This material is based upon work supported by National Science Foundation grants EAR-0810270, EAR-1215898, and EAR-1344280, as well as an&#160;NSF Graduate Research Fellowship.

1. Simulation Software
<ol>
	<li>Use the software described in this section.
	<ol>
		<li>Download and install the free/open-source multi-agent modeling language and simulation platform, NetLogo (Available: <a href="http://ccl.northwestern.edu/netlogo/">http://ccl.northwestern.edu/netlogo/</a>, version 5.1 or later). 
		Note: This software is available at no cost and runs on all major operating systems (Windows/Mac/Linux).</li>
		<li>Download the two specific simulation script files (mousedrop.nlogo and <e...

<ol>
	<li>Huettel, M., Webster, I. T., Bordeau, B. P., J&#248;rgensen, B. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Porewater flow in permeable sediments. In: The benthic boundary layer: Transport processes and biogeochemistry. , 144-179 (2001).</li><li>Bencala, K. E., Walters, R. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Simulation+of+Solute+Transport+in+a+Mountain+Pool-and-Riffle+Stream+-+a+Transient+Storage+Model.">Simulation of Solute Transport in a Mountain Pool-and-Riffle Stream - a Transient Storage Model.</a> Water Resour Res. 19, 718-724 (1983).</li><li>Williams, D. D., Hynes, H. B. N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Occurrence+of+Benthos+Deep+in+Substratum+of+a+Stream.">Occurrence of Benthos Deep in Substratum of a Stream.</a> Freshwater Biol. 4, 233-255 (1974).</li><li>Benner, S. G., Smart, E. W., Moore, J. N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Metal+Behavior+during+Surface+Groundwater+Interaction,+Silver-Bow+Creek,+Montana.">Metal Behavior during Surface Groundwater Interaction, Silver-Bow Creek, Montana.</a> Environ Sci Technol. 29, 1789-1795 (1995).</li><li>Fuller, C. C., Harvey, J. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Reactive+uptake+of+trace+metals+in+the+hyporheic+zone+of+a+mining-contaminated+stream,+Pinal+Creek,+Arizona.">Reactive uptake of trace metals in the hyporheic zone of a mining-contaminated stream, Pinal Creek, Arizona.</a> Environ Sci Technol. 34, 1150-1155 (2000).</li><li>Jones, J. B., Mulholland, P. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Streams and Ground Waters. , (1999).</li><li>McKnight, D. M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Spectrofluorometric+characterization+of+dissolved+organic+matter+for+indication+of+precursor+organic+material+and+aromaticity.">Spectrofluorometric characterization of dissolved organic matter for indication of precursor organic material and aromaticity.</a> Limnol Oceanogr. 46, 38-48 (2001).</li><li>Mulholland, P. J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Inter-biome+comparison+of+factors+controlling+stream+metabolism.">Inter-biome comparison of factors controlling stream metabolism.</a> Freshwater Biol. 46, 1503-1517 (2001).</li><li>Peterson, B. J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Control+of+nitrogen+export+from+watersheds+by+headwater+streams.">Control of nitrogen export from watersheds by headwater streams.</a> Science. 292, 86-90 (2001).</li><li>Goolsby, D. A., Battaglin, W. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Long-term+changes+in+concentrations+and+flux+of+nitrogen+in+the+Mississippi+River+Basin,+USA.">Long-term changes in concentrations and flux of nitrogen in the Mississippi River Basin, USA.</a> Hydrol Process. 15, 1209-1226 (2001).</li><li>Rabalais, N. N., Smith, L. E., Harper, D. E., Justic, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Effects+of+seasonal+hypoxia+on+continental+shelf+benthos.">Effects of seasonal hypoxia on continental shelf benthos.</a> Coast Est S. 58, 211-240 (2001).</li><li>Huettel, M., Gust, G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Impact+of+bioroughness+on+interfacial+solute+exchange+in+permeable+sediments.">Impact of bioroughness on interfacial solute exchange in permeable sediments.</a> Mar Ecol Prog Ser. 89, 253-267 (1992).</li><li>Cardenas, M. B., Wilson, J. L., Haggerty, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Residence+time+of+bedform-driven+hyporheic+exchange.">Residence time of bedform-driven hyporheic exchange.</a> Adv Water Resour. 31, 1382-1386 (2008).</li><li>Stonedahl, S. H., Harvey, J. W., Detty, J., Aubeneau, A., Packman, A. I. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Physical+controls+and+predictability+of+stream+hyporheic+flow+evaluated+with+a+multiscale+model.">Physical controls and predictability of stream hyporheic flow evaluated with a multiscale model.</a> Water Resour Res. 48, (2012).</li><li>Stonedahl, S. H., Harvey, J. W., W&#246;rman, A., Salehin, M., Packman, A. I. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+multiscale+model+for+integrating+hyporheic+exchange+from+ripples+to+meanders.">A multiscale model for integrating hyporheic exchange from ripples to meanders.</a> Water Resour Res. 46, (2010).</li><li>W&#246;rman, A., Packman, A. I., Marklund, L., Harvey, J. W., Stone, S. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Fractal+topography+and+subsurface+water+flows+from+fluvial+bedforms+to+the+continental+shield.">Fractal topography and subsurface water flows from fluvial bedforms to the continental shield.</a> Geophys Res Lett. 34, (2007).</li><li>Tonina, D., Buffington, J. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+three-dimensional+model+for+analyzing+the+effects+of+salmon+redds+on+hyporheic+exchange+and+egg+pocket+habitat.">A three-dimensional model for analyzing the effects of salmon redds on hyporheic exchange and egg pocket habitat.</a> Can J Fish Aquat Sci. 66, 2157-2173 (2009).</li><li>Elliott, A. H., Brooks, N. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Transfer+of+nonsorbing+solutes+to+a+streambed+with+bed+forms:+Theory.">Transfer of nonsorbing solutes to a streambed with bed forms: Theory.</a> Water Resour Res. 33, 123-136 (1997).</li><li>Elliott, A. H., Brooks, N. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Transfer+of+nonsorbing+solutes+to+a+streambed+with+bed+forms:+Laboratory+experiments.">Transfer of nonsorbing solutes to a streambed with bed forms: Laboratory experiments.</a> Water Resour Res. 33, 137-151 (1997).</li><li>W&#246;rman, A., Packman, A. I., Marklund, L., Harvey, J. W., Stone, S. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Exact+three-dimensional+spectral+solution+to+surface-groundwater+interactions+with+arbitrary+surface+topography.">Exact three-dimensional spectral solution to surface-groundwater interactions with arbitrary surface topography.</a> Geophys Res Lett. 33, (2006).</li><li>Janssen, F., Cardenas, M. B., Sawyer, A. H., Dammrich, T., Krietsch, J., de Beer, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+comparative+experimental+and+multiphysics+computational+fluid+dynamics+study+of+coupled+surface-subsurface+flow+in+bed+forms.">A comparative experimental and multiphysics computational fluid dynamics study of coupled surface-subsurface flow in bed forms.