Prediction of residual stress distribution in multi-stacked thin film by curvature measurement and iterative FEA

International Nuclear Information System (INIS)

Choi, Hyeon Chang; Park, Jun Hyub

2005-01-01

In this study, residual stress distribution in multi-stacked film by MEMS (Micro-Electro Mechanical System) process is predicted using Finite Element Method (FEM). We develop a finite element program for REsidual Stress Analysis (RESA) in multi-stacked film. The RESA predicts the distribution of residual stress field in multi-stacked film. Curvatures of multi-stacked film and single layers which consist of the multi-stacked film are used as the input to the RESA. To measure those curvatures is easier than to measure a distribution of residual stress. To verify the RESA, mean stresses and stress gradients of single and multilayers are measured. The mean stresses are calculated from curvatures of deposited wafer by using Stoney's equation. The stress gradients are calculated from the vertical deflection at the end of cantilever beam. To measure the mean stress of each layer in multi-stacked film, we measure the curvature of wafer with the film after etching layer by layer in multi-stacked film

Curvature bound from gravitational catalysis

Science.gov (United States)

Gies, Holger; Martini, Riccardo

2018-04-01

We determine bounds on the curvature of local patches of spacetime from the requirement of intact long-range chiral symmetry. The bounds arise from a scale-dependent analysis of gravitational catalysis and its influence on the effective potential for the chiral order parameter, as induced by fermionic fluctuations on a curved spacetime with local hyperbolic properties. The bound is expressed in terms of the local curvature scalar measured in units of a gauge-invariant coarse-graining scale. We argue that any effective field theory of quantum gravity obeying this curvature bound is safe from chiral symmetry breaking through gravitational catalysis and thus compatible with the simultaneous existence of chiral fermions in the low-energy spectrum. With increasing number of dimensions, the curvature bound in terms of the hyperbolic scale parameter becomes stronger. Applying the curvature bound to the asymptotic safety scenario for quantum gravity in four spacetime dimensions translates into bounds on the matter content of particle physics models.

Closing Gaps in Geometrically Frustrated Symmetric Clusters: Local Equivalence between Discrete Curvature and Twist Transformations

Directory of Open Access Journals (Sweden)

Fang Fang

2018-05-01

Full Text Available In geometrically frustrated clusters of polyhedra, gaps between faces can be closed without distorting the polyhedra by the long established method of discrete curvature, which consists of curving the space into a fourth dimension, resulting in a dihedral angle at the joint between polyhedra in 4D. An alternative method—the twist method—has been recently suggested for a particular case, whereby the gaps are closed by twisting the cluster in 3D, resulting in an angular offset of the faces at the joint between adjacent polyhedral. In this paper, we show the general applicability of the twist method, for local clusters, and present the surprising result that both the required angle of the twist transformation and the consequent angle at the joint are the same, respectively, as the angle of bending to 4D in the discrete curvature and its resulting dihedral angle. The twist is therefore not only isomorphic, but isogonic (in terms of the rotation angles to discrete curvature. Our results apply to local clusters, but in the discussion we offer some justification for the conjecture that the isomorphism between twist and discrete curvature can be extended globally. Furthermore, we present examples for tetrahedral clusters with three-, four-, and fivefold symmetry.

Regional surface geometry of the rat stomach based on three-dimensional curvature analysis

Energy Technology Data Exchange (ETDEWEB)

Liao Donghua [Center of Excellence in Visceral Biomechanics and Pain, Aalborg Hospital, DK-9100 Aalborg (Denmark); Zhao Jingbo [Center of Excellence in Visceral Biomechanics and Pain, Aalborg Hospital, DK-9100 Aalborg (Denmark); Gregersen, Hans [Center of Excellence in Visceral Biomechanics and Pain, Aalborg Hospital, DK-9100 Aalborg (Denmark)

2005-01-21

A better understanding of gastric accommodation and gastric perception requires knowledge of regional gastric geometry and local gastric tension throughout the stomach. An analytic method based on medical imaging data was developed in this study to describe the three-dimensional (3D) rat stomach geometry and tension distribution. The surface principal radii of curvatures were simulated and the surface tension was calculated in the glandular and non-glandular region of the stomach at pressures from 0 Pa to 800 Pa. The radii of curvature and tension distribution in the stomach were non-homogeneous. The radii of curvature in the glandular stomach were larger than those in the non-glandular region at pressures less than 100 Pa (P < 0.001). When the pressure increased to more than 200 Pa, the radii of curvature in the non-glandular stomach was larger than in the glandular stomach (P < 0.05). The curvature and tension distribution mapping using medical imaging technology and 3D models can be used to characterize and distinguish the physical behaviour in separate regions of the stomach.

Regional surface geometry of the rat stomach based on three-dimensional curvature analysis

International Nuclear Information System (INIS)

Liao Donghua; Zhao Jingbo; Gregersen, Hans

2005-01-01

A better understanding of gastric accommodation and gastric perception requires knowledge of regional gastric geometry and local gastric tension throughout the stomach. An analytic method based on medical imaging data was developed in this study to describe the three-dimensional (3D) rat stomach geometry and tension distribution. The surface principal radii of curvatures were simulated and the surface tension was calculated in the glandular and non-glandular region of the stomach at pressures from 0 Pa to 800 Pa. The radii of curvature and tension distribution in the stomach were non-homogeneous. The radii of curvature in the glandular stomach were larger than those in the non-glandular region at pressures less than 100 Pa (P < 0.001). When the pressure increased to more than 200 Pa, the radii of curvature in the non-glandular stomach was larger than in the glandular stomach (P < 0.05). The curvature and tension distribution mapping using medical imaging technology and 3D models can be used to characterize and distinguish the physical behaviour in separate regions of the stomach

RodZ promotes MreB polymer formation and curvature localization to determine the cylindrical uniformity of E. coli shape

OpenAIRE

Bratton, Benjamin; Morgenstein, Randy; Shaevitz, Joshua; Gitai, Zemer

2017-01-01

Cell shape in bacteria is determined by the cell wall, which is synthesized by a variety of proteins whose actions are coordinated by the actin-like MreB protein. MreB uses local geometric cues of envelope curvature to avoid the cell poles and localize to specific regions of the cell body. However, it remains unclear whether MreB's curvature preference is regulated by additional factors, and which features of MreB are essential for specific aspects of rod shape growth, such as cylindrical uni...

Local curvature analysis for classifying breast tumors: Preliminary analysis in dedicated breast CT

International Nuclear Information System (INIS)

Lee, Juhun; Nishikawa, Robert M.; Reiser, Ingrid; Boone, John M.; Lindfors, Karen K.

2015-01-01

Purpose: The purpose of this study is to measure the effectiveness of local curvature measures as novel image features for classifying breast tumors. Methods: A total of 119 breast lesions from 104 noncontrast dedicated breast computed tomography images of women were used in this study. Volumetric segmentation was done using a seed-based segmentation algorithm and then a triangulated surface was extracted from the resulting segmentation. Total, mean, and Gaussian curvatures were then computed. Normalized curvatures were used as classification features. In addition, traditional image features were also extracted and a forward feature selection scheme was used to select the optimal feature set. Logistic regression was used as a classifier and leave-one-out cross-validation was utilized to evaluate the classification performances of the features. The area under the receiver operating characteristic curve (AUC, area under curve) was used as a figure of merit. Results: Among curvature measures, the normalized total curvature (C_T) showed the best classification performance (AUC of 0.74), while the others showed no classification power individually. Five traditional image features (two shape, two margin, and one texture descriptors) were selected via the feature selection scheme and its resulting classifier achieved an AUC of 0.83. Among those five features, the radial gradient index (RGI), which is a margin descriptor, showed the best classification performance (AUC of 0.73). A classifier combining RGI and C_T yielded an AUC of 0.81, which showed similar performance (i.e., no statistically significant difference) to the classifier with the above five traditional image features. Additional comparisons in AUC values between classifiers using different combinations of traditional image features and C_T were conducted. The results showed that C_T was able to replace the other four image features for the classification task. Conclusions: The normalized curvature measure

Curvature and temperature of complex networks.

Science.gov (United States)

Krioukov, Dmitri; Papadopoulos, Fragkiskos; Vahdat, Amin; Boguñá, Marián

2009-09-01

We show that heterogeneous degree distributions in observed scale-free topologies of complex networks can emerge as a consequence of the exponential expansion of hidden hyperbolic space. Fermi-Dirac statistics provides a physical interpretation of hyperbolic distances as energies of links. The hidden space curvature affects the heterogeneity of the degree distribution, while clustering is a function of temperature. We embed the internet into the hyperbolic plane and find a remarkable congruency between the embedding and our hyperbolic model. Besides proving our model realistic, this embedding may be used for routing with only local information, which holds significant promise for improving the performance of internet routing.

Local curvature entropy-based 3D terrain representation using a comprehensive Quadtree

Science.gov (United States)

Chen, Qiyu; Liu, Gang; Ma, Xiaogang; Mariethoz, Gregoire; He, Zhenwen; Tian, Yiping; Weng, Zhengping

2018-05-01

Large scale 3D digital terrain modeling is a crucial part of many real-time applications in geoinformatics. In recent years, the improved speed and precision in spatial data collection make the original terrain data more complex and bigger, which poses challenges for data management, visualization and analysis. In this work, we presented an effective and comprehensive 3D terrain representation based on local curvature entropy and a dynamic Quadtree. The Level-of-detail (LOD) models of significant terrain features were employed to generate hierarchical terrain surfaces. In order to reduce the radical changes of grid density between adjacent LODs, local entropy of terrain curvature was regarded as a measure of subdividing terrain grid cells. Then, an efficient approach was presented to eliminate the cracks among the different LODs by directly updating the Quadtree due to an edge-based structure proposed in this work. Furthermore, we utilized a threshold of local entropy stored in each parent node of this Quadtree to flexibly control the depth of the Quadtree and dynamically schedule large-scale LOD terrain. Several experiments were implemented to test the performance of the proposed method. The results demonstrate that our method can be applied to construct LOD 3D terrain models with good performance in terms of computational cost and the maintenance of terrain features. Our method has already been deployed in a geographic information system (GIS) for practical uses, and it is able to support the real-time dynamic scheduling of large scale terrain models more easily and efficiently.

The Role of Membrane Curvature in Nanoscale Topography-Induced Intracellular Signaling.

Science.gov (United States)

Lou, Hsin-Ya; Zhao, Wenting; Zeng, Yongpeng; Cui, Bianxiao

2018-05-15

allowing the visualization of membrane deformation at the cell membrane-to-substrate interface with nanometer precision and demonstrate that vertical nanostructures induce local curvatures on the plasma membrane. These local curvatures enhance the process of clathrin-mediated endocytosis and affect actin dynamics. We also present evidence that vertical nanostructures can induce significant deformation of the nuclear membrane, which can affect chromatin distribution and gene expression. Finally, we provide a brief perspective on the curvature hypothesis and the challenges and opportunities for the design of nanotopography for manipulating cell behavior.

Cosmic curvature tested directly from observations

Science.gov (United States)

Denissenya, Mikhail; Linder, Eric V.; Shafieloo, Arman

2018-03-01

Cosmic spatial curvature is a fundamental geometric quantity of the Universe. We investigate a model independent, geometric approach to measure spatial curvature directly from observations, without any derivatives of data. This employs strong lensing time delays and supernova distance measurements to measure the curvature itself, rather than just testing consistency with flatness. We define two curvature estimators, with differing error propagation characteristics, that can crosscheck each other, and also show how they can be used to map the curvature in redshift slices, to test constancy of curvature as required by the Robertson-Walker metric. Simulating realizations of redshift distributions and distance measurements of lenses and sources, we estimate uncertainties on the curvature enabled by next generation measurements. The results indicate that the model independent methods, using only geometry without assuming forms for the energy density constituents, can determine the curvature at the ~6×10‑3 level.

Introducing quantum Ricci curvature

Science.gov (United States)

Klitgaard, N.; Loll, R.

2018-02-01

Motivated by the search for geometric observables in nonperturbative quantum gravity, we define a notion of coarse-grained Ricci curvature. It is based on a particular way of extracting the local Ricci curvature of a smooth Riemannian manifold by comparing the distance between pairs of spheres with that of their centers. The quantum Ricci curvature is designed for use on non-smooth and discrete metric spaces, and to satisfy the key criteria of scalability and computability. We test the prescription on a variety of regular and random piecewise flat spaces, mostly in two dimensions. This enables us to quantify its behavior for short lattices distances and compare its large-scale behavior with that of constantly curved model spaces. On the triangulated spaces considered, the quantum Ricci curvature has good averaging properties and reproduces classical characteristics on scales large compared to the discretization scale.

Curvature Entropy for Curved Profile Generation

Directory of Open Access Journals (Sweden)

Koichiro Sato

2012-03-01

Full Text Available In a curved surface design, the overall shape features that emerge from combinations of shape elements are important. However, controlling the features of the overall shape in curved profiles is difficult using conventional microscopic shape information such as dimension. Herein two types of macroscopic shape information, curvature entropy and quadrature curvature entropy, quantitatively represent the features of the overall shape. The curvature entropy is calculated by the curvature distribution, and represents the complexity of a shape (one of the overall shape features. The quadrature curvature entropy is an improvement of the curvature entropy by introducing a Markov process to evaluate the continuity of a curvature and to approximate human cognition of the shape. Additionally, a shape generation method using a genetic algorithm as a calculator and the entropy as a shape generation index is presented. Finally, the applicability of the proposed method is demonstrated using the side view of an automobile as a design example.

3D face recognition with asymptotic cones based principal curvatures

KAUST Repository

Tang, Yinhang

2015-05-01

The classical curvatures of smooth surfaces (Gaussian, mean and principal curvatures) have been widely used in 3D face recognition (FR). However, facial surfaces resulting from 3D sensors are discrete meshes. In this paper, we present a general framework and define three principal curvatures on discrete surfaces for the purpose of 3D FR. These principal curvatures are derived from the construction of asymptotic cones associated to any Borel subset of the discrete surface. They describe the local geometry of the underlying mesh. First two of them correspond to the classical principal curvatures in the smooth case. We isolate the third principal curvature that carries out meaningful geometric shape information. The three principal curvatures in different Borel subsets scales give multi-scale local facial surface descriptors. We combine the proposed principal curvatures with the LNP-based facial descriptor and SRC for recognition. The identification and verification experiments demonstrate the practicability and accuracy of the third principal curvature and the fusion of multi-scale Borel subset descriptors on 3D face from FRGC v2.0.

3D face recognition with asymptotic cones based principal curvatures

KAUST Repository

Tang, Yinhang; Sun, Xiang; Huang, Di; Morvan, Jean-Marie; Wang, Yunhong; Chen, Liming

2015-01-01

The classical curvatures of smooth surfaces (Gaussian, mean and principal curvatures) have been widely used in 3D face recognition (FR). However, facial surfaces resulting from 3D sensors are discrete meshes. In this paper, we present a general framework and define three principal curvatures on discrete surfaces for the purpose of 3D FR. These principal curvatures are derived from the construction of asymptotic cones associated to any Borel subset of the discrete surface. They describe the local geometry of the underlying mesh. First two of them correspond to the classical principal curvatures in the smooth case. We isolate the third principal curvature that carries out meaningful geometric shape information. The three principal curvatures in different Borel subsets scales give multi-scale local facial surface descriptors. We combine the proposed principal curvatures with the LNP-based facial descriptor and SRC for recognition. The identification and verification experiments demonstrate the practicability and accuracy of the third principal curvature and the fusion of multi-scale Borel subset descriptors on 3D face from FRGC v2.0.

Estimation of Curvature Changes for Steel-Concrete Composite Bridge Using Fiber Bragg Grating Sensors

Directory of Open Access Journals (Sweden)

Donghoon Kang

2013-01-01

Full Text Available This study is focused on the verification of the key idea of a newly developed steel-concrete composite bridge. The key idea of the proposed bridge is to reduce the design moment by applying vertical prestressing force to steel girders, so that a moment distribution of a continuous span bridge is formed in a simple span bridge. For the verification of the key technology, curvature changes of the bridge should be monitored sequentially at every construction stage. A pair of multiplexed FBG sensor arrays is proposed in order to measure curvature changes in this study. They are embedded in a full-scale test bridge and measured local strains, which are finally converted to curvatures. From the result of curvature changes, it is successfully ensured that the key idea of the proposed bridge, expected theoretically, is viable.

SU-F-T-24: Impact of Source Position and Dose Distribution Due to Curvature of HDR Transfer Tubes

Energy Technology Data Exchange (ETDEWEB)

Khan, A; Yue, N [Rutgers University, New Brunswick, NJ (United States)

2016-06-15

Purpose: Brachytherapy is a highly targeted from of radiotherapy. While this may lead to ideal dose distributions on the treatment planning system, a small error in source location can lead to change in the dose distribution. The purpose of this study is to quantify the impact on source position error due to curvature of the transfer tubes and the impact this may have on the dose distribution. Methods: Since the source travels along the midline of the tube, an estimate of the positioning error for various angles of curvature was determined using geometric properties of the tube. Based on the range of values a specific shift was chosen to alter the treatment plans for a number of cervical cancer patients who had undergone HDR brachytherapy boost using tandem and ovoids. Impact of dose to target and organs at risk were determined and checked against guidelines outlined by radiation oncologist. Results: The estimate of the positioning error was 2mm short of the expected position (the curved tube can only cause the source to not reach as far as with a flat tube). Quantitative impact on the dose distribution is still in the process of being analyzed. Conclusion: The accepted positioning tolerance for the source position of a HDR brachytherapy unit is plus or minus 1mm. If there is an additional 2mm discrepancy due to tube curvature, this can result in a source being 1mm to 3mm short of the expected location. While we do always attempt to keep the tubes straight, in some cases such as with tandem and ovoids, the tandem connector does not extend as far out from the patient so the ovoid tubes always contain some degree of curvature. The dose impact of this may be significant.

Gaussian curvature elasticity determined from global shape transformations and local stress distributions: a comparative study using the MARTINI model.

Science.gov (United States)

Hu, Mingyang; de Jong, Djurre H; Marrink, Siewert J; Deserno, Markus

2013-01-01

We calculate the Gaussian curvature modulus kappa of a systematically coarse-grained (CG) one-component lipid membrane by applying the method recently proposed by Hu et al. [Biophys. J., 2012, 102, 1403] to the MARTINI representation of 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC). We find the value kappa/kappa = -1.04 +/- 0.03 for the elastic ratio between the Gaussian and the mean curvature modulus and deduce kappa(m)/kappa(m) = -0.98 +/- 0.09 for the monolayer elastic ratio, where the latter is based on plausible assumptions for the distance z0 of the monolayer neutral surface from the bilayer midplane and the spontaneous lipid curvature K(0m). By also analyzing the lateral stress profile sigma0(z) of our system, two other lipid types and pertinent data from the literature, we show that determining K(0m) and kappa through the first and second moment of sigma0(z) gives rise to physically implausible values for these observables. This discrepancy, which we previously observed for a much simpler CG model, suggests that the moment conditions derived from simple continuum assumptions miss the effect of physically important correlations in the lipid bilayer.

3D skin surface reconstruction from a single image by merging global curvature and local texture using the guided filtering for 3D haptic palpation.

Science.gov (United States)

Lee, K; Kim, M; Kim, K

2018-05-11

Skin surface evaluation has been studied using various imaging techniques. However, all these studies had limited impact because they were performed using visual exam only. To improve on this scenario with haptic feedback, we propose 3D reconstruction of the skin surface using a single image. Unlike extant 3D skin surface reconstruction algorithms, we utilize the local texture and global curvature regions, combining the results for reconstruction. The first entails the reconstruction of global curvature, achieved by bilateral filtering that removes noise on the surface while maintaining the edge (ie, furrow) to obtain the overall curvature. The second entails the reconstruction of local texture, representing the fine wrinkles of the skin, using an advanced form of bilateral filtering. The final image is then composed by merging the two reconstructed images. We tested the curvature reconstruction part by comparing the resulting curvatures with measured values from real phantom objects while local texture reconstruction was verified by measuring skin surface roughness. Then, we showed the reconstructed result of our proposed algorithm via the reconstruction of various real skin surfaces. The experimental results demonstrate that our approach is a promising technology to reconstruct an accurate skin surface with a single skin image. We proposed 3D skin surface reconstruction using only a single camera. We highlighted the utility of global curvature, which has not been considered important in the past. Thus, we proposed a new method for 3D reconstruction that can be used for 3D haptic palpation, dividing the concepts of local and global regions. © 2018 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Computational methods for investigation of surface curvature effects on airfoil boundary layer behavior

Directory of Open Access Journals (Sweden)

Xiang Shen

2017-03-01

Full Text Available This article presents computational algorithms for the design, analysis, and optimization of airfoil aerodynamic performance. The prescribed surface curvature distribution blade design (CIRCLE method is applied to a symmetrical airfoil NACA0012 and a non-symmetrical airfoil E387 to remove their surface curvature and slope-of-curvature discontinuities. Computational fluid dynamics analysis is used to investigate the effects of curvature distribution on aerodynamic performance of the original and modified airfoils. An inviscid–viscid interaction scheme is introduced to predict the positions of laminar separation bubbles. The results are compared with experimental data obtained from tests on the original airfoil geometry. The computed aerodynamic advantages of the modified airfoils are analyzed in different operating conditions. The leading edge singularity of NACA0012 is removed and it is shown that the surface curvature discontinuity affects aerodynamic performance near the stalling angle of attack. The discontinuous slope-of-curvature distribution of E387 results in a larger laminar separation bubble at lower angles of attack and lower Reynolds numbers. It also affects the inherent performance of the airfoil at higher Reynolds numbers. It is shown that at relatively high angles of attack, a continuous slope-of-curvature distribution reduces the skin friction by suppressing both laminar and turbulent separation, and by delaying laminar-turbulent transition. It is concluded that the surface curvature distribution has significant effects on the boundary layer behavior and consequently an improved curvature distribution will lead to higher aerodynamic efficiency.

Scalar curvature in conformal geometry of Connes-Landi noncommutative manifolds

Science.gov (United States)

Liu, Yang

2017-11-01

We first propose a conformal geometry for Connes-Landi noncommutative manifolds and study the associated scalar curvature. The new scalar curvature contains its Riemannian counterpart as the commutative limit. Similar to the results on noncommutative two tori, the quantum part of the curvature consists of actions of the modular derivation through two local curvature functions. Explicit expressions for those functions are obtained for all even dimensions (greater than two). In dimension four, the one variable function shows striking similarity to the analytic functions of the characteristic classes appeared in the Atiyah-Singer local index formula, namely, it is roughly a product of the j-function (which defines the A ˆ -class of a manifold) and an exponential function (which defines the Chern character of a bundle). By performing two different computations for the variation of the Einstein-Hilbert action, we obtain deep internal relations between two local curvature functions. Straightforward verification for those relations gives a strong conceptual confirmation for the whole computational machinery we have developed so far, especially the Mathematica code hidden behind the paper.

Longitudinal surface curvature effect in magnetohydrodynamics

International Nuclear Information System (INIS)

Bodas, N.G.

1975-01-01

The two-dimensional motion of an incompressible and electrically conducting fluid past an electrically insulated body surface (having curvature) is studied for a given O(1) basic flow and magnetic field, when (i) the applied magnetic field is aligned with the velocity in the basic flow, and (ii) the applied magnetic field is within the body surface. 01 and 0(Re sup(1/2)) mean the first and second order approximations respectively in an exansion scheme in powers of Resup(-1/2), Re being the Reynolds number). The technique of matched asymptotic expansions is used to solve the problem. The governing partial differential equations to 0(Resup(-1/2)) boundary layer approximation are found to give similarity solutions for a family of surface curvature and pressure gradient distributions in case (i), and for uniform basic flow with analytic surface curvature distributions in case (ii). The equations are solved numerically. In case (i) it is seen that the effect of the magnetic field on the skin-friction- correction due to the curvature is very small. Also the magnetic field at the wall is reduced by the curvature on the convex side. In case (ii) the magnetic field significantly increases the skin-friction-correction due to the curvature. The effect of the magnetic field on the O(1) and O(Resup(-1/2)) skin friction coefficients increases with the increase of the electrical conductivity of the fluid. Also, at higher values of the magnetic pressure, moderate changes in the electrical conductivity do not influence the correction to the skin-friction significantly. (Auth.)

Connections and curvatures on complex Riemannian manifolds

International Nuclear Information System (INIS)

Ganchev, G.; Ivanov, S.

1991-05-01

Characteristic connection and characteristic holomorphic sectional curvatures are introduced on a complex Riemannian manifold (not necessarily with holomorphic metric). For the class of complex Riemannian manifolds with holomorphic characteristic connection a classification of the manifolds with (pointwise) constant holomorphic characteristic curvature is given. It is shown that the conformal geometry of complex analytic Riemannian manifolds can be naturally developed on the class of locally conformal holomorphic Riemannian manifolds. Complex Riemannian manifolds locally conformal to the complex Euclidean space are characterized with zero conformal fundamental tensor and zero conformal characteristic tensor. (author). 12 refs

Gaussian curvature elasticity determined from global shape transformations and local stress distributions : a comparative study using the MARTINI model

NARCIS (Netherlands)

Hu, Mingyang; de Jong, Djurre H.; Marrink, Siewert J.; Deserno, Markus

2013-01-01

We calculate the Gaussian curvature modulus (k) over bar of a systematically coarse-grained (CG) one-component lipid membrane by applying the method recently proposed by Hu et al. [Biophys. J., 2012, 102, 1403] to the MARTINI representation of 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC). We

Robust estimation of adaptive tensors of curvature by tensor voting.

Science.gov (United States)

Tong, Wai-Shun; Tang, Chi-Keung

2005-03-01

Although curvature estimation from a given mesh or regularly sampled point set is a well-studied problem, it is still challenging when the input consists of a cloud of unstructured points corrupted by misalignment error and outlier noise. Such input is ubiquitous in computer vision. In this paper, we propose a three-pass tensor voting algorithm to robustly estimate curvature tensors, from which accurate principal curvatures and directions can be calculated. Our quantitative estimation is an improvement over the previous two-pass algorithm, where only qualitative curvature estimation (sign of Gaussian curvature) is performed. To overcome misalignment errors, our improved method automatically corrects input point locations at subvoxel precision, which also rejects outliers that are uncorrectable. To adapt to different scales locally, we define the RadiusHit of a curvature tensor to quantify estimation accuracy and applicability. Our curvature estimation algorithm has been proven with detailed quantitative experiments, performing better in a variety of standard error metrics (percentage error in curvature magnitudes, absolute angle difference in curvature direction) in the presence of a large amount of misalignment noise.

Measurements of the Curvature of Protrusions/Retrusions on Migrating Recrystallization Boundaries

DEFF Research Database (Denmark)

Zhang, Yubin; Godfrey, A.; Juul Jensen, Dorte

2009-01-01

Two methods to quantify protrusions/retrusions and to estimate local boundary curvature from sample plane sections are proposed. The methods are used to evaluate the driving force due to curvature of the protrusions/retrusions for partially recrystallized pure nickel cold rolled to 96% reduction...

Automatic quantification of local and global articular cartilage surface curvature

DEFF Research Database (Denmark)

Folkesson, Jenny; Dam, Erik B; Olsen, Ole F

2008-01-01

The objective of this study was to quantitatively assess the surface curvature of the articular cartilage from low-field magnetic resonance imaging (MRI) data, and to investigate its role in populations with varying radiographic signs of osteoarthritis (OA), cross-sectionally and longitudinally...

Public and private space curvature in Robertson-Walker universes.

Science.gov (United States)

Rindler, W.

1981-05-01

The question is asked: what space curvature would a fundamental observer in an ideal Robertson-Walker universe obtain by direct local spatial measurements, i.e., without reference to the motion pattern of the other galaxies? The answer is that he obtains the curvatureK of his “private” space generated by all the geodesics orthogonal to his world line at the moment in question, and that ˜K is related to the usual curvatureK=k/R 2 of the “public” space of galaxies byK=K+H 2/c2, whereH is Hubble's parameter.

Correlation between local hemodynamics and lesion distribution in a novel aortic regurgitation murine model of atherosclerosis.

Science.gov (United States)

Hoi, Yiemeng; Zhou, Yu-Qing; Zhang, Xiaoli; Henkelman, R Mark; Steinman, David A

2011-05-01

Following surgical induction of aortic valve regurgitation (AR), extensive atherosclerotic plaque development along the descending thoracic and abdominal aorta of Ldlr⁻/⁻ mice has been reported, with distinct spatial distributions suggestive of a strong local hemodynamic influence. The objective of this study was to test, using image-based computational fluid dynamics (CFD), whether this is indeed the case. The lumen geometry was reconstructed from micro-CT scanning of a control Ldlr⁻/⁻ mouse, and CFD simulations were carried out for both AR and control flow conditions derived from Doppler ultrasound measurements and literature data. Maps of time-averaged wall shear stress magnitude (TAWSS), oscillatory shear index (OSI) and relative residence time (RRT) were compared against the spatial distributions of plaque stained with oil red O, previously acquired in a group of AR and control mice. Maps of OSI and RRT were found to be consistent with plaque distributions in the AR mice and the absence of plaque in the control mice. TAWSS was uniformly lower under control vs. AR flow conditions, suggesting that levels (> 100 dyn/cm²) exceeded those required to alone induce a pro-atherogenic response. Simulations of a straightened CFD model confirmed the importance of anatomical curvature for explaining the spatial distribution of lesions in the AR mice. In summary, oscillatory and retrograde flow induced in the AR mice, without concomitant low shear, may exacerbate or accelerate lesion formation, but the distinct anatomical curvature of the mouse aorta is responsible for the spatial distribution of lesions.

Bacterial cell curvature through mechanical control of cell growth

DEFF Research Database (Denmark)

Cabeen, M.; Charbon, Godefroid; Vollmer, W.

2009-01-01

The cytoskeleton is a key regulator of cell morphogenesis. Crescentin, a bacterial intermediate filament-like protein, is required for the curved shape of Caulobacter crescentus and localizes to the inner cell curvature. Here, we show that crescentin forms a single filamentous structure...... that collapses into a helix when detached from the cell membrane, suggesting that it is normally maintained in a stretched configuration. Crescentin causes an elongation rate gradient around the circumference of the sidewall, creating a longitudinal cell length differential and hence curvature. Such curvature...... can be produced by physical force alone when cells are grown in circular microchambers. Production of crescentin in Escherichia coli is sufficient to generate cell curvature. Our data argue for a model in which physical strain borne by the crescentin structure anisotropically alters the kinetics...

The Relationship Between Surface Curvature and Abdominal Aortic Aneurysm Wall Stress.

Science.gov (United States)

de Galarreta, Sergio Ruiz; Cazón, Aitor; Antón, Raúl; Finol, Ender A

2017-08-01

The maximum diameter (MD) criterion is the most important factor when predicting risk of rupture of abdominal aortic aneurysms (AAAs). An elevated wall stress has also been linked to a high risk of aneurysm rupture, yet is an uncommon clinical practice to compute AAA wall stress. The purpose of this study is to assess whether other characteristics of the AAA geometry are statistically correlated with wall stress. Using in-house segmentation and meshing algorithms, 30 patient-specific AAA models were generated for finite element analysis (FEA). These models were subsequently used to estimate wall stress and maximum diameter and to evaluate the spatial distributions of wall thickness, cross-sectional diameter, mean curvature, and Gaussian curvature. Data analysis consisted of statistical correlations of the aforementioned geometry metrics with wall stress for the 30 AAA inner and outer wall surfaces. In addition, a linear regression analysis was performed with all the AAA wall surfaces to quantify the relationship of the geometric indices with wall stress. These analyses indicated that while all the geometry metrics have statistically significant correlations with wall stress, the local mean curvature (LMC) exhibits the highest average Pearson's correlation coefficient for both inner and outer wall surfaces. The linear regression analysis revealed coefficients of determination for the outer and inner wall surfaces of 0.712 and 0.516, respectively, with LMC having the largest effect on the linear regression equation with wall stress. This work underscores the importance of evaluating AAA mean wall curvature as a potential surrogate for wall stress.

Shape discrimination by total curvature, with a view to cancer diagnostics

DEFF Research Database (Denmark)

Gardner, R.J.; Hobolth, Asger; Jensen, Eva Bjørn Vedel

2005-01-01

This paper investigates the use of total curvature for shape discrimination of objects via profiles of their planar sections (not assumed to be star shaped). Methods of estimating total curvature from observation of a finite number of points on the boundary of the object are investigated, includi...... a simple discrete approximation method and various interpolation methods. Total curvature is capable of revealing shape differences on a local scale, as demonstrated by the analysis of two data sets of malignant and normal or benign tumour cell nuclear profiles....

Waterfall field in hybrid inflation and curvature perturbation

International Nuclear Information System (INIS)

Gong, Jinn-Ouk; Sasaki, Misao

2011-01-01

We study carefully the contribution of the waterfall field to the curvature perturbation at the end of hybrid inflation. In particular we clarify the parameter dependence analytically under reasonable assumptions on the model parameters. After calculating the mode function of the waterfall field, we use the δN formalism and confirm the previously obtained result that the power spectrum is very blue with the index 4 and is absolutely negligible on large scales. However, we also find that the resulting curvature perturbation is highly non-Gaussian and hence we calculate the bispectrum. We find that the bispectrum is at leading order independent of momentum and exhibits its peak at the equilateral limit, though it is unobservably small on large scales. We also present the one-point probability distribution function of the curvature perturbation

Waterfall field in hybrid inflation and curvature perturbation

Energy Technology Data Exchange (ETDEWEB)

Gong, Jinn-Ouk [Instituut-Lorentz for Theoretical Physics, Universiteit Leiden, 2333 CA Leiden (Netherlands); Sasaki, Misao, E-mail: jgong@lorentz.leidenuniv.nl, E-mail: misao@yukawa.kyoto-u.ac.jp [Yukawa Institute for Theoretical Physics, Kyoto University, Kyoto 606-8502 (Japan)

2011-03-01

We study carefully the contribution of the waterfall field to the curvature perturbation at the end of hybrid inflation. In particular we clarify the parameter dependence analytically under reasonable assumptions on the model parameters. After calculating the mode function of the waterfall field, we use the δN formalism and confirm the previously obtained result that the power spectrum is very blue with the index 4 and is absolutely negligible on large scales. However, we also find that the resulting curvature perturbation is highly non-Gaussian and hence we calculate the bispectrum. We find that the bispectrum is at leading order independent of momentum and exhibits its peak at the equilateral limit, though it is unobservably small on large scales. We also present the one-point probability distribution function of the curvature perturbation.

On the improvement of two-dimensional curvature computation and its application to turbulent premixed flame correlations

International Nuclear Information System (INIS)

Chrystie, R S M; Burns, I S; Hult, J; Kaminski, C F

2008-01-01

Measurement of curvature of the flamefront of premixed turbulent flames is important for the validation of numerical models for combustion. In this work, curvature is measured from contours that outline the flamefront, which are generated from laser-induced fluorescence images. The contours are inherently digitized, resulting in pixelation effects that lead to difficulties in computing curvature of the flamefront accurately. A common approach is to fit functions locally to short sections along the flame contour, and this approach is also followed in this work; the method helps smoothen the pixelation before curvature is measured. However, the length and degree of the polynomial, and hence the amount of smoothing, must be correctly set in order to maximize the precision and accuracy of the curvature measurements. Other researchers have applied polynomials of different orders and over different segment lengths to circles of known curvature as a test to determine the appropriate choice of polynomial; it is shown here that this method results in a sub-optimal choice of polynomial function. Here, we determine more suitable polynomial functions through use of a circle whose radius is sinusoidally modulated. We show that this leads to a more consistent and reliable choice for the local polynomial functions fitted to experimental data. A polynomial function thus determined is then applied to flame contour data to measure curvature of experimentally acquired flame contours. The results show that there is an enhancement in local flame speed at sections of the flamefront with a non-zero curvature, and this agrees with numerical models

The Spatial Structure of Planform Migration - Curvature Relation of Meandering Rivers

Science.gov (United States)

Guneralp, I.; Rhoads, B. L.

2005-12-01

Planform dynamics of meandering rivers have been of fundamental interest to fluvial geomorphologists and engineers because of the intriguing complexity of these dynamics, the role of planform change in floodplain development and landscape evolution, and the economic and social consequences of bank erosion and channel migration. Improved understanding of the complex spatial structure of planform change and capacity to predict these changes are important for effective stream management, engineering and restoration. The planform characteristics of a meandering river channel are integral to its planform dynamics. Active meandering rivers continually change their positions and shapes as a consequence of hydraulic forces exerted on the channel banks and bed, but as the banks and bed change through sediment transport, so do the hydraulic forces. Thus far, this complex feedback between form and process is incompletely understood, despite the fact that the characteristics and the dynamics of meandering rivers have been studied extensively. Current theoretical models aimed at predicting planform dynamics relate rates of meander migration to local and upstream planform curvature where weighting of the influence of curvature on migration rate decays exponentially over distance. This theoretical relation, however, has not been rigorously evaluated empirically. Furthermore, although models based on exponential-weighting of curvature effects yield fairly realistic predictions of meander migration, such models are incapable of reproducing complex forms of bend development, such as double heading or compound looping. This study presents the development of a new methodology based on parametric cubic spline interpolation for the characterization of channel planform and the planform curvature of meandering rivers. The use of continuous mathematical functions overcomes the reliance on bend-averaged values or piece-wise discrete approximations of planform curvature - a major limitation

On the calculation of principle curvatures of the left-ventricular surfaces.

Science.gov (United States)

Claus, Piet; Choi, Hon Fai; D'hooge, Jan; Rademakers, Frank E

2008-01-01

A local description of the shape of the left ventricle is relevant in assessing the process of adverse ventricular remodeling, associated with most cardiac pathologies, and in monitoring reverse remodeling by therapy. To quantify local shape of the left ventricle, one can calculate the curvature of its epicardial or endocardial surface. The 3D geometry of the heart and especially the ventricles, can typically be described using finite element meshes. From a mathematical point of view these meshes provide a local parametrization of the surface in the 3-dimensional space. We discuss the analytic derivation of the principle curvatures of the left-ventricular surfaces given their smooth finite-element meshes and apply this derivation to assess the regional shape of the normal porcine left ventricle.

Sequence periodicity in nucleosomal DNA and intrinsic curvature.

Science.gov (United States)

Nair, T Murlidharan

2010-05-17

Most eukaryotic DNA contained in the nucleus is packaged by wrapping DNA around histone octamers. Histones are ubiquitous and bind most regions of chromosomal DNA. In order to achieve smooth wrapping of the DNA around the histone octamer, the DNA duplex should be able to deform and should possess intrinsic curvature. The deformability of DNA is a result of the non-parallelness of base pair stacks. The stacking interaction between base pairs is sequence dependent. The higher the stacking energy the more rigid the DNA helix, thus it is natural to expect that sequences that are involved in wrapping around the histone octamer should be unstacked and possess intrinsic curvature. Intrinsic curvature has been shown to be dictated by the periodic recurrence of certain dinucleotides. Several genome-wide studies directed towards mapping of nucleosome positions have revealed periodicity associated with certain stretches of sequences. In the current study, these sequences have been analyzed with a view to understand their sequence-dependent structures. Higher order DNA structures and the distribution of molecular bend loci associated with 146 base nucleosome core DNA sequence from C. elegans and chicken have been analyzed using the theoretical model for DNA curvature. The curvature dispersion calculated by cyclically permuting the sequences revealed that the molecular bend loci were delocalized throughout the nucleosome core region and had varying degrees of intrinsic curvature. The higher order structures associated with nucleosomes of C.elegans and chicken calculated from the sequences revealed heterogeneity with respect to the deviation of the DNA axis. The results points to the possibility of context dependent curvature of varying degrees to be associated with nucleosomal DNA.

Non-linear realizations and higher curvature supergravity

Energy Technology Data Exchange (ETDEWEB)

Farakos, F. [Dipartimento di Fisica e Astronomia ' ' Galileo Galilei' ' , Universita di Padova (Italy); INFN, Sezione di Padova (Italy); Ferrara, S. [Department of Theoretical Physics, Geneva (Switzerland); INFN - Laboratori Nazionali di Frascati, Frascati (Italy); Department of Physics and Astronomy, Mani L. Bhaumik Institute for Theoretical Physics, U.C.L.A., Los Angeles, CA (United States); Kehagias, A. [Physics Division, National Technical University of Athens (Greece); Luest, D. [Arnold Sommerfeld Center for Theoretical Physics, Muenchen (Germany); Max-Planck-Institut fuer Physik, Muenchen (Germany)

2017-12-15

We focus on non-linear realizations of local supersymmetry as obtained by using constrained superfields in supergravity. New constraints, beyond those of rigid supersymmetry, are obtained whenever curvature multiplets are affected as well as higher derivative interactions are introduced. In particular, a new constraint, which removes a very massive gravitino is introduced, and in the rigid limit it merely reduces to an explicit supersymmetry breaking. Higher curvature supergravities free of ghosts and instabilities are also obtained in this way. Finally, we consider direct coupling of the goldstino multiplet to the super Gauss-Bonnet multiplet and discuss the emergence of a new scalar degree of freedom. (copyright 2017 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

Mimicking the cosmological constant: Constant curvature spherical solutions in a nonminimally coupled model

International Nuclear Information System (INIS)

Bertolami, Orfeu; Paramos, Jorge

2011-01-01

The purpose of this study is to describe a perfect fluid matter distribution that leads to a constant curvature region, thanks to the effect of a nonminimal coupling. This distribution exhibits a density profile within the range found in the interstellar medium and an adequate matching of the metric components at its boundary. By identifying this constant curvature with the value of the cosmological constant and superimposing the spherical distributions arising from different matter sources throughout the universe, one is able to mimic a large-scale homogeneous cosmological constant solution.

Curvature-induced symmetry breaking in nonlinear Schrodinger models

DEFF Research Database (Denmark)

Gaididei, Yuri Borisovich; Mingaleev, S. F.; Christiansen, Peter Leth

2000-01-01

We consider a curved chain of nonlinear oscillators and show that the interplay of curvature and nonlinearity leads to a symmetry breaking when an asymmetric stationary state becomes energetically more favorable than a symmetric stationary state. We show that the energy of localized states...

The curvature coordinate system

DEFF Research Database (Denmark)

Almegaard, Henrik

2007-01-01

The paper describes a concept for a curvature coordinate system on regular curved surfaces from which faceted surfaces with plane quadrangular facets can be designed. The lines of curvature are used as parametric lines for the curvature coordinate system on the surface. A new conjugate set of lin...

Principal Curvature Measures Estimation and Application to 3D Face Recognition

KAUST Repository

Tang, Yinhang

2017-04-06

This paper presents an effective 3D face keypoint detection, description and matching framework based on three principle curvature measures. These measures give a unified definition of principle curvatures for both smooth and discrete surfaces. They can be reasonably computed based on the normal cycle theory and the geometric measure theory. The strong theoretical basis of these measures provides us a solid discrete estimation method on real 3D face scans represented as triangle meshes. Based on these estimated measures, the proposed method can automatically detect a set of sparse and discriminating 3D facial feature points. The local facial shape around each 3D feature point is comprehensively described by histograms of these principal curvature measures. To guarantee the pose invariance of these descriptors, three principle curvature vectors of these principle curvature measures are employed to assign the canonical directions. Similarity comparison between faces is accomplished by matching all these curvature-based local shape descriptors using the sparse representation-based reconstruction method. The proposed method was evaluated on three public databases, i.e. FRGC v2.0, Bosphorus, and Gavab. Experimental results demonstrated that the three principle curvature measures contain strong complementarity for 3D facial shape description, and their fusion can largely improve the recognition performance. Our approach achieves rank-one recognition rates of 99.6, 95.7, and 97.9% on the neutral subset, expression subset, and the whole FRGC v2.0 databases, respectively. This indicates that our method is robust to moderate facial expression variations. Moreover, it also achieves very competitive performance on the pose subset (over 98.6% except Yaw 90°) and the occlusion subset (98.4%) of the Bosphorus database. Even in the case of extreme pose variations like profiles, it also significantly outperforms the state-of-the-art approaches with a recognition rate of 57.1%. The

Awareness Becomes Necessary Between Adaptive Pattern Coding of Open and Closed Curvatures

Science.gov (United States)

Sweeny, Timothy D.; Grabowecky, Marcia; Suzuki, Satoru

2012-01-01

Visual pattern processing becomes increasingly complex along the ventral pathway, from the low-level coding of local orientation in the primary visual cortex to the high-level coding of face identity in temporal visual areas. Previous research using pattern aftereffects as a psychophysical tool to measure activation of adaptive feature coding has suggested that awareness is relatively unimportant for the coding of orientation, but awareness is crucial for the coding of face identity. We investigated where along the ventral visual pathway awareness becomes crucial for pattern coding. Monoptic masking, which interferes with neural spiking activity in low-level processing while preserving awareness of the adaptor, eliminated open-curvature aftereffects but preserved closed-curvature aftereffects. In contrast, dichoptic masking, which spares spiking activity in low-level processing while wiping out awareness, preserved open-curvature aftereffects but eliminated closed-curvature aftereffects. This double dissociation suggests that adaptive coding of open and closed curvatures straddles the divide between weakly and strongly awareness-dependent pattern coding. PMID:21690314

Measuring the composition-curvature coupling in binary lipid membranes by computer simulations

International Nuclear Information System (INIS)

Barragán Vidal, I. A.; Müller, M.; Rosetti, C. M.; Pastorino, C.

2014-01-01

The coupling between local composition fluctuations in binary lipid membranes and curvature affects the lateral membrane structure. We propose an efficient method to compute the composition-curvature coupling in molecular simulations and apply it to two coarse-grained membrane models—a minimal, implicit-solvent model and the MARTINI model. Both the weak-curvature behavior that is typical for thermal fluctuations of planar bilayer membranes as well as the strong-curvature regime corresponding to narrow cylindrical membrane tubes are studied by molecular dynamics simulation. The simulation results are analyzed by using a phenomenological model of the thermodynamics of curved, mixed bilayer membranes that accounts for the change of the monolayer area upon bending. Additionally the role of thermodynamic characteristics such as the incompatibility between the two lipid species and asymmetry of composition are investigated

Measuring the composition-curvature coupling in binary lipid membranes by computer simulations

Energy Technology Data Exchange (ETDEWEB)

Barragán Vidal, I. A., E-mail: vidal@theorie.physik.uni-goettingen.de; Müller, M., E-mail: mmueller@theorie.physik.uni-goettingen.de [Institut für Theoretische Physik, Georg-August-Universität, Friedrich-Hund-Platz 1, 37077 Göttingen (Germany); Rosetti, C. M., E-mail: carla@dqb.fcq.unc.edu.ar [Centro de Investigaciones en Química Biológica de Córdoba, Departamento de Química Biológica, Facultad de Ciencias Químicas, Universidad Nacional de Córdoba, Ciudad Universitaria, Córdoba (Argentina); Pastorino, C., E-mail: pastor@cnea.gov.ar [Departamento de Física de la Materia Condensada, Centro Atómico Constituyentes, CNEA/CONICET, Av. Gral. Paz 1499, 1650 Pcia. de Buenos Aires (Argentina)

2014-11-21

The coupling between local composition fluctuations in binary lipid membranes and curvature affects the lateral membrane structure. We propose an efficient method to compute the composition-curvature coupling in molecular simulations and apply it to two coarse-grained membrane models—a minimal, implicit-solvent model and the MARTINI model. Both the weak-curvature behavior that is typical for thermal fluctuations of planar bilayer membranes as well as the strong-curvature regime corresponding to narrow cylindrical membrane tubes are studied by molecular dynamics simulation. The simulation results are analyzed by using a phenomenological model of the thermodynamics of curved, mixed bilayer membranes that accounts for the change of the monolayer area upon bending. Additionally the role of thermodynamic characteristics such as the incompatibility between the two lipid species and asymmetry of composition are investigated.

On Gauss-Bonnet Curvatures

Directory of Open Access Journals (Sweden)

Mohammed Larbi Labbi

2007-12-01

Full Text Available The $(2k$-th Gauss-Bonnet curvature is a generalization to higher dimensions of the $(2k$-dimensional Gauss-Bonnet integrand, it coincides with the usual scalar curvature for $k = 1$. The Gauss-Bonnet curvatures are used in theoretical physics to describe gravity in higher dimensional space times where they are known as the Lagrangian of Lovelock gravity, Gauss-Bonnet Gravity and Lanczos gravity. In this paper we present various aspects of these curvature invariants and review their variational properties. In particular, we discuss natural generalizations of the Yamabe problem, Einstein metrics and minimal submanifolds.

Implementing quantum Ricci curvature

Science.gov (United States)

Klitgaard, N.; Loll, R.

2018-05-01

Quantum Ricci curvature has been introduced recently as a new, geometric observable characterizing the curvature properties of metric spaces, without the need for a smooth structure. Besides coordinate invariance, its key features are scalability, computability, and robustness. We demonstrate that these properties continue to hold in the context of nonperturbative quantum gravity, by evaluating the quantum Ricci curvature numerically in two-dimensional Euclidean quantum gravity, defined in terms of dynamical triangulations. Despite the well-known, highly nonclassical properties of the underlying quantum geometry, its Ricci curvature can be matched well to that of a five-dimensional round sphere.

Lectures on mean curvature flows

CERN Document Server

Zhu, Xi-Ping

2002-01-01

"Mean curvature flow" is a term that is used to describe the evolution of a hypersurface whose normal velocity is given by the mean curvature. In the simplest case of a convex closed curve on the plane, the properties of the mean curvature flow are described by Gage-Hamilton's theorem. This theorem states that under the mean curvature flow, the curve collapses to a point, and if the flow is diluted so that the enclosed area equals \\pi, the curve tends to the unit circle. In this book, the author gives a comprehensive account of fundamental results on singularities and the asymptotic behavior of mean curvature flows in higher dimensions. Among other topics, he considers in detail Huisken's theorem (a generalization of Gage-Hamilton's theorem to higher dimension), evolution of non-convex curves and hypersurfaces, and the classification of singularities of the mean curvature flow. Because of the importance of the mean curvature flow and its numerous applications in differential geometry and partial differential ...

Curvature of fluctuation geometry and its implications on Riemannian fluctuation theory

International Nuclear Information System (INIS)

Velazquez, L

2013-01-01

Fluctuation geometry was recently proposed as a counterpart approach of the Riemannian geometry of inference theory (widely known as information geometry). This theory describes the geometric features of the statistical manifold M of random events that are described by a family of continuous distributions dp(x|θ). A main goal of this work is to clarify the statistical relevance of the Levi-Civita curvature tensor R ijkl (x|θ) of the statistical manifold M. For this purpose, the notion of irreducible statistical correlations is introduced. Specifically, a distribution dp(x|θ) exhibits irreducible statistical correlations if every distribution dp(x-check|θ) obtained from dp(x|θ) by considering a coordinate change x-check = φ(x) cannot be factorized into independent distributions as dp(x-check|θ) = prod i dp (i) (x-check i |θ). It is shown that the curvature tensor R ijkl (x|θ) arises as a direct indicator about the existence of irreducible statistical correlations. Moreover, the curvature scalar R(x|θ) allows us to introduce a criterium for the applicability of the Gaussian approximation of a given distribution function. This type of asymptotic result is obtained in the framework of the second-order geometric expansion of the distribution family dp(x|θ), which appears as a counterpart development of the high-order asymptotic theory of statistical estimation. In physics, fluctuation geometry represents the mathematical apparatus of a Riemannian extension for Einstein’s fluctuation theory of statistical mechanics. Some exact results of fluctuation geometry are now employed to derive the invariant fluctuation theorems. Moreover, the curvature scalar allows us to express some asymptotic formulae that account for the system fluctuating behavior beyond the Gaussian approximation, e.g.: it appears as a second-order correction of the Legendre transformation between thermodynamic potentials, P(θ)=θ i x-bar i -s( x-bar |θ)+k 2 R(x|θ)/6. (paper)

Curvature-induced microswarming and clustering of self-propelled particles

Science.gov (United States)

Bruss, Isaac; Glotzer, Sharon

Non-equilibrium active matter systems exhibit many unique phenomena, such as motility-induced phase separation and swarming. However, little is known about how these behaviors depend on the geometry of the environment. To answer this question, we use Brownian dynamics simulations to study the effects of Gaussian curvature on self-propelled particles by confining them to the surface of a sphere. We find that a modest amount of curvature promotes phase separation by altering the shape of a cluster's boundary. Alternatively, particles on surfaces of high curvature experience reduced phase separation and instead form microswarms, where particles share a common orbit. We show that this novel flocking behavior is distinct from other previously studied examples, in that it is not explicitly incorporated into our model through Vicsek-like alignment rules nor torques. Rather, we find that microswarms emerge solely due to the geometric link between orientation and velocity, a property exclusive to surfaces with non-zero Gaussian curvature. These findings reveal the important role of local environment on the global emergent behavior of non-equilibrium systems. Center for Bio-Inspired Engineering (DOE Award # DE-SC0000989).

Strong Light Localization and a Peculiar Feature of Light Leakage in the Negative Curvature Hollow Core Fibers

Directory of Open Access Journals (Sweden)

Andrey D. Pryamikov

2017-11-01

Full Text Available In this paper we would like to continue a discussion started in our previous work and devoted to the mechanism of light localization in hollow core microstructured fibers with a noncircular core-cladding boundary. It has been shown in many works that, for waveguide microstructures with different types of core-cladding boundary shape, the positions of the transmission bands’ edges can be predicted by applying the well-known anti–resonant reflecting optical waveguide (ARROW model. At the same time, the ARROW model cannot explain the strong light localization and guiding at high material loss inside the transmission bands which are observed in negative curvature hollow core fibers, for example. In this paper we want to clarify our previous findings and consider the light localization process from another point of view, namely, by comparing the light leakage process in waveguide microstructures with different shapes of the core-cladding boundary. The results are discussed based on the ARROW model and a new approach associated with the consideration of spatial dispersion occurring under the interaction of the air core mode with the core-cladding boundary.

