• Climate of an ultra hot Jupiter: Spectroscopic phase curve of WASP-18b with HST/WFC3

      Arcangeli, Jacob; Désert, Jean-Michel; Parmentier, Vivien; Stevenson, Kevin B.; Bean, Jacob L.; Line, Michael R.; Kreidberg, Laura; Fortney, Jonathan J.; Showman, Adam P.; Univ Arizona, Dept Planetary Sci; et al. (EDP SCIENCES S A, 2019-05-28)
      We present the analysis of a full-orbit, spectroscopic phase curve of the ultra hot Jupiter (UHJ) WASP-18b, obtained with the Wide Field Camera 3 aboard the Hubble Space Telescope. We measured the normalised day-night contrast of the planet as >0.96 in luminosity: the disc-integrated dayside emission from the planet is at 964 +/- 25 ppm, corresponding to 2894 +/- 30 K, and we place an upper limit on the nightside emission of <32 ppm or 1430 K at the 3 sigma level. We also find that the peak of the phase curve exhibits a small, but significant offset in brightness of 4.5 +/- 0.5 degrees eastward. We compare the extracted phase curve and phase-resolved spectra to 3D global circulation models and find that broadly the data can be well reproduced by some of these models. We find from this comparison several constraints on the atmospheric properties of the planet. Firstly we find that we need efficient drag to explain the very inefficient day-night recirculation observed. We demonstrate that this drag could be due to Lorentz-force drag by a magnetic field as weak as 10 gauss. Secondly, we show that a high metallicity is not required to match the large day-night temperature contrast. In fact, the effect of metallicity on the phase curve is different from cooler gas-giant counterparts because of the high-temperature chemistry in the atmosphere of WASP-18b. Additionally, we compared the current UHJ spectroscopic phase curves, WASP-18b and WASP-103b, and show that these two planets provide a consistent picture with remarkable similarities in their measured and inferred properties. However, key differences in these properties, such as their brightness offsets and radius anomalies, suggest that UHJ could be used to separate between competing theories for the inflation of gas-giant planets.
    • Gallbladder Perforation Secondary to Enteric Fever: An Interesting Case of Acute Abdomen

      Malik, Mustafa N; Mahmood, Tayyab; Tameez Ud Din, Asim; Aslam, Shehroz; Imtiaz, Maria; Univ Arizona, Internal Med (CUREUS INC, 2019-04-22)
      Enteric fever is a common infectious disease, especially in countries with poor sanitation and in the tropics. It is caused mainly by Salmonella typhi and accounts for nearly 27 million cases worldwide and 200,000 deaths annually. Enteric fever involves the reticuloendothelial system such as bone marrow, spleen, and liver. As it mostly involves the Peyer's patches of the terminal ileum, enteric perforation occurs commonly. However, gallbladder perforation can also occur, though not very often. Ultrasound as well as computerized tomography (CT) abdomen and pelvis lack specificity for detecting gallbladder perforations in enteric fever. Diagnosis is usually confirmed intraoperatively when the gallbladder is visualized and perforation is seen. Gallbladder perforation is usually seen in acute cholecystitis when the gallbladder becomes necrotic and gangrenous. In acalculous cholecystitis, perforation is rare. Enteric fever is one of the rarest causes of acalculous cholecystitis, leading to perforation. Here, we present the case of a 20-year-old man who presented with fever for 10 days along with loose stools, vomiting, and acute abdomen. Labs showed leukopenia, positive Typhidot test but X-ray erect abdomen and ultrasound abdomen and pelvis were nonspecific. Only after resuscitation and exploration of the abdomen was it found that the gallbladder had multiple perforations. The patient was improved after eight days of postoperative intravenous antibiotics. This is a unique and rare presentation of such a common infectious disease.
    • Development of a Medical Student Cardiopulmonary Resuscitation Elective to Promote Education and Community Outreach

