Technical Program of the 1st Stanford Mechanical Engineering … · 2015. 5. 1. · Technical Program of the 1st Stanford Mechanical Engineering Conference (MECON), May 1, 2015 T11

ENGINEERINGMECHANICAL ENGINEERING CONFERENCE

Technical Program of the 1st Stanford Mechanical Engineering Conference

Organization CommitteeAlexander M Zöllner, Charbel Eid, Martin Winterkorn, Xiaolin Zheng, Ellen Kuhl

May 1, 2015

Technical Program of the 1st Stanford Mechanical Engineering Conference (MECON),May 1, 2015

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Conference Program

Talks

Session 1T1. Computational modeling of electrokinetic transport in micro-and nano-poresShima Alizadeh and Ali Mani 1

T2. A fast sparse solver for finite-element matricesAmirhossein Aminfar and Eric Darve 2

T3. Bending moments to business models: An entrepreneurshipcase studyMatt Bandelt, Jose Gutierrez, and Kezia Alfred 3

T4. Scalable metal nanowire arrays and composites for thermalmanagementMichael T Barako, Shilpi Roy-Panzer, and Kenneth E Goodson 4

T5. Sol-flame synthesis of cobalt-doped TiO2 nanowiresLili Cai and Xiaolin Zheng 5

T6. Modeling noise and lease soft costs improves wind farm de-signLe Chen and Erin MacDonald 6

Session 2T7. Phase field modeling for nanowire growthYanming Wang, Paul C McIntyre, and Wei Cai 7

T8. Patient-specific airway wall remodeling in chronic lung dis-easeMona Eskandari and Ellen Kuhl 8

T9. Anchor loss modeling in MEMS resonatorsDustin D Gerrard, Eldwin J Ng, and Thomas W Kenny 8

T10. How fluid mechanics complicates combustion experimentsKevin P Grogan and Matthias Ihme 9

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T11. Universal meshes: Computing conforming triangulations forcurved domainsHardik Kabaria and Adrian Lew 10

T12. Drag force and diffusivity of small cylinder in free moleculeflowChangran Liu, Zhigang Li, and Hai Wang 11

Session 3T13. Quantification of a traditional assay for gentle touch in C.elegansAdam L Nekimken, Eileen A Mazzochette, and Beth L Pruitt 11

T14. Droplet-based microfluidics in the diagnosis of tuberculosisFengjiao Lyu, Yunfei Cheng, and Sindy KY Tang 12

T15. Strain-enhanced relaxation regulates nonlinear elasticity inbiopolymer gelsSungmin Nam and Ovijit Chaudhuri 13

T16. Cooperative collision avoidance via proximal message pass-ingHao Yi Ong and J Christian Gerdes 14

T17. Passive wing morphing in flapping wingsAmanda K Stowers and David Lentink 15

T18. Toward magnetic guidance of microcatheters in the brainLizmarie Comenencia Ortiz, Margaret Koehler, andAllison M Okamura 15

PostersP1. mSTAR Thermal enclousar modelingAbdulrahman Alfauwaz 16

P2. High surface area supercapacitors based on manganese oxidenanoparticlesJoaquin Camacho, Changran Liu, and Hai Wang 17

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P3. TugBot – Using gecko adhesion to pull large weightsGregory M Campbell, David L Christensen, andMark R Cutkosky 17

P4. Evaluating alternative fuels in aviation gas turbinesSerena E Carbajal and Matthias Ihme 18

P5. Towards field identification of mosquitoes via mobile phonebased acoustic classificationErica Castillo, Haripriya Mukundarajan, and Manu Prakash 18

P6. In-situ ovenization of highly doped Lame-mode silicon res-onatorsYunhan Chen, Eldwin J Ng, and Thomas W Kenny 19

P7. An energy-based approach for finite element modeling ofcollagen-swelling interactionXi Cheng, Steven J Petsche, and Peter M Pinsky 20

P8. Measuring aerodynamic weight support in birds from takeoffto landingDiana D Chin and David Lentink 21

P9. Acl injury and its effects on osteoarthritisDaniel Concha 22

P10. A robust, ultra-stable, flight ready optical cavity systemGrant Cutler, Daniel DeBra, and Drew Nelson 23

P11. Viscoelastic modeling of brain tissue by nanoindentationRijk de Rooij and Ellen Kuhl 24

P12. Structured light 3D surface reconstruction of birdsMarc E Deetjen and David Lentink 25

P13. Design and experimental evaluation of a skin-stretch hapticdevice for improved control of brain-computer interfacesDarrel R Deo, Sean M Sketch, and Allison M Okamura 26

P14. Design of a novel device to improve physician fatigue in theoperating roomPablo A Escobar and Lauren Aquino Shlulzas 26

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P15. Measurements of the thermal conductivity and specific heatof degenerately doped siliconCamille LM Everhart, Tim English, and Thomas W Kenny 27

P16. Temperature effects on 1:1 modal coupling for Q-factor en-hancement of a disk resonatorIan B Flader, Chae H Ahn, and Thomas W Kenny 28

P17. A novel platform for testing the cell adhesion mechanicsand myogenic function of induced pluripotent stem cell derivedcardiomyocytesJoy A Franco, Alexandre JS Ribeiro, and Beth L Pruitt 29

P18. Canonical problems in fluid-particle interaction in a radiationenvironmentSwetava Ganguli 30

P19. A novel haptic fMRI interface with a four-bar linkage and adynamically decoupled rotation axisHari Ganti, Samir Menon, and Oussama Khatib 31

P20. Fast parameter and state estimation with the Spectral KalmanFilter: An application for CO2 injection in heterogeneous domainsHojat Ghorbanidehno, Peter Kitanidis, and Eric Darve 32

P21. 3D vibrational measurements and axes of rotation of middleear ossicles in the mousePeter K Gottlieb, Charles R Steele, and Sunil Puria 33

P22. Predicting weight support based on wake measurements of aflying bird in still airEric Gutierrez and David Lentink 34

P23. Improved controllers for POMDPS and decentralizedPOMDPsRavi Haksar and Sanjay Lall 34

P24. Survey-based research methods in engineering education re-searchAngela Harris, Emily Cao, and Shannon Gilmartin 35

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P25. Flow reactor study of combustion characteristics of variousfuelsDaniel H Hernandez, David Llanos, and Craig T Bowman 36

P26. Instrumented mouthguard measurements of head rotation inhuman mild traumatic brain injuryFidel Hernandez and David B Camarillo 37

P27. Synchronization of similar nonlinear MEMS oscillatorsDaniel Heywood, Yushi Yang, and Thomas W Kenny 37

P28. Analysis of a novel aerodynamic force measurement systemfor drones and birdsBen Hightower 37

P29. Hopping spacecraft/rover hybrids for the exploration of smallsolar system bodiesBenjamin Hockman and Marco Pavone 38

P30. The influence of axonal elongation on the developing brainMaria Holland and Ellen Kuhl 39

P31. Inertial capacitive sensor platform: Co-fabricated accelerom-eters, pressure sensor, thermometerVu A Hong, Chae H Ahn, and Thomas W Kenny 40

P32. Characterizing and operating a MEMS disk resonator gyro-scopeJulia Huynh, Chae H Ahn, and Thomas W Kenny 40

P33. In vivo measurement of lift force in hovering hummingbirdsRivers Ingersoll and David Lentink 41

P34. Shared control of the automated vehicle: A Wizard of OzstudyMishel Johns and Wendy G Ju 42

P35. Experimental test bed for facilitating human-robot interac-tionsKirsten Kaplan, Kirk Nichols, and Allison M Okamura 42

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P36. Synchronous universal droplet logic and controlGeorgios Katsikis, James Cybulski, and Manu Prakash 43

P37. Optofluidic ultrahigh-throughput detection of fluorescentdropsMinkyu Kim, Ming Pan, and Sindy KY Tang 44

P38. Sensitivity of shock-boundary layer interaction to geometricperturbationsJi Hoon Kim, Laura M Campo, and John K Eaton 44

P39. How lovebirds maneuver rapidly using super-fast head sac-cades and image feature stabilizationDaniel Kress, Evelien van Bokhorst, and David Lentink 45

P40. Ex vivo evaluation of an instrumented mouthguardCalvin Kuo, Brad Hammoor, and Lyndia Wu 46

P41. Developing an in-house production method for carbon fibersandwich force platesCarl Lawhon, Rivers Ingersoll, and David Lentink 46

P42. Rapid stress relaxation in hydrogels promotes homogeneouscartilage matrix formation by chondrocytesHongpyo Lee 47

P43. A computational model predicts the changes in brain shapeduring Alzheimer’s diseaseJames Lehto Miller and Ellen Kuhl 48

P44. Artificial crystal of mechanical strain-textured molybdenumdisulfideHong Li and Xiaolin Zheng 49

P45. Mass transfer to reacting surfaces with small non-reactingdefectsTiras Lin and Eric Shaqfeh 50

P46. Full scale simulation of an integrated monolithic heat sinkfor thermal management of a high power density GaN-SiC chipTanya Liu, Farzad Houshmand, and Kenneth E Goodson 51

