Greatest Curvature Research Articles

On critical levels of ecological status for macrozoobenthic communities in Peter the Great Bay of the Japan Sea: model studies

Representative sets of biotic and abiotic parameters were taken from maps of their distribution at the sea bottom, using interpolation. Good correspondence between real and modeled data was noted that allowed to engage the latter for correct estimation of the mean explained variance (MEV) by regression analysis. The magnitude and structure of MEV variability depended on external influence that proves possibility of its application as a measure for total effect of abiotic factors. Among many variants of the ecological stress index (PES), the more convenient for modeling was that one with the maximum correlation between distribution density or biomass of certain taxa and the total density or biomass of macrozoobenthos at stations (in samples). This approach provides better biological plausibility, as well, so as the benthic dwellers, like other animals, are very diverse in size and interspecific relations, that’s why the distribution density of a species correlates well with either total density or total biomass, and the same for biomass of a species. Results of in situ studies of PES dependence on MEV were confirmed by modeling with virtual MEV values. The difference between real and modeled PES values was statistically insignificant, but the MEV ranged wider in the models with virtual values and the dependence curve had weaker inflection when reached a plateau. The final dependence is S-shaped (r2 = 0.939), with the greatest curvature at 85.4 % of MEV (PES of 15 %), and the point of minimum or beginning of growth (beginning of the model curve plateauing) at 94.0 % of MEV (PES of 36 %). These levels are critical for macrozoobenthos communities. The PES level for the 2nd critical level was previously estimated as 30 %, but this value was corrected to 36 % by calculation with biologically more reasonable method.

Heat release surrogates for NH3/H2/N2–air premixed flames

The present study investigates the performance of NH, NH2, O-atom, and H-atom as heat release rate (HRR) surrogates for NH3/H2/N2–air premixed flame through simulations. The simulations are conducted across different pressures, reactant inlet temperatures, fuel blend compositions, and equivalence ratios. Cantera is used to simulate one-dimensional (1D) freely propagating flames to investigate the spatial correlations of the species with the HRR. PeleLMeX, a low-Mach direct numerical simulation (DNS) code with Adaptive Mesh Refinement (AMR), is used to simulate two-dimensional (2D) flame-vortex interactions to investigate the temporal correlations including stretch effects. Three different mechanisms (Jiang et al. 2020; Glarborg et al. 2018; Okafor et al. 2018) were considered in the 1D flame simulations, whereas only the Jiang mechanism was considered in the flame-vortex simulations. The HRR surrogate performance for the 2D flames is evaluated at two different locations: (1) the centerline and (2) the flame cusp. The cusp is defined as the region in the flame front with the greatest curvature and the centerline encounters the highest tangential strain rate. The 1D flame results suggest that, although there is not uniformly good spatial correlation for HRR across all flame conditions, NH is the best overall as a HRR surrogate for laminar flames. The 2D flame results, however, suggest that O-atom and H-atom have satisfactory temporal correlations at different conditions—the former for rich flames, the latter for high-pressure flames. These simulations provide guidance to experimental measurements of surrogate HRR markers in unsteady multi-dimensional flames using laser diagnostics to detect species such as NH, O-atom, and H-atom.

A divide-and-conquer algorithm for curve fitting

Curve fitting is still an open problem which draws attention from many applications, such as computer-aided design, computer-aided manufacturing and reverse engineering. Splines such as Bézier, B-Spline and NURBS curves are usually employed in engineering applications and are intensively used for fitting purposes. The optimization of their shapes and localization parameters, however, is a very complex task. The literature presents many methods which empirically set some important parameters, such as the number of control points. As guessing such a value is difficult, this paper presents a new method to choose it through a multi-curve fitting method, based on linear least square optimizations, using a divide-and-conquer algorithm and an error tolerance threshold. Four prime procedures compose the method: the conquer step fits curves over subset point clouds; the combine step glues curve segments together with some selective continuity; the divide step splits subsets which are not properly fitted yet; and the merge step blends curve segments together. Several curve setups were tested in well-known benchmarks, using four-division strategies: bisection, error balance, point with the greatest curvature and point with the smallest curvature. The developed method allows for fast computation even for larger point clouds, and it was able to properly reconstruct each tested shape, even with the addition of synthetic noise. We also demonstrate that it can be significantly faster than a single-curve fitting using the same number of control points. • A multiple curve fitting approach using iterative multi-control-point insertion. • A divide-and-conquer algorithm allows for fast curve fitting. • Point cloud division strategies have their own pros and cons in curve fitting. • Adequate error tolerance balances quality and simplicity in curve fitting.

