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881.
王渤洪 《变流技术与电力牵引》2005,(1):7-12
车辆用涡流制动的原理正好是高速列车所感兴趣的,不过对硬件结构和供电方面又提出了很苛求的要求.此外,控制技术的管理较复杂.为此在ICE 3动车组上是首次批量使用这种涡流制动. 相似文献
882.
Design of Nonlinear Controllers for Active Vehicle Suspensions Using Parameter-Varying Control Synthesis 总被引:1,自引:0,他引:1
Ian J. Fialho Gary J. Balas 《Vehicle System Dynamics: International Journal of Vehicle Mechanics and Mobility》2000,33(5):351-370
Nonlinear suspension controllers have the potential to achieve superior performance compared to their linear counterparts. A nonlinear controller can focus on maximizing passenger comfort when the suspension deflection is small compared to its structural limit. As the deflection limit is approached, the controller can shift focus to prevent the suspension deflection from exceeding this limit. This results in superior ride quality over the range of road surfaces, as well as reduced wear of suspension components. This paper presents a novel approach to the design of such nonlinear controllers, based on linear parameter-varying control techniques. Parameter-dependent weighting functions are used to design active suspensions that stiffen as the suspension limits are reached. The controllers use only suspension deflection as a feedback signal. The proposed framework easily extends to the more general case where all the three main performance metrics, i.e., passenger comfort, suspension travel and road holding are considered, and to the design of road adaptive suspensions. 相似文献
883.
L. Fouillé J. -S. Broc B. Bourges J. Bougnol P. Mestayer 《Recherche - Transports - Sécurité》2012,28(3-4):190-200
The authors present a recent development in the use of classic travel demand models (TDMs) to environmental impact assessment of transport, far from its initial target. By comparing previous cases found in the literature (Chester, Seoul, Florence, Brisbane and Saint-Etienne) with their present works (Eval-PDU in Nantes), the authors notice that their predecessors tend to be evasive on their use of TDM. Hence, traffic data are little discussed in these works, while their works constitute one of the main stakes in this kind of study. Indeed, the hypotheses for traffic modeling are impacting the next steps of the modeling chain (pollutants emission/dispersion). The importance of this first modeling stage implies that relevant attention has to be brought to their assumptions and input data. 相似文献
884.
J. Lucas M. A. Houghton I. G. Masheter 《International Journal of Automotive Technology》2012,13(6):853-860
A system has been researched over the past 3 years for reducing the exhaust pollutants from diesel engines for light commercial vehicles. The system researched achieves Euro 6 standards for reduction of polluting gases (CO, HC, PM, NO). It consists of 4 main sections: 1. A heater and heat exchanger (HE); 2. A CO/HC oxidising catalyst (D°C); 3. Pt catalyst on a diesel particulate filter (DPF); 4. A NO reducing reaction (SCR) within the DPF. The system operates as follows. The exhaust gas contains oxidising gases, namely both O2 and NO2. The levels of CO and HC are oxidised by O2 to CO2 for temperatures above 200°C. Carbon (PM) is oxidised to CO2 by NO2 but requires a temperature above 250°C. The operating exhaust temperature of 300°C is ideal for the removal of NO by using the Pt catalyst and the CO generated within the DPF. The heater is required to be able to raise the exhaust temperature at any time to 300°C in order to optimise the performance of the system, since diesel engine exhaust temperatures vary between 160°C (slow speeds) to 350°C (high speeds). Considerable heat is required (??3 kW) to maintain the exhaust gas for a 2l engine at 300°C for engine idle conditions. Therefore a heat exchanger is required to re-circulate the input heat and thereby reduce the maximum power consumption to a maximum of 500W over the engine full operating test cycle. This energy is supplied by the engine battery and alternator. Experimental results have been obtained for the exhaust from a Kubota diesel engine and the reductions in exhaust emissions of 83% (CO/ HC), 58% (NOx) and 99% (PM) were obtained. The PM was continuously cleaned so that there was no build up of back pressure. 相似文献
885.
Efficient estimation of extreme non-linear roll motions using the first-order reliability method (FORM) 总被引:1,自引:0,他引:1
Jørgen Juncher Jensen 《Journal of Marine Science and Technology》2007,12(4):191-202
In on-board decision support systems, efficient procedures are needed for real-time estimation of the maximum ship responses
to be expected within the next few hours, given online information on the sea state and user-defined ranges of possible headings
and speeds. For linear responses, standard frequency domain methods can be applied. For non-linear responses, as exhibited
by the roll motion, standard methods such as direct time domain simulations are not feasible due to the required computational
time. However, the statistical distribution of non-linear ship responses can be estimated very accurately using the first-order
reliability method (FORM), which is well known from structural reliability problems. To illustrate the proposed procedure,
the roll motion was modelled by a simplified non-linear procedure taking into account non-linear hydrodynamic damping, time-varying
restoring and wave excitation moments, and the heave acceleration. Resonance excitation, parametric roll, and forced roll
were all included in the model, albeit with some simplifications. The result is the mean out-crossing rate of the roll angle
together with the most probable wave scenarios (critical wave episodes), leading to user-specified specific maximum roll angles.