Model-independent Constraints on Cosmic Curvature and Opacity

Energy Technology Data Exchange (ETDEWEB)

Wang, Guo-Jian; Li, Zheng-Xiang; Xia, Jun-Qing; Zhu, Zong-Hong [Department of Astronomy, Beijing Normal University, Beijing 100875 (China); Wei, Jun-Jie, E-mail: gjwang@mail.bnu.edu.cn, E-mail: zxli918@bnu.edu.cn, E-mail: xiajq@bnu.edu.cn, E-mail: zhuzh@bnu.edu.cn, E-mail: jjwei@pmo.ac.cn [Purple Mountain Observatory, Chinese Academy of Sciences, Nanjing 210008 (China)

2017-09-20

In this paper, we propose to estimate the spatial curvature of the universe and the cosmic opacity in a model-independent way with expansion rate measurements, H ( z ), and type Ia supernova (SNe Ia). On the one hand, using a nonparametric smoothing method Gaussian process, we reconstruct a function H ( z ) from opacity-free expansion rate measurements. Then, we integrate the H ( z ) to obtain distance modulus μ {sub H}, which is dependent on the cosmic curvature. On the other hand, distances of SNe Ia can be determined by their photometric observations and thus are opacity-dependent. In our analysis, by confronting distance moduli μ {sub H} with those obtained from SNe Ia, we achieve estimations for both the spatial curvature and the cosmic opacity without any assumptions for the cosmological model. Here, it should be noted that light curve fitting parameters, accounting for the distance estimation of SNe Ia, are determined in a global fit together with the cosmic opacity and spatial curvature to get rid of the dependence of these parameters on cosmology. In addition, we also investigate whether the inclusion of different priors for the present expansion rate ( H {sub 0}: global estimation, 67.74 ± 0.46 km s{sup −1} Mpc{sup −1}, and local measurement, 73.24 ± 1.74 km s{sup −1} Mpc{sup −1}) exert influence on the reconstructed H ( z ) and the following estimations of the spatial curvature and cosmic opacity. Results show that, in general, a spatially flat and transparent universe is preferred by the observations. Moreover, it is suggested that priors for H {sub 0} matter a lot. Finally, we find that there is a strong degeneracy between the curvature and the opacity.

Integrating 3D seismic curvature and curvature gradient attributes for fracture characterization: Methodologies and interpretational implications

Energy Technology Data Exchange (ETDEWEB)

Gao, Dengliang

2013-03-01

In 3D seismic interpretation, curvature is a popular attribute that depicts the geometry of seismic reflectors and has been widely used to detect faults in the subsurface; however, it provides only part of the solutions to subsurface structure analysis. This study extends the curvature algorithm to a new curvature gradient algorithm, and integrates both algorithms for fracture detection using a 3D seismic test data set over Teapot Dome (Wyoming). In fractured reservoirs at Teapot Dome known to be formed by tectonic folding and faulting, curvature helps define the crestal portion of the reservoirs that is associated with strong seismic amplitude and high oil productivity. In contrast, curvature gradient helps better define the regional northwest-trending and the cross-regional northeast-trending lineaments that are associated with weak seismic amplitude and low oil productivity. In concert with previous reports from image logs, cores, and outcrops, the current study based on an integrated seismic curvature and curvature gradient analysis suggests that curvature might help define areas of enhanced potential to form tensile fractures, whereas curvature gradient might help define zones of enhanced potential to develop shear fractures. In certain fractured reservoirs such as at Teapot Dome where faulting and fault-related folding contribute dominantly to the formation and evolution of fractures, curvature and curvature gradient attributes can be potentially applied to differentiate fracture mode, to predict fracture intensity and orientation, to detect fracture volume and connectivity, and to model fracture networks.

Some Inequalities for the -Curvature Image

Directory of Open Access Journals (Sweden)

Daijun Wei

2009-01-01

Full Text Available Lutwak introduced the notion of -curvature image and proved an inequality for the volumes of convex body and its -curvature image. In this paper, we first give an monotonic property of -curvature image. Further, we establish two inequalities for the -curvature image and its polar, respectively. Finally, an inequality for the volumes of -projection body and -curvature image is obtained.

Sensitive zone parameters and curvature radius evaluation for polymer optical fiber curvature sensors

Science.gov (United States)

Leal-Junior, Arnaldo G.; Frizera, Anselmo; José Pontes, Maria

2018-03-01

Polymer optical fibers (POFs) are suitable for applications such as curvature sensors, strain, temperature, liquid level, among others. However, for enhancing sensitivity, many polymer optical fiber curvature sensors based on intensity variation require a lateral section. Lateral section length, depth, and surface roughness have great influence on the sensor sensitivity, hysteresis, and linearity. Moreover, the sensor curvature radius increase the stress on the fiber, which leads on variation of the sensor behavior. This paper presents the analysis relating the curvature radius and lateral section length, depth and surface roughness with the sensor sensitivity, hysteresis and linearity for a POF curvature sensor. Results show a strong correlation between the decision parameters behavior and the performance for sensor applications based on intensity variation. Furthermore, there is a trade-off among the sensitive zone length, depth, surface roughness, and curvature radius with the sensor desired performance parameters, which are minimum hysteresis, maximum sensitivity, and maximum linearity. The optimization of these parameters is applied to obtain a sensor with sensitivity of 20.9 mV/°, linearity of 0.9992 and hysteresis below 1%, which represent a better performance of the sensor when compared with the sensor without the optimization.

Brane cosmology with curvature corrections

International Nuclear Information System (INIS)

Kofinas, Georgios; Maartens, Roy; Papantonopoulos, Eleftherios

2003-01-01

We study the cosmology of the Randall-Sundrum brane-world where the Einstein-Hilbert action is modified by curvature correction terms: a four-dimensional scalar curvature from induced gravity on the brane, and a five-dimensional Gauss-Bonnet curvature term. The combined effect of these curvature corrections to the action removes the infinite-density big bang singularity, although the curvature can still diverge for some parameter values. A radiation brane undergoes accelerated expansion near the minimal scale factor, for a range of parameters. This acceleration is driven by the geometric effects, without an inflation field or negative pressures. At late times, conventional cosmology is recovered. (author)

Regularized strings with extrinsic curvature

International Nuclear Information System (INIS)

Ambjoern, J.; Durhuus, B.

1987-07-01

We analyze models of discretized string theories, where the path integral over world sheet variables is regularized by summing over triangulated surfaces. The inclusion of curvature in the action is a necessity for the scaling of the string tension. We discuss the physical properties of models with extrinsic curvature terms in the action and show that the string tension vanishes at the critical point where the bare extrinsic curvature coupling tends to infinity. Similar results are derived for models with intrinsic curvature. (orig.)

Transformation (normalization) of slope gradient and surface curvatures, automated for statistical analyses from DEMs

Science.gov (United States)

Csillik, O.; Evans, I. S.; Drăguţ, L.

2015-03-01

Automated procedures are developed to alleviate long tails in frequency distributions of morphometric variables. They minimize the skewness of slope gradient frequency distributions, and modify the kurtosis of profile and plan curvature distributions toward that of the Gaussian (normal) model. Box-Cox (for slope) and arctangent (for curvature) transformations are tested on nine digital elevation models (DEMs) of varying origin and resolution, and different landscapes, and shown to be effective. Resulting histograms are illustrated and show considerable improvements over those for previously recommended slope transformations (sine, square root of sine, and logarithm of tangent). Unlike previous approaches, the proposed method evaluates the frequency distribution of slope gradient values in a given area and applies the most appropriate transform if required. Sensitivity of the arctangent transformation is tested, showing that Gaussian-kurtosis transformations are acceptable also in terms of histogram shape. Cube root transformations of curvatures produced bimodal histograms. The transforms are applicable to morphometric variables and many others with skewed or long-tailed distributions. By avoiding long tails and outliers, they permit parametric statistics such as correlation, regression and principal component analyses to be applied, with greater confidence that requirements for linearity, additivity and even scatter of residuals (constancy of error variance) are likely to be met. It is suggested that such transformations should be routinely applied in all parametric analyses of long-tailed variables. Our Box-Cox and curvature automated transformations are based on a Python script, implemented as an easy-to-use script tool in ArcGIS.

Mesoscale computational studies of membrane bilayer remodeling by curvature-inducing proteins

Science.gov (United States)

Ramakrishnan, N.; Sunil Kumar, P. B.; Radhakrishnan, Ravi

2014-01-01

Biological membranes constitute boundaries of cells and cell organelles. These membranes are soft fluid interfaces whose thermodynamic states are dictated by bending moduli, induced curvature fields, and thermal fluctuations. Recently, there has been a flood of experimental evidence highlighting active roles for these structures in many cellular processes ranging from trafficking of cargo to cell motility. It is believed that the local membrane curvature, which is continuously altered due to its interactions with myriad proteins and other macromolecules attached to its surface, holds the key to the emergent functionality in these cellular processes. Mechanisms at the atomic scale are dictated by protein-lipid interaction strength, lipid composition, lipid distribution in the vicinity of the protein, shape and amino acid composition of the protein, and its amino acid contents. The specificity of molecular interactions together with the cooperativity of multiple proteins induce and stabilize complex membrane shapes at the mesoscale. These shapes span a wide spectrum ranging from the spherical plasma membrane to the complex cisternae of the Golgi apparatus. Mapping the relation between the protein-induced deformations at the molecular scale and the resulting mesoscale morphologies is key to bridging cellular experiments across the various length scales. In this review, we focus on the theoretical and computational methods used to understand the phenomenology underlying protein-driven membrane remodeling. Interactions at the molecular scale can be computationally probed by all atom and coarse grained molecular dynamics (MD, CGMD), as well as dissipative particle dynamics (DPD) simulations, which we only describe in passing. We choose to focus on several continuum approaches extending the Canham - Helfrich elastic energy model for membranes to include the effect of curvature-inducing proteins and explore the conformational phase space of such systems. In this

Mesoscale computational studies of membrane bilayer remodeling by curvature-inducing proteins

Energy Technology Data Exchange (ETDEWEB)

Ramakrishnan, N., E-mail: ramn@seas.upenn.edu [Department of Chemical and Biomolecular Engineering, University of Pennsylvania, Philadelphia, PA-19104 (United States); Department of Bioengineering, University of Pennsylvania, Philadelphia, PA-19104 (United States); Department of Biochemistry and Biophysics, University of Pennsylvania, Philadelphia, PA-19104 (United States); Sunil Kumar, P.B., E-mail: sunil@physics.iitm.ac.in [Department of Physics, Indian Institute of Technology Madras, Chennai, 600036 (India); Radhakrishnan, Ravi, E-mail: rradhak@seas.upenn.edu [Department of Chemical and Biomolecular Engineering, University of Pennsylvania, Philadelphia, PA-19104 (United States); Department of Bioengineering, University of Pennsylvania, Philadelphia, PA-19104 (United States); Department of Biochemistry and Biophysics, University of Pennsylvania, Philadelphia, PA-19104 (United States)

2014-10-01

Biological membranes constitute boundaries of cells and cell organelles. These membranes are soft fluid interfaces whose thermodynamic states are dictated by bending moduli, induced curvature fields, and thermal fluctuations. Recently, there has been a flood of experimental evidence highlighting active roles for these structures in many cellular processes ranging from trafficking of cargo to cell motility. It is believed that the local membrane curvature, which is continuously altered due to its interactions with myriad proteins and other macromolecules attached to its surface, holds the key to the emergent functionality in these cellular processes. Mechanisms at the atomic scale are dictated by protein–lipid interaction strength, lipid composition, lipid distribution in the vicinity of the protein, shape and amino acid composition of the protein, and its amino acid contents. The specificity of molecular interactions together with the cooperativity of multiple proteins induce and stabilize complex membrane shapes at the mesoscale. These shapes span a wide spectrum ranging from the spherical plasma membrane to the complex cisternae of the Golgi apparatus. Mapping the relation between the protein-induced deformations at the molecular scale and the resulting mesoscale morphologies is key to bridging cellular experiments across various length scales. In this review, we focus on the theoretical and computational methods used to understand the phenomenology underlying protein-driven membrane remodeling. Interactions at the molecular scale can be computationally probed by all atom and coarse grained molecular dynamics (MD, CGMD), as well as dissipative particle dynamics (DPD) simulations, which we only describe in passing. We choose to focus on several continuum approaches extending the Canham–Helfrich elastic energy model for membranes to include the effect of curvature-inducing proteins and explore the conformational phase space of such systems. In this description

Mesoscale computational studies of membrane bilayer remodeling by curvature-inducing proteins

International Nuclear Information System (INIS)

Ramakrishnan, N.; Sunil Kumar, P.B.; Radhakrishnan, Ravi

2014-01-01

Biological membranes constitute boundaries of cells and cell organelles. These membranes are soft fluid interfaces whose thermodynamic states are dictated by bending moduli, induced curvature fields, and thermal fluctuations. Recently, there has been a flood of experimental evidence highlighting active roles for these structures in many cellular processes ranging from trafficking of cargo to cell motility. It is believed that the local membrane curvature, which is continuously altered due to its interactions with myriad proteins and other macromolecules attached to its surface, holds the key to the emergent functionality in these cellular processes. Mechanisms at the atomic scale are dictated by protein–lipid interaction strength, lipid composition, lipid distribution in the vicinity of the protein, shape and amino acid composition of the protein, and its amino acid contents. The specificity of molecular interactions together with the cooperativity of multiple proteins induce and stabilize complex membrane shapes at the mesoscale. These shapes span a wide spectrum ranging from the spherical plasma membrane to the complex cisternae of the Golgi apparatus. Mapping the relation between the protein-induced deformations at the molecular scale and the resulting mesoscale morphologies is key to bridging cellular experiments across various length scales. In this review, we focus on the theoretical and computational methods used to understand the phenomenology underlying protein-driven membrane remodeling. Interactions at the molecular scale can be computationally probed by all atom and coarse grained molecular dynamics (MD, CGMD), as well as dissipative particle dynamics (DPD) simulations, which we only describe in passing. We choose to focus on several continuum approaches extending the Canham–Helfrich elastic energy model for membranes to include the effect of curvature-inducing proteins and explore the conformational phase space of such systems. In this description

Mesoscale computational studies of membrane bilayer remodeling by curvature-inducing proteins.

Science.gov (United States)

Ramakrishnan, N; Sunil Kumar, P B; Radhakrishnan, Ravi

2014-10-01

Biological membranes constitute boundaries of cells and cell organelles. These membranes are soft fluid interfaces whose thermodynamic states are dictated by bending moduli, induced curvature fields, and thermal fluctuations. Recently, there has been a flood of experimental evidence highlighting active roles for these structures in many cellular processes ranging from trafficking of cargo to cell motility. It is believed that the local membrane curvature, which is continuously altered due to its interactions with myriad proteins and other macromolecules attached to its surface, holds the key to the emergent functionality in these cellular processes. Mechanisms at the atomic scale are dictated by protein-lipid interaction strength, lipid composition, lipid distribution in the vicinity of the protein, shape and amino acid composition of the protein, and its amino acid contents. The specificity of molecular interactions together with the cooperativity of multiple proteins induce and stabilize complex membrane shapes at the mesoscale. These shapes span a wide spectrum ranging from the spherical plasma membrane to the complex cisternae of the Golgi apparatus. Mapping the relation between the protein-induced deformations at the molecular scale and the resulting mesoscale morphologies is key to bridging cellular experiments across the various length scales. In this review, we focus on the theoretical and computational methods used to understand the phenomenology underlying protein-driven membrane remodeling. Interactions at the molecular scale can be computationally probed by all atom and coarse grained molecular dynamics (MD, CGMD), as well as dissipative particle dynamics (DPD) simulations, which we only describe in passing. We choose to focus on several continuum approaches extending the Canham - Helfrich elastic energy model for membranes to include the effect of curvature-inducing proteins and explore the conformational phase space of such systems. In this

Principal Curvature Measures Estimation and Application to 3D Face Recognition

KAUST Repository

Tang, Yinhang; Li, Huibin; Sun, Xiang; Morvan, Jean-Marie; Chen, Liming

2017-01-01

-based local shape descriptors using the sparse representation-based reconstruction method. The proposed method was evaluated on three public databases, i.e. FRGC v2.0, Bosphorus, and Gavab. Experimental results demonstrated that the three principle curvature

Anatomical study of the radius and center of curvature of the distal femoral condyle

KAUST Repository

Kosel, Jü rgen; Giouroudi, Ioanna; Scheffer, Cornie; Dillon, Edwin Mark; Erasmus, Pieter J.

2010-01-01

In this anatomical study, the anteroposterior curvature of the surface of 16 cadaveric distal femurs was examined in terms of radii and center point. Those two parameters attract high interest due to their significance for total knee arthroplasty. Basically, two different conclusions have been drawn in foregoing studies: (1) The curvature shows a constant radius and (2) the curvature shows a variable radius. The investigations were based on a new method combining three-dimensional laser-scanning and planar geometrical analyses. This method is aimed at providing high accuracy and high local resolution. The high-precision laser scanning enables the exact reproduction of the distal femurs - including their cartilage tissue - as a three-dimensional computer model. The surface curvature was investigated on intersection planes that were oriented perpendicularly to the surgical epicondylar line. Three planes were placed at the central part of each condyle. The intersection of either plane with the femur model was approximated with the help of a b-spline, yielding three b-splines on each condyle. The radii and center points of the circles, approximating the local curvature of the b-splines, were then evaluated. The results from all three b-splines were averaged in order to increase the reliability of the method. The results show the variation in the surface curvatures of the investigated samples of condyles. These variations are expressed in the pattern of the center points and the radii of the curvatures. The standard deviations of the radii for a 90 deg arc on the posterior condyle range from 0.6 mm up to 5.1 mm, with an average of 2.4 mm laterally and 2.2 mm medially. No correlation was found between the curvature of the lateral and medial condyles. Within the range of the investigated 16 samples, the conclusion can be drawn that the condyle surface curvature is not constant and different for all specimens when viewed along the surgical epicondylar axis. For the portion

Local distribution and franchising rights

International Nuclear Information System (INIS)

Penick, V.; Grant, R.; McKelvey, S.; Cramm, K.

1998-01-01

A summary of local distribution and franchising rights in Nova Scotia and New Brunswick is presented. The Gas Distribution Act calls for two distinct sets of regulations : broad regulations to be made by the provinces, and more technical procedural regulations to be made by the Utility and Review Board. The focus of this paper is on how municipalities will be affected by the regulations and how franchising within a local area will work. The overall objective is to ensure free competition in gas sales

Local distribution and franchising rights

Energy Technology Data Exchange (ETDEWEB)

Penick, V. [McInnes, Cooper and Robertson, Halifax, NS (Canada); Grant, R.; McKelvey, S. [Stirling Scales, NB (Canada); Cramm, K. [Maritimes NRG, Halifax, NS (Canada)

1998-12-31

A summary of local distribution and franchising rights in Nova Scotia and New Brunswick is presented. The Gas Distribution Act calls for two distinct sets of regulations : broad regulations to be made by the provinces, and more technical procedural regulations to be made by the Utility and Review Board. The focus of this paper is on how municipalities will be affected by the regulations and how franchising within a local area will work. The overall objective is to ensure free competition in gas sales.

Curvature Entropy for Curved Profile Generation

OpenAIRE

Ujiie, Yoshiki; Kato, Takeo; Sato, Koichiro; Matsuoka, Yoshiyuki

2012-01-01

In a curved surface design, the overall shape features that emerge from combinations of shape elements are important. However, controlling the features of the overall shape in curved profiles is difficult using conventional microscopic shape information such as dimension. Herein two types of macroscopic shape information, curvature entropy and quadrature curvature entropy, quantitatively represent the features of the overall shape. The curvature entropy is calculated by the curvature distribu...

Curvature-Induced Instabilities of Shells

Science.gov (United States)

Pezzulla, Matteo; Stoop, Norbert; Steranka, Mark P.; Bade, Abdikhalaq J.; Holmes, Douglas P.

2018-01-01

Induced by proteins within the cell membrane or by differential growth, heating, or swelling, spontaneous curvatures can drastically affect the morphology of thin bodies and induce mechanical instabilities. Yet, the interaction of spontaneous curvature and geometric frustration in curved shells remains poorly understood. Via a combination of precision experiments on elastomeric spherical shells, simulations, and theory, we show how a spontaneous curvature induces a rotational symmetry-breaking buckling as well as a snapping instability reminiscent of the Venus fly trap closure mechanism. The instabilities, and their dependence on geometry, are rationalized by reducing the spontaneous curvature to an effective mechanical load. This formulation reveals a combined pressurelike term in the bulk and a torquelike term in the boundary, allowing scaling predictions for the instabilities that are in excellent agreement with experiments and simulations. Moreover, the effective pressure analogy suggests a curvature-induced subcritical buckling in closed shells. We determine the critical buckling curvature via a linear stability analysis that accounts for the combination of residual membrane and bending stresses. The prominent role of geometry in our findings suggests the applicability of the results over a wide range of scales.

Flow rate impacts on capillary pressure and interface curvature of connected and disconnected fluid phases during multiphase flow in sandstone

Science.gov (United States)

Herring, Anna L.; Middleton, Jill; Walsh, Rick; Kingston, Andrew; Sheppard, Adrian

2017-09-01

We investigate capillary pressure-saturation (PC-S) relationships for drainage-imbibition experiments conducted with air (nonwetting phase) and brine (wetting phase) in Bentheimer sandstone cores. Three different flow rate conditions, ranging over three orders of magnitude, are investigated. X-ray micro-computed tomographic imaging is used to characterize the distribution and amount of fluids and their interfacial characteristics. Capillary pressure is measured via (1) bulk-phase pressure transducer measurements, and (2) image-based curvature measurements, calculated using a novel 3D curvature algorithm. We distinguish between connected (percolating) and disconnected air clusters: curvatures measured on the connected phase interfaces are used to validate the curvature algorithm and provide an indication of the equilibrium condition of the data; curvature and volume distributions of disconnected clusters provide insight to the snap-off processes occurring during drainage and imbibition under different flow rate conditions.

Curvature distribution within hillslopes and catchments and its effect on the hydrological response

NARCIS (Netherlands)

Bogaart, P.W.; Troch, P.A.A.

2006-01-01

Topographic convergence and divergence are first order controls on the hillslope and catchment hydrological response, as evidenced by similarity parameter analyses. Hydrological models often do not take convergence as measured by contour curvature directly into account; instead they use comparable

A locally adaptive normal distribution

DEFF Research Database (Denmark)

Arvanitidis, Georgios; Hansen, Lars Kai; Hauberg, Søren

2016-01-01

entropy distribution under the given metric. The underlying metric is, however, non-parametric. We develop a maximum likelihood algorithm to infer the distribution parameters that relies on a combination of gradient descent and Monte Carlo integration. We further extend the LAND to mixture models......The multivariate normal density is a monotonic function of the distance to the mean, and its ellipsoidal shape is due to the underlying Euclidean metric. We suggest to replace this metric with a locally adaptive, smoothly changing (Riemannian) metric that favors regions of high local density...

Some Inequalities for the Lp-Curvature Image

Directory of Open Access Journals (Sweden)

Xiang Yu

2009-01-01

Full Text Available Lutwak introduced the notion of Lp-curvature image and proved an inequality for the volumes of convex body and its Lp-curvature image. In this paper, we first give an monotonic property of Lp-curvature image. Further, we establish two inequalities for the Lp-curvature image and its polar, respectively. Finally, an inequality for the volumes of Lp-projection body and Lp-curvature image is obtained.

Pricing local distribution services in a competitive market

International Nuclear Information System (INIS)

Duann, D.J.

1995-12-01

Unbundling and restructuring of local distribution services is the focus of the natural gas industry. As a result of regulatory reforms, a competitive local distribution market has emerged, and the validity of traditional cost-based regulation is being questioned. One alternative is to completely unbundle local distribution services and transform the local distribution company into a common carrier for intrastate transportation services. Three kinds of alternative pricing mechanisms are examined. For firm intrastate transportation services, cost-based pricing is the preferred method unless it can be shown that a competitive secondary market can be established and maintained. Pricing interruptible transportation capacity is discussed

Curvature properties of four-dimensional Walker metrics

International Nuclear Information System (INIS)

Chaichi, M; Garcia-Rio, E; Matsushita, Y

2005-01-01

A Walker n-manifold is a semi-Riemannian manifold, which admits a field of parallel null r-planes, r ≤ n/2. In the present paper we study curvature properties of a Walker 4-manifold (M, g) which admits a field of parallel null 2-planes. The metric g is necessarily of neutral signature (+ + - -). Such a Walker 4-manifold is the lowest dimensional example not of Lorentz type. There are three functions of coordinates which define a Walker metric. Some recent work shows that a Walker 4-manifold of restricted type whose metric is characterized by two functions exhibits a large variety of symplectic structures, Hermitian structures, Kaehler structures, etc. For such a restricted Walker 4-manifold, we shall study mainly curvature properties, e.g., conditions for a Walker metric to be Einstein, Osserman, or locally conformally flat, etc. One of our main results is the exact solutions to the Einstein equations for a restricted Walker 4-manifold

Research on improved design of airfoil profiles based on the continuity of airfoil surface curvature of wind turbines

DEFF Research Database (Denmark)

Chen, Jin; Cheng, Jiangtao; Shen, Wenzhong

2013-01-01

Aerodynamic of airfoil performance is closely related to the continuity of its surface curvature, and airfoil profiles with a better aerodynamic performance plays an important role in the design of wind turbine. The surface curvature distribution along the chord direction and pressure distributio...

A remark about the mean curvature

International Nuclear Information System (INIS)

Zhang Weitao.

1992-11-01

In this paper, we give an integral identity about the mean curvature in Sobolev space H 0 1 (Ω) intersection H 2 (Ω). Suppose the mean curvature on Γ=δΩ is positive, we prove some inequalities of the positive mean curvature and propose some open problems. (author). 4 refs

Finger vein extraction using gradient normalization and principal curvature

Science.gov (United States)

Choi, Joon Hwan; Song, Wonseok; Kim, Taejeong; Lee, Seung-Rae; Kim, Hee Chan

2009-02-01

Finger vein authentication is a personal identification technology using finger vein images acquired by infrared imaging. It is one of the newest technologies in biometrics. Its main advantage over other biometrics is the low risk of forgery or theft, due to the fact that finger veins are not normally visible to others. Extracting finger vein patterns from infrared images is the most difficult part in finger vein authentication. Uneven illumination, varying tissues and bones, and changes in the physical conditions and the blood flow make the thickness and brightness of the same vein different in each acquisition. Accordingly, extracting finger veins at their accurate positions regardless of their thickness and brightness is necessary for accurate personal identification. For this purpose, we propose a new finger vein extraction method which is composed of gradient normalization, principal curvature calculation, and binarization. As local brightness variation has little effect on the curvature and as gradient normalization makes the curvature fairly uniform at vein pixels, our method effectively extracts finger vein patterns regardless of the vein thickness or brightness. In our experiment, the proposed method showed notable improvement as compared with the existing methods.

A generic double-curvature piezoelectric shell energy harvester: Linear/nonlinear theory and applications

Science.gov (United States)

Zhang, X. F.; Hu, S. D.; Tzou, H. S.

2014-12-01

Converting vibration energy to useful electric energy has attracted much attention in recent years. Based on the electromechanical coupling of piezoelectricity, distributed piezoelectric zero-curvature type (e.g., beams and plates) energy harvesters have been proposed and evaluated. The objective of this study is to develop a generic linear and nonlinear piezoelectric shell energy harvesting theory based on a double-curvature shell. The generic piezoelectric shell energy harvester consists of an elastic double-curvature shell and piezoelectric patches laminated on its surface(s). With a current model in the closed-circuit condition, output voltages and energies across a resistive load are evaluated when the shell is subjected to harmonic excitations. Steady-state voltage and power outputs across the resistive load are calculated at resonance for each shell mode. The piezoelectric shell energy harvesting mechanism can be simplified to shell (e.g., cylindrical, conical, spherical, paraboloidal, etc.) and non-shell (beam, plate, ring, arch, etc.) distributed harvesters using two Lamé parameters and two curvature radii of the selected harvester geometry. To demonstrate the utility and simplification procedures, the generic linear/nonlinear shell energy harvester mechanism is simplified to three specific structures, i.e., a cantilever beam case, a circular ring case and a conical shell case. Results show the versatility of the generic linear/nonlinear shell energy harvesting mechanism and the validity of the simplification procedures.

Quantitative analysis of spinal curvature in 3D: application to CT images of normal spine

Energy Technology Data Exchange (ETDEWEB)

Vrtovec, Tomaz; Likar, Bostjan; Pernus, Franjo [University of Ljubljana, Faculty of Electrical Engineering, Trzaska 25, SI-1000 Ljubljana (Slovenia)

2008-04-07

The purpose of this study is to present a framework for quantitative analysis of spinal curvature in 3D. In order to study the properties of such complex 3D structures, we propose two descriptors that capture the characteristics of spinal curvature in 3D. The descriptors are the geometric curvature (GC) and curvature angle (CA), which are independent of the orientation and size of spine anatomy. We demonstrate the two descriptors that characterize the spinal curvature in 3D on 30 computed tomography (CT) images of normal spine and on a scoliotic spine. The descriptors are determined from 3D vertebral body lines, which are obtained by two different methods. The first method is based on the least-squares technique that approximates the manually identified vertebra centroids, while the second method searches for vertebra centroids in an automated optimization scheme, based on computer-assisted image analysis. Polynomial functions of the fourth and fifth degree were used for the description of normal and scoliotic spinal curvature in 3D, respectively. The mean distance to vertebra centroids was 1.1 mm ({+-}0.6 mm) for the first and 2.1 mm ({+-}1.4 mm) for the second method. The distributions of GC and CA values were obtained along the 30 images of normal spine at each vertebral level and show that maximal thoracic kyphosis (TK), thoracolumbar junction (TJ) and maximal lumbar lordosis (LL) on average occur at T3/T4, T12/L1 and L4/L5, respectively. The main advantage of GC and CA is that the measurements are independent of the orientation and size of the spine, thus allowing objective intra- and inter-subject comparisons. The positions of maximal TK, TJ and maximal LL can be easily identified by observing the GC and CA distributions at different vertebral levels. The obtained courses of the GC and CA for the scoliotic spine were compared to the distributions of GC and CA for the normal spines. The significant difference in values indicates that the descriptors of GC and

Quantitative analysis of spinal curvature in 3D: application to CT images of normal spine

International Nuclear Information System (INIS)

Vrtovec, Tomaz; Likar, Bostjan; Pernus, Franjo

2008-01-01

The purpose of this study is to present a framework for quantitative analysis of spinal curvature in 3D. In order to study the properties of such complex 3D structures, we propose two descriptors that capture the characteristics of spinal curvature in 3D. The descriptors are the geometric curvature (GC) and curvature angle (CA), which are independent of the orientation and size of spine anatomy. We demonstrate the two descriptors that characterize the spinal curvature in 3D on 30 computed tomography (CT) images of normal spine and on a scoliotic spine. The descriptors are determined from 3D vertebral body lines, which are obtained by two different methods. The first method is based on the least-squares technique that approximates the manually identified vertebra centroids, while the second method searches for vertebra centroids in an automated optimization scheme, based on computer-assisted image analysis. Polynomial functions of the fourth and fifth degree were used for the description of normal and scoliotic spinal curvature in 3D, respectively. The mean distance to vertebra centroids was 1.1 mm (±0.6 mm) for the first and 2.1 mm (±1.4 mm) for the second method. The distributions of GC and CA values were obtained along the 30 images of normal spine at each vertebral level and show that maximal thoracic kyphosis (TK), thoracolumbar junction (TJ) and maximal lumbar lordosis (LL) on average occur at T3/T4, T12/L1 and L4/L5, respectively. The main advantage of GC and CA is that the measurements are independent of the orientation and size of the spine, thus allowing objective intra- and inter-subject comparisons. The positions of maximal TK, TJ and maximal LL can be easily identified by observing the GC and CA distributions at different vertebral levels. The obtained courses of the GC and CA for the scoliotic spine were compared to the distributions of GC and CA for the normal spines. The significant difference in values indicates that the descriptors of GC and CA

Investigating the effect of tablet thickness and punch curvature on density distribution using finite elements method.

Science.gov (United States)

Diarra, Harona; Mazel, Vincent; Busignies, Virginie; Tchoreloff, Pierre

2015-09-30

Finite elements method was used to study the influence of tablet thickness and punch curvature on the density distribution inside convex faced (CF) tablets. The modeling of the process was conducted on 2 pharmaceutical excipients (anhydrous calcium phosphate and microcrystalline cellulose) by using Drucker-Prager Cap model in Abaqus(®) software. The parameters of the model were obtained from experimental tests. Several punch shapes based on industrial standards were used. A flat-faced (FF) punch and 3 convex faced (CF) punches (8R11, 8R8 and 8R6) with a diameter of 8mm were chosen. Different tablet thicknesses were studied at a constant compression force. The simulation of the compaction of CF tablets with increasing thicknesses showed an important change on the density distribution inside the tablet. For smaller thicknesses, low density zones are located toward the center. The density is not uniform inside CF tablets and the center of the 2 faces appears with low density whereas the distribution inside FF tablets is almost independent of the tablet thickness. These results showed that FF and CF tablets, even obtained at the same compression force, do not have the same density at the center of the compact. As a consequence differences in tensile strength, as measured by diametral compression, are expected. This was confirmed by experimental tests. Copyright © 2015 Elsevier B.V. All rights reserved.

Polarized curvature radiation in pulsar magnetosphere

Science.gov (United States)

Wang, P. F.; Wang, C.; Han, J. L.

2014-07-01

The propagation of polarized emission in pulsar magnetosphere is investigated in this paper. The polarized waves are generated through curvature radiation from the relativistic particles streaming along curved magnetic field lines and corotating with the pulsar magnetosphere. Within the 1/γ emission cone, the waves can be divided into two natural wave-mode components, the ordinary (O) mode and the extraordinary (X) mode, with comparable intensities. Both components propagate separately in magnetosphere, and are aligned within the cone by adiabatic walking. The refraction of O mode makes the two components separated and incoherent. The detectable emission at a given height and a given rotation phase consists of incoherent X-mode and O-mode components coming from discrete emission regions. For four particle-density models in the form of uniformity, cone, core and patches, we calculate the intensities for each mode numerically within the entire pulsar beam. If the corotation of relativistic particles with magnetosphere is not considered, the intensity distributions for the X-mode and O-mode components are quite similar within the pulsar beam, which causes serious depolarization. However, if the corotation of relativistic particles is considered, the intensity distributions of the two modes are very different, and the net polarization of outcoming emission should be significant. Our numerical results are compared with observations, and can naturally explain the orthogonal polarization modes of some pulsars. Strong linear polarizations of some parts of pulsar profile can be reproduced by curvature radiation and subsequent propagation effect.

Discrete Curvature Theories and Applications

KAUST Repository

Sun, Xiang

2016-08-25

Discrete Di erential Geometry (DDG) concerns discrete counterparts of notions and methods in di erential geometry. This thesis deals with a core subject in DDG, discrete curvature theories on various types of polyhedral surfaces that are practically important for free-form architecture, sunlight-redirecting shading systems, and face recognition. Modeled as polyhedral surfaces, the shapes of free-form structures may have to satisfy di erent geometric or physical constraints. We study a combination of geometry and physics { the discrete surfaces that can stand on their own, as well as having proper shapes for the manufacture. These proper shapes, known as circular and conical meshes, are closely related to discrete principal curvatures. We study curvature theories that make such surfaces possible. Shading systems of freeform building skins are new types of energy-saving structures that can re-direct the sunlight. From these systems, discrete line congruences across polyhedral surfaces can be abstracted. We develop a new curvature theory for polyhedral surfaces equipped with normal congruences { a particular type of congruences de ned by linear interpolation of vertex normals. The main results are a discussion of various de nitions of normality, a detailed study of the geometry of such congruences, and a concept of curvatures and shape operators associated with the faces of a triangle mesh. These curvatures are compatible with both normal congruences and the Steiner formula. In addition to architecture, we consider the role of discrete curvatures in face recognition. We use geometric measure theory to introduce the notion of asymptotic cones associated with a singular subspace of a Riemannian manifold, which is an extension of the classical notion of asymptotic directions. We get a simple expression of these cones for polyhedral surfaces, as well as convergence and approximation theorems. We use the asymptotic cones as facial descriptors and demonstrate the

Comprehensive Use of Curvature for Robust and Accurate Online Surface Reconstruction.

Science.gov (United States)

Lefloch, Damien; Kluge, Markus; Sarbolandi, Hamed; Weyrich, Tim; Kolb, Andreas

2017-12-01

Interactive real-time scene acquisition from hand-held depth cameras has recently developed much momentum, enabling applications in ad-hoc object acquisition, augmented reality and other fields. A key challenge to online reconstruction remains error accumulation in the reconstructed camera trajectory, due to drift-inducing instabilities in the range scan alignments of the underlying iterative-closest-point (ICP) algorithm. Various strategies have been proposed to mitigate that drift, including SIFT-based pre-alignment, color-based weighting of ICP pairs, stronger weighting of edge features, and so on. In our work, we focus on surface curvature as a feature that is detectable on range scans alone and hence does not depend on accurate multi-sensor alignment. In contrast to previous work that took curvature into consideration, however, we treat curvature as an independent quantity that we consistently incorporate into every stage of the real-time reconstruction pipeline, including densely curvature-weighted ICP, range image fusion, local surface reconstruction, and rendering. Using multiple benchmark sequences, and in direct comparison to other state-of-the-art online acquisition systems, we show that our approach significantly reduces drift, both when analyzing individual pipeline stages in isolation, as well as seen across the online reconstruction pipeline as a whole.

Curvature force and dark energy

International Nuclear Information System (INIS)

Balakin, Alexander B; Pavon, Diego; Schwarz, Dominik J; Zimdahl, Winfried

2003-01-01

A curvature self-interaction of the cosmic gas is shown to mimic a cosmological constant or other forms of dark energy, such as a rolling tachyon condensate or a Chaplygin gas. Any given Hubble rate and deceleration parameter can be traced back to the action of an effective curvature force on the gas particles. This force self-consistently reacts back on the cosmological dynamics. The links between an imperfect fluid description, a kinetic description with effective antifriction forces and curvature forces, which represent a non-minimal coupling of gravity to matter, are established

Experimental study of curvature effects on jet impingement heat transfer on concave surfaces

Directory of Open Access Journals (Sweden)

Ying Zhou

2017-04-01

Full Text Available Experimental study of the local and average heat transfer characteristics of a single round jet impinging on the concave surfaces was conducted in this work to gain in-depth knowledge of the curvature effects. The experiments were conducted by employing a piccolo tube with one single jet hole over a wide range of parameters: jet Reynolds number from 27000 to 130000, relative nozzle to surface distance from 3.3 to 30, and relative surface curvature from 0.005 to 0.030. Experimental results indicate that the surface curvature has opposite effects on heat transfer characteristics. On one hand, an increase of relative nozzle to surface distance (increasing jet diameter in fact enhances the average heat transfer around the surface for the same curved surface. On the other hand, the average Nusselt number decreases as relative nozzle to surface distance increases for a fixed jet diameter. Finally, experimental data-based correlations of the average Nusselt number over the curved surface were obtained with consideration of surface curvature effect. This work contributes to a better understanding of the curvature effects on heat transfer of a round jet impingement on concave surfaces, which is of high importance to the design of the aircraft anti-icing system.

Numerical calculation and analysis of single-curvature polyhedron hydro-bulging process for manufacturing spherical vessels

International Nuclear Information System (INIS)

Dong Jianling; Zhang Fengke; Yin Dejian

2005-01-01

Single-curvature polyhedron hydro-bulging technology is a new technology for manufacturing spherical vessels and it has a good application foreground. This technology has been used in practice. But the designing and manufacturing of polyhedron is based on experiences, and the final quality of spherical vessels cannot be forecast quantitatively. In the paper, the FEM code, MARC, is used to simulate the hydrobulging process of a single-curvature polyhedron, including loading and offloading. And the distributions of stress and strain are acquired as well as other important data. Comparing with the experimental results, it shows that single-curvature polyhedron hydro-bulging process can be simulated well by the FEM code. (authors)

Emergent gravity in spaces of constant curvature

Energy Technology Data Exchange (ETDEWEB)

Alvarez, Orlando; Haddad, Matthew [Department of Physics, University of Miami,1320 Campo Sano Ave, Coral Gables, FL 33146 (United States)

2017-03-07

In physical theories where the energy (action) is localized near a submanifold of a constant curvature space, there is a universal expression for the energy (or the action). We derive a multipole expansion for the energy that has a finite number of terms, and depends on intrinsic geometric invariants of the submanifold and extrinsic invariants of the embedding of the submanifold. This is the second of a pair of articles in which we try to develop a theory of emergent gravity arising from the embedding of a submanifold into an ambient space equipped with a quantum field theory. Our theoretical method requires a generalization of a formula due to by Hermann Weyl. While the first paper discussed the framework in Euclidean (Minkowski) space, here we discuss how this framework generalizes to spaces of constant sectional curvature. We focus primarily on anti de Sitter space. We then discuss how such a theory can give rise to a cosmological constant and Planck mass that are within reasonable bounds of the experimental values.

Zero curvature-surface driven small objects

Science.gov (United States)

Dou, Xiaoxiao; Li, Shanpeng; Liu, Jianlin

2017-08-01

In this study, we investigate the spontaneous migration of small objects driven by surface tension on a catenoid, formed by a layer of soap constrained by two rings. Although the average curvature of the catenoid is zero at each point, the small objects always migrate to the position near the ring. The force and energy analyses have been performed to uncover the mechanism, and it is found that the small objects distort the local shape of the liquid film, thus making the whole system energetically favorable. These findings provide some inspiration to design microfluidics, aquatic robotics, and miniature boats.

Tubular bending and pull-out forces in high-curvature well bores

International Nuclear Information System (INIS)

Dareing, D.W.; Ahlers, C.A.

1991-01-01

This paper is concerned with drag forces developed on tubulars in high-curvature well bores typically found in drainhole and horizontal drilling. The dog-leg severity of these types of boreholes are considerably higher than those typically found in conventional directional drilling. The objective of the study was to determine the significance of bending stiffness on drag forces in the pull-out mode. The method of analysis treats the tubular as a multi-spanned curved beam under tension and solves for radial displacements, slope, shear and bending moment over each span. Calculations show that bending stiffness is a minor factor provided there are no locally severe dog legs superimposed in the high-curvature well bore

Substrate Curvature Regulates Cell Migration -A Computational Study

Science.gov (United States)

He, Xiuxiu; Jiang, Yi

Cell migration in host microenvironment is essential to cancer etiology, progression and metastasis. Cellular processes of adhesion, cytoskeletal polymerization, contraction, and matrix remodeling act in concert to regulate cell migration, while local extracellular matrix architecture modulate these processes. In this work we study how stromal microenvironment with native and cell-derived curvature at micron-meter scale regulate cell motility pattern. We developed a 3D model of single cell migration on a curved substrate. Mathematical analysis of cell morphological adaption to the cell-substrate interface shows that cell migration on convex surfaces deforms more than on concave surfaces. Both analytical and simulation results show that curved surfaces regulate the cell motile force for cell's protruding front through force balance with focal adhesion and cell contraction. We also found that cell migration on concave substrates is more persistent. These results offer a novel biomechanical explanation to substrate curvature regulation of cell migration. NIH 1U01CA143069.

Restructuring local distribution services: Possibilities and limitations

Energy Technology Data Exchange (ETDEWEB)

Duann, D.J.

1994-08-01

The restructuring of local distribution services is now the focus of the natural gas industry. It is the last major step in the ``reconstitution`` of the natural gas industry and a critical clement in realizing the full benefits of regulatory and market reforms that already have taken place in the wellhead and interstate markets. It could also be the most important regulatory initiative for most end-use customers because they are affected directly by the costs and reliability of distribution services. Several factors contribute to the current emphasis on distribution service restructuring. They include the unbundling and restructuring of upstream markets, a realization of the limitations of supply-side options (such as gas procurement oversight), and the increased diversity and volatility of gas demand facing local distribution companies. Local distribution service is not one but a series of activities that start with commodity gas procurement and extend to transportation, load balancing, storage, and metering and billing of services provided. There are also considerable differences in the economies of scale and scope associated with these various activities. Thus, a mixture of supply arrangements (such as a competitive market or a monopoly) is required for the most efficient delivery of local distribution services. A distinction must be made between the supply of commodity gas and the provision of a bundled distribution service. This distinction and identification of the best supply arrangements for various distribution service components are the most critical factors in developing appropriate restructuring policies. For most state public utility commissions the criteria for service restructuring should include pursuing the economies of scale and scope in gas distribution, differentiating and matching gas service reliability and quality with customer requirements, and controlling costs associated with the search, negotiation, and contracting of gas services.

Environmental influences on DNA curvature

DEFF Research Database (Denmark)

Ussery, David; Higgins, C.F.; Bolshoy, A.

1999-01-01

DNA curvature plays an important role in many biological processes. To study environmentalinfluences on DNA curvature we compared the anomalous migration on polyacrylamide gels ofligation ladders of 11 specifically-designed oligonucleotides. At low temperatures (25 degreesC and below) most......, whilst spermine enhanced theanomalous migration of a different set of sequences. Sequences with a GGC motif exhibitedgreater curvature than predicted by the presently-used angles for the nearest-neighbour wedgemodel and are especially sensitive to Mg2+. The data have implications for models...... for DNAcurvature and for environmentally-sensitive DNA conformations in the regulation of geneexpression....

Numerical Investigation on Fluid Flow in a 90-Degree Curved Pipe with Large Curvature Ratio

Directory of Open Access Journals (Sweden)

Yan Wang

2015-01-01

Full Text Available In order to understand the mechanism of fluid flows in curved pipes, a large number of theoretical and experimental researches have been performed. As a critical parameter of curved pipe, the curvature ratio δ has received much attention, but most of the values of δ are very small (δ<0.1 or relatively small (δ≤0.5. As a preliminary study and simulation this research studied the fluid flow in a 90-degree curved pipe of large curvature ratio. The Detached Eddy Simulation (DES turbulence model was employed to investigate the fluid flows at the Reynolds number range from 5000 to 20000. After validation of the numerical strategy, the pressure and velocity distribution, pressure drop, fluid flow, and secondary flow along the curved pipe were illustrated. The results show that the fluid flow in a curved pipe with large curvature ratio seems to be unlike that in a curved pipe with small curvature ratio. Large curvature ratio makes the internal flow more complicated; thus, the flow patterns, the separation region, and the oscillatory flow are different.

Amplification of curvature perturbations in cyclic cosmology

International Nuclear Information System (INIS)

Zhang Jun; Liu Zhiguo; Piao Yunsong

2010-01-01

We analytically and numerically show that through the cycles with nonsingular bounce, the amplitude of curvature perturbation on a large scale will be amplified and the power spectrum will redden. In some sense, this amplification will eventually destroy the homogeneity of the background, which will lead to the ultimate end of cycles of the global universe. We argue that for the model with increasing cycles, it might be possible that a fissiparous multiverse will emerge after one or several cycles, in which the cycles will continue only at corresponding local regions.

Distribution costs -- the cost of local delivery

International Nuclear Information System (INIS)

Winger, N.; Zarnett, P.; Carr, J.

2000-01-01

Most of the power transmission system in the province of Ontario is owned and operated as a regulated monopoly by Ontario Hydro Services Company (OHSC). Local distribution systems deliver to end-users from bulk supply points within a service territory. OHSC distributes to approximately one million, mostly rural customers, while the approximately 250 municipal utilities together serve about two million, mostly urban customers. Under the Energy Competition Act of 1998 local distribution companies will face some new challenges, including unbundled billing systems, a broader range of distribution costs, increased costs, made up of corporate taxes or payments in lieu of taxes and added costs for regulatory affairs. The consultants provide a detailed discussion of the components of distribution costs, the three components of the typical budget process (capital expenditures, (CAPEX), operating and maintenance (O and M) and administration and corporate (GA and C), a summary of some typical distribution costs in Ontario, and the estimated impacts of the Energy Competition Act (ECA) compliance on charges and rates. Various mitigation strategies are also reviewed. Among these are joint ventures by local distribution companies to reduce ECA compliance costs, re-examination of controllable costs, temporary reduction of the allowable return on equity (ROE) by 50 per cent, and/or reducing the competitive transition charge (CTC). It is estimated that either one of these two reductions could eliminate the full amount of the five to seven per cent uplift in delivered energy service costs. The conclusion of the consultants is that local distribution delivery charges will make up a greater proportion of end-user cost in the future than it has in the past. An increase to customers of about five per cent is expected when the competitive electricity market opens and unbundled billing begins. The cost increase could be mitigated by a combination of actions that would be needed for about

Glauber theory and the quantum coherence of curvature inhomogeneities

CERN Document Server

Giovannini, Massimo

2017-01-12

The curvature inhomogeneities are systematically scrutinized in the framework of the Glauber approach. The amplified quantum fluctuations of the scalar and tensor modes of the geometry are shown to be first-order coherent while the interference of the corresponding intensities is larger than in the case of Bose-Einstein correlations. After showing that the degree of second-order coherence does not suffice to characterize unambiguously the curvature inhomogeneities, we argue that direct analyses of the degrees of third and fourth-order coherence are necessary to discriminate between different correlated states and to infer more reliably the statistical properties of the large-scale fluctuations. We speculate that the moments of the multiplicity distributions of the relic phonons might be observationally accessible thanks to new generations of instruments able to count the single photons of the Cosmic Microwave Background in the THz region.

Manifolds of positive scalar curvature

Energy Technology Data Exchange (ETDEWEB)

Stolz, S [Department of Mathematics, University of Notre Dame, Notre Dame (United States)

2002-08-15

This lecture gives an survey on the problem of finding a positive scalar curvature metric on a closed manifold. The Gromov-Lawson-Rosenberg conjecture and its relation to the Baum-Connes conjecture are discussed and the problem of finding a positive Ricci curvature metric on a closed manifold is explained.

Integration of length and curvature in haptic perception.

Science.gov (United States)

Panday, Virjanand; Tiest, Wouter M Bergmann; Kappers, Astrid M L

2014-01-24

We investigated if and how length and curvature information are integrated when an object is explored in one hand. Subjects were asked to explore four types of objects between thumb and index finger. Objects differed in either length, curvature, both length and curvature correlated as in a circle, or anti-correlated. We found that when both length and curvature are present, performance is significantly better than when only one of the two cues is available. Therefore, we conclude that there is integration of length and curvature. Moreover, if the two cues are correlated in a circular cross-section instead of in an anti-correlated way, performance is better than predicted by a combination of two independent cues. We conclude that integration of curvature and length is highly efficient when the cues in the object are combined as in a circle, which is the most common combination of curvature and length in daily life.

Right thoracic curvature in the normal spine

Directory of Open Access Journals (Sweden)

Masuda Keigo

2011-01-01

Full Text Available Abstract Background Trunk asymmetry and vertebral rotation, at times observed in the normal spine, resemble the characteristics of adolescent idiopathic scoliosis (AIS. Right thoracic curvature has also been reported in the normal spine. If it is determined that the features of right thoracic side curvature in the normal spine are the same as those observed in AIS, these findings might provide a basis for elucidating the etiology of this condition. For this reason, we investigated right thoracic curvature in the normal spine. Methods For normal spinal measurements, 1,200 patients who underwent a posteroanterior chest radiographs were evaluated. These consisted of 400 children (ages 4-9, 400 adolescents (ages 10-19 and 400 adults (ages 20-29, with each group comprised of both genders. The exclusion criteria were obvious chest and spinal diseases. As side curvature is minimal in normal spines and the range at which curvature is measured is difficult to ascertain, first the typical curvature range in scoliosis patients was determined and then the Cobb angle in normal spines was measured using the same range as the scoliosis curve, from T5 to T12. Right thoracic curvature was given a positive value. The curve pattern was organized in each collective three groups: neutral (from -1 degree to 1 degree, right (> +1 degree, and left ( Results In child group, Cobb angle in left was 120, in neutral was 125 and in right was 155. In adolescent group, Cobb angle in left was 70, in neutral was 114 and in right was 216. In adult group, Cobb angle in left was 46, in neutral was 102 and in right was 252. The curvature pattern shifts to the right side in the adolescent group (p Conclusions Based on standing chest radiographic measurements, a right thoracic curvature was observed in normal spines after adolescence.

Curvature and torsion in growing actin networks

International Nuclear Information System (INIS)

Shaevitz, Joshua W; Fletcher, Daniel A

2008-01-01

Intracellular pathogens such as Listeria monocytogenes and Rickettsia rickettsii move within a host cell by polymerizing a comet-tail of actin fibers that ultimately pushes the cell forward. This dense network of cross-linked actin polymers typically exhibits a striking curvature that causes bacteria to move in gently looping paths. Theoretically, tail curvature has been linked to details of motility by considering force and torque balances from a finite number of polymerizing filaments. Here we track beads coated with a prokaryotic activator of actin polymerization in three dimensions to directly quantify the curvature and torsion of bead motility paths. We find that bead paths are more likely to have low rather than high curvature at any given time. Furthermore, path curvature changes very slowly in time, with an autocorrelation decay time of 200 s. Paths with a small radius of curvature, therefore, remain so for an extended period resulting in loops when confined to two dimensions. When allowed to explore a three-dimensional (3D) space, path loops are less evident. Finally, we quantify the torsion in the bead paths and show that beads do not exhibit a significant left- or right-handed bias to their motion in 3D. These results suggest that paths of actin-propelled objects may be attributed to slow changes in curvature, possibly associated with filament debranching, rather than a fixed torque

Spin-curvature interaction from curved Dirac equation: Application to single-wall carbon nanotubes

Science.gov (United States)

Zhang, Kai; Zhang, Erhu; Chen, Huawei; Zhang, Shengli

2017-06-01

The spin-curvature interaction (SCI) and its effects are investigated based on curved Dirac equation. Through the low-energy approximation of curved Dirac equation, the Hamiltonian of SCI is obtained and depends on the geometry and spinor structure of manifold. We find that the curvature can be considered as field strength and couples with spin through Zeeman-like term. Then, we use dimension reduction to derive the local Hamiltonian of SCI for cylinder surface, which implies that the effective Hamiltonian of single-wall carbon nanotubes results from the geometry and spinor structure of lattice and includes two types of interactions: one does not break any symmetries of the lattice and only shifts the Dirac points for all nanotubes, while the other one does and opens the gaps except for armchair nanotubes. At last, analytical expressions of the band gaps and the shifts of their positions induced by curvature are given for metallic nanotubes. These results agree well with experiments and can be verified experimentally.

