Implementation and validation of a three degrees of freedom steering-system model in a full vehicle model

This paper describes the coupling between a three degrees of freedom steering-system model and a multi-body truck model. The steering-system model includes the king-pin geometry to provide the correct feedback torque from the road to the steering-system. The steering-system model is combined with a validated tractor semi-trailer model. An instrumented tractor semi-trailer has been tested on a proving ground and the steering-wheel torque, pitman-arm angle, king-pin angles and drag-link force have been measured during steady-state cornering, a step steer input and a sinusoidal steering input. It is shown that the steering-system model is able to accurately predict the steering-wheel torque for all tests and the vehicle model is accurate for vehicle motions up to a frequency where the lateral acceleration gain is minimum. Even though the vehicle response is not accurate above this frequency, the steering-wheel torque is still represented accurately.     

Environmental impact assessment of sediment dumping in the southern Baltic Sea using meiofaunal indicators

An experimental sediment dumping was carried out in the southern part of the Mecklenburg Bight in June 2001. Foraminiferans and ostracods from superficial sandy sediment were studied in a time series from before dumping until March 2004 in order to assess changes in associations and recolonization patterns of both groups. Additionally, an area sampling covering the dumping site and its surroundings from 15.5 to 20.7 m water depth made it possible to compare associations inside and outside the dumping area as well as the water depth dependent distribution of foraminiferans and ostracods. Salinity values vary within the high alpha-mesohaline and low polyhaline range. The dominating species are Ammotium cassis (Foraminifera) and Sarsicytheridea bradii (Ostracoda). The diversity is low (Fisher alpha index from 0.4 to 3.2 for foraminiferans and 1.0 to 2.5 for ostracods), but higher within the dumping site samples. These higher values are explainable by input of allochthonous tests and valves representing additional species. After the sediment dumping it took two and a half years to re-establish the total foraminiferan association and the total foraminifer/ostracod ratio within the dumping site. Total foraminiferan abundance increases remarkably with water depth (mean 83 tests in 100 ml) driven by higher nutrient availability and more suitable salinity and temperature values within the zone of the oscillating halocline. The distribution of shallow water species such as Cribroelphidium excavatum, Eucythere argus and Hirschmannia viridis, within the transient water layer A. cassis, Nodulina dentaliniformis, S. bradii and Palmoconcha laevata and below Eggerella scabra indicate the depth position of the halocline. Water depth and sediment dumping influence are the main driving factors for the distribution of foraminifer and ostracod associations within the study area. However, a significant sedimentological difference between samples inside and outside the dumping area is not recognizable.     

Environmental benefits analysis of electric vehicles in the Czech Republic

The article evaluates the environmental benefits of electric vehicles using well-to-wheel analysis in the Czech Republic. The power consumption per kilometer is determined from the combined cycle of the New European Driving Cycle. Using information from the integrated registry of polluters and mandatory disclosures of the CEZ company the specific harmful emissions production per 1 kW h of electricity is determined. The combination of electricity consumed and the production of harmful emissions per 1 kW h of electricity determine the indirect harmful emissions of an electric vehicle per kilometer. Computer simulation of the indirect production of harmful emissions is performed on the Mitsubishi MiEV engine, typical for an electric vehicle.     

Floating car based travel times for city logistics

City logistics routing requires time-dependent travel times for each network link. We rely on the concept of Floating Car Data (FCD) to develop and provide such travel times. Different levels of aggregation in the determination of time-dependent travel times from a database of historical FCD are presented and evaluated with regard to routing quality. Furthermore, a Data Mining approach is introduced, allowing for a substantial reduction of the volume of input data required for city logistics routing. The different approaches are investigated and evaluated by a huge amount of FCD collected for the urban area of Stuttgart, Germany. The results show that the Data Mining approach enables efficient provision of time-dependent travel times without a significant loss of routing quality for city logistics applications.     

Regulating CO2 emissions of transportation in Europe: A CGE-analysis using market-based instruments

This paper analyzes the use of market-based emission regulation instruments to address the carbon dioxide emissions of transportation. Simulations with a static multi-region computable general equilibrium model show that including transportation into the European emission trading system is superior to a closed emission trading system for transportation or a tax-based approach. Furthermore, we show that exempting transportation from emission regulation is the most favorable approach in terms of welfare. This counterintuitive result is due to a large tax-interaction effect caused by high pre-existing fuel taxes in the transport sector.     

