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SUNFEST at Penn

Summer 2005

From left to right: David Cohen, Roman Geykhman, Kejia Wu, Louie Huang, Ann Nguyen, Adam Wang, Robert Calan, Olga Paley, Ebenge Usip, Miguel Perez Tolentino, Hal Paver.

Robert Callan (Electrical Engineering) - University of Pennsylvania

Liquid Flow Measurements Using A Pyroelectric Anemometer

Advisor: Dr. J.N. Zemel

ABSTRACT: The transport of fluids through pipes is an essential part of many industrial processes, requiring an accurate measurement of the flow. The measurement of natural gas flow in pipelines and the precise proportions of reactants flowing into a reaction chamber are but two examples. Many flow meters have been developed based on a wide variety of operating principles. Properties, such as physical size, speed, measurement accuracy, cost, reliability, and difficult recalibration often limit the usefulness of these meters in different applications.

The device investigated in this study is the Pyroelectric Anemometer (PA). Its operation is based on the convective heat loss from the device to the fluid in gas flows and standard heat transfer theory accounted nicely for the experimental data in previous research. This project addresses the pyroelectric anemometer's response to liquid flows. A test system was built and data were collected. These measurements were compared to gas flows and a previously derived fluid flow model. View Paper | View Slides

David Cohen (Mechanical Engineering) - The University of Pennsylvania

Learning Legged Locomotion Over Extreme Terrain

Advisor: Dr. Daniel Lee

ABSTRACT:  Currently, legged locomotion over obstacles remains a great challenge in robotics. The equations describing so-called “extreme” walks are highly complex, and the contact forces between the robot and its environment are not easily modeled. A major research goal in the field of robotics is to develop capacity for “extreme” walks while keeping computations tractable.

This study was designed to create a method for making a Sony Aibo walk up a 1-inch step consistently. Project activities focused on finding ways to apply simple models for generating walks onto the step. Once the study identified a class of “extreme” walks in lower dimensions, parameters were hand-tuned in an effort to assess whether a prospective class of walks was appropriate or not.

As a result of the work completed in this study, both a 35 mm and a 50 mm step were scaled successfully by the Sony Aibo. Avenues for future work include: 1) the development of an automatic system for determining footfall order and step displacements, 2) a method for automatic primitive identification and switching, 3) refinements to the fields employed, and 4) extensions to extreme dynamic locomotion. View Paper | View Slides

Roman Geykhman (Electrical and Systems Engineering) - Universityof Pennsylvania

Working Toward a Better Vision-Based Obstacle Detection Method

Advisor: Dr. Dan Lee

ABSTRACT: Obstacle detection is a vital component of any autonomous mobile robotics application. Vision-based systems for obstacle detection offer the advantage of using relatively inexpensive and readily available video cameras to supply a mobile robot with information about its environment. The key challenge, however, is that cameras supply too much information and complicate the efficient, automated extraction of meaningful features from raw images. Fast and effective obstacle acquisition from this input is still an unsolved problem in robotics.

This paper documents the experimental development of an accurate and efficient vision-based obstacle detection method using the Learning Applied to Ground Robotics (LAGR) experimental platform. The LAGR platform is designed to test algorithms for the successful autonomous navigation of an unmanned vehicle through rural terrain, relying almost entirely on vision to collect information about the environment. The platform is equipped with two pairs of stereo cameras, each with a dedicated Pentium-M computer committed to processing its input and converting it into meaningful information about obstacles present in the platform's environment.

