another classification is micro, mild and full hybrids which makes the distinction on the basis of functionality. The common energy storage systems in hybrid vehicles are batteries, supercapacitors and high speed flywheels. This paper aims to review a specific type of hybrid vehicle which involves the internal combustion engine (ICE) as the prime mover and the high speed flywheel as an energy storage device. Such hybrids are now attracting considerable interest given their potential for low cost. It is hence timely to produce a review of research and development in this subject. The flywheel is coupled to the drive line with a continuous variable transmission (CVT). The CVT can be of various types such as electrical, hydraulic or mechanical but usually in this case it is a non-electrical one. Different configurations are possible and the paper provides a timeline of the development of such powertrains with various examples. These types of hybrid vehicles have existed as prototypes for many decades and the authors believe that their development has reached levels where they can be considered serious contenders for production vehicles.     

Finite element modeling of static tire enveloping characteristics

To investigate static tire enveloping characteristics, a three dimensional (3-D) finite element model is proposed. The vertical stiffness of the tire is studied on a flat surface with and without cleat. Tire rubber materials and cord layers are represented independently using “rebar” elements available in MSC Marc Mentat. Comparisons of numerical and experimental results are given to show the validity of the proposed model. It is shown that after a certain displacement, the results of the proposed model agree well with experimental results. In addition, the model results show that regardless of the type of the cleat placed under the rim center (hub center), all vertical force curves intersect after a certain displacement, which indicates typical static enveloping characteristics. Moreover, another typical characteristic of the radial tires that is unlike those of bias-ply constructions confirms that the contact patch does not expand laterally after a level vertical load is applied to the tire, which is directly related to fuel consumption and tire tread life.