GTRI: Discover How You Can Begin Creating The Next with GTRI

GTRI is the innovation hub for the industry’s award-winning, nationally renowned researchers, engineers, and industry professionals who are dedicated to solving some of the nation’s most complex problems. As the highly-regarded, applied research and development division of the Georgia Institute of Technology (Georgia Tech) — one of the nation’s top-ranked research universities — GTRI is comprised of more than 2,400 scientists, engineers, support professionals, and students

A Fast Monte Carlo Simulation for the International Linear Collider Detector

The following paper contains details concerning the motivation for, implementation and performance of a Java-based fast Monte Carlo simulation for a detector designed to be used in the International Linear Collider. This simulation, presently included in the SLAC ILC group's org.lcsim package, reads in standard model or SUSY events in STDHEP file format, stochastically simulates the blurring in physics measurements caused by intrinsic detector error, and writes out an LCIO format file containing a set of final particles statistically similar to those that would have found by a full Monte Carlo simulation. In addition to the reconstructed particles themselves, descriptions of the calorimeter hit clusters and tracks that these particles would have produced are also included in the LCIO output. These output files can then be put through various analysis codes in order to characterize the effectiveness of a hypothetical detector at extracting relevant physical information about an event. Such a tool is extremely useful in preliminary detector research and development, as full simulations are extremely cumbersome and taxing on processor resources; a fast, efficient Monte Carlo can facilitate and even make possible detector physics studies that would be very impractical with the full simulation by sacrificing what is in many cases inappropriate attention to detail for valuable gains in time required for results

Next-Generation Wireless Sensing System for Transportation Infrastructure Safety

Researchers at the National Center for Transportation Systems Productivity and Management (NCTSPM) are developing an advanced wireless monitoring system that not only weighs vehicles, it also captures data that can help measure the structural integrity of bridges and their response to traffic

Lifetime studies of 130nm nMOS transistors intended for long-duration, cryogenic high-energy physics experiments

Future neutrino physics experiments intend to use unprecedented volumes of liquid argon to fill a time projection chamber in an underground facility. To increase performance, integrated readout electronics should work inside the cryostat. Due to the scale and cost associated with evacuating and filling the cryostat, the electronics will be unserviceable for the duration of the experiment. Therefore, the lifetimes of these circuits must be well in excess of 20 years. The principle mechanism for lifetime degradation of MOSFET devices and circuits operating at cryogenic temperatures is via hot carrier degradation. Choosing a process technology that is, as much as possible, immune to such degradation and developing design techniques to avoid exposure to such damage are the goals. This requires careful investigation and a basic understanding of the mechanisms that underlie hot carrier degradation and the secondary effects they cause in circuits. In this work, commercially available 130nm nMOS transistors operating at cryogenic temperatures are investigated. The results show that the difference in lifetime for room temperature operation and cryogenic operation for this process are not great and the lifetimes at both 300K and at 77K can be projected to more than 20 years at the nominal voltage (1.5V) for this technology

Impact on Construction Loads on Steel Diaphragm Bridge Design

PI#0016159Bridges are critical structures, serving an important function that is vital to the safe and economical conveyance of people and goods throughout Georgia. They are designed with specifications to carry loads including their self-weight and a design vehicle load, among others, when they are in service. Satisfying all design specifications is crucial to the structure\u2019s strength, stiffness, stability, and durability throughout its lifetime. In addition to the in-service dead and live load conditions, bridges are also designed to accommodate various loading conditions during the construction process. In some cases, these construction load and associated stability requirements are the governing load conditions for some of the bridges\u2019 components. Georgia Department of Transportation (GDOT) has recently allowed the substitution of steel diaphragms for concrete diaphragms in its bridges

Best Practices and Specifications for Massive Concrete Drilled Shafts

PI# 0016327American Concrete Institute (ACI) Guide to Mass Concrete defines massive (mass) concrete as \u201cany volume of concrete with dimensions large enough to require that measures be taken to cope with the generation of heat from hydration of the cement and attendant volume change to minimize cracking.\u201d Specifically, in the case of drilled shafts, Georgia Department of Transportation defines mass concrete to be any shaft with a greater than six-foot diameter. Once a drilled shaft has been classified as mass concrete, additional general GDOT specifications for mass concrete apply. These specifications detail temperature, material selection, thermal control, placing, and curing. Because the current specification lacks details specific to drilled shafts, a multitude of methods can be used, which can reduce the economic efficiency of the structure. Additionally, because the specifications are vague, the contractor and designer often avoid the specification by installing multiple smaller shafts in place of one single larger shaft. This practice of adding multiple smaller shafts often adds additional cost and the possibility for less effective designs. This project developed best practices and specifications for mass concrete drilled shafts to reduce the hesitance for use in practice and promote better overall construction practice. The objectives of the research are to: (1) understand the major deterrents from utilizing mass concrete for drilled shafts in practice, (2) determine and specify the appropriate thermal conditions, monitoring, and other requirements for drilled shafts specific to Georgia, (3) utilize ongoing GDOT research for temperature control to determine best practices for application on drilled shafts, and (4) make recommendations to GDOT for specifications to advance best practices

