Influence of shock absorber wearing on vehicle brake performance

In order to safely maintain a vehicle, it is necessary to verify the most important systems that affect safety during Periodic Motor Vehicle Inspections (PMVIs). In a previous paper, a test method and validation criteria were suggested by the authors to verify shock absorber status during PMVIs, as they are a fundamental component that may wear out during a vehicle’s life. In this paper, variations of the performance of the vehicle’s brakes resulting from shock absorber wearing have been analyzed, in order to confirm whether the suggested criteria is valid for taking into account longitudinal forces and pitch movement on the vehicle. A simulation-based study was conducted with several configurations of a worn damper on a vehicle driving on two virtual roads: smooth and undulating. The results confirmed that the damping coefficient established as an acceptable value to verify the shock absorber status in PMVIs is also valid considering the forces involved in a braking maneuver.     

Effect of intake valve swirl on fuel-gas mixing and subsequent combustion in a CAI engine

A fully three-dimensional model was used to investigate the optimal value for intake valve lift in a CAI engine. Uniform mixing in the engine is a key parameter that affects the auto-ignition reliability and thermal efficiency. The method of intake of the air supply often determines the uniformity (or quality) of the fuel-air mixture. In this paper, four strategies were applied for controlling the swirl intensity of intake air. The variation of the intake valve lift induces different swirling and tumbling intensities. Both experimental data and 1D WAVE software (Ricardo, Co.) were coupled with the 3D model to provide pressure and temperature boundary conditions. The initial condition of the EGR mass fraction was also provided by the 1D model. The benchmark scenario (Case 1) was considered as a valve lift with 2 mm for all intake valves. We found that an intake valve lift of 6 mm with the other intake valve closed (i.e., Case 5) yielded the largest swirling (helical motion in the axial direction) and tumbling, which in turn rendered optimal fuel-gas mixing. We also found that fuel distribution affected the auto-ignition sites (or spot). The better the mixing, the greater the gas temperature and combustion efficiency achieved, as seen in Case 5. The NOx level, however, was increased due to the gas temperature. The optimal operating condition is selected from the viewpoints of environmental protection and combustion efficiency.     

Type synthesis of function-generating mechanisms for seat suspensions

Mechanisms with “negative” stiffness are a unique tool used to significantly improve vibration isolation for a vehicle driver via upgrade of the seat suspension. However, connection of such mechanisms to the suspension results in errors in the function generation process, and in most cases, makes motion impossible. An approach to type synthesis is presented in order to make this process more predictable, easy and thus more practical for the upgrade process. Structural classification of the suspensions is presented, and -an atlas of function-generating mechanisms for suspensions that reveals the effect of “negative” stiffness is completed. All of the function-generating mechanisms appear in the atlas as result of enumeration. Structural properties of novel and existing mechanisms are compared. Finally, some advantages in practical use of novel suspensions with “negative” stiffness are illustrated.     

When strike comes to town… anticipated and actual behavioural reactions to a one-day,pre-announced,complete rail strike in the Netherlands

We conducted secondary analysis on data collected among rail users, days before and after a national rail strike in the Netherlands. Our aim was to compare anticipated and actual behavioural reactions to the rail strike, investigate associations with traveller and trip characteristics, and perceived behavioural control and satisfaction with the chosen alternative. Forty-four percent of the people who had anticipated to travel by train on the day of the strike abandoned their trip, 24% switched to car as driver, 14% switched to another mode (as passenger), 18% stayed with the train and rescheduled the planned activity to another day. Almost half of people who had anticipated travelling by car expected to change behaviour as well. Multinomial logistic regression showed low preference for car among rail users. Considerable marginal effects were found for several variables, e.g.: young people and females were less likely to switch to car; short and middle distance trips were less likely abandoned or switched to another day; commute and business trips were more likely done by car, and business trips less likely cancelled. Despite high levels of perceived behavioural control and satisfaction with the chosen alternative, permanent modal shift as result of this strike is not expected.     

Ranking of factors contributing to higher performance in the ocean transportation industry: a multi-attribute utility theory approach

Ocean transportation has been mainly studied from an economic and strategic point of view. This paper adopts an operations management approach aiming at the identification of the value-adding attributes that characterize the ocean transportation industry. This is achieved by using Johansson et al.'s 1 four value metrics—service, quality, cost, time—which are used for the identification of the contribution that different factors make to the total created value. In this paper, multi-attribute utility theory (MAUT) has been used to measure and compare the value of different processes of various sectors of the ocean transportation industry. The application of MAUT methodology is illustrated with an example from the four sectors of the industry: liner, dry bulk, liquid bulk and specialized. Results suggest that there is strong emphasis placed by ocean transportation companies on quality and that there is differentiating importance put on service and cost by different sectors. Time is seen as the lowest value contributor by all four sectors of the surveyed companies.     

Do observations adequately resolve the natural variability of oceanic turbulence?