Data Analysis and Visualization in the Tasks of the Project Solutions Multicriteria Optimization

The accumulation of data on project management processes and standard solutions has made relevant research related to the use of knowledge engineering methods for a multi-criteria search for options that set optimal settings for project environment parameters. Purpose: Development of a method for searching and visualizing groups of projects that can be evaluated based on the concept of dominance and interpreted in terms of project variables and performance indicators. Methods: The enrichment of the sample while maintaining an implicit link between the project variables and performance indicators is carried out using a predictive neural network model. A set of genetic algorithms is used to detect the Pareto front in the multidimensional criterion space. The ontology of projects is determined after clustering options in the solution space and transforming the cluster structure into the criterion space. Automation of the search in the multidimensional space of the Pareto front greatest curvature zone, which determines the equilibrium design solutions, their visualization and interpretation are carried out using a tree map. Results: A tree map is constructed at any dimension of the criterion space and has a structure that has a topological correspondence with projections of shared cluster images from a multidimensional space onto a plane. For various types of transformations and correlations between performance indicators and project variables, it is shown that the areas of the Pareto front greatest curvature are determined either by the contents of the whole cluster or by part of the variants representing the "best" cluster. If an undivided rectangle of a cluster is adjacent to the upper right corner of a tree map, then its representatives in the criterion space are well separated from the rest of the clusters and, when maximizing performance indicators, are closest to the ideal point. All representatives of such a cluster are effective solutions. If the winning cluster contains dominant options inside the decision tree, then the ”best" cluster is represented by the remaining options that set the optimal settings for the project variables. Practical relevance: The proposed methods of searching and visualizing groups of projects can be used when choosing the conditions of resource and organizational and economic modeling of the project environment, ensuring the optimization of risks, cost, functional, and time criteria.

Multi-patient study for coronary vulnerable plaque model comparisons: 2D/3D and fluid\u2013structure interaction simulations

Several image-based computational models have been used to perform mechanical analysis for atherosclerotic plaque progression and vulnerability investigations. However, differences of computational predictions from those models have not been quantified at multi-patient level. In vivo intravascular ultrasound (IVUS) coronary plaque data were acquired from seven patients. Seven 2D/3D models with/without circumferential shrink, cyclic bending and fluid–structure interactions (FSI) were constructed for the seven patients to perform model comparisons and quantify impact of 2D simplification, circumferential shrink, FSI and cyclic bending plaque wall stress/strain (PWS/PWSn) and flow shear stress (FSS) calculations. PWS/PWSn and FSS averages from seven patients (388 slices for 2D and 3D thin-layer models) were used for comparison. Compared to 2D models with shrink process, 2D models without shrink process overestimated PWS by 17.26%. PWS change at location with greatest curvature change from 3D FSI models with/without cyclic bending varied from 15.07% to 49.52% for the seven patients (average = 30.13%). Mean Max-FSS, Min-FSS and Ave-FSS from the flow-only models under maximum pressure condition were 4.02%, 11.29% and 5.45% higher than those from full FSI models with cycle bending, respectively. Mean PWS and PWSn differences between FSI and structure-only models were only 4.38% and 1.78%. Model differences had noticeable patient variations. FSI and flow-only model differences were greater for minimum FSS predictions, notable since low FSS is known to be related to plaque progression. Structure-only models could provide PWS/PWSn calculations as good approximations to FSI models for simplicity and time savings in calculation.