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P47. Probing the viscoelasticity of the C. elegans bodyFrederic Loizeau, Sylvia Fechner, and Beth L Pruitt 51

P48. The obstacle is the pathRichard Lui, Zach Chase, and Joseph Funke 52

P49. Geometric analysis and fluid structure interaction simulationof Abdominal Aortic Aneurysm (AAA) formationMoritz Mangold, Alexander M Zoellner, and Ellen Kuhl 53

P50. Smart products that can elicit meaningful interactions withusersNikolas Martelaro and Wendy G Ju 54

P51. Design of a feathered morphing robot wingLaura Matloff and Amanda K Stowers 55

P52. Study of a turbulent mixing model with an optimization ap-proachPedro Milani, Kevin Ryan, and John K Eaton 56

P53. Timing of unstructured takeovers in automated drivingBrian K Mok, Mishel Johns, and Wendy G Ju 56

P54. Ultrafine manganese oxide nanoparticles synthesized by flamestabilized on a rotating surfaceNick J Montes, Joaquin Camacho, and Hai Wang 57

P55. Flame synthesis of WO3 nanowires for efficient photoelec-trochemical water-splittingKoosha Nassiri Nazif and Xiaolin Zheng 58

P56. Quantifying butterfly effect for large eddy simulations usingLyapunov exponentsGabriel Nastac and Matthias Ihme 58

P57. Design of teleoperated robotic framework for training sur-geonsDouglas Onyango, Kamran Shamaei, and Allison M Okamura 58

P58. 3D Modeling of the human middle ear cavityJared Ostdiek 59

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P59. Model predictive control in an occluded environmentVivian Zhang and J Christian Gerdes 60

P60. Underwater robotic exploratoriumAli Parsaei and Oussama Khatib 60

P61. From the campus to the workplace: Using mixed methods re-search designs to identify challenges and opportunities in today’sengineering workJerrod Peterson, Samantha Brunhaver, and Helen L Chen 61

P62. A tactile, patient-specific brain model for preoperative sur-gical trainingCaitlin Ploch, Chris Mansi, and Ellen Kuhl 62

P63. Fast linear solvers and preconditioners for sparse and densematricesHadi Pouransari, Pieter Coulier, and Eric Darve 63

P64. Effect of film density on wet etch rate in low temperatureplasma-enhanced atomic layer deposited silicon nitrideJ Provine, Peter Schindler, and Fritz B Prinz 64

P65. Modeling a flow-through desalination system for enhancedsalt removalYatian Qu, Michael Stadermann, and Juan Santiago 64

P66. Virtual reality for birdsWill RT Roderick, Daniel Kress, and David Lentink 65

P67. Damping mechanisms in dual-ring resonatorsJanna Rodriguez, Yushi Yang, and Thomas W Kenny 65

P68. Thermal cycling of polymer solar cellsNicholas Rolston, Veerle Balcaen, and Reinhold H Dauskardt 66

P69. A bidomain finite element model of the whole heartFrancisco Sahli, Daniel Hurtado, and Ellen Kuhl 67

P70. Advanced combustion diagnostics development and applica-tionsDavid V Salazar and Ronald K Hanson 67

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P71. On-road autonomous driving simulatorSrinath Sibi, Sonia A Baltodano, and Wendy G Ju 68

P72. Exploratory study of atherosclerotic plaque using synchro-tron X-ray diffractionHerbert P Silva and Drew Nelson 69

P73. Design of a hand-held device with 3-degree-of-freedom hap-tic feedbackDongsuk Shin, Jung Hwa Bae, and Mark R Cutkosky 69

P74. Analysis of scalar mixing using X-ray computed tomographyand large-eddy simulationsSadaf Sobhani, Jared Dunnmon, and Matthias Ihme 69

P75. Finite element model of the organ of Corti micromechanicsin the mouse cochleaJoris AM Soons, Charles R Steele, and Sunil Puria 71

P76. Effect of low temperature chemistry in gas turbine engines:A computational and theoretical studyAlessandro Stagni, Jeff O’Brien, and Matthias Ihme 72

P77. Free flight stabilization to lateral gusts in parrotletsAndrea Stein, Daniel Kress, and David Lentink 72

P78. A detailed 10 year review of medical device additive manu-facturing researchKatherine J Stephenson 73

P79. A compliant robotic hand for marine explorationHannah S Stuart, Shiquan Wang, and Mark R Cutkosky 74

P80. Optimization and uncertainty minimization of the founda-tional fuel chemistry modelYujie Tao, Gregory P Smith, and Hai Wang 75

P81. Homework and student learningAutumn Turpin, Kai Jun Chew, and Peggy Boylan-Ashraf 76

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P82. Optical coherence tomography and indentation: A methodfor assessing interfacial bond strength in osteochondral implantsScott Uhlrich, Alberto Arvayo, and Marc E Levenston 77

P83. Plume characterization of a high directed energy plasmasource for material interaction studiesThomas C Underwood, Keith T Loebner, andMark A Cappelli 77

P84. Noise, but not uncoupled-stability, reduces realism and like-ability of bilateral teleoperationJulie M Walker, Nick Colonnese, and Allison M Okamura 78

P85. Energy flow in the cochlea: Passive and active mechanismsYanli Wang, Sunil Puria, and Charles R Steele 79

P86. Enabling next-generation of gas turbine and alternative fuelutilization: Hybrid approach to combustion chemistry of jet fuelsRui Xu and Hai Wang 80

P87. Reduction of carbon dioxide on semiconductorsShang Zhai 80

P88. Trajectory smoothing for car-like robots with elastic bandmethodZhijie Zhu, Edward Schmerling, and Marco Pavone 81

P89. Design of smart adhesive for bondlines monitoring in aircraftstructuresYitao Zhuang, Fotis Kopsaftopoulos, and Fu-kuo Chang 82

P90. Designing a robot for ballistic perching and climbingNitin Bandaru, Matt Estrada, and Mark R Cutkosky 82

P91. Influence of photosensitizer concentration and irradiance onarticular cartilage bond strengthAlberto Arvayo, Chun Hua Zheng, and Marc E Levenston 82

P92. Comparing the transient osmotic swelling of articular carti-lage and meniscal fibrocartilage in confined compressionEva Gabriela Baylon and Marc E Levenston 83

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Index of Authors 85

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T1. Computational modeling of electrokinetic transport inmicro- and nano-poresShima Alizadeh and Ali Mani

A reduced order model has been developed to study the nonlinear elec-trokinetic behaviors emerging in the transport of ionic species throughmicro-scale and nano-scale porous media. In this approach a porousstructure is modeled as a network of long and thin pores. By assumingtransport equilibrium in the thin dimensions for each pore, a 1D trans-port equation is developed in the longitudinal direction covering a widerange of conditions including extreme limits of thick and thin electricdouble layers. This 1D model includes transport via diffusion, electro-migration and wide range of advection mechanisms including pressuredriven flow, electroosmosis, and diffusion osmosis. The area-averagedequations governing the axial transport from different pores are coupledat the pore intersections using the proper conservation laws. Moreover,an asymptotic treatment has been included in order to remove singular-ities in the limit of small concentration. The proposed method providesan efficient framework for insightful simulations of porous electroki-netic systems with applications in water desalination and energy stor-age.

T2. A fast sparse solver for finite-element matricesAmirhossein Aminfar and Eric Darve

We introduce a fast direct solver for sparse matrices arising from thefinite element discretization of elliptic PDEs. We use a fast direct multi-frontal solver as a preconditioner and use iterative refinement to achievemachine accuracy. This approach combines the advantages of direct anditerative schemes to arrive at a fast, robust and accurate solver. We willshow that this solver is much faster and more memory efficient com-pared to a conventional multi-frontal solver. Furthermore, the solver canbe applied to both structured and unstructured meshes in a similar man-ner. We build on our previous work and utilize the fact that dense frontal

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and update matrices in the multi-frontal algorithm can be representedas hierarchically off-diagonal low-rank (HODLR) matrices. Using thisidea, we replace all large dense matrix operations in the multi-frontalelimination process with HODLR operations to arrive at a faster andmore memory efficient multi-frontal solver.

T3. Bending moments to business models: An entrepreneur-ship case studyMatt Bandelt, Jose Gutierrez, and Kezia Alfred

This reports on the progress of an instructional technique that teachesimportant solid mechanics concepts within the context of an entrepreneur-ship case study and lab. This study has taken place over six quarters ofENGR-14 spanning three years, reaching over 500 Stanford engineeringsophomores.

This instructional technique is called scenario-based learning (SBL)and is accomplished by combining business school-style case study fea-turing a realistic entrepreneurial scenario with a typical engineering lab.The real world SBL scenarios introduce several entrepreneurial con-cepts, such as business models, mission statements, and SWOT analysis,in the context of product development that requires calculation of staticforces that lead to design and sourcing decisions. Three engineering labson forces, moments, bending stresses and mechanical advantage helpresolve the business problem presented in the case scenario. Custom-designed web-based videos and other interactive materials support thebusiness/entrepreneurial concepts and well as the lab procedures.

