The federal republic of Germany: the federal ministry of transport

The continued liberalization of the airline market in the European Community offers the prospect of competition in terms of price, frequency of service and many other attributes. Understanding these factors that influence passenger demand and incorporating them into a demand function poses a substantial theoretical and empirical challenge. A basis for estimating demand functions is the logit model. This paper examines the value of a logit share model in explaining how the share of airlines between airports varies as a function of measured and unmeasured attributes. It shows how demand functions are necessary for understanding a competitive market and evaluates the progress to date in identifying accurate coefficients of the logit function.     

Book reviews

The European Community Transport Policy: Towards a Common Transport Policy. By Jurgen Erdmenger (Gower Publishing Co. 1984) [Pp. 155.] £14.50.

Transport Reform: Changing the Rules. By Stephen Plowden. P.S.I. No. 642 (London: Institute, 1985.) [Pp. 250.] £6.50. ISBN 0–85374–258–8.

The Atlas of British Railway History. By Michael Freeman and Derek Aldcroft (London: Croom Helm, 1985.) [Pp. 128.] £12.95.

Losing Track. By Kerry Hamilton and Stephen Potter (Routledge & Kegan Paul in association with Channel Four, 1985.) [Pp. viii + 152.] £7.95. Paperback.     

International Symposium on the Ice Carrying Trade at Sea

Overmanning and restrictive labour practices are major causes of low productivity in Indian ports. Proposals are put forward for a programme of reforms to support investment in modern cargo handling systems.     

Novel experimental strategy for high resolution AFM imaging of membrane-associated bacterial toxins

Bacterial pore-forming toxins （PFTs） are essential virulence factors of many human pathogens. Knowl- edge of their structure within the membrane is critical for an understanding of their function in pathogenesis and for the development of useful therapy. Atomic force microscopy （AFM） has often been employed to structurally interrogate many membrane proteins, including PFTs, owing to its ability to produce sub-nanometer resolution images of samples under aqueous solution. However, an absolute prerequisite for AFM studies is that the samples are single-layered and closely-packed, which is frequently challenging with PFTs. Here, using the prototypical member of the cholesterol-dependent cytolysin family of PFTs, perfringolysin O （PFO）, as a test sample, we have developed a simple, highly robust method that routinely produces clean, closely-packed samples across the entire specimen surface. In this approach, we first use a small Teflon well to prepare the supported lipid bilayer, remove the sample from the well, and then directly apply the proteins to the bilayer. For reasons that are not clear, bilayer preparation in the Teflon well is essential. We anticipate that this simple method will prove widely useful for the preparation of similar samples, and thereby enable AFM imaging of the greatest range of bacterial PFTs to the highest possible resolution.     

Robust traffic assignment model: Formulation,solution algorithms and empirical application

ABSTRACT

The deterministic traffic assignment problem based on Wardrop's first criterion of traffic network utilization has been widely studied in the literature. However, the assumption of deterministic travel times in these models is restrictive, given the large degree of uncertainty prevalent in urban transportation networks. In this context, this paper proposes a robust traffic assignment model that generalizes Wardrop's principle of traffic network equilibrium to networks with stochastic and correlated link travel times and incorporates the aversion of commuters to unreliable routes.

The user response to travel time uncertainty is modeled using the robust cost (RC) measure (defined as a weighted combination of the mean and standard deviation of path travel time) and the corresponding robust user equilibrium (UE) conditions are defined. The robust traffic assignment problem (RTAP) is subsequently formulated as a Variational Inequality problem. To solve the RTAP, a Gradient Projection algorithm is proposed, which involves solving a series of minimum RC path sub-problems that are theoretically and practically harder than deterministic shortest path problems. In addition, an origin-based heuristic is proposed to enhance computational performance on large networks. Numerical experiments examine the computational performance and convergence characteristics of the exact algorithm and establish the accuracy and efficiency of the origin-based heuristic on various real-world networks. Finally, the proposed RTA model is applied to the Chennai road network using empirical data, and its benefits as a normative benchmark are quantified through comparisons against the standard UE and System Optimum (SO) models.     

Effect of nozzle orifice diameter on diesel spray tip penetration according to various spray models for CFD simulation with widely varying back pressure

CFD simulations of spray tip penetration with the standard KIVA3V, ‘original gas jet’ and ‘Normal gas jet profile with breakup length formula’ (NGJBL) spray models were performed to investigate the effects of nozzle orifice size and ambient gas density combinations on the spray penetration. The accuracy of the CFD simulation results was estimated by comparing them with available experimental data. The ambient gas density was varied in 12 kg/m³ intervals from 12 to 69 kg/m³ for each nozzle orifice diameter. The nozzle orifice diameters used were 119, 140, 183 and 206 mm. A total of 20 cases in the CFD simulations were considered with combinations of the 4 nozzle orifice diameters and 5 ambient gas densities. CFD simulations with the NGJBL spray model were more accurate than those with either the standard KIVA3V or gas jet spray models as the nozzle orifice diameter and ambient gas density was increased. The NGJBL and original gas jet model is more effective in predicting the spray tip penetration near the nozzle tip region.     

Nanoparticle emission characteristics and reduction strategies by boost pressure control and injection strategies in a passenger diesel engine

This research attempted to analyze nanoparticles and other harmful exhaust emissions in accordance with injection strategies and air-fuel ratio (AFR) changes for small diesel engines. The emission characteristics were analyzed in the medium-speed condition, which is the main driving range of a diesel engine. In the case of particulate matter (PM), the number of particles was measured, analyzed, and compared to identify the correlation and emission characteristics of nanoparticles by using a dilution device and condensation particle counter (CPC), which are international standards for particle measurement recommended by the Particulate Measurement Programme (PMP). The engine torque tended to be reduced as pilot injections were added, and the torque was increased by the increased boost pressure, but reduced by the exhaust pressure increase in a part of the low-load range. The number of nanoparticles was not influenced greatly by the change in AFR, but the reduction effect on the PM weight was great depending on the boost pressure increase. In addition, the number of nanoparticles tended to increase as the fuel injection timing became closer to TDC in all conditions, and its difference became larger with an increase in AFR. In addition, in the case of the pilot injection, nanoparticle emission showed similar characteristics depending on the main injection timing, but it was increased by advanced injection timing when performing the main injection only, and the number of the nanoparticles increased as pilot injections were added. Last, the optimal conditions for EMS calibration were analyzed by selecting the conditions of torque reduction and NOx increase within 5 % from all of the engine operating conditions; optimized conditions are presented.