Search

Your search keyword '"Hugenholtz, Chris H."' showing total 235 results
Start Over Author "Hugenholtz, Chris H."
235 results on '"Hugenholtz, Chris H."'

8. High-frequency measurements of aeolian saltation flux: Field-based methodology and applications

Author

Martin, Raleigh L., Kok, Jasper F., Hugenholtz, Chris H., Barchyn, Thomas E., Chamecki, Marcelo, and Ellis, Jean T.

Subjects
Physics - Geophysics, Physics - Atmospheric and Oceanic Physics
Abstract

Aeolian transport of sand and dust is driven by turbulent winds that fluctuate over a broad range of temporal and spatial scales. However, commonly used aeolian transport models do not explicitly account for such fluctuations, likely contributing to substantial discrepancies between models and measurements. Underlying this problem is the absence of accurate sand flux measurements at the short time scales at which wind speed fluctuates. Here, we draw on extensive field measurements of aeolian saltation to develop a methodology for generating high-frequency (25 Hz) time series of total (vertically-integrated) saltation flux, namely by calibrating high-frequency (HF) particle counts to low-frequency (LF) flux measurements. The methodology follows four steps: (1) fit exponential curves to vertical profiles of saltation flux from LF saltation traps, (2) determine empirical calibration factors through comparison of LF exponential fits to HF number counts over concurrent time intervals, (3) apply these calibration factors to subsamples of the saltation count time series to obtain HF height-specific saltation fluxes, and (4) aggregate the calibrated HF height-specific saltation fluxes into estimates of total saltation fluxes. When coupled to high-frequency measurements of wind velocity, this methodology offers new opportunities for understanding how aeolian saltation dynamics respond to variability in driving winds over time scales from tens of milliseconds to days., Comment: 61 pages, 14 main text figures, 4 supporting figures, 2 tables

Published
2016

14. Low-cost fixed sensor deployments for leak detection in upstream oil and gas: operational analysis and discussion of a prototypical program

Author

Barchyn, Thomas E., Hugenholtz, Chris H., Gough, Tyler, Vollrath, Coleman, and Gao, Mozhou

Abstract

Low-cost fixed sensors are an emerging option to aid in the management and reduction of methane emissions at upstream oil and gas sites. They have been touted as a cost-effective continuous monitoring technology to detect, localize, and quantify leaks. However, to support emissions management, the efficacy of low-cost fixed sensors must be assessed in the context of the sites, technologies, methods, work practices, action thresholds, and outcomes that constitute a broader program to manage and reduce emissions. Here, we build on technology-focused research and testing by defining a prototypical low-cost fixed sensor program framework as considered from an operational perspective. We outline potentially large operational cost penalties and risks to industry relative to incumbent programs. Most costs are caused by: (i) follow-up callouts, (ii) non-target emissions, and (iii) maintenance requirements. These represent core areas for improvement. Together the framework and discussion point to significant economic and operational challenges with low-cost fixed sensor leak detection programs and highlight the need for careful consideration in regulations and emissions management program design.

Published
2023
Full Text
View/download PDF

15. Dune Convoy

Author

Diniega, Serina, Hugenholtz, Chris H., Hargitai, Henrik, editor, and Kereszturi, Ákos, editor

Published
2015
Full Text
View/download PDF

42. Frosted granular flow: A new hypothesis for mass wasting in martian gullies

Author

Hugenholtz, Chris H.

Subjects
Astronomy, Earth sciences
Abstract

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.icarus.2008.04.010 Byline: Chris H. Hugenholtz Keywords: Mars; Mars; surface; Earth; Geological processes Abstract: Recent gully deposits on Mars have been attributed to both wet and dry mass wasting processes. In this paper frosted granular flow (FGF) is presented as a new hypothesis for recent mass wasting activity in martian gullies. FGF is a rare type of granular flow observed on a talus slope in the Province of Quebec, Canada [Hetu, B., van Steijn, H., Vandelac, P., 1994. Geogr. Phys. Quat. 48, 3-22]. Frost reduces dynamic inter-particle friction, enabling flows to mobilize onto relatively low slope gradients (25-30[degrees]) compared to those involving dry granular flow of the same material (35-41[degrees]). Resulting erosional and depositional features include straight to sinuous channels, levees and digitate to branching arrangements of terminal deposits. Similar features are commonly found in association with geologically-young gully systems on Mars. Based on terrestrial observations of FGF processes the minimum criteria required for their occurrence on Mars include: (i) readily mobilized, unconsolidated sediment at the surface; (ii) an upper slope gradient at or near the angle of repose; (iii) frost accumulation at the surface; and (iv) triggering by rock fall. All four conditions appear to be met in many areas on present-day Mars though triggering mechanisms may vary. Compared to terrestrial FGFs, which are lubricated by thin liquid films at inter-particle contacts, those occurring on Mars are more likely lubricated by vaporization of CO.sub.2 and small amounts of H.sub.2O frost that becomes incorporated in the translating mass. Some recent mass wasting activity in martian gullies, therefore, could be interpreted as the product of FGF. Author Affiliation: Department of Geography, University of Lethbridge, 4401 University Drive W., Lethbridge, AB T1K 3M4, Canada Article History: Received 17 January 2008; Revised 8 April 2008

Published
2008

43. Effects of sand supply on the morphodynamics and stratigraphy of active parabolic dunes, Bigstick Sand Hills, southwestern Saskatchewan

Author

Hugenholtz, Chris H., Wolfe, Stephen A., and Moorman, Brian J.

Subjects
Geodynamics -- Research, Geology, Stratigraphic -- Research, Sand dunes -- Research, Earth sciences, Research
Abstract

Abstract: Sand supply is a major controlling factor on parabolic dune form and stratigraphy in inland settings. In this study, aerial photographs, ground-penetrating radar (GPR), and stratigraphic analysis document the [...]

Published
2008

Catalog

Books, media, physical & digital resources
See catalog results