</a> Wat Resour Res. 48, (2012).</li><li>Shen, H. W., Fehlman, H. M., Mendoza, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Bed+Form+Resistances+in+Open+Channel+Flows.">Bed Form Resistances in Open Channel Flows.</a> J Hydraul Eng-Asce. 116, 799-815 (1990).</li><li>Ma, J., Nickerson, J. V. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Hands-on+simulated,+and+remote+laboratories:+A+comparative+literature+review.">Hands-on simulated, and remote laboratories: A comparative literature review.</a> Acm Comput Surv. 38, (2006).</li><li>Nersessian, N. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Conceptual+change+in+science+and+in+science+education.">Conceptual change in science and in science education.</a> Synthese. 80, 163-183 (1989).</li><li>Magin, D., Kanapathipillai, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Engineering+students'+understanding+of+the+role+of+experimentation.">Engineering students' understanding of the role of experimentation.</a> European Journal of Engineering Education. 25, 351-358 (2000).</li><li>Shin, D., Yoon, E. S., Lee, K. Y., Lee, E. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+web-based,+interactive+virtual+laboratory+system+for+unit+operations+and+process+systems+engineering+education:+issues,+design+and+implementation.">A web-based, interactive virtual laboratory system for unit operations and process systems engineering education: issues, design and implementation.</a> Comput Chem Eng. 26, 319-330 (2002).</li><li>Smith, P. R., Pollard, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+Role+of+Computer-Simulations+in+Engineering-Education.">The Role of Computer-Simulations in Engineering-Education.</a> Comput Educ. 10, 335-340 (1986).</li><li>Gillet, D., Ngoc, A. V. N., Rekik, Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Collaborative+web-based+experimentation+in+flexible+engineering+education.">Collaborative web-based experimentation in flexible engineering education.</a> Ieee T Educ. 48, 696-704 (2005).</li><li>Subramanian, R., Marsic, I. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=ViBE:+Virtual+biology+experiments.">ViBE: Virtual biology experiments.</a> Proceedings of the 10th international conference on World Wide Web. , 316-325 (2001).</li><li>Blikstein, P., Fuhrmann, T., Greene, D., Salehi, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Bifocal+Modeling:+Mixing+Real+and+Virtual+Labs+for+Advanced+Science+Learning.">Bifocal Modeling: Mixing Real and Virtual Labs for Advanced Science Learning.</a> Proceedings of Idc 2012: The 11th International Conference on Interaction Design and Children. , 296-299 (2012).</li><li>Freeze, R. A., Cherry, J. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Groundwater. , (1979).</li><li>Todd, D. K., Mays, L. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Groundwater Hydrology. , (2005).</li><li>Box, G. E., Draper, N. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Empirical Model-Building and Response Surfaces. , (1987).</li><li>Flavell, J. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Metacognition+and+cognitive+monitoring:+A+new+area+of+cognitive&#8211;developmental+inquiry.">Metacognition and cognitive monitoring: A new area of cognitive&#8211;developmental inquiry.</a> American Psychologist. 34, 906 (1979).</li><li>Bransford, J. D., Brown, A. L., Cocking, R. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> How People Learn. , (2000).</li><li>Pintrich, P. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+role+of+metacognitive+knowledge+in+learning,+teaching,+and+assessing.">The role of metacognitive knowledge in learning, teaching, and assessing.</a> Theor Pract. 41 (4), 219-225 (2002).</li><li>Zohar, A., Ben David, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Paving+a+clear+path+in+a+thick+forest:+a+conceptual+analysis+of+a+metacognitive+component.">Paving a clear path in a thick forest: a conceptual analysis of a metacognitive component.</a> Metacogn Learn. 4, 177-195 (2009).</li><li>Fox, A., Boano, F., Arnon, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Impact+of+losing+and+gaining+streamflow+conditions+on+hyporheic+exchange+fluxes+induced+by+dune-shaped+bed+forms.">Impact of losing and gaining streamflow conditions on hyporheic exchange fluxes induced by dune-shaped bed forms.</a> Water Resour Res. 50, 1895-1907 (2014).</li><li>Norman, F. A., Cardenas, M. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Heat+transport+in+hyporheic+zones+due+to+bedforms:+An+experimental+study.">Heat transport in hyporheic zones due to bedforms: An experimental study.</a> Water Resour Res. 50, 3568-3582 (2014).</li><li>Precht, E., Huettel, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Rapid+wave-driven+advective+pore+water+exchange+in+a+permeable+coastal+sediment.">Rapid wave-driven advective pore water exchange in a permeable coastal sediment.</a> J Sea Res. 51, 93-107 (2004).</li><li>Salehin, M., Packman, A. I., Paradis, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Hyporheic+exchange+with+heterogeneous+streambeds:+Laboratory+experiments+and+modeling.">Hyporheic exchange with heterogeneous streambeds: Laboratory experiments and modeling.</a> Water Resour Res. 40, (2004).</li><li>Cardenas, M. B., Wilson, J. L., Zlotnik, V. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Impact+of+heterogeneity,+bed+forms,+and+stream+curvature+on+subchannel+hyporheic+exchange.">Impact of heterogeneity, bed forms, and stream curvature on subchannel hyporheic exchange.</a> Water Resour Res. 40, (2004).</li><li>Sawyer, A. H., Cardenas, M. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Hyporheic+flow+and+residence+time+distributions+in+heterogeneous+cross-bedded+sediment.">Hyporheic flow and residence time distributions in heterogeneous cross-bedded sediment.</a> Water Resour Res. 45, (2009).</li><li>Boano, F., Camporeale, C., Revelli, R., Ridolfi, L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Sinuosity-driven+hyporheic+exchange+in+meandering+rivers.">Sinuosity-driven hyporheic exchange in meandering rivers.</a> Geophys Res Lett. 33, (2006).</li><li>Cardenas, M. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+model+for+lateral+hyporheic+flow+based+on+valley+slope+and+channel+sinuosity.">A model for lateral hyporheic flow based on valley slope and channel sinuosity.</a> Water Resour Res. 45, (2009).</li><li>Tonina, D., Buffington, J. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Hyporheic+exchange+in+gravel+bed+rivers+with+pool-riffle+morphology:+Laboratory+experiments+and+three-dimensional+modeling.">Hyporheic exchange in gravel bed rivers with pool-riffle morphology: Laboratory experiments and three-dimensional modeling.</a> Water Resour Res. 43, (2007).</li><li>Harbaugh, A. W., Banta, E. R., Hill, M. C., McDonald, M. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> MODFLOW-2000, the US Geological Survey modular ground-water model: User guide to modularization concepts and the ground-water flow process. , (2000).</li></ol>

