Methodology for bus structure torsion stiffness and natural vibration frequency prediction based on a dimensional analysis approach

Engineering bus design requires testing of bus structures prototypes in order to guarantee a certain level of strength and an appropriate static and dynamic behavior of the bus superstructure when exposed to road loads. However, experimental testing of real bus structures is very expensive as it requires expensive resources and space. If testing is done on a scale bus model the previous required expenses are considerably reduced. Therefore, a novel methodology based on dimensional analysis applied to bus structure prediction to evaluate the bus structure static and dynamic performance is proposed. The static performance is evaluated attending to torsion stiffness and the dynamic in terms of the natural vibration frequencies and rollover threshold. A scale bus has been manufactured and dimensionless parameters have been defined in order to project the results obtained in the scale bus model to a larger model. Validation of the proposed methodology has been carried out under experimental and finite element analysis.     

Vehicle sensor data-based analysis on the driving style differences between operating indoor simulator and on-road instrumented vehicle

Abstract

Indoor simulator and on-road instrumented vehicle are the most popular ways to analyze driving behaviors by using collected Vehicle Sensor Data (VSD). However, for a same driver, the driving performance could be different in the real world and in the simulated world. Even though many studies have been conducted to discover the differences of driving behaviors in these two circumstances, little research has focused on analyzing the differences in driving style, which can provide more integrated knowledge of a driver from the natural structure, stimulus–response mechanism, of driving behaviors. Therefore, in this paper, the driving styles in both the real world and the simulated world are extracted by implementing the nonnegative matrix factorization method on the collected VSD data. Through this analysis, the driving style differences can be quantitatively described and discussed in detail. It is found that the drivers tend to be more unstable and sometimes aggressive when driving the simulator and the deviation in the perception of temporal gap in two circumstances is also discovered. The research findings are particularly valuable to calibrate the driving simulator and construct more reliable driving behavior models.     

不同加载幅值下考虑层间界面条件和侧向剪力作用的柔性铺面响应

该文进行了一个三维有限元参数量化的粘弹性路面响应研究,由于不同的轮胎配置:双轮和宽基轮胎在3种温度(5、25和40℃)和两种速度(8、72 km/h);还有影响路面响应的3种因素:移动车轮荷载幅值(连续,梯形),层间界面条件(简单的摩擦和粘弹性模型)和横向力共同对路面响应的影响进行了研究.研究发现连续加载幅值,不但可以模拟路面对运动轮荷载的响应,并且是一种比目前使用的梯形荷载幅值更准确的研究模型.粘弹性模型极大地提高了双轮胎对预测路面的响应,而简单的摩擦模型更接近宽基轮胎的实地测量.侧向剪力是积极改善预测轮底的表面磨损和底部热拌沥青(沥青)基层的较小程度上的应变.研究表明:使用连续加载幅值和非均匀压力分布模拟移动轮,侧向剪切力和适当的界面摩擦可显著改善有限元模型对车辆加载路面响应的预测能力.     

船用柴油机组调速系统仿真研究

模拟电力系统的模拟研究中,柴油机及其调速系统直接影响系统机电暂态过程的准确性,对于判别系统受到大扰动后的暂态稳定和受到小扰动后的静态稳定性具有重要意义。从电站柴油发电机组的运动方程出发,在柴油机及其调速器数学模型的基础上,利用数字仿真计算机实时计算模拟转矩指令,用以控制一套高性能交流调速系统,从而实现电站柴油发电机组中柴油机及其调速器与系统转动惯量的数模混合模拟。实验表明,该模拟系统通用性强,响应速度快,准确性较高。     

A multiobjective chance constrained programming model for supplier selection under uncertainty

Risk management is an inherent part of supplier selection. While companies are enjoying the benefits of outsourcing, risks brought by this practice should be taken into account in the process of decision making. This paper presents a multiobjective stochastic sequential supplier allocation model to help in supplier selection under uncertainty. Demand for products, capacities at suppliers as well as transportation and other variable costs are the main sources of uncertainty and are modeled using probability distributions. Disruptions are exogenous events and the model provides proactive mitigation strategies against disruptions by assigning backup suppliers who can be used in case of a default at a primary supplier. When there is no disruption, the model’s solution is an optimal supplier order assignment, considering operational risks.     

Experimental study of drillship resistance performance in open and closed state of moonpool北大核心CSCD

[Objective] This paper carries out an experimental study of a multi-function dirllship model with moonpool structure in towing tank, aiming at analyzing the effects of the moonpool structure on the ship resistance in open and closure condition.[Methods]Taking a dirllship as the research object, the ship motion response in regular and irregular waves is investigated. The resistance of the ship in hydrostatic water and waves is measured with tension sensors, and the acceleration characteristics of the bow, midship and stern are analyzed by acceleration sensors.[Results]The results indicate that hull resistance under light load conditions is greater when open moonpool, while hydrostatic water resistance with closed moonpool is greater under design load conditions. The closed moonpool in regular waves reduces stern acceleration by 58.2%, bow resistance by 46.7% and heave response by 41.8%. The peak of resistance at the bow in irregular waves is about ten times higher than that at the stern, and the peak of resistance occurs more often when the moonpool is open at the same time.[Conclusions]The experimental study shows that the difference in load conditions changes the waterplane area and affects the hull resistance in hyrostatic water. In contrast, the closure of the moonpool not only reduces acceleration and resistance, but also improves surge and heave. As such, this paper can provide references for the structural design of drillships with moonpools. © 2023 Journal of Nanjing Agricultural University. All rights reserved.     

Links between subjective and objective evaluations regarding the steering character of automobiles

This work presents an experiment on the relationships between subjective and objective evaluations of vehicle handling. Ten cars were examined objectively in several open-loop driving dynamics manoeuvres and subjectively by test persons in typical traffic situations. Results are extracted from a stationary test (the Slowly Increasing Steer Test), and a dynamical test (the Frequency Response Test). The subjective measurements are obtained from drivers on a rural road course via a questionnaire, which was developed to separately investigate the quantity level perception, the so-called “Niveau”, and the more qualitative “Liking”. These subjective “measurements” are embedded into a two-channel definition of “Steering Comfort” as a genus for “Steering Discomfort” and “Character”. The article concentrates on developing a statistical method for the consideration of correlations amongst the subjective/objective data. In doing so, the variance in example subjective Niveau ratings can be significantly explained by several objective quantities. Indicators for co-domains of validated discomfort characteristics and hints for endeavouring character Liking ranges are detected.     

The economics behind the awarding of terminals in seaports: Towards a research agenda

Terminal concessions in seaports have only recently gained interest in academic circles. Issues such as the allocation mechanisms (to be) used for granting those concessions, the determination of the concession term and concession fees, as well as the inclusion of special clauses aimed at assuring that the terminal operator will act in the interest of the port authority and the wider community, are increasingly relevant to both academics and the port industry. So far, insights from established economic theories have rarely been applied to terminal concessions in seaports. It, therefore, remains to be seen which kind of awarding procedure would be best for which type of terminal concession. This contribution provides a detailed overview of the different phases of the terminal awarding process, including a classification scheme for awarding procedures, and contains an extensive discussion on the economic issues that require further investigation. The paper concludes by proposing a comprehensive research agenda on the topic.