Dr. Robert P. Ewing (Toby) PhD Soil
Physics, 1992, University of Minnesota Research
Assistant Professor ewing@iastate.edu 

Research Interests:
Porous media fundamentals. My research concentration is in the use of percolation theory, network modeling, and random walk models in porous media. I'm particularly interested in the role of heterogeneity and spatial structure in determining material properties. Applications: simulation of initial DNAPL migration for improved prediction in expedited site characterization; movement and dissolution of NAPL ganglia (including enhanced oil recovery); sorption, desorption, and fate of organic chemicals.
Radioactive Waste (Mis)Management. I became peripherally involved in the Yucca Mountain Project around 2000, and have stayed involved in research on radioactive waste. In a broad sense this is an application of my work in percolation theory, which works well in describing rocks with low pore connectivity.
Image and Signal Analysis. This has long been a
secondary research interest, particularly for discrimination and measurement
of objects and identification of patterns. Applications: root
length measurement;
quantification
of color images; image classification from spectral signatures;
precision agriculture.
What I love about my job:
E I get paid to ask questions. Can you beat that?! Of course, I'm also supposed to find ways to answer them...
E Working closely with graduate students. I work with a lot of students; Ifve served on the committees of just a few:
Yanhui Hu (Chem. Eng.): developing a model of NAPL ganglia stability and dissolution
Pavel Iassonov (Geology): modeling use of vibration in enhanced oil recovery
Wenqing Li (Chem. Eng.): experiments on vibrationinduced movement of oil ganglia
Wen Deng (Geology): porescale modeling of vibratory stimulation and ganglion breakup
Claire Hruby (Ag. & Biosys. Eng.): microbial transport in soils
Sitha Ketpratoom (Agronomy): infiltration
E Teaching. I taught undergraduate earth sciences at Drake University for 2 years. It taught me a lot about the material, but more importantly, I found that I loved making the material mean something to others. I've also taught soil physics and hydrogeology here at Iowa State.
E Reviewing papers and proposals. It can be timeconsuming, but I like to think that I'm improving another person's work. Plus I learn a lot by studying other people's work.
E Programming. Turning strange ideas into specific instructions, then finding out how dumb I am when it doesn't work. A combination of "wow, this is cool" and ego crash. Try it.
E Data analysis. I used to be scared of math, but now it's my friend. And therefs always more to learn.
E The Earth Sciences. I still don't understand why EVERYONE isn't fascinated with soil, plants, weather, and the intricacies of the world around us.
E The people. Much of the fun of research and teaching is working with interesting people, growing with them in understanding and (one always hopes) wisdom.
Selected Publications:
Ewing, R. P., C. Liu, and Q. Hu (2012), Modeling intragranular diffusion in lowconnectivity granular media, Water Resour. Res. 48, W03518, doi:10.1029/2011WR011407.
Ewing, R. P., Q. Hu, and C. Liu (2010), Scaledependence of intragranular porosity, tortuosity, and diffusivity, Water Resour. Res. 46, doi. 10.1029/2009WR008183.
Hunt, A. G. and R. P. Ewing (2009), Percolation theory for flow in porous media (2nd Ed.), Lecture notes in physics 771, 319 pp., Springer.
Ewing, R. P. and R. Horton (2007), Thermal conductivity of a cubic lattice of spheres with capillary bridges, J. Phys. D: Appl. Phys. 40, 4959?4965.
Ewing R. P. and A. G. Hunt (2006), Dependence of the electrical conductivity on saturation in real porous media, Vadose Zone J. 5, 731?741.
Kaleita, A. L., B. L. Steward, R. P. Ewing, D. A. Ashlock, M. E. Westgate, and J. L. Hatfield (2006), Novel analysis of hyperspectral reflectance data for detecting onset of pollen shed in maize, Trans. Amer. Soc. Agric. Biol. Eng. 49, 1947?1954.
Ewing, Robert P. and Brian Berkowitz (2001), Stochastic porescale growth models of DNAPL migration in porous media, Adv. Water Resour. (special issue on porescale modeling) 24, 309323. Abstract.
Ewing, R. P. and R. Horton (1999), Quantitative color image analysis of agronomic images, Agron. J. 91,148153.
Ewing, Robert P. and Brian Berkowitz (1998), A generalized growth model for simulating initial migration of dense nonaqueous phase liquids, Water Resour. Res. 34, 611622.
Berkowitz, Brian and Robert P. Ewing (1998), Percolation theory and network modeling applications in soil physics, Surv. Geophys. 19, 2372, 1998
Kaspar, T. C. and Robert P. Ewing (1997), ROOTEDGE: Software for measuring root length from desktop scanner images, Agron. J. 89, 932940.
Ewing, Robert P. and Thomas C. Kaspar (1995), Accurate perimeter and length measurement using a boundary chord algorithm, J. ComputerAssisted Micros. 7, 91100.
Ewing, Robert P. and S. C. Gupta (1993), Modeling percolation properties of random media using a domain network, Water Resour. Res. 29, 31693178.
Ewing, Robert P. and S. C. Gupta
(1993), Percolation and permeability in partially structured networks, Water Resour. Res. 29, 31793188.