      Panchal, Ashish; Keim, Samuel; Ewy, Gordon; Kern, Karl; Hughes, Kate E; Beskind, Daniel; Univ Arizona, Emergency Med (CUREUS INC, 2019-04-20)
      Introduction: One of the barriers to improving cardiac arrest survival is the low rate of cardiopulmonary resuscitation (CPR) provision. Identifying this as a public health issue, many medical students often assist in training the community in CPR. However, these experiences are often short and are not associated with structured resuscitation education, limiting the student's and the community's learning. In this assessment, we identified a need and developed a curriculum, including defined goals and objectives, for an undergraduate medical education (UME) elective in CPR. Methods: At an academic university environment with a strong UME program, we developed a longitudinal UME elective in CPR. The curriculum is a four-year longitudinal experience, which satisfies two weeks of their fourth year of medical school. The curriculum includes structured training over the four-year period in the fundamentals of resuscitation science (through didactics, journal club, and hands-on skills training), in addition to structured community CPR teaching. The elective concludes with a final hands-on summative appraisal. Data concerning medical student program enrollment, CPR training events conducted, venues of events, and the number of individuals trained were collected over a five-year period. Results: The CPR elective was developed with clear goals and objectives based on identified needs. Over the five-year period, 186 medical students completed the CPR longitudinal elective, accounting for 8.4% of the total medical student population. Students completed curriculum requirements and satisfied both didactic and hands-on training with all students passing the final summative appraisal. Over the five-year period, students trained 8,694 people in bystander CPR. The summative evaluation had a 100% pass rate. Conclusion: Implementation of a longitudinal CPR elective improved resuscitation science education for medical students and fostered increased community CPR training. This describes one local effort to improve resuscitation science education and training for medical students. Further work will need to be done to evaluate the impact of UME resuscitation curricula on medical student career choice and resuscitation outcomes.
    • Initial data for general relativistic simulations of multiple electrically charged black holes with linear and angular momenta

      Bozzola, Gabriele; Paschalidis, Vasileios; Univ Arizona, Dept Phys; Univ Arizona, Dept Astron (AMER PHYSICAL SOC, 2019-05-17)
      A general relativistic, stationary, and axisymmetric black hole in a four-dimensional asymptotically flat spacetime is fully determined by its mass, angular momentum, and electric charge. The expectation that astrophysically relevant black holes do not posses charge has resulted in a limited number of investigations of moving and charged black holes in the dynamical, strong-field gravitational (and electromagnetic) regime, in which numerical studies are necessary. Apart from having a theoretical interest, the advent of multimessenger astronomy with gravitational waves offers new ways to think about charged black holes. In this work, we initiate an exploration of charged binary black holes by generating valid initial data for general relativistic simulations of black hole systems that have generic electric charge and linear and angular momenta. We develop our initial data formalism within the framework of the conformal transversetraceless (Bowen-York) technique using the puncture approach and apply the theory of isolated horizons to attribute physical parameters (mass, charge, and angular momentum) to each hole. We implemented our formalism in the case of a binary system by modifying the publicly available TWOPUNCTURES and QUASILOCALMEASURES codes. We demonstrate that our code can recover existing solutions and that it has excellent self-convergence properties for a generic configuration of two black holes.
    • Dark matter interpretation of the ANITA anomalous events

      Heurtier, Lucien; Mambrini, Yann; Pierre, Mathias; Univ Arizona, Dept Phys (AMER PHYSICAL SOC, 2019-05-17)
      The ANITA collaboration recently reported the detection of two anomalous upward-propagating extensive air showers exiting the Earth with relatively large emergence angles and energies in the range O(0.5-1) EeV. We interpret these two events as coming from the decay of a massive dark matter candidate (m(DM) greater than or similar to 10(9) GeV) decaying into a pair of right-handed neutrinos. While propagating through the Earth, these extremely boosted decay products convert eventually to tau-leptons which lose energy during their propagation and produce showers in the atmosphere detectable by ANITA at emergence angles larger than what Standard Model neutrinos could ever produce. We performed Monte Carlo simulations to estimate the propagation and energy loss effects and derived differential effective areas and number of events for the ANITA and the IceCube detectors. Interestingly, the expected number of events for IceCube is of the very same order of magnitude as the number of events observed by ANITA but at larger emergence angles, and energies less than or similar to 0.1 EeV. Such features match perfectly with the presence of the two upward-going events IceCube-140109 and IceCube-121205 that have been exhibited from a recent reanalysis of IceCube data samples.
    • Effective field theory of force-free electrodynamics