This project focuses on the use of low-level filtering and curve-fitting techniques to enable mobile robots to extract enough information about surrounding obstacles to successfully avoid them. The study is focused on developing and testing new and preexisting algorithms that will also enable the robot to avoid false detection without expending too much computation time in the process. The algorithms will be implemented in C and MATLAB code and tested on board the LAGR platform using both real-time and prerecorded stereo image pairs. View Paper | View Slides

Louie Huang (Electrical and Systems Engineering) - University of Pennsylvania

Path Planning Mobile Robotics

Advisor: Dr. George Pappas

ABSTRACT: One of the fundamental problems in the field of robotics is path determination and motion planning. The project described in this paper focuses on path determination in a known environment. The goal is to enable a mobile robot to successfully navigate an environment according to a specified temporal logic formula. On a high level, temporal logic formulas can effectively provide the robot with directions on where and when to go. As part of this project, a program will be developed to formulate a continuous path plan that will fulfill the temporal logic formula supplied for the robot to follow.

In this project, the ActivMedia Pioneer 3-DX robot will be used. This robot model was chosen because it is preconfigured for basic navigation. Preprogrammed with algorithms for shortest path determination, obstacle avoidance, and localization, the Pioneer 3-DX is also capable of new navigation techniques that can be programmed in C and C++. Maps of known environments can be generated by the Pioneer 3-DX. A graphical user interface program will utilize these maps in conjunction with user supplied directions as expressed by a temporal logic formula to construct a path plan. The path determined by the program can then be relayed back to the robot for implementation. View Paper | View Slides

An Nguyen (Bioengineering) - University of Pennsylvania

Effects Of Cross-Linking On Mechanical Function In The Degenerate Nucleus Pulposus  

Advisor: Dawn M. Elliott 

ABSTRACT: 

Background Context: In the United States, the most prevalent cause of disability of workers under 45 years of age is low back pain. Past research suggests that there is a link between low back pain and intervertebral disc degeneration. One of the earliest known components of disc degeneration is a decrease in proteoglycan content in the nucleus pulposus, which in turn leads to changes in mechanical properties. In this study, the effects of proteoglycan content and collagen cross-linking on swelling behavior were investigated.

Study Design: Swelling pressure of the nucleus pulposus was measured in a confined compression experiment. The effects of two injectable agents were studied. The first was Chondroitinase ABC (ChABC), which is an enzyme that breaks down proteoglycan. ChABC was used to model disc degeneration. In addition, genipin -- a cross-linking agent that promotes the cross-linking of fibers in the disc’s collagen network -- was also used.

Objectives: The main objective of this study was to determine the effects of cross-linking on the mechanical properties of degenerate nucleus pulposus. The first step was to determine baseline swelling pressure for control or normal sheep discs. The second was to determine the concentration of ChABC needed to mimic the degeneration found in human discs. The final step of the study was to investigate the potential of genipin required to restore the mechanical function in degenerate discs.

Results: The average swelling pressure measured for normal sheep discs was 0.21 + 0.13 MPa. The optimal ChABC dose was 0.5 U with an average swelling pressure of 0.082 + 0.04 MPa. The average swelling pressure for the 0.5% genipin group and 0.5% genipin + 0.5 U ChABC were 0.15 + 0.07 MPa and 0.083 MPa, respectively.

Conclusion: Though findings from this study were inconclusive, they do not eliminate the potential of genipin as a treatment for disc degeneration. This warrants further investigation into effects of cross-linking using genipin and the mechanisms by which genipin increases cross-linking. View Paper | View Slides

Olga Paley (Chemical Engineering) - University of California, Berkely

ApplyingImmunohistochemistry and Reverse Transcription Pcr To Intervertebral Disc Degeneration In An Animal Model

Advisor: Dr. Dawn Elliott

ABSTRACT:

STUDY DESIGN: Devise a set of protocols for immunohistochemical (IHC) and gene expression analysis that will permit the measurement of changes that occur during degeneration in the lumbar intervertebral disc of a rat model.

OBJECTIVES: Quantify how the composition of the disc changes with degeneration in the animal model and prove that these changes correspond to those within a degenerate human disc, supporting the rat as a valid model of spinal disc degeneration. In the future, use the model to determine mechanisms for the degenerative process.