In conjunction, the flume demonstration and particle tracking simulations provide a comprehensive introduction to hyporheic flow for a range of audiences. Participants of all levels are provided visual evidence for the occurrence of hyporheic exchange induced by bedforms, and the strong variability in subsurface flow paths under bedforms. These procedures can be used as a simple demonstration of porewater flow for undergraduates or K-12 students, or it can be used in graduate courses in conjunction with a more in-depth p...

As surface water moves in a stream, river, or tidal zone it creates head gradients that drive water into and out of the sediments1. In fluvial systems the portion of the streambed sediments where this exchange occurs is known as the hyporheic zone2,3. This zone is important because many nutrients and pollutants are stored, deposited, or transformed within the hyporheic zone4-9. The amount of time a tracer spends in the sediment is called a residence time. Both residence times and the locations of the flow paths affect the transformation processes. Improved understanding of the processes affecting flow through the sediment is needed to predict solute transport in rivers and address large environmental problems resulting from propagation of materials such as nutrients (e.g., coastal hypoxia10,11). In spite of the significance of hyporheic exchange, it is often not described in undergraduate courses in hydrology, fluid mechanics, hydraulics, etc. Educators wishing to add hyporheic exchange to their courses could find it useful to have experimental and numerical visualizations that clearly show this process.
Stream channel sinuosity, surrounding groundwater levels, and streambed topography (i.e., bars, bedforms, and biogenic mounds) all affect hyporheic exchange to varying degrees12-17. This study focused on bedforms, such as dunes and ripples, which are usually key geomorphic features affecting hyporheic flow14,15. We created a numerical simulation and laboratory experiment to visualize flow through a regular series of bedforms. This simulation is based on a body of previous research relating hyporheic flow paths to readily observable system characteristics15,18-21. As this research forms the scientific background for the simulation, a brief summary of the key aspects of the theory follows. Bedform topography, T(x), is given by:
Equation 1: 
<img alt="Equation 1" src="/files/ftp_upload/53285/53285eq1.jpg" />
where H is twice the amplitude of the bedform, k is the wavenumber, and x is the longitudinal dimension parallel to the average streambed surface. An example of this bedform topography is shown in Figure 1.
<img alt="Figure 1" src="/files/ftp_upload/53285/53285fig1.jpg" /> 
Figure 1. Parameter definitions and settings controlled by the user. In Interface, tracer particles are released in a flux-weighted manner at the water/sediment interface and tracked through the sediment. If show-paths? is &#8220;on&#8221; the water tracers mark where they have been, showing their paths. When a tracer returns to the surface water, this changes the total number of tracers in the system, when re-drop? is set to &#8220;off&#8221;. The cumulative residence time distribution plot shows this change by plotting the ratio of the number of tracers remaining in the sediment bed to the initial number as a function of time. If re-drop? is &#8220;on&#8221; then tracers that leave the system are replaced in the same flux-weighted manner as original particles, and the cumulative plot is disabled. <a href="https://www.jove.com/files/ftp_upload/53285/53285fig1large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<table fo:keep-together.within-page="1">
	<tbody>
		<tr>
			<td>Parameter Name</td>
			<td>Units</td>
			<td colspan="3">Definition</td>
			<td>Interface</td>
			<td>Mousedrop</td>
		</tr>
		<tr>
			<td>Lambda (&#955;)</td>
			<td>cm</td>
			<td colspan="3">Wavelength of bedform (see Figure 1)</td>
			<td><img alt="checkmark" src="/files/ftp_upload/53285/checkmark.jpg" /></td>
			<td><img alt="checkmark" src="/files/ftp_upload/53285/checkmark.jpg" /></td>
		</tr>
		<tr>
			<td>BedformHeight (H)</td>
			<td>cm</td>
			<td colspan="3">Twice the bedform amplitude (see Figure 1)</td>
			<td><img alt="checkmark" src="/files/ftp_upload/53285/checkmark.jpg" /></td>
			<td><img alt="checkmark" src="/files/ftp_upload/53285/checkmark.jpg" /></td>
		</tr>
		<tr>
			<td>BedDepth (D)</td>
			<td>cm</td>
			<td colspan="3">Depth of the sediments (see Figure 1)</td>
			<td><img alt="checkmark" src="/files/ftp_upload/53285/checkmark.jpg" /></td>
			<td><img alt="checkmark" src="/files/ftp_upload/53285/checkmark.jpg" /></td>
		</tr>
		<tr>
			<td>HydrCond (K)</td>
			<td>cm/s</td>
			<td colspan="3">Hydraulic Conductivity</td>
			<td><img alt="checkmark" src="/files/ftp_upload/53285/checkmark.jpg" /></td>
			<td><img alt="checkmark" src="/files/ftp_upload/53285/checkmark.jpg" /></td>
		</tr>
		<tr>
			<td>Porosity (&#952;)</td>
			<td></td>
			<td colspan="3">Porosity</td>
			<td><img alt="checkmark" src="/files/ftp_upload/53285/checkmark.jpg" /></td>
			<td><img alt="checkmark" src="/files/ftp_upload/53285/checkmark.jpg" /></td>
		</tr>
		<tr>
			<td>ChannelVelocity (U)</td>
			<td>cm/s</td>
			<td colspan="3">Mean velocity in the surface water or channel</td>
			<td><img alt="checkmark" src="/files/ftp_upload/53285/checkmark.jpg" /></td>
			<td><img alt="checkmark" src="/files/ftp_upload/53285/checkmark.jpg" /></td>
		</tr>
		<tr>
			<td>Depth (d)</td>
			<td>cm</td>
			<td colspan="3">Water depth (see Figure 1)</td>
			<td><img alt="checkmark" src="/files/ftp_upload/53285/checkmark.jpg" /></td>
			<td><img alt="checkmark" src="/files/ftp_upload/53285/checkmark.jpg" /></td>
		</tr>
		<tr>
			<td>Slope (S)</td>
			<td></td>
			<td colspan="3">Slope of the bedforms and water surface</td>
			<td><img alt="checkmark" src="/files/ftp_upload/53285/checkmark.jpg" /></td>
			<td><img alt="checkmark" src="/files/ftp_upload/53285/checkmark.jpg" /></td>
		</tr>
		<tr>
			<td>NumParticles</td>
			<td></td>
			<td colspan="3">The number of particles released into the system.</td>
			<td><img alt="checkmark" src="/files/ftp_upload/53285/checkmark.jpg" /></td>
			<td></td>
		</tr>
		<tr>
			<td>TimeX (Time1, Time2..)</td>
			<td>min</td>
			<td colspan="3">Time at which each color change occurs</td>
			<td></td>
			<td><img alt="checkmark" src="/files/ftp_upload/53285/checkmark.jpg" /></td>
		</tr>
		<tr>
			<td>Simulation Buttons</td>
			<td></td>
			<td colspan="3">Definition</td>
			<td>Interface</td>
			<td>Mousedrop</td>
		</tr>
		<tr>
			<td>Setup</td>
			<td></td>
			<td colspan="3">Set&#8217;s up the simulation using parameters shown</td>
			<td><img alt="checkmark" src="/files/ftp_upload/53285/checkmark.jpg" /></td>
			<td><img alt="checkmark" src="/files/ftp_upload/53285/checkmark.jpg" /></td>
		</tr>
		<tr>
			<td>go/stop</td>
			<td></td>
			<td colspan="3">Starts and stops the simulation</td>
			<td><img alt="checkmark" src="/files/ftp_upload/53285/checkmark.jpg" /></td>
			<td><img alt="checkmark" src="/files/ftp_upload/53285/checkmark.jpg" /></td>
		</tr>
		<tr>
