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Scott Hansen

Expertise

I am an applied mathematician and hydrogeologist with expertise concerning a wide variety of topics and techniques. These include inverse problems, integral transforms, DNAPLs, mobile-immobile zone methods, anomalous transport, random walks (including CTRW), and heterogeneous porous media. Some areas in which I have focused my efforts are highlighted below, each accompanied by a list of related accomplishments:

Contaminant hydrogeology

  • Developed an analytic solution for dissolution of residual multicomponent NAPL.
  • Developed an analytic solution for first-order decay chains in parallel, discrete fractures.
  • Developed a Laguerre function-based technique for grafting arbitrary, time varying Type I boundary conditions onto analytic transport models.
  • Developed computational suite for analysis of coupled dissolution and subsurface transport.
  • Studied the weathering of creosote in the subsurface, and showed the possibility of PAH and phenolic plumes emanating from a single source NAPL body becoming disjoint.
  • Studied the forensic identification of Aroclors (commercially available PCB mixtures), and showed the infeasibility of identifying them in the absence of inverse transport models.

Random walk methods

  • Developed the RP-CTRW technique, a simplified continuous-time random walk (CTRW) approach for modeling upscaled advective transport in heterogeneous media.
  • Derived a non-conservative generalized master equation for anomalous transport subject to A + B -> 0 reactions.
  • Presented a new, non-constructive proof of the reflection principle for 1D random walks on a lattice.

Reactive transport

  • Developed reactive particle tracking codes for diffusion-reaction systems.
  • Derived a three-way relationship between reaction radius for fixed-radius reactive PT schemes, the mass action law for reaction-diffusion equations, and Fickian diffusion constant (assuming mixing-limited conditions).
  • Incorporated bimolecular reaction into the CTRW for anomalous dispersion-reaction systems (under rate-limited conditions).

Education

Ph.D. (Civil Engineering), Queen's University, 2012

M.Sc. (Mathematics), University of Toronto, 2007

B.Sc. (Mathematics and Engineering), Queen's University, 2004

 

LANL Positions

Postdoctoral Research Associate (EES-16), 2015-Present

 

Awards

Major recent awards:

2013 – 2015 Azrieli Foundation - Postdoctoral Fellowship

2013 Weizmann Institute of Science - Dean of Faculty Postdoctoral Fellowship

2009 – 2012 Natural Science and Engineering Research Council [Canada] - Alexander Graham Bell Canada Graduate Scholarship

 

Publications

The following are my refereed journal publications as of June 2015. Up-to-date information is listed on Google Scholar:

S.K. Hansen and B. Berkowitz (2015). Integrodifferential formulations of the continuous-time random walk for solute transport subject to bimolecular A + B → 0 reactions. Physical Review E 91, 032113.

S.K. Hansen and B. Berkowitz (2014). Interpretation and nonuniqueness of CTRW transition distributions: insights from an alternative solute transport formulation. Advances in Water Resources 74, pp. 54–63.

S.K. Hansen, H. Scher and B. Berkowitz (2014). First-principles derivation of reactive transport modeling parameters for particle tracking and PDE approaches. Advances in Water Resources 69, pp.146–158.

S.K. Hansen and B.H. Kueper (2014). A new model for coupled multicomponent NAPL dissolution and aqueous-phase transport, with application to creosote dissolution in discrete fractures. Water Resources Research 50, pp. 58–70.

S.K. Hansen (2013). Semianalytic solution for transport of a two-member decay chain in discrete parallel fractures. Water Resources Research 49, pp. 6105–6110.

S.K. Hansen (2011). On the effects of a totally reflecting barrier on an unbiased 1D random walk. Physica Status Solidi B 248(9), pp. 2112–2119.

S.K. Hansen and B.H. Kueper (2011). Forensic Misidentification of Aroclor Sources in Fractured Bedrock Due to "Chromatographic" Polychlorinated Biphenyl (PCB) Congener Separation. Environmental Forensics 12(1), pp. 25-34.

S.K. Hansen and B.H. Kueper (2009). An efficient method for asymptotic solution to some linear PDEs having arbitrary time-varying type I boundary conditions. Applied Mathematics and Computation 207(1) pp. 273-278.

S.K. Hansen and B.H. Kueper (2007). An analytical solution to multi-component NAPL dissolution equations. Advances in Water Resources 30(3), pp. 382-388.

R.K. Rowe, T. Mukunoki, R.J. Bathurst, S. Rimal, P. Hurst and S. Hansen (2007). Performance of a geocomposite liner for containing Jet A-1 spill in an extreme environment. Geotextiles and Geomembranes 25(2), pp. 68-77..