Current Issue : October - December Volume : 2019 Issue Number : 4 Articles : 5 Articles
The literature has shown that ordinary least squares estimator (OLSE) is not best when the explanatory variables are related, that is,\nwhen multicollinearity is present. This estimator becomes unstable and gives a misleading conclusion. In this study, a modified\nnew two-parameter estimator based on prior information for the vector of parameters is proposed to circumvent the problem of\nmulticollinearity. This new estimator includes the special cases of the ordinary least squares estimator (OLSE), the ridge estimator\n(RRE), the Liu estimator (LE), the modified ridge estimator (MRE), and the modified Liu estimator (MLE). Furthermore, the\nsuperiority of the new estimator over OLSE, RRE, LE, MRE, MLE, and the two-parameter estimator proposed by Ozkale and\nKaciranlar (2007) was obtained by using the mean squared error matrix criterion. In conclusion, a numerical example and a\nsimulation study were conducted to illustrate the theoretical results....
This article focuses on indirect coil guns used for launching non-magnetic objects.\nA mechatronic model, coupling electrical, mechanical, and electromagnetic models, is proposed.\nThis model is applied to the optimization of a kicking system used on limited size robots for propelling\nreal soccer balls at the RoboCup. Working with an existing coil gun, we show that fine tuning its\nsetup, especially the initial position and the length of the non-magnetic plunger extension, leads to\nan increase in the ball speed of 30% compared to previous results....
The Phase Locked Loop controller parameters are the key-point that affects\nthe dynamic performance of the autonomous microgrid. They have to be optimally\ntuned to guarantee enhanced overall system stability. In this paper,\ntwo-microgrid plant with their associate PWM inverter connected to the ac\nmain grid and the load is used as an example to demonstrate the capabilities\nof the proposed system. The Phase Locked Loop controller is designed and\ntuned using the Simulating Annealing algorithm. This algorithm is used to\nselect the Phase Locked Loop PI controller gains with optimal percentage\novershoot, rise time and settling time. The controller is tested during the\ntransition between grid-connected and autonomous operation and in reverse\norder. The controller is compared with Ziegler and Nichols P and PI controllers.\nIt shows the effectiveness and the extraordinary control response of the\nproposed control technique with respect to percentage overshoot, rise time\nand settling time control parameters compared to the conventional one....
Compared with conventional well, herringbone-like laterals wells can increase\nthe area of oil release, and can reduce the number of wellhead slots of\nplatforms, and also can greatly improve the development efficiency. Based on\nthreshold pressure gradient in heavy oil reservoir, and the applied principle of\nmirror reflection and superposition, the pressure distribution equation of\nherringbone-like laterals wells is obtained in heavy oil reservoir. Productivity\nmodel of herringbone-like laterals wells is proposed by reservoir-wellbore\nsteady seepage. The example shows that the productivity model is great accuracy\nto predict the productivity of herringbone-like laterals wells. The model\nis used to analyze the branching length, branching angle, branching symmetry,\nbranching position and spacing and their effects on productivity of herringbone-\nlike laterals wells. The principle of optimizing the well shape of herringbone-\nlike laterals wells is proposed....
Sustainable transportation systems play a key role in the socio-economic development\nof a country. Microscopic simulation models are becoming increasingly useful tools in designing,\noptimizing, and evaluating the sustainability of transportation systems and concerned management\nstrategies. VISSIM, a microscopic traffic simulation software, has gained rapid recognition in the field\nof traffic simulation. However, default values for different input parameters used during simulation\nneed to be tested to ensure a realistic replication for local traffic conditions. This paper attempts to\nmodel driving behavior parameters using the microscopic simulation software VISSIM through a case\nstudy in the Khobar-Dammam metropolitan areas in Saudi Arabia. VISSIM default values for dierent\nsensitive parameters such as lane change distances, additive and multiplicative parts of desired safety\ndistances, the number of preceding vehicles spotted, amber signal decisions, and minimum headway\nwere identified to be most sensitive and significant parameters to be calibrated to precisely replicate\nfield conditions. The simulation results using default values produced higher link speed, larger queue\nlength, and shorter travel times than those observed in the field. However, measures of effectiveness\n(MOEs) obtained from calibrated models over desired simulation runs were comparable to those\nobtained from field surveys. All compared MOEs used to validate the model matched within a range\nof 5-10% to the field-observed values....
Loading....