Similarity In Thickness Research Articles

Ship Hull Resistance Prediction from Model Tests with a Resistance Similitude Simulator

Depending on model sizes and test speeds, model Reynolds numbers are typically one to two orders of magnitude less than those occurring at full scale. The region of laminar flow is significantly larger on a model surface than at full scale. Turbulence stimulators (TSs) are extensively applied in model resistance tests to simulate ship boundary layer flow. Because of lack of theoretical guidance, the size, shape, and location of turbulent stimulators used in each test facility are typically selected based on experience gained in each laboratory, and parasitic drag induced by TSs is subtracted from measured model resistance in some test facilities and not subtracted in other facilities. If turbulence stimulation can be specified in such a way as to achieve momentum thickness similarity between the model and full scale, the form factor will be constant, so a simple scaling formula can be applied to predict ship resistance. Ship resistance can be predicted from measured model resistance with the application of this simple scaling formula. The article describes how for a given body geometry, ship Reynolds number and model Reynolds number, a unique TS (size, shape, and location) can be designed based on three equations derived in this article. This uniquely designed TS is termed the "resistance similitude simulator" in this article. The parasitic drag induced by the simulator is a part of the similarity solution and does not need to be subtracted from measured model resistance. 1. Introduction The ability to predict resistance plays an important role in the design of a ship or submarine. An accurate prediction of the drag of the vessel is required for the propulsor design and to determine the required power. The resistance of the vessel also strongly influences its lifetime operation costs. Although computational methods are now commonly used to estimate ship resistance, model tests are still heavily relied on, and scaling formulae are used to relate model data to full-scale performance.

Core surprise: What's inside a plate boundary?

Despite the fact that 90% of global seismicity occurs at plate boundary faults, our understanding of their internal structure is lacking. It’s not easy to see inside a plate boundary fault – typically composed of a high-strain fault core surrounded by a fractured damage zone – and when we can, it often requires expensive drilling projects that yield limited information on the internal structure of the whole fault. Understanding the internal structure of large faults is crucial, because their chemical and mechanical properties control how and where earthquakes rupture, nucleate and propagate. This in turn limits the size of the earthquake or the amount of radiated seismic energy, and consequently the severity of surface damage. The 1999 magnitude 7.7 earthquake along the Chelungpu plate boundary fault, for example – the second deadliest earthquake in Taiwan’s recorded history – saw significant variations in slip and ground motion at different locations along the fault which resulted in large local variations in casualties and damage. Subsequent field investigations related these variations to changes in the fault’s structure (i.e., clay width, geometry), which in turn controlled how the fault moved.

Optimization of nanofibrillation degree of chitin for induction of plant disease resistance: Elicitor activity and systemic resistance induced by chitin nanofiber in cabbage and strawberry

Chitin has not been extensively used in agriculture owing to its handling difficulties despite its utilizable functions such as induction of disease resistance and growth promotion in plants. Chitin nanofiber (CNF), which has an elicitor activity to induce plant disease resistance, can be handled like a water-soluble material, because of its high dispersibility. To determine the potential use of CNF in agriculture, the nanofibrillation degree of chitin for elicitor activity and its effect on the disease resistance against pathogens were examined in cabbage and strawberry plants. The similarity in thickness and length of CNF to that of polymeric chitin was sufficient to induce elicitor activity in both plants. Cabbage and strawberry plants, which were grown in a mixture of soil and CNF with optimized specification, challenged with fungal pathogens showed a reduction in the number of spots caused by Alternaria brassicicola and lesion size by Colletotrichum fructicola, respectively. Gene expression analysis revealed that the defense-related genes in cabbage plant grown in CNF-containing soil were significantly upregulated before and after pathogen infection. These results indicate that CNF can systemically induce disease resistance in cabbage and strawberry plants and is a promising natural-based material to control diseases in cultivated plants.

A Skeletal Similarity Metric for Quality Evaluation of Retinal Vessel Segmentation

The most commonly used evaluation metrics for quality assessment of retinal vessel segmentation are sensitivity, specificity, and accuracy, which are based on pixel-to-pixel matching. However, due to the inter-observer problem that vessels annotated by different observers vary in both thickness and location, pixel-to-pixel matching is too restrictive to fairly evaluate the results of vessel segmentation. In this paper, the proposed skeletal similarity metric is constructed by comparing the skeleton maps generated from the reference and the source vessel segmentation maps. To address the inter-observer problem, instead of using a pixel-to-pixel matching strategy, each skeleton segment in the reference skeleton map is adaptively assigned with a searching range whose radius is determined based on its vessel thickness. Pixels in the source skeleton map located within the searching range are then selected for similarity calculation. The skeletal similarity consists of a curve similarity, which measures the structural similarity between the reference and the source skeleton maps and a thickness similarity, which measures the thickness consistency between the reference and the source vessel segmentation maps. In contrast to other metrics that provide a global score for the overall performance, we modify the definitions of true positive, false negative, true negative, and false positive based on the skeletal similarity, based on which sensitivity, specificity, accuracy, and other objective measurements can be constructed. More importantly, the skeletal similarity metric has better potential to be used as a pixelwise loss function for training deep learning models for retinal vessel segmentation. Through comparison of a set of examples, we demonstrate that the redefined metrics based on the skeletal similarity are more effective for quality evaluation, especially with greater tolerance to the inter-observer problem.

