Nov 19, 2019

Ep 226: Allen Garner - Prof., Agricultural and Biological Engineering, Purdue University

Professor, Agricultural and Biological Engineering
Purdue University
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Show notes

Allen’s intro to the Naval Reactors Program (0:26)
0:26-11:29 (Allen discusses his introduction to nuclear power in the Naval Reactors Program)

Q: Tell me about your nuclear start in the Navy.
A: Allen Garner got his start with nuclear while in the Navy and still serves in the Navy Reserves. This is a part-time role that he juggles with his role as a professor at Purdue University. Allen starting doing submarine work in the Navy, focusing on prevention of mutual interference. He studied nuclear engineering at the University of Illinois as a Naval ROTC student, eventually placed in the submarine force by the Naval Reactors. The Naval Reactors Program is responsible for managing and administering the Naval nuclear propulsion program, including submarines, aircraft carriers, and research and development of Naval nuclear propulsion.

After Allen went through Naval Nuclear Power School, he completed Prototype, where he learned nuclear hands-on, and Submarine Officer Basic Course, where he learned the basics of the submarines. He then went on to his Junior Officer tour on the USS Pasadena as the reactor controls assistant and chemistry and radiological controls assistant. During Allen’s tour, the submarine went through an analog-to-digital instrumentation change out. The Navy has a few remaining prototype areas which uses moored training ships that are brought into port to train operators. During training, operators go through many different ways to cover the reactor in emergency situations.

Post-graduate biomedical research (11:29)
11:29-22:23 (Allen reviews his post-graduate research in bioelectrics at Old Dominion University and in nuclear engineering at the University of Michigan)

Q: Where did you go after the Navy?
A: After ROTC during his undergraduate studies, Allen Garner took a leave of absence from the Navy to get his first Master’s degree at the University of Michigan. Allen did theoretical studies of crossed-field devices, which are used in RADAR systems in the Navy and the Air Force. A crossed-field device has a parallel plate with voltage in the middle, creating an electric field. The magnetic field is perpendicular to the plates, which turns the electrons. Towards the end of his Junior Officer tour, Allen put in for the Navy to send him to shore duty and was sent to Norfolk, Virginia. He did bioelectric research at Old Dominion University (ODU), which uses intense non-ionizing radiation to modify biological cells. When a voltage is applied, the water in the membrane moves and pushes proteins and lipids out of the way. This creates holes which, if big enough, all everything to leak out and the cell to die. If the size of the holes is controlled, things can be inserted and the hole can reseal.

Allen’s advisor at ODU worked on intracellular manipulation. Inside the cell, mitochondria play a critical role in regulating apoptosis. If the cells aren’t dying properly and don’t undergo apoptosis, cancer can develop. Nanopulses can be used to charge mitochondria and allow them to leak enzymes that initiate the apoptotic pathway. The apoptotic pathway is massive and extremely complicated.

After finishing up at Old Dominion, Allen returned to the University of Michigan to work on his PhD in nuclear engineering. One topic he studied was modeling tumor growth. Tumors are very evolved structures which work symbiotically with the body, growing by diffusion and bringing in blood vessels to continue to feed them. The recruitment of the vasculature, or mastocytosis, makes certain tumors spread. Allen loved biology in high school and considered majoring in genetic engineering, which he picked up at ODU and in his PhD program before going to work for GE.

Electromagnetic physics research at GE (22:23)
22:23-40:10 (Allen explains his research at GE in electromagnetic interference how he applied it non-linear transmission line research at Purdue)

Q: What did you do at GE?
A: Allen Garner was originally hired into GE as a biomedical engineer, which morphed over time into an electrical engineering position, and eventually an electromagnetic physicists. He was brought on to work on a project involving microscopy. Allen got involved in radiation detection instrumentation and non-proliferation early on, later working on satellite visualization in terms of resolution calculations. During his last five years at GE, Allen spent most of his time modeling thermal stresses on flip switches for satellites. The RF lab would make very small chips to be used on the satellites, but the temperatures in space were much different than on Earth. Shrinkage happens due to the temperature coefficient which creates forces that are strong on sharp angles. Allen used finite element analysis to calculate where the strongest forces were.

Another one of Allen’s projects at GE was focused on electromagnetic interference. It was originally funded by GE Plastics, who was looking to increase their market share. Plastic is a dielectric, but it can’t be used to shield electromagnetic radiation. Things are going to become more and more electric and electromagnetic interference becomes more of a concern. The question was whether plastic can be made more shielding by making it look more like a metal. Percolation is when a composite material and filled with a filler material to make it look like the metal material. The aspect ratio of the material determines the percentage volume loading of filler material to make it look like a metal. Finite difference time domain is important in electromagnetic radiation because things vary with change. Allen hit upon a semi empirical method that allowed him to develop fitting parameters that would be predictive. Experiments with stainless steel in different aspect ratios were completed and results fed into the predictive model.

Purdue University has funding from the Office of Naval Research to take these concepts and apply it to a non-linear transmission line. A transmission line is a cable with dielectrics represented by a combination of capacitors and inductors. If the capacitance is changed to be a function of voltage and/or the inductor varies with current, a non-linear transmission line is created. The non-linearity creates an electric shockwave which generates a radiofrequency signal. This can then be used to drive a high power microwave system to project a radar or a pulse.

Current Projects at Purdue (40:10)
40:10-49:16 (Allen summarizes current, ongoing research projects at Purdue related to electron emissions, gas breakdown, and nanoelectronics)

Q: What’s another project you’re working on at Purdue?
A: Allen Garner has two other projects at Purdue, one funded by the Air Force and one funded by the Navy, which look at electron emission and gas breakdown. A plasma has ions going around and voltage is applied to cause electrons to move. As electrons are stripped, they interact with the neutral particles which adds on to the standard secondary emission that helps to drive Paschen’s Law. Allen’s group has analytically derived equations that show how the breakdown voltage varies linearly as the gap distance is reduced. Practical applications include microsatellites, propulsion and combustion, and biomedical applications. The angle of the electrons creates field enhancement. One experiment shows where the transitions between the emissions regime, which has never been looked at before. Another student derived a triple point, or a nexus, which is an intersection of different mechanisms. This student put in collisions, standard space charge limited emission, and field emission, showing where all three mechanisms intersect. The nexus between thermionic emission, space charge limited emission, and field emission was also looked at. Understanding how these mechanisms interplay assists in design. As devices are made smaller and smaller, an important question is related to the impact of heat.

Some of Purdue’s projects on the bio side are potentially very interesting. One looks at antibiotic-resistant microorganisms and using electric pulses with drugs to treat them. On the non-bio side, there are a lot of applications in nanostructures and nanoelectronics, such as how 5G waves interact with the structures.

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