Students were tested pre-and-post the SBL case study/lab experi-ences to determine changes in engineering and entrepreneurial contentknowledge, entrepreneurial self-efficacy and career intent. Results showthat students can increase their knowledge of targeted entrepreneurshipconcepts without diminishment of learning core engineering concepts.

While the case study experience did not significantly change en-trepreneurial career intentions it did grow students’ perceived entre-preneurial self-efficacy (as measured by confidence in business skills),

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which can be a precursor to changing career intent. The case study expe-rience also appealed to a broad spectrum of students with career interestsranging from working for a start-up to working for an established globalbusiness. The implications of entrepreneurial case study instruction arediscussed.

Presenters for this research will include three student TAs who helpeddevelop the curricular materials and teach the labs in class. If chosenfor a podium presentation, we will deliver the talk in PechaKucha-style,which is the same style E-14 students use for their final classroom pre-sentation.

T4. Scalable metal nanowire arrays and composites for ther-mal managementMichael T Barako, Shilpi Roy-Panzer, and Kenneth E Goodson

Thermal management of microelectronics often requires materials thatsimultaneously provide tailored thermal properties along with one ormore additional functionalities in unique combinations that are not avail-able in natural materials. Thermal interfaces (i.e. between a heat sourceand a heat sink) require a material that exhibits both high thermal con-ductivity to efficiently transfer heat across the interface and mechanicalcompliance to alleviate mechanical stresses caused by thermal expan-sion. However, most commercially-available thermal interface materialsare predominantly either thermally conductive (e.g. solder) or mechan-ically compliant (e.g. thermal grease). Over the past decade, alignedcarbon nanotube arrays have received much attention for thermal appli-cations. However, the complex morphology, high defect density, and de-manding synthesis conditions have largely limited the thermal conduc-tivity, scalability, and applications of carbon nanotube arrays. Instead,we propose the use of vertically-aligned metal nanowire (NW) arraysand composites to combine the high thermal conductivity of alignedmetal filaments with additional thermal, mechanical, or chemical prop-erties derived from the interstitial volume, such as flexibility due to theirhigh aspect ratio.

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In the present work, copper NW arrays are synthesized via template-assisted electrodeposition, which is an inexpensive and scalable tech-nique to grow NW arrays directly onto devices and substrates over cen-timeter-sized areas. This method employs a sacrificial porous membraneto mask a substrate while copper is electrochemically deposited into thepores, forming NWs with diameters ranging from 50-1000 nm, lengthsup to 30 microns, and packing densities in excess of 20%. The effectivethermal conductivity of the NW array is measured using a frequency-domain electrothermal measurement technique. We report a measuredaxial effective thermal conductivity of the array to as high as 58 W/m/K.Since these arrays are highly anisotropic due to the preferential vertical-alignment of the NWs, the lateral thermal conductivity is found to bemore than an order of magnitude smaller than the cross-plane conductiv-ity. We further demonstrate the ability to infiltrate the interstitial spaceof these arrays with an organic phase change material to form a ther-mally capacitive composite that can passively buffer thermal transientsand hotspots. The enhanced thermal conductivity and capacitance ofthese composites can increase device performance and lifetime in appli-cations ranging from portable consumer electronics to aerospace powerelectronics.

T5. Sol-flame synthesis of cobalt-doped TiO2 nanowiresLili Cai and Xiaolin Zheng

Doping nanowires (NWs) is of crucial importance for a range of appli-cations due to the unique properties arising from both impurities incor-poration and nanoscale dimensions. However, existing doping methodsface the challenges of simultaneous control over the morphology, crys-tallinity, dopant distribution and concentration at the nanometer scale.Here, we present a controllable and reliable method, which combinesversatile solution phase chemistry and rapid flame annealing process(sol-flame), to dope TiO2 NWs with cobalt (Co). The sol-flame dopingmethod not only preserves the morphology and crystallinity of the TiO2NWs, but also allows fine control over the Co dopant concentration by

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varying the concentration of cobalt precursor solution. Characteriza-tions of the TiO2:Co NWs show that Co dopants exhibit 2+ oxidationstate and substitutionally occupy Ti sites in the TiO2 lattice. The Codopant concentration significantly affects the oxygen evolution reaction(OER) activity of TiO2:Co NWs, and the TiO2:Co NWs with 12 at.%of Co on the surface show the highest OER activity with a 0.76 V re-duction of the overpotential with respect to undoped TiO2 NWs. Thisenhancement of OER activity for TiO2:Co NWs are attributed to bothimproved surface charge transfer kinetics and increased bulk conductiv-ity. With the demonstrated controllability, we believe that the sol-flamedoping method will be a general and promising technique for effectivedoping of diverse nanostructured materials.

T6. Modeling noise and lease soft costs improves wind farmdesignLe Chen and Erin MacDonald

The Department of Energy (DOE) uses the metric Cost-of-Energy (COE)to assess the financial viability of renewable energy technologies andmake policy decisions. Current wind farm research focuses on decreas-ing COE by reducing hardware costs and optimizing turbine layouts.These hardware-related costs, which make up approximately 79% of to-tal annualized cost for a land-based wind farm, have detailed sub-modelsin the DOE’s estimation of COE. Non-hardware costs, termed soft costs,make up approximately 21% of total cost, yet are only represented withgeneral assumptions. This work expands these assumptions to more de-tailed models of the costs of landowner acquisition (lease costs) andnoise disturbance compensation. It offers significant improvements inCOE and makes early-stage farm design more efficient. A wind-farm-layout-optimization-under-uncertainty model is enhanced with proba-bilistic compensation models of landowners’ lease costs and noise ac-ceptance, based on nine different landowner compensation profiles. Thesystem-level model was tested on a 10 km2 area of land in Iowa with 22landowners and 12 residences. It includes the realistic constraint that all

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landowners are offered the same compensation structure even thoughthey have different profiles. Thus, the optimization must determine if”expensive” landowners with access to excellent wind resource will in-crease the compensation package for all. The model predicts COEs re-markably close to real-world costs, eliminating the need for ”calibra-tion” mark-up terms that typically represent soft-costs. Wind energypolicy-makers can use this model to promote new areas of soft-cost-focused research.

T7. Phase field modeling for nanowire growthYanming Wang, Paul C McIntyre, and Wei Cai

Nanowires (NWs) have promising applications in many fields such asintegrated circuits, solar cells or batteries, for their special electronicand optical properties. Vapor-liquid-solid (VLS) process is a widelyused NW growth method; however, many fundamental questions includ-ing the nucleation failure and growths kinking are still not fully under-stood. The answers to these questions are important for better control ofthe NW orientation, yield and quality required for industry applications.Therefore, a 3D computational model for studying VLS mechanism thatcan both capture the realistic NW morphology and reach the experimen-tal time scale is critically needed. We developed a 3D multi-phase fieldmodel for VLS NW growth. The model captures the equilibrium cat-alyst droplet shape on the substrate prior to NW growth. For the NWgrowth process, the model captures the NW tapering and sidewall facetsin good agreement with experimental observations. The model predictsthe steady-state NW growth velocity is a linear function of the vaporchemical potential and the inverse of catalyst diameter, providing a con-firmation of the Gibbs-Thomson effect in nanowire growth. The modelis applied to study the instability of the catalyst droplet on top of the NW,which is important for understanding the onset of growth kinking. Thefree energies are evaluated at different stages during the NW structuraltransition induced by a perturbation force. These data are presented as

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an energy landscape that can be used to examine the preferred kinkingdirections and estimate the corresponding energy barriers.

T8. Patient-specific airway wall remodeling in chronic lungdiseaseMona Eskandari and Ellen Kuhl

Chronic lung disease, such as bronchitis and asthma, affects more than aquarter of the adult population. The occlusion of the airway is attributedto pressure and growth remodeling mechanisms: airway constrictiondue to the thickening and contraction of the smooth muscle surroundingthe airway wall acts as an induced pressure, and airway inflammationdue to the influx of cells at the inner airway wall lining acts as an inducedgrowth. These mechanisms initiate critical failure conditions and buck-ling modes that lead to inward folding and progressive airflow obstruc-tion. Since the number of folds has been correlated with the degree ofocclusion, pressure and growth buckling modes in the airways have beenextensively studied for the limiting case of idealized, uniform, circu-lar cross sections. However, the behavior of imperfect, non-cylindrical,continuously branching airways, as found in the human body, remainsunknown. Here we demonstrate the ability to predict folding in three-dimensional patient-specific airways using the nonlinear field theoriesof mechanics. We perform systematic parametric studies and adopt asurrogate measure for lumen narrowing for non-symmetric geometries.Using finite element analysis for a growing bi-material structure with astiff inner mucosal layer and a soft outer submucosal core, we simulatepressure and growth loading on five various Y-branch segments createdfrom magnetic resonance imaging. Our results suggest that folding andobstruction behavior due to pressure and growth are insensitive to thespecific airway geometry; essentially, the mucosal thickness, submu-cosal thickness, and mucosal to submucosal stiffness ratio dictate thedegree of airflow obstruction in the various segments. We find that thelevel of impact these parameters have on the folding pattern depends onthe loading mechanism. Our results agree with clinical observations and

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could help explain the mechanics of airway obstruction in chronic lungdisease.

