The galvanic corrosion behavior of the metal combinations 15 CDV6/MDN138 and 15 CDV6/MDN250, with 1:1 area ratio, has been studied in natural seawater using the open well facility of CECRI's Offshore Platform at Tuticorin for a year. The open circuit potentials of MDN138, MDN250, and 15 CDV6 of the individual metal, the galvanic potential and galvanic current of the couples 15 CDV6/MDN138 and 15 CDV6/MDN250, were periodically monitored throughout the study period. The calcareous deposits on MDN138 and MDN250 in galvanic contact with 15 CDV6 were analyzed using XRD. The electrochemical behavior of MDN138, MDN250, and 15 CDV6 in seawater was studied using an electrochemical work station. The surface characteristics of MDN138 and MDN250 in galvanic contact with 15 CDV6 have been examined with a scanning electron microscope. The results of the study reveal that the galvanic protection offered by15 CDV6 to MDN250 and MDN138 in natural seawater amounts to 93% and 98%, respectively, implying that the galvanic protection offered by 15 CDV6 is continuous and effective, which has been further evinced from the adherent nature of the calcareous deposit film comprising compounds such as CaCO_3(calcite, aragonite, and vaterite), MgCO_3(magnesite),Mg(OH)_2(brucite), and MgO(brucite). 相似文献
This paper proposes a frequency-based assignment model that considers travellers probability of finding a seat in their perception of route cost and hence also their route choice. The model introduces a “fail-to-sit” probability at boarding points with travel costs based on the likelihood of travelling seated or standing. Priority rules are considered; in particular it is assumed that standing on-board passengers will occupy any available seats of alighting passengers before newly boarding passengers can fill any remaining seats. At the boarding point passengers are assumed to mingle, meaning that FIFO is not observed, as is the case for many crowded bus and metro stops, particularly in European countries. The route choice considers the common lines problem and an user equilibrium solution is sought through a Markov type network loading process and the method of successive averages. The model is first illustrated with a small example network before being applied to the inner zone of London’s underground network. The effect of different values passengers might attach to finding a seat are illustrated. Applications of the model for transit planning as well as for information provision at the journey planner stage are discussed. 相似文献
Site selection is a key factor in any aquaculture operation, affecting both success and sustainability. Moreover, it can solve conflicts between different coastal activities, making a rational use of the coastal space. Geographical information systems (GIS) have become of increased significance for environmental planning and assessment mainly because of the need to compare a great number of spatially related data, and because it can be used to couple these spatial data with their attributes and overlay them. This study used GIS and related technology to build a spatial database using those criteria which were considered to have any influence in integrating marine fish-cage culture within the tourism industry in Tenerife. Criteria were grouped in three submodels (distance to beaches, nautical sports, and viewshed), which were combined to generate a final output showing the most suitable areas for cage culture development in coexistence with tourism. Most areas of the coastline of Tenerife were identified as being suitable (56%) or very suitable (46%), suggesting that marine cage aquaculture could be developed on the island in coexistence with the well-established tourism industry. 相似文献
A three-level procedure for assessing jack-up foundation stability for more or less homogenous soils is described. The objective is to provide a rational framework for these assessments that ensures their safe operation in extended year-round operations and enables their use in deeper waters than at present.
The three levels of the procedure have to be entered successively as long as foundation stability cannot be proven. The first level is a screening exercise and essentially replaces the well-known preload check. The second level compares factored foundation loads resulting from a structural analysis with foundation capacities obtained with ultimate bearing capacity formulae. The most refined third level assesses whether the displacements associated with these loads lead to an acceptable situation, i.e. capacity increase and/or load redistribution that does not result in collapse of the jack-up unit.
Since, for maximum benefit, this third-stage analysis requires a non-linear foundation model to be linked with the structural package used: such a tool is provided in the paper. Examples are given to demonstrate the impact of the assessment procedure.
This procedure forms part of the overall in-house approach to the assessment of jack-ups and has already been offered to the jack-up industry as part of the continuing efforts towards establishing common and accepted standards for jack-up assessments. Further developments have been identified and will be pursued. 相似文献
This paper studies changes in the relationship between household car ownership and income by household type. Ordered response probit models of car ownership are estimated for a sample of households repeatedly at six time points to track the evolution of income elasticities of car ownership over time. Elasticities of car ownership are found to change over time, questioning the existence of a unique equilibrium point between demand and supply that is implicitly assumed in traditional cross-sectional discrete choice car ownership models. Moreover, different household types and households that underwent household type transitions showed differing patterns of change in elasticities. Observed trends in car ownership and income clearly show behavioral asymmetry where the elasticity of procuring an additional car is greater than that of disposing a car. This too shows the inadequacy of traditional cross-sectional models of car ownership which tend to predict symmetry in behavior. The study suggests the importance of incorporating dynamic trends into the forecasting process, which can be accomplished through the use of longitudinal data. 相似文献
A novel regulation system for a vehicle generator and lead-acid battery is proposed in this paper. By integrating the regulation method, the output voltage of the generator is determined and controlled by the algorithm to save electrical energy and protect the lead-acid battery. The regulation algorithm is implemented in Matlab/Simulink, and the logic function of the system is verified using the dSPACE/AutoBox workbench. The experimental results show that the new algorithm improves the performance of the fuel economy of the vehicle and the battery state-of-health compared to the traditional control method. 相似文献