			<td>Step</td>
			<td></td>
			<td colspan="3">Clicking step causes one time step to pass.&#160; This allows users to slow down the code and see exactly what happens in 100 sec.</td>
			<td><img alt="checkmark" src="/files/ftp_upload/53285/checkmark.jpg" /></td>
			<td></td>
		</tr>
		<tr>
			<td>clear paths</td>
			<td></td>
			<td colspan="3">Clears all he blue particle paths from the screen</td>
			<td><img alt="checkmark" src="/files/ftp_upload/53285/checkmark.jpg" /></td>
			<td><img alt="checkmark" src="/files/ftp_upload/53285/checkmark.jpg" /></td>
		</tr>
		<tr>
			<td>Advance to next time</td>
			<td></td>
			<td colspan="3">This causes the program to run until the next color change time (TimeX)</td>
			<td></td>
			<td><img alt="checkmark" src="/files/ftp_upload/53285/checkmark.jpg" /></td>
		</tr>
		<tr>
			<td>mouse-drop</td>
			<td></td>
			<td colspan="3">This button must be clicked before particles may be placed in the subsurface by clicking on locations in the subsurface.</td>
			<td></td>
			<td><img alt="checkmark" src="/files/ftp_upload/53285/checkmark.jpg" /></td>
		</tr>
		<tr>
			<td>show-paths?</td>
			<td></td>
			<td colspan="3">If show-paths? is &#8220;on&#8221; the water particles leave a trail of blue showing where they have been (see Figure 1).</td>
			<td><img alt="checkmark" src="/files/ftp_upload/53285/checkmark.jpg" /></td>
			<td><img alt="checkmark" src="/files/ftp_upload/53285/checkmark.jpg" /></td>
		</tr>
		<tr>
			<td>re-drop?</td>
			<td></td>
			<td colspan="3">If re-drop? is &#8220;on&#8221; the particles are replaced in a flux weighted manner for every particle, which exits the system, and the cumulative plot does not work.&#160; When a particle exits the hyporheic zone the number of particles in the system decreases if re-drop? is &#8220;off&#8221; (see Figure 1).</td>
			<td><img alt="checkmark" src="/files/ftp_upload/53285/checkmark.jpg" /></td>
			<td></td>
		</tr>
	</tbody>
</table>
Table 1. Hyporheic Parameters and Simulation Controls. Each parameter, button, and slider that can be adjusted by the user is given in this table along with a definition.
In this simulation, two processes induce fluid velocity in the sand bed. The first is due to the interactions of the stream flow with bedforms. The velocity head at the water/sediment interface induced by bedforms is also approximately sinusoidal, and shifted by a quarter wavelength from the bedform itself22. The amplitude of the velocity head function at the surface-subsurface interface has been approximated from measurements as16:
Equation 2: 
<img alt="Equation 2" src="/files/ftp_upload/53285/53285eq2.jpg" />
where U is the mean surface water velocity, g is the gravitational constant, and d is the depth of the water (shown in Figure 1). The velocity head function is then given by:
Equation 3: 
<img alt="Equation 3" src="/files/ftp_upload/53285/53285eq3.jpg" />
This head function can then be used to calculate the bedform-based component of the subsurface velocity functions by solving the Laplace equation with a constant sand bed depth20. The second component of the porewater velocity is determined by the slope of the system, S, which corresponds to a gravitational head gradient that yields flow in the downstream direction proportional to <img alt="S/sqrt(1 + S^2)" src="/files/ftp_upload/53285/53285eq_S_inline.jpg" />. The final functions for porewater velocity are:
Equation 4: 
<img alt="Equation 4" src="/files/ftp_upload/53285/53285eq4.jpg" />
Equation 5: 
<img alt="Equation 5" src="/files/ftp_upload/53285/53285eq5.jpg" />
where u is the longitudinal velocity component, v is the vertical velocity component, K is the average hydraulic conductivity of the sediment, is the average porosity of the sediments, y is the vertical coordinate, and D is the depth of the sediments.
Particle tracking simulations were created, which use the NetLogo modeling language and simulation platform23. The two implementations (Mousedrop.nlogo and Interface.nlogo) use these equations to model hyporheic flow with the same simulation core. The primary difference is the initial locations of the tracer particles. Mousedrop allows the user to place simulated tracer anywhere within the subsurface. Subsurface velocity equations 4 and 5 are used to move the tracer to simulate dye injection experiments. In Interface, tracer is always placed along the surface/subsurface boundary in a flux-weighted manner. This mimics the delivery of dissolved and suspended material from the surface water into the porewater, which is crucial to understanding hyporheic exchange. The tracer then moves within the subsurface until it again reaches the stream water. Tracing the dye paths in the flume and simulating the paths using NetLogo yields the streamlines of the flowfield, as long as the flow conditions and bedform morphology remain steady during the period of observation. Interface.nlogo creates a cumulative residence time distribution, which shows the ratio of the number of tracer particles remaining in the sediments to the initial number of tracer particles placed at time 0 as a function of time.
As discussed in a recent literature survey24, there remains considerable debate within the educational research community about the relative merits of hands-on laboratory experiments versus simulated labs and computer models. On the one hand, some feel that &#8220;hands-on experience is at the heart of learning&#8221;25, and caution that cost-savings arguments may be fueling the replacement of hands-on lab activities by computer-based simulations, to the detriment of student understanding26. On the other hand, some researchers in science/engineering education argue that simulations are at least as effective as traditional hands-on labs27, or discuss the benefits of computer-simulation in fostering student-centered &#8220;discovery learning&#8221;28. While consensus has not been reached, many researchers have concluded that, ideally, computer simulations should supplement, rather than supplant, hands-on laboratory experiments29,30. There have also been initiatives within science and engineering education to simultaneously couple physical experimentation and real-world sensing with computer simulations of the phenomena; see, e.g., &#8220;bifocal modeling&#8221;31.
Students can gain a deeper conceptual knowledge and a better understanding of the scientific research process by interacting with both a physical system, and a computer-based simulation of that system. This procedure involves having students perform a solute transport experiment that demonstrates gravitational and bedform-induced hyporheic exchange flow, and match their own experimental setup and results with a computer simulation of the same phenomena. This comparison facilitates important student-learning outcomes, and a deeper discussion of the scientific method, and interplay between model/theory-building and empirical validation through data collection. After performing this comparison, students can also take advantage of the benefits of computer-based simulation to quickly explore a multitude of alternative scenarios by changing model parameters.