No Association between Cortical Gyrification or Intrinsic Curvature and Attention-deficit/Hyperactivity Disorder in Adolescents and Young Adults

Directory of Open Access Journals (Sweden)

Natalie J. Forde

2017-04-01

Full Text Available Magnetic resonance imaging (MRI studies have highlighted subcortical, cortical, and structural connectivity abnormalities associated with attention-deficit/hyperactivity disorder (ADHD. Gyrification investigations of the cortex have been inconsistent and largely negative, potentially due to a lack of sensitivity of the previously used morphological parameters. The innovative approach of applying intrinsic curvature analysis, which is predictive of gyrification pattern, to the cortical surface applied herein allowed us greater sensitivity to determine whether the structural connectivity abnormalities thus far identified at a centimeter scale also occur at a millimeter scale within the cortical surface. This could help identify neurodevelopmental processes that contribute to ADHD. Structural MRI datasets from the NeuroIMAGE project were used [n = 306 ADHD, n = 164 controls, and n = 148 healthy siblings of individuals with ADHD (age in years, mean(sd; 17.2 (3.4, 16.8 (3.2, and 17.7 (3.8, respectively]. Reconstructions of the cortical surfaces were computed with FreeSurfer. Intrinsic curvature (taken as a marker of millimeter-scale surface connectivity and local gyrification index were calculated for each point on the surface (vertex with Caret and FreeSurfer, respectively. Intrinsic curvature skew and mean local gyrification index were extracted per region; frontal, parietal, temporal, occipital, cingulate, and insula. A generalized additive model was used to compare the trajectory of these measures between groups over age, with sex, scanner site, total surface area of hemisphere, and familiality accounted for. After correcting for sex, scanner site, and total surface area no group differences were found in the developmental trajectory of intrinsic curvature or local gyrification index. Despite the increased sensitivity of intrinsic curvature, compared to gyrification measures, to subtle morphological abnormalities of the cortical surface we found

Collineations of the curvature tensor in general relativity

Indian Academy of Sciences (India)

Curvature collineations for the curvature tensor, constructed from a fundamental Bianchi Type-V metric, are studied. We are concerned with a symmetry property of space-time which is called curvature collineation, and we briefly discuss the physical and kinematical properties of the models.

Haptic perception of object curvature in Parkinson's disease.

Directory of Open Access Journals (Sweden)

Jürgen Konczak

2008-07-01

Full Text Available The haptic perception of the curvature of an object is essential for adequate object manipulation and critical for our guidance of actions. This study investigated how the ability to perceive the curvature of an object is altered by Parkinson's disease (PD.Eight healthy subjects and 11 patients with mild to moderate PD had to judge, without vision, the curvature of a virtual "box" created by a robotic manipulandum. Their hands were either moved passively along a defined curved path or they actively explored the curved curvature of a virtual wall. The curvature was either concave or convex (bulging to the left or right and was judged in two locations of the hand workspace--a left workspace location, where the curved hand path was associated with curved shoulder and elbow joint paths, and a right workspace location in which these joint paths were nearly linear. After exploring the curvature of the virtual object, subjects had to judge whether the curvature was concave or convex. Based on these data, thresholds for curvature sensitivity were established. The main findings of the study are: First, 9 out 11 PD patients (82% showed elevated thresholds for detecting convex curvatures in at least one test condition. The respective median threshold for the PD group was increased by 343% when compared to the control group. Second, when distal hand paths became less associated with proximal joint paths (right workspace, haptic acuity was reduced substantially in both groups. Third, sensitivity to hand trajectory curvature was not improved during active exploration in either group.Our data demonstrate that PD is associated with a decreased acuity of the haptic sense, which may occur already at an early stage of the disease.

A Basic Inequality for Submanifolds in Locally Conformal almost ...

Indian Academy of Sciences (India)

For submanifolds tangent to the structure vector field in locally conformal almost cosymplectic manifolds of pointwise constant -sectional curvature, we establish a basic inequality between the main intrinsic invariants of the submanifold on one side, namely its sectional curvature and its scalar curvature; and its main ...

Straight-line string with curvature

International Nuclear Information System (INIS)

Solov'ev, L.D.

1995-01-01

Classical and quantum solutions for the relativistic straight-line string with arbitrary dependence on the world surface curvature are obtained. They differ from the case of the usual Nambu-Goto interaction by the behaviour of the Regge trajectory which in general can be non-linear. A regularization of the action is considered and a comparison with relativistic point with curvature is made. 5 refs

Curvature of random walks and random polygons in confinement

International Nuclear Information System (INIS)

Diao, Y; Ernst, C; Montemayor, A; Ziegler, U

2013-01-01

The purpose of this paper is to study the curvature of equilateral random walks and polygons that are confined in a sphere. Curvature is one of several basic geometric properties that can be used to describe random walks and polygons. We show that confinement affects curvature quite strongly, and in the limit case where the confinement diameter equals the edge length the unconfined expected curvature value doubles from π/2 to π. To study curvature a simple model of an equilateral random walk in spherical confinement in dimensions 2 and 3 is introduced. For this simple model we derive explicit integral expressions for the expected value of the total curvature in both dimensions. These expressions are functions that depend only on the radius R of the confinement sphere. We then show that the values obtained by numeric integration of these expressions agrees with numerical average curvature estimates obtained from simulations of random walks. Finally, we compare the confinement effect on curvature of random walks with random polygons. (paper)

The curvature calculation mechanism based on simple cell model.

Science.gov (United States)

Yu, Haiyang; Fan, Xingyu; Song, Aiqi

2017-07-20

A conclusion has not yet been reached on how exactly the human visual system detects curvature. This paper demonstrates how orientation-selective simple cells can be used to construct curvature-detecting neural units. Through fixed arrangements, multiple plurality cells were constructed to simulate curvature cells with a proportional output to their curvature. In addition, this paper offers a solution to the problem of narrow detection range under fixed resolution by selecting an output value under multiple resolution. Curvature cells can be treated as concrete models of an end-stopped mechanism, and they can be used to further understand "curvature-selective" characteristics and to explain basic psychophysical findings and perceptual phenomena in current studies.

Integration of length and curvature in haptic perception

NARCIS (Netherlands)

Panday, V.; Bergmann Tiest, W.M.; Kappers, A.M.L.

2014-01-01

We investigated if and how length and curvature information are integrated when an object is explored in one hand. Subjects were asked to explore four types of objects between thumb and index finger. Objects differed in either length, curvature, both length and curvature correlated as in a circle,

A Field Theory with Curvature and Anticurvature

Directory of Open Access Journals (Sweden)

M. I. Wanas

2014-01-01

Full Text Available The present work is an attempt to construct a unified field theory in a space with curvature and anticurvature, the PAP-space. The theory is derived from an action principle and a Lagrangian density using a symmetric linear parameterized connection. Three different methods are used to explore physical contents of the theory obtained. Poisson’s equations for both material and charge distributions are obtained, as special cases, from the field equations of the theory. The theory is a pure geometric one in the sense that material distribution, charge distribution, gravitational and electromagnetic potentials, and other physical quantities are defined in terms of pure geometric objects of the structure used. In the case of pure gravity in free space, the spherical symmetric solution of the field equations gives the Schwarzschild exterior field. The weak equivalence principle is respected only in the case of pure gravity in free space; otherwise it is violated.

Evolution of the curvature perturbations during warm inflation

International Nuclear Information System (INIS)

Matsuda, Tomohiro

2009-01-01

This paper considers warm inflation as an interesting application of multi-field inflation. Delta-N formalism is used for the calculation of the evolution of the curvature perturbations during warm inflation. Although the perturbations considered in this paper are decaying after the horizon exit, the corrections to the curvature perturbations sourced by these perturbations can remain and dominate the curvature perturbations at large scales. In addition to the typical evolution of the curvature perturbations, inhomogeneous diffusion rate is considered for warm inflation, which may lead to significant non-Gaussianity of the spectrum

Weyl tensors for asymmetric complex curvatures

International Nuclear Information System (INIS)

Oliveira, C.G.

Considering a second rank Hermitian field tensor and a general Hermitian connection the associated complex curvature tensor is constructed. The Weyl tensor that corresponds to this complex curvature is determined. The formalism is applied to the Weyl unitary field theory and to the Moffat gravitational theory. (Author) [pt

Signed zeros of Gaussian vector fields - density, correlation functions and curvature

CERN Document Server

Foltin, G

2003-01-01

We calculate correlation functions of the (signed) density of zeros of Gaussian distributed vector fields. We are able to express correlation functions of arbitrary order through the curvature tensor of a certain abstract Riemann Cartan or Riemannian manifold. As an application, we discuss one- and two-point functions. The zeros of a two-dimensional Gaussian vector field model the distribution of topological defects in the high-temperature phase of two-dimensional systems with orientational degrees of freedom, such as superfluid films, thin superconductors and liquid crystals.

Surface meshing with curvature convergence

KAUST Repository

Li, Huibin; Zeng, Wei; Morvan, Jean-Marie; Chen, Liming; Gu, Xianfengdavid

2014-01-01

Surface meshing plays a fundamental role in graphics and visualization. Many geometric processing tasks involve solving geometric PDEs on meshes. The numerical stability, convergence rates and approximation errors are largely determined by the mesh qualities. In practice, Delaunay refinement algorithms offer satisfactory solutions to high quality mesh generations. The theoretical proofs for volume based and surface based Delaunay refinement algorithms have been established, but those for conformal parameterization based ones remain wide open. This work focuses on the curvature measure convergence for the conformal parameterization based Delaunay refinement algorithms. Given a metric surface, the proposed approach triangulates its conformal uniformization domain by the planar Delaunay refinement algorithms, and produces a high quality mesh. We give explicit estimates for the Hausdorff distance, the normal deviation, and the differences in curvature measures between the surface and the mesh. In contrast to the conventional results based on volumetric Delaunay refinement, our stronger estimates are independent of the mesh structure and directly guarantee the convergence of curvature measures. Meanwhile, our result on Gaussian curvature measure is intrinsic to the Riemannian metric and independent of the embedding. In practice, our meshing algorithm is much easier to implement and much more efficient. The experimental results verified our theoretical results and demonstrated the efficiency of the meshing algorithm. © 2014 IEEE.

Surface meshing with curvature convergence

KAUST Repository

Li, Huibin

2014-06-01

Surface meshing plays a fundamental role in graphics and visualization. Many geometric processing tasks involve solving geometric PDEs on meshes. The numerical stability, convergence rates and approximation errors are largely determined by the mesh qualities. In practice, Delaunay refinement algorithms offer satisfactory solutions to high quality mesh generations. The theoretical proofs for volume based and surface based Delaunay refinement algorithms have been established, but those for conformal parameterization based ones remain wide open. This work focuses on the curvature measure convergence for the conformal parameterization based Delaunay refinement algorithms. Given a metric surface, the proposed approach triangulates its conformal uniformization domain by the planar Delaunay refinement algorithms, and produces a high quality mesh. We give explicit estimates for the Hausdorff distance, the normal deviation, and the differences in curvature measures between the surface and the mesh. In contrast to the conventional results based on volumetric Delaunay refinement, our stronger estimates are independent of the mesh structure and directly guarantee the convergence of curvature measures. Meanwhile, our result on Gaussian curvature measure is intrinsic to the Riemannian metric and independent of the embedding. In practice, our meshing algorithm is much easier to implement and much more efficient. The experimental results verified our theoretical results and demonstrated the efficiency of the meshing algorithm. © 2014 IEEE.

Curvature constraints from the causal entropic principle

International Nuclear Information System (INIS)

Bozek, Brandon; Albrecht, Andreas; Phillips, Daniel

2009-01-01

Current cosmological observations indicate a preference for a cosmological constant that is drastically smaller than what can be explained by conventional particle physics. The causal entropic principle (Bousso et al.) provides an alternative approach to anthropic attempts to predict our observed value of the cosmological constant by calculating the entropy created within a causal diamond. We have extended this work to use the causal entropic principle to predict the preferred curvature within the 'multiverse'. We have found that values larger than ρ k =40ρ m are disfavored by more than 99.99% peak value at ρ Λ =7.9x10 -123 and ρ k =4.3ρ m for open universes. For universes that allow only positive curvature or both positive and negative curvature, we find a correlation between curvature and dark energy that leads to an extended region of preferred values. Our universe is found to be disfavored to an extent depending on the priors on curvature. We also provide a comparison to previous anthropic constraints on open universes and discuss future directions for this work.

An Efficient Local Algorithm for Distributed Multivariate Regression

Data.gov (United States)

National Aeronautics and Space Administration — This paper offers a local distributed algorithm for multivariate regression in large peer-to-peer environments. The algorithm is designed for distributed...

Higher-order curvature terms and extended inflation

International Nuclear Information System (INIS)

Wang Yun

1990-01-01

We consider higher-order curvature terms in context of the Brans-Dicke theory of gravity, and investigate the effects of these terms on extended inflationary theories. We find that the higher-order curvature terms tend to speed up inflation, although the original extended-inflation solutions are stable when these terms are small. Analytical solutions are found for two extreme cases: when the higher-order curvature terms are small, and when they dominate. A conformal transformation is employed in solving the latter case, and some of the subtleties in this technique are discussed. We note that percolation is less likely to occur when the higher-order curvature terms are present. An upper bound on α is expected if we are to avoid excessive and inadequate percolation of true-vacuum bubbles

A Scalable Local Algorithm for Distributed Multivariate Regression

Data.gov (United States)

National Aeronautics and Space Administration — This paper offers a local distributed algorithm for multivariate regression in large peer-to-peer environments. The algorithm can be used for distributed...

Constraining inverse curvature gravity with supernovae

Energy Technology Data Exchange (ETDEWEB)

Mena, Olga; Santiago, Jose; /Fermilab; Weller, Jochen; /University Coll., London /Fermilab

2005-10-01

We show that the current accelerated expansion of the Universe can be explained without resorting to dark energy. Models of generalized modified gravity, with inverse powers of the curvature can have late time accelerating attractors without conflicting with solar system experiments. We have solved the Friedman equations for the full dynamical range of the evolution of the Universe. This allows us to perform a detailed analysis of Supernovae data in the context of such models that results in an excellent fit. Hence, inverse curvature gravity models represent an example of phenomenologically viable models in which the current acceleration of the Universe is driven by curvature instead of dark energy. If we further include constraints on the current expansion rate of the Universe from the Hubble Space Telescope and on the age of the Universe from globular clusters, we obtain that the matter content of the Universe is 0.07 {le} {omega}{sub m} {le} 0.21 (95% Confidence). Hence the inverse curvature gravity models considered can not explain the dynamics of the Universe just with a baryonic matter component.

Hamiltonian analysis of curvature-squared gravity with or without conformal invariance

Science.gov (United States)

KlusoÅ, Josef; Oksanen, Markku; Tureanu, Anca

2014-03-01

We analyze gravitational theories with quadratic curvature terms, including the case of conformally invariant Weyl gravity, motivated by the intention to find a renormalizable theory of gravity in the ultraviolet region, yet yielding general relativity at long distances. In the Hamiltonian formulation of Weyl gravity, the number of local constraints is equal to the number of unstable directions in phase space, which in principle could be sufficient for eliminating the unstable degrees of freedom in the full nonlinear theory. All the other theories of quadratic type are unstable—a problem appearing as ghost modes in the linearized theory. We find that the full projection of the Weyl tensor onto a three-dimensional hypersurface contains an additional fully traceless component, given by a quadratic extrinsic curvature tensor. A certain inconsistency in the literature is found and resolved: when the conformal invariance of Weyl gravity is broken by a cosmological constant term, the theory becomes pathological, since a constraint required by the Hamiltonian analysis imposes the determinant of the metric of spacetime to be zero. In order to resolve this problem by restoring the conformal invariance, we introduce a new scalar field that couples to the curvature of spacetime, reminiscent of the introduction of vector fields for ensuring the gauge invariance.

Novel tilt-curvature coupling in lipid membranes

Science.gov (United States)

Terzi, M. Mert; Deserno, Markus

2017-08-01

On mesoscopic scales, lipid membranes are well described by continuum theories whose main ingredients are the curvature of a membrane's reference surface and the tilt of its lipid constituents. In particular, Hamm and Kozlov [Eur. Phys. J. E 3, 323 (2000)] have shown how to systematically derive such a tilt-curvature Hamiltonian based on the elementary assumption of a thin fluid elastic sheet experiencing internal lateral pre-stress. Performing a dimensional reduction, they not only derive the basic form of the effective surface Hamiltonian but also express its emergent elastic couplings as trans-membrane moments of lower-level material parameters. In the present paper, we argue, though, that their derivation unfortunately missed a coupling term between curvature and tilt. This term arises because, as one moves along the membrane, the curvature-induced change of transverse distances contributes to the area strain—an effect that was believed to be small but nevertheless ends up contributing at the same (quadratic) order as all other terms in their Hamiltonian. We illustrate the consequences of this amendment by deriving the monolayer and bilayer Euler-Lagrange equations for the tilt, as well as the power spectra of shape, tilt, and director fluctuations. A particularly curious aspect of our new term is that its associated coupling constant is the second moment of the lipid monolayer's lateral stress profile—which within this framework is equal to the monolayer Gaussian curvature modulus, κ¯ m. On the one hand, this implies that many theoretical predictions now contain a parameter that is poorly known (because the Gauss-Bonnet theorem limits access to the integrated Gaussian curvature); on the other hand, the appearance of κ¯ m outside of its Gaussian curvature provenance opens opportunities for measuring it by more conventional means, for instance by monitoring a membrane's undulation spectrum at short scales.

Diffusive real-time dynamics of a particle with Berry curvature

Science.gov (United States)

Misaki, Kou; Miyashita, Seiji; Nagaosa, Naoto

2018-02-01

We study theoretically the influence of Berry phase on the real-time dynamics of the single particle focusing on the diffusive dynamics, i.e., the time dependence of the distribution function. Our model can be applied to the real-time dynamics of intraband relaxation and diffusion of optically excited excitons, trions, or particle-hole pair. We found that the dynamics at the early stage is deeply influenced by the Berry curvature in real space (B ), momentum space (Ω ), and also the crossed space between these two (C ). For example, it is found that Ω induces the rotation of the wave packet and causes the time dependence of the mean square displacement of the particle to be linear in time t at the initial stage; it is qualitatively different from the t3 dependence in the absence of the Berry curvature. It is also found that Ω and C modify the characteristic time scale of the thermal equilibration of momentum distribution. Moreover, the dynamics under various combinations of B ,Ω , and C shows singular behaviors such as the critical slowing down or speeding up of the momentum equilibration and the reversals of the direction of rotations. The relevance of our model for time-resolved experiments in transition metal dichalcogenides is also discussed.

Binding-energy distribution and dephasing of localized biexcitons

DEFF Research Database (Denmark)

Langbein, Wolfgang Werner; Hvam, Jørn Märcher; Umlauff, M.

1997-01-01

We report on the binding energy and dephasing of localized biexciton states in narrow ZnSe multiple quantum wells. The measured binding-energy distribution of the localized biexcitons shows a width of 2.2 meV centered at 8.5 meV, and is fairly independent of the exciton localization energy. In fo...

The curvature function in general relativity

International Nuclear Information System (INIS)

Hall, G S; MacNay, Lucy

2006-01-01

A function, here called the curvature function, is defined and which is constructed explicitly from the type (0, 4) curvature tensor. Although such a function may be defined for any manifold admitting a metric, attention is here concentrated on this function on a spacetime. Some properties of this function are explored and compared with a previous discussion of it given by Petrov

Curvature of Indoor Sensor Network: Clustering Coefficient

Directory of Open Access Journals (Sweden)

2009-03-01

Full Text Available We investigate the geometric properties of the communication graph in realistic low-power wireless networks. In particular, we explore the concept of the curvature of a wireless network via the clustering coefficient. Clustering coefficient analysis is a computationally simplified, semilocal approach, which nevertheless captures such a large-scale feature as congestion in the underlying network. The clustering coefficient concept is applied to three cases of indoor sensor networks, under varying thresholds on the link packet reception rate (PRR. A transition from positive curvature (“meshed” network to negative curvature (“core concentric” network is observed by increasing the threshold. Even though this paper deals with network curvature per se, we nevertheless expand on the underlying congestion motivation, propose several new concepts (network inertia and centroid, and finally we argue that greedy routing on a virtual positively curved network achieves load balancing on the physical network.

Inverse curvature flows in asymptotically Robertson Walker spaces

Science.gov (United States)

Kröner, Heiko

2018-04-01

In this paper we consider inverse curvature flows in a Lorentzian manifold N which is the topological product of the real numbers with a closed Riemannian manifold and equipped with a Lorentzian metric having a future singularity so that N is asymptotically Robertson Walker. The flow speeds are future directed and given by 1 / F where F is a homogeneous degree one curvature function of class (K*) of the principal curvatures, i.e. the n-th root of the Gauss curvature. We prove longtime existence of these flows and that the flow hypersurfaces converge to smooth functions when they are rescaled with a proper factor which results from the asymptotics of the metric.

Curvature driven instabilities in toroidal plasmas

International Nuclear Information System (INIS)

Andersson, P.

1986-11-01

The electromagnetic ballooning mode, the curvature driven trapped electron mode and the toroidally induced ion temperature gradient mode have been studies. Eigenvalue equations have been derived and solved both numerically and analytically. For electromagnetic ballooning modes the effects of convective damping, finite Larmor radius, higher order curvature terms, and temperature gradients have been investigated. A fully toroidal fluid ion model has been developed. It is shown that a necessary and sufficient condition for an instability below the MHD limit is the presence of an ion temperature gradient. Analytical dispersion relations giving results in good agreement with numerical solutions are also presented. The curvature driven trapped electron modes are found to be unstable for virtually all parameters with growth rates of the order of the diamagnetic drift frequency. Studies have been made, using both a gyrokinetic ion description and the fully toroidal ion model. Both analytical and numerical results are presented and are found to be in good agreement. The toroidally induced ion temperature gradients modes are found to have a behavior similar to that of the curvature driven trapped electron modes and can in the electrostatic limit be described by a simple quadratic dispersion equation. (author)

Gas-leak localization using distributed ultrasonic sensors

Science.gov (United States)

Huseynov, Javid; Baliga, Shankar; Dillencourt, Michael; Bic, Lubomir; Bagherzadeh, Nader

2009-03-01

We propose an ultrasonic gas leak localization system based on a distributed network of sensors. The system deploys highly sensitive miniature Micro-Electro-Mechanical Systems (MEMS) microphones and uses a suite of energy-decay (ED) and time-delay of arrival (TDOA) algorithms for localizing a source of a gas leak. Statistical tools such as the maximum likelihood (ML) and the least squares (LS) estimators are used for approximating the source location when closed-form solutions fail in the presence of ambient background nuisance and inherent electronic noise. The proposed localization algorithms were implemented and tested using a Java-based simulation platform connected to four or more distributed MEMS microphones observing a broadband nitrogen leak from an orifice. The performance of centralized and decentralized algorithms under ED and TDOA schemes is analyzed and compared in terms of communication overhead and accuracy in presence of additive white Gaussian noise (AWGN).

Statistical mechanics of paths with curvature dependent action

International Nuclear Information System (INIS)

Ambjoern, J.; Durhuus, B.; Jonsson, T.

1987-01-01

We analyze the scaling limit of discretized random paths with curvature dependent action. For finite values of the curvature coupling constant the theory belongs to the universality class of simple random walk. It is possible to define a non-trivial scaling limit if the curvature coupling tends to infinity. We compute exactly the two point function in this limit and discuss the relevance of our results for random surfaces and string theories. (orig.)

GDP growth and the yield curvature

DEFF Research Database (Denmark)

Møller, Stig Vinther

2014-01-01

This paper examines the forecastability of GDP growth using information from the term structure of yields. In contrast to previous studies, the paper shows that the curvature of the yield curve contributes with much more forecasting power than the slope of yield curve. The yield curvature also...... predicts bond returns, implying a common element to time-variation in expected bond returns and expected GDP growth....

On hyperbolic U4 manifolds with local duality

International Nuclear Information System (INIS)

Wallner, R.P.

1982-01-01

We use the decomposition of the Riemann/Cartan curvature 2-forms Ωsup(ij) in terms of their irreducible parts under the Lorentz group to examine the irreducible content of self- and anti-self double dual curvature forms Ωsup(+-ij) and their further refinements involving left and right duals. In the case of local duality (i.e. Ωsup(ij) = Ωsup(+-ij) locally), some consequences to curvature and torsion are easily derived in this way. As Riemann/Cartan space-times (U 4 -space-times) are subject to generalized gravity theories, some (vacuum) field equations proposed there are also taken into considerations. As an application to the various decompositions of curvature and torsion we point out their utility in the search of exact solutions of U 4 -field equations. To simplify notations and calculations, the calculus of exterior forms is used throughout. (Author)

Face recognition based on depth maps and surface curvature

Science.gov (United States)

Gordon, Gaile G.

1991-09-01

This paper explores the representation of the human face by features based on the curvature of the face surface. Curature captures many features necessary to accurately describe the face, such as the shape of the forehead, jawline, and cheeks, which are not easily detected from standard intensity images. Moreover, the value of curvature at a point on the surface is also viewpoint invariant. Until recently range data of high enough resolution and accuracy to perform useful curvature calculations on the scale of the human face had been unavailable. Although several researchers have worked on the problem of interpreting range data from curved (although usually highly geometrically structured) surfaces, the main approaches have centered on segmentation by signs of mean and Gaussian curvature which have not proved sufficient in themselves for the case of the human face. This paper details the calculation of principal curvature for a particular data set, the calculation of general surface descriptors based on curvature, and the calculation of face specific descriptors based both on curvature features and a priori knowledge about the structure of the face. These face specific descriptors can be incorporated into many different recognition strategies. A system that implements one such strategy, depth template comparison, giving recognition rates between 80% and 90% is described.

Six-dimensional localized black holes: Numerical solutions

International Nuclear Information System (INIS)

Kudoh, Hideaki

2004-01-01

To test the strong-gravity regime in Randall-Sundrum braneworlds, we consider black holes bound to a brane. In a previous paper, we studied numerical solutions of localized black holes whose horizon radii are smaller than the AdS curvature radius. In this paper, we improve the numerical method and discuss properties of the six-dimensional (6D) localized black holes whose horizon radii are larger than the AdS curvature radius. At a horizon temperature T≅1/2πl, the thermodynamics of the localized black hole undergo a transition with its character changing from a 6D Schwarzschild black hole type to a 6D black string type. The specific heat of the localized black holes is negative, and the entropy is greater than or nearly equal to that of the 6D black strings with the same thermodynamic mass. The large localized black holes show flattened horizon geometries, and the intrinsic curvature of the horizon four-geometry becomes negative near the brane. Our results indicate that the recovery mechanism of lower-dimensional Einstein gravity on the brane works even in the presence of the black holes

Generalized Curvature-Matter Couplings in Modified Gravity

Directory of Open Access Journals (Sweden)

Tiberiu Harko

2014-07-01

Full Text Available In this work, we review a plethora of modified theories of gravity with generalized curvature-matter couplings. The explicit nonminimal couplings, for instance, between an arbitrary function of the scalar curvature R and the Lagrangian density of matter, induces a non-vanishing covariant derivative of the energy-momentum tensor, implying non-geodesic motion and, consequently, leads to the appearance of an extra force. Applied to the cosmological context, these curvature-matter couplings lead to interesting phenomenology, where one can obtain a unified description of the cosmological epochs. We also consider the possibility that the behavior of the galactic flat rotation curves can be explained in the framework of the curvature-matter coupling models, where the extra terms in the gravitational field equations modify the equations of motion of test particles and induce a supplementary gravitational interaction. In addition to this, these models are extremely useful for describing dark energy-dark matter interactions and for explaining the late-time cosmic acceleration.

A curvature theory for discrete surfaces based on mesh parallelity

KAUST Repository

Bobenko, Alexander Ivanovich

2009-12-18

We consider a general theory of curvatures of discrete surfaces equipped with edgewise parallel Gauss images, and where mean and Gaussian curvatures of faces are derived from the faces\\' areas and mixed areas. Remarkably these notions are capable of unifying notable previously defined classes of surfaces, such as discrete isothermic minimal surfaces and surfaces of constant mean curvature. We discuss various types of natural Gauss images, the existence of principal curvatures, constant curvature surfaces, Christoffel duality, Koenigs nets, contact element nets, s-isothermic nets, and interesting special cases such as discrete Delaunay surfaces derived from elliptic billiards. © 2009 Springer-Verlag.

Modeling of liquid–gas meniscus for textured surfaces: effects of curvature and local slip length

International Nuclear Information System (INIS)

Gaddam, Anvesh; Garg, Mayank; Agrawal, Amit; Joshi, Suhas S

2015-01-01

Surface texturing at the micro/nanolevel allows air to be trapped in sufficiently small cavities, thereby reducing the flow resistance over the surface in the laminar regime. The nature of the liquid–gas meniscus plays an important role in defining the boundary condition and it depends on the flow conditions and geometrical properties of textures. In the present work, we employ the unsteady volume of fluid model to investigate the behavior of the liquid–gas meniscus for ridges arranged normal to the flow direction to substantiate the frictional resistance of flow in a microchannel. It is found that the assumption of ‘zero shear stress’ at the liquid–gas interface grossly overpredicts the effective slip length with meniscus curvature and local partial slip length playing the dominant role. Numerical simulations performed in the laminar regime (20  <  Re  <  120) over single layered ridges normal to the flow direction revealed the effect of texture geometry on the reduction in pressure drop. In single layered structures, lotus-like geometries exhibited a greater reduction in drag (more than 30%) when compared to all other texture geometries. It is recognized that the flow experiences expansion and contraction cycles as it flows over the transverse ridges increasing the frictional resistance. Our findings will help to modify the boundary condition at the liquid–gas meniscus for accurate modeling in the laminar regime and to optimize the texture geometry to improve drag reduction. (paper)

Maximal hypersurfaces and foliations of constant mean curvature in general relativity

International Nuclear Information System (INIS)

Marsden, J.E.; Tipler, F.J.; Texas Univ., Austin

1980-01-01

We prove theorems on existence, uniqueness and smoothness of maximal and constant mean curvature compact spacelike hypersurfaces in globally hyperbolic spacetimes. The uniqueness theorem for maximal hypersurfaces of Brill and Flaherty, which assumed matter everywhere, is extended to specetimes that are vacuum and non-flat or that satisfy a generic-type condition. In this connection we show that under general hypotheses, a spatially closed universe with a maximal hypersurface must be Wheeler universe; i.e. be closed in time as well. The existence of Lipschitz achronal maximal volume hypersurfaces under the hypothesis that candidate hypersurfaces are bounded away from the singularity is proved. This hypothesis is shown to be valid in two cases of interest: when the singularities are of strong curvature type, and when the singularity is a single ideal point. Some properties of these maximal volume hypersurfaces and difficulties with Avez' original arguments are discussed. The difficulties involve the possibility that the maximal volume hypersurface can be null on certain portions; we present an incomplete argument which suggests that these hypersurfaces are always smooth, but prove that an a priori bound on the second fundamental form does imply smoothness. An extension of the perturbation theorem of Choquet-Bruhat, Fischer and Marsden is given and conditions under which local foliantions by constant mean curvature hypersurfaces can be extended to global ones is obtained. (orig.)

Translating solitons to symplectic and Lagrangian mean curvature flows

International Nuclear Information System (INIS)

Han Xiaoli; Li Jiayu

2007-05-01

In this paper, we construct finite blow-up examples for symplectic mean curvature flows and we study symplectic translating solitons. We prove that there is no translating solitons with vertical bar α vertical bar ≤ α 0 to the symplectic mean curvature flow or to the almost calibrated Lagrangian mean curvature flow for some α 0 . (author)

Evaluation and mitigation of potential errors in radiochromic film dosimetry due to film curvature at scanning.

Science.gov (United States)

Palmer, Antony L; Bradley, David A; Nisbet, Andrew

2015-03-08

This work considers a previously overlooked uncertainty present in film dosimetry which results from moderate curvature of films during the scanning process. Small film samples are particularly susceptible to film curling which may be undetected or deemed insignificant. In this study, we consider test cases with controlled induced curvature of film and with film raised horizontally above the scanner plate. We also evaluate the difference in scans of a film irradiated with a typical brachytherapy dose distribution with the film naturally curved and with the film held flat on the scanner. Typical naturally occurring curvature of film at scanning, giving rise to a maximum height 1 to 2 mm above the scan plane, may introduce dose errors of 1% to 4%, and considerably reduce gamma evaluation passing rates when comparing film-measured doses with treatment planning system-calculated dose distributions, a common application of film dosimetry in radiotherapy. The use of a triple-channel dosimetry algorithm appeared to mitigate the error due to film curvature compared to conventional single-channel film dosimetry. The change in pixel value and calibrated reported dose with film curling or height above the scanner plate may be due to variations in illumination characteristics, optical disturbances, or a Callier-type effect. There is a clear requirement for physically flat films at scanning to avoid the introduction of a substantial error source in film dosimetry. Particularly for small film samples, a compression glass plate above the film is recommended to ensure flat-film scanning. This effect has been overlooked to date in the literature.

Curvature reduces bending strains in the quokka femur

Directory of Open Access Journals (Sweden)

Kyle McCabe

2017-03-01

Full Text Available This study explores how curvature in the quokka femur may help to reduce bending strain during locomotion. The quokka is a small wallaby, but the curvature of the femur and the muscles active during stance phase are similar to most quadrupedal mammals. Our hypothesis is that the action of hip extensor and ankle plantarflexor muscles during stance phase place cranial bending strains that act to reduce the caudal curvature of the femur. Knee extensors and biarticular muscles that span the femur longitudinally create caudal bending strains in the caudally curved (concave caudal side bone. These opposing strains can balance each other and result in less strain on the bone. We test this idea by comparing the performance of a normally curved finite element model of the quokka femur to a digitally straightened version of the same bone. The normally curved model is indeed less strained than the straightened version. To further examine the relationship between curvature and the strains in the femoral models, we also tested an extra-curved and a reverse-curved version with the same loads. There appears to be a linear relationship between the curvature and the strains experienced by the models. These results demonstrate that longitudinal curvature in bones may be a manipulable mechanism whereby bone can induce a strain gradient to oppose strains induced by habitual loading.

Lecture notes on mean curvature flow, barriers and singular perturbations

CERN Document Server

Bellettini, Giovanni

2013-01-01

The aim of the book is to study some aspects of geometric evolutions, such as mean curvature flow and anisotropic mean curvature flow of hypersurfaces. We analyze the origin of such flows and their geometric and variational nature. Some of the most important aspects of mean curvature flow are described, such as the comparison principle and its use in the definition of suitable weak solutions. The anisotropic evolutions, which can be considered as a generalization of mean curvature flow, are studied from the view point of Finsler geometry. Concerning singular perturbations, we discuss the convergence of the Allen–Cahn (or Ginsburg–Landau) type equations to (possibly anisotropic) mean curvature flow before the onset of singularities in the limit problem. We study such kinds of asymptotic problems also in the static case, showing convergence to prescribed curvature-type problems.

Automated leak localization performance without detailed demand distribution data

NARCIS (Netherlands)

Moors, Janneke; Scholten, L.; van der Hoek, J.P.; den Besten, J.

2018-01-01

Automatic leak localization has been suggested to reduce the time and personnel efforts needed to localize
(small) leaks. Yet, the available methods require a detailed demand distribution model for successful
calibration and good leak localization performance. The main aim of this work was

Dynamic curvature sensing employing ionic-polymer–metal composite sensors

International Nuclear Information System (INIS)

Bahramzadeh, Yousef; Shahinpoor, Mohsen

2011-01-01

A dynamic curvature sensor is presented based on ionic-polymer–metal composite (IPMC) for curvature monitoring of deployable/inflatable dynamic space structures. Monitoring the curvature variation is of high importance in various engineering structures including shape monitoring of deployable/inflatable space structures in which the structural boundaries undergo a dynamic deployment process. The high sensitivity of IPMCs to the applied deformations as well as its flexibility make IPMCs a promising candidate for sensing of dynamic curvature changes. Herein, we explore the dynamic response of an IPMC sensor strip with respect to controlled curvature deformations subjected to different forms of input functions. Using a specially designed experimental setup, the voltage recovery effect, phase delay, and rate dependency of the output voltage signal of an IPMC curvature sensor are analyzed. Experimental results show that the IPMC sensor maintains the linearity, sensitivity, and repeatability required for curvature sensing. Besides, in order to describe the dynamic phenomena such as the rate dependency of the IPMC sensor, a chemo-electro-mechanical model based on the Poisson–Nernst–Planck (PNP) equation for the kinetics of ion diffusion is presented. By solving the governing partial differential equations the frequency response of the IPMC sensor is derived. The physical model is able to describe the dynamic properties of the IPMC sensor and the dependency of the signal on rate of excitations

Cosmological backreaction within the Szekeres model and emergence of spatial curvature

Energy Technology Data Exchange (ETDEWEB)

Bolejko, Krzysztof, E-mail: krzysztof.bolejko@sydney.edu.au [Sydney Institute for Astronomy, School of Physics A28, The University of Sydney, Sydney, NSW, 2006 (Australia)

2017-06-01

This paper discusses the phenomenon of backreaction within the Szekeres model. Cosmological backreaction describes how the mean global evolution of the Universe deviates from the Friedmannian evolution. The analysis is based on models of a single cosmological environment and the global ensemble of the Szekeres models (of the Swiss-Cheese-type and Styrofoam-type). The obtained results show that non-linear growth of cosmic structures is associated with the growth of the spatial curvature Ω{sub R} (in the FLRW limit Ω{sub R} → Ω {sub k} ). If averaged over global scales the result depends on the assumed global model of the Universe. Within the Swiss-Cheese model, which does have a fixed background, the volume average follows the evolution of the background, and the global spatial curvature averages out to zero (the background model is the ΛCDM model, which is spatially flat). In the Styrofoam-type model, which does not have a fixed background, the mean evolution deviates from the spatially flat ΛCDM model, and the mean spatial curvature evolves from Ω{sub R} =0 at the CMB to Ω{sub R} ∼ 0.1 at 0 z =. If the Styrofoam-type model correctly captures evolutionary features of the real Universe then one should expect that in our Universe, the spatial curvature should build up (local growth of cosmic structures) and its mean global average should deviate from zero (backreaction). As a result, this paper predicts that the low-redshift Universe should not be spatially flat (i.e. Ω {sub k} ≠ 0, even if in the early Universe Ω {sub k} = 0) and therefore when analysing low- z cosmological data one should keep Ω {sub k} as a free parameter and independent from the CMB constraints.

Continuous-Curvature Path Generation Using Fermat's Spiral

Directory of Open Access Journals (Sweden)

Anastasios M. Lekkas

2013-10-01

Full Text Available This paper proposes a novel methodology, based on Fermat's spiral (FS, for constructing curvature-continuous parametric paths in a plane. FS has a zero curvature at its origin, a property that allows it to be connected with a straight line smoothly, that is, without the curvature discontinuity which occurs at the transition point between a line and a circular arc when constructing Dubins paths. Furthermore, contrary to the computationally expensive clothoids, FS is described by very simple parametric equations that are trivial to compute. On the downside, computing the length of an FS arc involves a Gaussian hypergeometric function. However, this function is absolutely convergent and it is also shown that it poses no restrictions to the domain within which the length can be calculated. In addition, we present an alternative parametrization of FS which eliminates the parametric speed singularity at the origin, hence making the spiral suitable for path-tracking applications. A detailed description of how to construct curvature-continuous paths with FS is given.

Influence of Coanda surface curvature on performance of bladeless fan

Science.gov (United States)

Li, Guoqi; Hu, Yongjun; Jin, Yingzi; Setoguchi, Toshiaki; Kim, Heuy Dong

2014-10-01

The unique Coanda surface has a great influence on the performance of bladeless fan. However, there is few studies to explain the relationship between the performance and Coanda surface curvature at present. In order to gain a qualitative understanding of effect of the curvature on the performance of bladeless fan, numerical studies are performed in this paper. Firstly, three-dimensional numerical simulation is done by Fluent software. For the purpose to obtain detailed information of the flow field around the Coanda surface, two-dimensional numerical simulation is also conducted. Five types of Coanda surfaces with different curvature are designed, and the flow behaviour and the performance of them are analyzed and compared with those of the prototype. The analysis indicates that the curvature of Coanda surface is strongly related to blowing performance, It is found that there is an optimal curvature of Coanda surfaces among the studied models. Simulation result shows that there is a special low pressure region. With increasing curvature in Y direction, several low pressure regions gradually enlarged, then begin to merge slowly, and finally form a large area of low pressure. From the analyses of streamlines and velocity angle, it is found that the magnitude of the curvature affects the flow direction and reasonable curvature can induce fluid flow close to the wall. Thus, it leads to that the curvature of the streamlines is consistent with that of Coanda surface. Meanwhile, it also causes the fluid movement towards the most suitable direction. This study will provide useful information to performance improvements of bladeless fans.

Substrate curvature gradient drives rapid droplet motion.

Science.gov (United States)

Lv, Cunjing; Chen, Chao; Chuang, Yin-Chuan; Tseng, Fan-Gang; Yin, Yajun; Grey, Francois; Zheng, Quanshui

2014-07-11

Making small liquid droplets move spontaneously on solid surfaces is a key challenge in lab-on-chip and heat exchanger technologies. Here, we report that a substrate curvature gradient can accelerate micro- and nanodroplets to high speeds on both hydrophilic and hydrophobic substrates. Experiments for microscale water droplets on tapered surfaces show a maximum speed of 0.42  m/s, 2 orders of magnitude higher than with a wettability gradient. We show that the total free energy and driving force exerted on a droplet are determined by the substrate curvature and substrate curvature gradient, respectively. Using molecular dynamics simulations, we predict nanoscale droplets moving spontaneously at over 100  m/s on tapered surfaces.

Effect of nano-scale curvature on the intrinsic blood coagulation system

Science.gov (United States)

Kushida, Takashi; Saha, Krishnendu; Subramani, Chandramouleeswaran; Nandwana, Vikas; Rotello, Vincent M.

2014-11-01

The intrinsic coagulation activity of silica nanoparticles strongly depends on their surface curvature. Nanoparticles with higher surface curvature do not denature blood coagulation factor XII on its surface, providing a coagulation `silent' surface, while nanoparticles with lower surface curvature show denaturation and concomitant coagulation.The intrinsic coagulation activity of silica nanoparticles strongly depends on their surface curvature. Nanoparticles with higher surface curvature do not denature blood coagulation factor XII on its surface, providing a coagulation `silent' surface, while nanoparticles with lower surface curvature show denaturation and concomitant coagulation. Electronic supplementary information (ESI) available: Physical properties and scanning electron micrographs (SEM) of silica NPs, intrinsic coagulation activity after 3 h. See DOI: 10.1039/c4nr04128c

Effect of Plate Curvature on Blast Response of Structural Steel Plates

Science.gov (United States)

Veeredhi, Lakshmi Shireen Banu; Ramana Rao, N. V.; Veeredhi, Vasudeva Rao

2018-04-01

In the present work an attempt is made, through simulation studies, to determine the effect of plate curvature on the blast response of a door structure made of ASTM A515 grade 50 steel plates. A door structure with dimensions of 5.142 m × 2.56 m × 10 mm having six different radii of curvatures is analyzed which is subjected to blast load. The radii of curvature investigated are infinity (flat plate), 16.63, 10.81, 8.26, 6.61 and 5.56 m. In the present study, a stand-off distance of 11 m is considered for all the cases. Results showed that the door structure with smallest radius of curvature experienced least plastic deformation and yielding when compared to a door with larger radius of curvature with same projected area. From the present Investigation, it is observed that, as the radius of curvature of the plate increases, the deformation mode gradually shifts from indentation mode to flexural mode. The plates with infinity and 16.63 m radius of curvature have undergone flexural mode of deformation and plates with 6.61 and 5.56 m radius of curvature undergo indentation mode of deformation. Whereas, mixed mode of deformation that consists of both flexural and indentation mode of deformations are seen in the plates with radius of curvature 10.81 and 8.26 m. As the radius of curvature of the plate decreases the ability of the plate to mitigate the effect the blast loads increased. It is observed that the plate with smaller radius of curvature deflects most of the blast energy and results in least indentation mode of deformation. The most significant observation made in the present investigation is that the strain energy absorbed by the steel plate gets reduced to 1/3 rd when the radius of curvature is approximately equal to the stand-off distance which could be the critical radius of curvature.

On Riemannian manifolds (Mn, g) of quasi-constant curvature

International Nuclear Information System (INIS)

Rahman, M.S.

1995-07-01

A Riemannian manifold (M n , g) of quasi-constant curvature is defined. It is shown that an (M n , g) in association with other class of manifolds gives rise, under certain conditions, to a manifold of quasi-constant curvature. Some observations on how a manifold of quasi-constant curvature accounts for a pseudo Ricci-symmetric manifold and quasi-umbilical hypersurface are made. (author). 10 refs

SLED phenomenology: curvature vs. volume

International Nuclear Information System (INIS)

Niedermann, Florian; Schneider, Robert

2016-01-01

We assess the question whether the SLED (Supersymmetric Large Extra Dimensions) model admits phenomenologically viable solutions with 4D maximal symmetry. We take into account a finite brane width and a scale invariance (SI) breaking dilaton-brane coupling, both of which should be included in a realistic setup. Provided that the brane tension and the microscopic size of the brane take generic values set by the fundamental bulk Planck scale, we find that either the 4D curvature or the size of the extra dimensions is unacceptably large. Since this result is independent of the dilaton-brane couplings, it provides the biggest challenge to the SLED program. In addition, to quantify its potential with respect to the cosmological constant problem, we infer the amount of tuning on model parameters required to obtain a sufficiently small 4D curvature. A first answer was recently given in http://dx.doi.org/10.1007/JHEP02(2016)025, showing that 4D flat solutions are only ensured in the SI case by imposing a tuning relation, even if a brane-localized flux is included. In this companion paper, we find that the tuning can in fact be avoided for certain SI breaking brane-dilaton couplings, but only at the price of worsening the phenomenological problem. Our results are obtained by solving the full coupled Einstein-dilaton system in a completely consistent way. The brane width is implemented using a well-known ring regularization. In passing, we note that for the couplings considered here the results of http://dx.doi.org/10.1007/JHEP02(2016)025 (which only treated infinitely thin branes) are all consistently recovered in the thin brane limit, and how this can be reconciled with the concerns about their correctness, recently brought up in http://dx.doi.org/10.1007/JHEP01(2016)017.

Curvature collineations for the field of gravitational waves

International Nuclear Information System (INIS)

Singh, K.P.; Singh, Gulab

1981-01-01

It has been shown that the space-times formed from a plane-fronted gravity wave and from a plane sandwich wave with constant polarisation admit proper curvature collineation in general. The curvature collineation vectors have been determined explicitly. (author)

Local invariants vanishing on stationary horizons: a diagnostic for locating black holes.

Science.gov (United States)

Page, Don N; Shoom, Andrey A

2015-04-10

Inspired by the example of Abdelqader and Lake for the Kerr metric, we construct local scalar polynomial curvature invariants that vanish on the horizon of any stationary black hole: the squared norms of the wedge products of n linearly independent gradients of scalar polynomial curvature invariants, where n is the local cohomogeneity of the spacetime.

Local gradient estimate for harmonic functions on Finsler manifolds

OpenAIRE

Xia, Chao

2013-01-01

In this paper, we prove the local gradient estimate for harmonic functions on complete, noncompact Finsler measure spaces under the condition that the weighted Ricci curvature has a lower bound. As applications, we obtain Liouville type theorem on Finsler manifolds with nonnegative Ricci curvature.

Remarks on the boundary curve of a constant mean curvature topological disc

DEFF Research Database (Denmark)

Brander, David; Lopéz, Rafael

2017-01-01

We discuss some consequences of the existence of the holomorphic quadratic Hopf differential on a conformally immersed constant mean curvature topological disc with analytic boundary. In particular, we derive a formula for the mean curvature as a weighted average of the normal curvature of the bo......We discuss some consequences of the existence of the holomorphic quadratic Hopf differential on a conformally immersed constant mean curvature topological disc with analytic boundary. In particular, we derive a formula for the mean curvature as a weighted average of the normal curvature...

Cosmic curvature from de Sitter equilibrium cosmology.

Science.gov (United States)

Albrecht, Andreas

2011-10-07

I show that the de Sitter equilibrium cosmology generically predicts observable levels of curvature in the Universe today. The predicted value of the curvature, Ω(k), depends only on the ratio of the density of nonrelativistic matter to cosmological constant density ρ(m)(0)/ρ(Λ) and the value of the curvature from the initial bubble that starts the inflation, Ω(k)(B). The result is independent of the scale of inflation, the shape of the potential during inflation, and many other details of the cosmology. Future cosmological measurements of ρ(m)(0)/ρ(Λ) and Ω(k) will open up a window on the very beginning of our Universe and offer an opportunity to support or falsify the de Sitter equilibrium cosmology.

Radion stabilization in higher curvature warped spacetime

Energy Technology Data Exchange (ETDEWEB)

Das, Ashmita [Indian Institute of Technology, Department of Physics, Guwahati, Assam (India); Mukherjee, Hiya; Paul, Tanmoy; SenGupta, Soumitra [Indian Association for the Cultivation of Science, Department of Theoretical Physics, Kolkata (India)

2018-02-15

We consider a five dimensional AdS spacetime in presence of higher curvature term like F(R) = R + αR{sup 2} in the bulk. In this model, we examine the possibility of modulus stabilization from the scalar degrees of freedom of higher curvature gravity free of ghosts. Our result reveals that the model stabilizes itself and the mechanism of modulus stabilization can be argued from a geometric point of view. We determine the region of the parametric space for which the modulus (or radion) can to be stabilized. We also show how the mass and coupling parameters of radion field are modified due to higher curvature term leading to modifications of its phenomenological implications on the visible 3-brane. (orig.)

Effect of diffraction and film-thickness gradients on wafer-curvature measurements of thin-film stress

International Nuclear Information System (INIS)

Breiland, W.G.; Lee, S.R.; Koleske, D.D.

2004-01-01

When optical measurements of wafer curvature are used to determine thin-film stress, the laser beams that probe the sample are usually assumed to reflect specularly from the curved surface of the film and substrate. Yet, real films are not uniformly thick, and unintended thickness gradients produce optical diffraction effects that steer the laser away from the ideal specular condition. As a result, the deflection of the laser in wafer-curvature measurements is actually sensitive to both the film stress and the film-thickness gradient. We present a Fresnel-Kirchhoff optical diffraction model of wafer-curvature measurements that provides a unified description of these combined effects. The model accurately simulates real-time wafer-curvature measurements of nonuniform GaN films grown on sapphire substrates by vapor-phase epitaxy. During thin-film growth, thickness gradients cause the reflected beam to oscillate asymmetrically about the ideal position defined by the stress-induced wafer curvature. This oscillating deflection has the same periodicity as the reflectance of the growing film, and the deflection amplitude is a function of the film-thickness gradient, the mean film thickness, the wavelength distribution of the light source, the illuminated spot size, and the refractive indices of the film and substrate. For typical GaN films grown on sapphire, misinterpretation of these gradient-induced oscillations can cause stress-measurement errors that approach 10% of the stress-thickness product; much greater errors occur in highly nonuniform films. Only transparent films can exhibit substantial gradient-induced deflections; strongly absorbing films are immune

Robust modal curvature features for identifying multiple damage in beams

Science.gov (United States)

Ostachowicz, Wiesław; Xu, Wei; Bai, Runbo; Radzieński, Maciej; Cao, Maosen

2014-03-01

Curvature mode shape is an effective feature for damage detection in beams. However, it is susceptible to measurement noise, easily impairing its advantage of sensitivity to damage. To deal with this deficiency, this study formulates an improved curvature mode shape for multiple damage detection in beams based on integrating a wavelet transform (WT) and a Teager energy operator (TEO). The improved curvature mode shape, termed the WT - TEO curvature mode shape, has inherent capabilities of immunity to noise and sensitivity to damage. The proposed method is experimentally validated by identifying multiple cracks in cantilever steel beams with the mode shapes acquired using a scanning laser vibrometer. The results demonstrate that the improved curvature mode shape can identify multiple damage accurately and reliably, and it is fairly robust to measurement noise.

Manipulating lipid membrane architecture by liquid crystal-analog curvature elasticity (Presentation Recording)

Science.gov (United States)

Lee, Sin-Doo

2015-10-01

Soft matters such as liquid crystals and biological molecules exhibit a variety of interesting physical phenomena as well as new applications. Recently, in mimicking biological systems that have the ability to sense, regulate, grow, react, and regenerate in a highly responsive and self-adaptive manner, the significance of the liquid crystal order in living organisms, for example, a biological membrane possessing the lamellar order, is widely recognized from the viewpoints of physics and chemistry of interfaces and membrane biophysics. Lipid bilayers, resembling cell membranes, provide primary functions for the transport of biological components of ions and molecules in various cellular activities, including vesicle budding and membrane fusion, through lateral organization of the membrane components such as proteins. In this lecture, I will describe how the liquid crystal-analog curvature elasticity of a lipid bilayer plays a critical role in developing a new platform for understanding diverse biological functions at a cellular level. The key concept is to manipulate the local curvature at an interface between a solid substrate and a model membrane. Two representative examples will be demonstrated: one of them is the topographic control of lipid rafts in a combinatorial array where the ligand-receptor binding event occurs and the other concerns the reconstitution of a ring-type lipid raft in bud-mimicking architecture within the framework of the curvature elasticity.

Error in the determination of the deformed shape of prismatic beams using the double integration of curvature

Science.gov (United States)

Sigurdardottir, Dorotea H.; Stearns, Jett; Glisic, Branko

2017-07-01

The deformed shape is a consequence of loading the structure and it is defined by the shape of the centroid line of the beam after deformation. The deformed shape is a universal parameter of beam-like structures. It is correlated with the curvature of the cross-section; therefore, any unusual behavior that affects the curvature is reflected through the deformed shape. Excessive deformations cause user discomfort, damage to adjacent structural members, and may ultimately lead to issues in structural safety. However, direct long-term monitoring of the deformed shape in real-life settings is challenging, and an alternative is indirect determination of the deformed shape based on curvature monitoring. The challenge of the latter is an accurate evaluation of error in the deformed shape determination, which is directly correlated with the number of sensors needed to achieve the desired accuracy. The aim of this paper is to study the deformed shape evaluated by numerical double integration of the monitored curvature distribution along the beam, and create a method to predict the associated errors and suggest the number of sensors needed to achieve the desired accuracy. The error due to the accuracy in the curvature measurement is evaluated within the scope of this work. Additionally, the error due to the numerical integration is evaluated. This error depends on the load case (i.e., the shape of the curvature diagram), the magnitude of curvature, and the density of the sensor network. The method is tested on a laboratory specimen and a real structure. In a laboratory setting, the double integration is in excellent agreement with the beam theory solution which was within the predicted error limits of the numerical integration. Consistent results are also achieved on a real structure—Streicker Bridge on Princeton University campus.

