Dynamics of Tidally-Driven Flows in Coral Reef Shelves: Observations from Autonomous and Fixed Instruments

The present work examines the hydrodynamics of the inner-shelf region, focusing on tidally-driven alongshore flows over coral reef shelves. This study draws on field data collected in O’ahu, Hawai’i using fixed and mobile assets to develop new modes of observational research.First, a theoretical model is developed to describe how autonomous underwater vehicle (AUV)-based water velocity measurements are influenced by a surface wave field. The model quantifies a quasi-Lagrangian, wave-induced velocity bias as a function of the local wave conditions, and the vehicle’s depth and velocity using a first-order correction to the linear wave solution. The theoretical bias is verified via field experiments over a range of wave and current conditions. The analysis considers velocity measurements made using a REMUS-100 AUV, but the findings apply to any small AUV (vehicle size ≪ wavelength) immersed in a wave field. The observed wave-induced biases [O(1–5) cm/s] can be significant, and can be comparable to steady flow velocities for inner-shelf regions.Second, a new approach to estimate lateral turbulent Reynolds stresses (u′v′) in wavy coastal environments using acoustic Doppler current profilers (ADCPs) is described. The performance of the proposed method is evaluated via comparisons with independent acoustic Doppler velocimeter (ADV)-based stress estimates at two sites, and the vertical structure of the tidally-averaged turbulent Reynolds stresses is examined for an unstratified, tidally-driven flow over a rough coral reef seabed in weak waves. Observations and analysis indicate that lateral stresses are sustained by the cross-shore gradient of the mean alongshore flow, and driven by bottom-generated turbulence. Scaling considerations suggest that cross-shore transport by lateral turbulent mixing could be relevant to coral reef shelves with steep cross-reef slopes and rough bottoms.Finally, a tidally-driven alongshore flow over a forereef shelf is examined using AUV-based spatial velocity measurements along with time series data of the alongshore pressure gradient. Ensemble phase averages of AUV-based velocities reveal characteristics akin to an oscillatory boundary layer, with the nearshore flow leading the offshore flow in phase and with a corresponding velocity magnitude attenuation near the shallower regions of the reef. Analysis of the depth-averaged alongshore momentum equation indicates that the cross-shore structure and evolution of the alongshore flow is well described by a balance between local acceleration, barotropic pressure gradient, and bottom drag. This primary balance allows the estimation of a spatially-averaged drag coefficient as a function of cross-shore distance over depths spanning from 24 to 6 m. Seabed roughness data suggest that larger scales, with wavelengths of O(10 m), are more relevant than smaller meter-scale roughness for drag

PRISM (Polarized Radiation Imaging and Spectroscopy Mission): an extended white paper

PRISM (Polarized Radiation Imaging and Spectroscopy Mission) was proposed to ESA in May 2013 as a large-class mission for investigating within the framework of the ESA Cosmic Vision program a set of important scientific questions that require high res- olution, high sensitivity, full-sky observations of the sky emission at wavelengths ranging from millimeter-wave to the far-infrared. PRISM’s main objective is to explore the distant universe, probing cosmic history from very early times until now as well as the structures, distribution of matter, and velocity flows throughout our Hubble volume. PRISM will survey the full sky in a large number of frequency bands in both intensity and polarization and will measure the absolute spectrum of sky emission more than three orders of magnitude bet- ter than COBE FIRAS. The data obtained will allow us to precisely measure the absolute sky brightness and polarization of all the components of the sky emission in the observed frequency range, separating the primordial and extragalactic components cleanly from the galactic and zodiacal light emissions. The aim of this Extended White Paper is to provide a more detailed overview of the highlights of the new science that will be made possible by PRISM, which include: (1) the ultimate galaxy cluster survey using the Sunyaev-Zeldovich (SZ) e↵ect, detecting approximately 106 clusters extending to large redshift, including a char- acterization of the gas temperature of the brightest ones (through the relativistic corrections to the classic SZ template) as well as a peculiar velocity survey using the kinetic SZ e↵ect that comprises our entire Hubble volume; (2) a detailed characterization of the properties and evolution of dusty galaxies, where the most of the star formation in the universe took place, the faintest population of which constitute the di↵use CIB (Cosmic Infrared Background); (3) a characterization of the B modes from primordial gravity waves generated during inflation and from gravitational lensing, as well as the ultimate search for primordial non-Gaussianity using CMB polarization, which is less contaminated by foregrounds on small scales than thetemperature anisotropies; (4) a search for distortions from a perfect blackbody spectrum, which include some nearly certain signals and others that are more speculative but more informative; and (5) a study of the role of the magnetic field in star formation and its inter- action with other components of the interstellar medium of our Galaxy. These are but a few of the highlights presented here along with a description of the proposed instrument