SUMMARY OF BACKGROUND DATA: Rodents have been widely used as models to study disc degeneration. The chemical changes within the human disc have also been extensively studied by various methods 5,6,7,8,9. However, the research to understand the same chemical changes in the rat has been limited.

METHODS: IHC staining of the lumbar intervertebral discs of healthy adult rats (as a basis) began with fixing thin slices of paraffin-embedded tissue onto glass slides. The samples were then treated with an antibody specific to the chosen antigen that was then coupled to a biotin-labeled secondary antibody. Finally, the antigens were localized using colorimetric staining. Reverse transcription -polymerase chain reaction (RT-PCR) was also employed to understand gene expression changes within the disc. An RNA extraction was first performed, then RT-PCR to create first-strand cDNA, and finally, standard PCR to amplify a desired gene.
RESULTS: The nucleus pulposus on the slide experienced some degradation during the fixing and staining procedures. The collagen I staining proved the most problematic, with staining occurring within the inner annulus and nucleus, a result contradictory with literatur. Collagen II primarily stained within the inner annulus, as hypothesized. Finally, aggrecan stained as expected, but there was evidence of significant background effects. The gene expression work produced results for aggrecan, collagen I, and fibronectin, proving that the protocol employed for the RNA extraction and RT-PCR was effective.

CONCLUSIONS: A number of techniques were established for IHC and RT-PCR, but further development is needed. There is significant evidence that the staining was problematic due to background effects. Thus, the continuation of the study will focus on perfecting the fixation and sectioning procedure and doing regular histological staining to insure a sample which does not disintegrate and stains evenly. The preliminary gene expression work’s success leads to the conclusion that more specific results may be achieved by splitting the nucleus from the annulus. These results can be quantified and compared by normalizing them to a standard gene. View Paper | View Slides

Miguel Pérez Tolentino (Physics and Electronics)- University of Puerto Rico at Humacao

Study On The Implementation Of Sintered Ltcc And Graphite As A Sacrificial Material For The Fabrication Of Microcombustors

 Advisors: Jorge Santiago Aviles

ABSTRACT

The micro-combustor is a compact, sub-millimeter device that burns hydrocarbon fuels homogeneously as a source of power. It efficiently converts heat generated by combustion into electric power, and has the potential to replace batteries in portable applications that require long-term power. The possible benefits of these devices include their ability to provide greater energy and power density, higher temperatures and greater efficiency as a heat source. Also this technology can have many applications such as military portable systems, consumer portable system, and chemical control reaction systems.

The problem we are addressing is the fabrication of a gas fuel micro-combustor for a compact, portable electric power generator using thermoelectric elements. This device has been fabricated [1] using a competing technology, which is more complex, time consuming and therefore more expensive.

The materials to be used for the construction of this device are fundamentally Low Temperature Co-Fired Ceramic (LTCC) and Graphite. The fabrication of this device will rely essentially on a thermal process (sintering of the LTCC tapes). The instruments that will be use for the fabrication / characterization include: a furnace for sintering the ceramics, a heated press for the ceramics lamination, and a thermal laser and a numerically controlled milling machine for the patterning and machining of the tape.

In order to obtain a sense of the flow behavior within the device, numerous simulations have been made using a commercial program call FEMLAB. This program will take into consideration a diversity of parameters to measure such as the speed, pressure, fluid Reynolds Number, among others.

The main objective of this project is to complete the fabrication of a small combustor that contains fundamentally three inputs, one output and a combustion area. In one of its inputs a combustible gas (hydrogen) is injected, and oxygen from the air as an oxidizer flows through the other two inputs. The gases are mixed in the combustion area. A flame is initiated in the combustion area to burn the fuel / oxidizer mixture.

It is hoped that the combustor fabrication will be completed as designed. The parameters that characterize its combustion and power are expected to be consistent with its application as an electrical generator by means of the thermoelectric effect.

