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931.
Coleen L. Moloney Michael A. St John Kenneth L. Denman David M. Karl Friedrich W. Köster Svein Sundby Rory P. Wilson 《Journal of Marine Systems》2011,84(3-4):106-116
Marine food web dynamics are determined by interactions within and between species and between species and their environment. Global change directly affects abiotic conditions and living organisms, impinging on all trophic levels in food webs. Different groups of marine researchers traditionally study different aspects of these changes. However, over medium to long time scales perturbations affecting food webs need to be considered across the full range from nutrients to top predators. Studies of end-to-end marine food webs not only span organism sizes and trophic levels, but should also help align multidisciplinary research to common goals and perspectives. Topics are described that bridge disciplinary gaps and are needed to develop new understanding of the reciprocal impacts of global change on marine food webs and ocean biogeochemistry. These include (1) the effects of nutrients on biomass and production, (2) the effects of varying element ratios on food web structure and food quality, (3) bulk flows of energy and material in food webs and their efficiencies of transfer, (4) the ecological effects of species richness and the roles of microbial organisms, (5) the role of feeding behaviour in food web dynamics and trophic controls, (6) the spatial dynamics of communities and links between different food webs, (7) the combined effects of body size and behaviour in determining dynamics of food webs, and (8) the extent to which the ability of marine organisms (and communities) to adapt will influence food web dynamics. An overriding issue that influences all topics concerns the time and space scales of ecosystem variability. Threads link different nodes of information among various topics, emphasizing the importance of tackling food web studies with a variety of modelling approaches and through a combination of field and experimental studies with a strong comparative approach. 相似文献
932.
Michael B. Lowry 《Transportation》2010,37(1):39-58
This paper investigates the potential for deliberation as a means for public participation in shaping public policy. The paper
begins with a summary of deliberative democracy and other concepts that recently have motivated an interest for online deliberation.
Next, the paper describes a case study in which 133 public participants deliberated over a regional transportation improvement
decision. The deliberation occurred entirely over the internet and lasted for 31 days. The participants wrote hundreds of
posts (comments) and made thousands of post-ratings (statements of agreement or disagreement). The posts and three questionnaires
are analyzed quantitatively and qualitatively to assess the nature of the deliberation and the participants’ perception of
their experience. A negative binomial regression is used to examine which participant characteristics are associated with
writing more posts. 相似文献
933.
Earl J. Baker Robert E. Deyle Timothy S. Chapin John B. Richardson 《Coastal management》2013,41(3):294-317
Five coastal counties in Florida were studied to assess the effect of state-mandated local comprehensive plan policies on hurricane evacuation clearance times and public shelter demand. Numbers of residential units in 2002 and at the time of plan approval were estimated from property parcel data. Abbreviated transportation models were used to calculate 2002 evacuation times and shelter demand and to ascertain the impacts of post-plan residential growth within hurricane hazard areas. Calculated increases in clearance times and shelter demand are not in concert with the state's mandate to maintain or reduce clearance times. State law currently limits the leverage of the state planning agency to compel local governments to implement the required comprehensive plan policies. We recommend a concurrency management strategy that parallels the state's requirement to provide adequate transportation facilities to accommodate the impacts of future residential growth. Such a policy could be employed in other states as well. 相似文献
934.
The study examines 20-years of data on 36 world principal fleets and on worldfleets in general, analyses their developments, and particularly their safety records in terms of accidental total loss rates. This study confirms that the open-registry ships tend toward substandard ships. However, some open-registry countries' safety records are quite acceptable. It finds that the safety record of developing maritime countries as a group is better than that of developed maritime countries, of which some are worse than the world average. 相似文献
935.
M. Isinibilir L. Svetlichny E. Hubareva I.N. Yilmaz F. Ustun G. Belmonte B. Toklu-Alicli 《Journal of Marine Systems》2011,84(1-2):18-27
During 2005–2008 species composition, abundance patterns, natural mortality rates and salinity effects on zooplankton were studied in the Bosphorus regions of the Black and Marmara Seas. The tendencies to diminish for abundance and biomass of the Black Sea originated zooplankton species and to increase for the proportion of their carcasses in the direction from the Black Sea toward the Marmara Sea were found. The mortality in the Black Sea species increased with depth in the Marmara Sea. The contribution of organic matter of carcasses of the Black Sea originated organisms to bacterial processes in the deep strata of the Marmara Sea was estimated. Different salinity and temperature regimes restrict mutual penetration of the species in these seas. 相似文献
936.