<table border="0" cellpadding="0" cellspacing="0" width="1244">
	<tbody>
		<tr height="21">
			<td height="21" style="height:21px;width:117px;">Flume</td>
			<td style="width:199px;">Engineering Laboratory Design</td>
			<td style="width:125px;">Custom</td>
			<td style="width:804px;">Laboratory flume with clear sides for 24-48 hours</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Flowmeter</td>
			<td>Rosemount&#160;</td>
			<td>8800 vortex&#160;</td>
			<td style="width:804px;">This is located inside the recirculation loop of the flume</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Sand</td>
			<td>US. Silica</td>
			<td>F30</td>
			<td style="width:804px;">Research-grade sand to form a layer 10-20 cm deep throughout the flume</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;">Dye</td>
			<td>Samples from food companies</td>
			<td></td>
			<td style="width:804px;">Water-soluble food grade dye made into an aqueous solution.&#160; Dark colors like red, blue and green work best. (Avoid food dyes in propylene glycol)</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Syringe</td>
			<td>HSW</td>
			<td>4100.000V0</td>
			<td style="width:804px;">5-10 mL, e.g. HSW Norm-Ject 2-part disposable syringe</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Pipetting Needle</td>
			<td>Cadence Science</td>
			<td>7942</td>
			<td>14-gage, 6-in blunt end,&#160; to inject the dye deep into the sand.</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;">Digital Camera</td>
			<td>Any</td>
			<td></td>
			<td style="width:804px;">Digital camera with steady tripod (Time lapse cameras can be used to collect rapid evenly spaced data.)&#160; We used a Nikon D7000.</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Ruler</td>
			<td>Any</td>
			<td></td>
			<td style="width:804px;">Transparent is best.</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Measuring Tape</td>
			<td>Any</td>
			<td></td>
			<td style="width:804px;"></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Netlogo Software</td>
			<td>CCL</td>
			<td></td>
			<td><a href="http://ccl.northwestern.edu/netlogo/">http://ccl.northwestern.edu/netlogo/</a></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Mousedrop.nlogo</td>
			<td>Netlogo Commons</td>
			<td align="right">4259</td>
			<td><a href="http://modelingcommons.org/browse/one_model/4259">http://modelingcommons.org/browse/one_model/4259</a></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Interface.nlogo</td>
			<td>Netlogo Commons</td>
			<td align="right">4258</td>
			<td><a href="http://modelingcommons.org/browse/one_model/4258">http://modelingcommons.org/browse/one_model/4258</a></td>
		</tr>
	</tbody>
</table>

visualizing hyporheic flow through bedforms using dye experiments and simulation

Advective exchange between the pore space of sediments and the overlying water column, called hyporheic exchange in fluvial environments, drives solute transport in rivers and many important biogeochemical processes. To improve understanding of these processes through visual demonstration, we created a hyporheic flow simulation in the multi-agent computer modeling platform NetLogo. The simulation shows virtual tracer flowing through a streambed covered with two-dimensional bedforms. Sediment, flow, and bedform characteristics are used as input variables for the model. We illustrate how these simulations match experimental observations from laboratory flume experiments based on measured input parameters. Dye is injected into the flume sediments to visualize the porewater flow. For comparison virtual tracer particles are placed at the same locations in the simulation. This coupled simulation and lab experiment has been used successfully in undergraduate and graduate laboratories to directly visualize river-porewater interactions and show how physically-based flow simulations can reproduce environmental phenomena. Students took photographs of the bed through the transparent flume walls and compared them to shapes of the dye at the same times in the simulation. This resulted in very similar trends, which allowed the students to better understand both the flow patterns and the mathematical model. The simulations also allow the user to quickly visualize the impact of each input parameter by running multiple simulations. This process can also be used in research applications to illustrate basic processes, relate interfacial fluxes and porewater transport, and support quantitative process-based modeling.