We are using FEMLAB, a commercially available numerical analysis software package for the simulation process.

As means to practice the lamination process, where the LTCC and graphite are bonded by means of uni-axial forces and heat, an experiment was carried out using pencil leads (0.5mm and 0.7mm in diameter) as source of graphite. Three parameters, force, temperature and time, were used to control the pencil lead lamination to LTCC. The parameters were 1,100 -1,300 pounds, 100º to 200ºF, and 15 to 20 minutes, respectively. By sintering the LTCC (after the lamination with pencil leads), micro-channels were formed, taking the characteristics of graphite leads morphology. In other words, graphite serves as a sacrificial material in the formation of channels or conduits. View Paper | View Slides

Ebenge Usip (Physics) - University of Southern California

Thin-Film Polypropylene Capacitors

Advisor: Dr. Jorge Santiago-Aviles

ABSTRACT: The focus of this project was to determine the dielectric constant of polypropylene doped with various ethynol porphyrins at different concentration levels in order to determine if the degree of conjugation within ethynol porphyrin oligomers would increase the capacitance of naked polypropylene films. The research procedure for this study began by forming a capacitor with a film of polypropylene as the dielectric material. The capacitance was then measured and the dielectric constant was calculated. In order to deposit the film, polypropylene was spin-cast. Over the course of this study the capacitance values for polypropylene films doped with the compounds ZnTPP, ZnO1, ZnO3, Zn 3,5 and Zn 2,6 were studied. The capacitance values have shown a significant increase, roughly one million times greater than naked polypropylene although this value is inherently flawed due to inaccurate measurements of film thickness. View Paper | View Slides

Adam Wang (Electrical Engineering) - University of Texas at Austin

Handheld Device for Remotely Measuring Brain Function

Advisor: Dr. Britton Chance

ABSTRACT: Infants, and especially premature infants, are carefully monitored while in their incubators, and their brain health is of great concern. While it is currently the preferred procedure to attach a device to a patient’s forehead for monitoring pulse rate and oxygen levels in the brain, the development of a remote handheld system would make it possible to spot check patients from a distance, without having to deal with the obtrusiveness of attaching probes. Additionally, past studies have shown that measuring changes in blood volume and oxygen levels in the forebrain can be used to study brain function. Current work suggests that affordable and safe handheld devices for contact systems can be built from inexpensive components such as LEDs and photodiodes to measure these parameters.
The goals of this project were to study the aspects of, analyze the feasibility of, and suggest a design for a handheld device capable of remotely sensing brain function by employing the basic building blocks of near-infrared technology. As part of the project, experiments have been designed to simulate the uses – such as finding the arterial pulse and tracking changes in blood volume and oxygen levels in the brain – of a handheld remote sensing device for measuring brain health and function. In this study, remote sensing has demonstrated promising results for use over small distances. This paper also includes suggestions for extending remote sensing over greater distances for use in more practical, real world situations. View Paper | View Slides

Kejia Wu (Electrical and System Engineering) - University of Pennsylvania

Fabrication of micro-polarizer array with polymer thin film

Advisors: Jan Van der Spiegel, Viktor Gruev

ABSTRACT: In this project, significant advancements have been made in creating an array of micro-polarizers using a polymer thin film in order to extract various polarization parameters about the imaged environment. The array of micro-polarizers is to be integrated with custom-made VLSI image sensor in order to create a complete low power real-time bio-inspired polarization sensitive imaging sensor. Two different photoresists, i.e. positive and negative photoresist, are used for patterning the polarization thin-film. The advantages and disadvantages of both procedures are analyzed in details. The isotropic properties of the etching procedure of the thin-film are compared between oxygen plasma and reactive ion etching. The optimum isotropic etching is outlined as a function of temperature, pressure and gases flow. Finally, we have summarized the complete procedure for creating a micro-polarize array with sub-µm precision.  View Paper | View Slides

Download the 2005 SUNFEST Report.

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