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«Strengthening the Nation through Diversity, Innovation & Leadership in STEM San Antonio,Texas · October 3-6, 2013 Get Connected! Connect with the ...»

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generated by an electron beam entering water. This research project involves the use of optical spectroscopy in a large (~1 cm) liquid cell using very high energy electrons (MeV). This approach, however, is not suitable for use in an electron microscope. By using a small (1 um³) liquid cell volume of 30,000 eV energy electrons, liquid-phase, electronbeam-induced deposition (LP-EBIP) provides higher purity, faster process rates, and far greater material flexibility than its gas-phase counterpart. The research process consists of 2 parts. First, we set up a laser spectroscopy system consisting of vacuum-compatible parts and that uses lock-in detection to reduce noise and laser light level fluctuations. Second, we determined the limit of detection for an analog species with an absorption spectrum similar to the solvated electrons and identified a dye for which the red laser absorbs strongly near 630 nm wavelength. Our optical spectroscopy results shows that this system works and that the dyes are strongly absorbent. If we can detect the solvated electron concentration, we will place the set up in the electron microscope, fire an electron beam into water, and measure the change in detector voltage. This technique will further understanding of electron-beaminduced processing in liquids.

SAT-277

OPTIMIZING A WIRELESSLY POWERED AC-DC BOOSTER FOR BIOMEDICAL IMPLANTS

Marissa Buell1, Nehad Dababo1, Rene Figueroa1, Peter Moala1, Hao Jiang2.

Cañada College, Redwood City, CA, 2San Francisco State University, San Francisco, CA.

1 Implanted medical devices (IMDs) have served to increase longevity for years. Wireless charging of IMDs decreases the need for periodic invasive surgery. One way to accomplish this is through a pulse width modulated (PWM) ACDC boost converter that uses a full-wave rectifier to convert the voltage from a low AC input to a high DC output. To generate the appropriate PWM signal, a microcontroller measures the frequency of the AC input from a small auxiliary coil parallel to the primary receiver coil. By aligning the rising edge of the control signal with the AC input, the boosted voltage is sufficient enough to overcome the turn-on voltage of the two diodes. Previously, motor-controlled rotating magnets were used to deliver power to the implant, which resulted in an optimized output from a duty cycle of 56 to 62% for the generated sinusoidal waveform. In the current experiment, a pair of inductive coils is used to generate the AC voltage. Using a transmitter coil in place of the rotating magnets allows for high-frequency operation and an adjustable waveform. From a square wave input, the output voltage is maximized with a duty cycle of 78% for the control signal. Through this method, a DC voltage of 5 V is generated from an AC input of 200 mV. Using LTspice software and a printed circuit board to illustrate the achieved results, this research aims to prove the increased efficiency achieved by using the paired inductive coils and the optimization of the duty cycle through alteration of the PWM signal.

FRI-276

HIGH-SPEED SIGNAL INTEGRITY

Juan Negrón, Anibal Mas, Manuel Jimenez, Steven Bangdiwala, Jose Fuentes.

University of Puerto Rico at Mayagüez, Mayagüez, PR.

In modern technology, digital and analog interconnections conflict when operating at high frequency values ( 1 GHz). It is important for designers to understand the impact on signals due to features arising in a printed circuit board (PCB) layout. Before signals can be improved, a detailed analysis must be carried out for the conductors, the transmission lines, and different PCB materials. A particular layout could use microstrip lines instead of striplines.

Different levels of performance could arise from the materials like FR4, R04350B, or Megtron6, or if the connections use a single-ended or differential lines. In this project, we describe the chain analysis that needs to be carried out to assess the effectiveness of a layout and to later use this information to devise potential topological improvements.

Some of the specific tools that allow us to analyze the integrity of high-speed signals in PCB designs include an impedance-matching analysis throughout the line to obtain expected values of insertion loss, return loss, and time domain response (TDR). The use of ADS and the subprogram Line Calc make the analysis a lot easier, allowing for the finding of specific parameters needed to maintain signal quality. At the end of this process, we have understood how signals and traces interact. Further research will allow us to devise ways for improving these layouts to obtain better signal quality.