The use of a simulation in conjunction with experiments allows students to observe the similarities and differences between idealized mathematical models and more complex real systems. Figure 4 shows an example comparing dye injection photographs with Mousedrop simulations. The initial photograph is used to determine the placement of the simulated dye tracer at time zero, and then the simulation is run for 34.2 min and compared with a photograph taken at that time. Overall the model does an exce...

Watch this Scientific Journal Video about Visualizing Hyporheic Flow Through Bedforms Using Dye Experiments and Simulation at JoVE.com

Visualizing Hyporheic Flow Through Bedforms Using Dye Experiments and Simulation

This manuscript describes how to create regular bedforms in a flume, visualize flow through the bedforms, and use computer simulations to simulate the hyporheic flow. The computer simulations compare well with the experimental observations. This coupled simulation and experiment is well-suited for both research and educational purposes.

Advective exchange between the pore space of sediments and the overlying water column, called hyporheic exchange in fluvial environments, drives solute ...

visualizing-hyporheic-flow-through-bedforms-using-dye-experiments

Research

JoVE Journal

Engineering

12.0K ビュー.  St. Ambrose University. This manuscript describes how to create regular bedforms in a flume, visualize flow through the bedforms, and use computer simulations to simulate the hyporheic flow. The computer simulations compare well with the experimental observations. This coupled simulation and experiment is well-suited for both research and educational purposes. 

ビデオ: Visualizing Hyporheic Flow Through Bedforms Using Dye Experiments and Simulation

This manuscript describes how to create regular bedforms in a flume, visualize flow through the bedforms, and use computer simulations to simulate the hyporheic flow.  The computer simulations compare well with the experimental observations.  This coupled simulation and experiment is well-suited for both research and educational purposes.

analyzing mitochondrial morphology through simulation supervised learning

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This article explains how to use simulation-supervised machine learning for analyzing mitochondria morphology in fluorescence microscopy images of fixed cells.

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The present protocol describes an ideal solution to train novices in the use of point-of-care ultrasound devices for the practical clinical skill of visually assessing distinct individual anatomical vascular conditions prior to and during an intended venous vascular cannulation using point-of-care ultrasound in a patient.

Training Novices in POCUS for Vascular Cannulation Using Simulation Models

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Nuclear magnetic resonance (NMR) spectroscopy can characterize structural protein dynamics in a residue-specific manner. We provide a hands-on protocol for recording NMR 15N R1 and R2 relaxation and {1H}-15N heteronuclear Overhauser effect (hetNOE) experiments, sensitive to the picoseconds to nanoseconds...

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Astrocytes are morphologically complex cells, exemplified by their multiple processes and bushy territories. To analyze their elaborate morphology, we present a reliable protocol to perform intracellular Lucifer yellow iontophoresis in lightly fixed...

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The siphon breaking phenomenon was investigated experimentally and a theoretical model was proposed. A simulation program based on the theoretical model was developed and the results of the simulation program were compared with experimental results. It was concluded that the results of the simulation program matched the experimental results...

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Simulation, Fabrication and Characterization of THz Metamaterial Absorbers

Metamaterials (MM), artificial materials engineered to have properties that may not be found in nature, have been widely explored since the first theoretical1 and experimental demonstration2 of their unique properties. MMs can provide a highly controllable electromagnetic response, and to date have been demonstrated in every technologically relevant spectral range including the optical3, near IR4, mid IR5 , THz6 , mm-wave7 , microwave8 and radio9 bands. Applications include perfect lenses10, sensors11, telecommunications12, invisibility cloaks13 and filters14,15. We have recently developed single band16, dual band17 and broadband18 THz metamaterial absorber devices capable of greater than 80% absorption at the resonance peak. The concept of a MM absorber is especially important at THz frequencies where it is difficult to find strong frequency selective THz absorbers19. In our MM absorber the THz radiation is absorbed in a thickness of ~ &lambda;/20, overcoming the thickness limitation of traditional quarter wavelength absorbers. MM absorbers naturally lend themselves to THz detection applications, such as thermal sensors, and if integrated with suitable THz sources (e.g. QCLs), could lead to compact, highly sensitive, low cost, real time THz imaging systems.

This protocol outlines the simulation, fabrication and characterization of THz metamaterial absorbers. Such absorbers, when coupled with an appropriate sensor, have applications in THz imaging and spectroscopy.

Metamaterials (MM),  artificial materials engineered to have properties that may not be found in  nature, have been widely explored since the first ...

Measuring Material Microstructure Under Flow Using 1-2 Plane Flow-Small Angle Neutron Scattering

A new small-angle neutron scattering (SANS) sample environment optimized for studying the microstructure of complex fluids under simple shear flow is presented. The SANS shear cell consists of a concentric cylinder Couette geometry that is sealed and rotating about a horizontal axis so that the vorticity direction of the flow field is aligned with the neutron beam enabling scattering from the 1-2 plane of shear (velocity-velocity gradient, respectively). This approach is an advance over previous shear cell sample environments as there is a strong coupling between the bulk rheology and microstructural features in the 1-2 plane of shear. Flow-instabilities, such as shear banding, can also be studied by spatially resolved measurements. This is accomplished in this sample environment by using a narrow aperture for the neutron beam and scanning along the velocity gradient direction. Time resolved experiments, such as flow start-ups and large amplitude oscillatory shear flow are also possible by synchronization of the shear motion and time-resolved detection of scattered neutrons. Representative results using the methods outlined here demonstrate the useful nature of spatial resolution for measuring the microstructure of a wormlike micelle solution that exhibits shear banding, a phenomenon that can only be investigated by resolving the structure along the velocity gradient direction. Finally, potential improvements to the current design are discussed along with suggestions for supplementary experiments as motivation for future experiments on a broad range of complex fluids in a variety of shear motions.

A shear cell is developed for small-angle neutron scattering measurements in the velocity-velocity gradient plane of shear and is used to characterize complex fluids. Spatially resolved measurements in the velocity gradient direction are possible for studying shear-banding materials. Applications include investigations of colloidal dispersions, polymer solutions, and self-assembled structures.