The procedure is computationally very effective and can thus be applied to real-time determination of ship-specific combinations
of heading and speed to be avoided in the actual sea state. 相似文献
886.
It is known that the network design problem with the assumption of user optimal flows can be modeled as a 0–1 mixed integer programming problem. Instead, we formulate the network design problem with continuous investment variables subject to equilibrium assignment as a nonlinear optimization problem. We show that this optimization problem is equivalent to an unconstrained problem which we solve by direct search techniques. For convex investment cost functions, the performance of both Powell's method and the method of Hooke and Jeeves is approximately the same with respect to computational requirements for a 24 node, 76 arc network. For the case of concave investment functions, Hooke and Jeeves was superior. The solution to the concave continuous model was very similar to that of the 0–1 model. Furthermore, the required solution time was far less than that required by the corresponding discrete model of the same network. The advantages and disadvantages of the continuous approach as well as the computational requirements are discussed. 相似文献
887.
D.J. Buckley 《Transportation Research Part B: Methodological》1979,13(2):167-179
The work deals with the assignment of traffic to a two-dimensional continuous representation of a traffic network. An important aspect of the treatment is that the reciprocal of the speed on each road in the network is at all times a linear function of the flow on that road. This speed-flow relationship is generalized to two-dimensional space using travel intensities and taking account of road densities, so that there is direct dependence of speeds upon flows at all points regardless of their location. There is also dependence of flows upon speeds at all points because Wardrop's first assignment principle is adopted. That is, for a given O-D pair, journey times on all routes actually used are identical, and less than journey times on all other possible routes. This results in the identification for each O-D pair of an “assignment zone”, an area within which all trips between that O-D pair are made, and beyond which no such trips are made. For a single O-D pair the assignment zone is identified by ?m, the maximum angular divergence of a path from the straight line between O and D. Paths are then assumed to be bilinear so that for a single O-D pair the assignment zone is a parallelogram. Journey times, speeds, lateral displacement and other related quantities are obtained as functions of the flow Q between O and D. The work is extended to three O-D pairs located at the extremities of an equilateral triangle and four O-D pairs located at the corners of a square. At low flows these two configurations are trivial extensions of the single O-D pair problem because assignment zones do not overlap. At higher flows account is taken of this tendency to overlapping, so that although they do not overlap they do touch, becoming kite-shaped. Origins and destinations are assumed to be at the periphery of small circles of arbitrary radius. The work is inelegant to the extent that it involves a numerical integration but it is possible that this might eventually be circumvented. 相似文献
888.
王渤洪 《变流技术与电力牵引》2005,(3):15-22
车辆用涡流制动的原理正好是高速列车所感兴趣的,不过对硬件结构和供电方面又提出了很苛求的要求,此外,控制技术的管理较复杂.为此在ICE3动车组上是首次批量使用这种涡流制动. 相似文献
889.
锰粉加工工人心血管功能的调查研究 总被引:2,自引:1,他引:1
对 55 名锰粉加工工人和 56 名对照工人的调查结果显示,工人工作地点 Mn O2 浓度几何均值为 196 m g/m 3 (锰尘 017~22.24 m g/m 3 ),样品超标率 887% 。接触组头晕头痛、睡眠障碍、容易疲劳和记忆不良的主诉率明显高于对照组( P<005~001)。接触组和对照组的心电图异常、高血压和低舒张压检出率未见显著性差异,其心率、 P R间期、 Q R S波、收缩压和舒张压的均值比较也没有显著性差异。接触组心电图异常和低舒张压的 O R分别是 1.56(95% 可信区间为 070~3.50)和 2.08(95% 可信区间为 018~23.57)。 相似文献
890.
P. Gaspar I. Szaszi J. Bokor 《Vehicle System Dynamics: International Journal of Vehicle Mechanics and Mobility》2003,40(4):193-228
Summary The mixed µ synthesis for active suspension problems is proposed. Applying this method the real parametric uncertainties can be taken into consideration, which is more realistic than the traditional approaches, and the design process yields a less conservative compensator than other robust control design methods. The concept of the active suspension design using full-car models to handle the uncertain components is presented. The result of the mixed µ method is compared with the complex µ synthesis, and the passive system. 相似文献