Methods of determining choice probability in utility maximising multiple alternative models

Methods of estimating choice probabilities between multiple alternatives are described, within the context of various methods of specifying the degree of correlation between the alternatives. A utility maximising framework is assumed. The models described are based either on the logit family or multinomial probit. Two new methods of analytical approximation for the multinomial probit model are introduced, which appear to show significant advantages over the traditional Clark method. Some comparative results of choice probability estimates are presented to support this contention. The conclusion discusses the relative usefulness of different choice estimation methods for different types of problem.     

Sensitivity Analysis of Vehicle Design Attributes in Frequency Domain

This paper presents a procedure for determining the sensitivity matrices of a vehicle dynamic system in the frequency domain as derivatives of the transfer function matrix with respect to system parameters. First and second order logarithmic sensitivity functions which possess normalized coefficients have been introduced to enhance analysis. The sensitivity analysis of amplitude-frequency characteristics on changes of selected parameters of a 3 degree-of-freedom vehicle handling model has been performed. It has been demonstrated that the general sensitivity measure proposed can be used to determine the combined influence of system parameters divided into groups such as design, environmental, driver, kinematic, etc., on the multi-parameter system response, prior to determining their order of influence within the groups.     

The West African coastal upwelling filaments and cross-frontal water exchange conditioned by them

One of the important problems in the oceanography of the wind-driven upwelling regions of the Ocean is the investigation of water exchange processes in the coastal zone. Satellite data (thermal and colour imagery) have changed our view on these processes after the relatively recent discovery of cold, chlorophyll-rich, narrow (< 50 km wide) offshore flowing filaments off the west coasts of North America, North and South Africa. On the basis of satellite IR images and oceanographic original and archive data we investigated systems of filaments in the northwest and southwest African upwelling regions. The spatial distribution of filaments was analyzed. It was found that seasonal variability of the filaments' location depends upon the general intensity of upwelling motion along the coast during the year. The main statistical characteristics of filaments were obtained. An example of the three-dimensional velocity structure of the filament was presented. In order to estimate the intensity of cross-frontal exchange process due to filaments, a special procedure was proposed. The values of the velocity of cross-frontal water exchange produced by filaments in these upwelling zones are obtained. It was shown that upwelling filaments play an important role in water exchange between the coastal zone and the open ocean. A non-dimensional parameter which characterizes the permeability of oceanic fronts for water exchange due to mesoscale dynamical structures was introduced and estimated.     

The influence of workplace environment on lung function of shopkeepers working near National Highway in Jalgaon: A note

The inferior ambient air quality was observed near highway passing through Jalgaon urban center. Among the pollutants critical level of particulates are observed at the roadside during May 2003 to April 2004. The shopkeepers working at the highway sides are at high risk of exposure to the air pollution caused by heavy highway traffic. The lung function test of the shopkeepers shows significant decrease in forced vital capacity, forced expiratory volume in one second and peak expiratory flow rate. The regular periodic health checkup and use of nose mask will protect the health of shopkeepers working near National Highway passing through Jalgaon urban center.     

Glacial–interglacial changes in the accumulation rates of major biogenic components in Southern Indian Ocean sediments

In this study we compare major biogenic components (opal-A, carbonate, and organic carbon) and authigenic uranium accumulation rates from the southeastern Indian Ocean for both Holocene and glacial periods. Integrated accumulation rates across the whole Indian sector of the Southern Ocean indicate that the burial of organic carbon which is held approximately constant, contrasts with lower biogenic silica and carbonate burial rates during glacial intervals. In addition, higher glacial accumulation rates of authigenic uranium are found in the sediments of the Polar Front Zone (PFZ) and the Sub-Antarctic zone (SAZ) than anywhere in the modern Southern Ocean. This suggests more reducing conditions in the PFZ and SAZ during the last glacial maximum. The simplest explanation of a northward shift of the PFZ cannot explain such changes. Glacial sediment burial changes result probably from deep water decrease in oxygen levels and increase in CO₂ due to combination of two processes: (1) hydrologic changes and (2) continuous organic carbon export fluxes to the seafloor. Such shifts in chemical conditions could have enhanced the dissolution of carbonates and better preserved the organic carbon in sediments, leading in significant changes of biogenic silica/C_org and CaCO₃/C_org flux ratios.     

Electronically Controllable Vehicle Suspensions

The basic functions which suspensions must perform are described and categories of controllable suspensions based on the required amount of control power are defined. The kinds of devices which can be used in controllable suspensions are discussed as well as several basic control philosophies. Finally, fundamental theoretical and practical limitations in suspension performance are indicated.     

Relaxation approaches to large scale bus driver scheduling problems

The bus driver scheduling (BDS) problem in a transit company consists of establishing, at minimum cost, a list of work-days in which a driver is assigned to each bus in the given time-table and all clauses of the union contract are respected. In this paper we present a general mathematical programming formulation for the BDS problem. Because, in general, the problem is too large to be solved directly, we introduce a relation of the problem and three different solution approaches. Computational results obtained on real life problems indicate that mathematical programming techniques can solve the BDS problem efficiently.     

International comparison of market risks across shipping-related industries

This paper compares the behaviour of shipping and shipping-related company stock returns to reveal whether systematic risk differs from the average in the market and across sub-sectors of the maritime industry. Following an extensive collection of information through a postal questionnaire survey, 108 publicly listed shipping and shipping-related companies, across stock exchanges of the world, are classified by sector according to their core business activity. The Capital Asset Pricing Model (CAPM) is employed for the period 1996-1999 to model stock returns and measure sector βs (systematic risk). Stock returns over the period are mostly negative. The systematic risks of the Drilling and Offshore sectors are significantly higher than those of all other sectors, but are not different from each other. There is no significant difference between the systematic risks of the Bulk, Tanker, Container and Ferry sectors. The systematic risk of the Cruise sector lies somewhere between these two groups. There is no difference in the systematic risk of companies that diversified within shipping or shipping-related industries when compared to companies that diversified in other areas. Over all companies in the sample, βis lower than the market average, and so are the βs of the Ferry, Tanker, Bulk, Container and Yard sectors. Only the βof the Drilling sector is statistically higher than one, while the Cruise, Diversified and Offshore sectors are statistically one.