Error Control in Distributed Node Self-Localization

Directory of Open Access Journals (Sweden)

Ying Zhang

2008-03-01

Full Text Available Location information of nodes in an ad hoc sensor network is essential to many tasks such as routing, cooperative sensing, and service delivery. Distributed node self-localization is lightweight and requires little communication overhead, but often suffers from the adverse effects of error propagation. Unlike other localization papers which focus on designing elaborate localization algorithms, this paper takes a different perspective, focusing on the error propagation problem, addressing questions such as where localization error comes from and how it propagates from node to node. To prevent error from propagating and accumulating, we develop an error-control mechanism based on characterization of node uncertainties and discrimination between neighboring nodes. The error-control mechanism uses only local knowledge and is fully decentralized. Simulation results have shown that the active selection strategy significantly mitigates the effect of error propagation for both range and directional sensors. It greatly improves localization accuracy and robustness.

The speed-curvature power law of movements: a reappraisal.

Science.gov (United States)

Zago, Myrka; Matic, Adam; Flash, Tamar; Gomez-Marin, Alex; Lacquaniti, Francesco

2018-01-01

Several types of curvilinear movements obey approximately the so called 2/3 power law, according to which the angular speed varies proportionally to the 2/3 power of the curvature. The origin of the law is debated but it is generally thought to depend on physiological mechanisms. However, a recent paper (Marken and Shaffer, Exp Brain Res 88:685-690, 2017) claims that this power law is simply a statistical artifact, being a mathematical consequence of the way speed and curvature are calculated. Here we reject this hypothesis by showing that the speed-curvature power law of biological movements is non-trivial. First, we confirm that the power exponent varies with the shape of human drawing movements and with environmental factors. Second, we report experimental data from Drosophila larvae demonstrating that the power law does not depend on how curvature is calculated. Third, we prove that the law can be violated by means of several mathematical and physical examples. Finally, we discuss biological constraints that may underlie speed-curvature power laws discovered in empirical studies.

Locally Minimum Storage Regenerating Codes in Distributed Cloud Storage Systems

Institute of Scientific and Technical Information of China (English)

Jing Wang; Wei Luo; Wei Liang; Xiangyang Liu; Xiaodai Dong

2017-01-01

In distributed cloud storage sys-tems, inevitably there exist multiple node fail-ures at the same time. The existing methods of regenerating codes, including minimum storage regenerating (MSR) codes and mini-mum bandwidth regenerating (MBR) codes, are mainly to repair one single or several failed nodes, unable to meet the repair need of distributed cloud storage systems. In this paper, we present locally minimum storage re-generating (LMSR) codes to recover multiple failed nodes at the same time. Specifically, the nodes in distributed cloud storage systems are divided into multiple local groups, and in each local group (4, 2) or (5, 3) MSR codes are constructed. Moreover, the grouping method of storage nodes and the repairing process of failed nodes in local groups are studied. The-oretical analysis shows that LMSR codes can achieve the same storage overhead as MSR codes. Furthermore, we verify by means of simulation that, compared with MSR codes, LMSR codes can reduce the repair bandwidth and disk I/O overhead effectively.

Forecasting an invasive species’ distribution with global distribution data, local data, and physiological information

Science.gov (United States)

Jarnevich, Catherine S.; Young, Nicholas E.; Talbert, Marian; Talbert, Colin

2018-01-01

Understanding invasive species distributions and potential invasions often requires broad‐scale information on the environmental tolerances of the species. Further, resource managers are often faced with knowing these broad‐scale relationships as well as nuanced environmental factors related to their landscape that influence where an invasive species occurs and potentially could occur. Using invasive buffelgrass (Cenchrus ciliaris), we developed global models and local models for Saguaro National Park, Arizona, USA, based on location records and literature on physiological tolerances to environmental factors to investigate whether environmental relationships of a species at a global scale are also important at local scales. In addition to correlative models with five commonly used algorithms, we also developed a model using a priori user‐defined relationships between occurrence and environmental characteristics based on a literature review. All correlative models at both scales performed well based on statistical evaluations. The user‐defined curves closely matched those produced by the correlative models, indicating that the correlative models may be capturing mechanisms driving the distribution of buffelgrass. Given climate projections for the region, both global and local models indicate that conditions at Saguaro National Park may become more suitable for buffelgrass. Combining global and local data with correlative models and physiological information provided a holistic approach to forecasting invasive species distributions.

Extrinsic and intrinsic curvatures in thermodynamic geometry

Energy Technology Data Exchange (ETDEWEB)

Hosseini Mansoori, Seyed Ali, E-mail: shossein@bu.edu [Department of Physics, Boston University, 590 Commonwealth Ave., Boston, MA 02215 (United States); Department of Physics, Isfahan University of Technology, Isfahan 84156-83111 (Iran, Islamic Republic of); Mirza, Behrouz, E-mail: b.mirza@cc.iut.ac.ir [Department of Physics, Isfahan University of Technology, Isfahan 84156-83111 (Iran, Islamic Republic of); Sharifian, Elham, E-mail: e.sharifian@ph.iut.ac.ir [Department of Physics, Isfahan University of Technology, Isfahan 84156-83111 (Iran, Islamic Republic of)

2016-08-10

We investigate the intrinsic and extrinsic curvatures of a certain hypersurface in thermodynamic geometry of a physical system and show that they contain useful thermodynamic information. For an anti-Reissner–Nordström-(A)de Sitter black hole (Phantom), the extrinsic curvature of a constant Q hypersurface has the same sign as the heat capacity around the phase transition points. The intrinsic curvature of the hypersurface can also be divergent at the critical points but has no information about the sign of the heat capacity. Our study explains the consistent relationship holding between the thermodynamic geometry of the KN-AdS black holes and those of the RN (J-zero hypersurface) and Kerr black holes (Q-zero hypersurface) ones [1]. This approach can easily be generalized to an arbitrary thermodynamic system.

Extrinsic and intrinsic curvatures in thermodynamic geometry

International Nuclear Information System (INIS)

Hosseini Mansoori, Seyed Ali; Mirza, Behrouz; Sharifian, Elham

2016-01-01

We investigate the intrinsic and extrinsic curvatures of a certain hypersurface in thermodynamic geometry of a physical system and show that they contain useful thermodynamic information. For an anti-Reissner–Nordström-(A)de Sitter black hole (Phantom), the extrinsic curvature of a constant Q hypersurface has the same sign as the heat capacity around the phase transition points. The intrinsic curvature of the hypersurface can also be divergent at the critical points but has no information about the sign of the heat capacity. Our study explains the consistent relationship holding between the thermodynamic geometry of the KN-AdS black holes and those of the RN (J-zero hypersurface) and Kerr black holes (Q-zero hypersurface) ones [1]. This approach can easily be generalized to an arbitrary thermodynamic system.

A Numerical Study on the Impeller Meridional Curvature of High Pressure Multistage Pump

Energy Technology Data Exchange (ETDEWEB)

Kim, Deok Su; Jean, Sang Gyu; Mamatov, Sanjar [Hyosung Goodsprings, Inc., Busan (Korea, Republic of); Park, Warn Gyu [Pusan Nat’l Univ., Busan (Korea, Republic of)

2017-07-15

This paper presents the hydraulic design an impeller and radial diffuser of a high-pressure multistage pump for reverse osmosis. The flow distribution and hydraulic performance for the meridional design of the impeller were analyzed numerically. Optimization was conducted based on the response surface method by varying the hub and shroud meridional curvatures, while maintaining the impeller outlet diameter, outlet width, and eye diameter constant. The analysis results of the head and efficiency with the variation in the impeller meridional profile showed that angle of the front shroud near the impeller outlet (εDs) had the highest effect on head increase, while the hub inlet length (d1i) and shroud curvature (Rds) had the highest effect on efficiency. From the meridional profile variation, an approximately 0.5% increase in efficiency was observed compared with the base model (case 25).

Analysis of growth patterns during gravitropic curvature in roots of Zea mays by use of a computer-based video digitizer

Science.gov (United States)

Nelson, A. J.; Evans, M. L.

1986-01-01

A computer-based video digitizer system is described which allows automated tracking of markers placed on a plant surface. The system uses customized software to calculate relative growth rates at selected positions along the plant surface and to determine rates of gravitropic curvature based on the changing pattern of distribution of the surface markers. The system was used to study the time course of gravitropic curvature and changes in relative growth rate along the upper and lower surface of horizontally-oriented roots of maize (Zea mays L.). The growing region of the root was found to extend from about 1 mm behind the tip to approximately 6 mm behind the tip. In vertically-oriented roots the relative growth rate was maximal at about 2.5 mm behind the tip and declined smoothly on either side of the maximum. Curvature was initiated approximately 30 min after horizontal orientation with maximal (50 degrees) curvature being attained in 3 h. Analysis of surface extension patterns during the response indicated that curvature results from a reduction in growth rate along both the upper and lower surfaces with stronger reduction along the lower surface.

Damage assessment using flexibility and flexibility-based curvature for structural health monitoring

International Nuclear Information System (INIS)

Catbas, F N; Gul, M; Burkett, J L

2008-01-01

As a result of the recent advances in sensors, information technologies and material science, a considerable amount of research has been conducted in the area of smart infrastructures. While there are many important components of a smart infrastructure, an automated and continuous structural health monitoring (SHM) system is a critical one. SHM is typically used to track and evaluate the performance of a structure, symptoms of operational incidents, anomalies due to deterioration and damage during regular operation as well as after an extreme event. Successful health monitoring applications can be achieved by integrating experimental, analytical and information technologies on real-life operating structures. However, real-life investigations must be backed up by laboratory benchmark studies for validating theory, concepts, and new technologies. For this reason, a physical bridge model is developed to implement SHM methods and technologies. In this study, different aspects of model development are outlined in terms of design considerations, instrumentation, finite element modeling, and simulating damage scenarios. Different damage detection methods are evaluated using the numerical and the physical models. Modal parameter estimation studies are carried out to reliably identify the eigenvalues, eigenvectors and modal scaling from the measurement data. To assess the simulated damage, modal flexibility-based displacements and curvatures are employed. Structural behavior after damage is evaluated by inspecting the deflected shapes obtained using modal flexibility. More localized damage simulations such as stiffness reduction at a joint yield a very subtle stiffness decrease. In this case, the writers use a baseline to identify damage and also investigate the use of curvature as a complementary index. Curvature is advantageous for certain cases where the displacement results do not provide substantial changes. Issues related to using curvature as a damage identification

Positive spatial curvature does not falsify the landscape

Science.gov (United States)

Horn, B.

2017-12-01

We present a simple cosmological model where the quantum tunneling of a scalar field rearranges the energetics of the matter sector, sending a stable static ancestor vacuum with positive spatial curvature into an inating solution with positive curvature. This serves as a proof of principle that an observation of positive spatial curvature does not falsify the hypothesis that our current observer patch originated from false vacuum tunneling in a string or field theoretic landscape. This poster submission is a summary of the work, and was presented at the 3rd annual ICPPA held in Moscow from October 2 to 5, 2017, by Prof. Rostislav Konoplich on behalf of the author.

Curvature perturbation and waterfall dynamics in hybrid inflation

International Nuclear Information System (INIS)

Abolhasani, Ali Akbar; Firouzjahi, Hassan; Sasaki, Misao

2011-01-01

We investigate the parameter spaces of hybrid inflation model with special attention paid to the dynamics of waterfall field and curvature perturbations induced from its quantum fluctuations. Depending on the inflaton field value at the time of phase transition and the sharpness of the phase transition inflation can have multiple extended stages. We find that for models with mild phase transition the induced curvature perturbation from the waterfall field is too large to satisfy the COBE normalization. We investigate the model parameter space where the curvature perturbations from the waterfall quantum fluctuations vary between the results of standard hybrid inflation and the results obtained here

Curvature perturbation and waterfall dynamics in hybrid inflation

Energy Technology Data Exchange (ETDEWEB)

Abolhasani, Ali Akbar [Department of Physics, Sharif University of Technology, Tehran (Iran, Islamic Republic of); Firouzjahi, Hassan [School of Physics, Institute for Research in Fundamental Sciences (IPM), P.O. Box 19395-5531, Tehran (Iran, Islamic Republic of); Sasaki, Misao, E-mail: abolhasani@mail.ipm.ir, E-mail: firouz@mail.ipm.ir, E-mail: misao@yukawa.kyoto-u.ac.jp [Yukawa Institute for Theoretical Physics, Kyoto University, Kyoto 606-8502 (Japan)

2011-10-01

We investigate the parameter spaces of hybrid inflation model with special attention paid to the dynamics of waterfall field and curvature perturbations induced from its quantum fluctuations. Depending on the inflaton field value at the time of phase transition and the sharpness of the phase transition inflation can have multiple extended stages. We find that for models with mild phase transition the induced curvature perturbation from the waterfall field is too large to satisfy the COBE normalization. We investigate the model parameter space where the curvature perturbations from the waterfall quantum fluctuations vary between the results of standard hybrid inflation and the results obtained here.

Local freedom in the gravitational field revisited

International Nuclear Information System (INIS)

Pareja, Maria Jesus; MacCallum, Malcolm A H

2006-01-01

Maartens et al (1997 Class. Quantum Grav. 14 1927) gave a covariant characterization, in a (1 + 3) formalism based on a perfect fluid's velocity, of the parts of the first derivatives of the curvature tensor in general relativity which are 'locally free', i.e. not pointwise determined by the fluid energy-momentum and its derivative. The full decomposition of independent curvature derivative components given in earlier work on the spinor approach to the equivalence problem enables analogous general results to be stated for any order: the independent matter terms can also be characterized. Explicit relations between the two sets of results are obtained. The 24 Maartens et al locally free data are shown to correspond to the ∇Ψ quantities in the spinor approach, and the fluid terms are similarly related to the remaining 16 independent quantities in the first derivatives of the curvature

Local freedom in the gravitational field revisited

Energy Technology Data Exchange (ETDEWEB)

Pareja, Maria Jesus [Institute for Astronomy and Astrophysics, University of Tuebingen, Auf der Morgenstelle 10, D-72076 Tuebingen (Germany); MacCallum, Malcolm A H [School of Mathematical Sciences, Queen Mary, University of London, Mile End Road, London E1 4NS (United Kingdom)

2006-08-07

Maartens et al (1997 Class. Quantum Grav. 14 1927) gave a covariant characterization, in a (1 + 3) formalism based on a perfect fluid's velocity, of the parts of the first derivatives of the curvature tensor in general relativity which are 'locally free', i.e. not pointwise determined by the fluid energy-momentum and its derivative. The full decomposition of independent curvature derivative components given in earlier work on the spinor approach to the equivalence problem enables analogous general results to be stated for any order: the independent matter terms can also be characterized. Explicit relations between the two sets of results are obtained. The 24 Maartens et al locally free data are shown to correspond to the {nabla}{psi} quantities in the spinor approach, and the fluid terms are similarly related to the remaining 16 independent quantities in the first derivatives of the curvature.

Influence of implant rod curvature on sagittal correction of scoliosis deformity.

Science.gov (United States)

Salmingo, Remel Alingalan; Tadano, Shigeru; Abe, Yuichiro; Ito, Manabu

2014-08-01

Deformation of in vivo-implanted rods could alter the scoliosis sagittal correction. To our knowledge, no previous authors have investigated the influence of implanted-rod deformation on the sagittal deformity correction during scoliosis surgery. To analyze the changes of the implant rod's angle of curvature during surgery and establish its influence on sagittal correction of scoliosis deformity. A retrospective analysis of the preoperative and postoperative implant rod geometry and angle of curvature was conducted. Twenty adolescent idiopathic scoliosis patients underwent surgery. Average age at the time of operation was 14 years. The preoperative and postoperative implant rod angle of curvature expressed in degrees was obtained for each patient. Two implant rods were attached to the concave and convex side of the spinal deformity. The preoperative implant rod geometry was measured before surgical implantation. The postoperative implant rod geometry after surgery was measured by computed tomography. The implant rod angle of curvature at the sagittal plane was obtained from the implant rod geometry. The angle of curvature between the implant rod extreme ends was measured before implantation and after surgery. The sagittal curvature between the corresponding spinal levels of healthy adolescents obtained by previous studies was compared with the implant rod angle of curvature to evaluate the sagittal curve correction. The difference between the postoperative implant rod angle of curvature and normal spine sagittal curvature of the corresponding instrumented level was used to evaluate over or under correction of the sagittal deformity. The implant rods at the concave side of deformity of all patients were significantly deformed after surgery. The average degree of rod deformation Δθ at the concave and convex sides was 15.8° and 1.6°, respectively. The average preoperative and postoperative implant rod angle of curvature at the concave side was 33.6° and 17.8�

Discrimination of curvature from motion during smooth pursuit eye movements and fixation.

Science.gov (United States)

Ross, Nicholas M; Goettker, Alexander; Schütz, Alexander C; Braun, Doris I; Gegenfurtner, Karl R

2017-09-01

Smooth pursuit and motion perception have mainly been investigated with stimuli moving along linear trajectories. Here we studied the quality of pursuit movements to curved motion trajectories in human observers and examined whether the pursuit responses would be sensitive enough to discriminate various degrees of curvature. In a two-interval forced-choice task subjects pursued a Gaussian blob moving along a curved trajectory and then indicated in which interval the curve was flatter. We also measured discrimination thresholds for the same curvatures during fixation. Motion curvature had some specific effects on smooth pursuit properties: trajectories with larger amounts of curvature elicited lower open-loop acceleration, lower pursuit gain, and larger catch-up saccades compared with less curved trajectories. Initially, target motion curvatures were underestimated; however, ∼300 ms after pursuit onset pursuit responses closely matched the actual curved trajectory. We calculated perceptual thresholds for curvature discrimination, which were on the order of 1.5 degrees of visual angle (°) for a 7.9° curvature standard. Oculometric sensitivity to curvature discrimination based on the whole pursuit trajectory was quite similar to perceptual performance. Oculometric thresholds based on smaller time windows were higher. Thus smooth pursuit can quite accurately follow moving targets with curved trajectories, but temporal integration over longer periods is necessary to reach perceptual thresholds for curvature discrimination. NEW & NOTEWORTHY Even though motion trajectories in the real world are frequently curved, most studies of smooth pursuit and motion perception have investigated linear motion. We show that pursuit initially underestimates the curvature of target motion and is able to reproduce the target curvature ∼300 ms after pursuit onset. Temporal integration of target motion over longer periods is necessary for pursuit to reach the level of precision found

New power distribution challenges at the local scale

International Nuclear Information System (INIS)

Delage, Marion; Cadoux, Florent; Petit, Marc

2016-01-01

Distribution grids are facing the connection of both more and more variable distributed generation sources and new loads such as electric vehicles. Then distribution grid operators evolve to distribution system operators (DSOs) with new flexibilities (power control of distributed energy sources) to complete their traditional planning and operation tools. In the future, additional distributed resources could be used, such as demand response and storage. DSOs are becoming actors of a global electrical system where power balancing must be ensured at the European level with local constraints (congestion and voltage), and with power flows from transmission to distribution grids but also inside the distribution grid or from distribution to transmission. Sensors and data availability are key issues to enable these transformations. This paper defines some general concerns and present European issues with illustrations from the French electrical system. (authors)

The role of curvature in silica mesoporous crystals

KAUST Repository

Miyasaka, Keiichi

2012-02-08

Silica mesoporous crystals (SMCs) offer a unique opportunity to study micellar mesophases. Replication of non-equilibrium mesophases into porous silica structures allows the characterization of surfactant phases under a variety of chemical and physical perturbations, through methods not typically accessible to liquid crystal chemists. A poignant example is the use of electron microscopy and crystallography, as discussed herein, for the purpose of determining the fundamental role of amphiphile curvature, namely mean curvature and Gaussian curvature, which have been extensively studied in various fields such as polymer, liquid crystal, biological membrane, etc. The present work aims to highlight some current studies devoted to the interface curvature on SMCs, in which electron microscopy and electron crystallography (EC) are used to understand the geometry of silica wall surface in bicontinuous and cage-type mesostructures through the investigation of electrostatic potential maps. Additionally, we show that by altering the synthesis conditions during the preparation of SMCs, it is possible to isolate particles during micellar mesophase transformations in the cubic bicontinuous system, allowing us to view and study epitaxial relations under the specific synthesis conditions. By studying the relationship between mesoporous structure, interface curvature and micellar mesophases using electron microscopy and EC, we hope to bring new insights into the formation mechanism of these unique materials but also contribute a new way of understanding periodic liquid crystal systems. © 2012 The Royal Society.

The role of curvature in silica mesoporous crystals

KAUST Repository

Miyasaka, Keiichi; Bennett, Alfonso Garcia; Han, Lu; Han, Yu; Xiao, Changhong; Fujita, Nobuhisa; Castle, Toen; Sakamoto, Yasuhiro; Che, Shunai; Terasaki, Osamu

2012-01-01

Silica mesoporous crystals (SMCs) offer a unique opportunity to study micellar mesophases. Replication of non-equilibrium mesophases into porous silica structures allows the characterization of surfactant phases under a variety of chemical and physical perturbations, through methods not typically accessible to liquid crystal chemists. A poignant example is the use of electron microscopy and crystallography, as discussed herein, for the purpose of determining the fundamental role of amphiphile curvature, namely mean curvature and Gaussian curvature, which have been extensively studied in various fields such as polymer, liquid crystal, biological membrane, etc. The present work aims to highlight some current studies devoted to the interface curvature on SMCs, in which electron microscopy and electron crystallography (EC) are used to understand the geometry of silica wall surface in bicontinuous and cage-type mesostructures through the investigation of electrostatic potential maps. Additionally, we show that by altering the synthesis conditions during the preparation of SMCs, it is possible to isolate particles during micellar mesophase transformations in the cubic bicontinuous system, allowing us to view and study epitaxial relations under the specific synthesis conditions. By studying the relationship between mesoporous structure, interface curvature and micellar mesophases using electron microscopy and EC, we hope to bring new insights into the formation mechanism of these unique materials but also contribute a new way of understanding periodic liquid crystal systems. © 2012 The Royal Society.

Optical distribution of local oscillators in future telecommunication satellite payloads

Science.gov (United States)

Benazet, Benoît; Sotom, Michel; Maignan, Michel; Berthon, Jacques

2017-11-01

The distribution of high spectral purity reference signals over optical fibre in future telecommunication satellite payloads is presented. Several types of applications are considered, including the distribution of a reference frequency at 10 MHz (Ultra-Stable Reference Oscillator) as well as the distribution of a radiofrequency oscillator around 800 MHz (Master Local Oscillator). The results of both experimental and theoretical studies are reported. In order to meet phase noise requirements for the USRO distribution, the use of an optimised receiver circuit based on an optically synchronised oscillator is investigated. Finally, the optical distribution of microwave local oscillators at frequencies exceeding 20 GHz is described. Such a scheme paves the way to more advanced sub-systems involving optical frequency-mixing and optical transmission of microwave signals, with applications to multiple-beam active antennas.

Single Lipid Molecule Dynamics on Supported Lipid Bilayers with Membrane Curvature

Directory of Open Access Journals (Sweden)

Philip P. Cheney

2017-03-01

Full Text Available The plasma membrane is a highly compartmentalized, dynamic material and this organization is essential for a wide variety of cellular processes. Nanoscale domains allow proteins to organize for cell signaling, endo- and exocytosis, and other essential processes. Even in the absence of proteins, lipids have the ability to organize into domains as a result of a variety of chemical and physical interactions. One feature of membranes that affects lipid domain formation is membrane curvature. To directly test the role of curvature in lipid sorting, we measured the accumulation of two similar lipids, 1,2-Dihexadecanoyl-sn-glycero-3-phosphoethanolamine (DHPE and hexadecanoic acid (HDA, using a supported lipid bilayer that was assembled over a nanopatterned surface to obtain regions of membrane curvature. Both lipids studied contain 16 carbon, saturated tails and a head group tag for fluorescence microscopy measurements. The accumulation of lipids at curvatures ranging from 28 nm to 55 nm radii was measured and fluorescein labeled DHPE accumulated more than fluorescein labeled HDA at regions of membrane curvature. We then tested whether single biotinylated DHPE molecules sense curvature using single particle tracking methods. Similar to groups of fluorescein labeled DHPE accumulating at curvature, the dynamics of single molecules of biotinylated DHPE was also affected by membrane curvature and highly confined motion was observed.

New curvature-torsion relations through decomposition of the Bianchi identities

International Nuclear Information System (INIS)

Davies, J.B.

1988-01-01

The Bianchi Identities relating asymmetric curvature to torsion are obtained as a new set of equations governing second-order curvature tensors. The usual contribution of symmetric curvature to the gravitational field is found to be a subset of these identities though with an added contribution due to torsion gradients. The antisymmetric curvature two-tensor is shown to be related to the divergence of the torsion. Using a model of particle-antiparticle pair production, identification of certain torsion components with electroweak fields is proposed. These components obey equations, similar to Maxwell's that are subsets of these linear Bianchi identities. These results are shown to be consistent with gauge and other previous analyses

Effects on Buildings of Surface Curvature Caused by Underground Coal Mining

Directory of Open Access Journals (Sweden)

Haifeng Hu

2016-08-01

Full Text Available Ground curvature caused by underground mining is one of the most obvious deformation quantities in buildings. To study the influence of surface curvature on buildings and predict the movement and deformation of buildings caused by ground curvature, a prediction model of the influence function on mining subsidence was used to establish the relationship between surface curvature and wall deformation. The prediction model of wall deformation was then established and the surface curvature was obtained from mining subsidence prediction software. Five prediction lines were set up in the wall from bottom to top and the predicted deformation of each line was used to calculate the crack positions in the wall. Thus, the crack prediction model was obtained. The model was verified by a case study from a coalmine in Shanxi, China. The results show that when the ground curvature is positive, the crack in the wall is shaped like a “V”; when the ground curvature is negative, the crack is shaped like a “∧”. The conclusion provides the basis for a damage evaluation method for buildings in coalmine areas.

Advanced Curvature Deformable Mirrors

Science.gov (United States)

2010-09-01

ORGANIZATION NAME(S) AND ADDRESS(ES) University of Hawaii ,Institute for Astronomy,640 North A‘ohoku Place, #209 , Hilo ,HI,96720-2700 8. PERFORMING...Advanced Curvature Deformable Mirrors Christ Ftaclas1,2, Aglae Kellerer2 and Mark Chun2 Institute for Astronomy, University of Hawaii

Effect of nano-scale curvature on the intrinsic blood coagulation system

Science.gov (United States)

Kushida, Takashi; Saha, Krishnendu; Subramani, Chandramouleeswaran; Nandwana, Vikas; Rotello, Vincent M.

2014-01-01

The intrinsic coagulation activity of silica nanoparticles strongly depends on their surface curvature. Nanoparticles with higher surface curvature do not denature blood coagulation factor XII on its surface, providing a coagulation ‘silent’ surface, while nanoparticles with lower surface curvature shows denaturation and concomitant coagulation. PMID:25341004

A geometric construction of the Riemann scalar curvature in Regge calculus

International Nuclear Information System (INIS)

McDonald, Jonathan R; Miller, Warner A

2008-01-01

The Riemann scalar curvature plays a central role in Einstein's geometric theory of gravity. We describe a new geometric construction of this scalar curvature invariant at an event (vertex) in a discrete spacetime geometry. This allows one to constructively measure the scalar curvature using only clocks and photons. Given recent interest in discrete pre-geometric models of quantum gravity, we believe is it ever so important to reconstruct the curvature scalar with respect to a finite number of communicating observers. This derivation makes use of a new fundamental lattice cell built from elements inherited from both the original simplicial (Delaunay) spacetime and its circumcentric dual (Voronoi) lattice. The orthogonality properties between these two lattices yield an expression for the vertex-based scalar curvature which is strikingly similar to the corresponding hinge-based expression in Regge calculus (deficit angle per unit Voronoi dual area). In particular, we show that the scalar curvature is simply a vertex-based weighted average of deficits per weighted average of dual areas

A geometric construction of the Riemann scalar curvature in Regge calculus

Science.gov (United States)

McDonald, Jonathan R.; Miller, Warner A.

2008-10-01

The Riemann scalar curvature plays a central role in Einstein's geometric theory of gravity. We describe a new geometric construction of this scalar curvature invariant at an event (vertex) in a discrete spacetime geometry. This allows one to constructively measure the scalar curvature using only clocks and photons. Given recent interest in discrete pre-geometric models of quantum gravity, we believe is it ever so important to reconstruct the curvature scalar with respect to a finite number of communicating observers. This derivation makes use of a new fundamental lattice cell built from elements inherited from both the original simplicial (Delaunay) spacetime and its circumcentric dual (Voronoi) lattice. The orthogonality properties between these two lattices yield an expression for the vertex-based scalar curvature which is strikingly similar to the corresponding hinge-based expression in Regge calculus (deficit angle per unit Voronoi dual area). In particular, we show that the scalar curvature is simply a vertex-based weighted average of deficits per weighted average of dual areas.

Long-term Results of Ventral Penile Curvature Repair in Childhood.

Science.gov (United States)

Golomb, Dor; Sivan, Bezalel; Livne, Pinhas M; Nevo, Amihay; Ben-Meir, David

2018-02-01

To assess the postpubertal outcome of ventral penile curvature repaired in infancy in terms of recurrence and aesthetics. Postpubertal patients treated for hypospadias and ventral penile curvature in infancy at a tertiary medical center were invited to undergo assessment of the quality of the repair. Findings were compared between patients with a straight penis after skin release and patients who required dorsal plication. The cohort included 27 patients of mean age 16.5 years who were reported with straight penis after surgery. Postpubertal curvature was found in 6 of 14 patients (43%) successfully treated by skin release and 10 of 13 patients (77%) who underwent dorsal plication (P = .087). Significant curvature (≥30 degrees) was found in 1 of 14 patients in the skin-release group and 4 of 13 in the dorsal plication group (P = .16). Rates of redo urethroplasty were 2 of 14 (14%) and 5 of 10 (50%), respectively. Patient satisfaction with the appearance of the penis did not differ significantly. Ventral penile curvature repaired in infancy often recurs after puberty. The need for dorsal plication has a trend-level association with recurrence of penile curvature in puberty. It might also be related to the degree of postpubertal penile curvature and the need for redo urethroplasty. Procedure type does not affect patient satisfaction with the postpubertal appearance of the penis. Copyright © 2017 Elsevier Inc. All rights reserved.

On ripples and rafts: Curvature induced nanoscale structures in lipid membranes

International Nuclear Information System (INIS)

Schmid, Friederike; Dolezel, Stefan; Meinhardt, Sebastian; Lenz, Olaf

2014-01-01

We develop an elastic theory that predicts the spontaneous formation of nanoscale structures in lipid bilayers which locally phase separate between two phases with different spontaneous monolayer curvature. The theory rationalizes in a unified manner the observation of a variety of nanoscale structures in lipid membranes: Rippled states in one-component membranes, lipid rafts in multicomponent membranes. Furthermore, we report on recent observations of rippled states and rafts in simulations of a simple coarse-grained model for lipid bilayers, which are compatible with experimental observations and with our elastic model

On the scalar curvature of self-dual manifolds

International Nuclear Information System (INIS)

Kim, J.

1992-08-01

We generalize LeBrun's explicit ''hyperbolic ansatz'' construction of self-dual metrics on connected sums of conformally flat manifolds and CP 2 's through a systematic use of the theory of hyperbolic geometry and Kleinian groups. (This construction produces, for example, all self-dual manifolds with semi-free S 1 -action and with either nonnegative scalar curvature or positive-definite intersection form.) We then point out a simple criterion for determining the sign of the scalar curvature of these conformal metrics. Exploiting this, we then show that the sign of the scalar curvature can change on connected components of the moduli space of self-dual metrics, thereby answering a question raised by King and Kotschick. (author). Refs

On a curvature-statistics theorem

International Nuclear Information System (INIS)

Calixto, M; Aldaya, V

2008-01-01

The spin-statistics theorem in quantum field theory relates the spin of a particle to the statistics obeyed by that particle. Here we investigate an interesting correspondence or connection between curvature (κ = ±1) and quantum statistics (Fermi-Dirac and Bose-Einstein, respectively). The interrelation between both concepts is established through vacuum coherent configurations of zero modes in quantum field theory on the compact O(3) and noncompact O(2; 1) (spatial) isometry subgroups of de Sitter and Anti de Sitter spaces, respectively. The high frequency limit, is retrieved as a (zero curvature) group contraction to the Newton-Hooke (harmonic oscillator) group. We also make some comments on the physical significance of the vacuum energy density and the cosmological constant problem.

On a curvature-statistics theorem

Energy Technology Data Exchange (ETDEWEB)

Calixto, M [Departamento de Matematica Aplicada y Estadistica, Universidad Politecnica de Cartagena, Paseo Alfonso XIII 56, 30203 Cartagena (Spain); Aldaya, V [Instituto de Astrofisica de Andalucia, Apartado Postal 3004, 18080 Granada (Spain)], E-mail: Manuel.Calixto@upct.es

2008-08-15

The spin-statistics theorem in quantum field theory relates the spin of a particle to the statistics obeyed by that particle. Here we investigate an interesting correspondence or connection between curvature ({kappa} = {+-}1) and quantum statistics (Fermi-Dirac and Bose-Einstein, respectively). The interrelation between both concepts is established through vacuum coherent configurations of zero modes in quantum field theory on the compact O(3) and noncompact O(2; 1) (spatial) isometry subgroups of de Sitter and Anti de Sitter spaces, respectively. The high frequency limit, is retrieved as a (zero curvature) group contraction to the Newton-Hooke (harmonic oscillator) group. We also make some comments on the physical significance of the vacuum energy density and the cosmological constant problem.

Intensity-Curvature Measurement Approaches for the Diagnosis of Magnetic Resonance Imaging Brain Tumors

Directory of Open Access Journals (Sweden)

Carlo Ciulla

2015-11-01

Full Text Available This research presents signal-image post-processing techniques called Intensity-Curvature Measurement Approaches with application to the diagnosis of human brain tumors detected through Magnetic Resonance Imaging (MRI. Post-processing of the MRI of the human brain encompasses the following model functions: (i bivariate cubic polynomial, (ii bivariate cubic Lagrange polynomial, (iii monovariate sinc, and (iv bivariate linear. The following Intensity-Curvature Measurement Approaches were used: (i classic-curvature, (ii signal resilient to interpolation, (iii intensity-curvature measure and (iv intensity-curvature functional. The results revealed that the classic-curvature, the signal resilient to interpolation and the intensity-curvature functional are able to add additional information useful to the diagnosis carried out with MRI. The contribution to the MRI diagnosis of our study are: (i the enhanced gray level scale of the tumor mass and the well-behaved representation of the tumor provided through the signal resilient to interpolation, and (ii the visually perceptible third dimension perpendicular to the image plane provided through the classic-curvature and the intensity-curvature functional.

Local features with large spiky non-Gaussianities during inflation

International Nuclear Information System (INIS)

Abolhasani, Ali Akbar; Firouzjahi, Hassan; Khosravi, Shahram; Sasaki, Misao

2012-01-01

We provide a dynamical mechanism to generate localized features during inflation. The local feature is due to a sharp waterfall phase transition which is coupled to the inflaton field. The key effect is the contributions of waterfall quantum fluctuations which induce a sharp peak on the curvature perturbation which can be as large as the background curvature perturbation from inflaton field. Due to non-Gaussian nature of waterfall quantum fluctuations a large spike non-Gaussianity is produced which is narrowly peaked at modes which leave the Hubble radius at the time of phase transition. The large localized peaks in power spectrum and bispectrum can have interesting consequences on CMB anisotropies

Statistical mechanics of surfaces with curvature dependent action

International Nuclear Information System (INIS)

Jonsson, T.

1987-01-01

We review recent results about discretized random surfaces whose action (energy) depends on the extrinsic curvature. The surface tension scales to zero at an appropriate critical point if the coupling constant of the curvature term is taken to infinity. At this critical point one expects to be able to construct a continuum theory of smooth surfaces. (orig.)

Integrated analysis on static/dynamic aeroelasticity of curved panels based on a modified local piston theory

Science.gov (United States)

Yang, Zhichun; Zhou, Jian; Gu, Yingsong

2014-10-01

A flow field modified local piston theory, which is applied to the integrated analysis on static/dynamic aeroelastic behaviors of curved panels, is proposed in this paper. The local flow field parameters used in the modification are obtained by CFD technique which has the advantage to simulate the steady flow field accurately. This flow field modified local piston theory for aerodynamic loading is applied to the analysis of static aeroelastic deformation and flutter stabilities of curved panels in hypersonic flow. In addition, comparisons are made between results obtained by using the present method and curvature modified method. It shows that when the curvature of the curved panel is relatively small, the static aeroelastic deformations and flutter stability boundaries obtained by these two methods have little difference, while for curved panels with larger curvatures, the static aeroelastic deformation obtained by the present method is larger and the flutter stability boundary is smaller compared with those obtained by the curvature modified method, and the discrepancy increases with the increasing of curvature of panels. Therefore, the existing curvature modified method is non-conservative compared to the proposed flow field modified method based on the consideration of hypersonic flight vehicle safety, and the proposed flow field modified local piston theory for curved panels enlarges the application range of piston theory.

Shaped input distributions for structural damage localization

DEFF Research Database (Denmark)

Ulriksen, Martin Dalgaard; Bernal, Dionisio; Damkilde, Lars

2018-01-01

localization method is cast that operates on the premise of shaping inputs—whose spatial distribution is fixed—by use of a model, such that these inputs, in one structural subdomain at a time, suppress certain steady-state vibration quantities (depending on the type of damage one seeks to interrogate for......). Accordingly, damage is localized when the vibration signature induced by the shaped inputs in the damaged state corresponds to that in the reference state, hereby implying that the approach does not point directly to damage. Instead, it operates with interrogation based on postulated damage patterns...

A 1 + 5-dimensional gravitational-wave solution. Curvature singularity and spacetime singularity

Energy Technology Data Exchange (ETDEWEB)

Chen, Yu-Zhu [Tianjin University, Department of Physics, Tianjin (China); Li, Wen-Du [Tianjin University, Department of Physics, Tianjin (China); Nankai University, Theoretical Physics Division, Chern Institute of Mathematics, Tianjin (China); Dai, Wu-Sheng [Nankai University, Theoretical Physics Division, Chern Institute of Mathematics, Tianjin (China); Nankai University and Tianjin University, LiuHui Center for Applied Mathematics, Tianjin (China)

2017-12-15

We solve a 1 + 5-dimensional cylindrical gravitational-wave solution of the Einstein equation, in which there are two curvature singularities. Then we show that one of the curvature singularities can be removed by an extension of the spacetime. The result exemplifies that the curvature singularity is not always a spacetime singularity; in other words, the curvature singularity cannot serve as a criterion for spacetime singularities. (orig.)

The influence of jaw's curvature on the results of the Brazilian disc test

Directory of Open Access Journals (Sweden)

Ch.F. Markides

2016-04-01

Full Text Available The general contact problem of a disc squeezed between jaws of arbitrary curvature is considered employing Muskhelishvili's complex potentials. Taking advantage of the general solution introduced, the closed-form expressions for the stresses along strategic loci (loaded rim, loaded diameter, disc's center are obtained, in terms of the ratio ρ of the disc's to the jaw's curvature. Then, the effect of ρ (as well as that of the relative stiffness of the disc's and jaw's materials dictating the contact arc on the stress distribution along these loci is explored. It is concluded that, for both smooth contact (zero friction and contact with friction, the role of the jaw's curvature is significant not only along the disc-jaw contact arc (as it could be expected, but also all along the loaded diameter. On the other hand, it is indicated that the stress field at the disc's center is more or less insensitive to the jaw's curvature assuming that ρ lies within the range (0, 0.67 or in other words within the limits defined by the two standardized suggestions, i.e. that of American Society for Testing and Materials (ASTM (plane loading platens with ρ = 0 and that of International Society for Rock Mechanics (ISRM (curved jaws with ρ = 0.67. The upper limit of this range is a kind of compromise between the need to make the stress field at the disc's center independent of the boundary conditions while keeping at the same time the contact angle large enough to reduce the stress concentration and the risk for premature fracture initiation far from the disc's center. For jaws with radius of curvature exceeded by that suggested by ISRM, the stress field at the disc's center is significantly influenced. Especially for jaws with radius approaching that of the disc, the stress field at the disc's center is dramatically distorted rendering Hondros' formula inapplicable and the test results erroneous.

Numerical and Theoretical Investigations Concerning the Continuous-Surface-Curvature Effect in Compressor Blades

Directory of Open Access Journals (Sweden)

Yin Song

2014-12-01

Full Text Available Though the importance of curvature continuity on compressor blade performances has been realized, there are two major questions that need to be solved, i.e., the respective effects of curvature continuity at the leading-edge blend point and the main surface, and the contradiction between the traditional theory and experimental observations in the effect of those novel leading-edge shapes with smaller curvature discontinuity and sharper nose. In this paper, an optimization method to design continuous-curvature blade profiles which deviate little from datum blades is proposed, and numerical and theoretical analysis is carried out to investigate the continuous-curvature effect on blade performances. The results show that the curvature continuity at the leading-edge blend point helps to eliminate the separation bubble, thus improving the blade performance. The main-surface curvature continuity is also beneficial, although its effects are much smaller than those of the blend-point curvature continuity. Furthermore, it is observed that there exist two factors controlling the leading-edge spike, i.e., the curvature discontinuity at the blend point which dominates at small incidences, and the nose curvature which dominates at large incidences. To the authors’ knowledge, such mechanisms have not been reported before, and they can help to solve the sharp-leading-edge paradox.

Curvature evolution of 200 mm diameter GaN-on-insulator wafer fabricated through metalorganic chemical vapor deposition and bonding

Science.gov (United States)

Zhang, Li; Lee, Kwang Hong; Kadir, Abdul; Wang, Yue; Lee, Kenneth E.; Tan, Chuan Seng; Chua, Soo Jin; Fitzgerald, Eugene A.

2018-05-01

Crack-free 200 mm diameter N-polar GaN-on-insulator (GaN-OI) wafers are demonstrated by the transfer of metalorganic chemical vapor deposition (MOCVD)-grown Ga-polar GaN layers from Si(111) wafers onto SiO2/Si(100) wafers. The wafer curvature of the GaN-OI wafers after the removal of the original Si(111) substrate is correlated with the wafer curvature of the starting GaN-on-Si wafers and the voids on the GaN-on-Si surface that evolve into cracks on the GaN-OI wafers. In crack-free GaN-OI wafers, the wafer curvature during the removal of the AlN nucleation layer, AlGaN strain-compensation buffer layers and GaN layers is correlated with the residual stress distribution within individual layers in the GaN-OI wafer.

Turbulent boundary layer heat transfer experiments: Convex curvature effects including introduction and recovery

Science.gov (United States)

Simon, T. W.; Moffat, R. J.; Johnston, J. P.; Kays, W. M.

1982-01-01

Measurements were made of the heat transfer rate through turbulent and transitional boundary layers on an isothermal, convexly curved wall and downstream flat plate. The effect of convex curvature on the fully turbulent boundary layer was a reduction of the local Stanton numbers 20% to 50% below those predicted for a flat wall under the same circumstances. The recovery of the heat transfer rates on the downstream flat wall was extremely slow. After 60 cm of recovery length, the Stanton number was still typically 15% to 20% below the flat wall predicted value. Various effects important in the modeling of curved flows were studied separately. These are: the effect of initial boundary layer thickness, the effect of freestream velocity, the effect of freestream acceleration, the effect of unheated starting length, and the effect of the maturity of the boundary layer. An existing curvature prediction model was tested against this broad heat transfer data base to determine where it could appropriately be used for heat transfer predictions.

Higher Curvature Gravity from Entanglement in Conformal Field Theories

Science.gov (United States)

Haehl, Felix M.; Hijano, Eliot; Parrikar, Onkar; Rabideau, Charles

2018-05-01

By generalizing different recent works to the context of higher curvature gravity, we provide a unifying framework for three related results: (i) If an asymptotically anti-de Sitter (AdS) spacetime computes the entanglement entropies of ball-shaped regions in a conformal field theory using a generalized Ryu-Takayanagi formula up to second order in state deformations around the vacuum, then the spacetime satisfies the correct gravitational equations of motion up to second order around the AdS background. (ii) The holographic dual of entanglement entropy in higher curvature theories of gravity is given by the Wald entropy plus a particular correction term involving extrinsic curvatures. (iii) Conformal field theory relative entropy is dual to gravitational canonical energy (also in higher curvature theories of gravity). Especially for the second point, our novel derivation of this previously known statement does not involve the Euclidean replica trick.

Amphipathic motifs in BAR domains are essential for membrane curvature sensing

DEFF Research Database (Denmark)

Bhatia, Vikram K; Madsen, Kenneth L; Bolinger, Pierre-Yves

2009-01-01

BAR (Bin/Amphiphysin/Rvs) domains and amphipathic alpha-helices (AHs) are believed to be sensors of membrane curvature thus facilitating the assembly of protein complexes on curved membranes. Here, we used quantitative fluorescence microscopy to compare the binding of both motifs on single...... nanosized liposomes of different diameters and therefore membrane curvature. Characterization of members of the three BAR domain families showed surprisingly that the crescent-shaped BAR dimer with its positively charged concave face is not able to sense membrane curvature. Mutagenesis on BAR domains showed...... that membrane curvature sensing critically depends on the N-terminal AH and furthermore that BAR domains sense membrane curvature through hydrophobic insertion in lipid packing defects and not through electrostatics. Consequently, amphipathic motifs, such as AHs, that are often associated with BAR domains...

Distributed formation tracking using local coordinate systems

DEFF Research Database (Denmark)

Yang, Qingkai; Cao, Ming; Garcia de Marina, Hector

2018-01-01

This paper studies the formation tracking problem for multi-agent systems, for which a distributed estimator–controller scheme is designed relying only on the agents’ local coordinate systems such that the centroid of the controlled formation tracks a given trajectory. By introducing a gradient...... descent term into the estimator, the explicit knowledge of the bound of the agents’ speed is not necessary in contrast to existing works, and each agent is able to compute the centroid of the whole formation in finite time. Then, based on the centroid estimation, a distributed control algorithm...

On the curvature of transmitted intensity plots in broad beam studies

International Nuclear Information System (INIS)

El-Kateb, A.H.

2000-01-01

Transmission of a broad beam of gamma rays of 81- and 356-keV energies from 133 Ba is studied singly and dually. This study is the first to deal with the curvatures of the intensity plots. The targets are dextrose solutions of percentage concentrations up to 0.125 and soil containing water with concentrations up to 0.319. The logarithmic intensity plots are expressed in terms of a polynomial in the concentration. The curvatures of the plots are measured and calculated on the basis of the theoretical mass attenuation coefficients. The results are discussed in conjunction with buildup factors and the probability of photoelectric and Compton interactions. The curvatures show maxima when incoherent interaction prevails. This is evidently proved in case of the single 356-keV and of the dual 81- and 356-keV applied energies. Comparison is performed between the measured and calculated curvatures. The concept of curvature is applied and discussed for published results of narrow beam geometry. Correspondingly, this is the first search to introduce curvature instead of buildup as a measure for transmitted collided photons

Evolution of curvature perturbation in generalized gravity theories

International Nuclear Information System (INIS)

Matsuda, Tomohiro

2009-01-01

Using the cosmological perturbation theory in terms of the δN formalism, we find the simple formulation of the evolution of the curvature perturbation in generalized gravity theories. Compared with the standard gravity theory, a crucial difference appears in the end-boundary of the inflationary stage, which is due to the non-ideal form of the energy-momentum tensor that depends explicitly on the curvature scalar. Recent study shows that ultraviolet-complete quantum theory of gravity (Horava-Lifshitz gravity) can be approximated by using a generalized gravity action. Our paper may give an important step in understanding the evolution of the curvature perturbation during inflation, where the energy-momentum tensor may not be given by the ideal form due to the corrections from the fundamental theory.

Vibration Analysis of Circular Arch Element Using Curvature

Directory of Open Access Journals (Sweden)

H. Saffari

2008-01-01

Full Text Available In this paper, a finite element technique was used to determine the natural frequencies, and the mode shapes of a circular arch element was based on the curvature, which can fully represent the bending energy and by the equilibrium equations, the shear and axial strain energy were incorporated into the formulation. The treatment of general boundary conditions dose need a consideration when the element is incorporated by the curvature-based formula. This can be obtained by the introduction of a transformation matrix between nodal curvatures and nodal displacements. The equation of the motion for the element was obtained by the Lagrangian equation. Four examples are presented in order to verify the element formulation and its analytical capability.

Discrete gravity as a topological field theorywith light-like curvature defects

Energy Technology Data Exchange (ETDEWEB)

Wieland, Wolfgang [Perimeter Institute for Theoretical Physics,31 Caroline Street North, Waterloo, ON N2L 2Y5 (Canada)

2017-05-29

I present a model of discrete gravity as a topological field theory with defects. The theory has no local degrees of freedom and the gravitational field is trivial everywhere except at a number of intersecting null surfaces. At these null surfaces, the gravitational field can be singular, representing a curvature defect propagating at the speed of light. The underlying action is local and it is studied in both its Lagrangian and Hamiltonian formulation. The canonically conjugate variables on the null surfaces are a spinor and a spinor-valued two-surface density, which are coupled to a topological field theory for the Lorentz connection in the bulk. I discuss the relevance of the model for non-perturbative approaches to quantum gravity, such as loop quantum gravity, where similar variables have recently appeared as well.

A major QTL controls susceptibility to spinal curvature in the curveback guppy

Directory of Open Access Journals (Sweden)

Dreyer Christine

2011-01-01

Full Text Available Abstract Background Understanding the genetic basis of heritable spinal curvature would benefit medicine and aquaculture. Heritable spinal curvature among otherwise healthy children (i.e. Idiopathic Scoliosis and Scheuermann kyphosis accounts for more than 80% of all spinal curvatures and imposes a substantial healthcare cost through bracing, hospitalizations, surgery, and chronic back pain. In aquaculture, the prevalence of heritable spinal curvature can reach as high as 80% of a stock, and thus imposes a substantial cost through production losses. The genetic basis of heritable spinal curvature is unknown and so the objective of this work is to identify quantitative trait loci (QTL affecting heritable spinal curvature in the curveback guppy. Prior work with curveback has demonstrated phenotypic parallels to human idiopathic-type scoliosis, suggesting shared biological pathways for the deformity. Results A major effect QTL that acts in a recessive manner and accounts for curve susceptibility was detected in an initial mapping cross on LG 14. In a second cross, we confirmed this susceptibility locus and fine mapped it to a 5 cM region that explains 82.6% of the total phenotypic variance. Conclusions We identify a major QTL that controls susceptibility to curvature. This locus contains over 100 genes, including MTNR1B, a candidate gene for human idiopathic scoliosis. The identification of genes associated with heritable spinal curvature in the curveback guppy has the potential to elucidate the biological basis of spinal curvature among humans and economically important teleosts.

Geometry-specific scaling of detonation parameters from front curvature

International Nuclear Information System (INIS)

Jackson, Scott I.; Short, Mark

2011-01-01

It has previously been asserted that classical detonation curvature theory predicts that the critical diameter and the diameter-effect curve of a cylindrical high-explosive charge should scale with twice the thickness of an analogous two-dimensional explosive slab. The varied agreement of experimental results with this expectation have led some to question the ability of curvature-based concepts to predict detonation propagation in non-ideal explosives. This study addresses such claims by showing that the expected scaling relationship (hereafter referred to d = 2w) is not consistent with curvature-based Detonation Shock Dynamics (DSD) theory.

An Amphipathic Helix Directs Cellular Membrane Curvature Sensing and Function of the BAR Domain Protein PICK1.

Science.gov (United States)

Herlo, Rasmus; Lund, Viktor K; Lycas, Matthew D; Jansen, Anna M; Khelashvili, George; Andersen, Rita C; Bhatia, Vikram; Pedersen, Thomas S; Albornoz, Pedro B C; Johner, Niklaus; Ammendrup-Johnsen, Ina; Christensen, Nikolaj R; Erlendsson, Simon; Stoklund, Mikkel; Larsen, Jannik B; Weinstein, Harel; Kjærulff, Ole; Stamou, Dimitrios; Gether, Ulrik; Madsen, Kenneth L

2018-05-15

BAR domains are dimeric protein modules that sense, induce, and stabilize lipid membrane curvature. Here, we show that membrane curvature sensing (MCS) directs cellular localization and function of the BAR domain protein PICK1. In PICK1, and the homologous proteins ICA69 and arfaptin2, we identify an amphipathic helix N-terminal to the BAR domain that mediates MCS. Mutational disruption of the helix in PICK1 impaired MCS without affecting membrane binding per se. In insulin-producing INS-1E cells, super-resolution microscopy revealed that disruption of the helix selectively compromised PICK1 density on insulin granules of high curvature during their maturation. This was accompanied by reduced hormone storage in the INS-1E cells. In Drosophila, disruption of the helix compromised growth regulation. By demonstrating size-dependent binding on insulin granules, our finding highlights the function of MCS for BAR domain proteins in a biological context distinct from their function, e.g., at the plasma membrane during endocytosis. Copyright © 2018 The Author(s). Published by Elsevier Inc. All rights reserved.

Gravitational effective action at second order in curvature and gravitational waves

International Nuclear Information System (INIS)

Calmet, Xavier; Pryer, Daniel; Capozziello, Salvatore

2017-01-01

We consider the full effective theory for quantum gravity at second order in curvature including non-local terms. We show that the theory contains two new degrees of freedom beyond the massless graviton: namely a massive spin-2 ghost and a massive scalar field. Furthermore, we show that it is impossible to fine-tune the parameters of the effective action to eliminate completely the classical spin-2 ghost because of the non-local terms in the effective action. Being a classical field, it is not clear anyway that this ghost is problematic. It simply implies a repulsive contribution to Newton's potential. We then consider how to extract the parameters of the effective action and show that it is possible to measure, at least in principle, the parameters of the local terms independently of each other using a combination of observations of gravitational waves and measurements performed by pendulum type experiments searching for deviations of Newton's potential. (orig.)

