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991.
This article presents a mathematical model for sizing optimization of undamped trusses subjected to dynamic loading leading to fatigue. The combined effect of static and dynamic loading, at steady state, is considered. An optimization model, whose objective is the maximization of the safety factor of these trusses, is developed. A new quantity (equivalent fatigue strain energy) combining the effects of static and dynamic stresses is presented. This quantity is used as a global measure of the proximity of fatigue failure. Therefore, the equivalent fatigue strain energy is minimized, and this seems to give a good value for the maximal equivalent static stress. This assumption is verified through two simple examples. The method of moving asymptotes is used in the optimization of trusses. The applicability of the proposed approach is demonstrated through two numerical examples; a 10-bar truss with different loading cases and a helicopter tail subjected to dynamic loading. 相似文献
992.
Waleed S. Mohammed Xija Gu Joachim Meier Peter W.E. Smith 《Journal of Modern Optics》2013,60(7):1033-1049
In this paper we present a simple and novel method to maximize on-axis coupling efficiency to radially symmetric fibers without the need for extra free space optical elements. The method is based on inserting a segment of step-index multimode fiber (MMF), cleaved to a particular length, between the input fiber and the output fiber (OF). The MMF segment modifies the input field to match the guided modes in the OF. Using this technique we show that, by inserting an appropriate length MMF segment, it is theoretically possible to obtain a coupling coefficient as high as ?0.8 dB between a single mode fiber and a graded index ring-shaped fiber and ?0.32 dB for a multi-shell fiber. Our experimental measurements showed good agreement with theoretical predictions for the ring fiber. 相似文献
993.
Mapundi K. Banda Mohammed Seaïd Guido Thömmes 《International journal for numerical methods in engineering》2009,77(6):878-900
A lattice Boltzmann method (LBM) is applied to problems of dispersion in two‐dimensional water flows. The water flow is modelled by shallow water equations. A two‐distribution lattice Boltzmann equation algorithm is presented to solve the pollutant transport problem within the framework of shallow water flow. One distribution models the shallow water flow. The other distribution models the pollutant transport. Flow characteristics and concentration profiles of dispersive species are obtained at various flow regimes. For fast water flow, the concentration profiles are highly affected by the flow advection and become completely different from those at slow water flow. Numerical results are presented for pollutant transport in bounded and open channel flows. The proposed LBM is also used to simulate a pollution event in the Strait of Gibraltar. The obtained results indicate that the present method is useful for the investigation of transport phenomena by shallow water flows in complex geometries and practical flow problems. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
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995.
K. Mohammed P. W. M. Corbett D. Bowen A. R. Gardiner J. Buckman 《Journal of Petroleum Geology》2002,25(3):281-296
Solution seams have been identified as a significant component in the Ashgillian (Upper Ordovician) Mamuniyat Formation sandstone reservoir in the El-Sharara-A field (SW Libya). They have been observed in cores with a frequency of up to 25 solution seams per metre, and they have a permeability of 1–6mD in a reservoir whose permeability is otherwise 100–1,000mD. The reservoir sandstones (quartz arenites) were deposited as shallow-marine shoreline sands associated with glacial outwash deposits. The potential of solution seams to act as permeability baffles has not previously been considered in reservoir engineering models of this field. In this study, by measurement of permeability and subsequent reservoir simulation, we show that solution seams are likely to have had a negligible effect on effective horizontal permeability, and a small but positive effect on vertical sweep efficiency (due to reduced vertical permeability). Solution seams are present in many Palaeozoic reservoirs in North Africa, and may be particularly significant (in terms of their effect on production) in relatively poor quality reservoirs. 相似文献
996.
997.
998.
This paper presents a photovoltaic-peak power-cutting (PV-PPC) system capable of cutting peak load power. The proposed system is composed of a PV generator, DC–DC converter, storage battery, and an inverter. The function of the proposed PV-PPC system is to use PV energy to cut the peak load power in response to the change in the load demand and generating power. Four possible power flow scenarios are examined in detail through the bidirectional operation of the DC–DC converter and inverter, through the charging and discharging of the battery. The suggested PV-PPC system operation algorithm first selects the operational state by using differentiated charge and load information, with a simple structure to enable stopping in the case of system failure, and operates depending on the selected state. Then, the analysis modelling and operational control algorithm of the PV-PPC-generation system are performed in detail. Finally, the simulation and experimental results are presented to confirm the validity of the system. 相似文献
999.
This paper introduces an approach to controlling an industrial robot using human brainwaves as a means of communication. The developed approach starts by establishing a set of training sessions where an operator is enquired to think about a set of defined commands for the robot and record the brain activities accordingly. The results of the training sessions are then used on the shop floor to translate the brain activities to a set of robot control commands. An industrial case study is carried out to assist the operator in coordinating a collaborative assembly task of a car engine manifold. 相似文献
1000.
Drill-pipe corrosion is a critical issue for any drilling operation, particularly under high-pressure, high-temperature downhole conditions. However, most laboratory studies have been conducted under ambient and static conditions, with only a few downhole studies based on flow loop showing inconsistent results. In this study, we proposed a novel simple method to simulate pipe corrosion/erosion in a reservoir-like environment under both the static and dynamic conditions and investigated the influences of wellbore conditions, including temperature, pressure and salinity of water-based drilling fluids, on the corrosion behaviour of the drill pipe. The results showed that the erosion effect of the drilling fluid (without drilled cuttings) was negligible. Furthermore, we found that the corrosion rate increased with an increase in the temperature, pressure and rotational speed; however, it decreased with an increase in the salinity. In addition, the proposed method can be used to simulate other complicated conditions. 相似文献