      Gralla, Samuel E.; Iqbal, Nabil; Univ Arizona, Dept Phys (AMER PHYSICAL SOC, 2019-05-14)
      Force-free electrodynamics (FFE) is a closed set of equations for the electromagnetic field of a magnetically dominated plasma. There are strong arguments for the existence of force-free plasmas near pulsars and active black holes, but FFE alone cannot account for the observational signatures, such as coherent radio emission and relativistic jets and winds. We reformulate FFE as the effective field theory of a cold string fluid and initiate a systematic study of corrections in a derivative expansion. At leading order the effective theory is equivalent to (generalized) FFE, with the strings comprised by magnetic field line world sheets. Higher-order corrections generically give rise to nonzero accelerating electric fields (E . B not equal 0). We discuss potential observable consequences and comment on an intriguing numerical coincidence.
    • The abductive approach to synthetic autonomous reasoning

      Baker, Victor; Univ Arizona, Dept Hydrol & Atmospher Sci (SPIE-INT SOC OPTICAL ENGINEERING, 2019-05-13)
      Abductive inference, as defined by Charles S. Peirce, involves (1) observation of a surprising fact, (2) formulating (guessing) a proposition which, if true, would explain this fact as a matter of course, (3) and provisional acceptance of the proposition as true, (4) leading to its being taken as a premise for subsequent deduction, the consequences of which will then be related to further observations via induction-surprises from which can then trigger new abductive inferences, and so forth. Peirce limited this process to human reasoning because he viewed thought as a semiosis (flow of signs) continuous between the human mind and the world, such that (1) the human subject is in thought, as opposed to thought being in the subject, and that (2) there is an intrinsic ability of human beings to "guess right" as a consequence of this continuity of mind and world. The challenge posed by this view of thinking is that, unlike a human subject, any vehicle for autonomous reasoning is a newly created object that is separate from the world. It cannot be what Martin Heidegger termed a "being-in-the-world" because of the artificial separation of its thought from the world viewed as semiosis.
    • Paths to non-deterministic autonomy: practical and qualitative considerations towards a Hawking-Musk-esque nightmare

      Fink, Wolfgang; Univ Arizona, Coll Engn, Visual & Autonomous Explorat Syst Res Lab (SPIE-INT SOC OPTICAL ENGINEERING, 2019-05-17)
      Current computational approaches, such as Artificial Intelligence, artificial neural networks, expert systems, fuzzy logic, fuzzy-cognitive maps, other rule-based approaches, etc., fundamentally do not lend themselves to building non-deterministic autonomous reasoning systems. Especially for AI, high hopes were raised more than 50 years ago, but AI has largely failed to deliver on its promises and still does. As such, the paper discusses different ingredients and approaches towards completely non-deterministic autonomous systems that are based on and exhibit critical capabilities, such as, but not limited to, self-organization, self-configuration, and self-adaptation. As such, any two initially identical autonomous systems will exhibit diverging and ultimately completely unpredictable developmental trajectories over time, once exposed to the same or similar environment, and even more so, once exposed to different environments.
    • FIREBall-2: advancing TRL while doing proof-of-concept astrophysics on a suborbital platform

      Hamden, Erika T.; Hoadley, Keri; Martin, Christopher; Schiminovich, David; Milliard, Bruno; Nikzad, Shouleh; Augustin, Ramona; Balard, Philippe; Blanchard, Patrick; Bray, Nicolas; et al. (SPIE-INT SOC OPTICAL ENGINEERING, 2019-05-13)
      Here we discuss advances in UV technology over the last decade, with an emphasis on photon counting, low noise, high efficiency detectors in sub-orbital programs. We focus on the use of innovative UV detectors in a NASA astrophysics balloon telescope, FIREBall-2, which successfully flew in the Fall of 2018. The FIREBall-2 telescope is designed to make observations of distant galaxies to understand more about how they evolve by looking for diffuse hydrogen in the galactic halo. The payload utilizes a 1.0-meter class telescope with an ultraviolet multi-object spectrograph and is a joint collaboration between Caltech, JPL, LAM, CNES, Columbia, the University of Arizona, and NASA. The improved detector technology that was tested on FIREBall-2 can be applied to any UV mission. We discuss the results of the flight and detector performance. We will also discuss the utility of sub-orbital platforms (both balloon payloads and rockets) for testing new technologies and proof-of-concept scientific ideas.
    • AI and the transcendence of true autonomy