Shell strength and fishing damage to the smooth clam (Callista chione): simulating impacts caused by bivalve dredging

The smooth clam Callista chione is exploited by a fleet of dredgers along the southwestern coast of Portugal and suffers from a high incidence of shell damage. The force required to break C. chione shells in relation to fishing impacts and dredge damage is quantified. Fishing trials and shell-strength measurements (compression and compaction experiments) were performed to determine whether shell damage was attributable to the direct impact of the dredge teeth or to sediment compaction. A three-dimensional model of C. chione was subjected to simulated force by the finite element method. Analyses of damage areas and breakage patterns revealed two groups of samples, one containing the samples from compression experiments and another with the samples from dredging and compaction experiments, suggesting that most shell damage was attributable to compaction within the sediment. Information is provided to help improve the design of bivalve dredges, by increasing both length and angle of the dredge teeth, which would reduce the compaction force and distribute it differentially within the sediment, forcing upward movement of the bivalves.info:eu-repo/semantics/publishedVersio

Estimating Sample Size for Usability Testing

One strategy used to assure that an interface meets user requirements is to conduct usability testing. When conducting such testing one of the unknowns is sample size. Since extensive testing is costly, minimizing the number of participants can contribute greatly to successful resource management of a project. Even though a significant number of models have been proposed to estimate sample size in usability testing, there is still not consensus on the optimal size. Several studies claim that 3 to 5 users suffice to uncover 80% of problems in a software interface. However, many other studies challenge this assertion. This study analyzed data collected from the user testing of a web application to verify the rule of thumb, commonly known as the “magic number 5”. The outcomes of the analysis showed that the 5-user rule significantly underestimates the required sample size to achieve reasonable levels of problem detection

Psychological Capital Profiles and Their Relationship With Internal Learning in Teams of Undergraduate Students

This study aims to analyze the relationship between psychological capital profiles and internal learning in teams. The participants in this study were 480 undergraduate students. We performed a cluster analysis using the SPSS and yielded four distinct psychological capital profiles. The student profile with the highest scores in self-efficacy, optimism, hope, and resilience (Profile 2-Fully PsyCap) exhibited also the highest scores of internal learning in teams. On the other hand, the student profile with the lowest scores in self-efficacy, optimism, hope, and resilience (Profile 1- Empty PsyCap) presented the lowest scores of internal learning in teams. It is also noteworthy that there was no significant relationship between the profile with a positive combination between self-efficacy and hope (profile 4) and the profile that presents the optimism as the only positive psychological capability (profile 3), in the way they relate to internal learning in teams, which led us to reject the second hypothesis of the study. This study reinforces the role of psychological capital in academic settings and suggests that psychological capital profiles can affect internal learning in teams differentially

The influence of psychological capital on internal learning in teams: The mediating role of the perceived team structure

Whereas past research on internal learning has focused on evaluating how the observed learning rates affect collaborative interactions among the various actors, we extend this literature by analyzing internal learning in teams and the role of psychological capital in this process. This study aims to analyze the mediating role of the perceived team structure in the relationship between positive psychological capital and internal learning in teams. Therefore, a self-report questionnaire was applied to 480 college students to test this relationship, using structural equation modeling. The results confirmed the mediating role of the perceived team structure in the relationship between psychological capital and internal learning in teams. Our work underlines the role of psychological capital in academic settings. On the other hand, due to rapid changes in today’s society, university students who will be future employees need to cultivate psychological capital in order to achieve better learning outcomes

Enhancing Internal Learning in Teams: The Role of Network Centrality and Psychological Capital of Undergraduate Students

This study aims to analyze the mediating role of psychological capital (PsyCap) in the relationship between network centrality and internal learning in teams. A questionnaire was administered to 480 undergraduate students to test this relationship. The results confirmed the positive relationship between network centrality and internal learning in teams, and a mediating role of PsyCap in the relationship between student network centrality and internal learning in teams. This study suggests that it is important to promote centrality in advice networks among undergraduate students. In addition, this study might raise awareness among students, teachers, and public policymakers about the need to promote a socially responsible environment in higher education institutions.info:eu-repo/semantics/publishedVersio

