轨道交通的自主化列车控制和自主化运营

简述了地铁中采用自主化列车控制及自主化列车运营技术的目的、实现方式,以及与目前成熟的无人驾驶系统的比较,并对不同自主化控制等级进行了定义。建议在目前CBTC(基于通信的列车控制)系统之上逐级引入自主化,最终实现从CBTC到全自主化的演进。     

Second-order hydrodynamic effects on an arrangement of two concentric truncated vertical cylinders

The second-order diffraction problem by a piston-like arrangement that consists of two concentric surface piercing cylinders is considered. The developed matched axisymmetric eigenfunction expansion solution methodology in cylindrical co-ordinates is based on the semi-analytical formulation of the velocity potentials in the various fluid regions which are defined by the geometry of the two-body arrangement. The main difficulty associated with the specific configuration originates from the fact that the geometry defines two fluid regions that extend up to the free surface in which the inhomogeneous second-order free surface boundary condition has to be fulfilled. To this end the associated velocity potentials in these regions are decomposed into a number of components defining the so-called ‘free’ and ‘locked’ waves. The latter are calculated by solving the resulting Sturm–Liouville problems. The seek second-order velocity potential in the whole fluid domain is then derived by enforcing matching conditions for the radial velocities and the fluid pressures at the cylindrical boundaries of adjacent fluid domains. Numerical results concerning the second-order hydrodynamic loading and the wave run-up on the cylinders are given, whereas special attention is given at incident wave frequency regions where the first-order exciting wave forces attain maximum values due to the resonant fluid motions in the moonpool.     

Biological effects of Mississippi River nitrogen on the northern gulf of Mexico—a review and synthesis

The Mississippi River currently delivers approximately 1.82 Tg N year⁻¹ (1.3×10¹¹ mol N year⁻¹) to the northern Gulf of Mexico. This large input dominates the biological processes of the region. The “new” nitrogen from the river stimulates high levels of phytoplankton production which in turn support high rates of bacterial production, protozoan and metazoan grazing, and fisheries production. A portion of the particulate organic matter produced in the pelagic food web sinks out of the euphotic zone where it contributes to high rates of oxygen consumption in the bottom waters of the inner shelf, resulting in the development of an extensive zone of hypoxia each summer. In spite of the significance of this river system to the coastal ocean of the northern gulf, we do not have an adequate understanding of the inputs, processing and ultimate fates of river nitrogen. Here we review available literature on this important system and propose a conceptual model showing how biological processes evolve in the river plume between the point of discharge and the point where plume waters are fully diluted by mixing with oceanic water.     

Late-Quaternary changes in productivity of the Southern Ocean

Paleoceanographic records based on new proxies of export production have been constructed for the South Atlantic sector of the Southern Ocean. A radionuclide-ratio proxy of particle flux (¹⁰Be/²³⁰Th) and the accumulation rate of authigenic uranium, which responds to the flux of organic carbon to the sea bed, both indicate a dramatic increase, compared to the present, in the export production of the Subantarctic zone (approximately the region between the present-day positions of the Subtropical Convergence and the Antarctic Polar Front) during glacial periods. If the South Atlantic is representative of the entire Southern Ocean, then export production in the Southern Ocean during the Last Glacial Maximum was substantially greater than at present. Previous studies, focusing on the burial of biogenic opal, failed to recognize the glacial increase in export production of the Southern Ocean because of a strong non-linearity between accumulation rates of opal and of organic carbon.     

Spatial and temporal variability of size-fractionated biomass and primary production in the Ross Sea (Antarctica) during austral spring and summer

The results of a study on the spatial and temporal dynamics of size-fractionated biomass and production of phytoplankton in the Ross Sea during the austral spring and summer are reported. The spring cruise took place in the offshore Ross Sea from 14 November to 14 December 1994. Sampling was carried out on a transect of 27 stations distributed from 76.5 to 72.0°S along 175°E, and covered the three main Antarctic environments of the polynya open waters, the marginal ice zone and the pack ice area. Three subsystems were identified. The subsystem of the polynya was characterised by the predominance of the micro- and nano-planktonic fractions, chlorophyll (Chl a) concentrations from 69.6 to 164.7 mg m⁻² and production rates from 0.68 to 1.14 g C m⁻² day⁻¹. The second subsystem, the marginal ice zone, showed a relative increase of the micro-planktonic fraction, high biomass levels (from 99.64 to 220 mg Chl m⁻²) and production rates from 0.99 to 2.7 g C m⁻² day⁻¹. The subsystem of the pack ice area had a phytoplankton community dominated by the pico-planktonic fraction and showed low biomasses (from 19.4 to 37.7 mg Chl m⁻²) and production rates (0.28 to 0.60 g C m⁻² day⁻¹). Selective grazing by krill is considered an important factor in determining the size structure of the phytoplankton communities. The summer study consisted of a time series carried out in inshore waters of Terra Nova Bay from 12 January to 8 February 1990. In a well stabilised water column and with high levels of PAR always available, the primary production rates of a community dominated by micro-plankton varied from 0.52 to 1.2 g C m⁻² day⁻¹ (average 0.84). A high P/B ratio, up to 3, and a remarkably elevated mean phaeopigment (Phaeo)/Chl a ratio of 2.4 indicated an active removal of biomass by grazing, confirmed by the presence of faecal pellets in quantities reaching 6000 m⁻³ in the upper 50 m. The peculiarities of the inshore versus offshore environments in terms of community size structure, production processes and their implications as regards the food web are discussed.     