      Tarbell, Mark; Univ Arizona, Coll Engn, Visual & Autonomous Explorat Syst Res Lab (SPIE-INT SOC OPTICAL ENGINEERING, 2019-05-13)
      For more than sixty years, the "Holy Grail" of computer science has been to build an intelligent, autonomous system, one that is self-aware and capable of rational thought. The founders of Artificial Intelligence recently gave a grim assessment of their field: AI and neuroscience are fixated on the details of implementation, without a fundamental architecture in sight.(1) No one has ever articulated the design for an autonomous system, so how can one be built? Modern AI/AGI efforts attempt to achieve this goal through elaborate rules-based computation and biology-inspired computing topologies, while actively ignoring the need for a fundamental architecture. This publication introduces a novel architecture and fundamental operating theory behind true autonomy, breaking with the standard principles of AI the very principles that have kept AI from achieving its own goals.
    • Social Identity and Group Emotion: Media Effects and Support for Military Intervention

      Bradshaw, Seth; Kenski, Kate; Univ Arizona (USC ANNENBERG PRESS, 2019)
      This study examines how news coverage of terrorist threats affects emotions that then shape support for antiterrorism policies, presidential approval, and attitudes toward Muslims. Using a national sample, news stories were experimentally manipulated to emphasize terrorist threats (high/low) and depictions of U.S. military strength (high/low). Results show that group-based anger-when people thought about themselves as Americans-mediated the relationships between threat coverage and antiterrorism policies, whereas group-based fear did not. On the other hand, group-based fear mediated the relationship between threat coverage and negative attitudes toward Muslims, whereas group-based anger did not. When people thought about themselves as individuals, neither anger nor fear mediated these relationships.
    • Contrasting Pre-Mei-Yu and Mei-Yu Extreme Precipitation in the Yangtze River Valley: Influencing Systems and Precipitation Mechanisms

      Wang, Xiaokang; Dong, Xiquan; Deng, Yi; Cui, Chunguang; Wan, Rong; Cui, Wenjun; Univ Arizona, Dept Hydrol & Atmospher Sci (AMER METEOROLOGICAL SOC, 2019-09-16)
      The mei-yu season over the Yangtze-Huai Rivers basin, typically occurring from mid-June to mid-July, is one of three heavy-rainfall periods over China and can contribute 50% of the annual precipitation. In this study, the first and second heaviest daily precipitation events at the Wuhan station have been selected to represent typical mei-yu and pre-mei-yu precipitation events where the differences in the atmospheric thermodynamic characteristics, precipitation nature, influencing systems, and mechanisms are investigated. During the mei-yu case, moist air mainly came from the South China Sea. Precipitation occurred south of the mei-yu front where abundant moisture and favorable thermodynamic conditions were present. The main influencing systems include a stable blocking pattern and strong and stable western Pacific subtropical high in the midtroposphere, and a small yet intense mesoscale cyclonic vortex in the low troposphere. Rainfall in Wuhan was continuous, caused by a well-organized convective line. A heavy rainband was located along the narrow band between the elongated upper-level jet (ULJ) and the low-level jet (LLJ) where the symmetric instability was found in the midtroposphere near Wuhan. Quite differently, for the pre-mei-yu precipitation case, moist air primarily came from the Beibu Gulf and the Bay of Bengal. Precipitation happened in the low-level convective instability region, where a short-wave trough in the midtroposphere and a mesoscale cyclonic vortex in the low-troposphere were found. Precipitation in Wuhan showed multiple peaks associated with independent meso-beta-scale convective systems. A rainstorm occurred at the exit of the LLJ and the right entrance of the ULJ, where convective instability exited in the mid- to low troposphere.
    • 2D broadband beamsteering with large-scale MEMS optical phased array

