Advanced search options

Advanced Search Options 🞨

Browse by author name (“Author name starts with…”).

Find ETDs with:

in
/  
in
/  
in
/  
in

Written in Published in Earliest date Latest date

Sorted by

Results per page:

Sorted by: relevance · author · university · dateNew search

You searched for +publisher:"University of Colorado" +contributor:("Jeffrey Knutsen"). Showing records 1 – 3 of 3 total matches.

Search Limiters

Last 2 Years | English Only

No search limiters apply to these results.

▼ Search Limiters


University of Colorado

1. Browning, James R. Effects of Right Ventricular Diastolic Dysfunction on Coherent Flow Structures in the Human Right Atrium and Right Ventricle.

Degree: PhD, Mechanical Engineering, 2016, University of Colorado

Heart disease, the leading cause of death in the US, is a complex pathology which may manifest in several ways including morphological and hemodynamic changes in the heart and circulatory system. Recent advances in time resolved cardiac magnetic resonance imaging (4DMRI) have allowed for characterization of blood flow in the right ventricle (RV) and right atrium (RA), including calculation of vorticity and circulation, and qualitative visual assessment of coherent flow patterns. This thesis presents background on heart disease, specifically right ventricular diastolic dysfunction (RVDD), and 4DMRI tools and techniques used for quantitative and qualitative analysis of cardiac flows in the normal and disease states. Results of a preliminary study of right heart vorticity in subjects with RVDD are presented which inform the direction of later analysis. 4DMRI data is characterized to evaluate its suitability for quantitative and qualitative study of the RVDD pathology. Results of a 34 subject study or 20 RVDD patient and 14 normals are presented in which a significant difference is found in early diastolic right heart vorticity between the normal and pathologic group. A qualitative visual analysis is presented of differences and similarities in 3D flow structures between a single normal and RVDD subject at peak systole, peak early diastole, and late diastole in which several differences in 3D flow are observed. The thesis ends with observations regarding right heart three-dimensional flow characteristics of the RVDD pathology and the use of 4DMRI as a research tool for the study of right heart pathologies. Advisors/Committee Members: Jean Hertzberg, Brett Fenster, Joyce Schroeder, Jeffrey Knutsen.

Subjects/Keywords: 4D flow cardiac MRI; diastolic dysfunction; lambda2; right ventricle; vortex; Biomedical Engineering and Bioengineering

Record DetailsSimilar RecordsGoogle PlusoneFacebookTwitterCiteULikeMendeleyreddit

APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Browning, J. R. (2016). Effects of Right Ventricular Diastolic Dysfunction on Coherent Flow Structures in the Human Right Atrium and Right Ventricle. (Doctoral Dissertation). University of Colorado. Retrieved from http://scholar.colorado.edu/mcen_gradetds/118

Chicago Manual of Style (16th Edition):

Browning, James R. “Effects of Right Ventricular Diastolic Dysfunction on Coherent Flow Structures in the Human Right Atrium and Right Ventricle.” 2016. Doctoral Dissertation, University of Colorado. Accessed February 21, 2019. http://scholar.colorado.edu/mcen_gradetds/118.

MLA Handbook (7th Edition):

Browning, James R. “Effects of Right Ventricular Diastolic Dysfunction on Coherent Flow Structures in the Human Right Atrium and Right Ventricle.” 2016. Web. 21 Feb 2019.

Vancouver:

Browning JR. Effects of Right Ventricular Diastolic Dysfunction on Coherent Flow Structures in the Human Right Atrium and Right Ventricle. [Internet] [Doctoral dissertation]. University of Colorado; 2016. [cited 2019 Feb 21]. Available from: http://scholar.colorado.edu/mcen_gradetds/118.