T9. Anchor loss modeling in MEMS resonatorsDustin D Gerrard, Eldwin J Ng, and Thomas W Kenny

High quality factor (Q) resonators are often desired for applications suchas clocks and gyroscopes. In bulk acoustic wave resonators and flexuralmode resonators the quality factor may be limited by anchor loss. In thisstudy we investigate the effect that various anchor geometries have onanchor loss in a 52 MHz width extensional mode bar resonator. Identi-cal bar resonators with five different anchor geometries were fabricatedusing an epi-seal encapsulation process and the Q was measured usingringdown. The simulated width extensional mode was shown to haveslight aberrations due to variations in anchor geometry. The measuredQs are between 20k and 180k depending on anchor geometry and areat least an order of magnitude below the simulated thermoelastic dis-sipation quality factor (QTED). The experimental Q is also below thatof gas and Akhiezer damping and shows no strong temperature depen-dence providing evidence that anchor loss is the primary energy lossmechanism. We model the anchor loss Q using a perfectly matchedlayer (PML) in COMSOL which simulates the amount of energy thatis transferred from the MEMS resonator into the substrate. We presenthow PML geometry and mesh type influences simulated frequency andQ. The PML model in COMSOL provides a predicted Q and as well asquantitative information on the total energy in the system and the energyflux from the resonator into the substrate.

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T10. How fluid mechanics complicates combustion experi-mentsKevin P Grogan and Matthias Ihme

In recent years, increased attention has been paid to low-temperatureignition phenomena as new combustion technologies seek to operatewithin this regime. However, accurate chemical-kinetic models withinthis regime are difficult to validate against experiments due to the in-creased sensitivity of the fuel chemistry. Two experimental apparatusesused to study the low-temperature ignition of fuels are shock-tubes andrapid compression machines. For both apparatuses, the effects of fluidmechanics on ignition can become appreciable leading to increased un-certainty in ignition delay measurements. Hence, the topics of this talkare the non-ideal fluid mechanics of each apparatus and the regimes inwhich they become non-negligible. The fluid mechanics of these appa-ratuses are analyzed using an array of techniques from highly detailedsimulations to scaling arguments. From this, operation guidelines forthese combustion experiments are developed.

T11. Universal meshes: Computing conforming triangula-tions for curved domainsHardik Kabaria and Adrian Lew

We introduce a method to mesh the domain bounded by a smooth bound-ary in three dimension immersed in a mesh of tetrahedra. The mesh fol-lows by mapping a specific collection of triangular faces in the mesh tothe boundary and perturbing the nearby vertices to ensure a valid tetra-hedralization. Two types of volume meshes follow: (a) a mesh that ex-actly meshes the boundary, and (b) meshes that approximate the bound-ary to any order, by interpolating the map over the selected faces; i.e.,an isoparametric approximation to the boundary. The map we use todeform the faces is that of the constrained closest point projection tothe boundary. We extend the map to perturb the neary by nodes. Weformulate conditions for the mapping to define a homeomorphism be-

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tween each face and its image as well as the tetrahedrons in the surfaceneighborhood and its image. These are conditions on some of the tetra-hedra intersected by the boundary, and they essentially state that eachsuch tetrahedron should: (a) have a small enough diameter, and (b) havetwo of its dihedral angles be acute. We provide explicit upper boundson the mesh size, and these can be computed on the fly. We present thelocal optimization problem to improve the quality of tetrahedra in theresulting mesh. We showcase the quality assured resulting meshes withseveral numerical examples. Most importantly we do not alter the con-nectivity of the background mesh to achieve a conforming tetrahedral-ization. This is an important feature for problems in which the geometryevolves or changes, since it could be possible for the background meshto never change as the geometry does. We present the extension of thealgorithm that works for generalized background meshes, that allowsthe usage of adaptively refined background meshes.

T12. Drag force and diffusivity of small cylinder in free mole-cule flowChangran Liu, Zhigang Li, and Hai Wang

Aerodynamic drag force, diffusivity and electric mobility of long-chainmolecules, nanorods and nanotubes in fluid media are of great impor-tance to a large range of problems. Such problems include size classifi-cation of fibres aerosols, identification of long-chain biomolecules, gas-phase synthesis, processing, characterization of nanotubes and nanorod,and the transport of long-chain alkanes in reacting flows and fuel com-bustion. These problems are generally far removed from Stokes flow.Historically and in the area of reacting and combusting flow simula-tions, the transport properties of chain-like molecules have been treatedwith the Chapman-Enskog theory with the assumption that the interac-tions of these molecules with the gas media may be treated by spheri-cal, isotropic potentials. The validity of this assumption, however, wasnever examined in detail. Recent molecular dynamics evidence indeedsuggests the spherical potential assumption to be inaccurate. This work

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proposes analytical solutions for aerodynamic drag force on cylindri-cal nanoparticle in free molecule flow. The derivation is based on thegas kinetic theory and accounts for the effect of intermolecular interac-tions between the nanoparticle and the gas media. Two limiting colli-sion models, specular and diffuse scattering, are investigated. In the dragforce formulations, the interaction is described by the collision integrals,which can be tabulated if the potential energy function of interactions isknown. The result of our derivation in rigid body limit agrees with Dah-neke’s solution, which has been supported experimentally. Expressionsfor binary diffusivity of chain-like molecules in common bath gases arealso obtained from the drag and the Stokes-Einstein relation.

T13. Quantification of a traditional assay for gentle touch inC. elegansAdam L Nekimken, Eileen A Mazzochette, and Beth L Pruitt

The sense of touch is involved in almost all of our daily activities, yetwe do not understand how it works on a molecular level. The nematodeC. elegans is used as a model organism to study the sense of touch dueits simple neural network, vast genetic toolkit, and deterministic cellu-lar development. A common method for measuring the touch sensitivityof worm mutants is to lightly touch them with a fine hair and observethe probability that a behavioral response occurs. This assay does notisolate one part of the mechanotransduction signal pathway and is lim-ited by its lack of quantitative measurement of the forces being applied.More recently, we have created quantitative microscale tools for apply-ing µN forces to worms and study their response. To establish contextfor our new tools, we are measuring the forces applied by volunteers inthe traditional assay. For the traditional assay to be useful, each experi-menter must be able to consistently apply the same forces to the wormbeing tested. Preliminary results indicate that applied horizontal forcesare minimal and the forces are mostly within 50% of the average forcefor a given volunteer.

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T14. Droplet-based microfluidics in the diagnosis of tubercu-losisFengjiao Lyu, Yunfei Cheng, and Sindy KY Tang

In this work, we demonstrate a method for the rapid detection of BlaC,a β -lactamase naturally expressed by Mycobacterium tuberculosis, in-tended for the diagnosis of Tuberculosis (TB). The method is basedon the compartmentalization of bacteria in picoliter droplets at limit-ing dilutions such that each drop contains one or no cells. The co-encapsulation of a fluorogenic substrate probe for BlaC allows the quan-tification of bacteria by enumerating the number of fluorescent drops.Quantification of 10 bacterial cells per mL is demonstrated. Further-more, the encapsulation of single cell in drops maintains the specificityof the detection scheme even when the concentration of bacteria that donot express BlaC exceeds that expressing BlaC by one million-fold.

T15. Strain-enhanced relaxation regulates nonlinear elasticityin biopolymer gelsSungmin Nam and Ovijit Chaudhuri

The extracellular matrix (ECM) is an assembly of structural proteinsthat provides physical support and biochemical signaling to cells in tis-sues. The mechanical properties of the ECM have been found as keyregulators for cell behaviors such as migration, development, and dif-ferentiation. Gels formed from ECM protein biopolymers such as type Icollagen or fibrin are commonly used to mimic the ECM microenviron-ment for 3D cell culture models of tissue. One of the most striking fea-tures of these biological gels is that they exhibit nonlinear elasticity andstiffen at low strains. Recent studies have proposed that cells are ableto sense and respond to this nonlinear elasticity. However, these gelsare also viscoelastic and exhibit stress relaxation, with the resistance toa deformation relaxing over time. Little is known about the connec-tion between nonlinear elasticity and viscoelasticity. Here, we reportthat as strain is increased, not only do biopolymer gels stiffen, but they

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also exhibit faster stress relaxation, reducing the timescale over whichelastic energy is dissipated. Mechanistically, this strain enhanced stressrelaxation can be explained by force dependent unbinding of crosslinksbetween biopolymers. A computation model of biopolymer networksincorporating force-dependent unbinding of biopolymers followed byslow rebinding to the networks captures the experimentally measuredresults. These results reveal the interplay between nonlinear elastic-ity and viscoelasticity in biopolymer gels, and highlight the complexityof the ECM mechanics that are likely sensed through cellular mechan-otransduction.