      Wang, Youmin; Zhou, Guangya; Zhang, Xiaosheng; Kwon, Kyungmok; Blanche, Pierre-A.; Triesault, Nicholas; Yu, Kyoung-sik; Wu, Ming C.; Univ Arizona, Coll Opt Sci (OPTICAL SOC AMER, 2019-04-29)
      Optical-phased arrays (OPAs) enable complex beamforming, random-access beam pointing, and simultaneous scan and tracking of multiple targets by controlling the phases of two-dimensional (2D) coherent emitters. So far, no OPA can achieve all desirable features including large 2D arrays, high optical efficiency, wideband operation in wavelengths, fast response time, and large steering angles at the same time. Here, we report on a large-scale 2D OPA with novel microelectro-mechanical-system (MEMS)-actuated phase shifters. Wavelength-independent phase shifts are realized by physically moving a grating element in the lateral direction. The OPA has 160 x 160 independent phase shifters across an aperture of 3.1 mm x 3.2 mm. It has a measured beam divergence of 0.042 degrees x 0.031 degrees, a field of view (FOV) of 6.6 degrees x 4.4 degrees, and a response time of 5.7 mu s. It is capable of providing about 25,600 rapidly steerable spots within its FOV. The grating phase shifters are optimized for the near-infrared telecom wavelength bands from 1200 to 1700 nm with 85% optical efficiency. (C) 2019 Optical Society of America under the terms of the OSA Open Access Publishing Agreement
    • How Partisan Online Environments Shape Communication with Political Outgroups

      Shmargad, Yotam; Klar, Samara; Univ Arizona (USC ANNENBERG PRESS, 2019)
      Social media provide opportunities to consume and share political news in echo chambers, but also to communicate with members of political outgroups. Exposure to political outgroups is often portrayed as the normatively desirable option, although empirically it has mixed effects. With an experimental study, we find that participants who regularly interact with political outgroups on social media share more politically moderate news articles when we assign them to an audience of mostly outgroup versus ingroup members. On the other hand, those who are accustomed to an online echo chamber subsequently polarize when faced with an outgroup audience. Our study holds implications for how a person's online social setting can shape downstream political interactions, and, more broadly, our findings highlight the importance of incorporating pretreatment measures to understand how online environments influence political behavior.
    • Seasonal Variability of Deuterium in the Upper Atmosphere of Mars

      Mayyasi, Majd; Clarke, J.; Bhattacharyya, D.; Chaufray, J. Y.; Benna, M.; Mahaffy, P.; Stone, S.; Yelle, R.; Thiemann, E.; Chaffin, M.; et al. (AMER GEOPHYSICAL UNION, 2019-03-20)
      Measurements by multiple Mars Atmosphere and Volatile Evolution mission instruments, obtained between November 2014 and November 2017, are analyzed to produce deuterium properties in the upper atmosphere of Mars. We show here, for the first time, the seasonal distribution and variability of D densities, temperatures, and estimated Jeans escape rates at the exobase (200 km). Within the data constraints, it is found that the variations in D properties are similar for the northern and southern hemispheres, and peak near southern summer solstice. Trends in the D Lyman-alpha brightness, temperature, density, and escape rate are increasing during the beginning of the dust storm season, peak near southern summer solstice, and decrease toward the end of the dust storm season. This suggests that seasonal drivers at Mars cause deuterium in the upper atmosphere to become globally enhanced when Mars is closest to the Sun and during the Martian dust season when water is provided to the upper atmosphere by subsurface, hydrological, and dust storm dynamics. Plain Language Summary Water escape at Mars can be examined by analyzing the properties of present day hydrogen and its isotope deuterium. The ratio of the abundance of these two atoms at the upper atmosphere of Mars can provide limitations to the preferential escape of one over the other and can provide information on the present rate of escape of water from the upper atmosphere. The results from this work can be paired with estimates of what early Mars and the Sun were like in order to provide estimates for the early water content on ancient Mars. In this paper, the most comprehensive set of observations of deuterium from Mars are analyzed, and the resulting properties of deuterium in the upper atmosphere of Mars are presented.
    • A Migration Model for the Polar Spiral Troughs of Mars