Gravitational effective action at second order in curvature and gravitational waves

Energy Technology Data Exchange (ETDEWEB)

Calmet, Xavier; Pryer, Daniel [University of Sussex, Department of Physics and Astronomy, Brighton (United Kingdom); Capozziello, Salvatore [Universita di Napoli ' ' Federico II' ' , Dipartimento di Fisica ' ' E. Pancini' ' , Naples (Italy); Istituto Nazionale di Fisica Nucleare (INFN), Naples (Italy); Gran Sasso Science Institute, L' Aquila (Italy)

2017-09-15

We consider the full effective theory for quantum gravity at second order in curvature including non-local terms. We show that the theory contains two new degrees of freedom beyond the massless graviton: namely a massive spin-2 ghost and a massive scalar field. Furthermore, we show that it is impossible to fine-tune the parameters of the effective action to eliminate completely the classical spin-2 ghost because of the non-local terms in the effective action. Being a classical field, it is not clear anyway that this ghost is problematic. It simply implies a repulsive contribution to Newton's potential. We then consider how to extract the parameters of the effective action and show that it is possible to measure, at least in principle, the parameters of the local terms independently of each other using a combination of observations of gravitational waves and measurements performed by pendulum type experiments searching for deviations of Newton's potential. (orig.)

Gravitational effective action at second order in curvature and gravitational waves

Science.gov (United States)

Calmet, Xavier; Capozziello, Salvatore; Pryer, Daniel

2017-09-01

We consider the full effective theory for quantum gravity at second order in curvature including non-local terms. We show that the theory contains two new degrees of freedom beyond the massless graviton: namely a massive spin-2 ghost and a massive scalar field. Furthermore, we show that it is impossible to fine-tune the parameters of the effective action to eliminate completely the classical spin-2 ghost because of the non-local terms in the effective action. Being a classical field, it is not clear anyway that this ghost is problematic. It simply implies a repulsive contribution to Newton's potential. We then consider how to extract the parameters of the effective action and show that it is possible to measure, at least in principle, the parameters of the local terms independently of each other using a combination of observations of gravitational waves and measurements performed by pendulum type experiments searching for deviations of Newton's potential.

Gravitational effective action at second order in curvature and gravitational waves.

Science.gov (United States)

Calmet, Xavier; Capozziello, Salvatore; Pryer, Daniel

2017-01-01

We consider the full effective theory for quantum gravity at second order in curvature including non-local terms. We show that the theory contains two new degrees of freedom beyond the massless graviton: namely a massive spin-2 ghost and a massive scalar field. Furthermore, we show that it is impossible to fine-tune the parameters of the effective action to eliminate completely the classical spin-2 ghost because of the non-local terms in the effective action. Being a classical field, it is not clear anyway that this ghost is problematic. It simply implies a repulsive contribution to Newton's potential. We then consider how to extract the parameters of the effective action and show that it is possible to measure, at least in principle, the parameters of the local terms independently of each other using a combination of observations of gravitational waves and measurements performed by pendulum type experiments searching for deviations of Newton's potential.

Directable weathering of concave rock using curvature estimation.

Science.gov (United States)

Jones, Michael D; Farley, McKay; Butler, Joseph; Beardall, Matthew

2010-01-01

We address the problem of directable weathering of exposed concave rock for use in computer-generated animation or games. Previous weathering models that admit concave surfaces are computationally inefficient and difficult to control. In nature, the spheroidal and cavernous weathering rates depend on the surface curvature. Spheroidal weathering is fastest in areas with large positive mean curvature and cavernous weathering is fastest in areas with large negative mean curvature. We simulate both processes using an approximation of mean curvature on a voxel grid. Both weathering rates are also influenced by rock durability. The user controls rock durability by editing a durability graph before and during weathering simulation. Simulations of rockfall and colluvium deposition further improve realism. The profile of the final weathered rock matches the shape of the durability graph up to the effects of weathering and colluvium deposition. We demonstrate the top-down directability and visual plausibility of the resulting model through a series of screenshots and rendered images. The results include the weathering of a cube into a sphere and of a sheltered inside corner into a cavern as predicted by the underlying geomorphological models.

Global and local consistencies in distributed fault diagnosis for discrete-event systems

NARCIS (Netherlands)

Su, R.; Wonham, W.M.

2005-01-01

In this paper, we present a unified framework for distributed diagnosis. We first introduce the concepts of global and local consistency in terms of supremal global and local supports, then present two distributed diagnosis problems based on them. After that, we provide algorithms to achieve

Quantitative analysis and prediction of curvature in leucine-rich repeat proteins.

Science.gov (United States)

Hindle, K Lauren; Bella, Jordi; Lovell, Simon C

2009-11-01

Leucine-rich repeat (LRR) proteins form a large and diverse family. They have a wide range of functions most of which involve the formation of protein-protein interactions. All known LRR structures form curved solenoids, although there is large variation in their curvature. It is this curvature that determines the shape and dimensions of the inner space available for ligand binding. Unfortunately, large-scale parameters such as the overall curvature of a protein domain are extremely difficult to predict. Here, we present a quantitative analysis of determinants of curvature of this family. Individual repeats typically range in length between 20 and 30 residues and have a variety of secondary structures on their convex side. The observed curvature of the LRR domains correlates poorly with the lengths of their individual repeats. We have, therefore, developed a scoring function based on the secondary structure of the convex side of the protein that allows prediction of the overall curvature with a high degree of accuracy. We also demonstrate the effectiveness of this method in selecting a suitable template for comparative modeling. We have developed an automated, quantitative protocol that can be used to predict accurately the curvature of leucine-rich repeat proteins of unknown structure from sequence alone. This protocol is available as an online resource at http://www.bioinf.manchester.ac.uk/curlrr/.

Spinal curvature and characteristics of postural change in pregnant women.

Science.gov (United States)

Okanishi, Natsuko; Kito, Nobuhiro; Akiyama, Mitoshi; Yamamoto, Masako

2012-07-01

Pregnant women often report complaints due to physiological and postural changes. Postural changes during pregnancy may cause low back pain and pelvic girdle pain. This study aimed to compare the characteristics of postural changes in pregnant compared with non-pregnant women. Prospective case-control study. Pregnancy care center. Fifteen women at 17-34 weeks pregnancy comprised the study group, while 10 non-pregnant female volunteers comprised the control group. Standing posture was evaluated in the sagittal plane with static digital pictures. Two angles were measured by image analysis software: (1) between the trunk and pelvis; and (2) between the trunk and lower extremity. Spinal curvature was measured with Spinal Mouse® to calculate the means of sacral inclination, thoracic and lumbar curvature and inclination. The principal components were calculated until eigenvalues surpassed 1. Three distinct factors with eigenvalues of 1.00-2.49 were identified, consistent with lumbosacral spinal curvature and inclination, thoracic spine curvature, and inclination of the body. These factors accounted for 77.2% of the total variance in posture variables. Eleven pregnant women showed postural characteristics of lumbar kyphosis and sacral posterior inclination. Body inclination showed a variety of patterns compared with those in healthy women. Spinal curvature demonstrated a tendency for lumbar kyphosis in pregnant women. Pregnancy may cause changes in spinal curvature and posture, which may in turn lead to relevant symptoms. Our data provide a basis for investigating the effects of spinal curvature and postural changes on symptoms during pregnancy. © 2012 The Authors Acta Obstetricia et Gynecologica Scandinavica© 2012 Nordic Federation of Societies of Obstetrics and Gynecology.

Supervisor Localization: A Top-Down Approach to Distributed Control of Discrete-Event Systems

International Nuclear Information System (INIS)

Cai, K.; Wonham, W. M.

2009-01-01

A purely distributed control paradigm is proposed for discrete-event systems (DES). In contrast to control by one or more external supervisors, distributed control aims to design built-in strategies for individual agents. First a distributed optimal nonblocking control problem is formulated. To solve it, a top-down localization procedure is developed which systematically decomposes an external supervisor into local controllers while preserving optimality and nonblockingness. An efficient localization algorithm is provided to carry out the computation, and an automated guided vehicles (AGV) example presented for illustration. Finally, the 'easiest' and 'hardest' boundary cases of localization are discussed.

Sensitivity of the CSR self-interaction to the local longitudinal charge concentration of an electron bunch

CERN Document Server

Li, R

2001-01-01

Recent measurements of the coherent synchrotron radiation (CSR) effects indicated that the observed emittance growth and energy modulation due to the orbit-curvature-induced bunch self-interaction are sometimes bigger than predictions based on Gaussian longitudinal charge distributions. In this paper, by performing a model study, we show both analytically and numerically that when the longitudinal bunch charge distribution involves concentration of charges in a small fraction of the bunch length, enhancement of the CSR self-interaction beyond the Gaussian prediction may occur. The level of this enhancement is sensitive to the level of the local charge concentration.

Inference for Local Distributions at High Sampling Frequencies: A Bootstrap Approach

DEFF Research Database (Denmark)

Hounyo, Ulrich; Varneskov, Rasmus T.

of "large" jumps. Our locally dependent wild bootstrap (LDWB) accommodate issues related to the stochastic scale and jumps as well as account for a special block-wise dependence structure induced by sampling errors. We show that the LDWB replicates first and second-order limit theory from the usual...... empirical process and the stochastic scale estimate, respectively, as well as an asymptotic bias. Moreover, we design the LDWB sufficiently general to establish asymptotic equivalence between it and and a nonparametric local block bootstrap, also introduced here, up to second-order distribution theory....... Finally, we introduce LDWB-aided Kolmogorov-Smirnov tests for local Gaussianity as well as local von-Mises statistics, with and without bootstrap inference, and establish their asymptotic validity using the second-order distribution theory. The finite sample performance of CLT and LDWB-aided local...

Differential geometric structures of stream functions: incompressible two-dimensional flow and curvatures

International Nuclear Information System (INIS)

Yamasaki, K; Iwayama, T; Yajima, T

2011-01-01

The Okubo-Weiss field, frequently used for partitioning incompressible two-dimensional (2D) fluids into coherent and incoherent regions, corresponds to the Gaussian curvature of the stream function. Therefore, we consider the differential geometric structures of stream functions and calculate the Gaussian curvatures of some basic flows. We find the following. (I) The vorticity corresponds to the mean curvature of the stream function. Thus, the stream-function surface for an irrotational flow and that for a parallel shear flow correspond to the minimal surface and a developable surface, respectively. (II) The relationship between the coherency and the magnitude of the vorticity is interpreted by the curvatures. (III) Using the Gaussian curvature, stability of single and double point vortex streets is analyzed. The results of this analysis are compared with the well-known linear stability analysis. (IV) Conformal mapping in fluid mechanics is the physical expression of the geometric fact that the sign of the Gaussian curvature does not change in conformal mapping. These findings suggest that the curvatures of stream functions are useful for understanding the geometric structure of an incompressible 2D flow.

Landmark Optimization Using Local Curvature for Point-Based Nonlinear Rodent Brain Image Registration

Directory of Open Access Journals (Sweden)

Yutong Liu

2012-01-01

Full Text Available Purpose. To develop a technique to automate landmark selection for point-based interpolating transformations for nonlinear medical image registration. Materials and Methods. Interpolating transformations were calculated from homologous point landmarks on the source (image to be transformed and target (reference image. Point landmarks are placed at regular intervals on contours of anatomical features, and their positions are optimized along the contour surface by a function composed of curvature similarity and displacements of the homologous landmarks. The method was evaluated in two cases (=5 each. In one, MRI was registered to histological sections; in the second, geometric distortions in EPI MRI were corrected. Normalized mutual information and target registration error were calculated to compare the registration accuracy of the automatically and manually generated landmarks. Results. Statistical analyses demonstrated significant improvement (<0.05 in registration accuracy by landmark optimization in most data sets and trends towards improvement (<0.1 in others as compared to manual landmark selection.

Modern approaches to discrete curvature

CERN Document Server

Romon, Pascal

2017-01-01

 This book provides a valuable glimpse into discrete curvature, a rich new field of research which blends discrete mathematics, differential geometry, probability and computer graphics. It includes a vast collection of ideas and tools which will offer something new to all interested readers. Discrete geometry has arisen as much as a theoretical development as in response to unforeseen challenges coming from applications. Discrete and continuous geometries have turned out to be intimately connected. Discrete curvature is the key concept connecting them through many bridges in numerous fields: metric spaces, Riemannian and Euclidean geometries, geometric measure theory, topology, partial differential equations, calculus of variations, gradient flows, asymptotic analysis, probability, harmonic analysis, graph theory, etc. In spite of its crucial importance both in theoretical mathematics and in applications, up to now, almost no books have provided a coherent outlook on this emerging field.

The Riemann-Lovelock curvature tensor

International Nuclear Information System (INIS)

Kastor, David

2012-01-01

In order to study the properties of Lovelock gravity theories in low dimensions, we define the kth-order Riemann-Lovelock tensor as a certain quantity having a total 4k-indices, which is kth order in the Riemann curvature tensor and shares its basic algebraic and differential properties. We show that the kth-order Riemann-Lovelock tensor is determined by its traces in dimensions 2k ≤ D < 4k. In D = 2k + 1 this identity implies that all solutions of pure kth-order Lovelock gravity are 'Riemann-Lovelock' flat. It is verified that the static, spherically symmetric solutions of these theories, which are missing solid angle spacetimes, indeed satisfy this flatness property. This generalizes results from Einstein gravity in D = 3, which corresponds to the k = 1 case. We speculate about some possible further consequences of Riemann-Lovelock curvature. (paper)

Curvature-driven acceleration: a utopia or a reality?

International Nuclear Information System (INIS)

Das, Sudipta; Banerjee, Narayan; Dadhich, Naresh

2006-01-01

The present work shows that a combination of nonlinear contributions from the Ricci curvature in Einstein field equations can drive a late time acceleration of expansion of the universe. The transit from the decelerated to the accelerated phase of expansion takes place smoothly without having to resort to a study of asymptotic behaviour. This result emphasizes the need for thorough and critical examination of models with nonlinear contribution from the curvature

Curvature-driven acceleration: a utopia or a reality?

Energy Technology Data Exchange (ETDEWEB)

Das, Sudipta [Relativity and Cosmology Research Centre, Department of Physics, Jadavpur University, Calcutta-700 032 (India); Banerjee, Narayan [Relativity and Cosmology Research Centre, Department of Physics, Jadavpur University, Calcutta-700 032 (India); Dadhich, Naresh [Inter University Centre for Astronomy and Astrophysics, Post Bag 4, Ganeshkhind, Pune 411 007 (India)

2006-06-21

The present work shows that a combination of nonlinear contributions from the Ricci curvature in Einstein field equations can drive a late time acceleration of expansion of the universe. The transit from the decelerated to the accelerated phase of expansion takes place smoothly without having to resort to a study of asymptotic behaviour. This result emphasizes the need for thorough and critical examination of models with nonlinear contribution from the curvature.

On differential radiodiagnosis of ulcerations of the greater curvature of the stomach

International Nuclear Information System (INIS)

Portnoj, L.M.; Nefedova, V.O.; Turovskij, B.M.; Marchenko, V.A.; Osadchij, P.A.; Konina, E.A.

1980-01-01

The problems connected with the differential diagnosis of ulcerations of the greater curvature of the stomach are considered on the base of analysis of 176 observations of ulcerated forms of cancer and 14 benign injuries localized in this area. Emphasizing the great importance of the X-ray method for such diagnosis, the authors give recommendations concerning the methods of the common X-ray examination of the stomach and the interpretation of the details of the X-ray appearance: they also point to the advisability of using pneumogastrography in some cases

Berry Curvature in Magnon-Phonon Hybrid Systems.

Science.gov (United States)

Takahashi, Ryuji; Nagaosa, Naoto

2016-11-18

We study theoretically the Berry curvature of the magnon induced by the hybridization with the acoustic phonons via the spin-orbit and dipolar interactions. We first discuss the magnon-phonon hybridization via the dipolar interaction, and show that the dispersions have gapless points in momentum space, some of which form a loop. Next, when both spin-orbit and dipolar interactions are considered, we show anisotropic texture of the Berry curvature and its divergence with and without gap closing. Realistic evaluation of the consequent anomalous velocity is given for yttrium iron garnet.

A Comparative Assessment of Spalart-Shur Rotation/Curvature Correction in RANS Simulations in a Centrifugal Pump Impeller

Directory of Open Access Journals (Sweden)

Ran Tao

2014-01-01

Full Text Available RANS simulation is widely used in the flow prediction of centrifugal pumps. Influenced by impeller rotation and streamline curvature, the eddy viscosity models with turbulence isotropy assumption are not accurate enough. In this study, Spalart-Shur rotation/curvature correction was applied on the SST k-ω turbulence model. The comparative assessment of the correction was proceeded in the simulations of a centrifugal pump impeller. CFD results were compared with existing PIV and LDV data under the design and low flow rate off-design conditions. Results show the improvements of the simulation especially in the situation that turbulence strongly produced due to undesirable flow structures. Under the design condition, more reasonable turbulence kinetic energy contour was captured after correction. Under the low flow rate off-design condition, the prediction of turbulence kinetic energy and velocity distributions became much more accurate when using the corrected model. So, the rotation/curvature correction was proved effective in this study. And, it is also proved acceptable and recommended to use in the engineering simulations of centrifugal pump impellers.

Geometric effects of 90-degree vertical elbows on local two-phase flow parameters

International Nuclear Information System (INIS)

Yadav, M.; Worosz, T.; Kim, S.

2011-01-01

This study presents the geometric effects of 90-degree vertical elbows on the development of the local two-phase flow parameters. A multi-sensor conductivity probe is used to measure local two-phase flow parameters. It is found that immediately downstream of the vertical-upward elbow, the bubbles have a bimodal distribution along the horizontal radius of the pipe cross-section causing a dual-peak in the profiles of local void fraction and local interfacial area concentration. Immediately downstream of the vertical-downward elbow it is observed that the bubbles tend to migrate towards the inside of the elbow's curvature. The axial transport of void fraction and interfacial area concentration indicates that the elbows promote bubble disintegration. Preliminary predictions are obtained from group-one interfacial area transport equation (IATE) model for vertical-upward and vertical-downward two-phase flow. (author)

Supervisor localization a top-down approach to distributed control of discrete-event systems

CERN Document Server

Cai, Kai

2016-01-01

This monograph presents a systematic top-down approach to distributed control synthesis of discrete-event systems (DES). The approach is called supervisor localization; its essence is the allocation of external supervisory control action to individual component agents as their internal control strategies. The procedure is: first synthesize a monolithic supervisor, to achieve globally optimal and nonblocking controlled behavior, then decompose the monolithic supervisor into local controllers, one for each agent. The collective behavior of the resulting local controllers is identical to that achieved by the monolithic supervisor. The basic localization theory is first presented in the Ramadge–Wonham language-based supervisory control framework, then demonstrated with distributed control examples of multi-robot formations, manufacturing systems, and distributed algorithms. An architectural approach is adopted to apply localization to large-scale DES; this yields a heterarchical localization procedure, which is...

A curvature theory for discrete surfaces based on mesh parallelity

KAUST Repository

Bobenko, Alexander Ivanovich; Pottmann, Helmut; Wallner, Johannes

2009-01-01

We consider a general theory of curvatures of discrete surfaces equipped with edgewise parallel Gauss images, and where mean and Gaussian curvatures of faces are derived from the faces' areas and mixed areas. Remarkably these notions are capable

Curvature, metric and parametrization of origami tessellations: theory and application to the eggbox pattern

Science.gov (United States)

Nassar, H.; Lebée, A.; Monasse, L.

2017-01-01

Origami tessellations are particular textured morphing shell structures. Their unique folding and unfolding mechanisms on a local scale aggregate and bring on large changes in shape, curvature and elongation on a global scale. The existence of these global deformation modes allows for origami tessellations to fit non-trivial surfaces thus inspiring applications across a wide range of domains including structural engineering, architectural design and aerospace engineering. The present paper suggests a homogenization-type two-scale asymptotic method which, combined with standard tools from differential geometry of surfaces, yields a macroscopic continuous characterization of the global deformation modes of origami tessellations and other similar periodic pin-jointed trusses. The outcome of the method is a set of nonlinear differential equations governing the parametrization, metric and curvature of surfaces that the initially discrete structure can fit. The theory is presented through a case study of a fairly generic example: the eggbox pattern. The proposed continuous model predicts correctly the existence of various fittings that are subsequently constructed and illustrated.

Curvature, metric and parametrization of origami tessellations: theory and application to the eggbox pattern.

Science.gov (United States)

Nassar, H; Lebée, A; Monasse, L

2017-01-01

Origami tessellations are particular textured morphing shell structures. Their unique folding and unfolding mechanisms on a local scale aggregate and bring on large changes in shape, curvature and elongation on a global scale. The existence of these global deformation modes allows for origami tessellations to fit non-trivial surfaces thus inspiring applications across a wide range of domains including structural engineering, architectural design and aerospace engineering. The present paper suggests a homogenization-type two-scale asymptotic method which, combined with standard tools from differential geometry of surfaces, yields a macroscopic continuous characterization of the global deformation modes of origami tessellations and other similar periodic pin-jointed trusses. The outcome of the method is a set of nonlinear differential equations governing the parametrization, metric and curvature of surfaces that the initially discrete structure can fit. The theory is presented through a case study of a fairly generic example: the eggbox pattern. The proposed continuous model predicts correctly the existence of various fittings that are subsequently constructed and illustrated.

Holonomy Attractor Connecting Spaces of Different Curvature Responsible for ``Anomalies''

Science.gov (United States)

Binder, Bernd

2009-03-01

In this lecture paper we derive Magic Angle Precession (MAP) from first geometric principles. MAP can arise in situations, where precession is multiply related to spin, linearly by time or distance (dynamic phase, rolling, Gauss law) and transcendentally by the holonomy loop path (geometric phase). With linear spin-precession coupling, gyroscopes can be spun up and down to very high frequencies via low frequency holonomy control induced by external accelerations, which provides for extreme coupling strengths or "anomalies" that can be tested by the powerball or gyrotwister device. Geometrically, a gyroscopic manifold with spherical metric is tangentially aligned to a precession wave channel with conic or hyperbolic metric (like the relativistic Thomas precession). Transporting triangular spin/precession vector relations across the tangential boundary of contact with SO(3) Lorentz symmetry, we get extreme vector currents near the attractor fixed points in precession phase space, where spin currents remain intact while crossing the contact boundaries between regions of different curvature signature (-1, 0, +1). The problem can be geometrically solved by considering a curvature invariant triangular condition, which holds on surfaces with different curvature that are in contact and locally parallel. In this case two out of three angles are identical, whereas the third angle is different due to holonomy. If we require that the side length ratio corresponding to these angles are invariant we get a geodesic chaotic attractor, which is a cosine map cos(x)˜Mx in parameter space providing for fixed points, limit cycle bifurcations, and singularities. The situation could be quite natural and common in the context of vector currents in curved spacetime and gauge theories. MAP could even be part of the electromagnetic interaction, where the electric charge is the geometric U(1) precession spin current and gauge potential with magnetic effects given by extra rotations under the

First contact: understanding the relationship between hominoid incisor curvature and diet.

Science.gov (United States)

Deane, Andrew

2009-03-01

Accurately interpreting fossil primate dietary behaviour is necessary to fully understand a species' ecology and connection to its environment. Traditional methods developed to infer diet from hominoid teeth successfully group taxa into broad dietary categories (i.e., folivore, frugivore) but often fail to represent the range of dietary variability characteristic of living apes. This oversimplification is not only a consequence of poor resolution, but may also reflect the use of similar fallback resources by closely related taxa with dissimilar diets. This study demonstrates that additional dietary specificity can be achieved using a morphometric approach to hominoid incisor curvature. High-resolution polynomial curve fitting (HR-PCF) was used to quantify the incisor curvatures of closely related hominoid taxa that have dissimilar diets but similar morphological adaptations to specific keystone resources (e.g., Gorilla gorilla beringei vs. G. g. gorilla). Given the key role of incisors in food processing, it is reasonable to assume that these teeth will be at least partially influenced by the unique selective pressures imposed by the mechanical loading specific to individual diets. Results from this study identify a strong correlation between hominoid dietary proportions and incisor linear dimensions and curvature, indicating that more pronounced incisor curvature is positively correlated with higher levels of frugivory. Hard-object frugivores have the greatest mesiodistal and cervico-incisal curvature and dedicated folivores have the least curved incisors. Mixed folivore/frugivores are morphological intermediates between dedicated folivores and hard- and soft-object frugivores. Mesiodistal curvature varied only in the degree of curvature; however, cervico-incisal curvature was shown to differ qualitatively between more frugivorous and more folivorous taxa. In addition to identifying a greater range of dietary variability among hominoids, this study also

Curvature-Continuous 3D Path-Planning Using QPMI Method

Directory of Open Access Journals (Sweden)

Seong-Ryong Chang

2015-06-01

Full Text Available It is impossible to achieve vertex movement and rapid velocity control in aerial robots and aerial vehicles because of momentum from the air. A continuous-curvature path ensures such robots and vehicles can fly with stable and continuous movements. General continuous path-planning methods use spline interpolation, for example B-spline and Bézier curves. However, these methods cannot be directly applied to continuous path planning in a 3D space. These methods use a subset of the waypoints to decide curvature and some waypoints are not included in the planned path. This paper proposes a method for constructing a curvature-continuous path in 3D space that includes every waypoint. The movements in each axis, x, y and z, are separated by the parameter u. Waypoint groups are formed, each with its own continuous path derived using quadratic polynomial interpolation. The membership function then combines each continuous path into one continuous path. The continuity of the path is verified and the curvature-continuous path is produced using the proposed method.

Inflation in a shear-or curvature-dominated universe

International Nuclear Information System (INIS)

Steigman, G.; Turner, M.S.

1983-01-01

We show that new inflation occurs even if the universe is shear-or (negative) curvature-dominated when the phase transition begins. In such situations the size of a causally coherent region, after inflation, is only slightly smaller (by powers, but not by exponential factors) than the usual result. The creation and evolution of density perturbations is unaffected. This result is marked contrast to 'old' inflation, where shear- or curvature-domination could quench inflation. (orig.)

Inflationary scenario from higher curvature warped spacetime

International Nuclear Information System (INIS)

Banerjee, Narayan; Paul, Tanmoy

2017-01-01

We consider a five dimensional warped spacetime, in presence of the higher curvature term like F(R) = R + αR 2 in the bulk, in the context of the two-brane model. Our universe is identified with the TeV scale brane and emerges as a four dimensional effective theory. From the perspective of this effective theory, we examine the possibility of ''inflationary scenario'' by considering the on-brane metric ansatz as an FRW one. Our results reveal that the higher curvature term in the five dimensional bulk spacetime generates a potential term for the radion field. Due to the presence of radion potential, the very early universe undergoes a stage of accelerated expansion and, moreover, the accelerating period of the universe terminates in a finite time. We also find the spectral index of curvature perturbation (n s ) and the tensor to scalar ratio (r) in the present context, which match with the observational results based on the observations of Planck (Astron. Astrophys. 594, A20, 2016). (orig.)

Inflationary scenario from higher curvature warped spacetime

Energy Technology Data Exchange (ETDEWEB)

Banerjee, Narayan [Indian Institute of Science Education and Research Kolkata, Department of Physical Sciences, Nadia, West Bengal (India); Paul, Tanmoy [Indian Association for the Cultivation of Science, Department of Theoretical Physics, Kolkata (India)

2017-10-15

We consider a five dimensional warped spacetime, in presence of the higher curvature term like F(R) = R + αR{sup 2} in the bulk, in the context of the two-brane model. Our universe is identified with the TeV scale brane and emerges as a four dimensional effective theory. From the perspective of this effective theory, we examine the possibility of ''inflationary scenario'' by considering the on-brane metric ansatz as an FRW one. Our results reveal that the higher curvature term in the five dimensional bulk spacetime generates a potential term for the radion field. Due to the presence of radion potential, the very early universe undergoes a stage of accelerated expansion and, moreover, the accelerating period of the universe terminates in a finite time. We also find the spectral index of curvature perturbation (n{sub s}) and the tensor to scalar ratio (r) in the present context, which match with the observational results based on the observations of Planck (Astron. Astrophys. 594, A20, 2016). (orig.)

The dark side of curvature

International Nuclear Information System (INIS)

Barenboim, Gabriela; Martínez, Enrique Fernández; Mena, Olga; Verde, Licia

2010-01-01

Geometrical tests such as the combination of the Hubble parameter H(z) and the angular diameter distance d A (z) can, in principle, break the degeneracy between the dark energy equation of state parameter w(z), and the spatial curvature Ω k in a direct, model-independent way. In practice, constraints on these quantities achievable from realistic experiments, such as those to be provided by Baryon Acoustic Oscillation (BAO) galaxy surveys in combination with CMB data, can resolve the cosmic confusion between the dark energy equation of state parameter and curvature only statistically and within a parameterized model for w(z). Combining measurements of both H(z) and d A (z) up to sufficiently high redshifts z ∼ 2 and employing a parameterization of the redshift evolution of the dark energy equation of state are the keys to resolve the w(z)−Ω k degeneracy

Local viscosity distribution in bifurcating microfluidic blood flows

Science.gov (United States)

Kaliviotis, E.; Sherwood, J. M.; Balabani, S.

2018-03-01

The red blood cell (RBC) aggregation phenomenon is majorly responsible for the non-Newtonian nature of blood, influencing the blood flow characteristics in the microvasculature. Of considerable interest is the behaviour of the fluid at the bifurcating regions. In vitro experiments, using microchannels, have shown that RBC aggregation, at certain flow conditions, affects the bluntness and skewness of the velocity profile, the local RBC concentration, and the cell-depleted layer at the channel walls. In addition, the developed RBC aggregates appear unevenly distributed in the outlets of these channels depending on their spatial distribution in the feeding branch, and on the flow conditions in the outlet branches. In the present work, constitutive equations of blood viscosity, from earlier work of the authors, are applied to flows in a T-type bifurcating microchannel to examine the local viscosity characteristics. Viscosity maps are derived for various flow distributions in the outlet branches of the channel, and the location of maximum viscosity magnitude is obtained. The viscosity does not appear significantly elevated in the branches of lower flow rate as would be expected on the basis of the low shear therein, and the maximum magnitude appears in the vicinity of the junction, and towards the side of the outlet branch with the higher flow rate. The study demonstrates that in the branches of lower flow rate, the local viscosity is also low, helping us to explain why the effects of physiological red blood cell aggregation have no adverse effects in terms of in vivo vascular resistance.

Thermodynamic curvature for a two-parameter spin model with frustration.

Science.gov (United States)

Ruppeiner, George; Bellucci, Stefano

2015-01-01

Microscopic models of realistic thermodynamic systems usually involve a number of parameters, not all of equal macroscopic relevance. We examine a decorated (1+3) Ising spin chain containing two microscopic parameters: a stiff parameter K mediating the long-range interactions, and a sloppy J operating within local spin groups. We show that K dominates the macroscopic behavior, with varying J having only a weak effect, except in regions where J brings about transitions between phases through its conditioning of the local spin groups with which K interacts. We calculate the heat capacity C(H), the magnetic susceptibility χ(T), and the thermodynamic curvature R. For large |J/K|, we identify four magnetic phases: ferromagnetic, antiferromagnetic, and two ferrimagnetic, according to the signs of K and J. We argue that for characterizing these phases, the strongest picture is offered by the thermodynamic geometric invariant R, proportional to the correlation length ξ. This picture has correspondences to other cases, such as fluids.

Phase-space curvature in spin-orbit-coupled ultracold atomic systems

Science.gov (United States)

Armaitis, J.; Ruseckas, J.; Anisimovas, E.

2017-04-01

We consider a system with spin-orbit coupling and derive equations of motion which include the effects of Berry curvatures. We apply these equations to investigate the dynamics of particles with equal Rashba-Dresselhaus spin-orbit coupling in one dimension. In our derivation, the adiabatic transformation is performed first and leads to quantum Heisenberg equations of motion for momentum and position operators. These equations explicitly contain position-space, momentum-space, and phase-space Berry curvature terms. Subsequently, we perform the semiclassical approximation and obtain the semiclassical equations of motion. Taking the low-Berry-curvature limit results in equations that can be directly compared to previous results for the motion of wave packets. Finally, we show that in the semiclassical regime, the effective mass of the equal Rashba-Dresselhaus spin-orbit-coupled system can be viewed as a direct effect of the phase-space Berry curvature.

Distributed Power Allocation for Wireless Sensor Network Localization: A Potential Game Approach.

Science.gov (United States)

Ke, Mingxing; Li, Ding; Tian, Shiwei; Zhang, Yuli; Tong, Kaixiang; Xu, Yuhua

2018-05-08

The problem of distributed power allocation in wireless sensor network (WSN) localization systems is investigated in this paper, using the game theoretic approach. Existing research focuses on the minimization of the localization errors of individual agent nodes over all anchor nodes subject to power budgets. When the service area and the distribution of target nodes are considered, finding the optimal trade-off between localization accuracy and power consumption is a new critical task. To cope with this issue, we propose a power allocation game where each anchor node minimizes the square position error bound (SPEB) of the service area penalized by its individual power. Meanwhile, it is proven that the power allocation game is an exact potential game which has one pure Nash equilibrium (NE) at least. In addition, we also prove the existence of an ϵ -equilibrium point, which is a refinement of NE and the better response dynamic approach can reach the end solution. Analytical and simulation results demonstrate that: (i) when prior distribution information is available, the proposed strategies have better localization accuracy than the uniform strategies; (ii) when prior distribution information is unknown, the performance of the proposed strategies outperforms power management strategies based on the second-order cone program (SOCP) for particular agent nodes after obtaining the estimated distribution of agent nodes. In addition, proposed strategies also provide an instructional trade-off between power consumption and localization accuracy.

Development of neural network for analysis of local power distributions in BWR fuel bundles

International Nuclear Information System (INIS)

Tanabe, Akira; Yamamoto, Toru; Shinfuku, Kimihiro; Nakamae, Takuji.

1993-01-01

A neural network model has been developed to learn the local power distributions in a BWR fuel bundle. A two layers neural network with total 128 elements is used for this model. The neural network learns 33 cases of local power peaking factors of fuel rods with given enrichment distribution as the teacher signals, which were calculated by a fuel bundle nuclear analysis code based on precise physical models. This neural network model studied well the teacher signals within 1 % error. It is also able to calculate the local power distributions within several % error for the different enrichment distributions from the teacher signals when the average enrichment is close to 2 %. This neural network is simple and the computing speed of this model is 300 times faster than that of the precise nuclear analysis code. This model was applied to survey the enrichment distribution to meet a target local power distribution in a fuel bundle, and the enrichment distribution with flat power shape are obtained within short computing time. (author)

Forelimb bone curvature in terrestrial and arboreal mammals

Directory of Open Access Journals (Sweden)

Keith Henderson

2017-04-01

Full Text Available It has recently been proposed that the caudal curvature (concave caudal side observed in the radioulna of terrestrial quadrupeds is an adaptation to the habitual action of the triceps muscle which causes cranial bending strains (compression on cranial side. The caudal curvature is proposed to be adaptive because longitudinal loading induces caudal bending strains (increased compression on the caudal side, and these opposing bending strains counteract each other leaving the radioulna less strained. If this is true for terrestrial quadrupeds, where triceps is required for habitual elbow extension, then we might expect that in arboreal species, where brachialis is habitually required to maintain elbow flexion, the radioulna should instead be cranially curved. This study measures sagittal curvature of the ulna in a range of terrestrial and arboreal primates and marsupials, and finds that their ulnae are curved in opposite directions in these two locomotor categories. This study also examines sagittal curvature in the humerus in the same species, and finds differences that can be attributed to similar adaptations: the bone is curved to counter the habitual muscle action required by the animal’s lifestyle, the difference being mainly in the distal part of the humerus, where arboreal animals tend have a cranial concavity, thought to be in response the carpal and digital muscles that pull cranially on the distal humerus.

Heat transfer through turbulent boundary layers - The effects of introduction of and recovery from convex curvature

Science.gov (United States)

Simon, T. W.; Moffat, R. J.

1979-01-01

Measurements have been made of the heat transfer through a turbulent boundary layer on a convexly curved isothermal wall and on a flat plate following the curved section. Data were taken for one free-stream velocity and two different ratios of boundary layer thickness to radius of curvature delta/R = 0.051 and delta/R = 0.077. Only small differences were observed in the distribution of heat transfer rates for the two boundary layer thicknesses tested, although differences were noted in the temperature distributions within the boundary layer

Curvature effects in two-dimensional optical devices inspired by transformation optics

KAUST Repository

Yuan, Shuhao

2016-11-14

Light transport in curved quasi two-dimensional waveguides is considered theoretically. Within transformation optics and tensor theory, a concise description of curvature effects on transverse electric and magnetic waves is derived. We show that the curvature can induce light focusing and photonic crystal properties, which are confirmed by finite element simulations. Our results indicate that the curvature is an effective parameter for designing quasi two-dimensional optical devices in the fields of micro and nano photonics. © 2016 Author(s).

Quantifying the Relationship Between Curvature and Electric Potential in Lipid Bilayers

DEFF Research Database (Denmark)

Bruhn, Dennis Skjøth; Lomholt, Michael Andersen; Khandelia, Himanshu

2016-01-01

Cellular membranes mediate vital cellular processes by being subject to curvature and transmembrane electrical potentials. Here we build upon the existing theory for flexoelectricity in liquid crystals to quantify the coupling between lipid bilayer curvature and membrane potentials. Using molecular...... dynamics simulations, we show that head group dipole moments, the lateral pressure profile across the bilayer and spontaneous curvature all systematically change with increasing membrane potentials. In particu- lar, there is a linear dependence between the bending moment (the product of bending rigidity...

Distal root curvatures in mandibular molars: analysis using digital panoramic X-rays.

Science.gov (United States)

Fuentes, R; Farfán, C; Astete, N; Navarro, P; Arias, A

2018-01-01

The aim of this study was to describe the degree of curvature in distal roots in the first and second permanent mandibular molars in a Chilean patient sample. A cross-sectional descriptive study was conducted in which digital panoramic X-rays were analysed. Examinations of patients under 18 years, with signs of distortion or alteration in the contrast or the presence of pathologies that affected visualisation of the roots and pulp-chamber floor of the teeth to be analysed were excluded. Using the AutoCad software, an angle was drawn to represent the curve of the root in its different thirds, drawing lines inside the root canal from the pulp-chamber floor to the dental apex. Using the classic definition of dilaceration (root curvature > 90°), its prevalence was established. 412 teeth and roots were analysed, finding a dilaceration prevalence of 0.73% (n = 3). 84.72% of the roots presented some type of curvature. The middle third had the highest percentage of curvatures and the greatest average of angular curvature, whereas the cervical third was the straightest. No significant differences were found between the degree of curvature and the gender of the subjects, except for the apical third of tooth 3.6. The analysis of curvature by root third offers to the clinician a better perspective of the directional change of the roots and does not limit it to just the presence of curves in the apical third. The report of the angular degree of the curvatures, in addition to the prevalence of dilacerations, informs to the clinicians about the likelihood of finding difficulties when treating root canals. (Folia Morphol 2018; 77, 1: 131-137).

The spinning particle with extrinsic curvature

International Nuclear Information System (INIS)

Dhar, A.

1988-01-01

We construct and analyse an action for the spinning particle which contains an extrinsic curvature term. A possible generalization of this construction to the case of the spinning string is also discussed. (orig.)

Curvature effects on the electronic and transport properties of semiconductor films

Science.gov (United States)

Batista, F. F.; Chaves, Andrey; da Costa, D. R.; Farias, G. A.

2018-05-01

Within the effective mass approximation, we study the curvature effects on the electronic and transport properties of semiconductor films. We investigate how the geometry-induced potential resulting exclusively from periodic ripples in the film induces electronic confinement and a superlattice band structure. For fixed curvature parameters, such a confinement can be easily tuned by an external electric field, hence features of the superlattice band structure such as its energy gaps and band curvature can be controlled by an external parameter. We also show that, for some values of curvature and electric field, it is possible to obtain massless Dirac bands for a smooth curved structure. Moreover, we use a wave packet propagation method to demonstrate that the ripples are responsible for a significant inter-sub-band transition, specially for moderate values of the ripple height.

On the asymptotically Poincaré-Einstein 4-manifolds with harmonic curvature

Science.gov (United States)

Hu, Xue

2018-06-01

In this paper, we discuss the mass aspect tensor and the rigidity of an asymptotically Poincaré-Einstein (APE) 4-manifold with harmonic curvature. We prove that the trace-free part of the mass aspect tensor of an APE 4-manifold with harmonic curvature and normalized Einstein conformal infinity is zero. As to the rigidity, we first show that a complete noncompact Riemannian 4-manifold with harmonic curvature and positive Yamabe constant as well as a L2-pinching condition is Einstein. As an application, we then obtain that an APE 4-manifold with harmonic curvature and positive Yamabe constant is isometric to the hyperbolic space provided that the L2-norm of the traceless Ricci tensor or the Weyl tensor is small enough and the conformal infinity is a standard round 3-sphere.

Influence of topography on landscape radiation temperature distribution

International Nuclear Information System (INIS)

Florinsky, I.V.; Kulagina, T.B.; Meshalkina, J.L.

1994-01-01

The evaluation of the influence of topography on landscape radiation temperature distribution is carried out by statistical processing of digital models of elevation, gradient, aspect, horizontal, vertical and mean land surface curvatures and the infrared thermal scene generated by the Thermovision 880 system. Significant linear correlation coefficients between the landscape radiation temperature and elevation, slope, aspect, vertical and mean landsurface curvatures are determined, being —0-57, 0 38, 0-26, 015, 013, respectively. The equation of the topography influence on the distribution of the landscape radiation temperature is defined. (author)

Measurement of curvature and twist of a deformed object using digital holography

International Nuclear Information System (INIS)

Chen Wen; Quan Chenggen; Cho Jui Tay

2008-01-01

Measurement of curvature and twist is an important aspect in the study of object deformation. In recent years, several methods have been proposed to determine curvature and twist of a deformed object using digital shearography. Here we propose a novel method to determine the curvature and twist of a deformed object using digital holography and a complex phasor. A sine/cosine transformation method and two-dimensional short time Fourier transform are proposed subsequently to process the wrapped phase maps. It is shown that high-quality phase maps corresponding to curvature and twist can be obtained. An experiment is conducted to demonstrate the validity of the proposed method

Numerical studies of transverse curvature effects on transonic flow stability

Science.gov (United States)

Macaraeg, M. G.; Daudpota, Q. I.

1992-01-01

A numerical study of transverse curvature effects on compressible flow temporal stability for transonic to low supersonic Mach numbers is presented for axisymmetric modes. The mean flows studied include a similar boundary-layer profile and a nonsimilar axisymmetric boundary-layer solution. The effect of neglecting curvature in the mean flow produces only small quantitative changes in the disturbance growth rate. For transonic Mach numbers (1-1.4) and aerodynamically relevant Reynolds numbers (5000-10,000 based on displacement thickness), the maximum growth rate is found to increase with curvature - the maximum occurring at a nondimensional radius (based on displacement thickness) between 30 and 100.

Influence of firing time and framework thickness on veneered Y-TZP discs curvature.

Science.gov (United States)

Jakubowicz-Kohen, Boris D; Sadoun, Michaël J; Douillard, Thierry; Mainjot, Amélie K

2014-02-01

The objective of the present work was to study the curvature of very thinly, veneered Y-TZP discs of different framework thicknesses submitted to different firing times. Fifteen 20-mm-wide Y-TZP discs were produced in three different thicknesses: 0.75, 1, 1.5mm. One disc from each group was left unveneered while the others were layered with a 0.1mm veneering ceramic layer. All discs underwent five firing cycles for a total cumulative firing time of 30 min, 1, 2, 5 and 10h at 900°C. The curvature profile was measured using a profilometer after the veneering process and after each firing cycle respectively. A fitted curve was then used to estimate the, curvature radius. The coefficient of thermal expansion (CTE) measurements were taken on veneering, ceramic and Y-TZP beam samples that underwent the same firing schedule. Those data were used to calculate the curvature generated by CTE variations over firing time. All bilayered samples exhibited a curvature that increased over firing time inversely to framework thickness. However non-veneered samples did not exhibit any curvature modification. The results of the present study reveal that even a very thin veneer layer (0.1mm) can induce a significant curvature of Y-TZP discs. The dilatometric results showed that Tg and CTE, variations are not sufficient to explain this curvature. A chemical-induced zirconia volume, augmentation located at the framework sub-surface near the interface could explain the sample, curvature and its increase with firing time. Copyright © 2013 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

Study of the localization of slaughterhouses and distribution center of broilers agroindustries in Distrito Federal

Directory of Open Access Journals (Sweden)

Eliane Almeida do Carmo

2011-02-01

Full Text Available The work investigated the localization of an avian industry and optimized its net, from the corporatives to the consumers, determining the amount of slaughterhouses and distribution centers that the concern should possess and their localization in order to minimize costs. From the collection of real data and by utilizing tools of Geographic Information Systems and binary linear programming, the optimum setting for the net as well the setting of several alternative scenarios were determined. The objective function utilized minimizes the sum of the costs of the slaughterhouse localization, the costs of the localization of the distribution center, the production costs and shipment of the living chickens from the corporatives to the slaughterhouse, the costs of slaughter and shipment as far as the distribution center and the storage costs in the distribution center and shipment to the end clients. The optimum scenario obtained takes into account only the establishment of a slaughterhouse and a distribution center of increased capacity, standing out scale gains. The results support the localization of slaughterhouses close to the coporatives and distribution centers close to the clients submitted to the several restrictions imposed by the local reality.

Discrete Curvatures and Discrete Minimal Surfaces

KAUST Repository

Sun, Xiang

2012-01-01

This thesis presents an overview of some approaches to compute Gaussian and mean curvature on discrete surfaces and discusses discrete minimal surfaces. The variety of applications of differential geometry in visualization and shape design leads

Curvature effects in carbon nanomaterials: Exohedral versus endohedral supercapacitors

OpenAIRE

Huang, Jingsong; Bobby,; Sumpter, Bobby G.; Meunier, Vincent; Yushin, Gleb; Portet, Cristelle; Gogotsi, Yury

2010-01-01

Capacitive energy storage mechanisms in nanoporous carbon supercapacitors hinge on endohedral interactions in carbon materials with macro-, meso-, and micropores that have negative surface curvature. In this article, we show that because of the positive curvature found in zero-dimensional carbon onions or one-dimensional carbon nanotube arrays, exohedral interactions cause the normalized capacitance to increase with decreasing particle size or tube diameter, in sharp contrast to the behavior ...

A non-differential elastomer curvature sensor for softer-than-skin electronics

International Nuclear Information System (INIS)

Majidi, C; Kramer, R; Wood, R J

2011-01-01

We extend soft lithography microfabrication and design methods to introduce curvature sensors that are elastically soft (modulus 0.1–1 MPa) and stretchable (100–1000% strain). In contrast to existing curvature sensors that measure differential strain, sensors in this new class measure curvature directly and allow for arbitrary gauge factor and film thickness. Moreover, each sensor is composed entirely of a soft elastomer (PDMS (polydimethylsiloxane) or Ecoflex ® ) and conductive liquid (eutectic gallium indium, eGaIn) and thus remains functional even when stretched to several times its natural length. The electrical resistance in the embedded eGaIn microchannel is measured as a function of the bending curvature for a variety of sensor designs. In all cases, the experimental measurements are in reasonable agreement with closed-form algebraic approximations derived from elastic plate theory and Ohm's law

A non-differential elastomer curvature sensor for softer-than-skin electronics

Science.gov (United States)

Majidi, C.; Kramer, R.; Wood, R. J.

2011-10-01

We extend soft lithography microfabrication and design methods to introduce curvature sensors that are elastically soft (modulus 0.1-1 MPa) and stretchable (100-1000% strain). In contrast to existing curvature sensors that measure differential strain, sensors in this new class measure curvature directly and allow for arbitrary gauge factor and film thickness. Moreover, each sensor is composed entirely of a soft elastomer (PDMS (polydimethylsiloxane) or Ecoflex®) and conductive liquid (eutectic gallium indium, eGaIn) and thus remains functional even when stretched to several times its natural length. The electrical resistance in the embedded eGaIn microchannel is measured as a function of the bending curvature for a variety of sensor designs. In all cases, the experimental measurements are in reasonable agreement with closed-form algebraic approximations derived from elastic plate theory and Ohm's law.

COM-LOC: A Distributed Range-Free Localization Algorithm in Wireless Networks

NARCIS (Netherlands)

Dil, B.J.; Havinga, Paul J.M.; Marusic, S; Palaniswami, M; Gubbi, J.; Law, Y.W.

2009-01-01

This paper investigates distributed range-free localization in wireless networks using a communication protocol called sum-dist which is commonly employed by localization algorithms. With this protocol, the reference nodes flood the network in order to estimate the shortest distance between the

Local, distributed topology control for large-scale wireless ad-hoc networks

NARCIS (Netherlands)

Nieberg, T.; Hurink, Johann L.

In this document, topology control of a large-scale, wireless network by a distributed algorithm that uses only locally available information is presented. Topology control algorithms adjust the transmission power of wireless nodes to create a desired topology. The algorithm, named local power

Embedded positive constant r-mean curvature hypersurfaces in Mm × R

Directory of Open Access Journals (Sweden)

Cheng Xu

2005-01-01

Full Text Available Let M be an m-dimensional Riemannian manifold with sectional curvature bounded from below. We consider hypersurfaces in the (m + 1-dimensional product manifold M x R with positive constant r-mean curvature. We obtain height estimates of certain compact vertical graphs in M x R with boundary in M x {0}. We apply this to obtain topological obstructions for the existence of some hypersurfaces. We also discuss the rotational symmetry of some embedded complete surfaces in S² x R of positive constant 2-mean curvature.

Climate Controls AM Fungal Distributions from Global to Local Scales

Science.gov (United States)

Kivlin, S. N.; Hawkes, C.; Muscarella, R.; Treseder, K. K.; Kazenel, M.; Lynn, J.; Rudgers, J.

2016-12-01

Arbuscular mycorrhizal (AM) fungi have key functions in terrestrial biogeochemical processes; thus, determining the relative importance of climate, edaphic factors, and plant community composition on their geographic distributions can improve predictions of their sensitivity to global change. Local adaptation by AM fungi to plant hosts, soil nutrients, and climate suggests that all of these factors may control fungal geographic distributions, but their relative importance is unknown. We created species distribution models for 142 AM fungal taxa at the global scale with data from GenBank. We compared climate variables (BioClim and soil moisture), edaphic variables (phosphorus, carbon, pH, and clay content), and plant variables using model selection on models with (1) all variables, (2) climatic variables only (including soil moisture) and (3) resource-related variables only (all other soil parameters and NPP) using the MaxEnt algorithm evaluated with ENMEval. We also evaluated whether drivers of AM fungal distributions were phylogenetically conserved. To test whether global correlates of AM fungal distributions were reflected at local scales, we then surveyed AM fungi in nine plant hosts along three elevation gradients in the Upper Gunnison Basin, Colorado, USA. At the global scale, the distributions of 55% of AM fungal taxa were affected by both climate and soil resources, whereas 16% were only affected by climate and 29% were only affected by soil resources. Even for AM fungi that were affected by both climate and resources, the effects of climatic variables nearly always outweighed those of resources. Soil moisture and isothermality were the main climatic and NPP and soil carbon the main resource related factors influencing AM fungal distributions. Distributions of closely related AM fungal taxa were similarly affected by climate, but not by resources. Local scale surveys of AM fungi across elevations confirmed that climate was a key driver of AM fungal

Some curvature properties of quarter symmetric metric connections

International Nuclear Information System (INIS)

Rastogi, S.C.

1986-08-01

A linear connection Γ ji h with torsion tensor T j h P i -T i h P j , where T j h is an arbitrary (1,1) tensor field and P i is a 1-form, has been called a quarter-symmetric connection by Golab. Some properties of such connections have been studied by Rastogi, Mishra and Pandey, and Yano and Imai. In this paper based on the curvature tensor of quarter-symmetric metric connection we define a tensor analogous to conformal curvature tensor and study some properties of such a tensor. (author)

No large scale curvature perturbations during the waterfall phase transition of hybrid inflation

International Nuclear Information System (INIS)

Abolhasani, Ali Akbar; Firouzjahi, Hassan

2011-01-01

In this paper the possibility of generating large scale curvature perturbations induced from the entropic perturbations during the waterfall phase transition of the standard hybrid inflation model is studied. We show that whether or not appreciable amounts of large scale curvature perturbations are produced during the waterfall phase transition depends crucially on the competition between the classical and the quantum mechanical backreactions to terminate inflation. If one considers only the classical evolution of the system, we show that the highly blue-tilted entropy perturbations induce highly blue-tilted large scale curvature perturbations during the waterfall phase transition which dominate over the original adiabatic curvature perturbations. However, we show that the quantum backreactions of the waterfall field inhomogeneities produced during the phase transition dominate completely over the classical backreactions. The cumulative quantum backreactions of very small scale tachyonic modes terminate inflation very efficiently and shut off the curvature perturbation evolution during the waterfall phase transition. This indicates that the standard hybrid inflation model is safe under large scale curvature perturbations during the waterfall phase transition.

Intracellular magnetophoresis of amyloplasts and induction of root curvature

Science.gov (United States)

Kuznetsov, O. A.; Hasenstein, K. H.

1996-01-01

High-gradient magnetic fields (HGMFs) were used to induce intracellular magnetophoresis of amyloplasts. The HGMFs were generated by placing a small ferromagnetic wedge into a uniform magnetic field or at the gap edge between two permanent magnets. In the vicinity of the tip of the wedge the dynamic factor of the magnetic field, delta(H2/2), was about 10(9) Oe2.cm-1, which subjected the amyloplasts to a force comparable to that of gravity. When roots of 2-d-old seedlings of flax (Linum usitatissimum L.) were positioned vertically and exposed to an HGMF, curvature away from the wedge was transient and lasted approximately 1 h. Average curvature obtained after placing magnets, wedge and seedlings on a 1-rpm clinostat for 2 h was 33 +/- 5 degrees. Roots of horizontally placed control seedlings without rotation curved about 47 +/- 4 degrees. The time course of curvature and changes in growth rate were similar for gravicurvature and for root curvature induced by HGMFs. Microscopy showed displacement of amyloplasts in vitro and in vivo. Studies with Arabidopsis thaliana (L.) Heynh. showed that the wild type responded to HGMFs but the starchless mutant TC7 did not. The data indicate that a magnetic force can be used to study the gravisensing and response system of roots.

Curvature function and coarse graining

International Nuclear Information System (INIS)

Diaz-Marin, Homero; Zapata, Jose A.