Helen B. Bendall 《Maritime Policy and Management》2013,40(4):277-284
Fluidized-bed boiler systems have sparked the enthusiasm of many in the past few years as an answer to many technological problems as alternate energy sources are investigated. Although still barely out of the experimental stage, ship designers are mooting the possibility of fluidized-bed combustion technology being applied in ship propulsion. This paper outlines briefly its process and discusses the economics of such a venture. 相似文献
937.
The early warning of incidents on urban arterial roads in a congested city can reduce delay, accidents and pollutant emission. Freeway incident detection systems implemented in recent years may not be suitable for arterial incidents. Arterial incident detection is more difficult. The traffic flow on an arterial road is not conserved from the upstream end of a road link to the downstream end because urban traffic does turn in and out of side‐streets, car‐parks and local residences. Roadside friction such as kerbside parking and shopping traffic also tends to create apparent incidents which are in fact frequent and normal events. This paper develops a definition for an arterial incident and describes a case study on an arterial road in Melbourne, Australia. The study shows that detectors upstream of an incident are more useful for incident detection than downstream detectors. It also identifies occupancy and speed as the appropriate parameters to characterise and detect arterial incidents. 相似文献
938.
Identification and quantification of plankton bloom events in the Baltic Sea by continuous pCO2 and chlorophyll a measurements on a cargo ship 总被引:4,自引:1,他引:3
Continuous measurements of the surface water CO2 partial pressure (pCO2) and the chlorophyll a fluorescence were performed in the Baltic Sea using a fully automated measurement system deployed on a cargo ship. The ship commuted regularly at two day intervals between the Mecklenburg Bight (Luebeck) and the Gulf of Finland (Helsinki). The pCO2 data collected during June 2003 and September 2004 were used to identify biological production events such as the spring bloom and the midsummer cyanobacteria bloom in five different sub-regions. To quantify the net biomass production, the decrease of the total CO2, NCT (normalized to a uniform alkalinity), during the production periods was calculated using the pCO2, temperature and salinity records and the mean alkalinity. Taking into account the CO2 air/sea exchange and the formation of dissolved organic carbon, a simple mass balance yielded the net production of particulate organic carbon which represents the total biomass. The chlorophyll a concentrations obtained from the fluorescence data showed peaks that in most cases coincided with the production maxima and thus supported the interpretation of the pCO2 data. The production during both the spring bloom (2004) and the midsummer nitrogen fixation period (2003) increased by a factor of about three from the southwest to the northeast. For the spring bloom our estimates were significantly higher than those based on the winter nutrient supply and Redfield C / N and C / P ratios. This indicated the existence of additional nutrient sources such as dissolved organic nitrogen, early nitrogen fixation and preferential P mineralization. Midsummer NCT minima were observed only in 2003 and used to quantify the nitrogen fixation activity and to characterize its interannual variability. 相似文献
939.
Recent advances in traffic control methods have led to flexible control strategies for use in an adaptive traffic control system (ATCS). ATCS aims at controlling the imminent traffic, which is yet to arrive and hence not known perfectly. Therefore, volume prediction is an essential part. Associated with the prediction are two aspects: resolution and accuracy. Recent studies indicate a tradeoff between prediction resolution and accuracy: finer resolutions, larger errors. It is imperative to study the relationship and tradeoff between the control strategy, prediction resolution, and its associated error, which are crucial to the development of ATCS. This study investigates this relationship through an extensive simulation of scenarios in Hong Kong with a recently developed dynamic traffic control model, DISCO. Based on the Hong Kong scenarios conducted with DISCO, the major findings include: (i) the importance of resolution outweighs that of error; (ii) dynamic timing plans generally outperform time‐invariant timing plans; (iii) up to a certain extent, overestimated predictions lead to better results than underestimated predictions. 相似文献
940.
Evaluation of automotive forward collision warning and collision avoidance algorithms 总被引:2,自引:0,他引:2
K. Lee H. Peng 《Vehicle System Dynamics: International Journal of Vehicle Mechanics and Mobility》2005,43(10):735-751
Collision warning/collision avoidance (CW/CA) systems target a major crash type and their development is a major thrust of the Intelligent Vehicle Initiative. They are a natural extension of adaptive cruise control systems already available on many car models. Many CW/CA algorithms have recently been proposed but the existing literature mainly focuses on algorithm development. Evaluations of these algorithms have been usually based on subjective ratings. The main contribution of this paper is the utilization of a naturalistic driving data set for the evaluation of CW/CA algorithms. We first collect manual driving data from the ICCFOT project, then process the data by Kalman smoothing, and finally identify 'threatening' and 'safe' data sets according to vehicle brake inputs and vehicle range behavior. Five CW/CA algorithms published in the literature are evaluated against the identified data sets. The performance of these algorithms is determined through a performance metric commonly used in signal detection and information retrieval under unbalanced data population. 相似文献