Estimating Sample Size for Usability Testing

One strategy used to assure that an interface meets user requirements is to conduct usability testing. When conducting such testing one of the unknowns is sample size. Since extensive testing is costly, minimizing the number of participants can contribute greatly to successful resource management of a project. Even though a significant number of models have been proposed to estimate sample size in usability testing, there is still not consensus on the optimal size. Several studies claim that 3 to 5 users suffice to uncover 80% of problems in a software interface. However, many other studies challenge this assertion. This study analyzed data collected from the user testing of a web application to verify the rule of thumb, commonly known as the “magic number 5”. The outcomes of the analysis showed that the 5-user rule significantly underestimates the required sample size to achieve reasonable levels of problem detection

Thermal Latency adds to Lesion Depth after Application of High-Power Short-Duration Radiofrequency Energy: Results of a computer-modeling study

[EN] Introduction: The use of ultra-short RF pulses could achieve greater lesion depth immediately after the application of the pulse due to thermal latency. Methods and results: A computer model of irrigated-catheter RF ablation was built to study the impact of thermal latency on the lesion depth. The results showed that the shorter the RF pulse duration (keeping energy constant), the greater the lesion depth during the cooling phase. For instance, after a 10-second pulse, lesion depth grew from 2.05 mm at the end of the pulse to 2.39 mm (17%), while after an ultra-short RF pulse of only 1 second the extra growth was 37% (from 2.22 to 3.05 mm). Importantly, short applications resulted in deeper lesions than long applications (3.05 mm vs. 2.39 mm, for 1-and 10-second pulse, respectively). While shortening the pulse duration produced deeper lesions, the associated increase in applied voltage caused overheating in the tissue: temperatures around 100 degrees C were reached at a depth of 1 mm in the case of 1-and 5-second pulses. However, since the lesion depth increased during the cooling period, lower values of applied voltage could be applied in short durations in order to obtain lesion depths similar to those in longer durations while avoiding overheating. Conclusion: The thermal latency phenomenon seems to be the cause of significantly greater lesion depth after short-duration high-power RF pulses. Balancing the applied total energy when the voltage and duration are changed is not the optimal strategy since short pulses can also cause overheating.This work was supported by the Spanish "Plan Estatal de Investigacion, Desarrollo e Innovacion Orientada a los Retos de la Sociedad" under Grant TEC2014-52383-C3 (TEC2014-52383-C3-1-R) and by the National Scientific and Technical Research Council - Argentina "Proyecto de Investigacion Orientado" (PIOCONICET-UNAJ 0001).Irastorza, RM.; D Avila, A.; Berjano, E. (2018). Thermal Latency adds to Lesion Depth after Application of High-Power Short-Duration Radiofrequency Energy: Results of a computer-modeling study. Journal of Cardiovascular Electrophysiology. 29(2):322-327. doi:10.1111/jce.13363S32232729

Predictive Modelling and Multiscale NDE Methods in Failure Assessment of Thermal Barrier Coatings

The use of thermal barrier coatings (TBCs) allows advanced gas turbine engines to operate at a temperature higher than the incipient melt temperature of the superalloy from which the engine components are made, thereby enhancing the performance and efficiency of the engine. However, delamination cracks initiated in these coatings during service limit their applications. This investigation analysed the effects of thermal cycling on the structure, thermo-mechanical properties and lifetime of Ni-based superalloy samples coated with a TBC. The results indicate that the coating system exhibits substantial changes during its life, with the thermo-mechanical properties of the TBC layers being highly sensitive to temperature and cyclic oxidation. The current study also presents a new finite element model that describes the evolution of the stress state within a thermal barrier coating subjected to thermal cycling loading. This computational framework was used to identify the optimal design parameters through a newly proposed sensitivity index, so that TBCs can be engineered with improved lifetime. Photoluminescence piezo-spectroscopy has been used to identify non-destructively the onset of microcracks and monitor their propagation through a proposed local damage factor that combines spectral shape evolution with peak shift. The computational spectral simulation was based on coupling the finite element model for the calculation of stress with an external routine for the prediction of luminescence spectra. A new non-destructive multi-sensor diagnostics procedure based on the combination of imaging- and laser-based techniques was presented. It has been demonstrated that it can accurately determine the remaining life of high-temperature coatings, and therefore it represents an important development direction for improving the reliability of TBCs. It is concluded that the results obtained in this research were quite satisfactory, which suggests that further model development and field testing of the non-destructive methodology are warranted for predictive failure assessment of thermal barrier coating systems. Keywords Thermal barrier coating Material properties Finite element modeling Photoluminescence piezo-spectroscopy Non-destructive evaluatio