2010-01-01

A classic theorem in the theory of connections on principal fiber bundles states that the evaluation of all holonomy functions gives enough information to characterize the bundle structure (among those sharing the same structure group and base manifold) and the connection up to a bundle equivalence map. This result and other important properties of holonomy functions have encouraged their use as the primary ingredient for the construction of families of quantum gauge theories. However, in these applications often the set of holonomy functions used is a discrete proper subset of the set of holonomy functions needed for the characterization theorem to hold. We show that the evaluation of a discrete set of holonomy functions does not characterize the bundle and does not constrain the connection modulo gauge appropriately. We exhibit a discrete set of functions of the connection and prove that in the abelian case their evaluation characterizes the bundle structure (up to equivalence), and constrains the connection modulo gauge up to ''local details'' ignored when working at a given scale. The main ingredient is the Lie algebra valued curvature function F S (A) defined below. It covers the holonomy function in the sense that expF S (A)=Hol(l=∂S,A).

Local Flexibility Market Design for Aggregators Providing Multiple Flexibility Services at Distribution Network Level

Directory of Open Access Journals (Sweden)

Pol Olivella-Rosell

2018-04-01

Full Text Available This paper presents a general description of local flexibility markets as a market-based management mechanism for aggregators. The high penetration of distributed energy resources introduces new flexibility services like prosumer or community self-balancing, congestion management and time-of-use optimization. This work is focused on the flexibility framework to enable multiple participants to compete for selling or buying flexibility. In this framework, the aggregator acts as a local market operator and supervises flexibility transactions of the local energy community. Local market participation is voluntary. Potential flexibility stakeholders are the distribution system operator, the balance responsible party and end-users themselves. Flexibility is sold by means of loads, generators, storage units and electric vehicles. Finally, this paper presents needed interactions between all local market stakeholders, the corresponding inputs and outputs of local market operation algorithms from participants and a case study to highlight the application of the local flexibility market in three scenarios. The local market framework could postpone grid upgrades, reduce energy costs and increase distribution grids’ hosting capacity.

Curvature-Controlled Topological Defects

Directory of Open Access Journals (Sweden)

Luka Mesarec

2017-05-01

Full Text Available Effectively, two-dimensional (2D closed films exhibiting in-plane orientational ordering (ordered shells might be instrumental for the realization of scaled crystals. In them, ordered shells are expected to play the role of atoms. Furthermore, topological defects (TDs within them would determine their valence. Namely, bonding among shells within an isotropic liquid matrix could be established via appropriate nano-binders (i.e., linkers which tend to be attached to the cores of TDs exploiting the defect core replacement mechanism. Consequently, by varying configurations of TDs one could nucleate growth of scaled crystals displaying different symmetries. For this purpose, it is of interest to develop a simple and robust mechanism via which one could control the position and number of TDs in such atoms. In this paper, we use a minimal mesoscopic model, where variational parameters are the 2D curvature tensor and the 2D orientational tensor order parameter. We demonstrate numerically the efficiency of the effective topological defect cancellation mechanism to predict positional assembling of TDs in ordered films characterized by spatially nonhomogeneous Gaussian curvature. Furthermore, we show how one could efficiently switch among qualitatively different structures by using a relative volume v of ordered shells, which represents a relatively simple naturally accessible control parameter.

Cosmological signatures of anisotropic spatial curvature

International Nuclear Information System (INIS)

Pereira, Thiago S.; Marugán, Guillermo A. Mena; Carneiro, Saulo

2015-01-01

If one is willing to give up the cherished hypothesis of spatial isotropy, many interesting cosmological models can be developed beyond the simple anisotropically expanding scenarios. One interesting possibility is presented by shear-free models in which the anisotropy emerges at the level of the curvature of the homogeneous spatial sections, whereas the expansion is dictated by a single scale factor. We show that such models represent viable alternatives to describe the large-scale structure of the inflationary universe, leading to a kinematically equivalent Sachs-Wolfe effect. Through the definition of a complete set of spatial eigenfunctions we compute the two-point correlation function of scalar perturbations in these models. In addition, we show how such scenarios would modify the spectrum of the CMB assuming that the observations take place in a small patch of a universe with anisotropic curvature

Cosmological signatures of anisotropic spatial curvature

Energy Technology Data Exchange (ETDEWEB)

Pereira, Thiago S. [Departamento de Física, Universidade Estadual de Londrina, 86057-970, Londrina – PR (Brazil); Marugán, Guillermo A. Mena [Instituto de Estructura de la Materia, IEM-CSIC, Serrano 121, 28006, Madrid (Spain); Carneiro, Saulo, E-mail: tspereira@uel.br, E-mail: mena@iem.cfmac.csic.es, E-mail: saulo.carneiro@pq.cnpq.br [Instituto de Física, Universidade Federal da Bahia, 40210-340, Salvador – BA (Brazil)

2015-07-01

If one is willing to give up the cherished hypothesis of spatial isotropy, many interesting cosmological models can be developed beyond the simple anisotropically expanding scenarios. One interesting possibility is presented by shear-free models in which the anisotropy emerges at the level of the curvature of the homogeneous spatial sections, whereas the expansion is dictated by a single scale factor. We show that such models represent viable alternatives to describe the large-scale structure of the inflationary universe, leading to a kinematically equivalent Sachs-Wolfe effect. Through the definition of a complete set of spatial eigenfunctions we compute the two-point correlation function of scalar perturbations in these models. In addition, we show how such scenarios would modify the spectrum of the CMB assuming that the observations take place in a small patch of a universe with anisotropic curvature.

On $L_p$ Affine Surface Area and Curvature Measures

OpenAIRE

Zhao, Yiming

2015-01-01

The relationship between $L_p$ affine surface area and curvature measures is investigated. As a result, a new representation of the existing notion of $L_p$ affine surface area depending only on curvature measures is derived. Direct proofs of the equivalence between this new representation and those previously known are provided. The proofs show that the new representation is, in a sense, "polar" to that of Lutwak's and "dual" to that of Sch\\"utt & Werner's.

On harmonic curvatures of a Frenet curve in Lorentzian space

International Nuclear Information System (INIS)

Kuelahci, Mihriban; Bektas, Mehmet; Erguet, Mahmut

2009-01-01

In this paper, we consider curves of AW(k)-type, 1 ≤ k ≤ 3, in Lorentzian space. We give curvature conditions of these kind of curves. Furthermore, we study harmonic curvatures of curves of AW(k)-type. We investigate that under what conditions AW(k)-type curves are helix. Some related theorems and corollaries are also proved.

Scalable and Fully Distributed Localization in Large-Scale Sensor Networks

Directory of Open Access Journals (Sweden)

Miao Jin

2017-06-01

Full Text Available This work proposes a novel connectivity-based localization algorithm, well suitable for large-scale sensor networks with complex shapes and a non-uniform nodal distribution. In contrast to current state-of-the-art connectivity-based localization methods, the proposed algorithm is highly scalable with linear computation and communication costs with respect to the size of the network; and fully distributed where each node only needs the information of its neighbors without cumbersome partitioning and merging process. The algorithm is theoretically guaranteed and numerically stable. Moreover, the algorithm can be readily extended to the localization of networks with a one-hop transmission range distance measurement, and the propagation of the measurement error at one sensor node is limited within a small area of the network around the node. Extensive simulations and comparison with other methods under various representative network settings are carried out, showing the superior performance of the proposed algorithm.

FULLY AUTOMATED GIS-BASED INDIVIDUAL TREE CROWN DELINEATION BASED ON CURVATURE VALUES FROM A LIDAR DERIVED CANOPY HEIGHT MODEL IN A CONIFEROUS PLANTATION

Directory of Open Access Journals (Sweden)

R. J. L. Argamosa

2016-06-01

Full Text Available The generation of high resolution canopy height model (CHM from LiDAR makes it possible to delineate individual tree crown by means of a fully-automated method using the CHM’s curvature through its slope. The local maxima are obtained by taking the maximum raster value in a 3 m x 3 m cell. These values are assumed as tree tops and therefore considered as individual trees. Based on the assumptions, thiessen polygons were generated to serve as buffers for the canopy extent. The negative profile curvature is then measured from the slope of the CHM. The results show that the aggregated points from a negative profile curvature raster provide the most realistic crown shape. The absence of field data regarding tree crown dimensions require accurate visual assessment after the appended delineated tree crown polygon was superimposed to the hill shaded CHM.

Curvature perturbation spectra from waterfall transition, black hole constraints and non-Gaussianity

Energy Technology Data Exchange (ETDEWEB)

Bugaev, Edgar; Klimai, Peter, E-mail: bugaev@pcbai10.inr.ruhep.ru, E-mail: pklimai@gmail.com [Institute for Nuclear Research, Russian Academy of Sciences, 60th October Anniversary Prospect 7a, 117312 Moscow (Russian Federation)

2011-11-01

We carried out numerical calculations of a contribution of the waterfall field to the primordial curvature perturbation (on uniform density hypersurfaces) ζ, which is produced during waterfall transition in hybrid inflation scenario. The calculation is performed for a broad interval of values of the model parameters. We show that there is a strong growth of amplitudes of the curvature perturbation spectrum in the limit when the bare mass-squared of the waterfall field becomes comparable with the square of Hubble parameter. We show that in this limit the primordial black hole constraints on the curvature perturbations must be taken into account. It is shown that, in the same limit, peak values of the curvature perturbation spectra are far beyond horizon, and the spectra are strongly non-Gaussian.

Curvature perturbation spectra from waterfall transition, black hole constraints and non-Gaussianity

International Nuclear Information System (INIS)

Bugaev, Edgar; Klimai, Peter

2011-01-01

We carried out numerical calculations of a contribution of the waterfall field to the primordial curvature perturbation (on uniform density hypersurfaces) ζ, which is produced during waterfall transition in hybrid inflation scenario. The calculation is performed for a broad interval of values of the model parameters. We show that there is a strong growth of amplitudes of the curvature perturbation spectrum in the limit when the bare mass-squared of the waterfall field becomes comparable with the square of Hubble parameter. We show that in this limit the primordial black hole constraints on the curvature perturbations must be taken into account. It is shown that, in the same limit, peak values of the curvature perturbation spectra are far beyond horizon, and the spectra are strongly non-Gaussian

Estimation of Curvature Changes for Steel-Concrete Composite Bridge Using Fiber Bragg Grating Sensors

OpenAIRE

Kang, Donghoon; Chung, Wonseok

2013-01-01

This study is focused on the verification of the key idea of a newly developed steel-concrete composite bridge. The key idea of the proposed bridge is to reduce the design moment by applying vertical prestressing force to steel girders, so that a moment distribution of a continuous span bridge is formed in a simple span bridge. For the verification of the key technology, curvature changes of the bridge should be monitored sequentially at every construction stage. A pair of multiplexed FBG sen...

Multiobjective memetic estimation of distribution algorithm based on an incremental tournament local searcher.

Science.gov (United States)

Yang, Kaifeng; Mu, Li; Yang, Dongdong; Zou, Feng; Wang, Lei; Jiang, Qiaoyong

2014-01-01

A novel hybrid multiobjective algorithm is presented in this paper, which combines a new multiobjective estimation of distribution algorithm, an efficient local searcher and ε-dominance. Besides, two multiobjective problems with variable linkages strictly based on manifold distribution are proposed. The Pareto set to the continuous multiobjective optimization problems, in the decision space, is a piecewise low-dimensional continuous manifold. The regularity by the manifold features just build probability distribution model by globally statistical information from the population, yet, the efficiency of promising individuals is not well exploited, which is not beneficial to search and optimization process. Hereby, an incremental tournament local searcher is designed to exploit local information efficiently and accelerate convergence to the true Pareto-optimal front. Besides, since ε-dominance is a strategy that can make multiobjective algorithm gain well distributed solutions and has low computational complexity, ε-dominance and the incremental tournament local searcher are combined here. The novel memetic multiobjective estimation of distribution algorithm, MMEDA, was proposed accordingly. The algorithm is validated by experiment on twenty-two test problems with and without variable linkages of diverse complexities. Compared with three state-of-the-art multiobjective optimization algorithms, our algorithm achieves comparable results in terms of convergence and diversity metrics.

Multiobjective Memetic Estimation of Distribution Algorithm Based on an Incremental Tournament Local Searcher

Directory of Open Access Journals (Sweden)

Kaifeng Yang

2014-01-01

Full Text Available A novel hybrid multiobjective algorithm is presented in this paper, which combines a new multiobjective estimation of distribution algorithm, an efficient local searcher and ε-dominance. Besides, two multiobjective problems with variable linkages strictly based on manifold distribution are proposed. The Pareto set to the continuous multiobjective optimization problems, in the decision space, is a piecewise low-dimensional continuous manifold. The regularity by the manifold features just build probability distribution model by globally statistical information from the population, yet, the efficiency of promising individuals is not well exploited, which is not beneficial to search and optimization process. Hereby, an incremental tournament local searcher is designed to exploit local information efficiently and accelerate convergence to the true Pareto-optimal front. Besides, since ε-dominance is a strategy that can make multiobjective algorithm gain well distributed solutions and has low computational complexity, ε-dominance and the incremental tournament local searcher are combined here. The novel memetic multiobjective estimation of distribution algorithm, MMEDA, was proposed accordingly. The algorithm is validated by experiment on twenty-two test problems with and without variable linkages of diverse complexities. Compared with three state-of-the-art multiobjective optimization algorithms, our algorithm achieves comparable results in terms of convergence and diversity metrics.

A high resolution electron microscopy investigation of curvature in carbon nanotubes

Science.gov (United States)

Weldon, D. N.; Blau, W. J.; Zandbergen, H. W.

1995-07-01

Evidence for heptagon inclusion in multi-walled carbon nanotubes was sought in arc-produced carbon deposits. Transmission electron microscopy revealed many curved nanotubes although their relative abundance was low. Close examination of the micrographs in the regions of expected heptagon inclusion shows that the curvature is accomplished by folding or fracture of the lattice planes. This observed phenomenon contradicts the theoretical modelling studies which predict stable structures with negative curvature accomplished by heptagon/pentagon pairs. A possible explanation for curvature in single-walled tubes is presented based on a molecular mechanics geometry optimisation study of spa inclusion in a graphite sheet.

Curvature contributions to the static electrical properties of push-pull molecules

International Nuclear Information System (INIS)

Squitieri, Emilio

2005-01-01

Calculations of the curvature contribution to the diagonals components of the static dipole moment (μ), polarizability (α), first (β) and second (γ) hyperpolarizability of push-pull molecules are presented. This contribution was obtained from the analytical evaluation of electrical properties method using the harmonic zero-point energy. The valence-bond charge-transfer model was employed to obtain the field-dependent force constant and their derivates with respect to electric field. Our results show a relationship between the curvature and electronic contributions. We have also found that the curvature contribution is important in a numerical estimation of β and γ

Frame-Covariant Formulation of Inflation in Scalar-Curvature Theories

CERN Document Server

Burns, Daniel; Pilaftsis, Apostolos

2016-01-01

We develop a frame-covariant formulation of inflation in the slow-roll approximation by generalizing the inflationary attractor solution for scalar-curvature theories. Our formulation gives rise to new generalized forms for the potential slow-roll parameters, which enable us to examine the effect of conformal transformations and inflaton reparameterizations in scalar-curvature theories. We find that cosmological observables, such as the power spectrum, the spectral indices and their runnings, can be expressed in a concise manner in terms of the generalized potential slow-roll parameters which depend on the scalar-curvature coupling function, the inflaton wavefunction, and the inflaton potential. We show how the cosmological observables of inflation are frame-invariant in this generalized potential slow-roll formalism, as long as the end-of-inflation condition is appropriately extended to become frame-invariant as well. We then apply our formalism to specific scenarios, such as the induced gravity inflation, H...

The scalar curvature problem on the four dimensional half sphere

CERN Document Server

Ben-Ayed, M; El-Mehdi, K

2003-01-01

In this paper, we consider the problem of prescribing the scalar curvature under minimal boundary conditions on the standard four dimensional half sphere. We provide an Euler-Hopf type criterion for a given function to be a scalar curvature for some metric conformal to the standard one. Our proof involves the study of critical points at infinity of the associated variational problem.

Quantum field theory with a momentum space of constant curvature (perturbation theory)

International Nuclear Information System (INIS)

Mir-Kasimov, R.M.

1978-01-01

In the framework of the field-theoretical approach in which the off-the-mass shell extension proceeds in the p-space of constant curvature, the perburbation theory is developed. The configurational representation of the de Sitter space is introduced with the help of the Fourier transformation of the group of motions. On the basis of a natural generalization of the Bogolyubov causality condition to the case of the new configurational representation a perturbation theory is constructed with the local in xi space Lagrangian density fucntion. The obtained S matrix obeys the reguirement of translation invariance. The S matrix elements are given by convergent expressions

Probing interaction and spatial curvature in the holographic dark energy model

International Nuclear Information System (INIS)

Li, Miao; Li, Xiao-Dong; Wang, Shuang; Wang, Yi; Zhang, Xin

2009-01-01

In this paper we place observational constraints on the interaction and spatial curvature in the holographic dark energy model. We consider three kinds of phenomenological interactions between holographic dark energy and matter, i.e., the interaction term Q is proportional to the energy densities of dark energy (ρ Λ ), matter (ρ m ), and matter plus dark energy (ρ m +ρ Λ ). For probing the interaction and spatial curvature in the holographic dark energy model, we use the latest observational data including the type Ia supernovae (SNIa) Constitution data, the shift parameter of the cosmic microwave background (CMB) given by the five-year Wilkinson Microwave Anisotropy Probe (WMAP5) observations, and the baryon acoustic oscillation (BAO) measurement from the Sloan Digital Sky Survey (SDSS). Our results show that the interaction and spatial curvature in the holographic dark energy model are both rather small. Besides, it is interesting to find that there exists significant degeneracy between the phenomenological interaction and the spatial curvature in the holographic dark energy model

Discrete Curvatures and Discrete Minimal Surfaces

KAUST Repository

Sun, Xiang

2012-06-01

This thesis presents an overview of some approaches to compute Gaussian and mean curvature on discrete surfaces and discusses discrete minimal surfaces. The variety of applications of differential geometry in visualization and shape design leads to great interest in studying discrete surfaces. With the rich smooth surface theory in hand, one would hope that this elegant theory can still be applied to the discrete counter part. Such a generalization, however, is not always successful. While discrete surfaces have the advantage of being finite dimensional, thus easier to treat, their geometric properties such as curvatures are not well defined in the classical sense. Furthermore, the powerful calculus tool can hardly be applied. The methods in this thesis, including angular defect formula, cotangent formula, parallel meshes, relative geometry etc. are approaches based on offset meshes or generalized offset meshes. As an important application, we discuss discrete minimal surfaces and discrete Koenigs meshes.

Plan curvature and landslide probability in regions dominated by earth flows and earth slides

Science.gov (United States)

Ohlmacher, G.C.

2007-01-01

Damaging landslides in the Appalachian Plateau and scattered regions within the Midcontinent of North America highlight the need for landslide-hazard mapping and a better understanding of the geomorphic development of landslide terrains. The Plateau and Midcontinent have the necessary ingredients for landslides including sufficient relief, steep slope gradients, Pennsylvanian and Permian cyclothems that weather into fine-grained soils containing considerable clay, and adequate precipitation. One commonly used parameter in landslide-hazard analysis that is in need of further investigation is plan curvature. Plan curvature is the curvature of the hillside in a horizontal plane or the curvature of the contours on a topographic map. Hillsides can be subdivided into regions of concave outward plan curvature called hollows, convex outward plan curvature called noses, and straight contours called planar regions. Statistical analysis of plan-curvature and landslide datasets indicate that hillsides with planar plan curvature have the highest probability for landslides in regions dominated by earth flows and earth slides in clayey soils (CH and CL). The probability of landslides decreases as the hillsides become more concave or convex. Hollows have a slightly higher probability for landslides than noses. In hollows landslide material converges into the narrow region at the base of the slope. The convergence combined with the cohesive nature of fine-grained soils creates a buttressing effect that slows soil movement and increases the stability of the hillside within the hollow. Statistical approaches that attempt to determine landslide hazard need to account for the complex relationship between plan curvature, type of landslide, and landslide susceptibility. ?? 2007 Elsevier B.V. All rights reserved.

Lipid clustering correlates with membrane curvature as revealed by molecular simulations of complex lipid bilayers.

Directory of Open Access Journals (Sweden)

Heidi Koldsø

2014-10-01

Full Text Available Cell membranes are complex multicomponent systems, which are highly heterogeneous in the lipid distribution and composition. To date, most molecular simulations have focussed on relatively simple lipid compositions, helping to inform our understanding of in vitro experimental studies. Here we describe on simulations of complex asymmetric plasma membrane model, which contains seven different lipids species including the glycolipid GM3 in the outer leaflet and the anionic lipid, phosphatidylinositol 4,5-bisphophate (PIP2, in the inner leaflet. Plasma membrane models consisting of 1500 lipids and resembling the in vivo composition were constructed and simulations were run for 5 µs. In these simulations the most striking feature was the formation of nano-clusters of GM3 within the outer leaflet. In simulations of protein interactions within a plasma membrane model, GM3, PIP2, and cholesterol all formed favorable interactions with the model α-helical protein. A larger scale simulation of a model plasma membrane containing 6000 lipid molecules revealed correlations between curvature of the bilayer surface and clustering of lipid molecules. In particular, the concave (when viewed from the extracellular side regions of the bilayer surface were locally enriched in GM3. In summary, these simulations explore the nanoscale dynamics of model bilayers which mimic the in vivo lipid composition of mammalian plasma membranes, revealing emergent nanoscale membrane organization which may be coupled both to fluctuations in local membrane geometry and to interactions with proteins.

What is the role of curvature on the properties of nanomaterials for biomedical applications?

Science.gov (United States)

Gonzalez Solveyra, Estefania; Szleifer, Igal

2016-05-01

The use of nanomaterials for drug delivery and theranostics applications is a promising paradigm in nanomedicine, as it brings together the best features of nanotechnolgy, molecular biology, and medicine. To fully exploit the synergistic potential of such interdisciplinary strategy, a comprehensive description of the interactions at the interface between nanomaterials and biological systems is not only crucial, but also mandatory. Routine strategies to engineer nanomaterial-based drugs comprise modifying their surface with biocompatible and targeting ligands, in many cases resorting to modular approaches that assume additive behavior. However, emergent behavior can be observed when combining confinement and curvature. The final properties of functionalized nanomaterials become dependent not only on the properties of their constituents but also on the geometry of the nano-bio interface, and on the local molecular environment. Modularity no longer holds, and the coupling between interactions, chemical equilibrium, and molecular organization has to be directly addressed in order to design smart nanomaterials with controlled spatial functionalization envisioning optimized biomedical applications. Nanoparticle's curvature becomes an integral part of the design strategy, enabling to control and engineer the chemical and surface properties with molecular precision. Understanding how nanoparticle size, morphology, and surface chemistry are interrelated will put us one step closer to engineering nanobiomaterials capable of mimicking biological structures and their behaviors, paving the way into applications and the possibility to elucidate the use of curvature by biological systems. WIREs Nanomed Nanobiotechnol 2016, 8:334-354. doi: 10.1002/wnan.1365 For further resources related to this article, please visit the WIREs website. © 2015 Wiley Periodicals, Inc.

The Influence of Shoreline Curvature on Rates of Shoreline Change on Sandy Coasts

Science.gov (United States)

Murray, A. B.; Lauzon, R.; Cheng, S.; Liu, J.; Lazarus, E.

2017-12-01

The sandy, low-lying barrier islands which characterize much of the US East and Gulf coasts are popular spots to live and vacation, and are often heavily developed. However, sandy shorelines and barriers are also naturally mobile landforms, which are vulnerable to sea level rise and storms and can experience high rates of shoreline change. Many previous studies have attempted to understand and quantify the factors that contribute to those rates of shoreline change, such as grain size, underlying geology, sea level rise, and anthropogenic modification. Shoreline curvature has not been considered in such analyses, but previous research has demonstrated that subtle coastline curvature (and therefore alongshore variation in relative offshore wave angle) can result in gradients in net alongshore transport that cause significant shoreline erosion or accretion. Here we present the results of a spatially extensive analysis of the correlation between shoreline curvature and shoreline change rates for the sandy shorelines of the US East and Gulf coasts. We find that, for wave-dominated sandy coasts where nourishment and shoreline stabilization do not dominate the shoreline change signal (such as parts of Texas, North Carolina, and Florida), there is a significant negative correlation between shoreline curvature and shoreline change rates over 1 - 5 km and decadal to centurial space and time scales. This correlation indicates that a portion of the coastal erosion (and accretion) observed in these areas can be explained by the smoothing of subtle coastline curvature by gradients in alongshore transport, and suggests that shoreline curvature should be included in future attempts to understand historical and future rates of shoreline change. Shoreline stabilization, especially through beach nourishment, complicates the relationship between curvature and shoreline change. Beach construction during nourishment creates a seaward convex curvature in the part of the shoreline moves

Soliton surfaces via a zero-curvature representation of differential equations

International Nuclear Information System (INIS)

Grundland, A M; Post, S

2012-01-01

The main aim of this paper is to introduce a new version of the Fokas–Gel’fand formula for immersion of soliton surfaces in Lie algebras. The paper contains a detailed exposition of the technique for obtaining exact forms of 2D surfaces associated with any solution of a given nonlinear ordinary differential equation which can be written in the zero-curvature form. That is, for any generalized symmetry of the zero-curvature condition of the associated integrable model, it is possible to construct soliton surfaces whose Gauss–Mainardi–Codazzi equations are equivalent to infinitesimal deformations of the zero-curvature representation of the considered model. Conversely, it is shown (proposition 1) that for a given immersion function of a 2D soliton surface in a Lie algebra, it is possible to derive the associated generalized vector field in the evolutionary form which characterizes all symmetries of the zero-curvature condition. The theoretical considerations are illustrated via surfaces associated with the Painlevé equations P1, P2 and P3, including transcendental functions, the special cases of the rational and Airy solutions of P2 and the classical solutions of P3. (paper)

Harmonic curvatures and generalized helices in En

International Nuclear Information System (INIS)

Camci, Cetin; Ilarslan, Kazim; Kula, Levent; Hacisalihoglu, H. Hilmi

2009-01-01

In n-dimensional Euclidean space E n , harmonic curvatures of a non-degenerate curve defined by Ozdamar and Hacisalihoglu [Ozdamar E, Hacisalihoglu HH. A characterization of Inclined curves in Euclidean n-space. Comm Fac Sci Univ Ankara, Ser A1 1975;24:15-23]. In this paper, we give some characterizations for a non-degenerate curve α to be a generalized helix by using its harmonic curvatures. Also we define the generalized Darboux vector D of a non-degenerate curve α in n-dimensional Euclidean space E n and we show that the generalized Darboux vector D lies in the kernel of Frenet matrix M(s) if and only if the curve α is a generalized helix in the sense of Hayden.

Mean cortical curvature reflects cytoarchitecture restructuring in mild traumatic brain injury

Directory of Open Access Journals (Sweden)

Jace B. King

2016-01-01

Full Text Available In the United States alone, the number of persons living with the enduring consequences of traumatic brain injuries is estimated to be between 3.2 and 5 million. This number does not include individuals serving in the United States military or seeking care at Veterans Affairs hospitals. The importance of understanding the neurobiological consequences of mild traumatic brain injury (mTBI has increased with the return of veterans from conflicts overseas, many of who have suffered this type of brain injury. However, identifying the neuroanatomical regions most affected by mTBI continues to prove challenging. The aim of this study was to assess the use of mean cortical curvature as a potential indicator of progressive tissue loss in a cross-sectional sample of 54 veterans with mTBI compared to 31 controls evaluated with MRI. It was hypothesized that mean cortical curvature would be increased in veterans with mTBI, relative to controls, due in part to cortical restructuring related to tissue volume loss. Mean cortical curvature was assessed in 60 bilateral regions (31 sulcal, 29 gyral. Of the 120 regions investigated, nearly 50% demonstrated significantly increased mean cortical curvature in mTBI relative to controls with 25% remaining significant following multiple comparison correction (all, pFDR < .05. These differences were most prominent in deep gray matter regions of the cortex. Additionally, significant relationships were found between mean cortical curvature and gray and white matter volumes (all, p < .05. These findings suggest potentially unique patterns of atrophy by region and indicate that changes in brain microstructure due to mTBI are sensitive to measures of mean curvature.

Curvature Derivative Surface used to characterize the complexity of the seafloor around St. John, USVI

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — Curvature was calculated from the bathymetry surface for each raster cell using the ArcGIS 3D Analyst "Curvature" Tool. Curvature describes the rate of change of...

Atomic fine structure in a space of constant curvature

International Nuclear Information System (INIS)

Bessis, N.; Bessis, G.; Shamseddine, R.

1982-01-01

As a contribution to a tentative formulation of atomic physics in a curved space, the determination of atomic fine structure energies in a space of constant curvature is investigated. Starting from the Dirac equation in a curved space-time, the analogue of the Pauli equation in a general coordinate system is derived. The theoretical curvature induced shifts and splittings of the fine structure energy levels are put in evidence and examined for the particular case of the hydrogenic n=2 levels. (author)

Effects of ethylene on the kinetics of curvature and auxin redistribution in gravistimulated roots of Zea mays

Science.gov (United States)

Lee, J. S.; Evans, M. L.

1990-01-01

We tested the involvement of ethylene in maize (Zea mays L.) root gravitropism by measuring the kinetics of curvature and lateral auxin movement in roots treated with ethylene, inhibitors of ethylene synthesis, or inhibitors of ethylene action. In the presence of ethylene the latent period of gravitropic curvature appeared to be increased somewhat. However, ethylene-treated roots continued to curve after control roots had reached their final angle of curvature. Consequently, maximum curvature in the presence of ethylene was much greater in ethylene-treated roots than in controls. Inhibitors of ethylene biosynthesis or action had effects on the kinetics of curvature opposite to that of ethylene, i.e. the latent period appeared to be shortened somewhat while total curvature was reduced relative to that of controls. Label from applied 3H-indole-3-acetic acid was preferentially transported toward the lower side of stimulated roots. In parallel with effects on curvature, ethylene treatment delayed the development of gravity-induced asymmetric auxin movement across the root but extended its duration once initiated. The auxin transport inhibitor, 1-N-naphthylphthalamic acid reduced both gravitropic curvature and the effect of ethylene on curvature. Since neither ethylene nor inhibitors of ethylene biosynthesis or action prevented curvature, we conclude that ethylene does not mediate the primary differential growth response causing curvature. Because ethylene affects curvature and auxin transport in parallel, we suggest that ethylene modifies curvature by affecting gravity-induced lateral transport of auxin, perhaps by interfering with adaptation of the auxin transport system to the gravistimulus.

Existence of conformal metrics on spheres with prescribed Paneitz curvature

International Nuclear Information System (INIS)

Ben Ayed, Mohamed; El Mehdi, Khalil

2003-07-01

In this paper we study the problem of prescribing a fourth order conformal invariant (the Paneitz curvature) on the n-spheres, with n ≥ 5. Using tools from the theory of critical points at infinity, we provide some topological conditions on the level sets of a given function defined on the sphere, under which we prove the existence of conformal metric with prescribed Paneitz curvature. (author)

Existence of conformal metrics on spheres with prescribed Paneitz curvature

CERN Document Server

Ben-Ayed, M

2003-01-01

In this paper we study the problem of prescribing a fourth order conformal invariant (the Paneitz curvature) on the n-spheres, with n >= 5. Using tools from the theory of critical points at infinity, we provide some topological conditions on the level sets of a given function defined on the sphere, under which we prove the existence of conformal metric with prescribed Paneitz curvature.

Formulae for the determination of the elements of the E\\"otvos matrix of the Earth's normal gravity field and a relation between normal and actual Gaussian curvature

OpenAIRE

Manoussakis, G.; Delikaraoglou, D.

2011-01-01

In this paper we form relations for the determination of the elements of the E\\"otv\\"os matrix of the Earth's normal gravity field. In addition a relation between the Gauss curvature of the normal equipotential surface and the Gauss curvature of the actual equipotential surface both passing through the point P is presented. For this purpose we use a global Cartesian system (X, Y, Z) and use the variables X, and Y to form a local parameterization a normal equipotential surface to describe its ...

Curvature tensor copies in affine geometry

International Nuclear Information System (INIS)

Srivastava, P.P.

1981-01-01

The sets of space-time and spin-connections which give rise to the same curvature tensor are constructed. The corresponding geometries are compared. Results are illustrated by an explicit calculation and comment on the copies in Einstein-Cartan and Weyl-Cartan geometries. (Author) [pt

Resolving curvature singularities in holomorphic gravity

NARCIS (Netherlands)

Mantz, C.L.M.; Prokopec, T.

2011-01-01

We formulate a holomorphic theory of gravity and study how the holomorphy symmetry alters the two most important singular solutions of general relativity: black holes and cosmology. We show that typical observers (freely) falling into a holomorphic black hole do not encounter a curvature

Biharmonic Submanifolds with Parallel Mean Curvature Vector in Pseudo-Euclidean Spaces

Energy Technology Data Exchange (ETDEWEB)

Fu, Yu, E-mail: yufudufe@gmail.com [Dongbei University of Finance and Economics, School of Mathematics and Quantitative Economics (China)

2013-12-15

In this paper, we investigate biharmonic submanifolds in pseudo-Euclidean spaces with arbitrary index and dimension. We give a complete classification of biharmonic spacelike submanifolds with parallel mean curvature vector in pseudo-Euclidean spaces. We also determine all biharmonic Lorentzian surfaces with parallel mean curvature vector field in pseudo-Euclidean spaces.

Biharmonic Submanifolds with Parallel Mean Curvature Vector in Pseudo-Euclidean Spaces

International Nuclear Information System (INIS)

Fu, Yu

2013-01-01

In this paper, we investigate biharmonic submanifolds in pseudo-Euclidean spaces with arbitrary index and dimension. We give a complete classification of biharmonic spacelike submanifolds with parallel mean curvature vector in pseudo-Euclidean spaces. We also determine all biharmonic Lorentzian surfaces with parallel mean curvature vector field in pseudo-Euclidean spaces

A prescribing geodesic curvature problem

International Nuclear Information System (INIS)

Chang, K.C.; Liu, J.Q.

1993-09-01

Let D be the unit disk and k be a function on S 1 = δD. Find a flat metric which is pointwise conformal to the standard metric and has k as the geodesic curvature of S 1 . A sufficient condition for the existence of such a metric is that the harmonic extension of k in D has saddle points. (author). 11 refs

Linearized curvatures for auxiliary fields in the de Sitter space

Energy Technology Data Exchange (ETDEWEB)

Vasiliev, M A

1988-09-19

New consistent linearized curvatures in the de Sitter space are constructed. The sequence of actions, describing bosonic and fermionic gauge auxiliary fields, is found based on these curvatures. The proposed actions are parametrized by two integer parameters, n greater than or equal to 0 and m greater than or equal to 0. The simplest case n=m=0 corresponds in the flat limit to the auxiliary fields of 'new minimal' supergravity. The hamiltonian formulation is developed for the auxiliary fields suggested; hamiltonians and first- and second-class constraints are constructed. Using these results, it is shown that the systems of fields proposed possess no dynamical degrees of freedom in de Sitter and flat spaces. In addition the hamiltonian formalism is analysed for some free dynamical systems based on linearized higher-spin curvatures introduced previously.

Higher curvature corrections to primordial fluctuations in slow-roll inflation

International Nuclear Information System (INIS)

Satoh, Masaki; Soda, Jiro

2008-01-01

We study higher curvature corrections to the scalar spectral index, the tensor spectral index, the tensor-to-scalar ratio, and the polarization of gravitational waves. We find that there are cases where the higher curvature corrections cannot be negligible in the dynamics of the scalar field, although they are always negligible energetically. Indeed, it turns out that the tensor-to-scalar ratio could be enhanced and the tensor spectral index could be blue due to the Gauss–Bonnet term. We estimate the degree of circular polarization of gravitational waves generated during the slow-roll inflation. We argue that the circular polarization could be observable with the help of both the Gauss–Bonnet and the parity violating terms. We also present several examples to reveal observational implications of higher curvature corrections for chaotic inflationary models

The geometric curvature of the lumbar spine during restricted and unrestricted squats.

Science.gov (United States)

Hebling Campos, Mário; Furtado Alaman, Laizi I; Seffrin-Neto, Aldo A; Vieira, Carlos A; Costa de Paula, Marcelo; Barbosa de Lira, Claudio A

2017-06-01

The main purpose of this study was to analyze the behavior of the geometric curvature of the lumbar spine during restricted and unrestricted squats, using a novel investigative method. The rationale for our hypothesis is that the lumbar curvature has different patterns at different spine levels depending on the squat technique used. Spine motion was collected via stereo-photogrammetric analysis in nineteen participants (11 males, 8 females). The reconstructed spine points at the upright neutral position and at the deepest position of the squat exercise were projected onto the sagittal plane of the trunk, a polynomial was fitted to the data, and were quantified the two-dimensional geometric curvature at lower, central and higher lumbar levels, besides the inclination of trunk and lumbosacral region, the overall geometric curvature and overall angle of the lumbar spine. The mean values for each variable were analysed with paired t-test (Psquat techniques and these effects are also reduced in unrestricted squats. The data collected in the study are evidence that during barbell squats the lumbar curvature has different patterns at different spinal levels depending on the exercise technique. The lower lumbar spine appears to be less overloaded during unrestricted squats.

Generalization of the swelling method to measure the intrinsic curvature of lipids

Science.gov (United States)

Barragán Vidal, I. A.; Müller, M.

2017-12-01

Via computer simulation of a coarse-grained model of two-component lipid bilayers, we compare two methods of measuring the intrinsic curvatures of the constituting monolayers. The first one is a generalization of the swelling method that, in addition to the assumption that the spontaneous curvature linearly depends on the composition of the lipid mixture, incorporates contributions from its elastic energy. The second method measures the effective curvature-composition coupling between the apposing leaflets of bilayer structures (planar bilayers or cylindrical tethers) to extract the spontaneous curvature. Our findings demonstrate that both methods yield consistent results. However, we highlight that the two-leaflet structure inherent to the latter method has the advantage of allowing measurements for mixed lipid systems up to their critical point of demixing as well as in the regime of high concentration (of either species).

Comparative effectiveness of metal ions in inducing curvature of primary roots of Zea mays

Science.gov (United States)

Hasenstein, K. H.; Evans, M. L.; Stinemetz, C. L.; Moore, R.; Fondren, W. M.; Koon, E. C.; Higby, M. A.; Smucker, A. J.

1988-01-01

We used five cultivars of Zea mays (Bear Hybrid WF9 * 38MS, B73 * Missouri 17, Yellow Dent, Merit, and Great Lakes Hybrid 422) to reinvestigate the specificity of metal ions for inducing root curvature. Of 17 cations tested, 6 (Al3+, Ba2+, Ca2+, Cd2+, Cu2+, Zn2+) induced curvature. Roots curved away from Al3+, Ba2+, and Cd2+. Roots curved away from low (0.1 millimolar) concentrations of Cu2+ but toward higher (1-5 millimolar) concentrations. Roots initially curved away from Zn2+ but the direction of the subsequent curvature was unpredictable. In most cases, roots of all cultivars curved towards calcium. However, in some tests there was no response to calcium or even (especially in the cultivars Merit and B73 * Missouri 17) substantial curvature away from calcium. The results indicate that the induction of root curvature is not specific for calcium. The results are discussed relative to the possible role of calmodulin as a mediator of ion-induced root curvature.

A Self-Organizing Incremental Neural Network based on local distribution learning.

Science.gov (United States)

Xing, Youlu; Shi, Xiaofeng; Shen, Furao; Zhou, Ke; Zhao, Jinxi

2016-12-01

In this paper, we propose an unsupervised incremental learning neural network based on local distribution learning, which is called Local Distribution Self-Organizing Incremental Neural Network (LD-SOINN). The LD-SOINN combines the advantages of incremental learning and matrix learning. It can automatically discover suitable nodes to fit the learning data in an incremental way without a priori knowledge such as the structure of the network. The nodes of the network store rich local information regarding the learning data. The adaptive vigilance parameter guarantees that LD-SOINN is able to add new nodes for new knowledge automatically and the number of nodes will not grow unlimitedly. While the learning process continues, nodes that are close to each other and have similar principal components are merged to obtain a concise local representation, which we call a relaxation data representation. A denoising process based on density is designed to reduce the influence of noise. Experiments show that the LD-SOINN performs well on both artificial and real-word data. Copyright © 2016 Elsevier Ltd. All rights reserved.

No Large Scale Curvature Perturbations during Waterfall of Hybrid Inflation

OpenAIRE

Abolhasani, Ali Akbar; Firouzjahi, Hassan

2010-01-01

In this paper the possibility of generating large scale curvature perturbations induced from the entropic perturbations during the waterfall phase transition of standard hybrid inflation model is studied. We show that whether or not appreciable amounts of large scale curvature perturbations are produced during the waterfall phase transition depend crucially on the competition between the classical and the quantum mechanical back-reactions to terminate inflation. If one considers only the clas...

Protein shape and crowding drive domain formation and curvature in biological membranes

NARCIS (Netherlands)

Frese, R.N.; Pamies, Josep C.; Olsen, John D.; Bahatyrova, S.; van der Weij-de Wit, Chantal D.; Aartsma, Thijs J.; Otto, Cornelis; Hunter, C. Neil; Frenkel, Daan; van Grondelle, Rienk

2007-01-01

Folding, curvature, and domain formation are characteristics of many biological membranes. Yet the mechanisms that drive both curvature and the formation of specialized domains enriched in particular protein complexes are unknown. For this reason, studies in membranes whose shape and organization

2,2'-Bis(monoacylglycero) PO4 (BMP), but Not 3,1'-BMP, increases membrane curvature stress to enhance α-tocopherol transfer protein binding to membranes.

Science.gov (United States)

Baptist, Matilda; Panagabko, Candace; Nickels, Jonathan D; Katsaras, John; Atkinson, Jeffrey

2015-03-01

Previous work revealed that α-tocopherol transfer protein (α-TTP) co-localizes with bis(monoacylglycero)phosphate (BMP) in late endosomes. BMP is a lipid unique to late endosomes and is believed to induce membrane curvature and support the multivesicular nature of this organelle. We examined the effect of BMP on α-TTP binding to membranes using dual polarization interferometry and vesicle-binding assay. α-TTP binding to membranes is increased by the curvature-inducing lipid BMP. α-TTP binds to membranes with greater affinity when they contain the 2,2'-BMP versus 3,1'-BMP isomers.

Food availability and accessibility in the local food distribution ...

African Journals Online (AJOL)

Objectives: The objective was to understand the local food distribution system in Avian Park, with a focus on food availability and accessibility. Study design: This was a quantitative food store survey that employed semi-structured interviews and focus group discussions. Setting: The study was conducted in Avian Park, ...

Correlations between gravitropic curvature and auxin movement across gravistimulated roots of Zea mays

Science.gov (United States)

Young, L. M.; Evans, M. L.; Hertel, R.

1990-01-01

We compared the kinetics of auxin redistribution across the caps of primary roots of 2-day-old maize (Zea mays, cv Merit) seedlings with the time course of gravitropic curvature. [3H] indoleacetic acid was applied to one side of the cap in an agar donor and radioactivity moving across the cap was collected in an agar receiver applied to the opposite side. Upon gravistimulation the roots first curved upward slightly, then returned to the horizontal and began curving downward, reaching a final angle of about 67 degrees. Movement of label across the caps of gravistimulated roots was asymmetric with preferential downward movement (ratio downward/upward = ca. 1.6, radioactivity collected during the 90 min following beginning of gravistimulation). There was a close correlation between the development of asymmetric auxin movement across the root cap and the rate of curvature, with both values increasing to a maximum and then declining as the roots approached the final angle of curvature. In roots preadapted to gravity (alternate brief stimulation on opposite flanks over a period of 1 hour) the initial phase of upward curvature was eliminated and downward bending began earlier than for controls. The correlation between asymmetric auxin movement and the kinetics of curvature also held in comparisons between control and preadapted roots. Both downward auxin transport asymmetry and downward curvature occurred earlier in preadapted roots than in controls. These findings are consistent with suggestions that the root cap is not only the site of perception but also the location of the initial redistribution of effectors that ultimately leads to curvature.

Gauge and non-gauge curvature tensor copies

International Nuclear Information System (INIS)

Srivastava, P.P.

1982-10-01

A procedure for constructing curvature tensor copies is discussed using the anholonomic geometrical framework. The corresponding geometries are compared and the notion of gauge copy is elucidated. An explicit calculation is also made. (author)

Curvature effect on nuclear 'pasta': Is it helpful for gyroid appearance?

International Nuclear Information System (INIS)

Nakazato, Ken'ichiro; Iida, Kei; Oyamatsu, Kazuhiro

2011-01-01

In supernova cores and neutron star crusts, nuclei are thought to deform to rodlike and slablike shapes, which are often called nuclear pasta. We study the equilibrium properties of the nuclear pasta by using a liquid-drop model with curvature corrections. It is confirmed that the curvature effect acts to lower the transition densities between different shapes. We also examine the gyroid structure, which was recently suggested as a different type of nuclear pasta by analogy with the polymer systems. The gyroid structure investigated in this paper is approximately formulated as an extension of the periodic minimal surface whose mean curvature vanishes. In contrast to our expectations, we find, from the present approximate formulation, that the curvature corrections act to slightly disfavor the appearance of the gyroid structure. By comparing the energy corrections in the gyroid phase and the hypothetical phases composed of d-dimensional spheres, where d is a general dimensionality, we show that the gyroid is unlikely to belong to a family of the generalized dimensional spheres.

FY 2016 Status Report: CIRFT Testing Data Analyses and Updated Curvature Measurements

Energy Technology Data Exchange (ETDEWEB)

Wang, Jy-An John [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Wang, Hong [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

2016-08-01

This report provides a detailed description of FY15 test result corrections/analysis based on the FY16 Cyclic Integrated Reversible-Bending Fatigue Tester (CIRFT) test program methodology update used to evaluate the vibration integrity of spent nuclear fuel (SNF) under normal transportation conditions. The CIRFT consists of a U-frame testing setup and a real-time curvature measurement method. The three-component U-frame setup of the CIRFT has two rigid arms and linkages to a universal testing machine. The curvature of rod bending is obtained through a three-point deflection measurement method. Three linear variable differential transformers (LVDTs) are used and clamped to the side connecting plates of the U-frame to capture the deformation of the rod. The contact-based measurement, or three-LVDT-based curvature measurement system, on SNF rods has been proven to be quite reliable in CIRFT testing. However, how the LVDT head contacts the SNF rod may have a significant effect on the curvature measurement, depending on the magnitude and direction of rod curvature. It has been demonstrated that the contact/curvature issues can be corrected by using a correction on the sensor spacing. The sensor spacing defines the separation of the three LVDT probes and is a critical quantity in calculating the rod curvature once the deflections are obtained. The sensor spacing correction can be determined by using chisel-type probes. The method has been critically examined this year and has been shown to be difficult to implement in a hot cell environment, and thus cannot be implemented effectively. A correction based on the proposed equivalent gauge-length has the required flexibility and accuracy and can be appropriately used as a correction factor. The correction method based on the equivalent gauge length has been successfully demonstrated in CIRFT data analysis for the dynamic tests conducted on Limerick (LMK) (17 tests), North Anna (NA) (6 tests), and Catawba mixed oxide (MOX

On Mass, Spacetime Curvature, and Gravity

Science.gov (United States)

Janis, Allen I.

2018-01-01

The frequently used analogy of a massive ball distorting an elastic sheet, which is used to illustrate why mass causes spacetime curvature and gravitational attraction, is criticized in this article. A different analogy that draws on the students' previous knowledge of spacetime diagrams in special relativity is suggested.

Black hole production in particle collisions and higher curvature gravity

International Nuclear Information System (INIS)

Rychkov, Vyacheslav S.

2004-01-01

The problem of black hole production in trans-Planckian particle collisions is revisited, in the context of large extra dimensions scenarios of TeV-scale gravity. The validity of the standard description of this process (two colliding Aichelburg-Sexl shock waves in classical Einstein gravity) is questioned. It is observed that the classical spacetime has large curvature along the transverse collision plane, as signaled by the curvature invariant (R μνλσ ) 2 . Thus quantum gravity effects, and in particular higher curvature corrections to the Einstein gravity, cannot be ignored. To give a specific example of what may happen, the collision is reanalyzed in the Einstein-Lanczos-Lovelock gravity theory, which modifies the Einstein-Hilbert Lagrangian by adding a particular 'Gauss-Bonnet' combination of curvature squared terms. The analysis uses a series of approximations, which reduce the field equations to a tractable second order nonlinear PDE of the Monge-Ampere type. It is found that the resulting spacetime is significantly different from the pure Einstein case in the future of the transverse collision plane. These considerations cast serious doubts on the geometric cross section estimate, which is based on the classical Einstein gravity description of the black hole production process

Curvature correction of retinal OCTs using graph-based geometry detection

Science.gov (United States)

Kafieh, Raheleh; Rabbani, Hossein; Abramoff, Michael D.; Sonka, Milan

2013-05-01

In this paper, we present a new algorithm as an enhancement and preprocessing step for acquired optical coherence tomography (OCT) images of the retina. The proposed method is composed of two steps, first of which is a denoising algorithm with wavelet diffusion based on a circular symmetric Laplacian model, and the second part can be described in terms of graph-based geometry detection and curvature correction according to the hyper-reflective complex layer in the retina. The proposed denoising algorithm showed an improvement of contrast-to-noise ratio from 0.89 to 1.49 and an increase of signal-to-noise ratio (OCT image SNR) from 18.27 to 30.43 dB. By applying the proposed method for estimation of the interpolated curve using a full automatic method, the mean ± SD unsigned border positioning error was calculated for normal and abnormal cases. The error values of 2.19 ± 1.25 and 8.53 ± 3.76 µm were detected for 200 randomly selected slices without pathological curvature and 50 randomly selected slices with pathological curvature, respectively. The important aspect of this algorithm is its ability in detection of curvature in strongly pathological images that surpasses previously introduced methods; the method is also fast, compared to the relatively low speed of similar methods.

Vertex Normals and Face Curvatures of Triangle Meshes

KAUST Repository

Sun, Xiang

2016-08-12

This study contributes to the discrete differential geometry of triangle meshes, in combination with discrete line congruences associated with such meshes. In particular we discuss when a congruence defined by linear interpolation of vertex normals deserves to be called a ʼnormal’ congruence. Our main results are a discussion of various definitions of normality, a detailed study of the geometry of such congruences, and a concept of curvatures and shape operators associated with the faces of a triangle mesh. These curvatures are compatible with both normal congruences and the Steiner formula.

Experimental and numerical investigation of laser forming of cylindrical surfaces with arbitrary radius of curvature

Directory of Open Access Journals (Sweden)

Mehdi Safari

2016-09-01

Full Text Available In this work, laser forming of cylindrical surfaces with arbitrary radius of curvature is investigated experimentally and numerically. For laser forming of cylindrical surfaces with arbitrary radius of curvature, a new and comprehensive method is proposed in this paper. This method contains simple linear irradiating lines and using an analytical method, required process parameters for laser forming of a cylindrical surface with a specific radius of curvature is proposed. In this method, laser output power, laser scanning speed and laser beam diameter are selected based on laser machine and process limitations. As in the laser forming of a cylindrical surface, parallel irradiating lines are needed; therefore key parameter for production of a cylindrical surface with a specific radius of curvature is the number of irradiating lines. Hence, in the proposed analytical method, the required number of irradiating lines for production of a cylindrical surface with a specific radius of curvature is suggested. Performance of the proposed method for production of cylindrical surface with a specific radius of curvature is verified with experimental tests. The results show that using proposed analytical method, cylindrical surfaces with any radius of curvature can be produced successfully.

Quantitative three-dimensional analysis of root canal curvature in maxillary first molars using micro-computed tomography.

Science.gov (United States)

Lee, Jong-Ki; Ha, Byung-Hyun; Choi, Jeong-Ho; Heo, Seok-Mo; Perinpanayagam, Hiran

2006-10-01

In endodontic therapy, access and instrumentation are strongly affected by root canal curvature. However, the few studies that have actually measured curvature are mostly from two-dimensional radiographs. The purpose of this study was to measure the three-dimensional (3D) canal curvature in maxillary first molars using micro-computed tomography (microCT) and mathematical modeling. Extracted maxillary first molars (46) were scanned by microCT (502 image slices/tooth, 1024 X 1024 pixels, voxel size of 19.5 x 19.5 x 39.0 microm) and their canals reconstructed by 3D modeling software. The intersection of major and minor axes in the canal space of each image slice were connected to create an imaginary central axis for each canal. The radius of curvature of the tangential circle was measured and inverted as a measure of curvature using custom-made mathematical modeling software. Root canal curvature was greatest in the apical third and least in the middle third for all canals. The greatest curvatures were in the mesiobuccal (MB) canal (0.76 +/- 0.48 mm(-1)) with abrupt curves, and the least curvatures were in the palatal (P) canal (0.38 +/- 0.34 mm(-1)) with a gradual curve. This study has measured the 3D curvature of root canals in maxillary first molars and reinforced the value of microCT with mathematical modeling.

Higher Curvature Supergravity, Supersymmetry Breaking and Inflation

CERN Document Server

Ferrara, Sergio

2017-01-01

In these lectures, after a short introduction to cosmology, we discuss the supergravity embedding of higher curvature models of inflation. The supergravity description of such models is presented for the two different formulations of minimal supergravity.

Local Information as a Resource in Distributed Quantum Systems

Science.gov (United States)

Horodecki, Michał; Horodecki, Karol; Horodecki, Paweł; Horodecki, Ryszard; Oppenheim, Jonathan; Sende, Aditi; Sen, Ujjwal

2003-03-01

A new paradigm for distributed quantum systems where information is a valuable resource is developed. After finding a unique measure for information, we construct a scheme for its manipulation in analogy with entanglement theory. In this scheme, instead of maximally entangled states, two parties distill local states. We show that, surprisingly, the main tools of entanglement theory are general enough to work in this opposite scheme. Up to plausible assumptions, we show that the amount of information that must be lost during the protocol of concentration of local information can be expressed as the relative entropy distance from some special set of states.