Improving the Methodology for Calculating the Bearing Capacity of Eccentrically Compressed Reinforced Concrete Elements Based on the Use of the Refined Curvilinear Deformation Diagrams of Concrete and Reinforcement

The article proposes a new approach to improving the methodology for calculating the bearing capacity of the eccentrically compressed reinforced concrete elements for cases of their loading with large eccentricities. The basis of this technique is considered as a modified version of the deformation model for the reinforced concrete resistance force. The main feature of this model is the energy approach to transforming the reference diagrams of compression and concrete tension into the diagrams of non-uniform deformation, corresponding to the stress-strain state of the compressed and stretched zones of concrete in the cross section of the eccentrically compressed reinforced concrete structures. This way there is no falling branch in the concrete diagrams obtained by this method. A calculation diagram of the steel reinforcement deformation with a physical yield point was taken as a partial function, consisting of one linear and two non-linear equations. The proposed method also shows the possibility of taking into account the greatest curvature of an eccentrically compressed reinforced concrete element in the plane of its loading. The article presents all the necessary dependencies allowing the theoretical value of the carrying capacity of an eccentrically compressed reinforced concrete element determination. The results of the numerical studies performed using the design software developed by the authors for the personal computer are given.

A New Method for Characterizing Mechanical Properties of Meat Product under Stress-Relaxation Based on Gaussian Curve-Fitting

Texture profile analysis has been shown as an effective method for evaluating the quality of meats under different modes. The most common texture profile analysis mode, the two-bite test, is widely used to simulate chewing; however, the consistency is not always satisfactory. In the present study, another test mode (stress-relaxation test) was applied and the data were fitted to Gaussian function using 12 coefficients. A series of indices (X1: the X-value of the point had greatest curvature of the fitted curve; X2: the x-value of the point that the tangential slope of the fitted curve was –0.01; X2-X1: X2 minus X1; Y2: the y-value of the point that the tangential slope of the fitted curve was –0.01) was chosen from the fitted curve to estimate the texture in the stress-relaxation test, and the coefficient of variation of the indices of the two methods was also evaluated. In general, the new method showed improved consistency that may be suitable for evaluation of meat texture.

Structural salience and the nonaccidentality of a gestalt.

We perceive structure through a process of perceptual organization. Here we report a new perceptual organization phenomenon-the facilitation of visual grouping by global curvature. Observers viewed patterns that they perceived as organized into collections of curves. The patterns were perceptually ambiguous such that the perceived orientation of the patterns varied from trial to trial. When patterns were sufficiently dense and proximity was equated for the predominant perceptual alternatives, observers tended to perceive the organization with the greatest curvature. This effect is tantamount to visual grouping by maximal curvature and thus demonstrates an unprecedented effect of global structure on perceptual organization. We account for this result with a model that predicts the perceived organization of a pattern as function of its nonaccidentality, which we define as the probability that it could have occurred by chance. Our findings demonstrate a novel relationship between the geometry of a pattern and the visual salience of global structure.

Curvature and tortuosity of the superficial femoral artery: a possible risk factor for peripheral arterial disease

Atherosclerosis in the superficial femoral artery (SFA) resulting in peripheral arterial disease is more common in men than women and shows a predilection for the region of the adductor canal. Blood flow patterns are related to development of atherosclerosis, and we investigated if curvature and tortuosity of the femoral artery differed between young men and women and if differences resulted in adverse flow patterns. Magnetic resonance imaging (MRI) and computational fluid dynamics (CFD) were combined in 18 young adult volunteers (9 men) to assess the relationship of flow features to likely sites of future atherosclerosis formation. Subjects underwent MRI of the right SFA, three-dimensional vascular geometry was reconstructed, and measures of tortuosity and curvature were calculated. Tortuosity and curvature were significantly greater for men than women, and this was related to increased body surface area, body mass index, or weight in men. In both sexes, "tortuosity" increased from the midthigh to the popliteal fossa. The greatest curvature was found within the distal quarter of the SFA. CFD modeling was undertaken on MRI-based reconstructions of the SFA. Wall shear stresses (WSS) were extracted from the computations. WSS showed greater spatial variation in the men than in the women, and the men exhibited lower mean WSS. These data indicate that sex differences related to body size and anatomical course of the femoral artery may contribute to the enhanced risk of focal atherosclerosis in the adductor canal.