The performance effect of innovation in shipping companies

The aim of this study is to investigate how innovation contributes to company performance in Norwegian shipping and to extend our knowledge concerning what organizational and inter-organizational factors influence innovation in shipping firms. The study is based on a survey of 46 Norwegian shipping companies. We find that innovation contributes to firm performance. We also find that a conscious strategy, strategy involvement, external relationships, especially market relationships, and productivity slack have a significant positive effect on the degree of innovation. The results are dependent upon the companies' degree of differentiation and the type of innovation.     

Some properties of international maritime statistics

This paper tests two fundamental hypotheses concerning international maritime statistics. The first one deals with the question of stationary of the maritime market statistics. The second hypothesis tested is the assumption that the international maritime statistical time series are not distributed according to a normal of Guassian probability law, but rather belong to the same family of distributions with distinctly different critical parameters. Through well documented statistical methods, the paper concludes that the international freight rates observed on a day to day basis are generated by a random walk process. The paper finds that the shipping industry's conventioal wisdom is essentially correct. 'Last done' is as good a forecast of tomorrow's freight rate as any other generated by more sophisticated forecasting methods. Furthermore, freight rates and secondhand tonnage prices fluctuate closely together. The freight rates are generated by stochastic processes fully described by the Paretian family of distributions. The critical parameters of these distribution, the characteristic exponents, are such that the risk conscious ship operator can indeed reduce his exposure to risk by securing a correct set of freight rate contracts.     

-statistic is the ratio between a normal (0,1) distributed variable and the square root of a centrally distributed chi-square variable divided by its expected value, i.e., its degree of freedom.

This paper evaluates empirically some very common theories of the freight rate generating process in the time charter markets. After a review of the most common assumptions made of the way time charter rates are set, the hypotheses are identified as follows: (a) the Zannetos Hypothesis, (b), the Lagged Zannetos Hypothesis, (c) the Koyck Lag Hypothesis, (d) the Rational Expectation Hypothesis, and (e) the Conventional Wisdom Hypothesis. These hypotheses are tested using statistical cointegration analysis that includes both an Augmented Dickey-Fuller (ADF), and a Johansen likelihood ratio test. Confronted with the data, hypotheses (a) and (b) are rejected outrightly. In the Koyck Lag case, the ADF statistic seem to confirm the hypothesis. A closer look at the numbers reveals that all of the impact on the time charter rates comes from the lagged dependent variable. Hence, the Koyck Lag Hypothesis is rejected. In the Rational Expectation case, the two tests conflicted. Based on the fact that the Rational Expectation Hypothesis includes the lagged dependent variable and that the Johansen test has been found to be a more robust test than the ADF test, the Rational Expectation Hypothesis is rejected. The fifth hypothesis is a reflection of the general bulk industry perception that the time charter rate is impacted by changes in the comparable spot rate and not much by the spot rate levels. In this case both the ADF and the Johansen test accepted the hypothesis for all markets. Thus, the paper concludes that the conventional market explanation of the time charter freight rate setting process is essentially correct-spot rate changes matter spot rate levels do not.     

A note on the age of radioactive tracers

The age of a water mass is often estimated experimentally using the radio-age computed from the distribution of a radioactive tracer (radiocarbon, helium–tritium). Deleersnijder et al. [J. Mar. Syst. 28 (2001) 229.] have shown that the radio-age underestimates the age of the water and is larger than the age of the radioactive tracer used for its evaluation. This result is generalized here to radio-ages computed from the ratio of two radioactive tracers. The differences between the different ages are also studied analytically and numerically as functions of the decay rate of the radioactive tracers.For small decay rates, the difference between the age of the water mass and the radio-age is shown to be proportional to the decay rate. It depends also on the level of mixing in the system; even radioactive tracers with small decay rates can provide poor estimates of the age of the water mass in a strongly diffusive flow. For small half lives, both the radio-age and the age of radioactive tracers decrease as the inverse of the square root of the decay rate.The same analysis applies to some extent to the estimates of the age of a water mass from stable tracers with known time dependent sources (e.g. chloroflurocarbons).