Development of GDOT Ultra-High Performance Concrete for Bridge Deck Closure Pours

PI#0015961The use of precast prestressed girders with composite precast deck panels along with the use of precast prestressed deck bulb-T girders provide for more economical bridges because of their ability to utilize accelerated bridge construction techniques. The use of concrete deck panels and deck bulb-T systems require the use of closure pours between the units. Ductal\u2122, a proprietary ultra-high performance concrete (UHPC), has been shown to provide an outstanding link between deck segments for closure pours as narrow as 6-in, but Ductal is expensive. This research develops a concrete based on locally available materials (GDOT-UHPC), which has a direct tensile strength greater than 750 psi and ductility and toughness under tensile loads such that the concrete can develop the tensile yield stress of #5 (\u215d-in. diameter) reinforcing bars within a 5-in. embedment length. Minimizing the width of the closure between deck and bulb-T units provides further economies by greatly simplifying formwork and eliminating shoring. Testing assured not only the short development length of reinforcement but also ultimate strength capacity of transverse and longitudinal closure pours. Further, best practices for formwork, closure design, UHPC mixing and placement, and quality assessment are considered

Safety and Illumination of Rural and Suburban Roundabouts (Phase II)

RP19-11This project focused on establishing the relationship between the presence/absence or levels of illumination and other geometric and traffic characteristics on nighttime safety at rural and suburban roundabouts. Eighty roundabouts from thirty-seven counties across Georgia were selected to provide a wide range of conditions in terms of illumination layout, illumination levels, number of legs, number of circulating lanes, daily entering volumes, approach speeds, etc. for field measurements of illumination levels. Urban roundabouts with significant pedestrian activity were excluded. Field data collection at each site included both direct measurements of illumination levels as well as a civil site survey to verify the geometric characteristics of the roundabout and were conducted by measurement teams from Georgia Institute of Technology and Georgia Southern University. The resulting data were processed, joined, and aggregated to the individual site level and used to establish statistical relationships between observed nighttime crash rates, severity, and crash types (e.g., single vs. multiple vehicles, impaired drivers, etc.) and underlying geometric factors and measured illuminance levels. The variation in observed crash rates were modeled against known parameters of the roundabouts to develop a predictive model as to how single vehicle nighttime crash rates were impacted by illumination and other factors. As expected, multiple vehicle crashes showed no statistically significant dependence on illumination levels as the vehicles themselves, through their head- and taillights, are important contributors to nighttime visibility at the roundabout. This was not the case for single vehicle crashes. Single vehicle crashes were shown to increase for 3-leg roundabouts for illumination values less than 5 lux. No such trend was observed in either 4 or 5-leg roundabouts and these sites showed no statistically significant variation in nighttime single vehicle crash rates at any level of illumination. An overarching conclusion of the study is that there was no observed evidence of illumination values exceeding 5 lux resulting in a statistically significant reduction in nighttime crash rates for rural and suburban roundabouts. These results suggest that for rural and suburban roundabouts with no significant pedestrian volumes, illumination values significantly lower than current standards may still prove effective as a safety treatment and that, in the absence of a need to protect pedestrians or cyclists at nighttime at a particular location, a reduction in lighting levels or the use of passive retroreflective safety treatments may be a cost-effective treatment

High efficiency cadmium and zinc telluride-based thin film solar cells

Polycrystalline Cd{sub 1-x}Zn{sub x}Te and Cd{sub 1-x}Mn{sub x}Te films with a band gap of 1.7 eV were successfully grown on glass/SnO{sub 2}/CdS substrates by molecular beam epitaxy (MBE) and metal-organic chemical vapor deposition (MOCVD), respectively. Polycrystalline Cd{sub 1-x}Zn{sub x}Te films grown by MBE resulted in uniform composition and sharp interfaces. However, polycrystalline Cd{sub 1-x}Mn{sub x}Te films grown by MOCVD showed nonuniform compositions and evidence of manganese accumulation at the Cd{sub 1-x}Mn{sub x}Te/CdS interface. We found that manganese interdiffuses and replaces cadmium in the CdS film. By improving the CdTe/CdS interface and, thus, reducing the collection function effects, the efficiency of the MOCVD CdTe cell can be improved to about 13.5%. MBE-grown CdTe cells also produced 8%--9% efficiencies. The standard CdTe process was not optimum for ternary films and resulted in a decrease in the band gap. Recent results indicate that CdCl{sub 2} + ZnCl{sub 2} chemical treatment may prevent the band-gap reduction, and that chromate etch (rather than bromine etch) may provide the solution to contact resistance in the ternary cells