      Bramson, A. M.; Byrne, S.; Bapst, J.; Smith, I. B.; McClintock, T.; Univ Arizona, Dept Phys; Univ Arizona, Lunar & Planetary Lab (AMER GEOPHYSICAL UNION, 2019-04-23)
      Mars' iconic polar spiral troughs are 400-1,000-m-deep depressions in the north polarlayered deposits. As the north polarlayered deposits accumulate, troughs migrate approximately poleward, anti-parallel to the local wind patterns. Insolation is suspected to drive ice retreat through sublimation. Sublimation at the trough wall produces a growing sublimation lag that modulates further retreat; however, winds move material off the retreating slope faces, thinning the lag. Discontinuities in stratigraphy seen by radar highlight Trough Migration Paths (TMPs), which provide a record of the troughs' position, formation, and evolution to the present day. We investigate two adjacent troughs presently near 87 degrees N to evaluate the mass balance conditions at those sites. We constrain the contribution of insolation-induced sublimation to the migration in the observed TMPs. We present a phenomenological model that combines our simulations of the sublimation conditions at paleo-trough surfaces with accumulation rates to create synthetic TMPs that are tunable to the observations. Models using nominal values of lag diffusivity, albedo, and atmospheric water vapor abundance and in which the trough walls have been covered in a lag on the order of millimeters thick and formed 2.3Myr ago match the observed trough migration and align with expectations of trough ages. Thicker lags, and/or older troughs, would generate TMPs of constant slope, which does not match the observed paths. We demonstrate the viability of our new theoretical model for predicting conditions that lead to trough migration, allowing us to connect observable TMPs to Martian climate processes. Plain Language Summary Mars' iconic polar spiral troughs are depressions in Mars' northern polar ice cap. The positions of these troughs have migrated poleward over time. Exposure to the Sun's radiation is suspected to drive retreat of the ice through sublimation (ice transitioning directly into vapor without a liquid phase). When ice sublimates, it leaves behind any dust that was within the ice, protecting the ice from further sublimation. Winds, however, have thinned this dust cover, allowing the troughs to continue migrating. Ice layering in subsurface radar data map out the migration paths of the troughs, which provide a record of the troughs' position from their formation to the present day. We investigate ice stability conditions at two adjacent troughs and present a new theoretical model for trough migration. We model sublimation of the trough walls and combine our simulations with previously proposed ice accumulation rates for Mars' north pole to create synthetic trough migration paths. In comparing our models to the observations of trough migration, we find that the trough walls have been covered in millimeters-thick dust over 2.3Myr, consistent with previously hypothesized ages. Our physical modeling approach allows us to connect the observable trough migration paths to Martian climate processes.
    • Acoustic source localization in non-homogenous plates

      Yin, Shenxin; Cui, Zhiwen; Kundu, Tribikram; Univ Arizona, Dept Civil & Architectural Engn & Mech (SPIE-INT SOC OPTICAL ENGINEERING, 2019-04-01)
      In a nonhomogeneous specimen, if the acoustic source and receiving sensors are located in different media then the acoustic source localization becomes very difficult. In this paper, a recently developed source localization technique is extended to non-homogeneous plates by appropriately considering and modeling the refraction phenomenon. The modified technique is applied to two-layered structure. The proposed new technique gives a relatively simple way to localize the acoustic source without the need to solve a system of nonlinear equations, and thus it avoids the problem of multiplicity, converging to local minima instead of global minimum and giving wrong solution. The proposed technique works for both isotropic and anisotropic structures. The finite element simulation shows that this modified technique considering refraction at material interfaces can localize the acoustic source better than when this modification is not considered.
    • An assessment of in-field non-destructive testing methods for detection of internal defects in standing live trees