Council of Science Editors:

Browning JR. Effects of Right Ventricular Diastolic Dysfunction on Coherent Flow Structures in the Human Right Atrium and Right Ventricle. [Doctoral Dissertation]. University of Colorado; 2016. Available from: http://scholar.colorado.edu/mcen_gradetds/118


University of Colorado

2. Adhikari, Birendra. Separation challenges and optimizations of sustainable algae and lignocellulose based biofuels.

Degree: PhD, Mechanical Engineering, 2015, University of Colorado

Algae and lignocellulosic biomass are viewed as viable renewable energy sources. However, higher cost of production is a major hurdle to make them competitive with fossil fuel sources. In case of algae fuel, the larger material and energy input required for the growth and processing is making algal biofuel both environmentally and economically unsustainable. In case of lignocellulosic biomass, the cost of unit operation steps, including that of enzymatic hydrolysis, to produce monomer sugars is very high. These problems gave us key engineering opportunities to investigate better extraction methods of lipids from algae and continuous enzymatic hydrolysis of lignocellulosic biomass. We performed techno-economic and life-cycle analysis of five probable ‘algae to fuel’ processes and came up with the conclusion that the extraction and dewatering of algae are the major bottlenecks. We hypothesized and tested an extraction method of lipids from wet algae with a ‘novel’ solvent mixture of diesel and isopropanol so that the lipids can be extracted directly from wet algae with a cheaper overall cost without actually killing the algae. We found out that algal lipids can be extracted using this ‘novel’ extraction method and the algae can also regrow in certain extraction conditions. The batch enzymatic hydrolysis is very inefficient method of hydrolysis of lignocellulosic biomass. We hypothesized and tested a membrane based reactor system for continuous hydrolysis of lignocellulosic biomass so that the monomer sugars, inhibitors during the hydrolysis, can remain low in concentration in the reactor and because of that, the reaction rate and overall conversion can go up. Our techno-economic study suggested that the continuous system can be cheaper than the batch mode of production. We learned that the complex nature of the lignocellulosic slurry makes the system difficult to design due to clogging and settling of biomass in the reactor and adjoining tubes. To understand this aspect, a fundamental study of the fluid dynamics of the biomass in a membrane module with the goal of designing a better header that can ‘mitigate’ clogging of the membrane structure (tubes and/or module) was done using OpenFOAM. We found out that certain geometries of membrane arrangement in a membrane module are preferable to some other ones. Advisors/Committee Members: John Pellegrino, Jonathan Stickel, Yifu Ding, Daven Henze, Jeffrey Knutsen.

Subjects/Keywords: membrane separation; reactor design; techno-economic analysis; Biomechanical Engineering; Mechanical Engineering

Record DetailsSimilar RecordsGoogle PlusoneFacebookTwitterCiteULikeMendeleyreddit

APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Adhikari, B. (2015). Separation challenges and optimizations of sustainable algae and lignocellulose based biofuels. (Doctoral Dissertation). University of Colorado. Retrieved from http://scholar.colorado.edu/mcen_gradetds/110

Chicago Manual of Style (16th Edition):

Adhikari, Birendra. “Separation challenges and optimizations of sustainable algae and lignocellulose based biofuels.” 2015. Doctoral Dissertation, University of Colorado. Accessed February 21, 2019. http://scholar.colorado.edu/mcen_gradetds/110.

MLA Handbook (7th Edition):

Adhikari, Birendra. “Separation challenges and optimizations of sustainable algae and lignocellulose based biofuels.” 2015. Web. 21 Feb 2019.

Vancouver:

Adhikari B. Separation challenges and optimizations of sustainable algae and lignocellulose based biofuels. [Internet] [Doctoral dissertation]. University of Colorado; 2015. [cited 2019 Feb 21]. Available from: http://scholar.colorado.edu/mcen_gradetds/110.

Council of Science Editors:

Adhikari B. Separation challenges and optimizations of sustainable algae and lignocellulose based biofuels. [Doctoral Dissertation]. University of Colorado; 2015. Available from: http://scholar.colorado.edu/mcen_gradetds/110