Moment-Curvature Behaviors of Concrete Beams Singly Reinforced by Steel-FRP Composite Bars

Directory of Open Access Journals (Sweden)

Zeyang Sun

2017-01-01

Full Text Available A steel-fiber-reinforced polymer (FRP composite bar (SFCB is a kind of rebar with inner steel bar wrapped by FRP, which can achieve a better anticorrosion performance than that of ordinary steel bar. The high ultimate strength of FRP can also provide a significant increase in load bearing capacity. Based on the adequate simulation of the load-displacement behaviors of concrete beams reinforced by SFCBs, a parametric analysis of the moment-curvature behaviors of concrete beams that are singly reinforced by SFCB was conducted. The critical reinforcement ratio for differentiating the beam’s failure mode was presented, and the concept of the maximum possible peak curvature (MPPC was proposed. After the ultimate curvature reached MPPC, it decreased with an increase in the postyield stiffness ratio (rsf, and the theoretical calculation method about the curvatures before and after the MPPC was derived. The influence of the reinforcement ratio, effective depth, and FRP ultimate strain on the ultimate point was studied by the dimensionless moment and curvature. By calculating the envelope area under the moment-curvature curve, the energy ductility index can obtain a balance between the bearing capacity and the deformation ability. This paper can provide a reference for the design of concrete beams that are reinforced by SFCB or hybrid steel bar/FRP bar.

Incorporating contact angles in the surface tension force with the ACES interface curvature scheme

Science.gov (United States)

Owkes, Mark

2017-11-01

In simulations of gas-liquid flows interacting with solid boundaries, the contact line dynamics effect the interface motion and flow field through the surface tension force. The surface tension force is directly proportional to the interface curvature and the problem of accurately imposing a contact angle must be incorporated into the interface curvature calculation. Many commonly used algorithms to compute interface curvatures (e.g., height function method) require extrapolating the interface, with defined contact angle, into the solid to allow for the calculation of a curvature near a wall. Extrapolating can be an ill-posed problem, especially in three-dimensions or when multiple contact lines are near each other. We have developed an accurate methodology to compute interface curvatures that allows for contact angles to be easily incorporated while avoiding extrapolation and the associated challenges. The method, known as Adjustable Curvature Evaluation Scale (ACES), leverages a least squares fit of a polynomial to points computed on the volume-of-fluid (VOF) representation of the gas-liquid interface. The method is tested by simulating canonical test cases and then applied to simulate the injection and motion of water droplets in a channel (relevant to PEM fuel cells).

Effects of curvature and rotation on turbulence in the NASA low-speed centrifugal compressor impeller

Science.gov (United States)

Moore, Joan G.; Moore, John

1992-01-01

The flow in the NASA Low-Speed Impeller is affected by both curvature and rotation. The flow curves due to the following: (1) geometric curvature, e.g. the curvature of the hub and shroud profiles in the meridional plane and the curvature of the backswept impeller blades; and (2) secondary flow vortices, e.g. the tip leakage vortex. Changes in the turbulence and effective turbulent viscosity in the impeller are investigated. The effects of these changes on three-dimensional flow development are discussed. Two predictions of the flow in the impeller, one with, and one without modification to the turbulent viscosity due to rotation and curvature, are compared. Some experimental and theoretical background for the modified mixing length model of turbulent viscosity will also be presented.

Profile Curvature Derivative Surface used to characterize the complexity of the seafloor around St. John, USVI

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — Profile curvature was calculated from the bathymetry surface for each raster cell using the ArcGIS 3D Analyst "Curvature" Tool. Profile curvature describes the rate...

Risk analysis for a local gas distribution network

International Nuclear Information System (INIS)

Peters, J.W.

1991-01-01

Cost control and service reliability are popular topics when discussing strategic issues facing local distribution companies (LDCs) in the 1990s. The ability to provide secure and uninterrupted gas service is crucial for growth and company image, both with the public and regulatory agencies. At the same time, the industry is facing unprecedented competition from alternate fuels, and cost control is essential for maintaining a competitive edge in the market. On the surface, it would appear that cost control and service reliability are contradictory terms. Improvement in service reliability should cost something, or does it? Risk analysis can provide the answer from a distribution design perspective. From a gas distribution engineer's perspective, projects such as loops, backfeeds and even valve placement are designed to reduce, minimize and/or eliminate potential customer outages. These projects improve service reliability by acting as backups should a failure occur on a component of the distribution network. These contingency projects are cost-effective but their longterm benefit or true value is under question. Their purpose is to maintain supply to an area in the distribution network in the event of a failure somewhere else. Two phrases, potential customer outages and in the event of failure, identify uncertainty

Post- and interseismic deformation due to both localized and distributed creep at depth (Invited)

Science.gov (United States)

Hetland, E. A.; Zhang, G.; Hines, T.

2013-12-01

There are two end-member representations of the ductile lithosphere (i.e., the lower crust and uppermost mantle) commonly used in models of post- and interseismic deformation around strike-slip faults: either (1) laterally homogeneous ductile layers, with sharp contrasts in rheological properties between the layers, in which creep is distributed; or (2) discrete extensions of the fault at depth in which creep is fully localized. The most realistic representation of the ductile lithosphere on earthquake cycle time scales likely falls between these two end-members. Researchers have considered both distributed and localized creep when interpreting post- and interseismic deformation, although the two mechanisms are most commonly treated separately, with the localized creep often approximated by kinematic slip on planar faults. There are a few noteworthy models that considered the feedback between both distributed and localized creep, although those models were largely constrained to 2D geometries of infinite length faults. The thickness of shear zones in the ductile lithosphere may be comparable to the locking depth of the fault, and the existence of a deep shear zone does not preclude the possibility that some distributed creep occurs in the surrounding lithosphere. Furthermore, variations in rheology, including both rheological models and their parameters, may be more subtle than the discrete contrasts typically assumed. In this presentation, we consider models of postseismic deformation following a finite length, strike-slip fault, as well as models of interseismic deformation around an infinite length strike-slip fault. Both sets of models are capable of localized and distributed creep at depth, and use Maxwell viscoelasticity. We show that the horizontal surface velocities during the early postseismic period are most sensitive to the viscosity of the shear zone; however during much of the interseismic period the shear zone is not apparent from the surface

ON THE CURVATURE OF DUST LANES IN GALACTIC BARS

International Nuclear Information System (INIS)

Comeron, Sebastien; MartInez-Valpuesta, Inma; Knapen, Johan H.; Beckman, John E.

2009-01-01

We test the theoretical prediction that the straightest dust lanes in bars are found in strongly barred galaxies, or more specifically, that the degree of curvature of the dust lanes is inversely proportional to the strength of the bar. The test uses archival images of barred galaxies for which a reliable nonaxisymmetric torque parameter (Q b ) and the radius at which Q b has been measured (r(Q b )) have been published in the literature. Our results confirm the theoretical prediction but show a large spread that cannot be accounted for by measurement errors. We simulate 238 galaxies with different bar and bulge parameters in order to investigate the origin of the spread in the dust lane curvature versus Q b relation. From these simulations, we conclude that the spread is greatly reduced when describing the bar strength as a linear combination of the bar parameters Q b and the quotient of the major and minor axes of the bar, a/b. Thus, we conclude that the dust lane curvature is predominantly determined by the parameters of the bar.

Generic Properties of Curvature Sensing through Vision and Touch

Directory of Open Access Journals (Sweden)

Birgitta Dresp-Langley

2013-01-01

Full Text Available Generic properties of curvature representations formed on the basis of vision and touch were examined as a function of mathematical properties of curved objects. Virtual representations of the curves were shown on a computer screen for visual scaling by sighted observers (experiment 1. Their physical counterparts were placed in the two hands of blindfolded and congenitally blind observers for tactile scaling. The psychophysical data show that curvature representations in congenitally blind individuals, who never had any visual experience, and in sighted observers, who rely on vision most of the time, are statistically linked to the same mathematical properties of the curves. The perceived magnitude of object curvature, sensed through either vision or touch, is related by a mathematical power law, with similar exponents for the two sensory modalities, to the aspect ratio of the curves, a scale invariant geometric property. This finding supports biologically motivated models of sensory integration suggesting a universal power law for the adaptive brain control and balance of motor responses to environmental stimuli from any sensory modality.

Constant scalar curvature hypersurfaces in (3 + 1) -dimensional GHMC Minkowski spacetimes

Science.gov (United States)

Smith, Graham

2018-06-01

We prove that every (3 + 1) -dimensional flat GHMC Minkowski spacetime which is not a translation spacetime or a Misner spacetime carries a unique foliation by spacelike hypersurfaces of constant scalar curvature. In other words, we prove that every such spacetime carries a unique time function with isochrones of constant scalar curvature. Furthermore, this time function is a smooth submersion.

Linear response to long wavelength fluctuations using curvature simulations

Energy Technology Data Exchange (ETDEWEB)

Baldauf, Tobias; Zaldarriaga, Matias [School of Natural Sciences, Institute for Advanced Study, Princeton, NJ (United States); Seljak, Uroš [Physics Department, Astronomy Department and Lawrence Berkeley National Laboratory, University of California, Berkeley, CA (United States); Senatore, Leonardo, E-mail: baldauf@ias.edu, E-mail: useljak@berkeley.edu, E-mail: senatore@stanford.edu, E-mail: matiasz@ias.edu [Stanford Institute for Theoretical Physics, Stanford University, Stanford, CA (United States)

2016-09-01

We study the local response to long wavelength fluctuations in cosmological N -body simulations, focusing on the matter and halo power spectra, halo abundance and non-linear transformations of the density field. The long wavelength mode is implemented using an effective curved cosmology and a mapping of time and distances. The method provides an alternative, more direct, way to measure the isotropic halo biases. Limiting ourselves to the linear case, we find generally good agreement between the biases obtained from the curvature method and the traditional power spectrum method at the level of a few percent. We also study the response of halo counts to changes in the variance of the field and find that the slope of the relation between the responses to density and variance differs from the naïve derivation assuming a universal mass function by approximately 8–20%. This has implications for measurements of the amplitude of local non-Gaussianity using scale dependent bias. We also analyze the halo power spectrum and halo-dark matter cross-spectrum response to long wavelength fluctuations and derive second order halo bias from it, as well as the super-sample variance contribution to the galaxy power spectrum covariance matrix.

Gaussian curvature on hyperelliptic Riemann surfaces

Indian Academy of Sciences (India)

Indian Acad. Sci. (Math. Sci.) Vol. 124, No. 2, May 2014, pp. 155–167. c Indian Academy of Sciences. Gaussian curvature on hyperelliptic Riemann surfaces. ABEL CASTORENA. Centro de Ciencias Matemáticas (Universidad Nacional Autónoma de México,. Campus Morelia) Apdo. Postal 61-3 Xangari, C.P. 58089 Morelia,.

The Riemann-Lovelock Curvature Tensor

OpenAIRE

Kastor, David

2012-01-01

In order to study the properties of Lovelock gravity theories in low dimensions, we define the kth-order Riemann-Lovelock tensor as a certain quantity having a total 4k-indices, which is kth-order in the Riemann curvature tensor and shares its basic algebraic and differential properties. We show that the kth-order Riemann-Lovelock tensor is determined by its traces in dimensions 2k \\le D

Factors affecting root curvature of mandibular first molar

International Nuclear Information System (INIS)

Choi, Hang Moon; Yi, Won Jin; Heo, Min Suk; Kim, Jung Hwa; Choi, Soon Chul; Park, Tae Won

2006-01-01

To find the cause of root curvature by use of panoramic and lateral cephalometric radiograph. Twenty six 1st graders whose mandibular 1st molars just emerged into the mouth were selected. Panoramic and lateral cephalometric radiograph were taken at grade 1 and 6, longitudinally. In cephalometric radio graph, mandibular plane angle, ramus-occlusal place angle, gonial angle, and gonion-gnathion distance(Go-Gn distance) were measured. In panoramic radiograph, elongated root length and root angle were measured by means of digital subtraction radiography. Occlusal plane-tooth axis angle was measured, too. Pearson correlations were used to evaluate the relationships between root curvature and elongated length and longitudinal variations of all variables. Multiple regression equation using related variables was computed. The pearson correlation coefficient between curved angle and longitudinal variations of occlusal plane-tooth axis angle and ramus-occlusal plane angle was 0.350 and 0.401, respectively (p 1 +0.745X 2 (Y: root angle, X 1 : variation of occlusal plane-tooth axis angle, X 2 : variation of ramus-occlusal plane angle). It was suspected that the reasons of root curvature were change of tooth axis caused by contact with 2nd deciduous tooth and amount of mesial and superior movement related to change of occlusal plane

Determination of stress distribution in III-V single crystal layers for heterogeneous integration applications

Energy Technology Data Exchange (ETDEWEB)

Jackson, M.; Hayashi, S. [Dept. of Materials Science and Engineering, University of California, Los Angeles, CA 90095 (United States); Goorsky, M.S.; Sandhu, R.; Chang-Chien, P.; Gutierrez-Aitken, A.; Tsai, R. [Northrop Grumman Space Technology, Redondo Beach, CA 90278 (United States); Noori, A.; Poust, B. [Dept. of Materials Science and Engineering, University of California, Los Angeles, CA 90095 (United States); Northrop Grumman Space Technology, Redondo Beach, CA 90278 (United States)

2007-08-15

Double crystal X-ray diffraction imaging and a variable temperature stage are employed to determine the stress distribution in heterogeneous wafer bonded layers though the superposition of images produced at different rocking curve angles. The stress distribution in InP layers transferred to a silicon substrate at room temperature exhibits an anticlastic deformation, with different regions of the wafer experiencing different signs of curvature. Measurements at elevated temperatures ({<=}125 C) reveals that differences in thermal expansion coefficients dominate the stress and that interfacial particulates introduce very high local stress gradients that increase with increased temperature. For thinned GaAs substrates (100 {mu}m) bonded using patterned metal interlayers to a separate GaAs substrate at {approx}200 C, residual stresses are produced at room temperature due to local stress points from metallization contacts and vias and the complex stress patterns can be observed using the diffraction imaging technique. (copyright 2007 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

Procedure of non-contacting local mass density and mass density distribution measurements

International Nuclear Information System (INIS)

Menzel, M.; Winkler, K.

1985-01-01

The invention has been aimed at a procedure of non-contacting local mass density and/or mass density distribution measurements i.e. without the interfering influence of sensors or probes. It can be applied to installations, apparatuses and pipings of chemical engineering, to tank constructions and transportation on extreme temperature and/or pressure conditions and aggressive media influences respectively. The procedure has utilized an ionizing quantum radiation whereby its unknown weakening and scattering is compensated by a suitable combination of scattering and transmission counter rate measurements in such a way that the local mass densities and the mass density distribution respectively are determinable

An optomechatronic curvature measurement array based on fiber Bragg gratings

International Nuclear Information System (INIS)

Chang, Hsing-Cheng; Lin, Shyan-Lung; Hung, San-Shan; Chang, I-Nan; Chen, Ya-Hui; Lin, Jung-Chih; Liu, Wen-Fung

2014-01-01

This study investigated an optomechatronic array-integrated signal processing module and a human–machine interface based on fiber Bragg grating sensing elements embedded in an elastic support matrix that involves using a self-located electromagnetic mechanism for curvature sensing and solid contour reconstruction. Using bilinear interpolation and average calculation methods, the smooth and accurate surface contours of convex and concave lenses are reconstructed in real-time. The elastic supporting optical sensing array is self-balanced to reduce operational errors. Compared with our previous single-head sensor, the sensitivity of the proposed array is improved by more than 15%. In the curvature range from −20.15 to +27.09 m −1 , the sensitivities are 3.53 pm m for the convex measurement and 2.15 pm m for the concave measurement with an error rate below 8.89%. The curvature resolutions are 0.283 and 0.465 m −1 for convex and concave lenses, respectively. This array could be applied in the curvature measurement of solar collectors to monitor energy conversion efficiency or could be used to monitor the wafer-level thin-film fabrication process. (paper)

Wind-tunnel investigation of aerodynamic efficiency of three planar elliptical wings with curvature of quarter-chord line

Science.gov (United States)

Mineck, Raymond E.; Vijgen, Paul M. H. W.

1993-01-01

Three planar, untwisted wings with the same elliptical chord distribution but with different curvatures of the quarter-chord line were tested in the Langley 8-Foot Transonic Pressure Tunnel (8-ft TPT) and the Langley 7- by 10-Foot High-Speed Tunnel (7 x 10 HST). A fourth wing with a rectangular planform and the same projected area and span was also tested. Force and moment measurements from the 8-ft TPT tests are presented for Mach numbers from 0.3 to 0.5 and angles of attack from -4 degrees to 7 degrees. Sketches of the oil-flow patterns on the upper surfaces of the wings and some force and moment measurements from the 7 x 10 HST tests are presented at a Mach number of 0.5. Increasing the curvature of the quarter-chord line makes the angle of zero lift more negative but has little effect on the drag coefficient at zero lift. The changes in lift-curve slope and in the Oswald efficiency factor with the change in curvature of the quarter-chord line (wingtip location) indicate that the elliptical wing with the unswept quarter-chord line has the lowest lifting efficiency and the elliptical wing with the unswept trailing edge has the highest lifting efficiency; the crescent-shaped planform wing has an efficiency in between.

Curvature correction of retinal OCTs using graph-based geometry detection

International Nuclear Information System (INIS)

Kafieh, Raheleh; Rabbani, Hossein; Abramoff, Michael D; Sonka, Milan

2013-01-01

In this paper, we present a new algorithm as an enhancement and preprocessing step for acquired optical coherence tomography (OCT) images of the retina. The proposed method is composed of two steps, first of which is a denoising algorithm with wavelet diffusion based on a circular symmetric Laplacian model, and the second part can be described in terms of graph-based geometry detection and curvature correction according to the hyper-reflective complex layer in the retina. The proposed denoising algorithm showed an improvement of contrast-to-noise ratio from 0.89 to 1.49 and an increase of signal-to-noise ratio (OCT image SNR) from 18.27 to 30.43 dB. By applying the proposed method for estimation of the interpolated curve using a full automatic method, the mean ± SD unsigned border positioning error was calculated for normal and abnormal cases. The error values of 2.19 ± 1.25 and 8.53 ± 3.76 µm were detected for 200 randomly selected slices without pathological curvature and 50 randomly selected slices with pathological curvature, respectively. The important aspect of this algorithm is its ability in detection of curvature in strongly pathological images that surpasses previously introduced methods; the method is also fast, compared to the relatively low speed of similar methods. (paper)

Physical and Geometric Interpretations of the Riemann Tensor, Ricci Tensor, and Scalar Curvature

OpenAIRE

Loveridge, Lee C.

2004-01-01

Various interpretations of the Riemann Curvature Tensor, Ricci Tensor, and Scalar Curvature are described. Also, the physical meanings of the Einstein Tensor and Einstein's Equations are discussed. Finally a derivation of Newtonian Gravity from Einstein's Equations is given.

Relativistic electron flux dropout due to field line curvature during the storm on 1 June 2013

Science.gov (United States)

Kang, S. B.; Fok, M. C. H.; Engebretson, M. J.; Li, W.; Glocer, A.

2017-12-01

Significant electron flux depletion over a wide range of L-shell and energy, referred as a dropout, was observed by Van Allen Probes during the storm main phase on June 1, 2013. During the same period, MeV electron precipitation with isotropic pitch-angle distribution was also observed in the evening sector from POES but no EMIC waves were detected from either space- or ground-based magnetometers. Based on Tsyganenko empirical magnetic field model, magnetic field lines are highly non-dipolar and stretched at the night side in the inner magnetosphere. This condition can break the first adiabatic invariant (conservation of magnetic moment) and generate pitch-angle scattering of relativistic electron to the loss cone. To understand the relative roles of different physical mechanisms on this dropout event, we simulate flux and phase space density of relativistic electrons with event specific plasma wave intensities using the Comprehensive Inner Magnetosphere and Ionosphere (CIMI) model, as a global 4-D inner magnetosphere model. We also employ pitch-angle scattering due to field line curvature in the CIMI model. We re-configure magnetic field every minute and update electric field every 20 seconds to capture radial transport. CIMI-simulation with pitch-angle scattering due to field line curvature shows more depletion of relativistic electron fluxes and better agreement to observation than CIMI-simulation with radial transport only. We conclude that pitch-angle scattering due to field line curvature is one of the dominant processes for the relativistic electron flux dropout.

Regional Distribution Shifts Help Explain Local Changes in Wintering Raptor Abundance: Implications for Interpreting Population Trends

Science.gov (United States)

Paprocki, Neil; Heath, Julie A.; Novak, Stephen J.

2014-01-01

Studies of multiple taxa across broad-scales suggest that species distributions are shifting poleward in response to global climate change. Recognizing the influence of distribution shifts on population indices will be an important part of interpreting trends within management units because current practice often assumes that changes in local populations reflect local habitat conditions. However, the individual- and population-level processes that drive distribution shifts may occur across a large, regional scale and have little to do with the habitats within the management unit. We examined the latitudinal center of abundance for the winter distributions of six western North America raptor species using Christmas Bird Counts from 1975–2011. Also, we considered whether population indices within western North America Bird Conservation Regions (BCRs) were explained by distribution shifts. All six raptors had significant poleward shifts in their wintering distributions over time. Rough-legged Hawks (Buteo lagopus) and Golden Eagles (Aquila chrysaetos) showed the fastest rate of change, with 8.41 km yr−1 and 7.74 km yr−1 shifts, respectively. Raptors may be particularly responsive to warming winters because of variable migration tendencies, intraspecific competition for nesting sites that drives males to winter farther north, or both. Overall, 40% of BCR population trend models were improved by incorporating information about wintering distributions; however, support for the effect of distribution on BCR indices varied by species with Rough-legged Hawks showing the most evidence. These results emphasize the importance of understanding how regional distribution shifts influence local-scale population indices. If global climate change is altering distribution patterns, then trends within some management units may not reflect changes in local habitat conditions. The methods used to monitor and manage bird populations within local BCRs will fundamentally change as

Regional distribution shifts help explain local changes in wintering raptor abundance: implications for interpreting population trends.

Directory of Open Access Journals (Sweden)

Neil Paprocki

Full Text Available Studies of multiple taxa across broad-scales suggest that species distributions are shifting poleward in response to global climate change. Recognizing the influence of distribution shifts on population indices will be an important part of interpreting trends within management units because current practice often assumes that changes in local populations reflect local habitat conditions. However, the individual- and population-level processes that drive distribution shifts may occur across a large, regional scale and have little to do with the habitats within the management unit. We examined the latitudinal center of abundance for the winter distributions of six western North America raptor species using Christmas Bird Counts from 1975-2011. Also, we considered whether population indices within western North America Bird Conservation Regions (BCRs were explained by distribution shifts. All six raptors had significant poleward shifts in their wintering distributions over time. Rough-legged Hawks (Buteo lagopus and Golden Eagles (Aquila chrysaetos showed the fastest rate of change, with 8.41 km yr(-1 and 7.74 km yr(-1 shifts, respectively. Raptors may be particularly responsive to warming winters because of variable migration tendencies, intraspecific competition for nesting sites that drives males to winter farther north, or both. Overall, 40% of BCR population trend models were improved by incorporating information about wintering distributions; however, support for the effect of distribution on BCR indices varied by species with Rough-legged Hawks showing the most evidence. These results emphasize the importance of understanding how regional distribution shifts influence local-scale population indices. If global climate change is altering distribution patterns, then trends within some management units may not reflect changes in local habitat conditions. The methods used to monitor and manage bird populations within local BCRs will fundamentally

Distributed model predictive control for constrained nonlinear systems with decoupled local dynamics.

Science.gov (United States)

Zhao, Meng; Ding, Baocang

2015-03-01

This paper considers the distributed model predictive control (MPC) of nonlinear large-scale systems with dynamically decoupled subsystems. According to the coupled state in the overall cost function of centralized MPC, the neighbors are confirmed and fixed for each subsystem, and the overall objective function is disassembled into each local optimization. In order to guarantee the closed-loop stability of distributed MPC algorithm, the overall compatibility constraint for centralized MPC algorithm is decomposed into each local controller. The communication between each subsystem and its neighbors is relatively low, only the current states before optimization and the optimized input variables after optimization are being transferred. For each local controller, the quasi-infinite horizon MPC algorithm is adopted, and the global closed-loop system is proven to be exponentially stable. Copyright © 2014 ISA. Published by Elsevier Ltd. All rights reserved.

Non-Euclidean geometry and curvature two-dimensional spaces, volume 3

CERN Document Server

Cannon, James W

2017-01-01

This is the final volume of a three volume collection devoted to the geometry, topology, and curvature of 2-dimensional spaces. The collection provides a guided tour through a wide range of topics by one of the twentieth century's masters of geometric topology. The books are accessible to college and graduate students and provide perspective and insight to mathematicians at all levels who are interested in geometry and topology. Einstein showed how to interpret gravity as the dynamic response to the curvature of space-time. Bill Thurston showed us that non-Euclidean geometries and curvature are essential to the understanding of low-dimensional spaces. This third and final volume aims to give the reader a firm intuitive understanding of these concepts in dimension 2. The volume first demonstrates a number of the most important properties of non-Euclidean geometry by means of simple infinite graphs that approximate that geometry. This is followed by a long chapter taken from lectures the author gave at MSRI, wh...

Weyl curvature tensor in static spherical sources

International Nuclear Information System (INIS)

Ponce de Leon, J.

1988-01-01

The role of the Weyl curvature tensor in static sources of the Schwarzschild field is studied. It is shown that in general the contribution from the Weyl curvature tensor (the ''purely gravitational field energy'') to the mass-energy inside the body may be positive, negative, or zero. It is proved that a positive (negative) contribution from the Weyl tensor tends to increase (decrease) the effective gravitational mass, the red-shift (from a point in the sphere to infinity), as well as the gravitational force which acts on a constituent matter element of a body. It is also proved that the contribution from the Weyl tensor always is negative in sources with surface gravitational potential larger than (4/9. It is pointed out that large negative contributions from the Weyl tensor could give rise to the phenomenon of gravitational repulsion. A simple example which illustrates the results is discussed

Polar localization of Escherichia coli chemoreceptors requires an intact Tol–Pal complex

Science.gov (United States)

Santos, Thiago M. A.; Lin, Ti-Yu; Rajendran, Madhusudan; Anderson, Samantha M.; Weibel, Douglas B.

2014-01-01

Summary Subcellular biomolecular localization is critical for the metabolic and structural properties of the cell. The functional implications of the spatiotemporal distribution of protein complexes during the bacterial cell cycle have long been acknowledged; however, the molecular mechanisms for generating and maintaining their dynamic localization in bacteria are not completely understood. Here we demonstrate that the trans-envelope Tol–Pal complex, a widely conserved component of the cell envelope of Gram-negative bacteria, is required to maintain the polar positioning of chemoreceptor clusters in Escherichia coli. Localization of the chemoreceptors was independent of phospholipid composition of the membrane and the curvature of the cell wall. Instead, our data indicate that chemoreceptors interact with components of the Tol–Pal complex and that this interaction is required to polarly localize chemoreceptor clusters. We found that disruption of the Tol–Pal complex perturbs the polar localization of chemoreceptors, alters cell motility, and affects chemotaxis. We propose that the E. coli Tol–Pal complex restricts mobility of the chemoreceptor clusters at the cell poles and may be involved in regulatory mechanisms that co-ordinate cell division and segregation of the chemosensory machinery. PMID:24720726

Time distributions of recurrences of immunogenic and nonimmunogenic tumors following local irradiation

International Nuclear Information System (INIS)

Suit, H.D.; Sedlacek, R.; Fagundes, L.; Goitein, M.; Rothman, K.J.

1978-01-01

Three hundred and fourteen mice received single-dose irradiation of the right leg and thigh as treatment of an 8-mm mammary carcinoma isotransplant, and were then observed until death, usually by 1000 days. The time distributions of death due to local recurrence, radiation-induced sarcoma, distant metastasis in the absence of local regrowth, second primary, intercurrent disease, and unknown causes have been evaluated. The times for the transplant tumor inoculum to grow to an 8-mm tumor and the times of death due to local regrowth, distant metastasis, or induced tumor were all approximately log-normally distributed. Of the 128 recurrences, the latest-appearing 3 were at 300, 323, and 436 days; no recurrences were noted during the time period from 436 to 1000 days. These findings have been interpreted to mean that in some cases absolute cure of mice of the tumor in the leg was achieved by radiation alone at the dose levels employed. Radiation-induced sarcomas began to appear after 300 days. The time of appearance of the radiation-induced tumors was inversely related to radiation dose. Similar data for an immunogenic fibrosarcoma show that recurrences appeared earlier and were more closely bunched with respect to time than the recurrences of mammary carcinoma. The time distribution of the development of radiation-induced tumors in non-tumor-bearing animals was also approximately long-normally distributed; the slope of the time distribution curve was the same as that for radiation-induced tumors in mice which had been treated for tumor

Curvature tensors and unified field equations on SEX/sub n/

International Nuclear Information System (INIS)

Chung, K.T.; Lee, I.L.

1988-01-01

We study the curvature tensors and field equations in the n-dimensional SE manifold SEX/sub n/. We obtain several basic properties of the vectors S/subλ/ and U/sub λ/ and then of the SE curvature tensor and its contractions, such as a generalized Ricci identity, a generalized Bianchi identity, and two variations of the Bianchi identity satisfied by the SE Einstein tensor. Finally, a system of field equations is discussed in SEX/sub n/ an done of its particular solutions is constructed and displayed

Local multiplicity adjustment for the spatial scan statistic using the Gumbel distribution.

Science.gov (United States)

Gangnon, Ronald E

2012-03-01

The spatial scan statistic is an important and widely used tool for cluster detection. It is based on the simultaneous evaluation of the statistical significance of the maximum likelihood ratio test statistic over a large collection of potential clusters. In most cluster detection problems, there is variation in the extent of local multiplicity across the study region. For example, using a fixed maximum geographic radius for clusters, urban areas typically have many overlapping potential clusters, whereas rural areas have relatively few. The spatial scan statistic does not account for local multiplicity variation. We describe a previously proposed local multiplicity adjustment based on a nested Bonferroni correction and propose a novel adjustment based on a Gumbel distribution approximation to the distribution of a local scan statistic. We compare the performance of all three statistics in terms of power and a novel unbiased cluster detection criterion. These methods are then applied to the well-known New York leukemia dataset and a Wisconsin breast cancer incidence dataset. © 2011, The International Biometric Society.

Cosmic censorship, persistent curvature and asymptotic causal pathology

International Nuclear Information System (INIS)

Newman, R.P.A.C.

1984-01-01

The paper examines cosmic censorship in general relativity theory. Conformally flat space-times; persistent curvature; weakly asymptotically simple and empty asymptotes; censorship conditions; and the censorship theorem; are all discussed. (U.K.)

The effects of curvature on the flow field in rapidly rotating gas centrifuges

International Nuclear Information System (INIS)

Wood, H.G.; Jordan, J.A.

1984-01-01

The effects of curvature on the fluid dynamics of rapidly rotating gas centrifuges are studied. A governing system of a linear partial differential equation and boundary conditions is derived based on a linearization of the equations for viscous compressible flow. This system reduces to the Onsager pancake model if the effects of curvature are neglected. Approximations to the solutions of the governing equations with and without curvature terms are obtained via a finite-element method. Two examples are considered: first where the flow is driven by a thermal gradient at the wall of the centrifuge, and then for the flow being driven by the introduction and removal of mass through the ends of the centrifuge. Comparisons of the results obtained show that, especially for the second example, the inclusion of the terms due to curvature in the model can have an appreciable effect on the solution. (author)

Controllable soliton propagation based on phase-front curvature in asymmetrical nonlocal media

Science.gov (United States)

Zhang, Huafeng; Lü, Hua; Luo, Jianghua; Sun, Lihui

2016-08-01

The influence of phase-front curvature on the dynamical behavior of the fundamental mode soliton during its transmission in asymmetrical nonlocal media is studied in detail and the phase-front curvature can be imposed on the fundamental mode soliton by reshaping or phase imprinting technologies. By changing the phase-front curvature or its imposed position, controllable soliton propagation in asymmetrical nonlocal media can be achieved. Project supported by the National Natural Science Foundation of China (Grants Nos. 11547007 and 11304024), the Innovation Personnel Training Plan for Excellent Youth of Guangdong University Project (Grant No. 2013LYM_0023), and the Yangtze Fund for Youth Teams of Science and Technology Innovation (Grant No. 2015cqt03).

Curvature-driven instabilities in the Elmo Bumpy Torus (EBT)

International Nuclear Information System (INIS)

Abe, H.; Spong, D.A.; Antonsen, T.M. Jr.; Tsang, K.T.; Nguyen, K.T.

1982-01-01

Curvature-driven instabilities are analyzed for an EBT configuration which consists of plasma interacting with a hot electron ring whose drift frequencies are larger than the growth rates predicted from conventional magnetohydrodynamic (MHD) theory. Stability criteria are obtained for five possible modes: the conventional hot electron interchange, a high-frequency hot electron interchange (at frequencies greater than the ion-cyclotron frequency), a compressional instability, a background plasma interchange, and an interacting pressure-driven interchange. A wide parameter regime for stable operation is found, which, however, severely deteriorates for a band of intermediate mode numbers. Finite Larmor radius effects can eliminate this deterioration; moreover, all short-wavelength curvature-driven modes are stabilized if the hot electron Larmor radius rho/sub h/ satisfies (kappa/sub perpendicular/rho/sub h/) 2 > 2Δ/[Rβ/sub h/(1 + P'/sub parallel//P'/sub perpendicular/)], where kappa/sub perpendicular/ is the transverse wavenumber, Δ is the ring half-width, R is the mid-plane radius of curvature, β/sub h/ is the hot electron beta value, and P' is the pressure gradient. Resonant wave-particle instabilities predicted by a new low frequency variational principle show that a variety of remnant instabilities may still persist

The zero curvature formulation of the KP and the sKP equations

International Nuclear Information System (INIS)

Barcelos Neto, J.; Das, A.; Panda, S.; Roy, S.

1992-01-01

The Kadomtsev-Petviashvili equation is derived from the zero curvature condition associated with the gauge group SL(2,R) in 2+1 dimensions. A fermionic extension of the KP equation is also obtained using the zero curvature condition of the super group OS p (2/1), which reduces upon appropriate restriction to the Kupershmidt equation. (author). 17 refs

Curvature Effects on the Vibration Characteristics of Doubly Curved Shallow Shells with General Elastic Edge Restraints

Directory of Open Access Journals (Sweden)

Hui Shi

2015-01-01

Full Text Available Effects of curvature upon the vibration characteristics of doubly curved shallow shells are assessed in this paper. Boundary conditions of the shell are generally specified in terms of distributed elastic restraints along the edges. The classical homogeneous boundary supports can be easily simulated by setting the stiffnesses of restraining springs to either zero or infinite. Vibration problems of the shell are solved by a modified Fourier series method that each of the displacements is invariably expressed as a simple trigonometric series which converges uniformly and acceleratedly over the solution domain. All the unknown expansion coefficients are treated equally as a set of independent generalized coordinates and solved using the Rayleigh-Ritz technique. The current method provides a unified solution to the vibration problems of curved shallow shells involving different geometric properties and boundary conditions with no need of modifying the formulations and solution procedures. Extensive tabular and graphical results are presented to show the curvature effects on the natural frequencies of the shell with various boundary conditions.

3D Facial Similarity Measure Based on Geodesic Network and Curvatures

Directory of Open Access Journals (Sweden)

Junli Zhao

2014-01-01

Full Text Available Automated 3D facial similarity measure is a challenging and valuable research topic in anthropology and computer graphics. It is widely used in various fields, such as criminal investigation, kinship confirmation, and face recognition. This paper proposes a 3D facial similarity measure method based on a combination of geodesic and curvature features. Firstly, a geodesic network is generated for each face with geodesics and iso-geodesics determined and these network points are adopted as the correspondence across face models. Then, four metrics associated with curvatures, that is, the mean curvature, Gaussian curvature, shape index, and curvedness, are computed for each network point by using a weighted average of its neighborhood points. Finally, correlation coefficients according to these metrics are computed, respectively, as the similarity measures between two 3D face models. Experiments of different persons’ 3D facial models and different 3D facial models of the same person are implemented and compared with a subjective face similarity study. The results show that the geodesic network plays an important role in 3D facial similarity measure. The similarity measure defined by shape index is consistent with human’s subjective evaluation basically, and it can measure the 3D face similarity more objectively than the other indices.

Accuracy evaluation of automatic quantification of the articular cartilage surface curvature from MRI

DEFF Research Database (Denmark)

Folkesson, Jenny; Dam, Erik B; Olsen, Ole F

2007-01-01

for intersubject comparisons. Digital phantoms were created to establish the accuracy of the curvature estimation methods. RESULTS: A comparison of the two curvature estimation methods to ground truth yielded absolute pairwise differences of 1.1%, and 4.8%, respectively. The interscan reproducibility for the two...

Higher-order momentum distributions and locally affine LDDMM registration

DEFF Research Database (Denmark)

Sommer, Stefan Horst; Nielsen, Mads; Darkner, Sune

2013-01-01

description of affine transformations and subsequent compact description of non-translational movement in a globally nonrigid deformation. The resulting representation contains directly interpretable information from both mathematical and modeling perspectives. We develop the mathematical construction......To achieve sparse parametrizations that allow intuitive analysis, we aim to represent deformation with a basis containing interpretable elements, and we wish to use elements that have the description capacity to represent the deformation compactly. To accomplish this, we introduce in this paper...... higher-order momentum distributions in the large deformation diffeomorphic metric mapping (LDDMM) registration framework. While the zeroth-order moments previously used in LDDMM only describe local displacement, the first-order momenta that are proposed here represent a basis that allows local...

Norm of the Riemannian Curvature Tensor

Indian Academy of Sciences (India)

We consider the Riemannian functional R p ( g ) = ∫ M | R ( g ) | p d v g defined on the space of Riemannian metrics with unit volume on a closed smooth manifold where R ( g ) and d v g denote the corresponding Riemannian curvature tensor and volume form and p ∈ ( 0 , ∞ ) . First we prove that the Riemannian metrics ...

Zero curvature conditions and conformal covariance

International Nuclear Information System (INIS)

Akemann, G.; Grimm, R.

1992-05-01

Two-dimensional zero curvature conditions were investigated in detail, with special emphasis on conformal properties, and the appearance of covariant higher order differential operators constructed in terms of a projective connection was elucidated. The analysis is based on the Kostant decomposition of simple Lie algebras in terms of representations with respect to their 'principal' SL(2) subalgebra. (author) 27 refs

Random paths with curvature dependent action

International Nuclear Information System (INIS)

Ambjoern, J.; Durhuus, B.

1986-11-01

We study discretized random paths with a curvature dependent action. The scaling limits of the corresponding statistical mechanical models can be constructed explicitly and are either usual Brownian motion or a theory where the correlations of tangents are nonzero and described by diffusion on the unit sphere. In the latter case the two point function has an anomalous dimension η = 1. (orig.)

A non-local variable for general relativity

International Nuclear Information System (INIS)

Kozameh, C.N.; Newman, E.T.

1983-01-01

The usual description of differential geometry and general relativity is in terms of local fields, e.g. the metric, the curvature tensor, etc, which satisfy local differential equations. The authors introduce a new non-local field (Z) from which the local fields can be derived. Basically Z, though it is non-local, should be thought of as a function on the bundle of null directions on a space-time. The program can be divided into two parts; first the authors want to show the geometric meaning of and the relationship between Z and the local field. Then they want to provide field equations (non-local) for Z which will be equivalent to the vacuum Einstein equations for the local field. (Auth.)

Curvature and Strength of Ni-YSZ Solid Oxide Half-Cells After Redox Treatments

DEFF Research Database (Denmark)

Faes, Antonin; Frandsen, Henrik Lund; Pihlatie, Mikko

2010-01-01

One of the main drawbacks of anode-supported solid oxide fuel cell technology is the limited capability to withstand reduction and oxidation (“RedOx”) of the Ni phase. This study compares the effect of RedOx cycles on curvature and strength of half-cells, composed of a nickel-yttria-stabilized-zi......One of the main drawbacks of anode-supported solid oxide fuel cell technology is the limited capability to withstand reduction and oxidation (“RedOx”) of the Ni phase. This study compares the effect of RedOx cycles on curvature and strength of half-cells, composed of a nickel...... it is calculated analytically from the force. In this calculation the thermal stresses are estimated from the curvature of the half-cell. For each treatment, more than 30 samples are tested. About 20 ball-on-ring samples are laser cut from one original 12×12 cm2 half-cell. Curvature and porosity are measured...

Localizing Value of Pain Distribution Patterns in Cervical Spondylosis

OpenAIRE

Bunyaratavej, Krishnapundha; Montriwiwatnchai, Peerapong; Siwanuwatn, Rungsak; Khaoroptham, Surachai

2015-01-01

Study Design Prospective observational study. Purpose To investigate the value of pain distribution in localizing appropriate surgical levels in patients with cervical spondylosis. Overview of Literature Previous studies have investigated the value of pain drawings in its correlation with various features in degenerative spine diseases including surgical outcome, magnetic resonance imaging findings, discographic study, and psychogenic issues. However, there is no previous study on the value o...

Regional Distribution Shifts Help Explain Local Changes in Wintering Raptor Abundance: Implications for Interpreting Population Trends

OpenAIRE

Paprocki, Neil; Heath, Julie A.; Novak, Stephen J.

2014-01-01

Studies of multiple taxa across broad-scales suggest that species distributions are shifting poleward in response to global climate change. Recognizing the influence of distribution shifts on population indices will be an important part of interpreting trends within management units because current practice often assumes that changes in local populations reflect local habitat conditions. However, the individual- and population-level processes that drive distribution shifts may occur across a ...

Application of Learning Methods to Local Electric Field Distributions in Defected Dielectric Materials

Science.gov (United States)

Ferris, Kim; Jones, Dumont

2014-03-01

Local electric fields reflect the structural and dielectric fluctuations in a semiconductor, and affect the material performance both for electron transport and carrier lifetime properties. In this paper, we use the LOCALF methodology with periodic boundary conditions to examine the local electric field distributions and its perturbations for II-VI (CdTe, Cd(1-x)Zn(x)Te) semiconductors, containing Te inclusions and small fluctuations in the local dielectric susceptibility. With inclusion of the induced-field term, the electric field distribution shows enhancements and diminishments compared to the macroscopic applied field, reflecting the microstructure characteristics of the dielectric. Learning methods are applied to these distributions to assess the spatial extent of the perturbation, and determine an electric field defined defect size as compared to its physical dimension. Critical concentrations of defects are assessed in terms of defect formation energies. This work was supported by the US Department of Homeland Security, Domestic Nuclear Detection Office, under competitively awarded contract/IAA HSHQDC-08-X-00872-e. This support does not constitute an express or implied endorsement on the part of the Gov't.

Harmonic Differential Quadrature Analysis of Soft-Core Sandwich Panels under Locally Distributed Loads

Directory of Open Access Journals (Sweden)

Xinwei Wang

2016-11-01

Full Text Available Sandwich structures are widely used in practice and thus various engineering theories adopting simplifying assumptions are available. However, most engineering theories of beams, plates and shells cannot recover all stresses accurately through their constitutive equations. Therefore, the soft-core is directly modeled by two-dimensional (2D elasticity theory without any pre-assumption on the displacement field. The top and bottom faces act like the elastic supports on the top and bottom edges of the core. The differential equations of the 2D core are then solved by the harmonic differential quadrature method (HDQM. To circumvent the difficulties in dealing with the locally distributed load by point discrete methods such as the HDQM, a general and rigorous way is proposed to treat the locally distributed load. Detailed formulations are provided. The static behavior of sandwich panels under different locally distributed loads is investigated. For verification, results are compared with data obtained by ABAQUS with very fine meshes. A high degree of accuracy on both displacement and stress has been observed.

Model-independent curvature determination with 21cm intensity mapping experiments

Science.gov (United States)

Witzemann, Amadeus; Bull, Philip; Clarkson, Chris; Santos, Mario G.; Spinelli, Marta; Weltman, Amanda

2018-04-01

Measurements of the spatial curvature of the Universe have improved significantly in recent years, but still tend to require strong assumptions to be made about the equation of state of dark energy (DE) in order to reach sub-percent precision. When these assumptions are relaxed, strong degeneracies arise that make it hard to disentangle DE and curvature, degrading the constraints. We show that forthcoming 21cm intensity mapping experiments such as HIRAX are ideally designed to carry out model-independent curvature measurements, as they can measure the clustering signal at high redshift with sufficient precision to break many of the degeneracies. We consider two different model-independent methods, based on `avoiding' the DE-dominated regime and non-parametric modelling of the DE equation of state respectively. Our forecasts show that HIRAX will be able to improve upon current model-independent constraints by around an order of magnitude, reaching percent-level accuracy even when an arbitrary DE equation of state is assumed. In the same model-independent analysis, the sample variance limit for a similar survey is another order of magnitude better.

The effect of spontaneous curvature on a two-phase vesicle

International Nuclear Information System (INIS)

Cox, Geoffrey; Lowengrub, John

2015-01-01

Vesicles are membrane-bound structures commonly known for their roles in cellular transport and the shape of a vesicle is determined by its surrounding membrane (lipid bilayer). When the membrane is composed of different lipids, it is natural for the lipids of similar molecular structure to migrate towards one another (via spinodal decomposition), creating a multi-phase vesicle. In this article, we consider a two-phase vesicle model which is driven by nature's propensity to maintain a minimal state of elastic energy. The model assumes a continuum limit, thereby treating the membrane as a closed three-dimensional surface. The main purpose of this study is to reveal the complexity of the Helfrich two-phase vesicle model with non-zero spontaneous curvature and provide further evidence to support the relevance of spontaneous curvature as a modelling parameter. In this paper, we illustrate the complexity of the Helfrich two-phase model by providing multiple examples of undocumented solutions and energy hysteresis. We also investigate the influence of spontaneous curvature on morphological effects and membrane phenomena such as budding and fusion. (paper)

Dark Energy, scalar-curvature couplings and a critical acceleration scale

CERN Document Server

Navarro, Ignacio

2008-01-01

We study the effects of coupling a cosmologically rolling scalar field to higher order curvature terms. We show that when the strong coupling scale of the theory is on the 10^{-3}-10^{-1}eV range, the model passes all experimental bounds on the existence of fifth forces even if the field has a mass of the order of the Hubble scale in vacuum and non-suppressed couplings to SM fields. The reason is that the coupling to certain curvature invariant acts as an effective mass that grows in regions of large curvature. This prevents the field from rolling down its potential near sources and makes its effects on fifth-force search experiments performed in the laboratory to be observable only at the sub-mm scale. We obtain the static spherically symmetric solutions of the theory and show that a long-range force appears but it is turned on only below a fixed Newtonian acceleration scale of the order of the Hubble constant. We comment on the possibility of using this feature of the model to alleviate the CDM small scale ...

Curvature and the visual perception of shape: theory on information along object boundaries and the minima rule revisited.

Science.gov (United States)

Lim, Ik Soo; Leek, E Charles

2012-07-01

Previous empirical studies have shown that information along visual contours is known to be concentrated in regions of high magnitude of curvature, and, for closed contours, segments of negative curvature (i.e., concave segments) carry greater perceptual relevance than corresponding regions of positive curvature (i.e., convex segments). Lately, Feldman and Singh (2005, Psychological Review, 112, 243-252) proposed a mathematical derivation to yield information content as a function of curvature along a contour. Here, we highlight several fundamental errors in their derivation and in its associated implementation, which are problematic in both mathematical and psychological senses. Instead, we propose an alternative mathematical formulation for information measure of contour curvature that addresses these issues. Additionally, unlike in previous work, we extend this approach to 3-dimensional (3D) shape by providing a formal measure of information content for surface curvature and outline a modified version of the minima rule relating to part segmentation using curvature in 3D shape. Copyright 2012 APA, all rights reserved.

Experimental investigation of localized stress-induced leakage current distribution in gate dielectrics using array test circuit

Science.gov (United States)

Park, Hyeonwoo; Teramoto, Akinobu; Kuroda, Rihito; Suwa, Tomoyuki; Sugawa, Shigetoshi

2018-04-01

Localized stress-induced leakage current (SILC) has become a major problem in the reliability of flash memories. To reduce it, clarifying the SILC mechanism is important, and statistical measurement and analysis have to be carried out. In this study, we applied an array test circuit that can measure the SILC distribution of more than 80,000 nMOSFETs with various gate areas at a high speed (within 80 s) and a high accuracy (on the 10-17 A current order). The results clarified that the distributions of localized SILC in different gate areas follow a universal distribution assuming the same SILC defect density distribution per unit area, and the current of localized SILC defects does not scale down with the gate area. Moreover, the distribution of SILC defect density and its dependence on the oxide field for measurement (E OX-Measure) were experimentally determined for fabricated devices.

The influence of road curvature on fatal crashes in New Zealand

DEFF Research Database (Denmark)

Haynes, Robin; Lake, Iain R.; Kingham, Simon

2008-01-01

Bends in roads can cause crashes but a recent study in the UK found that areas with mostly curved roads had lower crash rates than areas with straighter roads. This present study aimed to replicate the previous research in a different country. Variations in the number of fatal road crashes...... occurring between 1996 and 2005 in 73 territorial local authorities across New Zealand were modelled against possible predictors. The predictors were traffic flow, population counts and characteristics, car use, socio-economic deprivation, climate, altitude and road characteristics including four measures...... of average road curvature. The best predictors of the number of fatal crashes on urban roads, rural state highways and other rural roads were traffic flow, speed limitation and socio-economic deprivation. Holding significant factors constant, there was no evidence that TLAs with the most curved roads had...

Fractional charge and inter-Landau-level states at points of singular curvature.

Science.gov (United States)

Biswas, Rudro R; Son, Dam Thanh

2016-08-02

The quest for universal properties of topological phases is fundamentally important because these signatures are robust to variations in system-specific details. Aspects of the response of quantum Hall states to smooth spatial curvature are well-studied, but challenging to observe experimentally. Here we go beyond this prevailing paradigm and obtain general results for the response of quantum Hall states to points of singular curvature in real space; such points may be readily experimentally actualized. We find, using continuum analytical methods, that the point of curvature binds an excess fractional charge and sequences of quantum states split away, energetically, from the degenerate bulk Landau levels. Importantly, these inter-Landau-level states are bound to the topological singularity and have energies that are universal functions of bulk parameters and the curvature. Our exact diagonalization of lattice tight-binding models on closed manifolds demonstrates that these results continue to hold even when lattice effects are significant. An important technological implication of these results is that these inter-Landau-level states, being both energetically and spatially isolated quantum states, are promising candidates for constructing qubits for quantum computation.

Curvature effects on carbon nanomaterials: Exohedral versus endhohedral supercapacitors

Energy Technology Data Exchange (ETDEWEB)

Huang, J; Sumpter, B. G.; Meunier, V.; Yushin, G.; Portet, C.; Gogotsi, Y.

2011-01-31

Capacitive energy storage mechanisms in nanoporous carbon supercapacitors hinge on endohedral interactions in carbon materials with macro-, meso-, and micropores that have negative surface curvature. In this article, we show that because of the positive curvature found in zero-dimensional carbon onions or one-dimensional carbon nanotube arrays, exohedral interactions cause the normalized capacitance to increase with decreasing particle size or tube diameter, in sharp contrast to the behavior of nanoporous carbon materials. This finding is in good agreement with the trend of recent experimental data. Our analysis suggests that electrical energy storage can be improved by exploiting the highly curved surfaces of carbon nanotube arrays with diameters on the order of 1 nm.

Curvature effects in carbon nanomaterials: Exohedral versus endohedral supercapacitors

Energy Technology Data Exchange (ETDEWEB)

Huang, Jingsong [ORNL; Sumpter, Bobby G [ORNL; Meunier, Vincent [ORNL; Gogotsi, Yury G. [Drexel University; Yushin, Gleb [Georgia Institute of Technology; Portet, Cristelle [Drexel University

2010-01-01

Capacitive energy storage mechanisms in nanoporous carbon supercapacitors hinge on endohedral interactions in carbon materials with macro-, meso-, and micropores that have negative surface curvature. In this article, we show that because of the positive curvature found in zero-dimensional carbon onions or one-dimensional carbon nanotube arrays, exohedral interactions cause the normalized capacitance to increase with decreasing particle size or tube diameter, in sharp contrast to the behavior of nanoporous carbon materials. This finding is in good agreement with the trend of recent experimental data. Our analysis suggests that electrical energy storage can be improved by exploiting the highly curved surfaces of carbon nanotube arrays with diameters on the order of 1 nm.

Study of Climate Change Impact to Local Rainfall Distribution in Lampung Provinces

Directory of Open Access Journals (Sweden)

Tumiar Katarina Manik

2016-08-01

Full Text Available Global warming which leads to climate change has potential affect to Indonesia agriculture activities and production. Analyzing rainfall pattern and distribution is important to investigate the impact of global climate change to local climate. This study using rainfall data from 1976-2010 from both lowland and upland area of Lampung Province. The results show that rainfall tends to decrease since the 1990s which related to the years with El Nino event. Monsoonal pattern- having rain and dry season- still excist in Lampung; however, since most rain fell below the average, it could not meet crops water need. Farmers conclude that dry seasons were longer and seasonal pattern has been changed. Global climate change might affect Lampung rainfall distribution through changes on sea surface temperature which could intensify the El Nino effect. Therefore, watching the El Nino phenomena and how global warming affects it, is important in predicting local climate especially the rainfall distribution in order to prevent significant loss in agriculture productivities.

Berry Curvature and Nonlocal Transport Characteristics of Antidot Graphene

Directory of Open Access Journals (Sweden)

Jie Pan

2017-09-01

Full Text Available Antidot graphene denotes a monolayer of graphene structured by a periodic array of holes. Its energy dispersion is known to display a gap at the Dirac point. However, since the degeneracy between the A and B sites is preserved, antidot graphene cannot be described by the 2D massive Dirac equation, which is suitable for systems with an inherent A/B asymmetry. From inversion and time-reversal-symmetry considerations, antidot graphene should therefore have zero Berry curvature. In this work, we derive the effective Hamiltonian of antidot graphene from its tight-binding wave functions. The resulting Hamiltonian is a 4×4 matrix with a nonzero intervalley scattering term, which is responsible for the gap at the Dirac point. Furthermore, nonzero Berry curvature is obtained from the effective Hamiltonian, owing to the double degeneracy of the eigenfunctions. The topological manifestation is shown to be robust against randomness perturbations. Since the Berry curvature is expected to induce a transverse conductance, we have experimentally verified this feature through nonlocal transport measurements, by fabricating three antidot graphene samples with a triangular array of holes, a fixed periodicity of 150 nm, and hole diameters of 100, 80, and 60 nm. All three samples display topological nonlocal conductance, with excellent agreement with the theory predictions.

