Literatura académica sobre el tema "Marine Transport"

This thesis investigates the marine transport-inventory system of Coastal British Columbia. The intrinsic characteristics of marine log transportation in this region are the vulnerability of marine transportation to adverse weather conditions and the presence of time-related economic costs. The system is confined to the Powell River operation. Three origins, one storage area and three pulp log types are considered. The formulated problem is classified as a sequential decision-making process. A deterministic model using the network flow theory and a simulation model using GPSS are developed. Due to considerable uncertainty in the system operation, the computer simulation model is selected. The model includes all of the important system variables and their interactions and assesses alternative operational doctrines by calculating variation in a key aspect of system performance, total logistic cost. It is found that: 1) the use of barges as the transportation mode leads to the least logistic cost, 2) the second best transportation alternative is the direct shipment of logs from origins to the mill and 3) if higher value saw log is considered, the log-taxi alternative may become attractive. However, to improve the capability of the developed model, more information on the salt contamination and teredo damage and accurate estimation of cost consequences of a mill shutdown are required. Future works should focus on these areas.<br>Applied Science, Faculty of<br>Civil Engineering, Department of<br>Graduate

Thesis (Ph. D.)--University of Oregon, 2004.<br>Typescript. Includes vita and abstract. Includes bibliographical references (leaves 215-240). Also available for download via the World Wide Web; free to University of Oregon users.

L'utilisation d'un modele numerique tridimensionnel a permis d'etudier d'une part un ecoulement caracteristique en zone cotiere a forte bathymetrie, d'autre part, le transport de sediment. L'influence de la bathymetrie et de la stratification sur l'evolution d'un courant et de la surface libre est analysee. Cette etude se concretise par une simulation realiste de la section du courant nord face a la baie de monaco. Le transport du sable et de la vase est considere sous l'action d'un courant et de la houle. Puis, une etude sur le transport des particules organique permet d'evaluer la production primaire dans la colonne d'eau

The transport of organic solutes from sea water by the molluscan integument occurs via a Na⁺-dependent cotransport process. Although much is known about the mechanism of this transport, little attention has been given to the influence of environmental parameters on this process. One highly variable parameter to intertidal animals is salinity. Intertidal habitats are routinely exposed to periodic changes in external salinity from ∼0 to ∼425 mM Na⁺, representing a range of ∼0 to ∼1000 mOsM osmotic concentration. This study examined the effect of salinity on organic solute transport and cell volume regulation in the gill of two representative intertidal animals, Mytilus edulis and Mytilus californianus. Integumental organic solute transport was found to adapt to reduced salinity in a 2-stage response. There was an initial, steep inhibition of transport that was far greater than predicted from the reduction of external Na⁺ alone. However, within 10 min. of acclimation to the dilute medium, transport recovered to the level predicted by the external Na⁺ concentration. Long-term acclimation to reduced salinity resulted in no upregulation of integumental transport. Thus, the degree of adaptation of integumental organic solute to reduced external salinity was always defined by the availability of external Na⁺ for the transport process. The exposure to reduced salinity also resulted in a change of cell volume. The gill preferentially lost organic solutes but spared inorganic ions following long-term acclimation to reduced salinity. Short-term acclimation of gill tissue to reduced salinity resulted in a rapid Volume Regulatory Decrease (VRD) which served to restore cell volume toward the control value. This short-term VRD did not involve the substantial loss of organic solutes, but was probably mediated by the efflux of K⁺ (and a counter anion) across the basolateral membrane. The loss of inorganic ions during brief exposures to reduced salinity conserves metabolically expensive organic compounds. The loss of organic solutes during long-term acclimation to reduced salinity may be due to the decreased Na⁺ gradient which reduces the ability of integumental transport to maintain the high solute concentrations in gill tissue of control animals.

In the context of biological invasions, ship transport plays an important role in the transference of species around the world. During this process organisms are exposed to several stressful conditions, which do not prevent them to arrive in areas where they did not occur before. The marine invertebrates Carcinus maenas and Mytilus galloprovincialis natives in Portugal, have already established stable invasive populations in several regions worldwide. This study exposed organisms of both species to stress conditions similar to what occurs in ballast tanks and on ship hulls. Results showed a high survival of pre-stressed Mytilus galloprovincialis individuals when compared to non pre-stressed organisms when exposed to air exposure, hyposalinity and heat events. However when Carcinus maenas was exposed to heat stress, there was no significant difference between groups with a different stress history. These findings suggest that transport on ships is not only a vector of dispersal but also a vector capable to increase the resistance to stress conditions in potential species invaders by selection of resistant individual; Resumo: "Transporte marítimo de espécies marinhas invasoras e sua resistência ao stress" No contexto das invasões biológicas, o transporte marítimo desempenha um papel importante contribuindo para a transferência de espécies em todo o mundo. Durante este processo os organismos são expostos a variadas condições de stress que não os impede de chegar a áreas onde não ocorriam anteriormente. Os invertebrados marinhos Carcinus maenas e Mytilus galloprovincialis nativos em Portugal, já estabeleceram populações invasoras estáveis em várias regiões do mundo. Neste estudo, submeteram-se organismos de Carcinus maenas e Mytilus galloprovincialis a condições de stress semelhante ao que ocorre em tanques de água de lastro e em cascos de navios. Os resultados mostram uma maior sobrevivência dos indivíduos Mytilus galloprovincialis pré – expostos a condições de stress quando comparado com organismos sem uma prévia exposição a esses eventos de stress, quando expostos ao ar, baixa salinidade e altas temperaturas. No entanto, quando Carcinus maenas foi exposto a temperaturas mais altas, não houve diferença significativa entre os grupos com diferentes exposições ao stress aplicado. Estes resultados sugerem que o transporte marítimo não é apenas um vetor de dispersão mas também um vector capaz de aumentar a resistência a condições de stress em potenciais espécies invasoras, nomeadamente através da seleção dos indivíduos mais resistentes.