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Experiments on Ultrasonic Lubrication Using a Piezoelectrically-assisted Tribometer and Optical Profilometer

Friction and wear are detrimental to engineered systems. Ultrasonic lubrication is achieved when the interface between two sliding surfaces is vibrated at a frequency above the acoustic range (20 kHz). As a solid-state technology, ultrasonic lubrication can be used where conventional lubricants are unfeasible or undesirable. Further, ultrasonic lubrication allows for electrical modulation of the effective friction coefficient between two sliding surfaces. This property enables adaptive systems that modify their frictional state and associated dynamic response as the operating conditions change. Surface wear can also be reduced through ultrasonic lubrication. We developed a protocol to investigate the dependence of friction force reduction and wear reduction on the linear sliding velocity between ultrasonically lubricated surfaces. A pin-on-disc tribometer was built which differs from commercial units in that a piezoelectric stack is used to vibrate the pin at 22 kHz normal to the rotating disc surface. Friction and wear metrics including effective friction force, volume loss, and surface roughness are measured without and with ultrasonic vibrations at a constant pressure of 1 to 4 MPa and three different sliding velocities: 20.3, 40.6, and 87 mm/sec. An optical profilometer is utilized to characterize the wear surfaces. The effective friction force is reduced by 62% at 20.3 mm/sec. Consistently with existing theories for ultrasonic lubrication, the percent reduction in friction force diminishes with increasing speed, down to 29% friction force reduction at 87 mm/sec. Wear reduction remains essentially constant (49%) at the three speeds considered.

We present a protocol for using a piezoelectrically-assisted tribometer and optical profilometer to investigate the dependence of ultrasonic wear and friction reduction on linear velocity, contact pressure, and surface properties.

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The use of Finite Element (FE) simulation software to adequately predict the outcome of sheet metal forming processes is crucial to enhancing the efficiency and lowering the development time of such processes, whilst reducing costs involved in trial-and-error prototyping. Recent focus on the substitution of steel components with aluminum alloy alternatives in the automotive and aerospace sectors has increased the need to simulate the forming behavior of such alloys for ever more complex component geometries. However these alloys, and in particular their high strength variants, exhibit limited formability at room temperature, and high temperature manufacturing technologies have been developed to form them. Consequently, advanced constitutive models are required to reflect the associated temperature and strain rate effects. Simulating such behavior is computationally very expensive using conventional FE simulation techniques.
This paper presents a novel Knowledge Based Cloud FE (KBC-FE) simulation technique that combines advanced material and friction models with conventional FE simulations in an efficient manner thus enhancing the capability of commercial simulation software packages. The application of these methods is demonstrated through two example case studies, namely: the prediction of a material's forming limit under hot stamping conditions, and the tool life prediction under multi-cycle loading conditions.

The following paper presents a novel FE simulation technique (KBC-FE), which reduces computational cost by performing simulations on a cloud computing environment, through the application of individual modules. Moreover, it establishes a seamless collaborative network between world leading scientists, enabling the integration of cutting edge knowledge modules into FE simulations.

The use of Finite Element (FE) simulation software to adequately predict the outcome of sheet metal forming processes is crucial to enhancing the ...

Digital Printing of Titanium Dioxide for Dye Sensitized Solar Cells

Silicon solar cell manufacturing is an expensive and high energy consuming process. In contrast, dye sensitized solar cell production is less environmentally damaging with lower processing temperatures presenting a viable and low cost alternative to conventional production. This paper further enhances these environmental credentials by evaluating the digital printing and therefore additive production route for these cells. This is achieved here by investigating the formation and performance of a metal oxide photoelectrode using nanoparticle sized titanium dioxide. An ink-jettable material was formulated, characterized and printed with a piezoelectric inkjet head to produce a 2.6 &#181;m thick layer. The resultant printed layer was fabricated into a functioning cell with an active area of 0.25 cm2 and a power conversion efficiency of 3.5%. The binder-free formulation resulted in a reduced processing temperature of 250 &#176;C, compatible with flexible polyamide substrates which are stable up to temperatures of 350 &#730;C. The authors are continuing to develop this process route by investigating inkjet printing of other layers within dye sensitized solar cells.

This paper investigates the suitability of inkjet printing for the manufacturing of dye-sensitized solar cells. A binder-free TiO2 nanoparticle ink was formulated and printed onto a FTO glass substrate. The printed layer was fabricated into a cell with an active area of 0.25 cm2 and an efficiency of 3.5%.

Silicon solar cell manufacturing is an expensive and high energy consuming process. In contrast, dye sensitized solar cell production is less ...

Under the design conditions of a research reactor, the siphon phenomenon induced by pipe rupture can cause continuous outward flow of water. To prevent this outflow, a control device is required. A siphon breaker is a type of safety device that can be utilized to control the loss of coolant water effectively.
To analyze the characteristics of siphon breaking, a real-scale experiment was conducted. From the results of the experiment, it was found that there are several design factors that affect the siphon breaking phenomenon. Therefore, there is a need to develop a theoretical model capable of predicting and analyzing the siphon breaking phenomenon under various design conditions. Using the experimental data, it was possible to formulate a theoretical model that accurately predicts the progress and the result of the siphon breaking phenomenon. The established theoretical model is based on fluid mechanics and incorporates the Chisholm model to analyze two-phase flow. From Bernoulli&#39;s equation, the velocity, quantity, undershooting height, water level, pressure, friction coefficient, and factors related to the two-phase flow could be obtained or calculated. Moreover, to utilize the model established in this study, a siphon breaker analysis and design program was developed. The simulation program operates on the theoretical model basis and returns the result as a graph. The user can confirm the possibility of the siphon breaking by checking the shape of the graph. Furthermore, saving the entire simulation result is possible and it can be used as a resource for analyzing the real siphon breaking system.
In conclusion, the user can confirm the status of the siphon breaking and design the siphon breaker system using the program developed in this study.

The siphon breaking phenomenon was investigated experimentally and a theoretical model was proposed. A simulation program based on the theoretical model was developed and the results of the simulation program were compared with experimental results. It was concluded that the results of the simulation program matched the experimental results well.

