The structure of dissipation in the western Irish Sea front

We report on an intensive campaign in the summer of 2006 to observe turbulent energy dissipation in the vicinity of a tidal mixing front which separates well mixed and seasonally stratified regimes in the western Irish Sea. The rate of turbulent dissipation ε was observed on a section across the front by a combination of vertical profiles with the FLY dissipation profiler and horizontal profiles by shear sensors mounted on an AUV (Autosub). Mean flow conditions and stratification were obtained from a bed mounted ADCP and a vertical chain of thermistors on a mooring. During an Autosub mission of 60 h, the vehicle, moving at a speed of ~ 1.2 m s^− 1, completed 10 useable frontal crossings between end points which were allowed to move with the mean flow. The results were combined with parallel measurements of the vertical profile of ε which were made using FLY for periods of up to 13 h at positions along the Autosub track. The two data sets, which show a satisfactory degree of consistency, were combined to elucidate the space–time variation of dissipation in the frontal zone. Using harmonic analysis, the spatial structure of dissipation was separated from the strong time dependent signal at the M₄ tidal frequency to yield a picture of the cross-frontal distribution of energy dissipation. A complementary picture of the frontal velocity field was obtained from a moored ADCP and estimates of the mean velocity derived from the thermal wind using the observed density distribution. which indicated the presence of a strong (0.2 m s^− 1) jet-like flow in the high gradient region of the front. Under neap tidal conditions, mean dissipation varied across the section by 3 orders of magnitude exceeding 10^− 2 W m^− 3 near the seabed in the mixed regime and decreasing to 10^− 5 W m^− 3. in the strongly stratified interior regime. The spatial pattern of dissipation is consistent in general form with the predictions of models of tidal mixing and does not reflect any strong influence by the frontal jet.     

Working on the train: from ‘dead time’ to productive and vital time

The conventional approach to the study of travel time is to see it as ??dead time??, i.e. time that should be minimized. In this paper, we study time-use on trains, especially in relation to the use of information and communication technology for work purposes. The empirical results are based on a survey of rail travellers in Norway in 2008. It was found that a high proportion of ordinary commuters and business people work on board while travelling by train, i.e. 35?% of commuters and 43?% of business people. Nearly every fourth commuter gets their travel time approved as working hours. Most respondents had some sort of electronic device with them on board, and 25?% travelling for work-related purposes use a laptop computer. Only 10?% report that their travel time is of no use. Knowledge of how travel time is utilized is indispensable in the discussion about the evaluation of travel time in cost-benefit analysis. The use of travel time can also be important for choice of transport mode in the assessment of travel time versus work options.     

Overview of new technology information systems for public transport passengers in French towns

Cost–benefit analysis (CBA) for transport investments is particularly useful for situations where a large number of investments have to be ranked against each other. This study draws on experiences from the development of the Swedish National Transport Investment Plan 2010–21. We study how CBA results were used in the process of shaping the investment plan and what influence they had on investment decisions. In particular, we compare the planners' rankings versus the politicians' rankings. We find that planners' rankings of investments are influenced by benefit–cost ratios (BCRs), in particular for low and moderate BCRs, while the politicians' rankings are not. By interviewing planners about how CBA was used in the process, we clarify what role CBA actually played in the planning process. We find that not only did the CBAs play a role in investment selection, they also forced investment design to be more cost-efficient. Furthermore, we explore planners' implicit valuations, as revealed by their investment selection, finding that freight benefits were implicitly valued higher and traffic safety lower than the officially recommended CBA weights. Finally, we identify the most important areas for improvement of CBA state-of-practice methodology.     

Non-Linear Behavior of a Rubber Isolator System Using Fractional Derivatives

A non-linear rubber isolator included in a dynamic system is examined where influences of dynamic amplitude and frequency are investigated through measurements and modeling. The frequency dependence of the isolator is modeled by a fractional calculus element while a frictional component accounts for its amplitude dependence. The model works in the time-domain and simulations of harmonic and non-harmonic motion are compared to measurements. Good agreement is obtained in a wide frequency and amplitude range for a freely oscillating one degree of freedom system, with the isolator acting as a coupling between exciting foundation and mass, and for a single isolator showing the typical amplitude dependence known as the Payne effect. The model is found to be superior to the commonly applied Kelvin-Voigt element in modeling the dynamic isolator properties.     

Transport telematics in urban systems-a backcasting Delphi study

This paper includes a presentation of the results from a scenario study on transport telematics in urban passenger transport. An international Delphi panel of 100 experts from 20 countries replied to questions on the feasibility and impact of a restricted number of different technical scenarios. The results show that most experts see substantial potential for limiting certain transport problems if there is broad implementation of transport telematics as described in this study. The majority of experts favoured a scenario based on extended public transport information. In that scenario, environmental gains were in practice paid for in terms of less comfortable trips and longer travel times.