Archives—March 2011

Challenges in Developing Software for Space Trajectory Optimization Problems. Closing the Gap between Theory and Practice.

Thursday March 31, 2011 4:00-5:00 p.m.
ME-EM building, Room 112

Dr. Juan Senen Senent
Research Engineer at Odyssey Space Research

Consider designing a spacecraft trajectory that will visit as many asteroids as possible using the least amount of propellant, in the shortest amount of time, with only a tiny engine. Now, consider designing the trajectory of a spacecraft that collects as many pieces of space debris using minimum propellant. What these problems have in common is that in order to solve them, a large and complex optimization problem has to be solved. Developing software to solve these problems in a fast and accurate way is in itself a challenge. But if we take into account that the software has to be general enough to solve other trajectory optimization problems, should incorporate state of art algorithms while maintaining legacy code, should run in single computing environments and also in computer clusters and should also help the designer to understand the solution by graphically interacting with it, the software development process becomes as complicated as the problem it is trying to solve. This presentation will outline some of the challenges encountered while developing the Copernicus trajectory tool as well as examples of trajectory optimization problems solved with this tool.

Erythrocyte Polarizability: Nonlinear Electrokinetics in Medical Microdevices

Thursday March 24, 2011 4:00-5:00 p.m.
ME-EM building, Room 112

Associate Professor Adrienne R. Minerick
Chemical Engineering-Michigan Technological University

The controlled manipulation of bioparticles with electric fields has become ubiquitous in biotechnology laboratories, usually in the form of gel or capillary electrophoresis. However, creative use of electric fields for bioparticle manipulation in microdevices has also opened doors to opportunities in medical diagnostics. Such analytical microdevices are also referred to as lab-on-a-chip or micro total analytical systems (uTAS) and offer the potential for rapid, point-of-care diagnostics with implications in geographically remote medical situations. With relatively small electric fields, neutral matter can be manipulated: cells can be accelerated or trapped, proteins can be separated, DNA can be precisely focused, and other separations/purifications can be conducted at low concentrations.

This talk wilI focus on a subset of electrokinetics known as dielectrophoresis (DEP) for the analyis of erythrocytes (red blood cells). Dielectrophoresis is the polarizability of neutral & charged particles in a non-uniform alternating current electric field or a spatially non-uniform direct current field. Recent work in our lab has demonstrated that DEP can be utilized for rapid blood typing, recognition of membrane molecule expression, and hemolysis. Two microdevices have been tested with the ABO-Rh blood groups including a batch AC perpendicular electrode confrguration and a continuous sorting DC microchannel with bifurcation and remote electrode configuration. Membrane molecule expression has been systematically tested by comparing the DEP signatures of neat erythrocytes and those subjected to a B(1 -3)-galactosidase enzymatic reaction to digest the A and B polysaccharides from the membrane surface. The presence or absence of the Rh transmembrane protein is also discernable from the DEP signatures. Lastly, hemolysis has also been demonstrated in the low frequency range. By merging the fields of microfluidics, electrokinetics, and biology, handheld microdevices capable of rapidly screening and quantifying diseases, infections, or other ailments may one day become commonplace in medicine.

Nanoscale Thin Film Evaporation and Water Transport for Efficient Energy Systems

Thursday March 17, 2011 4:00-5:00 p.m.
ME-EM building, Room 112

Dr. Shalabh Maroo
Massachusetts Institute of Technology

Novel cooling technologies are required which can meet present cooling demands for concentrated solar irradiation levels of over 1000 sun in concentrated photovoltaic systems to enable major advancements in solar conversion technologies as well as many other important energy systems. Nucleate boiling heat transfer and thermal management devices based on micro-thin film evaporation have shown heat fluxes of only ~ 5 MW/m2. My research focuses on utilizing the concepts of disjoining and capillary pressures in nano-thin film evaporation to achieve ultra high heat fluxes. Nano-film evaporation occurs at the interline region in the three-phase contact line during bubble nucleation and growth. Molecular dynamics simulations were performed to study the evaporation of a nanoscale meniscus. Non-evaporating thin film formation, Hamaker constant of the film and ultra high heat fluxes(~ 100 MW/m2 ) were obtained, and the existence of high absolute negative liquid pressure in nano-films was confirmed. This property of sustaining high negative pressures in liquids at nanoscale can be engineered to provide passive transport of liquid, and applied in power devices to attain significantly higher heat rejection rates.

Transport of water in nanometer and sub-nanometer pores is of fundamental interest. Zeolites, which are porous aluminosilicate minerals, provide a perfect crystalline structure towards this research goal. The aim is to achieve desalination by size-based exclusion of solvated ions through zeolite created membranes, which has the potential to advance desalination technologies. MFI zeolites, which have a pore diameter of about 0.56 nm, are being studied via molecular dynamics simulations and experiments. As the size of a water molecule is roughly 0.28-0.3 nm in diameter, the pore size restricts the flow of water into a molecular chain presenting an extraordinary physical behavior. The water molecular structure inside these subnanometer pores is determined, and the effect of surface charges on water transport is evaluated based on energy analysis. It is also shown that very local energy equilibrium of one water molecule can affect the overall transport behavior in the pores.

Agent-Based Informatics for Autonomous Microgrids

Thursday March 3, 2011 4:00-5:00 p.m.
ME-EM building, Room 112

Dr. Steven Y. Goldsmith
Distinguished Member of the Technical Staff at Sandia National Laboratories

It is a foregone conclusion among power systems experts that localized microgrids based on fine-grained distribution of small capacity generators and fine-grained control of loads using advanced power grid informatics will limit the scope of cascading failures, reduce transmission losses and C02 emissions, enable renewable source penetration, and generally improve the reliability of electrical service throughout the entire grid. However, the current centralized grid coordination and control architecture is inadequate for managing distributed power grids. Centralized SCADA functions requiring substantial human-in-the-loop decision and intervention cannot scale, i.e. cannot decide proper actions, nor decide in time, for the number of independent generation and load resources implied by highly distributed autonomous microgrids. This talk will present an overview Sandia’s technical approach to the power grid informatics challenges posed by distributed autonomous microgrids. The basis of our approach is to leverage advanced multi-agent system (MAS) technology to develop the collective decision functions and interaction protocols necessary to harmonize the competing and common interests among, and coordinate the actions of, a heterogeneous society of autonomous power agents. The presentation will exhibit the general MAS architecture and highlight some fundamental research issues being investigated through development testing on a small computational cluster.