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High-Performance Computing for Fluid Flow and Heat Transfer
Published in W.J. Minkowycz, E.M. Sparrow, Advances in Numerical Heat Transfer, 2018
There are various times related to computer execution. User time is the amount of time the CPU is active for a given process excluding operating system overhead. System time is the amount of time the operating system is active for the given process. Elapsed time (or wall clock time) is the difference between the time when the time process begins on a given processor and the time that it ends. This is the total time the process runs.
Experimental research on vehicle active suspension based on time-delay control
Published in International Journal of Control, 2023
Kaiwei Wu, Chuanbo Ren, Yang Nan, Lin Li, Shipeng Yuan, Sujuan Shao, Zehao Sun
Given the above problems, this paper proposes a time-delay control strategy and analyses the vibration response of the vehicle body under multi-frequency and different single-frequency excitations. A new optimisation method of time-delay control parameters is proposed; that is, the optimisation problem of random excitation is transformed into the optimisation problem of constant force in discrete time intervals. The objective function is designed to establish the quantitative relationship among the system time-domain vibration response, time-delay feedback control parameters, and external excitation to estimate the disturbance generated by the simplified model of vehicle ride comfort in real time. The frequency domain scanning method is used to analyse the stability interval of the suspension system to ensure the stability of the time-delay control system. Finally, the active suspension hardware-in-the-loop test results and numerical simulation methods verify the proposed control strategy.
A budget allocation strategy minimizing the sample set quantile for initial experimental design
Published in IISE Transactions, 2021
Ziwei Lin, Andrea Matta, Shichang Du
In addition to the simulation model, two kinds of analytical method are also applied. One is an Open Jackson Network, denoted as which assumes all inter-arrival times and processing times are independently and exponentially distributed. Also, the parts in the same order are assumed to arrive one by one rather than in batches. The formulas are used in the Open Jackson Network and the average system time is used as the estimation of the objective function. The other analytical method, denoted as is developed assuming there is no interaction between different orders and that the processing times are deterministic. Compared with the simulation model, these two analytical methods are fast in execution. They require about a total of 5 seconds and 0.5 seconds to run all the feasible solutions in the same laptop, respectively.
The conditional probability of travel speed and its application to short-term prediction
Published in Transportmetrica B: Transport Dynamics, 2019
Zheng Zhu, Liang Tang, Chenfeng Xiong, Xiqun (Michael) Chen, Lei Zhang
The open source statistical package R is used for model training and predicting (Ihaka and Gentleman 1996). We apply the package ‘neuralnet’ to work with NN models (Günther and Fritsch 2010), and the modified globally convergent algorithm was used for training NN (Anastasiadis, Magoulas, and Vrahatis 2005). Package ‘e1071’ is used to develop SVR models (Dimitriadou et al. 2011). The system time function in R is used to record the training time of different models of the training dataset (around 10,080 samples). This paper utilizes the mean absolute relative error (MARE) to measure the accuracy, given by where i denotes the loop station, T is the number of time steps in the testing dataset. We use MARE instead of other absolute error measures because loop stations with different speed patterns (e.g. average values and standard deviations) are predicted in this paper; and absolute error measures can be better in adaptive traffic management and control applications.