Distribution of plankton lipids and their role in the biological transformation of Antarctic primary production

Production and transfer of lipid through the Antarctic food web is reviewed for the Indian Ocean sector. The slow settling fine particles showed a marked inter-annual variability in biochemical composition with an increase in lipid content as % organic carbon. Comparison of the fatty acid spectra of different size categories of organic particles indicated that fine particles are dominated by saturated, monoenoic and branched acids, while larger material (50–100 μm, 200–500 μm net collected fractions) displayed a signature dominated by polyunsaturated acids. Zooplankton taxa displayed different strategies of lipid accumulation. Lipid content was highest in Thysanoessa macrura females and copepodite stages of Calanus propinquus. Relatively low levels were recorded for juveniles and male stages of euphausiids. Reserve lipids varied with species: C. propinquus showed equal content of triglycerides and wax esters, T. macrura showed a dominance of wax esters and Euphausia superba and Themisto gaudichaudii accumulated only triglycerides. Computed as carbon equivalent and integrated over 200 m, lipids in slow settling particles represented 22.6% of annual primary production. Similar computation with mesozooplankton and E. superba data on biomass and population structure from several summer cruises indicated values of carbon accumulation as lipid reserves and egg production of 4.2 and 0.1% of annual primary production for copepods and 4.4 and 3.8% for E. superba. When all trophic levels are considered, the overall mean exceeded 30% of annual primary production.     

The female antennules of Paracyclops (Cyclopoida: Cyclopidae): their significance for systematics

The setation patterns of female antennules of some Paracyclops species are analysed with reference to the hypothetical 28-segmented antennule of ancestral copepod proposed by Huys and Boxshall in 1991. Comparison between Paracyclops species has revealed a setation pattern common to all species thus far examined. Several modifications of the female antennules have been identified as apomorphic states and can be used in phylogenetic studies. P. waiariki has 12-segmented antennules and exhibits more plesiomorphic characters than the reduced 8-segmented antennules of other species, such as P. fimbriatus. The results confirm that simple segment numbers are unusable as characters in cladistic analysis. Both P. affinis and P. yeatmani, for example, have 11-segmented antennules but analysis of segmental homologies has revealed that the 11-segmented state is convergent in these two species.     

Phytoplankton dynamics related to water mass properties in the Gulf of Gabes: Ecological implications

The spatial distribution of chlorophylls and carotenoids was recorded throughout the Gulf of Gabes (South Ionian Sea) in March 2007, and was related to patterns of the physical structure and the nutrient concentrations.Two distinct water masses were identified based on the temperature and salinity (T–S) analysis: a cool and less salty Modified Atlantic Water (MAW) and a saltier Mediterranean Mixed Water (MMW). There was no significant difference in the mean nitrogen and phosphate concentrations between MMW and MAW, although the silica values were significantly higher in MAW. The Integrated chlorophyll a mean value was about 4 mg m^? 2, with a maximum of 13 mg m^? 2 at MAW stations.Higher Chlorophyll a records in typical MAW stations were mainly due to chlorophytes, which contributed up to 58% of the pigments concentrations in the MAW and about 46% in the MMW. The contribution of chlorophytes to total Chlorophyll a was found to be relatively stable throughout the water column. The contribution of diatoms, which were twofold higher in the MMW than in the MAW, did not exceed 17% of chlorophyll a and was mainly due to subsurface maxima. The chlorophytes, pelagophytes, prymnesiophytes and cryptophytes all together accounted for more than 77% of total chlorophyll a in the MAW and about 67% in the MMW.There were statistically significant differences between MMW and MAW in the pigment contribution of cyanobacteria and pelagophytes. These two taxa accounted for 13% and 24% of chlorophyll a respectively in the MAW and MMW indicating that these differences concerned phytoplankton classes at relatively low contributions to total chlorophyll a.     

A decomposition method for surrogate models of large scale structures

Analysis is computationally the most expensive part of optimization. Surrogate models, which are approximate but faster statistical models, can be used in place of more precise but more computer-intensive methods like finite element method to improve efficiency. Unfortunately, the surrogate models are limited by the number of model parameters. So large-scale problems cannot be fully defined by a single surrogate model. Furthermore, current domain decomposition methods cannot be used with black-box models. This study presents a novel approach to design thin-walled structures using surrogate models that overcome the curse of dimensionality by a special decomposition method. A parametric panel structure is defined as a building block. An interface is developed to maintain compatibility across the blocks. Finally, an iterative algorithm finds the displaced state using only local information. Three test structures are used to show the convergence of the algorithm for static analysis. In these sample cases, number of steps required for convergence of the error did not change with the number of panels. This approach offers many benefits including automatic design creation and optimization, effective usage of stream processors and model reuse.     

Model course to revalidate deck officers’ competences using simulators

In accordance with Part A, Chapter I, Section I/11 Revalidation of Certificates of the Standards of Training, Certification and Watchkeeping for Seafarers (STCW) 2010 Convention, continued evaluation of professional competence shall be established, among others, by successfully completing an approved training course or courses. Every master, officer and radio operator holding a certificate issued or recognised under any chapter of the convention other than chapter VI, who is serving at sea or intends to return to sea after a period ashore, shall be required, at intervals not exceeding 5 years, to demonstrate continued professional competence, in order to continue to qualify for seagoing service. The main objective of this research is to design a model course using simulation technology to train and demonstrate seafarers’ competence in accordance with the provisions of STCW Code for existing seafarers who need to revalidate their professional maritime certificates also in accordance with the standards governing the use of simulators, Reg I/12 of 2010 STCW Code. The purpose of this revalidation simulation-based model course is to assist maritime training institutes and their teaching staff in organising and introducing specific training courses for revalidation of certificates of competence (CoCs) as well as enhancing, updating or supplementing existing training material where the quality and effectiveness of the training courses may thereby be improved. Only those STCW competences relating to ship bridge simulators will be considered for the model course scenario development and testing.