The Influence of Canal Curvature on the Mechanical Efficacy of Root Canal Irrigation In Vitro Using Real-Time Imaging of Bioluminescent Bacteria

There are no quantitative data on the mechanical efficacy of irrigation in the removal of bacteria from curved canals. This study quantitatively analyzed the effects of root canal curvature and preparation size on the mechanical efficacy of irrigation using 33 mandibular single-rooted bicuspids allocated to groups according to root canal curvatures, group 1 (straight) 4 to 8 degrees, group 2 (intermediate curvature) 15 to 19 degrees, and group 3 (greatest curvature) 24 to 28 degrees. Teeth were sequentially instrumented to sizes 27/.04, 36/.04, and 46/.04 using a crown-down technique. Suspensions of the bioluminescent reporter strain Pseudomonas fluorescens 5RL (1.5 × 10 6 cells) were inoculated into canals of sterilized teeth after each sequential instrumentation. Canals were irrigated with 6 ml of irrigant delivered 1 mm from working length using a 30-gauge needle. Remaining bacteria were quantified using real-time bioluminescent imaging. Irrigation was significantly less effective in 24 to 28 degrees curvature canals prepared to size 27/.04 compared to 46/.04 (p < 0.007, repeated-measures ANOVA).

Reliability and Accuracy of Techniques for Surface Area Measurements of Wounds and Scars

The applicability of simple methods to measure the size of pathological skin lesions for management and research has been poorly studied to date. The interobserver reliability and accuracy (validity) was established for planimetry by photography and planimetry by tracing on a transparent sheet in this study. Drawings of 25, 50, and 75 cm(2) were created on 3 locations with increasing curvature (back, thigh, and forearm) in 20 healthy volunteers. Three investigators evaluated the drawings by both planimetry techniques. Both techniques showed a good reliability (r >or= 0.82, intraclass correlation) for 25 cm(2) areas. Planimetry by photography was more reliable than planimetry by tracings for the 50 -and 75-cm(2) areas and was more accurate than planimetry by tracing for all areas except for the area with the greatest curvature, the forearm. The study permits the conclusion that planimetry by photography is more suitable for surface area measurements than planimetry by tracing except for extremely curved body parts, where it is likely that effects of distortion supervene.

Manipulating the "straightness" and "curvature" of patterns of interaural cross correlation affects listeners' sensitivity to changes in interaural delay.

The purpose of this study was to test the hypothesis that stimuli characterized by "straight" trajectories of their patterns of cross correlation foster greater sensitivity to changes in interaural temporal disparities (ITDs) than do stimuli characterized by more "curved" trajectories of their patterns of cross correlation. To do so, sensitivity to changes in ITD was measured, as a function of duration, using a set of "reference" stimuli that yielded differing relative amounts of straightness within their patterns of cross correlation while keeping the dominant trajectory at or near midline. The relative amounts of straightness were manipulated by employing specific combinations of bandwidth, ITD, and interaural phase disparity (IPD) of Gaussian noises centered at 500 Hz. The results were consistent with expectations in that the patterning of the threshold ITDs revealed increasingly poorer sensitivity as greater and greater curvature was imposed on the dominant, "midline," trajectory. The variations in threshold ITD across the stimulus conditions can be accounted for quite well quantitatively by assuming either that the listeners based their judgments on changes in the position of the most central peak of the cross-correlation function or that they based their judgments on changes in the centroid of a second-level cross-correlation function. In a second experiment, binaural detection was measured using a subset of the reference stimuli as maskers. As expected, sensitivity was poorest with the maskers characterized by the greatest curvature, which were also those having the lowest interaural correlation.

