Browsing by Author "Kasarda, Mary"
Now showing 1 - 5 of 5
Results Per Page
Sort Options
- Airflow sensing with arrays of hydrogel supported artificial hair cellsSarlo, Rodrigo (Virginia Tech, 2015-01-19)Arrays of fully hydrogel-supported, artificial hair cell (AHC) sensors based on bilayer membrane mechanotransduction are designed and characterized to determine sensitivity to multiple stimuli. The work draws upon key engineering design principles inspired by the characteristics of biological hair cells, primarily the use of slender hair-like structures as flow measurement elements. Many hair cell microelectromechanical (MEMS) devices to sense fluid flow have already been built based on this principle. However, recent developments in lipid bilayer applications, namely physically encapsulated bilayers and hydrogel interface bilayers, have facilitated the development of AHCs made primarily from biomolecular materials. The most current research in this field of "membrane based AHCs," shows promise, yet still lacks the modularity to create large sensor arrays similar to those in nature. This paper presents a novel bilayer based AHC platform, developed for array implementation by applying some of the core design principles of biological hair cells. These principles are translated into key design, fabrication and material considerations toward improved sensor sensitivity and modularity. Single hair cell responses to base excitation and short air pulses are to investigate the dynamic coupling between hair and bilayer membrane transducer. In addition, a spectral analysis of the AHC system under varying voltages and air flow velocities helps to build simple, predictive models for the sensitivity properties of the AHC. And finally, based on these results, we implement a spatial sensing strategy that involves mapping frequency content to stimulus location by "tuning" linear, three-unit arrays of AHCs. Individual AHC sensors characterization results demonstrate peak current outputs in the nanoamp range and measure flow velocities as high as 72 m/s. Characterization of the AHC response to base excitation and air pulses show that membrane current oscillates with the first three bending modes of the hair. Output magnitudes reflect of vibrations near the base of the hair. A 2 degree-of-freedom Rayleigh-Ritz approximation of the system dynamics yields estimates of 19 N/m and 0.0011 Nm/rad for the equivalent linear and torsional stiffness of the hair's hydrogel base, although double modes suggest non-symmetry in the gel's linear stiffness. The sensor output scales linearly with applied voltage (1.79 pA/V), avoiding a higher-order dependence on electrowetting effects. The free vibration amplitude of the sensor also increases in a linear fashion with applied airflow pressure (3.39 pA/m s??). Array sensing tests show that the bilayers' consistent spectral responses allow for an accurate localization of the airflow source. However, temporal variations in bilayer size affect sensitivity properties and make airflow magnitude estimation difficult. The overall successful implementation of the array sensing method validates the sensory capability of the bilayer based AHC.
- On-Demand Big Data Analysis in Digital RepositoriesXie, Zhiwu; Chen, Yinlin; Jiang, Tingting; Griffin, Julie; Walters, Tyler; Tarazaga, Pablo Alberto; Kasarda, Mary (Springer International Publishing, 2015-12-18)We describe a use and reuse driven digital repository integrated with lightweight data analysis capabilities provided by the Docker framework. Using building sensor data collected from the Virginia Tech Goodwin Hall Living La- boratory, we perform evaluations using Amazon EC2 and Container Service with a Fedora 4 repository backed with storage in Amazon S3. The results con- firm the viability and benefits of this approach.
- A Sample of Best Practices to Support Veterans in Attending and Completing Engineering Degree ProgramsKasarda, Mary; McCrery, Ennis McNeer; DePauw, Karen P.; Byrd, Carson; Mikel-Stites, Max; Ray, Victor; Pierson, Mark; Brown, Eugene F.; Hall, Simin; Soldan, David L.; Gruenbacher, Don; Schulz, Noel; Vogt, Blythe; Hageman, William B.; Natarajan, Rekha; Olson, Rick; Kramer, Kathleen; Lord, Susan (Veterans in Society: Changing the Discourse, 2013-04-15)This paper describes some sample best practices identified by three institutions, Virginia Tech, Kansas State University, and the University of San Diego to support the recruitment, transition, and retention of veterans in engineering degree programs. These three institutions represent a subset of the initial cadre of institutions receiving planning grants from the National Science Foundation to facilitate and support veterans in their pursuit of undergraduate and graduate engineering degrees, particularly when utilizing their "GI Bill" benefits. Best practices presented here include a website to co-locate veterans' campus resources virtually, a slide show "video" to highlight the mechanics of graduate school and finding the right program, models to help institutions give military veterans academic credit for military training, results of a regional institutional networking workshop on veterans issues, and strategies to better attract and recruit veterans to engineering degree programs.
- A System Identification Technique Using Bias Current Perturbation for the Determination of the Magnetic Axes of an Active Magnetic BearingSpangler, Dewey; Prins, Robert; Kasarda, Mary (MDPI, 2017-03-28)Inherent in every Active Magnetic Bearing (AMB) are differences between the expected geometric axes and the actual magnetic axes due to a combination of discrepancies, including physical variation from manufacturing tolerances and misalignment from mechanical assembly, fringing and leakage effects, as well as variations in magnetic material properties within a single AMB. A method is presented here for locating the magnetic axes of an AMB that will facilitate the accurate characterization of the bearing air gaps for potential improvement in field tuning, performance analyses and certain shaft force measurement techniques. This paper presents an extension of the application of the bias current perturbation method for the determination of the magnetic center to the determination of magnetic axes for the further development of accurate current-based force measurement techniques.
- Towards Use And Reuse Driven Big Data ManagementXie, Zhiwu; Chen, Yinlin; Griffin, Julie; Walters, Tyler; Tarazaga, Pablo Alberto; Kasarda, Mary (2015-06-03)We propose a use and reuse driven big data management approach that fuses the data repository and data processing capabilities in a co-located, public cloud. It answers to the urgent data management needs from the growing number of researchers who don’t fit in the big science/small science dichotomy. This approach will allow researchers to more easily use, manage, and collaborate around big data sets, as well as give librarians the opportunity to work alongside the researchers to preserve and curate data while it is still fresh and being actively used. This also provides the technological foundation to foster a sharing culture more aligned with the open source software development paradigm than the lone-wolf, gift-exchanging small science sharing or the top-down, highly structured big science sharing. To materialize this vision, we provide a system architecture consisting of a scalable digital repository system coupled with the co-located cloud storage and cloud computing, as well as a job scheduler and a deployment management system. Motivated by Virginia Tech’s Goodwin Hall instrumentation project, we implemented and evaluated a prototype. The results show not only sufficient capacities for this particular case, but also near perfect linear storage and data processing scalabilities under moderately high workload.