The application of air-coupled ultrasonic systems and signal processing to the interrogation of concrete

This thesis describes the application of ultrasound to the interrogation of concrete for the retrieval of quantitative information. In particular the use of air-coupled ultrasound is applied for the first time with recent improvement in ultrasonic technology making this possible. Broadband capacitance transducers are used in tandem with pulse compression to deliver and receive ultrasonic signals with greatly improved SNR’s. Pulse compression involves the cross correlation of a chirp signal to record accurate ultrasonic time of flights. This metric is used to makes structural inferences about concrete and to compare contact and non-contact ultrasonic systems. This comparison reveals that concrete strength estimation from ultrasonic pulse velocity (UPV), alone is inaccurate. Other metrics such as aggregate content and humidity should also be considered. A study in to the effect of humidity on the UPV is presented and a correction factor obtained that normalises UPV around a humidity that could be considered normal to a temperate climate. Images of reinforcement bars embedded in concrete are presented using the pulse compression technique. Time-frequency (t-f) analysis is applied to ultrasonic chirp signals. Extensive simulation is carried out and a comparison between three different methods presented. This ensures accurate tracking of the ultrasonic chirp signals, which allows for frequency scattering to be examined. T-f analysis is then applied to real ultrasonic signals and it is shown how frequencies spectrums of received chirps can be de-noised using the Hough transform. Images of embedded defects are then presented. The Superheterodyne technique is then described and applied to concrete interrogation. Although not overly successful it is shown how energy distributions of received tone burst signals vary with time and the need for further work is discussed

The application of air-coupled ultrasonic systems and signal processing to the interrogation of concrete

This thesis describes the application of ultrasound to the interrogation of concrete for the retrieval of quantitative information. In particular the use of air-coupled ultrasound is applied for the first time with recent improvement in ultrasonic technology making this possible. Broadband capacitance transducers are used in tandem with pulse compression to deliver and receive ultrasonic signals with greatly improved SNR’s. Pulse compression involves the cross correlation of a chirp signal to record accurate ultrasonic time of flights. This metric is used to makes structural inferences about concrete and to compare contact and non-contact ultrasonic systems. This comparison reveals that concrete strength estimation from ultrasonic pulse velocity (UPV), alone is inaccurate. Other metrics such as aggregate content and humidity should also be considered. A study in to the effect of humidity on the UPV is presented and a correction factor obtained that normalises UPV around a humidity that could be considered normal to a temperate climate. Images of reinforcement bars embedded in concrete are presented using the pulse compression technique. Time-frequency (t-f) analysis is applied to ultrasonic chirp signals. Extensive simulation is carried out and a comparison between three different methods presented. This ensures accurate tracking of the ultrasonic chirp signals, which allows for frequency scattering to be examined. T-f analysis is then applied to real ultrasonic signals and it is shown how frequencies spectrums of received chirps can be de-noised using the Hough transform. Images of embedded defects are then presented. The Superheterodyne technique is then described and applied to concrete interrogation. Although not overly successful it is shown how energy distributions of received tone burst signals vary with time and the need for further work is discussed.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Improving the Image, Identity, and Reputation of Urban School Systems

This collective qualitative case study explores the ways American urban school districts engage in image management and reputation building activities to sustain their on-going organizational improvement efforts and maintain public support. The study catalogues the internal and external communication and media relations strategies utilized by three urban districts to manage their public image, identity, and reputation. District officers were found to be generally aware of their district's image in the community, their own role in projecting and improving that image, and the positive or negative identity of the employees in relation to the district's image. The concepts of organizational adaptive instability and mutability were found to be most important to urban district leaders as they all described their response to organizational challenges by sharing information with internal and external stakeholders and focusing on long-term improvement efforts. Accountability for effectiveness and efficiency was found to be the most dominant theme related to reputation. This study suggests that urban districts need to manage their public image through a well developed communications plan that focuses on projecting a district image of continuous improvement, clearly defines roles in district communication, and utilizes professional communications expertise

Identification and quantification of gaseous organic compounds emitted from biomass burning using two-dimensional gas chromatography/time-of-flight mass spectrometry

The current understanding of secondary organic aerosol (SOA) formation within biomass burning (BB) plumes is limited by the incomplete identification and quantification of the non-methane organic compounds (NMOCs) emitted from such fires. Gaseous organic compounds were collected on sorbent cartridges during laboratory burns as part of the fourth Fire Lab at Missoula Experiment (FLAME-4), with analysis by two-dimensional gas chromatography/time-of-flight mass spectrometry (GC×GC/TOFMS). The sensitivity and resolving power of GC×GC/TOFMS allowed the acquisition of the most extensive data set of BB NMOCs to date, with measure ments for 722 positively or tentatively identified compounds. Estimated emission factors (EFs) are presented for these compounds for burns of six different vegetative fuels, including conifer branches, grasses, agricultural residue, and peat. The number of compounds detected from individual burns ranged from 129 to 474, and included extensive isomer groups. For example, 38 monoterpene isomers were observed in the emissions from coniferous fuels; the isomeric ratios were found to be consistent with those reported in relevant essential oils, suggesting that the composition of such oils may be very useful when predicting fuel-dependent terpene emissions. Further, eleven sesquiterpenes were detected and tentatively identified, providing the first reported speciation of sesquiterpenes in gas-phase BB emissions. The calculated EFs for all measured compounds are compared and discussed in the context of potential SOA formation

