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891.
A. Esnaola I. Ulacia B. Elguezabal E. Del Pozo De Dios J. J. Alba I. Gallego 《International Journal of Automotive Technology》2016,17(6):1013-1022
The development and validation of a modular composite impact structure is presented in the present paper. Quasi-static and dynamic impact tests of the composite components and a full frontal crash test of a vehicle prototype with composite impact structures manufactured by a new UV-pultrusion process have been performed. The results have demonstrated the feasibility of composite impact structures for crash applications with high specific energy absorption values compared with current metallic crash structures. Furthermore, due to the high production capacity of this new manufacturing process, cost-effective composite impact structures for mass-production of conventional cars may be feasible. Finally, a multimaterial numerical model as design tool for crashworthiness applications has also been validated. Different accelerations measured in the crash test have been accurately predicted as well as the crash behaviour of the composite impact structures. 相似文献
892.
893.
In recent years, railway tunnels in karst areas have frequently suffered flooding after high-intensity rainfall, which seriously affects the safety of tunnel operation and the order of transportation, and even interrupts the traffic. Based on the water hazard case in the Yuanbaoshan Tunnel on the Zhijin-Bijie Railway Line, this paper explores the causes of lining damage in terms of geology, rainfall, and the design and construction of water hazard sections, and puts forward the treatment technology for tunnel water hazards with the core concept of "making full use of existing structures and employing open drainage methods in key sections". Besides, this paper simulates and analyzes the formation of hazards and the treatment effect through numerical simulation. The results show that the subjective causes for the damage in tunnel linings include an insufficient understanding of the water-bearing formations at the geological investigation stage, the underestimation of water hazard risks posed by high-intensity rainfall during construction, and the unimproved waterproof and drainage system in the design alteration, while the objective reasons include the development of karst near the tunnel section that passes through the stratum, the strong connectivity of water conduits, and the high-intensity rainfall in a certain period of time on the tunnel site. As for the simulation results, they show that the increase of external water pressure caused by the sudden rise in groundwater level after rainstorm significantly increases the internal force of linings, and eventually leads to a much lower safety factor of sidewall linings and large scale damage, which is in consistency with the characteristics of the actual on-site damage. After on-site emergency treatment, the tunnel structure has become stable and even encountering unprecedentedly heavy rainfall twice, the tunnel has still remained in a good condition. Since then, no water hazards and other disasters have occurred, which proves that the treatment plan is valid. © 2022, Editorial Office of "Modern Tunnelling Technology". All right reserved. 相似文献
894.
This article uncovers that the BIMCO/ISF manpower survey, both in its data collection and methodology, could be improved upon. It suggests that there is no lack of seafarers in number, but in quality. The major potential supply/demand countries are identified. China has not only the potential to become, it has actually become, a top manpower supplier. Some traditional maritime nations, with the decreasing demands of their national fleets, have become labour supply country, which could contribute in excess of 44000 seafarers to foreign ships. There is a need and opportunity for co-operation on maritime training between suppliers and demanders. 相似文献
895.
The average annual daily traffic (AADT) volumes can be estimated by using a short period count of less than twenty‐four hour duration. In this paper, the neural network method is adopted for the estimation of AADT from short period counts and for the determination of the most appropriate length of counts. A case study is carried out by analysing data at thirteen locations on trunk roads and primary roads in urban area of Hong Kong. The estimation accuracy is also compared with the one obtained by regression analysis approach. The results show that the neural network approach consistently performed better than the regression analysis approach. 相似文献
896.
This paper proposes on-glass 4×4 MIMO antennas with broad bandwidth and high radiation gain, suitable for receiving WiBro internet applications in a commercial sedan. For the individual antenna body, we used a triangular-shaped patch that most efficiently satisfies broad-matching bandwidth. Then the inside of the triangular patch was partially removed to broaden the driver’s field of view. To obtain detailed design parameters that exhibit optimum radiating performance, we used a genetic algorithm (GA) in conjunction with a full wave EM simulator and varied the feeding locations of four antennas so as to increase throughput capacity for effective data transmission. The proposed antenna showed ?10 dB matching bandwidth and a measured average gain of about 4.77 dBi along the bore-sight direction (θ = 90°, ? = 180°) in the entire WiBro band (2.3–2.4 GHz). To confirm the MIMO performance in a real situation, we measured the commercial WiBro signal using the proposed antennas in an urban environment. The correlation coefficients among the antennas were calculated, and the result revealed an average value of 0.105. 相似文献
897.
