Rafael Perez

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Recent advancements in mobile technology allow Global Positioning System (GPS)-enabled cell phones provide a variety of real-time location-based services (LBS). This paper reports on the design, implementation, and testing of such a service, the Travel Assistant Device (TAD), that aids transit riders with special needs to use public transportation. TAD is a(More)
Next-generation transportation surveys will utilize Global Positioning Systems (GPS) to collect trip data. Due to their ubiquity, GPS-enabled mobile devices are becoming promising for use as survey tools. TRAC-IT is a mobile phone application that records travel behavior by collecting real-time GPS data and requiring minimal input from the user for data(More)
Periodic stimulation of an aggregate of spontaneously beating cultured cardiac cells displays phase locking, period-doubling bifurcations and aperiodic "chaotic" dynamics at different values of the stimulation parameters. This behavior is analyzed by considering an experimentally determined one-dimensional Poincar6 or first return map. A simplified version(More)
— Advanced location based services have the ability to track users with Global Positioning System (GPS)-enabled cell phones in real-time. These applications share a common problem; the continuous calculation and transmission of GPS fixes from the mobile phone to a server consumes a considerable amount of energy and increases data transmission costs.(More)
RATIONALE Clinical trial design in interstitial lung diseases (ILDs) has been hampered by lack of consensus on appropriate outcome measures for reliably assessing treatment response. In the setting of connective tissue diseases (CTDs), some measures of ILD disease activity and severity may be confounded by non-pulmonary comorbidities. METHODS The(More)
This paper describes the initial phase of a study of ecolinguistic-based social media analytics aimed at understanding the frequency, semantics, context and potential persuasive influence of social media conversations about energy issues, metaphors, frames and behaviors. Our broad research question asked, " How does the online conversation about energy(More)
A heuristic technique is presented that applies simulated annealing search to derive mathematical equations that model a pilot for an X-CELL 60 helicopter. The technique uses a pre-defined alphabet of formulas and combines them to create a mathematical model of the system controller or pilot. The proposed technique provides a new tool that can be used to(More)