Mechanical and Aerospace Engineering Faculty Publications

Analysis of Water Footprint of a Photobioreactor Microalgae Biofuel 1 Production System from Blue, Green and Lifecycle Perspectives

Jason C. Quinn — Mon, 03 Jun 2013 11:50:32 PDT

Microalgae are currently being investigated as a feedstock for the commercial production of transportation fuels, due to their potential scalability and sustainability advantages over conventional feedstocks. The water consumption of microalgae has been postulated to be a resource barrier for large-scale production. This study presents an assessment of the water footprint (WF) of a closed photobioreactor-based biofuel production system, where microalgae cultivation is simulated with geographical and temporal resolution. The assessment focuses on the WF as modeled for four different fuel conversion pathways, and in 10 continental US locations corresponding to high productivity yields. The WF is comprehensively assessed using a hybrid approach which combines process and economic input-output lifecycle analysis method, using three metrics: blue, green and lifecycle WF. Results show that the blue WF of microalgae biofuels varies between 23 and 85 m3·GJ-1 depending on process and geographic location. The green WF shows that microalgae cultivation may reduce the required local water withdrawals. Water credits from the co-products vary with allocation methods and end uses, from credits of less than 4 m3·GJ-1 up to credits of 334 m3·GJ- 1. Results for the net lifecycle WF with coproduct credits varies between 80 and -291 m3·GJ-1. Discussion focuses on the sensitivity of microalgae biofuels WF and highlights potential local and national strain of water resources relative to other fuels and biofuels.

Assess the Accuracy of the Variational Asymptotic Plate and Shell Analysis Using the Generalized Uni

Luciano Demasi et al. — Thu, 28 Feb 2013 13:11:37 PST

The accuracy of the Variational Asymptotic Plate and Shell Analysis (VAPAS) is assessed against several higher order, zig zag and layerwise theories generated by using the invariant axiomatic framework denoted as Generalized Unified Formulation (GUF). These theories are also compared against the elasticity solution developed for the case of a sandwich structure with high Face to Core Stiffness Ratio. GUF allows to use an infinite number of axiomatic theories (Equivalent Single Layer theories with or without zig zag effects and Layerwise theories as well) with any combination of orders of the displacements and it is an ideal tool to precisely assess the range of applicability of the Variational Asymptotic Plate and Shell Analysis or other theories in general. In fact, all the axiomatic theories generated by GUF are obtained from the kernels or fundamental nuclei of the Generalized Unified Formulation and changing the order of the variables is “naturally” and systematically done with GUF. It is demonstrated that VAPAS achieves accuracy comparable to a fourth (or higher) order zig-zag theory or lower-order layerwise theories with the least number degrees of freedom. The differences between the axiomatic Zig-zag models and VAPAS are also assessed. Range of applicability of VAPAS will be discussed in detail and guidelines for new developments based on GUF and VAPAS are provided.

DNAD, a Simple Tool for Automatic Differentiation of Fortran Codes Using Dual Numbers

Wenbin Yu et al. — Wed, 06 Feb 2013 14:31:14 PST

DNAD (dual number automatic differentiation) is a simple, general-purpose tool to automatically differentiate Fortran codes written in modern Fortran (F90/95/2003) or legacy codes written in previous version of the Fortran language. It implements the forward mode of automatic differentiation using the arithmetic of dual numbers and the operator overloading feature of F90/95/2003. Very minimum changes of the source codes are needed to compute the first derivatives of Fortran programs. The advantages of DNAD in comparison to other existing similar computer codes are its programming simplicity, extensibility, and computational efficiency. Specifically, DNAD is more accurate and efficient than the popular complex-step approximation. Several examples are used to demonstrate its applications and advantages.

Geographical Assessment of Microalgae Biofuels Potential Incorporating Resource Availability

Jason C. Quinn et al. — Mon, 05 Nov 2012 11:40:55 PST

Previous assessments of the economic feasibility and large-scale productivity of microalgae biofuels have not considered the impacts of land and carbon dioxide (CO2) availability on the scalability of microalgae-based biofuels production. To accurately assess the near-term productivity potential of large-scale microalgae biofuel in the US, a geographically realized growth model was used to simulate microalgae lipid yields based on meteorological data. The resulting lipid productivity potential of Nannochloropsis under large-scale cultivation is combined with land and CO2 resource availability illustrating current geographically feasible production sites and corresponding productivity in the US. Baseline results show that CO2 transport constraints will limit US microalgae based bio-oil production to 4% of the 2030 Department of Energy (DOE) alternative fuel goal. The discussion focuses on synthesis of this large-scale productivity potential results including a sensitivity analysis to land and CO2 resource assumptions, an evaluation of previous modeling efforts and their assumptions regarding the transportation of CO2, the feasibility of microalgae to meet DOE 2030 alternative fuel goals, and a comparison of the productivity potential in several key regions of the US.

X-Ray Line Broadening Characterization of Strain Inhomogeneity in Textured Copper

David D. Sam — Thu, 02 Feb 2012 14:12:47 PST

Orientation and Strain Dependence of Stored Energy of Cold Work in Axisymmetric Copper

David D. Sam — Thu, 02 Feb 2012 14:12:44 PST

Coordinate Free Tensorial Representation of N-Point Correlation Functions for Microstructure by Harmonic Polynomials

David D. Sam — Thu, 02 Feb 2012 14:12:41 PST

Effective Yield Behavior for Mixtures of Elastic/Plastic Materials

David D. Sam — Thu, 02 Feb 2012 14:12:39 PST

Grain Boundary Phenomena and Shear Localization in Aluminum Bicrystals: Correlation Between Predictive Models and Experiment

David D. Sam — Thu, 02 Feb 2012 14:12:36 PST

Orientation Imaging Microscopy: A New Tool for High Resolution Interrogation of Material Microstructure

David D. Sam — Thu, 02 Feb 2012 14:12:33 PST

Shear Localization Studies in Aluminum Bicrystals: Misorientation and Grain Boundary Effects

David D. Sam — Thu, 02 Feb 2012 14:12:30 PST

Coordinate-Free Tensorial Representations of the Orientation Distribution Function

David D. Sam — Thu, 02 Feb 2012 14:12:27 PST

Yielding in Polycrystals: Computation of a New Upper Bound Using Two-Point Statistics

David D. Sam — Thu, 02 Feb 2012 14:12:23 PST

Yielding in Polycrystals: An Improvement on Taylor’s Upper Bound

David D. Sam — Thu, 02 Feb 2012 14:12:21 PST

Yielding in Polycrystals: Improvements on Taylor’s Upper Bound Using Higher Order Statistics of the Microstructure and Comparison to Universal Upper and Lower Bounds

David D. Sam — Thu, 02 Feb 2012 14:12:18 PST

Effective Yield Behavior and Homogenization for Polycrystals

David D. Sam — Thu, 02 Feb 2012 14:12:16 PST

Bounds to the Effective Yield Behavior of Materials with Random Microstructure

David D. Sam — Thu, 02 Feb 2012 14:12:13 PST

The Role of Two-Point Correlation Functions for Microstructure in Predictive Models of Polycrystalline Plasticity

David D. Sam — Thu, 02 Feb 2012 14:12:11 PST

The Role of Microstructure in Homogenized Descriptions of the Continuum Yield Surface

David D. Sam — Thu, 02 Feb 2012 14:12:08 PST

Simulation of Scale-Dependent Hardness of Stamping of Single Crystals

David D. Sam — Thu, 02 Feb 2012 14:12:05 PST