Identification and quantification of gaseous organic compounds emitted from biomass burning using two-dimensional gas chromatography–time-of-flight mass spectrometry

The current understanding of secondary organic aerosol (SOA) formation within biomass burning (BB) plumes is limited by the incomplete identification and quantification of the non-methane organic compounds (NMOCs) emitted from such fires. Gaseous organic compounds were collected on sorbent cartridges during laboratory burns as part of the fourth Fire Lab at Missoula Experiment (FLAME-4) and analyzed by two-dimensional gas chromatography-time-of-flight mass spectrometry (GC x GC-ToFMS). The sensitivity and resolving power of GC x GC-ToFMS allowed the acquisition of the most extensive data set of BB NMOCs to date, with measurements from 708 positively or tentatively identified compounds. Estimated emission factors (EFs) are presented for these compounds for burns of six different vegetative fuels, including conifer branches, grasses, agricultural residue, and peat. The number of compounds meeting the peak selection criteria ranged from 129 to 474 among individual burns, and included extensive isomer groups. For example, 38 monoterpene isomers were observed in the emissions from coniferous fuels; the isomeric ratios were found to be consistent with those reported in relevant essential oils, suggested that the composition of such oils may be very useful when predicting fuel-dependent terpene emissions. Further, 11 sesquiterpenes were deteched and tentatively identified, providing the first reported speciation of sesquiterpenes in gas-phase BB emissions. The calculated EFs for all measured compounds are compared and discussed in the context of potential SOA formation

Resistance to Mild Cold Stress is Greater in Both Wild-Type and Long-Lived GHR-KO Female Mice.

Adapting to stress, including cold environmental temperature (eT), is crucial for the survival of mammals, especially small rodents. Long-lived mutant mice have enhanced stress resistance against oxidative and non-oxidative challenges. However, much less is known about the response of those long-lived mice to cold stress. Growth hormone receptor knockout (GHR-KO) mice are long-lived with reduced growth hormone signaling. We wanted to test whether GHR-KO mice have enhanced resistance to cold stress. To examine the response of GHR-KO mice to cold eT, GHR-KO mice were housed at mild cold eT (16 °C) immediately following weaning. Longevity results showed that female GHR-KO and wild-type (WT) mice retained similar lifespan, while both male GHR-KO and WT mice had shortened lifespan compared to the mice housed at 23 °C eT. Female GHR-KO and WT mice housed at 16 °C had upregulated fibroblast growth factor 21 (FGF21), enhanced energy metabolism, reduced plasma triglycerides, and increased mRNA expression of some xenobiotic enzymes compared to females housed at 23 °C and male GHR-KO and WT mice housed under the same condition. In contrast, male GHR-KO and WT mice housed at 16 °C showed deleterious effects in parameters which might be associated with their shortened longevity compared to male GHR-KO and WT mice housed at 23 °C. Together, this study suggests that in response to mild cold stress, sex plays a pivotal role in the regulation of longevity, and female GHR-KO and WT mice are more resistant to this challenge than the males

Three-dimensional structure of a cold-core Arctic eddy interacting with the Chukchi Slope Current

A rapid, high‐resolution shipboard survey, using a combination of lowered and expendable hydrographic measurements and vessel‐mounted acoustic Doppler current profiler data, provided a unique three‐dimensional view of an Arctic anti‐cyclonic cold‐core eddy. The eddy was situated 50 km seaward of the Chukchi Sea shelfbreak over the 1000 m isobath, embedded in the offshore side of the Chukchi Slope Current. The eddy core, centered near 150 m depth, consisted of newly ventilated Pacific winter water which was high in nitrate and dissolved oxygen. Its fluorescence signal was due to phaeopigments rather than chlorophyll, indicating that photosynthesis was no longer active, consistent with an eddy age on the order of months. Subtracting out the slope current signal demonstrated that the eddy velocity field was symmetrical with a peak azimuthal speed of order 10 cm s‐1. Its Rossby number was ~0.4, consistent with the fact that the measured cyclogeostrophic velocity was dominated by the geostrophic component. Different scenarios are discussed regarding how the eddy became embedded in the slope current and what the associated ramifications are with respect to eddy spin‐down and ventilation of the Canada Basin halocline

Chagas Disease in a Domestic Transmission Cycle in Southern Texas, USA

After three dogs died from acute Chagas cardiomyopathy at one location, an investigation was conducted of the home, garage, and grounds of the owner. A serologic study was conducted on stray dogs, and an ecologic niche model was developed to predict areas where the vector Trypanosoma gerstaeckeri might be expected