A Two‐Tailed Phosphopeptide Crystallizes to Form a Lamellar Structure

AbstractThe crystal structure of a designed phospholipid‐inspired amphiphilic phosphopeptide at 0.8 Å resolution is presented. The phosphorylated β‐hairpin peptide crystallizes to form a lamellar structure that is stabilized by intra‐ and intermolecular hydrogen bonding, including an extended β‐sheet structure, as well as aromatic interactions. This first reported crystal structure of a two‐tailed peptidic bilayer reveals similarities in thickness to a typical phospholipid bilayer. However, water molecules interact with the phosphopeptide in the hydrophilic region of the lattice. Additionally, solid‐state NMR was used to demonstrate correlation between the crystal structure and supramolecular nanostructures. The phosphopeptide was shown to self‐assemble into semi‐elliptical nanosheets, and solid‐state NMR provides insight into the self‐assembly mechanisms. This work brings a new dimension to the structural study of biomimetic amphiphilic peptides with determination of molecular organization at the atomic level.

A Two-Tailed Phosphopeptide Crystallizes to Form a Lamellar Structure.

The crystal structure of a designed phospholipid‐inspired amphiphilic phosphopeptide at 0.8 Å resolution is presented. The phosphorylated β‐hairpin peptide crystallizes to form a lamellar structure that is stabilized by intra‐ and intermolecular hydrogen bonding, including an extended β‐sheet structure, as well as aromatic interactions. This first reported crystal structure of a two‐tailed peptidic bilayer reveals similarities in thickness to a typical phospholipid bilayer. However, water molecules interact with the phosphopeptide in the hydrophilic region of the lattice. Additionally, solid‐state NMR was used to demonstrate correlation between the crystal structure and supramolecular nanostructures. The phosphopeptide was shown to self‐assemble into semi‐elliptical nanosheets, and solid‐state NMR provides insight into the self‐assembly mechanisms. This work brings a new dimension to the structural study of biomimetic amphiphilic peptides with determination of molecular organization at the atomic level.

The primate connectome in context: Principles of connections of the cortical visual system

Which principles determine the organization of the intricate network formed by nerve fibers that link the primate cerebral cortex? We addressed this issue for the connections of primate visual cortices by systematically analyzing how the existence or absence of connections, their density as well as laminar patterns of projection origins and terminations are correlated with distance, similarity in cortical type as well as neuronal density or the thickness of cortical areas. Analyses were based on four extensive compilations of qualitative as well as quantitative data for connections of the primate visual cortical system in macaque monkeys (Felleman and Van Essen 1991; Barbas 1986; Barbas and Rempel-Clower 1997; Barone et al. 2000; Markov et al. 2014). Distance and thickness similarity were not consistently correlated with connection features, but similarity of cortical type, determined by qualitative features of laminar differentiation, or measured quantitatively as the areas' overall neuronal density, was a reliable predictor for the existence of connections between areas. Cortical type similarity was also consistently and closely correlated with characteristic laminar connection profiles: structurally dissimilar areas had origin and termination patterns that were biased to the upper or deep cortical layers, while similar areas showed more bilaminar origins and terminations. These results suggest that patterns of corticocortical connections of primate visual cortices are closely linked to the stratified architecture of the cerebral cortex. In particular, the regularity of laminar projection origins and terminations arises from the structural differences between cortical areas. The observed integration of projections with the intrinsic cortical architecture provides a structural basis for advanced theories of cortical organization and function.

The Mediterranean Ridge backstop and the Hellenic nappes

The core of the Mediterranean Ridge backstop consists of a pile of Hellenic nappes that migrated outward from the Aegean continent within the adjacent Mediterranean basins during late middle Miocene, about 15 Ma, and the present Mediterranean Ridge has developed since that time by accretion of a new wedge. The arguments we use are: (1) a similarity in thickness, seismic velocity and structure between the backstop and the Hellenic nappes in southern Peloponnesus; (2) the geometry of the westward limit of the backstop that is the one expected from the amount of relative displacement of the nappes on land; (3) an agreement between the estimated ages of the present accretionary wedge and the period of activity of two major faults connecting the backstop to the adjacent Aegean continent. The seaward limit of the backstop is situated about 170 km southwest of western Crete where the displacement of the nappes is maximal and it is close to the margin near the Ionian islands where their displacement is small. We assume that the Hellenic subduction zone migrated southwestward relative to Eurasia during middle Miocene and that the corresponding gravity collapse of the Aegean continent was maximum at this time because the westward extrusion of Anatolia had not yet started.

Limestone of the Daiichi Kashima Seamount and the fate of a subducting guyot: fact and speculation from the Kaiko “Nautile” dives

The Daiichi-Kashima Seamount subducting in the Japan Trench has two reef-capped flat tops with different depths, which are bounded by a nearly straight scarp. The western (inboard) crest is 5300–5450 m deep, and the eastern (outboard) one is 3880–4000 m deep. A variety of shallow-water reefoid limestones studied by the Kaiko “Nautile” dives not only confirms the similarity in thickness and lithologies, but also establishes an approximate biostratigraphic correlation between the two reefoid caps, based for the first time on the orbitolinid foraminifers ( Orbitolina (Mesorbitolina) parva from the western block and O. (M.) texana from the eastern block). This conclusion supports the interpretation that the present topography of the seamount has resulted from a subduction-induced faulting of a once single reef-capped guyot. A plausible scenario of the fate of a subducting Early Cretaceous guyot in the Western Pacific is outlined as exemplified by the Daiichi-Kashima Seamount.