大型基础设施系统设计中的风险及概率

在大型基础设施系统中,不可避免地会出现重大的不确定性,因而,无法确保已建系统的安全性和可靠性.有功能失效甚至破坏的可能,同时也有相应的规避风险的措施.从实用角度出发,不确定性可以分为两大类:数据型(又称偶然型)不确定性和知识型(又称认知型)不确定性.前者可以通过对数据的观察来评估,而后者则需要主观判断.系统地分析了这两...     

Estimation of copepod production in a flooded savanna of Venezuela

This is the first contribution to the copepod production in Venezuelan tropical savannas. Total abundance, biomass, production and mean P/B ratio of nauplii, copepodids and adults were determined in interdaily samples from a flooded, embanked savanna during February and March (end of dry season), and May (beginning of rainy season). Highest values of biomass and total production were recorded during dry season (61.5 mg m⁻³, 153.8 mg m⁻³ day⁻¹, respectively), compared to the rainy season (5.6 mg m⁻³, 45.9 mg m⁻³ day⁻¹). The last values are related to a low population density found during rainy season. Highest production were observed in copepodids at the end of the dry season. Significant differences of production between nauplii and copepodid stages, as well as between nauplii and adults, were also found.     

New filtering technique for on-board torque estimation

A new computationally efficient filtering algorithm based on the Kaczmarz projection method for reconstruction of the first harmonic of a periodic signal is presented. The algorithm allows the recovery of combustion quality information from noise-contaminated engine speed measurements. The algorithm is verified using a spark-ignition six-cylinder engine in the torque estimation problem.     

Neural network model for designing automotive devices using SMD LED

The advantages offered by the electronic component LED (Light Emitting Diode) have resulted in a quick and extensive application of this device in the replacement of incandescent lights. In this combined application, however, the relationship between the design variables and the desired effect or result is very complex and renders it difficult to model using conventional techniques. This paper consists of the development of a technique using artificial neural networks that makes it possible to obtain the luminous intensity values of brake lights using SMD (Surface Mounted Device) LEDs from design data. This technique can be utilized to design any automotive device that uses groups of SMD LEDs. The results of industrial applications using SMD LED are presented to validate the proposed technique.     

Development of probabilistic pedestrian fatality model for characterizing pedestrian-vehicle collisions

Pedestrian-related accidents are considered to be the most serious of traffic accidents due to the associated high fatality rates. In Korea, pedestrian fatalities accounted for approximately 40% of all traffic-related fatalities in 2004. Significant efforts have been made to develop effective countermeasures for pedestrian-vehicle collisions. A basis for devising such countermeasures is to understand the characteristics of pedestrian-vehicle collisions. This study develops a pedestrian fatality model capable of predicting the probability of fatality in pedestrian-vehicle collisions. Binary logistic regression and a probabilistic neural network (PNN) are employed to estimate the probability of pedestrian fatality. Pedestrian age, vehicle type and collision speed are used as independent variables of the fatality model. The models developed herein are valuable tools that can be used to direct safety policies and technologies associated with pedestrian safety.     

机构法结合遗传算法优化拱桥设计

对结构工程师来说,设计优化正变得日益重要。该文描述了一种结合机构法和遗传算法进行整体化设计优化的方法。前种方法是当前英国交通部采用的一种主要的计算拱的工具;后者是强有力的数值函数优化方法。文中显示了英国肯特Teston桥和一系列其它样本设计优化的试算结果及相关的算法有效性数据。建议本方法为涉及现存桥梁的评估、维护和修理及新拱桥设计的结构工程师的设计辅助工具。     

Brazil’s new vehicle front impact safety standards — ABNT NBR 15300-1 & ABNT NBR 15300-2 or ABNT NBR 15300-3: Is the manufacturerer choice the safest for the passenger?

To increase car passenger safety, the Brazilian National Traffic Council (CONTRAN) released Resolution 221, which defines the maximum passenger and driver biomechanical criteria in the event of a vehicle frontal impact. The vehicle maximum allowed biomechanical injury criteria will be enforced from January 2012 for new vehicles and in January 2014 for vehicles in production before January 2014. To standardize the test method to measure the driver and front passenger injury values in a frontal crash, Resolution 221 states that the tests must be performed according to the ABNT NBR 15300-1 standard, followed by the ABNT NBR 15300-2 standard or the ABNT NBR 15300-3 standard. The use of ABNT NBR 15300-2 or ABNT NBR 15300-3 standards is a free choice for the manufacturer of the vehicle. The ABNT NBR 15300-1 + 15300-2 test is similar to the FMVSS 208 standard in the United States in terms of its vehicle frontal impact test perpendicular to a rigid barrier with the use of seat belts by male model dummies. The test according to ABNT NBR 15300-1 + 15300-3 follows the European ECE R94 and 96/79/EC standards. However, ABNT NBR 15300-2 focuses on occupant protection during vehicle deceleration rather than occupant protection during vehicle deformation in a crash test. ABNT NBR 15300-3 tests occupant protection during vehicle deformation more than it tests occupant protection during vehicle deceleration. Therefore, this paper aims to show the types of test results produced by the ABNT NBR 15300-2 and ABNT NBR 15300-3 standards and their differences concerning occupant protection verification and discuss the manufacturer??s freedom of choice.     

Optimal Control of Four Wheel Steering Vehicle

This paper derives a method of controlling four wheel steering using optimal control theory. The purpose of control is to minimize the sideslip angle at the center of gravity. The control method feeds forward the steering wheel angle and feeds back the yaw velocity and the sideslip angle to the front and rear wheel angles. Theoretical studies show that the sideslip angle is reduced to zero even in the transient state, and that the understeer characteristic and frequency response can be changed regardless of the vehicle static margin. This Paper also examines various characteristics of the influence of the side force nonlinearities of tires and crosswinds.     

Simulation and Visualisation of the Dynamic Behaviour of an Overhead Power System with Contact Breaking

For high speed rail traffic it is necessary to design overhead power systems which minimize the contact loss between pantograph head and contact wire. To predict how different design solutions will behave it is favourable to model and simulate the dynamic behaviour. In this paper a model of an overhead power system is specified and used in simulation. The model is suitable for simulation with contact loss since it includes specifications of impact conditions between pantograph head and contact wire. Two sets of equations of motion are specified, one for the contact case and one for the non-contact case. The model also includes lateral movement of the wire due to the zigzag span and friction between the pantograph head and the contact wire. It is shown how to make animations of the system behaviour using a MCAE-system. The animations are made using a geometrical model of the system together with results from numerical simulations.

Through the examples provided, use of the mathematical model and the geometrical model is presented. The response is visualised as time histories and phase plane diagrams of different coordinates and as animations of the total system response. The different types of visualisations make an excellent combination when studying the system behaviour of different design solutions.

In one example, simulation using the linearised set of equations gives the same results as simulation using the set of fully nonlinear equations, due to periodic response and the simple alternation of contact conditions. It is shown that the situation when any of the parameters vary suddenly is possible to simulate using the fully nonlinear equations of motion.     

Force Control in Electrohydraulic Active Suspensjons

For a simple vehicle active suspension system complete optimality and zero steady state body displacements may be achieved if the axle and body accelerations, and other easily measured quantities, are included in the performance index. Apart from not requiring an observer, this also allows the optimal feedback gains to be determined for an arbitrary body spring rate. In a theoretical example, model parameters matching those of an experimental test rig are employed. The results of computer simulations, with and without an electrohydraulic servovalve and actuator, are compared to demonstrate the effects of inner loop gain on force control. Aspects of the system behaviour including lockup are commented upon.