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FRI-277

INCREASING AXIAL RESOLUTION IN WIDEFIELD MICROSCOPY USING DECONVOLUTION METHODS

Charlene Cuellar1, Nikhil Chacko2.

Contra Costa Community College, San Pablo, CA, 2University of California, Santa Barbara, Santa Barbara, CA.

1 Optical microscopy, used alongside computational methods, has led to higher resolution images for biological imaging purposes. Although great improvements have been made in the imaging field, there still exists the difficulty of matching the axial resolution with that of the lateral resolution due to the built-in optics of any microscope. The most common method of acquiring images of a three-dimensional structure in multidimensional microscopy is to image the structure of interest in different focal planes, referred to as optical-sectioning microscopy. However, this results in unwanted contamination from adjacent planes not in focus and explains the resolution disparity. Though there have been attempts at alleviating the problem with physical modifications, as in confocal microscopy, we focus Engineering on investigating computational reconstruction methods for improving the axial resolution in images acquired with more conventional methods, as in widefield microscopy. Our imaging setup is modeled as a shift-invariant system, and we imaged nearly point sources (fluorescent beads) to obtain the point spread function (PSF) that describes the microscope’s response for each point in the image. We use the knowledge of the PSF as a basis for the deconvolution algorithm to improve the quality of the acquired images. We also analyze how data from multiple angles can compensate for the reduced axial resolution and attempt to piece them all together to obtain one final image with improved axial resolution. We demonstrate our results using zebrafish as our model system.





FRI-274

SENSOR TEMPERATURE-SENSITIVITY ANALYSIS

Jose Salgado1, Clifton Roozeboom2, Beth Pruitt2.

Cañada College, Redwood City, CA, 2Stanford University, Stanford, CA.

1 Over the past several decades, sensors have had a big influence on everyday objects. Commercial applications for sensor technology include pressure sensors, light intensity sensors, temperature sensors, and so forth. Sensors are extremely important in our daily lives because they are used in aircraft, automobiles, computers, cellphones, and more. The Stanford Microsystems Laboratory is developing multifunctional integrated sensors for the environment (M-FISes) that enable simultaneous monitoring of 10 parameters: temperature, humidity, light intensity, pressure, wind speed, wind direction, magnetic field, and acceleration in three axes on one 10 x 10 mm silicon die. M-FISes provide significant cost, size, and power savings because they allow us to measure ten functions simultaneously instead of having ten individual devices. One of the most important properties of a good sensor is that it is sensitive to only the measured parameter. Temperature is a parameter that affects the sensitivity of most sensors in M-FISes, so we must be able to compensate for temperature effects. To determine the temperature sensitivity for every sensor, we used an oven and exposed M-FISes to a wide range of temperatures and measured all of the sensors’ outputs simultaneously.

M-FISes were ideal for temperature compensation because all of the functions are integrated in a single device. By using multiple tests, we measured an average output error from each sensor due to temperature. This analysis allows us to calculate the temperature coefficient of offset (TCO) and the coefficient of sensitivity (TCS), which will be used to compensate for variations in temperature.

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ENGINEERING (GENERAL) FRI-281

DEVELOPMENT OF A COMPUTER-AIDED MODEL TO SIMULATE PHYSICAL EXPERIMENTS ON PROSTHETIC

LINERS Shawn O’Donnell, Esteban Ruiz.

University of Pittsburgh, Pittsburgh, PA.

The prosthetic limb serves an essential purpose for people with an extremity amputation. It is imperative that the prosthetic limb maintain a proper fit to the user. The prosthetic liner is a vital component of a prosthesis as it ensures user comfort as well as a secure fit. The current production of prosthetic liners often results in swelling and abrasion to the residual limb area. Additionally, many prosthetic limb users experience dermatological conditions as well as buildup of bacteria, moisture, and odor. The ultimate goal is to conduct research and testing on alternative materials and fit of prosthetic liners to address the current flaws. Mechanical properties of candidate replacement materials are modeled using SolidWorks, a computer drafting and design program. Mechanical characteristics of the materials will be evaluated using the modeling software’s finite element analysis (FEA) capability. Variables included in the tests will include Young’s modulus and Poisson’s ratio to identify shear strength, compressibility, and tensile strength.