Especially in high Reynolds number, naturally-occurring flows, turbulence is a highly variable process. It is challenging to measure yet it is vital that we do so in order to quantify the internal transports of mass, nutrients, energy and momentum. Isolated turbulence profiles are difficult to interpret; systematic sampling and subsequent averaging are necessary. Confidence in our ability to properly sample turbulence arises from intergroup comparisons, comparisons with other methods to assess mixing coefficients and, most fundamentally, the constraints imposed by the governing fluid dynamics on both energy losses via viscous dissipation caused by turbulence and on the mixing that results from turbulence. Several examples in which fluid processes have been isolated from the full range of oceanic motions are reviewed in this light. These examples show how observationally-derived estimates of turbulence dissipation or mixing are consistent with larger scale constraints. The larger oceanographic problem of defining the full geographic variability of mixing remains.     

Fatigue analysis of butt welded AH36 steel joints: Thermographic Method and design S–N curve

The traditional methods of fatigue assessment of welded joints have some limitations, and are extremely time consuming. In order to overcome these difficulties, the Thermographic Method (TM), based on thermographic analyses, has been applied to predict the fatigue behaviour of butt welded joints, made of AH36 steel, largely used in shipbuilding. Experimental tests have been carried out to assess the fatigue capability in terms of S–N curves and fatigue limits. The predictions of the fatigue capability obtained resorting to the Thermographic Method show a good agreement with those derived from the traditional procedure. Moreover, the fatigue design recommendations were compared to the experimental data in order to analyse the reliability of the codes.     

Recent sedimentary study of the shelf of the Basque country

The Northern Iberian margin of the Spanish Basque country (provinces of Gipuzkoa and Viscaia) is characterized by a narrow continental platform, which receives inputs of riverine particulate matter from the numerous riverine systems located within the Basque country. This particulate matter is subsequently deposited within the Bay of Biscay, and Gouf de Capbreton [Frouin, R., Fiuza, A.F.G., Ambar, I., Boyd, T.J., 1990. Observations of a poleward surface current off the coasts of Portugal and Spain during winter. Journal of Geophysical Research 95 (C1), 679–691]. The main goal of this study is to establish a map of the surface sediment distribution of the Basque continental shelf and more specifically to map the muddy patch located at the eastern side of that continental shelf.Three oceanographic cruises were conducted in 2003 and 2004. From these campaigns 340 surface samples, 12 short cores and 3 gravity cores have been collected over the mid and outer shelf from depths ranging between 50 m and 150 m deep. 3 seismic profiles were obtained across the shelf mud patch using a Sparker device.Sediment grain-size analyses were performed by the classical physical method of sieving and use of settling columns. The POC (Particular Organic Carbon) amounts in sediment and water samples were determined using the Strickland and Parsons' method [Strickland, J.D.H., Parsons, T.R., 1972. Determination of particulate carbon. In : A practical handbook of seawater analysis. Fisheries ResearchBoard of Canada, Ottawa, pp. 207−211] as adapted by Etcheber [Etcheber, H., 1981. Comparaison des diverses méthodes d'évaluation des teneurs en matières en suspension et en carbone organique particulaire des eaux marines du plateau continental aquitain. Journal de Recherche Océanographique VI (2), 37−42]. Radioisotopic measurements (²¹⁰Pb_exc) were made using a semi-planar germanium detector coupled to a multichannel analyser. Radiographical analysis was performed with an X-ray equipment (SCOPIX®) coupled with a radioscopy instrumentation and processing unit.Firstly, a detailed sedimentological map of this shelf has been produced and secondly, geophysical surveys have precisely mapped the geometry of the main mud patch on the continental shelf. In the mud patch itself the rates of sedimentation are between 0.13 and 0.50 cm yr^− 1. The maximum rate of sedimentation is located in the central mud patch, whereas the minimum rate of deposition occurs close to the rocky outcrops. These results seem to be in agreement with the estimation of the total thickness of the mud patch revealed by seismic profiles. The central part corresponds to the maximum thickness of 7 m.Interpretations of the associated oceanic current forcing factors (current direction, wave fetch and wind directional modes) relating to the identified sediment depositional zones are also undertaken.     

Multi‐criteria analysis for evaluating the impacts of intelligent speed adaptation

Road safety is a policy priority due to the high casualties and costs associated with road accidents. Since speed is a major cause of road accidents, in‐vehicle speed limiters or Intelligent Speed Adaptation (ISA), seems a promising solution. ISA implementation, however, is hindered by large uncertainties, for example about the impacts of ISA, the way users might respond to ISA, and the relationship between speed and accidents. Traditional Multi‐Criteria Analysis (MCA) has limitations in handling these uncertainties. We present an MCA approach based on exploratory modeling, which uses computational experiments to explore the multiple outcomes of ISA policies (safety, emissions, throughput, and cost) across a range of future demand scenarios, functional relationships for performance criteria, and user responses to ISA. As an illustration, by testing the impacts of different ISA penetration levels on two driver groups, we show that when compliance with ISA is expected to be low, a policy aimed only at novice drivers outperforms other ISA policies on safety improvement.