Regional and Temporal Nonuniformity of Shape and Wall Movement in the Normal Left Ventricle

Asymmetry of left ventricular (LV) shape and asynchrony of regional LV movement have been described in the normal human heart, but never correlated to each other. In 16 normal subjects, right anterior oblique ventriculography was used to obtain volumes, regional wall motion (centerline method) and curvature (windowed Fourier series approximation of contours) over the entire cardiac cycle. The apex had the greatest curvature, while the posterior wall had a negative end-diastolic curvature that decreased further at early-systole and became positive at end-systole. The anterior region had the greatest and the anteroapical region the least fractional shortening. Asynchrony was evident as a delayed contraction of the infero- and anteroapical regions, and as a greater rate of late-systolic shortening of the anterior wall than that of the apex. Shape changes and shortening were dyssynchronous in the apical regions where the greatest changes occurred at early diastole. Temporal and regional nonuniformity of shape and movement exists in normal subjects. Dyssynchrony between shape and regional contraction of the apical regions deserves further studies.

Shape Dependence of Emission from Microdisk Lasers

The emission characteristics of GaAs Whispering Gallery microdisk lasers have been investigated for different disk shapes and sizes. Elliptical structures showed a substantial increase in the emission intensity from the sides of the disk with the greatest curvature, while stadium-shaped disks did not support any laser emission. Deformation of circular disks towards squares reduces the number of resonant modes for lasing but does not eliminate lasing totally; thus operation with non-Whispering-Gallery modes is possible, and this implies that such operation may be relevant even for circularly symmetrical lasers.

Quantitative evaluation of left ventricular shape in anterior aneurysm.

The purpose of the study was to analyze left ventricular (LV) shape in post-infarction anterior aneurysm by utilizing quantitative analysis of wall curvature. Forty-one patients (39 men, 2 women; mean age 56 years) subjected to surgical intervention for LV aneurysm complicating an anterior myocardial infarct were retrospectively evaluated. In all patients the presence of resectable aneurysmal tissue had been confirmed by direct surgical examination. Patients with inferior myocardial infarction and patients who had undergone percutaneous transluminal coronary angioplasty (PTCA) or bypass surgery were excluded. Pre-intervention ventriculograms (RAO projection) were analyzed. LV wall excluded. Pre-intervention ventriculograms (RAO projection) were analyzed. LV wall motion was studied by applying the centerline method. Regional curvature of end-diastolic and end-systolic outlines was calculated at 90 equidistant points from aortic corner (point 1) to mitral plane (point 90). Patients with LV anterior aneurysm show a typical pattern of alterations in wall curvature, which is characterized by a shifting of the angiographic apex (the point with the greatest curvature) towards the mitral plane, and by a sharp shift of curvature values at the antero-basal and infero-apical regions, marking the borders of the sac. These hinge points closely correspond to the external limits of wall motion abnormalities. Significant correlations were found between degree of regional curvature alterations and severity of global LV dysfunction, as indicated by decrease of ejection fraction and increase of end-systolic volume. In conclusion, quantitative evaluation of LV shape by means of wall curvature analysis allows recognition of the characteristic morphologic changes of the aneurysm, i.e., wall expansion and deformation.(ABSTRACT TRUNCATED AT 250 WORDS)

Myofilament overlap in swimming carp. II. Sarcomere length changes during swimming

Pages C289–C296: L. C. Rome and A. A. Sosnicki. “Myofilament overlap in swimming carp. II. Sarcomere length changes during swimming.” Page C295, left-hand column, paragraph 4, sentences beginning on line 3 should read: Dimery (3) calculated that in galloping rabbits, fibers undergo excursion of 1 μm (from 1.7 to 2.7 pm), in which there would be no less than 80% maximal tension generated. Cutts (2) using similar techniques concluded that bird muscles operate over ap0.5 μm excursion (from 1.7 to 2.2 μm). Page C295, right-hand column, paragraph 3, sentence beginning on line 2 should read: In the 20 ms it takes for the backbone to attain its greatest curvature, the red muscle (low Vmax) could only shorten ap0.2 μm down to 1.86 μm and hence must buckle.

MANUFACTURE OF COMPOSITE TEST SPECIMENS FOR DELAMINATION STUDIES

This paper describes the process for manufacturing high-quality test specimens for uses in evaluations of interlaminar tensile strength of laminated composites. The chosen specimen configuration is a curved beam which experiences interlaminar tension in the region of greatest curvature when the beam is subjected to 'opening' forces. The manufacturing process uses a lock-mold tooling approach, the principle of which relies upon the difference in coefficients of thermal expansion between the internal rubber mandrel and the surrounding steel female mold. With this method, compaction pressures above those provided by a typical autoclave can be achieved.