Key to the predictive understanding of many nearshore marine ecosystems is the transport of larvae by ocean circulation processes. Many species release thousands to billions of larvae to develop in pelagic waters, but only a few lucky ones successfully settle to suitable habitat and recruit to adult life stages. Methodologies for predicting the larval dispersal are still primitive, and simple diffusive analyses are still used for many important applications. In this study, we investigate mechanisms of larval dispersal using idealized simulations of time-evolving coastal circulations in the California Current system with Lagrangian particles as models for planktonic larvae. Connectivity matrices, which describe the source-to-destination relationships for larval dispersal for a given larval development time course, are used to diagnose the time–space dynamics of larval settlement. The resulting connectivity matrices are shown to be a function of several important time scales, such as the planktonic larval duration, the frequency and duration of larval release events and inherent time scales for the coastal circulations. Many important fishery management applications require knowledge of fish stocks on a year-to-year or generation-to-generation basis. For these short time scales (typically less than 1 year), larval dispersal is generally far from a simple diffusive process and the consideration of the stochastic and episodic nature of larval dispersal is required. This work provides new insights into the spatial–temporal dynamics of nearshore fish stocks. 相似文献
898.
A method to measure the crosslink density of carbon black was used to analyze the aging behavior of a radiator hose made of
carbon black filled EPDM (ethylene-propylene diene monomer) rubber under thermo-oxidative stresses. The crosslink density
and the strength of the skin of the rubber specimens initially decreased slightly but then increased over time. The elongation
at the break considerably reduced and did not show any similarity to the behaviors of the crosslink density. A possible cause
of this reaction might be from the formation of rigid sulphoxide crosslinks and the crosslinks produced by the reaction of
unvalcunized sulfurs. Aging the rubber specimens at 180°C caused a slight increase in the crosslink density and a large decrease
in tensile strength and elongation. The aging experiment also caused a rapid increase of microhardness in the surface skin
region. The formation of carbonyl groups in EPDM molecule chains and the formation of rigid sulphoxide crosslink, rather than
the crosslink density variation, may have had a large influence. The changing behaviours of the mechanical properties, molecule
chains and crosslinks showed significantly different characteristics in the skin and the interior with aging temperature and
time. 相似文献
899.
This paper proposes to deepen the relationship between mobility and tethering in peri-urban spaces, and provide new methodological avenues, capable of contributing to the build-up of key knowledge elements, that we feel are crucial in a company’s capacity to implement their own sustainability requirements. These key knowledge elements are primarily based on the results stemming from research entitled “Peri-urbanism testing models for living; peri-urban viability, in theory and in practice”. The aim of this research was to assess, at least potentially, the sustainability of periurban spaces, which have seen recent development, as they have benefited from a growing trend towards removing space and time restrictions, through the generalisation of mobility, at the centre of many societal issues today. 相似文献
900.
Thomas Richerol Andr Rochon Steve Blasco Dave B. Scott Trecia M. Schell Robbie J. Bennett 《Journal of Marine Systems》2008,74(3-4):825
In order to document long-term climate cycles and predict future climate trends for the Arctic, we need to look at the geological records to establish the link between historical and pre-historical sea-surface parameters. Dinoflagellate cysts (dinocysts) are used as proxy indicators of sea-surface parameters (temperature, salinity, sea-ice cover, primary productivity) jointly with transfer functions and a modern dinocyst reference database, to reconstruct the evolution of sea-surface conditions at decadal and millennial timescales. Here we present the surface distribution of recent dinocyst assemblages from 34 surface sediment samples collected on the Mackenzie Slope/Amundsen Gulf during the 2004 CASES (Canadian Arctic Shelf Exchange Study) cruise. Dinocyst concentrations in surface sediments are relatively high outside the Mackenzie plume area and increase gradually eastward toward Amundsen Gulf. The cysts of autotrophic dinoflagellates are dominant throughout the study area, while the maximum abundance of heterotrophic taxa is found within the Mackenzie plume. Hierarchical clustering analyses allowed defining two dinocyst assemblages. Assemblage I is located on the Mackenzie Slope and southern Amundsen Gulf, while Assemblage II is located within the Cape Bathurst Polynya area in northern Amundsen Gulf. Both assemblages are dominated by Operculodinium centrocarpum, but are distinguished on the basis of the relative abundance of Islandinium minutum, a taxon generally associated with sea ice. I. minutum is found in lower abundance in the Cape Bathurst Polynya. 相似文献