A Low-Cost Transfer Function Identification Technique for Automotive Suspensions

An alternative technique for identifying the transfer function of automotive suspension systems is presented in this paper. The method establishes a frequency response from which the transfer function can be determined by using a low cost test rig developed for the purpose. This results in a transfer function matrix which can include asymmetry in the suspension, tyre stiffness and damping. The technique is validated by comparing results for a two-wheeled trailer with those obtained on a conventional hydraulic test rig. Results from this procedure may be used to evaluate passive or active suspension systems or to feed into a suspension modelling process for such purposes as active suspension control strategy development.     

Increasing the capacity of an isolated merge by metering its on-ramp

Measurements taken downstream of freeway/on-ramp merges have previously shown that discharge flow diminishes when a merge becomes an isolated bottleneck. By means of observation and experiment, we show here that metering an on-ramp can recover the higher discharge flow at a merge and thereby increase the merge capacity. Detailed observations were collected at a single merge using video. These data revealed that the reductions in discharge flow are triggered by a queue that forms near the merge in the freeway shoulder lane and then spreads laterally, as drivers change lanes to maneuver around slow traffic. Our experiments show that once restrictive metering mitigated this shoulder lane queue, high outflows often returned to the median lane. High merge outflows could be restored in all freeway lanes by then relaxing the metering rate so that inflows from the on-ramp increased. Although outflows recovered in this fashion were not sustained for periods greater than 13 min, the findings are the first real evidence that ramp metering can favorably affect the capacity of an isolated merge. Furthermore, these findings point to control strategies that might generate higher outflows for more prolonged periods and increase merge capacity even more. Finally, the findings uncover details of merge operation that are essential for developing realistic theories of merging traffic.     

A statistical investigation of time-variant hull girder strength of aging ships and coating life

Risk- and reliability-based approaches are increasingly being applied in assisting inspection and maintenance planning. One of the keys to such approaches is properly predicting the hull girder strength (HG) of gradually degradated hull structures. The development has been limited by the lack of data on aging ships—validation of the developed methods has not been possible. To fill the gap of knowledge on hull strength of ships in service, this paper presents a database of as-gauged hull structures and a statistical study of the time-variant HG of tankers. The expanded data set was collected from 2195 as-gauged girth belts (transverse sections) of 211 single-hull tankers that were 12–32 years old. It was intended to (1) provide actual data on hull girder section modulus (HGSM) of tankers, (2) investigate the general trends of the change in the HG over ships’ service life, and (3) propose formulations for presenting time-variant HGSM and coating life.

The data set demonstrated a high variation of HGSM that changed over time. The mean value and standard deviation of HGSM loss were derived as functions of time. The probability density function (pdf) of coating life was also derived. Comparisons were made between previous studies on HG and the current data set. It was found that almost all previous studies showed much greater HG loss than what this database revealed. The refinement of existing calculations appears to be needed. The data set and statistical study were expected to form the basis for validating formulations of HG that are key components in risk- and reliability-based approaches.     

Characterizing European high speed train stations using intermodal time and entropy metrics

This paper presents a quantitative method for characterizing high speed train stations in terms of passenger intermodality. The aim of the procedure is two-fold: firstly, the method is to be used as an objective measure for comparing stations in order to detect suboptimal points and improve the performance of stations as nodal points; secondly, the method provides a means to embed intermodality into regional accessibility models, allowing comprehensive modelling at lower scales. The empirical base of the work comprises data from 27 European high speed rail stations, which is deemed an appropriate statistical sample for the whole European rail network. Using the entropy metric, we found that several different patterns emerged: there was a clear hierarchy of stations which was linked to their respective roles within the system, while strong constraints impeded stations from performing optimally as true intermodal nodes.     

Postembryonic stages of Nucellicola holmanae Lamb et al., 1996 (copepoda, poecilostomatoida), an endoparasite of the dog whelk Nucella lapillus (gastropoda)

The external morphology of the first three larval stages of Nucellicola holmanae is described. These stages were cultured from eggs found with the adults in the viscera of dog whelks collected from Robin Hood's Bay, North Yorkshire. The nauplius develops within the whelk. It moults to a metanauplius which is released as a free-swimming stage. The metanauplius moults to a free copepodid stage which exhibits a combination of characters typical of the first, second and third copepodid stages of other poecilostomatoid copepods. The infective copepodid stage which locates and penetrates the host is visible through the integument of this free-swimming copepodid.     

An object-oriented approach to transport modelling: Software development to calculate road traffic noise

A framework for developing object-oriented software in transport modelling in proposed and demonstrated with the implementation of the calculation of road traffic noise (CORTN). Major tasks in the life cycle of an object-oriented development process are identified, and illustrated with the implementation of TRANSOOP – a software library containing 33,000 lines of C++ programming code. Software re-use from this library to produce a object-oriented noise program is compared with conventional computer programming shows that almost 90 per cent of the lines of code were drawn from TRANSOOP. Advantages of the object-oriented approach are discussed.     

Characteristics and potential impacts of under-ice river plumes in the seasonally ice-covered Bothnian Bay (Baltic Sea)

The northernmost basin of the Baltic Sea, the Bothnian Bay, is ice-covered for about half the year. During this time, distinct under-ice river plumes develop, even seaward of the smallest rivers, that are substantially thicker and larger in extent than during the summer months. Wind mixing is negligible, and during late spring in April or May, the highest annual discharge occur while the sea is ice covered, thus providing conditions for the formation of extensive under-ice plumes. These plumes are characterised by high levels of trace elements (e.g., Al, Fe and Zn), organic matter (TOC and dissolved organic carbon [DOC]), nutrients and also optically active substances (colored dissolved organic matter, CDOM). The under-ice plumes provide an important pathway for undiluted transport of land-derived substances to the pelagic waters of the basin, affecting the salinity, chemistry and optical properties of coastal waters. Freshwater ice growth on the underside of an existing sea ice sheet also restricts the buildup of sea ice and under-ice algal communities, potentially in large areas along the coasts. Plume water influences the optical characteristics of coastal waters for a period of time after ice break-up, potentially affecting primary production in these areas. Furthermore, the formation of under-ice plumes potentially has a positive feedback on the ice season length due to freshening of the coastal waters (earlier freeze-up) and restricted oceanic heat flux (slower melting).     

Macroscopic location models revisited

Recent developments in residential location choice models have considered the individual as the basic unit of analysis and have attempted to model the actual choice process used by individuals in selecting residential location sites. This paper demonstrates that the choice model derived from these studies is a more general form of many macroscopic models of location used in the past. The prime difference between the two classes of model is seen to be the much wider range of factors and geographic settings which can be accounted for in disaggregate behavioural models of residential location choice.