Model-based monitoring techniques for leakage localization in distribution water networks

OpenAIRE

Meseguer Amela, Jordi; Mirats Tur, Josep Maria; Cembrano Gennari, Gabriela; Puig Cayuela, Vicenç

2015-01-01

This is an open access article under the CC BY-NC-ND license This paper describes an integrated model-based monitoring framework for leakage localization in district-metered areas (DMA) of water distribution networks, which takes advantage of the availability of a hydraulic model of the network. The leakage localization methodology is based on the use of flow and pressure sensors at the DMA inlets and a limited number of pressure sensors deployed inside the DMA. The placement of these sens...

ORNL Interim Progress Report on Static CIRFT Testing Curvature Data Update

Energy Technology Data Exchange (ETDEWEB)

Wang, Jy-An John [ORNL; Wang, Hong [ORNL

2016-10-10

Since the CIRFT tests reported in NUREG-7198 were generated, a number of factors that influence the recorded curvature measurement data were identified. In 2016, a data reanalysis task was undertaken to implement the lessons learned. This letter report provides the revised results of previous CIRFT tests, after implementing the following data reanalysis procedures: (A) experimental data smoothing and LVDT reset, (B) LVDT probe contact and sensor spacing correction for curvature data, and (C) LVDT probe dynamic vibration adjustment procedure development.

Influence of implant rod curvature on sagittal correction of scoliosis deformity

DEFF Research Database (Denmark)

Salmingo, Remel A.; Tadano, Shigeru; Abe, Yuichiro

2014-01-01

of the implant rod’s angle of curvature during surgery and establish its influence on sagittal correction of scoliosis deformity. STUDY DESIGN: A retrospective analysis of the preoperative and postoperative implant rod geometry and angle of curvature was conducted. PATIENT SAMPLE: Twenty adolescent idiopathic......BACKGROUND CONTEXT: Deformation of in vivo–implanted rods could alter the scoliosis sagittal correction. To our knowledge, no previous authors have investigated the influence of implanted-rod deformation on the sagittal deformity correction during scoliosis surgery. PURPOSE: To analyze the changes...... scoliosis patients underwent surgery. Average age at the time of operation was 14 years. OUTCOME MEASURES: The preoperative and postoperative implant rod angle of curvature expressed in degrees was obtained for each patient. METHODS: Two implant rods were attached to the concave and convex side...

Aftershock distribution as a constraint on the geodetic model of coseismic slip for the 2004 Parkfield earthquake

Science.gov (United States)

Bennington, Ninfa; Thurber, Clifford; Feigl, Kurt; ,

2011-01-01

Several studies of the 2004 Parkfield earthquake have linked the spatial distribution of the event’s aftershocks to the mainshock slip distribution on the fault. Using geodetic data, we find a model of coseismic slip for the 2004 Parkfield earthquake with the constraint that the edges of coseismic slip patches align with aftershocks. The constraint is applied by encouraging the curvature of coseismic slip in each model cell to be equal to the negative of the curvature of seismicity density. The large patch of peak slip about 15 km northwest of the 2004 hypocenter found in the curvature-constrained model is in good agreement in location and amplitude with previous geodetic studies and the majority of strong motion studies. The curvature-constrained solution shows slip primarily between aftershock “streaks” with the continuation of moderate levels of slip to the southeast. These observations are in good agreement with strong motion studies, but inconsistent with the majority of published geodetic slip models. Southeast of the 2004 hypocenter, a patch of peak slip observed in strong motion studies is absent from our curvature-constrained model, but the available GPS data do not resolve slip in this region. We conclude that the geodetic slip model constrained by the aftershock distribution fits the geodetic data quite well and that inconsistencies between models derived from seismic and geodetic data can be attributed largely to resolution issues.

Simultaneous reflectometry and interferometry for measuring thin-film thickness and curvature

Science.gov (United States)

Arends, A. A.; Germain, T. M.; Owens, J. F.; Putnam, S. A.

2018-05-01

A coupled reflectometer-interferometer apparatus is described for thin-film thickness and curvature characterization in the three-phase contact line region of evaporating fluids. Validation reflectometry studies are provided for Au, Ge, and Si substrates and thin-film coatings of SiO2 and hydrogel/Ti/SiO2. For interferometry, liquid/air and solid/air interferences are studied, where the solid/air samples consisted of glass/air/glass wedges, cylindrical lenses, and molded polydimethylsiloxane lenses. The liquid/air studies are based on steady-state evaporation experiments of water and isooctane on Si and SiO2/Ti/SiO2 wafers. The liquid thin-films facilitate characterization of both (i) the nano-scale thickness of the absorbed fluid layer and (ii) the macro-scale liquid meniscus thickness, curvature, and curvature gradient profiles. For our validation studies with commercial lenses, the apparatus is shown to measure thickness profiles within 4.1%-10.8% error.

MreB filaments align along greatest principal membrane curvature to orient cell wall synthesis

Science.gov (United States)

Szwedziak, Piotr; Wong, Felix; Schaefer, Kaitlin; Izoré, Thierry; Renner, Lars D; Holmes, Matthew J; Sun, Yingjie; Bisson-Filho, Alexandre W; Walker, Suzanne; Amir, Ariel; Löwe, Jan

2018-01-01

MreB is essential for rod shape in many bacteria. Membrane-associated MreB filaments move around the rod circumference, helping to insert cell wall in the radial direction to reinforce rod shape. To understand how oriented MreB motion arises, we altered the shape of Bacillus subtilis. MreB motion is isotropic in round cells, and orientation is restored when rod shape is externally imposed. Stationary filaments orient within protoplasts, and purified MreB tubulates liposomes in vitro, orienting within tubes. Together, this demonstrates MreB orients along the greatest principal membrane curvature, a conclusion supported with biophysical modeling. We observed that spherical cells regenerate into rods in a local, self-reinforcing manner: rapidly propagating rods emerge from small bulges, exhibiting oriented MreB motion. We propose that the coupling of MreB filament alignment to shape-reinforcing peptidoglycan synthesis creates a locally-acting, self-organizing mechanism allowing the rapid establishment and stable maintenance of emergent rod shape. PMID:29469806

Distributed push-pull estimation for node localization in wireless sensor networks

NARCIS (Netherlands)

Dang, Viet-Hung; Le Viet Duc, L Duc; Lee, Young-Koo; Lee, Sungyoung

A great deal of research achievements on localization in wireless sensor networks (WSNs) has been obtained in recent years. Nevertheless, its interesting challenges in terms of cost-reduction, accuracy improvement, scalability, and distributed ability design have led to the development of a new

Curvature controlled wetting in two dimensions

DEFF Research Database (Denmark)

Gil, Tamir; Mikheev, Lev V.

1995-01-01

. As the radius of the substrate r0→∞, the leading effect of the curvature is adding the Laplace pressure ΠL∝r0-1 to the pressure balance in the film. At temperatures and pressures under which the wetting is complete in planar geometry, Laplace pressure suppresses divergence of the mean thickness of the wetting...... term reduces the thickness by the amount proportional to r0-1/3...

Role of parallel flow curvature on the mitigation of Rayleigh-Taylor instability

International Nuclear Information System (INIS)

Sarmah, D.; Sen, S.; Cairns, R.A.

2001-01-01

The effect of a radially varying parallel equilibrium flow on the stability of the Rayleigh-Taylor (RT) mode is studied analytically in the presence of a sheared magnetic field. It is shown that the parallel flow curvature can completely stabilize the RT mode. The flow curvature also has a robust effect on the radial structure of the mode. Possible implications of these theoretical findings to recent experiments are also discussed

Observational constraints on dark energy and cosmic curvature

International Nuclear Information System (INIS)

Wang Yun; Mukherjee, Pia

2007-01-01

Current observational bounds on dark energy depend on our assumptions about the curvature of the universe. We present a simple and efficient method for incorporating constraints from cosmic microwave background (CMB) anisotropy data and use it to derive constraints on cosmic curvature and dark energy density as a free function of cosmic time using current CMB, Type Ia supernova (SN Ia), and baryon acoustic oscillation data. We show that there are two CMB shift parameters, R≡√(Ω m H 0 2 )r(z CMB ) (the scaled distance to recombination) and l a ≡πr(z CMB )/r s (z CMB ) (the angular scale of the sound horizon at recombination), with measured values that are nearly uncorrelated with each other. Allowing nonzero cosmic curvature, the three-year WMAP (Wilkinson Microwave Anisotropy Probe) data give R=1.71±0.03, l a =302.5±1.2, and Ω b h 2 =0.02173±0.00082, independent of the dark energy model. The corresponding bounds for a flat universe are R=1.70±0.03, l a =302.2±1.2, and Ω b h 2 =0.022±0.00082. We give the covariance matrix of (R,l a ,Ω b h 2 ) from the three-year WMAP data. We find that (R,l a ,Ω b h 2 ) provide an efficient and intuitive summary of CMB data as far as dark energy constraints are concerned. Assuming the Hubble Space Telescope (HST) prior of H 0 =72±8 (km/s) Mpc -1 , using 182 SNe Ia (from the HST/GOODS program, the first year Supernova Legacy Survey, and nearby SN Ia surveys), (R,l a ,Ω b h 2 ) from WMAP three-year data, and SDSS (Sloan Digital Sky Survey) measurement of the baryon acoustic oscillation scale, we find that dark energy density is consistent with a constant in cosmic time, with marginal deviations from a cosmological constant that may reflect current systematic uncertainties or true evolution in dark energy. A flat universe is allowed by current data: Ω k =-0.006 -0.012-0.025 +0.013+0.025 for assuming that the dark energy equation of state w X (z) is constant, and Ω k =-0.002 -0.018-0.032 +0.018+0.041 for w X (z

Nonsmooth differential geometry-an approach tailored for spaces with Ricci curvature bounded from below

CERN Document Server

Gigli, Nicola

2018-01-01

The author discusses in which sense general metric measure spaces possess a first order differential structure. Building on this, spaces with Ricci curvature bounded from below a second order calculus can be developed, permitting the author to define Hessian, covariant/exterior derivatives and Ricci curvature.

Predicting Posttraumatic Stress Symptom Prevalence and Local Distribution after an Earthquake with Scarce Data.

Science.gov (United States)

Dussaillant, Francisca; Apablaza, Mauricio

2017-08-01

After a major earthquake, the assignment of scarce mental health emergency personnel to different geographic areas is crucial to the effective management of the crisis. The scarce information that is available in the aftermath of a disaster may be valuable in helping predict where are the populations that are in most need. The objectives of this study were to derive algorithms to predict posttraumatic stress (PTS) symptom prevalence and local distribution after an earthquake and to test whether there are algorithms that require few input data and are still reasonably predictive. A rich database of PTS symptoms, informed after Chile's 2010 earthquake and tsunami, was used. Several model specifications for the mean and centiles of the distribution of PTS symptoms, together with posttraumatic stress disorder (PTSD) prevalence, were estimated via linear and quantile regressions. The models varied in the set of covariates included. Adjusted R2 for the most liberal specifications (in terms of numbers of covariates included) ranged from 0.62 to 0.74, depending on the outcome. When only including peak ground acceleration (PGA), poverty rate, and household damage in linear and quadratic form, predictive capacity was still good (adjusted R2 from 0.59 to 0.67 were obtained). Information about local poverty, household damage, and PGA can be used as an aid to predict PTS symptom prevalence and local distribution after an earthquake. This can be of help to improve the assignment of mental health personnel to the affected localities. Dussaillant F , Apablaza M . Predicting posttraumatic stress symptom prevalence and local distribution after an earthquake with scarce data. Prehosp Disaster Med. 2017;32(4):357-367.

Optimal distribution of temperature points in μSR measurement of local field

International Nuclear Information System (INIS)

Pełka, R.; Zieliński, P.M.; Konieczny, P.; Wasiutyński, T.

2013-01-01

Three possible distributions of temperature points in the μSR measurement of local field (order parameter) are discussed. The least square method is applied to estimate the scale of the deviations of the fitted parameters from the true values. It indicates that the distribution corresponding to a uniform section of the order parameter values (uniform-in-signal) incurs the smallest errors. The distribution constructed on the basis of the zeros of the Chebyshev polynomials yields comparable uncertainties, while the uniform-in-temperature distribution turns out to be least effective incurring considerably larger errors. These findings can be useful while planning an order parameter measurement in the μSR experiment

Dual curvature acoustically damped concentrating collector. Final technical report

Energy Technology Data Exchange (ETDEWEB)

Smith, G.A.; Rausch, R.A.

1980-05-01

A development program was conducted to investigate the design and performance parameters of a novel, dual curvature, concentrating solar collector. The reflector of the solar collector is achieved with a stretched-film reflective surface that approximates a hyperbolic paraboloid and is capable of line-focusing at concentration ratios ranging from 10 to 20X. A prototype collector was designed based on analytical and experimental component trade-off activities as well as economic analyses of solar thermal heating and cooling systems incorporating this type of collector. A prototype collector incorporating six 0.66 x 1.22 m (2 x 4 ft) was fabricated and subjected to a limited thermal efficiency test program. A peak efficiency of 36% at 121/sup 0/C (250/sup 0/F) was achieved based upon the gross aperture area. Commercialization activities were conducted, including estimated production costs of $134.44/m/sup 2/ ($12.49/ft/sup 2/) for the collector assembly (including a local suntracker and controls) and $24.33/m/sup 2/ ($2.26/ft/sup 2/) for the reflector subassembly.

A Local Scalable Distributed EM Algorithm for Large P2P Networks

Data.gov (United States)

National Aeronautics and Space Administration — his paper describes a local and distributed expectation maximization algorithm for learning parameters of Gaussian mixture models (GMM) in large peer-to-peer (P2P)...

Self-similar slip distributions on irregular shaped faults

Science.gov (United States)

Herrero, A.; Murphy, S.

2018-06-01

We propose a strategy to place a self-similar slip distribution on a complex fault surface that is represented by an unstructured mesh. This is possible by applying a strategy based on the composite source model where a hierarchical set of asperities, each with its own slip function which is dependent on the distance from the asperity centre. Central to this technique is the efficient, accurate computation of distance between two points on the fault surface. This is known as the geodetic distance problem. We propose a method to compute the distance across complex non-planar surfaces based on a corollary of the Huygens' principle. The difference between this method compared to others sample-based algorithms which precede it is the use of a curved front at a local level to calculate the distance. This technique produces a highly accurate computation of the distance as the curvature of the front is linked to the distance from the source. Our local scheme is based on a sequence of two trilaterations, producing a robust algorithm which is highly precise. We test the strategy on a planar surface in order to assess its ability to keep the self-similarity properties of a slip distribution. We also present a synthetic self-similar slip distribution on a real slab topography for a M8.5 event. This method for computing distance may be extended to the estimation of first arrival times in both complex 3D surfaces or 3D volumes.

Numerical study on the incompressible Euler equations as a Hamiltonian system: Sectional curvature and Jacobi field

Science.gov (United States)

Ohkitani, K.

2010-05-01

We study some of the key quantities arising in the theory of [Arnold "Sur la geometrie differentielle des groupes de Lie de dimension infinie et ses applications a l'hydrodynamique des fluides parfaits," Annales de l'institut Fourier 16, 319 (1966)] of the incompressible Euler equations both in two and three dimensions. The sectional curvatures for the Taylor-Green vortex and the ABC flow initial conditions are calculated exactly in three dimensions. We trace the time evolution of the Jacobi fields by direct numerical simulations and, in particular, see how the sectional curvatures get more and more negative in time. The spatial structure of the Jacobi fields is compared to the vorticity fields by visualizations. The Jacobi fields are found to grow exponentially in time for the flows with negative sectional curvatures. In two dimensions, a family of initial data proposed by Arnold (1966) is considered. The sectional curvature is observed to change its sign quickly even if it starts from a positive value. The Jacobi field is shown to be correlated with the passive scalar gradient in spatial structure. On the basis of Rouchon's physical-space based expression for the sectional curvature (1984), the origin of negative curvature is investigated. It is found that a "potential" αξ appearing in the definition of covariant time derivative plays an important role, in that a rapid growth in its gradient makes a major contribution to the negative curvature.

Carriers' localization and thermal redistribution in post growth voluntarily tuned quantum dashes' size/composition distribution

International Nuclear Information System (INIS)

Alouane, M.H. Hadj; Helali, A.; Morris, D.; Maaref, H.; Aimez, V.; Salem, B.; Gendry, M.

2014-01-01

This paper treats the impact of post growth tuned InAs/InP quantum dashes' (QDas) size/composition distribution on carriers' localization and thermal redistribution. The spread of this distribution depends on the experimental conditions used for the phosphorus ion implantation enhanced intermixing process. Atypical temperature-dependent luminescence properties have been observed and found to be strongly dependent on the amount of QDas size/composition dispersion. The experimental results have been reproduced by a model that takes into account the width of the QDas localized states distribution and consequent thermally induced carriers' redistribution. This model gives critical temperature values marking the beginning and the end of carriers delocalization and thermal transfer processes via an intermixing induced carrier's transfer channel located below the wetting layer states. -- Highlights: • We examine optical properties of post growth tuned QDas size/composition distribution. • Carriers' localization and thermal redistribution within inhomogeneously intermixed QDas are the origin of the atypical temperature-dependent luminescence properties. • Localized states ensemble's model is successively used to interpret the experimental results. • The carriers thermal transfer processes occur via an intermixing induced channel located below the wetting layer states. • Intermixing degree strongly influence the critical temperatures marking the beginning and the end of the carriers thermal transfer processes

Curvature computation in volume-of-fluid method based on point-cloud sampling

Science.gov (United States)

Kassar, Bruno B. M.; Carneiro, João N. E.; Nieckele, Angela O.

2018-01-01

This work proposes a novel approach to compute interface curvature in multiphase flow simulation based on Volume of Fluid (VOF) method. It is well documented in the literature that curvature and normal vector computation in VOF may lack accuracy mainly due to abrupt changes in the volume fraction field across the interfaces. This may cause deterioration on the interface tension forces estimates, often resulting in inaccurate results for interface tension dominated flows. Many techniques have been presented over the last years in order to enhance accuracy in normal vectors and curvature estimates including height functions, parabolic fitting of the volume fraction, reconstructing distance functions, coupling Level Set method with VOF, convolving the volume fraction field with smoothing kernels among others. We propose a novel technique based on a representation of the interface by a cloud of points. The curvatures and the interface normal vectors are computed geometrically at each point of the cloud and projected onto the Eulerian grid in a Front-Tracking manner. Results are compared to benchmark data and significant reduction on spurious currents as well as improvement in the pressure jump are observed. The method was developed in the open source suite OpenFOAM® extending its standard VOF implementation, the interFoam solver.

A linearization time-domain CMOS smart temperature sensor using a curvature compensation oscillator.

Science.gov (United States)

Chen, Chun-Chi; Chen, Hao-Wen

2013-08-28

This paper presents an area-efficient time-domain CMOS smart temperature sensor using a curvature compensation oscillator for linearity enhancement with a -40 to 120 °C temperature range operability. The inverter-based smart temperature sensors can substantially reduce the cost and circuit complexity of integrated temperature sensors. However, a large curvature exists on the temperature-to-time transfer curve of the inverter-based delay line and results in poor linearity of the sensor output. For cost reduction and error improvement, a temperature-to-pulse generator composed of a ring oscillator and a time amplifier was used to generate a thermal sensing pulse with a sufficient width proportional to the absolute temperature (PTAT). Then, a simple but effective on-chip curvature compensation oscillator is proposed to simultaneously count and compensate the PTAT pulse with curvature for linearization. With such a simple structure, the proposed sensor possesses an extremely small area of 0.07 mm2 in a TSMC 0.35-mm CMOS 2P4M digital process. By using an oscillator-based scheme design, the proposed sensor achieves a fine resolution of 0.045 °C without significantly increasing the circuit area. With the curvature compensation, the inaccuracy of -1.2 to 0.2 °C is achieved in an operation range of -40 to 120 °C after two-point calibration for 14 packaged chips. The power consumption is measured as 23 mW at a sample rate of 10 samples/s.

Dynamic Double Curvature Mould System

DEFF Research Database (Denmark)

Jepsen, Christian Raun; Kristensen, Mathias Kræmmergaard; Kirkegaard, Poul Henning

2011-01-01

The present paper describes a concept for a reconfigurable mould surface which is designed to fit the needs of contemporary architecture. The core of the concept presented is a dynamic surface manipulated into a given shape using a digital signal created directly from the CAD drawing of the design....... This happens fast, automatic and without production of waste, and the manipulated surface is fair and robust, eliminating the need for additional, manual treatment. Limitations to the possibilities of the flexible form are limited curvature and limited level of detail, making it especially suited for larger...

Investigating undergraduate students’ ideas about the curvature of the Universe

Directory of Open Access Journals (Sweden)

Kim Coble

2018-06-01

Full Text Available [This paper is part of the Focused Collection on Astronomy Education Research.] As part of a larger project studying undergraduate students’ understanding of cosmology, we explored students’ ideas about the curvature of the Universe. We investigated preinstruction ideas held by introductory astronomy (ASTRO 101 students at three participating universities and postinstruction ideas at one. Through thematic analysis of responses to questions on three survey forms and preinstruction interviews, we found that prior to instruction a significant fraction of students said the Universe is round. Students’ reasoning for this included that the Universe contains round objects, therefore it must also be round, or an incorrect idea that the big bang theory describes an explosion from a central point. We also found that a majority of students think that astronomers use the term curvature to describe properties, such as dimensions, angles, or size, of the Universe or objects in the Universe, or that astronomers use the term curvature to describe the bending of space due to gravity. Students are skeptical that the curvature of the Universe can be measured, to a greater or lesser degree depending on question framing. Postinstruction responses to a multiple-choice exam question and interviews at one university indicate that students are more likely to correctly respond that the Universe as a whole is not curved postinstruction, though the idea that the Universe is round still persists for some students. While we see no evidence that priming with an elliptical or rectangular map of the cosmic microwave background on a postinstruction exam affects responses, students do cite visualizations such as diagrams among the reasons for their responses in preinstruction surveys.

Generating ekpyrotic curvature perturbations before the big bang

International Nuclear Information System (INIS)

Lehners, Jean-Luc; Turok, Neil; McFadden, Paul; Steinhardt, Paul J.

2007-01-01

We analyze a general mechanism for producing a nearly scale-invariant spectrum of cosmological curvature perturbations during a contracting phase preceding a big bang, which can be entirely described using 4D effective field theory. The mechanism, based on first producing entropic perturbations and then converting them to curvature perturbations, can be naturally incorporated in cyclic and ekpyrotic models in which the big bang is modeled as a brane collision, as well as other types of cosmological models with a pre-big bang phase. We show that the correct perturbation amplitude can be obtained and that the spectral tilt n s tends to range from slightly blue to red, with 0.97 s <1.02 for the simplest models, a range compatible with current observations but shifted by a few percent towards the blue compared to the prediction of the simplest, large-field inflationary models

Imprint of spatial curvature on inflation power spectrum

International Nuclear Information System (INIS)

Masso, Eduard; Zsembinszki, Gabriel; Mohanty, Subhendra; Nautiyal, Akhilesh

2008-01-01

If the Universe had a large curvature before inflation there is a deviation from the scale invariant perturbations of the inflaton at the beginning of inflation. This may have some effect on the cosmic microwave background anisotropy at large angular scales. We calculate the density perturbations for both open and closed universe cases using the Bunch-Davies vacuum condition on the initial state. We use our power spectrum to calculate the temperature anisotropy spectrum and compare the results with the Wilkinson microwave anisotropy map five year data. We find that our power spectrum gives a lower quadrupole anisotropy when Ω-1>0, but matches the temperature anisotropy calculated from the standard Ratra-Peebles power spectrum at large l. The determination of spatial curvature from temperature anisotropy data is not much affected by the different power spectra which arise from the choice of different boundary conditions for the inflaton perturbation.

Distributed temperature sensors development using an stepped-helical ultrasonic waveguide

Science.gov (United States)

Periyannan, Suresh; Rajagopal, Prabhu; Balasubramaniam, Krishnan

2018-04-01

This paper presents the design and development of the distributed ultrasonic waveguide temperature sensors using some stepped-helical structures. Distributed sensing has several applications in various industries (oil, glass, steel) for measurement of physical parameters such as level, temperature, viscosity, etc. This waveguide incorporates a special notch or bend for obtaining ultrasonic wave reflections from the desired locations (Gage-lengths) where local measurements are desired. In this paper, a multi-location measurement wave-guide, with a measurement capability of 18 locations in a single wire, has been fabricated. The distribution of these sensors is both in the axial as well as radial directions using a stepped-helical spring configuration. Also, different high temperature materials have been chosen for the wave-guide. Both lower order axi-symmetric guided ultrasonic modes (L(0,1) and T(0,1)) were employed. These wave modes were generated/received (pulse-echo approach) using conventional longitudinal and shear transducers, respectively. Also, both the wave modes were simultaneously generated/received and compared using shear transducer for developing the distributed helical wave-guide sensors. The effect of dispersion of the wave modes due to curvature effects will also be discussed.

Curvature profiles as initial conditions for primordial black hole formation

International Nuclear Information System (INIS)

Polnarev, Alexander G; Musco, Ilia

2007-01-01

This work is part of an ongoing research programme to study possible primordial black hole (PBH) formation during the radiation-dominated era of the early universe. Working within spherical symmetry, we specify an initial configuration in terms of a curvature profile, which represents initial conditions for the large amplitude metric perturbations, away from the homogeneous Friedmann-Robertson-Walker model, which are required for PBH formation. Using an asymptotic quasi-homogeneous solution, we relate the curvature profile with the density and velocity fields, which at an early enough time, when the length scale of the configuration is much larger than the cosmological horizon, can be treated as small perturbations of the background values. We present general analytic solutions for the density and velocity profiles. These solutions enable us to consider in a self-consistent way the formation of PBHs in a wide variety of cosmological situations with the cosmological fluid being treated as an arbitrary mixture of different components with different equations of state. We obtain the analytical solutions for the density and velocity profiles as functions of the initial time. We then use two different parametrizations for the curvature profile and follow numerically the evolution of initial configurations

Model-independent curvature determination with 21 cm intensity mapping experiments

Science.gov (United States)

Witzemann, Amadeus; Bull, Philip; Clarkson, Chris; Santos, Mario G.; Spinelli, Marta; Weltman, Amanda

2018-06-01

Measurements of the spatial curvature of the Universe have improved significantly in recent years, but still tend to require strong assumptions to be made about the equation of state of dark energy (DE) in order to reach sub-percent precision. When these assumptions are relaxed, strong degeneracies arise that make it hard to disentangle DE and curvature, degrading the constraints. We show that forthcoming 21 cm intensity mapping experiments such as Hydrogen Intensity and Real-time Analysis eXperiment (HIRAX) are ideally designed to carry out model-independent curvature measurements, as they can measure the clustering signal at high redshift with sufficient precision to break many of the degeneracies. We consider two different model-independent methods, based on `avoiding' the DE-dominated regime and non-parametric modelling of the DE equation of state, respectively. Our forecasts show that HIRAX will be able to improve upon current model-independent constraints by around an order of magnitude, reaching percent-level accuracy even when an arbitrary DE equation of state is assumed. In the same model-independent analysis, the sample variance limit for a similar survey is another order of magnitude better.

Bed shear stress distribution in straight channels with arbitrary cross section

DEFF Research Database (Denmark)

Christensen, Henrik Bo; Fredsøe, Jørgen

1998-01-01

The bed shear stress distribution in straight open channels is affected by mechanisms as bed curvature of the cross section profile, shear diffusion, and secondary currents. This paper compares some analytical and numerical methods to estimate the bed shear stress distribution. The methods...

Myocardial distribution of I131-labeled hexadecenoic acid in relation to the dog local coronary flow

International Nuclear Information System (INIS)

Riche, F.; Busquet, G.; Pilichowski, P.; Wolf, J.E.; Mathieu, J.P.; Comet, M.; Pernin, C.; Vidal, M.; Vincens, M.; Godart, J.

1981-01-01

20 anesthetized and thoracotomized dogs are studied. The local myocardial blood flow is measured with sup(99m)Tc human albumin microspheres. The intramyocardial distribution of the 16-I(131)-9-hexadecenoic acid in relation to local blood flow is studied in basal conditions (7 dogs), after experimental infarction (6 dogs) and postischemic reactive hyperhemia (7 dogs). We conclude that during basal condition, after infarction but not during reactive hyperhemia, the distribution of the labeled fatty acid reflect the local variations of blood flow [fr

An evaluation of canal curvature at the apical one third in type II mesial canals of mandibular molars

Directory of Open Access Journals (Sweden)

Hye-Rim Yun

2012-05-01

Full Text Available Objectives The purpose of this study was to evaluate the buccolingual curvature at the apical one third in type II mesial canals of mandibular molars using the radius and angle of curvature. Materials and Methods Total 100 mandibular molars were selected. Following an endodontic access in the teeth, their distal roots were removed. #15 H- or K-files (Dentsply Maillefer were inserted into the mesiobuccal and mesiolingual canals of the teeth. Radiographs of the teeth were taken for the proximal view. Among them, type II canals were selected and divided into two subgroups, IIa and IIb. In type IIa, two separate canals merged into one canal before reaching the apex and in type IIb, two separate canals merged into one canal within the apical foramen. The radius and angle of curvature of specimens were examined. Results In type II, mean radius of curvature in mesiolingual and mesiobuccal canals were 2.82 mm and 3.58 mm, respectively. The radius of the curvature of mesiolingual canals were significantly smaller than that of mesiobuccal canals in type II, and especially in type IIa. However, there were no statistically significant differences in radius of curvature between mesiobuccal and mesiolingual canals in type IIb and there were no significant differences in angle of curvature between type IIa and IIb. Conclusion In this study, type II mesial canals of mandibular molars showed severe curvature in the proximal view. Especially, mesiolingual canals of type IIa had more abrupt curvature than mesiobuccal canals at the apical one third.

Distribution of Ωk from the scale-factor cutoff measure

International Nuclear Information System (INIS)

De Simone, Andrea; Salem, Michael P.

2010-01-01

Our Universe may be contained in one among a diverging number of bubbles that nucleate within an eternally inflating multiverse. A promising measure to regulate the diverging spacetime volume of such a multiverse is the scale-factor cutoff, one feature of which is bubbles are not rewarded for having a longer duration of slow-roll inflation. Thus, depending on the landscape distribution of the number of e-folds of inflation among bubbles like ours, we might hope to measure spatial curvature. We study a recently proposed cartoon model of inflation in the landscape and find a reasonable chance (about 10%) that the curvature in our Universe is well above the value expected from cosmic variance. Anthropic selection does not strongly select for curvature as small as is observed (relative somewhat larger values), meaning the observational bound on curvature can be used to rule out landscape models that typically give too little inflation.

Convective mass transfer in helical pipes: effect of curvature and torsion

Energy Technology Data Exchange (ETDEWEB)

Litster, S.; Djilali, N. [University of Victoria, Department of Mechanical Engineering, Victoria, BC (Canada); Pharoah, J.G. [University of Victoria, Department of Mechanical Engineering, Victoria, BC (Canada); Queen' s University at Kingston, Department of Mechanical Engineering, Kingston, ON (Canada)

2006-03-01

A 3D numerical analysis of the flow and mass transfer in helical pipes is presented. The interpretation of the flow patterns and their impact on mass transfer is shown to require a non-orthogonal pseudo-stream function based visualization. The strong coupling between torsion and curvature effects, and the resulting secondary flow regimes are well characterized by a parameter combining both the Dean (Dn) and Germano numbers (Gn). For membrane separation applications, helical modules combining high curvature with low torsion would alleviate concentration polarization and yield appreciable flux improvement. (orig.)

Papapetrou's naked singularity is a strong curvature singularity

International Nuclear Information System (INIS)

Hollier, G.P.

1986-01-01

Following Papapetrou [1985, a random walk in General Relativity ed. J. Krishna-Rao (New Delhi: Wiley Eastern)], a spacetime with a naked singularity is analysed. This singularity is shown to be a strong curvature singularity and thus a counterexample to a censorship conjecture. (author)

On the projective curvature tensor of generalized Sasakian-space ...

African Journals Online (AJOL)

space-forms under some conditions regarding projective curvature tensor. All the results obtained in this paper are in the form of necessary and sufficient conditions. Keywords: Generalized Sasakian-space-forms; projectively flat; ...

Carbohydrate distribution and 14C-photosynthates uptake in the curved fruits of cucumber

Energy Technology Data Exchange (ETDEWEB)

Kanahama, K. [Yamagata univ., Tsuruoka (Japan); Saito, T.

1988-12-15

The major carbohydrates in cucumber fruit were reducing sugars, which increased to the highest concentration of about 2.0% of fresh weight at harvest for fresh fruit, that is, 6-8 days after flowering and 73-116g in fresh weight. Starch was highest in concentration at flowering although it was negligible as compared with sugars. Reducing sugar concentration was higher in the core (septum and placenta) than in the flesh (receptacle and pericarp). Moreover, it was higher outside than inside the curvature at the curvature increasing stage, while the reverse was true at the curvature decreasing stage. Labelled carbon was fed to the single leaf on the same node as the fruit. Twenty hours after feeding, {sup 14}C-activity was higher in carpel II (outside the curvature and opposite to the tendril) than in carpels I (facing the stem) and III (inside the curvature and facing the tendril) when fed at the curvature increasing stage. When fed at the curvature decreasing stage after the curvature maximum stage had been attained, {sup 14}C-activity was higher in carpel III than in carpels I and II. From these results, it was suggested that the curvature of cucumber fruit occurred due to the competition among the carpels, in uptake of carbohydrates under limited photosynthesis. Each carpel is presumed to be different in sink activity according to its congenital developmental order and stages. Differential carbohydrate translocation due to localization of vascular bundle connections between leaves and fruit is improbable.

Endoscopes and robots for tight surgical spaces: use of precurved elastic elements to enhance curvature

Science.gov (United States)

Remirez, Andria A.; Webster, Robert J.

2016-03-01

Many applications in medicine require flexible surgical manipulators and endoscopes capable of reaching tight curvatures. The maximum curvature these devices can achieve is often restricted either by a strain limit, or by a maximum actuation force that the device's components can tolerate without risking mechanical failure. In this paper we propose the use of precurvature to "bias" the workspace of the device in one direction. Combined with axial shaft rotation, biasing increases the size of the device's workspace, enabling it to reach tighter curvatures than a comparable device without biasing can achieve, while still being able to fully straighten. To illustrate this effect, we describe several example prototype devices which use flexible nitinol strips that can be pushed and pulled to generate bending. We provide a statics model that relates the manipulator curvature to actuation force, and validate it experimentally.

Translating Solitons of Mean Curvature Flow of Noncompact Submanifolds

International Nuclear Information System (INIS)

Li Guanghan; Tian Daping; Wu Chuanxi

2011-01-01

We prove the existence and asymptotic behavior of rotationally symmetric solitons of mean curvature flow for noncompact submanifolds in Euclidean and Minkowski spaces, which generalizes part of the corresponding results for hypersurfaces of Jian.

Curvature and elasticity of substitution: what is the link?

Czech Academy of Sciences Publication Activity Database

Matveenko, Andrei; Matveenko, V.

2014-01-01

Roč. 10, č. 2 (2014), s. 7-20 ISSN 1800-5845 Grant - others:UK(CZ) GAUK 308214 Institutional support: PRVOUK-P23 Keywords : curvature * elasticity of substitution * production function Subject RIV: AH - Economics

On M-theory fourfold vacua with higher curvature terms

International Nuclear Information System (INIS)

Grimm, Thomas W.; Pugh, Tom G.; Weißenbacher, Matthias

2015-01-01

We study solutions to the eleven-dimensional supergravity action, including terms quartic and cubic in the Riemann curvature, that admit an eight-dimensional compact space. The internal background is found to be a conformally Kähler manifold with vanishing first Chern class. The metric solution, however, is non-Ricci-flat even when allowing for a conformal rescaling including the warp factor. This deviation is due to the possible non-harmonicity of the third Chern-form in the leading order Ricci-flat metric. We present a systematic derivation of the background solution by solving the Killing spinor conditions including higher curvature terms. These are translated into first-order differential equations for a globally defined real two-form and complex four-form on the fourfold. We comment on the supersymmetry properties of the described solutions

Total curvature and total torsion of knotted random polygons in confinement

Science.gov (United States)

Diao, Yuanan; Ernst, Claus; Rawdon, Eric J.; Ziegler, Uta

2018-04-01

Knots in nature are typically confined spatially. The confinement affects the possible configurations, which in turn affects the spectrum of possible knot types as well as the geometry of the configurations within each knot type. The goal of this paper is to determine how confinement, length, and knotting affect the total curvature and total torsion of random polygons. Previously published papers have investigated these effects in the unconstrained case. In particular, we analyze how the total curvature and total torsion are affected by (1) varying the length of polygons within a fixed confinement radius and (2) varying the confinement radius of polygons with a fixed length. We also compare the total curvature and total torsion of groups of knots with similar complexity (measured as crossing number). While some of our results fall in line with what has been observed in the studies of the unconfined random polygons, a few surprising results emerge from our study, showing some properties that are unique due to the effect of knotting in confinement.

Thermodynamic curvature of soft-sphere fluids and solids

Science.gov (United States)

Brańka, A. C.; Pieprzyk, S.; Heyes, D. M.

2018-02-01

The influence of the strength of repulsion between particles on the thermodynamic curvature scalar R for the fluid and solid states is investigated for particles interacting with the inverse power (r-n) potential, where r is the pair separation and 1 /n is the softness. Exact results are obtained for R in certain limiting cases, and the R behavior determined for the systems in the fluid and solid phases. It is found that in such systems the thermodynamic curvature can be positive for very soft particles, negative for steeply repulsive (or large n ) particles across almost the entire density range, and can change sign between negative and positive at a certain density. The relationship between R and the form of the interaction potential is more complex than previously suggested, and it may be that R is an indicator of the relative importance of energy and entropy contributions to the thermodynamic properties of the system.

On a class of graphs with prescribed mean curvature

International Nuclear Information System (INIS)

Duong Minh Duc; Costa Salavessa, I.M. de

1989-11-01

We study a class of quasilinear elliptic equations on the unit ball of R n and apply these results to get the existence of graphs with prescribed mean curvature on n-hyperbolic spaces. (author). 18 refs

Combined local current distribution measurements and high resolution neutron radiography of operating direct methanol fuel cells

Energy Technology Data Exchange (ETDEWEB)

Schroeder, Alexander; Wippermann, Klaus [Forschungszentrum Juelich GmbH (Germany). Inst. of Energy Research, IEF-3: Fuel Cells; Sanders, Tilman [RWTH Aachen (DE). Inst. for Power Electronics and Electrical Drives (ISEA); Arlt, Tobias [Helmholtz Centre Berlin (Germany). Inst. for Applied Materials

2010-07-01

Neutron radiography allows the investigation of the local fluid distribution in direct methanol fuel cells (DMFCs) under operating conditions. Spatial resolutions in the order of some tens of micrometers at the full test cell area are achieved. This offers the possibility to study practice-oriented, large stack cells with an active area of several hundred cm{sup 2} as well as specially designed, small test cells with an area of some cm{sup 2}. Combined studies of high resolution neutron radiography and segmented cell measurements are especially valuable, because they enable a correlation of local fluid distribution and local performance [1, 2]. The knowledge of this interdependency is essential to optimise the water management and performance respecting a homogeneous fluid, current and temperature distribution and to achieve high performance and durability of DMFCs. (orig.)

Effects of curvature on rarefied gas flows between rotating concentric cylinders

Science.gov (United States)

Dongari, Nishanth; White, Craig; Scanlon, Thomas J.; Zhang, Yonghao; Reese, Jason M.

2013-05-01

The gas flow between two concentric rotating cylinders is considered in order to investigate non-equilibrium effects associated with the Knudsen layers over curved surfaces. We investigate the nonlinear flow physics in the near-wall regions using a new power-law (PL) wall-scaling approach. This PL model incorporates Knudsen layer effects in near-wall regions by taking into account the boundary limiting effects on the molecular free paths. We also report new direct simulation Monte Carlo results covering a wide range of Knudsen numbers and accommodation coefficients, and for various outer-to-inner cylinder radius ratios. Our simulation data are compared with both the classical slip flow theory and the PL model, and we find that non-equilibrium effects are not only dependent on Knudsen number and accommodation coefficient but are also significantly affected by the surface curvature. The relative merits and limitations of both theoretical models are explored with respect to rarefaction and curvature effects. The PL model is able to capture some of the nonlinear trends associated with Knudsen layers up to the early transition flow regime. The present study also illuminates the limitations of classical slip flow theory even in the early slip flow regime for higher curvature test cases, although the model does exhibit good agreement throughout the slip flow regime for lower curvature cases. Torque and velocity profile comparisons also convey that a good prediction of integral flow properties does not necessarily guarantee the accuracy of the theoretical model used, and it is important to demonstrate that field variables are also predicted satisfactorily.

Local and Widely Distributed EEG Activity in Schizophrenia With Prevalence of Negative Symptoms.

Science.gov (United States)

Grin-Yatsenko, Vera A; Ponomarev, Valery A; Pronina, Marina V; Poliakov, Yury I; Plotnikova, Irina V; Kropotov, Juri D

2017-09-01

We evaluated EEG frequency abnormalities in resting state (eyes closed and eyes open) EEG in a group of chronic schizophrenia patients as compared with healthy subjects. The study included 3 methods of analysis of deviation of EEG characteristics: genuine EEG, current source density (CSD), and group independent component (gIC). All 3 methods have shown that the EEG in schizophrenia patients is characterized by enhanced low-frequency (delta and theta) and high-frequency (beta) activity in comparison with the control group. However, the spatial pattern of differences was dependent on the type of method used. Comparative analysis has shown that increased EEG power in schizophrenia patients apparently concerns both widely spatially distributed components and local components of signal. Furthermore, the observed differences in the delta and theta range can be described mainly by the local components, and those in the beta range mostly by spatially widely distributed ones. The possible nature of the widely distributed activity is discussed.

Asymmetric vibrations of shells of revolution having meridionally varying curvature and thickness

International Nuclear Information System (INIS)

Suzuki, Katsuyoshi; Kosawada, Tadashi; Miura, Kazuyuki.

1988-01-01

An exact method using power series expansions is presented for solving asymmetric free vibration problems for shells of revolution having meridionally varying curvature and thickness. The gaverning equations of motion and the boundary conditions are derived from the stationary conditions of the Lagrangian of the shells of revolution. The method is demonstrated for shells of revolution having elliptical, cycloidal, parabolical, catenary and hyperbolical meridional curvature. The natural frequencies are numerically calculated for these shells having second degree thickness variation. (author)

Effect of local automatic control rods on three-dimensional calculations of the power distribution in an RBMK

International Nuclear Information System (INIS)

Pogosbekyan, L.R.; Lysov, D.A.; Bronitskii, L.L.

1993-01-01

Numerical simulators and information systems that support nuclear reactor operators must have fast models to estimate how fuel reloads and control rod displacement affect neutron and power distributions in the core. The consequences of reloads and control rod displacement cannot be evaluated correctly without considering local automatic control-rod operations in maintaining the radial power distribution. Fast three-dimensional models to estimate the effects of reloads and displacement of the control and safety rods have already been examined. I.V. Zonov et al. used the following assumptions in their calculational model: (1) the full-scale problem could be reduced a three-dimensional fragment of a locally perturbed core, and (2) the boundary conditions of the fragment and its total power were constant. The last assumption considers approximately how local automatic control rods stabilize the radial power distribution, but three dimensional calculations with these rods are not considered. These assumptions were introduced to obtain high computational speed. I.L. Bronitskii et al. considered in more detail how moving the local automatic control rods affect the power dimensional in the three-dimensional fragment, because, with on-line monitoring of the reload process, information on control rod positions is periodically renewed, and the calculations are done in real time. This model to predict the three-dimensional power distribution to (1) do a preliminary reload analysis, and (2) prepare the core for reloading did not consider the effect of perturbations from the local automatic control rods. Here we examine a model of a stationary neutron distribution. On one hand it gives results in an acceptable computation time; on the other it is a full-scale three-dimensional model and considers how local automatic control rods affect both the radial and axial power distribution

Using geometric algebra to represent curvature in shell theory with applications to Starling resistors.

Science.gov (United States)

Gregory, A L; Agarwal, A; Lasenby, J

2017-11-01

We present a novel application of rotors in geometric algebra to represent the change of curvature tensor that is used in shell theory as part of the constitutive law. We introduce a new decomposition of the change of curvature tensor, which has explicit terms for changes of curvature due to initial curvature combined with strain, and changes in rotation over the surface. We use this decomposition to perform a scaling analysis of the relative importance of bending and stretching in flexible tubes undergoing self-excited oscillations. These oscillations have relevance to the lung, in which it is believed that they are responsible for wheezing. The new analysis is necessitated by the fact that the working fluid is air, compared to water in most previous work. We use stereographic imaging to empirically measure the relative importance of bending and stretching energy in observed self-excited oscillations. This enables us to validate our scaling analysis. We show that bending energy is dominated by stretching energy, and the scaling analysis makes clear that this will remain true for tubes in the airways of the lung.

Curvature vector smart sensing with a long-period fibre grating probed by artificial intelligence

International Nuclear Information System (INIS)

Costa, R Z V; Possetti, G R C; De Arruda, L V R; Muller, M; Fabris, J L

2010-01-01

This work shows a curvature vector sensing device based on a single long-period grating written in a commercial photosensitive optical fibre. The sensing approach uses an artificial neural network based on multilayer perceptrons for data analysis. Curvatures from 0.00 to 3.13 m −1 and angular orientations from 0 to 180° were measured with the device, with combined standard uncertainties of 0.05 m −1 and 1.5°, respectively. The root mean square errors for curvature and angular orientation were 0.0008 m −1 and 0.3° in the training stage and 0.002 m −1 and 0.9° in the test stage, respectively

Correlation Functions of the Energy Momentum Tensor on Spaces of Constant Curvature

CERN Document Server

Osborn, H

2000-01-01

An analysis of one and two point functions of the energy momentum tensor on homogeneous spaces of constant curvature is undertaken. The possibility of proving a c-theorem in this framework is discussed, in particular in relation to the coefficients c,a, which appear in the energy momentum tensor trace on general curved backgrounds in four dimensions. Ward identities relating the correlation functions are derived and explicit expressions are obtained for free scalar, spinor field theories in general dimensions and also free vector fields in dimension four. A natural geometric formalism which is independent of any choice of coordinates is used and the role of conformal symmetries on such constant curvature spaces is analysed. The results are shown to be constrained by the operator product expansion. For negative curvature the spectral representation, involving unitary positive energy representations of $O(d-1,2)$, for two point functions of vector currents is derived in detail and extended to the energy momentu...

On the geometry of null cones to infinity under curvature flux bounds

International Nuclear Information System (INIS)

Alexakis, Spyros; Shao, Arick

2014-01-01

The main objective of this paper is to control the geometry of a future outgoing truncated null cone extending smoothly toward infinity in an Einstein-vacuum spacetime. In particular, we wish to do this under minimal regularity assumptions, namely, at the (weighted) L 2 -curvature level. We show that if the curvature flux and the data on an initial sphere of the cone are sufficiently close to the corresponding values in a standard Minkowski or Schwarzschild null cone, then we can obtain quantitative bounds on the geometry of the entire infinite cone. The same bounds also imply the existence of limits at infinity, along the null cone, of naturally scaled geometric quantities. In Alexakis and Shao (2013 Bounds on the Bondi energy by a flux of curvature arXiv:1308.4170), we will apply these results in order to control various physical quantities—e.g., the Bondi energy and (linear and angular) momenta—associated with such infinite null cones in vacuum spacetimes. (paper)

Adjuvant Maneuvers for Residual Curvature Correction During Penile Prosthesis Implantation in Men with Peyronie's Disease.

Science.gov (United States)

Berookhim, Boback M; Karpman, Edward; Carrion, Rafael

2015-11-01

The surgical treatment of comorbid erectile dysfunction and Peyronie's disease has long included the implantation of an inflatable penile prosthesis as well as a number of adjuvant maneuvers to address residual curvature after prosthesis placement. To review the various surgical options for addressing curvature after prosthesis placement, with specific attention paid to an original article by Wilson et al. reporting on modeling over a penile prosthesis for the management of Peyronie's disease. A literature review was performed analyzing articles reporting the management of penile curvature in patients undergoing implantation of an inflatable penile prosthesis. Reported improvement in Peyronie's deformity as well as the complication rate associated with the various surgical techniques described. Modeling is a well-established treatment modality among patients with Peyronie's disease undergoing penile prosthesis implantation. A variety of other adjuvant maneuvers to address residual curvature when modeling alone is insufficient has been presented in the literature. Over 20 years of experience with modeling over a penile prosthesis have proven the efficacy and safety of this treatment option, providing the surgeon a simple initial step for the management of residual curvature after penile implantation which allows for the use of additional adjuvant maneuvers in those with significant deformities. © 2015 International Society for Sexual Medicine.

Constant scalar curvature hypersurfaces in extended Schwarzschild space-time

International Nuclear Information System (INIS)

Pareja, M. J.; Frauendiener, J.

2006-01-01

We present a class of spherically symmetric hypersurfaces in the Kruskal extension of the Schwarzschild space-time. The hypersurfaces have constant negative scalar curvature, so they are hyperboloidal in the regions of space-time which are asymptotically flat

Influence of piezoceramic to fused silica plate thickness on the radii of curvature of piezoelectric bimorph mirror

International Nuclear Information System (INIS)

Libu, M.; Susanth, S.; Vasanthakumari, K. G.; Dileep Kumar, C. J.; Raghu, N.

2012-01-01

Piezoelectric based bimorph mirrors (PBM) find extensive use in focusing of x-ray beams. Many optical instruments require use of PBM whose radii of curvature can be tuned precisely. The 100 mm and 300 mm PBMs were fabricated with varying piezoelectric to fused silica plate thicknesses. The radii of curvature of free standing mirrors were measured as a function of voltage and it was found to decrease with increasing voltage. For a given piezoelectric plate thickness, as the fused silica thickness increases, the radii of curvature was found to increase owing to increase in stiffness of the mirror. On the other hand, for a given fused silica plate thickness, when the piezoelectric plate thickness is increased, the radii of curvature are decreased for a given electric field, due to increase in generated force. This study brings out the influence of piezoceramic to fused silica plate thickness on the radii of curvature of PBM.

Spatial Distribution Of Local Markets In Ife North Local Government Area

Directory of Open Access Journals (Sweden)

OMOTOYE-OMISORE Oyelola

2015-08-01

Full Text Available Researches have been carried out in the past by several authors concerning agricultural marketing without the use of geospatial techniques. This research therefore is meant to show the efficacy of Geographical Information System GIS in local market distribution. The role of market place as a man-made feature where goods and services are exchanged for the purpose of satisfying human needs cannot be overemphasized especially in the general development of villages and towns. This study shows the effectiveness of GIS without the use of metrics method to determine the agricultural market locations and closeness of the markets in Ife North Local Government area. Different kinds of people bring their goods from far and near villages for sale and sustainability in this research both primary and secondary data were collected. Primary data includes the use of Global Positioning System GPS receiver to collect coordinate points of the existing markets. It also involves verbal interview with market women. While secondary data were sourced from administrative maps and satellite images of the area of study it was geo-referenced and digitized. Arc Map was used to run average nearest neighbor analysis. Base on the analysis performed the major constraint facing the market people is poor road network which affect majority of the farmers in transporting their goods from remote villages as indicated in this study. As a result new markets sites were proposed with the use of geospatial techniques for easy accessibility.

Curvature-Induced Bunch Self-Interaction for an Energy-Chirped Bunch in Magnetic Bends

International Nuclear Information System (INIS)

Rui Li

2008-01-01

Within the realm of classical electrodynamics, the curvature-induced bunch collective interaction in magnetic bends can be studied using effective forces in the canonical formulation of the coherent synchrotron radiation (CSR) effect. As an application of this canonical formulation, in this paper, for an electron distribution moving ultrarelativistically in a bending system, the dynamics of the particles in the distribution is derived from the Hamiltonian of the particles in terms of the bunch internal coordinates. The consequent Vlasov equation manifests explicitly how the phase-space distribution is perturbed by the effective CSR forces. In particular, we study the impact of an initial linear energy chirp of the bunch on the behavior of the effective longitudinal CSR force, which arises due to the modification of the retardation relation as a result of the energy-chirping-induced longitudinal-horizontal correlation of the bunch distribution (bunch tilt) in dispersive regions. Our study demonstrates clearly the time delay (or retardation) of the behavior of the effective longitudinal CSR force on a bunch in responding to the change of the bunch length in a magnetic bend. Our result also shows that the effective longitudinal CSR force for a bunch under full compression can have sensitive dependence on the transverse position of the test particle in the bunch for certain parameter regimes

Flow Curvature Effects for VAWT: a Review of Virtual Airfoil Transformations and Implementation in XFOIL

DEFF Research Database (Denmark)

van der Horst, Sander; van de Wiel, Jelmer E.; Ferreira, Carlos Simao

2016-01-01

Blades on a Vertical Axis Wind Turbine (VAWT) experience curved streamlines, caused by the rotation of the turbine. This phenomenon is known as flow curvature and has effects on the aerodynamic loading of the blades. Several authors have proposed methods to account for flow curvature, resulting...

Local Voltage Control in Distribution Networks: A Game-Theoretic Perspective

Energy Technology Data Exchange (ETDEWEB)

Zhou, Xinyang; Tian, Jie; Chen, Lijun; Dall' Anese, Emiliano

2016-11-21

Inverter-based voltage regulation is gaining importance to alleviate emerging reliability and power-quality concerns related to distribution systems with high penetration of photovoltaic (PV) systems. This paper seeks contribution in the domain of reactive power compensation by establishing stability of local Volt/VAr controllers. In lieu of the approximate linear surrogate used in the existing work, the paper establishes existence and uniqueness of an equilibrium point using nonlinear AC power flow model. Key to this end is to consider a nonlinear dynamical system with non-incremental local Volt/VAr control, cast the Volt/VAr dynamics as a game, and leverage the fixed-point theorem as well as pertinent contraction mapping argument. Numerical examples are provided to complement the analytical results.