Infarct expansion: Pathologic analysis of 204 patients with a single myocardial infarct

The reasons for the marked variability in expansion of myocardial infarcts are unknown. To examine this question, the hearts in 204 patients with a single myocardial infarct, autopsied at The Johns Hopkins Hospital and studied after coronary arteriography and fixation in distension, were reviewed. There were 58 (28%) hearts with marked infarct expansion, 34 (17%) with moderate expansion and 112 (55%) with no or minimal expansion. The degree of expansion was greater in larger, more transmural infarcts (p less than 0.001). Infarcts with greater expansion had significantly more endocardial thrombus (p less than 0.001) and endocardial fibroelastosis (p less than 0.01). Larger heart weight and degree of left ventricular hypertrophy had a significant negative correlation with infarct expansion (p less than 0.05). A markedly greater degree of expansion was noted in the 101 infarcts (50%) caused by lesions in the distribution of the left anterior descending coronary artery as compared with the 57 infarcts (28%) secondary to right coronary lesions and the 46 infarcts (23%) in the distribution of the left circumflex coronary artery (p less than 0.001). The results show that expansion is associated with large infarcts but is less marked in hearts with ventricular hypertrophy. Expansion occurs predominantly in infarcts in the left anterior descending coronary artery distribution, that is, regions of the left ventricular myocardium with the greatest curvature. These results suggest that the degree to which an infarct expands may be influenced by the preinfarction thickness of the ventricular wall.

Vascular smooth muscle orientation in curved branches and bifurcations of human cerebral arteries.

Two approaches were developed for determining reference axes and positions associated with bending tubular arteries and bifurcations from the human middle cerebral branching system. In the region of the bifurcation the orientation of groups of two-dimensional nuclear vectors was determined by the method of roses and average alignment. The reference axes and positions for these groups were determined from physical reconstructions of two bifurcations. The overall pattern in the bifurcation region was found to be random but there were significant differences between group orientations. The three-dimensional arterial direction vectors for three sections, from the bending arteries of one bifurcation, were determined. By taking the dot product of the three-dimensional nuclear vectors and these direction vectors, the pitch of individual nuclei was determined. The average pitch was 2.45 degrees +/- 3.20 (SD for N = 8) with the largest mean pitch (6.14 degrees) in the branch with the greatest curvature. Possible use of the three-dimensional approach for determination of smooth muscle orientation at bifurcations is discussed in general terms.

A multifilamentary Nb&amp;lt;inf&amp;gt;3&amp;lt;/inf&amp;gt;Sn dipole magnet

A one meter long, 8 cm aperture dipole magnet has been constructed from prereacted Nb 3 Sn multifilamentary conductor. The conductor is in the form of a wide braid formed from 95 wires of 0.3 mm dia. each containing 1045 filaments of niobium in a copper-tin matrix. After braiding and compacting the conductor was heat treated to form the Nb 3 Sn filaments. The braid was then wound into a dipole of the ISA type using techniques similar to those employed in the construction of magnets from the more conventional NbTi braid. Voltage taps were attached to the conductor at appropriate positions so that the effect of mechanical stress could be observed at the bends of greatest curvature. The effective resistivity of the bent regions of the conductor showed a marked dependance on the bend radius varying from 7 × 10-10ohm-cm at a radius of 0.6 cm to approx, 10-10ohm-cm at 1.0 cm measured at a field of 3 T and a current density of 3.7 × 104Amps/cm2. While the bending of the conductor during coil fabrication did lead to some damage of the Nb 3 Sn filaments, it was not the factor limiting coil performance. The connection between the coil halves in the magnet was resistive and limited the maximum coil current to 2650 amps, well below the short sample limit. An improved method of coil interconnection is being used in future magnets in this series and should make it possible to extend the measurements to higher fields and current densities.