T16. Cooperative collision avoidance via proximal messagepassingHao Yi Ong and J Christian Gerdes

Trajectory planning, formation flying, and guidance and collision warn-ing for large, complex networks have been major areas of research in re-cent years. Such networks include unmanned vehicle formations, satel-lite swarms, and cooperative robots. From a control perspective, struc-tural constraints on information flow constitute one of the major diffi-culties facing the use of large networks: each agent in the network mustact based on limited information and even with global information, de-termining optimal inputs may be computationally prohibitive. Further,vehicles often have limited sensing, actuation, and computation capabil-ities, which require the guidance and control algorithms of the networksto be both simple and computationally efficient. This guidance and con-trol problem can be captured as a multi-vehicle Cooperative CollisionAvoidance (CCA) problem. In CCA, networked vehicles share obstacleand inter-vehicle collision avoidance constraints with their neighbors,which are encoded in their objective functions. The objective functionsfurther encode operating costs such as fuel consumption and constraintson trajectory deviations and control inputs.

We propose a distributed controller to solve CCA. We consider a net-work of vehicles, each with its own dynamic constraints and objective.

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The problem is to minimize the total network objective function subjectto the vehicles’ individual constraints and their shared collision avoid-ance constraints over a given time horizon. The proposed controller, aproximal message passing (PMP) algorithm, is iterative: At each iter-ation, every vehicle passes simple messages to its neighbors and thensolves a convex program that minimizes its own objective function anda simple regularization term that only depends on the messages it re-ceived in the previous iteration. As a result, the method is completelydecentralized and needs no global coordination other than synchronizingiterations. The problems that each vehicle solves can be done extremelyefficiently and in parallel. We demonstrate the method on several exam-ples using a model predictive control framework.

T17. Passive wing morphing in flapping wingsAmanda K Stowers and David Lentink

Man made robots have great difficulty in cluttered environments thatbirds, bats and insects navigate easily. In these situations, animals areable to morph their wings in complex manners to avoid collision or dam-age. From dynamic analysis and robotic experiments, we predict thatthe combination of flapping wings and a wrist joint may aid in recoveryfrom obstacle impact such as a branch. During flapping flight, centrifu-gal accelerations drive wings to unfold to their full wingspan withoutrequiring use of muscles and tendons. This enables wingspan recoverypost obstacle impact using minimal effort. We demonstrate this effectin a 40 cm wingspan robot flapping in the range of 5-17 Hz. The robothas two flapping wings and is constructed with an unactuated joint at thewrist allowing the wings to passively adjust sweep angle in response todisturbances. Experiments show that following impacts, or after releasefrom being held shut, the flapping wing will passively unfold withinone to two flaps. Modeling the motion using the inertial properties ofthe wing during flapping predicts this unfolding is caused by centrifu-gal acceleration of the hand wing. For the wing amplitudes and foldratios of bird, bat and insect wings, our model predicts that their wings

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can recover passively from impact in approximately one half to one fullwingbeat.

T18. Toward magnetic guidance of microcatheters in the brainLizmarie Comenencia Ortiz, Margaret Koehler, and Allison M Okamura

Aneurysms, stroke, and other diseases in the brain can be reached andtreated using catheters guided through the vascular system. However,current brain microcatheters have limited reach because they must bepushed and steered from outside the body and are too large to navigatethe narrow and tortuous geometries in deep brain vasculature. Magnet-ically steered brain microcatheters can enable enhanced manipulationof the catheter tip. We propose to use a single permanent magnet toapply both force and torque to the microcatheter tip in order to bettersteer microcatheters in deep brain vasculature. As a scaled proof ofconcept, we attach a cylindrical magnet to a microcatheter tip and ap-ply force and torque using an actuator magnet controlled by a three-degree- of-freedom planar robot. Resulting deflection and curvatureof the microcatheter tip demonstrate increasing deflection with coupledforce and torque guidance. A scaled experimental study of the cathetersteering in curved tubing demonstrates feasibility of combined magneticforce/torque guidance for brain microcatheter applications. Applica-tions of this work include delivery of treatments for brain disease anddeep brain stimulation via a minimally invasive approach.

P1. mSTAR Thermal enclousar modelingAbdulrahman Alfauwaz

Precision physics experiments in a space flight require highly stablethermal environments, especially if the experiments are targeted for earthorbits where eclipses will cause large temperature variation. We havebeen designing and modeling a thermal system with sub micro-kelvinstability to maintain the thermal environment of the cavity for a Mini

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Space-Time Asymmetry Research (mSTAR) mission. Our design iscomprised of multiple alternative layers of conductive materials andvacuum isolations with supporting spacers in between. The materialselection of the spacers support has been done after numerous simu-lations. We first simulate and analyze passive control which includesconduction through spacers and radiation between shields. Also, wesimulate the active thermal control by modeling heaters and tempera-ture sensors. The active thermal control consists of multiple stages ofPID control with different set-temperatures. Each stage has its own con-trol loop and circuit driver. The first and second stages are to be used asisolation of the inner shields from any thermal disturbance coming fromsatellite subsystems and/or radiation from space. The third and fourthstages are to maintain the stability and uniformity of the inner shield.In addition, we minimize the power needed to run the heaters, becauseof the limitation of power sources in space. The PID control parameterswere chosen to meet the requirements of each shield. We present our de-sign prototype with results from both experiments and simulations. Wehave modeled different boundary conditions with range of temperaturesto assure that the design capability is in the range of 0.1 micro-Kelvinstability and uniformity. COMSOL was used to simulate the thermalenvironment and thermal active control by PID techniques.

P2. High surface area supercapacitors based on manganeseoxide nanoparticlesJoaquin Camacho, Changran Liu, and Hai Wang

Supercapacitors are commonly incorporated into the design of noveltransportation and power management systems. In this work, man-ganese oxide based supercapacitors were fabricated and characterizedas a function of manganese oxidation state and particle size. The FlameStabilized on a Rotating Surface technique was used to efficiently syn-thesize nanoparticles and control the particle size (under 20 nm) witha narrow size distribution. In addition, the technique was used in thiswork to control the oxidation state of manganese oxide nanoparticles.

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Mn(IV) oxide, Mn(III) oxide, and Mn(II,III) oxide were synthesizedand integrated into high surface area supercapacitors. The pseudocapac-itance and charge storage mechanisms were evaluated for each oxidationstate. Typical particle sizes reported for supercapacitor applications arearound 20 nm and the particles sizes used in this work are about half thissize. This reduction in size increases the surface area density by a factorof 4 and thus the performance is expected to increase substantially. Thecapacitance and cycling life was determined by cyclic voltammetry andgalvanostatic charging.

P3. TugBot – Using gecko adhesion to pull large weightsGregory M Campbell, David L Christensen, and Mark R Cutkosky

Gecko adhesive is a unique fabrication that allows us to react to verylarge forces in shear, but easily remove the adhesive by relaxing theforce. Usually only viable in very small strips, recent developments ingecko adhesion have allowed us to form wider layers such that manyadhesives working in parallel can support over 100 pounds on a smoothsurface. This project addresses how this scaling allows a relatively large,10 pound, robot to use gecko adhesive in a practical way. The prototypetakes the idea of a tugboat, such that nearly all components present onthe robot are critical for either power or actuation. Combined with thepower of gecko adhesion, this allows the robot to theoretically drag over100 times its weight.

P4. Evaluating alternative fuels in aviation gas turbinesSerena E Carbajal and Matthias Ihme

This project is part of the National Jet Fuel Combustion Program, whichis sponsored by the Federal Aviation Agency (FAA) and a joint effortbetween several universities. The goal of this project is to develop pre-dictive modeling tools to enable the computational certification of alter-native fuels for aviation engines. Specific focus of this research is on the

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modeling and simulation of flame stabilization, multicomponent spraycombustion, and engine re-light. The outcome of this project ensuresthat these alternative fuel options will burn cleanly and reliability in air-craft gas turbine engines. As part of modeling these fuels, a CFD modelmust be created for a single combustor within a gas turbine engine, ad-dressing the following three main issues. First, the computational modelrequires the consideration of diffusion holes that are used for cooling.However, resolving each of these holes would substantially increase thediscretization, making such simulation infeasible. Second, the injectorrequires precise placement within the combustor in order to fully entrainmost of the air through its swirlers. Lastly, modeling the liquid fuel isimportant due to the evaporation rate and location of the spark within thecombustor. By addressing these three issues, a fuel can be introducedinto the model to determine whether or not it meets the performance re-quirements as specified by the FAA.

