publications


Variability of Particulate Matter and Air Quality at Street Level in New York City
 

-Parker, Granville; Castaldi, Ottavio; Sanchez, Justin; Ramamurthy, Prathap; Hrisko, Joshua

Measurements were taken at street level using air quality sensors that measure particulate matter, temperature, and humidity. The research goal is to combine hands-on data acquisition at high spatial resolution with GIS post-processing to quantify the spatial and temporal variability of particulate matter concentration (PM 2.5) along crowded streets in New York City. Due to their fine size and low density, PM 2.5 remains in the atmosphere for longer periods of time and can bypass the biological filters of the human nose and throat and penetrate deep into the lungs and potentially enter the circulatory system. PM 2.5 is a by-product of automobile combustion and is believed to be a primary cause of respiratory malfunction in urban environments. Street level concentration of PM2.5 is observed across two different routes that witness significant pedestrian traffic in Manhattan; observations will be conducted along these routes at various time periods. The study used the AirBeam community air quality monitor that simultaneously tracks PM 2.5 concentration along with GPS, air temperature and relative humidity.


Vertical Structure of Heat and Momentum Transport in the Urban Surface Layer

-Hrisko, Joshua; Ramamurthy, Prathap; Gonzalez, Jorge

Vertical transport of heat and momentum is investigated in the urban surface layer (USL) using air temperature and 3-component velocity measurements logged by a 40-m tall flux tower consisting of five sonic anemometers, each sampling at 10Hz. The Obukhov length is used to delineate dominantly convective periods, which are further subdivided into stability categories (weakly unstable, very unstable, etc.). Eddy covariance techniques are then used to calculate turbulent fluxes to reveal the effects of instability and height (AGL) on vertical momentum and heat transfer. During periods of increased instability the vertical heat flux deviates from the results given by the accepted theory. Further analysis of primary quadrant sweeps and ejections also indicate deviations from the theory, alluding that ejections dominate during convective periods for sensible heat, but equally contribute with sweeps for momentum transfer. Lastly, frequency domain methods are employed to quantify energy production and dominant length scales. Cospectra for both momentum and heat experience shifts in frequency and energy, suggesting that the efficiency of transport and eddy production in urban atmospheric flows are non-linearly dependent upon the height and instability. Collectively, these results demonstrate similarity breakdown for heterogeneous terrain, and reaffirm that revised and improved methods for characterizing heat and momentum transport in urban areas is needed. These implications could ultimately advance weather prediction and estimation of scalar transport for urban areas susceptible to weather hazards and large amounts of pollution.


Multiple Chip Module Cooling Using Vapor Chamber

Escobar-Vargas, Sergio; Kumari, Niru; Ferrer, Ernesto; Shih, Rocky; Anthony, Sarah; Hrisko, Joshua; Wan, Zhimin

This document describes the characterization of vapor chambers as cooling devices for multiple chip modules. The work consists of experiments and theory of vapor chambers. It includes developing and building the testing system, selecting the control and monitoring parameters, designing the vapor chamber, performing experiments, analyzing measurements, and drawing recommendations for vapor chamber selection and operation. The experiments include typical operation conditions found in electronics e.g. power dissipations up to 250 W, power densities up to 100 W/cm^2, and operating temperatures up to 45 C among other parameters. The main outcome of this work is that vapor chamber performs better than a solid heat spreader under specific conditions and the guidelines are included in the conclusions section; other outcomes include correlations and quantification of vapor chamber thermal resistance functionality to the control parameters.


Detectability Prediction for a Thermoacoustic Sensor in the Breazeale Nuclear Reactor Pool
 

-Hrisko, Joshua; Smith, James A.; Garrett, Steven L.

This thesis reports the first quantitative measurements of the vibroacoustic background noise levels and the reverberation time in the 70,000 gallon (265 m^3) pool used to cool the Breazeale Nuclear Reactor on Penn State's University Park campus. These measurements are used to provide an estimate for the detectability of a pure tone generated by a thermoacoustic engine that will be placed in the E-6 fuel position within that reactor's core to act as a self-powered, acoustically-telemetered thermoacoustic sensor (TAC Sensor) capable of measuring coolant temperature (based on the radiated frequency) and neutron
flux (based on the radiated amplitude).


The vibroacoustical environment in two nuclear reactors

-Hrisko, Joshua; Garrett, Steven L.; Smith, Robert W.; Smith, James A.; Agarwal, Vivek

Laboratory experiments have suggested that thermoacoustic engines can be incorporated within nuclear fuel rods. Such engines would radiate sounds that could be used to measure and acoustically-telemeter information about the operation of the nuclear reactor (e.g., coolant temperature or fluxes of neutrons or other energetic particles) or the physical condition of the nuclear fuel itself (e.g., changes in porosity due to cracking, swelling, evolved gases, and temperature) that are encoded as the frequency and/or amplitude of the radiated sound [IEEE Measurement and Instrumentation 16(3), 18–25 (2013)]. For such acoustic information to be detectable, it is important to characterize the vibroacoustical environments within reactors. We will present measurements of the background noise spectra (with and without coolant pumps) and reverberation times within the 70,000 gallon pool that cools and shields the fuel in the 1 MW research reactor on Penn State’s campus using two hydrophones, a piezoelectric projector, and an accelerometer. Background vibrational measurement taken at the 250 MW Advanced Test Reactor, located at the Idaho National Laboratory, from accelerometers mounted outside the reactor’s pressure vessel and on plumbing, will also be presented to determine optimal thermoacoustic frequencies and predict signal-to-noise ratios under operating conditions. [Work supported by the U.S. Department of Energy.]