Thermal transport across GaN and SiC Interface

by Vinay Chauhan

Noon – 12:30pm E525

The heat flux in GaN based high-electron mobility transistors (HEMTs) can reach up to a few kW/cm2 which can lead to failure of devices in case of poor heat dissipation. The thermal interface resistance between the GaN and the substrate material is the major obstruction in the heat flow path, mainly effected by the thermal conductivity of the substrate and the lattice mismatch. The previously developed models showed good concurrence of thermal interface resistance with experimental data at high temperatures (>300 K) but failed to follow the physics at low temperatures. The proposed experiments will enable us to find the reliable thermal properties related to the interface, and thus help in improving and developing the models.

SLS is starting back up again for the Spring Semester January 31st!

If you are interested in presenting at the Student Lecture Series this semester, please submit a title and the desired date and time to the SLS Chair Elijah Jans jans.2@osu.edu. All slots will be filled on a first come first serve basis. Further details, including the format and schedule can be found in the overview and schedule tabs.

Want to improve your presenting skills? Want to show-off your research to your friends and class-mates? Sign up to give a talk at the Fall 2017 Student Lecture Series. Don’t have anything ready to present… not a problem come listen to your classmates discuss their work over pizza and learn by example.

The Student Lecture Series is a student run forum for graduate and BS/MS students from the MAE Department to present their work. The series is designed to provide opportunities for students to develop their technical presentation skills, promote the research of the department, and encourage faculty and student discussions of research. The low stress and informal atmosphere fosters a positive learning environment in which faculty and students of all levels can interact and learn from each other.

If you are interested in presenting at the Student Lecture Series this semester, please submit a title and the desired date and time to the SLS Chairs Mike Adam adams.1169@osu.edu or Elijah Jans jans.2@osu.edu. All slots will be filled on a first come first serve basis. Further details, including the format and schedule can be found in the overview and schedule tabs.

Using Dynamic Simulations to Investigate Muscle Forces during the Sit to Stand Transfer and Stair Climbing

By: Elena Caruthers

Noon – 1 pm E100

Abstract: While activities of daily living such as rising from a chair or climbing stairs are performed with relative ease by healthy adults, they are considered to be some of the most challenging activities in the home, especially for the elderly and those with lower limb pathologies such as knee osteoarthritis. Current rehabilitation strategies used for these populations are not 100% effective as some patients do not have significant improvements in pain or the ability to rise from a chair or climb stairs. In order to potentially improve and inform targeted intervention programs, the role of individual muscles needs to be investigated further. I will describe the utility of experimental tools such motion capture, which has been used for movies like Avatar, and how they can be used in joint with dynamic simulations to study the behavior of individual muscles, including estimating individual muscle forces produced during a task. I will also discuss the work my collaborators and I did to investigate muscle forces generated when rising from a chair or during stair climbing in a young, healthy population and how these results can be used in the future to help inform current rehabilitation strategies for populations that experience difficulty completing those tasks.

Bio: Elena Caruthers received a B.S. degree in engineering (with a mechanical emphasis) and a B.A. in dance from Hope College in 2012. She is currently pursuing her doctoral degree at The Ohio State University in Mechanical Engineering, working for Dr. Robert Siston in the Neuromuscular Biomechanics Laboratory. While at Ohio State, she was awarded the National Science Foundation Predoctoral Fellowship in 2013 and was selected to be an instructor for mechanics of materials at Ohio State through the Future Faculty Program in the 2015-16 school year. Her research interests include lower limb muscle function during activities of daily living in healthy and pathological populations as well as engineering education.

Due to the engineering expo, we will have our next meeting one week from today!

Impulse and Foot Placement Control in Human Running

By: Nidhi Seethapathi

Noon – 12:30pm E525

Abstract: Constant-speed human running is not exactly periodic. For instance, the body states of the person during the flight phase fluctuate about a mean value. Despite these noise-like deviations, people are able to run without falling down. Here, we examine how these natural state fluctuations are controlled using ground reaction forces and foot placement during running. We use natural step-to-step variability to infer such control. We find that most of the deviation in the sideways and fore-aft speed at mid-flight is nullified by a corrective impulse in the following foot-strike. In achieving this, people modulate the negative part of the ground reaction force more than the positive part. Further, we find that foot placement is used a control more in the sideways direction than in the fore-aft direction. The methods and results in this work can be used to better understand how such a controller for running differs in professional runners who are more practiced.

Join us on Wednesday for the first meeting of Student Lecture Series! Enjoy pizza and soda while we discuss recent changes, followed by a presentation by Mike Adams – Applications and Materials for Solid State Energy Conversion.

Quantification of Spatial Error in Electrical Impedance Mapping of Soft Tissues

By: Michael Karnes

Noon – 12:30pm E525

Abstract: Colorectal cancer (CRC) is the third most prevalent and fatal cancer in America with an expected 49,700 deaths in the year 2015. Resection remains the most effective treatments of CRC metastases producing 5-year survival rates above 50%. This research investigates the feasibility of implementing an impedance mapping (IM) instrument for the task of identifying tumor interfaces. The electrical properties of ex vivo hepatic tissues containing CRC metastases are characterized from 100 Hz to 1 MHz. The CRC metastases had significantly different conductivities and permittivities than the surrounding hepatic tissue. Porcine-bovine tissue phantoms were used to quantify the performance of an IM device in interface identification in soft tissues. The spatial accuracy and precision of IM using a for electrode linear platinum probe with a 1.5 mm pitch and 5 mm measurement step size was capable of accurately predicting tissue interface locations within a 3 mm range with 95% confidence.

Biography: Michael Karnes is a mechanical engineering PhD student working with Dr. Alper Yilmaz in the Photogrammetry and Computer Vision Lab. His undergraduate studies were conducted at Miami University. His master’s degree focusing on spectral impedance imaging of biological tissues was completed at the Ohio State in fall 2015 semester.

A Computational Study of Unstart in a Dual-Mode Scramjet

By: Logan Riley

Noon – 12:30pm E525

Abstract: Scramjets (Supersonic Combusting Ramjets) are an efficient air-breathing propulsion system for hypersonic (Mach>5) flight. Such high speed operation makes for a challenging flight environment featuring high aerodynamic and thermal loads, unsteady turbulence and shock wave/boundary layer interactions (SBLIs), and short residence times in which to mix and burn fuel. One of the most difficult problems in maintaining controlled scramjet flight is mitigating the potential for unstart of the scramjet engine. Unstart may occur when pressure in the combustor increases as a result of heat release leading to thermal choking. Unstart can lead to increased aerodynamic loads or, in the extreme case, the loss of the vehicle entirely. Since the mechanisms of unstart are not fully understood, we would like to leverage computations to explore the phenomenology of unstart in a scramjet flowpath. For this talk, we will explore unstart in a dual-mode scramjet in the presence of inlet distortion using results from unsteady Reynolds-Averaged Navier-Stokes (RANS) computations based on experimental work performed at the Air Force Research Lab (AFRL).