P5. Towards field identification of mosquitoes via mobile phonebased acoustic classificationErica Castillo, Haripriya Mukundarajan, and Manu Prakash

P6. In-situ ovenization of highly doped Lame-mode siliconresonatorsYunhan Chen, Eldwin J Ng, and Thomas W Kenny

Silicon MEMS resonators, which typically have large temperature coef-ficients of frequency (TCf) of about -30 ppm/◦C, require compensationto achieve temperature stability that is comparable to quartz crystal os-cillators for high-precision applications. Various compensation schemeshave been reported in the past. While passive compensation can effec-tively reduce the frequency deviation to the ppm range, active temper-ature control methods have the potential to achieve a better frequencystability. Ovenization is one of the active compensation methods that in-

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corporates micro-ovens which utilize Joule heating to elevate and main-tain the resonators at a desired temperature, and, as a result, stabilizesthe resonant frequency. In this work, we demonstrate a new methodof ovenizing Lame-mode silicon resonators to achieve better frequencystability over a large range of ambient temperature. A highly dopedp-type Lame resonator with orientation shows a frequency de-viation of 300ppm across the temperature range of -40~+80◦C and aturnover point at ~+75◦C. Operating near the turnover point temperaturegives better control stability as the resonator is insensitive to control er-ror. The 4-point measurement of the in situ resistance (R) of the squareresonator serves as a thermometer as R has a positive linear correlationwith resonator temperature. The same current that is used for resistancemeasurement heats the resonator directly and is controlled by a feed-back loop to maintain a constant resistance value R in order to operatethe resonator at an elevated target operating temperature to minimizethe deviation of resonant frequency for different ambient temperatures.Preliminary results show a steady-state frequency stability improved bymore than 100x over the temperature range of interest. Moreover, areal-time frequency measurement of a compensated resonator subjectto 5◦C/min ambient temperature ramps show a frequency stability of~5ppm, and no frequency hysteresis is observed during both ramping upand down of the ambient temperature. A lookup table can be incorpo-rated with feedback controller to further reduce the residual temperaturedependence of frequency and achieve a frequency stability of sub-ppmlevel.

P7. An energy-based approach for finite element modeling ofcollagen-swelling interactionXi Cheng, Steven J Petsche, and Peter M Pinsky

The corneal stroma, the principal structural layer of the cornea, likeother soft, highly-hydrated and charged collagenous tissues such as car-tilage and intervertebral disc, is a polyelectrolyte gel consisting of amixture of interacting fluid, solid and ionic phases. Modeling the biome-

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chanical behavior of the cornea and other hydrated connective tissuesin a fully three-dimensional context presents a challenge. Current fi-nite element-based models treat the volumetric behavior of the tissue byassuming incompressible or nearly-incompressible elasticity. This ap-proach is convenient but cannot describe the swelling behavior of thetissue or its steady-state volumetric compressibility. On the other hand,modeling by use of triphasic theories introduces numerical challengesthat render the approach too impractical for realistically complex prob-lems. The aim of the current work is to explore a novel energy-basedapproach for characterizing the tissue osmotic pressure and bulk behav-ior and to assess its suitability as a basis for efficient finite element ap-proximation.

A structural model of the in vivo cornea which accounts for tissueswelling behavior, for the three-dimensional organization of stromalfibers, and for collagen-swelling interaction is proposed. Modeled asan electrolyte gel in thermodynamic equilibrium, the free energy is ad-ditively decomposed into components which characterize the behaviorof the tissue under general deformations. For the ex vivo cornea, we usethe mean-field approximation of the Helmholtz free energy for a binaryelectrolyte which measures the energy of fixed charge, the osmotic en-ergy of mobile ions, and the dielectric free energy. To account for activeendothelial ionic transport in the in vivo cornea, we show that the stro-mal mobile ions satisfy a modified Boltzmann distribution, and leadingto a modified free energy. Under reasonable assumptions we obtain ananalytical form for the modified free energy functional which is convexin volume dilation and provides the key variational ingredient for thefinite element formulation.

The approach can be easily implemented within a standard finiteelement framework using only the displacement field. The collagen-swelling model is employed to predict free and confined swelling ofstroma in an ionic bath. Swelling resulting from surgical alteration ispredicted for the first time. Corneal swelling in Fuch’s corneal dystro-phy is employed as an illustration of how the model can be adapted tocertain pathological conditions.

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P8. Measuring aerodynamic weight support in birds fromtakeoff to landingDiana D Chin and David Lentink

Flapping flight is a convergent solution utilized by many animals andsome biomimetic robots for effective aerial locomotion. The transitionsto and from the air during takeoff and landing are also critical compo-nents of every flight, so studying how forces are generated both duringthese transitions and in steady flight can provide valuable insight forimproving aerial robots and for understanding the movement ecology ofanimal flight. Studies have shown that takeoff forces in birds are gener-ated predominately by their hind limbs. Once airborne, the aerodynamicforces needed to reach and maintain steady flight are generated by theirwings, primarily during each downstroke. These forces also help birdsdecelerate prior to landing, when force production is transferred back tothe hind limbs again. Although some studies have measured takeoff andlanding forces in the past, very few have quantitatively studied the tran-sition of force generation from the legs to the wings, and no studies havedone so through the direct measurement of the aerodynamic forces pro-duced in flight. By utilizing a new aerodynamic force platform (AFP),we can now directly quantify all of these forces for freely flying birds.The AFP acts as a physical control volume designed to capture aero-dynamic forces produced during flight. Two instrumented perches oneither side of the setup record the horizontal and vertical forces gener-ated by the hind legs as the birds take off and land. Combining thesein vivo force measurements with kinematic analysis will subsequentlyprovide a much more accurate and complete understanding of the entireflight process of birds from takeoff to landing.

P9. Acl injury and its effects on osteoarthritisDaniel Concha

Osteoarthritis affects millions of people around the world and can havedebilitating effects on their daily lives by making commonplace activi-

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ties such as walking a struggle. While the progression of osteoarthritisis understood to be correlated with a continuous degradation of artic-ular joint cartilage in the knees, the underlying cause of the disease isnot well understood. It has been noted that tearing the anterior cruci-ate ligament (ACL) vastly increases a person’s likelihood for develop-ing early-onset osteoarthritis. While reconstructive surgery is used torestore the patient’s athletic capabilities, there seem to be underlyingeffects in an ACL rupture which encourage the initiation of osteoarthri-tis. Studies indicate that while ACL reconstruction corrects for exces-sive tibia displacement relative to the femur along the sagittal plane, ithas many secondary effects which simultaneously alter gait kinematics.These changes in gait lead to altered concentrations and distributions ofloading on the knee cartilage as well. Other studies suggest that thismodified knee loading can have damaging effects on knee cartilage byinitiating a degenerative pathway which leads to continuous cartilagedegradation. This study aims to better understand the underlying con-nection between ACL reconstruction and early onset osteoarthritis. 50subjects with reconstructed ACLs at 2 years post-operation are analyzedthrough gait analysis, a walking activity and blood draws, and MRI. Gaitanalysis is completed using a marker-based system with a point clustertechnique to acquire subject kinematics. Blood is drawn from the sub-jects immediately before and 5.5 hours after 30 minutes of walking ona treadmill to compare blood serum COMP levels after simulation (in-dicative of cartilage health). Lastly, MRI scans are taken of the subjects’knees. It is anticipated that altered gait as evidenced by the gait analy-sis will correlate with more severe degradation of the articular cartilageas illustrated in the MRI scans and that percent change in COMP lev-els will more closely resemble that of an osteoarthritic subject than ahealthy one.

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P10. A robust, ultra-stable, flight ready optical cavity systemGrant Cutler, Daniel DeBra, and Drew Nelson

A frequency stabilized laser could be used for gravity wave detection,observing variations in the speed of light, improved time keeping withoptical clocks, and precise measurement of distance. One common ap-proach to laser frequency stabilization involves locking the laser to anoptical cavity, made by separating two mirrors by a spacer. The laseris locked to the cavity by continuously adjusting its frequency such thatit resonates between the mirrors. The stability of the spacer’s length istherefore transferred to the laser’s frequency. State of the art labora-tory based optical cavity systems are able to approach the lower limitof stability set by Brownian motion for the cavity spacer and mirrors.More mechanically robust and less stable optical cavities have also beendesigned for satellites, and for terrestrial non-laboratory use.

The goal of this project is a robust, space flight ready optical cavitysystem. Not only must this system survive the accelerations of launchaboard a rocket, but while in orbit, it must stabilize the laser frequencystability to one part in 1016 for 6000 seconds.

This project is being approached as a multi-objective, multi-disci-plinary optimization problem combined with rigorous use of the finiteelement method and the application of principles of precision engineer-ing. A key part of the design strategy is the identification of a partic-ular spacer shape whose length is minimally sensitive to inertial reac-tion forces at the interface with a kinematic support structure. Potentialspacer shapes are evaluated using a combination of the finite elementand optical ray tracing methods. A challenge in the use of the finite el-ement method is achieving an adequate level of precision and accuracyin calculating strains on the order of 10-16. A generalized parametricfinite element model has been built which allows design iterations to beautomatically generated and evaluated by a genetic algorithm optimizer.Multiple design iterations are evaluated in parallel on Stanford’s Barleycomputer cluster.

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P11. Viscoelastic modeling of brain tissue by nanoindentationRijk de Rooij and Ellen Kuhl

Human brain tissue is subjected to a wide range of mechanical load-ing rates and time scales, from quasi-static neurodevelopment to veryhigh rate brain impact. High loading rates are critical in traumatic braininjury and the mechanical properties of brain tissue play an importantrole in this loading regime. Recent studies also suggest that mechani-cal properties of brain tissue are important in the slow loading regimeof brain development. Due to this wide range of time scales, it is ofvital interest to characterize the dependence of the brain tissue proper-ties on time. Multiple experiments indicate a viscoelastic behavior ofbrain tissue as it experiences a stress relaxation. Mathematical modelsof stress relaxation include two time scales to characterize the elasticand viscous components of the brain tissue behavior. Here, we present aquantification of these two time scales based on experimental relaxationdata obtained by nano-indentation of bovine brain tissue. We indenteda flat circular punch 250um into brain tissue using displacement con-trol, held the punch in place, and measured the reaction force on theindenter. To determine the two viscoelastic time scales of brain tissue,we obtained the least-square error approximation of the relaxation datawith a multi-term Prony series. Each term in the Prony series representsa different time scale of the material. We found the best fit for a two-term, Prony series approximation. Our measurements suggest that thetwo time constants are very similar for gray and white matter; they takevalues of 5s and 170s. We validated these time scales using frequencysweep experiments.