      Taskhiri, Mohammad Sadegh; Hafezi, Mohammad Hadi; Holloway, Damien; Turner, Paul; Univ Arizona, Dept Civil Engn & Engn Mech (SPIE-INT SOC OPTICAL ENGINEERING, 2019-04-01)
      Harvesting trees that contain internal defects such as knots and cracks are neither financially nor environmentally sustainable. In hardwood plantations, it is impossible to produce sawlogs from knotty or cracked timber. The challenge is to identify internal defects in a timely and cost-effective manner prior to harvesting. The aim of this paper is to investigate non-destructive testing (NDT) methods to rapidly detect the presence of internal defects in standing live trees in plantation plots. The study highlights that whilst several methods exist, few have been actively applied in-field harvesting operations to optimise log handling and to increase transportation efficiencies. Key constraints are portability of the NDT equipment for use in-field, speed versus accuracy of measurements undertaken and the usability of different evaluation approaches for decision-support. In this paper, the field assessment involved using two non-destructive techniques, ground penetrating radar (GPR) and ultrasonics that use electromagnetic and ultrasonic sound waves respectively to penetrate the internal structure of standing trees. These assessment techniques can assist forest growers to more accurately evaluate the quality of growing stems in the field. They also open the opportunity to investigate differences across a wide selection of growing conditions and forest types to generate data that may support the generation of a software algorithm for predictive imputation of likely internal defect rates within particular forests and under particular growing conditions. The plan being to integrate this predictive imputation software into existing geographical information systems owned by industry partners to enable accurate mapping of land areas where high ratios of defects are likely to be detected to further optimise infield harvesting.
    • Acoustic source localization in anisotropic plates without knowing their material properties: an experimental investigation

      Sen, Novonil; Gawroński, Mateusz; Packo, Pawel; Uhl, Tadeusz; Kundu, Tribikram; Univ Arizona, Dept Civil & Architectural Engn & Mech; Univ Arizona, Dept Aerosp & Mech Engn (SPIE-INT SOC OPTICAL ENGINEERING, 2019-04-01)
      An integral aspect of modern infrastructural engineering is to constantly monitor the health of a structure either actively or passively in order to ensure its safe performance throughout the design life. For passive structural health monitoring, it is important to estimate the location of an acoustic source that may be caused by events such as impact of a foreign object with the structure, failure of a structural element, formation of cracks, etc. Such an acoustic source generates acoustic waves that propagate through the medium. These waves can be captured by ultrasonic sensors mounted on the structure at some pre-selected locations and, subsequently, analyzed to predict the location of the acoustic source. Over the years, several researchers have proposed techniques for acoustic source localization in both isotropic and anisotropic structures. While acoustic source localization in isotropic structures is relatively simple, introduction of anisotropy adds a layer of difficulty to the problem due to the fact that waves do not propagate with the same speed in all directions. This study presents acoustic source localization techniques for anisotropic plates based on the analysis of the wave front shapes typically observed in anisotropic plates and presents experimental verification of the techniques. Three different geometric shapes are considered as the assumed wave front shapes: a rhombus, an ellipse and a parametric curve. A slightly modified version of the rhombus-based technique from the original approach is proposed. The experimental study is performed on two plates with different degrees of anisotropy.
    • Linear and non-linear analysis of composite plates using guided acoustic waves

      Alnuaimi, Hamad; Amjad, Umar; Russo, Pietro; Lopresto, Valentina; Kundu, Tribikram; Univ Arizona, Aerosp & Mech Engn Dept; Univ Arizona, Dept Civil & Architectural Engn & Mech (SPIE-INT SOC OPTICAL ENGINEERING, 2019-04-01)
      Guided acoustic wave techniques have been found to be very effective for damage detection. In this investigation Lead Zirconate Titanate (PZT) transducers are used to generate guided acoustic waves for structural health monitoring of a variety of composite specimens. Multiple sets of composite plate specimens are inspected for impact induced damage detection using PZT transducers. Composite samples are divided into two groups for comparative studies i.e. glass fiber composites and basalt fiber composites. They are damaged by impactors having different levels of impact energy. A chirp signal is excited and propagated through the specimens in a single sided excitation/detection setup to investigate the damages induced by impacts of varying intensity. Signal processing of the recorded signals for damage analysis involved both linear and nonlinear analyses. Linear ultrasonic analysis such as change in the time-of-flight of the propagating waves, Fast Fourier Transform and S-Transform of the recorded signals were tried out while the nonlinear ultrasonic analysis involved the Sideband Peak Count or the SPC technique.