Under the design conditions of a research reactor, the siphon phenomenon induced by pipe rupture can cause continuous outward flow of water. To prevent ...

Simultaneous Measurement of Turbulence and Particle Kinematics Using Flow Imaging Techniques

Numerous problems in scientific and engineering fields involve understanding the kinematics of particles in turbulent flows, such as contaminants, marine micro-organisms, and/or sediments in the ocean, or fluidized bed reactors and combustion processes in engineered systems. In order to study the effect of turbulence on the kinematics of particles in such flows, simultaneous measurements of both the flow and particle kinematics are required. Non-intrusive, optical flow measurement techniques for measuring turbulence, or for tracking particles, exist but measuring both simultaneously can be challenging due to interference between the techniques. The method presented herein provides a low cost and relatively simple method to make simultaneous measurements of the flow and particle kinematics. A cross section of the flow is measured using a particle image velocimetry (PIV) technique, which provides two components of velocity in the measurement plane. This technique utilizes a pulsed-laser for illumination of the seeded flow field that is imaged by a digital camera. The particle kinematics are simultaneously imaged using a light emitting diode (LED) line light that illuminates a planar cross section of the flow that overlaps with the PIV field-of-view (FOV). The line light is of low enough power that it does not affect the PIV measurements, but powerful enough to illuminate the larger particles of interest imaged using the high-speed camera. High-speed images that contain the laser pulses from the PIV technique are easily filtered by examining the summed intensity level of each high-speed image. By making the frame rate of the high-speed camera incommensurate with that of the PIV camera frame rate, the number of contaminated frames in the high-speed time series can be minimized. The technique is suitable for mean flows that are predominantly two-dimensional, contain particles that are at least 5 times the mean diameter of the PIV seeding tracers, and are low in concentration.

The technique described herein offers a low cost and relatively simple method to simultaneously measure particle kinematics and turbulence in flows with low particle concentrations. The turbulence is measured using particle image velocimetry (PIV), and particle kinematics are calculated from images obtained with a high-speed camera in an overlapping field-of-view.

Numerous problems in scientific and engineering fields involve understanding the kinematics of particles in turbulent flows, such as contaminants, marine ...

A 100 KW Class Applied-field Magnetoplasmadynamic Thruster

Applied-field magnetoplasmadynamic thrusters (AF-MPD thrusters) are hybrid accelerators in which electromagnetic and gas dynamic processes accelerate plasma to high speed; they have considerable potential for future space applications with the significant advantages of high specific impulse and thrust density. In this paper, we present a series of protocols for designing and manufacturing a 100 kW class of AF-MPD thruster with water-cooling structures, a 130 V maximum discharge voltage, a 800 A maximum discharge current, and a 0.25 T maximum strength of magnetic field. A hollow tantalum tungsten cathode acts as the only propellant inlet to inhibit the radial discharge, and it is positioned axially at the rear of the anode in order to relieve anode starvation. A cylindrical divergent copper anode is employed to decrease anode power deposition, where the length has been reduced to decrease the wall-plasma connecting area. Experiments utilized a vacuum system that can achieve a working vacuum of 0.01 Pa for a total propellant mass flow rate lower than 40 mg/s and a target thrust stand. The thruster tests were carried out to measure the effects of the working parameters such as propellant flow rates, the discharge current, and the strength of applied magnetic field on the performance and to allow appropriate analysis. The thruster could be operated continuously for significant periods of time with little erosion on the hollow cathode surface. The maximum power of the thruster is 100 kW, and the performance of this water-cooled configuration is comparable with that of thrusters reported in the literature.

The goal of this protocol is to introduce the design of a 100 kW class applied-field magnetoplasmadynamic thruster and relevant experimental methods.

Applied-field magnetoplasmadynamic thrusters (AF-MPD thrusters) are hybrid accelerators in which electromagnetic and gas dynamic processes accelerate ...

Visualizing Uniaxial-strain Manipulation of Antiferromagnetic Domains in Fe1+YTe Using a Spin-polarized Scanning Tunneling Microscope

The quest to understand correlated electronic systems has pushed the frontiers of experimental measurements toward the development of new experimental techniques and methodologies. Here we use a novel home-built uniaxial-strain device integrated into our variable temperature scanning tunneling microscope that enables us to controllably manipulate in-plane uniaxial strain in samples and probe their electronic response at the atomic scale. Using scanning tunneling microscopy (STM) with spin-polarization techniques, we visualize antiferromagnetic (AFM) domains and their atomic structure in Fe1+yTe samples, the parent compound of iron-based superconductors, and demonstrate how these domains respond to applied uniaxial strain. We observe the bidirectional AFM domains in the unstrained sample, with an average domain size of ~50-150 nm, to transition into a single unidirectional domain under applied uniaxial strain. The findings presented here open a new direction to utilize a valuable tuning parameter in STM, as well as other spectroscopic techniques, both for tuning the electronic properties as for inducing symmetry breaking in quantum material systems.

Visualizing Uniaxial-strain Manipulation of Antiferromagnetic Domains in Fe1+YTe Using a Spin-polarized Scanning Tunneling Microscope

Using uniaxial strain combined with spin-polarized scanning tunneling microscopy, we visualize and manipulate the antiferromagnetic domain structure of Fe1+yTe, the parent compound of iron-based superconductors.

The quest to understand correlated electronic systems has pushed the frontiers of experimental measurements toward the development of new experimental ...

Automated Delivery of Microfabricated Targets for Intense Laser Irradiation Experiments

Described is an experimental procedure that enables high-power laser irradiation of microfabricated targets. Targets are brought to the laser focus by a closed feedback loop that operates between the target manipulator and a ranging sensor. The target fabrication process is explained in detail. Representative results of MeV-level proton beams generated by irradiation of 600 nm thick gold foils at a rate of 0.2 Hz are given. The method is compared with other replenishable target systems and the prospects of increasing the shot rates to above 10 Hz are discussed.

A protocol is presented for automated irradiation of thin gold foils with high intensity laser pulses. The protocol includes a step-by-step description of the micromachining target fabrication process and a detailed guide for how targets are brought to the laser&#39;s focus at a rate of 0.2 Hz.

Described is an experimental procedure that enables high-power laser irradiation of microfabricated targets. Targets are brought to the laser focus by a ...