Forces will be applied to the material using the computer program. Validation of the model will be accomplished using physical testing on representative samples of the materials of interest. Mechanical forces relative to the previous forces will be placed on the material using a stationary jig and a movable piston. After review of the results, a prototype prosthetic liner will be constructed from the materials that show the highest potential for success. Finally, clinical tests must be performed on subject patients to determine the level of compatibility that the liner shows when used as advertised.

ENGINEERING SCIENCES/MECHANICS/PHYSICS

SAT-300

MOBILE CARBON DIOXIDE AND OXYGEN GRADIENT SAMPLER: ANALYZER ON THE MOVE

Alejandro Prieto1, Britton Stephens2, Brian Bevirt2.

Front Range Community College, Longmont, CO, 2National Center for Atmospheric Research, Boulder, CO.

1 We are building a compact oxygen (O2) and carbon dioxide (CO2) gradient sampler for investigating the relationships between exchanges of oxygen and carbon dioxide in a variety of locations. Measurements of local O2:CO2 flux ratios can help us better understand carbon and nutrient cycling by trees and soils. Microorganisms typically use organic carbon as a form of food, consuming O2 and producing CO2 through the respiration process. Nitrifying bacteria acquire their energy by oxidizing ammonium (NH4+) to nitrate (NO3-). We expect CO2 and O2 soil flux ratios to be close to -1 unless N is undergoing nitrification. If the process of nitrification is occurring, then the ratio between CO2 and O2 should be shifted toward more O2 consumption by the soil which will affect near-soil O2:CO2 gradients. More extensive measurements of O2:CO2 ratios can also help improve estimates of global terrestrial carbon fluxes. The mobility of this instrument will allow us to collect local data from different parts of an ecosystem, including respiration and photosynthesis, and in both natural and agricultural settings. The system uses infrared CO2 and fuel-cell O2 analyzers, each equipped with two detector cells. We minimize measurement drift by rapid switching of 2 inlet gas streams between the 2 sample cells on the O2 sensor and by occasionally measuring air from two compressed air cylinders with known CO2 and O2 differences. The data acquired by this instrument will aid future analyses and contribute to testing models of CO2, O2, and N cycling.

SAT-282

FEASIBILITY OF THE LABVIEW REAL-TIME OPERATING SYSTEM FOR USE AS A TELESCOPE POINTING

CONTROL SYSTEM

Stanley Edwin1, Scott Sewell2, Dan Marsh2, Brandon Larson2.

University of Alaska Fairbanks, Fairbanks, AK, 2National Center for Atmospheric Research, Boulder, CO.

1 Solar telescope pointing requirements have increased over the past decade as research has driven finer and finer spatial scales. The purpose of this research is to use a real-time operating system (RTOS) to create a control system with a higher responsiveness within this spatial resolution. Existing methods for solar telescope tracking use a

192 UNDERGRADUATE POSTER ABSTRACTS

traditional desktop operating system. A drawback of using traditional operating systems is the requirement to handle and process interrupts. These inherent latencies can extend the turnaround time from pointing error sensor to control feedback. We perform a quantitative comparison between Windows 7 (64-bit) and LabVIEW RTOS in controlling the position of a lever arm influenced by flow from a fan.

ENVIRONMENTAL ENGINEERING

SAT-284

CONTRAIL EFFECTS ON GROUND-BASED SOLAR IRRADIANCE

Marina Fernandez, David Larson, Carlos F.M. Coimbra.

Engineering University of California, San Diego, La Jolla, CA.

The impact of aircraft condensation trails (contrails) on ground-based solar irradiance measurements and therefore solar power plant output, has yet to be formally analyzed for use in solar resourcing and integration. This work quantifies the effects of persistent contrails on direct normal irradiance (DNI) using high-fidelity solar irradiance measurements and sky imaging. Contrails were identified using sky images from the Coimbra Solar Forecast Engine Lab’s observatory at the University of California, San Diego, and then correlated to intra-minute, ground-based irradiance measurements. Selecting contrails that specifically blocked the sun allowed us to observe their effect on ground irradiance, specifically on DNI data, as opposed to more general effects on the global and diffuse irradiance.



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