PA6: Contributed Session

Room: Old Main Academic Center 1030

Webex Link

Chair:  Shanti Bhushan, Mississippi State University

S. Yaser Samadi, Southern Illinois University

Time: 4:00 pm - 4:20 pm (CST)

Title: Dimension Reduction for Multivariate Autoregressive Models


The classical vector autoregressive (VAR) models have been widely used to model multivariate time series data, because of their flexibility and ease of use. However, the VAR model suffers from overparameterization particularly when the number of lags and number of time series get large.  There are several statistical methods of achieving dimension reduction of the parameter space in VAR models. In this talk, we introduce the reduced-rank VAR model (Velu et al., 1986; Reinsel and Velu, 2013) which restricts the rank of the parameter matrix in one direction, and the envelope VAR model (Wang and Ding, 2018) which is another solution to overcome the overparameterization problem. Then, we propose a new parsimonious VAR model by incorporating the idea of envelope models into the reduced-rank VAR. We show the strength and efficacy of the proposed model through some simulation studies and a real economic dataset.

Morgan Baker,  Mississippi State University

Time: 4:20 pm - 4:40 pm (CST)

Title: Computational investigation of GDI injector fouling effects on spray characteristics


Throughout the world, regulations are increasing with regards to carbon emissions and fuel consumption. To combat such policies, gasoline direct injection (GDI) engines have been the focus to improve engine performance and fuel economy. They are able to reduce engine knocking, improve cold starting, and have more precise control of the air-fuel ratio. However, GDI engines have the disadvantage of increased particulate matter (PM) emissions while emission regulations are becoming stricter. Previous research found that GDI injector deposits are most commonly formed on the injector tip surface and in the injector nozzle holes. The current study seeks to investigate injector fouling’s impact on spray structure and spray performance, including penetration length and flow restriction, in comparison to a clean injector through 3D Eulerian simulation using the CFD tool.

(joint work with Nayeon Lee, Greg Burgreen, Shanti Bhushan, and Joonsik Hwang)

Nicolae Herisanu, University Politehnica Timisoara

Time: 4:40 pm - 5:00 pm (CST)

Title: Study on heat transfer in MHD viscoelastic fluid of second grade over a stretching porous sheet with electromagnetic effects and nonuniform source/sink


This work is devoted to the study of non-Newtonian fluid of second grade model. We assume that the flow and the heat transfer in MHD viscoelastic fluid is subject to convective boundary conditions in the presence of electromagnetic field and nonuniform heat source/sink. The flow is considered over a porous sheet. The governing partial differential equations are converted as ordinary differential equations using suitable similarity transformations. The effects of different physical parameters such as second grade viscoelastic parameter, thermal radiation parameter or Eckert number are investigated. Several closed form analytical approximate solutions for dimensionless stream function and temperature are presented for some particular cases.

 (joint work with Bogdan Marinca and Vasile Marinca).