Our results indicate that the viscoelastic response of both gray mat-ter and white matter brain tissue can be characterized well using a two-term Prony series approximation. This suggests that brain tissue pos-sesses two distinct time scales; an elastic and a viscous time scale. Themechanistic interpretation of these time scales plays a critical role inunderstanding the rheological behavior of the mammalian brain, and,ultimately, its response to high-impact loading.

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P12. Structured light 3D surface reconstruction of birdsMarc E Deetjen and David Lentink

Birds fly effectively through complex environments, and in order to un-derstand the strategies that enable them to outperform current drones,we need to determine the shape and movement of their wings. Previ-ous studies focused on measuring general kinematics parameters suchas wing stroke, but the actual shape and twist of the wing has not beenresolved. The shape of the wing’s upper surface is of particular interest,because it determines the boundary layer’s sensitivity to flow separationduring undisturbed flight. When birds fly in environments where windgusts are prevalent, such as cities, they rely on their ability to dynam-ically morph their wings to control flight path. In order to study howdynamic wing morphing enables birds to fly efficiently in both calmand turbulent conditions, we seek to quantify the external shape of thewing with high time resolution. We developed a high-speed camera andprojector setup to record structured light projected on our white birds,parrotlets, at 3000 Hz. By projecting time-coded stripe patterns anal-ogous to a barcode onto the parrotlets, which effectively act as flyingprojection screens, we can identify stripe correspondences on the bird’swings. 3D reconstruction is achieved using these corresponding edges inaddition to the calibration of the camera-projector system. We have ex-perimented with using a high-speed color camera to filter multicoloredprojected images in order to encode extra information in every frame.By projecting horizontal and vertical stripes in different colors and us-ing their correspondences over four consecutive images, we aim for abetter overall resolution of the reconstructed surface independent of thebird’s orientation. This tool will enable us to quantify how birds changetheir wings dynamically as an inspiration for novel morphing wing de-signs.

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P13. Design and experimental evaluation of a skin-stretchhaptic device for improved control of brain-computer inter-facesDarrel R Deo, Sean M Sketch, and Allison M Okamura

Robotic systems, such as prosthetics and exoskele- tons, offer peoplesuffering from motor impairments a chance to regain lost physical func-tionality. However, the neural control that individuals are able to ex-ert over these robots is currently limited. This is due to both lack ofcontrol authority in many degrees of freedom and insufficient sensoryfeedback through the human-robot interface. We propose that hapticfeedback is paramount for accurate and efficient control of robots viabrain-computer interfaces (BCIs). Skin stretch at the fingertip is a novelform of haptic feedback for improving BCI-based robot control. In thispaper, we describe the design of a BCI-driven skin-stretch device, assessseveral control paradigms for this device, and evaluate its effectivenessin a small user study. We show that BCI-based movement-intent clas-sification improved in the presence of skin-stretch feedback for 3 of 4healthy individuals controlling a computer cursor via an inexpensive,commercial electroencephalography-based (EEG) BCI.

P14. Design of a novel device to improve physician fatigue inthe operating roomPablo A Escobar and Lauren Aquino Shlulzas

P15. Measurements of the thermal conductivity and specificheat of degenerately doped siliconCamille LM Everhart, Tim English, and Thomas W Kenny

Reduction of the elastic modulus’ temperature-dependence for heavilydoped silicon has spurred recent interest in its use for resonators and in-ertial sensors. In order to design thermal isolation structures, or to accu-

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rately predict damping from thermoelastic dissipation (TED), it is nec-essary to determine the thermal properties of doped silicon near roomtemperature. Current data in the literature is limited in this range. Here,we present device designs, measurement methods, and results, pertinentto MEMS designers. The results presented here have utility largely fordesigners of devices made of degenerately doped silicon. For those forwhom the quality factor (Q) is the key figure of merit, much of their de-sign time is spent minimizing dissipative sources. With device geometrydesigned to minimize anchor damping and maximize the Q, TED oftenends up as a significant limiting factor of this effort. TED, caused by thecoupling between thermally induced strain and strain-induced heat-flow,is dependent on the thermal diffusivity of the material. Subsequently, amechanically resonating structure cannot be optimized without knowingits thermal conductivity and specific heat to a high degree. This is alsotrue for those designing ”ovenized” devices, where silicon is used forthermal isolation. In this study, specialized thermal conductivity test-structures from three heavily doped SOI wafers were analyzed using the”3-omega” method. This method allows both the thermal conductivityand the heat capacity of a material sample to be obtained from a ther-mally modulated output voltage signal.

P16. Temperature effects on 1:1 modal coupling for Q-factorenhancement of a disk resonatorIan B Flader, Chae H Ahn, and Thomas W Kenny

We have investigated the impact on the dynamics of MEMS resonatorsarising from coupling between independent modes. Quality factor isan important metric used to evaluate resonator dynamic performancefor many applications. This work shows that 1:1 modal coupling cangreatly enhance resonator quality factor, and the temperature effects ofthe coupling are investigated. The Q for the mode shape of interest istypically less than 10k, while utilizing 1:1 modal coupling it was possi-ble to enhance the quality factor to over 60k.

Modal coupling in the disk resonator was achieved by geometric de-

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sign to bring the natural frequencies of the translational and torsionaldisk modes close. The primary, translational, mode was driven intoresonance. The frequency split between the translational and torsionalmodes was further reduced by applying a slow varying bias voltage tothe device. This tuning is achieved through a well-known phenomenonknown as electrostatic softening. At the matched bias condition, wherethe frequency split between the two modes is minimized, we see themaximum quality factor enhancement for the coupled system. The am-plification was controllable through the applied bias voltage.

The devices were 600 µm diameter disk gyroscopes, fabricated us-ing an epitaxial polysilicon encapsulation process. Silicon as a mate-rial has inherently strong temperature dependencies. The temperaturecharacteristics concerned in this work are the resonator’s temperaturecoefficient of resonant frequency (TCF) and temperature coefficient ofthe quality factor (TCQ). Despite each mode shape having different de-pendencies of TCF and TCQ, it is shown that the resonances could stillbe tuned over a large range of temperatures. Also, the quality factorenhancement could be amplified further knowing the TCQ relations foreach mode shape.

P17. A novel platform for testing the cell adhesion mechanicsand myogenic function of induced pluripotent stem cell de-rived cardiomyocytesJoy A Franco, Alexandre JS Ribeiro, and Beth L Pruitt

Cardiac related diseases remain a leading cause of death throughoutthe world. Though induced pluripotent stem cell derived cardiomy-ocytes (iPS-CMs) show promise as a future treatment to these diseases,progress in this field is limited by existing cell culture technologies. Cur-rent iPS-CM cell culture techniques suffer from high cost, poor repeata-bility, and a lack of experimental control over the cell-binding mecha-nisms that are of great interest to researchers. In this work we develop anovel platform for culturing single iPS-CMs that aims to overcome theselimitations. Our platform consists of an array of micron-scale patches of

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engineered photoreactive elastin-like protein (ELP-d), where each patchis capable of hosting a single iPS-CM. Preliminary results show that (1)iPS-CMs are both able to adhere to and contract against ELP-d and that(2) ELP-d is well suited for the microcontact printing methods used inmanufacturing this platform. This technology overcomes current chal-lenges by utilizing a lower cost biomaterial (ELP-d) whose biochemicalcomposition is controlled by using protein-engineering methods. ELP-d is easily altered to control the availability of cell binding sites. Thiscapability will generate new avenues in investigating the roles of celladhesions in the maturation and myogenic function of iPSC-CMs. Themechanobiological mechanisms underlying these roles can therefore beelucidated with this platform and generate knowledge that will advancethe field of stem cell therapies.

P18. Canonical problems in fluid-particle interaction in a ra-diation environmentSwetava Ganguli

There are innumerable examples where the coupled interaction of a dis-persed phase in a fluid with fluid turbulence and radiation determines thephysical phenomena that govern the system. Specifically, the problemof high-efficiency solar energy conversion which is the focus of PSAAPII (Predictive Science Academic Alliance Program II) is one such man-ifestation. Significant scientific and engineering progress can be madefrom a better understanding of the physics governing this complex in-teraction. Towards this goal, we design a set of simpler test cases (unitproblems) of increasing complexity which highlight the interaction ofsubsets of the aforementioned phenomena, so that individual aspects ofthe problem can be independently tested, studied and their effects canbe quantified. In this talk, we present two such unit problems that de-scribe the response of a fluid medium to a finite size particle that isheld fixed either at a constant temperature or is heated using a radiantheat flux. These two problems are designed to isolate and quantify thefinite-size effects of the particle, effect of direct radiation incident on

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the particle and the two-way coupled thermal interaction between par-ticle and fluid under suitable regimes of Reynolds, Biot, Brinkman andEclet numbers. Three key results emerge from this analysis - (1) Thephysics of the problems are studied in detail, (2) A framework to solve anon-linear partial differential equation analytically is demonstrated thatis used to track uncertainties of various quantities of interest, and, (3)Inspired from the physical solutions, a set of manufactured solutionsfor verification of low-Mach compressible CFD codes for particle-ladenflows is developed.