University of Colorado

3. Hansen, Curt Benjamin. Buried Explosive-Induced Blast Characterization by Geotechnical Centrifuge Modeling.

Degree: PhD, Mechanical Engineering, 2016, University of Colorado

A comprehensive experimental regime was conducted to advance the understanding of the mechanistic phenomena of buried, explosive-induced soil responses using geotechnical centrifuge modeling. To address experimental gaps in the current literature, this research documents the high-rate dynamic soil behavior under explosive loads with parametric variations of charge size, burial depth, and g-level in conjunction with post-detonation static measurement of blast-excavated craters. The novel integration of a high-speed imaging system into the centrifuge domain, placed in close-proximity to the blast, enabled a rigorous in-flight characterization of the transient, multiphasic soil blast mechanics including initial soil deformation, early soil disaggregation, gas-particle interactions, and soil dome evolution. The results indicate that initial soil surface motions appear progressively later, post-detonation, with elevated acceleration. Furthermore, the data demonstrates that gravity-induced confining stresses reduce the temporal and spatial soil disaggregation flow kinematics. Crater dimensions, measured by a laser profilometer, exhibit a gravity-dependent decrease and a new, dimensionless coupling function correlates the physical ejecta dynamics to the crater dimensional statics evident in the buried blast phenomena. Piezoelectric sensors, embedded coincident to the test-specified burial depth and recorded simultaneous to soil ejecta kinematics, measure ground shock transmissivity as a function of radial distance from the charge, with parametric variations in explosive mass and in-situ soil conditions. This research also developed a computational model of the buried, blast event in a dry soil medium within an advanced, 3-dimensional, multi-material, arbitrary Lagrangian-Eulerian (ALE) framework and implemented in an explicit finite element solver. The empirically-determined soil ejecta velocities and crater dimensions demonstrate reasonable correspondence to the numerical model. Significantly, the ground shock peak accelerations and stresses data exhibit close agreement to the numerical predictions. An in-depth analysis compares this study’s empirical scaling relationships, in both dimensional and dimensionless form to a compilation of past field and centrifuge results and demonstrates their favorable correlation to full-scale explosive events. The parametric study of soil ejecta kinematics and crater morphology progressed to an in-depth investigation of buried, explosive-induced kinetic energy transfer to an overlying target. To address experimental gaps in the current literature, this research documents the near-field resultant force impacts and rigid-body dynamics under explosive loads, instead of the conventional discrete measurement methods, with parametric variations of target height, explosive mass, burial depth, g-level, target geometries, and in-situ soil conditions. The design and fabrication of a novel, laboratory-scale blast impact device, the Blast Impact Response Gage (BIRG), integrated… Advisors/Committee Members: Ronald Y.S. Pak, Richard Regueiro, Mark Rentschler, Rong Long, Jeffrey Knutsen.

Subjects/Keywords: buried blast loading; centrifuge modeling; crater morphology; high-explosives; impulse; soil ejecta rheology; Civil Engineering; Mechanical Engineering

Record DetailsSimilar RecordsGoogle PlusoneFacebookTwitterCiteULikeMendeleyreddit

APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Hansen, C. B. (2016). Buried Explosive-Induced Blast Characterization by Geotechnical Centrifuge Modeling. (Doctoral Dissertation). University of Colorado. Retrieved from https://scholar.colorado.edu/mcen_gradetds/146

Chicago Manual of Style (16th Edition):

Hansen, Curt Benjamin. “Buried Explosive-Induced Blast Characterization by Geotechnical Centrifuge Modeling.” 2016. Doctoral Dissertation, University of Colorado. Accessed February 21, 2019. https://scholar.colorado.edu/mcen_gradetds/146.

MLA Handbook (7th Edition):

Hansen, Curt Benjamin. “Buried Explosive-Induced Blast Characterization by Geotechnical Centrifuge Modeling.” 2016. Web. 21 Feb 2019.

Vancouver:

Hansen CB. Buried Explosive-Induced Blast Characterization by Geotechnical Centrifuge Modeling. [Internet] [Doctoral dissertation]. University of Colorado; 2016. [cited 2019 Feb 21]. Available from: https://scholar.colorado.edu/mcen_gradetds/146.

Council of Science Editors:

Hansen CB. Buried Explosive-Induced Blast Characterization by Geotechnical Centrifuge Modeling. [Doctoral Dissertation]. University of Colorado; 2016. Available from: https://scholar.colorado.edu/mcen_gradetds/146

.