An exploratory analysis of observed and latent variables affecting intercity train service quality in developing countries

Transportation - Service quality (SQ) and customer satisfaction as perceived by 1037 passengers on intercity train services in Bangladesh were examined using structural equation modeling to explain...     

Practical Frequency and Time Optimal Design of Passive Linear Vibration Isolation Mounts

Summary In this paper we examine a linear one-degree of freedom vibration isolator mount. The linearity of the system allows us to analyze its frequency and time response characteristics analytically. Optimal damping and stiffness values for the isolator are obtained by minimizing certain cost functions, which are the Root Mean Square (RMS) of the absolute acceleration and the relative displacement. These RMS cost functions are used to create a design chart for the isolator parameters. This is very useful particularly in the presence of physical constraints such as a limit in relative displacement. The time response of the system for a unit step input is also considered to gain an insight into the transient characteristics of the system. We obtain an optimal value for the damping ratio of the system in order to minimize the transmitted acceleration. Combining the frequency and time response analyses leads to an optimal value for the mount natural frequency and damping ratio satisfying both time and frequency domains. The results are verified numerically using measured acceleration as input.     

Deep water mass characteristics and interannual variability in the North and Central Aegean Sea

The characteristics and interannual variability of the deep water masses in the North and Central Aegean Sea are being investigated through the data sets of the Hellenic Navy Hydrographic Service (HNHS) and the MEDATLAS 1997 project. In the period between 1987 and 1993, the densest deep water in the Mediterranean has been produced in the Aegean Sea (with σ_θ densities reaching up to 29.6 kg/m³), contributing to what has been called the Eastern Mediterranean Transient. The examination of time series of mean integrated values of θ, S and σ_θ below the depth of 500 dbar reveals the significant deep water density increase after 1987 in all of the deep basins in the area. Data suggest that the density increase of 1987–1988 is mainly attributed to a temperature drop, while in 1993, an even more intense density increase is observed, characterized this time by an abrupt salinity increase. We assume that the increased salinity necessary to produce deep water masses with the observed characteristics was not locally produced but rather advected from the Levantine through the South Aegean. After 1993, no new deep water formation episodes have been observed. A series of Θ–S diagrams derived from HNHS CTD casts covering the period between 1993 and 2000, depict the different characteristics of the deep water masses in the area. As 1993 marks the end of the formation period, observed differences between basins in that year must be attributed to different deep water formation sites. Thereafter, the stagnating deep water in the North and Central Aegean basins has been slowly gaining buoyancy by losing salt and gaining heat. The rate at which this phenomenon takes place varies between different deep basins. It is suggested that these variations are linked to the different volumes of each basin as well as to the general circulation features of the Aegean Sea.     

The significance of the International Tribunal for the Law of the Sea for the shipping industry

The International Tribunal for the Law of the Sea (ITLOS) was established by the 1982 United Nations Convention on the Law of the Sea as a body to settle disputes between States Parties to the Convention regarding the interpretation or application of the Convention s provisions, including provisions concerning the exercise of the powers of States over shipping and the discharge by states of their responsibilities and obligations in relation to ships.ITLOS is competent to deal with disputes in which a State is alleged to have wrongly interfered with or otherwise restrained the operation of a vessel when it is in a port of the State or within the territorial sea or exclusive economic zone of the State.In its previous judgments, ITLOS has provided clarifications of some important areas of the law of the sea concerning the operation and regulation of shipping by flag States and other states.ITLOS plays a key role in the regime of the Law of the Sea Convention relating to the prompt release of ships and their crews that are arrested or detained in a foreign port.ITLOS also has the possibility to serve as ajudicial organ for the settlement of disputes under other maritime agreements and contracts, if the parties to the agreements or contracts agree to confer jurisdiction on it.There are many advantages to be gained by States and shipping operators from using ITLOS as the body for the settlement of disputes under agreements. These advantages include savings in time and expenses.     

Validation of a MATLAB Railway Vehicle Simulation Using a Scale Roller Rig

A 1/5 scale roller rig has been constructed for use in analysing the dynamic behaviour of railway vehicles. The roller rig includes a servo hydraulic system to allow a realistic input of track irregularities at the rollers and instrumentation is fitted to allow measurement of the position and acceleration of the bodies. This paper reports on the first stage in validating the behaviour of the roller rig using a relatively simple, linear computer model constructed in MATLAB. Initial results show good correlation between the behaviour seen on the roller rig and that predicted by the model.     

Underwater noise from maritime sources and impact on marine life

Underwater Sound is essential for marine animal functioning. Sound levels from human sources in the marine environment interfere with sound-mediated behaviour in marine animals when shipping coincides with areas or pathways that are vital for animal populations. The impact of human-generated underwater sound to ecosystem functioning and biodiversity receives increasing attention, although as yet it has not been included in the work of international organisations, such as the IMO. At MEPC 55 a document on ships striking whales was discussed; it was noted that disturbed whale hearing might hamper the recognition of a ship approaching.     

Quantifying copepod kinematics in a laboratory turbulence apparatus

We describe application of a new apparatus that permits simultaneous detailed observations of plankton behavior and turbulent velocities. We are able to acquire 3D trajectories amenable to statistical analyses for comparisons of copepod responses to well-quantified turbulence intensities that match those found in the coastal ocean environment. The turbulence characteristics consist of nearly isotropic and homogeneous velocity fluctuation statistics in the observation region. In the apparatus, three species of copepods, Acartia hudsonica, Temora longicornis, and Calanus finmarchicus were exposed separately to stagnant water plus four sequentially increasing levels of turbulence intensity. Copepod kinematics were quantified via several measures, including transport speed, motility number, net-to-gross displacement ratio, number of escape events, and number of animals phototactically aggregating per minute. The results suggest that these copepods could control their position and movements at low turbulence intensity. At higher turbulence intensity, the copepods movement was dominated by the water motion, although species-specific modifications due to size and swimming mode of the copepod influenced the results. Several trends support a dome-shaped variation of copepod kinematics with increasing turbulence. These species-specific trends and threshold quantities provide a data set for future comparative analyses of copepod responses to turbulence of varying duration as well as intensity.     

Shipping freight derivatives: a survey of recent evidence

In an industry that is characterized by highly volatile prices, seasonality, strong business cycles, cyclicality and capital intensiveness, risk management is extremely important. Ship-owners and charterers face enormous risks, which emanate from fluctuations in freight rates, bunker prices, interest rates, foreign exchange rates and vessel values. These risks substantially affect the interplay between revenue and cost. Modern risk management techniques, involve the use of financial derivatives products, some of which have been developed exclusively for protecting (hedging) against the adverse price fluctuations of the aforementioned sources of risk in shipping. By using derivatives products, ship-owners and charterers can secure (stabilize) the level of their future income or costs and thus reduce uncertainty and unforeseen volatility of their cash-flow. To explore the importance of hedging freight rate risk in shipping operations, a survey of recent empirical evidence that has appeared in economic studies has been conducted. Developments over the past 20 years have been fast, with certain amount of research carried, which has helped to understand better the special features of these derivatives markets. They are all summarized in the current study, which can provide the stepping stone for further work in the area of shipping derivatives and risk management in shipping.