P19. A novel haptic fMRI interface with a four-bar linkageand a dynamically decoupled rotation axisHari Ganti, Samir Menon, and Oussama Khatib

Combining haptics and functional neuroimaging promises to enable in-teractive motor neuroscience experiments using virtual simulations, yetengineering stiff, responsive, and transparent Haptic fMRI Interfaces(HFIs) remains a challenge. Neuroscience experiments require stiff andresponsive devices for high-resolution hand tracking and for simulat-ing realistic objects in virtual worlds. In addition, device transparencyprevents potential neuroscience confounds by ensuring that subject mo-tions are not affected by the device’s friction, inertia, and dynamics.Finally, operating in an MRI environment restricts the set of permis-sible materials, and requires motors to be placed far from the scannerbore. We address the challenge of engineering HFIs that meet thesecriteria with a combination of experiment-driven material selection andanalysis-driven design.

Here, we present a novel Haptic fMRI Interface, HFI v3.2, whose de-sign is modular, which allows rapid customization to optimize the trade-off between device transparency and stiffness. HFI v3.2 uses a four-barlinkage with an in-plane orthogonal rotational axis, which provide threetranslational degrees-of-freedom that span the entire MRI workspace.We estimated the device’s stiffness using finite element analysis by ap-plying end-effector forces within our expected operating range: 5-10N

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static and 10-15N (1-1.5g) dynamic forces. The resulting end-effectordeflections– indicative of device stiffness– improved upon its predeces-sor, HFI v2.5. Optimizing part selection, machining quality, and ma-terial choice, however, remain the final determinants of device quality,and we used our analysis results to selectively reinforce high-stress loci.By focusing on critical areas, we are able to increase device stiffnesswhile minimizing overall device inertia.

P20. Fast parameter and state estimation with the SpectralKalman Filter: An application for CO2 injection in heteroge-neous domainsHojat Ghorbanidehno, Peter Kitanidis, and Eric Darve

The Kalman Filter has been widely used for dynamic monitoring inreservoir engineering, and has recently gained popularity in hydroge-ologic applications. A common characteristic of such applications isthat the physical processes of interest are greatly affected by preferen-tial flow (e.g., contaminant spreading, CO2 leakage), which can onlybe delineated if the problem is finely discretized into a large numberof unknowns. However, for problems with large numbers of unknowns(e.g., larger than 10,000), the Kalman Filter has prohibitively expensivecomputation and storage costs. The EnKF, which is typically used toreduce the cost of computing the covariance in such cases convergesslowly to the best estimate, and for a reasonable number of realizations,the estimate may not be accurate, especially for strongly heterogeneoussystems. We present the Spectral Kalman Filter, a new Kalman Fil-ter implementation that has a dramatically reduced computational costcompared to the full Kalman Filter, with comparable or higher accuracythan the EnKF for the same computational cost. Our algorithm’s compu-tational efficiency is achieved by a recurrence that updates small cross-covariance matrices instead of large covariance matrices, in combinationwith a low-rank approximation of the noise covariance matrix. In addi-tion, instead of computing the expensive Jacobian matrix, a matrix-freemethod is used to obtain sensitivities. Finally, the error of our method

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can be explicitly controlled by reducing the time between matrix up-dates. The frequency of these updates is controlled independently fromthe data assimilation steps. We demonstrate the performance of theSpectral Kalman Filter for the joint estimation of domain properties andstate evolution by assimilation of quasi-continuous data during a hypo-thetical CO2 injection in a strongly heterogeneous domain.

P21. 3D vibrational measurements and axes of rotation ofmiddle ear ossicles in the mousePeter K Gottlieb, Charles R Steele, and Sunil Puria

The presence of three distinct ossicles in the middle ear is a ubiqui-tous and uniquely mammalian trait, yet the benefits conferred by thiscomplicated anatomy are still debated. One hypothesis contends thatthis system allows multiple modes of rotation to minimize the effects ofossicular inertia at higher frequencies of vibration. The mouse middleear provides a particularly interesting test of this theory. The malleusincludes a relatively massive prominence known as the orbicular apoph-ysis, which causes the first principal axis of the malleus to lie almostorthogonal to the manubrium and the anatomical axis defined by the go-nial attachment and the short process of the incus. A previous 1D study(Dong et al., Hearing Research 2012) suggested that despite the orbicu-lar apophysis, the ossicles vibrated primarily about the anatomical axis.In the absence of true 3D measurements, however, it is difficult to drawstrong conclusions about this motion.

The 3D velocity of 12-15 points along the ossicular chains of adultwild-type CD-1 mice was measured using a Polytec CLV-3D laser Dopplervibrometer. SyncAv was used to generate pure-tone stimuli while pres-sure within 1mm of the tympanic membrane was synchronously recordedusing an ultrasonic probe tube microphone. The ossicular transfer func-tion, or the velocity divided by the pressure at the tympanic membrane,was calculated for each point. 3D models of the ossicles were recon-structed from a µCT scan, and the principal axes of rotation were cal-culated. The 3D motion of the ossicles was then calculated using a

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least-squares fitting algorithm.

The magnitude of the ossicular transfer function at all points rosesteeply from low frequencies up to above 10kHz, after which it gen-erally remained flat. While the ossicles moved primarily together as arigid body at low frequencies, there was considerable slippage betweenthe malleus and incus at higher frequencies. The angle between therotational axes of the ossicles and their first principal axes varied withfrequency.

Our measurements are consistent with previous results in finding theossicular transfer function in mice to act like a high-pass filter. These 3Dmeasurements demonstrate more complex modes of vibration, however,with frequency-dependent rotational axes that depart from the anatomi-cal axis.

P22. Predicting weight support based on wake measurementsof a flying bird in still airEric Gutierrez and David Lentink

The wake development of a freely flying Pacific Parrotlet (Forpus co-elestis) was examined in still air. The bird was trained to fly from perchto perch through a laser sheet while wearing custom-made laser safetygoggles. This enabled a detailed study of the evolution of the vorticesshed in its wake using high-speed particle image velocimetry at 1000 Hzin the plane transverse to the flight path. The measurement started whenthe bird was a wingbeat in front of the laser sheet and stopped after ittraveled a few wingbeats beyond the laser sheet. The instantaneous liftforce that supports body weight was calculated based on the velocityfield, using both the Kutta-Joukowski and the actuator disk quasi-steadymodel. During the first few flaps, both models predict an instantaneouslift that is reasonably close to the weight of the bird. Several flaps awayfrom the laser sheet, however, the models predict that the lift steadilydeclines to about 50% of the weight of the bird. In contrast to earlierreports for bat wakes in wind tunnels, these findings for bird wakes in

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still air suggest that the predictive strength of quasi-steady force calcu-lations depends on the distance between the animal and the laser sheet.

P23. Improved controllers for POMDPS and decentralizedPOMDPsRavi Haksar and Sanjay Lall

P24. Survey-based research methods in engineering educationresearchAngela Harris, Emily Cao, and Shannon Gilmartin

Engineering research develops engineering principles, explores the phe-nomena associated with these principles and the scientific theorems un-derlying them, and identifies ways that science can be applied to engi-neering processes. Engineering education research explores the educa-tional environments in which these engineering principles are learned,and the experiences of students learning them. Engineering educationresearch leads to insights that not only help students to prepare for theirprofessional futures, but also support faculty and institutions in design-ing more effective educational environments. In doing so, education re-search can enrich the types, quality, and innovativeness of engineeringresearch.

In order to address questions related to engineering education, re-searchers employ many methodologies in their research designs, oftendrawing from methods in the social sciences. This presentation willdescribe one such method: survey-based research. Using the recent En-gineering Majors Survey as an example, we will describe the details ofdeveloping, executing, and analyzing a survey of engineering students,including the questionnaire design and piloting process, institutional andstudent sampling methods, and descriptive survey data analysis meth-ods. The Engineering Majors Survey, which is funded by the National

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Science Foundation through the National Center for Engineering Path-ways to Innovation (Epicenter), is being administered in early 2015 toroughly 30,000 engineering juniors and seniors at a nationally repre-sentative sample of 27 engineering schools in the U.S. As of mid-March2015, over 7,000 students have visited the survey. This presentation willdiscuss response rates and the process by which a large survey datasetis built.

To further show the divers

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Technical Program of the 1st Stanford Mechanical Engineering … · 2015. 5. 1. · Technical Program of the 1st Stanford Mechanical Engineering Conference (MECON), May 1, 2015 T11